Fatty acid mixture crystallization using solvents

Crystallization of a Fatty Acid Mixture Using Spray Evaporation of Highly Volatile Solvents... 

Distillation By-Products. Of the CTO distiHation by-products, ie, pitch, heads, and DistiHed TaH Oil (DTO), only the last, a unique mixture of rosin and fatty acids, has significant commercial value. Pitch and heads are used as fuel the former has a fuel value of 41,800 kj/kg. TaH oil heads have outstanding solvent properties, but also have a bad odor, which is hard to remove. They contain a relatively high fraction of palmitic acid which can be recovered by crystallization. 

The recovery of phytosterols or their concentration is the third step in their isolation. Methyl esters of fatty acids are distilled to raise the phytosterol content up to 50% by weight. Molecular distillation can be used for phytosterols. Phytosterol concentrates are used as raw materials for steroid drug preparation via microbial fermentation, in which the pure form of phytosterols are not necessary. The final recovery of phytosterols can be achieved by crystallization (physical), solvent extraction (chemical), or crystallization with additives via adduct formation and separation (physicochemical). Organic solvents or solvent mixtures composed of low- and high-polarity solvents and water are used for crystallization of phytosterols... 

The solubility of salicylic acid for example depends on its concentration, on the type of oil used as vehicle, or on the ratio in the solvent mixture. Fatty oils except castor oil have limited solubilising properties for sahcyUc acid (Table 12.10). Higher concentrations in oily solutions usually need the addition of castor oil to avoid crystallisation and crystal growth. 

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