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Carbon monoxide hydrogenation over alkali-promoted Rh/Al2O3, Rh/V2O3/SiO2 and Rh/ThO2/SiO2

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  • Economics


PII: S0166-9834(00)82427-6 Applied Catalysis, 35 (1987) 141-152 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 141 Carbon Monoxide Hydrogenation over Alkali- Promoted Rh/A1203, Rh/V,O,/SiO, and Rh/ThOz/SiOz B.J. KIP*, E.G.F. HERMANS and R. PRINS Laboratory of Inorganic Chemistry and Catalysis, Eindhoven University of Technology, P.O. Box 513,560O MB Eindhoven (The Netherlands) (Received 31 March 1987; accepted 14 June 1987) ABSTRACT Addition of Li, Na, K and Cs to a 1.5 wt% Rh/Al,O, catalyst resulted in a decrease of the hydrocarbon formation rate, while the methanol formation rate was almost unaffected. The over- all result is an increased oxygenate selectivity at a decreased total activity. The oxo-selectivity increased in the order unpromoted < Li < Na< K < Cs. The results suggest that the main role of the alkali promoter is to decrease the carbon monoxide dissociation reaction. Rh/SiO, catalysts promoted with ThO, or V,O, had higher C&-oxygenate selectivities and a higher activity than a Rh/Si02 catalyst. Addition of Li, Na, K and Cs did not increase the oxo- selectivity of the ThO,- and V,O,-promoted Rh/SiO, catalysts. Independent of the kind of alkali added, it mainly decreased the activity and lowered the hydrogenation rate, suggesting that the added alkali blocked the special perimeter sites which are held responsible for the ThO, and V,O,, promotion effect or that the added alkali formed a mixed oxide with the promoter oxide. Alkali ions, therefore, did not improve the catalytic behaviour of the ThO,- and V,O,-promoted Rh/SiO, catalysts. INTRODUCTION The hydrogenation of carbon monoxide over supported rhodium catalysts produces both hydrocarbons and oxygenated compounds such as alcohols and aldehydes [ l-111. From an economic point of view, C,-oxygenates are the favoured products [ 121. Modification of the catalytic behaviour of rhodium catalysts by the support [l-4] or by a promoter [ 5-111 has been a topic of

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