Wet oxidation

About: Wet oxidation is a research topic. Over the lifetime, 3094 publications have been published within this topic receiving 61536 citations.

Catalytic wet air oxidation of phenol with air and micellar molybdovanadophosphoric polyoxometalates under room condition

Abstract: Micellar molybdovanadophosphoric polyoxometalate (POM) catalysts [(C n H 2 n +1 )N(CH 3 ) 3 ] 3+ x PV x Mo 12− x O 40 ( x = 1, 2, 3; n = 8, 12, 14, 16, 18) were prepared and used for catalytic wet air oxidation (CWAO) of phenol. X-ray photoelectron spectrum (XPS), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) were used to characterize the resulting samples. The best catalytic activity was obtained over (C 16 TA) 6 PV 3 Mo 9 O 40 , which showed 95.3% degradation efficiency, 98.5% COD removal and 93.0% TOC reduction with air under room condition toward complete degradation product CO 2 within 90 min. The leaching test showed that the POM micellar catalysts have an excellent stability and can be used as heterogeneous catalysts for about six times.

Wet air oxidation of nitro-aromatic compounds: Reactivity on single- and multi-component systems and surface chemistry studies with a carbon xerogel

Abstract: The treatment of dinitrophenol (DNP) and trinitrophenol (TNP), typically found in the effluents from the process of mononitrobenzene (MNB) synthesis, was investigated by wet air oxidation in both non-catalytic (WAO) and catalytic (CWAO) conditions, operating as two phase and three phase reactors, respectively. In the first case, the effect of treating DNP and TNP separately (single-component system) or using mixtures of these compounds (multi-component systems) was assessed by analysing the decrease of the individual pollutant concentration, the total organic carbon (TOC) evolution and the reaction by-products. Of the various systems screened, it was possible to conclude that the presence of DNP enhances the overall oxidation in multi-component systems. TNP is not oxidized individually but totally degraded in the presence of DNP. The observed reactivities were correlated with the number and type of functional groups attached to the aromatic ring and the HO induced denitration may be considered as the main reaction mechanism. Concerning the CWAO experiments, two catalysts were synthesized in this study, a carbon xerogel (CX) and a nanosized cerium oxide (CeO 2 ), using sol–gel and solvothermal methodologies, respectively, and tested for the degradation of the multi-component system. The CX catalyst operating in slurry conditions was found to be highly active and led to practically complete removal of DNP and TNP, total bleaching of color and 83% mineralization after 120 min of reaction. The best catalyst was thoroughly characterized. An increase in the concentration of carboxylic acid groups at the catalyst surface was observed by TPD analysis of the catalyst after the reaction, followed by a decrease in the concentration of phenolic and quinone functional groups. The catalyst surface modification was a consequence of the large amounts of nitrates produced from the model compounds. Nitrites were not detected and, therefore, CWAO seems to be a potential treatment which can be coupled with a biological process to remove the nitrates formed during the reaction.

Wet thermal oxidation of GaN

Abstract: Thermal oxidation of GaN was conducted at 700–900°C with O2, N2, and Ar as carrier gases for 525–630 Torr of H2O vapor. Upon oxidation of both GaN powders and n-GaN epilayers, the monoclinic β-Ga2O3 phase was identified using glancing angle x-ray diffraction. The chemical composition of the oxide was verified using x-ray photoelectron spectroscopy. In experiments conducted using GaN powder, the oxide grew most rapidly when O2 was the carrier gas for H2O. The same result was obtained on n-type GaN epilayers. Furthermore, the thickness of the oxide grown in H2O with O2 as the carrier gas was found to be proportional to the oxidation time at all temperatures studied, and an activation energy of 210±10 kJ/mol was obtained. Scanning electron microscopy revealed a smoother surface after wet oxidation than was reported previously for dry oxidation. However, cross-sectional transmission electron microscopy revealed that the wet oxide/GaN interface was irregular and non-ideal for devicefabrication, even more so than the dry oxide/GaN interface. This observation was consistent with poor electrical properties.

Activity and stability of iron-containing pillared clay catalysts for wet air oxidation of phenol

Abstract: Catalytic wet air oxidation of an aqueous phenol solution over Fe–Al pillared catalyst was conducted in a stirred tank and packed bed reactor. Semi-batch experiments in the stirred tank reactor were designed to investigate the effects of temperature, air pressure, initial phenol concentration, catalyst loading, and catalyst size on the conversion of total organic carbon. The catalyst exhibited an important activity in degrading total organic carbon at mild conditions. Its internal mass transfer resistance was assessed over different catalyst sizes via a chosen criterion. Packed bed runs were conducted under selected temperature and pressure (170 °C, 3.2 MPa) over a long duration (240 h). Various characterization methods were employed for fresh and aged pillared clay catalysts. Occurrence of catalyst deactivation by carbonaceous deposits during the packed bed operation was observed through scanning electron microscopy (SEM) and elemental analysis. Insignificant metal leaching was observed because trace amounts of metal elements were detected in the hot acidic liquid solution.

Paper mill waste sludge oxidation and product recovery

Abstract: Paper mill waste sludges are subjected to wet air oxidation whereby organic materials are converted to innocuous oxidation products, and the inorganic filler materials, e.g., titanium dioxide, clay and the like, are recovered in a form suitable for reuse.