Surfactant-Template/Ultrasound-Assisted Method for the Preparation of Porous Nanoparticle Lithium Zirconate

Porous nanoparticle lithium zirconate (Li2ZrO3) was prepared using an ultrasound-assisted surfactant-template method in the liquid-state reaction. The CO2 adsorption performance of the prepared materials was tested under various conditions and compared with that of Li2ZrO3 prepared by the simple surfactant-template method (porous, without sonication) and the conventional soft-chemistry route. The results indicated a better adsorption rate and capacity of porous nanopowders, whether assisted with ultrasound or not, in comparison with the traditional sample. This behavior is mainly due to a less aggregated powder structure and porous framework, facilitating gas and ion diffusion to and from the particle layers. However, the porous adsorbent prepared without sonication exhibited instability during cyclic operation, limiting its application for long-time use. Sonication time and surfactant concentration were found to be key parameters for controlling the crystallite size and the BET surface area. The porous Li2ZrO3 sample prepared with less surfactant and a shorter irradiation time (sample A) had the most favorable sorption kinetics and capacity among all studied samples. The maximum uptake capacity of 22 wt % for sample A compared to 15.2 wt % for the conventional sample (sample J, fabricated by the soft-chemistry method), obtained under a 100% CO2 stream, suggested a noticeable improvement in sorption behavior of the proposed adsorbents compared with traditional Li2ZrO3. Moreover, the adequate cyclic stability of porous powders prepared by sonication identify these materials as promising CO2 acceptors, particularly for integrated sorbent/catalyst systems such as that used for sorption-enhanced steam methane reforming (SESMR). CO2 adsorption experimental data for sample A were successfully modeled at various CO2 partial pressures using a double-exponential equation.