水热法制备ZrO_(2)催化甘油酯交换反应性能

Catalytic Performance of ZrO_(2) Prepared by Hydrothermal Method for Transesterification of Glycerol

采用水热法制备了ZrO_(2)催化剂,用于催化甘油(GLY)与碳酸二甲酯(DMC)酯交换反应合成碳酸甘油酯(GC)。考察了焙烧温度对催化剂性能的影响,并采用粉末X射线衍射(XRD)、N_(2)等温吸附-脱附、程序升温脱附(TPD)等手段对ZrO_(2)催化剂进行了表征。结果表明,ZrO_(2)催化性能高度依赖于其表面中强碱性位点密度,当焙烧温度为600℃时,所制备的ZrO_(2)-600催化剂表面中强碱性位点密度较大;在反应温度90℃下反应90 min, GLY转化率为96.1%,GC选择性为86.2%。重复使用第3次时,由于ZrO_(2)表面碱性位点密度减小、孔道坍塌以及部分ZrO_(2)样品溶解在DMC中,GLY转化率和GC选择性均显著下降。

ZrO_(2) catalysts were prepared by the hydrothermal method for catalyzing the synthesis of glycerol carbonate(GC)from the ester exchange reaction of glycerol(GLY)with dimethyl carbonate(DMC).The effect of calcination temperature on the catalytic performance was investigated,and the ZrO_(2) catalysts were characterized by powder X-ray diffraction(XRD),isothermal adsorption-desorption of N_(2),and temperature programmed desorption(TPD).The results show that the catalytic performance of ZrO_(2) catalysts is highly dependent on the density of strongly basic sites on their surfaces.At the calcination temperature of 600℃,the prepared ZrO_(2)-600 catalysts have a high density of strongly basic sites on the surface;at the reaction temperature of 90℃for 90 min,the GLY conversion is 96.1%and the GC selectivity is 86.2%.When the ZrO_(2) catalysts are used repeatedly for the third time,the GLY conversion and GC selectivity decrease significantly due to the decrease in the density of basic sites on the ZrO_(2) surface,pore collapse,and the dissolution of partial ZrO_(2) sample in DMC.