Fractionation of Pinus radiata by ethanol-based organosolv process

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%.

Pyrolysis of Chilean Southern Lignocellulosic Biomasses: Isoconversional Kinetics Analysis and Pyrolytic Products Distribution

“…However, hemicellulose is found in higher proportions in EN and EC as they are fast-growing trees that need to produce more hemicellulose than other polymers. As a result of the high content of hemicellulose formed mainly by mannose monomers rather than lignin, such species might sometimes be considered semi-hard, mainly if they are felled at an early age [ 28 , 29 ]. Similarly, PR and NO had a higher lignin content than the other samples, but the difference was that because PR is a softwood, the lignin is primarily composed of guayacil units, whereas NO is also composed of syringil [ 28 ].…”

“…The Ea determined by the three techniques had somewhat higher values at low PR conversions (0.05) (KAS and FWO = 170 kJ·mol −1 , FR = 148 kJ·mol −1 ) that declined as the conversion rose to 0.25, stabilised, and essentially stayed constant up to the high conversions (0.75). Such results are related to PR as a soft wood with a lot of lignin in the intercellular walls, which shields the cellulose and hemicellulose [ 29 ]. To leave the hemicellulose and cellulose unprotected, so that they might later decay, some lignin linkages must be broken in the first reaction, mainly an interpolymeric bond cleavage reaction.…”