A microstructured membrane reactor system for dehydrogenation of - PowerPoint PPT Presentation

A microstructured membrane reactor system for dehydrogenation of liquid organic hydrogen carriers Energie Lab 2.0 meets Neo Carbon Energy Workshop Helsinki 15.02.17 – Martin Cholewa Institute for Micro Process Engineering H 2 H 2 www.kit.edu KIT – The Research University in the Helmholtz Association

Outline Introduction of LOHC Background Reactor concept Results Experiments with the membrane modules Simulation High pressure experiments Summary and Outlook Martin Cholewa – Workshop Helsinki 2 28.02.2017 Institute for Micro Process Engineering, KIT

Introduction H 2  Storage and transport of hydrogen Hydrogenation  Hydrogen used in a fuel cell or ic- H 2 lean H 2 rich engine Dehydrogenation H 2 Charge: Hydrogenation of unloaded carrier Storing: Organic kept at room temperature Discharge: Dehydrogenation at ~ 200-400 °C Energy density of various hydrogen storage systems for mobility. 1 1 J. von Wild, R. Freymann and M. Zenner, Potentiale von alternativen Wasserstoffspeicherungstechnologien, VDI-Berichte: Innovative Fahrzeugantriebe, 2008, vol. 2030, pp. 273 – 298 Martin Cholewa – Workshop Helsinki 3 28.02.2017 Institute for Micro Process Engineering, KIT

Introduction Liquid Organic Hydrogen Carrier Methylcyclohexane Hydrogen mass capacity: ~ 6.2 wt.% ~ 600 Nm 3 H 2 / m 3 LOHC Δ H R (298 K)= + 204.8 kJ/mol + 68.3 kJ mol -1 H 2 Perhydro-dibenzyl-toluene 1 + Can use the existing distribution ways + No high pressure or low temperature is needed + High energy density Δ H R (298 K)= + 639 kJ/mol + 71 kJ mol -1 H 2 1: Brückner, N., Obesser, K., Bösmann, A., Teichmann, D., Arlt, W., Dungs, J. and Wasserscheid, P. (2014), Evaluation of Industrially Applied Heat-Transfer Fluids as Liquid Organic Hydrogen Carrier Systems. ChemSusChem, 7: 229 – 235. Martin Cholewa – Workshop Helsinki 4 Institute for Micro Process Engineering, KIT

Membrane reactor In-situ hydrogen removal H 2 Separation Pd-Membrane MCH TLU + 3 H 2 Reaction membrane Catalyst Pd-based Heating   Microchannels: Highly efficient Integration of membranes: Beneficial for heat and mass transfer reaction and separation  High surface to volume ratio  In-situ selective H 2 removal shifts reaction equilibrium to product side  Good thermal coupling of endothermic reaction and heating  H 2 purification directly from reaction zone zone  High system compactness Martin Cholewa – Workshop Helsinki 5 28.02.2017 Institute for Micro Process Engineering, KIT

Membrane reactor In-situ hydrogen removal  Reactor plate for catalyst bed with pillars  Microchannels for transport of the permeated hydrogen Holder  Swagelock fitting for connection to the experimental setup  electrically heated Martin Cholewa – Workshop Helsinki 6 28.02.2017 Institute for Micro Process Engineering, KIT

Membrane reactor In-situ hydrogen removal Permeate: 17 microchannels, length: 20 mm, width: 0.2 mm Pd membrane: 12.5 μ m thick H 2 H 2 catalyst catalyst Metal sheet powder powder with 70 µm pillar holes pillar pillar pillar 1 mm Feed/Retentate: catalytic fixed-bed, 4 pillars in width zone length: 20 mm, distance pillars: 1 mm Martin Cholewa – Workshop Helsinki 7 28.02.2017 Institute for Micro Process Engineering, KIT

Membrane Reactor Thermodynamics High Temperature and low pressure preferred – endothermic reaction p = 1 bar p = 1 bar T = 623 K p = 30 bar p = 30 bar T = 673 K p= 30 bar, pm = 3 bar T = 573 K 1.0 1.0 1.0 conversion [-] conversion / - conversion / - 0.5 0.5 0.5 0.0 0.0 0.0 500 500 600 600 700 700 0 20 40 60 Temperature / K Temperature / K pressure [bar]  Membrane could avoid limitation  Steep decrease of conversion with higher pressure  with 3 bar permeate pressure still  Temperature as driving force high separation and conversion Martin Cholewa – Workshop Helsinki 8 28.02.2017 Institute for Micro Process Engineering, KIT

Experimental 1 wt.% Pt - Catalyst Reaction/ Reactor conditions varied: Al 2 O 3 BET-surface in 28.9  Pressure 9 - 30 bar m²/g cat Dispersion in 47.4  Bed height 500 - 2000 µm % 200 – 300 Size in µm  Membrane thickness 4 - 16 µm (particle) Is the hydrogen separation efficient ? 50 µm Pt distribution (EPMA How stable are the membrane and the catalyst ? recording) H. Kreuder, Catalyst development for the dehydrogenation of MCH in a microstructured membrane reactor - for heat storage by a Liquid Organic Reaction Cycle. Cat. Today 242, 2015. Martin Cholewa – Workshop Helsinki 9 28.02.2017 Institute for Micro Process Engineering, KIT

Results Membrane reactor Catalyst performance ? Influence of mass transfer ?  High Conversion  Good separation efficiency through  Good catalyst stability microchannels p H2 1.0 100 90 p* H2 0.9 p H2,perm 80 conversion / % efficiency / -- 0.8 70 60 Membrane 0.7 50 Catalyst bed 40 2000 µm Microreactor, 9 bar, 400 °C catalyst bed height: 0.6 30 1000 µm Berty, 1 bar, 365 °C 500 µm Membrane, 9 bar, 350 °C 20 0.5 0 200 400 600 800 1000 0 1000 2000 3000 200µm 2000µm -1 flow rate / ml min tos / min Separation experiments with H 2 :N 2 75:25 mixtures Martin Cholewa – Workshop Helsinki 10 28.02.2017 Institute for Micro Process Engineering, KIT

Results Membrane reactor Catalyst performance ? Influence of mass transfer ?  High Conversion  Good separation efficiency through  Good catalyst stability microchannels 1.0 100 90 0.9 80 conversion / % efficiency / -- 0.8 70 60 0.7 50 40 2000 µm Microreactor, 9 bar, 400 °C catalyst bed height: 0.6 30 1000 µm Berty, 1 bar, 365 °C 500 µm Membrane, 9 bar, 350 °C 20 0.5 0 200 400 600 800 1000 0 1000 2000 3000 -1 flow rate / ml min tos / min Separation experiments with H 2 :N 2 75:25 mixtures Martin Cholewa – Workshop Helsinki 11 28.02.2017 Institute for Micro Process Engineering, KIT

ሶ ሶ Results membrane modules Comparison hydrogen recovery factor / - 1.00 1.00 Hydrogen recovery factor: Conversion MCH / - n H2,perm 0.75 0.75 n H2,total 0.50 0.50  Thinner membrane shows despite of lower conversion 0.25 0.25 same level of hydrogen 12 µm Pd - Membrane separation 4 µm Pd - Membrane 0.00 0.00 0 500 1000 1500  Still total separation is low tos / min MCH conversion with 1wt.% Pt/Al 2 O 3 catalyst in membrane module, tmod = 250 kg s m -3 , p = 9 bar, T=350° C Redesign of the module for the existing test rig Martin Cholewa – Workshop Helsinki 12 28.02.2017 Institute for Micro Process Engineering, KIT

Simulation Optimization with 1-D model / Simulation original module 1.0 / Exp. Conversion, hydrogen recovery / - 0.9 0.8 Conclusion from Experiments and Simulation: 0.7 0.6  lower bed depth 0.5 0.4  Higher membrane area to 0.3 catalyst ratio 0.2 0.1 0.0 8.0E+05 1.0E+06 1.2E+06 1.4E+06 pressure / Pa Comparison with simulation at T=350 °C, tmod = 125 kg s m -3 Constant reactor volume but 4 times higher membrane surface area Martin Cholewa – Workshop Helsinki 13 28.02.2017 Institute for Micro Process Engineering, KIT

Simulation Optimization with 1-D model / Simulation original module 1.0 / Simulation rescaled module Conversion, hydrogen recovery / - / Exp. Reactor is wider and longer 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 8.0E+05 1.0E+06 1.2E+06 1.4E+06 pressure / Pa Extrapolation with simulation for new geometry at T=350 °C, tmod = 125 kg s m -3 Martin Cholewa – Workshop Helsinki 14 28.02.2017 Institute for Micro Process Engineering, KIT

Results Comparison between large and small module small module (12 µm membrane) large module (16 µm membrane) 1.0 1.0 0.9 0.9 Conversion Methylcyclohexane / - 0.8 0.8 hydrogen recovery factor / - 0.7 0.7  Higher hydrogen 0.6 0.6 recovery and conversion of MCH 0.5 0.5 at same pressure 0.4 0.4 level 0.3 0.3 0.2 0.2 0.1 0.1 0.0 0.0 0 500 1000 1500 2000 2500 3000 tos / min at 9 bar to 13 bar, 350 °C and τ mod = 125 (kg s)/m³ Martin Cholewa – Workshop Helsinki 15 28.02.2017 Institute for Micro Process Engineering, KIT

Results High pressure experiment with large module 1.0 1.0 25 bar 28 bar 31 bar Hydrogen recovery factor / -  Almost total amount of 0.8 0.8 hydrogen separated Conversion / - 0.6 0.6  But conversion 0.4 0.4 significantly lower 0.2 0.2 Conversion H 2 recovery factor 0.0 0.0 0 500 1000 1500 2000 2500 tos / min Conversion and hydrogen recovery at high pressures with module B at 350°C, tmod = 125 kg s m -3 , Separation efficiency was determined with measured permeate flow and calculated amount of produced hydrogen Martin Cholewa – Workshop Helsinki 16 28.02.2017 Institute for Micro Process Engineering, KIT

Membrane Stability Influence of Regeneration Regeneration of catalyst by oxidation at 400°C and following reduction T = 350°C, p = 8 bar, τ mod = 250 kg*s/m 3 , X Eq = 99.5%  Coke can be removed by oxidation regeneration step and activity is restored H. Kreuder et al., Heat storage by the dehydrogenation of methylcyclohexane - Experimental studies for the design of a microstructured membrane reactor. International Journal of Hydrogen Energy , 2016 Martin Cholewa – Workshop Helsinki 17 28.02.2017 Institute for Micro Process Engineering, KIT