Technology development of fatty acids obtaining from soapstok using saponification

Abstract

The processing of oil refining waste is essential from economic and environmental points of view. An important issue is the processing of soapstock to extract fatty acids, which are raw materials for various industries. The two-stage method of fatty acids obtaining from soapstock using saponification with sodium hydroxide solution and decomposition with sulfuric acid is investigated. The peculiarity of the work is the study of the influence of soapstock saponification conditions on the key efficiency indicators of fatty acid extraction: yield and neutralization number. A sample of soapstock was obtained as a result of alkaline neutralization of sunflower oil. Soapstock quality corresponds to DSTU 5033 (CAS 68952-95-4): mass fraction of total fat – 68.5 %, fatty acids – 62.6 %, neutral fat – 5.9 %. Rational saponification conditions were determined: duration (85 min.) and concentration of sodium hydroxide solution (45 %). After saponification, the soapstock was subjected to decomposition with sulfuric acid under the following conditions: temperature 90 °C, duration 40 min. Under the rational saponification conditions, the yield of fatty acids (91.8 %) and the neutralization number (187.1 mg KOH/g) were determined. The obtained fatty acids correspond to the first-grade fatty acids according to DSTU 4860 (CAS 61788-66-7). Acid indicators: mass fraction of moisture and volatile substances – 1.5 %, mass fraction of total fat – 98.0 %, cleavage depth – 69.2 % oleic acid. The use of the soapstock saponification stage before decomposition leads to an improvement in the quality indicators and an increase in the neutralization number of fatty acids by 4 %, yield – by 16.2 %. The results of the study make it possible to produce fatty acids from soapstock by two-stage technology with high yield and neutralization number.