Y分子筛催化异丁烷/丁烯烷基化反应中焦组分的吸附模拟

Adsorption Simulation of Coke Precursors in Isobutene/Butane Alkylation Over Y Zeolite

选取分子筛催化异丁烷/丁烯烷基化反应过程中不同结构类型和碳数的焦组分模型化合物,采用分子模拟方法计算模型化合物在Y分子筛孔道内Brnsted(B)酸中心附近的稳定吸附构象,研究焦组分在Y分子筛孔道内的吸附能力差异性和堵孔效应。结果表明,不同结构类型焦组分的吸附能力由强到弱的顺序依次为烯烃类、烷基苯类、烷基萘类、烷烃类、烷基环己烷类、烷基萘烷类;焦组分碳数的增加对焦组分与B酸中心之间的相互作用并无影响;直链类焦组分对Y分子筛的孔道内呈二维空间占据,环状类焦组分对Y分子筛的孔道内呈三维空间占据,而双环类焦组分在X方向上对所在十二元环孔道的径向空间占据更大,堵孔效应更明显。

Selecting different structure and carbon number model compounds of coke precursors generated in isobutane/butene alkylation reaction process,the adsorption energy and stable adsorption conformation of coke precursor model compounds near Br nsted acid sites of Y zeolite were calculated by using molecular simulation methods.Then the adsorption capacity difference and channel blocking effect for coke precursors were investigated based on the calculated results.It was observed that the order of adsorption ability for coke precursors from strong to weak is olefin,alkyl benzene,alkyl-naphthalene,alkane,alkyl-cyclohexane and alkyl-naphthalane.Coke precursor’s carbon number has no impact on the interaction between coke precursor and Br nsted acid site.The straight chain coke precursor compounds occupy two-dimensional space in Y zeolite channel after adsorption,and the cyclic coke precursor compounds occupy three-dimensional space in Y zeolite channel.Especially,bicyclic coke compounds have a larger occupation in the radial space of 12-member ring channels from X direction,which indicates more serious pore blocking effect.