Preparation Of Porous Silicon-based Anhydrous Liquid Absorbent And Its CO₂ Absorption Performance

The large-scale use of fossil energy has led to a sharp increase in CO₂ emissions,causing a series of environmental problems worldwide.As one of the concentrated sources of CO₂ emissions,thermal power plants account for more than 30%of global CO₂ emissions.Therefore,it is imminent to reduce CO₂ emissions from thermal power plants.For power plants already built and under construction,post-combustion CO₂capture is currently the most direct and effective method.Obviously,the performance of carbon capture materials has a decisive influence on the efficiency of post-combustion capture.Liquid absorbents have the advantages of high capture efficiency,easy continuous operation,etc,but the disadvantages of easy decomposition and loss,high regeneration energy consumption;solid adsorption materials have the advantages of low regeneration energy consumption and no equipment corrosion,but they also have poor selectivity,and they are not suitable for large-scale application.Therefore,it is of great significance to study the CO₂ absorption performance of new materials for carbon capture.In this paper,with amine-modified porous silicon-based microspheres as the host microporous units,and 2-[2-（dimethylamino）ethoxy]ethanol（DMEE）as the guest solvent,porous silicon-based anhydrous liquid absorbent was prepared for CO₂absorption,which owned both solid and liquid properties.The physical properties,CO₂selectivity,and CO₂ absorption performance under dry and wet conditions were studied.The main conclusions are as follows:（1）Porous silicon-based anhydrous liquid absorbent was successfully prepared,and its density and viscosity both decreased with the increase in temperature and increased with the increase of the concentration of the host microporous units.When the concentration of the host microporous units is 20 wt%,the viscosity of the absorbent is as high as 267.98 m Pa·s,resulting in an increase in the mass transfer resistance of the absorbent.（2）CO₂ bubble dynamics,operating parameters and characteristics of the absorbent are important factors that affect the CO₂ absorption performance.The experimental results show that a smaller the bubble volume and a smaller bubble movement rate,are more favorable for CO₂ absorption,but the effect of bubble volume change is greater than that of bubble movement rate;CO₂ absorption capacity increases first and then decreases with increasing temperature,and the maximum appeares at 57℃;when the mixed gas flow increases,the absorption rate and absorption capacity increase;with the increase of the concentration of the host microporous units,the absorption capacity first increases and then decreasing.When the concentration of the host microporous units reaches 12wt%,the absorption capacity is the largest;when the amine group loading of porous silicon-based microspheres increases,the absorption capacity will increase first and then decrease,and its absorption performance is best when the amine group loading is 50 wt%.Among them,the absorption performance is best when PEI600 amine groups are loaded.The absorption capacity still reaches 95%after 5 cycles,and the regeneration temperature is only 80℃,indicating that it has good cycle stability and low regeneration energy consumption.（3）Water vapor has a great influence on the chemical properties and absorption performance of the absorbent.The experimental results show that:water vapor can significantly increase the CO₂ absorption capacity of the absorbent,but the absorption rate enhancement effect is not obvious;when the moisture content of the mixed gas is90%,the absorption capacity reaches 0.974 mmol/g,which is about 2 times as much as that under the condition of dry mixed gas when the reaction time is close to 250 min,but the absorbent is still not saturated;with the increase of operating temperature,although the CO₂ absorption capacity increases,the penetration absorption q_b and presaturation absorption q_s increase first After the decrease,and the best values are obtained at 57℃;as the concentration of the host microporous units increases,the CO₂ absorption capacity and q_bincrease,but q_s increases first and then decreases.A maximum appeares when the concentration of the host microporous units is 12 wt%;directly adding water in the absorbent can significantly improve the absorption capacity and absorption rate;the absorption capacity after 5 absorption-desorption cycles is 1.19 times as much as the initial absorption capacity,and regeneration experiments was carried at 90℃.After the first cycle regeneration,the initial absorption rate is accelerated,but there is no significant change in the subsequent cycles,which shows that the absorbent has good cycle stability under moisture.