Magnesium iron aluminum hydroxosalts and oxide catalysts for oxidative dehydrogenation of alkanes and alcohols

Methods are developed for the synthesis of precursors for oxide catalysts containing iron hydroxocarbonate and magnesium aluminum hydroxocarbonate with hydrotalcite-type layered structure and decavanadate and paramolybdate ions in anionic interlayers. These precursors are used to synthesize oxide catalysts for oxidative dehydrogenation of alcohols and alkanes with high selectivity and good yields of the desired product in conversion of ethane to ethylene and alcohols to carbonyl compounds.     

Bimetallic oxide nanoparticles confined in ZIF‐67‐derived carbon for highly selective oxidation of saturated C–H bond in alkyl arenes

Zeolite imidazolate frameworks (ZIFs) have recently emerged as an ideal type of carbon precursors with abundant tailorability. In this work, a series of ZIF‐derived porous carbon catalysts have been prepared with encapsulation of bimetallic oxide nanoparticles via simple thermal treatment. The composition and structure of these catalysts were confirmed in detail by different characterization methods. The bimetallic oxide (Mn/Co, Fe/Co, and Cu/Co) nanoparticles were encapsulated in the nitrogen‐doped graphitized carbon matrix. Moreover, the hierarchically porous structure and carbon defects were successfully constructed in the carbon catalysts. Additionally, in the selective oxidation of saturated C–H bonds in alkyl arenes, the carbon catalysts demonstrate outstanding performance for the oxidation of C–H bonds to corresponding carboxyl groups. This was due to their unique structure can greatly promote mass transfer and molecular oxygen activation, resulting in high conversion and high selectivity. Remarkably, this work here could also provide a novel strategy to the controllable synthesis of metal–organic frameworks (MOFs)‐derived carbon catalysts for enhanced performance in heterogeneous catalysis.     

Ni-Mo氮化物催化剂:合成及其丙烷氨氧化催化性能简

分别采用溶胶-凝胶法、旋转蒸发微波干燥法、共沉淀法、浸渍法和机械混合法制备Ni-Mo氧化物前驱体. 以H₂和N₂的混合气为氮化气体,采用程序升温氮化法合成了镍钼氮化物催化剂. 利用X射线衍射、总氮含量分析、X射线光电子能谱及H₂程序升温还原对Ni-Mo氧化物前体及氮化物催化剂进行了表征. 将上述Ni-Mo氮化物催化剂用于丙烷氨氧化反应中. 结果表明,Ni-Mo氧化物前驱体的制备方法影响其氮化物催化剂上丙烷氨氧化反应性能. Ni-Mo氮化物催化剂中氮物种的移动性及反应性对产物丙烯腈选择性的影响较大,共沉淀法制备的催化剂存在大量的活性氮物种,因而具有良好的催化丙烷氨氧化反应活性.     

Copper-containing catalysts for the oxidative dehydrogenation of organic compounds

A method of doping magnesium aluminum hydrotalcites, which are precursors for oxidative dehydrogenation oxide catalysts of various compositions, with copper(II) was developed, and copper(II)-containing oxide catalyst samples were synthesized. The catalytic properties of these catalysts were studied in the oxidative dehydrogenation of ethane, propane, and hexane. The conversion of ethane into ethylene on the copper-containing catalysts was established to proceed with high selectivities (90?C97%) and at low temperatures (400?C450°C).     

Spectroscopic study of nickel hydroxyde,nickel carbonate-hexahydrate and nickel hydroxocarbonate

The electronic and IR-spectra of nickel hydroxocarbonate are investigated. Since the solid substance is amorphous these studies are the only source of information about the bonding mode of the hydroxo- and carbonate groups in it. The spectra of the hydroxocarbonate were compared with the spectra of the nickel hydroxide and the nickel carbonate-hexahydrate. Correlation analysis of the vibrational spectra was made. It was proved that the solid nickel hydroxocarbonate contains molecular groups which differ from those in solid nickel hydroxide and nickel carbonate and that hydroxocarbonate is an individual chemical compound whose structure is similar to the structure of nickel hydroxide and nickel carbonate-hexahydrate.     

Preparation of filter catalysts with the use of alkoxides

New methods for the synthesis of poly(organyloxy)elementoxanes containing Zr, Zr−Y, Al−Ba (Ca, Sr, Ce, Zr) and La−Sr−Co have been developed. The application of these elementoxanes as oxide precursors in the preparation of catalyst supports, catalytic coatings and filter catalysts has been studied.     

Ytterbium-Containing Magnesium–Aluminum Hydroxo Salts with a Hydrotalcite-Type Structure

A method is developed for inserting ytterbium into Mg–Al hydroxo salts that have a hydrotalcitetype layered structure, as well as for the chemical analyses of complex hydroxo salts containing ytterbium in various combinations with magnesium, aluminum, chromium, vanadium, molybdenum, and niobium. The formation conditions of these hydroxo salts have been studied by potentiometric titration, their samples have been prepared, and X-ray diffraction patterns recorded. The prepared hydroxo salt samples have been tested as precursors for oxide catalysts of oxidative dehydrogenation (ODH) of alkanes.     

Surface solid-state interactions in copper-nickel-cement catalysts for hydrogenation of oxygen

The surface phase composition of alumocalcium cement-supported CuO and CuO-NiO catalysts prepared by chemical mixing has been studied using the method of thermo-vacuum curves of electric conductivity. The deactivation of these catalysts due to overheating to 800 °C under conditions of hydrogenation of oxygen is rationalized by the partial extraction of CuO (and NiO) from the stabilizing structure of the support solid solutions and by sintering of the extracted oxides and the reduced metallic phase. Complete regeneration of the CuO-NiO-talum catalysts can be achieved if a considerable amount (20%) of copper hydroxocarbonate is added.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1559–1562, September, 1994.     

Europium oxide containing catalysts for oxidative dehydrogenation of alkanes

A method is developed to incorporate europium into Mg–Al hydrotalcites, which are precursors for oxide catalysts of oxidative dehydrogenation (ODH) of alkanes; samples of oxide catalysts are prepared, where europium oxide and gallium, magnesium, aluminum, chromium, vanadium, molybdenum, and niobium oxides are contained in various combinations. The catalytic properties of these catalysts in the reactions of ethane, propane, and butane ODH are studied. The incorporation of europium into some of our studied multicomponent catalysts enhances the reaction selectivity and increases yields of desired products.     

镁铁和镁铁铝催化剂氢还原过程的研究

以水滑石为前体 ,制备了镁铁和镁铁铝复合氧化物催化剂 ,运用原位穆斯堡尔谱研究了催化剂在H2 气氛中的还原行为。结果表明 :由于Mg、Al的加入和固溶体的形成 ,相对地稳定了FeO物相 ,阻碍了H2 对铁离子的还原 ,使得Fe2 进一步还原为金属Fe0 的能力减弱 ;在还原过程中催化剂首先生成含Fe2 的固溶体FeO MgO或FeO MgO Al2O3,然后再完全还原成金属Fe0。     

In situ Raman studies during sulfidation, and operando Raman-GC during ammoxidation reaction using nickel-containing catalysts: a valuable tool to identify the transformations of catalytic species

Ni-containing catalysts are investigated under reaction conditions for two different cases, during sulfidation, with Ni-Mo based catalysts, and during ammoxidation reaction, with the Ni-Nb catalysts. It is shown how Raman spectroscopy can follow some of the transformations of these catalysts upon different treatments. For the NiMo/Al(2)O(3)-SiO(2) system it was possible to identify some of the sulfided Mo species formed during the sulfidation of the oxide precursors, while for the bulk Ni-Nb oxide catalysts the simultaneous reaction-Raman results strongly suggest that the incipient interaction between niobium and nickel oxides at low Nb/Ni atomic ratios is directly related to catalytic activity, and that a larger size well-defined NiNb(2)O(6) mixed oxide phase is not active for this reaction. Moreover, the promotion by niobium doping appears to be limited to a moderate niobium loading. It was found that in situ and operando Raman are valuable techniques that allowed the identification of active Mo-S and Ni-Nb species under reaction conditions, and that are not stable under air atmospheres.     

Magnesium oxide nanotubes: synthesis,characterization and application as efficient recyclable catalyst for pyrazolyl 1,4-dihydropyridine derivatives

Magnesium oxide nanotubes were prepared by electrospinning technique. The nanocatalysts have been characterized by various sophisticated techniques, including XRD, SEM, and TEM. The activities of these NT catalysts are promoting pyrazolyl 1,4-dihydropyridine syntheses have been extensively investigated. Various advantages associated with these protocols simple workup procedure, short reaction times, high yields and reusability of the catalyst.     

焙烧条件对金催化剂的结构及其催化CO氧化性能的影响

采用共沉淀法和金属有机配合物固载法,分别制备了负载型金催化剂,并考察了焙烧条件对其催化CO氧化性能的影响。实验结果表明,焙烧温度和时间对催化剂的结构和活性的影响显著,不同的金属氧化物负载的金催化剂具有不同的最佳焙烧温度。DTA-TG分析结果确定了催化剂稳定结构的形成温度;XRD测试结果显示,在最佳焙烧条件下得到的催化剂,其载体为具有一定结晶度的金属氧化物。     

A Chromatographic Effect Observed during Deposition of Cu-Mn Precursors on Active Carbon

The possibility of appearance of a chromatographic effect during the deposition of Cu-Mn precursors on active carbon with a view to obtaining supported oxide catalysts with a definite active phase composition has been investigated. By impregnation of the support with aqueous solutions of copper and manganese nitrates and subsequent drying at 110 degrees, two types of samples have been obtained: one-component and two-component ones. They have been characterized by chemical analysis, IR spectroscopy, EPR analysis, and magnetic and adsorption measurements. It has been established that during the preparation of two-component precursors the chromatographic effect is not very strong. Due to the complex chemical nature of the active carbon surface, the copper and manganese ions are adsorbed at different sites. On the basis of the isoelectric point of the active carbon and the pH value of the impregnating solutions, a scheme for the occurrence of adsorption processes has been proposed. The porous texture of the active carbon permits deposition of the precursor at definite surface sites; due to this it is very promising as a support of two-component oxide catalysts. Copyright 2000 Academic Press.     

醇预处理载体制备的 Ir-Re/SiO2催化剂上甘油氢解反应

甘油是生物柴油的副产物,将其转化为高附加值的化学品,能提高生物柴油产业的经济性.1,3-丙二醇是聚酯和聚氨酯的单体,也用于合成医药和用作有机合成中间体,甘油直接催化氢解反应制1,3-丙二醇极具发展潜力.另外,甘油是生物质转化的重要平台分子之一,与目标产物的分子结构相比较,生物质平台分子通常含有过多的含氧基团,尤其是多余的羟基,通过甘油氢解反应研究多羟基的选择性活化和脱除,可以加深对生物质脱氧规律的认识.因此,研究甘油氢解反应制1,3-丙二醇催化剂和工艺,不仅具有潜在的应用前景,而且具有重要理论价值.然而,目前的甘油氢解催化剂性能还不够高,我们希望通过一些表面改性的方法处理载体硅胶,从而改变金属前驱体与载体表面的作用.因此,本文使用 C1–C4的正构醇处理硅胶载体,其负载的 Ir-Re催化剂上甘油氢解反应转化率从42.7%提高到59.5%,仲羟基脱除收率从21.6%提高到28.3%.研究发现,当处理载体所用正构醇的碳数从1增加到3时,对应催化剂上甘油转化率逐渐增加至最高;但当使用更正丁醇时,对应催化剂上甘油转化率下降.为了探究催化剂活性改变的原因,我们首先采用红外光谱(FT-IR)和氮气物理吸附确定烷氧基基团嫁接到硅胶载体上.程序升温还原结果发现,预处理载体相应的催化剂开始还原温度降低,表明在这些催化剂上形成了颗粒尺寸较小的Ir粒子. X-射线衍射分析发现,在新鲜的和使用后的催化剂上均未检测出Re物种的衍射峰,说明Re高度分散于催化剂表面.吸附吡啶的FT-IR结果表明,未处理和丙醇预处理硅胶负载的催化剂上均没有强酸位,它们的B/L酸比值相近,约为3.3.催化剂的吸附COFT-IR结果表明, CO线性吸附于Ir/SiO2催化剂上的主要吸收峰位置在2084 cm–1;而Re的加入使得该吸收峰红移,表明Ir和ReOx物种之间存在相互作用.透射电镜(TEM)、H2-程序升温脱附和NH3-程序升温脱附结果发现,醇预处理催化剂上具有更多的Ir-ReOx界面,而界面位点的数量与甘油转化率大小一致,表明Ir-ReOx位点可能就是甘油氢解的活性中心.反应后催化剂的TEM结果表明,醇预处理催化剂上的Ir颗粒要小于未处理催化剂的,其中丙醇预处理硅胶负载的催化剂上Ir粒径最小.这是由于醇处理催化剂上存在很多孤立的Si–OH,它们与金属前驱体相互作用有利于形成较小的金属颗粒.这些孤立的Si-OH则是由于表面烷氧基基团的隔离作用所形成的.当处理载体所用正构醇的碳数从1增加到3时,烷氧基的碳链变长,分隔作用越好,阻止金属前驱体聚集的程度越强,因而Ir物种和Re物种的分散度增加.但是当处理醇的碳数增加到4时,形成的表面烷氧基基团可能阻止了Re物种和Ir物种间相互作用,从而使得Ir和Re物种的分散度均降低,相应催化剂活性随之降低.     

Shape-Controlled Nanocrystals for Catalytic Applications

The activity, selectivity, and long-term stability of catalyst nanoparticles can be enhanced by shape modulation. Such shaped catalytic nanocrystals have well-defined surface crystalline structures on which the cleavage and recombination of chemical bonds can be rationally controlled. Metal and metal oxide nanocrystals have been synthesized in various shapes using wet chemistry techniques such as reducing metal precursors in the presence of the surface-capping agents. The surface-capping agents should be removed prior to the catalytic chemical reaction, which necessitates clean catalytically active surface. The removal process should be performed very carefully because this removal often causes shape deformation. A few examples in which the surface-capping agents contribute positively to the chemical reactions have been reported. The examples described in this review include shaped metal, metal composite, and metal oxide nanocrystals that show enhanced catalytic activity, selectivity, and long-term stability for various gas-phase, liquid-phase, or electrocatalytic reactions. Although most of the studies using these shaped nanocrystals for catalytic applications have focused on low-index surfaces, nanocrystals with high-index facets and their catalytic applications have recently been reported. By bridging surface studies with nanoparticle catalysts using shape modulation, catalysts with improved properties can be rationally designed.     

含钯类水滑石衍生复合氧化物Pd/M3AlO(M=Mg,Co, Ni,Cu, Zn)催化剂上氯苯的催化氧化

采用共沉淀法制备了系列含Pd类水滑石材料, 类水滑石基体为M3Al-HT (M=Mg, Co, Ni, Cu, Zn), 经焙烧制备出含Pd类水滑石衍生复合氧化物催化剂. 通过X射线衍射(XRD), 热重-差热分析(TG-DTG), H2程序升温还原(H2-TPR), O2程序升温脱附(O2-TPD)和N2吸脱附等表征技术手段研究了不同二价金属元素对含Pd类水滑石衍生复合氧化物催化剂物理化学性质及其对挥发性有机污染物氯苯催化氧化性能的影响. XRD和TG-DTG结果表明, 不同二价金属元素, 除Cu外, 都能形成类水滑石层状结构, Pd在不同类水滑石前驱物中均能良好分散. 不同的二价金属元素对催化剂性能的影响不同, 其中Pd/Co3AlO催化剂表现出最高的氯苯催化氧化活性, 其起燃温度和全转化温度分别为182和283 ℃. H2-TPR和O2-TPD测试表明, Pd和类水滑石衍生复合氧化物存在着协同作用, Pd的引入促进了复合氧化物的还原, 从而影响氧化物的氧化还原性能. Pd/M3AlO系列催化剂的活性主要受催化剂的氧化还原性能及其表面活性氧物种的影响.     

高效WO3掺杂MCF催化剂的合成及其在环戊烯选择氧化制戊二醛反应中的应用

以钨酸钠和正硅酸乙酯为前驱体直接合成高含量WO₃掺杂介孔氧化硅泡沫(MCF)催化剂. 在773 K焙烧后显示出更高的热稳定性. 小角X射线散射, N₂-物理吸附和透射电子显微镜结果表明钨物种嵌入后, 材料仍保持MCF特征的三维织构介孔特征. 紫外拉曼和紫外可见漫反射光谱结果表明钨物种主要以孤立的或者低聚态的氧化钨形式存在, 所以在氧化钨质量分数(w)低于20%时氧化钨物种能够高度分散在载体上. 在环戊烯选择氧化制戊二醛反应中, 反应16 h 后环戊烯的转化率达到100%, 戊二醛的产率达到83.5%. 催化剂重复利用实验表明催化剂的稳定性较好, 没有钨物种的脱落. 这种优异的催化性能归结于合适的氧化钨含量和高分散的钨物种.     

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds and their morphology and application in catalysis: III. Catalytic properties of massive Ni-Mo sulfide catalysts synthesized using mechanochemical activation

The precursors of massive Ni-Mo catalysts for hydrotreating processes, which were synthesized by the mechanochemical activation of a mixture of nickel hydroxocarbonate NiCO₃·2Ni(OH)₂·nH₂O and ammonium paramolybdate (NH₄)₆Mo₇O₂₄ · 4H₂O, were sulfidized. Their structure was studied by X-ray diffraction analysis and high-resolution electron microscopy. It was found that MoS₂ packets, which are characterized by the presence of structural defects and geometric curvature, are the constituents of the massive catalysts. The catalyst also includes a phase of Ni₃S₂ and regions containing a complex Ni-Mo-S phase. The catalytic tests of the synthesized catalysts in the model reactions of 1-methylnaphthalene and dibenzothiophene conversions showed that the catalyst whose precursor was a heteropoly compound with the Anderson structure after the stage of mechanochemical activation exhibited the highest activity.     

乙烷选择氧化制乙酸的研究进展

乙烷选择氧化制乙酸是缓解资源短缺、实现低碳烷烃高附加值利用的重要技术.该反应常用的催化剂有杂多酸、钒磷氧化物以及多金属氧化物,其中多金属氧化物催化剂,尤其是Mo-V体系,由于具有高的热稳定性和好的催化活性被广泛研究.我们从催化剂的性质、反应动力学及反应机理方面综述了 Mo-V催化剂在乙烷选择氧化制乙酸方面的研究进展.