Water gas shift catalysts for hydrogen production from biomass steam gasification

- Iron/ceria based catalysts supported on 30 or 45 ppi foams for HTWGS reaction.
- Similar activity for 30 or 45 ppi catalysts by increasing gas hourly space velocity.
- H2O/CO ratio ≥ 2 improves activity and limits carbon deposition during HTWGS.
- Carbon deposition and increase in particle size limited to HTWGS beginning.
- Steady state when activity, carbon deposition and particle size stabilized.

Iron/ceria based catalysts were developed for high temperature Water Gas Shift (WGS) reaction in order to increase hydrogen content in the syngas at the outlet of a steam biomass gasifier working at atmospheric pressure. Alumina foam was used as support to deposit ceria and iron phase to prepare catalysts. The use of ceramic foams with different porosities (30 ppi and 45 ppi) assured a very low pressure drop in the process. The optimal conditions for WGS were determined in line with conditions occurring after gasification. The activity of the 45 ppi catalyst in the WGS reaction at 450 °C (CO conversion = 50%) can be reached by the 30 ppi catalyst by adjusting the gas hourly space velocity. The amount of carbon deposition observed on the catalyst, under the gas mixture representative of the syngas at the gasifier outlet, can be limited by the addition of steam (S/C ratio ≥ 2). These conditions also led to less stable carbon. Characterizations on the spent catalyst indicated the in-situ activation of the catalyst with no over-reduction of iron oxide. The stabilization of the catalytic activity could be related to the stabilization of both the particle size and carbon deposition. The carbon formation rate (decreasing exponential curve) stabilization could be associated to the beginning of a steady state, the carbon remaining on the catalyst being at the lowest stable form.