CHARACTERIZATION OF STABILITY AND POROSITY OF SAPO-40 USING M-XYLENE AS MODEL REACTION

The thermal and hydrothermal stability of SAPO-40 has been evaluated u sing the isomerization of m-xylene as model reaction. The characteriza tion of the porosity was also studied and compared to other well known structures, namely Y zeolite, mordenite and ZSM-5. The structural cha nges that occur under thermal treatments influence the activity and se lectivity of SAPO-40, while hydrothermal treatments do not significant ly change those properties. The results confirm the high stability of SAPO-40 under thermal and hydrothermal treatments. Catalytic tests and adsorption of cyclohexane indicate that regular large side pockets or lobes exist along the main channels of SAPO-40, which create a large void volume responsible for the high rate of adsorption, high amount o f adsorbed cyclohexane and the low shape selectivity in m-xylene isome rization.