Low cost catalytic sorbents for NOx reduction. 3. NO reduction tests using NH3 as reducing agent

Chars and activated chars obtained from a low-rank coal and doped with vanadium compounds (V2O5 and NH4VO3) and petroleum coke ash, PCA, (Main metal components: V, Fe and Ni) have been tested as catalytic sorbents for NO reduction. The reduction tests have been carried out in the presence of oxygen with the addition of ammonia as reducing agent. The sorbents prepared have shown to be active for NO reduction at low-temperature (150 °C). Higher reduction efficiencies than with the unloaded not activated char have been achieved. The sorbents most efficient are those prepared with activated chars. Doping with vanadium compounds significantly upgrades the behaviour of the activated char. For the samples prepared with PCA, slightly lower NO conversions are observed but it has been shown that PCA is perspective for producing transition metals doped activated carbons. e Chemistry affects the sample behaviour. In general terms, the reduction efficiency is promoted by a low acidic character of the surface. However, it cannot be stated that the highest efficiency corresponds to the samples with the lowest CO2/CO ratio. It reveals that the overall behaviour of the samples responds to a combined effect of the chemical surface of the carbon support and the catalytic activity of the vanadia loaded. The results obtained show that the pathway of reduction when ammonia is used corresponds to a catalytic heterogeneous reaction, in contrast to the uncatalized high temperature (350 °C) reduction observed when ammonia was not used as reducing agent.