改性超稳Y沸石负载的杂多酸铯盐在草莓酯合成反应中的催化性能

Catalytic Activity of Cs-Salts of 12-Phosphotungstic Acid Supported on Dealuminated Ultra-Stable Zeolite in Synthesis of Fructone-B

制备了一系列以脱铝超稳Y沸石(DUSY)为载体的磷钨酸(PW)及其铯盐催化剂,考察了催化剂在以乙酰乙酸乙酯和1,2-丙二醇为原料催化合成草莓酯反应过程中的性能。结果表明,在负载量(质量分数)为30%的Cs2.5H0.5PW/DUSY催化剂上的乙酰乙酸乙酯的转化率最高,达到95.3%,草莓酯的选择性为100%。得到了适宜的反应条件:反应温度363K,n(乙酰乙酸乙酯)∶n(1,2-丙二醇)=1∶1.5,催化剂占反应体系的质量分数为0.8%,带水剂环己烷占反应体系的质量分数为36%。经过5次反复使用后,负载型磷钨酸铯盐催化剂的催化活性仍较高,转化率达88.2%,而相应的负载型磷钨酸催化剂的催化活性却大幅度下降,转化率仅有31.2%。催化剂活性下降的主要原因是在极性反应体系中杂多酸化合物活性组分流失,而负载型磷钨酸铯盐良好的稳定性源于其难溶脱性。

A series of 12-phosphotungstic acid (PW) and their Cs salts catalysts supported on dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their catalytic activities were measured by synthesis of fructone-B from ethyl acetoacetate and 1,2 -propanediol. The catalyst with loading of Cs salt being 30% in mass, namely 30% Cs2.5H0.5 PW/DUSY, showed the highest activity of 95.3% conversion among all cesium salts of PW supported on DUSY, and selectivity of fructone-B being 100%. Optimal reaction conditions were: reaction temperature 363 K, mole ratio of ethyl acetoacetate to 1,2 - propanediol 1:1.5, reaction time 90 min, and mass fraction of catalyst and cyclohexane (as water removal agent) in the reaction medium were 0.8% and 36%, respectively. After 5 reaction cycles, the catalytic activity of 30% PW/DUSY catalyst drastically dropped to 31.2%, in contrast, 30% Cs2.5H0.5 PW/DUSY catalyst still showed a considerable conversion of 88.2%. The catalytic deactivation was mainly due to leaching of heteropoly species into polar reaction medium. The high catalytic stability of supported cesium salt of PW originated from low leachability of the latter.