Tailoring the structure and acid site accessibility of mordenite zeolite for hydroisomerisation of n-hexane

Autor: Dalibor Kaucky, Jaroslava Moravkova, Stepan Sklenak, Jiri Rathousky, Radim Pilar, Petr Sazama, Jana Pastvova
Rok vydání: 2018
Předmět:
Zdroj: Applied Catalysis A: General. 562:159-172
ISSN: 0926-860X
DOI: 10.1016/j.apcata.2018.05.035
Popis: Mordenite zeolites with diffusion-restricted access to the acid sites located in mono-dimensional 12-ring channels and 8-ring side pockets have found broad applications as catalysts for hydroisomerisation of linear C5 and C6 alkanes and other highly relevant acid-catalysed processes. The accessibility of the porous structure of mordenite (MOR) zeolite is traditionally enhanced by dealumination, but this is invariably connected with a dramatic reduction in the aluminium content and corresponding concentration of the acid sites in the zeolites. Here we describe the preparation of MOR zeolite with high micropore volume, three-dimensional supermicropores (d ∼ 7.5 A) and good acid site accessibility by concurrent extraction of Si and Al using postsynthesis fluorination-alkaline-acid treatment. The concurrent extraction of Si and Al enables formation of more developed supermicroporous structure and preservation of the molecular Si/Al. The procedure yields MOR with a crystalline structure in which the Si/Al ratio and the micropore volume can be tailored (Si/Al from ∼ 6, VMI up to 0.25 cm3.g−1) by the chemical conditions of the treatment. The Al-rich 3D supermicroporous structure with accessible Bronsted and Lewis active sites provides strongly enhanced activity, selectivity and long-term catalytic stability in the transformation of n-hexane into the corresponding branched isomers.
Databáze: OpenAIRE
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