Determination of Wax in Asphalt RAYMOND L. BETTS AND H. D. WIRSIG' Esso Laboratories, Process Division, Standard Oil Development Company, Elizabeth, N. J .
Ether, Squibb, U.S. P. Absolute alcohol A. S. T. M. naphtha Trichloroethylene, commercial Methyl-n-butyl ketone, commercial sec-Butyl acetate, boiling point 111-113" C. Colombian distillate cylinder oil, 188 viscosity S. S. U. at 210" F. (99" C.) Pennsylvania bright stock, 143 viscosity S. S. U. at 210' F. (99" C.). . This stock mas obtained by centrifuging Pennsylvania cylinder oil in 3 volumes of naphtha at -4" F. (-20' C.), EXPERIMENTAI,. Critical solution temperatures of waxes were obtained by weighing the wax in a bottle equipped with a stopper holding a thermometer. The cwrect volume of solvent was added and the mixture warmed until complete solution was obtained. The solution was then cooled slowly with frequent shaking and the temperature at which the first sign of turbidity appeared was taken as the point of limiting solubility of the wax in
AX may materially affect the properties of a n asphalt, and the magnitude of the effect will depend upon the specific nature of the wax and the amount present.
A small quantity of wax which has a strong tendency t o separate in large crystals will be decidedly more noticeable visually than a considerably larger quantity of a microcrystalline or amorphous wax, or one having a greater solubility in the asphalt. Consequently, a reliable procedure capable of evaluating both the character and quantity of wax present in an asphalt is desirable. Recent publications ( 2 , 6) of new methods on the determination of wax in asphalt suggested that the experience a t the Esso Laboratories on the same subject might be of interest. The Holde (4) method or the Hubbard ( 5 ) modification is frequently employed, but it has long been considered unsatisfactory because of the belief that waxes are destroyed by cracking, Ivhich results in erroneous conclusions regarding the quantity and nature of the wax present. This belief has been corroborated (7, 13, 15), and attempts t o reduce the error by limiting the time of distillation have not been particularly successful. Because of the limitations of the Holde procedure, other methods ( 1 , 9, 10, 12) have been developed but none has proved entirely satisfactory. Maass (S),on investigating various methods of treating the asphalt to obtain the oily constituents preparatory to dewaxing in 1 to 1 ether-alcohol or butanone, found that acid treating alone (12), treating with adsorbents with or without subsequent acid treating, or acid treating a t eleratell temperatures (IO), gave similar results but acid treating followed by distillation (9) gave low wax yields. Because of the conflicting opinions regarding the merits of the various procedures, nork was undertaken to study and compare the vaiious methods. The problem consisted of two parts: the selection of a suitable solvent in which residual ails are soluble and n axes are relatively insoluble, and the effect of the several treating methods on \\axes and on the recovery of these waxes nhen added to asphalt in knon n amounts.
Selection of Solvent MATERIALS.Paraffin wax, 124" F. (51' C.) melting oint. Petrolatum, 160' F. (71" C.) melting point. This petrofatum had a Tag-Robinson color of 15-18 when liquefied and was obtained from 132" F. (55" C.) melting point petrolatum by clay treating in 4 volumes of naphtha and allowing to settle at 70" F. (21" C.). : Present address,
-
Cloild Pc1r.t
OF.
AND SOLUBILITY FIGURE1. RELATION BETWEEN TEMPEFLATURE OF 124 F. (51 C.) MELTING POIXTWAXIN VARIOUSSOLVEKTS
U. S. Army.
O
TABLE I. CLOUDPOINTS OF SOLUTIONS OF WAXESIN VARIOUS SOLVENTS T a x Melting Point
Solvent Used
F. 124
.
160
(petro1atum)a
4
2.5 O F .
sec-Butyl acetate Methyl-n-butyl ketone 3 t o 1ether-alcohol A. ,S. T. M. naphtha Trichloroethylene
83 82 79 46 40
sec-Butyl acetate Methyl-n-butyl ketone A. S. ' I &I. . naphtha Trichloroethylene
131 130 91 i9
1.25
aF.
Concentration of Solution (Grams per 100 M1. of Solvent)
0.625
0.4
O F .
O F .
O F .
:: ..
2;51
E 6666 71
64
31
23
26 15
121 120
110 111
.. ..
70
61
54
......
. . . . . . . .
0.25
19
..
98 97 62
..
0.20
0.10
0,0625
O F .
O F .
O F .
:: ::: . . . . .
33 35
. . . . . . . . -3 8 -2 ...
.....
.,
,
.
,
. . . . .
46
36
80 82 40
...
0.04
0.032 0.020 0.016 0.010 0,005 0.0025
aF.
O F .
O F .
30 30 25 -11 - 14
.. .. ..
20 20 16
..
68 68 27
75 38 20
Solutions of 160' F. XI. P. petrolatum in 3 t o 1 ether-alcohol could be obtained only a t very low concentrations
478
O F .
.. ,. ..
O F .
8 9 5
O F .
O F .
-8 -8 -6
.. .. ..
. . . . . . . . . . . .
. . . . . . . . . . . . .
..
64 65 24 12
59 58 15
..
54 55 10 3
44 46
30 32
. . . . . . . . . .
August 15, 1943
ANALYTICAL EDITION
the solvent. Cloud points of the cylinder stocks and of wax-oil mixtures in each solvent were obtained in a similar manner, the weight of oil or wax plus oil being 2.5 grams per 100 ml. of solvent in all cases.
419
TABLE111. DEWAXIXG DIFFERENTIAL 160' F. M. P.
124O F. AI. P. Wax
.
Petrolatum
Verqllq
V.TEIIP
RESULTS.The cloud points of solutions of maxes in various solvents, containing the waxes in varying concentrations, are shown in Table I and illustrated graphically in Figures 1 and 2. These curves indicate that there is a semilogarithmic relationship between temperature and wax solubility a t temperatures above 50' F. (10" C.) R S reported in the literature, but a t lower temperatures there is a distinct deviation from linearity. There are no appreciable differences in the solubility of 124' F. (51" C.) melting point wax in 3 to 1 ether-alcohol, methyl-n-butyl ketone, and secbutyl acetate, but 160" F. (71" C.) melting point petroleum is much less soluble in the first solvent than in the others. All three solvents show much less solvent power for n ax than trichloroethylene or A. S. T. M. naphtha. Although solubility data using 1 to 1 ether-alcohol were not obtained nith these particular wax samples, other experiments showed that waxes are even less soluble in this mixture than in any of the other solvents. Cylinder oils (Table 11) are not particularly soluble in trichloroethylene and relatively insoluble in 1 to 1 ether al-
OF DEWAXED OILS IN TABLE11. MISCIBILITYTEMPERATURXS VARIOUSSOLVENTS IN 2.5 ~ E CENT R COXCENTRATIOS
Solvent
c.
F. Methyl-n-butyl ketone 3 t o 1 ether-alcohol sec-Butyl acetate A. S. T. M.naphtha 1 t o 1 ether-alcohol Trichloroethylene
Colombian 188 S. S. U' Viscosity 210' F. Distillate
143 S. S. U. Viscosity 210" F. Penn. Bright Stock
- 30
c.
F.
-- 434.4 0.0
-40 -36 -30 -40 +30
-40 -25 -31.7 -25 -31.7 26% insoluble a t room temperature 20 6.7
-
$20
-40.0 -37.2 -34.4 -40.0 1.1
-
6.7
Methyl-n-butyl ketone 3 t o 1 ether-alcohol see-Butyl acetate A. S. T. M. n a h t h a Trichloroethygne
Versus Colombian distillate F.
Penn. bright stock F.
Versus Colombian distillate F.
Penn. bright stock F.
122 114 113 86 20
112 119 108 71 20
170
160
161 131 59
156 116 59
...
...
cohol, showing that the latter solvent is not suitable for the separation of wax from oil. The other solvents studied show comparatively high solvent power for oils, and differ from one another only slightly. The "dewaxing differentials" which represent the differences in degrees Fahrenheit between the cloud points of solutions of the wax and of the oil, each present in a concentration of 2.5 grams per 100 ml. of solvent, are recorded in Table 111. Methyl-n-butyl ketone, sec-butyl acetate, and 3 to 1 ether-alcohol exhibit relatively high dewaxing differentials of approximately the same magnitude and appear to be the most effective solvents for dewaxing oil-wax mixtures. Of these three, the ether-alcohol is the least desirable mixture because of its high volatility, which makes it difficult to obtain solutions of high melting waxes in reasonable concentration. The presence of cylinder oils does not appreciably affect wax solubility, since the cloud points of solutions of oil-wax mixtures (Table IV) are substantially the same as those obtained when the wax alone was present in the same solvent in the same concentration (values shown in brackets). These results indicated that either methyl-n-butyl ketone or sec-butyl acetate would be satisfactory for separation of wax from oil. In order to confirm this conclusion, varying quantities of 124" F. (51' C.) melting point wax were mixed with sufficient 188 S. S. U. viscosity at 210' F. (99" C.) Colombian distillate to give 1.0-gram samples of wax plus oil. The mixtures were then
TABLEIv. CLOUDPOINTS O F SOLUTIONS O F OIL-WAX MIXTURES IN VARIOUS SOLVENTS ( I n all cases solutions contained 2.5 grams of oil plus wax per 100 ml. of solvent) Wax in r Cloud Pointsa Mixture 124' M. P. Wax 160' M. P. Petrolatum 79 a F. F . O F. F. F. F. 7
Solvent. hlethyl-n-Butyl Ketone
Solvent, sec-Butyl Acetate
0 5
Claud Point
-
OF.
FIGURE 2. RELATION BETWEEN TEMPERATERE AND SOLCBILITY OF 160" F. (71" C.) MELTINGPOINT PETROLATUM IN VARIOUS SOLVENTS
10 25 50 100
Solvent, 3 t o 1 Ether-Alcohol -35 42 (41) 52 64 71 (71) 79
-35 ..
.. .. .. ...
.
I
...
5 Figures in parentheses are cloud points of same wax in same concentration in solvent, b u t free from oil.
I N D U S T R I A L A N D E N G I N E E R I NG C H E M I S T R Y
480 T4BLE
Adsorbent Method
V. WAX RECOVERY
(From mixtures of 124' F. L l . P. wax and 188 S. S. U. viscosity a t 210' F. Colombian distillate in methyl-n-butyl ketone) Wax in 1.0 Gram of Recovered Wax Mixture Yield Melting point
-
7 -
T.4BLE
Gram
%
1.00 0.50 0.25 0.10 0.05
98 101 108 98 101
---SucharWax
% 1 2 3
4
O
F.
125 123 127 127 12.;
VI. EFFECTOF ADSORBFNTON FTAX YIELD SCHWARZ METHOD
Crude Oil Sample
0.19 0.22 0.98 0.17
Extraction time Hours 18 18 4
18
Vol. 15, No. 8
Bone Char (Fat-Free) Extraction Wax time % Hours 2.12 24 2.85 5 5.41 5 3.21 24
BY THE
Filtrol wax
% 7.55
11.45 11.03 9.27
dewaxed in 10 ml. of methyl-n-butyl ketone a t -4" F. (-20" C.) by a rocedure essentially the same as that described by Hubbard &). The results obtained are given in Table V and indicate that waxes can be recovered substantially unchanged with a precision of * 5 per cent.
Claims are made in the literature (1, 8, 14) that wax in asphalts can be obtained by dewaxing the oily constituents remaining after treatment of the asphalt with adsorbents. The adsorbent method has been used in these laboratories to determine the resin contents of asphalts and it has been found that the quantity of adsorbent required to give oils of a given color varies considerably with the nature of the asphalt. Since the quantity and character of the adsorbent were also found to have a marked effect on wax yield by the Schwarz method, tests were made to determine whether straight waxes could be recovered aftel, treatment with activated clay in the absence of asphalt. In order to determine the minimum quantity of adsorbent to use, samples of Venezuelan heavy flux were dissolved in 40 volumes of 86" B6. naphtha, and after separation of asphaltenes were treated with varying amounts of Super-Filtrol. About 8 to 10 grams of clay er gram of asphalt were required to yield a solution of 20 Tag-Rotinson color, Accordingly, 1-gram samples of 124" F. (51' C.) melting point wax and 160" F. (71" C.) melting point petrolatum (equivalent to 5 per cent by weight of a 20gram asphalt sample) were treated in the absence of asphalt in 800 ml. of 86" BB. naphtha with 160 grams of Super-F;ltrol. The clay-wax mixtures were then extracted in Soxhlet extractors for varying periods of time and the quantity and melting points of the waxes recovered were determined. A sample of Venezuelan heavy flux was also treated in a similar manner.
TABLE VII. EFFECTO F &RbNG SULFURIC ACID ON
Schwarz Method Following the selection of solvents suitable for the separation of wax from oil, a n examination was made of the Schwarz (10) method to determine the effect of the nature of the adsorbent on wax yield and the effect of strong sulfuric acid on refined waxes a t elevated temperatures. Sam les (10 grams) of various waxy crudes were digested at 350" I?(177" C.) with 96 per cent sulfuric acid until free from the odor of sulfur dioxide. The resulting coke was mixed with 35 grams of fat-free bone char, as recommended, or of Nuchar, and extracted in a Soxhlet with 400 ml. of 86" BB. naphtha until a few drops of extract showed practically no evidence of oil after evaporation on a watch glass. I n other cases, the coke was placed on a Gooch filter 4 cm. in diameter containing 10 grams of filtrol which had been dried for 16 hours a t 225" F. (107" C.) and.washed with 250 ml. of 86" BB. naphtha. I n all cases the resultlng oils, free of naphtha, were dewaxed in 20 volumes of 3 to 1 ether-alcohol by the Hubbard procedure.
It is evident (Table VI) t h a t the nature of the adsorbent has a very marked effect on wax yield and that excessively long periods of extraction would be necessary to separate the wax completely from the adsorbent. The higher yields obtained when the coke was washed on a Super-Filtrol bed suggests that this procedure is preferable. Later experience, however, demonstrated that much larger quantities of naphtha are required for washing than are specified here. The effect of strong acid on wax was studied by digesting 1.0-gram samples of 124" F. (51" C.) melting point paraffin wax and 165" F. (74" C.) melting point petrolatum in 90 per cent sulfuric acid at 400" F. (204" C.). [Th'is wax was obtained by crystallizing 160" F. (71" C.) melting point petrolatum from 4 volumes of sec-butyl acetate at 30" F. (- 1" C.) .] It was found (Table VII) that the waxes were readily attacked under conditions comparable to those employed in the Schwarz procedure, particularly in the case of the lower melting wax. I n view of these results it appears that the Schwarz method is unreliable for determining wax contents of oils.
Wax recovery, % M. P. of recovered wax, O
F.
WAX
Waxes Treated with 1 Cc. of 90% HzSOd per Gram of Wax 124" F. M. P. Wax 163'F. .M. P. Petrolatum 41.2 84.9
132
163
I n the case of the recovery of the waxes from the SuperFiltrol remaining from the treatment of their naphtha solutions, the paraffin wax could be effectively recovered by extracting for 9 hours, although a small amount of the higher melting waxes remained in the clay. On the other hand, only about 55 to 60 per cent of the high melting petrolatum could be recovered in a similar time and i t was by no means completely separated after 43 hours' extraction, the higher melting portions being the most difficult to remove. I n the extraction of the Super-Filtrol after decolorization of the naphtha solution of the asphalt, it was found that the oily constituents were substantially, but not sharply, removed after extracting the clay for 6 hours (Table VIII). The products obtained on longer periods of extraction were of resinous nature, becoming increasingly hard and dark in color. It is apparent from these results that the extraction time of 6 to 16 hours, commonly employed in the adsorbent method of asphalt analysis, would indicate lower melting and smaller amounts of wax than are actually present. Sufficient extraction to remove all wax is impracticable and in addition it is difficult to establish a well-defined end point.
Richardson or Acid-Treating Method A method which has been extensively used for the determination of wax in asphalts (12) involves the use of sulfuric acid to remove resins before dewaxing. I n view of the fact that hot sulfuric acid readily attacks and alters the properties of waxes, it appeared possible that cold acid may also have some effect. It was found, however, that 1-gram samples of 124" F. (51" C.) melting point paraffin wax and 160" F. (71" C.) melting point petrolatum dissolved in 500 ml. of 86" BB. naphtha are unaffected when repeatedly treated with
August 15, 1943
ANALYTICAL EDITION
481
a satisfactory separation of 124' E'. (51O C.) melting. ooint wax from oil.' This loivent is not convenient to use because of its high volatility which makes it difficult to obtain complete solution of oil and wax if there is an appreciable quantity of high melting waxes present. sec__ ___ Butyl acetate in the ratio of 20 ml. of solvent per gram of oil-wax mixture appeared to be a satisfactory dewaxing TABLE 1x. DETERMIXITIOS O F DEWAXIXG CONDITIONs SUITABLE FOR QGANTITAlIVE RECOVERY medium a t - 4' F. ( - 20" C.). OF WAXESADDEDTO OILY CONSTITUENTS The high wax yield a t a ratio 3 to 1 Etherof 10 to 1 indicated the Dewaxing Solvent Alcohol c Ether-sec-Butyl Acetate--presence of oils, although this Wax mixture, mi. of solwas not reflected particularly vent per gram of oil 10 10 10 10 10 10 20 10 204 Dewaxing temperature, in the melting points of the ' F. -4 -20 -4 -4 16 -4 -4 -4 -4 Ad$ed wax, melting point, products. It was found inF. 124 124 124 165 124 124 124 165 165 advisable to dewax a t tem.4dded wax, % of oils 15.5 14.8 14.6 13.7 13.9 15.2 15.2 15.0 28.8 Recovered wax, '% of oils 41.7 19.9 16.8 13.2 17.0 22.2 16.6 15.4 22.6 p e r a t u r e s a b o v e 16' F. Recovered wax, % of added wax 269.0 134.5 115.1 96.4 122.3 146.1 109.2 102.7 87.6 ( - 8.9O C.) as the wax loss due Recovered wax, melting to solubility in the solvent point, F. 108 121 122 147 123 123 123 158 15s would be greater than with a Wax recrystallized. twice the solvent a t the lower temperature.
TABLE VIII. EFFECT O F SUPER-FILTROL (ACTIKATED
CLAY) ON THE RECOVERY OF WAXES 160° F. 11 P.Petrolatum (Alone, S o 124' F. M. P.P a r a E n Wax (Alone, Venezuelan Heavy Flux N o Asphalt) Asphalt) bl. P. of -xr._. -P . nf -reiovered Extraction Oily Extraction recovered Extraction period constituents period Recovery wax period Recovery wax 1Yt. yo wt.yG Wt: 7. Hours of orag%nal F. Hours of asphalt HOUTS of orzgLnal F 0-6 48.20a 0 59.95 119 0 26.6b 10s 6-16 0.97 0-9 36.2 132 0-8 28.8 143 16-30 1.05 9-19 0.6 ... 8-2 1 13.3 157 ... ... ,.. 21-30 5.8 161 30-35 0.41 MI-4.1._ .?I A 1 fi.5 Total yield 50.63 ... 96.7 ... ... 80.1 ... a Combined material obtained b y decantation and subsequent extraction of clay for 6 hours b Material obtained from decanted solution prior Go extraction of clay.
--
In order to test the suitability of the acid-treating method using During the sec-butyl acetate as the dewaxing solvent for obtaining the wax was contents of asphalts, wax determinations were made on Venezuenot particularly soluble in 86' BB. naphtha and tended to lan heavy flux containing known amounts of added waxes. separate and collect a t the interface during acid treating. Twenty-gram samples of the asphalt alone and containing 2, 5, and 10 per cent by weight of 124' F. (51' C.) melting point wax Consequently in all subsequent work, acid treating was carOr 165' F. (74" c.) melting point petrolatum were refluxed with ried outat 1200 to 1300 F. (440 to 540 c.) using as asphalt 200 ml. of the 70' A. P. I. naphtha, filtered, and the asphaltenes solvent a 70" A. P. I. naphtha having a boiling range of washed with 300 ml. of hot na htha (120' F.) (49" C.). The solu140' t o 210' F. (60'to 99" C.). tion of petrolenes, maintainexat approximately 1200 F. (490 c,), was then acid-treated, neutralized, and freed from naphtha, I n preliminary tests of this method it was found that the yielding oily constituents which were dewaxed in 20 ml. of secminimum acid treatmentrequired varied with the nature and butyl acetate per gram of oil-wax mixture, at -4" F. (-20" C.). source of the asphalt. To be certain that the acid reaction was complete, acid treating and separating the sludge vere The results of preliminary determinations which were obcontinued until there was no change in the volume of acid tained in the development of the procedure, are given in after shaking with the solution. I n washing the naphtha Table X and show that over the range of 2 to 10 per cent of solution free from acid, emulsification diffi,ulties were exadded waxes both types of waxes can be recovered (total wax perienced which were overcome to a considerable degree by less the wax content of the original asphalt) in substantially washing with a solution of 25 grams of sodium sulfate in a their original form within 0.5 per cent and usually within mixture of 300 ml. of alcohol and 700 ml. of n-ater. The 0.2 per cent on the asphalt. The wax originally present in resulting naphtha-free oils were relatively insoluble in methylthe asphalt did not appear to influence the melting point of n-butyl ketone, although earlier studies indicated that this the added wax. I n contrast with these data are those (Table solvent was satisfactory for the separation of waxes from X) obtained by the Hubbard method on similar materials. cylinder oils. The significantly lower wax yield and the very great change Since the particular sample of methyln-butyl ketone employed did not prove satisfactory. a studv was made of the efficiency bf severai other solvents for TABLE X. RECOVERY BY ACIDTREATING, ALUMINUMCHLORIDE TREATING, AND HUBBARD (HOLDE) METHODSOF WAXESADDEDTO ASPHALTS dewaxing oi:y constituents from asphalts. Oils obtained by acid-treating Added Wax Recoverye Melting Wax Yield Melting of Added Venezuelan heavy flux Fyere first deMethod Asphalt Used point Asphalt of Asphalt Point Wax waxed by the selected solvent, then ' F. Weight % Weight % ' F. Weight % weighed amounts of wax were added to Acid Venezuelan heavy ... 0 2.41 133 ... 2 4.83 123 2.42 flux 124 the resulting oils, and the oil-wax mix124 5 7.73 123 5.32 124 10 12.44 123 10.03 tures were again dewaxed. The high 165 2 4.27 160 1.86 yield and low melting point of the 165 5 7.45 160 5.04 10 12.17 161 9.76 165 product obtained using 3 to 1 ether~ ~ b b ~ ~ ~~ d~ healTy ~ ~ ~ ~ l0 a n 1.12 121 ... 5.26 5.44 114 4.32 flux iiC alcohol (Table IX) indicated the relative 165 5.26 5.20 122 4.08 insolubility of heavy oils in this solvent. Aluminum Colombian, ... 0 3.06 120 ... 5.26 8.11 161 5.05 chloride 31/40 Penn. 165 Ether employed in a similar dilution (10 ml. of solvent per gram of oil-wax Total wax yield less wax in original asphalt. mixture) a t -4" F. (-20" C.) effected
98 per cent sulfuric acid a t room temperature. test it was observed that the high melting
Q
482
INDUSTRIAL AND ENGINEERING CHEMISTRY
in melting point when high melting petrolatum was present, are further indications that the waxes present in asphalts may be greatly altered by the Hubbard (Holde) method. When the specified 1 t o 1 ether-alcohol mixture is replaced by sec-butyl acetate as the dewaxing solvent in the Hubbard procedure, the wax yield is even lower (Table XI). There is little doubt, therefore, that the Holde procedure will not give reliable indications of either the quantity or melting points of waxes in asphalts. Since the acid-treating method appeared t o be without deleterious effect on waxes, i t was employed for the determination of waxes in asphalts from numerous crudes. I n the course of the work difficulty was experienced with emulsions and frequently the wax product obtained was very dark in color and sometimes did not have a satisfactorily distinct melting point. Consequently, experiments were carried out t o determine whether treatment of petrolenes with aluminum chloride instead of sulfuric acid would reduce these difficulties. Preliminary tests indicated .that emulsification was reduced, waxes mere unaffected by this reagent at the temperature of treatment, and wax added to
Vol. 15, No. 8
TABLE XI. EFFECTOF DEWAXING SOLVENT ON WAX CONTENTS BY THE HUBBARD (HOLDE)METHOD Wax added to asphalt Dewaxing solvent
Sone sec-butyl acetate
1:l ether alcohol
T a x yield, weight % Melting point, F.
0.74 122
0.61
...
of 124' F. M.P. 1:l ether- see-butyl
alcohol
acetate
4.43 115
3.05 117
asphalts could be recovered equally well, as illustrated by the Colombian 31/40 penetration asphalt in Table X.
Wax Contents of Asphalts by Acid and Aluminum Chlor3de Treating Methods
PROCEDURE. A 20-gram sample of as halt, weighed to the second decimal place, is spread over the wa?ls of a 500-ml. balloon flask, heat being applied if necessary. The asphalt is gently refluxed with 200 ml. of 70" A. P. I. naphtha until all tarry material has disappeared, then cooled slightly and mixed carefully with 5 rams of Filter-Cel (diatomaceous earth). The hot mixture is altered with the aid of suction through a percolating tube 5 cm. (2 inches) in diameter and 35 cm. (14 inches) in length and containing a cotton plug covered with a 1.25-cm. (0.5-inch) layer of Filter-Cel. The flask and residue on the filter are washed with portions of hot naphtha (about 120"F., equivalent to 48" C.), totaling 200 ml. The solution of petrolenes in naphtha is transferred to a 1000-ml. separatory funnel, hot naphtha being used to rinse the suction flask, and the separatory is placed in a steam-heated oven maintained a t 125-130' F. (51-54" C.). When temperature equilibrium is reached, the solution is treated with 10 or 20 ml. of 98 per cent sulfuric acid, and the sludge is allowed to settle out. After the sludge has been withdrawn, the acid treatment id repeated until the volume of recovered acid is unchanged after treatment. The solution is then neutralized with 5" B6. caustic soda and washed neutral to litmus, using a solution containing 25 grams of sodium sulfate in a mixture of 300 ml. of alcohol and 700 ml. of water, the temperature being kept at 120' to 130' F. (49" to 54' C.). When anhydrous aluminum chloride is wed. the solution-of petrolenes obtained as above is transferred to a 1000-ml. balloon flask and refluxed for 0.5 hour with 10 grams of the solid reagent. The mixture is then allowed to stand EQUILATERAL SPACING for 15 to 30 minutes a t 120" F. (51' C.), when (REMOVE ALL BURRS the supernatant solution is decanted to another flask, and the hot naphtha used to rinse the sludge is added thereto. The aluminum chloride treatment is repeated until there is only a slight formation of a red-colored sludge. Finally the solution is washed in a 1000-ml. separatory at 120' F. (49" C.) with 50 per cent alcohol until the wash is neutraL The neutral solution from either the acid or aluminum chloride treatment is dried in a 1- or 2-liter balloon flask by refluxing in a Dean and Stark apparatus until there is no further increase in the volume of water in the collecting tube, and then concentrated to 50 ml. by distillation. The concentrate together with small portions of hot naphtha used to rinse the flask is transferred to a tared 250-ml. beaker. The remaining naphtha is removed by careful eva oration on the steam bath and the resulting oify constituALL MATERIAL-BRASS OR BRONZE, ents are heated in an oven a t 230O.F. (110'C.) EXCEPT WHERE NOTED OTHERW4SE for 0.5 hour, then cooled and weighed to the ALL DIMENSIONS ARE IN INCHES. second decimal place. DEWAXING. The dewaxing equipment used is similar to that emplo ed by Hubbard, except that the funnel is ma& of brms rather than glass. This brrtss funnel, illustrated in Figure 3, is of the Buchner type, and is fitted with a long barrel, d , threaded at one end, by means of which it can be attached to the funnel cone, a, in such a manner as to fit tightly against the rforated filter plate, b. To prepare the funneche lqwer end of the filter tube is stoppered and sufficient dewaxing solvent added to fill the tube until the perforated filter plate placed in position e is just covered. A piece of snugly fitting No. 10 duck FIGURE 3. WAX FILTER
August 15, 1943
ANALYTICAL EDITION
483
filter cloth, c, is then placed on the plate and the funnel barrel OF WAXCONTENTS OF VARIOUSASPHALTSBY ALUMINUMCHLORIDE TABLEXII. COMFARISON is inserted and screwed down AND ACID-TREATING PROCEDURES tightly, thus firmly clamping Aluminum Chloride Method Acid Method the filter cloth in position. A -AYB-A7-B0.6-cm. (0.25-inch) layer of Melting Melting Melting Melting Asphalt Yield point Yield point Yield point Yield point Filter-Gel is placed on the Weight Weight Weight Weight cloth and moistened with 10 % F. % F. % F. % ' F. ml. of sec-butyl acetate, and 0.88 139 0.82 139 1.15 140 Kexn River, 127' F. S. P. 1.01 142 the assembled tube is placed in Mexican, 31/40 Penn. 0.95 138 0.80 141 1.79 134 1.82 135 a bell-shaped funnel which S'enezuelan lSO/ZOO Penn. 1.00 137 1.04 142 1.96 126 1.95 127 Colombian,'31/40 Penn. 3.03 126 3.08 126 5.63 122 5.33 122 serves as a cooling bath. Talco, 41/30 Penn. 3 . 3 9 163 3.03 162 6 . 3 4 153 6 . 5 4 154 A 3 * 0.01-gram sample of Mid-continent, binder C 5.12 148 4.82 149 6.34 136 6.71 142 the oily constituents is disSumatra residuum (high softening point) 4.44 148 ... ... 5.57 149 5.53 147 solved in 25 ml. of sec-butyl Sumatra. residuum (low acetate in a 50-ml. beaker, and softening point) 11.47 161 11.10 165 12 70 161 13.52 161 warmed on a hot plate sufficiently to obtain a clear solution. The resulting solution is transferred to thz prepared filter tube, usin 25 ml. of warm sec-butyl acetate to rinse the yields of wax, sometimes nearly twice as great, and the meltbeaker. After t8e contents of the tube have been gently stirred, ing points were nearly alm ays loner than those obtained by the tube is stoppered with a cork through which passes a therthe aluminum chloride method. Preliminary work on acid mometer adjusted so that its bulb is immersed in the solution. treating indicated that strong sulfuric acid w-as prone to reSlcohol is now added to the bell-shaped funneluntilit is within an inch of the funnel top, and three or four stoppered test tubes, each act with wax and resins, giving sulfonated products which containing 20 ml. of sec-butyl acetate, are immersed therein. The caused high wax yields and the production of very dark bath is chilled by the addition of dry ice and, duSing chilling, the colored materials that did not possess sharp melting points. contents of the tube are stirred occasionally until a temperature It was also found difficult to obtain what appeared to be of - 4 " F. (-20" C.) is reached, which is maintained constant for 15 minutes. The cork is removed from the bottom of the filter resin-free oils from some asphalts by treating mith 96 per cent tube, filtration is then carried out with the aid of suction, and the sulfuric acid. On treating with aluminum chloride no wax cake is stirred vigorously with a portion of prechilled solvent particular difficulty was experienced with a n y of the asphalts and again filtered. examined. For these reasons the aluminum chloride method Washing is repeated until the issuing liquid is colorless, then the cold alcohol is removed from the bath, and the apparatus allowed has been chosen for the wax determinations in these laborato come t3 room temperature. The filter assembly is removed, tories. Both methods indicate that asphalts contain larger dried Ivith a towel, and attached to a 250-ml. suction flask. Hot amounts of n-axes having higher melting points than can be 70" A. P. I. na htha is added to the tube, stirred vigorously, and obtained by the Holde procedure. withdrawn wit{ suction. Then naphtha ,(2@nil.) is added to the tube and, after the side arm of the suction flask has been stopSince completing this work tu-o new methods hare been pered, t,he combination is placed on a hot plate and rzfluxed until proposed for the determination of wax in asphalt. One condensate appears at the funnel top. After cooling slightly, method ( 2 ) uses isobutyl alcohol a t 130" F. (54" C.) to filtration is carried out with suction and the tube rinsed with separate resins from cil and wax. This may be satisfactory 70" A. P. 1. naphtha. The filtrate thus obtained is evaporated in a tared crystallizing dish on a steam bath and the resulting wax is when the waxes present are low melting, but if they have a heated at 230" F. (110" C.) to Fonstant weight, *0.001 gram. melting point apprcaching 160" F. (71' C.) it is improbable Wax melting points are obtained by the rotating thermometer that they n-ould remain in solution a t the temperature specimethod. A small quantity of wax is placed on the bulb of a therfied; consequently the method would not appear to be genmometer and warmed until the wax is in a molten condition, the thermometer is inserted in a test tube to protect it from air curerally applicable. The second proposed method ( 6 ) , using rents, then gently rotated, and the temperature at which solidipropane for deasphalting and deresining and hesone for defication occurs is recorded as the melting point. waxing the resulting oil-lyax mixtures, appears to be sound. The limited amount of data cited does not indicate whether DISCCSSION . 4 6 ~RESULTS. The relatively large asphalt the method is generally applicable to various types and grades sample (20 grams) is recommended to ensure sufficient oilof asphalts, but the results are in harmony with those obtained ivax mixture for the dewaxing step. Some high melting by the acid or aluminum chloride methods herein described in asphalts may contain as little as 10 per cent of oily conshowing that waxes in asphalts are higher melting and are stituents. Maintenance of a n elevated temperature during present in greater quantity than indicated by the Holde method. treating and filtering to obtain resin-free oils is probably not necessary in most cases, but it was found essential when anBibliography alyzing asphalts containing appreciable quantities of high Abraham, "Asphalts and Allied Substances", 4th ed., p. 992, melting waxes-e. g., wax determinations on a Sumatran asNew York, D. Van Nostrand Co., 1938. phalt carried out a t room temperature resulted in widely Grant and Hoiberg, Proc. Assoc. of Asphalt Paving Tech., 12, 87 (1940). deviating results and indicated that the waxes of higher meltGukhman and Goldberg, Aterbaldzhanskoe Nejtyanoe Khoz., ing point were lost. These losses were avoided by conducting No. 10,74 (Oct., 1929). the test at elevated temperatures. For the same reasons it Holde, D., "Kohlenwasserstoffole und Fette", 6th ed., p. 108, was found necessary to reflux with the naphtha in the filter Berlin, Julius Springer, 1924. Hubbard, P., and Reeve, C. S., U. S. Dept. Agr.. Bull. 314, 32 assembly when dissolving the wax cake from the filter after (1915). dewaxing. The brass filter tube was employed because i t is Knowles and Levin, IXD.ENG.CHEM.,ANAL. ED., 13, 314 durable, it is a good conductor of heat, and its design permits (1941). the wax cake to be broken up and mixed with the solvent, thus Littlejohn and Thomas, J . I n s t . Petroleum Tech., 16, 814 (1930). Maass, W., Petroleum 2..28, No. 21,l (1932). ensuring complete washing without in a n y way diminishing Marcusson, "Die natiirlichen und kiintslichen Asphalte", 2nd the efficiency of the filter bed. ed., p. 96, Leipzig, Wilhelm Engelmann, 1931. The results obtained in duplicate on a variety of asphalts Ibid., p. 326. by the sulfuric acid and aluminum chloride treating methods Piotrowski, W. J., and Burstin, H., Petroleum Z.,27, Asphalt und Strassenbau, No. 3 , 3 (1931). are shown in Table XII. It is apparent that either method Richardson, J . SOC.Chem. I n d . , 21, 690 (1902). would yield reproducible results and would serve t o classify Suida and Janish, Asphalt u n d Teer, 31,503 (1931). asphalts with respect t o both quantity and melting point of Suida and Kamptner. Ibid., 31, No. 26, 668 (1931). n-ases present. The acid method, hen-ever, gave higher Thomas and Tester, World Petroleum Cong.,2,547 (1933). O
