HYDROGENATION OF TOLUENE OVER LA0.8SR0.2FE1-XCOXO3-Z PEROVSKITE CATALYSTS

The hydrogenation of toluene over perovskites of composition La0.8Sr0. 2Fe1-xCoxO3-z (x = 0.0, 0.2, 0.5, 0.8 and 1.0) is reported. The cataly st material has been prepared by the coprecipitation method using male ic acid as the complexing agent. The activity for the gas phase reacti on of toluene and hydrogen at temperatures between 50 degrees C to 300 degrees C is reported for as-prepared and activated materials. The co nversion has been found to be nearly temperature-independent over the as-prepared perovskites with a maximum of 40% conversion found for a c omposition La0.8Sr0.2Fe0.5Co0.5O2.86. Activation by an oxygen treatmen t at 500 degrees C was successful to enhance the activity of the Co-ri ch perovskites. All of these catalysts show a complete conversion of t oluene at 100 degrees C, but activity decreases by time due to a reduc tion of the catalyst material. Again, La0.8Sr0.2Fe0.5Co0.5O2.86 exhibi ts the slowest loss of activity. A model for its special properties is mainly attributed to the p-type conduction behaviour. The conversion behaviour of the perovskite type catalysts investigated here is compar ed to the results obtained with noble-metal supported catalysts and it can be concluded, that the perovskites exhibit higher conversion rate s, maximum temperatures and higher cracking onset temperatures than th ese.