What chemicals will we need to capture CO2?

A number of solvents have been proposed for CO2 capture from post-combustion flue gas streams. Currently, the solvents furthest along in development are aqueous amine solutions, stemming from nearly a century of use and know-how developed within the natural gas industry. Of these, monoethanolamine (MEA) is perhaps the most well-known, thoroughly studied, and readily available, yet likely cannot meet the stringent energy and cost limitations required to economically achieve 90% CO2 capture at coal-fired power plants. Also in development are piperazine (PZ) and several hindered and 'advanced' amines, which show great potential to improve energy efficiency and stability, but are not yet produced on a scale approaching that of MEA. Many other novel solvents have also been proposed, but few have been taken beyond bench-scale activities. Eventually, as CO2 capture processes are broadly deployed worldwide, the solvent(s) with the most favorable economics and performance will need to be manufactured in annual quantities of 1 Mton or greater, effectively creating at least one new chemical of global industrial importance. With the ultimate goal of deep reductions in greenhouse gas (GHG) emissions in mind, the processes by which chemicals for CO2 capture are manufactured should also be considered in terms of their energy requirements, efficiencies, waste products, and CO2 emissions. This review begins to address some of these technical and economic questions by examining the manufacture of several amines that have been proposed for post-combustion CO2 capture, as well as the fundamental building block of all amines, ammonia. (c) 2012 Society of Chemical Industry and John Wiley & Sons, Ltd