Most Recent Advances in Diesel Engine Catalytic Soot Abatement: Structured Catalysts and Alternative Approaches

Abstract

<jats:p>Diesel engine emissions are typically composed of several hundred chemical compounds, partly present in the gas phase and partly in solid phase as particles, the so-called particulate matter or soot. The morphology of the catalyst is an important characteristic of soot particles’ abatement, since a good contact between catalyst and soot is mandatory. For practical purposes, the active species should be supported as a film on the structured carrier, in order to allow simultaneous soot filtration and combustion. This review focuses on the most recent advances in the development of structured catalysts for diesel engine catalytic soot combustion, characterized by different active species and supports, as well as by different geometric configurations (monoliths, foams, ceramic papers, or wire mesh); the most important peculiar properties are highlighted and summarized. Moreover, a critical review of the most recent advances in modeling studies is also presented in this paper. In addition, some highlights on some of the most recent alternative approaches proposed for limiting the soot emissions from diesel engines have been given, delineating feasible alternatives to the classical strategies nowadays used.</jats:p>

BaFe1−xNixO3 Catalysts for NOx-Assisted Diesel Soot Oxidation

“…Thus, a combination of diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) is employed as diesel after-treatment system to meet emission regulations [8,9]. However, DPF is made up of a ceramic honeycomb monolith coated with noble metals (Pt, Pt/Pd or Pd/Rh) [8,9], being these PGMs scarce and expensive [10,11].…”

Constructing a Pt/YMn2O5 Interface to Form Multiple Active Centers to Improve the Hydrothermal Stability of NO Oxidation

“…2−5 In addition, the latest China VI emission regulations on diesel vehicles have increased the mileage life of catalysts (up to 700 000 km) and put forward requirements on the durability of catalysts, which, standard to laboratory catalysts, are usually required to undergo 10 h of hydrothermal aging with 10% H 2 O/air at 800 °C, the NO activity of catalysts does not decrease. 6,7 Pt-based catalysts have been widely used for DOCs owing to their excellent performance. 8−11 At present, there are three main aspects to improve the hydrothermal stability of Pt-based catalysts: one is by tuning the uniformity of Pt nanoparticles, including their size, shape, and structure, to eliminate the difference in chemical potential, thus inhibiting the Ostwald ripening process.…”

“…Moreover, with increasingly stringent regulations and the increase of catalyst life requirements, as well as when the back-end DPF particulate matter accumulates to a certain extent, oil injection is required to remove soot particles by oxidation, resulting in a sharp increase in the tail gas temperature. Therefore, the temperature of the DOC catalyst bed at the front will also increase, reaching more than 650 °C. − In addition, the latest China VI emission regulations on diesel vehicles have increased the mileage life of catalysts (up to 700 000 km) and put forward requirements on the durability of catalysts, which, standard to laboratory catalysts, are usually required to undergo 10 h of hydrothermal aging with 10% H 2 O/air at 800 °C, the NO activity of catalysts does not decrease. , …”

Understanding the multiple interactions in vanadium-based SCR catalysts during simultaneous NOx and soot abatement

“…NO x and particulate matter (PM), as two major pollutants released from diesel engines, are typically removed sequentially by different catalytic components in the exhaust gas aftertreatment system. [1][2][3] The diesel particulate filter (DPF) is nowadays the widely employed technology for trapping particulate matter, 4 and the downstream wellestablished selective catalytic reduction (SCR) of NO x with ammonia is applied for NO x emission control. 3,5 Although such a combination can lead to very low emissions, it occupies a large volume, which is critical especially for lightduty vehicles.…”