*
INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1946
This polymerization of sulfur into long chains brings about the increase in viscosity with rising temperature (3, 7). Increase in temperature beyond 187" results in a shortening of the chains and, consequently, a falling off in the viscosity as shown in Figure 1. Reduction in the viscosity by the halogens, hydrogen sulfide, and hydrogen persulfides must be due to a reaction which shortens the chains. This scission is believe8 to take place with the halogen atoms taking terminal positions of the segments. Thus for chlorine we would have: ClSS-S
a
.
*
S-S-C1
or C1-S-S-S
*
S-S-S
I n the same manner hydrogen sulfide and persulfides shorten the chains with hydrogen as the terminal atoms of the segments. Such a mechanism would also explain why these substances persist so tenaciously in the liquid sulfur even when the mixture is kept far above their boiling points. There appears to be a great deal of uncertainty as to the direct combination of sulfur with iodine (9). While sulfur iodides may be made by indirect methods, the direct addition of iodine t o sulfur seems to have failed to produce them. The quick and tremendous reduction in the viscosity of sulfur above 160" C.
43
by minute amounts of iodine must indicate that some form of chemical combination does take place, and that it is rapid and quite persistent through a wide range in temperature, if the above mechanism for the reduckion of viscosity is sound. LITERATURE CITED
Ackley, C. S.,U. S.Patent 2,232,898 (Feb. 25, 1941). Bacon, R. F., and Fanelli, R., IND.ENQ.CHEM.,34,1043 (1942). Bacon, R. F., rand Fanelli, R., J . Am. Chem. Soc., 65, 639 (1943). Cain, G. A,, and Chatelain, J. B., U.6 . Patent 2,161,245 (June 6, 1939).
Darrin, M., IND.ENQ.CHEM.,20, 801 (1928). Duecker, W. W., Chem. & Met. Eng., 41, 583 (1934). Kauzmann, W., and Eyring, H., J . A m . Chem. SOC.,62, 3113 (1940).
Kobb6, W. H., Chem. & Met. Eng., 34, 163 (1927). Mellor, 5. W., "Comprehensive Treatise on Inorganic and Theoretical Chemistry", Vol. X, p. 653 (1930). Petty, G. M., Univ. of Pittsburgh, Bull. 30, 2 (Nov. 15, 1935). Powell, R. E., and Eyring, H., J . A m . Chem. SOC.,65,648 (1943). Read, H. L., U. S.Patent 2,341,572 (Feb. 4, 1944). Ibid., 2,341,573 (Feb. 15, 1944). Walton, J. H., and Parsons, L. B., J . A m . Chem. SOC.,43, 2539 (1921).
New Catalvsts for Friedel-Crafts Type Reactions J
A. N. SACHANEN AND P. D. CAESAR Socony-Vacuum Laboratories, Paulsboro, N . J . Various typical reactions, catalyzed by Friedel-Crafts catalysts or strong acids, may be carried out in the presence of heterogeneous catalysts of the silica-alumina type or homogeneous catalysts such as hydrogen halides or organic halides. The syntheses of anthraquinone and benzophenone are described as new examples of the application of such catalysts to conventional reactions of the Friedel-Crafts type. I
F
RIEDEL-Crafts chemistry was founded in 1877 when Friedel and Crafts discovered the condensation of aromatic hydrocarbons and alkyl or acyl halides with aluminum chloride. Since then, halides of aluminum, tin, zinc, iron, and other metals, and acids such as sulfuric, phosphoric, and anhydrous hydrofluoric have been found to catalyze a wide variety of condensation reactions. The scope of the condensation reactions has been greatly expanded in the last twenty-five years. The alkylation of paraffins and naphthenes, particularly of isoparaffins, is a recent development commercialized on a large scale in the production of high-octane hydrocarbons and fuels. These same catalysts have been applied to other types of reactions such as isomerization, transfer of radicals, and cracking. The application of silica-alumina and certain homogeneous catalysts t o reactions of these types presents new fields of scientific endeavor. SILICA-ALUMINA CATALYSTS
Active heterogeneous catalysts containing silica and alumina are produced either by activation of some natural clays or by synthesis. Silica gel, notwithstanding its enormous surface, does not catalyze the reactions described in the present paper. A small proportion of alumina, of the order of 1% by weight of the silica,
is sufficient to produce an active catalyst. Commercial cracking catalysts contain approximately 10% alumina. Oxides such as thoria or zirconia can be substituted for the alumina. Silicaalumina catalysts were first developed for the catalytic cracking of petroleum oils. Approximately 1,000,000 barrels of oil are now cracked daily over these catalysts. The alkylation of aromatic hydrocarbons with olefins, long established in Friedel-Crafts and strong acid syntheses, was the first application of silica-alumina to condensations of the FriedelCrafts type. Michel (11) described the condensation of naphthalene with propylene under pressure over fuller's earth to proSchollkopf (19) alkylated duce tetraisopropylnaphthalene. naphthalene with ethylene a t 230" C. under 20-40 atmospheres pressure over an activated hydrosilicate catalyst. Sachanen and O'Kelly (17) described the alkylation of benzene with propylene, butylenes, and amylenes over silica-alumina a t 450" C. and 100 atmospheres. Under these conditions the alkylation proceeded smoothly but was accompanied by partial cracking of the paraffinic side chains. As a result, toluene, ethylbenzene, and xylenes were produced in substantial yields. Destructive alkylation reactions Catalyzed by aluminum chloride, as observed by Ipatieff and co-workers (7), were carried out over silica-alumina catalysts by Sachanen and Davis (16). These investigators reacted benzene with pentanes over an activated clay for 45 minutes a t 480" C. and 1050 pounds per square inch. Twenty-eight per cent (by weight' of benzene charged) of alkylbenzenes boiling from 105-210" C. was produced. The application of silica-alumina to reactions formerly catalyzed by FriedelCrafts and strong acid catalysts was increased in scope by Hansford, Myers, and Sachanen (4) and by Thomas, Hoekstra, and Pinkston (8.9). These investigators dealkylated alkylaromatic hydrocarbons in the presence of silica-alumina at 450-550 C. An example of these reactions was the conversion of ethylbenzene to benzene and ethylene. O
0
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
44
TABLEI. SYNTHESISOF ANTHRAQUINOXE IN PRESENCE OF SrLrc.\-AI,unrrNa CATALYSTS
33 34 35 R u n No. 380 380 Temperature, C. . 380 Catalyst 180 180 180 Weight, grams 1 2 Fresh No. of regenerations Ratio, benzene to phthalic anhydride 8.3 7.8 7.8 Weight 14 14 14.8 Molar 5.1 5.1 5.1 Weight ratio, charge to catalyst 0.4 0.4 0.4 Contact time, sec. 22 23 22 Time on stream min. 77 91.5 9 2 . 0 Phthalio anhydride recovered, wt. % Antliraquinone yield, wt. % Based on total charge 0 87 0 . 7 7 0.69 Based on phthalio anhydride charged 7.8 6.8 6.4 Based on phthalio anhydride consumed 59 79 79.5 Theoretiaal ultimate (based on phthalic anhydride) 42.6 56.8 56.8
36 380
37 380
180 3
180 4
7.5 13.3 5.2 4.7 0.4 0.4 22.5 22 92.2 92.0 8.0 14.4
0 68 0.75 6,I 6.3 79
80
56.8
56.8
Hansford, Myers, and Sachanen (4)also described the conversion of alkylaromatic hydrocarboils by the transfer of alkyl radicals from one aromatic nucleus to another or by a dealkylationalkylation reaction catalyzed by silica-alumina a t 450-500 C. For example, O
+
CsHa(CH& CeHs +2Ci"CHs 2CsH4(CHa)z +CsHs(CHs)s 4-CoH6CH3
(1) (2)
These results are similar to those of Anschutz and Immendorff (1, d ) , Heise and Tohl (5),Boedtker and H a k e ( 9 ) ,Schorger (20), Lacourt (Q), and Ipatieff and Pines (8), who used aluminum chloride as a catalyst.
Vol. 38, No. 1
permit utilization of the reduced decomposition of the phthalic. anhydride resulting from the use of these lower temperatures. A sample of crude synthetic anthraquinone, analyzed by the reduction-oxidation technique described by Lewis (IO), was found to have a purity of about 95%. Table I shows the results of a series of five consecutive runs; each was made under similar rcaction conditions over the regenerated catalyst from the preceding run. The catalyst was regenerated by passing air through the catalyst bed a t 500-550" C. until the effluent gases were substantially free of carbon dioxide. I n this series no material balances were made on coke, gases, and benzene. Since benzene is substantially stable in the presence of silica-alumina catalysts under the conditions employed in these reactions, any benzene losses were considered to be mechanical losses. The phthalic anhydride, however, was recovered with care, and that consumed was considered to have been converted entirely to coke, gas, and anthraquinone. It is possible that more could have been recovered by flushing the catalyst with steani after each run and before each regeneration. The conversion per pass over the fresh catalyst was higher than that of the next four runs, but the ultimate yield was lower due to excessive cracking of the phthalic anhydride. The regencration of the catalyst lowered its condensing act'ivity somewhat but reduced its cracking activity even more. For this reason the ultimate yields were greatly increased after the catalyst had been regenerated a t least once. Anthraquinone can be synthesized in this manner in a onestage, continuous, or intermittent process: 0
0
SYNTHESIS OF ANTHRAQUINONE
The analogy between the catalytic effects of silica-alumina and The present commercial preparation of anthraquinone ic, a twoof Friedel-Crafts and strong acid catalysts is further supported stage batch process : by the condensation of benzene with phthalic anhydride over silica-alumina t o produce anthraquinone. The materials used in 0 0 0 this investigation were the usual C.P. grade of benzene and phthalic I1 I/ -C-H&O, anhydride. Synthetic silica-alumina catalysts were prepared @ ; l o by coprecipitation of the hydrous oxides in ratios of 9:1 t o 14:l -c-/ C-OH by weight. The apparatus included an electrically heated salt I/ 0 bath equipped with circulating system, and a reactor of one-inch i.p.s., extra-heavy, iron pipe of about 315-cc. capacity. The reAlthough the over-all yield of anthraquinone is higher than that actor was filled with silica-alumina catalyst. The benzene was obtained over silica-alumina catalysts, this process consumed 1.5 pumped by displacement with glycol into the bottom of the reto 2.0 moles of aluminum chloride per mole of phthalic anhydride actor by way of a preheater coil immersed in the salt bath. Nolcharged. The catalyst consumption using silica-alumina, howten phthalic anhydride was forced by air pressure from a heated, ever, is extremely low. The activity of this catalyst is not pergraduated, glass tube into the bottom of the reactor through a manently destroyed by one charge of phthalic anhydride and second preheater tube immersed in the salt bath. From the rebenzene. When the deposit of carbonaceous material on the actor the liquid product passed into a water-cooled condenser of catalyst has substantially reduced its activity, it is burned off, as Mnch inside diameter. The sudden change in rate of linear flow in the conventional cracking processes. I n this manner the life of the effluent gases into this relatively large cold chamber subof the silica-alumina may be extended to periods ranging from four stantially reduced the phthalic anhydride "fog" that otherwise months to a year. occurred. The uncondensed benzene and gases formed in the reThe conversion per pass over silica-alumina is small. However, action then passed through a filter into another smaller condenser the stability of the reactants and product at the temperature of t o remove the benzene. The anthraquinone was separated from the reaction and the short catalyst contact time permit the rethe unreacted phthalic anhydride by heating the solid product in covery of most of the benzene and phthalic anhydrides not conan excess of distilled water and filtering hot. The quantity of verted to anthraquinone, for recycling over the catalyst bed. phthalic anhydride recovered per pass was determined by titration of a n aliquot of the resulting solution with standard potasHOMOGENEOUS CATALYSTS sium hydroxide solution. Homogeneous catalysts include hydrogen chloride and a wide A reaction temperature of 370-385 O C. was found t o be most variety of inorganic halides, halogenated hydrocarbons, and satisfactory in this reactor. Higher temperatures resulted in exother organic compounds of low molecular weight which are relacessive decomposition of the phthalic anhydride. At lower temtively unstable and reactive a t elevated temperatures. peratures the anthraquinone condensed on the catalyst and in the The principal applications of these catalysts in the past has top of the reactor and was recovered only with difficulty. Howbeen limited to hydrogenation and cracking operations. Their ever, under reduced pressure the premature condensation of the description has been confined mostly t o patent literature. Pier, anthraquinone at 320-380 C. might be overcome. This would +
O
03)-
-fl
INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1946
CONDBNSATION OF BENZENEWITH TABLE 11. THERMAL BENZOYL CHLORIDE
Run No.
6 3 1 X18 4 220-230 340-350 260-260 260-270 260-270
Temperature, C. Ratio. benzene to benzovl chloride Weight Molar Reaction time, min. Benzoyl chloride recovered, wt. %
consumed Theoretical ultimate (based on benzoyl chloride)
1.65 3 60
1.65 3 60
1.65 3 180
1.65 8 60
1.66
36
0 0
0.0
15
42
21.0
25.0
37.0
27.6
20.0
56
67
97
73
64
87
67
97
a5
92
68
52
76
67
72
3
6
Kroenig, and Donath (19)found that organic chlorinated compounds and halides of sulfur are active hydrogenation catalysts. Pier, Simon, and Eisenhut (14) recommended ammonium chloride as a catalyst for hydrogenation of petroleum resins and asphalts. Storch and co-workers (21, 22) investigated the use of halogen-containing compounds as catalysts for hydrogenation of coal tars. Tropsch (24) claimed that the presence of chlorine or chlorinated organic compounds in the cracking of hydrocarbons produced greater yields a t lower temperatures than could be obtained in the noncatalytic process. According to Hessels, van Krevelen, and Waterman (6),cracking of methane is "induced" by halogen derivatives or sulfur compounds. The effect, however, seems to be very small. These catalysts have recently been employed in conventional Friedel-Crafts reactions. Sachanen and Davis' (16) alkylated benzene and phenol with olefins in the presence of small quantities of chloroform and other halogenated organic compounds a t temperatures of the order of 300" C. When phenol was condensed with amylene under these conditions in the presence of 5% chloroform by weight of total charge, the yield of amylphenols was 93% of theoretical. Schmerling and Durinsky (18) alkylated benzene with propylene at 300' C. in the presence of a small amount of hydrogen chloride. SYNTHESIS OF BENZOPHENONE
Nenitzescu and co-workers ( l a ) discovered that active aromatic hydrocarbons, such as diphenyl and naphthalene, could be alkylated and acylated with alkyl and acyl halides a t elevated temperatures without the addition of any extraneous catalyst. They were unable t o react relatively inactive aromatic compounds, such as benzene, in this manner. Under the conditions described in the present paper, benzene can be alkylated with alkyl halides and acylated with acyl halides in the absence of any separately added catalyst. The acylation of benzene with benzoyl chloride was the principal reaction of this type investigated. It is believed that this type of seemingly noncatalytic condensation reaction is analogous to that catalyzed by chlorinated or halogenated compounds. If the alkylation of benzene with olefins requires the catalytic action of a halogenated compound, the condensation of the same aromatic with a chlorinated hydrocarbon or benzoyl chloride should be possible without any extraneous catalyst, since the reactant containing chlorine is simultaneously a catalyst in this type of reaction. The materials used were C.P. benzene and benzoyl chloride. The apparatus consisted of a n Aminco superpressure unit, tomplete with rocker shaker, heating jacket, and stainless steel bomb of 2800-cc. capacity. The benzoyl chloride and benzene in a mole ratio of 1 to 3 were charged to the bomb before sealing it. The bomb was then placed in the heating jacket, which had been p r e heated to about 150' C. Under application of full heat, the temperature in the reactor was brought up to a desired range in
45
approximately one hour. After the run had proceeded for a predetermined period of time, the bomb was removed from the shaker and allowed to cool in air. When the bomb had cooled to about 90" C., the hydrogen chloride was released and the product, removed from the reactor with several benzene washes, was distilled from a side-arm distillation flask. The cut boiling from 270-325' C. solidified on cooling and was found t o be benzophenone of greater than 95% purity. From a mixture of a 10% potassium hydroxide solution and crude benzophenone, about 10 grams of benzophenone were steam-distilled. Recrystallization of this material from acetone gave colorless rhombic prisms melting a t 48.5-49' C. A mixture of these crystals with Eastman C.P. benzophenone gave a melting point of 48.5-49' C. Table I1 shows the general effects of time and temperature on the condensation of benzene with benzoyl chloride. Several conclusions can be drawn from this table. For a batch run, temperatures of the order of 260' C. and a reaction time of 2 to 8 houra appear t o be favorable conditions for the synthesis of benzophenone from thestandpoint of both conversion per pass and ultimate yield. Lower temperatures, 210-215 ' C., give lower conversions per pass without a noticeable increase in ultimate yield. Shorter reaction times also cause a reduced conversion per pass without increasing the yield. At higher temperatures, 345350' C., the conversion per pass and ultimate yield of benzophenone are lower thanat 260' C., as a result of excessive decomposition of benzoyl chloride. However, temperatures of about 345 ' C. and reaction times of 1 to 5 minutes might be optimum for continuous pressure units designed for precise time and temperature control. At present, benzophenone is made on a semicommercial scale by the reaction of benzoyl chloride with benzene a t moderate temperatures in the presence of anhydrous aluminum chloride. Although the yield of benzophenone by this process is of the order of 85% oftheoretical based on benzoyl chloride charged, the aluminum chloride consumption amounts t o about one pound per pound of benzoyl chloride charged. This loss of catalyst is undesirable and is eliminated in the process described here without a prohibitive reduction in ultimate yield of benzophenone. LITERATURE CITED
Anschtits, R., Ann., 235, 177-96 (1886). Anschfits, R., arid Immendorff, H., Ber., 18, 657-62 (1885). Boedtker, E., and Halse, 0. M., BUZZ. soo. chim., 19, 444-9 (1916).
Hansford, R. C., Myers, C. D., and Sachanen, A. N., IND. ENQ.CHSM.,37,671-5 (1945). Heise, R., and Tohl, A., Ann., 270,155-71 (1892). Hessels, W. J., Krevelen, D. W. van, and Waterman, H. I., J.SOC.Chem. Id.,58,323 (1939). Ipatieff, V. N., "Catalytic Reactions at High Pressures and Temperatures", p. 720 (1936). Ipatieff, V. N., and Pines, H., J. Am. Chem. SOC.,59, 56-60 (1937).
Laoourt, A,, Bull. 800. chim. Belg., 38, 1-20 (1929). Lewis, H. F., J. IND. ENQ. CHIM., 10, 425 (1918). Michel, R., U. S. Patents 1,741,472-3 (1929), Reissue 17,548 (1929); 1,766,344 and 1,767,302 (1930); 1,878,963 (1932). Nenitiescu, C. D., Isaoescu, D. H., and Ionescu, N. N., Ann., 491,210 (1931).
Pier. M., Kroenig, W., and Donath, E., U. S. Patent 2,118,940 (1938).
Pier, M., Simon, W., and Eisenhut, A. Zbid., 2,177,376 (1939). Sachanen,A. N., and Davis, S. B., Ibid., 2,234,984 (1941). Ibid., 2,361,355 (1944). Sachanen, A. N., and O'Kelly, A. A,, IND.ENQ.CHEM.,33, 1540 (1941). Schmerling, L., and Durinsky, A. W., U. S. Patent 2,357,978 (1944). Sohoillkopf,K., Ibid., 2,115,884 (1938). Schorger, A. W., J. Am. C h m . SOC.,39,2671-9 (1917). Storoh, H. H., IND.ENQ.CHEM.,37,340 (1945). Storch, H. H., Hirst, L. L., Fisher, C. H., Work, H. K., and Wagner, E". W., Ibid., 33,264 (1941). Thomas, C.L., Hoekstra, J., and Pinkston, J. T.,J. Am. Chem. SOC.,66, 1694 (1944). Tropsch, H., U. 8.Patent 2,063,133 (1936).
