Mixtures of potassium sulphate and iron sulphate as catalysts for water vapour gasification of carbon. 2. Wettability phenomena and reactions of the catalyst precursors

The interaction between carbon and a mixed catalyst (FeSO₄ with K₂SO₄, Fe/K mass ratio 1:5), which showed a superior catalytic activity in water vapour gasification of carbon, was studied by measuring the wettability of a fine-grained graphite, penetration into this material and the metal distribution after treatments in $\text{H}{}_2\text{H}{}_2\text{O}$ mixtures at various temperatures. The decomposition and conversion reactions were analysed by measuring the relative mass losses. It was found that the catalyst mixture forms a melt phase by 650 °C, whereas the pure sulphates are still present as powders. Penetration is complete after 2 h treatment at 700 °C. EPMA studies show a homogeneous distribution of Fe and K in the graphite substrate. The same treatment causes no significant change with the pure sulphates. The relative mass losses suggest that the melt may be composed of FeS, FeO, K₂S and KOH. It is assumed that the conversion of K₂SO₄ to K₂S or even KOH may be catalytically influenced by FeS, FeO or possibly Fe. Further studies are necessary to analyse the active state of the catalyst and especially the mutual catalytic activity of Fe and K.