Optimization of Tall Oil Pitch Saponification by Experimental Design

Sustainable recycling of wood chemical production wastes is one of the current issues of modern technology. As a by-product of the pulp and paper industry, tall oil pitch has found application as a potential source of phytosterols. Phytosterols or plant sterols are natural compounds, polycyclic alcohols structurally similar to steroids. Due to their biological activity, phytosterols are used in such areas as pharmaceutics and cosmetology, as functional products, etc., which makes them commercially attractive. This paper considers the stage of saponification of tall oil pitch, which yields free phytosterols from their esters with fatty and resin acids. A central composite design complemented by six star points was chosen to determine the combined effect of the three factors and to plan the minimum number of experiments; the response surface methodology was used to determine the optimal values of the variables. Regression models showing the impact of the basic technological factors (excess alkali, temperature and duration of saponification) on the degree of saponification of phytosterols in saponified tall oil pitch and esters in the obtained extract were developed based on the experimental data. A statistical analysis of the models was carried out. Their validity has been proved by means of analysis of variance. The experimental and predicted values closely correlated. The developed mathematical models in the regression polynomial form enable to find the optimal values of the input process variables using the Minitab software while simultaneously reaching the maximum degree of saponification (98,1 %) with the minimum value of the ether number in the extract (4 mg KOH/g): saponification temperature – 121.7 °C, process duration – 3.18 h, and excess alkali – 100 %. Thus, reliable models for predicting the degree of saponification of phytosterols and the ester number in the extract were obtained. These models can be used in industrial saponification of tall oil pitch. For citation: Korshunov A.O., Lavrenteva E.A., Lazarev M.A., Radbil’ A.B. Optimization of Tall Oil Pitch Saponification by Experimental Design. Lesnoy Zhurnal [Russian Forestry Journal], 2022, no. 1, pp. 173–187. DOI: 10.37482/0536-1036-2022-1-173-187