DE1920456C3 - Process for the preparation of aluminum alkyls - Google Patents

Description

The invention relates to a process for the preparation of aluminum alkyls of higher molecular weight by changing the Poisson distribution of the alkyl chain lengths of aluminum alkytane caused by the build-up reaction according to Ziegler from aluminum alkyls and low molecular weight olefins.

In the build-up reaction according to Ziegler low molecular weight aluminum alkyls, such as triethylaluminum or tripropylaluminum, or the corresponding Dialkyl aluminum hydrides, such as diethyl aluminum hydride, with low molecular weight olefins, preferably ethylene, converted to higher molecular weight aluminum trialkyls with extended alkyl chains. The build-up reaction runs z. B. according to the following equation:

(CjH ₄ I ₁ C ₂ H,

AIlC ₂ H,)., F »iC, H ₄ -> Al - (CJl ₄ I ₁ CJU

(C, H ₄ | X \ H,

SS

where ν. ν uiiil / ■ giiii / e are numbers in the range from 0 to 14 (on average 3 to 7) and (Ά + y + /) - n.

This build-up reaction in / B. in US-PS 2M 71 Mb «-) described. In the manufacture of aluminum triangles according to this method, however, the sympathetic (> o range of alkyl chain lengths must be accepted which can be statistically determined by the Poisson distribution:

IU ¹¹ C "

is reproduced, where Pn means the probability wedge that a certain hydrocarbon residue is formed in η additions of ethylene to the ethylaluminum bond originally present, and m means the average number of additions of ethylene per growing chain. From the point of view of process economy, this means that it has hitherto been necessary to accept undesired products, for example low molecular weight olefins or alcohols, in order to carry out the synthesis of the desired products.

It is also known that due to the building reaction aluminum alkyls obtained can be displaced by low molecular weight olefins. For example, can to react tridodecylaluminum with ethylene to form triethylaluminum and dodecene. While the build-up reaction therefore takes place a certain amount of displacement, and that which flows out of the reactor In addition to ethylene, the gas mixture contains other olefins.

In DT-AS 12 70 559 a process for the production of aluminum alkyls with extended Described alkyl radicals in which the difficulties caused by displacement during the build-up reaction be avoided in that one during the implementation of Isobutylalumi.niumverbindungen introduces an inert gas into the reaction mixture with * olefins. This is what is released as an intermediate Isobutene is quickly removed from the reaction system, so that no displacement reaction between the aluminum alkyl and the isobutene can take place. This process is largely uniform Chain extension to aluminum trialkyls achieved, but the alkyl chain length is still subject a Poisson distribution.

DT-AS 12 48 047 describes a process for the production of aluminum trialkyls in which the Poisson distribution of the alkyl chain length in the build-up product is influenced by subsequent displacement reactions and a new build-up reaction. However, this method is characterized by an extremely complicated procedure and is therefore difficult to control. Neither the two build-up reactions carried out nor the displacement reactions proceed quantitatively and irreversibly, so that different product mixtures are obtained, depending on the reaction conditions. Another disadvantage is that the heavy olefins split off in the displacement reaction often boil at temperatures similar to those of the low molecular weight aluminum trialkyls. For example, dodecene and triethylaluminum can only be separated from one another with difficulty by fractionation. This separation is possible at best by converting the aluminum compound with a suitable adduct-forming compound, 1. B. tetramethylammonium chloride, into an aclduct and then removing it in the heat.

The object of the invention is therefore to provide an improved one To create a process for the production of aluminum alkyls by a structural reaction, in which the Poisson distribution shifted the alkyl chain length of the building product towards an average alkyl chain length will. The method should also be simple and economical to carry out, and in particular the avoid complicated separation of the higher olefins from the low molecular weight aluminum alkyls.

The invention relates to a process for the preparation of aluminum alkyls with a higher molar

weight by changing the Poisson distribution the alkyl chain length of aluminum alkyls, which is caused by the synthesis reaction of aluminum alkyls with low molecular weight Olefins are obtained where Jen is characterized in that one

a) subjects a low molecular weight aluminum alkyl hydride to thermal olefin alkylation,

b) from the product of stage (a) with a low molecular weight olefin by a build-up reaction Produces aluminum alkyls and displaced olefins,

c) light olefins from the heavy olefins from the product of step (b) in a first separation Separating olefins and aluminum alkyls,

d) from the heavy olefins and aluminum alkyls in a second separation, the low molecular weight ones Separating aluminum alkyls and olefins,

e) recirculates the low molecular weight aluminum alkyls and the olefins from stage (d) to stage (a) and

Γι wins the higher molecular weight aluminum alkyls from stage (d) as a product

In the process of the invention, the synthesis product is first in a stream of light solvent and light olefins and a stream of heavy olefins, heavy solvent and aluminum trialkyls separated. The latter stream is then converted into a stream of heavy aluminum trialkyls and separated a stream of light aluminum trialkyls, heavy olefins and heavy solvent, followed by the latter stream is passed into a thermal olefin alkylation zone in which the heavy Olefins e.g. B. with a solution of triethylaluminum (ATÄ) and diethylaluminum hydride (ADÄH) in contact to be brought. Here the heavy definitions add up to the ADÄH and thus form Aluminum trialkyls (ATA), e.g. B. Diethyl (heavy olefin) aluminum. The separation in stages (c) and (d) takes place, for. B. by distillation.

The aluminum trialkyls produced according to the invention are valuable commercial products which are particularly suitable for the production of higher molecular weight olefins, e.g. B. by reverse or thermal displacement. They are also suitable for the production of alcohols in the plasticizer and detergent area by oxidation and subsequent hydrolysis. Are generally materials above _C8 preferred for these uses. This is due to the fact that Cb to Cio alcohols as plasticizers and C ₂ - to C ₂ 4-Liquor-Ie as detergent intermediates particularly preferred. Higher alkylenes and olefins are therefore understood to mean materials of Cu and higher, while lower alkylenes and olefins are understood to mean materials of C4 or below. The middle alkyls and olefins span the range from Cb to C19.

Any low molecular weight aluminum alkyls or alkyl aluminum hydrides can be used in the process of the invention can be used as starting materials. L) nier the olefins used for the build-up reaction ethylene and propylene are preferred. It has been found V) that higher olefins only dimerize.

In a preferred embodiment of the invention Process are triethylaluminum and / or diethylaluminum hydride of the build-up reaction subjected to ethylene. In the following, we use low molecular weight aluminum alkyls and dialkyl aluminum hydrides Aluminum compounds are understood to have 8 or fewer carbon atoms per alkyl radical

contain. Since alcohols and olefins of C ₈ and higher are generally the desired products, the process according to the invention is explained below with _{reference to the preferred separation between C 6} and C _8.

In the flow diagram of the process according to the invention shown in the drawing, ATÄ and ADÄH are passed via line 1 to distillation zone 2 in a heavy solvent. The ATÄ and ADÄH, together with a small amount of heavy solvent, pass overhead via line 3 to the thermal olefin alkylation zone 4. The solvent is returned via line 5 to the ATÄ / ADÄH production zone, not shown. The ATÄ / ADÄH is mixed with light solvent, which is fed in via line 6, and light (low molecular weight) ATA. mixed heavy olefin and heavy solvent from line 7, and the heavy olefin adds to the ADÄH to _{form AlR 3.} In general, there is an excess of the olefins, in order to ensure complete alkylation, which reach the build-up reactor 9 via line 8 together with AIR3 and solvent. The AIRj is a mixture of ATÄ and diethylalkylaluminum in which the alkyl corresponds to the olefin that reacts with the ADÄH. The AIR3 is subjected to the build-up reaction with ethylene, which is fed in via line 10, and the build-up product then passes via line 11 to fractionator 12. The light solvent and the light olefins are drawn off at the top via line 13 and fed to line 14. The light solvent is separated from the desired product in subsequent operations. The light olefins can later be used together with additional ethylene for a displacement reaction if olefins are desired as end products, and they can easily be separated from the alkylates or alcohols if alcohols are the desired product. In some cases it may be desirable to convert these light olefins to paraffins because the olefins are more easily oxidizable and are a source of carbonyl compounds and other impurities in the oxidation product. In this case this stream is hydrogenated. In any case, the AlR ₃ , the heavy olefins and the heavy solvent get from the fractionator 12 via the line 15 to the fractionator 16. The heavy AIRj then passes via line 17 to the discharge line 14 and then passes via line 18 for further processing. This can be a reverse displacement or an oxidation with subsequent hydrolysis. The overhead stream, consisting of _{low molecular weight AlR 3} , solvent and olefins from fractionator 16, passes via lines 19 and 7 to zone 4 where it is reacted with the ATÄ / ADÄH mixture in the manner previously described.

In the build-up reactor 9, a reverse displacement takes place to a certain extent, and the heavy ones Olefins accumulate in undesirable amounts. The line 20 is therefore provided with a valve 21. in order to allow such olefins to flow off from time to time. Thereby some of the light AlR also flows, and on the heavy solvent, but the amount is very small and these materials then get on via lines 14 and 18 to the further processing stages, where they are recovered be able.

To further illustrate how the alkyl chains of the ATA move towards materials with higher

Molecular weight extended within a certain range is shown in the table below Material partial balance shown. All figures are given in millions of kilograms. In the case shown lies the interest in materials of Cs and higher. It shows

that the product stream, e.g. B. Stream 17, a greatly changed distribution compared to stream 11 which comes from the build-up reactor. Similar results are obtained, for example, for Cio-alkyls and obtain higher alkyls.

Number C Overhead current 13 Ground stream 17 Overhead Stream 19 Loading I. I. from the solution from the construction from the construction slrom 11 for the 1 medium fractionator product fractionator product fractionator solvent
fraklionier I. Alkyls i
J 2 0.0 0.18 8.69 8.87 4th 0.0 3.20 29.11 32.31 6th 0.0 14.89 38.47 53.36 8th 0.0 36.11 23.09 59.20 10 0.0 43.31 6.93 50.25 12th 0.0 32.91 1.66 34.57 14th 0.0 19.83 0.20 20.03 16 0.0 10.10 0.0 10.10 18th 0.0 4.56 0.0 4.56 20th 0.0 1.90 0.0 1.90 22nd 0.0 0.75 0.0 0.75 24 0.0 0.29 0.0 0.29 26th 0.0 0.11 0.0 0.11 28 0.0 0.04 0.0 0.04 30th 0.0 0.01 0.0 0.01 32 0.0 0.00 0.0 0.00 total 0.0 168.20 108.16 276.36 Not implemented Olefins

2 1.32 0.0 0.0 1.32 4th 2.75 0.0 0.0 2.75 6th 3.56 0.0 0.0 3.56 8th 3.41 0.0 0.0 3.41 10 2.61 0.0 0.0 2.61 12th 0.0 0.18 7.42 7.60 14th 0.0 0.12 3.11 3.23 16 0.0 0.07 0.99 1.06 18th 0.0 0.04 0.19 0.23 20th 0.0 0.02 0.04 0.06 22nd 0.0 0.01 0.01 0.02 24 0.0 0.00 0.00 0.00 26th 0.0 0.00 0.00 0.00 28 0.0 0.00 0.00 0.00 30th 0.0 0.00 0.00 0.00 32 0.0 0.0 0.0 0.0 total 13.65 0.44 11.76 25.85 For this 1 Sheet drawings

Claims (1)

Claim: Process for the preparation of aluminum alkyls of higher molecular weight by changing the Poisson distribution of the alkyl chain lengths of aluminum alkyls, through the reaction of aluminum alkyls with low molecular weight olefins have been obtained, characterized in that that one> ° a) subjects a low molecular weight aluminum alkyl hydride to thermal piefinalkylation. b) from the product of stage (a) with a low molecular weight olefin by a build-up reaction Produces aluminum alkyls and displaced olefins, c) light olefins from the heavy olefins from the product of step (b) in a first separation Separating olefins and aluminum alkyls, d) from the heavy olefins and aluminum alkyls in a second separation, the low molecular weight ones Separating aluminum alkyls and olefins, e) recycling the low molecular weight aluminum alkyls and the olefins from stage (d) to stage (a) and f) the higher molecular weight aluminum alkyls from stage (d) wins as a product.