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 (Si≈ 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).