GB1560694A

GB1560694A - Process for producing butanediol or butenediol

Info

Publication number: GB1560694A
Application number: GB4120276A
Authority: GB
Original assignee: Mitsubishi Chemical Industries Ltd
Current assignee: Mitsubishi Chemical Corp
Priority date: 1975-10-06
Filing date: 1976-10-05
Publication date: 1980-02-06
Also published as: IT1069133B; CA1077523A; DE2645030A1; NL187156B; FR2327213A1; NL7610981A; NL187156C; FR2327213B1; DE2645030C2

Description

(54) PROCESS FOR PRODUCING BUTANEDIOL OR BUTENEDIOL (71) We, MITSUBISHI CHEMICAL INDUSTRIES LIMITED, a Japanese body corporate, of 5-2, Marunouchi 2-chome, Chiyoda-ku, Tokyo, Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a process for producing butanediol or butenediol and, in more particular, to a process for producing a diol comprising subjecting acetic diester of 1,4butanediol or 1 ,4-butenediol-2 to hydrolysis to obtain the corresponding butanediol or butenediol.

It has already been known that 1,4-butanediol is useful as an organic solvent or a raw material for tetrahydrofuran from which an organic solvent, such as 1 ,4-butanediol or y-butyrolactone, is derived and it has also been practiced that 1,4-diacetoxybutane is subjected to hydrolysis to obtain 1,4-butanediol.

From our intensive study of the production of a glycol, especially 1,4-butanediol or 1 ,4-butenediol-2, by hydrolysis of an acetic diester of a glycol, it has been found that 1,4-diacetoxybutane and 1,4-diacetoxybutene-2 are immiscible with water, but hydrolysis products thereof are miscible with water, and, in particular, the solubility of such acetic diester in water increases in the presence of the diol and monohydroxyacetoxybutane or monohydroxyacetoxybutene which is partial hydrolysis product of the diester, and, in conse pence, a homogeneous solution of diacetic ester in water can be obtained.It has also been found that the raw material acetic diester, its partial hydrolysis product monohydroxyacetoxybutane and the hydrolysis product diol form an azeotropic mixture, and, accordingly, if such hydrolysis products are recovered by azeotropic distillation from the reaction product and recirculated together with the raw material to the hydrolysis stage, the entire process can conveniently be carried out. Furthermore, it has been found that, by effecting the hydrolysis in two stages and recirculating a portion of the resulting hydrolysis products to predetermined hydrolysis stages, the efficiency of the process can be improved.

An object of this invention, accordingly, is to provide a process for producing 1,4butanediol or 1,4-butenediol-2 in high yield by subjecting 1,4-diacetoxybutane or 1,4diacetoxybutene-2 to hydrolysis.

Another object is to provide a process for producing 1 ,4-butanediol or 1 ,4-butenediol-2 by hydrolyzing 1 ,4-diacetoxybutane or 1 ,4-diacetoxybutene-2 wherein the hydrolysis is effected in a homogeneous aqueous system and an azeotropic mixture recovered from the hydrolysis product is recirculated to the hydrolysis stage thereby allowing the reaction to proceed smoothly, utilizing byproducts effectively and saving energy.

This invention will be explained in detail hereunder.

It is already known that 1 ,4-diacetoxybutene-2 and 1 4-diacetoxybutane which are the raw materials used in this invention are synthesized from butadiene and acetic acid by various oxidation acetoxylation processes. For example, 1,4-diacetoxybutene-2 is produced by reacting 1 ,4-butadiene, acetic acid and oxygen or an oxygen-containing gas in the presence of a palladium series catalyst through any process using a fixed bed, a fluidized bed or a suspended catalyst system.Examples of the catalyst which may be employed in this reaction include, for example, a homogeneous liquid catalyst, such as a Redox system of a palladium salt and a copper salt, and a solid catalyst of metallic palladium, platinum, rhodium, iridium or ruthenium or a salt thereof or a combination of such metal or salt with, as a cocatalyst, metallic copper, silver, zinc, nickel, chromium, iron, cobalt, cadmium, tin, lead, molyb denum, tungsten, antimony, tellurium, selenium, bismuth, an alkali metal or an alkaline earth metal or a salt thereof; in particular, a supported catalyst consisting essentially of metallic palladium and, as a metallic cocatalyst, at least one member selected from bismuth, selenium, antimony and tellurium.From the acetoxylation product thus obtained, a mixture of diacetoxybutenes such as 1,4-diacetoxybutene-2 and 3,4-diacetoxybutene-1 is separated by distillation and is used as the raw material in the reaction according to this invention; if desired, such mixture of diacetoxybutenes is subjected to isomer separation before use.

Alternatively, 1,3- and 1 ,4-dichlorobutenes, acetic acid and sodium acetate are reacted in the presence of a metal salt catalyst to obtain a mixture of diacetoxybutenes which may be used as such in the process according to this invention.

Diacetoxybutanes are produced by subjecting the mixture of diacetoxybutenes thus obtained to hydrogenation in the presence of a palladium or nickel catalyst, and may be used in the form of either a mixture or a single isomer of 1,4-, 1,2- or 1,3-diacetoxybutane separated. In the hydrogenation of the diacetoxybutene, butylacetate may often be byproduced depending upon the performance of the catalyst employed.

It is preferable to use diacetoxybutane having a purity of more than 99% which may be obtained by, for example, after degasification, subjecting the crude diacetoxybutane to distillation in a column under such conditions as, for example, the number of theoretical plates being from 15 to 25, at a bottom temperature of below 1900C., under a head pressure of from 50 to 200 Torr. and at a reflux ratio of from 1 to 5.

According to this invention, the diacetoxybutane or diacetoxybutene is contacted with a solid acid catalyst bed to effect hydrolysis. The solid acid catalyst may be silica-alumina, activated clay, silica or a cation exchange resin; in particular, a cation exchange resin is preferable, because it gives a higher hydrolysis rate and produces less amount of byproducts, typically tetrahydrofuran. A typical cation exchange resin is a sulfonic acid type strong acid cation exchange resin the matrix of which is a copolymer of styrene and divinyl benzene and it may be either gel type or porous type, for example, SK 1B, SK 103, SK 106, PK 206, PK 216 or PK 228 available from Mitsubishi Chemical Industries Limited, Tokyo, Japan.

The hydrolysis reaction is carried out at a temperature of, in general, from 30 to 1200C, preferably 40 to 100"C and more preferably 50 to 800C. The lower the temperature, the slower the reaction rate is, so too low a temperature requires a large amount of the catalyst; on the other hand, at too high a temperature, large amounts of byproducts such as tetrahydrofuran and dihydrofuran are formed to decrease the yield of the desired product.For example, where diacetoxybutane is hydrolyzed using "SK 1B" catalyst, the proportion of tetrahydrofuran to butanediol in the reaction product is 5:100 by weight at most at a temperature below 100"C and 23:100 by weight at 1200C, respectively whereas at a temperature above 140"C a half or a major amount of the product is the byproduct tetrahydrofuran.

Further, within the above temperature range, degradation of the cation exchange resin is prevented and dissolution of the resin is also reduced.

The pressure under which the reaction is carried out is not critical but a pressure under which boiling or undue bubbling of dissolved gas is prevented is preferred and, in general, such pressure is from atmospheric to 10 kg/cm2G.

A stoichiometric or excess amount of water to diacetoxybutene or diacetoxybutane is conveniently used, since the water is a reactant and also a solvent. In order to have the reaction proceed smoothly, it is preferred to conduct the reaction in a homogeneous aqueous system. The raw material acetoxybutane or diacetoxybutene can dissolve in an excessively large amount of water to form a homogeneous aqueous solution, and the larger the amount of water, the higher the conversion of the reactions; but too much water requires a large amount of heat in recovering butanediol or butenediol from the reaction product and this is uneconomical. On the other hand, too little water decreases the conversion and, in consequence, the recovery of butanediol or butenediol becomes difficult.Thus, according to this invention, the molar ratio of water to diacetoxybutane or diacetoxybutene ranges, in general, from 2 to 100:1, preferably 4 to 50:1.

In order to form a uniform aqueous solution to be supplied to the hydrolysis stage without using an excessively large amount of water and to effect the reaction smoothly according to this invention, it is essential that the raw material diacetoxybutane or diacetoxybutene be mixed with either (1) a portion of the reaction product from which water and acetic acid have been removed or (2) an azeotropic mixture of acetic diester, monohydroxyacetic ester and diol obtained from the reaction product from which water and acetic acid have been removed.

Although the removal of water and acetic acid from the reaction product may be effected in separate distillation stages, it should be noted that, if the reaction product is maintained in a state of high acetic concentration at high temperature, there is observed a reverse reaction with the result of lowering the yield of the desired diol. Thus, it is preferable to distil off substantially all of the water and acetic acid together. Further, in the distillation at a bottom temperature of distillation column above 210 C, the conversion of 1,4-butanediol into undesirable tetrahydrofuran is accelerated, so it is convenient to effect the distillation at a temperature, in general, up to 2000C, preferably up to 1900C.

A portion of the reaction product from which water and acetic acid have been distilled out is recirculated to the hydrolysis stage after being mixed with the raw material acetic diester and water. The amount to be recirculated may vary depending upon reaction conditions, such as, the reaction temperature, the proportion of components in the reaction system and the conversion of reaction. Further, it is convenient that the water separated by distillation from the water-acetic acid fraction be used in the hydrolysis stage in order to operate the process in a closed system; in this case, depending upon distillation conditions, the water often contains some acetic acid which facilitates the formation of a homogeneous aqueous solution of the feed material.For this reason, the amount to be recirculated cannot be standardized and is usually from 0.5 to 10 times, preferably 1 to 3 times by weight that of the sum of water and the raw material acetic diester.

Where an azeotropic mixture containing acetic diester, monohydroxyacetic ester and diol separated from the reaction product from which acetic acid and water have been removed is recirculated to the hydrolysis stage, the amount to be recirculated is usually less than the above case and, in general, from 0,05 to 10 times, preferably 0.1 to 1 time.

In Figs. 4-A and 4-B of the accompanying drawings, the equilbrium of the azeotropic mixture of 1,4-diacetoxybutane (1,4-DAB) which may contain 1,2- and 1,3-isomers and 1 ,4-butanediol (1,4-BG) is given and the horizontal axes represent the mol fraction of 1,4-DAB in the liquid phase (x: 1,4-DAB) and the vertical axes represent the azeotropic temperature and the mol fraction of 1,4-DAB in the gas phase (y: 1,4-DAB), respectively.

Figs. 5-A and 5-B of the accompanying drawings show the equilibrium of the azeotropic mixture of 1-hydroxy-4-acetoxybutane (1,4-HAB) and butanediol similar to that of Figs. 4-A and 4-B.

The constants of A12 and A21 according to Wilson's equation for the 1,4diacetoxybutane/ 1,4-butanediol system are 0.407 and 0.354, respectively. The Wilson's equation is disclosed in the Journal of the American Chemical Society, Vol. 86, p. 127 (1964) by G. M. Wilson.

Thus, the azeotropic distillation is conveniently carried out using a distillation column having the number of theoretical plates of from 20 to 90 and operated at a bottom temperature of from 150 to 200"C, under a head pressure of from 10 to 200 mmHg, preferably 30 to 100 mmHg and at a reflux ratio of from 1 to 10, preferably 2 to 5.

Where the raw material 1 ,4-diacetoxybutane or 1 ,4-diacetoxybutene-2 contains 1,2- and 1,3-isomers, the distillation of the reaction product is conducted so that 1,2- and 1,3-diols are distilled out as overhead, while the 1 ,4-diol product is recovered as a side stream, and the distillation column is operated at a reflux ratio of from 2 to 10, preferably 3 to 6.

If the raw material consists essentially of 1 ,4-diacetoxybutane or 1 ,4-diacetoxybutene-2, the azeotropic mixture is directly recirculated to the hydrolysis stage. On the other hand, if the raw material contains isomers, acetic acid and materials having boiling points lower than acetic acid are separated from the hydrolysis product by distillation in a first distillation column, and the residue is subjected to an azeotropic distillation in a second distillation column to obtain mixture containing monohydroxyacetic ester and acetic diester consisting of 1,4-, 1,2- and 1,3-isomers and the mixture is recirculated to the hydrolysis stage after separating 1,2- and 1,3-isomers.

From a practical point of view, however, it is convenient that such isomer separation be effected by removing 1,2- and 1,3-isomers as an overhead and 1,4-isomers of the acetic diester, monohyroxyacetic ester and diol as a side stream in the second column, the latter being recirculated.

Accompanying drawings of Figs. 1 to 3 illustrate flow sheets of apparatus suitable for the practice of the process according to this invention.

Embodiments of this invention will be explained hereunder referring to the drawings.

Although the embodiments are directed to the production of butanediol, it should be understood that butenediol is also equally produced by changing the raw material to diacetoxybutene.

Referring to Fig. 1, I represents a hydrolysis reactor which contains a solid acid catalyst bed, preferably a sulfonic acid type cationic exchange resin, and III represents a distillation column. The raw material acetic diester and water is supplied via pipe lines 10 and 12 to the reactor I while the hydrolysis product is recirculated via pipe line 22 to form a homogeneous aqueous solution. In order to facilitate the mixing of them, it is convenient to provide, for example, a dissolving tank with a stirrer before the reactor, or a stirring device or a static mixing device in the pipe line connecting with the reactor. Alternatively, trays or a packed layer may be provided in the upper space of the reactor.

The space velocity of the liquid reactants to be supplied to the reactor may vary depending upon, for example, the proportion of the acetic diester and water and the reaction tempera ture, and this value is, in general, from 0.05 to 10 [e/.hr], preferably 0.2 to 2 le/ehr].

The reaction product which contains unreacted raw material, monoester formed by partial hydrolysis and diol and acetic acid formed by hydrolysis is discharged from the reactor via pipe line 14 followed by passing through anion exchange resin vessel V to remove bisulfite ion dissolved from the cation exchange resin and transferring via pipe line 16 to distillation column III.In the distillation column, the water and the acetic acid are distilled off from the top via pipe line 18 while the residue is discharged via pipe line 20, a portion of said residue being recirculated to the hydrolysis reactor via pipe line 22 and the remaining portion being supplied via pipe line 24 to a subsequent processing stage (not shown), for example, the distillation of diol as well as of the unreacted diester and the acetic monoester partial hydrolysis product, the latter two, then, being recirculated to the reactor, if desired.

Fig. 2 shows another embodiment in which distillation of the reaction product is effected in two columns. The supply of the reactants to the reactor and the hydrolysis are conducted in way similar to those of Fig. 1.

The raw material acetic diester, water and the recirculating hydrolysis product are supplied via pipe lines 10, 12 and 22 to hydrolysis reactor I and the hydrolysis product is supplied, in turn, via pipe line 14 to anion exchange resin vessel V and via pipe line 16 to first distillation column III, from the top of column III, acetic acid, water and materials boiling lower than acetic acid are distilled out through piping 18, while the residue is discharged from the bottom and transferred via pipe line 20 to second distillation column IV. In the second column, an azeotropic mixture containing acetic diester, monohydroxymonoacetic ester and diol is removed from the top and is recirculated via pipe line 22 to the hydrolysis reactor.Where the reaction product contains 1,3- and 1,2-isomers, a fraction containing mainly 1,2- and 1,3isomers is distilled out from the top while a fraction containing mainly 1,4-isomers is removed as a side stream which is recirculated via pipe line 26 to the hydrolysis reactor. The residue of the second column is discharged from the bottom via pipe line 24 and is supplied to subsequent processing stage (not shown), for example, distillation or extraction to obtain the diol product.

Fig. 3 shows still another embodiment which is most suitable for this invention from the point of view of commercial practice. This embodiment involves two-stage hydrolysis. The first stage hydrolysis product is subjected to the second hydrolysis after removing acetic acid thereby increasing the conversion of hydrolysis remarkably.

To the first hydrolysis stage is supplied aqueous acetic acid recovered and recirculated from the second acetic acid distillation column and to the second hydrolysis stage are supplied the first acetic acid distillation column residue containing acetic diester, monohydroxyacetic ester and diol and a fraction containing monohydroxyacetic ester and acetic diester recovered from the unreacted raw material recovery column.

In Fig. 3, I and II are first and second hydrolysis reactors, III and IV are first and second acetic acid distillation columns, VI is a water-acetic acid separation column, VII is an unreacted raw material recovery column and VIII is a rectifying column. In the hydrolysis reactors, a solid acid catalyst, such as sulfonic acid type cation exchange resin, is packed.

The raw material diacetoxybutane, water and aqueous acetic acid recovered from the second acetic acid distillation column are supplied via pipe lines 10, 12 and 28, respectively, and mixed to form a homogeneous aqueous feed which is supplied to first hydrolysis reactor I.

The space velocity of the feed materials to the reactor is maintained at a level similar to that of Fig. 1. The reaction product from the first reactor is supplied via pipe line 16 to first acetic acid distillation column III. From the top of the first column, a fraction containing mainly water and acetic acid is distilled out and transferred via pipe line 18 to water-acetic acid separation column VI to which is optionally supplied via pipe line 30 an acetic acid fraction recovered from other reaction system, such as an acetoxylation system. Acetic acid is recovered from the bottom of separation column via pipe line 32 while a water fraction is recovered via pipe line 34 as a side stream and a low boiling fraction containing mainly tetrahydrofuran is removed from the top via pipe line 36.Where the raw material contains butylacetate which is a byproduct in the production of diacetoxybutane by hydrogenation of diacetoxybutene, the overhead containing butylacetate is separated into an aqueous layer and an oily layer, and the latter is conveniently recirculated to the second distillation column.

The water fraction recovered as above is supplied via pipe line 34 to second hydrolysis reactor II after being mixed with the first acetic acid distillation column residue containing mainly acetic diester, monohydroxyacetic ester and diol supplied via pipe line 20 and with a side stream from the unreacted raw material recovery column containing monohydroxyacetic ester and acetic diester supplied via pipe line 38.

The reaction product from the second reactor is supplied via pipe line 40 to second acetic distillation column IV in which substantially all of the water and acetic acid is distilled off from the top and recirculated to the first reactor via pipe line 28. In general, because the acetic acid formed in the first hydrolysis stage has been removed in the first acetic acid distillation column, the acetic acid present in this fraction is derived from the second hydrolysis and has a concentration of from about 7 to about 14% by weight. This acetic acid within such concentration range is capable of forming a uniform aqueous solution with the reactants to be supplied to the first hydrolysis stage and does not adversely affect the hydrolysis reaction.

The residue of the second distillation column contains mainly 1,4-butanediol, 1,4diacetoxybutane and 1-hydroxy-4-acetoxybutane and is transferred via pipe line 42 to unreacted raw material recovery column VII. From the top of the recovery column, a fraction containing diacetoxybutane, monohydroxyacetoxybutane and a small amount of butanediol is distilled off and recirculated to the second hydrolysis stage. However, where the liquid feed contains 1,4-isomer as well as 1,2- and 1,3-isomers, a fraction containing mainly 1,2- and 1,3-isomers is distilled off from the top and a fraction containing 1,4-isomers of unreacted acetic diester and monohydroxyacetic ester is removed as a side stream which is recirculated via pipe line 38 to the second hydrolysis stage.

The residue of the recovery column is supplied via pipe line 46 to rectifying column VIII.

The 1 ,4-butanediol product of a commercial grade is recovered as a side stream via pipe line 48, while the overhead is recirculated via pipe line 50 to the recovery column and the residue containing high boiling fraction is removed via pipe line 24 and subjected to a subsequent recovery process (not shown), if required.

As mentioned above, according to this invention the reaction is effected using a homogeneous aqueous solution prepared by mixing the raw material acetic diester, monohydroxyacetic ester, diol and optionally acetic acid, with the result that the reaction proceeds smoothly, the conversion of reaction is increased, the raw material is effectively utilized, whereby the desired product diol is obtained in high yield.

Further, if the process according to this invention is carried out in two-stage hydrolysis, each of the various fractions recovered from the distillation stages is recirculated to the specified preceding hydrolysis stages; thus, it is possible to effectively utilize acetic diester and monohydroxyacetic ester by recirculation, and thus to have the reaction proceed smoothly in a unform aqueous solution and to achieve high conversion of reaction. Moreover, this embodiment can save energy and is commercially useful in comparison with a process in which hydrolysis of acetic diester is effected in a single stage and the product diol is recovered from the hydrolysis product by distillation.

This invention will be explained in detail by means of Examples. However, it should be understood that this invention is in no way limited by these Examples.

Example 1: In this Example, the process was carried out utilizing the apparatus illustrated in Fig. 1.

The reaction vessel was made of stainless steel SUS 31 6L with an inner diameter of 10 cm and a length of 80 cm and packed with 3.0e of cation exchange resin, SK 1B H type available from Mitsubishi Chemical Industries Limited, Tokyo, Japan, to make a bed thickness 46 cm.

To the reactor were supplied downwardly 1 ,4-diacetoxybutane, water and the recirculating residue of the distillation column at a rate of 209.0 g/hr, 394.9 g/hr and 1177.5 g/hr, respectively, at a temperature of 60"C after being mixed in the supply tube. The liquid hydrolysis product was passed through a vessel packed with 0.5e of anion exchange resin, WA-20, available from Mitsubishi Chemical Industries Limited, and transferred to the distillation column which was made of stainless steel SUS 31 6L with an inner diameter of 40 mm and a length of 5 m and packed with 7 x 7 mm porcelain Raschig rings.The liquid product was supplied at 1 m below the top of the distillation column operated at a bottom temperature of 175"C, under a head pressure of 100 Torr. and a reflux ratio of 2.1, and the overhead and the residue were recovered at a rate of 472.6 g/hr and 1308.4 g/hr, respectively.

The composition of the residue was as follows: 1 ,4-diacetoxybutane 7.8% (by weight) 1 ,4-hydroxyacetoxybutane 43.0% 1 ,4-butanediol 49.0% A portion of the residue was recirculated to the reactor at a rate of 1177.5 g/hr and the remainder was supplied to a further purification system to separate and recover 1,4butanediol.

By the above continuous operation, the proportion of 1 ,4-butanediol supplied to the purification system was 59.3% molar on the basis of the raw material diacetoxybutane.

Comparative Example 1: The hydrolysis reaction was carried out according to procedures similar to those of Example 1 excepting that no liquid reaction product was recirculated; then, at the inlet of the reaction vessel, two liquid phases were observed and the reaction did not proceed smoothly.

The proportiono f 1,4-butanediol supplied into the purification system was only 10.3 % molar on the basis of the raw material diacetoxybutane.

Example 2: The procedures of Example 1 were repeated excepting that 1 ,4-diacetoxybutene-2 was used instead of the diacetoxybutane. There was observed a homogeneous liquid feed supplied to the reactor and the proportion of 1,4-butenediol-2 supplied to the purification system was 58.3% molar on the basis of the raw material.

Comparative Example 2: Procedures similar to those of Example 2 were followed excepting that no liquid residue was recirculated from the distillation column; then at the inlet of the hydrolysis reactor the feed was separated into two phases and the reaction did not proceed smoothly. The proportion of 1 ,4-butenediol-2 supplied to the purification system was only 9.8 % molar on the basis of the diacetoxybutene.

Example 3: The process was carried out according to Example 1 but the raw material diacetoxybutane contained 13.3% of 1,2-isomer and 1.3%, by weight, of 1,3-isomer.

The proportion of 1,4-butanediol supplied to the purification system was 58.5% molar.

Example 4: In this Example, the process was carried out using the apparatus illustrated in Fig. 2 in which the hydrolysis reactor and the anion exchange resin vessel were same as used in Example 1.

To the reactor were supplied downwardly 1 4-diacetoxybutane, water and the recirculating liquid from the second distillation column at a rate of 399.5 g/hr, 687.8 g/hr and 839.4 g/hr, respectively, at a temperature of 60"C after being uniformly mixed in the supply tube. The liquid reaction product was passed through a vessel packed with 0.5t of WA-20 anion exchange resin and supplied continuously to the first distillation column which was made of stainless steel SUS 31 6L with an inner diameter of 40 mm and a length of 5 m and packed with 7 x 7 mm porcelain Raschig rings.The supply of the feed was made at 1 m below the top of the column operated at a bottom temperature of 174"C, under a head pressure of 100 Torr. and at a reflux ratio of 2 to obtain an overhead at a rate of 880.9 g/hr and a residue at a rate of 1045.9 g/hr. The composition of the residue was as follows: 1 ,4-diacetoxybutane 20.7% (by weight) 1-hydroxy-4-acetoxybutane 52.0% 1 ,4-butanediol 27.3% The residue was transferred to the second distillation column which was made of stainless steel SUS 316L with an inner diameter of 30 mm and a length of 10.5 m and packed with Dickson packings (60 mesh and 60 mm) and operated at a bottom temperature of 176"C, under a head pressure of 78 mmHg and at a reflux ratio of 2.0.

An overhead having the following composition was obtained at a rate of 839.4 g/hr and was recirculated to the reactor: 1,4-diacetoxybutane 25.8% (by weight) 1-hydroxy-4-acetoxybutane 64.7% 1 ,4-butanediol 9.5% Also, a residue containing 99.6% by weight of 1,4-butanediol was obtained at a rate of 206.5 g/hr.

Thus, the yield of 1,4-butanediol recovered as the product was 99.52% molar on the basis of the raw material 1,4-diacetoxybutane.

Similar procedures were repeated using 1 ,4-diacetoxybutene-2 instead of the 1,4diacetoxybutane to obtain similar results.

Comparative Example 4: The process was carried out following the procedures of Example 4 excepting that no overhead from the second column ws recirculated to the reactor; then there was observed phase separation of the feed at the inlet of the reactor and the reaction did not proceed smoothly. The yield of 1,4-butanediol recovered from the second column was only 13.2% molar on the basis of the raw material 1,4-diacetoxybutane.

Example 5: In this Example, the raw material was 1,4-diacetoxybutane containing 1,2- and 1,3-isomers and the process was carried out utilizing the apparatus of Fig. 2 according to procedures similar to those of Example 4 excepting that the fraction recirculated to the reactor was a side stream from the second distillation column.

The feed materials supplied to the reactor were (1) a mixture containing 90.1% of 1,4-diacetoxybutane, 8.7% of 1,2-diacetoxybutane and 0.4%, by weight, of 1,3diacetoxybutane at a rate of 403.2 g/hr, (2) water containing 11.5%by weight of acetic acid at a rate of 706.6 g/hr and (3) a side stream fraction containing 1,4-diacetoxybutane, 1-hydroxy-4-acetoxybutane and 1,4-butanediol which was removed at 2.5 m below the top of the second column operated at a reflux ratio of 80. The overhead of the second column contained 1,2- and 1,3-isomers.

The yield of 1 ,4-butanediol recovered from the second column as a residue was 99.46% molar on the basis of the 1 ,4-diacetoxybutane.

Example 6: In this Example the process was carried out using the apparatus of Fig. 3.

The first hydrolysis reactor was made of stainless steel SUS 304 with an inner diameter of 2.5 m and a length of 10 m and packed with 30 m3 SK 1B H type cation exchange resin. To the reactor were supplied liquid diacetoxybutane, the circulating liquid from the second acid separator and feed water containing 17.4% by weight of acetic acid at a rate of 4151 kg/hr, 3866 kg/hr and 355 kg/hr, respectively, at 600C under 2 kg/cm2G. The liquid diacetoxybutane had the following composition: 1 ,4-diacetoxybutane 87.7% (by weight) 1 ,2-diacetoxybutane 8.4% 1-hydroxy-2-acetoxybutane 3.9% From the reactor, a residue having the following composition was removed at a rate of 8372 kg/hr.

H2O 27.2% (by weight) acetic acid 33.8% 1 ,4-diacetoxybutane 12.4% 1-hydroxy-4-acetoxybutane 16.7% 1 ,4-butanediol 4.7% 1 ,2-diacetoxybutane 1.9% others 3.3% The residue was supplied to the first acetic acid separation column which was made of stainless steel SUS 316 with an inner diameter of 2 m and a length of 5 m and containing 10 valve trays and operated at a bottom temperature of 1900C., under a head pressure of 100 Torr. and at a reflux ratio of 0.1 to obtain a distillate containing 55.4%by weight of acetic acid at a rate of 5109 kg/hr.The distillate was supplied to the water-acetic acid separation column which was made of stainless steel SUS 316 with an inner diameters of 2900 mm at recovery zone and 2000 mm at concentration zone and a length of 34 m and containing 64 perforated plates and operated at a bottom temperature of 125"C, under a head pressure of 400 Tort.

and at a reflux ratio of 570, and simultaneously, the recovered acetic acid (the concentration being 95.8% by weight) from the acetoxylation stage was supplied at a rate of 18172 kg/hr.

Recovered from the separation column were a low boiling fraction containing tetrahydrofuran at the top and an aqueous fraction containing 3.2% by weight of acetic acid at the 20th tray from the top as a side stream at a rate of 10 kg/hr and 2880 kg/hr, respectively.

The residue of the first acetic acid separation column (3264 kg/hr), the side stream of the water-acetic acid separation column (2880 kg/hr) and the side stream of the unreacted raw material recovery column (7223 kg/ hr) were supplied to the second hydrolysis reactor which was similar to and operated under the same conditions as for the first reactor.

The hydrolysis product having the following composition from the second reactor was supplied at a rate of 13365 kg/hr to the second acetic acid separation column the size and the operation conditions of which were the same as those of the first separation column: H2O 17.7% (by weight) acetic acid 11.2% 1,4-diacetoxybutane 13.1% 1-hydroxy-4-acetoxybutane 34.7% 1 ,4-butanediol 19.2% 1 ,2-diacetoxybutane 0.8% others 3.3% The overhead containing 38.9% by weight of acetic acid from the second separation column was recirculated to the first reactor at a rate of 3866 kg/hr.The residue was supplied to the unreacted raw material recovery column which was made of stainless steel SUS 304 with an inner diameter of 2900 mm and a length of 25 m and containing 60 valve trays and operated at a bottom temperature of 1900C, under a head pressure of 77 Torr. and at a reflux ratio of 80 and, simultaneously, the overhead of the rectifying column was supplied at a rate of 53 kg/hr. Recovered from the recovery column were an overhead containing 1,2-isomers, mainly 1,2-diacetoxybutane, at a rate of 393 kg/hr, a side stream at the 15th tray from the top containing 1,4-diacetoxybutane, 1-hydroxy-4-acetoxybutane and 1,4-butanediol at a rate of 7223 kg/hr, said side stream being recirculated to the second reactor, and a residue of the 1,4-butanediol product (purity being 99% by weight) at a rate of 1936 kg/hr.

The residue was supplied to the rectifying column which was made of stainless steel SUS 304 with an inner diameter of 1700 mm and a length of 17 m and having 21 valve trays and operated at a bottom temperature of 1900C, under a head pressure of 100 Torr. and at a reflux ratio of 40. Recovered from the rectifying column were a side stream of the 1,4 butanediol product at the 4th tray from the top, an overhead containing tetrahydrofuran and a small amount of 1,4-butanediol and a residue containing high boiling materials and a small amount of 1,4-butanediol at a rate of 1775 kg/hr, 53 kg/hr, and 55 kg/hr, respectively.

From the above Example 6, and also from the description of Fig. 3, it will be appreciated that the invention includes a process for producing 1 ,4-butanediol comprising contacting 1 ,4-diacetoxybutane and water with a solid acid catalyst in two reaction vessels characterized by the steps of: (a) continuously supplying 1 ,4-diacetoxybutane, water and an overhead obtained from a second acetic acid distillation column as in step (e) below to a first hydrolysis reactor to effect catalytic reaction, (b) supplying the liquid reaction product to a first acetic acid distillation column to distill off a water-acetic acid fraction, (c) separating water from said fraction in a water-acetic acid separation column, (d) supplying the residue obtained from the first acetic acid distillation column in the step (b), the water obtained from the step (c) and the recirculating liquid obtained from the step (f) below to a second hydrolysis reactor to effect catalytic reaction, (e) supplying the resulting liquid reaction product to a second acetic acid distillation column to obtain an overhead of water-acetic acid fraction which is recirculated to the step (a), (f) supplying the residue obtained from the second acetic acid distillation column to an unreacted raw material recovery column to recover unreacted diacetoxybutane and a monohydroxy- monoacetoxybutane-containing fraction, which are recirculated to the step (d), and (g) recovering the residue from the recovery column containing mainly 1,4-butanediol.

WHAT WE CLAIM IS: 1. A process for producing butanediol or butenediol comprising contacting a mixture containing water and diacetoxybutane or diacetoxybutene with a solid acid catalyst bed to effect hydrolysis, wherein a portion of the hydrolysis product from which water and acetic acid have been removed is mixed with said water and said raw material acetic diester to form a homogeneous aqueous solution which is then supplied to said bed.

2. A process as claimed in claim 1, wherein the hydrolysis product from which acetic acid and water have been removed is subjected to azeotropic distillation to obtain a mixture containing acetic diester, monohydroxyacetic ester and diol and said mixture is mixed with water and acetic diester to form a homogeneous aqueous solution which is then supplied to said bed.

3. A process as claimed in claim 1 or claim 2 wherein said diacetoxybutane is 1,4diacetoxybutane.

4. A process as claimed in any one of claims 1 to 3 wherein the proportion of the hydrolysis product to be mixed is from 0.5 to 10 times by weight that of the sum of the raw material diacetoxybutane or diacetoxybutene and water.

5. A process as claimed in any one of claims 1 to 4, wherein the proportion of said hydrolysis product to be mixed is from 1 to 3 times by weight that of the sum of said raw material diacetoxybutane or diacetoxybutene and water.

6. A process as claimed in claim 2, wherein the proportion of said mixture to be mixed is from 0.05 to 10 times by weight that of the sum of said raw material diacetoxybutane or diacetoxybutene and water.

7. A process as claimed in claim 2 wherein the proportion of said mixture to be mixed is from 0.1 to 1 time by weight that of the sum of said raw material diacetoxybutane or diacetoxybutene and water.

8. A process as claimed in claim 2, claim 6 or claim 7, wherein said azeotropic distillation is effected in a distillation column having the number of theoretical plates of from 20 to 90 and operated at a bottom temperature of from 150 to 2000C, under a head pressure of from 10 to 200 mmHg and at a reflux ratio of from 1 to 10.

9. A process for producing 1 ,4-butanediol comprising contacting 1 ,4-diacetoxybutane and water with a solid acid catalyst in two reaction vessels characterized by the steps of: (a) continuously supply 1,4-diacetoxybutane water and an overhead obtained from a second acetic acid distillation column as in step (e) below to a first hydrolysis reactor to effect catalytic reaction, (b) supplying the liquid reaction product to a first acetic acid distillation column to distill off a water-acetic acid fraction, (c) separating water from said fraction in a water-acetic acid separation column, (d) supplying the residue obtained from the first acetic acid distillation column in the step (b), the water obtained from the step (c) and the recirculating liquid obtained from the step (f) below to a second hydrolysis reactor to effect catalytic reaction, (e) supplying the resulting liquid reaction product to a second acetic acid distillation

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. butanediol product at the 4th tray from the top, an overhead containing tetrahydrofuran and a small amount of 1,4-butanediol and a residue containing high boiling materials and a small amount of 1,4-butanediol at a rate of 1775 kg/hr, 53 kg/hr, and 55 kg/hr, respectively. From the above Example 6, and also from the description of Fig. 3, it will be appreciated that the invention includes a process for producing 1 ,4-butanediol comprising contacting 1 ,4-diacetoxybutane and water with a solid acid catalyst in two reaction vessels characterized by the steps of: (a) continuously supplying 1 ,4-diacetoxybutane, water and an overhead obtained from a second acetic acid distillation column as in step (e) below to a first hydrolysis reactor to effect catalytic reaction, (b) supplying the liquid reaction product to a first acetic acid distillation column to distill off a water-acetic acid fraction, (c) separating water from said fraction in a water-acetic acid separation column, (d) supplying the residue obtained from the first acetic acid distillation column in the step (b), the water obtained from the step (c) and the recirculating liquid obtained from the step (f) below to a second hydrolysis reactor to effect catalytic reaction, (e) supplying the resulting liquid reaction product to a second acetic acid distillation column to obtain an overhead of water-acetic acid fraction which is recirculated to the step (a), (f) supplying the residue obtained from the second acetic acid distillation column to an unreacted raw material recovery column to recover unreacted diacetoxybutane and a monohydroxy- monoacetoxybutane-containing fraction, which are recirculated to the step (d), and (g) recovering the residue from the recovery column containing mainly 1,4-butanediol. WHAT WE CLAIM IS:

1. A process for producing butanediol or butenediol comprising contacting a mixture containing water and diacetoxybutane or diacetoxybutene with a solid acid catalyst bed to effect hydrolysis, wherein a portion of the hydrolysis product from which water and acetic acid have been removed is mixed with said water and said raw material acetic diester to form a homogeneous aqueous solution which is then supplied to said bed.

column to obtain an overhead of water-acetic acid fraction which is recirculated to the step (a), (f) supplying the residue obtained from the second acetic acid distillation column to an unreacted raw material recovery column to recover unreacted diacetoxybutane and a monohydroxy- monoacetoxybutane-containing fraction, which are recirculated to the step (d), and (g) recovering the residue from the recovery column containing mainly 1 ,4-butanediol.

10. A process as claimed in claim 9, wherein the raw material 1,4-diacetoxybutane contains 1,3- and 1,2-isomers and, in the step (f), an overhead containing mainly 1,3- and 1,2-isomers is distilled out while a side stream containing mainly 1,4 isomers of unreacted diacetoxybutane and monohydroxyacetoxybutane is recovered and recirculated to the step (d).

11. A process as claimed in claim 1 and substantially as hereinbefore described with reference to any one of the Examples.