CH620434A5 - Process for preparing alkylene carbonates - Google Patents

Abstract

The technical problem of preparing certain alkylene carbonates is solved by reacting the corresponding alkylene oxides with carbon dioxide, with the aid of a catalyst consisting of a hydroxylated protic substance and a nitrogenous base.

Description

The present invention relates to a process for the preparation of alkylencarbonates of formula

R

\

C

/

c

\

R. "

R "

0

0

II

0

in which, R, R ', R "and R'" can be hydrogen, an alkyl, aryl, cycloalkyl, alkylaryl radical consisting of reacting the corresponding alkylene oxides with carbon dioxide in the presence of a catalyst consisting of the combination of a protic substance of formula ROH, with R having the above meanings, with a nitrogen base.

It is known that alkylencarbonates are synthesized using catalysts made up of tetra-alkyl-ammonium halides at temperatures of about 200 ° C and C02 pressures

around 200 atmospheres: the use of these catalysts under the conditions mentioned presents considerable technical difficulties related to the construction of the plants or the onset of corrosion problems due precisely to the chemical nature of the 5 catalysts.

The process according to the present invention as defined in claim 1, allows the preparation of alkylencarbonates starting from alkylene oxides and C02 under mild conditions and in the absolute absence of halides. Examples of protic substances are water, methanol, ethanol, cyclohexanol, phenol, butanol, while the nitrogen base can be chosen from trimethylamine, triethylamine, pyridine, dimethylaniline and others. Interestingly, the nitrogenous base may also consist of a basic azin resin unsolvable in the reaction medium; this is generally the same alkylene oxide in the presence of a protic solvent, diluted or not, with any non-interacting solvent.

The catalyst is used in such quantities that the amount of the defective component varies from 0.1 to 30% 20 by weight with respect to the weight of alkylene oxide, while the relationship between the two components is not decisive, since it is possible to work with a excess of base or protic substance, although the latter is the preferred case.

The reaction is carried out at temperatures ranging from 25 ° C to 200 ° C, preferably in the 80-120 ° C range, and at pressures ranging from 1 to 100 atmospheres, preferably in the range from 1 to 30 atmospheres: the same can be conducted continuously or discontinuously, in a homogeneous or heterogeneous phase.

30 For example, with reference to the discontinuous procedure, the alkylene oxide, the nitrogen base and the protic substance are loaded into an autoclave and then CO2 is sent at the desired pressure. The mixture is heated in a bath to the desired temperature and the pressure is kept constant by feeding COa from a cylinder. When there is no longer any absorption, the autoclave is discharged and the liquid is distilled: the protic substance and the nitrogen base can be recovered and recycled.

On the contrary, if we refer to the continuous process, 40 this consists in allowing a mixture of alkylene oxide and protic substance under pressure of C02 to flow into a vertical reactor, heated to the desired temperature and filled with an unsalted basic resin. . The effluent is condensed and then distilled so that the 45-kylene oxide and the protic substance are released at the head which are recycled at the head of the reactor with C02 and the alkylene carbonate formed at the end.

The operating methods will in any case be illustrated by the following examples which have a general indication value.

50

Example 1

60 g of ethylene oxide, 15 g of CH3OH and 3.6 g of Et3N are introduced into a 300 cc autoclave equipped with a stirrer.

55 In the mixture C02 is sent at room temperature and 10 kg / cm2 of pressure, then it is heated to 50 ° C.

The pressure increases due to heating and is kept constant at its maximum value by continuously integrating the consumed C02. The reaction is followed by gas chromatography.

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

Example 2

65 We operate as in the previous example with the difference that the operating temperature remains at 80 ° C. After 60 minutes of reaction there is a conversion of 70% and a yield in ethylene carbonate of 68%.

3

620434

Example 3

We operate as in example 1 with the difference that the operating temperature is maintained at 110 ° C. After 60 minutes of reaction there is a conversion of 92% and a yield in ethylene carbonate of 90%.

Example 4

One operates as in example 1 with the difference that the C02 is fed at room temperature at a pressure of 30 kg / cm2 and the operating temperature is brought to 80 ° C.

After 60 minutes of reaction there is a conversion of 83% and a yield in ethylene carbonate equal to 81%.

Example 5

One operates as in example 1 with the only difference that triethylamine is not added.

After two hours of reaction, the slightest trace of ethylene carbonate is not noticed.

Example 6

One operates as in example 1 with the only difference that the reaction mixture is free of CH3OH.

After more than two hours of reaction, the smallest trace of ethylene carbonate is not noticed.

Example 7

Triethylamine is carried out as in example 2, which is replaced with an equimolar quantity of pyridine.

After 60 minutes of reaction there is a conversion of 60% and a yield in ethylene carbonate equal to 50%.

Example 8

5 One operates as in example 2 with the difference that the nitrogenous base is constituted by an equimolar quantity of di-methylaniline.

After 60 minutes of reaction there is a conversion of 68% and a yield of ethylene carbonate of 65%.

I

Example 9

In a 300 cc autoclave 79 g of propylene oxide, 15 g of CH3OH, 3.6 g of Et3N are introduced.

Operating at a T = 100 ° C and at P = 10 kg / cm, after 15 120 minutes there is a conversion of 70% and a yield of propylene-carbonate of 68%.

Example 10

A mixture consisting of 10 g of ethylene oxide and 15 20 of CHaOH is sent, via a pressure pump at a flow rate of 20 cc liq / h, to the head of a reactor where it comes into contact with a stream of CO2 which is also fed at the head of the reactor.

The latter, previously loaded with 50 g of re-25 basic sina (Amberlite 94 S) is thermostated at 80 ° C and subjected to a pressure of 30 kg / cm2.

The effluent at the bottom of the reactor is condensed and analyzed by ethylene carbonate.

There is an hourly productivity per kg of catalyst equal to 30 kg of ethylene carbonate.

v

Claims (5)

620434 2 CLAIMS 1. Process for the preparation of formula alkylene carbonates R. IS ni • R " Neither/ II 0 wherein R, R ', R "and R'" can be hydrogen, an alkyl, aryl, cycloalkyl, alkylaryl radical, consisting of reacting the corresponding alkylene oxides with carbon dioxide in the presence of a catalyst consisting of the combination of a protic substance of formula ROH, with R having the above meanings, with a nitrogen base. 2. Process according to claim 1, characterized in that the reaction is carried out in the presence of a quantity of catalyst such that the amount of the defective component varies from 0.1 to 30% by weight with respect to the weight of alkylene oxide. 3. Process according to claims 1 and 2 characterized in that the reaction is carried out at temperatures ranging from 0 to 200 ° C, preferably from 80 to 120 ° C. 4. Process according to claims 1, 2 and 3 characterized in that the reaction is carried out at pressures ranging from 1 to 100 atmospheres, preferably from 1 to 30 atmospheres.