Kinetic modeling of the ethylbenzene/xylene isomerization reaction over HZSM‐5 zeolites revisited

Abstract In this article, a binderless dealuminated HZSM‐5 zeolite (Si/Al = 41.4) was used as a catalyst for the isomerization of a mixture of ethylbenzene and xylene. The experimental results indicated that at low residence times the catalyst is effective to isomerize the ethylbenzene into xylenes. A comprehensive kinetic model considering chemisorption, surface chemical reactions, and diffusional processes was developed for this reaction. The intrinsic activation energy (71.99 kJ mol −1 ) for the surface reaction of ethylbenzene into m ‐xylene was calculated for the first time, and the corresponding intrinsic activation energies for o ‐xylene to m ‐xylene and m ‐xylene to p ‐xylene surface reactions were calculated to be 59.45 and 50.68 kJ mol −1 , respectively. Lower apparent values have been reported in the literature, and we rationalize that they correspond to multistep processes and intrinsically include a negative activation energy pertaining to chemisorption. The results also revealed that the ethylbenzene diffusion within the zeolite channels was four orders of magnitude smaller than p ‐xylene.