Abstract

A redox reaction scheme consisting of two steps as an alternate to the partial oxidation of methane (POX) for synthesis gas production is proposed. With the use of a thermodynamic analysis the CoWO₄ spinel was introduced as a new oxygen carrier material, capable to be reduced with methane (15% CH₄/Ar) and reoxidized with steam (30% H₂O/Ar) to produce syngas and hydrogen in each redox step, respectively. H₂ production is feasible during the regeneration of CoWO₄ by oxidation of reduced species (Co and W) with steam. CoWO₄ synthesis was performed using the solid state reaction. Characterization included: XRD, SEM and particle size determination. Redox-cycle performance was followed by TGA. Thermal stability of CoWO₄ was tested by exposing the material to ten consecutive reduction/oxidation (H₂/Ar, H₂O/Ar) cycles at 850°C and after. Results indicate that CoWO₄ showed no significant loss of activity. This stable behavior is associated to its crystalline structure, which allows the fixation of the active metals (Co + W) through the spinel structure, thus inhibiting particle nucleation and migration, which are the main causes of sintering after exposure to steam at high temperatures. The addition of Ni to CoWO₄ as a POX catalyst produced an enhancement of the reduction step of 20% in metal oxide conversion with respect to CoWO₄.

Recommended Citation

De Los Ríos, Thelma; Collins Martinez, Virginia; Delgado Vigil, Manuel D.; and López Ortiz, Alejandro (2007) "Synthesis, Characterization and Stability Performance of CoWO₄ as an Oxygen Carrier under Redox Cycles towards Syngas Production," International Journal of Chemical Reactor Engineering: Vol. 5: A30.
Available at: http://www.bepress.com/ijcre/vol5/A30