September 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
Ross, F. F., and Sharpe, G. C. H., J . Inst. Fuel, 23,20-4 (1950). Rueckel, W. C. (to Koppers Co., Inc.), U. S. Patent 2,470,112 (1950).
Russell, C. C., and Perch, M., preprint, Prod. Chem. C o d . , Am. Gas Assoc. (May 23-5,1949). Sabatier, J., Scientific Conferenceon Conservation and Utilization of Resources, Economics and Social Council, United Nations, Lake Success, E/Conf., 7/sect./w. 321,1949. Sachsse, H., Chemie-Ing.-Tech., 21, 129-35 (1949). Salvi, G., Riv. cmbustibili, 3 , 369-82 (1949). Savage, J. W., Rocky Mt. Oil Reptr., 6, No. 16,6 (1949). Zbid., 7, No. 10, 29 (1950). Semet-Solvay Co., Brit. Patent 612,076 (1948). Shaw, J. A,, and Koppers Co., Inc., Brit. Patent 621,873 (1949).
Shaw, J. A. (to Koppers Co,, Inc.), U. 8. Patent 2,471,550 (May 31, 1949). Zbid., U. S. Patent 2,490,840 (Dec. 13,1949). Sherwood,P. H., Chem. Eng., 56, No. 9,99-101 (1949). Simek, B. G., and Ludmila, J., Paliva a voda, 29,33-8 (1949). Simek. B. G., et al., Ibid., 29, 97-100 (1949). Smelyanskii, I. S., and Tsigler, V. D., Ogneupory, 14, 9-21 (1949).
Smith, J. R., el ul., Anal. Chem., 22, 867-40 (1950). Smith, T. B., Brit. Patent 572,917 (Oct. 29,1945). Smoluchowski, K,, Gaz, Woda i Tech. Sanit., 23, 160-2 (1949). Sneddon, R., Petroleum Eng., 21C, No. 7, 36-7 (1949). Standard Oil Development Co., Brit. Patent 630,458 (1949). Stanfield, K. E., and Frost, I. C., U.S. Bur. Mines, Rept. Invest. 4477 _ _ . 11949) . I
Stief, F., G‘trs-u.Wusserfuch,89, 193-9 (1948). Ibid., 90, 403-10 (1949). Stott, V. H.. and Hilliard, A., Iron & Coal Trades Rev., 158,256 (1949). Strohal, D., Arhiv. Kem., 18,81-6 (1946). Struck, P., Qas-u. Wasserfach,91, 16-20 (1950). Swinnerton, A. A., Can. Depl. Mines Resources, BUT. Mines, No. 825,19-24 (1943) (published 1948). Szasz, O.,Bdnydss. Kohdsz. Lapok, 81,86-91 (1948). Takizawa, M., Bull. Znst. Phgs. Chem. Reaearch (Tokyo), 20, 920-34 (1941); 21,83-7,375-9,438-47,644-50(1942).
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Tettweiler, R., Cas-u. Wmserfach, 90, 25-32, 68-9, 73-8 (1949) Thau, A., Brennstof-Wame Kraft, 1,72-4 (1949). Thau, A., Erdol u.Kohle, 2,127-33 (1949). Thau, A., “Leitfaden der Braunkohlenchemie,” Halle, W. Knapp, 1949. (247) Thau, A., “Brennstoffschwelung,” Bd. I. Schweltechnik und Schwelbetrieb,Halle, W. Knapp, 1949. (248) Thibaut, C. G., Pub. 17181. Recherche8 Sidemrgie, Ser. A., No. 3
(243) (244) (245) (246)
(1948). (249) Toenges, A. L., et aZ., U. 9. Bur. Mines, Tech. Paper 719 (1949); 721 (1949); 725 (1960). (250) Toporkov, V. Y., Stal, 8,404-13 (1948). (251) Tsiperovich, M. V., Ibid., 8,967-73 (1948). (252) Ulitskii, L. I., Ibid., 8,291-9,413-18 (1948). (253) United Kingdom Engineering Commission to Canada, “Cana-
dian Gas and Coking - Industries.” London. H. M. Stationerv Office, 1949. (254) Ussar, M., Berg-u huttenmann. Monatsh. montan. Hochschule Leoba, 94, 103-8 (1949).
Veit, P., Brenn8to.f-Chem.,31,14-22 (1950). Wang, R.T., J . Chem. Eng. China, 1 5 , 3 3 4 0 (1948). Wehrmann, F., Gas-u. Wasserfach,90,149-60 (1949). Weller, S., et al., IND. ENo. C ~ E M41, . , 973-3 (1949). West, F. J., and West’s Gas Improvement Co., Ltd., Brit. Patent 617,436 (1949). (260) Williamson, R. H., and Gardside, J. E., Gas WorEd, 130, 1999-
(255) (256) (257) (258) (259)
2001 (1949); 131,119-25 (1950). (261) Wilputte Coke Oven Corp., Brit. Patent 606,555 (1948). (262) Wilputte, L., and Wethly, F., U. S. Patent 2,488,952-3 (Nov. 22, 1949). (263) Wilson, P. J., and Well, J. H., “Coal, Coke, and Coal Chemicals,” New York, McGraw-Hill Book Co., 1950. (264) Wood, H. C., Brit. Eng., 31,1289-1303 (1949). (265) Woodall- Duckham Ltd., and Naah, C. W., Brit. Patent 619,021 (1949). (266) Wunsch, W., Bergbau-Arehiv., 9, 105 (1948). (267) Yzu, L., I.N.T.A. (Inst. nacl. tecnol. aeronaut.) (Madrid), Comun. No. 3 (1944). (268) Yzu, L., and Doblas, J., Ibid., NO.7 (1945). RECEIVED June 24, 1950
Pyrolytic a Decomposition of Hy .
VLADlMlR HAENSEL and MELVIN J STERBA UNIVERSAL OIL PRODUCTS COMPANY,RIVERSIDE, ILL.
I
N COMMON with the first two literature reviews (33, 34) of hydrocarbon decomposition reaotions, this summary includes a compilation and brief digest of material that has
appeared in the literature during the year ending in May 1950. During this past year there have appeared important contributions to the explanation of the mechanism of catalytic cracking. The first commercial Platforming unit went on stream in 1949, and the chemistry of the process waa disclosed early in 1950. The petroleum refining industry has continued to expand and modernize its cracking facilities, and has made use of the graphic panel to compact the instrumentation of certain new installations.
THERMAL CRACKING The literature of the past year suggests that most of the recent fundamental studies in thermal decomposition reactions have been concerned with reaction mechanisms, and that industrial developments are being directed toward the processing of heavy residual fractions, largely by methods which make coke and distillates as products. Partington, Stubbs, and Hinshelwood (67)have described the normal thermal decomposition of n-pentane as consisting of a
molecular rearrangement process and a chain reaction repressible by nitric oxide. Primary decomposition products, obtained in the presence of nitric oxide to suppress the chain reaction, indicate that the probabiKty of initial rupture at the C(2-3) linkage is about twice that at one of the C42-s) bonds. Furthermore, when the break occurs at the C(2-s) linkage, ethane and propylene are formed more frequently than ethylene and propane. The nature of the decomposition reactions of methane, ethane, and n-butane on an incandescent platinum filament at pressures of 10-6 mm. has been examined by Robertson (81) by the use of a mass spectrometer of high sensitivity. Ne concludes that the primary dissociation of methane on platinum at 1000” C. resulted in the formation of methyl radicals, but no methylene radicals could be detected. Ethane, propane, and butane were formed by radical recombination and hydrogen transfer. At 1050’ C., butane appeared t o undergo a selective fission a t the central C-C bond because the main products were ethane and ethylene, no CShydrocarbons and only traces of methane being observed. This selective type of rupture was attributed to the catalytic effect of the platinum filament rather than to the nature of the butane molecule ihelf.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Using a static type of reaction chamber, Stubbs and Hinshelwood (69, YO) have studied the reaction rates and mechanism for the thermal decomposition of the normal paraffins from propane through decane a t a temperature of 530' C. by observing the rate of pressure rise in the reaction zone. Evidence is provided to indicate that the normal decomposition consists of chain reactions and molecular rearrangement. These authors show that the chain reaction can be repressed by the presence of nitric oxide or propylene, and present data to show that either of these inhibitors reduces the initial reaction rate to the same limiting value. Thus, by inhibiting the chain reaction in their experiments the authors were able to study the molecular rearrangement process by itself. They conclude that over an initial pressure range of from 25 to 500 mm., the reaction order for a given paraffin increases with increasing pressure, and that at a given pressure the order increases somewhat as the paraffin series is ascended, The reaction is almost of first order at low pressures and approaches second order a t the higher pressures. At an initial pressure of 100 mm. they have obtained the following initial rates of pressure increases for the normal and inhibited reactions: No. of C Atoms
2 3 4 5 6 7 8
9 10
Normal -1.1 -0.1 0.4
0.7 0.95 1.1 1.26 1.4 1.5
Log Initial d p / d t Inhibited -2.1
-1.1 -0.4 0.1 0.4
0.6
0.75
0.9 1 .o
These values read from smoothed plots, can be regarded as relative initial decomposition rates a t 530' C. and a t a pressure of 100 mm. Madorsky, Straus, Thompson, and Williamson (49) have studied the thermal decomposition of polyethylene, polybutadiene, GR-S, polystyrene, polyisobutylene, and polyisoprene a t a pressure of 10-6 mm. a t temperatures of 300" to 475" C. in a specially designed apparatus wherein the decomposition products were removed from the reacting mass as they were formed. They found the relative stabilities of these high polymers to be i n the order named above, polyethylene and polybutadiene having equal stabilities. In the case of polyisobutylene and polyisoprene the yield of monomer, based on the decomposed portion of the polymer, was constant over a wide range of temperature, conversion, and duration of the experiment. On the other hand, the yield of monomers from polybutadiene decreased with a rise in temperature. Although the chain of polyethylene does not have distinctive marks to indicate the units from which it was built, the relative amount of small fragments up to about CS was fairly constant over the temperature range employed. The authors state that the relative number of scissions in the chain will be determined by the frequency of low-energy C-C bonds in the chain and by the steric hindrance of side chains to the escape of fragments. They show by indicating these low energy C-C bonds in the structural formulas of the various polymers that their experimental results confirm the above postulate. I n a later article, Madorsky (48) indicates that there are three mechanisms by which the high polymer chains can rupture: Small fragments of monomeric size break away from the ends of the long chain until the remaining fragment is small enough t o escape into the vapor phase; the polymer chain breaks a t random until the fragments are small enough to vaporize; or a mixture of the two occurs. He also postulates that the decomposition is due t o presence of free radicals in the environment of the reaction. Hepp, Spessard, and Randall have shown that olefin yields from their own (36) and other ethane cracking experiments can be related t o the depth of cracking expressed as per cent of equilib-
Vol. 42, No. 9
rium. Olefin yields decreased and methane yields increased sharply as the thermal decomposition approached 100% of equilibrium. The authors indicate that the value of 69,700 calories per gram mole for the activation energy of ethane decomposition as derived from other experiments is in agreement with their own work. The thermal decomposition of unsaturated hydrocarbons such as butadiene, isoprene, and isobutylene produces liquid materials which are very often yellow in color. Murphy and Duggan (64) have identified the main yellow product as dimethylfulvene by its absorption spectra, hydrogenated products, and its oxygen derivative. A procedure for the design of tubular heaters for the production of ethylene from mixtures of ethane and propane has been presented by Buell and Weber (14). Four test runs are reported on a commercial unit processing about 6,000,000 cubic feet per day of a mixture of 70% propane, 20% ethane, and 10% methane, at calculated reaction temperatures ranging from 1400' to 1470" F. Single-pass yields of 30 pounds of ethylene per 100 pounds of feed were obtained. Their reported reaction velocity constants for ethane and propane decomposition are distinctly lower than those reported by Schutt (64). Straight-run gasoline octane numbers are commonly improved in refinery operations by thermal reforming and by the addition of tetraethyllead. Feuchter (22)discusses the manner in which the most economical combination of reforming and lead addition can be obtained. Basing his studies on an East Texas crude, he has found that maximum profits are obtainable when thermally reforming a 275' to 400" F. boiling range naphtha so that its octane number is increased by about 14 units when a finished gasoline octane number (research method) of 84 is desired. Thermal reforming becomes more attractive when gasoline prices are low, and when butane prices are high, according to these studies. I n addition to the economic studies, the paper presents generalized correlations showing reformate, Ca, and 6 4 yields; volatility increase; molecular weight changes; octane number improvement; and lead susceptibility of the reformate, all as functions of dry gas yield and other minor variables. During the past year a new method for the continuous coking of heavy residual oils was announced (66, 6 7 ) . This process utilizes the principle of the continuous circulation of a stream of hot coke particles, produced in the process itself, which are brought into contact with a preheated oil charge. The deposition of coke on the particles occurs during the downward movement of the mass through a reactor. From the bottom of the reactor the coke particles pass by gravity t o an internally fired reheater, where they are brought to the proper temperature for recirculation by conventional elevators to the top of the reactor for the next pass through the coking zone. Successive increments of coke accumulate on the particles, and those of the desired size are removed from the process by classification as dry lump coal which is said to be of low volatile content and high mechanical strength. Product distribution comparable to conventional delayed coking is cited, although higher gas oil yields and lower coke yields are claimed for the continuous process. Schutte (65)has considered the economics of adding the abovedescribed type of continuous coking to a California refinery operating with topping, catalytic and thermal cracking, and treating facilities. If the coke is valued a t $10 per ton he concludes that it is more profitable to include coking in the refinery scheme, and that profitability increases as liquid fuel oil values become lower. The Curran coking process as described by Curran (19) involves the heating of heavy residual oils in a chamber having a rectangular cross section with a refractory floor which is heated from below and maintained a t 1800"to 2000"F. The ends of the coking ovens are closed by removable refractory-lined doors which are sealed in place during a run. The rate of oil feed to the oven is regulated so that the temperature of the vapors leaving
September 1350
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
does not fall below 850’ F., and after 1.5 to 3 hours when the coke bed is 6 to 8 inches thick the oil charge is stopped. After 2.5- to Chour drying period, the end doors are lifted and a motordriven ram which travels the entire length of the oven discharges the incandescent coke t o a quenching system. The complete oven cycle requires 6 t o 8 hours, and with multiple chambers whose cycles are staggered, the vapor overhead t o the fractionation system is nearly uniform in composition and volume. The coke is said to contain less than 2% volatile matter. A description of the equipment and procedure for hydraulic removal of coke from chamber-type thermal coking plants has been presented by Welsh (84). Hydraulic decoking is defined as a method of disrupting, removing, and transporting petroleum coke from vertical coke chambers by means of high pressure streams of water. Compared with the older cable method of coke removal, the hydraulic decoking technique was said to reduce clean-out time by 50% and at the same time allow a reduction of 45% in the number of men required for the clean-out crew. Because many refiners are processing catalytic cycle oils in thermal cracking equipment, it is of interest to compare such cracking results with those obtained from virgin feeds of equivalent gravity. McReynolds and Barron (47) have reported on the thermal cracking of 26 catalytic cycle oils ranging in gravity from 18.1’ to 42.5” A.P.I. Correlation of product yield and quality and plant capacity was developed. The authors conclude that catalytic cycle oils yield more fuel oil residue and leas gasoline than virgin gas oils of the same gravity. Furthermore, at a given viscosity the A.P.I. gravity of the fuel oil waa lower from cycle oil cracking than from the cracking of virgin oils.
CHEMICAL CONCEPTS OF CATALYTIC CRACKING Since the writing of the last review on this subject a considerable amount of information has appeared in the literature. Interestingly enough, a large part of the material deals with the attempt t o bring together the structure of the cracking catalyst and the reactions produced by the catalyst. There is agreement that the mechanism of catalytic cracking proceeds through the formation of the carbonium ion intermediate. The reactions of cracking] isomerization, hydrogen transfer, and alkylation all occur by the carbonium ion mechanism. A comparison of the catalytic cracking reactions, as an example of the carbonium ion mechanism, and of the thermal cracking reactions, as an example of the free radical mechanism has been given by Greensfelder, Voge, and Good (30). The authors show that in thermal craeking the experimental results agree well with the predicted value based on the Rice free radical theory, as modified by Kossiakoff and Rice. The main features of the thermal cracking reaction involve the formation of a complete sequence of normal a-olefins from a long-chain normal paraffin, large amounts of ethylene and propylene, and fairly considerable quantities of methane and ethane. On the other hand, catalytic cracking involves the formation of highly isomerized lower olefins and paraffins and only small amounts of methane and ethane. The hydrogen transfer reaction plays an important role in catalytic cracking, whereas it is only a minor reaction in thermal cracking. Activated carbon produces a cracking reaction which is different from both thermal and catalytic cracking. I n this particular case the products from cracking of n-hexadecane were 60% saturated but not branched. The authors (SI) characterize this type of cracking as a radical mechanism at an active surface, where the primary cracking products are combined with hydrogen atoms on the surface, thus preventing further cracking to smaller fragments. Thomas (73) and Greensfelder, Voge, and Good (30) have explained the mechanism of the cracking reaction from the standpoint of the carbonium ion reaction. The steps involved are: formation of the carbonium ion from a small amount of olefin and the acidic catalyst (HA); beta-cleavage of the carbonium ion, producing a lower olefin and a new carbonium ion; re-
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arrangement of the new carbonium ion to a secondary or tertiary carbonium ion and further cracking at the beta position; and, finally, when the point is reached where the chain becomes so short that cracking is no longer a rapid reaction, an exchange reaction with a higher molecular weight hydrocarbon to produce a new larger carbonium ion and a small paraffin. The chain is thus propagated. A number of viewpoints have been presented on the structure of the cracking catalyst. According to Thomas (73), the inclusion of a tetrahedral aluminum atom in the structure of tetrahedral silica results in the formation of a n A104 grouping which is unsatisfied by a whole valence unit. The residual hydrogenoxygen bonding is thus reduced to an awociation of hydrogen with four oxygen atoms and, aa a result, the composite exhibits strong acidic properties. The unit groupings of the active constituents are given for silica-alumina, silica-magnesia, silicazirconia, alumina-boria, and titania-boria. A similar view of the structure of the cracking catalyst has been presented by Tamele (7@, who postulates the formation of the acid sites by the condensation of the surface hydroxyl groups of the incompletely polymerized silica hydrogel vr-ith the hydroxyl groups of the hydroxylized aluminum ions. By contrast, Milliken, Mills, and Oblad (61)point out that the acidic materials formed upon interaction of silica and alumina hydrogel are extremely unstable; therefore, the acid structures suggested by Thomas (73) and Tamele (72)cannot be present in amounts sufficient to account for the activity of silica-alumina mixtures at the cracking temperatures. The authors suggest that “acids” are created a t elevated temperatures in the dry state. The amount of acid created, when, for example, the catalyst comes in contact with a base like quinoline, depends upon the extent of interfacial sharing of oxygen ions between silicon and aluminum ions, the hydroxyl content of the y-alumina present, and, finally, the base strength or polarizing capacity of t h e base. In order to explain the formation of carbonium ions, necessary for the cracking reaction in actual hydrocarbon processing, the authors postulate that stable carbonium ions are created b y structural changes in’ the catalyst. This is accomplished by a shift in coordination Jf the ‘‘active” aluminum ions (ions in t h e vicinity of tetrahedral silica) t o the four-coordinate or “acid” form. The reaction is reversible, so that desorption is possibIe through the tendency of the aluminum to go back to its sixcoordinated form. The poisoning of cracking catalysts by nitrogen compounds and potassium ion has been discussed by Mills, Boedecker, and Oblad (62). The authors show that quinoline sorbed on a silicaalumina catalyst is held physically as well as by chemisorption. The chemisorbed nitrogen base is not removed by flushing out with nitrogen, whereas the physically held base is removed by such a treatment. A cracking catalyst thus pretreated shows a substantially lower activity for cracking. The effect is general for basic nitrogen compounds, although some are less poisoning than others. A similar neutralization of the active centers of cracking catalyst was observed by the addition of potassium ion to the cracking catalyst. I n all cases exceedingly small amounts of basic material are required and the authors conclude that the major part of the surface does not contribute to the crarking activity of the catalyst. A considerable amount of work has been reported by Grenall (SI) on the hydrogen ion concentration in the Filtrol clay catalysts. The author determined this hydrogen ion content b y titration with alkali in the presence of 5% solution of sodium chloride as titration medium. The use of the sodium chloride solution was assumed to be beneficial from the standpoint of facilitating the exchange of a sodium ion for a hydrogen ion. The results indicate that there is a fairly good linear relationship between the temperature of calcination of the catalyst and the hydrogen ion content, the latter dropping to zero at 1560’ F. Added steam has a marked effect upon the hydrogen ion concen-
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 42, No. 9
Reactors and intermediate Heater, Pledorming Unit,
Old Dutch Refining Company,
tration, and a small amount of steam (up t o 20%) produces a large decrease in the hydrogen ion concentration. The chemistry of clay cracking catalysts has been discussed by Thomas, Hickey, and Stecker (74,who subjected a montmorillonite clay to acid extraction ,and followed the resulting material from the standpoint of structure and catalytic activity. It was found that under controlled conditions cold acid removes the baseexchangeable iona almost completely but it removes practically no aluminum, while hot acid treatment, removes aluminum from the clay, rcsulting in an increase in catalytic activity until a maximum is reached followed by a decrease. The authors postulate that one of the two octahedrally coordinated aluminum atoms is removed from the central layer together with two hydroxyl groups. The remaining octahedrally coordinated aluminum atom is changed to a tetrahedral coordination, resulting finally in a negative charge which requires the association of a hydrogen ion t o neutralize this charge. Thus, the catalyst becomes more acidic and, therefore, more active. The catalytic cracking of uns;tlametri&I diarylethanes was studied by May, Saunders, &,pa, and Dixon (60). It was found that in cracking these compounds over a low-surface kaolin and a high-surface silica-alumina catalyst, the rate of cracking decreases as the electronegativity of the substituents increasesfor example, chlorosubstitution in the ring reduces the rate of cracking to a large extent. Theae results are in accord with a carbonium ion mechanism of cracking;. The cracking of high-suIfur stocks w a investigated by Conn and Brackin (IT), who employed steam t o combat the poisoning effect of sulfur compounds. The conelmion is reached that the
Muskegon, Mich.
rate of sulfur poisoning depends upon the extent of hydration of the catalyst when i t comes into contact with the oil, as well aa upon the concentration of the sulfur compounds in the oil and the ability of the steam to replace the sulfur compounds.
INDUSTRIAL FEATURES Conn, Meehan, and Shankland (18)have reported the first commerical operating experience with silica-magnesia cracking catalyst. Their results confirm semicommercial scale predictions (60) that with this catalyst higher gasoline yields of lower octane rating are obtained than when silica-alumina catalyst is used at comparable operating conditions. It was found that activity maintenance was distinctly better with this catalyst, and the maintenance of cracking selectivity just as good as with silicaalumina, Because of the greater attrition resistance of silicamagnesia, make-up requirements to replace normal plant losses were only two thirds of those used for similar silica-alumina operations. An unusual feature of silica-magnesia catalyst waa the possibility of operating with regenerated catalyst carbon contents of as high as 4% without the uncontrolled coke production and excessive catalyst losses experienced with incompletely regenerated silica-alumina catalysts. During the course of the run, 315 days of which were reported on, the regeneration characteristics of the silica-magnesia catalyst showed a steady decline. At a maximum permissible regeneration temperature of 1050' F., and at a flue-gas oxygen content of 1.50/0,the residual equilibrium carbon content of the regenerated catalyst rose t o 4%, while at similar conditions the carbon content of regenerated silica-ahmina catalyst was constant a t about 0.5%.
September 1950
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
The performance of a sulfur-resistant (SR) natural catalyst has been compared by Thomas (76)with that of regular natural catalyst when processing feed stocks containing 2 t o 3% sulfur in a commercial fluid catalytic cracking unit. The following table shows his comparison of the properties of regular and ~ulfur-resistantnatural catalysts. AlaOa, % ' FenOl,
it
NaiO. Burface area, sq. meters/gram
Regular
BR
15.7 1.32 0.10 250-a25
40.9
0.42 0.05 130
Although steam hydration of regular catalyst in the regenerated catalyst standpipe was employed to suppress sulfur poisoning, the permissible steam rate was insufficient to protect this catalyst completely. As much as 20 tons per day of fresh regular natural catalyst addition was required to maintain activity in a unit containing a working inventory of 400 tons, whereas only 2 to 3 tons per day of fresh sulfur-resistant addition were needed to maintain the same cracking activity. Only 60% as much steam for dispersion and stripping is being used with sulfurresistant catalyst as was used when the regular grade was in the unit. Extensive plant operating and yield data are presented for the two catalysts, although at different conversion levels for each catalyst. Recognizing the adverse effect of certain metals on the selectivity and activity of cracking catalysts, Wrightson (86) has presented analytical methods for evtimating the iron, nickel, and vanadium contents of petroleum fractions. His methods are based on the development of colored solutions by reagents specific to each metal, and the measurement of color intensity by a spectrophotometric procedure. The effect of the depth of flashing of a reduced crude on the metal content of the overhead distillate is illustrated by analyses made by the author's method. According to Caesar (16), the decomposition reactions in suspensoid catalytic cracking have features which are common to both conventional thermal cracking and catalytic cracking. He suggests that the product distribution from suspensoid cracking is largely determined by thermal reactions, but it is modified to some extent by those reactions typical of catalytic cracking, such as isomerization, hydrogen transfer, and intramolecular condensations. It was claimed that the presence of catalyst powder in tubular heaters is effective in minimizing coke deposition by scouring the metal surfaces, or by the adsorption of heavy polymers which eventually would form coke in the tubes in the absence of catalyst. An operation in which a crude oil is charged directly to a fluid catalytic cracking unit along with gas oil has been described by Brown and Sterba (13). This particular Wyoming crude has a high sulfur content, a gasoline content of about 60%, but only 2.4% of asphalt bottoms remaining after a laboratory vacuum distillation. Its gasoline contains 0.44% sulfur, almost half of which appears in mercaptan combination. The processing of the entire crude in this manner accomplishes the refining steps of distillation, gasoline desulfurization, and catalytic cracking of the topped crude, all in one operation. The results of cracking an East Texas gas oil in once-through operation using a silica-alumina bead catalyst in moving bed pilot plant equipment have been presented by Schall, Dart, and Kirkbride (63). Conversions were varied from 50 to 80% by changes in space velocity and catalyst-to-oil ratios a t temperatures of 850" and 900' F. Their results have been presented graphically to show the effects of the above operating variables on product distribution and quality. Generalized correlations were developed to enable the prediction of the entire product distribution, and the extension of these charts to apply to different feed stocks was discussed. Similar data were presented by Olsen and Sterba (66) for the catalytic cracking of a mid-continent gas oil using a fluid silicaalumina catalyst in pilot plant equipment at temperatures of
1743
800°, 900°, and 950' F., and at a constant catalyst-to-oil ratio of 10. They concluded that the general effect of increasing reactor temperatures a t a given conversion was to produce less catalyst deposit, less gasoline, and greater quantities of light hydrocarbon fractions having higher olefin contents. Although the clear octane number of the gasoline was increased, its lead response was decreased by the use of high reactor temperatures. Working with Thermofor catalytic cracking pilot plant and commercial catalytic cracking data, McKean and Grandey (46) have developed equations and charts which enable the prcdiction of the effects of space velocity and catalyst-to41 ratio on conversion. An important feature of their equations is that they satisfy terminal conditions a t zero and 100% conversion, besides showing good agreement with experimental data in the middle range. This provides a sound basis for extrapolating data in either direction of conversion or severity. The economics of four typical refinery operations have bcen compared by Peavy, Weinrich, Hornaday, and No11 (68). In this study conventional thermal cracking was compared with Houdriflow catalytic cracking for which feed stock could be prepared by vacuum flashing, viscosity breaking, or thermal coking. These authors conclude that, at the crude and product price structure used, coking and viscosity breaking were the best methods for preparing catalytic cracking feed stocks. They point out the advantage of the use of catalytic cracking to minimize the production of residual fuel oil. A comprehensive precision analysis has been made by the National Bureau of Standards (9.9)of a gasoline produced by the Houdry fixed-bed catalytic cracking process a t undisclosed operating conditions. This essentially debutanized sample was found to contain 4.4% normal paraffis, 42.7% isoparaffis, 16.8% cycloparaffins, 31.9% aromatics, and 4.2% olefins. The aromatic portion was composed of 4.4% benzene, 20.5% toluene, 44.5% Ca aromatics, 26.1% COaromatics, and4.5% CIOand higher aromatics. The Cp alkylbenzene fraction was rather carefully resolved spectrographically by six different laboratories with good agreement among the cooperating groups. This should provide important data for comparison with the relative amounts of COaromatic isomers prescribed by thermodynarqic equilibria. Egloff (200) has summarized the advantages of modern refining processes being employed in the huge expansion of refining facilities which will have capacity to process 6,500,000 barrels per day of crude. He points out that this expansion involving the use of modern processes will result in improved product quality, and that these results were possible largely because of two factors: research and the competitive drive of the profit system. Such recent expansions which include catalytic cracking have been described for specific refineries in a symposium by Fisher (M), Frame (96),Siecke (88), Kincannon (43), Luton (&), Morgan (63),Jackson (SI), and others (1-3). Similar descriptions of r e cently installed catalytic cracking units have been given by McMurray (46)and Thornton (77). A recently installed quadruplereactor Houdriflow catalytic cracking unit having a height of 308 feet is said to be the tallest refinery structure in the world (6). The method used for the construction of a fluid catalytic craoking unit of the single-vessel type in a record time of 117 days has been described (7,IO). In a recently installed fluid catalytic cracking unit the spent catalyst stripper is located in the bottom section of the reactor to minimize structure height. Spent catalyst flows into the stripper through 30 flapper doors set a t three different elevations, and through 12 vertical slots located near the top of the stripper. This unusual feature of the stripper allows the catalyst to enter preferentially from the top of the dense bed in the reactor, regardless of the bed depth (891. A description of the method of application and the design details of a newly developed monolithic lining for the regenerators of fluid catalytic cracking units has been given by Uhl(79). He also describes the method of minimizing the erosion of flue gas gres-
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
sure control valves involving the insertion of a fixed pressure drop cxpansion chamber downstream from the control valve to reduce the total pressure drop in several successive stages. Thornton (76) and Foster (85)have described a fluid catalytic cracking unit designed to process a feed stock prepared by the propane deasphalting of a sour crude. This unit has an auxiliary reactor which is operated a t about 700" F. for the desulfurization of straight-run gasoline, kerosene, and Diesel fuel. Although the treated vapors from this reactor pass to a separate rerun column, it shares the regenerators with the main cracking reactor. The mechanical features of Colorado's first catalytic cracking unit, of the Thermofor type, have been described by Fenex, Hoge, and Friedman (21). Performance data are presented for the processing of Lance Creek gas oil a t a conversion of over 80% and at a recycle ratio of about 1 to 1, using natural clay catalyst. The world's largest fluid catalytic cracking unit went on stream during the past year. This unit, designed to process 36,000 barrels per day of fresh feed, has a reactor 35 feet in diameter and a regenerator 55 feet in diameter, which contains three stages of cyclone catalyst separators located a t the top of its hemispherical head ( f , 81 ). A departure from usual design practice was the specification of centrifugal instead of reciprocating compressors for handling the process gas from this unit. During the past year, the world's smallest commercial catalytic cracking unit went on stream (6). This unit, of the fluid type, has a design capacity of 1500 barrels per day. The organization of a wide variety of craftsmen, involving as many as 500 men a t one time, during the inspection and repair of fluid and Thermofor catalytic cracking units has been detailed in several papers ( 4 , 9, 15, 24, 35). It is pointed out that planning for these turnarounds begins when the unit is designed. In one instance (9) the 29,650 man-hours required for a 13-day turnaround are shown resolved into the 15 crafts involved. In another paper (8) the engineering procedure is outlined for completing a turnaround in 329 hours after a 608-day initial run of a 28,000-barrel-per-day catalytic cracking unit. The 37,213 manhours are shown resolved into 18 crafts. The graphic or pictorial instrument panel has been widely adopted in new catalytic cracking installations during the past year (12, 28,87, 78, 80). This panel utilizes miniature control and indicating instruments placed a t appropriate points in a simplified process flow diagram which is an integral part of the panel itself. In addition to providing a better visual picture of operating conditions, the panel is said to be less expensive than the conventional because it is prefabricated, is shipped as a packaged unit, and uses smaller instruments. A nomograph for computing weight hourly space velocity directly from instrument readings available to operators of catalytic cracking units has been presented by Gary (27). An instrument, described by Ramser and Hickey @9), is being used to indicate and record the quantity of catalyst being carried out of a fluid catalytic cracking unit by the flue gas stream. It consists of an optical element to measure catalyst concentration, and a Pitot tube to measure flue gas rate, both coupled so as to give readings in terms of instantaneous rate of solids loss.
REFORMING AND DEHYDROGENATION CHEMICAL CONCEPTS In describing the chemistry of the Platforming process Haensel (32)has pointed out that there are three major reactions involved. The first of these is the dehydrogenation of naphthenes to the corresponding aromatics. In the case of five-membered ring-type naphthenes the dehydrogenation is shown to be preceded by isomerization to the six-membered ring type. Another important reaction in Platforming is hydrocracking, which can be considered as a simultaneous cracking-isomerization-hydrogenation reaction as illustrated by the formation of isopentane (Z-methylbutane) and %-pentane from n-decane and hydrogen. The third contrib-
Vol. 42, No. 9
uting reaction is that of isomerization of paraffins as well as fivemembered ring naphthenes. In the case of n-heptane, the isomerization reaction was shown to be more rapid than hydrocracking a t high space velocities and nearly every possible heptane homer was produced. In addition to the three major reactions, there are others which include the dehydrocycliiation of paraffins to aromatics, and desulfurization by which virtually all of the combined sulfur is converted to hydrogen sulfide. On the other hand, certain reactions which are common to reforming processes are minimized or absent in the Platforming process. Thus, Platforming is said to be unique among reforming processes in that very little methane is produced, and substantially no catalyst deposit is formed. Because the formation of compounds of high molecular weight is eliminated in this process, Platformates do not require rerunning, The extent of these various reactions is balanced to give the optimum yield-octane number relationship and the desired product distribution by the proper preparation of the catalyat and the adjustment of operating conditions which include space velocity, pressure, temperature, and hydrogen recycle. Data are presented in the original paper to illustrate the effects of each of these operating variables on the yield and properties of the Platformate for the processing of a typical naphtha. Experimental data are presented to show that blends of equal parts of thermally cracked and straight-run gasoiines can he Platformed satisfactorily with substantial net hydrogen production. The reforming of naphtha in the presence of hydrogen has been investigated by Hughes, Stine, and Darling (38)using a coprecipitated chromia-alumina catalyst. The authors found that such a catalyst compares favorably in its performance with that of a molybdena-alumina (hydroforming) catalyst. As expected, increasing the partial pressure of hydrogen results in lower aromatic and olefin production as well as in a lower carbon formation. As the partial pressure of hydrogen is increased the hydrogen production decreases, so that a t about 200 pounds per square inch partial pressure this production amounts to about 50 cubic feet per barrel as compared to about 1700 cubic feet per bs,rrel in the absence of added hydrogen. Using contact time as a variable, the authors found that a t short times of contact the olefin production is high and the aromatic production is low, while the reverse is true a t long times of contact. Thus, it is postulated that the dehydrocyclisation reaction proceeds through an olefin and the effect of hydrogen pressure is that of opposing this initial dehydrogenation step. Such a mechanism is in line with the work of other investigators. The catalyst preparation involved the use of a pH of 10 during the precipitation of the slurry and the use of 18 to 30 mole % chromia in the catalyst composite. The dehydrogenation of indane was investigated by Rosenberg (6.2) using a chroniia catalyst a t 470" and 520" C. I t was found that the main reaction occurring was formation of indene, which took place to the extent of 50 to 55%. The carbon deposition was very high, amounting to 18% at 470" C. and 40% a t 520' C. The formation of cyclopentadiene from 1,a-pentadiene has been studied by Kennedy and Hetzel(4.2). It was found that the use of chromia on alumina, fused alumina, activated alumina, and silica gel gave results which were very similar, indicating that the reaction is essentially noncatalytic. The most successful approach to increased yield of cyclopentadiene was that of using low pressures (less than 30 mm. of mercury) wherein polymerization and other side reactions are decreased to a reasonable extent. The maximum once-through yield of cyclopentadiene was about 9% and was obtained at about 675" C. and 15 mm. of mercury pressure and using jack chain as the contacting medium. The calculated recycle yield of cyclopentadiene under these conditions is about 40%. The catalytic dehydrogenation of butenes was reported by Kearby (41), who describes modifications in composition of the 1707 catalyst. The main feature of this particular catalyst,
September 1950
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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which consists of 72.4% magnesia, 18.4% ferric oxide, 4.6% copper oxide, and 46% potassium oxide is the high selectivity and stability for the conversion of butanes to butadiene. The process is operated a t about 1200O F.,10 to 1 steam to hydrocarbon ratio, and a butene gaseous space velocity of 400 volumes (S.T.P.) per volume of catalyst per hour. It has been found that a t the operating conditions employed, the potassium carbonate is gradually depleted from the catalyst, so that i t is necessary to place a supply of potassium carbonate ahead of the catalyst. In such a way the activity of the catalyst could be maintained. The normal length of catalyst life in commercial operation is a few months. The author also discusses the effect of other promoters and catalysts supports upon the performance of the composites. Thus, i t was found that potassium, rubidium, and cesium are excellent promoters, while lithium and sodium are inferior. Among the catalysts supports it was found that active catalysts were obtained when the magnesia base is replaced by iron oxide, zinc oxide, copper oxide, beryllium oxide, or zirconium oxide. On the other hand, calcium oxide, aluminum oxide, silicon oxide, and titanium oxide as well as activated carbon are less satisfactory. Since that time a modified unsupported catalyst containing ferric oxide, chromic oxide, and potassium oxide has replaced the 1705 catalyst in most butadiene plants in view of longer life and ability to operate without intermittent regeneration a t high steam-butene ratios.
INDUSTRIAL FEATURES During the past year the first commercial Platforming unit went on stream. A description of this unit, along with operating conditions, yields, and product quality has been presented by Haensel (%), Bland (11), and Kastens and Sutherland (40). The flow through the reaction zone is through three fixed catalyst beds arranged in series with reheating of the effluent from the first and second beds. Inlet temperatures of 920’ F.to each bed are indicated, and a t a pressure of about 700 pounds per square inch the pressure drop through the reactors and reheaters is only 25 pounds per square inch. Because the catalyst does not require regeneration, the process flow is continuous. At a design throughput of 1500barrels per day of reactor charge having a leaded F-1octane number of 70.2,a 97.1% Platformate yield was obtained and it had a 94.7leaded octane number. The lead level waa 3 ml. per gallon in both cases; 4.5% of outside butane was required to bring the vapor pressure of the Platformate up to 10 pounds per square inch. The 0.08% sulfur content of the gasoline feed was reduced to 0.0019% in the Platformate, indicating a 97.5% desulfurization. The Platforming process replaced thermal reforming in a small Michigan refinery which also employs crude distillation, thermal cracking, and polymerization. In addition to quality improvement, the installation of the Platforming process has enabled this refiner to raise his over-all gasoline yield from 41.9% to 48010, based on crude input. Bland (11)points out that the Platformate, because i t is olefinfree, unusually low in sulfur content, and composed predominantly of isoparaffins and aromatics, has better stability and lead susceptibility than cracked gasolines. Operating costs of the order of 30 to 37 cents per barrel of feed are cited. These include labor, utilities, maintenance, taxes, insurance, royalty, and catalyst charges. In tracing the history of developments concerned with improving straight-run gasoline quality, Kastens and Sutherland (40) compare yields and octaqe number improvements obtainable by desulfurization, thermal reforming, polyforming, and hydroforming with those from Platforming. At any given research method octane number level, the yield obtainable by the Platforming process appeared to be distinctly better than from any of the other processes. Sutherland and Hanson ( 7 1 ) have noted that of the gasoline production in the United States, natural gasoline accounts for
Recycle Gas Compressors, Platforming Unit,
Old Dutch Refining Company, Muskegon, Mich.
17% of the total, and suggest that the Platforming process is ideal for their octane number improvement a t high liquid recoveries. They point out the advantage of by-passing the reactor section with the lighter fractions of the total gasoline feed, processing only the heavier fraction for maximum over-all yield of a given finished octane number. For the over-all yield to be optimum, the octane number of the unprocessed light end should be equatto or slightly higher than the desired final octane number (F-1 method with 3 ml. per gallon of tetraethyllead). The road ratings (F-8 B) of two Platformates are shown to be equal to or better than the research method (F-1)ratings a t engine speeds of lo00 r.p.m. or more, using Platformates leaded with from 1 to 3 mE. per gallon of tetraethyllead. Neal and Ames (66)describe the construction and operation of a cycloversion unit, and present plant data for the reforming of a gasoline from an octane number of 81 to about 88 (F-1with 3 ml. per gallon of tetraethyllead). It is reported (83)that because of the growing demand for benzene, one of the hydroformers in the Gulf Coast region is synthesizing benzene from cyclohexane and isomerized methylcyclopentane. LITERATURE CITED (1) Anon., Oil Gas J . , 47, No. 47, 184 (1949). (2) Ibid.. D. 178.. (3) Ibid., b. 222.’ (4) Ibid., 48, No. 5, 94 (1949). ( 5 ) Ibid., 48, No. 49, 56 (1950). (8) Ibid., 49, No. 1, 44 (1950). (7) Anon., P e t r o h m Ewineer, 21, No. 12, (2-48 (1949). (8) Anon., P e t r o h m Processing, 5, 148 (1950). (9) Anon., Petroleum Refiner, 28, No. 7, 118 (1949). (10) Ibid., 28, No. 11, 138 (1949). (11) Bland, W. F., Petroleum Proceasing, 5, 361 (1950). (12) Boyd, D. M., Jr., Ibid., 4, 979 (1949). (13) Brown, H. A., and Sterba, M. J., Ibid., 4, 878 (1949),. (14) Buell, C. K.,and Weber, L. J., Ibid.,5, 228 (1950).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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(15) Byrne, T. J., and Jenkins, F. M., Oil Gas J., 48, No. 46, 275 (1950). (16) Caesar, C. H., Pdroleum Processing, 4,887 (1949). (17) Conn, A. L., and Brackin, C. W., I n . ENG.CHEK., 41, 1717 (1949). (18) Conn, A. L., Mwhan, W. F., and Shankland, R. V., Chem. Eng. Progress, 46,176 (1950). (19) Curran, M. D., Oil Gaa J.,48, No. 15, 100 (1949). (20) Egloff, G., Zbid.,47, No. 47,162 (1949). (21) Fenex, J. E., Hope, A. W., and Friedman, L., Petrohm Refiner, 28, No. 8, 103 (1949). (22) Feuchter, C. F., C h Eng. Progress, 45,644 (1949). (23) Fisher, F. R., Oil Gas J.,47, No. 47, 160 (1949). (24) Foster, A. L., Petroburn Engineer,21, No. 8, C-7 (1949). (25) Ibid., 21, No. 12, C-6 (1949). (26) Frame, A. P., Oil Gae J., 47, No.47,177 (1949). (27) Gary, J. H., Petroleum ProcesPing, 4, 1104 (1949). (28) Gees, L., Petroleum Refiner,29, No. 3, 110 (1950). (29) Glasgow. A. R., Willingham, C. B., and Rossini, F. D., IND. ENG.CHEM.,41,2292 (1949). (30) Greensfelder, B. S., Voge, H. H., and Good, G. M., Ibid., 41, 2573 (1949). (31) Grenall, Alexander, 41, 1485 (1949). (32) Haensel, V., Oil Gae J . , 48, No. 47, 82 (1950). (33) Haensel, V., and Sterba, M. J., Im. ENG.CHEM.,40, 1660 (1948). (34) Bid., 41, 1914 (1949). (35) Hardcastle, C. A,, Oil Gas J., 48, No. 46, 261 (1950). (36) Hepp, H. J., S w r d , F. P., and Randall, J. H., IND.ENG. CHEM.,41, 2531 (1949). (37) Howard, G. E., Petroleum Refiner,29, No. 3, 107 (1950). (38) Hughes, E. C., Stine, H. M., and Darling, S. M., IND.ENG. CHEM.,41,2185 (1949). (39) Jackson, W. K., Oil Gas J., 47, No. 47,232 (1949). (40) Kastens, M. L., and Sutherland, R. E., IND.ENG.CHEM.,42, 582 (1950). (41) Kearby, K. K., Ibid., 42,295 (1950). (42) Kennedy, R. M., and Hetzel, S. J., Ibid., 42, 547 (1950). (43) Kincannon, L. E., Oil Gas J.,47, No. 47,207 (1949). (44) Luton, R. E., Ibid., 47, No. 47,213 (1949). (45) McKean, R. A., and Grandey, L. F., Chem. Eng. Progress, 46, 245 (1950). (46) McMurray, S. R., Petroleum Processing, 5, 26 (1950). (47) McReynolds, H., and Barron, J. M., Petroleum Refiner, 28, No. 4, 111 (1949). (48) Madorsky, S. L., Science, 111,360 (1950). (49) Madorsky, S. L.,Straus, S., Thompson, D., and Williamson, L., J. Research Natl. Bur. Standards, 42, 499 (1949). (50) May, D. R., Ssunders, K. W., Kropa, E. L., and Dixon, J. K., Faraday Society, “General Discussion on Heterogeneous Catalysis,” April 1950.
GEORGE F. LIsK, ALLIED CHEMICAL
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(51) Milliken, T. H., Jr., Mills, G. A., and Oblad, A. G., Ibid., April 1950. (52) Mills, G. A,, Boedecker, E. R., and Oblad, A. G., J . Am. Chem. Soc., 72, 1554 (April 1950). (53) Morgan, D. G., OiZGas J., 47, No. 47,218 (1949). (54) Murphy, M. T., and Duggan, A. C., J. Am. Chem. Soc., 71, 3347 (1949). (55) Neal, H. A,, and Ames, C. B., Petroleum Engineer, 21, No. 8, C16 (1949). (56) Olsen, C. R., and Sterba, M. J., Chem. Eng. Progress, 45, 692 (1 949). \ - - - - ,
(57) Partington, R. G., Stubbs, F. J., and Hinshelwood, C. N., J . Chem. SOC.,1949, 2674. (58) Peavy, C. C., Weinrich, W., Hornaday, G. F., and Noll. H. D.. Petroleum Refiner,28, No. 6, 117 (1949). (59) Ramser, J. H., and Hickey, J. W., Petroleum Processing, 4, 776 (1949). (60) Richardson, R. W., Johnson, F. B., and Robbins, L. V., Jr., IND. ENG.CHEM.,41, 1729 (1949). (61) Robertson, A. J. B., PTOC. Roy.SOC.(London), 199, 394 (1949). (62) Rosenberg, L. M., Doklady dkad. Nauk S. S. S. R, 64,401 (1949). (63) Schall, J. W., Dart, J. C., and Kirkbride, C. G., Chem. Eng, Progress, 45,746 (1949). (64) Schutt, H. C., Ibid., 43, 103 (1947). (65) Schutte, A. H., Oit Gas J.,48, No. 26,70 (1949). (66) Schutte, A. H., and Offutt,W. C., Ibid., 48, No. 10,QO(1949). (67) Schutte, A. H., and Offutt, W. C., Petroleum Processing, 4, 769 (1949). (68) Siecke, P., Oil Gas J.,47, No. 47, 186 (1949). (69) Stubbs, F. J., and Hinshelwood, C. N., Proc. Roy. SOC.(London), 200 A, No. 1063, 458 (1950). (70) Stubbs, F. J., and Hinshelwood, C. N., Ibid., 201 A, Y o . 1064,18 (1950). (71) Sutherland, R. E., and Hanson, D. D., Oil Gas J . , 48, No. 50. 177 (1950). (72) Tamele, M. W., Faraday Society, “General Discussion on Heterogeneous Catalysis,” April 1950. (73) Thomas, C. L., IND. ENG.CHEW,41, 2564 (1949). (74) Thomas, C. L., Hickey, John, and Stecker, Glen, Ibid., 42, 866 (1950). (75) Thomas, E. J., Oil Gas J.,48, KO.46, 221 (1950). (76) Thornton, D. P., Petroleum Processing, 4, 1336 (1949). (77) Ibid., 5 , 45 (1950). (78) Tvy,V. V., Petroleum Refiner,29, No. 3, 102 (1950). (79) zlhl, W. C.. Petroleum Processing, 5, 33 (1950). (80) Ibid., p. 361. (81) Weber, G.. Oil Gas J., 48, No. 30, 58 (1949). (82) Ibid., 48, No. 36, 51 (1950). (83) Ibid., 48, No. 49, 60 (1950). (84) Welsh, A. F., Petroleum Processing, 5, No. 2, 157 (1950). (85) Wrightson, F. M., Anal. Chem.,21, 1543 (1949). RECEIVED June 27, 1950.
NATIONAL ANILINE DIVISION,
DYE CORPORATION, NEW YORK, N. Y.
ITERATURE information concerning sulfonation is reviewed for the period beginning with the latter part of 1948 and continuing to about the end of 1949. The scope and coverage indicatad in the first (1.94) and second (1.95) reviews are continued.
THEORETICAL CONSIDERATIONS ALlPHATlC COMPOUNDS
Saturated Direct Sulfonation. COMPOUNDS CONTAINING SULFUR TRIOXIDE. Recent publications continue to emphasize the inertness of paraffinic hydrocarbons t o sulfonation with compounds containing sulfur trioxide (SS). Ae in the past, the literature is directed not to sulfonation of p a r a h s per se but rather to sulfonation of mixtures containing p a r a h together with naphthenic or other more reactive hydrocarbons in order to produce
sulfonate products in improved yield and/or quality (77, 158, 155). Thus, Mitchell (138) pretreated and then sulfonated mineral oil extracts with sulfuric acid with the aid of an amphoteric element halide-e.g., stannic chloride, boron trifluoride, and sodium borofluoride-in an inert solvent such as liquid sulfur dioxide, in order to inhibit formation of color and odor in the resulting sulfonate detergents. Ruedrich (155) added, prior to sulfonation, about 12% of an oil-soluble petroleum sulfonate to naphthenic-type lubricating oils in order to decrease acid sludge formation and t o increase the yields of resulting oil-soluble sulfonates by 10 to 36%. Gilbert (77) sulfonated substantially aromatic petroleum lubricating oils with acid sludge obtained from the sulfonation of petroleum lubricating oil fractions with sulfuric acid. He found that the yields of resulting oil-soluble (mahogany) sulfonates are equal or superior t o those obtained using sulfuric acid or oleum. Schowalter and Lienbacher (i77)secured sulfonate derivatives
