Synthesis And Properties Of Lithium Metatitanate For Carbon Dioxide Adsorption

Due to the rapid increase of the world′s population and explosive growth of theenergy, excessive emissions of CO₂destroy the carbon balance in the system of regionalecological, causing global warming. Therefore, the reduction of carbon dioxide emission isthe key to the response to the greenhouse effect. There are many methods to treat CO₂.Compared with other methods, adsorption has many advantages. Especially thehigh-temperature adsorption recycling CO₂in the exhaust gas source is a hot research area.Li₂TiO₃as a high temperature sorbent in the paper, Li₂TiO₃was synthesized bytraditional high temperature solid-phase between TiO2and Li2CO3. The CO₂sorptionabilities of Li₂TiO₃were researched. There were three researchful directions. On the onehand, preparing Li₂TiO₃by thermodynamic calcining made the Li+of lithium carbonateinfiltrate into the octahedra structure of TiO2. The influence of reaction temperature andtime on product was investigated. XRD was used to study the influence of calciningconditions on crystalline form; SEM was used to study the influence of calciningconditions on crystal morphology. On the other hand, single factor method was used tostudy the influence of some factors on CO₂adsorption on Li₂TiO₃, flux of gas, mass ofmaterial, adsorption temperature and time, volume percent of CO₂, cycle time wereinvestigated. Last, doping Na element on Li₂TiO₃was studied, the influence of differentdoping ratio on Li₂TiO₃as CO₂-adsorbent. XRD and SEM were used to study thecrystalline form and crystal morphology of Li₂TiO₃which was doped. Meanwhile, theeffect of doping Na element on Li₂TiO₃as CO₂-adsorbent by specific surface area wasresearched. Then the influence of Na-doped on CO₂adsorption cycle ability of Li₂TiO₃wasresearched. The adsorption behavior and mechanism of CO₂adsorption on Li₂TiO₃andNa-doped Li₂TiO₃were studied by Double-Shell Mechanism. The results could begeneralized as follow:（1） The best calcining conditions of precursor were800℃,20h. The crystallineform of Li₂TiO₃was complete, uniform, structured by XRD and SEM. The average particle size of the product increased when the calcining temperature increased, theinfluence of calcining time on average particle size was irregular.（2） CO₂adsorption on Li₂TiO₃was a reversible chemical reaction process. Li₂TiO₃incubated for180min at600℃in pure CO₂has the best adsorption effect by thermalgravimetric analysis. While the optimum flux of gas was above80mL/min, the mass ofadsorbent was under20mg, the mass increase percentage of adsorbent after CO₂adsorption was approximately about25.99%. The attenuation ratio reached67.03%afterfive times of adsorption-desorption of CO₂on Li₂TiO₃.（3） Li₂TiO₃had the best adsorption performance when n（TiO2）:n（Li2CO3）:n（Na2CO3）=1:0.97:0.03, which x=0.03, the mass increase percentage of material reached20.23%.Na-doped could improve the performance of CO₂adsorption on Li₂TiO₃from crystallineform and crystal morphology by XRD and SEM. The specific surface area of Li₂TiO₃andNa-doped Li₂TiO₃could not be measured, which could explain that there was no effect ofnitrogen adsorption on Li₂TiO₃and Na-doped Li₂TiO₃, and they had a better choiceadsorption. In addition, specific surface area had no impact on CO₂adsorption on materialsafter Na-doped. The attenuation ratio was14.28%after five times of adsorption-desorptionof CO₂on Na-doped Li₂TiO₃.（4） Pseudo-first order kinetic could describe the kinetics adsorption processes of CO₂on Li₂TiO₃. The Double-Shell Mechanism of CO₂adsorption on Li2ZrO3and Na-dopedLi2ZrO3at high temperature was referenced. Therefore, the adsorption behavior andmechanism of CO₂adsorption on Li₂TiO₃and Na-doped Li₂TiO₃at high temperature couldbe explained to some extent.