共查询到18条相似文献,搜索用时 212 毫秒
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本文综述了负载金催化剂在制备与应用方面研究的进展。讨论了负载纳米金催化剂活性的主要影响因素(制备方法、载体的选择、焙烧温度和预处理条件),详细地评述了负载金催化剂在化学工业和环境保护方面中应用的研究进展。本文涉及金催化剂在cO选择性氧化、乙炔氢氯化、水煤气变换反应、CO低温(常温)氧化、氮氧化物的还原催化应用。 相似文献
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以人工合成的双羟基金属氢氧化物ZnAl-LDHs为载体,将预先制备的金溶胶通过静电吸附的方式负载到载体上,获得了纳米金催化剂Au/ZnAl-LDHs,用X射线粉末衍射(XRD)表征了催化剂的物相,用透射电镜(TEM)观察了纳米金颗粒的粒径分布,以CO的常温催化氧化为模型反应,分别考察了金溶胶制备过程中金前体HAuCl4·6H2O的浓度和还原剂THPC的用量、负载过程的pH值以及金的负载量等因素对金催化剂的活性和稳定性的影响。结果表明:在制备金溶胶的过程中,降低HAuCl4·6H2O的浓度并提高还原剂THPC的用量,可以制备出粒径分布处于1~7nm之间、平均粒径仅3.87nm的负载型纳米金颗粒,其对CO的常温转化率为100%,且其催化活性的稳定性明显提高;而在金溶胶的吸附负载过程中,使体系的pH值处于6~7的范围,有利于金溶胶在ZnAl-LDHs载体上的吸附负载,从而得到实际负载量更接近理论负载量的金催化剂样品,当金的实际负载量接近1%(质量分数)时,能够确保对CO的常温氧化转化率达到100%。 相似文献
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电子产业对所使用的气体纯度要求越来越高,气体的纯化工艺变得尤为重要。文中引入了第五周期过渡金属、稀土金属,并考察这些助剂对Au/Fe2O3催化剂性能的影响规律,以期筛选出具有高活性和高稳定性的CO氧化负载型纳米Au/Fe2O3-MOx催化剂,为负载型纳米金催化剂在高纯气体生产领域的应用奠定良好的基础。 相似文献
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以介孔结构的复合ZrO2-TiO2为载体负载活性组分, 制备了具有高CO催化氧化活性的Pd/ZrO2-TiO2与PdCu/ZrO2-TiO2负载型催化剂。XRD、TEM研究结果表明: 活性组分Pd、Cu物种可均匀分散于介孔载体中。系统考察了不同的催化剂载体、制备方法和助催化剂等对该介孔复合材料CO催化氧化性能的影响, 结果表明: 以ZrO2-TiO2为载体的催化剂其CO催化氧化活性明显优于以介孔Al2O3或介孔SBA-15为载体的催化剂; 一步法制备的介孔Pd/ZrO2-TiO2催化剂其CO催化氧化的低温活性较浸渍法制备的Pd/ZrO2-TiO2有很大提高; 并且Pd和Cu物种共负载的介孔ZrO2-TiO2复合催化剂具有最优的CO催化氧化活性, 其CO的完全催化氧化温度可降至170℃, O2-TPD分析说明Pd和Cu之间的相互作用使得PdCu/ZT催化剂在更低温度具有氧化还原活性。 相似文献
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单分散纳米CeO_2和Cu-Ce-O催化剂的制备、表征及其催化性能 总被引:1,自引:0,他引:1
以硝酸铈、硝酸铜和氢氧化钠为原料,使用超声双雾化工艺实现微区反应制备了纳米CeO2粉体和掺铜CeO2复合粉体,并利用XRD、TEM、HR-TEM、FT-IR和BETN2等手段对其成分、物相结构、形貌及颗粒大小进行表征;并将所制备的粉体作为催化剂考察其对CO的催化氧化性能.结果表明,所制备的纳米CeO2粉体和掺铜CeO2复合粉体粒径均为4~5 nm,球形,粒度分布均匀,且单分散性好;CeO2催化剂粉体粒径越小、比表面积越大,对CO的催化氧化活性越高;Cu-Ce-O催化荆对CO具有最好的催化氧化活性,表明铜的掺入有利于明显提高CeO2催化剂在CO催化氧化反应中的低温活性,降低起燃温度. 相似文献
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Since Haruta et al. discovered that small gold nanoparticles finely dispersed on certain metal oxide supports can exhibit
surprisingly high activity in CO oxidation below room temperature, heterogeneous catalysis by supported gold nanoparticles
has attracted tremendous attention. The majority of publications deal with the preparation and characterization of conventional
gold catalysts (e.g., Au/TiO2), the use of gold catalysts in various catalytic reactions, as well as elucidation of the nature of the active sites and
reaction mechanisms. In this overview, we highlight the development of novel supported gold catalysts from a materials perspective.
Examples, mostly from those reported by our group, are given concerning the development of simple gold catalysts with single
metal-support interfaces and heterostructured gold catalysts with complicated interfacial structures. Catalysts in the first
category include active Au/SiO2 and Au/metal phosphate catalysts, and those in the second category include catalysts prepared by pre-modification of supports
before loading gold, by post-modification of supported gold catalysts, or by simultaneous dispersion of gold and an inorganic
component onto a support. CO oxidation has generally been employed as a probe reaction to screen the activities of these catalysts.
These novel gold catalysts not only provide possibilities for applied catalysis, but also furnish grounds for fundamental
research. 相似文献
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Kim KJ Song JK Shin SS Kang SJ Chung MC Jung SC Jeong WJ Ahn HG 《Journal of nanoscience and nanotechnology》2011,11(2):1605-1608
Gold catalysts supported on Co3O4 were prepared by co-precipitation (CP), deposition-precipitation (DP), and impregnation (IMP) methods. The Au/Co3O4 catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR) to understand the different activities for CO oxidation with different preparation methods. Gold particles below 5 nm supported on Co3O4 by DP method were found to be more exposed to the surface than those by CP and IMP methods, and this catalyst was highly active and stable in CO oxidation. Finally, catalytic activity of Au/Co3O4 catalyst for CO oxidation was strongly dependent on the gold particle size. 相似文献
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《Materials Research Bulletin》2006,41(2):406-413
Cobalt-containing SBA-15 supported gold catalysts for low-temperature CO oxidation were prepared and characterized by N2 adsorption/desorption, X-ray diffraction, transmission electron microscopy, inductively coupled plasma-atom emission spectroscopy and X-ray photoelectron spectroscopy techniques. The effects of cobalt and gold content on the catalyst activity were investigated in detail. Among them, 2% Au/40% Co/SBA-15 shows the highest activity, its complete conversion temperature for CO is at 273 K. It was believed that both the dispersion of Co3O4 and the high surface areas caused by SBA-15 contribute to the good activities of cobalt-containing SBA-15 supported gold catalysts. Furthermore, the strong metal-support interaction between gold and cobalt oxides is greatly related to the catalytic performance. 相似文献
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We study the catalytic capability of unsupported single-walled helical gold nanotubes Au(5,3) by using density functional theory. We use the CO oxidation as a benchmark probe to gain insights into high catalytic activity of the gold nanotubes. The CO oxidation, catalyzed by the Au(5,3) nanotube, proceeds via a two-step mechanism, CO + O2 --> CO2 +O and CO + O --> CO2. The CO oxidation is initiated by the CO + O2 --> OOCO --> CO2 + O reaction with an activation barrier of 0.29 eV. On the reaction path, a peroxo-type O-O-CO intermediate forms. Thereafter, the CO + O --> CO2 reaction proceeds along the reaction pathway with a very low barrier (0.03 eV). Note that the second reaction cannot be the starting point for the CO oxidation due to the energetically disfavored adsorption of free O2 on the gold nanotube. The high catalytic activity of the Au(5,3) nanotube can be attributed to the electronic resonance between electronic states of adsorbed intermediate species and Au atoms at the reaction site, particularly among the d states of Au atom and the antibonding 2pi* states of C-O and O1-O2, concomitant with a partial charge transfer. The presence of undercoordinated Au sites and the strain inherent in the helical gold nanotube also play important roles. Our study suggests that the CO oxidation catalyzed by the helical gold nanotubes is likely to occur at the room temperature. 相似文献
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《材料科学技术学报》2020,(5)
The interface between metal nanoparticles(NPs) and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface. However, the rational design of interfacial structure facilitating the charge transfer between the neighboring parts remains a challenge.Herein, a guided nucleation strategy based on redox reaction between noble metal precursor and supportsurface is introduced to construct epitaxial interfaces between Pt NPs and CeO_2 support. The Pt/CeO_2 catalyst exhibits near room temperature catalytic activity for CO oxidation that is benefited from the well-defined interface structure facilitating charge transfer from CeO_2 support to Pt NPs. Meanwhile, this general approach based on support-surface-induced-nucleation was successfully extended to synthesize Pd and Cu nanocatalysts on CeO_2, demonstrating its universal and feasible characteristics. This work is an important step towards developing highly active supported metal catalysts by engineering their interfaces. 相似文献
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Qingming Deng Lina Zhao Xingfa Gao Meng Zhang Youhua Luo Yuliang Zhao 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(20):3506-3513
The catalytic behavior of transition metals (Sc to Zn) combined in polymeric phthalocyanine (Pc) is investigated systematically by using first‐principles calculations. The results indicate that CoPc exhibits the highest catalytic activity for CO oxidation at room temperature with low energy barriers. By exploring the two well‐established mechanisms for CO oxidation with O2, namely, the Langmuir–Hinshelwood (LH) and the Eley–Rideal (ER) mechanisms, it is found that the first step of CO oxidation catalyzed by CoPc is the LH mechanism (CO + O2 → CO2 + O) with energy barrier as low as 0.65 eV. The second step proceeds via both ER and LH mechanisms (CO + O → CO2) with small energy barriers of 0.10 and 0.12 eV, respectively. The electronic resonance among Co‐3d, CO‐2π*, and O2‐2π* orbitals is responsible for the high activity of CoPc. These results have significant implications for a novel avenue to fabricate organometallic sheet nanocatalysts for CO oxidation with low cost and high activity. 相似文献
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Pt/Al(2)O(3)-CeO(2) nanocatalysts with Pt loading of 1% and ceria loading of 10, 20 and 30% were successfully prepared via wet impregnation method to be utilized in catalytic oxidation of BTX. The nanocatalysts were characterized using XRD, FESEM, TEM, N(2) adsorption, FTIR and TPR-H(2) techniques. The XRD patterns confirmed the formation of cerium oxide as the crystalline phase on alumina with the average crystallite size of 8.1-8.7 nm, derived by Scherrer equation. FESEM images confirmed that these nanocatalysts had ceria particles in nano-ranges. TEM analysis showed that platinum particles were fairly well dispersed on Al(2)O(3)-CeO(2) with an average size of 5-20 nm. BET surface area presented large surface area for nanocatalysts. TPR patterns showed that by adding 1% platinum to support, the reducibility is highly increased. These patterns also revealed the promoting effect of ceria on reducibility of Pt and Al(2)O(3). The results of toluene oxidation indicated that the synthesized nanocatalysts were highly active and able to remove nearly 100% of toluene and xylene and about 85% of benzene as representative VOCs. The presence of nanoparticles along with good characteristics of the synthesized nanocatalysts presented them as highly efficient materials for catalytic oxidation of VOCs. 相似文献