United States Patent (19) 11) Patent Number: 4,518,798 Kramer et al. (45) Date of Patent: May 21, 1985

(54) PREPARING ESTERS AND CARBOXYLIC Primary Examiner-Natalie Trousof FROM LOWER OLEFINS Assistant Examiner-Patricia M. Scott 75) Inventors: George M. Kramer; Walter Attorney, Agent, or Firm-Janet E. Hasak; Edward H. Weissman, both of Berkeley Heights, Mazer N.J.; Herbert C. Brown, West 57 ABSTRACT Lafayette, Ind.; Rowland Pettit, deceased, late of Austin, Tex., by Esters or carboxylic acids are prepared from olefins Flora H. Pettit, executrix containing at least two carbon atoms by reacting the olefin with in the presence of: 73) Assignee: Exxon Research and Engineering Co., (i) a first complex of a selected Lewis with the Florham Park, N.J. ester or , whichever is the reaction 21 Appl. No.: 428,930 product recovered; (ii) a second complex of the Lewis acid with an alco 22 Filed: Sep. 30, 1982 hol, if an ester is being prepared, or with water, if 51) Int. Cl...... C07C 51/14: CO7C 51/145; a carboxylic acid is being prepared; and CO7C 67/347 (iii) a metal carbonyl compound containing a Group 52 U.S. C...... 560/233; 562/521 IB transition metal in the first oxidation state; and 58 Field of Search ...... 560/233; 562/521 by recovering the reaction product(s). 56) References Cited The preferred olefin is propylene, the preferred ester to U.S. PATENT DOCUMENTS be prepared is methylisobutyrate, the preferred metal is Re. 31.010 8/1982 Gelbein ...... 560/233 copper and the preferred Lewis acid is boron trifluo 2.768,968 10/1956 Reppe et al...... 560/233 ride. 3,920,736 11/1975 Gaenzler et al...... 562/521 4.256,913 3/1981 Jung et al...... 560/233 17 Claims, No Drawings 4,518,798 1. 2 mixture of BF3 to generally under a pressure PREPARING ESTERS AND CARBOXYLIC ACIDS of 10-300 atm. Because the product is not easily recov FROM LOWER OLEFINS erable (the BF3 complexes therewith), the patent de scribes an elaborate distillation procedure for separating BACKGROUND OF THE INVENTION 5 the acid from the ester. 1. Field of the Invention It was discovered by Y. Matsushima, et al., Chem. The present invention relates to a process for prepar Letters, 433 (1973) that carbon monoxide is absorbed by ing esters and carboxylic acids from C2 or higher ole cuprous in BF3-water systems under atmospheric fins, preferably propylene, utilizing relatively mild reac pressure. Based on this discovery it was reported by Y. tion conditions and facile recovery procedures, and, in 10 Souma, Osaka Kogyo Gijutsu Shikensho Hokoku, 79, a further aspect, to a continuous process for such prepa 33b, 1-76 (1977) that in the presence of copper I or ration. silver I salt the Koch reaction may be conducted at 2. Description of Related Patents atmospheric pressures to convert linear olefins higher The conversion of propylene to its corresponding than propylene or branched olefins such as isobutylene carboxylic acid or esters is an important process for the 15 to their respective carboxylic acids and esters. The chemical manufacturing industry. For example, it has copper I or silver I salt effectively increases the carbon long been desired to find a convenient method for pre monoxide concentration in the acid solution and leads paring high octane motor fuels and we have discovered to facile trapping of cationic intermediates involved in that esters such as methylisobutyrate, which may be the reaction. prepared from propylene, can be employed as a minor 20 or major component of such motor fuels. In addition, SUMMARY OF THE INVENTION methylisobutyrate may be employed as a solvent or as an intermediate in the synthesis of methylmethacrylate. It has now been discovered that olefins containing at The Koch reaction, normally used to prepare carbox least two carbon atoms may be readily converted to ylic acids, provides a known path for the manufacture 25 their corresponding carboxylic acid or ester(s) under of esters or carboxylic acids when olefins are reacted relatively mild conditions by utilizing as the acid cata with carbon monoxide and an or water in the lyst solvent a mixture of a complex of Lewis acid:ester presence of an acid such as sulfuric or phosphoric acid, or Lewis acid:carboxylic acid and a complex of Lewis or boron trifluoride:water. The reac acid:alcohol or Lewis acid:water. The product is tion sequence can be represented in general as follows: 30 readily separated from the reaction mixture by adding an appropriate solvent thereto to extract the product, thus eliminating the necessity for distillation and facili tating the recovery of the Lewis acid for reuse. R-C=C-R' + H+ is SR-c-c-R'-- Specifically, the present invention provides a process R-C-C-R' -- CO R-C-C-R 35 for preparing esters or carboxylic acids from olefins -- containing at least two carbon atoms which comprises CO the steps of: -- (A) reacting said olefin or a mixture of said olefins -- with carbon monoxide in the presence of: R-c-f-r' + Roh S R-c-f-r 40 (i) a first complex of a Lewis acid with the ester or CO OC-Our-R' carboxylic acid, whichever is obtained as the reac -- tion product from step (B), wherein the Lewis acid H is characterized as being capable of forming a 1:1 molar complex with water which complex has an -- 45 acid strength measured by a Hammett Acidity function value, Ho, of at least - 8.0, and wherein R-c-f-r -H the molar ratio of Lewis acid to ester or carboxylic o-c--R" sR-c-f-a-or acid is from about 1:1 to 2:1; H R (ii) a second complex of said Lewis acid with a pri 50 mary or secondary alcohol, if an ester is being Generally, the Koch reaction is promoted when the prepared, or with water, if a carboxylic acid is acid is used in considerable excess over the amount of being prepared, wherein the molar ratio of Lewis olefin or alcohol (or water) and the temperature is kept acid to alcohol or water is from about 1:1 to 2:1 and relatively low. A major disadvantage of this preparative wherein the molar ratio of said first complex to said route, however, is that the conversion of ethylene and 55 second complex initially is about 1:1 to 20:1; and propylene, which are less reactive olefins than branched (iii) a metal carbonyl compound, wherein the metal is olefins, to their respective ester or acid forms requires a Group IB transition metal in the first oxidation temperatures of 100 to 150° C. and pressures of state and the molar ratio of the metal carbonyl 200-1000 atm, as disclosed in U.S. Pat. No. 2,378,009 compound to the Lewis acid present is from 1:10 to and in J. R. Roland, et al., J.A.C.S., 72, 2122 (1950). 60 1:100,000; and It is known from S. Pawlenko, Chem. Ing-Techn., (B) recovering the reaction product or mixture of 40, 52 (1968) that oxonium tetrafluoroborates of the products. type (ROH2) + (BF4) are catalysts for the batchesteri Due to the presence of an excess of a complex of fication of olefins such as ethylene and propylene, Lewis acid:ester or Lewis acid:carboxylic acid in addi which are ordinarily difficult to carboxylate, at 40-50" 65 tion to the complex of Lewis acid:alcohol or Lewis C. and 100-150 atm total pressure. acid:water, ready separation of the product from the U.S. Pat. No. 4,262,138 discloses the production of Lewis acid is achieved at completion of the reaction. methylisobutyrate from propylene using an equimolar The preferred mode to aid in recovery of the product is 4,518,798 3 4 to add to the reaction mixture a mixture of the alcohol The metal carbonyl compound which must be pres or water and an inert extractant with respect to the ent in the reaction mixture acts as a carbon monoxide reactants, products and catalyst or paraffinic liquid carrier, thereby allowing the process to be carried out extractant. This ready separation results in regeneration under milder conditions. The metal is a Group IB trans of the Lewis acid for use in a continuous as well as a tion metal of the Periodic Table such as copper or silver batch mode of operation. and is present in the carbonyl compound in 1ts first In a preferred aspect of the invention the metal car oxidation state. The carbonyl compound may be pre bonyl compound is a salt containing a copper-I or sil pared in situ by adding to the acidic system provided by ver-I carbonyl complex cation, the olefin is propylene the Lewis acid complex and alcohol a salt of the metal which is reacted with a primary alcohol, and the Lewis 10 in its first oxidation state. The metal in whatever its acid is BF3. form reacts with the carbon monoxide present in the Most preferably, the present invention is directed to a acidic reaction system to form the carbonyl compound. process for preparing methylisobutyrate which com Thus, metal salts which are applicable herein for in Situ prises: preparation of the metal carbonyl include Cu2O, Ag2O, (A) reacting propylene with carbon monoxide at 15 Cu2SO4, Ag2SO4, AgClO4 and the like, with Cu2O and about 50-70° C. and at a partial pressure of carbon Ag2O being preferred. The practitioner will recognize monoxide of about 4 to 6 atmospheres in the presence of that the reactivity of any of these salts with carbon (i) a copper carbonyl compound, wherein copper is in monoxide will depend on the type of acid system, the the first oxidation state, concentration of alcohol, the acid strength of the Lewis (ii) BF3:methylisobutyrate complex in an approxi 20 acid, the temperature of the system (e.g., silver oxide mately 1:1 molar ratio, and may need to be added to cold BF3 complex), the amount of metal added, the amount of complex and the molar (iii) BF3:methanol complex in an approximately 1:1 ratio of Lewis acid to ester in the complex. molar ratio, wherein the molar ratio of the BF3:me The amount of metal carbonyl compound in the reac thylisobutyrate complex to BF3:methanol complex 5 tion mixture will depend on many factors such as e.g., is from about 2.5:1 to 3.5:1 and the molar ratio of the type of metal and the reaction conditions, but gener the copper carbonyl compound to BF3 is from ally the amount will be expressed as the mole ratio of 1:200 to 1:300 and metal carbonyl to Lewis acid present in the reaction (B) recovering the methylisobutyrate as it is formed mixture, which ranges from about 1:10 to 1: 100,000, by displacement with a solution of methanol in an inert 30 preferably 1:100 to 1:1000, and most preferably 1:200 to extractant. :300. It is noted that methylisobutyrate is the preferred The complexes which must be present during the product herein as it has a number of important uses, e.g., reaction herein are a Lewis acid:ester complex and a as a high octane blending component in motor fuels, as Lewis acid:alcohol complex. The Lewis acid is defined a component of fragrances, and as an intermediate in 35 as having a coordination site available for accepting a manufacturing methylmethacrylate. pair of electrons donated by the Lewis base and as hav DESCRIPTION OF THE PREFERRED ing an acid strength sufficient to ensure that an acidic EMBODIMENTS complex with the alcohol will form. For purposes herein, the acid strength of the Lewis acid is defined in The olefin employed in the process of this invention terms of the Hammett Acidity function Ho of a 1:1 contains at least two carbon atoms, preferably C2-C20 molar complex of the Lewis acid with water, as defined olefins, and more preferably C2-C6 olefins. The olefins in M. J. Jorgenson and D. R. Hartter, J. Am. Chem. herein may be terminally or internally unsaturated lin Soc., 85, 878 (1963). This function measures the ability ear or branched olefins or may be mixtures thereof, such of protonic acids (the Lewis acid:water complex) to as the isomers of butylene (n-butylene and isobutylene). 45 protonate neutral molecules. The Lewis acid herein is Preferably the olefins are terminally unsaturated linear defined as being capable of forming a 1:1 molar complex olefins, more preferably ethylene or propylene, and with water which complex has a Hammett Acidity most preferably propylene. function greater than - 8.0, which is equivalent to the In the process herein described the olefin, e.g., propy strength of about 82% H2SO4. Representative Lewis lene, is reacted with carbon monoxide and with water, 50 acids include boron trifluoride, aluminum trichloride, if a carboxylic acid, e.g., isobutyric acid, is to be pre aluminum tribromide, boron trichloride, antimony pen pared, or with a primary or secondary alcohol, if an tafluoride, or mixtures thereof. Preferably BF3 or AiCl3 ester is desired. For purposes herein a primary alcohol is employed, and most preferably BF3. It is noted that is preferred, and more particularly a lower (e.g., the 1:1 molar complex of BF3 to water has a Hammett C1-C10) primary alcohol such as methanol, ethanol, 55 Acidity function of about - ll, as reported by C. H. propanol and butanol. Mixtures of may also be Rochester, Acidity Functions (New York:Academic employed, but a mixture of products will result. The Press, 1970), p. 52. most preferred alcohol herein is methanol, which will The complexed ester applicable herein is the ester produce methylisobutyrate. being produced in the reaction process. This ester For convenience, hereinafter throughout the specifi 60 should be comparably basic to or less basic than the cation, wherever the term "alcohol' is used, the word alcohol from which it is formed so that addition of "water” can be substituted, unless otherwise specified. alcohol to a solution of the complexed ester will dis Similarly, wherever the word "ester' appears, the term place the ester thereby forming a Lewis acid:alcohol "carboxylic acid' (which is the reaction product ob complex. During the reaction small amounts of side tained when water is used as the reagent rather than 65 products, including higher molecular weight esters, alcohol) may be substituted therefor, unless otherwise may be produced but are not detrimental to the opera noted. When propylene is the olefin being carbonylated, tion of the process and are displaced from their Lewis the carboxylic acid is isobutyric acid. acid complexes on addition of alcohol. 4,518,798 5 6 The Lewis acid:ester and Lewis acid:alcohol com While the invention is not limited to any particular plexes are prepared by adding to a mixture of the ester method of addition of ingredients, the sequence set and alcohol a sufficient amount of the Lewis acid to forth below is ordinarily followed for best results. A form from about 1:1 to about 2:1 molar complexes, with mixture of alcohol, ester and metal salt is placed in the the exact molar ratio dependent primarily on the Lewis reactor and a Lewis acid is added in an amount to yield acid and on the type of metal carbonyl compound, alco the molar ratios desired. The mixture is then saturated hol, and Lewis base employed, and on the reaction with carbon monoxide gas at between ambient and temperature. It is noted that with BF3 the ratios of BF3 reaction temperature until the desired pressure is to ester and of BF3 to alcohol will generally be about reached. Additional heat is thereafter applied to pro 1:1, whereas with AlCl3 and SbF5 the ratios of AlCl3 or 10 vide the desired reaction temperature, and olefin is SbF5 to ester and of AlCl3 or SbF5 to alcohol are gener added to the reaction mixture during stirring at a suffi ally between about 1:1 and 2:1. ciently slow rate to favor over polymeri The relative amounts of the ingredients present in the zation. If desired, additional alcohol may be added si reaction mixture are also important to the success of the multaneously with the olefin and, if so, is generally process herein. Such a delicate balance of ingredients is 15 added at the same or a slower rate to avoid an excess necessary both to provide sufficient reactivity in a rea thereof at any time. The reaction may be monitored by sonable period of time and to allow for ready separation withdrawing samples of the mixture during stirring at of the product from the reaction mixture. Thus, initially predetermined time intervals and analyzing the samples (before reaction) the mole ratio of the ester complex to for the amount of product(s) contained therein, as by the alcohol complex should range from about 1:1 to 20 nuclear magnetic resonance, gas chromatography, in 20:1, preferably from 2:1 to 10:1, and most preferably frared spectrometry, mass spectrometry or any other from about 2.5:1 to 3.5:1, to provide the proton activity suitable analytical techniques. necessary to guarantee the presence of sufficient The reaction is generally conducted at temperatures amounts of the metal carbonyl compound throughout of about 0°-90° C., preferably 20-75° C., and most the course of the reaction. Moreover, when uncon 25 preferably 50-70° C. Temperatures above about 90° C. plexed alcohol is added with the olefin, at any one time are undesirable, as the metal carbonyl compound may there should never be an excess of alcohol over the lose its carbonyl groups or undergo redox reactions and amount of complexed ester present in the system, to the olefin may polymerize at excessive temperatures. avoid, in particular, later difficulties in recovery of the The partial pressure of carbon monoxide for the reac product. In addition, the molar ratio of added alcohol to 30 tion is ordinarily maintained at 1-100 atm, preferably olefin should preferably be no greater than about 1:1. 1-10 atm, and most preferably 4 to 6 atm. The rate of addition of alcohol to the reaction mixture The product or products may be recovered by adding should thus be controlled to be about the same or less an appropriate solvent to the reaction mixture and ex than the rate of addition of olefin thereto and controlled tracting. This separation allows for either continuous or such that the molar ratio of ester to alcohol in the reac 35 batch processing. In the latter instance alcohol is al tor is always greater than 1:1. In addition, the olefin lowed to react with the catalytic system. This results in addition rate should be maintained, in units of moles of the release of esters which are displaced into the ex olefin per hour to moles Lewis acid:alcohol complex, at tractant. The product is removed and additional olefin between 1 to 20 and 5 to 1. is added. After reaction of the olefin, additional alcohol With respect to a specific catalyst system, the 40 is introduced and the cycle is repeated. In continuous amounts of reagents are tabulated below: operation the olefin and alcohol are added simulta neously with the extractant. The addition rates are ad justed so that the alcohol is added at or below the rate Catalyst System Mole Ratio Weight Ratio at which the olefin converts complexed alcohol to com Methylisobutyrate Preparation: 45 plexed ester. For many products a suitable extractant Methylisobutyrate:methanol 1 9:1 to 1:1 62.5:1 to 3.3:1 will consist of a non-polar solvent such as n-hexane. BF3:methylisobutyrate 1 In one typical continuous mode of operation for car BF3:methanol 1. : AlCl3:methylisobutyrate 1 : to 2:1 rying out the process herein, a mixture of propylene, ACl3:methanoi 1 : to 2:1 carbon monoxide, alcohol and hexane may be continu BF3:Cusalt 10:1 to 10:1 50 ously fed into a BF3:alcohol and BF3:ester solution. The BF3:Agsalt 10:1 to 10:1 hexane serves as an extractant for the ester being dis Operating Conditions: placed by incoming alcohol. The addition rates are A. Batch within above adjusted so that the alcohol is added at or below the rate B. Flow ranges Propylene:BF3/methylisobutyrate 1:20 to 5:1 at which propylene converts complexed alcohol to (nole per hour:mole) 55 complexed ester. Propylene:added methanol > 1:1 The invention is further illustrated by the following (mole:mole in reactor at all times) examples, which, however, are not to be taken as limit Methylisobutyrate:methanol > 1:1 ing in any respect. All parts and percentages, unless (mole:mole in reactor at all times) expressly stated to be otherwise, are by weight. 60 The reaction may be carried out in any apparatus EXAMPLE 1. which is suitable for conducting such a reaction, al This example illustrates the preparation of the pre though equipment adapted for high pressure reactions ferred product, methylisobutyrate, by the process of need not be employed. One particularly convenient this invention. apparatus for the reaction herein is an autoclave; how 65 A mixture of 0.312 mole of methanol and 0.975 mole ever, the process is not limited thereto. It is noted that of methylisobutyrate ester was blended with 0.01 mole equipment designed for a continuous mode of operation of Cu2O in a 300 ml magnetically driven autoclave. A may be utilized if the complex is regenerated for reuse. sample was withdrawn for analysis and the mixture was 4,518,798 7 8 saturated with BF3 gas at ambient temperature until the magnitude less severe than the pressures used in alterna pressure in the system began to rise. This occurred after tive processes disclosed for linear olefins. mole of BF3 per mole of alcohol and ester had been added. The excess BF3 was vented off, the temperature EXAMPLE 3 raised to 50 C. and carbon monoxide added until a 5 This example illustrates the preparation of isobutyric steady pressure of 4.9 atm (500 kPa) was obtained. The acid by the process of this invention. amount of CO absorbed by the system corresponded A mixture of 0.050 mole of water, 0.450 mole of iso closely to that needed to prepare a Cu(CO)4 complex butyric acid, and 0.01 mole of Cu2O was analyzed by and saturate the vessel at 500 kPa. H-NMR spectroscopy to determine the ratio of protons The reactor was then heated to 633 C. and 0.056 on the methyl groups of the isobutyric acid to the sum mole of propylene was added from a charging bomb. A of the water and acidic protons of the isobutyric acid. rapid increase and decrease in pressure followed the The mixture was then placed in a 300 ml autoclave as addition of propylene. After stirring for an hour a prod used in Example 1 and was saturated with BF3 gas at uct sample was collected from the autoclave. The initial ambient temperatures until the pressure in the system and product mixtures were analyzed by 3C nuclear 5 began to rise, i.e., after 1 mole of BF3 per mole of alco magnetic resonance. The data show that some of the hol and acid had been added. The excess BF was methanol in the feed was converted to methylisobuty vented off, the temperature raised to 60° C. and carbon rate. Within experimental error the conversion corre monoxide added until a steady pressure of 3.9 atm (400 sponds to a quantitative reaction of the added propylene kPa) was obtained. with methanol and carbon monoxide to form me 20 The reactor was then maintained at 60° C. and 0.076 thylisobutyrate. The 13CNMR spectra did not indicate mole of propylene was added from a charging bomb. the presence of products other than methylisobutyrate. After stirring for an hour a product sample was col The sensitivity of the analysis is such that no more than lected from the autoclave and analyzed by H-NMR for one percent of side products is believed to be present. the same proton ratio as was measured for the reactant The amounts of reactants and products, and the 13C 25 mixture. The spectra indicate that all of the water was NMR results, are indicated in Table I. The C-NMR converted to isobutyric acid. The amounts of reactants data were obtained by integration of the peaks pro and products, and the H-NMR results, are shown in duced by the methanol and ester. Table III. TABLE I 30 TABLE III REACTANTS MOLES WT. 2, BY 13C-NMR H-NMR ANALYSIS Methanol 0.312 11.2 11. 1.7 (Ratio of integrations Ester 0.975 88.9 88.4 of peaks of C3H6 0.056 CH3 to H') 1.287 Theory By H-NMR BF 35 Cu2O 0.01 REACTANTS MOLES PRODUCT, WT. 7, THEORY BY 13C-NMR H2O 0.050 Y Methanol 9.2 9.5 1.3 2 4.91 3 Ester 90.8 90.5 Isobutyric Acid 0,450 C3H6 0.076 BFs 0.500 CO s EXAMPLE 2 Cu2O 0.01 MOLE (if reaction This example compares the operating conditions re PRODUCTS is complete) quired to conduct the esterification of propylene using Isobutyric Acid 0.526 the instant system with those conditions required by 45 ) 6.0 two competitive processes for the carbonylation of H2O 0.0 linear olefins. The respective conditions are indicated in Table II. In summary, the present invention is seen to provide TABLE II 50 an improved method for the carbonylation of olefins U.S. Pat. No. Chen. Ing-Techn., Present wherein the presence of a metal carbonyl compound Parameters: 2,378,009 40, 52 (1968) Invention and of a specified Lewis acid complexed with an alco Olefin Ethylene Ethylene/ Propylene hol (or water) and complexed with the carbonylated or Propylene reaction product enables use of relatively mild reaction Catalyst BF3H2O HBF4H2O (ROH) BF3:CH3OH conditions and relatively simple recovery techniques. -- -- 55 While the invention has been described in connection ROH BF3:methyl isobutyrate with specific embodiments thereof, it will be under --- stood that it is capable of further modification, and this Cu(CO)4 application is intended to cover any variations, uses, or Temp. (C.) 100-150 40-50 63 3 adaptations of the invention, following, in general, the Pressure 200-000 100-150 5 60 (atm.) principles of the invention and including such depar Product Ester Acid Ester tures from the present disclosure as come within known or Ester or customary practice in the art to which the invention Operation Batch Batch or pertains and as may be applied to the essential features Fow hereinbefore set forth, and as fall within the scope of the Comparative examples. 65 invention. What is claimed is: The last column shows that the instant process can be 1. A process for preparing esters or carboxylic acids conducted at 5 atm., which is more than an order of from an olefin feed comprising between two and four 4,518,798 9 . 10 carbon atoms and added alcohol, if esters are being 8. The process of claim 1 wherein said reaction is prepared, or water, if carboxylic acids are being pre carried out at a temperature of about 0°-90° C. and at a pared, which process comprises the steps of: partial pressure of carbon monoxide of 1 to 100 atm. (A) reacting said olefin feed with carbon monoxide in 9. The process of claim 1 wherein said reaction is the presence of: carried out at a temperature of 20-75° C. and at a par tial pressure of carbon monoxide of 1 to 10 atm. (i) a first complex of a Lewis acid with the ester or 10. The process of claim 1 wherein said first complex carboxylic acid, whichever is obtained as the contains an ester and said second complex contains a reaction product from step (B), wherein the primary alcohol. Lewis acid is characterized as being capable of O 11. The process of claim 1 wherein the molar ratio of forming a 1:1 molar complex with water which said first complex to said second complex is about 2:1 to complex has an acid strength measured by a 10:1. Hammett Acidity function value, Ho, of at least 12. The process of claim 1 wherein the molar ratio of -8.0, and wherein the molar ratio of Lewis acid added alcohol or water to olefin is at all times no greater to ester or carboxylic acid is from about 1:1 to 15 than 1:1. 2:1; 13. The process of claim 1 or 12 wherein the reacting (ii) a second complex of said Lewis acid with a and recovering steps take place in a continuous mode. primary or secondary alcohol, if an ester is being 14. The process of claim 1 wherein the molar ratio of the metal carbonyl compound to the Lewis acid present prepared, or with water, if a carboxylic acid is O is from 1:00 to 1:1000. being prepared, wherein the molar ratio of 15. A process for preparing methylisobutyrate com Lewis acid to alcohol or water is from about 1:1 prising the steps of: to 2:1, wherein the molar ratio of said first com (A) adding propylene and methanol to a reaction plex to said second complex initially is about 1:1 system; to 20:1 and wherein the molar ratio of said ester 25 (B) reacting the propylene with carbon monoxide at or carboxylic acid to said alcohol or water, re about 50-70 C. at a partial pressure of carbon spectively, is at all times greater than 1:1; and monoxide of about 4 to 6 atmospheres in the pres (iii) a metal carbonyl compound, wherein the metal ence of: is a Group IB transition metal in the first oxida (i) a first complex of BF3 with methylisobutyrate tion state and the molar ratio of the metal car 30 having a molar ratio of BF3 to methylisobutyrate bonyl compound to the Lewis acid present is of about 1:1; from 1:10 to 1:100,000; and (ii) a second complex of BF3 with methanol having (B) recovering the reaction product or mixture of a molar ratio of BF3 to methanol of about 1:1, products by displacement with a solution of a pri wherein the molar ratio of said first complex to 35 said second complex is initially from about 2.5:1 mary or secondary alcohol in an inert extractant if to 3.5:1 and the molar ratio of added methanol to an ester is being produced or with water in an inert propylene is at all times no greater than 1:1 and extractant if a carboxylic acid is being produced. such that the molar ratio of said methylisobuty 2. The process of claim 1 wherein said metal carbonyl rate to said methanol is at all times greater than compound is a salt containing a copper- or silver-I 1:1; and carbonyl complex cation. (iii) a copper carbonyl compound wherein copper 3. The process of claim 2 wherein sid metal carbonyl is in the first oxidation state and the molar ratio compound is prepared in situ from cuprous oxide or of copper carbonyl compound BF3 is from 1:200 silver oxide. to 1:300; and 4. The process of claim 1 wherein said Lewis acid is 45 (C) recovering the methylisobutyrate as it is formed by displacement with a solution of methanol in an BF3 or AlCl3. inert extractant. 5. The process of claim 1 wherein said Lewis acid is 16. The process of claim 15 wherein said copper BF3 and the molar ratios in both the first and second carbonyl compound is prepared in situ from cuprous complexes are 1:1. 50 oxide. 6. The process of claim 1 wherein said olefin feed 17. The process of claim 15 wherein the methylisobu comprises ethylene and/or propylene. tyrate is recovered using n-hexane and the reacting and 7. The process of claim 1 wherein said olefin feed is recovering steps take place in a continuous mode. propylene. sk s : k k 55

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