Radostina Ivanova

Transition metal modified activated carbons from biomass and coal treatment products as catalysts for methanol decomposition

Copper, iron and cobalt supported on activated carbon materials are compared as catalysts in methanol decomposition in view of their potential application as intelligent carriers of hydrogen. The activated carbon supports were obtained from renewable agriculture waste (peach shell) or coal treatment by-products (coal tar pitch). The parent activated carbons and their transition metal modifications were characterized by nitrogen physisorption, XRD, UV–Vis, FTIR, Mössbauer spectroscopy and TPR in hydrogen, and the surface functional groups were determined by the Böhm method. It was assumed that the formation of transition metal modified activated carbon catalysts is a complex process which proceeds during the preparation procedure with the activity of the support and also during the catalysis by the influence of the reaction medium. The decisive effect of carbon basal planes over the texture and surface functionality of the support on the formation of transition metals active phase was assumed. Among the studied materials, cobalt modifications exhibited excellent catalytic activity and selectivity in methanol decomposition to H2 and CO despite the nature of the activated carbons used.

Activated carbon from waste biomass as catalyst support: formation of active phase in copper and cobalt catalysts for methanol decomposition

Activated carbons (AC) from various waste agriculture precursors with different texture and surface characteristics were obtained by different preparation procedures. These AC were used as a host matrix of mono- and bi-component copper and cobalt nanoparticles. The effect of carbon properties on the formation of copper/cobalt phases was studied by Boehm method, XRD, nitrogen physisorption, UV–Vis, FTIR, TPR–TG analysis and methanol decomposition as a catalytic test. The elucidation of activated carbons from waste biomass as catalyst support was based on the comparative study with similar materials supported on mesoporous silica KIT-6. It was demonstrated that contrary to KIT-6, the reduction properties of AC support hinders the formation of spinel CuCo2O4 phase in the bi-component materials, but provides formation of mixture of finely dispersed and highly active and selective in methanol decomposition Cu2O and CoO nanoparticles.

Cobalt and iron modified activated carbon from coal tar pitch: preparation and application as catalysts for methanol decomposition

Activated carbons were prepared from waste coal treatment by-products by different preparation and activation procedures and applied as a host matrix of nanodispersed cobalt and iron species. Thus obtained composites were characterized by nitrogen physisorption, XRD, UV–Vis, FTIR, TPR and tested as catalysts in methanol decomposition to hydrogen and CO. It was established that the activated carbon, prepared from waste coal treatment by-products could be successfully used for the preparation of highly active catalysts for methanol decomposition. The facilitated effect of surface functionality decrease on the dispersion and catalytic activity of loaded metal species was demonstrated.

Effect of porous structure on the formation of active sites in manganese hosted in ordered mesoporous silica catalysts for environmental protection

Recently ordered mesoporous silicas have been considered as suitable catalyst supports due to their high surface area, well developed porous volume and tuned size, shape and topology of mesopores. Among them SBA-15 and KIT-6 are most promising and studied materials as host matrix of metal/metal oxide nanoparticles. Both structures are characterized with cylindrical mesopores which are 2D- and 3D-packed in the SBA-15 and KIT-6 silicas, respectively. The flexibility of the oxidation state of manganese ensures high oxygen storage capacity of its oxides and provokes their wide application as catalysts in various redox processes. The aim of the current investigation is to clear the effect of pore topology in SBA-15 and KIT-6 mesoporous silicas on the state of the hosted in them manganese oxide nanoparticles. The samples were obtained by incipient wetness impregnation of silicas with manganese nitrate and conventional SiO2 was also used as a reference support. A complex of physicochemical techniques, such as nitrogen physisorption, X-ray diffraction, UV–Vis, XPS, FTIR and temperature-programmed reduction with hydrogen was used for samples characterization. The obtained modifications were tested as potential catalysts for environmental protection via total oxidation of VOCs (ethyl acetate) or hydrogen production from methanol as clean and effective alternative fuel. It was established that the porous structure of mesoporous silica supports influences in a complex way the catalytic behaviour of their manganese modifications, which is determined by the specificity of the reaction medium.