CUMENE CRACKING ON DODECATUNGSTOSILICIC ACID CATALYST

Cumene cracking on supported H4SiW12O40 was studied in the temperature range 150-244 degrees C using a constant how microreactor. In the ini tial periods of runs, besides the two predominant products benzene and propylene some less important amounts of C-4, C-5, and C-6 hydrocarbo ns as well as toluene and ethylbenzene were obtained. Based on these r esults and separate experiments with propylene and benzene, a reaction pattern was proposed. The side products vanished after some 10-20 min of run time during which there was rapid deactivation of the catalyst and a decrease from an initially high conversion to 20-30% conversion depending on temperature. From the mass balance the amount of carbona ceous deposit was estimated and it was shown that the precursors for i ts formation are propylene and cumene. Arrhenius plots of the rate con stants at a given coking degree indicate that below 170 degrees C at l ow coking degree it is the surface reaction which is the rate controll ing factor. Above this temperature the reaction is predominantly a dif fusion controlled process. (C) 1997 Academic Press