Strong and Weakly Acidic OH Groups of HY Zeolite into the Different Routes of Cyclohexene Reaction: An IR Operando Study
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Strong and Weakly Acidic OH Groups of HY Zeolite into the Different Routes of Cyclohexene Reaction: An IR Operando Study Bruno M. Santos1,3 · José L. Zotin1 · Françoise Maugé2 · Laetitia Oliviero2 · Weitao Zhao2 · Mônica A. P. da Silva3 Received: 25 July 2020 / Accepted: 4 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract IR operando study of cyclohexene reaction on HY zeolite (Si/Al = 15) was performed to determine the role of the OH groups located in the different zeolitic cages and the silanol groups (SiOH). A parallel between the product yield and type and amount of OH groups poisoned by coking and pyridine pulses was established. The role of silanol and zeolitic OH groups during cyclohexene conversion and the coverage rate of surface groups of the dealuminated HY zeolite, were evaluated by FT-IR operando study. At the beginning of the reaction, zeolite exhibited a very intense deactivation due to coke formation. Coke is initially deposited on strong acid sites, inhibiting the H-transfer activity. Further, coke formation decreased. At this stage of the reaction, pyridine addition markedly decreased the isomerization activity. In parallel, it is noted that mainly SiOH, OH groups at hexagonal prisms, and perturbed OH groups in sodalite cages were mainly affected, indicating that these groups are responsible for the isomerization steps. These results showed that even weakly acidic sites are active sites for isomerization reaction.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10562-020-03424-4) contains supplementary material, which is available to authorized users. * Bruno M. Santos [email protected] 1
Centro de Pesquisas e Desenvolvimento, PETROBRAS, Rio de Janeiro, Brazil
2
Normandie Univ, ENSICAEN, UNICAEN, CNRS, LCS, 14000 Caen, France
3
Escola de Química, Centro de Tecnologia, Universidade Federal Do Rio de Janeiro, Rio de Janeiro, Brazil
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Graphic Abstract In cyclohexene conversion, hydrogen transfer occurs on supercage OH groups of HY zeolite. In contrast, perturbed sodalite OH and hexagonal prisms OH, as well as SiOH groups, are responsible for isomerization steps, as revealed by pyridine pulse addition during the reaction.
Keywords Operando IR · Cyclohexene · Isomerization · Hydrogen transfer · Zeolite · HY · Acidity
1 Introduction Zeolites are widely used in petroleum industry as acid catalysts, for which the Brønsted acid sites (BAS) are usually associated with cracking and isomerization reactions. In hydrocracking processes, catalysts contain metals in addition to zeolites, which include a hydrogenation/dehydrogenation activity, resulting in bifunctional catalysts [1]. Due to stringent specifications of diesel, the incorporation of aromatic-rich streams to this fuel is limited because of their detrimental effect on density and cetane number. In this case, aromatic hydrogenation and ring-opening reactions of naphthenic compounds have been
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