湿式氧化-催化湿式氧化联用处理定影废水

采用湿式氧化(WAO)-催化湿式氧化(CWAO)两段工艺处理定影废水,重点考察了反应时间、温度、压力、pH等因素对WAO处理效果的影响,并进行了CWAO处理WAO出水氨氮的尝试,取得了较好的效果.实验确定WAO适宜的反应条件:温度为160℃、氧分压为1 MPa、反应时间为2 h、进水pH为4.8.该条件下的CODCr去除率达79%,出水pH为1.4.CWAO处理WAO出水时所选定的反应条件:pH为12.9、温度为250℃、氧分压为3 MPa、反应时间为2 h.采用CWAO和WAO联用的方法处理定影废水,CODCr去除率达99.8%,氨氮去除率达97.8%,pH为5.6.     

Development of Fe2O3-CeO2-TiO2/γ-Al2O3 as catalyst for catalytic wet air oxidation of methyl orange azo dye under room condition

In order to develop a catalyst with high activity and stability for catalytic wet air oxidation (CWAO) process at room temperature and atmospheric pressure, we prepared Fe₂O₃-CeO₂-TiO₂/γ-Al₂O₃ by consecutive impregnation, and determined its properties using BET, SEM, XRF, XPS and chemical analysis techniques. The degradation of an azo dye, methyl orange, in CWAO process with Fe₂O₃-CeO₂-TiO₂/γ-Al₂O₃ used as catalyst at room temperature and atmospheric pressure was also investigated, and the results show that the catalyst has an excellent catalytic activity in treating synthetic wastewater containing 500 mg/L methyl orange, and 98.09% of color and 96.08% of total organic carbon (TOC) can be removed in 2.5 h. The degradation pathway of methyl orange was analyzed by UV–vis and FT-IR spectra. The result of leaching tests shows the catalyst has an excellent stability with negligible leaching ions, and the leaching of Ce is effectively controlled by adding Ti, because Ce and Ti in the catalyst take the form of compound oxides, and the deactivation of the catalyst in successive runs is caused by the adsorption of intermediates on the surface and coverage of the active sites. The catalytic activity of the deactivated catalyst can be generally restored by rinsing it in hydrochloric acid followed by calcination.     

Catalytic wet air oxidation of butyric acid solutions using carbon-supported iridium catalysts

Aqueous solutions of butyric acid were treated by catalytic wet air oxidation using carbon-supported iridium catalysts in a stirred reactor. Under the operating conditions of 6.9 bar of oxygen partial pressure and 200 °C of temperature, conversions up to 52.9% after 2 h were obtained depending on the type of catalyst used. The effects of butyric acid initial concentration, loading of catalyst, oxygen partial pressure and temperature were investigated and the empirical rate law for acid conversion is presented. Oxidation intermediates such as propionic and acetic acid were identified. The heterogeneous catalyzed free-radical oxidation of butyric acid is discussed.     

Catalytic wet air oxidation of acetic acid over different ruthenium catalysts

Ruthenium catalysts were prepared by impregnation of different supports: ZrO₂, CeO₂, TiO₂, ZrO₂–CeO₂ and TiO₂–CeO₂. Their activities for acetic acid oxidation in aqueous solution were investigated in a stirred reactor at a reaction temperature of 200 °C and total pressure of 4 MPa. The order of the catalyst activity obtained was RuO₂/ZrO₂–CeO₂ > RuO₂/CeO₂ > RuO₂/TiO₂–CeO₂ > RuO₂/ZrO₂ > RuO₂/TiO₂, which corresponds to surface concentration of non-lattice oxygen (defect-oxide or hydroxyl-like group) of these catalysts. The non-lattice oxygen on the catalyst surface plays an important role in the catalytic activity.     

Rectorite as catalyst for wet air oxidation of phenol

Rectorite was characterized by XRF, BET, XRD, FT-IR, SEM and TPR, and investigated as catalyst for wet air oxidation of phenol in a batch reactor at 150 °C. The iron impurity, mainly presented as highly dispersed hematite, acted as active centers and showed good performance without significant iron leaching. The catalyst can be also used as adsorbent to remove leached iron in solution.     

Catalytic wet air oxidation of aqueous solution of 2-chlorophenol over Ru/zirconia catalysts

Ru loaded zirconia catalysts (Ru/ZrO₂) were found to be active in the catalytic wet air oxidation (CWAO) of 2-chlorophenol (2-CP) at relatively mild temperature. To optimize the reaction conditions, the effects of different operating parameters, such as the rotation speed, the reaction temperature, the total pressure, the initial concentration and the pH of the initial 2-CP solution on the catalytic activity of 3 wt.% Ru/ZrO₂ were evaluated. The activation energy for the CWAO of 2-CP over Ru/ZrO₂ was calculated to be 36 kJ mol⁻¹. The 2-CP removal rate is zero order with respect to the initial 2-CP concentration. The CWAO of 2-CP changes from first order (oxygen diffusion control) to zero order (kinetic control) with respect to the oxygen partial pressure when the total pressure is higher than 4 MPa. The conversion of 2-CP increases with the pH of the initial 2-CP solution. The dechlorination reaction is promoted at higher pH. However, too high pH limits the total mineralization of 2-CP because the adsorption of the reaction intermediates is hindered. It was also confirmed that Ru(NO)(NO₃)₃ is better than RuCl₃ to act as a ruthenium precursor.     

常温常压催化湿式氧化中Mo-Mn-Al-O催化剂的制备及活性

以Mn-Al-O为载体,钼酸盐为活性成分的前驱体,采用共沉淀-浸渍法制备出Mo-Mn-Al-O催化剂,使用ICP-OES、BET、XRD和XPS方法对其进行表征,研究其在常温常压下催化湿式氧化阳离子型染料废水的催化活性。实验结果表明,Mo的浸渍浓度为1.5 mol·L^-1、浸渍温度为55℃、焙烧时间为3 h和焙烧温度为400℃下制备出的Mo-Mn-Al-O催化剂对阳离子红GTL、阳离子红X-GRL、阳离子黄X-GL和阳离子蓝X-BL都有较好的催化性能。特别是,当催化剂投加量为2.72 g·L^-1时,反应1 h后对阳离子红GTL的脱色率和TOC去除率分别达到74.8%和64.5%。     

Multi-walled carbon nanotubes (MWNTs) as an efficient catalyst for catalytic wet air oxidation of phenol

Multi-walled carbon nanotubes (MWNTs) were used as a catalyst for catalytic wet air oxidation (CWAO) of phenol in a batch reactor. SEM, TEM and FT-IR technique were applied to investigate the microstructure and the surface functional group of the MWNTs. When the carboxylic groups (–COOH) are grafted onto the surface of the MWNTs, the functionalized MWNTs exhibit a good catalytic activity in CWAO of phenol. At a reaction temperature of 160 °C, oxygen pressure of 2.0 MPa and a phenol concentration of 1000 mg/L, 100% phenol and 76% TOC are removed after 120 min reaction.     

Fast catalytic degradation of organic dye with air and MoO3:Ce nanofibers under room condition

One-dimensional Ce doped MoO₃ nanofibers with different Ce doping amount have been synthesized by a combination method of sol–gel process and electrospinning technique. X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) were used to characterize the resulting samples. These fibers are interesting for a number of catalytic applications. The best catalytic activity was obtained over 11.86 wt.% CeO₂-doped MoO₃ with 98% degradation effect of 0.3 g L⁻¹ Safranin-T by air under room condition towards complete degradation products such as HCO₃⁻ and NO₃⁻ within 20 min. The leaching test showed that this MoO₃:Ce nanofiber catalyst has an excellent stability and can be used as a rapid heterogeneous catalyst for about ten times by simply treatment.     

催化湿式氧化技术处理甲醇制汽油的废水研究

甲醇制汽油是非石油资源合成技术中关键的一项工作,该工艺过程中产生大量的废水。采用高压釜作为反应器,以催化湿式氧化技术对甲醇制汽油（MTG）废水进行处理,催化剂为实验室制得的钌/铈锆复合氧化物催化剂,考察了反应温度、催化剂投加量、反应时间和搅拌转速对废水COD去除率的影响,结果表明,在反应温度240℃、催化剂投加量10 g/L、搅拌转速300 r/min的反应条件下,反应2 h后废水COD去除率达到98.68%。     

Catalytic wet air oxidation of ammonia over M/CeO2 catalysts in the treatment of nitrogen-containing pollutants

Ammonia, a well-known by-product of chemical, fertiliser and metallurgy industries, is also the most refractory product of nitrogen-containing compound oxidation. Consequently, NH₄⁺ is a key component of waste disposal of conventional processes like anaerobic digestion or nitrification/denitrification. Catalytic wet air oxidation (CWAO) process, able to eliminate organic matter with non toxic by-product formation, was investigated for ammonium ions removal from wastewater. Oxidation of aniline and of ammonia were carried out on mono- and bimetallic noble metal catalysts (Pt, Ru, Pd, etc.) prepared by impregnation and supported on cerium oxides. In liquid phase, at high temperature (150–250 °C) and high pressure of oxygen (20 bar), a Ru/CeO₂ catalyst is able to achieve the elimination of refractory nitrogenous organic products like aniline. The greatest interest of CWAO compared to the classical biological one, is that the selectivity towards molecular nitrogen is much higher (>90%). Indeed, in this process, ammonium ions give essentially N₂, via hydroxylamine and below 200 °C. At higher temperatures the rate of conversion is extremely high but nitrite and nitrate ions appear in the effluent. On a RuPd/CeO₂ catalyst, the optimal temperature for ammonia conversion is then 200 °C. In these conditions, the N₂ selectivity is up to 90%.     

催化湿式氧化处理农药废水的研究

利用担载型双金属活性组分催化剂，考察了反应温度、压力、进料空速和V（空气）：V（H2O）（体积比）等反应条件对催化湿式氧化处理某农药废水效果的影响。对于该种废水，在4．2MPa，245℃，空速为2．0h^-1，V（空气）：V（H2O）＝300的反应条件下，废水的COD去除率可达到91．3％。经处理后废水的BOD5／COD＞0．5，说明其可生化性能良好。     

Catalytic wet air oxidation of Kraft bleach plant effluents in a trickle-bed reactor over a Ru/TiO2 catalyst

Catalytic wet air oxidation of two acidic and alkaline Kraft bleach plant effluents (total organic carbon (TOC) content 1138 and 1331 mg l⁻¹, respectively) was investigated in a trickle-bed reactor at T=463 K and oxygen partial pressure of 8 bar. The reactor packed with titania or titania-supported ruthenium catalyst was operated in a low-interaction (LIR) trickle-flow regime either in continuous-flow or batch-recycle mode. In the off-gas, no carbon monoxide was detected in any of the runs. When the catalytic bed was composed of TiO₂ particles, moderate abatement of organic compounds from the bleach plant effluents was observed (TOC conversions up to 46 and 26%, respectively). The removal of parent organic material was further enhanced by deposition of metallic ruthenium (3 wt.%) on the titanium oxide support. In that case, the once-through oxidation produced decolorized outlet streams with TOC conversions as high as 89 and 88%, respectively. These values further increased to 98 and 95%, respectively, by running the trickle-bed reactor in the batch-recycle mode of operation; the residual carbon content in treated effluents was found in the form of acetic acid. No leaching of Ru or Ti was detected by ICP-AES analysis to the detection limits of 0.2 and 0.1 mg l⁻¹, respectively.     

Catalytic wet air oxidation of carboxylic acids at atmospheric pressure

Catalytic wet air oxidation of carboxylic acids (maleic acid, oxalic acid and formic acid) was carried out in a batch reactor operated at 160 psi or atmospheric pressure. Pt/Al₂O₃ and the sulfonated poly(styrene-co-divinylbenzene) resin were used as catalysts. Maleic acid was proved to be a refractory substance which could not be oxidized on the Pt/Al₂O₃ catalyst at all atmoshperic pressure, and needed high pressure and high temperature operation for its oxidation. On the contrary, oxalic acid and formic acid were readily oxidized into carbon dioxide and water at 353 K and atmospheric pressure. The pathways of maleic acid oxidation were proposed, and the conversion of maleic acid into oxalic acid was the rate-determining step. When the sulfonated resin catalyst was present together with the Pt/Al₂O₃ catalyst, maleic acid could be oxidized at 353 K and atmospheric pressure. The sulfonated resin catalyst was suggested to hydrolyze maleic acid into readily oxidizable compounds.     

湿式氧化催化剂的研究

摘要叙述了一型湿式氧化催化剂的研制情况和用于处理工业废水的效果,给出了有关小型试验结果。     

Catalytic wet air oxidation of low molecular weight carboxylic acids using a carbon supported platinum catalyst

Aqueous solutions of low molecular weight carboxylic acids, such as acetic, propionic and butyric acids, were treated by catalytic wet air oxidation (CWAO) using a carbon supported platinum catalyst. Oxidation in the presence of the catalyst, in a stirred reactor, was carried out at 200°C and 6.9 bar of oxygen partial pressure, with conversions (after 2 h) ranging from 59.4 to 75%, and selectivities to gaseous products of up to 100%. Initial rates for conversion varied from 184 (butyric acid) to 260 mmol h⁻¹ g_Pt⁻¹ (propionic acid). The activation energy for butyric acid conversion was found to be 56.7 kJ mol⁻¹.     

Catalytic wet air oxidation of olive oil mill effluents: 4. Treatment and detoxification of real effluents

Olive oil mill wastewater (OMW) generated by the olive oil extraction industry constitutes a major pollutant, posing severe environmental threats. It contains a high organic load and phytotoxic and antibacterial phenolic compounds which resist biological degradation. Platinum and ruthenium supported titania or zirconia were studied in the catalytic wet air oxidation (CWAO) of OMWs in a batch reactor and in a continuous trickle-bed reactor. CWAO experiments at 190 °C and 70 bar total air pressure confirmed the effective elimination of the TOC (total organic carbon) and of the phenolic content of actual diluted OMW. Simultaneously, toxicity towards Vibrio fischeri was reduced and a decrease in phytotoxicity occurred. The ruthenium catalysts were found stable over a long period of operation in a trickle-bed reactor.The biodegradability of the oxidized waste has been enhanced and this study also examined the feasibility of coupling CWAO and an anaerobic digestion treatment. The pretreatment of the OMW in the presence of a ruthenium catalyst reduced considerably the total phenolic contents of the wastewater, and produced an effluent suitable to be treated by anaerobic treatment with increased biomethane production compared to the untreated effluent.     

催化湿式氧化处理头孢氨苄废水

采用催化湿式氧化处理头孢氨苄废水,考察反应温度、进水pH及Cl-含量对RCT催化剂性能的影响,并对液体样品及催化剂进行了HPLC、TOC/TN、GC-MS、N2物理吸附-脱附及XRF表征。通过正交实验,得出最佳的工艺条件为:进水pH=4.8,Cl-浓度1 500 mg·L-1,反应温度260℃;对催化剂进行300 h连续寿命考察,废水TOC及TN去除率均超过90%,催化剂稳定性高,活性组分流失较少;废水经催化湿式氧化处理,水中残留的主要有机物均可生化降解。     

催化湿式氧化技术处理氯酯磺草胺生产废水的研究

采用催化湿式氧化技术处理生产氯酯磺草胺过程中产生的高浓度有机废水。实验表明制备的复合负载型催化剂CuO-Co3O4-MnO2/ZrO2-CeO2在处理该废水时具有较好的催化活性。通过对催化剂投加量、反应温度、氧气分压和废水pH等工艺条件的考察,得出最佳的工艺条件为：催化剂投加量10g/L、反应温度220℃、氧气分压2.5MPa、废水初始pH值10.5,在此条件下反应120min,CODCr去除率达到98.2%。     

Synthesis, characterization and catalytic application for wet oxidation of phenol of iron-containing clays

High-surface-area pillared clays (PILC) were prepared from naturally occurring montmorillonites by exchanging interlayer ions to polyoxocations containing (i) aluminum (Al₁₃-PILC), (ii) iron adsorpted onto Al₁₃-PILC, and (iii) iron and aluminum located within the same complex (Fe_0.8Al_12.2-PILC). The obtained Fe_0.8Al_12.2-PILCs were characterized by DR–UV–vis and IR spectroscopy, XRD, ESR, scanning electron microscopy and low temperature N₂ adsorption measurements. Important factors affecting catalyst activity and phenol removal efficiencies have been studied, i.e. the effect of pH, temperature, catalyst concentration and stability of the catalyst.