Catalytic conversion of methane to methanol with Cu-zeolite catalysts
Conversion of methane to methanol is an industrially very important process, as it provides a sustainable route from an abundant and clean component of natural gas to one of the main precursors for chemicals synthesis. An efficient stepwise process catalyzed by copper-exchanged zeolites has been suggested; however, a detailed understanding of the mechanism of such a zeolite-catalyzed conversion is still missing. One of the ongoing debates in studying copper-exchanged zeolites is the exact configuration of the available catalytic sites. Another open question is the mechanism of methane oxidation and regeneration of the copper oxide active site, and possible role of water in these processes. We use the state of the art theoretical methods to investigate the configurational manifold of the copper oxide active centers, and the nature of chemical interaction between the oxide center, zeolite framework, and the reacting molecules, as well as establishing possible mechanisms of the conversion of methane to methanol.
- Z. R. Jovanovic, J.-P. Lange, M. Ravi, A. J. Knorpp, V. L. Sushkevich, M. A. Newton, D. Palagin, and J. A. van Bokhoven, “Oxidation of methane to methanol over Cu-exchanged zeolites: Scientia gratia scientiae or paradigm shift in natural gas valorization?”, J. Catal. 385, 238 (2020).
- D. Palagin, V. L. Sushkevich, and J. A. van Bokhoven, “Water Molecules Facilitate Hydrogen Release in Anaerobic Oxidation of Methane to Methanol over Cu/Mordenite”, ACS Catal. 9, 10365 (2019).
- M. Ravi, V. L. Sushkevich, A. J. Knorpp, M. A. Newton, D. Palagin, A. B. Pinar, M. Ranocchiari, and J. A. van Bokhoven, “Misconceptions and challenges in methane-to-methanol over transition-metal-exchanged zeolites”, Nat. Catal. 2, 485 (2019).
- M. A. Newton, A. J. Knorpp, A. B. Pinar, V. L. Sushkevich, D. Palagin, and J. A. van Bokhoven, “On the Mechanism Underlying the Direct Conversion of Methane to Methanol by Copper Hosted in Zeolites; Braiding Cu K-Edge XANES and Reactivity Studies”, J. Am. Chem. Soc. 140, 10090 (2018).
- V. L. Sushkevich, D. Palagin, and J. A. van Bokhoven, “The Effect of the Active‐Site Structure on the Activity of Copper Mordenite in the Aerobic and Anaerobic Conversion of Methane into Methanol”, Angew. Chem. Int. Ed. 57, 8906 (2018).
- V. L. Sushkevich, D. Palagin, M. Ranocchiari, and J. A. van Bokhoven, “Selective anaerobic oxidation of methane enables direct synthesis of methanol”, Science 356, 523 (2017).
Active site structure determination for zeolite based materials
Determining the structure of metal species present within zeolites is of paramount importance for understanding of the mechanisms of the zeolite catalyzed reactions, and how these may depend on the type of metal sites present in the material. From the point of view of theory, modelling zeolites is a challenging problem. Fundamental understanding of these complex materials requires, on the one hand, a carefully refined structural model, that captures the essential chemistry of the system, and, on the other hand, an appropriately accurate description of the experimentally observed spectroscopic features of the system. We apply state-of-the-art ab initio methods to tackle this problem.
- A. J. Knorpp, A. B. Pinar, C. Baerlocher, L. B. McCusker, N. Casati, M. A. Newton, S. Checchia, J. Meyet, D. Palagin, and J. A. van Bokhoven, “Paired copper monomers in zeolite omega: the active site for methane-to-methanol conversion”, Angew. Chem. Int. Ed. (2021).
- V. L. Sushkevich, O. V. Safonova, D. Palagin, M. A. Newton, and J. A. van Bokhoven, “Structure of Copper Sites in Zeolites Examined by Fourier and Wavelet Transform Analysis of EXAFS”, Chem. Sci. 11, 5299 (2020).
- M. A. Newton, A. J. Knorpp, V. L. Sushkevich, D. Palagin, and J. A. van Bokhoven, “Active sites and mechanisms in the direct conversion of methane to methanol using Cu in zeolitic hosts: a critical examination”, Chem. Soc. Rev. 49, 1449 (2020); featured on the cover.
- L. Artiglia, V. L. Sushkevich, D. Palagin, A. J. Knorpp, K. Roy, and J. A. van Bokhoven, “In-situ X-Ray Photoelectron Spectroscopy Detects Multiple Active Sites Involved in the Selective Anaerobic Oxidation of Methane in Copper-Exchanged Zeolites”, ACS Catal. 9, 6728 (2019).
- D. Palagin, A. J. Knorpp, A. B. Pinar, M. Ranocchiari, and J. A. van Bokhoven, “Assessing the Relative Stability of Copper Oxide Clusters as Active Sites of a CuMOR Zeolite for Methane to Methanol Conversion: Size Matters?”, Nanoscale 9, 1144 (2017).
Water-gas shift on supported Pt particles
Supported platinum catalysts show high activity and excellent stability in the low temperature carbon monoxide oxidation and water-gas shift reactions that are important for a wide range of applications, such as fuel cell design or automotive emission control. However, no consensus on the catalytic mechanisms and atomic configurations of the active sites has been reached. In particular, the size of the catalytically active Pt nanoparticles, and, more specifically, whether platinum single atoms can act as active catalytic sites, remains an open question. We use DFT to elucidate the configurations and catalytic activity of the supported Pt species.
- X. Wang, A. Beck, J. A. van Bokhoven, D. Palagin, “Thermodynamic insights into strong metal-support interaction of transition metal nanoparticles on titania: simple descriptors for complex chemistry”, J. Mater. Chem. A 9, 4044 (2021).
- X. Wang, J. A. van Bokhoven, D. Palagin, “Atomically dispersed platinum on low index and stepped ceria surfaces: phase diagram and stability analysis”, Phys. Chem. Chem. Phys. 22, 28 (2020); highlighted in 2019 PCCP HOT Articles; featured on the cover.
- X. Wang, J. A. van Bokhoven, D. Palagin, “Ostwald ripening versus single atom trapping: towards understanding platinum particles sintering”, Phys. Chem. Chem. Phys. 19, 30513 (2017).
Theoretical Support for Materials Science
Theoretical chemistry is well suited for describing the formation and chemical behaviour of complex metal particles and phases, such as alloys. We actively collaborate with the experimental part of the LSK to help understanding the nature of the observed experimental phenomena.
- A. Beck, X. Huang, L. Artiglia, M. Zabilskiy, X. Wang, P. Rzepka, D. Palagin, M.-G. Willinger, and J. A. van Bokhoven, “The dynamics of overlayer formation on catalyst nanoparticles and strong metal-support interaction”, Nat. Commun. 11, 3220 (2020).
- M. Zabilskiy, V. L. Sushkevich, D. Palagin, M. A. Newton, F. Krumeich, and J. A. van Bokhoven, “The Unique Interplay between Copper and Zinc during Catalytic Carbon Dioxide Hydrogenation to Methanol”, Nat. Commun. 11, 2409 (2020).
- S. Saedy, D. Palagin, O. V. Safonova, J. van Bokhoven, A. A. Khodadadi, and Y. Mortazavi, “Understanding the Mechanism of Synthesis of Pt3Co Intermetallic Nanoparticles via Preferential Chemical Vapor Deposition”, J. Mater. Chem. A 5, 24396 (2017).
Metal-organic frameworks (MOFs) are attracting the scientific community because of their unique catalytic properties. We use theoretical methods to predict the MOF self-assembly and explain the distribution of cluster vacancies.
Identification of relevant reaction pathways in ever more complex composite materials and nanostructures poses a central challenge to computational materials discovery. Efficient global structure search, tailored to identify chemically-relevant intermediates, could provide the necessary first-principles atomistic insight to enable a rational process design. We modify a common feature of global geometry optimization schemes by employing automatically-generated collective curvilinear coordinates. The similarity of these coordinates to molecular vibrations enhances the generation of chemically meaningful trial structures for covalently bound systems.
- K. Krautgasser, C. Panosetti, D. Palagin, K. Reuter, and R. J. Maurer, “Global Structure Search for Molecules on Surfaces: Efficient Sampling with Curvilinear Coordinates”, J. Chem. Phys. 145, 084117 (2016).
- C. Panosetti, K. Krautgasser, D. Palagin, K. Reuter, and R. J. Maurer, “Global Materials Structure Search with Chemically-Motivated Coordinates”, Nano Lett. 15, 8044 (2015).