INDUSTRIAL A N D ENGINEERING CHEMISTRY
June, 1925
615
Alcohol Motor Fuel from Molasses’ I-Use of Cane Molasses for Manufacture of Motor Fuel By E. C. Freeland 721 LOWERLINE ST.,N E W
ject of inquiries and researches into a means for converting this total loss into a gain. At times great difficulty was experienced in disposing of the molasses, which accumulated in large quantities on sugar plantations. Usually part of i t was used as a cattle food, part as a fuel, and sometimes it was mixed with irrigation water going into the
ORLEANS, L A .
T h i s paper contains a general discussion of the equipmerit needed, m e t h o d s of m a n u f a c t u r e , yields, a n d cost d a t a of alcohol a n d alcohol-ether m o t o r fuels from c a n e molasses, w i t h special reference to their m a n u f a c t u r e o n sugar plantations. Reasons for the u s e of alcohol fuels, m e t h o d s of and the research problems Of the chemical i n d u s t r y a r e also considered.
portion was thrown awayin fact, firms have actually been paid to take the molasses away from the factories. 2-Since the regulations for the sale of beverage alcohol have come into force in many countries, sugar factories which formerly manufactured beverage alcohol from either a portion or the whole of the molasses have been obliged either to curtail production or abandon the manufacture of this product. Therefore, not only producers of molasses as such, but also distillers who use molasses as raw material, have become interested in industrial alcohol as a means of utilizing the equipment in the distilleries. This search for a new use for alcohol in large quantities by both sugar manufacturers and distillers has naturally stimulated interest in fuel alcohol. 3-Owing t o the occasional scarcity of gasoline and the high cost of motor fuel in foreign countries, manufacturers and owners of internal combustion engines are eager to find a cheaper fuel. Nearly all the sugar-producing countries are dependent on outside sources for gasoline and kerosene, and hence the manufacture and use of home-produced fuel is being fostered by the governments of these countries, notably the dependencies of France and England and several of the South American countries. The progress of all agricultural industries is dependent upon the introduction and successful use of mechanical means of cultivation, and if the use of agricultural machinery is to expand to these countries there must be a cheap and readily available source of fuel for operating tractors, pumping engines, and other equipment run by internal combustion engines. 4-The fact that the world’s supply of crude petroleum is decreasing rapidly has caused scientists and manufacturers to become interested in obtaining a new liquid fuel. In this count r y we have about 60 per cent of the present available petroleum resources and consume 80 per cent of the world’s production. The growing number of motor cars and internal combustion engines naturally calk for a greater production of fuel, and it follows that our dependence upon foreign sources of supply is increasing and we are drawing on the resources of other nations which in time will need the petroleum now being sent t o this country. The production of motor vehicles is increasing a t a far more rapid rate than the production of crude oil and i t is very likely that in the near future there will be a real shortage of motor fuel. Meigs2 states that during the period that the production 1 Presented before the Division of Sugar Chemistry at the 68th Meeting of the American Chemical Society, Ithaca, N. Y., September 8 to 13, 1924. * “Gasoline and Other Motor Fuels,” p. 15.
out radical changes in design, as explosive mixtures of the
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~ ~o ‘ , ~ ~a” , ~ & , ~ ‘ ~ e s ~~ Same and the subsequent burning of these explosives matters in the engine
::Fwi’;”,
~~~d~~~~~ same results. The raw material for alcohol manufacture is annually reproduced by
country; hence there is an inexhaustible supply which is susceptible of great expansion without encroachment on food supplies. Yield a n d Composition of Molasses
The yield of sugar from sugar cane is usually about 9 to 10 per cent of the weight of the cane. The waste or final molasses amounts to about 30 per cent on the weight of the raw sugar manufactured. This corresponds to about 50 to 60 gallons per ton of sugar, or about 5 to 6 gallons per ton of cane, the average weight of a gallon of molasses being about 12 pounds. I n factories that do not have modern machinery, or in countries where the sugar juices are not high in quality, the production of molasses is sometimes 40 to 50 per cent higher. It is thus seen that the daily production of molasses of a sugar plantation is comparatively large, a factory crushing 1000 tons of cane per day producing 5000 to 6000 gallons of molasses. The molasses usually contains 50 to 60 per cent total fermentable sugars, depending upon the efficiency of the factory. In addition to sucrose, dextrose, and levulose, cane molasses contains other sugars which are unfermentable, ash, nitrogenous matter, and other impurities. The approximate analysis is as follows: Water Ash Sucrose Reducing sugars
Per cent 18 to 22 6 to 8 30 to 40 16 to 2P
Nitrogen bodies Soluble gums Free acids Combined acids
Per cent 2.5 to 3.5 2 to 3 1 to 3 2 to 4
Fermentation
In the manufacture of alcohol from molasses the first procedure is the dilution of the molasses with from five to six times its volume of water. The specific gravity of the molasses going from the factory varies from 1.38 to 1.42 or 75 to 80 per cent total solids, and a t this density fermentation is White, J . SOL.Aulomotiuc Eng., 12, 361 (1919); A m . Petroleum Inst., Bull. 182; Boyd, T H t S JOURNAL, 13, 836 (1021).
~
s
616
INDUSTRIAL AND ENGINEERING CHEMISTRY
not practicable. It is diluted either in special mixing tanks or in the fermentation vats until the specific gravity is about 1.06 to 1.075, or about 15 to 18 per cent total solids. Sometimes the solution is heated during mixing in order to,sterilize it. Either after or during dilution the molasses mash is usually acidified with sulfuric acid, in order to prevent the growth of undesirable yeasts and other organisms which lower the yield of alcohol by forming acetic acid, esters, higher alcohols, and other undesirable substances. The amount of sulfuric acid added varies according to the quality of the molasses and the type of fermentation. A molasses of poor quality requires a larger proportion of sulfuric acid than good molasses, which ferments quickly, and a pure culture of yeast requires much less acid than when poorer methods of fermentation are used. The proper acidity of the mash is usually considered to be 0.15 to 0.20 per cent4 calculated as sulfuric acid, but often this amount is exceeded, sometimes being as high as 3 per cent on account of large quantities of free acid in the molasses. The amount of sulfuric acid usually added is from 0.75 to 1.0 gallon per 1000 gallons mash, no attempt being made to regulate the degree of acidity of the molasses solution. A uniform acidity should be maintained, as the yeast becomes acclimated to a certain degree of acidity and any change causes a decrease in its vitality and consequent decrease in rapidity of fermentation. The hydrogen-ion concentration of the mash should be kept uniform, if possible, as this factor regulates the growth of the yeast. In modern distilleries, after the mash is acidified it is seeded with fermenting mash prepared from a pure yeast culture, but in some tropical countries no seeding is done, the mash being fermented by adventitious fermentation brought about by the natural yeasts present in the molasses and dilution water. According to modern practice the pure yeast culture is introduced into the pure culture apparatus and allowed to multiply in a previously sterilized molasses solution. After this pure culture mash is in active fermentation, the greater part of it is used to seed a still larger quantity of sterilized mash in open yeast tubs, and the remaining portion is retained in the pure culture apparatus in order to insure a continuous supply of mash fermented under sterile conditions. The fermenting mash in the open vats is used to seed the total quantity of mash, which is used for the production of alcohol. The following table shows the different stages in which this progressive seeding with pure yeast culture takes place :
Vol. 17, No. 6
menting mash, in order to hasten alcoholic fermentation and thus keep down the growth of wild yeasts, which do not produce alcohol. The amount of ammonium sulfate added is usually 8 to 10 pounds per 1000 gallons of mash. Sometimes ammonium fluoride instead of sulfuric acid is used as an antiseptic agent, the amount being about 1 pound per 1000 gallons. If no chemicals are used as antiseptic agents, or some form of pure yeast culture of compressed yeast is employed, fermented mash is transferred from one mash vat to another. The practice of not using any agent a t all to promote fermentation of the mash is to be condemned, as this method produces a very poor grade of alcohol, containing a large proportion of acetic acid, esters, aldehydes, etc. The fermentation vats for fermenting 5500 gallons of molasses daily (33,000 gallons of mash) should be of approximately 80,000 to 90,000 gallons capacity in units of 5000 to 6000 gallons each. For tropical conditions small fermentation vats are preferable to large ones, as the temperature of the mash during fermentation is likely to go too high in thelatter, thus causing a loss of alcohol. Fermentation of the mash proceeds rapidly and is usually completed in 48 to 60 hours. During this period the temperature gradually rises to 35 “-37’ C. (95’-98’ F.). The specific gravity of the mash after fermentation is about 1.010 to 1.015, depending upon the sugar content of the molasses, original gravity of the mash, and method of fermentation. The alcohol content of the fermented mash is from 5.5 to 7 per cent by volume. Distillation
The mash is distilled as soon as possible after fermentation, in order to avoid loss of alcohol. Distillation of the alcohol from the mash is carried out in either intermittent batch stills or continuous column stills. The latter produce a much purer alcohol by eliminating fusel oil, esters, aldehydes, etc., and the steam consumption is much less-about 50 per cent of that of a combination of continuous beer still and periodic (batch) rectifier. The quality of the product is more uniform because the separation is continuous and the optimum operating conditions can be constantly maintained by automatic control. It is possible, however, to produce a high grade of alcohol with a periodic rectifier, although the quality of product is dependent upon the skill of the operator in controlling temperature and rate of distillation. The “heads” impurities, which have a lower boiling point than ethyl alcohol, are collected as the first fraction, the second is an intermediate grade of alPER 1000 GALLONS MA~H cohol, the third the pure fraction, and the fourth an intermeP U R E CULTURE APPARATUS: 110 gallons diate grade of alcohol and a residue of fusel oils, which have a Molasses 20 Ibs. Sulfuric acid higher boiling point than ethyl alcohol and which may be dis2 . 5 Ibs. Ammonium sulfate7 Specific gravity about 1.045 tilled over or worked up in a separate rectifying still, in order YEAST MULTIPLICATION VAT: to avoid fouling of the rectifying column. 120 to 150 gallons Molasses 10 Ibs. In the continuous process the fermented mash is first boiled Sulfuric acid 2.5 lbs. Ammonium sulfate in a beer still to separate all the alcohol from the mash, Specific gravity about 1.060 and this alcohol is afterwards concentrated and purified in the FERhlaBNTATION VATS: 1.50 to 200 gallons Molasses rectifying column, The alcohol is expelled from the mash in 8.25 to 8.76 Ibs. Sulfuric acid the beer still by blowing jets of steam into it, the mash being Specific gravity 1.065 to 1.070 spread in layers over a considerable surface. The mash enters The yeast multiplication vat is set with 10 to 12 per cent of near the top of the beer still and the steam jets are a t the fermenting yeast culture, whereas the fermentation vats are bottom, and as the steam rises it meets the mash and carries usually set with 5 to 8 per cent of fermenting mash. Some- off the alcohol vapor. The mash passes downwards over times larger quantities are used, especially in small fermenta- a series of perforated copper plates, or “decks,” upon which tion vats, in order to hasten fermentation. Large quantities of the alcohol vapor is partly condensed. The perforated decks yeast added to large vats, however, result in too rapid rise in allow an upward passage of alcohol vapor; but inasmuch as temperature. part of the alcohol is retained on each deck the vapor moving Even in distilleries not using pure yeast culture, ammonium upward near the top of the still must bubble through the mixsulfate as well as sulfuric acid is usually added to the fer- ture of alcohol and mash. This is accomplished by bending the edges of the perforations upward and placing over each 6 Scard, “Tropical Power Alcohol,” Wcsf India Commitfee Circular, a cap having slotted edges. The edges of the caps dip under August 4, 1921.
June, 1925
INDUSTRIAL .4AVD ENGINEERING CHEMISTRY
the surface of the alcohol-mash mixture, forming a liquid seal. The caps are slotted in order to break the vapor into small bubbles and thus increase the surface of the vapor coming in contact with the liquid on the decks. It is important that the vapor be brought into contact with a fresh supply of liquid on the deck, and for this reason a proper distribution of the liquid around the boiling caps is essential. Any stagnant areas of liquid on the decks will be quickly reduced to the same composition as the ascending vapor and no exchange of heat will take place while the remaining portion of the deck area is overtaxed, resulting in channeling of the alcohol solution down to the base chamber. On each deck an overflow pipe dips into the liquid on the plate below, so that when the level of the liquid on a deck reaches s certain point it overflows to the plate below. The function of the beer still is to strip the mash of all volatile components and to concentrate the distillate to 50-60 per cent alcohol by volume. I n the United States beer stills are sometimes made with perforated decks throughout, although occasionally perforated decks are used below the mash feed inlet pipe and boiling-cap decks above the feed pipe. Boiling-cap decks are much more efficient. but are difficult to clear of the deposits of solids usually present in the fermented mash. A continuous still operates on the principle that the vapor standing over a mixture of higher and less volatile liquids will contain a greater proportion of the higher volatile substances than is present in the liquid mixture. The purpose of both the beer still and the rectifying column is to subject the alcoholic liquid to a series of successive boilings. In this way each deck is a small still within itself receiving alcohol vapor from the deck below, condensing part of the impurities, and distilling the stronger spirit to the deck above. The efficiency of the decks will depend upon the thoroughness with which the vapors from the liquid of the deck below are brought into contact with the liquid on the deck above. These ascending vapors are a mixture of steam and alcohol, and in its passage through the liquid on the deck an exchange of heat is effected, resulting in the partial condensation of the less volatile steam and the vaporization of the more volatile alcohol in the liquid. In this way the temperatures decrease from the bottom to the top of a still while the concentration of the alcohol correspondingly increases. There are usually from twelve to fifteen plates in the beer still. By the time the mash reaches the lowest plate of the beer still, all the alcoho1,has been distilled and the de-alcoholized mash passes out through the mash heater, where part of the heat in it is transferred to the mash going into the still. Usually the de-alcoholized mash, or “lees,” is thrown away; but sometimes it is dried, burned, and afterwards used as a fertilizer, as it contains appreciable quantities of potash. Inasmuch as no mineral matter present in the molasses is lost during fermentation, the amount of recoverable potash is the same as that present in the molasses. Molasses contains’6 to 8 per cent ash, of which about 40 per cent is potash, SO that for every 1000 gallons (12,000 pounds) molasses fermented it is possible to recover 288 to 384 pounds KzO. Continuous stills are usually connected directly to continuous rectifying columns, although rectification may be accomplished in a separate still. When directly connected the alcohol vapors, which also contain steam and other impurities, pass upward from the top of the beer still into a reflux condenser, where part of the impurities are condensed and flow back into the top of the beer still. The alcohol vapor passes through the reflux condenser into the bottom of the rectifying column, which is of similar design to the beer still. The alcohol vapor is concentrated and purified in the rectifying column and the impurities are drawn off at the points of maximum concentration.
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The purified alcohol, being of higher boiling point than the “heads” impurities and of lower boiling point than the fusel oils, must be drawn off where there is minimum concentration of impurities, which is near the top of the rectifying column. The alcohol vapor passes from the top of the rectifying column into the condensers, where a spirit containing the very volatile (“heads”) impurities is condensed. The fusel oils, which are of higher boiling point than ethyl alcohol, are drawn off near the feed inlet of the rectifying column where they accumulate. For motor fuel production a two-column continuous still is usually used, although sometimes an additional purifying column is added. In a two-column continuous still, the rectifying column usually contains from thirty-five to fifty decks, whereas in a three-column still the purifying column is placed between the beer still and the rectifying column, and this purifying column contains about twenty-four decks, which in both rectifying and purifying columns are similar in design to those in the beer still.s Quality of Alcohol Produced
Alcohol for fuel purposes must not contain more than a small quantity of impurities that will cause corrosion, such a.s acids and esters, and especially fusel oils. The amount of acid should not be above 10 parts acetic acid per 100,OOO parts absolute alcohol, and the amount of esters calculated as ethyl acetate should not exceed 15 parts per 100,000 parts absolute alcohol. It is sometimes necessary to add dilute sodium hydroxide solution in the lower part of the rectifying coIu11111,in order completely to neutralize the acids in the alcohol and saponify the esters present. Such treatment should be given before the alcohol vapor is condensed, as neutralization of the liquid alcohol does not remedy the diaculty. The strength of fuel alcohol should be a t least 95 per cent by volume. Although the strength of the alcohol does not bear a constant ratio to the amount of impurities, nevertheless higher distillation temperatures are usually employed in the production of weak alcohol and this increases the amount of less volatile impurities. This is especially true with alcohol produced in stills designed for rum production, as they usually distil a spirit containing about 90 per cent alcohol and a large proportion of esters, acids, etc., which add to the quality of beverage alcohol but are deleterious for fuel purposes. The alcohol drawn off from the top of the continuous rectifying column is usually mixed with the final condensate containing the “heads” impurities, as the latter are not injurious to automobile engines. The very pure alcohol drawn off from the top of the rectifying column may be used for the production of ether, as it contains a minimum quantity of impurities, and the alcohol from the final condensers is used to mix with the ether. Yields h v Different Types of Fermentation8 Chllons molasses - -...-.-.. U. S. gallons abso55% fermoentable Per cent lute alcohol per sugars 42 Be. per TYPEO F FERMEN-of theo100 Ihs. fermentgallon absolute TATION retical able sugars alcohol Natural yeast 40 to 60 2 . 9 to 4 . 4 3 . 5 to 5 . 4 Compressed yeast 50 to 75 3 . 6 to 5 . 5 2 . 8 to 4 . 2 2 . 5 to 3 . 3 Antiseptic agents 70 to 85 5 . i to 6 . 2 Pure yeast culture S5 to 95 6 . 2 to 6 . 9 2 . 2 to 2 . 5 Table I-Alcohol
Yield of Alcohol
The theoretical yield of alcohol from hexose sugars is 51.1 per cent by weight, and from sucrose it is 53.8 per cent. In practice the theoretical yield is never attained, even under optimum conditions, on account of the presence of microorganisms in the mash which cause the production of substances 6 Robinson, “Elements of Fractional McGraw-Hill Book Company. 1 Louisiana Planler, 69, 13 (1917).
Distillation,” 1944, p. 142.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
618
of 96 Per c e n t Alcohol per 106 Gallons Molasses7 (Molasses 41.3’ Be. = 1.40 sp. gr.) -YIEI,D IN PER CENT OF THEORETICAL70 75 80 82 84 86 88 32.1 27.4 29.4 31.3 32.9 33.7 34.5 33.6 28.7 32.7 34.4 35.2 36.0 30.7 35.0 29.9 34.2 35.9 36.7 32.0 37.6 36.5 31.1 33.3 35.6 38.2 39.1 37.3 37.9 32.4 34.7 37.0 39.8 38.9 40.7 39.4 33.6 36.0 38.4 41.3 40.4 42.3 42.8 40.8 34.9 37.4 39.9 41.8 43.8 42.3 44.4 41.3 43.4 36.1 38.7 45.4 43.7 45.8 42.7 44.7 37.3 40.0 46.9 45.2 47.4 41.4 44.2 38.6 48.5 46.3 46.7 49.0 42.7 45.5 47.8 39.9 50.1 48.2 47.0 49.3 41.1 44.0 50.5 51.7
Vol. 17, No. 6
Table 11-Gallons Per cent fermentable sugar in molasses 44 46 48 50 52 54 56 58 A0 62 64 66
r
60 19.6 20.5 21.3 22.2 23.1 24.0 24.9 25.8 26.7 27.6 28.5 29.4
60 23.5 24.6 25.6 26.7 27.8 28.8 29.9 31.0 32.0 33.1 34.2 35.2
other than alcohol, such as esters, aldehydes, acetic acid, succinic acid, glycerol, and also on account of the presence in the molasses of salts and organic nonsugars, which aid in the production of these impurities. The alcohol yield depends primarily upon the type of fermentation employed and the kind of still in which the mash is distilled. Magne gives Tables I and I1 showing the yields of alcohol with good distillation equipment. Denaturation of Alcohol
The question of a standard denaturant for pure alcohol is occupying the attention of chemists all over the world, the high cost of denaturing power spirit being a t present a serious drawback to the extension of the fuel alcohol industry. Sir James Debbie* points out that a denaturant should satisfy the following requirements: 1-It should impart a taste or smell sufficiently disagreeable to prevent the alcohol from being drunk, even after diiution, sweetening, and flavoring. 2-It should not be easily removed by filtration, distillation, or other readily applied process. 3-It should be easily and certainly detected. 4-It should mix readily with the spirit without altering its properties in manufacturing operations. 5-It should not add materially to the cost of the alcohol.
Among the denaturants used a t present for power alcohol are the following: crude methanol (wood naphtha), pyridine bases, aniline oil, benzene, bone oil, acetone, mineral oils (gasoline and kerosene), ether, turpentine, tobacco oil, the distillate obtained from scrap vulcanized rubber (“caoutchoucine”), Simonsens oil. The use of an aniline dye, such as methyl blue, methyl violet, etc., to color the power alcohol is compulsory in some countries. The following formulas for denaturing power alcohol are given to show the ingredients used in several c o u n t r i e ~ : ~ UNITED STATES: 2 gallons wood alcohol 0 . 5 gallon pyridine
1
per 100 gallons
5 gallons ether 2 gallons benzine 1 gallon pyridine
i
0 . 5 gram methyl violet GERMANY : Wood naphtha 4 parts 1 part pyridine bases to which mixture is added 50 grams lavender and rosemary oil per liter To every 100 liters of alcohol 1.5 liters of above mixture are added, together with 0.25 liter methyl violet solution and 2.20 liters benzol “The Manufacture of Alcohol from Molasses and Cane Juice,” p. 22. J . SOC. Chem. I n d . , 89, 86R(1920). U. S. Internal Revenue Regulations 61; Simmonds, “Alcohol,” 1919, The Macmillan Co.; Monier-Williams, “Power Alcohol,” 1922, Oxford University Press. 7
8
*
90 35.2 36.8 38.4 40.0 41.6 43.2 44.8 46.5 48.0 49.6 51.2 52.8
92 36.0 37.7 39.3 40.9 42.6 44.2 45.8 47.5 49.0 50.7 52.4 54.0
-94 36.8 38.5 40.2 41.8 43.5 45.2 46.8 48.5 50.2 51.8 53.5 55.2
100 39.2 40.9 42.7 44.5 46.3 48.1 49.8 51.6 53.4 55.1 57.0 58.7
FRANCE: Ninety per cent wood naphtha containing 25% acetone with 2.5% pyroligneous impurities used as a denaturant and 10 liters of it is used per 100 gallons alcohol
The selection of a suitable denaturant for alcohol is of great importance in motor fuel manufacture, for the following reasons: I-The denaturant must not give motor spirit an obnoxious odor, as this will prejudice the public against it. Pyridine, for example, has a very objectionable odor and when alcohol denatured with pyridine is spilled on the hands the odor is very hard to remove. 2-It must not corrode the engine cylinders. Crude wood naphtha is not a good denaturant for this reason. 3-On evaporation it must not leave any residue to clog the fuel pipes, carburetor jets, etc. Some grades of crude aniline oil cannot be used because a very fine deposit settles out in the fuel tanks. If higher petroleum distillates are used, they should not leave any tarry residue. 4-The denaturant must be cheap, so that it will not add materially to the cost of the fuel.
The use of an aniline dye to color motor spirit is undesirable, as the public usually prefers a colorless liquid. Moreover, it is hard to color different quantities of alcohol to the same tint without the aid of colorimetric apparatus. The color of the tinted spirit gradually fades, and the fuel has to be recolored. Lots stored over different periods of time have different colors. The best denaturants for power alcohol are benzene, petroleum naphtha, and ether. Simonsens oillo and caoutchoucine” have been suggested. Simonsens oil is crude petroleum distilled under 300” C. Alcohol denatured with 0.5 per cent of this substance possesses an abominable taste without having an objectionable odor. Australia, South Africa, Portugal, East Africa, and British India have accepted this material as a denaturant. Caoutchoucine is the distillate obtained by heating vulcanized rubber and consists mainly of polyterpenes.
,
Ether Manufacture
per loo
2 gallons wood alcohol per 100 gallons 0 . 2 5 gallon pyridine 0 . 5 gallon benzine (kerosene) GREATBRITAIN: Spirits 90% Wood naphtha or methanol 9.5 yo Crude yridine 0.5% by volume mineral naphtha or petroleum and not less than Also 0.025 oz. methyl violet Der 100 aallons spirits Wood naphtha 2.%% Crude pyridine 0.5% Benzene 5% Methyl orange 0.05 0 2 .
-
I n order to obviate some of the difficulties attending the use of denatured alcohol as a motor fuel and to produce a fuel with greater commercial possibilities, substances have been added to increase the volatility, vapor pressure, and explosive range of the mixture, thereby enabling existing engines to be used with only slight modifications. Gasoline, benzene, acetone, ether, etc., have been proposed for this purpose, and some of these mixtures have been very successfully used. The use of ether in alcohol motor spirit mixtures has expanded, not only on account of its favorable physical and chemical properties, but also because it can be easily and cheaply produced from alcohol. Ether is very volatile, has a high vapor pressure, an extremely wide range of explosive mixture with air, and burns with no solid product of combustion, It is therefore possible to produce a fuel mixture from molasses which can be very successfully used in gasoline engines, giving great power, feed, and flexibility, combined with smoothness of operation and ease in starting. 10
Inlern. Slrgar J . , 28, 268 (1921); Norwegian Patent 23,679 (June 24,
1912). 11
Monier-Williams, “Power Alcohol,” p. 205.
June, 1925
IIVDUSTRIAL A N D ENGINEERING CHEMISTRY
The usual process of ether manufacture consists in heating a mixture of 9 parts by weight of concentrated sulfuric acid and 5 parts by weight of alcohol (equal parts by volume) in a lead-lined still to about 130" C. (266" F.), a t which temperature ether vapor begins to distil off. With constant addition of alcohol in proportion to the loss in volume of the original mixture, the formation of ether is maintained continuously. The temperature is kept constant in order to regulate the proportion of ether in the vapor, as below 130' C. much alcohol vapor passes over and above 140" C. ethylene gas is formed. The distillate of crude ether thus obtained contains sulfur dioxide, water, alcohol, and also the products of side reaction. In order to neutralize and purify the gas, the ether vapor is washed in a scrubbing apparatus with a dilute solution of sodium hydroxide and then rectified by further distillation in a rectifying column, similar to the same apparatus of an alcohol still. The ether generator is constructed of steel with a lead lining and is heated by means of a steam jacket or internal steam coils made of lead. The alcohol flows by gravity through perforated lead pipes into the generator. The scrubber is similar to the usual alcohol rectifying column, with a series of plates upon which are layers of sodium hydroxide solution. As the ether vapor bubbles through the solution it is neutralized. A continuous supply of sodium hydroxide is maintained in the scrubber by allowing the solution to run continuously into it, the spent solution being drained off a t the bottom of the apparatus. Recently, an ether-generating system especially designed for motor fuel production in tropical countries has been put on the market. This apparatus provides for the continuous production of a mixture of alcohol and ether without the use of refrigerating machinery, in a manner which obviates the necessity of denaturing the alcohol before it is used in the manufacture of ether and which will comply with all revenue regulations. The mixing of the alcohol and ether should be done continuously as the ether flows from the final condenser of the ether still, in order to prevent loss of ether by evaporation and also to reduce fire risk. The specific gravity of the final product should be regulated by a continuous recording device, such as the Bailey specific gravity recorder, which is of the compensating type and gives the specific gravity to the mixture a t any standard temperature (usually 15.5" C. or 60" F.) regardless of the actual temperature of the liquid. I n the manufacture of ether only a very high quality alcohol should be used in the ether still. The alcohol should be of as high strength as possible in order to lower the amount of rectification, and should contain a minimum quantity of acids and esters in order to obviate corrosion of the lead lining and pipes. A poor quality of alcohol neutralized with caustic soda cannot be used, for as soon as it comes in contact with ethyl sulfuric acid in the generators, the acids originally present in the alcohol will be liberated and corrosion will take place. The best grade of alcohol is that drawn off from the top of the rectifying column of the alcohol still, as it contains a minimum quantity of impurities and hence will have no deleterious action on the lead lining of the ether still. The sulfuric acid used in the generator should be free from nitric acid, which corrodes lead. The temperature of the alcohol and ether mixture should be as low as possible, in order to prevent loss of ether. I n tropical countries this temperature can easily be kept close to 27" C. ( 8 0 O F . ) . Automatic addition of the denaturant materials to the alcohol-ether mixture should be provided, so that these substances will be intimately mixed with the alcohol-ether fuel as it comes from the still. The denaturants should not be mixed or stirred into the fuel when it is in the storage tanks, as violent agitation will cause a loss of ether. The fuel
619
storage tanks should be located in a cool place, convenient to transportation facilities. The proportion of ether in the final mixture depends largely on the cost of ether manufacture, the quality of fuel desired, and local climatic conditions. Usually, from 25 to 35 per cent by volume of ether is used in the mixture, although the percentage may go as low as 20 or as high as 45. For general use in motor car engines, as a substitute for gasoline, a mixture containing 35 per cent ether and 65 per cent alcohol will be satisfactory. Yield of Ether from Alcohol
The theoretical yield of ether from alcohol is 74 parts by weight per 92 parts absolute alcohol, or 80.4.5 per cent. If 95 per cent alcohol is used, the theoretical yield is 76.41 per cent. The yield in actual practice is 90 to 92 per cent of the theoreticrtl, so that 100 gallons of 95 per cent alcohol will produce 78 to 80 gallons of ether, or 1.3 to 1.25 gallons 95 per cent alcohol per gallon ether. Cost of Manufacture
The cost of manufacturing alcohol and alcohol-ether motor fuels and their price as compared with that of gasoline will vary widely depending on local conditions. Cost of labor, the value of the molasses used, and the price of gasoline are the controlling factors in determining whether the manufacture of alcohol fuel will be profitable and also whether a market can be established. I n some countries remote from the channels of trade the value of the molasses is very low and the price of the gasoline high, consequently the production of alcohol fuel will be a profitable venture; whereas in countries that are near large markets where the price of gasoline is usurtlly low, the sale of molasses is more profitable. Table 111 shows the approximate cost of the equipment necessary to convert the entire amount of molasses produced from lo00 tons of cane per day into motor fuel. It is estimated that 5500 gallons of molasses are available for 24 hours and that 2.5 gallons of molasses are required per gallon of 95 per cent alcohol or 2.75 gallons per gallon of 65 per cent alcohol-35 per cent ether motor fuel. Both the alcohol and ether stills are designed to operate on a 24-hour basis, as operation of a continuous still only part of the day results in a considerable loss of time and material. The operation of the ether still should be continuous, as stopping and starting injures the lead equipment through expansion and contraction and also increases the chance of corrosion. Cost of E q u i p m e n t for a P l a n t Handling 5500 Gallons of Molasses per Day FERMENTING A N D YEASTING: Molasses heater, mixer and strainers; lead-lined acid tanks, molasses sterilizer; yeast tubes, fermenters, mash feed tanks $1 1,600 Pure yeast machine 3,500 ALCOHOL STILL: Continuous type, providing for fusel oils separation; automatic regulators, and efficient heat exchanger for utilizing waste heat of slop 24,500 ETHERGENERATOR AID RECTIFIER: Capacity 600 gallons per day, improved type; including patent system of condensation, automatic denaturing device, and specific gravity recorder 17,000 TANKSA N D PUMPS: Tanks for fusel oils, alcohol supply tanks, discards tank, motor fuel storage (17,000 gallons), molasses, water, mash, 7.400 and alcohol DumDs Air compressor, scale tanks 2;500 Plant piping and lighting 5,000 Boiler nlant i n nnn Molasses-storage tanks 6,000 Alcohol drums 6,000 Buildings 25,000 Sundry items 1,500 TOTAL . . . . . . . . . . . $120,000
Table 111-Estimated
._.___
The cost of manufacture of 65 per cent alcohol-35 per cent ether mixture will be approximately as follows, estimating 15 per cent interest and depreciation on $140,000 and an annual production of 300,000 gallons in 150 days:
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
620
Per day $140 60 40 40
Interest, depreciation, and insurance Fuel, 30 barrels oil a t $2 Chemicals and denaturants Supervision a n d labor
Per gallon $0.07 0.03 0.02 0.02 $0.4
$286 This estimate allows for a working capital of $10,000 and provides for the operat'ion of the plant only six months of the year, or during the sugar-producing season. If extra molasses is bought and converted into motor fuel, which is usually profitable in a plant, of this size, the cost per gallon will be decreased several cents, as by so doing the interest and depreciation charge per gallon will be materially reduced. By running the plant continuously the cost per gallon can be reduced t o about 10 cents. The estimate does not include the value of the molasses, which will vary widely, depending on local conditions. Assuming 1 gallon of gasoline to have a mileage value of 1.2 gallons of 65-35 per cent alcohol-ether fuel, the following table shows the total cost per gallon of alcohol fuel and also the cost of the equivalent of 1 gallon of gasoline: Cost of moValue of molasses in I Cost of lasses per gallon gallon of fuel production Cents Cents Cents 1 2.75 14 1 5 4.125 14 2 5.5 14 2.5 6.875 14 3 14 8.25 3.5 9.625 14 4 11.0 14 4.5 14 12.375 5 14 13.75 5.5 14 15.125 6 16.5 14
.
Cost of fuel equivalent to l Total cost gallon of gasoline Cents Cents 16.75 20.10 18.125 21.75 19.5 23.40 20.875 25.05 22.25 26.70 23.625 28.35 25.0 30.00 26,375 31.65 27.75 33.30 29.125 34.95 30.5 36.60
McCleary and Ageel* give the following formula for calculating the realization made on molasses by converting it into motor fuel and substituting it for competing oil fuels:
R
= realization for molasses, dollars per ton
Y = yield of alcohol fuel, gallons per ton molasses
K
= cost of competing fuel, dollars per gallon
f
= factor for converting gasoline into alcohol = cost of alcohol fuel, dollars per gallon
A YK R = - - Y A , or Y
(f
-A) f The following formula can be used to find the Yalue of the molasses per gallon: M = gallons molasses per gallon fuel V = value per gallon molasses m = cost of manufacture per gallon fuel E = eauivalent rrallons motor fuel -Der gallon gasoline G = cost per galion of gasoline [ ( M V ) m ]E = G Solving for value of molasses per gallon V: - mE v = GME Chemical Control
+
The production of alcohol motor fuel must be subject to careful chemical control in order that maximum yields and uniform product may be obtained. I n order to do this the following analytical data may be kept+ MOLASSES : Complete analysis Total amount fermented Total pounds sugars (calculated as glucose) MASH: Total amount fermented Density before fermentation . Density after fermentation Acidity before fermentation Acidity after fermentation 1 2 Report of Committee on Manufacture of Sugar and Utilization of By-products to Hawaiian Sugar Planters Association, 1922. 18 For Methods of Analysis see Assoc. O5cial Agr. Chem., Methods; Simmonds, "Alcohol," 1919, The Macmillan Co.
Vol. 17, No. 6
Reducing sugars in fermented mash .4lcohol in fermented mash Alcohol in spent mash (after distillation) Frequent bacteriological examination of yeast cultures and mash in order t o control fermentation
ALCOHOL: Amount produced Per cent absolute alcohol in commercial alcohol Per cent esters, aldehydes, acetic acid, etc., in alcohol Analysis of fusel oil ETHERSTILLCONTROL: Acidity of condensed steam (to locate leaks) Alkalinity of spent solution from scrubber Analysis of ethyl-sulfuric acid and sulfuric ether" Alcohol in condensed water from rectifying column ALCOHOL-ETHER MOTORFUEL: Total amount produced Per cent alcohol Per cent ether Amount alcohol in motor fuel Amount ether in motor fuel16 Acidity Amount denaturants YIELDS: Theoretical amount absolute alcohol possible from molasses -4mount absolute alcohol produced Per cent of theoretical yields obtained Gallons of molasses per gallon alcohol Gallons of molasses per gallon motor fuel Gallons of alcohol per gallon ether Gallons of alcohol per gallon molasses Gallons of motor fuel per gallon molasses CHEMICALS: Amount used Analysis and purity control of chemical used in manufacture Analysis and purity control of denaturants
Research Problems
The production of motor fuel from molasses may be classed as an infant industry. Although rapid strides have been made towards its stabilization since this product was first introduced, there are numerous problems still to be investigated; in fact, its establishment on a sound and permanent basis depends upon whether or not the difficulties can be overcome. Among the problems to be solved are the following: Use of Diferent R a w Materials for Alcohol Manufacture. Ormandy'6 estimates that 5 per cent of the American grain crop would yield sufficient motor fuel t o replace the gallons demanded in America. A study of the possibilities of tropical crops as raw material should be undertaken. More Ejicient Methods of Fermentation and Distillation. Increased yields of alcohol from molasses, and also of etherfrom alcohol, will lower the cost of production and thus allow the fuel to be sold a t a lower price. Methods of Producing Absolute Alcohol. The production of absolute alcohol for motor fuel purposes will eliminate many difficulties now encountered, as absolute alcohol will mix more readily with many substances than 95 per cent alcohol. Means of Stabilizing Ether. The amount of ether present in motor fuel mixtures gradually decreases through evaporation, owing to its high volatility. Moreover, autoxidation of ether takes place,'? forming ethyl peroxide, acetic aldehydes, and acetic acid. Means for reducing this loss should be studied. Composition of Fuel. The type of fuel produced a t present does not give maximum efficiency and better motor fuel mixtures should be developed. Denaturants. The present cost of denaturing alcohol is very high and very often the denaturant is not suitable. There is great need of a cheap and efficient denaturant. Cause of Corrosion in Engine Cylinder and Method of Prevention. A large amount of work has already been done on this problem, but further work is necessary in order to eliminate all corrosion and pitting of engine parts. Adaption of Fuel to Existing Engines and Development of N m Types of Engine. A means of securing better results, using alcohol fuel in existing engines, and the development of special alcoButler and Dunnicliff,J . SOC.Chem. Ind., 89, 146 T (1920). Freeland, Louisiana Planter, 69, 97 (19223. l e J . Intern. Petroleum Tech., 6, 33 (1918). 17 Clover, J . A m . Chem. Soc., 44, 1107 (1922).
14 1)
I N D U S T R I B L A X D ENGINEERIA7G CHEMISTRY
June, 1925
hol engines will increase the amount of work secured from this fuel and therefore extend its use. Regulations Regarding Manufacture of Industrial Alcohol. In almost every country where alcohol is manufactured, beverage and industrial alcohol are put on almost the same basis with regard to government regulation. A change in this system is essential to the establishment of the industrial alcohol industry. Patent Regulations. The following statements with regard to the motor fuel patent system in Great Britain are applicable to other countries as well, and explain the situation thoroughly:
'
A number of mixtures patented in Great Britain, containing alcohol, ether, fatty acids, combustible gases, etc , with or without hydrocarbons, contain nothing essentially new and patents shoiild not have been granted.18 It is felt by the Empire Motor Fuel Committee that great damage may be done to the'prospect of early production of new motor fuels, if disregard is shown b y Patent Office for the known miscibility within various limits of .alcohol, benzol, petrol, and other hydrocarbons. The committee wish to give warning t o the investing public that any claim to B master patent should in any conceivable circumstances be viewed with the maximum of doubt.19
Marketing. Means of establishing and maintaining a market for motor fuel should be studied; moreover, it should be sold a t a price in proportion to its fuel value. Alcohol motor fuel will never compete with gasoline unless the consumer is able to secure with it a greater mileage for a given sum. The motor car owner is reluctant t o change from a standard fuel to one that is not so well known, and the greatest inducement that can be offered is the ability to secure cheaper mileage without risk of damaging the motor car. Regulation of Quality of Product Marketed. A high-grade product must be manufactured if a market for alcohol fuel is t o be steadily maintained. It cannot hope to compete with gasoline 18 '0
Ormandy. 1nlei.n. S u g a r J . , 22, 402 (1919). Report of Ernpirc Xlotor Fuel Committee, 1920.
6 21
if quality standards are not maintained. One or two manufacturers of a low-quality product will often destroy the entire market for a commodity, even though there are numerous other producers who maintain high-quality standards. Unscrupulous retailers often add water to the motor fuel, and means for detecting this adulteration should be established. Educational Work. The education of the consumer as to the best means of securing satisfactory results is one of the most important factors in the establishment of an alcohol motor fuel industry on a sound and permanent basis. Even though a highgrade fuel is marketed a t a reasonable price, the industry will never prosper so long as each individual motor car owner has to make an experimental laboratory out of his own car and find out for himself the proper way of using alcohol in place of gasoline. The distillers who are attempting to introduce alcohol fuel into a new locality should certainly exert every possible effort to see that the operators understand how to secure maximum mileage.
Conclusion
Although the alcohol motor file1 industry has not yet been firmly established, its present rate of growth indicates that it will expand greatly in the near future. In almost every country the question of future fuel supplies for internal combustion engines is receiving thorough consideration, and it seems very likely that the use of alcohol will increase rapidly, especially if there is any diminution of the petroleum supply. In the United States, where there are greater supplies of refined petroleum than in any other part of the world, the sale of fuel mixtures, containing alcohol, benzene, and other substances, has already been started and probably large quantities of these mixtures will be used if the price of gasoline goes very much higher than the present lel-el.
Apparatus for Accurate Analysis of Small Quantities of Gas' By D. S. Chamberlin and D. M . Newitt LEHICHU N I V E R S I T Y ,
B E T H L E H E M , P A . . A N D I X P E H I A L C O L L E G E OF S C I E N C E A S D TECHNOLOGY, L O S O O N . E S G L . l N i n
HE demand for a device by which small amounts of gas (1 to 5 cc.) can be accurately analyzed, and which will eliminate the disadvantage of leaky taps, has led to the development of the apparatus shown in the figure. The apparatus works on the constant-volume principle. Take the zero reading by lowering H. Raise H until the U-tube is full of mercury. Transfer the sample to B and allow it to rise to the absorption vessel, A , by lowering H . (Note the special design of A to give the maximum surface for reagents.) Lower H until the surface of mercury is a t the mark E. Close the tap F , lower H to get the reading of gas pressure. Suck the reagent through K and F into B, remove any air, then by opening F slowly transfer reagent to A . Shake until absorption is complete. Cautiously turn F so that reagent is nearly all sucked away. Shut off F , half fill B with 1 per cent sulfuric acid. Let it rise into A . Wash well and suck away the acid as completely as possible through F . Lower H with F open, until the mercury is a t E. Shut F. Take a reading. Repeat ad infinitum. To clear all the gas from the apparatus, transfer to A , open L and F , and it will be drawn by suction into the pot, D. When once the gas has been taken in to the apparatus it does not pass through any taps or rubber connections during the analysis. The U-tube is calibrated in millimeters, the read1 Received LMarch 12, 1928 Presented before the Section of Gas and Fuel Chemistry a t t h e 69th Meeting of the Amerwan Chemical Society, Baltimore, M d , April 6 to 10 1925
ings can be made by a cathetometer to a fraction of a millimeter, an accuracy of 0.01 per cent. The samples of gas for analysis in this apparatus can be easily stored in test tubes over mercury.
Qm
4
