Raw Materials for Chemicals from Petroleum - ACS Publications

Raw Materials for Chemicals from Petroleum MARSHALL SITTIG, Ethyl Corp., New York, Ν. Y.

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on October 16, 2015 | http://pubs.acs.org Publication Date: June 17, 1954 | doi: 10.1021/ba-1954-0010.ch036

Β. H. WEIL, Research and Engineering Department, Ethyl Corp., Detroit, Mich.

Petroleum and natural gas are today being used in increasing quantities for the production of billions of pounds of chemicals— over 40% of the organic chemicals produced in the United States, and large quantities of such inorganic chemicals as sulfur and ammonia—although less than 1 % of the petroleum and natural gas produced is so consumed. This p a p e r deals with the literature on these substances, on the composition of commercially available fractions, the composition of refinery by-products, physical processes for separating specific materials, and the economics of specific raw materials, not from the standpoint of literature sources alone, as such, but rather b y w a y of an ex tensive bibliography attached to a topical discussion.

Petroleum, v i t a l to world economy as a source of fuels and lubricants) is a complex mix ture of hydrocarbons and minor impurities. I n the early days of the petroleum industry, petroleum products were separated by simple distillation and were simply mixtures of the original constituents, differing i n composition from one fraction to another i n accordance with the boiling points of the individual compounds. Later, with the advent of cracking, reforming, solvent extraction, and other methods of conversion and separation, the number of differently constituted fractions produced from petroleum by refiners began to swell logarithmically. Today, normal refining processes for fuels and lubricants yield hundreds of different streams—fractions of narrow or wide boiling ranges and widely va'rying chemical com positions. E v e n such impurities as hydrogen sulfide are available i n quantity i n a con centrated manner. When to these normal methods are added processes designed to pro duce or separate even more specific compounds or cuts for chemical use, i t can be seen that the refiner of petroleum is i n every sense the producer of a wide variety of chemical raw materials. I n other words, the raw materials for chemicals from petroleum are, quite evidently, petroleum and the products that are produced i n its refining to yield fuels and lubricants. M u c h the same is true for natural gas. A s i t comes from the ground, this material also is a mixture of compounds (albeit less complex than petroleum). I t , too, is chiefly used as a fuel, and its normal processing—removal of L P G (liquefied petroleum gas) and natural gasoline—is part of that picture. I n turn, L P G and natural gasoline are primarily used as fuels, although they are finding rapidly increasing use as chemical raw materials. In other words, " d r y " natural gas, L P G , and natural gasoline are themselves basic raw materials for the production of chemicals. A n y paper on the literature of raw materials for production of chemicals from petroleum and natural gas must therefore be concerned with the composition of these substances and their basic refined derivatives, with processes for the separation of pure chemical raw materials from these products, and with the basic economics involved. I n this paper, the literature of the raw materials for chemicals from petroleum has been covered, not from the standpoint of literature sources as such, but by way of an ex327

In LITERATURE RESOURCES; Advances in Chemistry; American Chemical Society: Washington, DC, 1954.

ADVANCES IN CHEMISTRY SERIES


328

tensive bibliography attached to a topical discussion of the raw materials aspect of the petroleum chemicals field. The initial manufacture of chemicals from petroleum raw materials was the manu facture of alcohols from olefinic refinery gases by the Standard O i l Co. (N.J.) i n 1919 (60). Other pioneering efforts i n the field involved synthesis of chemicals from hydrocarbon gases by Carbide and Carbon and the manufacture of oxygenated chemicals from natural gas by Cities Service O i l Co., dating from 1926 (61). According to Egloff (25), only 150,000 pounds of chemicals, principally isopropyl alcohol, were made from petroleum hydrocarbons i n the year 1925. Today, over 3,000,000,000 pounds of natural gas and petroleum compounds are being used yearly for the manufacture of chemicals. Egloff goes on to state that 4 0 % of the organic chemicals manufactured in the United States are made from petroleum raw materials. Amazingly enough, this volume of chemical production accounts for less than one-half of 1% of total crude oil and natural gas production, so large are our fuel and lubricant requirements. Egloff (25) foresees no great increase i n this percentage—forecasting that 1% of our petroleum and natural gas can supply the petrochemical industry of the year 2000.

Origin and Composition of Raw Materials Natural Gas. N a t u r a l gas is the simplest source of hydrocarbon raw materials for chemicals since i t consists of a small number of compounds which are easily separated. Nonhydrocarbon constituents include water vapor (up to 2.5% by volume, the saturation value), carbon dioxide (up to 9 5 % from some wells i n Mexico, New Mexico, and Colorado), inert gases (nitrogen and helium), and sulfur compounds (largely hydrogen sulfide). The hydrocarbon constituents of natural gas contain up to 8 carbon atoms. " W e t " natural gas contains larger proportions of the heavier hydrocarbons i n this range. According to Egloff (24), the United States produced and consumed about 7,800,000,000,000 cubic feet of natural gas i n 1950, of which less than 1 0 % was used for the manufacture of carbon black and chemicals. The compositions of some typical natural gas samples (71) are presented i n Table I . Table I.

Composition of Natural and Oil-Field Gases

gp Q (ΑΪΓ =Ύ.Όθ) "Na"

Percentage C o m p o s i t i o n of Constituents CÔ^ H2S CïÛ C H C H C Hio

r

Field

Ρ

Av. P a . dry A v . P a . wet Av. Okla. dry A v . O k l a . wet A v . Kansas d r y Kansas, N -rich A v . Texas d r y Texas, N - r i c h A v . W . Va. dry A v . W . V a . wet Av. La. dry A v . Calif, dry A v . C a l i f , wet Portero, M e x i c o p „ Pi Mexico 2

2

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0.65 2 0.90 1 0.65 1.00 1 0.60 5 0 . 9 5 88« 0.60 2 0 . 8 3 38& 0.70 0.95 0.60 0.65 2 0.85 2 1.16 . . 0 93 0 1

0.57-0:70

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10 5 14.0 16.3 2

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10.4

85 60 85 45 94 10 89 51 52

6

3

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92.5 87 68 36 64.5

8 4 1 16 12 8 3 9 4 2 .. 25 17 5 4 1 2 .. 3 2 1 .. .. 11 .. 10 5 2 1 18 13 6 4 4 2 1 0.5 1 .. .. 9 8 5 3 20 12 7 6.5 5.4 7.8 3.6 2.3

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0-1.4 0.1-2.2

11.7

17.3 8.2

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Including 1% helium. 6 I n c l u d i n g 2 % helium.

α

Natural Gasoline. N a t u r a l gasoline is produced from wet n a t u r a l gas or from casing-head gas b y compression or b y absorption under pressure. A d s o r p t i o n on carbon is another method of producing natural gasoline, but is little used i n this country. Natural gasolines commonly are composed of C4 to Cg hydrocarbons. The compositions of raw and stabilized natural gasolines are given in Table I I (17). A complete distillation analysis of unstabilized California natural gasoline has been published by Boultbee (6).


SITTIG AND WEIL—RAW MATERIALS FOR CHEMICALS FROM PETROLEUM

Table II.

Compositions of Natural Gasolines

A P I gravity, 60° F . Specific gravity, 6 0 ° / 6 0 ° F . Vapor pressure (Reid), lb./sq. in., 100° Percentage composition, vol. % Ethane Propane Isobutane n-Butane Isopentane w-Pentane Heavier


329

Raw

Stabilized

Debutanized

92.5 0.6309 60.0

77.8 0.6761 17.5

74.5 0.6869 11.0

1.5 14.7 10.2 30.3 4.8 15.0 23.5

1.5 15.3 7.2 21.0 55.0

3.2 8.5 24.5 63.8

The results of a precise fractionation of two West Texas natural gasolines have been presented by Ratzlow and Ruoho (69). Liquefied Petroleum Gas (LPG). Liquefied petroleum gas is produced from the overhead of natural gasoline stabilizing units and consists primarily of propane and butane (50). Carney and Meyer have summarized the potentialities of L P G as a chem ical raw material (13). Crude Oil. Crude petroleum consists essentially of mixtures of paraffinic, naphthenic, and aromatic hydrocarbons containing from 1 to over 70 carbon atoms per molecule and may contain dissolved gases or solids. The naphthenic hydrocarbons are based on cyclopentane or cyclohëxane or on fused C and Ce rings. There is no evidence of the existence of C , C , C7, or C7+ cycloparaffins i n crude oil. Olefins, diolefins, and acetylenes are absent. The aromatics are mainly benzene derivatives; naph thalene, tetralin, and their substituted derivatives have been isolated i n a few cases. Extensive treatments of the composition of crude petroleum appear i n "Chemical Constituents of Petroleum" (71) and i n "Science of Petroleum" (73). A summary of the components of crude oil and their approximate compositions, based on the data of Goldstein (36) and B o y d (7), is presented i n Table I I I . 5

3

Table III. Fraction Naphtha Gasoline Kerosene Gas oil Lube oil Residue

4

Composition of Fractions of Crude Petroleum

Boiling Range,

0

F.

80-450 100-400 330-530 450-625 (Does not distill)

Number of Carbon Atoms (. 4-12 9-16 15-25 20-70

Number of Carbon Atoms (7) 3-13 12-16 15-20 19-37 70 or more

Naphtha. T h e compositions of the naturally occurring naphthas from seven different crudes have been determined b y Forziati, Wellingham, M a i r , and Rossini (30). A l l were found to contain normal paraffins, isoparaffins, alkylcyclopentanes, alkylcyclohexanes, and aromatics i n varying proportions. The composition of naphtha from fluid catalytic cracking has been reported by Melpolder, Brown, Young, and Headington (55). Gasoline. A complete analysis of a H o u d r y - c r a c k e d gasoline i n terms of i n d i vidual hydrocarbon components has been published b y Glasgow, Willingham, and Rossini (35). The composition of gasoline from coal hydrogénation has been presented by Feldman and Orchin (28). Kerosene. A s shown i n Table I I I , kerosene hydrocarbons range from C to Cie as opposed to gasolines which range from C4 to C12, gas oils which range from C15 to C 5, and lubricating oils which range from C20 to C70. Goldstein (36) points out that the increasing number of isomers present i n fractions boiling above 200° F . makes full chem ical analysis impossible. Kerosene is used as a raw material for the manufacture of keryl benzene sulfonates (38). A close-cut, highly acid treated, or solvent refined material boiling in the range of 425 to 475° F . is used for this purpose. Petroleum Wax. Petroleum wax consists of solid hydrocarbons, mostly paraf9

2


330

A D V A N C E S IN

CHEMISTRY SERIES


finie, which occur i n crude oils, distillates, and residues and have a waxy structure and melting points above 30 to 35° C. (86 to 95° F.), according to Sachanen (71) : Goldstein (36) divides petroleum wax into three primary constituents : Paraffin wax—a mixture of solid normal paraffins with 18 to 35 carbon atoms and with a setting point up to 70° C ; the usual paraffin wax melts at 50 to 60° C. and is a mixture of C22 to C30 normal paraffins. Petroleum ceresins (microcrystalline waxes)—hard, brittle waxes melting above 70° C., sometimes as high as 95° C. They contain from 25 to 55 carbon atoms. They are much more soluble and give higher viscosity solutions than paraffin waxes of the same molecular weights. They are believed to be branched-chain paraffins with short side chains near the center of the fundamental long chain. They form very small crystals. Petrolatum wax—this wax may melt within the range of 35 to 80° C., is soft and plastic, and is probably more highly branched than the ceresins. Petroleum ceresins and petrolatum wax are isolated from residues. Paraffin wax, on the other hand, is almost invariably isolated from distillates by solvent extraction or precipitation followed by sweating or emulsion de-oiling. According to Sachanen (71), the wax content of lubricating oil fractions is commonly 10% =t 5%. Paraffin wax consists mainly of normal paraffin from C 2 3 H 4 8 to C 9Hco. Commercial products contain small amounts of naphthenes and branched paraffins. Microcrystalline waxes are predominantly of naphthene-containing paraffin structure according to M c K i t t r i c k , Henriques, and Wolff (52), and M i n c h i n (58). A review on petroleum waxes has been published by Hughes and Hardman (45). Refinery Vent Gases. Refinery vent gases arise from a variety of sources. The approximate yields from these various sources are shown i n Table I V (71). 2

Table IV.

Production of Refinery Vent Gases

Process

Gas Produced (Cu. Ft. per Bbl. Charge)

Cracking (mixed-phase) (receiver) Coking Stabilization (cracked gasoline) Straight-run distillation (60-70% overhead)

350 200 600 10

Cracked gases are the major item i n volume as well as i n importance as chemical raw materials; therefore, they will be discussed separately i n the next section. The composition of coking gases is similar to that of cracked gases, but coking gases are richer i n butane and heavier constituents. The gases from straight-run distillation and storage are very rich in heavier hydro carbons, as shown i n Table V . Table V.

Composition of Gases from Straight-Run Distillation Methane C C* C C 2

4

6

5% 10% 30% 35% 20%

Cracked Gases. Cracked gases are produced as by-products from a l l cracking operations. The quantity of such gases produced depends on many variables, such as the nature of the charging stock and process conditions (temperature, time, and pressure), as shown i n Table V I (71). Table VI.

Production of Cracked Gases

Cracking Conditions Mixed-phase, noncatalytic residual process with maximum gasoline yield (60-65%) One-pass catalytic (clay) cracking at 45% gasoline yield Vapor-phase cracking Nonresiduum thermal cracking to maximum gasoline, coke, and gas

Cracked Gas Produced (Cu. Ft. per Bbl. Charge) 500 200 1500 1000


SITTIG A N D W E I L — R A W

MATERIALS FOR CHEMICALS

F R O M PETROLEUM

331

The composition of receiver gases, produced directly from cracking units, differs substantially from that of stabilizer gases. This contrast is shown for cracked gases from mixed-phase (27) and vapor-phase (43) cracking i n Tables V I I and V I I I . The per cent of stabilizer gas i n the total volume of cracked gases depends on the condensation pressure and is close to 30 or 4 0 % of the total gas produced in cracking. Table VII.

Chemical Composition of Cracked Gases from Mid-Continent Kerosene Distillate


(Produced in mixed-phase process at 950° F . and 400 l b . / s q . in.)

Hydrogen and methane Ethane Ethylene Propane Propylene Butanes Butènes Butadiene Heavier

Table VIII.

30 L b . / S q . In.

Stabilizer

63.0 20.6 4.4 8.7 7.0 3.1 1.9 .. 9.1

11.3 18.6 2.2 19.5 14.5 10.3 7.6 6.9

Chemical Composition of Cracked Gases from Gulf Coast Crude (Produced in vapor-phase cracking)

Hydrogen and methane Ethane Ethylene Propane Propylene Butanes-butenes Higher

Receiver (30 L b . / S q . In.) 38.81 13.15 20.31 3.68 13.15 6.43 2.47

-

Stabilizer 11.37 12.35 15.56 44.87 13.86 1.99

It is seen that the olefin content is appreciably higher as a product of this hightemperature operation than was the case from mixed-phase cracking. Actually, olefin content increases with increasing temperature up to a maximum, then decreases due to decomposition of olefins to hydrogen and methane, as shown by Groll's results (39). A comparison of cracked gas compositions for a number of cracking processes has been presented by Sachanen (72), as shown i n Table I X . Table IX.

Composition of Cracked Gases from Various Processes Mixed-phase cracking

Hydrogen Methane Ethylene Ethane Propylene Propane Isobutane n-Butane Butènes Butadienes

3 35 3 20 7 15 2 8 7 ..

Reforming 7 40 4 18 6 10 3 7 5

Composition, Vol. % Vapor-phase cracking 7 30 23 12 14 4 1 2 6 1

Polyforming 7 50 8 25 3 6 1 ..

Cat cracking 7 18 5 9 16 14 16 5 10

Gases from catalytic cracking operations show a greater percentage of C and C4 hydrocarbons and hydrogen than do gases from thermal cracking. A high percentage of branched-chain hydrocarbons is also typical, as shown by the isobutane content. Modern trends i n the design of gas plants for catalytic cracking units have been discussed b y Gilmore and Bauer (34). Detailed analysis of gas streams i n a Thermofor gas plant are presented. The composition of the butane-butene ( B - B ) fraction resulting from mixed phase cracking has been reported by Snow (75) and may be compared with a similar analysis of the B - B fraction from Houdry cracking presented by Sachanen (71). The Houdry product is richer i n isobutane (53% vs. 11%), poorer i n isobutene (6% vs. 10%), and poorer i n butadiene (none vs. 0.9%). 3



332


Aromatics from Reforming Operations. T h e catalytic reforming of naphtha charge stocks to give high yields of aromatic hydrocarbons, i n addition to high octane gasolines, has assumed great importance i n recent years. Read has discussed the production of high purity aromatics for chemicals manu facture (70). Polymers. Olefins having 9 to 15 carbon atoms w i t h the unsaturation near the end of the molecule may be used to alkylate benzene to make alkyl benzene sulfonates, as outlined by Griesinger and Nevison (38). Such olefins may be economically prepared by propylene polymerization. Synthetic Crudes. Analyses of synthetic crudes made from natural gas have been published by Bruner (9) and are shown in Table X . Table X.

Compositions of Hydrocarbon Synthesis Products

Normal Pressure Fischer-Tropsch Wt. % of Olefins, total vol. % c + c Light oil Diesel oil Wax 3

4

14 47 28 11

45 37 14

Medium-Pressure Fischer-Tropsch Olefins, Wt. % of vol. % total 10 26 37 27

40 24 9

Hydrocol Process Olefins, Wt. % of vol. % total 32 56 8 4

82 85-90 75-85

Additional data on the compositions of both hydrocarbon and oxygenated products of hydrocarbon synthesis have been presented by Morrell et al. (59). The compositions of shale oils have been published* by Dinneen, B a l l , and Thorne (19) and by Cady and Seelig (12). Naphthenic Acids. Naphthenic acids are cycloparaffinic organic acids a n d usually are monocarboxylic. These acids occur i n crude oils and normally are recovered with the straight run gasoline and distillate oil fractions i n a topping unit. If these fractions are caustic scrubbed, the naphthenic acids are recovered as the sodium naphthenates (5). Sachanen (71) presents data on the occurrence of petroleum acids, which include fatty and naphthenic acids and phenols, but which are primarily naphthenic acids. The naphthenic acid contents of crude oils vary from 0.03% (Pennsylvania and East Texas) to 1.5% (California) and 1.6% (Russia and Roumania). The molecular weights of naphthenic acids range from 114 (for cyclopentane carboylic acid) to over 1000, according to Goldstein (36). Commercial naphthenic acids have a molecular weight range of 180 to 350. They are liquids of unpleasant odor and are usually dark i n color. The lower molecular weight acids are sparingly soluble i n water and are distillable at ordinary pressure. A commercial acid of average molecular weight 188 is reported as having a distillation range (10 to 90%) of 240° to 300° C . Acids with between 8 and 12 carbon atoms are monocyclic; those with 13 to 23 carbon atoms are bicyclic, probably with both dicyclopentane and fused ring systems present. The annual production of naphthenic acids has been stated to be of the order of 25,000,000 pounds per year (24). Pyhâlà (68) reports that distillates from two Russian petroleums contained 11 to 12 times as much naphthenic acids as the undistilled crude oils, indicating that, like the nitrogen bases, the naphthenic acids are mainly thermal decomposition products of more complex materials. Commercial naphthenic acids marketed i n the United States contain 5 to 2 5 % of o i l ; when corrected for oil content, the acid material shows acid numbers of 238 to 302, according to K l o t z and L i t t m a n (46). A review of the occurrence and composition of naphthenic acids i n petroleum has been presented by Lochte (51). Cresylic Acids. Cresylic acids, or petroleum phenols, are obtained from cracked distillates, such as heavy catalytic naphtha and cracked heating oil. T h e y usually exist i n these distillates i n amounts up to about 0.2% and are removed by extraction with a 10 to 4 0 % sodium hydroxide solution (77). The extract is subsequently steamed, then In LITERATURE RESOURCES; Advances in Chemistry; American Chemical Society: Washington, DC, 1954.


SITTIG AND WEIL—RAW MATERIALS FOR CHEMICALS FROM PETROLEUM

333

carbonated with carbon dioxide to spring the alkyl phenols from the naphthenic acid soaps (which remain i n solution). The product is subsequently distilled. Field, Dempster, and Tilson have published data (29) on the phenols extracted from a California cracked distillate and have compared these analyses with those of coal-tar phenols boiling i n a similar range. It has been found that catalytic naphthas contain about ten times as much cresylic acid as do thermal naphthas (32). The cresylic acid may easily be recovered by treatment with dilute caustic soda to give a product containing 2 0 % phenol, 2 5 % xylenols, 4 5 % cresols, and 1 0 % impurities. Removal of sulfur from this extract to give marketable cresylic acid is a problem, being solved by air blowing, partial neutralization, distillation, or a combination thereof. Sulfur Compounds. T h e sulfur present i n natural gas or i n refinery cracked gases is predominantly hydrogen sulfide and m a y range from 0 to 15 volume per cent. Sulfur compounds isolated from the lighter petroleum fractions include mercaptans (#SH), dialkyl sulfides and disulfides (RSR, RSSR), and cyclic sulfides such as thiophanes and thiophenes. M o s t crude oils contain sulfur, the usual amount being 1 to 2 % . Some of this sulfur is lost as hydrogen sulfide i n distillation of the crude, and most of the remainder is concen trated i n the higher-boiling fractions as shown in Table X I , taken from T a i t (78). Table XI.

Sulfur Content of Distillation Products (% wt.)

Crude oil Source Far East East Texas East Venezuela Iranian West Texas West Venezuela Kuwait

%s 0.15 0.36 0.55 1.4 2.0 2.2 2.45

Gasoline and Naphtha Total S Mercaptans 0.003 0.003 0.003 0.063 0.14 0.003 0.010

Kerosene Total S Mercaptans

0.003 0.012 0.011 0.087 0.17 0.023 0.015

0.01 0.03 0.05 0.15 0.62 0.20 0.16

0.003 0.003 0.003 0.008 0.09 0.003 0.004

Gas Oil Total S Mercaptans 0.003 0.003 0.003 0.004 0.05 0.003 0.003

0.15 0.28 0.35 0.90 1.6 1.0 1.3

Residue Total S 0.3 0.78 1.2 2.3 3.2 2.7 3.8

Above Data Converted to L b . S in Each Product/100 L b . S in Crude Far East East Texas East Venezuela Iranian West Texas West Venezuela Kuwait

Gasoline and Naphtha

Kerosene

Gas Oil

Residue

0.3 0.9 0.5 1.1 1.8 0.05 0.1

3.6 1.3 1.7 1.5 4.2 0.55 0.8

38.6 15.4 15.5 12.6 14.8 6.6 9.5

57.5 82.4 82.3 84.8 79.2 92.8 89.6

Sulfuric Acid Sludges. T h e water-soluble sulfonic acids resulting from the acid treatment of oils boiling under 550° F . are known as "green acids" i n the trade (38). These green acids are monobasic acids which cover a molecular weight range of 150 to 1000 and have the general formula C H n - 9 . S 0 (36). The oil-soluble sulfonates resulting from the acid treatment of oil boiling above 550° F . are typified b y the mahogany or white oil sulfonates. Mahogany sulfonates are most readily formed b y the action of fuming sulfuric acid on a naphthenic-type petroleum distillate. Following treatment of such a distillate with 40 v o l . % of acid, the oil is neu tralized and extracted with alcoholic caustic. The mahogany sulfonates are then freed of excess sodium sulfate and caustic by drying and redissolving i n a low-boiling hydrocarbon (38). Mahogany acids are monobasic acids of the general formula C , J l 2 n - i 2 . S 0 3 and have a molecular weight range of 350 to 500 (36). Nitrogen Compounds. T h e preparation of secondary amines from the nitrogen bases present i n California cracked petroleum has been discussed by M i l l e r (56). The bases were extracted b y contacting with 4 5 % aqueous sulfuric acid. The extract was diluted with water and allowed to stand for 12 to 24 hours. The aqueous layer was made alkaline, and a heart cut of nitrogen bases was distilled. Bratton and Bailey (8) have reported on the compositions of nitrogen bases extracted n

2

3



334


from thermally cracked gasoline. Seven homologs of pyridine as well as quinoline and quinaldine were found. I n addition to these compounds, Hackmann, Webant, and Gitsels have reported (4-1) nine other homologs of pyridine, five methyl and dimethylquinoline homologs, isoquinoline, two isoquinoline homologs, plus other unidentified com pounds. The nitrogen contents of 153 crude petroleums from all parts of the United States have been reported b y B a l l , Whisman, and Wenger (3). M o s t were below 0.10%, b u t a few contained as much as 0.7% nitrogen. Petroleum Coke. Petroleum coke is an important raw material from petroleum for the chemical i n d u s t r y . U n l i k e most petroleum raw materials which go i n t o organic synthesis, petroleum coke is important i n inorganic technology. Anodes for aluminum manufacture consume 600,000 tons of petroleum coke annually—18% of U . S . petroleum coke production. About 0.7 pound of petroleum coke is consumed for every pound of aluminum produced. The next most important chemical use is i n the manufac ture of graphite electrodes for the steel industry, a use which consumes about 5 % of cur rent coke production. Thomas has reviewed the petroleum coke picture over the last 25 years (80). Earlier reviews include those b y Stroud (76) and Gould (37). Petroleum coke has the approximate formula ( C H ) n , according to Thomas (79). 3

4

Processes for Separation of Pure Chemical Raw Materials from Petroleum Fractions M o s t processes which utilize petroleum raw materials require a prehminary separation of a more-or-less pure component from a petroleum fraction. A n exception to this is the direct oxidation of natural gas, as currently practiced by such companies as Celanese Corp., Tennessee Eastman Corp., and Cities Service O i l C o . In general, the important factors governing the supply of a petroleum raw material are the (1) composition and cost of the raw material, (2) quantity and quality of the hydrocarbon desired, and (3) processing steps required and their relation to existing re finery operations. Yields of individual hydrocarbons will vary from crude to crude. The picture is further complicated, as B o y d points out (7), b y difference i n refinery operations, available equipment, market conditions, and company policies. Absorption and Extraction. Separation m a y be accomplished b y gas absorption and solvent extraction. G A S ABSORPTION. O i l absorption may be used for the separation of ethylene from cracked gases, as outlined by K n i e l and Slages (47). Absorption i n cuprous salt solutions may also be used for the extraction of ethylene from gas streams, as outlined b y Sergeys (74).

SOLVENT EXTRACTION. Diethylene glycol extraction of benzene, toluene, and xylene from Platformates is one commercial method for the recovery of these materials. T h e process has been named the Udex process and has been described b y Read (70). Phenols may be removed from refinery wastes and recovered b y a multistage countercurrent extraction process such as practiced b y Ohio O i l (15). A mixed benzene-gasoline solvent is used i n the extraction process and is regenerated with caustic. A modified Edeleanu process for the recovery of aromatic hydrocarbons from petro leum fractions has been described (65). Distillation. D i s t i l l a t i o n processes are also used to effect separation of chem icals. EXTRACTIVE DISTILLATION. TWO important extractive distillation processes were placed i n commercial operation during World W a r I I : the recovery of butadiene from a C fraction using furfural as the entraîner (10, 11, 40, 4®, 44), and the segregation of tolu ene from petroleum fractions by means of phenol (20, 21, 23). The Shell benzene recovery process uses phenol or, i n special cases, other solvents such as cresylic acids or sulfolanes, to separate benzene from nonaromatics by extractive distillation. This process has been described by D u n n and Lieholm (22), and others (63). 4


SITTIG AND WEIL—RAW AZEOTROPIC

MATERIALS FOR CHEMICALS FROM PETROLEUM

DISTILLATION.

Methanol m a y be used

335

to separate

toluene

from

cracked motor fuel fractions (81), and the use of sulfur dioxide i n butane-butene separation has been reported b y Matuszak and F r e y (54). M a i r , Glasgow, a n d Rossini have discussed the laboratory aspects of hydrocarbon separation b y azeotropic distillation (53). LOW-TEMPERATURE

FRACTIONATION.

Low-temperature

fractionation is used to

separate 75% of the ethylene produced in the United States (62). Pratt and Foskett have described the separation of ethylene b y this method (66). Adsorption.

A d s o r p t i o n processes are now being used commercially.


HYPERSORPTION.

T h e applications of Hypersorption i n modern gas processing

plants have been outlined b y Berg (4).

T h e recovery of ethylene from refinery gas

streams is discussed, and analyses of process streams are presented. S I L I C A - G E L ADSORPTION.

T h e Arosorb process is an aromatic adsorption process

developed b y the Sun O i l C o . and uses silica gel to separate aromatics from naphtha reformates

(64).

Operating and investment

costs for Arosorption were presented as

follows: Capacity B P D aromatics Investment cost Operating cost, cents/gallon of aromatics

1000 $ 1,200,000 ôVs

2000 $1,900,000 5

Davis, Harper, and Weatherly have also described the Arosorb process (18). ION E X C H A N G E .

T h e removal of nitrogen bases from petroleum m a y be accom-

plished b y an ion exchange process (57). Crystallization.

C r y s t a l l i z a t i o n processes are also used i n separating chemicals.

E X T R A C T I V E CRYSTALLIZATION.

Extractive crystallization is a new process whereby

the desired component in a mixture is made to form an adduct, the adduct is crystallized out, and the desired component

is then recovered.

Urea forms such adducts with

straight-chain organic compounds, and thiourea forms adducts with branched-chain and ring compounds.

A review of the process has been published b y K o b e and Domask (48).

FRACTIONAL CRYSTALLIZATION.

T h e separation of ^-xylene from a Hydroform&te

by fractional crystallization has been described i n the literature (14)-

T h i s process is

operated commercially to produce para xylene as a raw material for Dacron fiber manufacture.

Economics of Specific Raw Materials for Chemicals T h e over-all size of the petroleum chemicals industry and its projected future production has been estimated b y various authorities.

Table XII.

Table X I I summarizes these data.

Total Output of the Petroleum Chemicals Industry

Year

Total Capital_Investment, Millions of Dollars (60)

1940 1945 1950 1955 1960 1965 1970 1975

350 1,000 1,600 ... 8,000 ... ... ...

2000

\\\

Output, Million Lb./Year _ ^Presidents Material^ Neuhaus & Sommer (60) Egloff (H) Policy Commission (67) 4,000 10,000 17,000 ... 64,000 ... ... ...

12,000 ... ... ... ... ...

20,240 29,240 37,470 45,610 54,180

48,000

'.Y.

W i t h this general predicted growth potential for the entire industry i n mind, it is now pertinent to examine the trends i n production and sales value of specific raw materials from petroleum, as taken from U . S . Tariff Commission publications (16).

These data

are summarized i n Table X I I I . Economic data on specific raw materials are not widely available since, like most cost data, they are frequently confidential i n nature.

General data on market trends and

market prices are all that are available in most cases.



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