A membrane contactor system for separating CO.sub.2 from a mixed gaseous feed stream comprising CO.sub.2, said contactor system comprising: (i) a composite membrane, said membrane having a permeate side and a retentate side; (ii) said retentate side being exposed to a mixed gaseous feed stream comprising carbon dioxide; (iii) said permeate side being exposed to a carbon dioxide capture organic solvent; (iv) said composite membrane comprising a porous layer and a non-porous selective polymer layer, said non-porous selective polymer layer selectively allowing transport of CO.sub.2 across the composite membrane from said mixed gaseous feed stream so that it dissolves in said capture solvent whilst limiting the transport of said capture solvent across the composite membrane.

A compound of the general formula (I)

##STR00001##

in which R.sub.1, R.sub.2 and R.sub.3 are independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; each R.sub.4 is independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; each R.sub.5 is independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; m is 2, 3, 4 or 5; n is 2, 3, 4 or 5; and o is an integer from 0 to 10. A preferred compound of the formula (I) is 2-(2-tert-butylaminoethoxy)ethylamine. Absorbents comprising a compound of the formula (I) have rapid absorption of carbon dioxide from fluid streams and are also suitable for processes for the simultaneous removal of H.sub.2S and CO.sub.2, where given H.sub.2S limits have to be observed but complete removal of CO.sub.2 is not required.

An improved process for deacidizing a gaseous mixture with reduced overall energy costs is described. The process involves contacting the gaseous mixture with at least one of a vaporizing compound, a vaporized compound, a vaporizing solution of compound and a vaporized solution of compound, and forming a liquid or solid reaction product that can be easily separated from the gaseous mixture.

Disclosed herein are methods of capturing CO2 from a gas source using electrochemically-enhanced amine capture to form a concentrated CO.sub.2 vapor, followed by sequestering CO.sub.2 from the concentrated vapor in a sequestration step. The sequestration step includes contacting the concentrated vapor with an aqueous sequestration solution comprising ions capable of forming an insoluble carbonate salt, such that the aqueous sequestration solution comprises the CO.sub.2, electrochemically basifying the sequestration solution, thereby precipitating a carbonate solid, separating the carbonate solids from the aqueous sequestration solution or the surface of the mesh.

An absorbent for desulfurization of combustion gas is provided. The absorbent includes about 1 to about 16 wt % of potassium carbonate (K.sub.2CO.sub.3); about 0.1 to about 10 wt % of a promoting agent including hindered cyclic amine, hindered cyclic amine bicarbonate, or a combination thereof; and a balance amount of water. In addition, a method of treating the combustion gas using the absorbent is provided.

An improved process for deacidizing a gaseous mixture with reduced overall energy costs is described. The process involves contacting the gaseous mixture with at least one of a vaporizing compound, a vaporized compound, a vaporizing solution of compound and a vaporized solution of compound, and forming a liquid or solid reaction product that can be easily separated from the gaseous mixture.

The present disclosure provides methods and apparatuses of recovering CO.sub.2 from a gas stream. The methods regenerate CO.sub.2 with high regeneration efficiencies, thereby lowering the overall energy cost for CO.sub.2 capture.

In a method of absorbing CO.sub.2 from a gas mixture the use of an absorption medium comprising water and at least one amine of formula (I) ##STR00001## where R.sup.1 is a (CH.sub.2).sub.n(XCH.sub.2CH.sub.2).sub.mYR.sup.3 radical where R.sup.3=hydrogen or an alkyl radical having from 1 to 6 carbon atoms, X and Y are each, independently of one another, NR.sup.3, oxygen, SO or SO.sub.2, where in the case of YSO and in the case of YSO.sub.2, R.sup.3 is not hydrogen, and YR.sup.3 can be an N-morpholinyl radical or an N-piperazyl radical, n=2 to 4, m=0 to 4 and R.sup.2 is hydrogen, an alkyl radical having from 1 to 6 carbon atoms or a radical R.sup.1, where m is not 0 when R.sup.2 is not a radical R.sup.1, YNR.sup.3 and YR.sup.3 is not an N-morpholinyl radical and not an N-piperazyl radical, makes it possible to avoid precipitation of a solid during the absorption of CO.sub.2 and a separation into two liquid phases during the regeneration of the absorption medium.

An improved process for deacidizing a gaseous mixture with reduced overall energy costs is described. The process involves contacting the gaseous mixture with at least one of a vaporizing compound, a vaporized compound, a vaporizing solution of compound and a vaporized solution of compound, and forming a liquid or solid reaction product that can be easily separated from the gaseous mixture.

A novel blend of piperazine (PZ) and a second amine compound is provided as a superior solvent for CO2 capture from coal-fired flue gas. Blending PZ with various second amine compounds can remediate the precipitation issue of concentrated PZ while maintaining its high CO2 absorption capacity and rate, and high resistance to oxidative degradation.