DE1169459B - Process for the production of alkylene carbonates - Google Patents

Description

Process for the preparation of alkylene carbonates It is known, alkylene carbonates by reacting alkylene oxides with carbon dioxide at elevated temperature and at produce elevated pressure in the presence of catalysts. Has as catalysts alkaline substances, such as sodium hydroxide on activated carbon, or organic ones Nitrogen bases such as pyridine and piperidine are used. Achieved by this procedure there are only moderate yields and, moreover, when using ethylene oxide, if this comes into contact with the catalyst in the absence of carbon dioxide Possibility of explosive polymerisation. It is also from the USA patent 2,773,070 known as catalysts for this conversion quaternary ammonium salts to use. In this patent it is already indicated that the bromides and Iodides are more effective than the chlorides and fluorides, but the iodides cause decomposition tend to form free iodine. Useful results are obtained with the bromine ions achieved, but the separation of the bromides from the alkylene carbonates requires great Care and is not without loss, especially with the most effective catalysts connected to catalyst and / or to alkylene carbonate. In the USA. Patent pens 2667497 and 2924608 is the use of alkaline earth metal halides, including also of magnesium subiodide, described as catalysts. The feasibility however, the reaction over a long period of time is difficult and the yields are insufficient.

It has now been found that alkylene carbonates can be obtained by reacting Alkylene oxides with carbon dioxide at elevated temperature and pressure in Presence of catalysts in very good yields in short reaction times as a result obtained by using a mixture of alkali halides and alkali carbonates as catalysts or oxides of metals of II. or III. Group of the periodic table used, wherein per mole of alkali halide 1 to 10 moles of alkali carbonate or oxides of metals the II. or III. Group of the Periodic Table.

In contrast to known processes, the new catalysts easily separated from the reaction mixture, and the process can be carried out without difficulty be carried out continuously over a longer period of time.

The starting materials are alkylene oxides, such as ethylene oxide and propylene oxide, suitable. Instead of pure carbon dioxide one can also use carbon dioxide-containing gases use, e.g. B. the gaseous reaction resulting from the air oxidation of ethylene product, which contains ethylene oxide and carbon dioxide.

This gaseous reaction product can, if appropriate after addition of further carbon dioxide, can be used directly for the process according to the invention. It is expedient to work with an excess of carbon dioxide to reduce the tendency to polymerize to prevent the ethylene oxide.

The catalysts used are mixtures of alkali halides and Alkali carbonates or oxides of metals of II. Or III. Periodic group System in the specified proportions. The use of alkali iodides for the synthesis of alkylene carbonates is the subject of an older proposal, however, the catalysts to be used in the process of the invention have an increased activity due to the synergistic effect of the alkali carbonates or the metal oxides concerned. Sodium bromide alone does not lead to satisfactory results Sales while with an appropriate addition of alkali carbonate or a corresponding metal oxide, however, good results can be achieved. Sodium chloride alone has little catalytic effect and on the other hand the alkali carbonates have or the oxides of metals of II. or III. Group of the periodic table alone no influence on the course of the reaction.

The amount of catalyst to be used varies within wide limits, you can, for example, 0.1 to 5 g of the mixture in question per mole to be prepared Use alkylene carbonate. The ratio of alkali halide to alkali carbonate or to the oxide of a metal of II. or III. Group of the periodic table within a molar ratio of 1: 1 to 1:10.

The reaction temperature is usually between about 100 and 2700 C, preferably 170 to 2300 C; it depends somewhat on the Art of the alkali halide used. If you use the iodides you already get Good yields at 120 ° C., but long reaction times are then required. If the temperature is increased to 180 to 200 C, the reaction time is shortened considerably.

Since the reaction is exothermic, heating occurs during the reaction a; in some cases it is advisable to dissipate the heat of reaction by cooling, to prevent an overly violent reaction.

For better dissipation of the heat of reaction one can also in the presence work from inert solvents. Ethers such as tetrahydrofuran, Dioxane and ethylene glycol dimethyl ether are suitable.

The process is expediently carried out at the pressure which is self-contained when the reactants are heated in a closed vessel adjusts. However, you can also, for. B. by injecting inert gas at even higher Pressing work. In general, the pressures used are between 50 and 150 at. With continuous operation, this pressure range is also used worked.

The alkali halides can be in solid form or also dissolved in the to be prepared alkylene carbonate are added to the reaction mixture. The alkali carbonates or oxides of metals of II. or III. Become a group of the periodic table added in solid form to the reaction mixture; if the reaction is carried out continuously, they can can be used as reactor filling.

The process can be carried out batchwise, e.g. B. in an autoclave, or continuously, e.g. B. according to the trickle process. The work-up the reaction mixture obtained can by distillation or recrystallization from a suitable solvent, e.g. B. from an alcohol. The catalysts can in the work-up from the distillation residue in a simple manner, for example by filtering off, if necessary after previous precipitation with aromatic Hydrocarbons, recovered and reused. When using of amines or amine salts as catalysts - it is not easy to find the basic ones Completely separate catalysts from the process product by distillation. Accordingly, these process products tend to be more or less during storage severe discoloration that can only be avoided through subtle cleaning processes can while the products obtained by the process according to the invention over can be kept unchanged for a long time.

Example 1 2100 g of ethylene oxide and 2150 g of carbon dioxide are combined with 5 g of sodium iodide and 3 g of lithium carbonate in a 10 l pressure vessel heated to 110 to 115 C. This results in a pressure of 75 atmospheres Drops to 40 atmospheres over the course of 8 hours. After the reaction mixture has cooled down 4150 g (98% of theory) of crude ethylene carbonate are obtained in the form of colorless Crystals that melt at 32 to 35G C.

Example 2 50 g of ethylene oxide and 55 g of carbon dioxide are 0.1 g of sodium iodide and 0.5 in heated to 160.degree. C. in a pressure vessel. at the reaction starts at this temperature. The temperature then increases over time the reaction to 188 ° C. The pressure falls from 85 to 45 in the course of 80 minutes atü from. After the reaction mixture has cooled down, 100 parts become almost colorless Ethylene carbonate with a melting point of 33 to 35 - C obtained. The yield is practically quantitative.

If one uses calcium, barium instead of magnesium oxide. Zinc- or cadmium oxide, the same results are obtained.

Example 3 50 g of ethylene oxide and 55 g of carbon dioxide are 0.1 g sodium iodide and 0.5 g aluminum oxide dried at 550 ° C. heated to 150 ° C. The reaction starts at this temperature. The reaction temperature increases within a few minutes to over 200G C, with the pressure rapidly increasing from about 80 40 atmospheres drop. After the reaction mixture has cooled down, the ethylene carbonate becomes obtained in a yield of 98 ovo of theory. The reaction is like this violent that it can only be controlled by cooling in larger batches.

Example 4 50 parts of ethylene oxide and 55 parts of carbon dioxide become Heated to 150 ° C. together with 0.5 g of sodium bromide and 0.5 g of annealed aluminum oxide.

The reaction starts quickly at this temperature.

Over the course of an hour, the temperature rises to 205-C while the pressure decreases from 60 to 25 atmospheres. After the reaction mixture has cooled down 100 g of almost colorless, crude ethylene carbonate with a melting point of 32 ° to 35 ° C. were obtained. the The yield is practically quantitative.

If the example is carried out without using aluminum oxide, in this way, after a reaction time of 4 hours, about 80 g of yellow-brown ethylene carbonate are obtained.

Example 5 58 g of propylene oxide and 55 g of carbon dioxide are combined with 0.1 g sodium iodide and 0.3 g lithium carbonate in a 250ccm reaction vessel heated to a temperature of 155 ° C.

This results in a pressure of 47 atü, which over the course of 6 Hours to 40 atmospheres. After the reaction mixture has cooled down, 102 g of crude, colorless propylene carbonate were obtained. The yield is practically quantitative.

After distillation, 100 g of pure propylene carbonate (98ovo der Theory) from Kp. 8 110 to 113? obtain.

Example 6 90 g of styrene oxide and 45 g of carbon dioxide are combined with 0.2 g potassium iodide and 0.5 g lithium carbonate in a 250 ccm pressure vessel heated to 165 ° C. This results in a pressure of 54 atm. After 6 hours the reaction is canceled. During this time the pressure has decreased to 30 atmospheres. 118 g of a brown-black, crystalline product are obtained from which by recrystallization from propanol 112 g of styrene carbonate from 52 to 53? Isolate C. permit.

Yield 91% of theory.

Example 7 70 g of butadiene monoxide and 50 g of carbon dioxide are combined with 0.5 g sodium iodide and 0.5 g lithium carbonate in a pressure vessel at 2000 ° C heated. After 3 hours the maximum pressure has dropped from 72 to 50 atmospheres. After this When the reaction mixture cools, 112 parts of crude vinyl ethylene carbonate are obtained. Distillation in vacuo gives 102 g (89.4 ovo of theory) of pure vinyl ethylene carbonate from Kr. 10 110 to 1140 C.

Example 8 740 g of methyl glycidyl ether and 420 g of carbon dioxide become together with 3 g of potassium iodide and 3 g of sodium carbonate in a pressure-stirred vessel Heated at 1800 C. After 3 hours, during which the pressure has decreased from 55 to 30 atmospheres, 1050 g of crude 1-methoxypropylene-2,3-carbonate are obtained. By subsequent Distillation in vacuo gives 984 g of the pure product of Kr. 1.5 98 bis 1040 C. The yield is 89 ovo der Theone.

Example 9 216 g of a mixture of a- and p-butylene oxide and 160 g carbon dioxide together with 0.5 g sodium iodide and 1.5 g aluminum oxide in heated to 1800 C in a pressure vessel. With the onset of the reaction increases the temperature to about 220 ° C, at the same time the pressure drops from 50 to 30 atü. After 3 hours, the reaction is terminated at a pressure of 30 atmospheres. After this When the reaction mixture cools, 310 g of crude reaction product is obtained, which at the subsequent distillation under reduced pressure 50 g of butylene oxide (predominantly p-butylene oxide) and 230g of a mixture of a- and p-butylene carbonate with a boiling point of 66 supplies up to 680 C. The yield, based on butylene oxide, is 910/0 of theory.

Example 10 2100 g of ethylene oxide and 2150 g of carbon dioxide are combined with 2.5 g sodium chloride and 20 g Sodium carbonate in a 101 capacity stirred pressure vessel heated to 2200 C. A pressure of 85 atm is established, which over the course of 22 hours drops to about 40atü. After the reaction mixture has cooled down one 3850g (91.70 / 0 of theory) of crude ethylene carbonate from F. 28 to 330 C.

If sodium carbonate is not used, the reaction will only take place in the course of the process from 27 hours with the same yield.

Example 11 2100 g of ethylene oxide and 2150 g of carbon dioxide are in a pressure vessel together with 2.5 g of potassium chloride and 20 g of potassium carbonate to 1700 C heated. After 18 hours the pressure has decreased from 80 atmospheres to 35 atmospheres. One relaxes the mixture and, after the reaction mixture has cooled, 3740 g (890/0 der Theory) Ethylene carbonate from F. 30 to 340 C.

Claims (2)

Claims: 1. Process for the production of alkylene carbonates by reacting alkylene oxides with carbon dioxide at elevated temperature and at elevated pressure in the presence of catalysts, characterized in that as Catalysts a mixture of alkali halides and alkali carbonates or oxides of metals of II. or III. Group of the Periodic Table used, where per mole of alkali halide 1 to 10 moles of alkali carbonate or oxides of metals of II. or III. Group of the Periodic Table. 2. The method according to claim 1, characterized in that the catalyst contains an alkali iodide as alkali halide. References considered: U.S. Patents No. 2511 942, 2 667 497, 2 773 070, 2924608.