(473b) Selective Oxidation of Guaiacol to Produce Organic Acid Over TS-1 With H2O2

Biomass has drawn an increasing attention in recent years as a renewable feedstock in response to the depletion of fossil fuels and the increasing concern over environmental protection. Lignin, with a highly branched polymer of substituted phenolic monomeric entities, is a important part of biomass (15-30 wt%).[1] Due to lignin's amorphous structure and high stability of its monomers (benzene ring), the utilization of lignin become a challenge of biomass industry.[2] Hydrodeoxygenation is a common method to produce fuel hydrocarbons, such as benzene, cyclohexane or methyl-cyclohexane form the model compounds of lignin.[3]

In this work we introduce an alternative way to utilization of lignin for production of useful chemaicals. We use H2O2 as the oxidants to selectively oxidize lignin model compounds such as guaiacol, catechol or syringol to organic acid. As we know that, organic acids are high value added polymer monomers or food additives.

As shown in scheme 1, when use H2O2 solutions as the oxidant and titanium silicalite zeolite (TS-1) as the catalyst, guaiacol and catechol can high selectively oxidized to maleic acid (selectivity: 20 mol%) and malic acid (selectivity:30 mol%) respectively. The byproducts are oxalic acid, fumaric acid, acrylic acid and formic acid.

In this work, the different oxidation pathway of guaiacol and catechol, as well as the catalysis mechanism of this selectively oxidation reaction will be discussed. Our work shown that, the utilization of lignin to produce high value added chemicals is feasible.

Reference

[1] Crawford, R. L. Lignin Biodegradation and Transformation; Wiley-Interscience: New York, 1981.

[2] Huber, G. W.; Iborra, S.; Corma, A. Chem. Rev. 2006,106, 4044--4098.

[3]a) Ind. Eng.Chem. Res. 1993, 32, 1535--1541; b) Angew. Chem., Int. Ed. 2007, 46, 7164--7183.