Ethanol Dehydrogenation to Acetaldehyde over Co@N-Doped Carbon

Aleksey N Chernov,Konstantin Yu Koltunov,Vladimir I Sobolev,Tatiana V Astrakova

doi:10.3390/catal11111411

Abstract

Cobalt and nitrogen co-doped carbon materials (Co@CN) have recently attracted significant attention as highly efficient noble-metal-free catalysts exhibiting a large application range. In a similar research interest, and taking into account the ever-increasing importance of bioethanol as a renewable raw material, here, we report the results on ethanol dehydrogenation to acetaldehyde over Co@NC catalysts. The catalyst samples were synthesized by a variety of affordable techniques, ensuring generation of various types of Co species incorporated in carbon, such as subnanosized cobalt sites and nano-sized particles of metallic cobalt and cobalt oxides. The catalytic activity was tested under both oxidative and non-oxidative gas-phase conditions at 200–450 °C using a fixed-bed flow reactor. The non-oxidative conditions proved to be much more preferable for the target reaction, competing, however, with ethanol dehydration to ethylene. Under specified reaction conditions, ethanol conversion achieved a level of 66% with 84% selectivity to acetaldehyde at 400 °C. The presence of molecular oxygen in the feed led mainly to deep oxidation of ethanol to COx, giving acetaldehyde in a comparatively low yield. The potential contribution of carbon itself and supported cobalt forms to the observed reaction pathways is discussed.

Highlights

Ethanol is one of the most important biomass-derived platform molecules [1,2]
In a similar research interest, and taking into account the ever-increasing importance of bioethanol as a renewable raw material, here, we report the results on ethanol dehydrogenation to acetaldehyde over Co@NC catalysts
The catalytic activity of Co@N-doped carbon materials has been studied with regard to the selective dehydrogenation of ethanol to acetaldehyde under both oxidative and non-oxidative gas phase conditions

Summary

Introduction

Given the ongoing trend towards using bioethanol as a renewable feedstock for the production of commodity chemicals, the development of heterogeneous catalysts for the selective conversion of ethanol into acetaldehyde, ethylene, acetic acid, ethyl acetate, propylene, 1-butanol, 1,3-butadiene and other key chemical intermediates continues to be a challenge [3,4,5] Both oxidative and non-oxidative dehydrogenations of ethanol to obtain acetaldehyde have been extensively studied, and many catalysts have been already tested in these reactions [3,4,5]. All the synthetic techniques require a high-temperature (700–1000 ◦C) pyrolysis of the catalyst precursor, yielding thereby quite similar materials consisting of nano-sized particles of metallic cobalt, cobalt oxides and subnanosized cobalt species The latter proved to be atomically-dispersed Co(II)-Nx sites incorporated in graphene/graphitic carbon [35]. In continuation of our long-standing interest in the selective conversion of ethanol into value added chemicals under both oxidative and non-oxidative reaction conditions [38,39,40], and in order to explore further the potential applicability limits of Co@NC type catalysts, we report the findings on the catalytic activity of Co@NC materials in the ethanol dehydrogenation reaction

Catalysts Characterization

Catalysts Preparation

Catalytic Performance Tests

Conclusions