Membrane reactors for improved processes: How to integrate reaction and separation in one apparatus

Transcription

1 Membrane reactors for improved processes: How to integrate reaction and separation in one apparatus Reinhard Schomäcker Fachgruppe Technische Chemie Institut für Chemie der TU Berlin 1. Classical concepts 2. Concepts for membrane reactors 3. Examples for reactions in membrane reactors 4. Problems to be solved before industrial scale application Vorlesung Membranreaktoren, , RS 1

2 Routes for Phenole Production H 2 SO 4 / NaOH SO 3 Na + NaOH Benzene sulfonate-route + HCl + 1/2 O 2 Cl + H 2 O Chlorobenzene-Route + Cl 2 OOH OH + C 3 H 6 + O 2 (H + ) Cumene-Process + H 2 OH O Phenole + O 2 - H 2 Anol/Anon-Dehydrogenation CH 3 COOH + O 2 + O 2 - CO 2 Toluene-Oxidation Vorlesung Membranreaktoren, , RS 2

3 Gas-Liquid-Reactors Fixed Bed Reactors Three Phase Reactors L G L G Katalysator G L G G L K+L K+L G G Vorlesung Membranreaktoren, , RS 3

4 A) Equilibrium problems Typical Problems A + B C + D Complete conversion of A requied Removal of C or D favourale B) Selectivity problems A + B C Main product C, By product D A + C D Solutions - Search for another chemistry (other reactants or reaction conditions) - Optimimized process - Improved process parameter (Temperature control) - Combination of reaction and separation Vorlesung Membranreaktoren, , RS 4

5 Thermodynamically controlled reactions A + B fi C + D Conventional Process A, B A, B, C, D Reactor Separation C, D (A, B) A and/or B Integrated Process Reactor and Separation A, B C, D (A, B) Vorlesung Membranreaktoren, , RS 5

6 Posssible combinations of reaction and separation processes Distillation Membranes Literature Ä Krishna, Krishna, R. R. Reactive Reactive Separations: Separations: more more ways ways to to skin skin a a cat cat Chem. Chem. Engng. Engng. Sci. Sci. (2002) (2002) Condensation Absorption Stripping Extraction Supercritical extraction Chromatography R E A C T O R Ultrafiltration In-situ precipitation Crystallization Pervaporation Pertraction Electrodialysis Sorption Ä Agar, Agar, D. D. W., W., W. W. Ruppel Ruppel Multifunctionale Multifunctionale Reaktoren Reaktoren für für die die heterogene heterogene Katalyse Katalyse Chem.-Ing.-Tech. Chem.-Ing.-Tech. 60(10): 60(10): (1988) (1988) Ä Westerterp, Westerterp, K.R. K.R. Multifunctional Multifunctional reactors reactors Chem. Chem. Engng. Engng. Sci. Sci. 47(9-10): (9-10): (1992) (1992) Ä Krishna, Krishna, R. R. A A systems systems approach approach to to multiphase multiphase reactor reactor selection selection Adv. Adv. Chem. Chem. Engng Engng 19: : (1994) (1994) Ä Lerou, Lerou, J.J., J.J., K.M. K.M. Ng Ng Chemical Chemical Reaction Reaction Engineering: Engineering: A A multiscale multiscale approach approach to to a a multiobjective multiobjective task task Chem. Chem. Engng. Engng. Sci. Sci. 51(10): 51(10): (1996) (1996) Ä Hoffmann, Hoffmann, U., U., K. K. Sundmacher Sundmacher Multifunktional Multifunktional Reaktoren Reaktoren Chem.-Ing.-Tech. Chem.-Ing.-Tech. 69(5): (5): (1997) (1997) Ä Agar, Agar, D.W. D.W. Multifunctional Multifunctional Reactors Reactors - - old old preconceptions preconceptions and and new new dimensions dimensions Chem. Chem. Engng. Engng. Sci. Sci. 54(10): (10): (1999) (1999) Vorlesung Membranreaktoren, , RS 6

7 Conventional methyl acetate-prozess MeOAc MeOH HOAc HOAc MeOH Reactor Catalyst Separation H 2 O Vorlesung Membranreaktoren, , RS 7

8 Reactive destillation MeOAc 45 AcOH H 2 SO 4 Rectifying section MeOAc Reactive section Eastman Kodak Process (one Column!) Stage number AcOH 15 MeOH Stripping section MeOH Water Acetic Acid MeOH MeOAc Water H 2 O Liquid phase mole fraction / [-] Vorlesung Membranreaktoren, , RS 8

9 Concepts for membrane reactors IUPAC A membrane reactor is an apparatus that integrates chemical reaction (catalysis) And separation Vorlesung Membranreaktoren, , RS 9

10 Concepts for membrane reactors Advantages: - Reduced investment because of different unit operations in one apparatus - Increased conversion for equillibrium reactions - Improved selectivities for partial oxidations and hydrogenations - Avoid/Reduce high volume circuits of solvents and feeds Disadvantages: - Reactions and separations at the same conditions (p,t) - Availability of required materials for construction of membrane reactors - Extended process development for integrated chem. processes Vorlesung Membranreaktoren, , RS 10

11 Concepts for membrane reactors Membrane properties - Permselectivity for product D - Permeability für reactant A - Permeability for reactant und catalytic activity - chemical und thermal stability Vorlesung Membranreaktoren, , RS 11

12 Example 1: Controlled Feed ( V & total = const) AIR MR= 33 % 33 % 33 % MR> 5 % 25 % 70 % MR< 70 % 25 % 5 % 0 V & C2H6 V & AIR V & AIR V & AIR 0 V & N2 products Seidel-Morgenstern, MPI Magdeburg Vorlesung Membranreaktoren, , RS 12

13 Example 2: Selektive Product removal fi C 6 H 12 C 6 H H 2 H R = 205 kj/mol Catalyst: 1% Pt on γ Al 2 O 3 Membrane: Vycor-Glas (Na 2 O-B 2 O 3 -SiO 2 ) L = 25 cm, D = 0,46 cm Membrane Permeate Reactants Products Sweep gas Catalyst Seidel-Morgenstern, MPI Magdeburg Vorlesung Membranreaktoren, , RS 13

14 Assumptions - isothermal conditions - one dimensional model satisfactory Sweep Feed catalyst z membrane r i r a r Mass balance for Feed- side: p 1 ( ) f V& x i 0 = - + D RT q z f Mass balance for membrane: 1 0 = ( r J i ) r r 2 f f, f xf, i ax 2 p RT z 2π r i Ji r= r + i q f R i Mass balance für Sweep-side: 0 = ( V& x ) 2 p 1 s s s, i s s, ± + D p x i π ra ax Ji r= r RT qs z RT z q a s Vorlesung Membranreaktoren, , RS 14

15 pressure conditions p f = p s = 1 bar temperature T = 473 K mole fraction (feed side) x 0 f,cyc = Vol-% mole fraction (sweep side) x 0 s,cyc = 0.0 Vol-% flow rate (feed side) V o f = 25 ml/min sweep ratio γ = V o s / (x0 f,cyc Vo f ) conversion X, % X eq x o f, cyc = 5.85 Vol-% sweep ratio γ, X eq x o f, cyc = 4.95 Vol-% sweep ratio γ, Vorlesung Membranreaktoren, , RS X eq x o f, cyc = 3.73 Vol-% sweep ratio γ, -

16 Membrane reactor Example 3: Catalysis in porous membranes k 1 k 2 H 2 / Pd H 2 / Pd Fixed Bed Reactor Reactant Reactant Product Product Vorlesung Membranreaktoren, , RS 16

17 Example 3: Characterisation of membranes Φ = 2 wt.% Polymer Φ = 10 wt.% Polymer Φ = 20 wt.% Polymer 30 µm 30 µm 30 µm S = 52 m 2 /g r P = 1800 nm S = 17 m 2 /g r P = 380 nm S = 12 m 2 /g r P = 250 nm Charakterisation of structure by: BET-measurements, Hg-Porosimetry Gas permeation experiments Vorlesung Membranreaktoren, , RS 17

18 Example 3: Experimental Set-Up (gas phase) φ 10mm Back scattering mode 5 ml 10 % PAA.-Disp. (450 mg PAA) 20 mg Pd 100 mg SE3010 0,5 ml NaBH 4 φ 65mm Vorlesung Membranreaktoren, , RS 18

19 Example 3: Comparison of Catalysts k 1 k 2 Umsatz %, Selektivität % Membran H 2 / Pd Pd auf Al 2O 3 (Schalenkalys.) 85,1 88,1 85,2 85,3 Poröse Katalysatoren Pd auf SiO 2 6,0 75,8 3, Pd auf C 70,6 Umsatz Propin Selektivität Propen 5 mg Pd T = 295 K P ges = 1 bar λ = 1,0 H 2 / Pd By-products C Umsatz = 1 C Selektivität = C 1 Verweilzeit / s Vorlesung Membranreaktoren, , RS 19 1,0 1,0 C C

20 Example 3: Variation of membrane structure % 10% 20% 30% PAA in cross-linked dispersion ε /% r p /mm 1,5 0,4 0,25 0,18 Umsatz Selektivität T = 25 C H 2 /Propin = 1/1 40 ml/min 2 mg Pd NaBH 4 SE3010 Vorlesung Membranreaktoren, , RS 20

21 p-sensor 1 Membrane test cell (liquid phase) stirrer H 2 Reservoir COD p-sensor 2 IR- Spektr. pump Fixed bed Membrane cell samples Vorlesung Membranreaktoren, , RS 21

22 Selectivity of partial hydrogenation COD + H 2 Pd 50 C /40 bar COE COA PAA-Pd membrane, ε = 50%, r P = 250 nm T= 50 C, p = 40 bar Vorlesung Membranreaktoren, , RS 22

23 Conversion vs. time at different flow rates Membrane F =20% 100 conversion increased flow rate X-14ml/min X-18ml/min X-22ml/min X-26ml/min X-30ml/min X-34ml/min time /min Vorlesung Membranreaktoren, , RS 23

24 Selectivity vs. time at different flow rates Membrane F = 20% Selectivity Increased flow rate X-14ml/min X-18ml/min X-22ml/min X-26ml/min X-30ml/min X-34ml/min time /min Vorlesung Membranreaktoren, , RS 24

25 Selectivity vs. conversion at different flow rates Membrane F =20% 100 increase flow rate 95 Selectivity V-pt 14ml/min V-pt 18ml/min V-pt 22ml/min V-pt 26ml/min V-pt 30ml/min V-pt 34ml/min conversion Vorlesung Membranreaktoren, , RS 25

26 Selectivity vs. conversion for membranes at different pore size flow rate 18ml/min Selectivity Membrane φ =30% Membrane φ =20% Membrane φ =10% conversion Vorlesung Membranreaktoren, , RS 26

27 flow rate: 34ml/min Selectivity of different catalyts selectivity membrane Φ 10% membrane Φ 20% membrane Φ 30% Pd/Al2O3 Pd/C conversion PAA-Pd membrane, ε = var. r P = f(ε) T= 50 C, p = 40 bar Vorlesung Membranreaktoren, , RS 27

28 Ceramic membranes for membrane reactors Vorlesung Membranreaktoren, , RS 28

29 Construction of ceramic modules Full ceramics test module (HITK) Al 2 O 3 -hollow f bre 0,6 mm diam. (HITK) Vorlesung Membranreaktoren, , RS 29

30 Problems to be solved Materials - Membranes with adjustable properties - Inpregnation with different active componentes - Fitting of different materials - Production of composite membranes - Concept for a cooled membrane reactor Methods - Charakterisation of catalytically active membranes -Two and three dimensional models for mass and heat balance Vorlesung Membranreaktoren, , RS 30

31 Approaches to solve the problems Developement of materials and modules in interdisziplinary teams from chemistry, chemical engineering, process technology and material science. Developement of models for scale up and process control of membrane reactors. Vorlesung Membranreaktoren, , RS 31