The thermochemical reactivity of silicate minerals in hydrogen and methane

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The thermochemical reduction of transition metal silicates, i.e. garnierite (Ni,Mg)6[(OH)8(Si2O7)], chrysocolla (Cu,Al)2H2Si2O5(OH4)·nH2O, dioptase CuSiO3·H2O, willemite Zn2SiO4, and hemimorphite Zn4Si2O7(OH)2·H2O has been studied. By means of combined thermogravimetric/mass spectrometric measurements, X-ray diffraction and analytical scanning electron microscopy it is shown that in a 5% H2/95% N2 or in a methane atmosphere the transition metals are selectively reduced at temperatures qualitatively corresponding to their electrochemical potential. Mixtures of elemental transition metals and quartz, SiO2, are obtained as solid products. Depending on the nature of the parent mineral, different mixtures of volatile products are obtained. Principal volatile product, however, is water vapour. The reduction in methane leads to the formation of syngas.

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The authors acknowledge the financial support of the Schweizerisches Bundesamt für Energiewirtschaft as well as the Fonds der Chemischen Industrie.

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Sazama, U., Reller, A. The thermochemical reactivity of silicate minerals in hydrogen and methane. Journal of Thermal Analysis 47, 357–364 (1996) doi:10.1007/BF01983977

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  • metal/silica products
  • syngas formation
  • thermochemical reduction
  • transition metal silicates