The effect of ethanol concentration of the SO2-ethanol-water (SEW) process liquor on the characteristics of Eldar pine (Pinus eldarica ) pulp

The SO2-ethanol-water (SEW) fractionation process is one of the most effective and high-performance platforms for biorefining lignocellulosic materials. Determining the most appropriate percentage of chemical compounds in the cooking liquor can increase process performance. The objective of this study was to investigate the effect of ethanol concentration in SEW cooking liquor on the properties of Pinus eldarica pulp. To achieve this, different ethanol concentrations (26-74%, w/w) in combination with varying percentages of water and fixed 12% SO2 were considered. Cooking was conducted in a laboratory digester at a maximum temperature of 135°C for 60 minutes for all treatments. The results showed that increasing the ethanol concentration to 53% decreased the pulp yield, but increasing it further to 74% increased the pulp yield. The kappa number of the pulp decreased as the ethanol concentration increased, but with a further increase in concentration, this was reversed. A slight increase in the pH of the cooking liquor (due to the increased ethanol concentration) significantly decreased pulp brightness. According to the selectivity curve, the best ethanol concentration used in the SEW process was 41%, which was consistent with the concentrations of 43.5% and 44% reported previously