MCM-41负载磷钨酸催化剂的制备及其对乙酰化反应的催化性能

采用水热合成法制备了介孔分子筛 MCM-41,并利用浸渍方法将磷钨酸负载在 MCM-41分子筛上,经煅烧得到 PW/MCM-41催化剂;利用 X 射线衍射、傅里叶变换红外光谱、N_2吸附-脱附和 NH_3程序升温脱附等手段对催化剂进行了表征;考察了 PW/MCM-41催化剂对苯甲醚及1,4-二甲氧基苯的乙酰化反应的催化性能。表征结果显示,磷钨酸负载到 MCM-41分子筛上后,保持了 Keggin 结构,MCM-41分子筛保持了介孔结构。实验结果表明,PW/MCM-41催化剂的活性随磷钨酸负载量的增大而降低;磷钨酸质量分数为30%的 PW/MCM-41催化剂上反应底物的转化率最高,使用该催化剂0.8 g,以10 mL 二氯甲烷为溶剂,在苯甲醚用量0.01 mol、乙酸酐用量0.02 mol、反应温度140℃、反应时间4 h 的条件下,苯甲醚转化率可达77.0%,对甲氧基苯乙酮的选择性为96.5%。

Synthesis of MCM-41 Supported Phosphotungstic Acid and Its Catalytic Performance in Acetylation

PW/MCM-41 catalyst was prepared by supporting phosphotungstic acid(PW)on mesoporous MCM-41 molecular sieves via impregnation and then calcination.The said molecular sieves were synthesized by hydrothermal method.The catalysts were characterized by means of XRD, FTIR,nitrogen adsorption and NH3-TPD.The original Keggin structure of PW and mesoporous structure of MCM-41 molecular sieves were maintained after supporting PW on MCM-41 molecular sieves.PW/MCM-41 catalyst was used in acetylation of 1,4-dimethoxybenzene or anisole.The catalyst activity decreased with increase of PW loading.PW/MCM-41 catalyst with 30%(mass fraction) PW is preferable.Using this catalyst in acetylation of anisole,conversion of 77.0% and selectivity of 96.5% to p-methoxy acetophenone were obtained under the conditions:140℃,4 h,10 mL dichloromethane as solvent,0.8 g catalyst,0.02 mol of acetic anhydride and 0.01 mol of anisole.