Influence of the reducing agent for lean NO sub(x) reduction over Cu-ZSM-5

A range of ethers, alcohols and alkanes were compared as reducing agents for NO sub(x) over a Cu-ZSM-5 lean NO sub(x) catalyst. The nature of the reducing agent was found to determine the degree of NO sub(x) reduction. Methanol and DME were virtually inactive as reductants over this catalyst, while higher ethers and alcohols showed high NO sub(x) conversion. A detailed study was performed to investigate the differences. Among the studied variables, the chemical structure of the reductant was found to be especially important. Despite having a lower reducing capacity than DME, ethylene glycol was active for NO sub(x) reduction. It is concluded that a C-C bond in the reducing agent is required for lean NO sub(x) reduction over Cu-ZSM-5. The absence of this bond in DME and methanol explains their low activity for NO sub(x) reduction over this catalyst.