Study of Di- and Polyamines as Activators in the Hot Potash Process for CO2 Capture

Abstract

An alarming rise in the atmospheric level of CO2 beyond safe limits has posed an immediate threat to mankind. It has become necessary to look for new economic processes for its capture and for options that can lead to reduction in the cost of existing processes. Hot potassium carbonate is one of the most viable processes. Efforts are continuously being made to improve on the capacity and rate of absorption of this solvent primarily by the use of activators. The latest activators in this category belong mostly to amines like piperazine and other cyclic nitrogen compounds. However, their study so far has been very haphazard. The first systematic study on alkanol monoamine activators was initiated and reported earlier by the authors. This paper extends the study and discusses the effect of some acyclic and cyclic diamines and polyamines as activators on absorption and regeneration of CO2 in K2CO3 solution. The effect of the cyclic or acyclic nature of the molecule, number of substituents, their chemical nature and their spatial arrangement was investigated. The parameters studied for this effect are rich and lean amine loading of CO2, CO2 regenerated and pKa of activators. Interestingly, it was observed that the bulkiness and spatial arrangement of substituents is the most dominant factor. An unsubstituted cyclic diamine (piperazine) performs best in enhancing the absorption capacity of solvent whereas diethylenetriamine is the best in enhancing rate of absorption. The study reveals no specific correlation of pKa value of the amines with their effect as activator.