Silicon carbide-based membranes with high soot particle filtration efficiency, durability and catalytic activity for CO/HC oxidation and soot combustion
Résumé
We report here the solution coatings of Diesel Particulate Filter (DPF)
with allylhydridopolycarbosilane (AHPCS)-based polymers leading to
supported silicon carbide (SiC)-based membranes with high temperature
soot particle filtration efficiency, durability and catalytic activity.
In a first part of the present study, our objective was to reduce the
pore size of DPF to filtrate finer particles without altering filtration
efficiency by coating DPF with an additional fine porous AHPCS-derived
SiC membrane. The latter is produced by dip-coating AHPCS on DPF
following by a pyrolysis of the AHPCS membrane-modified DPF at 1000
degrees C under argon. We investigated the influence of dip-coating
parameters and viscosity of different AHPCS solutions on the SiC
membrane-coated DPF by SEM, mercury porosimetry, XRD and
high-temperature thermogravimetric analysis. The evolution of the
filtration capacity has been determined with a synthetic gas bench. An
additional fine SiC membrane (-150 nm in thickness) prepared from a 10
vol% of AHPCS in THE deposited on DPF allowed maintaining filtration
efficiency as high as the virgin DPF while the pore size of the SiC
membrane coated-DPF decreased to filter finer particles. Results are
confirmed using a commercially-available polysiloxane (Si-C-O
precursor). Furthermore, the SiC membrane acted as a thermal barrier
coating and provided a better durability to the DPF by preventing
apparition of cracks after heat-treatment to 1500 degrees C under argon.
The use of mixed oxide and metallic phases formed in-situ in SiC
constitutes one of the solutions to generate new and effective catalytic
performances to membranes. Within this context, in a second part of the
study, we applied a reverse AHPCS-based microemulsion to combine SiC
and oxide phases in the same additional porous membrane. As a proof of
concept, we have prepared catalytically active Ce-O-Fe-Pt/SiC membrane
coated DPF after dip-coating and pyrolysis under argon. These materials
have been characterized and tested with regard to CO/HC oxidation and
soot combustion. Ce-O-Fe-Pt/SiC membrane coated DPF showed an activity
for CO conversion reaching a light off temperature T-50=270 degrees C
and the presence of the catalytic phase allowed burning soot at 486
degrees C. (C) 2015 Elsevier B.V. All rights reserved.