钌基氨合成催化剂研究进展

钌基催化剂被称为继铁基催化剂之后第二代氨合成催化剂。文中介绍了钌基氨合成催化剂的载体、钌的母体化合物和促进剂的研究进展以及在钌基催化剂上氨合成反应动力学。     

钌基氨合成催化剂作用机理及氧化物负载钌催化体系研究

介绍了钌基氨合成催化剂的最新研究进展,结合密度泛函理论计算综述了钌基氨合成催化剂的作用机理,包括钌表面对氮分子的吸附活化以及钌基氨合成催化剂上的氨合成反应动力学模型方面的研究成果。对氧化物载体的制备方法、修饰和复合手段、助剂种类及其在催化反应中的作用机理等进行了总结,探讨了钌基氨合成催化剂理论研究以及氧化物催化剂体系目前存在的问题。     

氨合成钌基催化剂的研究进展

近年来,钌基氨合成催化剂因其高活性、高稳定性和反应条件温和成为研究热点。综述国内外氨合成钌基催化剂的研究进展,重点介绍钌基催化剂载体、助剂和前驱体对氨合成反应性能的影响。石墨化程度高、导电性能良好的碳载体或氧化物与碳的复合载体是氨合成反应的良好载体;碱金属和碱土金属类助剂通过改变活性金属表面静电场,起到电子助剂的作用,并且碱土金属对反应的促进作用优于碱金属,稀土金属Sm能够抑制碳载体的甲烷化反应;与Ru Cl3相比,Ru3(CO)12是氨合成反应的理想前驱体。简介以电子化合物为载体的钌基氨合成体系,负载钌的高比表面积电子化合物C12A7:e-是强大的电子供体,能够提高氮气在钌上的解离程度,并能可逆地储存氢,有效抑制氢吸附对钌表面的毒害,从而大大提高氨合成反应活性。进一步开发温和条件下非贵金属高效氨合成催化剂将具有重要的理论和现实意义。     

钌基氨合成催化剂助剂研究进展

钌基氨合成催化剂由于具有低温、低压活性高的优点,而被誉为第二代氨合成催化剂.为了进一步节约能源,降低能耗,达到工业化的要求,国内外许多学者都在对钌基催化剂进行研究.而钌基催化剂中助剂的加入对催化剂活性有着非常大的影响.本文介绍了助剂的研究现状,对助剂的种类及其在催化反应过程所起的作用进行了总结,并介绍了助剂与载体之间的作用以及助剂我持次序的研究现状,旨在为我国进一步开发研制低温低压新一代氨合成催化剂提供参考.     

氨合成催化剂机械强度标准测定

本文简要地介绍了美国ASTM标准中的“催化剂和催化剂载体耐磨性”标准化测试方法。采用此方法测定了A110-1型氨合成催化剂的机械强度性能,并对测试结果作了讨论和评价。     

新型氨合成催化剂的选用和还原

介绍了氨合成催化剂的创新和发展、A301型和ZA-5型Fe1-xO基氨合成催化剂的性能特点及新型低温低压高活性氨合成催化剂的选择原则。以A301型催化剂为例,详细讨论了新型氨合成催化剂的升温还原方法。     

浅析新型合成氨催化剂的还原

介绍了氨合成催化剂的创新和发展、A301型和ZA-5型Fe1-xO基氨合成催化剂的性能特点及新型低温低压高活性氨合成催化剂的选择原则。以A301型催化剂为例,详细讨论了新型氨合成催化剂的升温还原方法。     

新型氨合成催化剂在大型装置中的应用

简要介绍几种新型氨合成催化剂性能,重点介绍Amomax-10型催化剂在几种大型合成塔中的应用情况,并对新型氨合成催化剂在大型合成塔中应用的节能效果简要报导,对如何更好的应用新型氨合成催化剂提出了建议.     

钌基氨合成催化剂的研究进展

钌基氨合成催化剂是一种在低温和较低压力下仍具有较高活性的负载型催化剂。综述了新型钌基氨合成催化剂的催化机理、国内外研究进展和工业应用情况,分析了催化剂中母体化合物、载体和促进剂等因素对催化剂活性的影响。钌基催化剂虽性能优良,但成本昂贵,因此探索新的活性组分、新的助剂与载体,研制出性能优良的钌基或非钌基催化剂是发展方向。     

影响Ru/MO_x氨合成催化剂活性关键因素

氨合成催化剂是多相催化领域中许多基础研究的起点,低温高活性的钌系催化剂为继熔铁催化剂之后的第二代氨合成催化剂。从影响氧化物负载的Ru基催化剂性能的关键因素出发,对氧化物载体的改性、助剂的作用并将其深入到反应条件下的化学状态等方面进行了分析和探讨,为新型高活性Ru基氨合成催化剂及其他多相催化剂的设计研发提供借鉴。     

Dispersion and Distribution of Ruthenium on Carbon-Coated Ceramic Monolithic Catalysts Prepared by Impregnation

Carbon-coated monolithic catalysts were prepared by dipcoating a cordierite substrate in a Furan resin, after which the ruthenium was incorporated by impregnation with a [RuCl₅]^2- complex. Immobilization of the precursor proceeded particularly via weak physisorption. Since the carbon-coated monolithic supports have a broad pore-size distribution, redistribution of the ruthenium precursor occurred upon drying due to capillary forces, resulting in low dispersion. A significant amount of ruthenium is present on the surface of the carbon inclusions located deep in the cordierite walls, making the diffusion path of the reactants to the active ruthenium sites considerably larger than the average carbon-coating thickness. For successful application of the carbon-coated monolithic catalysts in gas–liquid reactions, the deposition of carbon in the walls of the monolith should be prevented and maldistribution of ruthenium upon drying should be solved.     

Ru-Based Catalysts for H2 Production from Ammonia: Effect of 1D Support

Topics in Catalysis - This study reveals the effect of the catalytic 1D supports (carbon, ceria, alumina and titanate) for ruthenium particles on the low temperature release of hydrogen from...     

Reactivity of Ru-based catalysts in the oxidation of propene and carbon black

The relationship between the state of Ru on different supports and catalytic activity in the oxidation of propene and carbon black was investigated for catalysts prepared by different impregnation methods. It is demonstrated that the addition of ruthenium to ceria (CeO₂), alumina (Al₂O₃) and ceria–alumina significantly improves the reactivity: the temperature of carbon black oxidation decreases by 100–140 °C. It is also shown that the addition of Ru to the different supports is very beneficial for the total oxidation of propene. Temperature programmed reduction (TPR) experiments of the catalysts showed that the oxygen species of ruthenium oxides are reduced at low temperatures which is the main reason of its high reactivity in oxidation reactions.     

Electrocatalysts on supports—III. Electrocatalytic and adsorption properties of microdeposits and thin films of platinum group metals

The adsorption and electrocatalytic properties of the microdeposits of rhodium on gold, palladium on niobium, ruthenium and osmium on titanium, and palladium thin films on glass carbon and nickel have been investigated. It is shown that hydrogen adsorption on rhodium and ruthenium microdeposits is characterized by a low binding energy and that on palladium films by a high binding energy. The cathodic hydrogen evolution rate on ruthenium microdeposits and palladium films on glass carbon and nickel is lower than that on the corresponding bulk metals. These results are consistent with the assumption of the predominant effect of the electronic interaction between microdeposits and thin films on the one hand and the supports on the other, which affects the hydrogen adsorption energy parameters.     

Support Effect and Active Sites on Promoted Ruthenium Catalysts for Ammonia Synthesis

The catalytic activities of three supported, barium-promoted ruthenium catalysts for ammonia synthesis are reported. The three supports are silicon nitride (Si₃N₄), magnesium aluminum spinel (MgAl₂O₄), and graphitized carbon (C). The effect of the promoter on the activity is strongly dependent on the choice of support material in accordance with several previous observations. Here, this dependence is ascribed to a difference in the affinity of the promoter for the different supports. It is shown how it is possible to image the barium promoter present on the surface of ruthenium crystals in passivated catalysts by conventional high-resolution transmission electron microscopy (HRTEM). By comparison with in situ HRTEM images obtained lately from similar catalysts, and with reference to recent density functional theory (DFT) calculations, we suggest that active B₅-type sites on the surfaces of the ruthenium crystals are promoted by nearby promoter atoms via electrostatic interactions.     

Hydrogenation of succinic acid to γ-butyrolactone (GBL) over ruthenium catalyst supported on surfactant-templated mesoporous carbon

Mesoporous carbon support (denoted as STC) was prepared by a surfactant-templating method for use as a support for ruthenium catalyst. For comparison, porous carbon (denoted as TC), spherical carbon (denoted as SC), and microporous carbon (denoted as DC) supports were also prepared by a templating method, hydrothermal method, and direct carbonization method, respectively. Ruthenium catalysts supported on carbon supports (Ru/C) were then prepared by an incipient wetness impregnation method. The Ru/C (Ru/DC, Ru/SC, Ru/TC, and Ru/STC) catalysts were characterized by FE-SEM, N₂ adsorption–desorption isotherm, BET, XRD, and HR-TEM analyses. Liquid-phase hydrogenation of succinic acid to γ-butyrolactone (GBL) was carried out over Ru/C catalysts in a batch reactor. In the hydrogenation of succinic acid, Ru/STC catalyst showed the highest conversion of succinic acid and the highest yield for GBL. The superior catalytic performance of Ru/STC catalyst compared to the other catalysts (Ru/TC, Ru/SC, and Ru/DC) was due to fine dispersion of ruthenium (ruthenium surface area). Thus, ruthenium surface area played a key role in determining the catalytic performance in the liquid-phase hydrogenation of succinic acid to GBL over Ru/C catalysts.     

The influence of alkali metals on the activity of supported ruthenium catalysts for the water-gas shift reaction

This paper presents the results of the studies on the influence of alkali metals on the activity of ruthenium catalysts, which were supported on the products of α- and δ-iron oxide-hydroxide calcination. Modification of these supports with alkali metals, in particular potassium, rubidium and cesium, prior to deposition of ruthenium was found to increase the activity of Ru/Fe₂O₃ catalysts in the water-gas shift reaction. It was also established that the activity and stability of catalysts prepared on iron oxide obtained from α-FeOOH increased when the latter was modified with sodium ions. The favourable effect of sodium on the activity of the catalysts was shown to appear at a certain proportion of the base to the active component, i.e. ruthenium. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation and properties of ruthenium supported catalysts

Two types of impregnation solvents were suggested for preparation of the ruthenium supported catalysts. Charcoal, silica, alumina and titania supports were used. Special attention was paid to reduction and activation conditions of nonreduced and passivated forms, respectively. Hydrogenation of 1-heptene, cyclohexene, benzene and acetophenone in the liquid phase were studied using the prepared catalysts.     

活性炭载体预处理对Ru/C氨合成催化剂活性的影响

将活性炭在惰性气体保护下进行高温热处理,随后在 O2/N2体积比为10%条件下进行氧化处理。采用元素分析、物理吸附和XRD方法,考察了不同处理后炭载体的化学组分、表面织构和物相变化。以不同预处理的活性炭为载体,制备了钡助催钌催化剂,在425 ℃,10.0MPa和10 000 h^－1条件下进行氨合成活性测试。结果表明,1 800 ℃热处理导致活性炭部分石墨化,能有效消除非炭成分,同时炭载体的比孔容下降了90%。随后的氧化处理能使炭载体比表面得到有效的恢复,以扩孔处理的炭为载体制备的钌催化剂能够使活性金属在载体中均匀分散,制备出高活性的氨合成钌催化剂。     

Methanation of the carbon supports of ruthenium ammonia synthesis catalysts: A review

The propensity of carbon support for methanation in a hydrogen-containing medium is a problem for active ruthenium ammonia synthesis catalysts, since this leads to the degradation of the support and the sintering of the active component. This review analyses some key works on approaches to methanation inhibition and their results to show that, on the whole, an algorithm for solving the methanation problem has been found, i.e., the graphitization of carbon supports at high temperatures (up to 2000°C) and the introduction of ruthenium promoters, specifically alkali (Cs, K) and alkali-earth (Ba) oxides, whose role is to modify the electron state of ruthenium and block the surface of a carbon support to prevent it from interacting with active hydrogen. The most efficient catalyst not liable to methanation up to 700°C and a hydrogen pressure of 100 atm has been found. The resulting analysis can be useful in selecting and preparing Me/C catalysts in which Me represents metals of the VIII Group and others.