"-BUTANOL and ACETONE Raymond W y nkoop PUBLICKER C O M M E R C I A L A L C O H O L C O M P A N Y , P H I L A D E L P H I A , P E N N A
thesis of ethanol to acetaldehyde t o aldol to glycol t o butadiene. Oddly enough, in the light of our present experience, ethanol apparently never received very serious consideration from the British investigators. Fernbach, pursuing the problem for Strange and Graham, Ltd., succeeded in finding a bacillus which would ferment potatoes, but not cereals, to produce butanol and, incidentally, acetone. This discovery later became the subject of a British patent application which was eventually abandoned (5). I n 1912 Weizmann severed his connections with the British group and continued to work on the fermentation problem. He discovered a culture which appeared to have outstanding fermentation characteristics. It could ferment grains such as corn without the addition of any nutrient and without the necessity of first converting the starch into sugar. The first World War created a tremendous demand for acetone for use in airplane dopes and for the production of cordite, the British high explosive. The acetone which could be produced by calcium acetate manufacturers outside of Germany and Austria was far from enough to satisfy British demand. Strange and Graham, Ltd., contracted to supply acetone to the British Govrrnmrnt by thr Fernbarh process. However, production was uncertain and unsatisfactory owing to the inefficiency of the bacilli. The Weizmann process (10) was subsequently used in this plant instead of that of Fernbach, and marked progress was made in production. However, at that time a bushel of corn weighing 56 pounds produced only 10 or 11 pounds of solvents made up of approximately 60 parts butanol, 30 parts acetone, and 10 parts ethanol. Thus, 56 pounds of material had to be shipped from America to England to obtain 3 pounds of much needed acetone. With shipping space a t a premium, it became evident that the process had to be carried out closer to the source of raw material. A distiller was therefore converted to the Weizmann process a t Toronto, Canada, and later when we entered the war, the procrss v a s utilized in two distilleries a t Terre Haute, Ind. (4).
A brief history o f t h e butyl-acetonic fermentation industry is given. T h e striking similarity o f t h e past a n d present factors which have influenced the industry a r e noted. Process procedure a n d r a w material economics are pointed out. The more important phases o f the chemistry o f butanol and acetone are discussed, w i t h particular regard t o the derivatives which find use as solvents. The uses a n d importance o f both compounds and derivatives are pointed out.
T
HE investigations of processes to make these products were first carried out about thirty years ago as a result of the interest in the use of n-butanol as a starting point for the production of synthetic rubber. The commerical production of butanol, and the acetone simultaneously produced by the fermentation process, can be directly attributed to the demand for acetonr brought about by the first World War. Thus, the search for synthrtic rubber and the existence of a state of war furnished the impetus for the development of the butyl-acetonic fermentation industry. Today this country is making a determined effort to bring about the rapid production of a huge tonnage of synthetic rubber, but the use of butanol as a raw material is not part of the program. Today we are again in the midst of a World War and there is a huge production of butanol and acetone in this country; but in spite of this fact, present demand for thew products is in excess of the available supply. About 1910 rumors reached London from Germany that Fritz Haber had succeeded in making rubber from potatoes. I n the same year the firm of Strange and Graham, Ltd., hired Fernbach, Perkin, and Wcizmann to undertake research work on synthetic rubber, and the raw materials from which it might be made. The raw products to which consideration was givrn were isoamyl alcohol, acetone, and butanol from which isoprene, dimethylbutadiene, and butadiene could, respectively, be synthesized. Isoamyl alcohol was available only in relatively small quantities as a by-product of ethanol production, and the only source of acetone was through the wood distillation industry by destructive distillation of calcium acetate. On the other hand, n-butanol was not available at all. The British research workers prophetically surmised that butadiene was the best material for producing synthetic rubber, and decided that this could be made by the dehydration of butanol to butylene which, in turn, could be dehydrogenated to butadiene. The use of ethanol also as a raw material was outlined by Perkin (9) who mas the first to give the details of the now well known syn-
W E I Z M A N N PROCESS
The Weizmann process has already been described in detail (6) and will be merely outlined here. Corn is ground, digested under pressure with water, and cooled t o 98" F., and the resulting mash run into fermenters. These are then inoculated with a culture of proved purity, and the fermentation is complete in about 40 hours. Although ethanol fermentation gives off carbon dioxide only, butanol fermentation produces a gas containing approximately 60 per cent carbon dioxide and 40 per cent hydrogen by volume. The butanol process must be carried out in closed fermenters which can be thoroughly sterilized to ensure satisfactory fermentations, whereas ethanol can be made in open-top fermenters. To obtain optimum yields, the butanol mash has a starch or sugar content of only about half that of the mash used for alcohol frrmentation. No use for butanol was found during the war except that at Toronto some of it was dehydrated to butylene, treated with sulfuric acid, and subsequently hydrolyzed to sec-butanol. This was catalytically dehydrogenated to methyl ethyl ketone Tvhich was used as a partial substitute for acetone. However, around
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December, 1943
INDUSTRIAL AND ENGINEERING CHEMISTRY
the close of the war i t was found that butyl acetate made from butanol was a n exceedingly efficient substitute for amyl acetate made from fusel oil, and t h a t it was also a n excellent solvent for nitrocellulose. As a result of this finding, butanol rather than acetone became the main production objective, especially as the demand for acetone reached a rather low ebb after the end of the first World War. The ability t o produce butanol and butyl acetate in practically unlimited quantities, as compared to the limited supply of byproduct fusel oil, was the foundation stone which resulted in the development of the nitrocellulose lacquer industry. Because of the unlimited availability of a satisfactory solvent, nitrocellulose lacquers began t o be used in the place of oleoresinous finishes on automobiles. It can be stated without exaggeration that butanol was, t o a considerable extent, responsible for the mass production of automobiles. Instead of the three to four weeks required for a car t o receive its coats of finish, the time was cut to t h a t many hours. It is difficult to visualize how many acres of floor space would be required to finish a half million or more cars per month if almost a month were required for the finishing process. The rapid growth of the demand for butanol resulted in efforts to produce it by means other than the Weizmann process. It is now made synthetically from either acetylene or ethanol as the raw material. Each of these products can easily be converted into acetaldehyde which is condensed to aldol, and this, in turn, is changed t o crotonaldehyde. Subsequent hydrogenation of this product results in the formation of butanol. The fermentation process too has changed, in that many new oultures have been found which will ferment molasses instead of grains. Little has been reported formally concerning the many sugar fermentations which produce good yields of butanol, although the patent literature is full of claims. The descriptions and economic evaluations of sugar fermentations using blackstrap molasses have been worked out rather well by several investigators, among whom Arroyo is prominent (2). Mezzandroli and Magno also pioneered in the use of sugar fermenters (7),and the Russian literature reports use of the Weizmann bacillus t o ferment mixtures of grain and molasses with the use of nutrients (8). At the time the United States entered the present war, molasses had entirely supplanted corn and other grains as the raw material for butanol fermentation. However, the shortage of tankers and the submarine situation almost eliminated the importation of molasses so t h a t the Weizmann process is again being used in butanol fermentation plants with grains as the raw material. With the exception of minor improvements, the process of producing butanol by fermentation is about back where i t was twenty-five years ago. However, it should be borne in mind t h a t the products of the butyl-acetonic fermentation must compete against synthetics which have a stable raw material cost, while agricultural products, cereals in particular, have fluctuated wildly in price in recent years. It is not unreasonable t o assume, then, that substitution of molasses for grains, even in the grain belts, will continue t o be common. The availability of acetone as a by-product of the butyl-acetonic fermentation eliminated the production of the former by the wood distillation industry. However, the demand for acetone as a result of its low price and new uses has grown enormously so t h a t today more is being produced synthetically than by fermentation. The production of synthetic acetone is based on propylene from oil refinery gases. This i s converted into isopropanol by sulfation and subsequent hydrolysis, and the alcohol in turn is oxidized or dehydrogenated t o acetone. Catalytic conversion of acetylene and steam and of acetaldehyde and steam to acetone over alkaline catalysts also seems promising. C H E M I C A L PROPERTIES
The chemical reactions of both butanol and acetone are well known, and only a few will be mentioned. Acetone is condensed to diacetone alcohol in the liquid phase by means of an alkaline
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catalyst. This ketoalcohol is a n excellent solvent for both nitrocellulose and cellulose acetate. While it was originally made to be used as a solvent, t h e greater part of the production finds its way into hydraulic brake fluids. Diacetone alcohol can be dehydrated with acid to form mesityl oxide which, in turn, can be catalytically hydrogenated t o methyl isobutyl ketone. Mesityl oxide is a n excellent solvent for esters, oils, gums, and rubberlike materials; methyl isobutyl ketone finds use in many liquid-liquid extraction processes, especially those involving water solutions of organic acids. It is one of the more easily obtainable water-insoluble ketones. Of great commercia1 importance is the reaction by which acetone is pyrolyzed t o ketene and methane. The availability of cheap acetone and the fact t h a t ketene reacts directly with anhydrous acetic acid t o form acetic anhydride has been of great benefit to the cellulose acetate industry. Less expensive acetic anhydride has resulted in substantially reducing the cost of cellulose acetate for use in fibers, plastics, and films. T h e process of using n-butanol t o make sec-butanol and methyl ethyl ketone at Toronto has already been referred to. This is no longer economical, as sec-butanol is now being made in quantity from butylenes from oil refinery gases. Butanol can be catalytically dehydrogenated t o butyraldehyde. This product was originally combined with amines t o make rubber accelerators. However, far greater quantities are now being utilized for the manufacture of polyvinyl butyral resins which, when made into sheets and properly plasticized, are now in general use as the “sandwich filler” in safety glass. USES OF A C E T O N E
After the first World War ended, t h e largest uses for acetone were as solvent in acetylene cylinders and for nitrocellulose for use in photographic films, cements, and dopes, but as the material became cheaper new uses were found. I n the Govers process (6),a mixture of acetone and benzene is used t o dewax lubricating oils. T h e rapidly growing cellulose acetate industry utilizes substantial quantities of acetone as a solvent, and it is used as the extraction medium in the production of insulin. However, probably as much acetone is converted into such products as acetic anhydride, diacetone alcohol, mesityl oxide, and substituted quinoline antioxidants as is used for direct solvent purposes. USES OF B U T A N O L
The Aronovsky process (1)for wood pulping uses a mixture of water and butanol in the digesters in place of the various chemicals usually utilized for wood digestion. It is claimed t h a t cellulose of high alpha content can be produced by this process, t h a t a pure lignin is obtained, and t h a t no plant is needed for the recovery of chemicals which cannot be dumped into streams. In this process the butanol can be relatively easily recovered by injecting live steam into the digester mass. The nitrocellulose lacquer industry continues t o be the chief user of butanol. Here about 80 per cent of the butanol is employed in the form of butyl acetate so t h a t until several years ago, 75-80 per cent of the butanol consumed in industry was in the form of the acetic ester. The expansion in the uses of ureaformaldehyde resins in the coating industry has recently changed this proportion. Butanol is used both in the resin kettle as the reaction medium and also as one of the solvents in the finish coating material. The result has been the sale of a larger proportion of butanol as such than was the case in the past. Recently a great deal of interest has been shown in the largescale production of 2,3-butyleneglycol by bacterial fermentation. Because of its low volatility, the recovery of the glycol presents a special problem. One proposal is t o extract the glycol from the fermented mash with butanol; 2 gallons of butanol would be used for each gallon of mash.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Another relatively new material (cellulose acetate butyrate) for plastics and coatings involves the use of butanol. Butyric acid is made by the two-stage oxidation of butanol, first in the vapor phase to butyraldehyde, and then in the liquid phase t o butyric acid. The use of butanol in the form of butyraldehyde for making polyvinyl butyral resins has already been mentioned. Since a plasticizer may, in most cases, be considered a nonvolatile solvent, mention should be made of the more important plasticizers produced from butanol. Butanol itself is used t o a small degree in the plasticizing of rubber. Dibutyl phthalate is one of the best plasticizers for nitrocellulose lacquers, for phenol-formaldehyde punch-stock resins, for other cellulose esters, and for flashless nonhygroscopic explosives. Dibutyl sebacate is the preferred plasticizer for the polyvinyl butyral resin. Thus, in safety glass butanol finds use both in producing the resinous material itself and as a plasticizer for it. Butanol owed its original growth to its use in nitrocellulose lacquers. Newer finishing materials have since appeared, although nitrocellulose lacquers continue to be sold in large volume. Even though the nitrocellulose lacquer usage may greatly diminish, it appears that the demand for butanol will continue; this product, either by itself or in the form of derivatives, plays an important part either as a solvent, a plasticizer, or an ingredient of many other products utilized in the finishing industry. Alkhough born in the first World War at which time it was con-
Vol. 35, No. 12
sidered an almost unusable by-produet, butanol is now playing an important part in our present war effort. There is every indication that it will continue to be needed for many peacetime uses. ACKNOWLEDGMENT
The author wishes to acknowledge the services of Charles L. Gabriel who found time to assist and to give advice well seasoned by twenty years of experience in the butyl-acetonic fermentation industry. LITERATURE CITED
Aronovsky, S. I., and Gortner, R. A.. IND.ENQ.CHEM..28 1270-6 (1936). Arroyo, R., J. Agr. Una'v. Puerto Rico, 18, 463-79 (1934). Fernbach, A , Brit. P a t e n t Application 21,073. Gabriel, C. L., IND. ENG.CHEM.,20, 1063-76 (1928). Govers, I?. X. (to Indian Refining Co.), U. S. P a t e n t 1,945,350 (Jan. 30, 1934). Killeffer, D. H., IXD.ENG.CZEM.,19, 46-50 (1927). Mezzandroli, G., a n d Magno, G., Giorn. chim. i n d . applicata, 10, 551-4 (1928). Microbiology (U. 5. S. R.), 8 , N o . 1, 38-55 (1939). Perkin, W. H . , Jr., J. SOC.Chem. Ind., 31, 616-24 (1912). Weizmann, C., Brit. P a t e n t 4845 (1912). PRESENTED as part of the Symposium on Solvents before the Division of Industrial and Engineering Chemistry at the 105th Meeting of the AxnRrcaN CHBMICAL SOCIETY, Detroit, X c h . Other papers in the symposium were printed in Ootober and on page 1230 of this issue.
High-pressure Absorption of c.G.K I R K B R I D E '
AND
J. W.
BERTETTP
P A N A M E R I C A N R E F I N I N G C O R P O R A T I O N . T E X A S CITY. T E X A S
I
N RECENT years there has been active interest in various methods of recovering distillate from high-pressure gas fields. This is particularly true of the Gulf Coast Region, inasmuch as state regulations have been established which do not permit wasteful processes for recovering the distillate. The regulations necessitate returning the residue gas to the reservoir from which i t originated, unless the gas can be sold for a useful purpose. By returning lean gas to the reservoir, the pressure on the formation is maintained a t the maximum, and there is very little loss of distillate due to retrograde condensation on the sand in the formation. The return of lean gas to the reservoir entails considerable compressor capacity which is dependent upon the difference in pressure between the input wellhead and that of the lean gas before compression. It is desirable from the standpoint of maintaining compressor capacity a t a minimum to carry out the recovery of distillate a t as near wellhead pressure as possible. Of course, other factors must be considered t o establish the optimum pressure. If retrograde condensation alone is used to recover the distillate, the separator pressure will ordinarily be about 500 to 1000 pounds per square inch at maximum distillate recovery. This leaves much to be desired since the wellhead pressures of many of the distillate fields are in excess of 3000 pounds; however, if higher separator pressure is used, the recovery of distillate declines rapidly. Furthermore, even at the optimum separator pressure, the efficiency of distillate recovery is not so high as desired. 1 2
Present address, Magnolia Petroleum Company, Dallas, Texas. Present address, Root Petroleum Company, El Dorado, Ark.
High-pressure absorption, on the other hand, is a method which should permit more efficient recovery of distillate at higher pressure. The design of high-prcssure absorbers, however, requires a knowledge of phase equilibrium at high pressure in systems with various types of lean oil. Few data are available which can be used as a basis for design. Few of the systems investigated and reported approach conditions which would be anticipated in a high-pressure absorber. The first paper which even approached anticipated conditions in a high-pressure absorber was that of Kata and Hachmuth ( 1 ) . They determined equilibrium constants of methane, ethane, propane, butanes, pentanes, and hexanes in a system of natural gas and a mid-continent crude oil at 40°, 120D,and 200' F. over a pressure range of atmospheric t o 3500 pounds per square inch. Figure 1 represents a n interpolation of their results for a temperature of 80" F. Their results showed that temperature affected the equilibrium constants much less above 800 pounds per square inch than at lower pressures; also, the effect of tcrnperature increased with increasing molecular weight of the hydrocarbon. Sage and Lacey ( 4 ) presented correlations of the equilibrium constant for methane in various binary systems, and showed that i t is not only a function of temperature and pressure but also of the chemical characteristics of the system. Sage, Hicks, and Lacey ( 3 ) recommended correlations, based on data available in the literature at the time, as the best available for solving problems on phase equilibria in production of crude oil and distillate. The most reliable of these correlations, however, were based entirely on the work of Katz and Hachmuth (1).
