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Thermal catalytic cracking of buriti oil (Mauritia flexuosa L.) over LaSBA-15 mesoporous materials
Fuel Processing Technology 92 (2011) 2099–2104
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Fuel Processing Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / f u p r o c
Thermal catalytic cracking of buriti oil (Mauritia flexuosa L.) over LaSBA-15 mesoporous materials Geraldo E. Luz Jr. a,⁎, Anne G.D. Santos b, Ana C.R. Melo c, Ricardo M. Oliveira c, Antonio S. Araujo c, Valter J. Fernandes Jr. c a b c
State University of Piauí, Department of Chemistry, 64002-150, Teresina-PI, Brazil State University of Rio Grande do Norte, Department of Chemistry, 59.610-210, Mossoró-RN, Brazil Federal University of Rio Grande do Norte, Institute of Chemistry, 59078-970, Natal-RN, Brazil
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Article history: Received 26 October 2010 Received in revised form 19 May 2011 Accepted 6 June 2011 Available online 2 July 2011 Keywords: Buriti oil Thermal catalytic cracking (TCC) LaSBA-15 Green diesel
a b s t r a c t In order to obtain a fuel with properties similar to diesel, the thermal catalytic cracking (TCC) of buriti oil was accomplished over LaSBA-15 mesoporous materials. In function of the Lewis acid sites and the unidirectional pore system of the LaSBA-15, this material presented good deoxygenating activity for TCC of the oil, resulting in a reduction of the oxygenate content in the organic liquid (OL) collected above 190 °C, obtaining as main product, a mixture of hydrocarbons similar to mineral diesel, called green diesel. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Economical aspects, social and environmental have been driving several studies in order to obtain alternative and renewable sources of liquid fuels that are “environmentally friendly”. Thus, vegetable oils have been attracting the interest of researchers for production of hydrocarbons and chemicals by the so-called thermal catalytic cracking (TCC) of vegetable oils [1–9]. In this process, vegetable oil is heated at temperatures ranging from 300 to 500 °C, in the presence of a solid catalyst. The products are obtained in four phases: gas, organic liquid (OL), aqueous and coke [1–7]. The compositions of the gas and organic phases are variable, and depend on the conditions although the gas phase is composed generally by CO, CO2, H2 and hydrocarbons with low molecular weight, while the aliphatic and aromatic hydrocarbons, oxygenated compounds, like fatty acids, alcohols, aldehydes and ketones are the main constituents of the organic liquid [2–7]. Furthermore, the organic liquid can be separated in fuel fractions with physicochemical properties similar to liquid fuels obtained from petroleum, such as diesel and gasoline [5–9]. Although a wide variety of reactions take place during the catalytic cracking of vegetable oil, the process can be divided in two basic steps called primary and secondary cracking, respectively [7,10–12]. In the first step, basically thermal, the triacyl glyceride chains are converted to fatty acids, light hydrocarbons and acrolein, while, in the second
⁎ Corresponding author. Fax: + 55 86 3213 7942. E-mail address: [email protected] (G.E. Luz). 0378-3820/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2011.06.018
step, there are cracking and radical reactions, besides deoxygenation, dehydrogenation, condensation, dehydration and aromatization reactions [2–4,7,8]. According to Idem et al. [3], the catalyst acts on the secondary cracking, and this action depends mainly on the porous structure and acidity. Whenever the cracking is realized over a crystalline porous solid, the carbon chain fragmentation is partially inhibited, becoming the process suitable for obtaining of organic liquid instead of the gas fraction, since molecules originated from primary cracking can diffuse through the pore channel of the catalyst. Furthermore, the presence of acid sites on the catalyst favors the deoxygenation of the fatty acids, among others reactions catalyzed by acid sites, as olefin condensation and aromatization [1,3,13,14]. In this context, the SBA-15 mesoporous molecular sieve can be applied as a catalyst for the TCC process, since it has a large pore size and high hydrothermal and thermal stability. Moreover, its mesopores are ordered in hexagonal form and unidirectional structure [15], which may facilitate the molecular diffusion. The pure silica SBA-15 presents low catalytic activity due to the absence of heteroatom active sites [16,17]. Therefore, it is of great importance to introduce a heteroatom into the mesopores of this molecular sieve, especially metals that can increase its acidity, as lanthanum, which also improves thermal and hydrothermal stability of a molecular sieve, when it is incorporated to that [16,18]. Due to the high metal ion solubility in strong acidic media, in which the hydrothermal synthesis of SBA-15 is usually performed, the metal incorporation into the SBA-15 is not an easy task. Thus, recent studies reported that the method of pH-adjustment of the synthesis gel at values higher than 2 is a way to facilitate the metal incorporation into SBA-15 [19–23]. As previously reported [24],
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lanthanum can be incorporated into the mesopores of SBA-15 as a thin layer of metal oxide through pH-adjustment synthesis method. The characterization of these catalysts indicated La-incorporation promotes Lewis acid sites inside mesopores of SBA-15 without change its pore structure. Another factor that affects the catalytic activity and product selectivity is the triglyceride composition. Unsaturated fatty acids are easily cracked, taking more radical reactions than the saturated ones [2,3]. The triglycerides constituted by fatty acids with long carbon chains favor the formation of hydrocarbons of high molecular weight [2]. Characteristics similar to that are observed in the buriti oil, a Brazilian native vegetable oil extracted from palm tree (Mauritia flexuosa L.), present ca. 80 wt.% of oleic acid in its composition [25,26]. The presented work aims to evaluate the LaSBA-15 mesoporous material as catalyst for the TCC of the buriti oil in order to obtain a hydrocarbon mixture similar to mineral diesel, called green diesel.
Fig. 1. Distillation system used in the cracking of the oil.
2. Experimental
Similar procedure has been used to thermal cracking (TC) of the oil, but without catalyst. All experiments were replicated five times.
2.1. Catalyst
2.3. OL characterization
Lanthanum-incorporated SBA-15 mesoporous molecular sieves (LaSBA-15) and pure silica SBA-15 were previously synthesized by direct synthesis method with pH-adjusting. The synthesis procedure and characterization of these materials (XRD, XRF, FTIR, TG/DTG, nitrogen sorption, and characterization of the active sites by ethanol dehydration) were described [24]. LaSBA-15 samples were designed as LaxSBA-15, where “x” refers to the Si/La molar in the synthesis gel. The pure silica sample was denominated as SiSBA-15.
Two organic liquid (OL) fractions were initially analyzed by acid index according to the AOCS Cd 3d-63 method. The OL obtained from the first fraction presents high acid index (N200 mg KOH/g), thus, only the OL derived from the second fraction was characterized by infrared spectroscopy and gas chromatography. Infrared analyses were carried out on a Bomem Fourier transformer infrared spectrophotometer (MB102) from a thin liquid film over a KBr window. The FTIR spectra correspond to the sum of 64 scans at a 4 cm − 1 spectral resolution. Hydrocarbons were identified by gas chromatography according to ASTM D2887 stander method in a Varian 450-GC gas chromatograph equipped with an automatic injector Varian CP-8400, flame ionization detector (FID) and a polydimethylsiloxane column CP SimDist (10 m, 0.53 mm, 0.88 μm). The Galaxie 1.9SP-2b software was used to capture and processing the data, providing the simulated distillation curves of the samples, based on standards (ASTM D 2887 Reference Gas Oil, Lot.2). The hydrocarbon quantification was done by gas chromatography in a Shimadzu gas chromatograph equipped with a polydimethylsiloxane column CBPI PONA-M50-042 (50 m, 0.15 mm, 0.42 μm), flame ionization detector (FID) and a PONA solution software. Split mode was used and the temperature profile for GC oven started at 35 °C, ramped at 2 °C/min to 250 °C, and held for 30 min. Based on the order of elution of hydrocarbons obtained by simulated distillation analysis, the peaks were identified.
2.2. Cracking reaction The buriti oil (M. flexuosa L.) was obtained from commercial sources and used without further purification. The fatty acid medium composition of buriti oil is displayed in Table 1 [25,26]. Thermal catalytic cracking (TCC) of the oil over SiSBA-15 and LaSBA-15 samples was carried out using a distillation system similar to that shown in Fig. 1. In each catalytic test, a mass of 100.0 g of oil and 1.0 g of catalyst were placed into the distillation system without stirring and heated at room temperature up to 450 °C with a heating rate of 10 °C/min. When the temperature inside the reactor achieved 360 °C the vapors left the balloon and entered into the condenser in temperatures (T) ranging from 150 to 250 °C. In these temperatures, two liquid fractions were obtained, one was collected in 150 °C ≤ T ≤ 190 °C, whereas the other was collected in T N 190 °C. These two fractions have been constituted by an aqueous fraction and an organic, respectively, which were separated by decantation and called organic liquid (OL). The amounts of both liquid fractions and of waste (unvaporized liquid, coke) were obtained, and the amount of gas fraction was estimated by stoichiometry. After that, the OL fractions were kept into a dark glass and stored in the absence of light for characterization.
Table 1 Fatty acid composition of buriti oil. Fatty acid
Wt.%
Oleic (18:1) Palmitic (16:0) Others
79.2 16.3 4.5
3. Results and discussion 3.1. Catalyst Characterization results of SiSBA-15 and LaSBA-15 samples, discussed in our previous work [24], indicated that the lanthanum was incorporated in two forms in the SBA-15: into the framework and within the mesopores, like a thin layer of lanthanum oxide. These two forms affect competitively the textural properties of the samples impregnated with lanthanum, especially the pore size. The ethanol dehydration has showed that the LaSBA-15 samples have weak Lewis acid and basic functionalities, indicating the presence of lanthanum oxide in these samples. Also, it was observed that acidity of LaSBA-15 samples increase with the decrease of the La-content (La25SBA15 b La50SBA-15 b La75SBA-15). Furthermore, the characterization of the SiSBA-15 has indicated that it shows high content of Si–O–Si superficial groups, which show basic catalytic activity. The textural properties of SiSBA-15 and LaSBA-15 samples are summarized in Table 2.
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Table 2 Physic-chemical properties of SiSBA-15 and LaSBA-15 samples. Sample
SBET (m2/g)
Smicro (m2/g)
Vp (cm3/g)
Vmicro (cm3/g)
Dp (nm)
w (nm)
SiSBA-15 La75SBA-15 La50SBA-15 La25SBA-15
589.8 775.4 720.2 557.5
90.9 73.6 54.3 72.8
1.46 1.31 1.18 1.49
0.04 0.03 0.02 0.03
7.21 4.27 5.35 5.37
4.12 7.59 6.79 7.07
SBET — surface area obtained by BET method; Smicro — microporous area; Vp — porous volume; Vmicro — microporous volume; Dp — BJH pore diameter calculated from the adsorption branch; w = a0 − Dp; w = wall thickness; a0 = unit cell.
Table 3 Mass balance of TC and TCC of the buriti oil over SiSBA-15 and LaSBA-15 samples. Sample
OL
OL1st
Thermal SiSBA-15 La75SBA-15 La50SBA-15 La25SBA-15
78.72 69.87 81.40 82.57 79.24
36.69 34.52 41.82 41.94 41.52
fraction
GD
Gases
Water
Waste
42.03 35.35 39.58 40.63 37.72
7.14 13.44 8.69 9.12 10.11
1.50 1.20 2.55 2.36 2.05
12.64 15.49 7.54 5.95 8.60
All quantitative results are relative to feedstock mass. GD (green diesel): OL 2nd fraction. All quantitative results are average value with standard deviation (SD) varying in the range 2.00–3.00 for OL, OL 1st fraction, GD and waste; 0.80–1.65 for gases; and 0.20– 0.50 for water.
3.2. Cracking of the oil The obtained results for thermal cracking (TC) and thermal catalytic cracking (TCC) of the oil at 450 °C are summarized in Table 3. Analyzing the quantitative results presented in Table 3, related to the process carried out under SiSBA-15, a reduction of the yield of OL is noted, with subsequent increase of gas yield, in comparison to thermal process, indicating that this catalyst promoted a fragmentation of the compounds derived from the primary cracking. This behavior may be related to the basic sites on the surface. The presence of basic sites in a catalytic solid inhibits the adsorption of primary cracking products on external surface of the solid during the TCC of vegetable oil, since these products are adsorbed preferentially on acid sites [3,4]. Table 3 also shows an increase in the conversion yield when TCC of the oil was carried out over LaSBA-15 samples. This fact is indicated by the yield of the OL and gas fractions, as compared with the TC process. This behavior may be related to the acid sites' presence on these samples. According to literature [5,6,14], acid sites allow the adsorption and subsequent deoxygenation of compounds derived from the primary cracking, promoting the cyclization, condensation and aromatization reactions, whose products can be present in organic liquid (OL).
Fig. 3. FT-IR absorption spectrum of the oil and of OL obtained from TC and TCC of that oil over SiSBA-15 and LaSBA-15 samples.
In relation to the water yield, although the LaSBA-15 sample presented yields higher than SiSBA-15, the obtained amounts of water were moderated, indicating that there was no preference for decarbonilation reaction. This behavior can be explained by the moderate acidity of the LaSBA-15 samples, which present Lewis acid sites [24], which favor the deoxygenation by decarboxylation reaction, as proposed in Fig. 2. Fig. 3 presents FT-IR absorption spectra of OL obtained from TC and TCC of the buriti oil. The spectrum of the oil shows absorbance bands characteristic of triacyl glyceride in the range from 1000 to 1300 cm − 1, and at 1740 cm − 1, related to C–O and C=O stretches, respectively. Also, it shows C–H stretches (CH2 and CH3) in the range from 2840 to 3000 cm − 1 [25,27]. The spectrum of OL shows absorbance bands fatty acid characteristic at 1712 cm − 1, and in range from 1210 to 1320 cm − 1, associated to C=O stretch and C–O stretch, respectively. Besides, it shows C–H stretches (CH2 and CH3) in range from 2840 to 3000 cm − 1, overloading to wide O–H stretch band [25,27]. These observations indicate that there was vegetable oil primary cracking, which promotes triacyl glyceride conversion into fatty acids, light hydrocarbons and some low oxygenates, such as alcohols, ketones and aldehydes [3,10]. Analyzing only the spectrum of OL, it is observed that characteristic bands of fatty acid (1712 cm − 1) have lower intensity for OL obtained from TCC over LaSBA-15 samples than that derived from TC. This fact evidences the deoxygenating action of catalytic solids on the secondary cracking of vegetable oil. Moreover, it is observed that the intensity of the absorbance bands related to fatty acid have shifted towards a lower value with the lanthanum content increasing, when TCC was carried out over LaSBA-15 samples. This behavior can be attributed to the acidity increase of these samples with lanthanum
Fig. 2. Mechanism proposed to fatty acid decarboxilation over LaSBA-15 samples in TCC of the oil.
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Table 4 Acid index of OL derived from of TC and TCC of the buriti oil over SiSBA-15 and LaSBA-15 samples. Sample
Acid index (mg KOH/g GD)
Standard deviation (SD)
Thermal SiSBA-15 La75SBA-15 La50SBA-15 La25SBA-15
70.02 75.30 12.30 17.71 26.69
1.91 1.02 1.00 1.12 0.90
content decreasing [24]. Due to that, La75SBA-15 was the catalytic solid that has had the best deoxygenating activity. The SiSBA-15 presented a behavior opposite to the LaSBA-15 sample. The OL obtained from TCC carried out over this sample presented FT-IR spectrum with fatty acid absorption bands (1712 cm − 1) most intense than that obtained from TC, indicating that this sample has inhibited the fatty acid deoxygenation. Similar result was observed for Idem et al. [3] and Williams and Horne [4] when TCC was carried out over basic solids. So, that fact suggests that SiSBA-15 has basic sites, which may be formed during its calcination, when silanol groups (Si–OH) are condensed and converted into Si–O–Si, as reported in our previous work [24]. Acid index of the OL (Table 4) reflect the FT-IR results. According to this table, LaSBA-15 samples have promoted a reduction of the OL acid index in comparison to TC process, indicating the deoxygenating action of these samples on TCC of the oil. Similar to the FT-IR results, acid index analyses have indicated that La75SBA-15 had the best deoxygenating action, promoting an OL with the lowest acid index. Moreover, it is observed that OL obtained over SiSBA-15 sample has shown higher index acid than all other OL, including that one obtained from TC. This behavior is in agreement with the FT-IR results, and reflects its low deoxygenating action, which is consequent of basic sites' presence on its surface. The chromatographic analyses of OL obtained from TC and TCC are shown in Fig. 4. Chromatograms shown in Fig. 4 indicate that there is a similar composition of OL derived from TC and those of OL obtained from TCC, evidencing that the catalytic solid did not change the composition of products of the vegetable oil cracking, as reported in literature [3–5,11,14,28]. On the other hand, it is also demonstrated in Fig. 4 that the product distributions were modified by the catalytic solid action. It was observed that the intensity of the peaks
Fig. 4. Chromatograms of OL obtained from TC and TCC of the oil over SiSBA-15 and LaSBA-15 samples.
Fig. 5. Selectivity to hydrocarbons (C5–C17) in OL derived from TC and TCC of the oil.
related to heavy hydrocarbons is higher in chromatograms of OL obtained in TCC than those obtained in TC. The opposite behavior was observed to light hydrocarbons. These behaviors become more evident when the chromatographic results are shown in terms of hydrocarbons selectivity in the range from C5 to C17, as shown in Fig. 5. Fig. 5 demonstrates that the selectivity to light hydrocarbons is higher in TC than those observed in TCC, whereas the selectivity to heavy hydrocarbons shows contrary behavior. This highest selectivity to heavy hydrocarbons in TCC can be related to high average pore size of catalytic samples, associated to their unidirectional mesoporous structure, in which the heavy compounds suffer diffusion, especially fatty acids derived from primary cracking [3,5,11]. This diffusion through pores inhibits carbonic chain fragmentation, allowing the obtaining of hydrocarbons similar to those present in mineral diesel. This behavior, especially in process carried out over LaSBA-15 samples, reinforces the idea that acid sites, generated by lanthanum incorporation, are within the mesopores of these samples, since, according to Williams and Horne [4], and Idem et al. [3], acid sites' presence on solid external surface would have promoted further product fragmentation and, consequently, a reduction of the heavy hydrocarbon selectivity would have been observed in TCC carried out over that samples. According to Fig. 5, La50SBA-15 was the sample that promoted the highest selectivity to heavy hydrocarbons. This fact can be related to its lower microporosity in comparison to other solid samples, as it can be observed in Table 2. This property reduces the fragmentation of the compounds, which is necessary to molecular diffusion through micropores, as previously observed for micro/mesostructured composites [6]. Analyzing the hydrocarbon selectivity, it is noted that in practically all processes, there was higher selectivity to C7, C8, C9, C14 and C15 hydrocarbons. This behavior can be associated to fatty acid composition of the oil esters, which have high contents of oleic (C18:1) and palmitic (16:0) acids. From oleic acid, it is possible to obtain C5, C7 and C9–C14 hydrocarbons through β-scission to the double bond, before fatty acid deoxygenation [2,3,29,30], followed by radical reactions (disproportion, condensation and β-scission to the radical carbon). Besides, through similar radical reactions, C6, C8–C13 can be obtained after deoxygenation of oxygenate fragment derived from β-scission to the double bond. Moreover, cyclic and aromatic hydrocarbons may be obtained from olefinic fragments also derived from acid oleic βscission. From palmitic acid, the C15 hydrocarbon is obtained through direct deoxygenation. An illustrative scheme of these processes is proposed in Fig. 6.
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Fig. 6. Reaction scheme of hydrocarbons obtained from oleic and palmitic acid derived from primary cracking of the butiri oil.
4. Conclusion From the thermal catalytic cracking (TCC) of buriti oil over LaSBA15 catalysts, it is possible to obtain an organic liquid (OL) fraction with low acid index, especially when this TCC process is accomplished over La75SBA-15, suggesting the deoxygenating activity of these catalytic solids. Furthermore, the large pore sizes and well ordered structure of the pores of the SBA-15 materials inhibited the carbonic chain fragmentation, allowing to obtain hydrocarbons with chains similar to those present in mineral diesel, designed Green Diesel. From TCC process of vegetal oils, it is possible to obtain new routes to obtain alternative and renewable fuel, with excellent quality and free of sulfur.
Acknowledgement The authors would like to thank the FAPEPI for the research scholarship, and the support from the PETROBRAS, ANP, FINEP and CNPq.
References [1] J.D. Adjaye, S.P.R. Katikaneni, N.N. Bakhshi, Catalytic conversion of a biofuel to hydrocarbons: effect of mixtures of H-ZSM-5 and silica-alumina catalysts on product distribution, Fuel Process. Technol. 48 (1996) 115–143. [2] R.O. Idem, S.P.R. Katikaneni, N. Bakhshi, Thermal cracking of canola oil: reaction products in the presence and absence of steam, Energy Fuels 10 (1996) 1150–1162. [3] R.O. Idem, S.P.R. Katikaneni, N. Bakhshi, Catalytic conversion of canola oil to fuels and chemicals: roles of catalyst acidity, basicity and shape selectivity on product distribution, Fuel Process. Technol. 51 (1997) 101–125. [4] P. Williams, P.A. Horne, The influence of catalytic type on the composition of upgraded biomass pyrolysis oils, J. Anal. Appl. Pyrolysis 31 (1995) 39–61. [5] F.A. Twaiq, N.A.M. Zabidi, A.R. Mohamed, S. Bhatia, Catalytic conversion of palm oil over mesoporous aluminosilicate MCM-41 for the production of liquid hydrocarbon fuels, Fuel Process. Technol. 84 (2003) 105–120.
[6] Y. Ooi, R. Zakaria, A.R. Mohamed, S. Bhatia, Synthesis of composite material MCM-41/beta and its catalytic performance in waste used palm oil cracking, Appl. Catal., A 274 (2004) 15–23. [7] A.O. Adebanjo, A.K. Dalai, N.N. Bakhshi, Production of diesel-like fuel and other valueadded chemicals from pyrolysis of animal fat, Energy Fuels 19 (2005) 1735–1741. [8] D.G. Lima, V.C.D. Soares, E.B. Ribeiro, D.A. Carvalho, E.C.V. Cardoso, F.C. Rassi, K.C. Mundim, J.C. Rubim, P.A.Z. Suarez, Diesel-like fuel obtained by pyrolysis of vegetable oils, J. Anal. Appl. Pyrolysis 71 (2004) 987–996. [9] F.A. Twaiq, A.R. Mohamed, S. Bhatia, Performance of composite catalysts in palm oil cracking for the production of liquid fuels and chemicals, Fuel Process. Technol. 85 (2004) 1283–1300. [10] P.A.Z. Suarez, S.M.P. Meneghetti, M.R. Meneghetti, C.R. Wolf, Transformação de triglicerídeos em combustíveis, materiais poliméricos e insumos químicos: algumas aplicações da catálise na oleoquímica, Quim. Nova 30 (2007) 667–676. [11] T.J. Benson, R. Hernandez, W.T. French, E.G. Alley, W.E. Holmes, Elucidation of the catalytic cracking pathway for unsaturated mono-, di-, and triacylglycerides on solid acid catalysts, J. Mol. Catal. A: Chem. 303 (2009) 117–123. [12] H. Yang, R. Yan, H. Chen, D.H. Lee, D.T. Liang, C. Zheng, Mechanism of palm oil waste pyrolysis in a packed bed, Energy Fuels 20 (2006) 1321–1328. [13] P.T. Williams, N. Nugranad, Comparison of products from the pyrolysis and catalytic pyrolysis of rice husks, Energy 25 (2000) 493–513. [14] T.L. Chew, S. Bhatia, Effect of catalyst additives on the production of biofuels from palm oil cracking in a transport riser reactor, Bioresour. Technol. 100 (2009) 2540–2545. [15] D. Zhao, Q. Huo, J. Feng, J. Kim, Y. Han, G.D. Stucky, Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered, hydrothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (1998) 6024–6036. [16] M.N. Timofeeva, S.H. Jhung, Y.K. Hwang, D.K. Kim, V.N. Panchenko, M.S. Melgunov, Y.A. Chesalov, J.S. Chang, Ce-silica mesoporous SBA-15-type materials for oxidative catalysis: synthesis, characterization, and catalytic application, Appl. Catal., A 317 (2007) 1–10. [17] M. Baca, E. Rochefoucauld, E. Ambroise, J. Krafft, R. Hajjar, P.P. Man, X. Carrier, J. Blanchard, Characterization of mesoporous alumina prepared by surface alumination of SBA-15, Microporous Mesoporous Mater. 110 (2008) 232–241. [18] A.S. Araujo, M. Jaroniec, Synthesis and properties of lanthanide incorporated mesoporous molecular sieves, J. Colloid Interface Sci. 218 (1999) 462–467. [19] Z. Mu, J.J. Li, Z.P. Hao, S.Z. Qiao, Direct synthesis of lanthanide-containing SBA-15 under weak acidic conditions and its catalytic study, Microporous Mesoporous Mater. 113 (2008) 72–80. [20] Q. Dai, X. Wang, G. Chen, Y. Zheng, G. Lu, Direct synthesis of cerium (III)-incorporated SBA-15 mesoporous molecular sieves by two-step synthesis method, Microporous Mesoporous Mater. 100 (2007) 268–275. [21] Z. Lou, R. Wang, H. Sun, Y. Chen, Y. Yang, Direct synthesis of highly ordered Co-SBA-15 mesoporous materials by the pH-adjusting approach, Microporous Mesoporous Mater. 110 (2008) 347–354.
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[22] M. Selvaraj, S. Kawi, Direct synthesis and catalytic performance of ultralarge pore GaSBA-15 mesoporous molecular sieves with high gallium content, Catal. Today 131 (2008) 82–89. [23] J. Aguado, G. Calleja, A. Carrero, J. Moreno, One-step synthesis of chromium and aluminium containing SBA-15 materials, Chem. Eng. J. 137 (2008) 443–452. [24] G.E. Luz Jr., S.H. Lima, A.C.R. Melo, A.S. Araujo, V.J. Fernandes Jr., Direct synthesis and characterization of LaSBA-15 mesoporous molecular sieves, J. Mater. Sci. 45 (2010) 1117–1122. [25] M.L.S. Albuquerque, I. Guedes Jr., P. Alcantra, S.G.C. Moreira, Infrared absorption spectra of (Mauritia flexuosa L.) oil, Vib. Spectrosc. 33 (2003) 127–131. [26] M.L.S. Albuquerque, I. Guedes Jr., P. Alcantra, S.G.C. Moreira, N.M. Barbosa Neto, D.S. Correa, S.C. Zilio, Characterization of (Mauritia flexuosa L.) oil by absorption and emission spectroscopies, J. Braz. Chem. Soc. 16 (2005) 1113–1117.
[27] X. Junming, J. Jianchun, C. Jie, Liquid hydrocarbon fuels obtained by the pyrolysis of soybean oils, Bioresour. Technol. 100 (2009) 4867–4870. [28] D. Kubicka, L. Kaluza, Deoxygenation of vegetable oils over sulfided Ni, Mo and NiMo catalysts, Appl. Catal., A 372 (2010) 199–208. [29] K.D. Maher, D.C. Bressler, Pyrolysis of triglyceride materials for the production of renewable fuels and chemicals, Bioresour. Technol. 98 (2007) 2351–2368. [30] E. Vonghia, D.G.B. Boocock, S.K. Konar, A. Leung, Pathways for the deoxygenation of triglycerides to aliphatic hydrocarbons over activated alumina, Energy Fuels 9 (1995) 1090–1096.
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Fuel Processing Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / f u p r o c
Thermal catalytic cracking of buriti oil (Mauritia flexuosa L.) over LaSBA-15 mesoporous materials Geraldo E. Luz Jr. a,⁎, Anne G.D. Santos b, Ana C.R. Melo c, Ricardo M. Oliveira c, Antonio S. Araujo c, Valter J. Fernandes Jr. c a b c
State University of Piauí, Department of Chemistry, 64002-150, Teresina-PI, Brazil State University of Rio Grande do Norte, Department of Chemistry, 59.610-210, Mossoró-RN, Brazil Federal University of Rio Grande do Norte, Institute of Chemistry, 59078-970, Natal-RN, Brazil
a r t i c l e
i n f o
Article history: Received 26 October 2010 Received in revised form 19 May 2011 Accepted 6 June 2011 Available online 2 July 2011 Keywords: Buriti oil Thermal catalytic cracking (TCC) LaSBA-15 Green diesel
a b s t r a c t In order to obtain a fuel with properties similar to diesel, the thermal catalytic cracking (TCC) of buriti oil was accomplished over LaSBA-15 mesoporous materials. In function of the Lewis acid sites and the unidirectional pore system of the LaSBA-15, this material presented good deoxygenating activity for TCC of the oil, resulting in a reduction of the oxygenate content in the organic liquid (OL) collected above 190 °C, obtaining as main product, a mixture of hydrocarbons similar to mineral diesel, called green diesel. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Economical aspects, social and environmental have been driving several studies in order to obtain alternative and renewable sources of liquid fuels that are “environmentally friendly”. Thus, vegetable oils have been attracting the interest of researchers for production of hydrocarbons and chemicals by the so-called thermal catalytic cracking (TCC) of vegetable oils [1–9]. In this process, vegetable oil is heated at temperatures ranging from 300 to 500 °C, in the presence of a solid catalyst. The products are obtained in four phases: gas, organic liquid (OL), aqueous and coke [1–7]. The compositions of the gas and organic phases are variable, and depend on the conditions although the gas phase is composed generally by CO, CO2, H2 and hydrocarbons with low molecular weight, while the aliphatic and aromatic hydrocarbons, oxygenated compounds, like fatty acids, alcohols, aldehydes and ketones are the main constituents of the organic liquid [2–7]. Furthermore, the organic liquid can be separated in fuel fractions with physicochemical properties similar to liquid fuels obtained from petroleum, such as diesel and gasoline [5–9]. Although a wide variety of reactions take place during the catalytic cracking of vegetable oil, the process can be divided in two basic steps called primary and secondary cracking, respectively [7,10–12]. In the first step, basically thermal, the triacyl glyceride chains are converted to fatty acids, light hydrocarbons and acrolein, while, in the second
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step, there are cracking and radical reactions, besides deoxygenation, dehydrogenation, condensation, dehydration and aromatization reactions [2–4,7,8]. According to Idem et al. [3], the catalyst acts on the secondary cracking, and this action depends mainly on the porous structure and acidity. Whenever the cracking is realized over a crystalline porous solid, the carbon chain fragmentation is partially inhibited, becoming the process suitable for obtaining of organic liquid instead of the gas fraction, since molecules originated from primary cracking can diffuse through the pore channel of the catalyst. Furthermore, the presence of acid sites on the catalyst favors the deoxygenation of the fatty acids, among others reactions catalyzed by acid sites, as olefin condensation and aromatization [1,3,13,14]. In this context, the SBA-15 mesoporous molecular sieve can be applied as a catalyst for the TCC process, since it has a large pore size and high hydrothermal and thermal stability. Moreover, its mesopores are ordered in hexagonal form and unidirectional structure [15], which may facilitate the molecular diffusion. The pure silica SBA-15 presents low catalytic activity due to the absence of heteroatom active sites [16,17]. Therefore, it is of great importance to introduce a heteroatom into the mesopores of this molecular sieve, especially metals that can increase its acidity, as lanthanum, which also improves thermal and hydrothermal stability of a molecular sieve, when it is incorporated to that [16,18]. Due to the high metal ion solubility in strong acidic media, in which the hydrothermal synthesis of SBA-15 is usually performed, the metal incorporation into the SBA-15 is not an easy task. Thus, recent studies reported that the method of pH-adjustment of the synthesis gel at values higher than 2 is a way to facilitate the metal incorporation into SBA-15 [19–23]. As previously reported [24],
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lanthanum can be incorporated into the mesopores of SBA-15 as a thin layer of metal oxide through pH-adjustment synthesis method. The characterization of these catalysts indicated La-incorporation promotes Lewis acid sites inside mesopores of SBA-15 without change its pore structure. Another factor that affects the catalytic activity and product selectivity is the triglyceride composition. Unsaturated fatty acids are easily cracked, taking more radical reactions than the saturated ones [2,3]. The triglycerides constituted by fatty acids with long carbon chains favor the formation of hydrocarbons of high molecular weight [2]. Characteristics similar to that are observed in the buriti oil, a Brazilian native vegetable oil extracted from palm tree (Mauritia flexuosa L.), present ca. 80 wt.% of oleic acid in its composition [25,26]. The presented work aims to evaluate the LaSBA-15 mesoporous material as catalyst for the TCC of the buriti oil in order to obtain a hydrocarbon mixture similar to mineral diesel, called green diesel.
Fig. 1. Distillation system used in the cracking of the oil.
2. Experimental
Similar procedure has been used to thermal cracking (TC) of the oil, but without catalyst. All experiments were replicated five times.
2.1. Catalyst
2.3. OL characterization
Lanthanum-incorporated SBA-15 mesoporous molecular sieves (LaSBA-15) and pure silica SBA-15 were previously synthesized by direct synthesis method with pH-adjusting. The synthesis procedure and characterization of these materials (XRD, XRF, FTIR, TG/DTG, nitrogen sorption, and characterization of the active sites by ethanol dehydration) were described [24]. LaSBA-15 samples were designed as LaxSBA-15, where “x” refers to the Si/La molar in the synthesis gel. The pure silica sample was denominated as SiSBA-15.
Two organic liquid (OL) fractions were initially analyzed by acid index according to the AOCS Cd 3d-63 method. The OL obtained from the first fraction presents high acid index (N200 mg KOH/g), thus, only the OL derived from the second fraction was characterized by infrared spectroscopy and gas chromatography. Infrared analyses were carried out on a Bomem Fourier transformer infrared spectrophotometer (MB102) from a thin liquid film over a KBr window. The FTIR spectra correspond to the sum of 64 scans at a 4 cm − 1 spectral resolution. Hydrocarbons were identified by gas chromatography according to ASTM D2887 stander method in a Varian 450-GC gas chromatograph equipped with an automatic injector Varian CP-8400, flame ionization detector (FID) and a polydimethylsiloxane column CP SimDist (10 m, 0.53 mm, 0.88 μm). The Galaxie 1.9SP-2b software was used to capture and processing the data, providing the simulated distillation curves of the samples, based on standards (ASTM D 2887 Reference Gas Oil, Lot.2). The hydrocarbon quantification was done by gas chromatography in a Shimadzu gas chromatograph equipped with a polydimethylsiloxane column CBPI PONA-M50-042 (50 m, 0.15 mm, 0.42 μm), flame ionization detector (FID) and a PONA solution software. Split mode was used and the temperature profile for GC oven started at 35 °C, ramped at 2 °C/min to 250 °C, and held for 30 min. Based on the order of elution of hydrocarbons obtained by simulated distillation analysis, the peaks were identified.
2.2. Cracking reaction The buriti oil (M. flexuosa L.) was obtained from commercial sources and used without further purification. The fatty acid medium composition of buriti oil is displayed in Table 1 [25,26]. Thermal catalytic cracking (TCC) of the oil over SiSBA-15 and LaSBA-15 samples was carried out using a distillation system similar to that shown in Fig. 1. In each catalytic test, a mass of 100.0 g of oil and 1.0 g of catalyst were placed into the distillation system without stirring and heated at room temperature up to 450 °C with a heating rate of 10 °C/min. When the temperature inside the reactor achieved 360 °C the vapors left the balloon and entered into the condenser in temperatures (T) ranging from 150 to 250 °C. In these temperatures, two liquid fractions were obtained, one was collected in 150 °C ≤ T ≤ 190 °C, whereas the other was collected in T N 190 °C. These two fractions have been constituted by an aqueous fraction and an organic, respectively, which were separated by decantation and called organic liquid (OL). The amounts of both liquid fractions and of waste (unvaporized liquid, coke) were obtained, and the amount of gas fraction was estimated by stoichiometry. After that, the OL fractions were kept into a dark glass and stored in the absence of light for characterization.
Table 1 Fatty acid composition of buriti oil. Fatty acid
Wt.%
Oleic (18:1) Palmitic (16:0) Others
79.2 16.3 4.5
3. Results and discussion 3.1. Catalyst Characterization results of SiSBA-15 and LaSBA-15 samples, discussed in our previous work [24], indicated that the lanthanum was incorporated in two forms in the SBA-15: into the framework and within the mesopores, like a thin layer of lanthanum oxide. These two forms affect competitively the textural properties of the samples impregnated with lanthanum, especially the pore size. The ethanol dehydration has showed that the LaSBA-15 samples have weak Lewis acid and basic functionalities, indicating the presence of lanthanum oxide in these samples. Also, it was observed that acidity of LaSBA-15 samples increase with the decrease of the La-content (La25SBA15 b La50SBA-15 b La75SBA-15). Furthermore, the characterization of the SiSBA-15 has indicated that it shows high content of Si–O–Si superficial groups, which show basic catalytic activity. The textural properties of SiSBA-15 and LaSBA-15 samples are summarized in Table 2.
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Table 2 Physic-chemical properties of SiSBA-15 and LaSBA-15 samples. Sample
SBET (m2/g)
Smicro (m2/g)
Vp (cm3/g)
Vmicro (cm3/g)
Dp (nm)
w (nm)
SiSBA-15 La75SBA-15 La50SBA-15 La25SBA-15
589.8 775.4 720.2 557.5
90.9 73.6 54.3 72.8
1.46 1.31 1.18 1.49
0.04 0.03 0.02 0.03
7.21 4.27 5.35 5.37
4.12 7.59 6.79 7.07
SBET — surface area obtained by BET method; Smicro — microporous area; Vp — porous volume; Vmicro — microporous volume; Dp — BJH pore diameter calculated from the adsorption branch; w = a0 − Dp; w = wall thickness; a0 = unit cell.
Table 3 Mass balance of TC and TCC of the buriti oil over SiSBA-15 and LaSBA-15 samples. Sample
OL
OL1st
Thermal SiSBA-15 La75SBA-15 La50SBA-15 La25SBA-15
78.72 69.87 81.40 82.57 79.24
36.69 34.52 41.82 41.94 41.52
fraction
GD
Gases
Water
Waste
42.03 35.35 39.58 40.63 37.72
7.14 13.44 8.69 9.12 10.11
1.50 1.20 2.55 2.36 2.05
12.64 15.49 7.54 5.95 8.60
All quantitative results are relative to feedstock mass. GD (green diesel): OL 2nd fraction. All quantitative results are average value with standard deviation (SD) varying in the range 2.00–3.00 for OL, OL 1st fraction, GD and waste; 0.80–1.65 for gases; and 0.20– 0.50 for water.
3.2. Cracking of the oil The obtained results for thermal cracking (TC) and thermal catalytic cracking (TCC) of the oil at 450 °C are summarized in Table 3. Analyzing the quantitative results presented in Table 3, related to the process carried out under SiSBA-15, a reduction of the yield of OL is noted, with subsequent increase of gas yield, in comparison to thermal process, indicating that this catalyst promoted a fragmentation of the compounds derived from the primary cracking. This behavior may be related to the basic sites on the surface. The presence of basic sites in a catalytic solid inhibits the adsorption of primary cracking products on external surface of the solid during the TCC of vegetable oil, since these products are adsorbed preferentially on acid sites [3,4]. Table 3 also shows an increase in the conversion yield when TCC of the oil was carried out over LaSBA-15 samples. This fact is indicated by the yield of the OL and gas fractions, as compared with the TC process. This behavior may be related to the acid sites' presence on these samples. According to literature [5,6,14], acid sites allow the adsorption and subsequent deoxygenation of compounds derived from the primary cracking, promoting the cyclization, condensation and aromatization reactions, whose products can be present in organic liquid (OL).
Fig. 3. FT-IR absorption spectrum of the oil and of OL obtained from TC and TCC of that oil over SiSBA-15 and LaSBA-15 samples.
In relation to the water yield, although the LaSBA-15 sample presented yields higher than SiSBA-15, the obtained amounts of water were moderated, indicating that there was no preference for decarbonilation reaction. This behavior can be explained by the moderate acidity of the LaSBA-15 samples, which present Lewis acid sites [24], which favor the deoxygenation by decarboxylation reaction, as proposed in Fig. 2. Fig. 3 presents FT-IR absorption spectra of OL obtained from TC and TCC of the buriti oil. The spectrum of the oil shows absorbance bands characteristic of triacyl glyceride in the range from 1000 to 1300 cm − 1, and at 1740 cm − 1, related to C–O and C=O stretches, respectively. Also, it shows C–H stretches (CH2 and CH3) in the range from 2840 to 3000 cm − 1 [25,27]. The spectrum of OL shows absorbance bands fatty acid characteristic at 1712 cm − 1, and in range from 1210 to 1320 cm − 1, associated to C=O stretch and C–O stretch, respectively. Besides, it shows C–H stretches (CH2 and CH3) in range from 2840 to 3000 cm − 1, overloading to wide O–H stretch band [25,27]. These observations indicate that there was vegetable oil primary cracking, which promotes triacyl glyceride conversion into fatty acids, light hydrocarbons and some low oxygenates, such as alcohols, ketones and aldehydes [3,10]. Analyzing only the spectrum of OL, it is observed that characteristic bands of fatty acid (1712 cm − 1) have lower intensity for OL obtained from TCC over LaSBA-15 samples than that derived from TC. This fact evidences the deoxygenating action of catalytic solids on the secondary cracking of vegetable oil. Moreover, it is observed that the intensity of the absorbance bands related to fatty acid have shifted towards a lower value with the lanthanum content increasing, when TCC was carried out over LaSBA-15 samples. This behavior can be attributed to the acidity increase of these samples with lanthanum
Fig. 2. Mechanism proposed to fatty acid decarboxilation over LaSBA-15 samples in TCC of the oil.
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Table 4 Acid index of OL derived from of TC and TCC of the buriti oil over SiSBA-15 and LaSBA-15 samples. Sample
Acid index (mg KOH/g GD)
Standard deviation (SD)
Thermal SiSBA-15 La75SBA-15 La50SBA-15 La25SBA-15
70.02 75.30 12.30 17.71 26.69
1.91 1.02 1.00 1.12 0.90
content decreasing [24]. Due to that, La75SBA-15 was the catalytic solid that has had the best deoxygenating activity. The SiSBA-15 presented a behavior opposite to the LaSBA-15 sample. The OL obtained from TCC carried out over this sample presented FT-IR spectrum with fatty acid absorption bands (1712 cm − 1) most intense than that obtained from TC, indicating that this sample has inhibited the fatty acid deoxygenation. Similar result was observed for Idem et al. [3] and Williams and Horne [4] when TCC was carried out over basic solids. So, that fact suggests that SiSBA-15 has basic sites, which may be formed during its calcination, when silanol groups (Si–OH) are condensed and converted into Si–O–Si, as reported in our previous work [24]. Acid index of the OL (Table 4) reflect the FT-IR results. According to this table, LaSBA-15 samples have promoted a reduction of the OL acid index in comparison to TC process, indicating the deoxygenating action of these samples on TCC of the oil. Similar to the FT-IR results, acid index analyses have indicated that La75SBA-15 had the best deoxygenating action, promoting an OL with the lowest acid index. Moreover, it is observed that OL obtained over SiSBA-15 sample has shown higher index acid than all other OL, including that one obtained from TC. This behavior is in agreement with the FT-IR results, and reflects its low deoxygenating action, which is consequent of basic sites' presence on its surface. The chromatographic analyses of OL obtained from TC and TCC are shown in Fig. 4. Chromatograms shown in Fig. 4 indicate that there is a similar composition of OL derived from TC and those of OL obtained from TCC, evidencing that the catalytic solid did not change the composition of products of the vegetable oil cracking, as reported in literature [3–5,11,14,28]. On the other hand, it is also demonstrated in Fig. 4 that the product distributions were modified by the catalytic solid action. It was observed that the intensity of the peaks
Fig. 4. Chromatograms of OL obtained from TC and TCC of the oil over SiSBA-15 and LaSBA-15 samples.
Fig. 5. Selectivity to hydrocarbons (C5–C17) in OL derived from TC and TCC of the oil.
related to heavy hydrocarbons is higher in chromatograms of OL obtained in TCC than those obtained in TC. The opposite behavior was observed to light hydrocarbons. These behaviors become more evident when the chromatographic results are shown in terms of hydrocarbons selectivity in the range from C5 to C17, as shown in Fig. 5. Fig. 5 demonstrates that the selectivity to light hydrocarbons is higher in TC than those observed in TCC, whereas the selectivity to heavy hydrocarbons shows contrary behavior. This highest selectivity to heavy hydrocarbons in TCC can be related to high average pore size of catalytic samples, associated to their unidirectional mesoporous structure, in which the heavy compounds suffer diffusion, especially fatty acids derived from primary cracking [3,5,11]. This diffusion through pores inhibits carbonic chain fragmentation, allowing the obtaining of hydrocarbons similar to those present in mineral diesel. This behavior, especially in process carried out over LaSBA-15 samples, reinforces the idea that acid sites, generated by lanthanum incorporation, are within the mesopores of these samples, since, according to Williams and Horne [4], and Idem et al. [3], acid sites' presence on solid external surface would have promoted further product fragmentation and, consequently, a reduction of the heavy hydrocarbon selectivity would have been observed in TCC carried out over that samples. According to Fig. 5, La50SBA-15 was the sample that promoted the highest selectivity to heavy hydrocarbons. This fact can be related to its lower microporosity in comparison to other solid samples, as it can be observed in Table 2. This property reduces the fragmentation of the compounds, which is necessary to molecular diffusion through micropores, as previously observed for micro/mesostructured composites [6]. Analyzing the hydrocarbon selectivity, it is noted that in practically all processes, there was higher selectivity to C7, C8, C9, C14 and C15 hydrocarbons. This behavior can be associated to fatty acid composition of the oil esters, which have high contents of oleic (C18:1) and palmitic (16:0) acids. From oleic acid, it is possible to obtain C5, C7 and C9–C14 hydrocarbons through β-scission to the double bond, before fatty acid deoxygenation [2,3,29,30], followed by radical reactions (disproportion, condensation and β-scission to the radical carbon). Besides, through similar radical reactions, C6, C8–C13 can be obtained after deoxygenation of oxygenate fragment derived from β-scission to the double bond. Moreover, cyclic and aromatic hydrocarbons may be obtained from olefinic fragments also derived from acid oleic βscission. From palmitic acid, the C15 hydrocarbon is obtained through direct deoxygenation. An illustrative scheme of these processes is proposed in Fig. 6.
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Fig. 6. Reaction scheme of hydrocarbons obtained from oleic and palmitic acid derived from primary cracking of the butiri oil.
4. Conclusion From the thermal catalytic cracking (TCC) of buriti oil over LaSBA15 catalysts, it is possible to obtain an organic liquid (OL) fraction with low acid index, especially when this TCC process is accomplished over La75SBA-15, suggesting the deoxygenating activity of these catalytic solids. Furthermore, the large pore sizes and well ordered structure of the pores of the SBA-15 materials inhibited the carbonic chain fragmentation, allowing to obtain hydrocarbons with chains similar to those present in mineral diesel, designed Green Diesel. From TCC process of vegetal oils, it is possible to obtain new routes to obtain alternative and renewable fuel, with excellent quality and free of sulfur.
Acknowledgement The authors would like to thank the FAPEPI for the research scholarship, and the support from the PETROBRAS, ANP, FINEP and CNPq.
References [1] J.D. Adjaye, S.P.R. Katikaneni, N.N. Bakhshi, Catalytic conversion of a biofuel to hydrocarbons: effect of mixtures of H-ZSM-5 and silica-alumina catalysts on product distribution, Fuel Process. Technol. 48 (1996) 115–143. [2] R.O. Idem, S.P.R. Katikaneni, N. Bakhshi, Thermal cracking of canola oil: reaction products in the presence and absence of steam, Energy Fuels 10 (1996) 1150–1162. [3] R.O. Idem, S.P.R. Katikaneni, N. Bakhshi, Catalytic conversion of canola oil to fuels and chemicals: roles of catalyst acidity, basicity and shape selectivity on product distribution, Fuel Process. Technol. 51 (1997) 101–125. [4] P. Williams, P.A. Horne, The influence of catalytic type on the composition of upgraded biomass pyrolysis oils, J. Anal. Appl. Pyrolysis 31 (1995) 39–61. [5] F.A. Twaiq, N.A.M. Zabidi, A.R. Mohamed, S. Bhatia, Catalytic conversion of palm oil over mesoporous aluminosilicate MCM-41 for the production of liquid hydrocarbon fuels, Fuel Process. Technol. 84 (2003) 105–120.
[6] Y. Ooi, R. Zakaria, A.R. Mohamed, S. Bhatia, Synthesis of composite material MCM-41/beta and its catalytic performance in waste used palm oil cracking, Appl. Catal., A 274 (2004) 15–23. [7] A.O. Adebanjo, A.K. Dalai, N.N. Bakhshi, Production of diesel-like fuel and other valueadded chemicals from pyrolysis of animal fat, Energy Fuels 19 (2005) 1735–1741. [8] D.G. Lima, V.C.D. Soares, E.B. Ribeiro, D.A. Carvalho, E.C.V. Cardoso, F.C. Rassi, K.C. Mundim, J.C. Rubim, P.A.Z. Suarez, Diesel-like fuel obtained by pyrolysis of vegetable oils, J. Anal. Appl. Pyrolysis 71 (2004) 987–996. [9] F.A. Twaiq, A.R. Mohamed, S. Bhatia, Performance of composite catalysts in palm oil cracking for the production of liquid fuels and chemicals, Fuel Process. Technol. 85 (2004) 1283–1300. [10] P.A.Z. Suarez, S.M.P. Meneghetti, M.R. Meneghetti, C.R. Wolf, Transformação de triglicerídeos em combustíveis, materiais poliméricos e insumos químicos: algumas aplicações da catálise na oleoquímica, Quim. Nova 30 (2007) 667–676. [11] T.J. Benson, R. Hernandez, W.T. French, E.G. Alley, W.E. Holmes, Elucidation of the catalytic cracking pathway for unsaturated mono-, di-, and triacylglycerides on solid acid catalysts, J. Mol. Catal. A: Chem. 303 (2009) 117–123. [12] H. Yang, R. Yan, H. Chen, D.H. Lee, D.T. Liang, C. Zheng, Mechanism of palm oil waste pyrolysis in a packed bed, Energy Fuels 20 (2006) 1321–1328. [13] P.T. Williams, N. Nugranad, Comparison of products from the pyrolysis and catalytic pyrolysis of rice husks, Energy 25 (2000) 493–513. [14] T.L. Chew, S. Bhatia, Effect of catalyst additives on the production of biofuels from palm oil cracking in a transport riser reactor, Bioresour. Technol. 100 (2009) 2540–2545. [15] D. Zhao, Q. Huo, J. Feng, J. Kim, Y. Han, G.D. Stucky, Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered, hydrothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (1998) 6024–6036. [16] M.N. Timofeeva, S.H. Jhung, Y.K. Hwang, D.K. Kim, V.N. Panchenko, M.S. Melgunov, Y.A. Chesalov, J.S. Chang, Ce-silica mesoporous SBA-15-type materials for oxidative catalysis: synthesis, characterization, and catalytic application, Appl. Catal., A 317 (2007) 1–10. [17] M. Baca, E. Rochefoucauld, E. Ambroise, J. Krafft, R. Hajjar, P.P. Man, X. Carrier, J. Blanchard, Characterization of mesoporous alumina prepared by surface alumination of SBA-15, Microporous Mesoporous Mater. 110 (2008) 232–241. [18] A.S. Araujo, M. Jaroniec, Synthesis and properties of lanthanide incorporated mesoporous molecular sieves, J. Colloid Interface Sci. 218 (1999) 462–467. [19] Z. Mu, J.J. Li, Z.P. Hao, S.Z. Qiao, Direct synthesis of lanthanide-containing SBA-15 under weak acidic conditions and its catalytic study, Microporous Mesoporous Mater. 113 (2008) 72–80. [20] Q. Dai, X. Wang, G. Chen, Y. Zheng, G. Lu, Direct synthesis of cerium (III)-incorporated SBA-15 mesoporous molecular sieves by two-step synthesis method, Microporous Mesoporous Mater. 100 (2007) 268–275. [21] Z. Lou, R. Wang, H. Sun, Y. Chen, Y. Yang, Direct synthesis of highly ordered Co-SBA-15 mesoporous materials by the pH-adjusting approach, Microporous Mesoporous Mater. 110 (2008) 347–354.
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G.E. Luz Jr. et al. / Fuel Processing Technology 92 (2011) 2099–2104
[22] M. Selvaraj, S. Kawi, Direct synthesis and catalytic performance of ultralarge pore GaSBA-15 mesoporous molecular sieves with high gallium content, Catal. Today 131 (2008) 82–89. [23] J. Aguado, G. Calleja, A. Carrero, J. Moreno, One-step synthesis of chromium and aluminium containing SBA-15 materials, Chem. Eng. J. 137 (2008) 443–452. [24] G.E. Luz Jr., S.H. Lima, A.C.R. Melo, A.S. Araujo, V.J. Fernandes Jr., Direct synthesis and characterization of LaSBA-15 mesoporous molecular sieves, J. Mater. Sci. 45 (2010) 1117–1122. [25] M.L.S. Albuquerque, I. Guedes Jr., P. Alcantra, S.G.C. Moreira, Infrared absorption spectra of (Mauritia flexuosa L.) oil, Vib. Spectrosc. 33 (2003) 127–131. [26] M.L.S. Albuquerque, I. Guedes Jr., P. Alcantra, S.G.C. Moreira, N.M. Barbosa Neto, D.S. Correa, S.C. Zilio, Characterization of (Mauritia flexuosa L.) oil by absorption and emission spectroscopies, J. Braz. Chem. Soc. 16 (2005) 1113–1117.
[27] X. Junming, J. Jianchun, C. Jie, Liquid hydrocarbon fuels obtained by the pyrolysis of soybean oils, Bioresour. Technol. 100 (2009) 4867–4870. [28] D. Kubicka, L. Kaluza, Deoxygenation of vegetable oils over sulfided Ni, Mo and NiMo catalysts, Appl. Catal., A 372 (2010) 199–208. [29] K.D. Maher, D.C. Bressler, Pyrolysis of triglyceride materials for the production of renewable fuels and chemicals, Bioresour. Technol. 98 (2007) 2351–2368. [30] E. Vonghia, D.G.B. Boocock, S.K. Konar, A. Leung, Pathways for the deoxygenation of triglycerides to aliphatic hydrocarbons over activated alumina, Energy Fuels 9 (1995) 1090–1096.