FI84814B - Process for producing formate - Google Patents

Description

1 84814

This invention relates to a process for the preparation of alkyl esters of formic acid by carbonylation of alcohols. Alkyl esters of formic acid can be easily hydrolyzed to formic acid itself, a valuable chemical used in the treatment of cereals and as a chemical intermediate.

It has previously been reported in Nippon Kagaku Kaishi 4 (1977), pages 457-465, that methanol can be carbonylated to methyl formate using 1,8-diazabicyclo [5.4.0] undec-7-ene or 1,5-diazabicyclo-15 [4,3,0] non-5-enes, which are cyclic amidines and are abbreviated DBU and DBN in this application, respectively.

It has now been found that a catalyst containing a mixture of amidine and epoxide results in a better conversion of the alcohol than the process of the above-mentioned publication.

Thus, according to the present invention, a process for preparing an alkyl ester of formic acid comprises reacting carbon monoxide with an alcohol in an effective amount of a compound containing an amidine group and a compound containing an epoxide group in the presence of a catalyst.

The term amidine refers to a compound containing the group "N" -C. The three free valences of the nitrogen atoms are preferably attached to carbon or hydrogen atoms and the free valence of the carbon to another carbon atom or nitrogen atom. In the latter case, the structure corresponds to guan-35 Therefore, in this specification, the term amidine is intended to include guanidine.

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The amidine may be a cyclic compound such as e.g.

1,5-diazabicyclo [4.3.0] non-5-ene of formula

c N

C/O

10 or 1,8-diazabicyclo [5.4.0] undec-7-ene of the formula

C/O

or 1,5,7-triazabicyclo [4.4.0] dec-5-ene of formula 20

B

0 25

The epoxide group-containing compound is preferably 1,2-alkylene oxide, such as lower alkylene oxide, e.g. ethylene oxide, 1,2-propylene oxide or 1,2-butylene oxide.

The molar ratio of the amidine group-containing compound to the epoxide group-containing compound is preferably 5: 1 to 1: 5.

The amount of the epoxy-imidine mixture of the catalyst is preferably 0.01 to 50% by weight, more preferably 1 to 20% by weight, of the amount of reactants.

The process is preferably carried out at an elevated pressure, for example at a pressure of 20 to 120 bar, and at an elevated temperature, for example at a temperature of 40 to 150 ° C.

The alcohol is preferably an alcohol having 1 to 10 carbon atoms, but may be an aralkyl alcohol, e.g. benzyl alcohol. Therefore, in this specification, the term alkyl 5 is intended to include aralkyl.

The alcohol is preferably a lower (e.g. 1-6 carbon atoms) aliphatic, primary or secondary alcohol, for example methanol, ethanol, n-propanol, isopropanol, n-butanol or secondary butanol. It is expedient to continuously supply carbon monoxide to the reaction zone to replace the carbon monoxide consumed in the reaction.

The term guanidine group means a group of the formula 15-N-

The free valencies of nitrogen atoms can bind to hydrogen or carbon atoms. The guanidine group may be included in a ring structure such as 1,5,7-triazabicyclo [4.4.0] dec-5-ene of the formula shown above.

In the case of acyclic guanidine, it is preferred that one or more of the nitrogen atoms be accompanied by inert organic substituents, for example lower alkyls having 1 to 6 carbon atoms, such as methyl, ethyl and propyl, which alkyl may be substituted, for example, by trialkoxy. -lyl) or monovalent organic ring structures,. 30 such as piperidinyl.

Acyclic guanidine may contain alkyl or substituted alkyl attached to its nitrogen atoms. Alkyl groups may contain 1 to 10 carbon atoms.

The invention is illustrated by the following examples. In all 35 examples, the reactants and products (except for carbon monoxide 4,84814) were kept in liquid form and the catalyst was used as a solution.

Example 1

Preparation of methyl formate from methanol To a stirred 100 ml high pressure autoclave were charged 23.9 g of methanol, 1.7 g of 1,2-propylene oxide and 3.6 g of 1,5-diazabicyclo [4.3.0] non-5-ene ( The autoclave was sealed, rinsed twice with carbon monoxide and finally heated to 60 ° C with stirring (1200 rpm). Rapid gas absorption occurred and the pressure was maintained between 48-56 bar by refilling from the cylinder. After 3 h, gas absorption had ceased and the autoclave was cooled to 0 ° C. gas chromatographic analysis of the liquid product showed a methanol conversion of 77% with a methyl formate formation selectivity of 98%.

Example 2

Preparation of methyl formate from methanol

Example 1 was repeated with the exception that 4.4 g of 1,8-diazabicyclo [5.4.0] undec-7-ene was used instead of 20 DBN. Analysis of the product mixture showed that the conversion of methanol was 46% with 95% methylformation formation selectivity.

Example 3 Preparation of methyl formate from methanol

Example 1 was repeated with the exception that 4.3 g of 1,5,7-triazabicyclo [4.4.0] dec-5-ene was used instead of DBN. Analysis of the product mixture showed that the conversion of methanol was 58% with a selectivity for methyl formate formation of 93%.

Example 4

Preparation of methyl formate from methanol

Example 1 was repeated with the exception that 3.6 g of N, N, N ', N'-tetramethylguanidine was used instead of DBN and the reaction was carried out at 80 ° C. Analysis of the product mixture 5,84814 showed a 12% methanol conversion with 85% methyl formate formation selectivity. Example 5

Preparation of methyl formate from methanol Example 1 was repeated with the exception that 2.1 g of 1,2-butene oxide was used instead of propylene oxide. Analysis of the product mixture showed that the conversion of methanol was 83% with a selectivity for methyl formate formation of 99%.

10 Example 6

Preparation of ethyl formate from ethanol 26 g of ethanol, 1.8 g of 1,2-propylene oxide and 3.9 g of DBN were charged to the autoclave described in Example 1. After rinsing twice with carbon monoxide, the autoclave was pressurized to 83 bar with carbon monoxide and heated to 80 ° C with stirring (1200 rpm). Rapid gas absorption occurred and the pressure was maintained between 75 and 85 bar by replenishment from the cylinder. After 40 minutes, gas absorption had ceased and the 20 autoclave was cooled to 0 ° C. Analysis of the product mixture showed an ethanol conversion of 67% and an ethyl formate formation selectivity of 98%.

Example 7 Preparation of n-propyl formate from n-propanol Example 3 was repeated with the exception that 26 g of n-propanol was used instead of ethanol. Analysis of the product mixture showed that the conversion of propanol was 81% with a selectivity for the formation of propyl formate of 98%.

30 Comparative test 1

Example 1 was repeated without propylene oxide. Analysis of the product mixture showed only 2% conversion of methanol. This experiment shows that DBN alone is not an effective carbonylation catalyst under the conditions of Example 1.

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Comparative test 2

Example 1 was repeated with the exception that 3.2 g of triethylamine was used instead of DBN. Analysis of the product mixture showed a conversion of methanol of 26% with a selectivity for the formation of methyl formate of 93%.

Compared to Example 1, this experiment shows that the combination of amidine and epoxide results in a much higher conversion of methanol than the combination of triethylamine and epoxide.

Claims (7)

1. A process for the preparation of an alkyl ester of formic acid, the process comprising the reaction of carbon monoxide with a primary or secondary C , and a lower alkylene oxide. 2. A process according to claim 1, characterized in that the ratio between the compound containing the amide group and the compound containing the epoxy group is 5: 1 - 1: 5. Process according to claim 1, characterized in that the amide is a guanidine compound. 15 4. A process according to claim 3, characterized in that the guanidine group is cyclic. 5. A process according to claim 3, characterized in that the guanidine group is acyclic and at least one nitrogen atom is attached to a monovalent inert organic substituent. 6. A process according to claim 3, characterized in that the three nitrogen atoms of the guanidine are added alkyl substituents or substituted alkyl substituents. 25 Process according to any of the preceding claims, characterized in that the pressure is 20 - 120 bar and the temperature is 40 - 150 ° C.