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The activity of single and two-component catalyst systems consisting of a partial oxidation catalyst and a reduction catalyst (Ag/Al 2 O 3 ), were investigated for selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with n -decane (HC) as a reductant. The single component Ag/Al 2 O 3 catalyst showed a maximum NO x conversion of 28% at 400 °C and formation of minor amounts of hydrocarbon cracking products. Co-presence of partial oxidation catalyst, especially metal/ZSM-5, along with Ag/Al 2 O 3 enhanced the NO x conversion of the composite catalysts. Among the composite catalysts, Zn/ZSM-5–Ag/Al 2 O 3 combination led to the most increase in NO x conversion. It was identified that the n -decane can be more effectively converted, on Zn/ZSM-5, to smaller hydrocarbons (such as ethene, propane and propene) intermediates. These in situ generated intermediates were found to enhance the NO x conversion of Zn/ZSM-5–Ag/Al 2 O 3 composite catalysts. Catalyst optimization showed that the NO x conversion increased with increase in zinc loading of up to 5 wt% in ZSM-5 and by increasing Zn/ZSM-5 content in the composite mixture catalyst. A combination of 17 mg of Ag/Al 2 O 3 and 33 mg of 5%Zn/ZSM-5 led to the most active catalyst showing a maximum NO x conversion of about 67% at 400 °C. |
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