Leonardo Lizarraga

Ionically conducting ceramics as active catalyst supports.

Philippe Vernoux,*,† Leonardo Lizarraga,† Mihalis N. Tsampas,† Foteini M. Sapountzi,† Antonio De Lucas-Consuegra,‡ Jose-Luis Valverde,‡ Stamatios Souentie, Costas G. Vayenas, Dimitris Tsiplakides, Stella Balomenou, and Elena A. Baranova †Universite de Lyon, Institut de Recherches sur la Catalyse et l’Environnement de Lyon, UMR 5256, CNRS, Universite Claude Bernard Lyon 1, 2 Avenue A. Einstein, 69626 Villeurbanne, France ‡Departamento de Ingenieria Quimica, Facultad de Ciencias y Tecnologias Quimicas, Universidad de Castilla-La Mancha, Avenida Camilo Jose Cela 10, 13005 Ciudad Real, Spain LCEP, Caratheodory 1 Street, Department of Chemical Engineering, University of Patras, Patras GR-26500, Greece Division of Natural Sciences, Academy of Athens, Panepistimiou 36 Avenue, GR-10679, Athens, Greece Chemical Process Engineering Research Institute (CPERI), Centre for Research and Technology−Hellas (CERTH), Thessaloniki, Greece Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur Ottawa, Ontario K1N 6N5, Canada

Effect of diesel oxidation catalysts on the diesel particulate filter regeneration process.

A Diesel Particulate Filter (DPF) regeneration process was investigated during aftertreatment exhaust of a simulated diesel engine under the influence of a Diesel Oxidation Catalyst (DOC). Aerosol mass spectrometry analysis showed that the presence of the DOC decreases the Organic Carbon (OC) fraction adsorbed to soot particles. The activation energy values determined for soot nanoparticles oxidation were 97 ± 5 and 101 ± 8 kJ mol(-1) with and without the DOC, respectively; suggesting that the DOC does not facilitate elementary carbon oxidation. The minimum temperature necessary for DPF regeneration was strongly affected by the presence of the DOC in the aftertreatment. The conversion of NO to NO(2) inside the DOC induced the DPF regeneration process at a lower temperature than O(2) (ΔT = 30 K). Also, it was verified that the OC fraction, which decreases in the presence of the DOC, plays an important role to ignite soot combustion.

Catalytic CO Oxidation over Au Nanoparticles Supported on Yttria-Stabilized Zirconia

Gold nanoparticles supported on yttria-stabilized zirconia (YSZ) were synthesized using a modified alcohol method which involves the stabilizing agent, polyvinylpyrrolidone (PVP). Two different average sizes (13.1 and 17.1 nm) of Au nanoparticles were synthesized. These catalysts were tested for gas phase CO oxidation. Since PVP is known to block the active Au sites, the catalysts were calcined at 300°C and 600°C in order to remove the PVP. Overall, higher catalytic activity was found for the smaller Au nanoparticles. It was also found that calcination is required in order to achieve activity, even though the particle size increases with this treatment. The effect of calcination temperature did not prove to be significant. It is demonstrated that O 2- ionically conductive YSZ is a promising catalyst support that can finely disperse and stabilize Au nanoparticles for CO oxidation.

Electrochemical promotion of propane oxidation on Pt deposited on a dense β″-Al2O3 ceramic Ag(+) conductor.

A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a β″-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that, upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation.

Ionically Conducting Ceramics for Soot Oxidation Mechanistic Study with 18O2 Isotopic Exchange

This study shows that Yttria-Stabilized Zirconia (YSZ) is an effective catalyst for soot particles oxidation. Soot oxidation already occurs from 270 degrees C. Temperature-Programmed Oxidation experiments with O-18(2) demonstrate the key-role of bulk oxygen species in the oxidation process. To the best of our knowledge, this is the first time that such a result is reported for a purely O-2-ionically conducting ceramic without any redox property. We assume that the soot oxidation takes place via a fuel-cell type electrochemical mechanism at the nanometric scale. Electrochemical oxidation of the soot takes place at the soot/YSZ interface while oxygen electrochemical reaction occurs at the triple phase boundary.

Electrochemical Promotion of Propane Combustion on Highly Dispersed Pt Nanoparticles

Pt nanoparticles, in a size range which varies from 3 to 20 nm, were dispersed in the porosity of a 7.5 µm-thick layer of LSCF-GDC electrode interfaced on a dense GDC membrane. Small positive polarizations (200 µA / 0.8V - 1.2V) can strongly increase the Pt nanoparticles catalytic performance for propane deep oxidation at low temperatures (267°C-338°C). 40%-enhancement of the propane conversion was achieved with apparent Faraday efficiency values up to 85. These results clearly demonstrate that metallic nanoparticles dispersed in the porosity of a mixed ionic electronic conducting electrode can be electropromoted.

Electrochemical Promotion of the Water-Gas Shift Reaction on Pt/YSZ

The effect of electrochemical promotion of catalysis was investigated for the water–gas shift reaction over porous Pt catalyst electrodes interfaced with 8%mol Yttria-stabilized Zirconia. A fuel cell type electrochemical reactor was used at temperatures from 300 C to 400 C, under PH2 O=PCO ratio values from 2.85 to 31. A negative order dependence of the catalytic reaction rate on PCO and a positive one on PH2 O was found under open-circuit and polarization conditions. Positive potential application (+2.5 V), i.e., O 2� supply to the catalyst surface, causes a small decrease in the catalytic reaction rate, while negative potential application (� 1.5 V) results in a pronounced rate increase, up to 200%, with apparent faradaic efficiency values up to 110. The rate increase obtained with negative polarization can be attributed to the weakening of the Pt–CO bond strength but also, to the increase in surface concentration of oxygen ion vacancies near the Pt-gas-support three-phase boundaries necessary for water dissociation.