Nanostructured Equimolar Ceria-Praseodymia for Total Oxidations in Low-O2 Conditions

Sartoretti, Enrico; Martini, F.; Piumetti, Marco; Bensaid, Samir; Russo, Nunzio; Fino, Debora

doi:10.3390/catal10020165

Cited by 19 publications

(12 citation statements)

References 59 publications

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“…Upon introduction of small amounts of a second lanthanide, the cube-shaped crystal is usually maintained, but it has been reported that at higher substituent levels, and under otherwise identical reaction conditions, the crystal morphology becomes increasingly rod-shaped, with a distribution of both crystal forms at intermediate compositions. This is exemplified by the case of praseodymium, where the same phenomenon has been reported independently by several different research groups: [105][106][107][108] at 25% Pr substitution and above, the rod-like crystal morphology is detected, and an example is shown in Figure 13. Praseodymium may also be found in the +4 oxidation state, and this has been inferred from the redox properties of some of these samples [106,108] and detected by X-ray spectroscopy in others [105,107].…”

Section: Rare Earth-substituted Ceriasupporting

confidence: 71%

“…Applications of rare earth-substituted ceria materials span the types of fields expected for these materials, from oxide ion conductors in solid oxide fuel cells, where the enhanced sinterability of fine powders into ceramics is beneficial [136,137,143,149,150], to catalysts for CO and soot oxidation, where the high surface and exposure of specific crystal faces may offer some benefits [103,105,107,108,113,115,132,133,135,[150][151][152][153]. Photocatalytic properties are of increasing focus for degradation of pollutants or organic transformations, and some of the rare earth-substituted materials have been screened for these applications [101,124,141,154].…”

Section: Rare Earth-substituted Ceriamentioning

confidence: 99%

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Solvothermal Synthesis Routes to Substituted Cerium Dioxide Materials

et al. 2021

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We review the solution-based synthesis routes to cerium oxide materials where one or more elements are included in place of a proportion of the cerium, i.e., substitution of cerium is performed. The focus is on the solvothermal method, where reagents are heated above the boiling point of the solvent to induce crystallisation directly from the solution. This yields unusual compositions with crystal morphology often on the nanoscale. Chemical elements from all parts of the periodic table are considered, from transition metals to main group elements and the rare earths, including isovalent and aliovalent cations, and surveyed using the literature published in the past ten years. We illustrate the versatility of this synthesis method to allow the formation of functional materials with applications in contemporary applications such as heterogeneous catalysis, electrodes for solid oxide fuel cells, photocatalysis, luminescence and biomedicine. We pick out emerging trends towards control of crystal habit by use of non-aqueous solvents and solution additives and identify challenges still remaining, including in detailed structural characterisation, the understanding of crystallisation mechanisms and the scale-up of synthesis.

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Section: Rare Earth-substituted Ceriasupporting

confidence: 71%

Section: Rare Earth-substituted Ceriamentioning

confidence: 99%

Solvothermal Synthesis Routes to Substituted Cerium Dioxide Materials

et al. 2021

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“…In the last years, a lot of research has been conducted for GPFs to optimize their efficiency and performance. Topics included filter structure [10], flow field [11], filter material [12], in particular for soot oxidation at absence of NO x and O 2 [13,14], soot storage and oxidation [15,16], oxygen storage [17], ash loading [18], and washcoat [19]. Typically, the temperature at the GPFs is high enough to oxidize the soot when there is available oxygen (e.g., during fuel cut-offs) [20].…”

Section: Introductionmentioning

confidence: 99%

Challenging Conditions for Gasoline Particulate Filters (GPFs)

et al. 2022

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The emission limit of non-volatile particles (i.e., particles that do not evaporate at 350 °C) with size >23 nm, in combination with the real driving emissions (RDE) regulation in 2017, resulted in the introduction of gasoline particulate filters (GPFs) in all light-duty vehicles with gasoline direct injection engines in Europe. Even though there are studies that have examined the particulate emissions at or beyond the current RDE boundary conditions, there is a lack of studies combining most or all worst cases (i.e., conditions that increase the emissions). In this study, we challenged a fresh (i.e., no accumulation of soot or ash) “advanced” prototype GPF at different temperatures (down to −9 °C), aggressive drive cycles and hard accelerations (beyond the RDE limits), high payload (up to 90%), use of all auxiliaries (air conditioning, heating of the seats and the rear window), and cold starts independently or simultaneously. Under hot engine conditions, the increase of the particulate emissions due to higher payload and lower ambient temperature was 30–90%. The cold start at low ambient temperature, however, had an effect on the emissions of up to a factor of 20 for particles >23 nm or 300 when considering particles <23 nm. We proposed that the reason for these high emissions was the incomplete combustion and the low efficiency of the three-way oxidation catalyst. This resulted in a high concentration of species that were in the gaseous phase at the high temperature of the close-coupled GPF and thus could not be filtered by the GPF. As the exhaust gas cooled down, these precursor species formed particles that could not be evaporated at 350 °C (the temperature of the particle number system). These results highlight the importance of the proper calibration of the engine out emissions at all conditions, even when a GPF is installed.

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“…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.…”

mentioning

confidence: 99%

“…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. They found that, thanks to its capability of releasing active oxygen species, this catalyst exhibited a remarkable activity and CO 2 selectivity at low oxygen concentrations.…”

mentioning

confidence: 99%