AlSi-ZSM-48沸石分子筛的合成及其催化性能

Syntheses of AlSi-ZSM-48 Zeolites and Their Catalytic Performance

考察了以廉价的 1,6 己二胺为模板剂合成AlSi ZSM 48沸石分子筛的条件及其在醚化碳四烯烃裂解生成丙烯和乙烯反应中的催化性能 .结果表明 ,合成体系的碱度和盐类的加入对AlSi ZSM 48沸石的合成影响极大 ,n(OH-) /n(Si)大于 0 15时得不到AlSi ZSM 48沸石 ,盐类如NaF和NaCl等的加入会抑制AlSi ZSM 48的生成 ,而更利于ZSM 5等杂晶的产生 .在醚化碳四烯烃的裂解反应中 ,AlSi ZSM 48表现出优越的催化性能 ,可以得到高收率的丙烯和乙烯 ,两种烯烃的总收率可达 40 %以上 .

ZSM-48 is a high silica zeolite with disordered structure consisting of ferrierite sheet linked via bridging oxygen located on mirror plates and characterized by ten-membered rings, with un￣interpenetrating linear channels and ideal dimensions of 0.53 nm×0.56 nm. In this paper, a series of AlSi-ZSM-48 zeolite samples with different n(SiO_2)/n(Al_2O_3) were synthesized successfully in the hydrothermal system which consisted of Na_2O, SiO_2, Al_2O_3 and H_2N(CH_2)_6NH_2, and the samples were characterized by XRD, SEM and TGA. The results showed that both the alkalinity of the system and the introduction of the salts played a key role in producing a pure crystal form of AlSi￣ZSM-48 zeolite. The suitable n(OH -)/n(SiO_2) was between 0.04 and 0.08. The salts, such as NaCl and NaF, restrained the formation of AlSi-ZSM-48, which would result in the formation of other crystal impurities, such as ZSM-5. The catalytic cracking of etherification C_4 olefins over AlSi-ZSM-48 zeolite was also investigated. The results showed that AlSi-ZSM-48 zeolite with n (SiO_2)/n (Al_2O_3)=200 was an excellent catalyst to produce propylene and ethylene. The total yield of propylene and ethylene could reach 40% in certain conditions.