Preparation And CO₂ Sorption Performance Of A Novel Aerogel Sodium-based Sorbent

Global warming is one of today’s great challenges. The mass emission of greenhouse gases (GHG) CO2 is the chief culprit of global warming. Combustion of fossil fuels results in huge CO2 emissions during the electricity generation process. Therefore, capturing CO2 from the coal-fired power plants is a potentially effective method for GHG control. Post-combustion CO2 capture technology using sodium-based solid sorbents has been developed duo to its low cost advantage and ease of operation. However, its application is limited by the low CO2 sorption capacity of Na2CO3. How to enhance the CO2 sorption capacity of the sodium-based sorbent is a big problem that researchers have to solve.The object of this paper is to develop a novel sodium-based sorbent with amine modification for low temperature CO2 capture in coal-fired power plants. The specific research includes the following parts:The loss rate of-NH2 and CO2 sorption capacity of sorbents using resorcinol/formaldehyde or TEOS as carrier precursors were compared to determine the load capacity of different carrier. Results indicated that APTES and TEOS can form strong chemical bond during the hydrolysis process, and the theoretical CO2 sorption capacity of the TEOS-based sorbents is also higher. Therefore, TEOS was chosen as the carrier precursor for NaN sorbent.The pore structure and CO2 sorption capacity of sorbents using 3-aminopropyltrimethoxysilane (APS) or 3-aminopropyltriethoxysilane (APTES) or diethylenetriamine (DETA) or triethylenetetramine (TETA) as amine precursor were tested to determine the best amine precursor. Results showed that APTES-based sorbent and TETA-based sorbent both have porous structure and high specific surface area. APTES was chosen as the amine precursor duo to its low cost advantage.The effect of drying method (include conventional drying, organic solvent sublimation drying and supercritical fluid drying) on the structure of NaN was discussed in this paper. The SCFD method maintained the gel structure well due to the disappearance of gas-liquid interface during this drying method. Results demonstrates that the optimized SCFD-NaN with APTES:Na2CO3:TEOS mole ratio of 1:1:1 reached the highest CO2 sorption capacity of 2.51mmol/g.The carbonation characteristic and regeneration behavior of NaN were also studied in this paper. Sorption conditions (include temperature and atmosphere) may change the reaction mechanism and reaction speed, thus, made an impact on the CO2 sorption capacity of NaN. Results showed that the CO2 sorption capacity of NaN increased when temperature rose from 30℃ to 50℃ but decreased when temperature rose from 50℃ to 80℃. Therefore,50℃ is thought to be the best sorption temperature for NaN sorbent. Moreover, the highest CO2 sorption capacity of NaN was achieved with a H2O:CO2 concentration ratio of 1:1 and the corresponding H2O concentration was 10%. Cyclic CO2 sorption and desorption performance showed that NaN was stable during 10 cycles. All the above results show that NaN is a high potential material for CO2 capture.The achievements of the above research includes:(1) Obtained the synthesizing mechanism of NaN sorbent using different ingredients (include Na2CO3, carrier precursors and amine precursors) and invented a sodium-based sorbent with amine modification (named NaN) synthesizing by 3-aminopropyltriethoxysilane (APTES), Na2CO3 and tetraethylorthosilicate (TEOS). (2) Optimized the sorbent preparation method and synthesized a mesoporous NaN sorbent using sol gel-supercritical fluid drying method. (3) Obtained the carbonation-regeneration mechanism of NaN sorbent, the results indicated that NaN had high CO2 sorption capacity and decent cyclic stability.