JP4212927B2 - Particulate matter removal catalyst in diesel engine exhaust gas - Google Patents
Particulate matter removal catalyst in diesel engine exhaust gas Download PDFInfo
- Publication number
- JP4212927B2 JP4212927B2 JP2003057875A JP2003057875A JP4212927B2 JP 4212927 B2 JP4212927 B2 JP 4212927B2 JP 2003057875 A JP2003057875 A JP 2003057875A JP 2003057875 A JP2003057875 A JP 2003057875A JP 4212927 B2 JP4212927 B2 JP 4212927B2
- Authority
- JP
- Japan
- Prior art keywords
- exhaust gas
- particles
- diesel engine
- particulate matter
- catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000013618 particulate matter Substances 0.000 title claims description 53
- 239000003054 catalyst Substances 0.000 title claims description 41
- 239000002245 particle Substances 0.000 claims description 73
- 229910052595 hematite Inorganic materials 0.000 claims description 52
- 239000011019 hematite Substances 0.000 claims description 52
- 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 52
- 239000013078 crystal Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 15
- 238000002441 X-ray diffraction Methods 0.000 claims description 10
- 229910000859 α-Fe Inorganic materials 0.000 claims description 9
- 229910052598 goethite Inorganic materials 0.000 claims description 7
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 claims description 7
- 229910006540 α-FeOOH Inorganic materials 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 35
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 23
- 229910002091 carbon monoxide Inorganic materials 0.000 description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 18
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- 239000007864 aqueous solution Substances 0.000 description 12
- 238000002485 combustion reaction Methods 0.000 description 11
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 10
- 230000003197 catalytic effect Effects 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000012360 testing method Methods 0.000 description 8
- 230000008929 regeneration Effects 0.000 description 7
- 238000011069 regeneration method Methods 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000001569 carbon dioxide Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 229910052717 sulfur Inorganic materials 0.000 description 6
- 239000011593 sulfur Substances 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000006386 neutralization reaction Methods 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000000635 electron micrograph Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 2
- 125000004430 oxygen atom Chemical group O* 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 231100000572 poisoning Toxicity 0.000 description 2
- 230000000607 poisoning effect Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 2
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 1
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 229920001410 Microfiber Polymers 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910001361 White metal Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910001963 alkali metal nitrate Inorganic materials 0.000 description 1
- 229910001964 alkaline earth metal nitrate Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- LFYJSSARVMHQJB-QIXNEVBVSA-N bakuchiol Chemical compound CC(C)=CCC[C@@](C)(C=C)\C=C\C1=CC=C(O)C=C1 LFYJSSARVMHQJB-QIXNEVBVSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000002283 diesel fuel Substances 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005183 environmental health Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 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
- 238000011068 loading method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- -1 phosphorus compound Chemical class 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000029058 respiratory gaseous exchange Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000010969 white metal Substances 0.000 description 1
Images
Description
【０００１】
【発明の属する技術分野】
本発明は、ディーゼルエンジンの排ガス中の粒子状物質（ＰＭ）を、効率よく完全燃焼させて除去することが可能な触媒に関するものである。
【０００２】
【従来の技術】
近年、ディーゼルエンジンから排出される粒子状物質（カーボン微粒子、ＳＯＦ（Soluble Organic Fraction［可溶有機成分］）、サルフェート等。以下、ＰＭ（Particulate Matter）と称す。）が環境衛生上大きな問題となっている。これは、ＰＭの粒子径がほとんど１ミクロン以下であるため、大気中に浮遊しやすく呼吸により人体内に取り込まれやすいことによるものである。このＰＭを除去する方法としては、フィルターによってＰＭを捕捉する方法やＰＭを燃焼除去する方法、或いはそれらを組み合わせた方法があり、最近では、後付でディーゼル自動車に装着可能なＤＰＦ（ディーゼルパティキュレートフィルター）も開発されている。そして、ＤＰＦが使用可能になったことを受けて東京都の環境確保条例（２０００年１２月制定）を始め、埼玉県の生活環境保全条例（２００１年７月制定）、千葉県のディーゼル自動車から排出される粒子状物質の排出に関する条例（２００２年３月制定）等、次々とＰＭを規制する条例を制定する地方自治体が現れてきている。
【０００３】
ＤＰＦは、排ガスに含まれるＰＭをフィルターでろ過して捕集し、燃焼させ、二酸化炭素に変えて排出することによってＰＭの排出量を低減させるものであり、（１）フィルターでＰＭを捕集し、自動車が稼動していないときに外部電源等を使用してフィルターを再生する間欠再生式ＤＰＦ、（２）二つのフィルターで交互にＰＭを捕集し、電熱線等により焼却してフィルターを再生する交互再生式ＤＰＦや、（３）触媒等の作用によってフィルターで捕集したＰＭを比較的低温で連続的に酸化除去しフィルターを再生する連続再生式ＤＰＦ、等が実用化されている。
【０００４】
しかしながら、間欠再生式ＤＰＦの場合は、装置が簡便で安価であるという利点はあるものの、一回の捕集量に限界があるため一度に長距離を走行する自動車には適用できないという問題があった。交互再生式ＤＰＦはこのような間欠再生式ＤＰＦの欠点を解消したものであるが、この方式ではＤＰＦ取付けスペースの確保や高性能発電機への交換が必要となるなど車両構造上の制約があるばかりか、１年程度でセンサー類、３年程度でフィルターの交換が必要になるという問題があった。
【０００５】
一方、連続再生式ＤＰＦとしては、例えば、ジョンソンマッセイ社（特許文献１等参照）のフィルターの前段に配設された酸化触媒によって排気ガス中のうち一酸化窒素（ＮＯ）を酸化して二酸化窒素（ＮＯ２）を生成し、排ガスの熱とＮＯ２によってフィルターに捕集されたＰＭを連続的に酸化して再生する方式のＤＰＦや、エンゲルハード社のフィルターに担持した触媒の作用でフィルターに捕集したＰＭを比較的低温で連続的に酸化して再生する方式のＤＰＦが提案されている。しかしながら、低硫黄軽油を燃料として使用する必要があること、及び排気温度が一定となる走行が一定比率以上となる走行条件を満たす必要があることから、ディーゼルエンジン車の全ての使用過程において有効なＤＰＦとは云えないものであった。
【０００６】
したがって、硫黄分を含有する通常の軽油であっても燃料として使用できたり、始動時や低速走行時のような低温であってもＰＭを燃焼除去しうる触媒の開発が各方面で検討されている。例えば、比較的低温下でも高い触媒活性を示すものとして、Ｐｔ（ＮＨ３）４（ＯＨ）２水溶液をシリカに含浸、乾燥後、水素で還元し、空気中で焼成してなるシリカに担持させた白金を触媒として使用する方法（特許文献２）や、固体担体と、該固体担体に担持される硝酸銀、アルカリ金属の硝酸塩、アルカリ土類金属の硝酸塩及び希土類元素の硝酸塩から選ばれる少なくとも一種を含む触媒成分からなる溶融塩型触媒（特許文献３）等が提案されている。
また、燃料として使用する軽油中の硫黄分による触媒の被毒や、サルフェートの生成量の増大を抑制するものとして、（ａ）耐火性無機酸化物、（ｂ）パラジウムおよび白金から選ばれる少なくとも１種の貴金属、ならびに（ｃ）ロジウムを含有する触媒（特許文献４）や、酸化銅（ＣｕＯ）が担持された担体及び該担体上に浸漬されている貴金属主触媒成分を含む触媒（特許文献５）等が提案されている。
更に、特許文献６−９には酸化鉄、特にα−Ｆｅ２Ｏ３を触媒として使用することが提案されていて、その場合、高温域におけるサルフェートの生成を抑制できる（特許文献６、７）旨の記載がある。しかしながら、どのような酸化鉄触媒を使用することが好ましいかについて充分な検討がなされておらず、未だ満足できるものとは云えなかった。
【０００７】
【特許文献１】
特開平１０−１５９５５２号公報
【特許文献２】
特許第２９６１２４９号公報
【特許文献３】
特開２００２−２１０３６８号公報
【特許文献４】
特許第３０６１３９９号公報
【特許文献５】
特開２００１−７９４０９号公報
【特許文献６】
特開平６−２１０１７２号公報
【特許文献７】
特開２００２−１１２３号公報
【特許文献８】
特開平１０−１７４８７８号公報
【特許文献９】
特開２００１−９８９２５号公報
【０００８】
【発明が解決しようとする課題】
本発明は、安価で、しかも白金属触媒に比べて硫黄による被毒の恐れの少ない酸化鉄を使用しているにもかかわらずＰＭの燃焼に充分な触媒活性を有するＰＭ除去触媒を提供することを目的とする。
【０００９】
【課題を解決するための手段】
本発明者等は鋭意検討した結果、結晶子サイズが１５０Å以下のヘマタイト（α−Ｆｅ２Ｏ３）が、従来公知の酸化鉄触媒に比べて極めて酸化触媒活性が高く、ＰＭを効率よく燃焼除去しうることを見いだし本発明に到った。
【００１０】
すなわち、本発明によれば
（１） ヘマタイト（α−Ｆｅ２Ｏ３）粒子からなるディーゼルエンジン排ガス中の粒子状物質除去触媒において、該ヘマタイト粒子のＰ含有量が０．００５重量％以下であって、ＣｕＫαでＸ線回折測定した際の結晶面（１０４）の結晶子サイズが１５０Å以下であることを特徴とするディーゼルエンジン排ガス中の粒子状物質除去触媒。
（２） 前記ヘマタイト粒子が紡錘状ゲーサイト（α−ＦｅＯＯＨ）粒子を２５０℃以上の温度で加熱処理して得られたものであることを特徴とする（１）記載のディーゼルエンジン排ガス中の粒子状物質除去触媒。
（３） （１）又は（２）に記載のディーゼルエンジン排ガス中の粒子状物質除去触媒を使用してＮＯ２の存在下でＰＭを燃焼除去することを特徴とするディーゼルエンジン排ガス中の粒子状物質の除去方法が提供される。
【００１１】
【実施の形態】
以下に、本発明の実施の形態を詳細に説明する。
本発明のディーゼルエンジン排ガス中のＰＭ除去触媒は、Ｐ含有量が０．００５重量％以下であって、ＣｕＫαでＸ線回折測定した際の結晶面（１０４）の結晶子サイズが１５０Å以下のヘマタイト（α−Ｆｅ２Ｏ３）粒子からなることを特徴とするものである。
したがって、ヘマタイト（α−Ｆｅ２Ｏ３）粒子中に不純物としてのリン（Ｐ）含有量が０．００５重量％を超えて存在している場合、触媒活性が不十分なためディーゼルエンジン排ガス中のＰＭ除去触媒として本発明の目的が達成できないので好ましくない。また、ヘマタイト（α−Ｆｅ２Ｏ３）粒子のＣｕＫαでＸ線回折測定した際の結晶面（１０４）の結晶子サイズが１５０Åを超えると同様にＰＭの燃焼に十分な触媒活性がないので好ましくない。
【００１２】
本発明において、結晶面（１０４）の結晶子サイズが１５０Å以下のヘマタイト（α−Ｆｅ２Ｏ３）粒子をディーゼルエンジン排ガス中のＰＭ除去触媒として用いるのは以下の理由によるものである。すなわち、ヘマタイト（α−Ｆｅ２Ｏ３）粒子はＸ線回折測定によって（０１２）面、（１０４）面、（１１０）面、（１１３）面、（０２４）面、（１１６）面、（２１４）面及び（３００）面の回折ピークが測定されるのであるが、その中でも（１０４）面、（０１２）面、（０２４）面、（２１４）面、とりわけ（１０４）面の回折ピークは酸素原子の配列状態を表す回折ピークであって、このピークがブロードになるほど酸素原子の配列が乱れている、つまり活性点ともなるべき面欠陥が多いことを示している。
一方、（１１０）面、（１１３）面、（１１６）面のように一般式（１１ｌ）面（ｌ＝３ｎ、ｎ＝０〜３の整数）で示される結晶面や（３００）面は鉄原子の配列状態を表す回折ピークであって、これらの結晶面の結晶子サイズが変化してもＰＭ除去触媒としての活性に大きな変化を生じないので本発明における結晶子サイズの比較として適用されるものではない。
【００１３】
このような結晶面（１０４）の結晶子サイズはＸ線回折測定の結果得られる結晶面（１０４）に基づくピークの半価幅から下記Ｓｈｅｒｒｅｒの式を用いて求めることができる。
Ｄ＝０．９λ／β・ｃｏｓθ
Ｄ：結晶子サイズ（Å）、λ：Ｘ線源の波長（＝１．５４０５Å）、β：回折ピーク半価幅（ラジアン）、θ：結晶面（１０４）の回折角（＝３３．１５１°）
【００１４】
そして、本発明のディーゼルエンジン排ガス中のＰＭ除去触媒に使用するヘマタイト粒子は、例えば、以下のようにして製造することができる。
紡錘状ヘマタイト粒子や針状ヘマタイト粒子は、第一鉄塩水溶液と水酸化アルカリ水溶液、炭酸アルカリ水溶液等のアルカリ水溶液との中和反応沈殿物を含む懸濁液中に添加剤の存在下又は不存在下で空気等の酸素含有ガスを通気することによって生成させた紡錘状や針状の含水酸化第二鉄粒子を空気中２５０℃以上、好ましくは２７０〜３５０℃で粒子形状を維持しながら加熱処理して得ることができる。
また、板状ヘマタイト粒子は、第一鉄塩水溶液とアルカリ水溶液との中和反応沈殿物をオートクレーブ中で加熱処理して得ることができる。
更に粒状ヘマタイト粒子は、第一鉄塩水溶液と水酸化アルカリ水溶液、炭酸アルカリ水溶液等のアルカリ水溶液との中和反応沈殿物を含む懸濁液中に空気等の酸素含有ガスを通気して粒状マグネタイト粒子を生成し、次いで当該マグネタイト粒子を空気中２００〜５００℃で粒子形状を維持しながら加熱処理して得ることができる。
【００１５】
本発明においては、上記方法によって得られるヘマタイト粒子のなかから上述した条件を満たすものであれば特に制限なく使用可能であり、粒子形状は紡錘状、針状、板状、そして球形、八面体、多面体、不定形等のほぼ等方形状を呈するいわゆる粒状の何れであっても良いが、紡錘状のヘマタイト粒子が望ましい。また、上記条件を満たすリン（Ｐ）含有量とするためには製造時の十分な洗浄や、原材料の選択、および通常加熱焼成時の焼結防止処理に用いられるヘキサメタリン酸ナトリウム等のリン化合物を使用しないことによって達成することができる。
【００１６】
また、ＣｕＫαでＸ線回折測定した際の結晶面（１０４）の結晶子サイズが上記条件を満たすためには、例えば、硫酸や硝酸等で表面を処理してヘマタイト粒子表面を荒らすことや、触媒活性の高い紡錘状含水酸化第二鉄粒子を加熱処理してヘマタイト粒子とする等の方法によって達成することができる。特に、紡錘状ゲータイト（α−ＦｅＯＯＨ）粒子は超微細繊維の束からなる微細構造を有していて、表面含水量が大きいことは勿論、２５０℃以上の温度、好ましくは２７０〜３５０℃の温度範囲で加熱処理することによって結晶構造中の水酸基間からも脱水して酸素原子の配列を示す結晶面（１０４）に面欠陥を生じ、この面の結晶子サイズが小さいヘマタイトが得られやすくなるので最も好ましい。この際に使用する紡錘状ゲータイト粒子としては、長軸径が０．０５〜１．５μｍ、好ましくは０．１〜０．３μｍ、軸比が１〜１８、好ましくは３〜１５、ＢＥＴ比表面積が３０〜２５０ｍ２／ｇ、好ましくは５０〜１５０ｍ２／ｇであり、得られるヘマタイト粒子としては、長軸径が０．０５〜１．５μｍ、好ましくは０．１〜０．３μｍ、軸比が１〜１８、好ましくは３〜１５、ＢＥＴ比表面積が３０〜２５０ｍ２／ｇ、好ましくは３０〜２００ｍ２／ｇである。
【００１７】
さて、本発明のディーゼルエンジン排ガス中のＰＭ除去触媒は、上述したヘマタイト粒子を担体に担持させた状態で使用するのであるが、この際に使用する担体としては、例えば、アルミナ、コージェライト、炭化珪素等をハニカム状、或いはフィルター状に一体成形したものを使用するのが一般的である。また、担持方法としてはヘマタイトを懸濁させたスラリー中に担体を浸積し、次いで乾燥させて担体に担持させる方法や、第一鉄塩の水溶液中に担体を浸積したのち、上述したヘマタイト粒子の製造手順に従ってヘマタイト粒子を生成することにより担体に担持させる方法等が挙げられるが特に限定はない。なお、本発明のディーゼルエンジン排ガス中のＰＭ除去触媒は、上記ヘマタイト粒子を使用することを必須要件とするものであるが、必要に応じて他の触媒活性を有する物質と混合して使用することも勿論可能である。
【００１８】
本発明のディーゼルエンジン排ガス中のＰＭ除去触媒は、同じヘマタイト粒子を使用しているにもかかわらずこれまでのヘマタイト粒子に比べてＰＭを完全燃焼させるのに十分な、高い触媒活性を有しているのであるが、特に、特許文献１にも記載されているＮＯ２の存在下、すなわち排ガス中に微量のＮＯ２を含有させることにより２５０℃以下の温度ででもＰＭを燃焼除去することができるという効果を有していて、しかもその際に一酸化炭素を発生させずに完全燃焼させることができる。なお、排ガス中に含有させる好ましいＮＯ２含有量は１００〜２０００ｐｐｍである。
【００１９】
【実施例】
以下に、本発明を実施例により具体的に説明する。
なお、使用したヘマタイト粒子は以下の通りである。
＜ヘマタイト粒子＞
Ａ１：紡錘状ヘマタイト粒子（ＢＥＴ比表面積：１００ｍ２／ｇ、平均粒子径：０．２５μｍ、軸比（長軸／短軸）：８、結晶面（１０４）の結晶子サイズ：６１Å、Ｐ含有量：０．００２％）
Ｐ含有量０．００２％の紡錘状ゲータイト粒子（ＢＥＴ比表面積：８０ｍ２／ｇ、平均粒子径：０．２５μｍ、軸比（長軸／短軸）：８）を３００℃で加熱処理することにより得た。このヘマタイト粒子のＸ線回折図形を図１に、電子顕微鏡写真を図２に示す。
Ａ２：ヘマタイト粒子（ＢＥＴ比表面積：１．８ｍ２／ｇ、平均粒子径：０．５０μｍ、軸比（長軸／短軸）：１、結晶面（１０４）の結晶子サイズ：５２８．５Å、Ｐ含有量：０．００４％）
試薬として市販されているヘマタイト粒子をそのまま使用した。
Ａ３：ヘマタイト粒子（ＢＥＴ比表面積：４３ｍ２／ｇ、平均粒子径：０．２５μｍ、軸比（長軸／短軸）：８、結晶面（１０４）の結晶子サイズ：１３０Å、Ｐ含有量：０．００２％）
Ｐ含有量０．００２％の紡錘状ゲータイト粒子（ＢＥＴ比表面積：８０ｍ２／ｇ、平均粒子径：０．２５μｍ、軸比（長軸／短軸）：８）を５００℃、1ｈ加熱処理することにより得た。
Ａ４：ヘマタイト粒子（ＢＥＴ比表面積：１１０ｍ２／ｇ、平均粒子径：０．２５μｍ、軸比（長軸／短軸）：８、結晶面（１０４）の結晶子サイズ：１１０Å、Ｐ含有量：０．１％）
Ｐ含有量０．００２％の紡錘状ゲータイト粒子（ＢＥＴ比表面積：８０ｍ２／ｇ、平均粒子径：０．２５μｍ、軸比（長軸／短軸）：８）１ｋｇをイオン交換水で邂逅した５％スラリーに、Ｐ濃度６．２ｗｔ％のヘキサメタリン酸ナトリウム溶液を１８ｇ添加混合し、その後イオン交換水にて水洗し、濾過および乾燥した。この乾燥物を５００℃、１ｈ加熱処理することにより得た。
【００２０】
また、ヘマタイト粒子のディーゼルエンジン排ガス中のＰＭ除去触媒としての性能は図３に示す試験装置１を用いて以下の方法で評価した。
まず、ディーゼルエンジン排ガス中のＰＭの主成分である煤とほぼ同等なＸ線回折図を与える活性炭をＰＭに模して使用し、活性炭とＰＭ除去触媒とを耐熱性ろ紙２上にと擦り込むように担持させて活性炭試験装置１に装着した。次いで適宜組成に調整したガスを試験装置１のガス供給口１１から供給し、所定温度におけるガス排出口１２がら排出されるガス中の一酸化炭素（ＣＯ）及び二酸化炭素（ＣＯ２）濃度を測定することによって触媒効果を評価した。
【００２１】
実施例１、比較例１、２
耐熱性ろ紙２上に活性炭０．１ｇとヘマタイト粒子（Ａ１）０．５ｇの混合物を擦り込むように担持させて図３に示す試験装置１内に装着し、１．６ｖｏｌ％の酸素を含有した窒素ガスを１Ｌ／分の流量で供給口１１から供給し、試験装置１内の温度を１５℃／分の昇温速度で加温した場合について、各温度における燃焼の結果発生する排出ガス中の一酸化炭素（ＣＯ）及び二酸化炭素（ＣＯ２）濃度を測定した。結果を図４に示す。また、比較のためにヘマタイト粒子を使用しない以外は実施例１と同様にした場合、及び結晶子サイズが５２８．５Åである市販のヘマタイト粒子（Ａ２）を使用して試験した結果を同じく図４に示す。
【００２２】
図４からも明らかなように、実施例１の本発明にかかるヘマタイト粒子（Ａ１）を触媒として使用した系では一酸化炭素（ＣＯ）が発生することなく活性炭が燃焼したのに対して、ヘマタイト粒子を含有していない比較例１の系では不完全燃焼していることを示す一酸化炭素（ＣＯ）が大量に発生した。また、結晶子サイズが１５０Åを遙かに超えるヘマタイト粒子（Ａ２）を使用した比較例２の系では燃焼開始温度が多少低温側に移行したものの活性炭を完全燃焼させる効果は殆ど見られなかった。
【００２３】
実施例２、比較例３
供給するガスを１０００ｐｐｍのＮＯ２ガスを含有した窒素ガスに代えた以外は実施例１、比較例１と同様にして燃焼の結果発生する排出ガス中の各温度における一酸化炭素（ＣＯ）及び二酸化炭素（ＣＯ２）濃度を測定した。結果を図５に示す。
【００２４】
図５からも明らかなように、実施例２の本発明にかかるヘマタイト粒子（Ａ１）を触媒として使用した系では実施例１の場合と同様に一酸化炭素を発生させることなく活性炭を完全燃焼させることができたのみならず、２００℃以下の低温（すなわち、アイドリング時やスタート時の排ガスで補助ヒーターを使用することなしに到達しうる温度）ででも燃焼させることができた。
一方、従来知られているように比較例３の系ではＮＯ２ガスの効果によって低温で燃焼させることは可能であったが、不完全燃焼に伴う一酸化炭素（ＣＯ）が多量に発生するなど、実用上は問題があった。
【００２５】
実施例３
ヘマタイト粒子（Ａ１）に代えて、ヘマタイト粒子（Ａ３）を使用した以外は実施例１と同様にして燃焼試験を行った。その結果、排ガス中一酸化炭素（ＣＯ）濃度が７１０℃にて最大値４００ｐｐｍ検出され、ほぼ完全燃焼させることができた。
【００２６】
比較例４
ヘマタイト粒子（Ａ１）に代えて、ヘマタイト粒子（Ａ４）を使用した以外は実施例１と同様にして燃焼試験を行った。その結果、排ガス中一酸化炭素（ＣＯ）濃度が６９０℃にて最大値３５００ｐｐｍ検出され、活性炭を完全燃焼させる効果は殆ど見られなかった。
【００２７】
【効果】
本発明のＰＭ除去触媒は、安価な鉄を原材料として使用しているにもかかわらず極めて良好な触媒活性を示した。しかも、ヘマタイト粒子は硫黄による被毒を受けにくいので低硫黄軽油を使用することなくＰＭを減少させる方法に道を開くものである。
【図面の簡単な説明】
【図１】本発明のＰＭ除去用触媒の一例を示すヘマタイト粒子（Ａ１）のＸ線回折図である。
【図２】本発明のＰＭ除去用触媒の一例を示すヘマタイト粒子（Ａ１）の電子顕微鏡写真である。
【図３】触媒作用について検討するための実験装置の模式斜視図である。
【図４】実施例１と比較例１、２の結果を示す一酸化炭素濃度−温度、及び二酸化炭素濃度−温度グラフである。
【図５】実施例２と比較例３の結果を示す一酸化炭素濃度−温度、及び二酸化炭素濃度−温度グラフである。
【符号の説明】
１ 実験装置
１１ 供給口
１２ 排出口
２ 耐熱性ろ紙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst that can efficiently and completely remove particulate matter (PM) in exhaust gas from a diesel engine.
[0002]
[Prior art]
In recent years, particulate matter discharged from diesel engines (carbon fine particles, SOF (Soluble Organic Fraction), sulfate, etc., hereinafter referred to as PM (Particulate Matter)) has become a major environmental health problem. ing. This is due to the fact that the particle size of PM is almost 1 micron or less, so that it easily floats in the atmosphere and is easily taken into the human body by breathing. As a method for removing PM, there are a method of capturing PM by a filter, a method of burning and removing PM, or a method of combining them. Recently, a DPF (diesel particulates) that can be attached to a diesel vehicle later. Filter) has also been developed. In response to the availability of the DPF, the Tokyo Metropolitan Environmental Security Ordinance (established in December 2000), the Saitama Prefecture Living Environment Conservation Ordinance (established in July 2001), and the Chiba Prefecture Diesel Vehicle Local governments have come up with regulations to regulate PM one after another, such as regulations on the emission of particulate matter (established in March 2002).
[0003]
DPF collects PM contained in exhaust gas by filtering it, burns it, changes it into carbon dioxide, and discharges it. (1) Collects PM with a filter. However, intermittent regeneration type DPF that uses an external power source to regenerate the filter when the vehicle is not in operation, (2) PM is collected alternately by two filters, and incinerated with heating wire, etc. An alternating regeneration type DPF that regenerates, (3) a continuous regeneration type DPF that regenerates a filter by continuously oxidizing and removing PM collected by a filter by the action of a catalyst or the like at a relatively low temperature, and the like have been put into practical use.
[0004]
However, although the intermittent regeneration type DPF has the advantage that the device is simple and inexpensive, there is a problem that it cannot be applied to a vehicle that travels a long distance at a time because the amount of collection at one time is limited. It was. The alternating regeneration type DPF eliminates the disadvantages of the intermittent regeneration type DPF, but this method has restrictions on the vehicle structure such as securing a DPF mounting space and replacement with a high performance generator. In addition, there was a problem that it was necessary to replace the sensor in about one year and the filter in about three years.
[0005]
On the other hand, as the continuous regeneration type DPF, for example, nitric oxide (NO) in the exhaust gas is oxidized by an oxidation catalyst disposed in front of a filter manufactured by Johnson Matthey (see
[0006]
Therefore, the development of a catalyst that can be used as fuel even for ordinary light oil containing sulfur, or that can burn and remove PM even at low temperatures such as when starting or running at low speed, has been studied in various fields. Yes. For example, in order to show high catalytic activity even at relatively low temperatures, silica is impregnated with a Pt (NH 3 ) 4 (OH) 2 aqueous solution, dried, reduced with hydrogen, and baked in air. A method of using platinum as a catalyst (Patent Document 2), a solid support, and at least one selected from silver nitrate, alkali metal nitrate, alkaline earth metal nitrate and rare earth element nitrate supported on the solid support A molten salt type catalyst (Patent Document 3) comprising a catalyst component is proposed.
Moreover, as a thing which suppresses the poisoning of the catalyst by the sulfur content in the light oil used as fuel, and the increase in the production amount of sulfate, at least one selected from (a) refractory inorganic oxide, (b) palladium and platinum. (C) a catalyst containing rhodium (Patent Document 4), a support on which copper oxide (CuO) is supported, and a catalyst containing a noble metal main catalyst component immersed on the support (Patent Document 5) ) Etc. have been proposed.
Further, Patent Document 6-9 proposes the use of iron oxide, particularly α-Fe 2 O 3 as a catalyst, in which case the generation of sulfate in a high temperature range can be suppressed (Patent Documents 6 and 7). There is a statement to that effect. However, sufficient study has not been made on what kind of iron oxide catalyst is preferably used, and it has not been satisfactory.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-159552 [Patent Document 2]
Japanese Patent No. 2961249 [Patent Document 3]
JP 2002-210368 A [Patent Document 4]
Japanese Patent No. 3061399 [Patent Document 5]
JP 2001-79409 A [Patent Document 6]
JP-A-6-210172 [Patent Document 7]
JP 2002-1123 A [Patent Document 8]
Japanese Patent Laid-Open No. 10-174878 [Patent Document 9]
Japanese Patent Laid-Open No. 2001-98925
[Problems to be solved by the invention]
The present invention provides a PM removal catalyst that is inexpensive and has sufficient catalytic activity for PM combustion despite the use of iron oxide that is less likely to be poisoned by sulfur compared to a white metal catalyst. With the goal.
[0009]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that hematite (α-Fe 2 O 3 ) having a crystallite size of 150 mm or less has a very high oxidation catalytic activity compared to a conventionally known iron oxide catalyst, and efficiently removes PM. We have found that this is possible and have arrived at the present invention.
[0010]
That is, according to the present invention, (1) In the particulate matter removal catalyst in diesel engine exhaust gas comprising hematite (α-Fe 2 O 3 ) particles, the P content of the hematite particles is 0.005 wt% or less. A particulate matter removal catalyst in diesel engine exhaust gas, wherein the crystallite size of the crystal plane (104) when X-ray diffraction measurement is performed with CuKα is 150 Å or less.
(2) The particles in diesel engine exhaust gas according to (1), wherein the hematite particles are obtained by heat-treating spindle-shaped goethite (α-FeOOH) particles at a temperature of 250 ° C. or higher. Catalyst for removal of particulate matter.
(3) Particulate matter in diesel engine exhaust gas, characterized in that PM is burned and removed in the presence of NO 2 using the particulate matter removal catalyst in diesel engine exhaust gas as described in (1) or (2). A method for removing material is provided.
[0011]
Embodiment
Hereinafter, embodiments of the present invention will be described in detail.
The PM removal catalyst in the exhaust gas of the diesel engine of the present invention has a hematite having a P content of 0.005% by weight or less and a crystallite size (104) of crystal plane (104) of 150 K or less when measured by X-ray diffraction with CuKα. It consists of (α-Fe 2 O 3 ) particles.
Therefore, when the content of phosphorus (P) as an impurity exceeds 0.005% by weight in the hematite (α-Fe 2 O 3 ) particles, the catalytic activity is insufficient, and thus in the diesel engine exhaust gas. The PM removal catalyst is not preferable because the object of the present invention cannot be achieved. Further, if the crystallite size of the crystal plane (104) when the X-ray diffraction measurement is performed with CuKα of hematite (α-Fe 2 O 3 ) particles exceeds 150 mm, it is preferable because there is not sufficient catalytic activity for PM combustion. Absent.
[0012]
In the present invention, hematite (α-Fe 2 O 3 ) particles having a crystal face (104) crystallite size of 150 １０４ or less are used as a PM removal catalyst in diesel engine exhaust gas for the following reason. That is, hematite (α-Fe 2 O 3 ) particles were measured by X-ray diffraction measurement using (012) plane, (104) plane, (110) plane, (113) plane, (024) plane, (116) plane, (214 ) And (300) plane diffraction peaks are measured. Among them, the (104) plane, (012) plane, (024) plane, (214) plane, particularly the (104) plane diffraction peaks are oxygen. This is a diffraction peak representing the arrangement state of atoms, and the broader this peak is, the more disordered the arrangement of oxygen atoms is, that is, the more surface defects that should be active sites.
On the other hand, crystal planes represented by the general formula (11l) plane (l = 3n, integers of n = 0 to 3) and (300) plane such as (110) plane, (113) plane, and (116) plane are iron. It is a diffraction peak representing the arrangement state of atoms, and even if the crystallite size of these crystal planes changes, it does not cause a great change in the activity as a PM removal catalyst, so it is applied as a comparison of crystallite size in the present invention. It is not a thing.
[0013]
Such a crystallite size of the crystal plane (104) can be obtained from the half width of the peak based on the crystal plane (104) obtained as a result of the X-ray diffraction measurement, using the following Serrer equation.
D = 0.9λ / β · cos θ
D: crystallite size (Å), λ: wavelength of X-ray source (= 1.5405Å), β: diffraction peak half width (radian), θ: diffraction angle of crystal plane (104) (= 33.151 ° )
[0014]
And the hematite particle | grains used for the PM removal catalyst in the diesel engine exhaust gas of this invention can be manufactured as follows, for example.
Spindle-like hematite particles and needle-like hematite particles are present in a suspension containing a neutralization reaction precipitate between a ferrous salt aqueous solution and an alkali aqueous solution such as an alkali hydroxide aqueous solution or an alkali carbonate aqueous solution in the presence or absence of an additive. Heat spindle-shaped or needle-shaped hydrous ferric oxide particles generated by ventilating oxygen-containing gas such as air in the presence of air at 250 ° C or higher, preferably 270-350 ° C while maintaining the particle shape. It can be obtained by processing.
The plate-like hematite particles can be obtained by heat-treating a neutralization reaction precipitate between a ferrous salt aqueous solution and an alkaline aqueous solution in an autoclave.
Furthermore, granular hematite particles are obtained by aerating an oxygen-containing gas such as air into a suspension containing a neutralization reaction precipitate between a ferrous salt aqueous solution and an alkali aqueous solution such as an alkali hydroxide aqueous solution or an alkali carbonate aqueous solution. Particles can be generated, and then the magnetite particles can be obtained by heat treatment at 200 to 500 ° C. in air while maintaining the particle shape.
[0015]
In the present invention, any of the hematite particles obtained by the above method can be used without particular limitation as long as the above conditions are satisfied, and the particle shape is a spindle shape, a needle shape, a plate shape, and a spherical shape, an octahedron, Although it may be any of so-called granular shapes having a substantially isotropic shape such as a polyhedron and an indeterminate shape, spindle-shaped hematite particles are desirable. Moreover, in order to make the phosphorus (P) content satisfying the above conditions, a phosphorus compound such as sodium hexametaphosphate used for sufficient washing during production, selection of raw materials, and anti-sintering treatment during normal heating and firing is used. This can be achieved by not using it.
[0016]
In addition, in order to satisfy the above condition, the crystallite size of the crystal plane (104) when X-ray diffraction measurement is performed with CuKα, the surface of the hematite particles is roughened by treating the surface with sulfuric acid or nitric acid, This can be achieved by a method of heat-treating highly active spindle-shaped hydrous ferric oxide particles into hematite particles. In particular, the spindle-shaped goethite (α-FeOOH) particles have a fine structure composed of a bundle of ultrafine fibers and have a high surface water content, of course, a temperature of 250 ° C. or higher, preferably a temperature of 270 to 350 ° C. Heat treatment in the range causes dehydration between the hydroxyl groups in the crystal structure to cause surface defects on the crystal plane (104) indicating the arrangement of oxygen atoms, and it is easy to obtain hematite with a small crystallite size on this plane. Most preferred. The spindle-shaped goethite particles used in this case have a major axis diameter of 0.05 to 1.5 μm, preferably 0.1 to 0.3 μm, an axial ratio of 1 to 18, preferably 3 to 15, and a BET specific surface area. Is 30 to 250 m 2 / g, preferably 50 to 150 m 2 / g, and the resulting hematite particles have a major axis diameter of 0.05 to 1.5 μm, preferably 0.1 to 0.3 μm, and an axial ratio. Is 1 to 18, preferably 3 to 15, and a BET specific surface area is 30 to 250 m 2 / g, preferably 30 to 200 m 2 / g.
[0017]
The PM removal catalyst in the exhaust gas of the diesel engine according to the present invention is used in a state where the above-described hematite particles are supported on a carrier. Examples of the carrier used in this case include alumina, cordierite, carbonization, and the like. In general, silicon or the like integrally formed in a honeycomb shape or a filter shape is used. In addition, as a loading method, a method in which the carrier is immersed in a slurry in which hematite is suspended and then dried and supported on the carrier, or after the carrier is immersed in an aqueous solution of ferrous salt, There are no particular restrictions on the method of supporting the carrier by generating hematite particles in accordance with the particle production procedure. In addition, although the PM removal catalyst in the diesel engine exhaust gas of the present invention is an essential requirement to use the above-mentioned hematite particles, it should be used by mixing with other substances having catalytic activity as necessary. Of course it is possible.
[0018]
The PM removal catalyst in the exhaust gas of the diesel engine of the present invention has a high catalytic activity sufficient to completely burn PM as compared with the conventional hematite particles, even though the same hematite particles are used. However, in particular, PM can be burned and removed even at a temperature of 250 ° C. or less in the presence of NO 2 described in
[0019]
【Example】
Hereinafter, the present invention will be specifically described by way of examples.
The hematite particles used are as follows.
<Hematite particles>
A1: Spindle-shaped hematite particles (BET specific surface area: 100 m 2 / g, average particle size: 0.25 μm, axial ratio (major axis / minor axis): 8, crystallite size of crystal plane (104): 61 mm, P content (Amount: 0.002%)
Heat treatment of spindle-shaped goethite particles having a P content of 0.002% (BET specific surface area: 80 m 2 / g, average particle size: 0.25 μm, axial ratio (major axis / minor axis): 8) at 300 ° C. Obtained. The X-ray diffraction pattern of this hematite particle is shown in FIG. 1, and the electron micrograph is shown in FIG.
A2: hematite particles (BET specific surface area: 1.8 m 2 / g, average particle size: 0.50 μm, axial ratio (major axis / minor axis): 1, crystallite size of crystal plane (104): 528.5 kg, P content: 0.004%)
Commercially available hematite particles were used as they were.
A3: hematite particles (BET specific surface area: 43 m 2 / g, average particle size: 0.25 μm, axial ratio (major axis / minor axis): 8, crystallite size of crystal plane (104): 130Å, P content: 0.002%)
Spindle-shaped goethite particles having a P content of 0.002% (BET specific surface area: 80 m 2 / g, average particle size: 0.25 μm, axial ratio (major axis / minor axis): 8) are heat-treated at 500 ° C. for 1 h. Was obtained.
A4: hematite particles (BET specific surface area: 110 m 2 / g, average particle size: 0.25 μm, axial ratio (major axis / minor axis): 8, crystallite size of crystal plane (104): 110Å, P content: 0.1%)
1 kg of spindle-shaped goethite particles having a P content of 0.002% (BET specific surface area: 80 m 2 / g, average particle size: 0.25 μm, axial ratio (major axis / minor axis): 8) were sprinkled with ion-exchanged water. 18 g of a sodium hexametaphosphate solution having a P concentration of 6.2 wt% was added to and mixed with the 5% slurry, then washed with ion-exchanged water, filtered and dried. This dried product was obtained by heat treatment at 500 ° C. for 1 h.
[0020]
Further, the performance of hematite particles as a PM removal catalyst in diesel engine exhaust gas was evaluated by the following method using the
First, activated carbon that gives an X-ray diffraction pattern almost equivalent to soot, which is the main component of PM in diesel engine exhaust gas, is used to simulate PM, and the activated carbon and the PM removal catalyst are rubbed onto the heat-
[0021]
Example 1, Comparative Examples 1 and 2
A mixture of 0.1 g of activated carbon and 0.5 g of hematite particles (A1) was rubbed on the heat-
[0022]
As apparent from FIG. 4, in the system using the hematite particles (A1) according to the present invention of Example 1 as a catalyst, activated carbon burned without generating carbon monoxide (CO), whereas hematite In the system of Comparative Example 1 containing no particles, a large amount of carbon monoxide (CO) indicating incomplete combustion was generated. Further, in the system of Comparative Example 2 using hematite particles (A2) having a crystallite size far exceeding 150 mm, although the combustion start temperature slightly shifted to the low temperature side, the effect of completely burning the activated carbon was hardly observed.
[0023]
Example 2 and Comparative Example 3
Carbon monoxide (CO) and carbon dioxide at each temperature in the exhaust gas generated as a result of combustion in the same manner as in Example 1 and Comparative Example 1 except that the gas to be supplied was changed to nitrogen gas containing 1000 ppm of NO 2 gas. The carbon (CO 2 ) concentration was measured. The results are shown in FIG.
[0024]
As is apparent from FIG. 5, in the system using the hematite particles (A1) according to the present invention of Example 2 as a catalyst, the activated carbon is completely burned without generating carbon monoxide as in Example 1. In addition, it could be burned even at a low temperature of 200 ° C. or lower (that is, a temperature that can be reached without using an auxiliary heater with exhaust gas at idling or at the start).
On the other hand, as conventionally known, the system of Comparative Example 3 could be burned at a low temperature due to the effect of NO 2 gas, but a large amount of carbon monoxide (CO) was generated due to incomplete combustion. There was a problem in practical use.
[0025]
Example 3
A combustion test was conducted in the same manner as in Example 1 except that hematite particles (A3) were used instead of hematite particles (A1). As a result, the carbon monoxide (CO) concentration in the exhaust gas was detected at a maximum value of 400 ppm at 710 ° C., and almost complete combustion was possible.
[0026]
Comparative Example 4
A combustion test was conducted in the same manner as in Example 1 except that hematite particles (A4) were used instead of hematite particles (A1). As a result, the carbon monoxide (CO) concentration in the exhaust gas was detected at a maximum value of 3500 ppm at 690 ° C., and the effect of completely burning the activated carbon was hardly observed.
[0027]
【effect】
The PM removal catalyst of the present invention showed very good catalytic activity despite using inexpensive iron as a raw material. In addition, hematite particles are less susceptible to sulfur poisoning, opening the way to reducing PM without using low sulfur gas oil.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction pattern of hematite particles (A1) showing an example of a PM removal catalyst of the present invention.
FIG. 2 is an electron micrograph of hematite particles (A1) showing an example of a PM removal catalyst of the present invention.
FIG. 3 is a schematic perspective view of an experimental apparatus for examining catalytic action.
4 is a graph of carbon monoxide concentration-temperature and carbon dioxide concentration-temperature showing the results of Example 1 and Comparative Examples 1 and 2. FIG.
5 is a graph of carbon monoxide concentration-temperature and carbon dioxide concentration-temperature showing the results of Example 2 and Comparative Example 3. FIG.
[Explanation of symbols]
1
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003057875A JP4212927B2 (en) | 2003-03-05 | 2003-03-05 | Particulate matter removal catalyst in diesel engine exhaust gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003057875A JP4212927B2 (en) | 2003-03-05 | 2003-03-05 | Particulate matter removal catalyst in diesel engine exhaust gas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2004267807A JP2004267807A (en) | 2004-09-30 |
| JP4212927B2 true JP4212927B2 (en) | 2009-01-21 |
Family
ID=33121130
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2003057875A Expired - Fee Related JP4212927B2 (en) | 2003-03-05 | 2003-03-05 | Particulate matter removal catalyst in diesel engine exhaust gas |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4212927B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4730709B2 (en) * | 2006-05-18 | 2011-07-20 | 株式会社豊田中央研究所 | NOx storage reduction catalyst |
| JP2009208025A (en) * | 2008-03-05 | 2009-09-17 | Univ Of Tokushima | Diesel engine exhaust gas cleaning filter |
| US8097554B2 (en) * | 2009-02-09 | 2012-01-17 | Airflow Catalyst Systems, Inc. | Apparatus for removing soot from diesel engine exhaust streams at temperatures at or below 150° C. |
| CN102000573B (en) * | 2010-09-29 | 2013-04-24 | 山西大学 | Modified activated carbon and application thereof |
| DE102019127801A1 (en) * | 2019-10-15 | 2021-04-15 | Technische Universität Bergakademie Freiberg | Precious metal-free catalyst for exhaust gas cleaning of CO2-neutral biomethane engines by oxidizing HCHO and CH4 |
-
2003
- 2003-03-05 JP JP2003057875A patent/JP4212927B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2004267807A (en) | 2004-09-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4317345B2 (en) | Low concentration CO-containing exhaust gas treatment method | |
| US20050239642A1 (en) | Catalytic filter for removing soot particulates from diesel engine exhaust and method of preparing the same | |
| US20060270548A1 (en) | Particle filter having a catalytically active coating to accelerate burning off accumulated soot particles during a regeneration phase | |
| JP5635410B2 (en) | Exhaust gas purification catalyst and purification method using the same | |
| JPH0459049A (en) | Catalyst for diesel engine exhaust gas cleanup | |
| JP4012320B2 (en) | Exhaust gas purification catalyst for lean combustion engine | |
| EA014127B1 (en) | Apparatus for treating diesel exhaust gases | |
| WO2009087852A1 (en) | Exhaust gas cleaner | |
| JP2008272659A (en) | Exhaust gas purification catalyst for automobile, exhaust gas purification catalyst system and purifying method of exhaust gas | |
| JP2005066559A (en) | Exhaust gas treatment catalyst and exhaust gas treatment method | |
| JPH10151348A (en) | Oxidation catalyst | |
| JP2008073654A (en) | Gas purification process, gas purification apparatus, and gas purification catalyst | |
| WO2008065819A1 (en) | Composite oxide for exhaust gas clean-up catalyst, exhaust gas clean-up catalyst, and diesel exhaust gas clean-up filter | |
| US6767526B1 (en) | Method for treating by combustion carbon-containing particles in an internal combustion engine exhaust circuit | |
| JP5023969B2 (en) | Exhaust gas component purification catalyst material and particulate filter with the catalyst material | |
| CN105727964B (en) | Three-dimensional composite oxide catalysts that are a kind of while eliminating NO and soot particulate object and its preparation method and application | |
| JP4212927B2 (en) | Particulate matter removal catalyst in diesel engine exhaust gas | |
| JPH0884911A (en) | Catalyst for decomposing nitrogen oxide and method for purifying diesel engine exhaust using the same | |
| US10226755B2 (en) | NOx storage reduction catalyst for purifying exhaust gas and exhaust gas purification method using said catalyst | |
| EP0722767A1 (en) | Catalyst for purifying exhaust gases | |
| JPH0768176A (en) | Catalyst for purification of exhaust gas from diesel engine | |
| JP2009208039A (en) | Catalyst for removing particulate matter and method for removing particulate matter by using the same | |
| JPH0462778B2 (en) | ||
| JP2006043683A (en) | Catalyst carrier and its manufacturing method and catalyst for cleaning exhaust gas | |
| JP3251009B2 (en) | Exhaust gas purification catalyst |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20060221 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20081010 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20081020 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20081029 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111107 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111107 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121107 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121107 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131107 Year of fee payment: 5 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| LAPS | Cancellation because of no payment of annual fees |