AZEOTROPIC ASSISTED TRANSVINYLATION TECHNOLOGY

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 TO ALL WHOM IT MAY CONCERN: Be it Known that we, Mortega Mokhtar-Zadeh, a citizen Iran, permanently residing in the united States of America, Charleston, West Virginia, and Rex Eugene Murray, a citizen 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. qaefccπrsund of the Tnveπtion i. fj β i-jj 9t -ft~ Invention The present invention relates to a process for prepari an al enyl derivative of a Bronsted acid by the transvinylation reaction of an alkenyl derivative of a firs 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 vei known. The reaction can be illustrated by the reaction c: vinyl-containing compound (R'CH ■ CH ; ) with an active hyo«.c containing compound (RX) , as in the ollowing: RX + R'CH - CH, "t"* RCH - CH, + R'X wherein R is carboxy, amido, aroxy, alkoxy, and the like; X hydrogen, hydroxyl, alkyl, aryl, and the like; and R' is carboxyl, amido, alkyl, substituted alkyl, aryl or substitv- aryl. Adel an, 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..." Adel;.-s. 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 3 reaction of vinyl acetate catalyzed with mercuric salts wa not restricted to carboxylie acids, but would occur with o compounds containing active hydrogen, such as acetoacetic ester and glycolic esters. Other researchers have demonstrated the versatility o the transvinylation reaction and its applicability to a wi 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 t vinyl interchange reaction between a vinyl ether and an alcohol using a palladium catalyst. Other sources report 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, ?t(II) and Rh(III) have been reported by A. Sabel, J. Smidt, R. Jira and H. Prigge, Che Ber.. 102, pp. 2939-2950 (1969), to catalyze the reaction. 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 f Pt, ∑r, Rh, Ru or Os s catalysts in a vapor phase transvinylation process. The experimental portion discloses the use of only palladium o 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 ?d are ci at col. 1, line 67, as the preferred metals. More recently, it has been discovered that ruthenium compositions are useful transvinylation catalysts for nume Bronsted acids and derivatives of Bronsted acids as disclo in U.S. application Serial Mo. 213,697, filed June 30, 198 and assigned to the assignee of the present application. invention disclosed therein relates to a process for the transvinylation of a vinyl derivative of a first Bronsted with a second Bronsted acid which comprises providing a li phase mixture containing the vinyl derivative of the first Bronsted acid and the second Bronsted acid in the presence 4 a ruthenium compound at a temperature at which transvinylat occurs, and recovering as a product of transvinylation the vinyl derivative of the second Bronsted acid. The benefici use of ruthenium-containing compounds as catalysts for transvinylation processes overcomes several deficiencies no 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, (viny product derivative) from other components of the transvinylation reaction mixture, including the starting reactants, the conjugate acid of the vinyl derivative of th first Bronsted acid and other side products produced by the reaction. For example, distillation, fractional distillati vacuum distillation and rotary evaporation have been used. For example, in U.S. Patent No. 3,188,319, vacuum distillat (Examples 1-3), fractional distillation (Examples 4, 7) , an distillation (Example 13), illustrate the use of various distillation techniques for the recovery of the vinyl produ 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 u for the separation and recovery of the vinyl product derivative. The serious process difficulties of separating the vin 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, suc 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 vin 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, w intensi ied in separations involving the distillation of mixtures of close boiling materials. The difficulty of separating close boiling materials was also recognized. Th solution to the separation problem taught in U.S. Patent No 3,337,611 involves the use of a molar excess of the carboxy acid relative to the molar concentration of the vinyl ester reactant in the transvinylation reaction. Distillation of vinyl product derivative remained the method of choice for recovery of total ester. See Col. 2, 11s. 48-51, Col. 4, 1 50-59, and Example l. Thus, despite the recognition of the advantages of usi transvinylation technology for making vinyl derivatives of Bronsted acids, transvinylation technology has not achieved widespread commercial significance because of the inefficie and economically unattractive methods that have been conventionally employed to separate and recover the vinyl product derivative from the transvinylation reaction mixtur 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 wher the vinyl product derivative has a boiling point very close the boiling point of the conjugate acid, i.e., the acid for 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 suc 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 t use of transvinylation technology commercially unattractive for the production of many monomers. Thus, there remains a need for a transvinylation proce in which the alkenyl product derivative, and in particular vinyl product derivative can be readily, facilely and CT/US91/08757 6 economically separated from the other components of the transvinylation reaction mixture, and, in particular, the conjugate acid of the alkenyl derivative of the first Bronst acid. A need for such a process is especially acute where t conjugate acid and alkenyl product derivative are close boilers, i.e., they have a boiling point close to one anothe 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 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 tha could be produced only at signi icantly 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 Bronst acid. Summar y 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 proces to separate the alkenyl product derivatives from other components of the transvinylation reaction mixture, includin the starting reactants, and especially the conjugate acid of the alkenyl derivative of the Bronsted acid employed as one o 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 alkenyl product derivative wherein the process is assiste azeotropic distillation to effect efficient and economica separation of the alkenyl product derivative from the oth components of the transvinylation reaction mixture. It is also an object of the invention to provide a transvinylation process having improved productivity, low equipment costs and lower operating costs. It is a further object of the invention to provide a transvinylation process having improved throughput owing the simplified separation and recovery of the alkenyl pro derivative. It is yet another object of the invention to provide transvinylation process for the preparation of an alkenyl product derivative in which the alkenyl product derivativ the conjugate acid of the alkenyl derivative of the Brons acid used as the reactant have close boiling points. It related object of the invention to provide a transvinylat process in which an alkenyl product derivative can be pro in a single stage reactor where the conjugate acid and th 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 i 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 derivati low in acidity. It is also an object of the invention to provide a transvinylation process which is versatile, and is capabl producing a mixture of alkenyl derivatives. 7 8 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(CH ; ),CR 2 - CR°R l 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 R°, R and R 2 are each individually one of hydrogen, alkyl of l to about 12 carbon atoms, cycloalkyl, aryl, alkyl ethers, and th like. Transvinylation as used herein includes both vinyl interchange and allyl interchange reactions. The novel process of the present invention applies equally to both type of interchange reactions. The invention thus provides a process for the preparatio 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 wit 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 suf iciently 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 l is a schematic illustration of the transvinylation process of the present invention, includin recovery of the alkenyl product derivative by azeotropic distillation, and Bronsted acid recycle. Petailed Description of the Invention The present invention provides a process for the faci preparation and separation of numerous alkenyl derivatives Bronsted acids formed by the transvinylation reaction of a alkenyl derivative of a first Bronsted acid R'(CH 2 ) β CR 2 » C 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(CH ; ),CR 2 * CR^R 1 ) from at least the conjugate acid (R'X) of the alkenyl derivative of the firs 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' (CH,).CR 2 » CR°R l β, i!* RCR 2 » CR°R l + R'X wherein R is carboxy, amido, aroxy, alkoxy, or the like; X hydrogen, hydroxyl, alkyl, aryl, or the like; n is zero or one; R' is carboxyl, amido, alkyl, substituted alkyl, aryl substituted aryl; and R°, R l and R 2 are each individually o hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl, ally1 ethers, and the like. The transvinylation reaction is an equilibrium exchan reaction with an equilibrium constant of about 1. S91/08757 10 Accordingly, when equimolar amounts of the alkenyl derivative of the first Bronsted acid (R« (CH,),CS. 2 » CR°R l ) 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(CH*>) a CR 2 • CR°R l ) and the second Bronsted acid (R'X) , and the transvinylation products, that is, the alkenyl product derivative of the second Bronsted acid (R(CH*,) a CR 2 * C ^ 1 ) 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(CH,) β CR 2 » CR°R') 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 distillatio is employed to assist the transvinylation process by providin a relatively simple, facile and economical method for the recovery of the alkenyl product derivative, (R(CH 2 ) β CR 2 ■ CR°R') 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 1 1 transvinylation reaction mixture is treated, if at all, pr to azeotropic distillation. Accordingly, an azeotropic ag is added to the transvinylation reaction mixture to form a 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 h boiling point at a temperature sufficiently different from boiling point of at least the conjugate acid (R'X) to allo the azeotrope to be separated from the transvinylation reaction mixture by azeotropic distillation. Where it is desirable to recover a mixture of the alk product derivative and the alkenyl derivative of the first Bronsted acid; it may or may not be necessary to also form azeotrope with the alkenyl derivative of the first Bronste acid depending on the relative boiling point of that alken derivative, the alkenyl product derivative azeotrope and o components in the transvinylation reaction mixture. If th boiling point of the alkenyl derivative of the first Brons acid is sufficiently different from the boiling point of t conjugate acid, or other components of the reaction mixtur from which it is to be separated (or both the conjugate ac and other components in the reaction mixture) , it may not necessary to form an azeotrope with the alkenyl derivative 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 whi it is to be separated are too close, it may be desirable t 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 alken product derivative to allow the derivative mixture to be separated and recovered. The azeotropic agent selected must be compatible with alkenyl product derivative. In addition, the azeotropic a forms with the alkenyl product derivative an azeotrope whi 12 has a boiling point sufficiently different from the other components of the transvinylation reaction mixture to permi 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 t transvinylation reaction mixture from which the azeotrope is to be separated be on the order of several degrees centigrad 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 derivati form a heterogeneous azeotrope, the solubility of the azeotropic agent and alkenyl product derivative in one anoth is minimal. Upon condensation of the azeotrope after distillation, the azeotropic agent and alkenyl product derivative will separate into two phases, so separation of t 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 recover*/ -t the alkenyl product derivative and of mixtur of the alkenyl product derivative ar.i the alkenyl derivative of the f.rst Bronsted acid. The specific product or product mixture to be produced will determine the manner in which th transvinylation reaction products are to be treated prior to A 3 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 i 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 derivativ of the first Bronsted acid may also be satisfactorily employed. Selection of an azeotropic agent capable of formin an azeotrope with both the alkenyl product derivative and wit the alkenyl derivative of the first Bronsted acid allows a mixture of those two derivatives to be separated and recovere 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 an the boiling point of the alkenyl product derivative are eithe both higher or both lower than the boiling point of the conjugate acid. The transvinylation uc ion is preferably carried out i the presence of a Ital st. ny of the well known transvinylation i i- s .: may be employed, including, for example, mercury and pa..adium based catalysts. Especially preferred transvinylation catalysts are the ruthenium-based 14 catalysts disclosed and claimed in U.S. application Serial 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, a 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 react, the transvinylation reaction mixture, which contains concentrations of the alkenyl derivative of the first Brons acid, the second Bronsted acid, the alkenyl product derivat 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 zon 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 t 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 unr?. :te«. ilkenyl derivative of --he first Bronsted acid and, optionally, to recycle that al e.-.; 1 . derivative back to the reactor by transfer line 20. To produce a mixture of the alkenyl product derivative and the alkenyl derivative of th first Bronsted acii, separation zone 18 is designed to separate only a portion of the alkenyl derivative (or none a all) from the alkenyl product derivative. In the illustrate 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 i recycled back to the reactor via transfer line 20. The seco Bronsted acid together with catalyst is recovered from separation zone 18 and is recycled to reactor 16 via transfe line 22. It will be appreciated that separation zone 18 may be included after azeotropic distillation, for example, where t separation zone is used primarily for the separation and recovery of catalyst after the alkenyl product derivative ha been separated from the transvinylation reaction mixture. The alkenyl product derivative, conjugate acid and, optionally, unreacted alkenyl derivative of the first Bronst 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 t alkenyl product derivative to be separated from the conjugat acid. The azeotrope preferably has a boiling point at least 10 β C different than the boiling point of the conjugate acid, although the azeotropic distillation assisted transvinylatio 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 boili point differential between the azeotrope and the conjugate acid (or the component) is on the order of two or three degrees centig- .de, especially where the monomer to be recovered is commercially . portant. It may or may not -». necessary to use an azeotropic age to form an azeotrope w.th the alkenyl derivative of the firs Bronsted acid in order to separate the alkenyl derivative of 16 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 alken derivative of the first Bronsted acid and the boiling point the conjugate acid are relatively close, i.e., on the order less than 15 degrees, then it may well be desirable to form azeotrope with the alkenyl derivative of the first Bronsted acid to effect efficient separation of the alkenyl derivativ 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 Bronst 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 th 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 th boiling point of the conjugate acid in order to assure that both the alkenyl derivative of the first Bronsted acid and t 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 ccr-.amplated tr.-it 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 illu.:crated embodiment, the azeotropic agent is shown to be fed near the top of column 24 through feed line 17 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 undesirable components during distillation. Because the temperature of the liquid near the top of the column is low than it is at other locations, adding the azeotroping agent near the top allows the agent to cool and thereby knock dow non-azeotroping components that may be near the top of the column. Also, where the azeotroping agent is water, there 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 skille 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 an alkenyl product derivative form a heterogeneous minimum boiling point azeotrope. As a result, the azeotrope is dra off the top of column 24 through transfer line 28 and transferred to decanter 30 where the azeotrope separates in two phases, the alkenyl product derivative and the azeotrop agent. Note that if a mixture of alkenyl product derivativ and alkenyl derivative of the first Bronsted acid is separa 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 w 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. Th alkenyl product derivative phase may, if desired, also be refluxed (as, for example, by return to distillation column 91/08757 18 through transfer line 33) to enhance rectification. The alkenyl product derivative is transferred to dryin column 36 via transfer line 38. In drying column 36, the alkenyl product derivative is dried by azeotropic drying, t azeotrope being taken off the column and transferred to eit the first decanter 30 and processed as described above, or transferred to a second decanter 40, in which phase separat of the alkenyl product derivative and azeotropic agent occu Alkenyl product derivative from the second decanter 40 is returned to drying column 36 via transfer line 42, while th azeotropic agent is processed as waste. Azeotropic agent f 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 b neutralized with a suitable base, such as, sodium bicarbonat 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 fro 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 fo subsequent use. It will be appreciated that in the event th the second Bronsted acid is not completely separated from th conjugate acid and the alkenyl product derivative in separation zone 18, the second Bronsted acid is separated fr 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 temperatur and pressure are not particularly critical to the practice o the invention, but they are related, and they are highly dependent on the particular separation to be carried out. 1 9 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, i 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 an 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 carr 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 som excess of the azeotroping agent may be employed, it is preferred to match the feed rate of the azeotroping agent wit ■ 1 20 the production rate of the alkenyl product derivative. After the initial charge, preferably the azeotropic agent fed to th distillation column is recovered from the two phase separatio 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" inyl moiety with the appropriate selection of the azeotroping agent. By way of illustration, suitable alkenyl derivatives are compounds of the formula -(CH,),-CR 2 - CR°R l wherein n is either zero or one, R°, R 1 and R 2 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, ally pivalate, allyl benzoate, allyl propionate, methallyl benzoate, methallyl pivalate, methylallyl propionate, allyl crotonate, allylmethacrylate, allylacrylate, and the like. Azeotropic distillation assisted transvinylation can als 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 derivativ 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, inyl embraces groups of the formula R°R l C - CR 2 - 2 1 wherein R°, R 1 and R 2 are each individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl, alky ethers, and the like. The Bronsted acid is any species whi 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 but rate, vinyl 2- ethyl 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- vinylsuccini ide, vinyl phenyl ether, vinyl methyl ether, vinyl ethyl ether, 2-chloroethyl vinyl ether, ethyl vinyl ether, 2-vinyloxyethanol, allyl vinyl ether, isopropyl viny ether, propyl vinyl ether, l-vinyloxy-2-propanol, 3-vinylox 1-ρropanol, butyl vinyl ether, isobutyl vinyl ether, bis(2- vinyloxyethyl)ether, 2-butylthioethyl vinyl ether, 2- butoxyethyl vinyl ether, 2-ethoxyethyl-2-vinyl-oxyethyl eth 2-ethylhexyl vinyl ether, 2-butoxyethyl 2-vinyl-oxyethyl ether, trimethylnonyl vinyl ether, N-vinyl 2-oxazolidinone, vinyloxyethyl acetate, 2-vinyloxyethyl pivalate, 2- vmyloxyethylacrylate, 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 practi of the invention are carboxylic acids such as monocarboxyli and polycarboxylie acids illustrated by acetic acid, propio acid, butyric acid, isobutyric acid, 2-methyl butyric acid, crotonic acid, pivalic acid and other neo-acids, stearic ac benzoic acid, terephthalic acid, isophthalic acid, phthalic acid, adipic acid, succinic acid, malic acid, aleic acid, polyacrylic acids, acrylic acid, methacrylic acid, cinnamic 22 acid, 2-ethylhexanoic acid, cyclohexanoic acid, and cyclohexenoic acid; amides such as 2-pyrrolidinone, 2- pyrrolidone, e-caprαlactam, 2-oxazolidinone, and succinimide; alcohols such as methanol, ethanol, n-propanol, isobutanol, fluorinated alkanαls such as l, l, l, 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] ; a ino 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 ono-ol, and the like. The preferred Bronsted acids are the carbox 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: 23 Al enyl derivative Bronsted Acid ?roduct vinyl acetate • +• pivalic acid - vinyl pivalate vinyl benzoate • +• pivalic acid - vinyl pivalate vinyl acetate • +• methacrylic acid - vinyl methacrylat 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-ethyihexanoa e 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 succinimi vinyl methyl ether - phenol - vinyl phenyl ethe vinyl chloride - aethanol - vinyl methyl ethe vinyl methyl ether - ethanol - vinyl ethyl ether vinyl acetate 2-oxazolidinone - N-vinyl 2-oxazolidinone vinyl acetate •* * ■ N-acetyl - N-vinyl ethyleneurea N-acetylethyleneu vinyl acetate -* • 2-hydroxyeth 1 - 2-vinyloxy thyl acetate acetate vinyl pivalate + 2-hydrox ethy1 - 2-vinyloxyethyl pivalate pivalate vinyl pivalate + 2-hydroxyethy1- - 2-vinylhydroxyeth acrylate acrylate As previously set forth, the azeotropic agent may be any agent that is capable of forming an azeotrope with the alkenyl 24 product derivative of the transvinylation reaction. For example, the azeotropic agent may form a binary azeotrope wit 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 i 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, ethanol 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: 0 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 25 derivative of the first carboxylic acid, if present. The minimum boiling point azeotrope has a boiling point greater than 10 β C different than the boiling point of the conjugate acid, the boiling point of the azeotrope being lower than th boiling point of the conjugate acid. In accordance with a preferred embodiment of the presen invention, an alkenyl derivative of a carboxylic acid having from l to 12 carbon atoms is prepared by the transvinylation reaction of vinyl acetate and a second carboxylic acid havin 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 transvinylati reaction mixture by azeotropic distillation with water as th azeotroping agent. Thus, in the transvinylation reaction described, acetic acid, which has a boiling point of about 116-118 β C is one of the products of the reaction. ater i used to produce a minimum boiling point heterogeneous azeotrope with the alkenyl product derivative. The azeotrop 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 reacti 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 derivati and acetic acid have boiling points that are close, and woul be very difficult to separate by fractional distillation, as can be seen in Table I below: 26 Table ; V-jnyl Ester vinyl -propionate -butyrate -crotonate -pivalate 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 86'C, 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 87 β C, and about 92 β C. 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 27 from carboxylic acids by ".he azeotropic distillation assiste 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. ? i vinyl propionate, 18wt.% acetic acid and 24wt.% propionic ac was charged to a 2 liter kettle. The kettle was equipped wi 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 condensi 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 viny 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 th range of about 78-79 β C. The azeotrope was analyzed by gas chromatography and found to contain 98.11% vinyl propionate, 0.639% acetic acid and 0.326% propionic acid. Sxapφle 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 28 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 ;; vinyl vinyl acetic crotonic acetal- crotoπate acetate acid acid dehvde Area% 46.14 31.22 10.23 10.28 0.074 The kettle was heated to 75"C and 1 ml water was added via addition funnel. inyl acetate/water and vinyl crotonate/water azeotropes were distilled at an overhead temperature ranging from 67°c-94 β C. The following fractions were collected, and when analyzed by gas chromatography were found to have the composition (area %) set forth in Table III below: 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. 29 E^pφje 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)2θCOCH3] n ,1,500 grams of vin acetate, and 6.0 grams of phenothiazine were charged to a l- 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 130-1 6°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 t 757 30 82°C. The gas chromatography area % analysis of the resultin 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 havin a boiling paint (observed) of 77-78°C. Upon condensation, th 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: *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, 78-79 β C) and distilled through a. short path column to give 2 of product. The analysis of the refined vinyl acrylate by gas chromatography is set forth in Table VI below: abl V vinyl vinyl acetic acrylate acetate aςjd, acetaldehvde 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. Sx ffplβ 4 This Example illustrates the preparation of vinyl crotonate by azeotropic assisted transvinylation of vinyl acetate wit:: 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)2θCOCH3] n» •••••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 91/08757 32 funnel (phenothiazine dissolved in vinyl acetate) . The unreacted vinyl acetate (b.p. 72-7 °C) was fractionated from the transvinylation mixture at a reflux ratio ranging from 5/: (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 93 β C. 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 VTI 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. 33 Ξxamols 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 50 β C 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. » 86 β C, 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 34 t emperature of 39.5 β C-94.5°C and the base temperature was l 20.8°C-126.2 β C. 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 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 (H2 β C and 116-118 β C, 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 35 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 sai.d 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-(CH 2 ) n -CR 2 =CR° 1 wherein R is carboxy, amido, aroxy, and alkoxy; n is either zero or one; and R°, R- 1 - and R 2 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 > * v 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 carboxylic acid while distilling 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-CR 2 - CR^ 1 wherein R is carboxy, amido, aroxy and alkoxy; R°, R~ , and R 2 are each individually one of hydrogen, alkyl of 1 to about 12 carbon atoms, cycloalkyl, aryl and alkyl ethers. 4 1 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.

Inventors: MOKHTARZADETH MORTEZA, MURRAY REX EUGENE, MOKHTARZADETH, MORTEZA, MURRAY, REX, EUGENE
Applicants: UNION CARBIDE CHEM PLASTIC, UNION CARBIDE CHEMICALS & PLASTICS TECHNOLOGY CORP
Application year: 1991
Main classification: C07C67
IPC codes: B01J23, C07B61, C07C67, C07C69