INDUSTRIAL AND ENGINEERING CHEMISTRY
1544
lines, since its octane blending value is 2-3 units higher than that of the aviation cut. On the other hand, this solvent fraction may also be employed as solvent naphtha of very high solvent power. Furthermore, cracking of this SOcalled solvent fraction results in lower boiling aromatics which may be used in the aviation cut. The properties of this solvent fraction are as follows: A. P. I. gravity Boiling range O F. Kauri-butandl No. Aniline point, O C. Color
(O
C)
31.5 300-424 (149-218) 81.8 - 38 Water-white t o very light yellow
This solvent material consists chiefly of propyl-, butyl-, and amylbenzenes. The total amount of unsaturates does not exceed 5 per cent by volume.
Reforming Cracked Gasolines with Benzene Destructive high-temperature alkylation of benzene with high-molecular-weight olefins found in cracked gasolines may also be performed. As a result the octane number and chemical stability of alkylated or reformed gasolines are considerably increased, owing to the formation of stable and high-octane alkyl benzenes. From 10 to 30 per cent of benzene by volume may be used for the alkylation under previously mentioned conditions-i. e., at temperatures around 850-950" F. and a t elevated pressures. The presence of activated clay is also beneficial to this process. The yield of reformed gasoline in the original boiling range is about 76 per cent by volume. Table V gives the results of alkylation of benzene with the olefins contained in two cracked gasolines.
Vol. 33, No. 12
The data of Table V show that cracked gasolines reformed with benzene by alkylation have improved octane numbers and stability. The response to tetraethyllead, however, is relatively poor, The chemical effect, furthermore, of reforming by alkylation is clearly shown by comparison of the chemical composition (in per cent by volume) of vapor-phasecracked gasoline before and after alkylation with 30 per cent benzene. Type of Compound Unsaturates Aromatics Nepht henes Paraffins
Cracked Gasoline 54 11 25 10
After Addition of 30% Benzene 3s
38 17 7
Same after Alkylation 11 58 26 5
Solvent cuts produced from cracked gasolines by alkylation of benzene and boiling between 160' and 210" C. have a very high Kauri-butanol number (83-85).
Acknowledgment We are indebted to J. B. Rather, in charge of General Laboratories, The Socony-Vacuum Oil Company, Inc., for permission t o publish this work, and to C. H. Schlesman, research director, for his helpful suggestions. We wish to acknowledge the able assistance of S. B. Davis in performing some of the experiments connected with this work.
Literature Cited (1) Blunck and Carmody, Baltimore Meeting, Am. Chem. Soc.,
April, 1939. (2) Francis, A. W., IND. EXQ.CHEM.,18, 821 (1926). (3) Frey and Hepp, Ibid., 28, 1439 (1936). (4) I. G . Farbenindustrie, Brit. Patent 316,951 (1928); 323,100 and
. ~ . ~
327.282 (1929). \ ,
TABLE V.
RESULTSOF REFORMING CRACKED GASOLINES BY ALEVLATION
A. P. I. Gravity Compn. of Gasoline Liquid-phase cracked 57.7 Same 3007 hrnaene (before alkylation) 48.1 Same 3 0 d bencene (aftcr alkylation) 41.4 Vapor-phase cracked 46.8 Same 80% benaene (beforealkylatlon) 41.8 Same 3 0 7 beniene (after alkylation) 37.3 Same 1 5 % benzene (before alkylation) 44.7 Same 15% bensene (after alkylation) 41.8 B y the Motor method.
+ + + + + +
Octane N0.a With 3 cc. T. E. L. 78.0 82.6 80.7 84.0 86.4 90.0 85.0 90.6
Clear 66.6 72.0 81.6 78.5 81.0 84.0 79.5 81.9
Acid Heat,
F.
> 100
> 100 32 1100
>loo 32 > 100
Ipatieff, "Catalytic Reactions at High Pressures and Tempeiatures", p. 653, New York, Macmillan Co., 1936. Ipatieff and Komarewsky, U. S. Patent 2,098,045 (1937). , Keith and Ward, Oil Gas J . , Nov. 28, 1935. (8) Oberfell and Frey, Ibid., Nov. 23 and 30, 1939. (9) Sachanen. "Conversion of Petroleum", pp. 28, 8 0 , New York. Reinhold Pub. Corp., 1940. (10) Ibid., p. 40. (11) Sch6llkopf, U. 5. Patent 2,115,884 (1938). (12) Waterman, Leendertee, and Makkink, J . I n s t . Petroleum Tech., 22, 333 (1936). ~
30
Q
PREBP~NTED before the Division of Petroleum Chemistry a t the 102nd Meeting of the American Chemical Society, Atlantic City, N. J.
Drying Heat-Sensitive Substances A Modified Flash-Drying System W. C. RONGSTED, J. B. GOTTFRIED, AND L. c. SWALLEN Corn Products Refining Company, Argo, Ill.
T
HIS paper describes a process for drying substances
which are sensitive to heat, and have fusion or solubility characteristics such that an unworkable mass of dough or liquid is formed if the wet material is warmed appreciably. It applies to cases where material being dried would undergo more or less fusion or be dissolved in residual solvents a t only a slightly elevated temperature. Particular application of this drying system has been made to the preparation of zein. The process for preparing eein
was described by one of the authors (2). This paper gives more details of the drying system and particularly points out the innovations required by the peculiar physical characteristics of zein. Zein is insoluble in water and is precipitated from alcoholic solution when the latter is mixed with wat,er. The doughy character of the zein when first precipitated is lost as soon 8 s sufficient contact has been maintained with cold water to ensure removal of the solvent. However, if the precipitated zein is heated slightly, its plastic and adhesive properties become evident. A temperature of 15" C. (59" F.) is the maximum which can be permitted without a noticeable softening effect, although slightly higher temperatures cause no great difficulty if the factors of time and mechanical action are
December, 1941
IN D U S T R I A L A N D E'N G I N E E R I N G C N E M I S T R Y
minimized. The temperatures attained in any of the usual drying conditions are entirely unacceptable; for example, laboratory samples of zein are dried in a refrigerator without external application of heat to ensure the absence of particles of fused zein. I n the early work on the zein process, a spray-drying system was used. The filtered product was dispersed t o form a suspension containing 20 to 22 per cent solids, which was then sprayed into a stream of hot air. For the most part the zein was dried in a satisfactory manner. However, it was impossible to prevent some of the particles from hitting the walls of the drying chamber before they had lost their adhesive character and thus causing the loss of a portion of the product as a deposit on the walls of the chamber. The spray-drying system was therefore not acceptable. The difficulties may have been due largely to design but may also have been largely fundamental. The Raymond flash-drying system combines drying and grinding into a single operation. I n this process a hot air stream is passed through an impact mill into which is fed the material being dried. If the original moisture content of the material is so great as to interfere with proper grinding or drying, the wet substance is mixed with sufficient dried product t o give satisfactory handling, grinding, and drying properties. It is fundamental that the moisture content be not too great to enable complete removal in one pass through the dryer. In its original form the Raymond flash-drying system is entirely unsuitable for use with zein. The filter cake is too wet to dry in a single step without adhering to various parts of the mill. If the wet zein filter cake is mked directly with the dry product, the residual heat, although not great, is sufficient to fuse the entire mass into balls of dough which cannot be redispersed. I n the processdescribed in this paper the difficulties mentioned above are overcomeby cooling the dried product with refrigerated air before returning it to the system. I n the flash-drying system, particles having surface moisture cannot be raised in temperature above the dew point of the surrounding air. However, a particle free from surface moisture will attain a somewhat higher temperature. I n the case of zein the original particle has a spongy structure which must be preserved in order to ensure proper absorption of water from the wet filter cake entering the drying system and, of greater importance, to ensure ready solubility of the dried product. Fusion is prevented for the most part by supplying the main drying system with a small deficiency of hot air so that a slightly damp product is obtained and the air is reduced in temperature almost to its dew point. A secondary drying system without recirculation completes the drying of that portion of the product not returning to the primary drying system. Details of the process are illustrated in Figure 1. Zein is obtained by extracting gluten meal with 85 per cent isopropyl alcohol, clarifying the extract, concentrating, and extracting the oil with hexane. The zein, ready for the precipitation step, is in the form of a solution having the consistency of a thick sirup and containing about 20 per cent protein. This solution is sprayed into a rapidly moving body of water (1) and is precipitated in a somewhat fibrous form. The precipitated zein is removed from the precipitating tank by flotation and, after a thorough mixing with water, is filtered on a string type filter.
1545
SYSTEM FIGURE1. FLOWSHEETOF ZEIN DRYINQ
Instead of being discharged in the customary manner, the filter cake passes over a metal plate about 4 inches wide, which is in the same plane as the strings approaching the discharge roll, and into the path of a rotating brush. The plate supports the filter cake so that it will not be broken before meeting the brush. This brush may be either of fiber or metal wire construction. The dimensions of the brush and its speed of rotation must be such that the proper degree of disintegration is obtained, and that the brush cleans itself by centrifugal action. The rapidly rotating brush causes the wet zein cake containing 70 to 75 per cent moisture to be broken up into a 6nely disintegrated form. This wet disintegrated zein is directed into a mixer by a jacket surrounding the brush. This close-fitting cylindrical jacket has an opening of such size and position that all particles thrown through it by the brush are directed into the mixer and not permitted to strike any parts of equipment where a massive layer might be built up. The jacket forces all particles not so directed to follow the brush through the next revolution. Into the mixer of the helical screw conveyor type is added partially dried and cooled product having a moisture content of 15 per cent and a temperature not above 60" F. This is fed in through a feeder a t such a rate that the feed return, on a dry substance basis, is about four times that of the filter cake. The mixer is so arranged that the material remains in it for an average time of about 12 minutes. This is sufficient to distribute the moisture in the cake evenly throughout the mass of entering material. The resulting mixture has a moisture content of approximately 35 per cent. It is essential that the temperature of the entering material and of the equipment be such that the moist zein is not subjected to temperatures higher than 60" F. before it reaches the drying chamber. The 35 per cent moisture material drops from the mixer directly into a hammer mill, the screen of which has '/$-inch
1546
INDUSTRIAL AND ENGINEERING CHEMISTRY
perforations. This mill is not intended actually to grind the product but simply to disperse the particles fed to it from the mixer so that no clusters of particles will enter the air stream. The zein passing the mill is sucked into a stream of air heated to 330" F., and passes through a drying chamber 32 feet high a t a velocity of 3500 to 6000 feet per minute. The air containing the zein is discharged directly into a cyclone. The temperature of the drying air is reduced to about 120" F. and the zein leaving the cyclone has a moisture content of 15 per cent. The zein leaving the cyclone enters an air stream having a velocity of 3500 feet per minute and is cooled to 40" F. It is not found advisable to use any type of mechanical seal between these air systems, and excessive interchange of air is prevented simply by proper balancing of the air pressure a t the point of transfer. The amount of air in this cooling system is sufficient to reduce the temperature of the zein to a
Vol. 33, No. 12
point below 60" F., after which it is collected in a cyclone. The cooled product is divided into two portions; one returns to the mixer as previously described, the other passes into a secondary drying system where it is in contact with air heated t o 225' F. and where the moisture content is reduced to approximately 6 per cent. The product from the secondary drying system is screened through a 60-mesh screen and passes to the storage bin. Since the tailings from this system have been subjected to somewhat unfavorable temperature conditions in the moist state, they are not particularly suitable for returning to the system and must find use where their particle size does not interfere.
Literature Cited (1) Horesi, A. C.,Flint, A. H., and Swallen,
L. C., 2,238,591(1941). (2) Swallen, L. C., IND.ENQ.CHEN.,33, 394 (1941).
U. 5. Patent
Effect of Wetting Agents on Electrodeposition of Nickel I
NFORMATION regarding the effects of wetting agents on nickel electrodeposits has been of comparatively recent origin. Patents (4) involving the use of such wetting agents as gluconates or sulfonated alcohols having more than three carbon atoms t o eliminate pitting in nickel deposits have been issued. Schlotter (7) used aromatic sulfonic acids or their salts to obtain bright nickel deposits. Schlotter (8) also obtained deposits having a grain size of less than 0.0001 mm. from a nickel sulfate bath containing nickel naphthalenetrisulfonate. Blount (2) used sodium alkyl aromatic sulfonates in hot nickel electrolytes to eliminate pitting in the deposits. The Newark Branch of the American Electroplater's Society ( I ) reported the use of sodium alkyl sulfates, alkyl naphthalene sulfonates, and fatty acid amides in nickel baths to prevent pitted deposits. It is believed (6) that pitting in nickel deposits is caused by bubbles of hydrogen, oxygen, or air collecting on the cathode surface and preventing the further deposition of nickel a t that point. Boiling the plating solution eliminates air pitting, and the use of nonpassive anodes eliminates oxygen pitting. Although hydrogen pitting continues to be a serious problem in nickel plating, the use of wetting agents holds considerable promise of offering a satisfactory solution. Briefly stated, the action of wetting agents ( 2 ) on electrodeposits is believed to be as follows: Wetting agents have the property of reducing the surface tension of aqueous systems. This, in turn, lowers the interfacial tension between the cathode and the electrolyte; thus any bubbles of hydrogen collecting on the cathode fail t o adhere and are forced to the surface of the bath by the hydrostatic pressure of the electrolyte. The result is a smooth, fine-grained, and pit-free deposit.
Experiments with Plating Baths
Six strongly and three mildly surface-active agents were added to the bath in different concentrations. Members of the former group were Igepon-T (represented by the formula
ROGERS F. DAVIS, KATHRYN &I. WOLFE, AND WESLEY G. FRANCE The Ohio State
University, Columbus, Ohio
CI.~H~S-CO-NH-CH~--CH~-SO~N~), Lyofix D. E. and Sapamine K. W. C. (belonging to the quaternary ammonium type of wetting compounds), Nekal B. X., 1,4-isopropyl naphthalene sulfonic acid, cetyl pyridinium bromide, and citronellal. The three mildly surface-active agents were o-nitrotoluene, m-tolualdehyde, and pyrrole. Liquid agents such as m-tolualdehyde, pyrrole, o-nitrotoluene, and citronellal were added t o 200-cc. volumes of bath in quantities of 0.01 to 0.5 cc. The other wetting agents-e. g., solids-were added in quantities up to 500 mg. A recent list of a variety of surface-active agents was given by Van Antwerpen (9). A plating bath (8) composed of 105 grams of nickel sulfate, 15 grams of nickel chloride, 15 grams of boric acid, 15 grams of ammonium chloride, and 1000 cc. of distilled water was employed. Sheet copper cathodes and rolled sheet nickel anodes were used in the plating cell. A copper coulometer served to measure the quantity of electricity passed through the solution. The current density maintained throughout the investigation was 1 ampere per sq. dm. The temperature varied from 25" to 28" C. The pH measurements were made with a Coleman glass electrode, before and after each electrolysis. Surface tensions were determined by means of a du Nouy tensiometer. The solution used for the measurement of the surface tension was prepared as follows: 200 cc. of the original plating bath were measured into a bottle with a buret. An accurately weighed quantity of a wetting agent was dissolved in distilled water in a volumetric flask. A pipet which could be read t o 0.01 cc. was used to transfer an accurate volume of the wetting agent solution to the 200-cc. bath, which was then shaken until the wetting agent was completely dissolved. An 11-cm.
