CO₂Adsorption From Confined Space Under Ambient Temperature By Modified Porous Materials

CO2would be harmful and needs to be removed in confined space, such as submarines and space capsules. A key function of environment control and life support system is the removal of metabolic CO2from the atmosphere in the living quarters. The system needs indicate that any future CO2sequestration technologies must be high efficiency, stable and secure, and then the device must be small, light, low energy consumption, durable and easy operation. In this paper, according to the advantages of adsorption method, we developed a series of solid amine adsorbents by impregnating TEPA and TETA into SBA-16and CNTs porous material support. This material removed CO2at a low concentration at ambient temperature, similar to cabin atmosphere conditions. The adsorption and desorption performance of the adsorbent was investigated at a fixed-bed column. The main conclusions are as follows:The solid amine adsorbents for CO2removal were developed by SBA-16and CNTs impregnated with TEPA or TETA. After impregnation, the shapes, fundamental channels and pore structures of adsorbents were not changed. But the surface area and pore volumn decreased remarkably with the increasing amine loading amounts. And the CO2adsorption capacity was changed with a contrary tendency.The maximum amount of amine loading in the pore channel was about30wt.%. After modification, the CO2adsorption capacity improved with the temperature (288-308K). When the temperature reached308K, the maximum capacity was3.37and2.65mmol·g-1fo CTP-30and CTT-30, respectively. The adsorption performance of modified SBA-16and CNTs was relatively stable afer5adsorption/desorption cycles.The CO2adsorption capacity of CTP-30was remarkably improved with the increasing temperature from2.52to3.56mmol·g-1with the increasing temperature from283to313K. And the adsorption of CO2on CTP-30was mainly chemisorption. The ratio of chemisorption capacity was no less than74%of total adsorption capacity. The shapes of the adsorption isotherms of for CTP-30corresponded to type I at various temperatures. The average isosteric heat of adsorption is32.68kJ·mol-1. The adsorption capacity was also influenced by moisture.It increased significantly from2.97to2.88mmol·g-1as the water vapor increased from0to2%but began to decrease from3.88to2.67mmol·g-1as the water vapor further increased from2to7%. As a preliminary assessment of the adsorption kinetics of these materials under low CO2concentration, the adsorption half time was measured using the fixed-bed column. The CTP-30also exhibited a relatively stable CO2regeneration performance in adsorption capacity after20cycles, which remained around3.68mmol·g-1. In all cases, the experimental data agreed with the predicated breakthrough model. The regression analysis values of the data were0.99or higher under various conditions.CTP-30exihibited an excellent regenerabtion performance. The TPD results indicated that CTP-30had two desorption peaks at313K and358K, respectively. And vacuum and temperature swing adsorption (VTSA) was used to regenerate CO2. The results implied that the regeneration can be operated at relatively low temperature (353K) and the efficiency was95%or higher.The initial desorption rate of CTP-30(5kPa,373K) was quicker than that in other conditions (0.71mmol·min-1) and the adsorbent could be completely regenerated in15min. According to the results, a two-bed device using CTP-30was conceptually designed to remove CO2in space station, alternating between adsorption and desorption process. The operation unite time was about30min.The bed volumn was about0.06mJ, the blowing rate was0.3m3·h-1and the consumption energy was22.9kWh·kg-1CO2. The device can support up to10astronauts working inside the space station simultaneously, and can keep the CO2concentration around0.3%. The results also have some practical value to the CO2capture in flue gas application.