Acid Strength Measurement of Zeolites by the TPD-IR Technique with Ammonia as Probe Molecule

An improved TPD-IR technique was developed recently. By which means, acid properties of Brønsted acid sites on HY zeolite and SAPO-34 zeolite were studied by an advanced TPD-IR technique with ammonia as probe molecule. Desorption activation energy (DAE) of the probe molecule adsorbed on zeolite was used as a measure of the acid strength. The result indicates the Brønsted acid sites of HY Zeolite or SAPO-34 zeolite were divided into two types with the strength of DAE of ammonia 43.4KJ/mol, 24.4KJ/mol and 33.2KJ/mol, 20.5KJ/mol. It is concluded that HY zeolite has the stronger Brønsted acid sites than that of SAPO-34 zeolite.