BRIEFS. Coating a ZrO2 layer on CaO nanoparticles significantly stabilized the solid CO2 sorbents in the presence of steam.ABSTRACT. CaO is an attractive CO2 acceptor, due to its good kinetics and high capture capacity, even under low CO2 concentration condition. The major problem associated with CaO acceptors is the loss of CO2 capture capacity during cyclic operations. The declining performance of the CaO acceptors is more pronounced in the presence of steam. In this paper we propose a method for fabrication of nano-CaO acceptors with a coated ZrO2 layer to improve the stability. The nano-CaO acceptor was prepared by thermaldecomposition method following a coating process by solgel, incipient wet impregnation or hydrolysis, respectively. The thermogravimetric analysis (TGA) of the cyclic process of CO2 carbonation/decarbonation revealed that the nanoCaO acceptors with sol-gel (CaO-SG) and wet impregnation (CaO-IM) coating have higher CO2 capture capacity and a longer life time than the uncoated ones. The capture capacity of CaO-IM declined after 14 cycles whereas CaO-SG remained stable upto 20 cycles. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectra were used to characterize the coated and uncoated nano-CaO structures. Combined characterization techniques showed that a CaZrO3 layer was formed around the nano-CaO particles by sol-gel coating. Multi-cycle carbonation/decarbonation processes were performed in absence and presence of steam in CO2 capture kinetic experiments as well as at the sorption enhanced reforming conditions, and CaO nanoparticles with surface CaZrO3 layer showed a promising cyclic stability.
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