Lignocellulosic Biomass Fractionation as a Pretreatment Step for Production of Fuels and Green Chemicals

One of the main constraints and the most costly step in the production of lignocellulosic ethanol is the biomass pretreatment step that aims at liberating the cellulose by dissolving the lignin and the hemicellulose fractions. For this reason, several pretreatment methods have been developed that aim at dissolving biomass lignin and hydrolysing the cellulosic part in order to maximize fermentation yields towards ethanol. In this work, delignification of a forestry residue was carried out via a Milox treatment and its variations. Formic acid with hydrogen peroxide (HP) was used as the delignifying agent and the effects of temperature and HP concentration were investigated. Hydrolysis of untreated and delignified biomass samples with hot water (HW) was also carried out to depolymerize the solid feed. HW hydrolysis of the untreated biomass was efficient at dissolving hemicellulose, while hydrolysis of the delignified biomass yielded a liquid with increased sugars concentration. When CO₂ was used to pressurize the reactor, xylose and glucose yields increased due to the acidity that CO₂ conferred to the HW. This allowed the utilization of lower temperatures, which led to the minimization of byproducts. The lignin residue from the Milox treatment was pyrolyzed in order to investigate its potential as a feedstock for thermal and catalytic pyrolysis. Organic bio-oil production was limited and water and gas production was high. The thermal pyrolysis bio-oil consisted of phenols and acids, while catalytic pyrolysis with ZSM-5 resulted in a bio-oil with increased aromatic hydrocarbons and phenols and reduced acids.