Investigation of Co-Based DeNOx Catalysts for the Treatment of Natural Gas Lean-Burn Engine Exhaust

The catalytic reduction of nitric oxide with methane in lean conditions has been investigated on cobalt-based powder and monolith catalysts such as Co-exchanged ferrierite, Co-exchanged beta zeolite and Co–ZrO2. From catalyst laboratory testing the following activity scale was obtained: Co-ferrierite > Co-beta >>> Co–ZrO2, suggesting a significant role of the support catalytic matrix. In the tests at the engine exhaust, the best results were obtained with Co-ferrierite, after water separation from the exhaust. However, in the presence of the high concentration of water, typical of the engine exhaust, the performances were dramatically reduced.