Title Science and Technology Indonesia e-ISSN:2580-4391 p-ISSN:2580-4405 Vol. 5, No. 3, July 2020 Research Paper Transesterification Reaction from Rice Bran Oil to Biodiesel over Heterogeneous Base Calcium Oxide Nanoparticles Catalyst Nur Fatin Sulaiman1, Abdul Rahim Yacob1, Siew Ling Lee1,2* 1Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Johor Bahru, MALAYSIA 2Centre for Sustainable Nanomaterials, Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, 81310 Johor Bahru, MALAYSIA *Corresponding author: lsling@utm.my Abstract This study focuses on the development of an alkaline earth metal oxide, calcium oxide (CaO) as heterogeneous base catalyst for biodiesel production. The intention for this study is to explore potential for the transformation of commercial calcium carbonate, CM-CaCO3 into CaO nanoparticles and further used as a heterogeneous base catalyst in single step transesterification reaction from rice bran oil to biodiesel. The prepared CaO was calcined under 10−3 mbar vacuum, at temperatures ranging from 100°C to 700°C. TGA-DTA results revealed that the CM-CaCO3 must be calcined above 600°C in order to form CaO. This is in accordance with FTIR results which specified the complete formation of CaO at 700°C. XRD revealed that the rhombohedral CaCO3 and hexagonal Ca(OH)2 had completely been disappeared, leaving only crystalline cubic CaO at 700°C. Interestingly, the larger BET surface area (11.5 m2g−1) and highest basicity (1.959 mmol/g) were observed for CaO calcined at 700°C (CaO-700). The CaO-700 nanoparticles were designated as a catalyst for the transesterification reaction of rice bran oil to give biodiesel. NMR and GC-FID results further confirmed the successful formation of biodiesel using CaO-700 as catalyst. Keywords Heterogeneous Catalyst; Nanoparticles; Biodiesel; Transesterification Received: 14 June 2020, Accepted: 13 July 2020 https://doi.org/10.26554/sti.2020.5.3.62-69 1. INTRODUCTION The physicochemical characteristics of a heterogeneous cata- lyst depend on their preparation techniques and the primary treatment process. There are many of research techniques are available to produce solid base catalyst such as hydration dehy- dration method (Aziz et al. (2012); Yacob and Sulaiman (2012)), sol gel (Corrêa et al. (2020)) and chemical vapor deposition (CVD) methods (Knözinger et al., 2000). In general, physical and chemi- cal properties such as surface area, particle size, morphology and basicity would a�ect each of catalytic activity. The signi�cance of heterogeneous base catalysts also became recognized for their environmentally sustainable qualities. Much signi�cant progress in catalytic materials and solid base-catalyzed reactions has been made over the past two decades (Hattori, 2001) It was reported by Hattori (2001), a strong basic strength of carbonate-free metal oxide surfaces could be developed after a high-temperature treatment. Surface defect that was detected by nitrogen adsorption analysis demonstrated important hetero- geneous catalytic sites that could enhance the reactivity of each reaction (Boro et al., 2012). As a result, the larger surface area implied good reactivity. Alkaline earth metal oxides including calcium oxide, CaO has basic characteristics as its oxides provide basic alkaline solutions when mixed with water. By transforming the basic oxide to hydroxides, the proton was transmitted from water to basic oxide. Alternatively, the solid basic oxides donated their electron pair to the reactants. It was documented that the alkaline earth metal oxide acted as a Brönsted base, while the water functioned as a Brönsted acid. In the biodiesel production, transesteri�cation reaction is the most widely studied utilizing alkaline earth metal oxide as solid base catalyst (Mazaheri et al. (2018); Dawood et al. (2018); Shan et al. (2016)). Biodiesel as one of the renewable energies can be produced from vegetable oils or animal fats. It consists of blend of long- chain alkyl esters such as methyl esters, which are used without modi�cation to the diesel engine as an alternative for petroleum oil. By using above resources, this biodiesel consisting of fatty acid alkyl ester is generally produced by transesteri�cation reac- tion. There are number of techniques to perform this reaction including supercritical process, common batch process, ultra- sonic technique and microwave method (Rathnam et al. (2020); Hakim et al. (2019); Sharma et al. (2019)). This present study focused on the preparation of CaO nanopar- ticles from commercial calcium carbonate, CM-CaCO3 under https://doi.org/10.26554/sti.2020.5.3.62-69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 vacuum atmosphere of 10−3 mbar at 100 to 800°C by thermal de- composition process. The basicity of the CaO nanoparticles was examined using back-titration method in order to investigate the relationship between basicity and calcination temperature. The prepared CaO nanoparticles were then used for the transes- teri�cation of rice bran oil to biodiesel as a heterogeneous base catalyst. Rice bran oil has been selected as it is unconventional, low-cost and low-grade vegetable oil that does not have much competition for food requirement. 2. EXPERIMENTAL SECTION 2.1 Materials In this research, the chemical reagents were used such as com- mercial calcium carbonate, CaCO3, hydrochloric acid, HCl, sodium hydroxide, NaOH, methanol, CH3OH and n-hexane, C6H14 with molecular weight 100.09 g/mol, 36.46 g/mol, 40.00 g/mol, 32.04 g/mol and 86.07 g/mol, respectively. All chemical reagents were purchased from QRëC. The rice bran oil, acquired from the local store was used for the transesteri�cation reaction. 2.2 Catalysts Preparation Calcium oxide, CaO nanoparticles were prepared using thermal decomposition method under vacuum atmosphere at various calcination temperatures ranging 100 to 800 ºC. The samples were labeled as CaO-100 to CaO-800 according to their calci- nation temperature. Approximately 0.4 g of the commercial CaCO3 powder was inserted in a quartz tube attached to vacuum line system. CM-CaCO3 precursor was calcined at 100 to 800 ºC in 10-3 mbar vacuum for 2 hours to produce about 0.2 g of CaO sample. The basicity of CaO nanoparticles was determined via back-titration method. For this purpose, CaO (100 mg) was dissolved in 10 mL of distilled water. After left for 24 hours, the slurry was obtained and then centrifuged. Neutralization of the resulting solution was performed using 0.05 M HCl (10 mL). Finally, titration with phenolphthalein as an indicator was carried out using NaOH (0.02 M) for the remaining acid (Yacob and Sulaiman, 2012). 2.3 Catalysts Characterizations The prepared CaO samples were characterized by using thermo- gravimetric analysis–di�erential thermal analysis (TGA-DTA), Fourier transform infrared (FTIR), X-ray di�raction (XRD), �eld emission scanning electron microscopy (FESEM), energy disper- sive X-ray (EDX) and nitrogen adsorption analysis (NA). The decomposition of CaCO3 was studied from TGA-DTA analysis using Mettler-Toledo Q100 instrument. About 15 mg sample was placed in a ceramic crucible and heated at temperature of 60 to 1000 ºC at 15 ºC/min with the �ow rate 50 mL/min of nitrogen gas. TGA analysis was performed to con�rm the optimum ac- tivation temperature in the preparation of CaO. Next, Fourier Transform Infrared Spectroscopy (FTIR) technique (wavenumber from 4000 to 400 cm−1) from Shimadzu 8300 was used to identify the functional groups (CM-CaCO3 and CaO samples). XRD anal- ysis was carried out to examine the crystallinity degree, crystal structure and crystallite size of CaCO3 and the prepared CaO samples. The XRD di�ractograms were obtained on a Siemens D5000 powder instrument using Cu-K� radiation (� = 0.15148 nm; kV = 40; mA = 40) with the 2� range from 10° to 90°. Monosorb Surface Area Analyzer model was used to evalu- ate the surface area of the prepared CaO samples. Prior to the analysis, powder sample (0.1 g) was degassed at 120 °C for 2 hours by vacuum pump to cool down the sample at room tem- perature. This treatment was performed to remove adsorbed gases and dead space. Besides, FESEM was used to examine the surface morphology, particles size and shape on the surface of CaO samples via Zeiss Supra 35 VP scanning electron micro- scope. The CaO samples were placed on the carbon dual-sided tape aluminum stub in a small vacuum chamber. All the CaO samples were coated with gold before the FESEM analysis. The elemental composition of the samples was con�rmed through EDX analysis. 2.4 Catalytic Transesteri�cation Reaction In the catalytic transesteri�cation reaction, the prepared CaO (0.1 g) together with 15.0 g of methanol and 10.0 g of rice bran oil were added into a two-neck round bottle �ask. The mixture was re�uxed at 65 ± 5 °C for 30 min, followed by cooling process at ambient temperature. The mixture was then centrifuged at 5000 rpm for 10 min to separate the solid catalyst from the solution. Three layers were obtained which consisted of an excess of methanol (top layer), a biodiesel (middle layer) and CaO with glycerol (bottom layer). The �rst and second layers were collected and placed into a separating funnel in order to separate the biodiesel and methanol. The biodiesel was collected for further characterization. 2.5 Product Analysis The quantitative production of biodiesel was identi�ed by nu- clear magnetic resonance (NMR). Methyl esters derived from the transesteri�cation reaction were analyzed by 1H NMR in CDCl3 using TMS as internal standard. The ratio between the peak of 3.6 ppm from methoxyl groups of methyl esters and 2.3 ppm from �-carbon CH2 groups of all fatty acid derivatives was used to calculate the percentage yield of methyl ester. Mean- while, the chemical composition of volatile and its abundance of biodiesel produced was determined using gas chromatogra- phy (GC) recorded from Hewlett Packard Gas Chromatography model 6890. Helium gas was used as the mobile phase and column DB-Wax with speci�cation 0.25 �m thicknesses, 30 m length and 0.20 mm internal diameter as the stationary phase with Flame Ionization Detector (FID). The dilution of biodiesel to n-hexane was 1:5 mL. The injector temperature rate was set at 40°C/5 min and the detector temperature was �xed at 300 °C for 15 minutes. The temperature was programmed at 5°C/min and the �ow rate was 10 mL/min. For this product analysis, approximately 1 �L of this mixture was injected into the GC. © 2020 The Authors. Page 63 of 69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 3. RESULTS AND DISCUSSION 3.1 Catalysts Characterizations 3.1.1 Thermogravimetric Analysis–Di�erential Thermal Analysis (TGA-DTA) In the preparation of CaO samples, thermogram TGA-DTA for the optimum activation temperature was identi�ed in the decom- position of CaCO3. Figure 1 illustrates the percentage weight loss for the decomposition of CaCO3 at di�erent temperature regions. Based on Figure 1, there are four major weight loss that occurred from the decomposition of CaCO3 to CaO at 60 to 700 °C. The �rst region occurred at temperature range of 60 to 100 °C was 1.6%. This occurrence was related to the removal of physically adsorbed water at CaCO3 surface. The second region showed that the percentage weight loss occurred at 100 to 250 °C was 1.3% due to the loss of hydroxyl groups on the surface that attached to Ca2+. Besides, the third region indicated the weight loss that occur at 250 to 600 °C was 1.4% due to the loss of carbonate group from CaCO3. The major weight loss occurred at 600 to 700 °C about 3.4% was related to the decomposition of calcium carbonate, CaCO3 to calcium oxide, CaO as in good agreement with Kristl et al. (2019). This weight loss implied the beginning formation of surface modi�ed CaO from removal of carbon dioxide, CO2 as the by-product. As shown in Figure 1, it could be inferred that decomposition of CaCO3 to CaO occurred at temperature higher than 600 °C. Therefore, as the sample weight remained constant after 700 °C, this temperature was considered suitable for complete decomposition of CaCO3 into CaO. Figure 1. TGA-DTA pro�le of CaCO3 sample 3.1.2 Fourier Transform Infrared (FTIR) Analysis Figure 4 illustrates the FTIR spectra for all prepared CaO samples calcined at temperatures of 100 to 800 °C. The peak at 3640 cm−1 demonstrates that O-H bond stretching vibration at surface water attached to Ca2+. As the temperature was increased from 100 to 800 °C, the band at 3640 cm−1 becomes smaller and disappeared. This indicated that the prepared CaO-700 did not contain water. This is in accordance with TGA-DTA data where the percentage weight loss occurred at temperature of 100 to 250 °C was most probably related with the loss of hydroxyl group at surface that attached to Ca2+. The minor bands at 2920 cm−1 and 2870 cm−1 were corresponded to the C=O bond stretching vibration from carbonate ion. The thin and intense band at 1796 cm−1 was also associated to the carbonate C=O bond. As increasing the temperature from 100 to 800 °C, the peak became smaller and disappeared due to the loss of C=O bond from the formation of CaO. Besides, the very strong bands at 1400 cm−1, 870 cm−1 and 848 cm−1 were related to the three di�erent elongation modes of C-O bond bending vibration. The peak at 2513 cm−1 shows the harmonic vibration of these elongation modes for C-O bond bending vibration. Figure 2. FTIR spectra of prepared CaO samples at various calcination temperatures of (a) CaO-100 at 100 ºC, b) CaO-200 at 200 ºC, (c) CaO-300 at 300 ºC, (d) CaO-400 at 400 ºC, (e) CaO-500 at 500 ºC, (f ) CaO-600 at 600 ºC, (g) CaO-700 at 700 ºC, and (h) CaO-800 at 800 ºC 3.1.3 X-ray Di�raction (XRD) Analysis Figure 3 shows the XRD di�ractograms for all prepared CaO samples at di�erent calcination temperatures from 100 to 700°C, while Table 1 represents XRD peaks assignment for CaO-600 and CaO-700. In this study, the temperature for decomposition of CaCO3 to CaO was determined by referring to the TGA-DTA and FTIR data which shows the optimum temperature of forming CaO started at 600°C and above. Based on Figure 2, as the temper- ature increased, the hexagonal of Ca(OH)2 peaks became smaller and the cubic CaO crystal started to appear. Finally, at 700°C, all the rhombohedral CaCO3 and hexagonal Ca(OH)2 totally disap- peared and only cubic CaO was detected. This was probably due to the sintering e�ect which changes the sample characteristic and hydroxides group have been eliminated from the sample, thus completely converted to CaO (Li et al., 2020). Furthermore, the crystallite size for the prepared CaO nanoparticles was cal- culated using Sherrer’s equation. The prepared surface modi�ed CaO was truly at nano size as in accordance with (Duan et al., 2007). From the calculation, it was found that CaO-700 was completely in cubic crystal structure with crystallite size of 38 nm. 3.1.4 Nitrogen Adsorption Analysis (NA) The speci�c BET surface area, SBET of CaO samples at di�er- ent calcination temperatures are listed in Table 2. The SBET shows an increasing pattern of CaO samples as the temperature increased from 100 to 700 ºC. The highest SBET obtained was CaO-700 with 11.5 m2g−1. The increased surface area could be © 2020 The Authors. Page 64 of 69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 Table 1. XRD peaks assignment for CaO-600 and CaO-700 Sample Angle, d (Å) d (Å) Miller Peaks 2� reference index, hkl Assignment hkl CaO-600 29.46 3.03 3.02 104 Rhombohedral 32.23 2.77 2.78 111 Cubic 37.36 2.41 2.41 200 Cubic 53.88 1.7 1.7 220 Cubic 64.21 1.45 1.45 311 Cubic 67.47 1.39 1.39 222 Cubic 79.78 1.2 1.2 400 Cubic CaO-700 32.26 2.77 2.78 111 Cubic 37.41 2.4 2.41 200 Cubic 53.86 1.7 1.7 220 Cubic 64.11 1.45 1.45 311 Cubic 67.39 1.39 1.39 222 Cubic 79.71 1.2 1.2 400 Cubic Figure 3. XRD di�ractograms of prepared CaO samples at various calcination temperatures of (a) CaO-100 at 100 ºC, b) CaO-200 at 200 ºC, (c) CaO-300 at 300 ºC, (d) CaO-400 at 400 ºC, (e) CaO-500 at 500 ºC, (f ) CaO-600 at 600 ºC, (g) CaO-700 at 700 ºC, and (h) CaO-800 at 800 ºC explained by the decomposition of CaCO3 to CaO and CO2 at higher calcination temperature. This treatment subsequently created defect sites as a cavity of prepared CaO to give the in- crement of its catalyst surface area. As the temperature reached at 800 °C, the SBET slightly decreased due to the sintering e�ect and particle agglomeration at high temperature. Similar �nding was reported previously (Hipólito and Martínez, 2020). 3.1.5 Field Emission Scanning Electron Microscopy- En- ergy Dispersive X-ray (FESEM-EDX) The structural changes in CM-CaCO3 during modi�cation was studied by using FESEM micrographs as illustrated in Figure 4 (a). The results demonstrated that CM-CaCO3 was a mixture of bulky particles which had oval shape agglomerates with each other. The morphology of CaO-700 is illustrated in Figure 4(b). The Table 2. The speci�c BET surface area, SBET of the prepared CaO calcined at various temperatures Sample Speci�c BET Surface Area, SBET (m2g−1) CaO-100 7.9 CaO-200 9 CaO-300 10.4 CaO-400 10.6 CaO-500 10.7 CaO-600 11 CaO-700 11.5 CaO-800 10.6 properties of the resulting modi�ed CaO samples were a�ected by the calcination temperature of CaCO3. It was found that the large pores were present between CaO particles that bond with each other. A FESEM image for CaO-700 showed the spherical particles coagulated to form agglomerates. Besides, Figure 5 (a) and (b) show the elemental composition by EDX analysis in CM-CaCO3 and CaO-700, respectively. It was found that CM- CaCO3 contained 19.88% weight percentage of carbon, 46.29% of oxygen and 33.83% of calcium, while CaO-700 contained 53.56% of oxygen and 46.44% of calcium. 3.1.6 Basicity of Calcium Oxide Nanoparticles The basicity of the catalyst is most signi�cant because this site would a�ect the chemical reactions. Thus, back titration method was performed to determine the basicity of the CaO nanoparti- cles. The basicity of the prepared CaO was correlated with tem- perature for decomposition of CM-CaCO3. In the back-titration method, distilled water was added to CaO and left for 24 hours © 2020 The Authors. Page 65 of 69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 Figure 4. FESEM images of (a) CM-CaCO3 (25kX); (b) CaO-700 (25kX) Figure 5. EDX elemental analysis for (a) CM-CaCO3; (b) CaO-700 to make the reaction to occur. Then, the H+ from water was adsorbed by lone pair of oxygen from CaO surface which corre- sponds to the amount of basic site (Eq. 1). The desired species, OH− was obtained by �ltering the slurry of extracted proton in CaO. Next, in the neutralization step, the OH− in clear solution reacted with the HCl to produce water and chloride ion, Cl− (Eq. 2). While in back titration step, the chloride ion, Cl− was further reacted with sodium hydroxide, NaOH and phenolphthalein in- dicator was used to detect the presence of OH− at the end of the reaction by giving pink color solution (Eq. 3). Figure 6 shows the basicity of the prepared CaO samples at di�erent calcination temperatures. Ca-O + H+⋯⋯OH− ⟶ Ca-O⋯⋯ H+ + OH− (1) OH− + HCl ⟶ H2O + Cl− (2) Cl− + NaOH ⟶ NaCl + OH− (3) Figure 6 shows that higher calcinations temperature gave the higher basicity which achieved maximum value at 700 °C. At lower temperature, the CaO nanoparticles surface was mostly covered with the OH centres, thus decreased the basicity. By increasing the temperature, more O2− centres started to develop, hence gave a higher basicity. This data is in good agreement with FTIR study that indicated the O-H bonds started to diminish at higher temperature of activation. In a previous study by Yacob et al. (2010), this �nding was also in accordance to that used MgO catalyst. It was proven that the basic sites of MgO was detected if the calcinations temperature was above 600 °C which was no free OH− groups detected by FTIR. Furthermore, basicity of CaO slightly decreased as the temperature reached 800 °C. The fracture of CaO molecular framework and the breaking of crystal structure can describe these results. Moreover, this graph proved that the highest basicity was obtained by CaO-700 sample which about 1.959 mmol/g. Based on the higher amount of basicity, the prepared CaO-700 was selected as heterogeneous base catalyst for the transesteri�cation of rice bran oil to biodiesel. Figure 6. Basicity of the prepared CaO samples at di�erent calcination temperatures 3.2 Biodiesel Analysis 3.2.1 Nuclear Magnetic Resonance (NMR) NMR is an important analytical technique that is used to deter- mine the quantitative production of biodiesel and the fatty acids mainly the common unsaturated fatty acids such as oleic and linoleic acids (Mantovani et al., 2020). From the previous studies, 1H NMR spectra had been interpreted for soybean oil which were 0.8 ppm related to terminal methyl hydrogen, a strong signal at 1.3 ppm indicates the methylenes of carbon chain, a multiplet signal at 1.6 ppm indicates the �-carbonyl methylenes, a triplet signal at 2.3 ppm related to �-carbonyl methylenes, 3.6 ppm from methoxy group and signal associated to unsaturation at 2.0 ppm, 2.8 ppm and 5.3 ppm indicates to allylic, bis-allylic and ole�nic hydrogen respectively (Atabani et al., 2019). The higher conver- sion of biodiesel was identi�ed if no signal appeared between 4.0 ppm to 5.2 ppm because H-1 and H-3 peaks (refer Figure 7) were corresponded to proton attached at glycerol carbons. Figure 7 shows the transesteri�cation process for biodiesel. Figure 7. Transesteri�cation process for biodiesel Figure 8 illustrates 1H NMR spectra of rice bran oil sample, while Figure 9 and Table 3 demonstrate the 1H NMR spectra and peaks assignment for the prepared biodiesel with di�erent times of reaction, respectively. As shown in Figure 8, there was no peak observed at 3.6 ppm that is an important indicator for presence of biodiesel samples. After the transesteri�cation reaction occurred, the peak at 3.6 ppm was determined due to the methoxyl group. The H-1 peak was observed at 4.096 ppm to 4.141 ppm and the H-3 peak was determined at 4.262 ppm to 4.302 ppm from the spectrum shown in Figure 9. In addition, Figure 9 illustrates that peak at 3.6 ppm appeared in all samples of biodiesel due to the © 2020 The Authors. Page 66 of 69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 methoxyl group (-O-CH3) present in the samples. The small H-1 and H-3 peaks at 4.0 ppm to 5.2 ppm which corresponded to protons attached at glycerol carbons can be seen at the reaction of 30 minutes until 150 minutes. Then, when the times of reaction increased, this peak was slightly disappeared due to the higher conversion for biodiesel production. As explained by Yoo et al. (2010), as transesteri�cation re- action proceeded, H-1, H-2 and H-3 would shift toward higher �eld as a result of the loss of high electron density of the acyl group, while the proton of acyl group could not shift when one or two of acyl groups migrated from triglycerides (TGs), yield- ing sn-diglycerides (sn-DGs) or sn-monoglycerides (sn-MGs). The proton of acyl groups resonates at 0.8-2.9 ppm in TGs (Yoo et al., 2010). Besides, the ratio between the peak of 3.6 ppm from methoxyl groups of methyl esters and 2.3 ppm from �-carbon CH2 groups of all fatty acid derivatives was calculated for the percentage yield of methyl ester (Shirley and Alesandro, 2008). From the calculation, CaO-700 produced 89.0% methyl esters or biodiesel from rice bran oil. Thus, NMR analysis proved that biodiesel was successfully prepared from single step transesteri- �cation of rice bran oil using the prepared CaO-700 catalyst. Figure 8. 1H NMR spectrum of rice bran oil sample Table 3. 1H NMR peaks assignment for biodiesel at di�erent reaction times Sample 1H NMR regions (ppm) Peaks assignment Biodiesel 0.850 – 0.900 -(CH2)n-CH3 1.230 – 1.290 -(CH2)n- 1.580 – 1.630 CH3O2-C-CH2-CH2- 1.960 – 2.060 -CH2-CH2-CH=CH2 2.270 – 2.300 CH3O2-C-CH2- 2.740 – 2.790 -CH=CH-CH2-CH=CH- 3.658 -O-CH3 4.100 – 4.160 -H2COOC(CH2)n-CH3 4.250 – 4.320 -H2COOC(CH2)n-CH3 5.240 – 5.380 -CH=CH- Figure 9. 1H NMR spectra of the prepared biodiesel at di�erent reaction times 3.2.2 Gas Chromatography – Flame Ionization Detector (GC-FID) Figure 10 illustrates the GC-FID chromatogram of the prepared biodiesel at 60 minutes, while Table 4 shows peaks assignment for retention times from GC-FID chromatogram for the pre- pared biodiesel. It was found that there were peaks due to the appearances of methyl laurate, methyl tetradecanoate, methyl palmitate, methyl palmitoleate, methyl stearate, methyl oleate, methyl linoleate and methyl tetracosanoate. Based on Table 4, it was found that the most methyl esters that present in the produced biodiesel were methyl tetradecanoate, methyl palmi- tate and methyl oleate. Thus, GC-FID analysis proved that the biodiesel was successfully prepared by single step transesteri�- cation of rice bran oil with methanol and the prepared CaO-700 catalyst. Figure 10. GC-FID chromatogram of prepared biodiesel at 60 minutes © 2020 The Authors. Page 67 of 69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 Table 4. Peak assignment for type of fatty acid methyl ester towards retention times from GC-FID chromatogram Type of fatty acid Retention Times, methyl ester min Methyl laurate 14.9 Methyl tetradecanoate 17.5 Methyl palmitate 19.8 Methyl palmitoleate 19.9 Methyl stearate 21.7 Methyl oleate 22 Methyl linoleate 23.4 Methyl tetracosanoate 27.5 3.3 Catalytic Activity 3.3.1 E�ect of Catalyst Loading The e�ect of catalyst loading towards production of biodiesel using di�erent loadings of catalyst which were 0.5% to 2.5% with 60 minutes reaction times as illustrated in Figure 11. From Figure 11, it shows that 1.0% catalyst loading gave the highest percent- age of conversion for biodiesel yield with 89.0%. For 0.5% catalyst loading, the percentage biodiesel production only gave 60.3%, indicating small surface area of the sample. Moreover, incom- plete production of FAME was due to an insu�cient amount of catalyst as reported by (Olutoye et al., 2016). As increasing the catalyst loading to 1.5% in the reaction, the percentage of biodiesel yield decreased due to its deactivation. The resistance produced by mixing reactant, product and solid catalyst could be the main reason of these results. Such �nding was in good agreement with Sulaiman et al. (2020) where it can inhibit the production of biodiesel. Figure 11. The percentage conversion for biodiesel with di�erent percentage catalyst loadings over CaO-700 3.3.2 E�ect of Reaction Times Figure 12 shows the e�ect of reaction times towards the produc- tion of biodiesel. Interestingly, it was found that the conversion for biodiesel was increased with increasing the reaction times from 30 to 210 minutes and gave 100% conversion of rice bran oil at 210 minutes. This result showed that the low production of biodiesel was found in 30 minutes. Sulaiman et al. (2020) have reported that it is due to the presence of the heterogeneous cat- alytic mass transfer system. When the reaction time increased to 60 minutes, it can provide more contact times between reactants and catalysts to give high frequent collision. Therefore, high FAME content in the transesteri�cation process can be achieved using an appropriate reaction time while forming adequate quan- tities of these triglyceride derivatives. Figure 12. The percentage conversion for biodiesel with di�erent reaction times over CaO-700 4. CONCLUSIONS The CaO nanoparticles was successfully prepared from commer- cial calcium carbonate, CM-CaCO3 by thermal decomposition method. The TGA-DTA data showed that there was no more weight loss occurs after 700°C and it veri�ed that CaCO3 was completely decomposed into CaO. The FTIR results supported the TGA-DTA data which indicated the formation of CaO from the decomposition of CaCO3 occurred at 500 to 600°C and com- pletely become CaO at 700°C. Besides, the XRD results con�rmed that all the rhombohedral CaCO3 and hexagonal Ca(OH)2 were totally disappeared and only cubic CaO existed at 700°C. The crystallite size of prepared CaO-700 nanoparticles was 38 nm that calculated from Sherrer’s equation. It veri�ed that CaO-700 was completely in cubic nanocrystal structure. For nitrogen ad- sorption analysis, CaO-700 gave the highest BET surface area (11.5 m2g−1), where catalytic reactions could e�ectively work at the surface-active sites. In addition, CaO-700 gave the highest ba- sicity with 1.959 mmol/g in order to achieve maximum biodiesel production. In the biodiesel analysis, NMR data con�rmed the presence of methoxyl group (-O-CH3). The percentage biodiesel production that calculated from the ratio between the peak of 3.6 ppm from methoxyl groups of methyl esters and 2.3 ppm from �-carbon CH2 groups of all fatty acid derivatives found that CaO-700 produced 89.0% of biodiesel at 60 minutes. GC-FID analysis veri�ed that the biodiesel was successfully prepared by single step transesteri�cation of rice bran oil with methanol and prepared CaO-700 as a catalyst with the presence of methyl laurate, methyl tetradecanoate, methyl palmitate, methyl palmi- toleate, methyl stearate, methyl oleate, methyl linoleate and methyl tetracosanoate. © 2020 The Authors. Page 68 of 69 Sulaiman et. al. Science and Technology Indonesia, 5 (2020) 62-69 5. ACKNOWLEDGEMENT The authors would like to thank the Ministry of Higher Educa- tion (MOHE), Malaysia and Universiti Teknologi Malaysia (UTM) for their �nancial funding through UTM Transdisciplinary Re- search Grant (Cost Center No. (Q.J130000.3554.07G57). N.F. Sulaiman thanks UTM for the PDRU Grant Vote No 04E70. REFERENCES Atabani, A. E., S. Shobana, M. N. Mohammed, G. Uğuz, G. Kumar, S. Arvindnarayan, M. Aslam, and A. H. Al-Muhtaseb (2019). 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Synthesis of biodiesel from rapeseed oil using supercritical methanol with metal oxide catalysts. Bioresource technology, 101(22); 8686–8689 © 2020 The Authors. Page 69 of 69 INTRODUCTION EXPERIMENTAL SECTION Materials Catalysts Preparation Catalysts Characterizations Catalytic Transesterification Reaction Product Analysis RESULTS AND DISCUSSION Catalysts Characterizations Thermogravimetric Analysis–Differential Thermal Analysis (TGA-DTA) Fourier Transform Infrared (FTIR) Analysis X-ray Diffraction (XRD) Analysis Nitrogen Adsorption Analysis (NA) Field Emission Scanning Electron Microscopy- Energy Dispersive X-ray (FESEM-EDX) Basicity of Calcium Oxide Nanoparticles Biodiesel Analysis Nuclear Magnetic Resonance (NMR) Gas Chromatography – Flame Ionization Detector (GC-FID) Catalytic Activity Effect of Catalyst Loading Effect of Reaction Times CONCLUSIONS ACKNOWLEDGEMENT