Development of oxygen-permeable membranes for the conversion of methane to syngas

Catalytic oxygen-permeable membranes for oxygen separation and partial oxidation of methane presently constitute one of the most promising routes for syngas production. Industrial applications, however, are limited by a number of stringent requirements for the catalytic membrane: the membrane should sustain an economically viable oxygen flux (j=10 ml cm-2 min-1) and should possess a high chemical and mechanical reliability at working temperatures in the course of long term operation. Obviously, the thinner the oxygen membrane, the higher the oxygen flux. However, thin membranes (about ten microns) are very difficult to handle because of their low mechanical strength. This problem can be solved by the deposition of a thin oxygen permeable membrane on a porous support. In this case the catalytic membrane will be assembled from (i) oxygen-permeable membrane, (ii) porous support and (iii) catalyst for partial methane oxidation. The catalyst is deposited either on the oxygen-permeable membrane surface or on the opposite surface of the porous support. The present proposal focuses on: 1. Development of a high oxygen-permeable membrane material based on (La,Sr)(Co,Fe)O3-x perovskites, 2. Stabilisation of the membrane material in a wide range of oxygen nonstoichiometry and oxygen partial pressure, 3. Optimisation of the oxygen fluxes of supported perovskite membranes and their mechanical stability by the deposition of a thin perovskite layer on porous ceramic supports, 4. Deposition of a catalyst for partial methane oxidation. The development of a highly efficient gas-tight perovskite membrane catalyst for the partial oxidation of methane is of interdisciplinary nature, which needs knowledge, accumulated both in the fields of catalysis and solid state chemistry. For this reason, R&D groups from both the Boreskov Institute of Catalysis (BIC) and the Institute of Solid State Chemistry and Mechanochemistry (ISSCM) will be involved from the Russian side. The BIC team has acquired great skills in the field of catalysis, particularly in the development of supported perovskite catalysts and gas-tight perovskite layers on the ceramic supports. The ISSCM team has strong expertise in the field of perovskite materials with high oxygen transport properties and measurement of the parameters of oxygen diffusion. Both teams have cooperated successfully in the development of supported perovskite membranes. In order to achieve the aims of the project the following main steps will be undertaken: 1. (La,Sr)(Co,Fe)O3-x perovskite oxides will be doped with aliovalent cations (e.g., Nb, Ta, W, Mo) in order to improve their oxygen permeability and to suppress possible phase transitions, 2. A kinetic study for evaluation of the oxygen diffusion coefficients by means of electrochemical techniques will be performed, 3. Techniques for the deposition of thin gas-tight perovskite layers (20-50 microns) on ZrO2-Y2O3 supports having different porosity will be developed, 4. The oxygen permeability of self-supported and supported membranes will be measured and optimised, 5. A kinetic study of methane activation over the perovskite membranes will be performed.