Studies on Processes for the Reduction in Acidity of Some Vegetable Oils Khln Htwe Nyunt', Khln Setn' , Bo Bothet] Abstract

Studies on Processes for the Reduction in Acidity of Some Vegetable Oils Khln Htwe Nyunt', Khln Setn' , Bo BoThet] Abstract. Plant oils are a promising alternative energy source offering a variety of economical and ecological advantages. Blodiesel is an alternativefuel produced from vegetable oils or fats through transesteriflcaUon reaction with methanol and sodium hydroxJde as catalyst. The ectdtty of these raw materials is given by free fatty acids that are transformed into soaps in the presence of a base and water. Since the formation of soap cause problems In the steps of washing and puriflcatJon of blodlesel. and decrease of yield. vegetable oils or fats with high acidity could not be used for the conventional process of aIkaUne catalysts. If free fatty adds are present, they can be removed or transformed into blodlesel using special pretreatment technologies. In this research two methods of deacidIfication such as neutralization andextraction were being explored for the reduction of acidity of some vegetable oils such as rice bran. palm and palm kernel oils having different acidities. The oUs were first pretreated by Illtratlon. degumming and winterization. The pretreated oils were then deacldtfled by either neutralization or extraction. It was found that neutralizatlon gave more reduction in acidity but percent yield was low. Stepwiseextraction made more yield of oils having low acidity less than 2.0. Keywords: biodtesel. rransestenftcanon. free fatty acids. deacidification, neutralization. extraction INTRODUCTION Oils. fats. and waxes belong to the class of compounds called lipids. which are insoluble in water, but soluble in ether and other organic solvents. The lipids have long been considered important as one of the three major classes of food materials. They differ from the other two, proteins and carbohydrates, in that they provide more than twice the number of calories per unit weight when converted to carbon dioxide and water. Hence. they were thought to be primarily products for storage of energy in plants and animals. Oils and fats are usually distinguished from one another by their melting points and. to some extent. by their sources. OHs are generally liquid at ordinary temperatures while fats are solid or semi-solid. The fats are usually of animal origin while oils are extracted from plant tissue. fish. or marine animals. Fats and oils ohtalned from animal or vegetable tissue are predominantly triglycerides with traces of mono- and dfglycendes. free fatty acids. phospholipids. I Dr.• Professor and Head. Department of Industria.l Chemistry. West YangonUniversity 2Associate Prof.....-(ReuL).lJeponment of!nduslrial Cberusry, W.,.Yangon UnMoslty 3 Demonstrator. Department oflndustrial Chemistry. WestYangon University WYU Research Journa12014. Vol.4 177 sterols, and other minor constituents. Procedures for refining and processing crude oils remove most of the trace constituents (Kent 1974). Fats and oils have always had an essential role as food for humankind. In addition. however. our modern industrial world has found many important applications for them. The largest consumption of fats forchemical raw materials is in making fattyacids. Oils are saponified. hydrogenated. epoxidized, and sulfonated to a great number of usable products. and fats are isomerized and interesterified, all to produce upgraded and more useful oils and fats (Austin 1984). Btodlesel fuel can also be made from new or used vegetable oils and animal fats. which are non-toxic, biodegradable. renewable resources. The most common process for making blodiesel is known as transesteriflcation. This process involves combining any natural oil (vegetable or animal) wtth virtually any alcohol. and a catalyst. The oils or fats with high acidity could not be used for the conventional process of alkaline catalysis. If free fatty acids are present, they can be removed or transformed into biodiesel using special pretreatment technologies. The main objectives of this research work are to explore suitable methods for the reduction of acidity of somevegetableoils such as rice bran. palmand palm kernel oils and to give moreyield of oils having low acidityyieldingmorebiodiesel. MATERIALS AND METHODS Raw Materials Crude rice bran oil samples with different acidities obtained from (01) Rice Bran all Plant, Kamayut Township Palm oil and palm kernel oil samples with different acidities obtained from Soap Factory No. (I), Hlalng Township Chemical Reagents Potassium hydroxide (SDH, Ana lar grade), dlethyl ether, phenolphthalein indicator (Laboratory chemicals, May & Baker Ltd.), ethyl alcohol (95 percent alcohol) and n-Hexane wereused. Apparatu s 100 ml, 250 ml conical flasks, analytical balance, pipette (25 ml), burette (25 ml wtth graduation in 0.05 ml divisions), hot-plate with temperature control, volumetric flasks (100 ml, 250 ml. 500 ml), water-bath (stainless steel), 500 ml separating funnels; desiccators and oven. 178 WYU Research Jouma 12014 . VolA Experimental Procedure The acid value is defined as the number of milligrams of potassium hydroxide required to neutralise the free fatty acid in one gram of oil. 1 gm of oil was weighed into a 100 m1 conical flask and dissolved in 30 ml of I:1 v/v mixture of previously neutralized ethanol and diethyl ether solution. While shaking. it was titrated with 0.1 N ethanolic potassium hydroxide solution until the pink colour did not change for at least 30 sec. The acid value of the oil sample was calculated as follows (Horwitz 1980). Vxfx 5.6l AV= weight of sample where V = volume orO.IN KOH solution f • factor of O.IN KOH solution Pretreatmemt of Oils Pretreatment of crude oil includes filtration. degumming and winterization. Rice bran oil. palm oil and palm kernel oil samples with different acidities were pretreated in these experiments. Materials Crude oil samples with different acidities Hot water (90'C) Concentrated phosphoric acid Apparatus 250 ml volumetric flask 2L beaker. IL beaker Magnetic stirrer Centrifuge machine 500ml se parating funnel Buchner funnel Filtration of Crude Oil 1000 ml of rice bran oil sample with acidi ty of AV 30.3 was filtered for the separation of impurities such as sludges , carbo hydrates and waxes by Buchner funnel. The same experiments for rice bran oil. palm oil and palm kernel oil samples with different acidities were also carried out. Acidities before and after filtration were detennined by me AOeS (American Oil Chemists' Society) method. The results are shown in Table 1. WYU Research Journal 2014 , VolA 179 Degumming of Filtered Oil with Hot Water at 90°C 500 ml of filtered rice bran oil sample with known acidity was carried out by using 2.5%v/v hal water (90'C) as degumming agent. The amount of all taken (500 mil. the amount of degumming agent used (2.5% v/v) . the agitation rate (200 rpm) and time (I5 minutes) were kept constant throughout the experiment. After the flocculated gums had been separated by centrifugation. the oil was washed and dried . The acidity. the volume and % yield of oil were also recorded. The same experiments for filtered palm oil and palm kernel oil samples with different acidities were also carried out by using 2.5%v/v hot water (9OOC) as degumming age nt. The results are shown in Table 2. Degumming of Filtered, Partially degummed Oil with Phosphoric Acid at 90°C 450 mi of filtered and partially degummed rice bran all sample with known acidity was taken and concentrated phosphoric acid (0.1 % v/v) was used as degumming agent at 900 e. The amount of oil taken (450 ml), the agitation rate (200 rpm) and time (1 5 minutes) were kept constant throughout the experiment. After the flocculated gums had been separated by centrifugation, the degummed oil was washed and dried . The acidity, the volume and % yield of oil were also record ed. The same experiments for filtered and partially degummed palm oil and palm kernel oil samples with different acidities were also carried out by using 0.1 % v/v phosphoric acid as degumming agent. The results are shown in Tab le 3. Winterization of Degummed Oil 400 ml of filtered and degummed rice bran oil sample was dewaxed by winterization at 12°C. The sample was placed in a It pyrex beaker and a gradual cooling to a temperature of 12°C was achieved by passing thermosta tically controlled cool water (9 ± 1°C) into the water j acket. A close tempe rature control was maintained with the aid of the two therm ometers and continuous stirring was provided throughout for 3 hours. After 3 hours. the acidity. the volume and % yield of the dewaxed oil were also recorded. The same experiments for filtered and degummed palm oil and palm kerne l oil samples with different acidities were also carried out. The results are shown in Table 3. Neutralization of Pretreated Oils 100 ml of pretreated palm oil sample with known acidity was preheated to 90°C. A calculated amount of caustic soda solution (20°Be) prepared (amount of caustic soda required was calculated for neutralizing the acidity of the degummed oil sample) was gradually added and the sample was kept under co nstant agitation for 15 min. The soa p and neutral oil formed were separated in the separating funneL Refined 180 WYU Research Jouma12014. VolA oil was washed with hot water. The washed solution was constantly checked with phenolphthalein indicator to ensure that the neutral all was free from soap. The washed oil was dried in the oven at llOOC. The addity and the yield percentage of neutralized. washed and dried oil sample were determined. The same experiment for pretreated palm kernel oil sample with different acidity was also carried out. The results areshown in Table 4. Extraction ofPretreated Oil Using Various Ratio DrOll to Solvent 50 ml of pretreated (filtered. fully degummed and winterized) rice bran 011 sample having an acidity of AV 42.3 was extracted with 95% ethanol using ihe 011 to solvent ratio of 1:6.

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