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M.a. Goula - One of the best experts on this subject based on the ideXlab platform.
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investigating the correlation between deactivation and the carbon deposited on the surface of ni al2o3 and ni la2o3 al2o3 catalysts during the biogas Reforming Reaction
Applied Surface Science, 2019Co-Authors: N.d. Charisiou, Lazaros Tzounis, Kyriaki Polychronopoulou, Victor Sebastian, Steve Hinder, M A Baker, M.a. GoulaAbstract:Abstract Ni/Al2O3 and Ni/La2O-Al2O3 catalysts were investigated for the biogas Reforming Reaction using CH4/CO2 mixtures with minimal dilution. Stability tests at various Reaction temperatures were conducted and TGA/DTG, Raman, STEM-HAADF, HR-TEM, XPS techniques were used to characterize the spent samples. Graphitized carbon allotrope structures, carbon nanotubes (CNTs) and amorphous carbon were formed on all samples. Metallic Ni0 was recorded for all (XPS), whereas a strong peak corresponding to Ni2O3/NiAl2O4, was observed for the Ni/Al sample (650–750 °C). Stability tests confirm that the Ni/LaAl catalyst deactivates at a more gradual rate and is more active and selective in comparison to the Ni/Al for all temperatures. The Ni/LaAl exhibits good durability in terms of conversion and selectivity, whereas the Ni/Al gradually loses its activity in CH4 and CO2 conversion, with a concomitant decrease of the H2 and CO yield. It can be concluded that doping Al2O3 with La2O3 stabilizes the catalyst by (a) maintaining the Ni0 phase during the Reaction, due to higher dispersion and stronger active phase-support interactions, (b) leading to a less graphitic and more defective type of deposited carbon and (c) facilitating the deposited carbon gasification due to the enhanced CO2 adsorption on its increased surface basic sites.
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The potential of glycerol and phenol towards H2 production using steam Reforming Reaction: A review
Surface & Coatings Technology, 2018Co-Authors: N.d. Charisiou, Kyriaki Polychronopoulou, A. Asif, M.a. GoulaAbstract:Abstract Hydrogen production via the steam Reforming of glycerol, the main by-product of biodiesel production, and the pyrolysis/gasification route of biomass are two processes that have drawn considerable attention by the scientific community due to their potential in reducing our dependence on fossil based sources and in mitigating the effects of greenhouses gases on our planet. However, the commercial exploitation of the processes depends on the development of cheap, active and stable catalysts. In the present review, the key literature on the glycerol and phenol steam Reforming Reactions is presented and discussed. The impact of crucial variables for both the Reactions at hand are discussed, such as active metal nature, metal loading, support, Reaction temperature, method of preparation, poisoning resistance and coking tolerance. For catalytic systems design purposes the aspect of how the catalyst physicochemical characteristics affect the catalytic performance is addressed. Particular attention is given at the issue of coke resistance of the catalysts due to its detrimental effect for the Reactions at hand. Natural materials, such as calcites, dolomites and olivines, utilized for the phenol steam Reforming Reaction are discussed.
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hydrogen production via the glycerol steam Reforming Reaction over nickel supported on alumina and lanthana alumina catalysts
International Journal of Hydrogen Energy, 2017Co-Authors: N.d. Charisiou, Kyriakos N. Papageridis, G Siakavelas, Lazaros Tzounis, Apostolos Baklavaridis, Kyriaki Polychronopoulou, M.a. GoulaAbstract:In the present work, a comparative study of Ni catalysts supported on commercially available alumina and lanthana-alumina carriers was undertaken for the glycerol steam Reforming Reaction (GSR). The supports and/or catalysts were characterized by PZC, BET, ICP, XRD, NH3-TPD, CO2-TPD, TPR and SEM. Carbon deposited on the catalytic surface was characterized by SEM, TPO and Raman. Concerning the Ni/LaAl sample it can be concluded that the presence of lanthana by: (a) facilitating the active species dispersion, (b) strengthening the interactions between nickel species and support, (c) increasing of the basic sites' population and redistributing the acid ones in terms of strength and density, provides a catalyst with improved performance for the GSR Reaction, in terms of activity, H2 production and long term stability. TPO and Raman indicate that the carbon on the Ni/LaAl catalyst was mostly amorphous and was deposited mainly on the support surface. For the Ni/Al catalyst, graphitic carbon was prevalent and likely covered its active sites.
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comparative study of ni co cu supported on γ alumina catalysts for hydrogen production via the glycerol steam Reforming Reaction
Fuel Processing Technology, 2016Co-Authors: Kyriakos N. Papageridis, N.d. Charisiou, G Siakavelas, D G Avraam, Lazaros Tzounis, Kalliopi Kousi, M.a. GoulaAbstract:Abstract Catalysts with active phase Ni, Co or Cu supported on γ-alumina were synthesized at constant loading (8 wt.%) and tested for the glycerol steam Reforming Reaction (GSR). The synthesized samples, at their calcined and/or their reduced form, were characterized by BET, ICP, XRD, DRS, NH 3 -TPD, CO 2 -TPD, TPR and SEM. The carbon deposited on their surface under Reaction conditions was characterized by TEM, TPO, TGA and Raman. Catalytic performance for the glycerol steam Reforming Reaction was studied in order to investigate the effects of Reaction temperature on: (i) glycerol total conversion, (ii) glycerol conversion to gaseous products, (iii) hydrogen selectivity and yield, (iv) selectivity of carbonaceous gaseous products, (v) selectivity of liquid products and (vi) molar ratios of H 2 /CO and CO/CO 2 in the gaseous products' mixture. The stability of all catalysts was also investigated through time on stream experiments. It was concluded that catalytic performance, including liquid products' distribution, depends on the acid-base properties of the materials. Specifically, a drastic drop in the activity of the Ni/Al catalyst was observed, while Co/Al and Cu/Al catalysts deactivate in a slower rate, confirming that coke deposition, associated with dehydration, cracking and polymerization Reactions, takes place on the catalyst's surface strong acid sites.
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A Ni/apatite-type lanthanum silicate supported catalyst in glycerol steam Reforming Reaction
RSC Advances, 2016Co-Authors: M.a. Goula, N.d. Charisiou, Pavlos K. Pandis, Vassilis N. StathopoulosAbstract:In the glycerol steam Reforming Reaction a 5 wt% Ni/La9.83Si4.5Fe1.5O26±δ catalyst was found to be active and up to 3.2 times more selective to H2 than a 5 wt% Ni/Al2O3 catalyst, especially at low temperatures (
Angelos M. Efstathiou - One of the best experts on this subject based on the ideXlab platform.
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The phenol steam Reforming Reaction towards H2 production on natural calcite
Applied Catalysis B-environmental, 2009Co-Authors: Domna A. Constantinou, José Luis García Fierro, Angelos M. EfstathiouAbstract:Abstract The steam Reforming of phenol towards H 2 production was studied in the 650–800 °C range over a natural pre-calcined (air, 850 °C) calcite material. The effects of Reaction temperature, water, hydrogen, and carbon dioxide feed concentrations, and gas hourly space velocity (GHSV, h −1 ) were investigated. The increase of Reaction temperature in the 650–800 °C range and water feed concentration in the 40–50 vol% range were found to be beneficial for catalyst activity and H 2 -yield. A similar result was also obtained in the case of decreasing the GHSV from 85,000 to 30,000 h −1 . The effect of concentration of carbon dioxide and hydrogen in the phenol/water feed stream was found to significantly decrease the rate of phenol steam Reforming Reaction. The latter was probed to be related to the reduction in the rate of water dissociation as evidenced by the significant decrease in the concentration of adsorbed bicarbonate and OH species on the surface of CaO according to in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)-CO 2 adsorption experiments in the presence of water and hydrogen in the feed stream. Details of the CO 2 adsorption on the CaO surface at different Reaction temperatures and gas atmospheres using in situ DRIFTS and transient isothermal adsorption experiments with mass spectrometry were obtained. Bridged, bicarbonate and unidentate carbonate species were formed under CO 2 /H 2 O/He gas mixtures at 600 °C with the latter being the most populated. A substantial decrease in the surface concentration of bicarbonate and OH species was observed when the CaO surface was exposed to CO 2 /H 2 O/H 2 /He gas mixtures at 600 °C, result that probes for the inhibiting effect of H 2 on the phenol steam Reforming activity. Phenol steam Reforming Reaction followed by isothermal oxygen titration allowed the measurement of accumulated “carbonaceous” species formed during phenol steam Reforming as a function of Reaction temperature and short time on stream. An increase in the amount of “carbonaceous” species with Reaction time (650–800 °C range) was evidenced, in particular at 800 °C (4.7 vs. 6.7 mg C/g solid after 5 and 20 min on stream, respectively).
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the phenol steam Reforming Reaction over mgo based supported rh catalysts
Journal of Catalysis, 2004Co-Authors: Kyriaki Polychronopoulou, J L G Fierro, Angelos M. EfstathiouAbstract:Abstract The phenol steam Reforming Reaction toward H2 formation has been investigated in the 575–730 °C range over MgO, CeO2, and ZrO2 single metal oxides and various mixed metal oxides such as Mg–Ce–O, Mg–Zr–O, and Mg–Ce–Zr–O, all prepared by the sol–gel method. The same Reaction has also been studied over Rh supported on these metal oxides. The effects of synthesis method of the Mg–Ce–Zr–O support (mechanical mixing versus sol–gel) and of Rh deposition (wet impregnation versus sol–gel) on the activity and H2 selectivity of the Reaction over the Rh/Mg–Ce–Zr–O catalyst have also been investigated. It was found that 0.5 wt% Rh/MgO and 0.1 wt% Rh/Mg–Ce–Zr–O catalysts, the supports of which were prepared by the sol–gel method, exhibit better performance when compared to a commercial Ni-based catalyst used for tar steam Reforming. In particular, Rh/MgO presented the highest H2 product concentrations and selectivities in the 575–730 °C range and no more than 20% drop in activity after 24 h of continuous Reaction (0.5% C6H5OH/40% H2O/He). It was found that steam Reforming of phenol is favored over very small Rh particles in the case of 0.1 wt% Rh/Mg–Ce–Zr–O catalyst. In particular, the specific integral Reaction rate of H2 production (mmol-H2 / (m2Rh s)) significantly increased by decreasing the Rh particle size from 2.7 to 1.2 nm. The effect of the partial pressure of water and phenol in the feed stream on catalyst activity was found to strongly depend on support chemical composition. More than one kind of carbonaceous species forming during Reaction has been identified with varying compositions and reactivities toward oxygen and steam. XPS studies suggested that the MgxZr1−xO2 phase present in the Mg–Ce–Zr–O support is reduced by H2 at 300 °C in the presence of very small Rh particles leading to the creation of oxygen vacant sites and diffusion of Zr toward the bulk of the crystal. As a result of this, the surface acidity and basicity of the Rh/Mg–Ce–Zr–O catalyst are expected to alter, thus influencing the hydrogen activity and selectivity of the Reaction.
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Characterization of carbonaceous species formed during Reforming of CH4with CO2over Ni/CaO-Al2O3catalysts studied by various transient techniques
Journal of Catalysis, 1996Co-Authors: M.a. Goula, Angeliki A Lemonidou, Angelos M. EfstathiouAbstract:Carbon dioxide Reforming of methane to synthesis gas at 750°C over 5 wt% Ni/CaO-Al2O3catalysts has been investigated with respect to effects of support composition (CaO to Al2O3ratio) on catalyst stability, amount and reactivity of carbon species formed during Reaction, and relative proportion of Reaction routes that lead to carbon formation (CH4vs CO2molecule). Temperature-programmed oxidation (TPO) and hydrogenation (TPH) experiments, following Reforming Reaction with 20% CH4/20% CO2/He and 20%13CH4/20% CO2/He mixtures, have been conducted for the aforementioned carbon characterization studies. Two kinds of carbon species (free of chemically bound hydrogen) were mainly found to accumulate on the catalyst surface, where the amount and reactivity of them are influenced by the CaO/Al2O3ratio used to deposit the nickel metal. Transient isothermal hydrogenation experiments of the carbon species formed during Reforming Reaction resulted in CH4responses, where the time of appearance of the CH4peak maximum in hydrogen stream as a function of hydrogenation temperature was used to obtain the intrinsic activation energy of the hydrogenation process. It was found that this activation energy is influenced by the support composition. TPO experiments conducted following Reforming Reaction with13CH4/CO2/He mixture have demonstrated that the relative amount of adsorbed carbon species formed via the CH4and CO2molecular routes was strongly dependent on support composition. H2temperature-programmed desorption, temperature-programmed reduction, and X-ray photoelectron spectroscopic measurements conducted over the present catalysts suggest that the nickel particle morphology and its size distribution must be influenced by the support composition, which in turn controls the origin, the kinetics, and the reactivity of carbon deposition under Reforming Reaction conditions. © 1990 Academic Press, Inc.
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Reforming of methane with carbon dioxide to synthesis gas over supported rhodium catalysts ii a steady state tracing analysis mechanistic aspects of the carbon and oxygen Reaction pathways to form co
Journal of Catalysis, 1996Co-Authors: Angelos M. Efstathiou, A Kladi, V A Tsipouriari, Xenophon E VerykiosAbstract:Steady-state tracing techniques have been applied to investigate mechanistic aspects of the CH4Reforming Reaction over CO2over Rh supported on yttria-stabilized zirconia (YSZ) and Al2O3as catalysts. It was found that the surface coverage of active carbon-containing species, which are found in the Reaction pathway to CO formation, is of the order of 0.2 over the Rh/Al2O3catalyst, while it is very small (θc< 0.02) over Rh/YSZ. The surface coverage of active oxygen-containing species which lead to the formation of CO is found to be very small over both Rh/Al2O3and Rh/YSZ catalysts. However, over the Rh/YSZ catalyst it was found that there exists a large reservoir of lattice oxygen species of the carrier which interact reversibly with gaseous CO2under Reforming Reaction conditions. A spillover of these lattice oxygen species onto the Rh surface seems to occur, contributing to the formation of CO and H2O. This Reaction route proceeds in parallel with the Reforming Reaction on the Rh surface.
N.d. Charisiou - One of the best experts on this subject based on the ideXlab platform.
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investigating the correlation between deactivation and the carbon deposited on the surface of ni al2o3 and ni la2o3 al2o3 catalysts during the biogas Reforming Reaction
Applied Surface Science, 2019Co-Authors: N.d. Charisiou, Lazaros Tzounis, Kyriaki Polychronopoulou, Victor Sebastian, Steve Hinder, M A Baker, M.a. GoulaAbstract:Abstract Ni/Al2O3 and Ni/La2O-Al2O3 catalysts were investigated for the biogas Reforming Reaction using CH4/CO2 mixtures with minimal dilution. Stability tests at various Reaction temperatures were conducted and TGA/DTG, Raman, STEM-HAADF, HR-TEM, XPS techniques were used to characterize the spent samples. Graphitized carbon allotrope structures, carbon nanotubes (CNTs) and amorphous carbon were formed on all samples. Metallic Ni0 was recorded for all (XPS), whereas a strong peak corresponding to Ni2O3/NiAl2O4, was observed for the Ni/Al sample (650–750 °C). Stability tests confirm that the Ni/LaAl catalyst deactivates at a more gradual rate and is more active and selective in comparison to the Ni/Al for all temperatures. The Ni/LaAl exhibits good durability in terms of conversion and selectivity, whereas the Ni/Al gradually loses its activity in CH4 and CO2 conversion, with a concomitant decrease of the H2 and CO yield. It can be concluded that doping Al2O3 with La2O3 stabilizes the catalyst by (a) maintaining the Ni0 phase during the Reaction, due to higher dispersion and stronger active phase-support interactions, (b) leading to a less graphitic and more defective type of deposited carbon and (c) facilitating the deposited carbon gasification due to the enhanced CO2 adsorption on its increased surface basic sites.
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The potential of glycerol and phenol towards H2 production using steam Reforming Reaction: A review
Surface & Coatings Technology, 2018Co-Authors: N.d. Charisiou, Kyriaki Polychronopoulou, A. Asif, M.a. GoulaAbstract:Abstract Hydrogen production via the steam Reforming of glycerol, the main by-product of biodiesel production, and the pyrolysis/gasification route of biomass are two processes that have drawn considerable attention by the scientific community due to their potential in reducing our dependence on fossil based sources and in mitigating the effects of greenhouses gases on our planet. However, the commercial exploitation of the processes depends on the development of cheap, active and stable catalysts. In the present review, the key literature on the glycerol and phenol steam Reforming Reactions is presented and discussed. The impact of crucial variables for both the Reactions at hand are discussed, such as active metal nature, metal loading, support, Reaction temperature, method of preparation, poisoning resistance and coking tolerance. For catalytic systems design purposes the aspect of how the catalyst physicochemical characteristics affect the catalytic performance is addressed. Particular attention is given at the issue of coke resistance of the catalysts due to its detrimental effect for the Reactions at hand. Natural materials, such as calcites, dolomites and olivines, utilized for the phenol steam Reforming Reaction are discussed.
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hydrogen production via the glycerol steam Reforming Reaction over nickel supported on alumina and lanthana alumina catalysts
International Journal of Hydrogen Energy, 2017Co-Authors: N.d. Charisiou, Kyriakos N. Papageridis, G Siakavelas, Lazaros Tzounis, Apostolos Baklavaridis, Kyriaki Polychronopoulou, M.a. GoulaAbstract:In the present work, a comparative study of Ni catalysts supported on commercially available alumina and lanthana-alumina carriers was undertaken for the glycerol steam Reforming Reaction (GSR). The supports and/or catalysts were characterized by PZC, BET, ICP, XRD, NH3-TPD, CO2-TPD, TPR and SEM. Carbon deposited on the catalytic surface was characterized by SEM, TPO and Raman. Concerning the Ni/LaAl sample it can be concluded that the presence of lanthana by: (a) facilitating the active species dispersion, (b) strengthening the interactions between nickel species and support, (c) increasing of the basic sites' population and redistributing the acid ones in terms of strength and density, provides a catalyst with improved performance for the GSR Reaction, in terms of activity, H2 production and long term stability. TPO and Raman indicate that the carbon on the Ni/LaAl catalyst was mostly amorphous and was deposited mainly on the support surface. For the Ni/Al catalyst, graphitic carbon was prevalent and likely covered its active sites.
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comparative study of ni co cu supported on γ alumina catalysts for hydrogen production via the glycerol steam Reforming Reaction
Fuel Processing Technology, 2016Co-Authors: Kyriakos N. Papageridis, N.d. Charisiou, G Siakavelas, D G Avraam, Lazaros Tzounis, Kalliopi Kousi, M.a. GoulaAbstract:Abstract Catalysts with active phase Ni, Co or Cu supported on γ-alumina were synthesized at constant loading (8 wt.%) and tested for the glycerol steam Reforming Reaction (GSR). The synthesized samples, at their calcined and/or their reduced form, were characterized by BET, ICP, XRD, DRS, NH 3 -TPD, CO 2 -TPD, TPR and SEM. The carbon deposited on their surface under Reaction conditions was characterized by TEM, TPO, TGA and Raman. Catalytic performance for the glycerol steam Reforming Reaction was studied in order to investigate the effects of Reaction temperature on: (i) glycerol total conversion, (ii) glycerol conversion to gaseous products, (iii) hydrogen selectivity and yield, (iv) selectivity of carbonaceous gaseous products, (v) selectivity of liquid products and (vi) molar ratios of H 2 /CO and CO/CO 2 in the gaseous products' mixture. The stability of all catalysts was also investigated through time on stream experiments. It was concluded that catalytic performance, including liquid products' distribution, depends on the acid-base properties of the materials. Specifically, a drastic drop in the activity of the Ni/Al catalyst was observed, while Co/Al and Cu/Al catalysts deactivate in a slower rate, confirming that coke deposition, associated with dehydration, cracking and polymerization Reactions, takes place on the catalyst's surface strong acid sites.
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A Ni/apatite-type lanthanum silicate supported catalyst in glycerol steam Reforming Reaction
RSC Advances, 2016Co-Authors: M.a. Goula, N.d. Charisiou, Pavlos K. Pandis, Vassilis N. StathopoulosAbstract:In the glycerol steam Reforming Reaction a 5 wt% Ni/La9.83Si4.5Fe1.5O26±δ catalyst was found to be active and up to 3.2 times more selective to H2 than a 5 wt% Ni/Al2O3 catalyst, especially at low temperatures (
Fagen Wang - One of the best experts on this subject based on the ideXlab platform.
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performance enhancement of methane dry Reforming Reaction for syngas production over ir ce0 9la0 1o2 nanorods catalysts
Catalysis Today, 2019Co-Authors: Fagen Wang, Yan Wang, Linjia Zhang, Leilei Xu, Hao Yu, Zhongcheng Li, Zhiyong DengAbstract:Abstract Ir catalysts supported on Ce0.9La0.1O2 nanorods and nanoparticles were comparatively investigated for syngas production from methane dry Reforming Reaction. The exposure of active {110} and {100} crystal planes in the Ir/Ce0.9La0.1O2- nanorods catalysts contributed to the stronger redox property and more oxygen vacancy than those in the Ir/Ce0.9La0.1O2-nanoparticles catalysts. These advantages facilitated activation and transformation of methane and carbon dioxide, giving an enhanced performance of methane dry Reforming Reaction over the Ir/Ce0.9La0.1O2-nanorods catalysts. The work demonstrated significant influences of support morphologies in obtaining stable catalysts for methane dry Reforming Reaction.
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study on different ceo2 structure stability during ethanol steam Reforming Reaction over ir ceo2 nanocatalysts
Applied Catalysis A-general, 2018Co-Authors: Fagen Wang, Linjia Zhang, Hao Yu, Long Zhao, Zhiyong DengAbstract:Abstract Structure stability of CeO2 nanoparticles and nanorods were studied for ethanol steam Reforming Reaction over Ir/CeO2 nanocatalysts. Characterizations of BET, XRD, HRTEM, H2-TPR and H2O-TPD et al. were applied to analyze surface areas, sizes, morphologies, redox properties and water activation of the nanocatalysts. Performance results revealed that Reaction patterns of ethanol steam Reforming Reaction were dependent on the structures of CeO2 supports, originating from different abilities in water activation. After long time stability tests conducted at high temperature of 923 K, the CeO2 nanoparticles maintained original polyhedral shape, while the CeO2 nanorods changed to polyhedrons. The shape variation of the nanorods was supposed to associated with OH groups combination and oxygen exchange in surface crystal planes of ceria nanorods, which diminished oxygen vacancies and reconstructed ceria morphology.
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enhanced catalytic performance of ir catalysts supported on ceria based solid solutions for methane dry Reforming Reaction
Catalysis Today, 2017Co-Authors: Fagen Wang, Leilei Xu, Jian Zhang, Yu Zhao, Hui Li, He Xing Li, Kai Wu, Juan Yang, Longzhu Zhang, Guo Qin XuAbstract:Abstract Methane dry Reforming Reaction was investigated over Ir catalysts supported on ceria-based solid solutions. The doping of Pr 6 O 11 or ZrO 2 into the matrix of ceria yields more oxygen defects, resulting in an improved redox property and enhanced metal-support interaction in Ir/Ce 0.9 M 0.1 O 2 (M = Pr, Zr) catalysts compared to Ir/CeO 2 catalyst. The Ir/Ce 0.9 M 0.1 O 2 (M = Pr, Zr) catalysts showed higher catalytic performance and better stability than the Ir/CeO 2 catalyst, which were assigned to positive effects of doping in maintaining Ir nanoparticles, stabilizing catalyst structure, and the strong metal-support interaction in reducing carbon deposition.
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tuning the metal support interaction in catalysts for highly efficient methane dry Reforming Reaction
Applied Catalysis B-environmental, 2016Co-Authors: Fagen Wang, Leilei Xu, Jian Zhang, Yu Zhao, Hui Li, He Xing Li, Kai Wu, Guo Qin Xu, Wei ChenAbstract:Abstract The metal-support interaction of Ir/Ce 0.9 Pr 0.1 O 2 catalyst is tuned by adopting different preparation techniques of deposition–precipitation (DP), co-precipitation (CP) and sequential precipitation (SP) to control the locations of Ir, improving catalytic performance in methane dry Reforming Reaction. Ir/Ce 0.9 Pr 0.1 O 2 -DP catalyst shows the highest catalytic performance and stability due to the unembedded Ir nanoparticles on catalyst surfaces, followed by Ir/Ce 0.9 Pr 0.1 O 2 -SP and Ir/Ce 0.9 Pr 0.1 O 2 -CP catalysts in which Ir species are either partially or fully embedded in Ce-Pr-O mixed oxides. Our results clearly demonstrate that the metal-support interaction plays important roles in controlling the catalyst sintering and carbonaceous deposition.
J L G Fierro - One of the best experts on this subject based on the ideXlab platform.
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improved stability of ni al2o3 catalysts by effect of promoters la2o3 ceo2 for ethanol steam Reforming Reaction
Catalysis Today, 2016Co-Authors: Paula Osoriovargas, Cristian H Campos, R M Navarro, J L G Fierro, Nicolas Floresgonzalez, Patricio ReyesAbstract:Abstract Ni-based catalysts supported on γ-Al2O3 modified by La2O3 and CeO2 promoters were prepared in the present work. The objective was to study the promotional effect of addition of 15 wt% La2O3 and different CeO2 contents on stability of Ni/Al2O3 catalysts for ethanol steam-Reforming Reaction. The physical chemical characteristics of the catalysts, activity and the carbon deposition on the catalyst surface were carried out by TEM, NH3-TPD, XRD, TPR, XPS, DRIFT, TPO-TG and Raman. The stability of Ni/γ-Al2O3 was effectively improved by addition of 15 wt% La2O3 and 10 wt% CeO2 as the carbon deposition rate was reduced 72% compared with catalyst supported on bare alumina. The role of promoters was to decrease the selectivity to ethylene by reduction of strong Lewis acid sites of γ-Al2O3 and the removing carbon deposits during Reaction, through both lanthanum oxycarbonate formations from La2O3 as the higher amount of mobile lattice oxygen induced by the CeO2 promoter. This catalyst showed good results of selectivity to H2, no presence of C2 intermediates above 723 K and it was stable up to 48 h of time-on-stream at 773 K. In addition, it was possible to recover part of the original catalyst activity after a reactivation process, in order to remove some carbon deposits as potential causes of deactivation.
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rh al2o3 la2o3 catalysts promoted with ceo2 for ethanol steam Reforming Reaction
Journal of Molecular Catalysis A-chemical, 2015Co-Authors: Paula Osoriovargas, Cristian H Campos, R M Navarro, J L G Fierro, Patricio ReyesAbstract:Abstract Rh-based catalysts supported on γ-Al2O3–La2O3 modified with CeO2 promoter were prepared in the present work. The objective was to study the promotional effect of the addition of different CeO2 contents and 15 wt% La2O3 on the stability of Rh/γ-Al2O3 catalysts for ethanol steam Reforming Reaction. The physico-chemical characteristics of the catalysts, activity and the deposition of carbon on the catalyst surface were surveyed by NH3-TPD, XRD, TPR, XPS, DRIFT, TPO-TG and Raman. The stability of Rh/γ-Al2O3 catalyst was effectively improved by the addition of 15 wt% La2O3 and 5 wt% CeO2, as the carbon deposition rate was reduced significantly (from 2.3 to 0.16 mgcoke gcat−1 h−1). The role of the promoter was to decrease the selectivity to ethylene by modification of Lewis acid sites on the support and the removal of carbon deposits during the Reaction. This is achieved through the formation of lanthanum oxycarbonate from La2O3 and higher amount of mobile lattice oxygen induced by the CeO2 promoter. This catalyst exhibited good selectivity to H2, with no presence of C2 intermediates above 723 K; in addition this catalyst was stable up to 48 h of time on stream at 773 K. Furthermore, the original activity of the catalyst was recovered through regeneration by the removal of some carbon deposits which are potential causes of deactivation.
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mechanistic aspects of the ethanol steam Reforming Reaction for hydrogen production on pt ni and ptni catalysts supported on γ al2o3
Journal of Physical Chemistry A, 2010Co-Authors: Maria Cruz Sanchezsanchez, Rufino Manuel Navarro Yerga, Dimitris I Kondarides, Xenophon E Verykios, J L G FierroAbstract:Mechanistic aspects of ethanol steam Reforming on Pt, Ni, and PtNi catalysts supported on γ-Al2O3 are investigated from the analysis of adsorbed species and gas phase products formed on catalysts during temperature-programmed desorption of ethanol and during ethanol steam Reforming Reaction. DRIFTS-MS analyses of ethanol decomposition and ethanol steam Reforming Reactions show that PtNi and Ni catalysts are more stable than the Pt monometallic counterpart. Ethanol TPD results on Ni, Pt, and NiPt catalysts point to ethanol dehydrogenation and acetaldehyde decomposition as the first Reaction pathways of ethanol steam Reforming over the studied catalysts. The active sites responsible for the acetaldehyde decomposition are easily deactivated in the first minutes on-stream by carbon deposits. For Ni and PtNi catalysts, a second Reaction pathway, consisting in the decomposition of acetate intermediates formed over the surface of alumina support, becomes the main Reaction pathway operating in steam Reforming of ...
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the phenol steam Reforming Reaction over mgo based supported rh catalysts
Journal of Catalysis, 2004Co-Authors: Kyriaki Polychronopoulou, J L G Fierro, Angelos M. EfstathiouAbstract:Abstract The phenol steam Reforming Reaction toward H2 formation has been investigated in the 575–730 °C range over MgO, CeO2, and ZrO2 single metal oxides and various mixed metal oxides such as Mg–Ce–O, Mg–Zr–O, and Mg–Ce–Zr–O, all prepared by the sol–gel method. The same Reaction has also been studied over Rh supported on these metal oxides. The effects of synthesis method of the Mg–Ce–Zr–O support (mechanical mixing versus sol–gel) and of Rh deposition (wet impregnation versus sol–gel) on the activity and H2 selectivity of the Reaction over the Rh/Mg–Ce–Zr–O catalyst have also been investigated. It was found that 0.5 wt% Rh/MgO and 0.1 wt% Rh/Mg–Ce–Zr–O catalysts, the supports of which were prepared by the sol–gel method, exhibit better performance when compared to a commercial Ni-based catalyst used for tar steam Reforming. In particular, Rh/MgO presented the highest H2 product concentrations and selectivities in the 575–730 °C range and no more than 20% drop in activity after 24 h of continuous Reaction (0.5% C6H5OH/40% H2O/He). It was found that steam Reforming of phenol is favored over very small Rh particles in the case of 0.1 wt% Rh/Mg–Ce–Zr–O catalyst. In particular, the specific integral Reaction rate of H2 production (mmol-H2 / (m2Rh s)) significantly increased by decreasing the Rh particle size from 2.7 to 1.2 nm. The effect of the partial pressure of water and phenol in the feed stream on catalyst activity was found to strongly depend on support chemical composition. More than one kind of carbonaceous species forming during Reaction has been identified with varying compositions and reactivities toward oxygen and steam. XPS studies suggested that the MgxZr1−xO2 phase present in the Mg–Ce–Zr–O support is reduced by H2 at 300 °C in the presence of very small Rh particles leading to the creation of oxygen vacant sites and diffusion of Zr toward the bulk of the crystal. As a result of this, the surface acidity and basicity of the Rh/Mg–Ce–Zr–O catalyst are expected to alter, thus influencing the hydrogen activity and selectivity of the Reaction.