【摘要】 用浸渍法制备了一系列S iO2负载的磷钨酸(PW12)及其铯盐(Cs2.5H0.5PW12)和钾盐(K2.5H0.5PW12)催化剂,考察了这些催化剂对乙酰乙酸乙酯与乙二醇缩合制苹果酯反应的催化性能,并以X射线衍射、N2吸附-脱附和Hamm ett指示剂等方法表征了催化剂的物化性能。用水处理实验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法测试。实验结果表明,在合成苹果酯的反应中,随磷钨酸(盐)负载量的增加,催化剂的活性有不同程度的增加,在负载量(质量分数)达到30%时,催化活性已基本不变,PW12/S iO2,Cs2.5H0.5PW12/S iO2,K2.5H0.5PW12/S iO2催化剂上,乙酰乙酸乙酯的转化率分别为69.8%,68.6%,68.4%,产物选择性为97%。催化剂的稳定性实验结果表明,催化剂失活与活性组分的流失有关,催化剂的稳定性顺序为:30%Cs2.5H0.5PW12/S iO2≈30%K2.5H0.5PW12/S iO2 30%PW12/S iO2。更多还原

【Abstract】 12-phosphotungstic acid(PW₁₂) and/or its Cs salt and K salt supported on SiO₂ were prepared by impregnation at ambient temperature.Their catalytic performances in synthesis of fructone by acetalization of ethyl acetoacetate with glycol were invetigated.Their properties were characterized by means of X-ray diffraction（XRD）,N₂ adsorption and Hammett indicator.The catalyst stability was evaluated by treatment with water,during which concentration of leached heterpoly compound was measured by ultraviolet-visual spectrophotometer.The catalyst activity rose with increase of PW₁₂（Cs-or K-salt）loading,and conversion of ethyl acetoacetate became steady when loading was more than 30%.For PW₁₂/SiO₂,Cs_2.5H_0.5PW₁₂/SiO₂ and K_2.5H_0.5PW₁₂/SiO₂ catalysts,selectivity of fructone was 97%,and conversions of ethyl acetoacetate was（69.8%,）68.6% and 68.4%,respectively.The treatment of catalysts with water showed that deactivation of catalyst related correspondingly with the amount of leached active heteropoly species,and stabilities of three catalysts were in the order of 30%Cs_2.5H_0.5PW₁₂/SiO₂≈30%K_2.5H_0.5PW₁₂/SiO₂30%PW₁₂/SiO₂.更多还原