October, 1941
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Acknowledgment The writer is deeply indebted to H. H. Storch, of the Bureau of Mines, whose advice and criticism were sought and generouuly given.
Literature Cited (1) Brewer, R. E., and Reyerson, L. H., IND. ENG.CHEM.,26, 734 (1934). (2) Ibid., 27, 1047 (1935).
(3) Clement, J. K., Adams, L. H., and Haskins, C. N., U. S. Bur. Mines, Bull. 7 (1911). (4) Fieldner, A. C., Hall, R. E., and Gallaway, A. E., U. S. Bur. Mines, Tech. Paper 479 (1930). (5) Furnas, C. C., U. 5. Bur. Mines, Bull. 361 (1932). (6) Haslam, R. T., Entwkistle, F. E., and Gladding, N. E., IND. ENG.CHEM.,17, 686 (1925).
1285
(7) Haslam, R. T., Hitchcock, F. L., and Rudow, E. W., Ibid., IS, 115 (1923). (8) Haslam. R.T.,Ward, J. T., and Boyd, J. H., Am. Gas Assoc. Proc., 1926,1083. (9) Lange, N. A., Handbook of Chemistry, pp. 1036-8 (1939). (10) Marson, C. B., and Cobb, J. W., Gas J.,175,882 (1926). (11) Pexton, S., and Cobb, J. W., Ibid., 163, 100 (1923). (12) Ibid., 167,161 (1924). (13) Ray, A. B., Chem. & Met. Eng., 28, 977 (1923). (14) Taylor, H. S., and Neville, H. A., J. Am. Chem. Soc., 43, 2066 (1921). (15) Thiele, E. W., and Haslam, R. T., IND.ENG. CHEW.,19, 882 (1927).
PRDS~NTDD under the title, “A Review of the Experimental Data Concerninn the Mechanism of the Water Gas Reaotion”. before the Division of Gas and Fuel Chemistry at the lOlst Meeting of the American Chemical Society, 8t. Louis. Mo. Published by permission of the Direotor, U. 8. Bureau of Mines.
Colloidal Stability of Asphalts Spot Tests with Partial Solvents that high-molecular asphalREDICTION of the servHANS F. WINTERKORN tenes surrounded by resinous ice behavior of asphaltic AND GEORGE W. ECKERT’ dispersing agents are distribmaterials by means of University of Missouri and Missouri State uted in a medium of oily and simple laboratory tests is imHighway Department, Columbia, Mo. resinous materials. According portant to both the asphalt to this picture and to well producer and the road builder. established colloidal principles The conventional physical concerning the stability of specification tests, which were The Oliensis spot test appears to be essendispersions, the colloidal stavaluable as quality indicators tially a method for the colloidal stability bility of an asphalt should deas long as only a few well-deof a bitumen. The great interest of users of pend on the effectiveness of fined asphalts were on the asphalts in this test indicates the practical the adsorbed resins as a transimarket, are failing in this importance of the colloidal stability and of tion zone from the physical role in view of the increasand chemical properties of ingly varied products which methods for its determination. Data are the asphaltenes to the propnow are sold under the collecpresented on the appearance of spots oberties of the surrounding liquid tive name of “asphaltic bitutained with a number of different solvents medium. The differences in men”. and solvent mixtures as well as results obtype and quantity of the It hrts been found that tained with the standard Oliensis proseveral phases obtaining in failure of bitumen to function various asphalts are reflected properly in a pavement is usucedure. It is hoped that these data help in in the behavior of the asally associated with excessive the understanding of the Oliensis test, and phalts toward partial solvents. hardening. AB long as this also that some of them may provide a basis Consequently, it is probable hardening is caused only by loss for the extension of this test into fields not that the colloidal behavior of volatiles, i t can easily be yet covered. of systems consisting of parremedied. On the other hand, tial solvents and bitumen may this hardening may be due to a not only permit specific conchange in the colloidal structure clusions concerning the colloidal stability of the systems of the bitumen. Therefore, methods which indicate or measunder consideration, but may also indicate the general colure the stability of this structure are likely to become inloidal stability of the bitumen, provided due regard is given creasingly important in the future testing of bitumen. Acto the chemical and physical character of both bitumen and cordingly, any method now available for this purpose desolvent. The latter provision indicates the necessity of workserves theoretical and experimental examination of its possiing with more than one solvent or one solvent ratio if we debilities and limitations. sire to obtain a general indication of the colloidal stability. From a colloidal viewpoint, asphalts may represent sols or any of the many possible gel-like atructures, depending upon I n the work described here, the spot test was employed as the prevailing conditions of temperature and pressure, their an indicator of the colloidal Stability. I n the standard prochemical and mechanical composition, and their previous cedure, as worked out by Oliensis ( I ) , 10.2 cc. of naphtha are history. However, the same general picture of bituminous added to 2 cc. of asphalt. After the asphalt is dissolved under structure is common to all these possible states-namely, controlled conditions, a spot is made by applying a drop to a No. 50 Whatman filter paper. Spots which have a dark nu1 Present address, The Texas Company, Beaoon, N. Y.
P
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
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VOl. 33, No. 10 ~
~~~
TABLB I.
PHYSICAL CONSTAKTS O F ASPH.4LTIc MATERIALS C D E F G H V en ezue1an Trinidad Smackover oil asphalt oxidized asphalt vacuum residual
A B Venezuelan oil asphalt
Identification Source Penetration grade LJpecific gravity Bitumen (sol. in CSd. 7” Insol. organic matte;,‘%Insol. inorganic matter, % Bitumen insol. in CCla % ’ Flash Doint (Cleveland oDen cupj. 0 F. Softening point, O C. Penetration (77’F., 100 g., 5 sec.) Ductility (77O F., 5 om./ see..), am. Loss on heating (50 g., 325’ F., 5 hr.), ,70 Penetration of residue (77‘ F.,.lOO g., 5 sec.) Ductility of 80-100 penetration residue, (77’ F., 5 cm./sec.) om. Beterogeneit; test
150/200 40/50 1.021 1.031 99.94 99.96 0.03 0.03 0.01 0.03 0.01 0.00
150/200 40/50 1.016 1.021 100 99.95 0.00 0.06 0.00 0.00 0.05 0.05
555 42.6
500 43.6
150
580 54.0 43
... 129
45
10
1504-
0.03
0.10
0.08 127
41
37
1504Keg. spot
Nip. spot
535 50.0
40
...
0.02
38
150f Keg. spot
505 67.0
153
150+
0.01
40/50 150/200 1.024 1.010 99.95 99.93 0.04 0.03 0.03 0.02 0.00 0.00
Nei.
N&. spot
spot
I J Smackover oxidized asphalt
150/200 40/50 1.017 1.033 99.94 99.94 0.05 0.05 0.01 0.01 0.00 0.00
200/250 40/50 1.014 1.000 99.97 99.76 0.04 0.03
575 38.2
665 42.6
515 42.8
162
156
... 0.02
... 0.00
144
141
150+ Neg. spot
150f Neg. spot
675 57.2 32 15040.00 30
...
Neg. spot
0.00 0.00
200
... 0.09 183 22 Neg. spot
0.20
0.03 545 82.5 40 4 0.03
36
... Neg.
spot
L
K
Dubbs residue S5/100
1.056 99.90 0.07 0.03 0.01
...
47.0 75 1504-
... ... ... Pos.
spot
150/200 1.058 99.92 0.04 0.04 0.00 ib:S
132
...
... ...
1504Pos. epot
TABLE 11. PHYSICAL CONSTANTS OF POSITIVE-SPOT LIQUID ASPHALTIChf ATERIALS’
2 7 8 -Kerosene cutbacks-
Identification
TYPE Source Specific gravity (60/60°F.) Flash point (Cleveland open cup), Furol viscosity, sec. 140’ F. 122O
Kansas O
F.
F.
Tests on residue Penetration a t 77O F. (100 g., 5 sec.) Ductilitg (5 cm./seo.), om. At 77 F. At 39.2’ F. yo sol. in CCh Loss on heating (50 g., 325’ F., 5 hr.) Residue of 80-100 penetration, % Ductility of SO-100 penetration residue (77O F.,5 cm./sec.), om.
1.028 170
10 Dubbs residue
Wyoming 1,067 1.063 165 160
141 ...
. 129 ..
56
5
11
15Of 0
0
1504-
94.66
94.58
97.63
.... .. ...
80
...
1.040 240
...
171
... ,. ,
0
... ... ...
... ... ...
97148 9.92 71.8
101
Better identifioation is given 0 These materials are not standard grades. by results of Marcusson analysis in Table 111, a n d comprehensive d a t a in reference (8). During processing these samples were subjected to excessive beating.
cleus or center, due to a small amount of material precipitated from the bitumen by the naphtha, are called “positive”, and bitumens giving this type of spot are designated as heterogeneous. Spots which are uniform throughout are called “negative”, and the bitumens giving them are designated as homogeneous. When the terms “homogeneous” or “heterogeneous” are used here without further qualification, they refer to the standard Oliensis procedure with the standard naphtha. For the testing of borderline cases Oliensis used different periods of standing time ( 2 ) . In the present investigation the following variations of the spot test were studied: Oliensis procedure (standard naphtha), variation of standing time, variation of ratio of naphtha to asphalt, use of naphtha-xylene, naphtha-hexane, and hexane-xylene mixtures in the Oliensis procedure, use of various solvents in the Oliensis procedure, and heating of bitumen-solvent mixtures. The solvents used were hexane, benzene, toluene, xylene, aniline, nitrobenzene, pyridine, carbon tetrachloride, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, furfural, cyclohexanol, cyclohexane, cyclohexene, tetrahydronaphthalene, decahydronaphthalene, and chlorobenzene.
Asphaltic Materials Tables I and I1 give the source and physical properties of the asphaltic materials, and Table I11 shows the group composition (Marcusson analysis). The Marcusson analysis was modified as described in a previous report (3). Hexane was used in place of petroleum ether, and the fuller’s earth was activated by heating at 160’ C. The acids and anhydrides were determined by conductometric titration. As a further refinement, the hexane extract from the fuller’s earth was mixed with more fuller’s earth and again extracted with hexane t o give a second separation. Thus, two resin extracts, resin 1 and resin 2, were obtained instead of one as in the previous procedure. This second extraction was not carried out on the four liquid asphaltic materials used in this work. The 5-gram samples of asphalt were dissolved in 10 cc. of benzene instead of 25 cc. because Borne of the asphalts (D, K, and L) did not settle out well after alcohol was added to make the acid determination. It is interesting to note that the asphalts from the same source, regardless of penetration, grade, or treatment in manufacture, gave the same color in the benzene-alcohol solvent mixture: K, L E, F A, B, C , D G, H, I, J
Orange (darkest) Dark yellow Light yellow Very pale yellow (lightest)
The contents of acids and acid anhydrides in the asphalts were less than 0.5 per cent of each. Thus, the acids or anhydrides cannot be regarded as a source of difference of behavior of these asphalts. There is no indication that the oxidation process has produced any acids in the Venezuelan asphalt or the Smackover material. The sum of the acids and anhydrides of the oxidized materials are only slightly higher than that of the nonoxidized material from the same source. A comparison of the asphaltene content with the type of asphalts leads to a correlation which might be expected but which does not seem to have been pointed out before. Oxidized asphalts have a higher asphaltene content than nonoxidized asphalts of the same penetration grade and from the same source. The range of asphaltene content of similarly treated asphalts of different sources may vary appreciably.
Results of Spot Test The results (Table IV) support the claims made for the standard spot test, that materials which have been cracked or subjected to abnormally high temperatures give positive spots as illustrated by the test results obtained on samples
INDUSTRIAL A N D ENGINEERING CHEMISTRY
October, 1941
1287
CONSISTENCY OF ASPHALT. The tests run in this investigation do not clearly indicate Total % Oil! the effects of variations in asResins (+ Resin (Double 2) by 1st phalt penetration upon the Total, % Extn.) Extn. appearance of the spot. It 100.27 67.74 62.26 100.31 58.99 53.39 would be logical to expect 100.05 53.33 51.02 that the h a r d e r r e s i d u e s , 46.42 36.90 99.48 98.19 61.99 54.48 which have undergone a longer 67.01 62.78 98.81 52.77 64.65 98.89 and in some cases a higher 97.94 45.92 61.92 temperature treatment than 55.61 45.13 99.56 82.76 99.24 43.28 the softer residues, would show 37.24 99.32 38.68 61.45 35.22 99.22 a greater tendency toward 64.57 ... heterogeneity than the softer 58.77 ... ... a s p h a l t s . The harder and 69.44 ... 54.66 softer vacuum Smackovers G and H and the harder and softer vacuum Trinidads E and I? do behave in this way. The reverse, however, seems to occur with vacuum Venezuelans A and B; sample A (150-200 penetration) appears to tend more toward heterogeneity than sample B (40-50 penetration) ; the naphtha-asphalt ratio, hexane-naphtha ratio, and standing time necessary to produce positive spots show this tendency. This reversal in the case of the Venezuelan asphalts may be due to such a factor as a difference in the treatment to which the two samples were subjected, but the exact history of these two asphalts is not known. HEXANE-NAPHTHA RATIO.Pure hexane gives positive spots for all the asphalts. Dispersing the homogeneous asphalts in hexane-naphtha solvent mixtures produces breaks from positive to negative spots a t different solvent ratios (i. e., hexane to naphtha) for the different materials. These solvent ratios show the same general differentiation of the colloidal stability of the asphalts as do the standing times and the dilution tests'with standard naphtha solvent. Comparisons of standing times, dilution tests, and hexane-naphtha ratios required to give positive spot tests are shown in Table IV. Results of the different testing methods (standing time, naphtha-asphalt ratio, and hexane-naphtha ratio) are parallel for asphalts from the same source. If all asphalts are considered, irrespective of source, a similar relation appears to exist in most cases, but exceptions are found which may or may not be due to special factors involved in the character or history of the sample.
TABLE 111. RESULTS OF MARCUSSON ANALYSIS Asphaltous Asphal- AFhy- % ' Oils Penetration tous drides, (Double Asphalt Grade Acids, % 7% Extn.) 0.19 0.08 33.50 A 150-200 0.30 0.07 26.54 B 40-50 0.25 0.01 28.32 150-200 C 40-50 0.17 26.97 D - _ _. 0.26 0.46 0.24 28.70 E 40-50 0.44 0.12 30.89 150-200 F 0.18 0.19 24.54 G 150-200 0.22 0.21 21.63 H 40-50 0.41 0.14 31.58 200-250 I 0.25 0.22 35.62 40-50 J 0.30 0.12 27.00 85-100 K 0.43 0.41 40.98 150-200 L 0.17 0.52 2 0.07 0.32 7 0.19 0.45 8 0.10 0.56 10
... ... ...
..... ..... ..... .....
...
% of Resin 1 (let Extn.) 18.12 20.94 26.01 17.45 21.18 26.66 36.41 37.62 21.21 25.09 25.58 14.75 12.95 12.65 21.46 17.27
% of Resin 2 (2nd Extn.) 34.14 32.45 25.01 19.45 33.30 36.12 28.24 24.30 23.93 7.67 11.68 20.47
... ... ... ...
Asphaltene, % 14.14 20.01 20.45 35.18 14.31 4.58 9.13 13.96 22.29 30.39 34.66 22.18 17.63 26.29 19.41 11.01
K,L, 2, 7,8,and 10. The spot test results are also influenced by the following additional factors: DEGREEOF DILUTION. If the degree of dilution necessary to obtain a positive spot is taken as an indication of relative colloidal stability, the method used in refining the asphalt (e. g., temperature and type of treatment such as vacuum, oxidation, etc.) and probably the colloidal structure of the crude from which it is derived appear to be determinants. (As a matter of fact, both these factors may be closely related to each other since the colloidal structure of the crude undoubtedly affects the reaction of the latter toward the subsequent refining process.) The effect of both these factors is indicated by the fact that all the oxidized as well as nonoxidized Venezuelan asphalts eventually showed positive spots, whereas the nonoxidized Trinidad and the nonoxidized Smackover asphalts did not give positive spots with the highest ratio of naphtha-asphalt used. This indicates a relatively higher compatibility in the system micelles-oil-naphtha in the case of the two latter types of asphalt than in the case of the oxidized and nonoxidized Venezuelan material. STANDING: TIME. I n the standing time tests, the oxidized asphalts from Venezuelan crude showed positive spots earlier than the nonoxidized asphalts from the same source, though it cannot be stated with certainty whether this was due solely to oxidation per se or to the combination of oxidation and high temperatures to which the oxidized asphalts may have been subjected. , TABLE IV.
Asphalt F
G
H I J E B A C D L K 8 2 10
Source Trinidad Smackover Smackover Smackover Smackover Trinidad Venesuela Venezuela Venezuela Venezuela Dubbs Dubbs Wyoming Wyoming Kansas Dubbs
ARRANQEMENT OF
A S P H A ~INS APPRO XI MAT^ ORDER OF DECRHIASINQ COLLOIDAL STABILITY'
Preparation Penetration Vacuum residue 150-200 Vacuum residue 150-200 Vacuum residue 40-50 Oxidized 200-250 Oxidized 40-50 Vacuum residue 40-50 Vacuum residue 40-50 Vacuum residue 150-200 Oxidized 150-200 Oxidized 40-50 Residue 150-200 Residue 85-100 Kerosene cutback Kerosene cutback Kerosene cutback Residue. slow-curing road oil
... ... .... ..
Days for Pos. Spot to Appear
.. ..
.. 77 77 46 14 3 1 1 0 0 0 0
0
NaphthaAsphalt Ratiob >11.3 11.3 >11.3 8.8 8.8 >11.3 10.0 7.5 6.3 6.3 < 5.1d < 5.1: < 5.1 < 5.1' < 5.16 < 5.14
HexaneNaphtha Ratioc 9.00 4.00 2.50 0.67 0.42 2.33 1.00 0.67 0.42 0.25 0 0 0 0 0
0
Tetrahydronaphthalene Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pos. (fajnt) Pos. (faint)
Decahydrona hthaL e cycloBenseAe hexane Toluene: Cyclol Xylene hexene Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Ne$. Neg. Neg. Pos. Pos. Pos.
Pos.
Nee. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Neg. Pos. Pos. Pos. Pos. Pos.
Nitrobenzene Pos. Pos.
Pos. Pos. Pos. Pos.
Pos.
Pos.
All tests on the liquid asphalts were made on the original materials and not on the residues from the distillation tests. The acetates, hexane, oyclohexanol, furfural, aniline, and p ridine gave positive spots with all asphalts. b Parts by volume ofnaphtha to 1 part by volume of asphalt. C Ratio in parts by volume; total volume of mixture used was the same in each test, d Xylene equivalent 85 Positive spot with'xylkne. a
@
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Of the asphalts which are heterogeneous if tested in standard naphtha, samples 2, 7 , 8, and 10 are also heterogeneous in pure xylene solvent. Asphalts K and L (Dubbs residue) have a xylene equivalent of 83 and 85 per cent, respectively. Xylene-naphtha and xylene-hexane gave nearly the same results, the hexane mixtures showing the break from positive to negative spots more sharply. Furfural substituted for the standard naphtha solvent gives positive spots with all asphalts. The nuclei of the spots are different in appearance from those obtained with positive spot materials in standard naphtha. I n the latter case they are dull black (characteristic of powdery asphaltenes), whereas the center spots obtained with the furfural solvents are shiny black and when first prepared are sticky. As the furfuralasphalt ratio is increased above the standard ratio 10.2 of solvent to 2 of asphalt, the center spot changes in appearance from shiny to dull. I n all cases some of the asphalt is insoluble in the furfural and sticks to the sides of the flasks. As the furfural-asphalt ratio is further increased, a new effect results -e. g., a lighter colored fringe which gives the spot the appearance of having two concentric nuclei and indicates a threephase system at this stage. The use of furfural does not show up differences between the individual asphalts to any great degree. The appearance of the spots made with ethyl, propyl, butyl, and amyl acetate changes as the solubility of the asphalt increases with increasing molecular weight of the aliphatic acetates. Shiny and sticky nuclei form with the lower acetates, while the shininess and stickiness disappear with the higher acetates. Benzene, toluene, decahydronaphthalene, tetrahydronaphthalene, chlorobenzene, cyclohexene, and cyclohexane give negative spots with practically all asphalts; aniline, nitrobenzene, pyridine, furfural, and cyclohexanol give positive spots with all the asphalts. The effect of the latter group of solvents indicates, in general, that for the same class of solvents the solvent power varies frequently with the surface tension of the solvent, but that there may be a vast difference in the reaction of solvents of equal surface tension but of different chemical type. For the six heterogeneous asphalts, K, L, 2, 7, 8, and 10, three groups are apparent from the types of spots formed with the different solvents: (a) K and L, (b) 2 and 10, and (c) 7 and 8. With the solvents carbon tetrachloride, benzene, xylene, and toluene, asphalts K and L give negative spots, and 2 and 10 give lighter center spots than do 7 and 8. With aniline, asphalts 7 and 8 give less intense center spots than 2 and 10. Decahydronaphthalene, tetrahydronaphthalene, cyclohexene, and cyclohexane show differences between asphalts 2 and 10 as compared to 7 and 8, but the differences are not so distinct as with the other solvents. Nitrobenzene and pyridine dispersed the heterogeneous asphalts better than they did the homogeneous materials.
Heating of Asphalt-Naphtha Solutions Since standing time is a means of differentiating between the colloidal stability of the asphalts, some method of obtaining the same results by quicker procedure with the same solvent was considered desirable. For this purpose solutions of asphalts A to J, inclusive, in Oliensis naphtha (ratio 2 to 10 cc.) were heated in stoppered flasks at 98-99" C. for 6 hours. Loss of solvent, which varied from 0.061 to 0.432 gram, was made up after the heating period. After the solutions cooled to room temperature, spot tests were made on the mixtures. Asphalts A and C alone were found to give positive nuclei and only to B slight extent. After standing a t room temperature for several hours, asphalts A, C, and D developed considerable residue in the fiasks and gave heavy positive spots. These heavy positive spots developed within about 10 hours after
Vol. 33, No. 10
the heat treatment was begun, whereas the same solutions left to stand a t normal temperature developed positive spots in, respectively, 3, 1, and 1 day; i t is clear, therefore, that the higher temperature had accelerated the development of the positive spot. This confirms the results of some investigations that Oliensis conducted during the summer and late fall of 1939. A similar 6-hour heat treatment was given the other homogeneous asphalts, which had developed positive spots only after 14 to 77 days. However, this preliminary heat treatment was not effective in producing a spot after standing for several days, and the test was discontinued; it may be that if the test had been continued until a spot had developed, the period required might have been less than the 14 to 77 days required when no heat treatment was applied. To study the immediate effects of relatively high temperatures upon asphalt-naphtha systems, heat-treated dispersions of asphalts A, C, and D (giving positive spots with heavy nuclei) were tested further. After 1-hour heating a t 98-99" C. and cooling to room temperature, all three asphalt solutions gave negative spots. After 16-hour standing a t room temperature, solutions A, C, and D again gave positive spots, but after an additional 3-hour heating a t 98-99' C. and cooling to room temperature, they again showed negative spots. After standing 44 more hours a t room temperature, the three solutions again became heterogeneous; but after an additional 3 hours (total 7 ) of heating at 9&99" C. and cooling to room temperature, asphalt C only developed a positive spot. However, after standing several days a t room temperature, all three asphalt solutions again showed considerable residue and gave heavy positive spots. Apparently, then, the immediate effect of heat is to help disperse or peptize the carbenoids, and this effect lasts for a few hours at room temperature, but the ultimate result of such heating seems to be a reduction of the time required a t normal temperature for the development of flocculation. We attempted to correlate the results of the spot tests with the group composition of the asphalts according to the data obtained in the Marcusson separation. This attempt failed for an obvious reason. The Marcusson separation gives only quantities of asphaltenes, resins, oils, etc., without identifying their chemical composition; this has been emphasized in previous work (3). However, the colloidal stability of bituminous dispersions depends as much on the chemical character as on the amounts of the different phases in the system. Therefore, correlation of group composition with results of spot tests can be expected and found only for asphalts of the same general chemical characteristics, or for asphalts of the same source that have undergone substantially the same refining treatment. This result is in line with the statement that the results of spot tests made with different dispersing agents are parallel only for bitumens of the same source and same refining treatment. For this reason one method of obtaining spot tests to indicate the inherent colloidal stability of asphalts would be to employ different solvents for asphalts of different sources and different (if chemically determinant) methods of preparation. It should not, be too difficult for manufacturers and users of products from certain sources to agree on these solvents.
Conclusions Variations in standing time as first suggested by Oliensis (8) or the use of varying proportions of naphtha-asphalt or naphtha-hexane as described here seem to make the spot test a more general method of differentiating or evaluating asphaltic materials which give negative spots by the Oliensis procedure. I n the case of asphaltic materials giving positive spots in this procedure, either the xylene equivalent may be
October, 1941
INDUSTRIAL AND ENGINEERING CHEMISTRY
used as fist proposed by Oliensis in 1936 (I), or other liquids may be employed whose solvent power diBerentiates between the relative heterogeneity of such bituminous materials. Solvents such as tetrahydronaphthalene, decahydronaphthalene, and cyclohexane should be of interest in this connection. The positive spots obtained with furfural and aniline, and particularly with pyridine and nitrobenzene (materials of high solvent power for asphalts), indicate that, while in general for the same class of solvents the solvent power varies frequently with the surface tension of the solvent, there may be a vast difference in the reaction upon asphalt of solvents of equal surface tension but of different chemical types.
1289
Acknowledgment The authors gratefully acknowledge constructive criticism of this work by E. F. Kelley, U. S. Public Roads Administration, F. V. Reagel of the Missouri State Highway Department, and especially by G. L. Oliensis of the Barber Asphalt Corporation. Literature Cited (1) Oliensis, G.L.,Proc. Am. 800. TestinQ Materials, 33, I1 (1933); 36,I1 (1936). (2) Oliensis, G. L., Proc. Montana Natl. B3uminous Conf.. 1939, 193,204. ( 3 ) Winterkorn, H.F., and Eckert, G. W., Assoc. Asphalt Paving Tech., Proc. Tech. Sessions, 11, 207-57 (1940).
Vapor-Phase Esterification of Benzoic Acid with Ethyl Alcohol J
Effect of Oxides on Catalytic Activity of Silicon Carbide and Alundum ARTHUR A. VERNON' AND BERTRAM M. BROWN' Rhode Island State College, Kingston, R. I.
The vapor-phase esterification of benzoic acid with ethyl alcohol was investigated using, as catalyst, twelve d a c u l t l y reducible oxides suspended on Alundum and on silicon carbide. Comparison with previously published results showed that the catalyst mass activity varies with the carrier for the same oxide and is related partly to the way in which the oxide adheres to the carrier. The best catalyst found was titanium oxide on Alundum at 370" C. A life test on this catalyst mass actually showed an increase in activity with time of use. The best catalyst from the point of view of extrapolated values was magnesium oxide on silicon carbide at 450" C. The relation between conversion and side reactions is emphasized.
salts were c. P. grade; the tungstic oxide was technical; the manganous nitrate waa a 50 er cent solution of c. P. grade. The Alundum waa 4-8 mest material furnished by the Norton Company and the silicon carbide was given by The Carborundum Company. The latter was crystal size No. 6.
TABLEI I. CATALYTIC EFFECTOF CARRIERS T:?.,
410 430 450 430 430
d i l i c o n CarbideS ace % apid vegcity % acid to side of acid to ester reactions 20 308 298 21 21 1 316 1 308 18 2 154 20 2 77 30 11
7 -
..
Space velocit of a d 282 289 298 289 145 72
Alundum%acid to ester 2 3 2 2 8 11
7% acid to side reactions 16 12 12 12 9 23
TABLE 11. CATALYTIC EFFECTOF ZIRCONIUMAND ALUMINUM OXIDESWITH CARRIERS
HE first paper of this series2 reported the results of an investigation on the esterification of benzoic acid with Tethyl alcohol, using as catalysts difficultly reducible oxides on silica gel. This paper gives the results of further work using silicon carbide and Alundum as carriers.
Experimental MAT~RIALS. U. S. P. benzoic acid was used as in the previous work while ethyl alcohol was distilled twice from calcium oxide and once from sodium. The titanium tetrachloride and the 1
r
Present address. Northeastern University, Boston. Mass.
-Zirconium Oxide-Aluminum Oxide S ace % apid S ace % apld Temp., vegoity %acid to side ,Temp., veccit %acid to s z e C. of acid to ester reactions C. of acic? to ester reactions
410 430 450 450 450 450
286 295 304 304 152 76
12 17 18 18 20 31
410 430 450 430 430 430
286 292 302 292 146 73
78 79 78 75 75 76
Silicon Carbide 2 410 1 430 2 450 3 430 3 430 430 11 Alundum 6 390
lo 12 12 15 15
410 430 410 410 410
286 295 304 295 148 74
43 49 49 49 51 5s
5 5 11 5 9 22
274
77
282 290 252 141 70
78 66 74 81 81
12 14 24 17 12 13
