Pub Date : 2017-03-03DOI: 10.1080/2055074X.2016.1275379
L. Merte, J. Gustafson, M. Shipilin, Chu Zhang, E. Lundgren
Graphical Abstract We have studied the oxidation and reduction of iron in an Fe-doped MgO single crystal by , and using ambient-pressure XPS and NEXAFS. Surface charging of the crystal was rendered manageable by the elevated temperatures and the gas atmospheres. The oxidation state of iron was found to shift reversibly between the and states, with a strong asymmetry in the rates; while oxidation by or was nearly complete at , reduction by began at , and was still incomplete at . Grazing-incidence XRD characterization of the crystal indicated the presence of octahedral, nanoscale inclusions assigned to the magnesioferrite spinel (). It is proposed that the redox behavior observed involves interconversion between the rock-salt (O) and spinel phases, with the more open lattice containing enabling more rapid ion diffusion and thus more facile oxidation compared to reduction.
{"title":"Redox behavior of iron at the surface of an O(100) single crystal studied by ambient-pressure photoelectron spectroscopy","authors":"L. Merte, J. Gustafson, M. Shipilin, Chu Zhang, E. Lundgren","doi":"10.1080/2055074X.2016.1275379","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1275379","url":null,"abstract":"Graphical Abstract We have studied the oxidation and reduction of iron in an Fe-doped MgO single crystal by , and using ambient-pressure XPS and NEXAFS. Surface charging of the crystal was rendered manageable by the elevated temperatures and the gas atmospheres. The oxidation state of iron was found to shift reversibly between the and states, with a strong asymmetry in the rates; while oxidation by or was nearly complete at , reduction by began at , and was still incomplete at . Grazing-incidence XRD characterization of the crystal indicated the presence of octahedral, nanoscale inclusions assigned to the magnesioferrite spinel (). It is proposed that the redox behavior observed involves interconversion between the rock-salt (O) and spinel phases, with the more open lattice containing enabling more rapid ion diffusion and thus more facile oxidation compared to reduction.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1275379","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48054484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-22DOI: 10.1080/2055074X.2016.1274118
V. Marchionni, Anastasios Kambolis, M. Nachtegaal, O. Kröcher, D. Ferri
Abstract The operando methodology dictates not only that catalysts are analysed during reaction while activity and selectivity are monitored by analytical methods, but also that the cell in which the measurement is carried out performs as a catalytic reactor. A cell (Chiarello et al., Rev. Sci. Inst. 85 (2014) 074102) used to conduct spectroscopy and diffraction measurements under operando conditions was tested for CO oxidation on a 2 wt% Pt/Al2O3 catalyst and compared with measurements in a conventional quartz catalytic reactor to demonstrate its suitability to derive kinetic data. High energy X-ray diffraction data were collected during alternate CO and O2 pulses under differential conditions to demonstrate the extent of loss of order of the Pt particles upon exposure to the O2 pulse. The presence of a surface oxide species places the catalyst in a higher activity regime compared to the fully reduced one.
{"title":"High energy X-ray diffraction and IR spectroscopy of Pt/Al2O3 during CO oxidation in a novel catalytic reactor cell","authors":"V. Marchionni, Anastasios Kambolis, M. Nachtegaal, O. Kröcher, D. Ferri","doi":"10.1080/2055074X.2016.1274118","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1274118","url":null,"abstract":"Abstract The operando methodology dictates not only that catalysts are analysed during reaction while activity and selectivity are monitored by analytical methods, but also that the cell in which the measurement is carried out performs as a catalytic reactor. A cell (Chiarello et al., Rev. Sci. Inst. 85 (2014) 074102) used to conduct spectroscopy and diffraction measurements under operando conditions was tested for CO oxidation on a 2 wt% Pt/Al2O3 catalyst and compared with measurements in a conventional quartz catalytic reactor to demonstrate its suitability to derive kinetic data. High energy X-ray diffraction data were collected during alternate CO and O2 pulses under differential conditions to demonstrate the extent of loss of order of the Pt particles upon exposure to the O2 pulse. The presence of a surface oxide species places the catalyst in a higher activity regime compared to the fully reduced one.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1274118","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45938737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-22DOI: 10.1080/2055074X.2016.1262569
G. Kalantzopoulos, F. Lundvall, A. Lind, B. Arstad, D. Chernyshov, H. Fjellvåg, D. Wragg
Abstract We have studied the structural behavior of SAPO-37 during calcination using simultaneous in situ powder X-ray diffraction (PXRD) and mass spectroscopy (MS) in addition to ex situ thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A spike in the unit cell volume corresponding to template removal (tracked using the occupancy of the crystallographic sites in the SAPO-37 cages) is revealed from the XRD data and is strongly correlated with the DSC curve. The occupancy of the different template molecules in the faujasite (FAU) and sodalite (SOD) cages is strongly related to the two mass loss steps observed in the TGA data. The templates act as a physical stabilizing agent, not allowing any substantial unit cell response to temperature changes until they are removed. The FAU cages and SOD cages have different thermal response to the combustion of each template. The FAU cages are mainly responsible for the unit cell volume expansion observed after the template combustion. This expansion seems to be related with residual coke from template combustion. We could differentiate between the thermal response of oxygen and T-atoms. The T–O–T angle between two double 6-rings and a neighboring T–O–T linkage shared by SOD and FAU had different response to the thermal events. We were able to monitor the changes in the positions of oxygen and T-atoms during the removal of TPA+ and TMA+. Large changes to the framework structure at the point of template removal may have a significant effect on the long-term stability of the material in its activated form.
{"title":"SAPO-37 microporous catalysts: revealing the structural transformations during template removal","authors":"G. Kalantzopoulos, F. Lundvall, A. Lind, B. Arstad, D. Chernyshov, H. Fjellvåg, D. Wragg","doi":"10.1080/2055074X.2016.1262569","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1262569","url":null,"abstract":"Abstract We have studied the structural behavior of SAPO-37 during calcination using simultaneous in situ powder X-ray diffraction (PXRD) and mass spectroscopy (MS) in addition to ex situ thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A spike in the unit cell volume corresponding to template removal (tracked using the occupancy of the crystallographic sites in the SAPO-37 cages) is revealed from the XRD data and is strongly correlated with the DSC curve. The occupancy of the different template molecules in the faujasite (FAU) and sodalite (SOD) cages is strongly related to the two mass loss steps observed in the TGA data. The templates act as a physical stabilizing agent, not allowing any substantial unit cell response to temperature changes until they are removed. The FAU cages and SOD cages have different thermal response to the combustion of each template. The FAU cages are mainly responsible for the unit cell volume expansion observed after the template combustion. This expansion seems to be related with residual coke from template combustion. We could differentiate between the thermal response of oxygen and T-atoms. The T–O–T angle between two double 6-rings and a neighboring T–O–T linkage shared by SOD and FAU had different response to the thermal events. We were able to monitor the changes in the positions of oxygen and T-atoms during the removal of TPA+ and TMA+. Large changes to the framework structure at the point of template removal may have a significant effect on the long-term stability of the material in its activated form.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1262569","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42313973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-21DOI: 10.1080/2055074X.2016.1277655
D. Martin, Donato Decarolis, R. Tucoulou, G. Martínez-Criado, Andrew M. Beale
Abstract It is well known that particle size plays an important role in catalytic activity although the reason(s) why significant changes in activity are observed to occur with small changes in size are not well understood. The presence of particular facets, metal-support interactions, and redox state etc., are also capable of playing a role. The difficulty in realising which features are pertinent in a catalytic process stems from issues regarding sample complexity in typical heterogeneous catalysts, as well as technical challenges with instruments used to investigate samples in terms of their sensitivity and capability to distinguish between a specific vs. ensemble response in catalytically active vs. spectator species. We show here how the combination of using a synthesis method which achieves a discrete dispersion of metal Pd nanoparticles with a very narrow particle size distribution (σ ~ 1 nm) in combination with nano-beam X-ray spectroscopy allows us to follow the changes in redox state with time. Importantly, the data are obtained in one example, from an illuminating spot containing ca. 20 nanoparticles with an extremely small size distribution.
{"title":"Towards the interrogation of the behaviour of a single nanoparticle under realistic catalytic reaction conditions","authors":"D. Martin, Donato Decarolis, R. Tucoulou, G. Martínez-Criado, Andrew M. Beale","doi":"10.1080/2055074X.2016.1277655","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1277655","url":null,"abstract":"Abstract It is well known that particle size plays an important role in catalytic activity although the reason(s) why significant changes in activity are observed to occur with small changes in size are not well understood. The presence of particular facets, metal-support interactions, and redox state etc., are also capable of playing a role. The difficulty in realising which features are pertinent in a catalytic process stems from issues regarding sample complexity in typical heterogeneous catalysts, as well as technical challenges with instruments used to investigate samples in terms of their sensitivity and capability to distinguish between a specific vs. ensemble response in catalytically active vs. spectator species. We show here how the combination of using a synthesis method which achieves a discrete dispersion of metal Pd nanoparticles with a very narrow particle size distribution (σ ~ 1 nm) in combination with nano-beam X-ray spectroscopy allows us to follow the changes in redox state with time. Importantly, the data are obtained in one example, from an illuminating spot containing ca. 20 nanoparticles with an extremely small size distribution.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1277655","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49227741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-21DOI: 10.1080/2055074X.2016.1263177
Zixue Ma, Zhenwei Wu, Jeffrey T. Miller
Abstract Silica supported, 2 nm Pt and Pt–Cu catalysts with different Cu:Pt atomic ratios and similar size were evaluated for propane dehydrogenation at 550 °C. Monometallic Pt showed low propylene selectivity of 61% at 20% conversion and a TOR of 0.06 s−1. For the Pt–Cu catalysts, the dehydrogenation selectivity and TOR continuously increased with increasing Cu level in the nanoparticle, to eventually 96% selective at 20% conversion with a TOR of 0.98 s−1 for a catalyst with a Cu:Pt atomic ratio of 7.3. Synchrotron in situ X-ray diffraction and X-ray absorption spectroscopy analysis showed that Pt–Cu catalysts with increasing Cu loading formed solid solution type bimetallic structures. For example, a Pt–Cu catalyst with Cu:Pt atomic ratio of 7.3 formed solid solution containing 87% Cu. In this catalyst, the Pt active sites were geometrically isolated by the inactive metallic Cu, which was suggested to be responsible for high selectivity to propane dehydrogenation. The Cu neighbors surrounding the Pt also likely modified the energy level of Pt 5d orbitals and contribute to a TOR about 16 times higher than that of monometallic Pt.
{"title":"Effect of Cu content on the bimetallic Pt–Cu catalysts for propane dehydrogenation","authors":"Zixue Ma, Zhenwei Wu, Jeffrey T. Miller","doi":"10.1080/2055074X.2016.1263177","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1263177","url":null,"abstract":"Abstract Silica supported, 2 nm Pt and Pt–Cu catalysts with different Cu:Pt atomic ratios and similar size were evaluated for propane dehydrogenation at 550 °C. Monometallic Pt showed low propylene selectivity of 61% at 20% conversion and a TOR of 0.06 s−1. For the Pt–Cu catalysts, the dehydrogenation selectivity and TOR continuously increased with increasing Cu level in the nanoparticle, to eventually 96% selective at 20% conversion with a TOR of 0.98 s−1 for a catalyst with a Cu:Pt atomic ratio of 7.3. Synchrotron in situ X-ray diffraction and X-ray absorption spectroscopy analysis showed that Pt–Cu catalysts with increasing Cu loading formed solid solution type bimetallic structures. For example, a Pt–Cu catalyst with Cu:Pt atomic ratio of 7.3 formed solid solution containing 87% Cu. In this catalyst, the Pt active sites were geometrically isolated by the inactive metallic Cu, which was suggested to be responsible for high selectivity to propane dehydrogenation. The Cu neighbors surrounding the Pt also likely modified the energy level of Pt 5d orbitals and contribute to a TOR about 16 times higher than that of monometallic Pt.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1263177","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46921108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-21DOI: 10.1080/2055074X.2016.1267296
J. Brazier, M. Newton, Elena M. Barreiro, S. Parry, L. A. Adrio, Christopher J. Mulligan, K. Hellgardt, K. K. Hii, P. Thompson, Rachel Nichols, B. Nguyen
Abstract The reduction of γ-Al2O3-supported PdO in flowing aqueous ethanol was investigated. Quick EXAFS (QEXAFS) performed at the Pd K-edge reveals that the presence of Cl can have a profound effect on the reduction process. At low loadings of Pd (1 wt-%), the size dependency of the process is inverted, compared to Cl-free samples. The extent of reduction was found to be dependent on loading/particles size. It is shown, using in situ QEXAFS at the Cl K- and Pd L3-edges, that residual Cl is not removed by the flowing solvent mixture, even at an elevated temperature of 350 K. The origins of these behaviours are discussed in terms of the differing effects that Cl may have when bonded to oxidic or reduced metal centres and the results were compared to earlier observations made on the effects of Cl on commercial polyurea encapsulated Pd ENCAT™ NP 30 catalysts.
{"title":"Effects of Cl on the reduction of supported PdO in ethanol/water solvent mixtures","authors":"J. Brazier, M. Newton, Elena M. Barreiro, S. Parry, L. A. Adrio, Christopher J. Mulligan, K. Hellgardt, K. K. Hii, P. Thompson, Rachel Nichols, B. Nguyen","doi":"10.1080/2055074X.2016.1267296","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1267296","url":null,"abstract":"Abstract The reduction of γ-Al2O3-supported PdO in flowing aqueous ethanol was investigated. Quick EXAFS (QEXAFS) performed at the Pd K-edge reveals that the presence of Cl can have a profound effect on the reduction process. At low loadings of Pd (1 wt-%), the size dependency of the process is inverted, compared to Cl-free samples. The extent of reduction was found to be dependent on loading/particles size. It is shown, using in situ QEXAFS at the Cl K- and Pd L3-edges, that residual Cl is not removed by the flowing solvent mixture, even at an elevated temperature of 350 K. The origins of these behaviours are discussed in terms of the differing effects that Cl may have when bonded to oxidic or reduced metal centres and the results were compared to earlier observations made on the effects of Cl on commercial polyurea encapsulated Pd ENCAT™ NP 30 catalysts.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1267296","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46440048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-16DOI: 10.1080/2055074X.2016.1263178
A. Rochet, Aline Ribeiro Passos, C. Legens, V. Briois
Abstract Insights into the nickel sulphide speciation of a dried oxidic Ni catalyst supported on delta-alumina were obtained by temperature-programmed sulphidation monitored by Quick-X-ray absorption with online mass spectrometry. Combination with Raman spectroscopy enabled the phase identification of sulphide phases isolated by multivariate curve regression with alternating least square analysis of the time-resolved X-ray absorption spectroscopy data.
{"title":"Sulphidation study of a dried Ni/Al2O3 catalyst by time-resolved XAS-MS combined with in situ Raman spectroscopy and multivariate Quick-XAS data analysis","authors":"A. Rochet, Aline Ribeiro Passos, C. Legens, V. Briois","doi":"10.1080/2055074X.2016.1263178","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1263178","url":null,"abstract":"Abstract Insights into the nickel sulphide speciation of a dried oxidic Ni catalyst supported on delta-alumina were obtained by temperature-programmed sulphidation monitored by Quick-X-ray absorption with online mass spectrometry. Combination with Raman spectroscopy enabled the phase identification of sulphide phases isolated by multivariate curve regression with alternating least square analysis of the time-resolved X-ray absorption spectroscopy data.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1263178","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46138274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-16DOI: 10.1080/2055074X.2017.1281717
N. Martin, Johan Nilsson, M. Skoglundh, Emma C. Adams, Xueting Wang, G. Smedler, A. Raj, D. Thompsett, G. Agostini, S. Carlson, K. Norén, P. Carlsson
Graphical Abstract Abstract Methane oxidation over Pd–Pt/ model catalysts calcined at three different conditions is investigated using operando diffuse reflectance infrared Fourier transform spectroscopy and mass spectrometry, and in situ X-ray absorption spectroscopy while cycling the feed gas stoichiometry between lean (net-oxidising) and rich (net-reducing) conditions. When calcined in air, alloy Pd–Pt nanoparticles are present only on catalysts subjected to elevated temperature () whereas calcination at lower temperature (500 ) leads to segregated Pt and Pd nanoparticles on the support. Here, we show that the alloy Pd–Pt nanoparticles undergo reversible changes in surface structure and composition during transient methane oxidation exposing a PdO surface during lean conditions and a metallic Pd–Pt surface (Pd enriched) under rich conditions. Alloyed particles seem more active for methane oxidation than their monometallic counterparts and, furthermore, an increased activity for methane oxidation is clearly observed under lean conditions when PdO has developed on the surface, analogous to monometallic Pd catalysts. Upon introducing rich conditions, partial oxidation of methane dominates over total oxidation forming adsorbed carbonyls on the noble metal particles. The carbonyl spectra for the three samples show clear differences originating from different surfaces exposed by alloyed vs. non-alloyed particles. The kinetics of the noble metal oxidation and reduction processes as well as carbonyl formation during transient methane oxidation are discussed.
{"title":"Study of methane oxidation over alumina supported Pd–Pt catalysts using operando DRIFTS/MS and in situ XAS techniques","authors":"N. Martin, Johan Nilsson, M. Skoglundh, Emma C. Adams, Xueting Wang, G. Smedler, A. Raj, D. Thompsett, G. Agostini, S. Carlson, K. Norén, P. Carlsson","doi":"10.1080/2055074X.2017.1281717","DOIUrl":"https://doi.org/10.1080/2055074X.2017.1281717","url":null,"abstract":"Graphical Abstract Abstract Methane oxidation over Pd–Pt/ model catalysts calcined at three different conditions is investigated using operando diffuse reflectance infrared Fourier transform spectroscopy and mass spectrometry, and in situ X-ray absorption spectroscopy while cycling the feed gas stoichiometry between lean (net-oxidising) and rich (net-reducing) conditions. When calcined in air, alloy Pd–Pt nanoparticles are present only on catalysts subjected to elevated temperature () whereas calcination at lower temperature (500 ) leads to segregated Pt and Pd nanoparticles on the support. Here, we show that the alloy Pd–Pt nanoparticles undergo reversible changes in surface structure and composition during transient methane oxidation exposing a PdO surface during lean conditions and a metallic Pd–Pt surface (Pd enriched) under rich conditions. Alloyed particles seem more active for methane oxidation than their monometallic counterparts and, furthermore, an increased activity for methane oxidation is clearly observed under lean conditions when PdO has developed on the surface, analogous to monometallic Pd catalysts. Upon introducing rich conditions, partial oxidation of methane dominates over total oxidation forming adsorbed carbonyls on the noble metal particles. The carbonyl spectra for the three samples show clear differences originating from different surfaces exposed by alloyed vs. non-alloyed particles. The kinetics of the noble metal oxidation and reduction processes as well as carbonyl formation during transient methane oxidation are discussed.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2017.1281717","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41309907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-14DOI: 10.1080/2055074X.2017.1278890
E. Gibson, E. Crabb, D. Gianolio, A. Russell, D. Thompsett, P. Wells
Abstract A combined operando XAFS/DRIFTS study on CeOx/Pt/Al2O3 catalysts has been performed during CO oxidation and provides insights into the changes in nanoparticle structure and adsorbed species during the reaction profile. The onset of CO2 formation is shown to be concurrent with a rapid re-oxidation of the Pt nanoparticles, evidenced by XAFS spectroscopy, and the loss of bridge bonded CO adsorbed on Pt, as shown by simultaneous DRIFTS acquisition. The continued appearance of linear bound CO on the catalyst surface is shown to remain long after catalytic light off. The interaction of Pt and CeOx is evidenced by the improved performance towards CO oxidation, compared to the non-CeOx modified Pt/Al2O3, and changes in the CO adsorption properties on Pt previously linked to Pt-CeO2 interfaces.
{"title":"Understanding the role of promoters in catalysis: operando XAFS/DRIFTS study of CeOx/Pt/Al2O3 during CO oxidation","authors":"E. Gibson, E. Crabb, D. Gianolio, A. Russell, D. Thompsett, P. Wells","doi":"10.1080/2055074X.2017.1278890","DOIUrl":"https://doi.org/10.1080/2055074X.2017.1278890","url":null,"abstract":"Abstract A combined operando XAFS/DRIFTS study on CeOx/Pt/Al2O3 catalysts has been performed during CO oxidation and provides insights into the changes in nanoparticle structure and adsorbed species during the reaction profile. The onset of CO2 formation is shown to be concurrent with a rapid re-oxidation of the Pt nanoparticles, evidenced by XAFS spectroscopy, and the loss of bridge bonded CO adsorbed on Pt, as shown by simultaneous DRIFTS acquisition. The continued appearance of linear bound CO on the catalyst surface is shown to remain long after catalytic light off. The interaction of Pt and CeOx is evidenced by the improved performance towards CO oxidation, compared to the non-CeOx modified Pt/Al2O3, and changes in the CO adsorption properties on Pt previously linked to Pt-CeO2 interfaces.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2017.1278890","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42746369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-14DOI: 10.1080/2055074X.2016.1266762
A. Kroner, M. Newton, M. Tromp, A. Russell, A. Dent, J. Evans
Abstract The effect of ceria doping by oxide surface modification and controlled metal surface modification (CSM) on the structure-function properties of Rh/γ-Al2O3 catalysts in the process of CO oxidation were studied by a combined array of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)/Energy Dispersive X-ray Absorption Fine Structure/Mass Spectrometry techniques applied simultaneously under time-resolved, in situ conditions in the temperature range of 298–573 K. The addition of each promoter element by CSM exhibits multiple effects on the catalysts structure. The DRIFTS/XAS studies indicate that CeOx facilitate the protection of Rh particles against extensive oxidation in atmospheres of air, O2 and CO, without reducing the coverage of oxidisable adsorbed CO.
{"title":"Time-resolved, in situ DRIFTS/EDE/MS studies on alumina supported Rh catalysts: effects of ceriation on the Rh catalysts in the process of CO oxidation","authors":"A. Kroner, M. Newton, M. Tromp, A. Russell, A. Dent, J. Evans","doi":"10.1080/2055074X.2016.1266762","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1266762","url":null,"abstract":"Abstract The effect of ceria doping by oxide surface modification and controlled metal surface modification (CSM) on the structure-function properties of Rh/γ-Al2O3 catalysts in the process of CO oxidation were studied by a combined array of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)/Energy Dispersive X-ray Absorption Fine Structure/Mass Spectrometry techniques applied simultaneously under time-resolved, in situ conditions in the temperature range of 298–573 K. The addition of each promoter element by CSM exhibits multiple effects on the catalysts structure. The DRIFTS/XAS studies indicate that CeOx facilitate the protection of Rh particles against extensive oxidation in atmospheres of air, O2 and CO, without reducing the coverage of oxidisable adsorbed CO.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1266762","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45311777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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