HYDRODEALKYLATION OF TOLUENE ON HZSM-5 ZEOLITES

The toluene transformation on the H-ZSM-5 zeolite was studied at 873 K, 2.0 MPa total pressure and with H-2/Toluene = 4 mol/mol. A quantitative correlation between the chemical composition of zeolites and concentration of weak and strong acid sites, measured by temperature programmed desorption of NH3 at 353-873 K, has been established. The initial reactions rates of toluene transformation on H-ZSM-5 zeolite were found and correlated with the acidity of the catalysts. It was observed that hydrodemethylation of toluene to benzene and methane is a parallel reaction to the aromatic nucleus hydrocracking and occurs on the strong acid sites independently to the structure (concentration) of these sites. An influence of the strong acid sites concentration on hydrocracking and dehydrocyclisation of an intermediary surface carbocation is discussed.