EXTRACTION OF DECANE AND HEXANE WITH SUPERCRITICAL PROPANE: EXPERIMENTS AND MODELING

International Journal of Chemical & Petrochemical Technology (IJCPT) ISSN 2277-4807 Vol. 3, Issue 2, Jun 2013, 71-82 TJPRC Pvt. Ltd. EXTRACTION OF DECANE AND HEXANE WITH SUPERCRITICAL PROPANE: EXPERIMENTS AND MODELING MARIO KABBOUR, MUHAMMAD SYARHABIL AHMAD & MIDHAT NABIL BIN AHMAD SALIMI School of Bioprocess Engineering, University Malaysia Perlis (UniMap), Arau, Perlis, Malaysia ABSTRACT This work describes the modeling of the supercritical propane extraction process for the propane-decane and propane-hexane fuel mixtures at various pressures and temperatures. A thermodynamic model based on the universal functional activity coefficient (UNIFAC) model carried out to evaluate activity coefficient's expression for each phase for the gaseous compounds' mixture in order to predict mutual solubility data and compared with the experimental data. The calculation of some of the parameters required for these calculations would be difficult if the solute or the heavy components such as hexane or decane were sensitive to temperature. Calculation along these lines is described and the physical basis for applying this method under the relevant condition discussed. The model approach, in particular, is that the mole fraction of the predicted mixture must be regarded as independent of pressure and temperature. KEYWORDS: Supercritical Propane, Activity Coefficient, UNIFAC Method, Propane-Decane, Propane-Hexane INTRODUCTION A lot of studies about supercritical fluid extraction for fuel mixtures have been reported, such as, extraction of bitumen using supercritical propane and ethane [1, 2], extraction of ethanol-octane fuel mixture using supercritical carbon dioxide [3], and extraction of lignite and oil shale with supercritical toluene and water [4, 5], etc. Wilson et al. 1936 were used the propane as a solvent in the first industrial supercritical fluids for a refinement of lubrication oils processes [6]. Supercritical propane is an ideal solvent in extraction of fuel mixture processes for the reasons: it is easily to get to supercritical state because of its critical pressure (4.26 MPa) and temperature (96.6 o C), immensely improve its solvent capabilities because of it is combines properties of both liquid and gas [7], and had the ability to dissolve material with high molecular weight. Phase equilibrium mutual solubility for supercritical propane as a solvent with hydrocarbon systems at high pressure and temperature are very important in many chemical processes such as gas hydrate in liquid natural gases LNG and liquid petroleum gases LPG processes. The using of equation of state or supercritical constant properties is not accurate enough because it would be only for prediction of solubility related to vapour phase. The estimation of some of the parameters required in the prediction would be difficult if the solute (heavy component) was a complex substance about which little was known apart from its structural formula. An alternative procedure for the prediction mutual solubility data is to apply activity coefficient expression of the UNIFAC model based on the thermodynamic type to each phase. The UNIFAC model is the most widely model used to predict the activity coefficient s expression for the binary and multicomponent system comparing with other models, such as, Wilson, non-random two liquid (NRTL), and universal quasi Chemical (UNIQUAC); because of its: (1) Simplicity and flexibility. (2) Ability to fit polar and nonpolar systems [8]. (3) Size and binary interaction parameters are available for more than 100 functional groups. (4) It is an open system and in the future more parameters and more function groups were filled in the UNIFAC list. (5) It is very popular and desirable in optimization, design, and synthesis of the separation process for the recent years because it is saving the

72 Mario Kabbour, Muhammad Syarhabil Ahmad & Midhat Nabil Bin Ahmad Salimi measurement time [9]. The UNIFAC model approach, in particular, is encouraging for the prediction's phase equilibria solubility, though interaction parameters (a C3H8/CH and a CH/C3H8 ) for the calculation's phase activity coefficient as well as Gibbs function, and its gradients at required pressures and temperatures. Calculations along these lines are described and the physical basis for applying this method under the relevant conditions discussed. The comparison of the experimental mutual solubility data with the theoretical mutual solubility data obtained from the thermodynamic model are shown in the present work. Theoretical values calculated from the model such as mutual phase's activity coefficients, Gibbs function, and its gradients are plotted against the propane at given pressures and temperatures. SUPERCRITICAL FLUID EXTRACTION The sample was loaded into the basket and was placed into the laboratory-scale supercritical fluid extraction system using propane as a solvent. The temperature was controlled by a thermostat ±1 o C and pressure was controlled by a back-pressure regulator. At the desired pressure, the compressed propane was continuously supplied through to the sample in the extraction vessel to extract at desired volumetric flow rate and temperature. Before the commencement of any of these experiment procedures, the vials were weighted and tagged for identification, and it is placed in a collection chamber to collect the extracted sample. The collected sample vial is then weighted again to determine the total amount of the extract. This allows for calculation of mole fraction of the extract. The extracts were taken and kept in vials and stored in - 10 o C for analysis. The samples were determined by Shimadzu Gas Chromatography AOC-20i, separated on (30m x 0.25) mm capillary column. The initial temperature was 160 o C, programmed to 250 o C at 5 min, which was maintained at 200 o C up to 10 min. Spilt injection were carried out with the split ratio of 10:1. Helium was used as a carrier gas, flow rate of 1.0 ml/min, and the injector temperature set at 250 o C. Figure 1: Supercritical Propane Apparatus Schematic Diagram, Propane Gas Cylinder (GC), Compressor (C), Pressure (PI), Regulation Valve (RV), Compressor Unit (CU), Extractor (E), Heat Exchanger (HF), Separator (S), Thermostat (T), on-off Valve (V), Cut-off Valve (CV), Pressure Indicator (PI), THERMODYNAMIC MODEL Temperature Indicator (TI), Flow Indicator (FI) The Universal Functional Activity Coefficient (UNIFAC) Model The Universal Functional Activity Coefficient (UNIFAC) model and similar expression for activity coefficients related to Hildebrand et al. 1970 [10]. The activity coefficients may be regarded as starting from the basic thermodynamic results as

Extraction of Decane and Hexane with Supercritical Propane: Experiments and Modeling 73 (1) (2) Where; is the total number of moles in system, is a restraint that the number of moles of all components except (i) remain constant during the differentiation process, is a molar excess Gibbs function of mixing, are similarly defined as the molar excess enthalpy of mixing and molar excess entropy of mixing respectively. Then [8, 13] (3) Using UNIFAC method [12, 14] for predicating activity coefficient for the present systems as follows (4) (5) Since; Subscript (i) identifies species, and (j) is a dummy index running over all species. Subscript (k) identifies subgroups and (m) is a dummy index running over all subgroups. Phase-Equilibrium Theory In order to present details calculations of mutual solubility for the system propane-heavy component (decane or hexane), it is necessary to define that is the mole fraction of component (i) based on the extract phase and is the mole fraction of component (i) based on the solute phase. Therefore and can be calculated from the activity coefficient data and for the phases and from the distribution factor and as [11] (6) (7) The procedure is as follows

74 Mario Kabbour, Muhammad Syarhabil Ahmad & Midhat Nabil Bin Ahmad Salimi Guessing initial K-value for each component given by Eq. 7 Use these guessed K-value to obtain the approximate mole fraction of component (i) in each layer as (8) (9) These values were then inserted at step (b) and cycle was repeated until the mole fractions calculated in step (b) showed negligible change from one step to the next. An alternative approach which was used in the UNIFAC calculations to establish analytic expressions for a function (Q) and its derivative with respect to mole fraction given us (10) (11) (12) (13) is the molar Gibbs function of mixing and from standard thermodynamic relations, it follow that should be negative at all points in a completely miscible system. If the system is partially miscible then will be a region over which is positive. In the latter case the points on versus curve corresponding to the equilibrium phase extract (E) and solute (S) have a common tangent Eq. 11. Where is the second gradient, taken at the mole fraction of the component (i) in the solvent-rich phase and gradient taken at mole fraction of component (i) in the solute-rich phase. If the good estimates of and for the mole fraction and were already available, the following routine was found to be satisfactory for locating and such that Eq. 11 was accurately obeyed. This procedure was repeated until no further adjustment was required. Eq. 11 was then satisfied and the mole fraction and specified the required calculated phase compressions. RESULTS AND DISCUSSIONS Using experimental data for the systems propane-decane and propane-hexane at pressure up to 6 MPa and at various temperatures together with the thermodynamic designed model used for calculating effective values of (a CH, C3H8 ) and (a C3H8, CH ) interaction as a function of pressure. The method used for the calculation in the present work based on UNIFAC procedure, to calculate activity coefficients described above. It would be necessary to calculate values such as properties for each system as activity coefficient, Gibbs function, and its gradients In order to examine feasibility studies experimental and theoretical data which are given in tables 3 and 4. Parameter (d 2 G/dx 2 i ) (molar Gibbs function second derivative) shows that it should be negative at all points in a completely miscible system. If the system is partially miscible these will be a region over which the parameter is positive. Figure 5 and 9 show parameter (d 2 G/dx 2 i ) for propane against propane mole fraction (X C3H8 ) at constant temperatures

Extraction of Decane and Hexane with Supercritical Propane: Experiments and Modeling 75 T=150 and 138 o C for propane-hexane and propane-decane at variable pressures, respectively. These curves confirm that the propane-hexane binary system always is miscible in the considered conditions. The miscibility decrease with increasing of mole fraction up to X C3H8 =0.7 and then increases for X C3H8 >0.7. Also the curves confirm propane-decane system is always miscible in the considered conditions, the miscibility decreases with increasing of solvent mole fraction up to X C3H8 =0.6 and then increases for X C3H8 >0.6. These systems confirm that a high pressure is not useful condition for supercritical extraction forever. Tables 3 and 4 show two phases equilibrium behaviour based on regular solution model, these data are compared with experimental data for propane-decane and propane-hexane. Figure 2 and 6 show activity coefficients for propane against propane mole fractions at constant temperatures T=150 and 138 o C and at variable pressures, also Figure. 3 and 7 show molar Gibbs function for Propane against Propane mole fractions (X C3H8 ) at constant temperatures T=150 and 138 o C and at variable pressures, Figure. 4 and 8 show gradient of molar Gibbs function for Propane calculated against Propane mole fraction at constant temperatures T=150 and 138 o C and at variable pressures. Table 1: Experimental Data for Propane-Decane at T=138, 170, 204.4 and 237.8 o C and at Various Pressures Together with Effective Values of Interaction Parameters (α C3H8/CH, α CH/C3H8 ) T=138 o C P (X E Decane) (X S Decane) MPa Exp Exp α C3H8/CH α CH/C3H8 6.5 0.33 0.025 80.00 3250.0645 1.05 0.54 0.08 89.00 2310.3276 1.4 0.63 0.11 296.5 1808.4932 2.1 0.74 0.19 30.00 1669.2466 2.75 0.78 0.25 89.00 2409.6331 4.1 0.805 0.39 10.0 2129.9226 5.5 0.810 0.5020 10.0 2500.5342 T=170 o C P (X E Decane) (X S Decane) MPa Exp Exp α C3H8/CH α CH/C3H8 0.20 0.370 0.02 89.50 3225.5549 0.65 0.675 0.07 195.3 3742.000 1.05 0.775 0.11 79.00 1972.9453 1.35 0.810 0.165 93.00 2066.3464 2.1 0.855 0.24 39.00 4004.0034 2.8 0.880 0.32 69.00 4102.6733 4.1 0.900 0.45 87.00 3243.2881 5.5 0.897 0.60 85.50 4037.7800 6.95 0.845 0.75 65.00 3761.3120 T=204.4 o C P (X E Decane) (X S Decane) MPa Exp Exp α C3H8/CH α CH/C3H8 0.3 0.72 0.70 734.50 1628.9836 0.7 0.842 0.55 10.00 3530.8047 1.0 0.892 0.4 83.000 4229.9668 1.45 0.910 0.305 97.500 4373.0400 2.05 0.930 0.215 112.00 4322.2119 2.8 0.939 0.165 118.50 4146.1675 4.1 0.950 0.10 126.50 4148.6338 5.55 0.937 0.04 116.50 3994.7559 T=237.8 o C P (X E Decane) (X S Decane) MPa Exp Exp α C3H8/CH α CH/C3H8 0.3 0.892 0.07 87.50 4905.5000 0.7 0.925 0.15 116.5 4320.5767 1.0 0.95 0.212 138.0 4276.3223 1.4 0.965 0.285 157.0 3391.7666

76 Mario Kabbour, Muhammad Syarhabil Ahmad & Midhat Nabil Bin Ahmad Salimi Table 1- Contd., 2.1 0.975 0.400 179.0 3451.6829 2.8 0.98 0.510 187.0 4439.6411 4.15 0.978 0.700 182.5 3967.2048 Table 2: The Experimental Data of Propane-Hexane System at T=150, 180 o C and at Various Pressure Together with Effective Values of Interaction Parameters (α C3H8/CH, α CH/C3H8 ) T=150 o C P (X E Hexane) (X S Hexane) MPa Exp Exp α C3H8/CH α CH/C3H8 2.1 0.61 0.75 145.6006 1249.0609 2.75 0.70 0.39 127.8996 1683.3613 3.5 0.75 0.49 137.9002 1432.4387 4.15 0.785 0.60 151.0010 1194.9880 4.85 0.79 0.695 162.3017 1034.6976 T=180 o C P (X E Hexane) (X S Hexane) MPa Exp Exp α C3H8/CH α CH/C3H8 2.2 0.36 0.13 114.0998 2993.3184 2.75 0.44 0.23 117.5997 2615.2815 3.5 0.58 0.58 469.7204 1029.3857 Table 3: The Comparison of the Experimental and Theoretical Supercritical Propane Solubility in Decane at T=138, 170, 204.4 and 237.8 o C and at Various Pressures T=138 o C P MPa X S C3H8 Exp X E C3H8 Exp X S C3H8 Model X E C3H8 Model 0.65 0.025 0.33 0.4615 0.6354 1.05 0.08 0.54 0.2613 0.7781 1.4 0.11 0.63 0.0536 0.9985 2.1 0.19 0.74 0.6180 0.6300 2.75 0.25 0.78 0.2424 0.7813 4.1 0.39 0.805 0.5935 0.6136 5.5 0.520 0.810 0.5902 0.6138 T=170 o C P X S C3H8 X E C3H8 X S C3H8 X E C3H8 MPa Exp Exp Model Model 0.20 0.02 0.370 0.3868 0.6774 0.65 0.07 0.675 0.6961 0.6696 1.05 0.11 0.775 0.5598 0.6635 1.35 0.165 0.810 0.4729 0.6974 2.1 0.24 0.855 0.5912 0.6208 2.8 0.32 0.880 0.5721 0.6140 4.1 0.45 0.900 0.4468 0.6434 5.5 0.60 0.897 0.4760 0.6278 6.95 0.75 0.845 0.5768 0.6170 T=204.4 o C P X S C3H8 X E C3H8 X S C3H8 X E C3H8 MPa Exp Exp Model Model 0.3 0.72 0.70 0.0742 1.00 0.7 0.842 0.55 0.5900 0.6124 1.0 0.892 0.4 0.5565 0.6044 1.45 0.910 0.305 0.3590 0.6935 2.05 0.930 0.215 0.06603 0.8697 2.8 0.939 0.165 0.020 0.9018 4.1 0.950 0.10 0.0059 0.9265 5.55 0.937 0.04 0.0288 0.8934

Extraction of Decane and Hexane with Supercritical Propane: Experiments and Modeling 77 CONCLUSIONS Table 3 - Contd., T=237.8 o C P MPa X S C3H8 Exp X E C3H8 Exp X S C3H8 Model X E C3H8 Model 0.3 0.892 0.07 0.5590 0.6067 0.7 0.925 0.15 0.9299 0.9404 1.0 0.95 0.212 0.0059 0.9322 1.4 0.965 0.285 0.0208 0.9588 2.1 0.975 0.400 0.0019 0.9784 2.8 0.98 0.510 0.005 0.9764 4.15 0.978 0.700 0.008 0.9674 Table 4: The Comparison of the Experimental and Theoretical Supercritical Propane Solubility in Hexane at T=150 and 180 o c and at Various Pressures T=150 o C P X S C3H8 X E C3H8 X S C3H8 X E C3H8 MPa Exp Exp Model Model 2.20 0.75 0.61 0.5201 0.7983 2.75 0.39 0.70 0.3893 0.7085 3.5 0.49 0.75 0.446 0.7638 4.15 0.60 0.785 0.5159 0.8245 4.85 0.695 0.79 0.5544 0.8562 T=180 o C P MPa X S C3H8 Exp X E C3H8 Exp X S C3H8 Model X E C3H8 Model 2.2 0.36 0.13 0.5312 0.5779 2.75 0.44 0.23 0.5064 0.5763 3.5 0.58 0.58 0.2200 0.9965 In this work, the experimental data for decane and hexane extraction using the supercritical propane at various pressures and temperatures reported together with the effective values of interaction parameters (α C3H8/CH, α CH/C3H8 ) obtained from the back-calculated equations of the thermodynamic model. In this treatment, the interaction parameter between the individual groups constituting the molecular is considered based on this work. Experimental and theoretical comparisons are shown in tables 3 and 4. The results shown that the pressure P=4.1 MPa with the temperature T=138 o C for propane-decane and the pressure P=2.75 MPa with the temperature T=150 o C for propane-hexane were performed mutual solubility about 38% and 29% percentages of decane and hexane, respectively. That gives good opportunity for this feasibility studies to have this material performed in the systems supercritical propane with hydrocarbon decane and hexane. ACKNOWLEDGEMENTS support. The authors wish to thank to University Malaysia Perlis Research Fund, project no. 9001-00305 for their financial NOMENCLATURE a JK H Q k R k q i r i Group interaction parameter. Mole fraction of component (A) Henry s Constant Area parameter, contribution of molecular group Volume parameter, contribution of molecular group Area parameter of component (i) Volume parameter of component (i)

78 Mario Kabbour, Muhammad Syarhabil Ahmad & Midhat Nabil Bin Ahmad Salimi Q γ ξ k α θ Table Contd., Gibbs function Activity coefficients Group surface area fraction Selectivity of a component Area fraction of component REFERENCES 1. Rose, J.L., Monnery, W.D., Chong, K. & Svrcek W.Y. (2001). Extraction data for the extraction of Peace River bitumen using supercritical ethane, Fuel, 80 (9), 1101-1110. 2. Rudzinski, W.E., & Aminabhavi, T.M. (2000). Review on extraction and identification of crude oil and related products using supercritical fluid technology, Energy and Fuels, 14 (2), 464-475. 3. Mario Kabbour., Muhammad Syarhabil Ahmad., & K. M. Kassim. (2012). Biodiesel purification developments based on carbon dioxide supercritical for biofuel-technology, The 2nd International Malaysia-Ireland Joint Symposium on Engineering, Science and Business (IMiEJS2012), 146-160. 4. Hu Haoquan., Zhang Jun., Guo Shucai., & Chen Guohua. (1999). Extraction of Huadian oil shale with water in sub-and supercritical states, Fuel, 78 (6), 645-651. 5. Hu Haoquan., Guo Shucai., & Hedden Kurt. (1998). Extraction of lignite with water in sub-and supercritical states, Fuel Processing Technology, 53 (3), 269-277. 6. Wilson, R.E., Keith Jr, P.C., & Haylett, R. E. (1936). Liquid propane use in dewaxing, deasphalting, and refining heavy oils, Industrial & Engineering Chemistry, 28 (9), 1065-1078. 7. Berkowitz Norbert., & Calderon Jaime., (1990). Extraction of oil sand bitumens with supercritical water, Fuel Processing Technology, 25 (1), 33-44. 8. Zhigang Lei., Biaohua Chen., Chengyue Li., & Hui Liu. (2008). Predictive molecular thermodynamic models for liquid solvents, solid salts, polymers, and ionic liquids, Chem. Rev, 108, 1419-1455. 9. Gmehling, J., & Möllmann, C. (1998). Ind. Eng. Chem. Res, 37, 3112. 10. Hildebrand, J. H., Prausnitz, J. M., & Scott, R. L. (1970). Regular and related solutions, Van Nostrand-Reinhold, New York. 11. King, M. B. (1969). Phase Equilibrium in Mixtures, Pergamum Press, UK. 12. Pollmann, P., & Lobbecke, M. (1996). UNIFAC activity coefficient derivatives, Gas. Sep. Purif,10 (3), 177-180. 13. Fredenslund, A., Gmehling, J., & Rasussen, P. (1977). Vapor-Liquid equilibria using UNIFAC, Elsevier Scientific Publication Company, Amsterdam, Oxford, New York. 14. Smith, J. M., H. Wess, C. V., & Abbott, M. M., Introduction to chemical engineering thermodynamic, McGraw- Hill Ind. (2005).

Extraction of Decane and Hexane with Supercritical Propane: Experiments and Modeling 79 APPENDICES Figure 2: Activity Coefficient for C 3 H 8 against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=150 ºC and at Variable Pressures Figure 3: Molar Gibbs Function for C 3 H 8 (G mixing m) against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=150 ºC and at Variable Pressures Figure 4: Gradient of the Molar Gibbs Function (dq C3H8 /dx C3h8 ) for C 3 H 8 Calculated against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=150 ºC and at Variable Pressures

80 Mario Kabbour, Muhammad Syarhabil Ahmad & Midhat Nabil Bin Ahmad Salimi Figure 5: Parameter (d 2 Q C3H8 /dx 2 C3H8) for C 3 H 8 Calculated against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=150 ºC and at Variable Pressures Figure 6: Activity Coefficient for C 3 H 8 against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=138 ºC and at Variable Pressures Figure 7: Molar Gibbs Function for C 3 H 8 (M ixing ) against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=138 ºC and at Variable Pressures

Extraction of Decane and Hexane with Supercritical Propane: Experiments and Modeling 81 Figure 8: Gradient of the Molar Gibbs Function (dq C3H8 /dx C3h8 ) for C 3 H 8 Calculated against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=138 ºC and at Variable Pressures Figure 9: Parameter (d 2 Q C3H8 /dx 2 C3H8) for C 3 H 8 Calculated against C 3 H 8 Mole Fraction (x C3H8 ) at Constant Temperature T=138 ºC and at Variable Pressures