Bi - MSU -4介孔分子筛催化过氧化氢氧化苯乙烯

摘要

Mesoporous molecular sieves Bi-MSU-4 were synthesized using Tween-40 as the template, TEOS as silicon source and Bi(NO3)3 ? 5H2O as bismuth source under the condition of normal temperature and pressure,and was used to catalyze the oxidation of styrene to benzaldehyde. The results of ther-modynamic calculation showed that the catalytic oxidation of styrene was irreversible reaction. The experimental results indicated that the optimum reaction condition was obtained as follows: reaction temperature (80-90) t,molar ratio of H2O2(30wt% ) to styrene 3. 37: 1 ,the dosage of methanol and the catalyst 40 mL and 0.15 g respectively. With the formation of the five member ring intermediate among Bi active sites,H2O2 and methanol,the energy of the system decreased and the five member ring intermediate produced a Bronsted acid centre,which had stronger oxidizability and could break the double bond of styrene. That account for better activity of Bi-MSU-4 for styrene oxidation to benzaldehyde with H2O2.%采用Tween - 40为模板剂,正硅酸乙酯为硅源,硝酸铋为铋源,在常温、常压条件下合成Bi - MSU -4介孔分子筛,并用于苯乙烯催化氧化反应.热力学计算表明,苯乙烯催化氧化反应为不可逆反应.在半间歇反应釜进行单因素及正交实验,结果表明,反应最佳温度(80 ～90)℃,过氧化氢与苯乙烯物质的量比为3.37:1,甲醇40 mL,催化剂用量0.15 g.对反应机理进一步分析推测,骨架Bi、过氧化氢及甲醇之间由于存在氢键而形成稳定的五元环过渡态,该五元环能释放出一个质子,使反应过程产生B酸中心,具有更强的氧化性,能够更好地解释碳碳双键断裂生成醛的实验现象.