摘要
利用X射线衍射、N2物理吸附与NH3-程序升温脱附等手段以及异辛烷加氢裂化探针反应研究了硅烷化处理对Pt/SAPO-11催化剂结构和酸性的影响,并考察了催化剂对正十二烷临氢异构化反应的催化性能.结果表明,硅烷化处理有效清除了样品外表面的酸性位,减少了发生在外表面的非选择性裂化反应.硅烷化处理后,催化剂对单支链异构体的选择性明显提高,尤其对单支链端甲基异构体的选择性显著提高,但催化剂的总体异构化选择性有所降低.硅烷化处理可能造成催化剂的孔口窄化,从而提高单支链异构体的选择性,但同时也导致其微孔孔道内裂化反应的增多.
The effect of silanization of SAPO-11 on the hydroisomerization of n-dodecane over Pt/SAPO-11 catalysts was studied. The SAPO-11 support was silanized by the chemical liquid deposition with tetraethoxysilane or tetrachlorosilicane. The Pt/SAPO-11 catalysts were characterized by X-ray diffraction, N2 adsorption, NH3- temperature-programmed desorption（TPD） and hydrocracking of 2,2,4-trimethylpentane. N2 adsorption and NH3-TPD results show that the micropore volume and the acidity of the catalysts are reduced after silanization, and the reaction rates of 2,2,4-trimethylpetane hydrocracking over the catalysts are also reduced. This indicates that the acidic sites on the external surface of SAPO- 11 are selectively deactivated by silanization. The selectivity for monobranched isomers over Pt/SAPO-11 is enhanced by silanization, which is ascribed to the shrink of pore mouths of SAPO-11 after silanization. Moreover, the total hydroisomerization selectivity decreases after silanization. Due to the shrink of pore mouths of the silanized catalysts, diffusion limitation to branched products might increase, leading to severe hvdrocracking reactions in micropores of the catalysts.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2005年第9期819-823,共5页
基金
中国科学院知识创新工程领域前沿项目资助(DICPK2003D4).
作者简介
汪哲明，男，1976年生，博士研究生．联系人：田志坚，Tel：（0411）84379151；E—mail：tianz@dicp．ac．cn．
