Change of structural features and relocalization of chemical components in the autohydrolyzed poplar wood chips enhance the accessibility of remaining components

Autohydrolysis of wood chips prior to separating lignin and cellulose is an effective method to pre-extract hemicelluloses, where the change of the structure and chemical composition in the hydrolyzed wood chips inevitably impact the subsequent separation efficiency of the remaining components. In this work, autohydrolysis of poplar wood chips under different intensity was carried out, and the relationships between the chemical/physical changes in the hydrolyzed wood chips and the accessibility of remaining components was evaluated. The results indicated that the removal of most hemicelluloses and minor lignin increased the porosity, specific surface area, and internal hydrophilicity of the wood chips, enhancing the accessibility of wood components to alkali solution as well as the diffusion of the alkali-soluble substance outward. The hydrophobic lignin or lignin-like substance accumulated on the surface of the wood chips could rapidly dissolve into the alkali solution, thus, having no adverse effect on the permeation of alkali solution into the wood chips, although they might create a barrier blocking the passage of water penetration.