March 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
complex nature of the corrogion processes and the numerous variations in environmental conditions, reliable results can be obtained only through the skillful adjustment of the various internal and external factors. The alternate immersion corrosion test has its chief advantage in allowing the investigator to set these variables in a relatively simple manner at fixed values, while varying those deemed to be important to the test. For example, with this equipment, oxygenation can be accomplished while the specimen is out of the corrosive medium but still retaining a liquid film on its surface. The velocity of the liquid past the specimen is controlled automatically by the duration of the cycle and the distance of descent of the sample into the solution. The continuous up and down movement of the specimen within or without the solution will avoid the uneven distribution of the corrosive conditions over the specimen. This will minimize localized attack which may not exist in actual service conditions. All parts of the specimen will be immersed almost simultaneously into the corrosive medium during the descending cycle, because the specimen is hanging from the platform in a horizontal position upon its thin edge. Based on the experimental data as listed in Tables I and 11, the reproducibility of results obtained from corrosion test carried out in this new equipment is in the range 1 to 7%. Inasmuch as a 10% accuracy is sufficient in this type of experiment, it appears
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that the results from these tests can be used as a basis for selecting material for construction purposes. The difficult variables are apparently controlled to a point that can match closely the actual conditions in service of the materials that are being considered, Furthermore, this apparatus may be employed advantageously for studying effects of variations in composition or heat treatment of a material. Besides experiments on titanium, corrosion tests on aluminum and stainless steel have been carried out. The results in these tests can be reproduced within the limit of about 5%. For more details about corrosion resistance of titanium, previous publication on this subject (9)should be consulted. Finally, the glass sewing thread used for hanging specimens is found t o be satisfactory to withstand the attack by acids, salts, and alkali solutions of medium strength. This thread consists of three strands containing 300 filaments per strand. It is strong enough to withstand a 60-pound pull. LITERATURE CITED
(1) “A.S.T.M. Standards,” Part I1 (B 192-44T), pp. 804-16, Philadelphia, American Society for Testing Materials, 1949. (2) Ma, C. C., and Peres, E. M., Jr., IND. ENQ.CHEM.,43, 675-9
(1951)
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RECEIVED for review May 19, 1951.
ACCEPTED August 22, 1951
Constant Liquid Feed Device A. H. MAUDE Hooker Electrochemical Co., Niagara Falls,
I
NVESTIGATIOKS on a laboratory scale of vapor phase reactions such as hydrogenation and chlorination, as well as many other reactions, require a controlled flow of liquid in the range of 0.1 t o 10 ml. per minute over lengthy periods of time. A complicating factor in maintaining a steady flow may be changes in back pressure due, for instance, t o changes in a catalyst bed. Many flow control devices have been developed, but all have limitations or defects. The device described here has proved particularly useful and adaptable. Plunger and gear pumps have a large field of utility, but they are particularly susceptible to damage by corrosion, and are consequently undependable for slow rates. Valves on plunger pumps frequently fail t o work satisfactorily if the pump is unduly slowed down. They sometimes become a source of metallic contamination. I n some cases displacement of the reactant b y a nonmiscible inert liquid solves the corrosion problem of the pump but in many cases is not practical. A plunger pump is apt t o deliver in pulsations, but generally can be adjusted for dropwise delivery. Control through a glass stopcock can be improved by filing tapered notches in the face of the plug and also b y extending the handle. But even this method is unsatisfactory for accurate control, owing t o the difficulty of resetting t o give a n identical flow and because a n almost infinitesimal solid speck or maldistribution of the lubricant may completely throw off the calibration. The use of capillary tubes under a controlled head is fairly satisfactory. The tube should be in a thermostatic bath such as an ice bath, as even slight changes in viscosity cause a dominating change in flow. The flow is very subject t o variation b y any trace of solid matter. Some adjustment is attainable by control of pressure, but t o change the flow substantially the tube needs t o be changed, which is a time-consuming and bothersome operation. Preparation of interchangeable tubes giving different desired flows is also not easy.
N. Y .
Devices based on displacement by a controlled flow of gas are subject t o changes in pressure and temperature. Displacement by a plunger device through a packing gland by means of a screw and gears is very satisfactory for some purposes, but cumbersome, and may lead t o metallic contamination. The device described is really a modification of that of Michaeli (1). T h e aim in making the modifications was t o simplify construction and add flexibility. T h e greater range of flows and accuracy in calibration was made possible by lengthening the controlling element, which is located in a more convenient position than in his apparatus. A thermostatic bath was added t o permit day and night operation under conditions of varying atmospheric temperature. An incidental advantage was observed in having an upward flow through the controlling element, in t h a t minute amounts of solid would settle before reaching it. I n Figure 1, A is a graduated t a p funnel. The glass rod or sealed glass tube or wire, E, makes a plunger which fits into D and can be slid u p and down in it so as t o permit exactly the required flow through t h e annulus Letween them. At F a combination of rubber tubes is used t o make a tight seal on both D and E but permit E t o be moved. Cylinder B standing in an overflow cu forms a thermostatic bath, holding ice water, for example. is a capillary tube about 1-mm. bore, forming a pressure equalizer and holding head h constant irrmpective of minor changes in back pressure and liquid level. If a tube of lar er diameter is used, an oscillating flow develops under some confitions. The flow can be observed and drops counted in the adapter! I , which feeds into the reactor. Usually the liquid has t o vaponze on entering the reactor and condensate is apt to reflux in this adapter. Some gas must be fed through H t o prevent this. Usually the gas is a reactant; if there is no aseous reactant a few bubbles a minute of nitrogen can be fed in. &are must be taken that no air is trapped in the tubing under E and that stopcock J is open when this plunger is manipulated, thus avoiding sucking in gas. An almost infinite ran e of flow rates is attainable by selecting suitable sizes for D a n f E . T h e effective head, h, is suitabIy about 3 inches. If it is much
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INDUSTRIAL AND ENGINEERING CHEMISTRY
v Figure 1. Apparatus
smaller, such incidents as having the equipment slightly out of vertical may have undue effect. Tube E should be marked so that no rotation between it and D need occur when making adjustments. Obviously these tubes are not truly concentric when ordinary glass tubing is used, and they are not truly straight. Any rotation should not change the cross-sectional rLrea of the
Vol. 44, No. 3
annulus but may change the shape of annulus a t some sections and thus change the flow. If a rubber band is placed around the upper portion of A and E, the lower end of the plunger is forced a t all times into contact with the wall of D remote from A and ensures identical positioning at all times, thus eliminating a possible source of inaccuracy. To make adjustments the gosition of the plunger may be measured and depressed or raised y a known amount and a calibration curve prepared. T h e control is rendered inaccurate if the annulus is made very short, say less than an inch. When a soluble gas such as chlorine is to be fed into the system with the liquid, it cannot be used for pressure equalization and a very slow feed of nitrogen can be supplied at K through a bubble bottle in sufficient quantity to bubble out from G as needed t o displace the liquid; any excess passes out through the constriction. R. I n this case it is inevitable that a t least a trace of the nitrogen enters the reactor. The stopcock L is provided t o permit calibration without dieconnecting the apparatus. To recharge A with minimum interruption t o t h e flow it is provided with certain attachments which are operated in this way: Stopcocks A l , N , and P are opened, t h e liquid is run in, A 1 is closed, the rubber bulb, Q is com ressed, P is closed, the bulb is released, drawing gas in througi G and establishing the required pressure, and N is then closed. These attachments obviously are not absolutely necessary but are advantageous. The accuracy of this instrument is mainly dependent on thorough cleanliness and good temperature control. I n some instances it is desirable to use a spiral down-flow arm on U-tube 11 to provide more complete temperature equalization. illternatively, the temperature of the liquid in funnel A can be maintained a t a fairly uniform temperature. LITERATURE CITED
(I) Nichaeli, I., Chomistrg & Induatrg, 1951, 126. RECEIVED f o r review J u n e 28, 1961.
~ C C E P T E DOctober
10, 1951
Hydrogenation of Shale Oil W. M. SMITH AND T. C. LANDRUM
G. E. PHILLIPS
Esso Laboratories, Baton Rouge, La.
Esso Laboratories, Elizabeth, N. J .
1J VIEW of the possible shortage of crude petroleum in the future, attention has been turned to the development of processes for the production of crude oils from other natural resources such as natural gas, coal, tar sands, and oil shale. It is with the latter raw material that this paper is concerned. The production of oil from shale is not a new concept (1, 5 , 6) but an established industry in various sections of the viorld which contain extensive oil shale deposits and are deficient in crude petroleum. In these locations, the comparatively high costs of mining, extracting, and refining shale oil do not prevent its use in competition with petroleum. I n this country, although shale oil is not now- competitive with petroleum, it may become so in the future. I n order t o provide a background of information on oil shale processing against this time, the Bureau of h!tines has set up a demonstration mine on a Xavy shale reserve in Colorado in order t o determine how shale can best be brought out into the open. The Bureau of Mines and private companies have studied the preparation of a crude shale oil from the mined shale and the preparation of salable refined products from the crude shale oil. The present paper describes one initial method of attack upon the latter phase of the oil shale problem-preparation of salable refined products from crude shale oil. Organic matter in oil shale is believed t o exist in t h e form of “kerogen,” a solid consisting of hydrocarbons in combination
with sulfur, nitrogen, and oxygen (6). In this, it differs fiorn crude petroleum, which exists as such in the pores of porous oil sands. Crude shale oil produced from the oil shale by decomposition of the kerogen by means of heat also differs from crude petroleum, in that it is highly unsaturated and has an extremely high content of nitrogen compounds. The presence of these nitrogen compounds in shale oil is believed to be responsible for the poor color stability and disagreeable odor of the products derived from it. It is this property of crude shale oil which makes necessary additional treating xhen shale oil is refined by conventional petroleum refining procedures. Established procedures for shale oil refining generally involve a combination of cracking plus distillation for separation into the various boiling range products and treatment of these products with sulfuric acid for removal of nitrogen compounds (1, 6). Such chemical refining treatment for improvement i n color btability and odor must of necessity be very carefully controlled in order t o prevent excessive losses of valuable reactive unsaturated hydrocarbons which occur in the shale oil by reason of the method of its preparation (destructive distillation of kerogen). I n an attempt t o minimize treating losses and thereby preserve volume, hydrogenation of the total crude shale oil was investigated. Recently published work by the Bureau of Mines (4)describes one manner of applying hydrogenation to the refining of shale oil.
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