JPH0240372B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a rare earth element colloidal liquid composition. Specifically, the present invention relates to a method for producing a rare earth element colloidal liquid composition for coating a catalyst carrier by vibrating, heating, etc. a precipitate obtained by reacting a soluble salt of a rare earth compound with ammonia. . A relatively thin film of activated alumina is supported on the surface of a honeycomb-shaped carrier made of a refractory material such as alumina, silica, alumina-silica, cordierite, mullite, and zirconia, and the catalyst carrier is coated with copper, nickel, cobalt, platinum, and palladium. A method of manufacturing a catalyst by impregnating and supporting a catalyst active component such as rhodium or the like is already known. Since the quality of this relatively thin layer of activated alumina (activated alumina coating) determines the catalyst performance, the activated alumina coating layer has a large surface area and does not peel off even when subjected to vibration or thermal shock. It is necessary to be firmly attached to the Furthermore, a method for improving the thermal properties of alumina by adding rare earth elements to the activated alumina coating layer has been proposed, for example, in U.S. Pat. No. 3,839,225; If an attempt is made to improve the thermal properties of alumina, a considerably large amount of rare earth elements is required, but on the other hand, the addition of a large amount of rare earth elements has the disadvantage that the properties of activated alumina are rather significantly lost. Furthermore, other methods for incorporating rare earth elements in the activated alumina coating layer have been proposed, for example in U.S. Pat. First, alumina coating is applied, then a soluble salt of a rare earth element is impregnated into the alumina coating layer, and calcined to convert the soluble salt of a rare earth element into an oxide of the rare earth element. Because rare earth elements were supported, the process was complicated, and corrosive gas was generated during drying and calcining of soluble salts of rare earth elements, which was an economic disadvantage because it shortened the life of the equipment used for alumina coating. In order to eliminate these drawbacks, the present inventors have developed a method for producing a colloidal liquid composition of rare earth elements that is highly active and has good adhesion and is suitable for alumina coating, and uses the liquid composition for alumina coating to coat rare earth elements. As a result of considering a method for adding soluble salts of rare earth elements, such as cerium nitrate, was added to a large excess of aqueous ammonia, thoroughly stirred and separated, and washing was repeated until the supernatant liquid had a pH of 10 or less. Afterwards, they discovered that a near-neutral liquid composition of cerium could be obtained by vigorously shaking and heating this precipitate, and they also discovered that the rare earth element liquid composition thus produced could be mixed with alumina sol or alumina slurry in any proportion. It has been found that when an alumina coating is applied using a conventional method, the catalytic activity and thermal properties after supporting a catalytic active component are significantly improved compared to an alumina coating obtained by a conventional method. In other words, since the rare earth element colloidal liquid composition produced by this production method contains almost no free ions, it can be added directly to an alumina liquid composition produced from boehmite (Japanese Patent Application Laid-Open No. 53-45314) in a short period of time. A uniform liquid composition is obtained without the phenomenon that gelation occurs over time and alumina coating cannot be applied, and even when alumina coating is performed by mixing it with an alumina slurry using γ-alumina etc., rare earth elements are not present. Because the particles are dispersed extremely uniformly and in a coarser particle size than when impregnated with soluble salts, and finer than when powdered oxide is mixed, adhesion to the carrier material during alumina coating is improved, and alumina It was found that the thermal properties of the catalyst were also improved and the catalytic activity was significantly improved. Hereinafter, a method for producing a rare earth element colloidal liquid composition for alumina coating for a catalyst carrier according to the present invention will be described in detail. A single salt or a mixture of two or more of soluble salts of rare earth elements such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, dysprosium, itteribium, etc.
An aqueous solution containing 1 mol is gradually added to an aqueous ammonia solution of 10 to 30 times, preferably 15 to 25 times the stoichiometric amount required to react with those salts, and is neutralized by stirring for 30 to 60 minutes. The order of neutralization is to add the soluble salt of the rare earth to the ammonia water, and it is also possible to add the soluble salt of the rare earth to the dilute ammonia water and simultaneously blow in the necessary amount of ammonia gas. If this operation is performed in reverse, a liquid composition of rare earth elements can be obtained in the end, but a highly catalytically active composition like the colloidal liquid composition produced by this production method cannot be obtained. After neutralization, the solution is allowed to stand, the supernatant liquid is removed by decantation, and the precipitate is separated using a centrifuge. Next, this precipitate is repulped into 20 to 30 g of deionized water, thoroughly stirred, and then separated using a centrifuge. If necessary, free ions are removed using a cation exchange resin and an anion exchange resin during repulping. If this operation is repeated, when repulping the precipitate, the precipitate and washing solution will not separate if left to stand naturally.When this state is reached, the suspended matter is separated using a centrifuge, the precipitate is taken out, and vibration treatment is performed. I went. The term "vibration treatment" as used herein refers to treatment in which the material is vigorously shaken for 30 minutes or more using a shaker or in the hand of an adult. If the suspension is then heated at a temperature of 60°C or higher, preferably 75 to 85°C, for 2 hours or more, preferably 2 to 4 hours, the viscosity of the suspension changes (increasing or decreasing depending on the type of rare earth salt). ) The color of the suspension changes markedly. When this state is reached, a colloidal liquid composition of rare earth elements according to the present invention is obtained. The colloidal liquid composition thus obtained can be kept as a uniform liquid composition even when stored for a long period of time, and the concentration of the rare earth element in the liquid composition can be adjusted by diluting it with water as necessary. Although this colloidal liquid composition can form an active oxide film (wash coating) as it is, it is usually better to mix it with an alumina slurry or an alumina liquid composition and use it for an activated alumina coating. This method is advantageous in terms of catalyst activity and raw material cost when used at low temperatures. Conventional methods for incorporating ceria into activated alumina coatings include, for example, U.S. Pat.
4206087, however, since the conventional method involves mixing powdered ceria and γ-alumina, it is not possible to disperse the ceria as uniformly as in the case of impregnating and supporting the ceria. When added in a large amount, the activity of γ-alumina decreases significantly. Furthermore, in the method of adding ceria to a liquid alumina composition to form an activated alumina coating, it is difficult to control the amount of ceria added and the catalytic activity does not improve. When soluble salts were added, it gelled within a short time and could not be used for activated alumina coatings. The colloidal liquid composition according to the present invention can be coated with activated alumina even when combined with either an alumina slurry or an alumina liquid composition, and has an appropriate viscosity that improves adhesion when coating with activated alumina. Since it has high catalytic activity itself, it has high catalytic activity even when mixed with alumina. The method of active alumina coating using the colloidal liquid composition of rare earth elements according to the present invention will be explained in detail below. Note that parts and percentages are based on weight unless otherwise specified. 25 to 95 parts of γ-alumina, preferably 60 to 90 parts, 1 to 70 parts of boehmite, preferably 5 to 30 parts, and 1 to 30 parts of acetic acid.
Add 5 to 50 parts, preferably 10 to 25 parts, of a colloidal liquid composition of a rare earth element to 100 parts of alumina slurry consisting of 30 parts, preferably 5 to 15 parts, and add water so that the pulp concentration is about 20%. Add and mix in a ball mill for at least 2 hours. If the obtained mixed alumina slurry is coated with activated alumina on a carrier material as required, the thin film containing the rare earth element according to the present invention can be firmly adhered to the carrier material. Another method is to use 5 to 25 parts of alumina liquid composition (Japanese Patent Application Laid-Open No. 53-45314), preferably 10 to 15 parts, and γ
- Add 5 to 50 parts, preferably 15 to 25 parts, of a colloidal liquid composition of a rare earth element to 100 parts of alumina slurry consisting of 10 to 30 parts of alumina, preferably 15 to 20 parts, so that the pulp concentration is 20% or more. By adding water to the mixture, mixing in a ball mill for 2 hours or more, and coating with activated alumina in the same manner, the thin film containing the rare earth element according to the present invention can be firmly adhered to the carrier material. The catalyst obtained by supporting catalytic active ingredients such as platinum, palladium, and rhodium on the support prepared in this way has a higher carbon monoxide, hydrocarbon and It was found that the purification performance of nitrogen oxides and its durability are excellent. As described above, the rare earth element colloidal liquid composition according to the present invention can be used in washes used for purifying carbon monoxide, hydrocarbons, and nitrogen oxides in automobile exhaust gas, industrial waste gas, household fuel waste gas, various deodorizing devices, etc. It can be applied to a very wide range of coatings. EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto. Example 1 In 80 parts by weight of 8 mol/aqueous ammonia
20 parts by weight of 0.2 mol/cerium nitrate was gradually added and stirred for 60 minutes. After stirring, the supernatant was allowed to stand still and the supernatant was decanted, and the remaining suspension was separated using a continuous centrifuge with a centrifugal force of 10,000 to 20,000 G. The precipitate was repulped with 60 parts by weight of deionized water.
The mixture was separated using a centrifuge in the same manner. 1 part by weight of deionized water was added to the resulting precipitate, which was vigorously shaken for 60 minutes using a shaker, and then heated at 85° C. for 2 hours to obtain a colloidal cerium liquid composition. At this time, the viscosity before and after shaking and heating should be measured using a rotational viscometer (Co., Ltd.).
Measured using a C-type viscometer manufactured by Tokyo Keiki Co., Ltd.
It dropped from 4200 cp to 850 cp, and the color tone changed from gray (it used to have a slight purple tinge) to purple.
The pulp concentration in the liquid composition was about 20%. 5 to 50 parts by weight of this liquid composition and γ-alumina 85
100 parts by weight of an alumina slurry consisting of 10 parts by weight of boehmite and 5 parts by weight of acetic acid and 400 parts by weight of water were mixed in a ball mill for 8 hours to obtain Wash Coating No. 1, a liquid composition for activated alumina coating containing rare earth elements. ~5 was prepared. Comparative Example 1 40 parts by weight of a 1N acetic acid solution was added to 50 parts by weight of alumina manufactured by Condea, and the mixture was kneaded for 10 minutes using a ribbon kneader. The kneaded product was then taken out from the kneader, placed in a sealed plastic container, and cured at room temperature for 60 minutes, and then dried for 16 hours in a dryer adjusted to 110°C.
After cooling this dry product to room temperature, it was gradually peptized in 117 parts by weight of water and cured for 5 hours with stirring to obtain a colloidal liquid composition. The alumina concentration was approximately 25%. From this, comparative liquid composition Wash Coating No. 14 was prepared. Comparative Example 2 Add 5 to 20 parts by weight of cerium oxide to 100 parts by weight of γ-alumina, 50 parts by weight of the colloidal liquid composition of Comparative Example 1, and 300 parts by weight of water, and mix in a ball mill for 16 hours to obtain a rare earth element-containing composition. Comparative wash coatings No. 15 to 17 were prepared. Example 2 A colloidal liquid composition was obtained in the same manner as in Example 1 using neodymium nitrate. In addition, when the viscosity was measured before and after shaking and heating in the same manner as in Example 1, it decreased from 4200 cp to 850 cp. 10 to 20 parts by weight of the obtained liquid composition, 10 parts by weight of an alumina liquid composition prepared in the same manner as in Comparative Example 1, and γ-
Alumina slurry 100 consisting of 20 parts by weight of alumina
parts by weight and 120 parts by weight of water were mixed in a ball mill for 10 hours to prepare a liquid composition for active alumina coating containing rare earth elements.
Nos. 6 and 7 were prepared. Example 3 Cerium oxide accounts for 49% of the total rare earth oxides, lanthanum oxide accounts for 33%, and praseodymium oxide accounts for 5%.
%, neodymium oxide in a proportion of 13%, 20 parts by weight of a rare earth element nitrate at a concentration of 0.3 mol/mole was gradually added to 70 parts by weight of 6 mol/ammonium water and stirred for 30 minutes. After stirring, the mixture was allowed to stand still and the supernatant liquid was decanted, and the remaining suspension was separated using a continuous centrifuge with a centrifugal force of 10,000 to 20,000 G.
It was repulped in 80 parts by weight of deionized water in the same manner as in Example 1 and separated using a centrifuge. 1 part by weight of deionized water was added to the resulting precipitate, which was vigorously shaken for 45 minutes using a shaker, and then heated at 75° C. for 150 minutes to obtain a colloidal rare earth element liquid composition. In addition,
When the viscosity was measured before and after shaking and heating in the same manner as in Example 1, it decreased from 4200 cp to 850 cp.
The pulp concentration of the liquid composition was approximately 28%. This liquid composition was used in the same manner as in Example 2 to prepare wash coatings Nos. 8 to 10 of liquid compositions for activated alumina coating containing rare earth elements. Example 4 15 parts by weight of a lanthanide group mixed nitrate obtained from a nitric acid extract of a rare earth raw material was added at a concentration of 0.4 mol/.
It was gradually added to 60 parts by weight of 9 mol/aqueous ammonia and stirred for 45 minutes. After stirring, the mixture was separated in the same manner as in Example 1. The precipitate was repulped with 150 parts by weight of deionized water and separated using a centrifuge in the same manner as in Example 1. 1 part by weight of deionized water was added to the resulting precipitate, which was vigorously shaken for 60 minutes using a shaker, and then heated at 80° C. for 2 hours to obtain a colloidal rare earth mixed liquid composition. In addition, when the viscosity was measured before and after shaking and heating in the same manner as in Example 1, it decreased from 4200 cp to 850 cp. The pulp concentration in the liquid composition was about 25%. Using this liquid composition, liquid compositions for activated alumina coating and wash coatings Nos. 11 to 13 were prepared in the same manner as in Example 1. Test Example A cordierite honeycomb carrier (cell density: 30 cells/in 2 ) was prepared using the activated alumina coating liquid compositions prepared in Examples 1 to 4 and the activated alumina coating compositions prepared in Comparative Examples 1 to ^2.
Approximately 15% alumina coating was applied to. After coating with alumina, it was calcined at 700°C for 3 hours. In Comparative Example 1, cerium nitrate was further impregnated at 2% (in terms of cerium oxide) based on the carrier weight, and the temperature was increased to 700°C.
It was calcined for 3 hours. In this honeycomb carrier 1, as palladium
Impregnated in an aqueous solution of a complex of palladium chloride containing 0.5 g and 1 part by weight of palladium with 2 parts by weight of azodicarbonamide, and then reduced with hydrogen at 500°C, followed by dinitrodiaminoplatinum containing 1.0 g of platinum and 1 weight of platinum. Wash coatings Nos. 1 to 17 were prepared by impregnating 2 parts by weight of azodicarbonamide and 1 part by weight of cystine in an aqueous solution of a complex, followed by hydrogen reduction at 500°C. Catalyst performance was determined based on the following test conditions:
A catalyst heat-treated in air at 850°C for 100 hours was evaluated, and the former was expressed as an initial purification rate, and the latter was expressed as a purification rate after durability. Catalyst performance test conditions Gas composition (volume basis) CO: 1.05% O ₂ : 0.9% H ₂ : 0.35% CO ₂ : 10% C ₃ H ₆ : 500 ppm H ₂ O: 10% NO: 500 ppm N ₂ : Balance Space velocity :75000Hr ^-1 Gas temperature 450℃ Test results are shown in Table 1.

[Table] *Although the rare earth liquid composition is not an oxide, it is described as an oxide to indicate the type of rare earth.

Claims (1)

[Claims] 1. A rare earth compound for coating a catalyst carrier, characterized in that a precipitate obtained by reacting a soluble salt of a rare earth compound with ammonia is filtered, washed, subjected to vibration treatment, and heated to 60°C or higher. A method for producing a colloidal liquid composition. 2 A rare earth colloidal liquid composition obtained by reacting a soluble salt of a rare earth compound with ammonia is filtered, washed, subjected to vibration treatment, and heated to 60°C or higher, and a colloidal alumina liquid composition is obtained. 1. A method for producing a rare earth colloidal liquid composition for coating a catalyst carrier, which comprises mixing the composition with a colloidal colloid and/or an alumina slurry.