Hemicelluloses extraction from pine sawdust: a kinetic study of spent liquor re-use

AREA, M.C.; CLAUSER, N.M.; VALLEJOS, M.E.; FELISSIA, F.E.; GUTIÉRREZ, S.

São Paulo

Congreso; ABTCP - CIADICYP 2018 51º ABTCP Congresso Internacional de Celulose e Papel e X Congresso Ibero-Americano de Pesquisa em Celulose e Papel; 2018

ABTCP - CIADICYP

Pine sawdust is an important lignocellulosic waste from the primary industrialization of wood in Argentina and Uruguay, so its valorization using the biorefinery platform could add new value chains into its forest industry. Hemicelluloses from lignocellulosic waste is abundant polymer with enormous potential for industrial applications. The chemical structure of the hemicelluloses allows their use as precursors for a wide range of chemicals such as alcohols, organic acids, and furanic compounds. In a biorefinery context, pine sawdust can be separated in a valuable cellulose solid fraction and the spent liquor. However, current alternatives for the valorization of hemicelluloses are commercially limited due to their high cost production. The spent liquor reuse for biomass deconstruction could be a promising strategy to reduce water usage in the system and capital and operating costs. However, it is necessary to perform experiments in order to evaluate how a concentrated extraction media can affect the hydrolysis process. The aim of this study was to analyze the re-use of the spent liquor in dilute acid pre-treatment for the hemicellulosic extraction and to determine a kinetic model of hexoses and pentoses solubilisation. Alkali pretreated pine sawdust was treated by dilute acid treatments to extract hemicelluloses (7.5 g/L H2SO4 at 150°C for 30 min and liquid to solid ratio 10:1). The spent liquor was re-used four times, in order to determine the variation in the sugar concentrations and their degradation compounds. The spent liquor composition from the diluted acid treatment was determined by HPLC. A simplified first order kinetic model for sugar release and decomposition was proposed. Using the experimental data of a diluted acid hydrolysis with fresh water, kinetic constants were obtained by parameter adjustment using maximum likelihood estimation method. The model was used to predict the sugar and degradation products of re-cycled experiments. Comparison between modelled and experimental data allows to say that the model suitably describes sugar solubilisation and decomposition. In order to consider the potential benefits of the re-use strategy, overall costs has to be analyzed in a biorefinery context including the resulting cellulose quality. However, the results obtained in this work allow to say that more than two recycles should not be suitable for pentoses or its derived valuable chemicals, as pentoses are strongly degraded. It could be useful for glucose- derived chemicals, and furfural or its derived chemicals.