JP5530288B2 - Carbon dioxide adsorption reducing agent and reduction method - Google Patents
Carbon dioxide adsorption reducing agent and reduction method Download PDFInfo
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- JP5530288B2 JP5530288B2 JP2010167366A JP2010167366A JP5530288B2 JP 5530288 B2 JP5530288 B2 JP 5530288B2 JP 2010167366 A JP2010167366 A JP 2010167366A JP 2010167366 A JP2010167366 A JP 2010167366A JP 5530288 B2 JP5530288 B2 JP 5530288B2
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims description 252
- 239000001569 carbon dioxide Substances 0.000 title claims description 125
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims description 125
- 238000000034 method Methods 0.000 title claims description 58
- 238000001179 sorption measurement Methods 0.000 title claims description 36
- 230000009467 reduction Effects 0.000 title claims description 17
- 239000003638 chemical reducing agent Substances 0.000 title claims description 14
- 150000001875 compounds Chemical class 0.000 claims description 104
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 35
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 34
- 239000013078 crystal Substances 0.000 claims description 30
- 239000007789 gas Substances 0.000 claims description 29
- 238000010438 heat treatment Methods 0.000 claims description 27
- 239000002772 conduction electron Substances 0.000 claims description 26
- 239000000843 powder Substances 0.000 claims description 25
- 229910052760 oxygen Inorganic materials 0.000 claims description 22
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 21
- 239000001301 oxygen Substances 0.000 claims description 21
- 239000007787 solid Substances 0.000 claims description 16
- 239000011261 inert gas Substances 0.000 claims description 11
- 239000010409 thin film Substances 0.000 claims description 11
- 238000002844 melting Methods 0.000 claims description 10
- 230000008018 melting Effects 0.000 claims description 10
- 230000000274 adsorptive effect Effects 0.000 claims 1
- 229910002090 carbon oxide Inorganic materials 0.000 claims 1
- 238000006722 reduction reaction Methods 0.000 description 16
- 238000006243 chemical reaction Methods 0.000 description 15
- 229910052751 metal Inorganic materials 0.000 description 15
- 239000002184 metal Substances 0.000 description 15
- 238000003795 desorption Methods 0.000 description 14
- 239000000126 substance Substances 0.000 description 14
- 239000011575 calcium Substances 0.000 description 12
- 239000000203 mixture Substances 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 8
- -1 heat and electricity Chemical compound 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 239000010936 titanium Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 229910021536 Zeolite Inorganic materials 0.000 description 6
- 238000000137 annealing Methods 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000010457 zeolite Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 238000010170 biological method Methods 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052500 inorganic mineral Inorganic materials 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000011707 mineral Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 238000011946 reduction process Methods 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000031700 light absorption Effects 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 2
- 231100000252 nontoxic Toxicity 0.000 description 2
- 230000003000 nontoxic effect Effects 0.000 description 2
- 230000029553 photosynthesis Effects 0.000 description 2
- 238000010672 photosynthesis Methods 0.000 description 2
- 238000000053 physical method Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 102220040233 rs79219465 Human genes 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 239000003440 toxic substance Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 238000004435 EPR spectroscopy Methods 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 239000000404 calcium aluminium silicate Substances 0.000 description 1
- 235000012215 calcium aluminium silicate Nutrition 0.000 description 1
- WNCYAPRTYDMSFP-UHFFFAOYSA-N calcium aluminosilicate Chemical compound [Al+3].[Al+3].[Ca+2].[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O WNCYAPRTYDMSFP-UHFFFAOYSA-N 0.000 description 1
- 229940078583 calcium aluminosilicate Drugs 0.000 description 1
- 235000011089 carbon dioxide Nutrition 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 235000019219 chocolate Nutrition 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 1
- 238000007750 plasma spraying Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 150000004032 porphyrins Chemical class 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 238000009700 powder processing Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 150000003333 secondary alcohols Chemical class 0.000 description 1
- 230000009919 sequestration Effects 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- ITRNXVSDJBHYNJ-UHFFFAOYSA-N tungsten disulfide Chemical compound S=[W]=S ITRNXVSDJBHYNJ-UHFFFAOYSA-N 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Images
Classifications
-
- Y02A50/2342—
Description
本発明は、複合金属酸化物からなる二酸化炭素の吸着還元剤及び該吸着還元剤を加熱する
だけで二酸化炭素を一酸化炭素に還元する方法に関する。
The present invention relates to an adsorption / reduction agent for carbon dioxide comprising a composite metal oxide and a method for reducing carbon dioxide to carbon monoxide simply by heating the adsorption / reduction agent.
二酸化炭素を一酸化炭素に還元する技術は、Ｃ１化学の原料として有用な一酸化炭素を製
造する方法として、また、環境問題において非常に重要である。人間の社会的活動により
大気中に放出される二酸化炭素は地球温暖化の原因の一つであることが知られており、近
年、大気中の二酸化炭素量を削減することが大きな課題となっている。
The technique of reducing carbon dioxide to carbon monoxide is very important as a method for producing carbon monoxide useful as a raw material for C1 chemistry and in environmental problems. Carbon dioxide released into the atmosphere by human social activities is known to be one of the causes of global warming. In recent years, reducing the amount of carbon dioxide in the atmosphere has become a major issue. Yes.
大気中の二酸化炭素量の削減方法としては、単に排出源からの排出量を減らす方法だけで
なく、排出された二酸化炭素の処理方法として、液化した二酸化炭素の海洋貯留に代表さ
れる物理的方法、植物の光合成を利用する生物的方法、及び吸着剤による吸着や、還元剤
による分解を利用する化学的方法が考案されている。
As a method of reducing the amount of carbon dioxide in the atmosphere, a physical method represented by marine storage of liquefied carbon dioxide as a method of treating the discharged carbon dioxide, as well as a method of simply reducing the amount of emissions from the emission source. In addition, biological methods utilizing plant photosynthesis and chemical methods utilizing adsorption by adsorbents and decomposition by reducing agents have been devised.
液化又は固化した二酸化炭素を海洋や地中に貯留する方法に関しては、長期的な隔離の安
定性や周辺環境への影響が未知であり、貯留には大きなエネルギーが必要になる。また、
光合成を利用する生物的方法も植林に広大な土地が必要であり、樹木の成長も待たなけれ
ばならないために短期的な二酸化炭素の削減効果は望みにくい。近年では生物的方法とし
てプランクトンを利用する方法も研究されているが、広大な面積の水面が必要になる。
Regarding the method of storing liquefied or solidified carbon dioxide in the ocean or in the ground, the long-term sequestration stability and the impact on the surrounding environment are unknown, and storage requires a large amount of energy. Also,
Biological methods using photosynthesis also require extensive land for afforestation, and the growth of trees must be waited for, so short-term effects of reducing carbon dioxide are unlikely. In recent years, a method using plankton as a biological method has been studied, but a large surface area of water is required.
一方で、化学的方法は物理的、生物的方法と比較して、エネルギーの低減や短期的な効果
が望める他、広大な土地が必要になることもない。さらに、化学的方法の内、排出源にお
いて還元剤を用いて二酸化炭素を分解する方法では、二酸化炭素の削減効果の他に、生成
物として一酸化炭素や蟻酸等が得られるので、二酸化炭素を資源として有効に転用できる
という利点もある。
On the other hand, compared to physical and biological methods, chemical methods can reduce energy and achieve short-term effects, and do not require vast land. Furthermore, among the chemical methods, the method of decomposing carbon dioxide using a reducing agent in the emission source can obtain carbon monoxide, formic acid, etc. as a product in addition to the effect of reducing carbon dioxide. There is also an advantage that it can be effectively diverted as a resource.
このような化学的方法として、硫化タングステン上に二酸化炭素と水素を導入し、加熱又
は太陽光の照射により二酸化炭素を一酸化炭素に転化する方法（特許文献１）、酸化鉄を
含む複合金属酸化物を触媒とし、二酸化炭素と水素を触媒に接触させて一酸化炭素を製造
する方法（特許文献２）、Ｆｅ及びＣｒを活性成分とする逆ＣＯシフト触媒又は活性アル
ミナを活性成分とする逆ＣＯシフト触媒の存在下にＨ2で還元する方法（特許文献３）、
ポルフィリン等の環状配位子化合物を活性成分として含有する還元触媒を用いる方法（特
許文献４）、酸化第一鉄を用いて二酸化炭素を炭素に還元する方法（特許文献５）、酸化
ニッケルを用いて二酸化炭素を一酸化炭素に還元する方法（特許文献６）等に関して特許
出願されている。また、高炉や発電所等からの燃焼排ガス中の二酸化炭素をゼオライトを
用いて物理吸着し分離する方法もある（特許文献７，８、９）。しかし、化学的方法は、
熱や電気といった二酸化炭素の分離や還元に要するエネルギーや、水素や触媒物質のコス
トに課題が残されている。
As such a chemical method, carbon dioxide and hydrogen are introduced onto tungsten sulfide, and carbon dioxide is converted into carbon monoxide by heating or irradiation with sunlight (Patent Document 1). Complex metal oxidation including iron oxide A method for producing carbon monoxide by contacting carbon dioxide and hydrogen with a catalyst using a product (Patent Document 2), a reverse CO shift catalyst using Fe and Cr as active components, or a reverse CO using active alumina as an active component A method of reducing with H 2 in the presence of a shift catalyst (Patent Document 3),
A method using a reduction catalyst containing a cyclic ligand compound such as porphyrin as an active component (Patent Document 4), a method of reducing carbon dioxide to carbon using ferrous oxide (Patent Document 5), and using nickel oxide A patent application has been filed regarding a method of reducing carbon dioxide to carbon monoxide (Patent Document 6). There is also a method of physically adsorbing and separating carbon dioxide in combustion exhaust gas from a blast furnace or a power plant using zeolite (Patent Documents 7, 8, and 9). But the chemical method is
Issues remain in the energy required for the separation and reduction of carbon dioxide such as heat and electricity, as well as the cost of hydrogen and catalytic materials.
ＣａＯ、Ａｌ2Ｏ3、ＳｉＯを構成成分とするアルミノケイ酸カルシウムは、鉱物名をマイ
エナイトと言い、その結晶と同型の結晶構造を有する化合物を「マイエナイト型化合物」
という。マイエナイト型化合物は、１２ＣａＯ・７Ａｌ2Ｏ3（以下、「Ｃ１２Ａ７」と記
す）なる代表組成を有し、Ｃ１２Ａ７結晶は、２分子を含む単位胞にある６６個の酸素イ
オンの内の２個が、結晶骨格で形成されるケージ内の空間に「フリー酸素」として包接さ
れているという、特異な結晶構造を持つことが報告されている（非特許文献１）。
Calcium aluminosilicate containing CaO, Al 2 O 3 , and SiO as constituent components is called a mayenite, and a compound having a crystal structure of the same type as the crystal is a “mayenite type compound”.
That's it. The mayenite type compound has a representative composition of 12CaO · 7Al 2 O 3 (hereinafter referred to as “C12A7”), and the C12A7 crystal has two of 66 oxygen ions in a unit cell containing two molecules. It has been reported that it has a unique crystal structure in which it is included as “free oxygen” in the space in the cage formed by the crystal skeleton (Non-patent Document 1).
２００３年以降、このフリー酸素イオンが種々の陰イオンで置換できることが明らかにさ
れた。特に、強い還元雰囲気にＣ１２Ａ７を保持すると、全てのフリー酸素を電子で置換
することができる。これは、化学式で、[Ｃａ24Ａｌ28Ｏ64]4+（ｅ-）4（以下、「Ｃ１２
Ａ７：ｅ−」と記す）と記述され、良好な電子伝導特性を示す（非特許文献２）。
Since 2003, it has been clarified that this free oxygen ion can be replaced by various anions. In particular, if C12A7 is held in a strong reducing atmosphere, all free oxygen can be replaced with electrons. This is a chemical formula, [Ca 24 Al 28 O 64 ] 4+ (e − ) 4 (hereinafter referred to as “C12
A7: e- ”), which shows good electron conduction characteristics (Non-patent Document 2).
本発明者らは、導電性マイエナイト型化合物であるＣ１２Ａ７：ｅ−及びＣ１２Ａ７と同
型化合物である１２ＳｒＯ・７Ａｌ2Ｏ3やＣ１２Ａ７と１２ＳｒＯ・７Ａｌ2Ｏ3との混晶
化合物とその製造法に関する発明を特許出願した（特許文献１０）。また、Ｃ１２Ａ７単
結晶を（イ）アルカリ金属又はアルカリ土類金属蒸気中で高温でアニールする方法、（ロ
）不活性イオンをイオン打ち込みする方法、又は、（ハ）還元雰囲気で融液から直接固化
する方法で、１×１０19／ｃｍ3以上の伝導電子を有するＣ１２Ａ７：ｅ−及びＣ１２Ａ
７と同型化合物が得られることを見出し、これらに関する発明を特許出願した（特許文献
１１）。
The present invention relates to C12A7: e- which is a conductive mayenite type compound and 12SrO · 7Al 2 O 3 which is the same type compound as C12A7, a mixed crystal compound of C12A7 and 12SrO · 7Al 2 O 3 and a method for producing the same. (Patent document 10). Also, C12A7 single crystal is (a) annealed at high temperature in alkali metal or alkaline earth metal vapor, (b) ion-implanted with inert ions, or (c) solidified directly from the melt in a reducing atmosphere. C12A7: e- and C12A having a conduction electron of 1 × 10 19 / cm 3 or more
It was found that the same type of compound as that of No. 7 was obtained, and a patent application was filed for an invention related thereto (Patent Document 11).
さらに、Ｃ１２Ａ７単結晶をチタン金属（Ｔｉ）蒸気中でアニールし、金属電気伝導性を
示すＣ１２Ａ７：ｅ−を得ることに成功し、その製法及び電子放出材料としてのその用途
に関する発明を特許出願した（特許文献１２）。金属電気伝導性を示すＣ１２Ａ７：ｅ−
に関しては、ＣａＣＯ3及びＡｌ2Ｏ3を１１：７で混合して、１３００℃で加熱した生成
物を金属Ｃａ蒸気雰囲気中で加熱することで粉末を直接合成することもできる（非特許文
献３）。
Furthermore, C12A7 single crystal was annealed in titanium metal (Ti) vapor to obtain C12A7: e- showing metal electrical conductivity, and a patent application was filed for an invention relating to its production method and its use as an electron-emitting material. (Patent Document 12). C12A7 showing metal electrical conductivity: e-
In regard to, the powder can be directly synthesized by mixing CaCO 3 and Al 2 O 3 at 11: 7 and heating the product heated at 1300 ° C. in a metallic Ca vapor atmosphere (Non-patent Document 3). ).
Ｃ１２Ａ７：ｅ−に包接される電子は、陽イオンである結晶骨格のケージ内に緩く結合し
ているために、電場印加又は化学的な手段により外部に取り出すことができる。本発明者
らは、外部に取り出された電子を還元反応に用いることができると考え、Ｃ１２Ａ７：ｅ
−に包接される電子でケトン化合物を還元し、２級アルコール及びジケトン化合物を製造
する方法を発明し、これを特許出願した（特許文献１３）。しかしながら、この製法では
Ｃ１２Ａ７：ｅ−を水中で用いるため、Ｃ１２Ａ７：ｅ−は分解してしまい、一工程につ
き一度しか使用できなかった。
Since the electrons included in C12A7: e- are loosely bonded in the cage of the crystal skeleton which is a cation, they can be extracted to the outside by electric field application or chemical means. The present inventors consider that electrons taken out to the outside can be used for the reduction reaction, and C12A7: e
Invented a method for producing a secondary alcohol and a diketone compound by reducing the ketone compound with electrons included in-, and applied for a patent (Patent Document 13). However, since C12A7: e- is used in water in this production method, C12A7: e- is decomposed and can be used only once per process.
さらに、Ａｌの一部をＧａ又はＩｎで置換したマイエナイト型化合物に係わる発明の出願
がなされており（特許文献１４）、これは、ＰＤＰ保護膜材料や、有機ＥＬデバイスにお
ける電荷注入材料など、高温加熱処理が必要とされる電極材料として適する。
Furthermore, an application for an invention related to a mayenite type compound in which a part of Al is substituted with Ga or In has been made (Patent Document 14), which includes high-temperature materials such as PDP protective film materials and charge injection materials in organic EL devices. It is suitable as an electrode material that requires heat treatment.
本発明の課題は、二酸化炭素から化学原料として有用な一酸化炭素を製造する方法や、大
気中へ排出される二酸化炭素量を化学的方法で処理して削減する方法において、高価な触
媒や還元剤等を使用しないで、かつ、熱や電気などの少ないエネルギー消費をもって二酸
化炭素を還元し、一酸化炭素を回収できる方法を提供することにある。
An object of the present invention is to provide an expensive catalyst or reduction in a method for producing carbon monoxide useful as a chemical raw material from carbon dioxide or a method for reducing the amount of carbon dioxide discharged into the atmosphere by a chemical method. An object of the present invention is to provide a method capable of reducing carbon dioxide and recovering carbon monoxide without using an agent or the like and with low energy consumption such as heat and electricity.
本発明者は、上記の目的を達成すべく鋭意検討を重ねた結果、導電性マイエナイト型化合
物を用いると、比較的低温で二酸化炭素を吸着できると共に、吸着した二酸化炭素を該化
合物を加熱するだけで高効率で一酸化炭素に還元処理できることを見出した。すなわち、
導電性マイエナイト型化合物は室温でも二酸化炭素を選択的に吸着することができ、該化
合物を加熱すると、吸着した二酸化炭素のＣＯへの還元が２００℃以下でも開始されるこ
とを見出した。すなわち、本発明者は、この導電性マイエナイト型化合物は、ゼオライト
のような物理吸着ではなく、化学吸着により二酸化炭素と強く結合し、一つの化合物で吸
着と還元の両機能を有することを見出した。
As a result of intensive studies to achieve the above object, the present inventor can adsorb carbon dioxide at a relatively low temperature and only heat the adsorbed carbon dioxide when using a conductive mayenite type compound. And found that carbon monoxide can be reduced with high efficiency. That is,
It has been found that the conductive mayenite type compound can selectively adsorb carbon dioxide even at room temperature, and when the compound is heated, the reduction of the adsorbed carbon dioxide to CO is started even at 200 ° C. or lower. That is, the present inventor has found that this conductive mayenite type compound strongly binds to carbon dioxide by chemical adsorption, not physical adsorption like zeolite, and has both adsorption and reduction functions with one compound. .
本発明は、１×１０19／ｃｍ3以上の伝導電子を有する導電性マイエナイト型化合物から
なることを特徴とする二酸化炭素の吸着還元剤、である。
The present invention is a carbon dioxide adsorption-reduction agent comprising a conductive mayenite type compound having a conduction electron of 1 × 10 19 / cm 3 or more.
導電性マイエナイト型化合物は、構造中に内包する酸化物イオン（Ｏ2 -,Ｏ2 2-）を置換し
た電子が伝導電子となり、Ｃ１２Ａ７の場合、組成式（［Ｃａ24Ａｌ28Ｏ64］4+（Ｏ2-）
2-x（ｅ-）2x）（０＜ｘ≦２）で示される。電子で置換させることにより、伝導電子を１
×１０15ｃｍ-3以上含ませることができる。伝導電子の理論的最大濃度はＣ１２Ａ７の場
合２．３×１０21ｃｍ-3である。伝導電子濃度が大きいほど還元能が大きいが、１×１０
18／ｃｍ3程度が二酸化炭素の還元作用を検出できる限界であり、伝導電子濃度は１×１
０19／ｃｍ3以上であることが好ましい。伝導電子濃度の最大値としては、単結晶では２
．３×１０21／ｃｍ3程度が可能である。
In the conductive mayenite type compound, electrons substituted for oxide ions (O 2 − , O 2 2− ) encapsulated in the structure become conduction electrons, and in the case of C12A7, the composition formula ([Ca 24 Al 28 O 64 ] 4 + (O 2- )
2-x (e − ) 2x ) (0 <x ≦ 2). By substituting electrons for conduction electrons,
× 10 15 cm −3 or more can be included. The theoretical maximum concentration of conduction electrons is 2.3 × 10 21 cm −3 for C12A7. The higher the conduction electron concentration, the greater the reducing ability, but 1 × 10
18 / cm 3 is the limit that can detect the reduction action of carbon dioxide, and the conduction electron concentration is 1 × 1.
It is preferably 0 19 / cm 3 or more. The maximum conduction electron concentration is 2 for single crystals.
. About 3 × 10 21 / cm 3 is possible.
この吸着還元剤の形状は、粉末、固体焼結体、薄膜、又は固体単結晶などのいずれでもよ
い。二酸化炭素は、吸着還元剤の表面に吸着される。
The adsorption reducing agent may have any shape such as a powder, a solid sintered body, a thin film, or a solid single crystal. Carbon dioxide is adsorbed on the surface of the adsorption reducing agent.
この吸着還元剤を室温に保持するか、２００℃以下に加熱し、乾燥空気中、乾燥酸素中、
又は不活性ガス雰囲気中で、二酸化炭素含有ガス、又は二酸化炭素を接触させて二酸化炭
素を吸着させる。次いで、二酸化炭素を吸着した状態の該化合物を２００℃以上、該化合
物の融点未満に加熱することによって、二酸化炭素を一酸化炭素に還元して該化合物から
脱離させる。この吸着処理は、導電性マイエナイト型化合物を加熱しないで室温で行うこ
とが好ましく、加温下で行う場合は２００℃以下が好ましい。２００℃を超えても吸着は
可能であるが、エネルギー効率上好ましくない。
This adsorption reducing agent is kept at room temperature or heated to 200 ° C. or less, in dry air, in dry oxygen,
Alternatively, carbon dioxide is adsorbed by contacting carbon dioxide-containing gas or carbon dioxide in an inert gas atmosphere. Next, the carbon dioxide-adsorbed compound is heated to 200 ° C. or higher and lower than the melting point of the compound to reduce carbon dioxide to carbon monoxide and desorb from the compound. This adsorption treatment is preferably performed at room temperature without heating the conductive mayenite type compound, and is preferably 200 ° C. or less when performed under heating. Although adsorption is possible even if it exceeds 200 degreeC, it is unpreferable on energy efficiency.
また、この吸着還元剤を２００℃以上、該化合物の融点未満に加熱し、乾燥空気中、乾燥
酸素中、又は不活性ガス雰囲気中で、二酸化炭素含有ガス、又は二酸化炭素を該化合物に
接触させることによって、吸着と同時に二酸化炭素を一酸化炭素に還元して該化合物から
脱離させる方法でもよい。前記の吸着及び／又は還元は加圧下、減圧下のいずれでも実施
できるが、大気圧下で行うことがエネルギー消費が少なくて済み好ましい。
Further, the adsorption reducing agent is heated to 200 ° C. or higher and lower than the melting point of the compound, and a carbon dioxide-containing gas or carbon dioxide is brought into contact with the compound in dry air, dry oxygen, or an inert gas atmosphere. Thus, a method of reducing carbon dioxide to carbon monoxide at the same time as adsorption and desorbing from the compound may be used. The adsorption and / or reduction can be carried out under pressure or under reduced pressure, but it is preferable to carry out the reaction under atmospheric pressure because it consumes less energy.
吸着プロセスと還元プロセスを分離して行う方法の場合は、混合ガス中の二酸化炭素を分
離、還元して生成物である一酸化炭素を回収するのに特に有効である。吸着プロセスと還
元プロセスが分かれているので、吸着プロセスで二酸化炭素のみを吸着させ、残りのガス
を排気した後に一酸化炭素を脱離させれば効率よく一酸化炭素を回収できる。同時に二酸
化炭素も脱離するが、脱離したガスを昇圧又は冷却することで二酸化炭素はドライアイス
になるので一酸化炭素と二酸化炭素の分離は容易である。ただし、吸着還元剤の昇温、冷
却を繰り返す必要があるので、吸着還元剤を高温に保持して、吸着プロセスと還元プロセ
スを同時に行う場合より余分なエネルギーを消費する。吸着プロセスと還元プロセスを同
時に行う場合は、高純度の二酸化炭素を還元して生成物である一酸化炭素を回収するのに
特に有効である。この方法は、反応系に二酸化炭素を循環させていればいずれ全て一酸化
炭素になる。また、この方法は、高純度の二酸化炭素や二酸化炭素混合ガスを処理して生
成した一酸化炭素を回収する必要がない場合にも有効である。
In the case of a method in which the adsorption process and the reduction process are separated, it is particularly effective for recovering carbon monoxide as a product by separating and reducing carbon dioxide in the mixed gas. Since the adsorption process and the reduction process are separated, carbon monoxide can be efficiently recovered by adsorbing only carbon dioxide in the adsorption process and desorbing carbon monoxide after exhausting the remaining gas. At the same time, carbon dioxide is also desorbed. However, by depressurizing or cooling the desorbed gas, the carbon dioxide becomes dry ice, so separation of carbon monoxide and carbon dioxide is easy. However, since it is necessary to repeat the temperature rise and cooling of the adsorption reducing agent, extra energy is consumed compared with the case where the adsorption reducing agent is kept at a high temperature and the adsorption process and the reduction process are performed simultaneously. When the adsorption process and the reduction process are performed at the same time, it is particularly effective for reducing high-purity carbon dioxide and recovering the product carbon monoxide. This method eventually becomes carbon monoxide as long as carbon dioxide is circulated in the reaction system. This method is also effective when there is no need to recover carbon monoxide generated by treating high purity carbon dioxide or a carbon dioxide mixed gas.
上記の加熱により一酸化炭素が主生成物として生成し、該化合物から脱離する。加熱によ
り一酸化炭素が生成するのは、二酸化炭素が導電性マイエナイト型化合物に化学吸着し、
該化合物に包接された伝導電子により二酸化炭素が活性化されるためと考えられる。ゼオ
ライトを用いた物理吸着はゼオライトの細孔に二酸化炭素を取り込む吸着であるが、導電
性マイエナイト型化合物は細孔の構造を持つものの、細孔の大きさは、ゼオライトの細孔
と比べて１／１０以下の大きさなので、ゼオライトのように内部に二酸化炭素は取り込め
ない。そこで、該化合物への二酸化炭素の吸着は、該化合物の最表面での解離吸着であろ
うと考えられる。
Carbon monoxide is produced as a main product by the above heating, and desorbed from the compound. Carbon monoxide is generated by heating because carbon dioxide is chemisorbed on the conductive mayenite type compound,
It is considered that carbon dioxide is activated by the conduction electrons included in the compound. Physical adsorption using zeolite is adsorption that incorporates carbon dioxide into the pores of the zeolite, but the conductive mayenite type compound has a pore structure, but the pore size is 1 compared to the pores of the zeolite. Since the size is / 10 or less, carbon dioxide cannot be taken inside like zeolite. Therefore, it is considered that the adsorption of carbon dioxide on the compound will be dissociative adsorption on the outermost surface of the compound.
二酸化炭素は、熱した炭素、亜鉛、鉄などの上を通すと一酸化炭素に還元されることが知
られているが、二酸化炭素は非常に安定な化合物で、２０００℃で２％ぐらい一酸化炭素
と酸素に解離するにすぎない、と言われる。本発明の方法では加熱温度にも依るがほぼ２
０％〜８０％程度が還元される。二酸化炭素の還元に繰り返し使用しても導電性マイエナ
イト型化合物の劣化（伝導電子の減少）はほとんどないが、繰り返し使用して該化合物の
導電性が低下した場合は、再度アニール等の方法で導電性を回復させることにより再使用
できる。
It is known that carbon dioxide is reduced to carbon monoxide when passed over hot carbon, zinc, iron, etc., but carbon dioxide is a very stable compound and is about 2% monoxide at 2000 ° C. It is said that it only dissociates into carbon and oxygen. In the method of the present invention, depending on the heating temperature, it is almost 2
About 0% to 80% is reduced. Even if it is used repeatedly for the reduction of carbon dioxide, there is almost no deterioration of the conductive mayenite type compound (reduction of conduction electrons). However, if the conductivity of the compound decreases after repeated use, it can be conducted again by a method such as annealing. Can be reused by restoring sex.
[導電性マイエナイト型化合物の定義]
本発明において、「マイエナイト型化合物」とは、鉱物のマイエナイトそれ自体、マイエ
ナイト型岩石、及び鉱物のマイエナイト結晶と同型の結晶構造を有する複合酸化物をいう
。導電性マイエナイト型化合物の代表組成は、式［Ｃａ24Ａｌ28Ｏ64］4+（Ｏ2-）2-x（
ｅ-）2x（０＜ｘ≦２）で示される。導電性マイエナイト型化合物は、例えば、焼結法で
製造したＣ１２Ａ７を、例えば、Ｃａ又はＴｉの金属蒸気中で、１１００℃付近でアニー
ルすることで得ることができる。導電性マイエナイト型化合物の製造方法自体は種々の方
法が公知であり、本発明では、これらの方法で得られた該化合物を適宜使用できる。
[Definition of conductive mayenite type compound]
In the present invention, the “mayenite-type compound” refers to a composite oxide having the same type of crystal structure as the mineral mayenite itself, the mayenite-type rock, and the mineral mayenite crystal. The representative composition of the conductive mayenite type compound is represented by the formula [Ca 24 Al 28 O 64 ] 4+ (O 2- ) 2-x (
e − ) 2x (0 <x ≦ 2) The conductive mayenite type compound can be obtained, for example, by annealing C12A7 produced by a sintering method in the vicinity of 1100 ° C. in a metal vapor of Ca or Ti, for example. Various methods for producing a conductive mayenite type compound are known, and in the present invention, the compound obtained by these methods can be used as appropriate.
マイエナイト型化合物の結晶は内径０．４ｎｍ程の籠状の構造（ケージ）がその壁面を共
有し、三次元的に繋がることで構成されている。通常、マイエナイト型化合物のケージの
内部にはＯ2-などの負イオンが含まれているが、上記のアニールによってそれらを伝導電
子に置換することが可能である。アニール時間を長くすることにより、導電性マイエナイ
ト型化合物中の伝導電子濃度は多くなる。
The crystal of the mayenite type compound is constituted by a cage structure (cage) having an inner diameter of about 0.4 nm sharing its wall surface and three-dimensionally connecting. Usually, negative ions such as O 2− are contained inside the cage of the mayenite type compound, but it is possible to replace them with conduction electrons by the above-mentioned annealing. By increasing the annealing time, the conduction electron concentration in the conductive mayenite type compound increases.
Ｔｉ金属蒸気中でアニールする場合は、２４時間程度アニールすれば、３ｍｍ厚の単結晶
マイエナイト型化合物でも、理論的最大の伝導電子濃度(Ｃ１２Ａ７の場合２．３×１０2
1ｃｍ-3)を有する導電性マイエナイト型化合物を得ることができる。また、化学量論組成
のマイエナイト型化合物の融液を還元雰囲気中で固化しても良い。還元雰囲気中の固化で
得られた導電性マイエナイト型化合物の伝導電子濃度は、１０21ｃｍ-3未満である。
When annealing in Ti metal vapor, annealing is performed for about 24 hours, even if a single crystal mayenite type compound having a thickness of 3 mm is used, the theoretical maximum conduction electron concentration (2.3 × 10 2 in the case of C12A7).
A conductive mayenite type compound having 1 cm −3 ) can be obtained. Further, a melt of a mayenite type compound having a stoichiometric composition may be solidified in a reducing atmosphere. The conductive mayenite type compound obtained by solidification in a reducing atmosphere has a conduction electron concentration of less than 10 21 cm −3 .
また、Ａｒ+イオンを高濃度にイオン打ち込みすることによっても作製できる。得られた
導電性マイエナイト型化合物中の伝導電子濃度は、光吸収帯の強度から求めることができ
る（１２ＣａＯ・７Ａｌ2Ｏ3の場合２．８ｅＶ）。伝導電子濃度が小さいときは、電子ス
ピン共鳴吸収帯の強度からも伝導電子濃度を求めることができる。
It can also be produced by implanting Ar + ions at a high concentration. The conduction electron concentration in the obtained conductive mayenite type compound can be determined from the intensity of the light absorption band (2.8 eV in the case of 12CaO · 7Al 2 O 3 ). When the conduction electron concentration is low, the conduction electron concentration can be obtained from the intensity of the electron spin resonance absorption band.
導電性マイエナイト型化合物は、上記の代表組成の式を構成するＣａの一部又は全てがＬ
ｉ、Ｎａ、Ｋ、Ｍｇ、Ｓｒ、Ｂａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃ
ｕ、Ｉｒ、Ｒｕ、Ｒｈ、Ｐｔからなる群から選ばれる少なくとも一種類以上の典型金属元
素、又は遷移金属元素で置換されていてもよい。また、この式を構成するＡｌの一部又は
全てがＢ、Ｇａ、Ｃ、Ｓｉ、Ｆｅ、Ｇｅからなる群から選ばれる少なくとも一種類以上の
典型金属元素、又は遷移金属元素で置換されていてもよい。さらに、上記の式を構成する
Ｏの一部又は全てがＨ、Ｆ、Ｃｌ、Ｂｒ、Ａｕからなる群から選ばれる少なくとも一種類
以上の典型元素又は金属元素で置換されていてもよい。
In the conductive mayenite type compound, a part or all of Ca constituting the formula of the above representative composition is L
i, Na, K, Mg, Sr, Ba, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, C
It may be substituted with at least one typical metal element selected from the group consisting of u, Ir, Ru, Rh, and Pt, or a transition metal element. Further, even if a part or all of Al constituting this formula is substituted with at least one kind of typical metal element or transition metal element selected from the group consisting of B, Ga, C, Si, Fe, Ge Good. Furthermore, part or all of O constituting the above formula may be substituted with at least one typical element or metal element selected from the group consisting of H, F, Cl, Br, and Au.
本発明の方法により、カルシウム、アルミニウム、酸素といったクラーク数上位の元素の
みで構成された安価で無毒性の化合物を用い、還元剤として高価な金属化合物や水素を用
いることなく、かつ、少ないエネルギー消費をもって、二酸化炭素を還元処理できる。ま
た、還元処理する二酸化炭素のガス圧を高圧にして該化合物に接触させなくても選択的に
化学吸着するので、二酸化炭素を高効率で分解することができる。また、１００容積％の
高濃度の二酸化炭素はもとより、排出ガス、天然ガス、大気中等に含有される高濃度乃至
低濃度の二酸化炭素も選択的に化学吸着し高効率で還元処理できる。
By using the method of the present invention, an inexpensive and non-toxic compound composed only of elements having a higher Clark number such as calcium, aluminum, and oxygen, without using an expensive metal compound or hydrogen as a reducing agent, and less energy consumption The carbon dioxide can be reduced. Further, since the gas is selectively chemisorbed without bringing it into contact with the compound by increasing the gas pressure of the carbon dioxide to be reduced, carbon dioxide can be decomposed with high efficiency. Further, not only 100% by volume of high concentration carbon dioxide but also high concentration to low concentration carbon dioxide contained in exhaust gas, natural gas, air, etc. can be selectively chemisorbed and reduced with high efficiency.
以下、本発明の二酸化炭素の還元処理方法（以下、「本発明の方法」という）について詳
細に説明する。本発明の方法は、導電性マイエナイト型化合物を用い、二酸化炭素を一酸
化炭素に還元する方法である。
Hereinafter, the carbon dioxide reduction treatment method of the present invention (hereinafter referred to as “method of the present invention”) will be described in detail. The method of the present invention is a method of reducing carbon dioxide to carbon monoxide using a conductive mayenite type compound.
本発明の方法に用いる導電性マイエナイト型化合物は、粉末、固体焼結体、薄膜、固体単
結晶など、その形状はいずれでもよい。また、担体に担持されていてもよい。薄膜、固体
単結晶以外はマイエナイト型化合物を経由することなく、原料から直接導電性マイエナイ
ト型化合物を製造できる。また、原料として、マイエナイト型鉱物、マイエナイトを含有
するスラグや焼却灰等も使用できる。
The conductive mayenite type compound used in the method of the present invention may have any shape such as powder, solid sintered body, thin film, solid single crystal and the like. Further, it may be supported on a carrier. A conductive mayenite type compound can be produced directly from the raw material without passing through the mayenite type compound except for the thin film and the solid single crystal. In addition, mayenite type minerals, slag containing mayenite, incinerated ash, and the like can be used as raw materials.
粉末の作製は、化学当量組成の導電性マイエナイト型化合物の原料の粉末を還元雰囲気下
で加熱すればよい。また、固体焼結体の作製は、化学当量組成のマイエナイト型化合物の
原料粉末を還元雰囲気下で１３００℃程度で加熱焼結し固化すれば良い。
The powder may be produced by heating the raw material powder of the conductive mayenite type compound having a chemical equivalent composition in a reducing atmosphere. The solid sintered body may be produced by heating and solidifying a mayenite type compound raw material powder having a chemical equivalent composition at about 1300 ° C. in a reducing atmosphere.
薄膜の作製は、マイエナイト型化合物の固体焼結体をターゲットに用い、パルスレーザー
堆積法（ＰＬＤ）、スパッター法、プラズマ溶射法などによりＭｇＯ、Ｙ3Ａｌ5Ｏ12など
の基板上に成膜したマイエナイト型化合物の薄膜を５００℃以上で加熱しながら再度ＰＬ
Ｄによりマイエナイト型化合物薄膜を堆積して一体化させる。再度のＰＬＤではプラズマ
化されたマイエナイト型化合物が還元剤として働き該薄膜を導電体化させる。
The thin film was formed on a substrate such as MgO, Y 3 Al 5 O 12 by pulse laser deposition (PLD), sputtering, plasma spraying, etc. using a solid sintered body of mayenite type compound as a target. PL again while heating the thin film of mayenite type compound above 500 ° C
A mayenite type compound thin film is deposited by D and integrated. In the PLD again, the plasma converted mayenite type compound acts as a reducing agent to convert the thin film into a conductor.
また、固体単結晶は、マイエナイト型化合物の原料粉末を１６００℃程度で融解した融液
を引き上げること（ＣＺ法）によりマイエナイト型化合物単結晶を作製し、該単結晶を真
空にしたガラス管中に金属Ｃａ粉末又はＴｉ粉末などと共に封入し還元雰囲気下で加熱す
ればよい。
In addition, the solid single crystal is prepared by forming a mayenite type compound single crystal by pulling up a melt obtained by melting the raw material powder of the mayenite type compound at about 1600 ° C. (CZ method), and placing the single crystal in a vacuumed glass tube. What is necessary is just to enclose with metal Ca powder or Ti powder etc., and to heat in a reducing atmosphere.
固体焼結体又は固体単結晶の導電性マイエナイト型化合物を粉末に加工することも可能で
ある。粉末加工は、乳鉢中での粉砕、ジェットミルによる粉砕などを用いることができる
。これらの方法により、伝導電子を１×１０19ｃｍ-3以上含むマイエナイト型化合物を作
製する。
It is also possible to process a solid sintered body or a solid single crystal conductive mayenite type compound into a powder. For powder processing, pulverization in a mortar, pulverization with a jet mill, or the like can be used. By these methods, a mayenite type compound containing 1 × 10 19 cm −3 or more of conduction electrons is produced.
なお、作製法により粉末、固体焼結体、薄膜、固体単結晶に関わらずそれらの表面から伝
導電子が抜けて本来の導電性が失われていることがある。その場合は、真空、不活性ガス
中、又は還元雰囲気下において９００℃以上〜該化合物の融点（１２５０℃）未満で加熱
し、最表面まで本来の導電性を回復させることが望ましい。
Note that, depending on the manufacturing method, conduction electrons may be lost from the surface of the powder, solid sintered body, thin film, solid single crystal, and the original conductivity may be lost. In that case, it is desirable to heat at 900 ° C. or higher to less than the melting point (1250 ° C.) of the compound in a vacuum, an inert gas, or a reducing atmosphere to restore the original conductivity to the outermost surface.
二酸化炭素は、反応器内や排出ガス流路中に設置した導電性マイエナイト化合物の粉末、
固体焼結体、薄膜、固体単結晶等に接触するように、乾燥空気中、乾燥酸素中、又は不活
性ガス中で供給する。供給する二酸化炭素を含有するガスを供給前に脱水処理してもよい
。
Carbon dioxide is a powder of conductive mayenite compound installed in the reactor and in the exhaust gas flow path,
It supplies in dry air, dry oxygen, or in an inert gas so that it may contact a solid sintered compact, a thin film, a solid single crystal, etc. A gas containing carbon dioxide to be supplied may be dehydrated before being supplied.
マイエナイト型化合物は大気中では、水の吸着が優先されてしまい、また、過剰な水分下
では化合物自体が分解してしまうので、二酸化炭素の化学吸着処理はできるだけ水分を含
有しない雰囲気、すなわち、水蒸気分圧１０-3気圧程度以下の雰囲気である乾燥空気中、
乾燥酸素中、又は不活性ガス雰囲気中で行うのが好ましい。導電性マイエナイト型化合物
の表面に付着している不純物を除去したり、導電性を十分に回復させたりするために該化
合物を真空、不活性ガス中、又は還元性ガス雰囲気において９００℃以上〜該化合物の融
点（１２５０℃）未満で加熱し、冷却した後に該化合物に二酸化炭素を化学吸着させるこ
とが好ましい。
Since the mayenite type compound is prioritized to adsorb water in the atmosphere, and the compound itself decomposes under excessive moisture, the chemical adsorption treatment of carbon dioxide is an atmosphere containing as little water as possible, that is, water vapor In dry air with an atmosphere of partial pressure of 10 -3 atmospheres or less,
It is preferable to carry out in dry oxygen or in an inert gas atmosphere. In order to remove impurities adhering to the surface of the conductive mayenite type compound or to sufficiently restore the conductivity, the compound is removed in a vacuum, an inert gas, or a reducing gas atmosphere at 900 ° C. or higher to It is preferable that the compound be chemically adsorbed with carbon dioxide after heating at a temperature lower than the melting point (1250 ° C.) of the compound and cooling.
次に、二酸化炭素を化学吸着した状態の該化合物を加熱することによって、二酸化炭素を
還元し、一酸化炭素を該化合物から脱離させる。加熱温度は２００℃以上〜該化合物の融
点（１２５０℃）未満とする。ＣＯの脱離ピークが最大値になる温度は７００℃程度なの
で、加熱温度は２００℃〜８００℃がより好ましい。加熱雰囲気は、乾燥空気中、乾燥酸
素中、又は不活性ガス雰囲気中でよい。５００℃未満であれば水分を含有していない乾燥
雰囲気が好ましい。５００℃以上では乾燥酸素雰囲気では伝導電子が酸素で置換されるた
め、不活性ガス雰囲気中が好ましい。
Next, by heating the compound in a state in which carbon dioxide is chemisorbed, the carbon dioxide is reduced and carbon monoxide is desorbed from the compound. The heating temperature is 200 ° C. or higher and lower than the melting point (1250 ° C.) of the compound. Since the temperature at which the CO desorption peak reaches a maximum value is about 700 ° C., the heating temperature is more preferably 200 ° C. to 800 ° C. The heating atmosphere may be in dry air, dry oxygen, or an inert gas atmosphere. If it is less than 500 degreeC, the dry atmosphere which does not contain a water | moisture content is preferable. Above 500 ° C., the conductive electrons are replaced with oxygen in a dry oxygen atmosphere, and therefore an inert gas atmosphere is preferable.
加熱の際の該化合物の昇温の方法は特に限定されず、ヒーター、赤外ランプ、通電加熱等
、処理装置に適した方法を選択すればよい。昇温速度が遅いほど二酸化炭素の還元効率は
上昇する。例えば、下記の実施例の結果では、昇温速度が５Ｋ／秒のときと比較して０．
５Ｋ／秒では二酸化炭素の分解効率は３０％から８０％に上昇する。
The method for raising the temperature of the compound during heating is not particularly limited, and a method suitable for the treatment apparatus such as a heater, an infrared lamp, and electric heating may be selected. The reduction efficiency of carbon dioxide increases as the rate of temperature rise is slower. For example, in the results of the following examples, the temperature rise rate is 0. 0 compared to when the rate of temperature increase is 5 K / second.
At 5 K / sec, the decomposition efficiency of carbon dioxide increases from 30% to 80%.
もちろん、二酸化炭素を流しながら該化合物をある温度で保持すれはその温度での該化合
物への化学吸着と一酸化炭素への還元による脱離が同時に起こる。したがって、該化合物
を２００℃以上、該化合物の融点未満に加熱し、乾燥空気中、乾燥酸素中、又は不活性ガ
ス雰囲気中で、二酸化炭素含有ガス、又は二酸化炭素を該化合物に接触させることによっ
て、二酸化炭素を一酸化炭素に還元させる方法も用いられる。ある温度に保持するという
ことは昇温速度を究極に遅くする(0K/sec)ということになる。ＣＯの脱離ピークが最大値
になる温度は７００℃程度なので、二酸化炭素の分解開始温度の２００℃以上、８００℃
以下の範囲で保持するのが最も好ましい。したがって、この場合、２００℃〜１０００℃
程度の高温排ガスを還元処理するのに適している。
Of course, if the compound is held at a certain temperature while flowing carbon dioxide, chemisorption to the compound at that temperature and desorption by reduction to carbon monoxide occur simultaneously. Therefore, by heating the compound to 200 ° C. or higher and lower than the melting point of the compound, contacting the compound with carbon dioxide-containing gas or carbon dioxide in dry air, dry oxygen, or inert gas atmosphere. A method of reducing carbon dioxide to carbon monoxide is also used. Holding at a certain temperature means that the rate of temperature rise is slowed down (0K / sec). Since the temperature at which the CO desorption peak reaches a maximum value is about 700 ° C., the decomposition start temperature of carbon dioxide is 200 ° C. or higher and 800 ° C.
Most preferably, the following range is maintained. Therefore, in this case, 200 ° C to 1000 ° C
It is suitable for reducing high temperature exhaust gas.
導電性マイエナイト化合物へ供給する二酸化炭素のガスの温度は実用上は室温が望ましい
が該化合物の融点（１２５０℃）未満であればよい。−７８．５℃以下だと導電性マイエ
ナイト化合物への二酸化炭素の吸着層が多層化してしまい、該化合物と新たに吸着すべき
二酸化炭素が接触しにくくなる。一方、二酸化炭素のガスの温度が７００℃〜１２５０℃
の高温では二酸化炭素の吸着量が低下する。したがって、好ましくは室温〜７００℃、よ
り好ましくは室温で大気圧の二酸化炭素を吸着させる。吸着させる二酸化炭素のガスの圧
力は、通常、高圧になる程、吸着の効率はよくなるが該化合物の場合は標準の大気圧（１
００ｋＰａ）又は大気圧未満でも十分な吸着能を有している。
The temperature of the carbon dioxide gas supplied to the conductive mayenite compound is preferably room temperature in practice, but may be lower than the melting point (1250 ° C.) of the compound. When the temperature is −78.5 ° C. or lower, the carbon dioxide adsorption layer on the conductive mayenite compound becomes multi-layered, and it becomes difficult for the compound and carbon dioxide to be newly adsorbed to come into contact with each other. Meanwhile, the temperature of carbon dioxide gas is 700 ° C to 1250 ° C.
At high temperatures, the amount of carbon dioxide adsorbed decreases. Accordingly, carbon dioxide at atmospheric pressure is preferably adsorbed at room temperature to 700 ° C., more preferably at room temperature. The pressure of the carbon dioxide gas to be adsorbed usually increases as the pressure increases, but in the case of the compound, the standard atmospheric pressure (1
00 kPa) or less than atmospheric pressure, it has sufficient adsorption capacity.
以下に、実施例に基づいて、本発明をより詳細に説明する。なお、実施例では、不確定な
要素を可能な限り排除するため、及び分解による生成物の同定に四重極質量分析装置を使
用しているので真空チャンバーを反応容器として使用した。
Below, based on an Example, this invention is demonstrated in detail. In the examples, in order to eliminate uncertain elements as much as possible, and because a quadrupole mass spectrometer is used for identification of products by decomposition, a vacuum chamber was used as a reaction vessel.
＜導電性マイエナイト型化合物の準備＞
伝導電子濃度が約２×１０21ｃｍ-3の導電性マイエナイト型化合物Ｃ１２Ａ７：ｅ−の板
を準備した。このＣ１２Ａ７：ｅ−の板は以下の方法で製造した。チョコラルスキー法で
作成したＣ１２Ａ７単結晶インゴットから、１３ｍｍ×３ｍｍ×０．５ｍｍの板を切り出
し、５ｇのＴｉ金属粉末と共に、石英管中に真空封入した。該石英管を電気炉に入れ、１
１００℃に２４時間保持した後、空冷した。得られたＣ１２Ａ７：ｅ−の板の伝導電子濃
度は、該Ｃ１２Ａ７：ｅ−の板の表面の光反射スペクトルを光吸収スペクトルに変換し、
２．８ｅＶの吸収バンドの強度から求めた。
<Preparation of conductive mayenite type compound>
A plate of the conductive mayenite type compound C12A7: e- having a conduction electron concentration of about 2 × 10 21 cm −3 was prepared. The C12A7: e- plate was produced by the following method. A 13 mm × 3 mm × 0.5 mm plate was cut out from a C12A7 single crystal ingot prepared by the chocolate ski method, and was vacuum-sealed in a quartz tube together with 5 g of Ti metal powder. Place the quartz tube in an electric furnace, 1
After maintaining at 100 ° C. for 24 hours, it was air-cooled. The conduction electron concentration of the obtained C12A7: e- plate converts the light reflection spectrum of the surface of the C12A7: e- plate into a light absorption spectrum,
It calculated | required from the intensity | strength of the absorption band of 2.8 eV.
得られたＣ１２Ａ７：ｅ−の板を８０％のリン酸水溶液で１０秒間化学エッチングした後
、蒸留水で５秒間洗浄しリン酸水溶液を取り除いた。その後、無水メタノール及び無水ア
セトンでそれぞれ５分間超音波洗浄した。
The obtained C12A7: e- plate was chemically etched with 80% phosphoric acid aqueous solution for 10 seconds and then washed with distilled water for 5 seconds to remove the phosphoric acid aqueous solution. Then, ultrasonic cleaning was performed for 5 minutes each with anhydrous methanol and anhydrous acetone.
次に、図３に示すように、試料（Ｃ１２Ａ７：ｅ−の板）１を通電加熱が行える試料ホル
ダーに取り付け、反応容器（図示せず）中に導入した。ここで、通電加熱が行える試料ホ
ルダーとは上記試料１の両端を機械的に固定するものである。その固定は２枚の金属片２
で試料１を挟み、ネジ３で締め付ける構造になっており、この金属片２は試料１に電源４
から通電する際の電極としての役割も持っている。
Next, as shown in FIG. 3, the sample (C12A7: e-plate) 1 was attached to a sample holder capable of conducting heating and introduced into a reaction vessel (not shown). Here, the sample holder capable of conducting heating is one that mechanically fixes both ends of the sample 1. The fixing is two pieces of metal 2
The sample 1 is sandwiched between and clamped with a screw 3, and the metal piece 2 is connected to the sample 1 with a
It also has a role as an electrode when energizing.
その後、真空ポンプを用いて反応容器の真空度を１×１０-5Ｐａ以下にして、Ｃ１２Ａ７
：ｅ−の板に電流を流し緩やかに１Ｋ／秒で昇温することで、Ｃ１２Ａ７：ｅ−の板及び
試料ホルダーに大気中で吸着した不純物を取り除いた。最終的に１０Ａの電流をＣ１２Ａ
７：ｅ−の板に流し１０００℃で１０分間加熱保持し、その後−５Ｋ／秒となるように電
流を調節し、室温まで冷却した。この加熱保持により板の最表面までＣ１２Ａ７：ｅ−本
来の導電性を回復させた。
Thereafter, the vacuum degree of the reaction vessel is reduced to 1 × 10 −5 Pa or less using a vacuum pump, and C12A7
: Impurities adsorbed on the C12A7: e-plate and the sample holder in the air were removed by passing a current through the e-plate and gradually raising the temperature at 1 K / sec. Eventually 10A current is C12A
7: Poured onto an e-plate, heated and held at 1000 ° C. for 10 minutes, then adjusted the current to −5 K / sec and cooled to room temperature. By this heating and holding, C12A7: e-original conductivity was recovered to the outermost surface of the plate.
＜導電性マイエナイト型化合物による二酸化炭素の吸着＞
次に、室温にて上記のＣ１２Ａ７：ｅ−の板が設置してある反応容器にリーク弁を介して
二酸化炭素を導入し、Ｃ１２Ａ７：ｅ−の板に二酸化炭素を吸着させた後、再び真空ポン
プを用いて反応容器内に残留した二酸化炭素を除去して二酸化炭素の吸着量を見積もった
。２Ｌ（Ｌａｎｇｍｕｉｒ：１×１０-6ｔｏｒｒのガス雰囲気に１秒間暴露することを１
Ｌとする単位）以上の二酸化炭素の導入で最小見積もりで試料の全表面原子数の１／３０
吸着した。
<Adsorption of carbon dioxide by conductive mayenite type compound>
Next, carbon dioxide is introduced through a leak valve into the reaction vessel in which the C12A7: e− plate is installed at room temperature, and the carbon dioxide is adsorbed on the C12A7: e− plate, and then vacuumed again. Carbon dioxide remaining in the reaction vessel was removed using a pump, and the amount of carbon dioxide adsorbed was estimated. 2 L (Langmuir: 1 × 10 −6 torr exposure to a gas atmosphere for 1 second
1/30 of the total surface atoms of the sample with a minimum estimate by introducing more carbon dioxide
Adsorbed.
＜導電性マイエナイト型化合物からの二酸化炭素と一酸化炭素の脱離＞
反応容器内に残留した二酸化炭素を除去した後、Ｃ１２Ａ７：ｅ−の板を通電加熱し、０
．５Ｋ／秒で１０００℃まで昇温して、脱離してくるガス種及び相対量を四重極質量分析
計で測定し、また、反応容器内の真空度の変化から脱離してくるガスの絶対量を測定し、
それぞれ、Ｃ１２Ａ７：ｅ−の板の加熱温度との関係を調べた。
<Desorption of carbon dioxide and carbon monoxide from conductive mayenite type compounds>
After the carbon dioxide remaining in the reaction vessel was removed, the C12A7: e- plate was energized and heated.
. The temperature is raised to 1000 ° C. at 5 K / second, the desorbed gas species and relative amounts are measured with a quadrupole mass spectrometer, and the absolute gas desorbed from the change in the degree of vacuum in the reaction vessel Measure the quantity,
The relationship with the heating temperature of the C12A7: e- plate was examined.
Ｃ１２Ａ７：ｅ−の板の温度が９０℃付近から二酸化炭素（ＣＯ2）、１３０℃付近から
一酸化炭素（ＣＯ）及び原子状酸素（Ｏ）の脱離を確認した。ＣＯ及びＯは１０００℃ま
での昇温で脱離が完了しなかったが１０００℃までの脱離量の相対比はＣＯ2：ＣＯ：Ｏ
＝１：８：２であり、脱離ガスの絶対量は脱離ガス分子の総数で約３×１０12個（約１×
１０13個／ｃｍ2）であった。
The desorption of carbon dioxide (CO 2 ) was confirmed when the temperature of the C12A7: e- plate was around 90 ° C., and carbon monoxide (CO) and atomic oxygen (O) were observed around 130 ° C. CO and O did not complete desorption at a temperature up to 1000 ° C., but the relative ratio of the desorption amount up to 1000 ° C. was CO 2 : CO: O
= 1: 8: 2, and the absolute amount of desorbed gas is about 3 × 10 12 (about 1 ×
10 13 pieces / cm 2 ).
なお、反応容器は超高真空（〜１×１０-6Ｐａ以下）にしても排気が追いつかないＣＯ2
とＣＯが残留してしまうので、単にそれらが吸着しただけではないことを確認するために
、上記と同様の操作を二酸化炭素を構成する酸素を安定同位体である18Ｏで置換したＣ18
Ｏ2で行ったところ、脱離ガスの成分がＣ18Ｏ2、Ｃ18Ｏ、18Ｏに変化した。図１は、０．
５Ｋ／秒で１０００℃まで昇温した際のＣ18Ｏ2、Ｃ18Ｏ、18Ｏの脱離量の温度依存性で
ある。
In addition, even if the reaction vessel is in an ultra-high vacuum (˜1 × 10 −6 Pa or less), the exhaust does not catch up with CO 2.
Because CO may remain with, C 18 simply because they confirm that not only adsorbed, and the similar procedure described above was replaced with 18 O oxygen stable isotopes constituting carbon dioxide
When performed with O 2 , the desorbed gas component changed to C 18 O 2 , C 18 O, and 18 O. FIG.
This is the temperature dependence of the amount of C 18 O 2 , C 18 O, and 18 O desorbed when the temperature is raised to 1000 ° C. at 5 K / sec.
反応容器に導入する二酸化炭素を低濃度のものに変更した以外は実施例１と同じ条件で
実施した。反応容器にリーク弁を介して二酸化炭素を１容積％含む乾燥酸素、又は二酸化
炭素を１容積％含む乾燥窒素を導入し、Ｃ１２Ａ７：ｅ−の板に二酸化炭素を吸着させた
後、真空ポンプを用いて反応容器に残留する該乾燥酸素又は該乾燥窒素を除去した。
It implemented on the same conditions as Example 1 except having changed the carbon dioxide introduce | transduced into a reaction container into a low concentration thing. After introducing dry oxygen containing 1% by volume of carbon dioxide or dry nitrogen containing 1% by volume of carbon dioxide into the reaction vessel through a leak valve, and adsorbing carbon dioxide on the C12A7: e- plate, Used to remove the dry oxygen or the dry nitrogen remaining in the reaction vessel.
二酸化炭素を１容積％含む乾燥酸素、又は二酸化炭素を１容積％含む乾燥窒素のいずれの
気体を導入した場合においても、Ｃ１２Ａ７：ｅ−の温度が９０℃付近から二酸化炭素（
ＣＯ2）、１３０℃付近から一酸化炭素（ＣＯ）及び原子状酸素（Ｏ）の脱離を確認した
。
In the case of introducing either dry oxygen containing 1% by volume of carbon dioxide or dry nitrogen containing 1% by volume of carbon dioxide, the temperature of C12A7: e-
CO 2 ), desorption of carbon monoxide (CO) and atomic oxygen (O) from around 130 ° C. was confirmed.
実施例１において、加熱温度の上限を１０００℃から５００℃に変更してＣＯ2吸着−昇
温脱離（５Ｋ／秒）の操作を１０回繰り返したところ、５００℃までの二酸化炭素と一酸
化炭素の脱離量の相対比、及び脱離ガスの絶対量に際立った変化は見られなかった（図２
参照）。図２に、１回目と１０回目のスペクトルのグラフを示す。ここで、１０回目は９
００℃まで上昇させており、スペクトルはその一部を示している。
In Example 1, when the upper limit of the heating temperature was changed from 1000 ° C. to 500 ° C. and the operation of CO 2 adsorption-temperature desorption (5 K / second) was repeated 10 times, carbon dioxide and monoxide up to 500 ° C. There was no significant change in the relative ratio of the amount of desorbed carbon and the absolute amount of desorbed gas (FIG. 2).
reference). FIG. 2 shows graphs of the first and tenth spectra. Here, the 10th time is 9
The temperature is raised to 00 ° C., and the spectrum shows a part of the spectrum.
実施例１の導電性Ｃ１２Ａ７：ｅ−の板に代えて粉末を用いた。
＜導電性マイエナイト型化合物の準備＞
ＣａＣＯ3及びＡｌ2Ｏ3の各粉末をＣａとＡｌの割合が１１：７となるように混合し、ア
ルミナ坩堝中にて１３００℃で６時間加熱した。得られた粉末をシリカガラス管内に挿入
し１×１０-4Ｐａの真空中で１１００℃で１５時間加熱した。これにより得た粉末３ｇを
、シリカガラス管内に金属Ｃａ粉末０．１８ｇとともに挿入し、７００℃で１５時間加熱
することにより内部を金属Ｃａ蒸気雰囲気として、伝導電子濃度が約２×１０21ｃｍ-3の
Ｃ１２Ａ７：ｅ−の粉末を得た。得られたＣ１２Ａ７：ｅ−粉末の伝導電子濃度は、拡散
反射スペクトルを光吸収スペクトルに変換し、２．８ｅＶの吸収バンドの強度から求めた
。
Instead of the conductive C12A7: e- plate of Example 1, powder was used.
<Preparation of conductive mayenite type compound>
Each powder of CaCO 3 and Al 2 O 3 was mixed so that the ratio of Ca and Al was 11: 7, and heated in an alumina crucible at 1300 ° C. for 6 hours. The obtained powder was inserted into a silica glass tube and heated at 1100 ° C. for 15 hours in a vacuum of 1 × 10 −4 Pa. 3 g of the powder thus obtained was inserted into a silica glass tube together with 0.18 g of metal Ca powder, and heated at 700 ° C. for 15 hours to make the inside a metal Ca vapor atmosphere, and the conduction electron concentration was about 2 × 10 21 cm −. 3 C12A7: e- powder was obtained. The conduction electron concentration of the obtained C12A7: e-powder was obtained from the intensity of the absorption band of 2.8 eV by converting the diffuse reflection spectrum into a light absorption spectrum.
次に、Ｃ１２Ａ７：ｅ−粉末をＴａで作製した坩堝に入れ、真空中に設置したプレート型
アルミナセラミックスヒーター（坂口電熱（株）製ＭＳ−２）上に設置した。その後、ヒ
ーターに通電し、真空度が１×１０-5Ｐａ以上にならないように３５０℃で２４時間加熱
することで、Ｃ１２Ａ７：ｅ−粉末、坩堝及びヒーターに大気中で付着したガスを脱離さ
せた。
Next, C12A7: e-powder was placed in a crucible made of Ta, and placed on a plate-type alumina ceramic heater (MS-2 manufactured by Sakaguchi Electric Heat Co., Ltd.) placed in a vacuum. After that, the heater is energized and heated at 350 ° C. for 24 hours so that the degree of vacuum does not become 1 × 10 −5 Pa or more, thereby desorbing C12A7: e-powder, crucible, and gas adhering to the heater in the atmosphere. I let you.
＜導電性マイエナイト型化合物による二酸化炭素の吸着＞
次に、室温にて上記の反応容器にリーク弁を介して二酸化炭素を導入し、Ｃ１２Ａ７：ｅ
−の粉末に二酸化炭素を吸着させた後、真空ポンプを用いて反応容器内に残留した二酸化
炭素を除去した。
<Adsorption of carbon dioxide by conductive mayenite type compound>
Next, carbon dioxide was introduced into the reaction vessel through a leak valve at room temperature, and C12A7: e
After carbon dioxide was adsorbed to the powder of −, carbon dioxide remaining in the reaction vessel was removed using a vacuum pump.
＜導電性マイエナイト型化合物からの二酸化炭素と一酸化炭素の脱離＞
その後、再びヒーターに通電しＣ１２Ａ７：ｅ−の粉末を加熱し、３００℃まで昇温して
、脱離してくるガス種を四重極質量分析計で測定したところ、一酸化炭素の脱離を確認し
た。
<Desorption of carbon dioxide and carbon monoxide from conductive mayenite type compounds>
Thereafter, the heater was energized again, the C12A7: e- powder was heated, the temperature was raised to 300 ° C., and the desorbed gas species was measured with a quadrupole mass spectrometer. confirmed.
［比較例１］
実施例１のＣ１２Ａ７：ｅ−の板の代わりに、電子を含まない化学当量組成のＣ１２Ａ７
単結晶の板を試料として用いて実施例１と同様の条件で操作を行った。実施例１と同様に
二酸化炭素の吸着が観察された。二酸化炭素を吸着した試料を加熱する際は、電子を含ま
ないＣ１２Ａ７単結晶は通電加熱が出来ないのでシリコン単結晶とＣ１２Ａ７単結晶を接
合してヒーターとして通電した。Ｃ１２Ａ７：ｅ−と同等のＣＯ2（Ｃ18Ｏ2）の脱離が観
測されたがＣＯ（Ｃ18Ｏ）の脱離は観測されなかった。
[Comparative Example 1]
Instead of the C12A7: e- plate of Example 1, C12A7 having a chemical equivalent composition containing no electrons
The operation was performed under the same conditions as in Example 1 using a single crystal plate as a sample. Carbon dioxide adsorption was observed as in Example 1. When heating the sample having adsorbed carbon dioxide, the C12A7 single crystal containing no electrons cannot be heated by heating, so the silicon single crystal and the C12A7 single crystal were joined and energized as a heater. The elimination of CO 2 (C 18 O 2 ) equivalent to C12A7: e- was observed, but no elimination of CO (C 18 O) was observed.
［比較例２］
比較例１のＣ１２Ａ７単結晶の板の代わりに、電気伝導度が小さい１×１０18ｃｍ-3の電
子を含む化学当量組成のＣ１２Ａ７薄膜試料を用いて比較例１と同様の条件で操作を行っ
た。実施例１と同様に二酸化炭素の吸着が観察された。二酸化炭素を吸着した試料を加熱
すると実施例１と同等のＣＯ2（Ｃ18Ｏ2）の脱離が観測されたがＣＯ（Ｃ18Ｏ）の脱離は
観測されなかった。
[Comparative Example 2]
In place of the C12A7 single crystal plate of Comparative Example 1, a C12A7 thin film sample having a chemical equivalent composition containing 1 × 10 18 cm −3 electrons with low electrical conductivity was used and operated under the same conditions as in Comparative Example 1. It was. Carbon dioxide adsorption was observed as in Example 1. When the sample on which carbon dioxide had been adsorbed was heated, CO 2 (C 18 O 2 ) desorption equivalent to that in Example 1 was observed, but no CO (C 18 O) desorption was observed.
本発明の方法は、カルシウム、アルミニウム、酸素といったクラーク数上位の元素のみか
らなる安価な無毒性の化合物を繰り返し使用し、金属化合物や水素等の還元剤を使用する
ことなく、二酸化炭素を還元し、高効率で一酸化炭素を生成することを可能とする。さら
に、本発明の方法は、二酸化炭素が排気ガスや大気などに混入している場合でも選択的に
二酸化炭素を化学吸着して、還元できることから二酸化炭素を含有する様々なガスに適用
できる。また、一酸化炭素は、燃料やＣ１化学の重要な原料化合物であるので、本発明の
方法は、二酸化炭素排出量の削減以外にも二酸化炭素の資源化に利用できる。
The method of the present invention repeatedly uses an inexpensive non-toxic compound consisting only of elements having a higher Clark number such as calcium, aluminum and oxygen, and reduces carbon dioxide without using a reducing agent such as a metal compound or hydrogen. This makes it possible to produce carbon monoxide with high efficiency. Furthermore, the method of the present invention can be applied to various gases containing carbon dioxide because it can be selectively chemisorbed and reduced even when carbon dioxide is mixed in exhaust gas or the atmosphere. In addition, since carbon monoxide is an important raw material compound for fuel and C1 chemistry, the method of the present invention can be used for recycling carbon dioxide in addition to reducing carbon dioxide emissions.
Claims (5)
特徴とする二酸化炭素の吸着還元剤。 A carbon dioxide adsorption reducing agent comprising a conductive mayenite type compound having conduction electrons of 1 × 10 19 / cm 3 or more.
あることを特徴とする請求項１記載の吸着還元剤。 The adsorptive reducing agent according to claim 1, wherein the shape of the conductive mayenite type compound is a powder, a solid sintered body, a thin film, or a solid single crystal.
るか、２００℃以下に加熱し、乾燥空気中、乾燥酸素中、又は不活性ガス雰囲気中で、二
酸化炭素含有ガス、又は二酸化炭素を該化合物に接触させて二酸化炭素を吸着させ、次い
で、二酸化炭素を吸着した状態の該化合物を２００℃以上、該化合物の融点未満に加熱す
ることによって、二酸化炭素を一酸化炭素に還元して該化合物から脱離させることを特徴
とする二酸化炭素の還元方法。 A conductive mayenite type compound having a conduction electron of 1 × 10 19 / cm 3 or more is kept at room temperature or heated to 200 ° C. or less, and is carbon dioxide in dry air, dry oxygen, or an inert gas atmosphere. Carbon dioxide is adsorbed by bringing the compound gas or carbon dioxide into contact with the compound to adsorb carbon dioxide, and then heating the compound in a state where carbon dioxide has been adsorbed to 200 ° C. or higher and lower than the melting point of the compound. A method for reducing carbon dioxide, comprising reducing to carbon oxide and desorbing from the compound.
、該化合物の融点未満に加熱し、乾燥空気中、乾燥酸素中、又は不活性ガス雰囲気中で、
二酸化炭素含有ガス、又は二酸化炭素を該化合物に接触させることによって、吸着と同時
に二酸化炭素を一酸化炭素に還元して該化合物から脱離させることを特徴とする二酸化炭
素の還元方法。 A conductive mayenite type compound having a conduction electron of 1 × 10 19 / cm 3 or more is heated to 200 ° C. or higher and lower than the melting point of the compound, and is dried in dry air, in dry oxygen, or in an inert gas atmosphere.
A method for reducing carbon dioxide, comprising bringing a carbon dioxide-containing gas or carbon dioxide into contact with the compound to reduce carbon dioxide to carbon monoxide and desorbing the compound simultaneously with adsorption.
化炭素の還元方法。 The carbon dioxide reduction method according to claim 3 or 4, wherein the adsorption and / or reduction is performed under atmospheric pressure.
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