Evaluation of Yield and Lignin Extraction from Eucalyptus grandis × Eucalyptus urophylla Wood Chips with the Hydrotropic Compound Sodium Xylenesulphonate (SXS)

Abstract

This study aimed to evaluate the yield and efficiency of lignin extraction from Eucalyptus grandis × Eucalyptus urophylla wood chips from treatments with sodium xylenesulphonate (SXS), and to determine their optimum conditions. First the wood's physical, chemical, and morphological properties were characterized. Then, the wood chips underwent treatments from a combination of the following factors: time, SXS concentration, and temperature. For each treatment the yield and lignin content remaining in wood chips was determined, from which optimum points were obtained for maximum yield and lignin extraction. The physical, chemical, and morphological characterization showed that the concerned wood showed values in line with those cited in previous literature. Treatments with SXS were efficient in lignin extraction. The treatment that provided the highest calculated yield of wood was 1 h, 0%, 117.5 ºC; and the greatest lignin extraction was with 12 h, 30%, 130 ºC, removing 39.6% of lignin from wood chips. In general, the treatment of E. grandis × E. urophylla wood chips with SXS was effective in extracting lignin. However, the calculated yield and lignin extraction showed antagonistic behaviors; therefore, in light of the objectives, a careful assessment is required when using this treatment on an industrial scale to seek a balance point between the two parameters.

Sequential fractionation of the lignocellulosic components in hardwood based on steam explosion and hydrotropic extraction

“…To enhance the removal of lignin during HEX, the extraction temperature was increased to 190 °C. A positive correlation between lignin removal and extraction temperature has been suggested previously for HEX of sugar cane [32] and hybrid Eucalyptus [42] using SXS. Due to the marginal effect of increases in hold-up time on the extraction efficiency after a certain stage [32], as we will also demonstrate below, the hold-up time was limited to 4 h at the higher temperature.…”

“…Figure 2a shows the effect of temperature on the extraction efficiency, during which the hold-up time was kept constant (150–190 °C for 4 h). Although a positive correlation between lignin removal and temperature has been suggested previously [32, 42], only incremental improvements were obtained in this study. Thus, the relative glucan and lignin content were 73–78 wt% and 13–15 wt%, respectively, under all conditions.…”

“…Due to the similarity of HEX conditions applied and the compositions of the treated materials, significant differences in lignin surface coverage and topochemistry are unlikely explanations for the discrepancy in hydrolyzability. It is more likely to be attributed to the different raw materials used—specifically the lower S/G ratio of the lignin in the birch–beech wood mixture compared with birch alone [42]. G lignin has a higher cellulase adsorption affinity than S lignin, which increases the unproductive binding of cellulases to lignin [56].…”

An extensive parameter study of hydrotropic extraction of steam-pretreated birch

“…This was done to represent the relative effect of each factor on the extraction of lignin within the range of factor values investigated in this study. Based on the results, lignin extraction correlated positively with temperature, consistent with previous findings that higher temperature increases lignin extraction during HEX of sugarcane bagasse and eucalyptus [24,30]. The residence time had linear and quadratic effects on lignin extraction, as shown by Eq.…”

“…To optimise the performance of HEX, the effects of the conditions that are applied must be understood. In the case of HEX with SXS as the hydrotrope, previous studies have examined the following ranges of conditions: temperature 60-190°C [24,25,29,30], residence time 0.5-12 h [23,24,30] and liquid-to-wood ratio 4-10 with regard to biomass loading (BL) [23,29,31]. Most studies have evaluated 1 or 2 of these parameters, but none has assessed all 3 and their possible interactions.…”