Hydrogenolysis of alkanes: reactions of n-butane on Ru/zeolite catalysts

Ru/13X zeolite catalysts containing 0.6, 2 and 5.7% Ru prepared by reduction or decomposition of the hexammine complex are active and stable for n-butane hydrogenolysis between 400 and 460 K, and show similar activation energies (150-160 kJ mol(-1)) and orders of reaction(-1.5 to -2 in H-2; 0.5-0.65 in n-butane); product selectivities show weak dependence on temperature and H-2 pressure, with preference for terminal bond scission. Oxidising either the decomposed or the reduced catalysts gave a marked increase in activity, a lower activation energy (120-130 kJ mol-1), higher orders of reaction in H-2 (similar to-0.9), lower orders in n-butane (similar to 0.2) and product selectivities that showed greater change with temperature and H-2 pressure; terminal bond scission was >90%. The change in character with oxidation was attributed to weaker H-2 chemisorption and a higher concentration of partially dehydrogenated C-4 species; the active phase may consist of very small particles of RuO2 confined within the supercages of the zeolite.