La助剂对Pd-AL2O3催化C3H8氧化性能的研究

采用不同稀土La前驱体浸渍掺杂改性Pd/γ-Al2O3催化剂,利用多功能催化性能评价装置测试不同催化剂的C3H8催化氧化性能,并通过H2-TPR、XRD、XPS等手段对催化材料进行结构表征,结果表明：La能促进贵金属钯分散,增强钯与载体相互作用,稳定高活性Pd2+物种,从而提高了催化剂的C3H8催化氧化性能。在选用不同La前驱体改性的Pd/γ-Al2O3催化剂中,硝酸镧改性效果最佳,能更好地促进活性金属钯的分散和Pd2+高活性物种的稳定。相比Pd/γ-Al2O3,La改性催化剂均降低了C3H8和NO的反应转化温度。选用不同La前驱体对催化活性影响存在差异的主要原因是La前驱体添加而引起的金属-载体相互作用和活性贵金属钯的分散状态变化。     

Pt/Al2O3催化剂用于NO氧化的活化效应研究

柴油机氧化催化剂(DOC)能将尾气中部分NO氧化成NO_2,一定浓度的NO_2有利于柴油机颗粒捕集器(DPF)的连续再生和提高选择性催化还原催化剂(SCR)对NO_x的转化效率。针对DOC的新鲜态Pt/Al_2O_3 催化剂经过1次程序升温NO催化氧化活性明显提升的现象(活化效应),采用原位红外漫反射实验(in situ DRIFTS)、氢气程序升温还原、X射线光电子能谱(XPS)和高分辨透射电子显微镜(HR-TEM)分析Pt/Al_2O_3催化剂相关过程的物理化学状态。分析结果表明,新鲜态Pt/Al_2O_3催化剂在300℃以下时载体上积累了大量的硝酸盐和亚硝酸盐物种,导致新鲜态催化剂活性不高;进一步的分析表明经一次程序升温后催化剂中与载体结合强的PtO_x物种的分解是引起活化效应的主要原因;经过3次程序升温反应,催化剂中Pt粒子的大小没有发生明显改变。     

镧助剂对Pd/Al_2O_3催化剂性能的影响

一氧化碳(CO)-亚硝酸甲酯(MN)气相氧化偶联合成草酸二甲酯(DMO)的反应是煤制乙二醇的关键转化步骤,现用的Pd/Al_2O_3催化剂中钯负载量高达1%。在催化剂制备过程中添加不同助剂,用催化燃烧热阻型检测系统考察其对合成反应的催化性能影响。表征分析表明,镧助剂可改善钯在载体上的分散;当La_2O_3/Al_2O_3=14 mg/g时,La_2O_3在载体表面以单层分散,制成的催化剂中钯分散性最好。性能评价结果显示,载钯量0.2%的催化剂具有较好的稳定性,在优化反应条件下,其性能甚至优于工业催化剂。     

绿色合成AMA反应中纳米Pd/C催化剂的失活和再生

在2-硝基-4-乙酰胺基苯甲醚(NMA)催化加氢合成2-氨基-4-乙酰胺基苯甲醚(AMA)反应中,规整纳米Pd/C催化剂表现出很好的催化活性和选择性。但Pd/C催化剂在反应的套用过程中表现出反应活性逐渐降低。通过XRD、BET、EDS、XPS等物性表征以及Na2S滴定法和原子吸收法测定Pd含量的研究表明,钯微晶的长大、钯流失、催化剂中毒等不是引起Pd/C催化剂失活的主要原因,而Pd/C催化剂表面金属钯活性位在反应后被2-氨基-4-乙酰胺基苯甲醚产物等有机物覆盖可能是导致其性能逐渐降低的关键。使用酸洗法可以去除反应后Pd/C催化剂表面覆盖的2-氨基-4-乙酰胺基苯甲醚等有机物,释放金属钯活性位,实现Pd/C催化剂的性能有较大程度的恢复;而其他方法对Pd/C催化剂活性恢复的效果不明显。     

Analysis of the Active Au Species on Au/α-Fe2O3 Catalyst

采用沉积沉淀法制备了CO低温氧化 Au/α-Fe2O3催化剂,利用 X 射线衍射(XRD)、X 射线光电子能谱(XPS)、BET 比表面测定、程序升温还原(H2-TPR)等表征技术,对比了制备过程 pH 值的微小变化、焙烧及光线照射对催化剂结构及催化性能的影响,探明了 Au/α-Fe2O3催化剂的活性物种。结果表明,110 ℃处理的 Au/α-Fe2O3催化剂表面同时存在 Au3+、Au0以及过渡态 Auδ+(0<δ<1),它们对 CO 氧化的活性顺序为 Au3+>Auδ+>Au0;pH 值为 8 条件下制备的催化剂 Au3+含量高、比表面积大,催化性能最好;高温焙烧使氧化态金还原的同时也使载体比表面积严重缩小,催化活性显著下降;紫外线照射可以引起 Au3+的逐渐还原以及 Au0 颗粒的生长,其催化失活作用弱于高温焙烧。     

焙烧气氛对Pt/Al_2O_3催化氧化CO和C_3H_6性能的影响（英文）

使用Pt(NH_3)_2(NO_2)_2作为前驱体,通过过量浸渍法制备Pt/Al_2O_3催化剂,并将其在4种不同的气氛(H_2、O_2、NO或NH_3)中进行焙烧。利用N_2吸脱附、X射线衍射、程序升温还原(H_2-TPR)、CO脉冲吸附、CO原位漫反射傅里叶变换红外光谱(CO in situ DRIFTS)等手段对催化剂的物化性质进行了表征。结果表明:由于还原性焙烧气氛导致了众多小尺寸和高分散的Pt纳米颗粒的生成,经1%(体积分数)H_2/N_2焙烧的Pt/Al_2O_3表现出最佳的CO和C_3H_6催化氧化性能。     

Au/α-Fe_2O_3 催化剂上金活性物种的分析(英文)

采用沉积沉淀法制备了CO低温氧化 Au/α-Fe2O3催化剂,利用 X 射线衍射(XRD)、X 射线光电子能谱(XPS)、BET 比表面测定、程序升温还原(H2-TPR)等表征技术,对比了制备过程 pH 值的微小变化、焙烧及光线照射对催化剂结构及催化性能的影响,探明了 Au/α-Fe2O3催化剂的活性物种。结果表明,110 ℃处理的 Au/α-Fe2O3催化剂表面同时存在 Au3+、Au0以及过渡态 Auδ+(0δ1),它们对 CO 氧化的活性顺序为 Au3+Auδ+Au0;pH 值为 8 条件下制备的催化剂 Au3+含量高、比表面积大,催化性能最好;高温焙烧使氧化态金还原的同时也使载体比表面积严重缩小,催化活性显著下降;紫外线照射可以引起 Au3+的逐渐还原以及 Au0 颗粒的生长,其催化失活作用弱于高温焙烧。     

茚虫威中间体合成用钯炭催化剂的载体研究

通过催化加氢合成茚虫威(indoxacarb)中间体反应用钯炭催化剂的性能对比,考察了钯炭催化剂的载体和载体预处理对催化剂性能的影响。实验结果表明:硝酸超声回流处理活性炭可以有效地去除活性炭中的杂质灰分,减小杂质对催化剂性能的影响;选择平均孔径大和比表面积高的活性炭为Pd/C催化剂载体可以获得较好的催化反应活性和选择性。     

SAPO-34分子筛的快速晶化及其NH3-SCR性能

相比单独采用三乙胺为模板剂,添加少量四乙烯五胺能明显加速SAPO-34分子筛的晶化过程,实现分子筛的快速合成。将快速合成的分子筛和商品分子筛经离子交换得到类似铜负载量的分子筛催化剂Cu/SAPO-34并进行NH_3-SCR性能测试。测试结果表明,Cu/SAPO-34催化剂表现出较好的NH_3-SCR活性,该类催化剂经750℃,10%H_2O,48h水热老化后展现出较新鲜态催化剂更优异的低温反应活性。相比商品化分子筛,快速合成所得催化剂有更优的高温活性和稳定性,具有良好的应用前景。     

新鲜和老化Pd/Al_2O_3密偶催化剂上催化C_3H_8转化催化性能（英文）

采用等体积浸渍法制备了以改性氧化铝为载体材料的Pd/Al_2O_3密偶催化剂,并采用H_2程序升温还原(H_2-TPR),CO化学吸附和X射线光电子能谱(XPS)对催化剂进行了表征。在模拟尾气条件下对催化剂的总包反应及与C_3H_8相关的单反应活性进行了测试。结果表明,老化处理后活性PdO_x数量下降,并伴随有金属态Pd~0的产生。老化后,起燃温度(T_(50))和完全转化温度(T_(90))分别提高了76和64℃,即催化剂低温活性比高温活性下降明显。对比新鲜和老化催化剂上单反应活性,结果表明,老化后无水条件下有NO参与的反应的低温活性下降显著。老化处理过程突出了NO对低温活性的抑制作用和H_2O对高温活性的促进作用。     

新鲜和老化Pd/Al2O3密偶催化剂上催化C3H8转化催化性能

采用等体积浸渍法制备了以改性氧化铝为载体材料的Pd/Al₂O₃ 密偶催化剂, 并采用H₂程序升温还原(H₂-TPR), CO 化学吸附和X射线光电子能谱(XPS)对催化剂进行了表征. 在模拟尾气条件下对催化剂的总包反应及与C₃H₈相关的单反应活性进行了测试. 结果表明, 老化处理后活性PdO_x 数量下降, 并伴随有金属态Pd₀的产生. 老化后, 起燃温度(T₅₀)和完全转化温度(T₉₀) 分别提高了 76 oC和64 oC, 即催化剂低温活性比高温活性下降明显. 对比新鲜和老化催化剂上单反应活性, 结果表明, 老化后无水条件下有NO参与的反应的低温活性下降显著. 老化处理过程突出了NO对低温活性的抑制作用和H₂O对高温活性的促进作用.     

Pdx-Co/C催化甲酸的电氧化性能研究

以活性碳(Vulcan XC-72)为载体,用化学还原法制备了不同Pd/Co摩尔比的Pdx-Co/C催化剂。用透射电镜(TEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)对催化剂进行了表征,采用循环伏安法考察了催化剂对甲酸电氧化反应的催化性能。结果表明,Pdx-Co复合催化剂粒子均匀分散在碳载体表面;催化剂中掺入的少量Co元素部分进入Pd晶格,形成了Pd-Co合金;随着Pd/Co摩尔比的增加,Pd颗粒粒径先增大后减小,催化活性也表现出相同的变化趋势;当Pd:Co=8:1时,所得Pd8-Co/C对甲酸氧化的催化活性最高,峰电流密度可达到15.907 mA/cm²。     

Effect of laser fluences on the structure of carbon nitride films deposited by direct current plasma assisted pulsed laser ablation

Carbon nitride films were deposited by direct current plasma assisted pulsed laser ablation of a graphite target under a nitrogen atmosphere at room temperature. The surface morphology, composition and bonding structure of the deposited films were characterized by atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, Raman, and X-ray photoelectron spectroscopy (XPS). The effect of laser fluences in the range 0.5–3 J/cm² on the surface morphology, composition and bonding structure of the carbon nitride films were systematically studied. As laser fluence is increased, AFM results show a great decrease in the surface roughness of carbon nitride films. FTIR and XPS results indicate an increase in the N/C ratio and the content of N atoms bonded to sp³ C, as well as a decrease in the content of H atoms and the content of N atoms boned to sp² C in the deposited films, and Raman spectra indicate an increase in the content of disordered sp² C atoms and the sp² cluster size. The increase in the film density and the decrease in the particle fraction contribute to the decrease of surface roughness with increasing laser fluence.     

Effect of fuel-to-nitrate ratio on the powder characteristics of nanosized CeO2 synthesized by mixed fuel combustion method

Synthesis of nanocrystalline ceria powders is carried out through the mixed fuel combustion approach by using different combinations of glycine and citric acid. The powders obtained with different fuel-to-nitrate (F/N) ratios are characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area analysis, and Raman spectroscopy. TGA and FTIR spectroscopy studies have revealed the presence of carbonaceous species and residual volatiles in the combustion synthesized ceria powders. It is observed that the variation of fuel-to-nitrate ratio has a profound influence on the carbonaceous residues from combustion, crystallite size (11-44 nm), surface area (9-39 m²/g) and morphology of the resultant powders. The Raman spectroscopy results on the variation of particle size with F/N ratio are consistent with the conclusions made from X-ray line broadening and BET surface area analysis.     

负载型纳米Pd/C的尺寸可控制备及其2,3,6-三氯吡啶加氢性能

在催化剂制备过程中引入氨羧络合剂(氨三乙酸三钠,NTA),通过配位作用稳定并保护Pd粒子,得到纳米Pd/C催化剂,研究了氨三乙酸三钠引入量对Pd/C催化剂结构的影响。通过X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电镜(TEM)及化学吸附(H_2-TPR)表征发现,与常规浸渍法制备的Pd/C催化剂相比,氨三乙酸三钠的引入能够有效减小Pd的平均粒径,并且通过调变氨三乙酸三钠的量可以获得Pd粒子不同大小的负载型Pd/C催化剂,随着氨三乙酸三钠引入量的增多(Pd摩尔含量的0.5、1、2倍),Pd粒径由5.7 nm减小至2.1 nm,但是继续增加氨三乙酸三钠的量(Pd摩尔含量的4倍),Pd粒径不再继续减小。当氨三乙酸三钠:Pd=1:1时,即Pd粒子大小约为4 nm时,催化剂获得了最佳催化反应性能,反应6 h原料全部转化,2,3-二氯吡啶的选择性可达76.86%。     

Preparation of nanometric CeO2–ZrO2–Nd2O3 solid solution and its catalytic performances

A kind of nanometric CeO₂–ZrO₂–Nd₂O₃ (CZN) solid solution for a carrier in the automotive three-way catalysts was synthesized by a coprecipitation method and characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption (BET), scanning electron microscopy (SEM) and oxygen storage capacity (OSC). For the purpose of comparison, an unincorporated CeO₂–ZrO₂ (CZ) was also synthesized. The XRD measurements disclose the prepared CeO₂–ZrO₂–Nd₂O₃ have a face-centered cubic fluorite structure and nanoparticle sizes. According to the results of XPS, Nd³⁺ ions can enter the CZ lattice and form a homogenous solid solution. Oxygen storage capacity measurements reveal that CeO₂–ZrO₂–Nd₂O₃ display high oxygen mobility at a low temperature. The results of the activity tests show that the catalyst exhibits good three-way catalytic activity and fairly wide range of air-to-fuel ratios.     

Electroless Ni-Co-P Coating of Cenospheres Using Ag(NH_3)_2~+ Activator

FLY ASH CENOSPHERES are primarily a by-productin power generation plants.Research is in progress toeffectively use this by-product to produce new usableand profitable materials as they pose major disposaland environmental problems.Fly ash cenospheres areunique,property stable,non-toxic,non-metallic hollowmicro-particles.Due to the unique hollow structure andphysical mechanics properties,Cu^Ag and other metalsare often coated on cenospheres to produce lightweightmetal matrix composites,w…     

Effect of reduction-oxidation treatment on the properties of VSb_3W-Al_2O_3 catalyst for propane ammoxidation

VSb3W-Al2O3 catalysts for propane ammoxidation were prepared by the conventional slurry method and new slurry method,namely,the reduction-oxidation slurry method.The effect of preparation methods on the physicochemical properties of VSb3W-Al2O3 catalysts were studied by N2 adsorption,XRD,XPS and Raman spectroscopy,and their catalytic performance for the ammoxidation of propane to acrylonitrile were tested.Compared with the VSb3W-Al2O3 catalyst prepared by the conventional slurry method,the VSb3W-Al2O3 catalyst prepared by the reduction-oxidation slurry method exhibited better propane conversion and acrylonitrile selectivity.This is due to that the reduction-oxidation treatment was advantageous for obtaining low valence state vanadium and high valence state antimony to form more rutile SbVO4,which is a vital active phase for propane ammoxidation.     

Preparation of platinum-iridium nanoparticles on titania nanotubes by MOCVD and their catalytic evaluation

Pt based catalysts are commonly used in several industrial processes involving hydrogenation and dehydrogenation reactions. New deposition methods as well as support materials are being investigated to generate new catalysts with superior catalytic activity. In this work, platinum-iridium (Pt-Ir) nanoparticles of about 5 nm in size were supported on titania (TiO₂) nanotubes by metal organic chemical vapor deposition (MOCVD). The TiO₂ nanotubes were prepared by an alkali hydrothermal method using sodium hydroxide solution at 100 °C, during 64.8 ks. Pt-Ir nanoparticles were obtained by controlling the MOCVD conditions at 400 °C and 66.6 kPa.Textural properties and particle size were investigated by nitrogen physisorption (BET method), X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy. Catalytic activity was measured in cyclohexene disproportion as the test molecule for hydrogenation/dehydrogenation reactions. The TiO₂ nanotubes exhibit a considerable high surface area of about 425,000 m²/kg, however, after calcination at 400 °C their nanotubular morphology was partially transformed. In spite of this change, the 5 nm Pt-Ir nanoparticles supported on TiO₂ nanotubes were more active in the cyclohexene disproportion reaction than conventional Pt-Ir/alumina catalysts in the whole range of temperatures investigated (50–250 °C). Hydrogenation reactions (high selectivity to cyclohexane) predominate at temperatures below 150 °C.