Mesoporous Ce Research Articles

The performance of manganese-based catalysts with Ce0.65Zr0.35O2 as support for catalytic oxidation of toluene

Mesoporous Ce0.65Zr0.35O2 composites are synthesized by co-precipitation method and a series of novel MnOx/Ce0.65Zr0.35O2 monolithic catalysts with different content of manganese oxides are prepared for toluene catalytic oxidation. The results show that the catalytic activity of Ce0.65Zr0.35O2 is promoted by introduction of manganese and influenced remarkably by the amount of MnOx. In particular, the catalyst with 15wt.% MnOx loading performs best activity in view of the lowest complete conversion temperature of 250°C at a GHSV of 12000h−1. According to the characterizations of N2 adsorption-desorption, XRD, SEM-EDX, H2-TPR, O2-TPD and XPS analyses, the superior catalytic activity could be attributed to the well-dispersed MnOx species, good low-temperature redox property, more Mn4+ species and more available surface and lattice oxygen species. Additionally, the optimized catalyst shows high stability during the thermal aging experiment and long-term testing experiment, and it also shows a good activity under the condition of high gas hourly space velocity, which presents a well application prospect.

Highly ordered macroporous–mesoporous Ce0.4Zr0.6O2 as dual-functional material in a polysulfide polymer

A highly hierarchically ordered macroporous–mesoporous Ce0.4Zr0.6O2 solid solution with crystalline framework walls was directly and simply prepared using polystyrene (PS) microspheres and a block copolymer as dual templates. The PS microspheres and block copolymer were assembled into colloidal crystals and mesoscopic rod-like micelles as macroporous and mesoporous templates, respectively, by a one-step process. This process offers a facile method to prepare hierarchically ordered porous materials. Compared to commercial ceria, the macroporous–mesoporous Ce0.4Zr0.6O2 material significantly improved the ultraviolet resistance and mechanical performance of a polysulfide polymer. Because the ordered macroporous–mesoporous Ce0.4Zr0.6O2 can disperse uniformly in the polysulfide polymer based on the open macroporous structure for diffusion and mobility and mesoporous structure for high surface areas. Furthermore, these results show that better-performing polysulfide polymers can be achieved by adding hierarchically structured materials.

A Durable Electrode for Solid Oxide Cells: Mesoporous Ce0.8Sm0.2O1.9 Scaffolds Infiltrated with a Sm0.5Sr0.5CoO3-δ Catalyst

Nanostructured metal oxides have received increasingly more attention due to their high specific surface area that may increase the active region of the material and hence enhance the performance of many electrochemical devices such as gas sensors or solid oxide fuel cells. However, it is still a major issue to keep these nanostructures stable at the high fabrication and operating temperatures of the electrochemical devices (e.g., solid oxide cells), typically over 1000°C and 700°C, respectively. In this work, thermally stable Ce0.8Sm0.2O1.9 mesoporous scaffolds were infiltrated with a Sm0.5Sr0.5CoO3-δ catalyst, which were then used as electrodes for solid oxide cells. The electrochemical properties of these nanocomposite electrodes in a symmetrical cell at 500–750°C were evaluated using electrochemical impedance spectroscopy. When tested at 700 °C for a long period of time, the cells showed no performance degradation but a 50 % reduction in the area specific resistance (ASR=0.08 Ω·cm2) after more than 200h of operation, suggesting that the mesoporous composites are promising electrodes for high-temperature electrochemical devices.

Hydrothermally prepared nanosized and mesoporous Ce0.4Zr0.6O2 solid solutions with shape dependence in photocatalysis for the degradation of methylene blue

The shape dependence of photocatalysis is confirmed.

Three-dimensional ordered mesoporous CeXZr1−XO2 for selective catalytic reduction removal of NOX with NH3

A series of highly ordered mesoporous CeXZr1−XO2 (x represents the mole ratio of Ce), were fabricated for NH3-SCR of NOX using KIT-6 as a hard template, which have been characterized by TEM, XRD, BET, BJH, XPS, H2-TPR, NH3-TPD and in-situ DRIFT, showing superior composite crystal microstructure, uniform mesopore diameter and larger surface area. Among all the mesoporous CeXZr1−XO2 samples (x=0, 0.25, 0.33, 0.5, 0.67, 0.75 and 1), mesoporous Ce0.67Zr0.33O2 showed the best NH3-SCR activity to clean NOX, and 100% NOX conversion ratio at 325°C can be reached, as well as excellent H2O or SO2 tolerance and best thermal stability. Furthermore, the addition of ZrO2 content enhanced the thermal performance and redox ability of mesoporous CexZr1−xO2, which were favorable for their excellent NH3-SCR performance. Finally, a possible redox reaction mechanism of NH3-SCR reaction over the mesoporous CeXZr1−XO2 was proposed.

ChemInform Abstract: Mesoporous CexCo1‐xCr2O4 Spinels: Synthesis, Characterization and Catalytic Application in Simultaneous Removal of Soot Particulate and NO.

AbstractThe title catalysts (x = 0‐0.15) are prepared via combustion of stoichiometric aqueous solutions of the metal nitrates and urea in air and subsequent calcination (600 °C, 4 h).

Synthesis, characterization and catalytic wet air oxidation property of mesoporous Ce1−xFexO2 mixed oxides

Nano-structured Ce1−xFexO2 mixed oxides with different Fe loading have been synthesized via co-precipitation route and were evaluated as heterogeneous catalysts for catalytic wet air oxidation of wastewater. The synthesized catalysts were characterized by XRD, FT-IR, TGA, N2 adsorption/desorption, FE-SEM, TEM and EDS. The influence of initial pH, reaction temperature, reaction time and catalyst dose has been evaluated for the removal of COD and color from paper industry wastewater. The catalytic performance of Ce1−xFexO2 mixed oxides was found to be superior to those of individual oxides of Ce and Fe. The molar ratio of Ce/Fe markedly influenced the activity of mixed oxides. Ce0.4Fe0.6O2 mixed oxide exhibited maximum COD (74%) and color (82%) removal under optimum experimental conditions. The biodegradability of wastewater increased from an initial level of 0.27–0.47 after treatment. The highest catalytic activity of Ce0.4Fe0.6O2 mixed oxide was strongly influenced by its high surface area, high pore volume, small particle size and high dispersion of Fe2O3 into ceria lattice.

Construction of Mesoporous Ce<SUB>0.5</SUB>Zr<SUB>0.5</SUB>O<SUB>2</SUB> from Different <I>Gemini</I> and Cetyltrimethylammonium Bromide Surfactants

Construction of Mesoporous Ce<SUB>0.5</SUB>Zr<SUB>0.5</SUB>O<SUB>2</SUB> from Different <I>Gemini</I> and Cetyltrimethylammonium Bromide Surfactants

Enhanced performance in NOx reduction by NH3 over a mesoporous Ce–Ti–MoOx catalyst stabilized by a carbon template

The mesopore Ce–Ti–MoOx catalyst stabilized by an in situ formed carbon template showed more than 90% NOx conversion at 175–425 °C for SCR of NOx with NH3. Increasing temperature in the presence of carbon template contributed to the narrow mesoporous distribution and excellent low-temperature SCR activity.

Sol-gel preparation of mesoporous cerium-doped FeTi nanocatalysts and its SCR activity of NOx with NH3 at low temperature

A series of cerium-doped mesoporous FeTi nanocatalysts were synthesized through a sol-gel method, and their performances for the selective catalytic reduction (SCR) of NOx with NH3 were explored. The mesoporous Ce(0.2) FeTi catalyst exhibited excellent low-temperature catalytic activity and high resistance to sulfur poisoning. A NOx conversion higher than 95 % was achieved at 200 °C over the Ce(0.2) FeTi catalyst. The strong interactions between cerium, iron oxides and titania in the Ce(0.2) FeTi catalyst resulted in a large amount of Ce3+, more active chemisorbed oxygen and more Bronsted acid sites, which contributed to the high catalytic activity for the SCR of NOx in the low-temperature region. The enhanced BET surface area and pore volume of its mesoporous structure also played an important role in its catalytic performance. Based on the DRIFTS analysis, an Eley–Rideal mechanism was proposed for the SCR over the Ce(0.2) FeTi mesoporous catalyst.

A complex and de-complex strategy to ordered mesoporous Ce0.5Zr0.5O2 with comprehensive pilot scale performances

Synthesis of ordered mesoporous ceria-zirconia (CeO2–ZrO2, M-CZ) solid solution in water-based conditions have challenged scientists for a long time due to the extremely different chemical properties of cerium and zirconium cations. This study discuss the synthesis of highly ordered mesoporous Ce0.5Zr0.5O2 solid solution in aqueous solution through a new complex and de-complex method using di-cationic Gemini as the template. The method takes advantage of the coordinative capability of citric acid (CA) to allow the coexistence of inorganic resources in mild basic solutions and uses the strong oxidic capability of H2O2 to precipitate Ce and Zr cations homogeneously. Through this strategy, the combination between inorganic–organic groups in aqueous solution was avoided, whereas coordination between inorganic–organic species was realized. Mechanisms show that the formation of peroxycarboxylic groups (–COOOH) from the reaction between metal-CA molecular and hydroxyl radical (OH) was the key process. Meso-scale micelles were formed during hydrothermal treatment, while hexagonally arranged pores with narrow size distribution were obtained in the calcination procedure. The surface area of the calcined product was 228 m2 g−1 with a pore volume of 0.7 cm3 g−1, whereas oxygen storage capacity was 652 μmol g−1. The M-CZ product illustrated fairly good pilot-scale three-way catalytic (TWC) performances thanks to the thin pore walls in the mesostructures. A complete (100%) conversion of CO and NOy at 340 °C was detected in the engine pedestal tests. The complex and de-complex strategy may provide a new route for the preparation of ordered mesoporous composite oxides.

Mesoporous Ce[sbnd]Pr[sbnd]O solid solution with efficient photocatalytic activity under weak daylight irradiation

In this study, the application of mesoporous CeO2 and Pr doped CeO2 (CePrO) as photocatalysts for the degradation of Rhodamine B (RhB) from aqueous solution was investigated. Mesoporous CeO2 and CePrO were prepared using SBA-15 as template. The resultant samples were characterized by XRD, N2 adsorption–desorption, Raman, UV–vis, TEM, FT-IR, and XPS techniques. The characterization results show that the synthesized CePrO has a 2D hexagonal structure, similar to that of the template, and possesses numerous oxygen vacancies. It is worth mentioning that the visible light adsorption intensity of CePrO is much higher than that of mesoporous ceria and bulk ceria, due to simultaneous formation of doping level and mesopores. The photodegradation of RhB illustrates that the synthesized mesoporous CePrO, especially 45% CePrO, performs excellent decolorization under weak daylight irradiation. Furthermore, a novel photodegradation mechanism was proposed based on the adsorption of H2O2 over the oxygen vacancy.

Mesoporous Ce1−x Mn x O2 mixed oxides with CuO loading for the catalytic total oxidation of propane

High-surface-area mesoporous Ce1−x Mn x O2 mixed oxides were prepared by a surfactant-assisted method of nanocrystalline particle assembly, and their catalytic properties for the total oxidation of propane were evaluated using a microreactor–GC system. The prepared Ce1−x Mn x O2 particles were nanoscaled with fluorite structure, possessing a mesoporous structure with uniform pore-size distribution, which demonstrated very high activity for the propane total oxidation. The promoting effect of CuO on the catalytic activity of Ce1−x Mn x O2 was also investigated, indicating that the addition of copper could improve the catalytic activity for propane conversion. The catalytic behavior depended on the Ce/Mn ratio, the surface area and the mesoporosity of the catalysts. The catalyst with the Ce/Mn ratio of 1.5 exhibited the highest catalytic activity, suggesting a good candidate for replacing noble metal catalysts in the propane total oxidation.

Visible-Light Active Mesoporous Ce Incorporated TiO<SUB>2</SUB> for the Degradation of 4-Chlorophenol in Aqueous Solution

Efficient visible-light active mesoporous Ce incorporated TiO2 nanoparticles have been prepared by sol-gel method using Pluranic P123 as the structure directing agent. Low angle XRD and BET analysis revealed the mesoporous nature of the nanoparticles. The incorporation of Ce4+ into TiO2 and Ti4+ into CeO2 is evident from the slight shift in their respective XRD patterns. XPS results exhibited +4 oxidation state for Ce and Ti ions. UV-DRS analysis of Ce incorporated TiO2 demonstrated red shift in the absorbance spectrum of TiO2, which is mainly due to the formation of Ce impurity states below the conduction band edge of TiO2. The photocatalytic activity of mesoporous Ce incorporated TiO2 nanoparticles has been evaluated in the degradation of 4-chlorophenol in aqueous solution under solar light illumination. Pure mesoporous TiO2 showed poor visible-light activity due to its small absorption of sun light. Mesoporous Ce incorporated TiO2 photocatalysts exhibited the highest photocatalytic activity compared to pristine mesoporous TiO2 and CeO2. The incorporation of Ce4+ in TiO2 played a major role in the enhancement of photocatalytic activity under sun light.

Facile synthesis of mesoporous Ce–Fe bimetal oxide and its enhanced adsorption of arsenate from aqueous solutions

The mesoporous Ce–Fe bimetal oxide (MCFO) was synthesized through a soft-template method and first applied in the adsorption of arsenate in aqueous solutions. The synthesized MCFO was characterized with BET surface area, X-ray diffraction (XRD), zeta potential, scanning electron microscope (SEM), and Fourier transform infrared (FTIR) analysis. The mesoporous structure of the MCFO was determined according to the characterization result. The adsorption efficiency of arsenate ions on the MCFO was studied as a function of initial As(V) concentration, contact time, pH, and coexistent anions. It was found that the adsorption isotherms could be well described by Langmuir model, and the calculated maximum adsorption capacity of MCFO-1 for As(V) was 91.74mgg−1, which was significantly greater than that of ordinary Ce–Fe bimetal oxide (CFO). The results showed that the adsorption kinetic data obeyed the pseudo-second order model. Lower pH was favorable for As(V) adsorption on the MCFO. Coexistent phosphate ions exhibited an obvious interference on As(V) adsorption, followed by silicate and fluoride ions. The analysis of BET and FTIR indicated that the high efficiency of As(V) adsorption on this Ce–Fe bimetal oxide (MCFO) was closely related to its uniform mesoporous structure and abundant surface hydroxyl groups.

Catalytic oxidation of CO and toluene over nanostructured mesoporous NiO/Ce0.8Zr0.2O2 catalysts

Mesoporous Ce0.8Zr0.2O2 oxides were prepared by a surfactant-assisted method of nanocrystalline particle assembly, and used as a support of nickel oxide nanocatalysts. The obtained mesoporous NiO/Ce0.8Zr0.2O2 nanocatalysts were characterized by XRD, N2 adsorption, TEM, H2-TPR and X-ray photoelectron spectroscopy techniques. The catalytic properties of the NiO/Ce0.8Zr0.2O2 nanocatalysts were evaluated by CO oxidation and toluene combustion. The results showed that the catalyst with 10 wt% NiO loading exhibited the highest catalytic activity for CO oxidation and toluene combustion.

Mesoporous Ce1−xZrxO2 solid solution nanofibers as high efficiency catalysts for the catalytic combustion of VOCs

Macroporous networks assembled by interconnected mesoporous Ce1−xZrxO2 solid solution nanofibers were prepared using an electrospinning technique followed by a self-sustaining combustion procedure. This hierarchical porosity helped the mass transfer and resulted in a much higher catalytic activity and stability for the catalytic combustion of volatile organic compounds than bulk and ordered mesoporous Ce1−xZrxO2 materials.

Synthesis of Hierarchical Macro-/Mesoporous Solid-Solution Photocatalysts by a Polymerization-Carbonization-Oxidation Route: The Case of Ce0.49Zr0.37Bi0.14O1.93

A hierarchical macro-/mesoporous Ce(0.49)Zr(0.37)Bi(0.14)O(1.93) solid-solution network has been synthesized on a large scale by means of a simple and general polymerization-carbonization-oxidation synthetic route. The as-prepared product has been characterized by SEM, XRD, TEM, BET surface area measurement, UV/Vis diffuse-reflectance spectroscopy, energy-dispersive X-ray spectroscopy (EDS), and photoelectrochemistry measurements. The photocatalytic activity of the product has been demonstrated through the photocatalytic degradation of methyl orange. Structural characterization has indicated that the hierarchical macro-/mesoporous solid-solution network not only contains numerous macropores, but also possesses an interior mesoporous structure. The mesopore size and BET surface area of the network have been measured as 2-25 nm and 140.5 m(2) g(-1), respectively. The hierarchical macro-/mesoporous solid-solution network with open and accessible pores was found to be well-preserved after calcination at 800 degrees C, indicating especially high thermal stability. Due to its high specific surface area, the synergistic effect of the coupling of macropores and mesopores, and its high crystallinity, the Ce(0.49)Zr(0.37)Bi(0.14)O(1.93) solid-solution material shows a strong structure-induced enhancement of visible-light harvest and exhibits significantly improved visible-light photocatalytic activity in the photodegradation of methyl orange compared with those of its other forms, such as mesoporous hollow spheres and bulk particles.

The synthesis of mesoporous Ce1−x Zr x O2 by modified evaporation-induced self-assembly method

Mesoporous Ce1−x Zr x O2 with high surface area was synthesized using a modified evaporation-induced self-assembly method that combined citric acid as complexing agent and cetyltrimethyl ammonium bromide as surfactant. The samples with different Ce/Zr molar ratio were characterized by thermogravimetry and differential thermal analysis, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, Brunauer–Emmett–Teller (BET), and Barrett–Joyner–Halenda methods. It was found that when the Zr molar fraction was larger than 0.3, a mixture of cubic phase and tetragonal phase was formed. Ce0.7Zr0.3O2 solid solution had the largest BET surface area (217 m2 g−1) and mesoporous structure. The catalytic performances of mesoporous Ce1−x Zr x O2 for CO oxidation were examined. Mesoporous Ce0.7Zr0.3O2 solid solution demonstrated the best catalytic activity due to the high surface area and an enhanced redox property caused by appropriate Zr4+ incorporation.

Hierarchical Organization and Catalytic Activity of High-Surface-Area Mesoporous Ceria Microspheres Prepared Via Hydrothermal Routes

Mesoporous Ce(OH)CO(3) microspheres with flowerlike three-dimensional (3D) hierarchical structure were successfully synthesized via different hydrothermal systems, including glucose/acrylic acid, fructose/acrylic acid, glucose/propanoic acid, and glucose/n-butylamine systems. After Ce(OH)CO(3) microspheres were calcined, mesoporous CeO(2) microspheres with the same flowerlike morphology as Ce(OH)CO(3) microspheres were obtained. Especially, flowerlike CeO(2) microspheres prepared via the glucose/acrylic acid system are composed of many interconnected mesoporous petal-like nanosheets with thicknesses of 40-60 nm and have high surface area (211 m(2) g(-1)), large pore volume (0.32 cm(3) g(-1)), and narrow pore size distribution ( approximately 3.8 nm in diameter). A possible formation mechanism of Ce(OH)CO(3) microspheres is proposed: the large N-containing organic compounds in situ produced in the above reaction systems played a crucial role in controlling the assembly of Ce(OH)CO(3) building blocks into the flowerlike Ce(OH)CO(3) microspheres. For trichloroethylene combustion, flowerlike CeO(2) microspheres were found to exhibit much higher catalytic activity than general CeO(2) prepared with the conventional methods and the T(10%) and T(90%) were as low as 100 and 204 degrees C, respectively.