US2922765A - Preparation of stable, concentrated koh slurries - Google Patents

Description

Jan. 26, 1960 J. HAPPEI. ET AL PREPARATIGN OF STABLE, CONCENTRATED KOH SLURRIES Filed Aug. l1, 1955 Inventors John Happel Charles J. Marsel i s i1 2,922,755 Patented Jan. 26, 1960 PREPARATIN F STABLE, CONCENTRATED KH SL E John Happel, Yonkers, and Charles l. Mai-sel, New York, N.Y.

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 speciiically, with a particularly useful method for the manufacture of 2-methyl-1,5hexadiene-Z-yne.

It has been previously known to produce various hydrocarbons having unsaturated bonds, including both double and triple bonds, 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 difficulty in their production even on laboratory and small batch type operations. Various ditiiculties are encountered in the application of the known methods, including the degradation and decomposition reactions ofboth the starting materials as well as the acetylenic olefin 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 concerned with improved means for producing acetylenic alcohols and includes improvements in addition to those described in copending application U.S. Serial No. 384,846, tiled 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 ybetween the acetylenic hydrocarbon with the carbonyl compound.

Certain of the organic compounds of the class of th alkyl-olenic acetylenes, especially 2-methyl-l,5-hexadiene-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 diiiiculties in their preparation by previously known methods.

ln 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 catalyst. The acetylenic alcohol produced as a result of this reaction can, if desired, thereafter be converted to an acetylenic olen hydrocarbon by a dehydration. The whoie 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 suspensions in a stable, usable, form involves considerable difliculty 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 effort to prepare stable potassium hydroxide suspensions and particularly using xylene as the suspension liquid. For 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 solidied, a tine suspension was obtained. The use of alcoholates was also investigated. Generally, difficulties 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.

lIt 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 s0 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, 1/2 part of oleic acid produced a stable emulsion which upon cooling resulted in a stable slurry of iinely divided potassium hydroxide suspended in xylene. Table l below lists some of the other materials which were tested.

TABLE I Time for Agent perceptible settling, hours Oleic acid 24. Oleic acid di1ncr 3. Mixed fatty acid rosin ester 1 Less than 1. Acetate salt of a diamine 2 Do. Vinyl acetate Do. Acetone Do. CarbitoL- Do.

1. A mixed fatty acid rosin ester made by condensing 15 moles ethylene oxide perlrnole of an acid mixture. The acid mixture consists of 70% abletic acid and the remainder, a mixture of oleic and. linoleic acids.

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

This process is especially applicable tov-the preparation of the 2-alkyl-1,5-hexadiene-3-ynes in which the alkyl I 3 j 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 aswell as aldehydes may also be employed. In addition, other alkyl olefinic acetylenic hydrocarbons can be prepared lby starting with other acetylenic compounds suc'has methyl acetylene, or diacetylene, and condensing with the appropriate ketone. It is 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 acetylene and especially some of the more reactive hydrocarbons which have additional doub1e 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 organic phase and anA aqueous phase and each is collected of the reaction volume is in the recirculating section and 80% is in the non-recirculating section.

The resulting reaction mixture from the condensation reaction vessel is then brought into contact with water in order to hydrolize the potassium salt of the acetylenic alcohol which is produced. Both the aqueous and organic phases are contacted in`a Vtower-which is provided with means to secure intimatemixing, 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 separately. The acetylenic alcoholfrom the condensation is contained in the xylene layer from which it may be separated by distillation, if desiredf" Depending on the boiling point of the alcohol produced Y by the condensation, other hydrocarbons than xylene may y be employed as diluents in the reaction in order to faciliconditions 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 employed.

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

With regard to making the slurry of potassium hydroxide, the temperature employed at atmospheric pres- Vsure can vary from about 140 C. (approximately the portion of xylene is employed. The concentrations of Y.

fatty acid, for example, oleic acid, which may be employed vary from about 1/2 to 5% by weight, with the preferred amount being 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 difiicult 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 hydrocarbonreactant and the'carbonyl compound reactant separately into the condensation system. Thus, there may be provided a first recirculating system in which the acetyleniohydrocarbon is reacted with the slurry of potassium hydroxide, and a second recirculating system into' which the resulting potassium acetylide slurry is mixed with-the aldehydeor ketone. This mixtureY is continuouslypassed through jaV reactor in which the condensation reaction occurs. ,The .condensation vessel must provide the holdup volume Vnecessary to allow the particular condensation reaction-to proceed to completion. densation reactor is such that it allows a reaction time 0f between 1 5 minutes and 1 hour. Thus, apprQXimtely tate separation of the product by distillation if this is desirable. In some cases, asrwhen further employing the alcohol as a chemical intermediate, it is preferable not to separate it from the diluent hydrocarbonin which it was produced.

On the other hand, the hydrocarbon-alcohol layer can bemixed 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 (2-methyl-1,5-hexadiene-3-yne) preferably as an overhead'product. Y

' The choice of operating temperatures is' not only governed bythe 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 hydrocarbonV reactants. These hydrocarbons varyV a great deal in degree of stability. For example, the condensation of acetone and vinyl acetylene can be conducted effectively at temperatures ranging from 20 to 40 C. without excessive side reaction polymerizations. Condensations involving such hydrocarbons as diacetylene canbest be effected at 0 to 10 C. or lower. The normally gaseous acetylenic hydrocarbons such as acetylene or methyl acetylene require slight'modications of the continuous procedure. Methyl acetylene is quite stable at high temperatures so that the preferred operation is at 20 to 30 C. Ywith suicient prescorresponding potassium acetylide, which then in'turn Preferably, the total volume of the con- Y is reactedV withthe desired ketone or aldehyde. Since aldehydes are generally more sensitive to elevated temperaturesvthan are ketones, lower temperatures are usually Nto be'preferred in condensation reactions involving aldehydes as reactants.

A number of unique and inventive features are embodied in this continuous method of operation. The con-V tinuous condensation of the acetylene compound and the carbonyl compoundV 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 theY hazards usually asso- Vciatedwith handling large quantities of the explosive and dangerous acetylenic compoundsare much reduced and eliminated. The immediate and'direct continuous dehydration of the acetylene condensation product with controlled amounts of sulfuric acid also has the advantage of minimizing the hold-up Vof unstable material and thereby avoiding substantial losses in yield of desired material. It is further highly desirable to eect 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 or other suitable solvent may be recycled and reused throughout the continuous reactor system. If desired, the potassium hydroxide as well as the acid dehydrating agent may also be recycled.

The following examples are intended to be for the Exampe 1 In a typical speciiic 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 parts of xylene and about 2 parts of commercial oleic acid. The xylenepotassium 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 solidiiied so that a suspensoid system consisting of` solid potassium hydroxide particles suspended in xylene resulted. Using this procedure a slurry was obtained which was found to be entirely stable at room temperatures (with occasional slight agitation) for periods up to several months. The total volume of the reaction systemV employed including both the recirculating and non-recirculating portion. The above described slurry and vinyl acetylene-acetone mixture were each fed into the system at a rate corresponding to 1 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 withv 75 parts of concentrated sulfuric acid and there was obtained a yield of 2-methyl-5-hexene-3-yne-2-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 l 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. Into this stable 6 suspension there was absorbed 0.924 mole (24 parts) of acetylene by slowly passing acetylene into a recirculating system comprising 20 parts by volume. 'Ihe 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-S-ol.

Example 3 The following example will best be understood if it is read in connection with the accompanying figure which is a schematic flow plan presented for the purpose of illustrating the process of the invention, although it is not intended to limit the invention specifically 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 1 and pelletedpotassium hydroxide is introduced by line 3. The slurry is prepared by continuously mixing the reactants at a ternperature of about C. with rapid agitation. After a suitable period of time, inreactor vessel A, the resulting finely divided `KOI-I-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 ilow 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 fixed gases in the system are vented through trap 8.

The reaction mixture is then brought into contact with water which is fed throughV 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 1S. 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 olen hydrocarbon. This dehyrated product passes by line 21 into phase separator H in which the gas phases 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 olf by line 22 and thence is passed into an acid recovery system, if desired.

In-washer I, the organic layer containing the desired acetylenic olefin hydrocarbon product, undehydrated alcohol, and xylene is contacted with water introduced by line 24. Wash water is removed yfrom 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, 2methyl1,5-hexadiene-3-yne, is removed from this column by overhead line 33. VThis overhead stream passes through a condenser, A partof the condensed liquid is returned to the column as reflux via line 34. The remainder is removed as product by line 3S. From the lower'portion of fractionation column I, a major portion of the bottoms stream of undehydrated alcohol and Xylene is recycled through line L20 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 purified 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 backto 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 to extraction tower E, in which the layer is contacted countercurrently with fresh Xylene introduced via line 17. The enriched xylene is passed through lines 16 and 20 and thence into line 14 to the dehydration reactor F. The stripped aqueous KOH solution is passed to vaporizrer 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.

References Cited in the le of thisvpatent UNITED STATES PATENTS 2,250,558 VVaughn July 29, 1941 2,385,546 Smith Sept. 25, 1945 2,394,608 Hansley V Feb. 12, 1946 2,455,677 Horeczy Dec. 7, 1948 2,460,969 Blino Feb.-8, 1949 2,579,257 Hansley et al. Dec. 18.r 1951 2,593,009 Clark et al. .Apr. 15, 1952 2,596,175 Rosenstein May 13, 1952 2,737,499 Grubb Mar. 6, 1956 2,742,517 1956 Fusco Apr. 17,

OTHER REFERENCES Johnson: Acetylenic Compounds, vol. 1, pages 3-21 (1946), Arnold & Co., London. Y

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