Renewable hydrogen production from chemical looping steam reforming of ethanol using xCeNi/SBA-15 oxygen carriers in a fixed-bed reactor

Abstract

Chemical looping steam reforming of ethanol using xCeNi/SBA-15 oxygen carriers was carried out at 650 °C under atmospheric pressure in a fixed-bed reactor. The mesoporous support SBA-15 was synthesized via hydrothermal method and the xCeNi/SBA-15 oxygen carriers were prepared by encapsulating CeO2 and NiO nanoparticles in SBA-15 using surfactant-assisted iso-volumetric impregnation method. Some techniques were conducted to characterize the oxygen carriers, including N2 adsorption–desorption, XRD, TEM, H2-TPR, ICP-OES, and DSC-TGA. It was observed that all the oxygen carriers exhibited high specific surface area (>435 m2/g) and large pore volume (>0.64 cm3/g). Small NiO particle size (e.g. 3.2 nm for 12CeNi/SBA-15), high dispersion and strengthened metal-support interaction were achieved by the CeO2 promotion. The ceria promoter not only inhibited the coke formation but facilitated the removal of coke deposition, and the coke deposition could be further eliminated in the air feed step, both of which resulted in long-term stability. Meanwhile, superior redox performance and shorter ‘dead time’ (e.g. 30 s for 12CeNi/SBA-15) were achieved on account of easier reducibility of NiO particles with increasing amount of CeO2. The oxygen carriers exhibited superior sinter resistance capacity and high activity and stability in CLSR process. The highest ethanol conversion (90.0%) and hydrogen selectivity (84.7%) were obtained for 12CeNi/SBA-15 even after 14 cycle stability test.