I-Corps: Selectively convert biomass-derived carbohydrates through a thermochemical process

William Marsh Rice University, Houston TX

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project lie in the areas of sustainability, green chemistry, and advanced manufacturing. Biomass-derived, non-food-based carbohydrates are an abundant and renewable source of carbon, but they are very difficult to process into any useful fuel, chemical or materials products. The proposed activity seeks the development of a new thermal approach to convert carbohydrates into high-value chemicals and chemical precursors, especially those that cannot be readily produced from petroleum or natural gas. The main limitation of the widely studied thermal process known as pyrolysis is that the generated products are too numerous to purify efficiently and economically. In spite of the wastefulness inherent in pyrolysis, one highly desirable class of compounds called anhydrosugars is still produced through carbohydrate pyrolysis at small scale. In particular, the anhydrosugar compound called levoglucosan, or LGA, is the starting material in the synthesis of several classes of natural products, like the important antiparasitic drug Avermectin and antibiotics. Greater accessibility and affordability of LGA would lead to greater accessibility and affordability of the eventual drug or medication. This I-Corps project initially focuses on levoglucosan (LGA) as the test case for demonstrating the improved pyrolysis technology. This technology is based on the newly researched concept of ring-locking, in which a sugar molecule is chemically modified prior to pyrolysis. LGA formation from glucose becomes the dominant reaction (1,6-elimination pathway) when an alkoxy or phenoxy group is attached to a specific location on the glucose ring. The substituent group inhibits the glucose ring from opening and fragmenting into non-anhydrosugar products (ring-opening pathway). In other words, ring-opening has a much higher activation barrier than 1,6-elimination, after the sugar ring is chemically modified. The selectivity to LGA increases from 2% to greater than 90% after pyrolysis of the chemically modified sugar. This improved pyrolysis technology can be applied to other sugars and complex carbohydrates.