摘要
以硅氧烷为改性剂,采用化学液相沉积法制备了系列改性HZSM-5催化剂,用X射线衍射(XRD)、低温N2物理吸附及程序升温氨脱附(NH3-TPD)表征了催化剂的物化性质,并在高压微型反应装置上考察了改性催化剂在甲苯歧化反应中的催化性能,详细考察了催化剂制备过程中沉积量、沉积时间和沉积次数对甲苯转化率和对二甲苯选择性的影响。结果表明,催化剂颗粒的内外层SiO2沉积不均匀,形成了蛋壳型的催化剂;SiO2主要沉积在ZSM-5晶粒的外表面,而内部结构和酸性影响不显著。改性催化剂可大幅度提高甲苯歧化的对位选择性;沉积时间对选择性影响不大,多次沉积、增加沉积剂量可提高对位选择性,且存在一个最佳沉积量。
A series of modified HZSM-5 catalysts by chemical liquid deposition (CLD) were prepared with the siloxane as a deposition agent. The catalysts were characterized by XRD, N_2-adsorption and NH_3-TPD techniques and their catalytic performance in the disproportionation of toluene were measured in the high-pressure fix-bed reactor. Effects of the CLD conditions, such as deposition amount, time and cycles, on the selectivity of p-xylene and conversion were investigated in detail. After CLD treatment, the eggshell-type catalyst could be produced due to the preferred deposition of SiO_2 on the outer shell of the catalyst particle. The CLD could significantly increase the selectivity of p-xylene without changing framework and acidity of ZSM-5. The para-selectivity was found to be improved substantially by increasing the amount of deposition agent and by the multi-cycle procedure, whereas it was influenced slightly by the deposition time. An optimal deposition amount existed for achieving high conversion and para-selectivity simultaneously.
出处
《南京工业大学学报（自然科学版）》
CAS
2004年第6期15-20,共6页
Journal of Nanjing Tech University(Natural Science Edition)
基金
江苏省高校自然科学基金(No.04KJ13530044)
