The Issue of Soot-Catalyst Contact in Regeneration of Catalytic Diesel Particulate Filters: A Critical Review

Abstract

Soot-catalyst contact represents the main critical issue for an effective regeneration of catalytic (i.e., catalyst-coated) diesel particulate filters (DPFs). Most of the literature reviews on this topic have mainly been focused on studies dealing with powdered soot-catalyst mixtures. Although the results obtained on powders surely provide significant indications, especially in terms of intrinsic activity of materials towards soot oxidation, they cannot be directly extended to DPFs due to completely different soot-catalyst contact conditions generated during filtration and subsequent regeneration. In this work, attention is devoted to catalytic DPFs and, more specifically, studies on both catalyst dispersion and soot distribution inside the filter are critically reviewed from the perspective of soot-catalyst contact optimization. The main conclusion drawn from the literature analysis is that, in order to fully exploit the potential of catalytic DPFs in soot abatement, both a widespread and homogeneous presence of catalyst in the macro-pores of the filter walls and a suitably low soot load are needed. Under optimal soot-catalyst contact conditions, the consequent decrease in the temperature required for soot oxidation to values within the temperature range of diesel exhausts suggests the passage to a continuous functioning mode for catalytic filters with simultaneous filtration and regeneration, thus overcoming the drawbacks of periodic regeneration performed in current applications.

Evaluating the Real-World NOx Emission from a China VI Heavy-Duty Diesel Vehicle

“…What's more, in the DOC unity, in addition to oxidation of CO and unburned hydrocarbons, NO conversion to NO 2 takes place, thus increasing the quite low NO 2 concentration in the exhaust gas (about 5% to 10% of total NOx). This increase in NO 2 concentration speeds up the passive regeneration process of DPF and, thus, largely affects the decrease in back pressure, enhancing the operating performance and prolonging the life-time of the aftertreatment device [8][9][10].…”

Filtration Efficiency and Regeneration Behavior in a Catalytic Diesel Particulate Filter with the Use of Diesel/Polyoxymethylene Dimethyl Ether Mixture

“…Generally, diesel soot spontaneously burns at temperatures over 600 • C. To lower the temperature required for soot oxidation, catalyst-coated DPFs (i.e., catalytic DPFs) are widely used [26]. Catalytic soot oxidation in cDPF depends not only on the catalyst's intrinsic activity but also on the quality of the soot-catalyst contact [27]. When fueling with diesel/PODE n mixture, both the particulate size and exhaust atmosphere differ, which further leads to changes in the DPF performance.…”

Two-dimensional numerical studies of particle motion and deposition in the channel of diesel particulate filters

“…Optimum structure of DPF requires low-pressure drop and regeneration frequency. The best strategy to lower both pressure drop and regeneration frequency is to operate a continuous filtration/regeneration process of catalyst-coated DPFs [9]. Scholars have done a lot of exploratory research on this topic, such as reducing CPSI (cells per square inch) [10] and altering channel shape [11], using unequal width for inlet and outlet channels [12][13][14].…”