共查询到18条相似文献,搜索用时 130 毫秒
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采用溶胶凝胶法制备了Cu-TiO_2/SiO_2催化剂,用XPS、XRD、SEM和UV-Vis对催化剂进行表征与分析。以催化剂对水中硝酸盐氮的还原效果为评价标准,研究其催化性能。结果表明:本实验条件下,当Cu~(2+)、TiO_2两者质量比是0. 5%时所制备的催化剂光催化还原水中NO_3-N效果最好,催化剂中的铜以CuO的状态存在,Cu掺杂不会严重影响催化剂中锐钛矿型TiO_2晶型结构和粒径。 相似文献
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随着工农业的迅速发展,人类大规模的固氮活动破坏了自然界氮素循环的平衡。水中硝酸盐氮的污染问题日渐引起人们的关注,去除水中硝酸盐的常规方法都有其难以克服的缺点。双金属催化还原法是一种新型的水脱氮技术,该方法具有反应速率快、生成氮气选择性高、能耗低且易操作等优点。文章在综述双金属催化还原水中硝酸根研究进展的基础上,重点对双金属催化剂性质、反应机理、传质过程、催化剂选择与制备进行了详细阐述,提出有效提高硝酸盐还原速度的同时控制反应发生的方向是该技术的关键;寻求高效、高选择性和稳定性的催化剂,探索多工艺组合及催化剂性能优化是该领域的研究方向。 相似文献
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采用分步浸渍法和共浸渍法制备系列Pd负载质量分数为1%的Pd-Cu/γ-Al2O3双金属催化剂,以氢气为还原剂研究其对水中硝酸盐催化脱除的性能。结果表明,催化剂中Cu与Pd物质的量比以及Cu、Pd的浸渍顺序对催化剂性能有重要影响,硝酸根转化率随着Cu与Pd物质的量比的增大而增大;硝酸根转化活性以Cu与Pd物质的量比为5∶1、先浸渍Pd再浸渍Cu所得催化剂较优;从氨氮选择性方面看,以先浸渍Cu后浸渍Pd制备的催化剂选择性较低,在Cu与Pd物质的量比为1∶1、先浸渍Cu再浸渍Pd所得催化剂较优。 相似文献
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通过以活性炭载体浸渍负载钯铜双金属制备的催化剂,利用半连续试验,研究了活性炭载体双金属催化剂对水中硝酸盐的催化还原去除的特点和规律.结果表明,在负载钯/铜原子比为1∶1、金属负载量Pd质量分数为1.2%、Cu质量分数为0.72%时,催化剂具有最佳的活性与选择性;最佳H2流量为100 mL· min-1,此时催化反应进行迅速,选择性较好;溶液pH过高或者过低对催化剂活性和选择性都有不利影响,适宜的溶液pH控制范围为4.5~5.5;对于初始质量浓度为100 mg·L-1的硝酸盐溶液,反应时间为2h时,硝酸盐去除率可达96%以上,氨氮生成率为22%. 相似文献
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以凹凸棒石黏土(APT)作载体,采用浸渍法制备双金属催化剂Pd-Cu/APT、单金属催化剂Pd/APT和Cu/APT,在连续流动微反装置上考察催化剂的CO催化氧化活性,采用N_2物理吸附/脱附、X射线粉末衍射和程序升温还原/脱附等手段对催化剂进行表征。结果表明,Pd-Cu/APT催化剂中Cu主要以CuCl形式存在,Pd高度分散与Cu之间产生了明显的相互作用,使Cu物种的还原温度大幅降低;经水蒸汽预处理增强了Pd-Cu/APT催化剂表面酸性,促进了催化活性的提高。在CO体积分数为0.5%、水蒸汽体积分数3.3%、空速6 000h^(-1)和常温反应条件下,CO转化率可达90%以上。 相似文献
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Adsorption and reduction of nitrate in water on hydrotalcite-supported Pd-Cu catalyst 总被引:2,自引:0,他引:2
The hydrotalcite-supported Pd-Cu catalysts were successfully prepared by the impregnation or coprecipitation method, and their adsorption and catalytic reduction activity for nitrate in water were evaluated. The catalysts were characterized by X-ray diffraction (XRD) and surface area (BET) analysis. The results demonstrated that hydrotalcite-supported Pd-Cu catalysts could significantly adsorb nitrate ions, and then, effectively catalytically reduce them. The excellent adsorption ability for nitrate resulted from the regenerated layer structure of calcined hydrotalcite catalyst in nitrate aqueous solution. Nitrate was forced into the interlayer space and adsorbed on the external surface. The adsorption kinetics and the adsorption isotherm could be well described by pseudo-second-order model and the Langmuir model, respectively. The comparison of catalytic reduction with the adsorption for nitrate indicated that catalytic hydrogenation activity for nitrate increased with increasing adsorption capacity; nitrate reduction on hydrotalcite-supported Pd-Cu catalysts was a consecutive and dynamic adsorption and catalytic hydrogenation process. In addition, the catalyst obtained by coprecipitation method, with intact regeneration of hydrotalcite structure and a high dispersion of active metals, hold higher adsorption and catalytic activity than that prepared by co-impregnation method. 相似文献
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以凹凸棒土(APT)为载体,NH3·H2O为沉淀剂,采用沉积-沉淀法制备Pd-Cu/APT催化剂。在连续流动微反装置上,考察不同沉淀温度对Pd-Cu/APT催化剂CO常温催化氧化性能的影响。利用N2物理吸附-脱附、XRD、FT-IR和H2-TPR等对Pd-Cu/APT催化剂进行表征。结果表明,不同沉淀温度制备的催化剂均含有Cu2Cl(OH)3和CuO两种形式的Cu物种,但与沉淀温度25℃和90℃制备的催化剂相比,沉淀温度70℃制备的催化剂具有更多的活性Cu2Cl(OH)3物种,这有利于Pd2+物种的再生,显著提高其CO常温催化氧化活性。 相似文献
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I. I. Obraztsova N. K. Eremenko G. Yu. Simenyuk A. N. Eremenko B. G. Tryasunov 《Solid Fuel Chemistry》2012,46(6):364-367
The catalytic activity of bimetallic Pd-Ni, Pd-Cu, and Pd-Ag catalysts in the reaction of nitrobenzene hydrogenation was studied. It was found that the rate of hydrogenation on the bimetallic catalysts was higher than that on palladium metal (palladium black), and it depended on catalyst preparation pro cedures. The catalytic activity of the bimetallic systems increased in the order Pd-Cu< Pd-Ag ? Pd-Ni. 相似文献
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《Catalysis communications》2007,8(5):773-776
The effects of acetic acid pretreatment for dried catalysts prepared from cobalt nitrate were investigated. Cobalt catalyst prepared from cobalt nitrate, followed by treatment of 2.2 M acetic acid, namely CoN/2.2Ac catalyst, showed the highest CO conversion as well as the lowest CO2 and CH4 selectivities in liquid-phase Fischer–Tropsch synthesis. On the contrary, cobalt catalyst prepared from cobalt acetate exhibited poor catalytic activity due to very low reduction degree of supported cobalt. The higher catalytic activity for CoN/2.2Ac catalyst could be ascribed to the formation of the mixture of cobalt nitrate and cobalt acetate with suitable ratio between them during acetic acid treatment, which led to an optimum balance between the dispersion and reduction degree of supported cobalt, eventually realizing the higher catalytic activity. Various catalysts were characterized by XRD, TPR and H2 chemisorption. 相似文献
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采用沉积-沉淀法制备Pd-Cu/凹凸棒土(PC/APT)催化剂,以CO氧化为探针反应,在连续流动微反装置上考察其常温潮湿环境下CO催化氧化性能。作为对比,同时采用常规浸渍法制备催化剂。通过N2物理吸附-脱附、XRD、FT-IR和TPR等对催化剂结构和性质进行表征。结果表明,与浸渍法制备的催化剂不同,采用沉积-沉淀法制备的PC/APT催化剂上Cu物种分别以Cu_2Cl(OH)_3和CuO形式存在,其中,Cu_2Cl(OH)_3物种与Pd物种间相互作用较强,催化剂还原性能显著提高,表现出良好的CO催化氧化活性。在空速6 000 h~(-1)、CO体积分数0.5%和水蒸汽体积分数3.3%条件下,采用沉积-沉淀法制备的PC/APT催化剂上CO转化率大于84%的时间不低于160 min。 相似文献
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采用助催化剂对丝光沸石进行改性,通过红外光谱(FT—IR)方法表征了该改性分子筛制备的催化剂样品表面酸性的变化,并探讨了酸性变化对甲苯歧化与烷基转移反应催化活性的影响。结果表明,助催化剂WO3的加入能有效地调节催化剂表面酸性,经氢气还原后催化剂B酸量随助催化剂量增加而增加,且与助催化剂相对含量呈对数关系;而L酸量随助催化剂相对含量的增加先上升,随后趋于平稳;催化剂的反应活性随助催化剂含量的增加而增加,但副反应也随之加大。 相似文献