Mise en forme d'un catalyseur de combustion de type perovskite pour les reacteurs a lit fixe et a lit fluidise, et pour les panneaux radiants

Abstract

The combustion of natural gas is used in many processes because of its energetic potential. In most applications natural gas is combusted by homogeneous gas phase reaction of nearly stoichiometric fuel/air mixtures producing high temperature flames (${>}1200\sp\circ$C). These flames are the source of formation of noxious NO$\sb{\rm x}$, one of the most serious pollutants.

The goal of this work was to develop techniques to make an active catalyst suitable for use in a fluidized bed reactor, in a fixed bed reactor and in a radiant panel. The activity of those catalysts were also evaluated.

Among several prepared and evaluated catalysts, a good activity was obtained for the following: (1) 32.5 wt% of perovskite impregnated on mineral fibers for a possible use in radiant panels; (2) 7.5 wt% of perovskite impregnated on porous alumino-silicate matrix particles for a possible use in fluidization beds; (3) 7.3 wt% of perovskite fixed on alumina particles for a possible use in fixed beds. This catalyst contains also 4% of silicate (4% base on the perovskite weight) which was added for a better adhesion of the perovskite on the support. The activity of these three catalysts compares very well with that of the powder perovskite. Furthermore, the physical forms of these catalysts have reasonably good mechanical resistance against wear.

For practical reasons and for comparison, two commercial catalyst (PROCATALYSE) were also used in our studies: Pd/Al$\rm\sb2O\sb3$, and Pt-Sn/Al$\rm\sb2O\sb3$. The results showed that the activity of our perovskite catalyst is significantly lower than that of Pd or Pt catalyst, except for the catalyst 32.5% perovskite on mineral fibers that compares to the Pt catalyst. (Abstract shortened by UMI.)

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The combustion of natural gas is used in many processes because of its energetic potential. In most applications natural gas is combusted by homogeneous gas phase reaction of nearly stoichiometric fuel/air mixtures producing high temperature flames (${>}1200\sp\circ$C). These flames are the source of formation of noxious NO$\sb{\rm x}$, one of the most serious pollutants.

The goal of this work was to develop techniques to make an active catalyst suitable for use in a fluidized bed reactor, in a fixed bed reactor and in a radiant panel. The activity of those catalysts were also evaluated.

Among several prepared and evaluated catalysts, a good activity was obtained for the following: (1) 32.5 wt% of perovskite impregnated on mineral fibers for a possible use in radiant panels; (2) 7.5 wt% of perovskite impregnated on porous alumino-silicate matrix particles for a possible use in fluidization beds; (3) 7.3 wt% of perovskite fixed on alumina particles for a possible use in fixed beds. This catalyst contains also 4% of silicate (4% base on the perovskite weight) which was added for a better adhesion of the perovskite on the support. The activity of these three catalysts compares very well with that of the powder perovskite. Furthermore, the physical forms of these catalysts have reasonably good mechanical resistance against wear.

For practical reasons and for comparison, two commercial catalyst (PROCATALYSE) were also used in our studies: Pd/Al$\rm\sb2O\sb3$, and Pt-Sn/Al$\rm\sb2O\sb3$. The results showed that the activity of our perovskite catalyst is significantly lower than that of Pd or Pt catalyst, except for the catalyst 32.5% perovskite on mineral fibers that compares to the Pt catalyst. (Abstract shortened by UMI.)