JP3843520B2 - Low temperature denitration catalyst, production method thereof, and low temperature denitration method - Google Patents
Low temperature denitration catalyst, production method thereof, and low temperature denitration method Download PDFInfo
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- JP3843520B2 JP3843520B2 JP03079097A JP3079097A JP3843520B2 JP 3843520 B2 JP3843520 B2 JP 3843520B2 JP 03079097 A JP03079097 A JP 03079097A JP 3079097 A JP3079097 A JP 3079097A JP 3843520 B2 JP3843520 B2 JP 3843520B2
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- 239000003054 catalyst Substances 0.000 title claims description 31
- 238000000034 method Methods 0.000 title claims description 17
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 51
- 239000007789 gas Substances 0.000 claims description 24
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- 229910044991 metal oxide Inorganic materials 0.000 claims description 17
- 150000004706 metal oxides Chemical class 0.000 claims description 17
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 16
- 229910052751 metal Inorganic materials 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 10
- 150000003839 salts Chemical class 0.000 claims description 10
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 9
- 239000003638 chemical reducing agent Substances 0.000 claims description 8
- 239000007864 aqueous solution Substances 0.000 claims description 7
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims description 7
- 239000011572 manganese Substances 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 4
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical group O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 4
- 230000001590 oxidative effect Effects 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 238000007872 degassing Methods 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N nitrate group Chemical group [N+](=O)([O-])[O-] NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 229910021529 ammonia Inorganic materials 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 150000004687 hexahydrates Chemical class 0.000 description 2
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 1
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical class [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- 235000013980 iron oxide Nutrition 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical class [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910001960 metal nitrate Inorganic materials 0.000 description 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 150000004690 nonahydrates Chemical class 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
- 230000035515 penetration Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 229910001935 vanadium oxide Inorganic materials 0.000 description 1
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、低温脱硝触媒及びその製造方法ならびに低温脱硝方法に関する。
【０００２】
【従来技術】
従来より、ボイラ等の固定式窒素酸化物発生源における脱硝手段としては、酸化バナジウムを触媒とし、アンモニアを還元剤として用い、窒素酸化物（ＮＯｘ）を選択的に還元する方法が広く知られており、実用化されるに至っている。
【０００３】
しかしながら、この触媒を用いる場合は、脱硝活性を上げるために３００℃以上に反応温度を高める必要がある。すなわち、反応温度を高温にすれば、担体であるチタニアがシンタリングを起こし、触媒性能の低下を引き起こす。その結果として、非常に高価なバナジウム触媒を比較的頻繁に交換する必要も生じる。
【０００４】
また、高い反応温度が要求されると、脱硝装置も、ボイラ出口直後、廃熱ボイラの伝熱部途中等の限られた箇所にしか設置できないため、装置の複雑化、耐熱材料の仕様による高額化、交換時の作業性の悪さ等の問題も生じる。
【０００５】
さらに、かかる従来技術では、集塵機出口の１５０℃以下の排気ガス或いは低温の製鉄所の焼結排気ガスの脱硝に適用しようとすると再加熱が必要となり、経済的な見地よりその適用は事実上困難である。
【０００６】
【発明が解決しようとする課題】
従って、本発明は、特に比較的低温で排気ガスの脱硝を行うことを主な目的とする。
【０００７】
【課題を解決するための手段】
本発明者は、上記の従来技術の問題に鑑み、鋭意研究を重ねた結果、特定の構成からなる触媒を一定条件下で用いる場合には、低温下であっても有効に脱硝できることを見出し、本発明を完成するに至った。
【０００８】
すなわち、本発明は、下記の低温脱硝触媒及びその製造方法ならびに低温脱硝方法に係るものである。
【０００９】
１．Ｍｎ、Ｆｅ、Ｃｏ及びＮｉの少なくとも１種の金属酸化物が活性炭素繊維に担持されている低温脱硝触媒。
【００１０】
２．Ｍｎ、Ｆｅ、Ｃｏ及びＮｉの少なくとも１種の金属塩の水溶液を活性炭素繊維に含浸し、減圧脱気した後、乾燥し、次いで酸化性雰囲気下２００〜３００℃で加熱処理して当該金属塩を金属酸化物とする低温脱硝触媒の製造方法。
【００１１】
３．上記１項に記載の触媒に、窒素酸化物を含むガスを還元剤の存在下で接触させることを特徴とする排気ガスの低温脱硝方法。
【００１２】
【発明の実施の形態】
以下、本発明をその実施の形態とともに詳細に説明する。
【００１３】
本発明の低温脱硝触媒は、Ｍｎ、Ｆｅ、Ｃｏ及びＮｉの少なくとも１種の金属酸化物が活性炭素繊維に担持されているものである。
【００１４】
担持させる金属酸化物としては、マンガン酸化物（ＭｎＯ2、ＭｎＯ、Ｍｎ2Ｏ3等）、鉄酸化物（Ｆｅ2Ｏ3、Ｆｅ3Ｏ4等）、コバルト酸化物（Ｃｏ2Ｏ3等）及びニッケル酸化物（ＮｉＯ等）の少なくとも１種を用いることができ、これらの酸化物の中においては、本発明の効果が得られる限り特にその酸化物の種類は制限されない。これらの中でも、マンガン酸化物が好ましく、特に二酸化マンガン（ＭｎＯ2）がより好ましい。金属酸化物の担持量は、最終製品の用途等に応じて適宜変更でき、通常は活性炭素繊維に対して５〜３０重量％程度、好ましくは１０〜１５重量％とする。
【００１５】
活性炭素繊維としては、金属酸化物を担持できる限り特に制限されず、公知のピッチ系、ＰＡＮ系等のものが使用でき、また市販の活性炭素繊維も使用することができる。この中でも、特にピッチ系活性炭素繊維が好ましい。また、活性炭素繊維の比表面積は、最終製品の用途等に応じて適宜設定することができるが、通常は５００〜１５００ｍ2／ｇ程度、好ましくは７００〜１０００ｍ2／ｇとする。
【００１６】
本発明の低温脱硝触媒は、例えば次の方法により製造することができる。まず、Ｍｎ、Ｆｅ、Ｃｏ及びＮｉの少なくとも１種の金属塩の水溶液を活性炭素繊維に含浸し、減圧脱気した後、乾燥し、次いで酸化性雰囲気下２００〜３００℃で加熱処理して当該金属塩を金属酸化物とする。
【００１７】
上記金属塩としては、水溶性のものであれば特に制限されないが、特に硝酸塩（例えば、硝酸マンガン（II）、硝酸鉄（III）等）を用いることが好ましい。これら金属塩は、水和物も含まれる。水溶液の濃度は、最終製品の担持量が上記範囲になれば特に限定されないが、通常は０．５〜１５重量％程度、好ましくは５〜１０重量％とすれば良い。
【００１８】
次いで、上記水溶液に活性炭素繊維を含浸させる。含浸させた活性炭素繊維を減圧下で脱気処理した後、乾燥する。減圧する程度は、通常１０-1〜１０Ｔｏｒｒ程度の圧力下とすれば良いが、この範囲外であっても良い。また、乾燥温度も、特に制限されず、通常は１００℃以下とすれば良い。
【００１９】
乾燥後、活性炭素繊維を加熱処理する。加熱温度は、含浸されている金属塩が金属酸化物として担持できる限りは特に制限されないが、通常は２００〜３００℃程度、好ましくは２８０〜３００℃とすれば良い。加熱雰囲気は、酸化性雰囲気下（例えば空気中）とすれば良く、好ましくは空気気流下とする。空気気流を用いる場合の流通量は、通常０．１〜１．０ｍ3／ｍｉｎ程度とすれば良い。
【００２０】
本発明の低温脱硝方法は、上記の本発明触媒に、窒素酸化物を含むガスを還元剤の存在下で接触させることを特徴とする。
【００２１】
本発明方法では、還元剤の存在下で窒素酸化物を含むガスとの接触を行うが、還元剤としては公知のものをそのまま使用でき、例えばアンモニア、水素、炭化水素等が使用できる。この中でも、特にアンモニアが好ましい。還元剤の含有量は、上記ガス中の窒素酸化物の濃度と等モル又はそれ以上の量とすれば良い。
【００２２】
窒素酸化物を含むガスの組成は、排気ガス等の組成のままでも良いが、特に窒素酸化物１０〜５０００ｐｐｍ（好ましくは２０〜３００ｐｐｍ）、酸素３ｖｏｌ％以上（好ましくは３〜１０ｖｏｌ％）及び水蒸気８０ｖｏｌ％以下（好ましくは５〜２０ｖｏｌ％）を含む組成とすることが好ましい。また、接触させる際の温度も特に制限されないが、通常は２００℃以下、好ましくは１００〜１５０℃で行えば良い。
【００２３】
接触させる方法は、特に制限されず、公知の方法に従えば良い。例えば、触媒を反応管等に充填し、その中に窒素酸化物を含むガスを流通させれば良い。このガスの流通量は、用いる触媒量等に応じて適宜定めることができる。
【００２４】
【作用】
本発明においては、低温脱硝触媒を通過する間に、ガス中に含まれる窒素酸化物が還元剤（例えばアンモニア）と反応し、無害な窒素と水蒸気に分解される。
その反応例を示すと下記（１）（２）の通りである。
【００２５】
４ＮＯ＋４ＮＨ3＋Ｏ2→４Ｎ2＋６Ｈ2Ｏ …（１）
６ＮＯ2＋８ＮＨ3→７Ｎ2＋１２Ｈ2Ｏ …（２）
活性炭素繊維の表面の金属酸化物にＮＯが吸着され、金属酸化物の強い酸化性能によりＮＯ2となる。生成した反応性の高いＮＯ2がアンモニアと反応し、Ｎ2とＨ2Ｏに還元される。Ｎ2とＨ2Ｏが脱離した後の金属酸化物は酸素により酸化され、酸化性金属酸化物表面が再生される。これらの反応が２００℃以下の低温で進行するのは、特に、活性炭素繊維のもつ２ｎｍ以下のミクロポア中でこれらの反応物質が凝縮し、ミクロな領域で高圧反応するためである。
【００２６】
【発明の効果】
本発明の脱硝方法によれば、排気ガス中等において低濃度から高濃度で含まれる窒素酸化物を特に１５０℃以下という低温下でも効率的に除去し、これを主として窒素と水に還元することが可能である。特に、常温〜１５０℃の温度で低濃度〜高濃度の窒素酸化物を通常４０〜８０％という高い除去率で脱硝することができる。
【００２７】
このような本発明方法では、ボイラ、エンジン、タービン等から排出される燃焼排気ガスの脱硝に有効であり、特に排煙処理装置、廃熱処理装置等の出口における比較的低温（通常２００℃以下）の排気ガスを効率良く脱硝することができる。
【００２８】
【実施例】
以下、実施例を示し、本発明の特徴をより一層明確にする。
【００２９】
実施例１〜６及び参考例７〜９
表１に示す条件で金属酸化物を活性炭素繊維に担持させて触媒をそれぞれ製造した。
【００３０】
【表１】
活性炭素繊維としては、ピッチ系活性炭素繊維（アドール（株）製）を用いた。試料名は「Ａ７」であり、その比表面積は７００ｍ2／ｇである。このピッチ系活性炭素繊維に、硝酸マンガン（II）６水和物、硝酸鉄（III）９水和物又は硝酸コバルト（II）６水和物の水溶液をそれぞれ含浸させた。含浸させた水溶液の濃度は、表１に示すように、最終的な金属酸化物の担持量として５〜１５重量％の範囲となるように調整した。
【００３２】
その後、デシケーター内で室温下、真空ポンプにより１０-1Ｔｏｒｒまで減圧し、各試料について脱気処理を施した。この処理によって、活性炭素繊維のミクロポア内への脱気と金属塩の浸透を促進することができる。次いで、これを１００℃の熱風下で１昼夜乾燥し、さらに空気気流下２００〜３００℃の範囲で１時間加熱処理し、上記金属硝酸塩を熱分解して金属酸化物とし、触媒をそれぞれ得た。
【００３３】
次に、得られた触媒を反応管（内径１５ｍｍ）に２．５ｇを充填し、温度６０〜１５０℃でガスを５００ｃｃ／ｍｉｎで流通した。ガス組成は、ＮＯ：２００ｐｐｍ、ＮＨ3：２００ｐｐｍ、Ｏ2：１０．５ｖｏｌ％、Ｎ2バランス、水分：８．１ｖｏｌ％とした。反応管より出口ガスを、化学発光式ＮＯｘ計（「ＥＣＬ−８８ＵＳ」、柳本製作所（株）製）により分析し、次式により脱硝率を算出した。
【００３４】
脱硝率（％）＝入口ＮＯ濃度(ppm)−出口ＮＯ濃度(ppm)／入口ＮＯ濃度(ppm) ×１００なお、脱硝率は、反応開始後３０時間後の安定化した状態の定常反応中における値を示す。
【００３５】
比較例１〜３
比較例１及び２として、金属酸化物を担持しないピッチ系活性炭素繊維（いずれもアドール（株）製、試料名「Ａ１５」及び「Ａ７」、比表面積はそれぞれ１５００ｍ2／ｇ及び７００ｍ2／ｇ）、並びに比較例３として従来技術であるバナジウム系触媒（Ｖ2Ｏ5／ＴｉＯ2）を用いて脱硝した。その結果も図１に示す。
【００３６】
図１の結果より、本発明の触媒を用いた脱硝によれば、もとの活性炭素繊維（比較例１及び２）或いは従来技術（バナジウム系触媒：比較例３）に比べて、全般的に１５０℃以下の低温における脱硝活性に優れていることがわかる。殊に、活性炭素繊維「Ａ７」にＭｎを１５％担持し、３００℃で熱分解して得た触媒を用いた実施例１では、脱硝率が９４％にも達した。
【図面の簡単な説明】
【図１】実施例及び比較例における脱硝効果と温度との関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a low-temperature denitration catalyst, a production method thereof, and a low-temperature denitration method.
[0002]
[Prior art]
Conventionally, as a denitration means in a stationary nitrogen oxide generation source such as a boiler, a method of selectively reducing nitrogen oxide (NOx) using vanadium oxide as a catalyst and ammonia as a reducing agent has been widely known. It has been put to practical use.
[0003]
However, when this catalyst is used, it is necessary to increase the reaction temperature to 300 ° C. or higher in order to increase the denitration activity. That is, if the reaction temperature is increased, titania as a support causes sintering, which causes a decrease in catalyst performance. As a result, very expensive vanadium catalysts need to be replaced relatively frequently.
[0004]
In addition, when a high reaction temperature is required, a denitration device can be installed only in a limited location, such as immediately after the boiler outlet, or in the middle of the heat transfer section of a waste heat boiler. Problems such as poor workability at the time of conversion and replacement also occur.
[0005]
Furthermore, in this conventional technique, reheating is necessary when applying to denitration of exhaust gas at 150 ° C. or less at the outlet of the dust collector or sintering exhaust gas at a low temperature steelworks, and its application is practically difficult from an economical point of view. It is.
[0006]
[Problems to be solved by the invention]
Therefore, the main object of the present invention is to denitrate exhaust gas particularly at a relatively low temperature.
[0007]
[Means for Solving the Problems]
In light of the problems of the prior art described above, the present inventors have conducted extensive research and found that when a catalyst having a specific configuration is used under certain conditions, it can be effectively denitrated even at low temperatures, The present invention has been completed.
[0008]
That is, the present invention relates to the following low-temperature denitration catalyst, its production method, and low-temperature denitration method.
[0009]
1. A low-temperature denitration catalyst in which at least one metal oxide of Mn, Fe, Co, and Ni is supported on activated carbon fibers.
[0010]
2. An activated carbon fiber is impregnated with an aqueous solution of at least one metal salt of Mn, Fe, Co and Ni, degassed under reduced pressure, dried, and then heat-treated at 200 to 300 ° C. in an oxidizing atmosphere. A method for producing a low-temperature denitration catalyst using a metal oxide as a catalyst.
[0011]
3. A method for low-temperature denitration of exhaust gas, comprising contacting the catalyst according to item 1 with a gas containing nitrogen oxides in the presence of a reducing agent.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with embodiments thereof.
[0013]
The low-temperature denitration catalyst of the present invention is one in which at least one metal oxide of Mn, Fe, Co, and Ni is supported on activated carbon fibers.
[0014]
As metal oxides to be supported, manganese oxides (MnO 2 , MnO, Mn 2 O 3 etc.), iron oxides (Fe 2 O 3 , Fe 3 O 4 etc.), cobalt oxides (Co 2 O 3 etc.) And at least one kind of nickel oxide (NiO or the like) can be used, and among these oxides, the kind of the oxide is not particularly limited as long as the effect of the present invention is obtained. Among these, manganese oxide is preferable, and manganese dioxide (MnO 2 ) is particularly preferable. The amount of the metal oxide supported can be appropriately changed according to the use of the final product, and is usually about 5 to 30% by weight, preferably 10 to 15% by weight with respect to the activated carbon fiber.
[0015]
The activated carbon fiber is not particularly limited as long as it can carry a metal oxide, and known pitch-based and PAN-based materials can be used, and commercially available activated carbon fibers can also be used. Of these, pitch-based activated carbon fibers are particularly preferable. The specific surface area of the activated carbon fiber can be appropriately set according to the use of the final product, but is usually about 500 to 1500 m 2 / g, preferably 700 to 1000 m 2 / g.
[0016]
The low-temperature denitration catalyst of the present invention can be produced, for example, by the following method. First, an activated carbon fiber is impregnated with an aqueous solution of at least one metal salt of Mn, Fe, Co, and Ni, degassed under reduced pressure, dried, and then heat-treated at 200 to 300 ° C. in an oxidizing atmosphere. The metal salt is a metal oxide.
[0017]
The metal salt is not particularly limited as long as it is water-soluble, but nitrates (for example, manganese (II) nitrate, iron (III) nitrate, etc.) are particularly preferably used. These metal salts include hydrates. The concentration of the aqueous solution is not particularly limited as long as the supported amount of the final product is within the above range, but it is usually about 0.5 to 15% by weight, preferably 5 to 10% by weight.
[0018]
Next, the activated carbon fiber is impregnated in the aqueous solution. The impregnated activated carbon fiber is degassed under reduced pressure and then dried. The degree of pressure reduction is usually a pressure of about 10 −1 to 10 Torr, but may be outside this range. Also, the drying temperature is not particularly limited, and may usually be 100 ° C. or lower.
[0019]
After drying, the activated carbon fiber is heated. The heating temperature is not particularly limited as long as the impregnated metal salt can be supported as a metal oxide, but is usually about 200 to 300 ° C, preferably 280 to 300 ° C. The heating atmosphere may be an oxidizing atmosphere (for example, in the air), preferably an air stream. The flow rate in the case of using an air stream is usually about 0.1 to 1.0 m 3 / min.
[0020]
The low temperature denitration method of the present invention is characterized in that a gas containing nitrogen oxides is brought into contact with the above-described catalyst of the present invention in the presence of a reducing agent.
[0021]
In the method of the present invention, contact with a gas containing nitrogen oxides is carried out in the presence of a reducing agent. Known reducing agents can be used as they are, for example, ammonia, hydrogen, hydrocarbons and the like. Among these, ammonia is particularly preferable. The content of the reducing agent may be equal to or higher than the concentration of nitrogen oxide in the gas.
[0022]
The composition of the gas containing nitrogen oxide may be the composition of exhaust gas or the like, but in particular, nitrogen oxide is 10 to 5000 ppm (preferably 20 to 300 ppm), oxygen is 3 vol% or more (preferably 3 to 10 vol%), and water vapor. A composition containing 80 vol% or less (preferably 5 to 20 vol%) is preferable. Further, the temperature at the time of contacting is not particularly limited, but is usually 200 ° C. or lower, preferably 100 to 150 ° C.
[0023]
The method for contacting is not particularly limited, and may be a known method. For example, the catalyst may be filled in a reaction tube or the like, and a gas containing nitrogen oxide may be circulated therein. The amount of gas flow can be determined as appropriate according to the amount of catalyst used.
[0024]
[Action]
In the present invention, while passing through the low-temperature denitration catalyst, nitrogen oxides contained in the gas react with a reducing agent (for example, ammonia) and decompose into harmless nitrogen and water vapor.
The reaction examples are as follows (1) and (2).
[0025]
4NO + 4NH 3 + O 2 → 4N 2 + 6H 2 O (1)
6NO 2 + 8NH 3 → 7N 2 + 12H 2 O (2)
NO is adsorbed to the metal oxide on the surface of the activated carbon fiber, and becomes NO 2 due to the strong oxidation performance of the metal oxide. The highly reactive NO 2 produced reacts with ammonia and is reduced to N 2 and H 2 O. The metal oxide after N 2 and H 2 O are desorbed is oxidized by oxygen, and the surface of the oxidizable metal oxide is regenerated. The reason why these reactions proceed at a low temperature of 200 ° C. or lower is that these reactants condense in the micropores of 2 nm or less of the activated carbon fiber and cause a high-pressure reaction in a microscopic region.
[0026]
【The invention's effect】
According to the denitration method of the present invention, nitrogen oxides contained in low to high concentrations in exhaust gas etc. can be efficiently removed even at a low temperature of 150 ° C. or less, and this can be mainly reduced to nitrogen and water. Is possible. In particular, it is possible to denitrate low to high concentration nitrogen oxides at a high removal rate of usually 40 to 80% at a temperature of normal temperature to 150 ° C.
[0027]
Such a method of the present invention is effective for denitration of combustion exhaust gas discharged from boilers, engines, turbines, etc., and is relatively low temperature (usually 200 ° C. or less) particularly at the outlet of a flue gas treatment device, waste heat treatment device or the like. The exhaust gas can be efficiently denitrated.
[0028]
【Example】
Hereinafter, an example is shown and the feature of the present invention is clarified further.
[0029]
Examples 1 to 6 and Reference Examples 7 to 9
Catalysts were produced by supporting metal oxides on activated carbon fibers under the conditions shown in Table 1.
[0030]
[Table 1]
As the activated carbon fiber, pitch-based activated carbon fiber (manufactured by Adol Co., Ltd.) was used. The sample name is “A7”, and the specific surface area is 700 m 2 / g. This pitch-based activated carbon fiber was impregnated with an aqueous solution of manganese nitrate (II) hexahydrate, iron nitrate (III) nonahydrate or cobalt nitrate (II) hexahydrate. As shown in Table 1, the concentration of the impregnated aqueous solution was adjusted to be in the range of 5 to 15% by weight as the final supported amount of metal oxide.
[0032]
Thereafter, the sample was depressurized to 10 −1 Torr with a vacuum pump at room temperature in a desiccator, and each sample was deaerated. By this treatment, degassing of activated carbon fibers into the micropores and penetration of the metal salt can be promoted. Next, this was dried for 1 day under hot air at 100 ° C., and further heat-treated in the range of 200 to 300 ° C. for 1 hour under an air stream, and the metal nitrate was thermally decomposed into metal oxides to obtain catalysts. .
[0033]
Next, 2.5 g of the obtained catalyst was filled in a reaction tube (inner diameter 15 mm), and gas was circulated at a temperature of 60 to 150 ° C. at 500 cc / min. The gas composition was NO: 200 ppm, NH 3 : 200 ppm, O 2 : 10.5 vol%, N 2 balance, and moisture: 8.1 vol%. The outlet gas from the reaction tube was analyzed by a chemiluminescence NOx meter (“ECL-88US”, manufactured by Yanagimoto Seisakusho Co., Ltd.), and the denitration rate was calculated by the following formula.
[0034]
Denitration rate (%) = Inlet NO concentration (ppm) −Outlet NO concentration (ppm) / Inlet NO concentration (ppm) × 100 Note that the denitration rate is a steady state reaction in a
[0035]
Comparative Examples 1-3
As Comparative Examples 1 and 2, it bears no metal oxide pitch-based activated carbon fibers (both Adol Co., sample name "A15" and "A7", respectively the specific surface area of 1500 m 2 / g and 700 meters 2 / g ), And Comparative Example 3 was denitrated using a vanadium catalyst (V 2 O 5 / TiO 2 ) which is a conventional technique. The results are also shown in FIG.
[0036]
From the results shown in FIG. 1, according to the denitration using the catalyst of the present invention, compared with the original activated carbon fibers (Comparative Examples 1 and 2) or the conventional technique (Vanadium catalyst: Comparative Example 3), It turns out that it is excellent in the denitration activity in the low temperature of 150 degrees C or less. In particular, in Example 1 using a catalyst obtained by supporting 15% of Mn on activated carbon fiber “A7” and thermally decomposing at 300 ° C., the denitration rate reached 94%.
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between a denitration effect and temperature in Examples and Comparative Examples.
Claims (10)
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| JP03079097A JP3843520B2 (en) | 1997-02-14 | 1997-02-14 | Low temperature denitration catalyst, production method thereof, and low temperature denitration method |
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| JP03079097A JP3843520B2 (en) | 1997-02-14 | 1997-02-14 | Low temperature denitration catalyst, production method thereof, and low temperature denitration method |
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| JP2005279508A (en) * | 2004-03-30 | 2005-10-13 | Matsushita Electric Ind Co Ltd | Prior-to-drying pretreatment method of three-dimensional structure body, exhausted gas purification filter and production method thereof |
| JP6079056B2 (en) * | 2012-08-28 | 2017-02-15 | 株式会社Ihi | Denitration apparatus and denitration method |
| CN102989466B (en) * | 2012-12-27 | 2015-04-15 | 北京石油化工学院 | Flue gas desulfurization and denitrification catalyst for reduction method and applications of catalyst |
| JP2016087587A (en) | 2014-11-10 | 2016-05-23 | トヨタ自動車株式会社 | EXHAUST GAS PURIFYING CATALYST FOR NOx SELECTIVE REDUCTION AND EXHAUST GAS PURIFYING METHOD |
| US20170232424A1 (en) | 2016-02-17 | 2017-08-17 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purification catalyst and production method thereof |
| CN108176403B (en) * | 2018-01-24 | 2020-09-29 | 四川农业大学 | Co-loaded activated carbon fiber3O4Method for preparing catalytic material |
| CN115155608A (en) * | 2022-05-09 | 2022-10-11 | 山西大学 | Method for enhancing performance of activated carbon-based low-temperature SCR denitration catalyst by utilizing iron component in activated carbon |
| CN116037115B (en) * | 2023-01-29 | 2024-09-24 | 石河子大学 | Foam nickel-based CO-SCR denitration catalyst and preparation method thereof |
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