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Title: Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM)

Abstract

Abstract This work reports on the characterization of LaRhO3 perovskite as a catalyst for dry reforming of methane. The catalyst was studied using CH4-temperature programmed reduction (TPR), H2-TPR, and temperature programmed surface reaction (TPSR), and the changes in the crystal structure of the catalyst due to these treatments were studied by X-ray diffraction (XRD). XRD pattern of the freshly calcined perovskites showed the formation of highly crystalline LaRhO3 and La2O3 phases. H2-TPR of the fresh calcined catalyst showed a shoulder at 342°C and a broad peak at 448°C, suggesting that the reduction of Rh in perovskite occurs in multiple steps. XRD pattern of the reduced catalyst suggests complete reduction of the LaRhO3 phase and the formation of metallic Rh and minor amounts of La(OH)3. The CH4-TPR data show qualitatively similar results as H2-TPR, with a shoulder and a broad peak in the same temperature range. Following the H2-TPR up to 950°C, the same batch of catalyst was oxidized by flowing 5 vol. % O2/He up to 500°C and a second H2-TPR (also up to 950°C) was conducted. This second H2-TPR differed significantly from that of the fresh calcined catalyst. The single sharp peak at 163°C in the second H2-TPR suggestsmore » a significant change in the catalyst, probably causedby the transformation of about 90 % of the perovskite into Rh/La2O3. This was confirmed by the XRD studies of the catalyst reduced after the oxidation at 500°C. TPSR of the dry reforming reaction on the fresh calcined catalyst showed CO and H2 formation starting at 400°C, with complete consumption of the reactants at 650°C. The uneven consumption of reactants between 400°C and 650°C suggests that reactions other than DRM occur, including reverse water gas shift (RWGS) and the Boudouard reaction (BR), probably as a result of in-situ changes in the catalyst, consistent with the H2-TPR results. TPSR, after a H2-TPR up to 950°C, showed that the dry reforming reaction did not light off until 570°C, which is much higher temperature than the one observed using fresh calcined catalyst. This shows that the uniform sites produced during the 950°C H2-TPR are catalytically less active than those of the fresh calcined catalyst, and that no significant side reactions such as RWGS or the Boudouard reaction occur. This suggests that reduction leads to the formation of a single type of sites which do not catalyze simultaneous side reactions.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Atomic-Level Catalyst Design (CALCD)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1383427
DOE Contract Number:  
SC0001058
Resource Type:
Journal Article
Journal Name:
Chemical Papers
Additional Journal Information:
Journal Volume: 68; Journal Issue: 9; Related Information: CALCD partners with Louisiana State University (lead); Clemson University; University of Florida; Georgia Institute of Technology; Grambling State University; Oak Ridge National Laboratory; Ohio State University; Pennsylvania State; Texas A&M University; Vienna University of Technology, Austria; University of Utrecht, Netherlands; Journal ID: ISSN 1336-9075
Country of Publication:
United States
Language:
English
Subject:
catalysis (heterogeneous), hydrogen and fuel cells, charge transport, carbon capture, carbon sequestration, materials and chemistry by design, synthesis (novel materials)

Citation Formats

Johansson, Ted, Pakhare, Devendra, Haynes, Daniel, Abdelsayed, Victor, Shekhawat, Dushyant, and Spivey, James. Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM). United States: N. p., 2014. Web. doi:10.2478/s11696-014-0566-2.
Johansson, Ted, Pakhare, Devendra, Haynes, Daniel, Abdelsayed, Victor, Shekhawat, Dushyant, & Spivey, James. Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM). United States. doi:10.2478/s11696-014-0566-2.
Johansson, Ted, Pakhare, Devendra, Haynes, Daniel, Abdelsayed, Victor, Shekhawat, Dushyant, and Spivey, James. Wed . "Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM)". United States. doi:10.2478/s11696-014-0566-2.
@article{osti_1383427,
title = {Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM)},
author = {Johansson, Ted and Pakhare, Devendra and Haynes, Daniel and Abdelsayed, Victor and Shekhawat, Dushyant and Spivey, James},
abstractNote = {Abstract This work reports on the characterization of LaRhO3 perovskite as a catalyst for dry reforming of methane. The catalyst was studied using CH4-temperature programmed reduction (TPR), H2-TPR, and temperature programmed surface reaction (TPSR), and the changes in the crystal structure of the catalyst due to these treatments were studied by X-ray diffraction (XRD). XRD pattern of the freshly calcined perovskites showed the formation of highly crystalline LaRhO3 and La2O3 phases. H2-TPR of the fresh calcined catalyst showed a shoulder at 342°C and a broad peak at 448°C, suggesting that the reduction of Rh in perovskite occurs in multiple steps. XRD pattern of the reduced catalyst suggests complete reduction of the LaRhO3 phase and the formation of metallic Rh and minor amounts of La(OH)3. The CH4-TPR data show qualitatively similar results as H2-TPR, with a shoulder and a broad peak in the same temperature range. Following the H2-TPR up to 950°C, the same batch of catalyst was oxidized by flowing 5 vol. % O2/He up to 500°C and a second H2-TPR (also up to 950°C) was conducted. This second H2-TPR differed significantly from that of the fresh calcined catalyst. The single sharp peak at 163°C in the second H2-TPR suggests a significant change in the catalyst, probably causedby the transformation of about 90 % of the perovskite into Rh/La2O3. This was confirmed by the XRD studies of the catalyst reduced after the oxidation at 500°C. TPSR of the dry reforming reaction on the fresh calcined catalyst showed CO and H2 formation starting at 400°C, with complete consumption of the reactants at 650°C. The uneven consumption of reactants between 400°C and 650°C suggests that reactions other than DRM occur, including reverse water gas shift (RWGS) and the Boudouard reaction (BR), probably as a result of in-situ changes in the catalyst, consistent with the H2-TPR results. TPSR, after a H2-TPR up to 950°C, showed that the dry reforming reaction did not light off until 570°C, which is much higher temperature than the one observed using fresh calcined catalyst. This shows that the uniform sites produced during the 950°C H2-TPR are catalytically less active than those of the fresh calcined catalyst, and that no significant side reactions such as RWGS or the Boudouard reaction occur. This suggests that reduction leads to the formation of a single type of sites which do not catalyze simultaneous side reactions.},
doi = {10.2478/s11696-014-0566-2},
journal = {Chemical Papers},
issn = {1336-9075},
number = 9,
volume = 68,
place = {United States},
year = {2014},
month = {1}
}