Model catalysts carbon monoxide hydrogenation

Lahtinen, J., Anraku, T., and Somotjai, G. A. 1993. Carbon monoxide hydrogenation on cobalt foil and on thin cobalt film model catalysts. J. Catal. 142 206-25. 

TI Carbon monoxide hydrogenation over cobalt catalyst in a tube-wall reactor Part II Modeling studies KW Fischer Tropsch synthesis modeling, carbon monoxide hydrogenation cobalt catalyst, tube wall reactor Fischer Tropsch reaction IT Hydrogenation catalysts... 

Kolbel et al. (K16) examined the conversion of carbon monoxide and hydrogen to methane catalyzed by a nickel-magnesium oxide catalyst suspended in a paraffinic hydrocarbon, as well as the oxidation of carbon monoxide catalyzed by a manganese-cupric oxide catalyst suspended in a silicone oil. The results are interpreted in terms of the theoretical model referred to in Section IV,B, in which gas-liquid mass transfer and chemical reaction are assumed to be rate-determining process steps. Conversion data for technical and pilot-scale reactors are also presented. 

The potential importance of homogeneous catalytic reactions in synthesis gas transformations (i.e., hydrogenation of carbon monoxide) has been widely recognized in recent years. In the first place, such systems could provide structural and mechanistic models for the currently more important, but more difficult to study, heterogeneous catalysts. Secondly, product selectivity is generally more readily achievable with homogeneous catalysts, and this would be an obviously desirable feature in an efficient process converting synthesis gas to useful chemicals and fuels. 

Carbon monoxide oxidation is a relatively simple reaction, and generally its structurally insensitive nature makes it an ideal model of heterogeneous catalytic reactions. Each of the important mechanistic steps of this reaction, such as reactant adsorption and desorption, surface reaction, and desorption of products, has been studied extensively using modem surface-science techniques.17 The structure insensitivity of this reaction is illustrated in Figure 10.4. Here, carbon dioxide turnover frequencies over Rh(l 11) and Rh(100) surfaces are compared with supported Rh catalysts.3 As with CO hydrogenation on nickel, it is readily apparent that, not only does the choice of surface plane matters, but also the size of the active species.18-21 Studies of this system also indicated that, under the reaction conditions of Figure 10.4, the rhodium surface was covered with CO. This means that the reaction is limited by the desorption of carbon monoxide and the adsorption of oxygen. 

Previous studies of direct reduction on iron ore pellets have been reviewed by Themelis(1), Bogdandy(2) and Huebler(3). Work on reduction by mixtures has been reported by Szekely(4) and Hughes et al(5). Modelling studies on countercurrent moving bed systems have been reported by Spitzer(6) for isothermal reduction in hydrogen, by Miller(7) for non-isothermal reduction in carbon monoxide and more recently by Tsay et al(8) and Kam and Hughes(9) for C0/H2 mixtures. However, since iron is known to be a catalyst for the water gas shift reaction, this reaction will influence the gas composition and therefore the extent of reduction. None of the previous analyses have considered this aspect and the objective of the present paper is to account for the overall reduction by inclusion of this reaction. 

EUROPT-1 has also proved to be of exceptional value as a model catalyst to which systematic modifications may be made. The effects on its catalytic properties of the addition of silver, titania and alumina [16], chlorine, oxygen, sulfur, ammonia, and carbon monoxide have all been examined [7]. Of particular interest is its ability to be modified by alkaloids of the cinchona family, becoming in consequence enantio-selective for the hydrogenation of methyl pyruvate... 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

Oxide catalysts are known to be effective for oxidation reactions. In this study, we wanted to produce carbon monoxide through partial oxidation of the biomass, as this could be expected to lead to a conversion of carbon monoxide into hydrogen via the water-gas shift reaction. An oxidization of the tarry product is also expected. By these two effects, improvement of the efficiency of the gasification is expected. Oxide catalyst is expected to enhance the oxidation reaction needed for this scenario. Since oxide catalyst is considerably cheaper than nickel catalyst, its use would make the whole gasification process more economical. Hence, we decided to examine the effect of oxide catalysts on gasification with partial oxidation using cellulose as a model compound. 

The turnover frequencies measured at different temperatures were comparable to those found for hydroformylations using other strategies [1,3,33,35]. To develop the kinetic model, the effects of the linalool and the catalyst concentration and of the total carbon monoxide and hydrogen pressure on the outcome of the hydroformylation were investigated. In all cases, the reaction rate was enhanced by a first-order dependence. The results were in good agreement with the calculated model. The activation energy was found to be 14.5 kcal mol h... 

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