A series of aluminum-extracted mordenites having different silica-alumina ratio were prepared by both acid-leaching and steam treatment.
For these catalysts, catalytic activities of toluene disproportionation reaction were measured at a point of view of deactivation properties and discussed with the results of nitrogen adsorption isotherm measurement as well as the ammonia adsorption study by infrared techniques.
It leads to the conclusion that a maximum point in catalytic activity appeared at about silica-alumina ratio of 22, which has been explained by the increased acid strength due to aluminum extraction, but fast coke formation at the beginning of catalyst use could rather give the better explanation. For the low catalytic activity of starting acidic mordenite having platinum metal, it could be explained with the coke formation on the crystal surface as well as the partial blocking of platinum grain in the pore channel, which makes reactant molecules diffuse difficultly.