DE1116017B - Process for removing the oxide film on aluminum surfaces for the production of active aluminum - Google Patents

Description

The invention relates to a process for the production of active aluminum, in particular for the production Organic aluminum compounds can be used by removing the on the Surface of the aluminum present oxide film.

It is known that organic aluminum compounds by direct reaction of aluminum with an olefin and hydrogen can be formed. Although aluminum is a very reactive metal, but usually covered by a very inert film of aluminum oxide, which causes the desired reaction completely prevented. So far it has proven to be very difficult to remove the oxide film, so as to expose the surface of the aluminum metal and carry out the desired reaction.

So far, the oxide film was removed by grinding the aluminum under a protective liquid or by spraying molten aluminum into a protective liquid medium through an inert atmosphere became. However, such processes are very expensive and difficult to achieve uniformity carry out.

It has now been found that the oxide film can be removed when a suspension of comminuted Aluminum in a compound of the general formula serving as a suspension medium

of the oxide film on aluminum surfaces

for the production of active aluminum

Applicant:

Koppers Company, Inc.,
Pittsburgh, Pa. (V. St. A.)

Representative: Dr. W. Schalk, Dipl.-Ing. P. Wirth,

Dipl.-Ing. G. E. M. Dannenberg

and Dr. V. Schmied-Kowarzik, patent attorneys,

Frankfurt / M., Große Eschenheimer Str. 39

Claimed priority:
V. St. v. America 5 February 1958 (No. 713 310)

Bucket Henry Dobratz, Pittsburgh, Pa. (V. St. Α.),
has been named as the inventor

R ₂ AlY,

in which R is hydrogen or an alkyl radical and Y is an alkyl radical, a small amount of one of the Activation promoting substance, in particular an alkali metal or a basic reacting compound an alkali metal is added and the suspension is then exposed to the action of hydrogen.

Suitable are e.g. B. lithium, sodium, potassium, rubidium and cesium and their oxides, hydroxides, Acetates (or other carboxylates), bicarbonates, carbonates and aluminates. Alkaline earth metals, such as calcium, Strontium and barium and their alkaline reacting compounds are also suitable, but to a lesser extent Dimensions than the alkali metals.

The alkali or alkaline earth metals or theirs used to promote the activation of the aluminum Alkaline compounds are, based on the total weight of the suspension medium used, in an amount of about 0.01 to about 10 percent by weight, preferably 0.05 to 0.5 percent by weight, applied.

These activation-promoting substances, which are usually soluble in the suspension medium, can either on its own or together with any of the components participating in the activation be admitted.

As mentioned, suitable suspension media are the aluminum alkyls and alkyl aluminum hydrides as well their mixtures. The aluminum alkyls are preferably used in the process according to the invention and alkyl aluminum hydrides are used, their alkyl groups Contain 2 to 20 carbon atoms. The aluminum alkyls and alkyl aluminum hydrides can either alone or as a solution in aliphatic and aromatic hydrocarbons. Suitable hydrocarbons are e.g. B. hexane, heptane, kerosene, benzene, toluene, xylene, cyclohexane, Methylcyclohexane, dimethylcyclohexane and the like As the time required for activation increases, the solution should contain at least 5% of an aluminum alkyl or alkyl aluminum hydride contain.

The amount of aluminum that is activated in a given amount of the suspension medium is limited only in that the resulting slurry must be flowable so as to be easy stirred and so the aluminum can be kept in suspension. It can be any commercially available shredded Aluminum seem to be used, however

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3 4

the so-called "grained" aluminum powder was loaded with less aluminum hydride. They were made to be similarly fit than the others. Achieved flaky and very lee results,
fine aluminum powders have proven to be very suitable ". -14
proven. Aluminum waste and turnings are ispie

also suitable, but because of their small size, they are 5 The procedure of Example 1 was repeated,

Surface in view of the later use, however, instead of 1000 parts diethyl

for the production of organic aluminum compounds aluminum hydride 1000 parts di-n-butylaluminum

less practical. hydride were added to the autoclave. There were

The method can achieve similar results at hydrogen pressures of
about 7 kg / cm ² up to about 700 kg / cm ² and at 10

Temperatures of 60 to 250 ⁰ C can be carried out. Example 5
Preferably, however, a pressure between 70 and

210 kg / cm ² and a temperature between about 120 The procedure according to Example 1 was repeated,

and 150 ⁰ C applied. Within certain limits, however, instead of 1000 parts of diethyl

the rate of activation increases with the 15 aluminum hydride 1000 parts of di-n-pentylaluminum

temperature and the hydrogen pressure. hydride were added to the autoclave. There were

The activation according to the invention is achieved similar results,
moderately carried out in a conventional autoclave, which is equipped with a stirrer, gas feed- Example 6
gen, inlet openings for liquids and solids 2 °

and pressure measuring and temperature regulating devices. 1000 parts were put into the autoclave according to Example 1

gen is provided. Triisobutylaluminum, 1000 parts of a crushed one

The following examples, in which the parts of commercial aluminum and IV2 parts of sodium are parts by weight mean, serve to explain the hydroxide beads given. The autoclave was method according to the invention. 25 sealed and initially a hydrogen pressure

of about 70 kg / cm ² . The autoclave was

Example 1 ^am * ^{heated to about} 135 ° C and the pressure to about

105 kg / cm ² set by possibly adding

An autoclave as just described, which has been carefully supplied with hydrogen. The temperature was cleaned and dried with nitrogen or argon kept 3 ° to 135 ⁰ C. In less than an hour with 1000 parts of diethylaluminum the pressure began to drop. Then hydride, 1000 parts of finely comminuted commercially available hydrogen was introduced into the autoclave, aluminum powder and 2 parts of sodium hydroxide - spheres were charged - ^{that the pressure of 105 kg / cm 2 was maintained.} The autoclave was then closed. The absorption of the was closed within 3 to 4 hours and hydrogen was passed in until hydrogen had ended and the aluminum was completely under pressure of about 70 kg / cm ² . The stirring activated. The device was set in motion as the gases were cooled and vented, the autoclave became a trap cooled with liquid nitrogen and its contents heated to 135 ° C. and the pressure maintained at about 50 to 60 parts of isobutane. In the course of the approximately 105 kg / cm ² adjusted by, if necessary, more activation, 50 to 60 parts of aluminum were introduced in hydrogen. Then the auto-40 diisobutyl aluminum hydride was converted. This Verklav kept for about 5 hours at 135 ⁰ C and during loss of aluminum is, however, compensated for by this time, a virtually constant pressure of that the remaining, about 940 parts Amount end 105 kg / cm ² maintained. After that, the aluminum aluminum had a larger surface that activated to minium. After cooling down to room, the chemical action in the formation of the di-iso temperature and release of the hydrogen can be attributed to the 45 butylaluminum hydride. As described by diethylaluminum hydride from aluminum already in Example 1, the alkyl inert liquid, such as benzene or heptane, can be removed by an inert carbon, under which it can be removed indefinitely without its hydrogen, causing the aluminum to lose activity, can be stored, pre-exposed as activated aluminum for later use, so that it is preserved from such substances as oxygen, 5 °,
that would destroy its activity is protected. Example 7
About 970 bis remain under the solvent

990 parts activated aluminum. The losses are The procedure of Example 6 was repeated,

on mechanical losses during filtration and washing, but instead of 1000 parts of triisobutyl

and 1000 parts of triethylaluminum are used for low losses due to the removed aluminum

attributed to miniumoxide. became. Activation was carried out in a similar manner.

. . Due to the lower molecular weight of the tri

Example 2 ethyl aluminum go in the formation of diethyl

The procedure according to Example 1 was repeated, aluminum hydrides lost about 100 parts of aluminum, the autoclave, however, instead of 1000 parts of di- 60

ethyl aluminum hydride with 1000 parts of di-n-propyl Example 8
aluminum hydride was charged. Similar results were obtained. The procedure of Example 6 was repeated. . but were used instead of triisobutylaluminum Example J, _{65 1000 parts of} T _r i_ _n _p _ro pyl _a luminium.

The procedure according to Example 1 was repeated, practically the same results were achieved,

However, the autoclave instead of 1000 parts of di- The loss of aluminum due to the formation of di-

ethylaluminum hydride with 1000 parts of diisobutyl-n-propylaluminum hydride was about 80 parts.

Example 9

The procedure of Example 6 was repeated, but instead of triisobutylaluminum 1000 parts of tri-n-octylaluminum were used. The results were practically the same; to completion however, it took 6 to 7 hours for hydrogen absorption. The loss of aluminum by formation of di-n-octylaluminum hydride was about 30 parts.

Example 10

To explain the effect of various aluminum activation promoting substances, the autoclave of Example 1 was charged with the following components: 500 g diisobutylaluminum hydride, * 5,500 g triisobutylaluminum, 1000 g of a commercially available comminuted aluminum and 0.05 gmol of a substance promoting the activation of aluminum. The autoclave was initially brought to a pressure of 49 kg / cm ² with hydrogen at room temperature. The stirrer was then started and the autoclave was heated to 135 ° C., the pressure increasing ^{to about 73.5 kg / cm 2.} During activation, the triisobutyl aluminum was converted to diisobutyl aluminum hydride. The time required to complete the reaction, which was determined on the basis of the hydrogen absorption, serves as a relative yardstick for the effectiveness of the activation-promoting substance, that is, the shorter the time, the more effective the activation-promoting substance is. A small amount of isobutane is formed by a side reaction, which is captured after activation is complete by sucking the gases out of the autoclave through a trap cooled with liquid nitrogen, in which the isobutane condenses. In order to remove virtually all of the isobutane from the autoclave, the pressure in the system was finally reduced to about 25 mm Hg. The amount of isobutane obtained is generally the smaller, the more effective the substance which promotes activation.

To further test the extent of activation and the effectiveness of the activation-promoting substance, 750 g of isobutylene were added to the autoclave after activation was complete. The autoclave was brought to a pressure of about 70 kg / cm ² with hydrogen and heated to 135 ^° C., whereupon the pressure was ^{adjusted to 105 kg / cm 2} and kept at this level by passing the required amount of hydrogen into the autoclave . By reacting with the activated aluminum and hydrogen, most of the isobutylene was converted to diisobutyl aluminum hydride. The remaining isobutylene was converted to isobutane. As soon as no more hydrogen was absorbed, the reaction was over. The isobutane was obtained by sucking the gases from the autoclave through a trap cooled with liquid nitrogen. The extent to which the aluminum is activated can be measured by the length of the reaction time and the amount of isobutane formed. So are z. B. short reaction times and small amounts of isobutane are a sign of good activation. The results obtained using a number of activation promoting agents are reported in the table below.

activation Gebil
detes Activated AIu- in the Tan of aluminum Iso miniuir Production of iso
butane Water- butane Diisobutylalu
minium hydride G Activation
promoting substance material-
absorp- G 50 tion 27 duration 39 Time 24 hours 59 V _- OLUiI
the) 37 3.6 74 Sodium acetate 4.3 37 3.6 130 Sodium hydroxide .. 4.7 45 4.5 62 Potassium Hydroxide ... 5.6 45 4.5 70 Sodium metal .... 5.9 35 5.9 Sodium... 7.0 5.1 Lithium hydroxide .. 7.5 5.5 Calcium hydroxide .. 6.0

Claims (6)

Patent claims: 1. A method for removing the oxide film on aluminum surfaces for the production of active aluminum, characterized in that finely divided aluminum is suspended in liquid aluminum alkyls and / or alkyl aluminum hydrides with the addition of an alkali or alkaline earth metal or a basic compound of one of these metals and in the temperature range from 60 to 250 ⁰ C is treated with hydrogen at pressures of 7 to 700 kg / cm ^2. 2. The method according to claim 1, characterized in that the basic reacting compound Sodium hydroxide is used. 3. The method according to claim 1 and 2, characterized in that the alkali or alkaline earth metal or the basic reacting compound in an amount of 0.01 to 10 percent by weight, based on the total weight of the suspension liquid. 4. The method according to claim 1 to 3, characterized in that the suspension liquid a solution of the aluminum alkyls and / or alkyl aluminum hydrides in an inert aliphatic or aromatic hydrocarbon, preferably at least a 5% solution is used. 5. The method according to claim 1 to 4, characterized in that the suspension is kept at a temperature of 120 to 150 ⁰ C and under a pressure of 70 to 210 kg / cm ² . 6. The method according to claim 1 to 5, characterized in that after the treatment has ended the suspension cooled to room temperature, the pressure reduced to atmospheric pressure and the suspension liquid is replaced by an inert, oxygen-free liquid. © 109 710/470 10.61