TiO2/MCM-41催化苯酚与碳酸二甲酯邻位烷基化研究

TiO_2/MCM-41 catalysts for ortho-selective alkylation of phenol with dimethyl carbonate

采用等体积浸渍法制备了一系列Ti O_2/MCM-41催化剂,并对其进行X射线衍射、N2吸附-脱附、吡啶吸附红外光谱、NH3程序升温脱附和CO_2程序升温脱附等手段对Ti O_2/MCM-41催化剂的结构性质进行了表征。在气相连续流动固定床反应器上,对催化剂催化性能进行了评价,并研究了催化剂结构及酸碱性对苯酚甲基化反应合成邻甲酚的影响。结果表明:MCM-41经Ti O_2改性后,Ti O_2/MCM-41催化剂上Lewis酸中心和弱碱性中心的数量都不断增加,催化剂酸碱中心的存在明显提高苯酚邻位甲基化反应的活性和邻甲酚选择性。过高的酸中心和碱中心数量会引起邻甲酚的进一步邻位甲基化。最佳工艺条件下,苯酚转化率为85.8%,邻甲酚选择性为60.1%。

A series of Ti O2/ MCM-41 catalysts were prepared by impregnation method. The catalysts were characterized by means of XRD,N2adsorption-desorption,Py-IR,NH3-TPD and CO2-TPD techniques. The performance of the catalysts for the production of ocresol by alkylation of phenol with DMC was evaluated in a continuous flow fixed-bed reactor. The influence of structural and acidicbasic properties of Ti O2/ MCM-41 catalysts on the alkylation activity were studied. Results indicate that the amount of the acidic sites and basic sites in the catalysts increase simultaneously after the Ti O2 modification. The co-existence of acidic sites and basic sites led to the higher methylation activity of phenol and ortho-selectivity for o-cresol. The subsequent methylation of o-cresol would be caused when the amount of acidic sites and basic sites are too high. Under the optimal conditions,the conversion of phenol is85. 8%,the yield of o-cresol is 60. 1%.