溶胶-凝胶法制备磷钨酸-硅胶催化合成苹果酯

采用溶胶-凝胶法制备了一系列磷钨酸-硅胶催化剂(PW/SG),考察了该催化剂催化乙酰乙酸乙酯与乙二醇液相缩合制备苹果酯的反应性能。实验结果表明,PW质量分数为40%时的PW/SG催化剂表现出最佳的催化活性;40%PW/SG催化剂制备苹果酯的最佳工艺条件为:n(乙酰乙酸乙酯)∶n(乙二醇)=1∶1.2,催化剂用量占反应物质量的0.36%,带水剂环己烷用量占反应物体积的30%,反应温度383K,反应时间90min;在此条件下,乙酰乙酸乙酯的转化率可达95.5%,苹果酯的选择性大于97%;催化剂稳定性实验表明,经5次重复使用,40%PW/SG催化剂的活性基本保持不变,乙酰乙酸乙酯转化率稳定在95.0%左右。

Synthesis of Fructone over Phosphotungstic Acid-Silica Catalysts Prepared by Sol-Gel Method

A series of phosphotungstic acid-silica gel catalysts(PW/SG)were prepared by sol-gel method.The catalytic performances of the catalysts were investigated in synthesis of fructone by liquid phase acetalization of ethyl acetoacetate with glycol in a batch reactor.40%PW/SG catalyst exhibits the best catalytic performance among these catalysts.The optimal reaction conditions are as follows:mole ratio of ethyl acetoacetate to glycol 1 ∶1.2,catalyst mass fraction in reactants 0.36%,volume fraction of cyclohexane as water removal agent in reaction medium 30%,reaction temperature 383 K and reaction time 90 min.In this case,conversion of ethyl acetoacetate can reach 95.5% and selectivity to fructone is 97% or more.Catalyst stability experiment show that the high catalytic activity of 40%PW/SG can be maintained and high conversion of 95.0% can be kept even after reusing the catalyst for 5 times.