Production of purified glycerol using sequential desalination and extraction of crude glycerol obtained during trans-esterification of Crotalaria juncea oil

Crude glycerol, produced as a by-product of catalytic methanolysis of Crotalaria juncea oil, was first separated from the methyl esters, then purified and analysed using GCMS. Impurities like soap, free fatty acids and fatty acid methyl esters are mainly present in the crude glycerol. A novel purification sequence, using acidification, neutralization, solvent extraction, decolourisation and finally pressure filtration through a membrane, was applied. Neutralization was carried out with four strong concentrated inorganic acids, namely phosphoric acid, sulphuric acid, hydrochloric acid, perchloric acid and acetic acid (organic). Neutralization produced potassium phosphate, potassium bi-sulphate, potassium chloride and potassium acetate, which were separated afterwards. A trade-off between common-ion, solubility and buffering effect is observed. Effects of various process parameters were optimized by Response Surface Methodology (RSM) using a Central Composite Design (CCD). The optimum condition for a 90.4% pure glycerol was estimated to have been attained at a pH of 3.26 and an adsorbent quantity of 0.933 gm with phosphoric acid (0.43 N).