Ethanol to Acetaldehyde Conversion under Thermal and Microwave Heating of ZnO-CuO-SiO2 Modified with WC Nanoparticles.

Alexander L Kustov,Gennady I Kapustin,Leonid M Kustov,Andrey L Tarasov,Igor V Mishin,Olga P Tkachenko

doi:10.3390/molecules26071955

Abstract

The nonoxidative conversion of ethanol to acetaldehyde under thermal and microwave heating was studied on mixed oxide ZnO-CuO-SiO2 catalysts modified with additives of tungsten carbide nanoparticles. The results revealed that the WC-modified catalyst exhibited superior activity and selectivity under microwave heating conditions. It is assumed that when microwave heating is used, hot zones can appear at the contact points of WC nanoparticles and active centers of the mixed oxide ZnO-CuO-SiO2 catalyst, which intensively absorb microwave energy, allowing the more efficient formation of acetaldehyde at moderate temperatures. Thermodynamic calculations of equilibrium concentrations of reagents and products allowed us to identify the optimal conditions for effective acetaldehyde production. The initial catalyst and the catalyst prepared by the coprecipitation of the oxides with the addition of WC were characterized by physicochemical methods (TPR-H2, XRD, DRIFTS of adsorbed CO). The active centers of the oxide catalyst can be Cu+ cations.

Highlights

Acetaldehyde (AA) is one of the most important intermediate aliphatic chemicals serving as the raw material for the production of acetic acid, acetic anhydride, ethyl acetate, pyridine and many other products [1]
It is assumed that when microwave heating is used, hot zones can appear at the contact points of with tungsten carbide (WC) nanoparticles and active centers of the mixed oxide ZnO-CuO-SiO2 catalyst, which intensively absorb microwave energy, allowing the more efficient formation of acetaldehyde at moderate temperatures
It was found that adding about 10 wt % of the WC nanopowder to the mixed oxide ZnO-CuO-SiO2 catalyst allows the catalyst to be heated by microwave energy to temperatures (200–400 ◦C) required for the nonoxidative dehydrogenation of ethanol

Summary

Introduction

Acetaldehyde (AA) is one of the most important intermediate aliphatic chemicals serving as the raw material for the production of acetic acid, acetic anhydride, ethyl acetate, pyridine and many other products [1]. The process of AA production by catalytic nonoxidative dehydrogenation of ethanol widely used in the 1960s–1970s of the last century has a number of advantages over other methods, such as acetylene hydration, ethylene oxidation and oxidative dehydrogenation of ethanol. These include the absence of toxic wastes, sufficiently mild reaction conditions and the production of hydrogen along with acetaldehyde, which can be used in other processes [2]. Ethanol dehydrogenation reaction with copper catalysts based on various oxides of SiO2, ZrO2, Al2O3, MgO and ZnO have been studied by many authors [4]. The highest selectivity for acetaldehyde was achieved in the presence of Cu/SiO2 and Cu/MgO catalysts (77.9% and 74.2%, respectively)

Objectives

Methods

Results

Conclusion