Corinne Petit - Academia.edu (original) (raw)

Papers by Corinne Petit

ChemSusChem

Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfull... more Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfully been employed as highly efficient, selective, and durable systems for CO 2 hydrogenation to substituted natural gas (SNG; CH 4) under an autothermal regime. The thermo-physical properties of DU and the unique electronic structure of f-block metal-oxides combined with a nickel active phase, generated an ideal catalytic assembly for turning waste energy back into useful energy for catalysis. In particular, Ni/UO x stood out for the capacity of DU matrix to control the extra heat (hot-spots) generated at its surface by the highly exothermic methanation process. At odds with the benchmark Ni/γ-Al 2 O 3 catalyst, the double action played by DU as a "thermal mass" and "dopant" for the nickel active phase unveiled the unique performance of Ni/UO x composites as CO 2 methanation catalysts. The ability of the weakly radioactive ceramic (UO x) to harvest waste heat for more useful purposes was demonstrated in practice within a rare example of a highly effective and long-term methanation operated under autothermal regime (i. e., without any external heating source). This finding is an unprecedented example that allows a real stepforward in the intensification of "low-temperature" methanation with an effective reduction of energy wastes. At the same time, the proposed catalytic technology can be regarded as an original approach to recycle and bring to a second life a lesssevere nuclear by-product (DU), providing a valuable alternative to its more costly long-term storage or controlled disposal.

Catalytic behavior of Ni containing catalysts in vaporeforming of methane with low H2O/CH4 ratio and free carbon deposition

Studies in Surface Science and Catalysis, 2000

ABSTRACT

Characterisation of the solid solution La(Ni,Fe)O3 prepared via a sol-gel related method using propionic acid

ABSTRACT

An investigation of metal-support interaction in bimetallic Pt-Mo catalysts deposited on silica and alumina

Surface Science, 1987

ABSTRACT

Journal of Molecular Catalysis A: Chemical, 2013

A study using in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy has tar... more A study using in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy has targeted carbon monoxide (CO) adsorption on the standard platinum (Pt) reference catalyst EuroPt-1. Reduced and non-reduced EuroPt-1 were analyzed in an infrared (IR) chamber which allowed the control of the CO atmosphere from temperatures ranging from −30 to 300 • C. The complex spectra of CO linearly adsorbed on highly dispersed Pt have been analyzed by using a combination of Fourier self-deconvolution and curve fitting. The linear-CO spectrum is composed of three main bands at 2096, 2083 and 2072 cm −1. These were attributed to the three different adsorption sites-faces, edges and corners-of the 55-atom cuboctahedron Pt particles. The adsorption site competition was followed as a function of the temperature and it was demonstrated that these sites were never completely covered with CO. Furthermore, nonreduced EuroPt-1 presented reversible oxygen binding at low temperature in competition with CO. At 300 • C, CO mainly occupied corner sites and a comparable state was approached for both catalysts by the removal of the oxygen from these corner sites.

Carbon, 2011

Well defined La-Ni-O oxide structures are prepared by a sol-gel like method and treated at three ... more Well defined La-Ni-O oxide structures are prepared by a sol-gel like method and treated at three different temperatures in order to modify their phases and degree of crystallinity, close to that of LaNiO 3 perovskite. It is observed that depending on the temperature of the treatment, three crystalline structures (LaNiO 3 , La 2 Ni 2 O 5 and La 4 Ni 3 O 10 ) are obtained, some of them containing an additional NiO phase. All these structures, characterized by X-ray diffraction and scanning and transmission electron microscopy before reduction, are used for the synthesis of multi-wall carbon nanotubes (MWCNTs) by the catalytic decomposition of methane. The reducibility of each phase under hydrogen is studied by programmed thermo reduction. After reduction and chemical vapor decomposition, inner and outer diameters of the MWCNTs are analyzed. It is found that these characteristics are strongly correlated to the structure of the oxides formed as catalytic precursors.

Biomass and Bioenergy, 2002

Tri-metallic and ternary oxide structures were prepared, characterised and tested for two ÿxed-be... more Tri-metallic and ternary oxide structures were prepared, characterised and tested for two ÿxed-bed catalytic applications: the reforming of methane with steam and CO2; and for conditioning the gas produced by biomass steam gasiÿcation in a uidised bed of olivine particles, with the aim of drastically reducing high and low molecular weight hydrocarbon concentrations in the product gas. Methane conversions higher than 90% were achieved for a synthetic gas feed mixture (similar of that produced in biomass gasiÿcation) using the catalyst formulation LaNi0:3Fe0:7O3 at 800 • C: the space time under reaction conditions was 0.05 s, and no carbon was formed for reaction periods of up to 150 h. The catalyst contained in a secondary ÿxed-bed reactor placed after the gasiÿer was able to convert about 90% by weight of the tar present in the raw gas at 800 • C: the space time under reaction conditions was 0:45 s, during which time no coke formation was observed on the catalyst surface.

Applied Catalysis A: General, 2004

A preparation method for gold catalysts supported on alumina by a simple contact between a gold s... more A preparation method for gold catalysts supported on alumina by a simple contact between a gold solution prepared with HAuCl 4 as precursor and alumina over a narrow range of pH is described. This method, direct anionic exchange (DAE), differs from the mainly used method deposition precipitation generally used and presents the advantage that no gold is lost during the filtration and washing steps, the expected loadings of 2% is obtained. Gold particles size obtained by DAE is very sensitive to evolution and nature of the gold chloro-hydroxy species in the solution and on the surface of the support. According to the evolution of these species obtained by substitution of Cl-by OHwith increasing the pH value, the type of bonding complex-support is proposed. The surface of alumina is also sensitive to changes in pH of the solution. The formation of large particles of metal gold due to the presence of chlorine is put in evidence and can be limited by a treatment with ammonia solution. This washing procedure leads to some loss of gold with a final amount of 1.5%. Measurements of gold particle size by HRTEM are given as a function of preparation. A study of the activity in CO oxidation reaction is undertaken and correlated with TEM analysis.

Journal of Materials Science and Chemical Engineering, 2021

Gold nanoparticles have been increasingly used in catalysis, biomedical imaging, biological and c... more Gold nanoparticles have been increasingly used in catalysis, biomedical imaging, biological and chemical sensing, drug delivery, etc. In this study, a straightforward method that allows one to monitor the synthesis of gold sols and their aging, before their fine characterization by sophisticated techniques and before their use is described. Indeed, the "Colloid Thin-Layer Chromatography" method allows one to check the quality of gold colloidal sols during the synthesis. It is also well adapted for monitoring the aging of the sol before the visual observation of its degradation.

SSRN Electronic Journal, 2022

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Nanoscale Advances, 2022

A full 3D analysis of the hierarchical porosity in Coscinodiscus sp. diatom structures was carrie... more A full 3D analysis of the hierarchical porosity in Coscinodiscus sp. diatom structures was carried out by using a multiscale approach that combines three advanced volumetric imaging techniques with resolutions...

American Journal of Analytical Chemistry, 2019

Thermal decomposition course of copper acetate monohydrate was monitored by combining diffuse ref... more Thermal decomposition course of copper acetate monohydrate was monitored by combining diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) coupled with µ gas chromatography-mass spectrometry (µGC-MS) with other analytical techniques (thermogravimetry analysis and in situ X-ray diffraction). Non-isothermal kinetic was examined in air and Ar. A complete analysis of the evolution of infrared spectra matched with crystalline phase transition data during the course of reaction allows access to significant and accurate information about molecular dynamics. While thermogravimetry gives broad conclusion about two steps reaction (dehydration and decarboxylation), in line approach (in situ X-ray and in situ DRIFT coupled to µGC-MS) is proposed as an example of a new robust and forward-looking analysis. While decomposition mechanism of copper acetate monohydrate is still not well elucidated yet previously, the present in-line characterization results lead to accurate data making the corresponding mechanism explicit.

Control of bulk and surface composition of doped Sm 2Sn 2O 7 pyrochlore. Relation between formation of O-Ba-Cl graftings and C 2-selectivity in the oxidative coupling of methane

Studies in surface science and catalysis

ABSTRACT

Beneficial effects of inorganic chlorine grafting on Sm 2Sn 2O 7 pyrochlore during oxidative coupling of methane

Studies in surface science and catalysis

ABSTRACT

Reduction of NOx in Lean Exhaust by Selective NOx-Recirculation (SNR-Technique) Part I: System and Decomposition Process

SAE Technical Paper Series, 1998

Influence of the precursors on the formation of a trimetallic defined structure. Application on Ni catalysts used for syngas obtention

Studies in Surface Science and Catalysis, 1998

ABSTRACT

Reducibility study of the LaMxFe1−xO3 (M = Ni, Co) perovskites

MRS Proceedings, 2000

ABSTRACTSolid solutions of LaMxFe1−xO3 (with M = Ni and Co) have been used in the Fischer- Tropsc... more ABSTRACTSolid solutions of LaMxFe1−xO3 (with M = Ni and Co) have been used in the Fischer- Tropsch reaction (CO + H2 → Hydrocarbons + CO2) and in the partial oxidation of methane (CH4 + 1/2 O2 → CO + 2 H2). In both catalytic reactions, the active catalyst is reported to be reduced metal particles; their size and their interactions with the support induce large differences in the product distribution.In the nickel system, after total reduction by TPR all catalysts exhibit ferromagnetic behavior at room temperature. In situ magnetization in 1 Tesla on cooling the sample under reducing atmosphere shows one magnetic transition for each sample indicating one Curie temperature. These Curie temperatures are in between those known for bulk nickel and iron and decrease with the initial nickel content of the perovskite. This indicates that nickel is reduced first and induces the reduction of iron, leading to the formation of an alloy.In the cobalt system, in situ magnetization on heating the ...

Hydrophobic gold catalysts: From synthesis on passivated silica to synthesis on few-layer graphene

Catalysis Today, 2014

ABSTRACT Hydrophobic gold catalysts have recently proven useful in increasing the efficiency of t... more ABSTRACT Hydrophobic gold catalysts have recently proven useful in increasing the efficiency of the aerobic oxidation of hydrocarbons in apolar liquid media. Catalytically active 3 nm gold nanoparticles can be dispersed on the surface of commercially available methyl-terminated silica by performing chemical reduction of triphenylphosphine gold(I) chloride in the presence of the support in an ethanol/dichloromethane mixture. This method is here applied to a home-made few-layer graphene which displays a pristine graphitic surface, as shown by thermogravimetric analysis. Since direct application of the protocol leads to much larger gold particles, the protocol of synthesis is subsequently adapted to the specific nature of the graphene support, in particular by performing the reaction under sonication. Further studies of the effect of several reaction parameters on both the average gold crystallite size determined by XRD and the deposition yields determined by elemental analysis reveal (1) the superiority of DMF in minimizing the gold particle size and (2) the impact of short reduction times on maximizing the deposition yields. Repeatability of the experiment is ensured by the development of an optimized protocol of synthesis, and in particular the identification of the most effective positions in the sonication bath.

Science and Technology of Advanced Materials, 2002

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ra... more Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe) 2 SiO 4 structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism. The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparation method and the calcination temperature. For calcination at 1100 8C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 8C), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH 4 þ CO 2) yielding 96% CO and 76% H 2. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system. Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.

Stabilisation of active nickel catalysts in partial oxidation of methane to synthesis gas by iron addition

Applied Catalysis A: General, 1999

Mixed LaNi x Fe (1−x) O 3 perovskite oxides (0≤x≤1) have been prepared by a sol–gel related metho... more Mixed LaNi x Fe (1−x) O 3 perovskite oxides (0≤x≤1) have been prepared by a sol–gel related method, characterised by X-ray diffraction (XRD), specific surface area measurements, transmission electron microscopy (TEM) coupled to an energy dispersive X-ray spectrometer (EDS). ...

ChemSusChem

Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfull... more Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfully been employed as highly efficient, selective, and durable systems for CO 2 hydrogenation to substituted natural gas (SNG; CH 4) under an autothermal regime. The thermo-physical properties of DU and the unique electronic structure of f-block metal-oxides combined with a nickel active phase, generated an ideal catalytic assembly for turning waste energy back into useful energy for catalysis. In particular, Ni/UO x stood out for the capacity of DU matrix to control the extra heat (hot-spots) generated at its surface by the highly exothermic methanation process. At odds with the benchmark Ni/γ-Al 2 O 3 catalyst, the double action played by DU as a "thermal mass" and "dopant" for the nickel active phase unveiled the unique performance of Ni/UO x composites as CO 2 methanation catalysts. The ability of the weakly radioactive ceramic (UO x) to harvest waste heat for more useful purposes was demonstrated in practice within a rare example of a highly effective and long-term methanation operated under autothermal regime (i. e., without any external heating source). This finding is an unprecedented example that allows a real stepforward in the intensification of "low-temperature" methanation with an effective reduction of energy wastes. At the same time, the proposed catalytic technology can be regarded as an original approach to recycle and bring to a second life a lesssevere nuclear by-product (DU), providing a valuable alternative to its more costly long-term storage or controlled disposal.

Catalytic behavior of Ni containing catalysts in vaporeforming of methane with low H2O/CH4 ratio and free carbon deposition

Studies in Surface Science and Catalysis, 2000

ABSTRACT

Characterisation of the solid solution La(Ni,Fe)O3 prepared via a sol-gel related method using propionic acid

ABSTRACT

An investigation of metal-support interaction in bimetallic Pt-Mo catalysts deposited on silica and alumina

Surface Science, 1987

ABSTRACT

Journal of Molecular Catalysis A: Chemical, 2013

A study using in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy has tar... more A study using in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy has targeted carbon monoxide (CO) adsorption on the standard platinum (Pt) reference catalyst EuroPt-1. Reduced and non-reduced EuroPt-1 were analyzed in an infrared (IR) chamber which allowed the control of the CO atmosphere from temperatures ranging from −30 to 300 • C. The complex spectra of CO linearly adsorbed on highly dispersed Pt have been analyzed by using a combination of Fourier self-deconvolution and curve fitting. The linear-CO spectrum is composed of three main bands at 2096, 2083 and 2072 cm −1. These were attributed to the three different adsorption sites-faces, edges and corners-of the 55-atom cuboctahedron Pt particles. The adsorption site competition was followed as a function of the temperature and it was demonstrated that these sites were never completely covered with CO. Furthermore, nonreduced EuroPt-1 presented reversible oxygen binding at low temperature in competition with CO. At 300 • C, CO mainly occupied corner sites and a comparable state was approached for both catalysts by the removal of the oxygen from these corner sites.

Carbon, 2011

Well defined La-Ni-O oxide structures are prepared by a sol-gel like method and treated at three ... more Well defined La-Ni-O oxide structures are prepared by a sol-gel like method and treated at three different temperatures in order to modify their phases and degree of crystallinity, close to that of LaNiO 3 perovskite. It is observed that depending on the temperature of the treatment, three crystalline structures (LaNiO 3 , La 2 Ni 2 O 5 and La 4 Ni 3 O 10 ) are obtained, some of them containing an additional NiO phase. All these structures, characterized by X-ray diffraction and scanning and transmission electron microscopy before reduction, are used for the synthesis of multi-wall carbon nanotubes (MWCNTs) by the catalytic decomposition of methane. The reducibility of each phase under hydrogen is studied by programmed thermo reduction. After reduction and chemical vapor decomposition, inner and outer diameters of the MWCNTs are analyzed. It is found that these characteristics are strongly correlated to the structure of the oxides formed as catalytic precursors.

Biomass and Bioenergy, 2002

Tri-metallic and ternary oxide structures were prepared, characterised and tested for two ÿxed-be... more Tri-metallic and ternary oxide structures were prepared, characterised and tested for two ÿxed-bed catalytic applications: the reforming of methane with steam and CO2; and for conditioning the gas produced by biomass steam gasiÿcation in a uidised bed of olivine particles, with the aim of drastically reducing high and low molecular weight hydrocarbon concentrations in the product gas. Methane conversions higher than 90% were achieved for a synthetic gas feed mixture (similar of that produced in biomass gasiÿcation) using the catalyst formulation LaNi0:3Fe0:7O3 at 800 • C: the space time under reaction conditions was 0.05 s, and no carbon was formed for reaction periods of up to 150 h. The catalyst contained in a secondary ÿxed-bed reactor placed after the gasiÿer was able to convert about 90% by weight of the tar present in the raw gas at 800 • C: the space time under reaction conditions was 0:45 s, during which time no coke formation was observed on the catalyst surface.

Applied Catalysis A: General, 2004

A preparation method for gold catalysts supported on alumina by a simple contact between a gold s... more A preparation method for gold catalysts supported on alumina by a simple contact between a gold solution prepared with HAuCl 4 as precursor and alumina over a narrow range of pH is described. This method, direct anionic exchange (DAE), differs from the mainly used method deposition precipitation generally used and presents the advantage that no gold is lost during the filtration and washing steps, the expected loadings of 2% is obtained. Gold particles size obtained by DAE is very sensitive to evolution and nature of the gold chloro-hydroxy species in the solution and on the surface of the support. According to the evolution of these species obtained by substitution of Cl-by OHwith increasing the pH value, the type of bonding complex-support is proposed. The surface of alumina is also sensitive to changes in pH of the solution. The formation of large particles of metal gold due to the presence of chlorine is put in evidence and can be limited by a treatment with ammonia solution. This washing procedure leads to some loss of gold with a final amount of 1.5%. Measurements of gold particle size by HRTEM are given as a function of preparation. A study of the activity in CO oxidation reaction is undertaken and correlated with TEM analysis.

Journal of Materials Science and Chemical Engineering, 2021

Gold nanoparticles have been increasingly used in catalysis, biomedical imaging, biological and c... more Gold nanoparticles have been increasingly used in catalysis, biomedical imaging, biological and chemical sensing, drug delivery, etc. In this study, a straightforward method that allows one to monitor the synthesis of gold sols and their aging, before their fine characterization by sophisticated techniques and before their use is described. Indeed, the "Colloid Thin-Layer Chromatography" method allows one to check the quality of gold colloidal sols during the synthesis. It is also well adapted for monitoring the aging of the sol before the visual observation of its degradation.

SSRN Electronic Journal, 2022

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Nanoscale Advances, 2022

A full 3D analysis of the hierarchical porosity in Coscinodiscus sp. diatom structures was carrie... more A full 3D analysis of the hierarchical porosity in Coscinodiscus sp. diatom structures was carried out by using a multiscale approach that combines three advanced volumetric imaging techniques with resolutions...

American Journal of Analytical Chemistry, 2019

Thermal decomposition course of copper acetate monohydrate was monitored by combining diffuse ref... more Thermal decomposition course of copper acetate monohydrate was monitored by combining diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) coupled with µ gas chromatography-mass spectrometry (µGC-MS) with other analytical techniques (thermogravimetry analysis and in situ X-ray diffraction). Non-isothermal kinetic was examined in air and Ar. A complete analysis of the evolution of infrared spectra matched with crystalline phase transition data during the course of reaction allows access to significant and accurate information about molecular dynamics. While thermogravimetry gives broad conclusion about two steps reaction (dehydration and decarboxylation), in line approach (in situ X-ray and in situ DRIFT coupled to µGC-MS) is proposed as an example of a new robust and forward-looking analysis. While decomposition mechanism of copper acetate monohydrate is still not well elucidated yet previously, the present in-line characterization results lead to accurate data making the corresponding mechanism explicit.

Control of bulk and surface composition of doped Sm 2Sn 2O 7 pyrochlore. Relation between formation of O-Ba-Cl graftings and C 2-selectivity in the oxidative coupling of methane

Studies in surface science and catalysis

ABSTRACT

Beneficial effects of inorganic chlorine grafting on Sm 2Sn 2O 7 pyrochlore during oxidative coupling of methane

Studies in surface science and catalysis

ABSTRACT

Reduction of NOx in Lean Exhaust by Selective NOx-Recirculation (SNR-Technique) Part I: System and Decomposition Process

SAE Technical Paper Series, 1998

Influence of the precursors on the formation of a trimetallic defined structure. Application on Ni catalysts used for syngas obtention

Studies in Surface Science and Catalysis, 1998

ABSTRACT

Reducibility study of the LaMxFe1−xO3 (M = Ni, Co) perovskites

MRS Proceedings, 2000

ABSTRACTSolid solutions of LaMxFe1−xO3 (with M = Ni and Co) have been used in the Fischer- Tropsc... more ABSTRACTSolid solutions of LaMxFe1−xO3 (with M = Ni and Co) have been used in the Fischer- Tropsch reaction (CO + H2 → Hydrocarbons + CO2) and in the partial oxidation of methane (CH4 + 1/2 O2 → CO + 2 H2). In both catalytic reactions, the active catalyst is reported to be reduced metal particles; their size and their interactions with the support induce large differences in the product distribution.In the nickel system, after total reduction by TPR all catalysts exhibit ferromagnetic behavior at room temperature. In situ magnetization in 1 Tesla on cooling the sample under reducing atmosphere shows one magnetic transition for each sample indicating one Curie temperature. These Curie temperatures are in between those known for bulk nickel and iron and decrease with the initial nickel content of the perovskite. This indicates that nickel is reduced first and induces the reduction of iron, leading to the formation of an alloy.In the cobalt system, in situ magnetization on heating the ...

Hydrophobic gold catalysts: From synthesis on passivated silica to synthesis on few-layer graphene

Catalysis Today, 2014

ABSTRACT Hydrophobic gold catalysts have recently proven useful in increasing the efficiency of t... more ABSTRACT Hydrophobic gold catalysts have recently proven useful in increasing the efficiency of the aerobic oxidation of hydrocarbons in apolar liquid media. Catalytically active 3 nm gold nanoparticles can be dispersed on the surface of commercially available methyl-terminated silica by performing chemical reduction of triphenylphosphine gold(I) chloride in the presence of the support in an ethanol/dichloromethane mixture. This method is here applied to a home-made few-layer graphene which displays a pristine graphitic surface, as shown by thermogravimetric analysis. Since direct application of the protocol leads to much larger gold particles, the protocol of synthesis is subsequently adapted to the specific nature of the graphene support, in particular by performing the reaction under sonication. Further studies of the effect of several reaction parameters on both the average gold crystallite size determined by XRD and the deposition yields determined by elemental analysis reveal (1) the superiority of DMF in minimizing the gold particle size and (2) the impact of short reduction times on maximizing the deposition yields. Repeatability of the experiment is ensured by the development of an optimized protocol of synthesis, and in particular the identification of the most effective positions in the sonication bath.

Science and Technology of Advanced Materials, 2002

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ra... more Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe) 2 SiO 4 structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism. The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparation method and the calcination temperature. For calcination at 1100 8C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 8C), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH 4 þ CO 2) yielding 96% CO and 76% H 2. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system. Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.

Stabilisation of active nickel catalysts in partial oxidation of methane to synthesis gas by iron addition

Applied Catalysis A: General, 1999

Mixed LaNi x Fe (1−x) O 3 perovskite oxides (0≤x≤1) have been prepared by a sol–gel related metho... more Mixed LaNi x Fe (1−x) O 3 perovskite oxides (0≤x≤1) have been prepared by a sol–gel related method, characterised by X-ray diffraction (XRD), specific surface area measurements, transmission electron microscopy (TEM) coupled to an energy dispersive X-ray spectrometer (EDS). ...