US2866781A

US2866781A - Separating non-acids from soap stocks

Info

Publication number: US2866781A
Application number: US597265A
Authority: US
Inventors: Richard R Chase; John C Bowers
Original assignee: Union Bag and Paper Corp
Current assignee: Union Bag and Paper Corp
Priority date: 1956-07-11
Filing date: 1956-07-11
Publication date: 1958-12-30
Anticipated expiration: 1975-12-30

Description

nited States SEPARATING N ON -ACIDS FROM SOAP STOCKS I Richard R. Chase and John C. Bowers, Savannah, Ga.,

assignors to Union Bag-Camp Paper Corporation, New York, N. Y., a corporation of Virginia Application `luly 11, 1956, Serial No. 597,265

2 Claims. (Cl. 26o-97.7)

by removing the undesirable unsaponiables, thus making the resulting product more valuable.

Another object of the invention is to provide a processy for obtaining a non-acid fraction, rich in sterols and other valuable constituents such as lignoceryl and other higher alcohols. Production of rened sterols or alcohols from this non-acid fraction may be accomplished by any of a number of well known methods. In the case of sterols, the purification may be by acid precipitation and crystallization.

Previous solvent separations of the non-acids from soap stocks have involved either extraction of dry soap or extraction of aqueous solutions of soaps. When dry soaps are used, an expensive drying operation followed by a difficult so-lid-liquid extraction makes the separations uneconomical. When aqueous solutions were used, as in U. S. Patent No. 2,530,809, it has always been necesT sary to use substantial quantities of a material such as low molecular weight alcohols within the solution to prevent emulsions. We have discovered that esters of a relatively low molecular weight aliphatic acid and a relatively low molecular weight alcohol can be used as extraction solvents for aqueous soap solutions without need for further materials to prevent emulsions. Itis therefore a further object of the invention to provide a process which greatlysimplifies the prior economically unattractive process and is a distinct improvement over it.

A further object of the invention is to provide a process which is simple, efficient and economical to operate.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relatio-n of one or more of such steps with respect to each of the others thereof, which will be exemplified in the process hereinafter disclosed, and the scope of the invention will be indicated in the claims.

In our process the separation is effected by countercurrent extraction of soap or soap material with a solvent. In the practice of this process, the following steps are employed:

(l) The soap may be dissolved in water to give a homogeneous mixture. In the event the starting material is not in soap form, it is tirst necessary to convert it to a soap by any of several processes, for example, by boiling with caustic soda solution. We have found that a, dilution of the soap with one to two parts of water is atent O ICC satisfactory. Although there is no reason why more or less water may not be used successfully, if desired, it should be pointed out that the lower limit is governed by the requirement that sufficient water must beadded to put all the soap in solution. With regard to the upper limit, additional amounts of water above those specified may be added, but large quantities will make the process uneconomical because of the necessity for handling an excessively large quantity of material, thus increasing both equipment costs and operating costs.

(2) The above aqueous solution of soap is subjected to extraction with the ester solvent. This may be done by any one of several methods, but countercurrent extraction is probably the most eicient. So far our extractions have been made in separatory tunnels, in a Podbielniak centrifugal extractor or in a mixer-settler extraction apparatus, although other extraction devices such as packed columns can also be used.

(3) The solution of unsaponiable material extracted from the soap may be washed with Water to free it from traces of the soap carried over. This water may then be used in making the original soap solution if desired. This washing step is not essential.

(4) The solutionof unsaponiables is freed of solvent by evaporatng and stripping. 1 (5) The extracted unsaponifiable material may be further processed to remove the sterols present by any of a number of methods such as crystallization from suitable solvents, acid refining, or further extraction with solvents as disclosed by Vogel and Christensen in U. S. Patent No. 2,499,430.

(6) The soaps of fatty and rosin acids which have Vbeen materially reduced in non-acid content by this process may be recovered in any convenient manner such as salting out or converting to oils. In most cases it would first be preferable to remove residual ester solvent by evaporation. Conversion to oils could then be made by treating with acids such as hydrochloricv or sulfuric. The resulting product which separates from the aqueous phase may be skimmed oi and is a distinct improvement over the starting material.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which the single figure shows a diagrammatical flow sheet and the arrangement of apparatus suitable for carrying out the invention.

Referring more particularly to the drawing, it will be seen that the apparatus .comprises an extractor which consists of a single column for extracting and washing the unsaponiable extract. It will be recognized that two columns or other extraction devices could be used equally well or that the washing step could be omitted if desired. The solvent enters the bottom of the extraction zone at 1 and flows up the column countercurrent to the soap solution, leaving at 2 after having extracted the non-acids and having been washed relatively free of both entrained and dissolved soaps. Water enters the top of the washing zone at 3 and falls through the rising solvent Washing out the soaps. In the claritication zone the water separates from the rising solvent and is drawn off at 4. This water containing soaps is mixed with the feed stock at 5 and the resulting soap solution enters the top of the extraction zone at 6. The soap solution falls through the extraction zone leaving the column at 7. The nonacids are freed of solvent in the still at 8, the recovered solvent 9 being returned to the bottom of the extraction zone at 1. The non-acids are withdrawn from the still to lstorage 10. The soaps leaving the column at 7 Vare stripped in still 11 of solvent and a portion of water in which the soaps are dissolved. Thesolvent is separated from the distilled water in decanter 12 and returned, together with the solvent produced in still 8, to the extraction zone at 1. The water from the decanter 13 will be saturated with solvent and for convenient recovery of this solvent it is returned to the column at 3 as part of the wash water. The solvent-free aqueous soap solution is removed from still 11 to aciditier `14. Here acid is added to convert the soaps to oils. It might be desirable to add all or part of the acid before stripping off the ester solvent in still 11 since addition of the acid at this earlier point would reduce foaming tendencies in this stripping operation. Two liquid phases are formed upon this acidification andthe oil phase is removed to storage while the aqueous phase containing salts in solution is discarded, processed for recovery of its chemical content, or otherwise disposed of. The relatively small amount of solid phase that is formed may be discarded.

The foregoing arrangement of apparatus and ow sheet are given for purpose of illustration. It will oe recognized that numerous variations of this apparatus may be used without departing from the spirit of the invention. The following specific examples will illustrate the practice of the invention. These are considered examples only and by no means` are intended to limit the extent of the materials used or `the modifications possible.

Example I As an example of our invention, 25 pounds of black liquor skimmings were dissolved in 50 pounds of water. The resulting mixture was pumped into the center of a Podbielniak centrifugal extractor while 9.5 gallons of isopropyl acetate `were being fed into the periphery. Under the inucnce of` centrifugal force, the lighter isopropyl acetate wasdisplaced toward the center by the heavier soap solution and the soap solution was thus extracted. Theisopropyl-acetate was removed from the center containing the non-acids while the soaps essentially free of non-acids were removed from the periphery. Analysis of the extract showed it contained solids which analyzed at least.84.4 percent non-acids. Conversion of the ratti nate to oil `gave an Ioil `of which only 0.8 percent was non-acids. Theextract was later reintroduced into the periphery of the Podbielniak `extractor while 6 gallons of water were being introduced at the center. This amount of water was chosen as it was the amount used to dilute the original skimmings. The washed extract, having been displaced tothe center, was removed while wash water containing the soaps was removed from the periphery. The wash water contained solids which analyzed 13.6 percent non-acids. The washed extract contained solids whichanalyzed by the same method 86.2 percent non-acids. Analysis `for soap content, however, indicated that these solids contained less than 1 percent soaps. The original skimmings when converted tooil gave an oil containing 8.1 percent non-acids. Thus a marked reduction was effected in the non-acid content of the oil. At the same time a non-acid material virtually free from soaps was separated.

Example II A solution of 1 part by weight of black liquor skimmings in 2 parts by weight of water was extracted with isopropyl acetate. The volume ratio of solvent to soap solution was 1:1. This extraction was done in a continuous manner in a three stage mixer-settler type `of extraction apparatus. A fourth mixer-settler stage was employed for washing the extract continuously. Crude oil made from the unextracted soap had an unsaponiable content of 8.5%. Crude oil made from the extracted soap had an unsaponiable content of 2.0%. The extracted material analyzed 88.1% unsaponitiables.

In the preceding examples the soap stock processed was black liquor skimmingsand the solvent employed was 4 isopropyl acetate. However the following solvents were also employed, not only with black liquor skimmings but also with tall oil pitch and cottonseed foots:

N-butyl acetate Iso-butyl acetate Sec-butyl acetate Ethyl acetate Ethyl propionate Amyl acetate Methyl amyl acetate Percent; Unsaponltiablus Material Before Ex- After Extraction traction Cottonsced Fonts 2.35 0. E4 Saponined tall oil pitch 28. 9. 90

It should be understood that the process of the present invention can be used equally well on any soap stocks, such as the soap from alkali refining of vegetable oils, soap made from the pitch that results from the distillation of tall oil or fatty acids, or other similar soap stocks con` taining non-acids.

We have found that extremely good extraction is obtained by our process in the temperature range of 80 to F., but higher or lower temperatures than the range specified may be used if desired. As heretofore explained, there is no upper limit to the dilution of soap stock which is satisfactory, but economics will, in a practical way, limit the extent of dilution that is desirable. Similarly, there is no known reason why practically any amount of isopropyl acetate or like solvent could not be used as long as it is enough to exceed the solubility of such solvent in the soap solution chosen. When a soap solution is made from one part of tall oil skimmings and one part of water, the minimum amount of isopropyl acetate that can be used at room temperature is about one volume of isopropyl acetate per volume of soap solution. t

From the foregoing description and accompanying drawing it will be apparent that the process of the present invention is a distinct improvement over previous solvent separations of the non-acids from soap stocks and is particularly advantageous in the case of aqueous solutions where it is possible to extract without the heretofore necessary addition of some materials such as alcohols to prevent emulsions.

Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

l. In a method of separating non-acid materials including sterols and higher alcohols from a product selected fromthe group consisting of crude tall oilsoap skimmings and cotton seed foots obtained by alkaline treatment thereof, the steps which comprise dissolving said product in water to form a water solution of said soap, extracting said non-acid materials from said soap solution with an ester selected from the group consisting of ethyl acetate, isopropyl acetate, normal butyl acetate, isobutyl acetate, secondary butyl acetate, amyl acetate, methyl amyl acetate, and ethyl propionate to provide a solvent solution of said non-acid material, removing residual ester solvent from bcth said solvent solution of the non-acid material and the said soap solution by evaporat-4 ing and stripping, acidifyng the solvent-free soap solution 5 lation during said extraction step.

References Cited in the le of this patent UNITED STATES PATENTS l0 2,296,952 Ross et al Sept. 29, 1942 2,315,584 Borglin Apr. 6, 1943 2,530,810 Christenson et al. Nov. 21, 1950

Claims

1. IN A METHOD OF SEPARATING NON-ACID MATERIALS INCLUDING STEROLS AND HIGHER ALCOHOLS FROM A PRODUCT SELECTED FROM THE GROUP CONSISTIG OF CRUDE TALL OIL SOAP SKIMMINGS AND COTTON SEED FOOTS OBTAINED BY ALKALINE TREATMENT THEREOF, THE STEPS WHICH COMPRISE DISSOLVING SAID PRODUCT IN WATER TO FORM A WATER SOLUTION OF SAID SOAP, EXTRACTING SAID NON-ACID MATERIALS FROM SAID SOAP SOLUTION WITH AN ESTER SELECTED FROM THE GROUP CONSISTING OF ETHYL ACETATE, ISOPROPYL ACETATE, NORMAL BUTYL ACETATE, ISOBUTYL ACETATE, SECONDARY BUTYL ACETATE, AMYL ACETATE, METHYL AMYL ACETATE, AND ETHYL PROPIONATE TO PROVIDE A SOLVENT SOLUTION OF SAID NON-ACID MATERIAL, REMOVING RESIDUAL ESTER SOLVENT FROM BOTH SAID SOLVENT SOLUTION OF THE NON-ACID MATERIAL AND THE SAID SOAP SOLUTION BY EVAPORATING AND STRIPPING, ACIDIFYING THE SOLVENT-FREE SOAP SOLUTION TO LIBERATE SOAP ACIDS THEREFROM AND SEPARATING SAID NONACID MATERIAL.