耐硫甲烷化中H2S浓度对MoO3/Al2O3和CoO-MoO3/Al2O3催化剂的影响

在0 到12 mL·L^-1 (体积分数φ=0.00%-1.20%) 范围内考察了不同H₂S 浓度对25% (质量分数, w)MoO₃/Al₂O₃和5% (w) CoO-25%MoO₃/Al₂O₃催化剂甲烷化性能的影响. 结果表明, 5%CoO-25%MoO₃/Al₂O₃的甲烷化活性随H₂S浓度的增加单调上升, 而25%MoO₃/Al₂O₃对H₂S浓度并不敏感. 对比这两种催化剂发现, 只有在H₂S浓度高于0.40% (φ) 时, 在25%MoO₃/Al₂O₃中添加Co助剂才会有促进作用; H₂S浓度低于0.40% (φ)时, Co助剂会抑制25%MoO₃/Al₂O₃催化剂的甲烷化活性. 分别对反应前后的催化剂表征发现, H₂S浓度的改变不会对两种催化剂的物理结构产生明显的影响, 而是通过影响催化剂表面的金属硫化物活性位来影响催化剂的甲烷化性能. 耐硫甲烷化反应体系中较高的硫含量下Co助剂才表现出对25%MoO₃/Al₂O₃催化剂的促进作用. 该研究明确了在MoO₃/Al₂O₃催化剂中添加Co助剂的硫化氢浓度范围, 为工业上选择合适的催化剂提供了依据.     

Pd@SiO2/Al2O3的制备及其催化氧化CO性能评价

从Pd纳米粒子出发制备具有核壳结构的Pd@SiO₂纳米粒子,并将其负载于不同形貌Al₂O₃载体上,制备出具有良好CO催化氧化活性的催化剂。以纳米球形Al₂O₃为载体时,Pd@SiO₂/Al₂O₃催化剂活性优于无核壳结构的Pd/Al₂O₃催化剂。将纳米Pd@SiO₂负载到球形和菱形Al₂O₃上,制备出Pd@SiO₂/Al₂O₃催化剂。结果表明:具有较大比表面积的Al₂O₃载体(球形)有利于Pd@SiO₂的分散,且SiO₂层可以抑制Pd粒子的团聚,能在一定程度上改善催化活性。而较小比表面积的载体(菱形)上出现了Pd@SiO₂的团聚,表现出较低的CO氧化活性,但在降低负载量后,CO氧化活性明显提高。该结果为推动新型热稳定、高效纳米三效催化剂的研发具有一定的启示意义。     

Fe2O3/Al2O3氧载体用于甲烷化学链燃烧：负载量与制备方法的影响

以不同方法制备了系列Fe₂O₃/Al₂O₃氧载体,采用XRD、H₂-TPR、CH₄-TPR、O₂-TPD和BET等分析技术对氧载体进行了表征。研究了不同Fe₂O₃负载量氧载体的甲烷化学链燃烧性能,考察了不同制备方法对Fe₂O₃/Al₂O₃氧载体结构、反应性和产物选择性的影响。结果表明,Fe₂O₃负载量对氧载体活性及产物中CO₂选择性的影响较大,负载量较低时氧载体活性较低且引起甲烷部分氧化产物CO含量增加。制备方法亦对氧载体与甲烷的反应活性有所影响,整体上共沉淀法制备的质量分数60％Fe₂O₃/Al₂O₃氧载体具有较高的氧化活性和化学链循环稳定性。其在反应温度850℃、反应时间15 min、30次循环后甲烷转化率及产物中CO₂选择性均未见明显降低。     

ZrO2修饰Al2O3纳米片负载钴催化剂的制备及其费托反应性能研究

通过水热法合成了Al₂O₃纳米片（Al₂O₃-CN）,采用浸渍法制备20%（质量分数）钴基催化剂,并应用于费托合成反应。制备的Al₂O₃-CN（226 m²/g）与商业氧化铝（Al₂O₃-C,249 m²/g）具有相近的比表面积,但Al₂O₃-CN孔尺寸分布更加集中。浸渍钴后,与Co/Al₂O₃-C催化剂相比,Co/Al₂O₃-CN催化剂表现出较高的还原度及更均匀的钴颗粒粒径分布。因此,Co/Al₂O₃-CN催化剂表现出更高的CO转化率和低的甲烷选择性。为了进一步提高Co/Al₂O₃-CN的催化性能,采用不同含量ZrO₂对Al₂O₃-CN进行修饰。表征结果表明,随着ZrO₂修饰量的增加,Al₂O₃-CN载体比表面积变化不明显,孔体积和孔径增大;相对应催化剂的钴颗粒粒径减小,活性位点数目增加。在相同反应条件下,经ZrO₂修饰催化剂CO转化率进一步提高,甲烷选择性降低。     

有序介孔氧化铝的制备及其在丁烯歧化中的应用

采用有机铝源及阴离子模板剂制备了高比表面积、大孔容、窄孔径分布的有序介孔氧化铝(Al₂O₃)载体, 研究了铝源水解速率、模板剂碳链长度以及洗涤介质等因素对有序介孔氧化铝载体合成的影响。实验结果表明,提高铝源水解速率和用乙醇溶剂洗涤Al₂O₃前躯体都有利于Al₂O₃载体形成有序介孔结构,所得Al₂O₃载体的孔径和孔体积随着模板剂碳链长度的增加而增大。分别用有序介孔Al₂O₃和普通介孔Al₂O₃为载体,采用浸渍法负载氧化铼(Re₂O₇)制备了铼基催化剂,并用于评价丁烯歧化合成丙烯的反应性能。实验结果表明,铼基有序介孔催化剂(Re/OMA)的丁烯歧化性能显著优于普通铼基介孔催化剂(Re/MA),丁烯转化率高于50%,丙烯选择性约60%,丙烯收率达30%,催化剂寿命明显延长。     

过渡金属修饰Fe2O3/Al2O3氧载体的Redox性能研究

采用冷冻干燥法分别制备了经Cu、Co、Mn、Ni修饰的Fe₂O₃/Al₂O₃氧载体。利用化学吸附仪,通过程序升温还原(H₂-TPR)和程序升温氧化(TPO)来研究经不同过渡金属修饰的Fe₂O₃/Al₂O₃与H₂和O₂的反应性能。实验发现,在Fe₂O₃/Al₂O₃中加入Cu、Co、Ni以后,氧载体与H₂的反应性都有提高,但是当在Fe₂O₃/Al₂O₃中加入Mn以后,氧载体的反应性和载氧能力反而下降。经Cu修饰的Fe₂O₃/Al₂O₃与H₂的反应性最高,且具有很好的反应稳定性,适合用于化学链燃烧。     

硝酸盐制备三维有序大孔金属氧化物材料研究

用硝酸盐、柠檬酸和乙醇/水按一定摩尔比配置成前驱物溶液, 采用胶晶模板法, 制备了三维有序大孔金属氧化物材料: Al₂O₃, CeO₂, Cr₂O₃, NiO, MgO, In₂O₃, CeO₂/Al₂O₃, Cr₂O₃/Al₂O₃和NiO/Al₂O₃. SEM观察表明, 材料中大孔有序排列, 大孔间由小孔相连, 形成三维规则的笼状网络结构. XRD和TEM测试表明, 大孔孔壁由具有纳米尺寸的金属氧化物粒子组成. 实验表明, 加入乙醇、柠檬酸, 提高溶液对胶球润湿性, 改善溶液渗透能力, 避免粒子团聚, 有利于有序大孔结构的形成. 这一研究表明, 根据硝酸盐的物理化学性质, 调整溶液组成, 选择合适的热处理温度, 能得到大孔排列有序、三维规整性好的大孔结构材料. 此法具有原料易得, 操作简单的特点, 是3DOM材料的一种新型高效制备路线.     

气相色谱法研究配位化合物的热稳定性(Ⅶ)——Ni(Ⅱ)、Co(Ⅱ)草酸配合物的热分解及产物的催化性能

镍(Ⅱ)、钴(Ⅱ)草酸配合物在氢气中热分解时产生CO₂和CO,并发生加氢催化反应.CoC₃O₄和NiC₂O₄的分解产物CO₂加氢活性很快降低;K₂O等具有分散金属的作用。CoC₂O₄/Al₂O₃和K₂^{[Co(C₂O₄)₂]}/Al₂O₃体系具有Al₂(C₃O₄)₃的分解特征。C₂O₄^2-在Al₂O₃表面能形成表面配合物,在Al₂O₃表面Co(Ⅱ)的还原较为困难。     

负载Pd基碳二选择加氢催化剂上乙炔加氢反应的原位红外光谱研究

以乙烯和乙炔为探针分子, 采用原位红外光谱技术研究了Pd-Ag/Al₂O₃和Pd/Al₂O₃催化剂上乙炔加氢反应, 通过乙炔吸附, 乙炔和氢的共吸附和交替吸附表征了催化剂表面吸附物种的变化. 结果表明, 在Pd-Ag/Al₂O₃催化体系中, 乙炔在Pd-Ag/Al₂O₃和Pd/Al₂O₃催化剂有着不同的吸附性能, 另外, 加氢反应会导致在催化剂表面形成由长分子链的烷烃组成的碳氢化合物层, 该吸附层与绿油有着相似的红外光谱特征, 最关键的是乙炔和氢的吸附顺序和碳氢化合物层的生成量之间存在着一定的关系, 这将直接影响催化剂的加氢性能.     

填料型固体酸的制备及其催化性能

用阳极氧化法制备了填料式Al₂O₃-Al载体,经浸渍H₂SO₄后再焙烧制得SO₄^2-/Al₂O₃-Al固体酸催化剂.用SEM,BET,XRD和NH3-TPD等手段对其进行了表征,结果显示,载体Al₂O₃膜为无定形结构,SO₄^2-/Al₂O₃-Al为中等酸强度的固体酸.用乙酸-乙醇酯化催化反应评估了该固体酸的催化性能,显示出催化剂具有较高的催化活性,且稳定性较好.     

Kinetics of thermal decomposition of nickel sulfate hexahydrate

The paper describes the kinetics of all the recorded steps of thermal decomposition of nickel sulfate hexahydrate in air. The thermal decomposition of the salt in air led to NiO at about 1060 K. The kinetic parameters, the activation energyE and the preexponential factorA, and the thermodynamic parameters, the entropy, enthalpy and free energy of activation were evaluated for the dehydration and decomposition reactions. Tentative reaction mechanisms are suggested for each step of the thermal decomposition.     

Development of a thermal conductivity cell with nanolayer coating for thermal conductivity measurement of fluids

Various techniques and methodologies of thermal conductivity measurement have been based on the determination of the rate of directional heat flow through a material having a unit temperature differential between its opposing faces. The constancy of the rate depends on the material density, its thermal resistance and the heat flow path itself. The last of these variables contributes most significantly to the true value of steady-state axial and radial heat dissipation depending on the magnitude of transient thermal diffusivity along these directions. The transient hot-wire technique is broadly used for absolute measurements of the thermal conductivity of fluids. Refinement of this method has resulted in a capability for accurate and simultaneous measurement of both thermal conductivity and thermal diffusivity together with the determination of the specific heat. However, these measurements, especially those for the thermal diffusivity, may be significantly influenced by fluid radiation. Recently developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. A thermal conductivity cell for measurement of the thermal properties of electrically conducting fluids has been developed and discussed.     

Parameter determination of a thermal desorption model

A new method for the analysis of thermal desorption spectra is presented, based on the experimental peak maximum functions for temperatureT _m(β) and pressureP _m(β) and a rigorous mathematical treatment. The resonant heating rate β_r is determined, satisfyingT _m(β_r)=T _r, whereT _r is the resonant temperature defined byA exp(−E _d/(RT _r))=1. Desorption energyE _d and frequency factorA can be determined simultaneously with relatively high robustness towards statistical experimental errors as demonstrated by computer-simulated thermal desorption spectra.     

Thermal Behaviour of Pharmacologically Active Lithium Compounds

The thermal decompositions of a series of simple lithium compounds (carbonate, sulfate, acetate, citrates, aspartates and glutamates) currently used in the treatment of manic-depressive psychosis and related disorders were investigated by means of TG and DTA measurements in oxygen atmosphere. Pyrolysis residues were characterized by infrared spectroscopy. The stabilities of the hydrates and intermediate phases generated during the degradation processes are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal Analysis in Studies of Technological Waste Materials to Be Subjected to Thermal Treatment

Attempt was made to evaluate the usefulness of thermoanalytical methods, combined with X-ray phase analysis and chemical analyses, for the study of thermal decomposition of waste materials to be subjected to thermal treatment. The object of the studies were petrochemical waste materials intended to be decomposed in a rotary furnace. Results are given of the studies of five selected waste materials. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of vapor‐phase‐formaldehyde treatments on thermal conductivity and diffusivity of ramie fibers in the range of low temperature

To understand the influence to thermal conductivity by bridging in the polymer fibers, the thermal conductivity, and thermal diffusivity of ramie fiber and those bridged by formaldehyde (HCHO) using vapor‐phase method (VP‐HCHO treatment) were investigated in the lower temperature range. The thermal conductivities of ramie fiber with and without VP‐HCHO treatments decreased with decreasing temperature. Thermal diffusivities of ramie fiber with and without VP‐HCHO treatments were almost constant in the temperature range of 250–50 K, and increased by decreasing temperature below 50 K. Thermal conductivity and thermal diffusivity of ramie fiber decreased by VP‐HCHO treatment. The crystallinities and orientation angles of ramie fibers with and without VP‐HCHO treatment were measured using solid state NMR and X‐ray diffraction. These were almost independent of VP‐HCHO treatment. Although tensile modulus decreased slightly by VP‐HCHO treatment, the decrease could not explain the decrease in thermal conductivity and diffusivity with decreasing sound velocity. The decrease of the thermal diffusivity and thermal conductivity by VP‐HCHO treatment suggested the possibility of the reduction of the mean free path of phonon by HCHO in VP‐HCHO treated ramie fiber. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2754–2766, 2005     

Photoacoustic infrared spectroscopy and thermophysical properties of syncrude cokes

This paper presents and interprets photoacoustic (PA) infrared spectra and four different thermophysical properties (thermal conductivity, thermal diffusivity, volumetric specific heat and thermal effusivity) for four sets of hydrocarbon cokes. A total of 12 samples, with varying histories, were analyzed. These cokes are a by-product of the upgrading of bitumen to Syncrude Sweet Blend (a blend of hydrotreated components), and were obtained from several locations in the thermal cokers operated by Syncrude Canada Ltd. in Fort McMurray, Alberta, Canada. PA infrared spectroscopy provides detailed information on the amount and type of residual aromatic hydrocarbons in cokes; aliphatic hydrocarbons are sometimes detected in smaller quantities. Three of the thermophysical properties (thermal conductivity, diffusivity and effusivity) display systematic differences among the cokes. On the other hand, volumetric specific heat hardly varies, a phenomenon that accounts for the observed proportionality between thermal diffusivity and conductivity. Analogous relationships exist between thermal effusivity and both thermal conductivity and thermal diffusivity for these cokes. The magnitudes of these three thermophysical properties tend to increase as aromatics contents, determined by PA spectroscopy, decrease.This revised version was published online in November 2005 with corrections to the Cover Date.     

Application of Thermal Analysis in Radiocarbon Dating

Thermal analysis combined with mass spectrometry was applied to radiocarbon dating procedures (age determination of carbon containing samples) to determine the optimal temperature range for the reduction of CO₂ over metallic cobalt of various particle sizes. Experiments were carried out to show the different catalytic activities of cobalt of particle sizes 1, 1–45 and 44 μm. The morphology of the cobalt samples and the deposited carbon were investigated. The quantification of CH₄ and CO formed during the reduction of CO₂ was done by means of pulse thermal analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal Behaviour of Ammonium Oxofluorotitanates(IV)

The thermal behaviour of ammonium oxofluorotitanates (NH₄)₃TiOF₅, (NH₄)₂TiOF₄ and NH₄TiOF₃ was investigated by thermoanalytical, X-ray and IR spectroscopic methods. The first decomposition stages under quasi-isobaric conditions are characterized by the formation of (NH₄)₂TiF₆ and ammonium oxofluorotitanate with the less content of ammonium and fluorine than in the initial compound. The decomposition process is accompanied by the Ti(IV) reducing due to ammonia evolved. The new ammonium oxofluorotitanate of high volatility was isolated and characterized. Ammonium-containing non-stoichiometric titanium oxyfluorides are the final products of thermal decomposition of ammonium oxofluorotitanates.This revised version was published online in November 2005 with corrections to the Cover Date.