负载型分子筛催化剂对甲苯的催化性能

采用不同类型分子筛浸渍负载活性组分Ru制备Ru/M(M=β、MCM-41、Y、ZSM-5)催化剂,考察其对甲苯的催化性能,并通过XRD、BET、SEM、XPS、H₂-TPR、NH₃-TPD等表征,分析催化剂的孔道结构、酸性位等物化结构对催化活性的影响.结果发现以贵金属Ru为活性组分,Y为载体的催化剂催化性能最优,在300℃左右,甲苯基本完全降解,CO2选择性接近99%,几乎无副产物生成.由此说明,适宜的孔径尺寸、丰富的酸性位、较好的氧化还原性能和较大的比表面积能有效促进分子筛催化剂对甲苯的催化氧化.     

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.     

制备方法对COxZr1-xO2催化剂结构和氧化甲苯性能的影响

采用沉淀法、水热法、热分解法和浸渍法制备了Co_xZr_(1-x)O_2催化剂,考察了制备方法对其结构及甲苯氧化性能的影响.通过TG、XRD、SEM、EDS和BET等方法表征了催化剂物化性质.结果表明,水热法制备的催化剂上钴物种和锆物种分散性好、颗粒均匀呈球形、比表面积大可达82.3 m~2·g~(-1)、孔结构发达,从而具有更好的催化氧化甲苯的性能,在空速20000 mL·(g·h)~(-1),浓度为0.1%时完全氧化甲苯的转化温度低至260℃.     

微波催化氧化法处理垃圾渗滤液的正交试验

在微波辐射条件下,采用活性炭与Fenton试剂处理垃圾渗滤液,并通过正交试验考察了微波辐射时间、pH、活性炭用量、硫酸亚铁用量和H2O2用量对处理效果的影响.结果表明:pH对处理效果的影响最大,其次为活性炭用量、微波辐射时间、硫酸亚铁用量和H2O2用量;在100 mL水样中,最佳处理条件为活性炭2 g、H2O20.2 mL、硫酸亚铁0.834 g、pH 6、微波辐射时间10 min,垃圾渗滤液中的COD去除率达到75.36%.     

催化氧化法处理对硝基酚钠生产废水的研究

研究了催化氧化法处理对硝基酚钠生产废水的工艺参数,COD去除率可达90％,探讨了从酚钠母注人中盐析酚的条件,回收量为15．86Kg酚钠／m^3废液,提出了综合治理酚钠废水的工艺流程。     

催化湿式氧化法预处理显影废水的研究

考察了催化湿式氧化法对医院显影废水进行预处理的可行性.紫外扫描结果表明,对甲氨基苯酚硫酸盐、对苯二酚等特征污染物被降解为小分子物质,在催化剂Ru/TiO2存在下,催化湿式氧化法与湿式氧化相比,有机物的降解更加彻底.通过考察催化剂用量、温度、压力及pH值等条件对CODCr去除率的影响,确定适宜的反应条件为:催化剂用量为2g·l-1,温度为220℃,压力为1.5MPa,pH为8.9.在上述反应条件下,CODCr去除率达62.5%,色度去除率达98%,BOD5/CODCr值由原来的0.07提高到0.45.     

浸渍液溶剂对负载型MnOx/MCM-41结构及其催化氧化甲苯性能的影响

以MCM-41为载体,用水、乙醇和乙二醇作为浸渍液溶剂制备了3种负载型催化剂MnO_x/MCM-41,采用XRD、TEM、H₂-TPR、O₂-TPD和XPS等对催化剂进行了表征,探究了浸渍液溶剂(水、乙醇、乙二醇)对MnO_x/MCM-41的结构及催化氧化甲苯性能的影响.结果表明,乙二醇作浸渍液溶剂可提高锰氧化物的分散度、氧化还原性和表面吸附氧的含量.因而,在相同的质量空速下(WHSV=50000 mL·g^-1·h^-1),相比于水溶液浸渍法制备的MnO_x/M-W(T₉₀=289℃)和乙醇溶液浸渍法制备的MnO_x/M-ET(T₉₀=277℃),乙二醇共浸渍法制备的MnO_x/M-EG具有最强的催化活性(T90=268℃);20 h的稳定性评价实验结果表明,MnO_x/M-EG具有较好的稳定性.     

CuO/zeolite catalyzed oxidation of gaseous toluene under microwave heating

The development of a combined process of catalytic oxidation and microwave heating for treatment of toluene waste gas was described in this work. Toluene, a typical toxic volatile organic compound, was oxidized through a fixed bed reaction chamber containing zeolite-supported copper oxide (CuO/zeolite) catalyst mixed with silicon carbide (SiC), an excellent microwave-absorbing material. The target compound was efficiently degraded on the surface of the catalyst at high reaction temperature achieved by microwave-heated SiC. A set of experimental parameters, such as microwave power, air flow and the loading size of CuO etc., were investigated, respectively. The study demonstrated these parameters had critical impact on toluene degradation. Under optimal condition, 92% toluene was removed by this combined process, corresponding to an 80%–90% TOC removal rate. Furthermore, the catalyst was highly stable even after eight consecutive 6-h runs. At last, a hypothetical degradation pathway of toluene was proposed based on the experimental data obtained from gas chromatography-mass spectrum and Fourier transform infrared spectroscopy analyses.     

Effect of Cu-ZSM-5 catalysts with different CuO particle size on selective catalytic oxidation of N,N-Dimethylformamide

● A series of Cu-ZSM-5 catalysts were tested for DMF selective catalytic oxidation. ● Cu-6 nm samples showed the best catalytic activity and N₂ selectivity. ● Redox properties and chemisorbed oxygen impact on DMF catalytic oxidation. ● Isolated Cu²⁺ species and weak acidity have effects on the generation of N₂. N, N-Dimethylformamide (DMF), a nitrogen-containing volatile organic compound (NVOC) with high emissions from the spray industry, has attracted increasing attention. In this study, Cu-ZSM-5 catalysts with different CuO particle sizes of 3, 6, 9 and 12 nm were synthesized and tested for DMF selective catalytic oxidation. The crystal structure and physicochemical properties of the catalyst were studied by various characterization methods. The catalytic activity increases with increasing CuO particle size, and complete conversion can be achieved at 300–350 °C. The Cu-12 nm catalyst has the highest catalytic activity and can achieve complete conversion at 300 °C. The Cu-6 nm sample has the highest N₂ selectivity at lower temperatures, reaching 95% at 300 °C. The activity of the catalysts is determined by the surface CuO cluster species, the bulk CuO species and the chemisorbed surface oxygen species. The high N₂ selectivity of the catalyst is attributed to the ratio of isolated Cu²⁺ and bulk CuO species, and weak acidity is beneficial to the formation of N₂. The results in this work will provide a new design of NVOC catalytic oxidation catalysts.     

Removal of toluene from air streams by cobalt-copper bimetallic catalysts supported on sepiolite

Abstract

Oxidative removal of toluene using copper and cobalt bimetallic catalysts with varying molar ratios supported on sepiolite was investigated. The catalysts prepared by a deposition precipitation method and were characterized using X-ray diffraction, nitrogen adsorption-desorption, field emission scanning electron microscopy, H₂-temperature-programmed reduction, transmission electron microscope, and inductive coupled plasma atomic emission spectroscopy. The species supported on sepiolite are Co₃O₄, CuO, and CuCo₂O₄. The activities of the tested catalysts increased in the order 0Co-4Cu/Sep <1Co-3Cu/Sep <4Co-0Cu/Sep <1Co-1Cu/Sep <3Co-1Cu/Sep. The latter exhibiting 90% toluene oxidative degradation at 288?°C within 15?h, having high selectivity towards CO₂, and being stable at 300?°C up to 15?h. In conclusion, this study showed that sepiolite has excellent properties as a support.     

Adsorption of toluene, ethylbenzene and xylene isomers on multi-walled carbon nanotubes oxidized by different concentration of NaOCl

Multi-walled carbon nanotubes (MWCNTs) were fabricated and oxidized by different concentrations of sodium hypochlorite (NaOCl) solutions. The untreated MWCNTs and modified MWCNTs were employed as adsorbents to study their characterizations and adsorption performance of toluene, ethylbenzene and xylene isomers (TEX) in an aqueous solution. The physicochemical properties of MWCNTs were greatly affected after oxidation, which influences TEX adsorption capacity. The 3% NaOCl-oxidized MWCNTs shows the greatest enhancement in TEX adsorption, followed by the 30% NaOCl. More interestingly, the 15% NaOCl-oxidized MWCNTs has lower adsorption capacities than untreated MWCNTs. The adsorption mechanism of TEX on treated MWCNTs is attributed to the combined action of hydrophobic interaction, π-π bonding interaction between the aromatic ring of TEX and the oxygen-containing functional groups of MWCNTs and electrostatic interaction. 3% NaOCl solution could not only introduce much oxygen-containing functional groups on MWCNTs, but also lead to less damage for the pore structure. This suggests that the CNTs-3% NaOCl is efficient adsorbent for TEX and that they may possess good potential for TEX removal in wastewater treatment.     

高级催化氧化法去除水中邻苯二甲酸酯的研究进展

普遍认为,邻苯二甲酸酯类物质（Phthalic Acid Esters,PAEs）是内分泌干扰物质（Endocrine Disrupting Chemicals,EDCs）,被广泛应用于增塑剂、化妆品中,具有致畸性,致癌性,致突变性以及拟/抗雌激素活性、拟/抗甲状腺激素活性等内分泌干扰特性。邻苯二甲酸酯类物质很容易扩散到环境中,在土壤、大气、水环境中均有检出,是环境中常见污染物,严重威胁人体健康和生态环境,已经引起国内外的广泛关注。在综述邻苯二甲酸酯类物质的物理化学性质、毒性影响、国内外天然水体、地下水和生活污水中的污染现状的基础上,讨论消除水环境中PAEs污染的强化混凝、吸附、膜处理、生物处理和高级氧化技术。高级氧化技术因其能够快速有效地去除饮用水和污水中不同种类的有机污染物而备受关注,且发展迅速。重点介绍了高级催化氧化法对水环境中PAEs的去除,包括催化湿式过氧化物氧化过程,催化臭氧氧化过程,光催化氧化过程,超声波、微波辅助催化氧化过程以及高级纳米催化氧化过程。其中,Fenton催化氧化技术在氧化过程中通过使用催化剂或协同紫外光等方式产生高度反应性羟基自由基,可无选择性地将PAEs完全降解为无毒无害的小分子物质,对PAEs的氧化去除效果最好。虽然在高级氧化过程中应用催化剂可大大提高氧化效率和降解程度,但催化氧化法耗能较大、催化剂消耗量大、受水体pH值的影响,且研究大多限于实验室阶段,未能大量投入工业应用,需要进一步发展创新。因此,开发新型高效催化剂、提高催化剂选择性、优化催化氧化反应条件、优化设计催化反应器、与其他技术耦合是水体中PAEs类环境激素污染控制技术的发展方向。     

响应面法在催化湿式氧化降解异佛尔酮中的应用

以Ru/TiZrO2为催化剂,采用催化湿式氧化法降解异佛尔酮废水,选择反应温度、氧气分压、反应时间、催化剂用量、初始pH为影响因素,以TOC去除率为响应值,采用响应面法研究影响因素及其交互作用对响应值的影响,建立二次多项式回归方程模型,并采用后退回归法进行模型精简.结果表明,反应时间和反应温度及其交互作用对TOC去除率影响极显著(P≤0.01);反应时间的二次项对TOC去除率影响显著(P≤0.05).随着反应温度的升高和反应时间的延长,TOC去除率逐渐提高.最后对模型进行验证,实验值与预测值具有很好的一致性,说明模型具有可靠的预测性,将该模型应用到催化湿式氧化中合理可行.质谱和离子色谱检测到异佛尔酮的降解产物主要为有机酮与小分子羧酸,由此提出对反应机理和降解途径的假设.     

包气带不同深度土壤对甲苯和三氯乙烯的吸附研究

采用批实验研究了华北平原地下水中检出率较高的三氯乙烯和甲苯在沿污水河包气带不同深度土壤中的吸附情况。从3个地点分析结果来看,其中有机碳（OC）的质量分数均较低（最高为1.01%）。在河床和近河处土壤对甲苯和三氯乙烯的吸附总体上呈现出浅部土壤吸附性强的特点。在实验浓度范围内,土壤中无机矿物对有机污染物（特别是三氯乙烯）的表面吸附扮演了重要角色。土壤对甲苯的吸附表现出了强烈的非线性,而对三氯乙烯的吸附表现出了良好的线性关系。甲苯的吸附与土壤有机碳质量分数的关系要比三氯乙烯更密切,这说明了吸附作用过程与有机化合物的分子结构、疏水性等方面的性质也有关系。     

ZnO-MgO/Al2O3吸附-臭氧催化氧化处理难降解有机废水

以活性氧化铝为载体,采用浸渍法制备催化剂,对甲基橙及草酸模拟废水进行处理.在中性条件下,臭氧催化氧化比单独臭氧氧化能提前30 min使得甲基橙溶液褪色,反应105 min时,臭氧催化氧化对TOC的去除率高达96.53%,比单独使用臭氧氧化对甲基橙TOC去除率提高了47.19%,在处理草酸废水时臭氧催化氧化对TOC去除率高达80.59%,比单独使用臭氧氧化对草酸TOC去除率提高了59.14%.在处理甲基橙及草酸的小试实验中催化剂对有机污染物的吸附作用起到了加快反应进行的作用.在对垃圾渗滤液超滤出水时,O₃与COD质量比为1:1时,臭氧催化氧化对COD去除率为49.09%,比单独使用臭氧氧化提高36.37%,臭氧催化氧化对TOC的去除率是单独使用臭氧氧化的2.54倍,在处理垃圾渗滤液纳滤浓水时,臭氧催化氧化对COD去除率高达88.72%,比单独使用臭氧氧化提高37.60%,并且臭氧催化氧化对TOC的去除率是单独臭氧氧化的1.6倍.臭氧催化氧化反应过程中产生的羟基自由基对有机物更快的反应速率.     

不同溶氧条件下九龙江口湿地沉积物一水界面氨氮释放与氧化规律

摘要：沉积物中氨氮（NH4^＋-N）的释放与氧化是河口湿地生态系统氮素生物地球化学循环的关键过程。本文通过室内模拟,构建饱和（BH）、好氧（HY）、缺氧（QY）和厌氧（YY）等四种上覆水溶氧（DO）条件,研究九龙江口湿地两种沉积物（红树林、光滩）中NH4^＋-N在沉积物-水界面的释放与氧化规律。结果表明,不同溶氧条件下,两种沉积物氨氮的释放、氧化存在显著差异。首先,红树林沉积物上覆水NH4^＋-NN的累积释放量是光滩沉积物的1．9-4．5倍,其中红树林沉积物上覆水NH4LN释放量分别达到1．64mg（BH）、2．07mg（HY）、3．47mg（QY）和3．20mg（YY）,而光滩沉积物则分别为0．85mg（BH）、1．00mg（HY）、0．77mg（QY）和1．27mg（YY）。在较高DO条件下两种沉积物NH。’一N均呈低释放状态,而在较低DO条件下则呈高释放状态。另外,四种溶氧条件下红树林沉积物NH4^＋-NN的释放速率（N43．73-78．51mg-m^-2-d^-1）和氧化速率（N26．19-40．68mg-m^-2-d^-1）均高于光滩（分别为N14．50-19．22mg-m^-2-d^-1和N8．89-22．53mg-m^-2-d^-1）,原因可能是红树林沉积物微生物种类丰富,群落多样性更高,矿化和硝化作用强烈。本文明晰了不同溶氧条件下河口红树林湿地沉积物NH4^＋-N的迁移转化过程,可促进滨海湿地的生态保护以及近海水域富营养化的控制。