DE1039059B - Process for the preparation of cyclooctatetraene - Google Patents

Description

Process for the preparation of cyclooctatetraene It is known that one Cyclooctatetraen by cyclizing polymerization of acetylene in the presence of nickel catalysts and in the presence of a solvent, e.g. B. a cyclic Ethers, such as tetrahydrofuran, produce at elevated temperature and pressure can. The catalysts used in the known processes are, in particular, the halides, Cyanides, rhodanides or enolates of nickel are used. All of these known methods each use a specific catalyst of this type, with additives only Activators, e.g. B. alkaline substances such as oxides, hydroxides, alcoholates, phenolates, Carbonates and cyanides of the alkali or alkaline earth metals, metal carbides or else Nitrogen bases can be used. Also additions of antioxidants to reduce it the formation of peroxide in solvents are known.

In the technical implementation of a continuous process however, those according to the known ones proved to be used for the preparation of cyclooctatetraene Process achieved reaction rates and thus the space-time yields achieved than too low. An increase in temperature increased the reaction rate, but at the same time led to increased resin formation due to excessive addition of catalyst.

It has now been found that the continuous production of Cyclooctatetraen by cyclizing polymerization of acetylene at elevated pressure and at elevated pressure Temperature in the presence of nickel catalysts and an anhydrous solvent is improved if mixtures of nickel cyanide with nickel enolates are used as catalysts or mixtures of different nickel enolates and / or mixtures of nickel complex compounds of o-aminophenols or -tbiophenols with nickel cyanide or nickel enolates used.

Mixtures are used as freshwater catalysts in the context of the invention made of nickel cyanide with nickel enolates. z. B. nickel acetoacetic ester. Nickel benzoyl acetate, Nickel acetylacetonate or nickel benzoyl acetonate, as well as mixtures of nickel enolates among each other, e.g. B. nickel acetoacetic ester with nickel acetylacetonate or nickel benzoyl acetic ester with nickel benzoylacetonate, or mixtures of nickel complex compounds of o-aminophenol or of the o-aminothiophenol used with nickel cyanides or nickel enolates. as A mixed catalyst composed of nickel acetylacetonate and Nickel acetoacetic ester proved. This mixture is in question for the reaction Coming solvents easily soluble. The mixing ratio of the components in the catalyst mixture used in each case can be changed within wide limits and lies between 10: 1 and 1:10 mol. It is preferable to work with catalyst mixtures, in which the mixing ratio is within the limits 1: 2 to 2: 1, e.g. B. with mixtures in which the components are present in approximately equivalent amounts.

The solvent used is cyclic ethers, e.g. B. tetrahydrofuran, or aromatic hydrocarbons, e.g. B. benzene, or mixtures of benzene with Tetrahydrofuran. The solvents used must be anhydrous and largely be peroxide-free, d. H. the water content must be below 0.01%. It is appropriate Use solvents that have a good dissolving power for the catalyst mixtures used own.

The use according to the invention of the mixed catalysts listed above offers the advantage of the stationary catalyst concentration in the continuous process below 0.3 O / o, based on the solvent, without reducing the reaction rate to belittle. To achieve the same reaction rate with the known Process, each working with a specific individual catalyst, must 1.5 to 3 times the amount can be used. This increased catalyst concentration always led to an increased formation of by-products.

It works at temperatures between 80 and 1800 C, preferably between 100 and 1400 C. The acetylene is. expediently in the form of acetylene-nitrogen mixtures. at 20 to 200 at. advantageously at 100 to 150 at. The space-time today is about 2.0 kg: l catalyst space / day. It can be a multiple, e.g. B. 5.0 up to 8.0 kg / l catalyst space / day, if one uses a lower cyclooctatetraene concentration, z. B. less than 10e / o, in the to be worked up on cyclooctatetraene Accepts raw product.

The inventive use of ÄIi schkatalysatoren makes the Addition of so-called activators, which in most cases lead to the formation of undesirable substances Byproducts, unnecessarily. On the other hand, antioxidants such as polyocyphenols can be used. Hydroquinone icylgallate and bisulfides. add in concentrations of up to 0.01%. An increased addition of anti-oxidation agents can reduce the reaction rate but have an unfavorable effect.

It is advantageous to use the process in the absence of oxygen, be it as a dissolved gas or in the form of peroxide compounds with the solvent. and hydroxyl-containing compounds such as water. In this case it can on any addition, e.g. B. of dehydrating agents such as calcium carbide, calcium hydride, Ethyl euoxide and antioxidants are dispensed with. Thieves Afaßiiahnie promotes the increase in the rate of reaction noticeably. But that has to be the case the synthesis of the acetylene-nitrogen mixture to be used from the last traces of oxygen to be freed. In the gas used, the oxygen content should be below 0.002%, the Moisture content below 0.05 g) 3 1 weigh.

When carrying out the process, one works in a known manner in ordinary high-pressure iron furnaces, because the material is absent is not exposed to high levels of exposure to corrosive materials.

In the synthesis of the cyclooctatetraene according to the invention, one can Increase the rate of reaction so far with reduced addition of catalyst. that the process can be carried out continuously with good throughputs is. The formation of the by-products is surprisingly increased in the case of Temperature working processes due to the significantly reduced residence times and suppressed by the reduced addition of catalyst.

Example 1 1001 water- and peroxide-free tetrahydrofuran. in which 0.3 percent by weight of a mixture of nickel acetoacetate and nickel acetylacetonate in a ratio of 1: 1 and 0.01 percent by weight Hydroquinone are dissolved. pumped in. At the bottom of the furnace are made every hour by several Nozzles 30 to 35 Nm3 of a mixture of 40 percent by volume acetylene and 60 percent by volume Introduced nitrogen. which is freed from oxygen as completely as possible beforehand became. A gas circulation pump circulates the gas mixture at 50 atmospheres. The oven temperature is set between 120 and 1250 ° C.

Working up gives 12 kg of cyclooctatetraene per hour in addition to small amounts of phenylbutadiene, benzene and solid reaction products. the The space-time yield is 1.9 kg of cyclooctatetraene per liter of contact space and day.

Example 2 Modifying the procedure described in Example 1 the feed is 0.2% of the catalyst mixture and without the addition of hydroquinone pumped in. The oxygen content in the synthesis gas is wavier than 0.002 percent by volume. The yields of cyclooctatetraene are practically the same as in Example 1.

Example 3 By a high pressure oven with 80 l content, which with a mixture of 30% benzene and 70% tetrahydrofuran is filled. will be at one Pressure of 18 at and acetylene at a temperature of 1200C in a cycle. Of the Acetylene partial pressure is about 15 at. The amount of gas circulating is 20 to 25 Nin: 3 / hour. This system also produces 100 liters of solvent per hour pumped from the above composition. There are 0 25 in the solvent n / o of a catalyst mixture of 1 part aminophenol nickel and 1.5 parts nickel acetylacetonate contained dissolved or dispersed. A guide tube is used in the synthesis furnace an internal fluid circulation is kept going according to the mammoth principle. which causes a temperature equalization and also a decrease in the dispersed aminophenol nickel prevented.

When the synthesis product is worked up by distillation, one obtains Hourly 6.5 to 7.0 kg Cyclooctatetraen fog some phenylbutadiene, benzene and polymeric by-products. The space-time dimension is 2.0 to 2.1 kg / l catalyst space and day.

Example 4 The synthesis furnace is operated in the same manner as in the case game 3 has been described. operated. This time a mixture is used as the catalyst of nickel cyanide and nickel acetoacetic ester in a ratio of 1: 1 and in one concentration of 0.3%, calculated on the solvent, was added.

5.7 kg of cyclooctatetraene are obtained per hour, which corresponds to one Space-time yield of 1.74 kg / l catalyst space and day.

Claims (3)

PATENT CLAIMS: 1. Process for the production of cyclooctatetraene by cvclizing polymerization of acetylene at increased pressure and at increased Temperature such as 100 to 140 C. in the presence of nickel catalysts such as nickel evanide or nickel enolates, and an anhydrous and practically peroxide-free solvent thereby marked. that mixtures of nickel cyanide are used as catalysts Nickel enolates or from various nickel enolates and / or from nickel complex compounds of o-aminophenols or thiophenols used with nickel yanides or nickel enolates. 2. The method according to claim 1, characterized. that as a catalyst a mixture of approximately equivalent amounts of nickel acetylacetonate and nickel acetoacetic ester is used. 3. Process according to Claims 1 and 2, characterized in that one the catalyst in concentrations of not more than 0.3 percent by weight, on the Calculated amount of solvent, used. Documents considered: German Patent No. 889 464; British Patent No. 706,629; Dear. Ann. d. Chem., Vol. 560, 1948, pp. 1 to 92.