Updated Progress of Methods and Approaches for the Separation of Crude Tall Oil

As a special case of bio-oil, crude tall oil (CTO) is a convenient renewable resource for manufacturing many valuable products, including fatty acids, rosin acids, and various neutrals (alcohols, sterols, fatty acid esters, hydrocarbons, etc.). Such an array of components imposes higher standards on the methodology for tall-oil refinement and fractionation, particularly at the commercial level. This review paper discusses current separation methods for generating high-value-added products from CTO. Special attention is given to solvent extraction as the most promising technique that may replace vacuum distillation in producing industrial chemicals with higher purity and at lower cost. Also highlighted are several limitations that prevent the industrial implementation of extraction-based fractionation schemes, as well as approaches to address these challenges. Finally, the analytical methodology for characterizing initial and refined CTO and assessing the quality of final products is illustrated through several practically relevant applications.