DE2223401A1 - Process for the production of aluminum oxide bodies - Google Patents

Description

N 677

PATENT INVOLVED

Norton Company, Worcester, Massachusetts, V.St.A.

Process for the production of aluminum oxide bodies

The invention relates to the manufacture of self-tied, individually Machined aluminum oxide body with a large effective surface and high purity for use as catalysts, catalyst carriers, Sorbents and for other uses.

Aluminum oxide bodies produced by conventional ceramic techniques have long been used as catalysts, catalyst carriers, Used sorbents and heat exchangers. So far, however, it has not been possible to use high-purity aluminum oxide hollow bodies or - to produce bodies with concave surfaces or surfaces of complex shape, which have large inner effective surfaces, because those made by normal ceramic processing techniques Bodies lack strength. In particular, reference is made here to bodies with wall thicknesses of less than 1.59 unu have a radius of curvature over 3 ^ 175 mm.

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According to the invention, a self-tied, solid, individually crafted one polycrystalline aluminum oxide Pormkörper with a larger effective surface than 10 m / g proposed which has a wall thickness of less than 1.59 mm in some places.

A method for producing a solid aluminum oxide body with a large effective surface is also proposed, which is characterized in that microcrystalline platelet-like (i.Orig, platy) boehmite is used Particle size below 100 microns mixed with a dilute aqueous monobasic acid, the acid being an anion with a Ion size, which is not larger than that of propionic acid, has to create a dry, free-flowing, fine-grained aggregate mixture to form, this mixture is molded into individual shaped bodies under pressure, these bodies are dried and burned.

There is also a raw batch for use in the inventive Proceedings proposed which small spheroidal Contains agglomerates of flaky boehmite particles, these particles being below 100 microns, which are relatively is dry, free flowing and uncompacted, wherein the individual particles in these agglomerates are diluted by one Surrounded by acid that is capable of promoting the dispersion of the platelets; and the acid is an anion with an ion size which is not larger than that of propionic acid.

The invention generally makes a new high purity alumina body with a high effective surface and complex or hollow shape accessible, which has sufficient strength for applications in chemical processes, such as in packing towers.

The superiority of the present invention emerges in the strength and purity of various shapes; ie pellets, saddle pieces and rings made of / ""'- aluminum oxide. The effective surface area of these bodies can be regulated over a wide range. The areas of primary interest are 10 bi. ^c ;

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, a /. ■; "■ ·· -O α- = 3

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and 100 to JX) O m / g. The effective surfaces of this order of magnitude can be presented in bodies with greater physical strength and chemical purity than others, up to now known aluminum oxide products with an equivalent effective surface. The ability to produce products with exceptional strength combined with a large effective surface and excellent purity, makes superior catalysts available in the classic form of pellets. Useful Catalysts can also be made in the form of saddles, as described in US Pat 2,639,909 that were previously inaccessible.

The use of aluminum oxide with a large effective surface area as a catalyst support or catalyst component is generally known from technical and patent literature. Metal salts are commonly deposited on the expanded surface of alumina. Such a deposition can take place by impregnation, precipitation and spraying of solutions of the metal salts onto the aluminum oxide particles. Such metal salt additions are usually made on Y * or O -alumina. The vast majority of alumina catalysts of commerce is "on ■ ')' -.. Made of alumina, the metal salts are deposited below to obtain metals or metal oxides A common example of such production, the impregnation of ') * alumina with nickel nitrate The aluminum oxide is immersed in an aqueous nickel nitrate solution; then removed and dried. The impregnated support is then heated to elevated temperatures to provide nickel oxide and NOp gas. Very often the nickel oxide is then reduced to nickel metal with hydrogen The catalytic activity of metal-aluminum combinations of this type depends on the effective surface area and the metal content of the finished catalyst.

Another common catalyst mass contains the deposition of noble metals on ^ "" - aluminum oxide with greater effectiveness Surface. He; There are numerous patents that support the deposition

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BAD ORlGJNAl

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Describe small amounts of platinum and palladium on aluminum oxide carriers with a large effective surface. Catalysts containing 0.01 to 2 % platinum and palladium on 'X' alumina are widely used in the petrochemical and chemical industries.

An advantage of the present invention is that it is effective for a given surface area and chemical purity Have catalysts of exceptional strength manufactured. The binding process also allows production at the same time formed catalysts. The appropriate metal salts can be added to the alumina and it becomes a Catalyst bodies formed by extrusion or other measures, When such a body is fired, it retains the high strength that can be observed without the addition of the metal salt. There are Catalysts have been made using this co-molding technique, which have a superior effective surface area and catalytic Have activity when compared with impregnated catalysts of the same metal content.

A particular advantage of the present invention is the great strength of the body produced, which makes the production of Allow saddle shapes or other desirable configurations that give a low pressure drop when placed in a reaction vessel be packed. Thus, the bodies of the present invention which are used as oxidation catalysts are as in Example 4 can be seen, particularly suitable for treating engine exhaust gases by inserting the catalyst into a Muffler or in a reaction chamber upstream of the exhaust. A similar benefit can be derived from the low pressure drop characteristic in the treatment of industrial exhaust gases to reduce pollution or to obtain useful products to be pulled. ·

The starting material of the present invention is flaky (non-fibrous) ^ -aluminium oxide monohydrate (Böhrnit)

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It has long been known that aluminum oxide is produced by the Hydrolysis of aluminum alcoholates produced has unusual properties. Alumina produced by hydrolysis Such alcoholates are produced is normally considered to be OC-alumina monohydrate after recovery and drying. The invention provides a way of processing such

O ^ -Aluminium oxide monohydrate to aluminum oxide bodies with unusual properties. It also provides a way of making co-formed catalysts that are of exceptional utility. An alumina made by the hydrolysis of alcoholates is commercially available from Continental Oil Company, Ponca City, Oklahoma, under the trade designation Catapal "S". Up to now, OC-alumina monohydrates made by the hydrolysis of aluminum alcoholates have been practically laboratory curiosities. The production of alumina of this type in large quantities by the Continental Oil Company under the name Catapal "S" has allowed extensive research into the machining properties of this rare type of alumina. According to the invention it has been found that small amounts (up to 5% by weight ) of various acids can be used to bind this aluminum oxide in bodies with satisfactory raw product strength. Firing these raw bodies between 200 ° and above leads to solid, pure catalyst carriers that are economically viable. Firing temperatures between 200 and 1000 ° are of particular interest, which result in supports with effective surfaces between 10 and 300 m / g. Products fired in this temperature range are primarily ^ -alumina or boehmite or mixtures thereof. Firing at higher temperatures leads to products with reduced effective surface areas and increasing amounts of C? Cr alumina. The following table lists acids that have been found to be useful binding agents and those that do. are less useful.

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Useful binders Poor binders

Hydrochloric acid sulfuric acid

Formic acid phosphoric acid

acetic acid

Propionic acid

nitric acid

The examples below will show that Catapal "S" are bound with small amounts of these useful binders can. CC aluminum monohydrates, which are more soluble through precipitation Aluminum si ^ ze are produced, require large concentrations the acid to give a suitable bond. In addition, phosphoric acid is generally known in the art as a useful binding agent known for alumina. It is a surprising development that it is a poor binder for alumina represents, which is produced by hydrolysis of alcoholates. It has also been found that crushing a part of the dried crude alumina made by acid binding and the incorporation of small percentages this crushed dried product in the original mixture increases the strength of the final fired product.

An important feature of this mixing process is that the liquid and alumina are combined to give a free flowing, _particulate , non-paste or dough-like mixture, as illustrated in the following examples. It is believed that the individual platelets of boehmite are partially dispersed in the particles by the action of the acid; in any event, the dispersion of the platelets is promoted by acids of the preferred type.

example 1

100 parts of Catapal "S" were poured into a high-intensity mixer (Hobart Trade mark). For this purpose, one part of a cellulosic binder was added. In a separate kettle were 2 parts

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90% formic acid and 60 parts water mixed. The dilute acidic solution was then added to the dry ingredients in the mixer. Mixing was continued for about 30 seconds.

This short mixing time resulted in a free flowing mixture which contained no separate liquid phase, namely the small spheroidal particles which are proportionate to contact Were dry * This mixture was then squeezed out and made 1.27 cm saddle pieces formed * These saddle pieces were then shaped Air dried overnight, then placed in an oven and heated to 700 ° C. The mean breaking strength of the saddle pieces in the upside down "ü" position was 4.536 kg.

Example 2

100 parts of alumina AI-1700-P from Harshaw Chemical Company (trade name), 8.5 parts of glacial acetic acid and 49 parts of water were mixed as in Example 1. The free flowing spheroidal mixture was then squeezed out and formed into 1.27 cm saddle pieces. The raw saddle pieces were air-dried overnight; then put in a shaft furnace and heated to 7OO ⁰ C. The mean breaking strength of this product was 4.536 kg.

Comparative experiment I

A mixture was prepared as in Example 1, with the exception that the mixing was carried out for several minutes until a paste-like, moist dough was obtained. Try, extruding this dough was unsuccessful.

VJenn the overmixed doughs using special conditions are extruded, the pellets or extrudates obtained are poorly laminated and easily break along these lamellations. Thus overmixing to a paste-like or dough-like consistency is not flawless, either from the standpoint of one

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easy malleability as well as the fact that a inferior product is produced.

The effect of the acid is likely to be that of attraction between the platelets in the original alumina particles is reduced. In the case of Catapal "S" these are located original particles range in size from about 1 micron to 40 microns in diameter at one between Mean values lying 15 and 25 microns.

Micrographs taken with an electron microscope reveal these particles as agglomerates of small boehmite platelets. the The effect of the acid on these particles or agglomerates is to reduce the attraction between the platelets, so that they are easily aligned as they compress. According to the invention a short, intensive mixing step is required so that the platelets reorientate when the Mixture is compacted, more in the molding step than in the mixing step. Extensive editing in Mixer aligns and compacts these flakes into a dough that is difficult to extrude and delivers a worse one Product. In all of the following examples, the mixing was carried out so that a mixture as in Example 1 is obtained.

Comparative experiment II

Not all lamellar or non-fibrous boehmites are suitable for the production of solid, homogeneous bodies according to the invention. Two boehmites: namely Catapal ¹¹ N "and Alcoa FI -aluminium oxide- are unsuitable. They are produced in fairly large particle sizes, on the order of 100 microns, and cannot easily be formed into compacted homogeneous bodies under the action of acid and compaction force.

It is believed that these materials are at fairly high temperatures treated or generated: i.e. higher than 1 ^ 0 C,

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which gives them a fairly low water content or water loss when igniting. Therefore, aluminas are manufactured or manufactured with particle sizes larger than 100 microns overheated during their formation is not preferred.

Example 3

90.72 kg of Catapal "S" were placed in a large high-intensity mixer (trade name Abbe). A mixture of 90% formic acid and water was sprayed into the mixture over a period of about j) 0 minutes. The amount of acid and water was such that 5 parts of 90% formic acid and 65 parts of water were added per 100 parts of Catapal "s".

The resulting mixture was relatively dry and free flowing and was composed of small (about 3> 18 mm) agglomerates the original alumina particles together. Some of these agglomerates were caked together and the lumps had one

Diameters ranging from 1.27 to 12.7 cm. These bigger ones Aggregates' were dry and could hand over to the smaller ones Agglomerates (about 3> 18 mm) are broken.

Special care had to be taken so as not to become pasty or wet dough consistency. This mixture was extruded into 3.18 mm pellets. The pellets were left overnight dried at room temperature, then fired at 500 ° C. The received Product had an average flat panel crush strength of 17.69 kg.

Example 4

A mixture of 100 parts of Catapal "s" alumina and 10 parts of cellulosic binder was placed in a high intensity mixer. 25 parts Cu (NO ^) ₂ . 3 HpO, 2 parts concentrated formic acid, and 70 parts water were mixed in a separate kettle to form an acidic copper nitrate solution. This solution was

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added to the alumina and mixed as in Example 1.

The resulting mixture was extruded and made into 1.27 cm saddle pieces shaped. The obtained saddle stems were air-dried, then fired at 500 ° C. The mean breaking strength this saddle piece was 7.26 kg with an effective surface area of 210 m / g. Noteworthy was the excellent one Strength of these catalyst chips compared to aluminum oxide chips without added copper.

Example 5

A mixture of 100 parts of Catapal ¹¹ S "alumina and 10 parts of cellulosic binder was placed in a high-intensity mixer. 2 parts of concentrated nitric acid were mixed with 70 parts of water in a separate kettle. The resulting mixture was extruded and formed into 1.27 cm saddle pieces. These saddle pieces were air-dried and fired at 500 ° C. The calcined saddle pieces were then impregnated with a solution of copper nitrate to a final copper content equal to that in Example 4, and fired again at 500 ⁰ C. Their average Endbruchfestigkeit was 2.72 kg and an effective surface area of about l60 m2 / g. It is noted that this catalyst prepared by impregnation alsaueh both in the breaking strength of the effective surface is worse than a similar Catalyst obtained by the co-molding technique described in Example 4 represents was.

Example 6

A mixture of 100 parts of Catapal "S" and 5 parts of cellulosic binder was placed in a high-intensity mixer. 75 parts Ni (NO ^) ₂ . 6 HpO and 2 parts concentrated nitric acid were mixed with 65 parts water. This acidic nickel nitrate solution was mixed with the dry ingredients as in Example 1.

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The resulting Geraisch was extruded, air dried and on Fired in air at 500 ° C and then under hydrogen at 300 ° C. The mean breaking strength of the end product was 5.44 kg

ο with an effective surface area of around 200 m / g.

Example 7

A mixture of 100 parts of Catapal "S" and 5 parts of cellulosic Binder was placed in a high intensity mixer. In a separate kettle, 2 parts of concentrated nitric acid were added 65 parts of water mixed. This acidic solution was then mixed with the dry ingredients mixed as in Example 1. The resulting mixture was extruded and formed into 1.27 cm saddle pieces.

The saddle pieces were air dried, then fired at 500 ° C. Next, they were immersed in a solution of nickel nitrate to the same recording as in the previous example, molded and fired again on Hydrogen at 500 ° C in air and at 3OO ⁰ C under V /. The mean ultimate breaking strength of these impregnated saddle pieces was 0.90 kg with an effective surface area of about 160 m / g. In this and the preceding example, the superiority of adding the catalyst components to the mixture prior to extrusion over the customary impregnation process is evident.

Example 8

A mixture of 75 parts of Catapal "S", 25 parts of Kaiser KCSA-M- -Aluminium oxide (trade name) and 2 parts of cellulosic binder was placed in a high intensity mixer. In a separate kettle, 2 parts of 90% formic acid and 75 parts were added V / asüer combined. This acidic solution became the dry ingredients as given in example 1. 2 parts of fat were added to this mixture. Extrusion aid added.

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The resulting mixture was extruded and made into 1.27 cm saddlebags shaped. These saddle pieces were air dried, then fired at 537 ° C. The effective surface obtained

was 221 m / g with an average flat plate breaking strength of 5Λ ^ kg. .

Example 9

A mixture of 75 parts of Catapal "S" and 25 parts of KCSA-M, a boehmite available from Kaiser Chemical Company was placed in a high intensity mixer. In a separate boiler became a solution of 4 parts of concentrated nitric acid, 15.85 parts of copper nitrate, 8.02 parts of chromium oxide and 62.5 parts Prepared water. This solution was added to the dry ingredients and mixed as in Example 1.

The resulting mixture was then extruded into 1.27 cm saddle pieces, Polygons have been air-dried and fired at 500 ° C. Its effective surface area was 206 m / g with a medium one Flat plate breaking strength of 9 * 52 kg.

Example 10

100 parts of KCSA-M alumina was placed in a high intensity mixer. In a separate cauldron was a. Solution of 2 parts of 90% formic acid combined with 90 parts of water. This acidic solution was then added to the dry ingredients as in Example 1. 1/4 χ 1/4 (? Inch) pellets were extruded from this mixture. These pellets were fired air-dried and 5OO ⁰ C. The effective surface

was 274 m / g with a mean flat plate fracture strength of 30.11 kg.

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Example 11

A mixture of 100 parts of Catapal "S" and 2 parts of cellulosic Binder * was placed in a high intensity mixer. In a separate kettle, 2 parts of 90% formic acid were added combined with 58 parts of water. This solution then became the dry ingredients as in example 1 given. To the resulting mixture, 1 part of fat was added and the mixing was added Continued for 15 seconds to disperse the fat.

The resulting mixture was then extruded into 1/4 χ 1/4 (inch) pellets. These pellets were air dried, then oven dried at 4-0.5 °. They were then fired at 500 ° C. The effective surface area obtained was 247 m / g with a flat sheet breaking strength of 11.79 kg.

Example 12

A mixture of 70 parts of Catapal "S" boehmite and 32 parts KCSA-M boehmite was placed in a high intensity mixer. In a separate kettle, an 8 part solution became more concentrated Nitric acid and 80 parts of water. This acidic solution then became the dry ingredients as in Example 1 given.

The resulting mixture was extruded into 1/4 χ 1/4 (inch) pellets. These pellets were air dried and oven dried at 40.5 ° C. They were then calcined at 500 ° C. The effective surface area obtained was 217 m2 / g flat sheet breaking strength of 56.7 kg.

Example 13

A mixture of 70 parts of Catapal "S" and 32 parts of KCSA-M was made put in a high-intensity mixer. In a separate kettle a solution of 4 parts of concentrated nitric acid and

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Prepared 80 parts of water. This acidic solution then became too
given to the dry ingredients as in Example 1.

The resulting mixture was extruded into 1/4 χ 1/4 (inch) pellets. These pellets were air dried and oven dried at 40.5 ° C. They were then calcined at 500 ° C. The effective surface area obtained was 216 m / g with a flat plate breaking strength of 44.91 kg.

- patent claims -

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Claims (1)

- 15 - N 677 Patent claims: [lj method for producing a solid aluminum oxide body with a large effective surface area by firing aluminum oxide, characterized in that a lamellar (i.orig. platy) boehm with a particle size of less than 100 microns is mixed with a thin aqueous monobasic acid solution, wherein the acid has an anion with an ion size that is not larger than that of propionic acid in order to form a dry, free-flowing, fine-grained mixture, this mixture is molded into shaped bodies under pressure, dried and the bodies are fired. 2. The method according to claim 1, characterized in that the acid is formic acid or nitric acid. j5. Process for the production of a solid aluminum oxide body with a large effective surface, characterized in that microcrystalline leaf-like boehm with a particle size below 100 microns with a dilute aqueous monobasic acid Mir .; ent, whereby the acid has an anion with an ion size not larger than that of propionic acid, in order to form a dry, free, small aggregate mixture, this device: ; cii under Dx'uck forms into individual porous bodies, these bodies dries and burns. '{■. Process according to Claim 2, characterized in that "■ jj '." Is acid formic acid or nitric acid. 209849/1065 - 16 - N 677 5. The method according to any one of claims J5 or 4, characterized in that that a catalyst-forming metal is added to the mixture of boehmite and acid before the body is formed by pressure or a metal compound is given. 6. raw batch for use in the method according to claim 2, characterized by small spheroidal agglomerates of leaf-like Boehmite particles with these particles below 100 microns lie, which are relatively dry, free flowing and uncompacted is, wherein the individual particles in these agglomerates are surrounded by a dilute acid, which disperses the Able to promote platelets, and the acid has an anion with an ion size that is not larger than that of propionic acid. Ro./Br. 209849/1069