In Situ DRIFTS Investigation of Ethylene Oxidation on Ag and Ag/Cu on Reduced Graphene Oxide
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In Situ DRIFTS Investigation of Ethylene Oxidation on Ag and Ag/Cu on Reduced Graphene Oxide Monique R. D’Oliveira1 · Jessica Rabelo1 · Amanda Garcez Veiga2 · Carlos Alberto Chagas3 · Martin Schmal1,4 Received: 19 December 2019 / Accepted: 3 April 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Reduced graphene oxide (rGO) was synthesized and impregnated with silver and silver/copper for in situ DRIFTS investigation of ethylene oxidation. The catalysts were characterized using different techniques. SEM micrographs showed that the metals are dispersed on the rGO surface. XPS results showed the presence of the metallic silver and copper as CuO and Cu2O oxides. The in situ DRIFTS showed that in both catalysts the total oxidation of ethylene reaction prevails besides the intermediate formation of acetaldehyde. The presence of Cu ions or CuO and C u2O at the surface indicate the presence of electronic structure, which may enhance the oxidation reaction.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10562-020-03208-w) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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Graphic Abstract
Keywords Reduced graphene oxide · Epoxidation of ethylene · Nanoparticles · Silver · Copper
1 Introduction Ethylene oxide (EO) is one of the major derivatives of ethylene. Characterized by a special reactivity, ethylene oxide can generate a series of fine chemicals for a wide range of applications. The main use of ethylene oxide is in the production of ethylene glycol, the main constituent of engine coolants, and in other diols (or glycols), which are used to make polyesters [1]. A particularly important class of industrial reactions involves the selective oxidation of hydrocarbons over heterogeneous Ag-based catalysts. In terms of scale and market value, the epoxidation of ethylene to form ethylene oxide is by far the most important industrial catalytic process performed on Ag catalysts [2]. In the commercial process for ethylene oxide production, ethylene epoxidation is performed on silver catalysts. Since the discovery of this reaction by Lefort, significant efforts have been made to improve the catalysts used in this process [3]. The uniqueness of Ag as an ethylene epoxidation catalyst is due to: (i) Ag–O bond strength, (ii) chemical nature of adsorbed oxygen species, and (iii) inability of Ag–O to activate the C-H
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bond of ethylene [4]. Studies showed that atomic oxygen is the active species for the partial oxidation of ethylene. Thus, the catalyst should be able to dissociate the oxygen molecule, which can be easily achieved on the transition metals as well as by Ag and Cu. On metals that do not activate CH bonds, the surface oxygen has been found to act as a Lewis base that promotes C–H activation. In the case of ethylene, it has been proposed that this initiates total combustion [5]. The oxid
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