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

Abstract

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 H₂; 0.5–0.65 in n-butane); product selectivities show weak dependence on temperature and H₂ 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 H₂ (∼−0.9), lower orders in n-butane (∼0.2) and product selectivities that showed greater change with temperature and H₂ pressure; terminal bond scission was >90%. The change in character with oxidation was attributed to weaker H₂ chemisorption and a higher concentration of partially dehydrogenated C₄ species; the active phase may consist of very small particles of RuO₂ confined within the supercages of the zeolite.