固载化N-羟基邻苯二甲酰亚胺在分子氧氧化二苯甲醇为二苯甲酮反应过程中的催化特性

Catalytic Characteristics of Immobilized N-hydroxyphthalimide in Oxidation of Benzhydrol to Diphenyl Ketone by Molecular Oxygen

采用简捷高效的方法在交联聚苯乙烯(CPS)微球表面同步合成与固载了N-羟基邻苯二甲酰亚胺(NHPI),制备了非均相催化剂CPS-NHPI微球,我们将其用于分子氧对二苯甲醇的氧化过程,探索研究了其催化性能与催化氧化机理,并考察了主要因素对其催化性能的影响.研究结果表明,将固体催化剂微球CPS-NHPI与过渡金属盐组合形成复合催化剂,可有效地催化分子氧对二苯甲醇的氧化过程.在几种过渡金属盐中,助催化效果的顺序是VO(acac)2>Co(OAc)2>Co Cl2>Mn(OAc)2.显然,乙酰丙酮氧钒盐的助催化效果最好.共催化体系CPS-NHPI+VO(acac)2可在温和条件(75℃、常压的氧气)下高效地将二苯甲醇催化氧化转变为二苯甲酮(二苯甲醇转化率为35.8%,且二苯甲酮是唯一产物),显示出良好的催化活性与优良的催化选择性,催化氧化反应遵循自由基链式反应的机理.体积比为7∶3的乙腈与乙酸乙酯的混合液为适宜的反应溶剂;VO(acac)2与固载NHPI的摩尔比为1∶15时,助催化剂的投加量较为适宜.固体催化剂CPS-NHPI还具有良好的再循环使用性能.

Synchronous synthesis and immobilization of N-hydroxyphthalimide（ NHPI） were realized on closslinked polystyrene（ CPS） microspheres,obtaining the heterogenous solid catalyst CPS-NHPI. In this investigation,CPSNHPI microspheres were used in the oxidation of benzhydrol as a secondary alcohol with molecular oxygen as oxidant,and their catalytic activity and the mechanism of the catalytic oxidation were investigated. The effects of the main factors on the catalytic oxidation reaction were researched in depth. The experimental results show that the catalyst microspheres CPS-NHPI in combination with transition metal salt can effectively catalyze the oxidation transformation of benzhydrol to diphenyl ketone by molecular oxygen. Among several transition metal salts,the order of co-catalytic effect is VO（ acac）2〉 Co（ OAc）2 Co 〉Cl2 〉Mn（ OAc）2. It is obvious that vanadyl acetylacetonate is the best co-catalyst. The compositional catalyst CPS-NHPI ＋ VO（ acac）2can highly effectively catalyzed the oxidation transforming of benzhydrol to diphenyl ketone（ 35. 8% conversion of benzhydrol and diphenyl ketone as only one product） under the mild conditions such as at 75 ℃ and with oxygen at ordinary pressure,displaying fine catalytic activity and excellent catalysis selectivity. The catalytic oxidation follows a mechanism of free radical chain reaction. The mixture of acetonitrile and ethyl acetate with a volume ratio of 7∶ 3 is the appropriate solvent,and 1∶ 15 as the molar ratio of VO（ acac）2to the immobilized NHPI,the added amount of the co-catalyst is the suitable. The solid catalyst CPS-NHPI has good cycling and reuse performance.