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

rjkee@mines.edu(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

GTL_March2016

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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Colorado School of Mines Earth • Energy • Environment

GTL_March2016

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

GTL_March2016

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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Colorado School of Mines Earth • Energy • Environment

GTL_March2016

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

GTL_March2016

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

GTL_March2016

Large-scale Fischer-Tropsch technology is mature, but process intensification is increasingly important

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Colorado School of Mines Earth • Energy • Environment

GTL_March2016

Fischer-Tropsch synthesis can be controlled to achieve desired syncrude compositions

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Colorado School of Mines Earth • Energy • Environment

GTL_March2016

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

GTL_March2016

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

GTL_March2016

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

GTL_March2016

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

GTL_March2016

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

GTL_March2016

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

GTL_March2016

Catalytic packed-bed models are developed to incorporate membrane transport

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Colorado School of Mines Earth • Energy • Environment

GTL_March2016

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

GTL_March2016

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

GTL_March2016

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

GTL_March2016

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