The behavior of resin acids during tall oil distillation

The behavior of resin acids during tall oil distillation was studied by analyzing samples from six industrial-scale processes. The same artifact resin acids were formed in all processes. However, the proportion of artifact resin acids in tall oil rosins varied from 8.3 to 18.3% of the resin acids. The lowest values were found for two processes utilizing thin-film evaporators. The yield of resin acids in the tall oil rosin fraction varied from 62 to 80% of the resin acids in the crude tall oil feeds. Dehydroabietic acid was formed in all processes, the amount in rosin being 14-44% more than in the crude tall oil feed. Of the abietic acid, only 45-82% was recovered in the tall oil rosin fraction. The distribution of various resin acids and their reaction products during distillation was determined. Major resin acid impurities in tall oil fatty acids were 8,15-pimaradien-18-oic acid and 8,15-isoprimaradien-18-oic acid, both formed chiefly during distillation, and two secodehydroabietic acid isomers common in crude tall oils. The reactions of resin acids leading to new isomers or non-acidic products are discussed. Some results of this work were presented at the 173rd American Chemical Society Meeting, New Orleans, March 1977.