Octobe~l9so
INDUSTRIAL AND ENGINEERING CHEMISTRY
and increases the deasphalted gas oil yield above the critical settler temperature. Increasin the avera e molecular weight of the solvent increases gas yield on reduced crude and, conversely, the deaspht!ted deoreasin the average molecular weight of the solvent decreases the deaa %altedgas oil yield. The dnradson carbon residue of deasphalted &asoil produced on average crude is decreased with increasing ylelds of aa halt and/or increasing propane to oil ratios when propane deasptaltin is conducted iihorizontal settlers. %he sulfur content in deasphalted gas oil is dependent upon the oulfur content in reduced crude and the per cent yield of asphalt produced in horizontal settlers. The penetration of asphalt produced from average Gulf Coastal reduced crude ap ars to be dependent u p p the calculated r cent carbon resige in asphalt and efficiency of separation o g h e asphalt and deasphalted gas dl phases.
oi
4
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and to recognize the cooperation of Carl W. Kraemer and Cecil Hutchinson of the Operating Department. The authors gratefully acknowledge the indispensable assistance of Charles E Smith, Jr., and Elmer N. Coulter in preparing the graphs. LITERATURE CITED
(1) Am. boo. Teeting Materiale Committee, “A.S.T.M. Standards on Petroleum Products and Lubrioanta,” Philadelphia, 1948. (2) Bray, Ulrio B., and Bahlke, W. H., in “The Science of Petroleum,”
by Dunstan, A. E.,Nash, A. W., Tizard, Henry, and Brooke, B. T.,Vol. 111, pp. 1966-71, London, Oxford University Prees, 1938.
(3) (4)
Kraemer, C. W., Oil Om J., 44, No. 47,228-33 (1946). Thompson, F. E. A., in “The Science of Petroleum,” by Dunrttan, A. E., Nash, A. W., Tizrtrd, Henry, and Brooks, B. T.. Vol. 111, p. 1853, London, Oxford University Press, 1938.
ACKNOWLEDGMENT
The authors wish to expreas their appreciation to the Cities Service Refining Corporation for permission to publish this paper
RECBIVBDDeoember 22, 1949. Presented et the Fifth Southweat Redo& Meeting of the A M B R I QCHBMIOAL ~ SOOIBTY, Oklahoma Ciay, Okla Deoember 8 t o 10, 1949.
Purification of Argon M. W. MALLETT Battelle Memorial Znatituw, Columbus, Ohio
A method of purifying argon in quantities permitting a flow rate of 15 liters or less per hour is described. The.oxygen and nitrogen impurities of commercial grade argon are gettered by titanium at 850’ C. Tests showed the. treated argon to be sufficiently free of active gases to prevent tarnishing of highly reactive heated uranium.
I
NERT atmospheres must be used during fabrication and heat
treatment of various metals, in particular titanium and airconium and their alloys. Argon is commonly used for this purpose. However, the commercial grades are of doubtful and varying purity (99.7 to 99.9%); the principal contaminant is nitrogen, plus about 0.001% hydrogen and 0.001% oxygen. Newton (I) haa pointed out that uranium metal is an exclellent scavenger for chemically active gages. Since uranium is a v d able in rather limited quantities, a more readily obtainable material was sought.
short aa possible. From the drying tower, the gas passes into a fused silica tube about 1 inch in diameter, whose central portion is filled with titanium powder (-20 60 mesh) for a length of about 10 inches. The powder is hcld in place by wads (0.5 inch long) of steel wool which are compressed somewhat 80 the powder will not run through them. Such a charge will contain about 160 grams of titanium powder. The flow r a t e and C+ pacities given here are based on a tube of these dimensions. For smaller charges, the flow rates and capacities will be proportionJly lower. Titanium, aa purchased, almost invariably has a high hydrogen content which must be removed by heating a t 850’ C in a vacuum for several hours. If hydrogen is not objectionable, the titanium can be used, as received, to remove oxygen and nitrogen. The titanium reaction chamber is heated at 850’ C. by a resistance-wound furnace when in use. Although there is mme evidence that a much faater flow rate is permissible, best resulb will be obtained with a rate of 15 liters or less of argon per hour. The titanium charge described will be enough to purify one third
+
PURIFICATION METHOD
Nearly all the commonly accepted gettering materials such as calcium and magnesium metals, barium-aluminum, bariummagnesium, and magnesium-lithium alloys were tested. Argon waa pasaed through a bed of the getter a t various flow rates. The temperature of the getter was varied, However, the treated argon invariably caused tarnishing, in 1 hour, of a polished test strip of uranium heated at 600’ C. Finally, titanium-metal powder waa found to purify the argon to the extent that the test strip showed no tarnish in 1.5 hours a t 600’ C. 3ecause the chemical properties of titanium and zirconium are similar, airconium should be equally satisfactory. However, titanium is to be preferred because it is more readily available, and, on a weight basis, it has twice the capacity of zirconium. A purification train capable of servicing a tight system, not exceeding about 5 liters in free volume, is shown in Figure 1. The argon cylinder is connected to a safety bubbler containing concentrated sulfuric acid or mineral oil. This seal relieves train pressures over 1 atmosphere. Next, the gas is passed through a drying tower containing anhydroua magnesium perchlorate. Rubber tubing connections should be aa few and as
ANHYDROUS MAGNESIUM pcAw4RAT€ RADIATION B M L E
y,
4 c e S q OR MINERAL OIL FLOW
RATE: IS LITERS PER
W R MAXIMUM
Figure 1. Train for Purifying Argon
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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of an ordinary cylinder of argon. After each day's use, the titanium should be removed from the tube and crushed to eliminate sintering effects. This also permits visual inspection of the condition of the titanium. The amount of oxide and nitride appearing on the surface of particles is often a better indication of the condition of the titanium getter than the amount of gas that has passed over it. If crushing does not produce a majority of clean metallic surfaces, the charge should be replaced. A higher operating temperature speeds up the reaction but, also, increases the rate of sintering, thus reducing the surface area available for gettering. If the titanium is in the form of lathe turnings, which do not pack so tightly, sintering is of less consequence and temperatures of 1000° to 1100' C. can be used to advantage. I t is evident that, since titanium is reactive with oxygen and nitrogen, it should never be exposed to air while hot. It is good practice to flush both the purification train and the working system with argon before heating the getter tube. Usually it will be desirable to have a second (duplicate) titanium tube and furnace to follow the first tube and to be operated in the same manner. This will serve as a safety factor, and when the titanium of the first tube is exhausted and discarded, the titanium from the second unit can be moved to the first position and a new batch of titanium placed in the second tube. Titanium metal used in this investigation was in the form of sintered granules derived from the hydride. Present cost is about $10 per pound. Approximately 1 pound is required per cylinder (220 cubic feet) of 99.7% argon. Titanium granules may be broken up in an iron mortar. Powder finer than 100 mesh tends to be pyrophoric and should be avoided. It also packs too tightly and slows the gas flow. Titanium reacts but slowly after 30 to 40 ml. of oxygen and/or nitrogen are absorbed per gram of titanium. It should then be discarded. The less costly titanium produced by magnesium or calcium reduction is equally satisfactory providing it is relatively free of
Vol. 42, No. 10
impurities such as oxides and chlorides. Oxides tend to inhibit gettering, and chlorides vaporize and contaminate the gae stream. In general, it is more difficult to crush into small sized particles the magnesium-reduced titanium than the more friable product of the hydride process. However, in laboratories where scrap lathe turnings or shaper chips of titanium are available, this presents no problem. The above recommendations were made from calculations based on argon containing 0.3% impurities present as oxygen and nitrogen. Carbon monoxide and carbon dioxide will also be removed. Water vapor and hydrocarbons tend to react with the titanium and release hydrogen, the only active gaa likely to remain unabsorbed in the purification train. In the usual case, however, only the original 0.001% hydrogen will remain in the purified product. In the majority of applications this low residual impurity can be tolerated. Nitrogen and oxygen can also be removed from helium by this method. In some setups, the purification method may be modified to advantage. If the work chamber is vacuum tight and no large amount of gas is likely to be released by the experimental material, then the getter may be placed in a closely connected side arm or hung in a perforated metal container in the work chamber itself. After thorough flushing and filling of the chamber with argon, the titanium is heated to 850' C. by high-frequency induction or by a resistance-wound furnace. Thie will purify the stagnant argon atmosphere. If chemically reactive gas is given off by the material being processed, heating of the titanium should be continued. If no gm is generated, the heating may be stopped after about 30 minutes. LITERATURE CITED
(1) Newton, A. 1947).
S.,Atomic Energy Commission, MDDC-724 (Jan. I.
RECEIVED March 14, 1950. This paper is based on work aponsored by tha O5ce of Naval Reaearch under Contract No. N5-ORI-Ill Teak Order 111.
Stvrenation of Fatty Acids J
J
P. 0. POWERS Battelle Memorial Institute, Columbus, Ohio
A study has been made of the products obtained by refluxing styrene with oleic, dehydrated castor, and linseed oil acids at 160' C., and by adding an equal weight of styrene to these acids at 225O, 250°, and 275' C. Separation of the reaction product has yielded no polystyrene and no uncombined acids. Rather a series of fatty acids, containing from 1 to 25 styrene segments per molecule, has been found to be present. No great difference in the type product was found from a fractionation of the acids, but the styrenated fatty acids formed at high temperatures appear to be considerably more soluble than those made at low temperatures. Oleic acid has been found to conibine with styrene under these conditions. Results obtained are consistent with the behavior of styrenated oils.
T
H E term styrenation has recently been used ( 4 ) to describe the addition of styrene to unsaturated compounds, particuIarly addition to the drying oils. This field has recently received considerable attention, and numerous styrenated oils and alkyds, which possess many valuable characteristics (1,S),are available commercially. Recent work (9,6, 7 ) has shown clearly that styrene combines readily with the drying oils but that conditions employed and
the type oil used must be carefully controlled if clear and homogeneous products are to be obtained. I t is imposeible to form clear copolymers with linseed oil when appreciable amounts of styrene are used, unless the oil has been oxidized. The use of mixtures of styrene and a-methylstyrene results in more compatible systems. Because attempts to saponify styrenated oila have not always led to a quantitative measure of the location of the added styrene and the glyceride structure results in much more complex addition products, this study was made of the addition of styrene to the fatty acids. It was decided to include oleic acid, since it apparently has not been established whether this acid undergoes styrenation. Linseed acids were included as representative of nonconjugated acids and dehydrated castor acids a8 representative of unsaturated acids containing conjugated acids. Reactions were run at 160' C. under reflux and also by adding the styrene dropwise to the acids a t 225', 250°, and 275' C. It was felt that, a t the higher temperatures, more soluble addition products might be obtained. EXPERIMENTAL WORK
Oleic acid was obtained from Baker and Adamson and linseed acids and dehydrated castor acids were obtained from Woburn Chemical Company. The distilled acids were used. Styrene
