(445e) Increasing Btp-X and C2-C3 Olefins in Methanol to Aromatics over Shape-Selective Zn-Si-HZSM-5
In MTA reaction over ZSM5 catalyst, benzene and toluene and xylene can undergo secondary alkylation reaction to form undesired A9+ aromatics, while p-X can isomerize to form m-X and o-X isomers on the external surface of the catalyst in presence of external surface acid sites. In addition to this, olefins can undergo hydrogen transfer reactions to form alkanes. With an objective to increase the selectivity of BTp-X and C2-C3 olefins, the catalysts should have characteristics like high shape selectivity, absence of external acid sites, aromatization ability and low hydrogen transfer activity.
In order to achieve these characteristics, first HZSM5 was doped by silica using chemical liquid deposition of polyphenyl methyl siloxane homopolymer to enhance shape selectivity and eliminate external surface acid sites to stop secondary alkylation, isomerization as well as hydrogen transfer reactions occurring on the external surface of the HZSM5. Further to increase aromatization activity and decrease hydrogen transfer reaction, surface passivated Si/HZSM5 was impregnated with Zn which is well known for its associated dehydrogenation capability. As a result, 1.5 wt% Zn/Si/HZSM5 exhibited a high selectivity of BTp-X and C2-C3 of 53% far higher than that of parent HZSM5 (23 %), Si/HZSM5 (40%), and 1 wt% Zn/HZSM5(28%). The obtained values of BTp-X+C2-C3 (53%) on 1.5 wt% Zn/Si/HZSM5 are higher in contrast to 29 % reported by Hu et al. (2017)3 in similar study.
- Conte, M.; Lopez-Sanchez, J. A.; He, Q.; Morgan, D. J.; Ryabenkova, Y.; Bartley, J. K.; Carley, A. F.; Taylor, S. H.; Kiely, C. J.; Khalid, K.; Hutchings, G. J., Modified zeolite ZSM-5 for the methanol to aromatics reaction. Catalysis Science & Technology 2012, 2 (1), 105-112.
- Niu, X.; Gao, J.; Miao, Q.; Dong, M.; Wang, G.; Fan, W.; Qin, Z.; Wang, J., Influence of preparation method on the performance of Zn-containing HZSM-5 catalysts in methanol-to- aromatics. Microporous and Mesoporous Materials 2014, 197, 252-261
- Hu, Q.; Huang, X.; Cui, Y.; Luo, T.; Tang, X.; Wang, T.; Qian, W.; Wei, F., High yield production of C2-C3 olefins and para-xylene from methanol using a SiO2-coated FeOx/ZSM-5 catalyst. RSC Advances 2017, 7 (46), 28940-28944.