Showing papers on "Wet oxidation published in 2002"
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) was used to investigate the valence state of cerium in unsupported composite Ce x Mn 1− x O 2− y catalysts.
553 citations
TL;DR: Alkaline wet oxidation was an efficient pre-treatment of wheat straw that resulted in solid fractions with high cellulose recovery and high enzymatic convertibility to glucose, and aromatic aldehyde formation was correlated to severe conditions with high temperatures and low pH.
404 citations
TL;DR: Titanium dioxide nanoparticles of both anatase and rutile phases were synthesized by hydrothermal treatment of microemulsions, and their photocatalytic activity for wet oxidation of phenol w...
Abstract: Titanium dioxide (TiO2) nanoparticles of both anatase and rutile phases were synthesized by hydrothermal treatment of microemulsions, and their photocatalytic activity for wet oxidation of phenol w ...
396 citations
TL;DR: Investigations of various CeO2 catalysts using XRD, 02-TPD, H2-TPR and catalytic wet air oxidation of phenol showed that CeO 2 calcined under higher thermal impact (designated as type A) displayed excellent catalytic ability for the redox reaction of organics.
115 citations
TL;DR: In this paper, the authors investigated the Catalytic Wet Air Oxidation (CWAO) process for ammonium ions removal from wastewater. And the greatest interest of CWAO compared to the classical biological one, is that the selectivity towards molecular nitrogen is much higher (>90%).
98 citations
TL;DR: In this article, the catalytic wet air oxidation (WAO) of p -coumaric acid (PCA) has been investigated over Fe- and Zn-promoted ceria catalysts.
Abstract: The catalytic wet air oxidation (WAO) of p -coumaric acid (PCA) has been investigated over Fe- and Zn-promoted ceria catalysts. The catalysts have been prepared by the coprecipitation method and have been characterized by X-ray diffraction (XRD), BET surface area, SEM–EDX and temperature programmed reduction (TPR). The oxidation reaction was carried out in a batch reactor under an air pressure of 2 MPa and in the temperature range 353–403 K. Fe-CeO 2 catalysts, with 20–50 mol% of iron, were found more effective than the unpromoted and Zn-promoted ceria catalysts. On the basis of characterization data, it has been suggested that the higher activity of the Fe-promoted catalysts is related to the modification of the structural and redox properties of the ceria oxide catalyst on addition of iron.
96 citations
TL;DR: PAC was found to be more suitable as compared with GAC for the adsorption and wet oxidative regeneration processes to treat the aqueous solution containing lower concentration of unhydrolyzed reactive dye.
88 citations
TL;DR: It is shown that hydroxyl radicals (HO*) and hydrogen peroxide (H2O2) play the role of intermediates in the initial phase of the oxidation reactions.
83 citations
TL;DR: In this article, the catalytic effect of two Keggin-type polyoxotung states, namely H 4 SiW 12 O 40 and Na 2 HPW12 O 40, on the wet air oxidation of azo dye acid Orange 7 (AO7; C dye =248 μM) at varying reaction temperatures (T =160-290 °C at P H 2 O= 0.6-3.0 MPa, respectively) was examined.
82 citations
TL;DR: The comparison of the efficiencies of different catalysts shows that Ce3Cu1 (3:1) catalyst is the best one when the reaction temperature is 200 degrees C, oxygen partial pressure, pH value, and reaction time is 30 min, the COD removal rate is over 90%.
64 citations
TL;DR: Extraction with hot water, if combined with oxidation, would probably reduce the cost of post treatment for the water and can be used as a feasible alternative technique for remediation of contaminated soils and sediments.
TL;DR: In this paper, the Sofnocarb A21 (5% CuO on activated carbon) was used for catalytic wet air oxidation of phenol and it was found that no copper leaching took place in the experiments using fresh catalyst, when the initial phenol concentration was lower than 1.5 kg/m3.
Abstract: Stability aspects of the Sofnocarb A21 catalyst (5% CuO on activated carbon) have been studied for catalytic wet air oxidation of phenol. The study focused on copper leaching, the main factor affecting the catalyst stability. It was found that no copper leaching took place in the experiments using fresh catalyst, when the initial phenol concentration was lower than 1.5 kg/m3. Nevertheless, copper leaching and fouling were observed through consecutive experiments reusing the catalyst, leading to deactivation of catalyst and therefore a lower phenol oxidation rate. The main reaction intermediates, namely acetic acid and p-benzoquinone, together with polymeric products are highlighted to be responsible for copper leaching and fouling. Nonetheless, the leaching of active substance measured for Sofnocarb A21 was much lower than those found for other catalysts (G-66 A, Sud Chemie, Germany) also used for catalytic decomposition of phenol. Basic conditions were demonstrated to be useful to prevent both copper lea...
TL;DR: In this article, the removal of organics from paper and pulp industrial waste was investigated employing wet oxidation and catalytic wet oxidation (CWO) techniques using a high-pressure reaction system.
Abstract: The removal of organics from paper and pulp industrial waste was investigated employing wet oxidation (WO) and catalytic wet oxidation (CWO) techniques using a high-pressure reaction system. Different types of catalysts prepared from single metals (transition/noble) and mixed metals (transition–transition/transition/noble metal) were used in the CWO studies. The paper and pulp liquor treatments were conducted in selected different environments such as (i) liquors with different organic concentrations, (ii) liquors with different pH (11–14), (iii) a range of reaction temperatures (413–463 K), (iv) different catalysts (Cu, Mn, Pd, Cu/Mn, Mn/Pd, Cu/Pd), (v) catalyst loading (1–8 g). The single transition (Cu, Mn) or noble metal (Pd) catalysts showed appreciable total organic removal, but the bi-metal catalysts (Cu/Mn, Cu/Pd, Mn/Pd ) exhibited even higher activity for organics removal. Much higher total organic carbon (TOC) removal (>84%) was achieved by using the CWO process. The TOC removed by the Cu/Pd catalyst was the highest, followed by the Mn/Pd and Cu/Mn catalytic system.
TL;DR: In this paper, the effects of the addition of hydroquinone as a free radical initiator and t -butanol as a scavenger on wet oxidation of phenol were studied in presence of this catalyst at near neutral conditions and also in a strongly alkaline medium.
TL;DR: Wet oxidation improved the ability of settling of sludge solids, as well as enhancing the treatment efficiency, and the volume of settled solids was decreased in the presence of Cu and H2O2.
TL;DR: In this article, the effects of two pre-treatment processes (alkaline wet oxidation and enzyme treatment with laccase) on lignocellulosic materials for applications in particleboards and fiberboards were evaluated.
Abstract: Wheat straw (Triticum aestivum) and beech (Fagus sylvatica), were used to evaluate the effects of two pre-treatment processes (alkaline wet oxidation and enzyme treatment with laccase) on lignocellulosic materials for applications in particleboards and fiberboards. Wheat straw and beech fibers reacted differently in the two processes. The chemical composition changed little following enzyme treatment. After alkaline wet oxidation, fibers enriched in cellulose were obtained. With both materials, almost all hemicellulose (80%) together with a large portion of the lignin were solubilised by alkaline wet oxidation, but essentially all cellulose remained in the solid fraction. Following enzyme treatment most material remained as a solid. For wheat straw, reaction with acetic anhydride indicated that both treatments resulted in more hydroxyl groups being accessible for reaction. The enzyme treatment gave a more reactive surface than alkaline wet oxidation for wheat straw, whereas the opposite was obser...
TL;DR: In this paper, carbon-supported iridium catalysts were used for catalytic wet air oxidation of butyric and iso-butyric acid aqueous solutions in a stirred reactor at 473 K and 0.69 MPa of oxygen partial pressure.
Abstract: Carbon-supported iridium catalysts were prepared by different incipient wetness impregnation methods and by organometallic chemical vapor deposition. The catalysts were characterized by N2 adsorption, TPD, SEM and H2 chemisorption measurements. The results obtained indicate a clear dependency of the metal-phase dispersion on the pre-treatment of the carbon support and the impregnation method. Their activity for catalytic wet air oxidation of butyric and iso-butyric acid aqueous solutions was investigated in a stirred reactor at 473 K and 0.69 MPa of oxygen partial pressure. The conversions obtained after 2 h were 43 and 52%, with respect to each carboxylic acid, when the most active catalysts were used. The measured conversions and initial reaction rates correlate well with the exposed metal area. A rate equation was determined from measurements of the initial reaction rates at different oxygen partial pressures, temperatures and catalyst mass loads. The results were modeled considering a heterogeneously catalyzed free-radical mechanism.
TL;DR: In this paper, the role of mass transfer in the formation of acetic acid in wet oxidation was studied and the model compound hydroquinone was used as a free radical generator.
TL;DR: In this paper, the authors describe the kinetics and an approach to the mechanism of the catalytic wet air oxidation of aqueous phenol, using copper oxide supported over activated carbon as a catalyst.
Abstract: This paper describes the kinetics and an approach to the mechanism of the catalytic wet air oxidation of aqueous phenol. Copper oxide supported over activated carbon was used as catalyst. Experimen...
Journal Article•
TL;DR: In this paper, the effects of Ce addition on the activity of Pt/Al2O3 catalysts were investigated for the wet oxidation of phenol, and it was shown that the Pt catalysts from the former showed much higher activity than that from the latter, because the former resulted in a better metal dispersion than the latter.
Abstract: The effects of Ce addition on the activity of Pt/Al2O3 catalysts were investigated for the wet oxidation of phenol. Platinum was impregnated on γ-Al2O3 by using two different precursors: one is anionic (i.e., H2PtCl6) and the other is cationic (i.e., Pt(NH3)4Cl2). The Pt catalysts from the former showed much higher activity than that from the latter, because the former resulted in a better metal dispersion than the latter. Cerium addition lowered the catalytic activity of Pt/Al2O3 catalysts from H2PtCl6, while it improved the activity of Pt/Al2O3 catalysts from Pt(NH3)4Cl2. The effect of Ce addition on the wet oxidation activity of Pt−Ce/Al2O3 could be explained by the differences in Pt dispersion and the Pt−Ce interactions.
TL;DR: In this paper, the regeneration of a commercial activated carbon (AC) was studied using the wet air oxidation (WAO) process in the temperature range 150−180 °C and an oxygen partial pressure of 0.718 MPa.
Abstract: The regeneration of a commercial activated carbon (AC) was studied using the wet air oxidation (WAO) process in the temperature range 150−180 °C and an oxygen partial pressure of 0.718 MPa. p-Nitrophenol (PNF) was used as the adsorbate. First, the oxidation process of PNF was studied. In the absence of AC, it was independent of the initial concentration of PNF at the conditions used in this work. The temperature and oxygen partial pressure exerted positive effects on the oxidation process. The activation energy of the PNF oxidation process and the reaction order with respect to oxygen were 134.8 kJ mol-1 and 0.55, respectively. The desorption process of PNF from the saturated AC was studied in the aforementioned temperature range. It was found to occur during the heating period, with an equilibrium being reached. The regeneration process was studied at these same temperatures, yielding an activation energy for PNF oxidation of 99.1 kJ mol-1. The isotherms of the virgin and regenerated AC and the phenol, m...
Patent•
17 Jul 2002
TL;DR: The main componens of copper base catalyst are copper, zinc, nickel, magnesium, aluminium, chromium, iron and partial oxide of rare earth metal, in which (by oxide content) CuO is 20-55%, ZnO, NiO orMgO is20-55, Cr2O3, Al 2O3 of Fe2O 3 is 10-40% and rare earth metals oxide is 0-10 as mentioned in this paper.
Abstract: The main componens of copper base catalyst are copper, zinc, nickel, magnesium, aluminium, chromium, iron and partial oxide of rare earth metal, in which (by oxide content) CuO is 20-55%, ZnO, NiO orMgO is 20-55%, Cr2O3, Al2O3 of Fe2O3 is 10-40% and rare earth metal oxide is 0-10%. Said catalyst can be made up by roasting catalyst precursor with hydrotalcite-like structure obtained by coprecipitation of salts of various metals. Said catalyst can effectively treat industrial organic waste water containing phenol, sulfosalicylic acid, H-acid and surfactant, etc., not only possesses higher catalytic activity, but also can control the loss of active components.
TL;DR: This work proposes a model that can describe the oxidation process via organic concentration characteristics such as chemical oxygen demand, biochemical oxygen demand and immediately available BOD and so can allow the prediction of biodegradability (i.e., BOD/COD ratio).
Abstract: In many cases, treatment of wastewaters requires a combination of processes that very often includes biological treatment. Wet oxidation (WO) in combination with biotreatment has been successfully used for the treatment of refractory wastes. Therefore, information about the biodegradability of wastewater solutes and particulates after wet oxidation is very important. The present work proposes a model that can describe the oxidation process via organic concentration characteristics such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), and immediately available BOD (IA BOD) and so can allow the prediction of biodegradability (i.e., BOD/COD ratio). The reaction mechanism includes the destruction of nonbiodegradable substances bytwo pathways: oxidation to carbon dioxide and water and oxidation to larger biodegradable compounds with their further degradation to smaller ones measured via IA BOD. The destruction of small biodegradable compounds to end products is also included in the model. The experiments were performed at different temperatures (170-200 degrees C) and partial oxygen pressures (0.5-1.5 MPa) in a batch stainless steel high-pressure autoclave. The model of concentrated thermomechanical pulp circulation water was selected for the experiments. The proposed model correlates with the experimental data well and it is compared with other WO models in the literature.
TL;DR: In this article, butyric acid was treated by catalytic wet air oxidation using carbon-supported iridium catalysts in a stirred reactor, under operating conditions of 6.9 bar of oxygen partial pressure and 200°C of temperature, conversions up to 52.9% after 2h were obtained depending on the type of catalyst used.
TL;DR: In this paper, a two-step reaction process was proposed to increase the acetic acid yield in a wet oxidation of lignocellulosic wastes, and the yield increased about twofold.
Abstract: To increase the acetic acid yield in a wet oxidation of lignocellulosic wastes, a new two-step reaction process is proposed. The first step produces 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (2-FA) by dehydration of monosaccharides which are formed by hydrolysis of polysaccharides under the condition of non-supply of oxygen. In the second step, HMF and 2-FA are oxidized to acetic acid with oxygen newly added. The yield increased about twofold.
TL;DR: In this paper, three kinds of Ru/CeO2 catalysts were prepared and the mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated.
Abstract: Three kinds of Ru/CeO2 catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO2, and TPR experiment showed that the reaction, RuO2 + 2H2 → Ru + 2H2O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.
TL;DR: In this article, a new process for producing calcium magnesium acetate (CMA) deicer with acetic acid, produced by wet oxidation of organic wastes, and Ca/Mg wastes is proposed.
Abstract: A new process for producing calcium magnesium acetate (CMA) deicer with acetic acid, produced by wet oxidation of organic wastes, and Ca/Mg wastes is proposed. Four kinds of representative organic waste were used as low-cost raw materials, for production of acetic acid, which was then converted to CMA by mixing with a Ca/Mg source such as oyster shells and industrial Mg wastes. The conversion efficiencies to acetic acid and from acetic acid to CMA achieved 14–16% and higher than 99%, respectively.
TL;DR: In this article, the authors used diamond-coated cantilevers for scanning capacitance microscopy (SCM) as an alternative for metalcoated probes in order to improve the stability of probes.
Abstract: Diamond-coated cantilevers have been used for scanning capacitance microscopy (SCM) as an alternative for metal-coated cantilevers in order to improve the stability of probes. It is shown that the diamond-coated probes produce adequate intensity of dC signal and high contrast for both p-type and n-type silicon samples and also provide superior endurance characteristics to metal-coated probes. Due to the robustness of the diamond-coated probes, we are able to evaluate the reproducibility of measurements and the homogeneity of the ultrathin oxide for both dry oxidation (heated up to 300 °C in air under ultraviolet illumination) and wet oxidation (immersed into a hydrogen peroxide solution at 70 °C). The dry oxidation shows better reproducibility, while the wet oxidation shows better homogeneity. Finally, comparison of SCM with secondary ion mass spectrometry measurement shows that diamond-coated probes can be used at least for one-dimensional quantitative SCM measurements without any significant effect of d...
TL;DR: In this paper, a twin study of the oxidation mechanism of (63Cu37Zn) brass foil in oxygen plasma and in alkaline aqueous solution is reported. Brass foil was exposed to low-pressure rf oxygen plasma in given working conditions and the resulting surface was studied by means of linear sweep voltammetry.