Effects of Fuel Type on Dual SCR Aftertreatment for Lean NOx Reduction

Alternate Pathway to Ammonia Formation in NOx Reduction: Direct Reaction of Acetylene and Nitrogen Atoms on Pt (111)

“…Although ammonia has been used effectively as a reductant for stationary sources, the injection of a urea-water solution (UWS) for deNOx in mobile sources remains problematic because of deposit formation issues at low temperatures and the possibility of ammonia slip . A recent solution to this problem is the use of one catalyst that produces ammonia from NOx, either a lean NOx trap (when rich) or a hydrocarbon SCR (HC-SCR) catalyst (when lean) − followed by an ammonia-SCR catalyst to maximize N 2 formation These dual catalyst systems offer the distinct advantage of avoiding ammonia and urea handling, while achieving high levels of NOx reduction without significant generation of N 2 O or release of ammonia.…”

The selective catalytic reduction of NO over Ag/Al2O3 with isobutanol as the reductant

“…One potential approach to addressing this issue is the selective catalytic reduction (SCR) of NO x using fuel-derived reductants over Ag/Al 2 O 3 catalysts. Previous studies have shown that these catalysts are more active for the SCR of NO x using alcohol, as other organic gas reductants exhibit limited NO x abatement without the addition of H 2 in the exhaust stream [3][4][5][6][7][8]. In particular, ethanol (EtOH) has been heavily investigated as a hydrocarbon (HC) reductant for NO x over Ag/Al 2 O 3 due to its prevalence in commercially available gasoline in the United States and its promising NO x reduction activity [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

“…The NH 3 generated over the Ag/Al 2 O 3 catalyst could be dealt with using an NH 3 slip catalyst such as those deployed in urea SCR systems, but the potential also exists for an alternative solution. Fisher et al and DiMaggio et al have proposed the idea of a dual-SCR configuration, which utilizes an upstream Ag/Al 2 O 3 catalyst and a downstream NH 3 SCR catalyst, such as a Cuexchanged zeolite[3,4]. At temperatures where peak NO x conversion occurs over the Ag/Al 2 O 3 catalyst, the NH 3 produced from NOx reduction will be stored on the downstream NH 3 SCR catalyst.…”