改性HZSM-5催化剂上甲苯-甲醇的烷基化反应的研究

采用浸渍法制得了P、B、Cu、Mg单组分及Mg、P、Si多组分复合改性的HZSM-5催化剂,通过XRD、BET、NH3-TPD等手段对改性前后催化剂的结晶度、孔结构及表面酸性进行了表征,在常压连续流动固定床反应装置上考察了改性HZSM-5在甲苯-甲醇烷基化制备对二甲苯反应中的催化性能,并对其微结构、表面酸性与择形选择性进行了关联。结果表明,P、B、Cu、Mg单组分改性的HZSM-5催化剂中,质量分数20%MgO改性使HZSM-5催化剂微孔面积和微孔容大幅下降,强酸显著降低,目标产物对二甲苯选择性明显提高(>60%);Mg、P、Si复合改性的HZSM-5催化剂中,改性剂之间的酸碱等相互作用对改性催化剂的开孔和表面酸性位的影响较大,与单组分改性相比复合改性效果不明显。

Alkylation of Toluene with Methanol over Modified HZSM-5 Catalysts

HZSM-5 molecular sieves modified with single-components such as P,B,Cu,Mg and multi-components such as Mg/Si,Mg/P and Mg/P/Si were prepared by impregnation,and characterized by means of XRD,BET and NH3-TPD.Selective alkylation of toluene with methanol was investigated in a fixed-bed down-flow reactor.Moreover,the microstructure and surface acidity of the modified HZSM-5 were correlated with the selectivity of para-xylene.The results show that the HZSM-5 modified with monocomponent 20% MgO has a high selectivity of para-xylene(>60%) due to the decrease of pore size and quantity of strong acid sites located in the surface of catalysts after modification,and the HZSM-5 modified with multi-components such as Mg/P/Si has no obvious effect on the promotion of p-xylene selectivity due to the interreaction of different modifiers.