JP4745271B2 - Nitrous oxide decomposition catalyst and treatment method of nitrous oxide-containing gas - Google Patents
Nitrous oxide decomposition catalyst and treatment method of nitrous oxide-containing gas Download PDFInfo
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- JP4745271B2 JP4745271B2 JP2007058248A JP2007058248A JP4745271B2 JP 4745271 B2 JP4745271 B2 JP 4745271B2 JP 2007058248 A JP2007058248 A JP 2007058248A JP 2007058248 A JP2007058248 A JP 2007058248A JP 4745271 B2 JP4745271 B2 JP 4745271B2
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- nitrous oxide
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- oxide
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- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 title claims description 182
- 239000003054 catalyst Substances 0.000 title claims description 120
- 239000001272 nitrous oxide Substances 0.000 title claims description 90
- 238000000034 method Methods 0.000 title claims description 48
- 238000000354 decomposition reaction Methods 0.000 title claims description 39
- 239000011148 porous material Substances 0.000 claims description 83
- 239000002994 raw material Substances 0.000 claims description 52
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 13
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 239000003638 chemical reducing agent Substances 0.000 claims description 4
- 238000001125 extrusion Methods 0.000 claims description 4
- 238000003672 processing method Methods 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 44
- 229910000480 nickel oxide Inorganic materials 0.000 description 42
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 28
- 239000000843 powder Substances 0.000 description 28
- 239000002131 composite material Substances 0.000 description 24
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 22
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 20
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 20
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- 238000000465 moulding Methods 0.000 description 14
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 12
- 229910017604 nitric acid Inorganic materials 0.000 description 12
- 239000002245 particle Substances 0.000 description 12
- 230000032683 aging Effects 0.000 description 11
- 230000000694 effects Effects 0.000 description 11
- 229910021529 ammonia Inorganic materials 0.000 description 10
- 229910000019 calcium carbonate Inorganic materials 0.000 description 10
- 150000001875 compounds Chemical class 0.000 description 10
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- 235000019698 starch Nutrition 0.000 description 5
- 238000003878 thermal aging Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
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- 239000005011 phenolic resin Substances 0.000 description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
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- 150000004679 hydroxides Chemical class 0.000 description 3
- 150000002816 nickel compounds Chemical class 0.000 description 3
- 150000002823 nitrates Chemical class 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
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- QQZMWMKOWKGPQY-UHFFFAOYSA-N cerium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QQZMWMKOWKGPQY-UHFFFAOYSA-N 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
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- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
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- 239000000395 magnesium oxide Substances 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
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- 239000000463 material Substances 0.000 description 2
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- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 2
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- IATRAKWUXMZMIY-UHFFFAOYSA-N strontium oxide Chemical compound [O-2].[Sr+2] IATRAKWUXMZMIY-UHFFFAOYSA-N 0.000 description 2
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- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
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- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
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- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical compound [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 description 1
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- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- 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
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Description
本発明は、亜酸化窒素分解用触媒および亜酸化窒素含有ガスの処理方法に関する。 The present invention relates to a nitrous oxide decomposition catalyst and a method for treating a nitrous oxide-containing gas.
燃焼排ガスや化学プラントなどから排出される各種産業排ガス中に含まれる亜酸化窒素（Ｎ２Ｏ）は、成層圏で分解して一酸化窒素を生成し、また高い温室効果を示すことから、その効率的な分解除去方法の開発が望まれている。例えば、アンモニアの接触酸化による硝酸製造プロセスにおいて亜酸化窒素が副生することが知られており、世界各地にある硝酸プラントから発生する亜酸化窒素を分解除去できれば地球温暖化の防止を促進することが可能となる。 Nitrous oxide (N 2 O) contained in various industrial exhaust gas discharged from combustion exhaust gas and chemical plants decomposes in the stratosphere to produce nitric oxide and shows high greenhouse effect. Development of an efficient decomposition and removal method is desired. For example, it is known that nitrous oxide is by-produced in the nitric acid production process by catalytic oxidation of ammonia, and if it can decompose and remove nitrous oxide generated from nitric acid plants in various parts of the world, it will promote prevention of global warming. Is possible.
そこで、亜酸化窒素を触媒に接触させて分解除去する方法として、酸化アルミニウムや酸化ジルコニウムのような担体にパラジウム、ニッケル、コバルトなどを担持した触媒を用いる方法（特許文献１）、疎水性アルミナにルテニウムおよび／またはロジウムと酸化ジルコニウムなどとを担持した触媒を用いる方法（特許文献２）、また、酸化ロジウムや酸化コバルトと、マンガン化合物と、アルカリまたはアルカリ土類金属化合物とを含有する触媒を用いる方法（特許文献３）などが提案されている。 Therefore, as a method for decomposing and removing nitrous oxide by contacting it with a catalyst, a method using a catalyst in which palladium, nickel, cobalt or the like is supported on a carrier such as aluminum oxide or zirconium oxide (Patent Document 1), or hydrophobic alumina. A method using a catalyst supporting ruthenium and / or rhodium and zirconium oxide (Patent Document 2), or using a catalyst containing rhodium oxide or cobalt oxide, a manganese compound, and an alkali or alkaline earth metal compound. A method (Patent Document 3) and the like have been proposed.
本発明の目的は、亜酸化窒素を効率よく分解除去し得る新規な亜酸化窒素分解用触媒、およびこの触媒に亜酸化窒素を含むガスを接触させて亜酸化窒素を効率よく分解除去する亜酸化窒素含有ガスの処理方法を提供することにある。 An object of the present invention is to provide a novel nitrous oxide decomposition catalyst capable of efficiently decomposing and removing nitrous oxide, and nitrous oxide for efficiently decomposing and removing nitrous oxide by contacting the catalyst with a gas containing nitrous oxide. It is providing the processing method of nitrogen-containing gas.
本発明者らは上記目的を達成すべく鋭意研究を進めた結果、以下に示すＡ成分、Ｂ成分およびＣ成分を含有し、しかも、全細孔容積と、０．３μｍ以上のポア径を有する細孔の容積との割合が特定の範囲にある、亜酸化窒素分解用触媒を用いることにより、上記目的を達成できることを見出し、本発明を完成するに至った。
Ａ成分：ＩＩＡ族元素から選ばれる少なくとも1種の元素
Ｂ成分：ＩＩＩＡ族元素から選ばれる少なくとも１種の元素
Ｃ成分：ニッケル
すなわち、本発明の亜酸化窒素分解用触媒は、Ａ成分としてＩＩＡ族元素から選ばれる少なくとも1種、Ｂ成分としてＩＩＩＡ族族元素から選ばれる少なくとも１種、また、Ｃ成分としてニッケルを含有し、０．３μｍ以上のポア径を有する細孔の容積が全細孔容積の５％以上を占めるものである。また、本発明の亜酸化窒素分解用触媒は、Ａ成分としてＩＩＡ族元素から選ばれる少なくとも1種、Ｂ成分としてＩＩＩＡ族元素から選ばれる少なくとも１種、また、Ｃ成分としてニッケルを含有する触媒組成物をハニカム状に押出成形して得られるハニカム状触媒であって、０．３μｍ以上のポア径を有する細孔の容積が全細孔容積の５％以上を占めるものである。
As a result of diligent research to achieve the above object, the inventors of the present invention contain the following A component, B component and C component, and have a total pore volume and a pore diameter of 0.3 μm or more. The inventors have found that the above object can be achieved by using a nitrous oxide decomposition catalyst having a ratio to the pore volume in a specific range, and have completed the present invention.
Component A: At least one element selected from Group IIA elements Component B: At least one element selected from Group IIIA elements Component C: Nickel
That is, the nitrous oxide decomposition catalyst of the present invention contains at least one selected from Group IIA elements as the A component, at least one selected from Group IIIA elements as the B component, and nickel as the C component, The volume of pores having a pore diameter of 0.3 μm or more occupies 5% or more of the total pore volume. The nitrous oxide decomposition catalyst of the present invention is a catalyst composition containing at least one selected from Group IIA elements as the A component, at least one selected from Group IIIA elements as the B component, and nickel as the C component. A honeycomb catalyst obtained by extruding a product into a honeycomb shape, wherein the pore volume having a pore diameter of 0.3 μm or more occupies 5% or more of the total pore volume.
本発明の亜酸化窒素含有ガスの処理方法は、上記亜酸化窒素分解用触媒を用いて亜酸化窒素含有ガスを処理することからなるものである。 The method for treating a nitrous oxide-containing gas according to the present invention comprises treating the nitrous oxide-containing gas using the above nitrous oxide decomposition catalyst.
本発明の亜酸化窒素分解用触媒は、高性能であって、亜酸化窒素を高い除去率をもって分解除去することができる。したがって、本発明の亜酸化窒素分解用触媒を用いることにより、亜酸化窒素含有ガスを効率よく浄化することができる。 The nitrous oxide decomposition catalyst of the present invention has high performance and can decompose and remove nitrous oxide with a high removal rate. Therefore, the nitrous oxide-containing gas can be efficiently purified by using the nitrous oxide decomposition catalyst of the present invention.
また、本発明の亜酸化窒素分解用触媒は、貴金属などの高価な金属成分を用いた従来の亜酸化窒素分解用触媒に匹敵する高い亜酸化窒素分解性能を示す。 Further, the nitrous oxide decomposition catalyst of the present invention exhibits high nitrous oxide decomposition performance comparable to conventional nitrous oxide decomposition catalysts using expensive metal components such as noble metals.
また、本発明の亜酸化窒素分解用触媒は、２５０〜９００℃の比較的低い温度範囲において、高い亜酸化窒素分解性能を示す。 Further, the nitrous oxide decomposition catalyst of the present invention exhibits high nitrous oxide decomposition performance in a relatively low temperature range of 250 to 900 ° C.
さらに、本発明の亜酸化窒素分解用触媒は、貴金属などの高価な金属成分を用いないので、安価である。 Furthermore, the nitrous oxide decomposition catalyst of the present invention is inexpensive because it does not use expensive metal components such as noble metals.
本発明の亜酸化窒素分解用触媒は、ハニカム状触媒として使用するときに、上記性能を特に効果的に発揮する。 The nitrous oxide decomposition catalyst of the present invention exhibits the above performance particularly effectively when used as a honeycomb catalyst.
本発明の亜酸化窒素分解用触媒（以下、単に「触媒」ということもある。）を構成するＡ成分は、ＩＩＡ族元素から選ばれる少なくとも１種、好ましくはＭｇ、Ｃａ、ＳｒおよびＢａから選ばれる少なくとも１種、より好ましくはＭｇおよびＣａから選ばれる少なくとも１種である。これら金属元素の形態は、特に限定されるものではないが、酸化物、炭酸塩、硫酸塩などである。Ａ成分は、その作用効果の一つとして、触媒の耐熱性を向上させる機能を有する。 The component A constituting the nitrous oxide decomposition catalyst of the present invention (hereinafter sometimes simply referred to as “catalyst”) is at least one selected from Group IIA elements, preferably selected from Mg, Ca, Sr and Ba. And at least one selected from Mg and Ca. The form of these metal elements is not particularly limited, and examples thereof include oxides, carbonates, sulfates and the like. A component has the function to improve the heat resistance of a catalyst as one of the effects.
Ａ成分の具体例としては、酸化マグネシウム、炭酸マグネシウム、硫酸マグネシウム、酸化カルシウム、炭酸カルシウム、硫酸カルシウム、酸化ストロンチウム、炭酸ストロンチウム、硫酸ストロンチウム、酸化バリウム、炭酸バリウム、硫酸バリウムなどが挙げられる。これらのうち、酸化マグネシウム、酸化カルシウムおよび炭酸カルシウムが好ましく、なかでも炭酸カルシウムは触媒の耐熱性改善に効果が高いため特に好ましい。炭酸カルシウムは、熱に対して比較的安定であり、６００℃程度の比較的低温の反応条件で使用する場合は、触媒中に炭酸カルシウムの形態で存在する。 Specific examples of the component A include magnesium oxide, magnesium carbonate, magnesium sulfate, calcium oxide, calcium carbonate, calcium sulfate, strontium oxide, strontium carbonate, strontium sulfate, barium oxide, barium carbonate, and barium sulfate. Of these, magnesium oxide, calcium oxide and calcium carbonate are preferable, and calcium carbonate is particularly preferable because it is highly effective in improving the heat resistance of the catalyst. Calcium carbonate is relatively stable to heat and is present in the form of calcium carbonate in the catalyst when used under relatively low temperature reaction conditions of about 600 ° C.
Ａ成分の原料としては、触媒調製工程において、上記形態を形成し得るものであればいずれでもよく、各元素の硝酸塩、塩化物、水酸化物、酢酸塩などを用いることができる。例えば、硝酸塩や塩化物を加水分解して水酸化物を経たり、あるいは、そのまま添加して触媒調製工程で熱処理により酸化物となるものを用いてもよい。さらに、前駆体として触媒調製時に存在せしめ、触媒の使用環境において、例えば、酸化物となる化合物もＡ成分の原料として用いることができる。 The raw material for the component A may be any material that can form the above-mentioned form in the catalyst preparation step, and nitrates, chlorides, hydroxides, acetates, and the like of each element can be used. For example, nitrates and chlorides may be hydrolyzed to form hydroxides, or added as they are and converted to oxides by heat treatment in the catalyst preparation step. Further, a compound which is present as a precursor at the time of catalyst preparation and becomes an oxide in the environment where the catalyst is used can also be used as a raw material for the component A, for example.
Ａ成分の含有量は、各元素の酸化物基準で、亜酸化窒素分解用触媒の１０〜９０質量％、好ましくは５０〜８０質量％である。１０質量％未満では、耐熱性改善効果が十分でなく、一方、９０質量％を超えると、Ｃ成分である酸化ニッケルの含有率が低下して高い亜酸化窒素分解効率が得られ難くなる。 Content of A component is 10-90 mass% of the catalyst for nitrous oxide decomposition | disassembly with respect to the oxide of each element, Preferably it is 50-80 mass%. If it is less than 10% by mass, the effect of improving heat resistance is not sufficient. On the other hand, if it exceeds 90% by mass, the content of nickel oxide, which is the C component, is reduced and it is difficult to obtain high nitrous oxide decomposition efficiency.
Ｂ成分は、ＩＩＩＡ族元素から選ばれる少なくとも１種、好ましくはＹやＬａ、Ｃｅ、Ｎｄなどのランタノイド元素から選ばれる少なくとも１種、より好ましくはＹ、ＣｅおよびＬａから選ばれる少なくとも１種である。これら金属元素の形態は、特に限定されるものではないが、酸化物であるのが好ましい。Ｂ成分は、その作用効果と一つとして、Ｃ成分である酸化ニッケルの粒子成長を抑制する機能を有している。 The component B is at least one selected from Group IIIA elements, preferably at least one selected from lanthanoid elements such as Y, La, Ce, and Nd, more preferably at least one selected from Y, Ce, and La. . The form of these metal elements is not particularly limited, but is preferably an oxide. The B component has a function of suppressing particle growth of nickel oxide, which is the C component, as one of its effects.
Ｂ成分の具体例としては、酸化イットリウム、酸化セリウムおよび酸化ランタンを挙げることができる。
Specific examples of the component B, mention may be made of yttrium oxide, cerium oxide and lanthanum oxide.
Ｂ成分の原料としては、各元素の酸化物以外に、炭酸塩、水酸化物、塩化物、硝酸塩、硫酸塩、酢酸塩や、ゾル状物などの酸化物の前駆体など、触媒調製工程において、酸化物となり得るものであればいずれも使用することができる。 In addition to the oxides of each element, the raw materials for component B include carbonates, hydroxides, chlorides, nitrates, sulfates, acetates, precursors of oxides such as sols, and the like in catalyst preparation processes. Any oxide can be used as long as it can be an oxide.
Ｂ成分の含有量は、各元素の酸化物基準で、亜酸化窒素分解用触媒の０．１〜３０質量％、好ましくは０．５〜２０質量％である。含有量が０．１質量％未満では、酸化ニッケルの粒子成長抑制効果が十分得られなくなる。また、３０質量％を超えても、添加による効果はそれ以上得られない。 Content of B component is 0.1-30 mass% of the catalyst for nitrous oxide decomposition | disassembly with respect to the oxide of each element, Preferably it is 0.5-20 mass%. When the content is less than 0.1% by mass, the particle growth suppressing effect of nickel oxide cannot be obtained sufficiently. Moreover, even if it exceeds 30 mass%, the effect by addition will not be acquired any more.
Ｃ成分は、ニッケルであり、具体的には、酸化ニッケルである。酸化ニッケルはＮｉＯであるが、ＮｉＯの機能を損なわない範囲で、Ｎｉ３Ｏ４、ＮｉＯ２やその他のニッケル酸化物が含まれていてもよい。さらに、酸化ニッケルは、他の金属酸化物との混合物として存在しても、あるいは、他の金属と固溶体または複合酸化物を形成してもよい。 The C component is nickel, specifically nickel oxide. Nickel oxide is NiO, but Ni 3 O 4 , NiO 2 and other nickel oxides may be included as long as the function of NiO is not impaired. Furthermore, nickel oxide may exist as a mixture with other metal oxides, or may form a solid solution or composite oxide with other metals.
Ｃ成分の原料としては、酸化ニッケルのほかに、触媒調製工程において、酸化ニッケルとなり得るものであればいずれも用いることができる。例えば、硝酸ニッケル、塩化ニッケル、水酸化ニッケル、酢酸ニッケル、炭酸ニッケルなどを用いることができる。 As the raw material for the component C, any material can be used in addition to nickel oxide as long as it can be nickel oxide in the catalyst preparation step. For example, nickel nitrate, nickel chloride, nickel hydroxide, nickel acetate, nickel carbonate, or the like can be used.
Ｃ成分の含有量は、酸化ニッケルとして、亜酸化窒素分解用触媒の１０〜９０質量％、好ましくは２０〜５０質量％である。１０質量％未満では、触媒の単位容積当りの性能が低くなり、所定の処理性能を得るためには、触媒の使用量が多くなって好ましくない。また、９０質量％を超えると、Ａ成分の含有量が少なくなり耐熱性改善の効果が十分得られなくなる。 Content of C component is 10-90 mass% of the catalyst for nitrous oxide decomposition | disassembly as nickel oxide, Preferably it is 20-50 mass%. If the amount is less than 10% by mass, the performance per unit volume of the catalyst is lowered, and in order to obtain a predetermined treatment performance, the amount of the catalyst used is increased, which is not preferable. Moreover, when it exceeds 90 mass%, content of A component will decrease and the effect of heat resistance improvement will not fully be acquired.
本発明の触媒におけるＡ成分、Ｂ成分およびＣ成分の含有量は、上述のとおり、Ａ成分：Ｂ成分：Ｃ成分＝１０〜９０％：０．１〜３０％：１０〜９０％（質量）（合計１００％）である。 Content of A component, B component, and C component in the catalyst of this invention is as above-mentioned, A component: B component: C component = 10-90%: 0.1-30%: 10-90% (mass) (100% in total).
本発明の触媒は、上記のＡ成分、Ｂ成分およびＣ成分を含有し、０．３μｍ以上のポア径を有する細孔の容積（以下、「０．３μｍ以上のポア径細孔容積」ということもある。）が全細孔容積の５％以上を占めるものである。０．３μｍ以上のポア径細孔容積の全細孔容積に対する割合は、５〜５０％であるのが好ましく、より好ましくは１０〜４０％である。上記割合が５％未満では、亜酸化窒素の触媒内部へのガス拡散が律速となり十分な亜酸化窒素の分解性能が得られにくくなる。また、５０％を超えても、それに見合う性能の向上はなく、かえってミクロポアの比率が小さくなることで比表面積の低下などを招くことになる。本発明の触媒の全細孔容積は、０．１〜０．６ｃｃ／ｇであることが好ましく、より好ましくは０．２〜０．４ｃｃ／ｇである。全細孔容積が０．１ｃｃ／ｇ未満では、触媒内部へのガス拡散が促進されず、亜酸化窒素の分解効率が低くなり、また、０．６ｃｃ／ｇを超えると、触媒の機械的強度の低下を招く。 The catalyst of the present invention contains the above-mentioned A component, B component and C component, and has a pore volume having a pore diameter of 0.3 μm or more (hereinafter referred to as “pore diameter pore volume of 0.3 μm or more”). May account for 5% or more of the total pore volume. The ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume is preferably 5 to 50%, more preferably 10 to 40%. When the ratio is less than 5%, gas diffusion of nitrous oxide into the catalyst is rate-determined, making it difficult to obtain sufficient nitrous oxide decomposition performance. Moreover, even if it exceeds 50%, there is no improvement in performance commensurate with it, and on the contrary, the ratio of micropores becomes small, leading to a decrease in specific surface area and the like. The total pore volume of the catalyst of the present invention is preferably 0.1 to 0.6 cc / g, more preferably 0.2 to 0.4 cc / g. If the total pore volume is less than 0.1 cc / g, gas diffusion into the catalyst will not be promoted, and the decomposition efficiency of nitrous oxide will be low. If it exceeds 0.6 cc / g, the mechanical strength of the catalyst will be reduced. Cause a decline.
本発明の０．３μｍ以上のポア径細孔容積および全細孔容積は、オートポア９４２０−ＩＩＩ（マイクロメリティクス社製）を用い水銀圧入法により測定した。 The pore diameter pore volume of 0.3 μm or more and the total pore volume of the present invention were measured by mercury porosimetry using Autopore 9420-III (manufactured by Micromeritics).
Ａ成分、Ｂ成分およびＣ成分を含む触媒組成物からなる本発明の触媒は、基本的に、次の方法によって調製することができる。 The catalyst of the present invention comprising a catalyst composition containing an A component, a B component and a C component can be basically prepared by the following method.
Ａ成分、Ｂ成分およびＣ成分の各元素を含む粉末状の原料化合物と適量の水と成形助剤などとを十分に混合し、所望形状に成形した後、乾燥し、３００〜９００℃、好ましくは４００〜７００℃の範囲で焼成する。この際、原料化合物の一部、例えば、Ｂ成分および／またはＣ成分について、その原料化合物を水に溶解したものを混合して所望の形状に成形し、上記と同様に乾燥、焼成することによって調製してもよい。
前述のとおり、Ｂ成分は、Ｃ成分である酸化ニッケルの粒子成長を抑制する効果を有していることから、酸化ニッケルの近傍に存在させることが好ましい。したがって、Ｂ成分原料およびＣ成分原料を実質的に均一に混合するか、あるいは、両者の固溶体を作成した後に、Ａ成分原料と混合し、上記の方法と同様にして、所望の形状に成形し、乾燥して、３００〜７００℃、好ましくは４００〜６００℃の範囲で焼成して調製するのが好ましい。
A powdery raw material compound containing each element of the A component, the B component and the C component, an appropriate amount of water, a molding aid and the like are sufficiently mixed, molded into a desired shape, dried, and 300 to 900 ° C., preferably Is fired in the range of 400 to 700 ° C. At this time, by mixing a part of the raw material compound, for example, the B component and / or C component, with the raw material compound dissolved in water to form a desired shape, and drying and firing in the same manner as described above It may be prepared.
As described above, the B component is preferably present in the vicinity of nickel oxide because it has the effect of suppressing particle growth of nickel oxide, which is the C component. Therefore, the B component raw material and the C component raw material are mixed substantially uniformly, or after preparing a solid solution of both, it is mixed with the A component raw material and molded into a desired shape in the same manner as described above. It is preferably prepared by drying and baking at 300 to 700 ° C, preferably 400 to 600 ° C.
上記のように、Ｂ成分原料とＣ成分原料とを、予め均一混合物や固溶体などとして複合させるのが好ましいが、このような複合粉末の調製方法には特に制限はなく、一般に用いられている、物理混合法、含浸担持法、それに、噴霧熱分解法、共沈法、均一沈殿法、表面析出法、ゾルゲル法や固相反応法などを用いることができる。具体的には、以下の方法が例示される。
（１）Ｂ成分原料およびＣ成分原料を共に粉末状で十分混合し、７００〜１０００℃で焼成して複合粉末を調製する。
（２）Ｂ成分原料またはＣ成分原料のどちらか一方を溶液として混合し、４００〜８００℃で焼成して複合粉末を調製する。
（３）Ｂ成分原料およびＣ成分原料のどちらも溶液として混合し、アルカリの添加などによる加水分解反応によって共沈させ、ろ過洗浄した後、４００〜８００℃で焼成し複合粉末を調製する。
As described above, it is preferable to combine the B component raw material and the C component raw material in advance as a uniform mixture or solid solution, but there is no particular limitation on the method for preparing such a composite powder, which is generally used. A physical mixing method, an impregnation supporting method, a spray pyrolysis method, a coprecipitation method, a uniform precipitation method, a surface precipitation method, a sol-gel method, a solid phase reaction method, and the like can be used. Specifically, the following method is exemplified.
(1) Both the B component raw material and the C component raw material are sufficiently mixed in powder form and fired at 700 to 1000 ° C. to prepare a composite powder.
(2) Either a B component raw material or a C component raw material is mixed as a solution and fired at 400 to 800 ° C. to prepare a composite powder.
(3) Both the B component raw material and the C component raw material are mixed as a solution, coprecipitated by a hydrolysis reaction such as addition of alkali, filtered and washed, and then fired at 400 to 800 ° C. to prepare a composite powder.
これらのなかでも、方法（２）および方法（３）が好適に用いられる。Ｂ成分の原料としては、各元素の酸化物、水酸化物、炭酸塩などの固体粉末として添加するより、塩化物、硝酸塩、酢酸塩などの水溶性塩やゾル状物を用いてＣ成分と複合せしめて均一混合物や複合酸化物、あるいは固溶体を形成させるのがよい。 Among these, the method (2) and the method (3) are preferably used. As a raw material for the B component, a water-soluble salt such as chloride, nitrate, acetate, or a sol is used instead of adding as a solid powder such as an oxide, hydroxide, or carbonate of each element. It is preferable to form a uniform mixture, a complex oxide, or a solid solution by compounding.
上記方法（２）および方法（３）において、焼成温度は４００〜８００℃が好ましく、より好ましくは５００〜７００℃である。焼成温度が４００℃未満では、粒子成長抑制効果が得られにくくなり、一方、焼成温度が８００℃を超えると、得られる複合粉末の比表面積が小さくなり好ましくない。 In the said method (2) and method (3), 400-800 degreeC is preferable and baking temperature is 500-700 degreeC more preferably. When the firing temperature is less than 400 ° C., it is difficult to obtain the effect of suppressing particle growth. On the other hand, when the firing temperature exceeds 800 ° C., the specific surface area of the resulting composite powder is undesirably small.
そして、本発明のＡ成分、Ｂ成分およびＣ成分を含み、０．３μｍ以上のポア径細孔容積が全細孔容積の５％以上を占める触媒の調製方法については、例えば、次の方法が挙げられる。
（ａ）ポア形成剤として、触媒の成形、焼成の際に揮発、分解する有機高分子化合物、活性炭、無機塩類などを添加、混合する。
（ｂ）各原料粉体の粒子径や粒度分布の異なるものを組み合わせる。
（ｃ）原料粉体の少なくとも一部を、金属炭酸塩や金属水酸化物などの、触媒の成形、焼成の際に揮発、分解して、ポアを形成し得る化合物の形態で添加する。
And about the preparation method of the catalyst which contains A component, B component, and C component of this invention, and the pore diameter pore volume of 0.3 micrometer or more occupies 5% or more of the total pore volume, the following method is, for example Can be mentioned.
(A) As a pore forming agent, an organic polymer compound, activated carbon, inorganic salts, etc. that volatilize and decompose during the molding and firing of the catalyst are added and mixed.
(B) Combining raw material powders having different particle sizes and particle size distributions.
(C) At least a part of the raw material powder is added in the form of a compound, such as a metal carbonate or metal hydroxide, which volatilizes and decomposes during formation and firing of the catalyst to form pores.
上記方法（ａ）で用いる有機高分子化合物については、ポアの形成に一般に用いられている有機高分子化合物であればいずれも使用することができる。その代表例としては、ポリエチレン樹脂、アクリル樹脂、フェノール樹脂、結晶性セルロースなどを挙げることができる。また、無機塩類についても同様であり、その代表例としては、硝酸アンモニウム、シュウ酸アンモニウム、炭酸アンモニウムなどを挙げることができる。これらの添加量は、全細孔容積や、全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合を考慮して適宜決定することができる。具体的には、例えば、２〜１０質量％（全成分原料の質量基準）の範囲の量を添加すればよい。 As the organic polymer compound used in the method (a), any organic polymer compound generally used for pore formation can be used. Typical examples include polyethylene resin, acrylic resin, phenol resin, crystalline cellulose and the like. The same applies to inorganic salts, and typical examples thereof include ammonium nitrate, ammonium oxalate, and ammonium carbonate. These addition amounts can be appropriately determined in consideration of the total pore volume and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume. Specifically, for example, an amount in the range of 2 to 10% by mass (based on the mass of all component raw materials) may be added.
上記方法（ｂ）で用いる原料粉体としては、平均粒子径が０．１〜３０μｍの範囲のものを使用することができる。 As a raw material powder used by the said method (b), the thing of the range whose average particle diameter is 0.1-30 micrometers can be used.
また、上記方法（ｃ）において、例えば、Ｃ成分原料の少なくとも一部として、炭酸ニッケルや水酸化ニッケルなどの、成形、焼成の際に分解して、ポアを形成し得るニッケル化合物を用いることにより、０．３μｍ以上のポアを形成することができる。前述のとおり、Ｂ成分とＣ成分とを予め均一混合物、複合酸化物や固溶体として複合するのが好ましい。したがって、Ｃ成分原料の一部をポア形成剤として添加する場合は、先ず最初に、全Ｃ成分原料の添加量の一部、例えば、Ｃ成分の５０〜９０質量％となる量のＣ成分原料とＢ成分原料とから複合体を調製し、この複合体と、Ａ成分原料、それに、残余のＣ成分原料、例えば、Ｃ成分の１０〜５０質量％となる量のＣ成分原料とを混合する際に、この残余のＣ成分原料として、その後の成形、焼成の際にポアを形成し得る、炭酸ニッケルや水酸化ニッケルを用いることにより、Ｂ成分とＣ成分との複合化とミクロポアの形成とを同時に行うことができ、より性能の高い触媒を得ることができる。同様に、Ｂ成分原料の少なくとも一部として炭酸セリウムや水酸化セリウムなどを添加してもよい。 In the method (c), for example, by using a nickel compound such as nickel carbonate or nickel hydroxide that can be decomposed during forming and firing to form pores as at least part of the C component raw material. , Pores of 0.3 μm or more can be formed. As described above, the B component and the C component are preferably combined in advance as a uniform mixture, composite oxide, or solid solution. Therefore, when a part of the C component raw material is added as a pore forming agent, first, a part of the total amount of the C component raw material, for example, an amount of the C component raw material that is 50 to 90 mass% of the C component And a B component raw material are prepared, and this composite is mixed with the A component raw material and the remaining C component raw material, for example, C component raw material in an amount of 10 to 50% by mass of the C component. At this time, as the remaining C component raw material, by using nickel carbonate or nickel hydroxide, which can form pores in subsequent molding and firing, the B component and C component can be combined and micropores can be formed. Can be performed simultaneously, and a catalyst with higher performance can be obtained. Similarly, cerium carbonate, cerium hydroxide, or the like may be added as at least part of the B component raw material.
上記方法（ａ）〜方法（ｃ）は適宜組み合わせて実施することができる。例えば、方法（ａ）と方法（ｃ）とを組み合わせることができる。 The above methods (a) to (c) can be carried out in appropriate combinations. For example, method (a) and method (c) can be combined.
上記のＡ成分、Ｂ成分およびＣ成分を含む、本発明の触媒のなかでも、亜酸化窒素含有ガスを処理する際の温度範囲での熱履歴を経た後も、Ｃ成分である酸化ニッケル（ＮｉＯ）の結晶粒子の凝集が少ない、すなわち、酸化ニッケル（ＮｉＯ）の結晶子径が小さいものが、亜酸化窒素の分解性能などの点から好ましい。 Among the catalysts of the present invention containing the above A component, B component and C component, nickel oxide (NiO) which is the C component even after passing through a thermal history in the temperature range when processing the nitrous oxide-containing gas. ) Is preferable in view of the decomposition performance of nitrous oxide and the like.
本発明の触媒における上記酸化ニッケル結晶粒子の凝集は、Ｂ成分原料とＣ成分原料とを、予め均一混合物や固溶体などとして複合させて得られる複合粉末に関し、特定の熱エージング処理を行った後の酸化ニッケルの結晶子径を測定することによって評価することができる。本発明の触媒においては、上記Ｂ成分とＣ成分とからなる複合粉末に関し、これを６００℃で４８時間熱エージング処理した後の酸化ニッケルの結晶子径が５０ｎｍ以下であるものが好ましい。この熱エージング処理後の酸化ニッケルの結晶子径が４０ｎｍ以下のものがより好ましい。 The agglomeration of the nickel oxide crystal particles in the catalyst of the present invention relates to a composite powder obtained by combining the B component raw material and the C component raw material in advance as a uniform mixture or solid solution, etc., after performing a specific heat aging treatment. It can be evaluated by measuring the crystallite diameter of nickel oxide. In the catalyst of the present invention, the composite powder composed of the B component and the C component is preferably one having a crystallite diameter of nickel oxide of 50 nm or less after heat aging treatment at 600 ° C. for 48 hours. More preferably, the crystallite diameter of nickel oxide after the thermal aging treatment is 40 nm or less.
上記「６００℃で４８時間熱エージング処理」とは、サンプルを電気炉内に置き、空気雰囲気下、６００℃で４８時間のエージング処理に供することを意味する。エージング処理後、サンプルを取り出し、粉末Ｘ線回折分析を行い、回折パターンから、酸化ニッケル（ＮｉＯ）の結晶子径をシェラー（ｓｃｈｅｒｒｅｒ）の式にしたがって求める。 The above-mentioned “thermal aging treatment at 600 ° C. for 48 hours” means that the sample is placed in an electric furnace and subjected to an aging treatment at 600 ° C. for 48 hours in an air atmosphere. After the aging treatment, a sample is taken out, powder X-ray diffraction analysis is performed, and the crystallite diameter of nickel oxide (NiO) is obtained from the diffraction pattern in accordance with Scherrer's formula.
上記熱エージング処理後の酸化ニッケルの結晶子径が５０ｎｍ以下となる触媒は、例えば、Ｂ成分とＣ成分との割合（酸化物の質量基準）を１／９９〜５０／５０とすることにより得られる。したがって、本発明の触媒において、Ｂ成分／Ｃ成分の質量比（酸化物換算）は、好ましくは１／９９〜５０／５０であり、より好ましくは１０／９０〜３０／７０である。Ｂ成分の割合が少ないと、使用条件下において酸化ニッケルの粒子成長を招き、その結果、触媒性能が低下しやすくなる。また、Ｂ成分の割合が多いと、Ａ成分やＣ成分の含有比率が低下するため、本発明の効果が得られ難くなる。 The catalyst in which the crystallite diameter of nickel oxide after the heat aging treatment is 50 nm or less is obtained, for example, by setting the ratio of the B component and the C component (mass basis of oxide) to 1/99 to 50/50. It is done. Therefore, in the catalyst of the present invention, the mass ratio of B component / C component (as oxide) is preferably 1/99 to 50/50, more preferably 10/90 to 30/70. When the ratio of the B component is small, nickel oxide particle growth is caused under the use conditions, and as a result, the catalyst performance tends to deteriorate. On the other hand, when the proportion of the B component is large, the content ratio of the A component and the C component is reduced, so that the effect of the present invention is hardly obtained.
本発明の触媒の形状については特に制限はなく、円柱状、円筒状（ペレット状）、リング状、球状、板状、ハニカム状、その他一体に成形されたものなど適宜選択することができる。この触媒の成形は、一般的な成形方法、例えば、打錠成形法、押出成形法などによって行うことができる。球状触媒の場合、その平均粒径は、通常、１〜１０ｍｍである。なお、上記ハニカム状のなかには、コルゲート状などの形態も含まれる。 The shape of the catalyst of the present invention is not particularly limited, and can be appropriately selected from a columnar shape, a cylindrical shape (pellet shape), a ring shape, a spherical shape, a plate shape, a honeycomb shape, and other integrally formed shapes. The catalyst can be molded by a general molding method such as a tableting molding method or an extrusion molding method. In the case of a spherical catalyst, the average particle diameter is usually 1 to 10 mm. The honeycomb shape includes a corrugated shape and the like.
また、本発明の触媒は、上記のような形状から適宜選択した所定の形状を有する担体の上に担持して、使用してもよい。この担体としては、この種の触媒の調製に一般に用いられている、例えば、シリカ、アルミナ、ジルコニア、チタニアなどのほかに、Ｓｉ、Ｔｉ、Ｚｒなどの２種以上からなる複合酸化物などを使用することができる。 The catalyst of the present invention may be used by being supported on a carrier having a predetermined shape appropriately selected from the above shapes. As this support, for example, in addition to silica, alumina, zirconia, titania and the like, which are generally used for the preparation of this type of catalyst, composite oxides composed of two or more of Si, Ti, Zr, etc. are used. can do.
本発明の触媒は、幾何学的表面積が大きく、圧力損失の低い、ハニカム状触媒として用いるのが好ましい。このハニカム状触媒は、押出成形法やシート状素子を巻き固める方法など一般によく知られている方法に従って製造することができる。ガス通過口（セル形状）の形は６角形、４角形、３角形またはコルゲーション形のいずれであってもよい。 The catalyst of the present invention is preferably used as a honeycomb catalyst having a large geometric surface area and low pressure loss. This honeycomb-shaped catalyst can be manufactured according to a generally well-known method such as an extrusion molding method or a method of winding and solidifying a sheet-like element. The shape of the gas passage port (cell shape) may be any of a hexagon, a quadrangle, a triangle, and a corrugation.
ハニカム状触媒の断面の開口率、目開きなどについては特に制限はなく、ハニカム状触媒に一般に用いられている開口率、目開き（セルの直径）などから適宜決定することができる。具体的には、例えば、断面の開口率は６０〜９０％とすることが好ましい。６０％以上とすることにより、圧力損失を低下できる。しかし、９０％を超えるとセル壁厚が非常に薄くなり強度が低下して実用的でなくなる。セルを隔てる隔壁の厚みは０．２〜０．８ｍｍであることが好ましい。この厚みが０．２ｍｍ未満では強度が低下し、一方、０．８ｍｍを超えると圧力損失が増加する。目開きは１．５〜５ｍｍであるのが好ましい。また、セル密度（セル数／単位断面）は２５〜３００セル／平方インチ（×２．５ｃｍ）であるのが好ましい。 There are no particular limitations on the aperture ratio, aperture, etc. of the cross section of the honeycomb catalyst, and it can be appropriately determined from the aperture ratio, aperture (cell diameter) and the like generally used for honeycomb catalysts. Specifically, for example, the opening ratio of the cross section is preferably 60 to 90%. By setting it to 60% or more, the pressure loss can be reduced. However, if it exceeds 90%, the cell wall thickness becomes very thin and the strength is lowered, making it impractical. The partition walls separating the cells preferably have a thickness of 0.2 to 0.8 mm. If this thickness is less than 0.2 mm, the strength decreases, while if it exceeds 0.8 mm, the pressure loss increases. The opening is preferably 1.5 to 5 mm. The cell density (number of cells / unit cross section) is preferably 25 to 300 cells / in 2 (× 2.5 cm).
上述のように、本発明の触媒のなかでも、Ａ成分、Ｂ成分およびＣ成分を含有し、０．３μｍ以上のポア径細孔容積が全細孔容積の５％以上であるハニカム状触媒が好適に用いられ、特に押出成形法により得られるハニカム状触媒が好適である。 As described above, among the catalysts of the present invention, there is a honeycomb catalyst containing the A component, the B component, and the C component and having a pore diameter pore volume of 0.3 μm or more of 5% or more of the total pore volume. A honeycomb-shaped catalyst which is preferably used and obtained by an extrusion method is particularly preferable.
上記ハニカム状触媒の好適な製造方法を述べると次のとおりである。
（Ｉ） 先ず、Ｂ成分原料とＣ成分原料とから、前述のように予め均一混合物や固溶体を形成し、Ｂ成分とＣ成分との複合粉末を得る。次に、この複合粉末とＡ成分原料とを、ポア形成剤としての、ポリエチレン樹脂、アクリル樹脂、フェノール樹脂、結晶性セルロースなどの有機高分子化合物等とともに、有機バインダーなどの成形助剤と適量の水などと十分に混合し、押出成形機でハニカム状に成形した後、５０〜１２０℃で乾燥し、３００〜７００℃、好ましくは４００〜６００℃で１〜１０時間、好ましくは２〜６時間焼成する。上記有機高分子化合物のほかに、押出成形機でハニカム状に成形した後、３００〜７００℃で焼成する際に、ポアを形成し得るものであればいずれも使用することができる。上記ポア形成剤の添加量は、上述のとおり、２〜１０質量％（全成分原料の質量基準）の範囲から適宜決定すればよい。
（ＩＩ） 上記方法（Ｉ）において、ポア形成剤の代わりに、Ｂ成分原料またはＣ成分原料の一部を、成形、焼成の際に分解して、ポアを形成し得る水酸化物や炭酸塩の形態で添加してもよい。特に、Ｃ成分原料として、水酸化ニッケルや炭酸ニッケルを添加するのが好ましい。この場合、Ｂ成分とＣ成分とからなる複合粉末中のＣ成分含量は、完成触媒の全Ｃ成分含量の５０〜９０質量％、好ましくは７０〜９０質量％とするのがよい。上記Ｃ成分含量が５０質量％未満では触媒の耐久性の低下を招く可能性がある。次に、上記複合粉末と、Ａ成分原料と、残余のＣ成分原料とを、有機バインダーなどの成形助剤と適量の水などと十分に混合し、押出成形機でハニカム状に成形した後、５０〜１２０℃で乾燥し、３００〜７００℃、好ましくは４００〜６００℃で１〜１０時間、好ましくは２〜６時間焼成する。この際、上記残余のＣ成分原料としては、押出成形機でハニカム状に成形した後、３００〜７００℃で焼成する際に、ポアを形成し得る水酸化ニッケルや炭酸ニッケルのようなニッケル化合物を用いる。なお、複合粉末を調製する際に用いるＣ成分原料とその後に用いる残余のＣ成分原料とは同一でも、異なっていてもよいが、残余のＣ成分原料としては、成形機でハニカム状に成形した後、３００〜７００℃で焼成する際にポアを形成し得る水酸化ニッケルや炭酸ニッケルのようなニッケル化合物を用いることが必要である。
A preferred method for producing the honeycomb catalyst will be described as follows.
(I) First, as described above, a uniform mixture or a solid solution is formed from the B component raw material and the C component raw material to obtain a composite powder of the B component and the C component. Next, the composite powder and component A raw material are combined with an organic polymer compound such as polyethylene resin, acrylic resin, phenol resin, and crystalline cellulose as a pore forming agent, and a molding aid such as an organic binder and an appropriate amount. After thoroughly mixing with water, etc., and forming into a honeycomb shape with an extruder, drying is performed at 50 to 120 ° C., and 300 to 700 ° C., preferably 400 to 600 ° C., 1 to 10 hours, preferably 2 to 6 hours. Bake. In addition to the organic polymer compound, any can be used as long as it can form pores when formed into a honeycomb shape by an extruder and then fired at 300 to 700 ° C. What is necessary is just to determine suitably the addition amount of the said pore formation agent from the range of 2-10 mass% (mass reference | standard of all component raw materials) as above-mentioned.
(II) In the above method (I), instead of the pore-forming agent, a B component raw material or a part of the C component raw material may be decomposed during molding and firing to form a pore or a carbonate. It may be added in the form of In particular, it is preferable to add nickel hydroxide or nickel carbonate as the C component raw material. In this case, the C component content in the composite powder composed of the B component and the C component is 50 to 90% by mass, preferably 70 to 90% by mass, based on the total C component content of the finished catalyst. If the C component content is less than 50% by mass, the durability of the catalyst may be lowered. Next, the composite powder, the A component raw material, and the remaining C component raw material are sufficiently mixed with a molding aid such as an organic binder and an appropriate amount of water, and formed into a honeycomb shape with an extruder, It is dried at 50 to 120 ° C. and calcined at 300 to 700 ° C., preferably 400 to 600 ° C. for 1 to 10 hours, preferably 2 to 6 hours. At this time, as the remaining C component raw material, a nickel compound such as nickel hydroxide or nickel carbonate that can form pores when formed into a honeycomb shape with an extruder and then fired at 300 to 700 ° C. Use. The C component raw material used when preparing the composite powder and the remaining C component raw material used thereafter may be the same or different, but the remaining C component raw material was formed into a honeycomb shape with a molding machine. Thereafter, it is necessary to use a nickel compound such as nickel hydroxide or nickel carbonate that can form pores when fired at 300 to 700 ° C.
上記ハニカム状触媒における、Ｂ成分／Ｃ成分の質量比（酸化物換算）は、上述のとおり、好ましくは１／９９〜５０／５０であり、より好ましくは１０／９０〜３０／７０である。 The mass ratio of B component / C component (as oxide) in the honeycomb catalyst is preferably 1/99 to 50/50, more preferably 10/90 to 30/70, as described above.
本発明の触媒は、２５０〜９００℃、好ましくは３５０〜７００℃、より好ましくは４００〜６００℃の範囲の反応温度で使用するのに適している。本発明の触媒を用いることにより、高価な白金族金属を用いなくても、５００℃以下の比較的低温でも亜酸化窒素を効果的に分解することができる。また、通常の酸化ニッケル系触媒は耐熱性に問題があって、上記のような使用条件においては、粒子成長を起こして、著しい熱劣化を招くが、本発明の触媒においては、このような粒子成長を効果的に抑制することができる。 The catalyst of the present invention is suitable for use at a reaction temperature in the range of 250-900 ° C, preferably 350-700 ° C, more preferably 400-600 ° C. By using the catalyst of the present invention, nitrous oxide can be effectively decomposed even at a relatively low temperature of 500 ° C. or less without using an expensive platinum group metal. In addition, a normal nickel oxide catalyst has a problem in heat resistance, and under the use conditions as described above, particle growth occurs and causes significant thermal degradation. In the catalyst of the present invention, such particles Growth can be effectively suppressed.
前記の「６００℃で４８時間熱エージング処理」は、例えば、３５０〜５００℃の反応温度となる硝酸プラントのテールガス処理を想定した加速耐久条件であり、６００℃で４８時間熱エージング処理後における、酸化ニッケル（ＮｉＯ）の結晶子径が５０ｎｍ以下であれば、白金系触媒に匹敵する優れた低温活性を維持することができる。 The above-mentioned “thermal aging treatment at 600 ° C. for 48 hours” is, for example, accelerated durability conditions assuming a tail gas treatment of a nitric acid plant having a reaction temperature of 350 to 500 ° C., and after the thermal aging treatment at 600 ° C. for 48 hours. If the crystallite diameter of nickel oxide (NiO) is 50 nm or less, excellent low-temperature activity comparable to that of a platinum-based catalyst can be maintained.
本発明の亜酸化窒素含有ガスの処理方法とは、上記の亜酸化窒素分解用触媒を用いて亜酸化窒素含有ガス中の亜酸化窒素を分解除去するものである。 The processing method of the nitrous oxide-containing gas of the present invention is to decompose and remove nitrous oxide in the nitrous oxide-containing gas using the nitrous oxide-decomposing catalyst.
亜酸化窒素含有ガスとしては、流動層ボイラ、下水汚泥焼却炉等の固定燃焼装置、乗用車やトラック等の輸送機関、それに、アジピン酸、グリオキザール、硝酸等を製造する化学プラント等から排出される亜酸化窒素含有ガスが挙げられる。 Nitrous oxide-containing gases include sub-combustible gas such as fluidized bed boilers, fixed combustion equipment such as sewage sludge incinerators, transportation vehicles such as passenger cars and trucks, and chemical plants that produce adipic acid, glyoxal, nitric acid, etc. Nitrogen oxide containing gas is mentioned.
亜酸化窒素含有ガス中の亜酸化窒素のガス濃度は、通常、０．０１〜１０容量％であり、好ましくは０．０２〜０．５容量％である。亜酸化窒素含有ガス中には、亜酸化窒素以外の成分として、窒素、酸素、二酸化炭素、一酸化炭素、水、水素、アンモニア、ＮＯｘ（ＮＯ、ＮＯ２）、ＳＯｘなどが含まれていてもよい。 The gas concentration of nitrous oxide in the nitrous oxide-containing gas is usually 0.01 to 10% by volume, preferably 0.02 to 0.5% by volume. The nitrous oxide-containing gas, as a component other than nitrous oxide, nitrogen, oxygen, carbon dioxide, carbon monoxide, water, hydrogen, ammonia, NOx (NO, NO 2) , also include such SOx Good.
本発明の亜酸化窒素含有ガスの処理方法は、亜酸化窒素を直接窒素と酸素とに分解するものであり、炭化水素、一酸化炭素、水素やアンモニアのような還元剤を添加しなくても亜酸化窒素含有ガスを処理することができる。反応温度は、２５０〜９００℃、好ましくは３５０〜７００℃、より好ましくは４００〜６００℃である。また、空間速度（ＳＶ）は、１，０００〜５０，０００ｈｒ−１、好ましくは２，０００〜２０，０００ｈｒ−１である。さらに、反応圧は１〜４０ｂａｒ、好ましくは１〜２０ｂａｒである。 The method for treating a nitrous oxide-containing gas according to the present invention directly decomposes nitrous oxide into nitrogen and oxygen without adding a reducing agent such as hydrocarbon, carbon monoxide, hydrogen or ammonia. A nitrous oxide-containing gas can be treated. The reaction temperature is 250 to 900 ° C, preferably 350 to 700 ° C, more preferably 400 to 600 ° C. The space velocity (SV) is 1,000 to 50,000 hr −1 , preferably 2,000 to 20,000 hr −1 . Furthermore, the reaction pressure is 1 to 40 bar, preferably 1 to 20 bar.
本発明の亜酸化窒素分解用触媒は、ＮＯｘ（ＮＯ、ＮＯ２）の共存下でも、優れた亜酸化窒素分解性能を示す。したがって、本発明の処理方法によれば、亜酸化窒素と共にＮＯｘ（ＮＯ、ＮＯ２）を含むガス中の亜酸化窒素を効率よく分解除去できる。従来の亜酸化窒素分解用触媒では、ＮＯｘが共存すると亜酸化窒素分解性能が低下することが知られており、通常、前処理でＮＯｘを除去してから亜酸化窒素を処理する方法が選ばれていた。ＮＯｘ存在下の亜酸化窒素分解性能の低下要因は明らかではないが、吸脱着速度の違いによる反応阻害やＮＯｘから派生する亜酸化窒素の副生等が考えられる。 The nitrous oxide decomposition catalyst of the present invention exhibits excellent nitrous oxide decomposition performance even in the presence of NOx (NO, NO 2 ). Therefore, according to the treatment method of the present invention, nitrous oxide in a gas containing NOx (NO, NO 2 ) together with nitrous oxide can be efficiently decomposed and removed. Conventional nitrous oxide decomposition catalysts are known to degrade nitrous oxide decomposition performance when NOx coexists, and usually a method of treating nitrous oxide after removing NOx in the pretreatment is selected. It was. Although the cause of the degradation of nitrous oxide decomposition performance in the presence of NOx is not clear, reaction inhibition due to the difference in adsorption / desorption rate, nitrous oxide byproduct derived from NOx, and the like are considered.
一般に亜酸化窒素分解反応は高温になるほど反応は促進されるのに対し、ＮＯｘのアンモニアによる選択的脱硝反応は温度が高くなるほど不利となるため、４００℃以下、好ましくは３００℃以下で処理される。したがって、従来の前段でＮＯｘを除去してから亜酸化窒素を処理する方法は熱効率的に好ましくない。例えば、硝酸プラントのテールガスに適用する場合に５００℃の排ガスを脱硝反応に適した温度に冷却してから再び昇温して亜酸化窒素分解反応に適した温度に昇温するというように非経済的な処理方法となっている。これに対し、本発明の触媒を用いると、亜酸化窒素を分解してからＮＯｘを除去することができるため、亜酸化窒素とＮＯｘとを含む排ガスを熱効率的に有利に処理することができる。 In general, the higher the temperature of the nitrous oxide decomposition reaction is, the more the reaction is promoted. On the other hand, the selective denitration reaction of NOx with ammonia becomes disadvantageous as the temperature increases. . Therefore, the conventional method of treating nitrous oxide after removing NOx in the previous stage is not preferable in terms of heat efficiency. For example, when applied to tail gas of a nitric acid plant, the temperature of the exhaust gas at 500 ° C. is cooled to a temperature suitable for the denitration reaction and then raised again to a temperature suitable for the nitrous oxide decomposition reaction. It is a typical processing method. On the other hand, when the catalyst of the present invention is used, NOx can be removed after nitrous oxide is decomposed, so that exhaust gas containing nitrous oxide and NOx can be treated efficiently and efficiently.
したがって、本発明の亜酸化窒素含有ガスの処理方法の一つは、亜酸化窒素とＮＯｘ（ＮＯ、ＮＯ２）とを含む排ガスを、本発明の触媒に接触させて、排ガス中の亜酸化窒素を分解する工程、次に、処理後のガスにアンモニア、尿素などの還元性物質を加えて、残存するＮＯｘ（ＮＯ、ＮＯ２）を分解除去（脱硝処理）する工程を含むものである。亜酸化窒素分解工程での温度は、２５０〜９００℃、好ましくは３５０〜７００℃、より好ましくは４００〜６００℃であり、脱硝処理工程の温度は、１５０〜５００℃、好ましくは２００〜４５０℃、より好ましくは２５０〜３５０℃である。 Accordingly, one of the methods for treating a nitrous oxide-containing gas according to the present invention is to bring an exhaust gas containing nitrous oxide and NOx (NO, NO 2 ) into contact with the catalyst of the present invention, so that nitrous oxide in the exhaust gas is present. Next, a step of adding a reducing substance such as ammonia or urea to the treated gas to decompose and remove the remaining NOx (NO, NO 2 ) (denitration treatment) is included. The temperature in the nitrous oxide decomposition step is 250 to 900 ° C, preferably 350 to 700 ° C, more preferably 400 to 600 ° C, and the temperature of the denitration treatment step is 150 to 500 ° C, preferably 200 to 450 ° C. More preferably, it is 250-350 degreeC.
排ガス中のＮＯとＮＯ２との濃度比は、特に限定されず、ＮＯｘ濃度として０．０００１〜０．５容量％であり、好ましくは０．３容量％以下である。 The concentration ratio between NO and NO 2 in the exhaust gas is not particularly limited, and is a NOx concentration of 0.0001 to 0.5% by volume, preferably 0.3% by volume or less.
上記脱硝処理工程は、脱硝処理に一般に用いられている条件下に実施することができる。還元性物質としてのアンモニアの添加量は、アンモニア／ＮＯｘのモル比が０．３／１〜３／１、好ましくは０．５／１〜１．５／１の範囲内で適宜選択することができる。尿素の場合はアンモニアのモル数の１／２である。脱硝触媒としては、チタニア、アルミナ、シリカ、ゼオライトなどの担体成分とＶ、Ｃｕ、Ｗ、Ｍｏ、Ｆｅなどの酸化物とを組み合わせたものを使用することができる。 The denitration treatment step can be performed under conditions generally used for denitration treatment. The amount of ammonia added as the reducing substance may be appropriately selected within a molar ratio of ammonia / NOx of 0.3 / 1 to 3/1, preferably 0.5 / 1 to 1.5 / 1. it can. In the case of urea, it is ½ of the number of moles of ammonia. As the denitration catalyst, a combination of a carrier component such as titania, alumina, silica, or zeolite and an oxide such as V, Cu, W, Mo, or Fe can be used.
本発明の亜酸化窒素含有ガスの処理方法は、例えば、硝酸製造プラントのテールガスの処理に好適である。硝酸の製造には、原料のアンモニアを８５０℃以上の高温で接触酸化してＮＯとし、さらに酸化してＮＯ２変換してから吸収塔で水に吸収させて硝酸を製造するプロセスが知られている。この硝酸プラントのテールガスとは、硝酸を吸収させた後のガスであり、テールガスは膨張タービンを経て外気に排出される。アンモニアを高温で酸化する際に亜酸化窒素が副生する。硝酸プラントのテールガスの代表的な組成は、亜酸化窒素が０．０３〜０．３５容量％、ＮＯｘが０．０１〜０．３５容量％、酸素が１〜４容量％、また、水が０．３〜２容量％である。なお、上記テールガスは、膨張タービンの手前でプロセス熱交換により、ガスの温度は３５０〜５００℃、圧力は４〜１１ｂａｒとなっている。 The method for treating a nitrous oxide-containing gas of the present invention is suitable for treating tail gas of a nitric acid production plant, for example. In the production of nitric acid, a process is known in which the raw material ammonia is contact oxidized at a high temperature of 850 ° C. or more to form NO, and further oxidized and converted to NO 2 , and then absorbed into water by an absorption tower to produce nitric acid. Yes. The tail gas of the nitric acid plant is a gas after the nitric acid is absorbed, and the tail gas is discharged to the outside air through the expansion turbine. Nitrous oxide is by-produced when ammonia is oxidized at high temperatures. The typical composition of the tail gas of the nitric acid plant is 0.03 to 0.35% by volume of nitrous oxide, 0.01 to 0.35% by volume of NOx, 1 to 4% by volume of oxygen, and 0% of water. 3 to 2% by volume. The tail gas has a gas temperature of 350 to 500 ° C. and a pressure of 4 to 11 bar by process heat exchange before the expansion turbine.
本発明の有利な実施態様を示している以下の実施例を挙げて、本発明を更に具体的に説明する。
（実施例１）
硝酸セリウム六水和物１４．９ｋｇを水１５ｋｇに溶解した液を水酸化ニッケル３０ｋｇに添加、混合し、１５０℃で１０時間乾燥した後、６００℃で５時間空気雰囲気下で焼成して、ＣｅＯ２／ＮｉＯ（Ｂ成分／Ｃ成分）が２０／８０の複合粉体（ＣＮ−１）を得た。
The invention is further illustrated by the following examples, which illustrate advantageous embodiments of the invention.
Example 1
A solution obtained by dissolving 14.9 kg of cerium nitrate hexahydrate in 15 kg of water was added to 30 kg of nickel hydroxide, mixed, dried at 150 ° C. for 10 hours, and then calcined at 600 ° C. for 5 hours in an air atmosphere. 2 / NiO (B component / C component) 20/80 composite powder (CN-1) was obtained.
上記複合粉体（ＣＮ−１）を６００℃で４８時間空気中で熱エージング処理を行った後、Ｘ線回折法により、酸化ニッケルの結晶子径を測定した。その結果、熱エージング処理前の結晶子径は２６ｎｍであり、熱エージング処理後の結晶子径は２８ｎｍであった。 The composite powder (CN-1) was heat-aged in air at 600 ° C. for 48 hours, and then the crystallite diameter of nickel oxide was measured by an X-ray diffraction method. As a result, the crystallite diameter before the heat aging treatment was 26 nm, and the crystallite diameter after the heat aging treatment was 28 nm.
上記複合粉体（ＣＮ−１）２０ｋｇ、炭酸カルシウム８０ｋｇ、ポア形成剤としてのフェノール樹脂（商品名：ベルパールＳ、カネボウ株式会社製）３．０ｋｇおよび成形助剤としてのデンプン２．０ｋｇに適量の水を加え、ブレンダーでよく混合した後、連続ニーダーで十分混練りし、目開き２．５ｍｍ、肉厚０．４ｍｍ、開口率７０．６％である、外形８０ｍｍ角、長さ５００ｍｍのハニカム状に押出成形した。 The composite powder (CN-1) 20 kg, calcium carbonate 80 kg, phenol resin as a pore forming agent (trade name: Bellpearl S, manufactured by Kanebo Co., Ltd.) 3.0 kg and starch as a molding aid 2.0 kg Add water, mix well with a blender, and knead well with a continuous kneader. Honeycomb shape with an opening of 2.5 mm, a wall thickness of 0.4 mm, and an aperture ratio of 70.6%. Extruded.
得られた成形物を６０℃で１時間乾燥した後、空気雰囲気下、５００℃で５時間焼成してハニカム状触媒（Ａ）を得た。このハニカム状触媒（Ａ）の組成は、Ａ成分／Ｂ成分／Ｃ成分（ＣａＣＯ３／ＣｅＯ２／ＮｉＯ）＝８０：４：１６（質量％）であった。このハニカム状触媒（Ａ）の細孔容積を水銀圧入式ポロシメーターにて測定し、その結果を図１に示した。このハニカム状触媒（Ａ）の全細孔容積は０．３３ｃｃ／ｇであり、この全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合は５０％であった。
（比較例１）
実施例１において、フェノール樹脂を添加しなかった以外は、実施例１と同様にしてハニカム状触媒（ａ）を製造した。このハニカム状触媒（ａ）の組成は、Ａ成分／Ｂ成分／Ｃ成分（ＣａＣＯ３／ＣｅＯ２／ＮｉＯ）＝８０：４：１６（質量％）であった。このハニカム状触媒（ａ）の細孔容積を実施例１と同様にして測定し、その結果を図２に示した。このハニカム状触媒（ａ）の全細孔容積は０．２３ｃｃ／ｇであり、この全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合は４％であった。
（実施例２）
実施例１で得られた複合粉体（ＣＮ−１）２０ｋｇ、炭酸カルシウム７０ｋｇ、ポア形成剤としての水酸化ニッケル１２．４ｋｇおよび成形助剤としてのデンプン２．０ｋｇに適量の水を加え、ブレンダーでよく混合した後、連続ニーダーで十分混練りし、以下、実施例１と同様にして、ハニカム状触媒（Ｂ）を得た。このハニカム状触媒（Ｂ）の組成は、Ａ成分／Ｂ成分／Ｃ成分（ＣａＣＯ３／ＣｅＯ３／ＮｉＯ）＝７０：４：２６（質量％）であった。このハニカム状触媒（Ｂ）の細孔容積を実施例１と同様にして測定し、その結果を図３に示した。このハニカム状触媒（Ｂ）の全細孔容積は０．３０ｃｃ／ｇであり、この全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合は３３％であった。
（実施例３）
硝酸ニッケル六水和物４０ｋｇと硝酸セリウム六水和物２．９ｋｇを水１００ｋｇに溶解して攪拌しながらアンモニア水を徐々に滴下してｐＨ＝８に調整し、そのまま一晩放置した。次に、沈殿物をろ過洗浄し、１５０℃で１０時間乾燥した後、７００℃で５時間焼成して、ＣｅＯ２／ＮｉＯ（Ｂ成分／Ｃ成分）が１０／９０の複合粉体（ＣＮ−２）を得た。
The obtained molded product was dried at 60 ° C. for 1 hour and then calcined at 500 ° C. for 5 hours in an air atmosphere to obtain a honeycomb catalyst (A). The composition of the honeycomb catalyst (A) was A component / B component / C component (CaCO 3 / CeO 2 / NiO) = 80: 4: 16 (mass%). The pore volume of the honeycomb catalyst (A) was measured with a mercury intrusion porosimeter, and the results are shown in FIG. The total pore volume of the honeycomb catalyst (A) was 0.33 cc / g, and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume was 50%.
(Comparative Example 1)
In Example 1, a honeycomb catalyst (a) was produced in the same manner as in Example 1 except that no phenol resin was added. The composition of the honeycomb catalyst (a) was A component / B component / C component (CaCO 3 / CeO 2 / NiO) = 80: 4: 16 (mass%). The pore volume of the honeycomb catalyst (a) was measured in the same manner as in Example 1, and the result is shown in FIG. The total pore volume of the honeycomb catalyst (a) was 0.23 cc / g, and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume was 4%.
(Example 2)
An appropriate amount of water was added to 20 kg of the composite powder (CN-1) obtained in Example 1, 70 kg of calcium carbonate, 12.4 kg of nickel hydroxide as a pore forming agent and 2.0 kg of starch as a molding aid, and blender was added. After mixing well, the mixture was sufficiently kneaded with a continuous kneader, and a honeycomb catalyst (B) was obtained in the same manner as in Example 1. The composition of the honeycomb catalyst (B) was A component / B component / C component (CaCO 3 / CeO 3 / NiO) = 70: 4: 26 (mass%). The pore volume of this honeycomb catalyst (B) was measured in the same manner as in Example 1, and the results are shown in FIG. The total pore volume of the honeycomb catalyst (B) was 0.30 cc / g, and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume was 33%.
(Example 3)
40 kg of nickel nitrate hexahydrate and 2.9 kg of cerium nitrate hexahydrate were dissolved in 100 kg of water and ammonia water was gradually added dropwise with stirring to adjust to pH = 8 and left as it was overnight. Next, the precipitate was filtered and washed, dried at 150 ° C. for 10 hours, and then calcined at 700 ° C. for 5 hours to obtain a composite powder (CN−) containing CeO 2 / NiO (B component / C component) of 10/90. 2) was obtained.
上記複合粉体（ＣＮ−２）を６００℃で４８時間空気中で熱エージング処理を行った後、Ｘ線回折法により、酸化ニッケルの結晶子径を測定した。その結果、熱エージング処理前の結晶子径は２７ｎｍであり、熱エージング処理後の結晶子径は３０ｎｍであった。 The composite powder (CN-2) was heat-aged in air at 600 ° C. for 48 hours, and then the crystallite diameter of nickel oxide was measured by an X-ray diffraction method. As a result, the crystallite diameter before the heat aging treatment was 27 nm, and the crystallite diameter after the heat aging treatment was 30 nm.
上記複合粉体（ＣＮ−２）２０ｋｇ、炭酸カルシウム７０ｋｇ、ポア形成剤としての炭酸ニッケル１５．９ｋｇおよび成形助剤としてのデンプン２．０ｋｇに適量の水を加え、ブレンダーでよく混合した後、連続ニーダーで十分混練りし、以下、実施例１と同様にして、ハニカム状触媒（Ｃ）を得た。このハニカム状触媒（Ｃ）の組成は、Ａ成分／Ｂ成分／Ｃ成分（ＣａＣＯ３／ＣｅＯ２／ＮｉＯ）＝７０：２：２８（質量％）であった。このハニカム状触媒（Ｃ）の細孔容積を実施例１と同様にして測定した。このハニカム状触媒（Ｃ）の全細孔容積は０．３２ｃｃ／ｇであり、この全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合は４１％であった。
（比較例２）
実施例３で得られた複合粉体（ＣＮ−２）３０ｋｇ、炭酸カルシウム７０ｋｇおよび成形助剤としてのデンプン２．０ｋｇに適量の水を加え、ブレンダーでよく混合した後、連続ニーダーで十分混練りし、以下、実施例１と同様にして、Ａ成分／Ｂ成分／Ｃ成分（ＣａＣＯ３／ＣｅＯ２／ＮｉＯ）＝７０：２：２８（質量％）であるハニカム状触媒（ｂ）を得た。このハニカム状触媒（ｂ）の全細孔容積は０．２５ｃｃ／ｇであり、この全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合は３％であった。
（比較例３）
炭酸ニッケルを５００℃で１０時間焼成して酸化ニッケル粉末を得た。この酸化ニッケル粉末について、６００℃で４８時間空気中で熱エージング処理を行った後、Ｘ線回折法により、酸化ニッケルの結晶子径を測定した。その結果、熱エージング処理前の結晶子径は１５ｎｍであり、熱エージング処理後の結晶子径は７５ｎｍであった。
An appropriate amount of water was added to 20 kg of the composite powder (CN-2), 70 kg of calcium carbonate, 15.9 kg of nickel carbonate as a pore-forming agent and 2.0 kg of starch as a molding aid, and after mixing well with a blender, continuous The mixture was sufficiently kneaded with a kneader, and a honeycomb catalyst (C) was obtained in the same manner as in Example 1. The composition of the honeycomb catalyst (C) was A component / B component / C component (CaCO 3 / CeO 2 / NiO) = 70: 2: 28 (mass%). The pore volume of the honeycomb catalyst (C) was measured in the same manner as in Example 1. The total pore volume of the honeycomb catalyst (C) was 0.32 cc / g, and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume was 41%.
(Comparative Example 2)
A suitable amount of water was added to 30 kg of the composite powder (CN-2) obtained in Example 3, 70 kg of calcium carbonate, and 2.0 kg of starch as a molding aid, mixed well with a blender, and then sufficiently kneaded with a continuous kneader. Thereafter, in the same manner as in Example 1, a honeycomb catalyst (b) having an A component / B component / C component (CaCO 3 / CeO 2 / NiO) = 70: 2: 28 (mass%) was obtained. . The total pore volume of the honeycomb catalyst (b) was 0.25 cc / g, and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume was 3%.
(Comparative Example 3)
Nickel carbonate was fired at 500 ° C. for 10 hours to obtain nickel oxide powder. The nickel oxide powder was subjected to a thermal aging treatment in air at 600 ° C. for 48 hours, and then the crystallite diameter of nickel oxide was measured by an X-ray diffraction method. As a result, the crystallite diameter before the heat aging treatment was 15 nm, and the crystallite diameter after the heat aging treatment was 75 nm.
上記酸化ニッケル粉末３０ｋｇ、炭酸カルシウム７０ｋｇおよび成形助剤としてのデンプン２．０ｋｇに適量の水を加え、ブレンダーでよく混合した後、連続ニーダーで十分混練りし、以下、実施例１と同様にして、Ａ成分／Ｃ成分（ＣａＣＯ３／ＮｉＯ）＝７０：３０（質量％）であるハニカム状触媒（ｃ）を得た。このハニカム状触媒（ｃ）の細孔容積を実施例１と同様にして測定し、その結果を図４に示した。全細孔容積は０．２７ｃｃ／ｇであり、この全細孔容積に対する０．３μｍ以上のポア径細孔容積の割合は１９％であった。
（性能評価方法）
ハニカム触媒を反応管に充填し、下記組成の合成ガスを下記条件下に導入した。
＜合成ガス組成＞
亜酸化窒素（Ｎ２Ｏ）：１０００ｐｐｍ、一酸化窒素（ＮＯ）：５００ｐｐｍ、酸素（Ｏ２）：３容量％、水（Ｈ２Ｏ）：０．５容量％、残り：窒素（Ｎ２）
＜反応条件＞
処理温度：５００℃、反応圧：５ｂａｒ、空間速度（ＳＶ）：１０，０００ｈｒ−１
上記合成ガスを導入してから１時間経過後、上記ハニカム触媒の入口および出口における合成ガス中の亜酸化窒素（Ｎ２Ｏ）濃度を非分散赤外線式Ｎ２Ｏ計（日本サーモエレクトロン（株）製、Ｍｏｄｅｌ ４６Ｃ−ＨＬ）により測定し、次式に従ってＮ２Ｏ除去率を算出した。結果を表１に示す。
Ｎ２Ｏ除去率（％）＝（入口Ｎ２Ｏ濃度−出口Ｎ２Ｏ濃度）／（入口Ｎ２Ｏ濃度）×１００
同様にして電気炉で６００℃で４８時間熱処理エージングした触媒についても前記反応条件で処理性能を測定し結果を表１に示した。
An appropriate amount of water is added to 30 kg of the above nickel oxide powder, 70 kg of calcium carbonate and 2.0 kg of starch as a molding aid, and after mixing well with a blender, the mixture is sufficiently kneaded with a continuous kneader. A honeycomb catalyst (c) in which A component / C component (CaCO 3 / NiO) = 70: 30 (mass%) was obtained. The pore volume of the honeycomb catalyst (c) was measured in the same manner as in Example 1, and the result is shown in FIG. The total pore volume was 0.27 cc / g, and the ratio of the pore diameter pore volume of 0.3 μm or more to the total pore volume was 19%.
(Performance evaluation method)
A honeycomb catalyst was filled in a reaction tube, and a synthesis gas having the following composition was introduced under the following conditions.
<Syngas composition>
Nitrous oxide (N 2 O): 1000 ppm, Nitric oxide (NO): 500 ppm, Oxygen (O 2 ): 3% by volume, Water (H 2 O): 0.5% by volume, Remaining: Nitrogen (N 2 )
<Reaction conditions>
Treatment temperature: 500 ° C., reaction pressure: 5 bar, space velocity (SV): 10,000 hr −1
One hour after the synthesis gas was introduced, the concentration of nitrous oxide (N 2 O) in the synthesis gas at the inlet and outlet of the honeycomb catalyst was measured using a non-dispersive infrared N 2 O meter (Nippon Thermo Electron Co., Ltd.). Manufactured, Model 46C-HL), and the N 2 O removal rate was calculated according to the following formula. The results are shown in Table 1.
N 2 O removal rate (%) = (inlet N 2 O concentration−outlet N 2 O concentration) / (inlet N 2 O concentration) × 100
Similarly, for a catalyst heat-treated at 600 ° C. for 48 hours in an electric furnace, the treatment performance was measured under the above reaction conditions, and the results are shown in Table 1.
本発明の亜酸化窒素分解用触媒および亜酸化窒素含有ガスの処理方法は、汚泥焼却炉等の燃焼排ガスや硝酸製造プロセス等の化学プラントから排出される亜酸化窒素を除去するのに用いることができる。 The catalyst for decomposing nitrous oxide and the method for treating a nitrous oxide-containing gas of the present invention can be used to remove nitrous oxide discharged from a combustion plant such as a sludge incinerator or a chemical plant such as a nitric acid production process. it can.
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