Potential of Ceria-Zirconia-Based Materials in Carbon Soot Oxidation for Gasoline Particulate Filters

Abstract

<jats:p>ZrO2 and Ce0.8Zr0.2O2 mixed oxides were prepared and tested in the oxidation of carbon soot at different oxygen partial pressures and degrees of catalyst/soot contact to investigate their activity under typical gasoline direct injection (GDI) operating conditions. Under reductive atmospheres, generation of oxygen vacancies occurs in Ce0.8Zr0.2O2, while no reduction is observed on ZrO2. Both materials can oxidize carbon under high oxygen partial pressures; however, at low oxygen partial pressures, the presence of carbon can contribute to the reduction of the catalyst and formation of oxygen vacancies, which can then be used for soot oxidation, increasing the overall performance. This mechanism is more efficient in Ce0.8Zr0.2O2 than ZrO2, and depends heavily on the interaction and the degree of contact between soot and catalyst. Thus, the ability to form oxygen vacancies at lower temperatures is particularly helpful to oxidize soot at low oxygen partial pressures, and with higher CO2 selectivity under conditions typically found in GDI engine exhaust gases.</jats:p>

Inherent Reactivity of Praseodymium-Modified Ceria-Zirconia Catalysts for Oxidation of Soot

“…catalyst. The high catalytic activity of ceria-zirconia for soot oxidation was attributed to the presence of surface/bulk oxygen to oxidize soot, and the oxidation of carbon occurs at the carbon/CZ interface with the formation of an oxygen vacancy, as mentioned in previous reports [26,8].…”

“…The ceriazirconia sample was prepared by the co-precipitation method and tested in the oxidation of carbon soot at different oxygen partial pressures. T50 as a function of the reaction atmosphere was studied for all the investigated catalysts and was found to be around 550, 400 and 370 °C under an inert, 1% O2/N2 and air atmosphere respectively [8]. A set of ceria, ceriazirconia and ceria-zirconia-praseodymia catalysts, prepared by solution combustion synthesis has been studied in soot oxidation reactions and T50, the temperature at which 50% conversion of soot takes place, was found to be 451, 469 and 444 °C, respectively [9].…”

Catalytic Materials for Gasoline Particulate Filters Soot Oxidation

“…Aneggi et al [38] carried out studies on Ce 0.8 Zr 0.2 O 2 and ZrO 2 focusing on the effect of oxygen concentration (i.e., 0% O 2 /N 2 , 1% O 2 /N 2 , and air) and of the type of soot/catalyst contact. For this purpose, three different contact conditions were employed with different degrees of carbon/catalyst interactions: in addition to the well-known loose contact (i.e., obtained by mixing soot and catalyst in a vial) and tight contact (i.e., obtained by grinding the mixture in an agate mortar) conditions, a third type of mixing was also realized by milling soot-catalyst powders in a high-energy mill (i.e., supertight contact conditions).…”

Catalytic Diesel and Gasoline Particulate Filters

“…This Special Issue includes three reviews [1][2][3] and three articles [4][5][6]. The review by Lisi et al [1] addresses the most important issue to an effective regeneration of catalytic (i.e., catalyst-coated) diesel particulate filters (DPFs): the contact between soot and catalyst.…”

“…This makes soot oxidation catalysts proposed for DPFs unsuitable for GPFs and, hence, justifies the recent scientific interest to develop materials that fit the peculiar gasoline operating conditions. In this framework, Aneggi and Trovarelli [5] compared the behavior of ceria-zirconia and zirconia in soot oxidation under oxygen-poor conditions, showing that lattice and surface oxygen in the former can help with oxidation at low oxygen partial pressure. Sartoretti et al [6] investigated a nanostructured equimolar ceria-praseodymia catalyst for different reactions, namely CO oxidation, ethylene and propylene total oxidation, and soot combustion, in low oxygen availability.…”