64
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Vol. 18, No. 1
Laboratory Distillation Analysis of Petroleum' With Special Reference to Southern California Crude Oils By Howard G. Vesper STANDARD OIL COMPANY OF CALIFORNIA, EL SEGUNDO, CALIF
capacity is necessary. It mittee XXI on Crude Petrohas been established, howleum of the A. S. T. M. is A discussion of the importance to the refiner of a ever, that for most purmethod of complete laboratory distillation analysis of now working On standard may poses method for the determinacrude oils in terms of refinery products, together with byusing apparation of the gasoline content a suggested method of procedure applicable to all Of much 'WacOf any given crude Oil* The classes of crudes for the determination of blending ity' This, Of course, ingasoline, motor gasolines, lamp oils, lubricating oils, method at present under and asphalts. consideration was proposed volves important savings in time, labor, and equipment. Of the A table gives results obtained by this method on by E' w' The common applicaStandard Oil Company of various southern California crude oils. tion of small-scale distillaNew Jersey. Briefly, it Drovides for the direct distion analysis was the procedure of Engler, who distilled tillation of 1 liter of the 100 cc. of the oil being tested, in the standard Engler 100-cc. crude through a 30-cm. (12-inch) chain tower. The volume flask. The fraction up to 150" C. was considered to be gaso- of distillate at a vapor temperature of 392" F. is noted, line, that from 150" to 300" C. to be illuminating oil, and the this volume divided by 0.9, and the distillation stopped remainder to be lubricating stock. Other forms of distilla- at this calculated volume. This procedure assumes the contion analysis based roughly on this general procedure have trol point of the gasoline distilled to be 90 per cent; hence, come into common usage in recent years, and have been the A. S. T. M. distillation on this gasoline shows 90 per used especially in determining the approximate composition cent over at 392' F., with a final boiling point of usually 437' F., both of which points are the limits for Navy specifiof various classes of petrqleum. Although such an analysis is helpful in giving an idea of cations gasoline. the general nature of an oil, it is of very little practical value This method, however, meets only part of the specificato the refiner, and hence an attempt has been made to work tions for Navy gasoline, and gives no consideration to the out a general method of distillation analysis that will furnish amount of lower-boiling hydrocarbons in the gasoline, which, the refiner with definite and accurate information regarding when cut as described above, will often show a 20 per cent the yields and qualities of any specified petroleum products. point of 230' F. or higher, as compared with a specification The method described has been worked out especially of 221" F. Hence, it is obvious that Dr. Dean's method is with regard to southern California crude oils, but, since it in reality a method for the determination of blending gasoline is largely based on temperature control rather than gravity, rather than motor gasoline. For this purpose, however, it probably can be applied to other classes of crudes with but it is very satisfactory. slight modification. However, it has not yet been tried on For the purposes of the complete distillation analysis of crude oil, however, it was considered advisable to combine, crudes produced east of the Rocky Mountains. The information required about any given sample of pe- if possible, the methods for the determination of gasoline troleum varies, of course, with the refinery and refinery with the rest of the procedure. This was found to be entirely conditions. Occasionally, the only requirement may be the practicable, and has been accomplished as follows. yield of some one definite product to meet definite speciDistillation of Crude Oil fications. At other times an exhaustive quality examination of the product or products may also be necessary. Hence, The basis of the complete distillation analysis is the SOno arbitrary distillation methods can be laid down, and the called "four-point" method of gasoline determination as procedure, although it should be as closely standardized as developed by the Standard Oil Company of California in possible, must be capable of enough latitude to meet any 1922. This method as first developed was not'entirely conditions. satisfactory, but with suitable modifications has been very The most common form of distillation analysis of crude oil successfully used. It consists, briefly, in a double distillation is its examination for gasoline content. This is generally of the crude to determine the gasoline content. The first divided into two parts-a determination of the amount of distillation of the crude is carried to a temperature of 500" F. 1 Received July 23, 1925. Presented before the joint session of the in the vapor, and is a simple topping operation. The reDivision of Petroleum Chemiqtry and the Section of Gas and Fuel Chemsulting naphtha is then distilled in a 500-cc. Hempel flask istry a t the 70th Meeting of the American Chemical Society, Los Angeles, to make the required gasoline and lamp oil. Calif., August 3 t o 8, 1925.
'
January, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Upon this double procedure depends the especial adaptability of this method to a complete distillation analysis. The preliminary topping operation provides t h e method with the flexibility necessary t o meet all varying conditions. It provides a supply of naphtha sufficient to make several runs to determine the gasoline and lamp oil without the necessity of re-running the crude. It furnishes a supply of tar, which is the starting point of the vacuum distillation to determine lubricating oil and asphalt. Since this topping operation is not critical as regards the actual determination of gasoline and other products, it follows that any size or type of still may be used in this preliminary run. This makes possible the use of a pressure still for crudes containing an excessive amount of water, and of a still of sufficient size to accommodate any desired charge. Thus, on a crude on which extensive information is desired, a large charge may be used and a large supply of naphtha and tar obtained for subsequent determinations of the actual products. The disadvantage of a double distillation is the danger of the loss of a small portion of the lighter hydrocarbons of the crude. This loss, however, can be made practically negligible by the use of suitable precautions. A condenser larger than the standard A. S. T. M. condenser is recommended to insure sufficient condensing surface. A coil condenser containing about 6 feet of 6/pinch brass tubing has been very successfully employed. The rate of distillation is slower until the lightest of the fractions have distilled over. The receiver must be immersed in an ice bath. If the crude being tested contains an excessive amount of light-boiling hydrocarbons, or if special accuracy is desired, a supplementary condenser of any convenient form, and maintained a t a temperature below -100" F. by an alcohol or acetone-solid carbon dioxide mixture, is recommended. With these precautions and with careful handling the double distillation has been found to check results of single distillations of crude for gasoline content well within the experimental limit of error, which is generally taken as about 0.5 per cent. For the determination of the products heavier than gasoline there is, of course, no difference between the two kinds of distillations. The topping operation is generally carried out in a seamless copper flask of about 4000 cc. capacity, the exact charge being determined by the requirements of the analysis. Copper has been found very satisfactory from the standpoints of efficient heat transfer and wear, but is not used where sulfur determinations are required because of possible action on the sulfur bodies of the crude. The topping operation is carried to a vapor temperature of 500" F. with a rate not to exceed 10 cc. per minute. The rate is slower during the first part of the distillation until the lighter boiling fractions have distilled over. A combination shield and flask support is generally used, and assists materially by confining the heat applied to the sides of the flask. With the apparatus described and with careful handling of the heating during the first part of the distillation until the water has been thrown over, crudes containing up to 10 per cent of water have been successfully handled. The question of handling crudes containing relatively large amounts of water is a serious one in southern California, because of the many well samples analyzed which are in this class. Crudes containing 75 per cent and more of water are sometimes encountered. This class of crude has been very successfully handled by the use of a small pressure still operating at pressures up to approximately 100 pounds per square inch. The oil is heated until this pressure is registered in the still, and is there maintained until the emulsified water is separated from the oil. The pressure is then carefully released, and the distillation carried on up to 500" F. vapor
65
temperature. During this operation the water will be found
to distil over very easily. This method of dehydration has been found very superior to the calcium chloride method of the Bureau of Mines,* and has been successfully carried out on crude oil emulsions containing up to 90 per cent water. The cutting temperature of 500" F. corresponds to a temperature of about 600" F. in the oil, a t which temperature practically no cracking takes place. This cut is always sufficiently deep for any gasoline determination, but it is sometimes necessary to go as high as 550" F. in the vapor in order to obtain a cut deep enough to determine yields and qualities of lamp oils. This, too, may be accomplished with practically no cracking if the rate of distillation is maintained to the end and the high heating is not sustained. It has occasionally been found necessary to go to still higher temperatures for special work, but this necessitates the use of steam, and is to be avoided, if possible, because of the difficulty of handling in a small way. Distillation of Naphtha
The naphtha obtained from the topping of the crude is distilled in a 500-cc. Hempel type distilling flask, equipped with a 15-cm. (6-inch) jack chain tower. Originally, the four-point method of cutting to obtain Navy specifications gasoline was to observe the amounts of distillate over a t the four control points of the resultant gasoline-namely, 221 ", 284", 392", and 437" F., and divide these readings, respectively, by 0.20, 0.50, 0.90, and 1. The distillation was con-
400
300
ZW
/oo
tinued to the lowest of these four calculated yields, and this fraction tested for Navy specifications gasoline by the standard A. s. T. M. gasoline distillation. This procedure was based on the assumption that the distillation curves of both the naphtha and the A. S. T. M. distillation of the gasoline were identical. This in reality is true only for the 50 per cent and 90 per cent points, and But. Minrs, Bull. 107.
66
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
the two curves show considerable divergence a t both the start and end of the distillations. (See figure) Because of this divergence at the 20 per cent point, it is obvious that heavy or weathered crudes which contain but small amounts of low-boiling hydrocarbons-in other words, crudes having a control point of 20 per cent-will give a gasoline showing a high 20 per cent point on the A. S. T. M. distillation when cut by this method. Likewise, light crudes that have a control point of 437" F. will often show a final boiling point of 445" F. or higher, because of the divergence at this temperature. Crudes cut a t the 50 or 90 per cent control points have been found to give accurate gasoline yields, because the curves are practically identical at these points; but it was obvious that some method of compensating for the variation at the 20 per cent and final control points was necessary to make the method accurate for any kind of crude. This has been accomplished as follows: The divergence of the two curves at the start of the distillation and up to their first crossing varies with the boiling points of the stock which go to make up the gasoline, or, in other words, with the slope of the four-point distillation curve. This curve is practically a straight line for temperatures above 200" F. This slope, in turn, varies directly with the amount of low-boiling fractions in the naphtha being tested, which may be measured as the total amount of distillate up to 200" F. From these facts an approximate relation between the amount of distillate over up to 200" F. and the divergence of the A. S. T. M. distillation curve from the four-point curve has been worked out, which compensates for the difference in boiling points a t the 20 per cent point. This procedure requires, first, the measurement of the total amount of gasoline distilled over up to 200" F. in the four-point naphtha distillation. If this is approximately 5 per cent or less of the amount of naphtha charged, the reading a t 221" F. is multiplied by 5 for the 20 per cent control point, because the two curves very nearly coincide in this case. (Curve I) If the fraction to 200' F. is approximately 5.5 to 6 per cent, it shows that the two curves diverge slightly, and hence the 221 O F. reading is multiplied by 4.5 (Curve II), and likewise, for about 6.5 per cent or over up to 200" F. the 221" F. reading is multiplied by 4 (Curve 111). KO factor of less than 4 has been found necessary for any crude. This method will give an A. S. T. M. distillation of the gasoline from any crude having a 20 per cent control point which will show a 20 per cent point of within 3 degrees of 221" F. The method of correction for the divergence of the two curves a t the end of the distillation is more simple. It has been found that, when the final boiling point is the control point of the gasoline, it is about 15 degrees higher than the temperature a t which the four-point distillation was stopped. Hence, the obvious prscedure was to make the specification for the final boiling point 420" F. in order that an A. S.T. M. distillation final of 437" F. might be obtained. This procedure, of course, gives only the yield of h'avy specifications motor gasoline. I n determining the yield of blending gasoline, the amount of distillate over a t a temperature of 392" F. is observed and divided by 0.90, and the distillation cut a t this yield. Other grades of gasoline may be determined as required by the application of similar procedures. Yields of lamp oils are generally determined by the desired final boiling point. The naphtha distillation is cut about 10" F. below this desired figure, when it is in the neighborhood of 500" F. Yields and tests of both the gasolines and lamp oils as determined by the above methods will be found to check refinery figures very closely.
Vol. 18, No, 1
Determination of Lubricating Oils and Asphalt I n order to determine the lubricating oils and asphalt in any crude, the tar residue from the topping operation described above is used as the charging stock for a vacuum distillation. In carrying out this distillation, the apparatus and procedure recommended by Dean, Hill, Smith, and Jacobs2 has been largely followed, and has been found to be very satisfactory. The degree of vacuum was set at 4 cm. Hg absolute pressure, in accordance with their request that this be made standard for vacuum distillation. The receiver used is of the Bruhl type and permits of making approximately 4 per cent cuts of the stock charged, if desired. It is generally true that the tests on an average medium grade of lubricating oil made from any given crude will give an accurate indication of all the grades of lubricating oil which might be made therefrom. If this information is desired, the procedure is to make cuts during the distillation, starting a t a temperature of about 450" to 476" F. at 4 cm. Hg absolute pressure. These cuts are then mixed to make a viscosity of approximately 500 seconds (Saybolt) a t 100" F., which is taken as being average viscosity of a medium heavy grade of lubricating oil stock. This gives the yield of this grade of lubricating oil and sufficient stock for making several tests to determine its quality. The most important of these is.the cold test, which will be found to check refinery results very closely. If different grades of lubricating oil are required, the temperature range of the cuts is varied accordingly, and the desired viscosity obtained by mixing. The vacuum distillation may also be utilized as a means of obtaining asphalt tests on the residue after distillation of the desired lubricating oil. The sulfur content of both the lubricating stock and the asphalt obtained by this method have been found to check refinery results very closely. Outline of Distillation Analysis Method A-Preliminary examination of the oil to be tested: (1) Gravity (2) Per cent sediment and water (3) Any other physical tests (viscosity, flash, etc.) B-Distillation of the crude oil: (1) Oil showing more than 5 to 10 per cent sediment and water, depending on the gravity: (a) Top in small pressure still of any convenient size, using pressures up to 100 pounds per square inch to break the emulsion. Run t o vapor temperature of 500" F. (2) Oil showing less than 5 t o 10 per cent sediment and water: (a) Top a t atmospheric pressure in any convenient flask to 500" F. in the vapor C-Distillation of the naphtha: (1) Motor gasoline content-Navy specifications: (a) Charge 300 to 400 cc. in a standard 500-cc. Hempel distilling flask and distil through a 15cm. (6-inch) jack chain tower by the modified four-point method. Observe per cent over at 200°, 221°, 284", 392", and 420" F. If the per cent over up to 200" F. is 5 per cent or less, multiply the per cent at 221' F. by 5 ; if it is 5.5 to 6 per cent multiply the per cent a t 221' F. by 4.5; if about 6.5 per cent or more, multiply the per cent a t 221' F. by 4. The per cent a t 284' F. is divided by 0.50; that a t 392' by 0.90; and that a t 420' by 1. Cut distillation a t the lowest of these yields. Standard A. S. T. M. condenser. Rate, 5 t o 6 cc. per minute. ( b ) Obtain a standard A. S. T. M. distillation on the above gasoline (c) If this does not come within 3' F. of the specifications for Navy gasoline, re-run to the correct yield ( d ) Obtain desired tests (2) Blending gasoline content: (a) Charge and run as above until per cent over a t 392' F. is observed. Divide this by 0.90 and cut at this indication
January, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
(6) Obtain standard A. S. T. M. distillation on this stock (c) Obtain desired tests (3) Lamp oil content: ( a ) Charge and run as above until the required grade of gasoline has been distilled off. Then continue until a temperature of approximately 10’ F. below the desired final boiling point of the lamp oil is reached, and cut the distillation ( b ) Obtain desired tests D-Distillation of the tar from B : (1) Charge 250 to 400 cc. in a 500-cc. Hempel distillation flask and distil under 4 em. absolute pressure (2) Make 4 per cent cuts in a Briihl receiver, starting with a temperature of 450’ F. in most cases ( a ) Mix these cuts t o obtain any desired viscosity, and make other desired tests (3) Obtain any desired tests on asphalt residue in the flask
It is realized that this outline is quite general in nature, and probably is capable of modification and improvement in many respects, but it has proved very successful in practice thus far, and is believed to be capable of extensire application. Results of Tests on S o u t h e r n California C r u d e Oils Navy Cold test on Gravity spec’n lubricating stock Lamp (Cor. for gasoline (Medium heavyograde) 011 FIELD % S. & W.) Per cent Per cent ’ F. F. 21.7 +4a Long Beach 8.3 +40 22.4 ... 13.9 ... ... 25.3 21.5 7.5 55 60 26.2 25.3 ... ... 28.9 31.0 ... ... Santa F e Springs 30.6 23.2 ... +65 60 32.7 29 4 17.0 ... 33.4 36.7 34.3 38.8 ... ... ... 36.9 40.2 ... 75 80 Inglewood 13.5 0.7 ... 10 15 17.7 8.4 11.1 - 10 15 19.9 11.0 10 15 22.3 14.5 ... 10 + 5 24.5 19.0 ... +45 +40 Huntington Beach 14.5 3.0 - 5 ... 10 - 5 19.1 4.1 ... 10 15.7 - 5 20.7 11.2 10 25.8 25.5 2.1 60 55 25.9 26.5 0 - 5 29.0 29.1 65 70 Dominguez 29.8 28.8 17.1 75 70 30.1 29.2 ... ... 31.7 35.5 ... 75 80 32.3 35.7 ... Torrance 15.0 1.9 0 - 5 11.2 22.1 +25 8.9 20 23.2 25.0 ... +35 +40 23.9 26.4 ... ... ... Rosecrans 36.7 43.2 +so 75 37.2 29.8 ... ... ... 38.6 40.6 41.0 49.1 33.4 75 80 42.1 59.1 Montebello 18.9 1.0 10 15 21.3 1.7 ... +l5 10 23.5 3.9 14.9 +45 +40 26.2 8.4 ... 26.8 7.9 *.. +45 +40 Whittier 17.4 0.8 - 5 10 19.3 3.2 11.6 - 5 - 10 21.1 3.5 ... 23.1 3.8 ... +35 30 Coyote 20.0 1.9 24.5 ... 8.7 60 26.1 14.1 14.9 28.8 27.2 30.7 32.8 ... ... 32.2 ... 36.2 +75 70
...
...
...
...
...
...
+
...
+-
+
+ ++ +
...
... ...
...
...
+..... . -
... ... ...
...
... ...
+. . . ...
+. . . ...
+ -
-
+
+ +... +...
+ +
... +...
+-
...
+... ... ...
+
$4;
... ...
+
Sulfuric Acid Absorption and Iodine Values of Various Petroleum Products and Cracked Distillates Obtained Therefrom-Correction I n our article under this title, THIS J o , ~ A L 17, , 1259 (1925), t h e last line in Table I1 should read (a) . . Cracked distillate. ( 6 ) Charging oil.” I n the graph entitled “Relation between Iodine Numbers and Weight of Samples of Cracked Distillate and Corresponding of Curves 1 and 2 should be Charging Stock,” the designations reversed: JACQUE C. MORRELL GUSTAVECLOPF
67
The Haglund Process for the Electrothermic Production of Pure Aluminium Oxide’ By Ture Robert Haglund RUNEBERGSOATAN 8, STOCKHOLM, SWEDBN
I .
X’ T H E Haglund process the impurities of the bauxite
e., iron oxide, silica, etc.,-are reduced with carbon in an electric furnace, which is run continuously. The most important new feature is that the resulting aluminium oxide slag contains a certain amount, about 15 to 25 per cent, of a sulfide, preferably aluminium sulfide, which at the temperature prevailing in the furnace dissolves the aluminium oxide. Through this agent the melting temperature of the slag is considerably lowered (the melting point of aluminium sulfide is about llOOo C., of aluminium oxide about 2200’ (2,). The sulfide-oxide slag is very fluid and therefore easy to tap, and separates easily and completely from the resulting alloy. As an additional advantage the aluminium oxide in the sulfide-oxide slag crystallizes when the slag is solidifying. The sulfide may be separated from the oxide crystals by a very simple operation. The aluminium sulfide may be manufactured by a separate operation and then charged together with the other raw materials, but it has proved advantageous to arrange the process so that the aluminium sulfide is formed in the process itself. Bauxite, carbon (coke or charcoal), and pyrotite (magnetic pyrite), or some other sulfide of a heavy metal are treated in an electric furnace. Aluminium sulfide is formed according to the following equation: -1.
+ 3C + 3 FeS = Al& + 3CO + 3Fe
It is assumed that aluminium is first reduced as metal and immediately reacts with ferrous sulfide forming aluminium sulfide. Twenty per cent of alumini.um sulfide in the sulfideoxide slag is sufficient for obtaining a pure aluminium oxide. I n addition to the carbon needed for the reduction of the impurities of the bauxite, therefore, enough carbon has to be added for the foregoing reaction, which results in the formation of about 20 per cent aluminium sulfide. Further, enough pyrotite, or other sulfide of a heavy metal, has to be added to transform the reduced aluminium into aluminium sulfide. If the bauxite is high in iron it has proved advantageous to treat it with hydrogen sulfide obtained by the decomposition of the aluminium sulfide-oxide slag. This treatment may be combined with a calcining of the bauxite. Through this sulfurizing of the bauxite the consumption of pyrotite in most cases will be reduced to one-third and the consumption of electric power will be reduced to about 75 per cent. Besides the aluminium sullide oxide slag a rather considerable quantity of pig iron containing all the silicon of the raw material is obtained. This iron separates readily a t the tapping of the furnace from the sulfide-oxide slag. The iron is very low in sulfur because of the high temperature in the furnace and of the greater affinity of the aluminium to sulfur. By regulating the rapidity of the cooling of the slag, crystals of different sizes can be obtained, which is important when manufacturing alumina for abrasive purposes. After cooling, the slag is crushed and treated with water in a suitable apparatus operating continuously. Hereby the slag is decomposed according to the equation: ALSa
+ 6 HpO = 2Al(OH)s + 3HrS
The hydrogen sulfide is carried off and used for sulfurizing the bauxite or for the manufacture of sulfur in a Claus fur1
Received July 29, 1925.
