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Open AccessArticle

Operando Dual Beam FTIR Study of Hydroxyl Groups and Zn Species over Defective HZSM-5 Zeolite Supported Zinc Catalysts

1
State Key Laboratory of Fine Chemicals and School of Chemical Engineering, Dalian University of Technology, No. 2 Linggong Road, Dalian 116024, China
2
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
*
Author to whom correspondence should be addressed.
Catalysts 2019, 9(1), 100; https://doi.org/10.3390/catal9010100
Received: 30 November 2018 / Revised: 2 January 2019 / Accepted: 10 January 2019 / Published: 17 January 2019
(This article belongs to the Special Issue Spectroscopy in Catalysis)
A series of defective ZSM-5 zeolites (~300 nm, SiO2/Al2O3 ratio of 55, 100, 480 and 950) were systematically studied by XRD, SEM, 29Si MAS NMR, argon physisorption, NH3-TPD and FT-IR technologies. The nature, the amount and the accessibility of the acid sites of defective ZSM-5 zeolites are greatly different from reported ZSM-5 zeolites with a perfect crystal structure. The Brønsted acid sites (Si(OH)Al) with strong acid strength and the Brønsted acid sites (hydroxyl nests) with weak acid strength co-existed over defective ZSM-5 zeolites, which leads to a unique catalytic function. Zn(C2H5)2 was grafted onto defective ZSM-5 zeolites through the chemical liquid deposition (CLD) method. Interestingly, FT-IR spectroscopic studies found that Zn(C2H5)2 was preferentially grafted on the hydroxyl nests with weak acid strength rather than the Si(OH)Al groups with strong acid strength over different defective ZSM-5 zeolites. In particular, home-built operando dual beam FTIR-MS was applied to study the catalytic performance of Zn species located in different sites of defective ZSM-5 zeolites under real n-hexane transformation conditions. Results show that Zn species grafted over hydroxyl nests obtain better dehydrogenative aromatization performance than Zn species over Si(OH)Al groups. This study provides guidance for the rational design of highly efficient alkane dehydrogenative aromatization catalysts. View Full-Text
Keywords: defective ZSM-5; hydroxyl nests; Si(OH)Al; Zn(C2H5)2; chemical liquid deposition; operando dual beam FT-IR spectroscopy defective ZSM-5; hydroxyl nests; Si(OH)Al; Zn(C2H5)2; chemical liquid deposition; operando dual beam FT-IR spectroscopy
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Lin, L.; Zhang, X.; He, N.; Liu, J.; Xin, Q.; Guo, H. Operando Dual Beam FTIR Study of Hydroxyl Groups and Zn Species over Defective HZSM-5 Zeolite Supported Zinc Catalysts. Catalysts 2019, 9, 100.

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