| Modified Nano-crystalline Ferrites for High Temperature WGS Membrane Reactor Applications (2009) | |||||||||||||
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| In the present study, selected metal ions (M = Cr, Mn, Co, Ni, Cu, Zn and Ce) were introduced into the iron oxide spinel lattice, and were screened for effectiveness for the HT WGS reaction. Simultaneous precipitation of Fe(III) nitrates along with the above mentioned metal nitrate(s) in an optimal concentration regime, resulted in the formation of high surface area nanosized catalysts. A noticeable interaction between iron and the other substitutent metal was interpreted from the formation of either inverse or mixed spinels of composition A(1-δ)Bδ[AδB(2-δ)]O4. The incorporation of metal cations into the hematite crystal structure modifies the magnetic field and also influences the reducibility of hematite particles, as observed from our Mössbauer and TPR studies, respectively. These effects strongly depend on the nature of the incorporated metal cation. The hyperfine shift parameters and isomer shift values obtained from Mössbauer support the nanoscale nature of the catalysts, in concurrence with the TEM analysis. Among all the catalysts tested, Fe/Cr and Fe/Ce were found to be most active and their activity approached the equilibrium conversion at higher temperatures. Keyword: HT WGS; nanosized; modified ferrites; Mössbauer; TPR; 2 | |||||||||||||
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