JP4047523B2 - Organochlorine decomposition method and catalyst - Google Patents
Organochlorine decomposition method and catalyst Download PDFInfo
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- JP4047523B2 JP4047523B2 JP2000212970A JP2000212970A JP4047523B2 JP 4047523 B2 JP4047523 B2 JP 4047523B2 JP 2000212970 A JP2000212970 A JP 2000212970A JP 2000212970 A JP2000212970 A JP 2000212970A JP 4047523 B2 JP4047523 B2 JP 4047523B2
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- 238000000354 decomposition reaction Methods 0.000 title claims description 31
- 239000003054 catalyst Substances 0.000 title claims description 26
- 238000000034 method Methods 0.000 title claims description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 60
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 36
- 150000004045 organic chlorine compounds Chemical class 0.000 claims description 28
- 229910052742 iron Inorganic materials 0.000 claims description 26
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 claims description 14
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 claims description 13
- 239000011019 hematite Substances 0.000 claims description 12
- 229910052595 hematite Inorganic materials 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 229910001868 water Inorganic materials 0.000 claims description 11
- 150000002013 dioxins Chemical class 0.000 claims description 10
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 6
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims 1
- 230000000694 effects Effects 0.000 description 25
- 239000000460 chlorine Substances 0.000 description 24
- 239000007789 gas Substances 0.000 description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- KVGZZAHHUNAVKZ-UHFFFAOYSA-N 1,4-Dioxin Chemical compound O1C=COC=C1 KVGZZAHHUNAVKZ-UHFFFAOYSA-N 0.000 description 9
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 8
- 229910010413 TiO 2 Inorganic materials 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 229910052801 chlorine Inorganic materials 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 229910000314 transition metal oxide Inorganic materials 0.000 description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 239000010453 quartz Substances 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 229910001902 chlorine oxide Inorganic materials 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 229910052598 goethite Inorganic materials 0.000 description 3
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 3
- 229910052815 sulfur oxide Inorganic materials 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- NUIURNJTPRWVAP-UHFFFAOYSA-N 3,3'-Dimethylbenzidine Chemical compound C1=C(N)C(C)=CC(C=2C=C(C)C(N)=CC=2)=C1 NUIURNJTPRWVAP-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical group [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000005115 demineralization Methods 0.000 description 1
- 230000002328 demineralizing effect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- RAQDACVRFCEPDA-UHFFFAOYSA-L ferrous carbonate Chemical compound [Fe+2].[O-]C([O-])=O RAQDACVRFCEPDA-UHFFFAOYSA-L 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 238000010525 oxidative degradation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 150000003071 polychlorinated biphenyls Chemical class 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Description
【０００１】
【発明の属する技術分野】
本発明は、例えば都市ゴミや産業廃棄物の焼却設備、鉄鋼電気炉、鉄鋼焼結機から排出されるダイオキシン等の有害物質の除去方法に関するものである。
【０００２】
【従来の技術】
遷移金属の酸化物は、日本化学会誌Ｖｏｌ．１９８９，ｐ．１３９（１９８９）に示されるように、有機塩素化合物の酸化分解活性を有することは知られている。これらを利用して、排ガス中の有機塩素化合物の触媒分解技術が開発されている。
【０００３】
触媒（第４１巻、２１０頁、１９９９年）に記載されているような、従来から窒素酸化物の接触還元触媒として使用されてきたＶ2Ｏ5−ＴｉＯ2系あるいは耐ＳＯx性を考慮したＶ2Ｏ5−ＴｉＯ2−ＷＯ3系の触媒による分解技術が実用化されている。これらの触媒は高価であるため一般にハニカムまたは粒状で、固定層として長期的に使用される。
【０００４】
また特開平１１−２６７５０７号公報に示されているような、酸化鉄触媒を用いたゴミ焼却炉のダイオキシンの抑制方法が開発されている。この方法は酸化鉄触媒をゴミ焼却炉の燃焼室または再燃室に吹き込み、ダイオキシンを抑制するものである。ここで用いられる酸化鉄は試薬から調整される。例えばゲータイト粉末は、第一鉄塩、水酸化アルカリ、炭酸アルカリおよびアンモニアから選ばれる１種または２種以上を用いて反応させ、得られた鉄の水酸化物や炭酸鉄等である第一鉄含有沈澱物を含む懸濁液中に、空気等の酸素含有ガスを通気してゲータイト粒子を生成させて得ることができる。またヘマタイト粉末は、前記ゲータイト粉末を空気中で２００〜８００℃の温度範囲で加熱脱水を行って得ることができる。さらにマグネタイト粉末は、前記ヘマタイト粉末を還元性雰囲気下、３００〜６００℃で加熱還元して得られる。
【０００５】
【発明が解決しようとする課題】
しかしながら、Ｖ2Ｏ5−ＴｉＯ2系あるいはＶ2Ｏ5−ＴｉＯ2−ＷＯ3系の触媒の場合は、固定層で使用するために、ダクトの途中に触媒層を設けなければならず、大規模な工事の必要があった。
【０００６】
また特開平１１-２６７５０７号公報の酸化鉄触媒では、大規模な工事を必要としないが、酸化鉄は、Ｖ2Ｏ5−ＴｉＯ2系あるいはＶ2Ｏ5−ＴｉＯ2−ＷＯ3系の触媒に比べて、塩素や硫黄酸化物と結びつきやすく、触媒活性が低下しやすい。このため長時間使用ができず、排ガス中への吹き込みによる短時間の使用となる。しかしダイオキシンを抑制するためには、排ガス中に絶えず吹き込む必要がある。しかし酸化鉄触媒は、上述のように複雑な工程を経て試薬から触媒を調整するため高価になる。このような高価な酸化鉄触媒を吹き込む場合、使用済みの酸化鉄触媒はダストとともに回収され、かつ排ガス中の塩素や硫黄酸化物により被毒されるため再使用が困難であり、ゴミ焼却の場合はダストとともに廃棄される。
【０００７】
また、上述のＶ2Ｏ5−ＴｉＯ2系あるいはＶ2Ｏ5−ＴｉＯ2−ＷＯ3系の触媒、または酸化鉄等の遷移金属酸化物は、有機塩素の分解活性は高いものの、Ｃｌ2の生成活性も高い。Ｃｌ2はＨＣｌと比べて反応活性が高く、炭素質と結びついてダイオキシン等の有機塩素化合物の再生成を起こしやすい。
【０００８】
【課題を解決するための手段】
本発明者は、上記の課題を解決するために鋭意研究した結果、触媒として鉄鉱石を用いることにより安価かつ効率的な有機塩素化合物分解が達成できることを見いだし本発明に至った。
【０００９】
すなわち、本発明は
（１）有機塩素化合物分解触媒として、鉄鉱石を使用する、有機塩素化合物であるモノクロロベンゼン又はダイオキシン類の分解方法であって、前記鉄鉱石は、Ｆｅを５０質量％以上、およびＡｌ２Ｏ３とＳｉＯ２の和を３質量％以上で含む、又は、更に結合水を４質量％以上で含むことを特徴とする有機塩素化合物の分解方法、
（２）前記鉄鉱石を２５０℃以上で使用前または使用中に加熱処理し、鉄鉱石中の含水酸化鉄をヘマタイトに変態せしめることを特徴とする（１）の有機塩素化合物の分解方法
（３）鉄鉱石よりなる有機塩素化合物であるモノクロロベンゼン又はダイオキシン類の分解触媒であって、前記鉄鉱石は、Ｆｅを５０質量％以上、およびＡｌ２Ｏ３とＳｉＯ２の和を３質量％以上で含む、又は、更に結合水を４質量％以上で含むことを特徴とする有機塩素化合物分解触媒、および
（４）前記鉄鉱石は、２５０℃以上で使用前または使用中に加熱処理し、鉄鉱石中の含水酸化鉄をヘマタイトに変態せしめ、Ｆｅ２Ｏ３の含有率を７０質量％以上かつ比表面積が１０ｍ２／ｇ以上であることを特徴とする（３）の有機塩素化合物分解触媒
である。
【００１０】
【発明の実施の形態】
以下、本発明を詳細に説明する。従来技術に示したように、遷移金属酸化物は、有機塩素化合物の分解活性に優れているが、触媒活性が強いためＣｌ2を生成しやすい。Ｃｌ2は反応活性が高いため、炭素質を塩素化し、ダイオキシン等の有機塩素化合物を再生成する。このため、遷移金属酸化物を分解触媒に使用した場合、有機塩素化合物が再生成することがあり、分解効率が低下する。
【００１１】
そこで種々の物質を探索した結果、鉄鉱石が有機塩素化合物の分解活性に優れ、かつ比較的Ｃｌ2の発生が抑制できることを見出した。鉄鉱石の主成分は酸化鉄であるが、脈石分としてアルミナ、シリカを含んでいる。これらの物質は有機塩素の分解活性は低いがＣｌ2生成を抑制する機能を有しているため、Ｃｌ2と炭素質によるダイオキシン等の有機塩素化合物の再生成を抑制できると考えられる。すなわち、アルミナ、シリカがある一定量以上存在することにより、遷移金属酸化物の有機塩素化合物分解活性を損なうことなくＣｌ2生成を抑制でき、効率的に有機塩素化合物を分解することができる。具体的にはＦｅの割合が５０質量％以上かつアルミナ（Ａｌ2Ｏ3）とシリカ（ＳｉＯ2）の合計が３質量％以上含有している鉱石が有機塩素化合物分解活性が高く、Ｃｌ2の生成活性が低い。いずれも上限の規定は特にない。ここでＦｅの割合が５０質量％未満、またはアルミナとシリカの合計が３質量％未満の場合、有機塩素化合物分解活性が低く、Ｃｌ2の生成活性が低くならず好ましくない。
【００１２】
さらに鉄鉱石の中でも分解活性の高い鉱石があることを見出した。その分解活性の高い鉱石とは、結合水を多く含んでいる鉱石であり、いわゆる含水酸化鉄が主成分の鉱石である。結合水を多く含んでいる鉱石は酸化鉄の結晶化度が比較的低いため、表面活性が高くかつ比表面積も大きいため有機塩素化合物の分解活性に優れる。具体的には、結合水を４質量％以上含有する鉄鉱石である。結合水の上限の規定は特にない。ここで結合水が４質量％未満の場合、比表面積が小さく、触媒作用の高い含水酸化鉄の割合が減少し好ましくない。
【００１３】
また、上述の結合水を多く含む鉱石は、２５０℃以上の温度で加熱することにより結合水を放出しヘマタイト（α−Ｆｅ2Ｏ3）に変態する。
【００１４】
【化１】
本方式で作製したヘマタイトは、元の含水酸化鉄および最初からヘマタイトとして鉱石中に存在しているヘマタイト系鉄鉱石よりも表面活性が高く、かつ比表面積も大きい。このため有機塩素化合物の分解活性が高くなっている。温度は２５０℃以上であれば、特に上限を規定しない。ここで、加熱温度が２５０℃未満の場合、ヘマタイトに変態せず好ましくない。雰囲気は、水素や一酸化炭素ガス等の還元性ガス以外であれば良く、例えば、空気、燃焼排ガス、窒素が好ましい。加熱時間は、温度が高いほど短くなるが、３００℃で３０分、好ましくは６０分以上を必要とする。また、比表面積が１０ｍ2／ｇ未満の場合、有機塩素化合物の分解活性が充分に発揮されないが、上記条件で作製した場合、ヘマタイトの比表面積は、１０ｍ2／ｇ以上とすることができ、有機塩素化合物の分解活性が向上すため、非常に好ましい。
【００１６】
本発明の鉄鉱石の使用形態であるが、鉄鉱石は、通常の触媒と比べて安価であるため、ある温度以上の排ガス温度を有するダクトに吹き込んで一過使用するのが好ましい。排ガス温度は２００℃以上、好ましくは２５０℃以上であれば有機塩素分解が効率的に進行する。鉄鉱石は塊状であるため充填層として使用可能であるが、塩素や硫黄酸化物と結合し活性が低下するため、充填層として使用する場合は、上流に酸性ガス除去装置（脱塩、脱硫装置）を設ける必要がある。
【００１７】
【実施例】
以下、実施例１〜３で本発明を具体的に説明する。
【００１８】
表１に示す組成の鉱石をそれぞれ実施例１および２、ならびに比較例１および２とし、これらの２００ｇを石英管に充填し、空気をベースガスとして、ダイオキシンの前駆体であるモノクロロベンゼンを１０００ｐｐｍの濃度に調整したガスを、１０００Ｎｃｍ3／ｍｉｎの流量で石英管に流通することにより、モノクロロベンゼンの分解実験を反応温度３００℃にて実施した。結果を合わせて表１に示す。ここでモノクロロベンゼンの分解率は、ガスクロマトグラフィーで石英管出側モノクロロベンゼン濃度を測定することによって算出した。またＣｌ2生成率は、モノクロロベンゼンのＣｌが全量Ｃｌ2に転化した場合を１００％として石英管出側塩素濃度を測定し、算出した。塩素濃度はオルトトリジン法にて分析を行った。比較例１および２ではモノクロロベンゼンの分解率は高いがＣｌ2が大量に生成していた。これに対して実施例１ではモノクロロベンゼンの分解率は比較例とほぼ同じであるが、Ｃｌ2生成が抑制されていた。さらに結合水、ＳｉＯ2、Ａｌ2Ｏ3の割合の高い実施例２ではモノクロロベンゼン分解率は向上し、Ｃｌ2生成がさらに抑制されていた。
【００１９】
【表１】
さらに実施例２の鉱石を２５０℃で４時間熱処理を行った鉱石（実施例３）と比較例２の鉱石を同様の熱処理を施した鉱石（比較例３）にて、上述の実施例１および２ならびに比較例１および２と同一実験条件にてモノクロロベンゼンの分解実験を実施した。その結果を表２に示す。表２に示すように、ヘマタイト（Ｆｅ2Ｏ3）の含有率は比較例３の方が多いが、実施例３ではＣｌ2の生成率はほとんど変化せずにモノクロロベンゼンの分解率のみが向上している。比較例３では熱処理を行っても分解性能の向上は見られなかった。比表面積の差が分解活性に効いているものと考えられる。
【００２１】
【表２】
次に、実施例１〜３および比較例２の鉱石を使用してダイオキシン除去性能を調査した。ここでダイオキシンはダイオキシン類を指し、ＰＣＤＤｓ，ＰＣＤＦｓ，ＰＣＢｓのことを意味している。
【００２３】
ゴミ焼却炉の電気集塵機後排ガスを分取し、酸性ガス除去後、３００℃まで昇温し鉱石の充填層に導いた。充填層入口、出口のダイオキシン濃度を測定し、除去率を算出した。比較例２ではほとんどダイオキシンが低減していないのに対して実施例１〜３ではダイオキシンが低減していた。実施例２と３で除去性能がほぼ同じになったのは、排ガス温度が３００℃であるため、実施例２において排ガスにより熱処理と同様の効果が得られたものと考えられる。
【００２４】
【表３】
【発明の効果】
以上、本発明を用いれば、製鉄原料である安価な鉄鉱石を利用してダイオキシンをはじめとする有機塩素化合物の分解・除去を経済的に行える。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing harmful substances such as dioxins discharged from, for example, incineration facilities for municipal waste and industrial waste, steel electric furnaces, and steel sintering machines.
[0002]
[Prior art]
Transition metal oxides are described in the Chemical Society of Japan, Vol. 1989, p. 139 (1989), it is known to have an oxidative degradation activity of an organic chlorine compound. Utilizing these, a catalytic decomposition technique for organochlorine compounds in exhaust gas has been developed.
[0003]
Considering the V 2 O 5 —TiO 2 system or SO x resistance, which has been conventionally used as a catalytic reduction catalyst for nitrogen oxides, as described in Catalysts (Vol. 41, 210, 1999). A decomposition technique using a V 2 O 5 —TiO 2 —WO 3 -based catalyst has been put into practical use. Since these catalysts are expensive, they are generally honeycomb or granular and are used for a long time as a fixed layer.
[0004]
In addition, a method for suppressing dioxins in a refuse incinerator using an iron oxide catalyst has been developed as disclosed in JP-A-11-267507. In this method, an iron oxide catalyst is blown into a combustion chamber or a reburning chamber of a garbage incinerator to suppress dioxins. The iron oxide used here is prepared from the reagent. For example, goethite powder is a ferrous iron or iron carbonate obtained by reacting with one or more selected from ferrous salt, alkali hydroxide, alkali carbonate and ammonia. It can be obtained by generating goethite particles by aeration of an oxygen-containing gas such as air into the suspension containing the contained precipitate. The hematite powder can be obtained by subjecting the goethite powder to heat dehydration in the temperature range of 200 to 800 ° C. in the air. Further, the magnetite powder is obtained by heating and reducing the hematite powder at 300 to 600 ° C. in a reducing atmosphere.
[0005]
[Problems to be solved by the invention]
However, in the case of a V 2 O 5 —TiO 2 or V 2 O 5 —TiO 2 —WO 3 catalyst, a catalyst layer must be provided in the middle of the duct in order to use it in a fixed layer. There was a need for extensive construction.
[0006]
Further, the iron oxide catalyst disclosed in JP-A-11-267507 does not require a large-scale construction, but iron oxide is a V 2 O 5 —TiO 2 or V 2 O 5 —TiO 2 —WO 3 catalyst. Compared with NO, it is easy to be combined with chlorine and sulfur oxides, and the catalytic activity tends to decrease. For this reason, it cannot be used for a long time, and is used for a short time by being blown into the exhaust gas. However, in order to suppress dioxins, it is necessary to continuously blow into the exhaust gas. However, the iron oxide catalyst becomes expensive because the catalyst is prepared from the reagent through complicated processes as described above. In the case of blowing such an expensive iron oxide catalyst, the used iron oxide catalyst is recovered together with dust and is poisoned by chlorine and sulfur oxides in the exhaust gas. Is discarded with dust.
[0007]
Also, V 2 O 5 -TiO 2 system or V 2 O 5 -TiO 2 -WO 3 based catalysts discussed above or transition metal oxides such as iron oxide, may, although degradation activity of organochlorine high, the Cl 2 High production activity. Cl 2 has a higher reaction activity than HCl, and is liable to regenerate organic chlorine compounds such as dioxin when combined with carbonaceous matter.
[0008]
[Means for Solving the Problems]
As a result of diligent research to solve the above problems, the present inventor has found that the use of iron ore as a catalyst can achieve an inexpensive and efficient organic chlorine compound decomposition, and has led to the present invention.
[0009]
That is, the present invention is (1) a method for decomposing monochlorobenzene or dioxins, which is an organic chlorine compound, using iron ore as an organic chlorine compound decomposition catalyst, wherein the iron ore contains 50 mass% or more of Fe, mETHOD degradation and Al 2 O 3 and including at the sum of SiO 2 3% by mass or more, or, organic chlorine compounds, characterized in that it comprises further a bound water at 4% by mass or more,
(2) The method for decomposing an organochlorine compound according to (1), wherein the iron ore is heat-treated at 250 ° C. or higher before or during use, and the hydrous iron oxide in the iron ore is transformed into hematite. ) A decomposition catalyst for monochlorobenzene or dioxins, which is an organic chlorine compound composed of iron ore, wherein the iron ore contains Fe in an amount of 50% by mass or more, and the sum of Al 2 O 3 and SiO 2 is 3% by mass or more. including, or even organic chlorine compound-decomposing catalyst comprising a bound water at 4% by mass or more, and (4) the iron ore is subjected to heat treatment before or during use at 250 ° C. or higher, iron The organochlorine compound decomposition catalyst according to (3), wherein the hydrous iron oxide in the stone is transformed into hematite, the content of Fe 2 O 3 is 70% by mass or more, and the specific surface area is 10 m 2 / g or more. is there.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. As shown in the prior art, transition metal oxides are excellent in the decomposition activity of organochlorine compounds, but are easy to produce Cl 2 due to their strong catalytic activity. Since Cl 2 has high reaction activity, it chlorinates carbonaceous matter and regenerates organic chlorine compounds such as dioxins. For this reason, when a transition metal oxide is used as a decomposition catalyst, an organic chlorine compound may be regenerated, resulting in a decrease in decomposition efficiency.
[0011]
Thus, as a result of searching for various substances, it was found that iron ore is excellent in the activity of decomposing organochlorine compounds and relatively suppresses the generation of Cl 2 . The main component of iron ore is iron oxide, but it contains alumina and silica as gangue. Although these substances have a low activity of decomposing organic chlorine but have a function of suppressing Cl 2 production, it is considered that regeneration of organic chlorine compounds such as dioxin by Cl 2 and carbonaceous matter can be suppressed. That is, when a certain amount or more of alumina and silica are present, Cl 2 generation can be suppressed without impairing the organochlorine compound decomposition activity of the transition metal oxide, and the organochlorine compound can be efficiently decomposed. Specifically at least 50% by mass percentage of Fe is and alumina (Al 2 O 3) and silica (SiO 2) total is higher chlorinated organic compound decomposing activity ores containing more than 3 wt% of the Cl 2 Production activity is low. There is no particular upper limit for either. Here, when the proportion of Fe is less than 50% by mass, or the total of alumina and silica is less than 3% by mass, the organochlorine compound decomposition activity is low and the Cl 2 production activity is not low, which is not preferable.
[0012]
Furthermore, it has been found that there is an ore with high decomposition activity among iron ores. The ore having a high decomposition activity is an ore containing a large amount of bound water, and is an ore mainly composed of so-called hydrous iron oxide. Since the ore containing a large amount of bound water has a relatively low crystallinity of iron oxide, it has a high surface activity and a large specific surface area, so that it has an excellent decomposition activity of organochlorine compounds. Specifically, it is an iron ore containing 4% by mass or more of bound water. There is no specific upper limit for bound water. Here, when the bound water is less than 4% by mass, the specific surface area is small, and the ratio of hydrous iron oxide having a high catalytic action is not preferable.
[0013]
Further, the ore containing a large amount of the above-mentioned bound water releases it by heating at a temperature of 250 ° C. or higher, and transforms into hematite (α-Fe 2 O 3 ).
[0014]
[Chemical 1]
The hematite produced by this method has higher surface activity and a larger specific surface area than the original hydrous iron oxide and the hematite iron ore that is present in the ore as hematite from the beginning. For this reason, the decomposition activity of organochlorine compounds is high. If temperature is 250 degreeC or more, an upper limit will not be prescribed | regulated in particular. Here, when the heating temperature is less than 250 ° C., it does not transform into hematite, which is not preferable. The atmosphere may be other than a reducing gas such as hydrogen or carbon monoxide gas. For example, air, combustion exhaust gas, and nitrogen are preferable. The heating time is shorter as the temperature is higher, but requires 30 minutes at 300 ° C., preferably 60 minutes or more. In addition, when the specific surface area is less than 10 m 2 / g, the decomposition activity of the organic chlorine compound is not sufficiently exhibited, but when produced under the above conditions, the specific surface area of hematite can be 10 m 2 / g or more, This is very preferable because the decomposition activity of the organic chlorine compound is improved.
[0016]
Although the iron ore of the present invention is used, iron ore is cheaper than a normal catalyst, and therefore, it is preferably used by being blown into a duct having an exhaust gas temperature higher than a certain temperature. If the exhaust gas temperature is 200 ° C. or higher, preferably 250 ° C. or higher, the organic chlorine decomposition proceeds efficiently. Since iron ore is agglomerated, it can be used as a packed bed. However, since it binds to chlorine and sulfur oxides and its activity decreases, when used as a packed bed, an acid gas removal device (demineralization / desulfurization device) is used upstream. ) Must be provided.
[0017]
【Example】
Hereinafter, the present invention will be specifically described in Examples 1 to 3.
[0018]
The ores having the compositions shown in Table 1 were designated as Examples 1 and 2, and Comparative Examples 1 and 2, respectively, 200 g of these were filled in a quartz tube, air was used as a base gas, and 1000 ppm of monochlorobenzene as a dioxin precursor was added. A monochlorobenzene decomposition experiment was performed at a reaction temperature of 300 ° C. by circulating a gas adjusted to a concentration through a quartz tube at a flow rate of 1000 Ncm 3 / min. The results are shown in Table 1. Here, the decomposition rate of monochlorobenzene was calculated by measuring the monochlorobenzene concentration on the exit side of the quartz tube by gas chromatography. The Cl 2 production rate was calculated by measuring the chlorine concentration at the quartz tube outlet side with 100% of the monochlorobenzene converted to Cl 2 as the total amount. The chlorine concentration was analyzed by the orthotolidine method. In Comparative Examples 1 and 2, the decomposition rate of monochlorobenzene was high, but a large amount of Cl 2 was produced. On the other hand, in Example 1, the decomposition rate of monochlorobenzene was almost the same as that of the comparative example, but Cl 2 production was suppressed. Furthermore, in Example 2 in which the proportions of bound water, SiO 2 and Al 2 O 3 were high, the monochlorobenzene decomposition rate was improved and Cl 2 production was further suppressed.
[0019]
[Table 1]
Further, the ore of Example 2 was heat-treated at 250 ° C. for 4 hours (Example 3) and the ore of Comparative Example 2 were subjected to the same heat treatment (Comparative Example 3). 2 and monochlorobenzene decomposition experiments were carried out under the same experimental conditions as in Comparative Examples 1 and 2. The results are shown in Table 2. As shown in Table 2, the content of hematite (Fe 2 O 3 ) is higher in Comparative Example 3, but in Example 3, the Cl 2 production rate hardly changes and only the monochlorobenzene decomposition rate is improved. is doing. In Comparative Example 3, no improvement in decomposition performance was observed even after heat treatment. The difference in specific surface area is considered to be effective for the decomposition activity.
[0021]
[Table 2]
Next, the dioxin removal performance was investigated using the ores of Examples 1 to 3 and Comparative Example 2. Here, dioxin refers to dioxins and means PCDDs, PCDFs, and PCBs.
[0023]
The exhaust gas was collected after the electric dust collector of the garbage incinerator, and after removing the acid gas, the temperature was raised to 300 ° C. and led to the packed bed of ore. The dioxin concentration at the inlet and outlet of the packed bed was measured and the removal rate was calculated. In Comparative Example 2, dioxin was hardly reduced, whereas in Examples 1 to 3, dioxin was reduced. The reason why the removal performance is almost the same in Examples 2 and 3 is that the exhaust gas temperature is 300 ° C., so it is considered that the same effect as the heat treatment was obtained by the exhaust gas in Example 2.
[0024]
[Table 3]
【The invention's effect】
As mentioned above, if this invention is used, decomposition | disassembly and removal of organic chlorine compounds including dioxin can be economically performed using the cheap iron ore which is a steelmaking raw material.
Claims (4)
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