Abstract
The lignocellulosic materials are promising feedstock to produce biofuels and bioproducts in the biorefinery framework. However, a pretreatment step is required to disrupt lignin-carbohydrate complex. In this work, the fractionation of Pinus radiata wood into its main components, cellulose-rich delignified solid, recovered lignin after precipitation, and soluble-in-black liquor hemicellulose, was studied. For this purpose, an organosolv process employing ethanol/water mixture as solvent in absence of a catalyst was carried out. The effects of operating conditions on delignified solid were evaluated by using a 23 central composite experimental design, being the responses delignified solid yield, delignification degree, hemicellulose content, and glucan content. The variables studied were temperature (170–200 °C), time (50–100 min), and ethanol concentration (40–60%). The increase of organosolv severity (temperature and time) and reduction of ethanol concentration favor the glucan enrichment of delignified solid, due to lignin removal and hemicellulose solubilization. A glucan content of more than 66% is obtained by applying temperature higher than 195 °C and time longer than 90 min, when 40 wt% alcohol concentration is used. The liquid fraction obtained during the organosolv process (black liquors) was used to recover lignin and hemicellulosic fractions solubilized. Furthermore, hemicellulose and lignin content of delignified solid was correlated with the thermal stability measured as T10%.
Highlights
The lignocellulosic materials are considered as a promising feedstock to be utilized in the sustainable production of liquid fuels and chemical products in the biorefinery framework [1,2,3]
The mathematical models with R-squared value are shown in Table 2, in which the effects with a significance level lower than 95% were neglected for regression models (F > 18.51 and P-value < 0.05)
The delignified solid yield varied between 44.6 and 79.6% in the studied condition range (Table 1). These results can be compared with values of organosolv process of lignocellulosic materials, such as 43–83% for wheat straw [28] or 51–81% for E. globulus wood [24]
Summary
The lignocellulosic materials are considered as a promising feedstock to be utilized in the sustainable production of liquid fuels and chemical products in the biorefinery framework [1,2,3]. The main advantages of these materials are that they do not compete with food, low cost, and availability. They are mainly composed of cellulose, hemicellulose, lignin, and extractives. These components form the lignocellulosic matrix, being strongly bonded through covalent or non-covalent bonds [2]. To overcome the strong recalcitrant structure of these lignocellulosic biomasses, the pretreatment is crucial step to get the partial destruction of complex formed by lignin-carbohydrates [4]. Many methods have been proposed as pretreatment of lignocellulosic materials, being classified
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