Hydrothermal CO2 Reduction by Glucose as Reducing Agent and Metals and Metal Oxides as Catalysts.

Maira I. Chinchilla,Fidel A. Mato,Ángel Martín,María D. Bermejo

doi:10.3390/molecules27051652

Maira I. Chinchilla, Fidel A. Mato + Show 2 more

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https://doi.org/10.3390/molecules27051652

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Journal: Molecules (Basel, Switzerland)	Publication Date: Mar 2, 2022
Citations: 8	License type: CC BY 4.0

Affiliation: University of Valladolid

Abstract

High-temperature water reactions to reduce carbon dioxide were carried out by using an organic reductant and a series of metals and metal oxides as catalysts, as well as activated carbon (C). As CO2 source, sodium bicarbonate and ammonium carbamate were used. Glucose was the reductant. Cu, Ni, Pd/C 5%, Ru/C 5%, C, Fe2O3 and Fe3O4 were the catalysts tested. The products of CO2 reduction were formic acid and other subproducts from sugar hydrolysis such as acetic acid and lactic acid. Reactions with sodium bicarbonate reached higher yields of formic acid in comparison to ammonium carbamate reactions. Higher yields of formic acid (53% and 52%) were obtained by using C and Fe3O4 as catalysts and sodium bicarbonate as carbon source. Reactions with ammonium carbamate achieved a yield of formic acid up to 25% by using Fe3O4 as catalyst. The origin of the carbon that forms formic acid was investigated by using NaH13CO3 as carbon source. Depending on the catalyst, the fraction of formic acid coming from the reduction of the isotope of sodium bicarbonate varied from 32 to 81%. This fraction decreased in the following order: Pd/C 5% > Ru/C 5% > Ni > Cu > C ≈ Fe2O3 > Fe3O4.

Highlights

Global warming is still one of the main worldwide concerns in the present time [1,2]
Glucose was used as a reducing agent, and metal and metal oxides (Cu, Ni, Pd/C 5%, Ru/C 5%, Fe2O3 and Fe3O4), as well as activated carbon (C), were used as catalysts
The yields of formic acid, acetic acid and lactic acid obtained by the reduction of ammonium carbamate were much lower than those observed when sodium bicarbonate was used as the carbon source

Summary

Introduction

Global warming is still one of the main worldwide concerns in the present time [1,2]. Chemical methods are used to convert it into valuable compounds such as urea and DME [6,7] One of the main difficulties faced in the chemical conversion of CO2 is the high thermodynamic stability of the compound [8]. The high costs and low yields of these techniques [10] have led to the study of other alternatives such as the hydrothermal treatment in which CO2 reduction takes places in water media at high pressures and temperatures [11–13]. In this process, water acts as hydrogen donor instead of H2, which is flammable and complex to store [14]

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