Mechanistic study of the dry reforming of propane to synthesis gas over a Ni/Mg(Al)O catalyst

The dry reforming of propane to synthesis gas over 2 wt.% Ni/Mg(Al)O has been investigated by means of partial pressure variation experiments, kinetic isotope effect and isotopic tracer studies, all at 600 °C. Partial pressure variation experiments gave reaction orders of 0.18 and 0.36 with respect to propane and carbon dioxide, respectively, indicating a high surface coverage under the chosen test conditions (C3H8:CO2:H2:N2 (%) = 10:30:10:50, GHSV = 13333 ml/h gcat). Switching to a deuterated feed did not induce any kinetic isotope effect, revealing that Csingle bondH bond rupture is not involved in the rate-limiting step. Isotopic tracer studies showed that the reverse water-gas shift reaction approaches equilibrium under the applied test conditions, demonstrating that CO2 activation is fast. Temperature-programmed deuteration of a used catalyst showed that C3 species dominate among the hydrocarbon species on the catalyst surface. Together, the above results led to the conclusion that Csingle bondC bond rupture is the rate-determining step of reaction. Isotopic tracer studies further showed (1) that methane is mainly formed as a primary product of reaction by propane dissociation followed by hydrogenation on Ni sites, and (2) the primary reaction selectivity favors C oxidation to CO over C hydrogenation to methane. Co-feeding methane and propane with CO2 showed that propane is converted significantly faster than methane.