A solution including at least one mixed acetal compound is used to remove hydrogen sulfide and/or mercaptans from a fluid stream, preferably a fluid gas stream. A mixed acetal compound, as provided in the general structure below, includes an N-glycosidic type bond. The mixed acetal includes nitrogen and oxygen as provided below. ##STR00001##

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

Provided is a method for treating an oil gas, which can realize high-efficiency separation for and recovery of gasoline components, C.sub.2, C.sub.3, and C.sub.4 components. The method first conducts separation of light hydrocarbon components from gasoline components, and then performs subsequent treatment on a stream rich in the light hydrocarbon components, during which it is no longer necessary to use gasoline to circularly absorb liquefied gas components, which significantly reduces the amount of gasoline to be circulated and reduces energy consumption throughout the separation process. Besides, in this method, impurities, such as H.sub.2S and mercaptans, in the stream rich in the light hydrocarbon components are removed first before the separation for the components. This ensures that impurities will not be carried to a downstream light hydrocarbon recovery section, thus avoiding corrosion issues caused by hydrogen sulfide in the light hydrocarbon recovery section.

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 absorbent for absorbing CO.sub.2 or H.sub.2S, or both of CO.sub.2 and H.sub.2S in a gas contains, as components, (a) a secondary linear monoamine, (b) a tertiary linear monoamine, and (c) a secondary cyclic diamine. When the concentration of the secondary linear monoamine (a) is more than 30% by weight and less than 45% by weight and the concentration of the tertiary linear monoamine (b) is more than 15% by weight and less than 30% by weight, absorbability of CO.sub.2 or H.sub.2S, or both of CO.sub.2 and H.sub.2S is good, and releasability of CO.sub.2 or H.sub.2S that have been absorbed during regeneration of the absorbent is good. The amount of steam of a reboiler used during regeneration of the absorbent in a CO2 recovery unit can be thus reduced.

The embodiments provide an acidic gas absorbent kept from deterioration, an acidic gas removal method using the absorbent, and an acidic gas removal apparatus using the same. The acidic gas absorbent contains an amine compound and water, and further contains superfine bubble containing inert gas wherein an average diameter of said superfine bubble is 150 nm or less. The acidic gas removal method provided here employs that absorbent. The acidic gas removal apparatus is equipped with a unit for introducing the superfine bubbles into the absorbent.

Disclosed is an absorbent containing an amine for absorption of an acid gas in a biogas, and a biogas purification system using the same.

Disclosed herein are scavenging compounds and compositions useful in applications relating to the production, transportation, storage, and separation of crude oil and natural gas. Also disclosed herein are methods of using the compounds and compositions as scavengers, particularly in applications relating to the production, transportation, storage, and separation of crude oil and natural gas.

A method for generating Renewable Natural Gas (RNG) from raw biogas is disclosed, in which carbon dioxide is removed from biogas to generate pipeline specification RNG by a combination of absorption and membrane processes. The absorption process provides for the initial bulk carbon dioxide removal. The membrane process provides for the simultaneous removal of carbon dioxide and water vapors to pipeline specification. The method is characterized by a reduced separation energy consumption as compared to stand-alone membrane and absorption unit separations for biogas upgrading.

A gas treatment method includes an absorption step in which a gas to be treated containing an acidic compound, such as carbon dioxide, is brought into contact, in an absorber, with a treatment liquid that absorbs the acidic compound; and a regeneration step in which the treatment liquid, having the acidic compound absorbed therein, is sent to a regenerator, and the treatment liquid is then heated to separate the acidic compound from the treatment liquid. In the regeneration step, a gas almost insoluble to the treatment liquid, such as hydrogen gas, is brought into contact with the treatment liquid.