IE43215B1 - The production of alkylene carbonates - Google Patents

Abstract

: In the preparation of alkylene carbonates having alkyl, aryl, cycloalkyl and aralkyl substituents, the corresponding alkylene oxides are reacted with carbon dioxide, the catalyst being a combination of a protic substance having the formula ROH, wherein R is either hydrogen or a radical as enumerated above, with a nitrogeneous basic substance selected from the group constituted by dimethylaniline, triethylamine, pyridine and a basic nitrogeneous resin which is insoluble in the reaction medium. The minor component (by weight) of catalyst being present in the range from 0.1% to 30% by weight of the alkylene oxide. The reaction is carried out at temperatures ranging from 0.degree.C to 200.degree.C and under a pressure comprised between 1 and 100 atmospheres.

Description

This invention relates to the production of alkylene carbonates. It is knov/n that alkylene carbonates can be synthesized from alkylene oxides and carbon dioxide by employing catalysts which are formed by tetralkylammoniurn halides at temperatures in the neighbourhood of 200°C and C02 pressures in the vicinity of 200 atmospheres.

The use of such catalysts under these conditions involves considerable technical difficulties which are associated with the construction of the installations or v/ith the occurrence of corrosion problems which are attributable to the chemical nature of the catalyst.

According to the present invention, there is provided a process for producing an alkylene carbonate having the formula: R' ,3 R‘ .0 3315 3 4 wherein each of R , R , R and R , which can be the same or different, is a hydrogen atom or a hydrocarbon radical, which process comprises reacting the corresponding alkylene oxide of formula : R1R2C- CR3R4 \/ with carbon dioxide in the presence of a catalyst constituted g by a mixture of a protic substance having the formula R OH, where P R is a hydrogen atom or a hydrocarbon radical, with a nitrogenous base.

Preferably each of R1, R2, R3, R4 and R5 is a hydrogen atom or an alkyl, aryl, cycloaikyl or aralkyl group.

The process according to the present invention enables alkylene carbonates to be prepared starting from alkylene oxides and C02 under less drastic conditions and without any halide being present at all.

Examples of suitable protic substances are water, methanol, ethanol, cyclohexane!, phenol and butanol; and examples of suitable nitrogeneous bases are trimethylamine, triethylamine, pyridine and dimethylaniline. The nitrogeneous base can also be constituted by a basic nitrogeneous resin which is insoluble in the reaction medium; generally the reaction medium is the alkylene oxide as such in the presence of the protic solvent, either diluted or undiluted, the diluent (when present) being any noninteracting solvent.

Preferably the catalyst is employed in an amount such that the quantity of the minor component (calculated on a weight basis) of the catalyst is in the range from 0.1% to 30% by weight of the alkylene oxide; the ratio between the two components of the catalyst is not critical, it being possible to operate with an excess of the basic substance or of protic substance.

The reaction is preferably carried out at a temperature in the range from 0°C to 200°C, more preferably in the range from 80°C to 120°C, under a pressure preferably ranging from 1 to 100 atmospheres, more preferably in the range from to 30 atmospheres; the reaction can be carried out either continually or batchwise, and either in a homogeneous or heterogeneous phase.

For example, when operating with the batch process, the alkylene oxide, nitrogeneous base and protic substance can be charged in an autoclave and then COg fed under the desired pressure. The mixture in the autoclave can then be heated on a bath at the desired temperature and the pressure maintained constant by feeding C02 from a bottle. As soon as no further absorption is noticed, the autoclave can be emptied and the liquid distilled; the protic substance and the nitrogeneous base can be recovered and recycled.

Conversely, when operating vrith the continuous process, there can be passed through a vertical reactor heated to the desired temperature and filled vrith a basic unsalified resin, a mixture of alkylene oxide and protic substance under a pressure of COg. The effluent is condensed and then distilled so that the overhead product is alkylene oxide and the protic substance which are recycled into the top of the reaction with the COg, whereas the bottom product is composed of the alkylene carbonate. 3 2 i S The present invention will now be illustrated by the following Examples 1 to 4 and 7 to 10, the remaining Example being comparative.

In the following Example, the term conversion has the following 5 meaning:amount of alkylene oxide which reacted - χ 100(%) amount of alkylene oxide fed and the term yield has the following meaning:number of moles of alkylene carbonate produced - X 100(%) number of moles of alkylene oxide fed EXAMPLE 1 Into a 300 ml autoclave equipped with a stirrer were introduced 60 grams of ethylene oxide, 15 grams of CH^OH and 3.6 grams of , '* Et3N (triethyiamine).

Carbon dioxide at room temperature and under a pressure of kilograms/square centimetre was blown through the mixture, and the latter was then heated to 50°C.

The pressure increased on account of the heating and was kept constant at its maximum value by continually feeding in C02 in an amount corresponding to the amount of reacted C02- The reaction was checked gas chromatographically.

After 60 minutes of reaction, there was conversion of 30% and a yield of ethylene carbonate of 29%.

EXAMPLE 2 A similar procedure to that of the preceding Example was i followed, the only difference being that the working temperature was maintained in the vicinity of 80°C (and not 50°C). After 60 minutes of reaction, a conversion of 70% and an ethylene carbonate yield of 68% were achieved.

EXAMPLE 3 A similar procedure to that of Example 1 was adopted, the only difference being that the working temperature was maintained in the vicinity of 110°C. After one hour of reaction, there was a conversion of 92% and an ethylene carbonate yield of 90%.

EXAMPLE 4 i A similar procedure to that of Example 1 was followed, the only difference being that C02 was fed at room temperature and under a pressure of 30 kilograms/square centimetre and the temperature of reaction was brought to and maintained at 80°C.

After 60 minutes of reaction a conversion of 83% and an ethylene carbonate yield of 81% were obtained.

EXAMPLE 5 (Comparative) A similar procedure to that of Example 1 was followed, the only exception being that no triethylamine was added.

After a 2 hour reaction no trace of ethylene carbonate was found.

EXAMPLE 6 (Comparative) A similar procedure to that of Example 1 was followed, the only difference being that no CH^OH was present.

After more than two hours of reaction not even the slightest 10 trace of ethylene carbonate was found.

EXAMPLE 7 A similar procedure to that of Example 2 was followed, the only difference being that triethylamine was replaced by an equimolar amount of pyridine.

After 60 minutes of reaction a conversion of 60% and an ’ ethylene carbonate yield of 50% were obtained.

EXAMPLE 8 A similar procedure to that of Example 2 was followed, the only difference being that in this case the triethylamine was replaced by an equimolar amount of dimethyl aniline.

After 60 minutes of reaction a conversion of 68% and an ethylene carbonate yield of 65% were obtained.

EXAMPLE 9 Into a 300 ml autoclave were introduced 79 grains of propylene oxide, 15 grams of CH^OH and 3.6 grams of EtgiT.

By working with a temperature of 100°C and a pressure of 10 kilograms/square centimetre, after 120 minutes there was a conversion of 70'/ and a propylene carbonate yield of 68/.

EXAMPLE 10 A mixture formed by 10 grams of ethylene oxide and 15 grams of CHjOH was fed, through a pressure pump and with a rate of flow of 20 liquid ml/hour, to the top of a reactor where it cane into contact with a stream of C02 likewise fed in at the top of the reuctor.

The reactor, which had previously been charged with 50 grams of basic resin (Amberlite 94 S), was thermostatically kept at a temperature of 80°C and subjected to a pressure of 30 kilograms/sq.cm.

The word Amberlite is a trade mark.

The effluent from the bottom of the reactor was condensed and, when analyzed, proved to be ethylene carbonate.

The output per hour for one kilogram of the CH^OH component of the catalyst was equal to 0.54 kilogram of ethylene carbonate.

Claims (9)

1. A process for producing an alkylene carbonate having the formula: 12 3 4 5 wherein each of R , R , R and R , which can be the same or different, is a hydrogen atom or a hydrocarbon radical, which process comprises reacting the corresponding alkylene oxide of formul a: ; r 1r2 c -cr 3 R 4 10 10 with carbon dioxide in the presence of a catalyst constituted by a mixture of a protic substance having the formula R^OH, where R 5 is a hydrogen atom or a hydrocarbon radical, with a nitrogeneous base. 1 ?

2. Ά process according to claim 1, wherein each of R , R , 3. 4 5 R , R and R is a hydrogen atom or an alkyl, aryl, cycloalkyl or aralkyl group.

3. A process according to claim 1 or 2, wherein the minor component (by weight) of the catalyst is present in the range from 0.1% to 30% by weight of the alkylene oxide.

4. A process according to claim 1, 2 or 3, wherein the reaction is carried out at a temperature in the range from 0°C to 200°C.

5. A process according to claim 4, wherein the reaction temperature is in the range from 80°C to 120°C.

6. A process according to any preceding claim, wherein the reaction is carried out under a pressure in the range from 1 to 100 atmospheres.

7. A process according to claim 6, wherein the reaction pressure is in the range from 1 to 30 atmospheres.

8. A process according to claim 1, substantially as described in any one of the foregoing Examples 1 to 4 and 7 to 10.

9. An alkylene carbonate whenever produced by a process according to any preceding claim.