An absorbent for selective removal of hydrogen sulfide over carbon dioxide from a fluid stream comprises an aqueous solution of a) a tertiary amine, b) a sterically hindered secondary amine of the general formula (I)

##STR00001##

in which R.sub.1 and R.sub.2 are each independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl, with the proviso that at least one R.sub.4 and/or R.sub.5 radical on the carbon atom bonded directly to the nitrogen atom is C.sub.1-4-alkyl or C.sub.1-4-hydroxyalkyl when R.sub.3 is hydrogen; x and y are integers from 2 to 4 and z is an integer from 1 to 4; where the molar ratio of b) to a) is in the range from 0.05 to 1.0, and c) an acid in an amount, calculated as neutralization equivalent relative to the protonatable nitrogen atoms in a) and b), of 0.05 to 15.0%. One preferred amine of the formula I is 2-(2-tert-butylaminoethoxy)ethanol. The absorbent allows a defined H.sub.2S selectivity to be set at pressures of the kind typical in natural gas processing.

An apparatus includes a captured carbon dioxide input. The captured carbon dioxide input is coupled to receive captured carbon dioxide from a direct air capture system. The apparatus uses the captured carbon dioxide as a low global warming refrigerant to provide cooling functionality in automotive, commercial, and industrial applications, or other operations involving low global warming refrigerants. In various embodiments, the apparatus is a refrigeration apparatus or a heat pump apparatus. Low global warming carbon dioxide refrigerant is natural, non-toxic, non-flammable, and abundant when obtained from a direct air capture system. Moreover, carbon dioxide refrigerant has a high heat transfer coefficient and has a global warming potential (GWP) of one. Carbon dioxide refrigerant is a more sustainable and efficient coolant option than common refrigerants, such as R22, R152, R404a, and R1234yf refrigerants.

The invention discloses methods and apparatus(es) for the removal and control of pollutants such as gases and suspended particulates in the air of an enclosed space or an outdoor environment by passing the air through absorbent media. The absorbent media includes any liquid, solid or combination of liquid and solid media that is capable of absorbing a material in which it comes in contact. In one aspect of the invention, formaldehyde is removed by air sparging through a liquid such as water, optionally containing additional scavenging agents.

An absorbent for selective removal of hydrogen sulfide from a fluid stream comprises an aqueous solution of a) a tertiary amine, b) a sterically hindered secondary amine of the general formula (I) ##STR00001##
in which R.sub.1 and R.sub.2 are each independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl, with the proviso that at least one R.sub.4 and/or R.sub.5 radical on the carbon atom bonded directly to the nitrogen atom is C.sub.1-4-alkyl or C.sub.1-4-hydroxyalkyl when R.sub.3 is hydrogen; x and y are integers from 2 to 4 and z is an integer from 1 to 4; where the molar ratio of b) to a) is in the range from 0.05 to 1.0, and c) an acid in an amount, calculated as neutralization equivalent relative to the protonatable nitrogen atoms in a) and b), of 0.05 to 15.0%. One preferred amine of the formula I is 2-(2-tert-butylaminoethoxy)ethanol. The absorbent allows a defined H.sub.2S selectivity to be set at pressures of the kind typical in natural gas processing.

The invention discloses methods and apparatus(es) for the removal and control of pollutants such as gases and suspended particulates in the air of an enclosed space or an outdoor environment by passing the air through absorbent media. The absorbent media includes any liquid, solid or combination of liquid and solid media that is capable of absorbing a material in which it comes in contact. In one aspect of the invention, formaldehyde is removed by air sparging through a liquid such as water, optionally containing additional scavenging agents.

A carbon dioxide absorbent is disclosed. The absorbent comprises organic amine, amino acid, and water, wherein said organic amine comprises tertiary amine and primary amine and/or secondary amine; and wherein amino acid is excess based on a stoichiometrical ratio of organic amine to amino acid in a reaction. A method for absorbing and desorbing carbon dioxide is further disclosed. In the absorbent system provided by the present disclosure, the conversion between primary (secondary) amine and (secondary) tertiary amine can be realized under the catalytic effect of amino acid with the changing of temperature, and carbon dioxide can be absorbed and desorbed effectively under a relatively low temperature.

The present invention relates to an absorbent, an absorbent system and a process for removing acidic gas such as CO.sub.2 from exhaust gases from fossil fuel fired power stations, from natural gas streams, from blast furnace oven off-gases in iron/steel plants, from cement plant exhaust gas and from reformer gases containing CO.sub.2 in mixtures with H.sub.2S and COS. The liquid absorbent, a mixture of amine and amino acid salt is contacted with a CO.sub.2 containing gas in an absorber and CO.sub.2 in the gas stream is absorbed into the liquid. The absorbed CO.sub.2 forms more than one type of solid precipitate in the liquid at different absorption stages. In a first absorption stage solid precipitate of amine bicarbonate is formed and is withdrawn as slurry from the bottom of a first absorber section. In a second absorption stage solid precipitate of alkali metal bicarbonate is formed and withdrawn as slurry at the bottom of a second absorber section. The slurry withdrawn from the first absorption section is heated to dissolve the precipitate with CO.sub.2 release in an amine flash regeneration tank. The slurry from the second precipitation stage is withdrawn from the bottom of the second absorber section and sent to a regenerator for desorption with CO.sub.2 release. The lean amine and amino acid salt mixture from the flash regenerator and desorber are mixed and returned to the top of the absorber. This absorbent system improves carbon dioxide removal efficiency due to its higher CO.sub.2 removal ability per cycle when compared with conventional amine, absorbent from organic acid neutralized with inorganic base and carbonate based absorbent system. It exhibits less solvent vaporization loss because part of the absorbent is in salt form.

The present invention relates to methods for improving carbon capture using entrained catalytic-particles within an amine solvent. The particles are functionalized and appended with a CO.sub.2 hydration catalyst to enhance the kinetics of CO.sub.2 hydration and improve overall mass transfer of CO.sub.2 from an acid gas.

Disclosed herein are acid gas absorbents that afford high acid gas (CO2) absorption amount per unit volume and high absorption speed and can prevent the absorbent components from diffusing. Also disclosed herein is a method and device for removing an acid gas, in which the energy required for separating the acid gas and regenerating the absorbent is reduced, are provided.

In a general aspect, interfacial surface structures for removing carbon dioxide from a gaseous feed are presented. In some cases, a method of removing carbon dioxide gas from a gaseous feed includes wetting surfaces of an interfacial surface structure in a gas-liquid contactor with an alkaline capture solution. The gaseous feed containing the CO.sub.2 gas is passed across the wetted surfaces of the interfacial surface structure to dissolve the CO.sub.2 gas in the alkaline capture solution. A CO.sub.2-rich alkaline capture solution is collected from the gas-liquid contactor. The CO.sub.2-rich alkaline capture solution includes dissolved CO.sub.2 gas from the gaseous feed.