Hydrogen production by chemical looping steam reforming of ethanol using oxygen carriers was carried out in a fixed-bed reactor. NiO/montmorillonite prepared by ultrasound assisted cation exchange impregnation method was used as oxygen carriers. The synthesized NiO/montmorillonite was characterized by N-2 adsorption-desorption, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), transmission electron microscopy (TEM), H-2 temperature-programmed reduction (H-2-TPR), H-2 pulse chemisorption, temperature-programmed reduction (TPO) and thermal gravimetric analysis (TGA). The characterization results showed the particle size, metal-support interaction, nickel dispersion interrelated with cation exchange capability and confinement effect of montmorillonite's lamellar structure. Activity and stability tests were conducted at 550 degrees C with a steam to carbon ratio of 4. The results showed that 20Ni-MMT possessed the best performance due to its strong sintering and coking resistance, and also presented the shortest 'dead time' due to its larger active surface area. Moreover, 20Ni-MMT exhibited the excellent coke elimination ability in the air feed step. (C) 2016 Elsevier B.V. All rights reserved.