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以硝酸镁为前驱体,苹果酸为配合剂,通过配合浸渍法制备了不同负载量的MgO/MCM-22催化剂.在气相连续流动固定床反应器上进行甲苯与碳酸二甲酯(DMC)烷基化合成对二甲苯的研究,并采用XRD、NH3-TPD、吡啶吸附IR、N2吸脱附等手段对催化剂进行表征.实验结果表明:以9%负载量的MgO/MCM-22分子筛为催化剂,在380℃反应物料配比n(甲苯)∶n(DMC)=4∶1、重时空速1 h-1的条件下,甲苯转化率为29.0%,对二甲苯选择性为48.2%.表征结果显示:采用配合浸渍的方法制备MgO改性MCM-22分子筛催化剂不仅可以有效覆盖分子筛外表面酸性位,而且不会影响其孔内的酸性位,从而可以在维持较高对二甲苯选择性的同时实现甲苯转化率的提高.
Magnesium nitrate was used as precursor and malic acid was used as complexing agent to prepare MgO / MCM-22 catalysts with different loadings by impregnation method.Toluene was reacted with dimethyl carbonate (DMC) in a continuous flow fixed-bed reactor XRD, NH3-TPD, pyridine adsorption IR, N2 adsorption-desorption and other means were used to characterize the catalyst.The experimental results showed that the catalyst was prepared with 9% loading of MgO / MCM-22 zeolite , The conversion of toluene was 29.0% and the selectivity of p-xylene was 48.2% under the condition of the ratio of n (toluene): n (DMC) = 4:1 and the weight hourly space velocity of 1 h-1 at 380 ℃. The results show that the preparation of MgO-modified MCM-22 zeolite catalyst by impregnation can not only effectively cover the acidic sites on the outer surface of the molecular sieve, but also does not affect the acidic sites in the pores. Therefore, At the same time to improve the conversion of toluene.