Preparation And High Temperature Of The Lithium Silicate Absorption Of Co In <sub> 2 </ Sub> Performance Studies

In recent years, the climate change resulted from the greenhouse effect has become a global environmental problem, so the absorption and separation of CO2 is also an urgent problem that needs to be solved. Li4SiO4 has the ability of cyclic absorption CO2 at high temperature, and it can be used to absorb CO2 from fossil fuel thermal power plant. Therefore, the study about Li4SiO4 preparation and performance of CO2 absorption has great significance for curbing the greenhouse effect. This paper use the cheap nature-mineral diatomite that are rich in Yunnan Province as raw materials to prepare Li4SiO4, and study CO2 absorption performance at high temperature. Preparation conditions of Li4SiO4, kinetic and reaction mechanism of CO2 absorption, performance of CO2 cyclic absorption and the structure and property of Li4SiO4 have been researched. The whole process is divided into the following four parts:(1) Using SiO2 and Li2CO3 as raw materials, Li4SiO4 was synthesized by high-temperature solid-state reaction, and the performance of CO2 absorption was studied. Under the preparation conditions (nLi:nSi in raw material is 4.2:1, the calcination temperature is 700℃, calcination time is 4 h), Li4SiO4 has the maximum absorption capacity of 14.73%at 620℃, and the slower absorption rate. According to the double exponential model, the obtained activation energies for the chemisorption and lithium diffusion process are E1= 109.142 kJ/mol and E2=37.971 kJ/mol, respectively.(2) Using diatomite and Li2CO3 as raw materials, Li4SiO4 was synthesized by high-temperature solid-state reaction, and the performance of CO2 absorption was studied. By the orthogonal experiment, we got the optimum preparative conditions: nLi:nSi is 5.2:1 in raw materials, the calcination temperature is 650℃, calcination reaction time is 6 h. Kinetic and reaction mechanism of CO2 absorption on Li4SiO4 was studied. The activation energies for two processes are E1=77.215 kJ/mol and E2=22.078 kJ/mol, respectively. Cyclic performance of the sample A2B2C1 prepared under the optimal conditions was studied in a series of ten consecutive cycles. The absorption capacity decreases from the first cycle of 33.36%to the tenth cycle of 31.17%, the absorption capacity only declines 2.19%.(3) Using diatomite and LiNO3 as raw materials, Li4SiO4 was prepared by the impregnation precipitation method, and the performance of CO2 absorption was studied. By the orthogonal experiment, the optimal conditions were obtained:nLi:nSi is 5.2:1 in raw materials, the temperature of water is 40℃, impregnating time is 6 h, aging time is 8 h, the calcination temperature is 650℃, calcination reaction time is 5 h. Under the optimal conditions, the CO2 absorption capacity reaches 34.02%. The activation energies for two process are E1=28.868 kJ/mol and E2=22.250 kJ/mol, respectively. Cyclic performance of the sample A3B2C2D2 prepared under the optimum conditions was studied in a series of sixteen consecutive cycles. The absorption capacity decreases from the first cycle of 34.14%to the sixteenth cycle of 27.70%, the absorption capacity only decline 6.44%.(4) Morphologies, specific surface area and phase component of Li4SiO4 were analyzed using SEM, IR, BET, XRD.