超声制备Mg(OH)_2催化剂用于环己酮Baeyer-Villiger反应

在低温条件下将超声辐射技术应用于水合法制备Mg(OH)_2催化剂,运用X射线衍射、傅里叶变换红外光谱和扫描电子显微镜等手段对催化剂进行了表征,同时考察了该催化剂对环己酮Baeyer-Villiger氧化反应合成ε-己内酯反应的催化性能。表征结果显示,经超声处理制得的Mg(OH)_2微粒小且分布均匀,粒径为100 nm左右,且其表面裸露了更多的羟基基团,能加速与H_2O_2的结合。以H_2O_2溶液(质量分数30%)为氧化剂、乙腈为溶剂、超声处理制得的Mg(OH)_2为催化剂,环己酮氧化合成ε-己内酯的适宜反应条件为:乙腈用量12 mL,环己酮29 mmol,n(H_2O_2):n(环己酮)=4.67,Mg(OH)_2催化剂相对于环己酮的质量分数为8.80%,反应温度70℃,反应时间10 h。在此条件下,环己酮的转化率为57%,ε-己内酯的选择性为100%。

Preparation of Magnesium Hydroxide Catalyst by Ultrasonic Treatment for Baeyer Villiger Oxidation of Cyclohexanone

Magnesium hydroxide was prepared by simple hydration of magnesium oxide at low temperature under ultrasonic and used as catalyst in Baeyer Villiger(BV) oxidation of cyclohexanone to ε caprolactone. The physical and chemical properties of the catalyst were analyzed by means of XRD, SEM and FTIR and its catalytic activity was evaluated. Mg(OH)_2 particles with ultrasonic treatment were fine and even with average diameter about 100 nm. The exposed -OH groups on surface of the particles could speed up the combination with oxidant H_2O_2 used in BV oxidation. Under optimal BV oxidation conditions: cyclohexanone 29 mmol,solvent acetonitrile 12 mL, oxidant H_2O_2 solution(mass fraction 30%), n(H_2O_2):n(cyclohexanone) 4.67, Mg(OH)_2 catalyst mass fraction 8.80%(based on cyclohexanone), reaction temperature 70 ℃ and reaction time 10 h, conversion of cyclohexanone and selectivity to ε caprolactone were 57% and 100%, respectively.