US2987557A - Process for manufacture of acetylenic alcohols - Google Patents

Description

June 6, 1961 J. HAPPEI. ETAL PROCESS FOR MANUFACTURE OF' ACETYLENIC ALCOHOLS Original Filed Aug. 1l, 1955 ZODAOm I9: l'

trum Ik@ OF 10k mDOtQ IZ mT tOhO t All om: m21 mrw a vom N5 s om mms KNHS: QmvGOtnI IO! Qmhm'jml a LWL- John Happel im Charles J. Morse! lnvenors Attorney United States Patent O 1 Claim. (Cl. 26o-63s) This invention is concerned generally with a continuous and commercially practical process for the production of acetylenic hydrocarbons by a series of interrelated and coacting steps, and more specifically, with a particularly useful method for the manufacture of 2-methyl1,5hexa diene-S-yne.

It has been previously known to produce various hydrocarbons having unsaturated bonds, including both double and triple fbonds, by thermal pyrolysis. This drastic technique is only applicable to the less complicated types of hydrocarbon structures. For instance, methyl acetylene has previously been made by the thermal pyrolysis method, but only in relatively low yields. However, it is substantially impossible to produce complicated molecular structures having a multiplicity of double and triple bonds by this method.

Organic compounds having both acetylenic bonds and olenic double bonds give especial diiculty in their production even on laboratory and small batch type operations. Various diticulties are encountered in the application of the known methods, including the degradation and decomposition reactions of both the starting materials as well as the acetylenic olen hydrocarbon products. Such `byproducts and side reactions result in both loss in yield of product as well as loss of the relatively expensive starting material.

The present invention is concer-ned with improved means for producing acetylenic alcohols and includes irnprovements in addition to those described in copending application U.S. Serial No. 384,846, filed October 8, 1953, now abandoned, of which the instant application is a continuation-in-part. This invention is more particularly concerned with the production of the acetylenic alcohols and employs valuable improvements in the condensation step between the acetylenic hydrocarbon with the carbonyl compound.

This application is a divisional application of U.S. Serial No. 527,828, tiled August 11, 1955, now U.S. Patent 2,922,765, issued January 26, 1960.

Certain of the organic compounds of the class of the alkyl olefinic acetylenes, especially 2-methyl-1,5hexa diene-B-yne, may be prepared by the process of this invention. This class of compounds contains both the acetylenic bond and multiple oleiinic bonds, and consequently gives the above described diiiculties in their preparation by previously known methods.

In general, the invention involves a method for synthesizing acetylenic hydrocarbons by the combination of carbonyl compounds which may be either aldehydes or ketones with either acetylene or acetylenic hydrocarbons in which caustic alkali is the most frequently used lcatalyst. The acetylenic alcohol produced as a result of this reaction can, if desired, thereafter be converted to an acetylenic oletin hydrocarbon by a dehydration. The whole series of steps is carried out in a practical manner on a continuous scale Without the usual hazards which are often encountered in this type of operation.

Although in the previous art, the use of suspensions of solid potassium hydroxide has been generally disclosed,

it has been found that the preparation of Such suspenice sions in a stable, usable form involves considerable diiculty and embraces novel features not previously known or disclosed. Although simple suspensions may be reasonably satisfactory when the condensation reaction is conducted in an agitated batch vessel, they give completely unsatisfactory results when they are of necessity, made up at a period of time previous to the reaction, and then used as feed to a continuous reactor.

Many techniques were attempted in an etort to prepare stable potassium hydroxide suspensions and particularly using xylene as the suspension liquid. F or instance, attempts were made using liquids other than Xylene. These included alkyl acetals and polyethers. The use of Carbitol (diethylene glycol monoethyl ether) was studied. Dibutyl acetal was also employed without success in attempts to prepare stable suspensions. Further, attempts Were made also to employ various so-called solubilizers such as mercaptans and phenols in preparing aqueous solutions containing a high percentage of potassium hydroxide. Another technique studied was that molten potassium hydroxide was sprayed into the reaction chamber and as the hydroxide particles solidified, a tine suspension was obtained. The use of alcoholates was also investigated. Generally, diiliculties are encountered in the preparation of the alcoholates or acetal. The alcoholates were made by reacting potassium metal with the appropriate alcohol. An attempt was also made to produce the alcoholates by reacting the alcohol with potassium hydroxide, and thereafter removing the water of reaction by distillation. This reaction was successful only with cresol, but this reagent did not produce condensation. None of the above schemes and methods were successful for use in continuous processes in which this reagent is used.

It was discovered quite surprisingly that solid potassium hydroxide particles can be suspended by the use of a relatively small proportion-of certain fatty acid salts of the alkalis. Using critical conditions of procedure, as will be described more particularly below, this technique yields unexpectedly and unusually stable suspensions of solid potassium hydroxide in hydrocarbon diluents or solvents, such as xylene and the like. Such suspensions so formed are outstandingly suited for use in continuous processes involving the condensation reactions.

In order to determine the various materials which can be satisfactorily used in preparing the stable slurries, a number of comparative experiments were made. In each instance the same procedure was employed. 50 parts of xylene and 25 parts of potassium hydroxide were heated together to about C. Under these conditions, 1/z part of oleic acid produced a stable emulsion which upon cooling resulted in a stable slurry of finely divided potassium hydroxide suspended in x-ylene. Table I below lists some of the other materials which were tested.

1A mixed fatty acid `r'ossiu ester made by condensing 15 moles ethylene oxide per mole of an acid mixture. The acid mixture consists of 70% ahietic acid and the remainder, a. mixture of oleic and linoleic acids.

2 Acetate salt of a diamine made by condensing acrylonitrile with a primary amine made from tallow.

This process is especially applicable'to the preparation of the 2alkyl1,5-hexadiene-3-ynes in which the alkyl group has from l to 5 carbon atoms. Although the process will be described in greater detail using as initial reactants, vinyl acetylene and acetone, other ketones such as methyl ethyl ketone or methyl vinyl ketone as well as aldehydes may also be employed. In addition, other alkyl oletinic acetylenic hydrocarbons can be prepared by starting with other acetylenic compounds such as methyl acetylene, or diacetylene, and condensing with the appropriate ketone. It isl desirable but not essential to use ketones since the dehydration step of the over-all process is well adapted to the dehydration of the tertiary alcohols produced by the condensation of ketone type compounds.

When employing reactants and materials of a hazardous nature such as acetlyene and especially some of the more reactive hydrocarbons which have additional double and triple bonds, it is obvious that a continuous process possesses substantial advantages. The amount of materials handled at any one time can be kept small enough so that in the event of an explosion or other mishap, no extensive damage will result. Furthermore, the operating conditions can be continuously and carefully regulated to avoid substantially completely undesirable polymerization reactions, while at the same time maintaining conditions for optimum yields of the desired condensation products. In fact, substantial commercial production of materials of this chemical type is practically impossible unless continuous production can be successfully ernJ ployed.

The general process of the invention may be described Yas follows, allowing for suitable variations in the operation. A slurry of potassium hydroxide in xylene is rst made up in an agitated reactor vessel using the special and highly advantageous procedure which is further described hereinbelow.

With regard to making the slurry of potassium hydroxide, the temperature employed at atmospheric pressure can vary from about 140 C. (approximately the boiling point of xylene) down to approximately 5 C. below which temperature the slurry tends to become gelatinous and is therefore more diiicult to handle. At higher pressures, higher temperatures can be employed. Lower temperatures are useful provided a relatively higher proportion of xylene is employed. The concentrations of fatty acid, for example, oleic acid, which may be employed vary from about V2 to 5% by weight, with the preferred amount Vbeing about 1% by weight. Higher concentrations are to be avoided because a very viscous slurry results. The preferred proportions of potassium hydroxide in diluent is approximately one part by weight of potassium hydroxide per two parts by weight of xylene. Concentrations as high as 1 to 1 have been employed but such proportions yield more concentrated slurries which are more diicult to handle and pump in the equipment.

A solution of an appropriate acetylenic hydrocarbon (vinyl acetylene) mixed with an appropriate carbonyl compound such as an aldehyde or ketone (acetone) is kept in storage in a'separate feed tank. The slurry of potassium hydroxide and the mixture of acetylenic hydrocarbon and carbonyl compound are fed into the recirculating portion of a condensation reaction system at different points. If desired, it is also feasible and possible to -feed the acetylenic hydrocarbon reactant and the carbonyl compoundreactant separately into the condensation system. Thus, there may be provided a n`rstrecirculating sysmately 20% of the reaction volume is in the recirculating section and 80% is in the non-recirculating section.

The resulting reaction mixture lfrom the condensation reaction vessel is then brought into contact with water in order to hydrolize the potassium salt of the acetlyenic alcohol which is produced. Both the aqueous and organic phases are contacted in a tower which is provided with means to secure intimate mixing, as for example, a perforated plate column. Contact in this column is preferably countercurrent. The overhead or upper fraction from the hydrolysis column is then separated into an organic phase and an aqueous phase and each is collected separately. The acetylenic alcohol from the condensation is contained in the xylene layer from which it may be separated by distillation, if desired.

Depending on the boiling point of the alcohol produced by the condensation, other hydrocarbons than xylene may be employed as diluents in the reaction in order to facilitate separation of the product by distillation if this is desirable. In some cases, as when further employing the alcohol as a chemical intermediate, it is preferable not to separate it from the diluent hydrocarbon in which it was produced.

On the other hand, the hydrocarbon-alcohol layer can be mixed with a solution of suitably controlled dilute sulfuric acid and this mixture is again continuously passed through a dehydrating zone such as a counter current contacting column at an elevated, controlled temperature during which period the alcohol from the condensation is dehydrated to the hydrocarbon. The mixture leaving this zone separates into two layers, an aqueous layer and a hydrocarbon layer. The hydrocarbon layer is then preferably subjected to a fractional distillation for the removal of the desired acetylenic olenic hydrocarbon (Z-methyl- 1,5-hexadiene-3-yne) preferably as an overhead product.

The choice of operating temperatures is not only governed by the properties of the postassium hydroxide slurry but also by the particular condensation reaction which it is desired to carry out. Higher reaction temperatures further the condensation reaction, but also favor polymerization of the acetylenic hydrocarbon reactants. These hydrocarbons vary a great deal in degree of stability. For example, the condensation of acetone and vinyl acetylene can be conducted effectively at temperatures ranging from 2O to 40 C. without excessive side reaction polymerizations. Condensations involving such hydrocarbons as diacetylene can best be effected at 0 to 10 C. or lower. The normally gaseous acetylenic hydrocarbons such `as acetylene or methyl acetylene require slight modifications of the continuous procedure. Methyl acetylene is quite stable at high temperatures so that the preferred operation is at 20 tov 30 C. with sucient pressure being maintained so that the methyl acetylene dissolves in the ketones or aldehyde with which it is being condensed. ln some cases, it is more desirable to conduct the operation in two steps whereby the acetylene is Ylirst 'reacted with the potassium hydroxide slurry to form the corresponding potassium acetylide, which then in turn is reacted with the desired ketone or aldehyde. Since .aldehydes Vare generally more sensitive to elevated temperatures than are ketones, lower temperatures are usual- Yly to be preferred incondensation reactions involving 'aldehydes as reactants.

A number of unique and inventive features are embodied in this continuous method of operation. The continuous condensation ofthe acetylene compound and the carbonyl compound in the presence of the potassium hydroxide slurry is `possible because of the discovery that the reaction takes place relatively rapidly under these conditions. The employment of a continuous reactor system has the advantage that the hazards usually associated with handling large quantities of the explosive and dangerous acetylenic compounds are much reduced and eliminated. The immediate and direct continuous dehydrationV of the acetylene condensationY product with controlled amounts of sulfuric acid also has the advantage of minimizing the hold-up of unstable material and thereby avoiding substantial losses in yield of desired material. It is further highly desirable to etect condensation, and, if desired, the dehydration of the resulting alcohol condensation product, in the presence of a relatively high boiling hydrocarbon diluent. The diluent should be selected such that it does not interfere with the entire condensation and dehydration reactions. The preferred hydrocarbon diluent for this purpose is xylene. The xylene which may be used can be either one of .the pure isomers or a mixture of two or more of the isomers such as is readily available commercially. The employment of a diluent such as xylene throughout the process has the advantage of maintaining a solvent in the presence of the usually unstable acetylenic polymers, which otherwise are quite explosive and present hazards when employed in the pure state. In carrying out this continuous operation, the xylene concentration is maintained throughout the reactor, the dehydrator and in the iinal distillation steps during which elevated still temperatures may be experienced and would otherwise cause excessive polymerization if the xylene were not present. This xylene were not present. This xylene or other suitable xylene or other suitable solvent may be recycled and reused throughout the continuous reactor system. If desited, the potassium hydroxide as well as the acid dehydrating agent may also'be recycled.

lThe following examples are intended to be for the purpose of illustration only and it is not intended in any way to limit the invention to the specific embodiments shown therein. All parts are by weight unless otherwise specified.

Example 1 ln a typical specific application of the above described process the preparation of 2-methyl-5-hexene-3-yne-2-ol was carried out by the condensation of acetone with vinyl acetylene.

The continuous condensation was carried out in an apparatus similar to that described below and sketched in the accompanying schematic flow diagram. A slurry of potassium hydroxide was made up in a blending apparatus using 80 parts of potassium hydroxide, 160 pants of xylene and about 2 parts of commercial oleic acid. The xylene-potassium hydroxide mixture was heated to about 140 C. (above the melting point of the potassium hydroxide), and the oleic acid was added. The mixture immediately formed an emulsion which was -agitated while undergoing cooling to 25 C. As the mixture cooled, the potassium hydroxide solidified so that a suspensoid systern consisting of solid potassium hydroxide particles suspended in xylene resulted. Using this procedure a slurry was obtained which was yfound to be entirely stable at room temperatures (with occasional slight agitation) for periods up -to several months. The total volume of the reaction system employed included both the recirculating and non-recirculating portion. The Iabove described slurry and vinyl acetylene-acetone mixture were each fed into the system at a rate corresponding to l part by volume per minute. Equimolar quantities of vinyl acetylene and acetone (0.855 mole of each) were used. The recirculating portion of the system operated -at 35 to 40 C. and the non-recirculating portion was maintained at slightly above room temperature at 25 C. The resulting reaction product was hydrolized with 75 parts of concentrated sulfuric acid and there was obtained a yield of 2-methyl-5-hexene-3-yne-Z-ol equivalent to 74% of the theoretical quantity.

Example 2 A stable slurry of potassium hydroxide was made up in a similar fashion as that described in Example 1 above, said slurry comprising 80 parts of potassium hydroxide (1.43 moles), and 160 parts of xylene and employing 2 parts of oleic acid as emulsifying agent. Ilnto this stable suspension there was -absorbed 0.924 mole (24 parts) of acetylene by slowly passing acetylene into a recirculating system comprising 20 parts by volume. 'I'he system was maintained at a .temperature of approximately 35 to 40 C. Subsequently, this suspension was passed into a second recirculating system into which an equivalent quantity of butyraldehyde was introduced, that is, 0.92 mole. Following this introduction, the mixture was passed into a non-recirculating chamber comprising 77 parts by volume. The resulting reaction product was hydrolyzed to obtain a good yield of l-hexyne-B-ol.

Example 3 The following example will best be understood if it is read in connection with the accompanying gure which is a schematic ow plan presented for the purpose of illustrating the process of the invention, although it is not intended to -limit the invention speciiically thereto.

The potassium hydroxide-xylene mixture is made up in vessel A which is a reactor, the contents of which are continuously agitated by stirrer 2. The make up xylene is introduced into vessel A by line 11 and pelleted potassium hydroxide is introduced by line 3. The slurry is prepared by continuously mixing the reactants at a temperature of about C. with rapid agitation. After a suitable period of time, in reactor vessel A, the resulting iinely divided KOH-xylene slurry is passed by line 4 through inlet line 5 into the condensation reaction system B. This system consists of two sections, one recirculating and the other non-recirculating. The KOH-xylene slurry is fed into the recirculating section of the reaction system; the circulation being maintained by means of pump 6. The acetylenic hydrocarbon (vinyl acetylene) and the ketone (acetone) in the xylene diluent, are simultaneously introduced into the recirculating section via line 7. The desired reaction temperature (about 40 C.) is maintained by controlling the coolant flow through an appropriate heat exchanger. The mixed reactants then pass through the non-recirculating section 9 where the condensation reaction 'between the acetylenic hydrocarbon (vinyl acetylene) and the ketone (acetone) is allowed to go to completion. Any ixed gases in the system are Vented through trap 8.

The reaction mixture is then brought into contact with water which is fed through line 10. This water dissolves the unused KOH and also hydrolyzes the potassium acetylide complexes. Complete hydrolysis is accomplished by contacting the aqueous and organic phases in the packed hydrolysis column C. The total mixture is then passed (after hydrolysis) by line 12 into separator D.

The organic layer containing unreacted vinyl acetylene, xylene, and desired condensation product passes via line 14 into dehydration reactor F. There is also introduced dilute sulfuric acid (about 30%) which enters the system 'by line 15. The aqueous layer from separator D is subsequently processed as described below. In dehydration reactor F, the condensation product is subjected to an elevated temperature whereby it is continuously dehydrated to the acetylenic olefin hydrocarbon. This dehydrated product passes by line 21 into phase separator H in which the gas phase which is principally unreacted acetylenic hydrocarbon is separated and passed via recycle line 23 into line 5 and thence into the condensation reaction system B. The organic layer obtained in separator H is drawn oi by line 22 and thence is passed into an acid `recovery system, if desired.

In washer I, the organic layer containing the desired acetylenic olen hydrocarbon product, undehydrated alcohol, and xylene is contacted with water introduced by line 24. Wash water is removed from the washer by line 25. The washed organic layer is then passed by line 26 into fractionating column I, wherein it is subjected to fractional distillation. Fractionating column I is preferably operated under reduced pressure. The desired hydrocarbon, Y2-rnethyl-1,5-heXadiene-3-yne, is removed from this column by overhead line 33. This overhead stream passes through a condenser. A part of the condensed liquid is returned to the column as reux via line 34. The remainder is removed as product by line 35. From the lower portion of fractionation column I, a major portion of the bottoms stream of undehydrated alcohol and Xylene is recycled through line 20 into line 14 and thence into dehydrator F. A smaller portion of the bottoms stream passes by line 27 into rerun column K. In this column, the Xylene diluent is continuously puried by removal of a polymer bottoms stream through line 28. The Xylene is removed overhead from column K by line 29 and passes through a condenser. A part is returned to column K by line 30 and the remaining portion passes through line 31 and is recycled 4back to the condensation and dehydration stages. Polymerization inhibitor can be added to the system by line 32, if desired.

The aqueous KOH layer containing some dissolved organic material is passed through line 13 t0 extraction tower E, in which the layeris contacted countercurrently Iwith fresh Xylene introduced via line 17. The enriched xylene is passed through lines 16 and 20 and 8y thence into line 14 to the dehydration reactor F. The stripped aqueous KOH solution is passed to vaporizer F in which water is removed by azeotropic distillation with Xylene to obtain anhydrous KOH which is removed by line 19 and which can be used in making up the initial slurry in vessel A.

What is claimed is:

A continuous process for the production of 2-methyl- S-hexene-3-yne-2-ol which comprises continuously dispersing solid potassium hydroxide in Xylene in the presence of from 1/2 to 5% by Weight of oleic acid, continuously contacting said dispersion with vinyl acetylene and acetone in the presence of xylene, and hydrolyzing the resulting product to produce 2-methyl-5-hexene-3-yne- 2-01.

References Cited in the le of this patent UNITED STATES PATENTS 2,394,608 Hansley Feb. 12, 1946 2,455,058 Herman Nov. 30, 1948 2,536,028 Brothman et al Jan. 2, 1951 2,579,257 Hansley et al. Dec. 1S, 1951 2,596,175 Rosenstein May 13, 1952 2,742,517 Fusco Apr. 17, 1956

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