Desulfurization of black liquor soap for production of crude tall oil with lower sulfur content.

Black liquor soap is used to produce tall oil with subsequent fractionation. The main distilled products are tall oil rosin and fatty acids, as well as pitch. The presence of sulfur compounds in tall products limits the number of their end-use applications. The existing methods for tall oil and tall oil-derived products desulfurization are expensive, time-consuming and non-universal. Desulfurization of sulfate soap can solve the problem of reducing the sulfur content in the tall oil and its fractions. By treatment with sodium hydroxide + sodium chloride aqueous solution and copper, the total sulfur content of softwood black liquor soap was reduced from 3120 to 197 ppm, and in the case of softwood + hardwood black liquor soap-from 2960 to 423 ppm. Minimum total sulfur contents of the tall oils obtained from desulfurized sulfate soaps were 165 and 410 ppm, respectively. [ABSTRACT FROM AUTHOR]