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Tusini E, Casapu M, Zimina A, Doronkin DE, Störmer H, Barthe L, Belin S, Grunwaldt JD. Structural Changes of Ni and Ni-Pt Methane Steam Reforming Catalysts During Activation, Reaction, and Deactivation Under Dynamic Reaction Conditions. ACS Catal 2024; 14:7463-7477. [PMID: 38779186 PMCID: PMC11110164 DOI: 10.1021/acscatal.3c05847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 02/14/2024] [Accepted: 03/19/2024] [Indexed: 05/25/2024]
Abstract
Ni-based catalysts are the most widely used materials to produce H2 in large-scale methane steam reformers under stationary conditions. For domestic applications such as fuel cells, H2 production involves the exposure of the catalysts to more dynamic conditions due to the daily startup and shutdown operation mode, making Ni-based catalysts susceptible to oxidation and deactivation. In this context, we report a systematic investigation of the structural changes occurring for monometallic Ni/MgAlOx and bimetallic NiPt/MgAlOx catalysts during methane steam reforming under transient conditions, comprising catalyst activation, operation, and deactivation processes. Besides extensive catalytic tests, the samples prepared by incipient wetness impregnation were characterized by complementary methods, including N2-physisorption, X-ray diffraction, H2-temperature-programmed reduction, and electron microscopy. Next, the structure of the Ni and Pt species was monitored under reaction conditions using time and spatially resolved in situ/operando X-ray absorption spectroscopy. The results obtained show that before catalyst activation by H2-reduction, nickel diffuses into the support lattice and forms mixed oxides with magnesium. In the activated catalysts, Ni is present in the metallic state or alloyed with Pt. A clear beneficial effect of the noble metal addition was identified on both the activity and stability of the bimetallic NiPt/MgAlOx catalyst. In contrast, the pronounced oxidation and reincorporation of Ni into the support lattice were observed for the monometallic sample, and these catalyst deactivation effects are hindered in the bimetallic Ni-Pt catalyst. Overall, the outcome of our study not only helps in understanding the catalyst activation/deactivation processes at an atomic level but also provides the basis for the rational development of improved methane steam reforming catalysts.
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Affiliation(s)
- Enrico Tusini
- Institute
for Chemical Technology and Polymer Chemistry, Karlsruhe Institute
of Technology (KIT), Engesserstraße 20, 76131 Karlsruhe, Germany
| | - Maria Casapu
- Institute
for Chemical Technology and Polymer Chemistry, Karlsruhe Institute
of Technology (KIT), Engesserstraße 20, 76131 Karlsruhe, Germany
| | - Anna Zimina
- Institute
for Chemical Technology and Polymer Chemistry, Karlsruhe Institute
of Technology (KIT), Engesserstraße 20, 76131 Karlsruhe, Germany
- Institute
of Catalysis Research and Technology, Karlsruhe Institute of Technology
(KIT), Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Dmitry E. Doronkin
- Institute
for Chemical Technology and Polymer Chemistry, Karlsruhe Institute
of Technology (KIT), Engesserstraße 20, 76131 Karlsruhe, Germany
- Institute
of Catalysis Research and Technology, Karlsruhe Institute of Technology
(KIT), Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Heike Störmer
- Laboratory
for Electron Microscopy, Karlsruhe Institute
of Technology (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany
| | - Laurent Barthe
- Synchrotron
SOLEIL, L’Orme des Merisiers BP48 Saint Aubin, 91192 Gif-sur Yvette, France
| | - Stephanie Belin
- Synchrotron
SOLEIL, L’Orme des Merisiers BP48 Saint Aubin, 91192 Gif-sur Yvette, France
| | - Jan-Dierk Grunwaldt
- Institute
for Chemical Technology and Polymer Chemistry, Karlsruhe Institute
of Technology (KIT), Engesserstraße 20, 76131 Karlsruhe, Germany
- Institute
of Catalysis Research and Technology, Karlsruhe Institute of Technology
(KIT), Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
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Okumura K, Morita S, Iiyoshi H, Takaba H. Formation and Segregation of a Pd-MgO Solid Solution Studied by X-ray Absorption Spectroscopy. ACS OMEGA 2023; 8:7507-7516. [PMID: 36872996 PMCID: PMC9979325 DOI: 10.1021/acsomega.2c06604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 01/24/2023] [Indexed: 06/18/2023]
Abstract
Thermal treatment of Pd nanoparticles or Pd(NH3)4(NO3)2 supported on MgO resulted in the formation of a solid solution of Pd-MgO, as evidenced by Pd K-edge X-ray absorption fine structure (XAFS). The valence of Pd in the Pd-MgO solid solution was determined to be 4+ from the comparison of X-ray absorption near edge structure (XANES) with reference compounds. A characteristic shrinkage of the Pd-O bond distance was observed in comparison with that of the nearest-neighboring Mg-O bond in MgO, which agreed with the density functional theory (DFT) calculations. The two-spike pattern was observed in the dispersion of Pd-MgO owing to the formation and successive segregation of solid solutions above 1073 K.
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Affiliation(s)
- Kazu Okumura
- Department
of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan
| | - Sachiko Morita
- Department
of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan
| | - Hikaru Iiyoshi
- Department
of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan
| | - Hiromitsu Takaba
- Department
of Environmental Chemistry and Chemical Engineering, School of Advanced
Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan
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Formation of Ir–MgO Solid Solutions Analyzed with X-ray Absorption Spectroscopy. CATALYSIS SURVEYS FROM ASIA 2022. [DOI: 10.1007/s10563-022-09378-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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