Improvements in Intimately Coupled Diesel Hydrocarbon Adsorber/Lean NOx Catalysis Leading to Durable Euro 3 Performance

Enhanced Sulfur Resistance of Pt-Pd/CeO₂-ZrO₂-Al₂O₃ Commercial Diesel Oxidation Catalyst by SiO₂ Surface Cladding

“…Therefore, we conjecture that, surface SiO2 layer did not largely close over the active sites of Pt-Pd/CZA catalyst because the SiO2 layer was porous, and hence catalytic activity of the SiO2/ Pt-Pd/CZA would not obviously be worse than that of the Pt-Pd/CZA catalyst, meanwhile this deduction is consistent with the activity and TPR test results. In addition, SiO2 layer is uniformly covered on the surface of the catalyst, as shown in Section 3.2.3, SiO2 is non-sulfating support which shows excellent sulfur resistance performance, 23,36,37 thus, we infer that sulfur resistance performance of SiO2/Pt-Pd/CZA catalyst would be improved by the surface coating of porous SiO2, which is confirmed by the sulfation test results.…”

Diesel aerosols and gases in underground mines: guide to exposure assessment and control.

“…In an LNC system, the reduction of NO X is achieved by reacting NO X with hydrocarbons in the presence of a catalyst. The conversion of both NO and NO 2 depends mostly on the 43 catalyst chemical formulation and configuration [Truex 1994;Kharas et al 1998] as well as the temperature window at which the catalyst has the highest activity. Several catalyst options exist for use in LNC systems (see Figure 9), but three groups have shown to be most effective: (1) (3) base metal oxides which are active at the highest temperatures (400-600, 752-1,112°F, an atypical range for most diesel applications).…”

“…Even though peak NO X reductions (measured in the laboratory) are frequently reported in excess of 80% (see Figure 9), performance of these catalysts over regulatory test cycles is usually limited to 20%-30% reduction. Higher reductions can be obtained using the strategies described above, but so far, the maximum achievable NO X conversion by LNC systems for diesel engines operated over real duty cycles has been 60% [Kharas et al 1998].…”