PETROLEUM INDUSTRY E. V. MURPHREE Sfondord Oil Development Co., 75 West 51st St., New York 19, N . Y .
The most extensive application o f catalysis to manufacturing operations i s that of the petroleum industry. Over 2,600,000 barrels per day of oil fractions are contacted with catalysts for conversion to more useful products. Major applications are catalytic cracking, alkylation, catalytic reforming, and polymerization. The future will undoubtedly bring substantial improvements in existing applications. Because of their large scale even relatively small improvements have large financial value. Mild hydrogenation of petroleum fractions for increasing stabili t y and sulfur removal will be advanced and greatly ex-
panded. Catalytic operations for higher octane will b e extended to lighter naphtha fractions for which existing catalytic reforming operations are not too well suited. A more efficient hydrogenation operation for converting heavy residual oil fractions to lighter products would have interesting possibilities. Substantial improvements should be possible in the application of catalysts to the production of oil products from natural gas, oi! shale, tar sands, and coal. Knowledge on the mechanism of various catalytic reactions will increase and will expedite the development of existing and new catalytic operations.
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desired products with gasoline of a given octane number, or higher octane number gasoline for a given yield, would be very desirable. It would also be desirable t o have cracking catalysts that ale lcas affected by use. Present catalysts decline in activity with use and also in selectivity-that is, with use they tend to produce somewhat more gas and coke a t the expense of gasoline. It is believed this loss in selectivity is to a major extent due to metal contaminants picked up by the catalyst from the feedstock and from the cracking unit. Because of the large volume of nialerials subjected to catalytic cracking very small improvements in cracking catalysts offer large financial returns. For example, a catalyst that would produce 1% more gasoline with correspondingly less coke and gas would represent, on the volume of material now being cracaked, an increased value of products of over $30,000,000 per year. As an alternate, if catalyst requirements could be reduced by lo%, the saving in catalyst cost a t the present catalytic cracking capacity would be of the order of $4,000,000 per year. There have been major advances, largely of an engineering character, in equipment for carrying out catalytic cracking-or viewed another way, in means of applying the catalyst t o the material to be cracked. These improvements simplified cracking units and reduced the eiae of the equipment required t o achieve a desired result. Figure 2 illustrates the change in size of a Fluid catalytic cracking unit of a given capacity. A major reduction in size has been achieved, largely through engineering. Somewhat similar developments have been made in other catalytic cracking processes. Increased Octane Number
APERS included in this symposium on catalysis in hydrocarbon chemistry by Taylor ( 2 ) and catalysis in synthetic liquid fuels processes by Storch ( 1 ) bear rather closely in many respects on the petroleum field. I n view of this, the discussion presented in this paper is confined to the future of catalysis for making normal oil products from crude oil and its fractions. The use of catalysis on a commercial scale in the petroleum industry started around 1930 and since that time has grown to amazing proportions. Today by far the major application of catalysis to manufacturing operations is by the petroleum industry. At present over 2,600,000 barrels per day of oil fractions are contacted with catalysts for conversion into more useful products. The supply of catalysts for the petroleum industry has grown into a large business aggregating over 900 tons per day. The present largest application of catalysis in the petroleum industry is catalytic cracking. Catalytic cracking capacity is now around 2,300,000 barrels per day and some 600 tons per day of catalysts are required t o supply the needs of this operation. Catalytic cracking has made possible economic production of today’s high octane number gasoline. The production of such high octane number gasoline has been a forward step, particularly for the consumer who owns a car which can fully utilize the gasoline. The higher compression ratio permitted by today’s gasoline allows more efficient engine performance, with the result that the consumer can get more effective energy out of a gallon of gasoline. Figure 1 is a plot of the average octane number of premium gasolines on the eastern seaboard for recent years. The highest compression ratio of new cars for the particular year is also shown. A major part of the improvement in octane number of gasoline since the war has been due to the widespread use of catalytic cracking. Catalysts consisting mainly of silica and alumina are almost exclusively used for catalytic cracking. These catalysts are either synthetic in nature or produced by treating bentonites. There has been some minor use of silica-magnesia catalyst. This catalyst differs from the silica-alumina catalyst in that it gives a higher yield of lower octane number liquid products. For most purposes the somewhat lower yield of liquid products having a higher octane number has been considered preferable by the industry. There has been no real improvement in synthetic silicaalumina catalyst since these catalysts were first produced commercially for catalytic cracking. There have been advances in the catalysts produced b y the treating of bentonites-largely in making them more closely approach the synthetic catalysts. Improved catalysts for catalytic cracking to give higher yields of 1442
Hydroforming, which is a nicthod of increasing the octane number of a naphtha or of producing aromatics by catalytic treatment in the presence of hydrogen, was developed just before the last war and widely practiced during the war to produce toluene for T N T as well as aromatics for aviation gasoline. The main reaction involved is the dehydrogenation of naphthenic compounds to aromatics with production of hydrogen. In addition, isomerization of various kinds occurs along with hydr Ocracking. A substantial amount of hydrogen is produced as a by-product of the over-all operation. Hydroforming was a major source of aromatics during the war and a t the peak the production of synthetic toluene from petroleum was around ten times the production from coal tar, which was the former source of toluene. Since the war most of the hydroforming plants have continued in operation and new ones have been built using modifird proc-
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esses. These plants are being operated t o produce aromatics such as benzene, toluene, xylenes, and still heavier aromatics, as well as to raise the octane number of motor gasoline. A large industry producing aromatics from petroleum has been built up by the use of this process and these aromatics have had wide uses for many purposes. It is expected t h a t the production of a r e matics as such from petroleum will continue to grow at a rapid rate.
COMPRESSION RATIO AND OCTANE NUMBER
line. Hydroforming in its present forms is not very effective for improving the octane number of light naphtha. It can convert naphthenes to aromatics but the over-all increase in octane number of the fraction obtained in this way is small. Isomerization of the fraction is one possibility, but even at thermodynamic equilibrium the octane number expected would be, on the average, only about 80. This could be improved by separation of higher octane fractions and recycle of lower octane fractions, but the separations appear difficult and expensive. A process is needed, such as a more effective aromatization process, which will convert the paraffinic constituents to high octane number materials with good yields.
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Hydrogenation Developments ta.0
r,
1936
1940
1944 Y E A R
1948
1952
7.0 .6.5-
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Figure 1
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1.
A still more important application of hydroforming and similar processes will be to increase the octane number of motor gasoline, which will allow the use of increased compression ratio and hence make possible the production of more efficient automotive engines. It is believed t h a t the trend toward higher octane number will continue since the added cost of producing higher octane number gasoline appears less than the advantage gained in the long run by the consumer. Catalytic reforming will represent a large application of catalysis. Catalytic reforming aids in producing a higher octane number for a given yield than normal thermal reforming and also makes i t possible to go t o a higher octane level than is feasible for thermal reforming. As of this summer a catalytic reforming capacity of approximately 100,000 barrels per day was in operation. Many new installations are planned and it seems likely that, ultimately, catalytic reforming in the United States may reach a level of 1,000,000 barrels per day or higher. It is expected that the future will bring considerable advance in catalytic reforming methods. This may take the form of more selective catalysts and cheaper methods of applying them. Present catalytic reforming is not very effective on paraffinic compounds and the main octane improvement comes from conversion of naphthenic compounds to aromatics. A process which would give a substantial conversion of paraffinic compounds to aromatics offers the possibility of still higher octane numbers and improved octane number yield relation. Such an operation may require the use of lower pressure or higher temperature, or both. Light virgin naphtha, which is normally considered as material from the C6 fraction up t o a boiling point of 225' F., is a future possibility for conversion to higher octane number material. The Cg portion of this fraction can readily be improved in octane number by isomerization to isopentane using Friedel-Crafts type catalyst, and this is very likely the most desirable method of improving the octane number of this particular constituent. There remains, however, a CS,225' F. fraction, representing about 10% on average crude, t h a t has an octane number, on the average, of about 66. With the continued trend to produce higher octane number gasoline, raising the octane number of this fraction will become important. At the present time this fraction is not normally processed but goes directly as a virgin stream into gaso-
July 1953
Various processes of hydroforming of heavy virgin naphtha produce substantial amounts of hydrogen as a by-product, the production being of the order of 700 cubic feet per barrel. If 1,000,000 barrels per day of heavy naphtha were treated b y these processes, the hydrogen production would be of the order of 700,000,000 cubic feet per day. This represents a large volume of hydrogen which may have many valuable uses. The hydrogen could be used for production of chemicals, such as ammonia, methanol, and the like, but it appears t h a t the more valuable uses are a p t t o be found in production or finishing of petroleum products. It has been found that the stability and other properties of light cracked naphthas and distillates are improved by a mild type of hydrogenation operation which has often been termed hydrofining. At the same time desulfurization t o any desired degree can be obtained. Treatment of lub oil fractions and waxes for final finishing b y hydrogenation may well turn out to be attractive. The hydrogenation required in these types of operations is actually very mild and the operations can be carried out a t relatively low pressure, say, under 1000 pounds per square inch. The hydrogen consumption is quite low. These finishing operations are alternates in many cases to finishing by treatment with MODEL
REACTOR
Figure 2.
ID
REACTOR
Schematic Comparison of Fluid Catalytic Cracking Units
sulfuric acid. The hydrofinishing operations have the advantage of essentially no loss in yield and elimination of atmospheric and water pollution problems involved when sulfuric acid is used. Under proper conditions, more satisfactory properties are in general obtained than with sulfuric acid. The substances hydrogenated are largely highly unstable compounds which are present in small amount. Sulfur Removal. The removal of sulfur compounds, either from crude petroleum or from the products obtained from refining crude petroleum, will grow in importance since many of the
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crudes now, being utilized are of relatively high sulfui content. Hydrogenation is a n ideal means of removing this sulfur since it can be accomplished with little or no loss in yield. Another application for the hydrogen produced from catalytic reforming operations is to improve the properties of cpcle gas oil from catalytic cracking for use in further cracking. The cycle stocks from catalytic cracking are aromatic in character and do not give as good yields on subsequent catalytic cracking as the virgin feed stock. By hydrogenation it is possible to convert the aromatic materials into naphthenic-type materials that can readily be cracked over catalyst with high yields. By such hydrogenation the cycle gas oil can be made equivalent to or better than the original virgin feed from a cracking standpoint. Reduced Fuel Oil Yield. Under present price levels for various petroleum products the production of residual fuel oil in the United States is definitely unattractive. Most processes that will reduce fuel oil yields show a high return. Those processes that give major reduction in fuel oil yield, above that which can be accomplished by distillation and viscosity breaking, are deasphalting with light hydrocarbons, coking, and direct catalytic cracking of reduced crude. I n the case of deasphalting, fuel oil yield is greatly reduced and in the case of coking or direct catalytic cracking fuel oil can be eliminated as a product. Domestic cue1 oil production now amounts to around 1,300,000 barrels per day, so the financial gains that would result from converting the fuel oil into higher value products would, because of the large volume, be very wbstantial-over $600,000,000 per year Heavy Crude Bottoms. The hydrogenation of heavy crude bottoms for conversion t o lighter products has been frequently considered in the past but has not proved economic because of the large investment and operating costs associated FTith hydrogen production and with the hydrogenation equipment itself +ks catalvtic reforming is more extensively applied, it would appear that there will be hydrogen in excess of that which can be utilized in the various finishing and desulfurization operations discussed. The volume of hydrogen left over will probably not be great enough to hydrogenate all heavy crude bottoms to lighter products but it could supply the hydrogen needed for so converting a substantial portion of these heavy crude bottoms. For this reason it is likely there will be revived interest in the hydrogenation of heavy crude bottoms to produce lighter products and an improved hydrogenation operation would certainly be most attractive. To be successful an operation must be developed that is considerably less expensive from the standpoint of investment and operating costs than those that have been used for hydrogenating heavy crude bottoms in the past. Catalysts are needed that will enable operation to be carried on a t lower piessures in cheaper forms of equipment.
Theoretical Advances
It is v-ell known that the octane number requirements of the engine of a new car increase subEtantially in the first 3000 to 6000 miles of use. This increase is believed due a t least in part to carbonaceous deposits formed in the combustion chambers of the engine. These deposits frequently cause preignition. The development of a catalyst to be added to the fuel or motor oil that would prevent these deposits from accumulating could be of very real benefit. The production of catalysts for a given catalytic operation is at the present time mainly a trial and error procedure. Different catalyst compositions are made up and tested and there is little theoretical background that can be applied in determining how to produce an optimum catalyst for a given operation. Much more needs to be knonrn about the mechanism by which catalysts work, and such information should give a clearer insight to the preparation of a catalyst for a given service. I t is expected that in the future considerable strides will be made in obtaining a better picture of how catalysts perform and this will be of great help in making improved catalysts. Sum ma ry The discussion in this paper has touched on some of the present applications of catalysts in the petroleum industry and on what some of the future trends may be. In summary, continued extension and advancement of catalytic processes in the petroleum industry may be expected. Catalytic cracking Rill likely continue to be the largest application but a rapid growth in catalytic reforming will occur. Because of this, many improvements in catalytic reforming should be realized. both from the standpoint of catalysts that will give more favorable yield-octane relationships and from the standpoint of catalysts that will allow the octane level that can economically be obtained to be increased. Along with improved catalysts, more efficient e uipment for applying catalytic reforming may be expected, wi% the result that the operation may be installed a t a loTver cost. Catalytic reforming when extensively applied will produce large quantitieE of hydrogen, and it is expected this hydrogen 71 ill find many uses for the refining of petroleum products and fractions. There is considerable economic incentive for conversion of heavy crude residues to lighter products and this may involve catalysis. In the field of product application there is need for a catalyst that can be so applied that it will continuously prevent the accumulation of the bulk of the deposits in the combustion chambers of automotive engines. Research now going on and to be carried out in the future on how catalysts perform should be most helpful in improving all types of catalytic operatione. literature Cited (1) Storch, H. H., IND. ENQ.CHEM., 45, 1444 (1953). (2) Taylor, H. S.,Ibid., 45, 1440 (1953). RECEIVED for reviex December 3, 1952.
ACCEPTED March 11, 1953.
Synthetic Liquid Fuel Processes HENRY H. STORCH Fuels-Technology Division, Bureau o f Mines, Brucefon, Pa.
HE chief raw materials other than petroleum for the manufacture of liquid fuels are oil shale and coal. The quantity of liquid fuel recoverable from our richest oil shale deposits (in Colorado, and Utah) is about billion barrels; that from our coal deposits is of the order of trillion barrele. A~~~~( 2 ) estimates that commercial scale plants producing liquid fuels from oil shale and coal will be operating by 1960 and by 1970, respectively, The time available for completion of development of processes (to an operable level) for manufacture of liquid fuels from oil shale is a t most 5 years and from coal about 15 years.
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liquid Fuel from Oil Shale Development work on the mining and retorting of oil shale is well advanced and involves no special problems in catalysis. The refining of crude shale oil for the production of chiefly liquid fuel for use in internal combustion engines involves special catalytic processing. The crude shale oil contains relatively large fractions of nitrogen and sulfur compounds, which must be converted to hydrocarbons. The processes developed thus far are: 1. Coking distillation of the crude shale oil, followed by hydrogenation of the coker distillate a t 100 atmospheres on a cobalt
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