June, 1931
INDUXTRIAL AND ENGINEERING CHEMISTRY Discussion
thixotropy Of plastic systems has been known for some time and the degree of thixotropy has been estimated by rough empirical tests, such as failure to pour from an inverted test tube. the mesent use of the KamDf viscometer represents the first attempt a t a quantitati;e evaluation of the thixotropic changes in consistency in terms of absolute viscosity or fluidity units. This instrument makes possible the investigation of thixotropy in plastic systems not previously suspected of being thixotropic. The use of the apparatus and methods described should ultimately lead to a clearer understanding of the phenomena to thixotropy and it5 relation to plasticity. It is planned to show in a future
679
publication that the thixotropic change in consistency with time follows a definite course and can be expressed by means of an empirical mathematical equation, the constantsof which completely describe the thixotropic nature of the plastic Literature Cited (1) Freundlich and Bercumshau, Kolloid-Z,, 40, 19 (1926), ( 2 ) Green, IND. END. CHEM.,I T , 726 (1925). (3) Haslam and Grady, I b i d . , Anal. Ed., 2, 66 (1930). KoJzord-Z**61* 165 (lQ30) (4) (5) Waring, Paper presented before Society of Rheology, Easton, Pa., Dec., 1930. (6) Williamson, Patterson, and Hunt, IND. END. CHEM, 21, 1111 (1929).
Asphalt from the Cracking Process' Gustav Egloff and Jacque C. Morrell UNIVERSAL OIL PRODUCTS COMPANY, 310 SOUTHMICHIGAN AvE., CHICAGO, ILL.
ARCUSSON (3) conThe production of asphalts from liquid residue deis present. They postulated siders the acidic or rived from the cracking process is reported herein. that oxidation of the sulfur s a p o n i f i a b l e subThe cracking reaction can be controlled so as to procompounds causes a simulduce essentially gas, gasoline, and asphaltic substances. taneous oxidation of the other stances present in asphalts as The quality of the asphalts produced may be so diconstituents. For example, asphaltogenic acids (these are rected as to be useful for paving, roofing, shingle the addition of 8 per cent sulconverted by heat into the anhydrides). the substances saturants, coating asphalts, flooring, and emulsions. fur to a residue from iMexican oil yielded, after blowing with adsorbable' b y fuller's earth from a petroleum-ether solution of the asphalts as resins, and air for 31 hours a t 225" C. (437" F.), a product with a softenthe insolubles in petroluem ether as asphaltenes. He states ( 2 ) ing point of 185" C. (365" F.) and a penetration of 7 mm. a t that the distillate from natural asphalts contains considerable 25' C. (77' F.), while under similar conditions of treatment organic acids, whereas very little acid passes over in the the addition of 12 per cent sulfur gave a product with a softening point of 200" C. (392' F.) and a penetration of 5 case of petroluem pitches. The generally accepted classification of the components in mm. The time required for a pronounced hardening by asphalt includes petrolenes extractable with petroleum ether oxidation may be reduced from 96 hours to 14 hours by the (hexane), asphaltenes extractable with carbon tetrachloride, addition of from 3 to 5 per cent sulfur. I n the cracking process, however, where no oxygen is presand carbenes extractable after above operations in cold ent and sulfur is practically absent when oils such as those carbon bisulfide. from Pennsylvania are treated, the above four chemical Chemistry of Asphalts processes for the formation of asphalt are reduced to polymerization and condensation. Very little is known about the chemistry of asphalts. Asphalt produced by cracking has a smaller percentage of They have been generally considered as being formed by hydrogen than the original charging stock or any fraction chemical processes such as oxidation, sulfuration, polymeriza- thereof; hence dehydrogenation is one of the chemical proction, and condensation. The term "condensation" as used esses by which such asphalt is formed. The resultant ashere refers to the combination of unlike molecules as dis- phaltic compounds may not be due t o direct dehydrogenation, tinguished from polymerization which refers to the com- but may form in several steps comprising dehydrogenation, bination of like or identical molecules. polymerization, condensation, intermolecular rearrangement, One plausible theory about the formation of asphalts by or combinations thereof. The course of the reactions is oxidation is that polycyclic compounds, acidic in character, suggested below: are formed during the intermediate stages of oxidation which Paraffins upon further heating change to anhydrides such as those of the polynaphthenic acids, with progressive condensation / \ Olefins4Naphthenes and polymerization. I I I It is well known that asphalt has been made by the reaction of sulfur and hydrocarbons in the absence of oxygen. This is probably brought about by a series of dehydrogenaI tions, forming hydrogen sulfide and hydrocarbon compounds of sulfur of a highly condensed character. Aromatics The presence of sulfur promotes oxidation. Brooks and Humphrey (1) stated that hydrocarbons of the saturated Condensation may take place between any of these prodand unsaturated type are more readily oxidized when sulfur ucts. It is shown by the present work that polymerization and 1 Received February 26, 1931. Presented before the Division of condensation accompanied by dehydrogenation may account Industrial and Engineering Chemistry at the 81st Meeting of the American for the formation of asphalts in the cracking process. Chemical Society, Indianapolis, Ind., March 30 to April 3, 1931.
M
4
INDUSTRIAL AND ENGINEERING CHEMISTRY
680
Vol. 23, No. 6
Table I-Asphalts
Produced f r o m Flashed Residues MIDCONTINENT A N D WESTTEXAS MIDCONTINENT PROPERTY KENTUCKYO Coating asphaltb Asphalt cementa CUSHINOd MIDCONTINEN Tb Specific gr; gravity a t 25' C. (77' F.) 1.075 1.065 1,099 1.0867 1.1195 Flash, OO C C. (" F.) 231 (448) ...... 171 (340) 1771 .(350) 15 Loss a t 16: 163' C. (325" F.), 7 0.58 Trace 1.7 0.765 Penetratio Penetration of residue a t 25' C. (77" F.),mm. 48 4.0 ..... 54 49 Softening point, a C. ( " F.) Sol 53 (127) 126 (259) 55 (131) 54 (129) 51 (123) Flc Float test a t 50" C. (122' F J , sec. 680 ...... 829 1210 693 Sol Solubility in CClr, % 93.8 96.9 ..... 91.2 92.7 Soluhility in CSr Sol 99.1 98.6 97.9 98.7 99.8 Paraffin scale (Reistle and Blade) Pa 5.3 ...... 2.63 3.6 2.17 carb Fixed carbon 17.2 19.0 20.0 17.8 20.2 Penetratioi at 25' C. (77' F.), mm. Penetration 100 5.5 100 97 103 Ductility a t 25O C C. (77' F . ) , cm. > 122 0.3 125 78 >122 Ductility a t 16' C. (60' F J , cm. > -~~ 122 . . ... .. . 63 ...... > 122 a 100-120 mm. penetration for macadamized roadq, D103-24T. b Coating asphalt, air-blown for 3 hours a t 254' C. (490' F,). c Asphalt cement for use in asphalt macadam pavements, D102-24T. d 85-100 mm. penetration for for macadamized roads, D102-24T. 100-120 mm. penetration used in building asphalt concrete roads or macadam roads, D103-24T.
.....
-
Formation of Asphalt by Cracking
Asphalts have been produced from cracked residuum and William M. Burton was an early worker in this art (4). One interesting feature of the present work is the formation of asphalt from fractions of Pennsylvania crude oils containing no asphalt or mixed-base crude oils which are more paraffinic than asphaltic. There are midcontinent crude oils from which asphalts are not made in commercial quantities. The production of asphalts from such crudes may be accomplished through the medium of the cracking process. The formation of asphalts from paraffin-base oils, such as those from Pennsylvania, is the most striking example of the synthesis of asphaltic material from paraffin hydrocarbons. Ordinarily cracking is considered a decomposition or breaking-down process; that is, higher boiling and higher molecular-weight hydrocarbons are converted by pyrolysis or thermal decomposition into hydrocarbons of lower molecular weight and lower boiling point. These reactions are accompanied by dehydrogenation,. polymerization, and condensation, resulting in the formation of hydrocarbons having the characteristic properties of pitches or asphalts. Table I shows the characteristics of paving asphalt residues resulting from the cracking of various fuel oils or topped crudes. These residues were made by the flashing operation of the cracking process. In this operation hydrocarbons are withdrawn from the reaction chamber and passed to a vaporizing chamber or zone of reduced pressure. The reduction in pressure causes the vaporization of controlled amounts of the liquid. The oil withdrawn from the vaporizing chamber is called "flashed residue." The vaporized hydrocarbon oils are generally returned to the heating zone for further treatment. One result of the flashing operation is the reduction of suspended carbonaceous or pitchy material in the residue. This is quite important in asphalt making, as the presence of such suspended material reduces the ductility of the asphalt. This operation also permits the production of asphalt while making the high yields of gasoline demanded of the modern cracking process. It is to be noted that the percentage of asphalt based on the charging stock to the cracking process is a function of the oil charged, the particular examples shown ranging in yield from 10 to 20 per cent. Table 11-Properties of Asphalt M a d e f r o m C u s h i n g Topped C r u d e by S t e a m Distillation a n d by Air-Blowing RESIDUEFROM AIR-BLOWN STEAM AT 232' C. DISTILLATION (450" F.) PROPERTY 71.5 70.2 Flashed residuum % Softening point 0' C. ( 0 F.) 51 (124) 63 (146) Penetration a t is' C. (770 F.), mm. 103 93 Ductility a t 25' C. (77' F.), cm. 40 11.3 Solubility in CSz $7 100 100 99.3 99.5 Solubility in CCL,
% '
In Table I1 the properties of asphalt made from flashed residuum from the cracking of a Cushing topped crude by steam distillation and by air-blowing are compared. It is
-I
observed that the air-blown product has a higher softening point and lower penetration and ductility than the residue from steam distillation. The asphalts from the flashed residues (Table I) meet A. S. T. M. D102-24T and D103-24T specifications in practically all respects except solubility in carbon tetrachloride] and the departure in this requirement is so slight as to have no practical significance. Similarly, the specifications for roofing or shingle saturants] coating asphalts, flooring asphalts, blowing stock, and soft emulsions may be met generally. Asphalt from Pennsylvania Crude-Oil Distillate
A kerosene distillate from Pennsylvania crude oil was cracked yielding approximately 10 per cent of residuum based on the oil processed. The residuum had the following characteristics : Gravity A P I . . .. . . . . . . . . . . . . . . . . . . . . . Sperific'gravky'at 16' C. (60° F.). . . . . . . . . . . Initial boiling point, C. (" F.),. . . . . . . . . . . % a t 3009 C. (572O F.) . . . . . . . . . . . . . . . . . . . . Flash point (Cleveland open cup), ' C. ( " F.) Fire point (Cleveland open cup), O C. (,' F . ) . % bottom settlings and water.. . . . . . . .. . . . . . Viscosity a t 50' C. (122' F.),sec.. . . . . . . . . . .
7.8 1.018 193 (380) 40 77 (170) 96 (205) 0 6 20
The flashed residuum was heated in an Engler flask to 260-288" C. (500-550° F.), and in one case air was blown through the hot mass until the desired penetration was obtained, while in the other case steam was blown through the mass. The residue in each case was analyzed for its asphaltic properties. Table I11 summarizes the properties of the two asphalts. Table 111-Properties of Asphalt M a d e f r o m Pennsylvania C r u d e by Air-Blowing a n d Steam-Blowing P r o p e r t y CRACKED RESIDUVM PROPERTY Air-blown Steam-blown % ' asphalt recovery on Pa. kerosene distillate 5.26 5.09 Specific gravity at 25' C. (77' F.) 1.116 1.099 105 103 Penetration a t 25" C. (77' F.), mm. 44 (112) 51 (123) Softening point (ring and ball), ' C. (" F.) 297 381 Float test -set 125 Ductility 'st 25' C. (77' F.), cm. 125 0.7 0.67 Volatility a t 163' C. (325' F.), % 70 Penetration of residue a t 25' C. (77' F.), mm. 60 188 (370) 202 (395) Flash point (Cleveland open cup)& C. ( " F.) 207 (405) 218 (425) Fire point (Cleveland open cup), C. (" F.) 99.86 99.59 Solubility in CSz, % 98.95 97.71 Solubility in CClr, % None h'one Water
The work on cracked residuum from Pennsylvania kerosene distillate is an excellent example of the synthesis of asphalt from paraffinic hydrocarbons, as well as of the fact that neither oxygen nor sulfur is required for the formation of asphalt. Literature Cited (1) Brooks and Humphrey, J. IND.ENG.CHEM.,9, 746-8 (1917). (2) Marcusson, Chem. Rev. Fetl. Harz-Ind., 18, 47-51 (1911). (3) Marcusson, 2. angew Chem., 49, 346 (1916); Chem.-Ztg., 44, 437 (1918). (4) U. S. Patent 1,055,707 (March 11, 1913).
