Gold Catalyst Mediates Transformation Of Biomass Feedstocks

As global demand and prices for petroleum-based feedstocks continue to rise, chemists are being challenged to devise processes that utilize biomass-derived feedstocks. In one of the latest developments, Claus H. Christensen and coworkers of the Center for Sustainable & Green Chemistry at the Technical University of Denmark, in Lyngby, have come up with a gold-catalyzed procedure for selective oxidation of the biomass-derived platform chemicals furfural and hydroxymethylfurfural to form their respective methyl esters (ChemSusChem, DOI: 10.1002/cssc200700033).

The research is reported this month in the inaugural issue of ChemSusChem, a journal published by Wiley-VCH that is focusing on the rapidly growing interface between chemistry and sustainability science.

The researchers used sodium methoxide in methanol solvent, an oxygen atmosphere, and gold deposited on titania nanoparticles to efficiently convert the hydroxyl and/or aldehyde groups of the furfurals to methyl esters. Methyl furoate formed from furfural is useful for flavor and fragrance applications and potentially as an industrial solvent. Furandimethylcarboxylate derived from hydroxymethylfurfural is a monomer that can replace terephthalic acid in plastics, the scientists note.

In collaboration with Danish enzyme producer Novozymes, Christensen's group is working on a large project funded by the Danish National Advanced Technology Foundation to see if this type of chemistry can be developed into viable industrial processes. "There is a great future for producing value-added chemicals from biomass, and it will most likely require intimate integration of biocatalytic and heterogeneous catalytic processes in order to achieve cost-competitive processes that are also environmentally friendly," Christensen says.

"Plant biomass is the only renewable source of carbon that can be used as a replacement for liquid fuels and chemicals," comments George W. Huber, a chemical engineer at the University of Massachusetts, Amherst. "To fully utilize our biomass resources, we must learn how to efficiently convert biomass-derived molecules into a range of fuels and chemicals that can replace our petroleum-derived resources."

Just as heterogeneous catalysis permits chemists and chemical engineers to convert petroleum-derived feedstocks into a suite of fuels and chemicals, Christensen's group is helping to show that heterogeneous catalysis can be used to convert carbohydrate-based feedstocks into usable fuels and chemicals by selective oxidation reactions, Huber adds.