DE1109659B - Process for the preparation of olefin oxidation products - Google Patents

Description

Process for the preparation of olefin oxidation products It is known Ethylene oxide in the gas phase by direct oxidation of ethylene with oxygen or To produce air on silver contacts. The disadvantage of this method is that that about 1/3 of the ethylene used burns to carbon dioxide and water and the ethylene oxide is obtained in very low concentrations. The reason for this lies in the relatively high reaction temperatures at which the rate of the combustion reaction is comparable to that of ethylene oxide formation. After this procedure one can do not work at lower temperatures, because then the conversions are too low and the concentration of ethylene oxide in the reaction product is too low.

It is also known to use a vanadium oxide catalyst instead of the silver catalyst to use. In this case, temperatures of 500 to 600 ° C. are used. At normal pressure, however, no ethylene oxide is formed at all, only Carbon dioxide. At a pressure of 200 torr, the amount of carbon dioxide is equal to that of ethylene oxide. Consequently one must use much lower pressures in order to achieve higher ones To achieve ethylene oxide yields. So very large systems are required and the throughputs are very low.

It is also known to use bound oxygen, as it is, for. B. in NO2 or Cu0 is present, according to the Kubierschky method in columns with methane for reaction bring to. However, ethylene oxide is only formed in traces.

It is also known that olefin coordination compounds are obtained from platinum salts or palladium salts and decompose them with water. However, only Aldehydes. Olefin oxides cannot be obtained in this way.

The addition of olefins to mercury compounds is also known in aqueous or alcoholic solution. Some of the olefins occur when cooking an oxidation, whereby the mercury is reduced to the metal. Form thereby The corresponding glycols, trimethylethylene, are oxidized from the propylene compounds becomes acetaldehyde in addition to acetone and the tetrahydroquinoline is oxidized to quinoline. However, the formation of olefin oxides was not observed in any case.

It has now surprisingly been found that ethylene or other olefins can be used such as propylene or butylene in the presence of molecular oxygen at elevated temperature in an alkaline to neutral medium and in a liquid aqueous phase with a compound from divalent mercury to the corresponding olefin oxides, such as ethylene oxide, Propylene oxide or butylene oxide can oxidize. Molecular oxygen can do both in concentrated, z. B. technically pure, as well as diluted form can be used, z. B. in the form of air or air enriched with oxygen.

Instead of pure olefins, olefin-containing gases can also be used, as it is, for example, in the case of low or high temperature pyrolysis (in the case of the latter after removal of the acetylene). Mixtures with other inert ones can also be used Gases such as hydrogen, carbon oxide, methane, ethane, propane, butane and higher hydrocarbons, as well as olefin; in particular ethylene-containing coke oven gases, from which expediently by a pre-cleaning of the hydrogen sulfide and the carbon dioxide are removed, used will.

The method can be used with reduced, but preferably with normal or increased pressure. In principle, you can work at any temperature below the critical temperature of the solution possible, but is preferred worked between 70 and 300 ° C. The lower temperature is limited by that the reaction rate becomes too slow. When using temperatures which go beyond the boiling point of the solution must be worked under overpressure, to prevent evaporation of the solution. But it can also prove to be beneficial prove to work with increased pressure even at temperatures below 100 ° C.

Complex compounds are preferably used as mercury compounds used, e.g. B. those that one by introducing olefins, in particular Ethylene in an aqueous solution of a mercury salt such as mercury (II) sulfate, nitrite, nitrate, fluoride, chloride, bromide, sulfite, cyanide, oxycyanide, rhodanide, -perchlorate and -chlorate. The latter two connections are possible because of the Formation of explosive mixtures is less recommended. Mercury sulphate has proven particularly useful.

The solution of the salt occurs in some cases only through additives a. Mercury sulphide, which is sparingly soluble in water, can be absorbed by KZS in Solution, as well as mercury iodide by potassium iodide.

Mercury compounds with organic anions can also be used, so z. B. mercury acetate and the salts with other carboxylic acids and their derivatives, Likewise solutions of mercury oxide in organic solutions, provided water is present, as is the case with the solution of mercury oxide in an aqueous solution of Acetamide.

All organic mercury also fall within the scope of this patent Compounds insofar as they are soluble in water or aqueous solvents. Particular mention should be made of the aqueous alcohol solutions, in which the olefin absorption occurs significantly more rapidly with the formation of mercury-alkoxyalkyl compounds.

Examples of organic mercury compounds are methyl mercury fluoride, Alkyl mercury hydroxides and salts (especially methyl mercury nitrate, which is found in Water is very soluble), phenylmercury salts with organic and inorganic Acids, olefin mercury chloride, ethanol mercury salts, ethyl ether mercury salts as well as the analogous compounds with higher olefins.

Here, too, it is possible that the compound is insoluble in pure water and only through the addition of acids, salts, alkalis or organic substances can be brought into solution as it is, for. B. p-Aminophenylmerkuriazetat the The case is that is insoluble in water, but in dilute acids, or else Easily dissolves in dilute alkalis and in aqueous aniline acetate solution. On too Mercury dimethylaniline should be noted, which is in cold; -diluted hydrochloric acid dissolves, as well as mercury-bissalicylic acid, which is insoluble in water, in aqueous Alkalis, however, is soluble.

The presence or occurrence of metallic mercury is a nuisance the reaction doesn't.

The mercury salt used should be present in an aqueous solution of olefin, especially ethylene, be readily soluble. Crucial for carrying out the reaction according to the invention, the p $ is by no means more acidic as p $ = 7 and should preferably be greater than 8. With a pil more acidic than 7 only acetaldehyde is produced.

Sometimes it may be advisable to add foreign salts. The Solutions can optionally be added to organic solvents, both those that are miscible with water as well as those that are immiscible with water are. In the latter case, you can choose to proceed either in separate Shifts works, e.g. B. layered a liquid hydrocarbon over the solution or by causing intensive mixing by means of stirring. These measures are taken to increase the solvency for the olefin.

The oxidation can be carried out so that the olefin and bringing the oxygen into contact with the solution at the same time, e.g. B. by the Solution pearls. However, it is also possible to first use the olefin in the solution to charge, then interrupt the introduction and only then the oxygen to be added to the loaded solution in order to remove the olefin oxide from the solution. These stages can be carried out by pumping the solution in two different vessels can also be carried out in one.

In particular, ethylene oxide can be produced by the above process. In addition, depending on the pH used, acetaldehyde is formed in varying amounts.

Example 148 g of mercury (II) sulfate are dissolved in 500 cm3 of cold water Suspended and brought into solution by introducing ethylene. To the clear one 65 g of sodium carbonate are added to the solution.

The solution is in an externally heatable and against heat radiation Well insulated reaction tube of 2 m length and 2 cm diameter filled and approximately heated to boiling. Through the solution is a mixture of 41 ethylene and hourly 1 1 oxygen passed through to set the ethylene oxide free. The gases are introduced through a frit at the lower end of the reaction tube. At the top At the end of the pipe is widened to a calming vessel on which a reflux condenser is put on.

After 2 days of reaction time, the exhaust gas contains 1.80 percent by volume of ethylene oxide, after 3 days 2.0 percent by volume of ethylene oxide. During the third day the Ethylene oxide content to 3.65 percent by volume. The gas leaving the reactor contained also acetaldehyde and some carbon dioxide. The analyzes were carried out by gas chromatography executed.

Claims (1)

Claim: Process for the preparation of olefin oxidation products, characterized in that olefins, in particular ethylene, in the presence of oxygen - optionally with dilution with inert gases for the reaction - at elevated temperature in the liquid aqueous phase and at pH values above 7, preferably between 8 and 14, implemented with mercury compounds. Documents considered: French Patent No. 1038 679; Petroleum, 13: 649-654 (1917); Chemikerzeitung, Vol. 42 (1918), pp. 345 to 351; Zeitschrift für angewandte Chemie, 32 (1919), pp. 233 to 235; Fuel Chemistry, 10 (1929), pp. 337 to 346; Chemical Reviews, 48, pp. 7 to 43 (1951); Journal of organic Chemistry, 18 (1953), 1617-1631.