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1.
Oxidation of bulk samples of 〈Al〉 by water and H2O/CO2 mixture at sub- and supercritical conditions for uniform temperature increase and at the injection of H2O (665 K, 23.1 MPa) and H2O/CO2 (723 K, 38.0 MPa) fluids into the reactor has been studied. Transition of 〈Al〉 into AlOOH and Al2O3 nanoparticles has been found out. Aluminum samples oxidized by H2O and H2O/CO2 fluids at the injection mostly consist of large particles (300-500 nm) of α-Al2O3. Those oxidized for uniform temperature increase contain smaller particles (20-70 nm) of γ-Al2O3 as well. Mechanism of this phenomenon is explained by orientation of oxygen in H2O polar molecules to the metal in the electric field of contact voltage at Al/AlOOH and Al/Al2O3 boundary. Addition of CO2 to water resulted in CO, CH4, CH3OH and condensed carbon, increase in size of Al2O3 nanoparticles and significant decrease in time delay. In pure CO2 〈Al〉 oxidation resulted in oxide film. Using temperature and time dependences of gaseous reactant pressure and Redlich-Kwong state equation, kinetics of H2 formation has been described and oxidation regularities determined. At aluminum oxidation by H2O and H2O/CO2 fluids, self-heating of the samples followed by oxidation rate increase has been registered. The samples of oxidized aluminum have been studied with a transmission electronic microscope, a thermal analyzer and a device for specific surface measurement. The effect of oxidation conditions on the characteristics of synthesized nanoparticles has been found out. 相似文献
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3.
Slaughterhouse wastewater treatment by combined anaerobic baffled reactor and UV/H2O2 processes 总被引:2,自引:0,他引:2
Weihua CaoMehrab Mehrvar 《Chemical Engineering Research and Design》2011,89(7):1136-1143
Combined processes of biological anaerobic baffled reactor (ABR) and UV/H2O2 at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater. In this study, the total organic carbon (TOC) loadings of 0.2-1.1 g/(L day) were used. The results revealed that combined processes had a higher efficiency to treat the synthetic slaughterhouse wastewater. Up to 95% TOC removal was obtained for an influent concentration of 973.3 mgTOC/L at the hydraulic retention time (HRT) of 3.8 days in the ABR and 3.6 h in the UV photoreactor. Meanwhile, up to 97.7% and 96.6% removal of chemical oxygen demand (COD) and 5-day carbonaceous biochemical oxygen demand (CBOD5) were observed in the ABR for the same influent concentration, respectively. Comparatively, for an influent concentration of 157.6 mgTOC/L, the UV/H2O2 process alone with the TOC loading of 0.06-1.9 g/(L h) was also studied, in which, up to 64.3%, 83.7%, and 84.3% of TOC, COD, and CBOD5 removal were observed, respectively, at the HRT of 2.5 h with hydrogen peroxide (H2O2) concentration of 529 mg/L. It was found that individual ABR and UV/H2O2 processes enhanced the biodegradability of the treated effluent by an increased CBOD5/COD ratio of 0.4 to 0.6. An optimum H2O2 dosage of 3.5 (mgH2O2)/(mgTOCin h) was also found for the UV/H2O2 process. 相似文献
4.
《Fuel》2003,82(2):147-151
The aim of this paper is to show how a cheap carbonaceous material such as low rank coal-based carbon (or char) can be used in the combined SO2/NO removal from exhaust gas at the linear gas velocity used in commercial systems (0.12 m s−1). Char is produced from carbonization and optionally activated with steam. This char is used in a first step to abate the SO2 concentration at the following conditions: 100 °C, space velocity of 3600 h−1, 6% O2, 10% H2O, 1000 ppmv SO2, 1000 ppmv NO and N2 as remainder. In a second step, when the SO2 concentration in the flue gas is low, NO is reduced to N2 and steam at the following experimental conditions: 150 °C, space velocity of 900 h−1, 6% O2, 10% H2O, 0-500 ppmv SO2, 1000 ppmv NO, 1000 ppmv NH3 and N2 as remainder.It has been shown that the presence of NO has no effect on SO2 abatement during the first step of combined SO2/NO removal system and that low SO2 inlet concentration has a negligible effect on NO reduction in the second step. Moreover, this char can be thermally regenerated after use for various cycles without loss of activity. On the other hand, this regenerated char shows the highest NO removal activity (compared to parent chars, either carbonized or steam activated) which can be attributed to the activating effect of the sulfuric acid formed during the first step of the combined SO2/NO removal system. 相似文献
5.
Ichiro Yamanaka Toshikazu Hashimoto Ryo Ichihashi Kiyoshi Otsuka 《Electrochimica acta》2008,53(14):4824-4832
Direct synthesis of H2O2 acid solutions was studied using a gas-diffusion cathode prepared from activated carbon (AC), vapor-growing-carbon-fiber (VGCF) and poly-tetra-fluoro-ethylene (PTFE) powders, with a new H2/O2 fuel cell reactor. O2 reduction to H2O2 was remarkably enhanced at the three-phase boundary (O2(g)-electrode(s)-acid(l)) at the [AC + VGCF] cathode. Fast diffusion processes of O2 to the active surface and of H2O2 to the bulk acid solutions were essential for H2O2 accumulation. Synergy of AC and VGCF was observed for the H2O2 formation. RRDE and cyclic voltammetry studies indicated that the surface of AC functioned as the active phase for O2 reduction to HO2, and VGCF functioned as an electron conductor and a promoter to convert HO2 to H2O2. A maximum H2O2 concentration of 353 mM (1.2 wt%) was accomplished under short-circuit conditions (current density 12.7 mA cm−2, current efficiency 40.1%, geometric area of cathode 1.3 cm2, reaction time 6 h). 相似文献
6.
Jianrong Ma Zhenyu Liu Qingya Liu Shijie Guo Zhanggen Huang Yong Xiao 《Fuel Processing Technology》2008
Supporting V2O5 onto an activated coke (AC) has been reported to significantly increase the AC's activity in simultaneous SO2 and NO removal from flue gas. To understand the role of V2O5 on SO2 removal, V2O5/AC is studied through SO2 removal reaction, surface analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) techniques. It is found that the main role of V2O5 in SO2 removal over V2O5/AC is to catalyze SO2 oxidation through a VOSO4-like intermediate species, which reacts with O2 to form SO3 and V2O5. The SO3 formed transfers from the V sites to AC sites and then reacts with H2O to form H2SO4. At low V2O5 loadings, a V atom is able to catalyze as many as 8 SO2 molecules to SO3. At high V2O5 loadings, however, the number of SO2 molecules catalyzed by a V atom is much less, due possibly to excessive amounts of V2O5 sites in comparison to the pores available for SO3 and H2SO4 storage. 相似文献
7.
Free acids of the iron substituted heteropoly acids (HPA), H7[(P2W17O61)FeIII(H2O)] (HFe1) and H18[(P2W15O56)2FeIII2(H2O)2] (HFe2) were prepared from the salts K7[(P2W17O61)FeIII(H2O)] (KFe1) and Na12[(P2W15O56)2FeIII4(H2O)2] (NaFe4), respectively. The iron-substituted HPA were adsorbed on to XC-72 carbon based GDLs to form HPA doped GDEs after water washing with HPA loadings of ca. 1 μmol. The HPA was detected throughout the GDL by EDX. Solution electrochemistry of the free acids are reported for the first time in sulfate buffer, pH 1-3. The hydrogen oxidation reaction was catalyzed by KFe1 at 0.33 V, with an exchange current density of 38 mA/cm2. Moderate activity for the oxygen reduction reaction was observed for the iron substituted HPA, which was dramatically improved by selectively removing oxygen atoms from the HPA by cycling the fuel cell cathode under N2 followed by reoxidation to give a restructured oxide catalyst. The nanostructured oxide achieved an OCV of 0.7 V with a Tafel slope of 115 mV/decade. Cycling the same catalysts in oxygen resulted in an improved catalyst/ionomer/carbon configuration with a slightly higher Tafel slope, 128 mV/decade but a respectable current density of 100 mA/cm2 at 0.2 V. 相似文献
8.
Yizhuan Yan 《The Journal of Supercritical Fluids》2010,55(2):623-634
A thermodynamic model based on the electrolyte NRTL activity coefficient equation and PC-SAFT equation-of-state is developed for CO2 solubility in aqueous solutions of NaCl and Na2SO4 with temperature up to 473.15 K, pressure up to 150 MPa, and salt concentrations up to saturation. The Henry's constant parameters of CO2 in H2O and the characteristic volume parameters for CO2 required for pressure correction of Henry's constant are identified from fitting the experimental gas solubility of CO2 in pure water with temperature up to 473.15 K and pressure up to 150 MPa. The NRTL binary parameters for the CO2-(Na+, Cl−) pair and the CO2-(Na+, SO42−) pair are regressed against the experimental VLE data for the CO2-NaCl-H2O ternary system up to 373.15 K and 20 MPa and the CO2-Na2SO4-H2O ternary system up to 433.15 K and 13 MPa, respectively. Model calculations on solubility and heat of solution of CO2 in pure water and aqueous solutions of NaCl and Na2SO4 are compared to the available experimental data of the CO2-H2O binary, CO2-NaCl-H2O ternary and CO2-Na2SO4-H2O ternary systems with excellent results. 相似文献
9.
Cyclic voltammetry and degradation of dimethylphthalate (DMP) revealed that the iron-substituted heteropolytungstate anion PW11O39Fe(III)(H2O)4− is an excellent indirect cathodic oxidative electrocatalyst in the presence of H2O2. PW11O39Fe(III)(H2O)4− can electrocatalyze the reduction of H2O2 to hydroxyl radicals via an inner-sphere electron transfer mechanism, which cause oxidative decomposition of DMP. Almost complete DMP removal and ca. 30% mineralization were obtained in less than 120 min in a mixed phosphate solution at pH 6.86 containing 0.1 mM DMP. MS analyses of the intermediates and final products suggested that glyoxal, oxalic acid and acetic acid are the main ring-opening products, besides some unstable hydroxylated aromatic intermediates. The effects of added H2O2 concentration, applied cathodic potential and DMP initial concentration on the degradation of DMP were also investigated. A concentration of 1.0 mM H2O2 and cathodic potential of −0.3 V were optimal conditions for DMP degradation in our experiments. At higher initial DMP concentrations degradation also occurred, but at a slower decay rate compared to lower initial concentrations. The present system thus represents a possible method to use PW11O39Fe(III)(H2O)4− as an indirect cathodic oxidative electrocatalyst in water and wastewater treatment. 相似文献
10.
Phenolic resin based activated carbon fibres (ACF) impregnated with oxides of various transition metals were investigated for the catalytic oxidation of SO2 into H2SO4. Oxidation was carried out in the packed bed tubular reactor in the presence of O2 and H2O. The activity of the various metals impregnated on ACF was observed to be in the order, Cu>Ni>Co>Cr. It was found that the metal oxides were dispersed as monolayer on ACF up to ~5% (w/w) loading, beyond which crystallites formation occurred. A kinetic mechanism for the catalytic oxidation of SO2 into H2SO4 was proposed and incorporated in a transport model developed to explain the experimental breakthrough data. 相似文献
11.
Vasilis G. Komvokis George E. Marnellos Iacovos A. Vasalos Kostas S. Triantafyllidis 《Applied catalysis. B, Environmental》2009,89(3-4):627-634
The effect of the pretreatment (inert, oxidative, and reducing) of Ru/γ-Al2O3 catalyst on its activity and stability in the decomposition of N2O in the absence or presence of O2, SO2, H2O and NOX was studied in the present work. Decomposition of pure N2O was slightly enhanced by the H2-pretreated catalyst (metallic Ru) compared to the O2- or He-pretreated ones, owing to a cyclic oxidation–reduction pathway of metallic Ru. The observed decrease of activity by O2 or H2O addition was reversible compared to SO2 which caused a strong, irreversible deactivation of the catalyst, irrespective of the type of pretreatment. This was attributed to the formation of stable sulphates, mainly those on RuO2 surface, which could only be removed by regeneration under reducing (H2 in He) atmosphere at temperatures of ca. 500 °C. Oxidative or inert regeneration required very high temperatures (i.e. >700 °C) in order to decompose these sulphates. A method of retaining N2O conversion activity very high (≥98%) for long reaction times is suggested and is based on frequent and short-time (ca. 10 min) regenerations of the catalyst under reducing atmosphere (ca. 5% H2 in He). The effect of co-feeding various reducing agents, such as CO or C3H6, on the N2O conversion activity in the presence of O2, SO2, H2O and NOX is negligible, mainly because they are oxidized at relatively low temperatures in the O2-rich feeds used in this study. 相似文献
12.
A monolayer of Keggin-type heteropolyanion [SiNi(H2O)W11O39]6− was fabricated by electrodepositing [SiNi(H2O)W11O39]6− on cysteamine modified gold electrode. The monolayer of [SiNi(H2O)W11O39]6− modified gold electrode was characterized by atomic force microscopy (AFM) and electrochemical method. AFM results showed the [SiNi(H2O)W11O39]6− uniformly deposited on the electrode surface and formed a porous monolayer. Cyclic voltammetry exhibited one oxidation peak and two reduction peaks in 1.0 M H2SO4 in the potential range of −0.2 to 0.7 V. The constructed electrode could exist in a large pH (0-7.6) range and showed good catalytic activity towards the reduction of bromate anion (BrO3−) and nitrite (NO2−), and oxidation of ascorbic acid (AA) in acidic solution. The well catalytic active of the electrode was ascribed to the porous structure of the [SiNi(H2O)W11O39]6− monolayer. 相似文献
13.
α-Al2O3 platelets were prepared by a molten salt synthesis method when NaAlO2 was used as raw material. The effects of the stirring rate during the gel preparation, heating temperature, type and addition amount of molten salts, addition of plate-like α-Al2O3 seeds, additives such as TiOSO4 and Na3PO4·12H2O on the morphology of α-Al2O3 were studied. High stirring rate during the gel preparation and high heating temperature not only help to restrain the overlapping of α-Al2O3 platelets, but also improve the size distribution. When the heating temperature increases to 1200 °C, most of α-Al2O3 platelets are hexagonal in its morphology, and the size of platelets becomes relatively uniform. When Na2SO4-K2SO4 flux is used instead of NaCl-KCl flux, it is easy to obtain α-Al2O3 platelets with a big size. When the molar ratio of salt to final Al2O3 powders increases to 4:1, most of α-Al2O3 platelets are hexagonal, and the overlapping of powders is inhibited. The addition of a small amount of plate-like seeds has a significant effect on the size of α-Al2O3 platelets. With the increase of seed amount, the diameter of α-Al2O3 platelets tends to decrease. The addition of 5.45 wt.% TiOSO4 results in the formation of hexagonal α-Al2O3 platelets with an average diameter of 5.1 μm and an average thickness of 1.4 μm. Thin α-Al2O3 platelets with a discal shape are obtained owing to the co-addition of 0.51 wt.% Na3PO4·12H2O and 3 wt.% TiOSO4. 相似文献
14.
P?nar Ergenekon Ercan GürbulakBülent Keskinler 《Chemical Engineering and Processing: Process Intensification》2011,50(1):16-21
In this study a novel sulfonation method for microporous polystyrene divinyl benzene copolymer (PSDBP) was introduced. In our sulfonation system gaseous SO2 is used as the sulfonation agent and planned to be obtained from waste gas streams. The proposed method, therefore, combines SO2 control and clean sulfonation technology in a single compact design.Molded polymeric monoliths of the PSDBP containing imprisoned H2O2 solution inside the pores (PSDBPH2O2) were produced in disk shapes. Dry gas mixture containing 3000 ppm SO2 is fed into PSDBPH2O2 disk reactor with a flow rate of 0.8 L/min and effluent gas composition in terms of SO2 was measured. Breakthrough curves for varied initial H2O2 amount were used to calculate SO2 adsorption capacity and sulfonation degree of the PSDBPH2O2 disks.Successful sulfonation of PSDBPH2O2 was verified by the changes in its morphological structure and formed sulfone bonds determined by SEM and IR analyses, respectively. Maximum adsorption capacity for PSDBPH2O2 for the initial H2O2 volume percentage of 13% was determined as 57 mg SO2/g polymer. It should be noted that SO2 adsorption was observed only in H2O2 imprisoned polymer disks. Sulfonation degree of PSDBPH2O2 which attained maximum SO2 amount is calculated as 10%. 相似文献
15.
Xinfang Yang Bo Zhao Yuqun Zhuo Changhe Chen Xuchang Xu 《Korean Journal of Chemical Engineering》2011,28(8):1785-1790
Gas effects on NO reduction by NH3 over sulfated CaO have been investigated in the presence of O2 at 700–850 °C. CO2 and SO2 have reversible negative effects on the catalytic activity of sulfated CaO. Although H2O alone has no obvious effect, it can depress the negative effects of CO2 and SO2. In the flue gas with CO2, SO2 and H2O co-existing, the sulfated CaO still catalyzed the NO reduction by NH3. The in situ DRTFTS of H2O adsorption over sulfated CaO indicated that H2O generated Br?nsted acid sites at high temperature, suggesting that CO2 and SO2 competed for only the molecularly adsorbed NH3 over Lewis acid sites with NO, without influencing the ammonia ions adsorbed over Br?nsted acid sites. Lewis acid sites shifting
to Br?nsted acid sites by H2O adsorption at high temperature may explain the depression of the negative effect on NO reduction by CO2 and SO2. 相似文献
16.
Selective oxidation of methanol to dimethoxymethane (DMM) was conducted in a fixed-bed reactor over an acid-modified V2O5/TiO2 catalyst. The influence of the acid modification on its structure, redox and acidic properties, and catalytic performance for methanol oxidation were investigated. The results indicated that the content of vanadia in the catalyst exhibits a vital influence on the dispersion of vanadium species, while the acid modification can enhance its surface acidity. Proper amounts of the acid (W() = 15%) and V2O5 (W(V2O5) = 15%) components loaded in the acid-modified V2O5/TiO2 catalyst are able to build a bi-functional circumstance that is favorable for the formation of DMM with high activity and selectivity. As a result, for the selective oxidation of methanol, the H2SO4-modified V2O5/TiO2 catalyst gives a much higher DMM yield at 150 °C than the unmodified one. 相似文献
17.
J.-i Hayashi T HiramaR Okawa M TaniguchiH Hosoda K MorishitaC.-Z Li T Chiba 《Fuel》2002,81(9):1179-1188
Flue-gas recycling combustion of a sub-bituminous coal and its rapid pyrolysis char at 1120 K has been simulated experimentally in a bubbling fluidized-bed. O2, CO2 and H2O, and NO or N2O were pre-mixed and fed into the bed together with coal/char particles with the O2 concentration in the exit gas maintained at 3.5 vol%. Increasing the inlet O2 concentration, thus increasing the O2 consumption rate and decreasing the flue-gas recycling ratio, caused the once-through conversion of fuel-bound nitrogen into N2O to decrease while the conversion to NO to remain unchanged. The in-bed reductions of NO and N2O were both first order with respect to the respective nitrogen oxide, with the rate constants to increase linearly with the rate of O2 consumption in the bed and thus also with that of char/volatiles consumption. This finding, which indicated linear increase in the concentrations of reactive species involved in NO/N2O reduction with the rate of O2 consumption, enabled consideration that the homogeneous and heterogeneous reduction rates of NO and N2O were proportional to the consumption rates of O2 by the volatiles and char, respectively. The rate analysis of the kinetic data revealed the relative importance of burning volatiles and char as the agents for the reduction of NO and N2O. While the reduction in the gas phase was fully responsible for the NO-to-N2O conversion, the reactions over the char surface governed the NO-to-N2 reduction. The volatiles and char had comparable contributions to the reduction of N2O to N2. The NO-to-N2 and N2O-to-N2 reductions over the char surface were, respectively, accelerated and decelerated by increasing the H2O concentration. 相似文献
18.
N ShirahamaS.H Moon K.-H ChoiT Enjoji S KawanoY Korai M TanouraI Mochida 《Carbon》2002,40(14):2605-2611
Adsorption and reduction of NO2 over pitch-based ACFs, both as received and calcined at 1100 °C, were studied in a range of concentrations (NO2, 250-1000 ppm; O2, 0-10%) and temperatures (30-70 °C). Repeated adsorption after regeneration at 300 °C, temperature-programmed desorption (TPD) and diffuse reflectance fourier transformation infrared spectroscopy (DRIFTS) were also applied to analyze the adsorbed NO2 species. Pitch-based ACFs showed rapid NO production and adsorption at 30 °C which stayed at similar conversions until the rapid breakthrough of NO2. A higher reaction temperature of 70 °C decreased the ratio of NO2 adsorption to reduction in the stationary state and shortened the breakthrough time. Higher NO2 concentration increased the rates of both adsorption and reduction to shorten breakthrough time, whereas the presence of oxygen changed the NO2 profiles by enhancing the NO2 adsorption rate and decreasing both the rate and the capacity of reduction. It must be noted that 10% O2 allowed still significant production of NO. The molar O/N ratio evolved from TPD decreased and converged to a constant value according to the NO2 adsorption time, showing that NOx species adsorbed on the ACF changed from NO2 to NO3 along with the time of NO2 adsorption. Such a trend was confirmed by DRIFTS spectra of adsorbed NO2. These results suggest two kinds of NO2 adsorption sites. Site 1 adsorbs NO2 molecules strongly, transferring one oxygen to another adsorbed molecule on a similar site to form NO3ad. Although oxygen in the gas phase oxidized adsorbed NO2 to some extent, especially in the initial stage, disproportionation is still dominant at 10% O2. Such disproportionation produces gaseous NO, leaving NO3 on the surface. Site 2 adsorbs NO2 weakly. Saturation of both sites terminates the adsorption and reduction and results in the breakthrough of NO2. Adsorbed NO3 produces both NO and NO2 when heated, leaving one or two oxygen atoms on the surface, which are evolved as CO and CO2 at the same time, restoring a stationary ability for adsorption and reduction of NO2 through carbon loss. 相似文献
19.
Fe2O3 catalysts supported on Al2O3 were used to remove nitrous oxide from the nitric acid plant simulated process stream (containing O2, NO and H2O). Catalysts were prepared by the coprecipitation method and were characterized for their physico-chemical properties by BET, XRD, AFM and TPR analysis. A strong influence of the post-preparation heating conditions on the structural and catalytic properties of the catalysts has been evidenced. Laboratory tests revealed 95% conversion of N2O at temperature 750 °C and a slight decrease in activity in the presence of H2O and NO. The catalysts were inert towards decomposition of NO. The pilot-plant reactor and real plant studies (up to 3300 h time-on-stream) confirmed high activity and very good mechanical stability of the catalysts as well as no decomposition of nitric oxide. 相似文献
20.
A kind of negative thermal expansion ZrW2O8 nanorods were synthesized using a hydrothermal method, followed with a post-annealing at 570 °C for 2 h. Effects of HCl concentration on the microstructure, morphology and negative thermal expansion property in resulting ZrW2O8 powders were investigated by X-ray diffraction (XRD) and transmission electron microscope (TEM). Results indicate that the formation of the precursor ZrW2O7(OH)2(H2O)2 significantly depends on the HCl concentration, and the precursors ZrW2O7(OH)2(H2O)2 can form in the 2-8 mol/L HCl solution. With increasing the concentration of the HCl solutions from 2 to 8 mol/L, the rod-like ZrW2O8 particles become more homogeneous, and the average dimension change from 10 μm × 0.5 μm to 700 nm × 50 nm. All the ZrW2O8 powders obtained in different conditions exhibit negative thermal expansion property, and the average negative thermal expansion coefficients from 15 °C to 600 °C decrease gradually with the increasing HCl concentration. 相似文献