Effect of acetic acid pretreatment on wood pore structure and fractal dimension

Abstract

The acetic acid pretreatment of wood chips has become one of the most promising technologies for biorefinery. This study aimed to provide a quantitative evaluation of the porosity variation during pretreatment based on the fractal dimension methodology. The acacia wood sample was pretreated by acetic acid under different temperatures (140 °C to 170 °C), followed by a three-stage disc-refining at high consistency, and was subsequently characterized by the low-temperature nitrogen adsorption method. The detailed data related to the fractal dimension were obtained by two well-established methods, namely, the Yu Boming (YBM) fractal and Frenkel Halsey Hill (FHH) fractal method. Both the acetic acid pretreatment and disc refining resulted in a higher fractal dimension, which indicated increased irregularity of the pore structure. The mechanism behind the temperature's effect, where the higher temperature led to a lower fractal dimension, was also explored. Compared to the FHH dimension, the fitting range of the YBM dimension was wider and it had a lower correlation coefficient.