Modified Ferrite Based Catalysts for Ultra-High Temperature Water Gas Shift Reaction for Membrane Reactor Applications
Ataullah Khan, Chemical and Materials Engineering Division, University of Cincinnati, 400 RH, Chemical and Materials Engineering Division, 0012, University of Cincinnati, Cincinnati, OH 45220 and Panagiotis (Peter) Smirniotis, Chemical & Materials Engineering Department, University of Cincinnati, 2600 Clifton Avenue, Cincinnati, OH 45221.
Ammonia assisted co-precipitation route was explored for high yield preparation of various modified ferrite catalysts using dilute metal nitrate precursor solutions. The modified ferrite-based inverse spinels were doped with various transition/non-transition and inner transition metals. The catalyst surface was selectively functionalized to attract CO (weak base), repel CO2 (weak acid) and retain water molecules. XRD measurements proved the existence of Fe2O3 type phases in the freshly prepared catalysts, which is pre-requisite for the active Fe3O4 inverse spinel phase; Fe3O4 type phases, were observed in the spent catalysts. Preliminary Raman characterization gave insight into the existence of Fe3O4 type phase in the spent catalysts, thus supporting the XRD analysis. The WGS tests were performed in H2 lean and exceedingly H2O-rich environments to mimic membrane reactor (MR) conditions. WGS activity was tested as function of operating temperature between 400 to 550 °C. An increase in WGS activity was observed as reaction temperature was raised, with maximum activity observed at 550 °C, interestingly this coincides with the temperature for the favorable operation of silicalite membranes. WGS activity (% CO conversion) as high as 94-97 % was observed in single pass. All the systems investigated in this study, exhibit good WGS activity with the only exception of Fe/Mn where F-T synthesis took place. Among all the systems studied Fe/Ce system is found to be very promising. These results are supported by intensive characterization studies.