膜—悬浮光催化降解反应器中催化剂活性及共其影响因素分析

考察了膜－悬浮光催化降解反应器小试系统在处理自配废水的连续运行中催化剂活性的变化。试验发现，经两周的连续运行，催化剂活性有明显降低，降为原催化剂活性的14％。分析引起催化剂活性降低的可能原因有：催化剂颗粒的聚集、有机污染物和无机垢体在催化剂表面的附着。采用超声波粉碎、次氯酸钠碱洗和盐酸酸洗的方法来恢复催化剂活性。结果表明，采用10％的盐酸清洗可使催化剂活性恢复到初始值的64％左右，效果最明显。推测由于水中硬度在催化剂表面形成的CaCO3沉淀是导致催化剂活性降低的最主要因素。     

MnOx/PG低温SCR催化剂二氧化硫中毒及再生特性

采用等体积浸渍法制备了锰氧化物负载凹凸棒石(MnO_x/PG)低温SCR(Selective Catalytic Reduction)催化剂,在含硫气氛中进行低温SCR催化脱硝反应后受SO_2的毒化作用而失活.考察了热处理和水洗两种再生方式及再生工艺条件对中毒后的MnO_x/PG催化剂活性恢复的影响.结果表明,热处理不能有效恢复催化剂活性,而水洗再生可以使中毒催化剂的活性完全恢复;两种再生方法的工艺条件均对催化剂活性恢复效果不大.通过BET、SEM、元素分析等表征手段对催化剂中毒机理和中毒前后性能变化进行分析.结果表明,硫酸铵盐和多聚SO_4~(2-)的形成是导致MnO_x/PG催化剂活性降低的主要原因.热处理使催化剂部分活性恢复的原因在于表面硫酸铵盐的分解,而水洗再生可以有效的去除催化剂表面的硫酸铵盐和SO_4~(2-)聚合体,进而催化剂活性完全恢复.     

纳米负载型V2O5-WO3/TiO2催化剂碱及碱土金属中毒

实验制备了陶瓷颗粒为骨架的纳米级V2O5-WO3/TiO2(C)催化剂,采用浸渍法模拟碱及碱土金属中毒,研究中毒对催化剂脱硝活性的影响,通过BET、XPS、NH3-TPD技术分析了碱及碱土金属对催化剂的失活作用.结果表明,碱及碱土金属K、Na、Ca能够明显降低催化剂脱硝活性,350℃时,K、Na中毒催化剂活性降低了约30%左右,Ca中毒催化剂降低了20%.碱及碱土金属没有改变催化剂表面物种组成,催化剂活性与催化剂表面强氨气吸附位数量具有线性关系,K、Na、Ca与催化剂表面活性酸位结合,使催化剂中毒.     

蜂窝状Mnx/PG-CC催化剂中低温CH_4-SCR脱硝性能

采用悬浮浆液法将凹凸棒石(PG)涂覆于堇菁石(CC)表面,制备PG-CC载体.将PG-CC载体以过饱和浸渍法经Mn(NO_3)_2前驱体溶液处理后依次干燥、煅烧制得Mnx/PG-CC整体式催化剂,应用于柴油车尾气净化处理.考察了制备参数(锰负载量、煅烧温度)和工况条件(氧气含量,CH_4/NO)对Mnx/PG-CC催化剂在CH_4-SCR反应中脱硝活性的影响.采用BET、FE-SEM、XRD、XPS和NO吸脱附等表征手段对催化剂的结构和形貌进行表征.结果表明,在锰负载量为11%、煅烧温度为300℃下所制得的催化剂具有较佳的CH_4-SCR脱硝活性,O_2含量为5%、CH_4/NO为1,反应温度为300℃时反应条件最优.锰氧化物活性组分在催化剂表面的高度分散和均匀分布有利于催化剂的CH_4-SCR脱硝活性提高,且有助于NO吸附在载体表面并形成硝酸盐中间体参与催化反应.     

Mnx/SEP(海泡石)催化剂低温NH_3-SCR脱硝性能

以Mn(CH_3COO)_2和KMnO_4为前驱体,采用原位生长法在海泡石(SEP)载体表面负载锰氧化物,制备Mnx/SEP催化剂应用于低温SCR脱硝反应.分别考察了制备工艺及反应条件等因素对Mnx/SEP催化剂低温NH_3-SCR脱硝活性的影响.采用BET、XRD、SEM、XPS等表征手段对催化剂的结构和形貌进行表征分析.结果表明,在锰负载量为8 wt%、n(Mn(CH_3COO)_2)/n(KMnO_4)为3∶2时所制备的催化剂具有较佳的NH_3-SCR低温脱硝活性.当空速为10000 h~(-1)、反应温度在100—250℃区间时,转化率为100%,表明该催化剂具有高空速适应性.锰氧化物活性组分在海泡石表面的均匀分布和高的分散性使催化剂具有较大的有效比表面积,有利于催化剂NH_3-SCR反应;此外n(Mn(AC)_2)/n(KMnO_4)对催化剂表面活性物种形态特别是表面Mn~(4+)/Mn~(3+)比具有显著影响,进而与催化剂的低温SCR脱硝活性紧密相关.     

Pd-Fe/C催化氯酚还原脱氯-氧化联合降解

以Pd和Fe为活性金属组分通过沉积沉淀法制备了负载型Pd-Fe/C双金属催化剂,针对氯酚类污染物进行催化还原脱氯和催化氧化的连续降解处理.通过ICP-MS、XRD和TEM对催化剂进行表征,证实0.5%Pd-0.5%Fe/C催化剂中活性金属组分Pd和Fe在载体表面分散性最好,催化剂比表面积达到718.8 m~2·g~(-1).在温和条件下,以水作为反应介质,研究了负载型Pd-Fe/C催化剂对4-氯苯酚(4-CP)和2,4-二氯苯酚(2,4-DCP)的连续降解过程和反应条件,以及催化剂的重复使用情况.考察了Pd和Fe的负载量及p H值对催化剂活性的影响,得到了最佳反应条件,以0.5%Pd-0.5%Fe/C为催化剂,20 min内完成4-CP和2,4-DCP的催化还原脱氯,产物都为苯酚;之后加酸调节pH=5,并加入H2O2继续进行催化氧化,苯酚被彻底降解为H_2O和CO_2,而且转化率在60 min内可以达到97.5%以上,从而实现4-CP和2,4-DCP的彻底降解.     

蜂窝式MnO_x/PG-CC催化剂的制备及低温选择性催化还原法脱硝性能

采用悬浮浆液法将凹凸棒石(PG)涂覆于堇青石蜂窝陶瓷(CC)基体上,制取PG-CC涂层载体,利用过饱和浸渍法负载MnOx制备MnOx/PG-CC催化剂应用于柴油车尾气SCR脱硝.考察了制备条件对催化剂低温SCR活性的影响,采用BET、SEM-EDS、XRD手段对催化剂的理化性质进行了分析表征,探讨了催化剂结构特性与活性间的构效关系.研究发现,堇青石基体经PG涂层后,对活性组分的一次负载量显著增加,由3%增至13%,对应的催化剂低温脱硝活性显著提高,在100℃脱硝活性由10%提高到78%.结果分析表明,堇青石基体经PG涂层后比表面积大幅度增加,可以承载更高的活性组分,且活性组分具有更好的分散性,从而使得催化剂的活性点增加;另一方面,PG涂层催化剂具有更高的表面Mn4+/Mn3+价态比,更有利于催化剂的低温选择性催化还原法(SCR)活性.活性组分Mn Ox与PG涂层之间的协同作用是导致催化剂低温SCR脱硝活性得以提升的关键因素.研究结果表明,通过对堇青石蜂窝基体进行凹凸棒石涂层后采用浸渍法负载锰氧化物,可制备出具有较高低温SCR活性的蜂窝式模块催化剂.     

载体酸蚀预处理对CuMnCeOx/堇青石催化氧化甲苯性能的影响

为解决蜂窝堇青石载体比表面积小、活性组分难以负载等问题，采用硝酸酸蚀堇青石载体并负载金属氧化物，制备了Cu-Mn-Ce/堇青石催化剂.分析了不同酸蚀强度下催化剂对甲苯催化燃烧差异的原因，在40%wt硝酸溶液中、50℃下酸蚀4 h条件下得到的催化剂对甲苯的催化性能最佳，与其他催化剂相比，其表面平均孔径为38.31 nm并有更佳的孔隙率，且在12—14 nm处以及20—30 nm处有更佳的孔径分布，其上活性组分分布极为分散，具有更小的活性颗粒尺寸.在与未经酸蚀预处理催化剂的比较中发现，经酸蚀预处理的催化剂具有更大的比表面积和多样的氧化物晶体类型，更高的Cu/Mn比例(1.72∶1.26)，其中Mn⁴⁺(31.1%)、Ce³⁺(27.5%)及Osur(50.9%)在其占比均高于未经酸蚀预处理催化剂.     

垃圾渗滤液湿式氧化催化剂Fe-Co-Pt-Ce/FSC的组分配比优化及表征

采用等量浸渍法制备不同金属组分配比的Fe-Co-Pt-Ce/FSC负载型催化剂,并用于催化湿式氧化垃圾渗滤液,以COD去除率、浊度去除率和垃圾渗滤液处理中p H值的变化评价催化剂的活性,以金属溶出浓度评价催化剂的稳定性,考察金属组分配比对催化剂活性和稳定性的影响.通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、热重-差热(TG-DTA)、孔结构、X射线衍射(XRD)和X射线光电子能谱法(XPS)表征优选催化剂的组构性能,结果表明,Fe_1Co_1Pt_1Ce_3/FSC催化剂表现出最佳的催化性能,其作用下垃圾渗滤液的COD去除率、浊度去除率和最低pH值分别为86.2%、99.9%和6.34,金属溶出浓度为2.88 mg·L~(-1);焙烧温度的提高使催化剂活性降低但是稳定性提高,适宜的焙烧温度是500℃;催化剂的比表面为240.6 m~2·g~(-1),活性组分在载体表面分布均匀,组分粒子尺寸约为8.02 nm;催化剂组分主要以FeO、CoO、Pt和CeO_2的形式存在,且催化剂的金属元素之间存在协同作用.     

K2SO4的添加对V2O5/AC催化/脱硫剂脱硫活性的促进作用

将K2SO4以等体积浸渍法担载在1wt%的V2O5/AC(V1/AC)催化/脱硫剂上,制备了K担载量分别为0.5wt%和1.0wt%的K2SO4-V1/AC催化剂.结果表明,K2SO4的担载显著促进了V1/AC催化/脱硫剂的脱硫活性,延长了SO2的穿透时间,增加了有效硫容;再生后二次脱硫活性基本得以恢复,促进作用继续保持,因此是该催化/脱硫剂的有效助剂.对于较高的K担载量(1.0%),适度升高再生温度至350℃有助于其二次活性的恢复.另外,在K2SO4担载的V1/AC催化剂上,脱硫过程中有K2SO4的形成,但只是中间产物而不是最终稳定产物,其对V1/AC催化/脱硫剂脱硫活性的促进作用,体现在中间物K2S2O7作为一个运输载体,促进了SO2的氧化产物SO3从催化剂氧化活性中心位置向周围孔道、储存位转移的过程,从而使得SO2的高转化率得以更长时间的保持.     

无机阴离子对TiO2/SiO2光催化降解酸性红B活性的影响

以酸性红B为模型化合物，分别考察了6种常见的无机阴离子对TiO2/SiO2复合光催化剂活性的影响，并考察了导致催化剂失活的无机阴离子的最低浓度。结果表明，除了HCO3^-能引起催化剂部分不可逆中毒外，其余5种离子并没有在催化剂形成占位。失活的催化剂通过简的HCl冲洗即可再生。另外，对催化剂的失活机制作了初步探讨。     

Experimental investigation of the efficiency of triple rinsing of agricultural containers regarding their characterization as non-hazardous wastes

The efficiency of water rinsing for removing fenthion from non-combustible used pesticide containers was investigated. Four hundred empty containers from four olive oil producing areas in Greece were studied. Following triple rinsing cleaning procedures, the amount of fenthion retained in the container ranged from 0.01% to 0.1% w/w of its initial concentration. Extraction was accomplished with acetone, and the extracts were analyzed with a capillary gas chromatographic system coupled with flame ionization detector. The results obtained showed that triple rinsing is an effective procedure for removing fenthion from used pesticide containers, since the remaining pesticide concentration was below the legislated threshold value. Consequently, the containers can be handled as non-hazardous solid wastes.     

负载型稀土复合氧化物燃烧催化剂的失活研究

本文探讨了负载型稀土复合氧化物燃烧催化剂在使用过程中失活的主要特征.通过XRD,TEM,BET比表面测定及不同使用期的活性测定.证实催化剂在使用后的4—8个月内,烧结是失活的主因;而XPS谱显示硫中毒有积累性,以SO_4~(2-)形式沉积于催化剂表面,构成了燃烧催化剂后期失活的主要因素.由于催化燃烧反应在较高的温度下进行,并充分供氧,所以积炭引起失活的可能性较小,这可以从孔容数据和一些电镜照片中得到证实.     

Influence of H2S and NH3 on biogas dry reforming using Ni catalyst: a study on single and synergetic effect

● NH₃ in biogas had a slight inhibitory effect on dry reforming. ● Coexistence of H₂S and NH₃ led to faster decline of biogas conversion. ● Regeneration was effective for catalysts deactivated under synergetic effect. Biogas is a renewable biomass energy source mainly composed of CH₄ and CO₂. Dry reforming is a promising technology for the high-value utilization of biogas. Some impurity gases in biogas can not be completely removed after pretreatment, which may affect the performance of dry reforming. In this study, the influence of typical impurities H₂S and NH₃ on dry reforming was studied using Ni/MgO catalyst. The results showed that low concentration of H₂S in biogas could cause serious deactivation of catalyst. Characterization results including EDS, XPS and TOF-SIMS confirmed the adsorption of sulfur on the catalyst surface, which was the cause of catalyst poisoning. We used air calcination method to regenerate the sulfur-poisoned catalysts and found that the regeneration temperature higher than 500 °C could help catalyst recover the original activity. NH₃ in the concentration range of 50–10000 ppm showed a slight inhibitory effect on biogas dry reforming. The decline rate of biogas conversion efficiency increased with the increase of NH₃ concentration. This was related to the reduction of oxygen activity on catalyst surface caused by NH₃. The synergetic effect of H₂S and NH₃ in biogas was investigated. The results showed that biogas conversion decreased faster under the coexistence of H₂S and NH₃ than under the effect of H₂S alone, so as the surface oxygen activity of catalyst. Air calcination regeneration could also recover the activity of the deactivated catalyst under the synergetic effect of H₂S and NH₃.     

Fe-Mn-sepiolite as an effective heterogeneous Fenton-like catalyst for the decolorization of reactive brilliant blue

A study of the decolorization of reactive brilliant blue in an aqueous solution using Fe-Mn-sepiolite as a heterogeneous Fenton-like catalyst has been performed. The Fourier transform infrared (FTIR) spectra of the catalyst showed bending vibrations of the Fe-O. The X-ray diffraction (XRD) patterns of the catalyst showed characteristic diffraction peaks of α-Fe₂O₃, γ-Fe₂O₃ and MnO. A four factor central composite design (CCD) coupled with response surface methodology (RSM) was applied to evaluate and optimize the important variables (catalyst addition, hydrogen peroxide dosage, initial pH value and initial dye concentration). When the reaction conditions were catalyst dosage= 0.4 g, [H₂O₂]= 0.3 mL, pH= 2.5, [reactive brilliant blue]_o = 50 mg·L⁻¹, and volume of solution= 500 mL at room temperature, the decolorization efficiency of reactive brilliant blue was 91.98% within 60 min. Moreover, the Fe-Mn-sepiolite catalyst had good stability for the degradation of reactive brilliant blue even after six cycles. Leaching of iron ions (<0.4 mg·L⁻¹) was observed. The decoloring process was reactive brilliant blue specific via a redox reaction. The benzene ring and naphthalene ring were first oxidized to open ring; these were then oxidized to the alcohol and carboxylic acid. The reactive brilliant blue was decomposed mainly by the attack of ·OH radicals including surface-bound ·OH radicals generated on the catalyst surface.     

New insights into mercury removal mechanism on CeO<Subscript>2</Subscript>-based catalysts: A first-principles study

First-principles calculations were performed to investigate the mechanism of Hg⁰ adsorption and oxidation on CeO₂(111). Surface oxygen activated by the reduction of Ce⁴⁺ to Ce³⁺ was vital to Hg⁰ adsorption and oxidation processes. Hg0 was fully oxidized by the surface lattice oxygen on CeO₂(111), without using any other oxidizing agents. HCl could dissociate and react with the Hg adatom on CeO₂(111) to form adsorbed Hg–Cl or Cl–Hg–Cl groups, which promoted the desorption of oxidized Hg and prevented CeO₂ catalyst deactivation. In contrast, O–H and H–O–H groups formed during HCl adsorption consumed the active surface oxygen and prohibited Hg oxidation. The consumed surface oxygen was replenished by adding O₂ into the flue gas. We proposed that oxidized Hg desorption and maintenance of sufficient active surface oxygen were the rate-determining steps of Hg⁰ removal on CeO₂-based catalysts. We believe that our thorough understanding and new insights into the mechanism of the Hg⁰ removal process will help provide guidelines for developing novel CeO₂-based catalysts and enhance the Hg⁰ removal efficiency.

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无机阳离子对TiO2光催化降解染料的影响

考察了6种无机阳离子对P-25 TiO2光催化降解染料的影响，结果发现，Cu^2 ，Mn^2 和Ni^2 对光催化反应有强烈的抑制作用，Ca^2 ，Mg^2 和Al^3 对光催化反应速率无明显的负影响．经X光电能谱(XPS)的分析，确定锰离子以氧化物的形式沉积在氧化钛表面，使催化剂不可逆的中毒．Cu^2 和Ni^2 通过俘获光致电子导致催化活性降低。     

Catalytic decomposition of low level ozone with gold nanoparticles supported on activated carbon

Highly dispersed gold nanoparticles were supported on coal-based activated carbon (AC) by a sol immobilization method and were used to investigate their catalytic activity for low-level ozone decomposition at ambient temperature. Nitrogen adsorption-desorption, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts before and after ozone decomposition. The results showed that the supported gold nanoparticles prepared with microwave heating were much smaller and more uniformly dispersed on the activated carbon than those prepared with traditional conduction heating, exhibiting higher catalytic activity for ozone decomposition. The pH values of gold precursor solution significantly influenced the catalytic activity of supported gold for ozone decomposition, and the best pH value was 8. In the case of space velocity of 120000h⁻¹, inlet ozone concentration of 50mg/m³, and relative humidity of 45%, the Au/AC catalyst maintained the ozone removal ratio at 90.7% after 2500min. After being used for ozone decomposition, the surface carbon of the catalyst was partly oxidized and the oxygen content increased accordingly, while its specific surface area and pore volume only decreased a little. Ozone was mainly catalytically decomposed by the gold nanoparticles supported on the activated carbon.     

Photocatalytic degradation of phosphamidon using Ag-doped ZnO nanorods

The photocatalytic degradation of the organo-phosphorous pesticide phosphamidon at low concentration in aqueous solution on Ag-doped ZnO nanorods was investigated. Nanosized Ag-doped ZnO rods were synthesized by using a microwave assisted aqueous method. High molecular weight polyvinyl alcohol was used as a stabilizing agent. Composition and structure were investigated using energy-dispersive X-ray spectroscopy (EDAX) and X-ray diffraction (XRD). The XRD pattern reveals that ZnO nanorods are of hexagonal wurtzite structure. The average crystallite size calculated from Scherrer's relation was found to be 30?nm. The effects of catalyst loading, pH value, and initial concentration of phosphamidon on the photocatalytic degradation efficiency using Ag-doped ZnO nanorods as a photocatalyst have been discussed. The results revealed that Ag-doped ZnO nanorods with a diameter of 30?nm showed highest photocatalytic activity at a surface density of 1?g?dm^?3. The catalyst doped with 0.2?mol% Ag is effective for the degradation of phosphamidon with visible light. This opens a new possibility to decompose pesticides that are present in wastewater.     

Degradation of antipyrine in the Fenton-like process with a La-doped heterogeneous catalyst

A La-doped Co-Cu-Fe catalyst was synthesized for the antipyrine (ANT) removal. The La-doped catalyst had higher ANT removal than the control (95% vs. 54%). La reduced the particle size and increased the specific surface area of catalyst. The aim of this study was to synthesize a novel lanthanum (La) doped catalyst and to investigate antipyrine removal in wastewater using the Fenton-like process with the catalyst. The La-doped Co-Cu-Fe catalyst was synthesized using the modified hydrothermal method. Results showed that the La-doped catalyst had higher specific surface area and lower particle size than the catalyst without La doping (i.e., the control) (267 vs. 163 m²/g and 14 vs. 32 nm, respectively). Under the conditions of catalyst dosage 0.5 g/L, H₂O₂ concentration 1.70 g/L, and NaHCO₃ 0.1 g/L, the antipyrine removal within 60 min using the Fenton-like process with the La-doped catalyst was much higher than that with the control (95% vs. 54%). The hydroxyl radical concentration with the La-doped catalyst within 60 min was two times higher than that with the control (49.2 vs. 22.1 mg/L). The high catalytic activity of La-doped catalyst was mainly attributed to its high specific surface area based on the X-ray photoelectron spectroscopy result. Our La-doped catalyst should have great potential to remove antipyrine in wastewater using the heterogeneous Fenton-like process.