Iraqi Journal of Chemical and Petroleum Engineering Vol.14 No.3 (September 2013) 1- 9 ISSN: 1997-4884 Synthesis, Characterization and Evaluation of Overbased Magnesium Fatty Acids Detergent for Medium Lubricating Oil Abdul Halim A-K Mohammed * , Mohammed R. Ahmad ** and Zainab A. K. Al-Messri ** *Chemical Engineering Department, College of Engineering, University of Baghdad ** Department of Chemistry, College of Science, University of Baghdad Abstract A series of overbased magnesium fatty acids such as caprylate, caprate, laurate, myristate, palmitate, stearate and oleate) were synthesized by the reaction of the fatty acids with active – 60 magnesium oxide and carbon dioxide (CO2) gas at 60 o C in the presence of ammonia solution as catalyst, toluene / ethanol solvent mixture (9:1vol/vol) was added. The prepared detergent additives were characterized by FTIR, 1 HNMR and evaluated by blending each additive in various concentrations with medium lubricant oil fraction (60 stock) supplied by Iraqi Midland Refineries Company. The total base number (TBN, mg of KOH/g) was determined, and the results of TBN were treated by using two-way analysis of variance (ANOVA) test. It was found that the number of carbons in the fatty acid (C8-C18) used for overbased detergent preparation had slight effect on the TBN of the oil, while detergent concentrations (1-5% wt/wt) had a significant effect on the TBN of the blended oil. The oxidation stability of the oil blends with 2% of overbased magnesium palmitate and overbased magnesium stearate detergents was evaluated, and the results showed that these blends gave higher oxidation stability compared with the blends with standard antioxidant supplied by Midland Refineries Company. Keywords: Overbased detergent, Fatty acid, Lubricant oil, TBN. Introduction Lubricants are an important family among products of the refining industry. A lubricant performs a number of critical functions, these include lubrication, cooling, cleaning and suspending, and protecting metal surfaces against corrosive damage [1]. Lubricant comprises a base fluid and an additive package. Additives can be defined as substances which improve the performance of lubricants, either by imparting new properties to a base oil (cleaning and suspending ability, antiwear performance, and corrosion control), or by enhancing properties already present (viscosity, viscosity index, pour point, and oxidation resistance). The use of additives began in the 1930’s and enormous growth has been seen since in both their production rates and the scope of their applications [2]. Modern equipment must be lubricated in order to prolong its lifetime. One of the most critical properties of the automotive lubricants, especially engine oils, is their ability to Iraqi Journal of Chemical and Petroleum Engineering University of Baghdad College of Engineering Synthesis, Characterization and Evaluation of Overbased Magnesium Fatty Acids Detergent for Medium Lubricating Oil 2 IJCPE Vol.14 No.3 (September 2013) -Available online at: www.iasj.net suspend undesirable products from thermal and oxidative degradation of the lubricant. It has been found necessary to incorporate detergent additives in oils for such service in order to avoid the engine failure [3]. Modern diesel engine lubricants derive most of their alkalinity from overbased detergents such as sulfonates/phenates/salicylates of calcium, or magnesium [4]. Over-based detergents are salts of alkaline earth metals such as calcium and magnesium that contain more alkaline metal than that required for their manufacture. Thus, they have both a good detergent property and an excellent ability to neutralize strong acids. Detergent additives prevent or disperse an accumulation of sludge in the crankcase at high or low temperatures [5]. The term “overbased” refers to the fact that the quantity of base incorporated in the particle cores is greater than that needed to neutralize the acid surfactant. The neutralizing strength of an overbased detergent is measured by its total base number (TBN). TBN is defined as the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 g of overbased detergent [6]. Recently, the use of environmentally friendly lubricant base oils [7-9] increased, as did the necessity of studying their environmentally friendly additives. New environmentally friendly overbased detergents were synthesized [10-14]. This work deals with preparation of lubrication oil overbased detergents from different fatty acid and testing their efficiency. Experimental Work Materials 1. Chemicals Table (1) shows the properties and manufacturers of the used chemicals. Table 1, Chemicals and their properties and manufactures No. Chemicals Molecular weight Mp., ο C Purity,% Supplier 1. Caprylic acid 144.22 15-17 98 BDH chemicals Ltd. 2. Capric acid 172.27 29-31 99 BDH chemicals Ltd. 3. Lauric acid 200.32 43-44 98 H and W Ltd. 4. Myristic acid 228.38 53-54 97 H and W Ltd. 5. Palmitic acid 256.43 61-63 99 BDH chemicals Ltd. 6. Stearic acid 284.48 67-69 95 MERCK 7. Oleic acid 282.47 13-14 97 H and W Ltd. 8. Magnesium oxide 40.31 _ 99 BDH chemicals Ltd. 9. Toluene 92.14 (Bp., ο C) 110-111 99 Fluka AG 10. Ethanol 46.07 (Bp., ο C) 79-81 95 BDH chemicals Ltd. 11. Ammonium hydroxide 17.03+aq _ 20-25 in water Fluka AG 12. CO2 gas 44 _ High purity National gas manufacturing company 2. Base Oil Base lubrication oil 40 stock and 60 stock supplied by Midland Refineries Company, 40 stock was used as a diluents in preparation of overbased magnesium fatty acid detergents, while 60 stock was used for preparation of oil blends with the prepared detergents. Abdul Halim A-K Mohammed, Mohammed R. Ahmad and Zainab A. K. Al-Messri -Available online at: www.iasj.net IJCPE Vol.14 No.3 (September 2013) 3 The properties of these oils were listed in table (2). Table 2, Properties of base lubricating oil 40 stock and 60 stock No. Specification 40 stock 60 stock Standard test method 1. Kinematic viscosity at 40 °C, cSt (mm²/s) 13.16 62.71 ASTM- D 445 2. Kinematic viscosity at 100 °C, cSt (mm²/s) 3.12 8.13 ASTM- D 445 3. Viscosity index 94 95 ASTM D- 2270 4. Specific gravity at 60/60 οF 0.856 0.88 ASTM D-4052 5. Pour point ,°C -12 -9 ASTM D-97 6. Flash Point (C.O.C),°C 198 240 ASTM D-92 7. Color 1.0 (Pale yellow) 2.5 (yellowish) ASTM D-1500 Instrumentation Fourier transform infrared (FTIR) spectra were recorded on Shimadzu FTIR-8400S Spectrophotometer, Department of Chemistry, College of Science , Baghdad university as KBr disc to detect the functional groups in the region 4000-400 cm -1 . 1 H-NMR spectra were recorded on a Burker model ultra-shield DPx- 400MHz, Cardiff University, U.K., using CDCl3 as solvent and tetramethylsilane Si(CH3)4 as internal reference . All data are given as chemical shifts δ (ppm) downfield from tetramethylsilane. Synthesis of Overbased Magnesium Fatty Acid Detergents The synthetic procedure of overbased magnesium fatty acids detergent is similar to that described by Yonglei Wang, and Wumanjiang Eli [13], but the xylene and methanol solvent change to toluene and ethanol, respectively. Different magnesium fatty acid detergents were prepared, using a three neck 500 mL round bottom flask fitted with a gas dispersion tube, condenser, and mechanical stirrer as a reactor shown in Fig. (1). 0.05 mol of the desired fatty acid and 20 g of diluents oil were added to the flask and dissolved in 100 mL of mixture of toluene and ethanol (9:1), then 20.15 g of active-60 magnesium oxide (0.5 mol) was added to the diluted mixture. The resulted mixture was stirred for 1 h and then heated up to 65 ο C. 10mL of ammonia solution was added to the mixture and 60 mL/min of gaseous CO2 for 3.5 h was then introduced into the reactor through gas dispersion tube via the gas flow meter. The desired overbased magnesium fatty acid detergent was obtained by filtration through fluted filter paper for residue removal, and filtrate evaporation to remove the solvents. Fig. 1, Schematic diagram of the reactor Formulation of Oil Blends Blends of different prepared overbased magnesium fatty acid detergents (C8 - C18:0 and C18:1) were prepared by dissolving each detergent in a mixture of toluene and xylene Synthesis, Characterization and Evaluation of Overbased Magnesium Fatty Acids Detergent for Medium Lubricating Oil 4 IJCPE Vol.14 No.3 (September 2013) -Available online at: www.iasj.net (1:1) at 60 ο C for 1 hour. The prepared 60 stock oil blends contain different dosages (1%, 2%, 3.5% and 5%) of each of synthesized detergent. Test Methods Total base number (TBN, mg of KOH/g) was determined according to American Society of Testing and Materials ASTM D-4739, This standard method is based on the potentiometric titration of the basic constituents in an oil with standardized hydrochloric acid to a fixed endpoint. Oxidation stability was determined according to IP 280, which measures the tendency for a lubricant to generate sludge and/or solid oxidation byproducts. Total oxidation products (TOP) include products formed from decomposition of hydro peroxides regardless of their chemical form. Thus, TOP is a good indicator of total conversion and overall extent of oxidation. Results and Discussion The chemical structure and total base number for the prepared magnesium overbased detergents are listed in table (3). Table 3, Nomenclature, structure, color and TBN of synthesized overbased detergents No. Abbreviation Common name Systematic name Chemical structure Color TBNmg KOH/g 1. C8:0 Magnesium caprylate Magnesium octoate (CH3(CH2)6COO)2Mg. nMgCO3 Pale yellow 76 2. C10:0 Magnesium caprate Magnesium decanoate (CH3(CH2)8COO)2Mg. nMgCO3 white 103 3. C12:0 Magnesium laurate Magnesium dodecanoate (CH3(CH2)10COO)2Mg. nMgCO3 white 123 4. C14:0 Magnesium myristate Magnesium tetradecanoate (CH3(CH2)12COO)2Mg. nMgCO3 Pale yellow 258 5. C16:0 Magnesium palmitate Magnesium hexadecanoate (CH3(CH2)14COO)2Mg. nMgCO3 Pale yellow 346 6. C18:0 Magnesium stearate Magnesium octadecanoate (CH3(CH2)16COO)2Mg. nMgCO3 white 420 7. C18:1 Magnesium oleate 9- Octadecenoic acid magnesium salt (CH3(CH2)7CH=CH- (CH2)7COO)2Mg. nMgCO3 Pale yellow 398 The structureof the synthesized compounds were confirmed by FTIR, and 1 H NMR spectroscopy as shown in table (4). FTIR spectra of the prepared compounds showed asymmetric 2918- 2927 cm -1 for (CH2) group, while symmetric stretching band for (CH2) group appeared between 2850- 2854 cm -1 . A band in the region 719-723 cm -1 refers to the methylene rocking vibration for straight chain [15]. The carboxylate ion gave a strong asymmetrical stretching band between 1578-1560 cm -1 [16]. 1 H NMR spectra of two of the prepared compounds (C16:0 and C18:0) showed the signals at  0.8 for CH3 and  1.2- 1.3 for (CH2)n because the long chain R group have resonances that occur over a very narrow range. The two protons near to carboxylate (CH2COO) appeared at  1.9-2.0 [17]. Abdul Halim A-K Mohammed, Mohammed R. Ahmad and Zainab A. K. Al-Messri -Available online at: www.iasj.net IJCPE Vol.14 No.3 (September 2013) 5 Table 4, FTIR and 1 H- NMR spectral data of synthesized overbased detergents No. Abbreviation Major FTIR absorptions cm-1 1H-NMR ( ppm) CH3 CH2 (C=O) δCH2 rocking CH3 (CH2)n CH2– CO 1. C8:0 as.2956 as.2927 s.2854 1577 723 2. C10:0 as.2958 as.2923 s.2854 1560 721 3. C12:0 as.2955 as.2924 s.2854 1578 721 4. C14:0 as.2954 as.2920 s. 2850 1560 721 5. C16:0 as.2954 as.2918 s.2850 1568 719 0.8 1.3 2.0 6. C18:0 as.2956 as.2922 s.2850 1571.8 721 0.8 1.2 1.9 7. C18:1 as.2955 as.2924 s.2854 1570 723 (=CH) 3006.8 The surfactants that are used to prepare the overbased detergent contain a polar hydrophilic head and a long, non-polar organic chain. The polar head-group typically links to calcium, magnesium or barium cations. The colloidal particle consists of a core of basic metal carbonate or a mixture of metal carbonate and metal hydroxide depending on the cation species. The core of the colloidal particle is stabilized by a monolayer of surfactant and the core radius is in a size range of 1.5 — 10 nm. [18] The schematic diagram of prepared overbased magnesium fatty acid detergent particle may be present in Fig. (2). Total base number were determined for the 60 stock oil blends with different overbased magnesium fatty acid detergent in different dosages according to ASTM D-4739, and the results are shown in table (5). The results of TBN were treated by using two-way analysis of variance (ANOVA) tests to measure the effects of two factors ,number of carbons in the synthesized overbased detergents (C8-C18) and their concentrations (1- 5% wt/wt) in the blended oil simultaneously. Fig. 2, Schematic diagram of prepared overbased detergent particle Table (6) shows the effect between subjects and summarized ANOVA. This table show the sum of squares, degree of freedom, mean squares, F- value and the significant test results .The significant level of using different carbon numbers in the detergent have a value of 0.620 which means that there is no significant difference because the significant level is greater than 0.05 (95% confidence), while the significant level obtained for Synthesis, Characterization and Evaluation of Overbased Magnesium Fatty Acids Detergent for Medium Lubricating Oil 6 IJCPE Vol.14 No.3 (September 2013) -Available online at: www.iasj.net blends with different weight percentage of different additives have the value 0.00, and this means that there is a significant difference in the effect of adding different percentage of detergent. Table 5, Total base number (TBN, mg of KOH/g) of blend oils No. w t% o f d e te rg e n t in t h e o il B la n k O il w it h o v e rb a se d M g - c a p ry la te ( C 8 ) O il w it h o v e rb a se d M g - c a p ra te (C 1 0 ) O il w it h o v e rb a se d M g - la u ra te ( C 1 2 ) O il w it h o v e rb a se d M g - m y ri st a te ( C 1 4 ) O il w it h o v e rb a se d M g - p a lm it a te ( C 1 6 ) O il w it h o v e rb a se d M g - o le a te ( C 1 8 :1 ) O il w it h o v e rb a se d M g - st e a ra te ( C 1 8 :0 ) 1. 1 0.87 1.63 1.41 1.63 1.66 1.69 1.71 2.84 2. 2 0.87 1.28 2.34 2.7 2.74 2.9 4.93 4.85 3. 3.5 0.87 4.9 5.6 5.8 5.9 8.8 10.4 10.9 4. 5 0.87 6.8 7.55 10.38 12.8 15.9 24.5 20.6 Table 6, The effect between subjects and summarized ANOVA. Source Sum of Squares Degree of freedom Mean Square F-value Significa nt Corrected model 167.467 6 27.911 0.745 0.620 Carbon compound 167.467 6 27.911 0.745 0.620 Correlated model 641.647 3 213.882 16.396 0.000 Weight added 641.647 3 213.882 16.396 0.000 Fig.s (3) and (4) show the TBN and efficiency of oil blends with prepared overbased magnesium fatty acid (C8– C18) detergents respectivly. These figures show that the overbased magnesium palmitate (C16) , stearate (C18:0) and oleate (C18:1) detergents give the higher TBN and efficiency. Since the cost of oleic acid is higher than palmitic and stearic acids, they can be recommended for lubricant oil detergent preparation. Usually the excepted percentage of detergent used for engine crankcase lubricants is not less than 2% [19]. For further, evaluation of the selected overbased magnesium palmitate and overbased magnesium stearate, the base oil (60 stock) as well as its blends with 2% by weight of detergents were subjected to severe oxidation condition in the presence of a soluble iron and copper catalyst at 120 ο C for 164 hours while being subjected to a constant one-liter/hour flow of oxygen. Fig. 3 The TBN of oil blends with prepared overbased magnesium fatty acid (C8–C18) detergents at different weight percentages Results given in table (7) show that the blends with 2% by weight overbased Mg-palmitate (C16) or overbased Mg-stearate (C18:0) have higher oxidation stability compared with the blend of the same oil with Abdul Halim A-K Mohammed, Mohammed R. Ahmad and Zainab A. K. Al-Messri -Available online at: www.iasj.net IJCPE Vol.14 No.3 (September 2013) 7 standard antioxidant used by Midland Refineries Company. Overbased detergents, especially organo-alkaline earth salt compounds, are type of metal deactivators antioxidants, which act as film-forming agents in two ways. First, they coat the metal surface, thus preventing metal ions from entering the oil. Second, they minimize corrosive attack of the metal surface by physically restricting access of the corrosive species to the metal surface [3]. Thus, the overbased magnesium palmitate and overbased magnesium stearate, can show an antioxidant effect, because the carbonate in their structure performs acid neutralization, and the linear structure of the soap forms the protective surface film. Fig. 4 The efficiency of oil blends with prepared overbased magnesium fatty acid (C8– C18) detergents Table 7, Oxidation stability results Characterization Blank Oil with overbased Mg-palmitate (C16) Oil with overbased Mg-stearate (C18:0) Standard Volatile acidity, mg of KOH/g 0.0025 0.0037 0.0037 0.0060 Soluble acidity, mg of KOH/g 0.2571 0.04939 0.01234 0.1230 Total acidity, mg of KOH/g 0.259 0.05309 0.01604 0.1290 Total sludge, wt% 0.280 0.01114 0.00 0.0880 Total Oxidation Products (TOP %) 0.363 0.0281 0.05146 0.1298 Conclusions 1. A series of overbased magnesium fatty acids (C8-C18:0 and C18:1) were synthesized and evaluated by blending each additive in various concentrations with 60 stock base oil, and the TBN was determined. 2. It was found that the number of carbons in the fatty acid (C8-C18) had slight effect on the TBN of the blended oil, while additive concentrations had a significant effect on the TBN of the blended oil. 3. Blends of 2% of overbased magnesium palmitate and overbased magnesium stearate detergents showed better oxidation stability than the standard antioxidant supplied by Midland Refineries Company. Acknowledgment The authors acknowledge Petroleum R and D Center /Ministry of Oil for financial support. Thanks are also due to Midland Refineries Company/Iraq for providing the base oils and the analyses of TBN and oxidation stability. We thank to Prof. Dr. Issam M. A. Shakir, Department of Chemistry, College of Science, University of Baghdad, for the (ANOVA) tests, and to Naeema J.Lami, Cardiff University, U.K., for NMR analysis. Synthesis, Characterization and Evaluation of Overbased Magnesium Fatty Acids Detergent for Medium Lubricating Oil 8 IJCPE Vol.14 No.3 (September 2013) -Available online at: www.iasj.net References 1- Rundnick, L.R., "Lubricant Additives: Chemistry and Applications", 2 nd Ed. New York, Taylor and Francis Group, (2009). 2- Stepina, V., and Vesely, V., "LUBRICANTS AND SPECIAL FLUIDS", Amsterdam: Elsevier, (1992). 3- Rizvi, S., "A comprehensive review of lubricant chemistry, technology, selection, and design", Baltimore, ASTM International, (2009). 4- Sharma, G.K. and Chawla, O.P., "Modeling of Lubricant Oil Alkalinity in Diesel Engines," Tribol. Int. 21, 5, 269-274 (1988). 5- Ahmed, N.S., Nasser, A.M., and Kamal, R.S., " Influence of Some Compounds as Antioxidants and Detergents/Dispersants for Lube Oil", Journal of Dispersion Science and Technology, 32:1067–1074, (2011) 6- Hudson, L.K., Eastoe, J., and Dowding, P.J., "Nanotechnology in action: Overbased nanodetergents as lubricant oil additives", Advances in Colloid and Interface Science, 123, 425–431, (2006). 7- DOLL, K., and ERHAN, S., "Synthesis of Carbonated Fatty Methyl Esters Using Supercritical Carbon Dioxide", J. Agric. Food Chem., 53, 9608-9614, (2005). 8- Tupotilvo, N., Ostrikov, V., and Kornev, A., "Plant oil derivatives as additives for lubricants" Chemistry and Technology of Fuels and Oils, 42, 192-195, (2006). 9- Wang, M., Morris, J., Tonnis, B., Pinnow, D., Davis, J., Raymer, P., and Pederson, G.," Screening of the Entire USDA Castor Germplasm Collection for Oil Content and Fatty Acid Composition for Optimum Biodiesel Production", J. Agric. Food Chem, 59, 9250–9256 (2011). 10- Wang, Y.; Eli, W., Liu, Y. and Long, L. "Synthesis of Environmentally Friendly Calcium Oleate Detergent", Ind. Eng. Chem. Res., 47, 8561-8565, (2008). 11- Wang, Y., Eli, W., Nueraimaiti, A., and Liu, Y." Synthesis and Characterization of Polyol Poly-12- Hydroxy Stearic Acid: Applications in Preparing Environmentally Friendly Overbased Calcium Oleate Detergent", Ind. Eng. Chem. Res., 48, 37. ( 2009). 12- Wang, Y. and Eli, W. "Synthesis of Biodegradable High-Alkali Magnesium Oleate Detergent", Ind. Eng. Chem. Res., 49, 2589, (2010) 13- Wang, Y. and Eli, W. "Synthesis of Environmentally Friendly Overbased Magnesium Oleate Detergent and High Alkaline Dispersant/Magnesium Oleate Mixed Substrate Detergent", Ind. Eng. Chem. Res., 49, 8902-8907, (2010). 14- Wang, Y. , Eli, W., Zhang, L., and Cai, G., "Synthesis of Environmentally Friendly Composite-Metal (Calcium andMagnesium) Oleate Detergent", Ind. Eng. Chem. Res., 50, 1530– 1535,( 2011). 15- Silverstein, R. M., Websters, F.X., and Kiemle, D.J, “Spectrometic identification of organic compounds", 7 th Ed., New York, John Wiely and Sons, (2005). 16- Lu, Y., and Miller, J.D., "Carboxyl Stretching Vibrations of Spontaneously Adsorbed and LB- Transferred Calcium Carboxylates as Determined by FTIR Internal Reflection", Spectroscopy Journal of Colloid and Interface Science,256,1,41-52,( 2002). 17- Crews, P., Rodriguez, J. and Jaspars, M., "Organic Structures Analysis", New York, (1998). 18- Wang, Y. and Eli, W.," Recent Advances in Colloidal Lubricant Detergents" China Petroleum Abdul Halim A-K Mohammed, Mohammed R. Ahmad and Zainab A. K. Al-Messri -Available online at: www.iasj.net IJCPE Vol.14 No.3 (September 2013) 9 Processing and Petrochemical Technology, 12, 7-12,(2010). 19- Eglin, M., (2003),"Development of combinational approach to lubricant additive characterization", Ph.D. Thesis, Swiss Federal Institute of Technology, Zurich.