Continuously regenerating Diesel Particulate Filters based on ionically conducting ceramics

• Yttria-Stabilized Zirconia (YSZ), an intrinsic ionic conductor, can oxidize soot.
• YSZ lattice ions are the active oxygen species for initiating the soot combustion.
• The soot oxidation process on YSZ involves a fuel-cell-type electrochemical mechanism.
• YSZ porous membranes were fabricated to simulate Diesel Particulate Filters.
• YSZ porous membranes are effective for soot filtering.

This study reports a mechanistic study of the soot oxidation on Yttria-Stabilized Zirconia (YSZ), a non-reducible oxide with intrinsic bulk oxygen mobility. Temperature-Programmed Oxidation (TPO) and isotope exchange experiments demonstrate the key role of bulk oxygen species in the oxidation process. When “intimate” soot/YSZ contact is achieved after in situ carbon deposition via propylene cracking, lattice oxygen ions are the predominant species involved in the oxidation reaction. Based on isotopic TPO experiments performed with different oxygen partial pressures in “tight” contact mode and oxygen exchange measurements, it is proposed that the ignition of the soot oxidation on YSZ can be described as a fuel-cell-type electrochemical mechanism at the nanometric scale. The efficiency of this electrochemical process seems to depend both on the YSZ/soot contact and on the oxygen partial pressure. In addition, YSZ porous membranes were fabricated in order to simulate porous walls of YSZ-based DPFs. These membranes are effective for soot filtering and soot oxidation with oxygen starts at temperatures over 430 °C, in real soot/catalyst contact.

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