JPS6137980B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention removes carbon monoxide and hydrocarbons from the air.
The present invention relates to an oxidation catalyst that can be oxidized and rendered harmless at temperatures ranging from a low temperature of around 100°C to a temperature higher than that, and a method for producing the same. As is well known, carbon monoxide is a typical inert gas, so there are very few catalysts that can oxidize it at low temperatures and render it harmless. Conventionally known catalysts include Mn, Cu, Co,
Hopcalite catalyst, which consists of Ag oxide, shows activity at room temperature, but its activity is lost in the presence of a small amount of moisture, and silver oxide catalyst and silver permanganate catalyst show activity even in the presence of moisture, but the reaction may be slow. However, they have drawbacks such as being stoichiometric, short-lived, and expensive. Further, catalysts using various metal oxides require complicated processing techniques to impart activity to the metal oxides. The present invention uses one or more types of Cu, Ag, Au, Zn, Cd, Hg, Ti, Zr, V,
Composite of hydroxides or oxides of transition metals such as Nb, Cr, Mo, Mn, Fe, Co, Ni, etc., to oxidize carbon monoxide and hydrocarbons at temperatures as low as about 100℃ and above. The purpose of the present invention is to provide a highly active catalyst and a method for producing the same. The ion-exchangeable montmorillonite and vermiculite used in the present invention both have layered crystal structures. One unit position of the crystal is a three-layer lattice of "silicate tetrahedron - octahedron centered on a hexacoordination ion - silicate tetrahedron", and these unit layers overlap in the C-axis direction of the crystal. Monovalent or divalent interlayer ions released from the charge balance of the three-layer lattice are coordinated between the unit layers, and in montmorillonite,
Na ⁺ , Li ^{+ ,} Ca ^{2+ ,} etc., and in vermiculite, Mg ²⁺ are mainly coordinated as interlayer ions, and these interlayer ions are surrounded by water molecules. The general chemical formula of montmorillonite is Wo. ₃₃ (Al3/5Mg1/3)(Si ₄ O ₁₀ )(OH) ₂ ·nH ₂ O. (However, W indicates an interlayer ion.) The general chemical formula of vermiculite is W _{0.6 to 0.9 Mg 3} (Si, Al) ₄ O ₁₀ (OH) _{2.2H 2} O. (However, W indicates an interlayer ion.) Montmorillonite exhibits remarkable hydration swelling property when exposed to water. In other words, when a lump or powder of montmorillonite is immersed in water, it draws a large amount of water molecules between the crystal layers and swells. , as it progresses further, the interlayer bond is finally broken, and the thickness becomes less than about 100 Å and 0.01 to 0.1
It is broken down into flake-like elementary particles with a diameter of μ. These elementary flakes are negatively charged in water to form a stable sol, and in this sol form, the surface area of montmorillonite is 200 m ² /g or more. Also, although vermiculite is not hydration-swellable, if a lump or powder of vermiculite that has been previously crushed into 60 meshes or more is suddenly placed in a heating furnace at 900 to 1,000 degrees Celsius, the interlayer hydration will occur. Due to vaporization and dehydration, it expands rapidly into an accordion shape, reducing its original thickness to 15 mm.
When the expanded body is crushed, flaky particles with a surface area of 10 to 15 m ² /g are obtained. Next, the properties of montmorillonite and vermiculite that are relevant to the present invention will be explained. (1) Ion exchange capacity: In water, interlayer ions have cation exchange properties, and the cation exchange capacity (CEC) is 80 to 150 meq/100g for montmorillonite and 100 to 150 meq/100g for montmorillonite and vermiculite. It is vermiculite. Ion exchange is performed by adding an electrolyte to a sol-like slurry of 1% or less for montmorillonite, and to a 3% or less slurry for vermiculite. (2) Complexity with metal hydroxide: Montmorillonite or vermiculite with ion exchange properties (hereinafter referred to as layered silicate minerals)
and Cu, Ag, Au, Zn, Cd, Hg, which will be described later.
Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Co, Ni
The composite of transition metals such as hydroxides can be achieved by the following two methods. The first method is to add an alkali to a slurry of cation-exchanged layered silicate minerals, hydroxylate the exchanged ions, and compound transition metal hydroxide between the crystal layers. It is possible to composite hydroxides of a plurality of transition metals by using up to five types of cations exchanged. Part 2 is a hydroxy cation form of a transition metal hydroxide prepared in advance, for example, M ₂ (OH) _2y-x (H ₂ O) x (where y is the valence number of the metal M, and x is 6 or less). However, the interlayer ions (Ma ⁺ and
This is a method of exchanging it with Li ⁺ ). The composite of the layered silicate mineral and transition metal hydroxide (hereinafter referred to as composite a) produced in this way is approximately
The powder obtained by heating and drying at 100°C has the activity of a solid acid. This composite a is made using montmorillonite because montmorillonite and vermiculite are fine particles in the form of flakes.
m ² /g or more, using vermiculite
It has a surface area of 10 m ² /g or more, which means that the contact area with gas increases, and the performance as a catalyst improves. This complex a is not one in which regular charges are neutralized. In other words, originally, the interlayer ion (indicated by W in the general chemical formula above) 1
One monovalent metal should be coordinated per metal, but in this complex a, the above metal is present in excess. For example, when iron hydroxide is combined with montmorillonite in the form of Fe ₂ (OH) ₅ (H ₂ O) instead of Fe (OH) ₃ , it forms [Fe ₂ (OH) ₅ (H ₂ O)].
3 A compound expressed as [Al3/5Mg1/3) (Si ₄ O ₁₀ ) (OH) ₂ ] is generated, and when combined with vermiculite, [Fe ₂ (OH) ₅ (H ₂ O)] is generated. _{0.6 ～ 0.9}・
A compound represented by [Mg ₃ (Si, Al) ₄ O ₁₀ (OH) ₂ ] is generated. In other words, [Fe(OH) ₅ (H ₂ O)]
This is an ion exchange reaction where ⁺ corresponds to the monovalent Na ⁺ and produces Fe-OH. This product polarizes the solid acid, or water molecule, to form H ₂ O→OH ^- +H ⁺ .
OH ^- combines with Fe ³⁺ and dissociates H ⁺ near it
It is of the Brønstedt acid type that attracted Fe ³⁺ on the surface of this layered silicate mineral
It shows the activity as described below depending on the bonding state between ions and oxygen on the surface of the layered silicate mineral. All of the complexes a produced by the ion exchange reaction exhibit activity. (3) Complex with transition metal oxide: Complex a as it is or with the addition of an oxidizing agent, and further heated at 200°C.
When heated at a temperature above, the transition metal hydroxide dehydrates and becomes a transition metal oxide. The activation mechanism in the present invention is a composite mechanism of the layered silicate mineral and the transition metal hydroxide, the layered silicate mineral, the transition metal, and the oxide, and the metal formed by this mechanism. This is due to the bonding state of hydroxyl group (OH) ^- and oxygen (O ^- or O ^2- ) with. That is, the surface of the layered silicate mineral is filled with silicate tetrahedral oxygen arranged in a hexagonal network. For example, the coordination number is 6.
When Cr ³⁺ undergoes alkali treatment or exchanges and coordinates with interlayer ions of the layered silicate mineral in the form of hydroxy cation, both eventually become W ⁺
It is exchanged in the state of [Cr ₂ (OH ⁾ ₅ (H ₂ O ₎ ] ⁺ or 2 [Cr (OH) _2.5 (H ₂ O) _0.5 ] _0.5+ , corresponding to the ^charge of However, in this Cr ion, OH is coordinated on the oxygen on the surface of the layered silicate mineral by hydrogen bonding. In this case, the electronegativity of the silicate tetrahedron is strong, so Cr ³⁺ is attracted, and schematically,

[Formula] (OH) and H ₂ O, such as the bond shown by the broken line in the three coordinate sites on the right, have weak bonds, and especially H ₂ O and the like are easily eliminated by drying, producing unsaturated coordinate sites. Although it varies depending on the type of exchange ion species and the combination of multiple ions, at 80 to 150°C, (OH) begins to dissociate, creating unsaturated coordination sites, which become active sites and generate O ^- , It is thought that it adsorbs O ^2- and desorbs it to oxidize CO and other hydrocarbons that require oxygen. In addition, a layered silicate mineral-transition metal oxide composite (hereinafter referred to as composite b) obtained by heating this composite a with or without an oxidizing agent is further activated. In other words, it has an unsaturated coordination site that can attach and detach active O ^- and O ^2- or directly adsorb C≡O.

It is thought that it exhibits the activity as shown in [Formula]. The above-mentioned activation mechanism is influenced by the bonding relationship between the metal and oxygen. This is because in the relationship between metals and oxygen, the following metals that form n-type semiconductor oxides with an excess of metal tend to form unsaturated coordination sites of the metal; It is thought that in the metal formed, the metal ions are strongly attracted to the oxygen on the layered silicate mineral side, so that the oxygen occupying the coordination site becomes weak and unstable in bond, and is easily attached and detached, exhibiting an oxidation catalytic effect. The activation mechanism of the present invention is applicable not only to the hydroxide of a single type of transition metal or the composite of a transition metal oxide and a layered silicate mineral as described above, but also to the combination of a layered silicate mineral and multiple types of metals. A composite of transition metal hydroxides and transition metal oxides in combination also exhibits activity. This method introduces a mutual interference effect due to the multicomponent composition, and the valence control method, that is, the excess of cations due to ions of different valences, causes the unsaturated arrangement to occur between different metal ions bonded to silicate on the same mineral particle. Create a seat,
The purpose is to encourage the expression of active oxygen when there is a lack of cations, and to cause the appearance of active sites through mutual interference between metal ions with different ionic radii, polarizability, coordination number, etc. The metals used in the present invention are transition metals, and are Ib (Cu, Ag,
Au), Hb (Zn, Cd, Hg), IVb (Ti, Zr), Vb
(V, Nb), Vb (Cr, Mo), Vb (Mn),
Vb (Fe, Co, Ni), etc. In particular, transition metals such as P-type semiconductors Cu ⁺ , Ag ⁺ , Mn ²⁺ , Cr ³⁺ , and n-type semiconductors Cu ²⁺ , Fe ²⁺ , Zn ²⁺ , Ti ⁴⁺ , V ⁵⁺ , etc. Although they are not oxides or semiconductors, the hydroxides of the transition metals mentioned above not only exhibit high activity, but are also economically preferable because they can be supplied at low cost, and do not generate harmful gases at high temperatures. By using hydroxides and oxides of transition metals such as iron and zinc, it is safe for humans and livestock and does not pollute the environment. These transition metal hydroxides or transition metal oxides may be used singly in combination with the layered silicate mineral as described above, but the activity becomes even higher when used in combination of two or more. . For example, Mn and Cu, Mu and Ag, Mn and Co and Ag, Mn and Cu
Good combinations of Co, Ag, Cu, Fe, V, etc.
Many other combinations are possible. These transition metals are used in the form of water-compatible salts, such as nitrates, hydrochlorides, sulfates, and the like. In order to ion-exchange the interlayer ions of the layered silicate mineral with the transition metal ions, about 1 to 2 moles of a transition metal salt is added to a dilute slurry of about 1% to 4% of the layered silicate mineral while stirring. Add an aqueous solution of If you continue stirring for another 30 to 60 minutes, ion exchange will take place during this time.
In that case, PH indicates acidity at the 2nd to 4th positions. Then 3~
Add 5N NaOH and stir while keeping the pH alkaline in the transition metal hydroxide forming region, then let stand. By the above operations, a complex in which the transition metal hydroxide is coordinated in the interlayer region of the layered silicate mineral is produced. Next, this composite product is separated by filtration or centrifugation, and washed with water until unreacted transition metal ions and ions by-produced by ion exchange are removed. Even if this composite a is heated without adding an oxidizing agent, the metal oxide dehydrates to become a transition metal oxide at 300° C. or higher. Another method of oxidation is to treat with alkali hydroxide, and if necessary, further treat with an oxidizing agent such as sodium hypochlorite or hydrogen peroxide, wash with water, and then dry and heat. Even during heat treatment, transition metal hydroxides become oxides. The composite of the layered silicate mineral and transition metal oxide (hereinafter referred to as composite b) thus produced is extremely highly active. In this composite b, it is possible to combine not only the oxide of a single metal but also the oxides of two or more metals. The method is a step of exchanging interlayer ions of the layered silicate mineral with transition metal ions,
An electrolyte solution that dissociates two or more types of cations may be added. The oxidation catalysts of composite a and composite b of the present invention can be used in the form of powder particles such as powder granules and pellets, depending on the purpose, and can also be molded into air permeable porous bodies, perforated bodies, honeycomb bodies, etc. used. The oxidation catalyst of the present invention can also be used in applications where there is a possibility of diffusion during use, such as combustion wicks in kerosene stoves,
It is used for purposes such as addition to briquettes, pea charcoal, tobacco leaves, etc. to achieve complete combustion and removal of Co. Next, examples of this invention will be shown. Example 1 Disperse 100 g of montmorillonite in 10 g of water, add 400 g of a 1 molar aqueous solution of ferric nitrate to this dispersion.
ml and 150 ml of a 1 molar aqueous solution of zinc nitrate were simultaneously added with stirring and stirring continued for about 1 hour. Next, 280ml of 5N NaOH aqueous solution was gradually added dropwise while stirring, and the pH of the suspension was stirred for about 24 hours after the dropwise addition was completed.
was 6.10. After separating this suspension into solid and liquid,
The solid phase portion was washed with water and dried at 110°C. As a result of examining this dried product by X-ray diffraction, differential thermal analysis, thermogravimetric analysis, and measurement of ion exchange capacity, etc., it was found that multiple metal hydroxides of iron and zinc were composited between the montmorillonite layers. This composite was further heated at 350° C. for 3 hours, and the hydroxide between the layers was changed into an oxide by a dehydration reaction, thereby obtaining an iron/zinc multiple metal oxide-montmorillonite composite. This composite was pulverized into 14 to 20 meshes to obtain a granular catalyst. In addition, the above-mentioned iron/zinc multi-metal hydroxide-montmorillonite composite before drying was made into a slurry with a solid content of about 20%, and this slurry was spread on a release paper and about
A film-like composite was obtained by drying at a temperature of 50°C. This film-like composite was heated at 350° C. for 3 hours to obtain a film of an iron/zinc multi-metal oxide-montmorillonite composite, which was used as a film-like catalyst. Further, this film was cut into a size of 1 mm square to obtain a flaky catalyst. Example 2 900 vermiculite grains approximately 2 mm square in size
The vermiculite that swelled by being placed in an electric furnace kept at ℃ for 5 minutes was washed several times with a 5N NaCl aqueous solution to replace interlayer ions with Na ions. This Na
5 g of type vermiculite particles were washed several times with a 0.2N zinc nitrate aqueous solution, and interlayer ions were further replaced with Z ²⁺ _o . 1 5g of this Zn type vermiculite
0.1N while stirring slowly.
of NaOH was added dropwise until the pH of the solution reached 8, and stirring was continued for an additional 24 hours after the dropwise addition was completed. After the stirring was completed, the solid content was washed several times with water and dried at 110°C.
As a result of taking a part of the dried material and pulverizing it and examining it by X-ray diffraction, differential thermal analysis, thermogravimetric analysis, and measurement of ion exchange capacity, it was found that zinc was compounded in the form of hydroxide between the vermiculite layers. I found out that Further, as a result of chemical analysis, the combined amount of zinc hydroxide was approximately 100 mg/g. This zinc hydroxide-vermiculite composite was further heated at 400°C for 3 hours to obtain a zinc oxide composite vermiculite. This composite was highly porous with a surface area of 27.5 m ² /g. Example 3 Vermiculite grains with a size of about 2 mm square are
It was placed in an electric furnace kept at 900℃ for 5 minutes to expand, then wet-pulverized in a ball mill for 3 hours, and then washed 5 times with a 5N sodium chloride solution to remove interlayer ions.
This was converted into Na ions and then sieved to prepare a dispersion liquid 3 with a concentration of 3% and a 200 mesh pass. To this dispersion, 150 ml of a 1M aqueous solution of ferric nitrate and 210 ml of a 1M aqueous solution of cupric nitrate were gradually added dropwise while stirring at the same time, stirring was continued for about 1 hour, and then 5N
The pH of the suspension was adjusted between 8 and 8.5 using an aqueous NaOH solution. In order to further combine V and Ag into the above composite, a predetermined amount of silver vanadate is added to this suspension. This silver vanadate is made by dissolving 20 g of ammonium vanadate in 250 ml of warm water, adding NaOH to make it alkaline, boiling it for about 10 minutes to volatilize the ammonia, and adding silver nitrate dissolved in pure water to this solution.
It is made by adding 3.0 g to cause precipitation of silver vanadate. This silver vanadate precipitate was added to the above suspension.
After stirring for 24 hours and repeating filtration and water washing, the solid content
It was dried at 110°C for 24 hours. As a result of X-ray diffraction, differential thermal analysis, and thermogravimetric analysis, it was confirmed that a composite metal hydroxide of the four types of metals was formed between the layers of vermiculite. Furthermore, it was confirmed through filtration and chemical analysis of the dry powder that the added metal was combined with vermiculite. The results of X-ray diffraction, differential thermal analysis, and thermogravimetric analysis of the above dried powder heated at 350°C for 3 hours showed that it changed to an oxide due to the dehydration reaction of the hydroxide between the layers, and that the four types of vermiculite and It was confirmed that a complex with metal oxide was formed. Example 4 A mixed aqueous solution of Fe 3+ and Cr ₃₊ (A) consisting of 160 ml of a 0.1 ^M aqueous solution of iron nitrate [Fe ₂ ( _{NO 3 ) 3} ] and 40 ml of a 0.1 M aqueous solution of chromium nitrate [Cr( ^{NO 3} ) 3 ]. To this, 200 mesh passes of a 1.0% dispersion (B) of vermiculite in which interlayer ions had been exchanged with Na ⁺ were gradually added over about 1 hour with stirring. In the reaction in this system, Fe ³⁺ +2.49OH ^- →
[Fe( _{OH) 2.49 ]} ^0.51+ and ^Cr3+ +2.49OH ^- → ^[ Cr
(OH) _2.49 ] _0.51+ gradually ^occurs , and at the same time, the hydroxy cations of Fe and Cr, which are the reaction products of these, are exchanged between the vermiculite layers by an ion exchange ^reaction with Na ⁺ between the vermiculite layers. It is compounded. The suspension obtained by the above reaction was filtered, washed with water, and then dried at 110°C. As a result of examining the obtained solid material by X-ray diffraction, it was confirmed that hydroxides of Fe and Cr were combined between the vermiculite layers. Further, this composite was heat-treated at 350° C. for 3 hours to obtain a multiple metal oxide-vermiculite composite of Fe and Cr. Example 5 75 ml of a 1M aqueous solution of iron chloride and 85 ml of a 1.7M aqueous solution of titanium sulfate were simultaneously added to montmorillonite 0.4% sol 5 with stirring, and after stirring for about 1 hour,
50 ml of 5N aqueous sodium hydroxide solution was slowly added dropwise, and the mixture was further stirred for 24 hours. The pH of this suspension was 5.25. After filtering and washing the solid matter with water, it was dried at 110°C for 1 hour. It was confirmed by X-ray diffraction that this product was a composite of multiple metal hydroxides of iron and titanium between the montmorillonite layers. further this
A multi-metal oxide-montmorillonite composite of iron and titanium was obtained by heat treatment at 400°C for 3 hours. As a result of measuring the surface acidity of this complex by n-butylamine titration method, an acid with a strength of PK = 4.6 was found.
It was found that 0.52 meg/g was present. The catalysts obtained in Examples 1 to 5 were tested for carbon monoxide oxidation performance in the following manner. The sample of Example 1 was a composite with hydroxide, consisting of 5 g of film with a wall thickness of 50 to 60 μm and a width of 20 mm (length approx.
10 cm) in a spiral shape with an outer diameter of 13 mm or less, and in the case of a composite with an oxide, 5 g of a 1 mm square flake was used. In addition, each sample of Examples 2 to 5 was made by pressurizing the composite with hydroxide to 200 to 300 kg/cm ² and molding it into a cylindrical body with a diameter of 20 mm x 5 mm, which was then crushed again to form 14 to 20 mesh pieces. This powder was used as a sample, and this powder was heated to obtain a composite with an oxide and used as a sample. 5 g of each was collected and used for testing. The catalyst activity test method is: inner diameter 15mm wall thickness 2mm length
Each sample was filled in the center of a 100 mm alumina porcelain tube, a thermometer was passed through the tube perpendicularly and airtightly placed, and air containing 6000 ppm of carbon monoxide gas was pumped through one end (inlet) of the tube at 1.0/min. Inject at a flow rate of 100 min. Heat the alumina porcelain tube from the outer periphery with a heating wire equipped with a variable resistor to maintain the sample filling part at a predetermined temperature. The gas that passed through the sample section was sampled from the other end (outlet) of the tube, and the carbon monoxide concentration was measured using the detector tube method.The results are shown in the table below.

[Table] As is clear from the above table, the oxidation catalyst of the composite of layered silicate mineral, metal hydroxide, and metal oxide of the present invention has excellent oxidation activity at temperatures of 100°C or higher. .

Claims (1)

[Scope of Claims] 1 Ion-exchanged Cu, Ag,
Au, Zn, Cd, Hg, Ti, Zr, V, Nb, Cr, Mo,
Oxidation catalyst containing hydroxides or oxides of transition metals such as Mn, Fe, Co, Ni, etc. 2 Cu, Ag, Au, Zn, Cd, Hg, Ti, Zr, V,
Transition metal ions such as Nb, Cr, Mo, Mn, Fe, Co, Ni, etc. are subjected to an ion exchange reaction with interlayer ions of montmorillonite or vermiculite, which have ion exchange properties, with or without alkali treatment, and finally Cu, Ag, Au, Zn, Cd, Hg, Ti, Zr, V,
A method for producing an oxidation catalyst, characterized by forming a composite in which transition metals such as Nb, Cr, Mo, Mn, Fe, Co, Ni, etc. are combined with hydroxides. 3 Interlayer ions of montmorillonite or vermiculite, which have ion exchange properties, are replaced with Cu, Ag,
Au, Zn, Cd, Hg, Ti, Zr, V, Nb, Cr, Mo,
After ion exchange with transition metal ions such as Mn, Fe, Co, Ni, etc., it is treated with alkali to form montmorillonite or vermiculite with Cu, Ag, Au, Zn,
Cd, Hg, Ti, Zr, V, Nb, Cr, Mo, Mn,
3. The method for producing an oxidation catalyst according to claim 2, wherein the oxidation catalyst is made into a composite with a hydroxide of a transition metal such as Fe, Co, or Ni. 4 Montmorillonite or vermiculite with ion exchange properties include Cu, Ag, Au, Zn, Cd,
Hg, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe,
Claim 2, characterized in that it is a composite of hydroxy-type cations of transition metals such as Co, Ni, etc.
1. Method for producing an oxidation catalyst as described in Section 1. 5 Cu, Ag, Au, Zn, Cd, Hg, Ti, Zr, V,
Transition metal ions such as Nb, Cr, Mo, Mn, Fe, Co, and Ni are subjected to an ion exchange reaction with interlayer ions of montmorillonite or vermiculite, which have ion exchange properties, with or without alkali treatment, and the final Cu, Ag, Au, Zn, Cd, Hg, Ti, Zr, V,
A method for producing an oxidation catalyst, which comprises forming a composite of transition metals such as Nb, Cr, Mo, Mn, Fe, Co, Ni, etc. combined with hydroxides, and then heating the composite.