INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Vol. 19, No. 10
Automotive Lubricants By L. W. Parsons TIDEWATER OK& C O M P A N Y , BAYONNE,N. J.
T
HE contributions of chemistry to t,he development of
automotive lubricants must be presented both from the standpoint of selecting raw material and of manufacturing this into a finished product in order t,o meet satisfactorily the requirements of ‘modern transportation. Automotive transportation in its broadest sense covers not only transportation on land, but also in the air, by water, and even by undersea craft; and for all such types of transportation the manufacturer, aided by the chemist and his eo-workers, has labored to produce lubricants with a sufficient factor of safety to permit operation of the above-mentioned vehicles under a wide variety of conditions. The manufacturer of lubricants recognizes a tremendous responsibility and, -considering the wide variation in type of vehicles, many of which must employ either the same or similar types of lubricants, he must always furnish a product which will function satisfactorily for the service intended. If a motorist were to start today in any type of car on a tour of the United States, passing from S e w York down the eastern coast, through Texas, Oklahoma, t’he midwestern territory, and on to the west coast, he would always be able t o secure satisfactory lubricants foi his car. This fact alone indicates the success which the refiner has attained in meeting the rapidly increasing demands for lubricating products. The average car owner pays much less attention t o motor oil and lubricants than to gasoline, and because of the concealed conditions under which various lubricants funct’ion, he cannot detect variations in quality or performance of lubricants so easily as in the case of gasoline. Very often the failure of lubricants is not noticed until some major breakdown occurs, requiring complete overhauling of the motor or other mechanism, and such failures are often ext’remely costly. That few of these occur is a remarkable tribute, not only to the designer of the vehicle, but t o the care and attention paid to the manufacture of lubricants. These methods of manufacture, although generally outlined in various periodicals, often seem to be wrapped in more or less of a mystery, and it will be one of the purposes of this paper to describe some of the current chemical problems involved in the course of producing the vast amount of motor oil used by the automobile industry, as well as the other types of lubricants connected with automotive transportation. Physico-Chemical Problems of the Refiner
One of the first problems of the refiner is t o select from the various types of crude oil furnished by Nature, in many cases unknown until actually brought t o the surface in huge quantities, first those types which are suitable only for socalled “topping” operations-namely, production of gasoline and residuum-and then those that are suitable and available for so-called “complete” refining-namely, for the production of gasoline, kerosene, gas oil, lubricating oil, and other fractions. By means of chemical and physical examination of the crude-oil samples submitted to the refiners from different fields, it is possible to determine their qualities and to obtain a n idea of the character of chemical and physical treatment t o be given them in order to make satisfactory lubricants. The pioneer work of refiners in various sections of the country, particularly the midcontiiient and California regions, in solving the chemical problems incidental to manufacturing lubricating oils from their crudes is a story which has never been adequately told and which has involved countless ap-
plications of modern chemistry and allied sciences to an extent wholly unrealized by many of us. Entire plant units have been built, modified, and scrapped, and an exhaustive study undertaken of various chemical and physical reagents known in order to produce the lubricants required. The modern refinery consists of a composite of many unit operations and individual plants and is much more complicated when lubricating oil is manufactured in addition to gasoline, fuel oil, and other products. Where lubricating crudes containing wax are processed, extreme care must be given to the refrigerating equipment and to the cold-pressing and cold-settling operations, in order to separate large amounts of wax from lubricating distillates and to provide a satisfactory lubricant, as well as to recover the wax in its refined form and secure proper realization for it. hIuch attention must be paid to the primary distillation of the lubricating-oil fractions in order to produce initially as satisfactory a stock as possible for further treatment. The separation of these fractions involves many physico-chemical problems. ACIDTF.EATxEm-The chemical treatment of many unfinished distillates with sulfuric acid, with the resultant loss of certain amounts of material, has long been severely criticized, somewhat justly to be sure, and other means and reagents have been proposed as substitutes for this acid. On paper and in the laboratory certain substitutes are fairly efficient, but for the mass production of lubricants, as required in the modern refinery, the cost of such materials, the complications due to losses, unusually expensive equipment, various side reactions taking place, and uncertainty of the quality of finished products, have prevented their universal adoption. In the acid-treating of certain lubricating distillates a variety of chemical reactions takes place, many of which are incompletely understood, but certain basic principles and conditions of treatment have been discovered, variations from which always produce a questionable product, thereby causing innumerable difficulties to the refiner. A study of pure materials known to occur in lubricating fractions has given a partial picture of the chemical types of compounds formed during acid treatment, their relative reactivities, their solubilities in various solvents, including the oil itself, and the means for removing a large part of the undesirable impurities. A steady decrease in the amount of acid for treating and its final elimination from the refining scheme is one of the fond hopes of the modern refiner. FrLTRaTIos---The finishing of many lubricating oils by the process of percolation through fuller’s earth or contact filtration by means of fine clays has received the careful attention of both chemists and chemical engineers in order to discover the types of reactions involved, as ne11 as the best chemical engineering methods for applying filtration in a large way. The exact nature and structure of fuller’s earth, a widely used product in the modern oil plant, has been the subject of continuous investigation for many years. The combined cheniical action and physical adsorption taking place a t the clay surface between the coloring matter in oil and the earth itself is sufficient to remove many of the impurities produced in previous refining operations and to assist in final preparation of a clean, stable lubricant for the ultimate consumer. Much work still remains to be done on a physico-chemical study of the activation of various clays and the reactions which take place when color-forming compounds are removed
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INDUSTRIAL A N D ENGi[NEERING CHEMISTRY
from lubricating distillates. The whole question of color in lubricating distillates is one of the most fascinating, complex, and challenging problems for modern chemistry to solve. Properties of Lubricating Oils
Starting with the pioneer work of Mabery and others in this country, and the researches of many foreign tvorkers on the properties of various lubricating fractions, a vast amount of information on the chemical and physical properties of lubricating oils from different crudes has been assembled, and from these data methods have been selected for the satisfactory processing of these lubricants. For many years empirical data have been used in classifying the physical characteristics of various oils, such as gravity, flash, fire, pour point, viscosity, carbon residue, color, emulsion, etc., and although some of these much-talked-about properties are fairly well classified as regards the various types of lubricating oil produced, nevertheless the exact significance of certain of these tests has yet to be determined in connection with the actual operation of the motor oil in the automobile engine. The mechanical means for producing these properties have been carefully studied with considerable success, but every day newer processes are being introduced in the oil refineries to replace older and more obsolete equipment, and many bid fair to transform the oil industry even more into a chemical engineering plant than it is today. The average refiner is so familiar with the general properties of lubricating oils from different crudes or from different parts of the country as to be able to tell from a brief physical and chemical examination of unknown products wliere they were made, how they were produced, and some of the properties of the oils in actual service. Lubrication Theory
Progressing from a study of empirical properties, inwstigatioiis have led to a detailed study of lubrication theory, the result of which has been to restore some order to the chaos which formerly existed and to point out the importance of considering the two well-defined fields of partial and fluid film lubrication and the well-known Z n / p relationship. The importance of viscosity at different temperatures has been emphasized, as well as the properties of oil films under a variety of operating conditions. d study of the properties of oil films in various government laboratories and the laboratories of several oil companies and the pioneer work of some of our research laboratories in the universities have furnished a valuable background for the information of lubricant manufacturers. Much additional work on both the chemical and physical properties of oil films is necessary in order to characterize more definitely the so-called property of “oiliness” and to avoid placing “oiliness” into the same category as has been done frequently with “catalysis”-namely, a refuse pile for incompletely understood information. Composition of Lubricants
Data on the exact chemical composition of lubricants are difficult to obtain and are not yet available, but sufficient knowledge has been secured to indicate the possibility that a certain type of chemical compounds-namely, unsaturated derivatives-may yet exert an important infiuence toward increasing the adsorption of oil films on metal surfaces. Many of these compounds are now being removed from lubricating oils and certain of them are probably of undesirable types. Further work, however, may indicate a situation analogous to the present one experienced on motor fuels, where formerly unsaturated compounds incidental to cracking processes and even cracked gasoline itself were severely condemned, whereas
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today some of these same products, when properly differentiated from the undesirable type of materials, are very satisfactory for producing the modern antiknock gasoline. Such a program calls for long-time fundamental research on the chemical composition of various lubricating cuts, with the hope of classifying properly the different types of such compounds and utilizing those which are beneficial, a t the same time removing during the refining operation those which are harmful. I n the development of this program chemistry must play an important part, particularly organic chemical analysis and synthesis. Several of the projects in petroleum research now being undertaken by the American Petroleum Institute bear on this particular field. Engine and Road Tests
The extent to which various lubricants are subjected to careful scrutiny by the oil refiner can hardly be realized by the average layman. I n addition to experimental examination of crudes for relative lubricating values, followed by a careful scientific control of the refining methods and products, it is necessary for the modern refiner who is marketing a well-established line of lubricants to supplement this work with extensive engine laboratory investigations, to determine the properties of lubricants when subjected to test on the engine block, and also to conduct various road tests in automotive equipment to determine the actual operation of lubricants under service conditions. Such engine laboratory and road test work demands all the facilities which modern chemical and physical science can make available to the refiner in assisting him to develop and market lubricants of satisfactory quality and of a reasonable factor of safety for automotive transportation. Many of the automobile companies and companies manufacturing accessories for automobiles maintain large research laboratories and a staff of men engaged directly on a study of the properties of lubricants, with particular reference to the individual problems of these concerns. These data are utilized as far as possible by the manufacturers of lubricants and automobiles. Design of engines and of lubricants for engines must go hand in hand. New Problems with Depletion of Crudes
When the crudes now available which can be processed easily into lubricating oils are depleted, the chemical problems incidental to manufacturing high-grade lubricants from relatively low-quality crudes will receive increased emphasis. The refiner must continue to use chemical research as an important tool in assisting to solve current processing difficulties. Increased emphasis must be placed on the primary distillation of lubricating fractions in order to produce a t this stage as high a quality product as possible and thus avoid excessive treating and finishing costs. To this end utilization of fractionating equipment, vacuum stills, flash vaporization, pipe stills, continuous treating devices, etc. , present many interesting problems. Such processes must be carefully considered in view of the rapidly changing developments in equipment and the distinct possibility that equipment which is satisfactory today may be either obsolete or entirely revamped within a short time. A proper balance must always be struck between the keen desire to apply the results of modern engineering and chemical research and the economic needs of an undertaking the size of the petroleum industry, where mass production of quality products is an important factor. Waxes and Solvents
,
Many data have been published on the microstructure of wax in distillates, which have yielded very fruitful results when applied to the practical processing and control of lubri-
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
cating distillates in the refinery and also to the characteristics of the finished lubricating oils. The physical and chemical chartges undergone by different waxes and oil-wax mixtures require much further work, and indications are that x-ray examination may also throw some light on this problem. A study of the properties of wax-bearing distillates has led to the adoption of means for the removal of wax by other than the conventional press method. Notable among these is the use of the supercentrifuge, which has already had extensive application, Other methods, such as solvent extraction, special types of pressing operations, etc., have been considered. The possible use of solvents-for example, liquid sulfur dioxide-which has been employed commercially in lightoil treating, must be considered in connection vith the processing of lubricating stocks. Variety of Lubricants
Various types of lubricants are required to meet the different service conditions of automotive transportation. Motor oil is by far the major product, but large amounts of grease, gear compounds, and miscellaneous oil mixtures are used. Other non-petroleum products, such as pure graphite, which is used for lubrication of springs and other parts of the car, play an important role. Today we have a variety of motor oils on the market developed as a result of extended research and applications of various theories prevalent regarding the desirable constituents of such products. These oils cover a wide range and include, among others, the following types: straight petroleum oils; oils adapted from the fatty acid theory of Wells and Southcombe; compounded oils, using fatty oil blends; oils compounded with metal soaps; various non-chatter oils for Fords; equilibrium oils, designed to minimize fuel dilution and promote easy starting in cold weather. All of these types are now being marketed and the extent to which they will develop in the future is a topic on which much speculation might be made, all of which is beyond the scope of this paper. Lubrication of Airplanes, Motor-Driven Ships, and Submarines
To cover adequately the lubrication of types of automotive equipment other than the motor car, brief reference must be made to the airplane, the motor-driven ship, and the submarine. For several years, particularly in Europe, satisfactory lubrication of airplane motors has kept pace with the great development in commercial aviation. I n this field various lubricants prepared from widely different crudes and by different manufacturers have proved very satisfactory, and recent long-distance flights have brought the satisfactory quality of modern lubricants again to the fore. Stability of product and sufficient flow of lubricant a t low temperatures are prime requisites. The lubrication of large Diesel engine units on modern motor-driven ships is another field where lubricants have been used with entire satisfaction. An unusual opportunity t o visit personally the engine room of one of our latest type of submarines revealed a vast power plant confined in small quarters, and here again both engines and lubricants are playing their part in propelling the undersea craft, a tribute alike to the designer of the engines, the fuels, and the lubricants used. It is understood that the cruising area of many submarines is limited by the amount of lubricant which can be carried, owing to excessively high consumption of lubricating oil. Ability of the lubricant to withstand very high temperatures is important. Development of lower consumption, however, is probably more a question of change in engine design than change in type of lubricant.
Vol. 19, No. 10
The advent of new high-speed motors for all kinds of transportation has presented lubrication problems demanding the careful attention of both designing and lubrication engineers. Careful research has made it possible to supply a satisfactory lubricant with a sufficient factor of safety for this type of work. Changes in Properties in Service
A study of the changes in properties of lubricants in service has received considerable attention from engineers and chemists. Oxidation of lubricating oils at high temperatures has been investigated carefully and a test devised for measuring this tendency. Many reactions take place concurrently with oxidation, and the exact significance of the test for comparing lubricating qualities of oils has not been finally determined. Valuable data have been secured, however, which should aid materially in future research work. The oxidation of oils, with resultant sludge and formation of undesirable products, is to be avoided as far as possible. A large amount of work is now under way in an effort to analyze the nature and amount of carbon deposits formed in engines, and to secure some relationship between carbon deposits and the properties of the lubricants used. The problem of cutting down dilution of lubricating oil by gasoline has received careful attention, both from the standpoint of examination of the properties of diluted oils and also means taken to decrease dilution. I n addition to various mechanical devices for preventing it and also special engine design, a series of equilibrium oils has been developed with a view to balancing the amounts of diluent absorbed and removed during operation of the car. The Cooperative Fuel Research, sponsored by the American Petroleum Institute, National Automobile Chamber of Commerce, Society of Automotive Engineers, and the Bureau of Standards, has paved the way with a large amount of fundamental data on fuel dilution and the behavior of both lubricants and fuels under various operating conditions. Research Projects Proposed and under Way
Brief reference to the facts mentioned in this paper indicates clearly the variety m d scope of problems, either solved or awaiting solution by the chemist and co-workers in allied sciences, in connection with the preparation of modern lubricants. A large amount of literature on this subject is already available and numerous research projects are under way toward a solution of these problems. The work of Brooks in collecting in one volume information on the chemistry of petroleum hydrocarbons and similar compounds has been of great value. Publications of the Society of Automotive Engineers, the work of the Petroleum Division of the AMERICAN CHEMICAL SOCIETY,the numerous researches of foreign chemists, and the valuable contributions of British societies on fuels and lubricants are especially worthy of recognition. To give proper credit for contributions on this subject would demand space far in excess of that available in this paper. Many principles of colloid chemistry have been applied in a study of the character and manufacture of lubricants, but considerable further work is necessary. I n addition to a study of the properties of oil films, other colloid problems, such as the structure of grease, which is a gel of soap and oil, the adsorptive properties of lubricants, the properties of emulsions, the protective colloids present in lubricating distillates, plasticity of oils, greases and gear lubricants, etc., are pressing for solution. The broad research program of the American Petroleum Institute, involving thirty-one separate subjects of fundamental research in the chemistry, physics, and geology of petroleum, is already under way and the results of these
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investigations should contribute materially to the existing knowledge of the constitution and reactions of petroleum hydrocarbons. Much of the initial work is necessarily concentrated on the lighter fractions of the crudes which are more available for study, but this will undoubtedly be extended later to cover the heavier lubricating cuts. A survey by Dunstan and Thole in 1923, on the properties of lubricants, referred to the difficulty in classifying properly the chemical composition of various lubricating oils and identifying the various types of hydrocarbon compounds. On account of the variety of petroleum oils as compared with vegetable and animal oils, the exact chemical composition is much more difficult to determine. A series of proposed research problems was given, which, in addition to several mentioned previously in this paper, included the following: (1) isolation and determination of the nature of hydrocarbons in lubricating oils which promote viscosity and oiliness; (2) determination of classes of hydrocarbons desirable in lubricants, with particular reference to their relative stability under operating conditions; (3) preparation and study of properties of pure esters of animal and vegetable oils with reference to their lubricating values; and (4) further investigation of the claim that free fatty acid is the active constituent of commercial fixed oils. The Consumer's Duty
The user of automotive equipment should realize the limitations of even the best refined motor oil manufactured, since it, as well as many other materials, is sub-
ject to certain changes in physical and chemical properties when in use. Probably very few devices are subjected often to more abuse and less intelligent care than the average automobile engine. If one reaches his destination on time the main object seems accomplished, regardless of the wear and tear on automotive equipment when improperly used and the resultant harmful effect on the lubricants themselves. Sufficient information must be available to permit the user of lubricants to distinguish between important and nonimportant physical and chemical characteristics, otherwise excessive demands for useless specifications on the part of the consumers will result in no end of difficulty for all concerned. Conclusion
Considerable credit must be given to the so-called practical refiner who for years manufactured satisfactory lubricants without much scientific control, since it is only during the past five or ten years that many of the basic principles underlying the processing of lubricating distillates have been discovered. Advanced as we are today, the large-scale operations are literally full of problems demanding satisfactory chemical solution and explanation. If this review has sueceeded in a small way to indicate the partial success already obtained by the chemist and his co-worker in allied branches of science and the marked need for further cooperative work between the scientist, the agencies engaged in petroleum research, and the practical refiner of lubricants, then the purpose of this paper will have been accomplished.
Antifreeze Compounds By D. B. Keyes UNIVERSITY OF
I
ILLINOIS, URBANA, ILL,
T WOULD not seem to be a difficult matter to produce
an ideal compound which would prevent water from freezing in automobile radiators under ordinary winter conditions. Only in recent years have the chemists of this country given the matter serious consideration and it is now generally appreciated that the problem was far from simple. Requirements of Ideal Antifreeze Compound
I n order to appreciate the complexity of the problem it is necessary only to review the requirements of an ideal antifreeze compound set up by automotive and chemical engineers. There is given below a list of the requirements combined from {he articles of several investigators : MAJOR REQUIREMENTS-(~) It should prevent freezing of the cooling medium at all ordinary temperatures. (2) It must not injure by corrosion any metal parts of the engine or radiator and must not soften or deteriorate the rubber connections. (3) There must be an adequate supply at a reasonable price. (4) It should be stable. MINORREQUIREMENTS-(~) It should have a low viscosity at all working temperatures. (2) Water solutions should have a high specific heat and a high heat conductivity. (3) It should not materially change the boiling point of the water. (4) It should not produce an unpleasant odor. (5) It should not attack automobile finishes. (6) It should keep its antifreezing property for a long period of time (low partial pressure). (7) It should have a low coefficient of expansion.
With the specifications before us it will be a very simple matter to review the various antifreeze compounds that
have been used and point out their good and bad characteristics. Oils
The various hydrocarbons, notably kerosene, have been used to replace water as a cooling medium, especially in tractors. These oils have not been without success, for actual tests1@*have shown that oil of various grades can be used satisfactorily in tractors if proper attention is paid to the cooling system, especially if the radiator and the cooling system are designed for the purpose. The general disadvantages of oil are as follows: (1) High viscosity a t low temperatures. (2) Low specific heat and low heat conductivity. (3) Oils, especially kerosene, soften and dissolve rubber. (4) Leaks permit oil to come through and the vapors are dangerous because inflammable. ( 5 ) High boiling point may cause overheating of engine. On the whole, the use of oils to replace water as a cooling medium in pleasure cars seems impossible. Salts Calcium chloride was for many years the popular antic freeze compound, possibly because it not only depressed the freezing point of water to a marked degree but it alss stayed in the system and was not lost by evaporation. It was cheap, easily obtained, and there was an adequate supply. I t s real fault, however, was that, in common with all chloride salts solution, it will corrode common metals. Where two metals join and a couple action is possible, this corrosion
* Numbers in t e x t refer to bibliography at end of paper.
