A correlation between structural changes in a Ni-Cu catalyst during decomposition of ethylene/ammonia mixture and properties of nitrogen-doped carbon nanofibers

Changes of a 65Ni25Cu10A1203 catalyst consisting of Ni-enriched and Cu-enriched alloys were investigated in the bulk and on the surface during the growth of nitrogen-doped carbon nanofibers （N-CNFs） by decomposition of a 50%C2I-I4/50%NH3 mixture using in situ X-ray diffraction （XRD） analysis, ex situ X-ray photoelectron spectroscopy （XPS） and transmission electron microscopy （TEM） techniques. It was shown that N-CNF growth at 450-650 ℃is accompanied by dissolution of carbon and nitrogen in the Ni-enriched alloy, whereas Cu-enriched alloy remains inactive. A correlation between nickel and copper surface concentrations and properties of N-CNFs in relation to the nitrogen content was found. It was demonstrated that phase composition of the catalyst during N-CNF growth determines the type of N-CNFs structure.

Decomposition of carbon dioxide hydrate in the samples of natural coal with different degrees of metamorphism

Methane and carbon dioxide hydrates are one of the possible forms in which these gases exist in natural coal(for more detailed discussion see Refs [1,2]). In this work, the decomposition of carbon dioxide hydrate in five samples of natural coal differing from each other in metamorphism degree was investigated experimentally. Carbon dioxide hydrate dispersed in coals was synthesized from water adsorbed in these coals. During a linear temperature rise in an autoclave with the coal + hydrate sample the hydrate decomposition manifests itself as a step of increase in gas pressure, accompanied by a decrease/stabilization of the temperature of coal sample. The dependencies of the amount of hydrate formed on initial coal humidity and on gas pressure during hydrate formation were studied. It was demonstrated that each coal sample is characterized by its own humidity threshold below which hydrate formation in natural coal is impossible. With an increase in gas pressure, the amount of water transformed into hydrate increases. For the studied coal samples, the decomposition of carbon dioxide hydrates proceeds within a definite temperature and pressure range, and this range is close to the curve of phase equilibrium for bulk hydrate.

Synthesis gas production on glass cloth catalysts modified by Ni and Co oxides

The catalytic activity of nanostructured low percent (1%) Co-Ni catalysts on the basis of glass fiber (GF) prepared by a"solution combustion" (SC) method was studied.The catalytic activity of the prepared samples was studied in the reaction of dry reforming of methane (DRM) with CO2.The obtained samples were characterized by a number of physico-chemical methods,including XRD,SEM,TEM,TGA and AFM.The active component was shown to be dispersed in the near-surface layer of the support as nanoparticles of 10—20 nm in size.The active component showed a Co3O4 or(Co,Ni)Co2O4 spinel structure,depending on the catalyst composition.The spinel structure of the active component interacted strongly with the carrier,providing resistance to carbonization,high catalytic activity toward DRM,and high activity and stability in oxidation reactions.

氧化钴和氮掺杂碳纳米管纳米复合物的催化与容量性质(英文)

The nanocomposites based on cobalt oxide and nitrogen-doped carbon nanofibers (N-CNFs) with cobalt oxide contents of 10–90 wt% were examined as catalysts in the CO oxidation and supercapacity electrodes. Depending on Со3О4 content, such nanocomposites have different morphologies of cobalt oxide nanoparticles, distributions over the bulk, and ratios of Со3+/Co2+ cations. The 90%Со3О4-N-CNFs nanocomposite showed the best activity because of the increased concentration of defects in N-CNFs. The capacitance of electrodes containing 10%Со3О4-N-CNFs was 95 F/g, which is 1.7 times higher than electrodes made from N-CNFs.