Conversion of waste cooking oil to jet biofuel with nickel-based mesoporous zeolite Y catalyst

Bioresource Technology 197 (2015) 289–294

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Conversion of waste cooking oil to jet biofuel with nickel-based mesoporous zeolite Y catalyst Tao Li, Jun Cheng ⇑, Rui Huang, Junhu Zhou, Kefa Cen State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China

h i g h l i g h t s  Mesoporous zeolite Y was used to convert waste cooking oils to jet biofuel.  Mesoporous zeolite Y exhibited high alkane and low aromatic hydrocarbon selectivity.  Reaction pathway for transforming waste cooking oil to jet biofuel was proposed.

a r t i c l e

i n f o

Article history: Received 2 July 2015 Received in revised form 13 August 2015 Accepted 14 August 2015 Available online 31 August 2015 Keywords: Mesoporous zeolite Y Waste cooking oil Reaction pathway

a b s t r a c t Three types of zeolites (Meso-Y, SAPO-34, and HY) loaded with nickel were used to convert waste cooking oil to jet biofuel. Mesoporous zeolite Y exhibited a high jet range alkane selectivity of 53% and a proper jet range aromatic hydrocarbon selectivity of 13.4% in liquid fuel products. Reaction temperature was optimized to produce quality jet biofuel. Zeolite Meso-Y exhibited a high jet range alkane yield of 40.5% and a low jet range aromatic hydrocarbon yield of 11.3% from waste cooking oil at 400 °C. The reaction pathway for converting waste cooking oil to jet biofuel was proposed. Experimental results showed that waste cooking oil mainly deoxygenated to heptadecane (C17H36) and pentadecane (C15H30) through the decarbonylation pathway for the first 3 h. Long chain alkanes cracked into jet range alkanes (C8–C16). Cycloalkanes and aromatic hydrocarbons were produced through cyclization and dehydrogenation pathways. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction The aviation industry is exploring solutions to reduce fuel consumption and greenhouse gas emissions in response to growing environmental concerns. Aviation fuel is a fuel especially designed for use in aircrafts. Jet fuels are the commonly used commercial aviation fuels and are currently produced from petroleum refining (Liu et al., 2013). Formulating aviation biofuels can help reduce the dependence on fossil fuel. Production of jet biofuel from biomass or biomass-derived feedstock should be developed. Traditional jet fuel mainly contains C8–C16 alkanes and aromatic hydrocarbons which are produced from petroleum refining. Jet fuels should meet very stringent specifications, which increases the difficulty of developing an alternative fuel for

Abbreviations: BET, Brunauer–Emmett–Teller; BJH, Barrett–Joyner–Halenda; FAME, fatty acid methyl ester; TPD, temperature programmed desorption of ammonia; GC–MS, gas chromatography–mass spectrometer. ⇑ Corresponding author. Tel.: +86 571 87952889; fax: +86 571 87951616. E-mail address: [email protected] (J. Cheng). http://dx.doi.org/10.1016/j.biortech.2015.08.115 0960-8524/Ó 2015 Elsevier Ltd. All rights reserved.

aviation compared with that for automobile applications (Verma et al., 2011). Several routes such as Fischer Tropsch synthesis and hydrotreating of vegetable oil, have been developed to produce aviation biofuels from biomass feedstock. Non edible oils, such as cantor oils, algae, jatropha, forest residue or municipal wastes are the major available resources for energy production (Hari et al., 2015). We previously used soybean as a feedstock for jet biofuel production (Cheng et al., 2014). Robota reported a multi-step process for cogenerating diesel and aviation fuel from algal lipids with very low yield (Robota et al., 2013). Approximately, over five million t of waste cooking oil is generated in the urban restaurant industry in China, of which 40–60% backflow to dining tables through various channels (Zhang et al., 2014). Utilization of reprocessed waste cooking oil (commonly known as gutter oil) in restaurants is a growing problem in China. Hydrotreating waste cooking oil is a promising method for jet biofuel production. Waste cooking oil is composed of triglycerides, and, long-chain carbon fatty acids. Therefore, diesel range carbon chains (C15–C18) can be produced by reaction pathways such as, dehydration, decarbonylation and decarboxylation. Biodiesel production from waste cooking

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oil using hydrodeoxygenation technology has been reported (Bezergianni et al., 2010; Bezergianni et al., 2009). Zeolites are widely used as catalyst supports in numerous applications in refining industries. Approximately 200 different zeolite structures had been discovered over the past century, but only a few structures have industrial application (Dhainaut et al., 2013). The small pore size of microporous zeolite limits access to large molecules such as triglycerides. Mesoporous zeolites have been conceived in response to the need of new application, such as the conversion of large biomolecules into valuable chemicals (Verboekend et al., 2012). Mesoporous zeolites can be applied for the catalytic conversion of bulky substrates. Reports on jet biofuel production from waste cooking oil are still rare. In this paper, three Ni-loaded zeolite catalysts are used for one-step conversion of waste cooking oil into jet range hydrocarbons. Mesoporous zeolite Y presented high alkane selectivity and low aromatic hydrocarbon selectivity. The reaction pathway of jet biofuel production from waste cooking oils is revealed. 2. Methods 2.1. Preparation of catalysts Ni(NO3)2
6H2O (P98.0% analytical standard) used in the experiments was purchased from Sinopharm Chemical Reagent Co Ltd, (Shanghai, China). Zeolites HY and SAPO-34 were purchased from the Catalyst Plant of Nankai University. Mesoporous zeolite Y was purchased from the Company of Fengxiang in Hang Zhou. Ni clusters supported on zeolite catalysts were prepared using a wetness impregnation method. The procedure used for synthesizing Ni (10 wt%)/zeolites catalysts is the same. Ni (10 wt%)/mesoporous zeolite Y catalyst was synthesized as follows: Ni(NO3)2
6H2O (2.97 g) was dissolved in 10 mL of deionized water. Then 5.4 g of mesoporous zeolite Y was added to the solution. The mixture was stirred for 4 h at ambient temperature and then dried in an oven at 70 °C for 8 h. The catalyst was calcined in air at 550 °C (heating rate = of 5 °C/min) for 4 h and reduced in hydrogen (flow rate = of 350 mL/min) at 500 °C (heating rate = of 4 °C/min) for 4 h.

mechanical stirrer. The waste cooking oil was dried in an oven to remove water before experimentation. In a typical run, 100 mL of waste cooking oil and catalysts with 20:1 mass ratio were loaded in the reactor. The reactor was sealed and filled with hydrogen to a pressure of 3 MPa at ambient temperature. The reaction was conducted with stirring at 500 rev/min at 390 °C for 8 h over Ni/HY, Ni/Mes-Y, and Ni/SAPO-34 catalysts. The liquid and solid products were separated by centrifugation after the reaction. Weight of the liquid products was measured on a balance and liquid compositions were analyzed on a GC–MS. 2.4. Analysis method of liquid products The liquid product samples were diluted at a ratio of 1:10 in chloroform and analyzed by an Agilent 6890N GC/5975B MSD equipped with a HP-5 capillary column. Injection temperature was set to 320 °C. High injection port temperature was used for reliable and direct quantification of fatty acids and triglycerides without chemical derivatization (Fu et al., 2010). Column temperature was initially increased from 30 to 80 °C at a rate of 2 °C/min, and then increased to 300 °C at a rate of 10 °C/min, which was maintained for 20 min. GC–MS results were quantified using a peak area normalization method based on peak area percentages of the identified components. All measurements were conducted in triplicate. The mean value and standard deviation were reported. 3. Results and discussion 3.1. Catalyst characterization The physicochemical properties such as BET surface, micropore volume, mesopore volume, pore size, acid density of Ni/HY,

Table 1 Physicochemical properties of catalysts. Catalysts

BET surface area (m2/g)

Micropore volume (cm3/g)

Mesopore volume (cm3/g)

Pore size (nm)

Acid density (mmol/g)

Ni/HY Ni/SAPO-34 Ni/Meso-Y

537.1 89.2 517.6

0.25 0.05 0.26

0.05 0.05 0.03

0.71 0.57 3.9

4.54 2.26 4.55

2.2. Characterization of catalysts

2.3. Preparation of jet range hydrocarbons Waste cooking oil used in experiments was collected from a restaurant in Zhejiang University, Hangzhou China. The jet range hydrocarbon preparation experiment was performed in a 500 mL batch reactor (Parr Instrument Company 4500) equipped with a

Ni/SAPO-34 Ni/HY Ni/Meso-Y

0.06

0.05

0.04

Intensity (a.u)

Nitrogen sorption isotherms were measured at 196 °C using a Micrometrics ASAP 2020 M system. Surface areas of catalysts were determined using the Brunauer–Emmett–Teller model. The micropore volumes of catalysts were determined using t-plot method. Mesopore volumes were determined using the Barrett–Joyner–Ha lenda (BJH) model. Micropore size distributions were determined using the Horvath–Kawazoe method. Mesopore size distributions were determined using the BJH model. Temperature programmed desorption of ammonia (NH3-TPD) experiments were conducted using a Micrometrics AutoChem II 2920 system. Catalyst (0.1 g) was loaded on the U-shaped tube at 300 °C and blown by highpurity He at 30 mL/min for 60 min. Then the catalyst was cooled at 20 mL/min by 10% NH3–He to 120 °C for 60 min. Finally, the catalyst was blown by high purity He at 30 mL/min for 60 min, and then heated to 800 °C at 10 °C/min. The acid density of catalysts was calculated as follows: 0.267 mmol/g  area of the NH3-TPD profiles.

0.03

0.02

0.01

0.00 100

200

300

400

500

Temperature (

600

700

800

)

Fig. 1. NH3-TPD profiles of Ni/SAPO-34, Ni/HY, and Ni/Meso-Y catalysts.

900

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Selectivity of jet range alkanes Selectivity of jet range aromatic hydrocarbons Selectivity of diesel Selectivity of intermediates

70

Selectivity of liquid products %

60

50

40

30

20

10

0

SAPO-34

HY

Meso-Y

(a) Selectivity of liquid products over zeolites HY, SAPO-34, Meso-Y

Selectivity of jet range hydrocarbons (%)

16

Zeolite SAPO-34 Zeolite Meso-Y Zeolite HY

14 12 10 8 6 4 2 7

8

9

10

11

12

13

14

15

16

17

Carbon numbers

(b) Selectivity of jet range hydrocarbon of various carbon numbers Yield of jet range alkanes Yield of jet range aromatic hydrocarbons Yield of diesel Yield of intermediates

45 40

Yield of liquid products %

35 30 25 20 15 10 5 0

HY

SAPO-34

Meso-Y

(c) Yields of liquid products over zeolites HY, SAPO-34, Meso-Y Fig. 2. Selectivities of jet range hydrocarbons converted from waste cooking oil over Ni/HY, Ni/SAPO-34 and Ni/Meso-Y catalysts under 3 MPa of hydrogen pressure at 390 °C.

Ni/SAPO-34 and Ni/Meso-Y catalysts refer to Table 1. NH3-TPD profile of Ni/SAPO-34 presented high peaks at 197.9 °C and 383.6 °C corresponding to weak and strong acidities (Fig. 1). The

acid density of Ni/SAPO-34 catalyst was 2.26 mmol/g. The NH3-TPD profiles of Ni/HY and Ni/Meso-Y were similar and both presented high peaks at 208.7 °C, 367.3 °C and 483.9 °C corresponding to

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Jet range alkane Jet range aromatic hydrocarbon Total jet biofuel Diesel

60 55

Yield of hydrocarbons (%)

50 45 40 35 30 25 20 15 10 5 0 370

380

390

400

410

Temperature (

420

430

)

(a) Yield of hydrocarbons under different reaction temperature 370 390 400 410 430

26 24

Selectivity of hydrocarbons (%)

22 20 18 16 14 12 10 8 6 4 2 0 C8

C9

C10

C11

C12

C13

C14

C15

C16

Carbon number

(b) Selectivity to hydrocarbons of different carbon number Fig. 3. Yields of hydrocarbons at 370–430 °C and selectivity to hydrocarbons with different carbon numbers over Ni/Meso-Y catalyst.

Table 2 Raw compositions of waste cooking oil detected on GC–MS.

3.2. Selecting Ni-loaded zeolite catalysts for quality jet biofuel production from waste cooking oil

Compositions

Methyl hexadecanoate

Methyl linoleate

Methyl oleate

Methyl stearate

Molecular formulas Peak area (%)

C17H34O2

C19H34O2

C19H36O2

C19H18O2

16.87

30.62

44.67

7.84

weak, moderate and strong acidities. The acid densities of Ni/HY and Ni/Meso-Y catalysts were 4.54 and 4.55 mmol/g, respectively.

Quality jet biofuel contained proper content of aromatic hydrocarbons. Excessively low aromatic hydrocarbon content leads to poor lubrication, whereas excessively high aromatic hydrocarbon content results in low heating value (Agusdinata et al., 2011). Niloaded zeolite catalysts were used to convert waste cooking oils into quality jet biofuel. Selectivity to jet range aromatic hydrocarbons over Ni/HY, Ni/SAPO-34 and Ni/Meso-Y were 23%, 6.1% and 13.4%, respectively (Fig. 2(a)). Catalyst Ni/HY exhibited the highest aromatic hydrocarbon selectivity, which reduced the heating value

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As shown in Fig. 2(c), yields of jet range alkanes, jet range aromatic hydrocarbons, diesel, and intermediates over Ni/HY, Ni/SAPO-34 and Ni/Meso-Y were 31.4%, 13.6%, 6.5%, 5.8%; 40.8%, 4.3%, 15.4%, 7.6%; 37.8%, 9.6%, 12.9%, and 8.6%, respectively (Fig. 2(c)). Ni/Meso-Y evidently presented the highest jet range hydrocarbon and proper jet range aromatic hydrocarbon selectivity.

of jet biofuel. Catalyst Ni/SAPO-34 exhibited the lowest aromatic hydrocarbon selectivity leading to poor lubrication of jet biofuel. These characteristics were probably due to the NH3-TPD profile of catalyst Ni/SAPO-34, which presented high peaks at 197.9 °C and 383.6 °C corresponding to weak and strong acidities. Catalyst Ni/Meso-Y exhibited proper aromatic hydrocarbon selectivity, which should be attributed to the mesopore in zeolite Meso-Y (3.9 nm). Selectivity to jet range alkane over Ni/HY, Ni/SAPO-34 and Ni/Meso-Y were 53%, 58% and 53% respectively. Catalyst Ni/SAPO-34 exhibited slightly higher jet range alkane selectivity than the other two catalysts. Selectivity to diesel over Ni/HY, Ni/SAPO-34, and Ni/Meso-Y were 10.6%, 22%, 18.1% respectively. Catalyst Ni/SAPO-34 exhibited the highest diesel selectivity, which should be attributed to the low acid density of Ni/SAPO-34 catalyst (2.26 mmol/g). Selectivity to intermediates over Ni/HY, Ni/SAPO-34 and Ni/Meso-Y were 9.8%, 10.8% and 11.6% respectively. Selectivity of jet range hydrocarbons of various carbon numbers (C8–C16) over catalyst Ni/HY was uneven-(Fig. 2(b)). However, selectivity of jet range hydrocarbons of various carbon numbers over catalysts Ni/Meso-Y and Ni/SAPO-34 was uniform.

3.3. Optimization of reaction temperature for quality jet biofuel production Reaction temperature was optimized to produce quality jet biofuel with high alkane and low aromatic hydrocarbon. At 370 °C, low yield of liquid hydrocarbons was observed and oligomerization occurred (Fig. 3(a)). Yield of jet range alkanes increased to 31.4%, while that of jet range aromatic hydrocarbons increased to 13.6%, when the reaction temperature was increased to 390 °C. Yields of jet range alkanes and jet range aromatic hydrocarbons further increased to 40.5% and 11.3% at 400 °C. These characteristics were due to the change in reaction pathway from oligomerization to cracking reaction. At 410 °C, the yield of jet range alkanes

100

Waste cooking oils Alkenes Cycloalkanes Aromatic hydrocarbons

80 18

Selectivity (%)

16 14 12 10 8 6 4 2 0 0

1

2

3

4

5

6

7

8

9

Reaction time (h)

(a) Selectivity to waste cooking oil and hydrocarbons at varied hours C8-C11 Alkanes C12-C14 Alkanes Pentadecane Hexadecane Heptadecane

30

Selectivity to alkanes (%)

25

20

15

10

5

0 0

1

2

3

4

5

6

7

8

9

Reaction time (h)

(b) Selectivity to alkanes at varied hours Fig. 4. Selectivities to waste cooking oils, hydrocarbons and alkanes at varied reaction times over Ni/Meso-Y catalyst.

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decreased to 31%, and the yield of jet range aromatic hydrocarbons increased to 21.6%. A portion of the alkane was converted to aromatic hydrocarbons through aromatization. At 430 °C, the yield of total jet range hydrocarbons and alkanes decreased to 35.6% and 14.1%, which was due to severe cracking reaction. Liquid hydrocarbons crack into gaseous products. Selectivities to jet range hydrocarbons with different carbon numbers are shown in Fig. 3(b). At 370 °C, C15 and C16 presented higher selectivity than the other hydrocarbons. At 430 and 410 °C, the short chain hydrocarbons (C8–C12) presented higher selectivity than the long chain hydrocarbons (C13–C16). This phenomenon should be attributed to severe cracking reaction. At 390 and 400 °C, selectivities of hydrocarbons with different carbon numbers were almost similar. Therefore, the optimal reaction temperature for jet biofuel production from waste cooking oils was 400 °C. 3.4. Reaction pathway of waste cooking oil to jet biofuel Compositions of waste cooking oil are shown in Table 2. Approximately, 89.6% of the fatty acid methyl esters (FAMEs) in waste cooking oils decomposed into hydrocarbons, such as heptadecane, pentadecane, short chain alkanes, cycloalkanes and alkenes through decarbonylation in the first hour, (Fig. 4). Increased selectivities were observed as follows: heptadecane from 0% to 19.87%, pentadecane from 0% to 13.41%, C8–C11 alkanes from 0% to 10.18%, and C12–C14 alkanes from 0% to 9.91%. In the second hour, the remaining FAMEs further decomposed into hydrocarbons. Increased selectivities were observed as follows: heptadecane from 19.87% to 24.1%, pentadecane from 13.41% to 17.04%, C8–C11 alkanes from 10.18% to 16%, and C12–C14 alkanes from 9.91% to 14.64%. In the third hour, the FAMEs were completely converted into hydrocarbons. The long chain hydrocarbons cracked into short chain hydrocarbons. Trends in selectivity were as follows: heptadecane decreased from 24.1% to 12.87%, pentadecane decreased from 17.04% to 9.34%, selectivity of C8–C11 alkanes increased to 19.16%, and C12–C14 alkanes decreased to 12.6%. In the fourth hour, selectivities of heptadecane and pentadecane continued to decrease to 9.87% and 7.45% respectively. From 5 h to 8 h, selectivities of C8–C11 alkanes, C12–C14 alkanes, heptadecane, pentadecane and hexadecane slightly changed. No aromatic hydrocarbons were observed from 1 h to 4 h. Selectivity of aromatic hydrocarbons increased to 12.1% from 5 h to 8 h. Therefore, decarbonylation and cracking reaction occurred from 0 to 2 h, of which decarbonylation was the major reaction. Pentadecane and heptadecane cracked into short chain alkanes from 2 h to 4 h, while aromatization occurred from 5 h to 8 h. Intermediates such as alkenes, and cycloalkanes were observed. Thus, we hypothesize that alkanes dehydrogenated to alkenes in the first step, and were then converted into cycloalkanes. Finally, the cycloalkanes dehydrogenated to aromatic hydrocarbons. The complete proposed reaction pathway is shown in Supplementary materials Fig. 1.

4. Conclusion A reaction pathway was proposed based on the experimental results on the conversion of waste cooking oil to jet biofuel. Waste cooking oil mainly deoxygenated to heptadecane (C17H36) and pentadecane (C15H30) via the decarbonylation pathway for the first 3 h. Long chain alkanes cracked into jet range alkanes (C8–C16). Cycloalkanes and aromatic hydrocarbons were produced through cyclization and dehydrogenation pathways. Zeolite Meso-Y exhibited a high jet range alkane yield of 40.5% and a low jet range aromatic hydrocarbon yield of 11.3% from waste cooking oil at 400 °C. Detailed deoxygenation mechanisms warrant further investigation. Acknowledgements This study was supported by the National Natural Science Foundation-China (51476141) and Zhejiang Provincial Natural Science Foundation-China (LR14E060002). Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.biortech.2015.08. 115. References Agusdinata, D.B., Zhao, F., Ileleji, K., Delaurentis, D., 2011. Life cycle assessment of potential biojet fuel production in the United States. Environ. Sci. Technol. 45, 9133–9143. Bezergianni, S., Dimitriadis, A., Kalogianni, A., Pilavachi, P.A., 2010. Hydrotreating of waste cooking oil for biodiesel production. Part I: Effect of temperature on product yields and heteroatom removal. Bioresour. Technol. 17, 6651–6656. Bezergianni, S., Voutetakls, S., Kalogianni, A., 2009. Catalytic hydrocracking of fresh and used cooking oil. Indust. Eng. Chem. Res. 48, 8402–8406. Cheng, J., Li, T., Huang, R., Zhou, J.H., Cen, K.F., 2014. Optimizing catalysis conditions to decrease aromatic hydrocarbons and increase alkanes for improving jet biofuel quality. Bioresour. Technol. 158, 378–382. Dhainaut, J., Daou, T.J., Bats, N., Harbuzaru, B., Lapisardi, G., Rouleau, L., Patarin, J., 2013. The influence of L-lysine and PDADMA on the crystal size and porosity of zeolite Y material. Micropor. Mesopor. Mater. 170, 346–351. Fu, J., Lu, X., Savage, P.E., 2010. Catalytic hydrothermal deoxygenation of palmitic acid. Energy Environ. Sci. 3, 311–317. Hari, T.K., Yaakob, Z., Binitha, N.N., 2015. Aviation biofuel from renewable resources: route, opportunities and challenges. Renew. Sustain. Energy Rev. 42, 1234–1244. Liu, G., Yan, B., Chen, G., 2013. Technical review on jet fuel production. Renew. Sustain. Energy Rev. 25, 59–70. Robota, H.J., Alger, J.C., Shafer, L., 2013. Converting algal triglycerides to diesel and HEFA jet fuel fractions. Energy Fuels 27, 985–996. Verma, D., Kumar, R., Rana, B.S., Sinha, A.K., 2011. Aviation fuel production from lipids by a single-step route using hierarchical mesoporous zeolites. Energy Environ. Sci. 4, 1667–1671. Verboekend, D., Vile, G., Perez-Ramirez, J., 2012. Hierarchical Y and USY zeolites designed by post-synthetic strategies. Adv. Funct. Mater. 22, 916–928. Zhang, H., Ozturk, U.A., Wang, Q.W., Zhao, Z.Y., 2014. Biodiesel produced by waste cooking oil: review of recycling modes in China, the US and Japan. Renew. Sustain. Energy Rev. 38, 677–685.