Effect Of Silica Support Research Articles

Effect of Silica Support on Electrostatics of Lipid Interfaces in Nano-Bio Hybrid Systems

Effect of Silica Support on Electrostatics of Lipid Interfaces in Nano-Bio Hybrid Systems

Homogeneous and heterogeneous sunflower oil methanolysis over 12-tungstophosphoric, sulfuric and boric acids

A series of acids with different strength acidity, heteropolyacid H3PW12O40 (HPW) and oxoacids, H2SO4 and H3BO3 were used as catalysts for the sunflower oil methanolysis with an oil/methanol ratio of 1/29, a reaction temperature of 60 °C and a reaction time of 3 h. The effect of silica support on the catalytic performance of HPW was investigated. (10–50 wt%) HPW supported on silica were characterized by XRD, FT-IR and N2 physisorption (BET specific surface areas, mean pore diameters and pore volumes). The fatty acid methyl esters, reaction products, were analyzed and quantified by gas chromatography. HPW and 30 wt% HPW/SiO2 have similar catalytic behavior with a biodiesel yield of 60–63 %. Side reactions were observed at 100 °C in the presence of 30 wt% HPW/SiO2 resulting in the formation of oxygenated products (alcohol, ketone, acid) in addition to fatty acid methyl esters, as evidenced by GC–MS. A plausible mechanism of supported heteropolyacid catalyzing the sunflower oil methanolysis is proposed.

A density functional theory study on the effect of silica support: Methane activation on nickel oxide clusters through a radical mechanism

Supported transition metal catalysts belong to an important family of catalyst in chemical industry, making the support effect to be a important issue in fundamental research. A theoretical computation using density functional theory (DFT) was performed to investigate the support effect of a silica model on the initial step of methane activation on NixOx (where, x=2, 3) clusters. The behavior of four reactions were studied by exploring their potential energy surfaces (PES), namely, (i) CH4 reacting with an unsupported Ni2O2 cluster, (ii) with a silica-supported Ni2O2 cluster, (iii) with an unsupported Ni3O3 cluster, and (iv) with an silica-supported Ni3O3 cluster. For each of these four reactions, only a radical mechanism was investigated, and the PESs with different spin states were explored. A spin transition process is involved for the reactions on the unsupported NixOx clusters, and no spin transition is required for the case of supported NixOx clusters. The reaction barrier as well as the reaction free energy is increased with the involvement of the model silica support. These results provide a deeper insight into the support effect on the CH bond activation of small alkanes in general and of methane in particular on supported transition metal catalysts.

Effect of Silica Support on V-Mg-O Catalysts during ODH of Propane: Experimental and Modeling using Genetic Algorithms

The effect of silica support on the V-Mg-O catalyst is studied for conducting the oxidative dehydrogenation (ODH) of propane on unsupported 30% V-Mg-O catalyst and the effect of silica support on the activity and selectivity of 30% V-Mg-O catalyst. Among the different loadings of support, the most selective catalyst is chosen for kinetic investigation using Genetic Algorithms. This also includes the effect of parameters like Propane to Oxygen ratio, Contact time and Temperature on the performance of catalysts. Later it is extended to other catalysts also. Modeling was done in the light of experimental data and the parameters in these models were estimated. The characterization of the catalysts was done to understand the behavior of the catalyst.

Effect of silica support on ruthenium-copper cluster morphology as determined by catalytic activity

Several silica supports impregnated with 1% Ru and a 1:1 atomic ratio of Ru:Cu in the bimetallic catalysts have been characterized by H/sub 2/ chemisorption, temperature programmed desorption and re-reduction, and several catalytic reactions of varying structure sensitivity. Clusters of Ru-Cu on one of the silicas, Cab-O-Sil HS5, is distinguished by the fact that only on this support is hydrogen chemisorption suppressed by added Cu. It is postulated that the morphology of the Ru-Cu clusters on HS5 involves a Cu-rich mixture of Ru and Cu on a Ru core. Clusters of Ru-Cu on other silicas appear to be more heterogeneous and have an associated pure Cu phase. Hydrogen spillover occurs with the latter morphology and both hydrogen chemisorption and spillover are suppressed by the morphology of clusters on HS5.