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

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.

The Effect of Ternary Catalyst Atomic Ratios (PtRuSn/C and PtRuNi/C) on Ethanol Electrooxidation for Direct Ethanol Fuel Cell

The effect of the different metal atomic ratios deposited on Vulcan XC-72R on ethanol electrooxidation reaction were investigated by producing of the ternary catalysts (PtRuSn/C and PtRuNi/C) in various atomic ratios (75:20:5, 75:15:10, 75:10:15, 75:5:20). All catalysts were prepared via polyol process. The nominal atomic ratios of the metals on the support were confirmed by EDX-SEM. The cyclic voltammetry was used to investigate the electrocatalytic activity of the catalysts. It was found that PtRuSn/C (75:10:15) showed the highest maximum current density of 3.25 mA/cm2 among all Sn containing catalysts. However, PtRuNi/C (75:5:20) also exhibited the high maximum current density of 2.66 mA/cm2 which was the maximum current density for Ni containing catalysts. Moreover, PtRuNi/C (75:5:20) exhibited the best activity and stability for ethanol electrooxidation reaction as showed in chronoamperometry tests. The current density at 3000 s was 0.54 mA/cm2. The size of the catalysts was about 1.9-3 nm measured by TEM. The catalyst also presented smaller particle size and better catalyst dispersion among all ternary catalysts. The addition of Sn facilitated the C-C bond breaking in molecule of ethanol while the addition of Ni facilitated better stability.