14-03: Combined acid catalysis for hydrothermal pretreatment of Miscanthus

Cellulolytic enzyme is an efficient catalyst during pretreatment of lignocellulosic biomass for the production of biofuels and chemicals. Unlike conventional catalyst sulfuric acid, it does not lead to further degradation of monosaccharides. However, the high costs prevent from its commercial application. Recently, a biomimetic approach with dicarboxylic acids has emerged to replace enzyme through mimicking the structure of enzyme catalytical domain. It allowed to significant cost reduction, but was still more expensive than sulfuric acid. In addition, problems associated with potential inhibitory effect of carboxylic acid on the fermentation microbes were concerned. In this study, we adopt the concept of combined acid catalysis for asymmetric synthesis, to design a combined acid system with sulfuric acid and efficient biomimetic acid catalysts. This strategy is to combine cost advantage of sulfuric acid and selectivity advantage of biomimetic catalysts. In our study, two promising biomimetic acids, maleic acid and triofluoroacetic acid (TFA) were applied to blend with sulfuric acid individually to form the combined catalysts. The influences of temperature, catalyst dosage, and blending ratio of two acids on the pretreatment performance were investigated. We observed that for all applied operating conditions, combined acid catalysts resulted in significantly higher monosaccharide yields (mainly xylose) than both of the individual acid catalysts, with roughly the same level of inhibitory by-products production. It indicated combined catalysts facilitate the hydrolysis of sugar polymers without remarkable improvement on the prevention of monosaccharides degradation. Catalytic mechanism in the combined system was further characterized and will be presented at the conference.