Optimization Of Preparation Conditions For Sol-gel Combustion Syhtesis Of Ca-based CO₂ Sorbents

The sol-gel combustion synthesis is one of the ways to synthesize modified calcium sorbents with prominently enhanced performance.For the purpose of optimizing the preparation conditions,in this paper,the research on the optimization of preparation conditions for sol-gel process,combustion process and thermal activation process related to sol-gel combustion synthesis were studied.Also,the effects of different preparation conditions on the micro-structure and properties of calcium-based sorbents were investigated.First,the hydrolysis,aging and drying stage of sol-gel process was investigated.Preparation conditions including molar ratio of citric acid to calcium nitrate,p H value of precursor solution and amount of water addition were studied and their effects on the prepared sorbents’micro-structure,physical property parameters and cyclic CO₂capture performance were determined by SEM,TEM,N₂adsorption instrument and STA.The results show that the optimal molar ratio of citric acid to calcium nitrate is 1:1,the optimal p H value of precursor solution is 2,and the optimal molar ratio of water to Ca²⁺ion is 80.Second,the combustion process of calcium sorbents was studied.The TG curves of combustion process was recorded by STA.The gaseous and solid products during combustion process was determined.Based on this,the chemical reaction equation during the combustion process was put forward.Moreover,preparation conditions including initial combustion temperatures and heating rates as well as their influence on the prepared sorbents were investigated.The results indicate that the optimal initial combustion temperature is 300℃and the optimal heating rate is 10℃/min.At last,the performance of the sorbents prepared by different temperatures,duration and heating rates of the thermal activation process were compared.It was found that the excessive temperature and thermal duration will aggravate the sintering effect of the sorbents,causing worse performance.And the optimal condition during thermal activation process is 850℃for 5 min.Finally,based on the conclusions above,the sorbent with the optimal performance was synthesized.Among all the preparation factors,the p H value of precursor solution matters most for the property of the sorbent.The optimal sorbent possesses an initial conversion of 98%.After 50 cycles,it is 52%.The conversion during50 cycles was improved over 20%on average comparing to the sorbent without optimization.