Fluid phase coexistence for the oxidation of cyclohexane in CO 2 expanded liquids: COSMO-SAC vs. molecular simulation

Transcription

1 Fluid phase coexistence for the oxidation of cyclohexane in CO 2 expanded liquids: COSMO-SAC vs. molecular simulation International Workshop Molecular Modeling an Simulation: Natural Science meets Engineering Frankfurt, 12 March, 2013 C.-M. Hsieh 1, T. Merker 2, S.-T. Lin 3, H. Hasse 2, J. Vrabec 1 1 Thermodynamics and Energy Technology, University of Paderborn, Germany 2 Lab. of Engineering Thermodynamics, University of Kaiserslautern, Germany 3 Department of Chemical Engineering, National Taiwan University, Taiwan

2 = Cyclohexane oxidation: industrial application Oxidation of cyclohexane to KA-oil (mixture of and ) Used for the production of adipic acid / Nylon 6.6 Usually, contact cyclohexane with air low conversion rates (~10%) Air (O 2 ) O + OH for high selectivity (~ 85%) COOH COOH HOOC COOH Use of supercritical carbon dioxide expanded media to improve the rates of conversion and selectivity (enhance the mobility of reactants and products)

3 Molecular models for investigated compounds 6 LJ-site Cyclohexane Cyclohexanone 7 LJ- site + m CO 2 3 LJ-site + Q O 2 =O OH 2 LJ-site + Q Cyclohexanol 7LJ-site + 3 q + CH - O + H q: point charge, m : point dipole, Q: point quadrupole Experimental measurements VLE Henry s law constant Molecular simulations ms2 Thermodynamic models COSMO-SAC Peng-Robinson EOS Mixtures investigated: 10 (10) binary, 6 (10) ternary, 2 (5) quaternary, 1 pentenary [1] T. Merker, et al.: J. Chem. Eng. Data, 56: 2477 (2011) [2] T. Merker, J. Vrabec, H. Hasse: J. Chem. Thermodyn., 49: 114 (2012) [3] S. Deublein, et al.: Comput. Phys. Commun., 182: 2350 (2011)

4 Development of molecular pure fluid models CO 0.8% 2 p 1.6% 0.9% =O OH p 3.0% CO 2 0.4% 0.4% p 3.0% p 2.7% =O OH Equation of state (EOS) Simulation DIPPR correlation [1] T. Merker, J. Vrabec, H. Hasse: J. Chem. Phys., 129: (2008) [2] T. Merker, C. Engin, J. Vrabec, H. Hasse: J. Chem. Phys., 132: (2010) [3] T. Merker, J. Vrabec, H. Hasse: Fluid Phase Equilib., 315: (2012) [4] T. Merker, J. Vrabec, H. Hasse: Soft Mater., 10: 3-25 (2012) 4

5 Molecular model of mixtures A σ AB, ε AB B σ A, ε A A B Prediction or ξ = 1 Fitting to ONE experimental datum of p(t,x) or H(T) σ B, ε B Interaction between A and B: Polar interaction: laws of electrostatics Lennard-Jones parameters: combination rule Modified Lorentz-Berthelot combining rule σ σ σ ε = + / 2 AB A B = ε ε AB A B

6 COSMO-SAC (G ex model) The activity coefficient of species i in mixture S is determined from: * res i / S * res i / i G G ln i / S ln RT Quantum mechanics Geometry opt. SG,comb i / S COSMO Residual contribution: Molecular interactions Combinatorial contribution: Size and shape effect (Staverman Guggenheim) s-profile Statistical mechanics Segment Activity Coefficient water Å 2 hexane 1-octanol [1] S.-T. Lin, S. I. Sandler: Ind. Eng. Chem. Res., 41: 899 (2002) [2] C.-M. Hsieh, et al.: Fluid Phase Equilib. 297, 90 (2010) (e/å 2 ) (e/å 2 ) Å 2 G RT * res i / S n i s m p i ( s )ln m S Å 2 ( s ) m

7 s-profiles of investigated compounds Cyclohexane (C 6 H 12 ) CO 2 O 2 Cyclohexanone (C 6 H 10 O) (e/å 2 ) (e/å 2 ) s-profiles for mixture: Cyclohexanol (C 6 H 12 O) p mix( s ) xi pi ( s ) i [1] C.-M. Hsieh, S.I. Sandler, S.-T. Lin: Fluid Phase Equilib.: 297, (2010). [2] T. Merker, C.-M. Hsieh, S.-T. Lin, J. Vrabec, H. Hasse: AIChE J. in press, (2013) Oxygene Carbon dioxide Cyclohexane Cyclohexanone Cyclohexanol

8 Peng-Robinson equation of state (PR EOS) p RT a v b v( v b) b( v b) VDW mixing rule a(t,x), b(x) PR EOS VLE, H(T) calculation COSMO-SAC G ex MHV1 mixing rule a(t,x), b(x) PRSV EOS Van der Waals mixing rule Modified Huron-Vidal 1st order E a xix j aiia jj 1k a a 1 i g b ij xi ln i j brt i birt 0.53 RT i bi b xibi bi bj i b xix j 1 l 2 ij i j Prediction: k ij = 0 and l ij =0. Or fitting to ONE experimental datum of p(t,x) or H(T) [1] D.Y. Peng, D.B. Robinson: Ind. Eng. Chem Fundam., 15: 59 (1976) [2] M.L. Michelsen: Fluid Phase Equilib., 60: 47 (1990) [3] R. Stryjek, J.H. Vera: Can. J. Chem. Eng., 64: 323 (1986)

9 Henry s law constant CO 2 O Experiment PR EOS (with k ij ) Simulation (Prediction) Simulation (with ij ) COSMO-SAC (Prediction) COSMO-SAC (with l ij ) =O =O OH OH [1] T. Merker, et al.: J. Chem. Thermodyn., 49: 114 (2012) [2] T. Merker, et al.: Fluid Phase Equilib., 315: 77 (2012)

10 Selected binary VLE (I) + OH O 2 + CO 2 CO 2 + =O Experiment PR EOS (with k ij ) Simulation (with ij ) Simulation (Prediction) COSMO-SAC (with l ij ) COSMO-SAC (Prediction)

11 Selected binary VLE (II) =O + OH Experiment PR EOS (with k ij ) Simulation (with ij ) Simulation (Prediction) COSMO-SAC (with l ij ) COSMO-SAC (Prediction)

12 Analysis of all 10 binary systems Rating from - - (0 points, very bad) to ++ (4 points, very good) Mixture Molecular Simulation COSMO-SAC Peng-Robinson EOS Prediction with ij Prediction with l ij Prediction with k ij O 2 + CO O O 2 + =O O 2 + OH CO CO 2 + =O CO 2 + OH =O OH =O OH Overall [1] T. Merker, C.-M. Hsieh, S.-T. Lin, J. Vrabec, H. Hasse: AIChE J. in press, (2013)

13 Henry s law constant for three ternary subsystems 313 K + Experiment Simulation (with ij ) COSMO-SAC (with l ij ) O 2 =O CO 2 OH [1] T. Merker, C.-M. Hsieh, S.-T. Lin, J. Vrabec, H. Hasse: AIChE J. in press, (2013)

14 Henry s law constant for two quaternary subsystems O K Experiment Simulation (with ij ) COSMO-SAC (with l ij ) CO 2 =O ( =O and OH are in equal-molar concentration) OH [1] T. Merker, C.-M. Hsieh, S.-T. Lin, J. Vrabec, H. Hasse: AIChE J. in press, (2013)

15 VLE of quaternary subsystems and pentenary system The composition (without O 2 and CO 2 ) of the fluid is constant: : mol/mol, =O : 0.35 mol/mol, OH : mol/mol p / MPa Pure O 2 CO 2 (with constant molar fraction 0.04 of O 2 in the mixture) CO 2 (with constant molar fraction 0.02 of O 2 in the mixture) 2 Pure CO K 0 0,0 0,2 0,4 0,6 0,8 1,0 x i / mol mol -1 + Experiment Simulation (with ij ) COSMO-SAC (with l ij ) [1] T. Merker, C.-M. Hsieh, S.-T. Lin, J. Vrabec, H. Hasse: AIChE J. in press, (2013)

16 Conclusions Good predictions from molecular simulation and COSMO-SAC Excellent accuracy achieved with binary parameters Capable to predict multi-component VLE Models can be used in industrial process design Molecular models can be used for atomistic simulations of e.g. fluid behavior in nanostructured catalysts

17 Thank You for Your Attention!

18 Values of binary interaction parameters in this work Mixture (i + j) ij l ij k ij O 2 + CO O 2 + C 6 H O 2 + C 6 H 10 O O 2 + C 6 H 12 O CO 2 + C 6 H CO 2 + C 6 H 10 O CO 2 + C 6 H 12 O C 6 H 12 + C 6 H 10 O C 6 H 12 + C 6 H 12 O C 6 H 10 O+C 6 H 12 O

19

20 CO 2 + OH CO =O + Experiment PR EOS (with k ij ) Simulation (with ij ) Simulation (Prediction) COSMO-SAC (with l ij ) COSMO-SAC (Prediction)

21 Contribution of molecular simulation powerful predictive capabilities (thermodynamic data) works under any physical conditions low cost Why is molecular simulation not a mainstream solution for thermodynamic data retrieval? suitable molecular models today s MS software: only a few independent properties new properties require implementation development is impossible for an inexperienced user

22 Peng-Robinson Equation of State (PR EOS) p RT a v b v( v b) b( v b) a i RT ci, T i p c, i Tc, i 2 b i RT p ci, ci, PR EOS + VDW Original Peng-Robinson i i i Van der Waals Mixing Rule a x x a a 1k b xibi i i j i j ii jj ij Prediction: k ij = 0 and l ij =0. Or fitting to ONE experimental datum of p(t,x) or H(T) [1] D. Y. Peng, D.B. Robinson: Ind. Eng. Chem. Fundam., 15: (1976) [2] R. Stryjek, J.H. Vera: Can. J. Chem. Eng., 64: (1986) [3] M. L. Michelsen: Fluid Phase Equilib., 60: (1990) PRSV EOS + MHV1 + COSMOSAC Peng-Robinson-Stryjek-Vera EOS i i i 3 T T i 1, i T c, i Tc, i Modified Huron-Vidal 1st-order Mixing Rule E a ai 1 g b xi ln brt i birt 0.53 RT i bi bi bj b xix j 1lij 2 i j