JP2007152303A - Hydrogen-producing catalyst - Google Patents
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- 239000003054 catalyst Substances 0.000 title claims abstract description 165
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 96
- 239000001257 hydrogen Substances 0.000 title claims abstract description 89
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 87
- 239000007789 gas Substances 0.000 claims abstract description 54
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 31
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 31
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910001928 zirconium oxide Inorganic materials 0.000 claims abstract description 20
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 8
- 229910052703 rhodium Inorganic materials 0.000 claims abstract description 8
- 238000002441 X-ray diffraction Methods 0.000 claims abstract description 7
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 7
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 5
- 238000002485 combustion reaction Methods 0.000 claims abstract description 5
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 claims abstract description 4
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 288
- 238000004519 manufacturing process Methods 0.000 claims description 81
- 238000011144 upstream manufacturing Methods 0.000 claims description 9
- 229910000510 noble metal Inorganic materials 0.000 abstract description 14
- 230000009257 reactivity Effects 0.000 abstract description 3
- 230000015556 catabolic process Effects 0.000 abstract 1
- 238000006731 degradation reaction Methods 0.000 abstract 1
- 238000006243 chemical reaction Methods 0.000 description 27
- 238000000746 purification Methods 0.000 description 24
- 241000264877 Hippospongia communis Species 0.000 description 16
- 238000001179 sorption measurement Methods 0.000 description 15
- 238000011156 evaluation Methods 0.000 description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000000446 fuel Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 239000000843 powder Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 238000006722 reduction reaction Methods 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 229910052878 cordierite Inorganic materials 0.000 description 4
- 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 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000010970 precious metal Substances 0.000 description 4
- 229910004625 Ce—Zr Inorganic materials 0.000 description 3
- 239000003463 adsorbent Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005470 impregnation Methods 0.000 description 3
- 238000004898 kneading Methods 0.000 description 3
- 239000000395 magnesium oxide Substances 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 3
- 238000001354 calcination Methods 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 239000008213 purified water Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910052684 Cerium Inorganic materials 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
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Hydrogen, Water And Hydrids (AREA)
- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
Description
本発明は、一酸化炭素と水から水素を生成する水素製造触媒に関し、特に自動車排ガス中でのＮＯｘ浄化用の水素の製造に関するものである。 The present invention relates to a hydrogen production catalyst that generates hydrogen from carbon monoxide and water, and more particularly to production of hydrogen for NOx purification in automobile exhaust gas.
地球温暖化防止，環境改善を目的に、自動車排ガス中の有害物質であるＣＯ（一酸化炭素），ＮＯｘ（窒素酸化物），ＨＣ（炭化水素）低減、そして温室ガスである二酸化炭素の削減が求められている。自動車排ガスから二酸化炭素を削減するには、エンジンを希薄燃料雰囲気で運転し、燃費を向上させなければならない。理論空燃比（約１４.６ ）で運転するガソリンエンジンの排ガス浄化には、三元触媒が用いられ、排ガス成分を利用してＣＯ，ＨＣの酸化とＮＯｘの還元を同時に行う。それより希薄な燃料雰囲気になる空気燃料比（以下リーン）で運転するエンジン（リーンバーンエンジン）では、排ガスに三元触媒で利用可能な量以上の酸素が含まれるため、還元反応が進行しにくく、ＮＯｘが浄化されにくい。これらを解決するため、リーン時に排ガス中のＮＯｘを触媒上に吸着し、一時的に理論空燃比より燃料が過剰な空気燃料比（以下リッチ）にするリーン・リッチ制御を行い、吸着したＮＯｘをリッチガス中のＨＣ，ＣＯ，Ｈ2 などで還元するリーンＮＯｘ触媒が知られている。 Reduction of CO (carbon monoxide), NOx (nitrogen oxide) and HC (hydrocarbon), which are harmful substances in automobile exhaust gas, and reduction of carbon dioxide, which is a greenhouse gas, for the purpose of preventing global warming and improving the environment It has been demanded. To reduce carbon dioxide from automobile exhaust, the engine must be operated in a lean fuel atmosphere to improve fuel economy. A three-way catalyst is used for exhaust gas purification of a gasoline engine operating at a theoretical air fuel ratio (about 14.6), and CO, HC oxidation and NOx reduction are simultaneously performed using exhaust gas components. In an engine (lean burn engine) that operates at an air fuel ratio (hereinafter lean) that produces a leaner fuel atmosphere, the exhaust gas contains more oxygen than can be used with a three-way catalyst, so the reduction reaction does not proceed easily. NOx is hardly purified. In order to solve these problems, NOx in the exhaust gas is adsorbed onto the catalyst during lean, and lean-rich control is performed to temporarily make the air fuel ratio (hereinafter rich) of the fuel excessive from the theoretical air-fuel ratio, and the adsorbed NOx is removed. A lean NOx catalyst that reduces with HC, CO, H 2 or the like in a rich gas is known.
ディーゼルエンジンは定常的にリーンで運転されるが、ガソリンのリーンバーンエンジンと同様にリーンＮＯｘ触媒を使用しリーン・リッチ制御を行うことによりＮＯｘの浄化が可能である。しかしディーゼルエンジンの排ガス温度は１５０から２５０℃であり、ガソリンリーンバーンエンジンと比較して１００℃程度低い。そのため、リーンＮＯｘ触媒を適用する場合、排ガスによって昇温される触媒の温度が１００℃程度低いために触媒活性が十分でなく、吸着したＮＯｘを還元しきれずＮＯｘ浄化率の低下が問題となる。特にリーン・リッチ制御を行う際に、リーンからリッチに切り替えた時のＮＯｘ浄化率の低下の幅が大きい。 Diesel engines are always operated lean, but NOx can be purified by performing lean / rich control using a lean NOx catalyst in the same manner as a gasoline lean burn engine. However, the exhaust gas temperature of a diesel engine is 150 to 250 ° C, which is about 100 ° C lower than that of a gasoline lean burn engine. Therefore, when a lean NOx catalyst is applied, the catalyst temperature raised by the exhaust gas is low by about 100 ° C., so that the catalytic activity is not sufficient, and the adsorbed NOx cannot be completely reduced, resulting in a decrease in the NOx purification rate. In particular, when performing lean / rich control, the range of reduction in the NOx purification rate when switching from lean to rich is large.
リッチガスにはＨＣ，ＣＯ，Ｈ2 などの還元成分が含まれているので、リッチ時はこの還元成分を利用してＮＯｘを還元する。１５０から２５０℃の低温での反応性は、ＣＯよりＨ2 が高い。そこで排ガス中のＣＯとＨ2Ｏ からＨ2 を製造し、そのＨ2 でＮＯｘを還元させる方法が考えられている。ＣＯとＨ2Ｏ からＨ2 を製造する反応は、水性ガスシフト反応と呼ばれ式（１）で表される。 Since the rich gas contains reducing components such as HC, CO, and H 2 , NOx is reduced using this reducing component when rich. The reactivity at low temperatures of 150 to 250 ° C. is higher for H 2 than for CO. Therefore, a method is considered in which H 2 is produced from CO and H 2 O in the exhaust gas, and NOx is reduced with the H 2 . The reaction for producing H 2 from CO and H 2 O is called a water gas shift reaction and is represented by the formula (1).
ＣＯ＋Ｈ2Ｏ→ＣＯ2＋Ｈ2 （１） CO + H 2 O → CO 2 + H 2 (1)
水性ガスシフト反応が進行しやすい触媒（以下水素製造触媒）をリーンＮＯｘ触媒に組み合わせることで、低温におけるＨ2でのＮＯｘの還元がおこなわれる。その結果、リーン・リッチ制御を行いディーゼルエンジン排ガスのＮＯｘを浄化することが可能になり、特に低温での窒素酸化物（以下ＮＯｘ）を効率良く浄化できる。 By combining a catalyst (hereinafter referred to as a hydrogen production catalyst) in which a water gas shift reaction easily proceeds with a lean NOx catalyst, NOx is reduced with H 2 at a low temperature. As a result, lean / rich control can be performed to purify NOx in diesel engine exhaust gas, and particularly nitrogen oxides (hereinafter referred to as NOx) at low temperatures can be efficiently purified.
水素製造触媒は貴金属を活性成分とし、酸化ジルコニウム（ＺｒＯ2 ），酸化マグネシウム（ＭｇＯ），アルミナ（Ａｌ2Ｏ3）−ＭｇＯ複合酸化物，ＴｉＢａＯ3 ，スピネルなどに担持して用いられる。 The hydrogen production catalyst contains a noble metal as an active component and is supported on zirconium oxide (ZrO 2 ), magnesium oxide (MgO), alumina (Al 2 O 3 ) -MgO composite oxide, TiBaO 3 , spinel, or the like.
上記Ｈ2 製造によりＮＯｘ浄化率は改善されるものの、Ｈ2 量の不足によりＮＯｘ浄化率が上がらない場合がある。そこで本発明の課題は、水性ガスシフト反応が進行しやすいＣＯとＨ2Ｏ からＨ2 を製造する水素製造触媒を提供することにある。 Although the NOx purification rate is improved by the production of H 2, the NOx purification rate may not increase due to an insufficient amount of H 2 . Accordingly, an object of the present invention is to provide a hydrogen production catalyst for producing H 2 from CO and H 2 O, in which a water gas shift reaction easily proceeds.
前記課題を解決するための本発明は、一酸化炭素と水から水素を生成する触媒において、Ｘ線回折パターンにおいて（１１１）面回折ピーク強度とバックグランドの比が４.３ 以上である酸化セリウムを含む酸化物とジルコニウム酸化物からなる担体に、Ｐｔ，Ｐｄ，Ｒｈから選ばれる貴金属を１つ以上含むことを特徴とする水素製造触媒にある。 The present invention for solving the above-mentioned problems is directed to a catalyst that generates hydrogen from carbon monoxide and water, and the ratio of (111) plane diffraction peak intensity to background is 4.3 or more in the X-ray diffraction pattern. The hydrogen production catalyst is characterized in that one or more precious metals selected from Pt, Pd, and Rh are contained in a support made of an oxide containing and zirconium oxide.
また、上記の水素製造触媒が、窒素酸化物を吸着又は吸蔵する機能を有する触媒層との二層構造になっていることが好ましい。触媒支持材上にコートされた窒素酸化物を吸着又は吸蔵する機能を有する触媒層と接して水素製造触媒を設けた場合、触媒支持材とは、例えばコージェライトやメタルである。 The hydrogen production catalyst preferably has a two-layer structure with a catalyst layer having a function of adsorbing or occluding nitrogen oxides. When the hydrogen production catalyst is provided in contact with the catalyst layer having a function of adsorbing or occluding nitrogen oxide coated on the catalyst support material, the catalyst support material is, for example, cordierite or metal.
もしくは、上記の水素製造触媒が、窒素酸化物を吸着又は吸蔵する機能を有する触媒の上流側に配置するとよい。 Or it is good to arrange | position said hydrogen production catalyst in the upstream of the catalyst which has the function to adsorb | suck or occlude a nitrogen oxide.
本発明の水素製造触媒は水素製造能力が高く、リーンＮＯｘ触媒を組み合わせることで、低温におけるリッチでのＮＯｘの還元が効率よくおこなわれる。その結果、リーン・リッチ制御を行うディーゼルエンジン排ガスの浄化において、水素製造触媒とリーンＮＯｘ触媒を組み合わせた触媒を用いることで、高ＮＯｘ浄化性能を実現できる。 The hydrogen production catalyst of the present invention has a high hydrogen production capacity, and by combining a lean NOx catalyst, NOx can be efficiently reduced in a rich manner at low temperatures. As a result, high NOx purification performance can be realized by using a catalyst that combines a hydrogen production catalyst and a lean NOx catalyst in purification of exhaust gas from a diesel engine that performs lean / rich control.
発明者らは、（１１１）面のピーク高さとバックグランドの比が高い酸化セリウムを含む酸化物に、ジルコニウム酸化物を担持し、更にＰｄｔ，Ｐｄ，Ｒｈから選ばれた貴金属を１種以上担持することとした。リッチガス中のＣＯとＨ2Ｏ からＨ2 を生成する能力が高いため、耐久処理後の触媒でもリーンからリッチに切り替わる時のＮＯｘ浄化性能を改善することが出来た。 The inventors support zirconium oxide on an oxide containing cerium oxide having a high (111) plane peak height and background ratio, and further support one or more precious metals selected from Pdt, Pd, and Rh. It was decided to. Since the ability to generate H 2 from CO and H 2 O in the rich gas is high, the NOx purification performance when the catalyst after the endurance treatment is switched from lean to rich can be improved.
ディーゼルエンジンの排ガス処理に適したリーンＮＯｘ触媒の開発では、リーン・リッチ制御を模擬したリーンガスとリッチガスを切り替えてＮＯｘ浄化性能を評価する。従来の触媒の耐久処理後のＮＯｘ浄化性能は、リーンからリッチに切り替わる時に大きく低下した。その原因として、貴金属の劣化が考えられた。触媒の活性は温度共に高まるので低温での活性は貴金属の劣化の影響を受けやすいからである。 In the development of a lean NOx catalyst suitable for exhaust gas treatment of diesel engines, NOx purification performance is evaluated by switching between lean gas and rich gas simulating lean / rich control. The NOx purification performance of the conventional catalyst after the endurance treatment is greatly reduced when the catalyst is switched from lean to rich. The cause was thought to be deterioration of precious metals. This is because the activity of the catalyst increases with temperature, and the activity at low temperatures is easily affected by the deterioration of the noble metal.
上記本発明では、Ｈ2 を生成する能力が高いので、気相中もしくはリーンＮＯｘ触媒から脱離するＮＯｘを浄化し貴金属への負担を軽減し、劣化した貴金属でも十分なＮＯｘ浄化性能が得られている。 In the present invention, since the ability to generate H 2 is high, NOx desorbed from the gas phase or the lean NOx catalyst is purified to reduce the burden on the noble metal, and sufficient NOx purification performance can be obtained even with deteriorated noble metal. ing.
リーンＮＯｘ触媒は、高比表面積のアルミナを担体とし、燃焼活性成分である貴金属、ＮＯｘ吸着材であるアルカリ金属、そして酸化セリウムを担持したものを使用できる。高比表面積のアルミナに貴金属を高分散させることで担体の焼結収縮，貴金属の凝集を抑制できる。また、酸化セリウムは、酸素過剰状態ではガス中から酸化セリウム中に酸素を取り込み、酸素不足状態ではガスに酸素を放出することで、ガス組成を平準化し、貴金属上での酸化・還元を助ける。 As the lean NOx catalyst, a catalyst having a high specific surface area alumina as a carrier and supporting a noble metal as a combustion active component, an alkali metal as a NOx adsorbent, and cerium oxide can be used. Sintering shrinkage of the carrier and aggregation of the noble metal can be suppressed by highly dispersing the noble metal in the alumina having a high specific surface area. In addition, cerium oxide takes oxygen from gas into cerium oxide in an oxygen-excess state and releases oxygen into the gas in an oxygen-deficient state, thereby leveling the gas composition and assisting oxidation / reduction on the noble metal.
水素製造触媒での、酸化セリウム上の水性シフト反応は式（２）から（４）と報告されている。 The aqueous shift reaction on cerium oxide with a hydrogen production catalyst is reported as equations (2) to (4).
ＣＯ＋σ＝ＣＯａｄ （２）
Ｈ2Ｏ＋Ｃｅ2Ｏ3＝２ＣｅＯ2＋Ｈ2 （３）
ＣＯａｄ＋２ＣｅＯ2＝ＣＯ2＋Ｃｅ2Ｏ3＋σ （４）
ａｄ：吸着、σ：金属の吸着サイト
CO + σ = COad (2)
H 2 O + Ce 2 O 3 = 2CeO 2 + H 2 (3)
COad + 2CeO 2 = CO 2 + Ce 2 O 3 + σ (4)
ad: Adsorption, σ: Metal adsorption site
Ｈ2の生成は、（１）ＣＯの金属への吸着（式(２)）、（２）Ｃｅ2Ｏ3へのＨ2Ｏの吸着と、ＣｅＯ2とＨ2の生成 (式(３))、(３) ＣｅＯ2 による金属上のＣＯの酸化（式(４)）、の順で進行する。 H 2 is produced by (1) adsorption of CO to metal (formula (2)), (2) adsorption of H 2 O to Ce 2 O 3 , and production of CeO 2 and H 2 (formula (3) ), (3) Oxidation of CO on metal with CeO 2 (formula (4)).
本発明の特徴は、Ｘ線回折パターンにおいて（１１１）面回折ピーク強度とバックグランドの比が４.３ 以上である酸化セリウムを用いたことにあるが、回折パターンにおいて回折ピークとバックグランドの比が高いことは、結晶性が高いことを示す。式（３），
（４）中の酸化セリウムの状態変化は、酸化セリウム中の酸素をＰｔ上でＣＯと反応させることで継続するので、結晶性が高い場合は、この酸化セリウム内の酸素の移動が容易になっていると思われる。そのため、水素製造能力が高くなったと予想される。
A feature of the present invention is that cerium oxide having a ratio of (111) plane diffraction peak intensity to background of 4.3 or more in the X-ray diffraction pattern is used. A high indicates that the crystallinity is high. Equation (3),
The state change of cerium oxide in (4) is continued by reacting oxygen in cerium oxide with CO on Pt. Therefore, when the crystallinity is high, the movement of oxygen in cerium oxide becomes easy. It seems that As a result, hydrogen production capacity is expected to increase.
更に、通常の酸化セリウムでもＺｒを含むと低温での水素製造能力がさらに向上した。酸化ジルコニウム担体にＰｔを担持した触媒では水素製造能力がほとんど見られないことから、酸化ジルコニウムにはシフト反応時の酸素の移動を補助する役割があると推測している。酸化セリウムに他の酸化物を含む場合の代表例としてＣｅ−Ｚｒ複合酸化物がある。その他の構成酸化物としてＬａ，Ｐｒ，Ｍｇ，Ｂａなどを含んでも構わない。また、自動車触媒用に用いられるＣｅ−Ｚｒ酸化物は、Ｚｒが酸化セリウムに固溶しているため、Ｘ線回折では酸化セリウムに近似したＣｅ−Ｚｒ複合酸化物のピークしか検出されない。しかし上記の場合には、ジルコニウム酸化物として存在していることが特徴である。 Furthermore, even when ordinary cerium oxide contains Zr, the hydrogen production capability at a low temperature is further improved. It is speculated that zirconium oxide has a role of assisting the movement of oxygen during the shift reaction because a catalyst in which Pt is supported on a zirconium oxide support hardly shows hydrogen production ability. A typical example of the case where cerium oxide contains another oxide is a Ce-Zr composite oxide. Other constituent oxides may include La, Pr, Mg, Ba and the like. In addition, since the Ce—Zr oxide used for automobile catalysts has a solid solution of Zr in cerium oxide, only a peak of the Ce—Zr composite oxide close to cerium oxide is detected by X-ray diffraction. However, the above case is characterized by being present as zirconium oxide.
貴金属の種類は、酸化セリウムに担持した場合に水素製造能力があることを確認した
Ｐｄ，Ｐｔ，Ｒｈを選択している。これらの貴金属は自動車触媒に使用しても安定であることがわかっている。貴金属の量は、要求される性能，コストに応じ決定される。もちろんＰｄ，Ｐｔ，Ｒｈを複数あるいは、すべてを担持してもかまわない。
As the type of noble metal, Pd, Pt, and Rh that have been confirmed to have hydrogen production ability when supported on cerium oxide are selected. These noble metals have been found to be stable when used in automotive catalysts. The amount of precious metal is determined according to the required performance and cost. Of course, plural or all of Pd, Pt and Rh may be supported.
本発明の水素製造触媒はリーンＮＯｘ触媒と組み合わせて使用でき、一触媒としてもよい。図３にリーンＮＯｘ触媒に、水素製造触媒をオーバーコートした二層形触媒のＣＯ転化率とＮＯｘ浄化率の関係を示す。試験は２００℃でリーンガスを３分、リッチガスを３分流通させたときのリッチの平均ＮＯｘ浄化率を測定することにより行った。ＣＯ転化率は、リッチガス中のＣＯをＨ2 に転化した割合を示す。図３より、ＣＯ転化率が高くなるとＮＯｘ浄化率が高くなることがわかる。その結果、リーンＮＯｘ触媒のＮＯｘ浄化性能へ水素が効果を示すことが明らかである。このように触媒上で製造した水素は、リーン
ＮＯｘ触媒のＮＯｘ浄化に寄与し、その効果はＣＯ転化率が高いほど高くなる。
The hydrogen production catalyst of the present invention can be used in combination with a lean NOx catalyst, and may be a single catalyst. FIG. 3 shows the relationship between the CO conversion rate and the NOx purification rate of a two-layer catalyst in which a lean NOx catalyst is overcoated with a hydrogen production catalyst. The test was conducted by measuring the rich average NOx purification rate when lean gas was passed for 3 minutes and rich gas was passed for 3 minutes at 200 ° C. CO conversion is the ratio obtained by the conversion of CO in the rich gas to H 2. FIG. 3 shows that the NOx purification rate increases as the CO conversion rate increases. As a result, it is clear that hydrogen has an effect on the NOx purification performance of the lean NOx catalyst. The hydrogen thus produced on the catalyst contributes to NOx purification of the lean NOx catalyst, and the effect becomes higher as the CO conversion rate is higher.
また、上記の水素製造触媒はリーンＮＯｘ触媒と混合して用いてもよい。 The above hydrogen production catalyst may be used as a mixture with a lean NOx catalyst.
本発明の水素製造触媒は、製造したＨ2 を利用してリーンＮＯｘ触媒に吸着したＮＯｘを還元する反応をさせるため、リーンＮＯｘ触媒の上流に位置することが効果的である。ここでいう上流側とは、内燃機関の排ガスの流路におけるエンジン側を意味する。 The hydrogen production catalyst of the present invention is effective to be located upstream of the lean NOx catalyst because the produced H 2 is used to reduce NOx adsorbed on the lean NOx catalyst. The upstream side here means the engine side in the exhaust gas flow path of the internal combustion engine.
水素製造触媒とリーンＮＯｘ触媒が物理的に接触している場合、離れている場合いずれの場合も水素製造触媒が排ガス流中でエンジン側、リーンＮＯｘ触媒がマフラー側に位置させることが望ましい。また、同一ハニカムの片端面に水素製造触媒と他端面にリーン
ＮＯｘ触媒を形成して車両に組み込み、水素製造触媒担持面をエンジン側にセットすることが簡便で望ましい。
In both cases where the hydrogen production catalyst and the lean NOx catalyst are in physical contact with each other, it is desirable that the hydrogen production catalyst be positioned on the engine side and the lean NOx catalyst on the muffler side in the exhaust gas flow. In addition, it is simple and desirable to form a hydrogen production catalyst on one end face of the same honeycomb and a lean NOx catalyst on the other end face and incorporate it in the vehicle, and set the hydrogen production catalyst carrying face on the engine side.
窒素酸化物吸着・吸蔵機能触媒と、水素製造触媒は、ハニカムにリーンＮＯｘ触媒と水素製造触媒を多層に形成、またはハニカムにリーンＮＯｘ吸着材と水素製造触媒を混合、吸着材を担持したハニカムと燃焼材を担持したハニカムを組み合わせて使うことができる。特にリーンＮＯｘ触媒と水素製造触媒の位置は、二層型の場合は、ガス流路側に水素製造触媒を配置することでリッチガス中のＣＯを効率的にＨ2 に転化し、リーンＮＯｘ触媒から脱離するＮＯｘを効率よく浄化させることができる。同一ハニカムの片端面に水素製造触媒と他短面にリーンＮＯｘ触媒を形成して水素製造触媒担持面を上流側にセットして車両に組み込む場合も、リッチガス中のＣＯを効率的にＨ2 に転化し、リーンＮＯｘ触媒から脱離するＮＯｘを効率よく浄化させることができる。 Nitrogen oxide adsorption / occlusion function catalyst and hydrogen production catalyst include a honeycomb in which a lean NOx catalyst and a hydrogen production catalyst are formed in multiple layers in a honeycomb, or a lean NOx adsorbent and a hydrogen production catalyst are mixed in a honeycomb and an adsorbent is supported. A honeycomb carrying a combustion material can be used in combination. In particular, in the case of a two-layer type, the position of the lean NOx catalyst and the hydrogen production catalyst is such that by disposing the hydrogen production catalyst on the gas flow path side, CO in the rich gas is efficiently converted to H 2 and desorbed from the lean NOx catalyst. The separated NOx can be purified efficiently. Even when a hydrogen production catalyst is formed on one end face of the same honeycomb and a lean NOx catalyst is formed on the other short face and the hydrogen production catalyst support face is set upstream and incorporated in the vehicle, CO in the rich gas is efficiently converted to H 2 . The NOx that is converted and desorbed from the lean NOx catalyst can be efficiently purified.
一体化せず水素製造触媒とリーンＮＯｘ触媒をそれぞれ別のハニカムで作製し、水素製造触媒をリーンＮＯｘ触媒の上流に配置しても同様の効果がある。 The same effect can be obtained if the hydrogen production catalyst and the lean NOx catalyst are made of different honeycombs without being integrated, and the hydrogen production catalyst is arranged upstream of the lean NOx catalyst.
前記、高結晶性の酸化セリウムもしくはセリウム複合酸化物にジルコニウム酸化物を添加した粉末への貴金属担持方法としては、含浸、及び混練方法を用いることができる。 As the method for supporting the noble metal on the powder obtained by adding zirconium oxide to highly crystalline cerium oxide or cerium composite oxide, impregnation and kneading methods can be used.
排ガス浄化触媒の形状は、通常の粒状，押出し成型した柱状，プレス成型したペレット型，蜂の巣状のハニカム型の、いずれも使用することができるが、圧損等の観点からハニカム型が好ましい。 As the shape of the exhaust gas purification catalyst, any of normal granular, extruded columnar, press-molded pellet type, and honeycomb type honeycomb type can be used, but the honeycomb type is preferable from the viewpoint of pressure loss and the like.
水素製造触媒と共に使用するリーンＮＯｘ触媒は、吸着型，吸蔵型いずれでも構わない。水素製造触媒の水素製造効果はいずれのリーンＮＯｘ触媒でも、低温でのＮＯｘ浄化性能向上に役立つ。
（実施例）
The lean NOx catalyst used together with the hydrogen production catalyst may be either an adsorption type or an occlusion type. The hydrogen production effect of the hydrogen production catalyst is useful for improving the NOx purification performance at low temperatures in any lean NOx catalyst.
(Example)
以下に本発明の実施例を示すが、この例に限定されるものではない。 Although the Example of this invention is shown below, it is not limited to this example.
以下は本発明の概要である。まず、窒素酸化物吸着・吸蔵機能触媒と水素製造触媒の二層型の一体化触媒の作製例を示す。一体化触媒では、コージェライトハニカムにリーン
ＮＯｘ触媒層を形成後、水素製造触媒層を形成する。
The following is an overview of the present invention. First, an example of producing a two-layered integrated catalyst of a nitrogen oxide adsorption / occlusion function catalyst and a hydrogen production catalyst is shown. In the integrated catalyst, the hydrogen production catalyst layer is formed after the lean NOx catalyst layer is formed on the cordierite honeycomb.
まず、リーンＮＯｘ触媒層の作製方法を示す。アルミナ，アルミナゾル、そして精製水を混合したスラリーをコージェライトハニカムに流し込み、乾燥・焼成を行いアルミナ層を形成した。Ｎａ，Ｋなどのアルカリ成分を水溶液にし、含浸法でアルミナ層に担持した。酸化セリウムなどのＯＳＣ（酸素貯蔵能）を有する酸化物を担持する場合は、硝酸塩など用い水溶液にしてアルミナ層に含浸した。そしてＰｄ，Ｐｔ，Ｒｈの貴金属水溶液をアルミナ層に含浸し、リーンＮＯｘ触媒層を作製した。 First, a method for producing a lean NOx catalyst layer will be described. A slurry in which alumina, alumina sol, and purified water were mixed was poured into a cordierite honeycomb and dried and fired to form an alumina layer. An alkaline component such as Na and K was made into an aqueous solution and supported on the alumina layer by an impregnation method. When supporting an oxide having OSC (oxygen storage ability) such as cerium oxide, the alumina layer was impregnated into an aqueous solution using nitrate or the like. Then, an alumina layer was impregnated with an aqueous noble metal solution of Pd, Pt, and Rh to produce a lean NOx catalyst layer.
なお、上述の含浸法の他に、混練法でも作製できる。混練法では、リーンＮＯｘ触媒層を形成するアルカリ成分，ＯＳＣを有する酸化物、そして貴金属を混合したスラリーを、コージェライトハニカムに流し込み、リーンＮＯｘ触媒層を形成する。 In addition to the above-described impregnation method, it can be produced by a kneading method. In the kneading method, a slurry in which an alkali component forming a lean NOx catalyst layer, an oxide containing OSC, and a noble metal are mixed is poured into a cordierite honeycomb to form a lean NOx catalyst layer.
水素製造触媒は、酸化セリウムに硝酸ジルコニウム水溶液を含浸し、空気中６００℃で焼成後、更にＰｄ，Ｐｔ，Ｒｈなどの水溶液を含浸させた後、空気中６００℃で焼成して、水素製造触媒粉末を得た。水素製造触媒粉末にシリカゾルと精製水を加えたスラリーを、リーンＮＯｘ触媒層を形成したハニカムに流し込み水素製造触媒層を形成した。 The hydrogen production catalyst is obtained by impregnating cerium oxide with an aqueous zirconium nitrate solution, calcining at 600 ° C. in air, further impregnating with an aqueous solution of Pd, Pt, Rh, etc., and calcining at 600 ° C. in air. A powder was obtained. A slurry obtained by adding silica sol and purified water to a hydrogen production catalyst powder was poured into a honeycomb having a lean NOx catalyst layer to form a hydrogen production catalyst layer.
なお、水素製造触媒作製時に、硝酸ジルコニウム水溶液に変えてあらかじめ、酸化ジルコニウム粉末混合する手法でも良い。 It should be noted that a technique of mixing zirconium oxide powder in advance instead of the zirconium nitrate aqueous solution may be used when preparing the hydrogen production catalyst.
図１は自動車用ディーゼルエンジン排ガスの後処理システムの一例である。エンジンの排ガス流路に三元触媒または酸化触媒が設けられ、その後段にススなどを除去するためにディーゼルパティキュレートフィルタ（ＤＰＦ）が設置され、そのさらに後段に本発明の窒素酸化物吸着・吸蔵機能触媒と水素製造触媒の一体化触媒が設置されている。 FIG. 1 shows an example of an aftertreatment system for automobile diesel engine exhaust gas. A three-way catalyst or oxidation catalyst is provided in the exhaust gas flow path of the engine, a diesel particulate filter (DPF) is installed in the subsequent stage to remove soot, and the nitrogen oxide adsorption / occlusion of the present invention in the subsequent stage. An integrated catalyst of functional catalyst and hydrogen production catalyst is installed.
図２は、水素製造触媒を、窒素酸化物を吸着又は吸蔵する機能を有する触媒の上流側に設置する場合を示す図である。図１中の窒素酸化物吸着・吸蔵機能触媒と水素製造触媒の一体化触媒にかえて、水素製造触媒とリーンＮＯｘ触媒をそれぞれ配置し、水素製造触媒が排ガスの上流側（エンジン側）に位置している。 FIG. 2 is a diagram showing a case where a hydrogen production catalyst is installed on the upstream side of a catalyst having a function of adsorbing or storing nitrogen oxides. In place of the integrated catalyst of nitrogen oxide adsorption / storage function catalyst and hydrogen production catalyst in Fig. 1, a hydrogen production catalyst and a lean NOx catalyst are arranged respectively, and the hydrogen production catalyst is located upstream of the exhaust gas (engine side) is doing.
窒素酸化物吸着・吸蔵機能を有する触媒と水素製造触媒との一体化触媒、もしくは水素製造触媒とリーンＮＯｘ触媒に排ガスを通し、エンジンから排出されるＮＯｘを浄化することができる。 NOx discharged from the engine can be purified by passing exhaust gas through an integrated catalyst of a catalyst having a nitrogen oxide adsorption / storage function and a hydrogen production catalyst, or a hydrogen production catalyst and a lean NOx catalyst.
この浄化方法では、窒素酸化物吸着・吸蔵機能触媒と、水素製造触媒の一体化触媒、もしくは水素製造触媒とリーンＮＯｘ触媒を通る排ガスは、該排ガス浄化触媒の上流側に配置されている三元触媒または酸化触媒、そしてＤＰＦを既に通った排ガスであることが必要である。 In this purification method, exhaust gas passing through an integrated catalyst of a nitrogen oxide adsorption / storage function catalyst and a hydrogen production catalyst, or a hydrogen production catalyst and a lean NOx catalyst, is a three-way element disposed upstream of the exhaust gas purification catalyst. It is necessary that the exhaust gas has already passed through the catalyst or oxidation catalyst and DPF.
窒素酸化物吸着・吸蔵機能一体化水素製造触媒では、水素製造触媒，リーンＮＯｘ触媒の両者の性能が合わさって、ＮＯｘを浄化する。リーンＮＯｘ性能が同一性能の場合、水素製造触媒の性能が高いほど、ＮＯｘの浄化性能が高いといえる。以下の各実施例では、水素製造触媒の性能を比較した。 In the hydrogen production catalyst integrated with nitrogen oxide adsorption / storage function, the performance of both the hydrogen production catalyst and the lean NOx catalyst is combined to purify NOx. When the lean NOx performance is the same, it can be said that the higher the performance of the hydrogen production catalyst, the higher the NOx purification performance. In each of the following examples, the performance of the hydrogen production catalyst was compared.
実施例１触媒は次の手順で作製した。酸化セリウム粉末に、硝酸ジルコニウム水溶液を含浸し乾燥，焼成し、ジルコニウム酸化物を形成した。酸化セリウムはＸＲＤの回折パターンにおいて、（１１１）面のピーク高さとバックグランドの比が９.５ を得られるもの（第一稀元素製）を使用した。更に、ジニトロジアンミンＰｔ水溶液を用いてＰｔを担持し、水素製造触媒粉末を得た。水素製造触媒粉末はハニカムに酸化セリウムを１３０ｇ／Ｌ担持した時にＰｔが２.７ｇ／Ｌ になるように調製した。ハニカムに、水素製造触媒粉末をウオッシュコートで酸化セリウムとして１３０ｇ／Ｌ担持した。 Example 1 A catalyst was prepared by the following procedure. A cerium oxide powder was impregnated with an aqueous zirconium nitrate solution, dried and fired to form zirconium oxide. As the cerium oxide, an XRD diffraction pattern having a ratio of the (111) plane peak height to the background of 9.5 (manufactured by the first rare element) was used. Further, Pt was supported using a dinitrodiammine Pt aqueous solution to obtain a hydrogen production catalyst powder. The hydrogen production catalyst powder was prepared so that Pt was 2.7 g / L when 130 g / L of cerium oxide was supported on the honeycomb. The honeycomb was loaded with 130 g / L of hydrogen production catalyst powder as cerium oxide with a wash coat.
水素製造能力は耐久処理後に評価した。水素製造触媒の水性ガスシフト反応の反応性を以下の試験で検証した。水素製造触媒評価試験のガス組成を表１に、評価パターンを図４に示す。図５に評価装置を示す。 Hydrogen production capacity was evaluated after endurance treatment. The reactivity of the water gas shift reaction of the hydrogen production catalyst was verified by the following test. The gas composition of the hydrogen production catalyst evaluation test is shown in Table 1, and the evaluation pattern is shown in FIG. FIG. 5 shows an evaluation apparatus.
評価では、固定床流通式反応管を用いた。触媒(１７mm×１７mm×長さ２１mm)は６ｍｌとした。評価は以下の手順で実施した。
（１）ストイキ昇温（前処理）
表１（ａ）のストイキガスを流通させ、触媒入口温度で室温から５５０℃まで２０℃／min にて昇温した。１００℃からはポンプで送液した水を反応管内に滴下し水蒸気として加えた。ＳＶは３００００ｈ-1とした。
（２）シフト反応評価
５５０℃に到達後、表１(ｂ)の水素製造触媒評価ガスに切り替え、降温しながら３００℃，２５０℃，２００℃，１５０℃でそれぞれ５分間保持した。ＳＶは５００００ｈ-1とした。触媒出口でガス中の水蒸気を水トラップで除去した後、ＣＯ，ＣＯ2 分析計（堀場製作所、ＶＩＡ−５１０）へ導いた。
In the evaluation, a fixed bed flow type reaction tube was used. The catalyst (17 mm x 17 mm x length 21 mm) was 6 ml. The evaluation was performed according to the following procedure.
(1) Stoichi temperature rise (pretreatment)
The stoichiometric gas shown in Table 1 (a) was circulated, and the temperature was increased from room temperature to 550 ° C. at a catalyst inlet temperature of 20 ° C./min. From 100 ° C., water fed by a pump was dropped into the reaction tube and added as water vapor. The SV was 30000 h −1 .
(2) Shift Reaction Evaluation After reaching 550 ° C., the hydrogen production catalyst evaluation gas shown in Table 1 (b) was switched to and maintained at 300 ° C., 250 ° C., 200 ° C., and 150 ° C. for 5 minutes while cooling. The SV was set to 50000h- 1 . After removing water vapor in the gas with a water trap at the catalyst outlet, it was led to a CO, CO 2 analyzer (Horiba, VIA-510).
比較例１は、ＸＲＤの回折パターンにおいてピーク高さとバックグランドの比が９.５の酸化セリウムにＰｔを担持しただけでジルコニウム酸化物を含まない。比較例２はXRDの回折パターンにおいてピーク高さとバックグランドの比が４.２ の酸化セリウムに酸化ジルコニウム，Ｐｔを担持した。比較例３は酸化ジルコニウムにＰｔを担持した。 Comparative Example 1 does not contain zirconium oxide, only Pt is supported on cerium oxide having a ratio of peak height to background of 9.5 in the XRD diffraction pattern. In Comparative Example 2, zirconium oxide and Pt were supported on cerium oxide having a peak height to background ratio of 4.2 in the XRD diffraction pattern. In Comparative Example 3, Pt was supported on zirconium oxide.
ＣＯシフト反応評価結果として、実施例１及び比較例１〜３のＣＯ転化率を表２に示す。ディーゼル排ガス温度の代表値として２００℃で試験した結果である。すべて、７００℃×２０ｈの熱処理を実施した。ここで、ＣＯ転化率は、ガス中のＣＯがＨ2 に転化された割合である。ガスには２％のＣＯを含むため、例えば、ＣＯ転化率１％は、２％ＣＯの１％を水素に転化し、０.０２％の水素を得たことを示す。 Table 2 shows the CO conversion rates of Example 1 and Comparative Examples 1 to 3 as the CO shift reaction evaluation results. It is the result of having tested at 200 degreeC as a typical value of diesel exhaust gas temperature. All were heat-treated at 700 ° C. for 20 hours. Here, the CO conversion rate is a ratio of CO in the gas converted to H 2 . Since the gas contains 2% CO, for example, a CO conversion of 1% indicates that 1% of 2% CO has been converted to hydrogen, yielding 0.02% hydrogen.
実施例１と比較例１のＣＯ転化率は、それぞれ、１２.４，６.２％であった。酸化セリウムに酸化ジルコニウムが含まれるとＣＯ転化率がほぼ２倍に高まった。ジルコニウム酸化物の存在がＣＯ転化率に寄与しているのが分かる。実施例１の触媒のＸ線回折パターンを図６に示す。回折ピークは酸化セリウムと酸化ジルコニウムに帰属された。比較例２のＣＯ転化率は１.２％ にとどまった。これより、ＣＯ転化率を高めるには結晶性の高い酸化セリウムにジルコニウム酸化物を担持することが必要であることが分かる。比較例３のＣＯ転化率は、ほぼゼロであった。このことはジルコニウム酸化物そのものがシフト反応をするわけではなく、酸化セリウムのシフト反応を酸化ジルコニウムが高めていることを示している。 The CO conversion rates of Example 1 and Comparative Example 1 were 12.4 and 6.2%, respectively. When cerium oxide contained zirconium oxide, the CO conversion increased almost twice. It can be seen that the presence of zirconium oxide contributes to the CO conversion. The X-ray diffraction pattern of the catalyst of Example 1 is shown in FIG. The diffraction peaks were assigned to cerium oxide and zirconium oxide. The CO conversion of Comparative Example 2 was only 1.2%. This shows that it is necessary to support zirconium oxide on cerium oxide having high crystallinity in order to increase the CO conversion. The CO conversion of Comparative Example 3 was almost zero. This indicates that zirconium oxide itself does not undergo a shift reaction, but that zirconium oxide enhances the shift reaction of cerium oxide.
ディーゼルエンジンを含むリーンバーン車の排ガス浄化用窒素酸化物吸着・吸蔵機能一体化水素製造触媒，水素製造触媒に利用できる。 It can be used as a hydrogen production catalyst and hydrogen production catalyst with integrated nitrogen oxide adsorption and storage function for exhaust gas purification of lean burn vehicles including diesel engines.
１…エンジン、２…三元触媒又は酸化触媒、３…ＤＰＦ、４…窒素酸化物吸着・吸蔵機能触媒，水素製造触媒の一体型触媒、５…水素製造触媒、６…窒素酸化物吸着・吸蔵触媒。
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Three-way catalyst or oxidation catalyst, 3 ... DPF, 4 ... Nitrogen oxide adsorption / occlusion function catalyst, Integrated catalyst of hydrogen production catalyst, 5 ... Hydrogen production catalyst, 6 ... Nitrogen oxide adsorption / occlusion catalyst.
Claims (3)
前記触媒はセリウム酸化物とジルコニウム酸化物を含む担体と、前記担体上に担持されたＰｔ，Ｐｄ，Ｒｈの少なくともいずれかとを有し、
前記セリウム酸化物はＸ線回折パターンにおいて（１１１）面回折ピーク強度とバックグランドの比が４.３ 以上である酸化セリウムを含むことを特徴とする水素製造触媒。 A hydrogen production catalyst for producing hydrogen from carbon monoxide and water,
The catalyst has a support containing cerium oxide and zirconium oxide, and at least one of Pt, Pd, and Rh supported on the support,
The hydrogen production catalyst according to claim 1, wherein the cerium oxide contains cerium oxide having a ratio of (111) plane diffraction peak intensity to background of 4.3 or more in an X-ray diffraction pattern.
2. The hydrogen production catalyst according to claim 1, wherein the hydrogen production catalyst is provided on an exhaust gas flow path of an internal combustion engine, and is disposed upstream of a catalyst having a function of adsorbing or storing nitrogen oxides. A hydrogen production catalyst.
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| JP2010240533A (en) * | 2009-04-02 | 2010-10-28 | Honda Motor Co Ltd | Method of cleaning nitrogen oxide |
| DE102009048121A1 (en) * | 2009-10-02 | 2011-04-07 | Technische Universität Bergakademie Freiberg | Device for exhausting combustion gases e.g. carbon dioxide, in motor vehicle, has reduction converter system arranged in exhaust gas stream of combustion plant and provided with electrically polar crystals |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2001300262A (en) * | 2000-04-18 | 2001-10-30 | Toyota Motor Corp | Exhaust gas purifying device and catalyst for purifying exhaust gas |
| JP2005521617A (en) * | 2002-03-28 | 2005-07-21 | ユーティーシー フューエル セルズ，エルエルシー | Ceria-based mixed metal oxide structure, its preparation and use |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2001300262A (en) * | 2000-04-18 | 2001-10-30 | Toyota Motor Corp | Exhaust gas purifying device and catalyst for purifying exhaust gas |
| JP2005521617A (en) * | 2002-03-28 | 2005-07-21 | ユーティーシー フューエル セルズ，エルエルシー | Ceria-based mixed metal oxide structure, its preparation and use |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010240533A (en) * | 2009-04-02 | 2010-10-28 | Honda Motor Co Ltd | Method of cleaning nitrogen oxide |
| DE102009048121A1 (en) * | 2009-10-02 | 2011-04-07 | Technische Universität Bergakademie Freiberg | Device for exhausting combustion gases e.g. carbon dioxide, in motor vehicle, has reduction converter system arranged in exhaust gas stream of combustion plant and provided with electrically polar crystals |
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