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二噁(英)降解方法的研究 总被引:1,自引:0,他引:1
二噁(左口右英)是一类剧毒有机氯化物,已被联合国环境署和世界卫生组织列为持久性有机污染物和一级致癌物质,能够对环境和人类的健康造成重大危害.脱氯降解是降低二噁毒性的有效途径.本文对二噁的光降解、热降解、生物降解和化学降解脱氯作了详尽的评述,比较了各种降解方法的优劣,指出多相催化加氢脱氯降解方法将是今后的发展方向. 相似文献
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采用化学还原法制备了纳米Fe0, 并研究了不同条件下纳米Fe0对2,4-二氯酚(2,4-DCP)的降解情况, 探讨了纳米Fe0降解2,4-二氯酚的反应途径. 结果表明, 纳米Fe0对2,4-二氯酚的去除作用包括吸附、脱氯、开环三种机制. 其中脱氯作用是一种界面反应, 发生在氯酚分子被吸附到Fe原子表面之后. 2,4-二氯酚可以脱去一个氯原子生成2-氯酚或4-氯酚, 也可以脱去两个氯原子生成苯酚. 随着氯酚初始浓度的增大, 其相对去除率略有降低, 但绝对降解量有较大提高. 温度不仅影响脱氯速率, 而且影响氯酚的去除途径. 温度较高时脱氯作用占主导地位, 先脱氯后开环, 温度较低时吸附作用占主导地位, 较易发生先开环后脱氯的情况. 相似文献
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金属氧化物对十氯联苯的降解研究 总被引:1,自引:0,他引:1
分别以市售的Fe2O3、MgO和CaO为催化剂,对十氯联苯(CB209)进行了催化降解研究.结果表明,MgO对CB209的降解具有较高的活性.在反应温度为300℃,反应时间为60 min时,MgO对CB209的降解效率达到98.9%.进一步研究表明,MgO催化降解CB209的动力学符合准一级动力学反应.通过GC-MS和GC-ECD,并结合衍生化实验,检测到九氯联苯、五氯苯和四氯苯、五氯苯酚、四氯苯酚和三氯苯酚等降解产物,进而推测出MgO催化降解CB209的过程中存在相互竞争的反应路径:氧化反应、碳碳桥键断裂和加氢脱氯. 相似文献
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本文主要研究阴极脱氯协同阳极(多孔Ti/BDD 电极)电催化氧化对于对氯苯酚的电化学降解过程. 在有无阳离子交换膜电解槽体系下电化学降解对氯苯酚的实验结果表明,对氯苯酚的矿化主要在阳极区进行;无隔膜电解槽体系下,对氯苯酚在阴极还原形成的氯离子迁移到阳极,在阳极表面进一步生成了具有强催化氧化作用的活
性氯,与阳极产生的羟基自由基协同降解对氯苯酚;在阳离子交换膜电解槽体系下,阴极产生的氯离子难以通过阳离子膜迁移至阳极区,无隔膜电解槽呈现出更好的降解效率. 结合高效液相色谱技术确定阳极室的中间产物为对苯二酚、邻苯二酚、对苯醌和苯酚等,阴极室的主要产物是苯酚,并根据中间产物提出了对氯苯酚的降解路径. 相似文献
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氯掺杂二氧化钛柱撑蒙脱土的合成及光催化性能 总被引:1,自引:0,他引:1
采用溶胶 凝胶法制备了氯掺杂二氧化钛柱撑蒙脱土催化剂。 利用XRD、SEM、UV-Vis-DRS、光致发光谱(PLS)、N2吸附-脱附和XPS等测试技术对其进行了表征。 结果表明,该催化剂具有明显的锐钛矿相结构,且氯掺杂与二氧化钛柱撑后,蒙脱土的层间结构没有完全被破坏;氯掺杂拓宽了其光吸收范围,在可见光区吸收增强;其带隙能由3.19 eV减小至3.14 eV;氯以阴离子形式存在于TiO2晶格中。 对硝基苯胺降解实验表明,氯掺杂可显著提高二氧化钛柱撑蒙脱土的光催化活性,氯掺杂量为6%(与钛的摩尔比)的催化剂具有较好光催化活性。 相似文献
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纳米级Pd/Fe双金属体系对水中2,4-二氯苯酚脱氯的催化作用 总被引:15,自引:0,他引:15
利用化学沉淀法制备了纳米级Fe和纳米级Pd/Fe双金属催化剂,研究了它们对2,4-二氯苯酚(2,4-DCP)还原脱氯的催化性能. 结果表明,纳米级颗粒具有较高的比表面积和表面反应活性,其BET比表面积可达12.4 m2/g,当Pd/Fe用量为6 g/L时,2,4-DCP脱氯率达到90%以上. 脱氯效率与pH值、温度、钯含量和Pd/Fe投加量等因素有关. 2,4-DCP在脱氯过程中先生成2-氯苯酚和4-氯苯酚,最终生成苯酚,而少量的2,4-DCP可直接降解成苯酚. 相似文献
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The gas phase hydrodechlorination of methanolic and mixed methanol/water solutions of 2-chlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol has been studied at 573 K over nickel/silica catalysts of varying (1.5–20.3 wt.% Ni) nickel loading. Each catalyst was 100% selective in promoting hydrodechlorination: the variation of catalytic activity and selectivity with time-on-stream is illustrated and catalyst deactivation is addressed. Dechlorination is quantified in terms of specific rate constants, phenol selectivity/yield and chlorine removal efficiencies. Increasing the nickel loading resulted in a marked increase in dechlorination efficiency while the introduction of water into the feed lowered the activity. 相似文献
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碳纳米管负载Pt-Sn-B非晶态催化剂催化氯代硝基苯 总被引:16,自引:0,他引:16
用浸渍-化学还原法制备了碳纳米管负载的Pt-Sn-B非晶态催化剂,并采用透射电子显微镜、X射线衍射、选区电子衍射、X射线能谱等表征手段研究了催化剂在碳纳米管表面的存在状态、组成及其非晶性质. 将此催化剂用于三种氯代硝基苯的液相催化加氢反应,结果表明该催化剂具有较好的加氢性能和较高的抑制脱卤性能. 在不添加脱卤抑制剂的情况下,三种氯代硝基苯的转化率均高于99.8%,脱卤率小于1.9%. 而将通用加氢催化剂用于相同的反应时,产物的脱卤率均高于8%. 碳纳米管的特殊结构与表面金属的非晶性质是影响氯代硝基苯加氢性能的主要因素. 讨论了碳纳米管与表面非晶态金属的作用规律及其与催化加氢性能的关系. 相似文献
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E. S. Lokteva S. A. Kachevskii A. O. Turakulova E. V. Golubina V. V. Lunin A. E. Ermakov M. A. Uimin A. A. Mysik 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(8):1300-1306
Metal-carbon nanocomposites based on nickel, palladium, and iron and bimetallic palladium-nickel-carbon nanocomposites were
for the first time used as catalysts of hydrodechlorination of chlorobenzene in the vapor phase in the atmosphere of hydrogen.
Nickel and Pd-Ni nanoparticles completely coated by a carbon layer not only were stable to oxidation and agglomeration but
also exhibited considerable activity in hydrodechlorination of chlorobenzene at temperatures much lower than those at which
dechlorination on carbon carriers occurred. The dependence of catalytic properties (activity, selectivity, and stability)
on temperature and nanocomposite composition was studied. Depending on the nature of the metal, the composition of bimetallic
particles and temperature the selectivity could be changed, and the reaction could be directed toward the formation of benzene
or cyclohexane. Carbon coating was stable under reaction conditions at least up to 350°C and did not hinder hydrodechlorination.
Substrate adsorption likely occurred on the outside carbon surface of composite particles. The activity and structure of Ni@C
composite remained almost unchanged after triple cycling over the temperature range from 50 to 350°C in a flow system. 相似文献
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Xinhuan Yan Junqing Sun Yongbin Fang Zhenyuan Xu Wenjing Wang 《Frontiers of Chemistry in China》2006,1(1):41-44
The Pt-Sn-B/carbon nanotubes (CNTs) catalyst was prepared by impregnation-chemical reduction method. Its catalytic performance
was evaluated by liquid-phase hydrogenation of chloronitrobenzene (CNB). The results showed that the catalyst had higher catalytic
performance than common hydrogenation catalysts. The conversion of CNB could reach 99.9%, and the dechlorination of chloroaniline
(CAN) was less than 1.9% when catalyzed by Pt-Sn-B/CNTs and more than 8.0% when catalyzed by common hydrogenation catalysts.
X-ray diffraction and selected area electron diffraction analysis showed that Pt-Sn-B/CNTs had an amorphous alloy structure
that can improve catalytic performance. Transmission electron micrograph image showed that the catalyst particles were highly
distributed on the surface of CNTs. The hydrodechlorination of CNB was mainly affected by the unique structure of CNTs and
the nature of the amorphous metals on the surface of CNTs. The relationship between the interaction of CNTs and amorphous
metals and the catalytic performance of the catalyst is also discussed.
Translated from the Chinese Journal of Catalysis, 2005, 26(3) (in Chinese) 相似文献
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V. A. Yakovlev V. I. Simagina S. N. Trukhan V. A. Likholobov 《Kinetics and Catalysis》2000,41(1):25-32
Liquid-phase hydrodechlorination of hexachlorobenzene was kinetically studied in the presence of both nickel (Ni/C) and palladium-promoted
nickel (2%PdNi/C) catalysts under different reaction conditions. Molecular hydrogen (at 1 and 20 atm) and sodium borohydride
(NaBH4) were used as reducing agents. In the presence of the nickel catalyst, the hydrodechlorination of C6Cl6 occurs via a consecutive mechanism (removal of one chlorine atom from the substrate at each stage), whereas with the 2%PdNi/C
catalyst, the transformation of C6Cl6 occurs via both consecutive and multiplet mechanism (with the elimination of several chlorine atoms without desorption of
the chloroaromatic substrate from the catalyst surface). The promotion of the nickel catalysts with palladium substantially
changes the selectivity of formation of intermediate products of C6C16 dechlorination. The mechanism of hydrodechlorination of hexachlorobenzene was suggested that explained the presence of only
certain products of partial dechlorination of hexachlorobenzene in the reaction medium. 相似文献
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Hui Min MA* Jens WOHLERS Uwe MEIERHENRICH Axel BERNECKER Vera SULING Wolfram THIEMANN Center for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing Department of Chemistry University of Bremen D- 《中国化学快报》2001,(3)
As a result of its widespread use in industry and agriculture1, 2,4,6-trichlorophenol (TCP) becomes one of the most important pollutants in the environment (aqueous systems and soils). Furthermore, TCP is persistent, and polychlorinated dibenzo-p-dioxins and dibenzo-furans have also been found in chlorophenol-contaminated soils2. Therefore, the removal of TCP from the environment has invoked a great attention3, and various treatment techniques have been proposed for this purpose, involving … 相似文献
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《中国化学快报》2020,31(10):2762-2768
Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal’s electrocatalytic hydrodechlorination performance in converting 2,4-dichlorophenol (2,4-DCP) to phenol. The specific activity of the Pd nanoparticles (Pd NPs) on defective polymer carbon nitride (Pd/PCN-x) reaches 0.09 min-1 m-2Pd, which is 1.5 times that of the Pd NPs supported on the perfect PCN (Pd/PCN-0). The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites, limiting the dechlorination progress. The PCN-x containing -C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs, and promote the preferential adsorption of 2,4-DCP rather than phenol, resulting in an enhanced dechlorination efficiency. 相似文献
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G. Ya. Gerasimov 《High Energy Chemistry》2001,35(6):389-393
The efficiency of the electron-beam treatment of power-plant flue gases for the removal of sulfur and nitrogen oxides was examined as applied to the removal of dioxins from the gases. A kinetic scheme of the process was proposed. It involves gas-phase and liquid-phase degradation of dioxin molecules by OH radicals formed under the action of ionizing radiation on gas macrocomponents. It was found that gas toxicity due to dioxins decreased by an order of magnitude at radiation doses typical of the method. 相似文献