US EPA

1226529 

Journal Article 

Catalysis in biopolymer chemistry 

Binder, JB 

2009 

Biopolymers such as proteins and polysaccharides are challenging yet crucial candidates for catalytic chemical modification. Proteins comprise as much as three-quarters of the human body exclusive of water and fat, while polysaccharides make up about two-thirds of plant dry mass. Consequently, proteins are critical targets for human health and polysaccharides are promising resources for renewable products. To address these challenges, we developed olefin metathesis reactions for decoration of proteins in water and catalytic chemistry for conversion of biomass into fuels and chemicals. Olefin metathesis is a revolutionary tool for chemical synthesis and water-tolerant metathesis catalysts hold promise for orthogonal chemical modification of proteins. We synthesized ruthenium olefin metathesis catalysts bearing both N-heterocyclic carbene and bidentate salicylaldimine ligands and discovered that this pairing enables efficient ring-closing metathesis of both dienes and enynes in methanol and methanol-water mixtures under air. Alternatively, we developed strategies for using conventional olefin metathesis catalysts for ring-closing and cross metathesis in homogeneous water-organic solvent mixtures. We also explored the production of renewable building blocks through chemical deconstruction of biomass. The privileged combination of chromium salts, halide additives, and cellulose solvents produces extraordinarily high yields of 5-hydroxymethylfurfural (HMF) from not only fructose and glucose but also cellulose and corn stover, enabling a two-step route to the liquid fuel 2,5-dimethylfuran. Further studies revealed that mannose, like glucose, is readily converted into HMF with chromium catalysts, while galactose is not. Moreover, chromium salts mediate the dehydration of xylose into furfural at unexpectedly low temperatures. These results provide mechanistic evidence for the intermediacy of ketoses in the chromium-catalyzed transformation of aldoses into furans. Using ionic liquid cellulose solvents we also invented a process for fast, efficient saccharification of biomass into sugars which can be fermented into ethanol by bacteria and yeasts. These results reflect the power of organic chemistry for constructing and dismantling biological materials. Organic matter, whether from humans or plants, is central to modern challenges in health and energy, and organic chemistry is the fundamental tool for its manipulation. 

USA, Wisconsin, Madison; USA, Wisconsin; Fuels; Cellulose; Proteins; Catalysts; Biomass; Solvents; Dissertations; biopolymers; Salts