Antimony (Sb) substituted Keggin structured ammonium salt of 12-molybdophsphoric acid (AMPA) materials were synthesized by acid precipitation method. The samples were obtained by increase of Sb atoms from 1 to 3 and corresponding decrease of Mo atoms from 11 to 9. The synthesized materials were thermal treated in the range of 300-500 degrees C. The catalytic performance of thermally treated Sb incorporated AMPA materials were examined for oxidation of chlorobenzene and the catalytic activity of Sb-AMPA samples was compared with activity of bulk AMPA. The materials were thoroughly analyzed by different techniques such as elemental analysis, TG, powder XRD, FTIR, SEM, N-2-physisorption,P-31 MAS NMR, XPS, DR UV-Vis and H-2-TPR techniques. The characterization results clearly indicated that Sb-AMPA samples possessed high thermal stability, relatively large surface area and easy reducibility compared to bulk AMPA. The synthesized samples also possessed high content of surface adsorbed oxygen species, which are responsible for superior catalytic activity. [GRAPHICS] .