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采用溶胶凝胶法将Dawson型磷钨酸负载于SiO2上,制备的负载型催化剂H6P2W18O62/SiO2,通过FTIR、XRD、SEM、TGA对其进行表征。结果表明,该Dawson型磷钨酸可以较均匀地分散在SiO2载体上,且在催化合成4-苯基-6-甲基-5-乙氧羰基-3,4-二氢嘧啶-2(H)-酮的Biginelli反应中表现出较高的催化活性。最佳反应条件为:在固定苯甲醛用量为0.04 mol条件下,n(苯甲醛)∶n(乙酰乙酸乙酯)∶n(尿素)=1∶1.5∶1.5,催化剂用量为反应物总质量的2.0%,反应温度为80℃,反应时间为75 min。在最优条件下,产品平均收率可达82.3%,催化剂重复利用10次后收率仍达57.2%。
Dawson-type phosphotungstic acid was supported on SiO2 by sol-gel method. The supported catalyst H6P2W18O62 / SiO2 was characterized by FTIR, XRD, SEM and TGA. The results show that the Dawson-type phosphotungstic acid can be more uniformly dispersed on the SiO2 support, and in the catalytic synthesis of 4-phenyl-6-methyl-5-ethoxycarbonyl-3,4-dihydropyrimidine-2 ) -one shows a high catalytic activity in the Biginelli reaction. The optimal reaction conditions are as follows: n (benzaldehyde): n (ethyl acetoacetate): n (urea) = 1: 1.5: 1.5 at a fixed amount of benzaldehyde of 0.04 mol, 2.0%, the reaction temperature was 80 ℃, the reaction time was 75 min. Under the optimal conditions, the average yield of the product reached 82.3%, and the yield of the catalyst still reached 57.2% after being repeatedly used for 10 times.