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Evidence of radical chemistry in catalytic methane oxybromination

Nature Catalysis volume 1, pages 363–370 (2018)Cite this article

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Abstract

Unravelling the pathways of catalytic methane functionalization sets the foundations for the efficient production of valuable chemicals and fuels from this abundant feedstock. The catalytic oxybromination of methane into platform compounds bromomethane and dibromomethane constitutes a prominent example, although it displays a puzzling reaction network that has been speculated to involve free-radical intermediates. Here, photoelectron photoion coincidence spectroscopy with synchrotron radiation was used to provide evidence of the evolution of gaseous methyl and bromine radicals over (VO)2P2O7 and EuOBr catalysts and the strong correlation between the formation of methyl radicals and the production of bromomethanes. Complemented by kinetic data on methane oxybromination and non-catalytic methane bromination, these results imply the surface-catalysed generation of bromine radicals and molecular bromine followed by the gas-phase methane bromination, which is rationalized by density functional theory calculations. The findings emphasize the role of both surface and gas-phase steps in halogen-mediated C–H bond activation over heterogeneous catalysts.

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Fig. 1: Kinetics of methane oxybromination, bromination and oxidation.
Fig. 2: PEPICO reactor set-up for radical detection.
Fig. 3: Radical detection in catalytic methane oxybromination.
Fig. 4: Reaction profile of catalytic methane oxybromination.

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References

  1. Ito, T. & Lunsford, J. H. Synthesis of ethylene and ethane by partial oxidation of methane over lithium-doped magnesium oxide. Nature 314, 721–722 (1985).

    Article  CAS  Google Scholar 

  2. Bodke, A. S., Olschki, D. A., Schmidt, L. D. & Ranzi, E. High selectivities to ethylene by partial oxidation of ethane. Science 285, 712–715 (1999).

    Article  CAS  Google Scholar 

  3. Guo, X. et al. Direct, nonoxidative conversion of methane to ethylene, aromatics, and hydrogen. Science 344, 616–619 (2014).

    Article  CAS  Google Scholar 

  4. Gärtner, C. A., van Veen, A. C. & Lercher, J. A. Oxidative dehydrogenation of ethane: common principles and mechanistic aspects. ChemCatChem 5, 3196–3217 (2013).

    Article  Google Scholar 

  5. Sattler, J. J. H. B., Ruiz-Martinez, J., Santillan-Jimenez, E. & Weckhuysen, B. M. Catalytic dehydrogenation of light alkanes on metals and metal oxides. Chem. Rev. 114, 10613–10653 (2014).

    Article  CAS  Google Scholar 

  6. Kwapien, K. et al. Sites for methane activation on lithium-doped magnesium oxide surfaces. Angew. Chem. Int. Ed. 53, 8774–8778 (2014).

    Article  CAS  Google Scholar 

  7. Grundner, S. et al. Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol. Nat. Commun. 6, 7546 (2015).

    Article  Google Scholar 

  8. Tomkins, P. et al. Isothermal cyclic conversion of methane into methanol over copper-exchanged zeolite at low temperature. Angew. Chem. Int. Ed. 55, 5467–5471 (2016).

    Article  CAS  Google Scholar 

  9. Latimer, A. A. et al. Understanding trends in C-H bond activation in heterogeneous catalysis. Nat. Mater. 16, 225–229 (2016).

    Article  Google Scholar 

  10. Gerceker, D. et al. Methane conversion to ethylene and aromatics on PtSn catalysts. ACS Catal. 7, 2088–2100 (2017).

    Article  CAS  Google Scholar 

  11. Driscoll, D. J., Martir, W., Wang, J. & Lunsford, J. H. Formation of gas-phase methyl radicals over MgO. J. Am. Chem. Soc. 107, 58–63 (1985).

    Article  CAS  Google Scholar 

  12. Luo, L. et al. Methyl radicals in oxidative coupling of methane directly confirmed by synchrotron VUV photoionization mass spectroscopy. Sci. Rep. 3, 1625 (2013).

    Article  Google Scholar 

  13. Hargreaves, J., Hutchings, G. & Joyner, R. Control of product selectivity in the partial oxidation of methane. Nature 348, 428–429 (1990).

    Article  CAS  Google Scholar 

  14. Horn, R. 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. Phys. Chem. Chem. Phys. 6, 4514–4521 (2004).

    Article  CAS  Google Scholar 

  15. He, J. et al. Transformation of methane to propylene: a two-step reaction route catalyzed by modified CeO2 nanocrystals and zeolites. Angew. Chem. Int. Ed. 51, 2438–2442 (2012).

    Article  CAS  Google Scholar 

  16. Paunović, V., Zichittella, G., Moser, M., Amrute, A. P. & Pérez-Ramírez, J. Catalyst design for natural-gas upgrading through oxybromination chemistry. Nat. Chem. 8, 803–809 (2016).

    Article  Google Scholar 

  17. Paunović, V. et al. Europium oxybromide catalysts for efficient bromine looping in natural gas valorization. Angew. Chem. Int. Ed. 56, 9791–9795 (2017).

    Article  Google Scholar 

  18. Ding, K. et al. Hydrodebromination and oligomerization of dibromomethane. ACS Catal. 2, 479–486 (2012).

    Article  CAS  Google Scholar 

  19. Lin, R., Amrute, A. P. & Pérez-Ramírez, J. Halogen-mediated conversion of hydrocarbons to commodities. Chem. Rev. 117, 4182–4247 (2017).

    Article  CAS  Google Scholar 

  20. Zichittella, G., Paunović, V., Amrute, A. P. & Pérez-Ramírez, J. Catalytic oxychlorination versus oxybromination for methane functionalization. ACS Catal. 7, 1805–1817 (2017).

    Article  CAS  Google Scholar 

  21. Kistiakowsky, G. B. & Van Artsdalen, E. R. Bromination of hydrocarbons. I. Photochemical and thermal bromination of methane and methyl bromine. Carbon-hydrogen bond strength in methane. J. Chem. Phys. 12, 469–478 (1944).

    Article  CAS  Google Scholar 

  22. Lorkovic, I. M. et al. Alkane bromination revisited: “reproportionation” in gas-phase methane bromination leads to higher selectivity for CH3Br at moderate temperatures. J. Phys. Chem. A 110, 8695–8700 (2006).

    Article  CAS  Google Scholar 

  23. Ding, K., Metiu, H. & Stucky, G. D. The selective high-yield conversion of methane using iodine-catalyzed methane bromination. ACS Catal. 3, 474–477 (2013).

    Article  CAS  Google Scholar 

  24. Li, B. & Metiu, H. Does halogen adsorption activate the oxygen atom on an oxide surface? I. A study of Br2 and HBr adsorption on La2O3 and La2O3 doped with Mg or Zr. J. Phys. Chem. C. 116, 4137–4148 (2012).

    Article  CAS  Google Scholar 

  25. Martir, W. & Lunsford, J. H. The formation of gas-phase π-allyl radicals from propylene over bismuth oxide and γ-bismuth molybdate catalysts. J. Am. Chem. Soc. 103, 3728–3732 (1981).

    Article  CAS  Google Scholar 

  26. Qi, F. Recent applications of synchrotron VUV photoionization mass spectrometry in combustion and energy research. Acc. Chem. Res. 10, 68–78 (2010).

    Google Scholar 

  27. Li, Y. et al. Effect of the pressure on the catalytic oxidation of volatile organic compounds over Ag/Al2O3 catalyst. Appl. Catal. B 89, 659–664 (2009).

    Article  CAS  Google Scholar 

  28. Jiao, F. et al. Selective conversion of syngas to light olefins. Science 351, 1065–1068 (2016).

    Article  CAS  Google Scholar 

  29. Osborn, D. L. et al. Breaking through the false coincidence barrier in electron-ion coincidence experiments. J. Chem. Phys. 145, 164202 (2016).

    Article  Google Scholar 

  30. Tang, X., Garcia, G. A. & Nahon, L. CH3 + formation in the dissociation of energy-selected CH3F+ studied by double imaging electron/ion coincidences. J. Phys. Chem. A 119, 5942–5950 (2015).

    Article  CAS  Google Scholar 

  31. Sztáray, B. et al. CRF-PEPICO: double velocity map imaging photoelectron photoion coincidence spectroscopy for reaction kinetics studies. J. Chem. Phys. 147, 13944 (2017).

    Article  Google Scholar 

  32. Oßwald, P. et al. In situ flame chemistry tracing by imaging photoelectron photoion coincidence spectroscopy. Rev. Sci. Instrum. 85, 025101 (2014).

    Article  Google Scholar 

  33. Hemberger, P., Custodis, V. B. F., Bodi, A., Gerber, T. & van Bokhoven, J. A. Understanding the mechanism of catalytic fast pyrolysis by unveiling reactive intermediates in heterogeneous catalysis. Nat. Commun. 8, 15946 (2017).

    Article  Google Scholar 

  34. Eränen, K., Lindfors, L. E., Klingstedt, F. & Murzin, D. Y. Continuous reduction of NO with octane over a silver/alumina catalyst in oxygen-rich exhaust gases: combined heterogeneous and surface-mediated homogeneous reactions. J. Catal. 219, 25–40 (2003).

    Article  Google Scholar 

  35. Hemberger, P., Trevitt, A. J., Gerber, T., Ross, E. & Da Silva, G. Isomer-specific product detection of gas-phase xylyl radical rearrangement and decomposition using VUV synchrotron photoionization. J. Phys. Chem. A 118, 3593–3604 (2014).

    Article  CAS  Google Scholar 

  36. Lias, S. G. et al. in NIST Chemistry WebBook: NIST Standard Reference Database (National Institute of Standards and Technology, 2008).

  37. Traeger, J. C. & McLoughlin, R. G. Absolute heats of formation for gas-phase cations. J. Am. Chem. Soc. 103, 3647–3652 (1981).

    Article  CAS  Google Scholar 

  38. Chang, Y.-C., Xiong, B., Bross, D. H., Ruscic, B. & Ng, C. Y. A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH4): determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH4 and CH4 +. Phys. Chem. Chem. Phys. 19, 9592–9605 (2017).

    Article  CAS  Google Scholar 

  39. Kaposi, O., Riedel, M., Vass-Balthazar, K., Sanchez, G. R. & Lelik, L. Mass-spectrometric determination of thermochemical data of CHBr3 and CBr4 by study of their electron impact and heterogeneous pyrolytic decompositions. Acta Chim. Acad. Sci. Hung. 89, 221 (1976).

    CAS  Google Scholar 

  40. DeCorpo, J. J., Bafus, D. A. & Franklin, J. L. Enthalpies of formation of the monohalomethyl radicals from mass spectrometric studies of the dihalomethanes. J. Chem. Thermodyn. 3, 125–127 (1971).

    Article  CAS  Google Scholar 

  41. Guan, Q. et al. The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules. Int. Rev. Phys. Chem. 33, 447–487 (2014).

    Article  CAS  Google Scholar 

  42. Person, J. C. & Nicole, P. P. Isotope effects in the photoionization yields and in the absorption cross sections for methanol, ethanol, methyl bromide, and ethyl bromide. J. Chem. Phys. 55, 3390–3397 (1971).

    Article  CAS  Google Scholar 

  43. Gans, B. et al. Determination of the absolute photoionization cross sections of CH3 and I produced from a pyrolysis source, by combined synchrotron and vacuum ultraviolet laser studies. J. Phys. Chem. A 114, 3237–3246 (2010).

    Article  CAS  Google Scholar 

  44. Bodi, A., Sztáray, B., Baer, T., Johnson, M. & Gerber, T. Data acquisition schemes for continuous two-particle time-of-flight coincidence experiments. Rev. Sci. Instrum. 78, 084102 (2007).

    Article  Google Scholar 

  45. Bodi, A. et al. Imaging photoelectron photoion coincidence spectroscopy with velocity focusing electron optics. Rev. Sci. Instrum. 80, 034101 (2009).

    Article  Google Scholar 

  46. Sztáray, B. & Baer, T. Suppression of hot electrons in threshold photoelectron photoion coincidence spectroscopy using velocity focusing optics. Rev. Sci. Instrum. 74, 3763–3768 (2003).

    Article  Google Scholar 

  47. Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

  48. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    Article  CAS  Google Scholar 

  49. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    Article  CAS  Google Scholar 

  50. Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Article  Google Scholar 

  51. Mayer, I., Zolotov, S. & Kassierer, F. The crystal structure of rare earth and yttrium oxybromides. Inorg. Chem. 4, 1637–1639 (1965).

    Article  CAS  Google Scholar 

  52. Henkelman, G., Uberuaga, B. P. & Jónsson, H. Climbing image nudged elastic band method for finding saddle points and minimum energy paths. J. Chem. Phys. 113, 9901–9904 (2000).

    Article  CAS  Google Scholar 

  53. Álvarez-Moreno, M., de Graaf, C., López, N., Maseras, F., Poblet, J. M. & Bo, C. Managing the computational chemistry big data problem: the ioChem-BD platform. J. Chem. Inf. Model. 55, 95–103 (2015).

    Article  Google Scholar 

  54. López, N. Computational Dataset for 'Evidence of Radical Chemistry in Catalytic Methane Oxybromination' (ioChem, 2018); https://doi.org/10.19061/iochem-bd-1-71.

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Acknowledgements

This work was supported by the Swiss National Science Foundation (project no. 200021-156107) and the Swiss Federal Office of Energy (contract no. SI/501269-01). D. Teschner from the Fritz Haber Institute of the Max Planck Society, Berlin; L. Szentmiklósi from the Centre for Energy Research, Hungarian Academy of Sciences, Budapest; and M. Moser are acknowledged for their help in performing prompt gamma activation analysis.

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Authors and Affiliations

  1. Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland

    Vladimir Paunović & Javier Pérez-Ramírez

  2. Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, Villigen, Switzerland

    Patrick Hemberger & Andras Bodi

  3. Institute of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology, Tarragona, Spain

    Núria López

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Contributions

J.P.-R. conceived and coordinated all stages of this research. V.P. prepared and characterized the catalysts, and performed and analysed the steady-state tests. V.P., P.H. and A.B. conducted operando PEPICO spectroscopy experiments. P.H. and A.B. analysed the results of PEPICO spectroscopy. N.L. conducted the DFT calculations. The data were discussed among all the authors. V.P., P.H. and J.P.-R. wrote the paper with feedback from the other authors.

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Correspondence to Javier Pérez-Ramírez.

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Paunović, V., Hemberger, P., Bodi, A. et al. Evidence of radical chemistry in catalytic methane oxybromination. Nat Catal 1, 363–370 (2018). https://doi.org/10.1038/s41929-018-0071-z

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