Showing papers on "Wet oxidation published in 2010"

Comprehensive Study of Pore Evolution, Mesostructural Stability, and Simultaneous Surface Functionalization of Ordered Mesoporous Carbon (FDU-15) by Wet Oxidation as a Promising Adsorbent

Abstract: Fuctionalization of porous carbon materials through chemical methods orientates the development of new hybrid materials with specific functions. In this paper, a comprehensive study of pore evolution, mesostructural oxidation resistance, and simultaneous surface functionalization of ordered mesoporous carbon FDU-15 under various oxidation conditions is presented for the first time. The mesostructure and pore evolution with increasing oxidative strength are retrieved from XRD, TEM, and N(2) sorption techniques. The textural properties can be conveniently manipulated by changing the oxidation parameters, including different oxidative solution, temperature, and duration. It is revealed that the mesoporous carbon FDU-15 shows excellent structural stability under severe oxidation treatments by acidic (NH(4))(2)S(2)O(8), HNO(3), and H(2)O(2) solutions, much more stable than the mesostructural analogue CMK-3 carbon prepared by the nanocasting method. The surface area and porosity deteriorate to a large extent compared to the pristine carbon, with the micropores/small mesopores as the major contribution to the deterioration. The micropore/small mesopore can be blocked by the attached surface oxides under mild oxidation, while reopened with more carbon layer dissolution under more severe conditions. Simultaneously, high densities of surface oxygen complexes, especially carboxylic groups, can be generated. The contents and properties of the surface oxygen-containing groups are extensively studied by FTIR, TG, elemental analyses, and water and ammonia adsorption techniques. Such surface-functionalized mesoporous carbons can be used as a highly efficient adsorbent for immobilization of heavy metal ions as well as functional organic and biomolecules, with high capacities and excellent binding capabilities. Thus, we believe that the functionalized mesoporous carbon materials can be utilized as a promising solid and stable support for water treatment and organic/biomolecules immobilization and may be applicable in drug delivery, separation, adsorption technology, and columns for GC and HPLC systems in the near future.

Wet oxidation process performed on a dielectric material formed from a flowable cvd process

Abstract: Methods of performing a wet oxidation process on a silicon containing dielectric material filling within trenches or vias defined within a substrate are provided. In one embodiment, a method of forming a dielectric material on a substrate includes forming a dielectric material on a substrate by a flowable CVD process, curing the dielectric material disposed on the substrate, performing a wet oxidation process on the dielectric material disposed on the substrate, and forming an oxidized dielectric material on the substrate.

Catalysis of Cu-Doped Co-Based Perovskite-Type Oxide in Wet Oxidation of Lignin To Produce Aromatic Aldehydes

Abstract: The aim of the present work was to investigate the influence of Cu substitution on the physicochemical properties of LaCo1−xCuxO3 (x = 0, 0.1, and 0.2) prepared by the sol−gel method, to clarify the relation between perovskite properties and their catalytic behaviors in the catalytic wet aerobic oxidation (CWAO) of lignin. X-ray diffraction (XRD), temperature-programmed reduction of H2 (H2-TPR), and X-ray photoelectron spectroscopy (XPS) indicated that Cu and Co were finely dispersed on the perovskite framework of the samples and an interaction between the Cu2+ and Co3+ sites in the perovskite lattice occurred. The percentages of surface chemisorbed oxygen species were 64.2, 75.2, and 81.1%, when x = 0, 0.1, and 0.2, respectively, obtained from O 1s XPS, indicating that the content of chemisorbed oxygen was improved with the increased content of Cu2+ in the mixed oxides. The samples were applied to the CWAO of lignin, and the experiments illustrated that the catalyst activity improved with an increase in ...

Mechanistic and kinetic insights into the wet air oxidation of phenol with oxygen (CWAO) by homogeneous and heterogeneous transition-metal catalysts

Abstract: The activity–selectivity pattern of homogeneous (Cu2+, Fe3+, Mn2+) and ceria-supported (CuCeOx, MnCeOx) transition-metal catalysts in the wet air oxidation of phenol (CWAO) has been probed using a stirred batch reactor with continuous oxygen feeding (T, 150 °C; P O 2 , 0.9 Mpa). Both non-catalytic and catalytic homogeneous wet air oxidations proceed via an unselective autocatalytic free-radical path leading mostly to refractory C1–C2 acids, while a Langmuir–Hinshelwood (L–H) mechanism accounts for the superior CWAO performance of the MnCeOx system. A thorough kinetic analysis of the studied systems on the basis of homogeneous autocatalytic free-radical and heterogeneous surface L–H reaction paths has been addressed. The kinetic constants of the various reaction steps show that the MnCeOx system prompts a fast adsorption of phenol with the consequent abatement of TOC, though a slow oxidation rate determines the buildup of carbonaceous deposits on the catalyst surface. Lower oxidation strength and extensive leaching definitively argue against Cu-based catalysts for the CWAO process.

Catalytic wet air oxidation of N,N-dimethylformamide aqueous solutions: Deactivation of TiO2 and ZrO2-supported noble metal catalysts

Abstract: N,N-dimethylformamide (DMF) is largely used as versatile solvent in various processes. It is thus present in large quantities in many industrial effluents. Oxidation of aqueous solutions of DMF with air was conducted at 180–230 °C under 50–70 bar total pressure in a batch reactor, in the absence or in the presence of heterogeneous noble metal catalysts (platinum, palladium, and ruthenium) supported on TiO2 or ZrO2. Under the examined reaction conditions, DMF decomposition and oxidation produced dimethylamine (DMA), methylamine (MA), and ammonium as the major N-containing products. Formic acid was also intermediately formed from the scission of the C–N bond. Nitrites and nitrates were only present in very low amounts. The addition of a catalyst accelerated the initial rates of DMF and TOC (total organic carbon) conversions, but the selectivity to N2 was low. The production of DMA and MA was demonstrated to be very much detrimental to the chemical stability of these catalysts. A dramatic leaching of the noble metals occurred because of the complexation with the free lone pair electrons on the nitrogen atom of these amines.

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.

Hydrogen peroxide-promoted-CWAO of phenol with activated carbon

Abstract: The effect of hydrogen peroxide as radical promoter in the wet air oxidation of phenol with activated carbon catalysts is studied in a trickle-bed reactor at 127 °C, 8 atm and 20–320 g AC h/g Phenol . The modifications that hydrogen peroxide induces on the radical reaction mechanism and the consequences on the effluent ecotoxicity are analyzed. The synergistic effect between oxygen and hydrogen peroxide in the initiation step of the reaction is verified. Hydroperoxy radicals, produced by the reaction between hydrogen peroxide and adsorbed oxygen, initiate the reaction on the carbon and in the liquid phase. They are responsible for the increased initial activity which provokes a faster removal of phenol and aromatic intermediates and, therefore, of the toxicity. The adsorbed oxygen on the carbon is crucial for the efficient consumption of hydrogen peroxide.

Catalytic wet air oxidation of formic acid over Pt/CexZr1―xO2 catalysts at low temperature and atmospheric pressure

Abstract: CexZr1−xO2-based Pt catalysts were investigated in the catalytic wet air oxidation (CWAO) of formic acid at low temperature (294–326 K) under atmospheric pressure in order to evaluate the impact of the high oxygen mobility over the ceria–zirconia supports on the catalytic performances The effect of the support composition, the Pt loading and the reaction conditions (reaction temperature, formic acid concentration, oxygen partial pressure) was studied The bare supports, in the absence of any active metal, appeared to be only slightly active The 0080 wt%Pt/Ce09Zr01O2 catalyst (05 g L−1) exhibited the best performances: 100% formic acid (5 g L−1) conversion was achieved after 360 min at 326 K under atmospheric pressure The reaction apparent activation energy was ca 36 ± 4 kJ mol−1 In the lowest temperature range (T ≤ 313 K), the initial reaction rate was proportional to the dissolved oxygen concentration and, accordingly, the reaction order with respect to oxygen was ca 1 ± 01 The oxygen transfer to the active site was rate limiting and formic acid saturated the catalyst surface More interestingly, from ca 326 K, the reaction order with respect to formic acid increased to ca 05 ± 01 and the reaction order with respect to oxygen decreased to 08 ± 01, indicating that oxygen might already be efficiently activated on the CexZr1−xO2 mixed oxide supports even under moderate temperature conditions

Catalyst for treatment of waste water, and method for treatment of waste water using the catalyst

Abstract: Disclosed are: a catalyst which can exhibit an excellent catalytic activity and excellent durability for a long period in the wet oxidation treatment of waste water; a wet oxidation treatment method for waste water using the catalyst; and a novel method for treating waste water containing a nitrogenated compound, in which a catalyst to be used has a lower catalytic cost, the waste water containing the nitrogenated compound can be treated at high purification performance, and the high purification performance can be maintained. The catalyst for use in the treatment of waste water comprises an oxide of at least one element selected from the group consisting of iron, titanium, silicon, aluminum, zirconium and cerium as a component (A) and at least one element selected from the group consisting of silver, gold, platinum, palladium, rhodium, ruthenium and iridium as a component (B), wherein at least 70 mass% of the component (B) is present in a region positioned within 1000 μm from the outer surface of the component (A) (i.e., the oxide), the component (B) has an average particle diameter of 0.5 to 20 nm, and the solid acid content in the component (A) (i.e., the oxide) is 0.20 mmol/g or more. The waste water treatment method uses a catalyst (a pre-catalyst) which is placed on an upstream side of the direction of the flow of the waste water and can convert the nitrogenated compound contained in the waste water into ammoniacal nitrogen in the presence of an oxidizing agent at a temperature of not lower than 100˚C and lower than 370°C under a pressure at which the waste water can remain in a liquid state and a downstream-side catalyst (a post-catalyst) which is placed downstream of the direction of the flow of the waste water and can treat the waste water containing ammoniacal nitrogen.

Wet oxidation of salicylic acid solutions.

Abstract: Salicylic acid is a frequent pollutant in several industrial wastewaters. Uncatalyzed wet air oxidation, which is a promising technique for the treatment of phenolic effluents, has not been analyzed yet for the removal of salicylic acid. The effect of different conditions of pH (1.3-12.3), pressure (1.0-4.1 MPa), temperature (413-443 K), and initial concentrations (1.45-14.50 mM) on the wet oxidation of salicylate/salicylic acid solutions have here been investigated. The pH value of the reaction media was found to be a key parameter for the rate of the oxidation process with an optimum at pH 3.1, when the concentrations of salicylic acid and salicylate were similar. The oxidation reaction followed pseudofirst-order kinetics with respect to salicylic acid and 0.82 order with respect to dissolved oxygen. Additionally, the evolution of the color during the wet oxidation was analyzed and discussed in relation with the formation of intermediate compounds. Then, a reaction pathway for the noncatalytic wet oxidation of the salicylic acid was proposed.

Catalytic Wet Air Oxidation of Oxalic Acid using Platinum Catalysts in Bubble Column Reactor: A Review

Abstract: Wastewater treatment and re-use of industrial process water are critical issue for the development of human activities and environment conservation. Catalytic wet air oxidation (CWAO) is an attractive and useful technique for treatment of effluents where the concentrations of organic pollutants are too low, for the incineration and other pollution control techniques to be economically feasible and when biological treatments are ineffective, e.g. in the case of toxic effluents. In CWAO, combustion takes place on a Pt/Al2O3 catalysts usually at temperatures several degrees below those required for thermal incineration. In CWAO process, the organic contaminants dissolved in water are either partially degraded by means of an oxidizing agent into biodegradable intermediates or mineralized into innocuous inorganic compounds such as CO2, H2O and inorganic salts, which remain in the aqueous phase. In contrast to other thermal processes CWAO produces no NOx, SO2, HCl, dioxins, furans, fly ash, etc. This review paper presents the application of platinum catalysts in bubble column reactor for CWAO of oxalic acid.

Efficient polymer-based nanocatalysts with enhanced catalytic performance in wet air oxidation of phenol

Abstract: In this paper we report the synthesis of robust and efficient nanocatalysts based on Pt-containing nanoparticles (NPs) formed in the pores of hypercrosslinked polystyrene (HPS) and their catalytic performance in the phenol CWAO under mild conditions. The Pt species were incorporated in HPS using wet impregnation of platinic acid in tetrahydrofuran followed by NaHCO3 treatment. The catalysts containing from 0.11 to 4.85 wt.% of Pt were studied by X-ray fluorescence analysis, transmission electron microscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and liquid nitrogen physisorption methods. The NP sizes were found to be independent of the amount of platinic acid used for impregnation, but rather controlled by the pores of HPS. Three types of Pt species: Pt(0), Pt(II), and Pt(IV), constituted the NP composition. The effects of the phenol and catalyst initial concentrations and temperature were investigated in the phenol CWAO. Removal of 97% of the phenol with 94.2% selectivity to CO2 and H2O were observed for the most active catalyst containing 0.95 wt.% Pt. These parameters are significantly higher than those for the conventional Al2O3–Pt catalyst with the similar amount of the active metal or for Pt(5%)/activated carbon.

Wet air oxidation of trinitrophenol with activated carbon catalysts: Effect of textural properties on the mechanism of degradation

Abstract: Activated carbons (ACs), with different activation degrees, were obtained by chemical activation of olive stones and tested for the removal of 2,4,6-trinitrophenol (TNP) from aqueous solutions by catalytic wet air oxidation (CWAO). These materials were characterized using different techniques (e.g., N 2 and CO 2 adsorption, temperature programmed desorption, immersion calorimetry and scanning electron microscopy). The non-catalytic oxidation of TNP in water, at 473 K and 0.7 MPa of oxygen partial pressure, is negligible, while the use of ACs as catalysts leads to complete removal of this organic compound. Competition between adsorption and catalytic oxidation reaction pathways, occurring simultaneously in the CWAO process, depends on the carbon porous texture. The extent of oxidation is given by the amount of nitrates formed during reaction. When a highly microporous carbon with large surface area ( S BET = 1530 m 2 /g) is used, all dissolved TNP is adsorbed and oxidation takes place in wide micropores. However, when using a carbon material with low surface area ( S BET = 121 m 2 /g) and low microporosity, TNP degradation will also occur on the external surface area, since there is enough TNP available in the bulk liquid media; in this case fast degradation takes place on the carbon macro–mesopores. Following that, the degradation mechanism is always heterogeneous but takes place in different ranges of porosity and depends on the amount of dissolved TNP. In addition, the surface chemistry of the carbon materials is modified during the CWAO process due to the presence of oxygen at the conditions employed.

Wet Air Oxidation of Aniline Using Carbon Foams and Fibers Enriched with Nitrogen

Abstract: Carbonized and activated textile acrylic fibers and melamine foams are tested as catalysts for the wet air oxidation of aniline. The use of carbon materials prepared from foams and fibers enriched with nitrogen improves the rate of aniline removal. Among all the prepared materials, a fiber carbonized at 850°C and activated during 12 h is the most effective material for both aniline and total organic carbon removal. The catalytic activity of this fiber is maintained in consecutive runs. In addition, a strong correlation was observed between the total organic carbon removal and the pyridinic-N group content on the catalyst surface.