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Micropore blocked core–shell ZSM-22 designed via epitaxial growth with enhanced shape selectivity and high n-dodecane hydroisomerization performance

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Abstract

A core–shell ZSM-22 (Z@S) was synthesized via epitaxial growth. The characterization results of Z@S validated that the acid sites located on the external surface of core ZSM-22 were passivated by the epitaxial shell of highly siliceous ZSM-22 and the acid strength of ZSM-22 remained unchanged. For comparison, highly siliceous and boron-containing ZSM-22 were also synthesized and characterized. In n-dodecane hydroisomerization, highly siliceous ZSM-22 almost without acid sites at the external surface achieved a much higher iso-dodecane selectivity than boron-containing ZSM-22 with weak acid sites. Z@S with strong acid sites and passivated surface acidity showed high activity and favored pore mouth catalysis but exhibited a lowered iso-dodecane selectivity. The reduced external surface acid sites enhanced the diffusion of n-alkane into the micropores, leading to severe cracking reaction caused by acid sites on the internal surface. Further modifying Z@S via micropore blockage could greatly inhibit cracking reaction inside the micropores and confine isomerization at the pore mouth of ZSM-22. This new ZSM-22 catalyst achieved higher activity and a higher iso-dodecane yield than catalysts with weak acidity.

Graphical abstract: Micropore blocked core–shell ZSM-22 designed via epitaxial growth with enhanced shape selectivity and high n-dodecane hydroisomerization performance

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Publication details

The article was received on 19 Sep 2018, accepted on 07 Nov 2018 and first published on 08 Nov 2018


Article type: Paper
DOI: 10.1039/C8CY01950A
Citation: Catal. Sci. Technol., 2018, Advance Article
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    Micropore blocked core–shell ZSM-22 designed via epitaxial growth with enhanced shape selectivity and high n-dodecane hydroisomerization performance

    P. Niu, H. Xi, J. Ren, M. Lin, Q. Wang, X. Chen, P. Wang, L. Jia, B. Hou and D. Li, Catal. Sci. Technol., 2018, Advance Article , DOI: 10.1039/C8CY01950A

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