EP-4736988-A1 - ACIDIC GAS-ABSORBING LIQUID AND ACIDIC GAS REDUCTION METHOD

Abstract

Provided are an acidic gas absorbing solution and acidic gas reducing method that enable reduction in energy required for recovering an acidic gas from a gas with less impact on solvent loss, even if the gas contains moisture. The acidic gas absorbing solution of the present invention is an acidic gas absorbing solution that reversibly absorbs and desorbs carbon dioxide, the acidic gas absorbing solution containing: an oxygen-containing polymer and an amine compound, wherein the oxygen-containing polymer has at least one group selected from the group consisting of an oxyalkylene group, a carbonate group, and an ester group, has a number-average molecular weight of 250 to 20000, has a boiling point of 200°C or more, and has a solubility parameter of 15.0 (MPa) 1/2 or more and less than 19.5 (MPa) 1/2 , and the amine compound has a solubility parameter of 13.0 to 25.5 (MPa) 1/2 .

Inventors

• IKAWA, Seiya
• SUZUKI, TOYOKAZU
• KOGUCHI, RYOHEI
• MACHIDA, HIROSHI
• NORINAGA, Koyo

Assignees

• AGC INC.
• NATIONAL UNIVERSITY CORPORATION TOKAI NATIONAL HIGHER EDUCATION AND RESEARCH SYSTEM

Dates

Publication Date

20260506

Application Date

20240612

Claims (8)

1. An acidic gas absorbing solution that reversibly absorbs and desorbs carbon dioxide, the acidic gas absorbing solution comprising: an oxygen-containing polymer; and an amine compound, wherein the oxygen-containing polymer has at least one group selected from the group consisting of an oxyalkylene group, a carbonate group, and an ester group, has a number-average molecular weight of 250 to 20000, has a boiling point of 200°C or more, and has a solubility parameter of 15.0 (MPa) 1/2 or more and less than 19.5 (MPa) 1/2 , and the amine compound has a solubility parameter of 13.0 to 25.5 (MPa) 1/2 .
2. The acidic gas absorbing solution according to claim 1, wherein the oxygen-containing polymer has a group represented as -OR at a terminus, the R is a hydrogen atom or a bonding group having 1 to 8 carbon atoms, and the bonding group is optionally linear or branched, optionally has an unsaturated bond, and optionally contains at least either one of a nitrogen atom and an oxygen atom.
3. The acidic gas absorbing solution according to claim 1, wherein the oxygen-containing polymer is at least one selected from the group consisting of polyether monool, polyether polyol, polyester polyol, polycarbonate polyol, and polyether polycarbonate polyol.
4. The acidic gas absorbing solution according to claim 1, wherein a difference between the solubility parameter of the oxygen-containing polymer and the solubility parameter of the amine compound is 7.0 (MPa) 1/2 or less.
5. The acidic gas absorbing solution according to claim 1, comprising the oxygen-containing polymer in an amount of 5 to 90% by mass and the amine compound in an amount of 5 to 90% by mass.
6. The acidic gas absorbing solution according to claim 1, for a recovery and/or separation process for an acidic gas.
7. An acidic gas reducing method, wherein the acidic gas absorbing solution according to any one of claims 1 to 6 and a gas comprising carbon dioxide and moisture are brought into contact to reduce carbon dioxide in the gas.
8. The acidic gas reducing method according to claim 7, wherein an organic phase comprising the oxygen-containing polymer and the amine compound is recovered from the acidic gas absorbing solution that has undergone phase separation through contact with the gas comprising carbon dioxide and moisture, and the organic phase is reused as an acidic gas absorbing solution for bringing into contact with a gas comprising carbon dioxide and water.

Description

Technical Field The present invention relates to an acidic gas absorbing solution and acidic gas reducing method that are useful for reducing an acidic gas in a gas. Background Art Known as a method for recovering an acidic gas, which is typified by carbon dioxide, from a gas is a method of absorbing and separating an acidic gas by using an acidic gas absorbing solution (hereinafter, also referred to as an absorbing solution, simply) containing an amine compound and an organic solvent, and desorbing the acidic gas absorbed in the absorbing solution from the absorbing solution by heating and recovering the acidic gas. Such an absorbing solution, which is also called a chemical absorbing solution, utilizes reversible reaction of formation and regeneration of an amine salt by an amine compound. From the viewpoint of energy saving for such acidic gas recovering methods, various methods have been proposed for reducing energy required for heating in desorbing an acidic gas from an absorbing solution. For example, PTL1 proposes a method of using an absorbing solution containing an amine compound and an organic solvent having a difference in solubility parameter from the amine compound within a specific range. In this method, a combination of an amine compound and an alcohol such as 1-butanol and 1-pentanol or an ether such as diethylene glycol diethyl ether is selected, thereby allowing a phenomenon in which an acidic gas-absorbed solution undergoes phase separation into a high-acidic-gas-content phase and a low-acidic-gas-content phase to be utilized. According to PTL1, heating the high-acidic-gas-content phase selectively for acidic gas desorption treatment reduces energy required for recovering the acidic gas compared to the case in which acidic gas desorption treatment is performed on the entire absorbing solution. Citation List Patent Literature PTL1: JP 6460974 B Summary of Invention Technical Problem Exhaust gases from thermal power plants and various industrial processes contain water vapor (moisture) in most cases. Accordingly, recovery of an acidic gas from such an exhaust gas requires a step of removing moisture in advance by heating treatment or the like. When reusing an absorbing solution, the absorbing solution is regenerated by allowing the absorbing solution to absorb an acidic gas from an exhaust gas containing moisture, and then subjecting the absorbing solution to acidic gas desorption treatment and separation and removal of moisture. In evaporating moisture by heating an exhaust gas or an absorbing solution to remove moisture, huge energy is required for heating in any cases. Even if a high-acidic-gas-content phase is heated solely for performing acidic gas desorption treatment using the absorbing solution described in PTL1, energy required for heating could not be sufficiently reduced due to the latent heat of water. In addition, in the absorbing solution described in PTL1, when an organic solvent as a component contained therein volatilizes, heating for absorbing solution regeneration through acidic gas desorption increases cost for a process to recover the solvent that has volatilized or for replenishing the organic solvent. Moreover, the absorbing solution has poor regeneration efficiency for reuse. The present invention has been made to solve such a problem, and an object of the present invention is to provide an acidic gas absorbing solution and acidic gas reducing method that enable reduction in energy required for recovering an acidic gas from a gas with less negative influence on solvent loss, even if the gas contains moisture. Solution to Problem The present invention is based on a finding that when an acidic gas absorbing solution containing a combination of a specific hydrophobic oxygen-containing polymer and an aqueous amine compound having a specific solubility parameter is allowed to absorb carbon dioxide, the acidic gas absorbing solution undergoes phase separation into an aqueous phase and an organic phase having carbon dioxide absorbed therein. The present invention provides the following means. [1] An acidic gas absorbing solution that reversibly absorbs and desorbs carbon dioxide, the acidic gas absorbing solution comprising: an oxygen-containing polymer; and an amine compound, wherein the oxygen-containing polymer has at least one group selected from the group consisting of an oxyalkylene group, a carbonate group, and an ester group, has a number-average molecular weight of 250 to 20000, has a boiling point of 200°C or more, and has a solubility parameter of 15.0 (MPa)1/2 or more and less than 19.5 (MPa)1/2, and the amine compound has a solubility parameter of 13.0 (MPa)1/2 to 25.5 (MPa)1/2.[2] The acidic gas absorbing solution according to [1], wherein the oxygen-containing polymer has a group represented as -OR at a terminus, the R is a hydrogen atom or a bonding group having 1 to 8 carbon atoms, and the bonding group is optionally linear or branched, optionally has an un