Preparation And CO₂ Adsorption Property Of Zeolite-based Lithium Orthosilicate

Since the industrial revolution, because of environment and climate have been changed by millions metric tonnes of CO₂ emissions which is attributed to exploitation and use of a large number of fossil fuels, CO₂ reduction and capture have attracted more and more attention of scholars in the fields of energy and environment. In this study, based on the existing research of lithium orthosilicate（CO₂ high-temperature solid adsorbent） and zeolite, lithium orthosilicate is synthesized by using mordenite as the silicon source, which is used to capture CO₂ for CO₂ reduction.First, zeolite-based lithium orthosilicate is synthesized from solid state reaction. The reaction temperature conditions of lithium carbonate and zeolite are tested by thermal analysis. The composition and structure changes of zeolite-based lithium orthosilicate which are influenced by raw material ratios, calcination temperature and heat preservation time are studied. The results show that:（1） Using zeolite as silicon source to synthesize zeolite-based lithium orthosilicate, could effectively reduce the calcined temperature of solid state reaction process. The fastest reaction rate temperature of zeolite and lithium carbonate is about 650 ℃, while the fastest reaction rate temperature of lithium carbonate and silica is about 710 ℃.（2）Raw material ratios, calcination temperature and the heat preservation time make differences to the composition and structure of zeolite-based lithium orthosilicate. When synthesis temperature is 650 ℃ and holding time is 4h, MAlO2 which come from zeolite can be kept the original structure, dispersed in zeolite-based lithium orthosilicate structure act as the microscopic carrier. Increasing of synthesis temperature or holding time can let MAlO2 enrich, combine with Li ions, and then turns into a new phase: lithium aluminate（LiAlO2）.（3） Not only zeolite-based lithium orthosilicate`s crystal lattice is distorted, but also normal grain growth is limited under influence of the MAlO2.Second, the CO₂ adsorption property of zeolite-based lithium orthosilicate is measured by thermogravimetric Analysis（TG） testing with temperature swing adsorption and isothermal adsorption at different CO₂ concentrations. For comparision, silica-based lithium orthosilicate which silicon source is SiO2 is studied under the same synthesis and characterization conditions. The results show that:（1） Under the influence of MAlO2, the CO₂ adsorption equilibrium temperature of zeolite-based lithium orthosilicate decreases.（2）The activation temperature of zeolite-based lithium orthosilicate adsorption of CO₂ has changed which compare with silica-based lithium orthosilicate. The first activation temperature section of zeolite-based lithium orthosilicate adsorption of CO₂ is in the vicinity of 450 ℃, which would not disappear with the decrease of CO₂ concentration of test, and the presence of this interval significantly improves the CO₂ adsorption properties of zeolite-based lithium orthosilicate at low temperature and low CO₂ concentration conditions.（3） The speed of CO₂ desorption after zeolite-based lithium orthosilicate adsorption of CO₂ is fast when the thermodynamic condition is satisfied, and the regeneration performance of zeolite-based lithium orthosilicate adsorption of CO₂ is as good as silica-based lithium orthosilicate.（5）The fits of theoretical models and experimental results confirm the speed of zeolite-based lithium orthosilicate adsorption of CO₂ is controlled by diffusion of CO₂ process.Final, combination of theoretical research results, K zeolite-based lithium orthosilicate is proposed which silicon source is K-zeolite come from cation exchange of zeolite and potassium chloride. K zeolite-based lithium orthosilicate shows better performance for capturing CO₂ at low temperature and low CO₂ concentrations conditions than zeolite-based lithium orthosilicate.