Hydrothermal CO2 reduction using biomass derivatives as reductants

Abstract

A wide range of organic substances, potentially derived from biomass, were tested as reductants for CO2 (as NaHCO3) in hydrothermal media. The reactions were carried out in batch reactors at 300 °C and 3 h. All the substances reduced CO2 to formic acid in yields up to 65%. These results agree to the mechanisms proposed in literature that suggested that reduction is carried out by primary or secondary alcohols. However, some substances without these groups gave significant yields to formic acid so new mechanisms were proposed. Out of all the compounds tested, glucose gave the highest yield to formic acid, probably due to its particular reaction pathways at the studied conditions. Effect of NaOH in the reaction using glucose was investigated to assure that formic acid is produced from bicarbonate. For ethanol and ethylenglycol, additional conditions were tested to study the dependence of the reaction with time and temperature.