Progress Report Of The Committee On Reference Catalyst, Catalysis Society Of Japan

G. Poneelet, P. Grange and P.A. Jacobs (Editors), Preparation of Catalysts III © 1983 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

775

PROGRESS REPORT OF THE COr1tlITTEE ON REFERENCE CATALYST, CATALYS IS SOCI ETV OF JAPAN Yu i chi ~1URAKAMI Department of Synthetic Chemistry, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464, Japan The committee on Reference Catalyst, Catalysis Society of Japan,was founded in 1978, after the conclusion of a symposiur:l on "Research by Using Reference Catalysts" in November, 1977. The objectives of the committee are to distribute reference catalysts, to collect and report the data on the reference catalysts, and to develop standard methods for catalyst characterization. Using reference catalysts generates solidarity and cooperation among individuals and laboratories. A wide variety of methods are used to characterize the catalysts and to evaluate catalytic properties, and each of the methods has SOr:le advantages over the others. The differences in the methods and/or catalysts result in the lack of common background for precise discussions. The reference catalysts make it possible to correlate wide variety of methods with each other and to develop discussions. This promotes cooperation among researchers and leads to a better understanding of catalysis. An important application, especially for the beginners, is the examination of methods for the characterization and the evaluation of catalytic performance by using reference catalysts.

ORGANIZATION Organization of the committee is as follows. Chairman: Prof. Yuichi Murakami Department of Synthetic Chemistry, Faculty of Engineering, Nagoya University, Chikusa, Nagoya 464, Japan Secretary: Dr. Hideyuki Matsumoto Research and Development Division, JGC Corporation, Bessho 1-14-1, Minami-ku, Yokohama 232, Japan Liaison: Prof. Tadashi Hattori Department of Synthetic Chemistry, Faculty of Engineering, Nagoya University, Chikusa, Nagoya 464, Japan The other committee members are Prof. H. Hattori (Hokkaido Univ.), Prof.

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S. Okazaki (Ibaragi Univ.), Dr. J. Take (Univ. of Tokyo), Prof H. Niiyama (Tokyo Inst. Tech.), Prof. S. Yoshida (Kyoto Univ.), Prof. T. Imanaka (Osaka Univ.), Prof. H. Arai (Kyushu Univ.), and Dr. I. Furuoya (Takeda Chern. Ind., Ltd.). Anyone can be given the catalysts through the committee members without any obligations and can take part in the activity of the committee. So~e projects and symposia have been organized by the users. ACTIVITY Ten commercial £atalysts and/or supports, shown in Table 1, were selected as Table 1 List of reference catalysts Catalyst Alumina« Alumina b Mark JRC-ALO-l JRC-ALO-2 Composition (wt%) Ig. loss 4.1 0.03 0.03 Fe203 0.03 0.22 Si02 0.03 0.04 Na20 Ti02 Sf 0.05 2.00 Pore volume (cm 3/g) 0.67 0.72 Surface area (m2/g)g 176 298 h h Remarks n,Y-A12 03 n- A1203 SilicaCatalyst Silica gel alumina Mark JRC-SIO-l JRC-SAH-l Composition (wt%) 3.05 Ig. loss 10.8 1. 31 28.61 A1203 CaD 1.73 G.05 0.02 Fe203 0.03 0.013 Na20 Sf 0.01 0.26 Pore volume (cm 3/g) 0.58 0.93 Surface area (m 2/g) 166 511 granular Remarks FCC type type

Alumina c JRC-ALO-3

Alumina d JRC-ALO-4

Alumina e JRC-ALO-5

0.01 0.01 0.3 0.01 N. D. 0.51 128 Y-A1203 h Silicaalumina JRC-SAL-2

0.01 0.01 0.01

0.68

11.0 13.75 0.02 0.012 0.43 0.73 560 FCC type

N.D. 0.66 174 Y-A1203 h Zeolite JRC-Z-l

0.02 0.57 0.41 253 n,Y-A1203 n Titanium oxide JRC- TIO-l

2.8

H20 1.66

N.D. 0.35 670 NaY type

4.73 72.6 anatase

a: prepared by tableting gibbsite produced by Bayer's Process and by calcinating

at 973 K. b: prepared by washing precipitate from sodium aluminate and aluminum sulfate and by calcinating at 723 K. c: prepared by tableting and calcinating powders of X,p-aluminas and gibbsite to form y-alumina and by calcinating again at 973 K. d: prepared by tableting and calcinating boemite powders to form y-alumina and by calcinating again at 973 K. e: prepared by drying desulfated aluminum hydrogel produced from aluminum sulfate and by calcinating at 82Jv873K. f: measured by N. Nojiri, M. Nakashima and N. Ii (t,litsubishi Petrochem., ref. 3). g: Surface areas of ALO-l 'VALO-5 were determined by the project mentioned below. h: determined from XRD patterns by K. Mukaida (Muroran Inst. Tech., ref. 1). The other data were given by the makers.

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Table 2 List of reference supported metal catalysts Number No.1 NO.2 No.3 No.4 No.5 No.5 No.7 No.8 No.9 JRC-Al JRC-A4 JRC-A4 JRC-S2 JRC-SAH JRC-SAL JRC-Zl JRC-A4 JRC-A4 ~1ark -0.5Pt -0.5Pt -5.0Pt -0.5Pt -0.5Pt -0.5Pt -0.5Pt -0.5Pd -0.5Rh ALO-l ALO-4 ALO-4 SIO-2a SAH-l SAL-2 Z-l ALO-4 ALO-4 Support Material PtClb PtClb PtClb PtClb PtNHC PtNHC PtNHC PdCl z RhC1 3 M~~~~ent(wt%) 0.50 0.50 5.1 0.50 0.54 0.72 0.5 0.50 0.50 e d Preparatian IMpd IMpd H1P IW IMPd IMPd IEf IMPd IMPd a: Bead type; Composition(wt%), Na zO(0.03i, FeZ03(0.01), Al z03(0.07), CaO(0.09); Pore volume, 1.lcm 3/g; Surface area, 280m /g. b: HzPtC16·6HzO. c: [Pt(NH3)4]C1Z' d: Impregnation. e: Incipient wetness. f: Ion exchange. No.1 '\,4 were prepared in Univ. of Tsukuba, No.5,6,8 and 9 in Nippon Engelhard, and No.7 in Kyushu Univ. the reference catalysts, and they have been distributed to more than one hundred laboratories of industries and academic institutions. For the projects of metal surface area, nine supported precious metal catalysts, listed in table 2, were prepared and distributed to more than twenty laboratories including Argentina. Several supported precious and non-precious metal catalysts are going to be added to the list. The following three projects were organized and are still continuing; the determination of BET surface area of reference alumina catalysts, the determination of metal surface area of supported precious metal catalysts, and the standardization of rapid determination of metal surface area by the pulse method of CO chemisorption. The following four symposia have been held and a fifth one is scheduled in October, 1982. (1) 1st annual symposium: General Properties of Reference Alumina Catalysts (Fukuoka, October, 1979). (2) 2nd annual symposium: Metal Surface Area (Sendai, September, 1980). (3) Special symposium: Metal Surface Area II (Nagoya, June, 1981). (4) 3rd annual symposium: Support Effect (Kyoto, October, 1981). Data reported in the first annual symposium were published in SHOKUBAI (CATALYST), a bulletin of Catalysis Society of Japan (ref. 1), and those reported in the special and the third symposia were published as preprints (ref.2,3). A part of data reported in the second symposium was briefly summarized in a report (ref. 4). RESULTS A wide variety of results have been reported, but only the subjects conducted cooperatively were briefly shown below. One would notice that the solidarity and collaboration are growing.

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1. BET Surface Area of Reference Alumina Catalysts. (T. Hattori, ref. 1,3) The project of the entitled subject was organized in 1979 after the first symposium. The objective of the project includes the re-examination of the procedures employed in individual laboratories as well as the determination of the BET surface areas. By reason of the former, it was decided that the measurement was done by the procedures which had been employed in individual laboratories. Only the pretreatment was fixed as follows: (1) drying catalysts at 383 K overnight, (2) allowing to cool and to stand for longer than 24 h in a desiccator, (3) weighing the sample,-and (4) evacuating at 573 K for 2 h. Eleven laboratories, listed in the appendix, participated in the project. Three laboratories employed the flow method and eight laboratories employed the static volumetric method. The surface area was calculated by the single point method in three laboratories employing the flow method, by the BET plot in seven laboratories, and by a new plot (Takagi plot), shown below, in one laboratory. l/v(l-x) = l/v m + (l-x)/xvmC The average surface areas thus determined per unit weight of evacuated catalysts were shown in Table 1. The scatters of the surface areas per unit weight of unevacuated catalysts were larger than those of evacuated catalysts. The latters were shown in Fig. 1. The scatters in the static method, shown by the empty in Fig. 1, were almost equal to those obtained in the SCI/IUPAC/NPL project(ref. 5). The scatters in the flow method, shown by the solid, were larger than those in the static method. The difference is larger on ALO-2 and 5 whose surface areas also are larger than the others. One of the reasons may be the non-linear relation between the response of thermal conductivity detector and the composition of He-N 2 mixture in the flow method. Fig. 2 shows another possible reason. The surface area increased with the evacuation temperature on all aluminas, but the effect was larger on ALO-2 and 5. This suggests that the effect of evacuation may be more significant in the flow method. Further examination will continue for the establishment of the flow method for the rapid determination of BET surface area. The other physical textures, such as pore volume, pore size distribution and XRD patterns, were reported by K. Mukaida (Muroran Inst. Tech., ref. 1). Surface areas, pore volumes, and pore size distributions were also measured by the adsorption of benzene (J. Kobayashi, Shizuoka Univ., ref. 1). The change of physical textures with calcination was reported by T. Inui, T. Miyake and Y. Takegami (Kyoto Univ., ref. 1,3). TEM microphotographs were reported by M. Yamada and H. Matsumoto (JGC Corp., ref. 3). 2. Acid Properties of Reference Alumina Catalysts. The variety of methods are used to characterize the acid properties of cata-

779

&---...L-_--'

ALO-l

1.0 o

(l)

L

c::I: (l)

u

o

4L

e55 0.9

o ALO-l

(l)

>

• ALO-2

o ALO-5

W.

L . . . - _.......

0.8

!

1.0 1.2 S,A, / S,A, (average)

Fig. 1. Frequency distribution of surface areas of reference aluminas. Open square, by static method; solid square, by flow method (ref. 1,3).

A ALO-3 • ALO-4

o ALO-S

0,8'----'-----'----'-----1 400 500 600 700 Evac. Temp. (K) Fig. 2. Effect of evacuation temperature on surface area. Evacuation period, 15 min. (N. Nojiri and M. Kurashige, Mitsubishi Petrochem., ref. 3).

lysts. Three methods have been applied to the reference alumina catalysts: microcalorimetric measurement of the differential heat of adsorption of ammonia (H. Yamaguchi, K. Tsutsumi and H. Takahashi, Univ. of Tokyo, ref. 1); temperature programmed desorption of n-butylamine (S. Ogasawara and S. Kanamaki, Yokohama Natl. Univ., ref. 1); and infrared spectra of adsorbed pyridine (J. Take and Y. Yoneda, Univ. of Tokyo, ref. 1). Microcalorimetry tells both the acid amount and strength, and is superior to others in the measure of acid strength. The acid strength is given by the immediate interaction energy of acid sites with the probe bases. TPD method also gives information on the amount and strength of acid sites. The acid strength is given in terms of desorption temperature. The product distribution gives information on the nature of acid sites (ref. 6). IR method is distinguished by the fact that it can tell the type (Bronsted or Lewis) of acid sites. It also gives the amount and strength of acid sites. The strength is given in terms of evacuation temperature of catalysts preadsorbing probe bases (ref. 7). These three methods are different from each other in the probe bases and in the measure of acid strength. In spite of these differences, good correlations were obtained among the acid amoun~measured by

780 1.0r------------~

0.8fc-,

.0

0.

u

o

+-J

I

0

E

(l)

~NU

:z:CJ)(l) > I

.::t

0.6-·

~

U I

C

I.-

I - _ . LI- _ . . L -I - _ . . LI- - - - - - I 0 . 4 L . . - _ I. L - _ . L

0.2

0.4

0.6

o

>.

o;

NH 3 (ad) by Calorimetric (mmol/g) (heat of ads.

>

80 kJ/mol)

Fig. 3. Comparison of acid amounts of reference aluminas measured by three methods (ref. 1).

0/0

three methods, as shown in Fig. 3. / Q <, The difference in absolute values 0.2 0 E may be due to the difference in E the strength of acid sites measI.ured. These correlations led to 0 the further effort cooperatively 0 u 0.1 made to obtain quantitative agree>. .0 ment between microcalorimetric o ALO-l TI and IR methods (J. Take et al, 0' A ALO-3 0 ref. 3,8). The evacuation tem>. c, perature was correlated with the 0 0.1 0.2 heat of adsorption by microcaloPy(ad) by IR (mmol/g) rimetry, and a linear relation Fig. 4. Comparison of acid strength was obtained between the heat of distribution measured by IR and microcalorimetric methods (ref. 3,9~ adsorption and the reciprocal of The evacuation temperature. amount of adsorbed pyridine with the heat of adsorption larger than various level was calculated from the infrared spectra by the aid of the above-mentioned linear relation, and was compared with those of adsorbed pyridine and ammonia measured by microcalorimetry. As shown in Fig. 4, quantitative agreement was obtained between microcalorimetry and IR method.

O}{{

s

/a

781

3. Metal Surface Area of Reference Supported Metal Catalysts. (H. Matsumoto, ref. 2,4; and N. Nojiri, ref. 11). The project of entitled subject was organized to give a chance for comparing the metal surface area measured by different researchers with different methods. Nine supported precious metal catalysts, shown in Table 2, were provided for the project and two symposia were held. As one of the objectives was the examination of the methods which had been employed, any of the experimental conditions were not fixed. The res~lts were summarized in Table 3. Participants in the project are listed in the appendix. It should be noted that the researchers in industry employed the dynamic (pulse) method of CO chemisorption, although the variety of methods were listed in Table 3. It was interesting that the results were rated high by industry researchers but low by university researchers. Most of the former felt that the results agreed pretty well with each other,except sample No.1, considering the difference in the experimental conditions and method, Table 3 Metal surface area of reference supported metal catalysts a Method

NO.1

Catalyst No.2 No.3 No.4 No.5

XRD N.D. N.D. XRD N.D. N.D. TEM 1.0 1.0 small TEM &5'1,10 7.0 Chemisorption methods CO pulse 49 78 CO pulse CO pulse 17 66 CO pulse 53 92 CO pulse 92 116 CO pulse 25 87 CO pulse 64 108 CO static 53 83 CO static 140 133 02 pulse 58 57 02 pul se 25 36 02 stati c 31 33 Hr0 2 pulse 76 124 46 02- H2 {02 44 titratn H2 130 144 H2 static 72 77 H2 TPR 56 60 CS2 7.6 34 poisoning

No.6

No.7

No.8 No.9

Reduction condition

22 22 N.D. N. D. N.D. 19 19 20 N.D. 2.2 6.8 1.0 0.9 1.8 1.7 1 & 2'1,3 & h6 2.5'1,4.5 - 0.6'1,1.5 6'1,9 1arge 53

26

53 66 78 62 67 56 84 44 28 28 94 36 108 67 45 23

28 29 21 34 22 11 6.3 7.6 25 13 38 16 19 8.9

44 39 45 47 56 55 59 66 95

38 1.7 0.4 31 43 0 8.5 0.7 55 0.6 48 5.0 51 0 58 101 84 33

15 21 47 12 61 44 39 43

16 13 20 4.7 55 1.8 9.3 1.8 52 5.6 7.5 35 2.2 32 27 2.8

60 79 63 73 138 95 110 32 172

198 147 50 158 160 33 228 112 281

42

99 94 271 86 146 90

21 95 96 94 66

-

473'U673K, lh 473'U673K 313K, 10min 453'U623K, 30mi n 723K, 10min 723K, 10min 723K, 10min 673K, 2.5h 573K, 1h 723K, 45min 823K, 30min 573K, 1h 823K, 30min 823K 823K 573K, 1h 773'U823K 423'U573K

aXRD and TEM, average diameter (nm) from XRD patterns and from TEM microphotograph. Chemisorption methods, cm 3-adsorbed gas/g-meta1.

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and they seemed to gain confidence in their methods. On the other hand, some of the latter held the view that the re-examination under standard conditions is necessary. These led to the project of standardization of rapid measurement of metal surface area by the pulse method of CO chemisorption for industrial purpose and a joint research on the dispersion of these catalysts. In the latter, good agreement was obtained among the chemisorption data by static and TPR methods and TEM data, when reversibly adsorbed species are taken into consideration (ref 9). Further, tbe remarkable change in HZ chemisorption by the treatment with HZ and Oz was observed, and the effect of the supports, especially the effect of sulphur content, on the change was examined by K. Kunimori et al. (Univ. of Tsukuba and Mitsubishi Petrochem., ref. 3, 10). 4. Standardization of Rapid Measurement of Metal Surface Area by Pulse Method of CO Chemisorption. (N. Nojiri, ref. 3, 11). In this project, the standard pretreatment condition was fixed as follows: (1) increasing temperature from room temperature to 673 K in an inert gas flow, (2) increasing temperature from 673 K to 723 K in HZ flow, (3) holding temperature at 7Z3 K for 0.5 h in HZ flow, (4) holding temperature at 7Z3 K for 0.5 h and then cooling to room temperature in an inert gas flow, and (5) measurement of CO chemisorption by the pulse method. But the other experimental conditions were not fixed. The results are shown in Table 4. Participants in the project are listed in It also was the appendix. Again a large scatter was observed on sanp l e No 1. reported that the data on sample No 1 was remarkably affected by the pretreatment condition, and a view that milder pretreatment may be favorable, especially for sample No 1 , was presented. On the other hand, the results on samples No 5 and 6 were reproducible. The results were devided into two groups: the first group is A and B, and the second, C, D, E, F and G. The Table 4 agreement in each group is excellent. In A, the CO Chemisorption a by pulse method after b effluents were collected in a Porapak trap at standard pretreatment dry-ice temperature and then analysed. In B, Catalyst the effluents were analysed with a 70cm column No.5 No.6 No.1 of activated carbon at 330 K. In the others, A 54 40 38 effluents flowed immediately to a thermal con44 38 B 51 60 43 C 38 ductivity detector. This difference would 46 56 D 38 55 44 cause the difference between two groups. The E 43 56 53 F 40 average experimental conditions were as follows. 44 53 G 49 The purification of carrier gas is not necestext. sary. r1easurement was done around room tempera-

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ture. The ratio of CO pulse size to catalyst weight vias about 1/1 (mm 3/mg). The interval of CO pulse was 2~3 min. The long interval may allow the desorption of reversibly adsorbed CO, and, therefore, it leads to the evaluation of only irreversibly adsorbed CO. The interval of 2~3 min may be sufficient to measure both reversibly and irreversibly adsorbed CO. The above mentioned joint research (ref. 9) concluded that the reversibly adsorbed species also should be taken into consideration to evaluate the degree of dispersion (percentage exposed). This project is stilt in progress and will be a subject of the fourth annual symposium scheduled~in October 1982. 5. Miscellaneous. In addition to the subjects mentioned above, several reports and comments on the reference catalysts have been presented in the symposia. Only the titles are shown below. (1) CH 4-D 2 exchange on reference alumina catalysts (H. Hattori, M. Uchiyama and K. Tanabe, Hokkaido Univ., ref. 1). (2) Surface reaction rate of dehydration of alcohols by pulse surface reaction rate analysis (PSRA) and an emmisionless infrared diffuse reflectance spectrometer (EDR) (T. Hattori, K. Shirai and V. Murakami, Nagoya Univ., ref. 1 and 12). (3) Turnover frequency of dehydration of sec-butylalcohol as a function of strength of Lewis acid sites (K. Nakacho, J. Take and V. Voneda, Univ. of Tokyo, comment in 3rd symposium). (4) Optimum reaction condition for the formation of ethyl ether in the dehydration of ethanol by a full automatic computer-operated reaction system in laboratory (V. Tsuchida and H. Niiyama, Tokyo Inst. Tech., comment in 3rd symposium). (5) Adsorption of Ni, Cu and Pt ions on reference aluminas (H. Niiyama, T. Ogiwara, N. Suyama and E. Echigoya, Tokyo Inst. Tech., ref. 1 and 2nd symposium). (6) IR spectra of dissociatively adsorbed hydrogen on reference supported metal catalysts (V. Soma, Univ. of Tokyo, 2nd symposium). (7) Hydrogenation of 1,3-butadiene on reference supported metal catalysts suspended in acid solution (H. Kita and K. Shimazu, Hokkaido Univ., 2nd symposium and ref. 3). (8) Methanation of CO over Ni-La203 supported on reference aluminas and over reference supported metal catalysts (T. Inui, T. Miyake and Y. Takegami, Kyoto Univ., ref. 1 and 3). (9) Support effect in the hydrogenation of cyclopentadiene on supported nickel catalysts (A. Sannomiya, M. Yano and Y. Harano, Osaka City Univ., ref. 3 and 13).

784

(10) Temperature programmed reduction of nickel catalysts supported on reference a1uminas and thier catalytic behavior in the methanation of CO and CO 2 (Y. Nakagawa and S. Ogasawara, Yokohama Nat1. Univ., comment in 3rd symposi um). REFERENCES 1 Data on Reference Catalysts, Shokubai, 22(1980)115, H. Matsumoto, Shokubai, 22(1980)107. 2 Preprints of Symposium on Metal Surface Area II, Nagoya, June 19, 1981. 3 Preprints of 3rd Imnual Symposium on Reference Catalysts, Kyoto, Oct. 11,1981. 4 H. Matsumoto, Shokubai, 22(1980)410. 5 D.H. Everett, G.D. Parfitt, K.S.W. Sing and R. Wilson, J. Appl. Chem. Biotechno1., 24(1974)199. 6 M. Takahashi, Y. Iwasawa and S. Ogasawara, J. Cata1., 45(1976)15. 7 J. Take, T. Ueda and Y. Yoneda, Bull. Chem. Soc. Japan, 51(1978)1581. 8 J. Take, H. Matsumoto, S. Okada, H. Yamaguchi, K. Tsutsumi, H. Takahashi and Y. Yoneda, Shokubai, 23(1981 )344. Further details will be published. 9 K. Kunimori, T. Uchijima, M. Yamada, H. Matsumoto, T. Hattori and Y. ~1urakami. Appl. Catal., submitted. 10 K. Kunimori, T. Okouchi and T. Uchijima, Chem. Lett., (1980)1513. K. Kunimori, Y. Ikeda, T. Okouchi, N. Nojiri, M. Soma and T. Uchijima, Shokubai, 23(1981) 365. 11 N. Nojiri, Shokubai, 23(1981 )488. 12 T. Hattori, K. Shirai, M. Niwa and Y. Murakami, React. Kinet. Catal. Lett., 15(1980)193. 13 A. Sannomiya, T. Tashiro, M. Yano and Y. Harano, Shokubai, 24(1982)112. APPENDIX Institutions participating in the project of BET surface area of aluminas Tanabe's lab., Hokkaido Univ.; Okazaki's lab., Ibaragi Univ.; Central Res. Lab., Idemitsu Kosan Co.; Mr. Takagi, Tokyo Inst. Tech.; Ogasawara's lab., Yokohama Natl. Univ.; Kinuura lab., JGC Corporation; Murakami's lab., Nagoya Univ.; Inui's l ab. , Kyoto Univ.; Yoshida's lab., Kyoto Univ.; Tsuchiya's lab., Yamaguchi Univ.; and Kagawa's lab., Nagasaki Univ .. Participants in the project of metal surface area S. Yoshida (Kyoto Univ.), T. Murata (JGC Corp.), A. Furuta and M. Yamada (JGC Corp.), H. Arai and Y. Kibe (Kyushu Univ.), Y. Akai (Idemitsu Kosan Co.), T. Hattori and Y. Murakami (Nagoya Univ.), E. Kikuchi (Waseda Univ.), K. Aika and O. Kato (Tokyo Inst. Tech.), K. Kunimori, S. Matsui, Y. Ikeda, E. Yamaguchi and T. Uchijima (Univ. of Tsukuba), K. Iida and T. Imai U~itsubishi Heavy Ind. Co.), and those participating in the following project. Participants in the project of standardization of rapid measurement of metal surface area by CO-pulse method S. Nishiyama and H. Niiyama (Tokyo Inst. Tech.), T. Mori (Gov. Ind. Res. Inst., Nagoya), E. Yasui and F. Haga (Nippon Oil Co.), T. Nakata and T. Sakurai (Nippon Engelhard), N. Nojiri and K. Kurashige (Mitsubishi Petrochem. Co.), T. Inui, T. Miyake and Y. Takegami (Kyoto Univ.), and T. Suzuki (Asia Oil Co.).

785 DISCUSSION ZHAO JIUSHENG Could you tell something about the measurement of the acid amount of Y-AI203: 1) Did you use the titration method, and if so, why? 2) What carrier gas have you used for the TPD study. Is there any difference when you use another carrier gas? 3) In the infrared measurements, have you distinguished the Lewis acid sites from the Bronsted ones? Y. MURAKAMI: 1) I do not think that the titration method is suitable for measuring the acidity of alumina catalysts, because the indicator turns into acidic color only after the alumina is treated in vacuum at high temperature and the amount of n-butylamine is too sensitive to the pretreatment. Further, the change of color of the indicator can hardly be controlled. 2) In the TPD method, nitrogen was used as a carrier gas with an FID detector. Although no attempt has been made to examine the effect of the carrier gas, I believe that any inert gas will give the same results. 3) Of course,Lewis and Bronsted acid sites were distinguished. On alumina catalysts, only coordinatively adsorbed pyridine on Lewis acid sites was observed on the IR spectra. Therefore, Fig. 4 in the text shows the relationship for the Lewis acid sites. The relationship for the Bronsted acid sites has also been examined by using H-ZSM 5, on which only pyridinium ion (Bronsted acid sites) was observed. A linear relationship has been obtained between the amount of adsorbed ammonia by microcalorimetry and the amount of adsorbed pyridine (pyridinium ion) by IR method. (Ref. 8 in the text) . J.J.F. SCHOLTEN The CO-pulse method may also be used in hydrogen as a carrier gas (McKee's method). The advantage is that: a. strongly chemisorbed hydrogen, still present from the reduction pretreatment, has not to be desorbed at temperatures as high as 500°C. Many metals sinter very strongly at this temperature. b. Pulsing is performed in the reduction hydrogen stream, and for many noble metals,the reduction temperature may be chosen very low (100°C,for instance). Sintering will not disturb the results. The hypothesis on which the method is based is that CO kicks off the hydrogen from the surface. This asks for further fundamental studies for various metals. G.C. BOND I can confirm that the method of pulsing CO in a H2 stream works perfectly well for the routine determination of Pd dispersion. The method was developed by myself and my colleagues in the Johnson Matthey laboratories in the mid-1960's. The problem of using CO in an inert carrier gas is not only that of removing adsorbed H remaining from the reduction, but also that of using an extremely pure (especially, 02-free) gas stream: if this is not done, consistent results cannot be expected. Y. MURAKAMI: (To Prof. Scholten and Prof. Bond). The project of metal surface area possesses two subjects: the research for true metal surface area and the standardization of rapid determination of metal surface area for pratical purpose. One might prefer to start the second subject after the first one, but industrial researchers are not so patient. They must determine the metal surface area of catalysts which are presently used and are going to be used. Actually, they determine it by their own methods. As the initial step of the second subject, the standardization of the most popular method has been undertaken. The next step is the examination of the standardized method for the final goal. For such purpose, it is necessary to solve the problems which have been raised, to compare the method with others, and to examine the applicability of the method to various catalysts. At present, these are in progress, and the first subject (basic research) will be of a great help in this step. The effect of the purity of the carrier gas is one of the ~roblems raised. It has been reported that the purity of the carrier gas has o"ly a little effect, as shown in Table 1, although a few contradictory results have also been privately communicated. The effect seems to depend on the metal and support. This

786 will be a topic of the next meeting of the committee. The CO-pulse method in hydrogen as a carrier gas has also been examined. The results, shown in Table 1, are in good agreement with those in He as carrier gas. Kicked off hydrogen also was measured by using nitrogen as a carrier gas, but the amount did not coincide with that of adsorbed CO, as shown in Table 1. This result may be examined further in relation to the comparison with other methods. It has been pointed out in the committee that the reduction temperature appears too high. Some contradictory results have been reported on the effect of the reduction temperature. This also will be a topic of the next meeting, and lower reduction temperatures will be employed for a new series of catalysts. A new series of catalysts listed in Table 2 has been prepared and distributed for the comparison with other methods and for the examination of the applicability of the method. The committee is ready to supply them to the foreign countries, although the total amount prepared is limited. TABLE 1.

Effect of the carrier gas on CO chemisorption CO chemisorbed and H2 kicked off

Carrier gas

He (purified

Catalyst

a)

He (unpurified) a) H2 (purified b) N2 (purified

CO (ads) CO(ads) CO (ads) H2 (des)

c c c d

No 1

No 5

No 6

48

44

38

52

44

38

48

44

37

35

31

29

a, by silica gel trap at 77K; b, by oxytrap; c, in cm d, kicked off H2 in cm 3 H2/9-P t. TABLE 2. Number 10 11

12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

3

CO/g-Pt;

List of the new series of catalysts Mark JRC-A4-0.5Pt JRC-A4-0.5Pt JRC-A4-0.5Pt JRC-A4-5.0Pt JRC-A4-5.0Pt JRC-A4-0.5Rh JRC-S3-0.5Rh JRC-A4-0.5Ru JRC-S3-0.5Ru JRC-A4-0.5Pd JRC-S3-0.5Pd JRC-A4-30Ni JRC-A4-50Ni JRC-S3-30Ni JRC-S3-50Ni JRC-A4-5.0Ni JRC-S3-5.0Ni

(1.0) a (0.5)a (0.1) a (1.0) a (0.2)a (2.0)b

(2.0)b

Metal

Metal content

Pt Pt Pt Pt Pt Rh Rh Ru Ru Pd Pd Ni Ni Ni Ni Ni Ni

0.5 wt % 0.5 0.5 5.0 5.0 0.5 0.5 0.5 0.5 0.5 0.5 30 50 30 50 5.0 5.0

a, expected dispersion; b, second batch.

Support A1203 A1203 A1203 A1203 A1203 A1203 Si02 A1203 Si02 A1203 Si02 A1203 A1203 Si02 Si02 A1203 Si02