β沸石催化剂上二异丙苯与苯反应机理及催化剂失活

STUDY ON THE REACTION MECHANISM OF DIPB WITH BENZENE OVER β ZEOLITE CATALYST AND CATALYST DEACTIVATION

采用Ｉｎ－ｓｉｔｕＩＲ和ＴＰＤ－ＩＴＤ研究了二异丙苯（ＤＩＰＢ）、异丙苯（ＩＰＢ）、苯和丙烯在改性β沸石催化剂上的吸附和反应。考察了１，３－ＤＩＰＢ和１，４－ＤＩＰＢ与苯烷基转移的反应性能、催化剂的酸性质和催化剂的稳定性。结果表明，１，３－ＤＩＰＢ与苯烷基转移反应主要按双分子反应ＳＮ２－１机理进行，而１，４－ＤＩＰＢ与苯主要按单分子反应ＳＮ１机理进行；１，３－ＤＩＰＢ和１，４－ＤＩＰＢ之间存在着异构化反应。改性β沸石催化剂失活原因是：（１）焦炭覆盖在部分酸性中心上，使得催化剂的活性下降；（２）烷基萘等相对分子质量较大、沸点较高的化合物沉积在催化剂的孔口或表面。

The adsorption and reaction of propylene benzene,isopropylbenzene (IPB) and diisopropylbenzene (DIPB) over modified β type zeolite catalyst were studied by using in situ IR and TPD ITD methods.The reaction performances,the acid property and the stability of catalyst were evaluated.It is proposed that the transalkylation reaction of 1,3 DIPB with benzene is conducted according to the SN 2 1 mechanism,while 1,4 DIPB with benzene according to the SN 1 mechanism.Isomerization reaction may take place between 1,3 and 1,4 DIPB.The reason for catalyst deactivation is suggested as (1) part of the active sites may be covered by coke and this directed to catalyst deactivation;(2)bigger moleculars,such as alkyl naphthalene etc.,may deposit in the pore or on the surface of the catalyst and this directed to pore blockage.