分子筛催化剂上正十六烷的临氢异构化反应_黄卫国

收稿日期:2002-12-27.　第一作者:黄卫国,男,1970年生,博士.

联系人:黄卫国.Tel :(010)62327551-3164;Fax :(010)62311290;E -mail :huangwg @ripp -sinopec .com .

文章编号:0253-9837(2003)09-0651-07

研究论文:651～657

分子筛催化剂上正十六烷的临氢异构化反应

黄卫国1,　李大东1,　石亚华1,　康小洪1,　孟宪波1,

王　奎1

,　董维正1

,　聂　红1

,　李　灿

2

(1中国石油化工股份有限公司石油化工科学研究院,北京100083;2中国科学院大连化学物理研究所催化基础国家重点实验室,辽宁大连116023)

摘要:对分子筛催化剂上正十六烷的临氢异构化反应进行了研究,考察了不同分子筛催化剂的活性和选择性,并对临氢异构化反应的产物分布进行了分析.在此基础上,对正十六烷的临氢异构化反应机理进行了初步探讨.结果表明,正十六烷在中

孔分子筛催化剂上的临氢异构化反应主要在分子筛外表面和孔口进行,分子筛的择形作用对异构选择性的影响有限.这与一般情况下低分子量正构烷烃在择形分子筛上的临氢异构化反应有所不同.临氢异构化反应的异构选择性主要取决于催化剂酸性组分的酸性质,弱酸和中等强度的酸对异构化反应有利,而催化剂的活性则由酸性组分中B 酸中心的数量和加氢组分的活性共同决定.关键词:铂,分子筛,氧化铝,正十六烷,临氢异构反应,反应机理中图分类号:O643 文献标识码:A

Hydroisomerization of n -Hexadecane on Zeolite Catalysts

HUANG Weiguo 1＊,LI Da dong 1,SHI Yahua 1,KANG Xiaohong 1,MENG Xianbo 1,

WANG Kui 1,DONG Weizheng 1,NIE Hong 1,LI Can 2

(1Res earch Institute of Petroleum Pro ces sing ,S INOPEC ,Beijing 100083,China ;2State K ey Laboratory of Catalysis ,

Dalian Institute of Chemical Physics ,The Chinese Academy of Sciences ,Dalian 116023,Liaoning ,China )

A bstract :Hydroisomerization of n -hexadecane on zeolite cataly sts w as studied and the reaction mechanism was discussed ,w hich may provide new clues to developing hydroisomerization catalysts with high selectivity .The catalysts w ere prepared as follows :zeolite and alumina were mixed and then extruded to make a support ,after drying and calcination ,platinum was loaded on by wet im pregnation with Pt (NH 3)4Cl 2solutio n .The hydroiso -merization of n -hexadecane w as carried out in a continuous fixed -bed reactor with dow n -flow .The catalysts w ere loaded in the reactor and reduced for 4h .Then n -hexadecane w as pumped into the reactor at different temperatures .The reaction results indicated that Pt /MCM -22and Pt /ZSM -5cataly sts show higher activity but lower selectivity than Pt /H βand Pt /SAPO -11cataly sts .The selectivity of Pt /SAPO -11is the hig hest ,mo re than 90%at the conversion of 80%.From the cracked product distribution ,it could be seen that ,for Pt /ZSM -5and Pt /H β,the fractions of small molecule products ,such as C 3,C 4and C 5,are more than those of long chain products ,but fo r Pt /SAPO -11,the cracked product distribution is nearly symmetrical ,w hich means that there is secondary cracking occurred fo r Pt /ZSM -5and Pt /H βbut no for Pt /SAPO -11.The symmetrical distribution of cracked products is the characteristics of large -pore zeolites or amo rphous cataly sts ,so it can be concluded that the hydroisomerization takes place on the external surface or at the pore mouth of SAPO -11,but not in the po re channel .The different zeolites showed different behavior fo r the isomerization ,w hich can be attributed to their different acidity .The strong acidity of MCM -22and ZSM -5leads to poor isomerization selectivity .SAPO -11has high selectivity ,indicating that the w eak and mild acids are favorable to the isomerization .Key words :platinum ,zeolite ,alumina ,n -hexadecane ,hydroisomerization ,reaction mechanism

第24卷第9期　Vol .24N o .9　

催　化　学　报

Chinese Journal of Catalysis

2003年9月

　September 2003