(TEAH)nH3-nPW12O40催化苯甲醇选择氧化及其反应机理  

Selective oxidation of benzyl alcohol catalyzed by(TEAH)_nH_(3-n)PW_(12)O_(40) and its reaction mechanism

作　　者：苏浩[1] 杨春[1] 

机构地区：[1]南京师范大学化学与材料科学学院、江苏省生物医药功能材料协同创新中心、江苏省生物功能材料重点实验室,江苏南京210097

出　　处：《催化学报》2014年第7期1224-1234,共11页

基　　金：江苏高校优势学科建设工程项目~~

摘　　要：以Keggin结构的磷钨酸和三乙胺(TEA)为原料,通过简单的酸碱反应合成了磷钨酸的TEA盐.并以它们为催化剂,考察了以H2O2为氧化剂、以水为溶剂的体系中苯甲醇选择氧化制备苯甲醛的反应性能.结果表明,(TEAH)nH3-nPW12O40(n=1,2,3)系列催化剂对苯甲醇的选择氧化反应有很高的活性和选择性,且可被分离和循环使用.在适宜的反应条件下,最佳催化剂(TEAH)H2PW12O40上,苯甲醇的转化率可达99.6%,苯甲醛的选择性为100%.还采用IR,31P NMR谱和元素分析技术,对催化剂和反应过程中催化剂物种的转化和分布进行了考察,进而导出了反应机理.在这个水--油两相反应中,(PW12O40)3-首先在H2O2的作用下,氧化降解为溶于水的小分子过氧物种(PO4(WO(O2)2)4)3-和自由W物种.(PO4(WO(O2)2)4)3-是真正的活性物种,可将部份溶于水层的苯甲醇氧化为苯甲醛,自身转变为失去活性氧的反应后物种(SAR).而SAR又可与自由W物种一起聚合为前驱体状态的(PW12O40)3-,完成催化循环.Several triethylamine （TEA） salts of phosphotungstic acid were synthesized by an acid-base reaction using a Keggin-type phosphotungstic acid and TEA, and used to catalyze the oxidation of benzyl alcohol to benzaldehyde in water with 30% aqueous hydrogen peroxide as oxidant. （TEAH）nH3-nPW12O40 （n = 1, 2, 3） were excellent catalysts for the reaction and could be isolated and recycled. With （TEAH）H2PW12O40, the conversion of benzyl alcohol and selectivity to benzaldehyde were as high as 99.6% and 100%, respectively, under optimized reaction conditions. The catalysts and their transformation and distribution during the reaction were investigated by IR, 31P NMR and analysis of the reaction system, and the reaction mechanism was deduced. In this water-oil biphasic reaction, （PW12O40）3- was first oxidized and degraded into small （PO4（WO（O2）2）4）3- and free tungsten species that were soluble in the aqueous phase upon reaction with H2O2. Then （PO4（WO（O2）2）4）3-, as the actual oxidant, oxidized benzyl alcohol soluble in the aqueous phase to benzaldehyde, and was converted into a SAR （species after reaction） after losing its active oxygen. The catalytic cycle was completed by the polymerization of the SAR with the free tungsten species back to larger catalyst precursor （PW12O40）3-, which was soluble in the oil phase.

关 键 词：苯甲醇 选择氧化 磷钨酸盐 机理 

分 类 号：O625.41[理学—有机化学]