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ScienceDirect Energy Procedia 79 (2015) 562 – 566

2015 International Conference on Alternative Energy in Developing Countries and Emerging Economies

The Application of Calcium Oxide and Magnesium Oxide from Natural Dolomitic Rock for Biodiesel Synthesis Achanai Buasria , Kanokphol Rochanakita, Wasupon Wongvitvichota, Uraiporn Masa-arda, Vorrada Loryuenyonga a

Department of Materials Science and Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom 73000, Thailand

Abstract The aim of this study was to analyze the catalytic performance of natural dolomitic rock as an environmentally friendly catalyst in the reaction of Jatropha Curcas oil with methanol under microwave-assisted transesterification. The dolomite was utilized as a source of calcium oxide (CaO) and magnesium oxide (MgO). The main characteristic of this rock is the high content of CaMg(CO3)2 which was transformed into CaO˜MgO mixed oxide by calcination. The activation method to improve the activity, basicity and stability of catalyst has been investigated. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption/desorption (BET) method. The effects of reaction variables such as reaction time, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated. The results indicated that the developed catalyst could also be reused feasibly up to three consecutive cycles. Overall, the potential of this low-cost heterogeneous base catalyst has been demonstrated for transesterification applications. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2015 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Organizing Committee of 2015 AEDCEE. Peer-review under responsibility of the Organizing Committee of 2015 AEDCEE

Keywords: biodiesel; natural dolomitic rock; CaO˜MgO mixed oxide; Jatropha Curcas oil

1. Introduction Biodiesel is renewable and environmentally friendly fuel which can be obtained by transesterification of vegetable oils or animal fats with methanol in the presence of both homogeneous and heterogeneous catalysts [1]. In the primary stage, the homogeneous catalysts were mentioned, where the high conversion

* Corresponding author. Tel.: +66-34-219-363; fax: +66-34-219-363. E-mail address: [email protected].

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Organizing Committee of 2015 AEDCEE doi:10.1016/j.egypro.2015.11.534

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of triglycerides (TG) into fat acid methyl esters (FAME) was achieved, but the post-treatment process to purify biodiesel was energy guzzling for the solubility of the homogeneous catalysts in the products. Then, the heterogeneous catalyst was developed, which simplified the transesterification by facilitating the separation and the purification, and it has been demonstrated to be more environmental [2]. Based-catalyzed transesterification reaction has been claimed to provide better conversion of vegetable oil to biodiesel compared with acid-catalyzed reaction. Dolomite is a type rock that can be found around the world which can be used as non-toxic base catalyst. Chemically, it consists of calcium carbonate (CaCO3), magnesium carbonate (MgCO3) and very small percentages of other compounds [3]. A review of temperature controlled experiments using fresh dolomite shows that basic calcium oxide (CaO) and magnesium oxide (MgO) are formed after the carbonate groups have decomposed. Dolomite is mainly used in agriculture and cement manufacturing. Its use as a catalyst in many processes such as gasification and reforming has attracted much attention, as it is cheap, has high basicity, and is environmentally friendly [4]. In this work, we have carried out transesterification using the natural dolomitic rock as an inexpensive and environment-friendly catalyst. The objective was to optimize the process for biodiesel production from Jatropha Curcas oil using renewable catalyst. A microwave-assisted production of biodiesel was applied in this research to expedite the chemical reaction and give a high product yields in a short time. The effects of reaction time, methanol/oil molar ratio, and catalyst loading were systematically investigated. 2. Materials and Methods Jatropha Curcas oil was purchased from Thai Physic Nut Oil Company Limited. The natural dolomitic rock was obtained from L.S.M. (1999) Company Limited. All chemicals were analytical-grade reagents (Merck). The CaO˜MgO mixed oxide catalysts were prepared by a calcination method. The dried dolomite was calcined at 900 qC in air atmosphere with a heating rate of 5 qC/min for 7 h. The solid result was crushed and sieved to pass 325-400 mesh screens. The products (25-35 ߤm) were obtained as white powder. The catalyst samples were stored in a desiccator that contains silica gel to remove the humidity (H2O) and carbon dioxide (CO2) of the residual desiccator atmosphere [5,6]. The derived catalyst was characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption/desorption (BET) method. The reactions were carried out in a 500 ml glass reactor equipped with condenser and mechanical stirrer at atmospheric pressure, placed inside a household microwave oven. The fixed 100 g of Jatropha Curcas oil and the desired amount of the derived catalysts were added to the reactor, and then the methanol was introduced to the oil at various methanol/oil molar ratios. The transesterification was operated with varied reaction time under microwave irradiation, and it was instantly stopped by rapid cooling in an ice bath. Composition of the FAME was analyzed with gas chromatograph-mass spectrometry (GC-MS) equipped with a flame ionization detector (FID). Yield of FAME was calculated by Equation (1): (1) where mi is the mass of internal standard added to the sample, Ai is the peak area of internal standard, mb is the mass of the biodiesel sample and Ab is the peak area of the biodiesel sample [7].

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3. Results and Discussion The dolomitic material is a double calcium and magnesium carbonate (CaMg(CO3)2), which when calcinated decomposes into CaO and MgO that are highly basic. XRD pattern was used to identify the crystallographic phase of calcined dolomite (Fig. 1). After the calcination step, the diffraction lines attributed of carbonate species disappear due to its liberation in the form of CO2, arising new diffraction lines with a lower intensity than raw dolomite which suggests a decrease of the particle size for calcined dolomite [8]. Thus, the diffraction lines located at 32, 37, 54 and 64q have been assigned to quicklime (CaO) and the diffraction lines located about 42 and 62q have been attributed to periclase (MgO). The morphology of calcined dolomite was evaluated by SEM (Fig. 1). The SEM image showed that calcined dolomite had a dense surface with heterogeneous distribution of particle sizes (irregular size) and smooth appearance.

Intensity (a.u.)

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Fig. 1. XRD pattern and SEM image of calcined dolomite at 900 qC during 7 h

The physical properties (surface area, mean pore diameter and pore volume) of the calcined dolomite are summarized in Table 1. The calcination process produces an increase of the specific surface area and a decrease of the particle size during the decarbonation process as revealed by XRD diffractograms and SEM micrographs [8,9]. Table 1. The physical properties of calcined dolomite catalyst Material

Surface Area (m2/g)

Pore Volume (cm3/g)

Mean Pore Diameter (Ao)

Calcined Dolomite

14.8

0.27

722

The yield of biodiesel was affected by reaction variables, such as reaction time, reaction temperature, alcohol/oil molar ratio, catalyst loading, speed of mixing, and reusability of catalyst. The reaction variables were associated with the type of catalysts used [10]. Therefore, the effect of reaction variables was studied in the presence of calcined dolomite catalyst. In the initial stages of the microwave-assisted transesterification reaction, production of biodiesel was rapid, and the rate diminished and finally reached equilibrium [7] in about 4 min (Fig. 2). This can be explained by that transesterification reaction between Jatropha Curcas oil and methanol is reversible, when the reaction time is long enough [6]. The lower methanol/oil ratios resulted in poor suspension of the slurry in the reacting solution, which possibly induced mass transfer problems thus resulting in lower activity. On the other hand and in accordance with reported literature, the activity steadily increased with higher methanol/oil molar ratios

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[11]. The FAME content increased significantly when the methanol/oil molar ratio was changed from 9 to 21. The high amount of methanol promoted the formation of methoxy species on the CaO surface, leading to a shift in the equilibrium in the forward direction, thus increasing the rate of conversion up to 95.88% (Fig. 2). 100

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Yield of FAME

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Fig. 2. Effect of reaction time and methanol/oil molar ratio on %yield of FAME

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Yield of FAME

In the absence of catalyst, there was no FAME formed in the reaction. A maximum conversion of 95.88% was obtained with CaO˜MgO mixed oxide catalysts loading of 4 wt% (Fig. 3). The lower yields at catalyst concentrations above 4 wt% were due to the formation of slurries which were too viscous for adequate mixing. This result implies that the transesterification of TG is strongly dependent on the amount of basic sites [12]. The reusability of the CaO˜MgO mixed oxide catalysts prepared at the optimum preparation conditions was investigated by carrying out subsequent reaction cycles. After 4 min of the reaction, the catalyst was separated from the reaction mixture by filtration followed by washing with methanol to remove any adsorbed stains. Afterwards it was dried at 80 °C in an oven for 12 h and was used again for second reaction cycle under the same reaction conditions as before. The results indicated that the yield decreased with the repeated use of the calcined dolomite catalyst and it exhibited poor catalytic activity after being used for more than two times. This deactivation was probably due to the structural changes leading to the failure to maintain the form of CaO or its transformation to other form such as Ca(OH) 2. This may also be due to the losses of some catalyst amount during the process of washing, filtration and calcination [7,13].

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Fig. 3. Effect of catalyst loading and reusability on %yield of FAME

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4. Summary The natural dolomitic rock has been successfully utilized as a renewable catalyst in the transesterification reaction of Jatropha Curcas oil with methanol. The experimental results show that derived catalyst had excellent activity and stability during reaction. The conversion of oil to FAME was optimized, under different reaction time, methanol/oil molar ratio, and catalyst loading. The optimum conditions, which yielded a conversion of oil of nearly 95% for activated dolomitic catalyst, were reaction time 4 min, methanol/oil molar ratio 18:1, and catalyst loading 4 wt%. The catalyst was used for 3 cycles and apparent low activity loss was observed. The physical and chemical properties of biodiesel produced conform to the available standards. Acknowledgements The authors acknowledge sincerely the Department of Materials Science and Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University and National Center of Excellence for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University for supporting and encouraging this investigation. References [1] Ilgen O. Reaction kinetics of dolomite catalyzed transesterification of canola oil and methanol. Fuel Process Technol 2012;95:62–6. [2] Niu SL, Huo MJ, Lu CM, Liu MQ, Li H. An investigation on the catalytic capacity of dolomite in transesterification and the calculation of kinetic parameters. Bioresour Technol 2014;158:74–80. [3] Nur ZAS, Taufiq-Yap YH, Nizah MFR, Teo SH, Syazwani ON, Islam A. Production of biodiesel from palm oil using modified Malaysian natural dolomites. Energy Convers Manage 2014;78:738–44. [4] Yoosuk B, Udomsap P, Puttasawat B. Hydration-dehydration technique for property and activity improvement of calcined natural dolomite in heterogeneous biodiesel production: Structural transformation aspect. Appl Catal A: Gen 2011;395:87–94. [5] Esipovich A, Danov S, Belousov A, Rogozhin A. Improving methods of CaO transesterification activity. J Mol Catal A: Chem 2014;395:225–33. [6] Buasri A, Chaiyut N, Loryuenyong V, Worawanitchaphong P, Trongyong S. Calcium oxide derived from waste shells of mussel, cockle, and scallop as the heterogeneous catalyst for biodiesel production. Sci World J 2013;2013:Article ID 460923. [7] Buasri A, Rattanapan T, Boonrin C, Wechayan C, Loryuenyong V. Oyster and Pyramidella shells as heterogeneous catalysts for the microwave-assisted biodiesel production from Jatropha curcas oil. J Chem 2015;2015:Article ID 578625. [8] Correia LM, Campelo NS, Novaes DS, Cavalcante Jr. CL, Cecilia JA, Rodríguez-Castellón E, Vieira RS. Characterization and application of dolomite as catalytic precursor for canola and sunflower oils for biodiesel production. Chem Eng J 2015;2695:35–43. [9] Ávila I, Crnkovie PM, Millioli FE. Methodology for the study of porosity in dolomite sulfation interrupted test. Quimic Nova 2010;33:1732–8. [10] Wei Z, Xu C, Li B. Application of waste eggshell as low-cost solid catalyst for biodiesel production. Bioresour Technol 2009;100:2883–5. [11] Salinas D, Araya P, Guerrero S. Study of potassium-supported TiO2 catalysts for the production of biodiesel. Appl Catal B: Environ vol. 2012;117-118:260–7. [12] Ngamcharussrivichai C, Totarat P, Bunyakiat K. Ca and Zn mixed oxide as a heterogeneous base catalyst for transesterification of palm kernel oil. Appl Catal A: Gen 2008;341:77–85. [13] Boro J, Thakur AJ, Deka D. Solid oxide derived from waste shells of Turbonilla striatula as a renewable catalyst for biodiesel production. Fuel Process Technol 2011;92:2061–7.