CeO2-catalyzed ozonation of phenol (original) (raw)
Related papers
Fundamentals and Catalytic Applications of CeO2-Based Materials
Chemical reviews, 2016
Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40(th) anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful th...
Industrial & Engineering Chemistry Research, 2017
Surface properties of nano-ceria can strongly affect the catalytic performance in oxidation reactions. In this work, a simple but efficient post-treatment, where H 2 O 2 is used as a complexing agent to dissolve Ce 3+ from the surface of CeO 2 nanorods with the help of ultrasonic treatment, is carried out to tune the surface properties and increase their catalytic performance for catalytic wet air oxidation (CWAO) of phenol. It is found that the dissolution of Ce 3+ from the surface of CeO 2 nanorods can create more surface defects and result in a much rougher surface. The H 2 O 2-ultrasonic treatment can also increase Ce 3+ concentration, create more surface oxygen vacancies, and narrow the band gap of CeO 2 nanorods. These properties
Materials Chemistry and Physics, 2017
CeO 2 nanoparticles have been prepared by gel combustion method. The as-prepared nanoparticles were calcined at 500, 550 and 600 C. The crystallite size of the nanoparticles has been determined using X-ray diffraction. Catalytic activity has been studied by measuring the Tafel slope in oxygen reduction reaction in cyclic voltammetery. The nanoparticles samples showed higher catalytic activity than bulk ceria sample. Surprisingly, smaller size nanoparticles with large surface area showed less catalytic activity than larger size nanoparticles. Positron annihilation, X-ray photo electron spectroscopy and photoluminescence studies indicated the presence of oxygen vacancies as well as larger surface defects. It has been found that surface defect concentration increased with the increase in calcination temperature and the catalytic activity of the nanoparticles is directly correlated to the surface defect concentrations.
Materials for Energy Infrastructure, 2015
Undoped and doped ceria were synthesized by a solid state reaction and a polymerized-complex method. Microstructural and phase development of M x Ce 1-x O 2-δ (M = Zr, Hf; 0 ≤ x ≤ 0.2) were examined using X-ray diffraction and scanning electron microscopy. Redox properties were investigated by thermogravimetric analysis and a remarkable increase of the oxygen storage capacity of ceria with increasing dopant concentration was demonstrated. Zr x Ce 1-x O 2 and Hf x Ce 1-x O 2 solid solutions at x = 0.2 were shown to release double the amount of oxygen during reduction compared to undoped ceria. The solid state reaction synthesis produces materials with excellent redox performance up to 15 mol% dopant concentration and is otherwise equivalent with materials produced by Pechini synthesis.
Longer ozonolysis time induced CeO2 hexagonal nanostructures from nanocubes
Materials Chemistry and Physics, 2019
Cerium oxide (CeO 2) nanostructures were synthesized using an ozonolysis assisted co-precipitation method, while varying the ozonolysis reaction times for 1, 2, 3 and 4 h in the systems. The effect of ozonolysis reaction time on the morphology and optical properties of CeO 2 was investigated. The resulting products were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), photoluminescence spectroscopy (PL) and BET surface area analysis. The XRD patterns confirm a face-centered cubic (FCC) CeO 2 having crystalline sizes ranging from 8.5 to 10 nm. From the TEM images, longer ozonolysis reaction times more completely transform the morphology of CeO 2 nanoparticles from a nanocube-like shape into hexagonal CeO 2 nanostructures. FTIR spectra show that the peaks in the region of 400-750 cm-1 are due to Ce-O stretching vibrations. The UV-Vis spectra of all samples show ACCEPTED MANUSCRIPT 2 strong absorption at 285 nm with a weak absorption peak around 360 nm. The band gap energy is independent of ozonolysis reaction time. The photoluminescence spectra show characteristics peaks of CeO 2 nanoparticles. Adsorption-desorption isotherms of CeO 2 show a typical IUPAC type IV pattern and their pore size is 3.28 nm.
In-situ fabrication of Ce-rich CeO2 nanocatalyst for efficient CO oxidation
Journal of Alloys and Compounds, 2019
Ceria is widely utilized in the field of CO catalysis due to its outstanding oxygen storage/release capacity (OSC/ORC). In this study, Ce precursor is successfully injected into the plasma electrolytic oxidation (PEO) film in silicate electrolyte through the addition of EDTA-2Na during PEO process. The atomic percentage (at. %) of Ce in PEO film can reach up to 14.80, which is the highest among all the related works. Annealing treatment in air ambient leads to the crystallization and oxidation reaction of Ce species, which mainly exist in the PEO film in amorphous phase and Ce 4.667 (SiO 4) 3 O. During the annealing process, CeO 2 nanocrystals (~100 nm) are
The Journal of Physical Chemistry B, 2005
Structural characteristics of nanosized ceria-silica, ceria-titania, and ceria-zirconia mixed oxide catalysts have been investigated using X-ray diffraction (XRD), Raman spectroscopy, BET surface area, thermogravimetry, and high-resolution transmission electron microscopy (HREM). The effect of support oxides on the crystal modification of ceria cubic lattice was mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahighly dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO 2 -SiO 2 sample primarily consists of nanocrystalline CeO 2 on the amorphous SiO 2 surface. Both crystalline CeO 2 and TiO 2 anatase phases were noted in the case of CeO 2 -TiO 2 sample. Formation of cubic Ce 0.75 Zr 0.25 O 2 and Ce 0.6 Zr 0.4 O 2 (at 1073 K) were observed in the case of the CeO 2 -ZrO 2 sample. Raman measurements disclose the fluorite structure of ceria and the presence of oxygen vacancies/Ce 3+ . The HREM results reveal well-dispersed CeO 2 nanocrystals over the amorphous SiO 2 matrix in the cases of CeO 2 -SiO 2 , isolated CeO 2 , and TiO 2 (anatase) nanocrystals, some overlapping regions in the case of CeO 2 -TiO 2 , and nanosized CeO 2 and Ce-Zr oxides in the case of CeO 2 -ZrO 2 sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO 2 is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of the mixed oxide systems is more than that of pure CeO 2 and is system dependent.
Catalytic ozonation of 4-chlorophenol and 4-phenolsulfonic acid by CeO2 films
Catalysis Communications, 2019
Ceria films (CeO 2(f)) were deposited on glass substrate by a spray pyrolysis method. The catalytic oxidation performance of CeO 2(f) was evaluated in the removal of 4-chlorophenol (4-CPh) and 4-phenolsulfonic acid (4-SPh). The catalytic oxidation reactions were carried out in water with ozone as an oxidant agent. Conventional and catalytic ozonation achieved complete removal of both compounds. Furthermore, TOC results showed higher catalytic activity with six CeO 2(f) films in comparison with conventional ozonation after 120 min for the oxidation of both 4-CPh and 4-SPh. After five consecutive reuses of CeO 2(f) , the similar TOC removal for 4-CPh demonstrated the ceria films stability.
Noble metal-free CeO 2 -based mixed oxides for CO and soot oxidation
Catalysis Today, 2017
Three-way catalytic technology' has been successfully implemented in automobile industries for cleaning of auto exhaust gases from 1980's onward. Supported noble metal catalysts with ceria (CeO 2) as the redox promoter have been employed for this technology. However, these catalytic materials have some drawbacks in terms of high light off temperature, catalyst poisoning and drop of activity, heavy metal pollution, etc. Hence, this technology is under active investigation throughout for the sake of better performance. Considerable research efforts have been devoted to develop new advanced materials. Noble metal-free CeO 2-based mixed oxides, which can be deployed as potential substitutes, have been investigated at length with the goal to overcome the limitations like loss of stability and activity at elevated temperatures, improvement of oxygen storage/release capacity (OSC), and so on. However, the use of proper dopants at optimum concentration and tuning of the shapes, size and morphology of the nanoparticles via controlled synthesis is a challenging task, since it improves the features of CeO 2. In this article, we have reviewed the influence of these factors on the properties of ceria-based materials and their catalytic efficiencies in CO and soot oxidation reactions.