Effect of template removal using plasma treatment on the structure and catalytic performance of MCM-22. Issue 28 (24th April 2018)

• Record Type: Journal Article
• Authors: Hu, Min; Zhao, Binran; Zhao, Dong-Yang; Yuan, Mei-Ting; Chen, Huiyong; Hao, Qing-Qing; Sun, Ming; Xu, Long; Ma, Xiaoxun
• Is Part Of: RSC advances. Volume 8:Issue 28(2018)
• Page Start: 15372
• Page End: 15379
• Publication Date: 2018-04-24
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c8ra00212f
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Template removal from MCM-22 using dielectric-barrier discharge (DBD) plasma could decrease the formation of extra-framework aluminum (EFAl) and increase the concentration of the acidic sites and external surface area of MCM-22. Abstract : To investigate the effect of template removal methods on the structure, properties and catalytic performance of the MCM-22 zeolite, dielectric-barrier discharge (DBD) plasma treatment and thermal calcination have been comparatively studied for the removal of hexamethyleneimine (HMI) from the two-dimensional layered precursor of MCM-22 (MCM-22(P)). The materials were characterized using FT-IR, TG, XRD, N2 adsorption at low temperature, NH3 -TPD, and 27 Al and 29 Si MAS NMR. The results revealed that the seven-membered heterocyclic compound HMI can be effectively removed from the MCM-22 zeolite, and the condensation of silanol groups on the neighboring surface of MWW nanosheets can be induced by DBD treatment. Compared with calcination, DBD treatment could preserve the structure well and decrease the formation of extra-framework aluminum. Consequently, the concentration of acidic sites over MCM-22 treated by DBD (MCM-22(DBD)) is higher than that over calcined MCM-22 (MCM-22(C)). Moreover, MCM-22(DBD) possesses a certain amount of external surface area derived from the intercrystal pores due to the inhibiting effect of the condensation of the silanol groups on the external surface of the MCM-22 crystals. The activity and product selectivity of the Fischer–Tropsch (FT) synthesis was investigated over cobalt supported on the obtained MCM-22 zeolites. Compared with Co/MCM-22(C), Co/MCM-22(DBD) shows a higher catalytic activity in the FT synthesis reaction. Moreover, Co/MCM-22(DBD) can effectively decrease CH4 selectivity and increase C5 –C20 liquid fuel selectivity.