SYNTHESIS OF PHENOL BY PARTIALPRESSURE EVAPORATION DONALD F. OTHMER AND CHARLES E. LEYES Polytechnic Institute, Bmoklp,
Phenol ham ban spthedmd by pzutkl-preasure evaporation methodo in both the sulfonation and fusion steps. B-e is donated in the presmea of a high-boSlhg naphtha cut; then the ead i u m -e sulfonate is neutdized and fuwd with caustic Boda under kenxene. The water of reaction or of sdution in each maw is removed by partial-pressure evaporation. C b m p a r k m with other sulfonation methods in ineluded, a n d the teohnieal and -nomic advantages of t h i s proeess are indicated. Good yields a n d low material w n t s are the prinfipal merite. Sulfonation can he carried out with the theoretical molecular ratios of b e n e and d d c a"d, whereas in the funionoperation, aqueous caustic mlutionsand aqueous solutions of sodium beneene sulfonats can be employed directly --again in practically theoretical proportions.
HENOL is one of the major raw materials of the organic chemical industry. During recent years the annual 'production in the United Statea has reached 70,ooO,OOO pounds, of which 75 to 80 per cent, or over 80 tons daily, was made synthetically. Commercial synthesis of phenol involves the hydroxylation of benzene in two stllgeg ns:
ClHIX --+ 'XIOH where X may be either the SO&- group (sulfonationmethod) or Cl- (halogenation method). Hydroxylation of benzene with hydrogen peroxide and dealkylation of higher phenols are of limited SigniEcance. Considering h t the sulfonation method, the reaction
C a
+
cr&soiH + Hi0
stops a t a limiting acid concentration of 66 per cent sulfur trioxide or 78 per cent d w i c acid which is the hydrate HSO,.I'/&O. For complete resction and utilization of benzene, one of the products must be removed 88 follows: (a) water as hydratea of sulfuric acid (exacid methcd); (b) water by distillation (Guyot, Barbet, Tyrer p r o c e m , 8, 8, 81); (c) benzene sulfonic acid (Dennis-Bull process,
%4).
The exceea acid method is the oldest and has very high material costs due to the large quantities of concentrated 1 T b a p . ~on pam 164 to S a l were pr-ted before the Diridon d Indlutrid and E n ~ b e i r Chmni.trp u nt the 100th Meatins d the Axmedean Chemical 8miety. D&&. M i d .
N. Y.
High-speed (lo00 r. p. m.) emulsifying sdmem with naphthp cuts b o i i in the range 170' to 2 0 0 0 c. gave optimum mults in sulfonation with either 94 or 98 per Cent sulfuric add. No sulfonen were found d e n s a large exof beneens was taken. A s d . a m o u n t of oharring omumed, but the oharred matexid w a s easily and Fompletdy removed during neutmhatlon. Best resulto in the funion stage were obtained w i t h 50 per cent apueous solutions of caustic soda (1.5 per OePt ex-) and of sodium benzene sulfonate. Here a h high-speed emulsifyiq adtatom were employed, d o w i n g reduction in the volume of kerosene a n d dving a sintered, readily mluble p d u c t . The exelusion of air in the fusion operation p r e v e n t s oxidation of the sodium phenolate as an additional advantage.
sulfuric acid employed, exceas of which must be later removed with lime or chalk. The importance of acid strength is e n dent, since with 94 per cent acid only 40 per cent of the d u r trioldde present is available for sulfonating, while with 100 per cent acid this Egure is 55 per cent; even with 105 per cent acid (5 per cent oleum), o d y about 60 per cent can be utilized. The attendant filtering and washing of a voluminous precipitate of calcium d a t e sludge together with the evaporation of large quantities of water after neutralisation constitute other major disadvantages. In the water removal methods, such ns those of Tym, Guyot, and Barbet, superheated benzene vapors are used to remove the water a t temperatures of about 160-180° C. This allows the u e of weaker acid (93 or 94 per cent) more completely and permits continuous operation. However, the high temperatures, long reaction times, and excess of b e may cause as much ns 30 per cent of the p d u c t to he diphenyl sulfone (18). Some charring (2 to 3 per cent) and evolution of sulfur dioxide also occur. The Dennis-Bull process removes the benzene sulfonic wid as a 2 per cent solution in b e and esn be made continuous. Here 98 or 105 per cent acid is passed countercurrently to a gravity flow of benzene at about 60' C. Spent acid is removed as 77 per cent sulfuric acid, requiring the u88 of a sulfur trioxide contact plant for reconcentration. The dfonic acid is dropped into water, giving a 80 per cent solution; e diasolvd is W d off. and the 2 per cent of the h Tbis, the most e5cient of the d o n a t i o n procesaas, r e q h large-wale installation and efficient bensene recovery since 49
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
pounds of benzene must be cycled per pound of benzene sulfonic acid produced. Furthermore, the same quantity of sulfuric acid must be cycled as in the excess acid method although the spent acid may be reconcentrated. All sulfonation methods require conversion of the benzene sulfonic acid to the sodium salt (by means of soda ash or byproduct sodium sulfite) and evaporation to dryness before fusion. For the fusion step, a batch operation, about 2.5 to 3 moles (25 to 50 per cent excess) of fused caustic soda are used (7) per mole of sodium benzene sulfonic acid, with about 10 to 20 per cent by weight of water to give a fusion a t about 300" to 330" C. Open hemispherical iron pots with agitators are employed; and about 9 hours are required for a 1500pound batch of phenol. The fusion mass is discharged into a measured quantity of phenol wash waters, the sodium sulfite reclaimed, and the phenol liberated by acidification and recovered by distillation. The major disadvantages of the fusion are the excess caustic soda required and the oxidation of sodium phenolate due to contact with air (60); maximum yields are 92 per cent (6); optimum yield of benzene to phenol is about 90 per cent for any process. I n the continuous halogenation processes, either alkaline or catalytic hydrolysis is used. I n the alkaline Dow process (IO,11) chlorobenzene, 25 per cent excess sodium carbonate, and water are reacted at 320" to 400" C. and 3000 pounds per square inch (211 kg. per sq. cm.) pressure to give free phenol in a yield of from 84 (16) to 95 per cent (7) of theory. Diphenyl oxide is a by-product, but its formation is said to be inhibited by including it to the amount of 10 per cent in the reaction charge (9). Considering the 70 per cent yield in the chlorination of benzene, the over-all yield of phenol from benzene is only about 66 per cent. The high operating pressures and temperatures as well as equipment cost restrict the use of this process to large operations; and markets must be maintained for disposal of the by-products-oand p-dichlorobenzene and diphenyl oxide. The Raschig or regenerative method (19) is the most recently developed commercial process and is based on the catalytically promoted reactions:
+
+ +
Ha0 ++HCl
Cd& HC1 0 +CeHsCl CeHsCl HzO +CeH60H
Material costs are low; theoretically only benzene and atmospheric oxygen are required. Conversions, however, are also low. Chlorination is accomplished with 15 to 20 per cent hydrochloric acid a t 200" to 250' C. in the presence of copperiron or copper-cobalt catalysts imbedded on activated alumina or Florida earth with a 12 per cent conversion per pass (7). Hydrolysis is assisted by active silica or phosphates of magnesium, calcium, and zinc a t 400" to 500" C., with a 10 per cent conversion per pass. Yields are not published, but about 3 per cent of the hydrochloric acid is lost (1, 17) owing to the formation of higher chlorinated products, while diphenyl oxide is also formed in the hydrolysis step, Corrosion and heat recovery are the important considerations. Kokatnur (IS) based his method on well-known principles of chemistry and chemical engineering in the process which a priori appears to have advantages. Either sulfonation or halogenation methods may use the process which involves (a)formation of an intermediate sulfonated or halogenated compound in the presence of an inert diluent, such as gasoline, (b) neutralization, and (c) hydroxylation with caustic soda under kerosene. Similarly, hydroxy derivatives of benzene homologs and naphthalene may be made.
Basis of Present Work The present investigation concerns phenol preparation using the Kokatnur method in both sulfonation and fusion
159
steps. The seemingly fundamental advantages of this partialpressure synthesis appeared large, even initially. I n the sulfonation the use of a high-boiling gasoline or naphtha cut as an inert diluent raises the boiling point of benzene considerably (at the start to 100" C. and later to as high as 170" C.), thus giving a much more rapid reaction rate particularly in the early stages. At these higher temperatures the vapor pressure of water over sulfuric acid becomes appreciable; and the use of an inert hydrocarbon material permits water entering with the acid, as well as that formed in the sulfonation, to be removed azeotropically. Thus molecular proportions of relatively dilute acid may be used instead of large excesses of concentrated acid, and the reaction should go to completion. The advantage of benzene a t these higher temperatures could be obtained otherwise only by a pressure of some 6 to 8 atmospheres. A high-boiling naphtha cut eliminates the necessity for using externally superheated benzene, as in the Guyot, Tyrer, and other water removal methods, and should thus contribute in preventing sulfone formation. I n the fusion step there is another application of the principle of partial-pressure distillation whereby the effective pressure of water vapor is increased by means of a high-boiling kerosene or gas oil cut. A reaction is obtained with the removal of most of the water at a lower temperature, which could otherwise be done only in vacuo. Thus the fusion temperature is materially reduced as azeotropic distillation removes water formed in the fusion, as well as any water brought in with the caustic or sulfonate. The covering by the hydrocarbon completely excludes air and thus avoids losses due to oxidation. The kerosene allows a much better heat control, prevents superheating, and gives a sintered reactionmasswhich is readily soluble in water. As will be shown later, the best yields and fusions were obtained from aqueous solutions of both caustic soda and sodium benzene sulfonate by evaporating water therefrom. Furthermore, it would seem that a continuous fusion might be developed.
Experimental Work on Sulfonation BACKGROUND AND ANALYTICAL PROCEDURE. The experimental work is a study of the various factors affecting sulfonation of benzene-namely, reaction temperature and time, agitation, method of adding reagents and proportions of reagents, acid concentration, and size of batches. The product from the runs varied from a brownish black viscous liquid to a solid black crystalline or tarry mass, and a special analytical procedure was necessary. Determinations of free sulfuric acid using barium chloride gave a black gummy precipitate which defied filtration. The dark solution of the reaction mass completely masked the color change on titration. The use of lime does not permit an accurate evaluation of the amount of free sulfuric acid and gives high results for benzene-sulfonic acid, due to the appreciable solubility of calcium sulfate. The method adopted was to dissolve a 5-10 gram sample of naphtha-free reaction product in 250 cc. of hot water, and to add 8-15 grams of solid barium carbonate in small portions, with occasional shaking, t o the hot solution. An excess of barium carbonate was used since this formed a nucleus for the coagulation of the colloidal charred material which also retained any sulfone or hydrocarbon present. The volume was then brought up to 500 cc., allowed to stand overnight, and then filtered through pleated paper. Filtrate contained the barium salts of sulfonic acids, while the precipitate included barium sulfate, excess barium
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 33, No. 2
TABLEI. EFFECTOF TEMPERATURE ON SULFONATION OF BENZESE" Analysis of Reaction Mass Run
NO.
Hydrocarb%n Range, C.
Max. HydroReaction carbon Tzmp., Water Off, Distd., C. cc. cc.
Time Required, Min.
Av. Reflux Rate, Cc./dn.
HC/HsO Ratio
Benzene sulfonic acid, %
Excess CeHa 816 0.10 5439 562 9.62 54,390 100-110 0.90 2958 505 5.87 3,290 2 140-150 22.4 144 3744 463 8.08 167.0 4 170-180 162 20.3 225 6.01 66.5 1349 0 Materials: bensene 1.00 mole, 78.1 grams; 98% sulfuric acid, 1.03 moles, 103.0 grams: hydrocarbon cut, 0.02) = 20.06 cc. b Temperature went up t o 158' C . during last 10 minutes, owing t o loss of benzene. 6 3
carbonate, charred material, sulfones, hydrocarbon, etc. The latter was washed three times with 25-50 cc. portions of hot water, followed by three washings with cold water (last washing gave less than 1 mg. solids). Filtrate and washings were evaporated to dryness in a casserole which was then placed in an oven a t 110' C. for 2 hours; the result was the formation of the salt (CsHsSOs)zBa.1I/%HzO. The salt was calcined to barium sulfate to determine the actual benzene sulfonic acid content by the corresponding factor. The washed precipitate was treated with (a)dilute hydrochloric acid to decompose excess barium carbonate, (!) more 1 per cent hydrochloric acid, ( c ) water until free of barium chloride, and (d) hot benzene to remove sulfones. Usually this benzene extract was colorless and showed no residue after evaporation. (Only two runs, both made with rather large excesses of benzene, showed traces of sulfone; in both instances diphenyl sulfone sublimed during sulfonation as white feathery crystals visible in the condenser.) The insoluble material was dried at 110' C. to constant weight, ignited to remove charred material, moistened with 3 N sulfuric acid, and reignited to constant weight of barium sulfate. Free sulfuric acid in the reaction was calculated from this final weight, while the difference between it and the sample taken for ignition was considered as charred material. The results for benzene monokulfonic acid by this 'IGURE 1. method are probably low in SnLFoNAT1oN an absolute sense, although Rms* check determinations agreed STIRRER, MERCIXLYSEAL,AND well within 1 per cent. Free OPENDECAXTER sulfuric acid values are somewhat more accurate. Charred material estimates, however, differed by as much as 3 to 5 per cent, because of the colloidal nature and consequent difficulty in filtration of some samples and the adhesive tendencies and moisture absorption of the material. I n no case was a total of 100 per cent obtained as the sum of the analyses for sulfonic acid, free sulfuric acid, and charred material. Unaccountables in the reaction mass varied from 1.4 up to about 20 per cent, and robably consisted of water, volatile hydrocarbon material, acicf-soluble charred matter, acid-soluble metallic salts (iron from agitators, etc.), and the accumulated errors and inaccuracies involved in the analytical procedure. APPARATUS.A 1-liter three-necked flask was equipped with an agitator and a vapor neck to a condenser. The condensate passed to a decanter as shown in Figure 1. The hydrocarbon werflowed, and the water settled to a 10-cc. buret attached to the bottom. The volume of the Y was also approximately 10 cc. At the start the buret was filled to a predetermined zero level with water, so that the volume of hydrocarbon standing in the decanter
Free HzSOI, %
Charred Material, %
Unacoounted material,
%
56.3 25.3 0 18.4 50.4 30.5 1.49 17.61 75.1 3.1 20.4 1.4 72.7 3.66 11.79 11.85 180 cc.; theoretical water content, 18 (103 X
+
could be varied between 11 and 19 cc. The water was withdrawn eriodically into a graduate, and the instantaneous value could e! estimated to 0.05 cc. The hydrocarbon layer passed through the side arm of the decanter which was vented, dropped into a thistle tube, and returned to the system through a trap. A glass sleeve with one end cut at an angle fitted loosely over the outlet of the decanter and rested in the thistle tube. It could easily be slipped aside and a 10-cc. graduate inserted under the outlet of the decanter t o measure the rate of reflux, which at a maximum was 12 to 15 cc. per minute. Thermometers were inserted in both the liquid and vapor phases. Heating was provided by means of a Bunsen burner, with or without an oil bath.
EFFECTO F TEMPER.4TURE. A series O f four l-mole SUIfonations was made, using 3 per cent excess of 98 per cent sulfuric acid and 180 cc. of hydrocarbon cuts with the following boiling ranges: 80" C. (excess benzene), 100-110" C., 140150" C., and 170-180" C. Table I gives data and Figure 2 shows the relation of hydrocarbon distilled to water removed. Figure 3 gives the analysis of the reaction mass. The two lower boiling runs were stopped after 8 or 9 hours, with only small quantities of water removed, whereas with the highest boiling cut the reaction was completed in less than 4 hours. Benzene sulfonic acid is formed pro5000 p o r t i o n a l l y to the 4500 amount of water distilled. Extrapolation 4000 of the curves of Figure 3 indicates a n 3500 ultimate conversion of about 51 per cent 3000 benzene sulfonic acid, Yd 2500 as would have been 6 e x p e c t e d from the g 2000 limiting acid concenm trations; yet the IS00 analysis for free sul$ furic acid (by extraa 1000 polation t o zero 5 500 water) is unaccount0 4 8 I2 16 20 23 ably low, not only in WATER REMOVED, U: the two cases here cited, but in two FIGURE2. EFFECT OF REACTION TEMPERATURE ON W A ~ R I1Eother runs (8 and MOVAL AND AMOUNT OF HYDRO28A) as well. I n the CARBON DISTILLED completed runs the free acid content is very low. The amount of charredlmaterial in the product increases rapidly with the quantity of water removed, especially after the removal of the amount equivalent to the water of reaction. The ratio of hydrocarbon distilled to water removed varies almost inversely with the boiling point; about three tines as much hydrocarbon must be distilled with a 140-150" C. cut as with a 170-180" C. cut, whereas with the still lower boiling materials (i. e., light naphtha or excess benzene) this quantity is 50 to 800 times greater. 0
8
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
Several other runs were made with the reaction held at spe60 cific temperatures (140" and 145" C.) by the g 50 addition of sufficient Y amounts of the lower 2 40 boiling cuts. None of these showed substang 30 4 tial i m p r o v e m e n t s . 20 Varsol No. 1, with a boiling range of 145" 10 to 203" C. and a specific gravity of 0.777 0 seemed suitable. WATER REMOVED, CC Therefore a quantity was acid-treated (with FIGURE 3. EFFECTOF WATER REMOVAL ON ANALYSXS OF RE10 per cent b y volume ACTION MASS FOR PRELIMINARY of 94 per cent sulfuric RUNSWITH 3 PERCENTEXCESS OF 98 PERCENTSULFURIC ACXD acid for hours under reflux and agitation). washed, and -fraction: ated to cuts boiling within 10" C. ranges; these cuts were used for the remainder of the experiments. AGITATORS.Agitation is known t o play a n important role in normal sulfonations. The degree of mixing attained in the early runs with a glass s t i r r e r was extremely small; hence tests were c o n d u c t e d with various other agitators. 70
A glass swiveltype agitator consisted of two glass blades, each 1 inch (2.5 cm.) long and '/z inch (1.27 om.) wide, rigidly joined by a glass torus on e'ach s i d e a n d hinged to the stirring rod by a glass pin, to permit insertion into t h e flask. The shaft was passed through a long mercury seal and was connected to the motor by a flexible r u b b e r
WATER REMOVED, CC
Run No. 4 9 8 11 10 13
TABLE 11.
HaSOd,
NO.
4 9 8 11 14
Glass agitator Steel wire propeller Steel wire Steel wire
98 98 94.4 94.4
10
13 18 .a
b
Steel propeller Steel wire Steel wire
Cut, 0. % Acid 170-180 98 170-180 98 170-180 98 170-180 94 190-200 98 190-200 98
Stirrer Glass agitator Steel pfopeller Steel wtre Steel wire Steel propeller Steel wire
EFFECT OF AQITATION AND
Type of Stirrer
Run
coupling. The speed was about 250 to 300 r. p. m. in runs 2 through 7. A stainless steel propeller mas cut from No. 26 gage Allegheny metal, with curved blades approximately 1 X 8/g inch (2.5 X 0.95 om.) pinned to a stainless steel shaft. A brass stuffing box, packed with asbestos fiber, was employed as seal. The stainless steel was badly attacked and after 8 hours of use was completely eaten away. About 400 t o 500 r. p. m. was used in runs 9 and 10. Several steel wire beaters were made using 3/ia-inch (4.&mm.) mild steel rod and No. 20 gage spring steel wire, fashioned into circles (two rings of 13/g-inch or 3.5-om. diameter) mounted at right angles. A stuffing box and split flange were made of 3/8inch aluminum plate to serve as bearin seal, and covering for the center neck of the flask. Gaskets of Reits asbestos filter sheet and packing of graphitized asbestos were satisfactory. A motor speed of 600 to 1000 r. p. m. gave good emulsification, but there was excessive vibration at higher speeds. The beater wires suffered considerable corrosion (about 1 per cent of weight per run); after four runs (15 hours) the wires had to be replaced. Wire beaters were used in all sulfonations after run 10.
EFFECT OF AGITATION.The same proportions of materials were used as in the temperature runs (3 per cent excess of 98 per cent acid, although in some trials 3 per cent excess of 94.4 per cent acid was substituted). Two series were made, the first consisting of five runs with 170-180" C. naphtha and the second, of three runs with a 190-200" C. cut. The data obtained are summarized in Table I1 and Figure 4, and show that thorough emulsification greatly reduces the amount of hydrocarbon required to remove the water. Thus, with a 170-180" C. naphtha cut, the over-all hydrocarbon-water distillation ratios for completed runs are: Speed R . P . hk 250-300 400-500 600-800 1000-1400
Glass agitator Stainless steel propeller Steel wire beater Steel wire beater
FIGURE4. EFFECT OF AGITATION ON WATERREMOVAL AND AMOUNT OF HYDROCARBON DISTILLED
%
98 98 94.Q
Max. Reaction Temp.,
Water
* c.
82
162
20.3
160 154 162 162 169 172 176
161
Evidently, also, the initial reaction is hastened, since with 170-180" C. hydrocarbon cut and 98 per cent acid, the time (from the start of refluxing) for the first water separating in the decanter was: Speed R. P. 250-300 400-500 800-1000
Initial Separation of Water, Min. 60 25 12
i k
Glass agitator Stainless steel propeller Steel wire beater
Little difference in reaction rate with 94 or 98 per cent acid was noted, provided sufficient agitation was available.
ACIDCONCENTRATION
Hydrocarbon Distd., Cc.
ON THE SULFONATION OF BENZENE" Analysis of Reaction Mass Av. Benzene sulfonio Free Charred Unaccounted Tiny Reflux Required, Rate HC/HzO acid, HaSO4, material, material, Min. Cc./Mik Ratio % % % %
18.0 6.8 25.2 26.7
170-180° C. Hydrocarbon Cut 1349 225 6.01 178 5.21 120 3.37 849 168 5.06 1279 168 7.62
66.5 51.5 69.8 33.7 47.9
18.1 20.6 25.0
190-200° C. Hydrocarbon Cut 597 110 5.43 94 4.87 457 340 159 2.14
33.0 22.2 13.6
$:
72.7
3.66
11.79
60.1 62.8
20.0 5.23 2.19
3.72 27.0 16.45
11.85 11.72 17.18 4.97 9.06
67.7
7.03 2.41 1.03
21.65 11.3 13.7
3.62 6.19 11.07
69.a
72.3
80.1 74.2
7.78
Materials: benzene, 1 00 mole 78.1 grams: sulfurio acid 1 03 mole. hydrocarbon cut 180 cc = 24.0 cc.; theoreticai water dontent for 98% a d d = 18'+ 2.06 = 20.1 oc.; for 94% said
No excess acid used, tfiioreticai water
Ratio, HC/HzO, Cc./Cc. 66.5 51 5 47 9 33.7
11.3
-
18 4- 6.45 = 24.5
00.
INDUSTRIAL AND ENGINEERING CHEMISTRY
162
Vol. 33, No. 2
OF REACTANTS ON SULFONATION OF BENZENE WITH 94.4 PER CENTSULFURIC ACID TABLE 111. EFFECTOF PROPORTIONS Analysis of Reaction Mass Run No. 12
:5"
Excess Reagent 3 mid
%$2%
Max. T:rnp., C. 167 166 166
Water
Off,
cc. 26.6
25.7
25.0
Hsdrocarbon Distd.,
cc. 848 631 985
Time Required, Min. 115 166 165
Av.
Reflux Rate, Cc./AMin.
7.37 3.80
5.97
Hydrocarbon recovery averaged about 86 per cent for these runs, with a maximum of 94.5 and a minimum of 81 per cent. Charring appeared to be slightly worse with the weaker acid and was excessive in all these runs (11 to 27 per cent of product for those completed). Neither the use of acid-treated hydrocarbon cuts nor of high-purity rather than technical grade benzene seemed t o have appreciable effect, and so proportions and method of addition of reactants were varied.
Benzenesulfonio HC/H%O acid, Ratio % 32.0 68.6 24.5 68.8 39.4 68.5
Sulfone,
Free acid,
Charred material,
%
%
%
%
0 0 0.61
3 74
18 84
8.82
7.17
0.94
11.0 12.1
Unaccounted material,
14.03
17.85
was added to the acid. Neither of these presented any advantage over the regular procedure for batch operation. LARGERSULFONATION RUNS. Six 2-3 mole experiments were carried out t o confirm the findings of smaller runs and to study the effect of increasing the size of the charge. Most of these were made in a 2-liter iron pot, and all used a closed decantation system:
A 2-liter iron pot, 5.75 inches (14.6 om.) inside diameter and 6.5 inches (16.5 om.) high inside (Figure 5), was equipped with a wire emulsifier made of No. 12 gage spring steel wire bent in a 2.5-inch (6.35-om.) diameter circle and mounted on a 6/la-inch (7.9-mm.) mild steel shaft, similar to those used in earlier runs. Provisions were made on the cover for vapor and liquid return lines (3/8- and '/e-inch iron pipe size, respectively), a thermometer well, an extra plugged 3/s-inch iron-pi e size opening, and a stuffing box for the agitator. The rim orthe ot was tapped for eight '/,-inch (6.35-mm.) bolts. The glass Enes were connected to the cover by simple packing glands made by calking a reducing coupling with asbestos by a bushing used as a follower. The vapor line was of 17-mm. outside diameter Pyrex tubing, with a glass tee connecting to a 15-inch (38.1-cm.) vertical condenser. The decanter under the condenser was blown from a 50-00. Pyrex cylinder, by sealing a 4-mm. bore stopcock on the side and a 2-mm. stopcock on the bottom. The decantation volume could be varied from about 2 to 15 cc. by maintaining different water levels; and the reflux rates up to about 25 ce. per minute could be conveniently measured by closing the side arm. EFFECTOF EXCESS The 4-mm. hydrocarbon return trap had a stopcock inserted for drainage and for removal of any water passing the decanter. R E A C T A N TASN D The return line extended almost to the bottom of the pot and MANNER OF ADDIwas vented above the decanter to equalize differences and permit TION. A s e r i e s of smooth flow. Another trap attached to the hydrocarbon return line permitted the addition of materials during a run. A glass three 1-mole runs tube carried gases from the top of the condenser to a funnel inwas carried out with verted in a beaker of water and allowed the absorption of acid FIGURB 5. APPARATUSFOR TEST 94.4 per cent sulfuric gases produced in the sulfonation. RUNSON SULFONATION AND FOR acid and 180-190" C, FUSIONS naphtha to determine 10,000 the effect of excess 0 " . acid and of excess benzene, respectively. These runs used 3 2 8,000 i per cent excess acid (control), 20 per cent excess benzene, and $ 20 per cent excess acid, as listed in Table 111. Steel wire E 6,000 z beaters running at 800-1000 r. p, m. were employed. Be4,000 tween the limits of 20 per cent excess of either acid or benzene 9 there was no appreciable effect on yield. With a large excess 2,000 of acid the free acid content of the product was higher, while with large excess of benzene, diphenyl sulfone was formed. 0 0 IO 20 30 40 50 60 70 80 The residual product from run 15 (20 per cent excess benzene) WATER REMOVED, CC showed only 0.61 per cent sulfone on analysis; yet the condenser and overhead system were covered with feathery white FIGURE 6. EFFECTOF NAPHTHA BOILING RANGE ON THE SULFONATION O F BENZENE FOR THREEprisms of sublimed diphenyl sulfone. The charred material MOLD RUNS in these three runs was roughly proportional t o the average reflux rate due to a probable greater benzene loss through the return line vent a t higher distillation rates. (Loss of benzene The cover was supported on an an le iron frame to which was also fastened the motor, pulley, a n t bearings for the agitator. increases excess acid and hence amount of char.) I n the light The pot was mounted on a movable rack so that it could be lowof this series, it is evident that excess acid increases char ered without disturbing the assembly attached to the cover. A while excess benzene increases sulfone so that probably a large flat burner for heating was permanently installed in the hood supexcess of either reagent is undesirable; and the use of even 3 porting the pot. Rubberized asbestos gaskets were found best for sulfonations, with graphitized asbestos in the stuffing box. per cent excess acid is probably not advantageous. In normal sulfonations it is customary to add the sulfuric The first tests were to determine the advisability of using a acid to the benzene, Therefore, two additional runs were naphtha of wider boiling range than the 10" C. cuts of the made, one in which the acid was added to the benzene-hydrosmall experiments. Runs 28 and 29 used 3 moles of benzene carbon mixture and the other in which benzene-hydrocarbon
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
DURING SULFONATION, BY TITRATABLIC IV. GAS FORMATION TION OB ABSORB~R WATERS
Sample
No. A
B
C
D E F
a
H I J
Water Removed Total, cc. Ca./mole
Absorption Time, Min.
Total Acidity Rate of H&04 a8 HsSOr, Formation Orams Mg./Min.'
Run 28, 3-Mole Batch with No Excess of 94.4% H ~ S O A 0.497 0.5 0.17 60 0.0298 0.517 60 0.0310 1.6 0.63 3.65 60 0.219 4.2 1.40 7.80 7.8 2.60 60 0.467 7.48 60 0.449 12.5 4.17 1.928 60 0.1155 17.4 5.80 3.45 60 0.207 23.3 7.77 31.5 60 1.89 32.4 10.80 105.1 60 6.31 43.0 14.33 411 60 24.6 60.7 20.23 Total
34.32
Run 32, 3-Mole Batch with No Excess of 98.3% Has04 A B
C D E
F
1.2 6.7 17.8 33.6 46.2 54.3
0.0525 0.420 1.875 11.7 16.3 13.6
0.4 2.23 5.93 11.2 16.4 18.1 Total
0.876 7.00 31.3 195 543 680
43.95
and the molecular equivalent of 94.4 per cent sulfuric acid. The speed of the stirrer was 600 r. p. m. I n run 28 straight acid-treated Varsol (145" to 203" C.) was used; in run 29 the heads were distilled off (about 35 per cent) and only the 170-203' C. cut was added. At the point when the water of reaction (54 cc.) was removed, the comparison was: Run NO.
28 29
Na htha Boiling $mange, 0 C. 145-203 170-203
Conditions at 54 Cc. Water Removed Tzmz., H C distd., Time required, eo. HC/HaO min. 161.2 580 154 8710 103.0 420 159 5560
It is apparent that the naphtha cut with the higher boiling range gives a more rapid reaction and a lower ratio of hydrocarbon to water distilled (Figure 6). The effect of agitation was also demonstrated in two other 3-mole runs and in rdn 29:
Run No. 29 25 32
Naphtha Boiling Range, O C. 170-203 170-203 170-203
Agitator Speed R. P. M. 600 1000 1000
Acid,
%
94.4 94.4 98.3
Condition8 a t 54 Cc. H10 Removed HC Time Temp., distd., HC/HzO required, * C. cc. ratio min. 5560 159 103.0 420 164 1320 24.5 360 1380 25.6 290 168
mole. Continued distillation allows the acid remaining t o char the hydrocarbon with no gain in yield of benzene sulfonic acid. Gas evolution as a function of water removed was also investigated by periodically titrating the water used as absorbing liquid for sulfuric acid. The gases consisted principally of sulfur trioxide with some sulfur dioxide in the latter stages, and occasionally hydrogen sulfide in the early stages (especially if the iron pot had been previously used for caustic fusions). Data for two runs are given in Table IV. The addition of small amounts (four 5-cc. portions) of benzene towards the latter stages of run 25 to make up for possible losses had no apparent effect on the rate of gas formation. A 36 per cent excess of benzene over theory (run 31) did reduce the gas formation t o a total of less than 1 gram of sulfuric acid with no sulfur dioxide but again resulted in the formation of considerable amounts of diphenyl sulfone in the overhead and absorber lines, although the reaction product showed less than 1 per cent on analysis. Table V lists a comparison of the experiments included in this series, and Table VI gives the complete data for run 32. One point of significance is that the charred material content was lowered to about 7-8 per cent, compared with previous values of 11-20 per cent, but the size of the charge was increased. The hydrocarbon recovery averaged 81 per cent. MATERIALBALANCESmade on numerous sulfonations showed material out to be low by from 4 t o as much as 15 per cent; in general, the differences were greater in iron than in glass. Considering run 32, with 98.3 per cent sulfuric acid : Qrams in CsHr 234.3 Has04 299.0 416.9 Naphtha Total
Qrams out Residual mass Samp1e8
-
470
6.5 476.5
950.2
Recovered hydrocarbon Benzene in above Water removed SOa in absorber waters S0a in aqueous dist.
333.0 12 54.3 35.9 0.56
-
912.3 Total in Total out
Loss
Here the effect of agitator speed i s much more pronounced on the hydrocarbon-water distillation ratio than had been indicated in the 1-mole experiments: With 1000 r. p. m. speed, the hydrocarbon-water ratio is just slightly lower for the weaker acid, but the time required is 24 per cent greater. The amount of charring as water was removed was studied in runs 28 and 29 by removing 5-gram samples from the still pot a t various intervals for analysis:
163
950.2 912.3 37.9
Analysis of Reaction Product CaH,SOsH Free Hzs04 Charred material Unaccounted material
'
8 2 . 0 yo 1.15 8.37 8.48
YIELDBASEDON BENZENE.Approximately 12 grams of benzene boiling below 90" C. were recovered by distillation of the hydrocarbon layer with a 10-inch (25.4om.) -glass-packed laboratory column. No Ha0 Removed Analysis of Reaction Mass, Yo Color Ppt.of credit was allowed for a 5-cc. fraction boilUnacwith ing-from 90" to 170" C., although this was Sample Time Min.' Total cc. Cc./mole Teomz.., CoHsSOoH Has01 Char counted BaCOa a t least 50 per cent benzene. Thus, there 0.17 109 37.6 25.5 0.5 28A 60 0.61 36.3 White 29H 430 54 0 18 159 68 5 12.7 3.6 15,2 Qra ish white were (234.3 - 12 =) 222.3 grams of 164 73.5 29J 460 71.6 23.87 5.0 6.9 14.6 Dars brown benzene actually used or lost, correspond169 73.4 0.5 29K 490 83.7 27.9 11.2 14.9 Black in@;to an 86.9 per cent yield of sulfonic acid based on benzene. Benzene goes (a) These data are plotted in Figure 7 and show no advantage in to reaction, (b) to the naphtha fraction from which it removing more water than the water of reaction plus the might return t o the next batch, (c) t o chemical decomposiwater in acid, which in this case is 18 5.8 cc. = 23.8 cc. per tion, and ( d ) t o mechanical and volatile losses. Volatile
+
INDUSTRIAL AND ENGINEERING CHEMISTRY
164
TABLE V.
DATAON LARGERRUNSIN
THE
Vol. 33, No. 2
SULFONATION OF BENZENE^ Analysis of Reaction Mass
Run No.
Hydrocarbon Range, c.
Max. Ttmp.,
C.
Water Off, Cc.
Hydrocarbon Distd., Ca.
Benzene sulfonio acid,
Free
Yo
%
26.1 84.8
gi.8
6.503
19.9 149.6 72.7 25.2
76 73.4 82.0
AV.
Bgitator Time Reflux Speed, Required, Rate! R. P. iM. Min. Cc./Min.
HC/HzO ratio
Charred Unacaounted material, material,
%
%
.7.37 ..
.9.33e ..
H2sOr i n Absorber Waters, Grams
Two-Mole Runs 20
316
180-190 170-200
170 166
50.2
48.0
1309 4070
600 GOO
5.87 5.33
223 765
38.97
0.168
Three-Mole Runs
25 28 29K 32d
170-190 145-200 170-200 170-200
165 155 169 168
70.2 60.7 83.7 54.3
1395 9080 6080 1420
1000 600 600 1000
410 590 490
3.41 15.39 12.40 4.90
290
...
..
3.0 0.5 1.15
...
. I .
7.3
49.64 34.32 5.77 43.95
24.0 14.9 8.48
11.2
8.37
Using a molal ratio of 94.4% sulfuric acid and 2 volumes of naphtha, and steel wire agitators. b hfade with 3 5 3 excess benzene. c Includes. 1% diphenyl sulfone in reaction product. d Made with 98.370 sulfuric acid.
a
losses may be attributed to leakage through the gasket, stuffing box, and connections, and to the fact that the reaction pot had to be opened and lowered as soon as a run was completed t o prevent e x c e s s i v e corrosion of the steel wire beater. The above yield includes both chemical and mechanic a1 losses, and it is obvious that the l a t t e r will b e much lower in a 0 4 8 12 16 20 24 28 plant operation WATER REMOVED, CC than in this small FIGURN 7. EFFECTOF WATER REtest; the yield MOVAL ON ANALYSIS OF REACTION will go up correMASS FOR TESTRUNSWITH MOLECULAR QUANTITIESOF BENZENE AND 94 spondingly. The PERCENTSULFURIC ACID losses of naphtha were about 20 per cent, although they would also be greatly reduced in production: ACIDB A L A N C (AS ~ 90s) IN: SO6 in HzSO4 299 X 0.983 X 80 = OUT: 901 as sulfonic acid (0.820 X 476.5 X 80)/98 = SO; a8 free HzSOr (0.0115X 476.5 X 80)/98 = In absorber waters (43.95 X 80)/98 In aqueous distillate (0.69 X 80)/98 =
-
240 grams 197.8 4.48 35.9 0.56
Loss
238.74 1.26
'
The data obtained between SUMMARY OF SULFONATION. runs of different sizes have certain discrepancies, For example, with 1-mole runs it was possible to get complete reactions in 3 t o 4 hours, whereas with 3-mole runs, 7 or more hours were required, Such differences are doubtless due to differences in the relations between size of charges and equipment, the degree of agitation (which cannot otherwise be specified), etc. Both the type and the speed of the agitator are important. An emulsifying stirrer, such as a steel wire beater, operating a t about 1000 r. p. m., was found to be the most effective. Optimum temperature for the sulfonation is between 160' and 170' C. where the reaction proceeds rapidly. Molecular proportions of benzene and either 94 or 98 per cent sulfuric acid can be employed with a naphtha cut of about 170' to 200' C. (two volumes to one of benzene) as the most desirable diluent.
Using theoretical proportions of acid and benzene, conversions of from 80 to 86.9 per cent of benzene were obtained. Some benzene always remained in the intermediate cut (90' to 170" C.) obtained in distilling the recovered naphtha, for which no correction was made. This would increase the yield another 2 t o 3 per cent in re-using this cut for the next batch; mechanical losses would also be much lower to give higher net yield in production. Free sulfuric acid in the reaction mixture is very low and is probably related inversely to the amount of charring produced. Thus, by removing just the water of reaction (18 cc. per mole), a residual mass is obtained containing 12 per cent free acid and 3 per cent charred material, and yet continuing the reaction to the point of theoretical water (18 6 or 24 cc. water per mole with 94 per cent acid) reduces the free acid t o 5 per cent and increases the charred material to 7 per cent of the total product. Sulfone formation does not occur unless there is a large excess of benzene and consequently a longer time of reaction. This agrees with Harvey and Stegman ( l a ) .
+
TABLE VI. DATAON 3-MOLE SULFONATION OF BENZENE WITH THEORETICAL RATIOOF 98.3 PERCEXTSULFURIC ACID(Run 32)s
Time
11:52 12:12 12:22 12:32 12:42 12:52 1:02 1:12 1:22 1:32 1:42 2:02 2:12 2:22 2:32 2:42
2:52 3:02 3: 12 3:22 3:32 3:42 3:52 4:02 4:12 4:22 4:32 4:42 4:52 5:02
Temp., Liquid
C. Vapor
111 116 118.7 120 123 125.2 129 130.5 132 133 135.9 138 139.2 140 142.9 144.9 147.5 149.5 152.3 155.3 157.1 159.8 161.2 162.8 163.8 164.5 166.9 167.2 168.0
79.3 83 83 83 91.5 98.8 98.7 100.1 100.1 101 101 103 110 117 119 120.8 123 123.5
...
Total HydroWater Reflux carbon Off Rate? Distd.. Cc.' Cc./Min. Cc.
...
126.5
127 127.5 126.3 128 129.2 128 127 122
93 94
Sainple NO.
Started heating Reflux started 0
0.2 0.4 0.7 1.0 1.2 2.0 2.8 3.3 5.7 6.7 8.7 9.9 11.4 13.5 15.5 17.8 19.8
4 4 4 4 4 8
9 8 8 7 6
21.6
24.1 26.8 30.2 33.6
446.2 ;:"
! 4
49.8 54.3
3 2
20 40 60 90 130 170 210 250 290 370 410 490 580 660 740 810 870 930 980 1030 1080 1140 1190 1240 1290 1330 1360 1380
A
B
C
D
E F
a A itation; steel wire beater at 1000 r. p. m.; naphtha cut: 540 oc. Varso?l. boiling at 170-203° C.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
Charring is the most serious difficulty despite the use of acid-treated stable hydrocarbons. The amount of charred material can be reduced to 3 per cent and can be consistently kept below 7 per cent of the total product. All of the charring does not result from decomposition of the naphtha, since 2 to 3 per cent charring is said to be normal in sulfonating benzene (12). The decrease in the amount of charring from an average of about 15 per cent with the 1-mole runs to about 7 per cent for the 3-mole runs is promising and indicates that with still larger charges, better agitation and control, and continued re-use of the same naphtha, charring may be reduced to a negligible limit. (More recent experiments on some other hydrocarbon fractions indicate their practical inertness under these conditions.) The recovery of naphtha was as high as 95 per cent in a well-controlled run. All of the loss is not due to charring, since much was probably due to volatile losses above mentioned for these small-scale experiments.
Neutralization of Sulfonation Product Prior to fusion with caustic soda and after liming out the excess sulfuric acid, the sulfonation product is converted to sodium benzene sulfonate by neutralization with by-product sodium sulfite or sodium carbonate. Because of low free sulfuric acid, it was a t first thought that the liming-out operation and consequent filtration could be omitted, and that neutralization could be effected by direct addition of sodium carbonate. This, however, proved unsatisfactory; unless the solution was diluted to about 20-25 per cent, bad foaming and bumping occurred. Filtration in acid or alkaline solution with or without filter aids did not remove any appreciable quantity of the charred matter. By dissolving the solid mass after neutralization in hot glacial acetic acid, diluting with water to about 20 per cent, and then filtering through decolorizing carbon, a creamy-white sodium benzene sulfonate was obtained (after evaporation of the acetic acid), which indicated that the colloidal charred matter was probably tarry acids. By heating the neutralization product up to 180-210" C., complete coagulation of the charred material was achieved in one case (run N-2) but this added operation was uneconomical.
RUNSIN PER TABLEVII. ANALYSISOF NEUTRALIZATION CENT
Run No. N-2 N-5 N-6 N-7 N-8 N-9
Moisture 9.05 7.67 2.99 2.27 0.0 9.40
NaaCOi 13.84 11.96 9.33 1.06 0.0 3.54
NanSOi 1.51 4.95 0.82 6.6 20.7 3.43
Charred Matter
0.0
2.02 22.1 6.8 0.0 0.0
CsHsSOsNa 75.6 67.4 64.76 84.27 79.3 83.7
Small amounts (2 per cent) of charred material in the sulfonate lower the yield of phenol appreciably and also cause difficulty in the subsequent filtration of the fusion mass and the kerosene recovery. However, as shown in the analytical procedure, the addition of barium carbonate to the sulfonation mixture carried down all of the impurities and gave a white, pure barium benzene sulfonate on subsequent filtration and evaporation. This principle was applied to a hot 50 per cent solution of the product of sulfonation, using a slight excess of calcium carbonate over the free sulfuric acid content (10 to 15 grams of calcium carbonate per mole of reaction product). After standing overnight, the black precipitate of calcium sulfate and adsorbed impurities was filtered off. Sodium carbonate was added to give a creamy-brown precipitate of calcium carbonate (from decomposition of the soluble calcium benzene sulfonate) and a clear filtrate, which on evaporation
165
gave a white char-free sodium benzene sulfonate. The double adsorption and filtering involved in this lime-soda treatment reduces the charred content to insignificance, and is undoubtedly the most economical procedure, especially since the volume of precipitates is very small compared with that of the liming operation used in the industry. Table VI1 gives the analysis of several neutralization batches, all of which were used in subsequent operations. Moisture was determined by drying to constant weight a t 140" C. Sodium carbonate was obtained by titration of a dilute solution with methyl orange as indicator. Barium chloride precipitation was used to get the sodium sulfate content and the occluded material taken as charred matter after drying to constant weight and ignition. The sodium benzene sulfonate was obtained by difference; but this figure may be as much as 2 per cent higher than the value obtained by analyzing it for sulfur by the combustion method. For example, N-9 showed 15.20 per cent sulfur; correcting for the 3.43 per cent sodium sulfate present gives 81.3 per cent as sodium benzene sulfonate. The higher figure (by difference) was used in the calculations for the fusion. Runs N-2 through N-7 were all sodium carbonate neutralizations. N-2 had the charred material coagulated by heating to 210" C. under kerosene. N-8 had a lime treatment from an excess acid sulfonation and had been baked a t 180" C. for several hours. Run N-9 was a lime operation.
Fusion The fusion as outlined by Kokatnur using kerosene represents a wide departure from conventional methods. The experimental work on this phase of the process involved a series of twenty-five small-scale batch runs concerned with the effects of type of caustic, excess caustic, quantity of kerosene, and agitation. Further research is in progress. The "fusion kerosene" was well in the gas oil range, as it was always a mixture of one volume of Bayol D-1 (boiling range 210-275" C., specific gravity 0.789) and two volumes of Markol (boiling range 295-425" C., specific gravity 0.838). Continued heating and use of caustic darkened it, but there is no other indication of its decomposition. APPARATUS. Most of the fusions were carried out in the 2liter cast iron reactor used in the sulfonations, which was equipped with an agitator, thermometer well, short still head, and downward condenser. A special compounded woven asbestos gasket was found to be necessary, since at the elevated temperatures (320' t o 355" C.) ordinary sheet, fiber, and rubberized asbestos leaked badly. A small laboratory motor was used for the preliminary runs with large volumes of kerosene, but with run F-10 and thereafter, a l/O-horsepower motor with a leather belt drive was installed. GENERALPROCEDURE. The caustic soda was mixed with sodium benzene sulfonate in the reactor, then the kerosene was added and slowly distilled off with sufficient water to show that the reaction was completed. After cooling, most of the kerosene was decanted, the fusion mass dissolved in hot water, the remainder of the kerosene separated, and the aqueous solution atered to remove traces of iron, charred matter (if present from sulfonations), etc. The clear dark solution (500-1100 cc.) was acidified with hydrochloric acid, and the phenol extracted by means of diisopropyl ether. Four to five extractions with 100150 cc. portions were sufficient; the residue from the last extract was less than 0.5 gram, boiling above 100' C. The bulk of the isopropyl ether was distilled off and the residue fractioned from a 250-cc. flask with a short glass still head and an 18-inch (45.7-cm.) silver condenser. Anintermediate cut of 90"to 175" C. was taken, then the phenol product from 175" to 185" C. The tails remaining in the flask (about 6 to 8 grams) containing a small amount of tar and possibly traces of higher phenols were
INDUSTRIAL AND ENGINEERING CHEMISTRY
166
Vol. 33, No. 2
*
-i
TABLE VIII.
EFFECTOF TYPEOF CAU6TIC ON
TEE
FUSION O F SODIU&lBENZENE SULFONATE'
Reaction Max. Phenol Yield R Kerosene, a HrO, t e , temp., Time, Run NaOH Used Mo!e No. Type Grams Percent Ratio cc. cc. HC/H*O cc./min. O C. min. Grama % fi F-2 Anhydrous crystal 60 2.62 247 19.0 17.3 1.57 329 170 36.0 91.3 Pellet 48 95 2.72 207.8 18.2 11.4 1.19 323 200 33.7 85.4 F-3 330 200 36.3 92.1 F-4 Soln. of flake 92 49 2.68 245 60.0 4.1 1.52 a CsHaSOaNa: 100 grams or 0.420 mole from neutralization charge N-2. kerosene: 1000 cc. or 822 grams per charge. b Anhydrous crystal caustic was wet with 25% by weight of kerosene, dr oontained 45 grams NaOH (98% pure). equivalent to 1.102 moles. ~
Distillation Data
TABLEIX. EFFECTOF AGITATIONON
THE
FUSIONOF SODIUM BENZENE SULFONATE
Reaction KaOH Solution Distillation Data. Max. Agitatora CaHsSOsNa Lot Mole Kerosene, HIO, Rate. temp., Time, Grams Mole No. Grama Percent ratio (10. cc. HC/HaO cc./m;n. C. min. Run No. R. P. M. F-10 B, 350 100 0.468 N-7 102 49.0 2.67 348.5 63.5 5.49 5.87 342 60 100 0.468 102 49.0 B, 1000 80 F-13 N-7 2.67 355 63 5.64 5.23 348 100 0.468 49.0 6.31 351 So, 900 102 65 F-15 N-7 2.67 397 63 7.09 0.468 100 102 F-12b N-7 49.6 2.70 2.13 5.68 344 B, 350 163 90 347 0.936 So-B, 400 200 ... 102 F-160 N-7 98.0 2.67 315 60 F-17d 0.936 N-7 49.6 2.65 351 200 200 So-B, 400 402 3i2' i.59 5.11 140 B = steel wire beater: Sa = iron plat,e, scraper; So-B = combination scraper with one beater wire, b 100 cc. of water added to sulfonate, giving 45.5% sqlution. e No kerosene used. 5 cc water added t o pellet oaustio and melted before sulfonate added. d 200 cc. of water idded i o sulfonate, giving 45.5% solution.
...
Phenol Yield Grams % 34.23 77.8 81.2 35.63 86.0 37.77 37.99 86.5 67.9 59.91 88.3 77.63
Q
TABLE X. EFFECTOF EXCESSLIQUIDCAUSTIC SODAON YIELDSOF PHENOL IN FUSION OF SODIUM B ~ N Z E NSTJLFONATE~ E ~
SaOH Solution Distillation Data Run CsHsSOnNa Lot LMole Kerosene, H20, Rate No. Grams Mole No. Grams Percent ratio 00. 00. HC/H*O cc./mi'n. 100 0.468 102 49.0 2.67 355 63 5.64 5.23 F-13 N-7 N-7 100 0.468 83 49.6 2.20 343 52 6.61 5.20 F-14 49.6 2.20 F-26 200 N-7 0.936 166 429 105 4.09 8.22 200 0.936 164 48.6 2.13 419 104 4.11 6.38 N-7 F-22 0.441 102 49.6 2.86 254 62 4.09 3.33 N-8 100 F-18 0.441 83 49.6 2.33 410 52 6.17 N-8 100 F-19 7.89 F-246 173 48.9 2.11 302 1.35 5.92 N-9 215 1,000 407 2.03 F-25b 166 48.9 296 1.31 5.69 N-9 215 1,000 387 D Kerosene 1000 cc. (822 grams) per charge. agitator, wire beater at 1000 r. p. m. b 180 00. of water added, giving a 49.4% so1;tion of sulfonate.
steam-distilled, and the aqueous distillate was reextracted with isopropyl ether to recover additional phenol. The intermediate outs and tail extractions from three fusions were combined because of their small amounts and refractionated to give additional quantities of phenol, which were then prorated to the individual runs according t o the proportional parts of each involved. The recovered ether and heads (boiling below 90" C.) were extracted with caustic, reprecipitated with hydrochloric acid, and again extracted with small quantities of ether and additional quantities of phenol recovered by fractionation; the latter was proportioned equally over the number of runs involved. This last correction amounts to about 1.1 grams (about 1 to 2 per cent) per run, and is due largely to phenol left wetting the condenser. Phenol yield is based on the total quantity actually recovered as outlined above. At this relatively early stage of the process the quality is better than that of much technical grade phenol sold and has a solidification point of 39.8"to 40.5" C. and a bromide-bromate titration of 98 to 99 per cent pure phenol. The yields as reported are probably low by about 2 per cent, owing t o inability to further handle the small quantities left in the final distillation flask, wetting the condenser, and left in the &a1 heads and tails.
EFFECT OF TYPEOF CAUSTIC. The variation in physical form of the caustic was the first point considered; and 0.5mole trials were carried out with approximately 35 per cent excess anhydrous crystal caustio (14) (made by concentrating 50 per cent caustic soda with kerosene following the method of Othmer and Jacobs, 18), pellet caustic, and a 50 per cent solution of flake caustic. The sodium benzene sulfonate (run N-2) contained approximately 1 mole of mater of hydration, was completely free of charred material, and gave a smooth reaction. A wire beater at about 600 r. p. m. was used as agitator. The essential data are listed in Table VIII, and Figure 8 gives the relation between the volumes of hydrocarbon and water distilled. The sharp bend in the curves occurs just a t the point where actual fusion commences (approxi-
Reaction Max. tzmz.., Time, min. 348 80 340 76 65 346 355 82 343 95 349 75 354 120 356 120
Phenol Yield Grams % ' 35.63 81.2 36.69 83.4 72.29 82.2 75.8 85.5 32.08 77.5 32.02 77.3 84.85 89.2 86.06 90.4
mately 267' C.), after which relatively large amounts of hydrocarbon are needed to remove the water of the reaction because of the relatively lower dehydration pressure of water. Liquid caustic (forming anhydrous crystal caustic, 1.4, in situ) and anhydrous crystal caustic are definitely better adapted to this process than the pellet or fused type, as shown by comparing runs F-4 and F-2 with F-3. EFFECTOF AGITATION.A series of six runs was made with three different types of agitators. A steel wire beater had two 2.5-inch (6.35-cm.) diameter circles and No. 12 gage spring steel wire mounted at right angles on a b/lrinch (7.9mm.) shaft, similar to those used in the sulfonation experiments. A scraper type of a flat piece of No. 22 gage iron, 23/4 X S/sinch (6.9 X 0.95 cm.) was cut to fit the curvature of the reactor and fitted into a 6/16-inch shaft. The third type was a combination scraper-beater made with 3/16-in~h(4.8mm.) holes drilled in the blades and one loop of 2.5-inch diameter No. 12 gage spring steel wire mounted a t right angles. The same neutralization charge (N-7) was used throughout, with a standard excess of about 33 per cent liquid caustic as listed in Table IX. Various pulley ratios gave measured speeds of 350-400, 900, and 1000 r. p. m. Unfortunately, these tests on agitation were limited by mechanical difficulties, principally vibration and splashing with the scraper type agitator at high speeds. All yields are relatively low, as would have been expected from the presence of a rather large amount of charred matter from the starting materials used. Run F-15, with a scraper type of agitator, gave a higher yield than the corresponding wire beater tests (F-10 and F-13), but the fusion product was badly splashed over the walls and cover; i t caked hard, with typical fused salt insolubility, and required 4 to 5 hours for solution as against about 20 to 30 minutes for the products of
*
WATER
REMOVE0,CC
FIGURE8 FUSION OF SODIUM BENZENE SULFONATE Kei osene-water distillation relatlons for 0 5-mole runs made with 30 per cent excess caustic soda
the wire emulsifier runs. This high yield can be obtained also with wire beaters by employing the sodium benzene sulfonate as a 50 per cent aqueous solution (F-12) without altering the amount of kerosene distilled but considerably reducing the kerosene-water distillation ratio. On the other hand, the scraper type stirrer required the distillation of 16 per cent more kerosene and gave a much higher ratio of hydrocarbon to water. OF AQUEOUSSOLUTIONS OB SODIUM BENTABLE XI. FUSION ZENE SULFONATE AND CAUSTIC SODA(Run F-25)"
Liquid Vapor Total Water Kerosene Temp., T:mZ., Distd., Off. Distd.b, c. cc. Cc. cc. Started heating 9 First dro; * ' 108 99 9 39 30 117 102 20 90 70 119 107 44 194 150 126 114 85 319 234 166 131 355 252 103 191 147 132 397 265 226.5 167 155 429 274 239 166 481 279 202 281 249 332 619 287 308 247 665 293 372 330 210 379 674 295 346 188 387 683 296 356 216 0 CsHsSOaNa: 215 grams or 1.000 mole from N-9 diss0,lved in 180 cc. water (49.4'7 solution); NaOH: 166 grams of liquld caustic, 48.9% NaOH (0.45% N a d O ~ s ) or , 2.03 moles, or 1.5% excess over theory; kerosene: 1000 cc. or 822 grams' agitator: steel wire beater at 1000 1'. p. m. 1, Kerosene fe&erv: 396 eo. bv decantation. 387 cc. bv distillation. 209 Time
...
...
The scraper-beater combination with aqueous sodiuni benzene sulfonate (run F-IT) was possibly more effective, but was limited to low-speed operation because of vibration. Again the product was fused rather than sintered, and the difficulty in dissolving as well as the time required caused this type to
TABLE XII. EFFECT O F KEROSENE
VOLUME
be discarded. Further runs were all carried out with wire beaters a t 1000 r. p. m. Run F-16, made as a control without kerosene but with the same sulfonate, agitation, and excess caustic as in F-16, resulted in a 20 per cent lower yield. The presence of additional quantities of water in the Kokatnur fusion, as when aqueous solutions of the sulfonate were used, appears to be beneficial to the conversion. EFFECT OF EXCESS CAUSTIC AND IMPURITIES. A series of eight fusions was made of both 0.5- and 1-mole proportions with 50 per cent caustic soda in excesses of 1.5 to 43 per cent, as shown in Table X. N o significant trend is shown between yield and excess caustic taken. I n the case of runs F-14 and F-26, the size of the charge was doubled (thus reducing the proportion of kerosene by 50 per cent) with no appreciable change in yield. The importance of impurities in the fiulfonation product is evident from these studies. Seutralization charge N-8, containing 20.7 per cent sodium sulfate (caused by improper neutralization of an excess acid sulfonation), was used in runs F-18 and F-19, and gave poor conversion. The presence of up to 10 per cent sodium sulfate is said to have no effect 011 the yield of phenol (6)in normal fusions; however, it is evident that a large amount of this solid matter will interfere with the ease of fusibility. This was found to be the case; the fusion m7as accompanied by constant crackling and popping in the still pot, and above 270" C. the rate of heating had to be slowed considerably to prevent the mass from blowing out of the pot (as it did in F-11). A control without kerosene (F-21) with 26 per cent excess pellet caustic and 5 per cent water, also carried out with this stock, showed 74.3 per cent phenol produced. With neutralization charge N-7 the charred material was previously indicated as responsible for the reduced yield. This was verified in the case of the char-free material (N-9) where conversions of 90 per cent or more were again obtained. The use of aqueous solutions of sodium benzene sulfonate in the fusion again have no effect on thevolume of hydrocarbon distilled (F-26 and F-22 against F-24 and F-25), although the kerosene-water distillation ratio is reduced by 67 per cent (Table XI, Figure 9). EFFECTOF REDUCTION IN KEROSENE VOLUME. In the previous experiments (P-12 and P-17) it was shown that doubling the size of the charges with the same volume of kerosene had no effect on the yield of phenol. This was not true in any of the prior runs such as F-5 through F-8, where conversions dropped some 10-20 per cent, owing primarily to inefficient agitation available with the small laboratory motor. When the fusion is carried out in glass apparatus a t about 260-270" C., the solid mass suddenly swells and becomes very flocculent and voluminous; and unless sufficient kerosene and suitable agitation are available, poor
REDUCTION ON FUSION OF SODIUM BENZENE SULFONATE WITH LIQUID Diatillation Data
~ u n Kerosene No. Vol., Cc. F-22 F-23 F-246 F-2Oa
1000 600 1000 600
C6n5SOsNa Grams Mole 200 200 215 215
0.936 0.936
1.000 1.000
Lot No. N-7 N-7 N-9 N-9
NaOH Solution Per ,Mole cent ratio 48.6 2.13 48.6 2.13 48.9 2.11 48.9 2.11
Grams 164 164 173 173
Agitated with a wire beater at 1000 r. p. m. b 180 cc. of water added, giving a 49.4% solution of sulfonate.
a
167
INDUSTRIAL AND BNGINEERLNQ CHEMISTRY
February, 1941
Kero- HzO, sene, oc. 00. HC/HaO 419 104 4.11 244 102 2.39 1 35 407 302 269 304 0.89
Rate, cc./ min. 6.88 4.94 5.92 6 38
Reaction Max. temp., Time, C. mm. 82 35.5 357 70 354 120 365 90
C-4USTIC SODAa
Yield Grams
%-
75.18 72.52 83 82 86.06
85 5 82.4 89
91
2 /
Val. 33, No. 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
168
fusion and low conversion will result. The substitution of a 1/6-horsepower motor furnished ample power and agitation, and permitted large reductions in kerosene requirements. Table XI1 shows that with 1000 r. p. m. wire emulsifier agitators, the volume of kerosene can be further reduced by 40 per cent without ill effects. Thus, a 70 per cent reduction in the volume of kerosene over the preliminary experiments is shown. Additional reductions in the kerosene volume could probably be obtained by increasing the size of the charge and installing a short fractionating column or possibly with a less wide-boiling kerosene (i. e., 300" to 400" C. range).
3. The excess of caustic soda can be varied from 1.5 to 48 per cent without affecting the conversion to phenol, using 50 per cent caustic solutions. The impurities in the sulfonate charged do affect the yields; charred material (probably containing tarry acids) and also large amounts of sodium sulfate reduce thc conversion from 5 to 10 per cent. 4. The sodium benzene sulfonate can be employed as a 50 per cent solution directly from the neutralization operations, and the evaporation and fusion with liquid caustic can thus be carried out in one step. The total volume of kerosene distilled is not affected by the presence of this quantity of water, but the distillation ratio of hydrocarbon to water is greatly reduced. Higher conversions to phenol are evidently favored by the presence of water in this partial-pressure method. This is proved by a comparison of the runs on different types of caustic, in which caustic solution was superior to anhydrous types, and with 50 per cent caustic solution where solutions of the sulfonate give better yields than does the dry salt. a. The kerosene recovery has been as high as 99.4 per cent and consistently above 98 per cent. Loss is due primarily to handling and filtering; there is no chemical loss. About 5.8 pounds of kerosene are med per pound of phenol produced, or 2.74 pounds of kerosene per pound of sodium sulfonate; but this quantity can probably be reduced by increasing the size of the charge, using a fractionating column to utilize the hydrocarbon better by forming a true azeotropic mixture, and perhaps using a kerosene with a different boiling range. The latter is evident from the increased fusion temperature obtained by decreasing the volume of kerosene (i. e., 350" C. for 600 cc. of kerosene against 330" for 2000 cc. per mole).
Comparison with Commercial Processes
100
50
0
50
100 150 200 250 WATER REMOVED, CC
300
FIGURE 9. EFFECT OF EXCESS CAUSTIC O N THE KEROSEXE-WATER DISTILLATION RATIOIN THE FUSIOX OF SODIUM BENZENE SULFONATE
KEROSENE RECOVERY should be complete since the kerosene is unaffected by the caustic treatment. However, there are small losses due to leakage through gaskets and handling, but with proper manipulation they can be reduced to negligible quantities. Leakage through the gasket depends upon the type of gasket material: using Gerard woven asbestos (fifteen runs), the average recovery of kerosene was 98.2 per cent; using graphitized heavy cardboard (one run), i t was 97.4 per cent; using 3/16-incli sheet asbestos (two runs), it was 94.4 per cent; and using rubberized asbestos (two runs), i t mas about 90 per cent. With the special woven gaskets, recovery of as high as 99.4 per cent (994 cc. out of 1000 cc. taken) and consistently above 98 per cent has been obtained. On the other hand, with the other types, there is considerable seepage of vapors and "smoking" a t the high temperatures encountered. With graphitized asbestos packing, the stuffing box was maintained vapor-tight in all these runs. Handling losses are due to adherence of kerosene to the reaction pot, flasks, filters, etc., and are sensibly constant, except in cases using material of high char content from the neutralization (such as N-6), which were omitted from the above discussion. SUMMARY OF FUSION. The experiments established 'that: 1. The process is well adapted to the use of liquid caustic soda solutions; better yields are obtained with aqueous solution than with fused types of caustic. 2. The design and speed of the agitator are important in determining physical state of the fusion product. A wire beater gives a porous sintered mass, whereas a scraper type gives a more typically fused, difficultly soluble product. Wire beaters also permit substantial reductions in the volume of kerosene required, provided sufficient agitation is available (1000 r. p. m.) with no effect on yield of phenol.
The data obtained on these small-scale operations do not justify a quantitative economic comparison with present commercial processes. However, some statements as to material costs and qualitative evaluations can be made. I n the normal sulfonation processes no actual costs for the production of benzene sulfonic acid have been cited in the literature. Assurning 98 per cent yield based on benzene, estimates can be made for raw material cost, and range from a minimum of about 1.73 cents per pound for the Dennis-Bull process to about 2.6 cents for excess acid treatments. Taking the optimum conditions in the partial-pressure method, yield of 86.9 per cent based on benzene (run 32) and a 95 per cent recovery of naphtha (run lo), gives 275 gallons of naphtha for a batch using 1000 pounds of benzene. At a 5 per cent loss, 13.75 gallons will have to be replaced a t an assumed cost of 15 cents per pound (including treating costs and losses, base price 10.5 cents per gallon): CsHe
98% H B O I
Lime Naphtha
1000 lb. 1280 Ih. 300 lb. 13.75 gal.
SO. 022/lb. 17.50/ton 8,50/ton 0.15/gal.
$22.00 11.20 1.28 2.06
186.54-2.09 cents/lb.
This is in essential agreement n i t h the figures cited above. A 5 per cent loss of naphtha in this process is equivalent to an assumed 0.1 per cent loss of benzene in the Dennis-Bull process (based on 1000 pounds of benzene in both cases) : Method Yield, % Sulfonic acid produced, I b . Solvent required Gallons Pounds Loss assumed Per cent Gallons Cost per gal., oenta c o s t of loss a S a p h t h a . b Benzene.
Partial-Pressure 86.9 1760 27%
18780 5 13.75 15 $2.06
Dennis-Bull 98 1985
13,350b 97,400b 0.1 13.4 16
$2.14
No concrete figures are available a5 to operating costs; but the partial-pressure sulfonation method will probably be slightly higher than the Dennis-Bull process, and about the same as the excess acid or water removal methods. Investment costs in all will probably be about the same order of magnitude.
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
February, 1941
Neutralization costb for the conversion of the sulfonation product to sodium benzene sulfonate will be approximately the same in all the sulfonation processes, since liming out charges have been included with the sulfonation. For the fusion operation, material costs can be better established. With normal fusion, from 25 to 50 per cent excess fused caustic soda or 2.5 to 3 moles of alkali per mole of sulfonate are generally taken (6, 7). Assuming the lower value (25 per cent excess) with 92 per cent yield and fused caustic a t $2.70 per 100 pounds, then on the basis of 1000 pounds of sulfonate, 633 pounds of caustic soda are required, costing $16.24 for the production of 547 pounds of phenol. Thus, the caustic cost is 2.97 cents per pound of phenol. Using the data obtained on partial-pressure fusions, with 90.4 per cent yield and 1.5 per cent excess of 50 per cent caustic solution at $1.925 per 100 pounds of caustic soda, 514 pounds of caustic soda will be required, costing $9.90. Allowing l per cent loss of kerosene a t 5 cents per gallon and 2.74 pounds of kerosene per pound of sulfonate (GOO cc. per gram mole), 20 cents is the kerosene loss for 538 pounds of phenol produced. For each pound of phenol, (9.90 0.20)/ 538 = 1.88cents caustic and kerosene cost, or a saving of 36.7 per cent in the basic price for the fusion step. I n the partial-pressure fusion, there are distinct advantages in addition to the lower material cost. I n the normal fusion process the melting point of the fused caustic is lowered by addition of water. According to Groggins (7) 40 to 50 gallons of water are added per ton of fused alkali, giving an 83 to 86 per cent solution of caustic soda. I n other words,, part of the water previously removed in the caustic dehydration pots is added in the present commercial processes, and most of this water again must be evaporated off during the course of the subsequent fusion. The sulfonate is generally added as a concentrated solution of about 25 per cent water content (@, and this water must also be removed. The use of 83 per cent caustic solution has already been suggested (16). In the kerosene type of fusion the aqueous solution of caustic eliminates the necessity of fused caustic with its higher price due to evaporation costs, its handling difficulties, as well as the subsequent dilution with water to lower its melting point. Othmer and Jacobs (18) showed that with partial pressure evaporation the fuel cost of dehydrating caustic solutions could be reduced to one third that of the usual fusion process. The sulfonate solution must be evaporated or concentrated in any of these processes; and by this partial pressure method the evaporation and fusion can be carried out simultaneously in the one apparatus, and thus present a further advantage of eliminating one unit operation as well as the equipment needed for it. Although no concrete data are available, i t is believed that the investment and operating cost will, a t most, be slightly higher than in the normal fusion and in the same order of magnitude. Reliable data are lacking for a thorough comparison of halogenation and sulfonation methods, but the following points may be made in an over-all comparison of processes for phenol production:
+
Material Cost Excess acid sulfonation and fusion Dennis-Bull sulfonation and fusion Partial-pressure sulfonation and fusion Dow process Raschig process
Operating Cost
Investment cost
High
Medium
Low
Medium
Low
Low
Low
Medium
Low
Medium Very ION
High
High Very high
a The operating costs in the Raschig process may range from very low to very high, depending upon the ability t o prevent interruption in the continuous operation, corrosion costs, and maintenance charges.
169
An installation of the Raschig process capable of producing 15,000,000 pounds of phenol per year has been reported (1, 17) to cost $2,000,000. A plant of similar capacity using one of the sulfonation methods could probably be installed for about one third of this cost. Assuming a ten-year life period for the apparatus and G per cent interest charges on the investment represent an investment depreciation charge of 2.1 cents per pound of phenol for the Raschig process, against 0.7 cent for the sulfonation method. Conclusions The application of partial-pressure methods to the synthesis of phenol may probably compete commercially because of the low material costs involved. The sulfonation step has advantages over the usual water removal methods in that externally superheated excess benzene is not required and sulfone formation is completely absent. Charring is not unfavorably great in amount but is the major disadvantage; however, a treatment has been devised to produce sodium benzene sulfonate completely free of charred material. The fusion stage appears promising since the excess of caustic can be reduced to 1.5 per cent over theory. I n addition, aqueous solution of both caustic soda and sodium benzene sulfonate can be employed. Furthermore, since the fusion is carried out under kerosene, oxidation of sodium phenolate by contact with air is eliminated. Acknowledgment The authors are indebted to V. R. Kokatnur, C. 0. Assmus, J. Vickers, and J. J. Jacobs of Autoxygen, Inc., for the use of their facilities in these researches, to J. C. Olsen for numerous suggestions, to E. Trueger for sulfur determinations, and to C. J. Leyes for the use of the larger equipment as well as much of the mechanics in adapting i t to the specific requirements of this work. Literature Cited (1) Anonymous, News Ed. ( A n . Chem. Soc.), 18, 921 (1940). (2) Barbet, P.A., U.8.Patent 1,459,081 (June 19, 1923). (3) Bull, H., Ibid., 1,247,499 (Nov. 20, 1917). (4) Dennis, L. M., I b i d . , 1,211,923 (Jan. 9); 1,212,612 (Jan. 16); 1,229,593 (June 12, 1917). (6) Dyson, G. M., Chem. A g e (London), 14, 70-3 (1926). (6) Eikhman, R. K., Shemyakin, M. M., and Vozhdaeva, V. N. Anilinokrasochnaya Prom., 4, 523-31 (1934). (7) Groggins, P. H., “Unit Processes in Organio Synthesis”, 2nd ed., New York, McGraw-Hill Book Co., 1938. ( 8 ) Guyot, A., Chimie et industrie, 2, 879-91 (1919). (9) Hale, W. J., and Britton, E. C. (to Dow Chemical Co.), U. S. Patent 1.806.798 (Mav 26. 1931). Ibid., 1,882.826 (Oct: 18; 1932); 1,925,321 (Sept. 5 , 1933). Hale, W. J., and Britton, J. W’.,Ibid., 1,882,824(Oct. 18, 1932). ENQ.CHEM.,16, 842-5 Harvey, A. W , and Stegman, G., IND. (1924). Kokatnur, V. R. (to Autoxygen, Inc.), U. S. Patent 2,111,973 (March 22, 1938). Kokatnur, V. R., patent pending. Mizoshita, T., Rept. Central Lab. S.Manchuria Ry. Co., 1929, 36; Chem. Abs., 25, 1812 (1931). Novoselov, A. F., Anilinokrasochnava PTom., 2, No. 3, 17-21 (1932’1.
Ol&;T. R., Chem. & M e t . Eng., 47, 770-5, (1940). Othmer, D. F., and Jacobs, J. J., Jr., IXD.E m . CHEM.,32, 164-60 (1940). Prahl, W., and Mathes, W. (to F. Raschig G. m. b. H.), U. S. Patent 1,964,768 (July 3, 1934); 2,035,917 (March 31, 1936). Rhodes, F. H., Jayne, D. W., and Bivins, F. H., IND. ENQ. C H ~ M 19, . , 804-7 (1927). Tyrer, D., U. S.Patent 1,210,725 (Jan. 2, 1917).
