A circulating fluidized bed unit was used to evaluate influences of lattice oxygen introduction over catalytic cracking of n-heptane over HZSM-5 catalyst in a continuous reaction fashion. The results demonstrated that V2O5/Al2O3, which functioned as lattice oxygen supplier, promoted conversion of n-heptane in a much larger extent, compared with fixed-bed reactor. It also improved yields of propylene and butylenes, and intensified formation of aromatics and coke. Besides lattice oxygen species, some adsorbed oxygen species also participated into the reaction. CO and H2O were formed as main oxygenated products. Steam introduction improved selectivity of propylene and butylenes, promoted desorption of strong adsorbed species in V2O5/Al2O3, and thus formation of coke was depressed: however, the damage to HZSM-5 framework was aggravated simultaneously. (C) 2011 Elsevier B.V. All rights reserved.