Highly dispersed iron-based catalysts are being examined for the initial stage of direct coal liquefaction. Ultrafine (< 10-nm) particles are produced by a variety of methods. Mossbauer spectroscopy, magnetometry, XAFS, electron microscopy, XRD line broadening, and BET surface area measurement are used to estimate the particle size of the catalyst precursor and, in some instances, of the phases found consequent to the reaction process. With Mossbauer and magnetization techniques, data have to be obtained over a range of temperatures, usually from 4 to 300 K. In addition, obtaining the particle size by Mossbauer spectroscopy requires a knowledge of the magnetic anisotropy energy. Far some XRD lines, the broadening is a consequence of the presence of fault planes rather than crystallite size. An examination of the Fe-S phase diagram shows that the phases found at room temperature could be different from those that ace present under liquefaction conditions. The utility of the characterization techniques will be evaluated, and comparative results that are available will be presented. In situ characterization of catalysts under simulated liquefaction conditions is required.

The hydrogenolysis of methyl formate to methanol was studied in a liquid-phase reactor using a heterogeneous copper catalyst. This reaction is part of a process to produce methanol from synthesis gas starting with the carbonylation of methanol to methyl formate. Raney copper was compared with copper-chromite for hydrogenolysis activity at 110 to 160°C. The inhibition of the hydrogenolysis reaction by carbon monoxide was found to be lower at higher temperatures. A rate equation was derived to include this temperature dependence. Also, carbon monoxide made by a side reaction, the decarbonylation of methyl formate, was carefully measured and shown to account for only 1 to 2% of the total methanol produced at these temperatures.

The slurry-phase reactor system is of interest in Fischer-Tropsch synthesis owing to the ability of the reactor system to efficiently remove the heat produced by the exothermic reaction. Iron-based catalysts are active for Fischer-Tropsch synthesis and for the water-gas shift reaction, and, in addition, are inexpensive. Hence, they have been examined in slurry-phase Fischer-Tropsch synthesis with CO-rich synthesis gas. The role of promoters, carbide phases, and oxide phases in iron-based catalysts is not well understood. The article reviews current knowledge of iron-based catalysts with reference to their application in slurry-phase Fischer-Tropsch synthesis. Areas of investigation requiring further research are identified.

A systematic temperature-programmed desorption (TPD) study of Mn-Fe catalysts was conducted. Hydrogen chemisorption on Mn-Fe catalysts is a highly activated process. Fe, MnO and MnFe2O4 related desorption spectra have been assigned. Hydrogen does adsorb on the spinel phase (MnFe2O4) in the form of activated adsorption. Carbon monoxide does not adsorb on the spinel phase. The results suggest that the spinel phase alone may not be an active phase for syngas conversion.

To examine the relation between catalytic and magnetic properties, the zero-field NMR spectra and hysteresis loops of cobalt supported on silica, alumina, magnesia, titania, and ZSM-5 with and without the promoter thoria were investigated. Cobalt was incorporated on the support by simple physical admixture of precipitated cobalt and support, and by aqueous impregnation technique. Our studies indicate that the particle sizes are consistently lower in the presence of thoria. Of all the catalysts examined, the Co/Th/TiO2 catalyst exhibits a high saturation magnetization value—about 20% higher than pure cobalt. In addition, the NMR spectrum of the aqueous impregnation Co/TiO2 catalyst is distinctly different from the rest. All the NMR lines are shifted to a higher frequency by about 4 MHz. These two features—enhancement of the magnetic moment of cobalt atoms and increases in the hyperfine field at the Co nucleus—clearly indicate that there occurs strong metal-support interaction between cobalt and titania support. The higher hydrocarbon yields observed by the earlier investigators with Co/TiO2 catalysts might be related to this phenomenon.

ChemInformVolume 21, Issue 36 Reviews ChemInform Abstract: Catalysts for Fischer-Tropsch R. D. SRIVASTAVA, R. D. SRIVASTAVA Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this authorV. U. S. RAO, V. U. S. RAO Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this authorG. CINQUEGRANE, G. CINQUEGRANE Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this authorG. J. STIEGEL, G. J. STIEGEL Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this author R. D. SRIVASTAVA, R. D. SRIVASTAVA Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this authorV. U. S. RAO, V. U. S. RAO Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this authorG. CINQUEGRANE, G. CINQUEGRANE Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this authorG. J. STIEGEL, G. J. STIEGEL Energy Technol. Cent., Pittsburgh, PA, USASearch for more papers by this author First published: September 4, 1990 https://doi.org/10.1002/chin.199036353Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue36September 4, 1990 RelatedInformation

The mechanism of synthesis gas conversion over cobalt-ZSM-5 catalysts to gasoline-range hydrocarbons has been examined. A correlation exists between the methane yield and the percentage aromatics in the liquid hydrocarbon product. This could be due to heat transfer effects or to the hydrogenolysis of propane and butane over cobalt, leading to the formation of additional methane. The formation of additional alkanes (propane and butane) is known to accompany the aromatization process. The percentage of methane made by the bifunctional catalyst 4.2% CoSiO2 + ZSM-5 was 1.7 times that made by the CoSiOm2 catalyst with a feed of H2CO = 1 at 280 °C, 21 atm, and WHSV = 0.77. An attempt was made to inhibit secondary hydrogenolysis reactions by the addition of copper to the cobalt catalyst. Under similar process conditions, this provided a very small help in keeping down the increase in percentage of methane upon the addition of ZSM-5. Addition of 5 and 10% propane to the synthesis gas showed no additional methane made by hydrogenolysis. If indeed some of the methane produced over cobalt-ZSM-5 catalysts is coming from hydrogenolysis of light alkanes, it is a small amount.

The Co-ZSM-5 and Co-ThO2-ZSM-5 catalysts are a particularly promising group of bifunctional zeolite catalysts used for the conversion of synthesis gas to gasoline-range hydrocarbons. Catalytic properties of these materials, such as activity and selectivity, depend upon the amount of the cobalt on the medium-pore zeolite ZSM-5, as well as upon the presence of promoters such as ThO2. These studies were undertaken to ascertain the effect of thoria upon the magnetic and structural nature of these catalysts. Zero-field nuclear magnetic resonance measurements have been made on a series of zeolite cobalt and cobalt-thoria catalysts with three different concentrations of Co (3, 6, and 9 wt. %). The catalysts were prepared by making physical admixtures of precipitated cobalt, or cobalt-thoria, and ZSM-5. The amount of thoria introduced ranged from 0.5 to 1.5 wt. %. After reduction of the catalyst samples, the normal metallic cobalt resonance line at 213.0 MHz (fcc) and the fault lines at 215.5 and 218.6 MHz were observed. In the unpromoted catalysts, a line at 210.7 MHz, which is lower than the fcc line frequency, and another line at 221.6 MHz, which is higher than the hcp line frequency, were observed. When the promoter thoria was added, there was a systematic absence of the hcp line in the unused catalyst. Previous catalytic tests had shown that small amounts of the promoter thoria (0.4 wt. %) significantly increase the liquid hydrocarbon yields. The change in catalytic behavior can be related to the changes in crystallite species and crystallite size.

The mechanism of synthesis gas conversion over cobalt-ZSM-5 catalysts to gasoline range hydrocarbons has been examined. There is a correlation between the methane yield and the percent aromatics in the liquid hydrocarbon product. This can be traced through the formation of additional alkanes (C/sub 3/H/sub 8/ and C/sub 4/H/sub 10/) accompanying the aromatization process. The alkanes undergo hydrogenolysis over cobalt leading to the formation of additional methane. The bifunctional catalysts 4.2% Co/SiO/sub 2/ + ZSM-5 made 1.7 times as much methane as Co/SiO/sub 2/ with a feed of H/sub 2//CO = 1 at 280/sup 0/C, 21 atm, and WHSV = 0.77. Under similar process conditions, 6.3% Co, 0.05% Cu/SiO/sub 2/ + ZSM-5 made nearly the same amount of methane as 6.3% Co, 0.05% Cu/SiO/sub 2/. Thus the addition of Cu to Co lowered the additional methane formation by reducing the rate of hydrogenolysis. C/sub 5+/ yield with the bifunctional catalyst increased from 72% to 76% upon the addition of Cu.

Molecular sieve aluminosilicates, such as ZSM-5 and mordenite, when impregnated with highly dispersed Fe, yield catalysts for the selective conversion of coal-derived syngas (CO+H2) to liquid hydrocarbon fuels. Fe performs the primary Fischer-Tropsch (FT) syngas to yield light olefins which are converted by the acidic (H+) and shape-selective function of the zeolite to high octane gasoline components. The physical aspects of the Fe-mordenite interaction studied by magnetic measurements, Mössbauer, and IR spectroscopy are reported and correlations with the catalytic properties are drawn. Mordenite samples with [SiO2/Al2O3] ratio in the range 12 – 60 were impregnated with 15 wt. % Fe using Fe3(CO)12; decarbonylation yielded superparamagmetic dispersions of γ-Fe2O3, in the range 1.4–5.0 nm; the smallest particles were obtained for a ratio=17. Hydrogen chemisorption also revealed a similar trend in Fe dispersions. No samples, other than the one with a ratio=60 and containing the largest particles could be carbided under usual conditions. The acidity of the mordenite and the aromatics fraction in liquid hydrocarbons from syngas conversion also showed maxima at a ratio=17. The presence of a strong metal-support interaction between Fe and mordenite was thus influenced by the varying ratios in the mordenite in a manner that paralleled the acidity and catalytic activity.

In this study it has been demonstrated that magnetic and chemisorptive techniques can be used to characterize metal speciation in catalysts such as Co/ZSM-5. In particular, the amounts of ion-exchanged cobalt and cobalt external to the zeolite can be estimated. These measurements enable one to intepret the catalytic activity and selectivity of the catalyst. In our attempts to introduce cobalt in cationic form in ZSM-5 we have used a temperature of 90/sup 0/C for exchange with aqueous cobalt nitrate solution. It appears that 0.9 wt % Co can be introduced into ZSM-5 of SiO/sub 2//Al/sub 2/O/sub 3/ = 38 under these circumstances. Co/ZSM-5 samples that were prepared by impregnation at room temperature with cobalt nitrate solution, showed approximately 2.2 wt % Co to be in a form not reducible to metallic cobalt. In earlier work the Co/ZSM-5 samples were subsequently washed with water to yield samples that contained 1.4 to 1.7 wt % Co. It is hence possible that exchange at temperatures lower than 90/sup 0/C would yield samples containing more than 0.9 wt % Co in ion-exchanged form. It is shown in this study that Co/sup 2 +//ZSM-5 can be back-exchanged and reduced to yield metallic cobalt supported onmore » H-ZSM-5. Chemisorption measurements are currently being carried out to determine the degree of dispersion of such samples. The back-exchanged samples are catalytically active in synthesis gas conversion. The method of back-exchange should be generally applicable for preparing metal-zeolite catalysts where it is desirable to free the zeolite of metal cations in order to restore the acidity to its original strength, and to have the metal on the exterior of the zeolite crystallites in a highly dispersed, catalytically active form. 14 refs., 2 figs., 3 tabs.« less

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTZeolite-supported cobalt catalysts for the conversion of synthesis gas to hydrocarbon productsAbolghasem Shamsi, V. Udaya S. Rao, Robert J. Gormley, Richard T. Obermyer, Richard R. Schehl, and John M. StencelCite this: Ind. Eng. Chem. Prod. Res. Dev. 1984, 23, 4, 513–519Publication Date (Print):December 1, 1984Publication History Published online1 May 2002Published inissue 1 December 1984https://pubs.acs.org/doi/10.1021/i300016a001https://doi.org/10.1021/i300016a001research-articleACS PublicationsRequest reuse permissionsArticle Views275Altmetric-Citations26LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Iron-impregnated medium pore zeolite ZSM-5 (pore opening of 5.5 Å) is an efficient catalyst for the conversion of synthesis gas (CO+H2) to high octane gasoline. Activity and selectivity of the ZSM-5 (Fe) depends upon the manner in which Fe is impregnated on ZSM-5. Magnetic and Mössbauer studies were conducted on catalysts prepared by two methods: (a) ferric nitrate impregnation and (b) carbonyl Fe3(CO)12 impregnation on the zeolite. These studies were conducted for various stages of preparation and after use of the catalysts. The carbonyl impregnated sample in the as-prepared form contained ultrafine γ-Fe2O3 of d = 60–66 Å, as evidenced by superparamagnetic behavior seen in magnetic and Mössbauer studies. In contrast, the as-prepared, nitrate impregnated sample showed α-Fe2O3 of approximate particle size of 100 Å. Both samples were reduced to about 80% metallic Fe in flowing H2. On exposure to synthesis gas, the carbonyl impregnated sample yielded a substantial amount of Fe3O4 in addition to χ carbide, wheres the nitrate impregnated sample exhibited ε, χ, and ϑ carbides. The steady catalytic activity and selectivity of the carbonyl impregnated sample can be related to the ultrafine iron dispersions leading to the observed phases in the used catalyst.

AIChE JournalVolume 28, Issue 5 p. 847-851 R & Note Reaction rate oscillations during Fischer-Tropsch synthesis on Fe-precipitated Nu-1 zeolite-type catalysts T. T. Tsotsis, T. T. Tsotsis Department of Chemical Engineering, University of Southern, California, Los Angeles, CA 90007Search for more papers by this authorV. U. S. Rao, V. U. S. Rao Pittsburgh Energy Technology Center, Pittsburgh, PA 15236Search for more papers by this authorL. M. Polinski, L. M. Polinski Pittsburgh Energy Technology Center, Pittsburgh, PA 15236Search for more papers by this author T. T. Tsotsis, T. T. Tsotsis Department of Chemical Engineering, University of Southern, California, Los Angeles, CA 90007Search for more papers by this authorV. U. S. Rao, V. U. S. Rao Pittsburgh Energy Technology Center, Pittsburgh, PA 15236Search for more papers by this authorL. M. Polinski, L. M. Polinski Pittsburgh Energy Technology Center, Pittsburgh, PA 15236Search for more papers by this author First published: September 1982 https://doi.org/10.1002/aic.690280527Citations: 15AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume28, Issue5September 1982Pages 847-851 RelatedInformation

Experiments were performed on ZSM-5 catalyst impregnated with 11.1% of iron (A) or 5.6% of iron and 4.5% of cobalt (B) and on Silicalite, a molecular sieve form of silica, impregnated with 13.6% of iron (C), 7.8% of iron and 0.9% of potassium (D), or iron and manganese in fixed-bed or continuous stirred tank laboratory reactors. Zeolite acidity played an important part in forming aromatics from synthesis gas (2:1 or 1:1 hydrogen/carbon monoxide ratio) by bifunctional catalysts, as demonstrated by comparison of the product slates from the A and C catalysts. The transition metal component impregnated into the zeolite played an important part in selectivity, as demonstrated by the liquid phase products from the A and B catalysts. D catalyst had an exceptionally high selectivity for production of C/sub 2/-C/sub 4/ olefins. The experiments were carried out at 280/sup 0/-300/sup 0/C and 21 bar, and magnetic studies were performed to characterize the transition metal component and detect the formation of bimetallic iron-cobalt clusters.

The medium pore zeolite ZSM-5 can be made within a wide range of values of the ratio SiO/sub 2//Al/sub 2/O/sub 3/. The crystal structures of ZSM-5 and Silicalite appear to be very similar. However, Silicalite has essentially no Al. Hence it appears that Silicalite is the limiting form of ZSM-5 when the Al concentration is vanishingly small. A comparison of the properties of ZSM-5 and Silicalite is shown. Silicalite provides an interesting contrast to ZSM-5 owing to the lack of acidity in the former. In comparing products from catalysts based on ZSM-5 and Silicalite, one can discern reactions which result from the acid function in ZSM-5. Our studies on bifunctional catalysts based on ZSM-5 and Silicalite were performed on zeolites or molecular sieves impregnated with Fe and/or Co. The aim was to convert synthesis gas (CO + H/sub 2/), which can be derived from the gasification of coal, to olefins or gasoline. In the case of the ZSM-based catalyst containing Fe, the transition metal catalyzes the hydrogenation of CO, and the acid function of the zeolite catalyzes the conversion of the oxygenates and olefins in the product to aromatics, resulting in a high octane gasoline product. Recent work from ourmore » laboratory has clearly shown that if Silicalite is used instead of ZSM-5 as the support, the production of aromatics is almost completely suppressed, and the product stream is rich in olefins. In the present article, molecular sieve based catalysts that can proide olefins are discussed, and some aspects of gasoline production using zeolite based catalysts as well as the control of shift activity are also being considered. 4 tables.« less