Heterogenized Molybdovanadophosphoric Acid on Amine-Functionalized SBA-15 for Selective Oxidation of Alkenes

H3PMo12O40 Immobilized on Amine Functionalized SBA-15 as a Catalyst for Aldose Epimerization

In this work various amount of phosphomolybdic acid (PMo) were immobilized on amine functionalized SBA-15 and used as heterogeneous catalysts in the epimerization of glucose in aqueous solution. 13.3PMo/NH₂-SBA-15 exhibited the best catalytic performance with a glucose conversion of 34.8% and mannose selectivity of 85.6% within two hours at 120 °C. The activation energy of 80.1 ± 0.1 kJ·mol^-1 was lower than that of 96 kJ·mol^-1 over the homogeneous H₃PMo₁₂O₄₀ catalyst. The catalytic activities of 13.3PMo/NH₂-SBA-15 for the transformation of some other aldoses including mannose, arabinose and xylose were also investigated.

Selective oxidation of methacrolein to methacrylic acid over H4PMo11VO40/C3N4-SBA-15

Molybdovanadylphosphoric acid (HPMV) was supported on a carbon nitride-modified SBA-15 (CN-SBA-15) molecular sieve to enhance its catalytic performance for oxidation of methacrolein (MAL) to methacrylic acid (MAA). HPMV/CN-SBA exhibited increased catalytic activity (20%) and five times greater MAA selectivity (98.9%) compared to bulk HPMV. HPMV supported on CN-SBA-15 exhibited much better catalytic performance as compared to that on other supports, such as KIT-6, HY zeolite, TiO₂, Al₂O₃, SiO₂, CNTs, and NH₃-modified CNTs. The supported HPMV was well characterized by FT-IR, XRD, SEM, N₂ physical desorption, TG-DTA, NH₃-TPD, CO₂-TPD, XPS, and solid-state NMR. The CN minimized the interaction between the silica support and HPMV. HPMV was successfully separated from SBA-15, which was restricted by CN to increase stability and prevent interaction between the catalysts and support that would lead to decomposition of the catalysts during calcination and reaction. HPMV reacted with amino groups on the CN, which improved MAA selectivity and enhanced the thermal stability of the supported heteropoly acid (HPA) catalysts. This work identifies a new approach to preparing highly efficient and stable supported HPA catalysts for oxidation reactions.

Molybdovanadylphosphoric acid (HPMV) was supported on a carbon nitride-modified SBA-15 (CN-SBA-15) molecular sieve to enhance its catalytic performance for oxidation of methacrolein (MAL) to methacrylic acid (MAA).

Homogeneous catalytic oxidation of styrene and styrene derivatives with hydrogen peroxide in the presence of transition metal-substituted polyoxotungstates

Homogeneous catalytic oxidation of styrene and styrene derivatives with H₂O₂ in the presence of polyoxotungstates.

Novel polyoxometalate silica nano-sized spheres: efficient catalysts for olefin oxidation and the deep desulfurization process

A novel method to prepare silica nano-sized particles incorporating polyoxometalates was developed leading to a new efficient heterogeneous oxidative catalyst.

Progress of the Application of Mesoporous Silica-Supported Heteropolyacids in Heterogeneous Catalysis and Preparation of Nanostructured Metal Oxides

Mesoporous silica molecular sieves are a kind of unique catalyst support due to their large pore size and high surface area. Several methods have been developed to immobilize heteropolyacids (HPAs) inside the channels of these mesoporous silicas. The mesoporous silica-supported HPA materials have been widely used as recyclable catalysts in heterogeneous systems. They have shown high catalytic activities and shape selectivities in some reactions, compared to the parent HPAs in homogeneous systems. This review summarizes recent progress in the field of mesoporous silica-supported HPAs applied in the heterogeneous catalysis area and preparation of nanostructured metal oxides using HPAs as precursors and mesoporous silicas as hard templates.

Structure and Catalytic Properties of Magnesia-Supported Copper Salts of Molybdovanadophosphoric Acid

The structure and stability of magnesia-supported copper salts of molybdovanadophosphoric acid (Cu(2)PMo(11)VO(40)) were characterized by different techniques. The catalyst was prepared in ethanol by impregnation because this solvent does not hurt texture of the water-sensitive MgO and Cu(2)PMo(11)VO(40). The Keggin-type structure compound may be degraded partially to form oligomerized polyoxometalate when supported on MgO. However, the oligomers can rebuild as the Keggin structure again after thermal treatment in air or during the reaction. Meanwhile, the V atoms migrate out of the Keggin structure to form a lacunary structure, as observed by Fourier transform IR spectroscopy. Moreover, the presence of Cu(2+) as a countercation showed an affirmative influence on the migration of V atoms, and the active sites derived from the lacunary species generated after release of V from the Keggin anion. The electron paramagnetic resonance data imply that V(5+) autoreduces to V(4+) in the fresh catalyst, and during the catalytic reaction a large number of V(4+) ions are produced, which enhance the formation of O(2-) vacancies around the metal atoms. These oxygen vacancies may also improve the reoxidation function of the catalyst. This behavior is correlated to higher catalytic properties of this catalyst. The oxidative dehydrogenation of hexanol to hexanal was studied over this catalyst. After reaction at 553.2 K for 50 h, catalytic properties did not decrease and exhibited higher selectivity (>96.0%) toward hexanal.