DE1047355B - Process for the purification of auxiliary fluids for the manufacture of polyolefins - Google Patents

Description

It is known that ethylene can be polymerized at pressures below about 100 atmospheres and at temperatures up to about 100.degree. In this process, catalysts are used which are composed of mixtures of organometallic compounds, in particular aluminum alkyl compounds, with compounds of metals from IV. To VI. Subgroups of the periodic system exist. Among these metal compounds, titanium compounds are particularly suitable, for example titanium tetrachloride (cf. Belgian patents 532 362 and 534 792 and "Angewandte Chemie", 67, 1955, pp. 541 to S47). In this synthesis, an auxiliary liquid is generally used in which the polyethylene formed is slurried. Preference is given to using auxiliary liquids which consist of aliphatic hydrocarbons in the boiling range of heavy gasoline or diesel oil.

It is expedient to use aliphatic hydrocarbon fractions, such as those from carbohydrate hydrogenation can be won. Such fractions contain, however, in addition to unsaturated Hydrocarbons still more or less large proportions of oxygen-containing compounds that at interfere with the implementation of the polymerization.

It has already been proposed for the purification of such hydrocarbon fractions such first at temperatures of 230 to 280 ° C ^p together with hydrogen over a hydrogenation catalyst, to conduct, for example, a nickel-containing catalyst, subsequently to be subjected to extraction by means of concentrated sulfuric acid and to dry to a neutral wash ( see patent 961,477). This procedure was proposed because saturated aliphatic hydrocarbons from carbohydrate hydrogenation were not sufficiently purified by a hydrogenation carried out at temperatures of 230 to 280 ° C. over nickel-containing catalysts to be able to be used as auxiliary liquid in olefin polymerization. After the hydrogenation, the so-called "oxygen content" determined with phenylisopropyl potassium, which shows the sum of all oxygen-containing compounds, including water, were too high. A treatment with concentrated sulfuric acid with neutral washing and drying was therefore considered necessary following the hydrogenation.

It has been found that this procedure can be considerably simplified and that the sulfuric acid treatment can be omitted. According to the invention, the purification of the mixtures of saturated aliphatic Hydrocarbons from carbohydrate hydrogenation, which are used as auxiliary liquids in the polymerization of ethylene at pressures

Methods for cleaning up

of auxiliary fluids for manufacture

of polyolefins

Applicant:

Ruhreheinie Aktiengesellschaft,
Oberhausen (RhId.) - Holten

Dr. Helmut Kolling, Duisburg-Hambprn,

and Nikolaus Geiser, Qberhausen (RhId.) - Holten,

have been named as inventors

below about 100 atü and temperatures up to about 100 ° C using polymerization agents, the mixtures of aluminum alkyi compounds and compounds of metals from IV. to VI. "Subgroups of the periodic system, in particular titanium chlorides, exist (method according to Ziegler), carried out in a simplified manner by initially adding these hydrocarbon mixtures to Temperatures from 230 to 280 ° C, preferably from 250 to 260 ° C, together with hydrogen via one Hydrogenation catalyst, preferably a nickel-containing catalyst, passed and then through a very careful drying, for example over fine-grained calcium chloride, to a water content of at most 15 ppm are brought. It has been found that they hydrogenated at about 250.degree Hydrocarbon fractions were therefore previously regarded as not sufficiently pure for olefin polymerization because they had not been dried sharply enough. The one determined with phenylisopropyl potassium "Oxygen content" was essentially through one

4-5 residual water content conditional. A drying over stony Calcium chloride, as it is usually carried out, usually does not achieve the goal. It It is necessary to distribute the calcium chloride very finely, preferably in powder form. The hydrogenated Hydrocarbon fractions are, if necessary after pre-drying over lumpy Calcium chloride, best passed from bottom to top through a column filled with fine-grained calcium chloride.

809 700/519

However, the process is not limited to this type of drying. There can be others, too known types of drying, provided they are sufficiently effective, are used. Good desiccant are large-surface substances, such as caustic alkalis applied to pumice gravel, e.g. B. potassium hydroxide.

The decisive factor for the inventive cleaning of the aliphatic hydrocarbon fractions from the Kohlenoxydhydrierung in addition to the good drying the hydrogenation at temperatures of 230-280 ⁰ C, preferably at 250 to 260 ° C., for metal catalysts. Nickel catalysts have proven particularly useful. The temperature range from 230 to 280 ° C is a prerequisite for successful cleaning. Usually, such catalysts are hydrogenated at much lower temperatures, for example at about 150 ° C. These temperatures are also sufficient to saturate the unsaturated constituents, but not to remove all oxygen-containing compounds to such an extent that the olefin polymerization is no longer disrupted.

The object of the process was to remove the oxygen-containing compounds from the mixtures to remove the hydrocarbons quantitatively, up to residual contents as they can only be achieved with the Fine determination method with phenylisopropylpotassium can be determined.

example

30th

A fraction of aliphatic hydrocarbons from the Fischer-Tropsch synthesis with boiling limits 80 to 190 ° C is reached from bottom to top through a pressure tube filled with a solid nickel catalyst 50 mm in diameter and 6 m in height. Composition of the catalyst: 100 parts nickel, 50 parts of diatomite, 10 parts of magnesium oxide. The pressure pipe was heated with the aid of a oil jacket, with a temperature of 255 ° C set became. Work was carried out at a hydrogen partial pressure of 30 atmospheres. 5 liters of hydrocarbon mixture were used per hour passed through. The hydrocarbon mixture emerging from the pressure tube was cooled to 20 ° C. and let down. then the hydrocarbon fraction was in each case from bottom to top by two consecutive, vertical pipes 150 mm in diameter and 3 m high, of which the first pipe with lumpy calcium chloride, the second tube was filled with powdered calcium chloride. The determination the water content with phenylisopropyl potassium resulted in an "oxygen content" of ppm.

Claims (3)

Patent claims: 1. Process for purifying the mixtures from saturated, aliphatic hydrocarbons the hydrogenation of carbons, which are used as auxiliary nuts in the polymerization of olefins, in particular of ethylene, at pressures below about 100 atmospheres and temperatures of up to about 100 ° C using polymerisation exciters, which are made from mixtures of aluminum alkyl compounds and compounds of metals from IV. to VI. Subgroup of the periodic system, especially titanium chlorides, exist, characterized in that these hydrocarbon mixtures are initially at temperatures from 230 to 280 ° C, preferably from 250 to 260 ° C, together with hydrogen via one Hydrogenation catalyst, preferably a nickel-containing catalyst, conducts and then it subjected to very careful drying, for example over fine-grained calcium chloride, until Water contents of a maximum of 15 ppm are reached. 2. The method according to claim 1, characterized in that optionally after predrying Over lumpy calcium chloride the hydrogenated product from bottom to top through a fine-grained Chlorine-calcium filled column is passed. 3. The method according to claim 1, characterized in that large surface area as the drying agent Substances such as caustic alkalis applied to pumice gravel, e.g. B. potassium hydroxide is used will. Considered publications:
German Patent Nos. 954905, 961 477;
German regulations No. 1 019 032, 1 021 524. © 809 700/519 12.58