SBA-15负载杂多化合物在苹果酯合成中的催化性能

用浸渍法制备了一系列中孔二氧化硅分子筛SBA-15负载的磷钨酸(PW)及其铯盐和钾盐催化剂,考察了其在乙酰乙酸乙酯与乙二醇缩合制苹果酯反应中的催化性能, 并以N2吸附,Hammett指示剂和FT-IR等手段表征了催化剂的物化性质, 在水处理试验中考察了催化剂的稳定性,溶脱到水中的杂多化合物浓度用紫外可见分光光度仪测定.结果表明,在合成苹果酯的反应中,当PW的负载量低于30%,杂多酸盐负载量低于20%时,固体催化剂无活性;催化剂在反复使用过程中活性下降的量与活性组分在极性体系中的溶脱量成对应关系,说明催化剂活性下降的主要原因是杂多酸(盐)活性组分的流失造成的,而负载磷钨酸铯盐良好的催化稳定性来源于磷钨酸铯盐的难溶脱性.

Catalytic Behavior of SBA-15 Supported Heteropoly Compounds in Synthesis of Fructone

Catalysts of 12-tungstophoric acid (PW), cesium salt of PW and potassium salt of PW supported on mesoporous silica SBA-15 with different loadings were prepared by impregnation, respectively. Their catalytic behaviors were investaged via the acetalization of ethyl acetoacetate with ethylene glycol to synthesize fructone. The physical and chemical properties of the catalysts prepared were characterized by N2 adsorption, Hammett indicator and FT-IR. The catalytic stability of the catalysts was evaluated by water treatment test, in which the concentration of the heteropoly compound leaking into the water was measured by ultraviolet-visual spectrophotometer. It is found that the catalysts have no activity in the synthesis of fructone when the loading of PW on SBA-15 is lower than 30% and the loading of Cs salt or K salt of PW on SBA-15 is lower than 20%. During repeatedly using, the deactivation of the catalysts prepared is closely associated with the leakage of active heteropoly species into the polar solvent. Since in the polar reaction system, the cesium salts of PW are water-tolerant, it causes the catalyst of supported cesium salts of PW on SBA-15 has higher catalytic stability.