Research On The Preparation And CO₂Capture Performance Of CaO Based Adsorbents

Environment changes and climate disasters, which is brought by excessiveemissions of greenhouse gases such as carbon dioxide, increasingly threatens humansurvival and long-term development. The carbon dioxide as the main anthropogenicgreenhouse gas is gaining increasing attention in the world. And carbon dioxideeffectively capture, storage and utilization technology is now developing. In the lightof the release of large quantities of high temperature carbon dioxide during coal tosubstitute natural gas (SNG) process, structure features and high temperature CO2adsorption performance of calcium oxide based sorbents, which adopted differentpreparation method, were studied.Using calcium acetate as a sorbent precursor, ethanol as a modification reagent,we studied the effects of different processing conditions on adsorption performance ofthe sorbents. We found that calcined calcium oxide sorbents, which were berespectively treated by water and ethanol solution, easily form loose and porousstructures at room temperature. The adsorption performances were significantlyimproved than the untreated sorbents, but the adsorption capacity with cycle numberincreasing evidently decreased. Among them, stability of the sorbent by ethanolsolution was better than that of the sorbent by pure water treatment, indicating thatethanol treatment could improve the stability of the adsorbent. It is suggested thatintroduction of ethanol decreases the solubility of the Ca solute. During the dynamicprecipitate solubility equilibrium process, particle size grown smaller and finally formnano-particles, exhibiting good stability. The effects of different concentration ofethanol solution on the adsorption performance of sorbents were studied. The resultsshowed that the adsorption performances of sorbents were significantly improvedwith increasing ethanol concentration. In order to further improve the stability ofsorbents, we investigated the steam effect on the sorbent performance. The resultsshowed that the initial adsorption uptake was70%and the18thcycle uptake was68%after introduction of4.8%water vapor, indicating that diffusion of water vapor couldobviously improve the stability of the adsorbent. And we found that the concentrationof water vapor had a important influence on the stability of sorbents We successfully prepared the meshed hollow sphere sorbent using colloidalcarbon spheres as a template and urea homogenous hydrolysis precipitation method,.Adsorption performance results showed that the stability of the hollow sphere sorbentimproved significantly. The initial adsorption uptake was74%and the18thcycleuptake was68%. Meshed structure was conducive to the diffusion of carbon dioxideinto the sorbent, while the hollow structure with large inner space could accommodatemore carbon dioxide gas. It leaded to quick reaction of internal and external carbondioxide in spheres, performing with a high initial adsorption capacity. Meanwhile, thehollow structure could slow down sintering of the sorbent and make the sorbent havebetter stability.