Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF ALKYL ESTERS AND GLYCERIN SIMULTANEOUSLY

Abstract

An improved process has been disclosed for the preparation of alkyl esters by simultaneous transesterification of glycerides and esterification of fatty acids in the presence of an acid catalyst. The raw materials containing glycerides and free fatty acids, 15-35 wt% CM alcohol are mixed with 1.75 - 5.0 wt% concentrated sulfuric acid as catalyst. The reaction mixture is heated to 40 - 120°C for 2-7 hrs, the phases are allowed to separate and the alkyl esters and glycerol are recovered.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2005 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION An improved process for the preparation of alkyl esters and glycerin simultaneously APPLICANTS Name : Excel Industries Limited Nationality: Indian Company Address: 184/87 Swami Vivekanand Road, Jogeshwari (W), 1 Mumbai 400102 , Maharashtra, India PREAMBLE TO THE DESCRIPTION The following specification particularly describes the nature of this invention and the manner in which it is to be performed : FIELD OF INVENTION This invention relates to an improved process for the preparation of alkyl esters and glycerine simultaneously. PRIOR ART Fatty acid alkyl esters particularly methyl esters derived generally from vegetable oils and fats or animal fats are important intermediates in the manufacture of olefins. Fatty acid methyl esters are also direct substitute for conventional petroleum based diesel and are also known as bio diesel. Besides the benefit of being generated from natural, renewable sources such as new or used vegetable oils and fats or animal fats, they also provide the added benefit of decreased emissions from combustion as compared to the combustion of petroleum based diesel. Biodiesel is thus a clean fuel. Alkyl esters are prepared by reacting the glycerides and free fatty acids present in the vegetable oils and fats or animal fats with an alcohol in the presence of a base or acid catalyst. The glycerides and free fatty acids are transesterified and esterified, respectively, to form alkyl esters. Base catalysts such as sodium or potassium hydroxides are more frequently used than acid catalysts, as the reaction time for transesterification is shorter in case of base-catalyzed reactions compared to acid-catalyzed reactions reported in the prior art. However, when a base catalyst is used, the reaction mass is obtained in form of an emulsion. Separation of the alkyl esters from the emulsion is tedious and cumbersome. Besides, the free fatty acids present in the oils or fats react with the base and precipitate as soap thereby reducing the amount of alkyl esters formed i.e. the yield. To overcome the problem of salt formation of free fatty acids, a two step process has been proposed in WO 02 28811. First step involves acid catalyzed esterification of free fatty acids with an alcohol. The second step involves neutralization of acid catalyst followed by conventional base-catalyzed transesterification of triglycerides with an alcohol. 2 However, neutralization of acid results in additional salt-waste and in this process the recovery scheme of residual free fatty acids is cumbersome. US Patent No 6,768,015 describes a method of making alkyl esters by reacting vegetable oil source including glycerides and / or free fatty acids with methanol in the presence of an acid catalyst. Methanol is used in excess of about 1 to 5 equivalents and acid catalyst used is about 0.0-0.5% preferably 0.1 to about 0.25% by weight. This method employs high temperatures of 80-200°C and pressures of 25 to 500 psia because of which it is expensive, energy consuming and difficult to carry out. It also does not describe the recovery of glycerine formed during the reaction. OBJECTS OF INVENTION An object of the invention is to provide an improved process for the preparation of alkyl esters and glycerine simultaneously, which is economical and simple to carry out and also energy saving. Another object of the invention is to provide a process for simultaneous transesterification of glycerides and esterification of fatty acids. Another object of the invention is to provide an improved process for the preparation of alkyl esters and glycerin simultaneously, which is of short duration. Another object of the invention is to provide an improved process for the preparation of alkyl esters and glycerin simultaneously, which eliminates soap formation and gives increased yield of alkyl esters. DETAILED DESCRIPTION OF THE INVENTION The present invention describes an improved process for the preparation of alkyl esters wherein a substantial advantage over prior art has been attained by carrying out the process under the novel set of parameters and the proportion of raw materials as disclosed hereunder. Employing this process, simultaneous transesterification and esterification of 3 glycerides and fatty acids respectively is possible at atmospheric pressure. The invention obviates the need to conduct reactions of glycerides and fatty acids separately. Moreover, the process of invention requires much less amount of alkanol compared to the processes reported in the prior art. According to the invention there is provided an improved process for the preparation of alkyl esters and glycerin simultaneously comprising a) reacting oils and/or fats with an alkanol in the presence of an acid catalyst under stirring, the weight percentages of alkanol and acid catalyst being 15 to 35 and 1.75 to 5.0 respectively, based on the weight of oils and/or fats, and the reaction being carried out at 40° to 120° C, preferably at 50° to 75° C; b) cooling the reaction mixture and allowing it to settle into an ester phase and a glycerin phase; c) and recovering the alkyl esters and glycerin from the ester phase and glycerin phase, respectively. According to an embodiment of the process, the alkyl esters are recovered from the ester phase by washing the ester phase with water and subjecting it to vacuum distillation to remove unreacted alkanol from the alkyl esters. According to an embodiment of the process, glycerin is recovered from the glycerin phase by a) neutralizing the glycerin phase with a base such as calcium carbonate; b) filtering the mixture to remove calcium sulfate formed and excess of calcium carbonate c) washing the mixture of calcium sulfate and calcium carbonate with water to recover glycerin adsorbed on it d) purifying the wash water containing glycerine by passing through activated charcoal; 4 e) filtering the wash water to remove impurities ; and f) subjecting the filtrate to vacuum distillation to remove the water. The acid catalyst used in the process of the invention is preferably concentrated sulfuric acid of > 90%.-purity. The alkanol used in the process of the invention is selected from methanol, ethanol, propanol and butanol, and is preferably methanol or ethanol. The base used for neutralization of glycerin phase is selected from compounds which form insoluble sulfate on reaction with sulfuric acid. Preferably the base used is barium or calcium carbonate and most preferably calcium carbonate. Oils and/or fats used in the process of the invention may be vegetable oils and fats selected from Azadirachta indica (Bitter neem), Sesamum indicum (Sesame), Glycine max (Soyabean), Jatropha curcas (Physic nut), Pongamia pinnata (Indian beech), Brassica napus (Rape seed), Gossypium hirsutum (Cotton seed) animal fats etc. According to the process of the invention transesterification and esterification are carried out simultaneously at temperature of 50 to 70° using alkanol and acid catalyst in weight percentages of 15 to 35 and 1.75 to 5.0 respectively, based on the weight of oil and/or fat source, to produce alkyl esters and glycerin simultaneously. Use of alkanol and acid catalyst in the above mentioned weight percentages reduces the reaction time to about 4 Vi hours. The process, therefore, is of short duration. Since base catalyst is not employed, the free fatty acids do not precipitate as soap thereby reducing losses in the process and increasing yield of alkyl esters. The following experimental examples are illustrative of the invention but not limitative of the scope thereof: 5 EXAMPLE - 1 Jatropha oil 1000 gms (Sp.Gr. 0.91, Volume approx 1098 m.l.) and methanol 300 m.l. (Sp.Gr. 0.79, weight 237 gms.) were charged in a glass reactor vessel equipped with condenser and stirring device. 20 m.l. (36 Gms) concentrated sulfuric acid was added to this reaction mass while stirring. The experimental assembly was equipped with temperature indicator and housed in a hot water bath with temperature control mechanism. The reaction mass was heated with the help of hot water bath to the pot temperature of 70°C, and steady reflux of methanol was observed keeping stirring continuous. Temperature and effective stirring was maintained for 4 hrs and 30 minutes. At the end of the reaction, it was cooled down to 30°C. The reaction mass was transferred to separating funnel and allowed to settle for few minutes till two phases separated clearly. The heavy phase was separated from the bottom, which was attributed to the mixture of glycerin, spent sulphuric acid and excess of methanol. The upper (lighter) phase was washed with 100 m.l. of water and washings(lower phase) was removed from the bottom of the separating funnel. The resultant product mixture was subjected to vacuum distillation at the temperature of 70°C and Vacuum of 600 mm Hg to remove any methanol or water. The resultant product was filtered through 10 filter. It was weighing 1002 Gms, Volume 1165 m.l. and Sp.Gr. 0.86. EXAMPLE 2 Example 2 was conducted using the same feed raw materials in the same quantity as in example 1, and using the same reaction conditions. The reaction mass was then subjected to vacuum distillation for the removal of excess methanol at the end of the reaction. It was then allowed to cool to 30°C, transferred to separating funnel and allowed to settle for few minutes till two phase separated out clearly. 6 The heavy phase was separated from the bottom, which was attributed to the mixture of glycerin and spent sulphuric acid. The product mixture (upper phase) was washed with 50 m.l. of water and the washings were removed from the bottom of the separating funnel. The resultant product mixture was subjected to vacuum distillation at the temperature of 70oC and Vacuum of 600 mm Hg to remove any methanol or water remained in the product. The resultant product was filtered through 10m filter. It was weighing 1002 Gms, volume 1164 m.l. and Sp.Gr. 0.86. The heavy phase separated as mixture of glycerin and spent sulphuric acid was treated with 50 Gms of Barium carbonate to remove acid part. The barium sulphate, with excess of Barium carbonate was separated by filtration, and washed with two 50 m.l. portions of distilled water to remove all glycerin attached to barium sulphate. The resulting dilute glycerin solution was treated with 2 Gms of activated charcoal, filtered and it was subjected to vacuum distillation to remove all water. The product glycerin weight 111 Gms and purity of 96% on G L C. EXAMPLE 3 The procedure as described in example 2 was repeated except Karanja oil i.e. oil from Pongamia pinnata (Indian Beech) was used in place of Jatropha oil. The resultant bio diesel product obtained was weighing 1004 Gms, Volume 1167 m.l. and Sp.Gr. 0.86. The heavy phase separated as mixture of glycerin and spent sulphuric acid was treated with 25 Gms of dry commercial calcium carbonate to remove acid part. The calcium sulfate formed and excess of calcium carbonate were separated by filtration and washed with two 50 m.l. portions of distilled water to remove all glycerin attached to gypsum. The resulting dilute glycerin solution was treated with 2 Gms of activated charcoal, filtered and it was subjected to vacuum distillation to remove all water. The product glycerin weight 110 Gms and purity of 96% as analyzed by G L C. 7 EXAMPLE 4 The procedure as described in example 3 was repeated except the quantity of methanol was reduced to 200 ml. The results are given in Table 1. EXAMPLE 5 The procedure as described in example 4 was repeated except rapeseed -(Raido) oil i.e. oil of Brassica napus was used in place of Karanja oil. The results are given in Table 1. 8 Table 1 Example No Feed Oil Methanol m.l. Reaction parameter Product Biodiesel Product Glycerin Source Weight Gms Sp.Gr. Temp.°C TimeHrs.Min Weight Gms Volume m.l. Sp.Gr. Weight Gms Volume m.l. Sp.Gr. 1 Jatropha 1000 0.91 300 72 to 75 4.30 1002 1165 0.86 Not purified 2 Jatropha 1000 0.91 300 72 to 75 4.15 1002 1164 0.86 111 90.0 1.237 3 Karanja 1000 0.92 300 72 to 75 4.30 1004 1167 0.86 110 89.5 1.230 4 Karanja 1000 0.92 200 72 to 75 4.30 1004 1166 0.86 111 90.5 1.225 5 Rapeseed 1000 0.91 200 72 to 75 4.00 1002 1165 0.86 102 78.5 1.300 EXAMPLES 6-11 Palmitic acid, Stearic acid, and Oleic acids were used as source of free fatty acids for the preparation of fatty acid esters. Esterification was carried out with 1.5 times in excess of stoichiometric amounts of methanol or ethanol. Stoichiometric amount of concentrated sulfuric acid was used as a catalyst. Reaction was carried out maintaining reflux of the alcohol for 4.00 hrs. After removal of un-reacted alcohol in the uppermost phase, phase consisting of fatty acid alkyl esters was washed with distilled water for the removal of any remaining alcohol, dried under vacuum and analyzed by using high performance liquid chromatography. Details of experimental parameters and results thereof are tabulated in table 2. 10 Table 2 Esterification details of Fatty Acids ExampleNo Acid Alcohol Reaction Product Biodiesel Name Weight Gms Name Weight gms PotTemp.°C Time Hrs. Min Weight Gms Volume m.l Sp.Gr. @30°C 6 Palmitic 250 Methanol 125 70 to 72 4.00 263 305 0.861 7 Palmitic 250 Ethanol 180 95 to 98 4.00 278 322 0.864 8 Stearic 250 Methanol 125 70 to 72 4.00 262 305 0.858 9 Stearic 250 Ethanol 180 95 to 98 4.00 276 317 0.871 10 Oleic 250 Methanol 125 70 to 72 4.00 262 304 0.862 11 Oleic 250 Ethanol 180 95 to 98 4.00 276 316 0.873 11 EXAMPLES 12 - 23 A 500 ml capacity autoclave type PTFE lined reaction vessel made of Stainless Steel 316 was used. The reaction vessel was charged with rapeseed oil, cottonseed oil (Gossypium hirsutum), Neem oil, (Azadirachta Indiaca) or Sesame oil (Sesamum indicum) as a source of triglyceride. Alcohols used were Methanol, Ethanol and n-propanol respectively. Quantity of alcohol used was about two times of the theoretical requirements. The reaction mixture was then heated to the temperature that allowed the pressure to increase up to about 5 atmospheres (5 Kgs per cm2). The vessel was subsequently cooled to stop the reaction. Excess of alcohol was recovered by distillation. After removal of un-reacted alcohol and lower phases consisting of sulphuric acid and glycerol, respectively, product was washed with two small amounts of distilled water to remove any alcohol or glycerol, and dried under vacuum to remove any water. Subsequently the product was analyzed using high performance liquid chromatography, and / or / Gas liquid Chromatography using capillary column. From chromatograms, it was seen that in the prolonged reaction time, (one hr or more) peaks of alkyl esters increased. Subsequently, peaks of un-reacted and intermediate compounds decreased and disappeared, demonstrating the high purity of the alkyl esters formed. Details of experiments are tabulated in Table 3. Weight of product biodiesel from Neem oil was somewhat lower compared to other oils, which may be because of presence of bitters and other compounds present in the oil. 12 Table 3 ExampleNo Oil Alcohol Reaction Condition Product Biodiesel Product Glycerin* Name Weight Gms Name Weight Gms Pressure Kg/cm2 Time Hrs. Min Weight Gms Volume m.l Weight Gms Volume m.l 12 Rapeseed 250 Methanol 55 4.75 to 5 2.30 250 291 27.5 22.5 13 250 Ethanol 80 4.75 to 5 3.00 261 302 27.6 22.5 14 250 Propanol 100 4.75 to 5 3.00 273 315 27.5 22.0 15 Cottonseed 250 Methanol 55 4.75 to 5 2.30 250 290 27.0 22.0 16 250 Ethanol 80 4.75 to 5 3.00 263 304 27.5 22.5 17 250 Propanol 100 4.75 to 5 3.00 274 316 27.0 22.0 18 Neem 250 Methanol 55 4.75 to 5 2.30 236 274 25.5 21.0 19 250 Ethanol 80 4.75 to 5 3.00 247 286 25.0 20.5 20 250 Propanol 100 4.75 to 5 3.00 258 298 25.0 20.0 21 Sesame 250 Methanol 55 4.75 to 5 2.30 251 292 28.0 23.0 22 250 Ethanol 80 4.75 to 5 3.00 263 305 27.5 22.5 23 250 Propanol 100 4.75 to 5 3.00 274 315 27.5 22.5 * Purity of product glycerin was in the range of 94 % to 95 % by weight. EXAMPLES 24 to 59 The batch-type glass reactor consists of 1000 ml capacity cylindrical vessel fitted with heating coil magnetic drive for stirrer and condenser were used. The reaction vessel was charged with Jatropha oil (Jatropha Curcas), cottonseed oil (Gossypium hirsutum), or Sesame oil (Sesamum indicum) as a source of triglyceride, mixed with Palmitic acid, Stearic acid or Oleic acid as added fatty acids in the tune of 10 % and 25 % to study the effect of high concentrations of free fatty acids in reaction mixture. Alcohols used were Methanol and Ethanol. Quantity of sulphuric acid as catalyst was calculated as (2% by weight of Oil + 98 Gms per mole of free fatty acid added) The reaction mixture was then heated to the temperature that allowed the alcohol to reflux for 4 hrs. After removal of un-reacted alcohol, the vessel was subsequently cooled to 30°C and lower phases consisting of sulphuric acid and glycerol was separated from the bottom of the vessel, and product was washed with two small amounts of distilled water to remove any alcohol or glycerol. The product biodiesel was dried under vacuum to remove any water. The product was analyzed during reaction using high performance liquid chromatography, and / or / Gas liquid Chromatography using capillary column. From chromatograms, it was observed that in the prolonged reaction time, (two hrs or more) area under the peak of alkyl esters increased and, that of un-reacted triglycerides, free fatty acids and intermediate compounds decreased and subsequently the peaks disappeared, demonstrating the high purity of the alkyl esters formed. Details of experiments are tabulated in table 4. 14 Table 4 (Effect of free fatty acid in reaction) Sr No Feed raw materials Reaction Condition Product Biodiesel Product Glycerin* Oil Weight Gms Fatty acid Weight Gms Alcohol Weight Gms PotTemp.°C Time Hrs. Min Weight Gms Volume m.l. Weight Gms Volume m.l. 24 Jatropha 500 Palmitic 50 Methanol 150 75 4.00 553 640 55.0 45.0 25 500 Stearic 50 Methanol 150 75 4.00 553 645 55.5 45.0 26 500 Oleic 50 Methanol 150 75 4.00 553 640 55.0 44.5 27 500 Palmitic 50 Ethanol 180 95 4.00 579 670 55.0 45.0 28 500 Stearic 50 Ethanol 180 95 4.00 578 670 55.0 45.0 29 500 Oleic 50 Ethanol 180 95 4.00 578 670 55.0 45.0 30 Cottonseed 500 Palmitic 50 Methanol 150 75 4.00 552 640 55.5 45.5 31 500 Stearic 50 Methanol 150 75 4.00 552 640 55.0 44.5 32 500 Oleic 50 Methanol 150 75 4.00 553 645 55.0 45.0 33 500 Palmitic 50 Ethanol 180 95 4.00 577 670 55.5 45.0 34 500 Stearic 50 Ethanol 180 95 4.00 578 670 55.5 45.5 35 500 Oleic 50 Ethanol 180 95 4.00 577 670 55.5 45.0 36 Sesame 500 Palmitic 50 Methanol 150 75 4.00 553 645 56.0 45.5 37 500 Stearic 50 Methanol 150 75 4.00 552 645 56.5 46.0 38 500 Oleic 50 Methanol 150 75 4.00 552 640 55.5 45.0 39 500 Palmitic 50 Ethanol 180 95 4.00 578 670 56.0 45.5 40 500 Stearic 50 Ethanol 180 95 4.00 579 670 56.5 46.0 41 500 Oleic 50 Ethanol 180 95 4.00 579 665 56.0 46.0 15 Table 4 (Cont.) Sr No Feed raw materials Reaction Condition Product Biodiesel Product Glycerin* Oil Weight Gms Fatty acid Weight Gms Alcohol Weight Gms PotTemp.°C Time Hrs. Min Weight Gms Volume m.l. Weight Gms Volume m.l. 42 Jatropha 500 Palmitic 125 Methanol 150 75 4.00 630 730 55.5 45.0 43 500 Stearic 125 Methanol 150 75 4.00 632 735 55.5 45.5 44 500 Oleic 125 Methanol 150 75 4.00 630 725 55.0 45.0 45 500 Palmitic 125 Ethanol 200 95 4.00 662 765 55.0 44.5 46 500 Stearic 125 Ethanol 200 95 4.00 663 765 55.5 45.5 47 500 Oleic 125 Ethanol 200 95 4.00 661 760 55.0 45.0 48 cottonseed 500 Palmitic 125 Methanol 150 75 4.00 631 730 55.5 45.0 49 500 Stearic 125 Methanol 150 75 4.00 632 730 55.0 45.5 50 500 Oleic 125 Methanol 150 75 4.00 632 735 55.0 45.0 51 500 Palmitic 125 Ethanol 200 95 4.00 661 765 55.5 45.5 52 500 Stearic 125 Ethanol . 200 95 4.00 662 765 55.0 44.5 53 500 Oleic 125 Ethanol 200 95 4.00 661 760 55.5 45.0 54 Sesame 500 Palmitic 125 Methanol 150 75 4.00 632 735 56.0 45.5 55 500 Stearic 125 Methanol 150 75 4.00 631 730 56.5 46.0 56 500 Oleic 125 Methanol 150 75 4.00 631 730 56.0 45.5 57 500 Palmitic 125 Ethanol 200 95 4.00 660 760 56.0 45.5 58 500 Stearic 125 Ethanol 200 95 4.00 661 760 56.5 46.0 59 500 Oleic 125 Ethanol 200 95 4.00 661 765 56.0 45.0 16 EXAMPLE 60: Experiment was conducted using 30 liters of expelled Ratanjyot oil (Jatropha Curcas) without any pretreatment for the removal of free fatty acids from the same source as used in the previous examples. The oil was charged to a 50 Liter capacity glass reactor cum distillation unit with bottom discharge facility and equipped with heating and cooling facilities and mechanical drive for mixing during the reaction. Condenser system was attached to the reactor vessel to prevent loss of alcohol during transesterification reaction and to recover excess alcohol at the end of the reaction. Provision for the temperature measurement was made to measure pot temperature and vapor temperature. The reactor was provided with the facility for vacuum distillation operation (Fig.l). Details of results of experiment no 60 are tabulated in the Table 5. EXAMPLE 61 : The procedure as described in Example 60 was repeated except that a mixture of 15 liters of Jatropha oil and 15 liters of Cottonseed oil was taken as the source of triglycerides and fatty acids. Details of results of experiment no 61 are tabulated in the Table 5. It is clear from the results given in Table 5 that blend of oil can be used for transesterification without any technical difficulty or significant effect on quantity or quality of the product biodiesel. ^ 17 Table 5 Experimental details for example 60 and 61 Example No 60 Example No 61 Feed Materials Sp.Gr. Volume Weight Sp.Gr. Volume Weight Jatropha Oil 0.91 30.0 Lit 27.3 Kgs 0.91 15 Lit 13.65 Kgs Cottonseed Oil - - - 0.92 15 Lit 13.80 Kgs Methanol Fresh 0.79 7.5 Lit. 5.925 Kgs 0.79 4.0 Lit. 5.920 Kgs Methanol Recovered 0.79 3.5 Lit. H2S0498% 1.83 300 m.l. 550 Gms 1.83 300 m.l. 550 Gms Reaction Conditions Temperature °C 73 to 75 °C 73 to 76 Time Hrs. Min 4.30 Hrs. Min 4.30 Methanol Recovered after reaction 0.79 3.64 2.875 Kgs 0.79 3.63 2.865 Kgs Crude Glycerin + H2S04 Collected From Bottom 3.560 Kgs 3.550 Kgs Impure Biodiesel 0.87 31.6 Lit 27.580 0.87 31.64 27.590 Water Wash to Biodiesel 1.0 1.5 Lit*2 3.0 1.0 1.5 Lit*2 3.0 Product biodiesel after Moisture removal 0.86 31.40 Lit 27.10 Kgs 0.86 31.65 Lit 27.30 Kgs Glycerin recovered after purification (94 %) 1.230 3050 m.l. 3.75 Kgs 1.235 3000 m.l. 3.705 Kgs 18 The analysis of product obtained in Examples 60 and 61 as shown in Table 6 clearly show that the process for the preparation of monoesters of fatty acids known as biodiesel is practically free from alcohol used for transesterification reaction and by-product glycerin formed during the reaction, thus capable of satisfying international standards of the fuel of the same category. Table 6: Properties of Product Biodiesel Specification Units Specification Excel Biodiesel Standard/ Specification ASTM D6751 EN14214 Experiment 60 Experiment 61 Introduction Date Dec 2001 2001 Density @15 g/cm3 Report 0.86-0.90 0.86 0.86 Viscosity@40 mm2/s 1.9-6.0 3.5-6.0 5.64@30 5.48@30 Flash Point 130 130 129 136. Pour Point Report Report Not analyzed Sulphur %max 0.05 0.01 2.2 ppm 1.8 ppm Total Nitrogen - - - 0.09 % 0.08 % Water max. mg/kg 0.05% 500 ppm 0.02 % 0.02 %. Cu Corrosion 3h/50 NO.3 Pass Pass Cetane No. 47 46 53.9 53.1 Cetane index 55.03 54.0 Methanol %mass 0.02 Below det. limit Below det. limit Ester Content %mass - 96.5 + 98.75 + 98.50 Monoglyceride %mass 0.8 Below det. limit Below det. limit Diglyceride %mass 0.20 Below det. limit Below det. limit Triglyceride %mass 0.03 Below det. limit Below det. limit Free Glycerol %mass 0.02 0.25 Below det. limit Below det. limit Total Glycerol %mass 0.24 115 ppm Below det. limit Below det. limit Alkaline Matter (Na,K) Report 360 ppm Na 0.8 ppm Na 0.8 ppm 19 Moreover, the by-product glycerin separated and washings used to make the biodiesel free of acid catalyst and glycerin was collected in a separate vessel equipped with stirrer. The dilute crude glycerin as obtained in Example 60 and 61 were treated with 6.5 Kg of barium carbonate and 4 Kg of calcium carbonate respectively to neutralize the acid. It was then filtered, washed with water to remove glycerin from BaSO4 or CaSO4 as the case may be, treated with activated charcoal to remove any coloured impurities and was subjected to vacuum at 80-90 oC to remove water. The properties of glycerin are given in Table 7. 20 Table 7: Properties of Product Glycerin Sr.No Test Unit Product Glycerin of Excel Biodiesel Experiment 60 Experiment 61 1 Description Clear, Colorless Viscous Liquid Clear, Colorless Viscous Liquid 2 pH 10 % Solution in C02 free water 6.85 6.73 3 Refractive Index « 25 no 1.45 1.44 4 Solubility in Water Miscible in all proportions Miscible in all proportions 5 Density Gms per m.l. 1.230 @30°C 1.235 @30°C 6 Level of Impurities Impurity Weight % Weight % 6.01 Sulphated Ash 0.0120 0.0150 6.02 Chlorides 0.00125 0.00150 6.03 Sulphate 0.0085 0.0100 6.04 Iron as Fe 30 ppm 25 ppm 6.05 Heavy metals as Pb 12 ppm 15 ppm 6.06 Esters of volatile fatty acids as Glycerol tributyrate 0.320 0.250 6.07 Fatty Acids as Stearic acid 0.01 0.01 6.08 Organic impurities Trace Trace 6.09 Reducing substances Trace Trace 6.10 Sugar as Glucose Present Present 21 WE CLAIM: 1. A process for production of alkyl esters of fatty acids effecting simultaneous transesterification of glycerides and esterification of free fatty acids by mixing the raw material containing glycerides and free fatty acids, 15-35 wt% C1-4 alcohol and 1.75 - 5.0 wt% concentrated sulfuric acid as catalyst, heating the reaction mixture to 40 - 120°C for 2-7 hrs., allowing the phases to separate and recovering the alkyl esters and/or glycerol 2. A process for production of alkyl esters of fatty acids effecting simultaneous transesterification of glycerides and esterification of free fatty acids by mixing vegetable oil or a mixture thereof as source of glycerides and free fatty acids, 15 -35 wt% CM alcohol and concentrated sulfuric acid catalyst taken as 1.75 - 2.0 % based on wt of oil + 40% based on wt of free fatty acid, heating the reaction mixture to 40 - 120°C for 2-7 hrs., allowing the phases to separate and recovering the alkyl esters and/or glycerol 3. A process as claimed in claim 1, wherein the source of glycerides and fatty acids is any natural or synthetic source such as vegetable or animal oil or fat or mixture thereof. Dated this 4th day of April 2005 22 Abstract An improved process has been disclosed for the preparation of alkyl esters by simultaneous transesterification of glycerides and esterification of fatty acids in the presence of an acid catalyst. The raw materials containing glycerides and free fatty acids, 15-35 wt% CM alcohol are mixed with 1.75 - 5.0 wt% concentrated sulfuric acid as catalyst. The reaction mixture is heated to 40 - 120°C for 2-7 hrs, the phases are allowed to separate and the alkyl esters and glycerol are recovered. 22 FEBRUARY 2006

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