Chuang Xing

Filter and buffer-pot confinement effect of hollow sphere catalyst for promoted activity and enhanced selectivity

To efficiently utilize the catalyst active sites and simultaneously enhance target hydrocarbon selectivity in Fischer–Tropsch synthesis (FTS), herein, we demonstrate a promising Co–Al2O3 hollow-sphere catalyst prepared by a two-pot route including hydrothermal carbonization and wet impregnation. Benefiting by plentiful mesopores on the shell, reactants could access the cavity inside and the active sites on the inner surface for further FTS reaction. Compared with conventional solid catalyst, the hollow structure provided a “buffer-pot” effect, where feed gas and preliminary product from the shell could mix completely at a low flow rate. Heavy hydrocarbons were further confined, leading to enhanced formation of lighter C5–C11 components, which more readily escaped out through the mesoporous shell, which thus played a “filter” role. Additionally, increased acidity on the shell generated more iso-paraffins and olefins in the final product. This concept displayed a great superiority in improving active metal activity and selective production from multiple products compared with conventional supported catalysts.

A solvent-free in situ synthesis of a hierarchical Co-based zeolite catalyst and its application to tuning Fischer–Tropsch product selectivity

As a distinctive supportable route, the solvent-free synthesis of zeolites not only minimizes the problems of conversional hydrothermal synthesis, but also greatly increases the product yields with advantageous characteristics, such as reduced waste production and a hierarchical pore structure. Herein, we demonstrate using in situ crystal Co/SiO2 to form a hierarchical catalyst with Co particles entrapped inside the ZSM-5 body via a solvent-free process. Na-type zeolite catalysts enhanced the production of gasoline-range (C5–C11) products, with Co@NaZSM-5 giving a high selectivity of 68% in the Fischer–Tropsch synthesis. Obviously, all characterizations showed that these solvent-free synthesized samples had high crystallization and a high surface area for mass transfer. This hierarchical zeolite has the potential to be applied to other similar materials owing to its convenient synthesis method, features, and outstanding results.

Study on new method and mechanism of low-temperature methanol synthesis

The methanol could be synthesized from the CO/CO<inf>2</inf>/H<inf>2</inf> on Cu/ZnO catalysts using alcohol solvent at 443 K and 3.0 Mpa. The activity of the catalyst with ZnO as carrier (Cu/ZnO) was the highest in all catalysts with Y<inf>2</inf>O<inf>3</inf>, La<inf>2</inf>O<inf>3</inf>, Al<inf>2</inf>O<inf>3</inf>, or MgO as carrier separately, and the 2-butanol as solvent exhibited the highest activity in this reaction. The studying results of the reaction mechanism show that at first adsorbed formate species were formed by adsorbing the CO/CO<inf>2</inf>/H<inf>2</inf> on Cu/ZnO catalyst, and then the 2-butyl formate was formed by the reaction of adsorbed formate species with 2-butanol, at last the 2-butyl formate is reduced by hydrogen atoms on Cu to form methanol. The 2-butanol used in this reaction not only significantly decreased the reaction temperature due to its promotional action, but also was not consumed due to its regeneration by hydrogenation of the 2-butyl formate, acting like a catalytic solvent.