Study on Activity of Activated Carbon/Fe3O4 Fused SiO2 Impregnated by CaO as Magnetic Recoverable Heterogeneous Catalyst to Produce Biodiesel from Cooked Oil Yudha Ramanda1*, Kevin Thomas1, Eko Sri Kunarti1 1Department
of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Yogyakarta 55281 Indonesia *e-mail:
[email protected]
ABSTRACT Synthesis of activated carbon/Fe3O4 fused SiO2 impregnated by CaO (AC/M@S/CaO) and study of its activity as a heterogeneous catalyst had been done. The Fe3O4 (M) nanoparticle had been prepared by sono-coprecipitation method. The Fe3O4 nanoparticle had been adsorbed onto activated carbon (AC) surface. To prevent Fe3O4 desorption, the AC/M nanocomposite had been fused by SiO2 (S) under ultrasonic irradiation. The nanocomposite matrix had been impregnated by CaO to make a basic heterogeneous catalyst. All materials were characterized by Fourier transform infra-red spectrophotometry (FTIR). Fe3O4 were also characterized by transmission electron microscopy (TEM). The activity of AC/M@S/CaO had been studied by sonochemical method. The product of transesterification had been analysed by gas chromatography – mass spectroscopy (GCMS). The TEM images showed the nanoparticle structure of Fe3O4. The FTIR spectra were confirmed the presence of AC/M@S/CaO. The study of the activity was conducted by sonicating cooked oil and methanol in the presence of heterogeneous catalyst. The data was proved that the optimum time for sonication was 30 minutes and optimum catalyst amount was 50 mg. The GC-MS spectra were confirmed that the product was Fatty Acid Methyl Esters (FAMEs), the components of biodiesel. Keywords: AC/M@S/CaO, Biodiesel, FAMEs, Heterogeneous catalyst, Sonochemical method INTISARI Sintesis karbon aktif/Fe3O4 terlapisi SiO2 terimpregnasi CaO (AC/M@S/CaO) dan kajian aktivitasnya sebagai katalis heterogen telah dilakukan. Nanopartikel Fe3O4 (M) dipreparasi melalui metode sono-koprepitasi. Nanopartikel Fe3O4 yang terbentuk lalu diadsorpsi pada permukaan karbon aktif (AC). Untuk menghambat pelepasan Fe3O4, nanokomposit AC/M dilapisi dengan SiO2(S) di bawah radiasi ultrasonik. Matriks nanokomposit tersebut diimpregnasi dengan CaO untuk membentuk katalis heterogen yang bersifat basa. Semua material dikarakterisasi menggunakan spektrofotometeri infra-merah transformasi Fourier (FTIR). Fe3O4 juga dikarakterisasi menggunakan mikroskop transmisi elektron (TEM). Aktivitas dari AC/M@S/CaO dikaji menggunakan metode sonokimia. Produk hasil transesterifikasi telah dianalisis menggunakan gas kromatografi – spektroskopi massa (GC-MS). Hasil citra TEM menunjukkan bentuk nanopartikel dari material Fe3O4. Spektra FTIR mengkonfirmasi keberadaan komposit AC/M@S/CaO. Uji aktivitas dilakukan dengan sonikasi sonikasi optimum adalah 30 menit dan massa optimum katalis adalah 50 mg. Hasil kromatogram GC dan spektra MS menunjukkan produk adalah metil ester asam lemak (FAMEs), komponen dari biodiesel . Kata Kunci: AC/M@S/CaO, Biodiesel, FAME, Katalis heterogen, Metode sonokimia
INTRODUCTION In this decade, green chemistry development leads researchers to develop new techniques to reuse natural resource and limit the production of waste. Every day food industry releases a tons of cooked oil waste. In the other hand, we need tons supplies of energy. This situation gives the researcher a background to develop a simple way to make cooked oil to be a useable energy. [1] The previous researches revealed that the effective way to transform cooked oil into fatty acid methyl esters (FAMEs) which can be used as a biodiesel. [2-4] However, those researches used homogeneous catalyst such as strong acid and strong base to get high activity. This route of synthesis produces a new acid-base waste, thus is less eco-friendly. The other researchers used heterogeneous catalyst to make FAMEs from cooked oil to produce less waste. [5] The heterogeneous catalysts are easy to recover and can be used again in another catalytic cycle. The big issue in this method is how to recover the heterogeneous catalyst. Another consequence from this method is a lower catalytic activity compared to homogenous catalyst. [6,7] This research develops a nanocomposite that has a good magnetic property. This magnetic property made the heterogeneous catalyst has a magnetic recoverability that resolves the recovery issue. The nanotechnology embedded in this material enhance the catalytic activity. EXPERIMENTAL SECTION Materials Cooked oils were brought from food industrial waste. Technical grade methanol and the other synthesis grade chemical reagents were purchased from Sigma-Aldrich. Instruments FTIR spectra were recorded on a Shimadzu Prestige-21 FT-IR spectrophotometer with KBr pellets method. GC chromatogram and MS spectra were recorded on a Shimadzu QP-2010S gas chromatography – mass spectroscopy. Sonication run on a Bransonic CPX2800H
ultrasonic cleanser. TEM images were recorded on a JEOL JEM-1400 transmission electron microscopy. Procedures Preparation of Fe3O4 nanoparticle As much as 6.02 g of FeCl3•6H2O and 4.08 g of FeSO4•7H2O soaked into 60 mL of ion free water and then aerated by N2 along synthesis. The solution stirred and added by 25 % NH3 solution until the pH was 10 and then the mixture was sonicated for an hour. After that, the solid was separated by external magnet and washed until the pH was 7. The solid was soaked into 100 mL of Sodium Citrate 0.2 M and soaked for overnight. After that, the solid was washed until the pH was 7 and dried for overnight. The solid prepared was characterized by FTIR and TEM. Adsorption of Fe3O4 nanoparticle onto activated carbon As much as 1.00 g of Fe3O4 was soaked into 100 mL of technical grade methanol. The solution was stirred and added 5.00 g of activated carbon. The mixture was sonicated for three hours. After that, as much as 1 mL Tetraethyl orthosilicate (TEOS) 98% solution was added and sonicated for more three hours. After that, the solid was separated by external magnet and washed until the pH was 7. Impregnation of CaO onto matrix As much as 1.00 g of matrix was soaked into 100 mL of distillated water. The mixture as stirred for an hour and then as much as 1.00 g of CaCO3 was added to the mixture. The mixture was sonicated for three hours and settled overnight. After that the solid was separated by external magnet and calcinated over 300⁰C for three hours. Study of catalytic activity An amount of catalyst was soaked into 50 mL of technical grade methanol. The mixture was added by 1.00 g of cooked oil then sonicated for several minutes. After that, the mixture was added by 30 mL distillate water. The solid was separated and dried for several hours.
RESULT AND DISCUSSION The transformation of cooked oil to biodiesel required transesterification reaction that change triglyceride into FAMEs. This is the transesterification reaction:
The reaction is reversible and runs slowly. To accelerate the chemical equilibrium, acid or basic catalyst can be added. In this research, the basic catalyst is activated carbon/Fe3O4 fused SiO2 impregnated by CaO. Preparation of Fe3O4 nanoparticle Catalyst in this research was developed to have a magnetic property by embedded Fe3O4 nanoparticle. The Fe3O4 was prepared by added NH3 to stoichiometric solution of Fe2+/Fe3+ (1:2). This results a solid magnetite by this reaction:
This reaction is reversible and more base are added will drive to form solid magnetite. The inert atmosphere like N2 prevented oxidation of Fe2+. Sodium citrate was added as capping agent to prevent crystal growth and produce nanomaterial. TEM images (Figure 1) confirmed the nanostructure of the magnetite with an average diameter around 20 nm. Impregnated of CaO and Fe3O4 onto activated carbon (AC) The Fe3O4 was adsorbed onto AC surface and then fused with silica to prevent Fe3O4 desorption that cause loss of magnetic recoverability. CaO was impregnated by impregnating CaCO3 onto AC surface and calcinating to release CO2 and form CaO as a solid basic catalyst. The presences of Fe3O4 and CaO were revealed by FTIR spectra (Figure 2). The FTIR spectra gives a trend of the composite where the spectrum of the
catalysts is the summation of Fe3O4, AC, and CaO spectra. The adsorption of CaO around 1500 cm-1 appeared to the catalyst spectrum. Magnetite adsorption around 600 cm-1 was also appear in the catalyst spectra. Those facts proved the presence of the composite. The magnetite embedded onto the catalyst is a nanomaterial, thus this composite is specific to a nanocomposite material. The study of activity At the first time, the amount of catalyst was variated to understand the effect of catalyst amount. The sonication time was set to 10 minutes The diagram (Figure 3) shows that addition of more catalyst enhanced the product mass up to 50 mg. after that, the diagram shows optimum amount trend. So, the optimum amount of catalyst in this system was 50 mg. After that, the sonication optimum time was revealed by sonication time variation. The amount of catalyst was set to the optimum amount. The diagram (Figure 4) shows the optimum trend and the reaction is optimum in 30 minutes. After 30 minutes, the chemical equilibrium was reached and neither catalyst amount nor sonication time will enhance the mass of product. The next study was the magnetic recoverability and the reusability of the catalyst. The sonication time and the catalyst amount was set to optimum. The diagram (Figure 5) shows that fused SiO2 activated carbon/Fe3O4 impregnated by CaO have a very good reusability as seen from % yields diagram and have very good magnetic recoverability as seen from % recovery diagram. After 10 catalytic cycles, % yields and % recovery only decrease up to 20 %. Because this system only used a very small amount of catalyst, those data proved that this material have a good magnetic recoverability and reusability.
Figure 1. TEM images of Magnetite
Figure 2. FTIR spectra
Figure 3. The effect of catalyst amount
Figure 4. The effect of sonication time
Figure 5. Magnetic recoverability and reusability Transesterification product All esterification product was extracted by distillate water and analysed by GC-MS. The chromatogram shows five major peaks. The MS spectra confirmed that those peaks are methyl myristate, methyl palmitate, methyl linoleate, methyl oleate, and methyl stearate, which were FAMEs, the component of biodiesel. CONCLUSION The synthesis of activated carbon/Fe3O4 fused SiO2 impregnated by CaO has been done. Instrumental analysis proved the appearance of AC, Fe3O4, and CaO. The study on activity revealed that the activity of catalyst increase with increase of catalyst amount up to 5518.75 % product relative mass on optimum amount compare to non-catalyzed product. The optimum catalyst amount is 50 mg and optimum sonication time is 30 minutes. The recoverability shows that 82.14 % of catalyst is recovered after 10 catalytic cycles. The reusability shows a good activity; the catalyst gives 80.27 % yield after 10 catalytic cycles. Those properties show that activated carbon/Fe3O4 fused SiO2 impregnated by CaO can be a potential heterogeneous catalyst to produce biofuel from cooked oil.
ACKWOLEDMENT This research is held under supported by AKUGAMA scholarship (Beasiswa Alumni Kimia Universitas Gadjah Mada). REFERENCES 1. Vyas, A.P., Verma, J.L., Subrahmanyam, 2010, Fuel, 89, 1-9. 2. Hernando, J., Leton, P., Matia, M.P., Novella, J.L., Alvarez-Builla, J., 2007, Fuel, 86, 1641-1644. 3. Lam, M.K., Lee, K.T., Mohamed, A.R., 2010, Biotechnol. Adv., 28, 500-518. 4. Serio, M.D., Tesser, R., Domiccoli, M., Cammarota, F., Nastasi, M., Santacesaria, E., 2005, J. Mol. Catal. A: Chem., 239, 111-115. 5. Borges, M.E., Diaz, L., 2012, Renew. Sustainable Energy Rev., 16, 2839-2849. 6. Park, Y.M., Lee, D.W., Kim, D.K., Lee, J.S., Lee, K.W., 2008, Catal. Today, 131, 238-243. 7. Serio, M.D., Tesser, R., Pengmei, Lu, Santacesaria, E., 2008, Energy Fuels, 22, 207-217.
