Solvent nature effect in preparation of perovskites by flame-pyrolysis - 1. Carboxylic acids

The effect of a series of carboxylic acids (C-2-C-8), as solvents for the preparation by flame spray pyrolysis of LaCoO3 catalyst for the flameless combustion of methane, has been investigated. Acetic acid showed to be unsatisfactory from several points of view: low phase purity of the catalyst, higher amount of unburnt carbonaceous residua, lower catalytic activity and low thermal stability. By increasing the carbon chain length of the solvent, the consequent increase of flame temperature led to an increase of crystal phase purity and of particle size and to a decrease of specific surface area of the catalyst. Catalytic activity showed only marginally affected by the last parameter, phase purity seeming more important. Thermal resistance showed directly related to flame temperature, i.e. to the combustion enthalpy of the solvent, but a relatively high amount of residual organic matter can negatively affect this property. (c) 2006 Elsevier B.V. All rights reserved.