US 2588435 A
Description (OCR text may contain errors)
Patented Mar. 11, 1952 PROCESS OF TREATING FATTY MATERIAL Christiaan van Loon, Dubbeldam, Eltje Smit, Dordrecht, Netherlands, and Willem van Rijn van Alkemade, Richmond, England, assignors to Lever Brothers Company, Cambridge, Mass., a corporation of Maine No Drawing. Application August 7, 1947, Serial No. 767,330. In the Netherlands June 19, 1942 Claims.
acids with low molecular monohydric alcohols are produced.
There are commercially available large amounts of very low grade fatty stocks, such as renderers tallow and grease, which contain large proportions of free fatty acids. These materials are dark brown or black, and the dark color is generally associated with a high free fatty acid content. These materials are quite unsatisfac tory for the production of white or light colored soaps, and it is not economical to refine and bleach such stocks by conventional methods.
In the esterification of a fatty acid with a low molecular alcohol it is usually found necessary to use an excess of alcohol. In known processes it has been found difficult to recover this excess alcohol owing to its content of water produced during the esterification process.
In accordance with the invention it has been found that fatty stocks having a high free fatty acid content, may be subjected to the combination treatment of first esterifying substantially all the free fatty acid with an alcohol of relatively high boiling point, and thereafter submitting the resulting reaction mass or mixture, including the products of said esterification, to
-alcoholysis with a low molecular weight monohydric alcohol to produce low molecular weight monohydric alcohol esters of fatty acids.
The objects achieved in accordance with the invention include provision of a process for recovering the fatty acid components in fatty stocks having a high content of free fatty acids; the provision of a process for obtaining high grade low molecular monohydric alcohol esters of fatty acids in a commercially advantageous maner; and other objects which will be apparent as details or embodiments of the invention are set forth hereinafter.
In accordance with the invention the free fatty I acids in the fatty stocks are substantially or completely esterified with any alcohol of relatively high boiling point, as the Water formed point of water but less than the boiling point of the high boiling alcohol. These are of necessity the limitations on the reaction temperature and the boiling point of the alcohol. Esterification should in general be carried out at relatively high temperatures, for example at 225 C., and in many cases it is desirable to do this under vacuum. As alcohols with high boiling point there can be used monohydric alcohols of high molecular weight such as cetyl alcohol, and polyhydric alcohols such as glycol and glycerol. Addition of an alcohol with high boiling point may not be necessary if the initial glyceride oil mixture to be treated contains partially esterified glycerol in the form of monoglycerides or diglycerides in such quantity that the unesterified hydroxyl groups are at least equivalent to the unesterified carboxyl groups in the free fatty acids. In other words a stoichiometric excess of free alcoholic groups relative to the free carboxylic groups in the reaction mixture is used to advantage, since in this way the free fatty acid content of the reaction mixture may be reduced comparatively quickly.
Preferably, however, the free fatty acids are esterified with an excess of high boiling point alcohol, as in this way the free fatty acids can be esterified comparatively quickly up to a fraction of one per cent. The esterification can be accomplished in any known manner and the known esterification catalysts can be used for the esterification, such as the alkaline catalyst in the illustrative example hereinafter.
In the subsequent step of alcoholysis there is no formation of free fatty acids, so that no losses of fatty acids occur in any subsequent refining. It will be seen that the alcoholysis frees a large part of the high boiling point alcohol which has been added for the purpose of esterifying the original free fatty acids, as well as a large proportion of any glycerol which may be present in the original material, and this alcohol and glycerol may be recovered for further use. It will be seen therefore that this high boiling point alcohol is consumed only in in the first step of the process of the invention, and that the subsequent step of forming the ester of the alcohol of low molecular Weight liberates the high boiling point alcohol again for further use. Thus when the glycerol or other high boiling point alcohol is re-used, the process becomes cyclic in which the. glycerol or other high boiling point alcohol is used as a means to transfer fatty acid radicals, alternately esterifying the hydroxyl groups of the glycerol with the high-molecular fatty acid and then liberating the glycerol or other high boiling point alcohol .by alcoholysis of the resulting ester with the low molecular weight alcohol.
In another variation of the process the glycerol for use in transferring fatty acid radicals alternately as described can be obtained by subjecting triglycerides to alcoholysis with the low molecular weight alcohol. The glycerol and partial glycerides thus formed may then be used for regenerating triglycerides by esterifying fatty acids therewith in accordance with the steps of the process heretofore explained.
In the following description of the invention glycerol is taken as illustrative of the high boiling point alcohol. The glycerol is added to the starting material in excess of that required for theoretical esterification to triglycerides, so that a mixture of monoglycerides, diglycerides and triglycerides is obtained. This mixture is then submitted to alcoholysis with an alcohol of low molecular Weight, for example, absolute ethyl alcohol in the manner known for the alcoholysis of triglycerides, and the greater part of both the glycerol added in the first stage and the glycerol present in the initial mixture separates off and can be recovered, for instance, by drawing off and Washing. The reaction mixture contains residual glycerides as Well as ethyl esters of fatty acids.
The reaction mixture obtained after alcoholysis can be utilized in a number of different ways. A few of these will be discussed below.
If refinery fatty acids or waste fats are taken and esterified with an excess of glycerol, and
then submitted to alcoholysis with potassium hydroxide as catalyst, a mixture is obtained which, when the free glycerol and alcohol have been removed, consists of residual glycerides, ethyl esters and some soap. Depending upon the type of initial material used, the quality of this mixture may be such that normal refining processes for oils are sufficient to obtain a usuable product consisting of residual glycerides and ethyl esters. The ethyl esters may, however, be separated from the glycerides by distillation, and the ethyl esters thus obtained in a particularly pure form. The remaining glycerides may then again undergo alcoholysis, so that a further portion of the glycerol is recovered and neutral ethyl esters are again formed.
Alcoholysis may be effected by any of the customary methods and may take place at the boiling point of the low molecular alcohol at atmospheric pressure with reflux cooling, or at somewhat higher pressure in a closed apparatus. It may also be carried out at a temperature below the boiling point, but in this case it must be continued for a longer period. In other words, the temperature, pressure and reaction time are not critical.
The known catalysts may be used for alcoholysis. It has been found, however, that alkali hydroxides or alkali compounds of polyhydric alcohols (for example, potassium glyceroxide) can be used with advantage as non-acid catalysts for alcoholysis. This means an appreciable simplification as compared with the use of alkali alcoholate which has to be prepared from an alkali metal, but which can be used. The alkali hydroxides are used in solid, dry form and are preferably dissolved in the alcohol first.
When using alkaline catalysts the free fatty acid remaining in the esters after esterification should preferably be neutralized with caustic soda or sodium carbonate and the estersbe carefully dried. A high soap content should be avoided, as this renders drying diificult.
For alcoholysis the alcohol must be free of water or at any rate contain very little water. Even 99% ethyl alcohol acts more slowly and less satisfactorily than absolute ethyl alcohol whilst 96% ethyl alcohol as such is not suitable for the process. Methyl alcohol is readily available in substantially anhydrous form. The low molecular weight alcohol is that usually used in the alcoholysis of fatty acid glycerides (see the U. S. Patents 2,177,407 and 2,271,619). Water should also be prevented from entering the reaction mixture during alcoholysis.
With suitable fatty acids or mixtures of fatty acids with glycerides as initial material the resulting products are suitable for the preparation of edible fats. In order to improve the taste, either the initial material or the products obtained by the process may be hardened and/or refined in any known manner.
Example 200 parts by weight of a mixture of free fatty acids and fat, consisting of 50% free fatty acids with a molecular weight of 272 and 50% hardened rape oil with a saponification number of 170, were mixed with 31.2 parts by weight of 98% glycerol and 0.28 parts by weight of sodium hydroxide (an alkaline esterification catalyst) in the form of a 4 normal solution. The free hydroxyl groups and carboxyl groups were in the ratio of 0996:0368. Esterification was effected by heating under vacuum, whilst a stream of hydrogen was passed through the mixture. After being heated for 3 hours at C. and for a further three and a half hours at C., the percentage of free fatty acid had dropped to 0.04% (as oleic acid).
To 200 parts by weight of the esterified mixture were added 64.4 parts by weight of absolute alcohol in which 0.6 part by Weight of sodium hydroxide had been dissolved. When this was boiled for 2 hours with reflux cooling and with all moisture excluded, a layer of glycerol separated out.
After removing the alcohol from the reaction mixture by distilling in a stream of hydrogen, 50 parts by weight of the soap-containing glycerol layer Were separated off and the ester layer was washed with warm water. 160 part by weight of ethyl esters were obtained from the ester layer by distilling with steam under vacuum, whilst 10 parts by weight of glycerides remained behind.
Methyl alcohol may be used in the above example in place of ethyl alcohol with comparable results.
1. The method which comprises reacting fatty glyceride stocks containing free fatty acids with a high boiling alcohol in the presence of an esterification catalyst and at a temperature above the boiling point of water at the reaction pressure, and said alcohol having a boiling point above said reaction temperature whereby water is removed during the reaction without too great a part of the high boiling alcohol evaporating and said free fatty acids in the stock are substantially completely esterified, and thereafter subjecting the reaction mixture to alcoholysis by reacting with a. low molecular weight monohydric alcohol to form low molecular weight monohydric alcohol esters of fatty acids.
2. The process of claim 1 wherein glycerol is used as the high boiling alcohol in the esterification step.
3'. The process of claim 1 in which the esterification step is carried out in the presence of an alkaline esterification catalyst.
4. The process of claim 1 in which glycerol is used as the high boiling alcohol and in which an alkali is used as a catalyst in the esterification step.
5. The process of claim 1 in which an alkali metal hydroxide dissolved in the low molecular weight monohydric alcohol is used as a catalyst in the alcoholysis step.
6. The process of claim 1 in which glycerol is used as the high boiling alcohol and the esterification is carried out in the presence of an alkaline catalyst, and in which the alcoholysis step is carried out in the presence of an alkali metal hydroxide dissolved in the low molecular weight monohydric alcohol as an alkaline catalyst.
'7. The process of claim 1 in which an alkali compound of a polyvalent alcohol is used as an alkaline catalyst in the alcoholysis step.
8. The process of claim 7 in which an alkali methyl glyceroxide is used as the alkaline catalyst in the alcoholysis step.
9. A cyclic process for treating fatty stocks consisting essentially of fatty acid glycerides and free fatty acids to convert substantially all of the free and chemically combined fatty acids in the stock into monohydric alcohol esters thereof, which comprises esterifying substantially all the free fatty acids in a portion of said stock with glycerol, alcoholyzing the fully esterified glyceride stock with a low-molecular monohydric alcohol, recovering glycerol from the alcoholysis mixture and recycling the same to process another portion of said fatty stock.
10. A cyclic process for treating fatty stocks consisting essentially of fatty acid glycerides and free fatty acids to convert substantially all of the free and chemically combined fatty acids in the stock into monohydric alcohol esters thereof,
and in which glycerol is used as a means to transfer the fatty acid radicals into monohydric alcohol esters, which comprises alternately esterifying substantially all the high molecular free fatty acids in said stock with glycerol under conditions in which the water formed is removed during the reaction, and then liberating the glycerol by alcoholysis of said esters with a low molecular monohydric alcohol, recovering glycerol from the alcoholysis mixture and recycling the glycerol to process another portion of said fatty stock.
CHRISTIAAN VAN LOON.
WILLEM VAN RIJN VAN ALKEMADE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,206,167 Edeler et a1. l July 2, 1940 2,271,619 Bradshaw Feb. 3, 1942 2,278,674 Segessemann Apr. 7, 1942 2,290,609 Goss July 21, 1942