Electrocatalytic Hydrogenation and Hydrogenolysis of Furfural and the Impact of Homogeneous Side Reactions of Furanic Compounds in Acidic Electrolytes

The electrochemical hydrogenation and hydrogenolysis (ECH) of furfural (FF) on a copper electrocatalyst has been investigated to produce biofuels and fine chemicals in an H-type batch reactor at room temperature. We report a systematic study of ECH of FF to gain a better understanding of the relationships between products and reaction conditions: current density, electrolyte, and cosolvent ratio in acidic solutions. The acidity of electrolytes had the most significant impact on the product distribution. Mildly acidic electrolytes mainly produced furfuryl alcohol (FA), while strongly acidic electrolytes produced both 2-methyl furan (MF) and FA. Also, the yield of products depended on the current density and reaction time when equivalent charge was transferred to the reaction. However, the mole balance accounting for FF, MF, and FA was not higher than 70% in any reaction condition when the theoretical amount of electrons for complete MF production from FF (e^-/FF = 4) was transferred to the system. The investigation of nonelectrochemical homogeneous side reactions suggested that the low mole balance in a mildly acidic electrolyte may be from the charge transfer promoted side reactions on the copper electrode. On the other hand, it was shown that the low mole balance in strongly acidic electrolytes was due to homogeneous side reactions.