JPH08290916A - Heat-resistant transition alumina and its production - Google Patents

Abstract

PURPOSE: To obtain a heat-resistant transition alumina large in the total volume of fine pores, having a high initial specific surface area and excellent in phosphorus-poisoning resistance by drying aluminum sulfate containing specific impurities in prescribed amounts to a prescribed water content under a prescribed drying condition and subsequently thermally decomposing the dried aluminum sulfate. CONSTITUTION: Lanthanum-containing aluminum sulfate containing aluminum in an amount of 100 pts.wt. (converted into alumina), sodium in an amount of <=0.10 pts.wt. (converted into Na2 O) lanthanum compounds in an amount of 1-12 pts.wt. (converted into La) and water in an amount exceeding 8 hydrates (converted into crystal water) is dried at a water-evaporating rate of 0.01-2.0mg/ sec per gram equivalent of Al2 (SO4 )3 into the dried product comprising the 8 hydrate or less, further dried into the dried product comprising the 6 hydrate or less and subsequently thermally decomposed into the subject alumina in a vertical gas flow contact type calcination oven. The produced alumina has a total fine pore volume of 0.6-2.0cc/g and good heat resistance expressed by an initial BET specific surface area of >=90m<2> /g and a BET specific surface area of >=60m<2> /g after heated at 1200 deg.C for 5hrs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant transition alumina and a method for producing the same, and more particularly to a catalyst for purifying automobile exhaust gas or a catalyst for purifying stationary engine exhaust gas, which is required to be resistant to phosphorus poisoning. The present invention relates to a heat resistant transition alumina suitable for a carrier and a method for producing the same.

[0002]

2. Description of the Prior Art Exhaust gas removal from internal combustion engines such as automobiles and motorcycles, as well as catalysts or catalyst carriers in the field of catalytic reactions at high temperatures such as gas turbines and boilers have become increasingly popular in recent years. Tend to. The carrier used in these fields is a catalyst carrier having a high specific surface area from the viewpoint of effective utilization of the catalyst component,
Usually, transitional alumina mainly composed of γ-alumina is often used. In addition, the use temperature of these carriers is 900 ° C. or higher, sometimes 1000 ° C., and even 1200 ° C. in some cases. Therefore, there is a demand for a catalyst carrier having excellent heat resistance with a small decrease in specific surface area even at high temperatures. Has been done.

However, as is well known, when transition alumina is exposed to a high temperature of 900 ° C. or higher, it undergoes a crystal transition into α-alumina crystals, and the specific surface area is remarkably reduced.

When a transition alumina is coated as a catalyst carrier on a molded product in the form of pellets or other forms, the structural change due to the crystal transition causes the coating layer to fall off or promote sintering of the catalyst component. Becomes

As a method for improving the thermal stability by preventing a decrease in the specific surface area of the transition alumina, it is known to add a rare earth element such as lanthanum or an element such as barium to the transition alumina.

For example, a method of depositing a rare earth substance on the above-mentioned alumina or alumina hydrate from a mixed solution of an aqueous solution in which alumina or alumina hydrate powder having a particle size of 500 microns or less is dispersed and a solution containing a rare earth substance. (JP-A-62-176542), a method in which a mixed solution of an aluminum alkoxide and a lanthanum alkoxide is hydrolyzed to obtain a sol, which is then gelled and baked (JP-A-63-242917) is known. Although it is
It is not known that the BET specific surface area exceeds 50 m ² / g after heat treatment at high temperature, for example, heat treatment at 1200 ° C. for 5 hours.

In view of these circumstances, the present inventor has a high initial BET specific surface area and excellent heat resistance with a small decrease in the specific surface area even at a high temperature of 1000 ° C. or higher. As a result of research for the purpose of finding a heat-resistant transition alumina that exhibits a large pore volume even when it is applied to the surface of a catalyst carrier having a low specific surface area, aluminum sulfate and a lanthanum compound are mixed, and the mixture is It was found that a transition alumina having a larger pore volume due to thermal decomposition after heating, a large initial specific surface area, and excellent heat resistance at high temperature can be obtained.
No. 14 was filed earlier. The transition alumina obtained by the method has a pore volume of 0.6 cc / g to 2.0 cc /
g, the initial specific surface area is 90 m ² / g or more, usually 100 m ² / g or more, and the BET specific surface area after baking at 1100 ° C. for 3 hours is 90 m ² / g or more, usually 100 m
^B / g of ² / g or more and after firing at 1200 ° C. for 3 hours
It has excellent heat resistance with an ET specific surface area of 50 m ² / g or more, and is suitable as it is, as a catalyst carrier of various shapes or a resin filler, or as a raw material for molding catalyst carriers of various shapes.

However, when the transition alumina obtained by the above method is applied as a catalyst carrier for the treatment of combustion exhaust gas containing a phosphorus compound, the above heat resistance may not be exhibited in some cases. The product yield may be low when adopting a high production efficiency firing method such as a rotary kiln, a flash calcination furnace, or a fluidized firing furnace for the thermal decomposition of the aluminum sulfate, and the combustion exhaust gas containing a phosphorus compound is treated. In this case, there has been a strong demand for the development of a transition alumina that exhibits excellent heat resistance and a production method having a high yield from the viewpoint of cost reduction.

[0009]

The object of the present invention is to have a large pore volume and a high initial BET specific surface area, and to obtain a high specific surface area even at a high temperature in contact with a combustion exhaust gas containing a phosphorus compound. An object of the present invention is to provide a transition alumina having excellent heat resistance with little decrease, and a method for producing heat resistant transition alumina capable of obtaining a high product yield even in a calcination method having industrially high production efficiency.

[0010]

In view of the above circumstances, the inventors of the present invention have made further diligent studies, and as a result, when adjusting the amount of specific impurities in the raw material aluminum sulfate to be thermally decomposed to a specific amount or less, A vertical-flow contact-type calcining furnace that has excellent heat resistance and that has a small decrease in specific surface area even if it is in contact with combustion exhaust gas containing a phosphorus compound and that has an industrially high production efficiency. When thermally decomposing aluminum sulfate using, when aluminum sulfate to be supplied to the firing furnace is dried under specific drying conditions up to a specific water content, it is found that a transition alumina that can satisfy all the above objects can be obtained. The present invention has been completed.

That is, the present invention has 1 to 12 parts by weight of lanthanum (converted to elements) with respect to 100 parts by weight of alumina,
Na ₂ O content of 0.10 parts by weight or less, pore volume of 0.6 cc / g to 2.0 cc / g, initial BET specific surface area of 90 m ² / g or more, after heat treatment at 1200 ° C. for 5 hours Another object of the present invention is to provide a heat-resistant transition alumina having a BET specific surface area of 60 m ² / g or more and having heat resistance, which is obtained by a heating / pyrolysis method of aluminum sulfate.

Further, according to the present invention, aluminum sulfate containing 100 parts by weight of alumina and 0.10 parts by weight or less of Na in terms of Na ₂ O and 1 to 12 parts by weight of a lanthanum compound as lanthanum (elemental basis). Another object of the present invention is to provide a method for producing a heat-resistant transition alumina, which comprises thermally decomposing after heating.

The present invention also relates to A in aluminum sulfate.
1 part is converted into alumina, and 0.10 parts by weight or less of Na in terms of Na ₂ O and 1 to 12 parts by weight of a lanthanum compound as lanthanum (elemental conversion) are contained in 100 parts by weight of the alumina. The evaporation rate of water from 1 g of aluminum sulfate [as Al ₂ (SO ₄ ) ₃ ] containing aluminum sulfate in excess of octahydrate in terms of crystal water is 0.01 mg / sec to 2.0 mg / sec.
Is heated and dried until aluminum sulfate having a water content corresponding to crystal water of not more than 8 hydrate is obtained, and the aluminum sulfate after drying is, if necessary, of water content corresponding to crystal water of not more than 6 hydrate. After being dried to aluminum sulfate, aluminum sulfate having a water content corresponding to the water of crystallization of the hexahydrate or less after drying is thermally decomposed in a vertical airflow contact type firing furnace to obtain transition alumina. The present invention provides a method for producing heat-resistant transition alumina.

[0014]

The present invention will be described in more detail below. The transition alumina of the present invention has a lanthanum (elemental conversion) of 1 to 1 with respect to 100 parts by weight of alumina in the transition alumina.
2 parts by weight, the Na ₂ O content is 0.10 parts by weight or less, and the transition alumina has a pore volume of 0.6 cc / g to 2.0.
A heat / pyrolysis method of aluminum sulfate having a heat resistance of cc / g and an initial BET specific surface area of 90 m ² / g or more and a BET specific surface area of 60 m ² / g or more after heat treatment at 1200 ° C. for 5 hours. It is a heat-resistant transition alumina.

As a method for producing such transition alumina,
The Al content in aluminum sulfate was converted to alumina, and Na was converted to Na ₂ O in an amount of 0.1 parts by weight based on 100 parts by weight of the alumina.
0 parts by weight or less, lanthanum compound (lanthanum equivalent)
1 to 12 parts by weight of aluminum sulfate is heated and then thermally decomposed.

The aluminum sulfate used as a raw material of the present invention is a transition alumina obtained after thermal decomposition, and the Na content in the transition alumina is 0.10 parts by weight or less based on 100 parts by weight of alumina calculated as Na ₂ O. Commercially available aluminum sulfate is usually produced by dissolving aluminum hydroxide obtained by the Bayer method with sulfuric acid, although it is not particularly limited (for example, a chemical product of 12394, p56). Reference, published by Kagaku Kogyo Nippo Co., Ltd.), Na ₂ O as an impurity from aluminum hydroxide was Al ₂ O
Approximately 0.20% by weight is contained with respect to ₃ . therefore,
In the present invention, aluminum sulfate synthesized using aluminum hydroxide having a low soda content as a raw material, specific aluminum sulfate synthesized from high-purity aluminum, high-purity aluminum hydroxide, high-purity alumina, etc., and further aluminum foil Aluminum sulfate, which is a by-product of treating an aluminum material with a sulfuric acid solution, is used. Further, aluminum sulfate obtained by thermally decomposing alum can also be used as a raw material. From the viewpoint of production cost, aluminum sulfate by-produced by treating commercially available low-soda aluminum hydroxide as a raw material with aluminum sulfate synthesized with sulfuric acid or an aluminum material is treated with a sulfuric acid solution, and the Al content in the aluminum sulfate is converted into alumina. Then
Na content is Na ₂ O based on 100 parts by weight of the alumina.
It is recommended to use aluminum sulfate in an amount of 0.10 parts by weight or less in conversion. The crystal form of aluminum hydroxide having a low soda content is not particularly limited, and the crystal form of Al ₂ O ₃ .nH ₂ O such as gibbsite, bayerite, beehmite, pseudo-boehmite, and amorphous aluminum hydroxide can be used. A powder or slurry represented by the chemical formula is used. The form of aluminum sulfate used as a raw material is Al ₂ (S
O ₄ ) ₃ · nH ₂ O [wherein n = 0 to 27] represented by solid or liquid aluminum sulfate is used. Also, basic aluminum sulfate Al ₂ (SO ₄ ) _3-X (OH) _2X
nH ₂ O can be used. The substitution amount x is not particularly limited as long as the obtained transition alumina has the performance of the present invention, but x is usually 0.4 or less. Also, aluminum sulfate containing a part of sulfuric acid can be used. When aluminum sulfate obtained by pyrolyzing alum is used as a raw material,
An undecomposed ammonium salt can be contained within the range having the performance of the present invention.

The initial BET specific surface area after thermal decomposition is 90.
m²/ G or more, the Na content is Na ₂Alumina converted to O
0.10 parts by weight or less of transition aluminum per 100 parts by weight
Aluminum sulphate as a raw material within the range
Other aluminum salts such as aluminum chloride, nitric acid
Aluminum, aluminum formate, aluminum lactate,
Aluminum oxide and aluminum acetate and alumina water
Combine with Japanese or aluminum alkoxide
Is also good.

Further, in the range where a transition alumina having a BET specific surface area of 90 m ² / g or more and a Na content of 0.10 parts by weight or less based on Na ₂ O in terms of Na ₂ O can be obtained, other metal elements are added. You may coexist in aluminum sulfate. For example, potassium, magnesium, calcium, barium, lanthanum, zirconium, copper, iron,
Platinum, palladium, rhodium, etc. may coexist.

In the present invention, lanthanum means that before aluminum sulfate is heated and pyrolyzed to form transition alumina,
It only needs to be in a mixed state with aluminum sulfate, and as aluminum sulfate containing a lanthanum compound, a method of mixing a lanthanum compound with aluminum hydroxide in the process of synthesizing aluminum sulfate, and adding sulfuric acid to this to react, aluminum sulfate The method of mixing a lanthanum compound is mentioned.

More specifically, aluminum hydroxide and a lanthanum compound may be mixed with water and sulfuric acid may be added to the mixed solution to prepare a lanthanum compound-containing aluminum sulfate, or a mixed solution of aluminum hydroxide and water may be used. A lanthanum compound-containing aluminum sulfate may be prepared by adding a mixture of a lanthanum compound and sulfuric acid. Alternatively, the lanthanum compound may be added after mixing aluminum hydroxide with water and adding sulfuric acid. It is also possible to use transition alumina obtained by firing aluminum hydroxide in the method for producing aluminum sulfate. In the process of synthesizing aluminum sulfate, when sulfuric acid is added to an aluminum hydroxide aqueous solution, heat is generated, and as the temperature rises, aluminum sulfate is produced. When aluminum sulfate is produced and then cooled, liquid or solid aluminum sulfate is obtained depending on the amount of water used.

When the other method of mixing aluminum sulfate and a lanthanum compound is adopted, when aluminum sulfate and a lanthanum compound are solid, when both are solid, one of them is made into an aqueous solution. The other may be added and dissolved, or may be added and dissolved at the same time in water, and when liquid aluminum sulfate is used, a solid or liquid lanthanum compound may be added and dissolved therein, It is desirable to evenly disperse aluminum and lanthanum ions in aluminum sulfate or a mixture thereof. Therefore, it is preferable to heat and stir the solution in the mixing and dissolving operations.

The lanthanum compound used in the present invention is preferably one which is uniformly dispersed in aluminum sulfate, and for example, lanthanum oxide, lanthanum acetate, lanthanum nitrate, lanthanum sulfate, lanthanum carbonate, lanthanum chloride and the like are applied.

As for the amount of Na ₂ O in the lanthanum compound, if the Na content in the obtained transition alumina is 0.10 parts by weight or less based on 100 parts by weight of alumina in terms of Na ₂ O,
The use of a lanthanum compound having a small amount of Na ₂ O is recommended, though there is no particular problem.

Further, other rare earth metal elements may be used within a range in which a transitional alumina having a BET specific surface area of 90 m ² / g or more and a Na content of 0.10 parts by weight or less based on Na ₂ O in terms of Na ₂ O can be obtained. For example, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, etc. may coexist.

The mixing ratio of the lanthanum compound in the transition alumina obtained in the present invention is about 1 to about 12 parts by weight as lanthanum element, preferably 100 parts by weight of the lanthanum compound in the obtained transition alumina. Is about 1 to 1
It is mixed in the range of 0 parts by weight.

When the mixing ratio of lanthanum to 100 parts by weight of alumina is less than 1 part by weight, the effect of suppressing the decrease of the specific surface area at high temperature is not sufficient. On the other hand, when the mixing amount is more than 12 parts by weight, 1200 ° C. A large decrease in specific surface area occurs when used at a certain level.

In the practice of the present invention, liquid or solid aluminum sulphate is then heated to evaporate water to dryness. Upon heating, the aluminum sulphate containing lanthanum compound must have at least water in excess of aluminum sulphate hexahydrate. More preferably, a transitional alumina having a higher heat resistance can be obtained in the form of a solution or a paste-like mixture containing 20 hydrates or more of water converted to water of crystallization of aluminum sulfate. When aluminum sulfate is in the form of a solid that exceeds hexahydrate, it dissolves into a liquid by heating and gradually increases in viscosity, and then foaming occurs,
When heating is further continued, it becomes a porous lump or aggregate. When aluminum sulfate is in a liquid state, it gradually increases in viscosity by heating and foams, and when heating is continued, it becomes a porous lump or aggregate. Since the degree of porosity at this point depends on the evaporation rate of water, rapid evaporation of water may be caused to obtain a more porous product. If the lanthanum-containing aluminum sulfate does not have water equivalent to more than hexahydrate when heated, it may be difficult to uniformly disperse the lanthanum in the aluminum sulfate, and after heating, drying and solidifying (hereinafter referred to as heat-drying). However, the desired transition alumina having excellent heat resistance cannot be obtained even by thermal decomposition. Such heating to dryness may be carried out by heating to dryness until the water content of hexahydrate or less in terms of water of crystallization of aluminum sulfate is obtained, and of course, anhydrous products may be dried.

The heating and drying methods include oven, oil bath, spray dry, flash dry, fluidized dry,
Medium fluidized drying, vacuum drying, kneader, drum dryer, ribbon dryer, rotary kiln, belt dryer, paddle dryer, far infrared dryer, microwave heater, microwave vacuum dryer, A known method such as a ventilation dryer can be used. The heating temperature is not particularly limited, but it is performed at about 100 ° C. to below the decomposition temperature of aluminum sulfate.

The heating and the thermal decomposition can be carried out by using the same heating device, but when the raw material for heating is a liquid, a large amount of water is evaporated, so that it is practical in terms of economy in the case of industrial scale production. Not relevant. Therefore, it is preferred that heating and pyrolysis be performed in separate steps.

The heated product (a lanthanum-containing aluminum sulfate dry solid product after the heat treatment) is then thermally decomposed to obtain transition alumina. As aluminum sulfate to be subjected to thermal decomposition, one having water of hexahydrate or less in terms of crystal water of aluminum sulfate is used. In the present invention, the transition alumina refers to a material in the process of heating aluminum hydroxide or the like to become α-alumina, not specifically exceeding the range used in the art, specifically, amorphous, pseudo γ, γ. , Δ,
It is a substance having a crystal form such as η, θ, κ, and χ, and is a transition alumina having γ, δ, and η crystals.

The temperature at which aluminum sulfate having water of hexahydrate or less in terms of water of crystallization of aluminum sulfate is thermally decomposed is not less than the thermal decomposition temperature of aluminum sulfate, and the BET specific surface area of the transition alumina produced by decomposition is 90 m. ² / g
As described above, the temperature may be such that the pore volume is 0.6 cc / g to 2.0 cc / g, and specifically, it is about 800 ° C. or higher to 1500 ° C. for 0.1 second to 100 hours in the atmosphere, preferably About 900 ° C. to 1500 ° C. for 0.5 seconds to 50 hours, more preferably 900 ° C. to 1300 ° C. for 10 minutes to 50 hours. When the thermal decomposition is performed in a reducing atmosphere, low temperature firing is possible.

As a thermal decomposition method, a rotary kiln,
Known methods such as instantaneous calcination, vertical air flow contact type firing furnace, filling firing furnace, fluidized firing, stationary firing, tunnel furnace, batch furnace, atmosphere furnace, vacuum furnace, pressure furnace, etc. may be used. The transition alumina after pyrolysis can be made into a transition alumina of a desired crystal form by selecting the pyrolysis conditions (pyrolysis temperature, time), but the transition of the desired crystal form can be obtained by firing separately after pyrolysis. It is also possible to adopt the method of using alumina.

The transition alumina obtained has a pore volume of 0.6.
If it is less than cc / g, the heat resistance is poor and the poisoning resistance of the catalyst is also poor. On the other hand, when it exceeds 2 cc / g, it is difficult to handle due to scattering and the like, and when it is dispersed in water such as for wash coat and used, problems such as increase in viscosity occur.

In order to obtain a heat-resistant transition alumina with a high product yield in the industrially highly efficient firing method, the Al content in aluminum sulfate is converted into alumina, and 100 parts by weight of the alumina is used. On the other hand, water containing more than 0.10 parts by weight of Na in terms of Na ₂ O and 1 to 12 parts by weight of a lanthanum compound as lanthanum (elemental equivalent) in terms of crystal water of aluminum sulfate, which exceeds octahydrate. Aluminum sulfate containing aluminum sulfate [Al ₂ (SO
₄ ) As ₃ ] The evaporation rate of water from 1 g is 0.0
The aluminum sulfate is heated and dried at 1 mg / sec to 2.0 mg / sec until it becomes aluminum sulfate having a water content corresponding to water of crystallization of octahydrate or less, and the heated aluminum sulfate is then heated in a vertical airflow contact type firing furnace. The method of thermal decomposition is recommended.

The evaporation rate of water of crystallization during heating and drying is 2.0
When it exceeds mg / sec, the obtained aluminum sulfate containing water corresponding to the water of crystallization of octahydrate or less is substantially foamed and weak in strength and powdered during thermal decomposition, resulting in vertical air flow contact. The yield cannot be reduced because the powder cannot be fired in the firing furnace or the powdered particles are scattered by the ventilation gas. When the evaporation rate of water of crystallization is less than 0.01 mg / sec, the drying rate is slow and the productivity is poor, which is not economical.
The drying step of aluminum sulfate is not particularly limited as long as it is equipment capable of drying at the above-mentioned drying speed, but known methods such as an oven, an oil bath, a ventilation dryer, a belt dryer, a rotary dryer, and a fluidized dryer are used. it can.
If the water content of aluminum sulfate after drying exceeds octahydrate, and if the drying is not performed under the above-mentioned drying conditions, the aluminum sulfate gradually increases in viscosity in the firing step, particles stick to each other, and then rapid foaming occurs. Since the occurrence strength is lowered, the gas is unbalanced in the aeration firing and the particles are scattered due to the destruction of the particles, and the yield is lowered, so that the aeration firing cannot be industrially inexpensively performed. When aluminum sulfate having an amount of water of crystallization that normally exceeds octahydrate is dried to aluminum sulfate that contains water corresponding to the amount of water of octahydrate or less, more specifically, it corresponds to the amount of water of crystallization of 10 hydrate or more. 6. Aluminum sulfate containing water, more preferably aluminum sulfate containing water corresponding to the amount of water of crystallization of 20 hydrate or more, and aluminum sulfate containing water corresponding to the amount of water of crystallization of 8 hydrate or less, usually 7. When the aluminum sulfate containing water corresponding to the amount of water of crystallization of 5 hydrates or less, more preferably aluminum sulfate containing the water corresponding to the amount of water of crystallization of 6 hydrates or less is substantially dried by the above method, Aluminum sulphate powder without foaming and without pulverization is obtained in the subsequent pyrolysis step. It is visually visible whether or not the obtained aluminum sulfate is substantially foamed, but it is 2 m.
The packing density was calculated by calculating the weight of the undried product, aluminum sulfate, whose size was adjusted to m to 6.7 mm, to completely remove the water of crystallization contained in the undried product. The value (average of 0.50 g / cc) was defined as the standard packing density of unfoamed aluminum sulfate, and the standard packing density was measured by the method described below, and the packing density of the corrected sample was compared. It is also possible to express the degree of foaming. In the present invention, the packing density is 0.45 g / c
Those less than c were judged to be substantially foamed. Sample packing density measurement / correction method: 100 g of dried aluminum sulfate was put in a 200 cc graduated cylinder, the cylinder was dropped 100 times from a height of 3 cm, and then the packing density (g / cc) was measured (of the dried product). (Packing density), then the weight of the dried product was measured, further heated at 500 ° C. for 2 hours to completely dehydrate the water of crystallization in the dried product, and then the weight was measured. I asked. Packing density of sample = Packing density of dry product × [500 ° C
Weight after dehydration / weight of dried product before dehydration at 500 ° C]

The thus-obtained substantially non-foamed aluminum sulfate is then thermally decomposed in a vertical airflow contact type firing furnace. Aluminum sulfate to be subjected to thermal decomposition is aluminum sulfate containing water equivalent to hexahydrate or less in terms of crystal water. The vertical airflow contact type firing furnace is one in which dried aluminum sulfate is filled in the firing furnace and pyrolyzed while being in contact with the airflow passing through the packed bed. III −
6th kiln (written by Masanori Kouto, published by Nikkan Kogyo Shimbun) No. 10
A known firing device such as a kiln (shaft kiln) described on pages 5 to 106 is applied. The contact between the vent gas and aluminum sulfate may be countercurrent or cocurrent, and may be batch or moving bed. However, a countercurrent moving bed system having excellent heat transfer is industrially advantageous and preferable.

The aluminum sulfate packed in the firing furnace has an average particle size of about 0.5 mm to about 50 mm, preferably about 1 m so that hot air can easily pass through the packed bed during thermal decomposition.
It is preferably used in the form of a lump or plate having a size of m to about 20 mm. Aluminum sulfate having such a shape may be obtained by heating the aluminum sulfate aqueous solution when the raw material is an aluminum sulfate aqueous solution, solidifying it into a plate or a lump while the aluminum sulfate has fluidity, or molding, and if necessary. It can be obtained by pulverizing this into a desired shape and then drying. Alternatively, the aqueous solution of aluminum sulfate can be cooled to a temperature below the solidification temperature without heating and then crushed into a desired shape and then dried. Further, when the raw material is a solid, it can be pulverized into a powder, then molded into a desired shape by an existing method such as rolling granulation or extrusion molding, and then dried. Of course, for the purpose of adjusting the particle size of the raw material, the molded product before or after drying can be sieved if necessary.

The calcination (decomposition) of aluminum sulfate in the vertical airflow contact type calcination furnace is carried out under the condition that the temperature is not lower than the thermal decomposition temperature of aluminum sulfate and the specific surface area of the transition alumina obtained after the decomposition is as high as possible. Generally, the temperature of the aluminum sulfate is about 700 ° C. to about 1000 ° C. in the atmosphere, and the ventilation gas temperature is 1 hour to 100 hours, preferably about 750.
Firing may be performed for about 5 hours to 20 hours at an aeration gas temperature of from ℃ to about 950 ℃.

The superficial linear velocity of the gas passing through the packed bed is in the range of about 0.01 Nm / s to about 1.0 Nm / s, preferably about 0.1 Nm / s to about 0.5 Nm / s. Although the cause is not clear, when the wind velocity exceeds 1.0 Nm / s and becomes large, the pore volume of the obtained transition alumina becomes small, and the heat resistance tends to decrease. If the superficial linear velocity of the gas is less than 0.01 Nm / s, it may be uneconomical because it takes a long time to perform the firing, probably because the generated decomposition gas is not replaced quickly.

The aeration gas used for firing is not particularly limited as long as it can reach the above temperature, heating air by combustion of ordinary fuel gas or fuel oil, heating air by electricity, heat medium, or the like, or You may use the gas which added steam, reducing gas, SOx gas, etc. to these. Further, when an aeration gas whose moisture concentration is adjusted to 20 ° C. or less at the dew point is used, transition alumina having a large specific surface area can be obtained, which is recommended.

The transition alumina thus obtained is
The pore volume is as large as 0.6 cc / g to 2.0 cc / g,
Initial BET specific surface area of 90 m ² / g or more, usually 1
More than 00 m ² / g, 1 lanthanum (element conversion)
By including 12 parts by weight, the BET specific surface area after heating at 1200 ° C. for 5 hours is also 60 m ² / g or more. In addition to having excellent heat resistance, the amount of Na in the transition alumina is Na ₂
Since it was 0.10 parts by weight or less in terms of O, the BET specific surface area was 9 even after heating at 700 ° C. for 3 hours in the presence of a phosphorus compound.
It has an excellent phosphorus poisoning resistance of 0 m ² / g or more,
It is used as it is, or after crushing, as a catalyst carrier or resin filler, or as a raw material for molding catalyst carriers of various shapes.

Further, as a raw material alumina for washcoat for coating the surface of a preformed body such as a ceramic honeycomb, it is lighter than its large pore volume and BET specific surface area, exhibits excellent activity, and has a high phosphorus poisoning resistance. It is expected to be applied as a carrier.

Particularly, it is suitable as a raw material for a wash coat of a honeycomb-shaped noble metal catalyst for a selective denitration reaction of a vehicle exhaust gas, a non-selective denitration reaction or a complete oxidation reaction. When the transition alumina of the present invention is applied as an automobile exhaust gas catalyst, washcohes are applied to honeycombs by a known method.
It is also possible to carry a noble metal selected from platinum, rhodium and palladium as a catalyst before or after wash coating. It is also possible to mix the transition alumina of the present invention with ceria for the wash coating. The catalyst thus obtained can be installed in an automobile exhaust gas converter and used under the condition that the maximum catalyst temperature is about 700 to 1100 ° C., which is the maximum operating temperature.

It is also possible to add a catalyst component such as platinum, palladium, rhodium, cerium, zirconium, barium, nickel, copper or iron to aluminum sulfate before thermal decomposition.

[0045]

As described in detail above, the heat-resistant transition alumina of the present invention uses aluminum sulfate containing a lanthanum compound with adjusted Na ₂ O concentration as a raw material (aluminum sulfate synthesis →) dissolution → drying → thermal decomposition. By a simple operation of → (impregnation), the pore volume is large, the initial specific surface area is high, and the specific surface area is small even when treating a gas containing a phosphorus compound. It provides a transitional alumina, and its industrial value is particularly great in the field of catalyst carriers for internal combustion engines such as automobiles.

[0046]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

The physical properties in the examples of the present invention were measured by the following methods. BET specific surface area; nitrogen adsorption method (measurement temperature 77K) S concentration; X-ray fluorescence analysis method Na ₂ O concentration; frame atomic absorption method

Foaming degree: Packing density (0.50 g) calculated from the weight of undried aluminum sulfate sized to 2 mm to 6.7 mm (using a JIS sieve) and the retained water of crystallization.
/ Cc) was defined as the standard packing density of unfoamed aluminum sulfate, and the standard density was compared with the packing density of the sample measured and corrected by the method described below to give a measure of the degree of foaming. Sample packing density measurement / correction method: 100 g of dried aluminum sulfate was put in a 200 cc graduated cylinder, the cylinder was dropped 100 times from a height of 3 cm, and then the packing density (g / cc) was measured (of the dried product). (Packing density), then the weight of the dried product was measured, further heated at 500 ° C. for 2 hours to completely dehydrate the water of crystallization in the dried product, and then the weight was measured. I asked. Packing density of sample = Packing density of dry product × [500 ° C
Weight after dehydration / weight of dried product before dehydration at 500 ° C]

Pore volume (cc / g); 1.5 g of transition alumina was put into an iron die having a diameter of 20 mm, and fixed by a cylinder from above and below, and 100 kg / cm ² was applied to the transition alumina in the die by a uniaxial pressing machine. Pressing is applied so that the molding pressure is applied, and after holding for 3 minutes, it is taken out to obtain a disk-shaped alumina molded body. The pore size distribution of this molded article is determined by mercury porosimetry, and the pore volume with a radius of 32 Å to 1000 Å is measured.

Heat resistance test: 2 g of transition alumina was put in a mullite crucible and heated at 1200 ° C. for 5 hours in a silicon dioxide furnace with a dew point of 15 ° C. in a steam-containing atmosphere of 1.5 liter / min. The specific surface area after heating was measured.

Phosphorus poisoning resistance test: When transition alumina is used as an automobile catalyst, about 100 g of alumina is used for one automobile, and a phosphorus compound (organic phosphorus) is used in 50,000 hours.
Is considered to be supplied from about 50 g of fuel and oil in terms of P. Therefore, in this example, 1.0 g of transition alumina and 2.9 g of triethyl phosphate (manufactured by Wako Pure Chemical Industries, special grade reagent) (0.5 g in terms of P) were used so that the effect of the phosphorus compound could be seen in a short time. It was placed in a mullite crucible with a lid and heated in a siliconit furnace at 700 ° C. for 3 hours, and then the specific surface area of the transition alumina was measured to check the phosphorus poisoning resistance.

Example 1 127 g of purified water was placed in a flask having a volume of 2 liters, and lanthanum acetate was added thereto so that the final desired transition alumina would be 3.0 parts by weight as 100 parts by weight of Al ₂ O ₃ as lanthanum element. , Lanthanum acetate was completely dissolved. Commercially available low Na ₂ O aluminum hydroxide (CL-303, N manufactured by Sumitomo Chemical Co., Ltd.) was added to the lanthanum acetate solution.
a ₂ O concentration (0.03%) 156 g was added and mixed to form a uniform slurry, which was then stirred with sulfuric acid 3
00 g was slowly added so as not to cause bumping, and the mixture was stirred for 1 hour to obtain transparent liquid aluminum sulfate. Next, this liquid aluminum sulfate was poured into a polypropylene container and left to cool to solidify. This solidified aluminum sulfate was crushed and sieved to 2 mm to 6.7 mm, then
It was dried at 0 ° C. for 10 hours and solidified. The obtained dried product was aluminum sulfate 5.5 hydrate, and visual observation of this dried product clearly showed foaming, and the packing density was measured and found to be 0.22 g / cc. The ratio of the weight of this sample after dehydration at 500 ° C and the weight of dried product before dehydration at 500 ° C was 0.7.
The packing density of the corrected sample was 0.17 g / cc. Then, this dry product was heated from room temperature to 95 in a box-type electric furnace.
After heating to 0 ° C at a heating rate of 250 ° C / hour, 950 ° C,
It was calcined for 20 hours and pyrolyzed to obtain transition alumina (most of which was γAl ₂ O _{3 as} a result of X-ray diffraction). When the physical properties of the obtained transition alumina were measured, the pore volume was 0.
69 cc / g, Na ₂ O amount of 0.05 parts by weight, initial BE
The T specific surface area was 144 m ² / g. The results of the heat resistance test and the phosphorus poisoning resistance test are shown in Table 1.

Example 2 Aluminum sulfate (Al₂
O₃Content 15.6% by weight, Na to alumina₂O content
65ppm of 80ppm, water as crystal water 17 hydrate)
Was added and heated to about 120 ° C. to melt. This melting
The final desired transition aluminum with stirring to aluminum sulfate
Al as lanthanum element in Na₂O ₃100 parts by weight
Lanthanum acetate was added to 4.0 parts by weight,
After the lanthanum acetate was completely dissolved, stirring was continued for another hour.
Then, liquid aluminum sulfate was obtained. Then this liquid sulfur
Pour aluminum oxide into a polypropylene container,
It was left to cool and solidify. This solidified aluminum sulfate
It was crushed and further dried at 180 ° C. for 10 hours. Got
The dried product was aluminum sulfate 5.5 hydrate. This dry
Solid products from room temperature to 950 ° C at a heating rate of 250 ° C / hour
After heating, it is baked at 950 ° C for 20 hours and thermally decomposed into transition aluminum.
(As a result of X-ray diffraction, most of the₂O₃Met)
Got The pore volume of the obtained transition alumina is 0.72c.
c / g, Na₂O amount is 100ppm, initial BET ratio surface
Product is 148m²/ G. Also get in this way
Heat resistance test and phosphorus poisoning resistance test of transition alumina
became. The results are shown in Table 1.

Example 3 653 g of the same aluminum sulfate as used in Example 2 was added,
Dry at 180 ° C for 10 hours (aluminum sulfate 5.5
Water salt), this dried product from room temperature to 950 ° C at 250 ° C /
After heating at 950 ° C. for 20 hours, it is pyrolyzed to produce transitional alumina (as a result of X-ray diffraction, most of γAl ₂
O was ₃₎ was obtained. 2 liter beaker with purified water 50
After adding 0 cc, lanthanum acetate in an amount of 4.0 parts by weight with respect to 100 parts by weight of Al ₂ O ₃ as the lanthanum element in the final desired transition alumina was added and completely dissolved. 100 g of the transition alumina obtained above was added to the lanthanum acetate aqueous solution thus obtained, and the mixture was stirred for 1 hour. Next, the obtained slurry is placed in an Airbus 11
After being dried at 0 ° C. for 12 hours, the lanthanum acetate was decomposed by baking at 490 ° C. for 2 hours to obtain a transition alumina containing lanthanum. The pore volume of the obtained transition alumina is 0.70 cc / g, the amount of Na ₂ O is 100 ppm, and the BET is
The specific surface area was 149 m ² / g. The heat resistance test and the phosphorus poisoning resistance test of the transition alumina thus obtained were performed. Table 1 shows the results.

Example 4 The amount of lanthanum added in Example 1 was changed to Al ₂ O ₃ 100.
Transition alumina was obtained in exactly the same manner except that lanthanum acetate was used so as to be 1.0 part by weight with respect to parts by weight. The initial BET specific surface area of the obtained transition alumina is 134 m ² / g
Met. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. Table 1 shows the results.

Example 5 In Example 2, the amount of lanthanum added was changed to Al ₂ O ₃ 100.
Transition alumina was obtained in exactly the same manner except that lanthanum acetate was used so as to be 1.0 part by weight with respect to parts by weight. The initial BET specific surface area of the obtained transition alumina is 120 m ² /
g. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. Table 1 shows the results.

Example 6 284 g of transition alumina obtained by the method of Example 1 and purified water 77
5 cc and 3.8 cc of acetic acid were put into a 2 liter pot,
It was crushed for 15 minutes with a ball mill. Separately, 244 g of cerium oxide (5 μm, 95 m ² / g), 370 cc of purified water, and 23 cc of acetic acid were put into a 2 liter pot, and the mixture was ground for 3 hours in a ball mill and divided into 3 parts. Alumina slurry
After removal from the pot, a chloroplatinic acid solution Al ₂
Pt was added to O _{3 at} a ratio of 1% and mixed with a stirrer for 1 hour. Further, one of the three divided cerium oxide slurries was added and mixed with a stirrer for 1 hour to prepare a slurry for wash coat. This washco
After immersing the cordierite honeycomb in the slurry,
A washcoat composition was obtained by drying at 0 ° C. and baking at 490 ° C. for 4 hours. The coat portion of the washcoat composition was peeled off from the honeycomb, and BE of the composition was removed.
The T specific surface area was measured and found to be 120 m ² / g.
A heat resistance test was conducted in the same manner as in Example 1. Table 1 shows the results.

Example 7 Solid aluminum sulfate was obtained in the same manner as in Example 1
It was dried in an air bath at 10 ° C. When weighed every hour during drying, the maximum evaporation rate was 0.3 m / g when converting aluminum sulfate having Al ₂ (SO ₄ ) ₃ to 1 g.
It was dried at g / sec. When dried for 24 hours, it was converted to water of crystallization of aluminum sulfate and dried up to the heptahydrate. This dried product was substantially free of visible foaming, and the packing density was measured and found to be 0.70 cc / g. The ratio of the weight of the sample after dehydration at 500 ° C. to the weight of the dried product before dehydration at 500 ° C. was 0.73, and the packing density of the sample after correction was 0.51 g / cc. Then, 50 cm of a 15 mmφ alumina ball was laid in an annular furnace in which an alumina core tube having an inner diameter of 70 mmφ and a length of 1 m was set vertically, and the dried product (sieved to 2 mm to 6.7 mm by sieving) 100 g was added. After the thermocouple for the furnace control was charged in the central part of the packed bed of the dried product, 15 mmφ alumina was charged to the upper part of the furnace tube on the dried product. The superficial linear velocity in the core tube from the bottom of the core tube is 0.3 Nm / s.
ec, introducing air whose humidity has been adjusted so that the dew point is 50 ° C., and the temperature of aluminum sulfate is 860 at 250 ° C./Hr.
After the temperature was raised to 0 ° C., it was kept at 860 ° C. for 16 hours, calcined, and thermally decomposed to obtain transition alumina (most of which was γ alumina as a result of X-ray diffraction). The recovery rate of transition alumina was calculated from the weight before and after firing, and was 98%. The initial BET specific surface area of the obtained transition alumina was measured to be 16
It was 2 m ² / g. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. Table 1 shows the results. For comparison, a packing density (corrected) of 0.17 cc / g of aluminum sulfate (maximum evaporation rate during drying: 5.2 mg / sec) obtained by drying according to the method of Example 1 was used in the same manner as above. Calcination and thermal decomposition yielded transition alumina, and the recovery rate of transition alumina was calculated from the weight before and after calcination.
It was 0%.

Example 8 Ammonium alum AlNH ₄ (SO ₄ ) ₂ 12H ₂ O alumina and Na ₂ O content of 50 ppm) were heated in a box electric furnace from room temperature to 650 ° C. at a heating rate of 250 ° C./hour. , 6
It was baked at 50 ° C. for 2 hours and thermally decomposed to obtain aluminum sulfate (as a result of X-ray diffraction, most of it was Al ₂ (SO ₄ ) ₃ ). Purified water 311 is added to a flask with a reflux tube having a volume of 2 liters.
After adding g and heating, add 342 g of the aluminum sulfate (water content is 0 water salt as crystal water) obtained above and add about 1
It was heated to 20 ° C. and melted. While stirring the molten aluminum sulfate, the final desired transitional alumina was used as a lanthanum element in an amount of 3.0 parts by weight per 100 parts by weight of Al ₂ O _3.
Lanthanum acetate was added to the mixture so that the amount of lanthanum acetate was completely dissolved, and the mixture was further stirred for 1 hour to obtain liquid aluminum sulfate. Next, this liquid aluminum sulfate was poured into a polypropylene container, left to cool and solidified. This solidified aluminum sulfate was crushed and further dried at 180 ° C. for 10 hours. The obtained dried product was aluminum sulfate 5.5 hydrate. After raising the temperature of this dried product from room temperature to 950 ° C. at a heating rate of 250 ° C./hour,
It was calcined at 0 ° C. for 20 hours and thermally decomposed to obtain transition alumina (most of which was γAl ₂ O _{3 as} a result of X-ray diffraction). The pore volume of the obtained transition alumina is 0.72 cc / g, Na
_The amount of ₂ O is 60 ppm, and the initial BET specific surface area is 143 m ^2.
/ G. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 A transition alumina was obtained by the same treatment as in Example 1 except that lanthanum acetate was not added, and the BET specific surface area was measured and found to be 134 m ² / g. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 By the same treatment as in Example 1, a transition alumina was obtained by using lanthanum acetate so that the final desired transition alumina would be 15 parts by weight with respect to 100 parts by weight of Al ₂ O ₃ as the lanthanum element. Was 70 m ² / g. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 1275 g of commercially available liquid aluminum sulfate (liquid bank manufactured by Sumitomo Chemical Co., Ltd., Al ₂ O ₃ content of 8.0% by weight) was placed in a flask having a volume of 2 liters, and in the final desired transition alumina. Lanthanum acetate was added as a lanthanum element to Al ₂ O _{3 in an amount} of 3.0 parts by weight, and completely dissolved with stirring. The lanthanum acetate-containing liquid aluminum sulfate was dried at 180 ° C. for 10 hours to dryness. This dried product was treated in the same manner as in Example 1 to obtain transition alumina. When the physical properties of this product were measured, the initial BET specific surface area was 133 m ² / g and the pore volume was 0.70.
The amount of cc / g and Na ₂ O were 0.23 parts by weight. A heat resistance test and a phosphorus poisoning resistance test were conducted in the same manner as in Example 1. The results are shown in Table 1.

[0063]

[Table 1]

Claims (5)

[Claims] 1. A lanthanum (converted to an element) of 1 to 12 parts by weight per 100 parts by weight of alumina, a Na ₂ O content of 0.10 parts by weight or less, and a pore volume of 0.6 cc / g.
~ 2.0 cc / g and initial BET specific surface area of 90 m ² /
A heat-resistant transition alumina obtained by a method of heating and decomposing aluminum sulfate, which has a BET specific surface area of 60 m ² / g or more after heat treatment at 1200 ° C. for 5 hours or more. 2. Al content in aluminum sulfate is converted to alumina, and Na is added to Na ₂ with respect to 100 parts by weight of the alumina.
A method for producing a heat-resistant transition alumina, comprising heating aluminum sulfate containing 0.10 parts by weight or less of O and 1 to 12 parts by weight of a lanthanum compound as lanthanum (element conversion), and then thermally decomposing it. 3. Aluminum sulphate containing lanthanum, aluminum sulphate containing Na in an amount of 0.10 parts by weight or less in terms of Na ₂ O per 100 parts by weight of alumina, and the aluminum sulphate in terms of alumina.
Lanthanum compound based on parts by weight (element conversion)
The method for producing a heat-resistant transition alumina according to claim 2, wherein the mixture is a mixture of 1 to 12 parts by weight. 4. The heat-resistant transition alumina according to claim 2 or 3, wherein the lanthanum-containing aluminum sulfate has water, when heated, which exceeds at least hexahydrate in terms of water of crystallization of aluminum sulfate. Manufacturing method. 5. The Al content in aluminum sulfate is converted to alumina, and Na is added to Na ₂ with respect to 100 parts by weight of the alumina.
A lanthanum-containing aluminum sulfate containing water in excess of octahydrate in terms of water of crystallization of aluminum sulfate containing 0.10 parts by weight or less of O and 1 to 12 parts by weight of lanthanum compound as lanthanum (element conversion). , Aluminum sulphate [as Al ₂ (SO ₄ ) ₃ ] Aluminum sulphate having a water content corresponding to crystallization water of octahydrate or less when the evaporation rate of water from 1 g is 0.01 mg / sec to 2.0 mg / sec. And the aluminum sulfate after the drying is dried until the aluminum sulfate has a water content corresponding to the water of crystallization of hexahydrate or less, if necessary.
4. A transition alumina is obtained by supplying aluminum sulfate having a water content corresponding to water of crystallization equal to or less than water salt to a vertical airflow contact type firing furnace and thermally decomposing in the firing furnace. Method for producing heat-resistant transition alumina of.