Influence of conditions of organosolvent cooking of birch biomass on yields and properties of ethanol-lignin

It was found that increasing of temperature from 160 to 200°С resulted in the increase of ethanol-lignin yields and the decrease of the amount of residual lignin in holocellulose. The amount of residual lignin obtained at 190°С in composition of hol-ocellulose was lowest (less than 10 % wt.) and the yield of organosolv lignin was high (about 18 % wt.). The maximal yield of lignin (20 % wt.) was obtained at 200°С but at this temperature the formation of char was observed. The increasing of the biomass loading from 10 to 25 g (with constant hydromodule) led to decrease of efficiency of lignin extraction to the solution from 18.4 to 11.4 % wt. At the same time obtained solid residue of holocellulose contained high amount of lignin that diminishes the value of the product. The catalytic effect of the alkali solution (NaOH) on the delignifica-tion process was studied. The addition of 0.1 mol/L of alkali resulted in sharp declianing of hemicelluloses content in liquid phase from 11.4 to 2 % wt. The following elevation of NaOH concentration led to increase of the yields of lignin with simultaneous increasing of sugars content in solution. The increase of the reaction time from 50 to 90 min led to insignificant rise of lignin yields in liquid phase from 11 to 18 % wt. Further increase of the reaction time did not showed a significant effect on the yield of the lignin (only 19 wt. %), at the simultaneous sharp decrease of the yield of the solid product. The optimal conditions for the process were found: loading of lignocellulosic biomass 10 g, temperature 190°C, reaction time 90 min, NaOH content 0.1 mol/L. The lignin obtained under these conditions is a highly pure and contains low amount of hemicelluloses (according FTIR data). The solid residue of cellulose is valuable product due to low content of lignin.

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