JP2008212898A - Catalyst for oxidatively removing methane, and oxidatively removing method of methane - Google Patents
Catalyst for oxidatively removing methane, and oxidatively removing method of methane Download PDFInfo
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 118
- 239000003054 catalyst Substances 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 47
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 57
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 34
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052742 iron Inorganic materials 0.000 claims abstract description 24
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 17
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 17
- 239000002131 composite material Substances 0.000 claims abstract description 15
- 229910052751 metal Inorganic materials 0.000 claims abstract description 8
- 239000002184 metal Substances 0.000 claims abstract description 8
- 238000006864 oxidative decomposition reaction Methods 0.000 claims description 30
- 229910017771 LaFeO Inorganic materials 0.000 claims description 14
- 239000007858 starting material Substances 0.000 claims description 12
- 239000013256 coordination polymer Substances 0.000 claims description 8
- 229920001795 coordination polymer Polymers 0.000 claims description 8
- YAGKRVSRTSUGEY-UHFFFAOYSA-N ferricyanide Chemical compound [Fe+3].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] YAGKRVSRTSUGEY-UHFFFAOYSA-N 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 239000002243 precursor Substances 0.000 claims description 7
- 239000007789 gas Substances 0.000 claims description 6
- HCMVSLMENOCDCK-UHFFFAOYSA-N N#C[Fe](C#N)(C#N)(C#N)(C#N)C#N Chemical compound N#C[Fe](C#N)(C#N)(C#N)(C#N)C#N HCMVSLMENOCDCK-UHFFFAOYSA-N 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- NNLJGFCRHBKPPJ-UHFFFAOYSA-N iron lanthanum Chemical compound [Fe].[La] NNLJGFCRHBKPPJ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 abstract description 15
- 229910052763 palladium Inorganic materials 0.000 abstract description 7
- 230000001590 oxidative effect Effects 0.000 abstract description 5
- 238000007254 oxidation reaction Methods 0.000 abstract description 3
- 230000003647 oxidation Effects 0.000 abstract description 2
- 238000006243 chemical reaction Methods 0.000 description 19
- 238000000975 co-precipitation Methods 0.000 description 8
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- -1 hexacyanoiron (III) potassium Chemical compound 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 229910000510 noble metal Inorganic materials 0.000 description 5
- 238000003746 solid phase reaction Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 239000012153 distilled water Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 238000010532 solid phase synthesis reaction Methods 0.000 description 3
- AWDBHOZBRXWRKS-UHFFFAOYSA-N tetrapotassium;iron(6+);hexacyanide Chemical compound [K+].[K+].[K+].[K+].[Fe+6].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] AWDBHOZBRXWRKS-UHFFFAOYSA-N 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009766 low-temperature sintering Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- TYRQHOOINMAEHH-UHFFFAOYSA-N [K].N#C[Fe](C#N)(C#N)(C#N)(C#N)C#N Chemical compound [K].N#C[Fe](C#N)(C#N)(C#N)(C#N)C#N TYRQHOOINMAEHH-UHFFFAOYSA-N 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000004523 catalytic cracking Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 229910003455 mixed metal oxide Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
Abstract
Description
本発明は、メタンの酸化的分解用触媒及びそれを用いたメタンの酸化的分解方法に関するものであり、更に詳しくは、ランタンと鉄を含有し、ランタンと鉄の原子比が実質的に１／１であり、かつ該ランタンと鉄は、ペロブスカイト構造を形成している複合金属酸化物からなるメタンの酸化的分解用触媒、その製造方法及び該触媒を用いたメタンの酸化的分解方法に関するものである。 The present invention relates to a catalyst for oxidative decomposition of methane and a method for oxidative decomposition of methane using the same. More specifically, the present invention contains lanthanum and iron, and the atomic ratio of lanthanum and iron is substantially 1 /. The lanthanum and iron are related to a catalyst for oxidative decomposition of methane comprising a composite metal oxide having a perovskite structure, a method for producing the same, and a method for oxidative decomposition of methane using the catalyst. is there.
天然ガスの主成分であるメタンは、酸化的に燃焼することで、熱エネルギーとして回収することができる。メタンを効率的に熱エネルギーとして利用するためには、６００℃以下の温度域で効率的に燃焼する必要がある。従来、かかるメタンの酸化的分解用の触媒としては、担体に活性金属としてパラジウムや貴金属を担持するものが知られていた。 Methane, the main component of natural gas, can be recovered as thermal energy by oxidative combustion. In order to efficiently use methane as thermal energy, it is necessary to efficiently burn in a temperature range of 600 ° C. or lower. Conventionally, a catalyst for supporting palladium or a noble metal as an active metal on a carrier has been known as a catalyst for oxidative decomposition of methane.
しかし、これらの触媒は、高価であることや、担体との相互作用の影響を大きく受けるため、調製が困難である。また、高温の反応中にシンタリングなどが起こり、触媒寿命も短いことなどから、パラジウムや貴金属を用いない安価で耐熱性の高い触媒が望まれている。一方、非金属系複合酸化物では、組成の均一性と共に高表面積な材料が望まれることから、触媒調製時に短時間でしかも低温で焼結する触媒が望まれている。 However, these catalysts are difficult to prepare because they are expensive and are greatly affected by the interaction with the support. In addition, since sintering and the like occur during a high-temperature reaction and the catalyst life is short, an inexpensive and highly heat-resistant catalyst that does not use palladium or a noble metal is desired. On the other hand, since non-metallic composite oxides are desired to have a high surface area as well as composition uniformity, a catalyst that sinters in a short time and at a low temperature during catalyst preparation is desired.
先行技術として、例えば、Ｒ．Ｓｐｉｎｉｃｃｉらは、非金属系複合酸化物であるＬａＦｅＯ３に注目して、Ｐｄ等の金属を含まない安価なメタンの燃料触媒を報告しているが、４８０℃で約２０％程度のメタン転換を可能とするものでしかなかった（非特許文献１）。効率的な熱エネルギーの利用には、更なる性能の向上が望まれている。 As prior art, for example, R.I. Spinicci et al. Reported an inexpensive methane fuel catalyst that does not contain metals such as Pd, focusing on LaFeO 3 , which is a non-metallic composite oxide. It was only possible (Non-Patent Document 1). For efficient utilization of thermal energy, further improvement in performance is desired.
一方、ペロブスカイト型酸化物は、高温での酸化雰囲気における熱安定性や酸素の移動性が高いことから、環境・エネルギー関連材料等として研究されているものが多い。このようなペロブスカイト型酸化物の調製法は、従来より、固相反応や共沈法が主流である。 On the other hand, perovskite oxides are often studied as environment / energy-related materials because of their high thermal stability and high oxygen mobility in an oxidizing atmosphere at high temperatures. Conventionally, a solid phase reaction or a coprecipitation method has been mainly used as a method for preparing such a perovskite oxide.
このような状況の中で、本発明者らは、上記従来技術に鑑みて、パラジウムや貴金属を用いない安価で耐熱性の高い触媒を開発することを目標として鋭意研究を重ねた結果、ヘキサシアノ鉄錯体を用いて架橋した六角多面型ヘテロ金属配位高分子をペロブスカイト構造の前駆体として調製したペロブスカイト型複合酸化物触媒を用いることで所期の目的を達成し得ることを見出し、本発明を完成するに至った。 Under such circumstances, in view of the above prior art, the present inventors have conducted extensive research with the goal of developing an inexpensive and heat-resistant catalyst that does not use palladium or noble metals. Discovered that the intended purpose can be achieved by using a perovskite-type complex oxide catalyst prepared by using a hexagonal polyhedral heterometallic coordination polymer crosslinked with a complex as a precursor of the perovskite structure, and completed the present invention. It came to do.
本発明は、このような観点の下になされたものであって、活性金属としてパラジウムや他の貴金属を一切含まない６００℃以下の温度領域で安定にメタンを酸化的に分解するペロブスカイト型酸化物触媒及びそれを用いたメタンの酸化的分解方法を提供することを目的とするものである。 The present invention has been made under such a viewpoint, and is a perovskite oxide that stably decomposes methane oxidatively in a temperature range of 600 ° C. or lower, which does not contain palladium or other noble metals as active metals. It is an object of the present invention to provide a catalyst and a method for oxidative decomposition of methane using the catalyst.
上記課題を解決するための本発明は、以下の技術的手段から構成される。
（１）ランタンと鉄を含有し、ランタンと鉄の原子比が実質的に１／１であり、かつ該ランタンと鉄は、ペロブスカイト構造を形成している複合金属酸化物からなることを特徴とするメタンの酸化的分解用触媒。
（２）複合金属酸化物中の金属が、ＬａＦｅＯ３の組成式を有し、ランタンと鉄とはペロブスカイト型酸化物を形成していることを特徴とする、前記（１）記載のメタンの酸化的分解用触媒。
（３）出発原料にヘキサシアノ鉄錯体を用いて架橋した六角多面型ヘテロ金属配位高分子を前駆体として複合金属酸化物を調製することを特徴とするメタンの酸化的分解用触媒の製造方法。
（４）前駆体が、ヘキサシアノ鉄（ＩＩＩ）酸ラクタン錯体であることを特徴とする、前記（３）記載のメタンの酸化的分解用触媒の製造方法。
（５）前記ヘテロ金属配位高分子を、空気中、６５０℃〜１０００℃で処理してランタン鉄ペロブスカイト金属酸化物とすることを特徴とする、前記（３）に記載のメタンの酸化的分解用触媒の製造方法。
（６）メタンの触媒を用いた酸化的分解方法において、ランタンと鉄を含有し、ランタンと鉄の原子比が実質的に１／１であり、かつ該ランタンと鉄は、ペロブスカイト構造を形成している複合金属酸化物からなる触媒を用いることを特徴とするメタンの酸化的分解方法。
（７）ランタン鉄ペロブスカイト金属酸化物を触媒として、６００℃以下でメタンを酸化することを特徴とする、前記（６）に記載のメタンの酸化的分解方法。
（８）メタンと酸素の混合ガスを触媒と接触させる、前記（６）記載のメタンの酸化的分解方法。
The present invention for solving the above-described problems comprises the following technical means.
(1) It contains lanthanum and iron, the atomic ratio of lanthanum and iron is substantially 1/1, and the lanthanum and iron are composed of a composite metal oxide that forms a perovskite structure. Catalyst for oxidative decomposition of methane.
(2) The oxidation of methane according to (1), wherein the metal in the composite metal oxide has a composition formula of LaFeO 3 , and lanthanum and iron form a perovskite oxide. Catalytic cracking catalyst.
(3) A method for producing a catalyst for oxidative decomposition of methane, comprising preparing a composite metal oxide using a hexagonal polyhedral heterometal coordination polymer crosslinked with a hexacyanoiron complex as a starting material as a precursor.
(4) The method for producing a catalyst for oxidative decomposition of methane according to the above (3), wherein the precursor is a hexacyanoferrate (III) lactan complex.
(5) Oxidative decomposition of methane as described in (3) above, wherein the heterometal coordination polymer is treated in air at 650 ° C. to 1000 ° C. to obtain a lanthanum iron perovskite metal oxide. For producing a catalyst for use.
(6) In an oxidative decomposition method using a catalyst of methane, lanthanum and iron are contained, the atomic ratio of lanthanum and iron is substantially 1/1, and the lanthanum and iron form a perovskite structure. A method for the oxidative decomposition of methane, comprising using a catalyst comprising a mixed metal oxide.
(7) The methane oxidative decomposition method according to (6) above, wherein methane is oxidized at 600 ° C. or lower using a lanthanum iron perovskite metal oxide as a catalyst.
(8) The methane oxidative decomposition method according to (6), wherein a mixed gas of methane and oxygen is brought into contact with a catalyst.
次に、本発明について更に詳細に説明する。
本発明は、メタンの酸化的分解用触媒であって、ランタンと鉄を含有し、ランタンと鉄の原子比が実質的に１／１であり、かつ該ランタンと鉄は、ペロブスカイト構造を形成している複合金属酸化物からなることを特徴とするものである。本発明では、出発原料にヘキサシアノ鉄錯体を用いて架橋した六角多面型ヘテロ金属配位高分子Ｌａ［Ｆｅ（ＣＮ）６］・Ｈ２Ｏをペロブスカイト構造体の前駆体として使用することにより、組成の均一性とともに低温焼結を可能にした触媒の調製方法及びペロブスカイト型酸化物触媒が提供される。
Next, the present invention will be described in more detail.
The present invention is a catalyst for oxidative decomposition of methane, which contains lanthanum and iron, the atomic ratio of lanthanum and iron is substantially 1/1, and the lanthanum and iron form a perovskite structure. It is characterized by comprising a complex metal oxide. In the present invention, a hexagonal polyhedral heterometallic coordination polymer La [Fe (CN) 6 ] · H 2 O crosslinked using a hexacyanoiron complex as a starting material is used as a precursor of the perovskite structure. A catalyst preparation method and a perovskite oxide catalyst that enable low-temperature sintering together with uniformity of the catalyst are provided.
また、本発明では、３次元の編み目状の特異な表面構造を有したペロブスカイト型酸化物触媒が提供される。また、本発明は、メタンを触媒を用いて酸化的分解する方法であって、ランタンと鉄を含有し、ランタンと鉄の原子比が実質的に１／１であり、かつ該ランタンと鉄はペロブスカイト構造を形成している複合金属酸化物からなる触媒を用いることを特徴とするものである。 The present invention also provides a perovskite oxide catalyst having a unique surface structure with a three-dimensional stitch shape. Further, the present invention is a method for oxidatively decomposing methane using a catalyst, comprising lanthanum and iron, wherein the atomic ratio of lanthanum and iron is substantially 1/1, and the lanthanum and iron are It is characterized by using a catalyst made of a composite metal oxide forming a perovskite structure.
本発明は、ランタンと鉄を含有する複合酸化物触媒の調製において、出発原料にヘキサシアノ鉄錯体を用いて架橋した六角多面型ヘテロ金属配位高分子をペロブスカイト構造体の前駆体とすること、及びランタンと鉄との原子比が実質的に１／１であること、を特徴とするものであり、かつ得られた触媒が、ペロブスカイト構造を形成していること、が必要であり、これによって、６００℃以下の低温でメタンを酸化的に分解できる触媒を調製することができる。 In the preparation of a composite oxide catalyst containing lanthanum and iron, the present invention uses a hexagonal polyhedral heterometallic coordination polymer crosslinked with a hexacyanoiron complex as a starting material as a precursor of a perovskite structure, and It is necessary that the atomic ratio of lanthanum and iron is substantially 1/1, and that the obtained catalyst forms a perovskite structure. A catalyst capable of oxidatively decomposing methane at a low temperature of 600 ° C. or lower can be prepared.
本発明の触媒を調製するには、先ず、ヘキサシアノ鉄（ＩＩＩ）酸カリウムを蒸留水に溶解させ、これと硝酸ランタンを同じ濃度になるように混合し、直後に沈殿するヘキサシアノ鉄（ＩＩＩ）酸ランタン錯体を吸引濾過し、蒸留水、メタノールで洗浄した後に、減圧下で乾燥する。得られたものは、ペロブスカイト構造体の中間体であるヘキサシアノ鉄錯体を用いて架橋した六角多面型ヘテロ金属配位高分子であるヘキサシアノ鉄（ＩＩＩ）酸ランタン錯体であり、これを空気中、例えば、５５０℃で２時間熱処理をする。その後、室温まで自然冷却し、ＬａＦｅＯ３の組成式で示されるペロブスカイト型の複合酸化物とする。 To prepare the catalyst of the present invention, first, potassium hexacyanoferrate (III) is dissolved in distilled water, and this and lanthanum nitrate are mixed so as to have the same concentration. The lanthanum complex is filtered by suction, washed with distilled water and methanol, and then dried under reduced pressure. What is obtained is a hexacyanoferrate (III) lanthanum complex which is a hexagonal polyhedral heterometallic coordination polymer crosslinked with a hexacyanoiron complex which is an intermediate of a perovskite structure, Heat treatment is performed at 550 ° C. for 2 hours. Thereafter, it is naturally cooled to room temperature to obtain a perovskite complex oxide represented by the composition formula of LaFeO 3 .
得られた複合酸化物のＸ線回折図は、ランタンと鉄からなるペロブスカイト型酸化物に帰属される回折パターンを示すものである。この複合酸化物の調製方法として、固相反応法や共沈法などがあるが、組成の均一性とともに低温焼結が可能である、ヘキサシアノ鉄（ＩＩＩ）カリウムを出発原料とする錯体法が望ましい。 The X-ray diffraction pattern of the obtained composite oxide shows a diffraction pattern attributed to the perovskite oxide composed of lanthanum and iron. As a method for preparing this complex oxide, there are a solid-phase reaction method and a coprecipitation method, but a complex method using hexacyanoiron (III) potassium as a starting material, which can be sintered at low temperature with a uniform composition, is desirable. .
上記三種類の調製法により得られた酸化物をＩＲスペクトルとＸＲＤによって分析した結果、錯体法では５５０℃以上で、ほぼ完全にペロブスカイト型酸化物ＬａＦｅＯ３の単相となることが分かった。これに対し、共沈法により調製した酸化物は、１０００℃でもＬａ２Ｏ３とＦｅ２Ｏ３が若干混合していた。また、固相反応法では、混合・熱処理（１０００℃）を繰り返し行っても、ＬａＦｅＯ３がほとんど生成していないことが分かった。 As a result of analyzing the oxides obtained by the above three preparation methods by IR spectrum and XRD, it was found that the complex method almost completely became a single phase of the perovskite oxide LaFeO 3 at 550 ° C. or higher. In contrast, the oxide prepared by the coprecipitation method had a slight mixture of La 2 O 3 and Fe 2 O 3 even at 1000 ° C. In the solid phase reaction method, it was found that even when mixing and heat treatment (1000 ° C.) were repeated, LaFeO 3 was hardly generated.
本発明の触媒を用いてメタンの酸化的分解を行う際には、メタンと酸素の混合ガスを触媒と接触させる。この場合、混合ガスを通気する前に、空気で予め触媒を酸化状態に保持するのが望ましい。反応圧力は、常圧であり、反応方式は、固定床流通方式が望ましい。 When performing oxidative decomposition of methane using the catalyst of the present invention, a mixed gas of methane and oxygen is brought into contact with the catalyst. In this case, it is desirable to keep the catalyst in an oxidized state with air in advance before venting the mixed gas. The reaction pressure is normal pressure, and the reaction system is preferably a fixed bed flow system.
錯体法により５００℃、６５０℃、８００℃及び１０００℃の各温度で調製したＬａＦｅＯ３を用いてＣＨ４の酸化反応を行い、ＣＨ４の転化率と反応温度の関係を調べた結果、いずれの反応温度でも、調製温度の低いＬａＦｅＯ３で転化率が高かった。また、５５０℃で調製した酸化物を用いてＣＨ４の転化率を（錯体法、共沈法、Ｆｅ２Ｏ３及びＬａ２Ｏ３を用いた場合、及び固相反応法について）比較した結果、どの反応温度でも、錯体法の場合が最もＣＨ４の転化率が高くなった。更に、１０００℃で調製した酸化物のＣＨ４転化率は、錯体法以外は、ＣＨ４転化率が著しく低いことが分かった。 As a result of conducting the oxidation reaction of CH 4 using LaFeO 3 prepared at 500 ° C., 650 ° C., 800 ° C. and 1000 ° C. by the complex method, and investigating the relationship between the conversion rate of CH 4 and the reaction temperature, Even at the reaction temperature, LaFeO 3 having a low preparation temperature had a high conversion rate. Further, the conversion rate of CH 4 using an oxide prepared in 550 ° C. (complex method, for coprecipitation, in the case of using Fe 2 O 3 and La 2 O 3, and a solid phase reaction method) result of comparison The conversion rate of CH 4 was the highest in the complex method at any reaction temperature. Furthermore, CH 4 conversion of oxides prepared at 1000 ° C., except complex method, CH 4 conversion was found to be significantly lower.
次に、本発明を実施例に基づいて具体的に説明するが、本発明は、以下の例によって何ら限定されるものではない。 EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following examples.
（１）触媒の調製
ヘキサシアノ鉄（ＩＩＩ）酸カリウム５０ｇを、できるだけ少量の蒸留水に溶解させ、１．７Ｍの硝酸ランタンをヘキサシアノ鉄（ＩＩＩ）酸カリウムと同濃度になるように混合し、直後に沈殿するヘキサシアノ鉄（ＩＩＩ）酸ランタンを吸引濾過し、蒸留水、メタノールで数回洗浄した後に、減圧下で乾燥した。
(1) Preparation of catalyst 50 g of potassium hexacyanoferrate (III) was dissolved in as little distilled water as possible, and 1.7 M lanthanum nitrate was mixed to the same concentration as potassium hexacyanoferrate (III). The lanthanum hexacyanoferrate (III) precipitated in the solution was suction filtered, washed several times with distilled water and methanol, and dried under reduced pressure.
得られたヘキサシアノ鉄（ＩＩＩ）酸ランタンは１００ｍｌ／ｍｉｎの空気気流中で室温から５５０℃まで５℃／ｍｉｎで昇温させた後に、２時間保持した。その後、室温まで自然冷却して、複合金属酸化物を得た。この複合金属酸化物中の金属は、ＬａＦｅＯ３の組成式で表されるもので、ランタンと鉄とはペロブスカイト型酸化物を形成していることが確認された。 The obtained lanthanum hexacyanoferrate (III) was heated from room temperature to 550 ° C. at 5 ° C./min in an air stream of 100 ml / min and held for 2 hours. Thereafter, it was naturally cooled to room temperature to obtain a composite metal oxide. The metal in this composite metal oxide is represented by the composition formula of LaFeO 3 , and it was confirmed that lanthanum and iron form a perovskite oxide.
（２）低温焼結
本実施例で得られたヘキサシアノ鉄（ＩＩＩ）カリウムを出発原料とする錯体法で調製した触媒のＸ線回折図から、錯体法では５５０℃で均一なペロブスカイト構造体が生成できることが確認された（図１）。これにより、本発明の触媒は、焼成を６００℃で実施していた既報（Ｒ．Ｓｐｉｎｉｃｃｉ ｅｔ ａｌ．，Ｍａｔｅｒｉａｌｓ Ｃｈｅｍｉｓｔｒｙ ａｎｄ Ｐｙｓｉｃｓ７６（２００２）２０−２５）の触媒に比べて、５０℃の低温焼結が可能であることが確認された。
(2) Low-temperature sintering From the X-ray diffraction pattern of the catalyst prepared by the complex method using hexacyano iron (III) potassium obtained in this example as a starting material, a uniform perovskite structure is formed at 550 ° C. by the complex method. It was confirmed that it was possible (FIG. 1). Accordingly, the catalyst of the present invention is sintered at a low temperature of 50 ° C. compared with the catalyst of the previous report (R. Spinicci et al., Materials Chemistry and Pythics 76 (2002) 20-25) in which calcination is performed at 600 ° C. Is confirmed to be possible.
（３）表面の特異構造
本実施例で得られた、ヘキサシアノ鉄（ＩＩＩ）カリウムを出発原料とする錯体法で調製した触媒は、図２に示すような特異な３次元の編み目構造を取るという特徴を有した触媒であり、この特徴のために、反応ガスメタンとの接触がより円滑になると考えられる。
(3) Specific surface structure The catalyst prepared by the complex method using hexacyanoiron (III) potassium as a starting material, obtained in this example, has a specific three-dimensional stitch structure as shown in FIG. It is considered that the catalyst has a characteristic, and the contact with the reaction gas methane becomes smoother due to this characteristic.
比較例１
実施例１で、ヘキサシアノ鉄（ＩＩＩ）カリウムを出発原料とする錯体法で調製した触媒を用いないで、共沈法及び固相法で調製した触媒は、特異な３次元の編み目状の表面構造を有しない触媒であることが確認された（図３）。
Comparative Example 1
In Example 1, the catalyst prepared by the coprecipitation method and the solid phase method without using the catalyst prepared by the complex method using hexacyano iron (III) potassium as a starting material, has a unique three-dimensional surface structure. (Fig. 3).
（メタンの酸化的分解）
実施例１の条件で、ヘキサシアノ鉄（ＩＩＩ）カリウムを出発原料とする錯体法（錯体分解法）で調製した触媒０．１ｇを充填した石英反応管に、混合ガス（メタン：Ｏ２＝１：６）を流速３０リットル／分を流して反応を行い、一定の時間の後の反応管出口ガスをガスクロマトグラフィーにかけた。その結果、メタンの転化率は温度とともに増大し、６００℃ではメタンの９２．９％が酸化的に分解され、二酸化炭素と水が連続的に生成した（図４）。
(Oxidative decomposition of methane)
A quartz reaction tube filled with 0.1 g of a catalyst prepared by a complex method (complex decomposition method) using hexacyanoiron (III) potassium as a starting material under the conditions of Example 1 was mixed with a mixed gas (methane: O 2 = 1: 1). The reaction was carried out at a flow rate of 30 liters / minute, and the reaction tube outlet gas after a certain time was subjected to gas chromatography. As a result, the conversion rate of methane increased with temperature. At 600 ° C., 92.9% of methane was decomposed oxidatively, and carbon dioxide and water were continuously generated (FIG. 4).
また、５００℃でも、５３．９％と高いメタンの分解活性を示し、文献（Ｒ．Ｓｐｉｎｉｃｃｉ ｅｔ ａｌ．，Ｍａｔｅｒｉａｌｓ Ｃｈｅｍｉｓｔｒｙ ａｎｄ Ｐｙｓｉｃｓ７６（２００２）２０−２５）の触媒（４８０℃、メタン転化率２５％程度）に比べて、２倍以上の高い触媒活性を有していることが確認された。 Further, even at 500 ° C., it showed a high methane decomposition activity of 53.9%, and the catalyst (480 ° C., methane conversion rate 25%) of the literature (R. Spinicci et al., Materials Chemistry and Physicals 76 (2002) 20-25). It was confirmed that the catalyst activity was twice or more as high as
比較例２
実施例２の反応条件で、ヘキサシアノ鉄（ＩＩＩ）カリウムを出発原料とする錯体法で調製した触媒を用いないで、共沈法、固相法（固相反応法）のそれぞれで調製した触媒を用いてメタンの酸化的分解を行った。その結果、特異な３次元網目構造を有している本発明のペロブスカイト型酸化物触媒が最も高い触媒活性を示していることが確認された（図４）。
Comparative Example 2
The catalyst prepared by the coprecipitation method and the solid phase method (solid phase reaction method) was used without using the catalyst prepared by the complex method using hexacyanoiron (III) potassium as the starting material under the reaction conditions of Example 2. The methane was oxidatively decomposed. As a result, it was confirmed that the perovskite oxide catalyst of the present invention having a unique three-dimensional network structure showed the highest catalytic activity (FIG. 4).
比較例３
実施例１でヘキサシアノ鉄（ＩＩＩ）カリウムを用いないで調製した酸化物を用いて、実施例２と同じ方法で実験を行った。その結果、ペロブスカイト構造を有している本発明の触媒が最も高い触媒活性を有していることが確認された（図４）。
Comparative Example 3
The experiment was performed in the same manner as in Example 2 using the oxide prepared in Example 1 without using potassium hexacyanoiron (III). As a result, it was confirmed that the catalyst of the present invention having a perovskite structure has the highest catalytic activity (FIG. 4).
比較例４
実施例１で硝酸ランタンを用いないで調製した酸化物を用いて、実施例２と同じ方法で実験を行った。その結果、ペロブスカイト構造を有している本発明の触媒が最も高い触媒活性を有していることが確認された（図４）。
Comparative Example 4
Using the oxide prepared in Example 1 without using lanthanum nitrate, the experiment was performed in the same manner as in Example 2. As a result, it was confirmed that the catalyst of the present invention having a perovskite structure has the highest catalytic activity (FIG. 4).
以上詳述したように、本発明は、メタンの酸化的除去用触媒及びメタンの酸化的除去方法に係るものであり、本発明により、３次元の網目状の特異な表面構造を有したメタンの酸化的分解用のペロブスカイト型酸化物ＬａＦｅＯ３を提供することができる。本発明のメタンの酸化的分解用触媒は、パラジウムや貴金属などの活性金属を全く含まない安価なものである。また、この触媒を用いることにより、メタンを容易に酸化分解することができ、効率的にメタンを熱エネルギーとして回収できる。本発明は、従来の固相法乃至共沈法により調製した酸化物触媒と比較してＣＨ４転化率が著しく高いペロブスカイト型酸化物触媒及び該触媒によるメタン酸化分解方法を提供するものとして有用である。 As described above in detail, the present invention relates to a catalyst for oxidative removal of methane and a method for oxidative removal of methane, and according to the present invention, methane having a unique three-dimensional network surface structure is provided. A perovskite oxide LaFeO 3 for oxidative decomposition can be provided. The catalyst for oxidative decomposition of methane of the present invention is an inexpensive catalyst that does not contain any active metals such as palladium and noble metals. Moreover, by using this catalyst, methane can be easily oxidatively decomposed, and methane can be efficiently recovered as thermal energy. INDUSTRIAL APPLICABILITY The present invention is useful as a perovskite oxide catalyst having a remarkably high CH 4 conversion rate as compared with an oxide catalyst prepared by a conventional solid phase method or coprecipitation method, and a methane oxidative decomposition method using the catalyst. is there.
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