GB2099821A

GB2099821A - Production of carboxylic acids from acyl fluorides formed by carbonylation

Info

Publication number: GB2099821A
Application number: GB8216301A
Authority: GB
Original assignee: Ashland Oil Inc
Current assignee: Ashland LLC
Priority date: 1981-06-05
Filing date: 1982-06-04
Publication date: 1982-12-15
Also published as: IT1210894B; GB2134113A; CA1176657A; GB2099821B; DE3221174C2; NL8202270A; JPS6024086B2; IT8221708A0; DE3221174A1; FR2507179A1; AU8460682A; AT389694B; KR840000462A; FR2507179B1; AU532972B2; GB8403476D0; CH657122A5; NL186959C; KR850001913B1; BE893417A

Abstract

A carboxylic acid, e.g., isobutyric acid, is produced by reacting an acyl fluoride, e.g., isobutyryl fluoride, with less than the total amount of water required to hydrolyze all of the acyl fluoride to the carboxylic acid under conditions whereby the anhydrous acid, e.g., HF, forms. The acyl fluoride has been produced by reacting an organic compound such as propylene with carbon monoxide and an anhydrous fluoride acid. Hydrolysis takes place at 20 to 150 DEG C at a pressure of 1 bar to 340 bars. The ratio of anhydrous hydrogen fluoride to acyl fluoride is within the range 0.01 to 95.5 parts by weight anhydrous hydrogen fluoride to 99.99 to 4.5 parts by weight of the acyl fluoride.

Description

SPECIFICATION Production of carboxylic acids from acylium anions formed by carbonylation This invention relates to the production of carboxylic acids from acyl fluorides formed by ca rbonylation.

More particularly the invention relates to formation of carboxylic acids by hydrolysis of acyl fluorides formed from carbon monoxide, anhydrous acid, and organic compound with one or more double bonds and/or esters.

The prior art such as British Patent 942,367 stresses the requirement of aqueous acid catalyst systems for production of carboxylic acid by carbonylation of compounds having one or more double bonds, or esters followed by further hydrolysis of the reaction products with excess water to produce carboxylic acids. In these processes, the aqueous acid medium is corrosive and expensive equipment is required. The prior art problems may be overcome by the process described herein for forming carboxylic acids.

Carboxylic acids, e.g. isobutyric acid, are formed by hydrolysis with less than the stoichiometric amount of water required to react with all of the acyl fluoride, e.g. isobutyryl fluoride, to form the carboxylic acid and to re-generate the anhydrous acid, e.g., hydrogen fluoride. The acyl fluoride is formed by the reaction of carbon monoxide, anhydrous hydrogen fluoride acid, and an organic compound capable of reacting with carbon monoxide and the anhydrous acid, e.g.

propylene, under conditions whereby an acyl fluoride, e.g. isobutyryl fluoride, forms. In other embodiments of the invention, part or all of the carboxylic acid, e.g., isobutyric acid, is separated from the hydrolyzed mixture and the remainder of the hydrolyzed mixture after part or all of the carboxylic acid is separated therefrom (e.g.

hydrogen fluoride, unreacted isobutyryl fluoride, unseparated isobutyric acid) is recycled to react with the organic compound (e.g. propylene) to form more acyl fluoride (e.g. isobutyryl fluoride).

The process according to the invention for producing a carboxylic acid from an acyl fluoride comprises the step of: hydrolyzing a mixture comprising an acyl fluoride formed by the reaction of carbon monoxide, anhydrous hydrogen fluoride acid and an organic compound described herein with less than the stoichiometric amount of water required for hydrolyzing all of the acyl fluoride in the mixture to the carboxylic acid. This reaction is carried out under conditions whereby the carboxylic acid forms and the acid is regenerated as described herein.

In other embodiments of the invention, the process further comprises the step or steps of: separating from (1) to one hundred (100) percent of the anhydrous hydrogen fluoride acid from the hydrolyzed mixture and recycling from one (1) to one hundred (100) percent of the separated anhydrous acid for reaction with carbon monoxide and the organic compound described herein to form more of the mixtures comprised of the acyl fluoride and the anhydrous acid.

In another embodiment of the invention, the process can comprise the step of: separating from one (1) to one hundred (100) percent of the carboxylic acid from the hydrolyzed mixture, and recycling from one (1) to one hundred (100) percent of the hydrolysis product mixture remaining after separation of the carboxylic acid therefrom, for reaction with carbon monoxide and the organic compound described herein to form more of the mixture comprised of the acyl fluoride product.

The reactants to form the acyl fluoride may be from any source, but must be free from deleterious material which interfere with the process described herein. The total amount of water in the reaction mixture to be hydrolyzed must be less than the stoichiometric amount of water required to react with all of the acyl fluoride formed.

The carbon monoxide may be from any source, but is preferably substantially free from water so as to maintain substantially anhydrous reaction conditions. The carbon monoxide may be diluted with other substances which do not interfere with the reaction. For example, dry synthesis gas or combustion gas may be used. It is preferred that dry carbon monoxide itself be used.

The organic compounds are those which are capable of reacting with carbon monoxide and the anhydrous hydrogen fluoride acid; that is, carbonylated for form an fluoride, for example, organic esters described herein or organic compounds having at least one double bond capable of carbonylating to an acyl fluoride described herein.

The organic esters are represented by the general formula

wherein R is an alkyl group having up to twenty carbon atoms, such as methyl, ethyl, dodecyl, eicosanyl. Preferably the alkyl group is methyl, ethyl, propyl, or isopropyl, with ethyl and isopropyl being the most preferred. R' is an alkyl group having from two to twenty carbon atoms, such as ethyl, propyl, t-butyl, dodecyl, eicosanyl.

Preferably, R' is ethyl or isopropyl, with isopropyl being the most preferred.

When an organic ester is used in the process described herein, any one of the esters mentioned herein may be used. It is preferable, however, to use isopropyl isobutyrate (2-propanol 2-methylpropionate), ethyl isobutyrate (ethanol 2-methylpropionate), isopropyl propionate (2-propanol propionate) or ethyl propionate (ethanol propionate), and it is especially preferred to use isopropyl isobutyrate or ethyl propionate.

Examples of organic compounds having at least one double bond capable of forming an acyl fluoride therewith (carbonylating to an acyl fluoride) which may be used in the process described herein are olefins of up to twenty carbon atoms, such as ethylene, propylene, butenes, 1 3-butadiene, dodecene. The olefins may be substituted with alkyl, aryl or cycloalkyl, or other substituents which do not interfere in the process described herein. Furthermore, the olefins may have multiple double bonds within the molecule which does not interfere in the process described herein such as 1,3-butadiene. Preferred olefins are ethylene, propylene, isobutene, 1butene, 2-butene, and 1 3-butadiene, and ethylene and propylene are highly preferred.

Although all of the organic compounds described herein may be used in the process described herein, propylene is especially preferred.

The hydrogen fluoride acid used for the preferred process to make the acyl fluoride described herein should be.substantially free from water; that is, anhydrous. The term "anhydrous" as used herein and in the claims refers to hydrogen fluoride acid which is substantially free from water, e.g., less than 2000 parts per million or if water is present, it does not interfere with the reaction to form the acyl anion.

The reaction of carbon monoxide, with an organic compound described herein and the anhydrous hydrogen fluoride acid described herein, can occur at temperatures of from zero degree Centrigrade (OOC) to one hundred degrees Centigrade (1 000C), the upper temperature being determined by side product formation.For the reaction between the preferred reactants described herein, the temperature can be from forty degrees Centrigrade (400C) to eighty degrees Centrigrade (800C), but preferably it is at about sixty degrees Centigrade (600 C). The carbon monoxide pressure can vary from one (1) bar (14.7 psia) to about 408 bars (6,000 psia), but generally it is from 34 bars (500 psia) to 340 bars (5,000 psia), and preferably from 102 bars (1,500 psia) to 136 bars (2,000 psia), the pressure being increased as required for the solubility of carbon monoxide in the anhydrous acid and to increase the productivity of the reactor.

The mole ratio of anhydrous acid to the organic compound described herein should be from 1:1 to 100:1, but generally it is from 10:1 to 20:1 and preferably about 1 5:1. The mole ratio of carbon monoxide tithe organic compound described herein is from 1:1 to 5:1 or higher, but preferably it is from 1,5:1 to 1:1 and corresponds to the saturation limit of carbon monoxide in the reaction mixture during and at the end of the reaction.

All of the carbon monoxide and anhydrous acid, e.g., anhydrous hydrogen fluoride which is to be reacted with the organic compound, should be thoroughly mixed prior to contacting with the organic compound described herein, e.g., propylene, then the organic compound is rapidly reacted while mixing with the premixed carbon monoxide and acid. Generally, the reaction, depending upon the pressure and the temperature, will occur within minutes to form an acyl fluoride, e.g. isobutyryl fluoride. The organic compound itself can be diluted with carbon monoxide or inert diluents, e.g., propane, prior to reaction with the anhydrous acid.

The reaction can be conducted in a semi-batch reactor, plug flow reactor, back mix reactor (CSTR), or other reactor known to those skilled in the art, but the preferred reactor is a plug flow reactor.

The hydrolysis reaction of the acyl fluoride e.g., isobutyryl fluoride, with water can occur at temperatures from twenty degrees Centigrade (200C) to one hundred fifty degrees Centigrade (1500C) and at pressures from 1 bar (14.7 psia) to 340 bars (5,000 psia), but normally it occurs at temperatures from forty degrees Centigrade (400C) to seventy degrees Centigrade (700C) and pressures at 6.8 bars (100 psia) to 204 bars (3,000 psia). The temperature and pressure being set to avoid the decomposition of the intended products, and to facilitate product separations.

It is preferred that the reactants be stirred during hydrolysis. In many cases, when rapid mixing is used, the hydrolysis reaction with the concurrent regeneration of the anhydrous acid, e.g., HF, can be completed within seconds to minutes.

The critical feature of the hydrolysis reaction is maintaining the mole ratio of water to the acyl fluoride product below 1 that is, the total amount of water reacted with the mixture comprised of the acylium anion product must be less than the amount of water required for all of the acyl fluoride to form the carboxylic acid.

The total amount of water may be injected into the mixture comprising the acyl fluoride, but preferably the water is added in partial amounts into the mixture comprising the acyl fluoride. The hydrolysis step is exothermic, and thus cooling may be required. The mixture may also contain carbon monoxide, unreacted organic compound, anhydrous hydrogen fluoride acid, and carboxylic acid. Preferably the mixture contains the anhydrous hydrogen fluoride acid, particularly when the acyl fluoride is isobutyryl fluoride.When isobutyryl fluoride is hydrolyzed, the ratio of the amount of anhydrous hydrogen fluoride to isobutyryl fluoride is in the range from 0.01 to 95.5 parts by weight of anhydrous hydrogen fluoride (AHF) to 99.99 to 4.5 parts by weight of isobutyryl fluoride (IBF), but preferably from 10.0 to 90.0 parts by weight of AHF to 90 to 10 parts by weight of IBF. The amount of anhydrous hydrogen fluoride acid in the mixture is dependent upon the efficient operation of the process, and the ease of separating the anhydrous hydrogen fluoride acid from the product mixture comprised of the acyl fluoride, e.g., isobutyryl fluoride, hydrogen fluoride, and carbon monoxide.

After the hydrolysis reaction is complete, which depends upon the reaction conditions as known to those skilled in the art, from one (1) to one hundred (100) percent of the carboxylic acid formed is separated from the product mixture of the hydrolysis reaction. Preferably from eighty (80) to one hundred (100) percent of the carboxylic acid is separated, and the remaining hydrolysis product mixture is recycled for further reaction with the reactants to form more acyl fluoride product. This recycle stream may contain carbon monoxide and/or anhydrous acid and/or unreacted organic compound and/or the unhydrolyzed acyl fluoride.

In another embodiment of the invention, from one (1) to one hundred (100) percent (preferably from eighty (80) to one hundred (100) percent) of the anhydrous hydrogen fluoride acid is separated from the hydrolysis product mixture and is recycled back for reaction to form more acyl fluoride. The recycle stream may contain small amounts of unseparated unhydrolyzed acyl fluoride and/or carboxylic acid and/or unreacted organic compound.

The separation can be by any of the known methods of separation, such as distillation or solvent extraction.

The following examples illustrate the invention described herein.

The following procedure was used to study the hydrolysis of isobutyryl fluoride based on 90 mole percent of the stoichiometric amount of water required to hydrolyze all of the isobutyryl fluoride to isobutyric acid, under semi-adiabatic conditions.

A two liter Hastelloy (Registered Trade Mark) C Parr reactor, equipped with water delivery system (used nitrogen at 500 psia), a themocouple connected to a continuous temperature recorder, and an air motor and stirrer adjusted to rotate at 1 ,000 revolutions per minute, was charged with a weighed amount of anhydrous hydrogen fluoride and isobutyryl fluoride (maintained at dry iceacetone temperature). After charging, the reactants and reactor are brought to the preselected temperature, and the temperature recorder is started. The weighed amount of water (90 wt.% of the stoichiometric amount required for reaction of all of the isobutyryl fluoride) is then injected. The initial temperature of the water was at room temperature. After hydrolysis was complete, the mixture was analyzed by gas chromatography.From the temperature-time recording, the temperature rises were noted.

Generally, the first was attributed to the heat of mixing, and the second was attributed to the hydrolysis reaction.

Example I A mixture of 57.6 grams of anhydrous hydrogen fluoride (10 wt. percent) and 464.9 grams of isobutyryl fluoride (90 wt. percent) at 26.80C was hydrolyzed by injecting 83.0 grams of water (at 21 oC). The reaction mixture temperature rose to 52.40C, then cooled over a 27-second period to 440 C, and then rose exponentially to 123 OC in 49 seconds. Two phases were observed at the beginning but not at the end of the hydrolysis. The reaction was complete, the analysis showed only isobutyric acid formed.

Example II A mixture of 25.5 grams of anhydrous hydrogen fluoride (5 wt. percent) and 488.9 grams of isobutyryl fluoride (95 wt. percent) at 24.1 OC was hydrolyzed with 87.1 grams of water at 21 OC. A temperature rise of 1 3.50C was observed. After twenty minutes when no further temperature rise was noted, the reactor was then externally heated to 51 OC, and a second temperature rise with a temperature change of 780C was observed over a 99-second interval.

The reaction was complete, the analysis showed only the formation of isobutyric acid.

Example Ill A mixture of 51.6 grams (10 wt. percent) anhydrous hydrogen fluoride and 464.5 grams (90 wt. percent) isobutyryl fluoride at 220 Centigrade was hydrolyzed by adding 83.2 grams of the water (at 21 OC) over a 25-second period.

Under these conditions no temperature rise due to mixing was observed. Instead, the temperature rose continuously from 220 Centigrade to 1040 Centigrade, and it was observed that the hydrolysis reaction was limited by the rate of water addition, thus indicating the preferred method of adding water at the rate at which hydrolysis occurs. The reaction was complete, the analysis showed only isobutyric acid formed. The experimental heat of hydrolysis calculated about 9.5 kcal per gram of isobutyric acid formed.

Example IV The following continuous process can be conducted to produce isobutyric acid by the process described herein.

A plug flow reactor is used for the formation of isobutyric acid from propene. It is formed from a forty (40) foot (12.19 metre) tube having a onehalf (21) inch (12.7 mm) internal diameter, with a premix section of about five (5) feet (1.52 m) and equipped with injection points at five-foot (1.52 m) intervals and a heater. The carbonylation reaction is conducted at 500C and 2,800 psig (192 bars) with propene, anhydrous hydrogen fluoride and carbon monoxide in a mole ratio of 1.0:14:1.3, at a flow rate of 3.2 Ibs. per hour (1.52 kilograms per hour).The anhydrous hydrogen fluoride and carbon monoxide is injected into the premix section where they are thoroughly mixed, and the propene is injected into the mixture of anhydrous hydrogen fluoride and carbon monoxide at five-foot (1.52 m) intervals, with the final addition being 30 feet (9.14 m) from the beginning of the reactor. After the reaction is complete, at the 35-foot (10.67 m) injection point, water is injected into the reactor where the hydrolysis occurs preferably at the rate at which hydrolysis occurs and isobutyric acid is formed. The amount of the water injected is less than the amount of isobutyryl fluoride formed.

This section of the reactor where the hydrolysis occurs is maintained at approximately 1000C and at a pressure of 2,800 psig (192 bars). The isobutyric acid and any heavy products, such as heavier oligomeric acids (which are less than 3 wt. percent), are separated from the final product mixture by simple distillation, and the remaining isobutyryl fluoride, carbon monoxide and anhydrous hydrogen fluoride is recycled with the carbon monoxide and anhydrous hydrogen fluoride that are being injected into the premix section of the reactor.

In another embodiment of the continuous reaction, prior to hydrolysis, the product mixture containing the acyl fluoride (isobutyryl fluoride) is passed to a separation unit where the excess carbon monoxide and from ten to ninety percent of the excess anhydrous hydrogen fluoride is removed, and recycled, while the remaining product mixture preferably having 10 parts by weight of anhydrous hydrogen fluoride to 90 parts by weight of isobutyl fluoride is hydrolyzed as described herein followed-by separation of isobutyric acid and recycling of the remaining product mixture of unreacted isobutyryl fluoride and anhydrous hydrogen fluoride.

While the invention has been described with reference to specific details of certain illustrative embodiments, it is not intended that it shall be limited thereby except insofar as such details appear in the accompanying claims.

Claims

1. A process for producing a carboxylic acid from an acyl fluoride product which comprises: hydrolyzing a mixture comprising an acyl fluoride with less than the stoichiometric amount of water required for hydrolyzing all of the acyl fluoride in the mixture to the carboxylic acid under condition whereby the carboxylic acid forms and the acid is regenerated from the anion; the acyl fluoride being formed from the reaction of carbon monoxide, anhydrous hydrogen fluoride acid and an organic compound capable of reacting with the carbon monoxide and anhydrous fluoride acid, under conditions whereby an acyl fluoride forms;; the organic compound being (1) an ester represented by the general formula

wherein R is an alkyl group having up to twenty carbon atoms, and R' is an alkyl group having from two to twenty carbon atoms, or (2) an olefin having up to twenty carbon atoms and having at least one double bond capable of forming an acylium anion product therewith; the temperature of hydrolysis being from twenty degrees Centigrade (200C) to one hundred and fifty degrees Centigrade (1 500 C) and the pressure from one (1) bar (14.7 psia) to three hundred forty (340) bars (5,000 psia);; the ratio of the anhydrous hydrogen fluoride to the acyl fluoride being within the range of from one hundredth (0.01) to ninety-five and five tenths (95.5) parts by weight of anhydrous hydrogen fluoride to ninety-nine and ninety-nine hundredths (99.99) to four and five tenths (4.5) parts by weight of the acyl fluoride.

2. A process as claimed in Claim 1 wherein the organic compound is isopropyl isobutyrate, ethyl isobutyrate, isopropyl propionate, or ethyl propionate.

3. A process as claimed in Claim 1 wherein the organic compound is isopropyl isobutyrate or ethyl propionate.

4. A process as claimed in Claim 1 wherein the organic compound is an olefin having up to twenty carbon atoms and having at least one double bond capable of forming an acyl fluoride therewith.

5. A process as claimed in Claim 1 wherein the organic compound is ethylene, propylene, isobutene, 1 -butene, 2-butene, or 1,3-butadiene.

6. A process as claimed in Claim 1 wherein the organic compound is ethylene.

7. A process as claimed in Claim 1 wherein the olefin is propylene and the acyl fluoride is isobutyryl fluoride.

8. A process as claimed in Claim 7 wherein the amount of water added is from seventy (70) to ninety-nine (99) percent of the amount of the isobutyryl fluoride.

9. A process as claimed in Claim 8 wherein the initial amount of anhydrous hydrogen fluoride in the mixture being hydrolyzed is from ten to ninety parts by weight and the initial amount of isobutyryl fluoride in the mixture being hydrolyzed is from ten to ninety parts by weight.

10. A process as claimed in any of Claims 1 to 9 wherein from eighty (80) to one hundred (100) percent of the carboxylic acid formed is separated from the product mixture and the remaining product mixture comprising anhydrous hydrogen fluoride is recycled for further reaction with carbon monoxide and the organic compound to form more acyl fluoride.

11. A process for the production of a carboxylic acid from an acyl fluoride substantially as described with particular reference to any of the Examples.

1 2. A carboxylic acid when prepared by a process as claimed in any of Claims 1 to 11.