Abstract
The behavior and operation parameters were analyzed for the hybrid LNT-SCR (Lean NOx-Trap–Selective Catalytic Reduction) system with advanced catalyst formulations. Pt-Ba-K/Al2O3 was used as an NSR (NOx Storage and Reduction) or LNT catalyst effective in NOx and soot simultaneous removal whereas Cu-SAPO-34 with 2 wt.% of copper inside the structure was the small pore zeolite employed as the SCR catalyst. Under alternating and cyclic wet conditions, feeding volumetric concentrations of 1000 ppm of NO, 3% of O2, 1.5% of water, 0.3% of CO2, and H2 as a reductant, the NOx-conversion values were above 95% and a complete mineralization to nitrogen was registered using θ ≤ 3 (20 s of regeneration) and a hydrogen content between 10,000 and 2000 ppm in the whole temperature range tested. An excess of hydrogen fed (above 1% v/v) during the rich phase is unnecessary. In addition, in the low temperature range below 250 °C, the effect is more noticeable due to the further ammonia production and its possible slip. These results open the way to the scale up of the coupled catalytic technologies for its use in real conditions while controlling the influence of the operation map.
Highlights
The increase in nitrogen monoxide emissions with the use of new biofuels has been proven in a motor bench [1]
The way of driving modifies the production of NOx and efficient catalytic after-treatment technologies are required to reduce the levels below the limits imposed by the Euro regulation
/VSCRperformance in DeNOx performance expressed as NOx and selectivity
Summary
The increase in nitrogen monoxide emissions with the use of new biofuels has been proven in a motor bench [1]. The way of driving modifies the production of NOx and efficient catalytic after-treatment technologies are required to reduce the levels below the limits imposed by the Euro regulation. NOx Storage and Reduction (NSR) technology is the most efficient in the removal of nitrogen oxides from diesel exhaust gases. Process, which is based on the mineralization of NOx to N2 and water with ammonia [6,7,8,9], requires the injection of an external reducing agent. The coupling of SCR and NSR technologies is being widely studied to solve these drawbacks [10,11,12,13,14,15]
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