Enhancement of separation selectivity of hemicellulose from bamboo using freeze-thaw-assisted p-toluenesulfonic acid treatment at low acid concentration and high temperature.

The cellulose-rich residual solids are obtained with p-toluenesulfonic acid (p-TsOH) treatment. However, better fractionation of hemicellulose and separation is difficult to obtain during treatment. This study aims at investigating the separation selectivity of bamboo hemicellulose using freeze-thaw-assisted p-TsOH (F/p-TsOH) treatment. The desired separation effect was achieved at freezing temperature -40 °C, freezing time 20 h, p-TsOH concentration 3.0 %, treatment temperature 130 °C and time 80 min. 93.26 % hemicellulose separation was found, which was 32.88 % higher than that of conventional p-TsOH treatment. Furthermore, the separation yield of lignin decreased significantly from 69.29 % to 13.98 %. The distinct lignin characteristic absorption peaks were found, while that of hemicellulose was difficult to observe. The fiber crystallinity index increased from 50.42 to 56.55 %. Furthermore, greater selectivity for hemicellulose separation was achieved. The results provide a new research thinking for efficient fractionation of lignocellulosic biomass by organic acid treatment.

Kinetics of Lignin Separation during the Atmospheric Fractionation of Bagasse with p-Toluenesulfonic Acid.

As a green and efficient component separation technology, organic acid pretreatment has been widely studied in biomass refining. In particular, the efficient separation of lignin by p-toluenesulfonic acid (p-TsOH) pretreatment has been achieved. In this study, the mechanism of the atmospheric separation of bagasse lignin with p-TsOH was investigated. The separation kinetics of lignin was analyzed. A non-simple linear relationship was found between the separation yield of lignin and the concentration of p-TsOH, the temperature and the stirring speed. The shrinking nucleus model for the separation of lignin was established based on the introduction of mass transfer and diffusion factors. A general model of the total delignification rate was obtained. The results showed that the process of lignin separation occurred into two phases, i.e., a fast stage and a slow stage. The results provide a theoretical basis for the efficient separation of lignin by p-TsOH pretreatment.

Efficient separation of bagasse lignin by freeze-thaw-assisted p-toluenesulfonic acid pretreatment.

Lignin separation is an important procedure that benefits multiple industries and in particular biomass transformation efforts. In this study, bagasse lignin was separated by freeze-thaw-assisted p-toluenesulfonic acid (p-TsOH) pretreatment. The optimal conditions were freezing temperature -60 °C, freezing time 8.0 h, thawing temperature 15 °C, p-TsOH concentration 60%, pretreatment temperature 70 °C, and time 20 min. Lower acid concentrations and temperatures were used compared with traditional p-TsOH pretreatment. The efficiency and selectivity of lignin separation were improved. It was attributed to freeze-thawing, which provided a more efficient physical channel for the effective penetration of p-TsOH. The separation, extraction and purity of lignin were improved to 89.76%, 78.22% and 77.89%, respectively. High separation, high extraction, high purity and large molecular weight lignin samples were obtained. In addition, the recovery and reuse of p-TsOH was enhanced. This provided a new method for the efficient and clean separation of lignin.