Max A. Mellmer

Integrated conversion of hemicellulose and cellulose from lignocellulosic biomass

Using gamma-valerolactone (GVL) as solvent, the cellulosic fraction of lignocellulosic biomass can be converted into levulinic acid (LA), while at the same conditions the hemicellulose fraction can be converted into furfural. This process allows for the conversion of hemicellulose and cellulose simultaneously in a single reactor, thus eliminating pre-treatment steps to fractionate biomass and simplifying product separation.

Production and upgrading of 5-hydroxymethylfurfural using heterogeneous catalysts and biomass-derived solvents

High yields of HMF from glucose can be achieved using biomass-derived solvents and a combination of solid Lewis and Bronsted catalysts in a salt-free reaction system. The HMF produced in this system can be oxidized to FDCA or hydrogenated to DMF, both being high-value chemicals.

Solvent Effects in Acid-Catalyzed Biomass Conversion Reactions**

Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is γ-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H-mordenite and H-beta.

Direct conversion of cellulose to levulinic acid and gamma-valerolactone using solid acid catalysts

Cellulose was converted with high yield (69%) to levulinic acid (LA) using Amberlyst 70 as the catalyst and using a solution of 90 wt% gamma-valerolactone (GVL) and 10 wt% water as the solvent, compared to the low yield of 20% obtained in water. The LA was upgraded to GVL without any neutralization or purification steps due to the solubilization of humins by the GVL solvent. High LA yields (54%) were also obtained from real biomass (corn stover).

Effects of γ-valerolactone in hydrolysis of lignocellulosic biomass to monosaccharides

The use of γ-valerolactone as solvent for acid-catalyzed biomass hydrolysis reactions increases reaction rates compared to reactions carried out in water. In addition, a low apparent activation energy for biomass hydrolysis and a higher value for monosaccharide conversion are displayed using GVL as solvent, leading to favorable energetics for monosaccharide production from biomass.

Increasing the revenue from lignocellulosic biomass: Maximizing feedstock utilization

Replacing petroleum by biomass can be economically feasible by generating revenue from the three primary biomass constituents. The production of renewable chemicals and biofuels must be cost- and performance- competitive with petroleum-derived equivalents to be widely accepted by markets and society. We propose a biomass conversion strategy that maximizes the conversion of lignocellulosic biomass (up to 80% of the biomass to useful products) into high-value products that can be commercialized, providing the opportunity for successful translation to an economically viable commercial process. Our fractionation method preserves the value of all three primary components: (i) cellulose, which is converted into dissolving pulp for fibers and chemicals production; (ii) hemicellulose, which is converted into furfural (a building block chemical); and (iii) lignin, which is converted into carbon products (carbon foam, fibers, or battery anodes), together producing revenues of more than

Effects of Water on the Copper-Catalyzed Conversion of Hydroxymethylfurfural in Tetrahydrofuran.

500 per dry metric ton of biomass. Once de-risked, our technology can be extended to produce other renewable chemicals and biofuels.

Solvent-enabled control of reactivity for liquid-phase reactions of biomass-derived compounds

Reaction kinetics were studied to quantify the effects of water on the conversion of hydroxymethylfurfural (HMF) in THF over Cu/γ-Al2 O3 at 448 K using molecular H2 as the hydrogen source. We show that low concentrations of water (5 wt %) in the THF solvent significantly alter reaction rates and selectivities for the formation of reaction products by hydrogenation and hydrogenolysis processes. In the absence of water, HMF was converted primarily to hydrogenolysis products 2-methyl-5-hydroxymethylfuran (MHMF) and 2,5-dimethylfuran (DMF), whereas reactions carried out in THF-H2 O mixtures (THF/H2 O=95:5 w/w) led to the selective production of the hydrogenation product 2,5-bis(hydroxymethyl)furan (BHMF) and inhibition of HMF hydrogenolysis.

Correction to “Selective Hydrogenation of Unsaturated Carbon–Carbon Bonds in Aromatic-Containing Platform Molecules”

The use of organic solvents in biomass conversion reactions can lead to high rates and improved selectivities. Here, we elucidate the effects of organic solvent mixtures with water on the kinetics of acid-catalysed dehydration reactions of relevance to biomass conversion. Based on results from reaction kinetics studies, combined with classical and ab initio molecular dynamics simulations, we show that the rates of acid-catalysed reactions in the liquid phase can be enhanced by altering the extents of solvation of the initial and transition states of these catalytic processes. The extent of these effects increases as the number of vicinal hydroxyl or oxygen-containing groups in the reactant increases, moving from an alcohol (butanol), to a diol (1,2-propanediol), to a carbohydrate (fructose). We demonstrate that the understanding of these solvation effects can be employed to optimize the rate and selectivity for production of the biomass platform molecule hydroxymethylfurfural from fructose.The choice of solvent system has important implications regarding the catalytic upgrading of carbohydrate-containing biomass. Here, Dumesic and co-workers study solvation effects in organic solvent/water mixtures and employ the obtained information to control the rate and selectivity of the acid-catalysed dehydration of fructose.

Selective Production of Levulinic Acid from Furfuryl Alcohol in THF Solvent Systems over H-ZSM-5

Carbon−Carbon Bonds in Aromatic-Containing Platform Molecules” Thomas J. Schwartz,†,‡ Spencer D. Lyman,‡ Ali Hussain Motagamwala,‡,§ Max A. Mellmer,‡,§ and James A. Dumesic*,‡,§ †Department of Chemical and Biological Engineering, University of Maine, Orono, Maine 04469, United States ‡Department of Chemical and Biological Engineering, University of Wisconsin−Madison, Madison, Wisconsin 53706, United States DOE Great Lakes Bioenergy Research Center, University of Wisconsin−Madison, Madison, Wisconsin 53726, United States