reactivity of modified Y zeolites towards hydrogen transfer reactions was studied with model reactions such as cyclohexene and o-xylene conversion .it has been found that on modified Y zeolites hydrogen transfer, isomerization and polymerization of cyclohexene take place simultaneously. as the al content of the SY zeolites decreases the initial activities for cyclohexene hydrogen transfer and isomerization reactions vary sim8larly with the strong acidity of the zeolites, the isomerization reactions vary similary with the strong acidity of the zeolites, the activities oncrease first and then decrease , displaying volcano-lie curves with maximum at Al/(Al+Si)=0.15.the zeolites deactivate quickly due to coke deposition , and then th4 activities decrease nomotonously with decreasing Al content. the reactivity of USY zeolite for hydrogen transfer reaction if lower than that of the SY zeolites, but its cracking activity is higher. the activities of both types of modified Y zeolites are lowered considerably after steam treatment at elevated temperature.o-xylene isomerization is accompanicd by disproportination reaction on modified Y zeolites. for SY zeolites the results of the o-xylene disproportionation reaction are consistent with that of the cyclohexene hydrogen transfer reaction. the data of these two reactions may be contradictory when a significant amount of lewis acid wites exists in the sample.

Key words: MODIFICATION, DIMETHYLBENZENE, HYDROGEN, DISPROPORTIONATION REACTION, CYCLOHEXENE, TRANSFER REACTIONS, ISOMERIZATION