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Jianguo Wang - One of the best experts on this subject based on the ideXlab platform.
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co Preferential Oxidation in h2 rich stream over a cuo ceo2 catalyst with high h2o and co2 tolerance
Fuel, 2013Co-Authors: Huaqing Zhu, Hui Wang, Zhangfeng Qin, Jianfei Ding, Lichun Huang, Jianguo WangAbstract:Abstract The CuO/CeO2 catalysts are prepared by an improved incipient wetness impregnation method with ammonia as chelating agent for CO Preferential Oxidation (PROX). The effects of CuO loadings of the catalysts and the presence of H2O and CO2 in the reaction stream on the catalytic performance are investigated. The CuO/CeO2 catalyst with 10.0 wt.% CuO loading has high activity and stability for the CO-PROX. In the long-term stability test under the realistic reaction condition with 10% H2O and 15% CO2 in the reactant stream, 100% CO conversion can maintain for 1600 h at 140–150 °C with 85–75% selectivity. The catalysts are characterized by means of XRD, H2-TPR, and CO-TPR. The results show that the high activity of the CuO/CeO2 catalyst is closely related to the fine-dispersed CuO species strongly interacting with CeO2 support.
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Preferential Oxidation of co in h2 rich stream over cuo ce1 xtixo2 catalysts
Applied Catalysis B-environmental, 2010Co-Authors: Huaqing Zhu, Hui Wang, Zhangfeng Qin, Lichun Huang, Jianguo WangAbstract:Abstract CuO/Ce 1− x Ti x O 2 prepared by sol–gel impregnation was used as catalysts for the Preferential Oxidation (PROX) of CO in H 2 -rich stream. The effects of support composition, catalyst calcination temperature as well as the presence of H 2 O and CO 2 in the reaction stream on the catalytic performance of CuO/Ce 1− x Ti x O 2 were investigated. The results indicated that the catalyst CuO/Ce 0.8 Ti 0.2 O 2 exhibits the highest activity and the optimal temperature for the catalyst calcination is 500 °C. The presence of H 2 O and CO 2 in the reaction stream has a negative effect on the catalytic activity and stability of CuO/Ce 0.8 Ti 0.2 O 2 . The negative effect of CO 2 on the catalyst stability is stronger than that of H 2 O, suggesting that the accumulation of carbonate species may be the main reason for catalyst deactivation. The characterization by means of XRD, HRTEM, and H 2 -TPR indicated that the doping of TiO 2 in CeO 2 enhances the surface area of the composite oxide support, decreases its particle size, and promotes the dispersion of active copper species. The strong interaction between TiO 2 and CeO 2 in the support as well as the interfacial interaction between CuO and the support may also contribute to the high catalytic activity of CuO/Ce 0.8 Ti 0.2 O 2 .
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deactivation of a au ceo2 co3o4 catalyst during co Preferential Oxidation in h2 rich stream
Journal of Catalysis, 2009Co-Authors: Hui Wang, Feixue Liang, Guofu Wang, Jianguo WangAbstract:Abstract The origins of the deactivation of a Au/CeO2–Co3O4 catalyst during CO Preferential Oxidation (PROX) are investigated in detail by means of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed Oxidation of oxygen (O2-TPO), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A possible mechanism involving –OOH intermediate is proposed and used to explain the deactivation in the long-term stability test of CO PROX. The aggregation or sintering of the Au particles is excluded from the origins of deactivation by HRTEM and XRD. The deactivation of the catalyst is mainly due to an intrinsic transformation in the chemical state of the gold species and the support oxides in the Au/CeO2–Co3O4 catalyst. The XPS, XRD, and H2-TPR results demonstrate the reduction of ionic Au to metallic Au and of cobalt oxide to cobaltous compound. The changes of the chemical states imply a structure reordering of the catalyst surface, which will suppress the supplement of active oxygen and the formation of –OOH species, inhibit the CO Oxidation reaction, and lead to the deactivation of the catalyst. The accumulation of carbonates and H2O on the deactivated catalyst is revealed by XPS, DRIFTS, O2-TPO, and a regeneration test. They are responsible for the complete deactivation of the catalyst. The hydration of the catalyst surface may play a more important role than the formation of carbonates in the deactivation of the catalyst.
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Preferential Oxidation of co in h2 rich stream over au ceo2 co3o4 catalysts
Catalysis Communications, 2008Co-Authors: Hui Wang, Feixue Liang, Guofu Wang, Huaqing Zhu, Zhangfeng Qin, Jianguo WangAbstract:Au/CeO2–Co3O4 catalysts with a Ce/Co atomic ratio from 0.1 to 0.6 were prepared by deposition–precipitation; their catalytic performance in Preferential Oxidation (PROX) of CO in H2 rich stream was investigated. Au/CeO2–Co3O4 exhibits much higher catalytic activity in CO PROX than Au/Co3O4 and Au/CeO2; over Au/CeO2–Co3O4, 100% CO conversion with 75% selectivity to CO2 can be achieved even at ambient temperature. Typically, for CO PROX at 80 °C over Oxidation pretreated Au/CeO2–Co3O4 (Ce/Co = 0.2), 91% CO conversion and 51% selectivity to CO2 can last for 260 h.
A Martinezarias - One of the best experts on this subject based on the ideXlab platform.
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characterization and catalytic properties of cuo ceo2 mgal2o4 for Preferential Oxidation of co in h2 rich streams
Applied Catalysis B-environmental, 2016Co-Authors: Abdelhakim Elmhamdi, Rafael Castaneda, Anna Kubacka, L Pascual, Kais Nahdi, A MartinezariasAbstract:Abstract Catalysts of copper (1 wt.%) supported on a CeO 2 /MgAl 2 O 4 mixed support have been prepared by using different pH values (pH ∼ 4, 8 and 10) in the impregnating solution of copper with the aim of favoring different situations of interaction between copper and the two support components. The catalysts have been characterized in detail by XRD, S BET measurement, HREM and associated techniques, XPS, H 2 -TPR and EPR which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of the catalytic properties of the samples for Preferential Oxidation of CO in a H 2 -rich stream (CO-PROX) complemented by operando -DRIFTS. Important structural/chemical/catalytic differences as a function of the pH of the impregnating solution are revealed. These are explained on the basis of the characteristics of the interfaces formed between the different components present in each catalyst which basically determine the catalytic properties in each case.
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Preferential Oxidation of co in excess h2 over cuo ceo2 catalysts performance as a function of the copper coverage and exposed face present in the ceo2 support
Catalysis Today, 2014Co-Authors: M Monte, D Gamarra, Z Schay, A Martinezarias, Lopez A Camara, Soren Birk Rasmussen, N Gyorffy, J C ConesaAbstract:Abstract CuO/CeO 2 catalysts where the support has different nanoparticle shapes exposing different lattice planes are examined for the Preferential Oxidation of CO in the presence of excess H 2 (CO-PROX reaction) in operando DRIFTS conditions. Even for catalysts with same surface concentration of Cu the selectivity for CO 2 formation is found close to 100% up to higher temperatures when the support is in form of nanocubes (exposing the less stable (0 0 1) lattice planes). DRIFTS data allow relating this to a higher stability of the Cu species forming the Cu + carbonyls associated to the high activity and selectivity, so that they are fully reduced at higher temperature in agreement with TPR data. DFT calculations show that CuO nanoparticles interact more strongly (distorting more their structure) with the CeO 2 (0 0 1) surface than with the (1 1 1) surface, while XRD indicates that the formation of well developed CuO nanocrystals is more difficult on nanocube shaped CeO 2 than on other CeO 2 morphologies. Also EPR spectra show that the CuO entities nucleate on the ceria nanocubes differently. The higher stabilization of the oxidized state indicated by DFT, together with the mentioned structural distortion, may be then the reason for the improved selectivity.
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inverse ceo2 cuo catalyst as an alternative to classical direct configurations for Preferential Oxidation of co in hydrogen rich stream
Journal of the American Chemical Society, 2010Co-Authors: Aitor Hornes, A Martinezarias, A B Hungria, Parthasarathi Bera, Lopez A Camara, Marcos Fernandezgarcia, Laura Barrio, Michael A Estrella, Gong Zhou, J J FonsecaAbstract:A novel inverse CeO2/CuO catalyst for Preferential Oxidation of CO in H2-rich stream (CO-PROX) has been developed on the basis of a hypothesis extracted from previous work of the group (JACS 2007, 129, 12064). Possible separation of the two competing Oxidation reactions involved in the process (of CO and H2, respectively) is the key to modulation of overall CO-PROX activity and is based on involvement of different sites as most active ones for each of the two reactions. Achievement of large size CuO particles and adequate CeO2−CuO interfacial configurations in the inverse catalyst apparently allows appreciable enhancement of the catalytic properties of this kind of system for CO-PROX, constituting an interesting alternative to classic direct configurations so far explored for this process. Reasons for such behavior are analyzed on the basis of operando-XRD, -XAFS, and -DRIFTS studies.
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Preferential Oxidation of co in rich h2 over cuo ceo2 operando drifts analysis of deactivating effect of co2 and h2o
Journal of Catalysis, 2009Co-Authors: D Gamarra, A MartinezariasAbstract:A catalyst of copper oxide supported on nanostructured ceria has been examined with the aim of exploring deactivating effects produced by CO2 or H2O presence on its activity for Preferential Oxidation of CO in a H2-rich stream. For this purpose, the catalyst is explored by means of operando-DRIFTS experiments. The results allow determining most relevant deactivating effects induced by CO2 and H2O. These are mainly related to modifications of interfacial sites upon formation of specific carbonates and a blocking effect induced by the presence of adsorbed molecular water, respectively, which limit redox/catalytic activity of the interfacial zone of the catalyst active for CO Oxidation. Such modifications are directly evidenced by the difficulties of ceria to promote the generation of partially reduced states at interfacial sites of the dispersed copper oxide particles or to propagate the reduction over such particles, which affects to the hydrogen Oxidation activity of the catalyst, leading on the whole to a general decrease of the CO-PROX performance of the system.
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catalytic processes during Preferential Oxidation of co in h2 rich streams over catalysts based on copper ceria
Journal of Power Sources, 2007Co-Authors: D Gamarra, Aitor Hornes, Zs Koppany, Z Schay, G Munuera, J Soria, A MartinezariasAbstract:Nanostructured catalysts based on combinations between oxidised copper and cerium entities prepared by two different methods (impregnation of ceria and coprecipitation of the two components within reverse microemulsions) have been examined with respect to their catalytic performance for Preferential Oxidation of CO in a H2-rich stream (CO-PROX). Correlations between their catalytic and redox properties are established on the basis of parallel analyses of temperature programmed reduction results employing both H2 and CO as reactants as well as by XPS. Although general catalytic trends can be directly correlated with the redox properties observed upon separate interactions with each of the two reductants (CO and H2), the existence of interferences between both reductants must be considered to complete details for such activity/redox correlation. Differences in the nature of the active oxidised copper–cerium contacts present in each case determine the catalytic properties of these systems for the CO-PROX process.
Tao Zhang - One of the best experts on this subject based on the ideXlab platform.
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local structure of pt species dictates remarkable performance on pt al2o3 for Preferential Oxidation of co in h2
Applied Catalysis B-environmental, 2021Co-Authors: Jian Lin, Yang Chen, Xiaoli Pan, Xiaodong Wang, Tao ZhangAbstract:Abstract State-of-the-art production of industrial hydrogen predominantly derives from the reforming of hydrocarbons. However, the unavoidable ∼1 % CO in this hydrogen resource usually poisons proton-exchange-membrane fuel cells (PEMFCs) and other applications. An effective solution to eliminate CO involves the Preferential Oxidation of CO in H2-rich stream (PROX). Here, we report that ∼1.4 nm Pt nanoparticles supported on inert substrate (Al2O3) can catalyze total CO conversion and CO2 selectivity in a temperature range from −30 to 120 °C. Detailed characterizations indicate that this remarkable performance is determined by the local structure of Pt active centers. The ensemble of Pt(OH) and metallic Pt plays a more critical role compared with PtOx or the only Pt°. On this ensemble, O2 activation is favored while CO adsorption is weakened and H2 adsorption is inhibited, which facilitate the Preferential Oxidation of CO rather than H2, thus enabling a broad temperature window for 100 % selective CO removal.
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highly active subnano rh fe oh x catalyst for Preferential Oxidation of co in h2 rich stream
Applied Catalysis B-environmental, 2016Co-Authors: Xiaodong Wang, Jian Lin, H R Guan, Tao ZhangAbstract:Abstract A novel catalyst formulation of 3.1 wt.% Rh/Fe(OH) x was prepared via a co-precipitation method and investigated for CO Preferential Oxidation in H 2 -rich stream. This catalyst exhibited a wider temperature range of 20–70 °C for CO total removal and better resistance to CO 2 and H 2 O compared with the standard gold catalyst, standing out as the best Rh-based catalyst ever. The Rh species were highly dispersed in a subnano scale of ∼1 nm and improved the reducibility of Fe(OH) x support. The adsorption of O 2 was thus promoted over the reduced support, together with the weakened CO adsorption over the Rh clusters, permitting a non-competitive Langmuir–Hinshelwood mechanism through the elementary reaction of CO (ad) + O (ad) . The reaction rate equation of r = k [CO] 0.73 [O 2 ] 0.64 and small apparent activation energy of 24 kJ mol −1 were then derived from the kinetic studies.
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highly efficient catalysis of Preferential Oxidation of co in h2 rich stream by gold single atom catalysts
ACS Catalysis, 2015Co-Authors: Tao Zhang, Botao Qiao, Jiaxin Liu, Yanggang Wang, Qingquan Lin, Xiaoyan Liu, Jingyue LiuAbstract:Preferential Oxidation of CO (PROX) in H2-rich stream is critical to the production of clean H2 for the H2-based fuel cells, which provide clean and efficient energy conversion. Development of highly active and selective PROX catalysts is highly desirable but proved to be extremely challenging. Here we report that CeO2-supported Au single atoms (Au1/CeO2) are highly active, selective, and extremely stable for PROX at the PEMFC working temperature (∼80 °C) with >99.5% CO conversion over a wide temperature window, 70–120 °C (or 50–100 °C, depending on the Au loading). The high CO conversion realized at high temperatures is attributed to the unique property of single-atom catalysts that is unable to dissociatively adsorb H2 and thus has a low reactivity toward H2 Oxidation. This strategy is proven in general and can be extended to other oxide-supported Au atoms (e.g., Au1/FeOx), which may open a new window for the efficient catalysis of the PROX reaction.
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remarkable effects of hydroxyl species on low temperature co Preferential Oxidation over ir fe oh x catalyst
Journal of Catalysis, 2014Co-Authors: Jian Lin, Xiaodong Wang, Botao Qiao, H R Guan, Chongyan Ruan, Wansheng Zhang, Tao ZhangAbstract:Fe(oh)(x)-supported noble metal catalysts exhibited good performance in low-temperature co Oxidation or co Preferential Oxidation (prox), which usually resulted from the high reducibility of fe(oh)(x,) however, we found here that the use of fe(oh) x promoted the formation of oh species during prox over ir/fe(oh)(x) catalysts, which not only greatly lowered the temperature for 100% co conversion, even to room temperature, but also improved the stability. these oh species originated from the reaction between the adsorbed o on fe2+ sites and the adsorbed h on ir sites. they changed the reaction route for the Oxidation of co through adsorbed co and oh with lower activation energy (ea: similar to 5.2 kj/mol) rather than through adsorbed co and o (ea: similar to 15.4 kj/mol). with further time-resolved mass spectroscopy and diffuse reflectance infrared spectroscopy, the oh species, prior to the adsorbed 0, were proved to react with co directly. (c) 2014 elsevier inc. all rights reserved.
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recent advances in Preferential Oxidation of co reaction over platinum group metal catalysts
ACS Catalysis, 2012Co-Authors: Tao ZhangAbstract:Preferential Oxidation of CO (PROX) is an important reaction for removing small amounts of CO to a parts-per-million level from the hydrogen-rich stream, which will be ultimately supplied as a fuel to polymer–electrolyte membrane fuel cells. The key to the application of PROX is to develop a highly active and selective catalyst that operates well in a wide temperature window (e.g., 80–180 °C) and has good resistance to CO2 and steam. In the past decades, various catalyst formulations have been developed, among which platinum group metal catalysts, including Pt, Ru, and Ir—in particular, those modified with promoters such as alkali metals and reducible metal oxides—have received a great deal of attention for their significantly improved catalytic activities in the low-temperature range. In this minireview, the recent advances of the platinum group metal catalysts for the PROX reaction are summarized, including performances of unpromoted and promoted catalysts, reaction mechanisms, and kinetics. In addition...
J A Odriozola - One of the best experts on this subject based on the ideXlab platform.
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gold supported on cuox ceo2 catalyst for the purification of hydrogen by the co Preferential Oxidation reaction prox
Fuel, 2014Co-Authors: Oscar H Laguna, Willinton Y Hernandez, M A Centeno, Gurutze Arzamendi, L M Gandia, J A OdriozolaAbstract:Hydrogen produced from the conversion of hydrocarbons or alcohols contains variable amounts of CO that should be removed for some applications such as feeding low-temperature polymer electrolyte membrane fuel cells (PEMFCs). The CO Preferential Oxidation reaction (PROX) is particularly well-suited for hydrogen purification for portable and on-board applications. In this work, the synthesis and characterization by XRF, BET, XRD, Raman spectroscopy and H2-TPR of a gold catalyst supported on a copper−cerium mixed oxide (AuCeCu) for the PROX reaction are presented. The comparison of this catalyst with the copper–cerium mixed oxide (CeCu) revealed that the experimental procedure used for the deposition of gold gave rise to the loss of reducible material by copper lixiviation. However, the AuCeCu solid was more active for CO Oxidation at low temperature. A kinetic study has been carried over the AuCeCu catalyst for the PROX reaction and compared with that of the CeCu catalyst. The main difference between the models affected the contribution of the CO adsorption term. This fact may be related to the surface electronic activity produced by the interaction of the cationic species in the AuCeCu solid, able to create more active sites for the CO adsorption and activation in the presence of gold.
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gold supported on metal doped ceria catalysts m zr zn and fe for the Preferential Oxidation of co prox
Journal of Catalysis, 2010Co-Authors: Oscar H Laguna, M A Centeno, Romero F Sarria, J A OdriozolaAbstract:Abstract A series of ceria oxides doped with 10 mol.% of Zr, Zn and Fe have been prepared by a pseudo sol–gel method throughout the thermal decomposition of the corresponding metallic propionates. With these supports, 1 wt.% gold catalysts were prepared by the deposition–precipitation method. All the solids were characterized by means of XRF, N 2 adsorption, XRD, Raman spectroscopy and SEM techniques, and their catalytic activity toward Preferential Oxidation of CO (PROX) reaction tested. The results showed solid solution when doping with Zr and Fe and ZnO surface segregation in the case of Zn. We demonstrate that gold dispersion depends on not only the oxygen vacancy concentration but also the nature of the doping agent. Finally, the catalytic activity was highly promoted by gold in all cases, being the doped gold catalysts more active than Au/CeO 2 at low temperature.
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modified cryptomelane type manganese dioxide nanomaterials for Preferential Oxidation of co in the presence of hydrogen
Catalysis Today, 2010Co-Authors: Willinton Y Hernandez, M A Centeno, F Romerosarria, Svetlana Ivanova, M Montes, J A OdriozolaAbstract:Abstract Transition metal (Cu, Co, Ni and Zn)-modified cryptomelane-type manganese dioxide nanomaterials were synthesized by the milling method. The obtained solids have been characterized by means of X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy (SEM and TEM), N2 adsorption–desorption measurements at 77 K, Raman spectroscopy and temperature programmed reduction (TPR-H2) showing similar structural and textural properties. All the solids were active in the Preferential Oxidation of CO in the presence of hydrogen (PROX), being the modified with copper the most active. The catalytic activity correlates fairly well with the TPR results, finding higher CO conversion for the material with higher reducibility (OMS-Cu). The O2 selectivity, measured as ([CO]in − [CO]out/2[O2]in − [O2]out) × 100, is very similar for all synthesized materials.
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iron modified ceria and au ceria catalysts for total and Preferential Oxidation of co tox and prox
Catalysis Today, 2010Co-Authors: Oscar H Laguna, M A Centeno, F Romerosarria, Gurutze Arzamendi, L M Gandia, J A OdriozolaAbstract:Abstract Iron-modified ceria supports containing different molar percentages of Fe (0%, 10%, 25%, and 50%) were synthesized by thermal decomposition of the metal propionates. The formation of a Ce–Fe oxide solid solution is evidenced through XRF, XRD, BET and Raman spectroscopy. For iron contents above 25% the formation of α-Fe2O3 was detected, pointing out the formation of the isolated oxides. The catalytic activity of the Fe-modified catalysts in the Total Oxidation of CO reaction (TOX) is higher than for the bare CeO2 material. The synergy between Ce and Fe shows a maximum for 10% Fe content (CeFe10), catalyst that shows the highest CO conversion per atom of Fe incorporated. Gold catalyst was also prepared on CeFe10 and its catalytic activity compared with Au/CeO2 catalyst. The addition of iron to the gold catalyst resulted in an enhancement of the catalytic activity for CO Oxidation especially at low temperature. This Au/CeFe10 catalyst was also active and selective with excellent stability in the Preferential Oxidation of CO (PROX) showing a higher CO conversion than the Au/CeO2 catalyst at temperatures below 150 °C being hardly affected by the presence of CO2 and H2O in the gas stream.
Hui Wang - One of the best experts on this subject based on the ideXlab platform.
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co Preferential Oxidation in h2 rich stream over a cuo ceo2 catalyst with high h2o and co2 tolerance
Fuel, 2013Co-Authors: Huaqing Zhu, Hui Wang, Zhangfeng Qin, Jianfei Ding, Lichun Huang, Jianguo WangAbstract:Abstract The CuO/CeO2 catalysts are prepared by an improved incipient wetness impregnation method with ammonia as chelating agent for CO Preferential Oxidation (PROX). The effects of CuO loadings of the catalysts and the presence of H2O and CO2 in the reaction stream on the catalytic performance are investigated. The CuO/CeO2 catalyst with 10.0 wt.% CuO loading has high activity and stability for the CO-PROX. In the long-term stability test under the realistic reaction condition with 10% H2O and 15% CO2 in the reactant stream, 100% CO conversion can maintain for 1600 h at 140–150 °C with 85–75% selectivity. The catalysts are characterized by means of XRD, H2-TPR, and CO-TPR. The results show that the high activity of the CuO/CeO2 catalyst is closely related to the fine-dispersed CuO species strongly interacting with CeO2 support.
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Preferential Oxidation of co in h2 rich stream over cuo ce1 xtixo2 catalysts
Applied Catalysis B-environmental, 2010Co-Authors: Huaqing Zhu, Hui Wang, Zhangfeng Qin, Lichun Huang, Jianguo WangAbstract:Abstract CuO/Ce 1− x Ti x O 2 prepared by sol–gel impregnation was used as catalysts for the Preferential Oxidation (PROX) of CO in H 2 -rich stream. The effects of support composition, catalyst calcination temperature as well as the presence of H 2 O and CO 2 in the reaction stream on the catalytic performance of CuO/Ce 1− x Ti x O 2 were investigated. The results indicated that the catalyst CuO/Ce 0.8 Ti 0.2 O 2 exhibits the highest activity and the optimal temperature for the catalyst calcination is 500 °C. The presence of H 2 O and CO 2 in the reaction stream has a negative effect on the catalytic activity and stability of CuO/Ce 0.8 Ti 0.2 O 2 . The negative effect of CO 2 on the catalyst stability is stronger than that of H 2 O, suggesting that the accumulation of carbonate species may be the main reason for catalyst deactivation. The characterization by means of XRD, HRTEM, and H 2 -TPR indicated that the doping of TiO 2 in CeO 2 enhances the surface area of the composite oxide support, decreases its particle size, and promotes the dispersion of active copper species. The strong interaction between TiO 2 and CeO 2 in the support as well as the interfacial interaction between CuO and the support may also contribute to the high catalytic activity of CuO/Ce 0.8 Ti 0.2 O 2 .
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deactivation of a au ceo2 co3o4 catalyst during co Preferential Oxidation in h2 rich stream
Journal of Catalysis, 2009Co-Authors: Hui Wang, Feixue Liang, Guofu Wang, Jianguo WangAbstract:Abstract The origins of the deactivation of a Au/CeO2–Co3O4 catalyst during CO Preferential Oxidation (PROX) are investigated in detail by means of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed Oxidation of oxygen (O2-TPO), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A possible mechanism involving –OOH intermediate is proposed and used to explain the deactivation in the long-term stability test of CO PROX. The aggregation or sintering of the Au particles is excluded from the origins of deactivation by HRTEM and XRD. The deactivation of the catalyst is mainly due to an intrinsic transformation in the chemical state of the gold species and the support oxides in the Au/CeO2–Co3O4 catalyst. The XPS, XRD, and H2-TPR results demonstrate the reduction of ionic Au to metallic Au and of cobalt oxide to cobaltous compound. The changes of the chemical states imply a structure reordering of the catalyst surface, which will suppress the supplement of active oxygen and the formation of –OOH species, inhibit the CO Oxidation reaction, and lead to the deactivation of the catalyst. The accumulation of carbonates and H2O on the deactivated catalyst is revealed by XPS, DRIFTS, O2-TPO, and a regeneration test. They are responsible for the complete deactivation of the catalyst. The hydration of the catalyst surface may play a more important role than the formation of carbonates in the deactivation of the catalyst.
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Preferential Oxidation of co in h2 rich stream over au ceo2 co3o4 catalysts
Catalysis Communications, 2008Co-Authors: Hui Wang, Feixue Liang, Guofu Wang, Huaqing Zhu, Zhangfeng Qin, Jianguo WangAbstract:Au/CeO2–Co3O4 catalysts with a Ce/Co atomic ratio from 0.1 to 0.6 were prepared by deposition–precipitation; their catalytic performance in Preferential Oxidation (PROX) of CO in H2 rich stream was investigated. Au/CeO2–Co3O4 exhibits much higher catalytic activity in CO PROX than Au/Co3O4 and Au/CeO2; over Au/CeO2–Co3O4, 100% CO conversion with 75% selectivity to CO2 can be achieved even at ambient temperature. Typically, for CO PROX at 80 °C over Oxidation pretreated Au/CeO2–Co3O4 (Ce/Co = 0.2), 91% CO conversion and 51% selectivity to CO2 can last for 260 h.