TY - JOUR

T1 - Propylene Transformation on Zn-Modified Zeolite

T2 - Is There Any Difference in the Effect of Zn2+ Cations or ZnO Species on the Reaction Occurrence?

AU - Gabrienko, Anton A.

AU - Arzumanov, Sergei S.

AU - Toktarev, Alexander V.

AU - Freude, Dieter

AU - Haase, Jürgen

AU - Stepanov, Alexander G.

N1 - Publisher Copyright: Copyright © 2019 American Chemical Society.

PY - 2019/11/14

Y1 - 2019/11/14

N2 - The peculiar role of either Zn2+ cations or small ZnO clusters located inside the zeolite pores in propylene transformation to aromatic hydrocarbons on Zn2+/H-ZSM-5 and ZnO/H-BEA zeolites has been analyzed. 13C MAS NMR and FTIR spectroscopic investigation has revealed similar properties of different Zn-sites with respect to propylene oligomerization. Both Zn2+ cations and ZnO species are capable to convert propylene to higher C6-C9 olefins which represent the precursors of simple benzene-based aromatics. The mechanism of such oligomerization has been inferred to include the following stages: (a) adsorption of propylene on the Zn-sites in the form of a Ï-complex; (b) transformation of the Ï-complex of propylene to σ-allylzinc surface species at elevated temperature; (c) formation of C6+ olefins; (d) transformation of oligomeric C6+ olefins to simple aromatic molecules (benzene, toluene, and xylenes). NMR evidences that Brønsted acid sites (BAS) of both zeolite samples are not involved in the oligomerization to a large extent although definitely contribute to oligomers formation. Involvement of BAS in propylene oligomerization on ZnO/H-BEA zeolite is higher because of their larger quantity in the sample. The oligomerization has been monitored to proceed mainly via allylzinc species owing to the olefin insertion into the reactive Zn-C bond. In such a way, selective formation of the C6-C9 olefins occurs which accounts for a particular set of aromatic products detected for propylene transformation on Zn-modified zeolites. ©

AB - The peculiar role of either Zn2+ cations or small ZnO clusters located inside the zeolite pores in propylene transformation to aromatic hydrocarbons on Zn2+/H-ZSM-5 and ZnO/H-BEA zeolites has been analyzed. 13C MAS NMR and FTIR spectroscopic investigation has revealed similar properties of different Zn-sites with respect to propylene oligomerization. Both Zn2+ cations and ZnO species are capable to convert propylene to higher C6-C9 olefins which represent the precursors of simple benzene-based aromatics. The mechanism of such oligomerization has been inferred to include the following stages: (a) adsorption of propylene on the Zn-sites in the form of a Ï-complex; (b) transformation of the Ï-complex of propylene to σ-allylzinc surface species at elevated temperature; (c) formation of C6+ olefins; (d) transformation of oligomeric C6+ olefins to simple aromatic molecules (benzene, toluene, and xylenes). NMR evidences that Brønsted acid sites (BAS) of both zeolite samples are not involved in the oligomerization to a large extent although definitely contribute to oligomers formation. Involvement of BAS in propylene oligomerization on ZnO/H-BEA zeolite is higher because of their larger quantity in the sample. The oligomerization has been monitored to proceed mainly via allylzinc species owing to the olefin insertion into the reactive Zn-C bond. In such a way, selective formation of the C6-C9 olefins occurs which accounts for a particular set of aromatic products detected for propylene transformation on Zn-modified zeolites. ©

KW - SOLID-STATE NMR

KW - MODIFIED ZSM-5 ZEOLITES

KW - PROMOTED H-ZSM-5 CATALYSTS

KW - POLYETHYLENE CHAIN GROWTH

KW - 2 ALTERNATIVE MECHANISMS

KW - BOND-SHIFT REACTION

KW - IN-SITU NMR

KW - METHANE ACTIVATION

KW - AROMATIC-HYDROCARBONS

KW - PROPANE AROMATIZATION

UR - http://www.scopus.com/inward/record.url?scp=85074785118&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.9b07672

DO - 10.1021/acs.jpcc.9b07672

M3 - Article

AN - SCOPUS:85074785118

VL - 123

SP - 27573

EP - 27583

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 45

ER -