catalytic processes for the conversion of natural …...gtl_march2016 catalytic processes for the...
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Catalytic processes for the conversion of natural gas to logistics fuels and chemicals
Robert J. Kee, Canan Karakaya, and Huayang Zhu Mechanical Engineering
Colorado School of MinesGolden, CO 80401
[email protected](303) 273-3379
Presented:KAUST Future Fuels Workshop
March 8, 2016
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
The recent abundance of inexpensive natural gas presents new opportunities
Gas is often “stranded” • Transportation is impractical • Convert to liquids
Opportunities for products • Logistics fuels • Commodity chemicals
Gas-to-liquids technology • Via syngas • Oxidative coupling • Direct dehydrogenation
Process intensification • Micro-channel reactors • Membrane reactors
Fracking technology has fundamentally changed the energy landscape
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Process intensification is defined broadly in terms of greatly increasing efficiency and reducing plant size
Fundamentals • Heterogeneous catalysis • Gas-phase kinetics • Chemically reacting flow • Membrane electrochemistry • Reforming, gas-to-liquids,…
Reactor engineering • Process intensification • Thermal management • Process up-scaling • Model-predictive control
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
In addition to combustion, there are numerous choices and processing pathways for natural gas
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Colorado School of Mines Earth • Energy • Environment
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The feed stoichiometry and the catalyst affect the reforming process and end-use of the syngas
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Natural-gas reforming is practiced on a very large industrial scale (over 50 million tonnes annually)
Significant opportunities for process intensification and efficiency improvement
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Rostrup-Nielsen & Sehested, Stud. Surf. Sci. Catal., 139:1, 2001
Equilibrium provides reasonable guidance
Avoiding coke and controlling H2/CO ratios are important process considerations
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
There are numerous challenges in developing reaction mechanisms for heterogeneous catalysis
Typical “Deutschmann” reaction mechanism
Establish the reaction pathways • Conceptual
Develop rate expressions • Modified Arrhenius form • Mean field approximation
Consistent with experimental measurements • Packed beds • Washcoated monoliths • Stagnation flows • Surface science
Microscopic reversibility • Need surface thermodynamics
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Microchannel reactors and integrated heat exchangers offer opportunities for major process intensification
Closely couple endothermic and exothermic processes
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Microchannel heat-exchangers and reactors have some inherent benefits
High performance and Compact
Low-Reynolds number flow • Constant Nusselt numbers • Constant Sherwood numbers
Small channel dimensions (< 1 mm) • High heat and mass transfer
Manifold design can be complex • Especially for counter flow • Cross flow is easier
Catalyst integration • Washcoat can be difficult • Replacement can be difficult
Kee, et al., Appl. Thermal Eng., 31:2004-2012, 2010
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Internal manifolds can be difficult to fabricate, especially for counter-flow designs
Kee, et al., Appl. Thermal Eng., 31:2004-2012, 2010
Fabrication processes affect manifold design
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
There are numerous challenges and opportunities in designing and developing micro-reactor technology
Thermal balance and alignment • Exotherms • Endotherms
Materials • Metals (more mature) • Ceramics (in development)
Manifold design • Counter-flow more difficult • Cross-flow easier
Catalyst maintenance • Regeneration • Replacement • Removable plates
Thybaut, et al., Chem. Ing. Tech., 86:1588–1870, 2014
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Colorado School of Mines Earth • Energy • Environment
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Three-dimensional modeling of the reactive flow and conjugate heat transfer assist design
Very large three-dimensional problem • Opportunities to accelerate chemistry via ISAT • Approximate small-channel flow as plug flow
Blasi and Kee, Comp. Chem. Eng., 84:36-42, 2016
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Our ceramic microchannel reactors show good performance for steam reforming and partial oxidation
Blakeley and Sullivan, Int. J. Hydrogen Energy, 41:3794-3802, 2016
S/C = 2.5GHSV=50000 h-1
Inert = 750 C
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Hydrogen and oxygen permselective membranes can improve reforming processes
H2: Palladium alloy Ceramic ion-transport
O2: Ceramic ion-transport Nano-porous ceramic
Membranes • Assist chemistry • Assist thermal control
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Air separation provides many opportunities for process intensification
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Ion-transport membranes represent a new and maturing technology for air separation
Opportunities for membrane-based in-situ air separation
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Miller, Chen, Carolan, Foster, Catal. Today, 228:152, 2014
An oxygen-transport membrane reactor integrates air separation and catalytic partial oxidation
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Colorado School of Mines Earth • Energy • Environment
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A composite tubular reformer integrates air separation, steam reforming, and partial oxidation
Integrated design achieves thermal integration
US Patents: 7686856 B2 (2010); 9115045 B2 (2015)
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Colorado School of Mines Earth • Energy • Environment
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Large-scale Fischer-Tropsch technology is mature, but process intensification is increasingly important
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Colorado School of Mines Earth • Energy • Environment
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Fischer-Tropsch synthesis can be controlled to achieve desired syncrude compositions
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Colorado School of Mines Earth • Energy • Environment
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Refinery-scale Fischer-Tropsch synthesis is being practiced commercially
Fixed-bed reactor Slurry-bubble reactor
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Velocys has developed and scaled microchannel reactor technology to commercial viability
Component scale • Millimeter-scale channels • Pressurized water coolant • Fe- or Co-based catalysts
Meter-scale reactorwww.velocys.com
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Oxidative coupling of methane (OCM) provides a “direct” route for converting methane to ethylene
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Oxidative coupling of methane provides a “direct” route to ethylene synthesis
• First reported by Keller and Bhasin, 1982• Process is controlled by methyl-radical formation• Catalyst is required, but gas-phase contributes significantly• H2O, CO2, and CO are unavoidable side products• Typical conditions 5 < CH4/O2 < 10 (inhibit full oxidation)
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Oxidative coupling of methane can be accomplished with two types of catalysts
• These catalysts are more complex than single metals• Much current modeling uses the Staunch mechanism
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Species and temperature profiles contribute great insight about the OCM process
Zohour, Noon, Senkan, ChemCatChem, 6:2815-2820, 2014
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016Zohour, Noon, Senkan, ChemCatChem, 6:2815-2820, 2014
Staging the catalyst bed and oxygen addition improves OCM performance
Limit local temperature excursions • Decrease full oxidation • Decrease catalyst degradation • Suggests oxygen membrane
Single-bed yield: 16% C2H4Double-bed yield: 21% C2H4
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Colorado School of Mines Earth • Energy • Environment
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Thybaut, et al., Chem. Eng. Tech., 86:1588-1870, 2014
Segmented unit processes can potentially deliver process intensification
• Two complementary product streams• Approach isothermal conditions• Segmentation improves both processes
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Colorado School of Mines Earth • Energy • Environment
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Segmented compression and expansion with intercooling and reheating improves gas turbines
Multistaging gas turbines improves efficiency • The Brayton cycle approaches the higher efficiency Ericsson cycle • Isothermal compression and expansion provides benefits
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Segmented designs can assist process efficiency, control, and maintenance
• Large number of segments approaches membrane behavior• Reactors can be easily removed and replaced• Spatially segmented oxygen/steam addition can be beneficial • Membranes do not easily accommodate local oxygen/steam control
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
There are likely ways to to exploit similarity principles in chemical processing
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Colorado School of Mines Earth • Energy • Environment
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Swirling tubular reactors may provide a route to achieve process uniformity in a OCM process
Achieve axial independence in long membrane tubes
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Colorado School of Mines Earth • Energy • Environment
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Methane dehydroaromatization (MDA) promises a ‘’direct” route from methane to benzene
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Methane dehydroaromatization (MDA) is a potential route to produce benzene from methane
Ideal global reaction • 6 CH4 = C6H6 + 9 H2
Process limitations • Equilibrium limit (~12% conversion) • Carbon deposits • Catalyst deactivation (few hours)
Hydrogen membranes • Remove H2, increase conversion • Competition with naphthalene
Steam addition • Attack naphthalene (C10H8) • Extend catalyst lifetime
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Colorado School of Mines Earth • Energy • Environment
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Bi-functional Mo/Zeolite catalysts are known to deliver MDA functionality
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
The active Mo structure is Mo2C incorporated into the zeolite structure
• Incorporate MoOx into the zeolite • Carburize MoOx to Mo2C during • Mo2C is active for CH4 activation • Mo deactivates zeolite acid sites • Typical Mo loading is 1-10 wt. %
Zhou, Zuo, Xing, J. Phys. Chem. C, 116:4060-4070, 2012
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
TEM and XRD confirm that crystal structure is preserved through processing
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
MDA chemistry on Mo/ZSM5 can be described by 54 elementary reaction steps
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Colorado School of Mines Earth • Energy • Environment
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Catalytic packed-bed models are developed to incorporate membrane transport
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Colorado School of Mines Earth • Energy • Environment
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Removing only H2 increases conversion, but competition with naphthalene is problematic
T = 700 ˚CGHSV = 1500 ml/g/h
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Steam can play a beneficial role in preventing (or delaying) catalyst fouling coke or PAH deposits
Low-concentration (~2%) steam is beneficial • Crack coke deposits on surfaces1
• Crack naphthalene, interrupt PAH growth2
Too much H2O is detrimental • Promote reforming chemistry • De-aluminate zeolite catalysts
Detailed kinetics remain to be developed • Reported experiments use excess H2O • Need low-level steam-naphthalene expts.
Models can use detailed reaction mechanisms • Assist design and operation
1. Ma, et al., Appl. Catal. A., 275:183-187, 20042. Buchireddy, et al., Energy Fuels, 24:2707-2715, 2010
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Colorado School of Mines Earth • Energy • Environment
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Our ongoing experiments are designed to elucidate the naphthalene-steam chemistry
Data needed for mechanism development
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Colorado School of Mines Earth • Energy • Environment
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A diverse set of membrane materials can be applied in gas-to-liquids technology
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Ion transport within ceramic mixed conductors can be represented with Nernst-Planck-Poisson models
Zhu, Ricote, Coors, Kee, Faraday Discussions, 182:49-74, 2015
Zhu and Kee, Intl. J. Hydrogen Energy, 41:2931-2943, 2016
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
There are numerous opportunities for process and reactor development across greatly disparate scales
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Colorado School of Mines Earth • Energy • Environment
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Acknowledgements
Office of Naval Research • Dr. Michele Anderson
CoorsTek, Inc. • Dr. Grover Coors
Colorado School Mines • Prof. Greg Jackson • Prof. Rob Braun • Prof. Sandrine Ricote • Prof. Ryan O’Hayre • Prof. Neal Sullivan (CFCC)
Air Force Office of Scientific Research Drs. Chiping Li and Mike Berman
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Colorado School of Mines Earth • Energy • Environment
GTL_March2016
Market forces can significantly affect the course of research and development for new technologies
Markets are volatile • Price cycles can be short
Sustained investments needed • 10-20 year development cycle