Bimetallic Gold-Silver Nanoparticles Supported on Zeolitic Imidazolate Framework-8 as Highly Active Heterogenous Catalysts for Selective Oxidation of Benzyl Alcohol into Benzaldehyde.

Xishi Tai,Wenping Zhang,Xiaojing Zhou,Lili Liu,Jie Zhou,Yongmei Yan

doi:10.3390/polym10101089

Xishi Tai, Wenping Zhang + Show 4 more

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https://doi.org/10.3390/polym10101089

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Journal: Polymers	Publication Date: Oct 1, 2018
Citations: 30	License type: CC BY 4.0

Affiliation: Weifang University

Abstract

The metal-organic zeolite imidazolate framework-8 (ZIF-8) supported gold-silver bimetallic catalysts with a core-shell structure (Au@Ag/ZIF-8 and Ag@Au/ZIF-8) and cluster structure (AuAg/ZIF-8) were successfully prepared by the deposition-redispersion method. Energy dispersive X-ray spectroscopy (EDS) elemental mapping images displayed that in the Au@Ag/ZIF-8 catalyst, Ag atoms were deposited on an exposed Au surface, and core-shell structured Au@Ag particles with highly dispersed Ag as the shell were formed. Additionally, the XPS investigation at gold 4f levels and silver 3d levels indicated that the Au and Ag particles of Au@Ag/ZIF-8, Ag@Au/ZIF-8, and AuAg/ZIF-8 were in a zero valence state. Among the resultant catalysts obtained in this study, Ag@Au/ZIF-8 catalysts showed the highest catalytic activity for the selective oxidation of benzyl alcohol, followed by AuAg/ZIF-8 and Au@Ag/ZIF-8. The turnover frequency (TOF) values were in the order of Ag@Au/ZIF-8 (28.2 h−1) > AuAg/ZIF-8 (25.0 h−1) > Au@Ag/ZIF-8 (20.0 h−1) at 130 °C within 1 h under 8 bar O2 when using THF as solvent. The catalysts of Au@Ag/ZIF-8 and Ag@Au/ZIF-8 with core–shell structures have higher benzaldehyde selectivities (53.0% and 53.3%) than the AuAg/ZIF-8 catalyst (35.2%) in the selective oxidation of benzyl alcohol into benzaldehyde. The effect of the solvent, reaction temperature, reaction time, and reaction pressure on benzyl alcohol conversion and benzaldehyde selectivity in benzyl alcohol selective oxidation over Au@Ag/ZIF-8, Ag@Au/ZIF-8, and AuAg/ZIF-8 were also investigated. All of the catalysts showed excellent performance at 130 °C under 8 bar O2 within 1 h when using THF as the solvent in the selective oxidation of benzyl alcohol to benzaldehyde. Moreover, the catalysts can be easily recycled and used repetitively at least four times.

Highlights

The selective catalytic oxidation of benzyl alcohols to benzaldehyde is one of the most fundamental transformations both in the laboratory and in the industrial synthetic chemistry [1,2]
Sun et al [8] found that the iron doped graphene (Fe–Gr) supported gold-palladium catalyst is beneficial to the generation of aldehydes in the selective catalysts showed superior catalytic activity and selectivity in the selective oxidation ofwere alcohols to oxidationhave of alcohols
Two steps have been used to synthesize the catalysts of Au@Ag/zeolite imidazolate framework-8 (ZIF-8), Ag@Au/Zeolite imidazolatethatframeworks (ZIFs)-8, and AuAg/ZIF-8

Summary

Introduction

The selective catalytic oxidation of benzyl alcohols to benzaldehyde is one of the most fundamental transformations both in the laboratory and in the industrial synthetic chemistry [1,2]. The catalytic performance of supported monometallic and supported bimetallic catalysts such as Au, Pd, Ag, Au–Cu, Au–Pd, and Cu–Ni for the selective oxidation of benzyl alcohol has been extensively studied [4,5,6,7,8]. 10, 1089 catalysts have showed superior catalytic activity and selectivity in the selective oxidation of alcohols to aldehydes [8,9,10]. Sun et al [8] found that the iron doped graphene (Fe–Gr) supported gold-palladium catalyst is beneficial to the generation of aldehydes in the selective catalysts showed superior catalytic activity and selectivity in the selective oxidation ofwere alcohols to oxidationhave of alcohols.

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