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Design of Catalytic Membrane Reactor for Oxidative Coupling of Methane A. S. Chaudhari F. Gallucci M. van Sint Annaland Chemical Process Intensification.

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Presentation on theme: "Design of Catalytic Membrane Reactor for Oxidative Coupling of Methane A. S. Chaudhari F. Gallucci M. van Sint Annaland Chemical Process Intensification."— Presentation transcript:

1 Design of Catalytic Membrane Reactor for Oxidative Coupling of Methane A. S. Chaudhari F. Gallucci M. van Sint Annaland Chemical Process Intensification – Department of Chemical Engineering and Chemistry - TU/e – The Netherlands Technical session 3 Process Intensification, May 2, 2012

2 1/ 34 Outline Introduction Design of catalytic membrane reactor o Packed bed membrane reactor o Hollow fiber catalytic membrane reactor Results Conclusions

3 2/ 34 Introduction Ethylene production Production of ethylene from natural gas Indirect conversion route (GTL) Synthesis gas (CO, H 2 ) via steam reforming of methane (SRM) Fischer-Tropsch gives higher hydrocarbons Direct conversion route Oxidative coupling of methane (OCM) to ethylene 2 CH 4 + O 2 C 2 H 4 + 2H 2 O

4 3/ 34 Introduction contd… Production of ethylene via oxidative coupling of methane [OCM] 2 CH 4 + O 2 C 2 H 4 + 2H 2 O CH 4 + 2O 2 CO 2 + 2H 2 O C 2 H 4 + 3O 2 2CO 2 + 2H 2 O Typical conversion-selectivity problem Highly exothermic Large methane recycle Maximum C 2 yield < 30%

5 4/ 34 Kinetics of OCM Reaction scheme Formation rates of C 2 H 4, C 2 H 6 and CO 2 (primary reactions) 2 CH 4 + ½ O 2  C 2 H 6 + H 2 O n = 1.0 m = CH O 2  CO H 2 O n = m = 1 Distributive O 2 feeding = membrane reactor

6 5/ 34 5 Novel Process Design Design a possible autothermal process in single multifunctional reactor o Integration of exothermic OCM and endothermic steam reforming of methane (SRM)   Htot = 0 o Advantages: −Increase methane utilization/conversion −OCM/SRM  Ethylene/synthesis gas production −Optimal heat integration Present investigation

7 6/ 34 Integration of OCM and SRM CH 4 + ½ O 2 → ½ C 2 H 4 + H 2 OΔH r = -140 kJ/mol CH O 2 → CO H 2 O ΔH r = -801 kJ/mol Combustion of ethane/ethylene CH 4 + H 2 O  3 H 2 + CO ΔH r = 226 kJ/mol Reforming of ethane/ethylene

8 7/ 34 Outline Introduction Design of catalytic membrane reactor o Packed bed membrane reactor o Hollow fiber catalytic membrane reactor Results Conclusions

9 8/ 34 Possible packed bed membrane reactor configurations for only OCM CH 4 + O 2 cooling CH 4 + O 2 CH 4 O2O2 Pre mixed adiabatic: very low C 2 yield for the high temperature and O 2 concentration Pre mixed : low C 2 yield at high O 2 concentration Distributive feeding: low C 2 yield for high temperature CH 4 O2O2 cooling Distributive feeding with cooling (Virtually isothermal):Highest yield  Extremely complicated reactor design

10 9/ 34 Packed bed membrane reactor concept Packed Bed membrane Reactor o Two cylindrical compartments separated by Al 2 O 3 membrane for O 2 distribution Cooling on particle scale SRM OCM Dual function catalyst particle

11 10/ 34 Integration on particle scale Influencing CH 4 mole flux to the particle centre Preventing C 2 mole flux to the particle centre 0 R Complete conversion of O 2 at OCM layer

12 11/ 34 Numerical model: Particle scale Kinetics from: OCM: Stansch, Z., Mleczko, L., Baerns, M. (1997) I & ECR, 36(7), p SRM: Nimaguchi and Kikuchi(1988). CES, 43(8), p-2295 Intraparticle reaction model Optimize the catalyst particle o Thickness of OCM catalytic layer o Thickness of SRM catalytic layer o Thickness of inert porous layer o Diffusion properties viz. porosity and tortuosity Advantages: o Strong intraparticle concentration profiles o Beneficial for C 2 selectivity o Vary r SRM : autothermal operation

13 12/ 34 Outline Introduction Design of catalytic membrane reactor o Packed bed membrane reactor o Hollow fiber catalytic membrane reactor Results Conclusions

14 13/ 34 Integration on single catalyst particle Results – influence on performance Methane consumption by dual function catalyst particle Influence on CH 4 conversion ~50% increase (Vs. OCM) Reforming diffusion limited SRM flow = f(X CH4 ) Presence sufficient H 2 O Proportional to  or  SRM Input: X CH4 = 0.4; X O2 = 0.005; X H2O = 0.5, r SRM = 0.5mm, r OCM = 0.5mm, r p = 1.5mm

15 14/ 34 Integration on single catalyst particle contd… Results – CO x production CO x production Large contribution of SRM OCM contrib. low  low p O2 Reforming diffusion limited Mainly CO production WGS on OCM cat  CO 2 Strong decrease by  OCM Loss of C 2 products by reforming? Input: X CH4 = 0.4; X O2 = 0.005; X H2O = 0.5, r SRM = 0.5mm, r OCM = 0.5mm, r p = 1.5mm

16 15/ 34 Integration on single catalyst particle contd… Losses of C 2 to reforming core Negligible (Maximum 3% ) at reactor inlet conditions What about the energy balance? Input: X CH4 = 0.4; X O2 = 0.005; X H2O = 0.5, r SRM = 0.5mm, r p = 1.5mm

17 16/ 34 Integration on single catalyst particle contd… Results: Energy production  OCM/SRM particle Vs only OCM particle o Variation of  ratio at constant r SRM : Distributed feeding of O 2  Q tot < 0.3 W  makes dual function catalysis possible Autothermal operation is possible   = Other options: Variation of r SRM, steam concentration Input: X CH4 =0.4; X H2O =0.5 T = 800 C; P = 150kPa; r OCM =0.25mm; r SRM = 0.5mm r p =1.5 mm

18 17/ 34 Numerical model: Reactor scale Two cylindrical compartments separated by  -Al 2 O 3 membrane for O 2 distribution Unsteady state heterogeneous reactor model coupled with intraparticle reaction model

19 18/ 34 Results: Only OCM: Distributed feed of O 2 Distributed feed of O 2 (CH 4 /O 2 = 4; L r = 2m): Distributed oxygen feeding  desirable Premixed Vs distributed feeding  cooled mode  T = 1000 C Vs 800 C Premixed Vs distributed feeding  Improved C 2 yield  > 10% Vs 36% For OCM  cooled reactor preferred with high yield of C 2 (36%)

20 19/ Results: Reactor scale for OCM/SRM Results – comparison of dual function process with only OCM Non-isothermal conditions: X CH4 = 0.3; X H2O = 0.4, CH 4 /O 2 = 4, r p = 1.5mm; r OCM = 0.25mm OCM adiabatic Vs r SRM = 20  m CH 4 conversion: 55% Vs 62%

21 20/ Results: Reactor scale for OCM/SRM Results – comparison of dual function process with only OCM Non-isothermal conditions: X CH4 = 0.3; X H2O = 0.4, CH 4 /O 2 = 4, r p = 1.5mm; r OCM = 0.25mm OCM adiabatic Vs r SRM = 20  m CH 4 conversion at optimum C 2 Yield: CH 4 conversion: 34% Vs 48% Max. C 2 Yield: 18% Vs 17%

22 21/ 34 Results: Reactor scale for OCM/SRM Results: OCM/SRM particle Vs only OCM o Influence on heat production Non-isothermal conditions: X CH4 = 0.3; X H2O = 0.4, CH 4 /O 2 = 4, r p = 1.5mm; r OCM = 0.25mm OCM (adiabatic mode) Vs OCM/SRM o Temperature decrease of C r SRM = 20  m  autothermal operation possible at L r = 1.2 m Advantages: Increased CH 4 conversion Nearly equal C 2 production at autothermal conditions Disadvanges: Complicated and expensive manufacturing of catalyst

23 22/ 34 Outline Introduction Design of catalytic membrane reactor o Packed bed membrane reactor o Hollow fiber catalytic membrane reactor Results Conclusions

24 23/ 34 Hollow fiber catalytic membrane reactor Hollow fiber dual function catalytic membrane reactor o Core SRM o Outer shell OCM Easier and less complicated manufacturing SRM OCM

25 24/ 34 2-D reactor model Hollow fiber model  Radial profiles Reactor model  Hollow fiber model in series  Axial profiles

26 25/ 34 Assumptions Isobaric conditions No interphase mass and heat transfer limitations No radial concentration profiles in the OCM and SRM compartments Uniform oxygen distribution

27 26/ 34 Cases Only OCM Dual function

28 27/ 34 Outline Introduction Design of catalytic membrane reactor o Packed bed membrane reactor o Hollow fiber catalytic membrane reactor Results Conclusions

29 28/ 34 Only OCM: Packed bed vs. Hollow fiber C 2 Yield o Isothermal: Packed bed (41%) > Hollow fiber (39%) o Adiabatic: Packed bed (18%) < Hollow fiber (21%) Hollow fiber reactor  better heat transfer effects Hollow Fiber Reactor (Solid line) : Fixed bed reactor (dotted line)

30 29/ 34 Hollow fiber: Dual function vs. only OCM C 2 Yield: o Isothermal: Dual function (29%) < only OCM (39%) o Adiabatic: Dual function (29%) > only OCM (27%) Maximum yield: CH 4 conversion is 64% Vs 41% (Dual function Vs only OCM) Dual function (Solid line) : Only OCM (dotted line)

31 30/ 34 Conclusions OCM / SRM integration in single multifunctional reactor o Reactor performance: Hollow fiber catalytic membrane reactor > Packed bed membrane reactor o Increased CH 4 conversion compared to only OCM o Simultaneous production of C 2 and syngas without heat exchange equipment Autothermal operation possible in both reactors The models presented here could be useful to provide the guidelines for designing and improving the overall performance of the process Outlook Experimental demonstration

32 31/ 34 Acknowledgments Thijs Kemp (HF model) and Jeroen Ramakers (experiments) Collaborations Prof. dr. Ir. Leon Lefferts (University of Twente, Netherlands) Financial support from NWO/ASPECT is gratefully acknowledged

33 32/ 34 Thank you

34 33/ 34 Recommendation Dense Hollow fiber In theory, 100% CH 4 conversion Distribute the SRM catalyst locally Syngas and ethylene are separated


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