The thermal analysis of n-butylamine (NBA) sorbed on FeHNaY zeolites has been studied. TG and DTG showed three distinct stages of weight loss. The first peak in the DTG, at 120-160 degrees C, was due to the physisorbed and weakly chemisorbed n-butylamine molecules. The second DTG peak was at 330-400 degrees C corresponding to the NBA molecules sorbed on sodium ions, or medium strength acidic centres. The third DTG peak was at 570-640 degrees C and can be attributed to the NBA molecules sorbed on ferric ions or strong Bronsted acidic centres. The DTC of NBA sorbed on NaY showed only two peaks. Owing to the thermal treatment at 500 degrees C, ferric ions in the supercages migrate to the sodalite cages or hexagonal prisms. As a result, the number of NBA molecules corresponding to the second and third peak was decreased. The nature of the interacting centres with the percentage of ion exchange and the migration of ferric ions is discussed.