Kajian Pemurnian Gliserol Hasil Samping Biodiesel Jarak Pagar Menggunakan Asam Nitrat, Sulfat, dan Fosfat

Abstract

About ±10% glycerol is produced as byproduct in KOH alkali-catalysis transesterification of Jatropha curcas oil and methanol. The glycerol contains some soluble impurities such as catalyst, soap, excess methanol, water, and other substances. The glycerol needs purification treatment so that glycerol can be utilized into other products. The first step in the glycerol purification is mineral acid addition to neutralize the base content and to split the soap content into salt and free fatty acid that are more easily separated from glycerol. The purposes of this research are to select the kind of acid that could separate the glycerol from the base catalyst and soap, to study the effect of the molar amount of added acid, and to identify the quality of salt as byproduct of glycerol purification with the best treatment. The experiments conducted in complete randomized factorial design, consisted of two treatment factors: kinds and molar amount of mineral acids. Kind of acids were HNO3 15.27 M, H2SO4 18.01 M, and H3PO4 14.74 M. Molar amount of acids were 54 mmol, 90 mmol, 126 mmol, 162 mmol, and 198 mmol (added into 200 g of glycerol). The observed response variables were pH of glycerol, glycerol content, and ash content of glycerol. The crude glycerol from KOH alkali-catalysis of Jatropha curcas biodiesel production contained: glycerol (40.48%), KOH (2.39%), soap (7.82%), evaporated compounds at 1050C (46.81%), and ash (5.16%). The kind and molar amount of mineral acid significantly affected the pH-value, glycerol content, and ash content. The treatment with 126 mmol H3PO4 14.74 M, in 200 grams glycerol, resulted highest glycerol content (78.77%), lowest ash content (1.085%), and pH-value 6.63. Precipitated salt produced from the best treatment contained (based on dry base, except evaporated compounds): K2O (13.17%), P2O5 (20.14%), chloride (2.67%), free acid (26.18%), and evaporated compounds at 1300C (33.93%).