JP5467394B2 - Carbon dioxide separation and recovery method by physical absorption method using ionic liquid - Google Patents
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- 238000000034 method Methods 0.000 title claims description 130
- 238000000926 separation method Methods 0.000 title claims description 117
- 238000010521 absorption reaction Methods 0.000 title claims description 105
- 239000002608 ionic liquid Substances 0.000 title claims description 84
- 238000011084 recovery Methods 0.000 title claims description 62
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title description 116
- 229910002092 carbon dioxide Inorganic materials 0.000 title description 60
- 239000001569 carbon dioxide Substances 0.000 title description 58
- 239000007788 liquid Substances 0.000 claims description 69
- 229910052739 hydrogen Inorganic materials 0.000 claims description 33
- 230000008569 process Effects 0.000 claims description 31
- 150000002430 hydrocarbons Chemical class 0.000 claims description 23
- 229930195733 hydrocarbon Natural products 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 21
- 150000001450 anions Chemical class 0.000 claims description 19
- 150000001768 cations Chemical class 0.000 claims description 19
- 239000004215 Carbon black (E152) Substances 0.000 claims description 16
- -1 alkyl pyridinium Chemical compound 0.000 claims description 15
- 239000002250 absorbent Substances 0.000 claims description 10
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- 238000006477 desulfuration reaction Methods 0.000 claims description 8
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- 125000003277 amino group Chemical group 0.000 claims description 5
- 125000000217 alkyl group Chemical group 0.000 claims description 4
- 238000010924 continuous production Methods 0.000 claims description 4
- 239000011828 neutral ionic liquid Substances 0.000 claims description 4
- 125000005210 alkyl ammonium group Chemical group 0.000 claims description 3
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 claims description 3
- 125000004185 ester group Chemical group 0.000 claims description 3
- 125000001033 ether group Chemical group 0.000 claims description 3
- 125000004417 unsaturated alkyl group Chemical group 0.000 claims description 3
- 125000000524 functional group Chemical group 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 255
- IQQRAVYLUAZUGX-UHFFFAOYSA-N 1-butyl-3-methylimidazolium Chemical compound CCCCN1C=C[N+](C)=C1 IQQRAVYLUAZUGX-UHFFFAOYSA-N 0.000 description 37
- 238000002474 experimental method Methods 0.000 description 34
- 239000001257 hydrogen Substances 0.000 description 30
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 27
- 238000000746 purification Methods 0.000 description 22
- 238000004817 gas chromatography Methods 0.000 description 16
- 229920002565 Polyethylene Glycol 400 Polymers 0.000 description 14
- 238000005516 engineering process Methods 0.000 description 14
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 14
- 239000000243 solution Substances 0.000 description 14
- JLFNLZLINWHATN-UHFFFAOYSA-N pentaethylene glycol Chemical compound OCCOCCOCCOCCOCCO JLFNLZLINWHATN-UHFFFAOYSA-N 0.000 description 12
- 238000011160 research Methods 0.000 description 12
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 11
- 230000008859 change Effects 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- 229910001868 water Inorganic materials 0.000 description 11
- 230000002378 acidificating effect Effects 0.000 description 10
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 10
- 230000036961 partial effect Effects 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 238000005265 energy consumption Methods 0.000 description 9
- 239000012528 membrane Substances 0.000 description 7
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- 238000011161 development Methods 0.000 description 6
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- 230000008929 regeneration Effects 0.000 description 6
- 238000011069 regeneration method Methods 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- 238000011088 calibration curve Methods 0.000 description 5
- 238000007906 compression Methods 0.000 description 5
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- 230000007423 decrease Effects 0.000 description 5
- 238000013461 design Methods 0.000 description 5
- 230000007613 environmental effect Effects 0.000 description 5
- 238000002955 isolation Methods 0.000 description 5
- 125000005010 perfluoroalkyl group Chemical group 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 229920002582 Polyethylene Glycol 600 Polymers 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- RAXXELZNTBOGNW-UHFFFAOYSA-O Imidazolium Chemical compound C1=C[NH+]=CN1 RAXXELZNTBOGNW-UHFFFAOYSA-O 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 150000002431 hydrogen Chemical class 0.000 description 3
- 238000011835 investigation Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229920001223 polyethylene glycol Polymers 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- FHDQNOXQSTVAIC-UHFFFAOYSA-M 1-butyl-3-methylimidazol-3-ium;chloride Chemical compound [Cl-].CCCCN1C=C[N+](C)=C1 FHDQNOXQSTVAIC-UHFFFAOYSA-M 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- KPAMAAOTLJSEAR-UHFFFAOYSA-N [N].O=C=O Chemical compound [N].O=C=O KPAMAAOTLJSEAR-UHFFFAOYSA-N 0.000 description 2
- HYGWNUKOUCZBND-UHFFFAOYSA-N azanide Chemical compound [NH2-] HYGWNUKOUCZBND-UHFFFAOYSA-N 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- YWXYYJSYQOXTPL-SLPGGIOYSA-N isosorbide mononitrate Chemical compound [O-][N+](=O)O[C@@H]1CO[C@@H]2[C@@H](O)CO[C@@H]21 YWXYYJSYQOXTPL-SLPGGIOYSA-N 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 238000012827 research and development Methods 0.000 description 2
- 238000001612 separation test Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 101710134784 Agnoprotein Proteins 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 150000001413 amino acids Chemical class 0.000 description 1
- 238000005349 anion exchange Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 description 1
- 229960001231 choline Drugs 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000003869 coulometry Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 230000009881 electrostatic interaction Effects 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 125000004051 hexyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 150000002460 imidazoles Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 125000002347 octyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000011941 photocatalyst Substances 0.000 description 1
- 229940068918 polyethylene glycol 400 Drugs 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 125000001453 quaternary ammonium group Chemical group 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 230000009919 sequestration Effects 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000002336 sorption--desorption measurement Methods 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- 229910021642 ultra pure water Inorganic materials 0.000 description 1
- 239000012498 ultrapure water Substances 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2
Landscapes
- Gas Separation By Absorption (AREA)
- Carbon And Carbon Compounds (AREA)
Description
本発明は、３成分以上の多成分混合ガスから、室温近辺の温度領域で、二酸化炭素を分離回収することを可能とする二酸化炭素分離回収方法に関するものであり、更に詳しくは、例えば、二酸化炭素−窒素系ガスに硫化水素又は低級の炭化水素系のガスが加わった多成分混合ガスから、イオン液体を用いて、二酸化炭素と硫化水素を同時に、又は二酸化炭素のみを選択的に分離回収する二酸化炭素の分離回収方法に関するものである。本発明は、例えば、化石燃料や天然ガスなどに含まれる多成分混合ガスから、上記温度領域で、二酸化炭素を分離回収する方法や、二酸化炭素の回収や水素の精製システムなどに好適に適用することが可能な多成分混合ガスからの二酸化炭素分離回収技術を提供するものである。 The present invention relates to a carbon dioxide separation and recovery method that makes it possible to separate and recover carbon dioxide from a multicomponent mixed gas of three or more components in a temperature range near room temperature, and more specifically, for example, carbon dioxide -Dioxide that selectively separates and recovers carbon dioxide and hydrogen sulfide at the same time or only from carbon dioxide using a ionic liquid from a multi-component mixed gas in which hydrogen sulfide or a lower hydrocarbon gas is added to nitrogen gas. The present invention relates to a method for separating and recovering carbon. The present invention is suitably applied to, for example, a method for separating and recovering carbon dioxide from a multicomponent mixed gas contained in fossil fuel, natural gas, or the like in the above temperature range, a carbon dioxide recovery, a hydrogen purification system, or the like. The present invention provides a technique for separating and recovering carbon dioxide from a multicomponent gas mixture.
地球温暖化ガスの中心である二酸化炭素を分離回収し、貯留する技術（ＣＣＳ）は、京都議定書の発効に見られるように、産業界のみならず社会的にも重要視されており、その研究開発は、国際的な課題となっている。このＣＣＳプロセスでは、二酸化炭素の分離回収に掛かるエネルギーは、特に大きく、全体の７０％近くにのぼると予想され、一層の低エネルギー化、低コスト化が望まれている。現在、アミノ基を持つ特定のアミン類化合物を用いた化学吸収法が、実用化に向けて、試験段階にあるが、この種の方法は、二酸化炭素再生プロセスでのエネルギー消費が著しく、新規な吸収液の開発が高く期待されている。 The technology that separates, collects and stores carbon dioxide (CCS), the center of global warming gas (CCS), is seen not only by the industrial world but also by society, as seen in the enforcement of the Kyoto Protocol. Development has become an international issue. In this CCS process, the energy required for the separation and recovery of carbon dioxide is particularly large and is expected to reach nearly 70% of the total, and further reduction in energy and cost is desired. At present, a chemical absorption method using a specific amine compound having an amino group is in a test stage for practical application. However, this type of method has a significant energy consumption in the carbon dioxide regeneration process, and is a novel method. The development of absorbent is highly expected.
一方、物理吸収による方法については、これまで、ＳＥＬＥＸＳＯＬ法によるケーススタディがあるのみで、ほとんど技術開発が進んでいない状況にあり、多くの研究課題が残されている。また、これまでに検討されている技術のほとんどは、二酸化炭素を常圧のガスとして回収するものであり、貯留や隔離を考えた場合には、高圧状態に圧縮する必要があり、そのためのエネルギーやコストも別に必要となる。 On the other hand, as for the method by physical absorption, there are only case studies based on the SELEXSOL method so far, and there is almost no technological development, and many research subjects remain. In addition, most of the technologies that have been studied so far recover carbon dioxide as a normal pressure gas, and when storage or sequestration is considered, it is necessary to compress it to a high pressure state. And costs are also required separately.
他方、水素燃料は、次世代のクリーンエネルギー源として注目され、燃料電池や水素燃料、自動車などへの応用研究が行なわれているが、それに伴い、水電解や光触媒など種々の方法を用いた水素製造技術の開発研究が盛んに進められている。その中でも、炭化水素系化合物を水蒸気あるいは部分酸化により改質し、引き続き、水性ガスシフト反応（ＣＯ＋Ｈ２Ｏ→ＣＯ２＋Ｈ２）により水素を製造する方法は広く用いられている。この場合、エネルギー源となる水素の製造に伴い副生される二酸化炭素の分離は必須であり、分離効率の改善は、水素製造コストを大幅に向上するものと期待される。 On the other hand, hydrogen fuel has been attracting attention as a next-generation clean energy source, and application research to fuel cells, hydrogen fuel, automobiles, etc. has been conducted, and accordingly, hydrogen using various methods such as water electrolysis and photocatalyst is used. Research and development of manufacturing technology is actively underway. Among them, a method is widely used in which hydrocarbon compounds are reformed by steam or partial oxidation and subsequently hydrogen is produced by a water gas shift reaction (CO + H 2 O → CO 2 + H 2 ). In this case, separation of carbon dioxide produced as a by-product in the production of hydrogen as an energy source is essential, and improvement in separation efficiency is expected to greatly increase hydrogen production costs.
これまで、水素精製技術として、圧力スイング吸着、膜分離、深冷分離などの方法が検討されているが、物理吸収法による研究例は見当たらないのが実情である。今後、水素の貯蔵や輸送などの観点から、高圧水素の需要が益々増加すると予想される。イオン液体を用いた物理吸収による分離精製法は、圧縮状態にある高圧ガスの処理に、非常に好適であり、クリーンな水素社会の実現に向けた重要技術と云える。 So far, methods such as pressure swing adsorption, membrane separation, and cryogenic separation have been studied as hydrogen purification techniques, but there are no examples of research using the physical absorption method. In the future, the demand for high-pressure hydrogen is expected to increase from the viewpoint of hydrogen storage and transportation. Separation and purification by physical absorption using an ionic liquid is very suitable for the treatment of high-pressure gas in a compressed state, and can be said to be an important technique for realizing a clean hydrogen society.
従来、先行技術として、例えば、イオン液体を主成分とした吸収液を用いて、酸性ガスと非酸性ガスからなる混合ガスを接触させて、酸性ガスを吸収させて分離精製するための吸収液について提案されている（特許文献１）。この文献では、アミノ基を持つイオン液体を用いて、化学吸収法により酸性ガスを除去しており、物理吸収によるガス分離精製法とは異なるものである。 Conventionally, as a prior art, for example, an absorbing liquid for separating and purifying an acidic gas by contacting the mixed gas composed of an acidic gas and a non-acidic gas by using an absorbing liquid mainly composed of an ionic liquid. It has been proposed (Patent Document 1). In this document, an acidic gas is removed by a chemical absorption method using an ionic liquid having an amino group, which is different from a gas separation purification method by physical absorption.
また、イオン液体を主成分とした吸収液を用いて、酸性ガスと非酸性ガスからなる混合ガスを接触させて、酸性ガスを吸収させて分離精製するための吸収液、及びその方法と装置について提案されている（特許文献２）。この方法は、イオン液体を用いた物理吸収によるガス分離精製法であるが、この方法では、吸収塔と再生塔とを用いて、ガスの分離精製を行っており、二酸化炭素を液化炭酸ガスとして回収することを目的としたプロセスである。 Also, an absorbing liquid for absorbing and separating an acidic gas by contacting a mixed gas composed of an acidic gas and a non-acidic gas using an absorbing liquid containing an ionic liquid as a main component, and a method and apparatus thereof. It has been proposed (Patent Document 2). This method is a gas separation purification method by physical absorption using an ionic liquid. In this method, gas separation and purification are performed using an absorption tower and a regeneration tower, and carbon dioxide is used as liquefied carbon dioxide gas. It is a process aimed at recovery.
これまでの研究（非特許文献１、２）により、イオン液体は、従来の物理吸収液より、優れた二酸化炭素吸収量を持つことが明らかとされている。例えば、従来の物理吸収液の代表的なものとしては、Ｓｅｌｅｘｏｌ法の呼称で知られるポリエチレングリコールをジメチルエステル化した吸収液などが挙げられる。 From previous studies (Non-Patent Documents 1 and 2), it has been clarified that the ionic liquid has a carbon dioxide absorption superior to that of the conventional physical absorption liquid. For example, a typical example of a conventional physical absorption liquid includes an absorption liquid obtained by dimethyl esterification of polyethylene glycol, which is known as the Selexol method.
それと類似の化学構造を有する、分子量が約４００と６００のポリエチレングリコールであるＰＥＧ４００、ＰＥＧ６００の二酸化炭素溶解度を、典型的な疎水性のイオン液体である、１−ブチル−３−メチルイミダゾリウム ビス（トリフルオロスルホニル）アミド（［ＢＭＩＭ］［Ｔｆ２Ｎ］）と比較すると、これらの吸収液の二酸化炭素溶解度は、モル分率表示では、顕著な違いが観察されない。 The carbon dioxide solubility of PEG400, PEG600, a polyethylene glycol having a similar chemical structure and a molecular weight of about 400 and 600, is compared with the typical hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis ( Compared with trifluorosulfonyl) amide ([BMIM] [Tf 2 N]), the carbon dioxide solubility of these absorbents is not significantly different in terms of mole fraction.
一方、二酸化炭素の溶解度を、吸収液の単位体積当りの二酸化炭素質量として表示すると、分子性の吸収液である、ＰＥＧ４００やＰＥＧ６００に対して、イオン液体［ＢＭＩＭ］［Ｔｆ２Ｎ］は、極めて高い二酸化炭素吸収量を示す。この結果は、従来の分子性の吸収液と比べて、イオン液体は、非常に高密度、かつ高濃度の吸収液であるため、単位体積当たりの濃度に換算した時に、極めて高いガス吸収量を示すことを意味する。 On the other hand, when the solubility of carbon dioxide is expressed as the mass of carbon dioxide per unit volume of the absorbing solution, the ionic liquid [BMIM] [Tf 2 N] is extremely different from the molecular absorbing solution PEG400 or PEG600. High carbon dioxide absorption. As a result, compared to conventional molecular absorption liquids, ionic liquids are very high-density and high-concentration absorption liquids. Therefore, when converted to concentrations per unit volume, extremely high gas absorption is achieved. It means to show.
ＰＥＧ４００、ＰＥＧ６００、並びに［ＢＭＩＭ］［Ｔｆ２Ｎ］のモル質量、密度、濃度、モル体積で比較すると、［ＢＭＩＭ］［Ｔｆ２Ｎ］は、ＰＥＧ４００やＰＥＧ６００に比べて、かなり濃度が高く、モル体積が小さいが、このことは、イオン液体中で、カチオンとアニオンは、静電的な相互作用により、かなり凝集し、過密な状態にあることを示している（非特許文献１−４）。 When compared in terms of the molar mass, density, concentration, and molar volume of PEG400, PEG600, and [BMIM] [Tf 2 N], [BMIM] [Tf 2 N] has a considerably higher concentration compared to PEG400 and PEG600. Although the volume is small, this indicates that in the ionic liquid, the cation and the anion are considerably aggregated due to electrostatic interaction and are in a dense state (Non-Patent Documents 1-4).
イオン液体の物理吸収法では、単位体積当りのガス吸収量が、実際のプロセスの処理量の目安となるため、上記の比較は、非常に重要である。また、同様にして、高二酸化炭素吸収性イオン液体の分子設計を進める上でも、イオン液体の単位体積当りの二酸化炭素吸収量が重要である。しかし、これまでのイオン液体の二酸化炭素溶解度のほとんどが、モル分率あるいは質量濃度で報告されている（非特許文献１、２）。イオン液体のガス吸収において、体積（密度）に関して記載されている文献（非特許文献３、６−８）は、極めて少ない。 In the physical absorption method of an ionic liquid, the above-mentioned comparison is very important because the gas absorption amount per unit volume is a measure of the actual process throughput. Similarly, the amount of carbon dioxide absorbed per unit volume of the ionic liquid is important in advancing the molecular design of the high carbon dioxide-absorbing ionic liquid. However, most carbon dioxide solubility of ionic liquids so far has been reported in terms of molar fraction or mass concentration (Non-Patent Documents 1 and 2). In the gas absorption of ionic liquids, there are very few documents (Non-patent Documents 3 and 6-8) related to volume (density).
ここで、それらについて、簡単に言及すると、Ｂｒｅｎｎｅｃｋｅら（非特許文献３、６）は、［ＢＭＩＭ］＋を、カチオンとして、種々のアニオンとの組み合わせのイオン液体［ＢＭＩＭ］Ｘの二酸化炭素吸収量について報告をしている。この文献では、モル分率表記では、二酸化炭素の溶解度は、次の順序、［ＮＯ３］−＜［Ｎ（ＣＮ）２］−，［ＢＦ４］−＜［ＣＦ３ＳＯ３］−＜［ＰＦ６］−＜［Ｎ（ＣＦ３ＳＯ２）２］−，［Ｃ（ＣＦ３ＳＯ２）３］−で、大きくなることが示されている。 Briefly referring to them, Brennecke et al. (Non-Patent Documents 3 and 6) show that carbon dioxide absorption amount of ionic liquid [BMIM] X in combination with various anions using [BMIM] + as a cation. Has reported on. In this document, in terms of molar fraction notation, the solubility of carbon dioxide is expressed in the following order: [NO 3 ] − <[N (CN) 2 ] − , [BF 4 ] − <[CF 3 SO 3 ] − <[ PF 6 ] − <[N (CF 3 SO 2 ) 2 ] − , [C (CF 3 SO 2 ) 3 ] − , indicating an increase.
すなわち、ペルフルオロアルキル（ＣＦ３）基の導入により、二酸化炭素吸収量は、増加する。一方で、ペルフルオロアルキル基を導入すると、イオン液体そのもののモル体積も一般に増加するため、単位体積当りの二酸化炭素濃度とすると、その差は小さくなる。しかし、それでも、ＣＦ３基を有するアニオンの二酸化炭素吸収量は高くなり、次の順序、［ＮＯ３］−＜［Ｎ（ＣＮ）２］−，［ＢＦ４］−，［ＣＦ３ＳＯ３］−＜［ＰＦ６］−，［Ｃ（ＣＦ３ＳＯ２）３］−，［Ｎ（ＣＦ３ＳＯ２）２］−で、大きくなることが示されている。 That is, the amount of carbon dioxide absorbed increases by the introduction of a perfluoroalkyl (CF 3 ) group. On the other hand, when a perfluoroalkyl group is introduced, the molar volume of the ionic liquid itself generally increases. Therefore, when the carbon dioxide concentration per unit volume is used, the difference becomes small. However, the amount of carbon dioxide absorbed by the anion having a CF 3 group is still high, and the following order: [NO 3 ] − <[N (CN) 2 ] − , [BF 4 ] − , [CF 3 SO 3 ] − <[PF 6 ] − , [C (CF 3 SO 2 ) 3 ] − , and [N (CF 3 SO 2 ) 2 ] − are shown to increase.
これらと同様に、イミダゾリウムカチオンの側鎖のアルキル基を、ブチル、ヘキシル、オクチルと延長した場合に、二酸化炭素吸収量がどのような影響を受けるかについては、モル分率でも、体積濃度ベースでも、ほとんど変化がないことが明らかとされている。 Similarly, how the carbon dioxide absorption is affected when the side chain alkyl group of the imidazolium cation is extended to butyl, hexyl, and octyl. But it is clear that there is little change.
更に、Ｂｒｅｎｎｅｃｋｅら（非特許文献７）は、多種多様のカチオンとアニオンから構成されるイオン液体の二酸化炭素吸収量について、アニオンとしては、上述の［Ｎ（ＣＦ３ＳＯ２）２］−（＝［Ｔｆ２Ｎ］−）に加え、ＰＦ６ −の３つのＦをＣ２Ｆ５やＣ４Ｆ９で置換した［ｅＦＡＰ］−や［ｂＦＡＰ］−が、良好な二酸化炭素収特性持つことを示している。また、この文献では、イミダゾリウムカチオンの側鎖をフッ素化した、［Ｃ６Ｈ４Ｆ９ＭＩＭ］＋も、大きな二酸化炭素吸収量を有している。これらの結果は、カチオン及びアニオンどちらのイオン種の場合にも、ペルフルオロアルキル基の導入が、二酸化炭素吸収量を増加させる上で、有効な手段であることが示されている。 Furthermore, Brenneecke et al. (Non-patent Document 7) described the above-mentioned [N (CF 3 SO 2 ) 2 ] − (= as the anion for the carbon dioxide absorption amount of an ionic liquid composed of various cations and anions. In addition to [Tf 2 N] − ), [eFAP] − and [bFAP] − in which three Fs of PF 6 − are replaced by C 2 F 5 and C 4 F 9 have good carbon dioxide yield characteristics. Show. In this document, [C 6 H 4 F 9 MIM] + , which is a fluorinated side chain of an imidazolium cation, also has a large carbon dioxide absorption. These results indicate that the introduction of a perfluoroalkyl group is an effective means for increasing the carbon dioxide absorption amount for both cation and anion ionic species.
一方、この文献では、［Ｔｆ２Ｎ］−を、アニオンとして固定し、カチオンを、［ＢＭＩＭ］＋から、［Ｎ４１１１］＋や［ｃｈｏｌｉｎｅ］＋などの４級アンモニウム系や、［ｂ２−Ｎｉｃ］＋にしても、ほぼ同等の二酸化炭素吸収量が得られることも指摘されている。これらのイオン液体の二酸化炭素吸収量は、Ｓｅｌｅｘｏｌ吸収液の値である４０ｇ−二酸化炭素／ｄｍ３（３．５ＭＰａ，４０℃）の２倍を容易に超えて、同条件で、〜１００ｇ−二酸化炭素／ｄｍ３に達するものである。 On the other hand, in this document, [Tf 2 N] − is fixed as an anion, and the cation is changed from [BMIM] + to a quaternary ammonium series such as [N 4111 ] + and [choline] +, or [b2-Nic]. It is also pointed out that even if + , almost the same amount of carbon dioxide absorption can be obtained. The amount of carbon dioxide absorbed by these ionic liquids easily exceeds twice the value of 40 g-carbon dioxide / dm 3 (3.5 MPa, 40 ° C.), which is the value of Selexol absorbent, and ˜100 g-dioxide under the same conditions. Carbon / dm 3 is reached.
このように、従来、イオン液体は、従来の物理吸収液より優れた二酸化炭素吸収量を持つことが知られているが、従来の研究例は、基本的には、イオン液体による二酸化炭素単独ないし２成分以下の混合ガスからの物理吸収による二酸化炭素の吸収性に関する研究に限られており、３成分以上の多成分混合ガスとして、二酸化炭素−窒素系ガスに他の成分ガスが共存する多成分混合ガス系からの二酸化炭素吸収性については報告例は無く、特に、硫化水素や低級炭化水素を含む多成分混合ガスからの二酸化炭素吸収性に関する研究例は報告されていない。従来、硫化水素あるいはハイドロカーボンを含んだ多成分ガスから二酸化炭素を分離吸収することは、単成分（Ｎ２／ＣＯ２）の場合に比べて非常に困難であり、脱硫プロセスや多段プロセスを採用することが不可欠とされていた。例えば、硫化水素あるいは低級の炭化水素を含んだ多成分混合ガス系では、硫化水を含む硫化水素系混合ガスの処理においては、脱硫プロセスが必要となると云う問題があり、また、低級の炭化水素系混合ガスの処理においては、メタンなどの炭化水素を分離するために、多段プロセスが必要となると云う問題があり、当技術分野においては、そのような脱硫プロセスや多段プロセスが不要で、高コストの設備を必要とすること無しに、しかも、硫化水素や低級の炭化水素の混入無しに、高精度に、二酸化炭素を分離回収することを可能とする、高精度、高効率、省エネルギーの低環境負荷型のプロセスで、３成分以上の多成分混合ガスからの二酸化炭素分離回収技術を開発することが強く要請されていた。 Thus, conventionally, ionic liquids are known to have better carbon dioxide absorption than conventional physical absorption liquids, but conventional research examples are basically carbon dioxide alone or ionic liquids. It is limited to research on carbon dioxide absorption by physical absorption from a gas mixture of 2 or less components, and as a multi-component gas mixture of 3 or more components, other components gas coexist with carbon dioxide-nitrogen gas There has been no report on carbon dioxide absorption from mixed gas systems, and in particular, there has been no report on research on carbon dioxide absorption from multi-component mixed gas containing hydrogen sulfide and lower hydrocarbons. Conventionally, it is very difficult to separate and absorb carbon dioxide from multi-component gas containing hydrogen sulfide or hydrocarbon, compared to the case of single component (N 2 / CO 2 ), and desulfurization process or multi-stage process is adopted. It was essential to do. For example, in a multi-component mixed gas system containing hydrogen sulfide or lower hydrocarbons, there is a problem that a desulfurization process is required in the treatment of a hydrogen sulfide mixed gas containing sulfurized water. In the processing of mixed gas, there is a problem that a multi-stage process is required to separate hydrocarbons such as methane. In this technical field, such a desulfurization process and a multi-stage process are not required, and the cost is high. High-precision, high-efficiency, low-energy environment that enables high-precision separation and recovery of carbon dioxide without the need for equipment and without the incorporation of hydrogen sulfide or lower hydrocarbons There has been a strong demand for the development of carbon dioxide separation and recovery technology from multi-component mixed gas of three or more components in a load type process.
このような状況の中で、本発明者らは、上記従来技術に鑑みて、物理吸収を原理とした低環境負荷型の分離回収プロセスにより３成分以上の多成分混合ガスからの二酸化炭素を分離回収する技術を開発することを目標として鋭意研究を積み重ねた結果、イオン液体を用いた二酸化炭素分離回収方法を開発することに成功し、本発明を完成するに至った。本発明は、物理吸収を原理とした低環境負荷型の分離回収プロセスにより３成分以上の多成分混合ガスからの二酸化炭素ガスを、イオン液体吸収液に接触させることにより、省エネルギー、低コストで分離回収することを可能とする二酸化炭素分離回収方法を提供することを目的とするものである。尚、本明細書では、二酸化炭素をＣＯ２、二酸化炭素−窒素系をＣＯ２−Ｎ２系、硫化水素をＨ２Ｓ、メタンをＣＨ４と記載することがある。 Under such circumstances, the present inventors separated carbon dioxide from a multicomponent mixed gas of three or more components by a low environmental load type separation and recovery process based on the principle of physical absorption in view of the above-described conventional technology. As a result of intensive research aimed at developing a technology for recovery, the inventors succeeded in developing a carbon dioxide separation and recovery method using an ionic liquid, and completed the present invention. In the present invention, carbon dioxide gas from a multi-component mixed gas of three or more components is brought into contact with the ionic liquid absorption liquid by a low environmental load type separation and recovery process based on the principle of physical absorption, thereby separating at low energy and cost. It is an object of the present invention to provide a carbon dioxide separation and recovery method that enables recovery. In this specification, the carbon dioxide CO 2, carbon dioxide - nitrogen based the CO 2 -N 2 system, it is possible to describe hydrogen sulfide H 2 S, methane and CH 4.
上記課題を解決するための本発明は、以下の技術的手段から構成される。
（１）少なくとも３成分から構成される多成分混合ガスから脱硫プロセスや多段プロセスを必要とすること無しにＣＯ２を分離回収する方法であって、
１）中性のイオン液体吸収液を用いた物理吸収法により、少なくともＣＯ ２ −Ｎ ２ 系とＨ ２ Ｓを含む３成分以上の多成分混合ガスから、ＣＯ ２ とＨ ２ Ｓを同時に分離回収し、あるいは、少なくともＣＯ ２ −Ｎ ２ 系と低級の炭化水素系ガスのＣＨ ４ を含む３成分以上の多成分混合ガスから、ＣＯ ２ のみを選択的に分離回収すること、２）ＣＯ ２ を含む多成分混合ガスに対するイオン液体吸収液の流量比（吸収液／ガス）が、０．１〜３の領域で、ガス分離を行うこと、を特徴とするＣＯ２分離回収方法。
（２）ＣＯ２−Ｎ２系とＨ２Ｓを含む３成分以上の多成分混合ガスが、Ｈ２Ｓ／ＣＯ２／Ｎ２から成るＨ２Ｓ系多成分混合ガスであり、ＣＯ２−Ｎ２系と低級の炭化水素系ガスのＣＨ ４ を含む３成分以上の多成分混合ガスが、ＣＨ４／ＣＯ２／Ｎ２から成るＣＨ４系多成分混合ガスである、前記（１）に記載のＣＯ２分離回収方法。
（３）中性のイオン液体吸収液が、陽イオン及び陰イオンからなるイオン液体であり、
１）前記陽イオンが、アルキルアンモニウム、アルキルピリジニウム、アルキルピロリジニウム、アルキルホスホニウム、又はアルキルイミダゾリウム、あるいは、それらアルキル鎖に不飽和アルキル部位、アミノ基、エーテル基、エステル基、又はカルボニル基の官能基がある陽イオンから成る、１種あるいは２種以上の陽イオンであり、
また、２）前記陰イオンが、ＰＦ６ −，ＢＦ４ −，ＣＦ３ＳＯ３ −，ＣＦ３ＣＦ２ＳＯ３ −，（ＣＦ３ＳＯ２）２Ｎ−，（ＣＦ３ＣＦ２ＳＯ２）２Ｎ−，（ＣＦ３ＣＯ）２Ｎ−，（ＣＦ３ＳＯ２）Ｎ（ＣＯＣＦ３）−，ＦＳＯ２ＮＳＯ２Ｆから成る、１種あるいは２種以上の陰イオンである、前記（１）又は（２）に記載のＣＯ２分離回収方法。
（４）温度２５〜６０℃の室温近辺の温度領域で、ガス分離を行う、前記（１）から（３）のいずれか１項に記載のＣＯ２分離回収方法。
（５）圧力１〜４ＭＰａの領域で、ガス分離を行う、前記（１）から（４）のいずれか１項に記載のＣＯ２分離回収方法。
（６）流通式ガス分離装置を用いた連続プロセスにより、多成分混合ガスからＣＯ２を分離回収する、前記（１）から（５）のいずれか１項に記載のＣＯ２分離回収方法。
The present invention for solving the above-described problems comprises the following technical means.
(1) A method for separating and recovering CO 2 from a multi-component mixed gas composed of at least three components without requiring a desulfurization process or a multi-stage process ,
1) Simultaneously separates and collects CO 2 and H 2 S from a multicomponent mixed gas containing at least a CO 2 —N 2 system and H 2 S by a physical absorption method using a neutral ionic liquid absorbent. and, alternatively, from three or more components of a multi-component mixed gas containing CH 4 at least CO 2 -N 2 system and a lower hydrocarbon gas, to selectively separate and recover only CO 2, 2) CO 2 a A CO 2 separation and recovery method , wherein gas separation is performed in a region where the flow rate ratio of the ionic liquid absorbing liquid to the multi-component mixed gas (absorbing liquid / gas) is 0.1 to 3 .
(2) CO 3 or more components of a multi-component mixed gas containing 2 -N 2 system and H 2 S is a H 2 S-based multicomponent gas mixture consisting of H 2 S / CO 2 / N 2, CO 2 - three or more components of a multi-component mixed gas containing CH 4 of N 2 system and a lower hydrocarbon gas is CH 4 system multicomponent gas mixture consisting of CH 4 / CO 2 / N 2, to (1) The CO 2 separation and recovery method described.
( 3 ) The neutral ionic liquid absorbing liquid is an ionic liquid composed of a cation and an anion,
1) The cation is an alkyl ammonium, alkyl pyridinium, alkyl pyrrolidinium, alkyl phosphonium, or alkyl imidazolium, or an alkyl group having an unsaturated alkyl moiety, an amino group, an ether group, an ester group, or a carbonyl group. One or more cations composed of cations with functional groups,
2) The anions are PF 6 − , BF 4 − , CF 3 SO 3 − , CF 3 CF 2 SO 3 − , (CF 3 SO 2 ) 2 N − , and (CF 3 CF 2 SO 2 ) 2. (1) or (1) or two or more types of anions consisting of N − , (CF 3 CO) 2 N − , (CF 3 SO 2 ) N (COCF 3 ) − , FSO 2 NSO 2 F The CO 2 separation and recovery method according to ( 2) .
(4) at a temperature range of a temperature around room temperature 25 to 60 ° C., perform gas separation, CO 2 separation and recovery method according to any one of (1) to (3).
(5) in the region of the pressure 1 to 4 MPa, perform gas separation, CO 2 separation and recovery method according to any one of (1) to (4).
(6) by a continuous process using a flow-type gas separation apparatus, the CO 2 is separated and recovered from a multicomponent gas mixture, CO 2 separation and recovery method according to any one of (1) to (5).
次に、本発明について更に詳細に説明する。
本発明は、３成分以上から構成される多成分混合ガスからＣＯ２を分離回収する方法であって、イオン液体吸収液を用いた物理吸収法により、少なくともＣＯ２−Ｎ２系とＨ２Ｓを含む多成分混合ガス、又はＣＯ２−Ｎ２系と低級の炭化水素系ガスを含む多成分混合ガスから、ＣＯ２とＨ２Ｓ、又はＣＯ２を分離回収することからなるＣＯ２分離回収方法、である。
Next, the present invention will be described in more detail.
The present invention is a method for separating and recovering CO 2 from a multi-component mixed gas composed of three or more components, and at least a CO 2 -N 2 system and H 2 S by a physical absorption method using an ionic liquid absorbent. multicomponent gas mixture containing or multicomponent gas mixture containing CO 2 -N 2 system and a lower hydrocarbon gas, CO 2 and H 2 S, or CO 2 consists of separating and recovering CO 2 separation and recovery Method.
本発明では、少なくともＣＯ２−Ｎ２系とＨ２Ｓを含む多成分混合ガスから、ＣＯ２とＨ２Ｓを同時に分離回収し、あるいは、少なくともＣＯ２−Ｎ２系と低級の炭化水素系ガスを含む多成分混合ガスからＣＯ２のみを選択的に分離回収すること、また、ＣＯ２−Ｎ２系とＨ２Ｓを含む多成分混合ガスが、Ｈ２Ｓ／ＣＯ２／Ｎ２からなるＨ２Ｓ系多成分混合ガスであり、ＣＯ２−Ｎ２系と低級の炭化水素系ガスを含む多成分混合ガスが、ＣＨ４／ＣＯ２／Ｎ２からなるＣＨ４系多成分混合ガスであること、また、低級の炭化水素系ガスが、ＣＨ４であること、を好ましい実施の態様としている。 In the present invention, CO 2 and H 2 S are simultaneously separated and recovered from a multicomponent mixed gas containing at least a CO 2 —N 2 system and H 2 S, or at least a CO 2 —N 2 system and a lower hydrocarbon system Selectively separating and recovering only CO 2 from a multi-component mixed gas containing a gas, and a multi-component mixed gas containing a CO 2 -N 2 system and H 2 S from H 2 S / CO 2 / N 2 becomes H 2 is S-based multicomponent gas mixture, multicomponent mixed gas containing CO 2 -N 2 system and a lower hydrocarbon gas, CH 4 / CO consists 2 / N 2 CH 4 system multicomponent gas mixture In addition, the preferred embodiment is that the lower hydrocarbon gas is CH 4 .
また、本発明は、ＣＯ２を含む多成分混合ガスに対するイオン液体吸収液の流量比（吸収液／ガス）が、０．１〜３の領域で、ガス分離を行うこと、また、温度２５〜６０℃の室温近辺の温度領域で、ガス分離を行うこと、また、圧力１〜４ＭＰａの領域で、ガス分離を行うこと、流通式ガス分離装置を用いた連続プロセスにより、多成分混合ガスからＣＯ２を分離回収すること、を好ましい実施の態様としている。 In the present invention, gas separation is performed in a region where the flow rate ratio of the ionic liquid absorbing liquid to the multicomponent mixed gas containing CO 2 (absorbing liquid / gas) is 0.1 to 3, and the temperature is 25 to 25. By performing gas separation in a temperature region around room temperature of 60 ° C., performing gas separation in a region of pressure of 1 to 4 MPa, and continuous process using a flow-type gas separation device, CO gas is separated from a multicomponent mixed gas. Separating and collecting 2 is a preferred embodiment.
本発明は、イオン液体に、ＣＯ２などを大量に物理吸収させる物理吸収法の手法を利用するものである。イオン液体は、カチオンとアニオンのみから構成され、室温付近以下に融点をもつ溶融塩であり、不揮発性・不燃性の性質を持ち、広い温度範囲で液体状態を維持し、化学的にも安定である。そのため、イオン液体は、蒸気圧がほぼ無視でき、各種ガス相や超臨界流体相へは溶出せず、大気中へのエミッションが無く、低環境負荷の化学プロセスを構築することが可能である。 The present invention utilizes a physical absorption method that physically absorbs a large amount of CO 2 or the like in an ionic liquid. An ionic liquid is a molten salt that consists only of cations and anions, has a melting point below room temperature, has non-volatile and non-flammable properties, maintains a liquid state over a wide temperature range, and is chemically stable. is there. For this reason, the ionic liquid has a substantially negligible vapor pressure, does not elute into various gas phases and supercritical fluid phases, does not emit into the atmosphere, and can construct a chemical process with a low environmental load.
また、イオン液体のガス吸収は、物理的な機構であるため、ガスを加圧、接触することで吸収させることができ、一方、減圧することで、吸収したガスを容易に取り出すことができる。これにより、化学吸収法などで必要となるガス回収のための熱エネルギーを大幅に節約することができ、減圧により吸収したガスを回収した後で、吸収液の再利用が容易である。更に、物理吸収の利点は、吸収量がガスの分圧に比例することで、特に、高圧ガスの分離・精製プロセスに好適である。 Moreover, since the gas absorption of the ionic liquid is a physical mechanism, it can be absorbed by pressurizing and contacting the gas, while the absorbed gas can be easily taken out by reducing the pressure. Thereby, the thermal energy for gas recovery required in the chemical absorption method or the like can be saved significantly, and the recovered liquid can be easily reused after the gas absorbed by the reduced pressure is recovered. Furthermore, the advantage of physical absorption is that the amount of absorption is proportional to the partial pressure of the gas, which is particularly suitable for high-pressure gas separation and purification processes.
本発明では、この性質を利用し、選択的にガスを吸収する分子ゲート機能を持った分離膜やマイクロリアクターを用いた接触吸収法によるガス分離精製が可能となる。また、イオン液体は、カチオンとアニオンの分子構造を自在に化学修飾できるデザイン溶媒と云われていることから、イオン液体の分子構造を、ＣＯ２分離回収の吸収液として、好適な構造とすることで、一層のプロセスの高効率化が可能となる。 In the present invention, by utilizing this property, gas separation purification by a contact absorption method using a separation membrane or a microreactor having a molecular gate function for selectively absorbing gas becomes possible. In addition, since the ionic liquid is said to be a design solvent that can freely chemically modify the molecular structure of the cation and anion, the molecular structure of the ionic liquid should be a suitable structure as an absorption liquid for CO 2 separation and recovery. Thus, it becomes possible to further increase the efficiency of the process.
近年、イミダゾリウムなどを陽イオンとし、ＰＦ６ −、ＢＦ４ −、（ＣＦ３ＳＯ２）２Ｎ−などを陰イオンとしたイオン液体は、単位体積当たりのＣＯ２などの酸性ガスの吸収量が極めて高く、一方で、Ｈ２やＮ２などの非酸性ガスはほとんど吸収しないことが明らかとされた。したがって、これらのイオン液体を吸収液として用い、混合ガスと接触させることで、ガスの分離精製が可能となると考えられる。 In recent years, an ionic liquid having imidazolium or the like as a cation and PF 6 − , BF 4 − , (CF 3 SO 2 ) 2 N − or the like as an anion absorbs an acidic gas such as CO 2 per unit volume. On the other hand, it was revealed that non-acidic gases such as H 2 and N 2 are hardly absorbed. Therefore, it is considered that separation and purification of the gas can be performed by using these ionic liquids as the absorbing liquid and bringing them into contact with the mixed gas.
また、本発明では、吸収液に１種あるいは２種以上からなるイオン液体が用いられるが、その場合、陽イオンとして、アルキルアンモニウム、アルキルピリジニウム、アルキルピロリジニウム、アルキルホスホニウム、アルキルイミダゾリウム、あるいは、それらアルキル鎖に不飽和アルキル部位、アミノ基、エーテル基、エステル基、カルボニル基などの官能基がある陽イオンなどを用いることが好ましく、また、陰イオンとして、ＰＦ６ −，ＢＦ４ −，ＣＦ３ＳＯ３ −，ＣＦ３ＣＦ２ＳＯ３ −，（ＣＦ３ＳＯ２）２Ｎ−，（ＣＦ３ＣＦ２ＳＯ２）２Ｎ−，（ＣＦ３ＣＯ）２Ｎ−，（ＣＦ３ＳＯ２）Ｎ（ＣＯＣＦ３）−，ＦＳＯ２ＮＳＯ２Ｆなどを用いることが好ましい。 In the present invention, one or more ionic liquids are used as the absorbing liquid. In this case, as the cation, alkyl ammonium, alkyl pyridinium, alkyl pyrrolidinium, alkyl phosphonium, alkyl imidazolium, or In addition, it is preferable to use a cation having an unsaturated alkyl moiety, an amino group, an ether group, an ester group, a carbonyl group or the like in the alkyl chain, and as anions, PF 6 − , BF 4 − , CF 3 SO 3 − , CF 3 CF 2 SO 3 − , (CF 3 SO 2 ) 2 N − , (CF 3 CF 2 SO 2 ) 2 N − , (CF 3 CO) 2 N − , (CF 3 SO 2 ) N (COCF 3 ) − , FSO 2 NSO 2 F or the like is preferably used.
ＣＯ２の分離回収技術については、化学吸収法、吸着法、膜分離法など、様々な方法により研究開発が進められており、エネルギーやコストの低減が図られている。火力発電所などの大規模固定発生源からＣＯ２を分離回収するプロセスでは、アルカノールアミン類やアミノ酸類をＣＯ２吸収液として用いる化学吸収法が、現時点における実用化技術として注目され、既に商用プラントとして、一部稼働している状況にある。 As for the CO 2 separation and recovery technology, research and development have been promoted by various methods such as a chemical absorption method, an adsorption method, and a membrane separation method, and energy and cost have been reduced. In the process of separating and recovering CO 2 from large-scale fixed sources such as thermal power plants, the chemical absorption method using alkanolamines and amino acids as CO 2 absorbents has attracted attention as a practical technology at the present time, and has already been commercialized. As a result, some are in operation.
しかしながら、化学吸収法は、吸収液再生コストが分離回収コストの５０％を占め、エネルギー消費が著しいという問題がある。したがって、コスト削減のため、１００℃以下の室温程度の廃熱源で駆動可能な低エネルギー再生型吸収液の開発が望まれている。また、これまで検討されてきた方法の多くは、ＣＯ２を常圧のガスとして回収するものである。しかし、回収したＣＯ２を貯留・隔離する際には、得られたガスを液体あるいは超臨界状態にある高圧ＣＯ２に変換する必要があり、この過程のエネルギー消費も甚だしいとされている。 However, the chemical absorption method has a problem that the absorption liquid regeneration cost accounts for 50% of the separation and recovery cost, and the energy consumption is significant. Therefore, in order to reduce costs, it is desired to develop a low energy regenerative absorbent that can be driven by a waste heat source of about 100 ° C. or less at room temperature. In addition, many of the methods that have been studied so far are to recover CO 2 as a normal pressure gas. However, when storing and sequestering the recovered CO 2 , it is necessary to convert the obtained gas into liquid or high-pressure CO 2 in a supercritical state, and energy consumption in this process is considered to be significant.
本発明で提案するイオン液体によるＣＯ２分離回収法は、物理吸収を原理とし、室温近辺での圧力操作のみで駆動できるため、従来の吸収液再生エネルギーコストなどを大幅に低減することが可能である。更に、イオン液体法では、回収条件を制御することで、ＣＯ２を高圧状態で回収することができ、貯留、隔離の際の圧縮エネルギーを軽減することができる。本発明者らの試算では、化学吸収法からイオン液体を用いた物理吸収法へ技術転換することにより、分離回収におけるエネルギー消費量が大幅に削減でき、分離回収から貯留、隔離までの技術全体としても、エネルギー消費量の低減が期待できる。 The CO 2 separation and recovery method using an ionic liquid proposed in the present invention is based on the principle of physical absorption and can be driven only by a pressure operation near room temperature, so that it is possible to significantly reduce the conventional absorption liquid regeneration energy cost and the like. is there. Furthermore, in the ionic liquid method, CO 2 can be recovered in a high-pressure state by controlling the recovery conditions, and the compression energy during storage and isolation can be reduced. According to the estimation by the present inventors, the energy consumption in separation and recovery can be significantly reduced by changing the technology from chemical absorption method to physical absorption method using ionic liquid, and as a whole technology from separation and recovery to storage and isolation. However, energy consumption can be expected to be reduced.
水素精製技術としては、これまで、圧力スイング吸着、膜分離、深冷分離などの方法が検討されているが、高圧条件における水素精製については、ほとんど実施の事例が無い。一方、水素の貯蔵や輸送を考えた場合には、高圧水素の需要は、今後、益々増加すると予想される。高圧水素精製では、対象とする混合ガス中の水素分圧を低下させること無く、分離精製を行うことが重要である。 As hydrogen purification techniques, methods such as pressure swing adsorption, membrane separation, and cryogenic separation have been studied so far, but there are almost no examples of hydrogen purification under high pressure conditions. On the other hand, considering the storage and transportation of hydrogen, the demand for high-pressure hydrogen is expected to increase further in the future. In high-pressure hydrogen purification, it is important to perform separation and purification without reducing the hydrogen partial pressure in the target mixed gas.
また、圧力スイング吸着法は、現在最も実用化が進んでいるが、吸脱着において圧力操作が不連続となるため、高圧条件での水素精製に適しているとは云いがたい。また、パラジウムなどの水素透過膜を利用した分離精製法は、一般に、分離膜の前後において圧力差が生じ、供給側より精製後の水素分圧は低くなってしまう。このため、精製した水素の再圧縮が必要となり、エネルギー的に不利となる。 Further, the pressure swing adsorption method is currently most practically used, but it is difficult to say that the pressure swing adsorption method is suitable for hydrogen purification under high pressure conditions because the pressure operation becomes discontinuous in adsorption / desorption. Further, in the separation and purification method using a hydrogen permeable membrane such as palladium, a pressure difference is generally generated before and after the separation membrane, and the hydrogen partial pressure after purification is lower than that on the supply side. This necessitates recompression of the purified hydrogen, which is disadvantageous in terms of energy.
一方、本発明で提案するイオン液体法は、これまでほとんど利用されていなかった物理吸収を原理とした分離回収法であり、イオン液体を混合ガスと接触させることにより、ＣＯ２などを選択的に吸収して取り除くことができる。このため、水素透過膜とは異なり、水素分圧を低下させること無く、高圧水素を精製することが可能である。高圧条件では、水素精製効率の向上が期待され、このことは、水素精製と圧縮を同時に行えることを示唆するものであり、オンサイト型の水素ステーションを想定した場合には、装置をコンパクト化することができ、非常に有利となる。 On the other hand, the ionic liquid method proposed in the present invention is a separation and recovery method based on the principle of physical absorption, which has been rarely used until now. By contacting the ionic liquid with a mixed gas, CO 2 or the like is selectively used. Can be absorbed and removed. For this reason, unlike the hydrogen permeable membrane, it is possible to purify high-pressure hydrogen without reducing the hydrogen partial pressure. Under high pressure conditions, improvement of hydrogen purification efficiency is expected. This suggests that hydrogen purification and compression can be performed at the same time. If an on-site type hydrogen station is assumed, the equipment will be made compact. Can be very advantageous.
本発明では、高ＣＯ２吸収性イオン液体の分子設計、合成を行うために、種々のイオン液体のＣＯ２吸収特性の調査を進めたところ、パーフルオロアルキル（ＣＦ３）基を有するアニオン類（例えば、ビス（トリフルオロスルホニル）アミドアニオン（［（ＣＦ３ＳＯ２）２Ｎ］−）など）から構成されるイオン液体が、優れた性能を示すことが明らかとなった。一方、カチオンは、既存のイミダゾール系以外のものも選択可能であることなどが示された。これらのイオン液体のＣＯ２吸収量は、当初に目標としたＳｅｌｅｘｏｌ吸収液の値である４０ｇ−ＣＯ２／ｄｍ３（３．５ＭＰａ，４０℃）の２倍を超えて、１００ｇ−ＣＯ２／ｄｍ３（同条件）に達するものである。 In the present invention, in order to perform molecular design and synthesis of a high CO 2 -absorbing ionic liquid, investigation of CO 2 absorption characteristics of various ionic liquids has been conducted. As a result, anions having a perfluoroalkyl (CF 3 ) group ( For example, it has been clarified that an ionic liquid composed of a bis (trifluorosulfonyl) amide anion (such as [(CF 3 SO 2 ) 2 N] − )) exhibits excellent performance. On the other hand, it was shown that cations other than the existing imidazole series can be selected. The amount of CO 2 absorbed by these ionic liquids exceeds twice the 40 g-CO 2 / dm 3 (3.5 MPa, 40 ° C.) which is the initially targeted value of Selexol absorbent, and is 100 g-CO 2 / dm 3 (same conditions) is reached.
次に、本発明では、ＣＯ２の選択性を評価するために、イオン液体を用いた物理吸収プロセスにおいて、硫化水素やメタンなどの他成分ガスが共存する場合の影響について、実際に、それらを含んだ混合ガスを用いて、ガス分離試験を行い、評価した。その結果、例えば、Ｈ２Ｓは、ＣＯ２と共に吸収分離されるが、炭化水素のＣＨ４は、ほとんど吸収されないことが明らかとなった。 Next, in the present invention, in order to evaluate the selectivity of CO 2 , in the physical absorption process using an ionic liquid, the effects when other component gases such as hydrogen sulfide and methane coexist are actually A gas separation test was performed and evaluated using the mixed gas. As a result, for example, it was revealed that H 2 S is absorbed and separated together with CO 2 , but the hydrocarbon CH 4 is hardly absorbed.
次に、本発明では、高圧条件における性能評価試験として、イオン液体の物理吸収法によるＣＯ２分離回収条件を調べるために、ガス分離装置を用いて、各温度（２５，４０，６０℃）で、所定圧力（１〜４ ＭＰａ）において、イオン液体の物理吸収法による標準ガス（窒素ベース２５％ＣＯ２）からのＣＯ２分離回収試験を実施した。 Next, in the present invention, as a performance evaluation test under high pressure conditions, in order to investigate the CO 2 separation and recovery conditions by the physical absorption method of ionic liquid, a gas separation device is used at each temperature (25, 40, 60 ° C.). At a predetermined pressure (1 to 4 MPa), a CO 2 separation and recovery test from a standard gas (nitrogen-based 25% CO 2 ) by a physical absorption method of an ionic liquid was performed.
本発明では、イオン液体を用いて、ガス分離装置を用いた物理吸収プロセスでＣＯ２を分離回収することが可能であるが、これに限らず、本発明では、例えば、実施例１に例示したような流通式ガス分離装置を用いた連続プロセスでＣＯ２を分離回収することも適宜可能である。 In the present invention, it is possible to separate and recover CO 2 using an ionic liquid by a physical absorption process using a gas separation device. However, the present invention is not limited to this, and in the present invention, for example, exemplified in Example 1 It is also possible to separate and recover CO 2 in a continuous process using such a flow type gas separation device.
イオン液体を吸収液として用いると、２５％含まれていたＣＯ２は、〜３％近くまで減少し、従来の分子性の吸収液を用いた場合に比べて、ＣＯ２の分離回収量を大幅に改善できることが明らかとなった。また、精製ガス中のＣＯ２濃度は、ガスの全圧（ＣＯ２分圧）を上げても、ほとんど変化せず、高圧ほど、単位吸収液当たりのＣＯ２分離回収量は、大きいことが確認された。 When ionic liquid is used as an absorption liquid, CO 2 contained in 25% is reduced to ~ 3%, and the separation and recovery amount of CO 2 is greatly increased compared with the case of using a conventional molecular absorption liquid. It became clear that it can be improved. In addition, the CO 2 concentration in the purified gas hardly changes even when the total gas pressure (CO 2 partial pressure) is increased, and it is confirmed that the higher the pressure, the larger the amount of CO 2 separated and recovered per unit absorbent. It was done.
次に、本発明では、イオン液体を用いた物理吸収法により、低エネルギーで、ＣＯ２を分離回収するプロセスの基本技術を構築した。これまで、本発明者らの研究（非特許文献１、２）により、イオン液体の物理吸収法では、アミン類化合物を用いた化学吸収法で必要な、ＣＯ２の回収エネルギー（〜１２０℃）が省略でき、消費エネルギーの低減が可能なこと、従来の分子性の吸収液を用いた物理吸収法のように、低温（〜０℃）でガスを吸収させる必要が無く、冷却エネルギーを節約できることなど、種々の利点や優位性が見出されている。 Next, in the present invention, a basic technology of a process for separating and recovering CO 2 with low energy by a physical absorption method using an ionic liquid is constructed. Until now, according to the research of the present inventors (Non-Patent Documents 1 and 2), in the physical absorption method of ionic liquid, the recovery energy of CO 2 (˜120 ° C.) necessary for the chemical absorption method using an amine compound. Can be omitted, energy consumption can be reduced, and there is no need to absorb gas at low temperatures (~ 0 ° C) unlike conventional physical absorption methods using molecular absorption liquids, and cooling energy can be saved. Various advantages and advantages have been found.
本発明では、イオン液体の物理吸収法によるＣＯ２分離回収技術を更に発展させるために、主に、以下の３項目、すなわち、１）高ＣＯ２吸収性イオン液体の分子設計、合成、２）高圧条件における性能評価試験、３）ＣＯ２選択性評価、を中心に、検討を進めて、種々のイオン液体のＣＯ２吸収特性の調査を進めた結果、パーフルオロアルキル（ＣＦ３）基を有するアニオン類（例えば、ビス（トリフルオロスルホニル）アミドアニオン（［（ＣＦ３ＳＯ２）２Ｎ］−）など）から構成されるイオン液体が、優れた性能を示すことを明らかとした。 In the present invention, in order to further develop the CO 2 separation and recovery technology based on the physical absorption method of ionic liquid, the following three items are mainly: 1) Molecular design and synthesis of high CO 2 absorbing ionic liquid, 2) As a result of investigations focusing on performance evaluation tests under high pressure conditions, 3) evaluation of CO 2 selectivity, and investigation of CO 2 absorption characteristics of various ionic liquids, it has a perfluoroalkyl (CF 3 ) group It was clarified that an ionic liquid composed of anions (for example, bis (trifluorosulfonyl) amide anion ([(CF 3 SO 2 ) 2 N] − ) and the like) exhibits excellent performance.
また、本発明では、ガス分離装置を用いて、各温度（２５，４０，６０℃）で、所定圧力（１〜４ＭＰａ）において、イオン液体の物理吸収法による標準ガス（窒素ベース２５％ＣＯ２）からのＣＯ２分離回収試験を実施したが、その結果、イオン液体を吸収液として用いると、２５％含まれていたＣＯ２は、〜３％近くまで減少し、従来の分子性の吸収液を用いた場合に比べて、ＣＯ２の分離回収量を大幅に改善できることが明らかとなった。 In the present invention, a standard gas (nitrogen-based 25% CO 2 ) by a physical absorption method of an ionic liquid is used at a predetermined pressure (1 to 4 MPa) at each temperature (25, 40, 60 ° C.) using a gas separation device. ) CO 2 separation and recovery test was carried out from, as a result, the use of ionic liquids as an absorbing solution, CO 2, which contained 25%, was reduced to 3% near conventional molecular absorption liquid It has been clarified that the amount of CO 2 separated and recovered can be greatly improved as compared with the case of using NO.
また、分析するガス中のＣＯ２濃度は、ガスの全圧（ＣＯ２分圧）を上げても、ほとんど変化せず、吸収液の単位体積当たりのＣＯ２分離回収量は、高圧ほど、大きいことが確認された。更に、本発明では、Ｈ２ＳやＣＨ４などの他成分ガスが共存する場合の影響について、実際に、それらを含んだ混合ガスを用いて、ガス分離試験を行い評価したが、その結果、Ｈ２Ｓは、ＣＯ２と共に吸収分離されるが、炭化水素のＣＨ４は、ほとんど吸収されないことが明らかとなった。 Further, the CO 2 concentration in the gas to be analyzed hardly changes even when the total pressure of the gas (CO 2 partial pressure) is increased, and the amount of CO 2 separated and recovered per unit volume of the absorbing liquid increases as the pressure increases. It was confirmed. Furthermore, in the present invention, the effect when other component gases such as H 2 S and CH 4 coexist was actually evaluated by performing a gas separation test using a mixed gas containing them. It was revealed that H 2 S is absorbed and separated together with CO 2 , but the hydrocarbon CH 4 is hardly absorbed.
従来、多成分混合ガス系では、例えば、Ｈ２Ｓを含むＨ２Ｓ系混合ガスの処理においては、脱硫プロセスが必要となると云う問題があり、また、低級炭化水素系混合ガスの処理においては、炭化水素を分離するために多段プロセスが必要となると云う問題があり、それらのプロセスにより、高エネルギー消費、高コスト化が不可避とされていた。これに対し、本発明では、３成分以上の多成分混合ガスからのＣＯ２分離回収に、イオン液体による物理吸収法を適用することにより、そのような脱硫プロセスや多段プロセスが不要で、高コストの設備を必要とすること無しに、しかも、Ｈ２Ｓやメタンなどの炭化水素の混入無しに、高精度に二酸化炭素を選択的に分離回収することを可能とする、高精度、高効率、省エネルギーの低環境負荷型のプロセスで、３成分以上の多成分混合ガスからのＣＯ２分離回収技術を提供することが可能である。 Conventionally, in a multi-component mixed gas system, for example, in the treatment of H 2 S gas mixture containing H 2 S, there is a problem that the desulfurization process required, also in the treatment of lower hydrocarbon gas mixture However, there is a problem that a multistage process is required to separate hydrocarbons, and high energy consumption and high cost are inevitable due to these processes. On the other hand, in the present invention, by applying a physical absorption method using an ionic liquid to CO 2 separation and recovery from a multicomponent mixed gas of three or more components, such a desulfurization process and a multistage process are unnecessary, and the cost is high. Highly accurate and highly efficient, enabling the selective separation and recovery of carbon dioxide with high accuracy without the need for such facilities and without the mixing of hydrocarbons such as H 2 S and methane. It is possible to provide a CO 2 separation and recovery technique from a multicomponent mixed gas of three or more components by an energy-saving and low environmental load type process.
一般に、物理吸収法は、他の方法と比較して、ガスの吸収量や処理量に優れ、例えば、北米を中心に、天然ガスや合成ガスなどのガス分離精製プラントで、多数の実績がある。近年では、石炭ガス化複合発電（ＩＧＣＣ）における改質ガスからのＣＯ２分離などで、その利用が期待されている。本発明により、ガス分離回収効率向上のために、温度、圧力などの条件の最適化、共存ガス成分の影響の検討、精密なプロセスの設計などが進展することで、クリーンで、低コスト、低消費エネルギーのイオン液体を用いた、物理吸収法によるガス分離回収プロセスが実用化可能になるものと期待される。本発明は、特に、発生源のガスが高圧状態である場合や、除去すべき酸性ガス成分が高濃度である場合に、有効である。 In general, the physical absorption method is superior to other methods in the amount of gas absorbed and treated, and has many achievements in gas separation and purification plants such as natural gas and synthesis gas, mainly in North America. . In recent years, its use is expected for CO 2 separation from reformed gas in combined gasification combined cycle (IGCC). With the present invention, to improve gas separation and recovery efficiency, the optimization of conditions such as temperature and pressure, the study of the influence of coexisting gas components, the design of precise processes, etc. are progressing, resulting in clean, low cost, low cost. It is expected that a gas separation / recovery process using a physical absorption method using an ionic liquid of consumed energy will become practical. The present invention is particularly effective when the source gas is in a high pressure state or when the acidic gas component to be removed has a high concentration.
本発明により、次のような効果が奏される。
（１）イオン液体による物理吸収により、３成分以上の多成分混合ガスからのＣＯ２を分離回収する方法を提供することができる。
（２）ＣＯ２−Ｎ２系とＨ２Ｓ、又はＣＯ２−Ｎ２系と低級の炭化水素系ガスを含む混合ガスから、ＣＯ２とＨ２Ｓ、又はＣＯ２を高圧状態で回収することができ、貯留、隔離の際の圧縮エネルギーやコストを軽減することができる。
（３）温度２５〜６０℃の室温近辺の温度領域で、ガス分離することが可能であり、化学吸収法と比べて、分離回収におけるエネルギー消費量を大幅に削減することができる。
（４）水素を含んだ混合ガスでは、水素分圧を低下させること無く、二酸化炭素を選択的に吸収して取り除くことが可能である。
（５）高圧条件では、水素精製と圧縮を同時に行うことが可能である。
（６）Ｈ２Ｓ系混合ガスの処理において、低圧から高圧へと多段に圧力調整するだけで、Ｈ２Ｓを前処理的に分取することが可能であり、これにより、脱硫プロセスを不要とすることができる。
（７）ＣＨ４系混合ガスの処理において、一段のプロセスで、ＣＨ４の混入無しにＣＯ２の分離吸収処理を実施することができる。
（８）高精度、高効率、省エネルギーの低環境負荷型のプロセスで、３成分以上の多成分混合ガスからのＣＯ２を分離回収するＣＯ２分離回収技術を提供することができる。
The present invention has the following effects.
(1) It is possible to provide a method for separating and recovering CO 2 from a multicomponent mixed gas of three or more components by physical absorption with an ionic liquid.
(2) CO 2 -N 2 system and H 2 S, or CO from a gas mixture containing 2 -N 2 system and a lower hydrocarbon gas, is recovered CO 2 and H 2 S, or CO 2 at high pressure It is possible to reduce the compression energy and cost during storage and isolation.
(3) Gas separation is possible in a temperature range of about 25 to 60 ° C. near room temperature, and energy consumption in separation and recovery can be greatly reduced as compared with the chemical absorption method.
(4) In the mixed gas containing hydrogen, carbon dioxide can be selectively absorbed and removed without lowering the hydrogen partial pressure.
(5) Under high pressure conditions, hydrogen purification and compression can be performed simultaneously.
(6) In the treatment of H 2 S-based mixed gas, H 2 S can be pretreated by simply adjusting the pressure from low pressure to high pressure in multiple stages, which eliminates the need for a desulfurization process. It can be.
(7) In the treatment of the CH 4 mixed gas, it is possible to carry out the CO 2 separation and absorption treatment without mixing CH 4 in a single process.
(8) with high accuracy, high efficiency, low environmental load type of energy saving process, it is possible to provide a CO 2 separation and recovery techniques for separating and recovering a CO 2 from three or more components of a multicomponent gas mixture.
次に、実施例に基づいて本発明を具体的に説明するが、本発明は、以下の実施例によって何ら限定されるものではない。 EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following Examples.
本実施例では、高圧条件における性能評価試験を行った。
（１）実験装置
本実施例で構築した流通式ガス分離実験装置の概略を図１に示す。また、流通式ガス分離実験装置の機種名（表中の番号は、図１と同符号）を、表１に示す。
In this example, a performance evaluation test under high pressure conditions was performed.
(1) Experimental apparatus FIG. 1 shows an outline of a flow-type gas separation experimental apparatus constructed in this example. Table 1 shows the model names of the flow-type gas separation experiment apparatus (the numbers in the table are the same as those in FIG. 1).
ガス分離実験装置は、吸収液と標準ガスを定常的に送液する２台のシリンジポンプ（１，５）、約３０ｍｌのサファイア窓付の高圧セルからなる気液混合・分離器、圧力計測・制御機器（１１−１３）、及びガス組成分析機器（１４，１５）、の４つの主要部分から構成される。 The gas separation experiment equipment consists of two syringe pumps (1, 5) that regularly send absorption liquid and standard gas, a gas-liquid mixing / separator consisting of a high-pressure cell with about 30 ml of sapphire window, It consists of four main parts: a control device (11-13) and a gas composition analysis device (14, 15).
（２）実験手順
ガス分離回収実験は、以下の手順で行なった。図１に示す流通式ガス分離実験装置において、循環ポンプ、恒温槽、冷却器を作動させ、シリンジポンプ、及び気液混合・分離器などを、所定の温度に保持した。測定条件を満たすために、必要な体積と、圧力を考慮し、それに合わせて、ポンプ−Ｂ（ガス側）と、ポンプ−Ａ（液体側）を、それぞれ標準ガスと吸収液で充填した。充填は、ポンプの出口側バルブ（ポンプ右側に設置）を閉じ、ポンプ入口側のバルブ（ポンプ左側）を開け、“Ｒｅｆｉｌｌ”ボタンを押して行った。
(2) Experimental procedure The gas separation and recovery experiment was conducted according to the following procedure. In the flow-type gas separation experiment apparatus shown in FIG. 1, the circulation pump, the thermostatic bath, and the cooler were operated, and the syringe pump, the gas-liquid mixer / separator, and the like were maintained at a predetermined temperature. In order to satisfy the measurement conditions, the necessary volume and pressure were taken into account, and pump-B (gas side) and pump-A (liquid side) were filled with standard gas and absorption liquid, respectively. Filling was performed by closing the outlet valve of the pump (installed on the right side of the pump), opening the valve on the inlet side of the pump (left side of the pump), and pressing the “Refill” button.
粘性の高い液体は、ゆっくり充填する（２ｍｌ／ｍｉｎ）か、又はポンプ停止後も時間をおき、遅れて充填が完了するのを待った。また、吸収液は、グローブボックス内で、密閉型の充填容器に移し替え、アルゴンをパージしながら充填することで、水分の混入を防いだ。 The highly viscous liquid was slowly filled (2 ml / min), or even after the pump was stopped, it was delayed until the filling was completed. In addition, the absorbing solution was transferred to a sealed filling container in the glove box and filled while purging with argon, thereby preventing moisture from being mixed.
ガスクロマトグラフィーを、以下の手順で起動した。すなわち、キャリアガスであるＨｅの元栓を開き、供給側の圧力ゲージが、所定のガス圧（０．４−０．５ＭＰａ）を保つことを確認した。また、ＧＣの“Ｐｒｉｍａｒｙ”バルブを所定位置まで開け、“Ｃａｒｒｉｅｒ Ｇａｓ”ゲージにより、１・２とも、Ｈｅが流れていることを確認した。 Gas chromatography was started by the following procedure. That is, the main stopper of the carrier gas He was opened, and it was confirmed that the pressure gauge on the supply side maintained a predetermined gas pressure (0.4-0.5 MPa). Further, the “Primary” valve of the GC was opened to a predetermined position, and it was confirmed that He was flowing in both 1 and 2 by the “Carrier Gas” gauge.
ＧＣと記録計のスイッチを入れて、ＩＮＪ温度を１２０℃に、ＣＯＬ温度を１００℃に設定し、１５〜２０分後に、温度モニターで、設定温度に達したことを確認した。Ｃｕｒｒｅｎｔを９０ｍＡに設定し、１時間くらい安定するのを待った。記録計の“ＭＯＮＩＴ”を押し、入力レベルを見て調節し、基準線をゼロにした。背圧弁全開のまま、圧力計のゼロ点補正を行った。また、この時点で、大気圧の値を記録し、以下、絶対圧として、圧力を制御した。なお、硫化水素ガスを使用する実験では、安全のため、背圧弁を閉じておいた。実験中は、最初にゼロ点補正した際の大気圧値を、そのまま使用し、その都度は、背圧弁の開閉は行わなかった。 The GC and recorder were turned on, the INJ temperature was set to 120 ° C., the COL temperature was set to 100 ° C., and after 15 to 20 minutes, it was confirmed that the set temperature was reached with a temperature monitor. The current was set to 90 mA and waited for about 1 hour to stabilize. Press the “MONIT” on the recorder, adjust the input level according to the input level, and set the reference line to zero. The zero point of the pressure gauge was corrected with the back pressure valve fully open. At this time, the value of atmospheric pressure was recorded, and the pressure was controlled as an absolute pressure hereinafter. In the experiment using hydrogen sulfide gas, the back pressure valve was closed for safety. During the experiment, the atmospheric pressure value when the zero point was first corrected was used as it was, and the back pressure valve was not opened or closed each time.
背圧弁からＧＣ側にある三方バルブを開け、ガスの流路を確保した。ガス側ポンプの出口側バルブを徐々に開き、標準ガスをラインへと流した。流量を、所定の値とし、“Ｒｕｎ”ボタンを押して、ポンプ−Ｂを作動させた。気液混合器内のスターラを回し始め、圧力計の表示が目的の圧力に達したら、背圧弁をゆっくりと開け、ＧＣ側トラップの排気管を液面下に下げて、気泡を見ながら調整した。ガスの流れが安定するまで、背圧弁を微調整しながら、３０分くらい保持した。 The three-way valve on the GC side from the back pressure valve was opened to secure a gas flow path. The outlet side valve of the gas side pump was gradually opened, and the standard gas was allowed to flow into the line. The flow rate was set to a predetermined value, and the “Run” button was pressed to activate the pump-B. Start turning the stirrer in the gas-liquid mixer, and when the pressure gauge display reaches the target pressure, slowly open the back pressure valve, lower the exhaust pipe of the GC side trap below the liquid level, and adjust while watching the bubbles . The back pressure valve was finely adjusted and held for about 30 minutes until the gas flow stabilized.
吸収液側ポンプのバルブを閉じたまま、“Ｒｕｎ”ボタンを押して、ポンプ−Ａを作動させた。圧力が目標値より少し高くなってから、出口側バルブを開け、反応器内部を観察し、ガスの気泡と吸収液の滴下を確認した。減圧弁、及び背圧弁を調節して、目標の圧力と気液分離器内の液量を適切に保持し、定常状態を保つようにした。 While the valve of the absorption liquid side pump was closed, the “Run” button was pushed to operate the pump-A. After the pressure became slightly higher than the target value, the outlet side valve was opened, the inside of the reactor was observed, and gas bubbles and dripping of the absorbing solution were confirmed. By adjusting the pressure reducing valve and the back pressure valve, the target pressure and the amount of liquid in the gas-liquid separator were appropriately maintained to maintain a steady state.
分析するガスのサンプリングを、以下の手順で行なった。分析するガスの種類に応じ、どちらのカラムを使うか確認した。混合ガス（ＣＯ２−Ｎ２系）と（ＣＨ４−ＣＯ２−Ｎ２系）の分析では、カラム（Ｓｈｉｎｃａｒｂｏｎ−ＳＴ）を使用し、混合ガス（Ｈ２Ｓ−ＣＯ２−Ｎ２系）では、カラム（Ｓｕｎｐａｋ−Ｓ）を使用した。分析ガスの流路に注意して、三方バルブの向きを換えた。 Sampling of the gas to be analyzed was performed according to the following procedure. It was confirmed which column to use depending on the type of gas to be analyzed. In the analysis of the mixed gas (CO 2 —N 2 system) and (CH 4 —CO 2 —N 2 system), a column (Shincarbon-ST) is used, and the mixed gas (H 2 S—CO 2 —N 2 system) is used. Then, a column (Sunpak-S) was used. Paying attention to the flow path of the analysis gas, the direction of the three-way valve was changed.
ＧＣ記録計の“ＭＯＮＩＴ”ボタンを押し、Ｃｈ１が“ＲＤＹ”になっていることを確認した。ガスと吸収液が平衡に達した後、ＧＣ側のサンプラーの“Ｉｎ”側、“Ｏｕｔ”側を共にＯＰＥＮにした後、三方バルブを所定のサンプラー側に切り替え、サンプラーに、分析ガスを流入させた。 Press the “MONIT” button on the GC recorder and confirm that Ch1 is “RDY”. After the gas and the absorption liquid reach equilibrium, the GC sampler “In” side and “Out” side are both set to OPEN, then the three-way valve is switched to the specified sampler side, and the analysis gas is allowed to flow into the sampler. It was.
サンプラーの “Ｉｎ”側のバルブを先に閉じ、三方バルブを排出側に切り替えた。〜３０秒待って、サンプラー内部を常圧にした後に、“Ｏｕｔ”側のバルブを閉じた。ＧＣ記録計の“Ｓｔａｒｔ”ボタンを押し、サンプラーのバルブを“Ｄｉｓｃｈａｒｇｅ”側に切り替え、分析するガスをカラムに送りこんだ。しばらく待ってから、バルブを“Ｃｈａｒｇｅ”に戻した。ガス分離実験装置を定常状態を保ち、分離するガスを複数回サンプリングし、分析値が一定するのを確認した。 The “In” side valve of the sampler was closed first, and the three-way valve was switched to the discharge side. After waiting 30 seconds, the inside of the sampler was brought to normal pressure, and then the “Out” side valve was closed. The “Start” button of the GC recorder was pushed, the valve of the sampler was switched to the “Discharge” side, and the gas to be analyzed was sent to the column. After a while, the valve was returned to “Charge”. The gas separation experimental apparatus was maintained in a steady state, and the gas to be separated was sampled a plurality of times to confirm that the analysis value was constant.
実験終了後、以下の手順で、ガス分離実験装置を停止した。吸収液側のポンプ−Ａを停止し、出口側バルブを閉めた。吸収液が止まったことを確認してから、標準ガス側のポンプ−Ｂを停止し、出口側バルブを閉めた。 After the experiment, the gas separation experiment apparatus was stopped by the following procedure. Pump-A on the absorption liquid side was stopped, and the outlet side valve was closed. After confirming that the absorbing solution had stopped, pump-B on the standard gas side was stopped and the outlet side valve was closed.
必要に応じて、減圧弁を操作して、反応器内部の液体を排出した。この時、ＧＣトラップの溶液が、排気管を逆流しないように注意した。硫化水素ガスでない場合は、先に、排気管を液面上まで引き上げておいた。ＧＣ側にある三方バルブ２ヶ所の流路が、排出側に開いていることを確認してから、背圧弁を徐々に開いて、ゆっくりとライン内部を大気圧に戻した。循環ポンプ、恒温槽、冷却器を停止した。 If necessary, the pressure reducing valve was operated to discharge the liquid inside the reactor. At this time, care was taken so that the GC trap solution did not flow back through the exhaust pipe. If it was not hydrogen sulfide gas, the exhaust pipe was first pulled up to the liquid level. After confirming that the flow paths of the three three-way valves on the GC side were open to the discharge side, the back pressure valve was gradually opened, and the inside of the line was slowly returned to atmospheric pressure. The circulation pump, thermostat, and cooler were stopped.
以下の手順で、ＧＣを停止した。サンプラーのバルブが“Ｃｈａｒｇｅ”側であること、“ＩＮ”と“ＯＵＴ”両方のバルブが閉じていること、を確認した。設定した温度、電流の値を、すべてゼロに戻し、扉を開放して、カラムの温度を下げた。３０分以上経過して、温度が十分に下がってから、扉を閉めて、ＧＣを停止した。キャリアガスであるＨｅの元栓を閉めた。 The GC was stopped by the following procedure. It was confirmed that the sampler valve was on the “Charge” side and that both the “IN” and “OUT” valves were closed. The set temperature and current values were all returned to zero, the door was opened, and the column temperature was lowered. After 30 minutes or more had passed and the temperature had dropped sufficiently, the door was closed and GC was stopped. The main plug of He as the carrier gas was closed.
（３）ガスクロマトグラフ装置の校正
ガスクロマトグラフィーは、混合ガスの種類によって、カラムと測定条件を変更した。使用したカラムと測定条件を、表２に示す。
(3) Calibration of gas chromatograph apparatus In gas chromatography, columns and measurement conditions were changed depending on the type of mixed gas. Table 2 shows the columns used and the measurement conditions.
ＣＯ２の分析値については、それぞれの測定条件において、濃度既知の３種類の標準ガス（５．２４，１３．８６，２４．９６％ＣＯ２ｉｎＮ２；東京高圧山崎（株））を用いて、校正した。Ｈ２ＳとＣＨ４については、各１種類の標準ガス（０．９８７％Ｈ２ＳｉｎＣＯ２−Ｎ２；ジャパンファインプロダクツ（株）、１．００％ＣＨ４ｉｎＣＯ２−Ｎ２；住友精化（株））を用いて、校正を行なった。ＣＯ２の校正結果を、図２〜４に、Ｈ２Ｓの校正結果を、図５に、ＣＨ４の校正結果を、図６に、それぞれ示す。 Regarding the analytical value of CO 2 , three standard gases of known concentrations (5.24, 13.86, 24.96% CO 2 inN 2 ; Tokyo High Pressure Yamazaki Co., Ltd.) are used under the respective measurement conditions. And calibrated. For H 2 S and CH 4, each one of the standard gas (0.987% H 2 SinCO 2 -N 2; Japan Fine Products (Ltd.), 1.00% CH 4 inCO 2 -N 2; Sumitomo Seika (Co., Ltd.) was used for calibration. The calibration results for CO 2 are shown in FIGS. 2 to 4, the calibration results for H 2 S are shown in FIG. 5, and the calibration results for CH 4 are shown in FIG.
（４）標準ガスと試料の取り扱い
本実施例では、３種類の標準ガスを用いた。それらの標準ガスの組成と供給元は、表３に示した通りである。
(4) Handling of standard gas and sample In this example, three types of standard gas were used. The compositions and sources of these standard gases are as shown in Table 3.
本発明では、疎水性の［ＢＭＩＭ］［Ｔｆ２Ｎ］を、イオン液体吸収液として、主に使用した。［ＢＭＩＭ］［Ｔｆ２Ｎ］は、以下の手順で合成、精製したものを用いた。まず、前駆体である［ＢＭＩＭ］Ｃｌを合成し、酢酸エチルで洗浄してから、乾燥した。乾燥した［ＢＭＩＭ］Ｃｌを、水に溶かし、ほぼ等量のＬｉ［Ｔｆ２Ｎ］水溶液を、氷浴上でゆっくりと滴下して、アニオン交換を行なった。その後、［ＢＭＩＭ］［Ｔｆ２Ｎ］中に残存したＬｉＣｌなどの水溶性の不純物を、超純水で洗浄した。洗浄は、洗浄液が中性、かつＡｇＮＯ３を滴下して、ＡｇＣｌ由来の白色沈殿が生成しないことを確認するまで続けた。 In the present invention, hydrophobic [BMIM] [Tf 2 N] is mainly used as the ionic liquid absorbing solution. [BMIM] [Tf 2 N] was synthesized and purified by the following procedure. First, the precursor [BMIM] Cl was synthesized, washed with ethyl acetate, and then dried. The dried [BMIM] Cl was dissolved in water, and an approximately equal amount of Li [Tf 2 N] aqueous solution was slowly dropped on an ice bath to perform anion exchange. Thereafter, water-soluble impurities such as LiCl remaining in [BMIM] [Tf 2 N] were washed with ultrapure water. The washing was continued until it was confirmed that the washing solution was neutral and AgNO 3 was dropped and no white precipitate derived from AgCl was formed.
精製した［ＢＭＩＭ］［Ｔｆ２Ｎ］は、真空ポンプを用いて、３４３Ｋで、３０時間以上乾燥して、十分に脱水を行なった（非特許文献２）。［ＢＭＩＭ］［Ｔｆ２Ｎ］中に含まれる水分量を、電量型カール・フィッシャー水分滴定計（京都電子，ＭＫＣ−５１０）で測定したところ、水分量は、質量分率で〜５０ｐｐｍ以下であることが確認された。 The refined [BMIM] [Tf 2 N] was sufficiently dehydrated by drying at 343 K for 30 hours or more using a vacuum pump (Non-patent Document 2). The amount of water contained in [BMIM] [Tf 2 N] was measured with a coulometric Karl Fischer moisture titrator (Kyoto Electronics, MKC-510). The amount of water was ˜50 ppm in terms of mass fraction. It was confirmed.
また、ガス分離精製実験で使用した［ＢＭＩＭ］［Ｔｆ２Ｎ］を、水で洗浄し、十分に乾燥した後、１Ｈ及び１３ＣＮＭＲで分析したところ、スペクトル上に、不純物と想定されるピークは現れず、ほぼ純粋な［ＢＭＩＭ］［Ｔｆ２Ｎ］を得ることができた。 [BMIM] [Tf 2 N] used in the gas separation and purification experiment was washed with water and sufficiently dried, and then analyzed by 1 H and 13 C NMR. Did not appear, and almost pure [BMIM] [Tf 2 N] could be obtained.
実際に再利用して、ガス分離精製実験を行ったところ、誤差範囲内で、定量的なデータを得ることができた。そこで、本発明では、図７に示した通り、［ＢＭＩＭ］［Ｔｆ２Ｎ］を、水で洗浄後、十分に乾燥して、ガス分離実験で、繰り返し使用した。 When the gas separation purification experiment was conducted by actually reusing it, quantitative data could be obtained within the error range. Therefore, in the present invention, as shown in FIG. 7, [BMIM] [Tf 2 N] was washed with water and then sufficiently dried, and repeatedly used in gas separation experiments.
一方、ポリエチレングリコール４００（キシダ化学、１級、分子量３８０〜４２０、以下、ＰＥＧ４００と略記する）は、モレキュラーシーブス４Ａ（Ａｌｄｒｉｃｈ）で乾燥後、フィルターでろ過して、使用した。使用したＰＥＧ４００の水分量は、〜３００ｐｐｍ以下であることを確認した。 On the other hand, polyethylene glycol 400 (Kishida Chemical Co., Ltd., first grade, molecular weight 380 to 420, hereinafter abbreviated as PEG400) was dried with molecular sieves 4A (Aldrich), filtered through a filter, and used. It was confirmed that the water content of the used PEG 400 was ˜300 ppm or less.
（５）イオン液体物理吸収法によるＣＯ２分離回収実験の経時変化
上記実験手順にしたがって行った、ガス分離実験の一例について説明する。本実施例では、高圧セルの容量と気液相の体積を考慮して、セル内における混合時間が３０分以上となるように、標準ガス、及び吸収液の流量を、約０．１〜０．６ｍｌ／ｍｉｎの範囲で制御した。ガス吸収における気液平衡が十分に達成されているかは、流量比（吸収液／標準ガス）を一定とし、それぞれの流量を変化させた場合に、同じ結果が得られるかにより確認した。
(5) Change with time of CO 2 separation and recovery experiment by ionic liquid physical absorption method An example of a gas separation experiment performed according to the above experimental procedure will be described. In this example, considering the capacity of the high-pressure cell and the volume of the gas-liquid phase, the flow rates of the standard gas and the absorbing liquid are about 0.1 to 0 so that the mixing time in the cell is 30 minutes or more. Control was made in the range of 6 ml / min. Whether the gas-liquid equilibrium in gas absorption was sufficiently achieved was confirmed by whether the same result was obtained when the flow rate ratio (absorbed solution / standard gas) was kept constant and the respective flow rates were changed.
例えば、流量比（吸収液／標準ガス）が、２となる実験を、吸収液とガスの流量を、それぞれ０．６と０．３ｍｌ／ｍｉｎとしたときと、吸収液とガスの流量を、０．４と０．２ｍｌ／ｍｉｎとしたときで、ほぼ同様の結果が得られることが確認されている。しかしながら、マグネチックスターラーバーによる強制的な撹拌を行なわないと、定常的な値を得ることは困難であった。 For example, in an experiment in which the flow rate ratio (absorbing liquid / standard gas) is 2, when the absorbing liquid and gas flow rates are 0.6 and 0.3 ml / min, respectively, the absorbing liquid and gas flow rates are: It has been confirmed that almost the same results can be obtained at 0.4 and 0.2 ml / min. However, it was difficult to obtain a steady value without forced stirring by a magnetic stirrer bar.
図８に、温度２５℃、圧力３ＭＰａ、流量比（吸収液／ガス＝（０．６ｍｌ／ｍｉｎ）／（０．３ｍｌ／ｍｉｎ））２において、混合ガス（ＣＨ４−ＣＯ２−Ｎ２）からＣＯ２分離回収実験を行ったときの、分析するガス中に含まれるＣＯ２濃度の経時変化を示す。図中の時間０は、所定の温度圧力条件において、吸収液、及び標準ガスを、一定流量で流し始めた時間を表す。 FIG. 8 shows a mixed gas (CH 4 —CO 2 —N 2 ) at a temperature of 25 ° C., a pressure of 3 MPa, and a flow rate ratio (absorbed liquid / gas = (0.6 ml / min) / (0.3 ml / min)) 2 . 2 shows the change with time of the CO 2 concentration contained in the gas to be analyzed when a CO 2 separation and recovery experiment is performed from the above. Time 0 in the figure represents the time when the absorbing liquid and the standard gas have started to flow at a constant flow rate under a predetermined temperature and pressure condition.
本条件では、セル内の吸収液、及び標準ガスが置き換わるのに、〜１時間近く掛かる。そのため、分析するガス中のＣＯ２濃度は、実験を開始してから２〜３時間は、緩やかに減少する。分析するガス中のＣＯ２濃度は、約３時間後から一定となるが、その後、±０．１％以内のデータが、４〜５点取得できた時点で、それらの平均と標準偏差を求め、その条件における分析するガス中のＣＯ２濃度とした。 Under this condition, it takes about ˜1 hour for the absorption liquid and the standard gas in the cell to be replaced. Therefore, the CO 2 concentration in the gas to be analyzed gradually decreases for 2 to 3 hours from the start of the experiment. The CO 2 concentration in the gas to be analyzed becomes constant after about 3 hours, but after that, when 4 to 5 points of data within ± 0.1% are obtained, the average and standard deviation are obtained. The CO 2 concentration in the gas to be analyzed under the conditions was used.
３成分系の混合ガスのガス分離回収実験も、同様の操作を行い、分析するガス中のそれぞれの濃度を求めた。分析するガス中におけるガス濃度の経時変化は、ガスの種類により大きく異なることは無く、ＣＯ２濃度が一定となる時間には Ｈ２ＳやＣＨ４の濃度も、ほぼ一定値を示した。 In the gas separation / recovery experiment of the ternary mixed gas, the same operation was performed to determine the respective concentrations in the gas to be analyzed. The time-dependent change in gas concentration in the gas to be analyzed did not vary greatly depending on the type of gas, and the concentrations of H 2 S and CH 4 showed almost constant values during the time when the CO 2 concentration was constant.
（６）イオン液体物理吸収法によるＣＯ２分離回収条件（２成分混合ガスＣＯ２−Ｎ２）
温度２５℃、圧力２ＭＰａにおいて、ＰＥＧ４００、及び［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として、流量を変化させて行なったＣＯ２分離回収実験の結果として、２成分混合ガス（ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２５℃、２ＭＰａ）を、表４に示す。
(6) CO 2 separation and recovery conditions by ionic liquid physical absorption method (binary component gas CO 2 —N 2 )
As a result of the CO 2 separation and recovery experiment conducted by changing the flow rate using PEG400 and [BMIM] [Tf 2 N] as the absorbing liquid at a temperature of 25 ° C. and a pressure of 2 MPa, a binary mixed gas (CO 2 / N 2) was obtained. Table 4 shows the results of the CO 2 separation experiment (25 ° C., 2 MPa) from FIG.
また、それぞれの吸収液を用いて、温度２５℃で、流量比（吸収液／ガス）を２と固定し、圧力を変化させたＣＯ２分離回収実験の結果として、２成分混合ガス（ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２５℃、流量比２）を、表５に、圧力２ＭＰａ、流量比２における、温度依存性の結果として、２成分混合ガス（ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２ＭＰａ、流量比２）を、表６に示す。 In addition, as a result of the CO 2 separation and recovery experiment in which each absorption liquid was used and the flow rate ratio (absorption liquid / gas) was fixed at 2 at a temperature of 25 ° C. and the pressure was changed, a binary mixed gas (CO 2 / N 2) CO 2 separation experimental results from (25 ° C., the flow rate ratio of 2), in Table 5, the pressure 2 MPa, at a flow rate ratio of 2, as a result of the temperature dependence, two-component mixed gas (CO 2 / N 2) CO 2 separation experimental results from the (2 MPa, the flow rate ratio of 2), are shown in Table 6.
表４の結果に基づき、２５℃、２ＭＰａにおいて、ＰＥＧ４００、及び［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として用いたとき、分析するガス中のＣＯ２濃度が、流量比（吸収液／標準ガス）に対して、どの様に変化するかを、図９に、プロットした。どちらの吸収液を用いた場合も、ガスの流量に対して、吸収液の流量を増加していくと、ＣＯ２濃度が急激に減少していくことが観察された。これは、ガス流量が大きい場合には、吸収液の溶解量に比べて、標準ガス中に含まれるＣＯ２が多く、全てのＣＯ２を吸収するのが困難であるためと考えられる。 Based on the results of Table 4, when PEG400 and [BMIM] [Tf 2 N] are used as the absorbing liquid at 25 ° C. and 2 MPa, the CO 2 concentration in the gas to be analyzed is the flow rate ratio (absorbing liquid / standard gas). 9 is plotted in FIG. 9. In either case, it was observed that the CO 2 concentration rapidly decreased as the absorption liquid flow rate increased with respect to the gas flow rate. This is presumably because when the gas flow rate is large, the amount of CO 2 contained in the standard gas is larger than the dissolved amount of the absorbing solution, and it is difficult to absorb all the CO 2 .
図９から明らかなように、流量比が〜０．５近くまで、ＣＯ２濃度は急激に下がり、その後は、緩やかに減少する。２５℃、２ＭＰａの標準ガス（２４．４５％ＣＯ２−７５．５５％Ｎ２）中に含まれるＣＯ２の体積モル濃度は、〜０．２ｍｏｌｄｍ−３程度であり、ＣＯ２分圧〜０．５ＭＰａにおける吸収液のＣＯ２溶解量は、［ＢＭＩＭ］［Ｔｆ２Ｎ］では、〜０．５ｍｏｌｄｍ−３程度であることから考えて、この結果は、妥当であると考えられる。 As is apparent from FIG. 9, the CO 2 concentration decreases sharply until the flow rate ratio is close to ˜0.5, and then gradually decreases. The volume molar concentration of CO 2 contained in a standard gas (24.45% CO 2 -75.55% N 2 ) at 25 ° C. and 2 MPa is about 0.2 moldm −3 , and the CO 2 partial pressure is 0 to 0. Considering that the amount of CO 2 dissolved in the absorbing solution at 0.5 MPa is about 0.5 moldm −3 in [BMIM] [Tf 2 N], this result is considered to be reasonable.
非常に興味深いことに、流量比〜０．５以下の領域でのＣＯ２濃度の減少傾向は、ＰＥＧ４００に比べて、［ＢＭＩＭ］［Ｔｆ２Ｎ］では、著しく大きい。また、［ＢＭＩＭ］［Ｔｆ２Ｎ］を用いた場合には、流量比を増加した時に到達するＣＯ２濃度が、〜４％未満と非常に小さい。ＰＥＧ４００を吸収液として用いた場合には、元々２４．４５％あったＣＯ２は、〜９％弱まで取り除かれ、全体の約６０％のＣＯ２を分離回収することができた。 Interestingly, the decreasing tendency of the CO 2 concentration in the region where the flow rate ratio is 0.5 or less is significantly larger in [BMIM] [Tf 2 N] than in PEG400. Also, when [BMIM] [Tf 2 N] is used, the CO 2 concentration reached when the flow rate ratio is increased is very small, less than ˜4%. When PEG400 was used as the absorbing solution, CO 2 that originally was 24.45% was removed to a little less than ˜9%, and about 60% of the total CO 2 could be separated and recovered.
一方、［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として用いた場合には、全体の〜８５％を超えるＣＯ２を容易に分離回収することが可能であった。すなわち、［ＢＭＩＭ］［Ｔｆ２Ｎ］を用いると、ＰＥＧ４００よりも、同条件において、ＣＯ２を〜２０％以上効率良く分離回収することができる。この結果は、前記したとおり、イオン液体の単位体積当りのＣＯ２吸収能力が、非常に優れていることに起因している。 On the other hand, when [BMIM] [Tf 2 N] was used as the absorbing liquid, it was possible to easily separate and recover CO 2 exceeding ˜85% of the total. That is, when [BMIM] [Tf 2 N] is used, CO 2 can be separated and recovered more efficiently by ˜20% or more under the same conditions as PEG400. As described above, this result is due to the very excellent CO 2 absorption capacity per unit volume of the ionic liquid.
表５の結果に基づき、２５℃において、流量比を２と固定した場合に、精製ガス中のＣＯ２濃度が、圧力の変化に伴い、どのような影響を受けるかを、図１０にプロットした。標準ガス中に含まれるＣＯ２の絶対量は、圧力増加にともない、大きくなるが、ＰＥＧ４００、及び［ＢＭＩＭ］［Ｔｆ２Ｎ］のどちらの吸収液を用いた場合も、分析するガス中のＣＯ２濃度に、変化はほとんど観察されなかった。 Based on the results in Table 5, how the CO 2 concentration in the purified gas is affected by the change in pressure when the flow rate ratio is fixed to 2 at 25 ° C. is plotted in FIG. . The absolute amount of CO 2 contained in the standard gas increases as the pressure increases, but CO 2 in the gas to be analyzed can be obtained using either PEG400 or [BMIM] [Tf 2 N]. Little change was observed between the two concentrations.
実験を行なった圧力範囲（全圧１〜４ＭＰａ、ＣＯ２分圧０．２５〜１ＭＰａ）では、ＣＯ２の吸収は、ほぼヘンリー則が成立することが予想されることから、矛盾が無い結果と云える。すなわち、吸収液の単位体積あたりのＣＯ２処理量は、より高圧ほど、大きくなることが実証された。 In the experimental pressure range (total pressure 1 to 4 MPa, CO 2 partial pressure 0.25 to 1 MPa), the absorption of CO 2 is expected to almost satisfy the Henry's law, so there is no contradiction. I can say. That is, it was proved that the CO 2 treatment amount per unit volume of the absorbing liquid increases as the pressure increases.
更に、表６の結果に基づき、２ＭＰａ、流量比２における、分析するガス中のＣＯ２濃度の温度依存性を、図１１に示した。一般に、同じ圧力条件であれば、ガスの物理吸収量は、低温ほど大きいため、ＣＯ２濃度は、温度上昇にともない増加することが予想される。実際、図１１から、ＰＥＧ４００、及び［ＢＭＩＭ］［Ｔｆ２Ｎ］どちらの吸収液の場合も、ほぼ同様に、ＣＯ２濃度は、温度に対し、緩やかな増加を示すことが確認された。 Furthermore, based on the results in Table 6, FIG. 11 shows the temperature dependence of the CO 2 concentration in the gas to be analyzed at 2 MPa and a flow rate ratio of 2. In general, under the same pressure condition, the physical absorption amount of gas is larger at lower temperatures, and therefore, the CO 2 concentration is expected to increase as the temperature rises. Actually, from FIG. 11, it was confirmed that the CO 2 concentration showed a gradual increase with respect to the temperature in both cases of the absorption liquids of PEG400 and [BMIM] [Tf 2 N].
このことは、イオン液体を用いた物理吸収法でも、低温の方が、より効率的にＣＯ２の分離回収を行なえることを示している。ただし、［ＢＭＩＭ］［Ｔｆ２Ｎ］の結果は、６０℃近くまで温度を上げても、２５℃のＰＥＧ４００の結果よりも、優れており、上記実験条件では、温度依存性が比較的小さいことが明らかとされた。 This shows that CO 2 can be separated and recovered more efficiently at lower temperatures even in a physical absorption method using an ionic liquid. However, the result of [BMIM] [Tf 2 N] is superior to the result of PEG 400 at 25 ° C. even when the temperature is increased to nearly 60 ° C., and the temperature dependence is relatively small under the above experimental conditions. It was made clear.
（７）３成分混合ガス（Ｈ２Ｓ−ＣＯ２−Ｎ２，ＣＨ４−ＣＯ２−Ｎ２）を用いたＣＯ２分離回収試験
Ｈ２Ｓ系の混合ガス（Ｈ２Ｓ−ＣＯ２−Ｎ２）を対象として、温度２５℃、圧力２ＭＰａで、［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として用い、流量比（吸収液／ガス）を変化させて、ＣＯ２分離回収実験を行った。その結果として、ＢＭＩＭ］［Ｔｆ２Ｎ］による混合ガス（Ｈ２Ｓ／ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２５℃、２ＭＰａ）を、表７に示す。
(7) CO 2 separation and recovery test using ternary mixed gas (H 2 S—CO 2 —N 2 , CH 4 —CO 2 —N 2 ) H 2 S-based mixed gas (H 2 S—CO 2 — N 2 ) was used as a target at a temperature of 25 ° C. and a pressure of 2 MPa, and [BMIM] [Tf 2 N] was used as an absorption liquid, and the flow rate ratio (absorption liquid / gas) was changed to perform a CO 2 separation and recovery experiment. . As a result, Table 7 shows the result (25 ° C., 2 MPa) of the CO 2 separation experiment from the mixed gas (H 2 S / CO 2 / N 2 ) using BMIM] [Tf 2 N].
また、温度２５℃において、流量比を２と固定し、圧力を増加させたときの結果として、［ＢＭＩＭ］［Ｔｆ２Ｎ］による混合ガス（Ｈ２Ｓ／ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２５℃、流量比２）を、表８に、圧力２ＭＰａ、流量比２において、温度を変化させたときの結果として、［ＢＭＩＭ］［Ｔｆ２Ｎ］による混合ガス（Ｈ２Ｓ／ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２ＭＰａ、流量比２）を、表９に示す。 In addition, at a temperature of 25 ° C., the flow rate ratio is fixed to 2 and the pressure is increased. As a result, CO from the mixed gas (H 2 S / CO 2 / N 2 ) by [BMIM] [Tf 2 N] The results of the two- separation experiment (25 ° C., flow rate ratio 2) are shown in Table 8 as a result of changing the temperature at a pressure of 2 MPa and a flow rate ratio of 2 (MIM) [Tf 2 N] mixed gas (H Table 9 shows the results (2 MPa, flow rate ratio 2) of the CO 2 separation experiment from 2 S / CO 2 / N 2 .
同様に、ＣＨ４系の混合ガス（ＣＨ４−ＣＯ２−Ｎ２）を対象として、［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として用いたＣＯ２分離回収実験の結果として、［ＢＭＩＭ］［Ｔｆ２Ｎ］による混合ガス（ＣＨ４／ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２５℃、２ＭＰａ）を、表１０に、また、［ＢＭＩＭ］［Ｔｆ２Ｎ］による混合ガス（ＣＨ４／ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２５℃、流量比２）を、表１１に、また、［ＢＭＩＭ］［Ｔｆ２Ｎ］による混合ガス（ＣＨ４／ＣＯ２／Ｎ２）からのＣＯ２分離実験の結果（２ＭＰａ、流量比２）を、表１２に、それぞれ流量依存性、圧力依存性、温度依存性をまとめて示す。 Similarly, as a result of a CO 2 separation / recovery experiment using [BMIM] [Tf 2 N] as an absorbing solution for a CH 4 -based mixed gas (CH 4 —CO 2 —N 2 ), [BMIM] [ The results of the CO 2 separation experiment (25 ° C., 2 MPa) from the mixed gas (CH 4 / CO 2 / N 2 ) by Tf 2 N] are shown in Table 10, and the mixed gas by [BMIM] [Tf 2 N] The results of the CO 2 separation experiment (25 ° C., flow rate ratio 2 ) from (CH 4 / CO 2 / N 2 ) are shown in Table 11 and also as a mixed gas (CH 4 / CO by [BMIM] [Tf 2 N]). The results (2 MPa, flow rate ratio 2) of the CO 2 separation experiment from ( 2 / N 2 ) are shown in Table 12 together with the flow rate dependency, pressure dependency, and temperature dependency, respectively.
２５℃、２ＭＰａにおいて、Ｈ２Ｓ系の３成分混合ガス（Ｈ２Ｓ−ＣＯ２−Ｎ２）から、［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として用いて、ＣＯ２分離回収実験を行った時に、精製ガス中のＣＯ２、及びＨ２Ｓの濃度が、流量比（吸収液／標準ガス）に対して、どの様に変化するかを、図１２に示した。図中、ＣＯ２の濃度変化は、左軸に、Ｈ２Ｓの濃度変化は、右軸に表されている。 25 ° C., at 2 MPa, the H 2 S-based ternary gas mixture (H 2 S-CO 2 -N 2), using as an absorption liquid [BMIM] [Tf 2 N] , subjected to CO 2 separation and recovery experiments FIG. 12 shows how the concentrations of CO 2 and H 2 S in the purified gas change with respect to the flow rate ratio (absorbed liquid / standard gas). In the figure, the CO 2 concentration change is shown on the left axis, and the H 2 S concentration change is shown on the right axis.
精製ガス中のＣＯ２、及びＨ２Ｓどちらの濃度も、流量比を増加していくと、顕著に低下することが明らかとされた。特に、Ｈ２Ｓ濃度は、現象が著しく、元々１％あったものが、その１／１０以下の０．０７％未満まで取り除かれる。この結果は、ＣＯ２濃度の減少以上であり、これまで報告は無いものの、Ｈ２Ｓの方が、イオン液体に対する溶解性は高い（ヘンリー定数は小さい）ことが伺える。一方、分析するガス中のＣＯ２濃度は、ＣＯ２／Ｎ２からなる２成分混合ガスの結果に比べて、１〜２％高い結果を示した。 It has been clarified that the concentrations of both CO 2 and H 2 S in the purified gas are significantly reduced as the flow rate ratio is increased. In particular, the phenomenon of the H 2 S concentration is remarkable, and what was originally 1% is removed to less than 1/10 or less than 0.07%. Although this result is more than the decrease in CO 2 concentration and has not been reported so far, it can be seen that H 2 S has higher solubility in ionic liquid (Henry constant is smaller). On the other hand, the CO 2 concentration in the gas to be analyzed was 1 to 2% higher than the result of the two-component mixed gas composed of CO 2 / N 2 .
２５℃、流量比２における、分析するガス中のＣＯ２、及びＨ２Ｓ濃度の圧力依存性を、図１３にプロットした。図１０の２成分混合ガス（ＣＯ２−Ｎ２）の場合と同様に、圧力に対するＣＯ２、及びＨ２Ｓの濃度変化は、ほとんど観察されなかった。 The pressure dependence of the CO 2 and H 2 S concentrations in the gas to be analyzed at 25 ° C. and a flow rate ratio of 2 is plotted in FIG. As in the case of the two-component mixed gas (CO 2 —N 2 ) in FIG. 10, almost no change in the concentration of CO 2 and H 2 S with respect to the pressure was observed.
一方、図１４に示したＣＯ２、及びＨ２Ｓ濃度の温度依存性も、２成分混合ガス（ＣＯ２−Ｎ２）と類似の傾向を示したが、より溶解性の高いＨ２Ｓでは、温度依存性がやや小さく見える。以上より、イオン液体を用いた物理吸収法では、Ｈ２Ｓ系の３成分混合ガス（Ｈ２Ｓ−ＣＯ２−Ｎ２）から、ＣＯ２とＨ２Ｓの２種類のガスを、同時に分離回収可能であることが明らかとされた。 On the other hand, the temperature dependence of the CO 2 and H 2 S concentrations shown in FIG. 14 also showed a tendency similar to that of the two-component mixed gas (CO 2 —N 2 ), but in the case of H 2 S having higher solubility, The temperature dependence looks a little small. As described above, the physical absorption method using an ionic liquid, the H 2 S-based ternary gas mixture (H 2 S-CO 2 -N 2), two kinds of gases CO 2 and H 2 S, at the same time isolation It was revealed that it could be recovered.
ＣＨ４系の３成分混合ガス（ＣＨ４−ＣＯ２−Ｎ２）から、［ＢＭＩＭ］［Ｔｆ２Ｎ］を吸収液として、ＣＯ２分離回収実験を行った結果について、精製ガス中のＣＯ２、及びＣＨ４濃度の流量比依存性、圧力依存性、温度依存性を、それぞれ図１５〜１７に示す。 From CH 4 system ternary mixed gas (CH 4 -CO 2 -N 2) , [BMIM] as [Tf 2 N] the absorption liquid, the result of CO 2 separation and recovery experiments, in the purified gas CO 2 15 and 17 show the flow ratio dependency, pressure dependency, and temperature dependency of CH 4 concentration.
図１５の流量依存性から、分析するガス中のＣＯ２濃度は、２成分系混合ガス（ＣＯ２−Ｎ２）の場合と同様に、流量比の増加に伴い減少し、流量比３では〜４％弱の値となることが確認された。すなわち、ＣＯ２濃度は、共存するＣＨ４の影響をほとんど受けないことが明らかとされた。 From the flow rate dependency of FIG. 15, the CO 2 concentration in the gas to be analyzed decreases with an increase in the flow rate ratio as in the case of the binary mixed gas (CO 2 —N 2 ). It was confirmed that the value was less than 4%. That is, it was clarified that the CO 2 concentration is hardly affected by the coexisting CH 4 .
一方、ＣＨ４濃度は、ＣＯ２の除去に伴い、僅かに増加するが、〜１．１％のままほとんど変化しなかった。これらの結果は、Ｈ２Ｓの場合とは全く逆に、ＣＨ４の、イオン液体に対する溶解性が、ＣＯ２よりもかなり劣ることを示している。実際に、Ｌｅｅら（Ｂ．−Ｃ．Ｌｅｅ，ａｎｄ Ｓ．Ｌ．Ｏｕｔｃａｌｔ，“Ｓｏｌｕｂｉｌｉｔｉｅｓ ｏｆ Ｇａｓｅｓ ｉｎ ｔｈｅ Ｉｏｎｉｃ Ｌｉｑｕｉｄ １−ｎ−Ｂｕｔｙｌ−３−ｍｅｔｈｙｌｉｍｉｄａｚｏｌｉｕｍ Ｂｉｓ（ｔｒｉｆｌｕｏｒｏｍｅｔｈｙｌｓｕｌｆｏｎｙｌ）ｉｍｉｄｅ，”Ｊ．Ｃｈｅｍ．Ｅｎｇ．Ｄａｔａ，２００６，５１，８９２）は、［ＢＭＩＭ］［Ｔｆ２Ｎ］中におけるＣＯ２や炭化水素系ガスの吸収量を調べ、プロパンなど低級の炭化水素系ガスのヘンリー定数がＣＯ２の値より大きいことを報告している。 On the other hand, the CH 4 concentration slightly increased with the removal of CO 2 , but remained almost unchanged at ˜1.1%. These results show that the solubility of CH 4 in ionic liquid is considerably inferior to CO 2 , contrary to the case of H 2 S. Indeed, Lee et al. (B.-C. Lee, and S.L. Data, 2006, 51, 892) investigates the absorption amount of CO 2 and hydrocarbon gas in [BMIM] [Tf 2 N], and the Henry constant of lower hydrocarbon gas such as propane is from the value of CO 2 . It is reported to be big.
図１６に示された通り、ＣＨ４濃度は、圧力に依らず、ほぼ〜１．１％を示し、ほとんどイオン液体中に溶解しないことが分かる。また、図１７でも、メタン濃度は、同様に、ほとんど温度変化を示さず、ＣＯ２の場合とは異なり、元々イオン液体に吸収されないＣＨ４の濃度は、温度を上げても、増加しないことが確認された。以上より、イオン液体を用いた物理吸収法により、ＣＨ４系の３成分混合ガス（ＣＨ４−ＣＯ２−Ｎ２）から、選択的かつ効率的にＣＯ２を分離回収可能であることが明らかとされた。 As shown in FIG. 16, it can be seen that the CH 4 concentration is approximately −1.1% regardless of the pressure, and hardly dissolves in the ionic liquid. Also in FIG. 17, the methane concentration shows almost no temperature change, and unlike the case of CO 2 , the concentration of CH 4 that is not originally absorbed by the ionic liquid may not increase even if the temperature is increased. confirmed. From the above, it is clear that CO 2 can be selectively and efficiently separated and recovered from a CH 4 -based three-component mixed gas (CH 4 —CO 2 —N 2 ) by a physical absorption method using an ionic liquid. It was said.
以上詳述したように、本発明は、イオン液体を用いた物理吸収法によるＣＯ２分離回収方法に係るものであり、本発明により、イオン液体による物理吸収を原理とするガス分離装置を用いたＣＯ２分離回収方法を提供することができる。本発明により、二酸化炭素を高圧状態で回収することができ、貯留、隔離の際の圧縮エネルギーを軽減することができる。本発明は、化学吸収法と比べて、分離回収におけるエネルギー消費量を大幅に削減することができる。本発明は、室温近辺の温度領域で、ガス分離することで、３成分以上の多成分混合ガスからＣＯ２を分離回収することを可能とするＣＯ２の分離回収技術を提供するものとして有用である。 As described above in detail, the present invention relates to a method for separating and recovering CO 2 by a physical absorption method using an ionic liquid, and the present invention uses a gas separation device based on the principle of physical absorption by an ionic liquid. A CO 2 separation and recovery method can be provided. According to the present invention, carbon dioxide can be recovered in a high pressure state, and the compression energy during storage and isolation can be reduced. The present invention can greatly reduce the energy consumption in separation and recovery as compared with the chemical absorption method. INDUSTRIAL APPLICABILITY The present invention is useful as a technique for providing a CO 2 separation and recovery technique that enables gas separation in a temperature range near room temperature to separate and recover CO 2 from a multicomponent mixed gas of three or more components. is there.
１、５ シリンジポンプ
２、３、６、７ バルブ
４、８ 逆止弁
９ 恒温水槽
１０ 温度センサー
１１ 背圧弁
１２ 圧力計
１３ 減圧弁
１４ ガスクロマトグラフィー（ＧＣ）
１５ ＧＣ記録計
1, 5 Syringe pump 2, 3, 6, 7 Valve 4, 8 Check valve 9 Constant temperature water tank 10 Temperature sensor 11 Back pressure valve 12 Pressure gauge 13 Pressure reducing valve 14 Gas chromatography (GC)
15 GC recorder
Claims (6)
１）中性のイオン液体吸収液を用いた物理吸収法により、少なくともＣＯ ２ −Ｎ ２ 系とＨ ２ Ｓを含む３成分以上の多成分混合ガスから、ＣＯ ２ とＨ ２ Ｓを同時に分離回収し、あるいは、少なくともＣＯ ２ −Ｎ ２ 系と低級の炭化水素系ガスのＣＨ ４ を含む３成分以上の多成分混合ガスから、ＣＯ ２ のみを選択的に分離回収すること、２）ＣＯ ２ を含む多成分混合ガスに対するイオン液体吸収液の流量比（吸収液／ガス）が、０．１〜３の領域で、ガス分離を行うこと、を特徴とするＣＯ２分離回収方法。 A method of separating and recovering CO 2 from a multicomponent mixed gas composed of at least three components without requiring a desulfurization process or a multistage process ,
1) Simultaneously separates and collects CO 2 and H 2 S from a multicomponent mixed gas containing at least a CO 2 —N 2 system and H 2 S by a physical absorption method using a neutral ionic liquid absorbent. and, alternatively, from three or more components of a multi-component mixed gas containing CH 4 at least CO 2 -N 2 system and a lower hydrocarbon gas, to selectively separate and recover only CO 2, 2) CO 2 a A CO 2 separation and recovery method , wherein gas separation is performed in a region where the flow rate ratio of the ionic liquid absorbing liquid to the multi-component mixed gas (absorbing liquid / gas) is 0.1 to 3 .
１）前記陽イオンが、アルキルアンモニウム、アルキルピリジニウム、アルキルピロリジニウム、アルキルホスホニウム、又はアルキルイミダゾリウム、あるいは、それらアルキル鎖に不飽和アルキル部位、アミノ基、エーテル基、エステル基、又はカルボニル基の官能基がある陽イオンから成る、１種あるいは２種以上の陽イオンであり、
また、２）前記陰イオンが、ＰＦ６ −，ＢＦ４ −，ＣＦ３ＳＯ３ −，ＣＦ３ＣＦ２ＳＯ３ −，（ＣＦ３ＳＯ２）２Ｎ−，（ＣＦ３ＣＦ２ＳＯ２）２Ｎ−，（ＣＦ３ＣＯ）２Ｎ−，（ＣＦ３ＳＯ２）Ｎ（ＣＯＣＦ３）−，ＦＳＯ２ＮＳＯ２Ｆから成る、１種あるいは２種以上の陰イオンである、請求項１又は２に記載のＣＯ２分離回収方法。 The neutral ionic liquid absorbing liquid is an ionic liquid composed of a cation and an anion,
1) The cation is an alkyl ammonium, alkyl pyridinium, alkyl pyrrolidinium, alkyl phosphonium, or alkyl imidazolium, or an alkyl group having an unsaturated alkyl moiety, an amino group, an ether group, an ester group, or a carbonyl group. One or more cations composed of cations with functional groups,
2) The anions are PF 6 − , BF 4 − , CF 3 SO 3 − , CF 3 CF 2 SO 3 − , (CF 3 SO 2 ) 2 N − , and (CF 3 CF 2 SO 2 ) 2. N -, (CF 3 CO) 2 N -, (CF 3 SO 2) N (COCF 3) -, consisting of FSO 2 NSO 2 F, which is one or more anions, according to claim 1 or 2 A method for separating and recovering CO 2 described in 1.
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