Sept., 1922
THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
The demands for petroleum are increasing in this country at the rate of about 50,000,000 bbls. a year. We have in prospect no source of fuel oil, gasoline, or gasoline substitute other than oil shale that promises to furnish even a minor part of this demand. T o meet this, even without making any allowances for the expected decrease in production from
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oil wells, will require each year the building of 75 shale-oil plants, each handling 2000 tons of oil shale daily, and each representing an investment of nearly a million dollars. And yet some men feel that the industrial need for chemical engineers and chemists is limited!
T h e Application of Chemistry t o t h e Conservation of Motor Fuels By Thomas Midgley, Jr., and T. A. Boyd CHIEFAND ASSISTANT CHIEF,FUELSECTION, GENERAL MOTORS RESEARCH CORPORATION, DAYTON,OHIO
T
HIRTY years ago the first antomo-
petroleum that did not keep pace with the rising demand for mot80rfuel: (1) By putting an increasing percentage of the distillate from the crude oil into the pasoline fraction; (2) by cracking heavier oils; and (3) by extracting liquid hydrocarbons from natural gas. K’ith the possible exception of further increases resulting from the cracking of heavier oils, the limit of the percentage of gasoline that can be obtained from crude oil has almost been reached. I n view of the situation that the production of petroleum has not kept, and apparently cannot keep, pace with the rapid increase in automotive transportation, this is a significant fact. FUTURE SUPPLYOF MQTOR FUEL One of the most serious questions with regard to the future of motor transportaTHOMAS MIDGLEY, JR. NEEDFOR LIQUIDFUEL tiin is that of the supply of liquid fuel. Automotive transportation, of which such a wide and es- A number of producers of petroleum have expressed the besentid use is now being made, and of which a large future lief that our reserve of petroleum will last indefinitely, and expansion is assured, is dependent for its existence upon an that there is every likelihood that no shortage of oil will ndeqiiate supply of liquid fuel. The use of motor vehicles occur.2 I n every case of this optimism that has come to has been built up around gasoline, a inaterial which only a our attention, however, no reason has been given for the few years ago was a troublesome by-product of petroleum opinion that our supply of petroleum is adequate for future refineries. As the number of automobiles in use increased, needs. this product, for which there had previously been very little Arecent estimate of the petroleurn reserves of the United demand, was gradually absorbed, until about, 1905 there States has been made jointly by the American Association was no longer a sufficient supply of the early highly volatile of Petroleum Geologidts and the United States Geological gasoline to operate the motor vehicles in use. Purvey. Their report, which was made public in January At this point gasoline began to assume a higher place in 1922, indicates that a t the present rate of consumption the refinery economics. It was no longer a by-product; but its domestic reserves of petroleum are sufficient to meet the production was extended in order to keep pace with the requirements of thc United States for only about 20 yrs. development of motor transportation, until it has now as- Of the 15,000,000,000 bbls. of petroleum which, on the basis sumed prodigious proportions. I n 1921 the production of of this estimate, was in the ground originally, about 40 per gasoline in the United States was over 5,000,000,000 ga1.l cent has so far been mined; and over 450,000,000 bbls., or This means that the petroleum refineries in the TJnited 5 per cent of the unmined reserve, are now being produced States are filling a 10,000-gal. tank car with gasoline every per year. minute of the y e x . While this estimate of the geologists is necessarily based Since 1909 the number of motor vehicles in use in the United Stater has increased over 3000 per cent, while during upon incomplete data and probably lacks the desired degree the stme period the production of petroleum has increased of accuracy, it is certain that our supply of petroleum is only about 150 per cent. The amount of gasoline necessary being rapidly depleted. If the domestic reserve of petroleum t o keep this rapidly increasing number of motor vehicles in should be three times the amount of this estimate, it would operation was supplied by refineries from a production of last, a t the present rate of consumption, only 60 yrs. It has been 60 yrs. since the Civil War. I n view of this conI The statistics used herein have been taken from the following sources: dition all possible conservation of materials that are suitable “Gasoline,” Refinery Statistics
bile had not yet been built in this country. To-day there are about 11,000,000 motor vehicles in the United States-one for every 10 persons in the country. I n the early days of the automobile it appeared to be only a troublesome and very expensive luxury. But the phenomenal increase in its use, the most of whicF has occurred within the last ten years indicates that the automobile is not ti, luxury but a necessity. It is a necessity because it meets in an aclmirable way one of the most fundamental needs of civilization, that of transportation. It has been said that the automobile represents the first great advance in individual transportation since man began to use the horse.
*
of U. S. Bureau of Mines; “Petroleum and Coal,“ U. S. Geological Survey; “Automobiles,” Automotive Industries, 46
(1922), No. 7.
2
American Petroleum Institute, Bull. 132 (1920);200 (1921).
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T H E JOURNAL OF INDUXTRIAL A N D ENGINEERING CHEMISTRY
Vol. 14, No. 9
for motor fuels should be a matter of vital concern to every citizen.
These changes, oiz., increasing the gear ratio a t the rear axle, and increasing the expansion ratio of the engine, should theoretically produce an excellent automobile, one giving XOURCES OB‘ LIQUIDFUELS, OTHER THAN PETROLEVM such high fuel economy that the salesman should hare no There are three potential sources, in addition to petroleum, trouble in marketing it. But the salesman’s problem is still to which we may look for some part of OUT future domestic unsolved. supplies of motor fuel : THE“KNOCK” 1. OILS FROM SHALE-The enormous deposits of shale in this This super-product of the mechanical and heat power country will undoubtedly be developed. But, even at the best, engineers does not function properly; but, when running it will be many years before quantity production of motor fuel on gasoline, it gives a very objectionable and disturbing from shale can be obtained. 2 . OILS FROM CoAL-The light oils produced in the carboniza- noise. This noise, which i.: metallic in sound, is called tion of coal make a desirable motor fuel. But, if all the bitumi- by motor mechanics a “knock,” the term usually being qualnous coal mined in the United States in 1921 had been so treated ified by an adjective such as “carbon,” ‘[spark,” “heat” as to yield 3 gal. of motor fuel per ton, the product would have amounted to less than 25 per cent of the gasoline produced during or “fuel.” The knock, as it occurs in the automobile engine of the present, when it is laboring a t wide open throttle, is the same period. 3. ALCOHOL-Vegetation offers a source of tremendous quan- familiar to everyone who has driven an automobile. But the tities of liquid fuel, the utilization of which awaits only a proper degree of intensity of this knock increases with the pressiire cheapening and simplification of the process of converting at which the fuel mixture is burned. So that, while in presentcellulose to a liquid suitable for motor fuel. day automobiles the knock is so slight as to be merely an unThe present production of liquid fuels from the three po- pleasantness thRt does no harm, its intensity in this redetential sources enumerated above is so small that, when com- signed engine of considerably reduced clearance volume pared with the enormous volume of motor fuel required, it becomes so great as to result not only in low of power but also is almost negligible. Therefore, while they offer a com- in actual damage to the engine, such as cracked spark plug forting reserve for the future, it will be many years before porcelains and broken piston tops. Because this phenomenon sufficient material can be obtained from these sources to of the ]mock stands as an apparently effectire barrier in the supply any considerahle percentage of the motor fuel require- way of obtaining better fuel economies from automotive ments of the country. Some means must be provided to engines, its remedy is the key to the solution of a great bridge the threatened gap between petroleum and the com- economic problem. The fact has been noted previously that this disturbance mercial production of large quantities of liquid fuels from is frequently called a “fuel knock.” This has arisen because other sources. its intensity is primarily a function of the chemical structure INCREAS~NG THE FUELECONOMY OF AUTOMOTIVE EKGINERof the fuel used. Thus, the disturbance that is present in The bePt way to accomplish this result is to increase the an engine when the fuel has the paraffin structure (gasoline) efficiency with which the energy of gasoline is utilized in entirely disappears if benzene or alcohol isused. But the automotive equipment, and thereby to obtain more “auto- chemical structure of motor fuel from a commercial standmobile-miles” per gallon of fuel. In itself, this is apparently point is a t present fixed within fairly narrow limits. The a simple problem for the mechanical engineer to solve. It use of petroleum oils as our commercial motor fuel is neceshas been demonstrated repeatedly that large increases in sary on account of the enormous volume required, and because fuel economy, or in number of miles per gallon of fuel, can of the small amounts of othcr fuels available. Gasoline is be obtained merely by changing the gear ratio in the rear an excellent fuel, except for the limitation it impose4 upon axle, so that the rear wheels make a greater number of revo- economy on account of its tendency to knock. The find step in the solution of the problem, then, is to eliminate the lutions per revolution of the motor than they did before. But unfortunately this simple expedient is not a practical knocking or detonating tendency of gasoline. solution of the problem, because such a change in gearing ELIMIXATIOK OF THE KNOCK produces a car that is lacking in accelerating and hill climbing It is well known that if substantial percentages of benzene ability to such an extent that people will not buy it. At the present price of motor fuel, economy is secondary to per- or alcohol are mixed with gasoline, the product can be used formance in the estimation of the public. Such a change in in motors of fairly high compressions without the objectionthe rear axle gear ratio not only transforms the car, but it able knock. But unfortunately 40 to 60 per cent of one of also converts what was a problem of mechanical engineering thcse materials must be added to gasoline to accomplish the desired result; and so the amounts of benzene and alcohol to an unsolvable one of salesmanship. Neverthelem, this change is the correct first step toward available are sufficient to treat only a very small part of the better fuel economy. So the problem must again be referred gasoline that is consumed. As the result of a large amount of work that has been done to thc engineer-not to the mechanical engineer, for he has done his part; but t o the heat power engineer and the phys- on this problem, a number of rhemical compounds have been icist. It is their problem to increase the torque delivered by discovered which exert such an influence on the combustion the engine so that the car with the reduced gear ratio may of highly compressed mixtures of gasoline and air that in regain its accelerating and hill climbing ability, and thereby the presence of R small fraction of one per cent of one of these materials gasoline can be used as fuel in engines of very high become a product that the salesman can sell. The solution of the problem again appears very simple. compressions. Recause of their remarkable effects, these According to the laws of thermodynamics, both the torque compounds have been named “coniprcssionizers” or “antiand the fuel economy of an engine are increased as its ex- knock materials.” Their effect is to change the combustion pansion ratio (in automotive practice, called compression of highly compressed mixtures of gasoline and air in such a ratio) is raised. Logically, then, the next step is to increase way that no knock results, but the burn becomes entirely the expansion ratio of the motor. This is accomplished by free from the disturbances th8t characterize detonating reducing the clearance volume above the piston, which in combustion. Some of these compounds are over 500 times turn increases the pressure at which the fuel mixture under- as effective as benzene. Thus, 0.04 per cent by volume of one goes combustion. of these materials in kerosene is equal in effect for the
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Sept., 1922
T H E JOURNAL OF INDUISTRIAL A N D ENGINEERING CHEMISTRY
euppression of detonation to about 25 per cent by volume of benzene in the same kerosene. A considerable number of these compounds of widely variant chemical compoeitions have been discovered. The results obtained in their investigation will be dealt with in a paper entitled "The Chemical Control of Gaseous Detonation with Particular Reference to the Internal-Combustion Engine," to be given at the September meeting of the AMERICAN CHEMICAL SOCIETY in Pittsburgh. The addition of an antiknock material to gasoline makes it possible to obtain very much greater fuel economies, became it permits such changes in design to be made that the fuel can be used more eficiently. Rut, unless the intensity of the knock in a given engine is so great as to rut down power, thc presence of an antiknock material in the fuel does not result in an increased luel economy. Since the addition of a small percentage of such a compound makes very little
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or no change in the energy of a given volume of gasoline, no increase in the mileage obtained per gallon can result lrom its uee, unless such changes are made in the engine that a larger percentage of the energy content of the gasoline can be utilized. Some of these antiknock materials have been rather widely used, particularly in airplane engjnes, and their great effectiveness and value have been demonstrated thereby. In view of the remarkable effects of these compounds and the good results that have been obtained in their use, it seems certain that it will be only n matter of time until all gasoline will be treated with an antiknock material, and automobile engines having higher compressions and giving considerably greater mileages per gallon will be used. The principal effect of the use of antiknock rompounds will be the much further removal of the time when the threatened exhaustion of our petroleum reserves will actually occiir.
Scientific Method in Rubber Compounding By C. 0.North THE RUBBERSERVIC~LABORATORIES CO., INC., AXRON,O H I O
Another factor which affects depolymerization is the type of accelerator employed. For example, p-nitrosodimethylaniline is a violent depolymerizer, as are several softeners or fluxing materials which are sometimes added to a compound for the purpose of making it easier to handle in the factory. Some softeners are powerful depolymerizers, others have little effect. For example, p.araffin is quite pronounced in its action, but castor oil is quite inert. Opposed to the depolymerizing action of heat and certain substances, we have vulcanization which ordinarily means sulfur addition. While we know many ways of reducing the size of the colloidal aggregates of rubber, yet we are limited to sulfur and sulfur chloride for commercial methods of linking them into larger units. Since vulcanization by sulfur chloride has such a small number of applications, it may be practically disregarded. Sulfur then is the principal depolymerizer. It counteracts the effects of heating and other depolymerizing influences. As will be readily appreciated, the more sulfur which must combine with rubber to produce technical cure, the poorer the product. For example, reclaims whose poor quality are well known will seldom be found to have a coefficient of vulcanization under 5. I n other words, the combined sulfur will be more than 5 per cent E F F E C T S O F TEMPERATURE AND TYPEO F ACCELERATOR of the rubber present. On the other hand, Whitby's compounds vulcanized with It is now generally understood that in vulcanizing or curing we have two effects which work in opposite directions. De- various dithiocarbamates and cured in from 3 to 5 min. a t polymerization or the reduction in size of the colloidal aggre- 287" F. (40 Ibs. steam) showed remarkably high tensile gates of rubber is a factor which tends to weaken or dete- strengths with a coefficient of vulcanization seldom over 1.5 riorate the final product. It is influenced primarily by heat and ordinarily less than 1. It is therefore generally realized and the time of heating. For example, it is not a factor at that the larger the colloidal aggregates in rubber vulcanized cures made a t 10 and 20 lbs. of steam pressure (namely, to the point of commercial cure, the- greater the tensile 239.4" and 258.8" F., respectively). This statement applies strength, the resistance to tearing and flexing, and the more even when the time of heating is as long as from 3 to 5 hrs. pliable and stretchy the article. Certainly when properly As the temperature rises, the time within which depolymer- vulcanized such compounds have longer life and stand up ization is not a decided factor grows smaller and smaller. better in service. A t 40 Ibs.' steam (287" F.) the range is from 1 hr. to 1 hr. 30 Aside from the advantage and more rapid turning over of min. At 60 lbs. (307" F.) it has narrowed down to from 15 equipment, shorter cures a t moderate temperatures are very t o 30 min. The higher the temperature, the shorter becomes desirable because of the increased service and durability of the time within which rubber may be heated without serious the product so prepared. It will be remembered that a few deterioration. years ago 3000 mi. was considered a remarkable record for
ERY satisfactory progress has been made during
V
the past few years in applying scientific methods to the problems of rubber compounding. This has been made possible through the development of new and improved methods of rubber testing which in turn have furnished us with a clearer conception of the underlying principles of compounding. The fist chemists to make a study of the art of compounding had before them the picture of steel. They were of the opinion Ibat the problems of rubber could be solved in a similar manner and consequenkly laid great stress on the development and application of chemical analysis. For example, they thought that coefficient of vulcanization was by far the best index of state of cure. They failed to realize that in rubber we have a mingling of both chemistry and physics. While strictly chemical problems are met in the vulcanizing reactions, yet the effects of pigments and other compounding ingredients belong within the field of physics. The coefficient of vulcanization is merely a measure of the quantity of sulfur which has become added to rubber. It is in no way a measure of the state of technical cure because of the factor known a s depolymerization.
