The Preparation And Catalytic Performance Of NiO Nanoarchitectures For Methane Activation

Worldwide reserves of petroleum and coal are projected to only last for a few decades along with the development of economic. As a kind of hydrocarbon,methane has attractd a lot of attention lately for its abundant feedstock and recycling character. It has become the optimum alternative for all the countries to explore and take advantage of methane to improve environment,maitain the sustainable development.Methane is a tetrahedral molecule with four equivalent C-H bonds formed by C sphybridization, the C-H bond energy is 435 kJ/mol, all these lead to thermodinamically strong of methane. As we can see, it’s difficult to convert methane to other useful chemicals. Conversion of methane is based the activation of methane, and all kinds of conversions need methane to be actived firstly--breaking the C-H bond under mild conditions. What’s more, as the most simple,stable,abundant alkane, methane activation is of great significance of reference and guidance. Catalysts for methane conversion in the reports are devided into nobel metal catalysts and non-noble metal catalysts.Nobel metal is better than non-noble as for catalytic activity, however, the reation still needs high temperature to perform. Based on the analysis above, we prepared catalysts with excellent activity via hydrothermal-calcined method, the effective catalysts can activate methane at low temperature, break the C-H bond.(1)Different morphologies of nickel oxide nanostructures were synthesized according to the reported paper, and applied to catalytic reaction of methane activity for the first time. NiO nanoplates with many pores can activate methane--break the C-H bond at low temperature of 100℃, which is 129℃ lower than the reported temperature in the area of non-noble metal,116℃ lower compared with noble metal catalysts. The following study shows that the special morphology of mesoporous wall is of catalytic activity, the reason has been explored through several characterization.(2)To promote the catalytic performance of NiO nanoplates, a series of Co3O4 supported NiO catalysts — 5%-50%Co3O4/NiO nonoparticles were prepared by hydrothermal method. Unlike pure NiO, the prepared samples were NiO supported with Co3O4. During the preparation, Co3O4 nanoparticles were added directly, which has never been repored before. The prepared Co3O4/NiO nonoparticles exhibit the shape of hexagonal flake with many pores.20%Co3O4/NiO nanoparticles are significantly more active than the other samples, they can activate methane-break the C-H bond at 50℃, which is 179℃ lower than the reported result,166℃ lower compared with noble metal catalysts. The reasons why 20%Co3O4/NiO nanoparticles are the most active are further revealed through a series of characterization:XPS,N2 adsorptio n-desorption, HRTEM, XRD. NiO loaded with Co3O4 is able to introduce new active sites--Co-O.More active sites provide more active oxygen species,which make it easier for methane to react at low temperature.(3)A new kind of Co doped NiO nanostructures in shape of hexagonal plates were prepared. Methane can be activated at the lowest temperature 50℃ by 1%Co/NiO nanoparticles among all the samples, which is 179℃ lower than the reported temperature in the area of non-noble metal catalysts,166℃ lower compared with noble metal catalysts. The methane activation measurements and characterization of XPS, N2 adsorption-desorption, HRTEM indicate 1%Co/NiO nanoparticles’ excellent catalytic activity, the reaction mechanism is developed as well. The reason why 1%Co/NiO nanoparticles have the excellent catalytic activity is that Co embeds in NiO lattice by replacing the position of Ni,doping of Co introduces new oxygen vacancies,which bring along more active oxygen species, favoring the catalytic reaction to performe at low temperature.In a word, the prepared NiO nanoplates with many pores can activate methane— break the C-H bond at a low temperature of 100℃,20%Co3O4/NiO nanoparticles and 1%Co/NiO nanoparticles can both activate methane,break the C-H bond at 50℃. All that above may provide a new perspective for the exploration of fresh effective catalysts applied in methane activation.