US2915564A - Reduction of fatty acid esters to produce alcohols - Google Patents

Description

Dec. 1, 1959 v. HANSLEY EI'AL 2,915,564

REDUCTION OF FATTY ACID ESTERS TO PRODUCE ALCOHOLS Filed April 15. 1955 METALLIC REDUCING E STER SODIUM ALGOH O L i (4 EQUIVALENTS) (2 EQUIVALENTS) (l EQUIVALENT) ESTER FEED MIXTURE CONDENSER RECOVERED HYDR LYSIS REDUC'NG wATERa ALCOHOL STEAM BY-PRODUGT HIGHER GAUSTIG ALCOHOL P SODA PRODUCT VIRGIL L. HANSLEY STUART SOHOTT INVENTOR.

United States Patent REDUCTION OF FATTY ACID ESTERS T0 PRODUCE ALCOHOLS Virgil L. Hansley and Stuart Schott, Cincinnati, Ohio,

assignors to National Distillers and Chemical Corporation, a corporation of Virginia Application April 15, 1955, Serial No. 501,522

11 Claims. (Cl. 260-638) This invention is generally related to the use of sodium for fatty acid ester reduction to yield higher molecular weight alcohols, and, more specifically, to improvements in the process whereby advantages are obtained by treating the esters of fatty acids directly with an alkali metal and a reducing alcohol in appropriate and critical amounts.

and under controlled conditions.

The reduction process for producing fatty alcohols was first carried out by employing, for instance, ethyl alcohol and sodium metal to reduce the fatty acid esters of glycerol which are the most commonly occurring ester constituents of fats and oils. This process has been found to be uneconomical and unsatisfactory commercially, particularly because of low yields of impure alcohol products.

An improvement was developed wherein a higher alcohol, such as a secondary or tertiary alcohol, was used as the reducing alcohol and an inert solvent or diluent was employed to keep the reduction mixture fluid. However, this has resulted in serious difficulties especially in the reduction of certain esters of the higher molecular weight fatty acids. Very stable emulsions were formed during working up of the reaction mixture resulting in prolonged separation difficulties and loss of reactants and products.

Recently, it has been discovered that advantages are achieved by converting the natural fatty esters to esters of the same types of alcohols as those used for the reduction. This can be accomplished by saponiflcation to obtain the free fatty acids followed by esterification or by transesterification. Such a preliminary treatment permits separation of the by-product glycerine prior to the sodium reduction and avoids the difliculties inherent in the problem of separating the valuable glycerine product and the caustic soda produced from the reduction step.

It has now further been found that these types of esters of reducing alcohols having more than 4 carbon atoms and fatty acids having from 12 to 22 carbon atoms, can be readily and advantageously reduced to the corresponding fatty acids using alkali metal and at least stoichiometric amounts of a selected reducing alcoholdirectly in a molten alkali metal alkoxide as the sole reaction medium. There is no need for an extraneous inert diluent to maintain the reaction mixture fluid.

Operating the process in this manner results in nuhandling, separation, drying and analysis of inert solventalcohol mixtures are completely avoided.

It is first necessary to convert the fatty acids or raw fats to esters of a reducing alcohol. These esters of fatty acids and reducing acohols having at least 4 carbon atoms which are used as starting reactants in the reduction can be readily prepared by direct esterification. Since the alkali metal alkoxides produced as the primary reaction products function as the fluid reaction media, the alcohol selected for preliminary formation of the fatty acid esters must yield a corresponding alkoxide whose melting point permits the formation of a fluid reaction mixture at reasonable temperatures. Thus, the alkali metal alkoxides formed during the reaction should have a fusion temperature of at least 130 C. and not over 200 C. Preferably, the upper fusion temperation of the alkoxides is not greater than 185 C.

This novel process lends itself most favorably to continuous or semi-continuous operation, although it can equally well be applied to batch reactions. However, as will be seen from the description in the examples below, numerous advantages are realized by operating the reduction to the fatty alcohols in a continuous manner.

The resulting fatty alcohol products of this simplified and improved reduction system are subsequently obtained in yields and purity equal to or better than those obtained by previously known reduction systems. Yields of 85-90% have been obtained with substantially no evolution of hydrogen. Any molecular hydrogen formed by reaction of sodium with alcohols represents a loss of reactants and an undesirable side reaction.

The basic chemistry involved in the alkali metal reduction of an ester of a fatty acid includes (1) a reduction step and (2) a hydrolysis step. Using sodium as the alkali metal, R as the fatty acid radical having from 12 to 22 carbon atoms, and R and R" as the organic radicals (same or different) derived from a reducing alcohol having at least 4 carbon atoms, these reactions can be represented by the following balanced equations showing stoichiometric equivalents.

Reduction step: i

Hydrolysis step:

Reactants are employed in substantially stoichiometrically equivalent amounts. Thus, there should be used 4 moles of alkali metal and 2 moles of reducing alcohol per mole of ester to be reduced. The reduction reaction can be run directly if the temperature is raised merous advantages. Auxiliary hydrocarbon solvents,

such as toluene and xylene as employed in prior art procto the point where the alkoxide mixture is molten. With appropriate choice of reactant components, the reaction mixture ofalkoxides is molten at temperatures above about 165 C. For instance, glyceryl, methyl, ethyl, and both normal and isopropyl esters give reduction mixtures too high melting, that is, above 200 C. However, higher molecular weight branched'chain' alcohol esters of the fatty acids, such as the methyl isobutyl carbinol esters, give very fluid mixtures in the range of to 200 C. In effect, the reduction reaction is conducted in the molten mixture of the sodium alkoxides as the reaction medium, the necessary sodium alkoxides being produced during the reduction reaction.

It has been found that sodium disperses readily with mild stirring throughout molten alkoxides into a finely divided state to give a sufliciently finely divided sodium dispersion for rapid reduction. The fatty acid ester to be reduced is pre-mixed with near the theoretical amount 3. of reducing alcohol, and the mixture of the two dropped into the dispersion of sodium in molten alkoxide. Preferably, the sodium is also in a molten condition and will be so .at the temperatures employed for reaction. The

.4 inally be obtained from coconutoil,.palmkerneloil, lard, beef tallow, palm oil, cottonseed oil, soy bean oil, corn oil, linseed oil, castor oil, tung oil, menhaden oil, rapeseed oil, olive oil, marine oils, and mixtures of such oils.

reducible mixture is added at a rate such that only a low They can be either hydrogenated or unhydrogenated. concentration of unreacted esters is present in the re- The invention will be further illustrated by the followacting mixture at any time. This is necessary to avoid ing typical examples although it is in no way intended to undesirable side reactions between the alkali metal and limit the scope of the invention thereto. All parts are by the esters. Under these reaction conditions, the reduction weight unless otherwise indicated.

proceeds substantially to completion as indicated by the EXAMPLE v hlgh yields actually obtamed compared to theoretical values. This example descrlbes a typical reaction for prelim- Upon completion of the reduction reaction, the reaction inary P p r fatty i Staftmg matffnals from mixture is quenched in Water, hydrolyzing the various fatty acids and a typlcal {educlfllg alcohol havlflg at least alcoholates to form the corresponding alcohols and so- Carbon at0m$- lnihlsepal'tlculalrpleparatlon, tallow diurn hydroxide. acids consisting predommantly of C to C fatty acids,

Two phases are f d as a result f h quenching and methyl isobutyl carbinol were employed as the reactoperation, an aqueous phase and a non-aqueous phase. ants I In the absence of inert materials, and employing the alke es rific tlon qmpm ntus dwas a stlll w th a 30 oxides as reaction media, there are no phase separation 20 Plateoldefshaw column l pp h a p y fif d difficulties encountered, and the result is an aqueous phase automatic reflux and heat-Input Control 10 malmaln containing dissolved sodium hydroxide and any dissolved Slant Pressure P acrossthesystem- Toluene was used quantities of the reducing alcohol used, depending on as thetallxilialy-solvent 10 remove Y*P Water solubilities, and a non-aqueous phase consisting of fatty at a lower P temPeTatur-e {1 than OtheF alcohol products with any water-insoluble portion of the 25 Wisfi be Possible using lng excess .carblnol alone. reducing alcohols. The non-aqueous phase is conven- The reflux iempefalufe was malntallled thc bp l iently separated and the fatty alcohols separated and puri- Point of the ternary aleotrope' Thfl mltlal P fied, for instance, by rectification. charge was as follows:

Although any the membeFS f alkali i l Class Tallow acids 500 parts (equiv. wt. 277). can be employed as reactants in this invention, it Is pre- Methyl isobutyl parts f rc to use sodlurn from the standpoint of economics Toluene 125 Parts (+300 parts). an aval ablhty. Sod1u n1 has been employed 1n the ex- Sulfuric acid 50 parts amples as a typical alkah metal.

h term reducing alcohol is used and is to be As the ,esterification proceeded, the extra toluene was derstood to mean aliphatic and alicyclic alcohols. These 35 added to malntaln the 125 P temperatufecan be branched chain or straight chain monohydric al- Based on the amount of Water formed the cstenfifm' cohols containing preferably four or more carbon atoms. was Fomplete 125 mmutes after heat was apphed The boiling point of the reducing alcohol should be such or 100 mmutes after the l of reflux' that efiicient separation from the product alcohols can P lsobutyl carbmol'fatty P ester recovered be made by distillation. Furthermore, it may be advan- 40 by dlstlnatlon was 975% f theoretlcal' It had an Y tageous to use a reducing alcohol that is the same as an droxyl Value of an acld value of and sapom' alcohol liberated or produced by the reduction reaction ficatlon value of the ester. Generally, secondary alcohols such as Constant 38 mlxtul'es 111 tills-System are! methyl isobutyl carbinol, cycloheXal'lol, methyl Y Toluene-carbinol, B.P. 110 C '6 vol. percent carbinol. hexanol, ethyl methyl carbinol and amyl methyl carbinol c bi p 94 C 40 l Percent t are preferred although the tertiary alcohols, such as ter- To1uene.water, 84' C 13.5 wt. percent water. tiary butyl and tertiary amyl alcohol, can also be used. a 27 vol. ercent water.

The following table shows the average percentage of The ternary system 83 3-vol. p rcent carbinol. fatty acid composition of commonly occurring fats and oils which can be used in this process. The fatty acids I EXAMPLE 2 are thus employed, of course, after being converted to The reduction equipment consisted of two parts, one the corresponding appropriate esters, as described above. for carrying out the reduction and another for the hy- Chemical 0000- Palm Beef Palm Cotton- Corn Lin- Castor Tung Menha- Rape- Olive .Formula nut Kernel Tal- Oil seed Oil seed Oil Oil den seed Oil Oil B Oil b low 6 Oil Oil .Qil Oil 12 2i02.-.. 48.0 52.0 0141111101---- 17.5 15.0 3.0 0.6 6.0 15 01133204--.. 8.8 7.5 29.2 43.8 20.2 7 s 5.4 16.0 9.2 l8H36O1.. 2.0 2.5 21.0 2.9 2.0 3.5 0 3 4.6 1.5 1.6 2.0

01511302-.-. 6.0 16.0 41.1 43.1 35.2 46.3 9.6 7 2 0 s 20.2 85.0 l8H32OZ... 2.5 1.0 2.0 9.5 41.7 41.8 42.6 a 6 30 14.5 4.0

Linolenic C gH3o0z--. 38. 1 2. l

Eleostearicun 0151141102.--. 94.6

Ricinoleic C15H3407 87.8

Coconut oil also contains 0.2% caproic acid, 8.0% caprylic acid, and 7.0% capric acid.

' Palm kernel also contains 3.0% caprylic acid and 3.0% eapric acid.

6 Beef tallow contains minor amounts of C and C unsaturated acids and other constituents. d Menhaden oil also contains 15.5% C unsaturated acids, 19% C unsaturated acids, and'l2%Gn'unsaturated'aeids.

e Rape-seed oil has 57.2% 021 unsaturated acids as main constituent.

Itcan 'beseen that many different kinds of acids derived from naturally occurring fats and oils can be .converted to the corresponding fatty alcohols and mixtures of fatty alcohols. These comprise fatty acids of both the saturated and unsaturated types having from 12-to 22 carbon atoms per molecule. The fatty acids can orig.

drolysis. A series of runs were carried out in the manner as hereinafter described. In each case, the metallic sodium was introduced into the reduction vessel after it had been purged with nitrogen. The vessel was equipped with heating equipment capable of reaching and maint g perat res from 0. to about 200 0.

7 reaction vessel. The heat generated caused vigorous refluxand rate of addition was accordingly adjusted. After all thereducible mixture was added, a short time of additional heating was permitted to complete the reduction.

The reaction mixture was then hydrolyzed. About 400-600 parts of water was added to a suitable hydrolysis vessel and heated to boiling. The entire reaction mixture while hot was then carefully added to the hydrolysis vessel. The hydrolysis proceeded rapidly and was complete in a few minutes. Heating was stopped and the aqueous caustic'phase was allowed to separate and was removed by decantation. Usually only a small part of the caustic soda separates, the remainder being held in a stable emulsion. When finally separated from the caustic solution, the xylene and reducing alcohol were substantially removed by steam distillation. The remaining impure higher fatty alcohol was then washed to remove suspended droplets of strong caustic and to eliminate the by-product fatty acid soaps formed in minor amounts through side reactions.

Table III below summarizes the poor results obtained by operating in this manner using inert diluents in the reduction step of the reaction. The operating difficulties caused by stable emulsions formed required extreme measures to overcome. These include complete acidification and great dilution with alcohol as described in the remarks in. Table III. Distillation residues were relatively high and in run No. IX, high ester and acid number values were obtained.

use after passage through condenser 3 and drier 4. Higher fatty alcohols are separated from hydrolyzer 2 as product, and by-product caustic soda is also recovered therefrom.

While there are above disclosed but a limited number of embodiments of the process of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is desired therefore that only such limitations be imposed on the appended claims as are stated therein.

What is claimed is:

1. A process for the production of fatty alcohols having from 12 to 22 carbon atoms per molecule which comprises treating the corresponding fatty acid esters of a reducing alcohol having at least 4 carbon atoms with an alkali metal and a reducing alcohol having at least 4 carbon atoms in amounts approximately stoichiometrically equivalent in a fluid reaction medium consisting essentially of molten alkali metal alkoxides having no extraneous inert diluents added thereto, at a temperature of at least 130 C., hydrolyzing the resulting reaction mixture and isolating said fatty alcohols therefrom.

2. A process for the production of fatty alcohols having from 12 to 22 carbon atoms which comprises continuously reacting metallic sodium and fatty acid esters of a reducing alcohol having at least 4 carbon atoms with an approximately stoichiometrically equivalent amount of a reducing alcohol having at least 4 carbon atoms, in a Table III Higher Alcohol Distil- Ester No. Acid No.

Product lation Higher Higher Run No. ,Solvent Residue, Alcohol, Alcohol, Remarks parts mg. mg.

parts percent KOH/gm. KOH/gm.

VIII.-." Toluene 89.5 82 6.5 Hydrolysis mixture formed very stable emulsion upon washing with distilled water. Broken by complete acidification.

IX Xylenen" 100 91.5 9.0 3. 51 1.32 Hydrolysis mixture formed stable emulsion upon washing with water. Acidification necessary to free higher alcohols from emulsion.

X -.do 96 88 9.1 0.52 0.19 Emulsion broken by addition of a large portion of methyl isobutyl carbinol (equal to amount of higher alcohol).

EXAMPLE 5 A schematic flow chart for continuous or semi-continuous operation is shownin the accompanying figure. The sodium metal in a molten state is added to reduction reactor 1 at least intermittently. Preferably a reaction medium containing molten sodium alkoxides is continuously maintained in reactor 1. The sodium (about 4 stoichiometric equivalents per equivalent of ester) is maintained in an agitated condition above its melting point. The mixture is agitated with a suitable mechanical stirrer or mixer. The reducing alcohol and the ester in the proportions of 2 stoichiometric equivalents of alcohol per equivalent of ester are mixed and added continuously, semi-continuously or at least intermittently to the reaction vessel 1. Heat developed by the reduction is most conveniently removed through the walls of the reactor vessel. For instance, an'external heat exchange or direct cooling system can be employed. The continuous or semi-continuous addition of the reducible mixture and the sodium is controlled to a rate such that the resulting heat can be removed to maintain the temperature of the reacting fluid mass in the range of about 160 to 185 C. At least intermittently, a portion of the reaction mixture is transferred into hydrolyzer '2. Herein, the mixture is contacted with steam and water to produce sodium hydroxide together with free fatty alcohols and regenerate the reducing alcohols. From the resulting mixture the regenerated reducing alcohol is removed, for instance, by

vaporization, condensed and return to storage and for refluid reaction mixture consisting essentially of molten sodium alkoxides having no extraneous inert diluents added thereto at a temperature of at least C. hydrolyzing the resulting reaction mixture and isolating from said molten reaction mixture fatty alcohols having from 12 to 22 carbon atoms per molecule.

3. A process according to claim 1 wherein the alkali metal is sodium.

- 4. A process according to claim 1 wherein the fatty esters reduced are the methyl isobutyl carbinol esters of fatty acids having from 12 to 22 carbon atoms.

5. A process for preparing fatty alcohols having from 12 to 22 carbon atoms per molecule which comprises reacting together about four molar equivalents of metallic sodium, about two molar equivalents of a reducing al cohol having at least 4 carbon atoms, and one molar equivalent of fatty acid esters of'a reducing alcohol having at least 4 carbon atoms, in a fluid reaction mixture consisting essentially of sodium alkoxides having no ex traneous inert diluents added thereto at temperatures in the range of from 130 to 200 C., thereafter hydrolyzing said reaction mixture, and isolating therefrom fatty al' cohols having from 12 to 22 carbon atoms per molecule.

6. The process according to claim 5 wherein the fatty esters are derived from tallow.

7. The process according to claim 5 wherein the fatty esters are derived from olive oil.

8. A continuous process for the production of fatty alcohols having from 12 to 22 carbon atoms per molecule, which comprises maintaining afluid'bo'dy of reacting The temperature was raised to about 170 C. Simultaneously and preferably, there was externally mixed two stoichiometrie equivalents of methyl isobutyl car binol with one stoichiometric equivalent of methyl isobutyl carbinol fatty acid ester for each four equivalents of sodium introduced into the reduction vessel.

When the temperature of the reaction mixture reached 160 C., the ester-reducing alcohol mixture was introduced at such a rate that the heat of reaction was readily and conveniently removed. Operating thus, the sodium alkoxide formed was in the molten state and thus served as a fluid reaction media throughout the course of the reaction. While the entire mixture was still molten, it was transferred to a heated, steam filled vessel for 6 EXAMPLE 3 Experiments V, VI and VII in Table II below show that simple alcohol esters such as methyl and including glycerides gave low yields or very impure higher alco hols. Attempts to hold the reaction mixtures fluid by raising the temperature above around 180 C. resulted in heavy evolution of hydrogen by side reactions. Hydrogen evolution represented a direct loss of sodium reducing power. The methyl ester yielded fatty alcohol products having a very high saponification number of 48.2 and an acid number value of 385, indicating incomplete reaction. The glycerides gave poor yields and yielded large amounts of reaction vessel residues.

Table II MIBC Wt. of Wt. 0t Temp, 'Ilme, Yield, Yield, Vol., Res., RunNo. Ester Sap. No. Ester, Sodium, as as C.v Min. parts Percent H L. pts.

parts parts Red. Solvent,

Ale, parts parts V Methyl Ester of 196 150 52.0 116 400 220-230 121.4 90.0 4.44 6.6

'1 low. (Cale) VI Soy Bean O1l 171 150 4.4 98.5 400 175-185 102 57.6 42.6 5.0 44.7 V11 Tallow 167.3 150 43.2 95.8 400 175-185 93 40.0 34.0 4.8 53.5

1 Indicates high acid and saponifieation value of product and an actual low fatty alcohol yield.

hydrolysis. The heating was continued with water and liberated reducing alcohol being allowed to reflux, until all higher fatty alcohol and reducing alcohol separated as a lighter, organic layer.

This organic layer was separated from the strong caus tic solution and washed to remove alkali. The methyl isobutyl carbinol was separated from the fatty alcohol by distillation. The fatty alcohol product can subsequently be subjected to rectification or such other puri fication steps as desired.

The data in Table I, set forth hereinafter, shows the results obtained by the continuous reduction of methyl isobutyl carbinol esters of both distilled and undistilled tallow fatty acids and olive oil fatty acids. Four continuous reductions were carried out with semi-continuous removal of reaction mixture to isolate products therefrom.

The yields obtained were consistently high and there was substantially no hydrogen evolved. Both the sapon-. ification numbers and the acid numbers of the products were low, indicating no appreciable amounts of unreduced ester or acid. No emulsions were encountered during the hydrolysis of the reaction mixtures.

.. EXAMPLE 4 In order to show the deleterious effect of the presence of an inert solvent or diluent in the reaction mixture, the following experiments are presented.

Approximately 150 parts of the methyl isobutyl carbinol ester of hardened tallow fatty acids, having a saponification number of 152.3 was admixed with about parts of methyl isobutyl carbinol as reducing alcohol to provide a reducible mixture for the reduction. This mixture was further diluted with about an equal volume of an inert diluent, toluene or xylene. About 40.5 parts of sodium, a 5% excess over the stoichiometric amount required according to the equation, was introduced into a suitable reaction vessel. The reaction vessel was equipped with an oil bath for heating and with a stirrer for mild agitation. An additional amount of about 50 parts of xylene was introduced into the reaction vessel with the sodium.

The oil bath and reaction vessel contents were adjusted to about 140 C. Agitation was provided to disperse the molten sodium after which the ester-reducing alcohol mixture was slowly and continuously added to the Table I Wt. of Wt. of MIBC Run No. Ester Sap. Ester, Sodium, as Red. Temp, Tim Yield, Yield, Vol., Res., No. parts parts A C. Min. parts percent HAL pts.

parts mixture consisting essentially of sodium alkoxides having no extraneous inert diluents added thereto, at least intermittently adding thereto the stoichiometrically equivalent amount of sodium, maintaining said sodium dispersed therein, simultaneously and at least intermittently adding thereto the stoichiometrically equivalent amounts of a mixture of reducing alcohol having at least 4 carbon atoms and the fatty acid esters of fatty acids having from 12 to 22 carbon atoms per molecule esterified with a reducing alcohol having at least 4 carbon atoms, maintaining said reacting mixture at temperatures in the range of from 130 to 200 C., at least intermittently removing at least a portion of said reacting mixture from said body hydrolyzing said removed reacting rnxture, and isolating from said removed portion fatty alcohols having from 12 to 22 carbon atoms per molecule.

9. The process according to claim 8 wherein the fatty esters are derived from tallow.

10. The process according to claim 8 wherein the fatty esters are derived from olive oil.

11. The process according to claim 8 wherein the reducing alcohol is methyl isobutyl carbinol.

References Cited in the file of this patent UNITED STATES PATENTS 1,971,743 Bertsch Aug. 28, 1934 2,460,969 Blinoff Feb. 8, 1949 2,494,366 Sprules et al. Jan. 10, 1950 2,563,044 Kamlet Aug. 7, 1951 2,607,806 Bigot Apr. 19, 1952 2,612,527 Anglaret Sept. 30, 1952 2,647,932 Blinka et al. Aug. 4, 1953 2,719,858 Hill Oct. 4, 1955 FOREIGN PATENTS 589,380 Great Britain June 18, 1947 OTHER REFERENCES Hansley: Ind. Eng. Chem, vol. 39, pp. 55-62 (1947). Hill et al.: Ind. Eng. Chem., Vol. 46, pp. 1917-21 (1954).

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF FATTY ALCOHOLS HAVING ING FROM 12 TO 22 CARBON ATOMS PER MOLECULE WHICH COMPRISES TREATING THE CORRESPONDING FATTY ACID ESTERS OF A REDUCING ALCOHOL HAVING AT LEAST 4 CARBON ATOMS WITH AN ALKALI METAL AND A REDUCING ALCOHOL HAVING AT LEAST 4 CARBON ATOMS IN AMOUNTS APPROXIMATLEY STOICHIOMETRICALLY EQUIVALENT IN A FLUID REACTION MEDIUM CONSISTING ESSENTIALLY OF MOLTEN ALKALI METAL ALKOXIDES HAVING NO EXTRANEOUS INERT DILUENTS ADDED THERETO, AT A TEMPERATURE OF AT LEAST 130*C., HYDROLYZING THE RESULTING REACTION MIXTURE AND ISOLATING SAID FATTY ALCOHOLS THEREFROM.

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