富氧条件下Co/ZSM-5催化剂对C_3H_8选择还原NO_x的性能

采用多种物理化学手段研究了在模拟的轻型柴油车尾气中不同Co担载量及Cu掺杂的Co/ZSM-5催化剂的Co组分分散状态、可还原性、NO吸附脱附性质对C3H8选择性催化还原NOx性能的影响。结果表明,浸渍法制备的Co/ZSM-5催化剂上既有外表面上的Co3+和Co2+物种,也有孔内的Co2+离子。富氧条件下Co/ZSM-5催化剂上C3H8选择性催化还原NOx的活性主要与ZSM-5载体孔外表面分散的CoOx物种中的钴离子可还原能力和NO吸附脱附性能密切相关。Co/ZSM-5催化剂上适宜的Co担载量约为4.0wt%,低担载量时随Co担载量增加,表面CoOx物种中钴离子可还原能力增强,C3H8选择性催化还原NOx的低温转化活性增加;高担载量时,随Co担载量增加,单位Co离子的NO吸附量的减少以及催化剂表面活性中心数的减少,导致了Co/ZSM-5催化剂NOx的转化率和催化剂比速率(k)的下降。孔外表面Co3O4晶体的存在使催化剂表面产生较强的NO吸附,并在高温时有利于C3H8的氧化燃烧,使C3H8选择性催化还原NOx的活性降低。     

富氧条件下Co/ZSM-5催化剂对C3H8选择还原NOx的性能

采用多种物理化学手段研究了在模拟的轻型柴油车尾气中不同Co担载量及Cu掺杂的Co/ZSM-5催化剂的Co组分分散状态、可还原性、NO吸附脱附性质对C₃H₈选择性催化还原NO_x性能的影响。结果表明,浸渍法制备的Co/ZSM-5催化剂上既有外表面上的Co³⁺和Co²⁺物种,也有孔内的Co²⁺离子。富氧条件下Co/ZSM-5催化剂上C₃H₈选择性催化还原NO_x的活性主要与ZSM-5载体孔外表面分散的CoO_x物种中的钴离子可还原能力和NO吸附脱附性能密切相关。Co/ZSM-5催化剂上适宜的Co担载量约为4.0wt%,低担载量时随Co担载量增加,表面CoO_x物种中钴离子可还原能力增强,C₃H₈选择性催化还原NO_x的低温转化活性增加;高担载量时,随Co担载量增加,单位Co离子的NO吸附量的减少以及催化剂表面活性中心数的减少,导致了Co/ZSM-5催化剂NO_x的转化率和催化剂比速率（k）的下降。孔外表面Co₃O₄晶体的存在使催化剂表面产生较强的NO吸附,并在高温时有利于C₃H₈的氧化燃烧,使C₃H₈选择性催化还原NO_x的活性降低。     

合成方法对Rh/CeO2-ZrO2-La2O3催化剂的结构、表面性能及DeNOx活性的影响

用沉积沉淀法合成两种不同系列的CeO2-ZrO2-La2O3混合氧化物(ZrO2和La2O3沉积CeO2粒子(标记为A-x)以及CeO2和La2O3沉积ZrO2粒子(标记为B-x)),并用作Rh催化剂的载体。XRD、拉曼、TPR、XPS和O2脉冲等表征结果显示出不同的沉积顺序将导致不同的结构和氧化还原性能,且B-x具有更高的氧迁移性、储氧能力和表面Ce浓度。当其负载Rh后,Rh/B-x催化剂具有更高的NO和CO转化率及N2选择性,且Ce的最佳含量为50at%。这可能归因于Rh负载于富铈表面形成更多有利于NO分解的表面Ce3+活性位。     

Mn-Mo-W-O_x脱硝催化剂活性组分的配伍优化

采用等体积浸渍法制备系列Mn-Mo-W-O_x/堇青石和Mn-Mo-W-O_x/TiO_2催化剂,用于选择性催化还原NO.通过Mn、Mo、W 3种元素不同配比对催化剂配伍进行优化,确立Mn-Mo-W-O_x最佳配比.采用XRD、N_2-BET、PyIR、SEM以及XPS等表征分析催化剂的固相结构、比表面积、酸量、表面形貌和表面元素.结果表明:当Mn/Mo/W元素摩尔比为10∶0.5∶1,载体为TiO_2时,催化剂的催化性能最优.适量Mo掺入Mn-W-O_x催化剂可以增大其比表面积,提高催化剂表面L酸酸量以及Mn~(4+)离子浓度,从而有效提高了催化剂高温活性.载体替换为TiO_2时催化剂的比表面积和酸量明显提高,从而增强了催化剂的脱硝性能.     

Pt/MOx(M=Ni,Fe,Co,Ce)催化剂上CO氧化反应中抗H2O与CO2的性能研究

我们研究了4种负载型Pt催化剂（1Pt/NiO、1Pt/FeO_x、1Pt/Co₃O₄和Pt/CeO₂）上不同反应条件下CO氧化活性及抗H₂O和CO₂性能.发现反应气氛中CO₂的加入与CO形成了竞争吸附,并在催化剂表面形成了碳酸盐物种堵塞了活性位,从而导致催化剂失活.反应气氛中H₂O的加入对1Pt/CeO₂催化剂的活性有所抑制,但对1Pt/FeO_x、1Pt/NiO和1Pt/Co₃O₄催化剂的活性却有促进作用.在1Pt/FeO_x和1Pt/CeO₂催化剂上的分步反应实验和动力学研究表明,尽管H₂O的加入在两种催化剂上均与CO形成了竞争吸附,但在1Pt/FeO_x催化剂上H₂O在载体表面解离形成的羟基更易与CO反应,开辟了新的反应途径,从而提高了反应性能.此外,H₂O的加入能有效分解该催化剂上的碳酸盐物种,从而保持了其稳定性.     

Effects of gold catalysts and thermal evaporation method modifications on the growth process of Zn1−xMgxO nanowires

In this paper, we investigate the roles of gold catalysts and thermal evaporation method modifications in the growth process of Zn_1−xMg_xO nanowires. Zn_1−xMg_xO nanowires are fabricated on silicon substrates with and without using a gold catalyst. Characterizations reveal that Mg acts in a self-catalyst role during the growth process of Zn_1−xMg_xO nanowires grown on catalyst-free substrate. The optical properties and crystalline quality of the Zn_1−xMg_xO nanowires are characterized by room temperature photoluminescence (PL) measurements and Raman spectroscopy, respectively. The Raman and PL studies demonstrate that the Zn_1−xMg_xO nanowires grown using the catalyst-free method have good crystallinity with excellent optical properties and have a larger band-gap in comparison to those grown with the assistance of gold.     

Influence of MgO contents on silica supported nano-size gold catalyst for carbon monoxide total oxidation

A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), O2 temperature-programmed desorption (O2-TPD), and inductively coupled with plasma atomic emission spectroscopy (ICP-AES) techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO (Mg/SiO2 weight ratio) shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.     

室温电化学沉积Ba1-xCaxMoO4多晶固溶体薄膜

近年发展起来的制备功能薄膜的电化学沉积技术,是软溶液工艺路线(Soft Solution Processing简记为SSP)中的重要技术[1]。与传统的薄膜制备技术相比,电化学沉积技术在反应控制、形貌控制、沉积速度、能量消耗、环境影响、薄膜晶化以及沉积设备等方面都有较明显的优势,同时避免了     

Effect of TiO2 Calcination Pretreatment on the Performance of Pt/TiO2 Catalyst for CO Oxidation

In order to improve the CO catalytic oxidation performance of a Pt/TiO₂ catalyst, a series of Pt/TiO₂ catalysts were prepared via an impregnation method in this study, and various characterization methods were used to explore the effect of TiO₂ calcination pretreatment on the CO catalytic oxidation performance of the catalysts. The results revealed that Pt/TiO₂ (700 °C) prepared by TiO₂ after calcination pretreatment at 700 °C exhibits a superior CO oxidation activity at low temperatures. After calcination pretreatment, the catalyst exhibited a suitable specific surface area and pore structure, which is beneficial to the diffusion of reactants and reaction products. At the same time, the proportion of adsorbed oxygen on the catalyst surface was increased, which promoted the oxidation of CO. After calcination pretreatment, the adsorption capacity of the catalyst for CO and CO₂ decreased, which was beneficial for the simultaneous inhibition of the CO self-poisoning of Pt sites. In addition, the Pt species exhibited a higher degree of dispersion and a smaller particle size, thereby increasing the CO oxidation activity of the Pt/TiO₂ (700 °C) catalyst.     

Characterization of Au-Rh/TiO2 catalysts by CO adsorption; XPS, FTIR and TPD experiments

On X-ray photoelectron spectra of the Au-Rh/TiO₂ catalysts the position of Au4f peak was practically unaffected by the presence of rhodium, the peak position of Rh3d, however, shifted to lower binding energy with the increase of gold content of the catalysts. Rh enrichment in the outer layers of the bimetallic crystallites was experienced. The bands due to Au⁰-CO, Rh⁰-CO and (Rh⁰)₂-CO were observed on the IR spectra of bimetallic samples, no signs for Rh⁺-(CO)₂ were detected on these catalysts. The results were interpreted by electron donation from titania through gold to rhodium and by the higher particle size of bimetallic crystallites.     

掺杂Zr4+对纳米Au/TiO2催化剂结构和性能的影响

采用氨水反滴加沉淀法合成了Zr4+掺杂的系列TiO2载体,以尿素溶液为沉淀剂,用沉积-沉淀法制备负载金催化剂。运用N2吸附-脱附(BET)、X射线衍射(XRD)、X射线荧光(XRF)、高分辨电镜(HR-TEM)和氨吸附红外光谱(NH3-IR)等技术对催化剂的结构与形貌进行了表征,并在色谱-微反应装置上考察了催化剂对CO氧化反应的活性。结果表明:(1)少量的Zr4+掺杂可形成锐钛矿型固溶体,且载体的比表面积增大;随着Zr4+掺杂量增加至10%以上,载体逐渐向无定形转变,同时比表面积急剧增大。(2)保持规整锐钛矿晶相的Zr4+掺杂载体,其表面Lewis酸位占有率较高,且具备结构缺陷,而无定形载体表面的Lewis酸位占有率大幅度降低。(3)载体表面的Lewis酸位以及结构缺陷有利于增强载体对Au颗粒的锚定作用,从而减弱焙烧过程中的颗粒聚集。(4)少量Zr4+掺杂入TiO2载体中,可以提高Au颗粒的抗烧结能力,焙烧所得的Au颗粒尺寸较小(3.63 nm),且表现出优异的催化活性,在常温下就可以将CO完全氧化。     

负载型P-Mo-V/SBA-15催化剂上的甲烷选择氧化反应

以磷钼钒杂多酸(H₅PMo₁₀V₂O₄₀)为前驱体、介孔SBA-15为载体, 采用浸渍法制备不同负载量的P-Mo-V氧化物催化剂. 在甲烷选择氧化反应中, 考察了负载量、反应温度、空速等对甲烷转化率和产物选择性的影响. 结果表明, 催化剂对甲烷选择氧化制甲醛具有较高活性, 甲烷转化率随负载量的增大和反应温度的升高而提高, 甲醛的选择性随负载量的增大先升后降. 反应温度为640 ℃、空速为48300 L•kg^－1•h^－1、氧化物负载量w＝2.89%时, 甲醛的时空产率最高(295 g•kg_cat^－1•h^－1). 多种表征表明, 氧化物负载量w≤2.89%时, P-Mo-V氧化物在载体介孔孔道内以高分散形式存在. 催化剂的酸性和氧化还原性质与负载量相关, NH₃-TPD和H₂-TPR的测试结果表明, 较弱的酸性位和较低还原温度的活性组分有利于甲烷选择氧化制甲醛.     

高活性Au/SnO2催化剂的制备及其在1,4-丁二醇氧化制γ-丁内酯反应中的催化应用

采用沉积沉淀法制备了一系列商业SnO₂负载的纳米Au催化剂, 通过电感耦合等离子体发射光谱、X射线粉末衍射、透射电镜和X射线光电子能谱等方法研究了溶液酸碱性、沉淀剂种类、Au负载量和焙烧温度等对催化剂性质的影响.结果表明, Au的负载量以及催化剂的焙烧温度对Au颗粒状态有较大影响.其中, 于573 K焙烧的3%Au/SnO₂催化剂在1,4-丁二醇氧化制备γ-丁内酯反应中的催化活性最好, TOF值是Au/TiO₂催化剂的15倍.这主要是由于SnO₂载体独特的性质对所负载的Au颗粒的影响.     

High performance CuO-CeO2 catalysts for selective oxidation of CO in excess hydrogen： Effect of hydrothermal preparation conditions

High performance CuO-CeO₂ catalysts for selective oxidation of CO in excess hydrogen were prepared by a hydrothermal method under different preparation conditions and evaluated for catalytic activities and selectivities. By changing the n_CTAB/n_Ce ratio and hydrothermal aging time, the catalytic activity of the CuO-CeO₂ catalysts increased and the operating temperature window, in which the CO conversion was higher than 99%, was widened. XRD results showed no peaks of CuO_x species and Cu-Ce-O solid solution were observed. On the other hand, Cu⁺ species in the CuO-CeO₂ catalysts, which was associated with a strong interaction between copper oxide clusters and cerium oxide and could be favorable for improving the selective oxidation performance of CO in excess H₂, were detected by H₂-TPR and XPS techniques.     

CO Oxidation on Cu/MgO-SiO2 Sol-Gel Derived Catalysts

Sol-gel Cu//MgOSiO₂ catalysts were prepared gelling tetraethoxysilane (TEOS), magnesium ethoxide and copper acetylacetonate at pH 3 and pH 9. The catalysts shown specific surface areas ca. 500 m²/g and 140 m²/g for pH 9 and pH 3 preparations respectively. Si(OH) and Si(OH)₂ hydroxy groups were observed by MAS-RMN spectroscopy in both preparations. CO₂-TPD and NH₃-TPD desorption thermograms showed that acid and basic sites were formed on the catalysts surface. It has been found that the catalysts having the highest density of basic sites were the catalysts showing the highest activity for the CO oxidation. It is proposed that the catalytic activity depends of the relative Cu⁼¹/Cu⁼² stability given by the support acidity.     

空气中合成固溶体荧光粉Ba2(Zn, Mg)Si2O7:Ce3+,Eu2+,Eu3+及其发光特性

采用高温固相法在空气中合成了Ba_1.97-yZn_1-xMg_xSi₂O₇:0.03Eu,yCe³⁺系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba_1.97-yZn_1-xMg_xSi₂O₇:0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu²⁺离子的4f⁶5d¹-4f⁷跃迁,590~725 nm红光区窄带谱源于Eu³⁺的⁵D₀-⁷F_J (J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu³⁺在Ba_1.97-yZn_1-xMg_xSi₂O₇基质中被还原成了Eu²⁺;当x=0.1时,荧光粉Ba_1.97Zn_0.9Mg_0.1Si₂O₇:0.03Eu的绿色发光最强,表明Eu³⁺被还原成Eu²⁺离子的程度最大。当共掺入Ce³⁺离子后,形成Ba_1.97-yZn_0.9Mg_0.1Si₂O₇:0.03Eu,yCe³⁺荧光粉体系,其发光随着Ce³⁺离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba_1.96Zn_0.9Mg_0.1Si₂O₇:0.01Ce³⁺,0.03Eu的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba₂Zn_0.9Mg_0.1Si₂O₇基质中的能量传递与发光机理。     

空气中合成固溶体荧光粉Ba_2(Zn,Mg)Si_2O_7∶Eu~(2+),Eu~(3+),Ce~(3+)及其发光特性

采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7∶0.03Eu,y Ce3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7∶0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f 65d1-4f 7跃迁,590~725 nm红光区窄带谱源于Eu3+的5D0-7FJ(J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7∶0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7∶0.03Eu,y Ce3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7∶0.03Eu,0.01Ce3+的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。     

Nanoceria Supported Gold Catalysts for CO Oxidation

Two types of CeO₂ nanocubes (average size of 5 and 20 nm, respectively) prepared via the hydrothermal process were selected to load gold species via a deposition‐precipitation (DP) method. Various measurements, including X‐ray diffraction (XRD), Raman spectra, high resolution transmission electron microscopy (HRTEM), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and temperature‐programmed reduction by hydrogen (H₂‐TPR), were applied to characterize the catalysts. It is found that the sample with ceria size of 20 nm (Au/CeO₂‐20) was covered by well dispersed both Au³⁺ and Au^δ+ (0 < δ < 1). For the other sample with ceria size of 5 nm (Au/CeO₂‐5), Au³⁺ is the dominant gold species. Au/CeO₂‐20 performed better catalytic activity for CO oxidation because of the strong CO adsorption of Au^δ+ in the catalysts. The catalytic activity of Au/CeO₂‐5 was improved due to the transformation of Au³⁺ to Au^δ+. Based on the CO oxidation and in situ DRIFTS results, Au^δ+ is likely to play a more important role in catalyzing CO oxidation reaction.     

用于NO_x低温下吸附还原的CoO_x/CeO_2二元氧化物的制备

研究了以多孔二氧化硅微球和活性炭为载体制备NOx吸附/还原催化剂的方法,摸索了最佳Ce/Co物质的量的比例。采用低温氮吸附方法测定了样品的BET比表面和孔容,利用XRD方法表征了样品中所掺杂的金属元素的晶型。研究发现:当nCe/nCo=75/25时,材料获得最佳NOx吸附能力,当以多孔二氧化硅微球作载体时,材料对于NOx的吸附主要来自CoOx和CeO2的二元氧化物;当以活性炭作为载体时,活性炭参与了NOx的吸附,因此其吸附容量大大提高。对NOx的吸附机理进行了探讨,并研究了样品的NH3还原性质。     

Pt/TiO2催化剂上CO氧化反应动力学研究

利用沉积沉淀法制备了Pt/TiO₂催化剂, 将其在不同温度下焙烧, 以得到不同颗粒尺寸的Pt. 并将这些样品用于CO催化氧化反应以及反应动力学研究. 结果表明: 焙烧温度对催化剂有明显影响, Pt 颗粒尺寸随着焙烧温度的升高而增加; 与此同时, CO催化活性随焙烧温度的升高呈先增加后降低的趋势, 其中, 400℃焙烧的样品表现出最高的催化活性. 反应动力学结果表明, 催化剂上CO氧化反应表观速率方程为r=5.4×10^-7p_CO^0.17p_O2^0.36,说明在该催化剂上CO氧化遵循Langmuir-Hinshelwood机理. 同时, 对催化剂进行了CO化学吸附红外光谱和O₂化学吸附表征. 结果表明, 随着焙烧温度的升高, 催化剂上CO和O₂吸附量均呈现先升高后降低的趋势, 这与反应结果和反应动力学方程一致, 说明反应受到催化剂表面上CO和O₂吸附浓度的影响. 而在400℃焙烧的催化剂上, CO和O₂吸附量均最高, 因此其反应活性也最好. 这可能是焙烧过程影响了Pt 和TiO₂之间的相互作用引起的.