Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst

G Model

ARTICLE IN PRESS

JAAP-3605; No. of Pages 5

Journal of Analytical and Applied Pyrolysis xxx (2015) xxx–xxx

Contents lists available at ScienceDirect

Journal of Analytical and Applied Pyrolysis journal homepage: www.elsevier.com/locate/jaap

Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst Lu Li a , Zhiyong Ding a , Kun Li a , Junming Xu b , Fusheng Liu a,∗ , Shiwei Liu a , Shitao Yu a,∗ , Congxia Xie c , Xiaoping Ge a a

College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, China Institute of Chemical Industry of Forest Products, Research Institute of New Technology CAF, Nanjing 210042, China c Key Laboratory of Eco-Chemical Engineering, Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China b

a r t i c l e

i n f o

Article history: Received 17 March 2015 Received in revised form 29 September 2015 Accepted 13 November 2015 Available online xxx Keywords: USY Catalytic cracking Waste cooking oil Liquid hydrocarbon fuels Recycling

a b s t r a c t The effective utilization of waste cooking oil (WCO) has been a focus of concern in recent years, and is an important environmental issue. In this work, catalytic cracking of WCO to produce liquid hydrocarbon fuels without any pre-processing has been studied using ultrastable zeolite USY as a catalyst. The USY exhibited higher catalytic activity for the cracking of WCO than traditional base catalysts such as Na2 CO3 and K2 CO3 . Moreover, the cracking of WCO generated fuels (containing C8 C9 alkanes or olefins) that have a similar chemical composition to gasoil-based fuels. The influences of temperature, time, and USY dosage on the cracking have been examined. Under conditions of temperature 430 ◦ C, reaction time 100 min, and m(USY):m(WCO) = 1:30, the yield of liquid products was over 64%. The USY could be reused up to six times without an apparent decrease in catalytic activity. XRD, FTIR, and N2 adsorption/desorption have been used to characterize the structures of the fresh and used USY. The results showed that USY having an integrated structure after use is an excellent catalyst for the cracking reaction. © 2015 Elsevier B.V. All rights reserved.

1. Introduction The amount of waste cooking oil (WCO) is increasing annually. Its cost-effective use to generate value-added products has received great attention in recent years [1–3]. A promising approach is to use WCO as a raw material to produce biofuel, which not only addresses environmental concerns regarding the treatment of WCO, but may also provide a clean technology for energy production [4]. Biodiesel, a biodegradable fuel and renewable form of energy, consists of monoalkyl esters of fatty acids and has been used as an alternative fuel in several countries [5–8]. The most widely used method to produce biodiesel is the transesterification of triacylglycerides using a homogeneous or heterogeneous catalyst [9]. Due to the complex composition of WCO, potentially containing sulfur and oxidized compounds besides hydrocarbons, a pre-treatment step is necessary if WCO is to be used as a raw material to produce bio-fuel by the transesterification method. Moreover, the traditional method produces a large amount of glycerol, which necessitates a costly

∗ Corresponding authors. Fax.: +86 53284022719. E-mail addresses: [email protected] (L. Li), [email protected] (F. Liu), [email protected] (S. Yu).

extraction procedure for its recovery [10,11]. In recent years, there has been increasing interest in the catalytic cracking of natural oils to produce biofuel [12]. Due to their low cost and high conversion rates, homogeneous alkaline catalysts are commonly used in industry for this purpose [13,14]. However, these catalysts cannot be recycled and the salt content in the biofuel would increase, which would lead to corrosion of the equipment. Based on the above premises, the development of new heterogeneous catalysts would seem to be an appropriate solution to overcome the problems associated with homogeneous catalysis. By this approach, the products would not contain impurities derived from the catalyst and the final cost of separation would be reduced. Heterogeneous catalysts are easily regenerated and reused, as well as environmentally friendly [7,15]. Among several heterogeneous acid catalysts, zeolites have been used for the production of biofuel from renewable sources [16–19], e.g., the cracking of biomass to generate products in the diesel or gasoline fraction, using large (Y and X) and medium to small (ZSM-5) pore zeolites, respectively [20,21]. In our previous work, USY was used to catalyze the cracking of rubber seed oil, and showed good catalytic activity and stability. The main objective of this study was to investigate the activity of ultrastable zeolite USY catalyst in the cracking of WCO without pre-treatment. The results showed that USY exhibited excellent

http://dx.doi.org/10.1016/j.jaap.2015.11.006 0165-2370/© 2015 Elsevier B.V. All rights reserved.

Please cite this article in press as: L. Li, et al., Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst, J. Anal. Appl. Pyrol. (2015), http://dx.doi.org/10.1016/j.jaap.2015.11.006

G Model JAAP-3605; No. of Pages 5

ARTICLE IN PRESS L. Li et al. / Journal of Analytical and Applied Pyrolysis xxx (2015) xxx–xxx

2 Table 1 Properties of the WCO. 140–147 Acid value (mgKOH/g)

Table 2 Effect of different catalysts on reaction resultsa . 107 Iodine value (g/100 g)

9.6–10 Peroxide value (meq/kg)

6.8–6.9 Moisture content (%)

catalytic activity and reusability in the reaction. In addition, the materials were characterized by XRD, N2 adsorption/desorption, and FTIR measurements after the sixth cycle. To the best of our knowledge, no article concerning the methods outlined here has hitherto been published. 2. Experimental 2.1. Chemicals and instrumentation WCO, USY, NaY, Si-MCM-41, and HZSM-5 were obtained from commercial sources and were used without further purification. The properties of WCO are shown in Table 1. Other materials, such as sodium carbonate (Na2 CO3 ) and potassium carbonate (K2 CO3 ), were purchased from Aldrich, and all materials were directly used after drying without further purification. chromatography–mass spectrometry (Agilent Gas 6890N/5973N) was used to analyze the compositions of the products. Separations were realized on an HP-5 column, 30 m × 0.25 mm × 0.25 ␮m, working between 70 ◦ C (2 min) and 280 ◦ C (20 min) at a heating rate of 5 ◦ C/min. Different classes of compounds present in the pyrolysates were confirmed by total-ion chromatogram (TIC) and selected-ion mass chromatogram analyses, in addition to fragmentation patterns and library matching (NIST). Compounds were identified according to pre-established criteria for analysis of the data. The dynamic viscosity was measured with an SYD-265C viscometer (GB/T265-88), and the gross calorific value was measured with a Well 8000 fast automatic calorimeter. Moisture was tested with an SF 101 trace moisture analyzer. X-ray powder diffraction patterns of the USY were obtained with an XB-3A instrument using monochromated CuK˛ radiation ( = 0.15418 nm). It was operated at 40 kV and 100 mA. Data were acquired with a step width of 0.02◦ and a scan speed of 2◦ /min over the diffraction range 2 = 2–40◦ . The surface area was calculated using the BET method based on adsorption data in the partial pressure (P/P0 ) range 0–0.1, and the pore diameter and pore volume were determined from the amount of N2 adsorbed at P/P0 = 1 using the BJH method. Infrared (IR) spectra of the USY were measured on a Bruker FT-IR Vertex 70 spectrometer in the range 4000–600 cm−1 by ATR. FTIR spectra of adsorbed pyridine were recorded on a Nicolet 6700 FTIR spectrometer. The sample was pressed into selfsupporting discs, placed in an IR cell, and treated under vacuum (10−6 Torr) at 423 K for 2 h. After cooling to room temperature, the sample was exposed to pyridine vapor for 2 min. Spectra (100 scans, 4 cm−1 resolution) were then recorded after evacuation (5 × 10−5 Torr) for 1 h at 423 K [22]. 2.2. Cracking of WCO Catalytic cracking experiments were carried out at temperatures ranging from 400 to 440 ◦ C in a 250 ml glass vessel. The WCO (W1 ) and catalyst (W2 ) were placed in the reactor and then heated by an external electrical resistance at a rate of 20 ◦ C/min. The temperature was measured at two positions (column temperature and bottom temperature) using calibrated thermocouples. When the temperature in the reactor reached 400 ◦ C, the WCO was cracked and vaporized. The vapor left the reactor through the rectification

Entry

1 2 3 4 5 6 7 a

Catalysts

Thermal cracking K2 CO3 Na2 CO3 HZSM-5 NaY USY Si-MCM-41

Yield/%

63.8 74.7 74.9 65.5 69.6 75.3 66.4

Yield/%

Coke/%

Liquid

Gas

45.3 46.9 55.8 38.8 51.5 58.7 45.7

18.5 27.8 19.1 26.7 18.1 16.6 20.7

36.2 25.3 25.1 34.5 30.4 24.7 33.6

WCO 10 g, m(catalyst):m(WCO) = 1:50, 400 ◦ C, 150 min.

column at temperatures ranging from 400 to 440 ◦ C. The vapor feed then entered into heat exchangers. As a result, the liquid fraction was obtained in the collector and weighed (W3 ). The residue in the reactor was weighed to give the coke yield (W4 ). The yield (wt.%) for WCO and yields (wt.%) for liquid, gas, and coke were calculated as follows: W1 + W2 − W4 Yield × 100% = % W1

;

W3 Yield(liquid) = × 100% % W1

;

Yield Yield(gas) Yield(liquid) = − % % %

;

W4 Yield(Coke) × 100% = % W1 2.3. Stability of USY The reusability of the USY was studied by deploying the used catalyst in consecutive reaction cycles under the optimum reaction conditions. After each use, the catalyst could be reused after calcination. After being used six times, the catalyst was examined by XRD, N2 adsorption/desorption, and FTIR. 3. Results and discussion 3.1. Catalytic cracking of WCO The activities of different catalysts in the cracking of WCO were investigated (Table 2). As can be seen from Table 2, USY showed almost the same catalytic activity as the traditional bases K2 CO3 or Na2 CO3 (entries 2, 3, and 6); the cracking yield reached 75.3% and the yield of liquid reached 58.7% using USY as catalyst (entry 6). The acidity of USY was characterized by the FTIR spectrum of adsorbed pyridine. The IR spectrum recorded after adsorption of pyridine at room temperature on a USY sample at 423 K is shown in Fig. 1. A band at 1479 cm−1 , attributable to pyridine adsorbed at a Lewis acid site, is observed [23,24]. At the same time, a band at 1535 cm−1 may be attributed to the pyridinium ion, implying the presence of Brønsted acidic sites on USY [25]. The results indicated that the cracking of WCO using USY as catalyst is a typical acid-catalyzed pyrolysis. According to the mechanism of acid-catalyzed pyrolysis [26], WCO was almost completely cracked into alkane and olefin. Therefore, USY is an excellent catalyst for the cracking of WCO. 3.2. Performance of cracking oil In order to identify the pyrolysis products, GC–MS analysis was carried out. The products derived from the thermal cracking using K2 CO3 , Na2 CO3 , or USY as catalysts were detected, and the results

Please cite this article in press as: L. Li, et al., Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst, J. Anal. Appl. Pyrol. (2015), http://dx.doi.org/10.1016/j.jaap.2015.11.006

G Model

ARTICLE IN PRESS

JAAP-3605; No. of Pages 5

L. Li et al. / Journal of Analytical and Applied Pyrolysis xxx (2015) xxx–xxx

3

1.0

yield yield of liquid products

Transmittance/%

0.8

0.6

0.4

82

62

80

60

0.2

84

Yield

Yield of liquid products/%

64

0

2

4

6

reused time 400

600

800

1000

1200

1400

1600

1800

2000

Fig. 2. Product yields showing the reusability of USY.

-1

Wavenumber(cm ) Fig. 1. FTIR spectrum of pyridine adsorbed on USY.

Table 3 The main components of cracking oil.a Catalysts

Yield of liquid /%

Components

Content/%

Na2 CO3

57.60

Nonane Decane Dodecane 1-Tridecylene Hexadecane

11.67 11.71 5.21 9.63 13.23

K2 CO3

57.40

2-Heptylene Nonane Hexadecane 8-Heptadecene Heptadecane

6.12 5.25 7.88 14.13 5.92

USY

60.20

1,3-Octadiene 1-Octylene Octane Nonane

14.89 13.31 16.39 32.58

Thermal cracking

41.20

1-Octylene Octane Nonane 4-Decene Hendecane

6.81 6.53 5.92 5.10 12.92

a

WCO 10 g, m(catalyst):m(WCO) = 1:50, 420 ◦ C, 150 min.

are shown in Table 3. From Table 3, it can be seen that the cracking oil obtained using USY as catalyst was rich in C8 C9 alkanes or alkenes; in particular, the content of nonane was more than 32%. However, the composition of the cracking oil obtained using K2 CO3 or Na2 CO3 as catalyst was very complex, with no single component being present at a level exceeding 15%. Similar results were obtained by thermal cracking. In summary, USY exhibits excellent selectivity in the cracking of WCO, which is evidently an intrinsic property of the zeolite [27]. The main properties of the cracking oil obtained from WCO using USY as catalyst are shown in Table 4. For comparison purposes, Table 4 also displays the properties of the cracking oil obtained from thermal cracking, using Na2 CO3 or K2 CO3 as catalysts, and specified values for petroleum-based fuel. The results show that the fuels derived from WCO using USY as catalyst possess acceptable values for the given properties compared to those for the petroleum-based fuel, and better values than those for the fuels obtained using traditional base catalysts or thermal cracking. The excellent properties of the fuel obtained from WCO using USY as catalyst may have been due to the prevalence of C8 C9 alkanes or alkenes therein [13].

Fig. 3. X-ray diffraction patterns of fresh and used USY.

3.3. Effects of reaction conditions on the cracking of WCO The effects of reaction conditions on the hydrolysis results are shown in Table 5. When the USY dosage was increased, both the cracking yield and the yield of liquid product increased. When m(USY):m(WCO) was increased from 1:50 to 1:30, the cracking yield increased from 75.3% (entry 1) to 76.8% (entry 3), and the yield of liquid product increased from 58.7% to 59.7%. However, when the USY dosage was further increased, the cracking yield was almost unchanged, but the yield of liquid product decreased (entries 4 and 5). Temperature also had a significant effect on the WCO cracking results. At 400 ◦ C, the yield was 76.8% (entry 3) under the given conditions. The yield gradually increased with increasing reaction temperature. When the temperature was increased to 430 ◦ C under otherwise identical conditions, the yield reached 82.3%, and the yield of liquid product was 64.6% (entry 8). Moreover, when the time was increased, the yield initially increased. However, when the time was further increased from 100 to 120 min, the yield was almost unchanged (entries 13–15). In summary, the optimum operating conditions for the catalytic cracking of WCO were as follows: WCO 10 g, m(USY):m(WCO) = 1:30, 430 ◦ C for 100 min. Under the above conditions, the cracking yield and yield of liquid product were 82.3% and 64.6%, respectively.

Please cite this article in press as: L. Li, et al., Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst, J. Anal. Appl. Pyrol. (2015), http://dx.doi.org/10.1016/j.jaap.2015.11.006

G Model

ARTICLE IN PRESS

JAAP-3605; No. of Pages 5

L. Li et al. / Journal of Analytical and Applied Pyrolysis xxx (2015) xxx–xxx

4 Table 4 Physical and chemical properties of cracking oil. Fuel properties (Catalysts)

Cracking oilThermal cracking Cracking oil Na2 CO3 Cracking oilK2 CO3 Cracking oilUSY Biodiesel[28] 0# diesel

93# gasoline

Density (g/cm3 ) Moisture content % Calorific value (MJ/kg) Dynamic viscosity (mm2 /s), 40 ◦ C Color

0.89

0.88

0.88

0.84

0.89

0.84

0.82

0.50

0.37

0.36

0.31

––

––

––

36.2

37.1

37.4

41.0

38

42.5

42.7

4.37

4.21

4.17

3.78

4.5

––

––

Brown

Yellow

Yellow

Faint yellow

––

Faint yellow Colorless

Table 5 Effect of reaction conditions on reaction results.a Entry

m(USY)/m(WCO)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 a

1:50 1:40 1:30 1:20 1:10 1:30 1:30 1:30 1:30 1:30 1:30 1:30 1:30 1:30 1:30

Temperature/◦ C

Time/min

Yield/%

Yield of liquid product/%

400 400 400 400 400 410 420 430 440 450 430 430 430 430 430

150 150 150 150 150 150 150 150 150 150 80 90 100 110 120

75.3 76.0 76.8 77.1 77.3 77.5 80.8 82.3 82.5 82.7 75.8 79.6 82.3 82.5 82.6

58.7 59.0 59.7 57.3 51.2 60.0 62.5 64.6 64.3 63.9 60.9 62.9 64.6 64.6 64.6

WCO 10 g, m(catalyst):m(WCO) = 1:50–10, 400–450 ◦ C, 80–150 min.

100

260

a

Adsorption Desorption

240

95

V/(cm3/g)

V/(cm 3/g)

Adsorption Desorption

90

220 200 180

85 80 75

160 140 0.0

b

0.2

0.4

0.6

0.8

1.0

70 0.0

0.2

P/P

0.4

0.6

0.8

1.0

P/P

Fig. 4. N2 adsorption–desorption isotherms of fresh USY (a) and used USY (b).

3.4. Reusability of USY The reusability of USY in the cracking of WCO was investigated, and the results are shown in Fig. 2. The USY could be reused up to six times without apparent decreases in the cracking yield or the yield of liquid product under the given conditions. Therefore, USY has good reusability for the cracking of WCO. It is well known that the main factor that affects the reusability of a zeolite is its structural stability under the reaction conditions. Hence, the structures of both fresh and used USY were studied by XRD, FTIR, and N2 adsorption/desorption (N2 ad/de). The preservation of the structure of fresh USY in used USY was verified by XRD (Fig. 3). The characteristic diffraction peaks of used USY were the same as those of fresh USY. However, the intensities of the peaks of used USY were weaker than those for USY. The results implied that the used USY retained the microporous structure, but that its crystallinity was slightly decreased [29]. The

Table 6 The structural parameters of fresh and used USY. Sample

BET surface area (m2 g−1 )

Average pore volume (nm)

BJH pore volume (cm3 g−1 )

Fresh USY Used USY

554.42 522.75

2.54 2.51

0.23 0.15

textural properties of the USY, as measured by N2 ad/de, revealed that all parameters were reduced after use (Fig. 4 and Table 6). The values obtained for micropore volumes and external areas implied that carbon deposition may have occurred in the pores of the used USY [30]. Fig. 5 shows the IR spectra of fresh and reused USY. It can be seen that the two spectra are almost identical, which demonstrates that there was almost no change in the structure of the zeolite after sixfold reuse [9]. The results were consistent with those from XRD. The loss of activity may have been due to carbon deposi-

Please cite this article in press as: L. Li, et al., Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst, J. Anal. Appl. Pyrol. (2015), http://dx.doi.org/10.1016/j.jaap.2015.11.006

G Model

ARTICLE IN PRESS

JAAP-3605; No. of Pages 5

L. Li et al. / Journal of Analytical and Applied Pyrolysis xxx (2015) xxx–xxx

5

201510426015), “11th National 5-year R&D plans in rural areas” (Grant Number: 2011BAD22B05) and the National Natural Science Foundation of China (Grant Number: 31100521 and 311570573).

used USY

Intensity

References

USY

4000 35 00 30 00 2500 20 00 1500 1000 wavenu mber/cm

500

-1

Fig. 5. IR spectra of fresh and used USY.

tion on the zeolite during use. Nevertheless, USY can be considered as an effective and reusable catalyst for the cracking of WCO. 4. Conclusion WCO can be completely cracked without pre-treatment by using USY as a catalyst. The cracking yield was 82.3% and the yield of liquid product was over 64% under the following conditions: m(USY):m(WCO) = 1:30, WCO 10 g, reaction temperature 430 ◦ C, and a total time of 100 min. The USY could be reused up to six times without an apparent decrease in the cracking yield or the yield of liquid product. This strategy could overcome the shortcomings associated with the traditional methods, such as the infeasibility of reusing the catalyst, equipment corrosion, tedious work-up procedures, and environmental problems. Acknowledgements This work was financially supported by The Taishan Scholar Program of Shandong, National Training Program of Innovation and Entrepreneurship for Undergraduates (Grant Number:

[1] N. Taufiqurrahmi, A.R. Mohamed, S. Bhatia, Bioresour. Technol. 102 (2011) 10686–10694. [2] A. Sınag, S. Gülbay, B. Uskan, S. Ucar, S.B. Ozgurler, J. Hazard. Mater. 173 (2010) 420–426. [3] Y.K. Ong, S. Bhatia, Energy 35 (2010) 111–119. [4] V.R. Wiggers, A. Wisniewski, L.A.S. Madureira, A.A. Chivanga Barros, H.F. Meier, Fuel 88 (2009) 2135–2141. [5] Z. Helwani, M.R. Othman, N. Aziz, W.J.N. Fernando, J. Kim, Fuel Process. Technol. 90 (2009) 1502–1514. [6] M. Zabeti, W.M.A.W. Daud, M.K. Aroua, Fuel Process. Technol. 90 (2009) 770–777. [7] F.C.G. Mattos, J.A.S. Souza, A.B.A.C. Cotrim, J.L. Macedo, J.A. Dias, S.C.L. Dias, G.F. Ghesti, Appl. Catal. A 423-424 (2012) 1–6. [8] D.Y.C. Leung, X. Wu, M.K.H. Leung, Appl. Energy 87 (2010) 1083–1095. [9] L.D. Borges, N.N. Moura, A.A. Costa, P.R.S. Braga, J.A. Dias, S.C.L. Dias, J.L. Macedo, G.F. Ghesti, Appl. Catal. A 450 (2013) 114–119. [10] B. Bharathiraja, S.P. Ayyappasamy, J. Jayamuthunagai, Waste Manage. 32 (2012) 1539–1547. [11] S. Kim, G Korea Patent 10 201 00053719. [12] E.C. Petrou, C.P. Pappis, Energy Fuels 23 (2009) 1055–1066. [13] J.M. Xu, J.C. Jiang, Y.J. Sun, J. Chen, Bioresour. Technol. 101 (2010) 9803–9806. [14] J.M. Xu, J.C. Jiang, Y.J. Sun, J. Chen, Bioresour. Technol. 100 (2009) 4867–4870. [15] S.A. Basha, K.R. Gopal, S. Jebaraj, Renew. Sustain. Energy Rev. 13 (2009) 1628–1934. [16] X. Liu, H. He, Y. Wang, S. Zhu, Catal. Commun. 8 (2007) 1107–1111. [17] M.D. Serio, R. Tesser, L. Pengmei, E. Santacesaria, Energy Fuels 22 (2008) 207–217. [18] B.H. Hameed, L.F. Lai, L.H. Chin, Fuel Process. Technol. 90 (2009) 606–610. [19] A. Aho, N. Kumar, K. Eranen, T. Salmi, M. Hupa, D.Y. Murzin, Fuel 87 (2008) 2493–2501. [20] (a) H.S. Heo, S.G. Kom, K.E. Jeong, Bioresour. Technol. 102 (2011) 3952–3957; (b) Alonso, Bond, Dumesic, Green Chem. 12 (2010) 1493–1513. [21] A. Corma, A. Martinez, Adv. Mater. 7 (1995) 137–144. [22] S. Damyanova, L. Petrov, M.A. Centeno, P. Grange, Appl. Catal. A 224 (2002) 271–284. [23] H. Knözinger, Adv. Catal. 25 (1976) 184–271. [24] C. Mortera, G. Cerato, Langmuir 6 (1990) 1810–1812. [25] S. Damyanova, P. Grange, B. Delmon, J. Catal. 168 (1997) 421–430. [26] K.D. Maher, D.C. Bressler, Bioresour. Technol. 98 (2007) 2351–2368. [27] R.R. Xu, W.Q. Pang, Chemistry-Zeolites and Porous Materials, Science Press, 2004. [28] M. Canakci, Bioresour. Technol. 98 (2007) 183–190. [29] G.F. Ghesti, J.L. Macedo, V.C.I. Parente, J.A. Dias, S.C.L. Dias, Micropor. Mesopor. Mater. 100 (2007) 27–34. [30] O.D. Mante, F.A. Agblevor, R. McClung, Fuel 108 (2013) 451–464.

Please cite this article in press as: L. Li, et al., Liquid hydrocarbon fuels from catalytic cracking of waste cooking oils using ultrastable zeolite USY as catalyst, J. Anal. Appl. Pyrol. (2015), http://dx.doi.org/10.1016/j.jaap.2015.11.006