Xia Yuan

Co-SBA-15-Immobilized NDHPI as a New Composite Catalyst for Toluene Aerobic Oxidation

AbstractA new composite catalyst was constructed by immobilizing active site N,N-dihydroxypyromellitimide (NDHPI) on the co-catalyst Co-doped mesoporous sieve SBA-15 through the chemical bond with the 3-(glycidoxypropyl) trimethoxysilicane used as the silylation agent. The catalyst was characterized by various means. The new catalyst showed significantly higher activity in toluene aerobic oxidation at 90 °C with acetonitrile as a solvent or under solvent-free condition compared with the NDHPI and co-catalyst independent system. The effects of the reaction conditions such as temperature, oxygen pressure, catalyst amount on the toluene oxidation over the immobilized catalyst were also investigated. After reuse for three times, the composite catalyst kept the activity without loss of Co from SBA-15.Graphical AbstractA new composite catalyst was constructed by immobilizing active site N,N-dihydroxypyromellitimide (NDHPI) on the co-catalyst Co-doped mesoporous sieve SBA-15 through the chemical bond with the 3-(glycidoxypropyl) trimethoxysilicane used as the silylation agent. The catalyst was characterized by various means. The catalytic performance of the composite was evaluated in toluene aerobic oxidation and the reuseability of the catalyst was also investigated.

Preparation of Titanium Modified TUD-1 Catalysts for Propylene Epoxidation

A three-dimensional sponge-like mesoporous, Ti-TUD-1 catalyst was synthesized by a direct hydrothermal treatment method. Its synthesis was modified to introduce more tetrahedral-coordinated Ti species into the framework of TUD-1 matrix, by controlling the hydrolysis of titanium and silicon sources. The TUD-1 catalyst was characterized by XRD, FT-IR, ICP-AES, UV-Raman, UV–vis DRS, BJH/BET and 29Si MAS NMR analyses, indicating that addition orders of substrate played a crucial role during the Ti-TUD-1 catalyst preparation, indicating the amount of tetrahedral-coordinated Ti species was closely related to the addition order of substrate. The presence of Ti species affected the internal structure and connectivity of TUD-1 matrix. The Ti-TUD-1 catalyst exhibited high catalytic activity, especially good PO selectivity, due to the tetrahedral-coordinated Ti species into the framework of TUD-1 matrix. Furthermore, the effect of the TBOT/TEOS and TEA/TEOS molar ratios, on the catalytic activity was also studied, demonstrating that adequate molar ratios promoted an improvement the catalytic activity. Textural properties of Ti-TUD-1 were related to the addition order of substrate. Ti-TUD-1 catalyst was synthesized by controlling the hydrolysis of titanium and silicon sources. Amount of tetrahedral-coordinated Ti species also depend on the addition order of substrate.Graphical Abstract

Sn-Modified NaY Zeolite Catalysts Prepared by Post-Synthesis Methods for Baeyer–Villiger Oxidation

The Sn–NaY zeolite catalysts, Sn–NaY-gas and Sn–NaY-liq, were prepared by two-step post-synthesis methods, through hydrothermal dealumination and the post-incorporation of Sn species using chemical vapor deposition and impregnation separately. The Sn-ion incorporation and the physicochemical properties of the catalysts were characterized by various techniques. The amount of Sn species that were incorporated into the zeolite framework depended closely on the Sn introduction method. Sn–NaY-gas was found to have more Lewis-acid tetracoordinated Sn sites, which led to a better catalytic performance in the Baeyer–Villiger oxidation of cyclohexanone. The higher Sn loadings in the Sn–NaY-liq (3.4%) resulted in many inactive amorphous extra-framework Sn species, which also caused partial blockage of the zeolite pores and led to a loss in catalytic efficiency. Therefore, chemical vapor deposition could be used to form more active Lewis acidic Sn sites.Graphical Abstract