An aqueous solvent composition is provided, comprising a nucleophilic component having one or more sterically unhindered primary or secondary amine moieties, a Brønsted base component having one or more basic nitrogen moieties, a water-soluble organic solvent, and water. A biphasic composition is provided, comprising one or more carbamate compounds, one or more conjugate acids of Brønsted base, a water-soluble organic solvent, and water. A biphasic CO.sub.2 absorption process is also provided, utilizing the biphasic solvent composition.

An absorbent for the selective removal of hydrogen sulfide over carbon dioxide from a fluid stream, wherein the absorbent contains an aqueous solution, comprising an amine of formula (I) and/or an amine of formula (II) wherein U—V—W is CH—O—CHR.sup.5, N—CO—CHR.sup.5 or N—CO—NR.sup.5; U′—V′—W is C—O—CR.sup.5; R.sup.1 is independently C.sub.1-C.sub.5-alkyl; R.sup.2 is selected from hydrogen and C.sub.1-C.sub.5-alkyl; R.sup.3 is independently selected from hydrogen and C.sub.1-C.sub.5-alkyl; R.sup.4 is independently selected from hydrogen and C.sub.1-C.sub.5-alkyl; R.sup.5 is selected from hydrogen, C.sub.1-C.sub.5-alkyl, (C.sub.1-C.sub.5-alkoxy)-C.sub.1-C.sub.5-alkyl, and hydroxy-C.sub.1-C.sub.5-alkyl; and x is an integer from 1 to 10. The absorbent has a reduced tendency for phase separation at temperatures falling within the usual range of regeneration temperatures for the aqueous amine mixtures and a low volatility in aqueous solvents. ##STR00001##

An aqueous solvent composition is provided, comprising a nucleophilic component having one or more sterically unhindered primary or secondary amine moieties, a Brønsted base component having one or more basic nitrogen moieties, a water-soluble organic solvent, and water. A biphasic composition is provided, comprising one or more carbamate compounds, one or more conjugate acids of Brønsted base, a water-soluble organic solvent, and water. A biphasic CO.sub.2 absorption process is also provided, utilizing the biphasic solvent composition.

The embodiments provide an acidic gas absorbent having low diffusibility, an acidic gas removal method employing the acidic gas absorbent, and also an acidic gas removal apparatus employing the absorbent. The acidic gas absorbent according to the embodiment comprises: a particular tertiary amine compound, such as, an alkyl dialkanol amine or a hydroxyalkyl piperazine; a halogen-free ionic surfactant; and an aqueous solvent. The embodiments provide not only the acidic gas absorbent but also an acidic gas removal method and apparatus employing the acidic gas absorbent.

The embodiments provide an acidic gas absorbent, an acidic gas removal method using the absorbent, and an acidic gas removal apparatus using the absorbent. The absorbent absorbs an acidic gas in a large amount and is hardly diffused. The acidic gas absorbent according to the embodiment comprises an amine compound represented by the following formula (1): ##STR00001##

The present invention relates to a dehydration composition and method of use thereof for drying gas streams, in particular natural gas streams, wherein the dehydration composition comprises (i) a glycol, (ii) an imidazole compound, and optionally (iii) one or more of an alkali metal carboxylate, an additional glycol different than (i), an alkanolamine, a phosphate acid, a salt of a phosphate acid, a borate acid, a salt of a borate acid, a sweetening agent, a low temperature viscosity improver, a corrosion inhibitor, an antifoaming agent, or mixtures thereof.

A process for absorbing carbon dioxide from a gas stream containing carbon dioxide, including contacting the gas stream with an aqueous composition having a substituted heteroaromatic compound including a six-membered heteroaromatic ring comprising 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.

An extraction solvent comprised of one or more ethyleneamines having structure (I), (II), or (III):

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where R.sub.1-R.sub.6 can independently be H, C.sub.1-C.sub.4 linear or branched alkyl, amido (RRNCO), or hydroxyalkyl, where each R in the amido group independently H or C.sub.1 alkyl, and where x ranges from 1 to 6, may be contacted with a hydrocarbon stream to remove or extract non-acidic contaminants, such as thiophenes, benzothiophenes, alkyl sulfides, alkyl disulfides, mercaptans, aromatics, oxygenates, metals, olefins, and combinations thereof, from the hydrocarbon stream. The extraction solvent may include co-solvents and the hydrocarbon stream may be in gas and/or liquid form.

An extraction solvent comprised of one or more ethyleneamines having structure (I), (II), or (III): ##STR00001##
where R.sub.1-R.sub.6 can independently be H, C.sub.1-C.sub.4 linear or branched alkyl, amido (RRNCO), or hydroxyalkyl, where each R in the amido group independently H or C.sub.1 alkyl, and where x ranges from 1 to 6, may be contacted with a hydrocarbon stream to remove or extract non-acidic contaminants, such as thiophenes, benzothiophenes, alkyl sulfides, alkyl disulfides, mercaptans, aromatics, oxygenates, metals, olefins, and combinations thereof, from the hydrocarbon stream. The extraction solvent may include co-solvents and the hydrocarbon stream may be in gas and/or liquid form.

An absorbent for the selective removal of hydrogen sulfide over carbon dioxide from a fluid stream, wherein the absorbent contains an aqueous solution, comprising an amine of formula (I) and/or an amine of formula (II) wherein UVW is CHOCHR.sup.5, NCOCHR.sup.5 or NCONR.sup.5; UVW is COCR.sup.5; R.sup.1 is independently C.sub.1-C.sub.5-alkyl; R.sup.2 is selected from hydrogen and C.sub.1-C.sub.5-alkyl; R.sup.3 is independently selected from hydrogen and C.sub.1-C.sub.5-alkyl; R.sup.4 is independently selected from hydrogen and C.sub.1-C.sub.5-alkyl; R.sup.5 is selected from hydrogen, C.sub.1-C.sub.5-alkyl, (C.sub.1-C.sub.5-alkoxy)-C.sub.1-C.sub.5-alkyl, and hydroxy-C.sub.1-C.sub.5-alkyl; and x is an integer from 1 to 10. The absorbent has a reduced tendency for phase separation at temperatures falling within the usual range of regeneration temperatures for the aqueous amine mixtures and a low volatility in aqueous solvents.

##STR00001##