Synthesis of ceria–zirconia mixed oxide from cerium and zirconium glycolates via sol–gel process and its reduction property (original) (raw)
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Synthesis of Ceria Zirconia Oxides using Solvothermal Treatment
MATEC Web of Conferences, 2018
Ceria oxide (CeO2) is widely used as catalyst with high oxygen storage capacity at low temperature. The addition of zirconia oxide (ZrO2) to CeO2 can enhance oxygen storage capacity as well as thermal stability. In this work, ceria zirconia oxides has been synthesized via a low temperature solvothermal treatment in order to produce ceria zirconia oxides composite with high oxygen storage capacity as electrolyte of solid oxide fuel cells (SOFC). Under solvothermal conditions, solvent may control the direction of crystal growth, morphology, particle size and size distribution, because of the controllability of thermodynamics and transport properties by pressure and temperature. Water, mixed of water and ethanol (70/30 vol/vol), and mixed of water and ethylene glycol (70/30 vol/vol) were used as solvent, while Ce(NO3)3 and ZrO(NO3)2 with 0.06 M concentration were used as precursor. The experiments were conducted at temperature of 150 °C and pressure for 2 h in a Teflon-lined autoclave ...
Arabian Journal of Chemistry, 2015
A series of mixed oxide catalysts Ce x Zr 1Àx O 2 with different compositions (x = 0.93, 0.80, 0.75, 0.60, 0.55, and 0.50) were synthesized by co-precipitation technique using ammonia as the precipitant agent. Textural and structural properties of calcined ceria-zirconia oxides were characterized by nitrogen adsorption, X-ray diffraction and Raman spectroscopy. The redox properties were investigated by temperature-programmed reduction measurement using H 2. The procedure of preparation as well as the composition has a great influence on the structural and textural properties of mixed oxides. Fluorite type oxides were shown to be a very interesting support for the total oxidation, since these materials led to the complete decomposition of ethyl acetate at rather low temperatures. Of the synthesized materials, Ce 0.5 Zr 0.5 O 2 showed the best catalytic activity.
Preparation of Ceria-Zirconia Mixed Oxide by Hydrothermal Synthesis
Modern Applied Science, 2015
Ceria-zirconia mixed oxides have been synthesized by hydrothermal synthesis process. Under hydrothermalconditions, water potential to control the direction of crystal growth, morphology, particle size and sizedistribution, because of the controllability of thermodynamics and transport properties by pressure andtemperature. The synthesis was carried out at temperatures of 150 − 200 oC and pressure of 5 MPa in a batchreactor. The reactor made of SUS 304 tube reactor with internal volume of 8.8 ml. The synthesized productswere calcined and characterized using SEM, XRD and FTIR. The results showed that the particles formed weresphere shaped particles with smooth morphology and the size of particle diameters were 35, 61, and 31 nm onaverage for reactions temperatures of 150, 180, and 200oC, respectively. The XRD pattern indicated thatceria-zirconia mixed powder was uniformly distributed in the structure to form a homogeneous solid solution.
New synthesis of pure Ce x Zr1−x O2 mixed oxides (0 ≤ x ≤ 1) by an epoxide sol–gel method
Journal of Sol-gel Science and Technology, 2010
Pure ceria-zirconia mixed oxides Cex Zr1−x O2 with high specific surface area were synthesized with a new epoxyde driven sol–gel route and characterized by thermal analysis, X-ray diffraction studies and transmission electron microscopy. This sol–gel method is cheap and uses only a few steps. The Cex Zr1−x O2 mixed oxides were obtained in the range of 0 ≤ x ≤ 1 (except for x = 0.8) and crystallised at 350 °C after decomposition of the gels. This temperature is very low in comparison with the other methods. The studies of the influence of different synthesis parameters (concentration of the sol and decomposition temperature) allowed us to determine the conditions to obtain the best homogeneity in the gel to avoid the formation of a mixture of phases instead of mixed oxides. This approach leads to the synthesis of oxide with specific surface area above 100 m2 g−1. The elaboration of an ambigel could increase this value up to 195 m2 g−1 for x = 0.5. This sol–gel synthesis offers new perspectives for these oxides in several applications. Generally, these oxides are difficult to obtain pure in large range of composition at low-temperature and with high specific surface area by other methods.
Catalytic activity of CeO2–ZrO2 mixed oxide catalysts prepared via sol–gel technique: CO oxidation
Catalysis Today, 2001
CeO 2 -ZrO 2 mixed oxide catalysts were prepared via a sol-gel technique and tested for carbon monoxide (CO) oxidation. Highly uniform nano-size solid solution particles of ceria-zirconia were attained under the conditions of this study (ca 100 • C). The stabilization of the surface areas of the catalysts can be achieved by the addition of zirconium. The CO oxidation activity of the mixed oxides was found to be dependent on Ce/Zr ratio, which relates to the degree of reducibility. The catalytic activity for CO oxidation decreases with a decrease in Ce/Zr ratio. This might be due to the difference in phase compositions of the mixed oxides. It can be postulated that the cubic phase, fluorite structure, which is mainly found in Ce 1−x Zr x O 2 (where x < 0.5) could be reduced easily than the tetragonal phase found in Ce 1−x Zr x O 2 (where x > 0.5). Among the mixed oxide catalysts, Ce 0.75 Zr 0.25 O 2 was reported to exhibit the highest activity for CO oxidation.
Catalysis Today, 2012
The effect of thermal aging on the physico-chemical properties of Ce-Zr oxides, as a function of Ce/Zr molar ratio, has been studied from the point of view of their application as catalytic nanomaterial. Homogeneous in size dimension and morphology, nanosized, single phase Ce-Zr solid solutions with various compositions were synthesized by the sol-gel like method. Upon thermal aging, important modifications of the textural and structural properties, which apparently create a strong effect on their catalytic performance, were observed. Their specific activity was found to be dependent on Ce/Zr molar ratio with the maximum observed over Ce 0.75 Zr 0.25 O 2. Higher surface area, smaller particles, lower amount of particles agglomerates as well as higher amount of crystal faces, edges, and corners generate better catalytic activity, especially as long as cubic symmetry of mixed oxides was maintained.
Catalytic properties of Ce x Zr1–x O2 prepared using a template in the oxidation of CO
Russian Journal of Physical Chemistry A, 2016
The catalytic activity in CO oxidation of Ce x Zr 1-x O 2 double oxides prepared using pine sawdust and cetyltrimethylammonium bromide (CTAB) as templates is compared. It is found by means of SEM and the low-temperature adsorption of N 2 that biomorphic oxides reproduce the macropore structure of the template. It is shown via XRD and Raman spectroscopy that all samples contained mixed ceria-zirconia oxide. The double oxides form a cubic phase with a lattice of the fluorite type at a ratio of Ce : Zr = 4, regardless of the nature of the template; when Ce : Zr = 1, the biomorphic mixed oxide forms a tetragonal phase. According to Raman spectroscopy and XRD it was shown that the distortion of the oxygen sublattice is higher in biomorphic samples. Energy dispersive analysis shows that Ca impurities were present in the biomorphic samples, introducing additional distortions in the lattice of double oxide and leading to the formation of anionic vacancies. It is found that when Ce : Zr = 4, the conversion of CO on biomorphic oxide in the range of 100-350°C is higher than that observed for Ce x Zr 1-x O 2 (CTAB); reducing the Ce : Zr ratio in the biomorphic sample to 1 results in a marked decrease in CO conversion at 100-200°C. It is concluded that these differences are due to changes in the mobility of the lattice oxygen.
Hydrothermal and Solvothermal Synthesis of Cerium-Zirconium Oxides for Catalyst Applications
Cerium oxide (CeO2) is a rare earth metal oxide that has high oxygen storage capacity at low temperature. In order to enhance this capacity, as well as its thermal stability, it is necessary to combine CeO2 with zirconium oxide (ZrO2). This work focuses on the synthesis of ceriumzirconium oxides by hydrothermal and solvothermal treatment at low temperature to obtain ones suitable for catalyst applications. The possibility of the application of ceria-zirconia oxide to the delignification reaction was investigated. The experiments were conducted at a constant pressure of 5 MPa, constant temperature of 150 o C, and constant synthesis time of 2 h, in an autoclave reactor made of SUS 316 with an internal volume of 100 mL. Precursor was prepared from Ce(NO3)3 and ZrO(NO3)2 at 0.06 M concentration, dissolved in various solvents. The solvents used were water, water/ethanol (70:30 vol/vol), and water/ethylene glycol (70:30 vol/vol). After hydrothermal and solvothermal synthesis, the colloid products were dried at 60 o C for 6 h and then calcined at 500 o C for 6 h. The characterizations of the particle products were analyzed using SEM and XRD. Furthermore, these products were used for the hydrothermal delignification process of wood biomass. The addition of ceria-zirconia particles dramatically increased the percentage of lignin removal from rapeseed wood up to 97.58%. Based on the results, ceria-zirconia oxide particles are effective for the pre-treatment of wood biomass in bio-refinery applications. Moreover, ceria-zirconia oxides may reduce the use of chemical compounds in the delignification process.
PPC and PETROMAT Symposium 2020
This study investigates the characteristics of Ce0.75Zr0.25O2 (CZO) incorporated with Nickel as transition metal. The CZO was successfully synthesized by the sol-gel synthesis to form Ce-Zr mixed oxide solid solution as required. Ni was incorporated into the CZO by impregnation method. The impact of nickel loading (10, 15, and 20 wt%) on the morphology, textural and chemical properties was investigated by various techniques, i.e. X-ray fluorescence spectroscopy (XRF), Brunauer-Emmet-Teller surface analysis (N2-BET), X-ray diffraction (XRD), ammonia temperature programmed desorption (NH3-TPD), hydrogen temperature programmed reduction (H2-TPR), simultaneous thermal analysis (STA), and scanning electron microscopy (SEM). It was found that as an increase in nickel loading, BET surface areas of the Ni/CZO catalysts were decreased whereas their acidity was slightly augmented and alternated in acid strength. Moreover, the altered reducibility of Ni/CZO catalysts was observed as changes in Nickel loading.