THE TRANSFORMATION OF 1,2,4-TRIMETHYLBENZENE - A PROBE REACTION TO MONITOR EXTERNAL SURFACE MODIFICATIONS OF HZSM-5

The transformation of 1,2,4-trimethylbenzene is proposed as a new prob e reaction to monitor the catalytic effects of inertisation of the ext ernal surface of HZSM-5. The external surface has been modified by coa ting ZSM-5 crystallites with an inert silicalite shell. At 723 K and a WHSV of 0.6 h(-1) it has been shown that the isomerisation products 1 ,2,3-trimethylbenzene and 1,3,5-trimethylbenzene reflect changes in ex ternal activity. The disproportionation products, 1,2,4,5-tetramethylb enzene and 1,2,3,5-tetramethylbenzene together are shown to indicate c hanges in overall activity and shape selective properties of the catal yst sample, The results correlate with those observed for the reaction of 1,3,5-triisopropylbrnzene and n-hexane cracking.