Solubilities of Oil and Waxes in Organic Solvents. I11 JOHNW. POOLE AND THEODORE A. MAKGELSDORF, Massachusetts Institute of Technology, Cambridge, Mass. in oil-exists. Continuing the work discussed in previous pa- provided only one phase-solvent pers, the effects of temperature and oil : solvent The relation apparently predicts calues of the ratio on the solubiliiy of parafin wax have been same degree of precision as those experimentally studied for butyl formate, n-butyl aldehyde, and determined. A graphical comparison of the relation with dielhyl carbinol, which solvenis chosen f r o m preexperimental data is presented, using the three vious work appeared to have definite promise. for which experimental data were the most solvents I n addition, from a consideration of all the data of the constants to be used complete. Values secured u p to the present, general equations have in the relation are given for a large number of been developed for wax solubility, applicable to soloents. all conditions of temperature or oil: solvent ratio,
I
EXPERIMEKTAL PROCEDURE
N PREVIOUS papers of this series (1, 2 ) solubility data
have been presented for waxes and oils in a considerable number of organic solvents. Most of these solvents were investigated only on a qualitative or serni-quantitative basis, the results of such investigations being sufficient to eliminate many solvents as prospects for dewaxing media. Quantitative solubility data were secured for :some of the most promising compounds and have been reported in previous papers. This paper presents results obtained through a continuation of the work. Furthermore, all data have been reviewed and examined to determine if there exist any recurring characteristics which may be used to predict solubilities without the necessity of complete quantitative experimentation. I n the work already reported, the Drocedure has been to determine the solubility- t em p e r a t u r e data for a commercial wax and a commercial Pennsylvania oil in the solvent under observation. A f t e r obtaining these data, three component mixtures have been used in order to show the effect of oil on FTax solubility. Most of the work of Fahnestock a n d M u r r a y ( 2 ) was directed toward this portion of the problem. The present experimental -51 I 1 I 0 5 I0 I5 20 25 30 TEMPERATURE M DECRES CENTIGRADE work, carried out by C. E. Lliddleton and FIGURE 1. TEMPERATURE-SOLUBILITY CURVESFOR WAX I N VARIOUSMIX- IT. H. Roberts, also TURES OF OILAND BUTYL FORMATEd e a l s m a i n l y with this same Dhase and considers the solvents butyl aldehyde, diethyl cariinol (symamyl alcohol), and butyl formate. Acetaldehyde was found too weakly miscible with hydrocarbons for such consideration.
Without essential variation the analytical procedure was identical with that used in previous work (2). The materials used were:
a
. d'
+Butyl aldehyde: b . p. 71-77O C sp. gr., 0.817 Butyl formate. b . 1d0-106.5° , s p . gr., 0.911 Diethql carbin'ol: p.. 110-120' 2.; s p gr., 0 . 8 3 0 Acetaldehyde: b . p. 20.8O C sp. g r . , 0 806 Pennsylvania l u b r i c h n g oil:" flash point, 405' C.; fire point, 465' F. ( 2 4 0 6 ' C . ) ; viscosity ( a t looo F. or 37.8" C . ) , 204 seconds; Saybolt Urnversal. pour 20' F.: sp. gr., 0.880 Conhercial.paraffin wax: m. p., 5 0 . 0 ° C.(A.S.T.M. Method D 22-47)
%:
.
In conformity with previous papers the results are presented graphically in Figures 1 to 3, which show the averaged solubility data as a function of temperature for v a r i o u s oil conc e n t r a t i o n . These f i g u r e s are self-explanatory.
GENERALEXPRESSION FOR WAX
SOLUBILITY By considering the d a t a p r e s e n t e d in the previous papers of this series as well as the r e s u l t s h e r e reported, it has been found that c e r t a i n analogies exist among all the solvents. 2. TEMPERATURE-SOLUBILITY \Then sol u bi l i t y , FIGURE CURVESFOR WAX IN VARIOUS MIXexpressed as grams of TURES OF O I L AND n - B u T Y L ALDEwax per 100 g r a m s HYDE of an oil-free solvent, is plotted on logarithmic paper against absolute temperature, it is found that with a few minor exceptions straight lines can be drawn from which the points do not deviate by more than the experimental error. Furthermore, these lines are found to be essentially parallel, which means that for any solvent the solubility of wax may be expressed by the general equation:
1215
1216
INDUSTRIAL AND ENGINEERING CHEMISTRY where W
=
Vol. 24, No. 11
W,+W.XL=W (2) total grams of wax dissolved by 100 grams of solvent, and oil associated with it
From this equation and each experimental value of W , a corresponding value of W , could be calculated. These values were plotted on logarithmic paper, when as before it was found that the points for any given solvent fell reasonably close to a straight line which was again essentially parallel to similar lines drawn for other solvents. I n short, the relationship between W eand temperature could be expressed as log W e = B(l0g T
FIGURE3.
TEMPERATURE-SOLUBILITY CURVES FOR WAX IN VARIOUSMIXTURES OF O I L AR'D DIETHYL CARBINOL
where T A
= =
W, K,
= =
log W , = A (log T - K,) (1) absolute temperature (" C. 273) a constant dependent on wax (for the wax u s d in this investigation it has the value 38.5) grams of wax per 100 grams of solvent a function
+
- K,)
(3)
which is the same in form as Equation 1. B again is a function of wax only, and K , a function of the solvent. When correlation was attempted on the above basis it was thought that K , might be a function of the oil used. It was found, however, from a comparison of a few solubility determinations made when using coastal oil instead of paraffin base, that the type of oil was of minor importance and that the value of K , depended mainly on the solvent used. As far as could be determined the total wax dissolved was the same whether the oil in question was paraffinic or naphthenic. Finally the quantity B was determined as 29.4, and K , was found to be related to K , by the expression:
It is evident that I K , = K , - 0.0268 (4) for a wax similar to $ the one used in this T h e greatest deviations of K , - K , from $ ' investigation the dethe r e c o m m e n d e d termination of W , a t = v a l u e 0.0268 were a single temperature, f o u n d t o b e 0.0061 permitting the and 0.0030 in the six evaluation of K,, will s s e t s of d a t a consuffice t o g i v e t h e OIL SOLVENT RATIO IL) sidered. temperature-soluOF OIL-SOL\EVT R 4 T I O O\ F R ~ C T I OF O V%'4X IR LURRIFIGURE 4. EFFECTS Combining E q u a bility relationship. ClTING O I L D E W 4 X E D BY PEVTASOL iT h R I O U S TEVPERITURES tions 3 and 4, Although - t h e expression seems adelog It', = 29.4(10g T - K , 0.0268) (5) quate for the pure solvents inrestigated, it does not give even approximate results for solutions containing oil. ObSubstitution of values of TV, and ?Yefrom Equations 1 and 5 into Equation 2 yields a value for viously some modification is necessary to provide for such three-comtotal solubility, W , given by: ponent mixtures. It was considered r e a s o n a b l e t o look upon the wax dissolved in a m i x t u r e of solvent and oil as consisting of two quantities, one being t h e a m o u n t c a r r i e d b y the solvent power of the material c o n s i d e r e d as the s o l v e n t , the remainder being held by the solvent power of the oil as it exists in s o l u t i o n . For c o n v e n i e n c e the former quantity was arbitrarily considered a s identical w i t h t h e s o l u b i l i t y of wax in pure solvent, the value of which was a l r e a d y known. Designating the portion due to 100 grams of s o l v e n t as W , and that due SLKNT to each 100 grams of oil as W e , FIGURE 6. AGREEMENT BETWEEN OBSERVED FIGURE 3. AGREEMENT BETWEEN O B t h e n t h e t o t a l d i s s o l v e d will AND CALCULATED VALUESOF WAX FRACSERVED AND CALCULATED VALUES OF equal W , p l u s t h e p r o d u c t of TION IN LUBRICATING OIL DEWAXED BY W A X FRACTION IIV A IAUBRICATING O I L W e and the oil : s o l v e n t r a t i o , DIETHYLCARBINOLAT VARIOUS TEMDEWAXED BY BUTYL ACETATEAT VARIPERATURES L,or OUS TEMPERATURES
E
6 E
+
OIL
RArm
I N D U S T R I A L A N D E N G I N E E R I N G C H E hl. I S T R Y
November, 1932
W where A B
=
= = loglo u =
loglo b
=z
+
aT* L4TB 38.5 29.4 -A.K, -B,K,
1217
(6)
By the use of Equation 6 or by s t e p w i s e use of the e q u a t i o n s f r o m w h i c h it is d e r i v e d , one may obtain bt7, the total wax dissolved in 100 grams of s o l v e n t and 100 L g r a m s of o i l a t any desired temperature, provided only that the constant K,, a characteristic of the solvent, has been determined from a single solubility determination of wax in pure solvent. Values of R,for the solvents studied so far are presented in Table I. J0-c + The c o n s t a n t s given f o r the do co
