Optimization Of Precipitation Processes Of Iron-Chromium Mixed Oixdes For Water Gas Shift Reaction

The iron-chromium mixed oxides catalysts for the water gas shift reaction were prepared by co-precipitation. The synthesized catalysts samples were studied comprehensively by Micro-Reactor-Chromatography, XRD, TEM, TPR, TG/DTA and Special Surface Analysis. Emphasis was to obtain the Iron-chromium mixed oxides with desired composition and texture by optimizing the precipitation and corresponding evolution process.The optimization of chromia content and preparation system shown the synthesized iron-chromium mixed oxides samples with 8% chromia via normal titration at reflux conditions presented both higher activity and robust heat-resistance.Investigations were carried out to study the effect of the final pH of precipitation reaction solution on the iron-chromium mixed oxides catalysts. The result indicated thatγ-Fe2O3 was the exclusive structure with different crystallization for the calcined catalysts samples and chromium ions replaced part of the lattice iron inγ-Fe2O3. The catalyst samples shown better activity when pH was controlled between 9~10. The chromia preventedγ-Fe2O3 crystal granule from growth. The excellent uniformity increased the special surface. The appropriate final pH resulted in Fe2+ with precipitation completely and enhanced the temperature ofγ-Fe2O3 reductive to Fe3O4 crystal, which favored the increasing of the heat-resistance.The ways of joining chromia and hydrothermal condition were studied. It was found that mixed mother solution of CrO3 and FeSO4 co-precipitated by NaOH solution and higher pressure ripening were benefit to the activity and heat-resistance for Fe-Cr catalyst. Iron-chromium mixed oxides with higher reductive temperature forγ-Fe2O3 to Fe3O4 increased the activity after heat-resistance. The hydrothermal condition in higher pressure improved the uniformity ofγ-Fe2O3 crystal grainand special surface.