TY - JOUR

T1 - Propane activation on Zn-modified zeolite. The effect of the nature of Zn-species on the mechanism of H/D hydrogen exchange of the alkane with Brønsted acid sites

AU - Arzumanov, Sergei S.

AU - Gabrienko, Anton A.

AU - Toktarev, Alexander V.

AU - Freude, Dieter

AU - Haase, Jürgen

AU - Stepanov, Alexander G.

N1 - Publisher Copyright: © 2019 Elsevier Inc. Copyright: Copyright 2019 Elsevier B.V., All rights reserved. Publisher Copyright: © 2019 Elsevier Inc.

PY - 2019/10/1

Y1 - 2019/10/1

N2 - Zn-modified zeolites exhibit high activity for the aromatization of C2+ alkanes. To understand the effect of Zn-species of different nature on propane molecules activation and transformation, the H/D hydrogen exchange of zeolite Brønsted acid sites (BAS) with deuterated propane-d8 has been investigated. Two samples of the Zn-modified zeolite containing exclusively either isolated Zn2+ cations (Zn2+/H-BEA) or small (ZnO)n clusters (ZnO/H-BEA) have been studied. Zn-species of either type work jointly with BAS and may provide the synergy effect for propane C[sbnd]H bond activation resulting in dramatic acceleration of the H/D exchange between propane and BAS. The accelerating effect of isolated Zn2+ cations is more pronounced compared to zinc oxide clusters. Moreover, the H/D exchange occurs regioselectively into the methyl groups of propane on Zn2+/H-BEA zeolite. For ZnO/H-BEA, the methylene group becomes also involved in the exchange after some induction period. Various mechanisms providing the regioselective H/D exchange on Zn2+/H-BEA as well as the involvement of the methylene group after the induction period on ZnO/H-BEA are discussed.

AB - Zn-modified zeolites exhibit high activity for the aromatization of C2+ alkanes. To understand the effect of Zn-species of different nature on propane molecules activation and transformation, the H/D hydrogen exchange of zeolite Brønsted acid sites (BAS) with deuterated propane-d8 has been investigated. Two samples of the Zn-modified zeolite containing exclusively either isolated Zn2+ cations (Zn2+/H-BEA) or small (ZnO)n clusters (ZnO/H-BEA) have been studied. Zn-species of either type work jointly with BAS and may provide the synergy effect for propane C[sbnd]H bond activation resulting in dramatic acceleration of the H/D exchange between propane and BAS. The accelerating effect of isolated Zn2+ cations is more pronounced compared to zinc oxide clusters. Moreover, the H/D exchange occurs regioselectively into the methyl groups of propane on Zn2+/H-BEA zeolite. For ZnO/H-BEA, the methylene group becomes also involved in the exchange after some induction period. Various mechanisms providing the regioselective H/D exchange on Zn2+/H-BEA as well as the involvement of the methylene group after the induction period on ZnO/H-BEA are discussed.

KW - H MAS NMR in situ

KW - Activation

KW - Brønsted acid sites

KW - H/D hydrogen exchange

KW - Mechanism

KW - Nature of Zn species

KW - Propane

KW - Zn-modified H-BEA zeolite

KW - Zn cations

KW - ZnO small clusters

KW - ZINC IONS

KW - C-13 MAS NMR

KW - ZN/MFI CATALYST

KW - DISSOCIATIVE ADSORPTION

KW - METHANE ACTIVATION

KW - HYDRIDE TRANSFER

KW - AROMATIC-HYDROCARBONS

KW - H-1 MAS NMR in situ

KW - LIGHT ALKANES

KW - HIGH-SILICA ZEOLITES

KW - ZSM-5 ZEOLITES

KW - Zn2+ cations

KW - Brensted acid sites

UR - http://www.scopus.com/inward/record.url?scp=85072571872&partnerID=8YFLogxK

U2 - 10.1016/j.jcat.2019.09.006

DO - 10.1016/j.jcat.2019.09.006

M3 - Article

AN - SCOPUS:85072571872

VL - 378

SP - 341

EP - 352

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

ER -