Characterization of new Co and Ru on α - WC catalysts for Fischer - Tropsch reaction . Influence of the carbide surface state

An investigation of the performances in Fischer-Tropsch reaction of 1wt% M/WC(X) (M = Co, Ru; X = A, B), where A is a tungsten carbide protected by free carbon and B is a clean tungsten carbide, was carried out. Supported catalysts performances were compared to those of the parent tungsten carbides at 473 K and 20 bar. It was found that WC(A) produces mainly hydrocarbons but also 20-40% alcohols, whereas WC(B) activity is only towards linear alkanes. Before catalytic test, a reduction in pure hydrogen allows obtaining Co 0 and Ru 0 dispersed on layers of free carbon covering the WC core for the WC(A), and on a surface free of oxygen for WC(B). Co as Ru dispersions are improved on WC(B) compared to WC(A). A direct consequence is that Co/WC(B) has a better activity than Co/WC(A). Ru-W alloy formation could be responsible of the inobservance of a better activity for Ru/WC(B). On contrary, addition of Ru on WC(A) highly increases the activity and the production of heavy hydrocarbons. This beneficial effect, not observed with cobalt, could be attributed to a better dispersion of ruthenium on a carbon polymeric surface of WC. ha l-0 03 42 70 1, v er si on 1 28 N ov 2 00 8 Author manuscript, published in "Journal of Molecular Catalysis A Chemical 259 (2006) 187-196" DOI : 10.1016/j.molcata.2006.06.015