ETHYL CHLORIDE PLANTUSINQTHE ETHYLENE PROCESS
GRAHAM EDGAR Ethyl gasoline began to spread rapidly. In 1924 a manufacturing elapsed since the first commerEthyl Gasoline,Corporation, New York, N. y. cia1 use of tetraethyllead in accident led to unwarranted fears gasoline, many facts about it have that the new product might reprebecome a matter of general knowledge. The genius of Kettersent a danger to public health, and early in 1925 sales were suspended for a year while the United States Public Health ing in recognizing the problem of knock; the researches of Service carried out an investigation of the problem. In 1926 Midgley, Boyd, and their associates on antiknock agents which sales were resumed, and for several years following, the volume culminated in the discovery of the effectiveness of tetraethylof business increased rapidly. Ethyl gasoline survived the lead ; the many investigations, theoretical and practical, first years of the great depression admirably, but by 1932, as stimulated by this discovery; the successful efforts of the oil in the case of many other premium products, the sales volume refiner to improve the antiknock value of gasoline by changes in refining methods; the improvements in automotive and airbegan to decline rapidly. Meanwhile, developments of the refining art had begun to bring about substantial increases craft engines made possible by antiknock fuels-all are familiar. The purpose of this paper is to survey briefly the present in the antiknock value of regular-grade gasoline. I n 1933 the status of the tetraethyllead industry, to discuss some of the use of tetraethyllead was initiated in regular-grade gasoline less familiar problems connected with manufacture and utilizaas an economical means of achieving a part of the needed antiknock value. tion, and to attempt to peer a short distance into the future. It is necessary to begin with a few dry figures. Gasoline Figure 1 shows the sales in the United States of Ethyl containing tetraethyllead was first put on public sale a t a gasoline, leaded regular gasoline, leaded and total aviation single service station in Dayton, Ohio, on February 1, 1923, gasoline, and total figures of the American Petroleum Instiunder the now familiar name of “Ethyl” gasoline. Immediate tute for gasoline sales from 1927 through the first half of acceptance of the new product indicated that the ordinary 1939. They show that the sales of Ethyl gasoline reached a fuel of that day was not satisfactory for even the low-commaximum in 1931; that the decline which followed was not pression automotive engine of the time, and the sale of affected measurably by the introduction of leaded regular
I
N THE sixteen years which have
1439
1440
INDUSTRIAL AND ENGINEERING CHEMISTRY
gasoline in 1933, and that from 1934 on, there has been a steady increase, until a t present the gallonage is nearly equal to that of 1931. They show that today about 75 per cent of all gasoline sold in the United States contains tetraethyllead. I n the aviation field, almost all gasoline of 80 octane number or better contains tetraethyllead; in fact, the performance of the modern military and transport plane is due in large part to the development of high-octane gasoline, a development in which tetraethyllead played an important role. 2000 1000
800
200
IO0 80 60 40
“27
1
‘28 ‘29 $30 5 1132 5 3 ’34155 1.361’37 ’3839
VOL. 31, NO. 12
Problems of Manufacture The manufacture of tetraethyllead has represented serious problems from the start. There was no “prior art” in the large-scale production of any organometallic compound, and knowledge had to be accumulated by gradual and sometimes painful experience. The progress that has been made may be illustrated by the fact that, although the original sales price to the petroleum industry was four times the present price, five years elapsed before Ethyl gasoline was “in the black”, and a t one time during that period a possible loss of several million dolIars was faced. Several years ago it became obvious that the capacity of the existing tetraethyllead plants a t Deepwater, N. J., would not long be adequate for an expanding business, and it was decided to locate a plant elsewhere. Baton Rouge, La., appeared to offer a satisfactory site from the standpoint of availability of raw materials, power, and transportation. The Ethyl Gasoline Corporation therefore purchased a plot of land in Baton Rouge, began construction shortly thereafter, and, by the end of 1938, had created a plant development equal in capacity to the plants a t Deepwater. As the Baton Rouge plants represent the most modern developments, they will be taken as the basis for a brief discussion of some of the manufacturing problems. Tetraethyllead is manufactured by the reaction of ethyl chloride with an alloy of sodium and metallic lead, and the immediate raw materials are therefore ethyl chloride, sodium, and lead. With the exception of metallic lead, none of these are available commercially in the quantities required, and for this reason, as well as in the interest of manufacturing economy, it was necessary to include their manufacture at Baton Rouge.
I HYDROGDV CHLORIC
ALCOHOL
STAEIILIZER GASES
FIQURE
ETHYLENE
2.
FLOW SHEET OF TETRAETHYLMANUFACTURE
LEAD
Figure 2 gives a flow sheet of the manufacturing operations. Salt, obtained from the adjoining works of the Solvay Company, is electrolyzed to produce sodium and chlorine. The sodium is melted with lead to form the alloy which, after grinding, is ready for the final reaction. The chlorine formed in the electrolysis is burned with hydrogen, obtained from the adjoining refinery of the Standard Oil Company of Louisiana, to form gaseous hydrochloric acid. Ethyl chloride is produced from hydrochloric acid by two distinct processes. The first is the familiar reaction with ethyl alcohol. The second is by reaction with ethylene. I n this process, refinery stabilizer gases consisting largely of propane are cracked and the cracked gases fractionated a t low temperatures ta separate the ethylene formed. This is allowed to react with hydrochloric acid gas at low temperature in the presence of a catalyst to produce ethyl chloride. The Baton Rouge plant is the first commercial development of
DECEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
1441
(Top) PLANTFOR MANUFACTURE OF TETRAETHYLLEAD AND INTERMEDIATES, BATONROUQE,LA. (Right) ETHYL-DOW PLANT,WITH ATLANTIC OCEAN IN BACKGROUND AND CAPEFEAR RIVERIN FOREQROUND
this method of manufacturing ethyl chloride. Ethyl chloride produced by either process is subjected to appropriate purification processes and is then ready for the final reaction with the lead-sodium alloy. The reaction may be represented by the equation: 4PbNa 4CzHoCl = Pb(CzH& 3- 4NaC1 3Pb
+
+
I n the manufacturing process the alloy and ethyl chloride are allowed to react a t moderate pressures and temperatures. At the completion of the reaction, the product is distilled with steam to separate the tetraethyllead, and the lead sludge is collected and resmelted to pig lead. Although the reaction appears simple, this appearance is illusory. Side reactions invariably occur, and the conditions under which the formation of tetraethyllead takes place with a minimum of side reaction have required extended study. Furthermore, tetraethyllead is thermally unstable, and the closest control of the reaction rate is essential to prevent the initiation of decomposition which may reach dangerous proportions. Tetraethyllead is poisonous and may be absorbed into the body by skin contact and inhalation of vapor, as well as by ingestion. This fact has necessitated the development of specialized equipment and well-controlled operating technique in order to safeguard the health of the operators. Ventilating equipment of unusual capacity must be provided; valves, stuffing boxes, and gaskets require special design, as an entire absence of leaks must be achieved; and emergency conditions must be provided for. Despite the difKculties inherent in the problem the safety record of the tetraethyllead industry has for many years been far better than that of any other lead industry, according to the best available figures. The Baton Rouge plants give a picture of a self-contained manufacturing development utilizing only the basio raw materials, and representing the most efficient and economic processes known to the art today. The total capacity is better than 60,000,000 pounds of tetraethyllead per year, and the plant has involved an investment of many millions of dollars.
I n addition to tetraethyllead, the finished antiknock fluid requires the addition of ethylene dibromide, ethylene dichloride, and dye. The latter two are purchased in the open market, but an adequate supply of ethylene &bromide at reasonable cost has represented a serious manufacturing problem for many years. Supplies of bromine are limited, and for this reason recourse was had a few years ago t o that great reservoir of raw materials, the sea. The dramatic success, both technical and economic, of the Ethyl-Dow plant a t Kure Beach, N. C., for producing ethylene dibromide from sea water, has been described.l Sea water contains an average of only 67 parts of bromine per million of water, or about one pound of bromine in 7.5 tons of water, but research has been equal to the task of extracting this minute amount. The sea water is acidified and 1
Stewsrt, L C., IND. ENG.CHEM.,26, 361-9 (1934).
1442
INDTJSTRIAL AND ENGINEERING CHEMISTRY
chlorinated; the bromine is blown out with air and concentrated by absorption, reliberated from .the concentrated solution, recovered by distillation, and finally allowed to react with ethylene to form the desired product, ethylene dibromide. As shown on page 1441, the present Ethyl-Dow plant has been substantially expanded since it was first described in 1934.
Problems of Utilization It might be thought that once the effectiveness of tetraethyllead as an antiknock had been discovered, and once methods for its manufacture had been developed, no further problems other than economic ones would remain. Nothing could he farther from the truth. I n the first place, tetraethyllead alone is unsuitable for use as an antiknock agent because of the effects of its combustion products. It was soon discovered that halogens, such as bromine and chlorine compounds, acted as corrective agents, but the development of the two exact compositions used today for automotive and aviation purposes, respectively, required years of study. Exhaustive tests on the dynamometer and millions of miles on the road, utilizing test technique developed specifically for the purpose, were necessary to establish the exact proportions of the constituents most satisfactory for the use for which they were intended. As developments continue in the automotive and aircraft field, it is necessary to continue active work in this field to determine whether or not changes in design or operating conditions may indicate the desirability of changes in the composition of the antiknock fluid. But aside from problems of this type, specific to tetraethyllead, it must be emphasized that lead is a part of the tremendous and intricate problem of the internal combustion engine and its fuel, a problem to which no answer can be assumed to be final. With the discovery that the tendency of fuel to knock limited the ability of the spark ignition engine to convert the energy of fuel into power, a problem was a t once set up for the petroleum industry to remove this limitation as far as economically possible, and for the automotive industry (including also the aircraft industry) to develop engines which would utilize efficieqtly the best available fuel, in so far as it might be economically possible. In the steps that have been taken toward the solution of these broad problems, tetraethyllead has played an important role. And the problems have been many and complex. Some of them have called for the joint efforts of both of these great industries. Methods of measuring the knocking tendency of fuels, methods of expressing these measurements, and interpretation of the remlts of such measurements have called for cooperative work by the technical staffs of the petroleum industry and the automotive industry. Contributions to our knowledge of the fundamental nature of knock, of the chemical reactions involved in both normal combustion and knock, and of the relation of the chemical structure of pure hydrocarbons to their tendency to knock, have come from 60th industries and have furnished a sound, theoretical basis for many practical applications. Some of the many problems have been peculiar to one or the other of the two industries. The petroleum refiner has been faced with the problem of producing from crude oil a motor fuel of progressively less and less tendency to knock. Many tools have been furnished him by his research staff. Cracking has been developed from what was originally merely a method of obtaining more gasoline from a barrel of crude oil to a method of changing the chemical structure of hydrocarbons in such a way as t o produce materials having little tendency to knock. In addition to the fundamental tools of temperature and pressure, the physical chemist has now
VOL. 31. NO. 12
given him the valuable instrument of catalysis. Tetraethyllead is always available to lessen the knocking tendency of the gasoline which may be produced, and the variation in its effectiveness with the nature of the refined product enters the economic picture in evaluating the merits of various refining processes. I n fact, today the refiner has so many tools a t his disposal that his chief problem seems to be the selection of the best ones for his own particular conditions of operation. The automotive and aircraft engineers have their own specific problems. They must keep constantly informed regarding the fuels that are available, and that may soon be available, and they must design their engines to utilize these fuels as efficiently as may be practicable. And with every increase in compression ratio, with every few pounds additional in brake mean effective pressure, a host of problems have presented themselves. Materials that were adequate many years ago-for example, for the construction of valves and spark plugs-are no longer adequate today. Cylinder head design, pistons, and piston rings may need improvement. New materials for bearings may be necessary. New lubrication problems may arise. The complex relation between spark advance and performance for fuels of different antiknock value needs constant study. A fuel induction system giving improved performance under one set of operating conditions may introduce many problems under other conditions. Outside of the passenger car field, such problems arise as the design of engines for the most economic operation of busses and trucks, and the evolution of the farm tractor from the relatively inefficient distillate burning job of a few years ago to the high-compression gasoline-burning tractor of today. The Ethyl Gasoline Corporation is directly neither of the petroleum industry nor the automotive industry, but it is a child of both industries, and as such, it has been able to participate in many of the developments outlined above. Its research laboratories a t Detroit and San Bernardino have not only studied problems specific to tetraethyllead but have contributed substantially to the important progress which has led to the fuel and the engine of today. Thus, tetraethyllead has been of service to the petroleum and automotive industries not only by providing a simple means of obtaining increased antiknock value, but also by aiding in the solution of the many technical problems that have confronted both industries. It cannot be said that any of these developments have been due to a feeling of pure altruism on the part of any member of either industry. They are the natural result of the American competitive system, and their net result is that the public today has vastly better fuels and vastly better automobiles, trucks, busses, tractors, and airplanes than i t had ten years ago. This is technical and economic progress a t its best and may it always continue!
The Future We have looked at the present and have found the tetraethyllead industry in a sound position. It possesses efficient and economical manufacturing plants, of adequate capacity, for both intermediate materials and finished product. A large portion of the oil industry finds its products economical for improvement in the antiknock value of every grade of gasoline. Its business has expanded steadily for a number of years. But what of the future? Vast progress has been made and will continue to be made by the oil refiner. What effect will these developments have on the use of antiknock compounds? It is often said that the safest method of predicting the future is to examine the past. By determining the rate and
INI)IJSTRIAI, AND EUGINEERING CHEMISTRY
DECEMBER, 1939
direction of the trends which have changed past conditions into present conditions, we have some reason to believe that we can tell not only where we have been and where we are, hut also, where we are going. When Ethyl gasoline was first put on the market, the octane number scale was unknown, and methods of measuring antiknock value were uncertain, to say the least. However, i t may be safely stated that the antiknock value of Ethyl gasoline, as first sold, was not so high as that of regular-grade gasoline today. The Ethyl of today is about 10 octane numbers better than i t was fifteen yeam ago. An approximately equivalent increase has occurred in the antiknock value of regular-grade gasoline, and even thirdgrade gasoline, a product of more recent years, has joined the procession of increasing quality. These deGelopments have permitted the automotive engine to be gradually increased in efficiency, and today a large proportion of modern automobiles require the best available fuel for knock-free operation, unless the spark be retarded well below t h e p o i n t of maximum power. There seems no reasbn to believe that these trends will not continue in the future. There appears to be a feeling in certain quarters that the automotive engine cannot utilize efiiciently fuels that are a p preciahly higher in antiknock value than those available today. In fact, testimony was recently presented to the Temporary National Economic Committee in Washington to the effect that the motor of today has reached the top in high compression ratio so that there is no need for improving gasoline quality further! Such arguments may be easily confuted by examining the facts in the case. I n considering the fuel of the future, we niust consider the automobile of the future, and although no one would be rash enough to predict the exact trends which may develop in the automotive field, enough data already exist to show that a number of ways exist ill which fuel of very high antiknock value may he efficiently utilized. In the past, the automotive engine has taken advantage of increasing fuel quality by increasing the compression rat.io, which increases both power per cubic inch of displacement and power per gallon of fuel. It is possible that in the future this trend may be the main one which will continue. This trend cannot be followed indefinitely, but it c a n he pursued v e r y much f a r t h e r than it has been. For example, several
(TOP)INTERIOR VIEW AND (in n r c l e ) LARGE VENTILIITXNG FAN,TETRAETHYLLEAD UNIT (Centw) SODIUMPLANT INTERIOR
(Bottom)
BLENDINGPLANT 1NTERIoR
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INDUSTRIAL AND ENGINEERING CHEMISTRY
BATTERYOF
COMPREsSoRa IN THE
ETEYIIFNEP U V T (aboue),
VOL. 31, NO. 12
Bh’D ETHYL CHLORIDE PLANT
Usrao THE Ar.cono~Paocnss (below)
years ago, the General Motors Corporation (to which 1 am indebted for permission to use certain data), carried out an elaborate research project to determine the possibilities of increasing compression ratio under conditions in which the antiknock value of the fuel was no longer the limiting factor. An automobile equipped with a valve-in-head engine was seiected for the investigation. The car WBS operated both on the dynamometer and on the road at a number of compression ratios and a number of gear ratios, and fuels were used which in each case were just capable of avoiding knock. The octane numbers of these fuels are a little uncertain since neither they nor the octane number requirements were determined by the conventional C . F. R. method, but approximately 69 octane fuel was required for the standard 5.25
compression ratio, ahout 95 octane number for 8.0 comprag sion ratio, and something hetter than 100 octane number for 10.3 compression ratio, Figure 3 compares the miles per gallon obtained by increasing the compression ratio when the gear ratio was adjusted until approximately constant lowspeed performance was obtained (under these conditions the high speed performance was better with the high compression ratios). The results are striking and show, for example, that at 40 miles per hour the miles per gallon improved from 12.5 at 5.25 compression ratio to 18 at 8.0 and 21 at 10.3. The average increase in economy, between 10 and 60 miles per hour, is about 45 per cent in going from 5.25 to 8.0 compression ratio under these conditions of constant performance.
DECEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
If we take the average retail price of gasoline as 19 cents per gallon, the driver of the 8.0 compression car could have paid 27.5 cents per gallon a t no increase in cents per mile, which would give the refiner a margin of 8.5 cents per gallon above
FIXED
'
ENGINE 'OISPL A h 0 MAX &RFORMANCE ATZO-M M P H
VARIED. COMPRESXN
RATLO AM
I
1
AXLE MT!O
j
his regular costs of 5 cents per gallon with which to attempt to produce the 95 octane gasoline required by the high compression car. Such an achievement would appear to be well within the eventual possibilities of the refinery technologist. But increase in compression ratio is only one of the methods by which the automotive engine may utilize fuels of high antiknock value. I n the development of the aircraft engine, where power per cubic inch of displacement is usually more important than thermal efficiency, it has been well demonstrated that a supercharged engine can utilize fuel of as high a n antiknock value as may be available. Already 100 octane number fuel is in wide use, and fuels above 100 octane number
1445
TABLE I. C. F. R. MOTORMETHOD OCTANENUMBER OF LEADTREATED REFERENCE FUEL WHICHPRODUCED INCIPIENT AT 1000 R. P. M. WITH 5.55 TO 1 COMPRESSION RATIO KNOCK Abs. Intake Manifold Pressure, In. H g
-Octane No. at Carburetor Air Temp. of80' F. 120° F. 170' F.
standard engine, and for the same engine supercharged to 10 inches of mercury above atmospheric pressure. (The figures for the supercharged engine are obtained by deducting from the total horsepower the power necessary to run the supercharger.) It is evident that the supercharged engine delivers a maximum horsepower nearly twice that of the unsupercharged engine. The octane number increase necessary to prevent knock in this engine a t varying amounts of supercharge is given in Table I. Thus, with 10- or 12-octane-number improvement in the fuel, it is possible almost to double the horsepower by supercharging. An interesting possible appli-
0.9
0.8
\
5s
0 3
E
0.7
5 ;
2 9 S u
14
2 6 0.6 -I
