Showing papers on "Wet oxidation published in 1996"
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TL;DR: Wet air oxidation is a process for oxidizing materials in a dilute aqueous matrix as discussed by the authors, which has been applied industrially to de-toxify dilute streams of organic (and oxidizable inorganic) materials in water.
Abstract: Wet Air Oxidation is a process for oxidizing materials in a dilute aqueous matrix. The usual temperature range, 150° to 320°C, requires high pressure to maintain a liquid phase. It has been applied industrially to de-toxify dilute streams of organic (and oxidizable inorganic) materials in water. High destruction efficiencies (99+%) have been demonstrated on a wide range of materials. The oxidation proceeds in a series of steps however, and some small residual species are resistant to further oxidation, eg. acetic acid. The liquid product usually shows a substantial residual chemical oxygen demand as a result, eg 25% or more of the original. A bio-treatment is usually provided for final clean-up.
253 citations
TL;DR: In this article, the main features of five commercially practised catalytic wet oxidation (CWO) processes for treating industrial waste waters have been analyzed and presented in this paper, along with highlights on several ongoing developments of new CWO technologies.
210 citations
TL;DR: Ru, Pt and Rh catalysts supported on titania, ceria or active carbon and a Mn/Ce composite oxide catalysts were prepared and their catalytic behavior in Wet Air Oxidation (20 bar O 2 ) of phenol and acetic acid were investigated.
181 citations
TL;DR: In this paper, an original approach to the treatment of phenolic aqueous wastes using H2O2 with heterogeneous catalysts was presented, which allowed total elimination of phenol and significant total organic carbon (TOC) removal under mild working conditions.
Abstract: This letter presents an original approach to the treatment of phenolic aqueous wastes using H2O2 with heterogeneous catalysts. The experimental results indicate that the system using Fe-ZSM-5 zeolite with MFI structure is promising since it allows total elimination of phenol and significant total organic carbon (TOC) removal under mild working conditions. Moreover, Fe-ZSM-5 remains active after after successive runs. Compared with processes using homogeneous catalysis, the possibility of induced pollution caused by the metal ions in the solution is avoided.
160 citations
TL;DR: The paper reviews the major results obtained and assesses the field of possible application of each of the processes, including wet air oxidation and Wet Peroxide Oxidation.
155 citations
TL;DR: In this paper, the effect of oxygen pressure and sodium carbonate addition on hemicellulose solubilization was investigated and it was shown that the two process parameters had little effect on the solubiliization of hemicella.
127 citations
TL;DR: In this paper, the authors investigated the catalytic oxidation of coumaric acid using various homogeneous and heterogeneous catalysts and found that the use of catalysts could increase the rate of destruction of p -coumaric acids compared to the uncatalyzed reaction, while the distribution of intermediate compounds was strongly dependent on the pH of the solution.
Abstract: The catalytic oxidation of p -coumaric acid, a compound representative of the polyphenolic fraction typically found in olive processing and wine-distillery wastewaters, has been investigated using various homogeneous and heterogeneous catalysts. Experiments have been performed with homogeneous Fe 2+ , Cu 2+ , Zn 2+ and Co 2+ ions at pH = 1, and with metal oxide catalysts in suspension at pH 3.5, 7 and 12. Additional uncatalyzed experiments have been performed and the results are compared to those of the catalyzed runs. The temperature was 403 K and the oxygen partial pressure was 2.8 MPa in all runs. The distribution of the reaction intermediates was determined, using HPLC and GCMS as the main analytical techniques, and reaction pathways are speculated. It was found that the use of catalysts could increase the rate of destruction of p -coumaric acid compared to the uncatalyzed reaction, while the distribution of the intermediate compounds was strongly dependent on the pH of the solution. A CuO·ZnO Al 2 O 3 heterogeneous catalyst was found to be effective for the oxidation of p -coumaric acid although leaching of dissolved metals to the solution was found to occur. The stability of the heterogeneous catalysts was investigated by measuring the extent of metal leaching into the solution. The results are discussed with respect to the impact of various conditions (catalyst, pH) on the oxidation of p -coumaric acid and compared to those of the uncatalyzed reaction, studied in previous work.
124 citations
TL;DR: In this paper, catalytic wet-air oxidation of aqueous solutions (5 g · l−1) of car-ylic acids (formic, oxalic, and maleic) was carried out with air at 293-463 K on carbon-supported platinum catalysts.
Abstract: Catalytic wet-air oxidation (CWAO) of aqueous solutions (5 g · l−1) of car☐ylic acids (formic, oxalic, and maleic) was carried out with air at 293–463 K on carbon-supported platinum catalysts. Platinum was loaded on active charcoal by cationic exchange, then reduced under H2. Homogeneous dispersions of 1–2 nm metal particles were obtained. CWAO reactions were performed at 1 or 15 bar air pressure in stirred, batch reactors. Total conversion of formic and oxalic acids into carbon dioxide was obtained under very mild conditions (air at atmospheric pressure, 326 K). The Pt/C catalyst was almost inactive for the oxidation of acetic acid but maleic acid was oxidized under moderate conditions (15 bar of air pressure, 405 K) which indicates that the degradation of this acid does not occur via acetic acid.
92 citations
TL;DR: The relationship between light absorption at 250 nm and the concentration of dissolved organic carbon varied between the sources which is attributed to the difference in the nature of organic compound, as measured by the relative molecular weight fractions in the DOC samples as mentioned in this paper.
Abstract: Dissolved organic carbon (DOC) from various organic matter sources was measured using spectrophotometric, wet oxidation, and dry combustion methods. The relationship between light absorption at 250 nm and the concentration of DOC varied between the sources which is attributed to the difference in the nature of organic compound, as measured by the relative molecular weight fractions in the DOC samples. Wet oxidation achieved only a partial oxidation of the DOC and the extent of oxidation varied between the sources. Dry combustion achieved the complete recovery of DOC. Both air drying and oven drying increased the concentration of DOC; whereas freeze drying had no effect on the concentration of DOC. DOC concentration increased with an increase in pH.
88 citations
TL;DR: In this article, a series of ceria-containing mixed oxides has been prepared and utilized as catalysts in the oxidation of acetic acid in water, and the best results are obtained with the ternary mixed-oxides CeO 2 -ZrO 2 −CuO and CeO2 -MnO x which benefit from a synergetic interaction between the two materials.
Abstract: A series of ceria-containing mixed oxides has been prepared and utilized as catalysts in the oxidation of acetic acid in water. The incorporation of even relatively small amounts of ZrO 2 and MnO x or CuO into the fluorite lattice of CeO 2 strongly enhances the redox properties of the material with a consequent promotion of the oxidation activity. The best results are obtained with the ternary mixed-oxides CeO 2 -ZrO 2 -CuO and CeO 2 -ZrO 2 -MnO x which benefit from a synergetic interaction between CeO 2 (whose properties are already modified by the presence of Zr) and CuO or MnO x . Analysis of metal ion concentration in the effluents after reaction indicates also a high stability of the mixed-oxide catalysts under the conditions employed.
70 citations
TL;DR: In this article, the effects of operating pressure and temperature on the chemical oxygen demand (COD) removal were investigated for high-concentration wastewater from a chemical company by wet air oxidation (WAO).
Abstract: Treatment of high-concentration wastewater from a chemical company by wet air oxidation (WAO) is studied. Experiments were conducted to investigate the effects of the operating pressure and temperature on the chemical oxygen demand (COD) removal. Both air and oxygen were employed as the oxygen supply for the WAO treatment process. Catalytic effects of copper sulfate, cobalt oxide, and zinc oxide on the WAO efficiency were also examined. It was found that over 50% of COD removal can be easily realized in an hour of WAO oxidation. Two kinetic models (first-order and generalized) were employed to represent the experimental data, and their fit to those experimental data was compared. The rate coefficients and the kinetic parameters of the two models were determined also.
TL;DR: In this paper, a transmission electron microscopy based study of AlGaAs-Al(oxide) heterolayers created by lateral sidewall wet oxidation was carried out, and the oxide phase formed as a consequence of the oxidation of AlAs to be γ•Al2O3, with the cubic Fd'3m structure.
Abstract: We have carried out a transmission electron microscopy based study of AlGaAs–Al(oxide) heterolayers created by lateral sidewall wet oxidation and identify the oxide phase formed as a consequence of the oxidation of AlAs to be γ‐Al2O3, with the cubic Fd 3m structure. The oxide‐semiconductor interface is weak and porous, possibly due to the high stress loads developed during oxidation, and we propose that the fast oxidation rates are a consequence of reactants transported to the oxidation front along the porous interface.
TL;DR: In this article, the wet air oxidation of aqueous solution of polyethylene glycol, a synthetic polymer used in a wide range of applications, has been investigated at temperatures from 383 to 513 K and oxygen partial pressures from 2 to 3 MPa.
TL;DR: In this article, a semi-empirical molecular orbital calculation of adsorbents and adsorbates was performed to determine the electronic state of adsorents and adorbates.
TL;DR: In this article, the effects of temperature and catalyst dosage on the pollutant (chemical oxygen demand or COD) removal were investigated for desizing wastewater, a typical high strength industrial wastewater, by catalytic wet air oxidation (WAO).
Abstract: Treatment of desizing wastewater, a typical high strength industrial wastewater, by catalytic wet-air oxidation (WAO) is studied. The desizing wastewater sample was obtained from a large textile dyeing and finishing plant. Experiments were conducted to investigate the effects of temperature and catalyst dosage (CuSO4 and CU(NO3)2) on the pollutant (chemical oxygen demand or COD) removal. It is observed that over 80% of the COD removal can be realized in an hour of the catalytic WAO process. A kinetic model was also developed and a two-stage, first-order kinetic expression was found to represent well the treatment reaction. The correlations between the reaction rate coefficients and the temperature and catalyst dosage were also determined.
TL;DR: In this paper, the lateral wet oxidation of Al(Ga)As layer is strongly influenced by its thicknesses and heterointerface structures as well as Al compositions, and the oxidation length decreases with decreasing AlAs thickness in the range of <80 nm and oxidation nearly stops at a thickness of ∼11 nm.
Abstract: Data are presented demonstrating that the lateral wet oxidation of Al(Ga)As layer is strongly influenced by its thicknesses and heterointerface structures as well as Al compositions. The oxidation length decreases rapidly with decreasing AlAs thickness in the range of <80 nm and oxidation nearly stops at a thickness of ∼11 nm. Also, the oxidation rate of AlxGa1−xAs decreases quickly with decreasing Al composition, providing a high degree of oxidation selectivity. AlGaAs layers on both sides of AlAs layer reduce the lateral oxidation rate which is enhanced by the stress induced by oxidized AlAs.
TL;DR: In this article, the batch oxidation of Coumaric acid has been investigated using a high-pressure reactor at temperatures varying from 403 to 523 K and pressures from 3 to 7 MPa.
TL;DR: In this article, the authors investigated the catalytic performance of aqueous solutions of polyethylene glycol of molecular weight 10000, a synthetic polymer used in a wide range of applications, using various metal oxide and noble metal heterogeneous catalysts.
Abstract: The catalytic oxidation of aqueous solutions of polyethylene glycol of molecular weight 10000, a synthetic polymer used in a wide range of applications, has been investigated using various metal oxide and noble metal heterogeneous catalysts. Catalysts were in slurry or in pellets, at temperatures from 383 K to 463 K and an oxygen partial pressure of 3 MPa. Additional uncatalysed experiments have been performed, and the results are compared to those of the catalysed runs. Reaction intermediates have been determined using HPLC and gel permeation chromatography as the main analytical techniques, and reaction mechanisms have been proposed. Noble metal catalysts were found to be more effective than metal oxide catalysts for oxidising polyethylene glycol, while with both noble metal and metal oxide catalysts the rate of total oxidation was significantly higher than that of the uncatalysed reaction. However, the use of heterogeneous catalysts was found to be responsible for prolonged induction periods, a phenomenon which did not occur significantly during the uncatalysed runs. A palladium supported on alumina catalyst was further studied with respect to its stability and deactivation.
TL;DR: In this article, a wet thermal oxidation method is proposed to passivate the electrochemically etched porous silicon and bright and stable photoluminescence is achieved by wet oxidation at relatively low temperatures of 400-500°C.
Abstract: A wet thermal oxidation method is proposed to passivate the electrochemically etched porous silicon. Bright and stable photoluminescence is achieved by wet oxidation at relatively low temperatures of 400–500 °C. The Fourier transform infrared absorption shows that the formation of SiH(O3), SiH(SiO2), SiH2(O2) bonds may be responsible to the stabilization of luminescence under the laser illumination.
TL;DR: In this article, a first-order, two-stage kinetics in terms of the component or COD concentration was analyzed for high concentration chemical wastewater containing phenol and/or phenolic compounds by catalytic wet air oxidation.
Abstract: Treatment of high concentration chemical wastewater containing phenol and/or phenolic compounds by catalytic wet air oxidation (WAO) is studied. Experimental results indicate that over 99% w/w removal of phenol or phenolic compounds can be efficiently achieved by the catalytic WAO process utilizing hydrogen peroxide as homogeneous oxidant. It is observed that the catalytic WAO process achieves high efficiency of phenol or phenolic compound oxidation at lower operating temperature (150°C or less) and pressure (0.5 MPa) than those of comparable conventional WAO processes. The experimental data also show that the oxidation reaction can be represented by a first-order, two-stage kinetics in terms of the component or COD concentration. The second-stage oxidation was observed to be slower than the first-stage. The activation energies obtained for oxidation of phenol and phenolic coumpounds reflect the speed of these two stage reactions.
01 Mar 1996-Journal of Environmental Science and Health Part A-toxic\/hazardous Substances & Environmental Engineering
TL;DR: In this article, the effect of [S2/O2] ratio and hydraulic loading rate on removal of sulphide and organics in a counter current reactor containing activated carbon was discussed.
Abstract: Anaerobic treatment of tannery wastewater in high rate close type reactors leaves sulphide in the range 31–795 mg/l, COD 395–1886 mg/l, BOD 65–450 mg/l and TOC 65–605 mg/l. Thus post anaerobic treatment of wastewater was required to meet discharging standard. High sulphide concentration present in treated wastewater may render aerobic biological treatment unsuitable. Hence, it became essential to include sulphide removal unit operation preceeding aerobic biological unit. Among the techniques available oxidation of sulphide by air using activated carbon as catalyst gained importance for its removal of COD, BOD and TOC inaddition to elimination of sulphide in wastewater. The effect of [S2‐/O2] ratio and hydraulic loading rate on removal of sulphide and organics in counter current reactor containing activated carbon were discussed. The percentage removal of COD, BOD, TOC and Sulphide from anaerobically treated wastewater were respectively 81, 85, 82 and 100. The sulphate content of catalytically oxi...
TL;DR: In this article, the photocatalytic degradation with TiO2 and Pt TiO 2 was applied to the conventional determination of dissolved organic nitrogens (DONs) in natural waters, and the results of initial formation rates of inorganic nitrogens suggested that the nitrate and nitrite were directly generated from DONs, in addition to the formation route of ammonium.
TL;DR: In this article, the catalytic effects of hydrophilic granulated active carbon black Chezacarb have been tested in the oxidation of dilute (5 000 ppm) aqueous solutions of phenol.
Abstract: The catalytic effects of hydrophilic granulated active carbon black Chezacarb have been tested in the oxidation of dilute (5 000 ppm) aqueous solutions of phenol. The research was focused on combined utilization of sorption and chemical (oxygen functional groups) properties of carbon black which support formation of free radicals in oxidation and on the catalytic effects of metals (Fe, Ni and V) present in the sorbent mentioned. The oxidation was carried out in a stainless steel autoclave of 1.25 l capacity. The reaction temperatures and the total pressures varied in the intervals of 120-160 °C and 3-5 MPa, respectively. The reaction mixture was analyzed by means of HPLC with UV detection (254 nm). The experimental data were evaluated by means of the ASPEN PLUS 9.2 program. The model of laboratory autoclave involved the reaction kinetics as well as the phase equilibria and dissolution of oxygen and carbon dioxide in the reaction mixture. Although the active carbon black shows a lower catalytic activity than the usual copper catalyst in the wet oxidation, it has the advantage of avoiding the undesirable releases of heavy metals in waste waters, which escapes accompany the application of copper catalysts.
TL;DR: In this paper, a model for CO oxidation in the boundary layer of a single char particle was developed, which includes char oxidation and a 56 reaction gas phase kinetic scheme coupled with the diffusive properties of the 12 species involved in the CO oxidation.
Abstract: A model is developed for CO oxidation in the boundary layer of a single char particle. The model includes char oxidation and a 56 reaction gas phase kinetic scheme which is coupled with the diffusive properties of the 12 species involved in the CO oxidation. The model is compared with the experimental data of Tognotti and co-workers. The temperature reached on ignition, the resulting CO 2 /CO ratio, and the effect of changing water vapor concentrations are well described. Studies on the effect of water concentration show that significant CO oxidation at low temperatures requires a high surrounding water concentration. The presence of water vapor or hydrogen is found to be necessary to obtain a high degree of CO oxidation at low temperatures; however, there is a minimum temperature below which significant CO oxidation in the boundary layer does not occur irrespective of how high the water concentration is. In addition, CO oxidation is negligible even at a surface temperature as high as 2500 K when water and hydrogen are absent. The model has also been applied to predict the effects of changing parameters. Catalytic acceleration of the rate of carbon oxidation, for example by the addition of calcium, leads to both a high particle temperature overshoot and a significant increase in CO oxidation over the particle surface.
TL;DR: In this paper, the relationship between roughness at the Si/SiO2 interface and the oxide thickness was investigated by means of a nondestructive measuring method, using the Si metaloxide-semiconductor (MOS) structure.
Abstract: The relationship between roughness at the Si/SiO2 interface and the oxide thickness was investigated by means of a nondestructive measuring method, using the Si metal-oxide-semiconductor (MOS) structure It was demonstrated that the Si/SiO2 interface roughness recovers during thermal oxidation This recovery process was also verified by observation with the transmission electron microscope (TEM) It was found that the recovery effect on the roughness at the Si/SiO2 interface depends on the oxidation process and that it is more significant in wet oxidation than in dry oxidation
TL;DR: In this paper, a cyclohe oxidation unit was used to detoxify an aqueous waste stream with regard to COD to meet local discharge standards, and the possibilities for recovery of Na2SO4 and C2C6 carboxylic acids were explored.
Patent•
24 Jul 1996
TL;DR: Disclosed as discussed by the authors is a process for wet oxidation treatment of high strength liquor or wastewater to destroy a substantial portion of the pollutants and produce an effluent stream containing a high solids content for recovery or disposal.
Abstract: Disclosed is a process for wet oxidation treatment of high strength liquor or wastewater to destroy a substantial portion of the pollutants and produce an effluent stream containing a high solids content for recovery or disposal. The liquor is treated by wet oxidation and separate vapor and liquid streams are removed from the wet oxidation reactor. The vapor stream is cooled and separated to give a liquid condensate phase and a gaseous phase. The liquid stream from the reactor is cooled and divided, with a portion of the liquid effluent sent to recovery or disposal, and a portion combined with the condensate phase. This low pollutant content stream is used to dilute the raw feed liquor and maintain a high solids concentration in the liquid effluent stream.
Patent•
02 May 1996
TL;DR: In this article, a method for the treatment of a waste water comprises subjecting the waste water to wet oxidation treatment with an oxygen-containing gas by the use of a catalyst under pressure such that the water retains the liquid phase thereof.
Abstract: A catalyst for the treatment of a waste water comprises an oxide and/or a composite oxide of manganese, the oxide and/or the composite oxide of at least one metal selected from the group consisting of iron, titanium, and zirconium, and optionally a precious metal. A method for the production of this catalyst is also disclosed. A method for the treatment of a waste water comprises subjecting the waste water to wet oxidation treatment with an oxygen-containing gas by the use of a catalyst under pressure such that the waste water retains the liquid phase thereof.
01 Jan 1996
TL;DR: In this article, the location in a relation inlet temperature vs. fuel mass fraction and the shape of extinction lines were analyzed for a wall cooled Hydrothermal Burner (WCHB) and a three-environment model was applied to verify one extinction line given from measurements with one specific kind of fuel.
Abstract: Summary For toxic and hazardous waste water to be disposed, in some cases Supercritical Wet Oxidation (SCWO) appears to be a suitable process. Due to corrosion and possible plugging in the presurised reaction vessels its industrial application is hardly realised. A reactor containing a Wall Cooled Hydrothermal Burner (WCHB) needn't be entered by preheated feedstreams and hence alleviates the two main problems mentioned above ( La Roche et al. [1] ). The economic viability of an industrial plant with this kind of configuration will strongly depend on the minimum fuel mass fraction that is required to keep the oxidation in the thermal regime of a flame. In this paper an attempt was made to find a theoretical background for both the location in a relation inlet temperature vs. fuel mass fraction and the shape of extinction lines. The aim was to verify one extinction line given from measurements with one specific kind of fuel without varying the geometric parameters of the burner. It was found that the application of a Three-Environment Model (3EM) can lead to reasonable results if the 3EM is extended by taking into account an enthalpy term. As a result, a list of ideas to reduce the fuel consumption, as well as a lower limit, could be found. In addition, the calculated extinction lines will help in comparisons and explanations of future experimental measurements.