RECENT PROGRESS IN WOOD FRACTIONATION TOWARDS COMPLETE VALORIZATION OF LIGNIN AND CARBOHYDRATES FOR ADVANCED FOREST BIOREFINERY

摘要

The concept of producing bioproducts, biofuel, and biochemicals through biorefining using lignocelluloses has been around for approximately a century. However current technologies for commercial scale production are not economically viable. Most of these technologies requires to process lignocelluloses at high temperatures and have difficulties for economic chemical recovery. For the past decade, we have devoted our efforts to advance the science and engineering critical to commercialization of biorefining technologies including the successful demonstration of the SPORL process for producing biojet fuel from forest residues in commercial aviation (Alaska Airline flight AS04 on Nov. 14, 2016 from Seattle to Washington DC). In this presentation, I will outline our past research work in the productions of biojet fuel. I will also report our recent discovery of the hydrotropic properties of recyclable aromatic acids, such as p-toluenesulfonic acid (p-TsOH), for potential low-cost and efficient fractionation of lignocelluloses through rapid and near-complete dissolution of lignin. Approximately 90% of poplar wood lignin can be dissolved at 80℃ in 20 min. p-TsOH fractionated wood into two fractions: (ⅰ) a primarily cellulose rich water-insoluble solid fraction that can be used for the production of high-value building blocks, such as lignocellulosic nanomaterials, dissolving pulp fibers, and/or sugars through subsequent enzymatic hydrolysis; and (ⅱ) a spent acid liquor stream containing mainly dissolved lignin that can be easily precipitated as lignin nanoparticles by diluting the spent acid liquor using water to below the minimal hydrotrope concentration. Hemicelluloses in the spent liquor were mainly in the form of xylose that can be dehydrated into furfural using the p-TsOH in the spent liquor after lignin precipitation without additional catalysts. Nuclear magnetic resonance analyses revealed that acid hydrotrope (p-TsOH) dissolved lignin (AHL) is carbohydrate free and not condensed with large molecular weight, low glass transition temperature, and very high content of β-aryl ether linkages (such as β-O-4), which can facilitate applications as a polymer in composites or further deploymerization through catalysis for producing lignin aromatics for chemicals. p-TsOH as a catalyst can be reused to achieve environmental sustainability.