Dry reforming of propane over supported Re catalyst

Fourier-transformed infrared spectroscopy revealed that there is no strong interaction between propane and Re/Al2O3 catalyst at 250-300 K producing di-σ-bonded propylene or propylidyne. Whereas CO2 is adsorbed mainly molecularly on supported Re reduced at 673 K, the presence of propane induces its dissociation even at 300 K resulting in the formation of adsorbed CO absorbing at ∼2041 cm−1. In addition, the co-adsorption of the two compounds 5% Re/Al2O3 at 373-573 K leads to the formation of formate species. Re/Al2O3 catalyzes the dehydrogenation and cracking of propane at 773-923 K. The selectivity of propylene formation is 43-74%. The addition of CO2 to propane dramatically affected the reaction pathway, and, instead of the dehydrogenation process, the formation of H2 and CO with a ratio of 0.56-0.61 became the dominant route. The highest conversion values were measured for the Re/Al2O3 reduced at 673 K. The steady-state conversion of propane also depended on the composition of the reacting gas mixture: it was ∼50% at C3H8/CO2 (1/3) and ∼80% at C3H8/CO2 (1/6). The deposition of carbon was observed, the extent of which can be lowered with increasing CO2 content of the reacting mixture. From the kinetic studies it was inferred that the CO2 is involved in the rate-determining step of the dry reforming of propane. As propylene was not detected or was detected only in traces, it was assumed that the hydrocarbon fragments formed in the activation of propane reacted quickly with adsorbed oxygen and CO2. A possible mechanism for the dry reforming of propane on Re catalysts is proposed.