JP2023157643A - Carbon dioxide occlusion reduction type catalyst - Google Patents
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- 239000003054 catalyst Substances 0.000 title claims abstract description 116
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 22
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 11
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 8
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 33
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 28
- 229910052707 ruthenium Inorganic materials 0.000 claims abstract description 24
- 239000011148 porous material Substances 0.000 claims abstract description 16
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 13
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 13
- 239000011734 sodium Substances 0.000 claims description 31
- 229910000272 alkali metal oxide Inorganic materials 0.000 claims description 11
- 238000002441 X-ray diffraction Methods 0.000 claims description 7
- 229910052708 sodium Inorganic materials 0.000 claims description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 2
- 230000003197 catalytic effect Effects 0.000 abstract description 6
- 238000006722 reduction reaction Methods 0.000 description 43
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 31
- 239000000843 powder Substances 0.000 description 24
- 230000007423 decrease Effects 0.000 description 19
- 230000000694 effects Effects 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 16
- 239000007789 gas Substances 0.000 description 14
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 12
- 239000000292 calcium oxide Substances 0.000 description 11
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 11
- 239000011232 storage material Substances 0.000 description 11
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 7
- -1 alkali metal salt Chemical class 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 4
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 3
- 238000006555 catalytic reaction Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 229910052792 caesium Inorganic materials 0.000 description 2
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 229910052701 rubidium Inorganic materials 0.000 description 2
- 239000004317 sodium nitrate Substances 0.000 description 2
- 235000010344 sodium nitrate Nutrition 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical class OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 150000001242 acetic acid derivatives 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
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- NQZFAUXPNWSLBI-UHFFFAOYSA-N carbon monoxide;ruthenium Chemical group [Ru].[Ru].[Ru].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-] NQZFAUXPNWSLBI-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical class OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- YLPJWCDYYXQCIP-UHFFFAOYSA-N nitroso nitrate;ruthenium Chemical compound [Ru].[O-][N+](=O)ON=O YLPJWCDYYXQCIP-UHFFFAOYSA-N 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- GTCKPGDAPXUISX-UHFFFAOYSA-N ruthenium(3+);trinitrate Chemical compound [Ru+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GTCKPGDAPXUISX-UHFFFAOYSA-N 0.000 description 1
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
本発明は、二酸化炭素（ＣＯ２）吸蔵還元型触媒に関し、より詳しくは、アルカリ金属を含有するＣＯ２吸蔵還元型触媒に関する。 TECHNICAL FIELD The present invention relates to a carbon dioxide (CO 2 ) storage-reduction catalyst, and more particularly to a CO 2 storage-reduction catalyst containing an alkali metal.
二酸化炭素（ＣＯ２）を原料としたメタン化反応は、近年の地球温暖化抑制のためのＣＯ２排出量削減の観点から注目されている。このようなメタン化反応に用いられる触媒としては、ＣＯ２吸蔵材としての酸化カルシウム（ＣａＯ）とメタン化触媒としてのルテニウム（Ｒｕ）とがアルミナ等の担体に担持されたＣＯ２吸蔵還元型触媒（例えば、特開２０２０－１１０７６９号公報（特許文献１）及びＡ．Ｂｅｒｍｅｊｏ－Ｌｏｐｅｚら、Ａｐｐｌｉｅｄ Ｃａｔａｌｙｓｉｓ Ｂ：Ｅｎｖｉｒｏｎｍｅｎｔａｌ、２０１９年、第２５６巻、１１７８４５（非特許文献１））が知られている。このＣＯ２吸蔵還元型触媒は、ＣＯ２を含むガスを流通させることによってＣＯ２を吸蔵し、還元ガス（例えば、Ｈ２）を流通させることによって吸蔵したＣＯ２を還元してメタン（ＣＨ４）を生成する。 BACKGROUND ART Methanation reactions using carbon dioxide (CO 2 ) as a raw material have attracted attention in recent years from the perspective of reducing CO 2 emissions to suppress global warming. Catalysts used in such methanation reactions include CO 2 storage reduction catalysts in which calcium oxide (CaO) as a CO 2 storage material and ruthenium (Ru) as a methanation catalyst are supported on a carrier such as alumina. (For example, JP 2020-110769 A (Patent Document 1) and A. Bermejo-Lopez et al., Applied Catalysis B: Environmental, 2019, Volume 256, 117845 (Non-Patent Document 1)) are known. This CO 2 storage reduction type catalyst stores CO 2 by passing a gas containing CO 2 and reduces the stored CO 2 by passing a reducing gas (for example, H 2 ) to produce methane (CH 4 ) . ) is generated.
しかしながら、ＣＯ２吸蔵材としてＣａＯを用いたＣＯ２吸蔵還元型触媒においては、吸蔵／還元時の動作開始温度が３２０℃と高温であるため、ＣＯ２吸蔵還元型触媒システムの作動時に熱エネルギーを過剰に投入する必要があり、システムのエネルギー効率が低下するという問題があった。 However, in a CO 2 storage reduction catalyst that uses CaO as a CO 2 storage material, the operation start temperature during storage/reduction is as high as 320°C, so thermal energy is consumed during operation of the CO 2 storage reduction catalyst system. There was a problem in that it was necessary to input an excessive amount of energy, reducing the energy efficiency of the system.
また、Ａ．Ｂｅｒｍｅｊｏ－Ｌｏｐｅｚら、Ａｐｐｌｉｅｄ Ｃａｔａｌｙｓｉｓ Ｂ：Ｅｎｖｉｒｏｎｍｅｎｔａｌ、２０１９年、第２５６巻、１１７８４５（非特許文献１）には、ＣＯ２吸蔵材としての酸化ナトリウム（Ｎａ２Ｏ）とメタン化触媒としてのルテニウム（Ｒｕ）とがアルミナ等の担体に担持されたＣＯ２吸蔵還元型触媒が記載されている。このＣＯ２吸蔵還元型触媒においても、吸蔵／還元時の動作開始温度が３７０℃と高温であるため、ＣＯ２吸蔵還元型触媒システムの作動時に熱エネルギーを過剰に投入する必要があり、システムのエネルギー効率が低下するという問題があった。また、非特許文献１には、Ｎａ２Ｏの含有量が少なくなるにつれて、メタンの生成量が少なくなることが示唆されている。 Also, A. Bermejo-Lopez et al., Applied Catalysis B: Environmental, 2019, Vol. 256, 117845 (Non-Patent Document 1) describes the use of sodium oxide (Na 2 O) as a CO 2 storage material and ruthenium (Ru) as a methanation catalyst. ) is supported on a carrier such as alumina, and a CO 2 storage reduction type catalyst is described. Even in this CO 2 storage reduction type catalyst, the operation start temperature during storage/reduction is as high as 370°C, so it is necessary to input excessive thermal energy when the CO 2 storage reduction type catalyst system is operated. There was a problem that energy efficiency decreased. Furthermore, Non-Patent Document 1 suggests that as the content of Na 2 O decreases, the amount of methane produced decreases.
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、低温においても優れたＣＯ２吸蔵性能とメタン化触媒活性を発現するＣＯ２吸蔵還元型触媒を提供することを目的とする。 The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide a CO 2 storage reduction catalyst that exhibits excellent CO 2 storage performance and methanation catalyst activity even at low temperatures. .
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、ＣＯ２吸蔵材としてのアルカリ金属とメタン化触媒としてのルテニウム（Ｒｕ）とがアルミナ等の担体に担持されたＣＯ２吸蔵還元型触媒において、アルカリ金属の含有量を特定の範囲内とすることによって、低温においても優れたＣＯ２吸蔵性能とメタン化触媒活性とが発現することを見出し、本発明を完成するに至った。 As a result of intensive research to achieve the above object, the present inventors have discovered that a CO 2 storage material in which an alkali metal as a CO 2 storage material and ruthenium (Ru) as a methanation catalyst are supported on a carrier such as alumina. The present inventors have discovered that by controlling the alkali metal content within a specific range in a reduced catalyst, excellent CO 2 storage performance and methanation catalyst activity can be achieved even at low temperatures, leading to the completion of the present invention. .
すなわち、本発明のＣＯ２吸蔵還元型触媒は、金属酸化物からなり、平均細孔径が３～５０ｎｍであり、細孔容積が０．３～１．５ｃｍ３／ｇである多孔質担体と、前記多孔質担体に担持されたルテニウムと、前記多孔質担体に担持されたアルカリ金属とを含有する触媒であり、前記ルテニウムの含有量が、前記多孔質担体とルテニウムとの合計含有量１００質量部に対して、１～５質量部であり、前記アルカリ金属の含有量が、前記触媒全体に対して、酸化物換算で２．８～４．５質量％であることを特徴とするものである。 That is, the CO 2 storage reduction catalyst of the present invention comprises a porous carrier made of a metal oxide, having an average pore diameter of 3 to 50 nm, and a pore volume of 0.3 to 1.5 cm 3 /g; The catalyst contains ruthenium supported on the porous carrier and an alkali metal supported on the porous carrier, and the ruthenium content is 100 parts by mass of the total content of the porous carrier and ruthenium. 1 to 5 parts by mass, and the content of the alkali metal is 2.8 to 4.5 mass% in terms of oxide based on the entire catalyst. .
本発明のＣＯ２吸蔵還元型触媒においては、前記アルカリ金属がナトリウムであることが好ましく、また、Ｘ線回折パターンにおいて、前記アルカリ金属の酸化物の結晶子径が４４ｎｍに相当する回折ピークが存在しないことが好ましい。 In the CO 2 storage reduction catalyst of the present invention, the alkali metal is preferably sodium, and in the X-ray diffraction pattern, there is a diffraction peak corresponding to a crystallite diameter of 44 nm of the alkali metal oxide. It is preferable not to do so.
本発明によれば、低温においても優れたＣＯ２吸蔵性能とメタン化触媒活性を発現するＣＯ２吸蔵還元型触媒を得ることが可能となる。 According to the present invention, it is possible to obtain a CO 2 storage reduction type catalyst that exhibits excellent CO 2 storage performance and methanation catalyst activity even at low temperatures.
以下、本発明をその好適な実施形態に即して詳細に説明する。 Hereinafter, the present invention will be explained in detail based on its preferred embodiments.
〔ＣＯ２吸蔵還元型触媒〕
本発明の二酸化炭素（ＣＯ２）吸蔵還元型触媒は、金属酸化物からなる多孔質担体と、前記多孔質担体に担持されたルテニウムと、前記多孔質担体に担持されたアルカリ金属とを含有する触媒である。
[ CO2 storage reduction catalyst]
The carbon dioxide (CO 2 ) storage reduction catalyst of the present invention contains a porous carrier made of a metal oxide, ruthenium supported on the porous carrier, and an alkali metal supported on the porous carrier. It is a catalyst.
本発明に用いられる担体は、金属酸化物からなる多孔質担体である。担体として多孔質のものを用いることによって、ガス成分が良好に拡散し、ＣＯ２吸蔵性能及びメタン化触媒活性が向上する。前記金属酸化物としては、ＣＯ２吸蔵還元型触媒の担体として用いられるものであれば特に制限はなく、例えば、アルミナ（Ａｌ２Ｏ３）、シリカ（ＳｉＯ２）、ジルコニア（ＺｒＯ２）、チタニア（ＴｉＯ２）等の公知の金属酸化物が挙げられる。これらの金属酸化物のうち、メタン化触媒活性が高くなるという観点から、アルミナ、チタニアが好ましく、アルミナがより好ましい。また、このような金属酸化物は、１種を単独で使用しても２種以上を併用してもよい。 The carrier used in the present invention is a porous carrier made of metal oxide. By using a porous carrier, gas components can diffuse well, and CO 2 storage performance and methanation catalyst activity are improved. The metal oxide is not particularly limited as long as it can be used as a carrier for a CO 2 storage reduction catalyst, and examples include alumina (Al 2 O 3 ), silica (SiO 2 ), zirconia (ZrO 2 ), and titania. Known metal oxides such as (TiO 2 ) may be used. Among these metal oxides, alumina and titania are preferred, and alumina is more preferred, from the viewpoint of increasing methanation catalyst activity. Further, such metal oxides may be used alone or in combination of two or more.
前記多孔質担体の平均細孔径は、３～５０ｎｍであり、５～２０ｎｍであることが好ましい。多孔質担体の平均細孔径が前記下限未満になると、ガス成分が十分に拡散せず、ＣＯ２吸蔵性能及びメタン化触媒活性が低下する傾向にあり、他方、前記上限を超えると、細孔構造の安定性が低下する傾向にある。 The average pore diameter of the porous carrier is 3 to 50 nm, preferably 5 to 20 nm. If the average pore diameter of the porous carrier is less than the above lower limit, the gas components will not diffuse sufficiently, and the CO 2 storage performance and methanation catalyst activity will tend to decrease.On the other hand, if it exceeds the above upper limit, the pore structure will deteriorate. stability tends to decrease.
また、前記多孔質担体の細孔容積は、０．３～１．５ｃｍ３／ｇであり、０．３～１．０ｃｍ３／ｇであることが好ましい。多孔質担体の細孔容積が前記下限未満になると、ガス成分が十分に拡散せず、ＣＯ２吸蔵性能及びメタン化触媒活性が低下する傾向にあり、他方、前記上限を超えると、多孔質担体の熱的安定性が低下する傾向にある。 Further, the pore volume of the porous carrier is 0.3 to 1.5 cm 3 /g, preferably 0.3 to 1.0 cm 3 /g. If the pore volume of the porous carrier is less than the above-mentioned lower limit, the gas components will not diffuse sufficiently, and the CO 2 storage performance and methanation catalyst activity will tend to decrease.On the other hand, if the pore volume of the porous carrier exceeds the above-mentioned upper limit, Thermal stability tends to decrease.
本発明のＣＯ２吸蔵還元型触媒においては、前記多孔質担体にルテニウム（Ｒｕ）が担持されている。このＲｕは、メタン化触媒として作用するものであり、具体的には、ＣＯ２吸蔵材に吸蔵されたＣＯ２が還元ガス（例えば、Ｈ２）と反応して還元されることによってメタン（ＣＨ４）が生成する際にＣＯ２の還元反応を促進するものである。 In the CO 2 storage reduction catalyst of the present invention, ruthenium (Ru) is supported on the porous carrier. This Ru acts as a methanation catalyst, and specifically, CO 2 stored in the CO 2 storage material reacts with a reducing gas (for example, H 2 ) and is reduced to produce methane (CH 4 ) promotes the reduction reaction of CO 2 when it is generated.
本発明のＣＯ２吸蔵還元型触媒において、Ｒｕの含有量は、前記多孔質担体とＲｕとの合計含有量１００質量部に対して、１～５質量部である。Ｒｕの含有量が前記範囲内にあると、ＣＯ２の還元反応が促進され、メタン化触媒活性が向上する。一方、Ｒｕの含有量が前記下限未満になると、ＣＯ２の還元反応が十分に促進されず、メタン化触媒活性が低下する。他方、Ｒｕの含有量が前記上限を超えると、前記多孔質担体の細孔が閉塞してＣＯ２吸蔵量が減少するため、ＣＯ２吸蔵性能が低下したり、Ｒｕが粒成長してメタン化触媒活性が低下したりする。 In the CO 2 storage reduction catalyst of the present invention, the content of Ru is 1 to 5 parts by mass based on 100 parts by mass of the total content of the porous carrier and Ru. When the Ru content is within the above range, the reduction reaction of CO 2 is promoted and the methanation catalyst activity is improved. On the other hand, if the Ru content is less than the lower limit, the reduction reaction of CO 2 will not be sufficiently promoted and the methanation catalyst activity will decrease. On the other hand, if the Ru content exceeds the upper limit, the pores of the porous carrier are blocked and the amount of CO 2 storage decreases, resulting in a decrease in CO 2 storage performance and grain growth of Ru, resulting in methane formation. Catalytic activity may decrease.
また、本発明のＣＯ２吸蔵還元型触媒においては、前記多孔質担体にアルカリ金属が担持されている。このアルカリ金属は、ＣＯ２吸蔵材として作用するものである。このようなアルカリ金属は、通常、酸化物、炭酸塩、炭酸水素塩の状態で前記多孔質担体に担持されている。 Furthermore, in the CO 2 storage reduction catalyst of the present invention, an alkali metal is supported on the porous carrier. This alkali metal acts as a CO 2 storage material. Such alkali metals are usually supported on the porous carrier in the form of oxides, carbonates, or bicarbonates.
前記アルカリ金属としては、例えば、リチウム（Ｌｉ）、ナトリウム（Ｎａ）、カリウム（Ｋ）、ルビジウム（Ｒｂ）、セシウム（Ｃｓ）が挙げられ、中でも、ＣＯ２吸蔵性能が更に向上するという観点から、Ｎａが好ましい。 Examples of the alkali metal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Among them, from the viewpoint of further improving CO 2 storage performance, Na is preferred.
本発明のＣＯ２吸蔵還元型触媒において、前記アルカリ金属の含有量は、前記触媒全体に対して、酸化物換算で２．８～４．５質量％である。前記アルカリ金属の含有量が前記範囲内にあると、低温においても優れたＣＯ２吸蔵性能とメタン化触媒活性とが発現する。一方、前記アルカリ金属の含有量が前記下限未満になると、ＣＯ２の吸蔵サイトが少なくなり、ＣＯ２吸蔵量が減少するため、ＣＯ２吸蔵性能及びメタン化触媒活性が低下する。他方、前記アルカリ金属の含有量が前記上限を超えると、前記多孔質担体の細孔が閉塞してＣＯ２吸蔵量が減少するため、ＣＯ２吸蔵性能及びメタン化触媒活性が低下する。また、前記アルカリ金属の酸化物の結晶子径が大きくなり、低温でのＣＯ２吸蔵性能とメタン化触媒活性とが低下する。前記アルカリ金属の含有量としては、低温でのＣＯ２吸蔵性能とメタン化触媒活性とが更に向上するという観点から、酸化物換算で２．８～４．２質量％が好ましく、３．０～４．０質量％がより好ましい。 In the CO 2 storage reduction type catalyst of the present invention, the content of the alkali metal is 2.8 to 4.5% by mass in terms of oxide based on the entire catalyst. When the content of the alkali metal is within the above range, excellent CO 2 storage performance and methanation catalyst activity are exhibited even at low temperatures. On the other hand, when the alkali metal content is less than the lower limit, the number of CO 2 storage sites decreases and the amount of CO 2 storage decreases, resulting in a decrease in CO 2 storage performance and methanation catalyst activity. On the other hand, when the content of the alkali metal exceeds the upper limit, the pores of the porous carrier are clogged and the amount of CO 2 storage decreases, resulting in a decrease in CO 2 storage performance and methanation catalyst activity. Moreover, the crystallite size of the alkali metal oxide increases, and the CO 2 storage performance and methanation catalyst activity at low temperatures decrease. The content of the alkali metal is preferably 2.8 to 4.2% by mass in terms of oxide, and 3.0 to 4.2% by mass in terms of oxide, from the viewpoint of further improving CO 2 storage performance and methanation catalyst activity at low temperatures. 4.0% by mass is more preferred.
また、本発明のＣＯ２吸蔵還元型触媒は、そのＸ線回折パターンにおいて、前記アルカリ金属の酸化物の結晶子径が４４ｎｍに相当する回折ピークが存在しないこと、すなわち、結晶子径が粗大なアルカリ金属の酸化物を含有しないことが好ましい。前記アルカリ金属の酸化物の結晶子径が４４ｎｍに相当する回折ピークが存在する、すなわち、結晶子径が粗大なアルカリ金属の酸化物を含有すると、低温でのＣＯ２吸蔵性能とメタン化触媒活性とが低下する傾向にある。なお、このような結晶子径が粗大なアルカリ金属の酸化物は、アルカリ金属の含有量が前記上限を超えると、生成しやすくなる。 In addition, the CO 2 storage reduction catalyst of the present invention has no diffraction peak corresponding to the crystallite size of 44 nm of the alkali metal oxide in its X-ray diffraction pattern, that is, the crystallite size is coarse. Preferably, it does not contain alkali metal oxides. If there is a diffraction peak corresponding to a crystallite size of 44 nm in the alkali metal oxide, that is, if an alkali metal oxide with a coarse crystallite size is contained, the CO 2 storage performance and methanation catalyst activity at low temperatures will decrease. is on the decline. Note that such alkali metal oxides having a coarse crystallite size are likely to be produced when the alkali metal content exceeds the above upper limit.
〔ＣＯ２吸蔵還元型触媒の調製方法〕
このような本発明のＣＯ２吸蔵還元型触媒は、例えば、以下のようにして調製することができる。すなわち、アルカリ金属塩を所定の質量比で含有する水溶液を調製し、この水溶液に、Ｒｕを担持した金属酸化物からなる多孔質担体を所定量添加した後、乾燥、焼成することによって、前記金属酸化物からなる多孔質担体にアルカリ金属とＲｕとが担持したＣＯ２吸蔵還元型触媒を得ることができる。また、アルカリ金属塩を所定の質量比で含有する水溶液を調製し、この水溶液に、金属酸化物からなる多孔質担体を所定量添加した後、乾燥、焼成して、前記金属酸化物からなる多孔質担体にアルカリ金属酸化物が担持したＣＯ２吸蔵材を調製し、このＣＯ２吸蔵材を、所定量のＲｕ塩が溶解した水溶液に添加した後、乾燥、焼成することによっても、前記金属酸化物からなる多孔質担体にアルカリ金属酸化物とＲｕとが担持したＣＯ２吸蔵還元型触媒を得ることができる。さらに、アルカリ金属塩及びＲｕ塩を所定の質量比で含有する水溶液を調製し、この水溶液に、金属酸化物からなる多孔質担体を所定量添加した後、乾燥、焼成することによっても、前記金属酸化物からなる多孔質担体にアルカリ金属酸化物とＲｕとが担持したＣＯ２吸蔵還元型触媒を得ることができる。
[Method for preparing CO 2 storage reduction catalyst]
Such a CO 2 storage reduction type catalyst of the present invention can be prepared, for example, as follows. That is, an aqueous solution containing an alkali metal salt in a predetermined mass ratio is prepared, a predetermined amount of a porous carrier made of a metal oxide supporting Ru is added to the aqueous solution, and then the metal is removed by drying and baking. A CO 2 storage reduction type catalyst in which an alkali metal and Ru are supported on a porous carrier made of an oxide can be obtained. Alternatively, an aqueous solution containing an alkali metal salt at a predetermined mass ratio is prepared, a predetermined amount of a porous carrier made of a metal oxide is added to this aqueous solution, and the porous carrier made of the metal oxide is dried and fired. The metal oxidation can also be achieved by preparing a CO 2 storage material in which an alkali metal oxide is supported on a solid carrier, and adding this CO 2 storage material to an aqueous solution in which a predetermined amount of Ru salt is dissolved, followed by drying and baking. It is possible to obtain a CO 2 storage reduction catalyst in which an alkali metal oxide and Ru are supported on a porous carrier made of aluminum. Furthermore, by preparing an aqueous solution containing an alkali metal salt and a Ru salt in a predetermined mass ratio, adding a predetermined amount of a porous carrier made of a metal oxide to this aqueous solution, and drying and baking, the metal A CO 2 storage reduction type catalyst in which an alkali metal oxide and Ru are supported on a porous carrier made of an oxide can be obtained.
焼成条件としては、アルカリ金属塩が酸化物、炭酸塩及び炭酸水素塩の状態に、Ｒｕ塩がＲｕに変換される条件であれば特に制限はないが、例えば、焼成温度としては、４００～６００℃が好ましく、４５０～５５０℃がより好ましく、また、焼成時間としては、１～５時間が好ましく、２～４時間がより好ましい。 There are no particular restrictions on the firing conditions as long as the alkali metal salts are converted into oxides, carbonates, and hydrogen carbonates, and the Ru salts are converted into Ru. C., more preferably 450 to 550.degree. C., and the firing time is preferably 1 to 5 hours, more preferably 2 to 4 hours.
前記アルカリ金属塩としては、例えば、アルカリ金属（Ｌｉ、Ｎａ、Ｋ、Ｒｂ、Ｃｓ）の硝酸塩、炭酸塩、酢酸塩が挙げられる。また、Ｒｕ塩としては、例えば、ニトロシル硝酸ルテニウム、硝酸ルテニウム、塩化ルテニウム、ルテニウムカルボニルが挙げられる。 Examples of the alkali metal salts include nitrates, carbonates, and acetates of alkali metals (Li, Na, K, Rb, and Cs). Examples of the Ru salt include ruthenium nitrosyl nitrate, ruthenium nitrate, ruthenium chloride, and ruthenium carbonyl.
〔ＣＯ２の吸蔵還元処理〕
このような本発明のＣＯ２吸蔵還元型触媒は、例えば、以下のようなＣＯ２の吸蔵還元処理に適用することができる。すなわち、本発明のＣＯ２吸蔵還元型触媒にＣＯ２を含むガスを接触させてＣＯ２を吸蔵させた後、このＣＯ２が吸蔵した前記ＣＯ２吸蔵還元型触媒に還元ガス（例えば、Ｈ２）を接触させることによって、吸蔵したＣＯ２が還元されてＣＨ４が生成する。また、本発明のＣＯ２吸蔵還元型触媒にＣＯ２とＨ２とを含むガスを接触させてＣＯ２を吸蔵させながら、吸蔵したＣＯ２と還元ガス（例えば、Ｈ２）とを反応させることによって、吸蔵したＣＯ２が還元されてＣＨ４が生成する。
[CO 2 storage and reduction treatment]
Such a CO 2 storage and reduction catalyst of the present invention can be applied to, for example, the following CO 2 storage and reduction treatment. That is, after the CO 2 storage reduction type catalyst of the present invention is brought into contact with a gas containing CO 2 to store CO 2 , a reducing gas (for example, H 2 ), the occluded CO 2 is reduced and CH 4 is produced. Alternatively, the CO 2 storage reduction catalyst of the present invention may be brought into contact with a gas containing CO 2 and H 2 to store CO 2 while causing the stored CO 2 to react with a reducing gas (for example, H 2 ). , the stored CO 2 is reduced and CH 4 is generated.
本発明のＣＯ２吸蔵還元型触媒は、低温においての優れたＣＯ２吸蔵性能とメタン化触媒活性を発現することから、上記のＣＯ２の吸蔵還元処理の開始時等の低温状態においても、過剰な熱エネルギーを供給せずに、ＣＯ２の還元とＣＨ４の生成を可能にする。 The CO 2 storage reduction catalyst of the present invention exhibits excellent CO 2 storage performance and methanation catalyst activity at low temperatures. It enables the reduction of CO 2 and the production of CH 4 without supplying significant thermal energy.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.
（実施例１）
イオン交換水に、硝酸ナトリウム（ＮａＮＯ３、富士フイルム和光純薬株式会社製、品番：１９２－０２５５５）を溶解し、得られた水溶液に、ルテニウム担持アルミナ粉末（Ｒｕ／Ａｌ２Ｏ３、エヌ・イーケムキャット株式会社製、品番：ＨＹＡｃ－５Ｅ Ｎ－Ｔｙｐｅ、Ｒｕ含有量：５質量％、アルミナ含有量：９５質量％、アルミナの平均細孔径：１３ｎｍ、アルミナの細孔容積：０．３８ｃｍ３／ｇ）を、得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して２．８質量％となるように添加した。得られた分散液を約２時間攪拌した後、２５０℃に加熱して蒸発乾固させた。得られた乾固物を１１０℃で１２時間乾燥させた後、５００℃で３時間焼成した。得られた触媒粉末（約６ｇ）を圧力１０００ｋｇ／ｃｍ２で１分間加圧した後、粉砕し、篩を用いて分級して、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（２．８）／Ｒｕ（４．９）／Ａｌ２Ｏ３（９２．３）〕を得た。
(Example 1)
Sodium nitrate (NaNO 3 , manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product number: 192-02555) was dissolved in ion-exchanged water, and ruthenium-supported alumina powder (Ru/Al 2 O 3 , N. Manufactured by Echem Cat Co., Ltd., product number: HYAc-5E N-Type, Ru content: 5% by mass, alumina content: 95% by mass, average pore diameter of alumina: 13 nm, pore volume of alumina: 0.38 cm 3 / g) was added so that the Na 2 O content in the resulting catalyst was 2.8% by mass based on the total catalyst. The resulting dispersion was stirred for about 2 hours and then heated to 250°C to evaporate to dryness. The obtained dried product was dried at 110°C for 12 hours and then calcined at 500°C for 3 hours. The obtained catalyst powder (approximately 6 g ) was pressurized at a pressure of 1000 kg/cm 2 for 1 minute, then pulverized and classified using a sieve . A catalyst powder [Na 2 O (2.8)/Ru (4.9)/Al 2 O 3 (92.3)] with a diameter of .5 to 1.0 mm was obtained.
（実施例２）
得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して３．７質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（３．７）／Ｒｕ（４．８）／Ａｌ２Ｏ３（９１．５）〕を得た。
(Example 2)
Al 2 O 3 was prepared in the same manner as in Example 1 , except that the Ru/Al 2 O 3 powder was added so that the Na 2 O content in the resulting catalyst was 3.7% by mass based on the entire catalyst. A catalyst powder with a diameter of 0.5 to 1.0 mm [Na 2 O (3.7)/Ru (4.8)/Al 2 O 3 (91.5)] supported by Na 2 O and Ru was Obtained.
（実施例３）
得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して４．５質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（４．５）／Ｒｕ（４．８）／Ａｌ２Ｏ３（９０．７）〕を得た。
(Example 3)
Al 2 O 3 was prepared in the same manner as in Example 1 except that the Ru/Al 2 O 3 powder was added so that the Na 2 O content in the resulting catalyst was 4.5% by mass based on the entire catalyst. A catalyst powder with a diameter of 0.5 to 1.0 mm [Na 2 O (4.5)/Ru (4.8)/Al 2 O 3 (90.7)] supported by Na 2 O and Ru was Obtained.
（比較例１）
得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して１．０質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（１．０）／Ｒｕ（４．９）／Ａｌ２Ｏ３（９４．１）〕を得た。
(Comparative example 1)
Al 2 O 3 was prepared in the same manner as in Example 1, except that the Ru/Al 2 O 3 powder was added so that the Na 2 O content in the resulting catalyst was 1.0% by mass based on the entire catalyst. A catalyst powder with a diameter of 0.5 to 1.0 mm [Na 2 O (1.0)/Ru (4.9)/Al 2 O 3 (94.1)] supported by Na 2 O and Ru was Obtained.
（比較例２）
得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して５．４質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（５．４）／Ｒｕ（４．７）／Ａｌ２Ｏ３（８９．９）〕を得た。
(Comparative example 2)
Al 2 O 3 was prepared in the same manner as in Example 1, except that the Ru/Al 2 O 3 powder was added so that the Na 2 O content in the resulting catalyst was 5.4% by mass based on the entire catalyst. A catalyst powder with a diameter of 0.5 to 1.0 mm [Na 2 O (5.4)/Ru (4.7)/Al 2 O 3 (89.9)] supported by Na 2 O and Ru was Obtained.
（比較例３）
得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して８．７質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（８．７）／Ｒｕ（４．６）／Ａｌ２Ｏ３（８６．７）〕を得た。
(Comparative example 3)
Al 2 O 3 was prepared in the same manner as in Example 1, except that the Ru/Al 2 O 3 powder was added so that the Na 2 O content in the resulting catalyst was 8.7% by mass based on the entire catalyst. A catalyst powder with a diameter of 0.5 to 1.0 mm [Na 2 O (8.7)/Ru (4.6)/Al 2 O 3 (86.7)] supported by Na 2 O and Ru was Obtained.
（比較例４）
得られる触媒においてＮａ２Ｏの含有量が触媒全体に対して１２．５質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＮａ２ＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔Ｎａ２Ｏ（１２．５）／Ｒｕ（４．４）／Ａｌ２Ｏ３（８３．１）〕を得た。
(Comparative example 4)
Al 2 O 3 was prepared in the same manner as in Example 1 except that the Ru/Al 2 O 3 powder was added so that the Na 2 O content in the resulting catalyst was 12.5% by mass based on the entire catalyst. A catalyst powder with a diameter of 0.5 to 1.0 mm [Na 2 O (12.5)/Ru (4.4)/Al 2 O 3 (83.1)] supported by Na 2 O and Ru was Obtained.
（比較例５）
硝酸ナトリウムの代わりに硝酸カルシウム（Ｃａ（ＮＯ３）２、富士フイルム和光純薬株式会社製、品番：０３９－００７３５）を用い、得られる触媒においてＣａＯの含有量が触媒全体に対して４．５質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は実施例１と同様にして、Ａｌ２Ｏ３にＣａＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔ＣａＯ（４．５）／Ｒｕ（４．８）／Ａｌ２Ｏ３（９０．７）〕を得た。
(Comparative example 5)
Calcium nitrate (Ca(NO 3 ) 2 , manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product number: 039-00735) was used instead of sodium nitrate, and the CaO content in the resulting catalyst was 4.5 with respect to the entire catalyst. A catalyst with a diameter of 0.5 to 1.0 mm in which CaO and Ru were supported on Al 2 O 3 was prepared in the same manner as in Example 1 except that the Ru/Al 2 O 3 powder was added in such a manner that the Ru/Al 2 O 3 powder was added in a mass %. A powder [CaO (4.5)/Ru (4.8)/Al 2 O 3 (90.7)] was obtained.
（比較例６）
得られる触媒においてＣａＯの含有量が触媒全体に対して８．７質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は比較例５と同様にして、Ａｌ２Ｏ３にＣａＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔ＣａＯ（８．７）／Ｒｕ（４．６）／Ａｌ２Ｏ３（８６．７）〕を得た。
(Comparative example 6)
CaO was added to Al 2 O 3 in the same manner as in Comparative Example 5, except that the Ru/Al 2 O 3 powder was added so that the CaO content in the resulting catalyst was 8.7% by mass based on the entire catalyst. A catalyst powder [CaO (8.7)/Ru (4.6)/Al 2 O 3 (86.7)] with a diameter of 0.5 to 1.0 mm was obtained, which was supported by Ru and Ru.
（比較例７）
得られる触媒においてＣａＯの含有量が触媒全体に対して１６．０質量％となるように前記Ｒｕ／Ａｌ２Ｏ３粉末を添加した以外は比較例５と同様にして、Ａｌ２Ｏ３にＣａＯとＲｕとが担持した、０．５～１．０ｍｍ径の触媒粉末〔ＣａＯ（１６．０）／Ｒｕ（４．２）／Ａｌ２Ｏ３（７９．８）〕を得た。
(Comparative Example 7)
CaO was added to Al 2 O 3 in the same manner as in Comparative Example 5, except that the Ru/Al 2 O 3 powder was added so that the CaO content in the resulting catalyst was 16.0% by mass based on the entire catalyst. A catalyst powder [CaO (16.0)/Ru (4.2)/Al 2 O 3 (79.8)] with a diameter of 0.5 to 1.0 mm was obtained, which was supported by Ru and Ru.
＜ＣＯ２のメタン化温度特性の評価＞
得られた触媒粉末を容積が２．４ｃｍ３となるようにステンレス鋼（ＳＵＳ）製反応管（内径：６ｍｍ）に充填し、この反応管を昇温脱離分析装置（ヘンミ計算尺株式会社製「ＴＰ－５０００」）に装着した。触媒床に、Ｈ２（４０％）＋ＣＯ２（１０％）＋Ｈｅ（残部）のＨ２／ＣＯ２含有ガスを１気圧下、流量４０ｍｌ／ｍｉｎの条件で流通させながら、触媒床を５０℃から３５０℃まで昇温速度５℃／ｍｉｎで昇温した。触媒床を５０℃以下に降温した後、再度、上記の条件にて触媒床を５０℃から３５０℃まで昇温速度５℃／ｍｉｎで昇温した。この２回目の昇温時において、触媒出ガス中のＣＯ２量を測定し、触媒入りガス中のＣＯ２量と触媒出ガス中のＣＯ２量とからＣＯ２転化率を求めた。その結果を図１に示す。図１に示した結果に基づいて、ＣＯ２転化率が５０％となる温度Ｔ５０を求めた。その結果を表１に示す。また、ＣＯ２吸蔵材（Ｎａ２Ｏ又はＣａＯ）の含有率に対してＴ５０をプロットした結果を図２に示す。
<Evaluation of CO 2 methanation temperature characteristics>
The obtained catalyst powder was filled into a stainless steel (SUS) reaction tube (inner diameter: 6 mm) to a volume of 2.4 cm 3 , and the reaction tube was heated using a temperature programmed desorption analyzer (manufactured by Henmi Slide Rule Co., Ltd.). TP-5000"). The catalyst bed was heated from 50°C while flowing H 2 /CO 2 -containing gas of H 2 (40%) + CO 2 (10%) + He (remainder) under 1 atm and at a flow rate of 40 ml/min. The temperature was raised to 350°C at a rate of 5°C/min. After the temperature of the catalyst bed was lowered to 50° C. or lower, the temperature of the catalyst bed was again raised from 50° C. to 350° C. at a temperature increase rate of 5° C./min under the above conditions. During the second temperature rise, the amount of CO 2 in the gas coming out of the catalyst was measured, and the conversion rate of CO 2 was determined from the amount of CO 2 in the gas containing the catalyst and the amount of CO 2 in the gas coming out of the catalyst. The results are shown in Figure 1. Based on the results shown in FIG. 1, the temperature T50 at which the CO 2 conversion rate becomes 50% was determined. The results are shown in Table 1. Further, FIG. 2 shows the results of plotting T50 against the content of the CO 2 storage material (Na 2 O or CaO).
表１及び図２に示したように、アルカリ金属の含有量（酸化物換算）を所定の範囲内とすることによって、Ｔ５０が低く、低温において優れた触媒活性を発現するＣＯ２吸蔵還元型触媒（実施例１～３）が得られることが確認された。一方、アルカリ金属の含有量（酸化物換算）が多くなりすぎると、Ｔ５０が高くなり、低温での触媒活性が低下することがわかった（比較例２～４）。 As shown in Table 1 and Figure 2, the CO 2 storage reduction catalyst has a low T50 and exhibits excellent catalytic activity at low temperatures by keeping the alkali metal content (in terms of oxide) within a predetermined range. It was confirmed that (Examples 1 to 3) could be obtained. On the other hand, it was found that when the alkali metal content (in terms of oxide) was too large, T50 increased and the catalytic activity at low temperatures decreased (Comparative Examples 2 to 4).
また、実施例３で得られたＣＯ２吸蔵還元型触媒は、アルカリ金属の含有量（酸化物換算）と同程度の含有量（酸化物換算）でアルカリ土類金属を含有する触媒（比較例５）に比べて、Ｔ５０が低く、低温での触媒活性が優れていることがわかった。 In addition, the CO 2 storage reduction type catalyst obtained in Example 3 was a catalyst containing an alkaline earth metal at a content (in terms of oxide) comparable to that of the alkali metal (in terms of oxide) (comparative example). It was found that the T50 was lower than that of 5), and the catalytic activity at low temperatures was excellent.
＜Ｘ線回折測定＞
得られた触媒粉末のＸ線回折パターンを、Ｘ線回折装置（株式会社リガク製「ＵｌｔｉｍａＩＶ」）を用い、ＣｕＫαをＸ線源として使用して測定した。その結果を図３に示す。
<X-ray diffraction measurement>
The X-ray diffraction pattern of the obtained catalyst powder was measured using an X-ray diffraction apparatus ("Ultima IV" manufactured by Rigaku Corporation) using CuKα as an X-ray source. The results are shown in FIG.
図３に示したように、Ｎａ２Ｏの含有量が８．７質量％以上の触媒（比較例３～４）においては、Ｎａ２Ｏの結晶子径が４４ｎｍに相当する回折ピークが観測されたが、Ｎａ２Ｏの含有量が４．５質量％以下のＣＯ２吸蔵還元型触媒（実施例２～３）においては、観測されなかった。この結果から、アルカリ金属の含有量が増加すると、結晶子径が４４ｎｍ以上の粗大な粒子が生成するため、低温での触媒活性が低下すると考えられる。 As shown in Figure 3, in the catalysts with a Na 2 O content of 8.7% by mass or more (Comparative Examples 3 to 4), a diffraction peak corresponding to a Na 2 O crystallite diameter of 44 nm was observed. However, it was not observed in the CO 2 storage reduction catalysts (Examples 2 and 3) in which the Na 2 O content was 4.5% by mass or less. From this result, it is considered that when the alkali metal content increases, coarse particles with a crystallite diameter of 44 nm or more are generated, and thus the catalytic activity at low temperatures decreases.
以上説明したように、本発明によれば、低温においても優れたＣＯ２吸蔵性能とメタン化触媒活性を発現するＣＯ２吸蔵還元型触媒を得ることが可能となる。したがって、本発明のＣＯ２吸蔵還元型触媒は、ＣＯ２浄化システムの始動時等の低温状態においてもＣＯ２を効率よく吸蔵してＣＨ４に還元することが可能な触媒として有用である。 As explained above, according to the present invention, it is possible to obtain a CO 2 storage reduction type catalyst that exhibits excellent CO 2 storage performance and methanation catalyst activity even at low temperatures. Therefore, the CO 2 storage reduction catalyst of the present invention is useful as a catalyst that can efficiently store CO 2 and reduce it to CH 4 even in low temperature conditions such as when starting up a CO 2 purification system.
Claims (3)
前記ルテニウムの含有量が、前記多孔質担体とルテニウムとの合計含有量１００質量部に対して、１～５質量部であり、
前記アルカリ金属の含有量が、前記触媒全体に対して、酸化物換算で２．８～４．５質量％である
ことを特徴とする二酸化炭素吸蔵還元型触媒。 a porous carrier made of a metal oxide and having an average pore diameter of 3 to 50 nm and a pore volume of 0.3 to 1.5 cm 3 /g; ruthenium supported on the porous carrier; A catalyst containing an alkali metal supported on a solid carrier,
The content of the ruthenium is 1 to 5 parts by mass with respect to 100 parts by mass of the total content of the porous carrier and ruthenium,
A carbon dioxide storage reduction catalyst characterized in that the content of the alkali metal is 2.8 to 4.5% by mass in terms of oxide based on the entire catalyst.
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