Reactions of propane and of n-butane with hydrogen over palladium catalysts

Abstract

On 5% Pd/SiO₂ and 5% Pd/Al₂O₃ catalysts, hydrogenolysis of propane affords ethane in high selectivity (S₂≈ 0.97–0.98); on the latter, the order in H₂ is –3.0 and the value of S₂ decreases as the H₂ pressure falls. The reaction of n-butane with H₂ gives chiefly methane and propane in almost equal amounts, except at the highest temperatures ( > 650 K) and the lowest H₂ pressure ( < 0.35 atm): the probability of central bond fission falls as the catalyst becomes deactivated by ‘carbon’ deposition to a value of ca. 0.05. Skeletal isomerisation to isobutane also occurs with low selectivity (S_i≈ 0.07–0.15). Product selectivities from n-butane are remarkably unaffected by alteration of temperature and of H₂ pressure, owing to the predominance of a single reaction pathway; the activation energy is high (250–320 kJ mol^–1) and the order in H₂ strongly negative (–3.0).