Wet oxidation

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

Lower toxicity route in catalytic wet oxidation of phenol at basic pH by using bicarbonate media

Abstract: Catalytic oxidation of phenol in aqueous solution has been studied by using bicarbonate as buffer reagent to keep the pH in the interval 7–8 (pH 8B) with a commercial catalyst based on copper. The oxidation route obtained at pH 8B is different and less toxic than that obtained at acid pH because of the dihydroxybenzenes are not formed at basic pH. To determine the phenol oxidation route several runs were carried out with phenol or the intermediates detected at pH 8B ( p -hydroxybenzoic, pyruvic, oxalic, acetic and formic acids, and traces of tetrahydroxy- p -benzoquinone), under a temperature of 140 °C and oxygen pressure of 16 bar. A basket stirred tank reactor (BSTR) and an up-flow fixed bed reactor (FBR) were used depending on the reactant employed. A radical mechanism on the catalyst surface has been elucidated to explain the oxidation route found. All the intermediates detected at pH 8B are more than one order of magnitude less toxic than phenol and copper was not leached from the catalyst at this pH. Moreover, higher mineralization than that obtained at acidic conditions was found at pH 8B.

Kinetics of Wet Air Oxidation of Phenol over a Novel Catalyst

Abstract: The wet air oxidation kinetics of an aqueous solution of phenol was studied over extrudates of an Al−Fe pillared clay catalyst in the temperature range of 90−150 °C and air pressure range of 0.8−2.5 MPa. The variables studied included reaction temperature, air pressure, solution pH, initial phenol concentration, and catalyst loading. The obtained findings are compared with those obtained using hydrogen peroxide oxidation. A group of kinetic models considering both the power-law and Langmuir−Hinshelwood approaches was evaluated to describe the catalytic kinetics of the phenol disappearance. The nonlinear dependence of the phenol conversion rate on the catalyst concentration was taken into account via the empirical power-law function of this variable. Finally, a kinetic model was discriminated on the basis of equilibrium adsorption of phenol and dissociated oxygen on two distinct types of active sites. The rate-controlling step was assumed to be the surface reaction between adsorbed reactant species. This m...

Reactive Dye House Wastewater Treatment. Use of Hybrid Technology: Membrane, Sonication Followed by Wet Oxidation

Abstract: To address problems associated with treatment of an aqueous waste stream from a reactive dye house, a model dye, turquoise blue CI25, was studied. A hybrid technology, membrane separation followed by sonication and wet oxidation, has been demonstrated to treat the wastewater for reuse and discharge. Experiments were first performed with the reactive dye solution in water. A nanofiltration membrane (MPT 30) was found to be suitable to concentrate the dye. The concentrate was then treated with a wet oxidation process. Kinetics studies were performed with and without catalyst, in the temperature range of 170−215 °C. The color destruction achieved was >99%. After process parameters were fixed, studies were conducted with the actual dye waste stream. The actual waste stream was found to be refractory for wet oxidation under the above conditions. Sonication of the concentrate obtained after membrane filtration, in the presence of CuSO4, made the waste stream amenable to wet oxidation. Sonication followed by wet...

Catalytic wet air oxidation of phenol with functionalized carbon materials as catalysts: reaction mechanism and pathway.

Abstract: The development of highly active carbon material catalysts in catalytic wet air oxidation (CWAO) has attracted a great deal of attention. In this study different carbon material catalysts (multi-walled carbon nanotubes, carbon fibers and graphite) were developed to enhance the CWAO of phenol in aqueous solution. The functionalized carbon materials exhibited excellent catalytic activity in the CWAO of phenol. After 60 min reaction, the removal of phenol was nearly 100% over the functionalized multi-walled carbon, while it was only 14% over the purified multi-walled carbon under the same reaction conditions. Carboxylic acid groups introduced on the surface of the functionalized carbon materials play an important role in the catalytic activity in CWAO. They can promote the production of free radicals, which act as strong oxidants in CWAO. Based on the analysis of the intermediates produced in the CWAO reactions, a new reaction pathway for the CWAO of phenol was proposed in this study. There are some differences between the proposed reaction pathway and that reported in the literature. First, maleic acid is transformed directly into malonic acid. Second, acetic acid is oxidized into an unknown intermediate, which is then oxidized into CO2 and H2O. Finally, formic acid and oxalic acid can mutually interconvert when conditions are favorable.