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Methane and Ethane Steam Reforming over MgAl2O4-Supported Rh and Ir Catalysts: Catalytic Implications for Natural Gas Reforming Application. Catalysts 2019. [DOI: 10.3390/catal9100801] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Solar concentrators employed in conjunction with highly efficient micro- and meso-channel reactors offer the potential for cost-effective upgrading of the energy content of natural gas, providing a near-term path towards a future solar-fuel economy with reduced carbon dioxide emissions. To fully exploit the heat and mass transfer advantages offered by micro- and meso-channel reactors, highly active and stable natural gas steam reforming catalysts are required. In this paper, we report the catalytic performance of MgAl2O4-supported Rh (5 wt.%), Ir (5 wt.%), and Ni (15 wt.%) catalysts used for steam reforming of natural gas. Both Rh- and Ir-based catalysts are known to be more active and durable than conventional Ni-based formulations, and recently Ir has been reported to be more active than Rh for methane steam reforming on a turnover basis. Thus, the effectiveness of all three metals to perform natural gas steam reforming was evaluated in this study. Here, the Rh- and Ir-supported catalysts both exhibited higher activity than Ni for steam methane reforming. However, using simulated natural gas feedstock (94.5% methane, 4.0% ethane, 1.0% propane, and 0.5% butane), the Ir catalyst was the least active (on a turnover basis) for steam reforming of higher hydrocarbons (C2+) contained in the feedstock when operated at <750 °C. To further investigate the role of higher hydrocarbons, we used an ethane feed and found that hydrogenolysis precedes the steam reforming reaction and that C–C bond scission over Ir is kinetically slow compared to Rh. Catalyst durability studies revealed the Rh catalyst to be stable under steam methane reforming conditions, as evidenced by two 100-hour duration experiments performed at 850 and 900 °C (steam to carbon [S/C] molar feed ratio = 2.0 mol). However, with the natural gas simulant feed, the Rh catalyst exhibited catalyst deactivation, which we attribute to coking deposits derived from higher hydrocarbons contained in the feedstock. Increasing the S/C molar feed ratio from 1.5 to 2.0 reduced the deactivation rate and stable catalytic performance was demonstrated for 120 h when operated at 850 °C. However, catalytic deactivation was observed when operating at 900 °C. While improvements in steam reforming performance can be achieved through choice of catalyst composition, this study also highlights the importance of considering the effect of higher hydrocarbons contained in natural gas, operating conditions (e.g., temperature, S/C feed ratio), and their effect on catalyst stability. The results of this study conclude that a Rh-supported catalyst was developed that enables very high activities and excellent catalytic stability for both the steam reforming of methane and other higher hydrocarbons contained in natural gas, and under conditions of operation that are amendable to solar thermochemical operations.
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Abstract
In this study, a directly irradiated, milli-scale chemical reactor with a simple nickel catalyst was designed for dry reforming of methane for syngas. A milli-scale reactor was used to facilitate rapid heating, which is conducive to combating thermal transience caused by intermittent solar energy, as well as reducing startup times. Milli-scale reactors also allow for a distributed and modular process to produce chemicals on a more local scale. In this setup, the catalyst involved in the reaction is located directly in the focal area of the solar simulator, resulting in rapid heating. The effects of mean residence time and temperature on conversion and energy efficiency were tested. The process, which is intended to store thermal energy as chemical enthalpy, achieved 10% thermal-to-chemical energy conversion efficiency at a mean residence time of 0.028 s, temperature of 1000 °C, and molar feed ratio of 1:1 CO2:CH4. A significant portion of the thermal energy input into the reactor was directed toward sensible heating of the feed gas. Thus, this technology has potential to achieve solar-to-chemical efficiency with the integration of recuperative heat exchange.
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Welte M, Warren K, Scheffe JR, Steinfeld A. Combined Ceria Reduction and Methane Reforming in a Solar-Driven Particle-Transport Reactor. Ind Eng Chem Res 2017; 56:10300-10308. [PMID: 28966440 PMCID: PMC5617332 DOI: 10.1021/acs.iecr.7b02738] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 08/18/2017] [Accepted: 08/22/2017] [Indexed: 11/28/2022]
Abstract
We report on the experimental performance of a solar aerosol reactor for carrying out the combined thermochemical reduction of CeO2 and reforming of CH4 using concentrated radiation as the source of process heat. The 2 kWth solar reactor prototype utilizes a cavity receiver enclosing a vertical Al2O3 tube which contains a downward gravity-driven particle flow of ceria particles, either co-current or counter-current to a CH4 flow. Experimentation under a peak radiative flux of 2264 suns yielded methane conversions up to 89% at 1300 °C for residence times under 1 s. The maximum extent of ceria reduction, given by the nonstoichiometry δ (CeO2-δ), was 0.25. The solar-to-fuel energy conversion efficiency reached 12%. The syngas produced had a H2:CO molar ratio of 2, and its calorific value was solar-upgraded by 24% over that of the CH4 reformed.
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Affiliation(s)
- Michael Welte
- Department of Mechanical and Process Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Kent Warren
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611-6250, United States
| | - Jonathan R Scheffe
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611-6250, United States
| | - Aldo Steinfeld
- Department of Mechanical and Process Engineering, ETH Zürich, 8092 Zürich, Switzerland
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Kageyama N, Devocht BR, Takagaki A, Toch K, Thybaut JW, Marin GB, Oyama ST. Interplay of Kinetics and Thermodynamics in Catalytic Steam Methane Reforming over Ni/MgO-SiO2. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.6b03614] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Naoki Kageyama
- Department
of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Brigitte R. Devocht
- Laboratory
for Chemical Technology, Ghent University, Tech Lane Ghent Science Park—Campus
A, Technologiepark 914, B-9052 Ghent, Belgium
| | - Atsushi Takagaki
- Department
of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- College
of Chemical Engineering, Fuzhou University, Fuzhou 350116, China
| | - Kenneth Toch
- Laboratory
for Chemical Technology, Ghent University, Tech Lane Ghent Science Park—Campus
A, Technologiepark 914, B-9052 Ghent, Belgium
| | - Joris W. Thybaut
- Laboratory
for Chemical Technology, Ghent University, Tech Lane Ghent Science Park—Campus
A, Technologiepark 914, B-9052 Ghent, Belgium
| | - Guy B. Marin
- Laboratory
for Chemical Technology, Ghent University, Tech Lane Ghent Science Park—Campus
A, Technologiepark 914, B-9052 Ghent, Belgium
| | - S. Ted Oyama
- Department
of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- College
of Chemical Engineering, Fuzhou University, Fuzhou 350116, China
- Environmental Catalysis and
Nanomaterials Laboratory, Department
of Chemical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0211, United States
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