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Adsorption and reactions of CH3Cl on Mo2C based catalyst
Journal of Molecular Catalysis A: Chemical 162 Ž2000. 335–352 www.elsevier.comrlocatermolcata
Adsorption and reactions of CH 3 Cl on Mo 2 C based catalyst ´ ´ T. Bansagi, J. Cserenyi ´ ) , L. Ovari, ´ ´ F. Solymosi Institute of Solid State and Radiochemistry, UniÕersity of Szeged and Reaction Kinetics Research Group of the Hungarian Academy of Sciences 1, P.O. Box 168, H-6701, Szeged, Hungary
Abstract The adsorption of CH 3 Cl on ZSM-5, Mo 2 CrZSM-5 and Mo 2 CrSiO 2 was investigated by temperature-programmed desorption ŽTPD. and Fourier transform infrared spectroscopy ŽFTIR.. The formation of methoxy species was clearly identified on all the three catalysts. Three elementary steps were considered to explain the absorption bands observed in the IR spectra and to describe the reaction products found at higher temperatures: Ži. the interaction of CH 3 Cl with the OH groups of ZSM-5, Žii. dissociation of CH 3 Cl yielding CH 3 , and Žiii. the elimination of HCl from the adsorbed CH 3 Cl to give CH 2 species. A new finding was the identification of the alkenyl carbocation formed on the Lewis acidic sites of ZSM-5. The decomposition of CH 3 Cl on ZSM-5 proceeded at 673 K with a high conversion yielding propylene, ethylene, butane, methane and benzene in decreasing selectivities. Deposition of Mo 2 C on ZSM only slightly modified the catalytic behavior of ZSM-5. Its promoter effect came into prominence on silica surface. q 2000 Published by Elsevier Science B.V. Keywords: Adsorption and reactions; CH 3 Cl; Mo 2 C-based catalyst
1. Introduction The catalytic conversion of methane into more valuable compounds has been the subject of intensive research during the last two decades. One of the ways is to convert methane to methyl chloride via oxychlorination reaction w1,2x, and then transform methyl chloride into light olefins and hydrochloric acid w3,4x. Pure and modified ZSM-5 is an effective catalyst for CH 3 C1 reaction, the product distribution sensitively depends on the reaction temperature and on the nature of the promoters w5–8x.
)
Corresponding author. These laboratories are parts of the Center for Catalysis, Surface and Material Science at the University of Szeged. 1
Recently, it was found that Mo 2 C deposited on the cavities of ZSM-5 is an active catalyst in the direct conversion of methane into benzene w9–12x. The same results were observed when the starting material was MoO 3rZSM-5 w13–15x, as MoO 3 was converted into Mo 2 C during the high temperature reaction w9–12x. It was thought that the primary role of Mo 2 C is to activate methane to produce CH 3 andror CH 2 species and then — through their coupling — ethane andror ethylene. The oligomerization and aromatization of these compounds proceed on the ZSM-5. In the subsequent studies, it was found that Mo 2 C also exerts a promoting influence even on the aromatization of ethane and propane, which occurs readily on ZSM-5 w16,17x. In the present work, an attempt is being made to examine the effect of Mo 2 C on the interaction and
1381-1169r00r$ - see front matter q 2000 Published by Elsevier Science B.V. PII: S 1 3 8 1 - 1 1 6 9 Ž 0 0 . 0 0 3 0 1 - 0
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J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
reaction of CH 3 C1 with ZSM-5. It is hoped that the results obtained may also contribute to the better understanding of the aromatization of methane on this catalyst.
2. Experimental Catalytic reactions were carried out at 1 atm of CH 3 Cl q Ar gas mixture containing 5% of CH 3 Cl in a fixed-bed, continuous flow reactor consisting of a quartz tube Ž10 mm i.d.. connected to a capillary tube. The flow rate was 12 mlrmin. Generally, 0.5 g of loosely compressed catalyst sample was used. Reaction products were analyzed by means of a Hewlett-Packard 5890 gas chromatograph using a Porapak QS column. The conversion of CH 3 Cl was calculated from the hydrogen balance. The selectivity values of product formation represent the fraction of methyl chloride that has been converted into specific products, taking into account the number of carbon atoms in the molecules. The decomposition of CH 3 Cl was also followed in a closed circulation system, where the analysis of products was performed by a mass spectrometer. Infrared spectroscopic measurements were made in a vacuum IR cell using self-supporting wafers of catalyst powders. Spectra were recorded with a Biorad ŽDigilab. Div.. Fourier transform IR spectrometer FTS 155. The H-ZSM-5 support was obtained by five times repeated ion exchange of Na-ZSM-5 ŽSirAls 55.0. with an aqueous solution of ammonium nitrate Ž1N., and calcined in air at 863 K for 5 h. Before catalytic measurements, each sample was oxidized in an O 2 stream at 973 K in situ and then flushed with Ar for 15 min. Hexagonal Mo 2 C was prepared by the method of Lee et al. w18x. Briefly, about 0.5 g of MoO 3 was heated in 1:4 methane–H 2 mixture flowing at 300 ml ŽSTP.rmin in a quartz cell with two stopcocks. Preparation temperature was increased rapidly to 773 K and at 30 Krh between 773 and 1023 K, and maintained at 1023 K for 3 h. Supported Mo 2 C was produced by the carburation of supported MoO 3 in the catalytic reactor, in a similar way as described above for the preparation of bulk Mo 2 C. MoO 3rZSM-5 and MoO 3rSiO 2 were
prepared by impregnating the supports with a basic solution of ammonium paramolybdate to yield a nominal 2 wt.% of MoO 3 . The suspension was dried at 373 K and calcined at 873 K for 5 h. Following the suggestion of Lee et al. w18x, the sample was deactivated at 300 K with air, or used in situ for catalytic studies. As Mo 2 C always contains excess carbon, the catalyst was treated with H 2 at 873 K before the catalytic measurements to remove this carbon species. The gases used were of commercial purity ŽLinde.. Ar Ž99.996%. and H 2 Ž99.999%. were deoxygenated with an oxytrap. The other impurities were adsorbed by a 5A molecular sieve at the temperature of liquid nitrogen.
3. Results 3.1. Adsorption of CH3 Cl 3.1.1. Temperature-programmed desorption (TPD) measurements The interaction of CH 3 Cl with the above catalysts has been first studied by means of TPD. A 0.5-g catalyst sample was kept in CH 3 Cl flow at 373 K for 10 min, afterwards, the reactor was washed with argon until no or only traces of CH 3 Cl was detected in the outlet gas; this required about 60 min. TPD spectra are shown in Fig. 1. CH 3 Cl desorbed from the ZSM-5 with a peak temperature Tp s 393 K. Methane and hydrogen were released only above 700 K. Similar features have been observed for the Mo 2 CrZSM-5 sample. The amount of CH 3 Cl desorbed was somewhat less, but the peak temperature was the same. At the same time, however, the formation of methane ŽTp s 420 K., ethylene ŽTp s 550 K. and propane was observed. 3.1.2. Infrared spectroscopic measurements The ZSM-5 sample exhibited the usual absorption bands at 3744, 3679 and 3612 cmy1 . These bands are assigned to terminal Si–OH groups, Al–OH groups and acidic bridging hydroxyls, respectively. The deposition of Mo 2 C onto ZSM-5 did not alter this picture, except that the intensity of the 3612 cmy1 band has been reduced by about 40%.
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Fig. 1. TPD spectra following the adsorption of CH 3 Cl on ŽA. ZSM-5 and ŽB. Mo 2 CrZSM-5 samples at 373 K.
Fourier transform infrared spectroscopy ŽFTIR. spectra of adsorbed CH 3 Cl on Mo 2 CrZSM-5 are shown in Fig. 2. Absorption bands observed at 2963, 2860, 1444 and 1350 cmy1 correspond well to different vibrations of adsorbed CH 3 Cl. The assignment of these bands is presented in Table 1. In the OH frequency region, reverse absorption bands devel-
oped at 3663 and 3612 cmy1 , and a broad band at 3175 cmy1 . Degassing the sample at room temperature resulted in the elimination of all bands, including the reverse absorption bands, indicating the weak interaction at 300 K. When the sample was kept in 10 Torr of CH 3 Cl at 473 K and evacuated at 300 K, both reverse bands at 3663 and 3612 cmy1 remained
Fig. 2. Ža. FTIR spectra of Mo 2 CrZSM-5 in the presence of CH 3 Cl Ž10 Torr. at 300 K Žthe spectrum of gas phase is subtracted., and after adsorption of CH 3 Cl at 473 Žb. and 573 K Žc.. In the latter two cases, the sample was degassed at 300 K.
a
2860 Žw .
1444 Žm . 1350 Žs .
2879
1455 1355
This work.
2963 Žw .
–
CH 3 Cl Mo 2 Cr ZSM-5 300 K a
2966
3042
n as ŽCH 3 .
n as ŽCH 2 . n s ŽCH 3 . n s ŽCH 2 . 2 d as ŽCH 3 . n ŽC5C . n as ŽCCC . d as ŽCH 3 . d ŽCH 2 . d s ŽCH 3 . r ŽCH 2 . v ŽCH 2 . n ŽC ` C . g ŽCH 2 .
CH 3 Cl gas w22 x
Assignments
1539 1509 1458 1470 1383
2927 2901 2860 Žm . Žvs . Žm . Žvs . Žs .
Žw . Žvw . Žw .
2958 Žw .
CH 3 Cl Mo 2 Cr ZSM-5 473 K a
Table 1 Characteristic vibrations of different adsorbed species
1441 Žw .
1464 Žw .
2939 Žw .
2859 Žm .
2961 Žm .
CH 3 Cl Mo 2 Cr SiO 2 473 K a
1180 Žs.
1370 Žm .
2930 Ž m .
CH 3 Mo 2 C w20 x
1190 Žm .
780
2940 Žs.
CH 2 Mo 2 C w19 x
1441,1340
1631, 1612
2975
3090
C2H4 ZSM-5 153 K a
1035 Žs.
1180 Žw .
1395 Žs.
2935 Žs.
3010 Žw .
di-s C 2 H 4 Ž 4=4 .-Cr Mo Ž110 . w23 x
1075 Žm .
1345 Žm .
1430 Žm .
2915 Žs.
CCH 3 Ž4=4 .-Cr Mo Ž110 . w23 x
Žm . Žms.
1350 Žms.
1465 Žw .
2885 2920
di-s propylene PtrSiO 2 w24 x
Žw ., Žm .
1466 Žs.
1481 Žw .
2937 Žw .
2859 Žm .
3001 2961
CH 3 O SiO 2 w27 x
Žm . Žm . Žw .
1452 Žw . 1492 Žw . 1399 Žm . 1384 Žm . 1348 Žm .
2940 2911 2882
2986 Ž s.
C 2 H 5O SiO 2 w26 x
1460 1380
2940 2885 2855
Žm . Žm .
Žm . Žs . Žw .
2965 Ž s.
C 3H 7O TiO 2 w25 x
338 J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
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changing their positions. New bands appeared at 2979 and 1388 cmy1 after treating the Mo 2 CrSiO 2 sample with CH 3 Cl at 673 K. The peaks observed at 473 K for Mo 2 CrSiO 2 also appeared on the IR spectrum of pure silica, but with much less intensities. The difference is that the 2939 and 1446 cmy1 bands are missing, and the bands at 2979 and 1388 cmy1 did not develop at 673 K. 3.2. Catalytic decomposition of CH3 Cl
Fig. 3. FTIR spectra of Mo 2 CrSiO 2 following the adsorption of CH 3 Cl at different temperatures. Ža. 473; Žb. 573 K; Žc. 673 K and degassing at 300 K.
practically unchanged, which is in contrast with the room temperature adsorption. In addition, relatively intense absorption bands developed at 2958, 2927, 2901 and 2860 cmy1 in the CH stretching region, and at 1539, 1509, 1470, 1458 and 1383 cmy1 in the CH deformation mode. This suggests an activated adsorption of CH 3 Cl. Further heating the sample in CH 3 Cl to 573 and then to 673 K caused only a slight attenuation of the bands observed after degassing at room temperature. A noteworthy difference was the elimination of the band at 1539 cmy1 . Similar measurements were performed with pure ZSM-5. IR spectra obtained in the presence of CH 3 Cl at room temperature exhibited practically the same spectral features as measured for Mo 2 CrZSM-5. No change in the nature of the weak interaction was experienced at 300 K. Treating the sample with 10 Torr of CH 3 Cl at different temperatures caused the appearance of the same bands as observed for Mo 2 CrZSM-5. The adsorption of CH 3 Cl on Mo 2 CrSiO 2 produced much weaker bands than on the previous samples, and yielded no observable change in the intense OH band of silica at 3746 cmy1 . To produce absorption bands surviving room temperature adsorption, we had to keep the sample again in the presence of gaseous CH 3 Cl at and above 473 K. In this case, bands were registered at 2961, 2939, 2859, 1446 and 1441 cmy1 . The spectra are shown in Fig. 3. We observed a slight enhancement of these bands with the increase of the adsorption temperature, without
3.2.1. Measurements in closed system The reaction of CH 3 Cl was first studied in a closed circulation system using a mass spectrometric analysis. A well measurable decomposition of CH 3 Cl on Mo 2 CrSiO 2 occurred above 650 K. The main
Fig. 4. Decomposition of CH 3 Cl on Mo 2 CrZSM-5 Žx., Mo 2 CrSiO 2 Žl. ZSM-5 Žv . and SiO 2 Ž'. at 743 K followed by mass spectrometric analysis. Conversion of CH 3 Cl ŽA., formation of HCl ŽB., C 2 H 4 ŽC. and CH 4 ŽD..
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340
products were CH 4 , C 2 H 4 and HCl. At 743 K, the CH 4rC 2 H 4 ratio is in the range of 4.5–4.9. Note that silica support is practically inactive towards the decomposition of CH 3 Cl. On the other hand, ZSM-5 alone is quite an effective catalyst yielding the same products: the CH 4rC 2 H 4 ratio varied between 1.0– 1.2. The deposition of Mo 2 C on ZSM-5 in highly dispersed state caused only little promoting effect both for the conversion and product distribution. The CH 4rC 2 H 4 ratio was about 3.2. The conversion of CH 3 Cl and the formation of products on different samples are displayed in Fig. 4. 3.2.2. Flow system More detailed measurements have been carried out in a flow system. At 673 K, the extent of the decomposition attained a value of 92–93% for ZSM5 and 72–73% for Mo 2 CrZSM-5. Both samples exhibited constant activity. The products in decreasing selectivities are propylene, butane, ethylene, methane and benzene. Ethane and propane were detected only in trace amounts. Results are collected in Table 2. The differences between the two samples are that more methane and benzene formed on the Mo 2 C-containing ZSM-5. The effect of Mo 2 C was more pronounced when it was deposited on silica, which was practically inactive at 673 K. In this case, the initial conversion was 4.2%, which slowly decreased to 1.2%. The product distribution basically differed from that observed for the previous samples: the selectivity to methane was 77% followed by
Table 2 Conversion of CH 3 Cl and selectivities for various products on different catalyst at 673 K ZSM-5
Mo 2 Cr ZSM-5
Mo 2 Cr SiO 2
92.5
72.5
4.2
1.0 16.0 – 54.0 – 26.0 0.5
5.0 17.0 – 53.0 – 17.0 5.0
77.0 18.0 – 4.0 – – –
ConÕersion %
SelectiÕities % CH 4 C2 H4 C2 H6 C3H6 C3H8 C 4 ’S C6 H6
ethylene Ž18%. and propylene Ž4%.. Note that the decomposition of CH 3 Cl on pure Mo 2 C in a flow system amounts only to 0.03–0.04% at 673 K.
4. Discussion 4.1. ReactiÕities of C x H y fragments on Mo2 C For the interpretation of the results obtained, it is helpful to summarize the main characteristics of different hydrocarbon fragments on Mo 2 C surface. Recently, we examined the adsorption and dissociation of CH 2 I 2 , CH 3 I and C 2 H 5 I on Mo 2 C and the reaction pathways of the hydrocarbons formed w19,20x. Whereas CH 2 and CH 3 underwent fast decomposition on Pt metals producing only minor quantities of C 2 compounds w21x on Mo 2 C, the tendency of the coupling of CH 2 and CH 3 was much greater than on these metals. Surprisingly, the formation of C 2 H 4 also occurred in the reaction of CH 3 on Mo 2 C, which was not detected at all for Pt metals w21x. In contrast with this, the reaction of C 2 H 5 did not differ much on Pt metals and Mo 2 C w20x: the C`C bond remained intact on both types of solids. 4.2. TPD and IR spectroscopic studies TPD measurements showed that following the adsorption of CH 3 Cl on ZSM-5 at 373 K, a fraction of it remained adsorbed and was released with a Tp s 393 K. The presence of Mo 2 C did not influence this peak temperature, suggesting that most of the CH 3 Cl adsorbed on the ZSM-5. That fact that the desorbing amount of CH 3 Cl somewhat decayed shows that Mo 2 C blocks some of the adsorption sites on the ZSM-5. In addition, the formation of other products was clearly enhanced by the presence of Mo 2 C. This feature indicates that Mo 2 C can induce the dissociation of CH 3 Cl at such a low temperature, where ZSM-5 alone is not effective. IR spectroscopic measurements suggest that CH 3 Cl adsorbs molecularly on all the three samples, ZSM-5, Mo 2 CrZSM-5 and Mo 2 CrSiO 2 at 300 K. Absorption bands detected are readily assigned to the vibrations of adsorbed CH 3 Cl w22x ŽTable 1.. All
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these bands were eliminated after evacuation at room temperature indicating the weakness of the adsorption. At and above 473 K, however, the nature of the adsorption basically altered. This was first exhibited by the development of reverse bands at 3669 and 3612 cmy1 in the OH frequency region for Mo 2 CrZSM-5 and ZSM-5, and the appearance of stable absorption bands at 2958, 2927, 2901, 2860, 1539, 1509, 1470, 1458 and 1383 cmy1 ŽFig. 2.. In order to facilitate the interpretation of these spectral features, the characteristic bands of all compounds possibly formed are collected in Table 1. As spectra measured after the adsorption of CH 3 Cl on ZSM-5 and Mo 2 CrZSM-5 at 473 K and subsequent evacuation at room temperature were almost identical, we can say that surface species originating these bands are bonded to the zeolite surface. It is important to point out that the intense band of CH 3 Cl at 1350 cmy1 is missing from the spectra taken at elevated temperatures, suggesting that intact CH 3 Cl did not remain on the surface. The reverse bands at 3669 and 3612 cmy1 unambiguously show the occurrence of a surface process between the OH groups of the zeolite and adsorbed CH 3 Cl CH 3 Cl Ža. q OH Ža. s CH 3 OŽa. q HCl Ž g .
Ž 1.
Similar spectral changes were found for acidic zeolite, HY-FAU, but were not observed for basic sample, NarNaY-FAU w28x. The formation of methoxy species has been identified by IR spectroscopy following the adsorption of CH 3 Cl on a number of oxides w29,30x. Its production was also established on PdrSiO 2 after the activation of CH 3 Cl by palladium w31x, and in the direct interaction of CH 3 stream with RhrSiO 2 , SiO 2 and TiO 2 w32,33x. Accepting this consideration, the bands at 2958 and 2860 cmy1 can be attributed to the nas ŽCH 3 . and nsŽCH 3 . modes, whereas the bands at 1470 and 1458 cmy1 to the das ŽCH 3 . and dsŽCH 3 . in CH 3 O. The more characteristic band at 1060 cmy1 due to the vibration of n ŽCO. in methoxy is missing, but the detection of this band on zeolite and silica is extremely difficult. In addition to the above process, we can also consider two other elementary reactions, the elimination of HCl CH 3 Cl Ža. s CH 2Ža. q HCl Ža.
Ž 2.
341
and the cleavage of Cl`C bond CH 3 Cl Ža. s CH 3Ža. q Cl Ža.
Ž 3.
The formation of both the CH 3 and the CH 2 species was observed in the dissociation of the corresponding iodo compounds on Mo 2 CrMoŽ100. surface in UHV system w19,20x. They existed on the surface up to 250–300 K. IR spectra presented in Fig. 2 also suggest that they have been converted into other surface species after their formation, which is consistent with their high reactivity. Accordingly, we can count with the coexistence of two or more adsorbed species on the surface at and above 473 K. The primary products of the coupling of CH 3 and CH 2 are ethane and ethylene. From these two compounds, ethylene forms a stable adsorbed species on the catalyst surface. However, on Mo 2 CrMoŽ100., even the more stable di-sbonded ethylene has been transformed into ethylidyne in the temperature range of 260–350 K w23x. The absence of absorption bands at 1430 and 1345 cmy1 due to das ŽCH 3 . and dsym ŽCH 3 . of ethylidyne excludes its formation in the present case. Note that neither di-s-bonded ethylene nor ethylidyne exists on ZSM-5. We can also consider the formation of adsorbed ethoxy, which could be a surface intermediate in the production of ethylene from CH 3 Cl w8x, as described in Scheme 1.
Ž4.
Ž5. As we identified propylene in the products of the catalytic transformation of CH 3 Cl, we propose the
342
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
Scheme 1.
insertion of a second carbene to ethoxy to give adsorbed propoxide, the decomposition of which yields propylene
Ž6. On the basis of broad absorption in the frequency range between 2800 and 3000 cmy1 ŽFig. 2., as well as on that of the vibration data of Table 2, we cannot exclude the contribution of vibrations of ethoxy and propoxy surface complexes to the observed absorption bands. However, neither of the adsorbed species assumed so far explains the origin of the intense band at 1509 cmy1 , which was detectable up to 573 K. This band has been identified following the adsorption of methanol and alkenes on protonic zeolites in a number of cases w34x, and was attributed to the nas ŽC–C– C. stretching mode of alkenyl carbocations having an extremely high extinction coefficient w34x. In the present case, its formation could occur in the strong interaction of propylene with the Lewis acidic sites ŽL. of ZSM-5 C 3 H 6Ža. q L
™LyH qC H y
3
q 5Ža.
Ž 7.
Control measurements confirmed this assumption, as exposing ZSM-5 to propylene at and above 473 K, a strong absorption band developed at 1509 cmy1 , which was eliminated only at 623 K.
The adsorption of CH 3 Cl on Mo 2 CrSiO 2 is also molecular and reversible at 300 K. A stronger interaction was measured only at and above 473 K, when absorption bands at 2961, 2939, 2859, 1464 and 1441 cmy1 remained on the spectrum after room temperature evacuation. These bands can be attributed to the different vibrations of methoxy species ŽTable 2.. On pure SiO 2 , the intensities of absorption bands, particularly in the low frequency regions, were much weaker, and the band at 1441 cmy1 was even missing. This suggests that the formation of methoxy on silica is promoted by Mo 2 C. It is very likely that CH 3 Cl dissociates on Mo 2 C ŽEq. 3., and the CH 3 formed migrates onto silica to give CH 3 O. This way of methoxy formation was proposed first in the case of PdrSiO 2 w31x. It is important to emphasize that we could not detect an absorption band at 1509 cmy1 for this sample under any experimental conditions. This is consistent with the consideration presented for the assignment of this band. For the formation of carbocations, the presence of surface acid centers is a prerequisite. Due to lack of this center on Mo 2 CrSiO 2 , carbocations cannot be produced. 4.3. Catalytic decomposition Studies performed in closed circulation system clearly showed that Mo 2 C deposited onto SiO 2 catalyzes the decomposition of CH 3 Cl. This was confirmed by the results obtained in a flow system, where the main products of the reaction were methane and ethylene, with a small amount of propylene. In this case, the main role of Mo 2 C is to initiate the dissociation of CH 3 Cl to produce CH 3 surface species. As was mentioned above, Mo 2 C is less reactive towards the complete decomposition of hydrocarbon fragments as compared to highly dispersed Pt metals, nevertheless, it also promotes their decomposition to surface carbon CH 3Ž a. s CH 2Ža. q H Ža.
Ž 8.
CH 2Ž a. s C Ža. q H 2Ž g .
Ž 9.
and the formation of methane. This latter reaction may occur in the hydrogenation of CH x species or in the disproportionation of CH 3 4CH 3Ž a. s 3CH 4Ž g . q C Ža.
Ž 10 .
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In addition, we may also count with the decomposition of ethylene on Mo 2 C surface. The situation was different on ZSM-5, which itself is an effective catalyst for the conversion of CH 3 Cl into C 2 –C 4 compounds w5–8x. The formation of these compounds are described by the Eqs. 4–6. We expected that due to the promoting effect of Mo 2 C on the dissociation of CH 3 Cl ŽEq. 3., a new route is opened for the production of carbene, CH 2 , which, reacting with methoxy species, yields ethylene. This expectation was, however, only partially fulfilled as the decomposition of CH 3 Cl occurred at somewhat lower temperature on Mo 2 C-doped ZSM-5 as compared to undoped ZSM-5. But at higher temperature, when ZSM-5 is active in the transformation of CH 3 Cl into other compounds, the effect of Mo 2 C could not come in prominence.
343
when methoxy species and alkene carbocation were identified by IR spectroscopy. Žii. The catalytic decomposition of CH 3 Cl proceeded with well measurable rate at and above 673 K yielding propylene, ethylene, butane, methane and benzene in decreasing selectivities. The formation of these products is described by the transient appearance of ethoxide and propoxide. Žiii. Mo 2 C only slightly influences the processes occurring on the active ZSM-5 catalyst. Živ. Its catalytic effect was exhibited in the case of Mo 2 CrSiO 2 when it promoted the cleavage of C`Cl bond in the CH 3 Cl.
Acknowledgements This work was supported by the OTKA F025610.
Appendix
5. Conclusions Ži. CH 3 Cl adsorbs reversibly on ZSM-5 at 300 K. Stronger interaction occurred at and above 473 K,
Numerical data, together with product analyses for each individual measurements plotted in Figs. 1 and 2 are compiled in Tables A1–A16 below.
Table A1 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 9.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.115 0.140 0.161 0.295 0.633 1.081 1.642 1.687 1.528
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
0.037 0.084 0.408 0.883 1.309 2.005 0.748 0.113
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.059 0.099 0.138 0.238 0.536 0.616 0.736 0.855 1.133
0.000 0.000 0.000 0.000 0.000 0.195 0.347 0.252 0.298
0.054 0.084 0.046 0.115 0.190 0.557 1.129 1.115 0.186
y0.002 0.043 0.023 0.058 0.093 0.287 0.570 0.535 0.089
0.019 0.059 0.298 0.516 0.357 0.059 0.099 y0.100
0.000 0.000 0.031 0.090 0.778 1.507 0.654 0.213
0.018 0.050 0.135 0.553 0.376 0.899 0.034 0.000
0.000 0.025 0.056 0.276 0.202 0.460 0.038 0.000
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
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344
Table A2 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 7.01 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.178 0.666 1.573 1.758 1.808 1.861 1.935 1.448 1.078
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
0.068 0.348 1.200 1.668 2.125 0.310 0.088 0.123
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.178 0.516 1.054 1.153 1.134 1.213 1.332 0.847 0.716
0.000 0.012 0.465 0.332 0.364 0.288 0.224 0.125 0.186
0.055 0.270 0.128 0.517 0.617 0.706 0.733 0.746 0.284
0.055 0.132 0.074 0.244 0.307 0.346 0.354 0.270 0.108
0.059 0.206 0.437 0.537 0.457 y0.001 y0.028 y0.100
0.000 0.097 0.475 0.933 1.040 0.166 0.000 0.000
0.009 0.120 0.582 0.423 1.206 0.263 0.117 0.222
0.000 0.075 0.289 0.225 0.578 0.119 0.001 y0.001
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
Table A3 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 6.38 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
y 5.204 y4.204 y3.903 y3.505 y3.204 y2.903 y2.505 y2.204 y1.903 y1.602
– – – – – – – – – –
0.302 0.867 0.950 1.217 1.540 1.818 2.175 2.682 2.035 1.678
0.281 0.676 0.636 0.815 1.412 1.213 1.451 1.651 1.293 0.616
0.000 0.043 0.112 0.222 0.149 0.383 0.326 0.623 0.553 0.679
0.017 0.283 0.344 0.356 0.001 0.426 0.739 0.799 0.351 0.768
y0.004 0.135 0.138 0.176 0.022 0.209 0.341 0.391 0.162 0.385
y5.204 y4.509 y4.204 y3.903 y3.505 y2.903 y2.505 y2.204 y1.903
y5.248 y4.549 y4.248 y3.947 y3.549 y2.947 y2.549 y2.248 y1.947
0.114 0.435 0.741 1.034 1.384 2.037 1.099 0.170 0.098
0.079 0.298 0.377 0.377 0.377 0.258 0.178 y0.028 y0.100
0.035 0.116 0.309 0.466 0.658 1.716 0.841 0.274 0.165
0.002 0.043 0.704 0.397 0.750 0.115 0.160 0.000 0.000
0.002 0.022 0.649 0.206 0.401 0.052 0.080 0.076 y0.033
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
345
Table A4 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 4.50 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.093 0.494 1.056 1.449 2.087 2.649 3.233 2.671 2.183
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
0.077 0.189 0.795 1.370 2.290 3.327 3.470 2.008 0.887
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.087 0.461 0.895 0.915 1.197 1.169 1.929 1.248 1.531
0.000 0.000 0.063 0.184 0.576 0.903 1.256 0.693 0.411
0.013 0.067 0.198 0.676 0.628 1.192 0.086 1.452 0.502
0.007 0.034 0.100 0.326 0.314 0.615 0.038 0.722 0.261
0.059 0.138 0.457 0.457 0.387 0.417 y0.100 y0.100 y0.100
0.000 0.000 0.111 0.490 1.419 2.187 3.566 2.108 0.987
0.039 0.096 0.453 0.852 0.981 1.468 0.000 0.000 0.000
0.021 0.045 0.226 0.429 0.497 0.745 y0.004 0.000 0.000
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
Table A5 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.111 0.226 0.732 1.149 1.568 1.873 2.098 2.176 2.069
y5.824 y4.824 y3.824 y2.824 y2.312 y1.824 y1.568 y1.312 y0.824
y5.824 y4.824 y3.824 y2.824 y2.312 y1.824 y1.568 y1.312 y0.824
0.100 0.252 0.670 1.712 3.056 4.445 3.948 3.651 1.760
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
0.099 0.178 0.616 0.855 1.193 1.173 1.551 1.492 1.153
0.000 0.000 0.000 0.100 0.268 0.471 0.459 0.560 0.742
0.024 0.095 0.229 0.409 0.202 0.439 0.173 0.145 0.349
0.091 0.258 0.537 0.537 0.557 y0.100 y0.100 y0.100 y0.100
0.000 0.000 0.036 0.902 2.377 3.960 4.032 3.738 1.854
0.0090 0.000 0.218 0.598 0.241 1.139 0.000 0.000 0.000
Swproductsx y DO 2 Žmmol. 0.012 0.047 0.113 0.215 0.095 0.210 0.085 0.021 0.175 0.000 0.006 0.121 0.325 0.119 0.554 y0.016 y0.013 y0.006
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
346
Table A6 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 4.50 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.522 y5.000 y4.522 y4.000 y3.522 y3.000 y2.522 y2.000 y1.520 y1.000
– – – – – – – – – –
0.154 0.295 y0.689 1.172 1.283 1.469 1.619 1.857 1.520 1.367
y6.000 5.522 y5.000 y4.522 y4.000 y3.522 y2.522 y2.000 y1.522 y1.240 y1.000
y5.504 y5.027 y4.504 y4.027 y3.504 y3.027 y2.027 y1.504 y1.027 y0.744 y0.504
0.043 0.069 0.141 0.204 0.368 0.859 2.426 3.168 3.808 3.946 3.725
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.139 0.258 0.497 0.974 0.935 1.094 0.895 1.213 1.332 0.895
0.000 0.000 0.199 0.198 0.371 0.381 0.407 0.552 0.201 0.466
0.015 0.076 0.002 0.003 0.007 0.000 0.682 0.178 0.004 0.010
0.000 0.039 0.009 0.003 0.030 0.006 0.365 0.086 0.017 0.004
0.035 0.051 0.099 0.138 0.258 0.317 0.258 0.059 y0.001 y0.068 y0.100
0.000 0.000 0.034 0.000 0.113 0.429 1.437 2.527 2.481 2.945 2.963
0.009 0.018 0.006 0.057 0.000 0.224 1.505 1.190 2.578 2.091 1.698
0.001 0.000 y0.002 y0.009 0.003 0.111 0.774 0.608 1.250 1.022 0.836
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene. Table A7 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.62 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.522 y5.000 y4.522 y4.000 y3.488 y3.000 y2.698 y2.000 y1.488 y1.000
– – – – – – – – – –
0.329 0.519 0.639 0.811 1.320 1.945 2.392 1.642 1.379 1.119
y5.509 y4.509 y3.509 y2.986 y2.509 y2.204 y1.903 y1.426 y1.225 y0.924
y4.995 y3.995 y2.995 y2.472 y1.995 y1.705 y1.404 y0.927 y0.726 y0.407
0.103 0.279 0.768 1.405 2.238 2.810 3.288 4.011 3.824 3.493
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.298 0.417 0.616 0.696 0.895 1.332 1.512 1.253 0.656 0.616
0.027 0.036 0.023 0.065 0.209 0.586 0.606 0.386 0.630 0.499
0.003 0.077 0.019 0.061 0.436 0.053 0.576 0.000 0.197 0.003
y0.001 0.011 0.019 0.011 0.220 0.026 0.302 y0.003 0.104 y0.001
0.103 0.274 0.470 0.429 0.449 0.298 0.218 y0.100 y0.100 y0.100
0.000 0.067 0.334 0.980 1.684 2.505 3.068 4.116 3.885 3.600
0.007 0.000 0.000 0.040 0.057 0.002 0.002 0.000 0.000 0.000
0.007 0.062 0.036 0.105 y0.048 y0.005 0.000 0.005 y0.039 0.007
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
347
Table A8 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.435 y4.912 y4.435 y3.912 y3.435 y2.912 y2.690 y2.312 y2.096 y1.903 y1.602
– – – – – – – – – – –
0.223 0.310 0.466 0.789 1.210 1.875 1.950 1.859 1.609 1.145 0.599
y5.440 y4.440 y3.903 y3.440 y2.917 y2.315 y1.950 y1.602 y1.397 y1.225 y0.924
y4.923 y3.923 y3.403 y2.923 y2.400 y1.798 y1.440 y1.102 y0.898 y0.730 y0.424
0.112 0.291 0.426 0.762 0.942 1.842 2.449 3.253 3.590 3.812 3.717
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.206 0.206 0.410 0.756 0.879 1.368 1.572 1.286 1.368 0.858 0.470
0.020 0.008 0.050 0.042 0.308 0.467 0.349 0.580 0.197 0.253 0.098
0.003 0.076 0.005 0.000 0.007 0.067 0.011 0.008 0.023 0.020 0.029
0.006 y0.020 y0.001 0.009 y0.016 0.027 y0.018 0.015 y0.021 y0.014 y0.002
0.144 0.286 0.258 0.516 0.510 0.449 0.532 0.178 0.079 y0.100 y0.100
0.000 0.027 0.163 0.100 0.221 1.376 1.980 2.116 2.510 3.918 3.822
0.000 0.008 0.000 0.084 0.445 0.033 0.000 1.732 1.939 0.000 0.000
0.032 0.030 y0.005 y0.062 0.234 0.016 0.013 0.767 0.938 0.006 0.005
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
Table A9 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 9.00 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.461 0.901 1.154 1.657 2.194 2.257 2.314 2.235 2.172
0.457 0.895 0.994 1.412 1.691 1.571 1.392 1.571 1.133
0.010 0.044 0.035 0.035 0.055 0.162 0.055 0.059 0.038
0.000 0.000 0.118 0.204 0.447 0.518 0.876 0.589 1.002
0.006 0.038 y0.007 y0.006 y0.001 y0.006 0.009 y0.016 0.001
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.678 y1.569 y1.312 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.678 y1.569 y1.312 y0.824
0.360 0.562 1.017 1.097 1.424 2.317 3.365 3.566 3.220 2.013 0.121
0.337 0.516 0.417 0.147 0.099 0.059 0.019 y0.001 y0.020 y0.060 y0.100
0.019 0.061 0.171 0.315 0.361 0.416 0.371 0.282 0.231 0.383 0.010
0.020 0.030 0.458 0.612 0.942 1.810 2.910 3.290 3.005 1.675 0.216
0.016 0.045 0.029 y0.023 y0.022 y0.032 y0.065 0.005 y0.004 y0.015 0.005
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
348
Table A10 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 7.01 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
– – – – – – – –
0.895 1.756 2.025 2.304 2.578 2.697 2.614 2.142
y5.824 y4.824 y3.824 y3.312 y2.824 y2.568 y2.312 y2.195 y2.064 y1.824 y1.312 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.568 y2.312 y2.195 y2.064 y1824 y1.312 y0.824
1.261 1.400 1.596 1.838 2.409 3.100 3.807 3.356 2.948 0.841 0.195 0.131
corr Ž DOact mmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
0.815 1.492 1.432 1.452 1.630 1.531 1.690 1.332
0.032 0.065 0.114 0.102 0.090 0.096 0.080 0.056
0.085 0.215 0.489 0.767 0.846 1.132 0.817 0.800
0.037 0.016 0.010 0.017 y0.012 0.062 y0.027 0.046
1.094 0.895 0.218 0.059 0.099 0.051 y0.021 y0.032 y0.061 y0.020 y0.100 y0.100
0.242 0.274 0.402 0.404 0.516 0.347 0.238 0.240 0.238 0.133 0.014 0.023
0.000 0.221 0.966 1.358 1.794 2.709 3.636 3.170 2.741 0.726 0.283 0.225
0.075 y0.010 y0.010 y0.017 0.000 0.007 0.046 0.022 0.001 y0.002 0.002 0.017
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
Table A11 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 6.38 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
y 5.505 y5.204 y4.509 y4.204 y3.903 y3.204 y2.903 y2.204 y1.903 y1.602 y0.999
– – – – – – – – – – –
0.599 0.935 1.774 2.257 2.533 2.814 2.847 3.002 3.035 2.712 2.059
0.556 0.934 1.691 1.850 1.929 1.770 1.909 1.810 1.730 1.531 1.531
0.022 0.043 0.067 0.095 0.121 0.254 0.114 0.102 0.176 0.108 0.099
0.029 0.000 0.046 0.328 0.485 0.783 0.810 1.080 1.123 1.053 0.428
0.008 0.042 0.030 0.016 0.002 y0.007 y0.014 y0.010 y0.006 y0.020 y0.001
y5.505 y4.509 y4.204 y3.903 y3.505 y3.204 y2.903 y2.505 y2.204 y2.028 y1.903
y5.549 y4.549 y4.248 y3.947 y3.549 y3.248 y2.947 y2.549 y2.248 y2.072 y1.947
0.677 0.953 0.969 1.051 1.482 1.827 2.444 3.400 2.816 2.373 0.489
0.668 0.537 0.198 0.138 0.059 0.051 0.039 0.011 y0.068 y0.076 y0.068
0.052 0.238 0.319 0.300 0.507 0.362 0.470 0.271 0.157 0.245 0.042
0.000 0.156 0.435 0.608 0.811 1.407 1.927 3.128 2.720 2.190 0.544
0.043 y0.022 y0.017 y0.005 y0.105 y0.007 y0.008 0.010 y0.007 y0.014 0.029
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalyst dissolved 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
349
Table A12 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 4.50 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.839 1.402 1.770 2.079 2.409 2.461 2.675 2.624 2.511
y5.824 y5.312 y4.824 y4.312 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
y5.824 y5.312 y4.824 y4.312 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
0.623 0.880 1.094 1.203 1.223 1.705 2.755 3.908 4.760 3.240 1.864
corr Ž DOact mmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
0.815 1.372 1.472 2.048 1.466 1.730 1.466 1.691 1.691
0.005 0.047 0.024 0.064 0.032 0.085 0.034 0.066 0.030
0.013 0.000 0.205 0.000 0.912 0.640 1.116 0.848 0.779
y0.006 0.017 y0.069 0.033 0.001 y0.006 y0.059 y0.019 y0.011
0.616 0.815 0.895 0.815 0.338 0.118 0.059 y0.061 y0.100 y0.100 y0.100
0.024 0.042 0.067 0.122 0.325 0.520 0.446 0.397 0.214 0.071 0.045
0.000 0.027 0.127 0.268 0.552 1.052 2.151 3.581 4.641 3.267 1.918
0.017 0.004 y0.005 0.002 y0.008 y0.015 y0.099 0.009 y0.005 y0.002 y0.001
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
Table A13 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
y 5.824 y5.312 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
1.086 1.717 2.303 2.522 2.739 3.081 2.948 2.880 2.833 2.767
0.994 1.472 1.491 1.507 2.248 1.969 2.566 1.663 1.790 1.468
0.015 0.005 0.059 0.060 0.072 0.134 0.046 0.068 0.039 0.050
0.091 0.224 0.779 0.940 0.422 0.985 0.327 1.157 1.005 1.248
0.014 y0.016 0.016 y0.15 0.003 0.007 y0.009 0.008 0.001 y0.001
y5.824 y5.312 y4.824 y3.824 y3.312 y2.824 y2.569 y2.312 y2.064 y1.824 y1.312 y0.824
y5.824 y5.312 y4.824 y3.824 y3.312 y2.824 y2.569 y2.312 y2.064 y1.824 y1.312 y0.824
0.968 1.379 1.834 2.032 2.259 2.935 3.956 4.937 5.240 4.890 3.623 2.605
0.755 0.994 1.094 0.576 0.218 0.039 y0.040 y0.060 y0.060 y0.080 y0.100 y0.100
0.044 0.234 0.189 0.399 0.514 0.351 0.546 0.605 0.421 0.231 0.149 0.071
0.190 0.150 0.543 1.061 1.513 2.514 3.400 4.359 4.863 4.672 3.542 2.599
0.021 y0.001 y0.008 0.004 y0.014 y0.031 y0.050 y0.033 y0.016 y0.067 y0.032 y0.035
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
350
Table A14 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-V ŽV ., respectively pH: 4.50 corr Ž DOact mmol.
log wALClx
log wAL-V ŽV .x
DO 2 Žmmol.
D wCh-E x Žmmol.
D wCh-olx Žmmol.
S wproductsx y DO 2
y 6.000 y5.522 y5.000 y4.522 y4.000 y3.522 y3.000 y2.522 y2.000 y1.522 y1.000
– – – – – – – – – –
0.567 0.989 1.480 1.746 1.969 2.109 2.330 2.498 2.616 2.725 2.583
0.454 0.974 1.352 1.332 1.531 1.492 1.452 1.452 1.490 1.531 1.293
0.015 0.017 0.023 0.029 0.069 0.050 0.068 0.067 0.069 0.072 0.063
0.099 0.000 0.111 0.380 0.357 0.600 0.782 0.930 1.055 1.102 1.231
y0.005 0.002 0.006 y0.005 y0.012 0.033 y0.028 y0.049 y0.002 y0.020 0.004
y6.000 y5.000 y4.522 y4.000 y3.522 y3.000 2.522 y2.000 y1.522 y1.000
y5.504 y4.504 y4.026 y3.504 y3.027 y2.504 y2.027 y1.504 y1.027 y0.504
0.546 0.580 0.705 0.849 1.266 2.277 3.724 5.091 4.203 3.214
0.496 0.377 0.179 0.417 0.059 y0.029 y0.084 y0.100 y0.100 y0.100
0.054 0.096 0.243 0.255 0.391 0.582 0.738 0.499 0.216 0.130
0.000 0.111 0.78 0.192 0.773 1.689 3.051 4.666 4.016 3.156
0.004 0.004 y0.005 0.015 y0.043 y0.035 y0.019 y0.026 y0.071 y0.028
Conditions: 2.468 M cyclohexene q 0.0125 M t-BHP q the corresponding catalysts dissolved in 8.00 cm 3 chlorobenzene.
Table A15 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-V ŽV ., respectively pH: 3.62 corr Ž DOact mmol.
log wALClx
log wAL-V ŽV .x
DO 2 Žmmol.
D wCh-E x Žmmol.
D wCh-olx Žmmol.
S wproductsx y DO 2
y 6.000 y5.698 y5.301 y5.000 y4.602 y4.124 y3.602 y2.999 y2.602 y2.301 y1.903 y1.602 y1.301 y1.125 y0.999
– – – – – – – – – – – – – – –
0.500 0.682 1.088 1.397 1.742 1.800 1.856 2.060 2.218 2.388 2.550 2.674 1.620 1.110 0.907
0.497 0.676 1.011 1.332 1.492 1.492 1.452 1.551 1.691 1.810 1.890 1.850 1.173 1.014 0.795
0.020 0.030 0.045 0.049 0.066 0.059 0.083 0.061 0.070 0.098 0.086 0.070 0.027 0.022 0.017
0.000 0.000 0.033 0.015 0.172 0.234 0.330 0.443 0.467 0.476 0.564 0.746 0.430 0.055 0.107
0.017 0.024 0.001 y0.001 y0.012 y0.015 0.009 y0.005 0.010 y0.004 y0.010 y0.008 0.010 y0.019 0.012
y5.810 y5.644 y5.509 y4.986 y4.509 y3.945 y3.509 y2.986 y2.685 y2.301 y1.903 y1.602 y1.301 y1.145
y5.296 y5.130 y4.995 y4.472 y3.995 y3.431 y2.995 y2.473 y2.172 y1.802 y1.404 y1.103 y0.802 y0.647
0.598 0.575 0.570 0.285 0.465 0.754 1.057 2.021 2.913 4.039 4.557 4.812 3.880 3.517
0.388 0.437 0.347 0.164 0.185 0.042 y0.019 0.022 y0.019 y0.068 y0.100 y0.100 y0.100 y0.100
0.077 0.066 0.081 0.083 0.094 0.357 0.249 0.377 0.349 0.318 0.304 0.301 0.152 0.155
0.113 0.0620 0.150 0.036 0.207 0.506 0.820 1.667 2.560 3.784 4.338 4.564 3.784 3.446
y0.020 y0.010 0.008 y0.002 0.021 0.151 y0.007 0.045 y0.023 y0.005 y0.015 0.047 y0.044 y0.016
Conditions: 2.468 M cyclohexene q 0.0125 M t-BHP q the corresponding catalysts dissolved in 8.00 cm 3 chlorobenzene.
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351
Table A16 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.912 y5.435 y4.913 y4.435 y4.009 y3.435 y2.912 y2.602 y2.213 y1.999 y1.602 y1.301 y1.125 y1.000
– – – – – – – – – – – – – –
0.513 0.782 0.989 1.129 1.508 1.883 2.399 2.619 2.777 2.638 2.404 2.286 2.243 2.198
y5.912 y5.435 y4.435 y3.435 y2.912 y2.612 y2.310 y2.033 y1.732 y1.404 y1.301 y1.146
y5.399 y4.923 y3.923 y2.923 y2.399 y2.098 y1.798 y1.521 y1.220 y1.059 y0.806 y0.651
0.414 0.506 0.571 0.759 1.364 2.152 2.964 3.809 4.836 3.643 3.396 2.920
corr Ž DOact mmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
0.511 0.695 0.980 1.009 1.327 1.613 1.816 1.770 1.939 1.878 1.770 1.810 1.690 1.472
0.017 0.033 0.026 0.031 0.031 0.053 0.090 0.089 0.134 0.085 0.065 0.076 0.064 0.061
0.000 0.058 0.000 0.111 0.102 0.224 0.501 0.766 0.732 0.662 0.567 0.390 0.478 0.655
0.015 0.004 0.017 0.022 y0.048 0.007 0.008 0.006 0.028 y0.013 y0.002 y0.010 y0.011 y0.010
0.316 0.287 0.075 y0.018 0.002 y0.003 y0.051 y0.072 y0.060 y0.100 y0.100 y0.100
0.061 0.079 0.088 0.195 0.291 0.316 0.506 0.436 0.342 0.256 0.131 0.130
0.023 0.129 0.380 0.561 1.045 1.713 2.506 3.405 4.512 3.446 3.318 2.921
y0.014 y0.011 y0.028 y0.021 y0.026 y0.126 y0.003 y0.040 y0.042 y0.041 y0.047 0.031
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
References w1x W.J.M. Pieters, W.C. Conner, E.J. Carlson, Appl. Catal. 11 Ž1984. 35. ´ Molnar, ´ Molnar w2x G.A. Olah, A. ´ in: G.A. Olah, A. ´ ŽEds.., Hydrocarbon Chemistry, Wiley-Interscience, New York, 1995. w3x K.J. Jeans, S. Halvorsen, E.B. Ofsted, in: D.M. Bibby, C.D. Chang, R.F. Howe, S. Yurchak ŽEds.., Methane Conversion, Elsevier, Amsterdam, 1988, p. 491. w4x P. Lersch, F. Bandermann, Appl. Catal. 75 Ž1991. 133. w5x C.E. Taylor, R.P. Noceti, R.R. Schehl, in: D.M. Bibby, C.D. Chang, R.F. Howe, S. Yurchak ŽEds.., Methane Conversion, Elsevier, Amsterdam, 1988, p. 483. w6x C.D. Chang, Catal. Rev. — Sci. Eng. 25 Ž1983. 1. w7x V.N. Rommanikov, K.G. Ione, Kinet. Katal. 25 Ž1984. 92. w8x Y. Sun, S.M. Campbell, J.H. Lunsford, G.E. Lewis, D. Palke, L.-M. Tau, J. Catal. 143 Ž1993. 32. w9x D. Wang, J.H. Lunsford, M.P. Rosynek, Top. Catal. 3 Ž4. Ž1996. 299. w10x F. Solymosi, A. Szoke, ˜ Catal. Lett. 39 Ž1996. 157.
w11x F. Solymosi, J. Cserenyi, A. Szoke, ´ ˜ T. Bansagi, ´ ´ A. Oszko, ´ J. Catal. 165 Ž1997. 150. w12x D. Wang, J.H. Lunsford, M.P. Rosynek, J. Catal. 169 Ž1997. 347. w13x L. Wang, L. Tao, M. Xie, G. Xu, Catal. Lett. 21 Ž1993. 35. w14x Y. Xu, S. Liu, L. Wang, M. Xie, X. Guo, Catal. Lett. 30 Ž1995. 135. w15x F. Solymosi, A. Erdohelyi, A. Szoke, ˜ ˜ Catal. Lett. 32 Ž1995. 43. w16x A. Szoke, ˜ F. Solymosi, Appl. Catal. A 142 Ž1996. 361. ´ ´ L. Egri, to be published. w17x F. Solymosi, R. Nemeth, L. Ovari, ´ w18x J.S. Lee, S.T. Oyama, M. Boudart, J. Catal. 106 Ž1987. 125. w19x F. Solymosi, L. Bugyi, A. Oszko, ´ I. Horvath, ´ J. Catal. 185 Ž1999. 249. w20x F. Solymosi, L. Bugyi, A. Oszko, ´ Catal. Lett. 57 Ž1999. 103. w21x F. Solymosi, in: E.G. Derouane ŽEd.., Catalytic Activation and Functionalisation of Light Alkanes, Kluwer Academic Publishing, Netherlands, 1998, pp. 369–388. w22x D.C Harris, M.D. Bertolucci, Symmetry and Spectroscopy, Oxford Univ. Press, New York, 1978, p. 224. w23x B. Fruhberger, I.G. Chen, J. Am. Chem. Soc. 118 Ž1996. ¨ 11599.
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w24x M.A. Chesters, C. De La Cruz, P. Gardner, E.M. McCash, P. Pudney, G. Shahid, N. Sheppard, J. Chem. Soc., Faraday Trans. 86 Ž15. Ž1990. 2757. w25x Y. Suda, T. Morimoto, M. Nagao, Langmuir 3 Ž1987. 99. w26x M.D. Driessen, V.H. Grassian, Langmuir 14 Ž1998. 1411. w27x E.A. Wovchko, J.C. Camp, J.A. Glass Jr., J.T. Yates Jr., Langmuir 11 Ž1995. 2592. w28x Z. Konya, I. Hannus, I. Kiricsi, Appl. Catal. B 8 Ž1996. 391. ´ w29x J.E. Crowell, T.P. Beebe Jr., J.T. Yates Jr., J. Chem. Phys. 87 Ž1987. 3668.
w30x T.P. Beebe Jr., J.E. Crowell, J.T. Yates Jr., J. Phys. Chem. 92 Ž1988. 1296. w31x J. Rasko, ´ I. Bontovics, F. Solymosi, J. Catal. 143 Ž1993. 138. w32x J. Rasko, ´ F. Solymosi, Catal. Lett. 46 Ž1997. 153. w33x J. Rasko, ´ F. Solymosi, Catal. Lett. 54 Ž1998. 49. w34x I. Kiricsi, H. Forster, Gy. Tasi and, J.B. Nagy, Chem. Rev. ¨ 99 Ž1999. 2085.
Adsorption and reactions of CH 3 Cl on Mo 2 C based catalyst ´ ´ T. Bansagi, J. Cserenyi ´ ) , L. Ovari, ´ ´ F. Solymosi Institute of Solid State and Radiochemistry, UniÕersity of Szeged and Reaction Kinetics Research Group of the Hungarian Academy of Sciences 1, P.O. Box 168, H-6701, Szeged, Hungary
Abstract The adsorption of CH 3 Cl on ZSM-5, Mo 2 CrZSM-5 and Mo 2 CrSiO 2 was investigated by temperature-programmed desorption ŽTPD. and Fourier transform infrared spectroscopy ŽFTIR.. The formation of methoxy species was clearly identified on all the three catalysts. Three elementary steps were considered to explain the absorption bands observed in the IR spectra and to describe the reaction products found at higher temperatures: Ži. the interaction of CH 3 Cl with the OH groups of ZSM-5, Žii. dissociation of CH 3 Cl yielding CH 3 , and Žiii. the elimination of HCl from the adsorbed CH 3 Cl to give CH 2 species. A new finding was the identification of the alkenyl carbocation formed on the Lewis acidic sites of ZSM-5. The decomposition of CH 3 Cl on ZSM-5 proceeded at 673 K with a high conversion yielding propylene, ethylene, butane, methane and benzene in decreasing selectivities. Deposition of Mo 2 C on ZSM only slightly modified the catalytic behavior of ZSM-5. Its promoter effect came into prominence on silica surface. q 2000 Published by Elsevier Science B.V. Keywords: Adsorption and reactions; CH 3 Cl; Mo 2 C-based catalyst
1. Introduction The catalytic conversion of methane into more valuable compounds has been the subject of intensive research during the last two decades. One of the ways is to convert methane to methyl chloride via oxychlorination reaction w1,2x, and then transform methyl chloride into light olefins and hydrochloric acid w3,4x. Pure and modified ZSM-5 is an effective catalyst for CH 3 C1 reaction, the product distribution sensitively depends on the reaction temperature and on the nature of the promoters w5–8x.
)
Corresponding author. These laboratories are parts of the Center for Catalysis, Surface and Material Science at the University of Szeged. 1
Recently, it was found that Mo 2 C deposited on the cavities of ZSM-5 is an active catalyst in the direct conversion of methane into benzene w9–12x. The same results were observed when the starting material was MoO 3rZSM-5 w13–15x, as MoO 3 was converted into Mo 2 C during the high temperature reaction w9–12x. It was thought that the primary role of Mo 2 C is to activate methane to produce CH 3 andror CH 2 species and then — through their coupling — ethane andror ethylene. The oligomerization and aromatization of these compounds proceed on the ZSM-5. In the subsequent studies, it was found that Mo 2 C also exerts a promoting influence even on the aromatization of ethane and propane, which occurs readily on ZSM-5 w16,17x. In the present work, an attempt is being made to examine the effect of Mo 2 C on the interaction and
1381-1169r00r$ - see front matter q 2000 Published by Elsevier Science B.V. PII: S 1 3 8 1 - 1 1 6 9 Ž 0 0 . 0 0 3 0 1 - 0
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reaction of CH 3 C1 with ZSM-5. It is hoped that the results obtained may also contribute to the better understanding of the aromatization of methane on this catalyst.
2. Experimental Catalytic reactions were carried out at 1 atm of CH 3 Cl q Ar gas mixture containing 5% of CH 3 Cl in a fixed-bed, continuous flow reactor consisting of a quartz tube Ž10 mm i.d.. connected to a capillary tube. The flow rate was 12 mlrmin. Generally, 0.5 g of loosely compressed catalyst sample was used. Reaction products were analyzed by means of a Hewlett-Packard 5890 gas chromatograph using a Porapak QS column. The conversion of CH 3 Cl was calculated from the hydrogen balance. The selectivity values of product formation represent the fraction of methyl chloride that has been converted into specific products, taking into account the number of carbon atoms in the molecules. The decomposition of CH 3 Cl was also followed in a closed circulation system, where the analysis of products was performed by a mass spectrometer. Infrared spectroscopic measurements were made in a vacuum IR cell using self-supporting wafers of catalyst powders. Spectra were recorded with a Biorad ŽDigilab. Div.. Fourier transform IR spectrometer FTS 155. The H-ZSM-5 support was obtained by five times repeated ion exchange of Na-ZSM-5 ŽSirAls 55.0. with an aqueous solution of ammonium nitrate Ž1N., and calcined in air at 863 K for 5 h. Before catalytic measurements, each sample was oxidized in an O 2 stream at 973 K in situ and then flushed with Ar for 15 min. Hexagonal Mo 2 C was prepared by the method of Lee et al. w18x. Briefly, about 0.5 g of MoO 3 was heated in 1:4 methane–H 2 mixture flowing at 300 ml ŽSTP.rmin in a quartz cell with two stopcocks. Preparation temperature was increased rapidly to 773 K and at 30 Krh between 773 and 1023 K, and maintained at 1023 K for 3 h. Supported Mo 2 C was produced by the carburation of supported MoO 3 in the catalytic reactor, in a similar way as described above for the preparation of bulk Mo 2 C. MoO 3rZSM-5 and MoO 3rSiO 2 were
prepared by impregnating the supports with a basic solution of ammonium paramolybdate to yield a nominal 2 wt.% of MoO 3 . The suspension was dried at 373 K and calcined at 873 K for 5 h. Following the suggestion of Lee et al. w18x, the sample was deactivated at 300 K with air, or used in situ for catalytic studies. As Mo 2 C always contains excess carbon, the catalyst was treated with H 2 at 873 K before the catalytic measurements to remove this carbon species. The gases used were of commercial purity ŽLinde.. Ar Ž99.996%. and H 2 Ž99.999%. were deoxygenated with an oxytrap. The other impurities were adsorbed by a 5A molecular sieve at the temperature of liquid nitrogen.
3. Results 3.1. Adsorption of CH3 Cl 3.1.1. Temperature-programmed desorption (TPD) measurements The interaction of CH 3 Cl with the above catalysts has been first studied by means of TPD. A 0.5-g catalyst sample was kept in CH 3 Cl flow at 373 K for 10 min, afterwards, the reactor was washed with argon until no or only traces of CH 3 Cl was detected in the outlet gas; this required about 60 min. TPD spectra are shown in Fig. 1. CH 3 Cl desorbed from the ZSM-5 with a peak temperature Tp s 393 K. Methane and hydrogen were released only above 700 K. Similar features have been observed for the Mo 2 CrZSM-5 sample. The amount of CH 3 Cl desorbed was somewhat less, but the peak temperature was the same. At the same time, however, the formation of methane ŽTp s 420 K., ethylene ŽTp s 550 K. and propane was observed. 3.1.2. Infrared spectroscopic measurements The ZSM-5 sample exhibited the usual absorption bands at 3744, 3679 and 3612 cmy1 . These bands are assigned to terminal Si–OH groups, Al–OH groups and acidic bridging hydroxyls, respectively. The deposition of Mo 2 C onto ZSM-5 did not alter this picture, except that the intensity of the 3612 cmy1 band has been reduced by about 40%.
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Fig. 1. TPD spectra following the adsorption of CH 3 Cl on ŽA. ZSM-5 and ŽB. Mo 2 CrZSM-5 samples at 373 K.
Fourier transform infrared spectroscopy ŽFTIR. spectra of adsorbed CH 3 Cl on Mo 2 CrZSM-5 are shown in Fig. 2. Absorption bands observed at 2963, 2860, 1444 and 1350 cmy1 correspond well to different vibrations of adsorbed CH 3 Cl. The assignment of these bands is presented in Table 1. In the OH frequency region, reverse absorption bands devel-
oped at 3663 and 3612 cmy1 , and a broad band at 3175 cmy1 . Degassing the sample at room temperature resulted in the elimination of all bands, including the reverse absorption bands, indicating the weak interaction at 300 K. When the sample was kept in 10 Torr of CH 3 Cl at 473 K and evacuated at 300 K, both reverse bands at 3663 and 3612 cmy1 remained
Fig. 2. Ža. FTIR spectra of Mo 2 CrZSM-5 in the presence of CH 3 Cl Ž10 Torr. at 300 K Žthe spectrum of gas phase is subtracted., and after adsorption of CH 3 Cl at 473 Žb. and 573 K Žc.. In the latter two cases, the sample was degassed at 300 K.
a
2860 Žw .
1444 Žm . 1350 Žs .
2879
1455 1355
This work.
2963 Žw .
–
CH 3 Cl Mo 2 Cr ZSM-5 300 K a
2966
3042
n as ŽCH 3 .
n as ŽCH 2 . n s ŽCH 3 . n s ŽCH 2 . 2 d as ŽCH 3 . n ŽC5C . n as ŽCCC . d as ŽCH 3 . d ŽCH 2 . d s ŽCH 3 . r ŽCH 2 . v ŽCH 2 . n ŽC ` C . g ŽCH 2 .
CH 3 Cl gas w22 x
Assignments
1539 1509 1458 1470 1383
2927 2901 2860 Žm . Žvs . Žm . Žvs . Žs .
Žw . Žvw . Žw .
2958 Žw .
CH 3 Cl Mo 2 Cr ZSM-5 473 K a
Table 1 Characteristic vibrations of different adsorbed species
1441 Žw .
1464 Žw .
2939 Žw .
2859 Žm .
2961 Žm .
CH 3 Cl Mo 2 Cr SiO 2 473 K a
1180 Žs.
1370 Žm .
2930 Ž m .
CH 3 Mo 2 C w20 x
1190 Žm .
780
2940 Žs.
CH 2 Mo 2 C w19 x
1441,1340
1631, 1612
2975
3090
C2H4 ZSM-5 153 K a
1035 Žs.
1180 Žw .
1395 Žs.
2935 Žs.
3010 Žw .
di-s C 2 H 4 Ž 4=4 .-Cr Mo Ž110 . w23 x
1075 Žm .
1345 Žm .
1430 Žm .
2915 Žs.
CCH 3 Ž4=4 .-Cr Mo Ž110 . w23 x
Žm . Žms.
1350 Žms.
1465 Žw .
2885 2920
di-s propylene PtrSiO 2 w24 x
Žw ., Žm .
1466 Žs.
1481 Žw .
2937 Žw .
2859 Žm .
3001 2961
CH 3 O SiO 2 w27 x
Žm . Žm . Žw .
1452 Žw . 1492 Žw . 1399 Žm . 1384 Žm . 1348 Žm .
2940 2911 2882
2986 Ž s.
C 2 H 5O SiO 2 w26 x
1460 1380
2940 2885 2855
Žm . Žm .
Žm . Žs . Žw .
2965 Ž s.
C 3H 7O TiO 2 w25 x
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339
changing their positions. New bands appeared at 2979 and 1388 cmy1 after treating the Mo 2 CrSiO 2 sample with CH 3 Cl at 673 K. The peaks observed at 473 K for Mo 2 CrSiO 2 also appeared on the IR spectrum of pure silica, but with much less intensities. The difference is that the 2939 and 1446 cmy1 bands are missing, and the bands at 2979 and 1388 cmy1 did not develop at 673 K. 3.2. Catalytic decomposition of CH3 Cl
Fig. 3. FTIR spectra of Mo 2 CrSiO 2 following the adsorption of CH 3 Cl at different temperatures. Ža. 473; Žb. 573 K; Žc. 673 K and degassing at 300 K.
practically unchanged, which is in contrast with the room temperature adsorption. In addition, relatively intense absorption bands developed at 2958, 2927, 2901 and 2860 cmy1 in the CH stretching region, and at 1539, 1509, 1470, 1458 and 1383 cmy1 in the CH deformation mode. This suggests an activated adsorption of CH 3 Cl. Further heating the sample in CH 3 Cl to 573 and then to 673 K caused only a slight attenuation of the bands observed after degassing at room temperature. A noteworthy difference was the elimination of the band at 1539 cmy1 . Similar measurements were performed with pure ZSM-5. IR spectra obtained in the presence of CH 3 Cl at room temperature exhibited practically the same spectral features as measured for Mo 2 CrZSM-5. No change in the nature of the weak interaction was experienced at 300 K. Treating the sample with 10 Torr of CH 3 Cl at different temperatures caused the appearance of the same bands as observed for Mo 2 CrZSM-5. The adsorption of CH 3 Cl on Mo 2 CrSiO 2 produced much weaker bands than on the previous samples, and yielded no observable change in the intense OH band of silica at 3746 cmy1 . To produce absorption bands surviving room temperature adsorption, we had to keep the sample again in the presence of gaseous CH 3 Cl at and above 473 K. In this case, bands were registered at 2961, 2939, 2859, 1446 and 1441 cmy1 . The spectra are shown in Fig. 3. We observed a slight enhancement of these bands with the increase of the adsorption temperature, without
3.2.1. Measurements in closed system The reaction of CH 3 Cl was first studied in a closed circulation system using a mass spectrometric analysis. A well measurable decomposition of CH 3 Cl on Mo 2 CrSiO 2 occurred above 650 K. The main
Fig. 4. Decomposition of CH 3 Cl on Mo 2 CrZSM-5 Žx., Mo 2 CrSiO 2 Žl. ZSM-5 Žv . and SiO 2 Ž'. at 743 K followed by mass spectrometric analysis. Conversion of CH 3 Cl ŽA., formation of HCl ŽB., C 2 H 4 ŽC. and CH 4 ŽD..
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340
products were CH 4 , C 2 H 4 and HCl. At 743 K, the CH 4rC 2 H 4 ratio is in the range of 4.5–4.9. Note that silica support is practically inactive towards the decomposition of CH 3 Cl. On the other hand, ZSM-5 alone is quite an effective catalyst yielding the same products: the CH 4rC 2 H 4 ratio varied between 1.0– 1.2. The deposition of Mo 2 C on ZSM-5 in highly dispersed state caused only little promoting effect both for the conversion and product distribution. The CH 4rC 2 H 4 ratio was about 3.2. The conversion of CH 3 Cl and the formation of products on different samples are displayed in Fig. 4. 3.2.2. Flow system More detailed measurements have been carried out in a flow system. At 673 K, the extent of the decomposition attained a value of 92–93% for ZSM5 and 72–73% for Mo 2 CrZSM-5. Both samples exhibited constant activity. The products in decreasing selectivities are propylene, butane, ethylene, methane and benzene. Ethane and propane were detected only in trace amounts. Results are collected in Table 2. The differences between the two samples are that more methane and benzene formed on the Mo 2 C-containing ZSM-5. The effect of Mo 2 C was more pronounced when it was deposited on silica, which was practically inactive at 673 K. In this case, the initial conversion was 4.2%, which slowly decreased to 1.2%. The product distribution basically differed from that observed for the previous samples: the selectivity to methane was 77% followed by
Table 2 Conversion of CH 3 Cl and selectivities for various products on different catalyst at 673 K ZSM-5
Mo 2 Cr ZSM-5
Mo 2 Cr SiO 2
92.5
72.5
4.2
1.0 16.0 – 54.0 – 26.0 0.5
5.0 17.0 – 53.0 – 17.0 5.0
77.0 18.0 – 4.0 – – –
ConÕersion %
SelectiÕities % CH 4 C2 H4 C2 H6 C3H6 C3H8 C 4 ’S C6 H6
ethylene Ž18%. and propylene Ž4%.. Note that the decomposition of CH 3 Cl on pure Mo 2 C in a flow system amounts only to 0.03–0.04% at 673 K.
4. Discussion 4.1. ReactiÕities of C x H y fragments on Mo2 C For the interpretation of the results obtained, it is helpful to summarize the main characteristics of different hydrocarbon fragments on Mo 2 C surface. Recently, we examined the adsorption and dissociation of CH 2 I 2 , CH 3 I and C 2 H 5 I on Mo 2 C and the reaction pathways of the hydrocarbons formed w19,20x. Whereas CH 2 and CH 3 underwent fast decomposition on Pt metals producing only minor quantities of C 2 compounds w21x on Mo 2 C, the tendency of the coupling of CH 2 and CH 3 was much greater than on these metals. Surprisingly, the formation of C 2 H 4 also occurred in the reaction of CH 3 on Mo 2 C, which was not detected at all for Pt metals w21x. In contrast with this, the reaction of C 2 H 5 did not differ much on Pt metals and Mo 2 C w20x: the C`C bond remained intact on both types of solids. 4.2. TPD and IR spectroscopic studies TPD measurements showed that following the adsorption of CH 3 Cl on ZSM-5 at 373 K, a fraction of it remained adsorbed and was released with a Tp s 393 K. The presence of Mo 2 C did not influence this peak temperature, suggesting that most of the CH 3 Cl adsorbed on the ZSM-5. That fact that the desorbing amount of CH 3 Cl somewhat decayed shows that Mo 2 C blocks some of the adsorption sites on the ZSM-5. In addition, the formation of other products was clearly enhanced by the presence of Mo 2 C. This feature indicates that Mo 2 C can induce the dissociation of CH 3 Cl at such a low temperature, where ZSM-5 alone is not effective. IR spectroscopic measurements suggest that CH 3 Cl adsorbs molecularly on all the three samples, ZSM-5, Mo 2 CrZSM-5 and Mo 2 CrSiO 2 at 300 K. Absorption bands detected are readily assigned to the vibrations of adsorbed CH 3 Cl w22x ŽTable 1.. All
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these bands were eliminated after evacuation at room temperature indicating the weakness of the adsorption. At and above 473 K, however, the nature of the adsorption basically altered. This was first exhibited by the development of reverse bands at 3669 and 3612 cmy1 in the OH frequency region for Mo 2 CrZSM-5 and ZSM-5, and the appearance of stable absorption bands at 2958, 2927, 2901, 2860, 1539, 1509, 1470, 1458 and 1383 cmy1 ŽFig. 2.. In order to facilitate the interpretation of these spectral features, the characteristic bands of all compounds possibly formed are collected in Table 1. As spectra measured after the adsorption of CH 3 Cl on ZSM-5 and Mo 2 CrZSM-5 at 473 K and subsequent evacuation at room temperature were almost identical, we can say that surface species originating these bands are bonded to the zeolite surface. It is important to point out that the intense band of CH 3 Cl at 1350 cmy1 is missing from the spectra taken at elevated temperatures, suggesting that intact CH 3 Cl did not remain on the surface. The reverse bands at 3669 and 3612 cmy1 unambiguously show the occurrence of a surface process between the OH groups of the zeolite and adsorbed CH 3 Cl CH 3 Cl Ža. q OH Ža. s CH 3 OŽa. q HCl Ž g .
Ž 1.
Similar spectral changes were found for acidic zeolite, HY-FAU, but were not observed for basic sample, NarNaY-FAU w28x. The formation of methoxy species has been identified by IR spectroscopy following the adsorption of CH 3 Cl on a number of oxides w29,30x. Its production was also established on PdrSiO 2 after the activation of CH 3 Cl by palladium w31x, and in the direct interaction of CH 3 stream with RhrSiO 2 , SiO 2 and TiO 2 w32,33x. Accepting this consideration, the bands at 2958 and 2860 cmy1 can be attributed to the nas ŽCH 3 . and nsŽCH 3 . modes, whereas the bands at 1470 and 1458 cmy1 to the das ŽCH 3 . and dsŽCH 3 . in CH 3 O. The more characteristic band at 1060 cmy1 due to the vibration of n ŽCO. in methoxy is missing, but the detection of this band on zeolite and silica is extremely difficult. In addition to the above process, we can also consider two other elementary reactions, the elimination of HCl CH 3 Cl Ža. s CH 2Ža. q HCl Ža.
Ž 2.
341
and the cleavage of Cl`C bond CH 3 Cl Ža. s CH 3Ža. q Cl Ža.
Ž 3.
The formation of both the CH 3 and the CH 2 species was observed in the dissociation of the corresponding iodo compounds on Mo 2 CrMoŽ100. surface in UHV system w19,20x. They existed on the surface up to 250–300 K. IR spectra presented in Fig. 2 also suggest that they have been converted into other surface species after their formation, which is consistent with their high reactivity. Accordingly, we can count with the coexistence of two or more adsorbed species on the surface at and above 473 K. The primary products of the coupling of CH 3 and CH 2 are ethane and ethylene. From these two compounds, ethylene forms a stable adsorbed species on the catalyst surface. However, on Mo 2 CrMoŽ100., even the more stable di-sbonded ethylene has been transformed into ethylidyne in the temperature range of 260–350 K w23x. The absence of absorption bands at 1430 and 1345 cmy1 due to das ŽCH 3 . and dsym ŽCH 3 . of ethylidyne excludes its formation in the present case. Note that neither di-s-bonded ethylene nor ethylidyne exists on ZSM-5. We can also consider the formation of adsorbed ethoxy, which could be a surface intermediate in the production of ethylene from CH 3 Cl w8x, as described in Scheme 1.
Ž4.
Ž5. As we identified propylene in the products of the catalytic transformation of CH 3 Cl, we propose the
342
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
Scheme 1.
insertion of a second carbene to ethoxy to give adsorbed propoxide, the decomposition of which yields propylene
Ž6. On the basis of broad absorption in the frequency range between 2800 and 3000 cmy1 ŽFig. 2., as well as on that of the vibration data of Table 2, we cannot exclude the contribution of vibrations of ethoxy and propoxy surface complexes to the observed absorption bands. However, neither of the adsorbed species assumed so far explains the origin of the intense band at 1509 cmy1 , which was detectable up to 573 K. This band has been identified following the adsorption of methanol and alkenes on protonic zeolites in a number of cases w34x, and was attributed to the nas ŽC–C– C. stretching mode of alkenyl carbocations having an extremely high extinction coefficient w34x. In the present case, its formation could occur in the strong interaction of propylene with the Lewis acidic sites ŽL. of ZSM-5 C 3 H 6Ža. q L
™LyH qC H y
3
q 5Ža.
Ž 7.
Control measurements confirmed this assumption, as exposing ZSM-5 to propylene at and above 473 K, a strong absorption band developed at 1509 cmy1 , which was eliminated only at 623 K.
The adsorption of CH 3 Cl on Mo 2 CrSiO 2 is also molecular and reversible at 300 K. A stronger interaction was measured only at and above 473 K, when absorption bands at 2961, 2939, 2859, 1464 and 1441 cmy1 remained on the spectrum after room temperature evacuation. These bands can be attributed to the different vibrations of methoxy species ŽTable 2.. On pure SiO 2 , the intensities of absorption bands, particularly in the low frequency regions, were much weaker, and the band at 1441 cmy1 was even missing. This suggests that the formation of methoxy on silica is promoted by Mo 2 C. It is very likely that CH 3 Cl dissociates on Mo 2 C ŽEq. 3., and the CH 3 formed migrates onto silica to give CH 3 O. This way of methoxy formation was proposed first in the case of PdrSiO 2 w31x. It is important to emphasize that we could not detect an absorption band at 1509 cmy1 for this sample under any experimental conditions. This is consistent with the consideration presented for the assignment of this band. For the formation of carbocations, the presence of surface acid centers is a prerequisite. Due to lack of this center on Mo 2 CrSiO 2 , carbocations cannot be produced. 4.3. Catalytic decomposition Studies performed in closed circulation system clearly showed that Mo 2 C deposited onto SiO 2 catalyzes the decomposition of CH 3 Cl. This was confirmed by the results obtained in a flow system, where the main products of the reaction were methane and ethylene, with a small amount of propylene. In this case, the main role of Mo 2 C is to initiate the dissociation of CH 3 Cl to produce CH 3 surface species. As was mentioned above, Mo 2 C is less reactive towards the complete decomposition of hydrocarbon fragments as compared to highly dispersed Pt metals, nevertheless, it also promotes their decomposition to surface carbon CH 3Ž a. s CH 2Ža. q H Ža.
Ž 8.
CH 2Ž a. s C Ža. q H 2Ž g .
Ž 9.
and the formation of methane. This latter reaction may occur in the hydrogenation of CH x species or in the disproportionation of CH 3 4CH 3Ž a. s 3CH 4Ž g . q C Ža.
Ž 10 .
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
In addition, we may also count with the decomposition of ethylene on Mo 2 C surface. The situation was different on ZSM-5, which itself is an effective catalyst for the conversion of CH 3 Cl into C 2 –C 4 compounds w5–8x. The formation of these compounds are described by the Eqs. 4–6. We expected that due to the promoting effect of Mo 2 C on the dissociation of CH 3 Cl ŽEq. 3., a new route is opened for the production of carbene, CH 2 , which, reacting with methoxy species, yields ethylene. This expectation was, however, only partially fulfilled as the decomposition of CH 3 Cl occurred at somewhat lower temperature on Mo 2 C-doped ZSM-5 as compared to undoped ZSM-5. But at higher temperature, when ZSM-5 is active in the transformation of CH 3 Cl into other compounds, the effect of Mo 2 C could not come in prominence.
343
when methoxy species and alkene carbocation were identified by IR spectroscopy. Žii. The catalytic decomposition of CH 3 Cl proceeded with well measurable rate at and above 673 K yielding propylene, ethylene, butane, methane and benzene in decreasing selectivities. The formation of these products is described by the transient appearance of ethoxide and propoxide. Žiii. Mo 2 C only slightly influences the processes occurring on the active ZSM-5 catalyst. Živ. Its catalytic effect was exhibited in the case of Mo 2 CrSiO 2 when it promoted the cleavage of C`Cl bond in the CH 3 Cl.
Acknowledgements This work was supported by the OTKA F025610.
Appendix
5. Conclusions Ži. CH 3 Cl adsorbs reversibly on ZSM-5 at 300 K. Stronger interaction occurred at and above 473 K,
Numerical data, together with product analyses for each individual measurements plotted in Figs. 1 and 2 are compiled in Tables A1–A16 below.
Table A1 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 9.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.115 0.140 0.161 0.295 0.633 1.081 1.642 1.687 1.528
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
0.037 0.084 0.408 0.883 1.309 2.005 0.748 0.113
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.059 0.099 0.138 0.238 0.536 0.616 0.736 0.855 1.133
0.000 0.000 0.000 0.000 0.000 0.195 0.347 0.252 0.298
0.054 0.084 0.046 0.115 0.190 0.557 1.129 1.115 0.186
y0.002 0.043 0.023 0.058 0.093 0.287 0.570 0.535 0.089
0.019 0.059 0.298 0.516 0.357 0.059 0.099 y0.100
0.000 0.000 0.031 0.090 0.778 1.507 0.654 0.213
0.018 0.050 0.135 0.553 0.376 0.899 0.034 0.000
0.000 0.025 0.056 0.276 0.202 0.460 0.038 0.000
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
344
Table A2 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 7.01 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.178 0.666 1.573 1.758 1.808 1.861 1.935 1.448 1.078
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
0.068 0.348 1.200 1.668 2.125 0.310 0.088 0.123
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.178 0.516 1.054 1.153 1.134 1.213 1.332 0.847 0.716
0.000 0.012 0.465 0.332 0.364 0.288 0.224 0.125 0.186
0.055 0.270 0.128 0.517 0.617 0.706 0.733 0.746 0.284
0.055 0.132 0.074 0.244 0.307 0.346 0.354 0.270 0.108
0.059 0.206 0.437 0.537 0.457 y0.001 y0.028 y0.100
0.000 0.097 0.475 0.933 1.040 0.166 0.000 0.000
0.009 0.120 0.582 0.423 1.206 0.263 0.117 0.222
0.000 0.075 0.289 0.225 0.578 0.119 0.001 y0.001
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
Table A3 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 6.38 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
y 5.204 y4.204 y3.903 y3.505 y3.204 y2.903 y2.505 y2.204 y1.903 y1.602
– – – – – – – – – –
0.302 0.867 0.950 1.217 1.540 1.818 2.175 2.682 2.035 1.678
0.281 0.676 0.636 0.815 1.412 1.213 1.451 1.651 1.293 0.616
0.000 0.043 0.112 0.222 0.149 0.383 0.326 0.623 0.553 0.679
0.017 0.283 0.344 0.356 0.001 0.426 0.739 0.799 0.351 0.768
y0.004 0.135 0.138 0.176 0.022 0.209 0.341 0.391 0.162 0.385
y5.204 y4.509 y4.204 y3.903 y3.505 y2.903 y2.505 y2.204 y1.903
y5.248 y4.549 y4.248 y3.947 y3.549 y2.947 y2.549 y2.248 y1.947
0.114 0.435 0.741 1.034 1.384 2.037 1.099 0.170 0.098
0.079 0.298 0.377 0.377 0.377 0.258 0.178 y0.028 y0.100
0.035 0.116 0.309 0.466 0.658 1.716 0.841 0.274 0.165
0.002 0.043 0.704 0.397 0.750 0.115 0.160 0.000 0.000
0.002 0.022 0.649 0.206 0.401 0.052 0.080 0.076 y0.033
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
345
Table A4 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 4.50 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.093 0.494 1.056 1.449 2.087 2.649 3.233 2.671 2.183
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
0.077 0.189 0.795 1.370 2.290 3.327 3.470 2.008 0.887
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.087 0.461 0.895 0.915 1.197 1.169 1.929 1.248 1.531
0.000 0.000 0.063 0.184 0.576 0.903 1.256 0.693 0.411
0.013 0.067 0.198 0.676 0.628 1.192 0.086 1.452 0.502
0.007 0.034 0.100 0.326 0.314 0.615 0.038 0.722 0.261
0.059 0.138 0.457 0.457 0.387 0.417 y0.100 y0.100 y0.100
0.000 0.000 0.111 0.490 1.419 2.187 3.566 2.108 0.987
0.039 0.096 0.453 0.852 0.981 1.468 0.000 0.000 0.000
0.021 0.045 0.226 0.429 0.497 0.745 y0.004 0.000 0.000
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
Table A5 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.111 0.226 0.732 1.149 1.568 1.873 2.098 2.176 2.069
y5.824 y4.824 y3.824 y2.824 y2.312 y1.824 y1.568 y1.312 y0.824
y5.824 y4.824 y3.824 y2.824 y2.312 y1.824 y1.568 y1.312 y0.824
0.100 0.252 0.670 1.712 3.056 4.445 3.948 3.651 1.760
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
0.099 0.178 0.616 0.855 1.193 1.173 1.551 1.492 1.153
0.000 0.000 0.000 0.100 0.268 0.471 0.459 0.560 0.742
0.024 0.095 0.229 0.409 0.202 0.439 0.173 0.145 0.349
0.091 0.258 0.537 0.537 0.557 y0.100 y0.100 y0.100 y0.100
0.000 0.000 0.036 0.902 2.377 3.960 4.032 3.738 1.854
0.0090 0.000 0.218 0.598 0.241 1.139 0.000 0.000 0.000
Swproductsx y DO 2 Žmmol. 0.012 0.047 0.113 0.215 0.095 0.210 0.085 0.021 0.175 0.000 0.006 0.121 0.325 0.119 0.554 y0.016 y0.013 y0.006
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
346
Table A6 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 4.50 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.522 y5.000 y4.522 y4.000 y3.522 y3.000 y2.522 y2.000 y1.520 y1.000
– – – – – – – – – –
0.154 0.295 y0.689 1.172 1.283 1.469 1.619 1.857 1.520 1.367
y6.000 5.522 y5.000 y4.522 y4.000 y3.522 y2.522 y2.000 y1.522 y1.240 y1.000
y5.504 y5.027 y4.504 y4.027 y3.504 y3.027 y2.027 y1.504 y1.027 y0.744 y0.504
0.043 0.069 0.141 0.204 0.368 0.859 2.426 3.168 3.808 3.946 3.725
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.139 0.258 0.497 0.974 0.935 1.094 0.895 1.213 1.332 0.895
0.000 0.000 0.199 0.198 0.371 0.381 0.407 0.552 0.201 0.466
0.015 0.076 0.002 0.003 0.007 0.000 0.682 0.178 0.004 0.010
0.000 0.039 0.009 0.003 0.030 0.006 0.365 0.086 0.017 0.004
0.035 0.051 0.099 0.138 0.258 0.317 0.258 0.059 y0.001 y0.068 y0.100
0.000 0.000 0.034 0.000 0.113 0.429 1.437 2.527 2.481 2.945 2.963
0.009 0.018 0.006 0.057 0.000 0.224 1.505 1.190 2.578 2.091 1.698
0.001 0.000 y0.002 y0.009 0.003 0.111 0.774 0.608 1.250 1.022 0.836
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene. Table A7 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.62 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.522 y5.000 y4.522 y4.000 y3.488 y3.000 y2.698 y2.000 y1.488 y1.000
– – – – – – – – – –
0.329 0.519 0.639 0.811 1.320 1.945 2.392 1.642 1.379 1.119
y5.509 y4.509 y3.509 y2.986 y2.509 y2.204 y1.903 y1.426 y1.225 y0.924
y4.995 y3.995 y2.995 y2.472 y1.995 y1.705 y1.404 y0.927 y0.726 y0.407
0.103 0.279 0.768 1.405 2.238 2.810 3.288 4.011 3.824 3.493
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.298 0.417 0.616 0.696 0.895 1.332 1.512 1.253 0.656 0.616
0.027 0.036 0.023 0.065 0.209 0.586 0.606 0.386 0.630 0.499
0.003 0.077 0.019 0.061 0.436 0.053 0.576 0.000 0.197 0.003
y0.001 0.011 0.019 0.011 0.220 0.026 0.302 y0.003 0.104 y0.001
0.103 0.274 0.470 0.429 0.449 0.298 0.218 y0.100 y0.100 y0.100
0.000 0.067 0.334 0.980 1.684 2.505 3.068 4.116 3.885 3.600
0.007 0.000 0.000 0.040 0.057 0.002 0.002 0.000 0.000 0.000
0.007 0.062 0.036 0.105 y0.048 y0.005 0.000 0.005 y0.039 0.007
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
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347
Table A8 Dependence of the oxidation of tetralin with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.435 y4.912 y4.435 y3.912 y3.435 y2.912 y2.690 y2.312 y2.096 y1.903 y1.602
– – – – – – – – – – –
0.223 0.310 0.466 0.789 1.210 1.875 1.950 1.859 1.609 1.145 0.599
y5.440 y4.440 y3.903 y3.440 y2.917 y2.315 y1.950 y1.602 y1.397 y1.225 y0.924
y4.923 y3.923 y3.403 y2.923 y2.400 y1.798 y1.440 y1.102 y0.898 y0.730 y0.424
0.112 0.291 0.426 0.762 0.942 1.842 2.449 3.253 3.590 3.812 3.717
corr Ž DOact mmol.
DwT-onex Žmmol.
DwT-olx Žmmol.
Swproductsx y DO 2
0.206 0.206 0.410 0.756 0.879 1.368 1.572 1.286 1.368 0.858 0.470
0.020 0.008 0.050 0.042 0.308 0.467 0.349 0.580 0.197 0.253 0.098
0.003 0.076 0.005 0.000 0.007 0.067 0.011 0.008 0.023 0.020 0.029
0.006 y0.020 y0.001 0.009 y0.016 0.027 y0.018 0.015 y0.021 y0.014 y0.002
0.144 0.286 0.258 0.516 0.510 0.449 0.532 0.178 0.079 y0.100 y0.100
0.000 0.027 0.163 0.100 0.221 1.376 1.980 2.116 2.510 3.918 3.822
0.000 0.008 0.000 0.084 0.445 0.033 0.000 1.732 1.939 0.000 0.000
0.032 0.030 y0.005 y0.062 0.234 0.016 0.013 0.767 0.938 0.006 0.005
Conditions: 2.759 M tetralinq 0.0125 M t-BHPq the corresponding catalyst dissolved in 8.00 cm3 chlorobenzene.
Table A9 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 9.00 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.461 0.901 1.154 1.657 2.194 2.257 2.314 2.235 2.172
0.457 0.895 0.994 1.412 1.691 1.571 1.392 1.571 1.133
0.010 0.044 0.035 0.035 0.055 0.162 0.055 0.059 0.038
0.000 0.000 0.118 0.204 0.447 0.518 0.876 0.589 1.002
0.006 0.038 y0.007 y0.006 y0.001 y0.006 0.009 y0.016 0.001
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.678 y1.569 y1.312 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.678 y1.569 y1.312 y0.824
0.360 0.562 1.017 1.097 1.424 2.317 3.365 3.566 3.220 2.013 0.121
0.337 0.516 0.417 0.147 0.099 0.059 0.019 y0.001 y0.020 y0.060 y0.100
0.019 0.061 0.171 0.315 0.361 0.416 0.371 0.282 0.231 0.383 0.010
0.020 0.030 0.458 0.612 0.942 1.810 2.910 3.290 3.005 1.675 0.216
0.016 0.045 0.029 y0.023 y0.022 y0.032 y0.065 0.005 y0.004 y0.015 0.005
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
348
Table A10 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 7.01 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y0.824
– – – – – – – –
0.895 1.756 2.025 2.304 2.578 2.697 2.614 2.142
y5.824 y4.824 y3.824 y3.312 y2.824 y2.568 y2.312 y2.195 y2.064 y1.824 y1.312 y0.824
y5.824 y4.824 y3.824 y3.312 y2.824 y2.568 y2.312 y2.195 y2.064 y1824 y1.312 y0.824
1.261 1.400 1.596 1.838 2.409 3.100 3.807 3.356 2.948 0.841 0.195 0.131
corr Ž DOact mmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
0.815 1.492 1.432 1.452 1.630 1.531 1.690 1.332
0.032 0.065 0.114 0.102 0.090 0.096 0.080 0.056
0.085 0.215 0.489 0.767 0.846 1.132 0.817 0.800
0.037 0.016 0.010 0.017 y0.012 0.062 y0.027 0.046
1.094 0.895 0.218 0.059 0.099 0.051 y0.021 y0.032 y0.061 y0.020 y0.100 y0.100
0.242 0.274 0.402 0.404 0.516 0.347 0.238 0.240 0.238 0.133 0.014 0.023
0.000 0.221 0.966 1.358 1.794 2.709 3.636 3.170 2.741 0.726 0.283 0.225
0.075 y0.010 y0.010 y0.017 0.000 0.007 0.046 0.022 0.001 y0.002 0.002 0.017
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
Table A11 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 6.38 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
y 5.505 y5.204 y4.509 y4.204 y3.903 y3.204 y2.903 y2.204 y1.903 y1.602 y0.999
– – – – – – – – – – –
0.599 0.935 1.774 2.257 2.533 2.814 2.847 3.002 3.035 2.712 2.059
0.556 0.934 1.691 1.850 1.929 1.770 1.909 1.810 1.730 1.531 1.531
0.022 0.043 0.067 0.095 0.121 0.254 0.114 0.102 0.176 0.108 0.099
0.029 0.000 0.046 0.328 0.485 0.783 0.810 1.080 1.123 1.053 0.428
0.008 0.042 0.030 0.016 0.002 y0.007 y0.014 y0.010 y0.006 y0.020 y0.001
y5.505 y4.509 y4.204 y3.903 y3.505 y3.204 y2.903 y2.505 y2.204 y2.028 y1.903
y5.549 y4.549 y4.248 y3.947 y3.549 y3.248 y2.947 y2.549 y2.248 y2.072 y1.947
0.677 0.953 0.969 1.051 1.482 1.827 2.444 3.400 2.816 2.373 0.489
0.668 0.537 0.198 0.138 0.059 0.051 0.039 0.011 y0.068 y0.076 y0.068
0.052 0.238 0.319 0.300 0.507 0.362 0.470 0.271 0.157 0.245 0.042
0.000 0.156 0.435 0.608 0.811 1.407 1.927 3.128 2.720 2.190 0.544
0.043 y0.022 y0.017 y0.005 y0.105 y0.007 y0.008 0.010 y0.007 y0.014 0.029
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalyst dissolved 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
349
Table A12 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 4.50 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.824 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
0.839 1.402 1.770 2.079 2.409 2.461 2.675 2.624 2.511
y5.824 y5.312 y4.824 y4.312 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
y5.824 y5.312 y4.824 y4.312 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
0.623 0.880 1.094 1.203 1.223 1.705 2.755 3.908 4.760 3.240 1.864
corr Ž DOact mmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
0.815 1.372 1.472 2.048 1.466 1.730 1.466 1.691 1.691
0.005 0.047 0.024 0.064 0.032 0.085 0.034 0.066 0.030
0.013 0.000 0.205 0.000 0.912 0.640 1.116 0.848 0.779
y0.006 0.017 y0.069 0.033 0.001 y0.006 y0.059 y0.019 y0.011
0.616 0.815 0.895 0.815 0.338 0.118 0.059 y0.061 y0.100 y0.100 y0.100
0.024 0.042 0.067 0.122 0.325 0.520 0.446 0.397 0.214 0.071 0.045
0.000 0.027 0.127 0.268 0.552 1.052 2.151 3.581 4.641 3.267 1.918
0.017 0.004 y0.005 0.002 y0.008 y0.015 y0.099 0.009 y0.005 y0.002 y0.001
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
Table A13 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 corr Ž DOact mmol.
logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
y 5.824 y5.312 y4.824 y3.824 y3.312 y2.824 y2.312 y1.824 y1.312 y0.824
– – – – – – – – –
1.086 1.717 2.303 2.522 2.739 3.081 2.948 2.880 2.833 2.767
0.994 1.472 1.491 1.507 2.248 1.969 2.566 1.663 1.790 1.468
0.015 0.005 0.059 0.060 0.072 0.134 0.046 0.068 0.039 0.050
0.091 0.224 0.779 0.940 0.422 0.985 0.327 1.157 1.005 1.248
0.014 y0.016 0.016 y0.15 0.003 0.007 y0.009 0.008 0.001 y0.001
y5.824 y5.312 y4.824 y3.824 y3.312 y2.824 y2.569 y2.312 y2.064 y1.824 y1.312 y0.824
y5.824 y5.312 y4.824 y3.824 y3.312 y2.824 y2.569 y2.312 y2.064 y1.824 y1.312 y0.824
0.968 1.379 1.834 2.032 2.259 2.935 3.956 4.937 5.240 4.890 3.623 2.605
0.755 0.994 1.094 0.576 0.218 0.039 y0.040 y0.060 y0.060 y0.080 y0.100 y0.100
0.044 0.234 0.189 0.399 0.514 0.351 0.546 0.605 0.421 0.231 0.149 0.071
0.190 0.150 0.543 1.061 1.513 2.514 3.400 4.359 4.863 4.672 3.542 2.599
0.021 y0.001 y0.008 0.004 y0.014 y0.031 y0.050 y0.033 y0.016 y0.067 y0.032 y0.035
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
350
Table A14 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-V ŽV ., respectively pH: 4.50 corr Ž DOact mmol.
log wALClx
log wAL-V ŽV .x
DO 2 Žmmol.
D wCh-E x Žmmol.
D wCh-olx Žmmol.
S wproductsx y DO 2
y 6.000 y5.522 y5.000 y4.522 y4.000 y3.522 y3.000 y2.522 y2.000 y1.522 y1.000
– – – – – – – – – –
0.567 0.989 1.480 1.746 1.969 2.109 2.330 2.498 2.616 2.725 2.583
0.454 0.974 1.352 1.332 1.531 1.492 1.452 1.452 1.490 1.531 1.293
0.015 0.017 0.023 0.029 0.069 0.050 0.068 0.067 0.069 0.072 0.063
0.099 0.000 0.111 0.380 0.357 0.600 0.782 0.930 1.055 1.102 1.231
y0.005 0.002 0.006 y0.005 y0.012 0.033 y0.028 y0.049 y0.002 y0.020 0.004
y6.000 y5.000 y4.522 y4.000 y3.522 y3.000 2.522 y2.000 y1.522 y1.000
y5.504 y4.504 y4.026 y3.504 y3.027 y2.504 y2.027 y1.504 y1.027 y0.504
0.546 0.580 0.705 0.849 1.266 2.277 3.724 5.091 4.203 3.214
0.496 0.377 0.179 0.417 0.059 y0.029 y0.084 y0.100 y0.100 y0.100
0.054 0.096 0.243 0.255 0.391 0.582 0.738 0.499 0.216 0.130
0.000 0.111 0.78 0.192 0.773 1.689 3.051 4.666 4.016 3.156
0.004 0.004 y0.005 0.015 y0.043 y0.035 y0.019 y0.026 y0.071 y0.028
Conditions: 2.468 M cyclohexene q 0.0125 M t-BHP q the corresponding catalysts dissolved in 8.00 cm 3 chlorobenzene.
Table A15 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-V ŽV ., respectively pH: 3.62 corr Ž DOact mmol.
log wALClx
log wAL-V ŽV .x
DO 2 Žmmol.
D wCh-E x Žmmol.
D wCh-olx Žmmol.
S wproductsx y DO 2
y 6.000 y5.698 y5.301 y5.000 y4.602 y4.124 y3.602 y2.999 y2.602 y2.301 y1.903 y1.602 y1.301 y1.125 y0.999
– – – – – – – – – – – – – – –
0.500 0.682 1.088 1.397 1.742 1.800 1.856 2.060 2.218 2.388 2.550 2.674 1.620 1.110 0.907
0.497 0.676 1.011 1.332 1.492 1.492 1.452 1.551 1.691 1.810 1.890 1.850 1.173 1.014 0.795
0.020 0.030 0.045 0.049 0.066 0.059 0.083 0.061 0.070 0.098 0.086 0.070 0.027 0.022 0.017
0.000 0.000 0.033 0.015 0.172 0.234 0.330 0.443 0.467 0.476 0.564 0.746 0.430 0.055 0.107
0.017 0.024 0.001 y0.001 y0.012 y0.015 0.009 y0.005 0.010 y0.004 y0.010 y0.008 0.010 y0.019 0.012
y5.810 y5.644 y5.509 y4.986 y4.509 y3.945 y3.509 y2.986 y2.685 y2.301 y1.903 y1.602 y1.301 y1.145
y5.296 y5.130 y4.995 y4.472 y3.995 y3.431 y2.995 y2.473 y2.172 y1.802 y1.404 y1.103 y0.802 y0.647
0.598 0.575 0.570 0.285 0.465 0.754 1.057 2.021 2.913 4.039 4.557 4.812 3.880 3.517
0.388 0.437 0.347 0.164 0.185 0.042 y0.019 0.022 y0.019 y0.068 y0.100 y0.100 y0.100 y0.100
0.077 0.066 0.081 0.083 0.094 0.357 0.249 0.377 0.349 0.318 0.304 0.301 0.152 0.155
0.113 0.0620 0.150 0.036 0.207 0.506 0.820 1.667 2.560 3.784 4.338 4.564 3.784 3.446
y0.020 y0.010 0.008 y0.002 0.021 0.151 y0.007 0.045 y0.023 y0.005 y0.015 0.047 y0.044 y0.016
Conditions: 2.468 M cyclohexene q 0.0125 M t-BHP q the corresponding catalysts dissolved in 8.00 cm 3 chlorobenzene.
J. Cserenyi ´ et al.r Journal of Molecular Catalysis A: Chemical 162 (2000) 335–352
351
Table A16 Dependence of the oxidation of cyclohexene with O 2 on the concentration of catalysts ALCl and ion-pair AL-VŽV., respectively pH: 3.00 logwALClx
logwAL-VŽV.x
DO 2 Žmmol.
y 5.912 y5.435 y4.913 y4.435 y4.009 y3.435 y2.912 y2.602 y2.213 y1.999 y1.602 y1.301 y1.125 y1.000
– – – – – – – – – – – – – –
0.513 0.782 0.989 1.129 1.508 1.883 2.399 2.619 2.777 2.638 2.404 2.286 2.243 2.198
y5.912 y5.435 y4.435 y3.435 y2.912 y2.612 y2.310 y2.033 y1.732 y1.404 y1.301 y1.146
y5.399 y4.923 y3.923 y2.923 y2.399 y2.098 y1.798 y1.521 y1.220 y1.059 y0.806 y0.651
0.414 0.506 0.571 0.759 1.364 2.152 2.964 3.809 4.836 3.643 3.396 2.920
corr Ž DOact mmol.
DwCh-Ex Žmmol.
DwCh-olx Žmmol.
Swproductsx y DO 2
0.511 0.695 0.980 1.009 1.327 1.613 1.816 1.770 1.939 1.878 1.770 1.810 1.690 1.472
0.017 0.033 0.026 0.031 0.031 0.053 0.090 0.089 0.134 0.085 0.065 0.076 0.064 0.061
0.000 0.058 0.000 0.111 0.102 0.224 0.501 0.766 0.732 0.662 0.567 0.390 0.478 0.655
0.015 0.004 0.017 0.022 y0.048 0.007 0.008 0.006 0.028 y0.013 y0.002 y0.010 y0.011 y0.010
0.316 0.287 0.075 y0.018 0.002 y0.003 y0.051 y0.072 y0.060 y0.100 y0.100 y0.100
0.061 0.079 0.088 0.195 0.291 0.316 0.506 0.436 0.342 0.256 0.131 0.130
0.023 0.129 0.380 0.561 1.045 1.713 2.506 3.405 4.512 3.446 3.318 2.921
y0.014 y0.011 y0.028 y0.021 y0.026 y0.126 y0.003 y0.040 y0.042 y0.041 y0.047 0.031
Conditions: 2.468 M cyclohexeneq 0.0125 M t-BHPq the corresponding catalysts dissolved in 8.00 cm3 chlorobenzene.
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