JUNE, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Dreyfus, H., French Patent 763,942 (May 9, 1934). Dunstan and Wheeler. British Patent 309.455 (Oct. 8. 1927). Egloff, Sohaad, and Lowry, J. Phgs. Chem., 34, 1617’(1930j. Ibid., 35, 3489 (1931). Ellis, Carleton, “Chemistry of Petroleum Derivatives,” pp. 135, 146, 181, 183, 214-17, New York, Chemical Catalog Co., 1934. Ibid., p. 149. Ibid., p. 285. Frey, F. E., IND. ENQ. CHEM.,26, 198-203 (1934). P Hague, E. N., and Wheeler, R. V., J. Chem. SOC.,1929, 378-93. Hanson, F. S., undergraduate thesis in chem. eng., Pa. State Coll., 1935. Hawk, Golden, Storch, and Fieldner, IRD. ENQ.CHEM.,24, 23-7 (1932). Hurd, C. D., “Pyrolysis of Carbon Compounds,” pp. 11, 148, 236, 330, New York, Chemical Catalog Co., 1929. Hurd, C. D., and Meinert, R. N., J.Am. Chem. SOC.,52,4978-90 (1930). Kassel, L. S., J. Am. Chem. SOC.,54, 3949-61 (1932). Kassel, L. S., “Kinetics of Homogeneous Gas Reactions,” p. 317, New York, Chemical Catalog Co., 1932. Lang, J. W., and Morgan, J. J., IND.ENQ.CHEM.,27, 937 (1935).
673
(20) Marek, L. F., and McCluer, W. B., Ibid.,23, 878-81 (1931). (21) Morgan, J. J., “A Textbook of American Gas Practice,” 2nd ed., pp. 583, 610, Lancaster, Pa., Lancaster Press, Inc., 1931. (22) Neumann and Jacob, 2. Elektrochem., 30, 557-76 (1924). (23) Odell, W. W., U. S. Bur. Mines, Rept. Investigations 2973 (Dec., 1929). (24) Porter, D. J., and Cryder, D. S., IND.ENQ.CHEM.,Anal. Ed., 7, 191 (1935). (25) Reich, G., Refiner Natural Gasoline Mfr., 11, 448 (1932). (26) Rice, F. O., and Herzfeld, K. F., J. Am. Chem. Soc., 56, 284-9 (1933). (27) Sabatier and Senderens, Compt. rend., 124, 1358 (1897). (28) Schulze, A., 2. angew. Chem., 29, 341 (1916). (29) Treadwell, W. D., and Tauber, F. A . , Helu. Chim. Acta, 2, 601-7 (1919). (30) Wright, C. C., and Gauger, A. W., IND.ENQ.CHEM.,26, 164-9 (1934). RECEIVEDMay 25, 1936. Abstracted from a thesis mbmitted by D. J. Porter t o the faculty of The Pennsylvania State College in partial fulfillment of the requirements for the degree of doctor of philosophy in chemical engineering.
CORN PROTEINS J. F. WALSH American Maize-Products Company, New York, N. Y.
U
SUALLY we think of corn proteins only as components
of animal feeds, and as such they have found extensive and ready markets. Then, too, in the wet milling industry they are classed as a process waste, and no intensive study of their possible increased value as industrial raw materials has been made. However, considerable work has been done on their isolation, identification, and characteristics since the early part of the nineteenth century; Gorham, Bizzio, Ritthausen, Dill, Chittenden, Clapp, and T. B. Osborne particularly have made available much of the necessary knowledge which has led to the development of the commercial production of a very complete range of industrial corn-component proteins. In composition and reactivity the corn proteins are similar in many respects to the natural and synthetic resin products, such as casein, shellac, cellulose derivatives, thermoplastic synthetic resins, and the protein components of soybeans. The corn proteins are not readily identified through the usual chemical reactions, but like other proteins they are separated and classified by their selective solubility in various solutions. Broadly, they are comprised of albumins which are soluble in water,, globulins which are soluble in dilute salt solutions, glutelins which are soluble in dilute alkali, and prolamines which occur only in grains and are soluble in aqueous alcohol solutions. The proteins constitute about 10 per cent of the weight of the corn substance. The major portion of these is isolated in gluten, the process waste left from the purification of starch. These gluten proteins are all substantially insoluble in water. The water-soluble albumins, and some of the more soluble globulins, have been previously removed from the corn in the steeping process from which they are isolated with the soluble salts by concentration; in this form they are used as a component of animal feeds, as noncoagulable soluble proteins, and as yeast and bacterial nutrients.
Types of Gluten Proteins The gluten is composed of approximately 50 per cent protein, 35 per cent starch, 5 per cent oil, and a small amount of fiber and mineral matter. Because of this high protein
content, the various industrial proteins are isolated from the gluten. At present these proteins include three general types-namely, the carbohydrate-free protein, the carbohydrate protein free of the aqueous-alcohol-soluble portion, and the aqueous-alcohol-soluble protein called “zein”; each is available in various special forms. The carbohydrate-free protein is produced in the form of carbohydrate oil-free, carbohydrate-free bleached, and carbohydrate oil-free bleached; all differ slightly in their characteristics and uses. As a group they are utilized principally a8 a plastic base, filler, and reactive component in cellulose derivatives and in natural and synthetic resins, and as a raw material for the preparation of amino acids, particularly glutamic acid and leucine; glutamic acid is the essential component of monosodium glutamate, the synthetic beef flavoring. An approximate analysis of the substantially carbohydrateoil-free bleached protein is: Moisture Protein Ash Oil
.
11.0%
76.5
1.2 1.1
80Yo a1coh ol-soluble Fiber Starch
35.8% 4.0
None
This group of whole proteins is, in general, thermoplastic, relatively light colored, and reactive to dilute alkali, formaldehyde, phenol, and aqueous alcohol solutions; they thus offer a base for a relatively wide range of plastic products and fillers. The carbohydrate proteins, free of alcohol-soluble portion, differ from the former type in that they are almost completely soluble in dilute alkali and substantially insoluble in aqueous alcohol solutions. Comprised principally of the glutelins and a small amount of globulins, they find use as fillers, as components of phenolic resins, and as bases in alkaline coating solutions.
Zein The third and most important group constitutes the aqueous-alcohol-soluble prolamines, or zein. First isolated in 1821 from corn or Zea mays by Gorham, it has attracted more attention than any of the other proteins because of its
INDUSTRIAL AND ENGINEERING CHEMISTRY
674
characteristic alcohol solubility. Its elementary composition is reported as Carbon Hydrogen Nitrogen
Sulfur
Oxygen
55.23y0 7.26 16.13 0.60 20.78
A typical analysis of a commercially produced product is :
It is a substantially white, odorless, tasteless, amorphous solid, similar in many of its properties and characteristics to shellac, casein, and cellulose esters; it is thermoplastic, has a high electric insulation value, is resistant to heat and stable to light and, although combustible, is nonflammable. It has a molecular weight of 20,000 and a specific gravity of 1.226, is amphoteric with an acid-combining power of 0.00012 a t pH 2.8, and has a base combining power of 0.00020 at pH 10.8; it is insoluble in water, dilute acids, anhydrous alcohols, turpentine, esters, oils, fats, ethers, ketones, chlorinated solvents, petroleum and coal-tar hydrocarbons, ammonia, borax, and sodium and potassium carbonates. Aqueous alcohols, strong organic acid solutions, dilute 0.5 per
VOL. 29, NO. 6
cent sodium and potassium hydroxide solutions, dilute ethylenediamine or monoethanolamine solutions, liquid ammonia, molten phenol, cresol, Petrex, rosin, and strong solutions of urea are very effective solvents. These properties show that zein affords an ideal base for plastic and organic solvents and for dilute aqueous alkaline coating solutions. Further, it is compatible with many of the cellulose derivatives, plasticizers, and synthetic and natural resins, and can be compounded to transparent, clear, glasslike, stable compounds, suitable for use in novelties, sheeting, and coatings, such as are now made from cellulose derivatives and natural and synthetic resins. Zein, as might be expected from its chemical characteristics, is relatively highly reactive, and thus offers a prospective base for new synthetic resins. It can also be readily hydrolyzed to a wide variety of amino acids. Since these proteins constitute about 10 per cent of the whole corn, the potential supply is large and is limited only by our corn production. Again the wet milling industry, through this group of proteins (particularly the prolamine zein) brings to the chemist another new tool, to the farm a new prospective outlet for corn, and to industry new products and economic values with potential trade expansion. RECEIVED March 20, 1937. Presented before the Midwest Conference of Agriculture, Industry, and Science, Omaha, Nebr., March 9, 1937.
Fractionation of Michigan Straight-Run Naphthas ICHIGAN gasoline was previously studied and found to contain substantial quantities of normal paraffins (2, 5). Of the many gasolines fractionated in this laboratory, none was found to contain as great a percentage of normal paraffins or to be as relatively simple as Michigan gasoline. Since the isolation of pure hydrocarbons from petroleum by methods that could be economical commercially is one of the objectives of this laboratory, additional studies were made of this gasoline. It is obvious that for the most advantageous isolation of a hydrocarbon by distil!ation, a large volume of a narrow boiling range charge should be used. Two naphthas, available commercially from the Pure Oil Company and having relatively narrow boiling ranges ae compared with the over-all gasoline, were fractionated.
Naphtha Boiling at 44-134" C. This naphtha had the following properties A. 9. T.M. Engler distn., C.: Initial b. p. 44
A. S. T. M. Engler distn., C.: 6_7 .
62
3c 4c 5(
6(
End point Gravity A P 1. ('otane h o . Procedure 345
104 113 134 71.4 41
The fractionation was made in the column described previously (3, 6). This column has the equivalent of seventy to seventy-five theoretical plates. Forty-five gallons were charged into the still and fractionated at a reflux ratio of about 40 to 1. The gasoline was divided into 179 fractions, each fraction consisting of 0.3 to 0.6 per cent of the charge.
S. LAWROSKI, C. 0. TONGBERG, A. H. MAZZAROLA, AND M. R. FENSKE The Pennsylvania State College, State College, Pa.
The results are given in Figure 1 and Tables I to 111. The refractive index curve is similar to the corresponding section in the fractionation of the over-all gasoline except that the valleys are lower, the peaks higher, and one portion of the benzene peak has flattened at a point corresponding to cyclohexane. Approximately 12 per cent of the charge is n-hexane with a boiling spread of 0.9"C., a refractive index of about 1.3811, and a purity of 90 to 93 mole per cent. Of course, the total percentage of n-hexane in the naphtha is greater than this figure, but at least this quantity is associated with this purity as obtained in one fractional distillation. The chief impurity is benzene. About half of the above material boils within 0.1"C. of n-hexane and contains 92 to 93 mole per cent n-hexane. Pure n-hexane could be readily obtained by refractionation, followed by nitration or distillation with tert-butyl alcohol (1, 4). The material boiling at 98.0' to 98.8' C., comprising 12.4 per cent of the charge, contains about 85 per cent n-heptane. About half of this material boils within 0.2' C. of n-heptane and has a purity of 90 mole per cent: on extraction with sulfuric acid its purity is increased to 92-93 per cent. The remaining impurity is mainly methylcyclohexane. Refractionation of the n-heptane fractions in a column with one hundred theoretical plates yielded pure n-heptane.
