Ruthenium versus platinum on cerium materials in wet air oxidation of acetic acid

{CeO2/Bi2Mo1−xRuxO6} and {Au/Bi2Mo1−xRuxO6} Catalysts for Low-Temperature CO Oxidation

Nowadays, one of the most important challenges that humanity faces is to find alternative ways of reducing pollutant emissions. CeO2/Bi2Mo1−xRuxO6 and Au/Bi2Mo1−xRuxO6 catalysts were prepared to efficiently transform carbon monoxide (CO) to carbon dioxide (CO2) at low temperatures. The systems were prepared in a two-step process. First, Bi2Mo1−xRuxO6 supports were synthesized through the hydrothermal procedure under microwave heating. Then, CeO2 was deposited on Bi2Mo1−xRuxO6 using the wet impregnation method, while the incipient impregnation method was selected to deposit gold nanoparticles. The CeO2/Bi2Mo1−xRuxO6 and Au/Bi2Mo1−xRuxO6 catalysts were characterized using SEM microscopy and XRD. Furthermore, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used. Tests were carried out for the supported catalysts in CO oxidation, and high conversion values, nearing 100%, was observed in a temperature range of 100 to 250 °C. The results showed that the best system was the Au/Bi2Mo0.95Ru0.05O6 catalyst, with CO oxidation starting at 50 °C and reaching 100% conversion at 186 °C.

Treatment of phenol by catalytic wet air oxidation: a comparative study of copper and nickel supported on γ-alumina, ceria and γ-alumina–ceria

Cu, Ni, CuO and NiO catalysts, prepared by wet impregnation with urea and supported on γ-Al₂O₃, CeO₂, and Al₂O₃–CeO₂, were evaluated for Catalytic Wet Air Oxidation (CWAO) of phenol in a batch reactor under a milder condition (120 °C and 10 bar O₂). The synthesized samples, at their calcined and/or their reduced form, were characterized by XRD, H₂-TPR, N₂ adsorption–desorption, SEM-EDS and DR-UV-Vis to explain the differences observed in their catalytic activity towards the studied reaction. The influence of the support on the efficiency of CWAO of phenol at 120 °C and 10 bar of pure oxygen has been examined and compared over nickel and copper species. The SEM-EDS results reveal that the spherical crystalline Cu and Ni were successfully deposited on the surface of γ-Al₂O₃, CeO₂, Al₂O₃–CeO₂ within 16–90 nm and that they were highly homogeneously dispersed. It was found that catalysts prepared from impregnation solutions of Cu(NO₃)₂·3H₂O and Ni(NO₃)₂·6H₂O with urea addition had different textural characteristics and degrees of dispersion of Cu and Ni species. The urea addition in the traditional wet impregnation method was essential to improve the reducibility and degree of dispersion in Ni, and to a lesser extent, in Cu. According to the characterization analysis of H₂-TPR and UV-VIS RD a structure–activity relationship can be determined. The chemical oxygen demand (COD) and GC analyses confirmed the effect of calcined and reduced species for Cu and Ni applied to the catalytic oxidation of phenol, showing their significant impact in the final performance of the catalyst.

Influence of the calcination and reduction treatment effects used to activate catalysts on the global catalytic performance on phenol oxidation over different supports.

Performance of various catalysts on treatment of refractory pollutants in industrial wastewater by catalytic wet air oxidation: A review

The tremendous increase of industrialization and urbanization worldwide causes the depletion of natural resources such as water and air which urges the necessity to follow the environmental sustainability across the globe. This requires eco-friendly and economical technologies for depollution of wastewater and gases or zero emission approach. Therefore, in this context the treatment and reuse of wastewater is an environmental friendly approach due to shortage of fresh water. Catalytic wet air oxidation (CWAO) is a promising technology for the treatment of toxic and non-biodegradable organic pollutants in the wastewater generated from various industries. Various heterogeneous catalysts have been extensively used for treatment of various model pollutants such as phenols, carboxylic acids, nitrogenous compounds and different types of industrial effluents. The present review focuses on the literature published on the performances of various noble and non-noble metal catalysts for the treatment of various pollutants by CWAO. Reports on biodegradability enhancement of industrial wastewater containing toxic contaminants by CWAO are reviewed. Detailed discussion is made on catalyst deactivation and their mitigation study and also on the various factors which affects the CWAO reaction.

Silver nanoparticles supported on zirconia–ceria for the catalytic wet air oxidation of methyl tert-butyl ether

In this work Ag nanoparticles supported on ZrO₂–CeO₂ promoted with different amounts of CeO₂ were synthesized by deposition–precipitation method in order to test the Catalytic Wet Air Oxidation (CWAO) of Methyl Tert-Butyl Ether (MTBE).

Catalytic wet air oxidation of high-concentration organic pollutants by upflow packed-bed reactor using a Ru–Ce catalyst derived from a Ru3(CO)12 precursor

The low loading Ru–Ce catalyst have high activity in CWAO due to a strong interaction with the support.

Catalytic wet air oxidation of m-cresol over a surface-modified sewage sludge-derived carbonaceous catalyst

Sewage sludge-derived carbonaceous materials (SW) treated with different kinds of acids were used as catalysts for catalytic wet air oxidation (CWAO) of m-cresol.

Catalytic wet air oxidation of 2-chlorophenol over sewage sludge-derived carbon-based catalysts

A sewage sludge derived carbon-supported iron oxide catalyst (FeSC) was prepared and used in the Catalytic Wet Air Oxidation (CWAO) of 2-chlorophenol (2-CP). The catalysts were characterized in terms of elemental composition, surface area, pHPZC, XRD and SEM. The performances of the FeSC catalyst in the CWAO of 2-CP was assessed in a batch reactor operated at 120°C under 0.9MPa oxygen partial pressure. Complete decomposition of 2-CP was achieved within 5h and 90% Total Organic Carbon (TOC) was removed after 24h of reaction. Quite a straight correlation was observed between the 2-CP conversion, the amount of iron leached in solution and the pH of the reaction mixture at a given reaction time, indicating a strong predominance of the homogeneous catalysis contribution. The iron leaching could be efficiently prevented when the pH of the solution was maintained at values higher than 4.5, while the catalytic activity was only slightly reduced. Upon four successive batch CWAO experiments, using the same FeSC catalyst recovered by filtration after pH adjustment, only a very minor catalyst deactivation was observed. Finally, based on all the identified intermediates, a simplified reaction pathway was proposed for the CWAO of 2-CP over the FeSC catalyst.

Influence of the different oxidation treatment on the performance of multi-walled carbon nanotubes in the catalytic wet air oxidation of phenol

Multi-walled carbon nanotubes (MWCNTs) functionalized by different oxidants (HNO(3)/H(2)SO(4), H(2)O(2), O(3) and air) have been used as catalysts for the wet air oxidation of phenol. To investigate the effect of the oxidation conditions on the structure of the functionalized MWCNTs, various characterization techniques, e.g., scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been used. The MWCNTs treated with O(3) and H(2)O(2) show higher amounts of oxygen-containing functional groups and carboxylic acid groups, and a weaker acidic nature, in comparison with those treated with other oxidizing agents. All the functionalized MWCNTs exhibit good activity in the catalytic wet air oxidation (CWAO) of phenol. However, the MWCNTs treated with O(3) show the highest activity with desirable stability in comparison with other functionalized MWCNTs, indicating that the functionalization of carbon nanotubes with O(3) is a very promising strategy in synthesizing efficient catalysts for CWAO.

Heterogeneous catalytic wet air oxidation of refractory organic pollutants in industrial wastewaters: a review

Catalytic wet air oxidation (CWAO) is one of the most economical and environmental-friendly advanced oxidation process. It makes a promising technology for the treatment of refractory organic pollutants in industrial wastewaters. Various heterogeneous catalysts including noble metals and metal oxides have been extensively studied to enhance the efficiency of CWAO. The present review is concerned about the literatures published in this regard. Phenolics, carboxylic acids, and nitrogen-containing compounds were taken as model pollutants in most cases, and noble metals such as Ru, Rh, Pd, Ir, and Pt as well as oxides of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Ce were applied as heterogeneous catalysts. Reports on their characterization and catalytic performances for the CWAO of aqueous pollutants are reviewed. Discussions are also made on the reaction mechanisms and kinetics proposed for heterogeneous CWAO and also on the typical catalyst deactivations in heterogeneous CWAO, i.e. carbonaceous deposits and metal leaching.

Preparation of InYO3 catalyst and its application in photodegradation of molasses fermentation wastewater

An InYO3 photocatalyst was prepared through a precipitation method and used for the degradation of molasses fermentation wastewater. The InYO3 photocatalyst characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy, surface area and porosimetry. Energy band structures and density of states were achieved using the Cambridge Serial Total Energy package (CASTEP). The results indicated that the photodegradation of molasses fermentation wastewater was significantly enhanced in the presence of InYO3 when compared with PbWO4. The calcination temperature was found to have a significant effect on the photocatalytic activity of InYO3. Specifically, InYO3 calcined at 700 degrees C had a considerably larger surface area and lower reflectance intensity and showed higher photocatalytic activity. The mathematical simulation results indicated that InYO3 is a direct band gap semiconductor, and its conduction band is composed of In 5p and Y 4d orbitals, whereas its valence band is composed of O 2p and In 5s orbitals.