富介孔分子筛催化剂催化偏三甲苯非临氢异构化

Non-Hydrogen Isomerization of Pseudocumene to Mesitylene Over Zeolite Catalyst With Rich-Mesopores

偏三甲苯(1,2,4-TMB)异构化制均三甲苯(1,3,5-TMB)是重整C9芳烃综合利用中的重要工艺,将3种具有十二元环孔道或孔穴的分子筛催化剂Hβ、HMOR和HMCM-22,用于非临氢条件下偏三甲苯液相异构化制均三甲苯反应。采用XRD、SEM、N_(2)物理吸附、NH_(3)-TPD、吡啶和2,6-二叔丁基吡啶吸附红外等方法对分子筛催化剂的织构和酸性质进行表征,揭示了分子筛结构、物化性质与催化偏三甲苯异构化性能之间的构效关系。结果表明,HMCM-22催化剂具有较大的外表面和大量的位于外表面十二元孔穴的Br?nsted酸中心,表现出很好的异构化活性和选择性。在此基础上,采用无机碱+有机碱组合的改性策略对HMCM-22孔结构和酸性进行调控,制备了富介孔的改性HMCM-22催化剂,并对其偏三甲苯异构化性能进行评价。结果表明,经碳酸铵和四乙基氢氧化铵改性后,HMCM-22催化剂的外表面积和孔体积增大,获得了更多可及的中强和强Bronsted酸中心,在温度310℃、压力3.0 MPa、质量空速0.8 h^(-1)和氮气流速15 mL/min的条件下,均三甲苯选择性和收率分别高达63.29%和23.78%,邻甲乙苯质量分数低于0.13%,HMCM-22催化剂具有很好的工业化应用前景。

The synthesis of mesitylene(1,3,5-TMB)by the isomerization of pseudocumene(1,2,4-TMB)is an important process in the comprehensive utilization of the reformed C9 aromatics.Three molecular sieve catalysts with 12-membered ring channels or pores,including Hβ,HMOR and HMCM-22,were used for non-hydrogen liquid-phase isomerization of pseudocumene.The textural and acid properties of zeolite catalysts were characterized by XRD,SEM,N_(2) physical adsorption,NH_(3)-TPD,Py-IR and DTBPy-IR techniques,thus revealing the structure-activity relationship between the structure,physicochemical properties of zeolites and the isomerization performance of pseudocumene.The results show that HMCM-22 catalyst presents high isomerization activity and selectivity,which can be ascribed to its large external surface and plenty of Br nsted acid sites in the 12-membered ring pores located on the external surface.Based on this,the modified HMCM-22 catalysts with rich-mesopores were prepared by a combined modification strategy,and the pore system and acidity of HMCM-22 were adjusted by both inorganic and organic base;moreover,the pseudocumene isomerization performance of the modified HMCM-22 catalysts was evaluated.The results show that after being modified by ammonium carbonate(AC)and tetraethyl ammonium hydroxide(TEAOH),the HMCM-22 catalysts possess large surface area,high pore volume,and more accessible medium-strong Br nsted acid sites.Under temperature of 310℃,pressure of 3.0 MPa,and mass space velocity of 0.8 h^(-1) with nitrogen flow rate of 15 mL/min,the selectivity and yield of mesitylene cam reach as high as 63.29%and 23.78%,respectively,and the o-ethylmethylbenzene mass fraction is lower than 0.13%.The HMCM-22 catalyst with rich-mesopores exhibits a good prospect of industrial application.