（TEAH）nH3-nPW12O40催化苯甲醇选择氧化及其反应机理

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）_nH_3-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，³¹PNMR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.

Selective oxidation of benzyl alcohol catalyzed by (TEAH)nH3-nPW12O40 and its reaction mechanism

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)_nH_3-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.