GB2092126A

GB2092126A - Substituted Alkylene Oxides from Substituted Alkylene Carbonates

Info

Publication number: GB2092126A
Application number: GB8102942A
Authority: GB
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1981-01-30
Filing date: 1981-01-30
Publication date: 1982-08-11

Abstract

Lithium, sodium and potassium fluorides are effective catalysts in a process for the preparation of a substituted ethylene oxide having the formula <IMAGE> wherein R is an alkyl, aryl, alkaryl or aralkyl group, which may be substituted or unsubstituted, by catalytic thermal decomposition of the corresponding substituted ethylene carbonate having the formula

Description

SPECIFICATION Substituted Alkylene Oxides from Substituted Alkylene Carbonates This invention concerns the conversion of substituted ethylene carbonates into substituted ethylene oxide by catalytic pyrolysis.

Substituted ethylene oxide or epoxides are well known in the art as monomers in preparation of resins of various types ranging from epoxy adhesive applications to elastomeric solvent-resistant polymers for use in making tubing, shoe soles and the like. Such epoxides are also useful for the preparation of polyols for use in polyurethane products. These epoxides may be prepared by the direct oxidation of an olefin but such a process has failed due to the formation of large amounts of byproducts and a very small amount of the desired epoxide. Other methods known in the art for producing substituted ethylene epoxides from substituted ethylene carbonates include the use of alkali metal carbonates as catalysts. This is disclosed in Offenlegungsschrift 1,940,205. Also U.S. Patent 2,851,469 (1958) describes the pyrolysis of ethylene carbonate with polyhalogenated hydrocarbon catalysts.

When alkali metal carbonates are used as catalysts as above, high temperatures are required which lowers the selectivities somewhat. U.S. Patent 2,851,469 above uses catalysts which are quite expensive.

A. L. Shapiro, S. Z. Leven and V. P. Chekhovskaya, Zh. Org. Kh., 5207 (1969); J. Org. Chem., USSR, 5, 200 (1969) describes pyrolysis of ethylene carbonate only with alkali metal halides. It has been surprisingly discovered that the conversion of substituted ethylene carbonates with alkali metal fluorides produces substituted ethylene epoxides in very high selectivities at high conversion. It is also surprising to note that the particular alkali metal halides discussed in the Shapiro reference act in a very different manner when substituted ethylene carbonates are used instead of the ethylene carbonates used by Shapiro. In fact, many of the catalysts suitable for ethylene oxide formation in Shapiro are inferior for propylene oxide formation from the respective carbonate and vice versa.

Thus the teachings in Shapiro were of very little use in predicting the activity of substituted ethylene carbonate conversion to substituted ethylene oxide.

The present invention provides a process for the preparation of a substituted ethylene oxide having the formula

wherein R is an alky, aryl, alkaryl or aralkyl group, which may be substituted or unsubstituted which comprises heating the corresponding substituted ethylene carbonate having the formula

wherein R is defined as above, in the presence of lithium fluoride, sodium fluoride or potassium fluoride as catalyst.

Preferably R is an alkyl group having from 1 to 20 carbon atoms and more preferably from 1 to 7 carbon atoms still more preferably wherein R has one carbon atom and the substituted ethylene carbonate is propylene carbonate.

A solvent may or may not be used depending on the catalyst and the carbonate chosen. It has been found useful to dissolve sufficient catalyst for a useful reaction rate, thus, if the carbonate is not a good solvent for the catalyst, a polar aprotic solvent may be used. Useful solvents used in the method of my invention are sulfolane (tetramethylene sulfone). This solvent has been found to be outstanding since it provides good catalyst solubility and has a high boiling point. In any event, the solvent used must be unreactive with both the catalyst and with the substituted ethylene carbonate and also with the reaction product. Examples of some suitable solvents are hydrocarbons, ethers, polyethers, ketones, esters, amides, nitro compounds, sulfoxides, sulfones, tertiary amines, chloro compounds, or any other unreactive compounds.Compounds which are not suitable may be exemplified by alcohols, primary or secondary amines and thiols. Use of a solvent is optional and inclusion is left to the preference of the operator.

The amount of catalyst necessary is dependent upon the particular halide catalyst chosen, and on the rate desired for the reaction to proceed. An excess of catalyst may be used, that is, more than is soluble in the reaction medium. This excess is not necessary, however. The minimum amount of catalyst necessary is a function of the desired rate considered with the temperature to be used for the reaction. The excess of catalyst is often preferred from an operational viewpoint so that the rate which the decomposition occurs may be controlled exclusively by the temperature. Amounts ranging from about 0.01 to 100 weight percent of substituted ethylene carbonate are recommended.

The pyrolysis temperature may range from about 1 600C to about 250 C or more if greater than atmospheric pressure is employed. The pressure may range from 0.05 atmospheres to about 10 atmospheres. These parameters are cited merely as guidelines and are not intended to limit the scope of the invention.

Example 1 Batch Reactions The following experiments in Table I were conducted by charging the substituted ethylene carbonate (200 gm) and catalyst to a glass reactor equipped with a mechanical stirrer, thermometer, 12 inch Vigreux column topped with K-type distillation head and dry ice condenser. The mixture was heated as indicated, the overhead collected and weighed and both overhead and bottoms, if any, analyzed by gas liquid chromatography. Calculations were performed as follows: wt. of Carbonate Charged--wt.

of Bottoms After Reaction (excluding catalyst) Conversion= x100 wt. of Carbonate Charged wt. of OverheadxG.C.% Oxide in Overheadx100 Selectivity*= . Conversion Theoretical Wt. Oxide from Carbonate Charged Percent Oxide**x 100 G.C. Selectivity= Percent Oxide**+Percent By Products** (excluding carbonate and CO2) *Subject to weighing and handling errors, G.C. Selectivity may be e better indication of the actual overhead composition.

**ln over head, as determined by gas-liquid chromatography Table 1 Run Catalyst Time Temp. Conver No. Carbonste (g) Ovhd. (g) (hr) Range C sion % 1 1,2-Propylene Cal2(5.0) 106 1.0 198-220 93.8 71.8 2 1,2-Propylene KF(1.0) 34 3.0 194-198 33.0 96.7 3 1,2-Propylene Mgl2(0.93) 101 1.5 210-211 97.1 68.4 *Oxide Selectivity (%) ** G.C. Selectivity (%) Note that calcium and magnesium iodides provide poor selectivities to propylene oxide. Also, the above shows a very high conversion using potassium fluoride whereas Shapiro et a!. disclosed no epoxide production using fluorides.

Example 2 The examples in Table 2 below point out the great discrepancies found between the prior art and the process of this invention. For example, alkali metal fluorides are reported by Shapiro above to give no ethylene oxide in the pyrolysis of ethylene carbonate. We have found that these fluorides operate as catalysts in the conversion of propylene carbonates to propylene oxide, however. Selectivities to propylene oxide vary depending on the alkali metal as observed in the table below.

Table 2 (Batch Reactions) Overhead Selectivity** Expt Temp. Conver- Propylene Allyl Yield C3 Fluoride No. OC sion % Oxide {%J Alcohol % Products { /O) Lithium 23 232 99.7 98 0* 32.5 Sodium 24 195-230 70.8 58 41 40 Potassium 25 1 94-1 98 37.6 97 2.9 29.9 *2% propionaldehyde constituted the remainder of the overhead **Percent product comprising the overhead, includes all C3 products produced.

These experiments in Table V were performed by heating 200 g propylene carbonate with 5 g catalyst and collecting the overhead with a dry ice condenser and receiver. Yields are calculated basis propylene oxide expected from the starting weight of propylene carbonate.

Claims

1. A process for the preparation of a substituted ethylene oxide having the formula

wherein R is an alkyl, aryl, alkaryi or aralkyl group, which may be substituted or unsubstituted which comprises heating the corresponding substituted ethylene carbonate having the formula

2. A process as claimed in Claim 1 wherein the substituted ethylene carbonate is heated in the presence of the catalyst at a temperature of from 150 to 3000C and a pressure of from 0.05 to 10 atmospheres.

3. A process as claimed in Claim 1 or 2 wherein the catalyst is present in an amount of from 0.01 to 100 weight percent of the substituted ethylene carbonate.

4. A process as claimed in any preceding Claim wherein R is an alkyl group having 1 to 20 carbon atoms.

5. A process as claimed in Claim 4 wherein R is an alkyl group having 1 to 7 carbon atoms.

6. A process as claimed in any preceding Claim wherein the substituted ethylene carbonate is propylene carbonate or butylene carbonate.

7. A process as claimed in any preceding Claim wherein the substituted ethylene carbonate is heated in the presence of a solvent.

8. A process as claimed in Claim 7 wherein the solvent is sulfolane.

9. A process as claimed in Claim 1 and substantially as hereinbefore described with reference to either Example.

10. Substituted ethylene oxides when prepared by a process as claimed in any of the preceding Claims.