Cross-polymerization between the model furans and phenolics in bio-oil with acid or alkaline catalysts

Abstract

Polymerization is a major challenge for the upgrading of bio-oil to biofuels, but is preferable for the production of carbon material from bio-oil. Understanding the mechanism for polymerization is of importance for tailoring property of carbon material. This study investigated the characteristics for the polymerisation of furfural, vanillin, their cross-polymerization and the impacts of catalysts on their polymerization. The results indicated that the organic acids like acetic acid and formic acid could catalyze the polymerisation of furfural, while H2SO4 or NaOH as catalyst could drastically enhance the degree of polymerization of furfural. Vanillin showed a higher tendency towards polymerization than furfural and H2SO4 or NaOH significantly facilitated the polymerization of vanillin via shifting the pasty product to solid polymer. The cross-polymerization between furfural and vanillin occurred even in the absence of catalyst, while the presence of H2SO4 or NaOH catalyst resulted in the formation of more solid polymer via cross-polymerization. The polymerisation reactions were accompanied with the consumption of –C=O via aldol addition/condensation reactions. In addition, the morphology and thermal stability of the polymers formed were affected by both the type of the catalysts employed, which can in turn enhance the cross-polymerization between furfural and vanillin.