溶剂化金属原子浸渍法制备高分散负载型催化剂——Ⅸ.K-Fe/硅沸石催化剂的XRD、TEM、XPS和磁测定表征

用溶剂化金属原子浸渍(SMAI)法和普通浸渍(CI)法两种不同的方法制备了组成相同的K-Fe/硅沸石催化剂。TEM,XRD,XPS和磁测定结果表明,SMAI K-Fe/硅沸有催化剂中铁的分散度和还原度都大于CI催化剂,SMAI催化剂中金属颗粒直径小于4nm,具有超顺磁性,而CI催化剂中金属颗粒较大,表现铁磁性。两种方法制备的催化剂反应前后金属的状态发生明显的改变,对CO+H_2反应的催化性质不同。     

RC和LC延迟触发器

对大功率延迟触发器中使用的氢闸流管的栅极点火特性,特别是延迟时间分散度做了比较细致的研究,对延迟时间做了理论计算,理论和实验符合得很好。本实验所用的延迟触发器输出电压幅度为3kV,电阻性负载的输出功率为十分之几兆瓦,最大时延50μs,改进型RC延迟器的时间分散度小于70ns,LC延迟触发器的时间分散度小于20ns。最后对进一步提高延迟时间的稳定性提出了若干改进措施。     

负载型Rh基催化剂上的CO加氢制乙醇反应：载体效应

Ethanol has great application prospects given it is an important essential chemical and a substitute for traditional energy sources. Currently, ethanol production is achieved through grain fermentation and petroleum-based ethylene hydration. However, the inefficient fermentation processes and increasingly depleted crude oil resources hinder the large-scale production of ethanol. Therefore, the development of alternative technologies for ethanol production has become an important issue. The direct production of ethanol from syngas (CO + H₂) is considered to be a new strategy to acquire high value-added products and achieve clean utilization of carbonaceous resources such as coal, natural gas, and biomass. Supported Rh-based catalysts have been extensively studied as the most promising and effective systems for the direct production of ethanol from syngas. The use of promoters and supports is generally effective in increasing the activity and ethanol selectivity of supported Rh-based catalysts. Fe is widely used in the research on Rh-based catalysts, as it is one of the most effective promoters for enhancing ethanol selectivity. In this work, with the aim of exploring the role of the support, we used the incipient wetness impregnation method to prepare Fe-promoted Rh-based catalysts supported by CeO₂, ZrO₂, and TiO₂ for the synthesis of ethanol from syngas. CO conversion of CO on the RhFe/TiO₂ catalyst was as high as 18.2% under the reaction conditions of 250 ℃ and 2 MPa, and the selectivity to ethanol in the alcohol distribution was 74.7%, which was much higher than that observed with RhFe/CeO₂ and RhFe/ZrO₂ under the same conditions. The characterization results showed that the specific surface of the catalyst followed the order RhFe/CeO₂ < RhFe/ZrO₂ < RhFe/TiO₂; the dispersion of Rh increased sequentially, and the particle size decreased in the same order. A larger specific surface area may favor the dispersion of the Rh species, and the highly dispersed Rh species would imply a greater number of active sites on the surface of the support. The results of H₂-temperature-programmed reduction indicated possible interactions between Rh and the support as well as between Rh and Fe, and partial reduction of TiO₂ under the experimental reduction conditions; however, the other supports did not undergo reduction. The results of X-ray photoelectron spectroscopy indicated that the RhFe/TiO₂ catalyst had the largest amount of Rh⁰ as well as Rh⁺ species. Thus, this catalyst has more (Rh_x⁰-Rh_y⁺)-O-Fe^δ+ active sites for the synthesis of ethanol, which greatly increases the ethanol selectivity. CO-temperature programmed desorption was used to confirm the CO adsorption capacity of different catalysts. The results showed that TiO₂ enhances the adsorption of CO due to the presence of more O vacancies and Ti³⁺ ions, which is beneficial to the improvement of the catalyst activity.     

超临界合成Pt修饰的TiO2用于光催化CO2还原制备太阳能燃料

考察了超临界条件下合成TiO2基光催化剂的性质,尤其是在超临界CO2下得到的分散在TiO2上Pt的特性,并与商品化TiO2性能进行了比较.另外,所得催化剂的光催化活性用CO2光还原制太阳能燃料进行了评价.结果表明,该催化剂可得到具有比商用TiO2更好或类似的性能(高比表面积、结晶度、表面羟基浓度,大的孔容、增强的可见光吸收、高的甲烷生成速率)而用于CO2还原制备燃料的反应中.这可归因于该催化剂超临界介质合成过程.     

W量对Pt/GaWZrOx催化剂结构及甘油选择氢解性能的影响

在甘油选择氢解制1,3-丙二醇(1,3-PDO)反应中, Pt-WO_x催化剂体系因其高活性和高选择性而受到研究者的广泛关注.本工作制备了W量不同的Ga掺杂GaWZrOx固体酸(GaWZ),然后作为载体采用浸渍法制备了Pt/GaWZ催化剂,系统考察了W的量对催化剂物化性质和催化性能的影响.CO化学吸附和X射线光电子能谱(XPS)表征发现,随着Ga WZ载体中W量的增加,其上负载的Pt的分散度先增加,在10%(w) W的Pt/GaWZ(10)催化剂上达到最高值86%,然后在15%(w) W时降低.紫外-可见漫反射(UV-Vis DRS)、傅里叶变换红外(FTIR)和XPS表征表明, Pt/GaWZ催化剂中的W与四方相ZrO2表面的Zr—OH基团存在较强作用,形成了单分散的WO_x物种;当大于7.5%(w) W时,开始出现第二层WO_x物种.单分散的WO_x物种可能是Pt分散度提高的重要原因.由程序升温氨脱附(NH3-TPD)和吡啶吸附红外(Py-IR)表征结果可见,W的量越高,催化剂的酸量越大,Br?nste...     

聚合物共混体系脆韧转变的逾渗阈值及其与分散度的关系

本文研究了聚合物共混体系脆韧转变的逾渗阈值及其影响因素。首次计算出共混体系的逾渗阈值φ_(sc)(等价于脆韧转变逾渗阈值)及临界基体层厚度Tc,并给出了φsc与分散相粒子分散度σg的关系式。此外,还首次得到了共混体系的冲击韧性(S_1)与应力体积分数(φs)的主曲线,并讨论了一个新的参数φso(上限应力体积分数)。研究结果表明:φsc不仅与粒径的分散度有关,而且还与基体、分散相间的界面粘接密切相关。     

热分解法制备的Co/SiO2催化剂上费-托合成反应性能

以无定形二氧化硅为载体,分别采用浸渍法和热分解法制备了钴基催化剂Co/A200-I和Co/A200-D,采用TG、XRD、TEM和TPR等手段对其进行了表征,并考察了这些催化剂在费-托合成反应中的性能。结果表明,浸渍法制备的Co/A200-I催化剂中钴颗粒没有规则的形状,但却具有较高的费-托合成反应活性;热分解法制备的Co/A200-D催化剂中钴颗粒呈一种球形二次结构,直径比较均匀,对于费-托合成反应具有较高的轻质烃选择性。此外,载体比表面积对催化剂结构也有较大的影响;相对于Co/A200-D催化剂,Co/A380-D催化剂的载体比表面积较大,这使得金属-载体间的相互作用较强而较难还原,但还原后Co/A380-D催化剂拥有较高的钴分散度和较好的反应活性     

高分散体系对化学平衡的影响

一、前言对于分散度不高的反应体系,表面效应可以忽略不计。但是,当体系的分散度较高时,表面效应就比较明显;对于这样的体系,如果用非分散体系的化学平衡理论处理的话,结果就会产生偏差,分散度越高,则偏差越大。关于高分散体系的化学平衡问题,作者查     

高分散度双金属催化剂的表面结构和反应性能

高分散度双金属催化剂的表面结构和反应性能林励吾（中国科学院大连化学物理研究所，大连１１６０２３）高分散度担载型金属催化剂已被广泛地应用于工业催化过程，各国学者对这类催化剂的表面结构进行了大量的研究。８０年代，双金属重整催化剂出现后，更多的研究集中在双...     

用矩分析法研究流动注射分析中化学反应对试样分散的影响

根据串联釜模型和统计矩分析法，通过实验证实了化学反应对分散度的影响；在同一流路中有化学反应的峰宽和二阶矩均比无化学反应的增大。并证明了二阶矩与１／４峰高处峰宽的平方成线性关系。同时给出了一个计算响应曲线统计矩的简易方法。