Roles of supports on reducibility and activities of Cu 3 P catalysts for deoxygenation of oleic acid: In situ XRD and XAS studies

This work demonstrates for the first time that SiO 2 and ultra-stable zeolite Y (USY) supports play significant roles in the reducibility of Cu 2 P 2 O 7 to form Cu 3 P, which consequently affects the selectivity of oleic acid deoxygenation. The formation of supported Cu 3 P nanoparticles during hydrogen reduction of Cu 2 P 2 O 7 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 Cu 2 P 2 O 7 to Cu 3 P occurs through several steps. In the first step, all supported Cu 2 P 2 O 7 precursors are reduced to metallic Cu. Then, copper particles on SiO 2 support react with phosphorus compounds and directly transform to Cu 3 P. On the other hand, copper particles on USY support partially transform to CuP 2 and Cu(OH) 2 before all converting to Cu 3 P. Despite multi-step transformations, Cu 2 P 2 O 7 /USY exhibits the lowest onset reduction temperature and provides Cu 3 P with a small particle size. The deoxygenation of oleic acid over Cu 3 P supported catalysts reaches nearly 100 % conversion. Both catalysts favor cyclization and aromatization to form cyclic and aromatic compounds. Cu 3 P/SiO 2 achieves higher dodecylbenzene yield (46 %) than Cu 3 P/USY (33 %). A proposed mechanism consists of hydrogenation of oleic acid and deoxygenation, then followed by cracking, cyclization, aromatization, and alkyl rearrangement.