碱金属改性对SAPO-34分子筛催化性能的影响

通过等体积浸渍法,制备得到碱金属(Li、Na、K、Rb、Cs)改性的SAPO-34催化剂。并在常压连续固定床反应器上评价了各催化剂的甲醇制低碳烯烃(MTO)的性能,同时对催化剂进行了XRD、FT-IR、NH₃-TPD等表征分析。结果表明,碱金属负载量为2%时,除Cs离子改性的催化剂低碳烯烃的选择性和寿命有所降低外,其他碱金属离子改性的SAPO-34催化剂低碳烯烃的选择性和寿命都有了明显的提高,尤其是Li离子改性的催化剂乙烯+丙烯的选择性达77%左右,寿命相对延长了2.5倍;将该催化剂再生3次后乙烯、丙烯的选择性几乎保持不变。

lnfluence of alkali metals-modification on catalytic properties of SAPO-34

The catalysts prepared by modifying SAPO-34 zeolite with alkali metals(Li, Na, K, Rb, Cs) in the way of incipient-wetness impregnation method were evaluated using methanol-olefin(MTO) reaction in the normal pressure continuous flowing fixed bed reactor. The structures of modified SAPO-34 catalysts were characterized by XRD, FT-IR, NH₃-TPD. The results show that lower olefins selectivity and lifetime are improved for 2% alkali-modified SAPO-34, compared with unmodified SAPO-34, except Cs-modified SAPO-34. Ethylene and propylene selectivity of Li-modified SAPO-34 catalyst are about 77% and its lifetime are prolonged by 2.5 times. After regeneration for three times, the selectivity of ethylene and propylene remains almost the same.