Journal articles: 'Ceria-based catalyst'

1

Flytzani-Stephanopoulos, Maria. "Nanostructured Cerium Oxide “Ecocatalysts”." MRS Bulletin 26, no. 11 (November 2001): 885–89. http://dx.doi.org/10.1557/mrs2001.229.

Full text

Abstract:

Catalysts based on cerium oxide are now used as effective oxidation systems in numerous environmental applications. Cerium oxide was introduced into the catalysis field relatively recently, in 1976, and not as a catalyst initially. Rather, it was chosen as the key oxygen-storage component of the three-way catalyst (TWC) used in automotive exhausts. Accordingly, ceria is used to extend the air/fuel ratio window in the exhaust gas, releasing or accepting oxygen, respectively, under fuel-rich or fuellean conditions, so that the noble metal catalyst operates at the desirable stoichiometric air/fuel ratio, at which it effectively converts all three gaseous pollutants—CO, hydrocarbons, and NO—to innocuous products. A solid solution of cerium and zirconium oxides is used in today's catalytic converters because of its higher oxygen-storage capacity (OSC) compared with pure ceria. In the years that followed the introduction of ceria into the catalytic converter, many additional merits of cerium oxide were realized, first as an active catalytic component of the TWC and subsequently as a catalyst and sorbent in various industrial applications. A review article by Trovarelli on ceria-based catalysts is a good recent compilation.

APA, Harvard, Vancouver, ISO, and other styles

2

Laitinen, Tiina, Satu Ojala, Eric Genty, Julien Brunet, Guy De Weireld, Christophe Poupin, Stéphane Siffert, Renaud Cousin, and Riitta L. Keiski. "On the Activity and Selectivity of CoAl and CoAlCe Mixed Oxides in Formaldehyde Production from Pulp Mill Emissions." Catalysts 10, no. 4 (April 13, 2020): 424. http://dx.doi.org/10.3390/catal10040424.

Full text

Abstract:

Contaminated methanol has very good potential for being utilized in formaldehyde production instead of its destructive abatement. The activities, selectivities and stabilities of cobalt–alumina and cobalt–alumina–ceria catalysts prepared by the hydrotalcite-method were investigated in formaldehyde production from emissions of methanol and methanethiol. Catalysts were thoroughly characterized and the relationships between the characterization results and the catalytic performances were drawn. The preparation method used led to the formation of spinel-type structures in the form of Co2AlO4 based on x-ray diffraction (XRD) and Raman spectroscopy. Ceria seems to be present as CeO2, even though interaction with alumina is possible in the fresh catalyst. The same structure is maintained after pelletizing the cobalt–alumina–ceria catalyst. The cobalt–alumina–ceria catalyst was slightly better in formaldehyde production, probably due to lower redox temperatures and higher amounts of acidity and basicity. Methanol conversion is negatively affected by the presence of methanethiol; however, formaldehyde yields are improved. The stability of the pelletized catalyst was promising based on a 16 h experiment. During the experiment, cobalt was oxidized (Co2+ → Co3+), cerium was reduced (Ce4+ → Ce3+) and sulfates were formed, especially on the outer surface of the pellet. These changes affected the low temperature performance of the catalyst; however, the formaldehyde yield was unchanged.

APA, Harvard, Vancouver, ISO, and other styles

3

Aneggi, E., V. Cabbai, A. Trovarelli, and D. Goi. "Potential of Ceria-Based Catalysts for the Oxidation of Landfill Leachate by Heterogeneous Fenton Process." International Journal of Photoenergy 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/694721.

Full text

Abstract:

In this study, ceria and ceria-zirconia solid solutions were tested as catalyst for the treatment of landfill leachate with a Fenton-like process. The catalysts considered in this work were pure ceria and ceria-zirconia solid solutions as well as iron-doped samples. All the catalysts were extensively characterized and applied in batch Fenton-like reactions by a close batch system, the COD (chemical oxygen demand) and TOC (total organic carbon) parameters were carried out before and after the treatments in order to assay oxidative abatement. Results show a measurable improvement of the TOC and COD abatement using ceria-based catalysts in Fenton-like process and the best result was achieved for iron-doped ceria-zirconia solid solution. Our outcomes point out that heterogeneous Fenton technique could be effectively used for the treatment of landfill leachate and it is worth to be the object of further investigations.

APA, Harvard, Vancouver, ISO, and other styles

4

Li, Boyu, Eric Croiset, and John Z. Wen. "Influence of Surface Properties of Nanostructured Ceria-Based Catalysts on Their Stability Performance." Nanomaterials 12, no. 3 (January 25, 2022): 392. http://dx.doi.org/10.3390/nano12030392.

Full text

Abstract:

As the poor cycling stability of CeO2 catalysts has become the major obstacle for applications of diesel particulate filters (DPF), it is necessary to investigate how to reduce their structural and compositional changes during soot oxidation. In this study, different ratios of Samarium (Sm) were doped into the lattice of CeO2 nanoparticles to improve the catalytic performance as well as surface properties. The stability was investigated by recycling the catalyst, mixing it with soot again, and repeating the thermogravimetric analysis (TGA) tests seven times. Consistent observations were expected for more cycles. It was found that doping 5%, 10%, and 20% samarium into the CeO2 lattice can improve the catalyst stability but at the cost of losing some activity. While the catalyst became more stable with the increasing Sm doping, the 10% Sm-doped catalyst showed the best compromise between stability and activity. Ce3+ and Oα were found to play important roles in controlling catalytic soot oxidation activity. These two species were directly related to oxygen vacancies and oxygen storage capacity of the catalyst. Sm-doped catalysts showed a minimized decrease in the Ce3+ and Oα content when the fresh and spent catalysts were compared.

APA, Harvard, Vancouver, ISO, and other styles

5

Dimitrov, Momtchil, Gloria Issa, Daniela Kovacheva, and Tanya Tsoncheva. "Novel Ceria and Ceria-based Nanocomposites as Potential Catalysts for Methanol Decomposition and Total Oxidation of Ethyl Acetate." Proceedings of the Bulgarian Academy of Sciences 75, no. 9 (September 30, 2022): 1287–94. http://dx.doi.org/10.7546/crabs.2022.09.05.

Full text

Abstract:

The focus of our study is the development of novel ceria-based materials that can be successfully used as catalysts in various environmentally friendly processes due to a significant improvement of ceria intrinsic characteristics. In particular, the combination of ceria with low-dimensional carbon materials such as graphene oxide (GO) and nanodiamond (ND) appears as a very promising approach. Actually, the decrease of ceria crystallite sizes deep in the nanoscale have been found to convert them into highly effective destructive adsorbent materials owing to their high surface area, strong adsorbability, and large number of highly reactive sites. Besides, the addition of a nanostructured carbon containing component (nanodiamond or graphene oxide) contributes to both mechanical and catalytic properties of the obtained nanocomposite hybrids. The results show that the novel ceria and ceria-based composite materials significantly outperform the hydrothermally obtained ceria catalyst used for comparison in both activity and selectivity to CO and hydrogen in the methanol decomposition reaction, and in the process of total oxidation of ethyl acetate due to their significantly improved redox behaviour and textural characteristics.

APA, Harvard, Vancouver, ISO, and other styles

6

Konsolakis, Michalis, and Maria Lykaki. "Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review." Catalysts 11, no. 4 (March 31, 2021): 452. http://dx.doi.org/10.3390/catal11040452.

Full text

Abstract:

The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.

APA, Harvard, Vancouver, ISO, and other styles

7

Frontera, Patrizia, Anastasia Macario, Angela Malara, Saveria Santangelo, Claudia Triolo, Fortunato Crea, and Pierluigi Antonucci. "Trimetallic Ni-Based Catalysts over Gadolinia-Doped Ceria for Green Fuel Production." Catalysts 8, no. 10 (October 2, 2018): 435. http://dx.doi.org/10.3390/catal8100435.

Full text

Abstract:

The present work concerns the characterization of trimetallic nickel catalysts, NiMoRe (Nickel/Molybdenum/Rhenium), NiMoCu (Nickel/Molybdenum/Copper) and NiMoCo (Nickel/Molybdenum/Cobalt), supported on gadolinia-doped ceria and the evaluation of their catalytic performance in the auto-thermal reforming of ethanol to hydrogen. Catalysts have been prepared by wet impregnation and characterized by XRD, SEM-EDX, TG-DSC, TEM, CHNS, H2-TPR and micro-Raman spectroscopy. The resistance of Ni-alloy catalysts to the carbon deposition and sulfur poisoning has been studied. All catalysts show a similar behavior in the auto-thermal reforming reaction: 100% of ethanol conversion and high selectivity to syngas products, up to 77 vol.%. At 800 °C the coke deposition is very low (less than 0.34 wt%). Sulfur content affects the selectivity and the activity of the catalysts, especially towards the coke formation: high sulfur content promotes the ethylene formation, therefore the amount of coke deposited on spent catalyst increases. NiMoCu seems to be the trimetallic catalyst less sensitive to this aspect.

APA, Harvard, Vancouver, ISO, and other styles

8

Beaudoux, Xavier, Matthieu Virot, Tony Chave, Grégory Durand, Gilles Leturcq, and Sergey I. Nikitenko. "Vitamin C boosts ceria-based catalyst recycling." Green Chemistry 18, no. 12 (2016): 3656–68. http://dx.doi.org/10.1039/c6gc00434b.

Full text

Abstract:

The facile, rapid, and complete reductive dissolution of CeO₂ and ceria-based oxides, known to be highly refractive materials towards dissolution, is reported for the first time in very mild conditions.

APA, Harvard, Vancouver, ISO, and other styles

9

Shih, Shao Ju, Jian Pu Huang, and Yu Jen Chou. "Formation Mechanism of Ceria Particles by Spray Pyrolysis." Advanced Materials Research 488-489 (March 2012): 169–74. http://dx.doi.org/10.4028/www.scientific.net/amr.488-489.169.

Full text

Abstract:

Ceria-based materials are widely used in industrial applications such as catalyst supports, catalysts and electrolytes. Various applications require different morphological particles. Spray pyrolysis (SP) is a well-known process for ceria particle fabrication because SP has the advantages of simple and continuous process. Although various studies have discussed the particle morphology formation of SP, some questions are still unclear. In order to solve these questions, this study investigates the morphology of ceria particles from various precursors using SP. By combining the experimental data of scanning electron microscopy, transmission electron microscopy and focused ion beam, the result suggests that the particle formation mechanism is highly correlated with factors of hydrophilic-hydrophobic properties of precursors. Therefore, the morphology mechanism of SP for the ceria particles is proposed .

APA, Harvard, Vancouver, ISO, and other styles

10

Di Stasi, Christian, Simona Renda, Gianluca Greco, Belén González, Vincenzo Palma, and Joan J. Manyà. "Wheat-Straw-Derived Activated Biochar as a Renewable Support of Ni-CeO2 Catalysts for CO2 Methanation." Sustainability 13, no. 16 (August 10, 2021): 8939. http://dx.doi.org/10.3390/su13168939.

Full text

Abstract:

Ceria- and urea-doped activated biochars were used as support for Ni-based catalysts for CO2 methanation purposes. Different materials were prepared and tested to find the best catalytic formulation. After several CO2 methanation experiments—carried out at 0.35–1.0 MPa and 300–500 °C—it was found that the most suitable catalyst was a wheat-straw-derived activated biochar loaded with 30 wt.% of CeO2 and 20 wt.% of Ni. Using this catalyst, a CO2 conversion of 65% with a CH4 selectivity of 95% was reached at 1.0 MPa, 400 °C, and 13,200 h−1. From the study of the influence of the gas hourly space velocity, it was deduced that the most likely reaction mechanism was a reverse water–gas shift reaction, followed by CO hydrogenation. N-doping of the carbon support as an alternative to the use of ceria was also investigated. However, both CO2 conversion and selectivity toward CH4 values were clearly lower than those obtained for the ceria-containing catalyst cited above. The outcomes of this work indicate that a renewable biomass-derived support can be effectively employed in the catalytic conversion of CO2 to methane.

APA, Harvard, Vancouver, ISO, and other styles

11

Aneggi, Eleonora, Carla de Leitenburg, and Alessandro Trovarelli. "Influence of Nanoscale Surface Arrangements on the Oxygen Transfer Ability of Ceria–Zirconia Mixed Oxide." Inorganics 8, no. 5 (May 12, 2020): 34. http://dx.doi.org/10.3390/inorganics8050034.

Full text

Abstract:

Ceria-based materials, and particularly CeO2–ZrO2 (CZ) solid solutions are key ingredient in catalyst formulations for several applications due to the ability of ceria to easily cycling its oxidation state between Ce4+ and Ce3+. Ceria-based catalysts have a great soot oxidation potential and the mechanism deeply relies on the degree of contact between CeO2 and carbon. In this study, carbon soot has been used as solid reductant to better understand the oxygen transfer ability of ceria–zirconia at low temperatures; the effect of different atmosphere and contact conditions has been investigated. The difference in the contact morphology between carbon soot and CZ particles is shown to strongly affect the oxygen transfer ability of ceria; in particular, increasing the carbon–ceria interfacial area, the reactivity of CZ lattice oxygen is significantly improved. In addition, with a higher degree of contact, the soot oxidation is less affected by the presence of NOx. The NO oxidation over CZ in the presence of soot has also been analyzed. The existence of a core/shell structure strongly enhances reactivity of interfacial oxygen species while affecting negatively NO oxidation characteristics. These findings are significant in the understanding of the redox chemistry of substituted ceria and help determining the role of active species in soot oxidation reaction as a function of the degree of contact between ceria and carbon.

APA, Harvard, Vancouver, ISO, and other styles

12

Tuyen, Le Thi Thanh, Dinh Quang Khieu, Hoang Thai Long, Duong Tuan Quang, Chau The Lieu Trang, Tran Thai Hoa, and Nguyen Duc Cuong. "Monodisperse Uniform CeO2Nanoparticles: Controlled Synthesis and Photocatalytic Property." Journal of Nanomaterials 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/8682747.

Full text

Abstract:

Ceria nanostructure-based catalysts have attracted much attention in recent years because of their unique physiochemical properties. Herein, we have presented a simple two-phase approach for the synthesis of ceria nanocrystals. Structural and morphological characterization by XRD and TEM showed that the as-synthesized monodisperse CeO2nanoparticles (NPs) had cubic fluorite crystal structure with average particle size about 6.75 nm. The effects of hydrothermal temperature, annealing time, and concentration of cerium nitrate on the nanostructures of the products were also investigated and discussed. In addition, the CeO2nanocrystals proved to be an effective catalyst for the photodegradation of blue methylene under UV illumination.

APA, Harvard, Vancouver, ISO, and other styles

13

Garcia, Xènia, Lluís Soler, Núria J. Divins, Xavier Vendrell, Isabel Serrano, Ilaria Lucentini, Jordi Prat, et al. "Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review." Catalysts 10, no. 3 (March 3, 2020): 286. http://dx.doi.org/10.3390/catal10030286.

Full text

Abstract:

The development of better catalysts is a passionate topic at the forefront of modern science, where operando techniques are necessary to identify the nature of the active sites. The surface of a solid catalyst is dynamic and dependent on the reaction environment and, therefore, the catalytic active sites may only be formed under specific reaction conditions and may not be stable either in air or under high vacuum conditions. The identification of the active sites and the understanding of their behaviour are essential information towards a rational catalyst design. One of the most powerful operando techniques for the study of active sites is near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), which is particularly sensitive to the surface and sub-surface of solids. Here we review the use of NAP-XPS for the study of ceria-based catalysts, widely used in a large number of industrial processes due to their excellent oxygen storage capacity and well-established redox properties.

APA, Harvard, Vancouver, ISO, and other styles

14

Kenzhin, Roman M., Evgeny A. Alikin, Sergey P. Denisov, and Aleksey A. Vedyagin. "Study on Thermal Stability of Ceria-Supported Rhodium Catalysts." Materials Science Forum 950 (April 2019): 190–94. http://dx.doi.org/10.4028/www.scientific.net/msf.950.190.

Full text

Abstract:

In the present work, the impact of the rhodium deposition on the thermal stability of ceria-based catalysts was studied. The samples were prepared by an incipient wetness impregnation of the support with aqueous solution of rhodium nitrate. The loading of Rh was 0.1 and 1 wt.%. The textural characteristics of the samples were examined by a low-temperature nitrogen adsorption. It was shown that the addition of rhodium intensifies the process of ceria agglomeration, which leads to the lower values of specific surface area along with increased average pore diameter after the aging at 1000 °C. Stability of the catalysts was investigated by means of a prompt thermal aging procedure. The high-loaded catalyst (1 wt.% Rh/CeO2) was more active than the 0.1 wt.% Rh/CeO2sample, while the stability of both the catalysts was excellent. It should be emphasized that the alumina-based reference samples with the similar rhodium loading were significantly less active and poorly stable.

APA, Harvard, Vancouver, ISO, and other styles

15

Rocha, Luiz Célio S., Mariana S. Rocha, Paulo Rotella Junior, Giancarlo Aquila, Rogério S. Peruchi, Karel Janda, and Rômulo O. Azevêdo. "Robust Multi-Objective Optimization for Response Surface Models Applied to Direct Low-Value Natural Gas Conversion Processes." Entropy 23, no. 2 (February 21, 2021): 248. http://dx.doi.org/10.3390/e23020248.

Full text

Abstract:

The high proportion of CO2/CH4 in low aggregated value natural gas compositions can be used strategically and intelligently to produce more hydrocarbons through oxidative methane coupling (OCM). The main goal of this study was to optimize direct low-value natural gas conversion via CO2-OCM on metal oxide catalysts using robust multi-objective optimization based on an entropic measure to choose the most preferred Pareto optimal point as the problem’s final solution. The responses of CH4 conversion, C2 selectivity, and C2 yield are modeled using the response surface methodology. In this methodology, decision variables, e.g., the CO2/CH4 ratio, reactor temperature, wt.% CaO and wt.% MnO in ceria catalyst, are all employed. The Pareto optimal solution was obtained via the following combination of process parameters: CO2/CH4 ratio = 2.50, reactor temperature = 1179.5 K, wt.% CaO in ceria catalyst = 17.2%, wt.% MnO in ceria catalyst = 6.0%. By using the optimal weighting strategy w1 = 0.2602, w2 = 0.3203, w3 = 0.4295, the simultaneous optimal values for the objective functions were: CH4 conversion = 8.806%, C2 selectivity = 51.468%, C2 yield = 3.275%. Finally, an entropic measure used as a decision-making criterion was found to be useful in mapping the regions of minimal variation among the Pareto optimal responses and the results obtained, and this demonstrates that the optimization weights exert influence on the forecast variation of the obtained response.

APA, Harvard, Vancouver, ISO, and other styles

16

Wang, Xi, Alexandre Westermann, Yi Shi, Ning Cai, Mathilde Rieu, Jean-Paul Viricelle, and Philippe Vernoux. "Electrochemical Removal of NOx on Ceria-Based Catalyst-Electrodes." Catalysts 7, no. 12 (February 16, 2017): 61. http://dx.doi.org/10.3390/catal7020061.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Davó-Quiñonero, Arantxa, Sergio López-Rodríguez, Cristian Chaparro-Garnica, Iris Martín-García, Esther Bailón-García, Dolores Lozano-Castelló, Agustín Bueno-López, and Max García-Melchor. "Investigations of the Effect of H2 in CO Oxidation over Ceria Catalysts." Catalysts 11, no. 12 (December 20, 2021): 1556. http://dx.doi.org/10.3390/catal11121556.

Full text

Abstract:

The preferential CO oxidation (so-called CO-PROX) is the selective CO oxidation amid H2-rich atmospheres, a process where ceria-based materials are consolidated catalysts. This article aims to disentangle the potential CO–H2 synergism under CO-PROX conditions on the low-index ceria surfaces (111), (110) and (100). Polycrystalline ceria, nanorods and ceria nanocubes were prepared to assess the physicochemical features of the targeted surfaces. Diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) shows that ceria surfaces are strongly carbonated even at room temperature by the effect of CO, with their depletion related to the CO oxidation onset. Conversely, formate species formed upon OH + CO interaction appear at temperatures around 60 °C and remain adsorbed regardless the reaction degree, indicating that these species do not take part in the CO oxidation. Density functional theory calculations (DFT) reveal that ceria facets exhibit high OH coverages all along the CO-PROX reaction, whilst CO is only chemisorbed on the (110) termination. A CO oxidation mechanism that explains the early formation of carbonates on ceria and the effect of the OH coverage in the overall catalytic cycle is proposed. In short, hydroxyl groups induce surface defects on ceria that increase the COx–catalyst interaction, revealed by the CO adsorption energies and the stabilization of intermediates and readsorbed products. In addition, high OH coverages are shown to facilitate the hydrogen transfer to form less stable HCOx products, which, in the case of the (110) and (100), is key to prevent surface poisoning. Altogether, this work sheds light on the yet unclear CO–H2 interactions on ceria surfaces during CO-PROX reaction, providing valuable insights to guide the design of more efficient reactors and catalysts for this process.

APA, Harvard, Vancouver, ISO, and other styles

18

Cortese, Marta, Concetta Ruocco, Vincenzo Palma, Pedro J. Megía, Alicia Carrero, and José A. Calles. "On the Support Effect and the Cr Promotion of Co Based Catalysts for the Acetic Acid Steam Reforming." Catalysts 11, no. 1 (January 18, 2021): 133. http://dx.doi.org/10.3390/catal11010133.

Full text

Abstract:

This work focuses on the support effect of the performances of Co based catalysts for acetic acid steam reforming. SBA-15, a well ordered hexagonal mesoporous silica structure, and CeO2 have been selected as the supports, with the impact of chromium addition also being investigated. Better acetic acid steam reforming performances have been recorded for CeO2 compared to SBA-15 supported catalysts and, in particular, the 7Co/CeO2 catalyst showed the highest values of acetic acid conversions with enhanced H2 yields below 480 °C, in comparison to the other investigated catalytic formulations. In addition, more pronounced coke depositions and acetone concentrations have been obtained with CeO2 supported catalysts, due to the tendency of ceria to catalyse the ketonization reaction. Chromium addition to Co/SBA-15 catalysts led to an enhancement in the activity towards acetic acid steam reforming, while on CeO2 supported catalysts no improvement in the catalysts’ activity was observed. However, on both SBA-15 and CeO2 supported catalysts, Cr addition reduced the amount of coke deposited on the catalysts surface.

APA, Harvard, Vancouver, ISO, and other styles

19

Tabakova, Ilieva, Petrova, Venezia, Karakirova, Liotta, and Avdeev. "Complete Benzene Oxidation over Mono and Bimetallic Pd—Au Catalysts on Alumina-Supported Y-Doped Ceria." Applied Sciences 10, no. 3 (February 6, 2020): 1088. http://dx.doi.org/10.3390/app10031088.

Full text

Abstract:

The protection of environment and human health stimulates intensive research for abatement of volatile organic compounds (VOCs) in the atmosphere. Complete catalytic oxidation is an efficient, environmentally friendly and economically feasible method for elimination of VOCs. This study aims to design high performing and cost-effective catalytic formulations by exploration of appropriate and economically viable supports. Alumina-supported ceria (30 wt.%) and Y2O3 (1 wt.%)-doped ceria were prepared by mechanical mixing and were used as support of mono Au (2 wt.%) and Pd (1 wt.%) and bimetallic Pd-Au catalysts. The characterization by textural measurements, X-ray powder diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), EPR (electron paramagnetic resonance) and temperature-programmed reduction (TPR) was carried out in order to clarify the relationship between catalyst composition, textural, structural and surface properties, reducibility and catalytic performance for complete benzene oxidation. Among all studied catalysts, Pd-based catalysts exhibited the best combustion activity. In particular, monometallic Pd on alumina supported Y-doped ceria attained 100% of complete benzene conversion at 180 °C. These catalytic materials have potential to meet stringent emission regulations in an economical and effective way.

APA, Harvard, Vancouver, ISO, and other styles

20

Zhu, Bin, Xiang Rong Liu, Ye Cheng, and Mi Lin Zhang. "Novel Catalytic Electrodes for High Performance Solid Oxide Fuel Cells Operated at Intermediate Temperatures." Key Engineering Materials 336-338 (April 2007): 428–33. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.428.

Full text

Abstract:

The all-ceria-composite ITSOFCs have demonstrated extraordinary fuel cell performances since the ceria-composite electrodes are very catalytic and conductive, and the ceria-composite electrolytes are highly conductive and also electrolytic, in addition to excellent compatibility between the electrolyte and electrodes based on the same ceria-based composite materials. The power density outputs from 200 to 800 mWcm-2, were obtained for temperatures between 400 and 700°C. The maximum power density 0.72 Wcm-2 (1500 mAcm-2) at 600°C and 0.82 Wcm-2 (1800 mAcm-2) at 700°C were achieved, respectively. These highly catalytic electrodes functioned extensively for many different fuels, such as hydrogen and hydrocarbon fuels, e.g., natural gas, coal gas, methanol and ethanol etc. In some special cases, the ITSOFCs with the ceria-composite electrodes could also work at as low as 200°C. All these good performances are based on the novel catalyst function of the ceria-composite electrodes and internal reforming mechanism.

APA, Harvard, Vancouver, ISO, and other styles

21

Santoro, Mariarita, Igor Luisetto, Simonetta Tuti, Silvia Licoccia, Claudia Romano, Andrea Notargiacomo, and Elisabetta Di Bartolomeo. "Nickel-Based Structured Catalysts for Indirect Internal Reforming of Methane." Applied Sciences 10, no. 9 (April 28, 2020): 3083. http://dx.doi.org/10.3390/app10093083.

Full text

Abstract:

A structured catalyst for the dry reforming of methane (DRM) was investigated as a biogas pre-reformer for indirect internal reforming solid oxide fuel cell (IIR-SOFC). For this purpose, a NiCrAl open-cell foam was chosen as support and Ni-based samarium doped ceria (Ni-SmDC) as catalyst. Ni-SmDC powder is a highly performing catalyst showing a remarkable carbon resistance due to the presence of oxygen vacancies that promote coke gasification by CO2 activation. Ni-SmDC powder was deposited on the metallic support by wash-coating method. The metallic foam, the powder, and the structured catalyst were characterized by several techniques such as: N2 adsorption-desorption technique, X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), focused ion beam (FIB), temperature programmed reduction (H2-TPR), and Raman spectroscopy. Catalytic tests were performed on structured catalysts to evaluate activity, selectivity, and stability at SOFC operating conditions.

APA, Harvard, Vancouver, ISO, and other styles

22

Borisov, Vadim A., Zaliya A. Fedorova, Victor L. Temerev, Mikhail V. Trenikhin, Dmitry A. Svintsitskiy, Ivan V. Muromtsev, Alexey B. Arbuzov, Alexey B. Shigarov, Pavel V. Snytnikov, and Dmitry A. Shlyapin. "Ceria–Zirconia-Supported Ruthenium Catalysts for Hydrogen Production by Ammonia Decomposition." Energies 16, no. 4 (February 9, 2023): 1743. http://dx.doi.org/10.3390/en16041743.

Full text

Abstract:

Сommercial cerium–zirconium oxide supports (Ce0.5Zr0.5O2, Ce0.75Zr0.25O2, and Ce0.4Zr0.5Y0.05La0.05O2) were used to prepare Ru/CeZrOx catalysts. According to the XRD and IR spectroscopy data, the supports consist of ceria-based substitutional solid solutions. The specific surface areas of supports and catalysts are similar and range from 71–89 m2/g. As shown by TEM and XRD methods, the size of support particles equals 6–11 nm. According to the TEM data, the size of ruthenium particles does not exceed 1.3 nm. The catalyst activity in the ammonia decomposition process was studied. The Ru/Ce0.75Zr0.25O2 catalyst at temperature 500 °C and GHSV 120,000 h−1 demonstrated the highest hydrogen productivity of 53.3 mmol H2/(gcat·min) and compares well with the best results reported in the literature. The kinetics of ammonia decomposition reaction were calculated using the Temkin–Pyzhov exponential expression. The developed mathematical model well described the experimental data. The studied catalysts demonstrated high activity for the ammonia decomposition reaction.

APA, Harvard, Vancouver, ISO, and other styles

23

Frontera, Patrizia, Angela Malara, Anastasia Macario, Mariachiara Miceli, Lucio Bonaccorsi, Marta Boaro, Alfonsina Pappacena, Alessandro Trovarelli, and Pier Luigi Antonucci. "Performance and Stability of Doped Ceria–Zirconia Catalyst for a Multifuel Reforming." Catalysts 13, no. 1 (January 10, 2023): 165. http://dx.doi.org/10.3390/catal13010165.

Full text

Abstract:

In the present work, the catalytic behavior of nickel-based catalysts supported on ceria/zirconia, undoped and doped with lanthanum and neodymium (3.5Ni/Ce0.8La0.5Nd0.2Zr0.13O2−x), was investigated under different reactions: steam reforming, partial oxidation and autothermal reforming of different fuels (methane, biogas, and propane). The catalytic properties of these catalysts were evaluated at a temperature of 800 °C, under atmospheric pressure, at GSHV = 120,000 h−1, using steam/carbon and oxygen/carbon ratio, respectively, of S/C = 2.5 and O/C = 0.5 and, in the case of autothermal conditions, with the addition of H2S (100 ppm) as a contaminant. Depending on the tested fuel, ATR, SR, and POX reactions over doped and undoped catalysts showed different results. In particular, the doped catalyst, due to neodymium and lanthanum doping, better distributed nickel species on the catalyst surface, promoting a higher concentration of defect groups and oxygen vacancies. This resulted in improved catalytic performance and resistance to deactivation. Endurance catalytic test also confirmed the beneficial effect of the doped catalysts.

APA, Harvard, Vancouver, ISO, and other styles

24

Gabrovska, Margarita, Ivan Ivanov, Dimitrinka Nikolova, Jugoslav Krstić, Anna Maria Venezia, Dorel Crişan, Maria Crişan, Krassimir Tenchev, Vasko Idakiev, and Tatyana Tabakova. "Improved Water–Gas Shift Performance of Au/NiAl LDHs Nanostructured Catalysts via CeO2 Addition." Nanomaterials 11, no. 2 (February 2, 2021): 366. http://dx.doi.org/10.3390/nano11020366.

Full text

Abstract:

Supported gold on co-precipitated nanosized NiAl layered double hydroxides (LDHs) was studied as an effective catalyst for medium-temperature water–gas shift (WGS) reaction, an industrial catalytic process traditionally applied for the reduction in the amount of CO in the synthesis gas and production of pure hydrogen. The motivation of the present study was to improve the performance of the Au/NiAl catalyst via modification by CeO2. An innovative approach for the direct deposition of ceria (1, 3 or 5 wt.%) on NiAl-LDH, based on the precipitation of Ce3+ ions with 1M NaOH, was developed. The proposed method allows us to obtain the CeO2 phase and to preserve the NiAl layered structure by avoiding the calcination treatment. The synthesis of Au-containing samples was performed through the deposition–precipitation method. The as-prepared and WGS-tested samples were characterized by X-ray powder diffraction, N2-physisorption and X-ray photoelectron spectroscopy in order to clarify the effects of Au and CeO2 loading on the structure, phase composition, textural and electronic properties and activity of the catalysts. The reduction behavior of the studied samples was evaluated by temperature-programmed reduction. The WGS performance of Au/NiAl catalysts was significantly affected by the addition of CeO2. A favorable role of ceria was revealed by comparison of CO conversion degree at 220 °C reached by 3 wt.% CeO2-modified and ceria-free Au/NiAl samples (98.8 and 83.4%, respectively). It can be stated that tuning the properties of Au/NiAl LDH via CeO2 addition offers catalysts with possibilities for practical application owing to innovative synthesis and improved WGS performance.

APA, Harvard, Vancouver, ISO, and other styles

25

Grabchenko, M., N. Mikheeva, G. Mamontov, M. Salaev, L. Liotta, and O. Vodyankina. "Ag/CeO2 Composites for Catalytic Abatement of CO, Soot and VOCs." Catalysts 8, no. 7 (July 16, 2018): 285. http://dx.doi.org/10.3390/catal8070285.

Full text

Abstract:

Nowadays catalytic technologies are widely used to purify indoor and outdoor air from harmful compounds. Recently, Ag–CeO2 composites have found various applications in catalysis due to distinctive physical-chemical properties and relatively low costs as compared to those based on other noble metals. Currently, metal–support interaction is considered the key factor that determines high catalytic performance of silver–ceria composites. Despite thorough investigations, several questions remain debating. Among such issues, there are (1) morphology and size effects of both Ag and CeO2 particles, including their defective structure, (2) chemical and charge state of silver, (3) charge transfer between silver and ceria, (4) role of oxygen vacancies, (5) reducibility of support and the catalyst on the basis thereof. In this review, we consider recent advances and trends on the role of silver–ceria interactions in catalytic performance of Ag/CeO2 composites in low-temperature CO oxidation, soot oxidation, and volatile organic compounds (VOCs) abatement. Promising photo- and electrocatalytic applications of Ag/CeO2 composites are also discussed.

APA, Harvard, Vancouver, ISO, and other styles

26

Zhan, Wangcheng, Shize Yang, Pengfei Zhang, Yanglong Guo, Guanzhong Lu, Matthew F. Chisholm, and Sheng Dai. "Incorporating Rich Mesoporosity into a Ceria-Based Catalyst via Mechanochemistry." Chemistry of Materials 29, no. 17 (August 15, 2017): 7323–29. http://dx.doi.org/10.1021/acs.chemmater.7b02206.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Hu, Yanping, Hengfang Jin, Jinrong Liu, and Dongsheng Hao. "Reactive behaviors of iron-based shift catalyst promoted by ceria." Chemical Engineering Journal 78, no. 2-3 (August 2000): 147–52. http://dx.doi.org/10.1016/s1385-8947(00)00133-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Zhang, Ce, Xiao-Dong Wen, Bo-Tao Teng, Yun Zhao, and Maohong Fan. "Catalytic effects of Zr doping ion on ceria-based catalyst." Fuel Processing Technology 131 (March 2015): 1–6. http://dx.doi.org/10.1016/j.fuproc.2014.11.010.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Kalubarme, Ramchandra S., Min-Seung Cho, Jae-Kook Kim, and Chan-Jin Park. "Ceria based catalyst for cathode in non-aqueous electrolyte based Li/O2batteries." Nanotechnology 23, no. 43 (October 11, 2012): 435703. http://dx.doi.org/10.1088/0957-4484/23/43/435703.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Sophiana, Intan Clarissa, Ferry Iskandar, Hary Devianto, Norikazu Nishiyama, and Yogi Wibisono Budhi. "Coke-Resistant Ni/CeZrO2 Catalysts for Dry Reforming of Methane to Produce Hydrogen-Rich Syngas." Nanomaterials 12, no. 9 (May 4, 2022): 1556. http://dx.doi.org/10.3390/nano12091556.

Full text

Abstract:

Dry reforming of methane was studied over high-ratio zirconia in ceria-zirconia-mixed oxide-supported Ni catalysts. The catalyst was synthesized using co-precipitation and impregnation methods. The effects of the catalyst support and Ni composition on the physicochemical characteristics and performance of the catalysts were investigated. Characterization of the physicochemical properties was conducted using X-ray diffraction (XRD), N2-physisorption, H2-TPR, and CO2-TPD. The results of the activity and stability evaluations of the synthesized catalysts over a period of 240 min at a temperature of 700 °C, atmospheric pressure, and WHSV of 60,000 mL g−1 h−1 showed that the 10%Ni/CeZrO2 catalyst exhibited the highest catalytic performance, with conversions of CH4 and CO2 up to 74% and 55%, respectively, being reached. The H2/CO ratio in the product was 1.4, which is higher than the stoichiometric ratio of 1, indicating a higher formation of H2. The spent catalysts showed minimal carbon deposition based on the thermo-gravimetry analysis, which was <0.01 gC/gcat, so carbon deposition could be neglected.

APA, Harvard, Vancouver, ISO, and other styles

31

Devlia, Jay, Louise Smith, Mark Douthwaite, Stuart H. Taylor, David J. Willock, Graham J. Hutchings, and Nicholas F. Dummer. "The formation of methanol from glycerol bio-waste over doped ceria-based catalysts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2176 (July 6, 2020): 20200059. http://dx.doi.org/10.1098/rsta.2020.0059.

Full text

Abstract:

A series of ceria-based solid solution metal oxides were prepared by co-precipitation and evaluated as catalysts for glycerol cleavage, principally to methanol. The catalyst activity and selectivity to methanol were investigated with respect to the reducibility of the catalysts. Oxides comprising Ce-Pr and Ce-Zr were prepared, calcined and compared to CeO 2 , Pr 6 O 11 and ZrO 2 . The oxygen storage capacity of the catalysts was examined with analysis of Raman spectroscopic measurements and a temperature programmed reduction, oxidation and reduction cycle. The incorporation of Pr resulted in significant defects, as evidenced by Raman spectroscopy. The materials were evaluated as catalysts for the glycerol to methanol reaction, and it was found that an increased defect density or reducibility was beneficial. The space–time yield of methanol normalized to surface area over CeO 2 was found to be 0.052 mmol MeOH m −2 h −1 , and over CeZrO 2 and CePrO 2 , this was to 0.029 and 0.076 mmol MeOH m −2 h −1 , respectively. The inclusion of Pr reduced the surface area; however, the carbon mole selectivity to methanol and ethylene glycol remained relatively high, suggesting a shift in the reaction pathway compared to that over ceria. This article is part of a discussion meeting issue ‘Science to enable the circular economy'.

APA, Harvard, Vancouver, ISO, and other styles

32

Zhang, Zhiyun, Jing Li, Wei Gao, Zhaoming Xia, Yuanbin Qin, Yongquan Qu, and Yuanyuan Ma. "Thermally stable sandwich-type catalysts of Pt nanoparticles encapsulated in CeO2 nanorod/CeO2 nanoparticle core/shell supports for methane oxidation at high temperatures." RSC Advances 6, no. 46 (2016): 40323–29. http://dx.doi.org/10.1039/c6ra05967h.

Full text

Abstract:

A sandwich-type Pt nanocatalyst encapsulated ceria-based core–shell catalyst (CNR@Pt@CNP) was designed and synthesized, which exhibited high catalytic activity and remarkably thermal-stability at high temperatures up to 700 °C.

APA, Harvard, Vancouver, ISO, and other styles

33

Schöneborn, Marcos, Thomas Harmening, Javier Giménez-Mañogil, Juan Carlos Martínez-Munuera, and Avelina García-García. "Improved NOx Storage/Release Properties of Ceria-Based Lean NOx Trap Compositions with MnOx Modification." Materials 12, no. 13 (July 2, 2019): 2127. http://dx.doi.org/10.3390/ma12132127.

Full text

Abstract:

Ceria/spinel-based lean NOx trap compositions with and without barium were modified with MnOx via incipient wetness impregnation. The effect of the MnOx layer on the aged materials (850 °C) as to the NOx storage and release properties was investigated via NOx adsorption (500 ppm NO/5% O2/balance N2) carried out at 300 °C in a dual-bed with a 1% Pt/Al2O3 catalyst placed upstream of the samples to generate sufficient amounts of NO2 required for efficient NOx storage. Subsequent temperature programmed desorption (TPD) experiments were carried out under N2 from 300 °C to 700 °C. The addition of MnOx to the barium free composition led to a slightly reduced NOx storage capacity but all of the ad-NOx species were released from this material at significantly lower temperatures (ΔT ≈ 100 °C). The formation of a MnOx layer between ceria/spinel and barium had a remarkable effect on ageing stability as the formation of BaAl2O4 was suppressed in favour of BaMnO3. The presence of this phase resulted in an increased NOx storage capacity and lower desorption temperatures. Furthermore, NOx adsorption experiments carried out in absence of the Pt-catalyst also revealed an unexpected high NOx storage ability at low NO2/NO ratios, which could make this composition suitable for various lean NOx trap catalysts (LNT) related applications.

APA, Harvard, Vancouver, ISO, and other styles

34

Odier, E., Y. Schuurman, and C. Mirodatos. "Non-stationary catalytic cracking of methane over ceria-based catalysts: Mechanistic approach and catalyst optimization." Catalysis Today 127, no. 1-4 (September 30, 2007): 230–37. http://dx.doi.org/10.1016/j.cattod.2007.03.059.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Tsai, Yu-Chih, Jechan Lee, Eilhann Kwon, Chao-Wei Huang, Nguyen Nhat Huy, Siming You, Pei-Syuan Hsu, Wen Da Oh, and Kun-Yi Andrew Lin. "Enhanced Catalytic Soot Oxidation by Ce-Based MOF-Derived Ceria Nano-Bar with Promoted Oxygen Vacancy." Catalysts 11, no. 9 (September 18, 2021): 1128. http://dx.doi.org/10.3390/catal11091128.

Full text

Abstract:

As CeO2 is a useful catalyst for soot elimination, it is important to develop CeO2 with higher contact areas, and reactivities for efficient soot oxidation and catalytic soot oxidation are basically controlled by structures and surface properties of catalysts. Herein, a Ce-Metal organic framework (MOFs) consisting of Ce and benzene-1,3,5-tricarboxylic acid (H3BTC) is employed as the precursor as CeBTC exhibits a unique bar-like high-aspect-ratio morphology, which is then transformed into CeO2 with a nanoscale bar-like configuration. More importantly, this CeO2 nanobar (CeONB) possesses porou, and even hollow structures, as well as more oxygen vacancies, enabling CeONB to become a promising catalyst for soot oxidation. Thus, CeONB shows a much higher catalytic activity than commercial CeO2 nanoparticle (comCeO) for soot oxidation with a significantly lower ignition temperature (Tig). Moreover, while soot oxidation by comCeO leads to production of CO together with CO2, CeONB can completely convert soot to CO2. The tight contact mode also enables CeONB to exhibit a very low Tig of 310 °C, whereas the existence of NO also enhances the soot oxidation by CeONB to reduce the Tig. The mechanism of NO-assisted soot oxidation is also examined, and validated by DRIFTS to identify the formation and transformation of nitrogen-containing intermediates. CeONB is also recyclable over many consecutive cycles and maintained its high catalytic activity for soot oxidation. These results demonstrate that CeONB is a promising and easily prepared high-aspect-ratio Ce-based catalyst for soot oxidation.

APA, Harvard, Vancouver, ISO, and other styles

36

Menegazzo, Federica, Cristina Pizzolitto, Elena Ghedini, Alessandro Di Michele, Giuseppe Cruciani, and Michela Signoretto. "Development of La Doped Ni/CeO2 for CH4/CO2 Reforming." C 4, no. 4 (November 7, 2018): 60. http://dx.doi.org/10.3390/c4040060.

Full text

Abstract:

Methane dry reforming (MDR) allows the transformation of carbon dioxide and methane, the two main greenhouse gases, into syngas. Given the high endothermicity of the process, it is necessary to produce a catalytic system that is very active, selective and resistant to coking deactivation; this work focuses on the development of a heterogeneous catalyst based on nickel supported on cerium oxide. Several strategies of synthesis of the catalysts were studied with particular attention to the lanthanum addition methodology. Both supports and catalysts, fresh and used, were deeply characterized by different techniques (N2 physisorption, TPR, XRD, SEM). The effect of temperature on activity and selectivity of the different catalysts was also studied. A positive effect of lanthanum addition is strongly related to the synthetic methodology. Incipient wetness impregnation of lanthanum precursor on an already calcined ceria has led to the best catalytic activity. This behaviour is due to a more effective interaction between nickel and the support, which results in a higher dispersion of the active phase. The structural modifications have led to an improvement of the redox pump of the ceria, reducing the formation of coke during the reaction and improving the stability on time on stream.

APA, Harvard, Vancouver, ISO, and other styles

37

Bhanushali, Jayesh T., Divya Prasad, Komal N. Patil, Gurram Venkata Ramesh Babu, Itika Kainthla, Kamaraju Seetha Rama Rao, Arvind H. Jadhav, and Bhari Mallanna Nagaraja. "The selectively regulated vapour phase dehydrogenation of 1,4-butanediol to γ-butyrolactone employing a copper-based ceria catalyst." New Journal of Chemistry 43, no. 30 (2019): 11968–83. http://dx.doi.org/10.1039/c9nj03067k.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Park, No-Kuk, Young Lee, Byung Kwon, Tae Lee, Suk Kang, Bum Hong, and Taejin Kim. "Optimization of Nickel-Based Catalyst Composition and Reaction Conditions for the Prevention of Carbon Deposition in Toluene Reforming." Energies 12, no. 7 (April 5, 2019): 1307. http://dx.doi.org/10.3390/en12071307.

Full text

Abstract:

In this study, nickel-based reforming catalysts were synthesized for the reforming of toluene, a major component of thinners and widely used as an organic solvent. The reaction characteristics of these catalysts were investigated by both steam reforming and auto-thermal reforming. Reforming aromatic hydrocarbons like toluene to produce synthesis gas is difficult because carbon deposition also occurs, and the deposition of carbon lowers the activity of the catalyst and causes a pressure drop during the reaction process. In order to maintain a stable reforming process, a catalytic reaction technique capable of suppressing carbon deposition is required. Steam reforming and auto-thermal reforming of toluene were used in this study, and the temperature of the catalyst bed was remarkably reduced, due to a strong endothermic reaction during the reforming process. By using scanning electric microscopy (SEM), X-ray diffraction (XRD), and temperature-programmed oxidation analysis, it is shown that carbon deposition was markedly generated due to a catalyst bed temperature decrease. In this study, optimum conditions for catalyst composition and the reforming reaction are proposed to suppress the formation of carbon on the catalyst surface, and to remove the generated carbon from the process. In addition, ceria and zirconia were added as catalytic promoters to inhibit carbon deposition on the catalyst surface, and the carbon deposition phenomena according to the catalyst’s promoter content were investigated. The results showed that the carbon deposition inhibition function of CeO2, via its redox properties, is insignificant in steam reforming, but is notably effective in the auto-thermal reforming of toluene.

APA, Harvard, Vancouver, ISO, and other styles

39

Aneggi, Eleonora, and Alessandro Trovarelli. "Potential of Ceria-Zirconia-Based Materials in Carbon Soot Oxidation for Gasoline Particulate Filters." Catalysts 10, no. 7 (July 9, 2020): 768. http://dx.doi.org/10.3390/catal10070768.

Full text

Abstract:

ZrO2 and Ce0.8Zr0.2O2 mixed oxides were prepared and tested in the oxidation of carbon soot at different oxygen partial pressures and degrees of catalyst/soot contact to investigate their activity under typical gasoline direct injection (GDI) operating conditions. Under reductive atmospheres, generation of oxygen vacancies occurs in Ce0.8Zr0.2O2, while no reduction is observed on ZrO2. Both materials can oxidize carbon under high oxygen partial pressures; however, at low oxygen partial pressures, the presence of carbon can contribute to the reduction of the catalyst and formation of oxygen vacancies, which can then be used for soot oxidation, increasing the overall performance. This mechanism is more efficient in Ce0.8Zr0.2O2 than ZrO2, and depends heavily on the interaction and the degree of contact between soot and catalyst. Thus, the ability to form oxygen vacancies at lower temperatures is particularly helpful to oxidize soot at low oxygen partial pressures, and with higher CO2 selectivity under conditions typically found in GDI engine exhaust gases.

APA, Harvard, Vancouver, ISO, and other styles

40

Shao, Hui Ping, Ye Ji, Xiao Ting Liu, and Zhi Meng Guo. "Preparation and Investigation of Magnetic Fluid with the Iron Oxide Spent Catalyst." Advanced Materials Research 356-360 (October 2011): 2079–83. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.2079.

Full text

Abstract:

The water-based magnetic fluid (WMF) and oil-based magnetic fluid (OMF) were prepared successfully with the iron oxide spent catalyst by mechanochemical method. The iron oxide spent catalyst contains about 75% magnetite, 15% alkali metal and 10% ceria. The experimental purpose is to reclaim the spent catalyst and decrease the environment pollution. In this paper, the peculiarity of magnetic fluids was characterized by VSM, XRD, and TGA, etc. As a result, the saturated magnetizations of water-based and oil-based MFs are 22.09 emu/g and 30.02 emu/g, respectively. Their particle sizes are 15.11 nm and 16.07 nm, respectively. The prepared MFs would be used in separating low density metal from scrap, thereby decreasing the environmental pollution. Therefore, not only good magnetic fluid was prepared with the spent catalyst for the first time, but also the spent catalyst was recycled in an effective way to reduce environmental pollution.

APA, Harvard, Vancouver, ISO, and other styles

41

Palma, Vincenzo, Eugenio Meloni, Simona Renda, and Marco Martino. "Catalysts for Methane Steam Reforming Reaction: Evaluation of CeO2 Addition to Alumina-Based Washcoat Slurry Formulation." C — Journal of Carbon Research 6, no. 3 (August 3, 2020): 52. http://dx.doi.org/10.3390/c6030052.

Full text

Abstract:

The effect of the addition of CeO2 to alumina-based washcoat slurry formulation on the methane steam reforming (MSR) reaction was investigated. Five Al2O3-CeO2-based washcoat slurries, differing from each other in the Al2O3/CeO2 ratio (nominal ratio equal to ∞, 0.042, 0.087, 0.250, 0.667) were prepared, dried and calcined; the resulting powders were loaded with nickel as an active metal and the obtained catalysts were tested in MSR reaction. Five cylindrical silicon carbide (SiC) monoliths were washcoated with the prepared slurries and their mechanical resistance was evaluated through the ultrasound adherence test. The activity tests results highlighted the best performance in terms of methane conversion and hydrogen selectivity of the powder catalyst, with the Al2O3/CeO2 percentage nominal ratio equal to 0.042. A structured catalyst was finally prepared by loading a SiC monolith with the most active catalytic formulation and tested in MSR reaction. The performance of the structured catalyst was evaluated in terms of methane conversion and its stability was verified in a time-on-stream test, which allowed for the evaluation of the carbon formation rate; furthermore, its activity was characterized by the estimation of the kinetic parameters. The results highlighted the beneficial effect of ceria addition on the catalytic activity; moreover, compared with data of the literature, the calculated carbon formation rate demonstrated a good resistance of the catalyst to coke formation.

APA, Harvard, Vancouver, ISO, and other styles

42

Palma, Vincenzo, Fausto Gallucci, Pluton Pullumbi, Concetta Ruocco, Eugenio Meloni, and Marco Martino. "Pt/Re/CeO2 Based Catalysts for CO-Water–Gas Shift Reaction: from Powders to Structured Catalyst." Catalysts 10, no. 5 (May 19, 2020): 564. http://dx.doi.org/10.3390/catal10050564.

Full text

Abstract:

This work focuses on the development of a Pt/Re/CeO2-based structured catalyst for a single stage water–gas shift process. In the first part of the work, the activity in water–gas shift reactions was evaluated for three Pt/Re/CeO2-based powder catalysts, with Pt/Re ratio equal to 1/1, 1/2 ad 2/1 and total loading ≈ 1 wt%. The catalysts were prepared by sequential dry impregnation of commercial ceria, with the salts precursors of rhenium and platinum; the activity tests were carried out by feeding a reacting mixture with a variable CO/H2O ratio, equal to 7/14, 7/20 and 7/24, and the kinetic parameters were determined. The model which better described the experimental results involves the water–gas shift (WGS) reaction and CO as well as CO2 methanation. The preliminary tests showed that the catalyst with the Pt/Re ratio equal to 2/1 had the best performance, and this was selected for further investigations. In the second part of the work, a structured catalyst, obtained by coating a commercial aluminum alloy foam with the chosen catalytic formulation, was prepared and tested in different reaction conditions. The results demonstrated that a single stage water–gas shift process is achievable, obtaining a hydrogen production rate of 18.7 mmol/min at 685 K, at τ = 53 ms, by feeding a simulated reformate gas mixture (37.61 vol% H2, 9.31 vol% CO2, 9.31 vol% CO, 42.19 vol% H2O, 1.37 vol% CH4).

APA, Harvard, Vancouver, ISO, and other styles

43

Pappacena, Alfonsina, Marta Boaro, Olga Šolcová, and Alessandro Trovarelli. "Ceria Based Materials with Enhanced OSC Properties for H₂ Production by Water Splitting Reaction." Advances in Science and Technology 93 (October 2014): 76–81. http://dx.doi.org/10.4028/www.scientific.net/ast.93.76.

Full text

Abstract:

A novel surfactant-assisted synthesis method was developed in our laboratory to enhance the oxygen storage capacity (OSC) and the thermo stability of a TWC catalyst based on zirconia and rare earth oxides. The same procedure was used to prepare ceria-zirconia compositions with different amount of ceria, either undoped or doped with La and Nd. The potential use of these materials in a two steps solar thermochemical water splitting cycle for the production of H2 was investigated. For this proposal the O2 release of the materials was measured through thermogravimetric analysis in N2 at 1573K. Then all prepared compositions were subjected to an aging treatment at temperature above 1573K in air or in N2 flow and their activity in producing H2 via water splitting at 1073K was evaluated with respect their structural evolution. The results obtained highlight that the reactivity depends on the temperature and atmosphere of the treatments and on the composition. The best result was obtained for the ceria rich composition treated at 1573K in N2 and for the corresponding doped composition treated in air.

APA, Harvard, Vancouver, ISO, and other styles

44

Choya, Andoni, Beatriz de Rivas, Jose Ignacio Gutiérrez-Ortiz, Juan Ramón González-Velasco, and Rubén López-Fonseca. "Synthesis, Characterization and Kinetic Behavior of Supported Cobalt Catalysts for Oxidative after-Treatment of Methane Lean Mixtures." Materials 12, no. 19 (September 27, 2019): 3174. http://dx.doi.org/10.3390/ma12193174.

Full text

Abstract:

The present work addresses the influence of the support on the catalytic behavior of Co3O4-based catalysts in the combustion of lean methane present in the exhaust gases from natural gas vehicular engines. Three different supports were selected, namely γ-alumina, magnesia and ceria and the corresponding catalysts were loaded with a nominal cobalt content of 30 wt. %. The samples were characterized by N2 physisorption, wavelength dispersive X-ray fluorescence (WDXRF), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction with hydrogen and methane. The performance was negatively influenced by a strong cobalt-support interaction, which in turn reduced the amount of active cobalt species as Co3O4. Hence, when alumina or magnesia supports were employed, the formation of CoAl2O4 or Co–Mg mixed oxides, respectively, with a low reducibility was evident, while ceria showed a lower affinity for deposited cobalt and this remained essentially as Co3O4. Furthermore, the observed partial insertion of Ce into the Co3O4 lattice played a beneficial role in promoting the oxygen mobility at low temperatures and consequently the catalytic activity. This catalyst also exhibited a good thermal stability while the presence of water vapor in the feedstream induced a partial inhibition, which was found to be completely reversible.

APA, Harvard, Vancouver, ISO, and other styles

45

Papavasiliou, Joan, Alexandra Paxinou, Grzegorz Słowik, Stylianos Neophytides, and George Avgouropoulos. "Steam Reforming of Methanol over Nanostructured Pt/TiO2 and Pt/CeO2 Catalysts for Fuel Cell Applications." Catalysts 8, no. 11 (November 15, 2018): 544. http://dx.doi.org/10.3390/catal8110544.

Full text

Abstract:

A research and technological challenge for fuel processors integrated with High Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFCs), also known as Internal Reforming Methanol Fuel Cells (IRMFCs), operating at 200–220 °C, is the development of highly efficient catalysts, which will be able to selectively (low CO and other by-products formation) produce the required quantity of hydrogen at these temperatures. In this work, various amounts of platinum were dispersed via deposition-precipitation (DP) and impregnation (I) methods onto the surface of hydrothermally prepared ceria nanorods (CNRs) and titania nanotubes (TNTs). These nanostructured catalysts were evaluated in steam reforming of methanol process targeting the operation level of IRMFCs. The (DP) method resulted in highly (atomically) dispersed platinum-based catalysts, as confirmed with Scanning Transmission Electron Microscopy (STEM) analysis, with a mean particle size of less than 1 nm in the case of 0.35 wt.% Pt/CNRs catalyst. Ultra-fine dispersion of platinum species correlated with the presence of oxygen vacancies, together with the enrichment of CNRs surface with active metallic phase resulted in a highly active catalyst achieving at 220 °C a hydrogen production rate of 5500 cm3 min−1 per g of loaded platinum.

APA, Harvard, Vancouver, ISO, and other styles

46

Azad, Abdul-Majeed, and Desikan Sundararajan. "A Phenomenological Study on the Synergistic Role of Precious Metals and the Support in the Steam Reforming of Logistic Fuels on Monometal Supported Catalysts." Advances in Materials Science and Engineering 2010 (2010): 1–15. http://dx.doi.org/10.1155/2010/681574.

Full text

Abstract:

Clean power source utilizing vast logistic fuel reserves (jet fuels, diesel, and coal) would be the main driver in the 21st century for high efficiency. Fuel processors are required to convert these fuels into hydrogen-rich reformate for extended periods in the presence of sulfur, and deliver hydrogen with little or no sulfur to the fuel cell stack. However, the jet and other logistic fuels are invariably sulfur-laden. Sulfur poisons and deactivates the reforming catalyst and therefore, to facilitate continuous uninterrupted operation of logistic fuel processors, robust sulfur-tolerant catalysts ought to be developed. New noble metal-supported ceria-based sulfur-tolerant nanocatalysts were developed and thoroughly characterized. In this paper, the performance of single metal-supported catalysts in the steam-reforming of kerosene, with 260 ppm sulfur is highlighted. It was found that ruthenium-based formulation provided an excellent balance between hydrogen production and stability towards sulfur, while palladium-based catalyst exhibited rapid and steady deactivation due to the highest propensity to sulfur poisoning. The rhodium supported system was found to be most attractive in terms of high hydrogen yield and long-term stability. A mechanistic correlation between the role of the nature of the precious metal and the support for generating clean desulfurized -rich reformate is discussed.

APA, Harvard, Vancouver, ISO, and other styles

47

Liu, Chen, Qin Zheng, and Yusheng Zhang. "Effect of Ceria Doping in Different Impregnation Steps on Ni-Based Catalysts Loading on TiO2-SiC for CO Methanation." Catalysts 12, no. 4 (April 11, 2022): 429. http://dx.doi.org/10.3390/catal12040429.

Full text

Abstract:

A series of TiO2-SiC supported Ni-based catalysts with and without ceria doping were prepared by a traditional impregnation method. CeO2 was introduced into the catalyst in different steps of the impregnation process. All the samples were characterized by N2 physisorption, XRD, TPR, and TGA, and were tested for the performance of CO methanation in a fixed-bed reactor under atmospheric conditions through the steam of H2/CO = 3 without diluent gas. All the Ni-based catalysts supported by TiO2-SiC exhibited the property of anti-sintering and could efficiently avoid carbon deposition occurring on catalysts. The experimental results show that the performance of all CeO2 doping samples (more than 80% of CO conversion) was better than the sample without CeO2 (around 20% of CO conversion). Introducing CeO2 after the dry step of impregnation achieved complete CO conversion at a lower temperature compared with its introduction through doping at the co-impregnation and step-impregnation methods. The results of further characterization indicate that the addition of CeO2 in different impregnation steps affected the dispersion of nickel on support, made the size of metal particles smaller, and changed the reducibility of catalysts.

APA, Harvard, Vancouver, ISO, and other styles

48

El Arrouji, Imane, Cuirong Chen, Jamil Toyir, Cherif Larabi, Kai C. Szeto, Aimery de Mallmann, Mostafa Taoufik, and Abdallah Oulmekki. "NH3-Selective Catalytic Reduction of NOx to N2 over Ceria Supported WOx Based Catalysts: Influence of Tungsten Content." Catalysts 11, no. 8 (August 9, 2021): 950. http://dx.doi.org/10.3390/catal11080950.

Full text

Abstract:

A series of HPW/CeO2 catalysts generated from 12-tungstophosphoric acid, H3PW12O40 (HPW), supported on ceria and presenting different tungsten loadings (2, 4.5, 9, 16, and 40 wt% W) were prepared and characterized by N2 physisorption, XRD, IR, Raman, and UV-Vis. The different characterization techniques suggested that low loading of tungsten resulted in mainly isolated sites, while high tungsten loading produced polymeric or tungsten clusters. Those materials exhibited high activity in NH3-SCR of NOx into N2. Moreover, the series of experiments indicated that low loading in tungsten (2% HPW/CeO2) displayed the highest activity with a remarkable N2 selectivity (99%) at medium-high temperature (300–515 °C), owing to the high amount of monomeric tungstate coverage on the catalyst surface.

APA, Harvard, Vancouver, ISO, and other styles

49

Ajakaiye Jensen, Lucy Idowu, Sara Blomberg, and Christian Hulteberg. "Effect of Pd and Ir as Promoters in the Activity of Ni/CeZrO2 Catalyst for the Reverse Water-Gas Shift Reaction." Catalysts 11, no. 9 (September 7, 2021): 1076. http://dx.doi.org/10.3390/catal11091076.

Full text

Abstract:

Catalytic conversion of CO2 to CO using reverse water gas shift (RWGS) reaction is a key intermediate step for many CO2 utilization processes. RWGS followed by well-known synthesis gas conversion may emerge as a potential approach to convert CO2 to valuable chemicals and fuels. Nickel (Ni) based catalysts with ceria-zirconia (Ce-Zr) support can be used to tune the metal-support interactions, resulting in a potentially enhanced CO2 hydrogenation rate and elongation of the catalyst lifespan. The thermodynamics of RWGS reaction is favored at high temperature for CO2 conversion. In this paper the effect of Palladium (Pd) and Iridium (Ir) as promoters in the activity of 10 wt%Ni 2 wt%Pd 0.1wt%Ir/CeZrO2 catalyst for the reverse water gas shift reaction was investigated. RWGS was studied for different feed (CO2:H2) ratios. The new active interface between Ni, Pd and Ir particles is proposed to be an important factor in enhancing catalytic activity. 10 wt%Ni 2 wt%Pd 0.1 wt%Ir/CeZrO2 catalyst showed a better activity with CO2 conversion of 52.4% and a CO selectivity of 98% for H2:CO2 (1:1) compared to the activity of 10%Ni/CeZrO2 with CO2 conversion of 49.9% and a CO selectivity of 93%. The catalytic activity for different feed ratios using 10 wt%Ni 2 wt%Pd 0.1 wt%Ir/CeZrO2 were also studied. The use of palladium and iridium boosts the stability and life span of the Ni-based catalysts. This indicates that the catalyst could be used potentially to design RWGS reactors for CO2 utilization units.

APA, Harvard, Vancouver, ISO, and other styles

50

Patel, Madhumita, Tarun K. Jindal, and Kamal K. Pant. "Kinetic Study of Steam Reforming of Ethanol on Ni-Based Ceria–Zirconia Catalyst." Industrial & Engineering Chemistry Research 52, no. 45 (October 30, 2013): 15763–71. http://dx.doi.org/10.1021/ie401570s.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Ceria-based catalyst'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles