Pub Date : 2017-02-07DOI: 10.1080/2055074X.2017.1281605
M. Newton
In 2002 Banares and co-workers [1,2] took the word “operando” to define what amounts to an experimental philosophy, one that goes somewhat beyond the term that had preceded it, namely “in situ”. The central difference between these two notions is that in situ only specifies a place, whereas operando implies a specific function whatever is “operando” is working. From this it is easily observed that whilst all operando experiments are in situ, not all in situ experiments are operando. Catalysis is founded upon chemical processes that are ideally arranged to form reaction cycles that complete molecular transformations, whilst the active elements within the catalyst are stable such that they may continue to facilitate the desired conversion. The range of chemical conversions that are desired to be achieved are incredibly diverse, as are the conditions or timescales in which they may be achieved. What operando study demands is that, whatever catalytic process is desired to be studied, every effort is made to parameterise a given experiment in a manner that respects, as closely as possible, that which might be experienced by the catalyst in a real application. Whether an ideal operando experiment has ever actually been realised – as the parameter space that should be ideally adhered to is considerable is debatable. However, far more important is the stimulus the operando philosophy has lent to research in the formulation of new experimental methods and approaches that pay much more attention to process conditions than had gone before. A clear requirement for the development of operando experimentation it that one is in possession of probes that can be applied under the conditions specified by the process: methods can address issues of structure (on a wide range of length and timescales), molecular function, and reactivity so that relevant and quantitative structure function relationships (QSARS) that define the catalysis may be established. Methods that make use of the scattering, absorption, or emission of X-rays are extremely good at interrogating the structure of materials, be it physical or electronic, on length scales from the Angstrom to those of laboratory scale reactors. X-rays also have an intrinsic capacity to penetrate matter that permits much flexibility to the design of suitable reactors within which they may be studied. Importantly, in their modern forms, they may also operate on kinetically relevant timescales. Methods founded upon X-rays make ideal companions to a variety of laboratory based methods that are generally applied to the study of catalytic systems. In parallel with the evolution of operando techniques, 3rd generation synchrotron sources have proliferated and the technology associated with them has advanced to such a degree that entirely new generations of experiments, have become possible since 2002. In this issue, therefore, we highlight some of the ways that these modern X-ray methods may be applied to furthering our under
{"title":"Operando catalysis using synchrotron methods","authors":"M. Newton","doi":"10.1080/2055074X.2017.1281605","DOIUrl":"https://doi.org/10.1080/2055074X.2017.1281605","url":null,"abstract":"In 2002 Banares and co-workers [1,2] took the word “operando” to define what amounts to an experimental philosophy, one that goes somewhat beyond the term that had preceded it, namely “in situ”. The central difference between these two notions is that in situ only specifies a place, whereas operando implies a specific function whatever is “operando” is working. From this it is easily observed that whilst all operando experiments are in situ, not all in situ experiments are operando. Catalysis is founded upon chemical processes that are ideally arranged to form reaction cycles that complete molecular transformations, whilst the active elements within the catalyst are stable such that they may continue to facilitate the desired conversion. The range of chemical conversions that are desired to be achieved are incredibly diverse, as are the conditions or timescales in which they may be achieved. What operando study demands is that, whatever catalytic process is desired to be studied, every effort is made to parameterise a given experiment in a manner that respects, as closely as possible, that which might be experienced by the catalyst in a real application. Whether an ideal operando experiment has ever actually been realised – as the parameter space that should be ideally adhered to is considerable is debatable. However, far more important is the stimulus the operando philosophy has lent to research in the formulation of new experimental methods and approaches that pay much more attention to process conditions than had gone before. A clear requirement for the development of operando experimentation it that one is in possession of probes that can be applied under the conditions specified by the process: methods can address issues of structure (on a wide range of length and timescales), molecular function, and reactivity so that relevant and quantitative structure function relationships (QSARS) that define the catalysis may be established. Methods that make use of the scattering, absorption, or emission of X-rays are extremely good at interrogating the structure of materials, be it physical or electronic, on length scales from the Angstrom to those of laboratory scale reactors. X-rays also have an intrinsic capacity to penetrate matter that permits much flexibility to the design of suitable reactors within which they may be studied. Importantly, in their modern forms, they may also operate on kinetically relevant timescales. Methods founded upon X-rays make ideal companions to a variety of laboratory based methods that are generally applied to the study of catalytic systems. In parallel with the evolution of operando techniques, 3rd generation synchrotron sources have proliferated and the technology associated with them has advanced to such a degree that entirely new generations of experiments, have become possible since 2002. In this issue, therefore, we highlight some of the ways that these modern X-ray methods may be applied to furthering our under","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2017.1281605","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48877093","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 : 2016-10-01DOI: 10.1080/2055074X.2016.1252548
J. Hargreaves
Abstract This short overview summarises some of the basic considerations which should be undertaken when the Scherrer equation is applied to reflection widths in X-ray diffraction patterns of heterogeneous catalysts in order to extract meaningful information. Frequently, little account has been taken of the apparent complications arising from the presence of microstructural strain and disorder such as that which can be introduced upon doping or of anisotropic effects and such considerations are highlighted. Graphical abstract Scanning electron micrograph showing the highly anisotropic nature of biogenic iron oxide found in a natural iron ochre source.
{"title":"Some considerations related to the use of the Scherrer equation in powder X-ray diffraction as applied to heterogeneous catalysts","authors":"J. Hargreaves","doi":"10.1080/2055074X.2016.1252548","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1252548","url":null,"abstract":"Abstract This short overview summarises some of the basic considerations which should be undertaken when the Scherrer equation is applied to reflection widths in X-ray diffraction patterns of heterogeneous catalysts in order to extract meaningful information. Frequently, little account has been taken of the apparent complications arising from the presence of microstructural strain and disorder such as that which can be introduced upon doping or of anisotropic effects and such considerations are highlighted. Graphical abstract Scanning electron micrograph showing the highly anisotropic nature of biogenic iron oxide found in a natural iron ochre source.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1252548","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043515","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 : 2016-10-01DOI: 10.1080/2055074X.2016.1234116
M. Mediero-Munoyerro, J. McGregor, L. McMillan, N. Al-yassir, P. Bingham, S. Forder, C. Gorin, S. Al-Khattaf, L. Gladden, P. Midgley
Abstract The structural changes that occur in a FeOx/γ-Al2O3 catalyst during the dehydrogenation of ethylbenzene in a fluidized CREC Riser Simulator have been investigated. Chemical and morphological changes are observed to take place as a result of reaction. Electron microscopy reveals the formation of needle-like alumina structures apparently enclosing iron oxide particles. The formation of such structures at relatively low temperatures is unexpected and has not previously been reported. Additionally, X-ray diffraction and Mössbauer spectroscopy confirmed the reduction of the oxidation state of iron, from Fe2O3 (haematite) to Fe3O4 (magnetite). Iron carbides, Fe3C and ɛ-Fe2C, were detected by electron microscopy through electron diffraction and lattice fringes analysis. Carbon deposition (coking) on the catalyst surface also occurs. The observed structural changes are likely to be closely correlated with the catalytic properties of the materials, in particular with catalyst deactivation, and thereby provide important avenues for future study of this industrially important reaction. Graphical abstract Fe2O3/Al2O3 catalyst undergoes chemical and morphological changes during ethylbenzene dehydrogenation forming Al2O3 needles which appear to contain reduced Fe3O4 particles. Fe3C also forms during reaction.
{"title":"Structural changes in FeOx/γ-Al2O3 catalysts during ethylbenzene dehydrogenation","authors":"M. Mediero-Munoyerro, J. McGregor, L. McMillan, N. Al-yassir, P. Bingham, S. Forder, C. Gorin, S. Al-Khattaf, L. Gladden, P. Midgley","doi":"10.1080/2055074X.2016.1234116","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1234116","url":null,"abstract":"Abstract The structural changes that occur in a FeOx/γ-Al2O3 catalyst during the dehydrogenation of ethylbenzene in a fluidized CREC Riser Simulator have been investigated. Chemical and morphological changes are observed to take place as a result of reaction. Electron microscopy reveals the formation of needle-like alumina structures apparently enclosing iron oxide particles. The formation of such structures at relatively low temperatures is unexpected and has not previously been reported. Additionally, X-ray diffraction and Mössbauer spectroscopy confirmed the reduction of the oxidation state of iron, from Fe2O3 (haematite) to Fe3O4 (magnetite). Iron carbides, Fe3C and ɛ-Fe2C, were detected by electron microscopy through electron diffraction and lattice fringes analysis. Carbon deposition (coking) on the catalyst surface also occurs. The observed structural changes are likely to be closely correlated with the catalytic properties of the materials, in particular with catalyst deactivation, and thereby provide important avenues for future study of this industrially important reaction. Graphical abstract Fe2O3/Al2O3 catalyst undergoes chemical and morphological changes during ethylbenzene dehydrogenation forming Al2O3 needles which appear to contain reduced Fe3O4 particles. Fe3C also forms during reaction.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1234116","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043462","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 : 2016-07-12DOI: 10.1080/2055074X.2016.1198545
Abdi Nemera Emana, S. Chand
Abstract Alkylation of benzene with ethanol was analyzed using shape selective boron–magnesium bimetallic HZSM-5 (Si/Al = 90) zeolite catalyst. The alkylation of benzene with ethanol (2:1 by volume) produces ethylbenzene as primary product and others like 1, 2-Diethylbenzene, 1, 4-Diethylbenzene, and xylene mixtures as secondary products. The physiochemical properties of catalyst were characterized by XRD, BET, TGA, FTIR, NH3-TPD, and FE-SEM. The feed and products were analyzed by gas chromatography and mass spectroscopy. B–Mg bimetallic catalysts supported on HZSM-5 zeolite catalyst with SAR = 90 were synthesized by the incipient wetness impregnation method and examined for alkylation of benzene with ethanol. Total metal loading of 5, 10, and 15% was used for catalyst synthesis. The highest selectivity of ethylbenzene (76.22%) was obtained by (Mg + B)-15%-HZSM-5 and the lowest ethylbenzene selectivity (49.15%) was obtained by (Mg + B)-5%-HZSM-5 using 2:1 benzene-to-ethanol ratio by volume. A reaction scheme with three parallel routes leading to the formation of ethylbenzene, diethylbenzene, and triethylbenzene was considered for the kinetic study. The kinetic parameters were determined using Langmuir–Hinshelwood–Hougen–Watson (LHHW)-type kinetic model. LHHW model could satisfactorily correlate the rate data and this model gives good fit between the experimental and calculated data.
{"title":"Kinetic study of alkylation of benzene with ethanol over bimetallic modified HZSM-5 zeolite catalyst and effects of percentage metal loading","authors":"Abdi Nemera Emana, S. Chand","doi":"10.1080/2055074X.2016.1198545","DOIUrl":"https://doi.org/10.1080/2055074X.2016.1198545","url":null,"abstract":"Abstract Alkylation of benzene with ethanol was analyzed using shape selective boron–magnesium bimetallic HZSM-5 (Si/Al = 90) zeolite catalyst. The alkylation of benzene with ethanol (2:1 by volume) produces ethylbenzene as primary product and others like 1, 2-Diethylbenzene, 1, 4-Diethylbenzene, and xylene mixtures as secondary products. The physiochemical properties of catalyst were characterized by XRD, BET, TGA, FTIR, NH3-TPD, and FE-SEM. The feed and products were analyzed by gas chromatography and mass spectroscopy. B–Mg bimetallic catalysts supported on HZSM-5 zeolite catalyst with SAR = 90 were synthesized by the incipient wetness impregnation method and examined for alkylation of benzene with ethanol. Total metal loading of 5, 10, and 15% was used for catalyst synthesis. The highest selectivity of ethylbenzene (76.22%) was obtained by (Mg + B)-15%-HZSM-5 and the lowest ethylbenzene selectivity (49.15%) was obtained by (Mg + B)-5%-HZSM-5 using 2:1 benzene-to-ethanol ratio by volume. A reaction scheme with three parallel routes leading to the formation of ethylbenzene, diethylbenzene, and triethylbenzene was considered for the kinetic study. The kinetic parameters were determined using Langmuir–Hinshelwood–Hougen–Watson (LHHW)-type kinetic model. LHHW model could satisfactorily correlate the rate data and this model gives good fit between the experimental and calculated data.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2016.1198545","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043447","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 : 2016-03-09DOI: 10.1080/2055074X.2015.1133269
Anjani Dubey, S. Kolekar, Edwin S. Gnanakumar, Kanak Roy, C. P. Vinod, C. Gopinath
Abstract An attempt has been made to bridge the material gap, existing between ideal single crystals and real-world powder nanocatalyst employed in surface science and heterogeneous catalysis, respectively. Simple wet chemical method (sol–gel and spin-coating deposition) has been applied to make continuous Ce1 − xZrxO2 (x = 0–1) (CZ) thin films with uniform thickness (~40 nm) and smooth surface characteristics. Uniform thickness and surface smoothness of the films over a large area was supported by a variety of measurements. Molecular beam (MB) studies of O2 adsorption on CZ surfaces reveals the oxygen storage capacity (OSC), and sticking coefficient increases from 400 to 800 K. Porous nature of Ce-rich CZ compositions enhances O2 adsorption and OSC, predominantly due to O-diffusion and redox nature, even at 400 K. A good correlation exists between MB measurements made on CZ films for oxygen adsorption, and OSC, and ambient pressure CO oxidation on powder form of CZ; this demonstrates the large potential to bridge the material gap. CZ was particularly chosen as a model system for the present studies, since it has been well-studied and a correlation between surface science properties made on thin films and catalysis on powder CZ materials could be a litmus test. Graphical abstract Ambient catalysis on ceria-zirconia nanocatalyst correlates well with surface properties measured through molecular beam on thinfilm and close the material gap.
{"title":"Porous thin films toward bridging the material gap in heterogeneous catalysis","authors":"Anjani Dubey, S. Kolekar, Edwin S. Gnanakumar, Kanak Roy, C. P. Vinod, C. Gopinath","doi":"10.1080/2055074X.2015.1133269","DOIUrl":"https://doi.org/10.1080/2055074X.2015.1133269","url":null,"abstract":"Abstract An attempt has been made to bridge the material gap, existing between ideal single crystals and real-world powder nanocatalyst employed in surface science and heterogeneous catalysis, respectively. Simple wet chemical method (sol–gel and spin-coating deposition) has been applied to make continuous Ce1 − xZrxO2 (x = 0–1) (CZ) thin films with uniform thickness (~40 nm) and smooth surface characteristics. Uniform thickness and surface smoothness of the films over a large area was supported by a variety of measurements. Molecular beam (MB) studies of O2 adsorption on CZ surfaces reveals the oxygen storage capacity (OSC), and sticking coefficient increases from 400 to 800 K. Porous nature of Ce-rich CZ compositions enhances O2 adsorption and OSC, predominantly due to O-diffusion and redox nature, even at 400 K. A good correlation exists between MB measurements made on CZ films for oxygen adsorption, and OSC, and ambient pressure CO oxidation on powder form of CZ; this demonstrates the large potential to bridge the material gap. CZ was particularly chosen as a model system for the present studies, since it has been well-studied and a correlation between surface science properties made on thin films and catalysis on powder CZ materials could be a litmus test. Graphical abstract Ambient catalysis on ceria-zirconia nanocatalyst correlates well with surface properties measured through molecular beam on thinfilm and close the material gap.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2015.1133269","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043395","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 : 2015-10-02DOI: 10.1080/2055074X.2015.1105618
M. Piumetti, F. Freyria, M. Armandi, G. Saracco, E. Garrone, G. Gonzalez, B. Bonelli
Abstract Pure and V-loaded mesoporous titania (with 2.5 wt-% V) were prepared by template-assisted synthesis and compared to commercial titania (Degussa P25), both as such and after vanadium loading. Mesoporous TiO2 occurred as pure anatase nanoparticles with higher surface area (SSA = 150 m2 g−1) than P25 (SSA = 56 m2 g−1). Degradation of the azo dye Acid Orange 7 by H2O2 was used as a test reaction: under UV light, no difference emerged between mesoporous TiO2 and P25, whereas in dark conditions, higher SSA of the mesoporous sample resulted in higher conversions. Under UV illumination, surface V5+ species inhibited photocatalytic activity, by forming inactive V4+ species. Similarly, in dark conditions, V5+ surface species reacted with H2O2, likely yielding ·O2H radicals and reducing to V4+. On the contrary, V-containing catalysts were very active after pretreatment with ascorbic acid, which reduced V5+ species to V3+species, the latter promoting very lively a Fenton-like reaction.
{"title":"Catalytic degradation of Acid Orange 7 by H2O2 as promoted by either bare or V-loaded titania under UV light, in dark conditions, and after incubating the catalysts in ascorbic acid","authors":"M. Piumetti, F. Freyria, M. Armandi, G. Saracco, E. Garrone, G. Gonzalez, B. Bonelli","doi":"10.1080/2055074X.2015.1105618","DOIUrl":"https://doi.org/10.1080/2055074X.2015.1105618","url":null,"abstract":"Abstract Pure and V-loaded mesoporous titania (with 2.5 wt-% V) were prepared by template-assisted synthesis and compared to commercial titania (Degussa P25), both as such and after vanadium loading. Mesoporous TiO2 occurred as pure anatase nanoparticles with higher surface area (SSA = 150 m2 g−1) than P25 (SSA = 56 m2 g−1). Degradation of the azo dye Acid Orange 7 by H2O2 was used as a test reaction: under UV light, no difference emerged between mesoporous TiO2 and P25, whereas in dark conditions, higher SSA of the mesoporous sample resulted in higher conversions. Under UV illumination, surface V5+ species inhibited photocatalytic activity, by forming inactive V4+ species. Similarly, in dark conditions, V5+ surface species reacted with H2O2, likely yielding ·O2H radicals and reducing to V4+. On the contrary, V-containing catalysts were very active after pretreatment with ascorbic acid, which reduced V5+ species to V3+species, the latter promoting very lively a Fenton-like reaction.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2015.1105618","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043310","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 : 2015-10-02DOI: 10.1080/2055074X.2015.1124191
M. Khan, M. Al-oufi, A. Tossef, Y. Al-Salik, H. Idriss
Abstract The photocatalytic water splitting activity of nanocomposite photocatalysts of TiO2 with CoOx was studied under UV and visible light, and the catalysts were characterized by XRD, XPS, and UV–vis techniques. The presence of CoOx enhances the hydrogen production activity of TiO2 by five times at an optimal loading of .2 wt. %. To investigate the role of CoOx, the photocatalytic activity was also studied under visible light and with different amounts of sacrificial agent. Our results indicate that the increasing activity was not due to increasing absorption of the visible light but most likely due to the role of CoOx nanoparticles as hole scavengers at the interface with TiO2. XPS Co2p analyses of CoO/TiO2 showed a considerable decrease in their signal after prolonged reaction time (44 h) when compared to that of the fresh catalyst. Because part of Co2+ cations is dissolved in solution, in neutral or acidic pH, the possible increase in the reaction rate upon their addition to TiO2 under UV excitation was investigated. No change in the reaction rate was observed upon, on purpose, addition Co2+ cations to TiO2 under UV excitation. Thus, one may rule out the reduction of Co2+ to Co0 with excited electrons within TiO2. In order to further increase the reaction rate, we have synthesized and tested a hybrid system composed of CoO and Pd nanoparticles (Pd wt. % = 0.1, 0.3, 0.5, and 1 wt. %) where 0.3 wt. % Pd – 2 wt. % CoO/TiO2 showed the highest rate.
{"title":"On the role of CoO in CoOx/TiO2 for the photocatalytic hydrogen production from water in the presence of glycerol","authors":"M. Khan, M. Al-oufi, A. Tossef, Y. Al-Salik, H. Idriss","doi":"10.1080/2055074X.2015.1124191","DOIUrl":"https://doi.org/10.1080/2055074X.2015.1124191","url":null,"abstract":"Abstract The photocatalytic water splitting activity of nanocomposite photocatalysts of TiO2 with CoOx was studied under UV and visible light, and the catalysts were characterized by XRD, XPS, and UV–vis techniques. The presence of CoOx enhances the hydrogen production activity of TiO2 by five times at an optimal loading of .2 wt. %. To investigate the role of CoOx, the photocatalytic activity was also studied under visible light and with different amounts of sacrificial agent. Our results indicate that the increasing activity was not due to increasing absorption of the visible light but most likely due to the role of CoOx nanoparticles as hole scavengers at the interface with TiO2. XPS Co2p analyses of CoO/TiO2 showed a considerable decrease in their signal after prolonged reaction time (44 h) when compared to that of the fresh catalyst. Because part of Co2+ cations is dissolved in solution, in neutral or acidic pH, the possible increase in the reaction rate upon their addition to TiO2 under UV excitation was investigated. No change in the reaction rate was observed upon, on purpose, addition Co2+ cations to TiO2 under UV excitation. Thus, one may rule out the reduction of Co2+ to Co0 with excited electrons within TiO2. In order to further increase the reaction rate, we have synthesized and tested a hybrid system composed of CoO and Pd nanoparticles (Pd wt. % = 0.1, 0.3, 0.5, and 1 wt. %) where 0.3 wt. % Pd – 2 wt. % CoO/TiO2 showed the highest rate.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2015.1124191","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043320","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 : 2015-10-02DOI: 10.1080/2055074X.2015.1105615
M. Piumetti, S. Bensaid, D. Fino, N. Russo
Abstract The catalytic reduction of nitrogen oxides (NOx) under lean-burn conditions represents an important target in catalysis research. The most relevant catalytic NOx abatement systems for Diesel engine vehicles are summarized in this short review, with focus on the main catalytic aspects and materials. Five aftertreatment technologies for Diesel NOx are reviewed: (i) direct catalytic decomposition; (ii) catalytic reduction; (iii) NOx traps; (iv) plasma-assisted abatement; and (v) NOx reduction combined with soot combustion. The different factors that can affect catalytic activity are addressed for each approach (e.g. promoting or poisoning elements, operating conditions, etc.). In the field of catalytic strategies, the simultaneous removal of soot and NOx using multifunctional catalysts, is at present one of the most interesting challenges for the automotive industry.
{"title":"Catalysis in Diesel engine NOx aftertreatment: a review","authors":"M. Piumetti, S. Bensaid, D. Fino, N. Russo","doi":"10.1080/2055074X.2015.1105615","DOIUrl":"https://doi.org/10.1080/2055074X.2015.1105615","url":null,"abstract":"Abstract The catalytic reduction of nitrogen oxides (NOx) under lean-burn conditions represents an important target in catalysis research. The most relevant catalytic NOx abatement systems for Diesel engine vehicles are summarized in this short review, with focus on the main catalytic aspects and materials. Five aftertreatment technologies for Diesel NOx are reviewed: (i) direct catalytic decomposition; (ii) catalytic reduction; (iii) NOx traps; (iv) plasma-assisted abatement; and (v) NOx reduction combined with soot combustion. The different factors that can affect catalytic activity are addressed for each approach (e.g. promoting or poisoning elements, operating conditions, etc.). In the field of catalytic strategies, the simultaneous removal of soot and NOx using multifunctional catalysts, is at present one of the most interesting challenges for the automotive industry.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2015.1105615","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043268","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 : 2015-10-02DOI: 10.1080/2055074X.2015.1105616
D. Das, J. Llorca, Montserrat Domínguez, A. Gayen
Abstract Single step combustion synthesized Cu (5–15 at.-%)/Ce0.8Zr0.2O2 materials containing highly dispersed copper have been assessed for methanol steam reforming (MSR). The activity patterns suggest Cu (10 at.-%)/Ce0.80Zr0.20O2 as the most active formulation, converting ~51% methanol at 300 °C at a gas hourly space velocity of 40,000 h-1 (W/F = 0.09 s). The in situ XPS experiments carried over the most active sample show a sharp falloff of Cu-surface concentration from a considerably high value of 26% before to 7.4% after the in situ MSR tests and it is associated with the complete reduction of oxidized Cu-species (Cu2+) to metallic copper (Cu0). These findings point to the sintering of copper during MSR which is attributed to be responsible for the deactivation observed with time on stream. Interestingly, the MSR activity is shown to be regenerated nearly completely through an intermediate in situ oxidation step in the consecutive cycles of methanol reforming.
摘要研究了单步燃烧合成Cu (5-15 at.-%)/Ce0.8Zr0.2O2高分散铜材料的甲醇蒸汽重整(MSR)性能。活动模式显示铜(10哦(%)/ Ce0.80Zr0.20O2作为最活跃的配方,将在300°C ~ 51%甲醇气体时空速的h - 40000 (W / F = 0.09 s)。最活跃的原位XPS实验样本显示大幅下降之前Cu-surface浓度相当高价值的26%至7.4%后原位MSR与完成相关测试,减少氧化Cu-species (Cu2 +)金属铜(Cu0)。这些发现表明，在MSR过程中，铜的烧结是导致随时间推移所观察到的失活的原因。有趣的是，在连续的甲醇重整循环中，MSR活性几乎完全通过中间的原位氧化步骤再生。
{"title":"Single step combustion synthesized Cu/Ce0.8Zr0.2O2 for methanol steam reforming: structural insights from in situ XPS and HRTEM studies","authors":"D. Das, J. Llorca, Montserrat Domínguez, A. Gayen","doi":"10.1080/2055074X.2015.1105616","DOIUrl":"https://doi.org/10.1080/2055074X.2015.1105616","url":null,"abstract":"Abstract Single step combustion synthesized Cu (5–15 at.-%)/Ce0.8Zr0.2O2 materials containing highly dispersed copper have been assessed for methanol steam reforming (MSR). The activity patterns suggest Cu (10 at.-%)/Ce0.80Zr0.20O2 as the most active formulation, converting ~51% methanol at 300 °C at a gas hourly space velocity of 40,000 h-1 (W/F = 0.09 s). The in situ XPS experiments carried over the most active sample show a sharp falloff of Cu-surface concentration from a considerably high value of 26% before to 7.4% after the in situ MSR tests and it is associated with the complete reduction of oxidized Cu-species (Cu2+) to metallic copper (Cu0). These findings point to the sintering of copper during MSR which is attributed to be responsible for the deactivation observed with time on stream. Interestingly, the MSR activity is shown to be regenerated nearly completely through an intermediate in situ oxidation step in the consecutive cycles of methanol reforming.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/2055074X.2015.1105616","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60043305","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 : 2015-07-03DOI: 10.1179/2055075815Y.0000000007
Y. Hao, M. Li, F. Cárdenas-Lizana, M. Keane
Abstract The gas phase (1 atm, 473-563 K) hydrogenation of butyronitrile has been studied over Pd/SiO2 and Ba-Pd/SiO2. Catalysts characterisation involved TPR, H2/NH3 chemisorption/TPD, XRD and TEM measurements. The incorporation of Ba with Pd resulted in the formation of smaller metal nano-particles (7 nm vs. 28 nm) with a resultant (seven-fold) higher H2 chemisorption and decreased total surface acidity (from NH3 chemisorption/TPD). Temperature related activity maxima were observed for both catalysts and are associated with thermal desorption of the nitrile reactant. Exclusivity to the target butylamine was achieved at T ≥ 543 K where Ba-Pd/SiO2 delivered higher selective hydrogenation rate (91 mol h −1 mol Pd -1 ) than Pd/SiO2 (54 mol h −1 mol Pd −1 ), attributed to greater availability of surface reactive hydrogen. Lower surface acidity served to minimise condensation to higher amines. The rate and selectivity to butylamine exceed those previously reported for gas phase operation.
{"title":"Production of Butylamine in the Gas Phase Hydrogenation of Butyronitrile over Pd/SiO2 and Ba-Pd/SiO2","authors":"Y. Hao, M. Li, F. Cárdenas-Lizana, M. Keane","doi":"10.1179/2055075815Y.0000000007","DOIUrl":"https://doi.org/10.1179/2055075815Y.0000000007","url":null,"abstract":"Abstract The gas phase (1 atm, 473-563 K) hydrogenation of butyronitrile has been studied over Pd/SiO2 and Ba-Pd/SiO2. Catalysts characterisation involved TPR, H2/NH3 chemisorption/TPD, XRD and TEM measurements. The incorporation of Ba with Pd resulted in the formation of smaller metal nano-particles (7 nm vs. 28 nm) with a resultant (seven-fold) higher H2 chemisorption and decreased total surface acidity (from NH3 chemisorption/TPD). Temperature related activity maxima were observed for both catalysts and are associated with thermal desorption of the nitrile reactant. Exclusivity to the target butylamine was achieved at T ≥ 543 K where Ba-Pd/SiO2 delivered higher selective hydrogenation rate (91 mol h −1 mol Pd -1 ) than Pd/SiO2 (54 mol h −1 mol Pd −1 ), attributed to greater availability of surface reactive hydrogen. Lower surface acidity served to minimise condensation to higher amines. The rate and selectivity to butylamine exceed those previously reported for gas phase operation.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075815Y.0000000007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65872299","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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