The construction of Mo6−δO3−-supported catalyst for low-temperature propylene gas-phase epoxidation by Cu modification

Insight into the Effect of Copper Substitution on the Catalytic Performance of LaCoO3-Based Catalysts for Direct Epoxidation of Propylene with Molecular Oxygen

“…It is postulated that the apparent variation at Raman shifts of 386 and 860 cm –1 appeared for the LaCo 0.8 Cu 0.2 O 3−δ sample due to oxygen vacancies caused by Cu doping. Such a phenomenon, however, was not observed for pure LaCoO 3 and CuO supported on LaCoO 3 …”

“…Another work which employed Cu/SiO 2 as a composite catalyst came to the similar conclusion (selectivity of 17.0%, conversion of 3.2%) . Although much efforts have been made toward the direct epoxidation of propylene with molecular oxygen, the reaction mechanism and active phase while using Cu-based catalysts still remain vague and contradictory. ,− …”

“…The Cu 2p 1/2 and Cu 2p 3/2 peaks corresponding to the binding energy of 954.9 and 934.6 eV were recorded. In addition, a strong Cu 2+ satellite peak was observed to appear at around 942.2 eV, which consisted of two adjacent peaks (the profiles of LaCo 0.8 Cu 0.2 O 3−δ only show a board peak), indicating the existence of Cu 2+ species. ,, Another two shoulder peaks located at 952.6 and 932.8 eV are attributed to the Cu 2 O or Cu 0 species (since the binding energy of Cu + and Cu 0 are very close). This demonstrated the considerable amount of Cu species in low valence for both two samples. ,, Further manifested by the shape of strong Cu 2+ satellite, the existence of Cu 2+ in CuO supported on LaCoO 3 is more conspicuous than LaCo 0.8 Cu 0.2 O 3−δ , indicated by its higher Cu 2+ /(Cu + + Cu 0 ) ratio as shown in Table .…”

“…Two distinct peaks located at 531.2 and 528.8 eV ascribing to electrophilic O ele and lattice oxygen O latt , respectively, can be observed for LaCoO 3 and CuO/LaCoO 3 samples. ,, By comparison, the binding energy assigned to lattice oxygen O ele for LaCo 0.8 Cu 0.2 O 3−δ samples became lower (582.80–528.63 eV). This could be due to the insertion of Cu inside LaCoO 3 perovskites structure and the formation of more oxygen vacancies owing to strong interaction between Co and Cu by sharing oxygen. − Since the surface adsorbed oxygen is related to the presence of oxygen vacancies in the crystal lattice, the O ele /O latt ratio of LaCo 0.8 Cu 0.2 O 3−δ was found to be higher than that of 5CuO/LaCoO 3 and LaCoO 3 , as shown in Table . This indicated much more electrophilic O ele existed, which is well in line with the results from subsequent result of O 2 -TPD .…”

Introduction of Bi‐Functional Cu/SiO2 for Modulating the Chemical States of MoO3‐Bi2SiO5/SiO2

“…The XPS spectra of Bi4 f also exhibits two peaks at 159.7 and 165.2 eV for MoO 3 ‐Bi 2 SiO 5 /SiO 2 sample that could be contributed to Bi 2 SiO 5 species associated with Bi 3+ (Figure b) . It can be seen that the binding energy of Bi4 f is lower on CS‐Bi 2 SiO 5 /SiO 2 than on MoO 3 ‐Bi 2 SiO 5 /SiO 2 , indicating that electronic effect can be found between Cu and Bi species through Bi‐O−Cu coordination structure.…”