固相外延生长法制备ZSM-5@Silicalite-1分子筛及其CO_(2)加氢耦合甲苯烷基化反应的影响  

Effect of ZSM-5@Silicalite-1 zeolites prepared by solid phase epitaxial growth method on CO_(2)hydrogenation and toluene alkylation reactions

作　　者：贾艺敏 牛鹏宇 贾丽涛[1] 林明桂[1] 郭荷芹[1] 肖勇[1] 侯博[1] 李德宝[1,3] JIA Yimin;NIU Pengyu;JIA Litao;LIN Minggui;GUO Heqin;XIAO Yong;HOU Bo;LI Debao(State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,Taiyuan 030001,China;University of Chinese Academy of Sciences,Beijing 100049,China;Dalian National Laboratory of Clean Energy,Dalian 116023,China)

机构地区：[1]中国科学院山西煤炭化学研究所煤炭高效低碳利用全国重点实验室,山西太原030001 [2]中国科学院大学,北京100049 [3]中国科学院洁净能源创新研究院,辽宁大连116023

出　　处：《燃料化学学报（中英文）》2024年第8期1115-1130,共16页Journal of Fuel Chemistry and Technology

基　　金：山西省重点研发计划(202102090301003)资助。

摘　　要：本研究采用固相法在ZSM-5表面外延生长Silicalite-1,制备出ZSM-5@Silicalite-1分子筛。同时制备高活性氧化物ZnZrOx,并与ZSM-5@Silicalite-1物理混合组成ZnZrOx/ZSM-5@Silicalite-1双功能催化剂,研究了CO_(2)加氢耦合甲苯烷基化催化性能。相比于ZnZrOx/ZSM-5催化剂,分子筛改性后的双功能催化剂提高了对二甲苯(PX)选择性。研究了晶化条件(硅源、晶化过程、晶化次数)对ZSM-5外延生长Silicalite-1的影响,以及Silicalite-1钝化层厚度对CO_(2)加氢耦合甲苯烷基化反应性能的影响。在400℃、3 MPa反应条件下,ZZO/1:3.5Z5-Na-SiO_(2)催化剂的甲苯转化率为12.0%,二甲苯选择性为77.4%,在二甲苯中对二甲苯选择性为73.4%。通过SEM、XRD、N2吸附-脱附、XPS、NH3-TPD、Py-FTIR等表征,研究了分子筛的结构和酸性质。结果表明,通过固相外延生长,延长ZSM-5的孔道,增加间二甲苯(MX)、邻二甲苯(OX)的扩散阻力,同时钝化外表面的酸性,可以有效提高对二甲苯(PX)的选择性。固相外延生长法改性ZSM-5分子筛,摒弃了以往堵塞孔以缩小孔口改性分子筛的缺点,在保证催化剂活性的同时提高了产物选择性。CO_(2)hydrogenation to synthesize high value-added aromatics is of great significance to alleviate the energy climate problem caused by CO_(2)emission.It is generally believed that the reaction course of CO_(2)hydrogenation of toluene coupled with alkylation to produce xylenes is as follows:firstly,CO_(2)reacts with H2 to produce methanol intermediates,and then the methanol intermediates react with toluene on zeolite catalysts to produce para-xylene(PX)by alkylation.According to the reaction pathway,it is necessary to construct a bifunctional catalyst with synergistic matching of the two process conditions to simultaneously realize the hydrogenation of CO_(2)to methanol intermediate and the alkylation of the intermediate and toluene to generate para-xylene.The ZnZrOx/ZSM-5 catalytic system,in which the ZnZrOx has strong thermal stability and CO_(2)activation ability,and the ZSM-5 has a good morphology selectivity for PX,is considered to be a promising CO_(2)hydrogenated toluene coupled alkylation catalyst.However,this system still suffers from low PX selectivity,mainly due to the presence of non-selective acidic sites on the outer surface of the zeolite or near the pore orifice,which leads to the generation of side reactions,such as deep methylation and toluene isomerization,and reduces the selectivity.In this paper,ZSM-5@Silicalite-1 zeolites were prepared by epitaxial growth of Silicalite-1 on the surface of ZSM-5 using solid-phase synthesis.At the same time,the highly active oxide ZnZrOx was prepared and physically mixed with ZSM-5@Silicalite-1 to form a ZnZrOx/ZSM-5@Silicalite-1 bifunctional catalyst to study the catalytic performance of CO_(2)hydrogenation coupled with toluene alkylation.Compared with the ZnZrOx/ZSM-5 catalyst,the modified zeolite improved the para-xylene(PX)selectivity.The effect of crystallization conditions(silicon source,crystallization process,and number of crystallizations)on the epitaxial growth of Silicalite-1 from ZSM-5 was investigated,as well as the effect of the thickness of the

关 键 词：MFI型分子筛 外延生长 对二甲苯 固相法 CO_(2)加氢耦合甲苯烷基化 

分 类 号：O643[理学—物理化学]