Abstract
Paulownia is a rapid-growth tree with a high biomass production rate per year and low demand of water, which make it very suitable for intercropping systems, as it protects the crops from adverse climatic conditions, benefiting the harvest yields. Moreover, these characteristics make Paulownia a suitable raw material able to be fractionated in an integrated biorefinery scheme to obtain multiple products using a cascade conversion approach. Different delignification pretreatments of biomass have been purposed as a first stage of a lignocellulosic biorefinery. In this study, the formosolv delignification of Paulownia wood was investigated using a second order face-centered factorial design to assess the effects of the independent variables (concentrations of formic and hydrochloric acids and reaction time) on the fractionation of Paulownia wood. The maximum delignification achieved in this study (78.5%) was obtained under following conditions: 60 min, and 95% and 0.05% formic and hydrochloric acid, respectively. In addition, the remained solid phases were analyzed to determine their cellulose content and cooking liquors were also chemically analyzed and characterized. Finally, the recovered lignin by precipitation from formosolv liquor and the pristine lignin (milled wood lignin) in Paulownia wood were characterized and compared by the following techniques FTIR, NMR, high-performance size-exclusion chromatography (HPSEC) and TGA. This complete characterization allowed verifying the capacity of the formosolv process to act on the lignin, causing changes in its structure, which included both phenomena of depolymerization and condensation.
Highlights
The current economic system, based on a linear model, has led to humankind’s overreliance on non-renewable fossil resources causing its depletion, besides entailing harmful consequences for the environment, society, economy and health [1]
Lignocellulosic materials (LCM) present a three-dimensional and recalcitrant structure mainly composed of cellulose, hemicelluloses and lignin
The formic acid delignification was carried out with the objective to obtain: (i) a high glucan content in the solid phase, potentially useful in later enzymatic hydrolysis stages, (ii) a high delignification degree and (iii) a high solubilization of hemicellulosic sugars, leading to a solid phase mainly composed of glucan
Summary
The current economic system, based on a linear model, has led to humankind’s overreliance on non-renewable fossil resources causing its depletion, besides entailing harmful consequences for the environment, society, economy and health [1]. In an attempt to mitigate this situation, in recent decades, an unceasing search for alternative strategies has been encouraged to find new and suitable production systems founded in the use of renewable resources as raw material within a biorefinery context. This would suppose a transition from the traditional linear economic model to a circular economy, more efficient and greener, moving the current trend towards a global and sustainable bioeconomy [2]. The selection of the adequate fractionation process is key to achieve an efficient utilization of all fractions
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