Oxidative Dehydrogenation of Propane to Propylene in the Presence of CO2 over Gallium Nitride Supported on NaZSM-5

Dehydrogenation of propane in the presence of CO2 (CO2-ODHP) is an important route for the synthesis of propylene and utilization of the waste CO2. In the present work, diverse GaN supported on NaZSM-5 catalysts (GaN/NaZSM-5) were prepared and applied in catalyzing CO2-ODHP. GaN could activate C-H bonds in propane and cover the medium to strong acidic sites of NaZSM-5 support, which could tune the adsorption capacities of reactant molecules and further suppress the occurrence of side reactions. The Si/Al molar ratio in GaN/NaZSM-5 impacted the propane and propylene adsorption capacities of the catalyst, which closely relates to the catalytic performances. Compared with the catalytic performances of other tested catalysts, the screened GaN/NaZSM-5 catalyst with a GaN loading of 5 wt % and the Si/Al molar ratio of 470 exhibited the best results, which probably derives from its highest propane but a low propylene adsorption capacity. In this way, propane could be strongly adsorbed on the catalyst and then activated by GaN and further dehydrogenated to propylene, which was quickly released to avoid cracking. Importantly, the catalytic performances stemmed from the strong interaction between GaN and the NaZSM-5 support via the formation of Si-O-GaN species, which was confirmed by X-ray photoelectron spectroscopy (XPS) results. The Si-O-GaN species reacted with propane to form Si-O-GaN-H species, and CO2 further reacted with Si-O-GaN-H to form the COOH intermediate and then release propylene, CO2 and Si-O-GaN active site. For the titled reaction, the catalyst could initially offer 45.0% conversion of propane and 28.3% yield of propylene at 600 degrees C. The present work not only provides a protocol for highly conversing propane to propylene but also proposes a method for tuning acidic characters of the NaZSM-5 support, which has potential application in alkane activation.