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摘要: 采用水热法合成了SAPO-5、SAPO1-1、SAPO-41分子筛，并以间二甲苯异构化反应为模型反应，考察了SAPO-5、SAPO-11、SAPO-41的催化性能；运用XRD、BET、吸附吡啶的FTIR等手段表征了SAPO的结构和酸性。结果表明，在合成投料比相同的情况下，SAPO-11具有最大的较强B酸量，表现出了最好的间二甲苯异构催化活性。SAPO-5因为较强B酸中心数目少，异构催化活性最差。三种分子筛的间二甲苯异构化催化活性和较强B酸中心的分布均呈SAPO-5＜SAPO-41≈SAPO-11顺序排列。较强B酸中心的分布是决定催化剂异构化活性的主要因素。中孔分子筛SAPO-11、SAPO-41孔道直径与对位产物的直径接近，对位选择性比大孔分子筛SAPO-5好。Abstract: Silicoaluminophosphate molecular sieves SAPO-5, SAPO-11 and SAPO-41 were synthesized and characterized by XRD, IR and pyridine adsorption IR. Their catalytic performances in isomerization of m-xylene were investigated. SAPO-11 owns the largest number of acid sites, particularly the strong Brnsted acid sites, and then exhibits the highest activity and selectivity to p-xylene; whereas low activity and selectivity were obtained over SAPO5 catalyst. The sequence of activity and the number of strong Brnsted acid sites of the SAPOs followed SAPO-5＜SAPO-41≈SAPO-11. Both SAPO-11 and SAPO-41 produce predominantly the p-xylene isomer due to their medium size pores.
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Key words:
- SAPO /
- isomerization /
- Brnsted acid sites /
- pore opening
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