Article pubs.acs.org/EF
Comparison of Hansen Solubility Parameter of Asphaltenes Extracted from Bitumen Produced in Different Geographical Regions Takashi Sato,† Sadao Araki,† Masato Morimoto,‡ Ryuzo Tanaka,§ and Hideki Yamamoto*,† †
Department of Chemical, Energy and Environmental Engineering Faculty of Environmental and Urban Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680, Japan ‡ Advanced Fuel Group, Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, 3-9 Toranomon 4-tyome, Minato-Ku, Tokyo 108-0014, Japan § Advanced Technology and Research Institute, Japan Petroleum Energy Center, 16-1 Onogawa, Tsukuba-Shi, Ibaragi 305-0053, Japan ABSTRACT: The Hansen solubility parameters (HSPs) of asphaltenes extracted from oil sand bitumen samples produced at Athabasca in Canada and also from a vacuum residue fraction (VR) produced in the Middle East were determined by the Hansen solubility sphere method. For calculation of HSPs, the solubilities of asphaltenes were determined using a dynamic light scattering (DLS) method by dissolving or dispersing the asphaltenes in various solvents and measuring the particle size distributions thereof. The particle diameters of asphaltenes in good solvents were lower than its detection limit (1, it is a poor solvent. Thus, RED can be used as an indicator of solubility.
RED = R a /R 0
The solubility parameter of a mixed solvent is calculated by the following equation:
2. EXPERIMENTAL SECTION 2.1. Theory of the Hansen Solubility Parameter. The solubility parameter δt [(MPa)1/2] used in solubility evaluation is defined by eq 1 using liquid cohesion energy E [J] and molar volume V [cm3/mol] (Hildebrand et al.)9 δt = (E /V )1/2
δi = ϕ1δi1 + ϕ2δi2
Hansen divided the cohesion energy E [J] of the Hildebrand solubility parameter into three factors (i.e., dispersion interactions Ed [J], dipole interactions Ep [J], and hydrogenbonding interaction Eh [J]), which can be expressed by the following:10
δd = (Ed /V )1/2
(2)
δp = (Ep/V )1/2
δ h = (E h /V )1/2 (3)
δt 2 = δd 2 + δp2 + δ h 2
(7)
where ϕ is the volume fraction of each of the mixed solvents and the lower subscripts 1 and 2 represent components 1 and 2, respectively. The lower subscript i represents d, p, or h (i.e., δi represents dispersion interaction, dipole interaction, or hydrogen-bonding interaction factors). 2.2. Materials. Asphaltenes used in this study were extracted from oil sand bitumen samples produced at Athabasca in Canada and from a VR fraction produced in the Middle East. Asphaltenes were extracted in the following manner: asphalt particles with diameters of 2.8 mm or less and heptane of a 20fold larger volume were placed in an extraction tank, and the mixture was then heated gradually at an initial pressure of 0.3 MPa under a nitrogen atmosphere. After about 40 min when the mixture was heated to 373 K, the internal pressure was increased to 1 MPa and the mixture was left in that state for 1 h. After cooling to about 303 K, the mixture was passed through a polytetrafluoroethylene (PTFE) filter having a pore diameter of 0.8 μm. The recovered cake and heptane in the amount equivalent to that first added were placed in the
(1)
E = Ed + Ep + E h
(6)
(4) 892
dx.doi.org/10.1021/ef402065j | Energy Fuels 2014, 28, 891−897
Energy & Fuels
Article
Table 1. Chemical Properties of Asphaltenes Used in This Work elemental analysis [wt%] asphaltene
C
H
N
S
O
Ni
V
others
H/C [−]
AMW [g/mol]
CaAs ArAs1
81.3 82.5
7.2 7.0
1.3 1.0
8.1 8.0
1.5 1.0
0.037 0.021
0.100 0.064
0.46 0.42
1.05 1.01
775 738
CaAs: Asphaltene extracted from bitumen produced from Canada. ArAs1: Asphaltene extracted from bitumen produced from the Middle East.
Table 2. Solubility Score of CaAs in Some Organic Solvents and Hansen Solubility Parameters of Used Organic Solvents Score [−] Solvents
δd (MPa) ]
δp [(MPa) ]
δh [(MPa) ]
δt [(MPa) ]
0.05 g/L
1 g/L
5 g/L
bromobenzene TCE dichlorobenzene chlorobenzene chloroform quinoline benzaldehyde toluene xylene pyridine benzene ethyl benzene methylene dichloride carbon disulfide THF 1,4-dioxane tetrachlorom ethane 1-chlorobutane nitrobenzene morpholine 2-phenyl ethanol aniline ethyl acetate cyclohexane MIBK MEK NMP acetone PGME pentane dimethylformamide γ-butyrolactone 1-butanol acetonitrile ethanol methanol
19.2 18.8 19.2 19.0 17.8 20.5 19.4 18.0 17.8 19.0 18.4 17.8 17.0 20.2 16.8 17.5 17.8 16.2 20.0 18.0 18.3 20.1 15.8 16.8 15.3 16.0 18.0 15.5 15.6 14.5 17.4 18 16.0 15.3 15.8 14.7
5.5 5.1 6.3 4.3 3.1 5.6 7.4 1.4 1.0 8.8 0.0 0.6 7.3 0.0 5.7 1.8 0.0 5.5 10.6 4.9 5.6 5.8 5.3 0.0 6.1 9.0 12.3 10.4 6.3 0.0 13.7 16.6 5.7 18.0 8.8 12.3
4.1 5.3 3.3 2.0 5.7 5.7 5.3 2.0 3.1 5.9 2.0 1.4 7.1 0.6 8.0 9.0 0.6 2.0 3.1 11.0 11.2 11.2 7.2 0.2 4.1 5.1 7.2 7.0 11.6 0.0 11.3 7.4 15.8 6.1 19.4 22.3
20.4 20.2 20.5 19.6 18.9 22.0 21.4 18.2 18.1 21.8 18.5 17.9 19.8 20.2 19.5 19.8 17.8 17.2 22.8 21.7 22.2 23.7 18.2 16.8 17.0 19.1 23.0 19.9 20.4 14.5 24.9 25.6 23.2 24.4 26.5 29.4
− − − − − − − 1 − − − − − − − 0 − 0 0 0 0 0 − 0 0 0 0 − − 0 − − − − − −
− 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 − − 1 − − − 1 1 1 1 1 − − 1 − − − − − − − − − − − − − − − − − − − − −
1/2
1/2
1/2
1/2
CaAs: Asphaltene extracted from bitumen produced from Canada. 1: Good solvents for CaAs. 0: Bad solvents for CaAs. −: No measurement.
and vanadium was analyzed by the inductively coupled plasma atomic emission spectrophotometry (ICP−AES). Average molecular weights of the asphaltenes were determined by gel permeation chromatography (JASCO Corporation, Gulliver) equipped with a refractive index detector (Shodex, RI-104) and a column (Shodex, KF-403HQ, inside diameter 4.6 mm, exclusion limits 70 000). The temperature of the column was 313 K, and the eluent was tetrahydrofuran. Retention time of asphaltene for the GPC measurement was converted to the molecular weight based on the retention time of polystyrenes (several molecular weights), decacyclene (molecular weight = 451), and 2,9,16,23-tetra-t-butyl-29H,31H-phthalocyanine (molecular weight = 739).
extraction tank and the extraction operation was repeated once again. In the description below, the asphaltenes extracted from the oil sand bitumen samples produced at Athabasca in Canada and a VR fraction produced in the Middle East are referred to as CaAs and ArAs1, respectively. The results of elemental analyses, H/C ratios, and average molecular weights of CaAs and ArAs1 are shown in Table 1. Elemental analysis of carbon, hydrogen, and nitrogen in asphaltenes were determined by CHNS elemental analyzer (Thermoquest Co. Ltd., EA1110CHNS-O).16 Analyses of amount of sulfur and oxygen in asphaltenes were carried out by combustion-ion chromatography and by JIS M8813, respectively. The amount of nickel 893
dx.doi.org/10.1021/ef402065j | Energy Fuels 2014, 28, 891−897
Energy & Fuels
Article
Table 3. Solubility Score of ArAs1 in Some Organic Solvents and Hansen Solubility Parameters of Used Organic Solvents solvents
δd [(MPa)1/2]
δp [(MPa)1/2]
δh [(MPa)1/2]
δt [(MPa)1/2]
score [−]
tetrahydronaphthalene bromobenzene TCE 1-bromonaphthalene chlorobenzene dichlorobenzene p-chlorotoluene chloroform quinoline toluene xylene benzaldehyde benzene carbon disulfide N-methylaniline ethyl benzoate methyl benzoate ethyl benzene pyridine 1,4-Dioxane THF methylene dichloride 1-chlorobutane cyclohexane nitrobenzene morpholine aniline 2-phenyl ethanol MIBK MEK tetrachloromethane NMP pentane
19.6 19.2 18.8 20.6 19.0 19.2 19.1 17.8 20.5 18.0 17.8 19.4 18.4 19.9 19.5 17.9 18.9 17.8 19.0 17.5 16.8 17.0 16.2 16.8 20.0 18.0 20.1 18.3 15.3 16.0 16.1 18.0 14.5
2.0 5.5 5.1 3.1 4.3 6.3 6.2 3.1 5.6 1.4 1.0 7.4 0.0 5.8 6.0 6.2 8.2 0.6 8.8 1.8 5.7 7.3 5.5 0.0 10.6 4.9 5.8 5.6 6.1 9.0 8.3 12.3 0.0
2.9 4.1 5.3 4.1 2.0 3.3 2.6 5.7 5.7 2.0 3.1 5.3 2.0 0.6 7.8 6.0 4.7 1.4 5.9 9.0 8.0 7.1 2.0 0.2 3.1 11.0 11.2 11.2 4.1 5.1 0.0 7.2 0.0
19.9 20.4 20.2 21.2 19.6 20.5 20.2 18.9 22.0 18.2 18.1 21.4 18.5 20.7 21.8 19.9 21.1 17.9 21.8 19.8 19.5 19.8 17.2 16.8 22.8 21.7 23.7 22.2 17.0 19.1 18.1 23.0 14.5
1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
ArAs1: Asphaltene extracted from bitumen produced from Middle East. 1: Good solvents for ArAs1. 0: Bad solvents for ArAs1.
2.3. Experimental Method. In this study, the particle diameters of the asphaltenes in 30 or more solvents were determined for evaluation of their solubilities. The average particle size of asphaltenes in solvents was measured by dynamic light scattering particle analyzer (Otsuka Electronics, FPAR-1000). Solubility evaluations based on particle size distribution were aimed at grouping the solvents for CaAs and ArAs1 into good and poor solvents. The many solvents were used to be located around the surfaces of the Hansen solubility sphere as much as possible, in order to improve the accuracy in preparing the Hansen solubility sphere. A mixture of solvent and an asphaltene was ultrasonicated in a desktop ultrasonic cleaning machine (Branson Ultrasonics, Emerson Japan, Ltd., B3510J-DTH) for 10 min, left to stand for 24 h, and ultrasonicated for an additional 5 min prior to measurement of particle size distribution. Average particle size of asphaltenes in solution after the ultrasonic treatment was measured using dynamic light scattering at 298 K and atmospheric pressure. The particle diameters of CaAs and ArAs1 were measured for 3 min (about 80 times of the cumulated number) at 298 K under atmospheric pressure. In the case of CaAs, the particle size distributions were determined at several concentrations. In addition, the particle size distributions of CaAs in toluene +
pentane and toluene + cyclohexane solvent systems were determined. The HSPs of asphaltenes were calculated by the Hansen solubility sphere created by the commercial software named the Hansen solubility parameters in practice (HSPiP).
3. RESULT AND DISCUSSION 3.1. Measurement of Asphaltene Particle Size by DLS. The particle size distributions of CaAs in 36 solvents were determined at an asphaltene concentration of 1 g/L; DLS observations indicated the absence of particles having a diameter of 1 nm or more in 15 solvents including toluene. The particle diameter of CaAs could be determined in a total of 21 solvents. According to a report by Mansur et al., the particle diameters of asphaltenes in toluene were 12, 14, 14, and 22 nm at concentrations of 0.01, 0.017, 0.02, and 0.025 w/v %, respectively. The particle size distribution of CaAs in toluene could not be successfully determined at a concentration of 0.017 g/L, which is equivalent to the concentration reported by Mansur et al. Because the DLS instrumentation used in this study was a high-sensitivity system (FPAR-1000), particle diameters in the range of 1−5000 nm would be measurable. For solvents in which the particle diameter could not be determined, the particle diameter of CaAs was considered to be not more than the detection limit (
