Gas phase catalysis of mixtures of mono-saccharides derived from hydrolysing lignocellulosic biomass with gamma-valeractone

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Mono-saccharides derived from lignocellulosic biomass have the potential to replace petroleum as a feedstock to produce specialty chemicals. The U.S. Department of Energy identified the Top 12 value added molecules from biomass. Glucose is a feedstock of four of these building blocks: succinic acid, 2,5 - furan dicarboxylic acid, glucaric acid and sorbitol. The reactions include partial oxidation (gluconic acid or lactic acid), hydrogenation (sorbitol) and oxidative dehydration (furans). Chemicals derived from furans are worth 3 times the price of refined glucose. The price of acrylic acid exceeds 2000 $/t (6 times refined glucose), which makes it an attractive target molecule. Process platforms to convert lignocellusic biomass include: (1) thermochemical; (2) enzymatic or chemical hydrolysis then fermentation; and (3) chemical hydrolysis and dehydration followed by catalytic upgrading. Thermochemical processes are poorly efficient and require additional steps to make fuels (either syngas to diesel, or pyrolysis oils that need to be purified). Fermentation requires long residence times and produces dilute solutions. Separation costs and energy requirements can be considerable and finally the large volumes of water must be treated. The latter process catalyses the reaction with low concentrations of acid and water and gamma-valeractone (GVL) as solvent. The cellulose is converted to 6-carbon sugars (C6), while the hemicellulose hydrolyzes to 5-carbon sugars (C5). After treating the GVL solution with CO2 at high pressure, a purification stage is required to neutralize the solution and reduce the GVL concentration further, otherwise it inhibits microbial growth. In this programme, rather than purifying the mixture of sugars and GVL, we inject the solution directly into a catalytic fluidized bed operating at temperatures greater than 400 oC. We have already demonstrated that mixed metal oxides catalyse xylose and glucose to similar carboxylic acids in fluidized beds operating in the gas phase. The hurdles that remain include atomizing a solution with a mixture of glucose, xylose and GVL, synthesizing a selective catalyst, producing fluidized bed micro-spheres and scaling up the reactor. The principal objective of this research program is to demonstrate high yields of carboxylic acids in a fluidized bed at a scale of 500 g. We subdivide the program into three projects: (1) select a catalyst system that converts monosaccharides/GVL/water solutions to carboxylic acids; (2) develop catalyst manufacturing capabilities to form attrition resistant micro-spheres either by spray drying, spray pyrolysis or wet impregnation; and (3) scale up the fluidized bed process particularly criteria to design the spargers for non-volatile substrates in aqueous solutions.