Disclosed is an adsorbent containing a metal oxide for adsorption of hydrogen sulfide in biogas, and a biogas purification system using the same.

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 natural gas pretreatment system includes: a carbon dioxide removal unit configured to remove carbon dioxide from the natural gas by bringing an absorption liquid and the natural gas into contact with each other; and a water removal unit configured to remove water by causing the natural gas to flow through a packed bed containing a water adsorbent. The packed bed contains a carbon dioxide adsorbent for adsorbing and removing the carbon dioxide that has not been completely removed in the carbon dioxide removal unit, and a concentration of the carbon dioxide contained in the natural gas is measured by an outlet-side carbon dioxide measurement unit on an outlet side of the water removal unit.

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

It has been discovered that mixed-alcohol production can utilize the waste tail gas stream from the pressure-swing adsorption section of an industrial hydrogen plant. Some variations provide a process for producing mixed alcohols, comprising: obtaining a tail-gas stream from a methane-to-syngas unit (e.g., a steam methane reforming reactor); compressing the tail-gas stream; separating the tail-gas stream into at least a syngas stream, a CO.sub.2-rich stream, and a CH.sub.4-rich stream; introducing the syngas stream into a mixed-alcohol reactor operated at effective alcohol synthesis conditions in the presence of an alcohol-synthesis catalyst, thereby generated mixed alcohols; and purifying the mixed alcohols to generate a mixed-alcohol product. Other variations provide a process for producing clean syngas, comprising: obtaining a tail-gas stream from a methane-to-syngas unit; compressing the tail-gas stream; separating the tail-gas stream into at least a syngas stream, a CO.sub.2-rich stream, and a CH.sub.4-rich stream; and recovering a clean syngas product.

A process for recovering sulfur and carbon dioxide from a sour gas stream, the process comprising the steps of: providing a sour gas stream to a membrane separation unit, the sour gas stream comprising hydrogen sulfide and carbon dioxide; separating the hydrogen sulfide from the carbon dioxide in the membrane separation unit to obtain a retentate stream and a first permeate stream, wherein the retentate stream comprises hydrogen sulfide, wherein the permeate stream comprises carbon dioxide; introducing the retentate stream to a sulfur recovery unit; processing the retentate stream in the sulfur recovery unit to produce a sulfur stream and a tail gas stream, wherein the sulfur stream comprises liquid sulfur; introducing the permeate stream to an amine absorption unit; and processing the permeate stream in the amine absorption unit to produce an enriched carbon dioxide stream.

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.

A process for selectively separating H.sub.2S from a gas mixture which also comprises CO.sub.2is disclosed. A stream of the gas mixture is contacted with an absorbent solution comprising one or more amines, alkanolamines, hindered alkanolamines, capped alkanolamines, or mixtures thereof. The H.sub.2S/CO.sub.2 selectivity of the absorbent solution is preferably greater than about 4.0 for an acid gas loading [mol(CO.sub.2+H.sub.2S)/mol(amine)] between about 0.2 and about 0.6, and is achieved by reducing pH of the absorbent solution.

The present invention relates to a method and a system for the removal of carbon dioxide (CO.sub.2) from solvents. In particular, the present invention relates to a method and a system for the removal of carbon dioxide (CO.sub.2) from carbon dioxide (CO.sub.2) rich solvents.

A process for selectively separating H.sub.2S from a gas mixture which also comprises CO.sub.2 is disclosed. A stream of the gas mixture is contacted with an absorbent solution comprising one or more amines, alkanolamines, hindered alkanolamines, capped alkanolamines, or mixtures thereof. The H.sub.2S/CO.sub.2 selectivity of the absorbent solution is preferably greater than about 4.0 for an acid gas loading [mol(CO.sub.2+H.sub.2S)/mol(amine)] between about 0.2 and about 0.6, and is achieved by reducing pH of the absorbent solution.