Disclosed herein is a method and system for CO.sub.2 removal from a gas stream using a diamine solvent having a Formula I

R.sup.1(R.sup.2)N-L.sup.1-NH—R.sup.3  Formula I. With respect to Formula I, each of R.sup.1 and R.sup.2 independently is aliphatic, cycloaliphatic, or R.sup.1 and R.sup.2 together with the nitrogen to which they are attached, form a heterocyclyl ring; L.sup.1 is aliphatic, cycloaliphatic, or L.sup.1 and R.sup.1 together with the nitrogen to which they are attached form a heterocyclyl ring; and R.sup.3 is aliphatic, cycloaliphatic, cycloalkylalkyl, or alkoxyalkyl. And/or the compound may have a viscosity of less than 75 cP at a CO.sub.2-loading of 40 mol % and at a temperature of 40° C.

A process for absorbing carbon dioxide from a gas stream containing carbon dioxide, including the steps of contacting the gas stream with an aqueous composition including a substituted heteroaromatic compound having a six-membered heteroaromatic ring with from 1 to 3 nitrogen atoms in the heteroaromatic ring and at least one substituent wherein at least one of the substituents is of formula —R.sup.1NH.sub.2 wherein R.sup.1 is selected from C.sub.1 to C.sub.6 alkylene and ethers of formula —R.sup.2—O—R.sup.3— wherein R.sup.2 and R.sup.3 are C.sub.1 to C.sub.3 alkylene

The principal approaches to reducing the effects of global warming seek to slow the increase in atmospheric CO2 levels as a result of fossil fuel combustion for energy production and transportation. A process for hybrid carbon capture and mineralization are disclosed. The process utilizes both flue gas from (e.g., power plants) and reject brine from (e.g., desalination process). The process includes providing flue gas to react with an amine solution to produce carbamate; processing the carbamate in a reactor to regenerate amine and to produce a carbonate; treating reject brine to provide a ready-made brine for carbonation reaction; and processing the carbamate with salt from treating the brine to produce a carbonate.

The absorption agent of the present invention contains water, an amine compound, and an organic solvent, and a value obtained by subtracting a solubility parameter of the organic solvent from a solubility parameter of the amine compound is 1.1 (cal/cm.sup.3).sup.1/2 or more and 4.2 (cal/cm.sup.3).sup.1/2 or less. The method for separation and recovery of an acidic compound of the present invention includes the steps of: bringing a mixed gas containing an acidic compound into contact with an absorption agent containing water, an amine compound, and an organic solvent to absorb the acidic compound into the absorption agent; causing the absorption agent that has absorbed the acidic compound to be phase-separated into a first phase containing the acidic compound in a high content and a second phase containing the acidic compound in a low content; and heating the first phase to release the acidic compound from the first phase.

A process for absorbing carbon dioxide from a gas stream containing carbon dioxide, including the steps of contacting the gas stream with an aqueous composition including a substituted heteroaromatic compound having a six-membered heteroaromatic ring with from 1 to 3 nitrogen atoms in the heteroaromatic ring and at least one substituent wherein at least one of the substituents is of formula —R.sup.1NH.sub.2 wherein R.sup.1 is selected from C.sub.1 to C.sub.6 alkylene and ethers of formula —R.sup.2—O—R.sup.3— wherein R.sup.2 and R.sup.3 are C.sub.1 to C.sub.3 alkylene.

Embodiments of a composition of the present invention for scavenging sulfides from hydrocarbon fluids and water generally include diaminol/diaminacetal provided in a chemical system, wherein the diaminol/diaminacetal is prepared by reacting one molar equivalent of glyoxal and two molar equivalents of a primary amine functionality. In various embodiments, the chemical system includes at least one component selected from surfactants, hydrotropes, alcohols, amines, amino acids, and ethers. Embodiments of a method for scavenging sulfides from hydrocarbon fluids and water is also provided.

In a process for removal of acid gases from a fluid stream the fluid stream is contacted with an absorbent to obtain a treated fluid stream and a laden absorbent. The absorbent comprises a diluent and a compound of the general formula (I) wherein R.sup.1 is C.sub.1-C.sub.3-alkyl; R.sup.2 is C.sub.1-C.sub.3-alkyl; R.sup.3 is selected from hydrogen and C.sub.1-C.sub.3-alkyl; and R.sup.4 is selected from hydrogen and C.sub.1-C.sub.3-alkyl. ##STR00001##

The invention provides a process for regenerating a liquid absorbent, including: contacting the liquid absorbent with a hydrophobic medium, wherein the liquid absorbent includes at least one amine of Formula (I)

##STR00001##

and degradation product thereof including at least one imine of Formula (II),

##STR00002##

wherein each Ar is independently an aromatic group and each R is independently selected from hydrogen, an organyl group and NH2; and selectively extracting the degradation product into or through the hydrophobic medium.

Various hydrogels are described which are useful for the regeneration of methyldiethanolamine which is used to scrub H.sub.2S/CO.sub.2. Methods of regenerating methyldiethanolamine using such hydrogels are also described.

Steric effects on amine sites beta to amide or ester functional groups are utilized to result in a family of CO.sub.2 solvents with an unprecedented hybridization of chemisorption and physisorption properties. These versatile solvents provide very high CO.sub.2 working capacities in applications typically involved with physical solvents such as Selexol, Genosorb, Fluor Solvent, Purisol, and Rectisol with the added benefit of operation near ambient conditions without the need for solvent chilling along with the potential for high pressure recovery of CO.sub.2. The non-aqueous BAC solvents can also be tailored for low partial pressure CO.sub.2 removal as required in such applications as biogas/landfill gas upgrading and CO.sub.2 removal from industrial processes such as cement and steel manufacturing where they benefit from lower energy requirements for regeneration compared to tradition aqueous amine solution, regeneration under 1 bar CO.sub.2 without steam stripping, reduced corrosion potential, reduced solvent loss, reduced environmental impact, higher volumetric CO.sub.2 uptake compared to standard commercialized processes involving physical solvents, and operation at ambient pressure without the need for feed gas compression.