1. Introduction World energy demand currently considered rising rapidly due to the increasing consumption of diesel fuels [1]. Biodiesel, a renewable green fuel with similar combustion properties to the diesel fuel conventionally produced through transesterification of oils with short-chain alcohols [2,3]. The use of biodiesel decreased the exhaust emission from such contaminants as CO2, NOX, and volatile hydrocarbons [4,5]. Such fuel materials also consumed through normal diesel engines. Indeed, biodiesel considered as a legitimate alternative to the diesel fuel [6]. Two approaches employed to convert raw feedstock to biodiesel fuels. One based upon conventional method of using KOH and NaOH commonly applied through batch reactors and resulting in high conversions of feedstocks into biodiesel. Base removal from the reaction media however; considered rather costly and high moisture content resulted in saponification reactions and formation of emulsions. A large amount of waste water was therefore; produced to effectively separate and refine methyl esters and glycerol products. Furthermore, the corrosion problems caused under acidic or alkaline conditions were also significant [7,8]. The second approach was due to use of heterogeneous catalysts known for their non-corrosive nature, environmentalfriendly composition and recyclability. These advantages made solid catalysts superior to their homogeneous counterparts. Numerous such materials as alkaline-earth metal oxides, alkaliloaded calcium and magnesium, basic zeolites as well as; different acidic/basic mixed metal oxides were investigated for the transesterification reaction resulting in a high-quality biodiesel 1

and glycerol as a by-product [9–12]. Some of these catalysts included; Ca/MgAl [13], SnO2/SiO2 metal oxides [14], Zn-La2O3 mixed metal oxides [15] and MgO [16,17]. In spite of their advantages, heterogeneous catalysts have their own shortcomings. Due to their low catalytic activity, severe reaction conditions often required (e.g.; high temperatures of >150 °C and long reaction times of >6 h) while possessing low catalytic stability due to significant leaching of components in the reaction media [17–20]. Sodium Zirconate [21] and KF/Ca-Mg-Al [22] were reported as active catalysts for biodiesel production under mild reaction conditions (1 atm, 338 K) albeit with significant leaching causing rapid deactivation. Calcium-based catalysts well-known for biodiesel production due to their low-cost and high catalytic performance. These species revealed a good stability as well due to the leaching of Ca into the reaction media [23–25]. Moreover, removal of Ca contaminants from the resulting biodiesel fuel required further processing. To enhance the activity and stability of the calciumbased catalysts, they were synthesized using CaO supported on or mixed with other metal oxides [26–29]. Boro and Konwar [28] reported that Li-doped CaO showed high catalytic activity (i.e.; 94% conversion) in the transesterification reaction. However, experiments proved that, some Li and CaO components leached from the catalyst during transesterification. CaO mixed with MgO showed acceptable catalytic activity, although some leaching was observed [17]. Thitsartarn and Kawi [29] reported that, with CaO-CeO2 synthesized by co-precipitation, the fatty acid methyl ester (FAME) yield of 90% was achieved even after 10 runs with the recycled catalyst. Despite the stability of the catalyst, reaction conditions of the process (at the reaction temperature of 85 °C and methanol to oil molar ratio of 20:1) were rather severe and the 90% of FAME yield was still below the EN 14214 specifications of 96.5% [30]. CaO mixed with La2O3 also showed a good catalytic activity (of 94% conversion) but the methanol to oil molar ratio of 20:1 was high, and the catalyst structure changed after exposure to air [15]. In light of these studies and to overcome the challenges and drawbacks of the heterogeneous catalysts, it seemed to be advantageous to synthesize a new catalyst with high activity and longterm stability suitable for continuous reactors. In the current investigation, a series of Ca-La catalysts were synthesized by co-precipitation technique and subsequently doped with lithium using a simple wet impregnation method. This was then utilized to produce biodiesel fuel. It was noteworthy to mention that, there were no preceding reports in the open literature on the production of biodiesel using Li-doped Ca-La catalysts. Hence, this was done for the first time in this work. Moreover, the catalyst composition, methanol to oil molar ratio and calcination temperature were optimized. Ultimately, the stability and reusability of the synthesized materials were undertaken.

2. Experimental

2.1. Materials Canola oil was obtained from a local market (Kadbanoo Co.) and used without additional processing. Its physicochemical properties were summarized in Table 1. Lanthanum nitrate hexahydrate [La(NO3)3.6H2O], lithium chloride (LiCl), methanol, and sodium hydroxide of analytical grade were purchased from the Merck Inc. Calcium nitrate tetrahydrate [Ca(NO3)2.4H2O] was obtained from the Sigma-Aldrich Co. Distilled water was used for solution preparation.

2.2. Catalyst preparation The Li/CaO-La2O3 catalysts were prepared using the following two-step method. First, CaOLa2O3 mixed oxide was prepared by co-precipitation method based upon the procedure outlined by Yan and Kim [24]. An aqueous solution of La and Ca precursors with Ca/La molar ratio of 2

3:1 was obtained. Afterward, 1 M solution of NaOH was added dropwise under the constant stirring rate of 60 rpm to increase and maintain the pH at 12. After the pH adjustment, the solution was stirred for 3 h at 60 °C in order to ensure the complete precipitation. The precipitate was then separated using a centrifuge at 6000 rpm and washed with deionized water several times. The precipitate was subsequently dried at 120 °C for 24 h and calcined at 700 °C for 3 h. In the second step, X wt% of Li (X = 0, 1, 3, 5, and 7) was impregnated on the CaO-La2O3 mixed oxide employing a rotary evaporator at 70 °C and 30 rpm under a vacuum. The solid powder was then collected, dried at 120 °C for 24 h and calcined at 700 °C for 2 h. Catalysts were named X%Li/Ca-La for simplicity.

2.3. Characterization Hammett indicators were used to measure the base strength of the catalyst samples (H_) [31]. Approximately 25 mg of the fresh catalyst was mixed with 0.5 ml of a methanol solution of the Hammett indicator. After 2 h, the solution reached the equilibrium, i.e. no additional change was observed in color. Bromthymol blue (H_=7.2), phenolphthalein (H_=9.8), indigo carmine (H_=12.2), 2, 4-dinitroaniline (H_=15.0), and 4-nitroaniline (H_=18.4) at a concentration of 0.02 mole.L-1, were used as indicators. The morphology of the Li/Ca-La nanostructures was investigated using a field emission scanning electron microscope (MIRA FEG-SEM). The surfaces of dried catalyst samples were coated with gold using a sputter coater (Pishtaz Engineering Co. High Vacuum Technology ACECR-Sharif University of Technology BranchIran) before FESEM analysis. The average surface area of catalysts was obtained from N2 adsorption/desorption measurements at 77 K using the BET method. Prior to analysis, all samples were degassed for at least 12 h in order to remove any adsorbed molecules from the pores and surfaces of the solid. Powder X-ray diffraction (XRD) patterns were taken with a Rigaku RU2000 rotating anode powder diffractometer (Woodlands, TX) equipped with Cu Kα radiation (40 kV, 200 mA), over a 2ϴ range of 20–120o with a step size of 3o/min. The FAME product was quantified by 1H-NMR (400 MHz FT-NMR Cryo Spectrometer Bruker) using integration values of the signals corresponding to methoxy protons and methylene.

2.4. Catalytic activity The Li/Ca-La catalysts were examined for their catalytic activity in the transesterification reaction under various reaction conditions. The catalysts were activated at 700 °C for 30 minutes in N2 flow before being used for reaction study. Each experiment was repeated three times to establish the approximate experimental error. The reactions took place in a 100 ml batch reactor consisting of a three-neck flask with a condenser equipped with a sampler, thermometer, magnetic stirrer to enhance mass transfer of immiscible reactants (oil and methanol) and a water bath to adjust the reaction temperature. All experiments were carried out under atmospheric pressure. In a typical transesterification reaction, canola oil and methanol with a 15:1 methanol to oil molar ratio and 5 wt% of catalyst in oil were charged into the flask. The reaction media was heated up to 65 °𝐶 (i.e.; the reflux temperature of methanol) with continuous stirring fixed at 400 rpm. Samples were withdrawn from the reaction media at specific time intervals (30 min) using a calibrated syringe. After each experiment, the catalyst was separated from the reaction mixture through filtration. A rotary evaporator was used to remove excess methanol from the reaction products. The samples were diluted with hexane and then analyzed by the 1H-NMR for FAME content evaluations.

2.5. Catalytic durability To investigate the durability of the prepared catalysts, 5 wt% catalyst was mixed with oil and methanol (i.e.; methanol to oil molar ratio of 15:1) and the reaction was performed at 65 °C. 3

After each reaction cycle of 2.5 h, the catalyst was filtered out of the liquid products and recovered. Afterward, a new batch of oil and methanol was added to the recovered catalyst into the reactor. In order to recover the used catalyst, it was washed with hexane so as to take away the adsorbed organic molecules from the catalyst’s surface. The resultant was then dried at 120 °C and activated at 700 °C for 30 min. Finally, the conversion of canola oil from each reaction cycle was obtained from the 1H-NMR analysis.

3. Results and discussion

3.1. Catalyst characterization The XRD patterns of X%Li/Ca-La (with X=0, 1, 3, 5, and 7) catalysts were shown in Fig. 1. All catalysts exhibited similar patterns. The un-doped catalyst showed the diffraction peaks related to the existence of La(OH)3 (2ϴ = 27.22°, 27.97°, 31.67°, 39.56°, 48.65°, 55.26° and 64.03°), Ca(OH)2 (2ϴ = 28.68°, 34.06°, 47.05° and 56.52°) and La2CaO (2ϴ = 49.58°). The XRD patterns of the Li-doped samples showed additional peaks at 2ϴ = 24.71°, 40.61°, 44.37° and 56.41° due to the presence of LiNO3 (JCPDS-01-1225), Li2O2 (JCPDS-09-0355), LiH (JCPDS03-1038), and Li2O (JCPDS-73-0593) phases in the structure of the Li-doped catalysts. Unlike the hydration of calcium and lanthanum, the presence of lithium oxides indicated the comparative stability of lithium-based phases after exposure to air. The Li-doped Ca-La samples showed the characteristic peaks (at 2ϴ=30.95° and 56.029°) referable to CaLi2 (JCPDS-06-0432) and La2CaO (JCPDS-42-0342) revealing that, the mixed metal structure of Li/Ca-La was formed. It was worth noting that, almost similar ionic radius of Ca (0.99 Å) compared with that of La (1.061 Å) permitted for easy substitution of La ion within the CaO lattice. According to Fig. 1, 1%Li/Ca-La sample showed similar diffraction patterns as compared with those for 3, 5, and 7%Li-doped catalysts. Diffraction peaks however; were considerably sharper in the first case (1%Li) indicating a larger particle size of it. This observation suggested that, the Li-doping enhanced the crystallization of the Ca-La species. Table 2 presented a summary of the BET surface area, basic strength, and catalytic performance of un-doped and Li-doped CaO-La2O3 mixed oxide catalysts. The measured surface area in this study showed a falling trend as the lithium content increased in the catalyst structure. For 1%Li/Ca-La catalyst the BET surface area was 18.23 m2/g being comparable with those of pure calcium and Li-doped calcium oxide [30,32]. Kaur and Ali [30] reported that, the surface area of the CaO was reduced from 8.1 to 1.3 m2/g when doped with lithium. This might have occurred due to the pore blocking after lithium impregnation. The impregnation of lithium onto the Ca-La however, did not significantly reduce the surface area of the catalyst. As revealed in Table 2, the basic strengths of prepared catalysts were raised drastically after Lidoping. This emphasized that, the Li-doped mixed oxides generally possessed higher basic strength than that of the un-doped one due to the presence of lithium in the structure of the catalyst. However, the basic strength was gradually reduced as the Li content increased from 1 to 7% in the catalyst. This was attributed to a lowering trend of the BET surface areas of the aforementioned utilized catalysts hence; a decreased extent of the encountered active sites meaning a reduction of the surface concentration of basic –OH and –O– groups appearing in the system. Moreover, this was also seen by other researchers [24] as well. Ultimately, these results were consistent with the obtained BET surface area and biodiesel conversion data. Fig. 2 showed the FESEM images of 1%Li/Ca-La catalyst indicating the formation of a porous catalyst in clusters of oval and irregular shaped particles (scale bar of 10 μm). The cluster-shape formation was attributed to the agglomeration of the catalyst particles during lithium doping by 4

wet impregnation. Further magnification of the FESEM image (scale bar of 500 nm) indicated that, the surface was made up of small spherical shaped particles with an average size of 80-120 nm.

3.2. Product analysis through the 1H-NMR The FAMEs were characterized by proton nuclear magnetic resonance (1H-NMR) analysis due to its quickness, simplicity, and non-destructiveness [33]. As illustrated in Fig. 3, in the spectrum of biodiesel (sample 1), the disappearance of glyceridic protons (4.2-4.4 ppm) and the appearance of a new peak at 3.7 ppm due to –OCH3 protons confirmed occurrence of the transesterification reaction of vegetable oils. The 1H-NMR spectra were used to estimate the FAME content through the following equation [32]: 2𝐼 %𝐶𝐹𝐴𝑀𝐸 = 100 [ 𝑀𝐸⁄3𝐼𝛼𝐶𝐻 ] (1) 2 Where the IME and I𝛼CH2 were the integration values of peaks corresponding to –OCH3 protons (at 3.7 ppm) and α-methylene protons (at 2.3 ppm); respectively in the 1H-NMR spectrum of biodiesel products.

3.3. Catalytic activity The effects of different parameters including the amount of doped Li (0, 1, 3, 5, and 7 wt%), calcination temperature (500 °C, 700 °C, and 900 °C), wt% of catalyst in oil (1, 3, 5, and 7 wt%) and the methanol to oil molar ratio (3:1, 9:1, 15:1, and 21:1) on catalyst performance were investigated and discussed in the following sections.

3.3.1. Effect of the Doped lithium ion concentration The series of catalysts with 0, 1, 3, 5, and 7 wt% of lithium loading was examined in the transesterification reaction performed at 65 °C with methanol to oil molar ratio of 15:1 in the presence of 5 wt% catalyst. The biodiesel conversion versus time was presented in Fig. 4 revealed an enhancement in conversion with an increase in Li content from 0 to 1%. Further increment in the Li content however; did not result in any significant increase in the rate of the transesterification reaction of the canola oil. This might be due to the formation of separated lithium hydroxide phases as well as; the decrement of BET surface area when excess Li was doped [15]. The catalyst with 1% Li content was therefore used to optimize other parameters including methanol to oil molar ratio, wt% of the catalyst, reaction time, and calcination temperature in order to achieve the highest activity in the transesterification reaction.

3.3.2. Effect of catalyst concentration Transesterification of canola oil with methanol (methanol to oil ratio of 15:1) at 65 °C was carried out using the 1, 3, 5, and 7 wt% of catalyst in oil for 1%Li/Ca-La sample. As illustrated in Fig. 5, lower catalyst loads resulted in a low conversion which simply attributed to the lower number of the active catalytic sites accessible for the reactants [34]. The time required to reach the EN 14214 specifications (96.5%) was found to be 2.5 h when a 5 wt% of catalyst was utilized. Further increase in the catalyst wt% did not significantly change the biodiesel conversion most possibly due to the fact that at higher catalyst contents, the reverse reaction and saponification occurred simultaneously in the reaction media [15]. The transesterification reactions were then performed using a 5 wt% of 1%Li/Ca-La catalyst to optimize other operating parameters previously mentioned above. As discussed earlier, the

5

activity of this catalyst was higher compared with those reported for transesterification of oil using calcium based catalysts in the open literature [28,29,32].

3.3.3. Effect of methanol to oil molar ratio The transesterification activity depended not only upon the lithium content, reaction time, and catalyst loading but also, relied upon the molar ratio of methanol to oil. Theoretically considering, three moles of methanol were needed to react with one mole of oil for complete conversion to biodiesel. Due to the reversible nature of the transesterification reaction, however, the reaction usually carried out with excess methanol to shift the reaction equilibrium in the forward direction to obtain the maximum FAME yield [35]. Due to the mass transfer resistance between the phases and the slower rate of the reaction in heterogeneously catalyzed transesterification, higher methanol to oil molar ratios employed to enhance the methyl ester yields [32,36]. To determine the optimum amount of methanol to oil molar ratio, the reactions were carried out with molar ratios of 3:1, 9:1, 15:1, and 21:1 using 5 wt% of the 1%Li/Ca-La catalyst. The results presented in Fig. 6 revealed that, low conversions obtained at lower methanol to oil molar ratios. The reaction conversion was observed to reach its maximum value of 96.3% in 2.5 h with methanol to oil molar ratio of 15:1. Further increase of the methanol to oil molar ratio did not result in any significant increase in conversion. It ought to be reiterated that, high methanol to oil molar ratios tended to increase the production cost of the biodiesel even if the excess methanol was recovered and reused.

3.3.4. Effect of calcination temperature It was reported that, the leaching of calcium based catalysts suppressed by performing the catalyst calcination at higher temperatures hence; improved the interaction between the catalyst components [23,37]. Furthermore, calcination temperature could affect the surface area and basicity of the catalyst [38]. The effect of this temperature on catalyst performance was investigated using the 1%Li/Ca-La catalyst under optimum reaction conditions (reaction temperature of 65 °C, methanol to oil molar ratio of 15:1 and catalyst amount of 5 wt%). Consequently, as displayed in Fig. 7, the optimum calcination temperature determined to be 700 °C.

3.4. Catalyst durability It was revealed through Fig. 8 that, conversions of 93.5, 89.1, 87.7 and 85.6% were obtained for the first four cycles of methanolysis of the canola oil using a recovered 1%Li/Ca-La catalyst. This indicated that, the understudied catalyst behaved consistently though with a marginal variation of conversions of up to 8.0%. In addition, the conversion in the last cycle was still more than that of the un-doped catalyst (78.7%) after 2.5 h of the reaction. Moreover, the stability of the prepared catalyst was demonstrated to be superior to the ones previously reported [13,30] in the open literature. Deactivation might have been attributed to the poisoning of the catalytic sites by the CO2 and/or leaching of the active species. Thus, used catalysts had to be calcined before used again for the next run to remove the adsorbed CO2 hence; reviving the active sites [34]. To study the leaching of active species (e.g.; Li+), 375 mg of 1%Li/Ca-La material was refluxed with 5.6 ml of methanol in the reactor for 2.5 h at 65 °C. Afterward, the catalyst was filtered out and the obtained methanol was used for the transesterification of canola oil (i.e.; methanol/oil molar ratio of 15:1) at 65 °C for 2.5 h. Under these conditions, insignificant conversion (of ~ 4%) of FAME was observed. Thus, the reaction mainly catalyzed by the heterogeneous catalyst pointing out towards the idea that, the leachate was negligible. Considering the aforementioned results it was 6

a foregone conclusion that, the 1%Li/Ca-La catalyst was stable during the transesterification reaction.

4. Conclusions The 1%Li/Ca-La catalyst prepared by co-precipitation followed by wet impregnation method revealed to be an active catalyst for transesterification of canola oil with methanol. There was a strong interaction amongst lithium, calcium, and lanthanum in the structure of this material. It was demonstrated that, the Lithium doping enhanced the basic strength, and the presence of lanthanum into the support structure maintained the BET surface area and the stability of the catalyst even after the lithium impregnation. Hence, the exceptional activity of the 1%Li/Ca-La catalyst was due to possessing of strong basic sites over the catalyst surface as well as; large particle sizes emphasized through the XRD, BET, FESEM and ionic (i.e.; basic) strength results. The synthesis of catalyst was simple, economic, and green utilizing materials readily available. The results also illustrated that, the Li/Ca-La catalyst was a stable material for the biodiesel production. All these rendered the synthesized catalyst in this work rather novel and promising for the transesterification purpose. References [1] M. Ghiaci, B. Aghabarari, A. Gil,;1; Fuel 90(11) (2011) 3382. [2] E. Martinez-Guerra, V.G. Gude,;1; Journal of Industrial and Engineering Chemistry 35 (2016) 14. [3] A. Galadima, O. Muraza,;1; Journal of Industrial and Engineering Chemistry 29 (2015) 12. [4] J.A. Melero, J. Iglesias, G. Morales,;1; Green Chem. 11(9) (2009) 1285. [5] P.D. Patil, V.G. Gude, S. Deng,;1; Industrial & Engineering Chemistry Research 48(24) (2009) 10850. [6] I.K. Hong, H. Jeon, H. Kim, S.B. Lee,;1; Journal of Industrial and Engineering Chemistry 42 (2016) 107. [7] B. Freedman, E.H. Pryde, T.L. Mounts,;1; Journal of the American Oil Chemists Society 61(10) (1984) 1638. [8] C. Ngamcharussrivichai, W. Meechan, A. Ketcong, K. Kangwansaichon, S. Butnark,;1; Journal of Industrial and Engineering Chemistry 17(3) (2011) 587. [9] W. Xie, M. Fan,;1; Chemical Engineering Journal 239 (2014) 60. [10] W. Xie, X. Yang, M. Fan,;1; Renewable Energy 80 (2015) 230. [11] A.P.S. Chouhan, A.K. Sarma,;1; Renewable and Sustainable Energy Reviews 15(9) (2011) 4378. [12] Z. Helwani, M.R. Othman, N. Aziz, J. Kim, W.J.N. Fernando,;1; Appl Catal A: Gen 363(1– 2) (2009) 1. [13] C.S. Castro, L.C.F. Garcia Júnior, J.M. Assaf,;1; Fuel Processing Technology 125 (2014) 7

73. [14] W. Xie, H. Wang, H. Li,;1; Industrial & Engineering Chemistry Research 51(1) (2012) 225. [15] Z. Wen, X. Yu, S.-T. Tu, J. Yan, E. Dahlquist,;1; Applied Energy 87(3) (2010) 743. [16] X. Liu, H. He, Y. Wang, S. Zhu,;1; Catalysis Communications 8(7) (2007) 1107. [17] G.R. Peterson, W.P. Scarrah,;1; Journal of the American Oil Chemists Society 61(10) (1984) 1593. [18] X. Bo, X. Guomin, C. Lingfeng, W. Ruiping, G. Lijing,;1; Energy & Fuels 21(6) (2007) 3109. [19] Q. Zhou, H. Zhang, F. Chang, H. Li, H. Pan, W. Xue, D.-Y. Hu, S. Yang,;1; Journal of Industrial and Engineering Chemistry 31 (2015) 385. [20] N. Supamathanon, J. Wittayakun, S. Prayoonpokarach,;1; Journal of Industrial and Engineering Chemistry 17(2) (2011) 182. [21] N. Santiago-Torres, I.C. Romero-Ibarra, H. Pfeiffer,;1; Fuel Processing Technology 120 (2014) 34. [22] L. Gao, G. Teng, J. Lv, G. Xiao,;1; Energy & Fuels 24(1) (2009) 646. [23] X. Liu, X. Piao, Y. Wang, S. Zhu, H. He,;1; Fuel 87(7) (2008) 1076. [24] S. Yan, M. Kim, S.O. Salley, K.Y.S. Ng,;1; Applied Catalysis A: General 360(2) (2009) 163. [25] R.O. Chinta Reddy Venkat Reddy and, and John G. Verkade,;1; Energy & Fuels 20(3) (2006) 1310. [26] W. Xie, L. Zhao,;1; Energy Conversion and Management 76 (2013) 55. [27] H. Wu, J. Zhang, Q. Wei, J. Zheng, J. Zhang,;1; Fuel Processing Technology 109 (2013) 13. [28] J. Boro, L.J. Konwar, D. Deka,;1; Fuel Processing Technology 122 (2014) 72. [29] W. Thitsartarn, S. Kawi,;1; Green Chemistry 13(12) (2011) 3423. [30] M. Kaur, A. Ali,;1; Renewable Energy 63 (2014) 272. [31] M.L. Granados, M.D.Z. Poves, D.M. Alonso, R. Mariscal, F.C. Galisteo, R. Moreno-Tost, J. Santamaría, J.L.G. Fierro,;1; Applied Catalysis B: Environmental 73(3–4) (2007) 317. [32] M. Kaur, A. Ali,;1; Renewable Energy 36(11) (2011) 2866. [33] G. Knothe,;1; Journal of the American Oil Chemists’ Society 78(10) (2001) 1025. [34] V. Mutreja, S. Singh, A. Ali,;1; Renewable Energy 62(0) (2014) 226. [35] A. Demirbas,;1; Energy Convers Manage 48(3) (2007) 937. 8

[36] M. Di Serio, M. Ledda, M. Cozzolino, G. Minutillo, R. Tesser, E. Santacesaria,;1; Industrial and Engineering Chemistry Research 45(9) (2006) 3009. [37] X. Yu, Z. Wen, H. Li, S.-T. Tu, J. Yan,;1; Fuel 90(5) (2011) 1868. [38] S. Yan, M. Kim, S. Mohan, S.O. Salley, K.Y.S. Ng,;1; Applied Catalysis A: General 373(1– 2) (2010) 104.

Fig. 1. Comparison of the powder XRD patterns of Ca-La support doped with 0, 1, 3, 5, and 7 wt% lithium (exposed to air) in this research.

Fig. 2. FESEM image of 1%Li/Ca-La catalyst synthesized in this research.

Fig. 3. Comparison of the 1H-NMR spectra of canola oil and sample 1 (1%Li/Ca-La, catalyst amount: 5 wt%, methanol/oil molar ratio: 15:1, reaction time: 2.5 h, and at 65 °C).

Fig. 4. Transesterification activities of X%Li/Ca-La (X = 0, 1, 3, 5, and 7) catalyst (Reaction conditions: catalyst amount = 5 wt%; methanol/oil molar ratio = 15:1; temperature = 65 °C).

Fig. 5. Effect of the catalyst loadings on the performance of 1%Li/Ca-La material for the transesterification reaction of canola oil to FAMEs (Reaction conditions: methanol/oil molar ratio = 15:1; temperature = 65 °C).

Fig. 6. Effect of methanol to oil molar ratio on the performance of 1%Li/Ca-La catalyst for the transesterification reaction of canola oil to FAMEs (Reaction conditions: catalyst amount = 5 wt%; temperature = 65 °C).

Fig. 7. Effect of calcination temperature on the activity of 1%Li/Ca-La catalyst for the transesterification reaction of canola oil to FAMEs (Reaction conditions: catalyst amount = 5 wt%; methanol/oil molar ratio = 15:1; temperature = 65 °C and reaction duration = 2.5 h).

Fig. 8. Durability of the recovered 1%Li/Ca-La catalyst towards the methanolysis of canola oil (Reaction conditions: catalyst amount = 5 wt%; methanol/oil molar ratio = 15:1; temperature = 65 °C and reaction time = 2.5 h).

Tables

Table 1. Chemical and physical properties of canola oil used in this research. Property

Unit

Value

Oleic acid

wt%

59

Linoleic acid

wt%

22

Linolenic acid

wt%

9

Palmitic acid

wt%

5 9

Stearic acid

wt%

3

Erucic acid

wt%

2

Saponification

mg KOH g-1

187

Acid value

mg KOH g-1

0.071

Water content

wt%

0.98

value

Table 2. Specific surface area, basic strength and conversion of the prepared catalysts a in this work. Catalyst

BET (m2g-1)

Basic strength

Conversion (%)

(H_) 1

0%Li/Ca-La

26.15

< 7.2

78.7

2

1%Li/Ca-La

18.23

12.2-15

96.3

3

1%Li (used)

12.84

12.2-15

93.5

4

3%Li/Ca-La

10.56

9.8-12.2

93.2

5

5%Li/Ca-La

7.78

9.8-12.2

93.1

6

7%Li/Ca-La

4.23

7.2-9.8

90.3

7

CaOb

8.1

9.8-10.1

-

8

3-Li/CaOb

1.3

15-18.4

-

a

Reaction condition: methanol/oil molar ratio = 15:1; temperature = 65 °C; reaction time = 2.5 h; catalyst amount = 5 wt% and calcination temperature = 700 °C. b Values are from reference [32].

TDENDOFDOCTD

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