可见光增强g-C_3N_4/Co_3O_4胶体催化剂的催化产氢性能

通过水热法制备了具有可见光增产氢高性能的g-C_3N_4/Co_3O_4胶体催化剂,采用XRD、TEM、SEM和EDS等分析样品的组成和形貌结构。催化产氢结果表明,光照条件下g-C_3N_4/Co_3O_4胶体催化剂具有极高的催化产氢活性,TOF值高达58.2 min~(-1),通过拟合温度动力学曲线,得到了催化反应的活化能为15.73 kJ·mol~(-1)。对样品进行UV-vis和PL测试发现,g-C_3N_4/Co_3O_4胶体催化剂具有极高的光能利用率和电子-空穴分离率,并进一步阐述了光能促进催化产氢的作用机理。     

CO3O4/MPS催化氧化NO性能

微乳法制备的介孔二氧化硅（MPS）负载Co3O4构成了Co3O4/MPS催化剂,考察了负载量、焙烧温度等制备条件和反应温度、空速、NO进口浓度、O2体积分数等操作条件对Co3O4/MPS催化氧化NO性能的影响,并对载体及催化剂进行了BET和XRD表征。结果表明：MPS比表面积远大于其它载体,Co3O4呈立方晶型,MPS负载25%的Co3O4在300 ℃下焙烧3 h得到催化剂的晶体颗粒最小,分散性好,具有最佳催化氧化活性和良好的稳定性,在NO进口浓度500 μL/L、O2体积分数10%、空速12 000 h－1的条件下,250 ℃时NO氧化率可达50%～60%（此时可获得最高的NOx吸收效率）,300 ℃氧化率达到80%以上,接近热力学平衡值。     

CuO对Co_3O_4-CeO_2催化剂富氢气条件下CO优先氧化性能的影响

CO优先氧化方法是去除富氢气CO中最为有效的方法,而且钴铈催化剂又受到重点研究和关注。通过共沉淀法制备不同CuO掺杂量的8Co_3O_4-1CeO_2-c CuO催化剂,使用透射电镜、高分辨透射电镜、X射线粉末衍射、N_2吸附-脱附和程序升温还原以及比表面积等测试手段对催化剂进行表征,并对其在富氢气条件下CO优先氧化性能进行研究。结果表明,掺杂适量CuO的钴铈催化剂,其催化活性较未添加CuO的催化剂明显提高,其中钴铈铜物质的量比为8∶1∶1的催化剂其CO完全转化温度降低至115℃,同时添加适量CuO的催化剂粒径明显减小,表面分散度改善,增强了Cu-Co-Ce间相互作用,具有较好的催化活性。     

Fe/γ-Al2O3催化剂上CO同时还原NO和SO2研究

研究了不同载体(γ - Al2O3 HZSM -5、TiO2、SiO2和MgO)负载Fe催化剂上CO还原NO反应及CO同时还原NO和SO2反应.结果表明,Fe/γ - Al2O3催化剂对CO与NO反应具有良好的催化活性,但随着反应时间的延长,催化剂很快失活;在CO和NO反应中加入SO2,可以明显改善Fe/γ-Al2O3催化剂对CO还原NO反应的活性稳定性;O2和H2O对催化剂活性的影响较大,CO2对催化剂的影响较小.XRD结果表明,FeS2是催化剂的活性中心,在CO与NO反应后,FeS2转变为催化惰性的Fe7S8而导致催化剂活性下降;在CO与NO及SO2反应体系中引入O2后,Fe/γ - Al2O3催化剂上的活性组分FeS2被氧化为Fe2O3,导致催化剂失活.     

负载方式对Ag/Co_3O_4催化剂催化氧化甲醛活性的影响

采用硬模板法原位负载(insitu)和后浸渍(post)法制备了介孔Ag/Co3O4和不负载的介孔Co3O4催化剂,考察了它们对甲醛的催化氧化活性,其中后浸渍法负载的催化剂(Ag/Co3O4-post)展示了最优的活性。对各催化剂样品的表征发现,Ag/Co3O4-post在负载Ag的制备过程中介孔结构塌陷,但同时其还原能力增强,并且暴露出最多的表面Co3+和缺陷氧,进而使其具有最强的催化氧化甲醛的活性。     

加热时间对Co_3O_4颗粒光催化性能的影响

以Co(NO_3)_2·6H_2O和CO(NH_2)_2为原料,十六烷基三甲基溴化铵为活性剂,采用水热-热分解法在不同加热时间(2 h、3 h、4 h、5 h)条件下制备纯相尖晶石结构的Co_3O_4颗粒。利用X射线衍射和电子扫描电镜研究Co_3O_4颗粒的结构和形貌,并以甲基橙为模拟废水,研究加热时间对Co_3O_4颗粒光催化性能的影响。结果表明,加热时间对Co_3O_4颗粒形貌影响很大,并直接影响其光催化性能。加热时间5 h制备的Co_3O_4结构疏松多孔,光催化性能最好,光照20 min,甲基橙降解率达95%。     

La2O3/AC催化剂在CO同时还原SO2和NO反应中的性能

以改性活性炭为载体,采用等体积浸渍法制备了La₂O₃/AC催化剂。采用XRD和BET手段对催化剂进行表征,使用微型固定床反应器考察催化剂的脱硫脱硝活性。结果表明,La₂O₃/AC催化剂对CO同时还原SO₂和NO具有良好活性,负载质量分数10%的La₂O₃/AC催化剂活性较好,SO₂和NO转化率达到90%的反应温度最低,分别为335 ℃和325 ℃;载体与活性组分之间存在协同作用,引入活性炭载体能够降低反应温度并提高催化活性。     

C3H6选择性催化还原NO催化剂Ag／γ—A12O3的研究

采用低负载量的(0～3％)Ag／γ-A12O3体系作为C3H6选择性催化还原(C3H3-SCR)NO的催化剂，考察了银负载量、反应温度、空速对NO转化率的影响．同时对于原料气中氧的作用进行了研究．结果表明：银负载量为1．5％时，催化剂表现出最高的反应活性；在考察的条件范围内，原料气中含氧对NO的还原有促进作用，适宜的氧浓度为0．27％；反应温度的过高会导致还原气中C3H6大幅度转化为CO2。     

焙烧温度对CuO/Co_3O_4-CeO_2催化剂CO优先氧化性能的影响

采用浸渍法制备了Cu O/Co3O4-Ce O2(Cu Co Ce10)催化剂,考察了在不同温度(250、300、350、400和450℃)焙烧后的样品在富氢气氛中对CO优先氧化反应的催化性能。应用BET、XRD、H2-TPR及XAFS技术详细表征了催化剂的结构与性能。结果表明,不同温度焙烧的催化剂中,铜物种均主要以Cu O相存在;350℃焙烧的Cu Co Ce10催化剂具有最大的比表面积和最好的氧化还原性能,在98~173℃的温度范围内能够将CO完全转化为CO2,呈现出最宽的CO优先氧化可操作温度窗口,以及良好的催化活性稳定性。     

Mn-Cu-Ce-Fe/REY系列催化剂上NH3选择性催化还原NO性能

采用正交实验设计和浸渍法制备Mn-Cu-Fe-Ce/REY催化剂。采用固定床微型反应器评价SO₂存在下催化剂在NH₃选择性催化还原NO反应中的活性,考察Mn、Cu、Fe和Ce各活性组分对催化剂活性的影响,并采用XRD、H₂-TPR和SEM等手段对催化剂进行表征。结果表明,Mn、Cu、Fe和Ce各活性组分对催化剂活性影响顺序为：Cu＞Fe＞Ce＞Mn,催化剂的氧化还原性能影响催化剂活性。     

Catalytic reduction of N2O with CH4 and C3H6 over Ag–Rh/Al2O3 bimetallic catalyst in the presence of oxygen

A study of nitrous oxide (N₂O) reduction with methane (CH₄) and propene (C₃H₆) in the presence of oxygen (5%) over Ag/Al₂O₃, Rh/Al₂O₃ and Ag–Rh/Al₂O₃ catalysts, with Ag and Rh loadings of 5 wt% and 0.05 wt% respectively, has been performed. From the results, it was observed that the Ag–Rh bimetallic catalyst was the most active for both nitrous oxide removal (more than 95%) and hydrocarbon oxidation. This high activity seems to be connected with a synergistic effect between Ag and Rh. The findings from X‐ray diffraction and X‐ray photoelectron spectroscopy studies showed also, that there were no strong interactions (eg alloying) between Ag and Rh. Copyright © 2005 Society of Chemical Industry     

CuO/Al2O3催化剂上CO还原NO反应条件的研究

为减小工业废气中氮氧化物对环境的污染,以多价态金属助剂修饰的Cu/Al₂O₃为催化剂,采用以CO为还原剂的催化还原法进行消除氮氧化物的研究,考察工艺条件对催化剂反应性能的影响。结果表明,反应温度240 ℃即可实现NO的完全转化,较低空速有利于催化剂长周期稳定运行,助剂最佳质量分数为6%,降低或提高助剂含量均不利于NO的完全转化,体系中CO含量影响催化剂性能,CO含量过高会打破催化剂活性中间体的动态平衡,导致催化剂快速失活,应严格控制CO含量。     

The effect of hydrogen on the selective catalytic reduction of NO in excess oxygen over Ag/Al2O3

The selective catalytic reduction (SCR) of nitrogen oxides (NO_x) by propane in the presence of H₂ on sol–gel prepared Ag/Al₂O₃ catalysts (0.5–5 wt.% Ag) was investigated. It was confirmed that hydrocarbon-assisted SCR of NO_x is remarkably enhanced by co-feeding hydrogen to a lean exhaust gas mixture (λ>1), attaining considerable activity within a wide temperature window (470–825 K). The samples had marginal activity at 575 K without co-fed H₂, but achieved up to 60% NO_x conversion in the presence of H₂ at a space velocity of 30,000 h⁻¹. NO₂ as NO_x feed component is not converted to N₂ by C₃H₈ to a substantial extent under lean conditions. This points to an activation route of NO through direct conversion to adsorbed nitrite/nitrate or to a dissociation of NO over Ag⁰, formed through short-term reduction by H₂. The nature of Ag species was characterized by X-ray diffraction, temperature-programmed reduction, pulse thermoanalytical measurements, electron microscopy and FTIR spectroscopy. It could be shown that Ag₂O nano-sized clusters are predominantly present on all samples, whereas formation of silver aluminate could not be confirmed. Nano-sized Ag₂O clusters can reversibly be reduced/reoxidized by H₂. A silver loading higher than 2 wt.% leads to a part of Ag₂O particles, which are thermally decomposed during calcination at 800 K or higher. The catalytic role of this metallic silver is still unclear. Formal kinetic analysis of catalytic data revealed that the activation energy of the overall reaction is significantly lowered in the presence of H₂. The presence of water does not change the activation energy. It is concluded that hydrogen reduces the nano-sized Ag₂O clusters to Ag⁰ on a short-term scale. Zero-valent silver promotes a dissociation pathway of NO_x conversion. The fact that more oxidized ad-species (nitrite/nitrate) are observed in the presence of H₂ is attributed to a dissociative activation of gas-phase oxygen on Ag⁰.     

富氧条件Co/H-ZSM-5催化剂上CH4选择催化还原NO的研究

采用离子交换法制备了一系列具有不同硅铝比和不同Co负载量的Co/H-ZSM-5催化剂样品。富氧条件下考察了硅铝比、Co负载量、空速、O₂浓度及酸位对催化剂选择催化还原活性的影响。并对其进行了XRD、BET、H₂-TPR和DRS-UV-vis等表征。催化结果表明，催化剂的催化活性随Co负载量的增加而增加，随硅铝比的增加而减少；NO转化率随着空速的增加而降低。O₂体积分数为2%时，NO达最大转化率。表征结果表明，Co²⁺为活性中心，酸中心的存在对催化活性有一定的促进作用。     

Selective catalytic reduction of NO by propene in excess oxygen on Pt- and Rh-supported alumina catalysts

A comparative study of Pt/alumina and Rh/alumina catalysts was performed for the selective catalytic reduction of NO with C₃H₆ in the presence of excess oxygen. Pt/alumina was more active for NO reduction at lower temperatures compared to Rh/alumina. However, the latter exhibited clearly superior performance in terms of selectivity to N₂. This makes Rh/alumina a more suitable catalyst for the selective catalytic reduction of NO under excess oxygen conditions. Detailed kinetic studies of the SCR of NO were performed on Pt/alumina and Rh/alumina to obtain low-temperature kinetic expressions for NO reduction and C₃H₆ oxidation in the presence and absence of NO. Qualitative similarities yet quantitative differences in these kinetic expressions appear to indicate the existence of two partially similar mechanistic schemes. One is based on the indirect participation of the reductant through reduction of the active sites, followed by dissociative adsorption of NO on reduced sites (applicable for Pt/alumina). The other is based on the direct participation of the reductant (apparently by its partial oxidation) in forming an activated intermediate species, followed by its interaction with activated NO (applicable for Rh/alumina).     

单分散Co3O4@SiO2核壳催化剂的制备及N2O催化分解性能

N₂O是一种重要的温室气体,且对臭氧层有很大的破坏作用,而直接催化分解法是除去N₂O最经济有效的方法之一。针对目前报道较多的钴氧化物催化剂活性较差的问题,将包覆型Co₃O₄核壳材料引入N₂O直接催化分解反应,利用核壳结构的限域特性与壳层的多孔孔道使Co₃O₄分散性增加,粒径减小,金属载体相互作用与接触反应界面增强,从而提高了催化剂在N₂O直接催化分解反应中的低温活性。此外,还制备了一系列不同金属含量的Co₃O₄@SiO₂球形核壳催化剂来研究包覆结构对催化剂性能的影响,通过X射线荧光光谱（XRF）、透射电镜（TEM）、X射线衍射（XRD）、N₂物理吸附、H₂-程序升温还原（H₂-TPR）等表征,证实在保证稳定单分散核壳结构的前提下,活性Co₃O₄位点越多,催化剂反应活性越好。     

Selective Catalytic Reduction of NO by C3H6 over Co/Al2O3 Catalyst with Extremely Low Cobalt Loading

In order to reveal the optimum Co loading, the selective catalytic reduction of NO with C₃H₆ over Co/Al₂O₃ catalyst was studied in a systematic fashion by varying the amount of cobalt oxide. It was found that upon loading a small amount of cobalt oxide (namely 0.5 wt% on a Co metal basis), the combination between Co(II) acetate salt and a high-purity alumina provided an active catalyst in the presence of excess oxygen and water. TPR measurement showed the presence of Co species other than CoAl₂O₄ spinel in the most excellent performance catalyst, from which the active sites should be produced.     

NO reduction performance of Rh paste catalyst on YSZ under steady state and forced oscillation electropromotion conditions

The technique of cyclic voltammetry was applied in conjunction with on-line catalytic product analysis to investigate the electrochemical promotion of NO reduction by C₃H₆ in presence of O₂ on Rh catalyst-electrode films on YSZ at temperatures 350–490 °C. Cyclic linear potential sweep amperometry under catalytic reaction conditions leads to cyclic non-Faradaic electrochemical modifications in the CO₂ formation and NO reduction rates which are compared to those obtained under steady state potentiostatic operation.