Alvim-Ferraz MCM

Fonseca e Almeida

J. M. Dias

Portuguese

Open Repository of the University of Porto

One Step and Two-Step Synthesis of FAMEs Using Waste Raw Materials

Repositório Aberto da Universidade do Porto

ONE STEP AND TWO-STEP SYNTHESIS OF FAMES USING WASTE RAW MATERIALS Joana M. Dias a*, Maria C. M. Alvim-Ferraz a, and Manuel F. Almeida b LEPAE, Faculdade de Engenharia, Universidade do Porto, R. Dr. Roberto Frias, 4200-465, Porto, Portugal a Departamento de Engenharia Química, b Departamento de Engenharia Metalúrgica e de Materiais  ABSTRACT The production of fatty acid methyl esters (FAMEs), an environmentally friendly diesel substitute, might be conducted using vegetable oils or animal fats as raw materials. At present, biodiesel production is made using virgin vegetable oils as raw materials; however, their high price, which sometimes approaches t at of the fossil diesel fuel, is becoming a huge problem. Additionally, the use of food oils for FAMEs production is controversial; reason why studying alternative raw materials is of major importance. The use of waste raw materials for bioenergy production is very appealing; however, due to the common characteristics of such materials, research is required to enable its application in a larger scale. Aiming the FAMEs production from waste animal fat at a larger scale, the usually high content of free fatty cids of the fats is a limiting factor, because fatty acids react with the catalyst during alkali transesterification, causing the formation of soaps. Because alkali transesterificaton is still considered the best option from an economic point of view (acceptable temperatures and atmospheric pressure are used), studying alternatives which might be easily adopted in current production process is very important. In the present study, the production of FAMEs from acid waste lard was studied considering a one-step alkali transesterification reaction and a two step reaction consisting of an acid esterification followed by an lkali transesterification. The two step synthesis was optimized considering the amount f acid catalyst used and the final product quality was evaluated. The one-step transesterification was ineffective du to the high acidity of the raw material. The proposed two-step reaction was effectiv  to enable acid wastes as single raw materials for biodiesel production with acceptable quality; however, low yields were obtained (65 wt%). The reaction conditions of the acid esterification reaction were selected being 65 ºC, 2.0 wt% H2SO4 and 5 h, which allowed obtaining a product with a viscosity of 4.81 mm2 s-1 and a purity of 99.6 wt%. As an alternative to lower the waste lard acidity and enable the one step synthesis, a mixture containing 25% waste lard and 75% soybean oil was used. Alkali transesterification of the mixture resulted in a product with a purity of 99.8 wt% and a yield of 77.8 wt%, showing that, despite the small fat incorporation used, blending might be an interesting alternative to recycle such wastes. Also, because in addition to using conventional andrelatively economical processes, some biodiesel properties depending on the raw material composition (such as the iodine value) might even be improved.                                                 * Corresponding author. Tel.: +351 22 5081976; Fax: +351 22 5081449. E-mail address: joana.dias@fe.up.pt. ONE STEP AND TWO-STEP SYNTHESIS OF FAMEs USINGWASTE RAW MATERIALSJoana M. Dias a, Maria C. M. Alvim-Ferraz a, Manuel F. Almeida bLEPAE, Faculdade de Engenharia, Universidade do Porto, R. Dr. Roberto Frias, 4200-465, Porto, Portugala Departamento de Engenharia Química,b Departamento de Engenharia Metalúrgica e de MateriaisLEPAE, Faculdade de Engenharia, Universidade do Porto, R. Dr. Roberto Frias, 4200-465, Porto, Portugala Departamento de Engenharia Química, b Departamento de Engenharia Metalúrgica e de Materiais,Tel. 00 351 225 081 976, E-mail. joana.dias@fe.up.ptEnabling waste animal fats instead of virgin vegetable oils for Biodiesel (Fatty acid methyl esters, FAMEs) synthesis;Evaluating FAMEs synthesis considering the use of a one-step alkali transesterification reaction and a two step reactionconsisting of an acid esterification followed by an alkali transesterification;Optimizing first step reaction considering the amount of catalyst used and quality of the final product;Evaluating the use of raw material mixtures to enable one-step FAMEs synthesis.OBJECTIVESTable 1: Methyl ester profile obtained using waste lard alone and a 75 wt % soybean oil and 25 wt % waste lard raw materials mixturea Calculat d from the methyl est r compositionRaw materials commonly used for FAMEs synthesis: virgin vegetable oilsAdvantages: perform well during alkali transesterification (Reaction B);Disadvantages: used for food purposes and expensive.Alternative raw materials for FAMEs synthesis: waste raw materialsThree major advantages: (i) do not compete with the food market; (ii)recycles waste; and (iii) reduces production costs;Disadvantages: High acid values present in waste fats (more abundant rawmaterial) does not allow alkali transesterification.Because alkali transesterification is still the most economically attractive FAMEssynthesis alternative, there is a need to enhance pretreatment of waste rawmaterials to enable further transesterificationSolutions: fat saponification / esterification (reaction A)Saponification: causes the loss of raw materialEsterification: uses all the raw materialINTRODUCTIONMATERIALS AND METHODS?C)A)901008-1)3540Fig. 1. Laboratory equipment. A) Experimental setup; B) SeparatoryFunnel showing biodiesel and glycerine after reaction; C) Gas Chromatograph; D) Karl Fischer titrator.Pork wastes were collected at a local butchery; fat was extracted by heating, the meltedproduct was separated from the solid residue, and after filtered at reduced pressure.Raw material characterization: i) composition by GC (Fig. 1C) (EN 14103 and NP ENISO 5508); ii) acid value by titration (NP EN ISO 660);Biodiesel characterization: : i) acid value by titration (EN 14104); ii) kinematicviscosity using capillary viscometers (ISO 3104) iii) water content by Karl Fischertitration (Fig. 1 D) (NP EN ISO 12937); iv) ester and linolenic acid methyl estercontents by GC (EN 14103); and, v) iodine value (annex B, EN 14214).Synthesis of biodiesel (Figure 1 A): Esterification + TransesterificationEsterification conditions (Reaction A): 120.0 g of the dehydrated lard; 55 ºC;6:1 methanol to fat molar ratio, 5h, H2SO4 (1.0 - 4.0% of lard weight);Transesterification conditions (Reaction B): esterified product; 65 ºC; 6:1 methanolto fat molar ratio, 1h, NaOH (1% of the esterified product weight).Products were after decanted (Figure 1B), excess methanol was recovered and catalystwas removed. Final product was dehydrated.D)+   3    CH3OH +  CatalystR1 – COO – CH3R2 – COO – CH3R3 – COO – CH3CH – OHCH2 – OHCH2 –OHCH – OOC – R2CH2 – OOC – R1CH2 – OOC – R3+   CH3OHCatalystR1 – COOH R1 – COO – CH3 H2OReaction A. Esterification of free fatty acids.Reaction B. Transesterification of oils and fats.B)Research is required to optimize its applicationin a larger scaleAKNOWLEDGMENTSProjecto QREN 3491, FatValue - Valorização de Subprodutos de CarnesJ. M. Dias thanks the FCT for the fellowship SFRD/BD/22293/2005RESULTS AND DISCUSSION Purity (% wt)Catalyst amount (wt %)0 1 2 3 4 54050607080Catalyst amount (wt %)0 1 2 3 4 5246ν(mm2s-2)Time (h)1.0 2.0 3.0 4.0 5.0Acid value (mg KOH g-10510152025301%2%3%4%B)A)Parameter Results EN 14214Water content (mean, wt %) 0.040 <0.05Acid value (mg KOH g-1)1 wt % H2SO4Other conditions (mean)1.130.142<0.50Kinematic viscosity at 40 ºC (mm2s-1)4.64 - 7.73 3.50 - 5.00Methyl ester content (wt %) 69.6 – 95.0 >96.5Linolenic methyl ester content (mean, wt %)1.4 <12.0Iodine value (mean, g I2/100g) 77 <120Table 1: Quality parameters of biodiesel from waste lard and the respective requirements according to EN 14214Fig. 2. Evolution of waste lard acid value during the esterification reaction.Fig. 4. GC chromatogram of waste lard FAMEs.Fig. 3. Viscosity (A) and Purity (B) of FAMEs using different catalyst amounts(6:1 molar ratio of methanol to lard, 55 ºC, 5h (dashed lines indicate minimum and maximum requirements according to EN 14214 for viscosity and minimum for purity)A waste lard/soybean oil (25/75 (wt%)) was studied as alternative raw material.Fat yield was 70 wt%; acid value was 14.57 mg KOH g-1 for the waste lard and 0.21 mgKOH g-1 for the soybean oil. Basic transesterification of the acid lard was ineffective.First reaction step: acid value tended to stabilise after 1h (Fig. 2) indicating reactioncompleteness within that period.Optimization of two-step synthesis considering product quality: Acid value was notwithin limit (Table 1) at the lowest catalyst concentration (less effectiveesterification); viscosity and purity were not always fulfilled; other evaluatedparameters were in agreement with EN 14214.For the same raw material, lower viscosity indicates insufficient methyl esterconversion; catalyst amount needed to be higher than 3wt% (Figure 3A) obtain aviscosity in agreement with EN 14214.Purity determination method uses methyl heptadecanoate (C17:0) as internalstandard; however, C17:0 might exist in animal fats affecting results. Analysis showed0.6 wt% of C17:0 (Fig.4) and further corrections were performed. Catalyst amountstrongly influenced biodiesel purity, only close to minimum using 3 wt% catalyst (Fig.3B); therefore, lower viscosities were indicating effective conversions.Two-step synthesis enabled the use of acid wastes for biodiesel production; 65 wt%yield was obtained, the same when using a waste lard/soybean oil mixture.Alkali transesterification of the mixture: yield of 77.8 wt%; purity of 99.8 wt%.The one-step transesterification of acid waste lard was ineffective due to the high acidity of the raw material.The proposed two-step synthesis enabled acid wastes as single raw materials for biodiesel production; however with low yields (65 wt%).Regarding the first step synthesis optimization, the best H2SO4 concentration was found to be 3 wt%, which allowed obtaining a product with a viscosity of4.72 mm2 s-1 and a purity of 95.0 wt%.Despite the small fat incorporation used, blending was found to be an interesting alternative to recycle such wastes enabling the use of one-step synthesis.CONCLUSIONS

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One Step and Two-Step Synthesis of FAMEs Using Waste Raw Materials

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