催化剂MnCe（y）Ox/TiO2的制备及其催化燃烧甲苯的活性

以TiO2为载体,采用浸渍法制备了不同配比的MnCe复合型催化剂,并采用X射线衍射(XRD)、氧气的程序升温脱附(O2-TPD)和氢气的程序升温还原(H2-TPR)对制备的催化剂进行表征,比较了催化剂催化氧化(燃烧)甲苯的活性。研究结果表明,所制备的催化剂MnCe(y)Ox/TiO2对甲苯有明显的催化活性。当Ce/(Mn+Ce)的摩尔比为0.1时,催化剂MnCe(0.1)Ox/TiO2的催化活性最高,甲苯的转化率达到90%时的温度为254℃。在催化剂MnOx/TiO2中掺杂少量的Ce元素,有利于活性组分Mn物种在载体表面上以更小颗粒而且更高的分散度存在,从而提高催化剂的催化活性。     

钛基LaxCe1-xTiyM1-yO3/γ-Al2O3催化剂的制备及催化燃烧性能

为提高钙钛矿型催化剂的活性,以γ-Al2O3为载体,采用等体积浸渍法制备负载型钙钛矿LaxCe1-xTiyM1-yO3/γ-Al2O3催化剂,考察了活性组分负载量、焙烧温度、A位元素配比和B位元素掺杂对催化剂催化燃烧甲苯性能的影响,并对催化剂进行XRD和BET表征。结果表明:催化剂的最佳制备条件是活性组分负载量为12%,焙烧温度为750℃,催化剂的最佳形式为La0.8Ce0.2 Ti0.8 Mn0.2 O3/γ-Al2 O3,在该催化剂的作用下,甲苯的起燃温度T50和完全转化温度T90分别为292℃和338℃;负载型钙钛矿催化剂保持了完整的钙钛矿结构,活性组分均匀分布在载体的孔道中,虽然会导致载体的比表面积有所降低,但催化剂可以更最大程度地分散,更有利于提高催化剂的催化活性。     

凹凸棒粘土负载CuO催化剂的制备及催化甲苯燃烧性能研究

以天然凹凸棒粘土为载体,采用沉积-沉降法制备出负载CuO的负载型CuO/凹凸棒(CuO/APT)催化剂。通过XRD、SEM、TEM和N2吸附等手段对所制备的催化剂结构性能进行表征,并采用连续流动微反-色谱装置考察其催化甲苯燃烧的催化性能。结果表明,所制备的CuO/APT催化剂具有纤维状一维纳米结构、比表面积高、活性组分纳米氧化铜在载体表面分散均匀,并且该催化剂具有优异的催化甲苯燃烧性能。     

铁系元素掺杂的Pt基疏水催化剂的制备及活性研究

以炭黑为载体、乙二醇为溶剂, 利用高压微波加热法分别制备了铁系元素(即Fe、Co、Ni三种元素)掺杂的Pt基二元催化剂. 采用TEM、XRD、EDX、XPS等手段分析了催化剂的微观结构. 活性金属粒子在炭黑载体表面分布均匀; Fe、Co、Ni掺杂后, 催化剂中活性金属粒子的粒径分布变窄, 平均粒径明显减小(由4.57nm分别降低至2.17、2.41、2.55nm); 催化剂中Pt存在Pt(0)、Pt(II)、Pt(IV)三种价态. 将催化剂分散于聚四氟乙烯乳液中, 采用自然浸渍法负载于泡沫镍, 制得Pt基疏水催化剂, 考查了其对氢-水液相交换反应的催化活性. 与单一Pt基疏水催化剂相比, 过渡金属掺杂后的二元疏水催化剂对氢-水液相交换反应的催化活性明显提高. 其催化活性由高到低依次为: PtFe/C/FN>PtCo/C/FN>PtNi/C/FN>Pt/C/FN. 催化活性的提高可能主要来源于催化剂活性金属粒径的减小. 此外, H₂O分子在Fe系元素表面的解离行为也有一定的贡献.     

大比表面三维介孔MCM-48分子筛负载Pt催化氧化甲苯EI北大核心

采用自合成大比表面三维有序介孔分子筛MCM-48(≈1400 m^(2)/g)为载体,其上负载Pt,获得负载型Pt/MCM-48,应用于甲苯催化燃烧,与微孔分子筛Silicalite-2、介孔分子筛材料SBA-15和MCM-41以及商用SiO_(2)等硅基载体相比,展示出优异的低温催化氧化性能。在此基础上,考察不同Pt负载量对负载型Pt/MCM-48催化燃烧甲苯性能的影响,筛选出的1%(质量分数)理论负载量的催化剂具备最佳催化氧化性能。对等体积浸渍法、原位合成法、甲醇法、乙二醇法等不同引入方式的考察发现,等体积浸渍法与原位合成法向载体上引入Pt的实际负载量接近于理论添加量,相比之下,甲醇法、乙二醇法等溶剂法获得Pt实际负载量远低于理论负载量。转化频率(turnover frequency, TOF)计算结果表明,甲醇法获得的Pt/MCM-48中Pt转化效率以及Pt原子利用率最高。BET,XPS,STEM以及H_(2)-TPR等表征充分证明,MCM-48超大的比表面为Pt的分散提供了有利条件,有助于获得高比例Pt^(0);有序的三维介孔结构则大大提高活性位点的可接近性,并减小甲苯分子的扩散阻力,因此呈现出优异的催化氧化甲苯性能。此外,GC-MS研究表明甲苯在Pt/MCM-48上首先转化为醛/酚/酸类中间产物,最终实现深度催化氧化成为二氧化碳。     

大比表面三维介孔MCM-48分子筛负载Pt催化氧化甲苯

采用自合成大比表面三维有序介孔分子筛MCM-48(≈1400 m²/g)为载体，其上负载Pt,获得负载型Pt/MCM-48,应用于甲苯催化燃烧，与微孔分子筛Silicalite-2、介孔分子筛材料SBA-15和MCM-41以及商用SiO₂等硅基载体相比，展示出优异的低温催化氧化性能。在此基础上，考察不同Pt负载量对负载型Pt/MCM-48催化燃烧甲苯性能的影响，筛选出的1%(质量分数)理论负载量的催化剂具备最佳催化氧化性能。对等体积浸渍法、原位合成法、甲醇法、乙二醇法等不同引入方式的考察发现，等体积浸渍法与原位合成法向载体上引入Pt的实际负载量接近于理论添加量，相比之下，甲醇法、乙二醇法等溶剂法获得Pt实际负载量远低于理论负载量。转化频率(turnover frequency, TOF)计算结果表明，甲醇法获得的Pt/MCM-48中Pt转化效率以及Pt原子利用率最高。BET,XPS,STEM以及H₂-TPR等表征充分证明，MCM-48超大的比表面为Pt的分散提供了有利条件，有助于获得高比例Pt⁰;有...     

H_2还原预处理CuO/γ-Al_2O_3催化剂对其催化燃烧甲苯活性的影响

用浸渍法和H2还原预处理法制备两种CuO/γ-Al2O3催化剂,并用N2吸附脱附、XRD、TPR和CO化学吸附对经H2还原处理前后的催化剂进行表征,比较两种催化剂催化氧化(燃烧)甲苯的活性。研究结果表明,与浸渍法制备的CuO/γ-Al2O3催化剂相比,经H2还原预处理,再次焙烧后得到的CuO/γ-Al2O3/HR催化剂对甲苯催化燃烧活性明显提高。XRD和TPR分析表明,H2还原预处理提高了催化剂表面活性组分CuO的分散度、还原能力,同时,还降低了CuO的晶体尺寸,从而提高了催化剂催化氧化甲苯的活性。     

用于水处理过程的铜催化剂制备及性能研究

高效催化臭氧化催化剂的研制是金属催化臭氧化技术发展的重点.采用浸渍法,以Al2O3为载体,制备了铜的负载型金属催化臭氧化催化剂.以松花江水的UV254去除率作为催化剂活性指标,通过正交试验,确定催化剂的最佳制备工艺.使用扫描电镜和比表面测定仪对催化剂结构进行了表征.实验结果表明:当浸渍液浓度为1 mol/L,浸渍时间为6 h,焙烧温度为300 ℃时,所制得的铜催化剂具有很高的催化活性.     

Mn、Fe和Cu氧化物在低温等离子体催化氧化甲苯体系中的活性比较

采用等体积浸渍法制备了MnOx/γ-Al2O3、FeOx/γ-Al2O3和CuOx/γ-Al2O3催化剂,测定了不同催化剂在低温等离子体场内分解甲苯的活性,用X射线衍射(XRD)、氢气程序升温还原(H2-TPR)技术对催化剂进行表征。结果表明催化剂分解甲苯的活性的顺序是MnOx/γ-Al2O3>FeOx/γ-Al2O3>CuOx/γ-Al2O3。催化剂分解臭氧的实验表明,不同催化活性组分对臭氧的催化分解性能顺序与对甲苯的分解性能顺序是一致的。MnOx/γ-Al2O3催化剂的Mn负载量对其催化活性有明显影响,Mn的含量为1%(质量分数)时,催化剂的活性最高,当能量密度为19J/L时,其对甲苯催化氧化的转化率接近100%。催化剂表征结果表明当Mn含量为1%(质量分数)时,氧化锰在载体γ-Al2O3上最接近单层分散量,此时活性组分与载体表面的相互结合力最强,在载体上有很好的分散性,从而表现出对甲苯分解的最好性能。     

NiO-MnO2/Al2O3催化臭氧化催化剂的制备及性能

采用浸渍法,以Al2O3为载体,制备了氧化镍和氧化锰复合的双组分负载型金属催化臭氧化催化剂.以松花江江水中UV254的去除率作为催化剂活性指标,通过正交试验,寻找催化剂的最佳制备工艺.实验结果表明:催化剂的最佳制备工艺为浸渍3h,活性组元体积比1:1,90℃干燥2h,400℃焙烧4h.通过扫描电镜对催化剂结构进行了表征;通过TG-DTA测试,分析了催化剂的热分解过程中反应速率、热效应和物质变化过程;运用XPS分析了催化剂表面元素的组成情况,催化剂的主要活性成分为MnO2.     

Optimized synthesis method for K/Co3O4 catalyst towards direct decomposition of N2O

The potassium-doped Co₃O₄ catalysts were prepared by impregnation of potassium sources on commercial cobalt carbonate and on the precursors synthesized by homogeneous precipitation, combustion with glycine, gradual oxidation, and hydrothermal methods. The activities of these catalysts for the direct decomposition of nitrous oxide in the presence of oxygen with or without water vapor were examined. The effects of potassium sources on the catalyst activity were also examined by impregnation of various potassium salts on commercial cobalt carbonate. The catalyst prepared by impregnation of an aqueous solution of KOH on commercial cobalt carbonate showed the highest activity. The catalysts prepared by various methods were analyzed by powder X-ray diffraction, N₂ adsorption, scanning electron microscope, temperature-programmed reduction with H₂, temperature-programmed desorption of O₂, and X-ray photoelectron spectroscopy. These results suggest that crystallite size and reduction property are key factors for the activity of the catalyst for the direct decomposition of nitrous oxide in the presence of oxygen.     

Preparation and characterization of nanosized gold catalysts supported on Co3O4 and their activities for CO oxidation

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.     

Effect of Co and Ce on silica supported manganese catalysts in the reactions of complete oxidation of n-hexane and ethyl acetate

Mono-component and bi-component catalysts, prepared by impregnation of silica with aqueous solution of Mn, Co, and Ce nitrates, were tested in the reactions of complete oxidation of n-hexane and ethyl acetate. The catalysts were characterized by powder X-ray diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The catalytic activity is significantly increased by the combination between manganese and cobalt, which is explained as a result of the high mobility of lattice oxygen, the simultaneous presence of Mn⁴⁺?CMn³⁺ couple, decrease in the strength of the Co?CO bond, and the predominance of Co in the second oxidation state on the catalyst surface. The decrease in catalytic activity of Mn?CCe sample is attributed to the predominance of Ce on the surface and lower mobility of the lattice oxygen.     

Catalytic activity of Co/MCM-41 and Co/SBA-15 materials in toluene oxidation

Cobalt-containing MCM-41 and SBA-15 mesoporous materials were prepared by the pH-adjusting of the impregnation solution. The modified materials were investigated by X-ray diffraction, N₂ physisorption, temperature-programmed reduction, DR UV–Vis diffuse reflectance, and FT-IR spectroscopy of adsorbed pyridine. The pH of the impregnation solution influences the surface charge of the mesoporous support and therefore determines the strength of interaction between the cobalt precursor and the mesoporous support. The formation of different cobalt oxide species in different ratios, depending on the pH of the impregnation solution, was established for both materials. The modified Co/MCM-41 and Co/SBA-15 materials were active in toluene oxidation. Their catalytic activity is predetermined by the nature, the reducibility, and the dispersion of the obtained cobalt oxide species.     

Preparation and characterization of PtRu nanoparticles supported on nitrogen-doped porous carbon for electrooxidation of methanol

N-doped porous carbon nanospheres (PCNs) were prepared by chemical activation of nonporous carbon nanospheres (CNs), which were obtained via carbonization of polypyrrole nanospheres (PNs). The catalysts, PtRu and Pt nanoparticles supported on PCNs and Vulcan XC-72 carbon black, were prepared by ethylene glycol chemical reduction. Transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy were employed to characterize samples. It was found that PCNs containing N function groups possess a large number of micropores. Uniform and well-dispersed Pt and PtRu particles with narrow particle size distribution were observed. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that alloy catalyst (Pt(1)Ru(1)/PCN) possessed the highest catalytic activity and better CO tolerance than the other PtRu and Pt-only catalysts; PtRu nanoparticles supported on PCN showed a higher catalytic activity and more stable sustained current than on carbon black XC-72. Compared to commercial Alfa Aesar PtRu catalyst, Pt(1)Ru(1)/PCN reveals an enhanced and durable catalytic activity in methanol oxidation because of the high dispersion of small PtRu nanoparticles and the presence of N species of support PCNs.     

Complete oxidation of ethylene over supported gold nanoparticle catalysts

Complete oxidation of ethylene was performed over supported noble metals or transition metals oxide catalysts and on monoliths under atmospheric pressure. Gold nanoparticles on Al2O3 or MxOy(M = Mo, Fe, Mn) were prepared by impregnation, coprecipitation, deposition, and dispersion methods. Nanoparticles prepared by impregnation method were irregular and very large above 25 nm, but those by coprecipitation and deposition method were uniformly nanosized at 4-5 nm. The gold nanoparticle were outstandingly active in catalyzing oxidation of ethylene. The activity order of these catalysts with preparation methods was deposition > coprecipitation > impregnation, and Au/Co3O4 prepared by deposition method showed the best performance in ethylene oxidation. The addition of gold particles to MxOy/Al2O3 catalyst enhanced the ethylene oxidation activity significantly. The main role of the gold nanoparticles apparently was to promote dissociative adsorption of oxygen and to enhance the reoxidation of the catalyst.     

石墨烯负载Pt-Co纳米粒子及其在氧化还原反应中的应用

采用微波-乙二醇方法还原氧化石墨烯和Pt(v)、Co(Ⅱ)粒子混合物,再经300℃H2还原,制备了石墨烯负载Pt-Co合金催化剂(Pt-Co/G).利用透射电镜、X-射线能谱、X-射线衍射和光电子能谱对所制催化剂进行表征.Pt-Co合金的粒径为3nm～8 nm,均匀地分散在石墨烯片上.与单金属的Pt/G和商品化的Pt/C催化剂相比,所制合金化的Pt-Co/G催化剂对氧还原反应展现出高的催化活性和可比拟的稳定性,显示了其在燃料电池中的应用潜力.     

Photo-degradation of acid green dye over Co-ZSM-5 catalysts prepared by incipient wetness impregnation technique

Co-ZSM-5 catalysts with different Co-loadings (2-30wt.%) were prepared by incipient wetness impregnation method. The prepared solid catalysts were characterized by X-ray diffraction, FTIR, in situ FTIR of pyridine adsorption and surface area measurements. The XRD data presented disintegration in the zeolitic crystalline structure accompanied by an increase in particle size of the prepared solids. New phases, Co(3)O(4) and Co(2)SiO(4), were detected with increasing the Co-loading, which indicate the strong interaction of cobalt ions with the ZSM-5 zeolite. FTIR study proved the presence of Co ions in stabilized sites inside the ZSM-5 framework. The in situ FTIR of adsorbed pyridine determined the type and relative strength of acidity on the surface of the prepared solids. The acidity switched from B-acid sites to L-acid sites with impregnation of cobalt ions in ZSM-5 zeolite. The acidity decreased with increasing Co-loading, which might be due to the destruction of zeolite framework and presence of new phases such as cobalt silicate and cobalt oxide on the surface. The surface texture characteristics changed with the promotion of ZSM-5 by cobalt ions, since a decrease of surface area, mean pore radius and pore volume was observed. The assessment of the catalytic activity was performed by the use of the photo-degradation of acid green (AG) dye as a probe reaction in presence of H(2)O(2) as an oxidant. The pH value controlled the degradation rate since a gradual increase of AG degradation rate was observed with increasing pH value and the optimum H(2)O(2) concentration was 61.6 mmol/l. It was found that, the AG degradation rate increased until an optimum value of Co-loading (ca. 10 wt.%), beyond which a monotonic decrease of reaction rate was recognized. The experimental data pointed to the importance of both the cobalt moieties and the zeolite framework structure in the AG degradation reaction.     

Preparation of carbon-supported PtCo nanoparticle catalysts for the oxygen reduction reaction in polymer electrolyte fuel cells by an electron-beam irradiation reduction method

We prepared carbon-supported PtCo bimetallic nanoparticles (PtCo/C) as electrode catalysts for the oxygen reduction reaction (ORR) at the cathodes in polymer electrolyte membrane fuel cells (PEFCs) by an electron-beam irradiation reduction method (EBIRM). An EBIRM allows nanoparticles to be easily prepared by the reduction of precursor ions in an aqueous solution irradiated with a high-energy electron beam. The structures of PtCo/C were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, and the techniques of X-ray diffraction and X-ray absorption near edge structure. It found for the first time that both PtCo alloy and Co oxide were prepared simultaneously on the carbon support by an EBIRM. The catalytic activity and durability of PtCo/C were evaluated by linear-sweep voltammetry and cyclic voltammetry, respectively. The addition of Co to Pt/C not only enhanced the catalytic activity for the ORR but also improved the catalytic durability. As the Co concentration increased, both behaviors became pronounced. These improvements are explained by the effects of both PtCo alloy and Co oxide. We demonstrated that an EBIRM can not only synthesize the alloy and oxide simultaneously on the carbon support but also mass-produce the electrode catalysts for PEFC cathodes.