Glycerolysis can be a useful alternative for lowering free fatty acid content present in the sustainable feedstock of waste cooking oil. In the present work, the effect of reaction parameters such as molar ratio of oil to glycerol (1:1, 1:2 and 1:3), catalyst NaOH concentration (0.875, 1.3 and 1.75 %-w of oil) and mass ratio of oil to co-solvent hexane (2:1, 4:1, 8:1) have been investigated. The reaction parameters have a remarkable effect on the free fatty acid (in term of acid value) of waste cooking oil. The final acid value decreased with an increased in molar ratio of oil to glycerol from 1:1 to 1:2. A significant reduction in acid value was not observed with a further increase in molar ratio of oil to glycerol. It has been observed that the optimum catalyst concentration of 1.3% can be reduced acid value from 12.2 to 1 mg KOH/g oil in 20 min. The addition of hexane as co-solvent affected the reaction rate due to immiscibility of the oil and glycerol phases. However, a suitable amount of co-solvent must be added to achieve an optimum of acid value reduction

Adisalamun, .

Annisa, Yulia

Mahlinda, .

Meldasari, Yanti

Supardan, M. Dani

English

Proceedings of The Annual International Conference, Syiah Kuala University - Life Sciences & Engineering Chapter

Proceedings of The 5th Annuual International Conference Syiah Kuala University (AIC Unsyiah) 2015In conjunction with The 8th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015September 9-11, 2015, Banda Aceh, Indonesia38Glycerolysis for Lowering Free FattyAcid ofWaste Cooking Oil1*M. Dani Supardan, 1Adisalamun, 2Yanti Meldasari, 2Yulia Annisa, 3Mahlinda1Department of Chemical Engineering, Syiah Kuala University,Darussalam, Banda Aceh23111, Indonesia2Department of Agriculture Product Technology, Syiah Kuala University,Darussalam, BandaAceh 23111, Indonesia3Balai Riset dan Standardisasi Industri Banda Aceh, Indonesia*Coorresponding Author: m.dani.supardan@che.unsyiah.ac.idAbstractGlycerolysis can be a useful alternative for lowering free fatty acid contentpresent in the sustainable feedstock of waste cooking oil. In the presentwork, the effect of reaction parameters such as molar ratio of oil to glycerol(1:1, 1:2 and 1:3), catalyst NaOH concentration (0.875, 1.3 and 1.75 %-wof oil) and mass ratio of oil to co-solvent hexane (2:1, 4:1, 8:1) have beeninvestigated. The reaction parameters have a remarkable effect on the freefatty acid (in term of acid value) of waste cooking oil. The final acid valuedecreased with an increased in molar ratio of oil to glycerol from 1:1 to 1:2.A significant reduction in acid value was not observed with a further increasein molar ratio of oil to glycerol. It has been observed that the optimumcatalyst concentration of 1.3% can be reduced acid value from 12.2 to 1 mgKOH/g oil in 20 min. The addition of hexane as co-solvent affected thereaction rate due to immiscibility of the oil and glycerol phases. However, asuitable amount of co-solvent must be added to achieve an optimum of acidvalue reduction.Key words: acid value, free fatty acid, glycerolysis, waste cooking oilIntroductionThe glycerolysis process has the capability of converting the free fatty acid (FFA) back totheir respective glyceride molecule. In glycerolysis, the glycerol reacts with the FFA to formmonoglycerides, diglycerides and triglycerides (Anderson, 1962). It produces a low FFAfeedstock that can be further processed using homogeneous base transesterification. Theadvantage of this approach is that no alcohol is needed during the pre-treatment process.The process has the potential of utilizing glycerol, a by-product from transesterificationthereby lowering the cost of process. However, the drawbacks of this method are its hightemperature requirement, relatively slow reaction rate and being limited by equilibrium,having two liquid phases, where the solubility of glycerin is rather limited in triglycerides(Felizardo et al., 2011). This has limited the application of glycerolysis in pre-treatment ofFFA for production of more valuable product. Despite of its potentiality in lowering high FFA,glycerolysis process has been commonly used to produce monoglycerides and diglycerides,which are widely used as surfactants and emulsifiers in food, cosmetic, and pharmaceuticalproducts.The glycerolysis process can be carried out via enzymatic, alkaline and acid catalyzedreactions (Sonntag, 1982). Most of the existing literature on glycerolysis utilizes hightemperature and low pressure in the process. The literature also shows that the importantvariables that affect the glycerolysis reaction are reaction temperature, type and amount ofProceedings of The 5th Annuual International Conference Syiah Kuala University (AIC Unsyiah) 2015In conjunction with The 8th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015September 9-11, 2015, Banda Aceh, Indonesia39catalyst, molar ratio of glycerol to oil, the mixing intensity and the reaction time(Noureddini et al., 2004; Felizardo et al., 2011; Gole and Gogate, 2014; Cai et al., 2015).Recently, Kombe et al. (2013) reported the application of low temperature glycerolysis forpre-treatment of oil with high FFA. Based on optimisation study, the highest glycerolysisefficiency of 98.67% were found to be temperature of 65°C, reaction time of 73 minutesand glycerol to oil mass ratio of 2.24.In this study, the low temperature base catalyzed glycerolysis has been applied for loweringof high FFA in waste cooking oil via homogeneous base catalyst. The effect of reactionparameters such as molar ratio of oil to glycerol, catalyst NaOH concentration  and massratio of oil to co-solvent hexane have been investigated.Materials and methodsMaterialsWaste cooking oil was collected from restaurants around Banda Aceh, Indonesia. Prior tothe use in the actual experiments, oil was filtered to remove the traces of particles and mudin the oil. The initial acid value of the oil was observed to be 12.2 mg of KOH/g of oil.Glycerol used in the experiments was of technical grade and NaOH (99%) in pellet formwere of analytical grade. All the chemicals were used as received from the supplier. Distilledwater, freshly prepared in the laboratory, was used for the preparation of solutions ofrequired concentrations.GlycerolysisGlycerolysis reaction was carried out in a glass batch reactor equipped with IKA RW20mechanical digital stirrer. Waste cooking oil was heated and maintained at a given settemperature. A specified portion of NaOH catalyst was dissolved in glycerol before mixingwith oil at 600 rpm using IKA RW20 mechanical digital stirrer. Then, the reaction mixturewas mixed and heated for the desired duration. The reaction temperature was keptconstant at 65 oC for all the experimental runs. Samples were taken at specific interval oftime. The sample was cooled to room temperature before separation and then poured intoa separating funnel and allowed to form two layers. The heavier phase glycerol, dissolvedcatalyst and other minor components from the oil easily separated as a lower layer. Theacid value of the upper layer was measured to monitor the progress of the reaction.Method of analysisThe main objective of glycerolysis is to reduce the free fatty content in oil, which can bemonitored in terms of the acid value of oil. The acid–base titration technique was used todetermine the acid value of oil. A standard solution of 0.1 M of alcoholic potassiumhydroxide was prepared by dissolving KOH in ethanol. A sample of 1 g of oil was dissolvedin ethanol and heated for 5–10 min. The known quantity of sample was then titratedagainst potassium hydroxide using phenolphthalein as an indicator.Results and DiscussionEffect of molar ratio of oil to glycerolGlycerolysis of FFA is a reversible reaction (Moquin et al., 2005). The reaction scheme isshown in Fig. 1. From the reaction stoichiometry, it is observed that 1 mol of glycerol isrequired to complete the reaction. As consequence, glycerol is usually taken in excessamount with an objective of driving the reaction in the forward direction.To investigate the effect of excess glycerol on the progress of the reaction, various oil toglycerol molar ratios of 1:1, 1:2 and 1:3 have been selected at constant catalystconcentration of 1.75 %-w. The change in acid value with the reaction time at differentProceedings of The 5th Annuual International Conference Syiah Kuala University (AIC Unsyiah) 2015In conjunction with The 8th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015September 9-11, 2015, Banda Aceh, Indonesia40molar ratio has been given in Fig. 2. It has been observed that the final acid value of oildecreases with an increase in molar ratio from 1:1 to 1:2 i.e., when a higher molar ratiothan stoichiometrically required ratio is used.Figure 1. Reaction scheme for glycerolysis of free fatty acidFigure 2. Effect of oil to glycerol molar ratio on reaction progressIt has been observed that a molar ratio of 1:2 and reaction time of 30 min is sufficient toreduce the acid value from 12.2 to 0.7 mg of KOH/g. With a further increase in the molarratio from 1:2 to 1:3, significant reduction in acid value was not observed. Similar trendshave been reported in the literature for different systems. Acid value reduction ofacidulated soap-stocks was achieved from 80 to 7.8 mg of KOH/g for 1:4 of oil to glycerolmolar ratio and 200 min of reaction time (Felizardo et al, 2011). The acid value wasreduced from 12 to 1 mg of KOH/g for a molar ratio of 1:2 and a reaction time of 150 minfor the case of animal fat as sustainable feedstock (Gerpen et al., 2004). Meanwhile,Kombe et al. (2013) reported that a glycerolysis efficiency of 99.72% could be obtained inglycerolysis of crude jatropha oil at optimum conditions 73 minutes of raection time, 1:4 ofglycerol to oil molar ratio and 65°C of reaction temperature.Effect of catalyst concentrationGlycerolysis was also studied by changing the catalyst concentration over the loading of0.875 to 1.75 %-w for molar ratio of oil to glycerol of 1:1. Figure 3 shows the change in theacid value with reaction time at different catalyst concentrations. It has been observed thatthe trend result was similar in terms of decreased in acid value with increase in the reactiontime. The final acid value also decreased with an increase in the catalyst concentration from0.875 to 1.3 %-w though beyond this optimum catalyst concentration, the reduction in finalacid value was significant.Based on the experiments with varying catalyst concentrations, it can be concluded that theoptimum catalyst loading of 1.3 %-w is sufficient for reducing acid value from 12.2 to 1 mgProceedings of The 5th Annuual International Conference Syiah Kuala University (AIC Unsyiah) 2015In conjunction with The 8th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015September 9-11, 2015, Banda Aceh, Indonesia41of KOH/g in 20 min. The role of catalyst is to provide the active surface for enhancing therate of reaction. An excess amount of catalyst, however, decreased the rate of reaction.Also, an excess amount of catalyst increases the load on the separation steps and henceselecting the optimum catalyst loading is very important. Cai et al. (2015) reported theoptimum NaOH catalyst concentration was 0.5% for glycerolysis of WCO with acid value of124.9 mg KOH/g at 210 °C of reaction temperature and 4 h of reaction time.Figure 3. Effect of catalyst concentration on reaction progressThe catalyst requirement is dependent on many factors such as reaction conditions and theproperties of feedstock. Selection of optimum catalyst loading is crucial for reducing the rawmaterial cost as well as in deciding the utility requirement for catalyst separation and finalproduct purification.Effect of co-solventIn a glycerolysis system, the mass transfer between the two phases of oil and glycerolbecomes a significant factor that affects the reaction rate due to immiscibility of the oil andglycerol phases. Co-solvent of hexane could be added to enhance the miscibility of thephases and speed up the reaction rate (Qian et al., 2010; Supardan et al., 2015). Theeffect of co-solvent of hexane addition on the rate of glycerolysis has been studied byvarying the oil to co-solvent weight ratio. The molar ratio of oil to glycerol at 1:1 andcatalyst concentration of 0.875 %-w of oil were kept constant for studying the effect of co-solvent addition. The progress of reaction, monitored in terms of the change in the acidvalue, at different oil to co-solvent weight ratio has been shown in Fig. 4.It has been observed that acid value generally decreases from an initial value of 12.2 mgKOH/g with an increase in the time of reaction. The final value obtained at the end of timeof 180 min was found to be dependent on the oil to co-solvent weight ratio. The final acidvalue reduced with an increase in the oil to co-solvent weight ratio from 2:1 to 8:1.As shown in Fig. 4, the final acid values of oil to co-solvent weight ratio of 2:1 and 4:1 arelower compared to the system without cosolvents. Based on the experimental results, it canbe concluded that the addition of co-solvent favors the reaction, which can be attributed tobetter homogeneity of the reaction mixture. However, a suitable amount of hexane must beadded to achieve an optimum biodiesel yield. The final acid value further increased at oil toco-solvent weight ratio of 8:1. It might be due to a dilution effect of the excess of hexane.Excessive addition of hexane into the reaction system also could increase the operatingProceedings of The 5th Annuual International Conference Syiah Kuala University (AIC Unsyiah) 2015In conjunction with The 8th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015September 9-11, 2015, Banda Aceh, Indonesia42cost. At oil to co-solvent weight ratio of 2:1, the reaction rate is maximum and sufficient tolower the acid value below the desired value required for further processing and hence itcan be considered as the optimum oil to co-solvent weight ratio.Figure 4. Effect of oil to co-solvent weight ratio on reaction progressConclusionIt has been observed that the reaction parameters such as molar ratio of oil to glycerol,catalyst concentration and mass ratio of oil to co-solvent hexane have a remarkable effecton the acid value of waste cooking oil. Generally, acid value decreased with an increased inthe time of reaction Experimental result showed that the final acid value decreased with anincreased in molar ratio of oil to glycerol from 1:1 to 1:2, however, a further increase inmolar ratio of oil to glycerol from 1:2 to 1:3 was not provided a significant reduction in finalacid value of oil. The acid value was reduced from 12.2 to 0.7 in 10 min by using catalystconcentration of 1.3%. Meanwhile, a suitable amount of hexane should be added to achievean optimum of acid value reduction. The lowest final acid value was achieved at a massratio of oil to hexane of 8:1. The results showed that glycerolysis is a promisingpretreatment for lowering free fatty acid of waste cooking oil. The glycerolysis led to theproduction of an intermediate material with a low content of free fatty acid that can be usedfor further processing such as transesterification reaction for the production of biodiesel .AcknowledgementThis work was supported by the Directorate Higher Education of the Republic of Indonesiaunder the project “Hibah MP3EI”.ReferencesAnderson, A.J.C. (1962). Refining of Oils and Fats for Edible Purposes. 2nd Edition,Pergamon Press, London, pp. 92-10Felizardo, P., Machado, J., Vergueiro, D., Correia, M.J.N., Gomes, J.P., Bordado, J.M.(2011). Study on the glycerolysis reaction of high free fatty acid oils for use asbiodiesel feedstock. Fuel Processing Technology 92:1225–1229Gerpen, J.V., Shanks, B., Pruszko, R., Clements, D. Knothe, G. Biodiesel ProductionTechnology, National Renewable Energy Laboratory, Colorado, August 2002–January2004, pp. 52–55.Proceedings of The 5th Annuual International Conference Syiah Kuala University (AIC Unsyiah) 2015In conjunction with The 8th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015September 9-11, 2015, Banda Aceh, Indonesia43Cai, Z.Z., Wang, Y., Teng, Y.L., Chong, K.M., Wang, J.W., Zhang, J.W., Yang, D.P. (2015).A two-step biodiesel production process from waste cooking oil via recycling crudeglycerol esterification catalyzed by alkali catalyst, Fuel Processing Technology,137:186-193Gole, V.L., Gogate, P.R. (2014). Intensification of glycerolysis reaction of higher free fattyacid containing sustainable feedstock using microwave irradiation. Fuel ProcessingTechnology 118:110–116Kombe, G.G., Temu, A.K., Rajabu, H.M., Mrema, G.D., Lee, K.T. (2013). Low TemperatureGlycerolysis as a High FFA Pre-Treatment Method for Biodiesel Production, Advancesin Chemical Engineering and Science 3:248-254Moquin, P.H.L., Temelli, F., King, J.W., Palcic, M.M. (2005). Kinetic Modeling of theGlycerolysis Reaction for Soybean Oils in Supercritical Carbon Dioxide Media, JAOCS,82:613-617Noureddini, H., Harkey, D., Gutsman, M.A. (2004). Continuous Process for the Glycerolysisof Soybean Oil. Journal of the American Oil Chemists’ Society, 81:203-207.Qian, J., Shi, H., Yun, Z. (2010). Preparation of biodiesel from Jatropha curcas L. oilproduced by two-phase solvent extraction. Bioresource Technology, 101:7025-7031Sonntag, N.O.V. (1982). Glycerolysis of Fats and Methyl Esters—Status, Review andCritique. Journal of the American Oil Chemists’ Society, 59:795-802.Supardan, M.D., Fahrizal, Moulana, R., Safrida, D., Satriana, Mustapha, W.A.W. (2015).Optimization of Process Parameters Condition for Biodiesel Production by ReactiveExtraction of Jatropha Seeds. Journal of Engineering Science and Technology,accepted

Glycerolysis for Lowering Free FattyAcid of Waste Cooking Oil

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Glycerolysis for Lowering Free FattyAcid of Waste Cooking Oil

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Proceedings of The Annual International Conference, Syiah Kuala University - Life Sciences & Engineering Chapter