Highly dispersed chromium oxide catalysts supported on mesoporous silica (Cr-MSU-x) were prepared via a (N0M n+)I0 pathway with the goal of achieving the high performance oxidative dehydrogenation of propane (ODHP) reaction. The resulting materials exhibited a mesopore structure resembling 3D wormhole-like holes, as characterized by N2 adsorption–desorption isotherms and HR-TEM. Catalytic experimental results revealed that the catalyst with a 0.028 Cr/Si molar ratio showed the highest catalytic activity among the catalysts studied. Two types of chromium species, isolated Cr(VI) and polymeric Cr(VI) species, were observed, as evidenced by H2-temperature-programmed reduction. They were designated as “hard Cr(VI)” and “soft Cr(VI)” sites, respectively. The initial composition of the soft Cr(VI) in the total Cr(VI) is a major determinant factor in the ODHP performance.

Due to its cost effectiveness and eco-friendliness, oxydehydration of glycerol is currently attracting considerable attentions. In an attempt to develop efficient catalyst for the reaction, tungsten incorporated molybdenum vanadium mixed oxide (MoVW) catalysts were designed based on computational calculations and mechanistic insights. By incorporating tungsten into molybdenum vanadium mixed oxide structure, the catalysts are active and selective not only for the dehydration of glycerol but also the subsequent oxidation of acrolein to acrylic acid. Through DFT calculations, we confirmed that tungsten species induced change in electron density of neighboring atoms, which leads to selective production of acrylic acid. Structural characterization demonstrates that the structure of such MoVW catalysts is similar to that of DFT models. The incorporated tungsten species enhanced the acid and redox properties of the catalyst, leading to high selectivity for acrylic acid (30.5%). It not only induced but also stabilized the reduced oxidation states of molybdenum and vanadium atoms, as confirmed by XPS and DFT calculations. Hence, a stable and selective production of acrylic acid was achieved with full glycerol conversion for 110 h. MoVW catalytic system with an additional acid catalyst bed exhibited remarkable selectivity for acrylic acid (47.2%), suggesting its potential for practical applications.

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The conversion of lignocellulose is a crucial topic in the renewable and sustainable chemical industry. However, cellulose from lignocellulose is not soluble in polar solvents, and is, therefore, difficult to convert into value-added chemicals. A strategy to overcome this drawback is the use of mesoporous carbon, which enhances the affinity between the cellulose and the catalyst through its abundant functional groups and large uniform pores. Herein, we report on the preparation of a Pt catalyst supported on a type of 3D mesoporous carbon inspired by Echinometra mathae (Pt/CNE) to enhance the interaction between the catalyst and a nonsoluble reactant. In the hydrolytic hydrogenation of cellulose, the abundant oxygen groups of CNE facilitated the access of cellulose to the surface of the catalyst, and the open pore structure permits cello-oligomers to effectively diffuse to the active sites inside the pore. The highly dispersed Pt performed dual roles: hydrolysis by in situ generating protons from H2 or water as well as effective hydrogenation. The use of the Pt/CNE catalyst resulted in an approximately 80 % yield of hexitol, the best performance reported to date. In direct conversion of hardwood powder, the Pt/CNE shows good performance in the production of sugar alcohols (23 % yield). We expect that the open-structured 3D carbon will be widely applied to the conversion of various lignocellulosic materials.

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