SOLVENT EXTRACTION JOSEPH C. ELGlN PRINCETON UNIVERSITY, PRINCETON, N. 1.
i i
i
P
ROGRESS and interest in the use of solvents t o separate the. components of mixtures by liquid-liquid and liquid-solid solvent extraction processes have continued. During the year few fundamental solvent extraction studies have been reported. Relatively few of the needed phase equilibrium and mechanism studies have been made as yet, and the basic engineering design data for equipment performance have not yet become available t o any extent. A number of such studies are known t o be in progress. Expansion of industrial solvent extraction processes, such as inthe areas of petroleum, hydrocarbon, and vegetable oil treating, has continued. Several previously proposed extraction processes have reached commercial fruition, and numerous additional applications of this operation t o complex separation and recovery problems have been proposed and patented. More specific information for several recently developed and previously cited processes became available during the year. Developments in liquid-liquid extraction have also been recently reviewed by Frey and Schiebel(33). Phase Equilibrium, Solubility, and Solvents. Solubility and tie-line data for a number of new systems were reported during the year (Table I).
TABLE I. PHASE EQUILIBRIUM DATA Temp., C. Ternary Systems Allyl alcohol-water-disllyl ethel: Ammonia-butylene-water Aniline with Cetane-benzene Cetane-cyclohexane Cetane-n-heDtane n-Heotane-chlohexane 25 Ethyl slcohoi-water Benzene-formic arid-bromoform Dicyanoethylamine with 25 Benzene-ci iclohexane Ethyl benzene-styrene 25 Toluene-troluoil 25 Ethyl aloohol-water-vinylidene chloride 2B Oleic acid-olive oil with Methanol (absolute) 25,96 18.5,25,96 8201 methanol-water 98% ethanol-water 18 5.25.96 Binary Ammonia-I-butene Temp. Y8. concn. System
Reference
(90)
(BO) (71)
(66) (68) (66) (63)
concn. aq. phase concn. solvent phase’ have also been reported for 2,3-b&ylene glycol as solute between water and diethyl cther, 1,2-dichloroethane, trichloroethylene, nsec-, and isobutanol, and aniline. Hoerr, Sedgewick and Ralston (39)measured the solubilities of the normal saturated fatty acids in toluene, xylene, nitrobenzene, dioxane, furfura,l, and nitromethane. I n furfural and nitromethane their solubilities were found t o be small. R7ith nitromethane, solubilities were so limited that the systems existed as two immiscible liquids over large ranges of concentration. Lingane and Meites (47) studied the various factors influencing the extraction of quadri- and quinquevalent vanadium from aqueous solutions by isopropyl ether in order to establish the optimum conditions for the separation of iron from vanadium by solvent extraction. The extractability of vanadium depends on its oxidation state, and is greatly influenced by the kind and concentration of acid present, the temperature, and the time of contact between the two Data (31)for the partition coefficient, K =
53
phases. Vanadium in the form of HVOBis readily extracted by isopropyl ether from its solutions in hydrochloric and sulfuric acids. Polansky and Kinney (64) report a large variety of active organic solvents and solvent mixtures which are good extractants for the humic acidlike products from nitric acid-treated bituminous coals. Many of the solvents reported leach 80-85% of the treated coal, leaving behind the mineral matter and fusain of the coal. Two promising commercial methods based on aqueous mixtures of organic solvents, such as acetone, acetonitrile, or ethyl alcohol, are reported, Information has been made available on the manufacture, properties, and use of the sulfolanes mentioned last year as new selective solvents (76). They are said t o be effective for both liquid-liquid and liquid-vapor extraction processes for separating mixtures of components having different degrees of saturation or polarity-for example, aromatics from paraffinics and naphthenes from olefins, in the desulfurization of petroleum fractions, and in the refining of vegetable oils. Their properties, including solubility and comparative data for the effect of the sulfolanes v8. other solvents on the volatility ratios for nonaromatics and toluene, and for the liquid-liquid extractive separation of toluene from a petroleum fraction, are given in detail. These solvents show higher selectivity on hydrocarbon mixtures than do most commonly used solvents. Methods of predicting solubility and tie-linedataindealing with solvent extraction processes continue to be a n important problem. Schiebel and Friedland (67) proposed a simple semiempirical method for correhting and predicting vapor-liquid equilibria for ternary systems from data for each of the three binary systems involved. The method, based on a graphical interpolation of the activity coefficients for the ternary systems, is also applicable t o liquid-liquid distribution data. The authors found the method t o agree with good accuracy with t h e published data on niae ternary systems. The method is claimed t o have broader application than previous methods and to be much simpler t o apply. T h e paper also contains a bibliography for previous methods of prediction. Tarasenkov (79) has found that the tie lines on the triangular diagram for a number of systems, when projected, intersect the base of the representative triangle a t a common point. His cquation, (a?cl - alc2) I; = (a*- 0 1 ) where a is concentration of the common coniponent miscible with both the upper (2) and the lower (1) layer, and c is concentration of one of the partially miscible components for the abscissa of the point of intersection with the base of the triangle, leads to a distribution ratio:
3 = -(c1 - IC) a2 (c2 - IC) This formula for the distribution of a was derived geometrically from the properties of the Gibbs or the Rosenbloom triangles Tarasenkov found i t t o give satisfactory agreement with the data for five or six well-known ternary systems, all of which involved water. Vapor-liquid and thermodynamic data in the form of activities and van Laar constants which may be useful in the treatment of liquid-liquid phase equilibria and solvent extraction processes were reported for a number of systems. Colburn and co-workers
INDUSTRIAL AND ENGINEERING CHEMISTRY
54
(35,65) reported such data for binary and ternary systems of nbutane, isobutane, and 1-butene with furfural together with methods of predicting the ternary equilibrium from the binary van Laar constants and the activity coefficients. Buell and Boatright (16) reported data for vapor-liquid equilibrium and described processes for the separation of C, hydrocarbons by extractive distillation v i t h furfural. Similar data were also reported (63)for the separation of butadiene from C phy$rocarbons by azeotropic distillation with ammonia. The comprehensive tabulation of azeotropes by Horshley (40) and that of the azeotropes of sulfides and halides by Lecat (46) will be useful in treating solvent extraction processes. Useful methods of predicting azeotropism in binary systems, together with the effect of pressure on azeotropic composition, have also been reported (14,
81,41). Mass Transfer and Equipment. Extensive investigation of transfer rates in, and performance of, liquid-liquid contacting equipment is much to be desired. Few studies were reported during the year. Employing the system nitrobenzene-acetic acid-water in a 1.36-inch diameter glass spray tower, Nandi and Viswanathan (55) found values of the over-all R.T.U. based on the nitrobenzene phase to be about 3 feet with either phase dispersed. They concluded t h a t 45% of the total extraction in a 3-foot-high column occurred within the first 6 inches, Poffenberger et aE. (63) reported the use of a 12-inch-diameter X 20-foot-high tower packed with Raschig rings t o recover ammonia from butylene by liquid-liquid extraction with water. Jones (44) applied a colloid mill to the contacting of two immiscible liquids, such as napht,ha with aqueous caustic or potassium hydroxides, to remove mercaptans A greater removal by this method is claimed than by conventional methods of contact. The Podbielniak centrifugal contactor is being applied t o the liquid-liquid extraction of penicilliii from aqueous solutions (6). Several patents were issued for novel forms of contactors for solvent extraction processes (7, 6.4, 83). Design and Process Data. Benedict (11) presented a comparison of multistage separation processes based on the concept of the separation factor and the equilibrium stage which should prove useful for the preliminary design consideration of such processes. Reviewing the application of the several graphical methods of estimating stage requirements in liquid-liquid countercurrent extraction, Skogan and Rogers (71) concluded that empirical adjustmepts are necessary in practical applications to design. They find the Hunter-Nash method applica.ble t o design problems if single-stage data for a wide range of solvent-oil ratios are known, and if multistage data are known for a t least one oil-solvent ratio on a given oil and solvent and the number of stages are determined. Smith (73) presented a n improved method for plotting ternary equilibrium data having all of the advantages and none of the disadvantages of the triangular diagram and the types of charts previously used. This involves plotting on rectangular paper, as ordinate, the percentage of the component normally represented by the vertical apex of the triangular diagram; and ma86
as abscissa, z = ( A
2w), where Wis thepercentage ofoneofthe
4
other components. Such a plot has advantages in t h a t the normal shape of the ternary curve is obtained; the coordinate scale can be changed a t will to enlarge the whole section for low solubility; tie lines are easily located; and a separate plot is unnecessary for their interpolation. Finally. on such a chart numerical calculation can replace the graphical method of measuring distances on the triangular diagram. Power consumption data for disperser and spiral turbine impellers in single liquids and in twophase immiscible systems were reported by Olney and Carlson (61). These authors correlated their data with similar data of others for different mixer designs in terms of a power functionReynolds number relation. The design and operation of a completely instrumented fur-
Vol. 40, No. 1
fural solvent-refining pilot unit, designed to discharge 5 gallons per hour of an Oklahoma city, 200-viscosity (Saybolt Universal seconds) a t 100' F., neutral oil with a solvent ratio of 22 to 1was described by Brown (15). For the solvent extraction of cottonseed and peanut oils, D'Aquin el al. (22) reported experimental work for the design and operation of pilot plant equipment and the development of such solvent extraction processes. Bestougeff and Darmouis (12) give data for the fractional extraction of asphaltenes from crude tars by selective solvents, and Gutierrez (38) has supplied data on the extraction of saccharin from aqueous solutions by the use of acetone. In laboratory extractions the latter succeeded in recovering over 98y0 of the saccharin present with very few c o n t a c k Commercial processes for the extraction of penicillin are described (6, 81). Dietz, Degering, and Schopmeyer (26)review the previous methods of recovering lactic acid from dilute solutions, including liquid-liquid extractions, and describe a new method based on converting the acid to a n ester in solution and extracting the latter with selective solvents such as chlorinated hydrocarbons. Process data are given for the extraction by l,%dichloroethane. Processes for producing cresylic acids from petroleum (4)involving their extraction with caustic soda solution in a vertical packed contactor, and for recovering tartrates from winery pomace (56) by continuous multistage countercurrent leaching, were described. Plant and operating results in applying the Holly-Mott process for contacting immiscible liquids in countercurrent agitated stages to the removal of monohydric phenols from gas works ammoniacal liquor are given by Rlurdock and Cuckney (57). A description, design data, and plant and economic evaluations for a pilot plant process for producing iron-free alum, involving as the key step the solvent precipitation of iron-free alum by ethanol, are given by Gee, Cunningham, and Heindl (34). Appropriate phase equilibrium data for the system aluminum sulfate-ethyl alcohol-water are given, and i t is stated that 97-9870 iron removal a t a n extraction efficiency of 98% can be obtained. Hunter and Bronm (43) investigated the dewaxing of mineral oils by liquid-liquid extraction by calculations using the ternary phase diagrams for cyclic hydrocarbons and cetane with aniline (42) and by the experimental extraction of a lube oil fraction with acetone in a pilot plant tower. They concluded in both cases that liquid-liquid extraction under these conditions yielded less satisfactory and less complete wax removal than do the present industrial low-temperature solvent extraction-crystallization methods. Fenske, Carlson, and Quiggle (50) reported vapor-liquid equilibrium data for the methylcyclohexane-toluene-aniline system and compared extractive distillation with liquid-Iiquid extraction for separations in such systems. Applications. Fuller information for several of the recently developed major commercial solvent extraction applications has become available. I n addition many new or improved smaller applications have been proposed or employed, many of which are the subject of patents. Industrial solvent refining of lubricating oils continues t o expand. Smoley and Fulton (74) describe with flow sheets the modern solvent refining, propane deasphalting, and solvent dewaxing processes for lubricating oils together vath recent developments in their application. Since the war, primarily because of eronomics, the refining industry has selected propane deasphalting plus a single solvent in the majority of cases. Furfural and phenol have had preference as the selective solvents. Most of the new developments in solvent refining center around improving the efficiency of the countercurrent extraction tower. A Comprehensive table of modern lubricant manufacturing plants built and being built, with location and capacities, is given in the reference. Two principal types of solvent dewaxing a t present are the benzol-ketone and the propane dewaxing processes. Additional recent descriptions of commercial extraction processes for refining and dewaxing lube oils are available (23, 70) Several developments during the past few years have been in the adapta-
January 1948
,
INDUSTRIAL AND ENGINEERING CHEMISTRY
tion of the benzol-ketone process t o the production of both crystalline and microcrystalline waxes. In the recently developed reverse-sequence process both zero-pour-point oil and low-oilcontent wax are produced by chilling the charge oil, mixed with solvent, t o an intermediate temperature, and removing the high-melting-point wax by filtration. The filtrate from this step is then chilled to subzero temperatures for the removal of low-melting-point waxes; the filtrate from this step contains the low-pour-test oil. Economy is obtained in this process by the use of incremental solvent injection involving the introduction of dilution solvent in small stages through the chilling train so that crystallization is carefully controlled using a minimum of solvent. The treatment of animal and vegetable oils by liquid-liquid extraction with a nonpolar solvent, liquid propane, developed commercially under the trade name of Solexol process, has been more fully described (3, 65). Several commercial installations are understood to be under construction. Extraction with liquid propane can be applied to separations, depending upon differences in molecular weight or of polarity, as well as to crystallizations based on the degree of saturation. The amount and kind of separation depend upon the contactifig temperature, since the solubility of various components varies. By varying temperatures, the fatty acids, lecithin, color and odor bodies, and vitamins may be removed from oils. The system may be used for solvent crystallization, much as propane is used for solvent dewaxing of petroleum stocks, to separate saturated oils or fats by crystallizing away from the unsaturated components. Several full scale plants, with capacities of 30 t o 40 tons of fat acids per day, are now in operation employing the so-called Emersol process for separating fatty acids (86,46,63). In this process the fatty acid mixture is dissolved in 90% methanol solution along with a small amount of glyceride a s a crystal promoter. It is then chilled in a multitubular agitated crystallizer equipped with motor-driven scrapers. The stearic acid which crystallizes is removed from the slurry, washed with a solvent on a rotary vacuum fXter, melted, and then charged t o a still for solvent recovery. The oleic &cid solution from the filter is then stripped of solvent. The cost of the process is stated t o be 65% less than that of the present method of pressing. Solvents other than methanol, such as acetone, can be used, but many do not yield the desirable granular needlelike crystals which permit ready separation. The recovery of vegetable oils from seeds and beans continues to be studied, improved, and developed commercially. Solvent extraction of oil seeds has been discussed and reviewed by Goss (37) and by MacGee (61),who cover theory, types of extractors, solvents, solvent recovery, applications, and the advantages and disadvantages of various prqcesses. The latter author cites fiftythree references. Several large scale solvent extraction plants for cottonseed oil have been installed and put into production (2,56). That of the Delta Products Company a t Wilson, Ark., the first full scale plant for cottonseed, has a capacity of 200 tons of c o t tonseed per day and is the first of three such plants planned by processors in this area. The process as developed in pilot plant operations is an application of the AllkChalmers solvent extraction process for soybeans, and involves steaming fbad flaking the seeds and extracting with hexane countercurrently. Color bodies distributed between oil and meal are removed from the oil by processing the extract to give an oil with a color said to be equivalent to or better than that of prime grade first oil. It is claimed that an extra yield of 45 pounds of oil per ton of seed, as compared with hydraulic methods, will be obtained with the new process. Less labor is also said to be required. A second cottonseed extraction plant using hexane as solvent has also been reported to be under construction in Texas (2). A description with flow sheet, solvents, plant layout, and equipment for such large scale plants for the solvent extraction of vegetable oils has been given by Tray and Bilbe (84),who further describe the commercial plants and processes just mentioned. McCormack (60) has investigated two methods of extracting
5s
oils from acorns, the centrifugal and continuous, using butanol aa the solvent, The oil extracted varied from 73 to about 90%. Buxton (17,19) describes the use of solvent extraction to separate constituents from animal and vegetable oils and reports the production of antioxidant concentrates by solvent extraction of crude wheat germ, corn germ, and soybean oils, which bodies are highly effective antioxidants for inhibiting the peroxidation of and vitamin A destwction in liver oils. He has patented a method of concentrating the fat-soluble vitamins by extracting a marine oil with a suitable solvent such as 2-propanol or diacetone alcohol (18). Solvent treatment and refining of fats and oils have been the subject of a number of patents (13, 49). Several patents have appeared for solvent extraction processes for separating components from tall oil. I n one case (86) tall oil is dissolved in sulfate tupentine and the solution extracted with furfural to produce an improved tall oil and a pleasant-odored turpentine. Freeman and Gloyer @2), after selective esterification of the free fatty acids with 1-5 carbon alcohols, extract the major portion of the fatty acid esters and sterols selectively in a paraffinic solvent such as naphtha, and the rosin acids in furfural or other polar solvents immiscible with naphtha. Spence (76) recovers lower fatty acids from dilute solutions by adsorption on activated carbon, removing water by vacuum distillation and then the concentrated acid from the carbon, by extracting with an organic solvent such as acetone or furfural. Andre (1)applied the selective solvent technique to the separation of the immediate principles of karite fat. Processes have been patented for the purification of furfural by liquid-liquid water extraction in the presence of a light hydrocarbon (62); for the defoaming of furfural solvents (89) by purification through liquid-liquid extraction with an aliphatic hydrocarbon immiscible with furfural, hexane being the most effective; and for the stabilization of furfural (62) by the addition of small amounts of substituted guanidines, thioureas, and naphthylamines, Other recently patented applications for extraction processes involved the separation of isomeric xylenes (8) by low temperature solvent crystallization in the presence of inert diluents, such as methyl, ethyl, and isopropyl alcohols, ketones, certain aliphatic hydrocarbons, and others; extracting aromatic hydrocarbons from naphthas (69); selectively extracting butadiene from liquid CIhydrocarbon mixtures (77, 78); separating aromatic hydrocarbons from their szeotropic mixtures with nonaromatic hydrocarbons, by liquid-liquid extraction with solvents which include sulfolane and sulfolene, alkylated sulfolenes, and sulfoanyl ethers and sulfides (88). Polyolefin glycols of high molecular weight are employed as selective solvents in the extraction of olefinic and aromatic hydrocarbons from para5nic ( 9 ) . In a process for separating diolefins from other hydrocarbons by the formation of diolefin sulfones, the dissociation of the sulfone into the component diolefin and sulfur dioxide is first carried out, and these two products are then separated through the use of selective solvents for either the diolefin or the sulfur dioxide (86). Liquid-liquid extraction with water is used to free crude acrylonitrile from acetylene polymers ( 2 4 ) . Lofton (48)purified impure chloroacetophenone from hydrochloric acid and acetophenone by extraction with naphtha in a closed system under pressure (48). In a process for preparing surface active agents, Ross and Potter (66) recover the resulting sulfanile halide from solution by liquid-liquid extraction with selective solvents such as nitromethane, methyl acetic acid, liquid sulfur dioxide, and then an equal volume of immiscible nonpolar solvent such as hexane, propane, or butane. f n the nitric acid Oxidation of naphthene and isomeric paraffins of similar boiling point, the by-product n i t r o p a r a h are selectively extracted from unreacted naphthenes by nitric acids of 50 to 95% concentration (27). I n a patented process for producing glycerol from sugar by yeast fermentation (60),the residue is finally treated with a suitable solvent such as butyl, benzyl, or ethyl alcohol, or acetaldehyde to recover the glyccrol. Schneider and Archibald (68), in producing ethers from propylene by sul-
s6
INDUSTRIAL AND ENGINEERING CHEMISTRY
furic acid absorption, selectively remove the ether from the acid with an ether solvent while bringing the olefins into contact with the acid. bran is In producing enzymes comercially~ dried tracted with water and filtered, and the enzyme precipitated from the filtrate by successive additions of ethanol (69). More information (6)has also become available on the use of solvents in the drying of lumber mentioned last year. The process depends on the. treatment of lumber with a water-miscible solvent such 5s acetone. LITERATURE CITED
AndrB, E., and Pradain, J., C m p t . rend., 224, 1445 (1947). Anonymous, Chem. Eng. News, 25, No. 14, 1000 (1947). Anonymous, Chem. I d s . , 59, No. 6, 1016 (1946). Ibid., 60, N o . 1,48 (1947). Zbid., 60, No. 2, 231 (1947). Anonymous, Instrumentation, 3, No. 1, 10 (1947). Arnold, J. C. (to Standard Oil Development Co.), Brit. Patents 584,876 and 584,892 (Feb. 5, 1947). Arnold, J. C., Brit. Patent 585,076 (Jan. 29, 1947). Ashburn, 13. B., U. S. Patent 2,414,252 (.Jan. 14, 1947). Avenarius, M. A., and Tarasenkov, D. N., J . Gen. Chem. (U.S.S.R.), 16, 1777 (1946). Benedict, M., Chem. Eng. Progress, 1, N o . 2 ; Trans Am. Inst. Chem. Engrs., 43, 41 (1947). Bestougeff, M., and Darmouis, R., Compt. rend., 224, 1365 (1947). Black, H. C., and Bollens, W.F., U. S. Patent 2,416,146 (Feb. 18, 1947). Britton, E. C., Nutting, H. S.,and Horshley, L. H., Anal. Chem., 19, 601 (1947). Brown, L. C., Oil Gas J., 46, No. 6, 112 (1947). Buell, C. K., and Boatright, R. G., IND. ENG.CHEY.,39, 695 (1947). Buxton, L. O., J . Am. Oil Chemists’ SOC.,24, 107 (1947). Buxton, L. O., U. S. Patents 2,412,561 and 2,412,766 (Dee. 17, 1946). Buxton, L. O., IND. ENG. CHEM.,39, 1171 (1947). Carbide and Carbon Chemicals Corp., unpublished rept. (1947). Coulson, E. A., and Herington, E. F. G., J..Chem. Soc., 1947, 597. D’Aquin, E. L., et al., Oil Mill Gaz., 51, No. 10, 117 (1947). David, R. A., and Huemmer, P. M., Chem. Eng. Progress, 43, No. 4, 174 (1947). Davis, H. S., U. S. Patent 2,417,635 (March 18, 1947). ENG.CHEM.,39, 126 (1947). Demmerle, R. L., IND. Dieta, A. A., Degering, E. F., and Schopmeyer, H. H., Ibid., 39, 82 (1947). Doumani, T. F., and Coe, C. S., U.S. Patent 2,420,938 (May 20, 1947). Durrum, E. L., Ibid., 2,407,820 (Sept. 17, 1946). Fairburn, A. W..Cheney, H. H., and Cherniavsky, A. J., Chem. Eng. PToyress, 43, No. 6, 279 (1947)., Fenske, M . R., Carlson, C. S., and Quiggle, D., IND.ENG. CHEM.,39, 1322 (1947). Freeman, G. G.. and Morrison, R. I., J . SOC.Chem. Ind., 661 216 (1947). Freeman, S. E., and Gloyer, S. W., U. 9. Patent 2,423,232 (July 1, 1947). Frey, *4.J., and Schiehel, E. G., Jubilee Vol. Emil Barell, 1946, p. 46. Gee, E. A,, Cunningham, W. K., and Heindl, R. A,, INO.ENG. CHEM.,39, 1178 (1947). Gerster, J. A., Mertes, T. S., and Colburn, A. P., Ibid., 39,’7787 (1947). Gordon, J., Soulhern P o w e r and Ind., 65, No. 7, 62, 73 (1947). Goss, W. H., Oil & Soap, 23, 348 (1946). Gutierres, F. H., A n d e s F l s . quZm (Madrid),42, 1105 (1946). Hoerr, C. W., Sedgewick, R. S., and Raliton, -4.W., 6.Oro. Chem., 11, 603 (1946).
Vol. 40, No. 1
(40) Horshley, L. H., Anal Chem., 19, 508 (1947). (41) Ibid.*p. 603* (42) Hunter, T. G., and Brown, T. F., IND.ENG.CHEx, 39, 1343 ,_^
.-
(lY41).
(43) Hunter, T. G., and Brown, T. F., paper presented at Am. Inst. Chem. Engrs. meeting, Detroit, ,Mich. (Nov. 1947). (44) jones, M. c. K., u. s. patent 2,420,544 ( M 13,~ 1947). ~ (45) Kistler. R. E.. Muckerheide. Y, J.. and hTvers. L. D.. Oil & Soap, 23,5, 146 (1946). (46) Leeat, M., Ann. SOC.Sci. Bruzelles, Ser. I, 61, 148; Bull. classe sci., Acad. roy. Belg., 33, 160 (1947). (47) Lingane, J. J., and Meites, L., Jr., J . Am. Chem. Soc., 68, 2443 (1946). (48) Lofton, W.M., Jr., U. S.Patent 2,414,418 (Jan. 14, 1947). (49) Lummus Co., Brit. Patent 568,203 (March 23, 1945). (50) McCormack, R. H., J . Am. Oil Chemists’ SOC.,24, 299 (1947). (51) MacGee, A. E., Paint Manuf., 17, 255 (1947). (52) Malen, B. J., U. S. Patent 2,412,823 (Dee. 17, 1946). (53) Marsel, C. J., and Sllen, H. D., Chem. Eng., 54, No. 6, 104 (1947). (54) Mensing, C. E., U. S. Patent 2,405,158 (Aug. 6, 1946). (55) Mertes. T. S.,and Colburn, A. P., IND.EKG.CHEM.,39, 797 (1947). (56) Metzner, E. K., Chem. Eng. PTogrcas, 43, N o . 4, 160 (1947). (57) Murdock, T. G., and Cuckney, M.,Trans. Inst. Chem. Engrs. (London), advance copy (Oct. 8,1946). (58) Nandi, S. K., and Viswanathan, T. R., Current Sci. (India), 15, 162 (1946). (59) Naragon, E. A., U. S. Patent 2,413,828 (Dec. 17, 1946). (60) Neuberg. C. A., and Roberts, I. S.,Ibid., 2,410,518 (Sov. 5, 1946). (61) Olney, R. B., and Carlson, G. J., Chem. Eng. Progress, 43, No. 9, 473 (1947). (62) Oosterhout, J. C. D., and Rody, T. C., U. S. Patent, 2,419,499 (April 22, 1947). (63) Poffenberger, N., et al., Trans. Am. Inst. Chem. Engrs., 42, 815 (1946). (64) Polansky, T. S., and Kinney. C. R., IND.ENG.CHEM.,39, 925 (1947). (65) Rius, A,, and Moreno, M. M., Annales F l s y quim (iMadrid), 42, 123 (1947). (66) Ross, J., and Potter, D. J., U. S. Patent, 2,424,420 (July 22, 1947). (67) Schiebel, E. G., and Friedland, D., ISD.ENG.CHEX.,39, 1329 (1947). (68) Schneider, H. G., and Archibald, F. M., Canadian Patent 440.811 (April 15, 1947). (69) Shellenberger, J. A., Chem. Eng., 54, No. 2, 130 (1947). (70) Skelton, W. E., Oil Gas J., 45, No. 42, 137 (1947). (71) Skogan, V. G., and Rogers, M. C.,I b i d . , 46, No. 13, 70 (1947). (72) Skripach, T. K., and Temkin, M. I., J . Phys. Chem. (U.S.S.R.), 20, 583 (1946). 1 (73) Smith, A. S., Chem. Eng., 54, No. 3, 123 (1947). (74) Smoley, E. R., and Fulton, D., Petroleum Processing (Aug. 1947). (75) Spence, O., U. S. Patent 2,422,504 (June 17, 1947). (76) Staaterman, H. G., et al., Chem. Ens. Progress, 43, No. 4, 216 (1947). (77) Standard Oil Co. of Calif., Brit. Patent 580,643 (Sept. 16, 1946). (78) Standairl Oil Development Co., Brit. Patent 581,006 (Sept. 27, 1946). (79) Tarasenkov, D. N., J . Gen. Chem. (U.S.S.R.),16, 1583 (1946).5 (80) Tarasenkov, D. N., and Avenarius, A. M., Ibid., 16,1577 (1946). (81) Taylor, T. H. &I., Chem. Eng. Progress, 43, No. 4, 155 (1947). (82) Thodos, G., and Weinang, C. F., U. S. Patent, 2,414,402 (Jan. 14, 1947). (83) Thompson, R. F., Ibid., 2,400,962 (May 20, 1946). (84) Tray, S E., and Bilbe, C. W., Chem. Eng., 54, No. 5, 139, 160 (19471, (85) Trimble, Floyd (to Quake1 Oats Co.), U. S. Patent 2,310,046 Feb. 2, 1943). (86) Upham, J. D., U. S. Patent, 2,399,837 (May 7, 1946). RECEIVED December 10, 10,ii.
END OF THIRD ANNUAL UNIT OPERATIONS REVIEW
