Catalytic amination of glycerol with dimethylamine over different type ofheteropolyacid/Zr-MCM-41 catalysts

Abstract

The effect of different type of heteropolyacid/Zr-MCM-41 catalysts on the catalytic amination of glycerol with dimethylamine to produce Dimethylamino-3-propanal was researched. Under the premise of their respective optimum loading amount, the specific surface area, pore volume and pore size of the H6P2W18O62/Zr-MCM-41(Cat-2) were higher than those of the H3PW12O40/Zr-MCM-41(Cat-1). Cat-1 exhibited more total acidity than that of Cat-2, which resulted in the higher glycerol conversion of Cat-1 at the beginning of the reaction, but the coke deposited on Cat-1 was more than that of Cat-2. The amount of Brønsted acid sites and ratio of B/(B + L) on Cat-2 were higher than that of Cat-1. Therefore, the catalytic stability, selectivity and yield of Dimethylamino-3-propanal of Cat-2 were higher than those of Cat-1, which proved that the Brønsted acid sites are good for the catalytic amination of glycerol with dimethylamine to produce Dimethylamino-3-propanal. The leaching ratio of Cat-2 is slightly more than that of Cat-1, because H6P2W18O62 is more hydrophilic than H3PW12O40. However, the stability of Cat-2 is higher than that of Cat-1, therefore, the main reason for deactivation of catalyst is the formation of carbon deposit during this reaction. And the reaction pathway of catalytic amination of glycerol with dimethylamine was proposed. Furthermore, the reaction temperature, GHSV and the molar ratio of dimethylamine/glycerol were optimized on Cat-2 catalyst. Under the optimum reaction conditions: 300 °C, H6P2W18O62 loading of 20 wt%, GHSV of 3 h−1, glycerol aqueous concentration of 10 wt%, dimethylamine aqueous concentration of 30 wt%, molar ratio of dimethylamine/glycerol of 2.5, the glycerol conversion, selectivity and yield of Dimethylamino-3-propanal were 95.6%, 80.8% and 77.2%, respectively.