Synthesis of Zeolite ZSM-5 on Raney Fe: High Hydrothermal Stability DeNOx Catalyst

摘要

The selective catalytic reduction(SCR) of nitric oxide by ammonia or hydrocarbons in the presence of excess oxygen is currently the most widespread method for the clean-up of the flue-gas. Although Cu-ZSM-5 zeolite has been found to possess higher activity as a potential DeNOx catalyst, it is severely poisoned by the H_2O that is unavoidably produced in the combustion process within the engine, and undergoes dealumination and physical breakdown by severe steaming under reaction conditions. Hall et al. [1,2] reported that "overexchanged" FeZSM-5 catalysts are more active than comparable CuZSM-5 preparations and are much more durable, but conventional ion-exchange method did not significantly raise the exchange level. In order to stabilize the activity for NO removal in the presence of water, ZSM-5 was grown in situ on Raney Ni. The Al source for synthesizing the zeolite is the residual Al in the Raney Ni, and hydrothermal and thermal stability were greatly improved in the SCR of NOx with ammonia. In present work, ZSM-5/Raney Fe was prepared and which was made catalytically active only by the thermal and/or hydrothermal treatment. The DeNOx activity and stability of the catalyst with ammonia as the reductant in the presence of excess oxygen, water and SO_2 were investigated.