engleski

Development of phases in the sol-gel derived mixed-metal-oxide (Al2O3-TiO2-ZnO) functional sorbent material

Currently the most thermodynamically efficient power conversion technology ; integrated gasification combined cycle (IGCC), reposes on turning conventional cheap carbon based fuels into syngas. Syngas can be stripped from impurities (primarily sulphide based) to achieve process efficiency and turbine protection in the high temperature desulfurization process (HTGD). Zincite was already shown as proven constitute of major regenerable HTGD sorbents. Here we investigate Aluminium-Titanium-Zinc mixed-metal-oxide system as a candidate for HTGD sorbent material. We expand composition to alumina and titania to facilitate mechanical durability and thermochemical stability, respectively. Sol-gel samples were prepared in wide compositional range from gahnite to Zn-titanate spinel ; i.e. gahnite was Ti-doped on the account of Al (0-100%). We monitored the thermal and structural evolution, to observe different mechanisms of phase formation, as a function of doping and temperature conditions. The significance of this work is the precise identification of the stability ranges of observed solid-solutions, whereas gahnite spinel and zinc-titanate spinels can interchange cations only in limited amounts, depending on the conditions, as confirmed from the structure refinement. It was observed that at high-temperatures solid-solutions exhibit quite different stability. More important, observed partial phase-separation at low-temperatures (which occur on behalf of different hygroscopy of the (Al, Ti)-Zn gels) significantly precludes the mechanisms of phase development at high-temperatures. Thereof, intermediate Zn-based phase was found to be responsible for the facilitated early zincite crystallisation. Microstructure and texture were commented accordingly. Performed characterisations allowed discussion what are the best compositions and conditions for the preparation of the ultimate sorbent.

Desulfurization, Sorbens, Mixed-metal-oxide

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