Mechanism and Kinetics for the Electrochemical Hydrogenation and Hydrogenolysis of Furfural in Acidic Media over Copper

Abstract

The use of electrochemical methods provides opportunities for processes that are more sustainable then their non-electrochemical counterparts. Electrochemical processes can operate in modular format and be used to store intermittent energy in the form of produced liquid fuel. One example of a process that can be done electrochemically is the hydrogenation and hydrogenolysis (ECH) of furfural. Furfural is derived from biomass, and through hydrogenation and hydrogenolysis it can be transformed to furfuryl alcohol and 2-methylfuran which are used as a binder and a fuel, respectively. In order for processes such as furfural ECH to move towards use outside of lab research, the kinetics and mechanism must be understood to allow for efficient design of new catalysts and ECH reactors. In this work we provide insights into the kinetics of the process in acidic media and proposed potential mechanisms.This kinetic analysis was done in acidic media of pH 0 (0.5M H2SO4) over copper flags. The kinetics of the ECH of furfural was investigated by varying the substrate concentration between 10 and 120 mM and potential between -500 and -800 mV vs RHE. The temperature was varied between 15°C to 45°C to develop Arrhenius plots and extract the activation energies of the parallel reactions.Three mechanisms were derived and compared to the data for the ECH of furfural: non-competitive Langmuir-Hinshelwood, competitive Langmuir-Hinshelwood, and Eley-Rideal, all with the assumption that furfuryl alcohol is not an intermediate species in the formation of 2-methylfuran.