WO1992009554A1 - Azeotropic assisted transvinylation technology - Google Patents

Abstract

A process for the preparation of an alkenyl derivative of a Bronsted acid by the transvinylation reaction of an alkenyl derivative of a first Bronsted acid with a second Bronsted acid includes azeotropic distillation of the transvinylation reaction mixture for the separation and recovery as a product the alkenyl derivative of the second Bronsted acid.

Description

Azeotropic Assisted Transvinylation Technology

SPECIFICATION

TO ALL WHOM IT MAY CONCERN:

Be it Known that we, Mortega Mokhtar-Zadeh, a citizen of Iran, permanently residing in the united States of America, at Charleston, West Virginia, and Rex Eugene Murray, a citizen of the United States of America, residing at Charleston, West Virginia, have invented a certain new and useful AZEOTROPIC ASSISTED TRANSVINYLATION, of which the following is a

specification. Bac kgrou nd of the Invention

1. Field of the Invention

The present invention relates to a process for preparing an alXenyl derivative of a Bronsted acid by the

transvinylation reaction of an alkenyl derivative of a first Bronsted acid with a second Bronsted acid, and, more

particularly to such a transvinylation process assisted by azeotropic distillation for economically and efficiently separating the desired transvinylation alkenyl product

derivative from the transvinylation reaction mixture.

2. Description of the Prior Art

Transvinylation or vinyl interchange technology is well known. The reaction can be illustrated by the reaction of a vinyl-containing compound (R'CH = CH₂) with an active hydrogen-containing compound (RX), as in the following:

RX + R'CH = CH₂ catalyst RCH = CH₂ + R'X wherein R is carboxy, amido, aroxy, alkoxy, and the like; X is hydrogen, hydroxyl, alkyl, aryl, and the like; and R' is carboxyl, amido, alkyl, substituted alkyl, aryl or substituted aryl.

Adelman, Journal Organic Chemistry, 14, pp. 1057-1077, 1949, at p. 1057, termed transvinylation "the 'Vinyl

Interchange' Reaction, to differentiate it from typical este interchange and ester-acid interchange reactions..." Adelman noted several advantages for preparing vinyl monomers by transvinylation, including, for example, the very mild

reaction conditions, the low yields of by-products and the relatively higher yield of monomers of greater purity and activity compared to monomers prepared by the reaction of acetylene with acids.

Adelman also noted that vinyl esters of dibasic acids were prepared much more easily by vinyl interchange than through the acetylene route, and he demonstrated that the reaction of vinyl acetate catalyzed with mercuric salts was not restricted to carboxylic acids, but would occur with other compounds containing active hydrogen, such as acetoacetic ester and glycolic esters.

Other researchers have demonstrated the versatility of the transvinylation reaction and its applicability to a wide range of Bronsted acids and derivatives of Bronsted acids, using a wide variety of different catalysts. For example, McKeon, et al., Tetrahedron. 28, pp. 227-232 (1972) show the vinyl interchange reaction between a vinyl ether and an alcohol using a palladium catalyst. Other sources report the transvinylation reaction between vinyl chloride and a

carboxylie acid.

The literature suggests that the preferred catalysts transvinylation reactions have been mercury and palladium based compounds. However, Pt(II) and Rh(III) have been reported by A. Sabel, J. Smidt, R. Jira and H. Prigge, Chem. Ber.. 102, pp. 2939-2950 (1969), to catalyze the reaction. In addition, Young, U.S. Patent 3,755,387, patented August 26, 1973, entitled: "A Vapor Phase Transvinylation Process", claims the use of supported Hg, Pd, Pt, Ir, Rh, Ru or Os salt catalysts in a vapor phase transvinylation process. The experimental portion discloses the use of only palladium or carbon, copper on carbon, iron on carbon, palladium/copper carbon, palladium/copper/iron on silica, mercuric acetate carbon, and mercuric chloride on carbon. Hg and Pd are cited, at col. 1, line 67, as the preferred metals.

More recently, it has been discovered that ruthenium compositions are useful transvinylation catalysts for numerous Bronsted acids and derivatives of Bronsted acids as disclosed in U.S. application Serial Mo. 213,697, filed June 30, 1988, and assigned to the assignee of the present application. The invention disclosed therein relates to a process for the transvinylation of a vinyl derivative of a first Bronsted acid with a second Bronsted acid which comprises providing a liquid phase mixture containing the vinyl derivative of the first Bronsted acid and the second Bronsted acid in the presence of a ruthenium compound at a temperature at which transvinylation occurs, and recovering as a product of transvinylation the vinyl derivative of the second Bronsted acid. The beneficial use of ruthenium-containing compounds as catalysts for transvinylation processes overcomes several deficiencies noted for other catalysts that had been used in transvinylation processes.

Various methods have been employed to separate the desired vinyl derivative of the second Bronsted acid, (vinyl product derivative) from other components of the

transvinylation reaction mixture, including the starting reactants, the conjugate acid of the vinyl derivative of the first Bronsted acid and other side products produced by the reaction. For example, distillation, fractional distillation, vacuum distillation and rotary evaporation have been used. For example, in U.S. Patent No. 3,188,319, vacuum distillation (Examples 1-3), fractional distillation (Examples 4, 7), and distillation (Example 13), illustrate the use of various distillation techniques for the recovery of the vinyl product derivative. U.K. Patent 1,486,443 describes a process for making high boiling point vinyl esters whose separation is facilitated by fractional distillation as the reaction

progresses. Solvent extraction techniques have also been used for the separation and recovery of the vinyl product

derivative.

The serious process difficulties of separating the vinyl product derivative, particularly for vinyl esters of

carboxylic acids, from the starting reactants and side

products of the reaction has been well known for years. As early as 1967 such problems were discussed in Bearden, U.S. Patent No. 3,337,611 (See Col. 1, 11s. 55-70). In the '611 patent, it was recognized that conventional techniques, such as distillation, for the separation of the vinyl product derivative from the peactants and by-products of the

transvinylation reaction resulted in high losses of the vinyl product derivative due to polymerization, particularly when mercury catalysts were employed, as well as the loss of starting materials. It was also recognized that losses of vinyl product derivative, especially high boiling esters, was intensified in separations involving the distillation of mixtures of close boiling materials. The difficulty of separating close boiling materials was also recognized. The solution to the separation problem taught in U.S. Patent No. 3,337,611 involves the use of a molar excess of the carboxylic acid relative to the molar concentration of the vinyl ester reactant in the transvinylation reaction. Distillation of the vinyl product derivative remained the method of choice for the recovery of total ester. See Col. 2, 11s. 48-51, Col. 4, 11s. 50-59, and Example 1.

Thus, despite the recognition of the advantages of using transvinylation technology for making vinyl derivatives of Bronsted acids, transvinylation technology has not achieved widespread commercial significance because of the inefficient and economically unattractive methods that have been

conventionally employed to separate and recover the vinyl product derivative from the transvinylation reaction mixture. Because fractionation or fractional distillation have

typically been employed to recover the vinyl product

derivative, separation and recovery of the vinyl product derivative has been found to be particularly difficult where the vinyl product derivative has a boiling point very close the boiling point of the conjugate acid, i.e., the acid formed from the vinyl derivative of the Bronsted acid used as the starting material during transvinylation, and/or the other components of the transvinylation reaction mixture. In such instances, separation by fractional distillation can be accomplished only by the use of very large, complex, and expensive distillation columns or not at all. The cost of such columns and the expense of operating them thus makes the use of transvinylation technology commercially unattractive for the production of many monomers.

Thus, there remains a need for a transvinylation process in which the alkenyl product derivative, and in particular the vinyl product derivative can be readily, facilely and economically separated from the other components of the transvinylation reaction mixture, and, in particular, the conjugate acid of the alkenyl derivative of the first Bronsted acid. A need for such a process is especially acute where the conjugate acid and alkenyl product derivative are close boilers, i.e., they have a boiling point close to one another, such as on the order of within 15 degrees of one another, especially within 5 degrees of one another. There is also a need in the art for a transvinylation process which includes a means for separating desirable transvinylation reaction product monomers and mixtures of monomers economically so as to permit the commercial production of many monomers and monomer mixtures that would otherwise not be produced or that could be produced only at significantly greater expense.

There is a more specific need for a transvinylation process that allows for the economical production of alkenyl product derivatives that boil close to the boiling point of the conjugate acid of the alkenyl derivative of the first Bronsted acid.

Summary of the Invention

The present invention provides an improved

transvinylation process for the preparation of an alkenyl derivative of a Bronsted acid. The improved transvinylation process of the present invention includes the use of

azeotropic distillation to assist the transvinylation process, to separate the alkenyl product derivatives from other

components of the transvinylation reaction mixture, including the starting reactants, and especially the conjugate acid of the alkenyl derivative of the Bronsted acid employed as one of the starting reactants, and to facilitate recovery of the alkenyl product derivative. The use of azeotropic

distillation for assisting transvinylation processes has not been recognized until this invention. Moreover, the benefit to be achieved by the use of azeotropic distillation to separate and recover the alkenyl product derivatives has not been appreciated heretofore. It is a primary object of the present invention to provide a transvinylation process for the preparation of an alkenyl product derivative wherein the process is assisted by azeotropic distillation to effect efficient and economical separation of the alkenyl product derivative from the other components of the transvinylation reaction mixture.

It is also an object of the invention to provide a transvinylation process having improved productivity, lower equipment costs and lower operating costs.

It is a further object of the invention to provide a transvinylation process having improved throughput owing to the simplified separation and recovery of the alkenyl product derivative.

It is yet another object of the invention to provide a transvinylation process for the preparation of an alkenyl product derivative in which the alkenyl product derivative and the conjugate acid of the alkenyl derivative of the Bronsted acid used as the reactant have close boiling points. It is a related object of the invention to provide a transvinylation process in which an alkenyl product derivative can be produced in a single stage reactor where the conjugate acid and the alkenyl product derivative are close boilers.

It is a further object of the present invention to provide a continuous process for the production of vinyl esters of carboxylie acids which permits the continuous removal of the vinyl ester of the carboxylic acid in an isolated form.

It is yet another object of the present invention to provide a transvinylation process which is capable of

producing a highly pure alkenyl product derivative, low in residual acidity. It is a more specific object of the invention to provide a transvinylation process which is capable of producing a highly pure vinyl product derivative, low in acidity.

It is also an object of the invention to provide a transvinylation process which is versatile, and is capable of producing a mixture of alkenyl derivatives. These and other objects and advantages of the invention will be apparent from the following description of the invention.

As used herein the term alkenyl product derivative means and refers to an alkenyl-containing compound having the formula R(CH₂)_aCR² = CR⁰R¹ resulting from the transvinylation reaction of an alkenyl derivative of a first Bronsted acid, and a second Bronsted acid, wherein R is carboxy, amido, aroxy, alkoxy, or the like, n is either zero or one, and R⁰, R¹ and R² are each individually one of hydrogen, alkyl of l to about 12 carbon atoms, cycloalkyl, aryl, alkyl ethers, and the like. Transvinylation as used herein includes both vinyl interchange and allyl interchange reactions. The novel process of the present invention applies equally to both types of interchange reactions.

The invention thus provides a process for the preparation of an alkenyl derivative of a Bronsted acid formed by the transvinylation reaction of an alkenyl derivative of a first Bronsted acid with a second Bronsted acid which comprises reacting an alkenyl derivative of the first Bronsted acid with a second Bronsted acid in the presence of a catalyst capable of catalyzing the transvinylation reaction, adding to the transvinylation reaction mixture an azeotropic agent capable of forming an azeotrope with at least the alkenyl product derivative of the second Bronsted acid and recovering by azeotropic distillation as a product of the transvinylation reaction an alkenyl derivative of the second Bronsted acid. The azeotropic agent and the alkenyl product derivative form an azeotrope whose boiling point is sufficiently different from the boiling point of at least the conjugate acid of the alkenyl derivative of the first Bronsted acid to permit the azeotrope and the conjugate acid to be separated by

distillation.

The azeotropic assisted transvinylation process in accordance with the present invention is versatile. The process may be used to prepare a single monomer of relatively high purity or it may be used to produce mixtures of monomers. The product objectives can be achieved by proper selection the azeotropic agent and separation tasks performed on the transvinylation reaction mixture prior to azeotropic

distillation.

Brief Description Of The Drawings

Figure 1 is a schematic illustration of the

transvinylation process of the present invention, including recovery of the alkenyl product derivative by azeotropic distillation, and Bronsted acid recycle.

Detailed Description of the Invention

The present invention provides a process for the facile preparation and separation of numerous alkenyl derivatives Bronsted acids formed by the transvinylation reaction of an alkenyl derivative of a first Bronsted acid R'(CH₂)_aCR² = CR⁰R¹, and a second Bronsted acid (RX), and assisted by the

azeotropic distillation of the transvinylation reaction mixture to separate the alkenyl product derivative of the second Bronsted acid (R(CH₂)_aCR² = CR⁰R¹) from at least the conjugate acid (R'X) of the alkenyl derivative of the first Bronsted acid. The process, which may be continuous, semi-continuous, batch, or semi-batch, may, in the case of an alkenyl derivative, be illustrated generally as follows:

RX + R' (CH₂)_aCR² = CR⁰R¹ catalyst RCR² = CR⁰R¹ + R'X wherein R is carboxy, amido, aroxy, alkoxy, or the like; X is hydrogen, hydroxyl, alkyl, aryl, or the like; n is zero or one; R' is carboxyl, amido, alkyl, substituted alkyl, aryl or substituted aryl; and R⁰, R¹ and R² are each individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl, alleyl ethers, and the like.

The transvinylation reaction is an equilibrium exchange reaction with an equilibrium constant of about 1. Accordingly, when equimolar amounts of the alkenyl derivative of the first Bronsted acid (R' (CH₂)_aCR² = CR⁰R¹) and the second Bronsted acid (RX) are allowed to react to equilibrium, approximately an equimolar mixture of the reactants, that is, the alkenyl derivative of the first Bronsted acid (R(CH₂)_aCR²= CR⁰R¹) and the second Bronsted acid (R'X), and the

transvinylation products, that is, the alkenyl product derivative of the second Bronsted acid (R(CH₂)_aCR² = CR⁰R¹) and the conjugate acid (R'X) of the alkenyl derivative of the first Bronsted acid, are present at the end of the reaction. Since all four components are present in the reaction mixture the mixture is referred to herein as the transvinylation reaction mixture. As is well known, the equilibrium reaction may be shifted to favor production of one of the reaction products by appropriate adjustment of the reactants and/or by removal of one or both the reaction products. Accordingly, the design parameters and product desired will determine whether the equilibrium is to be shifted and the manner in which it is to be shifted. Nevertheless, it is expected that the transvinylation reaction mixture will include both the alkenyl product derivative (R(CH₂)_aCR² = CR⁰R¹) and the conjugat acid (R'X). As is known, there can also be other reaction side products formed depending on the starting reactants that are used.

In accordance with the invention, azeotropic distillation is employed to assist the transvinylation process by providing a relatively simple, facile and economical method for the recovery of the alkenyl product derivative, (R(CH₂)_aCR² = CR⁰R¹) produced by the transvinylation reaction. The primary objective of azeotropic distillation is the recovery of the alkenyl product derivative or mixtures of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid. Stated another way, either the alkenyl product

derivative or a mixture of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid are to be recovered, regardless of the manner in which the transvinylation reaction mixture is treated, if at all, prior to azeotropic distillation. Accordingly, an azeotropic agent is added to the transvinylation reaction mixture to form an azeotrope with the alkenyl product derivative so that upon azeotropic distillation, at least the alkenyl product

derivative can be recovered. To that end, the azeotrope has a boiling point at a temperature sufficiently different from the boiling point of at least the conjugate acid (R'X) to allow the azeotrope to be separated from the transvinylation

reaction mixture by azeotropic distillation.

Where it is desirable to recover a mixture of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid; it may or may not be necessary to also form an azeotrope with the alkenyl derivative of the first Bronsted acid depending on the relative boiling point of that alkenyl derivative, the alkenyl product derivative azeotrope and other components in the transvinylation reaction mixture. If the boiling point of the alkenyl derivative of the first Bronsted acid is sufficiently different from the boiling point of the conjugate acid, or other components of the reaction mixture from which it is to be separated (or both the conjugate acid and other components in the reaction mixture), it may not be necessary to form an azeotrope with the alkenyl derivative of the first Bronsted acid. It may be possible and even

desirable to separate the alkenyl derivative of the first Bronsted acid with the azeotrope. However, if the boiling point of alkenyl derivative of the first Bronsted acid and component of the transvinylation reaction mixture from which it is to be separated are too close, it may be desirable to select an azeotropic agent or a combination of azeotropic agents that form an azeotrope with either or both of the alkenyl derivative of the first Bronsted acid or the alkenyl product derivative to allow the derivative mixture to be separated and recovered.

The azeotropic agent selected must be compatible with the alkenyl product derivative. In addition, the azeotropic agent forms with the alkenyl product derivative an azeotrope which has a boiling point sufficiently different from the other components of the transvinylation reaction mixture to permit the separation of the azeotrope from those components by azeotropic distillation in a suitable column. To that end, is preferred that the difference in the boiling point of the azeotrope and the boiling point of the other components of the transvinylation reaction mixture from which the azeotrope is to be separated be on the order of several degrees centigrade, most preferably about 10 degrees centigrade or more.

Separation by azeotropic distillation is generally less difficult and less expensive the greater the boiling point differential.

It will be appreciated that the azeotropic agent and alkenyl product derivative may form either a minimum boiling point azeotrope or a maximum boiling point azeotrope. The azeotropic agent may form either a heterogeneous or a

homogeneous azeotrope with the alkenyl product derivative. Where the azeotroping agent and the alkenyl product derivative form a heterogeneous azeotrope, the solubility of the

azeotropic agent and alkenyl product derivative in one another is minimal. Upon condensation of the azeotrope after distillation, the azeotropic agent and alkenyl product derivative will separate into two phases, so separation of the azeotropic agent from the alkenyl product derivative is facilitated. It is thus preferred that the azeotropic agent forms a heterogeneous azeotrope with the alkenyl product derivative. Use of an azeotropic agent that forms a

heterogeneous azeotrope simplifies the separation, recovery and purification of the alkenyl product derivative.

The azeotropic distillation assisted transvinylation process in accordance with the present invention is very versatile in that it allows for the preparation, separation and recovery of the alkenyl product derivative and of mixtures of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid. The specific product or product mixture to be produced will determine the manner in which the transvinylation reaction products are to be treated prior to azeotropic distillation. For example, the transvinylation reaction products may be treated to remove all or only a portion of the alkenyl derivative of the first Bronsted acid prior to azeotropic distillation. Where all of the alkenyl derivative of the first Bronsted acid is removed prior to azeotropic distillation, the alkenyl product derivative is separated from the transvinylation reaction mixture by azeotropic distillation and is subsequently recovered by separating the alkenyl product derivative from the azeotropic agent. Where only a portion of the alkenyl derivative of the first Bronsted acid is removed prior to azeotropic

distillation, a mixture of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid may be separated and recovered.

It will be appreciated that while the azeotropic agent is capable of forming an azeotrope with the alkenyl product derivative, an azeotropic agent that forms an azeotrope with both the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid may also be satisfactorily

employed. Selection of an azeotropic agent capable of forming an azeotrope with both the alkenyl product derivative and with the alkenyl derivative of the first Bronsted acid allows a mixture of those two derivatives to be separated and recovered from the transvinylation reaction mixture. Of course, it is also possible to separate and recover a mixture of the alkeny derivative of the first Bronsted acid and the alkenyl product derivative without first forming an azeotrope of the alkenyl derivative of the first Bronsted acid so long as the boiling point of the alkenyl derivative of the first Bronsted acid and the boiling point of the alkenyl product derivative are either both higher or both lower than the boiling point of the conjugate acid.

The transvinylation reaction is preferably carried out in the presence of a atalyst. Any of the well known

transvinylation catalyst may be employed, including, for example, mercury and palladium based catalysts. Especially preferred transvinylation catalysts are the ruthenium-based catalysts disclosed and claimed in U.S. application Serial No. 213,697, filed June 30, 1988, entitled Transvinylation Reaction, assigned to the same assignee of the present application.

Turning to Figure 1, there is illustrated a schematic representation of the preferred embodiment of the present invention. In the illustrated process 10, the reactants, namely the alkenyl derivative of the first Bronsted acid, and the second Bronsted acid are fed to reactor 16 through feed lines 12 and 14, respectively. Typically a polymerization inhibitor is included to prevent undesirable polymerization the vinyl monomer. Reactor 16 includes a catalyst for the transvinylation reaction. Reactor 16 is maintained at a temperature and pressure sufficient to effect the

transvinylation reaction. After the reactants are allowed to react, the transvinylation reaction mixture, which contains concentrations of the alkenyl derivative of the first Bronsted acid, the second Bronsted acid, the alkenyl product derivative and conjugate acid of the alkenyl derivative of the first Bronsted acid, and possibly catalyst is transferred from reactor 16 to a separation zone 18 through transfer line 17

In separation zone 18, various separation tasks may be performed on the transvinylation reaction mixture prior to azeotropic distillation. By way of example, separation zone IS may be used to separate a mixture of the alkenyl product derivative and the conjugate acid from the catalyst and any unreacted second Bronsted acid. The product objective of the reaction will determine whether the unreacted alkenyl

derivative of the first Bronsted acid is separated in whole in part from the alkenyl product derivative and conjugate a in separation zone 18. To produce pure alkenyl product derivative, separation zone 18 is designed to separate the unrelated alkenyl derivative ofthe first Bronsted acid and, optionally, to recycle that alkenyl derivative back to the reactor by transfer line 20. To produce a mixture of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid, separation zone 18 is designed to separate only a portion of the alkenyl derivative (or none at all) from the alkenyl product derivative. In the illustrated embodiment, all, or at least a portion of the alkenyl

derivative of the first Bronsted acid is removed from the transvinylation reaction mixture in separation zone 18 and is recycled back to the reactor via transfer line 20. The second Bronsted acid together with catalyst is recovered from

separation zone 18 and is recycled to reactor 16 via transfer line 22.

It will be appreciated that separation zone 18 may be included after azeotropic distillation, for example, where the separation zone is used primarily for the separation and recovery of catalyst after the alkenyl product derivative has been separated from the transvinylation reaction mixture.

The alkenyl product derivative, conjugate acid and, optionally, unreacted alkenyl derivative of the first Bronsted acid are transferred from separation zone 18 to distillation column 24 via transfer line 23 for azeotropic distillation. The azeotropic agent is capable of forming an azeotrope with at least the alkenyl product derivative in order to enable the alkenyl product derivative to be separated from the conjugate acid. The azeotrope preferably has a boiling point at least 10ºC different than the boiling point of the conjugate acid, although the azeotropic distillation assisted transvinylation process in accordance with the invention is useful where the difference in boiling point between the azeotrope and the conjugate acid (as well as other components of the

transvinylation mixture from which the alkenyl product derivative is to be separated) is significantly less. For example, the present invention is useful even when the boiling point differential between the azeotrope and the conjugate acid (or the component) is on the order of two or three degrees centigrade, especially where the monomer to be recovered is commercially important.

It may or may not be necessary to use an azeotropic agent to form an azeotrope with the alkenyl derivative of the first Bronsted acid in order to separate the alkenyl derivative of the first Bronsted acid from the conjugate acid depending on the relative boiling point of the alkenyl derivative of the first Bronsted acid, the alkenyl product derivative and the conjugate acid. In the event the boiling point of the alkenyl derivative of the first Bronsted acid and the boiling point of the conjugate acid are relatively close, i.e., on the order of less than 15 degrees, then it may well be desirable to form an azeotrope with the alkenyl derivative of the first Bronsted acid to effect efficient separation of the alkenyl derivative of the first Bronsted acid from the conjugate acid. However, if the boiling point of the alkenyl derivative of the first Bronsted acid and the conjugate acid are not close, and the boiling points of the alkenyl derivative of the first Bronsted acid and azeotrope of the azeotropic agent and the alkenyl product derivative are both either lower or higher than the boiling point of the conjugate acid, then the alkenyl

derivative of the first Bronsted acid may be separated

together with the alkenyl product derivative from the

conjugate acid without the use of an azeotropic agent for the alkenyl derivative of the first Bronsted acid.

It will be appreciated that it may be desirable to form an azeotrope of the alkenyl derivative of the first Bronsted acid even though the boiling point of the alkenyl derivative of the first Bronsted acid is sufficiently different from the boiling point of the conjugate acid in order to assure that both the alkenyl derivative of the first Bronsted acid and the azeotrope of the alkenyl product derivative boil either high or lower than the conjugate acid, and to thereby further assist in the separation of those components from the

conjugate acid. One azeotropic agent capable of forming an azeotrope with both the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid may be used.

is also contemplated that a mixture of azeotropic agents may be used, one for the alkenyl product derivative and one for the alkenyl derivative of the first Bronsted acid.

In the illustrated embodiment, the azeotropic agent is shown to be fed near the top of column 24 through feed line 25. Additionally, azeotropic agent recovered from the

decanter 30 (as described below) can, and preferably is, recycled to the azeotropic distillation column 24.

Independently of the source of the azeotropic agent, it is preferred to feed the azeotroping agent near the top of the azeotropic distillation column to assist in the separation of undesirable components during distillation. Because the temperature of the liquid near the top of the column is lower than it is at other locations, adding the azeotroping agent near the top allows the agent to cool and thereby knock down non-azeotroping components that may be near the top of the column. Also, where the azeotroping agent is water, there is less time and opportunity for the water to contact and

possibly hydrolyze the alkenyl product derivative of the azeotrope. However, it will be appreciated by those skilled in the art that the azeotropic agent can be fed to

distillation column 24 at other points in the column,

including, for example, in the middle, or near the bottom.

The azeotropic agent may also be added to the feed to

distillation column 24.

In the illustrated embodiment, the azeotropic agent and alkenyl product derivative form a heterogeneous minimum boiling point azeotrope. As a result, the azeotrope is drawn off the top of column 24 through transfer line 28 and

transferred to decanter 30 where the azeotrope separates into two phases, the alkenyl product derivative and the azeotropic agent. Note that if a mixture of alkenyl product derivative and alkenyl derivative of the first Bronsted acid is separated from the conjugate acid, then one phase will consist of a mixture of the alkenyl product derivative and the alkenyl derivative of the first Bronsted acid and the other phase will consist of the azeotropic agent. The azeotropic agent is recycled for use in azeotropic distillation column 24 (as illustrated by transfer line 32). Some of the azeotropic agent may be removed as waste through transfer line 34. The alkenyl product derivative phase may, if desired, also be refluxed (as, for example, by return to distillation column 24 through transfer line 33) to enhance rectification.

The alkenyl product derivative is transferred to drying column 36 via transfer line 38. In drying column 36, the alkenyl product derivative is dried by azeotropic drying, the azeotrope being taken off the column and transferred to either the first decanter 30 and processed as described above, or transferred to a second decanter 40, in which phase separation of the alkenyl product derivative and azeotropic agent occurs. Alkenyl product derivative from the second decanter 40 is returned to drying column 36 via transfer line 42, while the azeotropic agent is processed as waste. Azeotropic agent from decanter 40 may also be recycled for use in distillation column 24. Dried alkenyl product derivative is transferred purification column 44 where alkenyl product derivative is recovered. If desired, the alkenyl product derivative may be neutralized with a suitable base, such as, sodium bicarbonate, to remove residual acid.

Returning to the azeotropic distillation column 24, the conjugate acid of the vinyl ester of the first Bronsted acid which is produced during the transvinylation reaction remain at the column bottom. The conjugate acid is transferred from azeotropic distillation column 24 via transfer line 25 to an acid separation column 46 where the conjugate acid is

separated and recovered. The conjugate acid is recovered for subsequent use. It will be appreciated that in the event that the second Bronsted acid is not completely separated from the conjugate acid and the alkenyl product derivative in

separation zone 18, the second Bronsted acid is separated from the azeotrope in azeotropic distillation column 24 and is passed to acid separation column 46 with the conjugate acid. In acid separation column 46, the second Bronsted acid is separated from the conjugate acid and recycled via transfer line 48 to reactor 16.

The azeotropic distillation column operating temperature and pressure are not particularly critical to the practice of the invention, but they are related, and they are highly dependent on the particular separation to be carried out. Azeotropic distillation may be carried out at atmospheric pressure or it may be carried out under vacuum or under pressure. The lower limit on the operating pressure is related to the economical limitations on condenser

temperature. The upper pressure limit is dependent on the limitation of the column bottom temperature which, in turn, is dependent on the decomposition temperature of the components. Operating temperature, in turn, depends on the condensation temperature of the column condenser and on the decomposition temperature of the components. The low end of the operating temperature is preferably only about 10°C or so higher than the temperature of the cooling media. The upper end of the operating temperature, on the other hand, is preferably about 10°C lower than the decomposition temperature of the most decomposable component in the system. The operating

temperature and pressure are preferably chosen so that the condenser can be cooled easily and so that none of the components decompose. Where water is the azeotropic agent and the alkenyl product derivative may be susceptible to

hydrolysis (or where the conjugate acid is an unsaturated acid) it is preferred that azeotropic distillation be carried out under a vacuum so that the distillation column can be operated at lower temperature.

The type of azeotropic distillation column used to carry out the azeotropic distillation is not critical. The column may be a tray or a packed column. A packed column is

preferred due to a lower pressure drop across the column.

The rate at which the azeotroping agent is fed to the azeotropic distillation column depends on both the rate at which the alkenyl product derivative is produced and the concentration of the alkenyl product derivative in the azeotrope. For a given alkenyl product derivative and azeotropic agent, the feed rate of the azeotropic agent is preferably sufficient to permit all of the alkenyl product derivative fed to the column to form an azeotrope. While some excess of the azeotroping agent may be employed, it is preferred to match the feed rate of the azeotroping agent with the production rate of the alkenyl product derivative. After the initial charge, preferably the azeotropic agent fed to the distillation column is recovered from the two phase separation of the alkenyl product derivative and azeotropic agent in the decanter. Azeotropic agent from the decanter is simply recycled to the azeotropic distillation column to fill the needs of the distillation column, supplemented, if necessary, only to the extent that the azeotropic agent is removed from the system.

The azeotropic distillation assisted transvinylation process of the present invention can be used for the

preparation of numerous alkenyl product derivatives that do not contain a vinyl moiety with the appropriate selection of the azeotroping agent. By way of illustration, suitable alkenyl derivatives are compounds of the formula

-(CH₂)_a-CR² = CR⁰R¹ wherein n is either zero or one, R⁰, R¹ and R² are each

individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl, alkyl ethers, and the like.

Illustrative of suitable alkenyl product derivatives 1-propenyl benzoate (cis and trans), 1-propenyl pivalate (cis and trans), 2-propenyl benzoate and 2-propenyl pivalate, allyl pivalate, allyl benzoate, allyl propionate, methallyl

benzoate, methallyl pivalate, methylallyl propionate, allyl crotonate, allylmethacrylate, allylacrylate, and the like.

Azeotropic distillation assisted transvinylation can also be used for the preparation of numerous vinyl product

derivatives with the appropriate selection of the azeotroping agent. By way of illustration, the alkenyl product derivative may be any compound in which there is a vinyl group bonded to a Bronsted acid. Such compounds may be characterized as vinylated Bronsted acids, vinyl embraces groups of the formula

R⁰R¹C = CR²- wherein R⁰, R¹ and R² are each individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl, alkyl ethers, and the like. The Bronsted acid is any species which can act as a source of protons.

Illustrative of suitable alkenyl derivatives of a

Bronsted acid for the practice of the invention, are vinyl acetate, vinyl pivalate, vinyl benzoate, vinyl methacrylate, vinyl acrylate, vinyl propionate, vinyl cinnamate, vinyl cyclohexanoate, vinyl crotonate, vinyl butyrate, vinyl 2-methyl butyrate, vinyl isobutyrata, vinyl 2-methyl valerata, vinyl 2-ethylhexanoate, vinyl octanoata, vinyl decanoate, vinyl cyclohex-3-enoate, vinyl neodecanoate, vinyl

neononanoate, vinyl 2-propyl heptanoate, and other vinyl esters or neo-esters, N-vinyl pyrrolidinone, N-vinylsuccinimide, vinyl phenyl ether, vinyl methyl ether, vinyl ethyl ether, 2-chloroethyl vinyl ether, ethyl vinyl ether, 2-vinyloxyethanol, allyl vinyl ether, isopropyl vinyl ether, propyl vinyl ether, 1-vinyloxy-2-propanol, 3-vinylox 1-propanol, butyl vinyl ether, isobutyl vinyl ether, bis(2-vinyloxyethyl)ether, 2-butylthioethyl vinyl ether, 2-butoxyethyl vinyl ether, 2-ethoxyethyl-2-vinyl-oxyethyl ether, 2-ethylhexyl vinyl ether, 2-butoxyethyl 2-vinyl-oxyethyl ether, trimethylnonyl vinyl ether, N-vinyl 2-oxazolidinone, 2-vinyloxyethyl acetate, 2-vinyloxyethyl pivalate, 2-vinyloxyethylacrylate, vinyl chloride, vinyl sulfonamides, the like.

Preferred alkenyl derivatives are the vinyl esters of carboxylie acids and the vinyl alkyl or aryl ethers, mainly because they are commercially available.

Illustrative of suitable Bronsted acids for the practice of the invention are carboxylic acids such as monocarboxylic and polycarboxylie acids illustrated by acetic acid, propionic acid, butyric acid, isobutyric acid, 2-methyl butyric acid, crotonic acid, pivalic acid and other neo-acids, stearic acid, benzoic acid, terephthalic acid, isophthalic acid, phthalic acid, adipic acid, succinic acid, malic acid, maleic acid, polyacrylic acids, acrylic acid, methacrylic acid, cinnamic acid, 2-ethylhexanoic acid, cyclohexanoic acid, and

cyclohexenoic acid; amides such as 2-pyrrolidinone, 2- pyrrolidone, e-caprolactam, 2-oxazolidinone, and succinimide; alcohols such as methanol, ethanol, n-propanol, isobutanol, fluorinated alkanαls such as 1, 1, 1, 3 , 3 , 3-hexafluoro-2-propanol, monoethanolamine, diethanolamine, and

triethanolamine; phenolic compounds such as phenol,

resorcinol, and Bisphencl A [2 , 2-bis(4-hydroxyphenyl)propane] ; amino compounds which are sufficiently acidic such as

secondary aromatic amines , azoles, and the like; hydroxy esters such as hydroxalkyl acrylates (e.g. , 2-hydroxyethyl aery late, 2 -hydroxy ethyl methacrylate) and hydroxyalkyl alkanoates (e.g. , 2-hydtoxγethyl acetate, 2-hydroxyethyl pivalate) ; silanols such as dimethyl silan diol,

trimethylsilane mono-ol, and the like.

The preferred Bronsted acids are the carboxy lie acids , the alcohols , the amides, the imides, the phenolics, and the like.

Illustrative of transvinylation reactions that may be carried out by the process of the invention, are the

following:

Alkenyl derivative Bronsted Acid Product vinyl acetate + pivalic acid - vinyl pivalate vinyl benzoate + pivalic acid - vinyl pivalate vinyl acetate + methacrylic acid - vinyl methacrylate vinyl acetate + acrylic acid - vinyl acrylate vinyl acetate + benzoic acid - vinyl benzoate vinyl acetate + propionic acid - vinyl propionate vinyl acetate + salicyclic acid - vinyl salicylate vinyl acetate + cinnamic acid - vinyl cinnamate vinyl propionate - 2-ethylhexanoic acid - vinyl

2-ethyihexanoate vinyl acetate - cyclohexanoic acid - vinyl cyclohexano vinyl acetate + 2-ρyrrolidinone - N-vinyl

2-pyrrolidinone vinyl pivalate + 2-pyrrolidinone - N-vinyl

2-pyrrolidinone vinyl pivalate + succinimide - N-vinyl succinimide vinyl methyl ether - phenol - vinyl phenyl ether vinyl chloride - aethanol - vinyl methyl ether vinyl methyl ether + ethanol - vinyl ethyl ether vinyl acetate - 2-oxazolidinone - N-vinyl

2-oxazolidinone vinyl acetate + N-acetyl - N-vinyl

ethyleneurea N-acetylethyleneurea vinyl acetate + 2-hydroxyethyl - 2-vinyloxyethyl

acetate acetate

vinyl pivalate + 2-hydroxyethyl - 2-vinyloxyethyl

pivalate pivalate

vinyl pivalate + 2-hydroxyethyl - 2-vinylhydroxyethyl acrylate acrylate

As previously set forth, the azeotropic agent may be any agent that is capable of forming an azeotrope with the alkenyl product derivative of the transvinylation reaction. For example, the azeotropic agent may form a binary azeotrope with the alkenyl product derivative or, in the event it is

desirable to separate a mixture of esters, it may form an azeotrope with the alkenyl product derivative and with the alkenyl derivative of the first Bronsted acid. The boiling point differential between the azeotrope and the conjugate acid (and the alkenyl derivative of the first Bronsted acid if it is not separated from the reaction mixture prior to azeotropic distillation, and if an azeotrope is needed for it separation) is sufficient to allow the desired product to be separated, and is preferably at least about 10°C. By way of example and ndt in limitation, suitable azeotropic agents include water, either in the form of a liquid or as steam, cyclohexane, heptane, isopropanol, methanol and alkyl ether. Where the transvinylation reaction produces a vinyl ester of a carboxylic acid by the reaction of an alkenyl derivative of a first carboxylic acid and a second carboxylic acid, water is especially preferred because it forms a heterogeneous

azeotrope with both the alkenyl product derivative and with the alkenyl derivative of the first Bronsted acid. Upon condensation of the azeotrope, the water and alkenyl product derivative (and alkenyl derivative of the first Bronsted acid, if present) separate into two phases which can be separated in a decanter.

Water is the preferred azeotropic agent in

transvinylation reactions involving an organic acid having from 1 to 12 carbon atoms, and an alkenyl. derivative of a first carboxylic acid of the formula:

where R" is alkyl, aryl, cycloalkyl and has from 1 to about 12 carbon atoms. Water forms a minimum boiling point azeotrope with the alkenyl product derivative and with the alkenyl derivative of the first carboxylic acid, if present. The minimum boiling point azeotrope has a boiling point greater than 10ºC different than the boiling point of the conjugate acid, the boiling point of the azeotrope being lower than the boiling point of the conjugate acid.

In accordance with a preferred embodiment of the present invention, an alkenyl derivative of a carboxylic acid having from 1 to 12 carbon atoms is prepared by the transvinylation reaction of vinyl acetate and a second carboxylic acid having of from 1 to about 7 carbon atoms in the presence of a

ruthenium catalyst as described in copending application

Serial No. 213,697. The alkenyl product derivative is

effectively and efficiently separated from the transvinylation reaction mixture by azeotropic distillation with water as the azeotroping agent. Thus, in the transvinylation reaction described, acetic acid, which has a boiling point of about 116-118ºC is one of the products of the reaction. Water is used to produce a minimum boiling point heterogeneous

azeotrope with the alkenyl product derivative. The azeotrope has a boiling point lower than the boiling point of acetic acid. Removal of the alkenyl product derivative from the other components is facilitated.

The present invention is particularly useful for the preparation of vinyl pivalate, vinyl butyrate, vinyl

propionate and vinyl crotonate by the transvinylation reaction of vinyl acetate with pivalic acid, butyric acid, propionic acid, and crotonic acid, respectively. The products of the transvinylation reaction, i.e., the alkenyl product derivative and acetic acid have boiling points that are close, and would be very difficult to separate by fractional distillation, as can be seen in Table I below: Table I

B . P . ºC Aque ous Azeotrope

Vinyl Ester of Dry Ester B . P . ºC wt%

vinyl

-propionate 94 . 9 79 13

-butyrate 116. 7 87 .2 20 . 4

-crotonate 133. 9 92 31

-pivalate 112 86 17

The addition of a sufficient amount of water to the alkenyl product derivative in the azeotropic distillation apparatus forms an aqueous azeotrope with the vinyl pivalate, vinyl butyrate, vinyl propionate and vinyl crotonate. It has been discovered that vinyl pivalate and water form an

azeotrope having a boiling point of about 86ºC, while it is known that vinyl propionate, vinyl butyrate and vinyl

crotonate form azeotropes with water having boiling points, respectively, of about 94.9°C, about 87ºC, and about 92ºC. In all instances, the azeotrope has a boiling pcint substantially below the boiling point of acetic acid which allows the vinyl ester to be separated readily from acetic acid.

Because water forms a heterogeneous azeotrope with the vinyl ester, upon condensation of the azeotrope, it will separate into two phases, namely water and the vinyl ester, thereby facilitating simple recovery of the vinyl ester.

Thus, the azeotropic distillation assisted transvinylation process described herein can be used to make vinyl pivalate. vinyl butyrate, vinyl crotonate and vinyl propionate directly from vinyl acetate by transvinylation. The process is more economical than previously known transvinylation techniques because of the relative ease with which the vinyl ester can be separated from acetic acid.

The following Examples are illustrative of, but not in limitation of, the present invention. These Examples

illustrate the separability of vinyl esters and carboxylic acids and describe the preparation of a vinyl product ester from carboxylic acids by the azeotropic distillation assisted transvinylation process of the present invention.

Example 1

This Example demonstrates the feasibility of separating vinyl acetate, vinyl propionate, acetic acid and propionic acid. This mixture is believed to be typical of the

transvinylation reaction mixture after catalyst removal that would result from the preparation of vinyl propionate by the transvinylation of vinyl acetate and propionic acid. Water was used as the azeotropic agent.

A mixture consisting of 28wt.% vinyl acetate, 30wt.% vinyl propionate, 18wt.% acetic acid and 24wt.% propionic acid was charged to a 2 liter kettle. The kettle was equipped with a 15-tray Oldershaw distillation column, a condensing column connected to the outlet (top) of the distillation column and collection flask connected to the outlet end of the condensing column.

The mixture was heated and an initial reflux ratio of 10 was established. As the temperature of the kettle was

increased, it was found that the lower boiling point vinyl acetate was being separated from the mixture. After the vinyl acetate had been separated from the mixture, water was added to the top of the distillation column dropwise until about 15.4g of water had been added. An aqueous azeotrope of vinyl propionate formed, which had a boiling point (observed) in the range of about 78-79ºC. The azeotrope was analyzed by gas chromatography and found to contain 98.11% vinyl propionate, 0.639% acetic acid and 0.326% propionic acid.

Example 2

This Example illustrates the separating of vinyl acetate and vinyl crotonate from a mixture of vinyl acetate, acetic acid, vinyl crotonate and crotonic acid by azeotropic

distillation. This mixture simulates a transvinylation reaction mixture, after catalyst separation, that would be expected to result from the preparation of vinyl crotonate by the transvinylation reaction of vinyl acetate with crotonic acid.

A solution (8.8 ml) prepared from vinyl acetate (7.0 g), vinyl crotonate (7.0 grams), acetic acid (4.0 grams), and crotonic acid (2.0 grams) was charged to the kettle of a single-stage distillation apparatus. Gas chromatography analysis of this solution is set forth in Table II below:

Table II

vinyl vinyl acetic crotonic acetalcrotonate acetate acid acid dehyde

Area% 46. 14 31.22 10.23 10. 28 0.074

The kettle was heated to 75ºC and 1 ml water was added via addition funnel. Vinyl acetate/water and vinyl

crotonate/water azeotropes were distilled at an overhead temperature ranging from 67°C-94ºC. The following fractions were collected, and when analyzed by gas chromatography were found to have the composition (area %) set forth in Table III below:

Table III

vinyl vinyl acetic crotonic acetaloverhead crotonate acetate acid acid. dehyde

67-71ºC 5.04% 92.81% - - 1.73%

67° 7.50% 92.81% - - 0.53%

69-73° 10.56% 87.4 % 0.39% 0.11% 0.78%

76-34° 16.38% 82.3 % - - 0.58%

84-90° 42.17% 54.9 % 0.65% - 0.33%

90-93° 82.24% 13.8 % 0.78% 0.19% 0.37%

94° 95.9 % 1.33% 0.60% 0.13% 0.10%

It can be seen that vinyl crotonate and vinyl acetate can be separated and removed from a transvinylation reaction mixture through simple azeotropic distillation and without an elaborate fractionating column. Example 3

This Example illustrates the preparation of vinyl acrylate by azeotropic distillation assisted transvinylation of vinyl acetate and acrylic acid.

Three separate transvinylation runs were made. In each run 1,500 grams of acrylic acid, 1.91 grams of ruthenium catalyst having a formula [Ru(CO)₂OCOCH₃]_n,1,500 grams of vin acetate, and 6.0 grams of phenothiazine were charged to a 1-gallon autoclave. The reactor was pressurized and purged three times with carbon monoxide (50 psig) and then

pressurized to 50 psig. The reactor was heated to 130-136°C for a total of 4 hours. The reactor was cooled, vented, and the transvinylation mixture, containing the catalyst, vinyl acrylate, acetic acid, acrylic acid, and vinyl acetate, was discharged from the reactor.

The transvinylation mixtures of each run, respectively, 2,848 grams, 2,938 grams, 2,778 grams, were combined and the flashed distilled under vacuum to remove the transvinylation mixture (vinyl acetate, vinyl acrylate, acetic acid, and som acrylic acid) from the acrylic acid/ruthenium catalyst residue. The distillate was recovered.

The flash distilled transvinylation mixture was charged to a fractional distillation apparatus comprising a 12 L kettle equipped with a 24 tray Oldershaw column and a

fractionating head. Vinyl acetate was removed from the flas distilled transvinylation mixture before azeotropic

distillation. During vinyl acetate distillation operations, phenothiazine inhibitor (dissolved in vinyl acetate) was adde to the kettle and was fed down the column through the use of an addition funnel. The unreacted vinyl acetate (b.p. 72-73°C) was fractionated from the transvinylation mixture at a reflux ratio of 10/1. The majority of the residual vinyl acetate was purged from the column at the high (10/1) reflux ratio by gradually and briefly raising the head temperature to 82°C. The gas chromatography area % analysis of the resulting mixture is set forth in Table IV below:

Table IV

acrylic vinyl vinyl acetic

acid acrylate acetate acid acetaldehvde

34.587 45.317 0.341 13.208 0.134

The kettle was allowed to cool, thereby allowing the vapors to recede down the column. Water was then charged to the addition funnel on the top of the distillation column and formed a minimum boiling water/vinyl acrylate azeotrope having a boiling paint (observed) of 77-78°C. Upon condensation, the water/vinyl acrylate azeotrope separated into an organic

(upper) phase and an aqueous (lower) phase. The gas

chromatographic analyses (area %) of the azeotropic fraction (instantaneous samples of the organic overhead) are set forth in Table V below:

Table V

overhead vinyl vinyl acetic

(temp °C) acrylate acetate acid acetaldehyde

1 (77°) 96.013 3.301 0.367 0.059

2 (73°) 98.360 1.163 trace* 0.091

3 (73°) 98.541 1.012 trace* 0.098

4 (78-94°)** 97.319 0.995 0.489 0.244

5 (94°) 97.143 1.072 0.439 0.254

*In overhead samples 2 and 3, the acetic acid content was below the threshold of the gas chromatograph integrator.

**Not determined precisely.

The vinyl acrylate fractions were combined,

azeotropically dried (280 mm Hg, 78-79ºC) and distilled through a. short path column to give 2 L of product. The analysis of the refined vinyl acrylate by gas chromatography is set forth in Table VI below: Table VI

vinyl vinyl acetic

acrylate acetate acid acetaldehyde

98.427 1.247 0.024 0.035

Gas chromatographic analysis revealed that a highly pure product, low in acidity, was obtained using azeotropic

distillation assisted transvinylation. This Example thus demonstrates that the present invention provides a relatively simple process for obtaining high purity alkenyl product derivatives that are low in acidity directly and without the need for further processing to remove acid.

Example 4

This Example illustrates the preparation of vinyl crotonate by azeotropic assisted transvinylation of vinyl acetate with crotonic acid.

To a 1-gallon autcclave were charged 1,350 grams of crotonic acid, 0.9 grams of ruthenium catalyst having the formula [Ru(CO)₂OCOCH₃]_n,1.350 grams of vinyl acetate, and 2.7 grams of phenothiazine. The reactor was pressurized and purged three times with nitrogen (50 psig) and then

pressurized to 25 psig. The reactor was heated to 127-133°C for a total of 12 hours. The reactor was cooled, vented and the transvinylation mixture, containing the catalyst, vinyl crotonate, acetic acid, crotonic acid, and vinyl acetate, was discharged from the reactor.

The transvinylation mixture was flashed distilled under vacuum to remove the transvinylation products (vinyl acetate, vinyl crotonate, acetic acid, and some crotonic acid) from the crotonic acid/ruthenium catalyst residue.

The flash distilled transvinylation mixture was charged to a fractional distillation apparatus comprising a 3000 ml kettle equipped with a 25 tray Oldershaw column and a

fractionating head. During vinyl acetate distillation

operations, phenothiazine inhibitor was added to the kettle and was fed down the column through the use of an addition funnel (phenothiazine dissolved in vinyl acetate). The unreacted vinyl acetate (b.p. 72-73°C) was fractionated from the transvinylation mixture at a reflux ratio ranging from 5/1 (initially) to 10/1 (at the end of the distillation). The last minor amounts of vinyl acetate were purged from the column at the high (10/1) reflux ratio by gradually and briefly raising the head temperature to 93ºC.

The kettle was allowed to cool briefly, thereby allowing the vapors to recede down the column. Water (saturated with phenothiazine) was charged to the addition funnel on the top of the distillation column, in the same position as that used for the inhibitor feed, and formed a minimum boiling

water/vinyl crotonate azeotrope having a boiling point

(observed) of 92°C. Upon condensation, the water/vinyl crotonate azeotrope separated into an organic (upper) phase and an aqueous (lower) phase. Six azeotropic fractions were analyzed by gas chromatography. The compositions (by area %) of each of the fractions is set forth in Table VII below:

Table VII

Fraction vinyl vinyl acetic crotonic

No. crotonate acetata acid acid acetaldehyde1 93.473% 0.067% 0.452% - 0.473%

2 96.385 0.014 2.942 - 0.037

3 95.145 0.990 3.581 - 0.032

4 99.071 0.159 0.501 - 0.157

5 98.410 none 0.734 0.577 0.041

observed

6 44.985 none 25.007 14.594 0.523

observed

In both fractions 2 and 3, the column flooded and it is believed the water feed rate was too low to completely

azeotrope the vinyl crotonate. After fraction 3 was complete, the Oldershaw column was replaced with a Vigreux column to alleviate flooding. Improved separation resulted after the column was changed.

Example 5

This Example illustrates the preparation of vinyl

pivalate by azeotropic assisted transvinylation of vinyl acetate with pivalic acid.

A reactor was charged with 5,082 pounds of vinyl acetate, 4,854 pounds of pivalic acid, and ruthenium dicarbonyl acetat homopolymer (530g). The reactor was pressurized to 25 psi carbon monoxide (containing an oxygen atmosphere of 500-1000 ppm in the reactor, as required by the inhibitor

hydroquinone), and heated to 150°C for 7 hours. Analysis by gas chromatography of a reactor sample revealed the reaction had reached equilibrium. The reactor was cooled to 50ºC and the contents were flash distilled under vacuum. The

distillation residue, containing catalyst and pivalic acid, was discharged from the reactor.

Vinyl acetate was then fractionated from the distillate. After removal of vinyl acetate, the reaction mixture was subjected to azeotropic distillation to separate and recover vinyl pivalate.

The column bottoms from the vinyl acetate removal step were distilled by azeotropic distillation. A Koch-Seltzer column was used in conjunction with a thirty gallon decanter. The column bottoms, which contain crude vinyl pivalate

(preheated to 90°C) was fed to the column midpoint and water was fed to the top of the column via a reflux line. A vinyl pivalate/water azeotrope (b.p. = 86ºC, 17% by wt. water) was fractionated and distilled overhead. Pivalic acid, acetic acid, and heavies were removed from the bottom of the column. The azeotropic product was collected in the decanter where it phase separated. The bottom water layer was returned to the top of the azeotropic distillation column and the top vinyl pivalate layer was collected for final drying. During the operation the crude material was fed to the column; about 50% distilled overhead and about 50% was removed from the column base. Throughout the separation, the column top maintained a temperature of 39.5ºC-94.5°C and the base temperature was 120.8°C-126.2ºC. The yield for the azeotropic distillation was 97.3%.

The composition of the nine fractions from the azeotropic distillation is set forth in Table VIII below:

Table VIII

Fraction vinyl acetic vinyl pivalic

Number acetate acid oivalate acid

1 0.480 0.197 99.313 -

2 0.096 0.064 99.813 0.026

3 0.076 0.018 99.875 0.006

4 0.079 0.087 98.863 0.936

5 0.091 0.123 98.748 1.014

6 0.079 0.011 99.323 0.063

7 0.082 0.010 99.374 0.034

8 0.080 0.013 99.377 0.031

9 0.089 0.033 99.559 0.022

It can be seen from the analysis of fraction numbers 2, 3, 6, 7, 8 and 9 that azeotropic distillation was particularly effective for the recovery of high purity vinyl pivalate, low in acid content, and it is believed that no further processing of those fractions to remove acid would be required. During fractions 4 and 5, the water feed to the azeotropic

distillation column was undesirably fast. Too rapid a water feed resulted in fractions of pivalic acid that were higher in pivalic acid and acetic acid content than were desirable.

This Example demonstrates the remarkable advantages of the azeotropic distillation assisted transvinylation process of the present invention. With the present invention,

separation of vinyl pivalate and acetic acid which have very close boiling points (112ºC and 116-118ºC, respectively) is much simpler and cheaper, and preparation of vinyl pivalate by transvinylation of vinyl acetata and pivalic acid is

economically and commercially attractive.

The present invention thus provides for an improved transvinylation process in which the separation and recovery of the alkenyl product derivative is efficient and economical. Azeotropic distillation assisted transvinylation has improved productivity, lower equipment costs and lower operating costs than conventional fractionation or distillation due, at least in part, to the efficiency and ease of the separation and recovery of the alkenyl product derivative. The process is capable of producing highly pure alkenyl product derivatives, low in acidity, directly and without the need for further processing. Moreover, the invention makes economical the production of alkenyl product derivatives by transvinylation in a single stage reactor where the alkenyl product derivative and conjugate acid of the alkenyl derivative of the first Bronsted acid are close boilers.

Claims

We Claim:

1. A process for the preparation of an alkenyl derivative of a Bronsted acid by the transvinylation reaction of an alkenyl derivative of a first Bronsted acid with a second Bronsted acid which comprises reacting said alkenyl derivative of said first Bronsted acid with said second Bronsted acid in the presence of a catalyst, said catalyst being capable of catalyzing the transvinylation reaction whereby there is formed a reaction mixture comprising an alkenyl derivative of said second Bronsted acid and the conjugate acid of said alkenyl derivative of said first Bronsted acid, adding an azeotropic agent to the transvinylation reaction mixture, said azeotroping agent capable of forming azeotrope with at least said alkenyl derivative of said second Bronsted acid, and recovering by azeotropic distillation as a product of

transvinylation the alkenyl derivative of said second Bronsted acid.

2. The process of claim 1, wherein said azeotropic agent and said alkenyl derivative of said second Bronsted acid form an azeotrope having a boiling point lower than the boiling point of the conjugate acid of the alkenyl derivative of the first Bronsted acid, or said azeotropic agent and said alkenyl derivative of said second Bronsted acid form an azeotrope having a boiling point higher than the boiling point of the conjugate acid of the alkenyl derivative of the first Bronsted acid, or said azeotropic agent and said alkenyl derivative of said second Bronsted acid form a heterogeneous azeotrope so that phase separation of the azeotropic agent

and said alkenyl derivative of said second Bronsted acid occurs upon condensation of the azeotrope after distillation, or said azeotropic agent forms azeotropes with said alkenyl derivative of said second Bronsted acid and said alkenyl derivative of said first Bronsted acid to allow a mixture of said derivatives to be separated from the transvinylation reaction mixture and recovered.

3. The process of claim 1, including, after the

transvinylation reaction and prior to adding the azeotropic agent, feeding the transvinylation reaction mixture to a separation zone to separate the catalyst and second Bronsted acid from the other components of the transvinylation reaction mixture.

4. The process of claim 1, wherein the conjugate acid of the alkenyl derivative of the first Bronsted acid produced by the transvinylation reaction and remaining after azeotropic distillation of the alkenyl derivative of said second Bronsted acid, is recovered.

5. The process of claim 1, wherein said alkenyl product derivative is a compound of the formula

R-(CH₂)_n-CR²=CR⁰R¹ wherein R is carboxy, amido, aroxy, and alkoxy; n is either zero or one; and R⁰, R¹ and R² are each individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl, and alkyl ethers.

6. The process of claim 12, wherein said alkenyl product derivative is a compound selected from the group consisting of allyl pivalate, allyl benzoate, allyl propionate, allyl crotonate, allylmethacrylate, allylacrylate,

methallylbenzoate, methallyl pivalate, methallyl propionate, and mixtures thereof.

7. A process for the preparation of a vinyl derivative of a Bronsted acid by the transvinylation reaction of a vinyl derivative of a first Bronsted acid with a second Bronsted acid which comprises reacting said vinyl derivative of said first Bronsted acid with said second Bronsted acid in the presence of a catalyst, said catalyst being capable of catalyzing the transvinylation reaction whereby there is formed a reaction mixture comprising a vinyl derivative of said second Bronsted acid and the conjugate acid of said vinyl derivative of said first Bronsted acid, adding an azeotropic agent to the transvinylation reaction mixture, said

azeotroping agent capable of forming an azeotrope with at least said vinyl derivative of said second Bronsted acid, and recovering by azeotropic distillation as a product of

transvinylation the vinyl derivative of said second Bronsted acid.

8. The process of claim 7, wherein said azeotropic agent and said vinyl derivative of said second Bronsted acid form an azeotrope having a boiling point lower than the boiling point of the conjugate acid of the vinyl derivative of the first Bronsted acid, or said azeotropic agent and said vinyl

derivative of said second Bronsted acid form an azeotrope having a boiling point higher than the boiling point of the conjugate acid of the vinyl derivative of the first Bronsted acid, or said azeotropic agent and said vinyl derivative of said second Bronsted acid form a heterogeneous azeotrope so that phase separation of the azeotropic agent and said vinyl derivative of said second Bronsted acid occurs upon

condensation of the azeotrope after distillation, or said azeotropic agent forms azeotropes with said vinyl derivative of said second Bronsted acid and said vinyl derivative of said first Bronsted acid to allow a mixture of said derivatives to be separated from the transvinylation reaction mixture and recovered.

9. The process of claim 7, including, after the

transvinylation reaction and prior to adding the azeotropic agent, feeding the transvinylation reaction mixture to a separation zone to separate the catalyst and second Bronsted acid from the other components of the transvinylation reaction mixture.

10. The process of claim 7, wherein the conjugate acid of the vinyl derivative of the first Bronsted acid produced by the transvinylation reaction and remaining after azeotropic distillation of the vinyl derivative of said second Bronsted acid, is recovered.

11. The process of claim 7, wherein said vinyl derivative of said first Bronsted acid is a vinyl derivative of a carboxylic acid having of from 1 to about 12 carbon atoms, and said second Bronsted acid is a carboxylic acid having of from 1 to about 7 carbon atoms.

12. The process of claim 11, wherein said vinyl derivative of said first Bronsted acid is vinyl acetate, and said second Bronsted acid is an acid selected from the group consisting of propionic acid, acrylic acid, methacrylic acid, butyric acid, isobutyric acid, 2-methyl butyric acid, valeric acid, benzoic acid, cyclohexanoic acid, cyclohexenoic acid, pivalic acid, and crotonic acid.

13. The process of claim 7, wherein the azeotropic agent is water.

14. A process for the preparation of a vinyl ester of a carboxylic acid having of from 1 to about 12 carbon atoms by a transvinylation reaction comprising reacting a vinyl

derivative of a first carboxylic acid having from 1 to about 12 carbon atoms with a second carboxylic acid having from 1 to about 7 carbon atoms in the presence of a catalyst capable of catalyzing the transvinylation reaction to form a vinyl derivative of said second carboxylic acid, adding water to the transvinylation reaction mixture in an amount sufficient to form an azeotrope with at least the vinyl derivative of said second carboxyl ic acid whi le dist i l l ing said reaction products, and recovering by azeotropic distillation as a product of the transvinylation reaction the vinyl derivative of said second carboxylic acid.

15. The process of claim 14, wherein said vinyl derivative of said carboxylic acid having from 1 to about 7 carbon atoms that is prepared by said transvinylation reaction is vinyl pivalate and said second carboxylic acid is pivalic acid.

16. The process of claim 14, wherein said vinyl derivative of said first carboxylic acid is vinyl acetate, said catalyst is a ruthenium-based catalyst and said second carboxylic acid is a carboxylic acid selected from the group consisting of propionic acid, acrylic acid, methacrylic acid, butyric acid, isobutyric acid, 2-methyl butyric acid, valeric acid, benzoic acid, cyclohexanoic acid, cyclohexenoic acid, pivalic acid, and crotonic acid.

17. The process of claim 14, including, after the

transvinylation reaction and prior to adding the azeotropic agent, feeding the transvinylation reaction mixture to a separation zone to separate the catalyst and second Bronsted acid from the other components of the transvinylation reaction mixture.

18. The process of claims 7 and 14, wherein said vinyl product derivative is a compound of the formula

R-CR² = CR⁰R¹ wherein R is carboxy, amido, aroxy and alkoxy; R⁰, R¹ , and R² are each individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl and alkyl ethers.

19. The process of claim 18, wherein said vinyl product derivative is a compound selected from the group consisting of vinyl pivalate, vinyl methacrylate, vinyl acrylate, vinyl benzoate, vinyl propionate and vinyl crotonate, and mixtures thereof.