Potential vegetable oils of Indian origin as biodiesel feedstock An experimental study

Journal of Scientific AGARWAL & Industrial et al: Research POTENTIAL VEGETABLE OILS OF INDIAN ORIGIN AS BIODIESEL FEEDSTOCK Vol. 71, April 212, pp. 285-289 285 Potential vegetable oils of Indian origin as biodiesel feedstock An experimental study Madhu Agarwal*, Kailash Singh, Sushant Upadhyaya and S P Chaurasia Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur 32 17, India Received 29 September 211, revised 31 January 212; accepted 1 February 212 This study presents various vegetable oils from edible and non-edible sources for preparation of biodiesel using KOH as catalyst and methanol as alcohol. Maximum biodiesel yield from all vegetable oils was obtained under following optimum conditions: reaction temp., C; reaction time, 1 h; catalyst amount, 1% (by oil wt); and methanol to oil molar ratio, 6:1. Characteristics of biodiesel at optimum conditions were as per ASTM standards. Keywords: Biodiesel, Free fatty acid (FFA), Jatropha oil, Transesterification Introduction Biodiesel, a fatty ester of long chain fatty acids (C 12 -C 22 ) derived from vegetable oils or animal fats 1,2, is a renewable diesel fuel with less harmful emissions than petroleum-based diesel fuel except for slightly higher NOx levels (up to 5%). Biodiesel blended with petroleum diesel at levels less than 2% (v/v), generally performs similar to neat petroleum diesel. Direct use of vegetable oils in long run poses many problems (injector chocking, ring sticking, wax formation, carbon deposits, misfire, ignition delay and in fuel atomization), attributed to high viscosity, low volality, poly-unsaturation, high flash point, and low cetane number 2-5. Vegetable oils, modified by chemical methods (pyrolysis, microemulsion, dilution, and transesterification), can suitably be used in the engine, but chemical modification methods also have limitations in long run in diesel engine except by transesterification. For feedstocks having less free fatty acid (FFA) content, homogeneous base catalysts (NaOH, KOH, NaOCH 3 and KOCH 3 ) have been reported to be more suitable for transesterification providing better yield and fast conversion. For high FFA content of oils, two step transesterification (first by liquid acids and then by base catalyst) improves biodiesel yield 6. Use of solid base catalysts for biodiesel production is gaining importance due to its several advantages (no need of washing step, *Author for correspondence E-mail: madhunaresh@gmail.com reusability of catalyst, continuous operation etc.) over liquid base catalysts 7. Biodiesel fuels derived from different sources can have significantly varying fatty acid profiles and properties 8. Contamination with small amounts of glycerides significantly affects viscosity of biodiesel fuels 9. This study presents various vegetable oils of Indian origin for production of biodiesel using KOH as catalyst. Experimental Section Materials Different refined grade oils (, soybean, safflower,,, linseed, palm, and mahua) were purchased from local market. Jatropha and Karanj oils were procured from Udaipur oil mandi (India). Used frying oil was procured from local restaurants and halwais. Chemicals used as catalyst (methanol, KOH and NaOH) were of AR grade and CDH, Qualligence make. Standards used for fatty acid analysis of biodiesel were from Supelco Analytical. Other chemicals used for characterization of oils and biodiesel (CCl 4, HCL, Wig s reagent, etc.) were of AR grade and CDH make. Characterization of Oils and Biodiesel Physico-chemical characteristics [density, kinematic viscosity, acid value (AV), saponification value (SV), Iodine value (IV), etc] of vegetable oils (Table 1) were determined as per methods prescribed by American Society for Testing Materials (ASTM) and American Oil Chemists Society (AOCS). Fatty acid composition

286 J SCI IND RES VOL 71 APRIL 212 Table 1 Characteristics of different vegetable oils Oils Sp Viscosity Acid SV value IV Flash CP PP Mol gravity cp value mgkoh/g value point C C wt mgkoh/g oil g C oil I 2 / g oil Jatropha.88 43. 1.46 28. 18. 225 5. 2. 814.9 oil(a)* Jatropha.92 34.5 12.63 196.4 15.4 2 2. -1. 916. oil (B)** Sunflower.92 3.5.45 192. 11.8 265 7.2 3. 878.6 Mustard.91 32.2.74 192. 85.2 245 5. 1.5 8. Groundnut. 39.8.25 189.3 93.1 268 11. -6.1 8.2 Used.89 53. 1.95 185.1 115.3 288 1. -2. 918.8 frying oil () Jatropha oil (A)*, oil with low FFA content; Jatropha oil (B)**, oil with high FFA content was determined by preparing biodiesel (methyl esters) of different oils and analyzing by gas chromatography (GC) using DN Biodiesel, capillary column of length 3 m.i.d..32 mm film thicknesses.25 µm. Transesterification Transesterification of various vegetable oils was carrie d out in a batch reactor to prepare biodiesel. In the process, measured quantity of vegetable oil (dried by heating) was taken in the three necked round bottom flask (2.5 l) and preheated to C. Requisite quantity of catalyst was then dissolved/mixed in requisite amount of alcohol in case of homogeneous/heterogeneous system. Alcoholic catalyst solution was then added to the flask containing preheated oil; mixture was then stirred on magnetic stirrer at required temperature, and controlled by digital temperature controller (Triode India make). To prevent losses of alcohol due to heating, a total reflux condenser was attached with the reactor. After requisite batch time, stirrer was stopped and reaction mixture was cooled and transferred to separating funnel for phase separation by gravity. Glycerol, settled in bottom layer, was separated as a by-product and upper layer was washed with warm water to remove catalyst, excess alcohol, glycerol etc. from the product layer (biodiesel). Washing was continued till wash water got free from traces of alkaline catalyst (checked by phenolphthalein indicator). After washing, upper layer was collected in beaker and heated to remove trapped water molecules from biodiesel. After water was removed, biodiesel was stored in bottles for its characterization. Same procedure was followed for all batches only by changing the variable to be optimized. Biodiesel yield was measured as Yield (%) = x mass of biodiesel/mass of oil. Biodiesel purity was determined as methyl ester content in by GC analysis. Jatropha (B) oil with high FFA was subjected to two step transesterification, first with acid catalyst (sulfuric acid) to reduce FFA content and then second step with alkaline catalyst (KOH). Determination of Biodiesel [FAME (Fatty Acid Methyl Ester)] content or Purity of a Biodiesel Sample Freshly prepared biodiesel sample (1 ml) was diluted with hexane and injected (1µl) into GC column. Chromatograph obtained using conditions as used for standard FAME mixture was compared with standard FAME chromatograph by inserting calibration curve prepared from known concentration of FAME mixture. CLARITY software provides ester% in the sample. Results and Discussion Effect of Reaction Parameters on Yield and Characteristics of Biodiesel Effect of Alcohol Concentration Biodiesel was prepared from vegetable oils at different molar ratio of methanol to oil. Biodiesel yield is low at low alcohol concentration due to incomplete reaction (Fig. 1). At higher concentration, beyond 6:1 molar ratio of alcohol to oil, yield is almost constant with slight decrease, may be due to losses during washing step. Methanol with one polar hydroxyl group can work as an emulsifier that enhances emulsion causing separation of ester layer difficult from water layer 1. Reduction in FAME yield is also reported 11,12 at higher methanol to oil ratio.

AGARWAL et al: POTENTIAL VEGETABLE OILS OF INDIAN ORIGIN AS BIODIESEL FEEDSTOCK 287 12 Yield, % Yield, % 1 2 3 4 5 6 7 8 9 1 11 Methanol to oil molar ratio Jatropha (A) Groundnut Mustard jatropha (B) Fig. 1 Effect of methanol concentration on yield of biodiesel (Reaction temp., o C; reaction time, min; catalyst amount, 1% by oil wt) 3 2 1 2 12 Temp., o C Jatropha Fig. 3 Effect of reaction temperature on yield of biodiesel (Methanol to oil molar ratio, 6:1; reaction time, min; catalyst amount, 1% by oil wt) Effect of Catalyst Concentration Biodiesel was prepared from different oils with variation in the amount of catalyst (.5-2.% by oil wt). Biodiesel yield increases with increase in amount of catalyst (up to 1%) and then decreases slightly (Fig. 2). At lower concentration of catalyst, insufficient amount of catalyst result in incomplete reaction so lower yield. Higher concentration of catalyst decreases yield due to losses during washing step. Yield losses can be due to inadequate phase separation. It was observed that higher concentration of catalyst causes phase separation difficult in case of used frying oil. Soap formation in presence of high amount of catalyst is reported 13,14 to increase viscosity of reactants and thus lowers the rate of biodiesel production. Effect of Temperature Variation Biodiesel was prepared from different oils at different reaction temperatures. Biodiesel yield increases Yield, % Yield, % 2 Jatropha(A).5 1 1.5 2 2.5 3 2 1 Catalyst concentration, % by wt. of oil Fig. 2 Effect of catalyst concentration on yield of biodiesel (Methanol to oil molar ratio, 6:1; reaction temp., o C; reaction time, min) Jatropha(A) 2 Time, min Fig. 4 Effect of reaction time on yield of biodiesel (Methanol to oil molar ratio, 6:1; reaction temp., o C; catalyst amount, 1% by oil wt) with increase in reaction temperature up to C, thereafter it decreases (Fig. 3). Low yield at low temperature may be due to incomplete reaction. Low yield at high temperature may be due to acceleration of side saponification reaction of triglycerides 13,15-17, and due to that the most of methanol (bp 64.7 C) at this temperature remains in vapor phase, causing less conversion. Although a reflux condenser was used to condense back the methanol in reactor, conversion efficiency significantly decreases above C due to high rate of methanol vaporization. With reflux condenser, C can be taken as optimum temperature. Effect of Reaction Time Biodiesel, prepared from different oils, were collected at different reaction time from batch reactor. Biodiesel yield increases with increase in reaction time at the beginning, reaches a maximum at 15-3 min, remains relatively constant with further increase in reaction time (Fig. 4), and slightly decreases after min, may be due

288 J SCI IND RES VOL 71 APRIL 212 Table 2 Characteristics of biodiesel obtained at optimum conditions* Oils Specific Viscosity Flash Fire Cloud Pour gravity at C point point point point cp C C C C ASTM - 1.9-6. 13 - - - Standards for mm 2 /s biodiesel Sunflower.8 4.2 1 191-1 -4 Jatropha(A).8 4.6 1 191-3 -5 Used frying.864 4.26 162 176-6 -13 oil Groundnut.8 4.49 158 1-8 Mustard.8 4.2 173 195 2 Jatropha(B).866 4.78 156 172-2 -4 *Optimum conditions of reaction are: Methanol to oil molar ratio, 6:1; KOH conc., 1% by oil wt; reaction temp., C; and reaction time, min to hydrolysis of esters at longer time, causing more fatty acid to soap formation. Similar results are reported for other oils 2-4,14,18,19. Optimum Reaction Conditions and Characteristics of Biodiesel Optimum reaction conditions for biodiesel preparation using homogeneous catalyst in batch reactor were found as follows: reaction temp., C; reaction time, 1 h; catalyst (KOH) amount, 1% (by oil wt); and methanol to oil molar ratio, 6:1. Characteristics of biodiesel at optimized conditions are well within the prescribed limit of ASTM D6751 standards (Table 2). Other properties [Cetane number, unreacted glycerides (mono, di, triglycerides) and metal (Ca, Mg) content] need to be determined before biodiesel used as fuel in diesel engine. If proper reaction conditions are maintained, unreacted glycerides will be within limit of ASTM standard. Conclusions This study presents 6 vegetable oils, both from edible and non-edible sources, for preparation of biodiesel using KOH as catalyst and methanol as alcohol. Maximum biodiesel yield from all vegetable oils was obtained under following optimum conditions: reaction temp., C; reaction time, 1 h; catalyst amount, 1% (by oil wt); and methanol to oil molar ratio, 6:1. Alkaline transesterification is a fast reaction in homogeneous system, giving maximum conversion (-98%) in ½ h depending on raw material; beyond 1 h, reaction time had negative effect on yield of biodiesel due to reverse/backward reaction. If mechanical agitators are used, optimum conditions (temperature and reaction time) might get improved due to intense mixing, which is beneficial for commercial production. References 1 Khan A K, Research into biodiesel kinetics & catalyst development, MS Dissertation, The University of Queensland, Brisbane, Australia, 22. 2 Srivastava A & Prasad R, Triglycerides-based diesel fuels, Renewab Sustainable Energy Rev, 4 (2) 111-133. 3 Ma F & Hanna M A, Biodiesel production: a review1, Biores Technol, (1999) 1-15. 4 Sinha S, Agarwal A K & Garg S, Biodiesel development from rice bran oil: Transesterification process optimization and fuel characterization, Energy Convers Mgmt, 49 (28) 1248-1257. 5 Tiwari P, Kumar R & Garg S, Transesterification, Modeling and simulation of batch kinetics of non-edible vegetable oils for biodiesel production, in Annu AIChE Meet, San Francisco, 26. 6 Wang Y, Nie J, Zhao M, Ma S, Kuang L et al, Production of biodiesel from waste cooking oil via a two-step catalyzed process and molecular distillation, Energy Fuels, 24 (21) 214-218. 7 Zabeti M, Wan Daud W M A & Aroua M K, Activity of solid catalysts for biodiesel production: A review, Fuel Process Technol, (29) 7-777. 8 Knothe G, Designer biodiesel: Optimizing fatty ester composition to improve fuel properties, Energy Fuels, 22 (28) 1358-1364. 9 Allen C A W, Watts K C, Ackman R G & Pegg M J, Predicting the viscosity of biodiesel fuels from their fatty acid ester composition, Fuel, 78 (1999) 1319-1326. 1 Leung D Y C & Guo Y, Transesterification of neat and used frying oil: optimization for biodiesel production, Fuel Process Technol, 87 (26) 883-8. 11 Meng X, Chen G & Wang Y, Biodiesel production from waste cooking oil via alkali catalyst and its engine test, Fuel Process Technol, 89 (28) 851-857.

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