| As the substitute for crude oil, chemicals and transportation fuels production from abundant coal and natural gas has enjoyed great attention in the world. Coal and natural gas can be converted into syngas (CO+H2) and valuable organic compounds can be synthesized from syngas. Among these organic compounds, the manufacture of oil, methanol, and mixed alcohols has put into industrialization. It has been proven that Rh-based catalyst is very efficient for the formation of C2 oxygenates and has been extensively studied, two problems should be solved to realize the commercialization of C2 oxygenates: (1) The space-time yield (STY) of C2 oxygenates is still not high enough; (2) The selectivity towards C2 oxygenates should be improved.In this thesis, the influence of iron as a promoter on Rh-Mn-Li/SiO2 catalysts has been investigated. The results showed that the STY of C2 oxygenates increased unexpectedly from 331.6 up to 457.5 g/kg h when little Fe was added to Rh-Mn-Li/SiO2 catalyst, and the selectivity towards C2 oxygenates kept fortunately unchanged.The optimization of rhodium loading in Rh-Mn-Li-Fe/SiO2 catalysts showed that the high rhodium loading catalysts exhibited high activity for the formation of C2 oxygenates in low temperature, but its selectivity was very sensitive to reaction temperature, low rhodium loading catalysts showed low activity, while its selectivity towards C2 oxygenates was not so sensitive to reaction temperature, therefore the STY of C2 oxygenates of the catalysts with low Rh loading could be improved and reached a similar value to that of the catalysts with high Rh loading by increasing the reaction temperature. Under the same reaction conditions, the Rh efficiency(g-C2oxy/g-Rh h) of catalysts first increased with Rh loading, and then decreased, a maximum value appeared in the curve. This value shifted down to low Rh loading region with increase of reaction temperature. On the basis of consideration of various factors whichinfluence the process benefit such as the catalytic activity, the selectivity toward C2 oxygenates, Rh efficiency, and the operation cost, the favorable reaction temperature should be in the rangeof 583-593 K, and the optimized Rh loading be 1 ~2 wt.%.The influence investigation of the SiO2 carrier on the catalytic properties showed that SiO2 affected the activity of Rh-Mn-Li-Fe/SiO2 greatly.The results of in situ FT-IR showed that the addition of additives led to a red shift of linear-CO band over Rh-Mn-Li-Fe/SiO2 compared to that of Rh/SiO2, which could be attributed to the promotion effect of additives towards the CO activation on the Rh surface. The results of CO-TPD indicated the addition of promoters enhanced the quantity of strong adsorbed CO species on Rh-based catalysts. It allowed us to propose that Rh together with Mn, Li and Fe might form new active centers, which could adsorb and activate CO and thus enhanced the catalytic activity. The ratio of the formed CH4 quantity in TPSR and the desorbed CO amount in CO-TPD on the catalysts illustrated that the introduction of additives increased the non-dissociated CO on the catalyst and may therefore enhanced the CO insertion into CHx and thus favored the formation of C2 oxygenates.
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