FISCHER-TROPSCH SYNTHESIS OVER ZEOLITE- AND INORGANIC OXIDE-SUPPORTED RUTHENIUM CATALYSTS

Three preparation techniques {lcub}incipient-wetness using a solution of RuCl(,3), vapor-impregnation by Ru(,3)(CO)(,12), and ion-exchange with Ru(NH(,3))(,6)Cl(,3){rcub} have been used to prepare NaX, NaY, HY, KL, and NaMordenite zeolite-supported ruthenium catalysts. Different solvents (acetone and aqueous) and different pH values of aqueous solution were also used in preparing wet-impregnated catalysts. Decomposed and reduced catalysts were characterized by A.A., I.R., and hydrogen and carbon monoxide chemisorption measurements. The effects of preparation method and the type of support on the activity, product selectivity, and stability of the Ru catalysts in the Fischer-Tropsch synthesis were examined at temperatures in the range of 220-320(DEGREES)C, a pressure of 1 atm, a CO/H(,2) ratio of 1, and flow rates in the range GHSV = 1800-3600.; Catalytic behavior in the F-T synthesis was greatly influenced by the preparation method and the type of support. Catalysts prepared by the incipient-wetness method produced mainly methane. Catalysts prepared by vapor-impregnation had the best selectivities for olefins and higher hydrocarbons even though they had the smallest average Ru particle sizes. The specific activity was found to be mainly related to the particle size of Ru metal. The observed changes in adsorption and selectivity resulted from differences produced in metal location in/on the zeolite, type of cation in zeolite-support, and/or metal-zeolite interactions. However, there was no relationship between hydrogenation ability and chain-growth probability.; A series of inorganic compounds (Cr(,2)O(,3), MgO, ZrO(,2), CeO(,2), ThO(,2), SiO(,2), La(,2)O(,3), carbon, graphite, ZnO, and SnO) were also used as supports for Ru catalysts. Results showed that there are dramatic differences in activity and selectivity in CO hydrogenation over these catalysts. The best support in terms of activity was chromia which exhibited an anomalously high specific activity. The worst supports were SnO, ZnO, and activated carbon. Utilization of ZnO or La(,2)O(,3) as a support favored the formation of olefins and higher hydrocarbons.; The addition of electropositive elements (K, La, and Zn) to Ru/SiO(,2) catalysts were found to greatly affect the catalytic properties of Ru in the F-T synthesis. They enhanced olefin formation and higher hydrocarbon production. On the other hand, the specific activity was decreased with this addition. The strength of this promoting effect depended on the type of additive cations. It also depended on the support.