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1.
采用双表面活性剂模板(十六烷基三甲基溴化铵和聚乙二醇辛基苯基醚的混合物)分解法制备了不同原子比( nLa+ nCo)/( nLa+ nCo+ nZr)和不同温度焙烧的系列介孔混合氧化物催化剂La-Co-Zr-O。运用XRD、N 2吸附/脱附、XPS和H 2-TPR等技术对催化剂进行了表征,并以CO和C 3H 8氧化为模型反应,考察了组分配比和焙烧温度等参数对催化剂催化性能的影响。比表面积和孔径测试结果表明,样品具有很高的比表面积(108~266 m 2·g -1)和分布集中的孔径(3.4~3.9 nm),Zr含量较高的样品比表面积较大。XRD结果表明,样品中的活性组分钴物种主要以Co 3O 4形式存在;XPS和H 2-TPR结果表明,样品中可还原的晶格氧的数量、活动度以及表面钴原子浓度均与催化剂对CO和C 3H 8的氧化性能密切相关。原子比为0.5的样品中,较多的晶格氧易于在相对低温下还原;而原子比为0.7的样品表面钴原子浓度较高,这使得两样品均表现出较高的催化活性。经650 ℃焙烧的样品仍保持较高的比表面积(108 m 2·g -1)和分布集中的介孔孔径(最可几孔径约3.8 nm),且催化活性下降幅度也很小,表明该系列介孔催化剂具有优良的抗烧结能力和介孔热稳定性。 相似文献
2.
采用共沉淀法制备了系列Ce 0.5+xZr 0.4-xLa 0.1O 2-Al 2O 3催化剂, 其中0≤x≤0.4且Ce 0.5+xZr 0.4-xLa 0.1O 2与Al 2O 3的质量比为1:1. 考察了该系列催化剂对柴油车排放碳烟的催化燃烧性能, 并用低温N2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、氢气程序升温还原(H 2-TPR)和氧气程序升温脱附(O 2-TPD)等手段对催化剂进行了表征. 研究结果表明该系列催化剂均形成了具有立方萤石结构的固溶体. 当x=0.2时, Ce 3+离子在催化剂表面有一定的富集, 此时催化剂具有最大的β氧脱附峰和最好的表面还原性能, 同时具有良好的催化碳烟氧化活性, 碳烟在该催化剂的起燃温度为360 °C, 具有较好的应用前景. 相似文献
3.
以共沉淀法制得的Co 3O 4为载体, 采用两步法负载Au和Cu制得了一系列Au-Cu/Co 3O 4双金属催化剂, 考察了Au-Cu/Co 3O 4双金属催化剂完全催化氧化乙烯的性能, 并通过X射线衍射(XRD)、高分辨透射电镜(HRTEM)、H 2程序升温还原(H 2-TPR)和O 2程序升温脱附(O 2-TPD)对催化剂进行了表征. 活性测试结果表明: 负载型Au-Cu/Co 3O 4双金属催化剂的催化性能优于单一金属催化剂Au/Co 3O 4, 并且在Au负载量为4% (w, 质量分数)时, 与AuCu/Co 3O 4和Au 3Cu/Co 3O 4催化剂相比, AuCu 3/Co 3O 4催化剂的催化活性较好, 0 ℃时可催化转化15.3%的乙烯为CO 2和H 2O, 120 ℃时100%催化转化乙烯. XRD和HRTEM表明, AuCu 3/Co 3O 4催化剂中有Au-Cu合金相的生成, 而Au 3Cu/Co 3O 4催化剂中Cu主要以氧化物的形式存在. Au和Cu之间产生相互作用, 使活性相金属的粒径降低. H 2-TPR和O 2-TPD分析结果表明, AuCu 3/Co 3O 4催化剂具有较强的低温可还原能力和可提供的大量表面活性吸附氧物种, 促进了乙烯的完全催化氧化. 相似文献
4.
利用热分解法制备了结构明确的负载型纳米晶催化剂。在纳米晶成核和生长过程中加入一维ZnO纳米棒作为晶种,调控不同组分的纳米晶在 ZnO纳米棒表面均匀生长,从而获得了结构明确的 MnO/ZnO、Co 3O 4/ZnO、Co 3Mn 1/ZnO催化剂。透射电子显微镜(TEM)与 X 射线粉末衍射(XRD)结果显示,不同组分纳米颗粒都均匀分散在 ZnO 纳米棒表面。相对于 MnO/ZnO 和Co 3O 4/ZnO催化剂,Co 3Mn 1/ZnO催化剂在CO氧化反应中具有最佳的催化性能。在200 L·g cat-1·h -1的气时空速下,Co 3Mn 1/ZnO催化剂起活温度为 50 ℃,其 T100(CO 转化率达到 100% 时的温度)为 200 ℃;利用 X 射线光电子能谱(XPS)对不同催化剂进行了分析,结果显示,Co 3Mn 1/ZnO催化剂的氧空位比MnO/ZnO催化剂提高了30%以上,从而使其具有较高的CO氧化催化性能。更为重要的是,Co 3Mn 1/ZnO复合纳米晶催化剂的活化能(39.4 kJ·mol -1)远低于其它负载型纳米晶催化剂。 相似文献
5.
采用胶溶法制备了一系列碱土金属改性的ZrO 2-Al 2O 3, 并以其为载体采用等体积浸渍法制备了Pd-Rh密偶催化剂. 采用低温N 2吸附-脱附、X射线衍射(XRD)、氨气程序升温脱附(NH3-TPD)对载体样品进行了表征. 结果表明, 碱土金属的添加增大了ZrO 2-Al 2O 3的比表面积, Sr-Zr-Al样品经1000 °C焙烧5 h后具有最大的比表面积, 为164 m 2·g -1. 对催化剂进行了H 2程序升温还原(H 2-TPR)、X射线光电子能谱(XPS)和活性表征, 考察了催化剂对C 3H 8的转化活性. 测试结果表明, 添加碱土金属能有效提高催化剂上丙烷的转化活性. 相似文献
6.
直接甲醇燃料电池(DMFC)由于具有较多的优点而受到广泛的关注. 但是碳载Pt (Pt/C)阳极催化剂电催化活性低是限制其应用的一个主要问题. 为了提高Pt/C催化剂对甲醇氧化的电催化性能, 分别用CO 2, 空气, H 2O 2或HNO 3对常用作为载体的Vulcan XC-72碳黑进行预处理. 结果表明, 在用CO 2, 空气, HNO 3, H 2O 2处理的及未处理的碳黑作载体制得的Pt/C催化剂电极上, 甲醇氧化峰的峰电流密度顺序为39, 33, 32, 20和18 mA•cm -2, 表明用CO 2处理的碳载体制备的Pt/C催化剂对甲醇氧化有最好的电催化活性和稳定性. 其主要原因是用CO 2处理能减少碳黑表面的含氧基团和增加石墨化程度, 而使碳黑的电阻降低及Pt粒子在碳黑上的分散性变好. 相似文献
7.
采用共沉淀法制备了高性能低铈储氧材料Ce 0.35Zr 0.55Y 0.07La 0.03O 1.95(OSM,储氧材料)和胶溶法制备了耐高温、高比表面的La-Al 2O 3并以它们为载体,制备了一系列整体式铁基催化剂。考察了该系列催化剂对甲烷稀薄燃烧的催化性能,并用低温N 2吸附-脱附,储氧能力(oxygen storage capacity,OSC),XRD,XPS和H 2-TPR等测试手段对载体和催化剂进行了表征。活性测试结果表明所制得的整体式催化剂Fe/OSM+La-Al 2O 3可在50 000 h -1的高空速条件下使含量为1%的甲烷在474 ℃起燃,565 ℃完全转化;低温氮吸附-脱附测试结果表明,所制得的Ce 0.35Zr 0.55Y 0.07La 0.03O 1.95经1 050 ℃焙烧5 h后的BET比表面积达33 m 2·g -1,孔容为0.14 mL·g -1;La-Al 2O 3经1 050 ℃焙烧5 h后的BET比表面积达125 m 2·g -1,孔容为0.46 mL·g -1,是优良的催化剂载体;OSC测试结果表明,加入储氧材料(oxygen storage material(OSM))能增加催化剂的储氧性能,有利于催化活性的提高;XRD测试结果表明,OSM以均一固溶体存在;XPS测试结果表明,Fe 2O 3与OSM载体之间的相互作用最强;H 2-TPR测试结果表明,加入OSM能增加催化剂的还原性能,从而提高了催化活性。 相似文献
8.
采用浸渍和共沉淀两种方法分别制备了BaO改性的Pd/CeO 2-ZrO 2-La 2O 3-Al 2O 3催化剂.运用N 2吸附-脱附,X射线衍射(XRD),H 2程序升温还原(H 2-TPR),NH 3程序升温脱附(NH 3-TPD),透射电子显微镜(TEM)和X射线光电子能谱(XPS)对催化剂进行表征,并考察其对甲醇,CO, C 3H 8 和 NO的催化性能.活性测试结果表明,BaO的引入可明显改善Pd催化剂对甲醇,CO, C 3H 8和NO的催化活性,且浸渍法最佳,起燃温度( T50)分别降低了43,31,45和35 ℃.XRD,H 2-TPR及XPS结果表明,浸渍法引入BaO主要通过表面改性方式,强化Pd-Ce界面间的相互作用,改善催化剂的还原性能,进而提高催化剂的低温活性;而共沉淀法则是通过结构改性方式增加CeO 2晶格缺陷,加速活性氧物种的流动,Ce 3+浓度的增加是促使CO氧化活性显著提高的主要原因. 相似文献
9.
采用沉淀法制备了 Co 3O 4, 考察了焙烧和预处理条件对其结构、低温催化氧化 CO 性能的影响. 热重分析表明, 未经焙烧的样品以 Co(OH) 2CO 3 的形式存在, 150~400 oC 空气气氛中焙烧后, 样品以立方相 Co 3O 4 的形式存在. N2 吸附-脱附法、X 射线衍射、透射电镜及活性测试结果表明, 以纳米颗粒物存在的 Co 3O 4 的比表面积、颗粒尺寸、催化氧化 CO 活性与焙烧温度密切相关. 正电子湮没寿命谱、O 2-程序升温脱附与定温条件下 CO 氧化测试结果表明, 合适温度 (150~250 oC) 下 N 2 预处理有利于 Co 3O 4 表面氧空穴团的形成, 它在吸附活化分子氧以及 CO 催化氧化反应中起到关键作用. 同时讨论了预处理作用下Co 3O 4表面氧空穴的再构机制. 相似文献
10.
通过两步法成功合成了由纳米粒子组装成的柱状Co 3O 4。第一步是通过简单的冷凝回流法合成柱状CoC 2O 4·2H 2O。第二步将所制备的柱状CoC 2O 4·2H 2O在350℃下煅烧2 h,使其分解形成Co 3O 4而不破坏原始形貌。通过粉末X射线衍射(PXRD),X射线光电子能谱(XPS),氮气吸附-脱附,扫描电镜(SEM),高分辨率透射电子显微镜(HRTEM)和H 2程序升温还原(H 2-TPR)表征柱状Co 3O 4的物化性质。结果表明,柱状Co 3O 4对乏风甲烷燃烧的催化活性远远高于商业Co 3O 4。柱状Co 3O 4优异的催化性能可能归因于其表面较高的Co 3+含量,较高的表面吸附氧和大量暴露的{111}晶面族。 相似文献
11.
The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
12.
非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。 相似文献
13.
The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness. 相似文献
14.
Two vanilloids, (5 E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one ( 1) and 4-[3-hydroxydecyl]-2-methoxyphenol ( 2), isolated from the dried seeds of Grains of Paradise ( Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared. 相似文献
15.
In this review, the research of the author in the field of colloidal systems is summarized. The factors influencing colloidal stability are systematized and analyzed. Examples are presented to illustrate the practical utilization of the theory of stability of colloids and thin films.This review was prepared on the basis of the works of the author, which were awarded the State Premium for 1991 in the field of science and technology, chemistry section.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1708–1717, August, 1992. 相似文献
16.
Main hydration products of two cement pastes, i.e. CSH-gel, portlandite ( P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time ( th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with ( th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with ( th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700 oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
17.
用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。 相似文献
18.
The enthalpies of solution of several oxosulfides of rare-earth elements and the high-temperature enthalpies of oxosulfides
and oxosulfates of lanthanum and yttrium were measured using solution calorimetry and high-temperature microcalorimetry techniques.
Standard enthalpies of formation and some thermodynamic properties of oxosulfides and oxosulfates were calculated.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2 pp. 294–297, February, 1997. 相似文献
20.
针对恶臭测试的环境影响问题,提出了解决的实例方案,并对方案的要点及优缺点进行讨论,此方案在实际操作中具有较好的效果。 相似文献
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