Enhanced CO2 capture kinetics by using macroporous carbonized natural fibers impregnated with an ionic liquid

Abstract

In this research a new hybrid material was prepared to improve the kinetics and CO2 sorption capacity of an ionic liquid supported on the macroporous structure of carbonized agave bagasse fibers, which are low-cost renewable materials. The ionic liquid was 1-butyl-3-methylimidazolium acetate that has high affinity for CO2. The CO2 capture was assessed in a dynamic mode at atmospheric pressure by monitoring the weight change of the fibers in a thermogravimetric analyzer when passing a CO2 gas stream. The CO2 capture was evaluated on carbonized fibers (CF), acid washed carbonized fibers (CFw) and carbonized fibers impregnated with ionic liquid (IL) using a mass ratio that ranges from 1:10−3 to 1:1 (wt CFw: wt IL). The BET surface area of CF was 75 m2/g that decreased after the acid wash to 2 m2/g. However, after impregnation with IL, the surface area was maintained at 2 m2/g when using the lowest impregnation ratio (1:10−3). The impregnated sample with a mass ratio of 1:10−3 (CFwIL1:10−3) exhibited the highest sorption capacity (1.29 mmol CO2/g evaluated at 50 min of CO2 exposure) and sorption rate of 0.02 mmol CO2/min*g. These values were superior to those obtained by the IL (0.77 mmol CO2/g and 0.012 mmol CO2/min*g), which showed the synergy between the IL and the support in the CO2 capture. Finally, the cycles of CO2 capture (25 °C, 50 min) and thermal desorption (80 °C, 50 min, under nitrogen atmosphere) reported that the IL captured up to 1.07 mmol CO2/g but released only 41.5%, in contrast the impregnated carbon fibers (CFwIL1:10−3) captured 1.13 mmol CO2/g and released 91%. The rapid CO2 sorption-desorption processes and high reversibility of the impregnated carbon fibers suggest that this material could be used in CO2 concentrators.