Fe3(CO)12 impregnated ZSM-5: Characterization and liquefaction activity

CoJtoids und Surfaces. 4 (1682) 33X-342 Elsevier Scientific Puj .lishir g Company. Amsterdam

-

Printed in The Ne(hertands

Fe,(CG),r IMPREGNATED ZSM-5: CLPARACXERIZATION LIQUEFACITION

ACTIVITY

331

AND

J.M. STENCBL*, J.R. DIEfIL, L.J. DOUGLAS and C.A. SPlTLBP Pittsburgh Energy

Technology

J.E. CRAWFORD

and (3-A. WELSON*

Virgin&z Comtnoncuealth $V.S.A.)

Center, P-0.

University.

(Rcccefved January 18.1982;

Box

Department

tO940,

Pittsburgh. PA 15236

of Chtimistry,

Rkhmotzd.

(U.S.A.)

VA 23284

aecp&d January 20.1982)

ABSTRACT Depositfon of Fe,(CO),,

an ZSXZ-5 is described far the synthesis of shapemzlentive, conversion catalysts. The wt.46 of iron is varied from 1.6 to 21,196. These Fe/Z!XM-5 catalysts sre characterized by surface sensitive and bulk experimental technfques;, Variation in thatsire of iron iocotporatlon and its chemical state are discussed relative to the tron loading. Rrduction and calcination studies are reported describing mowth of iron crystallites am? variation in Fe-zeolite fnteractlons as a tImction of treatment conditions- Activity ct3t~:for the synthesis gas-to-gasdine reacHon am repotted for representative catalyst& Variations in observed activity as a ftinctlon of catalyst pretreatment Bra also pre=nted, bifunctional

cod

TNTRODUCi’ICN

The ability to synthesize zeatite materials has Introduced new viewpoints and possibilities into hetercigeneous catalysis. Within Ehe area of coal liquefaction, the shape selectivity of zeotites offers a means by which selected

liquid products can be produced at high activity rates. For example, the conversion of 1 :I I&:CO synthesisgas over a bifunctional Fe/ZSM-5 catalyst can produce a liquid hydrocarbon product of which 95% is in the.&I=, f gasoline range with a research a+ne number as high as 94 [ 11. By combining ZSM-5 with both iron and cobalt, dramatic changes occur in the product distribution, and the water gas shift reaction is suppressed [21_ Such changes have been described in tennq of synergisticeffects, with the iron and cohak forming .aniron-cobalt alloy of retativ+y constant morphology during catalyst activation and tise. In addition to these effects, the activity and selectitiityof a catalyst foti the synthesisgas-to:gasolinereaction are expected to be

influenced by the method of incorporation of the metal into the

+&,&ors

to whoin &orrespond&&

0166~622~82~0~00~060~$02.7S

should be add&.

8 1982 BIsevier Scientific Publishing Company

zeolite support, the nature of the interaction between the metal and the support, the metal loading, and the particle size 13) _ Supported metal cataIysts have traditionally been prepared by impregnation techniques that involve treatment of a support with an aqueous solution of a metal salt followed by calcinatiotr [41. In the F’e/ZSM-5 system, the decomposition of the iron nitrate during calcination usually produces iron oxides of relatively large crystallite size, We report on the characterization and activity testing of Fe@%%5, which was metal-loaded using a metal carbonyl cluster, Fe3(CO) , I_ This technique was developed in an effort to produce highly dispersed metal ctusters on the zeolite support and, through heat treatment, to control the size of these clusters f5j. A series of Fe] ZSM-5 catalysts was prepared with iron concentrations varying from L-6 to 21.1 wt.%. Surface sensitive and bulk experimental techniques were applied to describe these catalysts in as-received, calcined, and reduced forms, Some preliminary mtcroreactor activity tests are presented, EXPERIMENTAL

The ZSM-fi support was prepared in the NH:-form according to a reported procedure (61; the H*-fcrm of ZSM-5 was obtained fr*>m the NH:-form by calcination in air at 360°C prior to use. The FelZSM-5 catalysts, of varying wt.% iron concentrations, were prepared from the H*-form of ZSM-5 and Fe3(CO),z (Alfa Ventror. Division)+ by using an extmction Wchnique with cyclohexanc as the solvent IS]. All samples were dried uttder reduced pressure at room temperature prier to use. The wt.% iron was determined spectrophotometrically [ 71. In ,rhe following secttans, the v&.% iron will be referred to as % Fe, e.g., a catalyst with 4.4 wt.% icon wiB be designated as 4.4% Fe. Citaructerizutian The powdered catalysts were pressed into 13-mm diameter wafers under 8000 gm[cm2 peessure; these wafers con&i tute the as-received catalysts discussed in the following sections. Cakination and reduction of the wafers were facilitated by use of a tubular furnace and a specially designed sampie probe; this probe is similar to that described by Patterson et al. (83, but it has a removable head to enable transfer bet-seen instruments that have different sampling geometries. Reduction experiments were performed at 300°C and 500% for 16 h with a Hz flow of 600 cm3/mfn. CaMnation of *Reference herein to any specific cammerckt pmduct. pcoC@s8,or sedce is to facilitate understanding and daes uaf nece~arity lmpty its e&a-meat or favoring by the United States De_3ertment of Energy,

333

these catalysts was performed in air ;~tsimilar temperatures and for the same time, X-ray photoelectron spectra (XPS) were acquired on a McPherson RSCA 36 Spectrometer equipped with a Mg anode (Mg Ka = 1253.6 eV). AR binding energies were corrected for charging by assuming the ubiquitous carbon Is band to be at 284.6 eV. The pressure in the XPS sample chamber during spectral acquisition was 6.5 X 10-I Pa, Secondary ion mass spectra (SIMS) and ion scattering spectra (ISS) were recordrrd on a 3M Model 525 SiMS/ISS spectrometer by spectrally averaging 256 scans over a 10 min period. Isotopically pure 4He and ‘*He (Monsanto Research Corp.) were used as primary beam gzxs. The base pressure of the SIMS/KS instrument was 1.3 X lo1 Pa; spectra were acquired at 5.3 X lo- Pa 4He or 1°Ne pressure with 2keV primary ion energy. The K-l-raydiffraction data were collected on a Rigaku horizontal goniometet using a copper X-ray tube operated at 41_lkV and 35 mA, All measurements were made with a one-degree divergent slit, 0.3-mm receiving slit, receiving graphite monochromator, and scintillation counter with pulse height discrimination. All samples were packed into a glass holder with an opening 16 X 8 X 0.5 mm. No binder or adhesive was needed. Actiuity euutuatton The catalysts were pressed into l/S inch diameter pellets, reduced under Hi at 360 psig and 450% for 24 h, and then treated with I:1 synthesis gas at 300 psig aud 2BO”C for 24 h. Catalytic data were obtained by using a Chemical Data Systems Inc. Series 810 Continuous Flow-High Pressure mfcroreactor system. Conditions employed were 360 psig pressure of I:1 synthesis gas, GHSV lJlO0 h” and a reactor temperature of 300°C. The products abtained over a 48 h period from the microreactor were analyzd in two fractions_ The gaseous products, C,-C4 hydrocarbons, were analyzed by US@ of the gas chromatograph, which is an integral part of the microreactor. The liquid pi-oducts were collected in an iceeoobd trap, which was periodically drained. The oii layer was separated from the aqueou, layer, weighed, and analyzed. Analysis of the oil layer was accomplished by FIA chromatagraphy and by simulated distillation. RESULTS

The XPS spectra of the Fe 2p bands for ss-received and Ar’ sputtered 1.6, 4.4,7.9, and 21.1% Fe/ZSM-5 cataSysts are shown in Fig. 1 (a) and (b), respectively. The inknsity maxima for the Fe 2pS, spectra are at 710.6 f 0.2 eV for the as-received samples and 710.1 f 0.3 eV after Ar* sputtering. This difference may be associated with reduction effects of the Ar* beam, but it was also the result of difficulties in selecting an accmte peak position for the asymmetrical Fe baud. A 2~s~-2p~~ splitting of 13.4 f 0.06 eV is

334

observed for both of these sample sets. Peak shapes change with Ar* sputtering; the most obvious changes are found in 4.4% Fe/ZSM-5. Here a weak band at 719 eV for the as-received sample is absent after sputtering; a pro; minent shoulder near 7x5 eV appears after sputtering that has caused band broadening, and a very weak shoulder clearly evident in an expanded energy scafe occurs at 707 eV, These changes are also evident for the 1.6% Fc catalyst but are not as prominent. At 7.9 and 21.1% Fe, very small differences are observed. The effects of Ar* sputtiring are more noticeable in the 0 Is specter of the same cata$ysts, as shown in Fig. 2. Doublet structure is evident in spectra OP the as-received samples with binding energies of 532.1 * 0.2 eV and 529,9 -+ 0.2 eV. The XPS spectra of ZSM-5 and FeiOs reference compounds show that the 632 eV band is associated with the oxygen of ZSM-5 (O,), while the 536 eV band is due to oxygen of iron oxide (0~~). Argon sputtering &es not change the positions of the bands but daes after their relative intensities. For example, sputtering of the 1.6 and 4.4% Fe samples enhances the 0, peak refative to that of Ope, while the opposite intensity changes occur for the 7.9 and 21.1% Fe samples. In Fig. 3, ISS spectra of as-received, 300°C catcined, and 300°C reduced 4.4% E’elZSM-5 catalysts are shown. The oxygen peak in Fig. 3 Is at ElEo of 0.41, siticon is at 0.69, and iron, 0.79, Another major peak at 0.67 is asscrciated with chlorine. This contamination is the result of catalyst preparatiua techniques; and ib concentration, as determined by X-ray fbiorescence, is less than 02%. Reduction and c&ination decrease the chlorine peak intensity. The ISS sp~tral resufts of 4.4% Fe/ZSM-6 reduced at 500°C and calcined at 450°C are shown in Fig. 4. These spectra are similar to those in Fig. 3; however, chlorine is no longer observed, The 188 spectra are the average of 266 scans over approxknately 10 min with a total ‘He aputter time of 20 min at the end of the data acquisition. This acqubition mode was fotlowed after extensive testing in which it was found that for ISS analyses of zeolite catiysts, a 10-20 min scan period

yielded the most reproducible elemental surface concentrations, With an estimated IHe profiling rati of 0.6 AImin, the average samphng depth during

the 10 to 20 min spectral acquisition is approximately 7.5 A. At this depth the influence of carbon and other nonstoichiometric contamination is minimized, while measurement of elemental surface constituents is still possible. The primary reason for this repeatability is believed to he associated with the removal of unwanted contaminants on the external crystallite surface of ZSM-5 that arise from atmospheric exposure. Madey ct al. 191 have shown that atmospheric carbon contiination is much greater on zeolites than on AhO or SiO,. In the present study, an increase in iron concentration should relatively increase the carbon intensities in the XPS spectra if the carbon is associated primarily with the iron; Such an effect is not obsenred. Aho, removal of carbon by argon sputtering shouid uffe& ken intensities rnoie than silicon intensities if carbon is associated with iron, In fact; ZZieopposite

335

730

t

720

1

710 y t&a elNOlNG ENERGY.ev

7;o

,

710

k

pig. I. XPS ~ppectreof Fe 2p bands of Fel’ESEI-5 for as-received CR)and Ar’ sputlered (b) catatysh.

I

8

Fig.

2. Xl?S spectra

catalyab;

l f 0 ts bands of Fe/ZSM-5

for as-received (a) and Ar’ sputtered(b)

Pfg. 3. IS3 spectra of 4.4% FelZSM-6: (a) as-received;(b) caMned (c) reduced at 300-C/16 h in H,. Fig. 4. ESSspecrra of 4.4% Fe/ZSM-8: &WC/l6 h in air,

(a) reduced at SOO’CllG

at ~lO~Cll6

h in air;

h in G,;(b) catcined at

is found. Hence, carbon observed in XPS analyses of as-received Fe/ZSM-5 15 believed to be primarily associated with the ZSEn-6 and not the Iron. This carbon could con&t of that external to the ZSM-5 crystalfltes, a consequence of atmospheric exposure, and that IntenA to the ZSM-6, a possible by-product of catalyst synthesis. The XPS measurements do not &sting&h between these carbon forms. However, in XPS analyses of ZSMd by Itself, a 3S% decrease in the CjSi ratio is found after ion bombarchncnt. Similar changes are found for Fe/ZSM-5, Thus, a means to qualitatively descrI 31 t5c effect of iron on carbon concentrations may be to weight the observed C/:3 ratios with respect to iron concentrations. If this is done, the resulting c/St ratios are consistentty smaller as the iron concentration is increased; for the 21.1% Fe catalyst the ClSi ratio is appsoximateSy160% amaik than f-w tke 1.6% Fe catalyst. Such a difference indicates that the carbon adsorpticm si*xs are blocked by iron species. A graph which shows the Fe/S’i ratios for the 1.6 to 21.1% Fe as-recekved catalysts is shown in Fig. 5. Thtlse ratios were obtain& by measurementof the iron and silicon peak heights from ISS and of the peak areas from XPS. By applying a linear regression least squares fitting technique to t.hedr& fur the 1.6 +a 7.9% Fe catalysts, the correlation coefficient for a linear fit was found to be 0.98 for the XPS data and 6.99 for the IS@ .+ta, The slope of the h&ax fit for XPS is’O’,94 tid for ISS 531.92. The FejSi mtio, by e&apot&ion, is zero for the lSS and XPS data at iron loadings of 0.435%mtd 0.8S%, respectively.

337

Fig. 5. Comparison of ISS and XPS FelSi ratios far the asmceived Fe123hS-5 catalyab: (0) IS& We sputter; (0) XPS, ‘*AC sputterIri Fig. 6, the linear fits to the ISS data for 1.6 to IS% Fe loadings for asreceived, 300°C cakined, and 300°C redttcedcatalysts axe shown. The correIatfon coefficient for a linear fit is 0.995 for both the caMner1 and the reduced catalysts. The slope of the Fe/% ratio versus % Fe for the calcfned es is &85 with a lI3% Fe intercept when Fe/S is zero and for the I

I

I

I

o As receimved

t4 - - m Catclnsd,3ClO*C a Reduced. 3OWC

866

2

4

6

8

0

LA

2

4

6

Fig. 6. Comparison

of linear fits to ES data for 1.6 to 7.9% Fe toadings.

Fig_ 7. Comparison

at the f6S data fcr (0) as received, (m) 460%

reduced catalysts.

..

6

10

12

14

cakined, and (A) 600°C

338

reduced catalyst the slope is 0.74 with a 0.81% Fe intercept when Fe/Si is zero. Fig. 7 compares the ISS rcs~ltts for 506*C reduced, 450-C calcined, and as-received catalysts. A linear lit of the data for the reduced 1.6 to 7.9% Fe samples gives a correlation coefficient of 0.98. However, the data for the calcined catalysts do not follow such a linear dependence, Preliminary catalytic activity data show that both as-received and 5OO*C calcined forms of a 16.0B FejZSM-5 cat&y& function as effective catalysts for the hydragenation of carbon monoxide. However, the percent conversion of Cr3 and Hz, and the product distributions are different for the two catalysts (see Table 1).

Comparison of the XPS data for the as-received and sputtered catalysts in Figs. 1 and 2 provides a more detailed analysis of the Fe/ZSM-S system than is po&bIe if no sputtering had been done. The distinct band at 719 eV and the Fe 2~3~ peak shape in Fig, 1 for the 4.4% FE, catalyst indicate the preTABLE

1

Activity data for 16.0%

FeIzSM-S

C~~YS~S* --..__-_. As

Conve*abn 4%) CO H,

22 39

Total resctm effuent distribution (wt.%) co

7s

&,, LFO

t6

H/C

7

Hydrocarbon CH,

product dfstribMlon

(wt.%)

2

c: Liquid

49

28

19 9 32

17 11 4 40

38 36 26

9 60 32

92

93

0

LiquU poduct Aromatics Otefins Saturates

analysis

% boiling in the gasoline range (< 204°C) *Conditions

received

were 3aO*C, 309 psig of 1 :l synthesis gas with GHSV

1000 hi*.

339

sence of Fe3’ [lo. 111. The 719 eV band is al-:0 present in the 1.6 and 7.9% Ft loaded catalysts but with decreased intensity; the bandshapes for these two catalysts are slightIy different than for the 4.4% Fe catalyst. Argon ion sputtering produces the greatest change in band shape for the 4.4% Fe catalyst by increasing band intensity near 715 eV and removing the 719 eV band. This indicates that the reduction of Fe” to Fe’+ is a result of sputtering, while the broadening at 707 eV on the low energy side of the Fe 2p3@ peak shows that iron metal hris been formed. Broadening of the 707 and 715 eV bands is almost unnoticeable for the 1.6% Fe catalyst and completely absent in the 7.9% and 21.1% samples. In addition to depth profiling, Ar* sputtering can be expected to cause reduction of Fe’* to Fe2+ and pussibIy Fe*, and of Fe*+ to Fe O. The difficulty with which the iron in the 1.6% Fe samptes was reduced relative to the 4.4% samples is suggestive of a strong Fe-support interaction in the 1.6% Fe catalyst, Such an enhanced interactton can be anticipated where the iron consists of small clusters that are tightiy bound onto available zeolite adsorption sites. In addition, a “masking effect” due to overlying iran and iron campaundrr would be minimized at the fewer iron concentrations, thereby allowing observation of Fesupport interactions. As the ion concentration Zs increased, sites within or on the zeolite would become saturated, thereby decreasing Fe-zeolite interactions. LIecreased interactive effects could allow an increase in the size of the metal ctusters to occur and a change in the stable chemical state of the iron. Such reasoning, along with the XPS Fe Zp,, bandshapes, indicate the following sequence of iron oxidation strites in the as-received samples: at 1.6% Fe, nearly equal concentrations of Fe3 r and Fe2+ exist, at 4.4% Fe, the Fe’* concentratiou is increased relative to Pc2* and thereafter, the concentration of Fe3* increases relative to Fe**. Tile Qp, band of the as-received 4.4% Fe catalyst is approximately four timer; as intense as the 0~~ band of the 1.6% Fe sample, This is in constrast to an iron concentration ratio of 2.8 between the 4.4% and 1.6% Fe samples. Also, Ar* sputtering removes approximately S0% of the 0~~ in the 4.4% Fe sample but only 16% in the 1.6% catalyst. These results amplify the forcgoing discussion with respect to differences of the Fe-zeoIite interaction in these two catalysts. Furthermore, these results indicate that some iror. in the 1.6% Fe catalyst is strongly interacting and is associated with the zeolite in other than the weakly interacting oxidized surface species. The strongly interacting species is expected to be present as the iron content is increased, but the extent of iron oxide formation masks its observation. The Op,/Oz ratios are approximately equal for 13.8 and 21.1% Fe catalysts before and after Ar’ sputtering. This provides evidence for a decreased relative iron dispenGon at higher Fe loadings. X-ray diffractian data for the as-received catalysts, as shown in Table 2, confirm this conctusion by showing the presence of iion oxide compounds above 7.9% Fe concentrations. Below 7.9% Fe, no iron compounds are observe-3. kt 7.9% Fe, the X-ray data with respect to iron compound formation is

TABLE

2

X-ray diffraction data for Fe1ZSM-5 Major component ___-ZSbi-5 Fe@, ancIior v-Fe@, ZSBI-4 Fe,O, ant’lar y -F_e,O, ZSM -5

Percent Fe 21.1 13.8 7.9 5.8 a.4 1.6

-___

ZSBI-5 zsXI-5 ZSM-5 _______--_-_-___-__I__-_I-____-__-

--__Minor component

--

Fe&l, andlar y-Fe@,

irwonctusive, showing baseiine increases where these peaks should occur. The inabitity to identify iron compounds below 7.9% Fe could be caused by ttvo factors. First, the size of the iron crystallites could be cxtremeSy small, causing severe Line broadening. Here, iPon would contribute to the general background of the X-ray measurements and no discrete bands would be observed. Second, the iron could exist as relativety large amorphous oxi& particles, It is d%ficult to distinguish bet\vr?enthese two possibilities, but it k believed that the Impregnation method reported here favors formation uf very small metal clusters. Such an interpretation is justified by realizing that the Fe/PA ratios, as obtained from ISS and XPS, in these Fe,(C0)12 impregnated catalysts are IO+0 times greater than those found for Fe/ZSM-5 catalysts that were impregnated by iron nitrate incipient wetness techniques [ 12 J . If the iran partictos were large (- 150~3WA) in the Fe&O),, impregnated catalysts, the Fe/Si ratios tvould be expected to be similar to those that are loaded by metal nitrate impregnation, The Fe/Si ratios plotted in Fig. 6 show that as the iron loading is increased tn 7.9%, the coverage of the XSM-5 increases at a rate proportional to the toading, This indicates that the size of the iron particles for the l-6--7.9% Fe catalystg is approximately con&ant, Above 7.9% Fe, the decrease in the Fe/Elisfope suggests the formation of Iarger iran crystallitcs, X-ray data in Table 2 con&m such an interpretation., The difference in slope between the ISS and XPS data in rig. 5 is believed to resuft from the difference in sampling depth of these two techniques, ‘Lhe Fe/Si ratios from XPS analysis would be decreased because of a larger sampIing depth of Si 2p Actrons (- 103 eV) versus Fe Zp (- 710 eV). In addition, detiction sensitivity of iron relative to that of silicon may introduce differences in FelSi ratios for ISS and XPS data. At greater than 7.9% Fe Loadings, the FelSi slopes from the two techniques are equal; such behavior is expected as larger three-dimensional ccystallites are formed, which do not cover the ZSM-5 as much as they expand away from it, If the iron is deposited only on top of the support, it is expected that as the i;ton concentration approaches zera,, the FelSi ratio should aho tend to

341

zero. However, Fig. 5 shows Fe/Si ratios of zero when iron concentrations are in the region of 0.66 to 0.85%. Such behavior could be the result of two factors. First, a screening effect c:f the adsorbed species on the elements analyzed could case discrepancies in concentrations aa determined by XPS and ISS. This factor is expected lo be minimized by the reliance on data that were accumulated after sputter removal of such adsorbed species. Second, some of the iron could be shielded from observation because of its location within the inner cavities of the zeolite. Such shielding has been reported for carbon in ZSM-5 [ 13 1. If one iron atom per unit cell is incorporated into the zeolite structure or adsorbed within the ZSM-5 cavities, it will constitute approximately 1% by weight of the material_ The XPS data for the 1.6% Fe catalyst would be expected to be strongly infiuenced by this incorporated iron, and as its concentration is increased, the results of interactive effects would be less observable. The iacation of this incorporated iron is not known but more studies are in progress that may identify iron sites in ZSM-5 as has been done for Y zeolits [ 14,15] The Fe/Si ratios for 300°C reduced or calcined catalysts are approximately equal and three times smaller than the as-received catalysts (Fig. 6). This result would be anticfpatcd if the iron crystallite size was solely dependent upon heat treatment of the catalyst. ffowever, Fe/Si ratios for catalysts with 1.6 to 7.9% Fe after 560pC reduction and far the 1.6 to 4_4% Fe samples after 450°C calcination (Pig+ 7) are approximately equal to those found for the 300°C treated samples. Also, above 4.4% Fe, the Fe/Si ratios for catalysts calcined at 450°C are two to four times smaller than those for the rcduced samples. Large Fe--ZSM-5 interactive mecha:?kms, described previousiy for the 1.6% and 4.4% Fe, woutd be expected to decrease the influence of heat treatment on particle growth, Hence, Fe/Si ratios below 4.4% Fe for the 300*, 450*, and HlO”C treated catalysts show that by 3QO*C, the weakly interacting iron has grown to a particie size that is not further affected by heat treatment up to 5OO’C. By 7.9% Fe, the proportion of weakly intcracting iron has grown to a value that permits differences to occur as a function of treatment temperatures and gases. it should be noted from F&L 6 and 7 that the Fe/Si ratios for the treated samples reach zero when the wt.% Fe is similar to that for the as-received samples. This may indicate that the strongly interacting iron is still present after reduction and calcination. l

CONCLUSIONS

In general, ISS and XPS measurements on supported metal catalysts are not able to distinguish between metal species with strong or weak support interactions, However, by investigating a series of Fe/ZSM-5 catalysts prepared from Fe,(CO)i% using an extraction technique -,vith iron Ioadings of 1.6 to 21.1% Fe, we have been abh, by determination of Fe/Si ratios for each catalyst as a function of pretreatment conditions, to distinguish between these two types of species. It is concluded that each catalyst consists of a

342

small amount of iron (-0.8%) ljresent as a species, possibly in a non-oxide form, that strongly i_nteracbwith the support; and the reniahder of ths iron is a highly dispersed, weakly-interacting iron oxide kurfam spwies. It fs suggested that the strongly interacting iron may be incorporated into the pores

of the zeolite. Heat treatment up to 500°C results in an increase in Barticte size of the surface iron oxide, alt’nough the strongly interacting iron remains in the pores of the zeoIite. The activity of a catalyst for the synthesis gas-to-gasoline reaction is dependent upon its pretreatment; for a 16.0% Fe catalyst, both percent conversion nnd product distribution are different for as-receivedand cakined (SOO”C)sarirples. This difference in behavior may be associated with the difference in the physical and chemical properties of the weakly interaci;ing surface iron oxide species. More cstatytic data is needed for FeS(C0),a imprcgnated FejZSM-5 cat&y& in a&r to more completely correIatetheir physical characteri&& and pretreatment with the efffciency and selectivity ior the conueraion of synthesis gas to gasoline.

ACKNOWLBDGBMENTS

The authors wish to thank Dr. V.U.S. Rao of the Pittsburgh Energy Technology Center for the microreactor testing of the Fe/ZSM-5 catalyst. Part of this work was supported by D.O.E. Contract No, DE-ACZZ8OPC30055 and DOE Grant DE-FG22-80PC36228. REFERENCES 1

f 4 6

6 7 a 9 10 11 12 13 14 16

V.U.8. Rzto, RJ. Gormley, H.W. Pennline, L.C. Schneider and R.T. ahermeycr, Preprints, ACS Fuel Chemistry Div. Symp. 25 (1980) 119. V.US. Rae and RJ. Gormley, Hydrocarbon Processlag, 69 (11) (1980) 139. H,H. Niis and P.A. Jacobs, J. Catal. 66 (1980) 328. J.R. Anderson, ~~SC~uctu~of MetallEe Catatyylt,”Appendix 11,Academtc Preq London, 1976. O-A- Bfelsan,&l% Crawford. KJ_ Mbadcam, F.R. Brown and LE. Ufakowzky, 31st SE- Regional Meethg of the A,C.8., Roartoke, VA. 197% RJ. Argauer

and GSX. ILandoft, US.

A-O. Hill et at (Iron Suhcammittee 103 (1978)

391,

Patent 3=JW2,88cl tl972). of the Anafyticaf Cfethods Committee),

AnaSyst

D.I% I&y&n and D+M, Hercufw, J. Xthys+Chem. 80 (1976) 1700. T.E. Madey, C.D. Wqner and A. Joshi, J.,ELctrqn Spectro-sc. Relat, Phenom., 10 (1971) 359, N.S+:McInlJire and D-G. Zetatuk, AnaL t&m.. 49 (1977) 1521. C-R. B,ndt>. Surf, Sci., 66 (1977) 681, Y.f& Sterrwl, F.R, Brawn, LE. Makoiaky, S.S_ PoUack, Ld. Douglas and V.U.S. Rao, Pittsburgh Catafy& Stacfety Meeting, May 28;1980. S.L. Sutb, Q.D. Stucky and RJJ.BIattaer, J- Cat+&, 65 (1980) 174, W.N. UeIgs+ R.L_ &rt.en and M,, Baud*, J. Phys. C&IU., 73 (lS69) &970. R.L. aartea. W.N. Deland M. mUdati,‘Jxdd., 18 (1970) 90. T.A. PatWson, J.C. Cmer,