Roles of supports on reducibility and activities of Cu3P catalysts for deoxygenation of oleic acid: In situ XRD and XAS studies

Abstract This work demonstrates for the first time that SiO2 and ultra-stable zeolite Y (USY) supports play significant roles in the reducibility of Cu2P2O7 to form Cu3P, which consequently affects the selectivity of oleic acid deoxygenation. The formation of supported Cu3P nanoparticles during hydrogen reduction of Cu2P2O7 was carefully investigated by in situ X-ray diffraction (in situ XRD), and in situ X-ray absorption spectroscopy (in situ XAS). The results indicate that the transformation of Cu2P2O7 to Cu3P occurs through several steps. In the first step, all supported Cu2P2O7 precursors are reduced to metallic Cu. Then, copper particles on SiO2 support react with phosphorus compounds and directly transform to Cu3P. On the other hand, copper particles on USY support partially transform to CuP2 and Cu(OH)2 before all converting to Cu3P. Despite multi-step transformations, Cu2P2O7/USY exhibits the lowest onset reduction temperature and provides Cu3P with a small particle size. The deoxygenation of oleic acid over Cu3P supported catalysts reaches nearly 100 % conversion. Both catalysts favor cyclization and aromatization to form cyclic and aromatic compounds. Cu3P/SiO2 achieves higher dodecylbenzene yield (46 %) than Cu3P/USY (33 %). A proposed mechanism consists of hydrogenation of oleic acid and deoxygenation, then followed by cracking, cyclization, aromatization, and alkyl rearrangement.