Effect of Isopropanol on the Electrocatalytic Hydrodeoxygenation of Guaiacol to Cyclohexane in a Stirred Slurry Reactor: Factorial Experimental Design

Abstract

The production of cyclohexane through the hydrodeoxygenation of guaiacol is a kinetically challenging process in an aqueous electrocatalytic system. Adding isopropyl alcohol (IPA) as a polar protic solvent to the aqueous electrolyte in a stirred slurry reactor with a Pt/C catalyst, we demonstrated the production of cyclohexane by electrocatalytic hydrodeoxygenation of guaiacol along with intermediate products such as phenols and cyclohexanones. Univariate analysis was augmented with statistical experimental design and response surface methodology-based optimization to reveal the main and interaction effects of reaction variables such as IPA and methanesulfonic acid content in the catholyte under galvanostatic conditions. The addition of 25% vol. IPA in the catholyte composed of 1.0 M methanesulfonic acid, 0.25 M NaCl, and 0.1 M guaiacol was most effective for electrocatalytic guaiacol hydrodeoxygenation at -66 mA cm-2 superficial current density and 60 degrees C using 5 g/L 5% wt Pt/C catalyst in the stirred slurry reactor. Under these conditions, the energy requirement was low (5.9 Wh mol-1), and a high faradaic efficiency (69%) was obtained with a guaiacol conversion of 69.3% and a cyclohexane yield of 6.7%. Reaction network analysis revealed an additional pathway for guaiacol conversion in the presence of IPA involving anisole as the intermediate species. Reaction kinetic and mechanistic insights are also presented.