Effective dispersion of the active species over the support almost always guarantees high catalytic efficiency. To achieve this high dispersion, a favourable interaction of the active species with the support is crucial. We show here that the crystal structure of the titania support determines the interaction and consequently the nature of ruthenium particles deposited on the support. Similar crystal structures of RuO2 and rutile titania result in a good lattice matching and ensure a better interaction during the heating steps of catalyst synthesis. This helps maintain the initial good dispersion of the active species on the support also in the subsequent reduction step, leading to better activity and selectivity. This highlights the importance of understanding the physico-chemical processes during various catalyst preparation steps, because the final catalyst performance often depends on the type of intermediate structures formed during the preparation.

We investigate the influence of the aluminium content on the adsorption of hexane isomers at 293 K on MFI type zeolites (Si/Al ratios - SAR of 25, 100 and infinity). Adsorption isotherms were assessed with a home-made volumetric system. Temporal up-take curves were recorded using a manometric set-up combined with a Rubotherm suspension balance. All three isomers show dual site adsorption behaviour that is well described with a Dual Site Sips (DSS) model. The Si/Al ratio influences strongly the adsorption equilibrium properties. Regardless of the isomer type, the sample with SAR = 100 shows the highest saturation loadings. At the studied pressures the sorption order in the three samples is: n-hexane > 2-methylpentane > 2,3-dimethylbutane > 2,2-dimethylbutane. Generally, we found that the Henry constant increases with aluminium content Clear diffusional limitations are observed for the di-branched hexane isomers on all three zeolite samples. The sample with SAR = 100 gives the highest diffusion rates for the hexane isomers. Silicalite-1 is the most promising for enhancing gasoline octane numbers at 293 K, as it gives the highest equilibrium 2,3-dimethylbutane/2-methylpentane ratios.