Electrochemical Promotion of Epoxidation – EPOX

First part of this project deals on pure Ag-based catalytic coatings. The impact of their microstructure (thickness, porosity) on their catalytic properties with and without polarization will be carried out. Ag catalytic coatings will be deposited on two kinds of solid electrolyte (an O2- and Na+ ionic conductor) by two different deposition techniques: the screen-printing and the physical vapour deposition method (cathodic magnetron sputtering). In a second step, to improve the Ag dispersion, nanostructured composite catalysts containing Ag nanoparticles into an ionically conducting matrix will be prepared by reactive cathodic pulverization. Another route will deal with the deposition, by screen-printing, of a porous mixed ionic and electronic conducting interlayer in which Ag nanoparticles will be dispersed. Finally, a second metal will be associated with Ag to optimize the formulation. In parallel, a study will be carried out to understand the mechanism of the electrochemical promotion of ethylene epoxidation as well as the oxygen electrode reaction. High-level in-situ techniques will be implemented such as microscopy, Temperature-Programmed Desorption measurements, Raman spectroscopy, cyclic voltammetry and impedance spectroscopy.

• The screen-printing method leads to the preparation of thick and porous Ag coatings (10-25 µm) while the magnetron cathodic sputtering can achieve thin films (50 – 200 nm). The screening of catalytic performances has been performed for the propylene combustion. The optimized Ag film microstructure has been identified.
• The consortium has demonstrated, for the first time, that the catalytic activity for propylene of screen-printed Ag coatings deposited onto Yttria-Stabilized Zirconia (YSZ), an O2- conductor, can be tailored by current applications in a non-Faradaic manner. The predominant impact of current applications is to modify the reactivity of oxygen present on the Ag surface. Positive current applications increase the propylene conversion by producing more reactive oxygen species.
• Preparation and characterization of powders of mixed (ionic and electronic) conductors. Preliminary tests of deposition of these oxides on YSZ membranes.
• Preliminary tests of depositions by magnetron cathodic sputtering of Ag/YSZ nanocomposites.

• Kinetic study under polarization of the ethylene epoxidation on Ag coatings with optimized microstructures
• Kinetic and mechanism of the oxygen electrode reaction on Ag coatings with optimized microstructures in ethylene epoxidation conditions
• Preparation of beta-alumina solid electrolyte based catalysts (alkaline ionic conductor)
• Optimization of the preparation method of Ag/YSZ nanocomposites, characterizations and measurements of catalytic performances upon polarization.
• Optimization of the preparation method of porous mixed ionic and electronic conducting interlayers in which Ag nanoparticles will be dispersed. Characterizations and measurements of catalytic performances upon polarization.

1 submitted paper : I. Kalaitzidou, T. Cavoué, A. Boreave, L. Burel, F. Gaillard, L. Retailleau-Mevel, E. A. Baranova, M. Rieu, J.P. Viricelle, D. Horwat, P. Vernoux, Electrochemical Promotion of Propylene Combustion on Ag Catalytic Coatings, submitted to Catalysis Communications.

Communications:
I. Kalaitzidou, T. Cavoué, A. Boreave, E.A. Baranova, M. Rieu, J.-P. Viricelle, D. Horwat, P. Vernoux, Electrochemical Promotion of Propene Combustion on Ag Catalytic Coatings, 231st ECS Meeting, May 28-June 1, 2017, New Orleans, USA (oral communication).
T.-G.Truong, G. Pétaud, P. Vernoux, H. Kaper, Preparation and catalytic characterization of mixed conductors for CO and propane oxidation, EUROPACAT 2017, August 27 – 31st 2017, Florence, Italie (poster).
T-G. Truong, G. Pétaud, P. Vernoux, H. Kaper, Preparation and catalytic characterization of ionic conductors for CO and propane oxidation, GECAT 2017, Mai 2017, Oléron, France. (poster)

The EPOX consortium bridges together three academic laboratories with complementary skills: catalysis and electrocatalysis for IRCELYON, electrical and electrochemical characterizations of solid-gas systems for ARMINES, physical vapour deposition and surface science for IJL. SAINT-GOBAIN CREE is partner of EPOC, as a provider of catalytic supports and for its expertise on ionically conducting ceramics.
The principal objective of the EPOX project is to use the concept of Electrochemical Promotion of Catalysis (EPOC) for a direct and environmentally-friendly new route for epoxidation of ethylene in order to produce Ethylene Oxide with high selectivity and alkene conversion. This innovative process will eliminate the need for chlorinated hydrocarbons in the gas feed. EPOX will generate new knowledge by bringing together complementary skills on catalysis, electrocatalysis, surface and material sciences to develop new multifunctional nanodispersed catalytic materials. The EPOX project will solve the main issue of the electropromotion science: coupling dispersed catalysts at the nanometric scale with electrochemical activation. This breakthrough will open new perspectives for the systematic investigation of the role of promoters in other technological important systems, hence offering a route to design efficient catalytic formulations.