Preparation Of Liquid Suspension Absorbents Based On Porous Silica Microspheres For CO₂ Absorption

The global warming is more serious due to vast sums of CO₂ emission,which is the threats to human survival.Therefore,it is a focus issue to effectively reduce CO₂emission in recent years.Flue gas in coal fired power plant is the main CO₂ emission source,so it is urgent to reduce the CO₂ emission from flue gas.Currently,post-combustion capture technology is one of the most promising methods for controlling carbon dioxide emission in coal-fired power plant and the absorbents play a decisive role in CO₂ capture efficiency and energy consumption of post combustion process.Pure liquid absorbents have high energy consumption during regeneration,corrosion and degradation and solid materials for CO₂ capture is not mature and cannot be replaced liquid phase completely.Therefore,it is of great significance to develop novel absorbents with high capture efficiency and low energy consumption,and study its CO₂ capture performance.In order to make up the shortcomings of solid or pure liquid for CO₂ capture,liquid suspension absorbents in this work were prepared by suspending porous silica microspheres modified with amines in dimethyaminoethoxyethanol?DMEE?solvent,which showed high absorption amount,good cyclic stability and low energy consumption.Then the effects of microstructure for the main unit and amine on CO₂absorption/desorption performance were studied.The main conclusions are as follows:?1?The absorbents based on solid silica,hollow silica and porous silica were prepared.The results of CO₂ absorption experiment showed that DETA-PSMs/DMEE had higher absorption amount than DETA-SiO₂/DMEE and DETA-HSMs/DMEE.It was also found that the absorption capacities were higher but absorption time was shorter when the pressure became higher.Besides,the absorption capacities were lower but the absorption rate was higher with temperature increasing.?2?Content and molecular structure of amine had great influence on the absorption performance.For alkyl amine,small molecule was more favorable to CO₂ absorption but worse for cycle regeneration.In addition,it was found that the absorption capacities of absorbents modified with diethylenetriamine?DETA?were the highest and temperature had the least effect on its CO₂ absorption.For the polymer amine,the absorption capacities were higher but the cycle stability was poorer when the molecular weight of PEI was higher.On the other hand,It was found that the CO₂ absorption capacities of the absorbents by suspending porous silica microspheres modified with amines in DMEE?PEI?600?-PSMs/DMEE?increased initially and decreased afterwards with increasing PEI content.Besides,the CO₂ absorption capacities of PEI?600?-PSMs/DMEE were 2.1 times the sum absorption capacities of DETA-PSMs and pure DMEE.The regeneration efficiency of PEI-PSMs/DMEE could still reach92.0%in five cycles and its desorption temperature was only 80?,which had great energy saving potential.?3?A series of DETA-HSMs/DMEE and DETA-PSMs/DMEE with different microstructure were synthesized through improving forward methods and its CO₂absorption were studied.For the absorbents based on hollow silica,DETA-HSMs?N?/DMEE were the best for CO₂ absorption when the DETA content was no more than 40wt%,but DETA-HSMs?A?-2/DMEE had the most CO₂ absorption amount when DETA content were more than 40wt%.For porous silica microspheres,the results showed that the pore volume and average of samples increased gradually but specific surface area decreased when the quantity of organic agent added were more.Besides,organic agents could make topology and size of PSMs more uniform.Meanwhile,the absorption experiment indicated that the CO₂ absorption capacities were higher with pore szie of the main unit increasing and the highest absorption amount could be up to 1.2543 mmol/g.In addition,CO₂ absorption performance of DETA-PSMs/DMEE were better than DETA-HSMs/DMEE.This suggested that porous silica had a better ability for impregnating amine than hollow silica and absorbents based on the porous silica showed better CO₂ absorption performance.