Low-temperature NOx reduction over Cu-LTA and SmMnOx composite catalysts

Abstract

Low-temperature selective catalytic reduction of NOx with ammonia (NH3-SCR) over zeolite catalysts remains a great challenge in diesel exhaust purification. Herein, Cu-LTA zeolite with excellent hydrothermal stability was composited with a small proportion of SmMnOx oxides, the composite catalytic system efficiently resolves the low-temperature activity challenge encountered by Cu-LTA. The promoting pathways revealed the presence of active nitrite intermediates formed on SmMnOx by activating NO, that were able to migrate to the Cu-LTA and can be further decomposed on the Brønsted acid sites. Compared to the continuous deposition of nitrates in Cu-LTA, the presence of SmMnOx in composite catalysts efficiently reduced the accumulation of inert nitrate and improved the nitrate deposition phenomena. This innovative research would provide a rational strategy to break the barrier of limited low-temperature performance faced by zeolite catalysts, effectively promoting the NOx removal in vehicles sources.