Steam reforming of tar derived from walnut shell and almond shell gasification on red mud and iron-ceria catalysts

Catalytic steam gasification of shells (almond and walnut) was carried out in a flow-type double-bed microreactor. Temperature-programmed thermal steam gasification of shells was performed at 200-850 °C, followed by the catalytic gasification of volatiles (including tar) at different temperatures. The iron-ceria catalyst and red mud (as the iron oxide catalyst) were used as a catalytic bed material. Effects of the catalyst on tar decomposition and tar gasification were investigated. The iron-ceria catalyst enhanced both tar degradation and hydrogen production via the water-gas shift reaction. The tar conversions of 94% (for almond shell) and 100% (for walnut shell) were achieved at a very low temperature (600 °C). The red mud was found less active in tar decomposition because of the inhibition of sodium aluminum silicate hydrate to the activity of iron oxide.