Simultaneously Trans-Esterification and Amidification of Coconut Oil Into Cocamide-Dea Using Heterogeneous Catalyst

www.arpnjournals.com

SIMULTANEOUSLY TRANS-ESTERIFICATION AND AMIDIFICATION OF COCONUT OIL INTO COCAMIDE-DEA USING HETEROGENEOUS CATALYST

Zuhrina Masyithah, Lina Simanjuntak and Sicilya Ruth Yudhika Department of Chemical Engineering, Faculty of Engineering, Universitas Sumatera Utara Jalan Almamater, Medan, Indonesia E-Mail: [email protected]

ABSTRACT Cocamide-DEA were synthesized by trans-esterification of coconut oil to fatty acid methyl ester (FAME) followed by amidification of FAME with diethanolamine (DEA) using CaO as a heterogeneous catalyst. The triglycerides in coconut oil were trans-esterified with methanol catalyzed by potassium hydroxide in the first step of the reaction. The trans-esterification reaction occurred in 3 h and GC spectra confirmed that FAME obtained was 84.08%. Furthermore, the amidification of a reaction of FAME was investigated by using Box Behnken Design and optimized using Response Surface Methodology (RSM). Several effective parameters were evaluated in term of substrate mole ratio (4/1-6/1 DEA/FAME), the solvent ratio (2/1-4/1 v/wFAME), and reaction time (3-5 h) on the percentage of fatty acid conversion to Cocamide-DEA. The results showed that the effect of each variable, the effect of the quadratic variable and the effect of interaction between variables were significant on the yield. In contrast, the quadratic effect of solvent ratio has a negative effect, although it is not significant for cocamide DEA acquisition. The optimal condition from RSM obtained was substrate mole ratio of 4/1 (DEA/FAME), the solvent ratio of 3/1 (v/wFAME) and reaction time of 4 h. Under the above condition, the maximum fatty acid conversion of 84.65% was obtained.

Keywords: coconut oil, fatty acid methyl ester, diethanolamine, box behnken design, cocamide DEA.

INTRODUCTION amidification to fatty acid amide compounds. The most Coconut oil has been received increasing common reactions to produce fatty acid amides are by attention in recent years due to its health effect potential reacting carboxylic acids and amines using metal catalysts, and is the most stable and slowly oxidized vegetable oil, biocatalysts and microwave radiation [11]. Fatty acid so it is widely used in the food, pharmaceutical, cosmetic amides are one of the most functional organic molecules and hair oil industries [1]. Coconut oil is a triglyceride because they contain proteins and peptides which are which consists of 92% saturated fatty acids, most of them important polyamide groups [7]. Fatty acids amides are (about 70%) are medium chain fatty acids (MCFA), 6% very widely applied in industries such as natural products, are monounsaturated fatty acids and 2% polyunsaturated cleaning products, pharmaceutical products, agricultural fatty acids [2, 3]. The biggest content of coconut oil is chemicals, polymer materials, and lubricants [12, 13, 14]. lauric acid [4]. Lauric acid can be used as raw material for The development of economic and making surfactants, so applying coconut oil needs to be environmentally friendly amide synthesis continues to be developed because of their low cost and renewable. carried out. Heterogeneous catalysts can be a suitable One of the surfactants derived from coconut oil is choice because they meet the two criteria above and are cocamide DEA. Cocamide DEA is a surfactant obtained easily separated and recyclable [15]. Heterogeneous from the reaction between coconut oil and diethanolamine. catalysts are often more stable even though the reaction The surfactant from diethanolamine is mainly found in mechanism using heterogeneous catalysts is difficult to cleaning agents such as soaps and shampoo, hair dyes and learn and often unknown [16]. Calcium oxide (CaO) bath oils [5,6]. This material has the ability to increase which is non-toxic, inexpensive, and easily obtainable foaming ability, stabilize foam, increase solution viscosity, makes it the right choice to be used as a heterogeneous and is effective in cleaning without drying effects due to catalyst in the oxidation reaction [7]. Moreover, corrosion natural fatty acids from its vegetable oils [7, 8]. of equipment and environment contaminant are drawbacks Cocamide DEA synthesis starts from the reaction associated with the use of homogeneous catalyst [17]. of trans-esterification of coconut oil. Trans-esterification On the basis of the theory that has been reactions take place between triglycerides and alcohol, described, it is necessary to do research on the wherein the short chain of alcohol is converted to glycerol manufacture of nonionic surfactant cocamide DEA from from each unit of triglycerides from oil [9]. This process coconut oil and diethanolamine through amidification can use catalysts of acids, bases, and enzymes. For low reaction using CaO to obtain important information about free fatty acid content such as coconut oil, the use of an the effect of the interaction of the reaction variables on the alkaline catalyst for the trans-esterification process is surfactant synthesis produced. preferred, because of the lack of soap formation reaction so that separation and purification will be easier [10]. The methyl ester is produced by trans- esterification of coconut oil with alcohol and then is

www.arpnjournals.com

MATERIALS AND METHODS Table-2. The results of prediction on the regression coefficients. Materials An analytical grade of diethanolamine Term Coef. P (C4H11NO2), calcium oxide (CaO), isopropanol, Methanol Constant (Y) 84.6533 0.000 (CH3OH) and sodium hydroxide (NaOH) were obtained from Merck (Darmstadt, Germany). The coconut oil used Substrate mole ratio (X1) -4.3637 0.003 ® as commercial oil that is Braco . All others chemicals Solvent ratio (X2) -0.5400 0.525 were analytical grade and from Merck (Darmstadt, Reaction time (X ) -2.3462 0.031 Germany). 3 Experimental Design (X1)*(X1) -3.5204 0.029 In this study, the Box Behnken design was used (X2)*(X2) -2.6729 0.070 with three factors: the substrate mole ratio, the solvent ratio and the reaction time. Each factor was coded at three (X3)*(X3) -5.0004 0.008 levels: -1, 0 and +1. The range and level of variables in (X1)*(X2) -6.5950 0.002 RSM studies are given in Table-1. To carry out the (X )*(X ) -4.2575 0.013 experiments, one dependent parameter was measured as a 1 3 response [18]. (X2)*(X3) -3.4100 0.029 The regression equation after the analysis of R-Sq = total squared = 96.21% variance (ANOVA) gave the conversion of FAME as a function of substrate mole ratio (X1), a solvent ratio (X2) R-Sq(adj) = squares due to treatment = 89.40% and reaction time (X3). Table 2 shows the results of the Box Behnken experiments for studying the effect of three EXPERIMENTAL APPROACH independent variables along with the predicted mean and observed responses. Base-catalyzed trans-esterification The experimental approach was based on the Table-1. The independent variables and levels research by Venkateswarulu et al., as follows [19]. The investigated with the experimental values. coconut oil is placed in the reaction vessel and heated to achieve the temperature of 60oC. The initial solution was Coded Variables prepared by adding 1% of NaOH in 6/1 molar of methanol Test Substrate Solvent Conver- (coconut oil/methanol). This solution was added to Reaction Run mole ratio, sion, pretreated oil and stirred at 60oC for 60 min. After time, X3 ratio, X1 X2 Y (%) completion of the reaction, the mixture was placed in a 1 -1 -1 0 77.83 separating funnel. Upon the decantation, two phases were performed; the upper layer was methyl ester and was 2 1 -1 0 79.54 separated from the lower glycerol layer. The methyl ester 3 -1 1 0 90.57 was washed 3-5 times with ionized water to remove soap and excess NaOH. Finally, the product was dried over 4 1 1 0 65.90 Na2SO4 and the yield was calculated using GC. Often 5 -1 0 -1 77.85 some excess methanol was present in the reaction 6 1 0 -1 80.39 evaporator.

7 -1 0 1 80.39 CaO-catalyzed amidification 8 1 0 1 65.90 FAME and DEA at various of substrate mole ratios (4/1-6/1 DEA/FAME) were mixed according to the 9 0 -1 -1 76.13 experimental design in 250 mL vials. The experiments 10 0 1 -1 81.24 were performed in isopropanol at the ratio of isopropanol 11 0 -1 1 79.54 to FAME 2/1-4/1 (v/wFAME) and catalyst concentration of 4% (w/wFAME). The reaction mixture was shaken at 12 0 1 1 71.01 atmospheric pressure at 300 rpm, 70oC during 3-5 h. It 13 0 0 0 82.95 was removed by filtration and the resulting white solid was washed with acetone and dried at 70oC in a Rotary 14 0 0 0 84.65 Evaporator. 15 0 0 0 86.36 RESULTS AND DISCUSSIONS The study begins by observing the effect of one single variable on the response, FAME conversion. Observed three main variables on amidation, namely the substrate mole ratio, solvent ratio and reaction time.

www.arpnjournals.com

Effect of substrate mole ratio Observation of the effect of the substrate mole 1 h 2 h 3 h 4 h 5 h ratio to FAME conversion is shown in Figure-1. In the 100 substrate mole ratio varies from 2/1 to 6/1 with a fixed reaction time of 1 hour it appears that the conversion of 90 methyl esters to cocamide DEA tends to increase along 80 with the increase in the substrate mole ratio to certain 70 limits. The best FAME conversion was obtained at 6:1 substrate mole substrate and 1 hour reaction time of 60

89.96%. Conversion (%) 50 The importance of diethanolamine in large 40 quantities is due to the formation of six ring structures and 2/1 3/1 4/1 5/1 6/1 the importance of additional molecules from the amine so so it needs to be used at least two equivalents of Substrate Mole Ratio (DEA/FAME) diethanolamine to achieve high amide yields [7]. Figure-2. The effect of substrate mole ratio to FAME 100 conversion.

95 2/1 (DEA/FAME) 3/1 (DEA/FAME) 90 4/1 (DEA/FAME) 5/1 (DEA/FAME) 85 6/1 (DEA/FAME) 80 Conversion (%)Conversion 100 75 90 1/1 2/1 3/1 4/1 80 Solvent Ratio (v/wFAME) 70 60

50 Figure-1. The effect of solvent ratio to FAME conversion.

Conversion (%) 40 1 2 3 4 5 Effect of solvent ratio Reaction Time (h) Observation of the best types of solvents needed for the synthesis of cocamide DEA was carried out on the substrate mole ratio of 6/1 (DEA/FAME), 5% of catalyst Figure-3. The effect of reaction time on the conversion of concentration (w/wFAME), 3 hours of reaction time, 200 FAME. rpm of stirring speed and 80oC of temperature. The range of solvent ratio in this study is 1/1 - 4/1 (v/wFAME). The use of a 5% CaO catalyst and an optimal The results of determining the appropriate solvent temperature of 80oC as a fixed variable can also accelerate ratio are shown in Figure-2 where it is seen that the the reaction time. The temperature selection in this study highest FAME conversion was obtained at 2/1 solvent is based on the boiling point of isopropanol of 82.5oC so ratio of 90.57%. that it will optimize the work of the solvent. And CaO The use of the right solvent ratio can increase the catalyst is also a heterogeneous catalyst suitable for use in homogeneity of the substrate [13]. The amount of solvent various types of reactions and is often used in trans- may not completely dissolve the reactants and products. esterification reactions of triglycerides [7]. Other than that a large amount of solvent can dilute the reactants and catalysts so that it reduces the work of the Optimization process catalyst [20]. Based on the description above, a solvent The purpose of optimization is to find one or ratio of 2/1 (v/wFAME) is chosen for further research several acceptable solutions to critical values of one or because it provides optimum results. more of the objective functions. Optimization methods are important in practice, especially in engineering design, Effect of reaction time experimental test and trading decisions [21, 22]. The Box Observation of the effect of reaction time on the Behnken design enables the identification of the variables conversion of FAME is shown in Figure-3. Observations that play a significant role in cocamide DEA synthesis. were made at reaction time ranging from 1 hour to 5 Three variables were arranged for the optimization of the hours. It can be seen from the observation that the process. The independent variables, experimental range, conversion of methyl ester to cocamide DEA shows the and levels investigated in this study are given in Table 1. best results (89.96%) in a 1 hour reaction time with the substrate mole ratio of 6/1 (DEA/FAME).

www.arpnjournals.com

Model fitting and analysis of variance 4.0 Before conducting a mutual interaction study between the three observed variables, an analysis of variance and compilation of models that represented the – 3.5 – relationship of the three variables to the response was – carried out. The results of prediction on the regression – – coefficients summarized in Table-2 showed a coefficient 2 of determination R of 9.621, which means that the model 3.0 explains 96.21% of the variability in the data. The experimental results of the Box Behnken design were fitted with a second-order polynomial function for estimation of the conversion of FAME: (v/wFAME) Ratio Solvent 2.5

2 2 Y= -4.364X1 - 2.346X3 - 3.52X1 - 5X3 - 6.59X1X2 - 4.257X1X3 - 3.41X2X3 (1) 2.0 4.0 4.5 5.0 5.5 6.0 where, Y = FAME conversion (%) ; X1 = substrate mole Substrate Mole Ratio (DEA/FAME) ratio (DEA/FAME) ; X2= solvent ratio (v/wFAME) and Conversion (%) X3 = reaction time (h). The analysis of variance data in < 68 Table 2 is an adequate representation of the actual 68– 72 relationship between the response and significant variables 72– 76 (<0.005) and a satisfactory coefficient of determination 76– 80 2 80– 84 (R = 0.9621). Furthermore, it was found that the substrate 84– 88 mol ratio, ratio solvent, and temperature are more highly > 88 important for increase conversion. Strong interaction even Hold Values Time (h) 4 though less significant is between the substrate mole ratio and reaction time. Figure-4. Response contour plot of the effect of substrate Mutual effect of substrate mole ratio and solvent ratio mole ratio and solvent ratio. The mutual interaction between substrate mole ratio and solvent ratio appears to be highly significant as 5.0 indicated by the probability value of the interaction term is 0.002. The interpretation of the relevant data is in line with the contour plot in Figure-4. Increasing the amount of – 4.5 – amine causes an increase in the percentage of – amidification. A decrease in the percentage of conversion can be observed at higher DEA to FAME molar ratios. This indicates that DEA is a terminal inhibitor of CaO and 4.0 its influence can increase in a high solvent ratio due to the increase of substrate solubility. At a small substrate ratio, (h)Time where the excess fatty acid substrate is used, the amine will be esterified to amine esters which will reduce the 3.5 conversion of amines to amides.

3.0 4.0 4.5 5.0 5.5 6.0 Substrate Mole Ratio (DEA/FAME)

Conversion (%) < 70 70– 75 75– 80 80– 85 > 85

Hold Values Solvent Ratio (v/wFAME) 3

Figure-5. Response contour plot of the effect of reaction time and substrate mole ratio.

www.arpnjournals.com

Amine ester yield can be reduced by using high amine C=O for unsaturated esters is at wave number 1800-1700 -1 -1 concentrations in the reaction mixture [6]. However, in cm , vibration -CH3 at wave number 1446 cm and this condition, the excess amine which is not easily vibration of O-CH3 which shows biodiesel group at wave dissolved will inhibit the mass transfer of the system so number 1196 cm-1. C-O vibration for saturated esters is in that it will reduce the gain. Besides that, the use of excess the wave number 1030.98 cm-1 - 1240.08 cm-1 [24]. amine will increase the cost of the surfactant produced and 5.0 will complicate the purification of the product [8].

Mutual effect of reaction time and substrate mole ratio – 4.5 – Response contour plot in Figure-5 states the – effect of reaction time and substrate mole ratio on – o – cocamide synthesis at 70 C, 300 rpm, 4% catalyst – concentration and solvent ratio of 3/1 (v/wFAME). A high 4.0

percentage of FAME conversion (85%) can be achieved (h)Time by employing a wide range of reaction time from 3 to 5 hours. In this graph also shows the tendency of the conversion to decrease after a reaction time of 4.5 hours 3.5 and a substrate ratio of more than 5/1 (DEA/FAME). The optimum reaction time is obtained at the center of the ellipse, which is 4 hours and the mole ratio of the substrate 3.0 4/1-5/1 (DEA/FAME). 2.0 2.5 3.0 3.5 4.0 Prolonged reaction time can cause side reactions Solvent Ratio (v/wFAME) namely saponification of methyl esters and also the trans- Conversion esterification reaction of methyl esters with ethanolamine (%) < 72 [23]. Based on this theory, the time above 5 hours is likely 72– 74 to cause side reactions and reduce the yield of amides 74– 76 produced. 76– 78 78– 80 Mutual effect of reaction time and solvent ratio 80– 82 Figure-6 depicts the contour plot regarding the 82– 84 effects of reaction time and solvent ratio and their > 84 interactions on the synthesis of cocamide DEA at 5/1 Hold Values o Substrate Mole Ratio (DEA/FAME) 5 substrate mole ratio, 70 C temperature, 4% catalyst concentration and 300 rpm stirring speed. The maximum Figure-6. Response contour plot of the effect of reaction predicted conversion is located on the contour surface in time and solvent ratio. the smallest ellipse at 3.5 to 4 hours and the solvent ratio is

3/1 (v/wFAME). The use of the solvent ratio aims to dissolve the sample without reacting thus increasing the homogeneity of the reaction [17]. Alkyl ethanolamide and monoethanolamine surfactants are more soluble in polar alcohol solvents than nonpolar solvents. Alcohol is also a good solvent to dissolve between ethanolamine and ethanolamide products [14]. Based on this theory, the selection of the isopropanol solvent is considered appropriate. The amount of a small solvent does not completely dissolve the product and reactants. A large amount of solvent will dilute the reactant and reduce the Figure-7. Cocamide DEA spectrum result. catalyst work efficiency [20]. Based on the description above, the solvent ratio of 3/1 (v/wFAME) shows From the results of the FT-IR sample spectrum optimum results and is in accordance with the theory. test, showing the peak absorption in the wave area 1740.97 cm-1 shows the presence of groups C=O and 1113.49 cm-1, Identification of cocamide DEA 1167.76 cm-1, 1196.23 cm-1 indicating the presence of CO According to Silverstein et al., at the peak of group in this wave number region which shows the sample absorption in asymmetric and symmetric wave regions contains saturated and unsaturated ester groups, absorption -1 -1 -1 -1 2925 cm and 2855 cm showed the presence of groups of peaks of 1436 cm for groups -CH3, and 1196.23 cm for methylene compounds [24]. From the results of the FT-IR O-CH3 groups. Furthermore, the ester group will be sample spectrum test in Figure-7, it shows the peak converted to amide in further research on the manufacture absorption in the area of 2922.60 cm-1 and 2851.15 cm-1 of cocamide diethanolamine. indicates the presence of a methylene group. Vibration

www.arpnjournals.com

CONCLUSIONS [9] Azduwin K., Sahardi N. S., Ridzuan M. J .M. and Based Modeling and optimization of the Ahmad A.A. 2016. Transesterification of waste amidification of FAME from coconut oil with DEA using fryning oil (WFO) using waste chicken bone as a CaO catalyst were successfully performed by Box catalyst. J. Eng. App. Sci. 11: 2508-2513. Behnken Design and Response Surface Methodology. In comparison with the one factor at a time design, Box [10] Lin H. C. and Tan C. S. 2014. Continuous Behnken with RSM is more efficient. The R2 (0.9621) shows a high correlation between predicted and transesterification of coconut oil with pressurized experimental values. The obtainable model can be useful methanol in the presence of a heterogeneous catalyst. to design industrial-scale reactors for the synthesis of J. Taiwan Inst. Chem. Eng. 45: 495-503. cocamide DEA. [11] Tinnis F., Lunberg H. and Adolfsson H. 2012. Direct ACKNOWLEDGEMENTS catalytic formation of primary and tertiary amides This research was supported by Universitas from non-activated carboxlic acids, employing Sumatera Utara (USU) through research grant No. carbamates as amine Source. Adv. Synth. Catal. 354: 2590/UN5.1.R/PPM/USU/2018. 1-7.

REFERENCES

[12] Allen C., Liana A., Chhatwal R. and William J. M. J. [1] Moigradean D., Poiana M. A. and Gogoasa I. 2012. 2012. Direct amide formation from unactivated Quality characteristics and oxidative stability of carboxylic acids and amines. Chem. Commun. 48: coconut oil during storage. J. Agroaliment. Processes 666-668. Technol. 18: 272-276. [13] Masyithah Z., Ashari M., Annisa N., Erwin, Ginting [2] Khan M. S., Lari Q. H. and Khan M. A. 2016. A. 2018. Synthesis of palmitoyl-ethanolamide from Physico chemical and pharmacological prospective of palmitic acid and monoethanolamine: analysis of roghan-e-narjeel (coconut oil). Int. J. Pharm. Sci. Res. variance and surfactant characteristics. ARPN J. Eng. 7: 1286-1291. App. Sci. 13: 9352-9358

[3] Masyithah Z. 2017. Parametric study in production of [14] Wang X., Han Z., Chen Y., Jin Q. and Wang X. 2016. virgin coconut oil by fermentation method. Orient J. Scalable synthesis of oleoyl ethanolamide by Chem. 33: 3069-3076 chemical amidation in a mixed solvent. J. Am. Oil Chem. Soc. 93: 125-131. [4] Boemeke L., Marcadenti A., Busnello F. M. and Gottschall C.B.A. 2015. Effect of coconut oil on [15] Natthapon S. and Krit S. 2014. Optimization of human health. Open J. Endocr. Metab. Dis. 5: 84-87. methyl ester production from palm fatty acid distillate using single step esterification: a response surface [5] Vala G. S. and Kapadiya P. K. 2014. Medicinal methodology approach. ARPN J. Eng. App. Sci. 10: benefits of coconut oil. Int. J. Life Sci. Biotechnol. 7075-7079. Pharma Res. 2:124-126. [16] Lunberg H., Tinnis F. and Adolfsson H. 2012. Direct [6] Masyithah Z. and Herawan T. 2017. Optimization of amide of non-activated carboxylic acids and amines enzymatic synthesis of oleoyl-diethanolamide in catalysed by zirconium (IV) chloride. Chem. Eur. J. solvent-free system. J. Pure. App. Microbiol. 11: 18: 3822-3826. 1327-1336. [17] Al-Mulla E. A. J., Wan Yunus W. M. Z., Ibrahim N. [7] Kumar D., Kuk H. and Ali A. 2016. One-pot solvent- A. and Rahman M. Z. A. 2010. Enzymatic synthesis free synthesis of fatty acid alkanoamides from natural of fatty amides from palm olein. J. Oleo Sci. 59: 59- oil triglycerides using alkali metal doped cao 64. nanoparticles as heterogeneous catalyst. J. Ind. Eng. Chem. 38: 43-49. [18] Singh A. K. and Mukhopadhyay M. 2013. Optimization of lipase-catalyzed glyserolisis for mono [8] Masyithah Z., Sitohang L. V. and Sihombing M. P. and diglyceride production using response surface 2017. Synthesis of azelaic acid from oleic acid with methodology. Arab J. Sci.

green oxidant H2O2/H2WO4. ARPN J. Eng. App. Sci. 12: 7031-7038.

www.arpnjournals.com

[19] Venkateswarulu T.C., Raviteja C.V., Prabhaker K.V., Babu D.J., Reddy A.R., Indira M. and Venkatanarayana A. 2014. A Review on methods of transesterification of oils and fats in bio-diesel formation. Int. J. Chem Tech Res. 6: 2568-2576.

[20] Wang X., Chen Y., Jin Q., Huang J. and Wang X. 2013. Synthesis of linoleoylethanolamide. J. Oleo Sci. 62: 427-433.

[21] Brown H. M. 2013. Optimization of the production of lubricating oil from re-refined used lubricating oil using response surface methodology. ARPN J. Eng. App. Sci. 8: 749-756.

[22] Lee A., Chaibakhsh N., Rahman M. B. A., Basri M. and Tejo B.A. 2010. Optimized enzymatic synthesis of luvulinate ester in solvent-free system. Ind. Crops Prod. 32: 246-251.

[23] Zhang, J., D. Cai, S. Wang, Y. Tang, Z. Zhang, Y. Liu and X. Ga, 2014. Efficient method for the synthesis of fatty acid amide from soybean oil methyl ester catalysed by modified CaO. The Canadian J. Chem. Eng., DOI 10.1002/cjce.21948.

[24] Silverstein R. M., Webster F. X. and Kiemle D. J. 2005. Spectrometric identification of organic compounds. Seventh Edition. State University of New York. John Wiley and Sons Inc. New York.

2117