Primary conversion of lignocellulosic biomass for the production of furfural and levulinic acid

peer-reviewed ; The production of energy and chemicals from renewable resources has gained significant attention as a means to support the transition from fossil fuels towards clean and sustainable technologies. Due to its availability and rich carbohydrate composition, lignocellulosic biomass represents a valuable starting material and requires primary processes to unlock its components. The main focus of this research was to study and develop further knowledge on the primary steps of conversion of lignocellulosic materials, i.e. biomass fractionation, cellulose/ hemicellulose hydrolysis, and the production of furanic compounds (furfural, 5-hydroxymethylfurfural) and levulinic acid. In an initial stage, the fractionation of Miscanthus giganteus and sugarcane bagasse was investigated using hydrogen peroxide in formic acid solutions. This treatment removed more than 70% of the lignin in the feedstocks after 13 h at room temperature and after 15 min at temperatures over 150 oC. The use of hydrogen peroxide in formic acid under transient temperature facilitated the separation of >90% of the lignin and 80-98% of hemicellulose sugars, resulting in nearly pure cellulosic pulps. Likewise, lignin was recovered from the liquor and presented aromaticity properties proper of Organosolv lignins. The conversion of lignocellulosic biomass to levulinic acid and furfural via acid hydrolysis was undertaken using sulphuric acid as catalyst. Biomass feedstocks, including agricultural, municipal wastes (paper) and rotational crops from Brazil and Ireland, led to levulinic acid yields between 150 and 400 kg/ton dry biomass. Additionally, the kinetics of acid hydrolysis of Miscanthus to produce levulinic acid and furfural were studied at mild temperatures (150-200 oC) and high acid concentrations (0.10-0.53 M H2SO4). A two-stage process was found to maximise furfural (27.3 mol%) in a first reactor operated at 185 oC with 0.5 M H2SO4. A second stage leads to levulinic acid yields between 58-72 mol% at temperatures of 160-200 oC. A ...