Sulfonation with Sulfur Trioxide - Industrial & Engineering Chemistry


Sulfonation with sulfur trioxide: Detergent alkylate in a scraping-blade heat exchanger. Albert Abrams , Emery J. Carlson , Everett E. Gilbert , Henry...
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EMERY J. CARLSON, GREGORY FLINT, EVEREIT E. GILBERT, and HENRY R. NYCHKA

General Chemical Division, Allied Chemical h Dye Corp., Marristawn, N. J.

Suifonation With Su Operation in a Batch Pilot Plant, Model for Several Commercial Installations

,ears ago, General Chemical Division introduced stabilized liquid trioxide as an article of commerce, under the trademark Sulfan. Since then, the used for this reagent have grown rerqarkably. Process development work is being accelerated to utilize it as an efficient reagent for making important household and industrialproducts. I/EC reported the first laboratory process in 1953 (10). Here is the 100-fold pilot plant scale-up built because laboratory results looked so good. ?%is has paid off too, the pilot plant since serving ’as the prototype for several coltlrnercid.insfa lwll

-

276

INW-

AND - R I M

~

4

PUOT PLANT

study of the sulfonation

of one commercial brand of dodecylknm e with vaporized sulfur trioxide has bcm reported as showing promise (4). The Gndings of the present study c o n h that conduaion, and they have been extended to other available brands of the hydrocarbon. From the standpoint of engineering, a different technique of beat removal haa hen employed, and the hrst data are reported on recycle of the air d as the carrier gas for the vaporized sulfur trioxide. A remedy is advanced for a factor Cited earlier as a disadvantage for the use of sultur trioxide with this hydrocarbon-formation of sulfonic acid anhydride leading to objectionable “acid

drift.” A similar study was made of the sulfation of several grades of lauryl alcohol. trioxide In addition, the reactionof& with thm other products was considered to a minor extent: toluene, a petroleum lubricant raffmate, and a polyether alcohol made by condensing e,thylene oxide with aq alkylated phenol.

General Factors Underlying

Plan#Design The Thinking behind Plant Dcsign:

Simplicity. A major o maximuq simplicity d d

QyMlSRY

with acceptable product quality. This involved the me, wherever poapible, of inexpensive, readily available e q u i p ment. Design simplicity was inherent in the fact that the pilot plant, in its initial form, was a direct scale-up of the laboratory flask sulfonator 0pe;ation (70), which comprised two ordinary laboratory reaction flasks, one for vaporiza,tion of the sulfur trioxide and the other for the reaction proper. The m n t i a l pilot plant components, shown in generalized schematic form in Figures 1,2, and 3, were an air dryer, sulfur trioxide vaporizer,and kettlea for sulfonation and ncntrdization. Photographs of this pilot plant have been published [for airdrymg and metering system, sulfur trioxide vaporizer, and neutralization kettle (5), and for sulfonation kettle @)I. ~ e n b i l i t y . Flexibility was wsential, as it wad intended to study several proce s variables and to work with several different products Over a fairly wide tcmpcrature range (about 30‘ to 110’ c.). The most important variables are: ’ A. CooLmo. The sulfonation kettle was jacketed for water cooling. A shelland-tube beat exchanger was provided for external cooling of the reaction mixtux. Provison was made for use of either or both, as desired.

B. Recyc1.8 OF SULFUR TRIOXIDE CAR-

~

~ ~ pGAa. d l

Labpratoq data had shown

From pilot plant to commercial equipment: At left, the sulfonator of the pilot plant unit. At right i s the commercial equipment used by Emulsol Chemical Corp., Division of Witco, for manufacture of industrial sulfonates using SO?

that, for best results with dodecylbenzene or lauryl alcohol, the sulflir trioxide must be introduced as vapor diluted with about 13 volumes of dry air or other inert gas. O n an industrial scale, several substantial advantages were seen for recycle of this carrier gas : Drying capacity is greatly reduced, being required only for air used for startup; the probability of having the air dry a t all times is greater; variation in the air-sulfur trioxide ratio is facilitated; a purchased compressed gas-e.g., nitrogen-may be substituted for dried air in some cases, as it is used only a t startup; and effluent air, as obtained from once-through operation, is eliminated. In the initial work. the air was not recycled (Figure l ) , as it was desired to establish results parallel to ‘those obtained in the laboratory, where once-through operation had been employed. The plant was, however, constructed to allow subsequent change-over to recycle (Figure 2). C. DIRECTUSEOF LIQUDSULFUR TRIOXIDE. As shown in Figure 3, the plant was also designed so that liquid sulfur trioxide could be added directly to the reactor without vaporization. Although this procedure is obviously simpler, and therefore more drsirable, than that involving vaporization, it can be used only

278

in a few cases with exceptionally stable organic compounds. This report cites its use in the sulfonation of toluene. Optimum Batch Size. The size of the plant was scaled to process about one-half drum of raw material, yielding about two drums of finished aqueous slurry. This scale was considered convenient to operate, while still indicative of probable results on a commercial scale. The sulfur trioxide vaporizer. also operated batchwise, was designed to hold enough liquid sulfur trioxide for three to four average-sized runs. Too frequent refilling of the vaporizer was thereby avoided.

(Figure 5) were used exclusively for air recirculation. For direct use of liquid sulfur trioxide, the sulfonator vessel (12. Figure 4) but without gas sparger tube; external heat exchanger (14 and 15. Figure 4), optional, and not actually used with toluene sulfonation; and a neutralizing tank (16. Figure 4) were required. A liquid sulfur trioxide weigh tank was used, as represented in Figure 3. The liquid sulfur trioxide (Sulfan) was used directly from the original drum, with the drum on a platform scale above the sulfonator and feeding to it by gravity flow. Operating Data

Details of Pilot Plant

Schematic illustrations of the actual pilo’t plant equipment and layout for operating with vaporized sulfur trioxide are shown in Figures 4 and 5. Direct use of liquid sulfur trioxide is closely represented by Figure 3, and the limited equipment required is included. Items 6 through 17 were used in essentially the same manner for air oncethrough and air recirculated. Items 1 through 5, 18, and 1’9 were not required for air recirculation, but were retained in the pilot plant system to permit either type of operation, Items 20 through 31

INDUSTRIAL AND ENGINEERING CHEMISTRY

Most sulfonation test work was done with dodecylbenzene detergent alkylate and lauryl alcohol, employing sulfur trioxide vapor diluted with air by the procedures shown in Figures 4 and 5. Several available brands of each raw material were evaluated. Toluene was sufficiently stable to react directly with liquid sulfur trioxide by the method of Figure 3. Addition of a small percentage of sulfuric acid to dodecylbenzene before introduction of sulfur trioxide yields in some cases a final product of lighter color (7). A number of tests with this socalled “heel” process were accordingly included in the present study.

S U L FONAT1ON W I T H SO,

Operations and Materials Used A. Vaporized SO3 with dodecylbenzene 1. Air used once through, without heela,* 2. Air used once through, with heelb 3. Air recirculated, without heeW

B. Vaporized SO3 with lauryl alcohol 1. Air used once throughatb 2. Air recirculated" C. Liquid SO8 with toluene 1. Liquid SO3 used directly without vaporization or dilutiona a Cooling by jacket only. Cooling by jacket and heat exchanger

together. c Air recirculated with heel probably OK, but not tested.

,

A-1. Sulfonation of DodecylbenWITHOUT zene. AIR ONCETHROUGH, HEEL. Sulfonation Step. Load vaporizer, start bypass air, load sulfonator and agitate a t 500 to 600 r.p.m. Open vaporizer vapor lines, and apply air and heat-3000 to 4500 watts as needed, reduced to 1000 watts near end of batch. Maintain a vaporization rate of about 0.5 pounds of sulfur trioxide per minute, noting change in scale weight a t 10-minute intervals. Adjust heat exchange coolant to maintain a batch temperature of 45' C. maximum during the first half of the run and 55' C. during the second half. Remove heat and seal off vaporizer a t end of batch. The sulfonation reaction is essentially instantaneous; full reaction and heat evolution occur without lag as fast as sulfur trioxide is introduced. The reaction mixture does not foam, and the diluting air is rapidly disengaged. Dodecylbenzene (mol. wt. 240), Ib. SO8 applied (105% of theoretical), Ib. Dry diluting air, cu. ft./min. (bypass air, 20; vaporizer air, 10) 2 . 0 to Batch time, hours Batch temperature, O C., max. Water (added at end of batch only), lb.

180

63 30 2.5 55 2

Water Treatment for Anhydride Removal. After addition of the required sulfur trioxide, continue agitation of the sulfonic acid for 5 minutes and then promptly add about 2 pounds of water to the reaction mixture to hydrolyze a small amount of by-product sulfonic acid anhydride present in the reaction mixture and stabilize product color. [ These factors have been discussed in more detail ( 8 ) ;the presence of anhydride causes objectionable acid drift in the final slurry.] Continue recirculation and agitation of the batch for 5 minutes to ensure complete mixing of the added water. Apply cooling as needed to compensate for spontaneous .temperature rise of about 5' C. with the water addition. Caution:

R u n a quick control test for complete anhydride removal, comprising dispersion of 3 to 5 grams of reaction product in 100 ml. of distilled water. Clarity indicates the absence of anhydride, and turbidity its presence. The batch (approximately 240 pounds) is now ready for neutralization. Neutralization. During the sulfonation step, load the neutralizer vessel with 320 pounds of 10% aqueous sodium hydroxide, in slight deficiency of expected requirement, and made u p from water and concentrated caustic. R u n in sulfonic acid by gravity to neutralizer a t rate of about 5 to 10 pounds per minute. Apply cooling. Increase or decrease acid addition rate as required to maintain a neutralization temperature in the range of 45' to 50' C. Caution: During the first half of addition there is some lag between addition and reaction; during the last half, the acid, being more readily solubilized, neutralizes substantially as fast as added. Throughout, agitate a t a moderate speed, insufficient to aerate the batch. As last of acid is run in, check p H and add 10% caustic as required to bring final p H to 7.5. Allow 30 to 45 minutes for neutralization. A-2. AIR ONCE THROUGH WITH HEEL. Proceed essentially as with heel (A-1). Use 170 pounds of dodecylbenzene, 60.0 pounds of sulfur trioxide (105% of theory), 415 pounds of 10% sodium hydroxide, and 30 cu. feet per minute of diluent air. Also use 15 pounds of 96% sulfuric acid added to the dodecylbenzene charge. After loading sulfonator with the hydrocarbon and starting the liquid recirculation, pour the sulfuric acid into the sulfonator, seal the vessel, begin sulfur trioxide vaporization, and proceed as in A-1. After sulfonation omit the water treatment, and proceed with neutralitation step as in A-1. As with the "nonheel" batch. the acid heel sulfonic acid comprises one phase; it is entirely neutralized to yield a slurry of higher sodium sulfate content and somewhat more grainy texture. A-3. RECIRCULATED AIR WITHOUT HEEL. Change flow pattern from that of Figure 4 (A-1) to that of Figure 5 . Shut off from system the compressed air source, dryer, and direct sulfonator vent. Cut in the mist filters, blower, and free vent. Operate blower a t 40 cu. feet per minute, with 30 cu. feet per minute to vaporizer bypass. Otherwise, operate vaporizer, sulfonator kettle, and heat exchanger as for air once through (A-l), and use the same raw material weights-1 80 pounds of dodecylbenzene and 63.0 pounds of sulfur trioxide. Carry out water treatment and neutralization steps also as for air once through (A-1). Lauryl alcohol (mol. wt. 200), lb. SO8 applied (101% theory), Ib. Dry diluting air, total, cu. ft./min. Batch time, hours Batch temperature, O C.

180

73

25 to 30 3 to 4 35O min. ; 40'rnax.

B-1. Sulfation of Lauryl Alcohol. AIR USED ONCETHROUGH. Sulfation Step. The basic procedure is again much as in A-1, with essentially the same mechanical operations. Use a somewhat lower vaporization rate (2000 to 3000 watts). Caution: Control the sulfation temperature carefully throughout to as neai-40' C . as possible. Specifically avoid allowing the temperature to drop below 35' C. during the first half of the run; otherwise, the batch may disengage the spent air slowly and tend to swell. For best color, avoid temperatures much above 40' C. a t any time, by suitable adjustment of the cooling water rate and/or the vaporization rate. T o prevent possible solidification of product in the heat exchanger, temper the cooling water to the heat exchanger to 20' to 25' C., particularly during the first half of the batch, when its freezing point is a t a maximum, Do not add water to the batch. Neutralize promptly. Approximate weight, 250 pounds of lauryl acid sulfate. Water, initial charge, Ib. 25% NaOH (total 155 lb.), lb. Initial charge Added in increments Over-all caustic strength, 7% NaOH

400 50 105

Neutralization (to 30y0 active slurry). Use a "split" caustic procedure. Add lauryl acid sulfate a t 4 to 6 pounds per minute from the sulfonator to the initial weak caustic solution in the neutralizer Caution: Agitate moderately, avoiding aeration. Adjust cooling, and acid addition rate if needed, to maintain the temperature between 35'and 40' C. throughout the entire neutralization. When the initial caustic is almost consumed and the batch p H approaches neutrality, simultaneously add additional 25% caustic solution during the remainder of the acid addition. Maintain an alkaline p H a t all times, but avoid a n undue excess of caustic. Neutralize to a final p H of 8 a t 40' C. Allow 0.5 to 1 hour for acid addition. After acid addition is completed, continue slow agitation for 0.5 to 1 hour a t 40' C. to ensure complete neutralization of possible stray gelatinous lumps. Caution: Do not allow batch to become acidic. Continue to check the p H frequently and to add small increments of caustic as required, until a constant neutral p H is obtained and the "slurry" is smooth without evidence of lumps or curds. B-2. AIR RECIRCULATED. The transition for lauryl alcohol sulfation from air once through to air recirculated, B-I to B-2, is relatively the same as the transition for dodecylbenzene, A-1 to A-3. Change flow pattern as in A-3. Carry out sulfation as in B-1, but recirculate the diluent air. Neutralize the intermediate lauryl acid sulfate as in B-1 . C. Sulfonation of Toluene Directly with Liquid Sulfur Trioxide (auxiliary VOL. 50, NO. 3

MARCH 1958

279

. . ..

&..

,

SULFONATION WITH SOa

Figure 4

Table I.

Typical Analysis Shows Product from the Pilot Plant i s Suitable for Making Household Detergents Dodecylbenzene Sodium Sulfonate Sodium Lauryl Sulfate Air Once Through Air once Air Without With Air recirculated, through recirculated Type of Run heel (A-I) heel (A-2) without heel (A-3) (B-1) (B-2)

No. of runs averaged 3 3 Free oil, % of active" 1.4 1.4 Na~S04,% of active 3.4 12.4 Klett color-thelower the number, the better the color 95b 75b a "Active" designates pure sodium sulfonate. 10% active. 20% active. Measured on four batches only,

heat exchanger not used). Add 100 pounds (1.1 pound-moles) of toluene to sulfonator, agitate, and apply tap cooling water to jacket. Gradually add by gravity flow 88 pounds (1.1 poundmoles) of liquid sulfur trioxide; addition rate is determined by temperature of the reaction mixture. Add the sulfur trioxide just above the toluene surface through an extended pipe. Reaction is practically instantaneous, with no detectable lag in heat evolution. Caution: Limit sulfonation temperature during first half of sulfur trioxide addition to 70' C. maximum, and to 90' C. maximum during the second half of the addition. Allow 1 hour for the sulfur trioxide addition. The final toluenesulfonic acid mixture, containing by-product mixed isomeric ditolylsulfones, comprises one phase. As desired, convert to the sodium salt by dropping the toluenesulfonic acid gradually into the cooled neutralizing tank a t 60' C., preloaded with water and caustic of desired strength dependent upon concentration of product desired. The byproduct sulfones (20 pounds, dry) are precipitated and the sodium toluene sulfonate liquor is decanted or filtered. Product Evaluation The aqueous product slurries of dodecylbenzenesulfonate and lauryl sulfate

Table 11. Complete Mist Removal is Essential far Best Color No. of filter towers packed with glaEs 3 11/2 1 wool No. of runs averaged 3 2 1 Blower discharge, 7 4 p.s.i.g. Free oil, 100% active 1.5 2.2 1.6 basis NazSO1, 100% active 3.4 3.6 3.3 basis Klett color, 10% active 95 145 255

...

3

8

1

1.7 3.2

3.6 3.8

5.2 2.7

6O"ld

956

80C

were analyzed by a standard procedure (2). Average analytical data are summarized in Table I. I t is believed that over-all quality for both products indicates suitability for use in household detergent formulations. [Since the present work was completed (early in 1954), available commercial brands of dodecylbenzene have improved in quality. With alkylates now available, the free oil and Klett color figures should be lower than those reported in Table I . ] Analysis of a toluenesulfonic acid batch showed: sulfuric acid, 9.0 weight %; sulfone, 12 weight %. These figures are, respectively, somewhat higher and lower than those obtained in the laboratory (70). Some unreacted toluene is also present. Discussion of Process Variables

Dodecylbenzene. ALKYLATE QUAL Three domestic commercial alkylates were tested under comparable conditions by Procedure A-1. Product analyses-for free oil and inorganic sulfate were nearly the same. T w o of the three gave products of similar satisfactory color (Table I), but the third gave nqticeably darker slurries (Klett color over 300). These results confirmed those obtained in the laboratory (70)-several alkylates giving parallel satisfactory results with oleum may not perform similarly with sulfur trioxide, as the latter is a stronger reagent. Alkylate quality is of the utmost importance for obtaining satisfactory color in sulfur trioxide sulfonation. USEO F ACIDHEEL. Addition of a sulfuric acid heel-e.g., 9% of 96% acid based on the alkylate-to the hydrocarbon before introduction of the sulfur triITS.

Table 111.

Effect of Sulfur Trioxide-Alkylate Ratio on Product Analysis-5% Excess SO3 i s Optimum Type of Run A- 1 A-3

Mole ratio SO8 Free oil, 70of active Na2SO4,% of active Klett color, 10% active

282

1.04 2.1 3.5 75

1.06 1.6 3.1

90

INDUSTRIAL A N D ENGINEERING CHEMISTRY

1.04 2.0 3.1

...

1.05 1.6 3.2

100

1.06 1.4 3.6

105

oxide can improve product color (7). Of the three domestic alkylates tested, the two that gave satisfactory color without the heel showed only slight improvement with the heel (Table I). However, the third alkylate, which gave a comparatively poor color without the heel--Le., over 300-gave colors of 72 and 86 in two runs with the heel. Thus, it was possible to achieve substantially equally satisfactory colors with all three alkylates, but at the expense of higher inorganic sulfate content with the one requiring the heel. Use of the heel reduces the viscosity of the sulfonic acid, which slightly lowered the recirculation pump discharge pressure to the heat exchanger (Table IV). REQUIRED EXCESS SULFONATING AGENT. Laboratory data (70) had indicated the use of 1.05 moles of sulfur trioxide per mole of alkylate as optimum. As shown in Table 111, the pilot plant data confirmed the use of this ratio as desirable. Somewhat unexpectedly, the required excess of sulfur trioxide was the same, whether or not the air was recirculated. It is reasoned that only a relatively small percentage of the 5% excess sulfur trioxide used appears unreacted in the exit gas, and that it is substantially completely removed by reaction with the organic material deposited on the mist filters or transfer piping. MIST FILTRATIONFROM RECYCLED AIR. Efficient mist removal from the recycled air is essential for best product color (Table 11). Even if inferior product color were acceptable, troublesome mechanical fouling of the blower and vaporizer would eventually occur with inefficient mist removal. Medium glass wool was an effective filtering medium. Ceramic packings of various types and sizes proved unsatisfactory, as did a series of staggered baffle plates. As noted in Table 11, the effectiveness of filtration, as indicated by product color, increased as the number of packed towers was increased from one to three. As the towers were constructed of borosilicate glass. it was possible to follow visually the progressive accumulation of entrained organic matter. I t was concluded that to obtain good product color sufficient packing should be used that almost all the filtration occurred on the first two tow-ers, with the third remaining relatively clean. After each batch, the glass wool was either replaced or cleaned by flushing out the collected matter with water, followed by drying before reuse. As the packing tended to shred with each washing, it was never used for more than three batches. Care was taken to avoid too much filter capacity, because of the resulting excessive back pressure. A pressure drop of about 5 p.8.i.g. was taken across the three normally packed towers. [The remaining 2- to 3-pound pressure drop (of the 7 to 8 pounds available from the

SULFONATION W I T H SO3 Table IV. Back Pressure at Heat Exchanger Increases as Reaction Progresses Sulfonation ComBack pleted, Temp., Pressure, Typeof Run % C. P.S.I.G. A-1, without heel 0 16 4 (static) 50 73 83 92 97 100 0 55 82 92 100 0 45 56 75 90 97 100

49 47 51 56 56 55 21 62 50 47

5 9 12 14 17 20 4

Table V. Cooling Medium U Value" in Sulfonation of Dodecylbenzene Reaction Batch U Value, Batch U Value, Temp., Kettle Completed, Temp., Heat Exchangerb c. Jacket % O C. 10 28 20 25 40 15 50 57 9 75' 65 100 44 Water at 18' C., expressed as B.t.u./hr./sq. ft./AT(O F.).

$

a

a

34 40 59 60

62

46 36 29 19 10

Reactants inside tubes: cooling water in shell.

lished (70). The increasing viscosity of the reaction mixture as the sulfonation Table VI, Performance of Lauryl progresses was also reflected in the pilot Alcohol in Sulfation A-1, without plant by the increasing discharge pres-, heel 5 Free Oil, Klett Color, sure of the positive displacement pump 11 Lauryl Alcohol 100% Active 20% lictive 27 Basis Basis Brand No. delivering reaction mixture to the heat 43 42 exchanger ; this increase occurred despite 1 3.8 70 A-2, with heel 21 4 2 3.8 75-100' an increase in reaction temperature. This 43 5 3 4.3 55 is shown in Table I V for two batches 49 6 4 4.1 175 made by Procedure A-1 and terminated 48 8 5 Alcohol 2, color by visual estimate. 49 12 at different temperatures-the normal 50 14 55' C. and a lower level of 43' C. Pres53 16 sure drop across the exchanger is inHeat exchanger back pressure at 15 galcreased by a lower temperature. Also REQUIRED EXCESSSULFATING AGENT' lons per minute in sulfonation of dodecylbenzene. shown in Table I V is back pressure for a In the case of dodecylbenzene, the use o third run using Procedure A-2 with an a n excess of sulfur trioxide over that reacid heel; somewhat lower back presquired to complete sulfonation has no blower) was accounted for by the consures were obtained in this case, as would effect on free oil analysis of the product. stricted gas sparger tip, the static head in be expected from the lower viscosity. With lauryl alcohol, on the other hand, the sulfonation kettle, and the system The effective cooling surface of the such a n excess leads to high oils by prodpiping.] uct decomposition. I t is therefore esUSE O F EXTERNAL HEATEXCHANGER. kettle jacket was estimated a t 111/4 sq. feet, and that of the heat exchanger a t 50 sential not to exceed about 1.02 moles of Almost all dodecylbenzene sulfonations sq. feet. Heat loads during reaction sulfur trioxide per mole of alcohol-Le., were made with the heat exchanger in were then determined by measuring heat 41 pounds of sulfur trioxide per 100 operation, because of the marked saving gain and flow rate of the cooling water, pounds of alcohol of average molecular in batch time. In practice the heat exThe heat transfer rate, U [B.t.u./hr./sq. weight 200 (Table VII). changer served mainly to supplement ft./AT (" F.)], was then calculated (Table MISTFILTRATION OF RECYCLED AIR. cooling during the final, half of the sulfur O n the basis of limited observation, it V). The values for U drop sharply as trioxide addition, when the reaction mixreaction proceeds. I n commercial opwas concluded that, as with dodecylbenture became increasingly viscous, thus eration, higher values of U would be exzene, it is essential to filter the recycled air allowing addition of all the required sulpected, as the product would be passed thoroughly to ensure optimum product fur trioxide within 2 to 2.5 hours, a t a through the shell, leading also to less and to obviate equipment fouling in 55' C. maximum reaction temperature. pressure drop than in the present study, sulfating lauryl alcohol. The filtering In contrast, with vessel jacket cooling where the product was passed through arrangement found best for dodecylbenonly, 3.5 hours were required at the the tubes. zene also worked well for the alcohol. The higher batch temperature of 63" C. When Lauryl Alcohol. ALCOHOLQUALITY. only difference noted was that maximum a vaporization rate of approximately Four brands of lauryl alcohol were used mist entrainment with the alcohol oc0.75 pound per minute of sulfur trioxide in the pilot plant work; most of the curred during the initial part of the rewas reached near the end of the batch, work was carried out with two brands action, while with the hydrocarbon enthe full cooling capacity of both sulfona(1 and 2, Table VI). Although all trainment increased toward the end. tor and heat exchanger with 20' C. coolfour brands gave about the same values USE OF EXTERNAL HEATEXCHANGER. ing water was required to hold the reacfor free oil, there were differences in Lauryl sulfate differs from dodecylbention temperature a t or below 55" C. maxiproduct color, one being especially dark, zenesulfonic acid in two respects, which mum. While recirculation of the liquid There were no noticeable differences in have an important bearing on heat rereaction mixture through the heat explant operating characteristics, except moval: Lauryl sulfate is much less changer was maintained throughout the that one required a slightly higher neuviscous, and there is little change in entire run, cooling water to the exchanger tralization temperature to maintain the viscosity as sulfation proceeds; and it was used sparingly during the first half of aqueous slurry above the solidification solidifies a t a point not far below the rethe sulfur trioxide addition, with an inpoint. action temperature, crease in cooling as required during the last half. As the heat transfer rate per unit area decreased as the reaction proTable VII. Close Control of Reactant Ratio (2% Excess SOs) is Necessary for gressed and the viscosity increased correBest Results spondingly, the flow of cooling water -4lcohol 1 Alcohol 2 through the heat exchanger was steadily Molar ratio, SO3 to alcohol 1.00 1.02 1.04 0.96 1.00 1.04 increased to the maximum. Free oil, % of active 4.3 2.9 3.4 4.6 3.0 3.3 Viscosity data for dodecylbenzenesulNa~S04,% of active 2.3 2.6 3.8 1.5 2.1 4.2 fonic acid us. temperature have been pubVOL. 50, NO. 3

MARCH 1958

283

The moderate and relatively constant viscosity of lauryl sulfate means that the efficiency of heat exchange, and therefore the cooling requirements, are about

72). Several pilot plant runs were accordingly made on such a product, using air once through and cooling with jacket only.

Raw materials, Ib. Petroleum raffinate (Saybolt viscosity 200 at looo F.) Conditions Time, min. Temperature, O C. Start

Raw materials Ethylene oxide condensate, lb. SO3 used, Ib. SO3 absorbed, 1b.-mole

110 (0.27 Ib. mole) 23.5 (0.29 lb. mole, 10% excess) 0.26 to 0.28

70

7

SOa

50%

End Dilution

35 27 53 60 94% air and 6% SO8

Conditions Time, hours Temperature, Start

1.6 to 2.0

’ C.

20 to 26 (room temp.) 62 to 67 65 to 66 68 to 75 94% air and 6% SO3

50%

End Max. Dilution Product quality Free oil (basis 100% active), 70 Inorganic salts (basis 1 0 0 ~ oactive), % Klett color (20% aqueous s o h )

constant during the reaction. This is shown by the experimental values for L7 (Table VIII). It is interesting to contrast these figures with comparable data for dodecylbenzene in Table V. In Table I X are given data on the solidification points or partially sulfated lauryl alcohol. The temperature of solidification increases and then decreases as sulfation progresses. Cooling water temperatures substantially below those indicated resulted in objectionable coating of the cooling surface with solid. Tempered cooling water was therefore employed in the early stage of sulfation. Sulfation of Ethylene Oxide Condensate

The sulfated ethylene oxide condensates are important surfactants. Products based on the reaction product of nonylphenol with about 4 moles of ethylene oxide are of particular interest (77:

Table VIII. Cooling Medium U Value“ in Sulfation of Lauryl Alcohol Batch L‘ Value, Reaction Kettle Completed, Temp., Jacket O c. % 13 29 43 58 68 80

38 39 38 39 39 38

25 25 24 27 28 31

Water at 11’ C. ; expressed as B.t.u./hr./ sq. f t . / A T io F.). Table IX. Freezing Point of Reaction Mixture in Sulfation of Lauryl Alcohol Theoretical so3 Freezing Added, % Point, C. 0 (lauryl alcohol) 33 50

75

24 32 25 17

PO0

16

284

6.1 to 7.9 0.1 to 0.7 55 to 70

Examination of these data shows that this sulfation differs significantly from that of lauryl alcohol: 1. Absorption of applied sulfur trioxide is less efficient with the condensate, only about 90% of that applied having reacted. T o ensure actual absorption of one mole of sulfur trioxide per mole of organic compound it was necessary to apply 1.1 moles. 2. The reaction temperature (mainly 60’ to 70’ C.) is considerably higher for the condensate than for lauryl alcohol. This temperature range was found desirable in prior laboratory work to improve sulfur trioxide absorption and reduce foaming. Good product color showed that the condensate is much more stable than the alcohol. 3. Foaming was much more pronounced u i t h the condensate than with the alcohol, especially near the end of the sulfation, when the volume nearly doubled. As a result, the batch size indicated (110 pounds) is about the maximum allowable; batch size for the alcohol, on the other hand, was about 180 pounds. 4. Values of for the condensate decreased from 35 to 40 a t the middle of the run to about 15 a t the end. The value of U for lauryl alcohol remained constant throughout the sulfation (Table VIII). Factors 3 and 4 may be indicative of a viscosity increase as sulfation progressed, although this was not definitely established. Sulfonation of Petroleum Lubricant Raffinata Oil-soluble sulfonates obtained from lubricant fractions are used as ingredients for automotive lubricant additives. .4 laboratory study has shown that sulfur trioxide vapor is a practical reagent for this type of sulfonation ( 9 ) . One pilot plant batch was run on a material of this type, using air once through and cooling jacket only, with conditions as f0llOlVS :

INDUSTRIAL AND ENGINEERING CHEMISTRY

Absorption of sulfur trioxide was excellent, and no mechanical difficulty was experienced with stirring in spite of sludge separation. The sludge was water-dispersible and therefore easily washed from the reactor after removal of the acid product oil. The weight of oil charged could probably have been at least doubled without difficulty. I t is concluded that this general procedure is suitable for petroleum oil sulfonation, although the product from this particular run was not analyzed. Petroleum oils vary greatly in the consistency of sludge formed during sulfonation with sulfur trioxide ( 9 ) , and in some cases stirring is very difficult or even impossible. Acknowledgment

It is a pleasure to acknowledge the advice and assistance of Benjamin Veldhuis throughout this study, and of Sidney Hayes in designing and drawing the figures. References

(1) Allied Chemical and Dye Corp., General Chemical Division, Tech. Service Bull. SF-3 (1951). ( 2 ) Continental Oil Co., Petrochemical Dept., “Neolene 400, Intermediate for Synthetic Detergents,” 1955. (3) Flint, G., “Encyclopedia of Chemical Technology,” vol. 13, p. 501: New York, Interscience Encyclopedia, 1954. ( 4 ) Gerhart, K. R.., Popovac, D. O., J . Am. Oil Chemists’ SOC.31, 200 (1954). (5) Gilbert, E. E., Jones, E. P., IND. ENG.CHEM.45, 2047 (1953). ( 6 ) Zbid., p. 2049. (7) Gilbert, E. E., Moran, W. J,, Petry, J. K. (to Allied Chemical and Dye Corp.), U. S. Patent 2,723,990 (Nov. 15, 1953). (8) Gilbert, E. E., Veldhuis, B., IND. EKG.CHEX.,47, 2300 (1955). ( 9 ) Ibid., 49, 31 (1957). (10) Gilbert, E. E.,Veldhuis, B., Carlson, E. J., Giolito, S . L., Zbid., 45, 2065 (1953). (11) Jefferson Chemical Co., “Surfonic Nonyl Phenol-Ethylene Oxide Xdducts,” 1955. (12) Knowles, C. M., Ayo, J. J. (to General Aniline and Film Corp.), u. s. Patent 2,758,977 (-4ug. 14, 1956). RVCEIVED for review May 9, 1957 ACCEPTED July 30, 1957 Industrial and Engineering Group, Sixth Annual Meeting-in-Miniature, New Jersey Section, ACS, Newark, N. J., January 25, 1954 (in part).