Reduction of CuO into Cu with Guaiacol as a Model Compound of Lignin with a Homogeneous Catalyst of NaOH

Abstract

The reduction of CuO with a lignin model compound, guaiacol, is investigated, to develop a new and green method for both Cu smelting and the utilization of lignin. The results showed that CuO can be completely reduced into Cu and guaiacol selectively converted to carboxylic acids such as fumaric, maleic, acetic, and formic acids at a mild temperature of 250 °C. The presence of NaOH has a significant effect on enhancing the reduction of CuO and the selective yield of carboxylic acids. Two possible reaction pathways were proposed for the reduction of CuO with guaiacol. One pathway involves the oxidative decomposition of guaiacol into carboxylic acids. The other reaction pathway proceeds with the polymerization of guaiacol into oligomers, which can be reused for CuO reduction due to their easy hydrolyzation to monomers under hydrothermal conditions.

Effect and Mechanism of Aluminum(III) for Guaiacol–Glyoxylic Acid Condensation Reaction in Vanillin Production

“…Three resonance modes (I, II, and III, as shown in Scheme 3 ) were generated for the guaiacol negative ions under alkaline conditions. 53 When Al 3+ interacted with the ortho-position hydrogen atom (H A ) of phenolic hydroxyl group ( Scheme 3 a), the interaction of Al···H A allowed guaiacol attack on glyoxylic acid only through the para-position of the phenolic hydroxyl group. Resonance mode II was the nucleophile to attack the carbonyl group of glyoxylic acid by carbon negative ions to produce VMA.…”

Evaluation of low copper content antifouling paints containing natural phenolic compounds as bioactive additives

“…Green synthesis of metallic nanoparticles such as copper, silver and gold were carried out using pure compounds present in different plant essential oils, e.g. eugenol and guaiacol (Singh et al, 2010;Milczarek and Ciszewski, 2012;Subhankari and Nayac, 2013;Yin et al, 2014). Eugenol and guaiacol act as powerful reducing agents and probably would delay the oxidation process and dissolution of cuprous oxide at paintfilm/seawater interface.…”

Production of Acrylic Acid from Biomass-Derived Fumaric Acid under Hydrothermal Conditions

“…When fumaric acid is oxidized by CuO, Cu(II) bonds to the oxygen atom of the hydroxyl group, which linked to C1, resulting in theπ-bond between C2 and C3showing a negative valence, and the H of the hydroxyl group will transfer to the π-bond. Cu(II) is prone to take the electron away to produce Cu2O or Cu [29,42]. In this research, Cu(II) took the electron away, producing Cu2O, and led to the formation of a double bond between O of the hydroxyl group and C1, as well as a cleavage of the bond between C1 and C2, producing acrylic acid and CO2.During the reaction, fumaric acid can also react with water to produce malic acid, which is a side reaction.…”

“…Therefore, fairly high-purity fumaric acid is used in this study. Recently, many works have demonstrated that lignin models could also be oxidized into fumaric acid under hydrothermal conditions [26][27][28][29][30]. As a building block, fumaric acid has been widely studied [31].…”