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metatitanic acid nanocomposite and evaluation of its catalytic performance for aquathermolysis reaction of extra-heavy crude oil
Journal of Energy Chemistry 24 (2015) 472–476
Contents lists available at ScienceDirect
Journal of Energy Chemistry journal homepage: www.elsevier.com/locate/jechem
Synthesis of silica/metatitanic acid nanocomposite and evaluation of its catalytic performance for aquathermolysis reaction of extra-heavy crude oil Xueliang Liu a, Yiguang Li a, Zhijun Zhang a,∗, Xiaohong Li a, Mengyun Zhao b, Changming Su b a b
Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004, Henan, China Institute of Petroleum Exploration and Production, SINOPEC, Beijing 100083, China
a r t i c l e
i n f o
Article history: Received 6 February 2015 Revised 15 March 2015 Accepted 27 March 2015 Available online 8 August 2015 Keywords: SiO2 /H2 TiO3 nanocomposite Catalytic aquathermolysis Heavy oil Viscosity reduction
a b s t r a c t A lipophilic silica/metatitantic acid (denoted as SiO2 /H2 TiO3 ) nanocomposite was synthesized by hydrothermal reaction with surface-modified SiO2 as the lipophilic carrier. As-synthesized SiO2 /H2 TiO3 nanocomposite was used as a catalyst to promote the aquathermolysis reaction of extra-heavy crude oil thereby facilitating the recovering from the deep reservoirs at lowered temperature. The catalytic performance of the as-synthesized SiO2 /H2 TiO3 catalyst for the aquathermolysis reaction of the heavy oil at a moderate temperature of 150 °C was evaluated in relation to the structural characterizations by TEM, FTIR, XRD and FESEM as well as the determination of the specific surface area by N2 adsorption–desorption method. Findings indicate that as-synthesized SiO2 /H2 TiO3 nanocomposite exhibits an average size of about 20 nm as well as good lipophilicity and dispersibility in various organic solvents; and it shows good catalytic performance for the aquathermolysis reaction of the extra-heavy oil extracted from Shengli Oilfield of China. Namely, the assynthesized SiO2 /H2 TiO3 catalyst is capable of significantly reducing the viscosity of the tested heavy oil from 58,000 cP to 16,000 cP (referring to a viscosity reduction rate of 72.41%) at a mass fraction of 0.5%, a reaction temperature of 150 °C and a reaction time of 36 h, showing potential application in downhole upgrading heavy crude oils. © 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.
1. Introduction With the depletion of conventional crude oil, abundant heavy oil and oil sand as important hydrocarbon resources are increasingly attracting interest worldwide. The confirmed and controlled heavy oil reservoir in China has reached about 16 × 108 ton, less than that in Venezuela, Canada and USA [1]. However, the high viscosity and solidification of heavy oil and oil sand challenge their exploitation and transportation, and the recovery of the heavy oils is infeasible unless their viscosity is drastically reduced. To deal with this issue, researchers have developed many techniques including thermal recovery and cold production technology to promote heavy oil exploitation [2–5]. Among a variety of such techniques, steam stimulation is one of the most popular and effective technology for enhancing heavy oil recovery throughout the world, and it currently covers the recovery of approximately 80% of the heavy oil resources in China.
∗
Corresponding author. E-mail address: [email protected] (Z. Zhang).
Hyne and co-workers [6,7] discovered that superheated steam could not only reduce the viscosity but also react with some components of heavy oil thereby changing the properties and upgrading heavy oil and oil sand. More importantly, they found that the addition of catalysts helps to greatly increase the efficiency of aquathermolysis reaction and provide greater viscosity reduction of heavy oil. Recently many researches on aquathermolysis have been carried out [8–11], and some achievements of catalytic aquathermolysis have been obtained in oilfield tests [12–15]. Zhong et al. [16] used water soluble metal ions (Fe2+ , Cu2+ , Al3+ , Ni2+ , Co2+ , Mo2+ , Zn2+ , and Mn2+ ) as aquathermolysis catalysts to reduce the viscosity of extra-heavy oil at Liaohe Oilfield of China. Li et al. [17] found that the organic complexes of Fe3+ and Cu2+ as aquathermolysis catalysts can reduce the viscosity of the tested heavy oil at a rate of nearly 90%. Unfortunately, commonly used water-soluble aquathermolysis catalysts, due to poor compatibility with heavy oil, usually exhibit poor catalytic efficiency. Most of oil-soluble aquathermolysis catalysts (i.e., organometallics), though possessing better compatibility with heavy oil than the water-soluble counterparts, often rely on some organic solvents such as toluene and diesel oil as the carriers, which is less cost-effective and may cause environmental pollution as well.
http://dx.doi.org/10.1016/j.jechem.2015.06.005 2095-4956/© 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.
X. Liu et al. / Journal of Energy Chemistry 24 (2015) 472–476
Dispersed nanocatalysts, due to their high specific surface area and active surface sites, have obtained comprehensive research in petroleum industry [18,19]. Shokrlu and Babadagli [20] reported that some micro and nano metal particles are able to reduce the viscosity of heavy oil and oil sand subjected to simulated steam stimulation processes, but nano metal particles are liable to oxidation in atmosphere and lose catalytic activity, which limits their application in oil field exploitation. Jing et al. [21] found that modified SO4 2− /ZrO2 solid super acids have good catalytic performance on viscosity reduction of heavy oil, but the presence of water associated with aquathermolysis is harmful to their catalytic activity. Wen et al. and Zhang et al. demonstrated that polyoxometalates have catalytic performance on the viscosity reduction of heavy oil within the proximate condition of steam stimulation processes [22,23]. However, the expensive polyoxometalates are less competitive in terms of the application at oilfield. Viewing the above-mentioned researches all pre-set the catalytic temperature to be above 200 °C while the temperature of most of heavy oil reservoirs is below 150 °C, in the present research we pay special attention to the catalytic aquathermolysis at lowered temperatures of 120–180 °C. This paper reports the synthesis and structural characterization of lipophilic silica/metatitantic acid (denoted as SiO2 /H2 TiO3 ) nanocomposite as well as the evaluation of its catalytic performance for the aquathermolysis reaction of the extraheavy oil extracted from Shengli Oilfield. 2. Experimental 2.1. Reagents Titanium oxysulfate-sulfuric acid hydrate (TiOSO4 •xH2 SO4 •xH2 O, synthesis grade; Aladdin Industrial Corporation; Shanghai, China), sulfuric acid (H2 SO4 , analytical grade; Luoyang Haohua Chemical Reagent Company Ltd.; Luoyang, China), ammonia (NH3 •H2 O, analytical grade; Kaifeng Zhongtian Chemical Company Ltd.; Kaifeng, China), and ethanol (C2 H5 OH, analytical grade; Tianjin Fuyu Fine Chemical Company Ltd.; Tianjin, China) were commercially obtained and used without further treatment. Surface-modified silica was produced by Jiyuan Wangwu Nano Technology Company (Jiyuan, China), and extra-heavy oil sample (viscosity at 50 °C: 58,000 cP) was supplied by Shengli Oilfield. 2.2. Preparation of SiO2 /H2 TiO3 nanocomposite A proper amount of titanium oxysulfate was dissolved in 200 mL of distilled water. The dispersion of surface modified silica was added into resultant solution under 30-min vigorous stirring at room temperature. Then ammonia was dropwise added into the mixed solution to adjust the pH value to be about 8 and initiate hydrolysis affording a gel. As-formed gel was transferred into a polytetrafluroethylene lined autoclave and held at 160 °C for 8 h to yield hydrophobic SiO2 /H2 TiO3 nanocomposite. Hydrophilic metatitanic acid (H2 TiO3 ) was prepared in the same manners while no surfacemodified silica was introduced. 2.3. Catalytic aquathermolysis tests of heavy oil Catalytic aquathermolysis tests of the tested heavy oil were carried out in an LHG-3 high pressure reactor. Briefly, 100 g of the heavy oil and 0.5 g of the as-prepared catalyst dispersed in 100 mL of deionized water were sequentially added into the reactor. Then the reactor was sealed and heated to 150 °C at a rate of 2–3 °C/min in an XGRL-4A high temperature roller furnace to start aquathermolysis reaction at a rolling rate of 50 rpm and for duration of 24 h. Upon completion of the aquathermolysis reaction, the reaction mixture was naturally cooled
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to room temperature and then transferred into a 200-mL beaker, followed by high speed centrifugation to remove residual water and afford the heavy oil sample ready for structural characterization and viscosity measurements. 2.4. Characterization of catalyst and heavy oil A transmission electron microscope (TEM; JEM-2010, JEOL, Japan) was performed to observe the morphology and size of the asprepared H2 TiO3 and SiO2 /H2 TiO3 catalysts. The crystal structure of the products was analyzed by X-ray diffraction (XRD; Bruker Spectrum Instrument Company, Germany), and the XRD patterns were recorded at a scan rate of 0.02°/s over the 2θ range of 10°–90° with Cu-Kα radiation (40 kV and 40 mA) as the excitation source. The surface elements of SiO2 /H2 TiO3 nanocomposite were tested by Field Emission Scanning Electron Microscope (FESEM; Nova NanoSEM 450, Holland) through EDAS model. The organic species adsorbed on the surface of the as-prepared SiO2 /H2 TiO3 catalyst were analyzed with an AVATAR-360 Fourier transform infrared spectrometer (FTIR; Nicolet Instrument Company, USA). The as-synthesized catalyst was dried at 110 °C for 10 h and pressed into pellete with KBr, and then the FTIR spectra were recorded in the wavenumber range of 400–4000 cm−1 . A JW-BK 222 chemisorption surface area analyzer (Beijing JWBJ Science & Technology Company Ltd.; Beijing, China) was performed to determine the specific surface area of the as-prepared SiO2 /H2 TiO3 catalyst by classic BET (Brunauer–Emmett–Teller isotherm) method. The viscosity of the heavy oil samples before and after aquathermolysis tests was measured with a Brookfield DV-3 programmable viscometer at 50.00 °C. Approximately 15 g of the heavy oil was placed in the sample cup, heated with a Brookfield thermosel heater and equilibrated at 50.00 °C for 30 min. The viscosity reduction rate is calculated as η = (η0 - η)/η0 × 100%, where η (%) is the viscosity reduction rate of the heavy oil, η0 (cP) is the viscosity of the original heavy oil, and η (cP) is the viscosity of the heavy oil after the catalytic aquathermolysis reaction. The saturate, aromatic, resin and asphaltene (denoted as SARA) fractions of the tested heavy oil sample were determined by column chromatography according to the Industrial Specification of China Petroleum Standard SY/T 5119-2008 [24]. The asphaltenes were precipitated with n-hexane, and then the solution was concentrated and separated by a silica gel and neutral Al2 O3 column. The saturated hydrocarbon in the concentrated solution was separated by n-hexane, and the aromatic hydrocarbon was separated by the mixed solution of dichloromethane and anhydrous ethanol. Furthermore, the resin was separated by trichloromethane. 3. Results and discussion The dispersity of SiO2 /H2 TiO3 in water and xylol is shown in Fig. 1. As-prepared SiO2 /H2 TiO3 nanocomposite exhibits high hydrophobicity and good dispersity in organic solvents such as dimethylbenzene (xylol), toluene and diesel oil, which indicates that the nanocomposite possesses lipophilicity. This is because the surface-modified silica is highly hydrophobic and provides the SiO2 /H2 TiO3 nanocomposite with good dispersibility in organic phase like heavy crude oil. Fig. 2 presents the TEM images of pure H2 TiO3 , surface-modified SiO2 , and SiO2 /H2 TiO3 nanocomposite. It is seen that pure H2 TiO3 , with a particle size of 20–30 nm, has irregular shape (Fig. 2a). The average size of SiO2 /H2 TiO3 nanocomposite and surface-modified silica particles are about 20 nm (Fig. 2c) and 12 nm (Fig. 2b) respectively. Since TiO2+ tends to be absorbed and precipitated in the pore or on the surface of nanosilica before the formation of H2 TiO3 nanoparticles, the growth of H2 TiO3 crystal nucleus is restricted. As a result, H2 TiO3 nanoparticles formed on the surface or in the pores of the nanosilica exhibit an average size of only several nanometers (Fig. 2c).
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Fig. 1. The dispersity of SiO2 /H2 TiO3 nanocomposite in (a) water, (b) the mixture of water and xylol and (c) xylol.
Moreover, since the surface-modified SiO2 nanoparticles are partially coated by H2 TiO3 nanoparticles, as-prepared SiO2 /H2 TiO3 nanocomposite still retains hydrophobicity to some extent (Fig. 1). The specific surface areas of H2 TiO3 , SiO2 and SiO2 /H2 TiO3 , determined by N2 adsorption–desorption method, are 156, 280 and 208 m2 /g, respectively; and their total pore volumes are 0.130, 0.907 and 0.560 cm3 /g, respectively. These specific surface area data and total pore volume data of various samples well correspond to relevant TEM images. Namely, during the preparation of SiO2 /H2 TiO3 nanocomposite, TiO2+ is adsorbed and precipitated directly in the pores and on the surface of the modified silica nanoparticles, and the gel is dehydrated by hydrothermal reaction, thereby leading to smaller specific surface area and total pore volume of SiO2 /H2 TiO3 catalyst than pure nanosilica in association with the deposition of H2 TiO3 nanoparticles on the surface and in the pores of nanosilica. The EDS result of SiO2 /H2 TiO3 composite is exhibited in Fig. 3. The mass fractions of Ti, Si, O and C are 16.36%, 39.36%, 40.92% and 3.36% respectively, which reveals that the surface modified silica is partially covered by H2 TiO3 . Fig. 4 shows the FTIR spectra of surface-modified silica (Fig. 4a), SiO2 /H2 TiO3 (Fig. 4b) and H2 TiO3 (Fig. 4c). In Fig. 4(a), the absorption bands at 3427 cm−1 and 1634 cm−1 are assigned to the stretching vibration of O–H and bending vibration of H–O–H [25], which confirms the presence of adsorbed water in surface-modified SiO2 . The strong anti-symmetric stretching vibration band of Si–O–Si is located at 1096 cm−1 , and the symmetric stretching vibration and bending
vibration absorption bands of Si–O–Si are located at 470 cm−1 and 797 cm−1 , respectively (Fig. 4a and c). Besides, the absorption peaks of –CH3 and Si–CH3 (Fig. 4a) are located at 2966 cm−1 and 845 cm−1 , which confirms that the coupling agent is bonded with the nanosilica surface by covalent bond. The broad and strong absorption bands in the range of 3400–3100 cm−1 are assigned to the stretching vibration of –OH group (Fig. 4b and c), which reveals that there is a large amount of –OH on the surface of H2 TiO3 nanoparticles. Moreover, the absorption bands of SiO2 /H2 TiO3 at 2966 cm−1 and 845 cm−1 are much weaker than those of surface-modified silica, which is due to the strong absorption of –OH group of H2 TiO3 and indicates that the H2 TiO3 nanoparticles are deposited on the surface or in the pores of nanosilica, as evidenced by corresponding TEM images, EDS analysis and BET analytical data. The XRD patterns of as-prepared H2 TiO3 and SiO2 /H2 TiO3 are shown in Fig. 5. The diffraction peaks at 2θ = 25.3°, 37.8° and 47.1° are assigned to anatase TiO2 crystalline, and the carrier SiO2 particles are totally amorphous. Besides, the diffraction peaks of SiO2 /H2 TiO3 are broader and their intensity is weaker than that of corresponding peaks of pure H2 TiO3 , which is due to the introduction of amorphous silica. Moreover, as-prepared H2 TiO3 nanoparticles contain anatase TiO2 nuclei. Table 1 shows the viscosity reduction rate of the heavy oil after 24 h of aquathermolysis reaction at 150 °C and different SiO2 /H2 TiO3 catalyst dosages. When no SiO2 /H2 TiO3 catalyst is introduced into the reaction system, the viscosity of the heavy oil is reduced to some extent after the aquathermolysis reaction, which implies that, without the assistance of properly selected catalysts, high-temperature steam alone also exhibits some ability in reducing the viscosity of the tested heavy oil. When SiO2 /H2 TiO3 catalyst is added in the aquathermolysis reaction system, the viscosity of the tested heavy oil tends to reduce gradually with the increase of the catalyst dosage, and the viscosity reduction rate tends to rise significantly therewith. Particularly, the maximum viscosity reduction rate (58.62%) is obtained at a SiO2 /H2 TiO3 catalyst dosage of 0.50% (mass fraction), and further increase in the dosage of the catalyst does not favor further viscosity reduction. This could be because hydrogen bonds are formed between a large number of hydroxyl groups of the excess SiO2 /H2 TiO3 catalyst and the polar molecules of heavy oil, thereby resulting in the aggregation of the asphaltene and resin fractions of the tested heavy oil. Table 2 presents the viscosity reduction rate of the heavy oil after 24 h of aquathermolysis tests catalyzed by H2 TiO3 and SiO2 /H2 TiO3 catalysts at different reaction temperatures. It is seen that both hydrophilic H2 TiO3 catalyst and hydrophobic SiO2 /H2 TiO3 catalyst are able to reduce the viscosity of the tested heavy oil in the reaction
Fig. 2. TEM images of (a) pure H2 TiO3 , (b) surface-modified SiO2 and (c) SiO2 /H2 TiO3 nanocomposite.
X. Liu et al. / Journal of Energy Chemistry 24 (2015) 472–476
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Fig. 3. The EDS of SiO2 /H2 TiO3 . Table 1 Viscosity reduction rate of the heavy oil after 24 h aquathermolysis reaction at 150 °C and different SiO2 /H2 TiO3 catalyst dosages.
1 Heavy oil Untreated Treated with steam alone
Transmittance (%)
2 3
Treated with steam plus SiO2 /H2 TiO3
1: SiO2 3: H2TiO3 3500
3000
2500
Viscosity (cP)
Viscosity reduction rate (%)
— — 0.10 0.20
58000 40000 30000 26000
— 31.03 48.28 55.17
0.50 1.00 1.50
24000 36000 48000
58.62 37.93 17.24
Table 2 The viscosity reduction rate of the heavy oil after 24 h of aquathermolysis tests catalyzed by H2 TiO3 and SiO2 /H2 TiO3 catalysts at different reaction temperatures.
2: SiO2/H2TiO3
4000
Catalyst dosage (wt%)
2000
1500
1000
500
-1
Wavenumbers (cm ) Fig. 4. FTIR spectra of (1) SiO2 , (2) H2 TiO3 and (3) SiO2 /H2 TiO3 nanocomposite.
(101)
1: H2TiO3 2: SiO2
Reaction temperature (°C)
Catalyst
Viscosity (cP)
Viscosity reduction rate (%)
120 120 120
— H2 TiO3 SiO2 /H2 TiO3
38000 30000 30000
24.48 48.28 48.28
150 150 150
— H2 TiO3 SiO2 /H2 TiO3
40000 26000 19000
31.03 55.17 67.24
180 180 180
— H2 TiO3 SiO2 /H2 TiO3
32000 22000 14000
44.83 62.07 75.86
Intensity
3: SiO2/H2TiO3
3
2 1
10
20
30
40
50
60
70
80
2 theta (°) Fig. 5. XRD patterns of (1) H2 TiO3 , (2) SiO2 and (3) SiO2 /H2 TiO3 .
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temperature range of 120–180 °C; and they provide the same viscosity reduction rate at 120 °C. As the aquathermolysis temperature rises to 150 °C and 180 °C, the hydrophobic SiO2 /H2 TiO3 catalyst exhibits much better catalytic performance for the viscosity reduction of the heavy oil than the hydrophilic H2 TiO3 catalyst. This is because the highly hydrophilic H2 TiO3 coated on the hydrophobic silica results in a greatly lipophilicity of SiO2 /H2 TiO3 nanocomposite and more chance contact with the oil phase thereby effectively promoting the aquathermolysis reaction and providing a maximum viscosity reduction rate of 75.86% at 180 °C. Considering the actual conditions of heavy oil reservoir, we conducted a series of aquathermolysis tests at 150 °C and measured the viscosity reduction rate of the heavy oil at different reaction times. As listed in Table 3, the viscosity of the heavy oil is reduced by 55.17%
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X. Liu et al. / Journal of Energy Chemistry 24 (2015) 472–476
Table 3 Effect of aquathermolysis reaction time on viscosity reduction rate of heavy oil at 150 °C. Reaction time (h)
Viscosity (cP)
Viscosity reduction rate (%)
12 24 36 48 72
26000 19000 16000 18000 15000
55.17 67.24 72.41 68.97 74.14
Table 4 The SARA composition of the tested heavy oil before and after aquathermolysis reaction (150 °C, 36 h). Fractions
Saturated hydrocarbon Aromatic hydrocarbon Asphaltene Resin
Content (wt%) Before reaction
After reaction
19.03 28.83 26.42 25.72
26.19 33.15 18.07 22.59
after 12 h of aquathermolysis tests at 150 °C. As the reaction time is extended to 36 h, the viscosity of the tested heavy oil is reduced by 72.41%; and further extending reaction time gives slightly changed viscosity reduction rate. Thus it can be inferred that the aquathermolysis reaction of the tested heavy oil catalyzed by SiO2 /H2 TiO3 reaches the equilibrium after 36 h of reaction at 150 °C. The composition of the tested heavy oil before and after aquathermolysis reaction (150 °C, 36 h) is listed in Table 4. It is seen that the contents of the asphaltene fraction and resin fraction of the tested heavy oil decrease after aquathermolysis, and the contents of the saturated and aromatic hydrocarbons increase correspondingly indicating that the SiO2 /H2 TiO3 catalyst can effectively promote the catalytic aquathermolysis of the heavy oil at 150 °C. 4. Conclusions SiO2 /H2 TiO3 nanocomposite with good dispersibility in various organic solvents was prepared through hydrothermal reaction in the presence of surface-modified SiO2 as the lipophilic carrier.
As-prepared SiO2 /H2 TiO3 nanocomposite exhibits better catalytic performance for the aquathermolysis reaction of the heavy oil at 150 °C and 180 °C than the hydrophilic H2 TiO3 catalyst, because the highly hydrophilic H2 TiO3 coated on the hydrophobic silica results in the lipophilicity of SiO2 /H2 TiO3 nanocomposite and more chance to contact with oil phase thereby effectively promoting the aquathermolysis reaction. Particularly, the highest viscosity reduction rate of the tested heavy oil is achieved at a SiO2 /H2 TiO3 catalyst dosage of 0.5% and a temperature of 150 °C. This demonstrates that as-prepared SiO2 /H2 TiO3 catalyst may have significance in downhole upgrading heavy crude oils. Acknowledgments This research is financially supported by the National Natural Science Foundation of China (grant Nos. 21371047 and 21471047). References [1] Q.Y. Wang, H.J. He, Sino-Global Energy 18 (8) (2013) 33. [2] M.S. Rana, V. Sámano, Fuel 86 (9) (2007) 1216. [3] K. Tan, S. Wang, F. Cao, Contemporary Chem. Ind. (Dangdai Huagong) 43 (1) (2014) 97. [4] W. David, J. Wang, I.D. Gates, Fuel 117 (Part A) (2014) 431. [5] H.H. Pei, G.C. Zhang, J.J. Ge, Fuel 104 (2013) 372. [6] J.B. Hyne, J.W. Greidanus, Aquathermolysis of Heavy Oils. 2nd Int Conf, Caracas, Venezuela, 1982, p. 25. [7] P.D. Clark, J.B. Hyne, AOSTRA J. Res. (1990) 53. [8] H.F. Fan, Z.B. Li, T. Liang, J. Fuel Chem. Technol. 35 (1) (2007) 32. [9] Z.X. Fan, T.F. Wang, Y.H. He, J. Fuel Chem. Technol. 37 (6) (2009) 690. [10] Y.Q. Wang, Y.L. Chen, J. He, Energy Fuels 24 (3) (2010) 1502. [11] K. Chao, Y.L. Chen, J. Li, Fuel Process. Technol. 104 (2012) 174. [12] W.L. Qin, B.Y. Su, C.S. Pu, Acta Petrolei Sin. 25 (6) (2009) 772. [13] H.F. Fan, Y.J. Liu, F.L. Yang, Oilfield Chemistry 18 (1) (2001) 13. [14] H.F. Fan, Y.J. Liu, X.F. Zhao, Oil Drilling Prod. Technol. 23 (3) (2001) 42. [15] Y.L. Chen, Y.Q. Wang, C. Wu, Energy Fuels 22 (3) (2008) 1502. [16] L.G. Zhong, Y.J. Liu, H.F. Fan, International Improve Oil Recovery Conference, Kuala Lumpur, Malaysia, 2003. [17] J. Li, Y.L. Chen, H.C. Liu, Energy Fuels 27 (2013) 2555. [18] R. Hashemi, N.N. Nassar, P.P. Almao, Appl. Energy 133 (2014) 374. [19] S.K. Maity, J. Ancheyta, G. Marroquin, Energy Fuels 24 (2010) 2809. [20] Y.H. Shokrlu, T. Babadagli, J. Petrol. Sci. 119 (2014) 210. [21] P. Jing, Q.B. Li, M. Han, Petrochem. Technol. 36 (3) (2007) 237. [22] S.B. Wen, Y.J. Liu, Y.W. Song, J. Daqing Petrol. Inst. 28 (1) (2004) 25. [23] X.N. Zhang, S.Z. He, X.W. Zhang, J. Daqing Petrol. Inst. 29 (4) (2005) 33. [24] SY/T 5119-2008, Analysis method for fractions of rock extract and crude oil. [25] Q.Y. Deng, L. Liu, H.M. Deng, Spectral Analysis, Science Press, Beijing, 2007.
Contents lists available at ScienceDirect
Journal of Energy Chemistry journal homepage: www.elsevier.com/locate/jechem
Synthesis of silica/metatitanic acid nanocomposite and evaluation of its catalytic performance for aquathermolysis reaction of extra-heavy crude oil Xueliang Liu a, Yiguang Li a, Zhijun Zhang a,∗, Xiaohong Li a, Mengyun Zhao b, Changming Su b a b
Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004, Henan, China Institute of Petroleum Exploration and Production, SINOPEC, Beijing 100083, China
a r t i c l e
i n f o
Article history: Received 6 February 2015 Revised 15 March 2015 Accepted 27 March 2015 Available online 8 August 2015 Keywords: SiO2 /H2 TiO3 nanocomposite Catalytic aquathermolysis Heavy oil Viscosity reduction
a b s t r a c t A lipophilic silica/metatitantic acid (denoted as SiO2 /H2 TiO3 ) nanocomposite was synthesized by hydrothermal reaction with surface-modified SiO2 as the lipophilic carrier. As-synthesized SiO2 /H2 TiO3 nanocomposite was used as a catalyst to promote the aquathermolysis reaction of extra-heavy crude oil thereby facilitating the recovering from the deep reservoirs at lowered temperature. The catalytic performance of the as-synthesized SiO2 /H2 TiO3 catalyst for the aquathermolysis reaction of the heavy oil at a moderate temperature of 150 °C was evaluated in relation to the structural characterizations by TEM, FTIR, XRD and FESEM as well as the determination of the specific surface area by N2 adsorption–desorption method. Findings indicate that as-synthesized SiO2 /H2 TiO3 nanocomposite exhibits an average size of about 20 nm as well as good lipophilicity and dispersibility in various organic solvents; and it shows good catalytic performance for the aquathermolysis reaction of the extra-heavy oil extracted from Shengli Oilfield of China. Namely, the assynthesized SiO2 /H2 TiO3 catalyst is capable of significantly reducing the viscosity of the tested heavy oil from 58,000 cP to 16,000 cP (referring to a viscosity reduction rate of 72.41%) at a mass fraction of 0.5%, a reaction temperature of 150 °C and a reaction time of 36 h, showing potential application in downhole upgrading heavy crude oils. © 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.
1. Introduction With the depletion of conventional crude oil, abundant heavy oil and oil sand as important hydrocarbon resources are increasingly attracting interest worldwide. The confirmed and controlled heavy oil reservoir in China has reached about 16 × 108 ton, less than that in Venezuela, Canada and USA [1]. However, the high viscosity and solidification of heavy oil and oil sand challenge their exploitation and transportation, and the recovery of the heavy oils is infeasible unless their viscosity is drastically reduced. To deal with this issue, researchers have developed many techniques including thermal recovery and cold production technology to promote heavy oil exploitation [2–5]. Among a variety of such techniques, steam stimulation is one of the most popular and effective technology for enhancing heavy oil recovery throughout the world, and it currently covers the recovery of approximately 80% of the heavy oil resources in China.
∗
Corresponding author. E-mail address: [email protected] (Z. Zhang).
Hyne and co-workers [6,7] discovered that superheated steam could not only reduce the viscosity but also react with some components of heavy oil thereby changing the properties and upgrading heavy oil and oil sand. More importantly, they found that the addition of catalysts helps to greatly increase the efficiency of aquathermolysis reaction and provide greater viscosity reduction of heavy oil. Recently many researches on aquathermolysis have been carried out [8–11], and some achievements of catalytic aquathermolysis have been obtained in oilfield tests [12–15]. Zhong et al. [16] used water soluble metal ions (Fe2+ , Cu2+ , Al3+ , Ni2+ , Co2+ , Mo2+ , Zn2+ , and Mn2+ ) as aquathermolysis catalysts to reduce the viscosity of extra-heavy oil at Liaohe Oilfield of China. Li et al. [17] found that the organic complexes of Fe3+ and Cu2+ as aquathermolysis catalysts can reduce the viscosity of the tested heavy oil at a rate of nearly 90%. Unfortunately, commonly used water-soluble aquathermolysis catalysts, due to poor compatibility with heavy oil, usually exhibit poor catalytic efficiency. Most of oil-soluble aquathermolysis catalysts (i.e., organometallics), though possessing better compatibility with heavy oil than the water-soluble counterparts, often rely on some organic solvents such as toluene and diesel oil as the carriers, which is less cost-effective and may cause environmental pollution as well.
http://dx.doi.org/10.1016/j.jechem.2015.06.005 2095-4956/© 2015 Science Press and Dalian Institute of Chemical Physics. All rights reserved.
X. Liu et al. / Journal of Energy Chemistry 24 (2015) 472–476
Dispersed nanocatalysts, due to their high specific surface area and active surface sites, have obtained comprehensive research in petroleum industry [18,19]. Shokrlu and Babadagli [20] reported that some micro and nano metal particles are able to reduce the viscosity of heavy oil and oil sand subjected to simulated steam stimulation processes, but nano metal particles are liable to oxidation in atmosphere and lose catalytic activity, which limits their application in oil field exploitation. Jing et al. [21] found that modified SO4 2− /ZrO2 solid super acids have good catalytic performance on viscosity reduction of heavy oil, but the presence of water associated with aquathermolysis is harmful to their catalytic activity. Wen et al. and Zhang et al. demonstrated that polyoxometalates have catalytic performance on the viscosity reduction of heavy oil within the proximate condition of steam stimulation processes [22,23]. However, the expensive polyoxometalates are less competitive in terms of the application at oilfield. Viewing the above-mentioned researches all pre-set the catalytic temperature to be above 200 °C while the temperature of most of heavy oil reservoirs is below 150 °C, in the present research we pay special attention to the catalytic aquathermolysis at lowered temperatures of 120–180 °C. This paper reports the synthesis and structural characterization of lipophilic silica/metatitantic acid (denoted as SiO2 /H2 TiO3 ) nanocomposite as well as the evaluation of its catalytic performance for the aquathermolysis reaction of the extraheavy oil extracted from Shengli Oilfield. 2. Experimental 2.1. Reagents Titanium oxysulfate-sulfuric acid hydrate (TiOSO4 •xH2 SO4 •xH2 O, synthesis grade; Aladdin Industrial Corporation; Shanghai, China), sulfuric acid (H2 SO4 , analytical grade; Luoyang Haohua Chemical Reagent Company Ltd.; Luoyang, China), ammonia (NH3 •H2 O, analytical grade; Kaifeng Zhongtian Chemical Company Ltd.; Kaifeng, China), and ethanol (C2 H5 OH, analytical grade; Tianjin Fuyu Fine Chemical Company Ltd.; Tianjin, China) were commercially obtained and used without further treatment. Surface-modified silica was produced by Jiyuan Wangwu Nano Technology Company (Jiyuan, China), and extra-heavy oil sample (viscosity at 50 °C: 58,000 cP) was supplied by Shengli Oilfield. 2.2. Preparation of SiO2 /H2 TiO3 nanocomposite A proper amount of titanium oxysulfate was dissolved in 200 mL of distilled water. The dispersion of surface modified silica was added into resultant solution under 30-min vigorous stirring at room temperature. Then ammonia was dropwise added into the mixed solution to adjust the pH value to be about 8 and initiate hydrolysis affording a gel. As-formed gel was transferred into a polytetrafluroethylene lined autoclave and held at 160 °C for 8 h to yield hydrophobic SiO2 /H2 TiO3 nanocomposite. Hydrophilic metatitanic acid (H2 TiO3 ) was prepared in the same manners while no surfacemodified silica was introduced. 2.3. Catalytic aquathermolysis tests of heavy oil Catalytic aquathermolysis tests of the tested heavy oil were carried out in an LHG-3 high pressure reactor. Briefly, 100 g of the heavy oil and 0.5 g of the as-prepared catalyst dispersed in 100 mL of deionized water were sequentially added into the reactor. Then the reactor was sealed and heated to 150 °C at a rate of 2–3 °C/min in an XGRL-4A high temperature roller furnace to start aquathermolysis reaction at a rolling rate of 50 rpm and for duration of 24 h. Upon completion of the aquathermolysis reaction, the reaction mixture was naturally cooled
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to room temperature and then transferred into a 200-mL beaker, followed by high speed centrifugation to remove residual water and afford the heavy oil sample ready for structural characterization and viscosity measurements. 2.4. Characterization of catalyst and heavy oil A transmission electron microscope (TEM; JEM-2010, JEOL, Japan) was performed to observe the morphology and size of the asprepared H2 TiO3 and SiO2 /H2 TiO3 catalysts. The crystal structure of the products was analyzed by X-ray diffraction (XRD; Bruker Spectrum Instrument Company, Germany), and the XRD patterns were recorded at a scan rate of 0.02°/s over the 2θ range of 10°–90° with Cu-Kα radiation (40 kV and 40 mA) as the excitation source. The surface elements of SiO2 /H2 TiO3 nanocomposite were tested by Field Emission Scanning Electron Microscope (FESEM; Nova NanoSEM 450, Holland) through EDAS model. The organic species adsorbed on the surface of the as-prepared SiO2 /H2 TiO3 catalyst were analyzed with an AVATAR-360 Fourier transform infrared spectrometer (FTIR; Nicolet Instrument Company, USA). The as-synthesized catalyst was dried at 110 °C for 10 h and pressed into pellete with KBr, and then the FTIR spectra were recorded in the wavenumber range of 400–4000 cm−1 . A JW-BK 222 chemisorption surface area analyzer (Beijing JWBJ Science & Technology Company Ltd.; Beijing, China) was performed to determine the specific surface area of the as-prepared SiO2 /H2 TiO3 catalyst by classic BET (Brunauer–Emmett–Teller isotherm) method. The viscosity of the heavy oil samples before and after aquathermolysis tests was measured with a Brookfield DV-3 programmable viscometer at 50.00 °C. Approximately 15 g of the heavy oil was placed in the sample cup, heated with a Brookfield thermosel heater and equilibrated at 50.00 °C for 30 min. The viscosity reduction rate is calculated as η = (η0 - η)/η0 × 100%, where η (%) is the viscosity reduction rate of the heavy oil, η0 (cP) is the viscosity of the original heavy oil, and η (cP) is the viscosity of the heavy oil after the catalytic aquathermolysis reaction. The saturate, aromatic, resin and asphaltene (denoted as SARA) fractions of the tested heavy oil sample were determined by column chromatography according to the Industrial Specification of China Petroleum Standard SY/T 5119-2008 [24]. The asphaltenes were precipitated with n-hexane, and then the solution was concentrated and separated by a silica gel and neutral Al2 O3 column. The saturated hydrocarbon in the concentrated solution was separated by n-hexane, and the aromatic hydrocarbon was separated by the mixed solution of dichloromethane and anhydrous ethanol. Furthermore, the resin was separated by trichloromethane. 3. Results and discussion The dispersity of SiO2 /H2 TiO3 in water and xylol is shown in Fig. 1. As-prepared SiO2 /H2 TiO3 nanocomposite exhibits high hydrophobicity and good dispersity in organic solvents such as dimethylbenzene (xylol), toluene and diesel oil, which indicates that the nanocomposite possesses lipophilicity. This is because the surface-modified silica is highly hydrophobic and provides the SiO2 /H2 TiO3 nanocomposite with good dispersibility in organic phase like heavy crude oil. Fig. 2 presents the TEM images of pure H2 TiO3 , surface-modified SiO2 , and SiO2 /H2 TiO3 nanocomposite. It is seen that pure H2 TiO3 , with a particle size of 20–30 nm, has irregular shape (Fig. 2a). The average size of SiO2 /H2 TiO3 nanocomposite and surface-modified silica particles are about 20 nm (Fig. 2c) and 12 nm (Fig. 2b) respectively. Since TiO2+ tends to be absorbed and precipitated in the pore or on the surface of nanosilica before the formation of H2 TiO3 nanoparticles, the growth of H2 TiO3 crystal nucleus is restricted. As a result, H2 TiO3 nanoparticles formed on the surface or in the pores of the nanosilica exhibit an average size of only several nanometers (Fig. 2c).
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Fig. 1. The dispersity of SiO2 /H2 TiO3 nanocomposite in (a) water, (b) the mixture of water and xylol and (c) xylol.
Moreover, since the surface-modified SiO2 nanoparticles are partially coated by H2 TiO3 nanoparticles, as-prepared SiO2 /H2 TiO3 nanocomposite still retains hydrophobicity to some extent (Fig. 1). The specific surface areas of H2 TiO3 , SiO2 and SiO2 /H2 TiO3 , determined by N2 adsorption–desorption method, are 156, 280 and 208 m2 /g, respectively; and their total pore volumes are 0.130, 0.907 and 0.560 cm3 /g, respectively. These specific surface area data and total pore volume data of various samples well correspond to relevant TEM images. Namely, during the preparation of SiO2 /H2 TiO3 nanocomposite, TiO2+ is adsorbed and precipitated directly in the pores and on the surface of the modified silica nanoparticles, and the gel is dehydrated by hydrothermal reaction, thereby leading to smaller specific surface area and total pore volume of SiO2 /H2 TiO3 catalyst than pure nanosilica in association with the deposition of H2 TiO3 nanoparticles on the surface and in the pores of nanosilica. The EDS result of SiO2 /H2 TiO3 composite is exhibited in Fig. 3. The mass fractions of Ti, Si, O and C are 16.36%, 39.36%, 40.92% and 3.36% respectively, which reveals that the surface modified silica is partially covered by H2 TiO3 . Fig. 4 shows the FTIR spectra of surface-modified silica (Fig. 4a), SiO2 /H2 TiO3 (Fig. 4b) and H2 TiO3 (Fig. 4c). In Fig. 4(a), the absorption bands at 3427 cm−1 and 1634 cm−1 are assigned to the stretching vibration of O–H and bending vibration of H–O–H [25], which confirms the presence of adsorbed water in surface-modified SiO2 . The strong anti-symmetric stretching vibration band of Si–O–Si is located at 1096 cm−1 , and the symmetric stretching vibration and bending
vibration absorption bands of Si–O–Si are located at 470 cm−1 and 797 cm−1 , respectively (Fig. 4a and c). Besides, the absorption peaks of –CH3 and Si–CH3 (Fig. 4a) are located at 2966 cm−1 and 845 cm−1 , which confirms that the coupling agent is bonded with the nanosilica surface by covalent bond. The broad and strong absorption bands in the range of 3400–3100 cm−1 are assigned to the stretching vibration of –OH group (Fig. 4b and c), which reveals that there is a large amount of –OH on the surface of H2 TiO3 nanoparticles. Moreover, the absorption bands of SiO2 /H2 TiO3 at 2966 cm−1 and 845 cm−1 are much weaker than those of surface-modified silica, which is due to the strong absorption of –OH group of H2 TiO3 and indicates that the H2 TiO3 nanoparticles are deposited on the surface or in the pores of nanosilica, as evidenced by corresponding TEM images, EDS analysis and BET analytical data. The XRD patterns of as-prepared H2 TiO3 and SiO2 /H2 TiO3 are shown in Fig. 5. The diffraction peaks at 2θ = 25.3°, 37.8° and 47.1° are assigned to anatase TiO2 crystalline, and the carrier SiO2 particles are totally amorphous. Besides, the diffraction peaks of SiO2 /H2 TiO3 are broader and their intensity is weaker than that of corresponding peaks of pure H2 TiO3 , which is due to the introduction of amorphous silica. Moreover, as-prepared H2 TiO3 nanoparticles contain anatase TiO2 nuclei. Table 1 shows the viscosity reduction rate of the heavy oil after 24 h of aquathermolysis reaction at 150 °C and different SiO2 /H2 TiO3 catalyst dosages. When no SiO2 /H2 TiO3 catalyst is introduced into the reaction system, the viscosity of the heavy oil is reduced to some extent after the aquathermolysis reaction, which implies that, without the assistance of properly selected catalysts, high-temperature steam alone also exhibits some ability in reducing the viscosity of the tested heavy oil. When SiO2 /H2 TiO3 catalyst is added in the aquathermolysis reaction system, the viscosity of the tested heavy oil tends to reduce gradually with the increase of the catalyst dosage, and the viscosity reduction rate tends to rise significantly therewith. Particularly, the maximum viscosity reduction rate (58.62%) is obtained at a SiO2 /H2 TiO3 catalyst dosage of 0.50% (mass fraction), and further increase in the dosage of the catalyst does not favor further viscosity reduction. This could be because hydrogen bonds are formed between a large number of hydroxyl groups of the excess SiO2 /H2 TiO3 catalyst and the polar molecules of heavy oil, thereby resulting in the aggregation of the asphaltene and resin fractions of the tested heavy oil. Table 2 presents the viscosity reduction rate of the heavy oil after 24 h of aquathermolysis tests catalyzed by H2 TiO3 and SiO2 /H2 TiO3 catalysts at different reaction temperatures. It is seen that both hydrophilic H2 TiO3 catalyst and hydrophobic SiO2 /H2 TiO3 catalyst are able to reduce the viscosity of the tested heavy oil in the reaction
Fig. 2. TEM images of (a) pure H2 TiO3 , (b) surface-modified SiO2 and (c) SiO2 /H2 TiO3 nanocomposite.
X. Liu et al. / Journal of Energy Chemistry 24 (2015) 472–476
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Fig. 3. The EDS of SiO2 /H2 TiO3 . Table 1 Viscosity reduction rate of the heavy oil after 24 h aquathermolysis reaction at 150 °C and different SiO2 /H2 TiO3 catalyst dosages.
1 Heavy oil Untreated Treated with steam alone
Transmittance (%)
2 3
Treated with steam plus SiO2 /H2 TiO3
1: SiO2 3: H2TiO3 3500
3000
2500
Viscosity (cP)
Viscosity reduction rate (%)
— — 0.10 0.20
58000 40000 30000 26000
— 31.03 48.28 55.17
0.50 1.00 1.50
24000 36000 48000
58.62 37.93 17.24
Table 2 The viscosity reduction rate of the heavy oil after 24 h of aquathermolysis tests catalyzed by H2 TiO3 and SiO2 /H2 TiO3 catalysts at different reaction temperatures.
2: SiO2/H2TiO3
4000
Catalyst dosage (wt%)
2000
1500
1000
500
-1
Wavenumbers (cm ) Fig. 4. FTIR spectra of (1) SiO2 , (2) H2 TiO3 and (3) SiO2 /H2 TiO3 nanocomposite.
(101)
1: H2TiO3 2: SiO2
Reaction temperature (°C)
Catalyst
Viscosity (cP)
Viscosity reduction rate (%)
120 120 120
— H2 TiO3 SiO2 /H2 TiO3
38000 30000 30000
24.48 48.28 48.28
150 150 150
— H2 TiO3 SiO2 /H2 TiO3
40000 26000 19000
31.03 55.17 67.24
180 180 180
— H2 TiO3 SiO2 /H2 TiO3
32000 22000 14000
44.83 62.07 75.86
Intensity
3: SiO2/H2TiO3
3
2 1
10
20
30
40
50
60
70
80
2 theta (°) Fig. 5. XRD patterns of (1) H2 TiO3 , (2) SiO2 and (3) SiO2 /H2 TiO3 .
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temperature range of 120–180 °C; and they provide the same viscosity reduction rate at 120 °C. As the aquathermolysis temperature rises to 150 °C and 180 °C, the hydrophobic SiO2 /H2 TiO3 catalyst exhibits much better catalytic performance for the viscosity reduction of the heavy oil than the hydrophilic H2 TiO3 catalyst. This is because the highly hydrophilic H2 TiO3 coated on the hydrophobic silica results in a greatly lipophilicity of SiO2 /H2 TiO3 nanocomposite and more chance contact with the oil phase thereby effectively promoting the aquathermolysis reaction and providing a maximum viscosity reduction rate of 75.86% at 180 °C. Considering the actual conditions of heavy oil reservoir, we conducted a series of aquathermolysis tests at 150 °C and measured the viscosity reduction rate of the heavy oil at different reaction times. As listed in Table 3, the viscosity of the heavy oil is reduced by 55.17%
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Table 3 Effect of aquathermolysis reaction time on viscosity reduction rate of heavy oil at 150 °C. Reaction time (h)
Viscosity (cP)
Viscosity reduction rate (%)
12 24 36 48 72
26000 19000 16000 18000 15000
55.17 67.24 72.41 68.97 74.14
Table 4 The SARA composition of the tested heavy oil before and after aquathermolysis reaction (150 °C, 36 h). Fractions
Saturated hydrocarbon Aromatic hydrocarbon Asphaltene Resin
Content (wt%) Before reaction
After reaction
19.03 28.83 26.42 25.72
26.19 33.15 18.07 22.59
after 12 h of aquathermolysis tests at 150 °C. As the reaction time is extended to 36 h, the viscosity of the tested heavy oil is reduced by 72.41%; and further extending reaction time gives slightly changed viscosity reduction rate. Thus it can be inferred that the aquathermolysis reaction of the tested heavy oil catalyzed by SiO2 /H2 TiO3 reaches the equilibrium after 36 h of reaction at 150 °C. The composition of the tested heavy oil before and after aquathermolysis reaction (150 °C, 36 h) is listed in Table 4. It is seen that the contents of the asphaltene fraction and resin fraction of the tested heavy oil decrease after aquathermolysis, and the contents of the saturated and aromatic hydrocarbons increase correspondingly indicating that the SiO2 /H2 TiO3 catalyst can effectively promote the catalytic aquathermolysis of the heavy oil at 150 °C. 4. Conclusions SiO2 /H2 TiO3 nanocomposite with good dispersibility in various organic solvents was prepared through hydrothermal reaction in the presence of surface-modified SiO2 as the lipophilic carrier.
As-prepared SiO2 /H2 TiO3 nanocomposite exhibits better catalytic performance for the aquathermolysis reaction of the heavy oil at 150 °C and 180 °C than the hydrophilic H2 TiO3 catalyst, because the highly hydrophilic H2 TiO3 coated on the hydrophobic silica results in the lipophilicity of SiO2 /H2 TiO3 nanocomposite and more chance to contact with oil phase thereby effectively promoting the aquathermolysis reaction. Particularly, the highest viscosity reduction rate of the tested heavy oil is achieved at a SiO2 /H2 TiO3 catalyst dosage of 0.5% and a temperature of 150 °C. This demonstrates that as-prepared SiO2 /H2 TiO3 catalyst may have significance in downhole upgrading heavy crude oils. Acknowledgments This research is financially supported by the National Natural Science Foundation of China (grant Nos. 21371047 and 21471047). References [1] Q.Y. Wang, H.J. He, Sino-Global Energy 18 (8) (2013) 33. [2] M.S. Rana, V. Sámano, Fuel 86 (9) (2007) 1216. [3] K. Tan, S. Wang, F. Cao, Contemporary Chem. Ind. (Dangdai Huagong) 43 (1) (2014) 97. [4] W. David, J. Wang, I.D. Gates, Fuel 117 (Part A) (2014) 431. [5] H.H. Pei, G.C. Zhang, J.J. Ge, Fuel 104 (2013) 372. [6] J.B. Hyne, J.W. Greidanus, Aquathermolysis of Heavy Oils. 2nd Int Conf, Caracas, Venezuela, 1982, p. 25. [7] P.D. Clark, J.B. Hyne, AOSTRA J. Res. (1990) 53. [8] H.F. Fan, Z.B. Li, T. Liang, J. Fuel Chem. Technol. 35 (1) (2007) 32. [9] Z.X. Fan, T.F. Wang, Y.H. He, J. Fuel Chem. Technol. 37 (6) (2009) 690. [10] Y.Q. Wang, Y.L. Chen, J. He, Energy Fuels 24 (3) (2010) 1502. [11] K. Chao, Y.L. Chen, J. Li, Fuel Process. Technol. 104 (2012) 174. [12] W.L. Qin, B.Y. Su, C.S. Pu, Acta Petrolei Sin. 25 (6) (2009) 772. [13] H.F. Fan, Y.J. Liu, F.L. Yang, Oilfield Chemistry 18 (1) (2001) 13. [14] H.F. Fan, Y.J. Liu, X.F. Zhao, Oil Drilling Prod. Technol. 23 (3) (2001) 42. [15] Y.L. Chen, Y.Q. Wang, C. Wu, Energy Fuels 22 (3) (2008) 1502. [16] L.G. Zhong, Y.J. Liu, H.F. Fan, International Improve Oil Recovery Conference, Kuala Lumpur, Malaysia, 2003. [17] J. Li, Y.L. Chen, H.C. Liu, Energy Fuels 27 (2013) 2555. [18] R. Hashemi, N.N. Nassar, P.P. Almao, Appl. Energy 133 (2014) 374. [19] S.K. Maity, J. Ancheyta, G. Marroquin, Energy Fuels 24 (2010) 2809. [20] Y.H. Shokrlu, T. Babadagli, J. Petrol. Sci. 119 (2014) 210. [21] P. Jing, Q.B. Li, M. Han, Petrochem. Technol. 36 (3) (2007) 237. [22] S.B. Wen, Y.J. Liu, Y.W. Song, J. Daqing Petrol. Inst. 28 (1) (2004) 25. [23] X.N. Zhang, S.Z. He, X.W. Zhang, J. Daqing Petrol. Inst. 29 (4) (2005) 33. [24] SY/T 5119-2008, Analysis method for fractions of rock extract and crude oil. [25] Q.Y. Deng, L. Liu, H.M. Deng, Spectral Analysis, Science Press, Beijing, 2007.