Modern Methods in Heterogeneous Catalysis Research Fritz Haber Institute, Berlin, 14 November 2003 CatalyCatalytictic DistillationDistillation Kai Sundmacher1,2 1 Max-Planck-Institute for Dynamics of Complex Technical Systems Sandtorstraße 1, 39106 Magdeburg, Germany 2 Otto-von-Guericke-University Magdeburg, Process Systems Engineering Universitätsplatz 2, 39106 Magdeburg, Germany [email protected] Catalytic Distillation (CD) - Outline 3 Catalysts for Use in CD Processes 4 Modelling, Simulation, Experimental Validation 2 Fields of Application, CD Lecture Process Examples 5 Operational Process Behaviour 1 Basic Principles of CD CD Expert ! Modern Methods in Heterogeneous Catalysis Research Fritz Haber Institute, Berlin, 14 November 2003 Integration of Unit Operations in Multifunctional Reactors Raw Materials Main Products Recycle Physical Chemical/ Separation Separation Unit Biological Units for Units for Operations Units Reactants By-Products Multifunctional Multifunctional Reactors (e.g. Reactors (e.g. Fuel Cells) Reactive Mill) By-Products Multifunctional Reactors (Reactive Distillation / Absorption / Extraction / Adsorption Column) Possible Benefits from Multifunctional Reactor Concepts Synergetic interactions of chemical and physical unit operations may lead to: á increase of productivity from process intensification á increase of selectivity of reactions and/or separations á reduction of by-products and waste materials á more efficient (in situ) use of energy á inherent safety á improved environmental compatibility (e.g. by avoidance of hazardous solvents etc.). Reactor-Separator System for Isomerization A1 Û A2 Reaction Kinetics: Vapour-Liquid-Equil.: Design Variables: V k æ 1 x ö a x - Damköhler Number Da º R n 2 y = 2 F r = k x1 ç1- ÷ 2 - Number of Stages N K x 1+ (a -1)x2 here è 1 ø D - Product Quality x2 = X Operational Variables: L D, x D 2 - Reflux Ratio R º L / D CSTR A2 - Recycle Ratio j º B / F Distillation F, x F = 1 1 Column Thermodynamic Parameters: VR - equilibrium constant K A 1 VR N - relative volatility a º K2 / K1 A A 1 2 Kinetic Parameters: - reaction order n B - rate constant k Qi, Z., Sundmacher, K. (2000) Chem. Eng. Process, in preparation. Reactor-Separator System for Isomerization A1 Û A2 Design for Reaction Order n = 1 CSTR + Column on Top 25 X = 0.99 min j = 2 R ® ¥ D N L D, x2 K = 2, a = 1.5 = N A j = 5 n = 1 2 20 N Distillation j = 10 j = ¥ Column 15 F CSTR A j = ¥ 1 V Minimum Number of Stages, R 10 0 2 4 6 8 10 Damköhler Number, Da Qi, Z., Sundmacher, K. (2000) Chem. Eng. Process, in preparation Damköhler Number in CD Processes k ×V Da º R Damköhler number F for first order reactions Boiling temperature k = e catcSiteskapp (Tb ) Tb = Tb ( p, x) apparent + rate control catalyst concentration rate via pressure ! holdup of active sites constant temperature on catalyst + T is not a dynamic variable ! Reactive Distillation Column for Isomerization A1 Û A2 Reactive Distillation Column Influence of Reaction / Separation Daopt (N = 20) = 0.2 x 20 = 4 1,0 N = X = 92.5 % 100 50 20 Reactive L D 0,8 10 5 Azeotrope 2 R = L / D 1 X 0,6 Xeq = 66.6 % N Reaction / Separation: (CSTR) Da V k A e c = R µ c cat sites N F N NTSM 0,4 F Conversion, Total 0,2 a = 1.5 K = 2, n = 1 Reboiler R = 10 0,0 0,001 0,01 0,1 1 10 100 Da / N Qi, Z., Sundmacher, K. (2000) Chem. Eng. Process, in preparation. Design of Hybrid CD Column for Isomerization A1 Û A2 Hybrid Column with Influence of Catalyst Distribution Catalytic Stages 1,00 100 20 10 0,95 R = L / D 5 Base L D Case 20 0,90 19 X 2 18 . 0,85 . R = 1 . N = 20 . Ncat . Conversion, 0,80 3 2 a = 1.5 F 1 K = 2, n = 1 0,75 N = 20 Total Da = 4 Reboiler 0,70 2 4 6 8 10 12 14 16 18 20 Number of Catalytic Stages, Ncat Qi, Z., Sundmacher, K. (2000) Chem. Eng. Process, in preparation. Reactive Batch Distillation: MeOH + IA Û TAME Vapour phase: Vapour Flow V Composition yi Heating policy: V / V0 = H / H0 FCR MeOHV IAV TAMEV H+ Liquid phase: MeOHL + IAL TAMEL LCR Holdup H Composition xi Qreb Catalyst: Acidic Ion Exchange Resin (Vcat, cH+) Thiel, C.; Sundmacher, K.; Hoffmann, U. (1997) Chem. Eng. Sci. 52, 993-1005. Reactive Batch Distillation: Model Equations Mass Balances d xi * = ( xi - yi (x,T)) + Da ×(n i - xi n) × r (x,T) dt 1442443 14243 123 Separation by Influence of Reaction Distillation Stoichiometry Kinetics Damköhler Number Boiling Temperature k (T )×c ×V Da º + ref sites cat T = T(x, p) V& o Thiel, C.; Sundmacher, K.; Hoffmann, U. (1997) Chem. Eng. Sci. 52, 993-1005. Catalytic Batch Distillation for TAME-Synthesis: No Reaction (Da = 0) MeOH 2 stable nodes 1 unstable node (azeotrope) 1 saddle point (azeotrope) 1 separatrix MeOH of p = 10 bar Fraction Mole TAME IA Mole Fraction IA Thiel, C.; Sundmacher, K.; Hoffmann, U. (1997) Chem. Eng. Sci. 52, 993-1005. Catalytic Batch Distillation for TAME-Synthesis: Slow Reaction (Da = 10-4) MeOH 3 stable nodes 0 unstable nodes 2 saddle points 2 separaticds chemical equilibrium line MeOH of p = 10 bar Fraction Molenbruch Methanol Mole IA TAME MolenbruchMole Fraction Isoamylenof IA Thiel, C.; Sundmacher, K.; Hoffmann, U. (1997) Chem. Eng. Sci. 52, 993-1005. Catalytic Batch Distillation for TAME-Synthesis: Fast Reaction (Da = 10-3) MeOH 2 stable nodes 0 unstable nodes 1 saddle point 1 separatrix MeOH chemical equilibrium line of p = 10 bar Fraction Mole TAME IA Mole Fraction of IA Thiel, C.; Sundmacher, K.; Hoffmann, U. (1997) Chem. Eng. Sci. 52, 993-1005. Catalytic Batch Distillation for TAME-Synthesis: Reaction in Equilibrium (Da > 1) MeOH 2 stabile nodes 0 unstable nodes 1 saddle point 1 separatix MeOH of chemical equilibrium line p = 10 bar Fraction Molenbruch Methanol Mole TAME IA MoleMolenbruch Fraction Isoamylenof IA Thiel, C.; Sundmacher, K.; Hoffmann, U. (1997) Chem. Eng. Sci. 52, 993-1005. Studies of Side Reactions: Influence of Stage Damköhler Number 2 2 Main Rxn 2 B Û A + C xB - xA xC / Keq 0.1 x r* = r* = C Side Rxn 2 C ® 2 D main 2 side 2 (1 + 5 xC ) (1 + 5 xC ) aAC = 10 Keq = 0.25 1,0 aBC = 3 R = 3.8 Selectivity, S aDC = 13 S = 5.3 0,8 Variation A + D 0,6 of Da on stage 9 stages 0,4 B 20 stages Conversion, X Feed at 0,2 stage 20 9 stages 0,0 0,01 0,1 1 N = 38 C Stage Damköhler Number, Da Studies of Side Reactions: Influence of Catalyst Position Main Rxn 2 B Û A + C 2 2 * xB - xA xC / Keq * 0.1 xC Side Rxn 2 C ® 2 D rmain = 2 rside = 2 (1 + 5 xC ) (1 + 5 xC ) aAC = 10 Keq = 0.25 Selectivity, S 1,0 aBC = 3 R = 3.8 aDC = 13 S = 5.3 0,8 Da = 0.8 A + D 0,6 Conversion, X on stage Changing Position of Catalyst 0,4 B 5 stages Feed at 0,2 stage 20 0,0 5 10 15 20 25 30 N = 38 C Position of Catalyst Section Studies of Side Reactions: Influence of Catalyst Position (Da = 0.2, Reactive Stages = 5) A + D A + D * 2 B rmain xB - xA xC / Keq B * ~ 2 rside xC C C D D 0 0 A A 5 5 10 B 10 B 15 15 20 20 Stage Stage 25 25 30 30 C C 35 35 40 40 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,2 0,4 0,6 0,8 1,0 x x i i Mapping of Reactor-Separator Systems for Esterification: Alcohol + Acid Û Ester + H2O Fast r Rate, Reaction Slow Low Medium High see e.g.: Schoenmakers (1997) Relative Volatility, aH2O/Ester RD System based on Pre- and Side Reactors Ether Production Flow Scheme (Neste Oy) Advantages Pre-Reactors Side-Reactors l easy catalyst replacement l easy control of reactant-ratio l independent of specific catalyst packing l distillation column hydraulics and mass transfer not affected by catalyst structure CxHy l high Da/N-ratio achievable MeOH MeOH see e.g.: Aittamaa, J., Eilos, I., Jakkula, J., Lindqvist, P., US 5 637 777 (1997) Simple Guideline for CD Reactor Selection p Slow reactions: Da << 1 p Fast reactions: Da ³ 1 + reaction kinetics is limiting + mass transfer is limiting + high residence time + low residence time sufficient + hom. catalysis: high liquid holdup + hom. catalysis: low liquid holdup + het. catalysis: high catalyst holdup + het. catalysis: low catalyst holdup p Solution p Solution + tray column (bubble caps) + packed column + packed column with random packing + tray column with low holdup + column with external side reactors increase p Catalytic Distillation (CD) - Outline 3 Catalysts for Use in CD Processes 4 Modelling, Simulation, Experimental Validation 2 Fields of Application, CD Lecture Process Examples 5 Operational Process Behaviour 1 Basic Principles of CD CD Expert ! Modern Methods in Heterogeneous Catalysis Research Fritz Haber Institute, Berlin, 14 November 2003 Motives for Application of Reactive Distillation Motives Examples Overcoming Limitations Methanol + Acetic Acid Û Methyl Acetate + H2O of Chemical Equilibrium Methanol + Isobutene Û Methyl-tert.-butylether (MTBE) Formaldehyde + 2 Methanol Û Methylal + H2O Increase of Chlorohydrins ® Propylene Oxide + H2O ® Proplene Glycol Selectivity 2 Acetone ® Diacetone Alcohol ® Mesityl Oxide + H2O Reaction Problems Isobutane + 1-Butene ® Isooctane + 1-Butene ® C12H24 Use of Heat Propene + Benzene ® Cumene of Reaction Ethylene Oxide + H2O ® Ethylene Glycol Separation of m-Xylene / p-Xylene (Reactive Entrainer: Na-p-Xylene) Closely Boiling Mixtures Cyclohexene / Cyclohexane (Reactive Entrainer: Formic Acid) 1-Butene / Isobutene (Reactive Entrainer: Methanol / Water) Breaking of Methyl Acetate / Water ; Methyl Acetate / Methanol Problems Azeotropes (Entrainer: Acetic Acid) Separation High Purity Hexamethylene Diamine / Water (in Nylon 6,6 process) Separation (Reactive Entrainer: Adipic Acid) See e.g.: Sundmacher, K., Rihko, L., Hoffmann, U., Chem.