Comparative catalytic study on butene/isobutane alkylation over LaX and CeX zeolites: The influence of calcination atmosphere  

作　　者：Zhiqiang Yang Ruirui Zhang Honghua Zhang Hongguo Tang Ruixia Liu Suojiang Zhang 

机构地区：[1]School of Chemical Engineering&Technology,Tianjin University,Tianjin 300072,China [2]Beijing Key Laboratory of Ionic Liquids Clean Process,State Key Laboratory of Multiphase Complex Systems,CAS Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Sciences,100049 Beijing,China [3]School of Chemical Engineering,University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Chinese Journal of Chemical Engineering》2022年第6期173-183,共11页中国化学工程学报（英文版）

基　　金：This work was supported by the National Key Research and Development Program of China(2017YFA0206803);the National Natural Science Foundation of China(21878315);the Key Programs of the Chinese Academy of Sciences(KFZD-SW-413);the Key Programs of Innovation Academy for Green Manufacture,CAS(IAGM2020C17);K.C.Wong Education Foundation(No.GJTD-2018-04);the Major Program of National Natural Science Foundation of China(21890762).

摘　　要：Lanthanum-containing(LaX)and cerium-containing X zeolites(CeX)were prepared by a doubleexchange,double-calcination method.By changing the calcination atmospheres between nitrogen and air,the Ce^(IV) contents in CeX zeolites were adjusted and their impacts on physicochemical properties and catalytic performance in isobutane alkylation were established.The crystallinity of CeX zeolite was found to be negatively correlated with the Ce^(IV) content.This i s believed to be due to the water formed during the oxidation of Ce^(III),which facilitates the framework dealumination.As a consequence,calcining in air resulted in a great elimination of strong Brønsted acid sites while under nitrogen protection,this phenomenon was mostly hindered and the sample’s acidity was preserved.When tested in a continuously flowed slurry reactor,the catalyst lifetime for isobutane alkylation was found to be linearly related to the strong Brønsted acid concentration.In addition,Ce^(3+)was found more benefit for the hydride transfer compared with La^(3+),which is ascribed to the stronger polarization effect on the CH bond of isobutane.Moreover,the decline of hydride transfer activity can be slowed down by the catalytic cracking of the bulky molecules.Based on the product distribution,a new catalytic cycle of dimethylhexanes(DMHs)involving a direct formation of isobutene rather than tert-butyl carbocation was proposed in isobutane alkylation.

关 键 词：CeX zeolite Calcination atmosphere Isobutane alkylation Brønsted acid Hydride transfer 

分 类 号：TE624.4[石油与天然气工程—油气加工工程]