Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen

Upgrading Methane Sans Oxygen Direct routes to converting methane to higher hydrocarbons can allow natural gas to be used to provide chemical feedstocks. However, the reaction conditions needed to activate the strong C-H bond tend to overoxidize the products. Guo et al. (p. 616) report a high-temperature nonoxidative route that exposes methane to isolated iron sites on a silica catalyst. Methyl radicals were generated and coupled in the gas phase to form ethylene and aromatics along with hydrogen. The isolation of the active sites avoided surface reactions between the radicals that would deposit solid carbon. Methyl radicals that form at isolated iron sites in a silica matrix form gas-phase products and do not deposit solid carbon. The efficient use of natural gas will require catalysts that can activate the first C–H bond of methane while suppressing complete dehydrogenation and avoiding overoxidation. We report that single iron sites embedded in a silica matrix enable direct, nonoxidative conversion of methane, exclusively to ethylene and aromatics. The reaction is initiated by catalytic generation of methyl radicals, followed by a series of gas-phase reactions. The absence of adjacent iron sites prevents catalytic C-C coupling, further oligomerization, and hence, coke deposition. At 1363 kelvin, methane conversion reached a maximum at 48.1% and ethylene selectivity peaked at 48.4%, whereas the total hydrocarbon selectivity exceeded 99%, representing an atom-economical transformation process of methane. The lattice-confined single iron sites delivered stable performance, with no deactivation observed during a 60-hour test.

[1]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[2]  T. Marks,et al.  Sulfur as a selective 'soft' oxidant for catalytic methane conversion probed by experiment and theory. , 2013, Nature chemistry.

[3]  Hafner,et al.  Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium. , 1994, Physical review. B, Condensed matter.

[4]  Zhongmin Liu,et al.  Observation of heptamethylbenzenium cation over SAPO-type molecular sieve DNL-6 under real MTO conversion conditions. , 2012, Journal of the American Chemical Society.

[5]  A. Beale,et al.  Local and long range order in promoted iron-based Fischer–Tropsch catalysts: A combined in situ X-ray absorption spectroscopy/wide angle X-ray scattering study , 2009 .

[6]  Zhipan Liu,et al.  General rules for predicting where a catalytic reaction should occur on metal surfaces: a density functional theory study of C-H and C-O bond breaking/making on flat, stepped, and kinked metal surfaces. , 2003, Journal of the American Chemical Society.

[7]  X. Bao,et al.  Carbonaceous Deposition on Mo/HMCM-22 Catalysts for Methane Aromatization: A TP Technique Investigation , 2002 .

[8]  T. Barckholtz,et al.  C-H and N-H bond dissociation energies of small aromatic hydrocarbons , 1999 .

[9]  Qiang Fu,et al.  Interface-Confined Ferrous Centers for Catalytic Oxidation , 2010, Science.

[10]  G. Kresse,et al.  Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set , 1996 .

[11]  G. Kresse,et al.  Ab initio molecular dynamics for liquid metals. , 1993 .

[12]  Linsheng Wang,et al.  Bifunctional Catalysis of Mo/HZSM-5 in the Dehydroaromatization of Methane to Benzene and Naphthalene XAFS/TG/DTA/MASS/FTIR Characterization and Supporting Effects , 1999 .

[13]  K. D. de Jong,et al.  Iron particle size effects for direct production of lower olefins from synthesis gas. , 2012, Journal of the American Chemical Society.

[14]  Xiaofeng Yang,et al.  Single-atom catalysis of CO oxidation using Pt1/FeOx. , 2011, Nature chemistry.

[15]  D. Goodman,et al.  Hydrogen Production via Catalytic Decomposition of Methane , 2001 .

[16]  Qing Chen,et al.  Microwave Absorption Enhancement and Complex Permittivity and Permeability of Fe Encapsulated within Carbon Nanotubes , 2004 .

[17]  J. Lunsford,et al.  Characterization of a Mo/ZSM-5 catalyst for the conversion of methane to benzene , 1997 .

[18]  Ali Alavi,et al.  CO oxidation on Pt(111): An ab initio density functional theory study , 1998 .

[19]  Jack H. Lunsford The Catalytic Oxidative Coupling of Methane , 1995 .

[20]  Yuyang Li,et al.  Effect of the pressure on the catalytic oxidation of volatile organic compounds over Ag/Al2O3 catalyst , 2009 .

[21]  F. Qi,et al.  Electrospray/VUV single-photon ionization mass spectrometry for the analysis of organic compounds , 2009, Journal of the American Society for Mass Spectrometry.

[22]  Horia Metiu,et al.  Catalysis by doped oxides. , 2013, Chemical reviews.

[23]  T. H. Dunning Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen , 1989 .

[24]  Wei Chen,et al.  Enhanced ethanol production inside carbon-nanotube reactors containing catalytic particles. , 2007, Nature materials.

[25]  Jiasheng Huang,et al.  Dehydrogenation and aromatization of methane under non-oxidizing conditions , 1993 .

[26]  G. E. Keller,et al.  Synthesis of ethylene via oxidative coupling of methane: I. Determination of active catalysts , 1982 .

[27]  Van Santen,et al.  Pyrolysis of methane and the role of surface area , 1989 .

[28]  M. A. Ermakova,et al.  Decomposition of Methane over Iron Catalysts at the Range of Moderate Temperatures: The Influence of Structure of the Catalytic Systems and the Reaction Conditions on the Yield of Carbon and Morphology of Carbon Filaments , 2001 .

[29]  R. Friesner,et al.  Computing Redox Potentials in Solution: Density Functional Theory as A Tool for Rational Design of Redox Agents , 2002 .

[30]  J. Bitter,et al.  Supported Iron Nanoparticles as Catalysts for Sustainable Production of Lower Olefins , 2012, Science.

[31]  S. Takenaka,et al.  Ni/SiO2 catalyst effective for methane decomposition into hydrogen and carbon nanofiber , 2003 .

[32]  R. Anderson,et al.  Conversion of natural gas to liquids via acetylene as an intermediate , 2002 .

[33]  Angelos Michaelides,et al.  Insight into microscopic reaction pathways in heterogeneous catalysis , 2000 .

[34]  D. Truhlar,et al.  The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals , 2008 .

[35]  M. Scheffler,et al.  A Critical Assessment of Li/MgO-Based Catalysts for the Oxidative Coupling of Methane , 2011 .

[36]  J. E. Lyons,et al.  Catalysis research of relevance to carbon management: progress, challenges, and opportunities. , 2001, Chemical reviews.

[37]  H. Schwarz Chemistry with methane: concepts rather than recipes. , 2011, Angewandte Chemie.

[38]  B. Weckhuysen,et al.  Conversion of methane to benzene over transition metal ion ZSM-5 zeolites : I. Catalytic characterization , 1998 .

[39]  Linsheng Wang,et al.  Catalytic Dehydrocondensation of Methane with CO and CO2toward Benzene and Naphthalene on Mo/HZSM-5 and Fe/Co-Modified Mo/HZSM-5 , 1999 .

[40]  Martin Holena,et al.  Statistical Analysis of Past Catalytic Data on Oxidative Methane Coupling for New Insights into the Composition of High‐Performance Catalysts , 2011 .

[41]  Ola Olsvik,et al.  Pyrolysis of natural gas: chemistry and process concepts , 1995 .

[42]  Weixin Huang,et al.  Methyl Radicals in Oxidative Coupling of Methane Directly Confirmed by Synchrotron VUV Photoionization Mass Spectroscopy , 2013, Scientific Reports.

[43]  François Diederich 125 Years Angewandte Chemie , 2013 .

[44]  L. Curtiss,et al.  Gaussian-4 theory using reduced order perturbation theory. , 2007, The Journal of chemical physics.

[45]  Ola Olsvik,et al.  Pyrolysis of methane in the presence of hydrogen , 1995 .

[46]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[47]  Y. H. Kim,et al.  Structure and Density of Mo and Acid Sites in Mo-Exchanged H-ZSM5 Catalysts for Nonoxidative Methane Conversion , 1999 .

[48]  F. Larkins,et al.  Pyrolysis of Methane to Higher Hydrocarbons: A Thermodynamic Study , 1989 .

[49]  X. Bao,et al.  Recent progress in methane dehydroaromatization: From laboratory curiosities to promising technology , 2013 .

[50]  F. Qi,et al.  Recent developments in synchrotron vacuum ultraviolet photoionization coupled to mass spectrometry , 2011 .

[51]  R. Schlögl,et al.  Reactor for in situ measurements of spatially resolved kinetic data in heterogeneous catalysis. , 2010, The Review of scientific instruments.

[52]  G. Kresse,et al.  From ultrasoft pseudopotentials to the projector augmented-wave method , 1999 .

[53]  Blöchl,et al.  Projector augmented-wave method. , 1994, Physical review. B, Condensed matter.

[54]  J. Bokhoven,et al.  Non-oxidative methane conversion assisted by corona discharge , 2012 .

[55]  L. Curtiss,et al.  Gaussian-4 theory. , 2007, The Journal of chemical physics.

[56]  R. Schlögl,et al.  Gas phase contributions to the catalytic formation of HCN from CH4 and NH3 over Pt: An in situ study by molecular beam mass spectrometry with threshold ionization , 2004 .

[57]  Zhanjun Cheng,et al.  Catalytic decomposition of methane on impregnated nickel based anodes with molecular-beam mass spectrometry and tunable synchrotron vacuum ultraviolet photoionization , 2012 .

[58]  K. Burke,et al.  Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)] , 1997 .