Petroleum chemistry - Journal of Chemical Education (ACS Publications)

Jul 1, 1979 - Keywords (Audience):. General Public. Keywords (Domain):. History / Philosophy. Keywords (Feature):. Chemical Principles Revisited. Keyw...
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Petroleum Chemistry by Doris Kolb Illinois Central College East Peoria, IL 61635 in cooperation with Kenneth E. Kolb Bradley University Peoria. IL 61625

T h e chemistry of petroleum is a subject often ignored in standard chemistry courses. This is unfortunate because the petroleum refinery is one of the most important chemical nlants in the world. About half of our e n e r w needs in the bnited States are currently being met by petrxleum products (easoline. diesel fuel. furnace oil.. . oetroleum eases, etc.) and ;major skgmeut of our chemical industry depends for i& raw materials on petrochemicals (ethene, propene, hutenes, benzene, toluene, xylenes, etc.). T o overlook petroleum is to miss out on some of the most significant facets of contemporary chemistry. History Exactly how it originated no one knows. We believe petroleum to be of marine origin derived from living matter that existed perhaps as long as 500 million years ago. Radioactive dating indicates that even the newest oil deposits are a t least 50 million years old. Present theory holds that crude oil was produced through the action of anaerobic microbes lowering the oxygen and nitrogen content of what had been living organic matter. The earliest records we have of man usine oetroleum eo back to about 3000 B.C. At that time seepage; of aspha& bitumen were collected in Mesoootamia for wateroroofine ships and canals, for paving roads, for making biicks for building (by mixing with sand and fibers), and for use as a general purpose "glue". These uses continued in the Middle East until about 600 B.C. when those lands were subjugated, first by the Persians and then by the Greeks. The Greeks, who had plenty of stone and wood for building, apparently were not interested in this black sticky tar. Thus petroleum was largely neglected by ancient Greece, and its use was not passed on to the Romans and the rest of western Eurooe. Interest in petroleum did survive among t h e ~ r a b show, ever, and by 1000 A.D. they were distilling crude oil to ohtain kerosene for burning in order to produce light.. During the destruction of Cairo in 1077 A.D. kerosene was used to fuel the tire. Arab and Mongol armivs I)orh appear IO have used a type of i)errolrum fed tlamr thrower in thrir wars around 1200, bu? there seems to have been little, if any, technological carry-over to Europe. With the discoverv of the western hemisotiere and the oprning ut the New World, rherca was renewed interest in rhe use of i~etruleun~. since it wah both available and nevd(:d. Its first kajor use was a s caulking material for the big wooden sailing ships. Cuban asphalt deposits became important for the necessary job of periodic recaulking. The Cuban natives had long used petroleum, not only as acaulking compound but also as a liniment for sore muscles and cuts, and even as a kind of chewing gum. The Age of lllumlnatlon By the heginning of the 19th century the uses of petroleum were still rather trivial, but the industrial revolution had begun and urban areas were expanding. Though working hours were long and many workers were exploited, the overall standard of living started to rise. There was a need for better lighting as the cities continued to grow and became more ac-

tive in the evening. In London some illumination was obtained from bottled gas produced by thermal cracking of fish and whale oil. (It was from this cracked gas that Faraday discovered benzene in 1825.) In America, night time illumination came mainly from the fireplace and from bowls of animal fat or fish oil burning hv means of wicks. During the perrod 1830-50 several new illuminating fuels were developed. Camphene from turoentine (obtained bv steam distilling pine tree stumps) was k e d in this country as fuel for lanterns. Candles made from refined lard beean to be produced industrially. In Europe the production ofcoke for reducing iron ore resulted in large quantities of by-product coal oil. This oil, a mixture of hydrocarbons, was also found to he well suited for use as fuel in lanterns. In America the increased demand for illuminatine fuels niused llenjamin Sillitnun at Ysle University to study the wmposiriun ~rfprfroleum.He found rhar crude oil could he distilled to give-as much as 50% of a material similar to coal oil and thus useful for lighting. To satisfy the demand for more lighting fuel, Edwin Drake drilled the first oil well a t Titusville, Pennsylvania, in 1859. T h e oil was distilled to produce a fraction of hydrocarhons with about 9 to 18 carbons per molecule (called kerosene) for use as illuminating fuel. T h e more volatile fraction containine comnounds of 5 to 8 carbons ~ (called naphtha) found 1imited;se &a solvent, especially for paints. Often there was not much need for the naphtha, so the excess was simply dumped into the rivers (which occasionally caught fire!), an early example of industrial pollution. The heavy higher boiling oils were used for lubrication in place of animal and vegetable oils, which tended to be less stable. The material left after distillation, the asphaltic tar, was used for paving streets and waterproofing roofs. From 1859 until the 20th century the pnduction of ken~srnefor lighting and oils I'or lubricnrion ren~aii~ed the major uses of prrruleum. ~~



Impact of Autos and Electric Lights The beginning of the 20th century was a turning point in the history of petroleum. By 1900 two new technologies had appeared that would have a drastic effect not only onthe petroleum industry but on the whole of modern society. These were the electric light and the gasoline powered automobile. Since gasoline was a mixture of hydrocarbons of 5 to 12 carhons,pasoline was essentiallv iust another name for the often surpl& naphtha. The petroieim refiners could now sell kerosene for lighting and naphtha, or gasoline, for motor fuel. However, demand for gasoline soon began to sky-rocket along with production of automobiles. While a eallon of kerosene might suffice in a household for a week o; more, a gallon of gasoline could be burned in minutes. By 1910 there was a laree denland for naphtha nnd a surplua c l r kerusrnr, nor m l y be(XUSP kerosene was uied nt a muderatc rate but also hecause the electric light was replacing the kerosene lantern in the cities. During the first decade of the 20th centurv several American companies established laboratories for research. In 1910 a t the Standard Oil Co. (Indiana) William Burton initiated a study to increase the amount of gasoline available from a barrel of crude oil. Since kerosene had become a surplus ma~


Volume 56, Number 7, July 1979 / 465



terial, his approach was to try to convert it t o gasoline. 'The kerosene molecules were approximately twice the size of gasoline molecules, so perhaps they could he "cracked" into smaller molecules. Burton and his coworkers developed a process for subjecting the kerosene distillate to high temperatures (600-700°C) and cracking the molecules into smaller fragments. An idealized equation is shown here for cracking a 16 carbon molecule into two smaller ones with 8 carbons each.

Notice that one of the products is an alkene and the other an alkane. t311chu cracking pnxc~\si~ctuallygives a mixture of alknnti and alkenes, not lust two as shown here ) T h e pnxluct hydrocarbons containing5 to 12 carbons are useful as gasoline, while small molecules such as methane, ethene, and propene can be used as fuel to reach the temperatures needed for cracking. Thermal cracking had become a commercial process by 1913. So great had the demand for gasoline become that soon other oil companies were also using the Burton thermal cracking process. The original process was carried out in crude pressure-cooker type reactors. They had riveted seams that would often leak when they were heated. Workmen who tended these leaking reactors (which sometimes exploded) had a grimy, dangerous job. During the 1920's the batch operation was gradually replaced by one involving thermal treatment . only was this new of the oil as it flowed through - .p i -~ e s Not process continuous, but it also had the advantage of giving less coke formation. The inventor of this improved continuous process was C. P. Dubhs, whose full name happened to he Carbon Petroleum Duhbs. The Octane Scale

By 1920 the gasoline powered car, typified by Ford's model

T. was becominc nart of the American culture. No longer was the car a playti;& of the few; it was a practical means of transportation for many. It soon became clear that all gasoline was not equal in quality. Some gasolines seemed to cause excessiveengine noise. Chemists found that gasoline produced considerable preignition or "knock" if it contained mainly straight chain alkanes, such as hexane (C6H14), heptane (C?Hln). Even the lowest compression . , , and octane (CaHld. . engine would audibly knock when gasoline made u i o f these straight chain alkanes was used. However, branched chain alkanes had a greatly diminished tendency to knock. While normal octane was a very poor motor fuel, a hranched isomer, 2,2,4-tri-methylpentane ("isooctane"), was found to have excellent combustion properties. It was postulated that hranched alkanes burned in a more controllable manner than the straight chain compounds in an engine. An arbitrary gasoline rating scale was set up with isooctane assigned a rating of 100 and normal heptane given a rating of 0.

pn:ssim enginrs, ~,specinllyfor airplanec, later made it necessary to extend the octnnt. numtwr scale l~eyonclLOO.) While the octane numher scale is not a ~ e r f e c means t for ratine t s~.ule. gnsolinca qualily, it remains thr singlt: I ~ r s rating P e t r c h m wfinrrs stmetimes sneak in terms oi-research" octane number (RON) and sometimes of "motor" octane number (MON). RON values are ohtained by testing fuel in a single cylinder engine with variable compression ratio at 6M) rpm, with inlet air a t 52°C and a modest spark advance. MON values are obtained a t 900 rpm, with inlet air a t 149'C and a larger spark advance. Before 1973 RON values were the ones usually quoted to the public, but since 1973 the octane values posted on station pumps have been RON-MON averages. The average value better relates to the actual nerformance of the gasoline in an automobile engine. Concurrently with the introduction of this new average scale. refiners also lowered the octane quality of their gasolines by about two units. As a result some motorists began noticing knocking noises in their engines, even though they thought they were using the same gasoline they had always used. -

Before 1973 RON (Advertised)


100 94

(94) (88)

- - -

Premium Regular


(RON-MON) average

Since 1973 RON-MON Average (Posted on pumps) - - - - --

(97) ~


95 89



Diesel fuel does not have the same requirements as gasoline, more spontaneous ignition being desired in a diesel engine. Diesel oil consists of C l s C z s molecules with minimal branching, since straight chain hydrocarbons are preferred for diesel use. A cetane scale is used to rate diesel fuels, with cetane values of 100 and 0 having been arbitrarily assigned to cetane (n-hexadecane) and a-&hylnaphthal&e.

CH:ICH~CH~CH~CH~CH~CH~CH~CH~CH~CH~CH~CH~C cetane (cetane no. = 100)

0-methylnaphthalene (cetane no. = 0) Just as with the octane scale for gasoline, the cetane numher of a fuel is determined bv comparing- its performance in a . single cylinder variable compression engine with mixtures of these reference fuels. The hiaher the octane number of a fuel, the lower its cetane number will tend to be. A fuel with an octane number of 80 would have a cetane number of about 20. ~


Addition of Lead Compounds

normal heptane (octane no. 0)

iso-octane (octane no. 100) If a gasoline had the same knocking characteristics as a 50150 volume percent mixture of heptane and isooctane, it was said to have an "octane number" of 50. If it gave the same performance as a 25/75 mixture of heptane and isooctane, it was rated as "75 octane". (The development of very high com466 / Journal of Chemical Education

In the 1920's ~etroleumrefiners became interested in using additives to increase the octane rating of gasoline. Thomas Midgley had found that the addition of heavy metal compounds tn gasoline would decrease its tendency to knock. After much research he and his coworkers concluded that tetraethyl lead, Ph(C2Hs),, was an ideal additive. I t was a covalent compound, soluble in gasoline, and it gave a considerable increase in octane number. At first the lead compound was added a t the gas station, but because of its toxicity it was later added a t the refinery, along with a dye to indicate that the gasoline contained lead. The addition of lead, as both tetraethvl and tetramethvl derivatives, was so successful in raisingoctane number that its use increased each year. By the 1950's most easolines were "leaded", containing about 2.4 E of lead per gallon. For a typical gasoline the c a d additive boosted the octane numher by 7 to 9 units. In order to remove spent lead from the engine, a mixture

of 1,2-dichloroethane and 1,2-dihromoethane must also be added to leaded gasoline. These ornanic compounds supplv halogens that convert the lead metal to volatile lead halides, which then become part of the auto exhaust gas. The "ethyl f l u i d added to gasoline (about 3 ml per gallon) contains about 60% of the lead compound, roughly 40% of the mixed organic halides, and a little solvent, dye, and stabilizer. In 1967 the production of tetraethyl lead in the US. was 685 million vounds. Virtuallv all of it went into easoline. and the lead .

serious concern in recent years. Before 1970 there was very little unleaded gasoline on the market, hut by 1974 all gas stations were offering it. In fact, no-lead fuel had become a necessity for most new cars because to lower the amounts of their catalvtic converters (desiened . of carbon monoxide and unburned hydrocarbons in auto exhaust pas. so as to meet the clean air standards set bv the ~ n v i r & n e n t a lProtection Agency). Since lead poisons the catalyst in these converters, and since most new cars have them and cannot use leaded fuel, the demand for no-lead gasoline is rapidly increasing. Current federal regulations call for a phasing out of all leaded gasoline during the 1980's. Lead additives are the least expensive means for raising gasoline octane number. Their removal will necessitate an increase in certain refinery processes, such as catalytic reformine and alkvlation. which also increase octane number but a t &eater cost. his need for more refinery processing will result in increases both in the orice of aasoline andin the energy required to produce it. For the past several years another additive, methylcyclopentadienyl manganese tricarhonyl (MMT), has been used as an antiknock agent in unleaded gasoline, hut its use has now been ruled out because it is a potential health hazard. Recently methyl t-hutyl ether


(i.e., cycluhexanes are more abundant than cyclopentanes,which are in turn much more abundant than other ring systems). 5) The amount of aromatic hydrocarbons varies widely, depending on the source of the crude oil. Sometimes aromatic content is insignificant, but certain crude oils contain substantial quantities of alkylbenzenes. In one research project 234 different hydrocarbons were found to he present in-a single sample of crude oil. It is this complex mixture that is fed into pipelines to he separated and improved by the methods of refinery processing. The major processes used in a modern refinerv are discussed below. Crude Oil Distillation

After the crude oil is washed, it is then vaporized and sent through fractionating t m t n , where the oil is srpnratrd mtc, irncrims of h v d n e s r l n ~ n!I~irh similar Inding imint stid niolecular size. There are usuallv about five maioi fractions., their -amounts and exact composition depending on the particular crude oil being used. With the exception of the dissolved gases (methane, ethane, and propane) pure compounds are seldom separated hv distillinn crude oil. T h e followine distribution ofproducts is rather tipical. There is considerable variation Volume Percent

Boiling Point ("C)

Carbon Atoms (approx.range)



gas oil diesel oil lubricating oil residual oil paraftin wax


asohalt [tar)

k has shown promise as an octane number enhancer, and it is already being used by several companies with government appnwal. Modern Refining Processes

During the past 40 years a number of petroleum refininn processes have been developed to increaie the quantity and quality of gasoline, and also to produce the basic petrochemicals (methane, ethene...nrooene. . butenes. benzene. toluene.~. and the xylen&). ~etrochemicalscurrently amount to less than 5% of refinerv outvut: however, thev are a hiehlv imthat remains the refinery's primary reason'for being. impetus for development of several basic refining processes was the demand for high octane fuel for airplanes during World War I1 and then for the higher compression engines of post-war automohiles. As obtained from the well petroleum is a dark, viscous liquid usuallv containine dissolved inorganic salts and nanhthenic


acids. 3) Among the methyl branched compounds, 2-methyl alkanes 4)

Products natural gas, methane ethane, propane, butane liquefied petroleum gas (LPG) naphtha straight-run gasoline


historic livine matter.)

Common Names far

predominate. Cyelrdkanes present are those predicted by thermodynamics

in the composition of crude oils from different sources. Middle East petroleum, for example, is usually very rich in lower boiling hydrocarbons, while Mexican crude oil tends to be high in heavy oils'and residuals. The residual oil is normally vacuum distilled to produce more gas oil and a heavy oil (Cm-C,,) suitable for lubricating oil after the straight chain paraffin wax has been removed. The undistillable bottom material is a heavy tar suitable for paving and coating uses. Catalvtic Cracking Unlike the distillation process, which is a simple physical separation, most petroleum refining processes involve chemical reactions. In the cracking process the reaction involves splitting larger molecules into smaller ones by breaking carhon to carhon covalent bonds. lawe mdecules



alkanes + alkenes

(kernsene range) (gasnline range) The thermal crackine vrocess of the 1920's was lareelv " - replaced by catalytic p&esses during the 30's and 40's. Today more than a third of all crude oil is ultimately subjected to cracking. The catalyst most used today is silica-alumina (Si02, AI20,), often containing nickel or tungsten and used in the presence of a hydrogen atmosphere. a he silica-alumina promotes scission of carbon-carbon bonds, preferentially those near the middle of the chain, since they are weakest. The process is also called "hydrocracking" because it occurs in a hydrogen atmosphere, and it is sometimes called "fluid cracking" when a fluidized catalyst bed is used (the finely divided solid catalvst being.. k e. ~ in t a fluid-like state bv the upward moving stieam of gas). Catalytic cracking occirs a t a lower temperature (500°C) than thermal cracking, and it Volume 56. Number 7,July 1979 / 467

produces fewer small molecules and much less coke. The addition of Ni or W plus Hz has two advantages: (1) alkenes, which are gum-formers, are hydrogenated to alkanes, and (2) sulfur and nitrogen, which are potential air pollutants, are removed as H2S and NHs. Although thermal cracking is no longer important for making gasoline, a type of severe thermal cracking called "steam cracking" is the major process for producing the alkene petrochemicals-ethene, propene, and the hutenes. The use of steam in this high temperature (about 800°C) process reduces the partial pressureof the hydrocarhons in the system, which favors a greater yield of gaseous products, the volatile alkenes, s n d also reduces coke formation

gaseous hydrocarhons to gaso!ine. Alkylation has been used in petroleum refineries since the late 1930's. Today its role is growing as lead additives are being phased out of gasoline, since alkylation is an effective means for increasing octane numher. In the context of petroleum refining, alkylation means the combination of an alkene (such as propene, a hutene, or a pentene) with isobutane (2-methylpropane).

Catalytic Reforming T h e catalytic reforming process can convert a 6-9 carbon naphtha fraction of modest octane numher (about 60) to material of very high octane (10&110). This dramatic increase in octane numher results from the conversion of alkanes and cycloalkanes to aromatic compounds (benzene and alkylbenzenes) all of which have octane numhers ereater than 100. The product, called reformate, often contaiis more than 60% aromatics. In the following example







CH3CHzCH2CH2CH2CH2CH3 swoc CGHSCH~ n-heptane toluene (octane no. = 103) (octane no. = 0) normal heotane is converted to toluene. resultine in a oheuomenal increase of 103 octane units. he major Ltalys't for catalytic reforming is platinum on silica-alumina. One popular trade-marked process is called Platforming. The operation is also called "hydroforming", since it is carried out in an atmosphere of hydrogen. Many of the newer catalyst systems are bimetallic. containing - in addition to platinum a metal such as rhenium, which promotes aromatization of cyclohexanes to henzene. Typically a catalytic reformer operates around 500'C and 20 atm. With appropriate regeneration the platinum catalyst can he used for a decade or longer. This process was first commercialized durine World War I1 to make high octane fuel fur airplanes. It also provided toluene for making trinitrotoluene ('I'N'I'Jex~losives.S i t r e 1952 ref8,rmute has become the major source df henzene, toluene, and the xylenes (BTX) for the chemical industry, although this,represents a 3mall use as compared with gasoline. (The original commercial source for these aromatics was coal tar, which can supply only about 10%of the current demand. Besides producing high octane gasoline and BTX petrochemicals, catalytic reforming also produces large amounts of by-product hydrogen. The rapid growth of the ammonia fertilizer business during the 1950's was the direct result of this process. Needing to find a use for all their by-product hydrogen, refiners started building plants to combine it with nitrogen from the air to make ammonia by the Haber process.




'i H



Thus propene with isohutane produces a mixture of hranched heptanes. The heptane one might a t first expect, 2,2-dimethylpentane, is not produced, since the reaction involves carhonium ions that give rearranged molecules. Alkylation is usually catalyzed by HF or HzS04 and yields an alkane mixture in the 90 octane range.



Polymerization Another way to produce gasoline from smaller molecules is to polymerize an alkene such as propene. Perhaps oligomerize is a more accurate term. since the ~ r o d u c t are s dimers. trimers, and tetramers rather than longchain polymers. l he formation of the propene trimer is shown here

acid eat.



CH CH = -CH3

T h e catalyst used is an acid such as HzSO1 or H3PO4. The polymerization of propene actually yields a mixture of hranched alkenes of the molecular formulas CsH12. C9H18.and C12H24. These compounds have good octane numhers, but because thev are alkenes thev form eum uoon standinr. and so they must he hydrogenatei in order to give stable gasoline. For about ten vears, startina in the late 1940's.. nronene tet. . ratner was used in liirgt: w.ume t o alkylare hen~enefor makmg I 'l'htse AHS orudnlkvlben~enesuliw~dte~ A B Sdrwrrenti. ucts dominated the synthetic detergent market until'their resistance to biodegradation started causine environmental problems. It was the hranched structure of the propene tetramer that was causing the trouble. Today's heavy duty synthetic detergents are still mainly of the ABS type, hut now they are based on linear alkylhenzene sulfonates, which are much more biodegradable.

+ 3Hz % 2NH3 IW'C

Many petroleum companies went into large-scale ammonia nanufacture, hoping to convince farmers that they should 3oolv ammonia directlv to their fields as fertilizer. Needless .;say, they were highiy successful. Soon the mounting denand for ammonia fertilizers, alone with expanded refinery rses for hydrogen (e.g., hydrocracking and-hydrotreatiugj, :rested a need for hydrogen far in excess of what the catalytic .eformers could supply. Today much of that needed hydrogen s obtained by steam reforming of natural gas or naphtha.

lsomerization The isomerization process converts straight chain hydrocarbons to hranched mixtures. Although isomerization is a highly important reaction in refining processes (such as catalytic cracking and reforming), as a separate process isomerization is of minor importance in a modern oil refinery. Probably its main use today is for converting n-butane to isohutane, which is reacted with an alkene in the alkylation process.

4lkylation T h e alkylation process, although not as important as catllytic cracking or reforming, is a useful process for converting

The catalyst often used is a complex of platinum on alumina

168 / Journal of Chemical Education

plus aluminum chloride, which promotes isomerization a t temperatures ;as low 3s IOll°C. Mixtures of pentancs iuld hexnnt!s can also he isomeriznl to increase rheir uctnne rating from 66-70 to the high 90's Hydrogen. Treating

Since 1960 the fastest growing refining process has been catalytic hydrogenation. Just as cracking done in a hydrogen atmosphere gives less tar formation, hydrogenated feed materials can generally he used to avoid undesirable side reactions. Treatment with hydrogen can remove double bonds and eet rid of nitroeen and sulfur. Since these two elements are poisons for certain catalysts, hydrogen treatment results in loneer catalvst life. Nitroaen and sulfur compounds are undesirable in-fuels hecausethey produce oxides that are irritating air pollutants. The sulfur compounds, which are usually mercaptans, also have disagreeable odors which can give gasoline an unpleasant smell. Removal of double honds avoids the problems of gum and varnish formation.


Current Petroleum Use For the past several decades oil and gas have accounted for almost 3/4 of the U S . energy supply. Energy sources in the U.S. for 1970 and 1978 were: Oil Gas

Coal Hydroelectric Nuclear

A marked change is taking place in the amount of imported oil we use. Imports increased from 23% of our total oil used in 1970 to about 45% in 1977. As the following production figures indicate, petroleum production in the U S . reached its peak around 1970.

The major sources of our imported oil in 1978 were: Saudi Arabia (13%), Nigeria (11%), Venezuela (a%), Libya (a%), Alaeria (8%).Iran (7%).and Indonesia (6%),the remaining 39% cttin~ngFnm \,ariousoth( r w w t r i e ~ .I .t i ~ r l p a that r ~wtn~leum will cmtinur (,xert influence on [ ' . S forci~npt~licv. The Future of Petroleum In the near future, during the two decades remaining in this century, oil and gas will continue to provide the major portion of U.S. total energy. Distribution of the world's available oil will he a key prohlem, however, and the U S . will remain heavily dependent on imported oil. For the longer term, looking well into the 21st century, the role of petroleum as a major energy source will gradually decline. Several studies have predicted that maximum world-wide oil production will occur some time between 1990 and 2010. After that it will start

to diminish, just as it already has in the U S . Thus we must establish an active energy policy during the next decade to ensure a smooth transition as oil and gas are replaced by other energy sources. Energy conservation measures, although important, can only give us a little more time. We need to develop new energy sources. In the 21st century our limited supplies of oil and gas will become more treasured as sources for organic chemicals, especially for making fibers, plastics, and synthetic rubber. T h e role of coal will he greatly expanded. Not only will coal substitute directlv for oil and eas as fuel. hut coal will also he converted to gas and oil. The onv version will probably be accom~lishedhv some modification of the Fischer-Tro~sch catalytically combines these small molecules to give hydrocarbons. In the Bergius process finely powdered coal is hydrogenated to liquid hydrocarbons by breaking , u p the multi-ring systems present in coal. Both approaches still need considerable research and develbpment; and the plant investment will he enormous, so this synthetic oil and gas will be quite expensive. But it will he needed. There will probahly he some oil extracted from tar sands and shale, hut this oil will also he much more costly than the oil we merely pump out of wells. The conversion of plant and animal wastes to hydrocarbons will probably also contribute to our supplies of synthetic gas and oil. In a longer time frame, living green plants may become a source for hydrocarbon oils, to be made into new natural rubbers and other organic materials. Even though other energy sources will be supplying most of the world's energy needs in the 21st century, oil and gas (both natural and synthetic) will remain the primary sources for organic chemicals and synthetic organic materials. That uiscous, tarry liquid nature laid beneath the ground A hundred million yeor.s before man came upon the s w n e Can be transformed to maruelous new products irr h o w fi,undLike nylon, orlon, polyesters, polyethylene, S.vnthrtie rubber, plastics. films, adhesiues, drugs, o n d d y e s , And other things, some that we now can only dream about. Who knows what wondrous products man might someday synthesire From oil! Except, alas, that our supplies ore running out. The time is near when earth's prodigious flow o f oil may stop, (Wp'ue taken so much from theground, with no way to return it); Meanwhile we strive to tind and drnw out every precious drop, . . .And then, incredibly, we take the bulk of it and burn it.

References Henrrln..I.."WhntDlmd AreOcfanes?."l'hcrn Tech. 6. I 6 (19761. Hmmfeheek. R. .I.. "l'cfn,leum Pn~~erring-Principlesand Ajlplicatii~nr."McCraw-Hill, NPWY m k . 1959. H I L w ~1;. . I). Ib.'d!irrI."Mndarn Pelrulerrm Terhnol~,gy:4rhcd.. Halrfed Pre\r..Ihn Wiley. New Ymk. 1971. "Kirk-Othmer EncydpPdia,XChemieal'Pechn,,L~pu.'?nded..+,hn Wile).. New Ywk. 1968 Vol. IS. MrCrath, H. R.. and Charlnr. M. R. IEdilnrI. "Oriyin and Relining uf Petn,Ieum."ACS Advances in ('hemistry Series. NII. 10:I.ACS.Wnrhingtun. 1971. S~>illane. I. ..I.,rnd L.c,llin. H. P. I~d,tr,rsI."Helininr:Pelroleumfor Chomicalr."ACS ad^ vnnees in Chemistry Series. NII. 97.Al'S. Washingtun. 1971). Williamn,n. H. F., m d i>aum. A. R. Ilidilorsl, "The American Pmcdeum 1ndnrtry:'Vol. 1. 1859-1899.Nwlhvertern llniuersity I'rerr. Evanrlcri. 1969. Wliacwim. H. L e t al. lMiliir~1,"l'he Amerlcm I'~tn,lellm Indurtrv."Vd.11. 1899.19'19. Nml hwerlrrn I l n i r e r s i f ~Press, liuanrta#i.I9R:l.

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