DE1768458A1 - Process for the production of dialkyl carbonates from an ammonium compound of a carbonic acid half ester - Google Patents

Description

The invention relates to an improved process for the production of dialkyl carbonates from an ammonium compound a carbonic acid half-ester and in particular a process for the preparation of dialkyl carbonates by oxidation of a Adducts consisting of a tertiary amine, an alkanol and carbonyl sulfide.

Dimethyl carbonate (structural formula: CILtOCOOCH-) is a known reagent for organic syntheses of various chemical compounds and is normally used represented by the mutual action of phosgene and methyl alcohol. However, phosgene is relatively expensive and extremely poisonous. This manufacturing process for

tin Licht, Dipl.-WirtscnT-Ing. Axeman!

Patent attorneys Dipl.-Ing. Martin Licht, Drpl.-WirtschT-rng.AxenHansmapn, Dipl.-Phys. Sebastian Herrmann

Methyl carbonate is therefore expensive and dangerous at the same time.

Various other dialkyl carbonates can also be made for many reactions in organic synthesis and used. However, in many cases such carbonates are relatively expensive to manufacture. Metal alkyl carbonates such as sodium methyl carbonate with the formula CH-OCOONa are also useful organic intermediates for a range of synthetic reactions. However, sodium-containing carbonates such as sodium methyl carbonate are particularly costly and dangerous to handle when made by the usual methods that use relatively pure sodium metal. One usually proceeds in such a way that first methyl alcohol with metallic Sodium is associated to give sodium methoxide with the structural formula CH-ONa. then the methoxide is reacted with carbon dioxide so that the desired sodium alkyl carbonate is obtained.

The invention was therefore based on the object of providing an advantageous process for the preparation of dialkyl carbonates to accomplish.

The invention was based on the finding that dialkyl carbonates in a particularly advantageous manner from a Ammonium compound of a carbonic acid half-ester produced

109882/1906

can be. Adducts consisting of a tertiary amine, an alkanol and carbonyl sulfide are particularly suitable for this purpose (COS) exist. These adducts are with the help of suitable means for water absorption and / or a Oxidizing agent to the corresponding dialkyl carbonates oxidized. The use of an oxidizing agent reduces the reaction time required for the oxidation,

The invention therefore relates to a process for the production of dialkyl carbonates from an ammonium compound a carbonic acid half-ester, which is characterized by that an adduct consisting of a tertiary amine, an alkanol and carbonyl sulfide in an excess of the alkanol and in the presence of a suitable water absorbing agent and / or oxidizing agent at a temperature of at most about 100 C is oxidized, creating an organic carbonate, water, precipitated free sulfur and that tertiary amine are formed and the tertiary amine can be separated off in essentially unchanged form.

The ammonium compound of a carbonic acid half ester (or the adduct) is immediately converted into the corresponding Dialkyl carbonate is converted when you take the ammonium compound, which is dissolved in an alcohol, at low temperature oxidized. The oxidation is carried out for three hours in an autoclave at 25 ° C and an oxygen pressure of 2.2-5.25 kg / cm. The water absorbent like

109882/1906

for example calcium sulfate must be present in the solution containing the adduct during this time. In order to separate the dialkyl carbonate from the other constituents after the oxidation, the solution is filtered and then distilled. Filtration removes the precipitated free sulfur and the water-absorbing sulfur Funds separated. During the distillation, the alkanol is removed from the dialkyl carbonate.

Alkenols suitable for the process according to the invention are, for example, methanol, ethanol, isopropanol and Propanol. The alkanol should usually not contain more than three carbon atoms. The carbonyl sulfide-containing adducts, in the method according to the invention in the presence of Excess alkanol is oxidized, a further alkoxy radical is obtained from the alkanol medium to form the dialkyl carbonate. There can be any concentration of alkanol in the process can be used if this is sufficient to dissolve or disperse the tertiary amine.

The oxidation leading to the formation of the dialkyl carbonate is usually carried out under predominantly anhydrous conditions and using anhydrous reagents made, although it is not absolutely necessary. In addition, the oxidation can be prevalent in both anhydrous ale can also be carried out in an aqueous state in the presence of an oxidizing agent.

109882/1906

Dialkyl carbonates can according to the method of the invention are made from COS-containing adducts. The ones that contain COS According to the invention, adducts are oxidized to dialky carbonates, whereby free sulfur precipitates and water is formed. The tertiary amine of the product is released and can be recovered will. During the oxidation, the alkanol replaces the tertiary amine as a solvent or dispersant, so that the formation of of the dialkyl carbonate is completed. The oxidation is carried out at controlled low temperatures, which must be kept low enough so that not significant amounts of carbonyl sulfide gas are released, which is caused by Thermal decomposition of the product occurs in the course of the oxidation can. Such decomposition would adversely affect the final yield of the desired dialkyl carbonate. Consequently, the maximum temperature during oxidation depends on the particular adduct and the alkanol that is used is used as a solvent or dispersant, varies within certain limits, but is not more than about 100 ° C. In most cases the temperature range for the oxidation is between about 0 ° C and 100 ° C, preferably between about 0 C and 50 ° C. Temperatures below 0 ° C, reduce the reaction rate considerably, although they can be applied. Such temperatures are common, particularly for economic reasons undesirable.

109882/1906

The oxidation can be represented as follows:

ROCOSR'R ^{1 1} R ¹ '' NH + ROH + 1/20> ROCOOK + H ₃ O + S + NR ¹ R ' ¹ R'''

R, R ' _f R ¹¹ and R " ¹ can be an alkyl, a substituted alkyl, or other suitable radical.

The oxidation can lead to the formation of the dialkyl carbonate in any way at low temperature, provided that that in addition to the adduct, a certain agent is present in the alkanol solution or dispersion. This can one be water-absorbing agent that is insoluble and predominantly neutral in the solution or dispersion of the adduct the oxidation conditions according to the invention, i.e. towards the adduct, the solvent or dispersant (the alkanol) and the tertiary amine as well as towards the carbonyl sulfide, Sulfur and the dialkyl carbonate. For this purpose certain anhydrous inorganic salts can be used, e.g. anhydrous calcium sulfate, sodium sulfate or zinc sulfate. On the other hand, other water-absorbing substances can also be used, e.g. finely divided sieves (synthetic and natural zeolites), various clays such as attapulgite clay, certain bentonites, and similar water absorbing agents. Such absorbents should be in such a concentration

109882/1906

tration exist that at least a substantial part of the water produced by the reaction is absorbed. Preferably, the additive should absorb the entire amount of water. Generally a concentration of about 50-25O g of water absorbent per mole of product is used. Such an absorbent can already be present during the reaction which leads to the formation of the adduct or can be added to the solution or dispersion at any time before or during the oxidation, preferably to a point in time when the oxidation is not yet strongly in progress, in any case before the oxidation is complete. The water absorbing agent gives a large yield of the desired dialkyl carbonate. During the oxidation process, a reaction product (water) is absorbed. to a largely complete reaction,

It has also been found that, instead of the water-absorbing agent or additionally during the oxidation, certain oxidizing agents can be added to the solution or dispersion of the product. Such oxidizing agents are certain salts which accelerate the reaction rate in the oxidation of the product and also give a large yield of the desired dialkyl carbonate. Such salts should be at least to some extent soluble in the solution or dispersion in which the adduct

109882/1906

is available. In addition, the cations of the oxidizing agent change easily their value, for example in the transition from a higher to a lower oxidation level. For this purpose, depending on the solubility of the oxidizing agent used and of the alkanol, various halides, nitrates and sulfates of such valency-changing Metals used as solvents or dispersants for the adduct, e.g. iron, nickel, cobalt, copper, Mercury, palladium, platinum and gold, or salts of other metals that react in a similar way, making a good yield of the desired product and accelerated oxidation achieved.

Particularly suitable oxidizing agents (this is not intended to be a limitation) are depending on the as Solvent or dispersant used alkanol: ferric chloride, Nickel chloride, cobalt chloride, cupric sulfate, cobalt sulfate, Cuprin nitrate and cobalt nitrate. The oxidizing agent must be present during the oxidation. The oxidant is usually used in a relatively low concentration, e.g. about 1-15% by weight of the intermediate, although other concentrations can be used as will be described below. One Sufficient amount of the oxidizing agent must be present for a good yield of the end product and a shortened one Oxidation time can be achieved. The choice of each

109882/1906

Oxidizing agent will present no difficulty to those skilled in the art on the basis of the requirements described.

The oxidation is carried out, as described, at a low temperature in any suitable manner. the Alkanol solution or dispersion which contains the adduct can therefore, for example, at a temperature of about 25-30 ° C at atmospheric pressure 1-4 weeks oxygen or Exposed to air.

However, it is advisable to accelerate the oxidation so that the process becomes more economical. For this purpose, the alkanol solution or dispersion with the adduct and the selected additive, which consists of a water-absorbing agent or an oxidizing agent or both, can be placed in an autoclave, preferably in an autoclave with a stirrer, and under an oxygen cover at superatmospheric pressure, e.g. at an overpressure of 2.8 - 5.25 kg / cm ^ for about 2 - 24 hours. If an absorbent for water is present, this process step can usually be completed in 24 hours. However, as already mentioned, the oxidation time can be shortened considerably if one of the specified oxidizing agents is present in an effective concentration,

109882/1906

since the oxidizing agent increases the rate of oxidation. For example, is an oxidizing agent in the effective low concentration of about 1-15 percent by weight of the If the adduct is present, the oxidation can usually occur within 1-4 hours, in some cases even less Time to be carried out. If the oxidizing agent is present in a far higher concentration, i.e. in a concentration which corresponds approximately to the molar equivalent of the adduct, then the oxidizing agent not only improves the yield of dialkyl carbonate and largely reduces the reaction time, but makes a further feed unnecessary of oxygen during the reaction. When using an approximately equimolar concentration of the oxidizing agent in the alkanol solution or dispersion with the adduct, the oxidation takes place both in presence and in Absence of an oxygen or air blanket. There is no need using air or oxygen under superatmospheric pressure, e.g. in an autoclave with a stirrer, or the Exposing the solution or dispersion of the product to air or oxygen by prolonged standing. The reaction can can instead be carried out very quickly in an open or closed vessel at atmospheric pressure.

The use of an approximately equimolar concentration of the oxidizing agent also makes it economical

109882/1906

The reaction that leads to the formation of the adduct and the oxidation can be carried out in a single 2-step process. It is therefore possible to start from a solution or dispersion of approximately equimolar amounts of a selected tertiary amine and the oxidizing agent with an excess of the selected alkanol. This solution or dispersion can be reacted with carbonyl sulfide gas by bubbling it through at about 50 ° C or less. While this reaction is continued over a period of, for example, about 30 minutes, the COS-containing product is formed, which is oxidized to the desired dialkyl carbonate immediately after it is formed by the oxidizing agent. When an equimolar amount of the COS gas (in relation to the tertiary amine) has been absorbed by the solution or dispersion, the reaction which leads to the oxidation is also largely complete. After a short waiting time, e.g. 15-30 minutes, the solution or dispensing can be fractionated or treated in another final manner so that the dialkyl carbonate and the tertiary amine are separated from the excess alkanol, the precipitated sulfur and the water and the oxidizing agent can be won. It must be noted found that the reactions described can be carried out in a single reaction zone and ZVAR at most about 50 ⁰ C and in a time of about 30-60 minutes During this time

109882/1906

two reactions take place, namely the reaction which leads to the formation of the adduct and the oxidation. By such a thing simplified process, greater economic efficiency is achieved, since the overall duration and also the cost of the Plant are reduced.

The final treatment of the solution or dispersion containing the dialkyl carbonate can be carried out at will. For example, after the oxidation, the entire end product can first be filtered to separate the liquid from the solid components. The filtrate can then be fractionally distilled at low temperature, for example under vacuum. During the distillation, a slightly higher temperature can be used vf-xr ^ '^ n, Λ / α., Etie temperature above the temperature indicated for the formation of the product and the oxidation. However, it is also advisable to carry out the distillation at relatively low pressure and low temperature so that the yield of the dialkyl carbonate is not reduced.

Carbonyl sulfide-containing adducts can: iac ^v urine processes of the invention also be subjected to a reaction in which metallic derivatives of carbonates are formed. The adducts can be reacted with an inorganic salt (for example an alkariol-soluble salt) of a metal

109882/1906

BATH ORIGINAL

will. This reaction can be represented as follows) E ¹¹¹ OANHRR ¹ H ¹¹ + XY (inorganic salt) * R ¹ · ¹ OAX ¹¹ RNR ¹ R ¹ * + H

If, for example, triethylammonium o- ^{methyl carbonate is treated for 30 minutes at 50 °} C. in methanol with calcium chloride, then calcium methyl carbonate is formed

ϊ ft

CH ₃ OCO (C ₂ H -) - NH + CaClg ^ CH ₃ OCO) ₂ Ca + 2 (C ₂ H ₅ ) ₃ N + 2 HCl The products can then be fractionally distilled

will.

Calcium ethyl thiol carbonate with the structural formula (C ₂ H ₅₂ can be prepared by reacting calcium chloride and triisopropylammonium-o-ethylthiol carbonate in a suitable alcohol (ethyl alcohol or the like) at 20 ° C. The products are then separated. The isopropylammonium-o-ethyl thiol carbonate itself can, for example, be represented by the reaction of triisopropylamine in ethyl alcohol with COS in 30 minutes at 25 ° C.

The metallic organic carbonates are for vtte Uses of use. For example, metals that act catalytically can easily be incorporated into the carbonates which then act as a carrier of the metals. Such carbonates decompose easily in most cases

109882/1906

** ■ -: v H

Reacts with water and forms the inorganic carbonates of metals, an alcohol and a gas (CO or COS).

Calcium ethyl carbonate with the structural formula (CK OCO) ₂ Ca can be prepared by first reacting the corresponding tertiary amine (in ethyl alcohol) with carbon dioxide and then reacting the reaction product in alcohol with an alcohol-soluble, inorganic calcium salt. In this way, triisopropylamine can be allowed to react in ethyl alcohol at 20 ° C. for 15 minutes while bubbling NaCO _{3 gas.} The reaction goes as follows:

Oq _q

(C ₃ H ₇ ) N + C ₃ H ₅ OH + CO ₂ > C ₂ H ₅ OCO (C ₃ H ₇ ) ₃ NH

The product, ^ riisopropylammonium-o-ethyl carbonate can then reacted with calcium chloride at 25 ° C in ethyl alcohol in the following way:

2C H OCa (C "H) ΝΉ + CaCl> (C ₉ H OCO

The reaction products can be separated by filtration, so that pure calcium ethyl carbonate is in powder form results. This carbonate decomposes when water is added to ethyl alcohol, carbon dioxide (blown in) and Calcium carbonate:

0
(C ₂ H ₅ OCO) ₂ Ca + H ₂ O> 2C ₂ H ₅ OH + CO ₂ + CaCO ₃

109882/1906

Accordingly, the calcium ethyl carbonate can be treated as dry Powder for medical sterilization (in ethyl alcohol) be used. The calcium carbonate falls out of the aqueous Solution. Similarly, this gives dry sodium ethyl carbonate (produced by reaction of NaSH with triisopropylammonium-o-ethyl carbonate), ethyl alcohol

and sodium carbonate, if water is added: 0

Il

2C ₂ H ₅ OCONa + H ₂ O * 2C ₂ H OH + Na ₂ CO ₃ + CO ₂

The sodium ethyl carbonate is (as a dry powder) a basis for the medicinal ethyl alcohol.

Trimethylammonium methyl carbonate can also be easily converted into a desired metal derivative of methyl carbonate will. For example, sodium methyl carbonate can easily are obtained by treating a trimethylammonium methyl carbonate Methanol solution with a suitable concentration of the methanol-soluble sodium hydrosulphide (Na SH) Sodium methyl carbonate is formed in solution with trimethylammonium hydrosulfide. The solution can then be treated under reflux so that the trimethylammonium hydrosulfide in Trimethylamine and hydrogen sulfide is decomposed, which escapes from the solution as a gas. The trimethylamine can only are distilled off from the sodium methyl carbonate, so that the pure sodium methyl carbonate in the kethanol solution remains behind.

109882/1906

The following exemplary embodiments are intended to explain the process according to the invention in detail: Example 1

About 100 g of anhydrous sodium sulfate was added to a methanolic solution of an adduct consisting predominantly of irimethylamine-methanol-carbonyl sulfide. The solution was placed in an autoclave with a stirrer device and oxidized with stirring at 53 ° C. under an excess oxygen pressure of 4.2 kg / cm 2 over a period of 24 hours. After oxidation, the resulting solution from the autoclave was drawn off and the precipitated free sulfur and sodium sulfate under vacuum filtered and the ge wonnene filtrate in vacuo at about 20 ⁰ C to fractional distillation so that the trimethylamine, the excess methanol and dimethyl

109882/1906

carbonate were obtained separately. The trimethylamine was recovered in an amount which approximately corresponded to the original concentration in the methanol solution during the formation of the product and could be used again for the process according to the invention. The dimethyl carbonate was obtained in a yield of 25 % of the theoretical value and is a suitable reactant for a number of syntheses. It is also a valuable solvent and reagent,

The oxidation was carried out in a second experiment under the same conditions. However, there was no water-absorbing agent or no oxidizing agent present. There was no appreciable yield of dialkyl carbonate achieved.

In a third experiment (under the same conditions as in the first) 100 g of anhydrous calcium sulfate were used instead of 100 g of anhydrous sodium sulfate; A yield of 35 % of the theoretical value was obtained.

In a fourth experiment, 100 g of anhydrous calcium sulfate and 1 g of anhydrous cobalt chloride (CoCl ₂ ) were added to the solution with the adduct immediately before the oxidation in the autoclave. The duration of the entire oxidation was one hour, a yield of 75 % of the theoretical value of dimethyl carbonate was obtained,

In a fifth experiment, 1 g of anhydrous cobalt chloride (CoCl ₂ ) was used instead of the mixture of cobalt chloride and calcium sulfate. The yield of dimethyl carbonate

109882/1906

4t

was again 75 % of the theoretical value. This makes it clear that, at least in some cases, the oxidizing agent alone is just as effective as a mixture of oxidizing agent and water-absorbing agent in the same concentration.

In a sixth experiment, 200 g of attapulgite clay were used in place of the cobalt chloride . The yield of dimethyl carbonate was about 20 % of the theoretical value.

In a seventh experiment , attapulgite clay was replaced by 2 g of anhydrous cupric sulfate. The yield of dimethyl carbonate was 76 % of the theoretical value.

In an eighth experiment, 3 g of nickel bromide were used in place of the cupric sulfate. The yield was about 76 % of the theoretical value.

Example 2

The procedure of Example 1 was repeated with the difference that an ethylenediamine-methanol-carbonyl sulfide was used in place of the adduct .

In the first experiment of Example 2 , for example, 200 g of anhydrous sodium sulfate were used, while i »two-

109882/1906

No special agent (oxidizing agent or absorbent) was added to the tenth experiment. In the third, however, 200 g of anhydrous calcium sulfate were added. In the fourth experiment, 200 g of anhydrous calcium sulfate and 2 g of anhydrous cobalt chloride (CoCl-) were used. In the fifth experiment, 2 g of anhydrous cobalt chloride (CoCl _? ) And in the sixth 300 g of attapulgite clay were used. In the seventh experiment, 3 g of anhydrous cupric sulfate were added and in the eighth, 5 g of nickel bromide. The yield in the first experiment was 25 % of the theoretical value for the dimethyl carbonate, in the second 0 %, in the third 35 % _t, in the fourth 75 %, in the fifth 75 %, in the sixth 35 % _t, in the seventh 75 % and in the eighth 75%. In addition, as in Example 1, the reaction time is shortened from about 24 hours to about 1 hour when using an oxidizing agent alone or in conjunction with an anhydrous absorbent.

Example 3

The procedure of Example 2 was conducted in the same manner and the same number of experiments with the exception that an adduct of 1-azabicyclo (2,2,2) octane _i methanol and carbonyl sulphide was used. The yield was similar to that of Examples 1 and 2,

109882/1906

9fir

Example 4

The procedure of Example 3 was carried out using an adduct of 1-azabicyclo (3.2 _f 1) octane, methanol and carbonyl sulfide. Mostly similar results could be obtained.

Example 5

200 g of anhydrous calcium sulfate were added to the solution of an adduct of trimethylamine, ethanol and carbonyl sulfide. The solution was then oxidized for 24 hours at 25 ° C. and an excess oxygen pressure of 5.25 kg / cm in an autoclave with a stirrer. After the oxidation, the solution was filtered so that the solid components were separated off. Then fractional distillation was carried out and the diethyl carbonate was recovered. The yield of diethyl carbonate was approximately 25 % of the theoretical value.

In a similar experiment, about 2 grams of cobalt chloride was used in place of the 200 grams of calcium sulfate. The yield of diethyl carbonate is about 70 % of the theoretical value after oxidation of only one hour,

Example 6

The solution of an adduct from ~ rii ^; .Lr.ylaiu i.vi, n-propanol and carbonyl sulfide were added 200 g of calcium sulfate (to absorb the

109882/1906

BAD OWGfNAL

Water) added. The solution was then at 25 ° C and an oxygen pressure of 5.25 kg / cm in one Autoclave with stirrer for 24 hours oxidized. After the oxidation, the solution was filtered so that the solid components were removed. Then became fractionally distilled to obtain the di-n-propyl carbonate. The yield of di-n-propyl carbonate was about 15% of the theoretical value,

In a similar experiment, 2 g of cupric chloride (as an oxidizing agent) were used instead of the 200 g of calcium sulfate (as an absorbent for the water). The yield of di-n-propyl carbonate after an oxidation time of only one hour was approximately 70 % of the theoretical value,

Example 7

The solution of an adduct of trimethylamine, isopropanol and carbonyl sulfide were added 200 g of calcium sulfate (for absorption of the water). The solution was then placed in an autoclave at 2 5 C and an excess pressure of 5.25 kg / cm oxidized with a stirrer over 24 hours. After the oxidation, the solution was used to separate the filtered solids and then fractionally distilled to obtain the diisopropyl carbonate. The yield was approximately 10% of the theoretical value,

109882/1906

In a similar experiment, about 2 g of cobalt nitrate (as an oxidizing agent) was used instead of the 200 g of calcium sulfate (to absorb the water). The yield of diisopropyl carbonate was approximately 50 % of the theoretical value,

Example 8

Dimethyl carbonate was made by initially adding 180 g

Trimethylamine and 67 g of cupric chloride were dissolved in 300 cm of methanol. The resulting amine-alcohol-cupric chloride solution was then brought into contact with carbonyl sulfide gas in an autoclave with a stirrer at an overpressure of 3.5 kg / cm at approximately 25 ° C. for about 5 minutes until 15 g of carbonyl sulfide had been absorbed by the mixture. The mixture was then stirred at 25 ° C. for a further hour. The resulting mixture was fractionally distilled (under vacuum). The yield was 90 % dimethyl carbonate. The oxidation when using cuprichloride can be characterized as follows: ₀ 0

CH ₃ OCS (CH ₃ ) ₃ NH + 2CuCl ₂ + CH.OH> CH ₃ OC-OCH + 2CuCl +

(CH) ₃ N + 2HC1 + S

In a similar experiment, 65 g of cobalt chloride, CoCl _{3, were} used instead of 67 g of cupric chloride. The yield of dimethyl carbonate was the same.

109882/19 06

The method according to the invention thus creates a simple, relatively safe and fast and thus economical one Process for the production of dialcyl carbonates. from ammonium compounds of carbonic acid half-esters, The desired dialcyl carbonates can be used with GOS-containing adducts according to the invention by an oxidation at low temperature be won. In addition, the COS-containing adducts easy to convert into various carbonate end products. The reagents are not used up except of carbonyl sulfide and alkanol for the preparation the dialkyl carbonates or the metallic derivatives of the alkyl carbonates. The tertiary amine can always from the solution or "dispersion after the final treatment in such Form can be recovered that it according to the invention again can be used. «

As can be seen from the examples given, oxidation is an effective concentration of an absorbent for the water or an oxidizing agent of the type described to obtain a good yield the solution or the dispersion with the adduct is required. If desired, the solution or dispersion can be both Contain oxidizing agent as well as an absorbent for water.

109882/1906

Claims (8)

ATENTANWÄLTE Dipl.-Ing. MARTI N LI C HT Dr. REINHOLD SCHMIDT PATENTANWÄLTE LICHT, HANSMANN, HERRMANN 8 MÖNCHEN 2 · THERESiENSTRAssE 33 Dipl.-Wiilsch.-Ing. AXEL HANSMANN DiPL-PhVs-SEBASTIANHERRMANN - ZH- Retired from Munich, May 15, 1968 P 15 18 308.1 Your sign under sign (S 97 326 IVb / i2q) Η_ ^ SIGNAL OIL AND GAS COMPANY / Οθ4θθ Los Angeles, California Wilshire Blvd . 1010, V.St.A. Process for the production of dialky! Carbonates from an ammonium compound of a carbonic acid half-ester 1. A process for the preparation of dialkyl carbonates from an ammonium compound of a carbonic acid half ester, characterized in that an adduct consisting of a tertiary amine, an alkanol and carbonyl sulfide (COS) is present in an excess of the alkanol and in the presence of a suitable water-absorbing agent and / or oxidizing agent is oxidized at a temperature of at most about 100 ⁰ C, whereby an organic carbonate, water, auggefällter free sulfur and the tertiary amine are formed, and wherein the tertiary amine can be separated in substantially unchanged form. 2. The method according to claim 1, characterized in that the ^{water absorber} J ⁵ j ^ jJ? F. ^ £££ 1 is ^{insoluble in the} alkanol, Patent attorneys Dipl.-Ing. Martin Licht, Dipl.-Wirtich.-Ing. Axel Hansmann, Dipl.-Phys. Sebastian Herrmann essentially not with the reactants including the alkanol, the tertiary amine, of the adduct and the organic carbonate reacts and is added to the alkanol containing the adduct before the oxidation is largely complete. 3. The method according to claims 1 to 2, characterized in that that the water absorbing agent is anhydrous calcium sulfide anhydrous Is sodium sulfate or attapulgite clay. 4. The method according to claims 1 to 3, characterized in that, that the oxidizing agent contains an inorganic salt which during the oxidation at least partially in alkanol is soluble, the valence can easily change and that of the alkanol, which contains the adduct, before the end of the oxidation is added in an amount sufficient to obtain a good yield of the desired organic carbonate and to cause a substantial acceleration of the rate of oxidation. 5. The method according to claims 1 to 4, characterized in that the oxidizing agent is the alkanol before the reaction is added in an amount sufficient to oxidize the adduct to dialkyl carbonate without further oxidizing agents. 6. Process according to Claims 1 to 5, characterized in that the oxidizing _{agent is anhydrous cobalt chloride (CoCl 2} ) or cupric chloride. 109882/1906 7. The method according to claims 1 to 6, characterized in that that the adduct is oxidized by oxygen in the alkanol at above atmospheric pressure. 8. The method of claims 1 to 7, characterized in that as starting material, an adduct is selected which has been formed at the most about 50 ⁰ C. 109882/1906