Physicochemical properties of Ce-containing three-way catalysts and the effect of Ce on catalyst activity

Comparison of HC species from diesel combustion modes and characterization of a heat-up doc formulation

“…The reason for this is believed to be that the pre-oxidized pretreatment conditioning of the catalyst (due to the lightoff performance of the catalysts containing CeO 2 ) is known to be very sensitive to the pretreatment condition; either it is pre-oxidized or pre-reduced (Oh and Eickel., 1988, Nunan et al, 1992, Serre et al, 1993, Törncrona et al, 1997. Pre-oxidized pretreatment conditioning during the preconditioning procedure before the light-off test oxidizes Pt and Pd; thus, the interface between the noble metals and CeO 2 is probably inactive, thereby resulting in no improvement of the oxidation characteristics of the PtPd+CeO 2 catalyst (Oh and Eickel., 1988;Nunan et al, 1992;Serre et al, 1993;Törncrona et al, 1997).…”

Catalytic control of automotive NOx: a review

“…It promotes the water gas shift reactions, it stabilizes the dispersion of noble metals on Al O -support and it stores and releases O under net-oxidizing and net-reducing conditions respectively. The reduced surface of Ce in contact with reduced noble metals is the most effective state of the catalyst and greater activity is detected with decreasing CeO crystallite size (Nunan et al, 1992). Extensive research has been casrried out on catalytic reduction of NO with CO over supported Rh catalyst.…”

NOx Storage and Reduction for Diesel Engine Exhaust Aftertreatment

“…Today, three way catalysts (TWC) oxidize CO and HC to CO2 and H2O, and simultaneously reduce NOx to N2 in a very efficient way for conventional Otto gasoline engines [9][10][11][12]. The conventional gasoline engines operate at stoichiometric air/fuel ratio, A/F=14.63 (w/w) [13,14], which produces an exhaust gas with the exact balance of CO, H2 and HC (reducing species) needed to reduce NOx and O2 (oxidizing species). However, diesel engines operate with higher A/F ratios, from 20:1 to 65:1 [15], then producing an exhaust gas with oxygen in excess ( Table 2.…”

“…Lietti et al [84] reported that during reduction of stored nitrates at 100 °C, reaction (13) accounted for almost all the H2 consumption, demonstrating that stored nitrates were reduced efficiently and selectively (>90%) to ammonia. On increasing the reduction temperature, nitrogen formation was promoted due to reaction (15) where the formed ammonia continued to react further with stored nitrates to form nitrogen.…”