DE1072976B - Process for the production of aluminum oxide - Google Patents

Description

Aluminum oxide is available in both hydrate and in anhydrous form, often for a wide variety of purposes in the chemical industry and others Industries, especially in oil processing, used to a greater extent. The activated ones Shapes that are merely various physical modifications of alumina are especially known for their adsorptive capacity. Furthermore, aluminum oxide is used as a refractory material used for many purposes. So it has been found in the form of corundum to be suitable for manufacture certain refractory and ceramic materials., For other uses, the Aluminum oxide mixed with other compounds processed to take advantage of its valuable properties.

In the following, the word "aluminum oxide" means either anhydrous aluminum oxide or aluminum oxide hydrate or aluminum hydroxide, unless otherwise specified.

Up until now, aluminum oxide has been produced commercially by cleaning appropriate materials Ores, such as bauxite, or by precipitation of aluminum hydroxide from its salts, e.g. B. by addition an alkaline agent to aluminum chloride hexahydrate, the precipitate being washed and filtered will. For the purpose of usability in the so-called "platforming" process the aluminum oxide, which makes up the main part of the catalyst, must go through washed and filtered to remove unwanted impurities because the presence even small amounts of impurities are detrimental to the catalyst. Aluminum oxide, which is made from the commercially available aluminum chloride hexahydrate, so requires an extensive Washing and filtration to remove the impurities including excess chloride remove.

It has also long been known from scientific research that superheated vapor from molten aluminum decomposes to form oxide and hydrogen. A reaction temperature of 659 ° C. or higher is therefore required, which, apart from other inconveniences, is not very desirable for reasons of heat economy, apart from in industrial operations. In addition, at such temperatures an aluminum oxide is obtained in a modification which is completely unsuitable for most purposes. At the same point it is also mentioned that superheated steam from 300 to 350 ° C attacks pure aluminum more strongly than rolled or cast 99% aluminum over a test duration of 34 days. This scientific reference can also be used in the production process
of aluminum oxide

Applicant:

Universal Oil Products Company,
Des Piaines, 111. (V. St. A.)

Representative:

Dipl.-Ing. E. Jourdan and Dipl.-Ing. W. Weinkauff,
Patent attorneys, Frankfurt / M., Kronberger Str. 46

Claimed priority:
V. St. v. America July 27, 1953

Herman Samuel Bloch, Chicago, 111.,

and George Ladislav Hervert,

Downers Grove, III. (V. St. Α.),

have been named as inventors

Looking at the long reaction time is not viewed as a stimulus for an industrial process will.

On a technical scale, attempts have already been made to use aluminum oxide as aluminum metal to produce by the metal dissolved in an excess of mercury to form an amalgam and this is then reacted with steam to form aluminum oxide. But here is one large amount of mercury required as the amalgam only contains about 0.25% aluminum, so only one there is a slight amount of aluminum in the mercury.

Furthermore, it is known to produce aluminum oxide for industrial purposes in such a way that a Aluminum amalgam is formed, which is then dissolved in acidified water to form an aluminum oxide sol is implemented. The sol is then coated with an electrolyte such as ammonium hydroxide Creation of a gel coagulated. This process is laborious and lossy in terms of the consumption of reactants. The manufacture is because of Necessity to go through the stage of sol formation and coagulation, relatively cumbersome.

The invention is based on the finding that the reaction of aluminum metal with water under Formation of aluminum oxide in modifications suitable for technical purposes with an industrially useful

909709/421

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The reaction rate is feasible, complete conversion is required. In general if certain reaction conditions, namely before, leaflets are to be preferred. Aluminum beads, above all, constant stirring of the reaction mixture by dropping molten aluminum and the addition of a mercury catalyst as well as being made in water have proven to be very unsatisfactory small amounts of acid are used. Proven according to 5 digend. The epsilon alumina, weider In the invention, aluminum metal particles are quickly treated as passives on aluminum surfaces Stirring with water in excess in the presence of the coating forms, retarded among those here From metallic mercury or a mercury-revealed conditions the reaction is not noticeable, compound in an amount in the range of 0.00135 up to 6.75 mole percent mercury and in the presence of io temperature, the concentration or amount of a monobasic or polybasic, inorganic acid, mercury accelerator and the grade of Rüheiner polybasic, organic acid or a rene depending on the given mixture. While acidic salt of these acids, which means that the Ge a reaction at a temperature with only Mix in a stoichiometric less than 0.13 equivalent of mild stirring or agitation of the mixture monovalent acid anion, less than 15 paces, it runs very quickly when the mixture 0.50 equivalent divalent, inorganic acid is stirred vigorously. At a temperature of 300 ° C anions or less than 1.0 equivalent divalent, the reaction proceeds even if the reaction is slow, organic and trivalent, inorganic ren relatively quickly, with rapid stirring is and organic acid anions per equivalent of aluminum - the time required for complete conversion nium corresponding amount was added, significantly reduced at temperature 20.

temperatures below 374 ° C, especially 97 to Since it is necessary to have a liquid water phase

100 ° C, and a pressure at which the water can be kept above right, and the critical temperature of the

shot remains practically liquid, then you separate the water is 374 °, this temperature is not too

in excess water on slurried aluminum, because it is much easier to achieve an intimate

miniumoxide particles and dries them at temperature stirring and especially a mixture between

Doors up to 260 ° C to achieve the aluminum and water, if this

The quantity of mercury marked in the foregoing is in the liquid phase.

from 0.00135 to 6.75 mole percent corresponds to about 0.05 The mixture of a mercury accelerator and

up to 50 percent by weight of the aluminum metal. It is an acidic compound acts as a reaction accelerator

to be addressed equal or as low and catalytic, 30 niger. It was found that the mercury

because in chemical reactions the molecules bond with the aluminum reacts and closes

or atoms in reaction with each other, and reduced in terms of metallic mercury, which

on the high atomic weight of the mercury, which then apparently becomes amalgamated with the aluminum

200.61 compared to the atomic weight of aluminum. There is a difference in the catalytic

of 26.97, viewed in molar terms, this weight effect of the various mercury compounds,

quantities of mercury are relatively small. and apparently the distribution of the mercury

The method according to the invention offers the amalgam centers (which are probably cathodic significant advantage that the alumina are immediate) an important factor in the speed of the reaction in a time suitable for later use. A comparison between the reaction modification is obtained and in most felling speed 4 ° when using metallic len even to the usual washing and filtering. Mercury as an aid and a proportionate one which, as is well known, shows a certain amount of mercury compound Alumina is very troublesome and has considerable advantages for the mercury compound, though borrowed time required. metallic mercury itself is quite effective.

In the method according to the invention the 45 mercury z. B. reacts with the aluminum below Aluminum oxide either as a gel or in crystals Formation of aluminum oxide and metallic won. At temperatures from about 0 to about mercury. Other compounds react at a similar rate of -205 ° C, the gel formation is favored, while in Licher way, although they are not all the same reaction temperatures from about 205 to about 374 ° C induce habitual speeds when in equilibrium Crystals are generated. Implementation below 50 valent amounts can be used. Regarding the The particular conditions of the invention provides acidic compound is to be assumed that the acid is hydrogen in a very pure state as secondary anions through the formation of partial salts, the upper product, make the surface coating of the aluminum soluble

Preferably, aluminum is of high purity so that the aluminum compound is dissolved

to be assumed if high-purity aluminum oxide exposes 55 and more aluminum surface. In solution

is to be produced, preferably aluminum, the soluble aluminum compound can be produced by hydro-

Minium particles of at least 99.5% purity in Iyse form aluminum oxide and the acid anions

a size of no more than 25 mm and regenerate appropriately. Reactions of the kind described here

less than 12 mm used. In the presence of a catalytic amount of a

preferably distilled water is used. The counter acid accelerates.

War of some alloy metals is undesirable, as it is possible to obtain the weakly acidic solution

they apparently the reaction of aluminum with small amounts of common mineral acids, organic

Water delayed. Acids or acidic salts can be used.

The degree of particle size of the aluminum is. B. oxalic acid,

the reaction speed is also correct. A ge 65 malonic acid, succinic acid, maleic acid, phthalic acid,

powdered aluminum is therefore excellent. Gra- tartaric acid, and citric acid to the desired

nulated or spherical aluminum or aluminum gel formation, the lower water-

minium in strip form is also suitable; each soluble monobasic fatty acids. As sour-looking

larger, however, the particle size of the aluminum salts are the halides, z. B. Am-

metal loading, the longer time is for the 7 ° monium chloride, ammonium fluoride, ammonium chloride

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and ammonium iodide. For the purpose of gel formation foreign substances are not interfering, need the above is the ratio of acid anion to aluminum in precautions not to be taken. as the above limits of the stoichiometric by-product of the reaction, hydrogen is generated, Equivalent weights important. The monobasic, which is why a valve should be provided for draining Organic acids produce gels if the need to do so, if the result of the production of this water ratio Pressure build-up caused by monovalent acid anions in quantities of sub- stance can be avoided half 0.13 equivalents of acid anion per equivalent should. However, if the plant has this additional Aluminum is present, while the divalent, pressure is to withstand, it is necessary to the aquatic Acid anions are present in such quantities to continuously drain the substance.

is intended that the ratio is below about 0.5. The aluminum polyvalent acid anions produced according to the invention provide gels with an oxide requires no further washing and / or higher ratio of divalent, acidic anion tration before it z. B. is combined with other catalyst of less than 1.0 equivalents of acid anion per equivalent of ingredients, especially if an aluminum and higher; However, ratios with annealing of the aluminum oxide before the further Im about 1.0 are preferred, since ratios greater than 15 are impregnation. As a result, the use of excess free acid anions significantly reduces the cost of catalyst manufacture. For example, sulfuric acid forms gels not only in terms of time and with respect to the power ratios of SO ₄ ": Al '" less than about 0.5 equi-saving for the implementation of this measure, valent acid anion per equivalent of aluminum, but also in terms of costs for the washing trend the corresponding maximum amount for Cl ': Al ^:: ' 20 and filter system.

is about 0.13. The amount of mercury cata- When all of the aluminum metal is dissolved lysators will usually have been in the range of about 0.01, the mercury separates into shape up to about 50 percent by weight of the aluminum. of metallic spheres or as metallic soil concentrations of mercury and acid offsetting (depending on the amount available) and can Catalyzing binding below this range cannot be easily recovered.

effective the reaction, and concentrations above after the alumina has been produced

This area often leads to unwanted erosion, it can last for 2 to 24 hours or more for one

results. Temperature from about 93 to about 260 ° C partially

The mercury catalyst can be dried from the following.

Substances or a mixture of these consist: 30 For further use ^ which are not subject

Mercury, mercuric acetate, mercuroacetate, mercury of the invention can be before or after drying

benzoate, mercuric bromate, mercurobromate, mercuri- the aluminum oxide is mixed with other substances

bromide, mercurobromide, mercury bromide iodide, mer- be. '

curocarbonat, Mercurichlorat, Mercurichlorid, Mer- The following examples serve to illustrate the

curochlorid, mercurifluoride, mercurofluoride, Mereuri 35 invention.

iodide, mercurine nitrate, mercuronitrate, mercurioxalate, examples
Mercuric oxide, mercuric oxide, mercuric sulfate, mercuro-

sulfate, as well as mercury-nitrogen compounds, 1. Schnitzel made of highly refined aluminum z. B. ammoniacal mercury bromide and atnmon ¹ - from about 1.6 to 2.4 mm wide, 6.4 mm long basic mercury chloride. Almost any other mercury 40 and slightly more than 1.6 mm thick have been used to make a mercury-containing compound. position of aluminum oxide used. The purity

The drying of the aluminum oxide gel at different temperatures on the emission spectrograph gives aluminum oxide in the following analysis: 0.004% Fe, 0.005% Cu, various modifications. At about 0 to about 0.005% Mg, 0.02% Si and 0.02% Ca, the remainder Alu-205 ° C, mainly gibbsite is formed. An analysis 45 min. 60 g of these aluminum chips were in the aluminum oxide dried at 205 ° C. shows a curved pyrex flask of 5 l content mainly gibbsite, but there are traces of Böhbracht, which was equipped with two water condensers and one with another modification of a hydrated six-blade pyrex stirrer. The aluminum oxide, detectable. If the drying stirrer speed was increased to 450 revolutions temperature, the percentage set increased 50 per minute. 1485 g of distilled water, the amount of boehmite in the product accordingly, and 1.32 g of HgCl ₂ and 14.85 g of oxalic acid were added to the flask at about 345 ° C results in the analysis of the product, and the solution was subjected to a temperature Dry almost completely boehmite. temperature of 97 ° C brought. After 21 hours of stirring

The operation can be continuous or individually, 99.4 percent by weight of the aluminum

loads are carried out. If above 55 with the formation of a stiff aluminum oxide gel,

100 ° C is worked, it is of course necessary to set.

that the reaction vessel withstand the pressures. The alumina gel was decanted and allowed to stand. On a small scale, a rotatable pressure lock is autoclave for about 8 hours at 149 to 163 ° C expedient. When the applied tem- per- dries. The dried alumina was temperatures at or below the boiling point of 60 then ground and water through a 40-mesh sieve lying, the reaction can be sifted in a habitual manner.

Borrowed open plant can be made, in which 2. 23.5 g of aluminum of 99.9% purity in the form of a device for vigorous stirring or for the chips described in Example 1 were provided with circulation of the constituents. There a solution of 168 cm ^{3 of} a 1.29 mol. Hydrochloric acid is necessary, however, that the process equipment 65 is set up with 0.40 g of mercuric chloride at 99 to 100 ° C in the form of such materials that it is not converted into aluminum oxide hydrogel of water or aluminum and / or the used ones in about 20 hours. The product was a stiff, white catalyst to be attacked, so that no un-gel, the elements desired after separation from the mercury, which had settled in the desired aluminum bead, are introduced according to the anoxide product. However, when these 70 gave of Example 1 was worked up.

3. 18 g of aluminum chips about 1.6 to 2.4 mm wide, 6.4 mm long and about 1.6 mm thick were placed in an autoclave with a capacity of 1040 cm ³ , the inner walls of which were made of stainless steel. The aluminum was 99.9% pure. 200 g of water, 0.5 g of mercury and 0.05 equivalent of HCl per equivalent of aluminum were added to the aluminum particles. The autoclave was then closed at normal initial pressure and at 20 ° C. In order to work through the reaction mixture, the autoclave was set in rotation and heated to 300 ° C. by means of electrical elements. The experiment was continued for 3 hours at this temperature with a fluctuation of less than 5 ^° C. A maximum pressure of 119 atm was observed at 300 ° C. The autoclave and its contents were then cooled to 20 ° C. Hydrogen was obtained from the autoclave in an amount of 22.6 liters, measured at 0 ° C. and 160 mm of mercury.

The aluminum metal was found to be completely converted to fine particles of alumina. Of the Mercury catalyst was recovered as a small pond at the bottom of the autoclave. A comparison These results with a corresponding experiment omitting the hydrochloric acid showed that the reaction in the presence of hydrochloric acid about one and a half times as much It went quickly like without the hydrochloric acid accelerator.

Claims (3)

Patent claims: 1. Process for the production of aluminum oxide by reacting aluminum metal with Water in the presence of mercury and an acid, characterized in that there are aluminum metal particles while stirring with excess water in the presence of metallic mercury or a mercury compound in an amount from 0.00135 to 6.75 mole percent mercury and in the presence of a mono- or polybasic, inorganic Acid, a polybasic, organic acid or an acidic salt of these acids, which the mixture in a stoichiometric less than 0.13 equivalents of monovalent acid anions, less than 0.50 equivalents of divalent, inorganic acid anion or less than 1.0 equivalent of divalent organic and trivalent, inorganic and organic acid anions per equivalent of aluminum Amount was added at temperatures below 374 ° C, in particular 97 to 100 ° C, and a pressure at which the excess water remains practically liquid, treated that in the excess of water Slurried aluminum oxide particles are separated and at temperatures up to dries to 260 ° C. 2. The method according to claim 1, characterized in that aluminum metal particles with a Purity of at least 99.5% with a size of no more than 25 mm and less than 12.5 mm and pure, distilled water are fed to the reaction. 3. The method according to any one of claims 1 to 3, characterized in that the aluminum oxide particles after their separation from the reaction mixture for more than 2 hours at one temperature be dried in the range from 93 to 205 ° C. Considered publications:
Gmelin, "Handbook of Inorganic Chemistry", 8th edition, system no. 35, part B, 1934/35, p. 369. © 909 709/421 1.60