JP4974674B2 - Complex oxide - Google Patents
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- JP4974674B2 JP4974674B2 JP2006510786A JP2006510786A JP4974674B2 JP 4974674 B2 JP4974674 B2 JP 4974674B2 JP 2006510786 A JP2006510786 A JP 2006510786A JP 2006510786 A JP2006510786 A JP 2006510786A JP 4974674 B2 JP4974674 B2 JP 4974674B2
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- 239000002131 composite material Substances 0.000 claims description 140
- 238000001228 spectrum Methods 0.000 claims description 27
- 229910052684 Cerium Inorganic materials 0.000 claims description 25
- 229910052788 barium Inorganic materials 0.000 claims description 16
- 229910052712 strontium Inorganic materials 0.000 claims description 10
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 229910052771 Terbium Inorganic materials 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- 229910052791 calcium Inorganic materials 0.000 claims description 8
- 229910052759 nickel Inorganic materials 0.000 claims description 8
- 229910052758 niobium Inorganic materials 0.000 claims description 8
- 238000010304 firing Methods 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 5
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 4
- 229910052790 beryllium Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052746 lanthanum Inorganic materials 0.000 claims description 4
- 229910052749 magnesium Inorganic materials 0.000 claims description 4
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 41
- 239000003054 catalyst Substances 0.000 description 33
- 239000007864 aqueous solution Substances 0.000 description 25
- 238000000746 purification Methods 0.000 description 25
- 230000000052 comparative effect Effects 0.000 description 23
- 229910052726 zirconium Inorganic materials 0.000 description 21
- 239000000203 mixture Substances 0.000 description 20
- 238000000034 method Methods 0.000 description 17
- 150000003754 zirconium Chemical class 0.000 description 16
- ITZXULOAYIAYNU-UHFFFAOYSA-N cerium(4+) Chemical class [Ce+4] ITZXULOAYIAYNU-UHFFFAOYSA-N 0.000 description 15
- 230000002378 acidificating effect Effects 0.000 description 13
- 239000003426 co-catalyst Substances 0.000 description 13
- 238000005259 measurement Methods 0.000 description 13
- 230000000694 effects Effects 0.000 description 12
- 239000010955 niobium Substances 0.000 description 12
- 159000000009 barium salts Chemical class 0.000 description 10
- 229910052797 bismuth Inorganic materials 0.000 description 10
- 150000001621 bismuth Chemical class 0.000 description 10
- 238000001308 synthesis method Methods 0.000 description 10
- 239000011575 calcium Substances 0.000 description 9
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 9
- 230000002194 synthesizing effect Effects 0.000 description 9
- 230000033116 oxidation-reduction process Effects 0.000 description 7
- 229910004625 Ce—Zr Inorganic materials 0.000 description 6
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 238000002485 combustion reaction Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 4
- 238000000975 co-precipitation Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 238000006479 redox reaction Methods 0.000 description 4
- 229910052693 Europium Inorganic materials 0.000 description 3
- 229910000416 bismuth oxide Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 2
- 229910000420 cerium oxide Inorganic materials 0.000 description 2
- 238000010908 decantation Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 229910052735 hafnium Inorganic materials 0.000 description 2
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 150000002821 niobium Chemical class 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000010992 reflux Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- IATRAKWUXMZMIY-UHFFFAOYSA-N strontium oxide Chemical compound [O-2].[Sr+2] IATRAKWUXMZMIY-UHFFFAOYSA-N 0.000 description 2
- 159000000008 strontium salts Chemical class 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 description 1
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 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
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 125000005595 acetylacetonate group Chemical group 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 235000012538 ammonium bicarbonate Nutrition 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 159000000007 calcium salts Chemical class 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 150000002815 nickel Chemical class 0.000 description 1
- 229910000484 niobium oxide Inorganic materials 0.000 description 1
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 150000003681 vanadium Chemical class 0.000 description 1
- 229910001935 vanadium oxide Inorganic materials 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
- B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
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Description
本発明は、複合酸化物、特にガソリンや軽油の燃焼により供給されるエネルギーが駆動力となるエンジン、例えば自動車などの内燃機関から排出される排気ガスを浄化する排気ガス浄化触媒の助触媒に関するものである。 The present invention relates to a co-catalyst for an exhaust gas purification catalyst that purifies exhaust gas discharged from an internal combustion engine such as an automobile in which energy supplied by combustion of complex oxides, particularly gasoline and light oil, becomes a driving force. It is.
自動車などの内燃機関の排出する排気ガスには、人体又は環境に有害である炭化水素、一酸化炭素、窒素酸化物が含まれている。現在、一酸化炭素及び炭化水素を炭酸ガスと水に酸化し、窒素酸化物を窒素と水に還元する、いわゆる三元触媒が排気ガス浄化用触媒として使用されている。三元触媒は、例えば主触媒である白金、パラジウム、ロジウムの貴金属と助触媒である酸化セリウムを含有する酸化物又は複合酸化物がアルミナ、コージェライト等の触媒担体に担持された構成となっている。助触媒は、含有されるセリウムが、酸化雰囲気下で３価から４価に価数を変えて酸素を吸収し、還元雰囲気下で４価から３価に価数を変えて酸素を放出するという特性、いわゆる酸化還元能を有する。この酸化還元能により、エンジンの加速、減速による排気ガスの急激な雰囲気変化を緩和して、主触媒は高い効率で排気ガスを浄化することができる。助触媒としては、セリウムとジルコニウムを含有する複合酸化物（以下「Ｃｅ-Ｚｒ系複合酸化物」という。）が広く使用されている。現在使用されているＣｅ-Ｚｒ系複合酸化物は、３００℃以下という低温下における酸化還元能が十分でない為、エンジン始動時のようにエンジンの温度が低いときは、上述した雰囲気変化を緩和する効果が無く、主触媒の排気ガス浄化効率は低い。また、Ｃｅ-Ｚｒ系複合酸化物の酸化還元能は、気相である排気ガスと固相である助触媒の固気界面の反応による為、Ｃｅ-Ｚｒ系複合酸化物の比表面積が大きく影響する。そこで、Ｃｅ-Ｚｒ系複合酸化物は、９００℃以上の高温に曝された後においても、高い比表面積を維持することが重要である。 Exhaust gas discharged from an internal combustion engine such as an automobile contains hydrocarbons, carbon monoxide, and nitrogen oxides that are harmful to the human body or the environment. Currently, so-called three-way catalysts that oxidize carbon monoxide and hydrocarbons to carbon dioxide and water and reduce nitrogen oxides to nitrogen and water are used as exhaust gas purification catalysts. The three-way catalyst has a structure in which an oxide or composite oxide containing, for example, platinum, palladium, rhodium noble metals as main catalysts and cerium oxide as a promoter is supported on a catalyst carrier such as alumina or cordierite. Yes. The cocatalyst contains cerium that absorbs oxygen by changing the valence from trivalent to tetravalent in an oxidizing atmosphere and releases oxygen by changing the valence from tetravalent to trivalent in a reducing atmosphere. Characteristics, so-called redox ability. This oxidation-reduction capability can mitigate sudden changes in the exhaust gas atmosphere caused by engine acceleration and deceleration, and the main catalyst can purify the exhaust gas with high efficiency. As the promoter, a complex oxide containing cerium and zirconium (hereinafter referred to as “Ce—Zr complex oxide”) is widely used. The Ce-Zr-based complex oxides currently used have insufficient oxidation-reduction ability at a low temperature of 300 ° C. or lower, so when the engine temperature is low, such as when the engine is started, the above-described change in atmosphere is alleviated. There is no effect, and the exhaust gas purification efficiency of the main catalyst is low. In addition, the redox ability of Ce-Zr composite oxide is influenced by the specific surface area of Ce-Zr composite oxide because of the reaction at the solid-gas interface between the exhaust gas as the gas phase and the cocatalyst as the solid phase. To do. Therefore, it is important that the Ce—Zr-based composite oxide maintain a high specific surface area even after being exposed to a high temperature of 900 ° C. or higher.
一方、特許文献１には、三元触媒の助触媒として酸化セリウムと酸化ジルコニウムと酸化ビスマスとで構成される複合酸化物を用いることが開示されている。そして、この複合酸化物は、１０００℃以上において排気ガス浄化触媒の助触媒として使用した後も、３００℃以下という低温領域において高い酸化還元能を有するため、エンジン始動直後からエンジンが排出する排気ガスを浄化することができ、耐熱性に優れた助触媒として好適である、と記載されている。
しかしながら、特許文献１に開示されている複合酸化物は、確かに３００℃以下において酸化還元能を有するが、比表面積が小さいため、酸化還元反応の活性点が少なく三元触媒の助触媒として充分な性能を発揮し得ない虞がある。 However, the composite oxide disclosed in Patent Document 1 certainly has a redox ability at 300 ° C. or lower, but has a small specific surface area, so that it has few active sites for redox reaction and is sufficient as a co-catalyst for a three-way catalyst. There is a possibility that it may not be able to demonstrate the performance.
本発明は、かかる点に鑑みてなされたものであり、その目的とするところは、排気ガス浄化触媒の助触媒として、９００℃付近の高温に曝された後も大きな比表面積を有するとともに３００℃以下という低温領域において優れた酸化還元能を呈することができる耐熱性及び低温活性に優れた複合酸化物を提供することにある。 The present invention has been made in view of the above points, and the object of the present invention is to have a large specific surface area even after being exposed to a high temperature around 900 ° C. as a co-catalyst for an exhaust gas purification catalyst, and at 300 ° C. An object of the present invention is to provide a composite oxide excellent in heat resistance and low-temperature activity that can exhibit excellent redox ability in a low-temperature region as described below.
本発明の複合酸化物は、一般式（Ｃｅ１−ｘＺｒｘ）１−ｚ（Ａ１−ｙＢｙ）ｚＯδ（式中、ｘ，ｙ，ｚ，δはそれぞれ、０．０５≦ｘ≦０．９５、０．０１≦ｙ≦０．９９、０．０１≦ｚ≦０．３、１．３６５≦δ≦１．９９５を満たす数字である）で表され、Ａは、Ｂｉ，Ｖ，Ｔｉ，Ｎｂ，Ｗ，Ｆｅ，Ｐｒ，Ｔｂ及びＥｕからなる群の金属元素のうち少なくともＢｉを含み、Ｂは、Ｂａ，Ｓｒ，Ｃａ，Ｍｇ，Ｌａからなる群より選ばれた少なくとも一つを含む。 The composite oxide of the present invention has a general formula (Ce 1-x Zr x ) 1-z (A 1-y B y ) z O δ (wherein x, y, z, and δ are 0.05 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.99, 0.01 ≦ z ≦ 0.3, 1.365 ≦ δ ≦ 1.995), and A is Bi, Among the metal elements of the group consisting of V, Ti, Nb, W, Fe, Pr, Tb and Eu, at least Bi is included, and B is at least one selected from the group consisting of Ba, Sr, Ca, Mg and La including.
ここで、Ａは、３００℃以下という低温領域における酸化還元反応を活性化する金属元素である。Ｂは、複合酸化物の耐熱性を高めることができる金属元素である。 Here, A is a metal element that activates a redox reaction in a low temperature region of 300 ° C. or lower. B is a metal element that can increase the heat resistance of the composite oxide.
また、本発明の複合酸化物は、昇温還元スペクトルにおいて３００℃以下にピークを有し、且つ、９００℃において４時間焼成した後の比表面積が２０ｍ２／ｇ以上であることが好ましい。 In addition, the composite oxide of the present invention preferably has a peak at 300 ° C. or lower in the temperature reduction spectrum and has a specific surface area of 20 m 2 / g or more after firing at 900 ° C. for 4 hours.
また、本発明の複合酸化物は、希土類元素（Ｃｅ，Ｔｂ，Ｅｕ，Ｌａ及びＰｒを除く）、Ｎｉ、Ｃｕ、Ａｌ、Ｓｉ並びにＢｅからなる群より選ばれた少なくとも一つをさらに含んでいてもよい。 The composite oxide of the present invention further includes at least one selected from the group consisting of rare earth elements (excluding Ce, Tb, Eu, La and Pr), Ni, Cu, Al, Si and Be. Also good.
また、本発明の複合酸化物では、Ｂは、少なくともＢａを含んでいることが好ましい。 In the composite oxide of the present invention , B preferably contains at least Ba.
本発明の複合酸化物は、排気ガス浄化触媒の助触媒として、９００℃付近の高温に曝された後も大きな比表面積を有するとともに３００℃以下という低温領域においても優れた酸化還元能を呈することができる。 The composite oxide of the present invention has a large specific surface area as a co-catalyst for an exhaust gas purification catalyst even after being exposed to a high temperature around 900 ° C. and exhibits an excellent redox ability even in a low temperature region of 300 ° C. or lower. Can do.
以下、実施形態として、複合酸化物の組成及びその複合酸化物の排気ガス浄化触媒の助触媒としての性能を評価する方法を説明する。 Hereinafter, as an embodiment, a method of evaluating the composition of the composite oxide and the performance of the composite oxide as a promoter of the exhaust gas purification catalyst will be described.
本実施形態における複合酸化物は、一般式（Ｃｅ１−ｘＺｒｘ）１−ｚ（Ａ１−ｙＢｙ）ｚＯδ（式中、ｘ，ｙ，ｚ，δはそれぞれ、０．０５≦ｘ≦０．９５、０．０１≦ｙ≦０．９９、０．０１≦ｚ≦０．３、１．３６５≦δ≦１．９９５を満たす数字である）で表される。 The composite oxide in this embodiment has a general formula (Ce 1-x Zr x ) 1-z (A 1-y B y ) z O δ (wherein x, y, z, and δ are 0.05 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.99, 0.01 ≦ z ≦ 0.3, 1.365 ≦ δ ≦ 1.995).
元素Ａは、Ｂｉ，Ｖ，Ｔｉ，Ｎｂ，Ｗ，Ｆｅ，Ｐｒ，Ｔｂ及びＥｕからなる群の金属元素のうち少なくともＢｉを含む。そして、複合酸化物に対して元素Ａを添加することにより、複合酸化物にはイオン伝導性と電子導電性との両方が発現し、Ｃｅの低温における酸化還元能が向上する。また、元素Ａ自体が酸化還元能を有する場合もある。そして、元素Ａとして、複合酸化物には、Ｂｉ、Ｖ、Ｔｉ、Ｎｂが含まれていることが好ましい。 The element A contains at least Bi among the metal elements of the group consisting of Bi, V, Ti, Nb, W, Fe, Pr, Tb, and Eu. And by adding the element A with respect to complex oxide, both ion conductivity and electronic conductivity are expressed in complex oxide, and the oxidation-reduction ability of Ce in the low temperature improves. Further, the element A itself may have a redox ability. And as element A, it is preferable that Bi, V, Ti, and Nb are contained in complex oxide.
元素Ｂは、価数が２以上の陽イオンとなり得る塩基性を示す元素であって、Ｂａ、Ｓｒ、Ｃａ、Ｍｇ、Ｌａから選ばれる。これらは単独で、もしくは複数種を混合して用いることができる。そして、本実施形態における複合酸化物は、上記に記載した元素Ａ及び元素Ｂを含んでいるため、９００℃付近の高温に曝された後も大きな比表面積を有するとともに３００℃以下という低温領域においても優れた酸化還元能を呈することとなる。 The element B is an element showing basicity that can be a cation having a valence of 2 or more, and is selected from Ba, Sr, Ca, Mg, and La. These can be used alone or in combination of two or more. And since the complex oxide in this embodiment contains the element A and the element B described above, it has a large specific surface area even after being exposed to a high temperature around 900 ° C. and in a low temperature region of 300 ° C. or less. Will also exhibit excellent redox ability.
なお、元素Ｂを加えることにより元素Ａの添加により生じる複合酸化物の耐熱性の低下を抑制することができる理由は明らかではないが、本願発明者らは、本実施形態における複合酸化物において元素Ｂは不純物として作用し、そのために、９００℃付近という高温下での粒子成長を阻止するのではないか、と考えている。また、具体例として列挙した元素Ｂの中には、元素Ａの有する低温における酸化還元反応を活性化する作用を更に高める働きをする元素もある。 Although the reason why the decrease in heat resistance of the composite oxide caused by the addition of the element A can be suppressed by adding the element B is not clear, the inventors of the present application do not use the element in the composite oxide in the present embodiment. It is thought that B acts as an impurity, and therefore, may prevent grain growth at a high temperature of around 900 ° C. Further, among the elements B listed as specific examples, there is an element that further enhances the action of activating the redox reaction at a low temperature that the element A has.
また、一般式（Ｃｅ１−ｘＺｒｘ）１−ｚ（Ａ１−ｙＢｙ）ｚＯδにおいて、ｘが０．０５≦ｘ≦０．９５を満たす数字である複合酸化物は、実用上十分な耐熱性及び酸化還元能を有する。そして、ｘが０．２５≦ｘ≦０．７５を満たす複合酸化物では、その耐熱性及び酸化還元能は良くなり、ｘが０．４≦ｘ≦０．６を満たす複合酸化物では、その耐熱性及び酸化還元能は更に良くなる。また、一般式（Ｃｅ１−ｘＺｒｘ）１−ｚ（Ａ１−ｙＢｙ）ｚＯδにおいて、ｙが０．０１≦ｙ≦０．９９を満たす複合酸化物は、実用上十分な耐熱性及び低温活性を有する。そして、ｙが０．１≦ｙ≦０．９を満たす複合酸化物では、その耐熱性及び低温活性は良くなり、ｙが０．２≦ｙ≦０．８を満たす複合酸化物では、その耐熱性及び低温活性は更に良くなる。また、一般式（Ｃｅ１−ｘＺｒｘ）１−ｚ（Ａ１−ｙＢｙ）ｚＯδにおいて、ｚが０．０１≦ｚ≦０．３を満たす複合酸化物は、実用上十分に高い低温活性、酸化還元能及び耐熱性を有する。そして、ｚが０．０１≦ｚ≦０．２を満たす複合酸化物では、その低温活性、酸化還元能及び耐熱性は良くなり、ｚが０．０１≦ｚ≦０．１を満たす数字である複合酸化物では、その低温活性、酸化還元能及び耐熱性はさらに良くなる。 In the general formula (Ce 1-x Zr x) 1-z (A 1-y B y) z O δ, x is a composite oxide is a number satisfying 0.05 ≦ x ≦ 0.95 is practically Moreover, it has sufficient heat resistance and redox ability. And in the composite oxide where x satisfies 0.25 ≦ x ≦ 0.75, the heat resistance and oxidation-reduction ability are improved, and in the composite oxide where x satisfies 0.4 ≦ x ≦ 0.6, The heat resistance and redox ability are further improved. In the general formula (Ce 1-x Zr x) 1-z (A 1-y B y) z O δ, composite oxides y satisfies 0.01 ≦ y ≦ of 0.99 is practically sufficient Has heat resistance and low temperature activity. And, in the composite oxide where y satisfies 0.1 ≦ y ≦ 0.9, the heat resistance and low temperature activity are improved, and in the composite oxide where y satisfies 0.2 ≦ y ≦ 0.8, the heat resistance Properties and low temperature activity are even better. In addition, in the general formula (Ce 1-x Zr x ) 1-z (A 1-y B y ) z O δ , a composite oxide satisfying z of 0.01 ≦ z ≦ 0.3 is sufficiently practical. High low temperature activity, redox ability and heat resistance. And, in a complex oxide satisfying z ≦ 0.01 ≦ z ≦ 0.2, its low temperature activity, redox ability and heat resistance are improved, and z is a number satisfying 0.01 ≦ z ≦ 0.1. In the composite oxide, its low temperature activity, redox ability and heat resistance are further improved.
さらに、本実施形態における複合酸化物は、希土類元素（Ｃｅ，Ｔｂ，Ｅｕ，Ｌａ及びＰｒを除く）、Ｎｉ、Ｃｕ、Ａｌ、Ｓｉ並びにＢｅからなる群より選ばれた少なくとも一つをさらに含んでいてもよい。これらの金属元素は、複合酸化物に求められる特性により、適宜選択される。例えば、希土類元素（Ｃｅ，Ｔｂ，Ｅｕ，Ｌａ及びＰｒを除く）、Ａｌ、Ｓｉ及びＢｅを添加すると複合酸化物の耐熱性がさらに向上し、Ｎｉ及びＣｕを添加すると複合酸化物の排気ガス浄化効果が更に高められる。 Furthermore, the composite oxide in the present embodiment further includes at least one selected from the group consisting of rare earth elements (excluding Ce, Tb, Eu, La and Pr), Ni, Cu, Al, Si and Be. May be. These metal elements are appropriately selected depending on the characteristics required for the composite oxide. For example, the addition of rare earth elements (except Ce, Tb, Eu, La and Pr), Al, Si and Be further improves the heat resistance of the composite oxide, and the addition of Ni and Cu purifies the exhaust gas of the composite oxide. The effect is further enhanced.
また、本実施形態における複合酸化物は、９００℃付近の高温に曝された後も大きな比表面積を有するとともに３００℃以下という低温領域においても優れた酸化還元能を呈するという効果を奏する限りにおいて、上記金属元素以外の元素を含んでいてもよい。 In addition, the composite oxide in the present embodiment has a large specific surface area even after being exposed to a high temperature around 900 ° C. and exhibits an excellent redox ability even in a low temperature region of 300 ° C. or lower. Elements other than the above metal elements may be included.
本実施形態における複合酸化物は、公知の合成方法を用いて製造できるが、比表面積を大きくするという目的を達成するためには、共沈法により製造することが好ましい。さらに好ましくは、後述の実施例に記載のように、原料塩水溶液を加熱処理する工程を含む共沈法を用いる。 The composite oxide in the present embodiment can be produced using a known synthesis method, but it is preferably produced by a coprecipitation method in order to achieve the purpose of increasing the specific surface area. More preferably, a coprecipitation method including a step of heat-treating the raw salt aqueous solution is used, as described in the examples below.
本実施形態における複合酸化物の耐熱性は、９００℃において４時間焼成した後の比表面積の大きさで評価し、比表面積はＢＥＴ法を用いて測定する。この耐熱性の評価方法は、助触媒材料の耐熱性の評価として一般的に行われる方法である。そして、９００℃において４時間焼成した後の比表面積が２０ｍ２/ｇ以上である複合酸化物、好ましくは２５ｍ２/ｇ以上である複合酸化物、さらに好ましくは３０ｍ２/ｇ以上である複合酸化物は、排気ガス浄化触媒の助触媒として優れた酸化還元能を維持することができる。なお、比表面積の測定方法の詳細は、後述の実施例中で述べる。 The heat resistance of the composite oxide in this embodiment is evaluated by the size of the specific surface area after firing at 900 ° C. for 4 hours, and the specific surface area is measured using the BET method. This evaluation method of heat resistance is a method generally performed as evaluation of the heat resistance of the promoter material. A composite oxide having a specific surface area of 20 m 2 / g or more after firing at 900 ° C. for 4 hours, preferably a composite oxide of 25 m 2 / g or more, more preferably 30 m 2 / g or more. The product can maintain an excellent oxidation-reduction ability as a promoter of the exhaust gas purification catalyst. The details of the method for measuring the specific surface area will be described in Examples described later.
本実施形態における複合酸化物の排気ガス浄化触媒の助触媒としての酸化還元能は、昇温還元スペクトル（Temperature Programmed Reduction Spectra）を測定することにより推測することができる。そして、昇温還元スペクトルは、試料に対して水素ガスなどの還元ガスを流しながら試料を一定速度で昇温していき、各温度で還元に使用された還元ガスの量を測定することにより得られる。そのため、昇温還元スペクトルは、測定物質の還元能の温度依存性を表すスペクトルである。そして、より低温側にピークが現れている物質の方が、より低温において還元能を示すこととなり、より低温において排気ガス浄化触媒の助触媒として作用しうることとなる。具体的には、昇温還元スペクトルにおいて、３００℃以下にピークが現れていれば、３００℃以下において排気ガス浄化触媒の助触媒として作用しうることとなる。なお、昇温還元スペクトルの測定方法の詳細は後述の実施例中で述べる。 The oxidation-reduction ability of the composite oxide as a co-catalyst of the exhaust gas purification catalyst of the present embodiment can be estimated by measuring a temperature programmed reduction spectrum (Temperature Programmed Reduction Spectra). The temperature reduction spectrum is obtained by heating the sample at a constant rate while flowing a reducing gas such as hydrogen gas through the sample, and measuring the amount of reducing gas used for the reduction at each temperature. It is done. Therefore, the temperature reduction spectrum is a spectrum representing the temperature dependence of the reducing ability of the measurement substance. A substance having a peak on the lower temperature side exhibits a reducing ability at a lower temperature, and can act as a promoter of the exhaust gas purification catalyst at a lower temperature. Specifically, if a peak appears at 300 ° C. or lower in the temperature reduction spectrum, it can act as a promoter for the exhaust gas purification catalyst at 300 ° C. or lower. The details of the temperature reduction spectrum measurement method will be described later in Examples.
本実施例では、表１から３に示す組成式の複合酸化物を用いて、比表面積（単位：ｍ２／ｇ）及び昇温還元スペクトルを測定し、各複合酸化物の組成式または組成比との関係を調べた。 In this example, the specific surface area (unit: m 2 / g) and the temperature reduction spectrum were measured using the composite oxides having the composition formulas shown in Tables 1 to 3, and the composition formula or composition ratio of each composite oxide was measured. I investigated the relationship with.
＜各複合酸化物の合成方法＞
比表面積（単位：ｍ２／ｇ）及び昇温還元スペクトルを測定するにあたり、実施例１から８、参考例１から３及び比較例１から３で用いる複合酸化物を以下に示す手法で合成した。
−実施例１−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びバリウム塩を、Ｃｅ、Ｚｒ、Ｂｉ及びＢａのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｂａ＝０．４７５：０．４７５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。なお、一般に、ジルコニウム塩は数重量％のハフニウム（Ｈｆ）を含有している場合があり、ここで言うジルコニウムのモル量にはハフニウムのモル量も含まれている。そして、還流器付きフラスコを用いて、準備した水溶液に対して１００℃、１５時間の加熱処理を行い、加熱処理後、水冷によりその水溶液の温度を室温まで冷却した。それから、その水溶液を１００ｇ／Ｌの炭酸水素アンモニウム水溶液５Ｌを用いて中和した。そして、懸濁した中和後の水溶液をヌッチェを用いて固液分離した。得られた固体を、純水によりデカンテーションとろ過とを１０回繰り返す洗浄を行った後、箱型電気炉に入れて、空気中において５００℃、１０時間の焼成を行い、乳鉢を用いて粉砕した。これにより、表１に示す組成式（Ｃｅ０．５０Ｚｒ０．５０）０．９５（Ｂｉ０．５０Ｂａ０．５０）０．０５Ｏ１．９６２５の複合酸化物を得た。
−実施例２−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びバリウム塩を、Ｃｅ、Ｚｒ、Ｂｉ及びＢａのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｂａ＝０．４７５：０．４７５：０．０１２５：０．０３７５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表１に示す組成式（Ｃｅ０．５０Ｚｒ０．５０）０．９５（Ｂｉ０．２５Ｂａ０．７５）０．０５Ｏ１．９５６２５の複合酸化物を得た。
−実施例３−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びバリウム塩を、Ｃｅ、Ｚｒ、Ｂｉ及びＢａのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｂａ＝０．５７：０．３８：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．６Ｚｒ０．４）０．９５（Ｂｉ０．５Ｂａ０．５）０．０５Ｏ１．９６２５の複合酸化物を得た。
−実施例４−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びバリウム塩を、Ｃｅ、Ｚｒ、Ｂｉ及びＢａのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｂａ＝０．２３７５：０．７１２５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．２５Ｚｒ０．７５）０．９５（Ｂｉ０．５Ｂａ０．５）０．０５Ｏ１．９６２５の複合酸化物を得た。
−実施例５−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びストロンチウム塩を、Ｃｅ、Ｚｒ、Ｂｉ及びＳｒのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｓｒ＝０．４７５：０．４７５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９５（Ｂｉ０．５Ｓｒ０．５）０．０５Ｏ１．９６２５の複合酸化物を得た。
−実施例６−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びカルシウム塩を、Ｃｅ、Ｚｒ、Ｂｉ及びＣａのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｃａ＝０．４７５：０．４７５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９５（Ｂｉ０．５Ｃａ０．５）０．０５Ｏ１．９６２５の複合酸化物を得た。
−参考例１−
セリウム（ＩＶ）塩、ジルコニウム塩、ニオブ塩及びバリウム塩を、Ｃｅ、Ｚｒ、Ｎｂ及びＢａのモル比がＣｅ：Ｚｒ：Ｎｂ：Ｂａ＝０．４７５：０．４７５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９５（Ｎｂ０．５Ｂａ０．５）０．０５Ｏ１．９６２５の複合酸化物を得た。
−参考例２−
セリウム（ＩＶ）塩、ジルコニウム塩、バナジウム塩及びバリウム塩を、Ｃｅ、Ｚｒ、Ｖ及びＢａのモル比がＣｅ：Ｚｒ：Ｖ：Ｂａ＝０．４７５：０．４７５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９５（Ｖ０．５Ｂａ０．５）０．０５Ｏ１．９８７５の複合酸化物を得た。
−参考例３−
セリウム（ＩＶ）塩、ジルコニウム塩、ニオブ塩及びストロンチウム塩を、Ｃｅ、Ｚｒ、Ｎｂ及びＳｒのモル比がＣｅ：Ｚｒ：Ｎｂ：Ｓｒ＝０．４７５：０．４７５：０．０２５：０．０２５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表２に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９５（Ｎｂ０．５Ｓｒ０．５）０．０５Ｏ１．９８７５の複合酸化物を得た。
−実施例７−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩、バリウム塩及びニッケル塩を、Ｃｅ、Ｚｒ、Ｂｉ、Ｂａ及びＮｉのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｂａ：Ｎｉ＝０．４５：０．４５：０．０２５：０．０２５：０．０５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表３に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９（Ｂｉ０．５Ｂａ０．５）０．０５Ｎｉ０．０５Ｏ１．９１２５の複合酸化物を得た。
−実施例８−
セリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩、バリウム塩及びアルミニウム塩を、Ｃｅ、Ｚｒ、Ｂｉ、Ｂａ及びＡｌのモル比がＣｅ：Ｚｒ：Ｂｉ：Ｂａ：Ａｌ＝０．４５：０．４５：０．０２５：０．０２５：０．０５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表３に示す組成式（Ｃｅ０．５Ｚｒ０．５）０．９（Ｂｉ０．５Ｂａ０．５）０．０５Ａｌ０．０５Ｏ１．９３７５の複合酸化物を得た。
−比較例１−
セリウム（ＩＶ）塩、ジルコニウム塩及びビスマス塩を、Ｃｅ、Ｚｒ及びＢｉのモル比がＣｅ：Ｚｒ：Ｂｉ＝０．４７５：０．４７５：０．０５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。そして、還流器付きフラスコを用いて、準備した水溶液に対して１００℃、１５時間の加熱処理を行い、加熱処理後、水冷によりその水溶液の温度を室温まで冷却した。それから、冷却後の水溶液にアンモニア水溶液を用いて中和し、混合水溶液のｐＨをｐＨ＝８．５とした。そして、懸濁した中和後の水溶液をヌッチェを用いて固液分離した。得られた固体を、純水によりデカンテーションとろ過とを１０回繰り返す洗浄を行った後、箱型電気炉に入れて、空気中において５００℃、１０時間の焼成を行い、乳鉢を用いて粉砕した。これにより、表１に示す組成式（Ｃｅ０．５０Ｚｒ０．５０）０．９５Ｂｉ０．０５Ｏ１．９７５の複合酸化物を得た。
−比較例２−
セリウム（ＩＶ）塩、ジルコニウム塩及びバリウム塩を、Ｃｅ、Ｚｒ及びＢａのモル比がＣｅ：Ｚｒ：Ｂａ＝０．４７５：０．４７５：０．０５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、実施例１で用いた複合酸化物の合成方法に従って、表１に示す組成式（Ｃｅ０．５０Ｚｒ０．５０）０．９５Ｂａ０．０５Ｏ１．９５の複合酸化物を得た。
−比較例３−
セリウム（ＩＶ）塩、ジルコニウム塩を、Ｃｅ及びＺｒのモル比がＣｅ：Ｚｒ＝０．５：０．５であり、酸化物換算濃度が５０ｇ／Ｌとなるように調整して酸性の水溶液３Ｌを準備した。その後、比較例１で用いた複合酸化物の合成方法に従って、表１に示す組成式Ｃｅ０．５０Ｚｒ０．５０Ｏ２の複合酸化物を得た。
<Method for synthesizing each composite oxide>
In measuring the specific surface area (unit: m 2 / g) and the temperature-programmed reduction spectrum, the composite oxides used in Examples 1 to 8, Reference Examples 1 to 3 and Comparative Examples 1 to 3 were synthesized by the following method. .
Example 1
A cerium (IV) salt, a zirconium salt, a bismuth salt and a barium salt have a molar ratio of Ce, Zr, Bi, and Ba of Ce: Zr: Bi: Ba = 0.475: 0.475: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. In general, the zirconium salt may contain several weight% of hafnium (Hf), and the molar amount of zirconium mentioned here includes the molar amount of hafnium. And using the flask with a reflux, the heat processing for 100 degreeC and 15 hours were performed with respect to the prepared aqueous solution, and the temperature of the aqueous solution was cooled to room temperature by water cooling after heat processing. The aqueous solution was then neutralized with 5 L of a 100 g / L aqueous ammonium bicarbonate solution. Then, the suspended neutralized aqueous solution was subjected to solid-liquid separation using a Nutsche. The obtained solid was washed with decantation and filtration 10 times with pure water, then placed in a box-type electric furnace, baked in air at 500 ° C. for 10 hours, and pulverized using a mortar did. Thereby, a composite oxide having a composition formula (Ce 0.50 Zr 0.50 ) 0.95 (Bi 0.50 Ba 0.50 ) 0.05 O 1.9625 shown in Table 1 was obtained.
-Example 2-
A cerium (IV) salt, a zirconium salt, a bismuth salt and a barium salt have a molar ratio of Ce, Zr, Bi and Ba of Ce: Zr: Bi: Ba = 0.475: 0.475: 0.0125: 0.0375. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Then, according to the synthesis method of the composite oxide used in Example 1, the composition formula (Ce 0.50 Zr 0.50 ) 0.95 (Bi 0.25 Ba 0.75 ) 0.05 O 1 shown in Table 1. A composite oxide of 95625 was obtained.
Example 3
A cerium (IV) salt, a zirconium salt, a bismuth salt, and a barium salt have a molar ratio of Ce, Zr, Bi, and Ba of Ce: Zr: Bi: Ba = 0.57: 0.38: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Then, according to the synthesis method of the composite oxide used in Example 1, the composition formula (Ce 0.6 Zr 0.4 ) 0.95 (Bi 0.5 Ba 0.5 ) 0.05 O 1 shown in Table 2. .9625 composite oxide was obtained.
Example 4
A cerium (IV) salt, a zirconium salt, a bismuth salt, and a barium salt have a molar ratio of Ce, Zr, Bi, and Ba of Ce: Zr: Bi: Ba = 0.375: 0.7125: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Then, according to the synthesis method of the composite oxide used in Example 1, the composition formula (Ce 0.25 Zr 0.75 ) 0.95 (Bi 0.5 Ba 0.5 ) 0.05 O 1 shown in Table 2. .9625 composite oxide was obtained.
-Example 5
A cerium (IV) salt, a zirconium salt, a bismuth salt, and a strontium salt have a molar ratio of Ce, Zr, Bi, and Sr of Ce: Zr: Bi: Sr = 0.475: 0.475: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Thereafter, in accordance with the method for synthesizing the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.95 (Bi 0.5 Sr 0.5 ) 0.05 O 1 shown in Table 2 was used. .9625 composite oxide was obtained.
-Example 6
A cerium (IV) salt, a zirconium salt, a bismuth salt, and a calcium salt have a molar ratio of Ce, Zr, Bi, and Ca of Ce: Zr: Bi: Ca = 0.475: 0.475: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Thereafter, according to the method for synthesizing the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.95 (Bi 0.5 Ca 0.5 ) 0.05 O 1 shown in Table 2 was used. .9625 composite oxide was obtained.
-Reference Example 1-
A cerium (IV) salt, a zirconium salt, a niobium salt, and a barium salt have a molar ratio of Ce, Zr, Nb, and Ba of Ce: Zr: Nb: Ba = 0.475: 0.475: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Then, according to the synthesis method of the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.95 (Nb 0.5 Ba 0.5 ) 0.05 O 1 shown in Table 2. .9625 composite oxide was obtained.
-Reference example 2-
A cerium (IV) salt, a zirconium salt, a vanadium salt, and a barium salt have a molar ratio of Ce, Zr, V, and Ba of Ce: Zr: V: Ba = 0.475: 0.475: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Then, according to the synthesis method of the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.95 (V 0.5 Ba 0.5 ) 0.05 O 1 shown in Table 2. 9875 complex oxide was obtained.
-Reference example 3-
A cerium (IV) salt, a zirconium salt, a niobium salt, and a strontium salt have a molar ratio of Ce, Zr, Nb, and Sr of Ce: Zr: Nb: Sr = 0.475: 0.475: 0.025: 0.025. Then, an acidic aqueous solution 3 L was prepared by adjusting the oxide equivalent concentration to 50 g / L. Thereafter, according to the method for synthesizing the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.95 (Nb 0.5 Sr 0.5 ) 0.05 O 1 shown in Table 2. 9875 complex oxide was obtained.
- Example 7 -
The cerium (IV) salt, zirconium salt, bismuth salt, barium salt and nickel salt are mixed with a molar ratio of Ce, Zr, Bi, Ba and Ni of Ce: Zr: Bi: Ba: Ni = 0.45: 0.45: It was 0.025: 0.025: 0.05, and adjusted so that an oxide conversion density | concentration might be 50 g / L, 3 L of acidic aqueous solution was prepared. Then, according to the synthesis method of the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.9 (Bi 0.5 Ba 0.5 ) 0.05 Ni 0 shown in Table 3. A composite oxide of .05 O 1.9125 was obtained.
- Example 8 -
The cerium (IV) salt, zirconium salt, bismuth salt, barium salt and aluminum salt have a molar ratio of Ce, Zr, Bi, Ba and Al of Ce: Zr: Bi: Ba: Al = 0.45: 0.45: It was 0.025: 0.025: 0.05, and adjusted so that an oxide conversion density | concentration might be 50 g / L, 3 L of acidic aqueous solution was prepared. Thereafter, according to the method for synthesizing the composite oxide used in Example 1, the composition formula (Ce 0.5 Zr 0.5 ) 0.9 (Bi 0.5 Ba 0.5 ) 0.05 Al 0 shown in Table 3. A composite oxide of .05 O 1.9375 was obtained.
-Comparative Example 1-
The cerium (IV) salt, zirconium salt and bismuth salt have a molar ratio of Ce, Zr and Bi of Ce: Zr: Bi = 0.475: 0.475: 0.05 and an oxide equivalent concentration of 50 g / L. 3 L of acidic aqueous solution was prepared so that it might become. And using the flask with a reflux, the heat processing for 100 degreeC and 15 hours were performed with respect to the prepared aqueous solution, and the temperature of the aqueous solution was cooled to room temperature by water cooling after heat processing. Then, the aqueous solution after cooling was neutralized with an aqueous ammonia solution to adjust the pH of the mixed aqueous solution to pH = 8.5. Then, the suspended neutralized aqueous solution was subjected to solid-liquid separation using a Nutsche. The obtained solid was washed with decantation and filtration 10 times with pure water, then placed in a box-type electric furnace, baked in air at 500 ° C. for 10 hours, and pulverized using a mortar did. Thereby, a composite oxide having a composition formula (Ce 0.50 Zr 0.50 ) 0.95 Bi 0.05 O 1.975 shown in Table 1 was obtained.
-Comparative Example 2-
The cerium (IV) salt, zirconium salt, and barium salt have a molar ratio of Ce, Zr, and Ba of Ce: Zr: Ba = 0.475: 0.475: 0.05 and an oxide equivalent concentration of 50 g / L. 3 L of acidic aqueous solution was prepared so that it might become. Then, according to the composite oxide synthesis method used in Example 1, a composite oxide having a composition formula (Ce 0.50 Zr 0.50 ) 0.95 Ba 0.05 O 1.95 shown in Table 1 was obtained. .
-Comparative Example 3-
A cerium (IV) salt and a zirconium salt are adjusted so that the molar ratio of Ce and Zr is Ce: Zr = 0.5: 0.5, and the oxide equivalent concentration is 50 g / L. Prepared. Then, according to the composite oxide synthesis method used in Comparative Example 1, composite oxides having the composition formula Ce 0.50 Zr 0.50 O 2 shown in Table 1 were obtained.
以上の手法で複合酸化物を合成した後、各複合酸化物の比表面積及び昇温還元スペクトルを測定した。
＜比表面積の測定方法＞
５ｇの各複合酸化物を、最大容積が３０ｍｌである磁性るつぼの中に入れた。このとき、１つの磁性るつぼの中に一種類の複合酸化物のみを入れた。そして、予め９００℃の温度に設定しておいた電気炉に、５ｇの各複合酸化物が入った磁性るつぼを入れた。４時間後、電気炉からその磁性るつぼを取り出し、室温まで冷却させた。冷却後の各複合酸化物を２００ｍｇはかりとり、フローソーブＩＩ２３００（マイクロメトリック社製）を用いて、ＢＥＴ法（Brunauer-Emmett-Teller方法）により比表面積を測定した。
＜昇温還元スペクトルの測定方法＞
昇温還元スペクトルの測定には、自動昇温脱離分析装置ＴＰ５０００（大倉理研製）を用いた。具体的には、空気中において９００℃、４時間加熱した各複合酸化物５００ｍｇをＵ字型の石英管に充填させて、その石英管にＡｒガス９０％及びＨ２ガス１０％からなる混合ガスを流速３０ｍｌ／ｍｉｎ．で流通させながら、１０℃／ｍｉｎ．の昇温速度で、温度範囲５０℃から１０００℃まで測定を行った。
＜測定結果＞
表１から表３に、各複合酸化物の比表面積（単位：ｍ２／ｇ）の値及び昇温還元スペクトルにおいて最も低温側に現れるピークにおける温度の値（以下、「ピーク温度」という。）を示す。図１から図５に、各々、表１に記載の複合酸化物の昇温還元スペクトルを示す。
＜考察＞
まず、比表面積の測定結果からは、次のようなことがいえる。
After synthesizing the composite oxide by the above method, the specific surface area and the temperature-programmed reduction spectrum of each composite oxide were measured.
<Method for measuring specific surface area>
5 g of each composite oxide was placed in a magnetic crucible having a maximum volume of 30 ml. At this time, only one kind of complex oxide was put in one magnetic crucible. Then, a magnetic crucible containing 5 g of each composite oxide was put in an electric furnace that had been set to a temperature of 900 ° C. in advance. After 4 hours, the magnetic crucible was removed from the electric furnace and allowed to cool to room temperature. 200 mg of each composite oxide after cooling was weighed, and the specific surface area was measured by BET method (Brunauer-Emmett-Teller method) using Flowsorb II2300 (manufactured by Micrometric).
<Measurement method of temperature-programmed reduction spectrum>
For the measurement of the temperature-programmed reduction spectrum, an automatic temperature-programmed desorption analyzer TP5000 (manufactured by Okura Riken) was used. Specifically, 500 mg of each composite oxide heated in air at 900 ° C. for 4 hours is filled in a U-shaped quartz tube, and the quartz tube is a mixed gas composed of Ar gas 90% and H 2 gas 10%. At a flow rate of 30 ml / min. At 10 ° C./min. The temperature was measured from a temperature range of 50 ° C. to 1000 ° C.
<Measurement results>
Tables 1 to 3 show the specific surface area (unit: m 2 / g) value of each composite oxide and the temperature value at the peak appearing on the lowest temperature side in the temperature-programmed reduction spectrum (hereinafter referred to as “peak temperature”). Indicates. FIG. 1 to FIG. 5 show the temperature reduction spectra of the composite oxides listed in Table 1, respectively.
<Discussion>
First, the following can be said from the measurement result of the specific surface area.
表１に示すように、実施例１及び２の複合酸化物の比表面積の値は、比較例１の複合酸化物の比表面積の値よりも約３．５倍大きい。また、実施例２の複合酸化物の方が実施例１の複合酸化物よりも比表面積の値は大きい。そして、９００℃で４時間焼成した後の各複合酸化物の比表面積を測定している。以上より、Ｂａを加えることにより複合酸化物の耐熱性が高められている。 As shown in Table 1, the value of the specific surface area of the composite oxides of Examples 1 and 2 is about 3.5 times larger than the value of the specific surface area of the composite oxide of Comparative Example 1. Further, the value of the specific surface area of the composite oxide of Example 2 is larger than that of the composite oxide of Example 1. And the specific surface area of each complex oxide after baking at 900 degreeC for 4 hours is measured. From the above, the heat resistance of the composite oxide is enhanced by adding Ba.
また、実施例１の複合酸化物の比表面積が３０．８ｍ２／ｇであるため、モル比がＢｉ：Ｂａ＝１：１であるＢａを含んでいる複合酸化物は、Ｂｉを添加することによる高温での比表面積の低下を実用上可能な程度十分に阻止することができる。また、表１より、実施例２の複合酸化物の比表面積と比較例２の複合酸化物の比表面積とは、等しい値を示している。比較例２の複合酸化物にはＢｉが含まれていないため、比較例２の複合酸化物は９００℃で４時間焼成してもＢｉによる比表面積の低下が生じることはない。一方、実施例２の複合酸化物はＢｉが含まれているため、実施例２の複合酸化物を９００℃で４時間焼成すると比表面積が低下する虞はある。しかし、実施例２の複合酸化物の比表面積と比較例２の複合酸化物の比表面積とは同一の値を示しているため、モル比がＢｉ：Ｂａ＝１：３であるＢａを含んでいる複合酸化物は、Ｂｉ添加による高温での比表面積の低下を完全に阻止することができ、その結果、比表面積は実用上非常に有用な大きさを有することとなる。 Further, since the composite oxide of Example 1 has a specific surface area of 30.8 m 2 / g, Bi is added to the composite oxide containing Ba having a molar ratio of Bi: Ba = 1: 1. It is possible to sufficiently prevent the decrease in the specific surface area at a high temperature due to the practical use. Further, from Table 1, the specific surface area of the composite oxide of Example 2 and the specific surface area of the composite oxide of Comparative Example 2 show the same value. Since Bi is not contained in the composite oxide of Comparative Example 2, even if the composite oxide of Comparative Example 2 is baked at 900 ° C. for 4 hours, the specific surface area due to Bi does not decrease. On the other hand, since the composite oxide of Example 2 contains Bi, the specific surface area may decrease when the composite oxide of Example 2 is baked at 900 ° C. for 4 hours. However, since the specific surface area of the composite oxide of Example 2 and the specific surface area of the composite oxide of Comparative Example 2 show the same value, it contains Ba having a molar ratio of Bi: Ba = 1: 3. The composite oxide can completely prevent a decrease in the specific surface area at a high temperature due to Bi addition, and as a result, the specific surface area has a very useful size in practice.
なお、エンジンの排気ガス浄化触媒の助触媒としては、９００℃で４時間焼成した後の比表面積が２０ｍ２／ｇ以上であれば、一般に十分に実用的である。 In general, the co-catalyst for the exhaust gas purification catalyst of the engine is sufficiently practical if the specific surface area after calcination at 900 ° C. for 4 hours is 20 m 2 / g or more.
また、表２に示すように、実施例３から６及び参考例１から３の複合酸化物の比表面積は、２０ｍ２／ｇ以上であるため、実用上非常に有用な大きさである。換言すると、元素ＡとしてＮｂやＶを用いても、元素ＢとしてＳｒやＣａを用いても、比表面積を実用上有用な大きさとすることができる。さらに、表２に示すいずれの複合酸化物も２０ｍ２／ｇ以上の比表面積を有していることから、元素Ａ及び元素Ｂの組み合わせは特に限定されない。但し、後述するように、元素ＡにＢｉを必須構成元素として含むことによって、昇温還元スペクトルのピーク温度をより低下することができる。 In addition, as shown in Table 2, the specific surface areas of the composite oxides of Examples 3 to 6 and Reference Examples 1 to 3 are 20 m 2 / g or more, which is a very useful size in practical use. In other words, even if Nb or V is used as the element A and Sr or Ca is used as the element B, the specific surface area can be practically useful. Furthermore, since any composite oxide shown in Table 2 has a specific surface area of 20 m 2 / g or more, the combination of element A and element B is not particularly limited. However, as will be described later, by including Bi as an essential constituent element in the element A, the peak temperature of the temperature reduction spectrum can be further reduced.
また、表３に示すように、実施例１０及び１１の複合酸化物の比表面積は、２０ｍ２／ｇ以上であるため、実用上非常に有用な大きさである。そのため、ＮｉやＡｌが添加された複合酸化物であっても、その複合酸化物の比表面積を実用上非常に有用な大きさとすることができる。 Further, as shown in Table 3, the specific surface area of the composite oxides of Examples 10 and 11 is 20 m 2 / g or more, which is a very useful size in practical use. Therefore, even if it is a complex oxide to which Ni or Al is added, the specific surface area of the complex oxide can be made very useful in practice.
実施例１から４の結果より、複合酸化物におけるＣｅとＺｒとのモル比が異なっても、その複合酸化物の比表面積は、２０ｍ２／ｇ以上であり、実用上非常に有用な大きさである。 From the results of Examples 1 to 4, even if the molar ratio of Ce and Zr in the composite oxide is different, the specific surface area of the composite oxide is 20 m 2 / g or more, which is a very useful size for practical use. It is.
また、昇温還元スペクトルの測定結果からは、次のようなことがいえる。 Moreover, the following can be said from the measurement result of the temperature-programmed reduction spectrum.
表１並びに図１、２、３、４及び５に示すように、Ｂｉが含まれることによりピークは低温側へシフトすることがわかる。さらに、実施例１及び２の複合酸化物のピーク温度の方が比較例１の複合酸化物のピーク温度よりも低いため、Ｂａが含まれることにより複合酸化物の低温側の還元能が高まる。そして、実施例１及び２の複合酸化物においては３００℃以下にピークを備えているため、実施例１及び２の複合酸化物は、３００℃以下においても排気ガス浄化触媒の助触媒として作用することができる。 As shown in Table 1 and FIGS. 1, 2, 3, 4 and 5, it can be seen that the peak shifts to the low temperature side by including Bi. Furthermore, since the peak temperature of the composite oxides of Examples 1 and 2 is lower than the peak temperature of the composite oxide of Comparative Example 1, the inclusion of Ba increases the reducing ability on the low temperature side of the composite oxide. Since the composite oxides of Examples 1 and 2 have a peak at 300 ° C. or less, the composite oxides of Examples 1 and 2 function as a promoter for the exhaust gas purification catalyst even at 300 ° C. or less. be able to.
また、表２に示すように、実施例３から６の複合酸化物についても、その昇温還元スペクトルのピーク温度は３００℃以下である。そのため、実施例３から６の複合酸化物も、３００℃以下においても排気ガス浄化触媒の助触媒として作用する。換言すると、元素ＢとしてＳｒやＣａを用いても、その複合酸化物は３００℃以下においても排気ガス浄化触媒の助触媒として作用する。さらに、表２に示すいずれの複合酸化物も、３００℃以下のピーク温度を示しているため、元素Ａ及び元素Ｂの組み合わせは特に限定されない。
In addition, as shown in Table 2, the peak temperature of the temperature reduction spectrum of the composite oxides of Examples 3 to 6 is 300 ° C. or lower. Therefore, the composite oxides of Examples 3 to 6 also act as promoters for the exhaust gas purification catalyst even at 300 ° C. or lower. In other words, even with Sr and Ca as elemental B, also acts as a co-catalyst of the exhaust gas purifying catalyst in the
また、表３に示すように、実施例７及び８の複合酸化物についても、その昇温還元スペクトルのピーク温度は３００℃以下である。そのため、ＮｉやＡｌが添加された複合酸化物であっても、３００℃以下においても排気ガス浄化触媒の助触媒として作用する。 Moreover, as shown in Table 3, the peak temperature of the temperature reduction spectrum of the composite oxides of Examples 7 and 8 is 300 ° C. or lower. Therefore, even a complex oxide to which Ni or Al is added acts as a promoter for the exhaust gas purification catalyst even at 300 ° C. or lower.
実施例１から４の結果より、複合酸化物におけるＣｅとＺｒとのモル比が異なっても、昇温還元スペクトルのピーク温度の値がそれほど大きく変化することはなく、３００℃以下においても排気ガス浄化触媒の助触媒として作用する。 From the results of Examples 1 to 4, even if the molar ratio of Ce and Zr in the composite oxide is different, the peak temperature value of the temperature-reduction spectrum does not change so much, and the exhaust gas is also below 300 ° C. Acts as a co-catalyst for the purification catalyst.
そして、昇温還元スペクトルの測定結果及び比表面積の測定結果においては、次のようなことがいえる。 The following can be said in the measurement results of the temperature reduction spectrum and the measurement results of the specific surface area.
実施例１と比較例１とを比較すると、ピーク温度はいずれも３００℃以下であるが、比表面積は比較例１の複合酸化物がＢａを含んでいないために９．２ｍ２／ｇと著しく小さな値を示す。また、実施例１の測定結果と比較例２の測定結果とを比較すると、比表面積はいずれの場合も３０ｍ２／ｇ以上であるが、ピーク温度は比較例２の複合酸化物がＢｉを含んでいないために５５０℃と著しく高い温度を示す。そして、上記の測定結果は、実施例２の測定結果と比較例１の測定結果または比較例２の測定結果とを比較した場合にも該当する。以上より、比較例１の複合酸化物のようにＣｅとＺｒとＢｉとを含みＢａを含まない複合酸化物は、比表面積が小さいために排気ガス浄化触媒の助触媒として実用的に用いることはできず、比較例２の複合酸化物のようにＣｅとＺｒとＢａとを含みＢｉを含まない複合酸化物は、３００℃以下という低温領域においては排気ガス浄化触媒の助触媒としての触媒能を呈しないために排気ガス浄化触媒の助触媒として実用的に用いることはできない。すなわち、Ｃｅ−Ｚｒ系複合酸化物に、酸化ビスマス及び酸化バリウムの両方を添加することにより初めて、比表面積が２０ｍ２／ｇ以上であり且つ３００℃以下においても排気ガス浄化触媒の助触媒として実用上非常に有用な触媒能を呈することとなる。 When Example 1 and Comparative Example 1 are compared, the peak temperatures are all 300 ° C. or less, but the specific surface area is remarkably 9.2 m 2 / g because the composite oxide of Comparative Example 1 does not contain Ba. Indicates a small value. Further, when the measurement result of Example 1 and the measurement result of Comparative Example 2 are compared, the specific surface area is 30 m 2 / g or more in any case, but the peak temperature includes Bi in the composite oxide of Comparative Example 2 Therefore, it shows a remarkably high temperature of 550 ° C. And said measurement result corresponds also when the measurement result of Example 2 and the measurement result of the comparative example 1 or the measurement result of the comparative example 2 are compared. As described above, the composite oxide containing Ce, Zr, and Bi and not containing Ba like the composite oxide of Comparative Example 1 has a small specific surface area, so that it can be practically used as a promoter of the exhaust gas purification catalyst. The composite oxide containing Ce, Zr, and Ba and not containing Bi like the composite oxide of Comparative Example 2 has a catalytic ability as a promoter of the exhaust gas purification catalyst in a low temperature region of 300 ° C. or lower. Therefore, it cannot be used practically as a promoter for the exhaust gas purification catalyst. That is, for the first time by adding both bismuth oxide and barium oxide to a Ce-Zr composite oxide, it is practically used as a co-catalyst for an exhaust gas purification catalyst even when the specific surface area is 20 m 2 / g or more and 300 ° C. or less. In addition, a very useful catalytic ability is exhibited.
また、表２に記載の複合酸化物は、上述のように、実施例１及び２の複合酸化物と略同一の効果を奏する。そのため、Ｃｅ−Ｚｒ系複合酸化物に、酸化ビスマスの代わりに酸化ニオブや酸化バナジウムを添加し、酸化バリウムの代わりに酸化カルシウムや酸化ストロンチウムを添加しても、その複合酸化物は、比表面積が２０ｍ２／ｇ以上であり且つ３００℃以下においても排気ガス浄化触媒の助触媒として実用上非常に有用な触媒能を呈する。 Moreover, the composite oxides shown in Table 2 have substantially the same effects as the composite oxides of Examples 1 and 2 as described above. Therefore, even if niobium oxide or vanadium oxide is added instead of bismuth oxide and calcium oxide or strontium oxide is added instead of barium oxide, the composite oxide has a specific surface area. Even if it is 20 m 2 / g or more and 300 ° C. or less, it exhibits a practically very useful catalytic ability as a promoter of the exhaust gas purification catalyst.
また、表３に記載の複合酸化物は、上述のように、実施例１及び２の複合酸化物と略同一の効果を奏する。そのため、ＮｉやＡｌが添加された複合酸化物であっても、比表面積が２０ｍ２／ｇ以上であり且つ３００℃以下においても排気ガス浄化触媒の助触媒として実用上非常に有用な触媒能を呈する。 Moreover, the composite oxide described in Table 3 has substantially the same effect as the composite oxides of Examples 1 and 2 as described above. Therefore, even if it is a composite oxide to which Ni or Al is added, it has a practically very useful catalytic ability as a co-catalyst for an exhaust gas purification catalyst even when the specific surface area is 20 m 2 / g or more and 300 ° C. or less. Present.
なお、比表面積が２５ｍ２／ｇ以上であれば、より多くの酸化還元反応の活性点を有するため、比表面積が２５ｍ２／ｇ以上であることが好ましい。また、ピーク温度は２８０℃よりも低温であれば、より低温での排気ガス浄化触媒の助触媒として作用しうることとなる。 Incidentally, if the specific surface area set at 25m 2 / g or more, because they have active points more redox reaction, it preferably has a specific surface area of 25 m 2 / g or more. If the peak temperature is lower than 280 ° C., it can act as a promoter for the exhaust gas purification catalyst at a lower temperature.
ここで、本実施例において、元素ＡとしてはＢｉを例に挙げ、元素ＢとしてはＢａ，Ｃａ，Ｓｒを例に挙げたが、元素Ａ及び元素Ｂはこれに限定されることはない。元素ＡとしてはＢｉ，Ｖ，Ｔｉ，Ｎｂ，Ｗ，Ｆｅ，Ｐｒ，Ｔｂ及びＥｕからなる群の金属元素のうち少なくともＢｉを含んでいればよく、また、元素Ｂとしては、Ｂａ，Ｓｒ，Ｃａ，Ｍｇ，Ｌａからなる群より選ばれた少なくとも一つを含んでいればよい。従って、例えば、本実施例における複合酸化物として、Ｃｅ，Ｚｒ，Ｂｉ，Ｖ，Ｂａ，Ｓｒからなる複合酸化物としてもよい。また、複合酸化物の組成式は、（Ｃｅ１−ｘＺｒｘ）１−ｚ（Ａ１−ｙＢｙ）ｚＯδ（式中、ｘ，ｙ，ｚ，δはそれぞれ、０．０５≦ｘ≦０．９５、０．０１≦ｙ≦０．９９、０．０１≦ｚ≦０．３、１．３６５≦δ≦１．９９５を満たす数字である）で表される複合酸化物を用いることができる。また、比表面積が２０ｍ２／ｇ以上であり且つ３００℃以下においても排気ガス浄化触媒の助触媒として実用上非常に有用な触媒能を呈するという効果を奏する限り、複合酸化物に対して、上記金属元素以外の元素が添加されていてもよい。 In this embodiment, Bi is given as an example of the element A, and Ba, Ca, and Sr are given as examples of the element B. However, the element A and the element B are not limited to this. The element A only needs to contain at least Bi among the metal elements of the group consisting of Bi, V, Ti, Nb, W, Fe, Pr, Tb, and Eu, and the element B includes Ba, Sr, Ca And at least one selected from the group consisting of Mg and La. Therefore, for example, the composite oxide in this embodiment may be a composite oxide composed of Ce, Zr, Bi, V, Ba, and Sr. Further, the composition formula of the composite oxide is (Ce 1-x Zr x ) 1-z (A 1-y B y ) z O δ (wherein x, y, z, and δ are 0.05 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.99, 0.01 ≦ z ≦ 0.3, 1.365 ≦ δ ≦ 1.995). be able to. In addition, as long as the specific surface area is 20 m 2 / g or more and 300 ° C. or less has an effect of exhibiting practically very useful catalytic ability as a co-catalyst for the exhaust gas purification catalyst, Elements other than metal elements may be added.
また、本実施例における複合酸化物を合成する際に用いたセリウム（ＩＶ）塩、ジルコニウム塩、ビスマス塩及びバリウム塩などは特に限定しなかったが、水酸化物、塩化物、硝酸塩などの無機性塩であっても良く、また、アセチルアセトナト錯体などの有機性塩であってもよい。 Further, the cerium (IV) salt, zirconium salt, bismuth salt and barium salt used for synthesizing the composite oxide in this example were not particularly limited, but inorganic such as hydroxide, chloride, nitrate, etc. It may be an organic salt, or may be an organic salt such as an acetylacetonato complex.
また、本実施例における複合酸化物を合成する際には原料塩水溶液を加熱処理する工程を含む共沈法を用いて合成したが、これに限定されることはなく、固相反応法、加水分解法などの公知の合成方法を用いることができる。なお、比表面積を大きくするという目的を達成するためには、本実施例に記載したように、原料塩水溶液を加熱処理する工程を含む共沈法を用いて合成することが好ましい。 Moreover, when synthesizing the composite oxide in this example, it was synthesized using a coprecipitation method including a step of heat-treating the raw material salt aqueous solution, but the present invention is not limited to this. A known synthesis method such as a decomposition method can be used. In order to achieve the purpose of increasing the specific surface area, it is preferable to synthesize using a coprecipitation method including a step of heat-treating the raw material salt aqueous solution as described in this example.
また、複合酸化物を合成する際の焼成工程は、酸化雰囲気であっても、還元雰囲気であっても、または、これらの雰囲気を交互に繰り返し変更して行ってもよい。 Further, the firing step when synthesizing the composite oxide may be performed in an oxidizing atmosphere, a reducing atmosphere, or by alternately and repeatedly changing these atmospheres.
以上説明したように、本発明は、複合酸化物、特にガソリンや軽油の燃焼により供給されるエネルギーが駆動力となるエンジン、例えば自動車などの内燃機関から排出される排気ガスを浄化する排気ガス浄化触媒の助触媒などに利用することができる。
As described above, the present invention is an exhaust gas purification system that purifies exhaust gas discharged from an internal combustion engine such as an automobile, such as an automobile, whose driving force is energy supplied by combustion of complex oxides, particularly gasoline and light oil. It can be used as a catalyst cocatalyst.
Claims (4)
（式中、ｘ，ｙ，ｚ，δはそれぞれ、０．０５≦ｘ≦０．９５、０．０１≦ｙ≦０．９９、０．０１≦ｚ≦０．３、１．３６５≦δ≦１．９９５を満たす数字である）で表され、
Ａは、Ｂｉ，Ｖ，Ｔｉ，Ｎｂ，Ｗ，Ｆｅ，Ｐｒ，Ｔｂ及びＥｕからなる群の金属元素のうち少なくともＢｉを含み、
Ｂは、Ｂａ，Ｓｒ，Ｃａ，Ｍｇ，Ｌａからなる群より選ばれた少なくとも一つを含む、複合酸化物。General formula (Ce 1-x Zr x ) 1-z (A 1-y B y ) z O δ
(Wherein x, y, z, and δ are 0.05 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.99, 0.01 ≦ z ≦ 0.3, and 1.365 ≦ δ ≦, respectively. It is a number that satisfies 1.995),
A includes at least Bi among the metal elements of the group consisting of Bi, V, Ti, Nb, W, Fe, Pr, Tb, and Eu,
B is a composite oxide containing at least one selected from the group consisting of Ba, Sr, Ca, Mg, and La.
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| JP5190196B2 (en) | 2006-12-01 | 2013-04-24 | Ｄｏｗａエレクトロニクス株式会社 | Composite oxide for exhaust gas purification catalyst, exhaust gas purification catalyst, and diesel exhaust gas purification filter |
| WO2009044736A1 (en) * | 2007-10-01 | 2009-04-09 | Dowa Electronics Materials Co., Ltd. | Cerium-containing complex oxide, method of producing the same, pm combustion catalyst and diesel particulate filter |
| WO2009131118A1 (en) * | 2008-04-23 | 2009-10-29 | Ｄｏｗａエレクトロニクス株式会社 | Composite oxide for catalyst for exhaust gas purification, process for producing the same, coating composition for catalyst for exhaust gas purification, and filter for diesel exhaust gas purification |
| JP5503155B2 (en) * | 2009-01-30 | 2014-05-28 | 新コスモス電機株式会社 | Carbon monoxide removal filter |
| JP5229096B2 (en) * | 2009-05-11 | 2013-07-03 | トヨタ自動車株式会社 | Exhaust gas purification catalyst |
| CN103180046B (en) * | 2010-11-16 | 2016-11-16 | 尤米科尔股份公司及两合公司 | For removing the catalyst of denitrification from the aerofluxus of Diesel engine |
| PL2724776T3 (en) | 2011-06-01 | 2018-02-28 | Rhodia Operations | Complex oxide, method for producing same, and exhaust gas purification catalyst |
| JP2013129553A (en) * | 2011-12-21 | 2013-07-04 | Rhodia Operations | Compound oxide, production method thereof and exhaust gas purification catalyst |
| JP5706476B2 (en) * | 2013-07-01 | 2015-04-22 | 新コスモス電機株式会社 | Carbon monoxide oxidation catalyst and production method thereof |
| CN110002459A (en) * | 2019-04-12 | 2019-07-12 | 成都理工大学 | A kind of preparation method for mixing nickel europium boride |
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| JP2003071250A (en) * | 2001-06-18 | 2003-03-11 | Nissan Motor Co Ltd | Exhaust gas cleaning system |
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| JP2002097021A (en) * | 2000-09-19 | 2002-04-02 | Matsushita Electric Ind Co Ltd | High temperature conductive oxide, electrode for fuel cell and fuel cell using the same |
| JP4345909B2 (en) * | 2001-12-11 | 2009-10-14 | 吟也 足立 | Composite oxide having low-temperature redox ability and method for producing the same |
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| JP2003071250A (en) * | 2001-06-18 | 2003-03-11 | Nissan Motor Co Ltd | Exhaust gas cleaning system |
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| WO2005085137A1 (en) | 2005-09-15 |
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