FR2499988A1 - Alkylene oxide prodn. from cyclic carbonate - by pyrolysis over alkali fluoride catalyst - Google Patents

Abstract

Prodn. of alkylene oxides (I) comprises heating cyclic carbonates (II) in presence of Li, Na or K fluoride as catalyst. (R is opt. substd. (ar)alkyl or (alk)aryl; pref. 1-20 (1-7)C alkyl). Reaction is esp. at 150-300 deg. C and 0.05-10 bars, using 0.01-100 wt.% catalyst on wt. of (II). Pref. propylene or butylene carbonates are pyrolysed, opt. in presence of a solvent, esp. sulpholane. (I) are monomers used to make epoxy resin adhesives and to make polyols for polyurethane prodn. The fluoride catalysts give very high selectivity and high yields.

Description

 The present invention relates to the transformation of substituted ethylene carbonates into substituted ethylene oxides by catalytic pyrolysis.

 Substituted ethylene oxides or epoxides are known in the art as monomers used in the preparation of resins of different types having applications ranging from adhesive epoxies to elastomeric solvent-resistant polymers for use in the manufacture of tubular products, soles of shoes and the like. Such epoxides are also used to prepare polyols used in the manufacture of polyurethanes. These epoxides can be prepared by direct oxidation of an olefin, but such a process has failed due to the formation of large amounts of side products and a very small amount of the oxide that is sought. Other processes known in the art for the manufacture of substituted ethylene epoxides from substituted ethylene carbonates alkali metal carbonates are used as catalysts.

This is described in German application D 05 1 940 205.

Likewise in the U.S. patent. 2,651,469 (1950) describes the pyrolysis of ethylene carbonate using polyhalogenated hydrocarbon catalysts.

 If alkali metal carbonates are used as catalysts as indicated above this results in the use of high temperatures which somewhat lower the selectivities. In the U.S. patent 2 85 469 cited above, very expensive catalysts are used.

In the article by AL Shapiro, SZ Lewin and
VP Chekhovskaya, Zh. Org. Kh., 5,207 (1969); J. Org.

Chem., USSR, 5, 200 (1969) describes the pyrolysis of ethylene carbonate only in the presence of alkali metal halides. It has surprisingly been found that the transformation of substituted ethylene carbonates in the presence of alkali metal fluorides gives substituted ethylene epoxides with very high selectivities for a high yield. It has also been surprisingly noted that the alkali metal halides in particular discussed in the Shapiro article act very differently when the substituted ethylene carbonates are used in place of the ethylene carbonates used In fact, many catalysts that can be used in the formation of ethylene oxide by Shapiro are inferior in the formation of propylene oxide from the respective carbonate and vice versa.

 Thus the teachings of Shapiro have found little use in predicting the yield from the transformation of substituted ethylene carbonate into substituted ethylene oxide.

dans laquelle R est un groupe alkyle, aryle, aralkyle ou aralkyle, qui peut être substitué ou non, procédé caractérisé en ce qu'il consiste à chauffer le carbonate d'éthylène substitué correspondant répcndant à la formule

dans l-quellH R a la même définition que elle indiqua ci-deCsus, n présence de fluorure de lithium, de fluorure de sodium ou de fluorure de potassium, comme catalyseurs. The subject of the present invention is a process for the manufacture of a substituted ethylene oxide corresponding to the formula

in which R is an alkyl, aryl, aralkyl or aralkyl group, which may or may not be substituted, a process characterized in that it consists in heating the corresponding substituted ethylene carbonate corresponding to the formula

in l-quellH R has the same definition as indicated above, n presence of lithium fluoride, sodium fluoride or potassium fluoride, as catalysts.

 It is preferred that R is an alkyl group having from 1 to 20 carbon atoms and it is preferable that it has from 1 to 7 carbon atoms or that R is a carbon atom and any substituted ethylene carbon or propylene carbonate.

 A solvent is used or not depending on the nature of the catalyst and of the carbonate chosen. It has proved advantageous to dissolve enough catalyst to have a satisfactory reaction rate, thus if the carbonate is not a good solvent for the catalyst it is possible to use a polar aprotic solvent. Among the interesting solvents used in the process according to the invention, there may be mentioned sulfolana (tetramethylene sulfone). This solvent has proved to be extremely advantageous since it provides good solubility of the catalyst and it has a high boiling point. In any case, the solvent used must react neither with the catalyst nor with the substituted ethylene carbonate and not with the reaction product either. As an example of a suitable solvent, the following products may be mentioned: hydrocarbons, ethers, polyethers, ketones , esters, amides, nitro compounds, sulfoxides, sulfones, tertiary amines chlorinated compounds or any other non-reacting product. As an example of unsuitable products, mention may be made of alcohols, primary or secondary amines and thiols. The use of a solvent is optional and is left to the discretion of the operator.

 The amount of catalyst required depends on the choice of the particular halide and the rate of reaction that is desired. An excess of catalyst can be used, that is to say more than that which is soluble in the reaction medium. However, this excess is not necessary. The amount of catalyst required depends on the speed desired, taking into account the temperature used for the reaction. It is often preferred to use an excess of catalyst to facilitate control of the reaction since the rate at which decomposition occurs can be controlled exclusively by temperature. It is recommended to use amounts of substituted ethylene carbonate ranging from about 0.01 to 100% by weight.

 The pyrolysis temperature can be between approximately 1600C and approximately 2500C or between greater than the latter value if the pressure used is greater than atmospheric pressure. The pressure value can range from 0.05 bar to about 10 bar.

These parameters are only quoted for information without intending to limit the scope and spirit of the invention.

Example 1.

 Batch reactions.

The test results recorded in Table I were obtained by introducing the substituted ethylene carbonate (200 g) and the catalyst into a glass reaction chamber equipped with a mechanical stirrer, a thermometer, a column vigorous 30 cm. topped with a type K distillation head and a dry ice condenser. The mixture was heated as indicated, the text distillate was collected and weighed, and both the top distillate and possibly the tail of the distillate were analyzed by gas-liquid chromatography. The calculations were made as follows:
weight of carbonate introduced
weight of distillate tails
Transformation = after reaction (without catalyst) x 100
weight of -arborlate introduced
head distillate weight x% CG

head distillate oxide x 100
Selectivity * =: Transformatun
theoretical oxide weight from
carbonate introduced
Oxide percentage ** x 100
Selectivity =
GC percentage of oxide ** + percentage
of intermediate products **
(without carbonate and Cn2) * Possible errors in weighing and handling; CG selectivity can give a better indication of the actual composition of the top distillate.

** In the top distillate, as determined by gas-liquid chromatography.

TABLE I
Catalyst Distillate Test Duration Transforn Carbonate range (g) top (g) (h) temperature C%% 50 * SCG ** 1 1,2-propylene Cal2 (5.0) 106 1.0 198-220 93.8 71.4 71.8 2 1,2-propylene Kf (1.0) 34 3.0 194-198 33.0 67.6 96.7 3 1,2-propylene MgI2 (0.93) 101 1.5 210-211 97.1 62.6 68.4 * Selectivity of oxides (%) ** Selectivity of CG (%)
Calcium and magnesium iodides provide low selectivities for propylene oxide.

It can also be noted that a very high transformation is obtained using potassium fluoride while in the article by Shapiro et al. no epoxy production is indicated using fluorides.

Example 2.

 The examples in Table 2 below highlight the great difference discovered between the prior art and the process according to the invention.

However, it has been discovered in accordance with the invention that these fluorides behave as catalysts in the transformation of propylene carbonates into propylene oxide. The selectivities for propylene oxide vary depending on the alkali metal chosen as shown in the table below.

TABLE 2
(batch reactions)
Head distillate selectivity **
Test Temp. Transform- Alcohol Oxide Yield (%)
N (C) mation fluoride (%) propylene (%) allylic (%) produced in C3
Lithium 23,232 99.7 98 0 * 32.5
Sodium 24 195-230 70.8 58 41 40
Potassium 25 194-198 37.6 97 2.9 29.9 * 2% propionaldehyde made up the remainder of the overhead.

** Percentage of product including the top distillate containing all the C3 products obtained.

The test results recorded in Table 2 were obtained by heating 200 g of propylene carbonate and 5 g of catalyst and collecting the overhead by means of a dry ice condenser and a receiver. The yields were calculated on the basis of the propylene oxide which could be expected to be obtained from the starting weight of propylene carbonate.

Claims (8)

 1. Process for the production of substituted alkylene oxides corresponding to the formula

 in which R is an alkyl, aryl, alkaryl or aralkyl group which may or may not be substituted, by heating the corresponding substituted alkylene carbonates corresponding to the formula

 dals which R is defined as indicated above, in the presence of a catalyst, process characterized in that the catalyst is lithium fluoride, sodium fluoride or potassium fluoride.  2. Method according to claim 1, characterized in that the substituted alkylene carbonate is heated in the presence of the catalyst to a temperature between 150 and 3000C and at a pressure between 0.05 and 10 bars.  3. Method according to any one of the preceding claims, characterized in that the catalyst is present in an amount between 0.01 and 100% by weight of the substituted alkylene carbonate.  4. Method according to any one of the preceding claims, characterized in that R is an alkyl group comprising from 1 to 20 carbon atoms.  5. A process according to claim 4, characterized in that R is an alkyl group including 1 i! 7 carbon atoms.  6. Method according to any one of the preceding claims, characterized in that the substituted alkylene carbonate is propylene carbonate or butylene carbonate.  7. Method according to any one of the preceding claims, characterized in that the substituted ethylene carbonate is heated in the presence of a solvent.  8. Method according to claim 7, characterized in that the solvent is sulfolane.