IiVD UXTRIAL A N D ENGINEERING CHEMIXTRY
April, 1923
395
Losses in the Refining of Edible Oils’ By B. H. Thurman AMERICAN LINSEED OIL CO., NEW
YORK,
N.Y.
ACH kind of edible oil, and then treating with I n practice. two distincf kinds of losses attend the refining or oil presents a differlime and noting the color purification of any product. First, there is the production of waste, ent series of probof the oil before and after representing the impurifies removed, In most cases, these can be put lems with respect to losses, thelime treatment. Hulme to some use, and are then called by-products. In the refining procand will be discussed sepadiscovered that treatment esses of edible oils (as well as in most other refining operations) rately. For example, cocoof cottonseed oil with a there occurs another form of loss-actual disappearance of materials nut oil is usually filtered a t boric acid solution precipi-so that there is a shrinkage or difference between the weight of the mill, and for tJhisreason tates a colored body, and material receiued by the refinery and the total amountfinally delivered. and the fact that copra this body has been found It is with this shrinkage or physical loss, and not with direcflyfinanmeat is e x c e p t i o n a1 1y by the writer to be a phoscia1 or depreciation losscs, that this article is concerned. fibrous, it reaches the rephatide. finer in a much clearer condition than the other oils. Cottonseed, corn, soy, and peaBORICACID AND CAUSTIC SODA PRECIPITATIONS nut oils made in the United States average approximately The study of a number of oils showed that the removal of the same moisture and “meal” content (the latter usually the phosphatides lowered the free-fatty-acid content in each called “gasoline insoluble,” from the laboratory method used case 0.2 per cent, indicating the acidic character of the proto determine it). Imported peanut and soy oils are similar tein, or, possibly, that it is joined to a fatty acid radical. in moisture content, but contain less insoluble matter, a condition due probably to longer settling. Coconut oil may run SUMMARY OF BORIC ACID PRECIPITATE FROM COTTONSEED OIL Per cent slightly higher in moisture but lower in insoluble matter. Gross .......................................... 1.445 Less T. F. A. present ............................ PROCESS LOSSES 0 2 7
E
The next encounter the refiner has with losses occurs in the processes used for eliminating these impurities. Treatment with an alkali is the first operation. This is commonly looked upon as a process which merely removes the free fatty acids; but this is not its only purpose, and perhaps not always the most important. Sodium hydroxide removes not only the free fatty acids, but also the phosphatides and coloring matter, and is used universally on cottonseed, soy, and corn oils. Sodium carbonate will remove the free fatty acids, but relatively little of the coloring matter and phosphatides. Lime cannot be used at this stage on account of emulsion troubles, but it is interesting to note that in the case of cottonseed oil it removes some of the color which is unaffected by any of the soda alkalies, fuller’s earth, or bleaching carbon. This can be shown by first refining and bleaching cottonseed
..................... .......................................
N e t protein or phosphatides.. Plus meal
0.488
O X O
0.578
The table shows that the refiner pays lor 0.578 per cent of impurity (called “loss not fat”) in cottonseed oil which he cannot sell as oil, for phosphatides are removed, not only by boric acid, but also by sodium hydroxide, which removes also free fatty acids in the form of soap, and nonfatty material commonly regarded as “coloring matter.” The combined precipitate from the soda treatment of soap, the inevitable emulsified oil, phosphatides, and coloring matter constitute the refining residue known as “soap stock.” The following table (Page 396) shows the average analysis of soap stock from 80 tank cars of cottonseed oil, the average analysis of which m7as as follows: P. F. A.
Presented before the Division of Agricultural and Food Chemistry a t the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. 1
Moisture Gasoline insoluble
Per cent 1.3; 0.32 0.09
BORICACID PRECIPITATE FROM COMPOSITE OF 15 TANK CARSOF COTTONSEED 011. Per cent A--Boric acid 6.21 B-Moisture (from boric acid Analysis of C and D-Per cent solution) 32.63 3,03C (due t o meal, 0.0108) Pa06 C-Gasoline-solublea phospha0 . 6 6 d (due t o meal, 0.2900) N tide 4- oil 57.94 Analysis of Alcohol-Soluble Portion of Cf-Per cent F. F. A.h (oleic) 14.01 1 0.126 T.F. A. Constants T.P. A.i (by weight) 72.65 Basis of original oil 0 . 6 5 6 } Acid No. 196 (pure cotton oil F. A. 195) Pa05 2.26 J Iodine No. 106 (pure cotton oil F. A. 108) N 0.26 Analysis of Alcohol-Insoluble Portion of CQ-Per cent D-Gasoline insolubleb (meal) 3 62 F. F. A. (oleic) 12.33 T.F. A. (by weight)
TOTAL PRECIPITATES
1;:;;
P206
N
TOTAL ...... 100.406 Per rent Calculated t o original oil. I.45 Calculated t o original oil.. 0 . 0 9 C Calculated t o original oil. 0.075 d Calculated to original oil.. 0.016 e Calculated t o original oil.. 2.5 f Alcohol-soluble portion. 36.35 u Alcohol-insoluble portion. 21.59 h Free fatty acid.. z Total fatty acid.. NOTE:T h e alcohol-insoluble f a t t y acids from this treatment were oily, as distinguished from cotton-oil fatty acids, which solidify a t room temperature. The alcohol-insoluble portion, which contained 7.92 per cent phosphoric acid, was a transparent, cherry-colored, brittle wax, which did not melt at looo C . a b
. . ...
............. ............
396
I N D U S T R I A L A N D ENGINEERING CHEiWISTRY SOAPSTOCK ANALPSIS (Average from 80 cars of cottonseed oil)
Per cent 18.70 23.50 3.25
............... ............ ..................................... ..................... 45.60 .............................. ............. 91.05 8.95
Neutral oil (emulsified in soap stock) Fatty anhydrides (combined with NazO) Ash (NarO) Water (from NaOH solution). Total b y analysis.. Foreign matter not fat (by difference). Total soap stock (11.8 per cent of original oil)
......100.00
VOl. 15, No. 4
5-On acidulating coconut soap stock above 160’ F., 0.56 per cent of the fat in the soap stock is volatilized (Gwynn), equivalent to 0.049 per cent of the original oil. In the case of other oils, no loss of this character is known t o occur.
ACTIONOF BLEACHING AGENTS
After caustic refining the oil is bleached. Chemical bleaches are not used because they injure the flavor of the oil. Benzoyl peroxide has been tried, and while it has no The nonfatty matter including meal, calculated to original- apparent action on the glycerides, its bleaching effect is not oil basis, is 1.05 per cent. The total shrinkage of this oil due stable, the color reverting above 110’ C. to nonfatty impurities is as follows: On account of the nature of the bleaching process the term “bleaching” is not strictly accurate; what occurs is Per cent Moisture.. ...................................... 0.32 really a cleaning and decolorizing. The agents used are Meal ........................................... .09 fuller’s earth and carbon. They serve as scrubbing agents, Phosphatides and coloring matter .................. 0.96 and remove soap, moisture, and nonfatty mutter, as well as 1.37 coloring matter. The different kinds of earths used show Sodium hydroxide removes from peanut oil 0.2 to 0.4 per varying decolorizing effects on vegetable oils, and also a cercent nonfatty matter; from coconut oil 0.1 to 0.2 per cent; tain degree of oxidation. They absorb a quantity of oil, constituting a loss. The same is true ol carbon, with the from soy oil about 0.5 per cent. exception that it does not seem to oxidize the oil. The earths The emulsion phenomena during refining are interesting. When the caustic solution is added to the cold oil, a water- retain, even after steaming and washing, about 24 per cent or in-oil emulsion is first produced, which remains homogeneous more of oil on the dry-weight basis of the earth, and as it is even when 10 per cent of caustic solution is used. When not practicable to recover this, it represents the amount of heat is applied and the mixture continually stirred, the emul- oil actually lost in bleaching. No data can be given as to sion undergoes a complete reversal, becoming an oil-in-water whether earths have a selective retentivity for various emulsion a t which point the ‘lbreak” occurs-i. e., the re- oils, but from experiments now in process it would seem versed emulsion, being no longer miscible with oil, coagulates. that peanut oil is retained more tenaciously than other oils. The loss from bleaching depends on the amount and kind . The flakes of soap stock, consisting of an emulsion of soap, coloring matter, and phosphatides, are then allowed to settle. of decolorizing material used. On cottonseed, soy, and corn It is necessary to use sodium salts for this purpose. Lime, oils, about 1.5 per cent of bleach is used; and if the retention for example, produces a permanent water-in-oil emulsion is 30 per cent on the dry-earth basis, this represents 0.45 per which cannot be reversed by heating. This soap stock may cent loss of the oil treated. Peanut oil requires less earth, and be used by the soap-maker as is, or it may be first “split” the average loss of oil is about 0.3 per cent. Coconut oil is by digestion, by means of sulfuric acid, or by Twitchell usually bleached with 0.2 per cent carbon and 0.4 per cent reagent into free fatty acids, which are then purified by dis- earth. The average loss observed on 60 tank-car lots was 0.24 per cent. tillation.
PHYSICAL LOSSESI N REFININGOIL AND REWORKING SOAPSTOCK The physical loss or shrinkage incurred in handling soap stock is indirectly a charge against the refinery, and may be divided into five stages: 1-In the case of cottonseed oil, an average of 80 tank cars worked showed that 1.44 per cent of neutral oil was saponified, representing a loss of 0.08 per cent as glycerol. Peanut and soy oils saponify to the extent of about 0.7 per cent, the glycerol equivalent being 0.035 per cent. The treatment of coconut oil with caustic soda is done so rapidly that the amount of saponification is usually negligible, rarely amounting t o so much as 0 . 2 per cent. 2-When soap stock from cottonseed, soy, and peanut oils is acidified with sulfuric acid, a loss occurs by emulsion or adsorption with the carbonized nonfatty matter present, for the recovery of which no means has been found. This amounts to about 0.15 per cent of the oil worked. Coconut oil suffers a loss from this source of 0.85 per cent of the fat acidulated, which is equivalent to 0.075 per cent of the original oil. 3-Solubility losses apply t o coconut oil only. These have been found by Gwynn (results hitherto unpublished) t o be 0.56 per cent on fat acidulated, representing a loss of 0.049 per cent on original oil. &Hydrolysis, or splitting of glycerides on diluting soap stock, due to the presence of combined caustic soda, was found by Gwynn to be 0.028 per cent in the case of coconut oil. (Washing coconut oil with water and salt solution also results in some hydrolysis, the extent of which has not been determined.) No figures are available in the case of the other oils, but there is evidence that the hydrolysis is very much lower than that of coconut oil, and is probably negligible. The hydrolysis on acidulating soap stock probably applies to that of coconut oil only. It has been determined as 0.34 per cent or 0.029 per cent of the oil worked.
HYDROGENATION LOSSES If hydrogenation is carried out under the pressure system, where no gases are allowed to escape, there is a gain, increasing directly as the iodine number decreases. This gain, under factory conditions, is 0.04 per cent for coconut oil and 0.78 per cent for cottonseed oil, each oil being completely hydrogenated. When the open or bubbling system is used, there is a shrinkage due to distillation or entrainment of material by the hydrogen passing through the oil. The distillate is highly colored and of a foul odor, but can be recovered and used as soap stock and therefore does not constitute a physical loss. But the gain in weight due to hydrogenation is not as great in the open system as in the closed type, because a t high temperatures noncondensable gases are taken out which constitute a loss. LOSSES DURING DEODORIZATION The process of deodorization is the final step in the refining of edible oils. Various types of apparatus are used, and the choice of either steam or hydrogen is optional with the operator. In this operation, as in hydrogenation, entrainment and volatilization cause losses due in part to noncondensable products constituting part of the objectionable impurities. Small amounts of free fatty acids and coloring matter are also carried over in the gas current. In the case of coconut oil, there will be a loss due to solubility of the distillate in the condensing water. Assuming that the free fatty acid on coconut oil is 0.03 per cent, this loss amounts to 0.016 per cent, but in the case of the other oils is practically zero. Faulty operation of the deodorizer may a t times
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
April, 1923
increase the free-fatty-acid content, in which case this loss is greater. It has been shown that on some poor types of deodorizers the free-fatty-acid content of the distillate may amount to three times as much as could be accounted for by the free-fatty-acid content of the original oil. TTOLATILE MATTER LOST
DURING
DEODORIZATION Per cent
.......................... ............. ......................
Coconut,. Cottonseed and peanut., Soy and corn.. Beef tallow and oleostearin..
..........
0.40 0.12-0.35 0.36-0.75 1.5 -1.75
The volatile loss is determined by the difference between incoming and outgoing scale weights, after correcting for
397
condensed distillate. Soluble distillate is included as volatile loss, unless determined in the condensing water.
sUMaaARY OF L~~~~~~ ~TO (A) r I: ~ ~ ~ R I T IINE SOIL PURCHASGD REFININGPROCESSES
AND
(B)
coconut
Corn Peanut Soy 0.27 0.27 0.27 0.27 0.39 .11 .I1 .I1 .ll 0.037 0.458 . . . . . . . . . . . . . . . . . . . . 0.272 0.30 0.50 0.200 .... 0.080 0.035 0.035 0.000 0.150 . . . . . 0.150 0.150 0.075 0.000 0.000 0.000 0.000 0.065 .......................... 0.057 .................. 0,250 0.550 0.250 0.550 0.449 0.450 0.4.50 0.450 0.450 0.240
........................
Cotton
Moisture Gasoline insolublea.. . . . . . . . . . . . . . Phosphatides.. ................... Other nonfatty acid material.. Glycerol loss by saponification. Loss by emulsion.. Soluhility loss., Glycerol loss by hydrolysis.. Volatility loss.. Bleaching loss..
.... ..... ..... ............... .................. .................. - - - - TOTAL.. ....................... 2.270 1.380 1.565 2 . 0 6 5 1.513 0
Includes all dirt, solid organic matter (meal), and colloidal meal.
The Catalytic Ammonolysis of Beta-Naphthol and Chlorobenzene in t h e Vapor State' By A. M. Howald with Alexander Lowy UNIVERSITY 08 PITTSBURGH, PITTSBURGH, PA.
p-Naphthol and chlorobenzene mixed with ammonia were passed in the uapor state at definite temperatures over various contact materials. Alumina was the best catalyst'found for fhe ammonolysis of p-naphthol. Good yields of @-naphthylamine(90 to 95 per cent of the naphthol used) were obtained over a runge of conditions. A study of the yield of p-naphthylamine obtained as depending on the catalyst, temperature, ratio of the reactants, and the rate of their PART 1.
CONVERSION OF BETA-NAPHTHOL TO BETA-NAPHTHYLAMINE*
T"
POWouer
the catalyst was made. Curues showing the e&ct of the temperature and rate of POWof the yield of p-naphthylamine were obtained. Some conversion of chlorobenzene to aniline was effected. Yields were low (up to 7 per cent) and the catalyst depreciation was rapid. Reduced metals of the iron group were the only confact materials found to catalyze appreciably the ammonolysis of chlorobenzene.
as well as some others according to the equations:
IS study of the vapor-phase ammonolysis of P-naph" " 3@2 -(yJ-O-(yJ HzO thol was undertaken for several reasons. I n the first place, while this reaction was tried and found to be successful in the preparation of aliphatic amines2 from alcohols, yet the action of ammonia on the phenols and naphthols has not been studied. Then too, P-naphthylamine is a valuable dye intermediate and is prepared commercially in quantity. However, the autoclave reaction now in use is necessarily an intermittent one, while a vapor-phase reaction could be made continuous. Also, since the reaction of ammonia on @-naphtholhas already been successfully catalyzed by a homogeneous catalyst3 in liquid systems, a study of it in the gaseous state from the viewpoint of heterogeneous catalysis - might help to correlate these two branches of catalytic phe- etc., seemed probable. nomena. EXPERIMENTAL PART References to the literature on the preparation of P-naphthylamine by the autoclave process are given below.4 The experimental apparatus is shown in Fig. 1. It was Various reactions might be expected to take place when built with three objects in mind-namely, to get a definite mixtures of /?-naphthol vapor and ammonia gas are passed and known mixture of ammonia gas and &naphthol vapor, to over contact masses. A primary reaction to give P-naphthylbring this mixture into contact witha catalytic mass at ti known amine according to the following equation temperature, and to collect the products of the reaction. The general method of conducting experiments, most of which were of 1-hr. duration, was as follows: August 21, 1922. Abstract of a thesis presented by A. M. Howald in partial fulfilment of the requirements for the degree of Doctor of Philosophy, August, 1922. Patent applied for. 2 Compt. rend., 148 (1909),898. 8 J . prakt. Chem., 121 69 (1904),49. 1 ILid., [I] 32 (1870). 286: I b i d . , [l]32 (1870),540; Be?., 13 (1880), 1298,I b i d . , 13 (1880),1850;14 (1881),2343;16 (1883), 19; D. R P. 14,612 1 Received
*
(1880); 117,471 (1900); 121,683 (1901); 123,570 (1901); 126,536 (1901); J . pvakt. Chem., [2]69 (1904), 49;70 (1904), 345; 71 (1905). 433;76 (1907). 240; 77 (1908),403.
+
The inner tube t of the vaporizer V was replaced by a shorter one.not reaching to the surface of the p-naphthol B in the vaporizer. Stopcock c4 was turned off the tubes UI and UZand t o a waste ammonia line and c1 and cp turned in such a manner as either t o shunt ammonia from T by or through the wash bottles W,, W2, Wa, and W4, as the experiment required. A slow stream of ammonia was passed through the whole train for about 15 min. thoroughly flushing it out. The furnace F was brought slowly t o the required temperature, and the external heating coils HI and H1 turned on. The furnace having reached the required temperature the heating liquid I,in the outer jacket of the vaporizer V was made to boil and the flow of ammonia through the flowmeter M
