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Energy & Fuels 2007, 21, 3280–3283
Zeolite Y as a Heterogeneous Catalyst in Biodiesel Fuel Production from Used Vegetable Oil A. Brito, M. E. Borges,* and N. Otero Chemical Engineering Department, UniVersity of La Laguna, C/AVda. Astrofísico Fco. Sánchez s/n, Facultad de Química, 38200 La Laguna, Spain ReceiVed July 30, 2007. ReVised Manuscript ReceiVed September 4, 2007
Complete recycling of waste edible oil has recently attracted considerable attention as a worldwide social problem. Production of a biodiesel fuel from used vegetable oil is considered an important step in reducing and recycling waste oil. This technology employs used vegetable oil as a potential renewable alternative resource to fossil diesel fuel, and the transesterification reaction is the usual process to obtain biodiesel. The objective of this work is to study the transesterification of waste oil with methanol in the presence of several Y-type zeolites with different Al2O3 content. In this study, the reaction is carried out in a continuous tubular steel reactor using zeolite Y as catalyst, being tested at atmospheric pressure within a reactor temperature range of 200–476 °C and methanol/oil molar ratio of 6. The results show an important decrease of viscosity of the product obtained until values close to biodiesel specifications.
1. Introduction Complete recycling of waste edible oil has recently attracted considerable attention as a worldwide ecological issue. Production of biodiesel fuel from used vegetable oil is considered an important step in reducing and recycling this used oil. In this regard, several local governments have started collecting used melt-out oils from domestic consumption and have converted them to biodiesel fuel for public transport as an alternative to fossil diesel fuel .1–5 The main objective of the process of transformation of waste vegetable oil in biodiesel fuel is the reduction of its viscosity to values close to the origin fossil diesel oil, and transesterification reaction, defined as the substitution of the alcohol of an ester of an organic acid by a shorter chain alcohol, is the most used process to obtain a biodegradable and nontoxic biodiesel. The alcohols commonly used in the transesterification reaction are methanol and ethanol, but the latter gives more problems due to its water content. Compared to petroleum-based diesel, biodiesel has a more favorable combustion emission profile, such as low carbon monoxide, particulate matter, and unburned hydrocarbon emissions.6,7 Carbon dioxide produced by the combustion of biodiesel can be recycled by photosynthesis, thereby minimizing the impact of biodiesel combustion on the greenhouse effect. Biodiesel has a relatively high flash-point, which makes it less volatile and safer to transport or handle than petroleum diesel. * Corresponding author. E-mail:
[email protected]. (1) Tsai, W.; Chih-Chung, L.; Yeh, C. Renewable Sustainable Energy ReV. 2007, 11 (5), 838–857. (2) Canakci, M. Bioresour. Technol. 2007, 98, 183–190. (3) Leung, D.; Guo, Y. Fuel Process. Technol. 2006, 87 (10), 461– 472. (4) Wang, Y.; Ou, S.; Pengzhan, L.; Xue, F.; Tang, S. J. Mol. Catal. A: Chem. 2006, 252, 107–112. (5) Felizardo, P.; Correia, J.; Raposos, I.; Mendes, J.; Berkemeier, R.; Bordado, J. Waste Manage. 2006, 26, 487–494. (6) Agarwal, D.; Sinha, S.; Agarwal, A. Renewable Energy 2006, 31, 2356–2369. (7) Reyes, J.; Sepúlveda, M. Fuel 2006, 85, 1714–1719.
It has lubricating properties that can reduce engine wear and extend engine life.8 Many studies9–11 of alkali-catalyzed transesterification on the laboratory scale have been carried out, and this is the most frequently used process industrially. One limitation to the alkalicatalyzed process is its sensitivity to both water and free fatty acids. The use of waste cooking oil as a feedstock is of low cost, but usually, its level of free fatty acids is greater than 2 wt %. In this case, an acid-catalyzed system or heterogeneous catalysis would be preferable.11–15 A few studies have been reported using heterogeneous catalysis for oil transesterification reactions9,16–20 using both basic and acid solid catalysts. Heterogeneous catalysts can be easily removed from the reaction mixture, and therefore, there is no loss of catalyst. In this way, methyl esters and glycerols are obtained with great purity. In addition, there is no soap formation from free fatty acids, which makes it possible to use acid oils like waste cooking oil. (8) Zhang, Y.; Dubé, M. A.; McLean, D. D.; Kates, M. Bioresour. Technol. 2003, 89, 1–16. (9) Coteron, A.; Vicente, G.; Martinez, M.; Aracil, J. Recent Res. DeV. Oil Chem. 1997, 1, 109–114. (10) Ma, F.; Hanna, M. A. Bioresour. Technol. 1999, 70, 1. (11) Dubé, M.; Tremblay, A.; Liu, J. Bioresour. Technol. 2007, 98, 639– 647. (12) Freedman, B.; Pryde, E. H.; Molins, T. L. J. Am. Oil Chem. Soc. 1984, 61, 10. (13) Pryde, E. H.; Freedman, B.; Butterfield, R. O. J. Am. Oil Chem. Soc. 1986, 63, 1375. (14) Meher, L. C.; Vidya Sagar, D.; Naik, S. N. Renewable Sustainable Energy ReV. 2006, 10, 248–268. (15) Altiparmak, D.; Keskin, A.; Koca, A.; Gürü, M. Bioresour. Technol. 2007, 98, 241–246. (16) Leclercq, E.; Finiels, A.; Moreau, C.; Peterson, G. R.; Scarrah, W. P. J. Am. Oil Chem. Soc. 2001, 78, 1161. (17) Suppes, G. J.; Bockwinkel, K.; Lucas, S.; Botts, J. B.; Mason, M. H.; Heppert, A. J. J. Am. Oil Chem. Soc. 2001, 78, 139. (18) Choudary, B. M.; Lakshmi, M.; Venkat, C. H.; Araganathan, S.; Lakshmi, P.; Figueras, F. J. Mol. Catal. A: Chem. 2000, 159, 411–416. (19) Kim, H.; Kang, B.; Kim, M.; Park, Y.; Kim, D.; Lee, J.; Lee, K. Catal. Today 2004, 93, 315–320. (20) Furuta, S.; Matsuhashi, H.; Arata, K. Biomass Bioenergy 2006, 30, 870–873.
10.1021/ef700455r CCC: $37.00 2007 American Chemical Society Published on Web 10/10/2007
Zeolite Y as a Catalyst in Biodiesel Production
Recent research on transesterification has focused on the use of heterogeneous catalysts,21–30 and zeolites modified by alkali cation ion exchange have emerged as interesting solid bases.31,32 The main objective of this work is to study the transesterification of waste oil with methanol by a heterogeneous catalyst process in the presence of several Y-type zeolites with different Al2O3 content. 2. Experimental The chemical reagents were waste cooking oil and methanol (analytical grade, MERCK). Several Y-type zeolites, with different Al2O3 and Na2O percentage from Akzo Nobel Catalysts, have been tested. The installation for carrying out transesterification reaction experiments consists of a fixed-bed stainless steel AISI 304 reactor with a 2.6 cm internal diameter and 35 cm of total length, giving 7 cm of useful catalyst bed. It incorporates a controlled heating system and a thermowall where a 1.5 mm chromel–alumel thermocouple is housed, connected to a digital thermometer. The reactor is filled with the respective catalyst in order to study its activity in waste oil transesterification reaction. The reaction product leaves the reactor from a tap at the bottom via a finned tube which allows the products to cool before collection in a decantation system where two phases are separated. The biodiesel is the light phase, and the glycerin is the heavy one. The catalyst bed is regenerated using the same installation, preheating with nitrogen at a flowrate of 0.63 L N/min to the desired temperature (approx. 300 °C); then, sufficient flowrates are set to maintain 10% v/v oxygen at a constant total flowrate. The internal temperature of the bed is measured throughout the regeneration. The viscosity and density of transesterified light-phase products were measured to be used as an initial guideline to the degree of conversion to biodiesel. The methyl ester content of the samples was determined by gas chromatography after solid-phase extraction of the methyl esters with disposable silica cartridges (Sep-pak Plus, Waters). Polar and nonpolar phases are thus separated, and the latter is analyzed by gas chromatography with a flame ionization detector (FID) and a DB5 column, 50 m long with a 0.35 mm internal diameter, was used with He as carrier gas (40 °C for 5 min, 12 °C/min up to 325 °C). As an internal pattern, methyl undecanoate was used. The calibration pattern was a methyl ester mix (methyl decanoate, dodecanoate, tetradecanoate, palmitoate, stearate).
3. Results and Discussion 3.1. Catalytic Activity. The waste cooking oil used was characterized as a reagent for transesterification reaction. This particular oil was waste derived from a school canteen and presented the following features of interest in biodiesel preparation (Table 1). (21) Boocock, D.; Konar, S.; Mackay, A.; Chang, P.; Liu, J. Fuel 1992, 71, 1291. (22) Vonghia, E.; Boocock, D.; Konar, S.; Leung, A. Energy Fuel 1995, 9, 1090. (23) Katikanemi, S.; Adjaye, P.; Bakhshi, N. Can. J. Chem. Eng. 1995, 73, 484. (24) Furuta, S.; Matsuhashi, H.; Arata, K. Catal. Commun. 2004, 5, 721. (25) Cantrell, D.; Gillie, L.; Lee, A.; Wilson, K. Appl. Catal. A: Gen. 2005, 287, 183. (26) Sasidharan, M.; Kumar, R. J. Mol. Catal. A: Chem. 2004, 210, 93–98. (27) Jitputti, J.; Kitiyanan, B.; Rangsunvigit, P.; Bunyakiat, K.; Attanatho, L.; Jenvanitpanjakul, P. Chem. Eng. J. 2006, 116, 61–66. (28) Mbaraka, I.; Shanks, B. J. Am. Oil Chem. Soc. 2006, 83, 79–91. (29) Xie, W.; Li, H. J. Mol. Catal. A: Chem. 2006, 255, 1–9. (30) Xie, W.; Peng, H.; Chen, L. Appl. Catal. A: Gen. 2006, 300, 67– 74. (31) Suppes, G.; Dasari, M.; Doskocil, E.; Mankidy, P.; Goff, M. Appl. Catal. A: Gen. 2004, 257, 213–223. (32) Xie, W.; Huand, X.; Li, H. Bioresour. Technol. 2007, 98, 936– 939.
Energy & Fuels, Vol. 21, No. 6, 2007 3281 Table 1. Properties of Waste Oil property
value
density (15 °C) kinematic viscosity (40 °C) acid value refraction index (20 °C) turbidity iodine index CFPP sulfur content cloud point copper strip corrosion (3 h 50 °C) inflamability
0.92 g/mL 35.71–42.29 cSk 0.54–0.72 mg KOH/g 1.4754 10–18 NTU 136.7 g iodine/100 g sample 20 °C 27 mg/kg -7.0 °C 1a >100 °C
Table 2. Properties of Fresh Catalysts zeolite
Y307
Y411
Y530
Y756
Al2O3 (%) Na2O3 (%) SO4 (%) crystallinity (%) specific area (m2/g) mean pore size (Å)
18.1 0.16
12.2 0.21 0.23 112 678 6.109
5.6 0.18
