Preparation Of And CO₂ Capture Properties Of Li₂ZrO₃ Materials Via The Sol-gel Process

As a kind of high temperature CO2 adsorption materials, Lithium zirconate(Li2ZrO3) has been paid widely attention for its high CO2 capacity and excellent performance of adsorption/desorption cycle. The paper is aimed to prepare nono and porous Li2ZrO3 by the sol-gel method, as well as optimize the preparation process, and analyse the CO2 adsorption/desorption performance of the material. Moreover, the theory and simulation of CO2 adsorption/desorption is studied. The main details are as follows:(1) Lithium zirconate nanocrystals are prepared by using zirconium oxide chloride octahydrate and lithium nitrate as precursors, glycol(EG) as chelating agent, diluted hydrochloric acid as acid catalyst, Propylene oxide(PO) as gelation agent, water and ethanol as solvent. After 650℃ heat-treatment, the amorphous gel transforms to tetragonal phase. Li2ZrO3, and t-Li2ZrO3 transforms to m-Li2ZrO3 when get heat-treatment at 900℃. Due to the evaporation of Li2O, there exists not only m-Li2ZrO3 but also m-ZrO2 after 1000℃ heat-treatment. The particle size of the Li2ZrO3 nanocrystals differs from 50nm to 200nm.(2) Porous lithium zirconate monolith is prepared by using zirconium oxide chloride octahydrate and lithium acetate dehydrate as precursors,65% nitric acid as acid catalyst, PO as gelation agent, polyethylene oxide (PEO) (Mv=1×106)as phase separation inducer, water and ethanol as solvent. According to FT-IR, PEO is preferentially distributed into the liquid phase. Monolithic lithium zirconate xerogel with co-continuous structure is obtained under the condition of optimal starting compositions. It has a pore size mainly distributed between 0.3-1 μm and a porosity of 41.2%. After heat-treated at 400℃, the amorphous gel transforms to t-ZrO2, which changes to pure t-Li2ZrO3 when heat-treated at 650℃, and the macroporous structure is optimized by the heat-treatment process.(3) The paper is also focused on the investigation of CO2 capacity of t-Li2ZrO3 nanocrystals. t-Li2ZrO3 adsorbs more amount of CO2 than m-Li2ZrO3. The temperature plays an important role in the CO2 adsorption capacity as well. In the system of Li2Zr03 nanocrystals, as the temperature increases, the sample displays faster CO2 uptake rate, and its CO2 uptake is higher. On the contrary, the uptake rate and amount of CO2 decrease above 550℃. In consequence, the maximum absorption rate is obtained at 550℃ and the amount is found to be about 21 wt%. The synthesized Li2ZrO3 nanocrystals display excellent properties for CO2 capture-regeneration.(4)As to porous Li2ZrO3 materials, the uptake of CO2 increases with the increasing temperature, the maximum is 13.7wt% at 650℃. However, the amount of CO2 adsorbed decreases when the absorption-desorption is performed. Therefore, only if the porous structure is optimized, can the porous Li2ZrO3 materials be applied widely as high temperature CO2 adsorbents.