The Cr-doped ZSM-5 zeolites were synthesized by in-situ hydrothermal method and were used in studying Cr effect on catalytic cracking of n-butane to produce light olefins. Zeolite structure

chemical state of Cr species and acidity of zeolites were characterized by several techniques

including X-ray diffraction

nitrogen adsorption and desorption

ultraviolet visible diffuse reflectance spectroscopy

Raman spectroscopy

ammonia temperature-programmed desorption and pyrrolidine (Py)-FTIR. Cr species were found to partially incorporate in the ZSM-5 framework and present in the form of monodispersion. No significant difference in the weak acidity of zeolites at low Cr content. However

a small amount of Cr species in zeolites could significantly enhance conversion of n-butane and improve yield of ethylene and propylene. When the molar ratio of Cr/Al was 0.04

the conversion of n-butane was 99.6% and the yield of ethylene and propylene was 53.8% at reaction temperature of 650℃

which was 15.5% and 5.0% higher than those of unmodified ZSM-5

respectively. The superior catalytic performance could be attributed to synergistic effects of dehydrogenation of active Cr species and cracking function of the acidic zeolite

which promoted highly efficient conversion of n-butane.