采用复分解法制备出 Dawson 型磷钨酸铝(A1 H 3 P2 W18 O 62?n H 2 O)催化剂,通过 FT-IR、SEM、EDS、Py-IR 和 NH 3-TPD 对其进行了表征,并首次用于催化合成尼泊金丁酯.Py-IR 表征结果显示,A1 H 3 P2 W18 O 62?n H 2 O 同时具有 Br?nsted 酸中心和 Lewis酸中心.NH 3-TPD 测试结果表明 A1 H 3 P2 W18 O 62?n H 2 O 同时具有弱酸、强酸和超强酸中心,且以强酸中心为主.通过正交实验确定了合成尼泊金丁酯的优化工艺条件为催化剂用量4．9％(基于反应物质量),n (正丁醇)与 n (对羟基苯甲酸)＝3∶1,反应时间3．0 h,反应温度120℃.在此条件下,尼泊金丁酯收率可达93．2％.与单纯 Dawson 型磷钨酸或浓硫酸催化效果相比,尼泊金丁酯收率得到提高.A1 H 3 P2 W18 O 62?n H 2 O 易于回收和重复使用,当重复使用5次后,尼泊金丁酯收率仍为73．1％.
Dawson type aluminium phosphotungstate was prepared by the precipitation method,and character-ized by FT-IR,SEM,EDS,Py-IR and NH 3-TPD.Then it was used in the preparation of butylparaben as cata-lyst for the first time.Results of Py-IR reveal that A1 H 3 P2 W1 8 O 62 has both Br?nsted and Lewis acid centers. NH 3-TPD results show that A1 H 3 P2 W1 8 O 62 has weakly acidic sites,strong acid sites and super acid sites,the major part of acid sites are strong acid site.The optimum esterification conditions determined by orthogonal ex-periments were:mass ratio of catalyst to reactants,4.9%;molar ratio of n-butyl alcohol to p-hydroxyl benzoic acid,3∶1;the reaction temperature,120 ℃;the reaction time,3.0 h.Under these conditions,the yield of bu-tylparaben was up to 93.2%,which is higher than those with Dawson type phosphotungstic acid or concentrated sulfuric acid as the catalyst.A1 H 3 P2 W1 8 O 62 can be easily recycled and reused,the yield of butylparaben remains up to 73.1% after 5 cycles.
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