I X D USTRIAL AA'D ENGINEERING CHEMISTRY
April, 19%
365
Ferrous Selenide as a Contact Catalyst for Cracking' By Thomas Midgley, Jr., and C. A. Hochwalt GENERAL MOTORS RESEARCH CORP.,DAYTON, OHIO
OM13 of the materials which have been cited as catalysts for the cracking of petroleum oils contain one or mope elements that are known to exert a decided inh e n c e on the character of the combustion of gases.2 Thus, one of the best known of these substances, aluminium chloride,3 contains chlorine, which as an element and in some of its compounds induces detonation in gaseous combustion. I n a similar way, oil-soluble nitro compounds4 contain two elements that under certain conditions have a marked influence upon combustion. Nitrogen-oxygen compounds, such as nitrates and nitrites, have a decided effect in inducing detonation. On the other hand, nitrogen in the form of amines is a suppressor of detonation. In view of this fact, it was decided to test the effect on cracking of some compound of an element that is known to exert a rdatively large influence upon the character of combustion. Selenium was selected for this purpose on account of its marked ability to suppress gaseous detonation. The compound of selenium used was ferrous selenide.
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PREPARATION OF FERROUS SELENIDE Iron filings and selenium in atomic proportions were placed in an iron crucible and thoroughly fused together in an induction furnace. After cooling, the fused mass was ground out of the crucible by means of a sharp, flat drill. The finely divided ferrous selenide so obtained was stirred with kerosene to form a thin paste, which was then spread on pumice stone of about 1.3 to 2 em. size. The catalyst prepared in this may was placed in a steel tube wound with resistance wire for heating. The tube was well insulated, and the winding was so arranged that the temperature of the furnace could be controlled within reasonable limits. The temperature was determined by means of a potentiometer connected with thermocouples embedded in the wall of the furnace tube.
METHOD OF CONDUCTIXG CRACKING TESTS The furnace, charged with the catalyst as described above, was mounted vertically, and kerosene having the physical properties given in the second column of Table I was dripped 1
2
8 4
Received November 23, 1923. Midgley and Boyd, THIS JOURNAL, 14, 894 (1922). McAfee, U. S. Patent 1,127,466. House, British Patent 14,671 (June 25, 1907).
Original Kerosene Color ............................... Light yellow Odor. Sweet Cold HzSOp absorption, per cent.. 4 Temperature of dissolution with aniline, C. 60 3 Nitratahle material, per c e n t . . . . . . . . . . . . 2 tg 3 (?)
................................ ....... ...............................
Per cent Distilled F. I). 10
20 30 40 50 60 70 80 90 95 D. P. Per cent distilling below 200' C.
187 198 205 210 213 218 222 227 234 244 258 273 12 ~~
into the tube from a separatory funnel a t the rate of 3 to 4 drops per second. The temperature of the tube was maintained a t 500" C. throughout all the tests. The vapors issuing from the lower end of the cracking tube were passed through a condenser cooled by an ice bath.
EXAMINATIOX OF THE VARIOUS OILS The kerosene charged to the cracking furnace and the product obtained in each run were examined for solubility in cold sulfuric acid, temperature of dissolution with aniline, percentage content of nitratable material, and distillation range. The color and odor were also noted in each case. Comparison of the distillation range, the temperature of dissolution with aniline, and the percentage of nitratable material of a cracked oil with similar characteristics of the original kerosene gives some measure of the degree to which the oil has been cracked. For the purposes of this investigation the oil coming over below 200" C. was considered as the gasoline fraction. The temperature of dissolution of paraffi hydrocarbons with aniline is about 70" C. Aromatic hydrocarbons are miscible with aniline in all proportions, and ethylenic and naphthene hydrocarbons have a temperature of dissolution with aniline much below 70 C.6 Therefore, the temperature of dissolution with aniline taken together with the percentage of nitratable material serves as a means of denoting the degree of conversion of the paraffin hydrocarbons present in the original kerosene into unsaturated and aromatic bodies. The sulfuric acid absorption was obtained by determining the reduction in volume of the oil on shaking with an equal volume of cold sulfuric acid (1.84). The temperature of dissolution with aniline was obtained by determining the temperature at which a solution of equal parts of the oil and aniline separated as a sample was slowly cooled, the separation being indicated by the sudden appearance of a distinct and almost opaque cloudiness. This measurement was made in each case without previous removal of unsaturated and aromatic bodies from the oil. The distillation range was determined by distilling a 100-cc. sample in the standard apparatus for distilling gasoline as given in Bulletin 5 of the Committee on Standardization of Petroleum Specifications as published by the United States Bureau of Mines.6 O
6 6
Conzpt. r e d . , 168, 1111 (1919). Automotive Industries, 765 (1921).
TABLEI Kerosene Run over Pumice without Catalyst a t a Temperature of 600' C. Run 1 Run 2 Dark brown Dark brown Cracked Cracked 18 22 b4
52
15 18 Dislillation Temperatures, 140 180 195 203 209 215 220 226 234 248 269 264 25
Kerosene Run over FeSe at a Temperature of 580' C. Run 1 Run 2 Ydlow Yellow Cracked Cracked 28 28
24
45.2 42.5
46 44
Kerosene Run over FeCls at a Temperature of 500° C. Run 1 Run 2 Brown Brown HCI HC1 22 21 56.8 17
53 18
C.
41
70 135 170 190 201 210 216 223 233 242 257 272 39
94 180
193
204 210 217 222 227 235 249 270 275 27
70 154 184 197 207 212 218 224 234 247 268 272 32
c
Vol. 16, KO.4
INDUSTRIAL A X D ENGIiVEERI,2TG CHEMISTRY
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As a method of determining the amount of nitratable material in each oil, a 200-cc. sample was placed in a 0.5liter round-bottom flask. The sample was previously washed with concentrated sulfuric acid in order to remove unsaturated bodies. The flask and contents were thoroughly cooled, 50 cc. of nitrating mixture were added, and the kerosene and acid were well shaken with intermittent cooling. The nitrating mixture was composed of 150 grams sulfuric acid (1.84) and 100 grams of nitric acid (1.42). The acid layer was separated and the nitrating operation repeated three times, after which the remaining oil was thoroughly washed, first with sulfuric acid and then with water. The difference between the volumes before and after nitration was taken as a measure of the nitratable material. It is recognized, of course, that this value is somewhat high on account of unavoidable losses during nitration.
RESULTS A tabulation of characteristic data obtained in this investigation is given in Table I. It will be observed that when ferrous selenide was used as a catalyst the oil obtained showed a noticeably higher absorption in sulfuric acid and a marked increase in percentage of nitratable material. A decided increase in percentage of oil distilling below 200" C. was also obtained with ferrous selenide as catalyst. Another observation was that the cracked oil obtained when ferrous selenide was employed was yellow in color, whereas in the other case the color of the oil collecting in the receivers varied from brown to almost black. I n view of the data obtained in this investigation, ferrous selenide apparently has a decided catalytic effect on the cracking of petroleum oils, particularly with regard to the formation of nitratable material.
Determination of Silicon in Iron-Silicon Alloys by Their Physical Properties' By T. D. Yensen WESTIXGHOUSE E L E C T R I C & MANUFACTURING CO.,EASTPITTSBURGH, PA.
'HILE the determination of silicon in iron and steel by ordinary chemical analysis is a comparatively simple matter, its determination in lowcarbon alloys by certain physical tests is sometimes sufficiently accurate and is simpler and niuch less expensive than the chemical analysis. In the course of an investigation of the magnetic properties of iron-silicon alloys,2 the writer and co-workers have found two physical characteristics of these alloys that are readily determined, are simple functions of the silicon content, and a t the same time are not sensitive to variations in the heat treatment. These characteristics are (1) the electrical
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Received January 18, 1924. Paper presented a t t h e Midwinter Convention of American Institute of Electrical Engineers, Philadelphia, Pa., February, 1924.
resistance, and ( 2 ) the hardness. Sometimes one of these can be used%o advantage and sometimes the other. The relationship between silicon and electrical resistance is shown in Fig. 1. This curve, being composed of two straight lines with a bend a t Si = 0.36 per cent, can be expressed algebraically by the equations : For Si 5 0.35 p = 9.6 18.4 X Si p = 16.05 11.1 (Si - 0.35) For 0.35 5 Si 5 6.5 or
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For p d 16.05 Si = 0.0644 (p - 9.6) Si = 0.35 0.09 (p - 12.14) For 16.05 5 p 5 85 where Si = silicon content, in per cent p = electrical resistance a t 20 O C., in microhrns per cc.
+
1
9
-86 /00 FIG.1
1 . 2 ' 0
I 4 0 160 /BO 200 220 240 260 280 300 320 340 Hardness Number- % -kq per sqmm.
FIG. 2
