Reversible Transformation of Sub-nanometer Ga-based Clusters to Isolated [4]Ga(4Si) Sites Creates Active Centers for Propane Dehydrogenation

Reversible Transformation of Sub-nanometer Ga-based Clusters to Isolated [4]Ga(4Si) Sites Creates Active Centers for Propane Dehydrogenation Full article

Journal

Catalysis Science & Technology
ISSN: 2044-4761 , E-ISSN: 2044-4753

Output data

Year: 2024, Volume: 14, Number: 2, Pages: 379-390 Pages count : 12 DOI: 10.1039/d3cy01446k

Authors

Chen Zixuan ¹ , Serykh Alexander ² , Kierzkowska Agnieszka Marta ¹ , Gajan David ³ , Docherty Scott ⁴ , Yakimov Alexander ⁴ , Abdala Paula Macarena ¹ , Coperet Christophe ⁴ , Florian Pierre ⁵ , Fedorov Alexey ¹ , Müller Christoph Rüdiger ¹

Affiliations

1	Department of Mechanical and Process Engineering, ETH Zürich, Switzerland
2	Zelinsky Institute of Organic Chemistry, RAS, Moscow, Russia
3	Centre de RMN à hauts champs de Lyon, UMR 5082 (CNRS, ENS Lyon, Université Lyon 1), Université de Lyon, Villeurbanne F-69100, France
4	Department of Chemistry and Applied Biosciences, ETH Zürich, Switzerland
5	CNRS, CEMHTI UPR3079, Université d'Orléans, France

Ga-based propane dehydrogenation (PDH) catalysts are explored in industry as an alternative to PtSn and CrOx-based catalysts. Yet, at present, there is only limited understanding of the structural dynamics of surface sites in Ga-based PDH catalysts. Here, we employ atomic layer deposition (ALD) to engineer a sub-monolayer of Ga species on dehydroxylated silica, which serves as a model PDH catalyst. While the ALD-grown shell contains, after calcination at 500 °C, tetra- and pentacoordinate Ga3+ sites with both Si and Ga atoms in the second coordination sphere (i.e., [4]Ga(Si/Ga) and [5]Ga(Si/Ga) sites), its exposure to ambient air leads to sub-nanometer GaxOy(OH)z clusters with [4]Ga(Ga) and [6]Ga(Ga) sites, due to the hydrolysis of the Ga–O–Si linkages by the moisture of ambient air. When calcining the material at 650 °C, the [4]Ga(Ga) and [6]Ga(Ga) sites evolve leading to a silica surface dominated by isolated tetracoordinate [4]Ga(4Si) sites, that is, [([triple bond, length as m-dash]SiO)3Ga(XOSi[triple bond, length as m-dash])] sites, where X is H or [triple bond, length as m-dash]Si. Exposure of the dehydroxylated material with [4]Ga(4Si) sites to ambient air reforms the sub-nanometer GaxOy(OH)z clusters, indicating the reversibility of the Ga dispersion and agglomeration as a function of the extent of silica (de)hydroxylation. The presence of [4]Ga(4Si) sites coincides with a high performance in PDH, achieving an initial turnover frequency of ca. 12 h−1 and propene selectivity of ca. 85%, while deactivating by only 34% over 20 h of time on stream. Overall, our results highlight the dynamic nature of the dispersion and agglomeration of Ga3+ sites during the dehydroxylation (by calcination) and rehydration (ambient air exposure).

Chen Z. , Serykh A. , Kierzkowska A.M. , Gajan D. , Docherty S. , Yakimov A. , Abdala P.M. , Coperet C. , Florian P. , Fedorov A. , Müller C.R.
Reversible Transformation of Sub-nanometer Ga-based Clusters to Isolated [4]Ga(4Si) Sites Creates Active Centers for Propane Dehydrogenation
Catalysis Science & Technology. 2024. V.14. N2. P.379-390. DOI: 10.1039/d3cy01446k WOS Scopus OpenAlex

Web of science:	WOS:001125508800001
Scopus:	2-s2.0-85180117074
OpenAlex:	W4389063724

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