SOLID CO2 ADSORBENT BASED ON LINEAR POLYETHYLENIMINE AND NANO-SILICA FOR IMPROVED DESORPTION KINETICS

摘要

Anthropogenic carbon dioxide (CO2) emission is outpacing nature’s carbon cycle, driving an increase in CO2 concentration in the atmosphere, from 270 ppm in the pre-industrial times to more than 400 ppm presently. CO2 has been acknowledged as the most significant greenhouse gas (GHG) in both the scientific community and the public. The associated impacts of the continuous increase in CO2 concentration include global warming, rising sea levels, and ocean acidification. Many more are not identified and still in the process of being studied. To mitigate the problem, carbon capture and storage (CCS) and recycling (CCR) have been proposed. Among many processes developed for CO2 capture, the current benchmark technology is based on aqueous amine systems. They are well established and widely used for years. However, they suffer from several noteworthy drawbacks, making them less than optimal. The first is being energy intensive: in the regeneration step, amines, along with the large amounts of water to dissolve them, need to be heated to boiling temperatures. Second, amine loadings are limited due to the corrosion issues. Also, they undergo degradation over adsorption-desorption cycles. As an alternative, many solid CO2 adsorbents have been developed and investigated. One kind that employs branched polyethylenimines (BPEIs) impregnated silica attracted particular attention because of their effectiveness in capturing CO2 from various gas mixtures, including the air. BPEIs contain primary, secondary, and tertiary amines. Although primary amines are known to bind CO2 strongly in the adsorption step, they are generally reported to require more energy than secondary amines to desorb the CO2 during the regeneration step. Therefore, the use of a polymer containing only secondary amines, which binds less strongly with CO2, should theoretically necessitate a lower energy input for the endothermic desorption process.