Effect of cesium content on the structure and catalytic performances of heteropoly compounds in one-step synthesis of methylmethacrylate from methacrolein

Keggin-type heteropoly compounds (HPCs) H3.2-xCsCu0.25As0.1PMo11VO40 (x, 0-2.5) were used as catalysts for coupling reaction of methylmethacry late (MMA) from methacrolein (MAL) in this study. And the catalytic performance of the HPCs was investigated in the oxidation-esterification coupling reaction. Moreover, the HPCs were characterized by NH3-TPD, TG-pyridine-adsorption/desorption, N-2-adsorption/desorption, ICP, TG-DSC, FT-IR, XRD and TPR. These reactive results have been correlated to the acidity, surface area and reducibility. With the increasing of Cs content, surface area of the HPCs increased, while the acidity and reducibility decreased. Difference of the quantity of acid sites originated from the hydration protons being substituted by Cs+. Effects of Cs+ content on the reducibility of the HPCs indicated that Cs+ changed the structural stability of V as coordinating atoms and the proportion of the different reducible states of Mo6+.