Secondary reactions of propylene on Ga/-Al2O3 propane dehydrogenation catalysts

Supported Ga catalysts have been widely studied for propane dehydrogenation (PDH). In this study, Ga/gamma-Al2O3 catalysts were evaluated for PDH. The propylene selectivity decreased with increasing propane conversion. It is generally thought that propylene and light gas by-products occur from chemisorbed propane and are, therefore, primary products. By extrapolating the product selectivities to zero per cent propane conversion, the initial propylene selectivity was near 100% and is a primary product. The light gas selectivities, however, are near 0% indicating that these are secondary products. The direct reaction of propylene produced the same light gas products, e.g., methane, ethylene, propane, butenes and pentenes, observed for PDH and confirmed that these occur by an independent reaction of propylene. Thus, while the intrinsic PDH propylene selectivity is high, these secondary propylene reactions lower the selectivity, especially, at higher conversions and higher partial pressures.