US2356988A

US2356988A - Process for the separation of the constituents of tall oil

Info

Publication number: US2356988A
Authority: US
Inventors: Frederick H Gayer; Charles E Fawkes
Original assignee: Continental Research Corp
Current assignee: Continental Research Corp
Priority date: 1942-04-07
Filing date: 1942-04-07
Publication date: 1944-08-29
Anticipated expiration: 1961-08-29

Description

Patented Aug. 29, 1944 PROCESS FOR THE SEPARATION OF THE CONSTITUEN'IS F TALL OIL Frederick H. Gayer and Charles E. Fawkes, Chi-, cago, Ill., assignors to Continental Research Corporation, Chicago tion of Illinois Heights, Ill., a corpora- No Drawing. Application April 7, 1942, Serial No. 438,004

13 Claims.

This invention relates to an improved process for the separation and recovery of the major constituents of organic mixtures or oils containing both resin acids and fatty acids, and particu larly to the clean, sharp and economic separa- 'tion and recovery of the resin acids and the fatty acids from such mixtures or oils, and particularly from tall oil.

Tall oil is a. by-product of sulphate or kraft paper manufacture, and is obtained by acidification of the black liquor soap, which is salted out and rises to the surface of the black liquor on standing. The main constituents of tall oil include fatty acids, resin acids and unsaponifiable substances. While the bulk of the unsaponiflable matter consists of hydrocarbons, it also contains a considerable proportion of high-molecular weight cyclic alcohols belonging to the group of phytosterols.

Tall oil as such has found relatively little commercial use. It isv not suited for soap making on account of its dark color, its odor and its high resin acid content, nor can it be used as a substitute for rosin or other natural resins on account of its fatty acid content. on the other hand, the components of tall oil, especially the resin acids, fatty acids and phytosterol are of considerable commercial value. Therefore, a process for the sharp separation of the com-- ponents of tall oil would be of great commercial value, especially'in view of the vast potential supply of tall oil, resulting from the increasing importance of the sulphate process for paper making. Due to its low commercial value, tall oil is usually not even recovered in the present sulphate pulp establishments. I

The object of the present invention is the separation of tall oil into its fatty and resin acid portions respectively by a process which comprises the general steps of esterifying the fatty acids, neutralizing the resin acids and separating the fatty acid esters from the resin acid soaps. However, the method whereby we eflect this separation step in particular is radically new and diiferent. Compared to all previous methods, it

is simpler in execution, permits the use of simple equipment and involves the use of only low priced chemicals. Its chief advantage, however, is that in its typical and preferred form it does not require the use of a solvent.

Briefly, our process comprises esterifying the fatty acids and neutralizing the resin acids with aqueous alkali in such a way that the resulting resin acid soap solution contains a definite eoncentration of neutralized resin acids. On heating the esteriiied mixture so neutralized, we obtain a sharp separation of two layers. The upper layer is composed essentially of the major portion of the fatty acid esters and of the unsaponifiable matter, the lower layer being assentially a resin acid soap solution in water containing the balance of the esters and unsaponiflable. This residual portion of the esters and unsaponifiable which is dissolved in and forms a clear solution with the resin acid soap solution can be recovered by acidifying the soap solution to obtain a mixture of resin acids and the residual esters plus unsaponifiable, crystallizing the resin acids from the mixture, the resin acid content of which is now considerably higher than that of the original esterified mixture, removing the resin acid crystals, and subjecting the liquid oily portion to the same separating treatment as the original esterifled mixture-namely, neutralizing and producing a definite resin acid soap concentration, heating and separating the resulting layers.

We will now describe and illustrateby examples the individual steps in our process. Considering the variation in the composition of tall oils of difierent origin, it must be recognized that a certain latitude in procedure, in quantities, proportions, concentrations, temperatures, etc., is permissible within the limits outlined in this application.

Starting with a commercial grade of tall oil, we first esterify the fatty acids by reacting them with a low molecular weight, aliphatic, monohydrle alcohol, as for example methyl and ethyl alcohol, or the isomeric propyl, butyl or amyl alcohols. We eflect the esteriflcation at atmospheric pressure as for example by refluxing the tall oil with the alcohol in the presence of a catalyst. Or we may esterify at a superatmospherie pressure in the absence of a catalyst, as proposed in our co-pending application, Serial No. 427,536. In either case, the esteriflcation can be controlled in such a way as to include only the fatty acids, leaving the resin acids unreacted. Such esteriflcations are usually effected in the presence of an excess of the reacting alcohol which, after the esteriflcation of the fatty acids is complete, is removed by distillation. The oily product is now composed of resin acids, fatty acid esters and unsaponifiable. The resin acid content of this mixture can be determined exactly by titration. Since esterification of the fatty acids involves a slight increase of the weight of the mixture, the resin acid content of the esterifled mixture is, by necessity, slightly lower than that found by the usual analytical methods in the tall oil before esterification.

In the second stage of our process we neutralize the resin acids with an aqueous alkali such as, for example, sodium or potassium hydroxide or carbonate. Substantially complete neutralization of the resin acids is required, although slight deviations on either the acid or alkaline side are permissible and do not materially affect the results. For example, we may neutralize only 95% of the resin acids present, or we may add 5% of alkali in excess of that required for the neutralization of the resin acids without altering the nature of the subsequent separation. After neutralization, we have a mixture which consists essentially of the alkali soaps of the resin acids, fatty acid esters, unsaponifiable and water. Depending on the proportion of water present, the esters and unsaponifiable might form a transparent "solution with the resin acid soap solution, or, as the proportion of water is increased, the mixture assumes the appearance of an ordinary, coarse emulsion in which at least a portion of the esters and unsaponiiiable are dispersed as fine droplets. We found that the proportion of water to the resin acid soap dissolved in it is the critical factor which determines the colloid chemical behavior of the neutralized esterified mixture and makes a strictly quantitative expression of the elements entering into our process possible.

The quantitative relationship between water and resin acid soaps is expressed in a convenient form by the concentration of the resin acids present in water solution as soaps. This concept of resin acid concentration altogether disregards the presence of fatty acid esters and unsaponifiable. More specifically, this concentration is defined as the relationship of the weight of the resin acids before neutralization to the volume of the aqueous soap solution resulting after neutralization. The volume of the soap solution will be approximately equal to the volume of the resin acids and the volume of the alkali solution used plus any water added after neutralization. Assuming as a close approximation the specific gravity of the resin acids and that of the alkali solution as equal to one, the volume of the soap solution is easily obtained. The following example will show the simple calculation involved to obtain a desired resin acid concentration:

A tall oil in which the fatty acids were esterifled showed an acid number of 76. On the basis of an equivalent weight of 302 for the resin acids, this acid number corresponds to'a resin acid con tent of 41% by weight on the esterified mixture. 7

One hundred grams of the esterified mixture contaln 41 grams of resin acids, which require 138 cc. normal alkali for neutralization. 0n neutralizing the esterifled mixture with normal alkali, the volume of the resulting soap solution will be 41+136=177 cc., and we consider the soap solution as containing If it should be desired to obtain a soap solution containing 10% resin acids, the 41 grams of resin acids would have to be contained in 410 cc. of soap solution, and we would have to add to the above mixture 4l017'l=233 co. more water. We are aware that in a strictly scientific sense the volume of the soap solution is not the exact sum of the volume of the resin acids and the alkali solution. However, we have found that for our purpose the approximation introduced is sumciently precise and permits rapid calculation of the volume conditions involved. In the following specification and claims the term resin acid concentration is always used in the sense as here defined, namely, to denote the concentration of the resin acids (present as soaps) in the aqueous soap solution, or the number of grams of resin acid contained in cc. of soap solution.

What we now have discovered and claim as a novel invention is that neutralized esteriiied mixtures of tall oil in which the concentration of the resin acids as defined above ranges from between about 30% to about 5% can be separated into two liquid phases by raising the temperature of the mixture. The lighter phase, or upper layer, is composed of a portion of the fatty acid esters and unsaponiflable and contains substantially no resin acids or resin acid soaps. The heavier, or lower layer, is composed of an aqueous resin acid soap solution which retains the balance or the esters and unsaponifiable. By separating the two layers and further processing the lower layer, we can effect a complete separation of the esters and unsaponifiable from the resin acids.

Within the limits indicated, the proportion of the separated upper layer shows a constant increase as the concentration of the soap layer decreases. The ilrst signs of a separation appear with some tall oils at approximately 30%, with other tall oils only at about 20% resin acid concentration, in the form of a small oil layer floating on the surface of the soap solution. As the resin acid concentration is decreased by adding water, the upper layer gradually increases until it reaches an upper limit at a resin acid concentration of about 5% to 7% resin acids. Dilution beyond this point does not give any increase of the upper layer.

Until the lower limit of resin acid concentration is reached, the separation of the two layers is, at higher temperatures, rapid, the interface sharp and both layers are clear. on further decreasing the resin acid concentration, however, the separation of layers becomes incomplete and finally stops altogether, the mixture assuming again the appearance of an emulsion. With a tall oil of average composition, the highest obtainable proportion of the esters and unsaponiflable separated by this method is approximately 70% of the total esters plus unsaponifiable present in the original esterified mixture.

The following Table I shows the quantity and proportion of the ester plus unsaponiflabie separated as upper layer at different resin acid concentrations. In each determination 100 grams =23% resin acids assess:

oiesteriiiedmixturewereusedobtainedby Tam! Ester: and amponificble separated as am layer" at diflercat resin acid from 100 grants mailed Iii-stare elm-sand I acid (I lnted to M W" concuin totalcstus .ar'as. hints-med mixture 1 Pact-f Grill Percent No.1 25.0

10.5 19.4 114 aodzimsin acidaoamesters 16.6 41.0 04.4 an unsaponiiiable.-. 8.4 45.0 70.7 V 7.0 47.0 73.5 H a (I) .m (I) No. II: 11.8 41% resin-acids, 50% esters u no V 0.0 and unsaponinable I m a no 9 8.0 00.0 7 41.0 .5 5 1570.3v 25 I I) 6.0 10.9 45% resin acids, 55% esters 15 18.7 34.0 and unsaponiiiable 10 31.0 56. (033.4 81.7

" of the esters and unsaponiflable remaining in solution in the lower layer when the upper limit I of separation is reached is approximately onehalf the weight of the resin acids present in the original esterined mixture. Therefore, the lower the resin acid content of the esterifled mixture,

the lower will be the quantity of the esters and unsaponiflable remaining dissolved in the soap. and the higher will be the recovery of the esters and unsaponiflable as upper layer. The implications of this are obvious; A reduction of the resin acid content, either of the tall oil serving as starting material orof the esterliled mixture, will result in an increase of the proportion of esters and unsaponiflablc separated. For example, esteriiled mixture-No. 2 of Table I showed, on standing, copious crystallization of resin acids. After removing the crystals by filtration, we obtained an esteriiled mixture containing only 29% resin acids. On neutralizing this mixtureand diluting to a resin acid concentration of 7%, we obtained 80% of the total esters and unsaponiflable as separated upper layer. Synthetic mixtures containing 10% and 5% the total esters and unsaponiflable resiectively. Besides crystallization, the fatty acid portion could also be increased by fractional distillation of either the tall oil or the esterifled mixture.

The equipment required for the practice of this process is extremely simple. Open simple construction may be used provided they are equipped with means for raising the temperature to above atmospheric. Jacketed tanks or tanks equipped with steam coils may be used. We also may applylive steam for-raising the temperature, allowing for the dilution caused by the condensation of steam in determining the not take place at all.

final resin acid concentration. At room temperature or slightly "above, the separation of layers is too slow for practical purposes or does The separation is most rapid and sharp when the neutralized ester-flied mixture is heated near or to the boiling point of water. On discontinuing the heating, the lay- 81's separate, even in large batches, within a few minutes. r

The next step in our process is the separation of that portion of the estersand .unsaponiilable which remains dissolved in the resin acid soap solution. One method to eilect this separation comprises subjecting the. soap solution-to a hydrocarbon solvent extraction in the presence of a proportional amount of a neutral salt solution, until the soap layer is substantially free of esters and unsaponifiable. Such method whichcan be practiced on a commercial saleis more fully disclosed in our co-pending application SerialNo. 438,006, filed April 7, 1942. v herein preferred, method for separating the dissolved esters and. unsaponifiable from the soap solution comprises acidifying the soap solutionto recover a mixture of resin acids, estersand unsaponifiable, The composition. of this mixture is approximately 2 parts resin acids and 1 part esters and unsaponifiable. Onstanding, a large portion of the resin acids crystallizes. If crystaliization is slow, due to the high viscosity of the mixture, we may, as we prefer, add this mixture to a new batch of esterified mixture, let crystallize, remove the crystals, by filtration and subject the oil filtrate to the same'separating treatment as disclosed in the. present application, namely,

neutralizing the resin acids, vadjusting to such a resin acid concentration'jwhich will give the largest separation 'of upper layer, heating and separating. the resulting layers, Inpthe alternative we may add to the mixture obtained from f h the soap solution an inertsolv'ent, preferably a" H hydrocarbon solve'nt,to decrease the viscosity of the mixture sufliciently to speed up crystalliza- On continuously alternating these two steps, we can process large quantities-of ester'ifiedmixtures" resin acids gave separations of 93% and 97% of tion. On alternating the two steps, namelyjupper layer formation to separate the major portions of the esters and unsaponifiable, and crystallization of themixture obtained by acidification of the soap solution, weremove'alternat'ely a portion of estersand unsa'pon'ifiable in one step,

and a-portion of the resin acids'in the next step.

and obtain as products (1) amixture of fatty acid esters and unsaponifiable substantially-free of resin acids, and (2), crystalline resinlacids.

the fatty acid ester portion containing substantially' the total unsaponifiable matter. The esters and unsaponifiable may then be subjected to a tanksof Another and the acid and distill the esters to separate them from the major portion of the unsaponifiable. The crystalline crude resin acids also can be refined in accordance with the teaching of our aforesaid patent or any other known method for refining rosin.

If our starting material is refined tall oil, we obtain the fatty acid and resin acid portions in a refined form. The fatty acid esters in this case will contain substantially all of the unsaponifiable matter. For this reason, it is desirable to start with a refined tall 011 containing a low proportion of unsaponifiable.

The following examples are introduced to further illustrate our invention, but are not intended to limit the broad scope thereof:

Exams: I

' boiled gently for a few minutes and left to separate. The upper layer was clear and weighed 2.23 kilograms. The residual esters and unsaponifiable were extracted by adding to the lower layer 1.54 liters of a 25% sodium chloride solution, saturating with benzol and extracting. The

- extract contained 0.7 kilogram esters and unsaponifiable. The soap solution was acidified and the resin acids recovered.

EXAIPLI H 200 grams of an esterified mixture obtained by reacting tall oil and methanol at superatmospheric pressure and containing 41% resin acids, were neutralized with 4.2 normal sodium hydroxide solution and sufficient water added to produce a resin acid concentration of 7%. After heating the mixture to boiling temperature 79 grams fatty acid esters and unsaponiflable separated as upper layer. The lower layer was acidified with dilute sulphuric acid, the mixture of resin acids and fattty acid esters separated. dehydrated, mixed with 200 grams of fresh esterified mixture and let stand to crystallize. From the crystallized mixture, 50 grams resin acids were separated by filtration. The filtrate was neutralized and diluted to a resin acid concentration of 7%, heated and 94 grams fatty acid esters and unsaponifiable separated as upper layer. The lower layer was again acidified and the liberated components mixed with 150 grams fresh estelifled mixture. On crystallization, this mixture gave 65 grams crystalline resin acids. The liquid portion was again neutralized, adjusted to 7% resin acid concentration and 93 grams fatty acid esters and unsaponiilable obtained. The lower layer was again acidified, etc.

separation and acidificatim was repeated a number of times.

We claim as our invention:

1. A process for the separation and recovery of tall oil resin acids and fatty acids which comprises converting the fatty acids into their alkyl esters, substantially completely neutralizing the resin acids with an aqueoim alkali in dilution to provide a resin acid concentration of from about toabout5%. he'atlngthemixturetocause a separation of two layers and recovering the upper layer composed of the major portion of the fatty acid esters and imsaponifiable matter.

2.1iprocesfortheseparationandrecoven oftalloilresinaclds andfattyacidswhichcomprises converting the fatty acids into their alkyl esters, substantially completely neutralizing the resin acids with an aqueous alkali in dilution to provide a resin acid concentration of from about 30toabout5%,heatingthcmixtureatatemperature of approximately 100' 6., permitting the mixture to settle after termination of heatingto cause aseparafionoftwolayersandrecovering theupperlayercompoaedofthemajor 25 portion of the fatty acid esters and unsaponifia- 3o esters, substantially completely neutralizing the The cycle of crystallization, neutralization. layer resinacids withanaqueousalkaliindilution to provide a resin acid concentration of from about 30 to about 5%, heating the mixture at a superatmospheric temperature to came a separation of two layers, recovering the uwer layer composed of the major portion of the fatty acid esters and unsaponifiable matter and subjecting the lower layer to further treatment to separate and recover the remaining fatty acid ester content thereof and the resin acids.

4. The method of separating the constituents of a tall oil mixture wherein the fatty acids are in the form of their alkyl esters, which comprises substantially completely neutralising the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 30 to about 5%, heating the mixture to caus a separation of two layers and recovering the upper layer composed of the major portion of the fatty acid esters and unsaponifiable matter.

5. The method of separating the constituents of a mixture composed of tall oil fatty acids and resin acids wherein the fatty acids are in the form of their alkyl esters, which comprises substantially completely neutralising the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 30to about5%,heatingthemlxturetocame a separation of two layers and recovering the upper layer composed of the major portion of the fatty acid esters and matter.

8. The process of separating fatty acids from resin acids contained in tall oil which comprises reducing the normal resin acid content thereof. treating the remaining tall oil mixture by converting the fatty acids into their alb'l esters, substantially completely neutralising the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 30 to about 5%, heating the mixture to causeaseparationoftwolayersandncovenng 7. The process of separating fatty acids from.

' converting the fatty acids into their alkyl esters,

substantially completely neutralizing the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 20 to about 7%, heating the mixture to cause a separation of two layers and recovering the upper layer composedof the major portion of the fatty acidesters and unsaponifiable matter.

9. The process of separating fatty acids from resin acids contained in tall oil which comprises converting the fatty acids into their alkyl esters,

v substantially completely neutralizing the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 10 to about heating the mixture to cause a separation of .two layers and recovering the upper layer composed of the major portion of the, fatty acid esters and unsaponiflable matter.

10. The process of separating fatty acids from resin acids contained in tall oil which comprises converting the fatty acids into their alkyl esters, substantially completely neutralizing .the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 30 to about 5%, heating the mixture to cause a separation of two layers, recovering the upper layer composed of the major portion of the fatty acid esters and unsaponiflable matter, and subjecting the lower layer to extraction treatment to separate and recover the remaining fatty acid content from the resin acid soap solution.

11. The process of separating fatty acids from resin acids contained in tall oil which comprises converting the fatty acids into their alkyl sters, substantially completely neutralizing the resin acids with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to.,provide a resin acid concentration of from about 30 to about 5%, heating. the mixture to cause a separation of two layers, recovering the upper layer composed ofthe major portion of the fatty acid esters and unsaponiflable matter, acidifying the lower soap solution layer to form a mixture of resin acids and the residual esters plus unsaponiflable matter, crystallizing resin acids from the mixture .and returning the remaining oily filtrate portion to the neutralization step for further treatment in the process.

12. The process of separating fatty acids from resin acids contained .in tall 011 which comprises converting the fatty acids into their alkyl esters, permitting resin acids to crystallize out of solution and recovering them therefrom, substantially completely neutralizing the resin acids remaining in solution with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 30 to about 5%, heating the mixture to cause a separation of two layers and recovering the upper layer composed of the major portion of the fatty acid esters and unsaponiflable matter.

13. The process of separating fatty acids from resin acids contained in tall oil which comprises converting the fatty acids into their alkyl esters, mixing therewith a lower ,layer separated in the process as hereinafter set forth, permitting resin acids to crystallize out of solution and recovering them therefrom, substantially completely neutralizing the resin acids remaining in solution with an aqueous alkali and adjusting the aqueous content of the resulting soap solution to provide a resin acid concentration of from about 30 to about 5%, heating the mixture to cause a separation of two layers, recovering the upper layer composed of the major portion of the fatty acid esters contained in said solution, acidifying the lower layer to form a mixture of resin acids and the residual esters plus unsaponiflable matter and returning said resultant lower layer mixture for treatment in the process as hereinbefore set forth.

FREDERICK H. GAYER.

CHARLES E. FAWKES.