Gloria Issa

Silica supported copper and cerium oxide catalysts for ethyl acetate oxidation

The formation of active sites in the silica supported copper and cerium oxide bi-component catalysts for total oxidation of ethyl acetate was studied by Nitrogen physisorption, XRD, XPS, UV-Vis, Raman, FTIR of adsorbed CO spectroscopies and TPR. It was found that the interaction between the copper oxide nanoparticles and the supported on the silica ceria ones is realized with the formation of interface layer of penetrated into ceria lattice copper ions in different oxidative state. This type of interaction improves the dispersion of copper oxide particles and provides higher accessibility of the reactants to the copper active sites even at low copper amount.

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.

Formation of catalytic active sites in copper and manganese modified SBA-15 mesoporous silica

A series of copper and manganese oxides modified SBA-15 mesoporous silicas with different composition was prepared by incipient wetness impregnation with the corresponding nitrate precursors and compared with the analogous materials supported on conventional SiO2. Nitrogen physisorption, XDR, FTIR, UV–Vis and temperature programmed reduction with hydrogen were used for samples characterization. Their catalytic activity was tested in ethyl acetate oxidation and methanol decomposition. The ordered porous structure of the support facilitates the interaction between different metal oxide nanoparticles and increases their dispersion due to the formation of mixed oxide phase. The ethyl acetate oxidation on SBA-15 binary materials is suppressed due to the lower accessibility of the metal oxide particles, located deeply into the micro-meso pores of the support. The reaction medium which forms during the methanol decomposition provides the reduction/decomposition transformations with the mixed oxide phase. The final phase composition of finely dispersed Cu/CuO and MnOx particles stabilizes in a highly dispersed state into the porous matrix of SBA-15 support and increases the catalytic activity in methanol decomposition due to the appearance of synergistic effect between them.