-Synthetic
Detergents-
Sulfonation of Detergent Alkylates J. E. KIRCHER, E. L. MILLER, AND P. E. GEISER Continental Oil Co., Houston, Tex. r .
1 his description of commercial detergent alkylates includes physical properties such as molecular weight, boiling range, and color and their effects on sulfonation and the finished sulfonate. The discussion of the sulfonation procedure gives the strengths of acids used in the sulfonation reaction (from 98% sulfuric acid to sulfur trioxide); physical data for sulfonation with 20% oleum and with 100% sulfuric acid; and heat transfer data, viscosities, and specific gravities of sulfonic acids. Variables are weight ratios of acid to alkylate, temperatiires adhered to during sulfonation, and aging times and temperatures of the sulfonation mass. Spent acid separation variables include settling time and temperature and dilution of the reaction mass.
S
IXCE World War I1 there has occurred a phenomenal growth of synthetic detergents. Starting from a substantial industrial usage, the skyrocketing syndet industry has drawn its impetus chiefly from the wide acceptance for household uses (1!2-25,17) Alkyl aryl sulfonates, higher alcohol sulfates, and nonionics cqnstitute essentially 100% of the surfactants (active agents) used in the various syndet formulations. Though the volume distribution of the active agents used in the total production of syndets is not accurately known, it is believed that the sulfonates of detergent alkylates (alkyl aryl sulfonates) account for approximately 50% of the total. The purpose of this paper is to review the important factors involved in the sulfonation of detergent alkylates to produce surfactants for water systems. A considerable volume of oilsoluble sulfonates are now being used in lubricating oil detergent additives, rust inhibitors, emulsifying agents, etc. The early source of such products was petroleum mahogany soaps. Of recent years synthetic, oil-soluble sulfonates have been developed and are produced by the sulfonation of high molecular weight alkyl aryl hydrocarbons. In general, the same principles of sulfonation apply as for the detergent alkylates for water-soluble systems. The detergent alkylate, dodecylbenzene, derived from the alkylation of benzene with propylene tetramer, is specifically referred to in this presentation. Its preparation has been described by Sharrah and Feighner ( 1 1 ) . Sulfonation of aromatic hydrocarbons borders on the classical and has for years been a well-known, standard chemical reaction. The extensive use of alkyl aryl sulfonates in the highly competitive household field has resulted in the intensive study and refinement of the sulfonation process to meet the exacting qualitj requirements ( 7 , 16). The purpose of sulfonation is to achieve a product of proper balance of water-solubility necessary for the desired surface activity in water systems. This is accomplished by combining the water-soluble (hydrophilic) sulfonic acid group with the waterinsoluble (hydrophobic) detergent alkylate. I n the simplest terms, this is done by vigorously agitating a two-phase mixture of detergent alkylate and a molar excess of strong sulfuric acid. The excess sulfuric acid is necessary to gain essentially 100% sulfonation of the hydrocarbon. The temperature of the exothermic reaction is carefully controlled to prevent discoloration and formation of odor-producing bodies that result from scorching and other side reactions. The sulfonation reaction mixture can be processed in several ways to yield different forms of products. Such products are usually based on the sodium salt of the sul-
September 1954
fonic acid, but the ammonium and alkanolamine salts are also becoming popular. Sulfonates of detergent alkylates are processed for use as active agents in four main types of products that are used both for household and industrial applications:
1. Dry light-duty detergents and wetting agents containing 15 to 407, active agent with the balance almost entirely sodium sulfate 2. Dry heavy-duty detergents having 15 to 30% active agent compounded with various alkaline builders such as phosphates, silicates, and carbonates 3. Liquids of various concentrations of active agent that range from 15 to 60% 4. Dry flakes having approximately 85% active agent and 15% sodium sulfate
TABLE I.
QUALITY
REQUIREMENTS TOR DETERGEST AI~KYLATE SULFOXATES
Property Standard Color Paper white without bleaching Odor Minimum; must not develop with age Unsulfonated Must not exceed 2% and may be a s low as 1% based on hydrocarbon active agent; for extracted products this may be reduced t o 0.5% based on active agent Performance Must equal standards for foam, wetting, detergency. solubility and compatibility with builders Drying Formulated slurries of high solids content must be fluid and pumpable and should spray- and drum-dry t o free flowing solids Packaging Free-flowing, nontacky, minimum dusting in packaging operation, and noncaking in the package under humid conditions
QUALITY REQUIREiMENTS FOR FINISHED PRODUCTS
Recent improvements in quality of detergent alkylates and sulfonation techniques have resulted in an exacting quality standard for household and industrial products alike. Although the requirements of each type of product vary and each application presents special problems, it is possible to generalize to some extent. Some of the more important properties relating to the quality of detergent alkylate sulfonates are given in Table I. SULFONATION PROCESS
Figure 1 illustrates the usual sequence in the sulfonation prooedure to make the most common forms of sulfonate products. The sulfonation process can be carried out batchwise or continuously employing sulfuric acid ranging in strength from 98.0
INDUSTRIAL AND ENGINEERING CHEMISTRY
1925
to 104.57; (oleum). Recently considerable success has been
-7
i
I
I
achieved with the use of stabilized sulfur trioxide which is now commercially available. For this presentation, batch sulfonation is used t o illusisratethe variables of the sulfonation process. The adaptation of continuous processing to the sulfonation of detergent alkylates has, hoTvever, become so important that continuous sulfonation is discussed later. T o obtain a product of acceptable quality as preyiouslg defined, the folloiying important variables of sulfonat'ion must be carefully controlled. The optiniuni balance of variah1c.s must be determined for each plant design. 1. Strength of sulfonating agent 2. Ratio of sulfonating agent to detergent alkylate 3. Sulfonation temperature 4. Technique and time of addition oi sulfonating agent 5 . Degree of agitation 6. Temperature and t,imc of aging the sulfonation rcaction mass 7. Technique of neutralization of the sulfonic acid
1
S E T T L E 0 SEPARATE SCTTOM EXCESS AC,IU LAYER CPPROX 7 5 * % CONC.
NEUTRALIZE D I S C A R D EXCESS C C l D LAYER
\;
100 TEMPERATURE,
Figure 2.
FORMULATE INTO L I O U I D S OF VARIOUS COhCENTROTlONS
-
L I G H T DUTY DETTERGENT I 5 4 0 % ACTIVE 8 5 - 6 0 % NA,SO,
UPPER A R S O j H *
SULFONIC
1 i
A C I D OF
DETERGENT
HEAVY DUTY DETERGENTS I5%-3O%ACTIVE
1
i 8 5 % ACTIVE 15% N A 2 W q
I
I
1
85%-10 %BUILDERS
io1
iA1
iC!
*
L I G H T UUTY DETERGENTS I S - 4 0 % ACTIVE 85-60% NA,50,
150
when t,he viscosity is the greatest. 'The Reynolds number j~ calculated froin the formula X L 2 p / p (Q),where X is the speed of the turbine in revolutions per second, L is t'he impeller diameter in fcet, p is the fluid density in pounds per cubic feet, and p is the viscosity in pounds per foot second. The effect of temperature on the viscosity of the original suifonat,ion niixt>ureand on the viscosity of the sulfonic acid a,fter removal of excess sulfuric acid is given in Figure 2. The Teight ratio of 20%# oleum to hydrocarbon used in these laborat,ory sulfonations was 1.25 : 1. The maximum temperature during the acid addition and the I-hour aging period Fas 77" F. 2 . Cold brine (32" to 35" F.) is circulated through the cooling coil to cool the hydrocarbon to 50" F. Cooling may be achieved by circulating the hydrocarbon through an ext,ernal heat exchanger of proper capacity.
SLURRY-APPROX. 53% SOLIDS 8 5 % A C T I V E I B A S E D ON S O L I D S 1
1 1
--_J
140
I PO
OF
1-iscosities of Sulfonation 3Iass and Sulfonic
I
~
-
I
60
ALUYLATE
Figure 1. Flow Diagram for Production of JIajor Forms of Sulfonated Detergent Alkylate
Though not commonly considered a variable, the purity of the sulfonation agent, whether sulfuric acid, oleum, or sulfur trioxide and the caustic or other base used in the neutralization, is of critical importance. I n particu!ar, iron contamination affects the color of the sulfonate. For a given design of equipment, a preferred sulEonation procedure using 20% oleum (104.5% sulfuric acid) is carried out with a 1.25 weight ratio (3.2 mole ratio) of oleum to hydrocarbon a t 77" F. Batch Operation. The following procedure describes a typical pilot plant batch sulfonation: 1. Charge 60 pounds of dodecyibenzene to a 30-gallon glasslined, or 316 stainless steel, sulfonation vessel. The sulfonator should be jacketed and equipped with an internal cooling coil or external pipe heat exchanger (316 stainless) having approximately 1 square foot of cooling surface per 8 gallons of sulfonation capacity. The sulfonator should be equipped with a turbine agitator, one third to one half the diameter of the vessel, with a peripheral speed of 660 to 700 feet per minute. An agitator of this diameter and peripheral speed will give a Reynolds number of approximately 24,000 a t the end of the sulfonation period
1926
40/ ?:
8 0 9 : 00 I O '0 i E M C i R i T L D E 3UR NG A G O A3DITl0N Ah9 A G I N G
Figure 3.
I20 PER 035
: ,1
4G
*f
Effect of Sulfonation Temperature on Color of Sulfonate
3. With refrigeration appiied to the sulfonator and using maximum agit'ation, pump 75 pounds of 20%) oleum to the SUIfonator at a rate that will maintain an approximate maximum temperature of 77" F. The heat evolved for this process is approximately 175 B.t.u. per pound of hydrocarbon. 4. Following the acid addition, agitation of the sulfonatiou mass is continued for 2 hours at 77" F. without cooling. For different size sulfonators, this aging period will of necessity be varied. I n a laboratory sulfonation (where more intimate mixing is obtained) 1 hour is usually equivalent to approximately 2 hours in larger equipment. If acids of leseer strength are employed in the sulfonation reaction, the temperat'uree and/or acid ratios are of necessity higher to achieve products of equal color and unsulfonated hydrocarbon content (3).
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 46, No. 9
-Synthetic The control of temperature during sulfonation is extremely important in obtaining products of acceptable white color. The effect of temperature on color is illustrated by sulfonations using 101.5 and 100.5% sulfuric acid, Figure 3. The weight ratios of acid to hydrocarbon were 1.25: 1.00 and 1.50:1.00, respectively, for 104.5 and 100.5% sulfuric acid. The aging time for these laboratory sulfonations was 1 hour. Color measurements were made with an 8.8% aqueous solution (based on sulfonate content), in a Klett-Summerson photoelectric colorimeter, test tube model, using a No. 42 blue filter standardized against water. The purpose of aging the sulfonation mass is to reduce the unsulfonated hydrocarbon to the lowest possible content without prohibitively darkening the product because of prolonged contact with the spent sulfuric acid. The data in Figure 4 are in-
i
I
Detergents-
mately 85% active agent based on solids. Where spent acid disposal is a problem and lower active products are desired, the entire sulfonation mass may be neutralized by addition to the neutralizing medium, usually caustic soda. Keutralization of the entire sulfonation mass will produce a final slurry of about 50% activity based on solids. If, however, the excess sulfuric
I I
/
I
,
A
50
60
70 SULFURIC ACID CONCENTRATION WEIGHT PERCENT, IN SPENT ACID
BO
4)
Figure 6. Effect of Spent Acid Concentration on Composition of Sulfonic Acid Phase
AGING
Figure 4.
TEMPERATURE,
'F,
Effect of Aging Temperature on Residual Unsulfonated Oil
dicative of the effect of aging temperature on unsulfonated hydrocarbon content. These laboratory sulfonations utilized 100.5% sulfuric acid. The weight ratio of acid to hydrocarbon was 1.5: 1.00, the maximum temperature during acid addition was 104" F., and the aging time was 1 hour. Aging time is also important in reducing unsulfonated hydrocarbon content and must be determined for each type of sulfonation agent, temperature, and equipment design. The effect of aging time a t 77' F., on unsulfonated hydrocarbon, is shown in Figure 5. The weight ratio of 104.5% sulfuric acid to hydrocarbon used in this pilot plant sulfonation was 1.25: 1.00. After a sufficient aging time to achieve a maximum degree of sulfonation, the batch of sulfonic acid is then ready for further processing to the neutralized active agent. Either of two paths may be followed a t this point. Generally, the sulfonation mass is relieved of excess sulfuric acid prior to neutralization so as to obtain a neutralized slurry having approxi-
Figure 5.
September 1954
Effect of .4ging Time on Percentage of Residual Unsulfonated Oil
acid is removed from the sulfonation mass by "watering out". a product of 85 to 87% activity (based on solids) is obtained' The ratio of active agent to solids is necessarily dependent on the quantity of sulfuric acid that remains in the sulfonic acid. Watering out excess sulfuric acid is a standard method of diluting excess acid with water to obtain a satisfactory split between the sulfuric and sulfonic acid layers. By experience, it has been found that finished sulfonates of good color and lowest sulfate
HQSOP,
Acid, Lb.
Hydrocarbon, Lb.
HzSO4 after Completion of Sulfonation, %
104.5 104.5 100.;
1.05
1
1.40
1
96.5 98.2 93.5
100.5
1.50 1.66
1
Initial
7G
98
1.25
1
1
94.0 92.2
Lb. HzO t o D1lute HzsOa to -
78% 0.176
73% 0.236 0.324 0.304
63%
0.392 0,244 0.524 0.216 0.524 0 . 2 4 4 0.341 0.588 0.244 0.352 0 . 6 2 0
content (which is dependent on sulfuric acid inclusion) are obtained by diluting the excess acid to a strength of approximately 76 to 78% (Figure 6). A spent acid of this concentration can be shipped in ordinary steel tank cars. Experience has shown that times required for settling of the diluted spent acid may vary from 1 hour a t a 637, spent sulfuric acid concentration, to 4 to 6 hours when diluting to 76 to 78% Btrength. In plant scaleequipment, this 4- to6-hour settlingperiod must be increased to about 8 hours for satisfactory separation. Settling time is also somewhat dependent on the shape of the settling tank Different weight ratios of water required to dilute excess acid to different strengths are shown in Table I1 ( 3 ) . The separation of the two-phase acid system is normally done batchwise in a lead-lined, coned-bottom settling tank a t 122' to 130" F. The technique of water addition is critical and must be carefully controlled to obtain a sulfonate of satisfactory color. The method of water addition must ensure a maximum of dispersion and heat dissipation. Figure 7 illustrates the effects of the various spent acid dilutions on the colors of the sulfonates for the three sets of conditions given in Table 111. The maximum temperature of the sulfonation mass m-as 140' F. during dilution.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1927
Extended standing in the acid state also darkens the color of the finished sulfonate, but this effect is not shown in Figure 7 . The spent acid dilution is normally carried out by addition of rrater. I t is, holyever, possible to add the required amount of viater as crushed ice t,o the sulfonation mass without agitation, followed by agitation for approximately 10 minutes t,o complet? the dilution. The heat of fusion of the ice is sufficient, to hold the temperature of the batch to 140' F. This shortens the dilution time for approximately 1 hour to 10 minutes and a t the same
€0
65 U3NCENTRPTION
I
I
70
75
OF SPENT AGIO (PERCENT
80
Hrq1
Figure 7 . Effect of Spent kcid Concentration o n Color of Sulfonates
time eliminates most' of the external cooling required Tvhen dilution is made with water. To produce an 85 to 87% active slurry (solids basis) from the watered-out sulfonic acid, the following procedure is recommended: 1. A stainless steel neutralizer is charged n-ith approximately 94 pounds of 2 0 5 sodium hydroxide. The neutralizer should he approximately two and one half t,imes the capacity of the sulfonator and should be equipped with a heavy-dut,y agitator and an internal cooling coil. Before the neut,ralization is started, the caustic solution should first be cooled to 68" F. 2. The sulfonic acid should be fed t o the neut'ralizer a t a rate that will maint,ain a temperature of 122-130" F.
scribed illustrates t'he essential leaction conditions arid techi1iquc.s of the sulfonation process. Sull'onation has been adapted t o continuous operation. To do this, it is necessary to fir$t, intimately mix hydrocarbon and sulfuric acid. Once mixing has I I W J ~ achieved, sulfonation is alniost inst,antaneous. This iniimaie contact can be achieved h y use of well-lcnon-n devices such as colloid mills, centrifugal pump^, and other mechanical contactom, or even continuous operation of batch facilities. Following mixing, immediate heat dissipation is essential. This may l i c effected by an efficient heat exchanger. This step is followed 113' passing the sulfonation mixture continuously into an aging vessel where the reaction is completed. The effluent from the aging vessel is then diluted by thoroughly mixing Tvith J ~ Z I C I ' which is metered into the effluent. This mixture is passed into a heat exchanger to dissipate the heat of dilution. Separation of the diluted excess acid and sulfonic acid niay be done coiltinuously in a horizontal settling tank. The sulfonation maPs enters one end of the tank and the sulfonic acid layer discharges from the top a t the othcr end, with t>hesulEuric acid layer discharging from the bottom of the t,ank. Separation can alp0 i)c made by centrifugation. Seutralization of the sulfonic acid can also be carried ou1 rontinuously by metering the sulfonic acid and cauetic int>oa11 efficient mixture or contractor. This neutralization mixtui should be passed into a heat exchanger to dissipate the heat ( 1 neutralization. USE OF STABILIZED SULFUR TRIOXIDE
The use of stabilized sulfur trioxide for sulfonation of dotergent alkylates is a relatively new process compared to sulfuric: acid sulfonation. At, present, it,s use as a sulfonating agent i q confined to only a few companies, but interest in this process in rapidly increasing.
I t is essential that the sulfonic acid always be added t'o the caustic and not vice versa, or serious heat transfer difficulties may arise because of the extremely high film coefficients in t'he
TABLE111. EFFECTO F Wt. Ratio Acid: Hydrocarbon 104,5 1 . 2 5 : 1.oo 100,5 1 , 5 0 :1 .oo 98.0 1 .BG: 1.OO a Lehoratory equipment HzSOd,
70
SPEKT A C I D
GULFOSATE
DILUTIOK OX
M a x . Temp. during .Icid Addition, F.
77 104 122
COLOR O F
- 4 r i n ~ 2 . ~ Temp.,
Time.
77 122
1 1 1
' F. 131
hours
IO0
-f,
I
90
I10
IN2
150
I 170
TEMP 9.
viscous sulfonic acid. Should the neutralization temperature exceed 130" F., gels are sometimes formed and are difficult to handle. A 40% active product having 60% sodium sulfate niay be produced by neutralizing the ent'ire sulfonst,ion mixture with caustic soda, 1%-ithappropriate additions of sodium sulfate t o reach the desired activity. It, is, however, economically nioi'e advisable to prepare a 40yo active product from a high active slurry by addit,ion of sodium sulfate. If spent acid disposal is not. economically pract,ical, then such a product, may be produced by thc alternate method previously mentioned. The high active slurry or the 40% active product produced by sulfonation wit,h 20% oleum can be produced by alternate methods using lower strength acids. Such alternative processes require the appropria,te modification of variables and techniques as indicated previously. Continuous Operation. The batch sulfonation technique as de-
1928
Figure 8. '(-iscositg-Temperature Relationship for Sulfonation IIixture
One of the major problem encountered in sulfonation of detergent, alkylate with sulfur trioxide is a satisfactory method of iiitroducing the sulloriatiiig agent into the hydrocart,on. Tho heat, of reaction of anhydrous sulfur trioxide with dodecylbenzenc is much higher than that of oleum--306 13.t.u. (6) per pound of dodecylhenzene a? compared n-ith about 175 I3.t.u. per pound. This abnormally high heat of react>iorireciuir t o prevent charring. Several methods h a w been rited for illtroducing sulfur trioxide into the hydrocarbon. The use of sulfu? dioxide as a sulfonation solvent has given satisfactorj- results ( 2 , I O ) . One other method of sulfur trioxide introduction ip to dilute the sulfur trioxide vapor with air or nitrogen arid to pa": this diluted vapor into the hydrocarbon ( I , 4--6, 8). The most
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 46,No. 9
-Synthetic direct method for introducing sulfur trioxide into the hydrocarbon is its addition as a liquid. This, however, has shown no promise ( 6 ) . Even with extreme cooling and excellent agitation, the neutralized slurries are very dark in color and contain excessive amounts of free oil. The use of a diluent air stream for sulfur trioxide sulfonation has probably been more extensively investigated than other methods and is therefore described in greater detail. As previously noted, the problem of heat removal is serious in sulfonating with sulfur trioxide. It should be pointed out that, although dodecylbenzene has a relatively low viscosity (14 cp. a t 68" F.) and is quite easily agitated, the sulfonic acid is relatively viscous (5000 cp. a t 95' F,). This renders agitation more difficult and, therefore, heat removal much less efficient because of the high film coefficients of the sulfonic acid. Figure 8, taken from the literature (5,6), presents the viscositytemperature relationship of the reaction mass following addition of the sulfonation agent. Curve I illustrates the sulfonic acid prepared by use of sulfur trioxide. Viscosities were measured vith a Brookfield viscometer (spindle No. 3, 12 to 60 r.p.m,). Curve I1 applies to the sulfonation mixture obtained by sulfonation with 104.5y0 sulfuric acid. The viscosities of oleum sulionation mixtures a t 77' F. are much lower (500 cp.) (5) than are the viscosities of sulfonic acids obtained by sulfur trioxide sulfonation. I t is, however, possible to operate the sulfur trioxide process a t higher temperatures-122' to 140" F. Viscosities of these sulfonic acids a t 131' to 140' F. are approximately the same (550 to 800 cp.) (6) as oleum sulfonation mixtures at 77" F. A t these viscosities, relatively good agitation is possible, thus giving satisfactory heat removal from the sulfonation mass. A laboratory sulfonation apparatus is shown in Figure 9. A sulfonation using sulfur trioxide can be carried out as follows:
Detergents-
After the apparatus mas asscmbled as described, a slow stream of air was started through the system to prevent any hydrocarbon from entering the air inlet tube and thus having prolonged contact with the sulfur trioxide. The stirrer motor was started, the alkylate was poured into the reaction flask, and the flow of air was increased to 14 liters per minute. The sulfur trioxide was warmed to 95' to 104" F., and the air stream was directed through the sulfur trioxide vaporizer. The reaction temperature wasallowed to rise from 122' to 140' F. and was maintained at this temperature throughout the reaction period of 1 to 11/* hours. The sulfonic acid obtained was a clear reddish-brown oil. The sulfonic acid was neutralized by addition to 14% caustic a t a temperature not exceeding 122' F. The finished sulfonate was nearly white in color. A typical analysis of such a product ie: Per Cent Active 'Water Salt Oil Color
54 42
1 .g 1.8 55-60
If the neutralization of' the sulfonic acid immediately follows the completion of the sulfonation process, the product is much lighter in color than when several hours elapse between sulfonation and neutralization. In addition to the problem of heat transfer in the sulfur trioxide sulfonation proccss, there has also been noted a slow pH drift following neutralization, This pH drift is usually appreciable and will cause the slurry to become acidic even if an excess of caustic is used in the neutralization. Accompanying the pH drift or reversion, as it is sometimes called, there has also been a decrease in the free oil content of the slurry. These two phenomena are believed to be due to the slow breakdolm of anhyA reaction train was assembled in the folloaing order: An air drides of the sulfonic acids in the neutralized slurry, although this source (air or nitrogen), a silica gel drying chamber, a flowmeter, has not been proved conclusively. a sulfur trioxide vaporizer, safety flask, and sulfonation flask. The sulfonation flask used was approximately 75 mm. in diameter These anhydrides would no doubt analyze as frep oil inimeand was fitted with a perforated concentric inlet tube located apdiately after neutralization and, on standing, would hydrolyze proximately 40 mm. from the bottom of the flask. Total flask to give the pH drift accompanied by a decrease in free-oil content. depth was approximately 250 mm. The flask was equipped with In the formation of these anhydrides, 1 mole of water is probably a removable top which could be fitted with a stirrer, a thermometer, and an outlet tube. The stirring motor was a Sunbeam produced. This water reacts with sulfur trioxide giving rise to Pvlixmaster operated a t 700 r.p.m. sodium sulfate in the neutralized slurry. In view of this, the Raw materials were dodecylbenzene (250 grams) (1.05 moles, sodium sulfate in the slurry should be proportional to the anbasis mol. wt., 237), liquid sulfur trioxide (89 grams, 1.11 moles), hydride content and therefore to the acid drift to be anticipated. and dry air, 14 liters per minute. To some extent, this has been found to be true. Indications have been obtained that rapid addition of sulfur trioxide during sulfonation and/ or high temperature neutralization may moderate or completely overcome this reversion problem. The other technique used to SUIfonate detergent alkylate with sulfur trioxide is to use sulfur dioxide as a solvent (a, I O ) . The use of sulfur dioxide as the sulfonating solvent should tend to reduce oxidation, disulfonation, and other side reactions which could easily occur in the presence of a reagent such as liquid sulfur trioxide. This sulfur dioxidesulfur trioxide sulfonation process utilizes the evaporation of sulfur dioxide (b.p. 18°F.) as a means of heat removal. Neutralization is effected in the usual manner by addition of the sulfonic acid to the desired strength of caustic solution. Bleaching Process. Should the sulfoFigure 9. Laboratory Apparatus for Sulfonation with nation and neutralization procedures Sulfur Trioxide September 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
1929
previously described give a slurry that, is not of acceptable quality co!orwise, it is possible to improve the color of the dekrgent slurry by t’he applicat’ion of a bleach. Laboratory work ( 3 ) has shown that chlorine gas can be satisfactorily used as a bleach. However, this process is considerably more difficult and much more corrosive to stainless steel than is the standard hypochlorite met8hod. A recommended bleaching procedure using sodium hppochlorite is as follows: The pH of a high active slurry (50 to 55% water) is adjusted to approximately 6 or 7 by addition of a highly concentrated dodec?-lbenzenesulfonic acid. A solution of sodium hypochlorite containing approximat,e!y 15% XaOCl is slo~vlyadded, and the slurry is well agitated. Agitation of the mixture is continued for approximately 15 minutes at, a temperature of 122” t o 130” F. A nearly “paper mhit’e” slurry should be obt’ained from t’his bleaching procedure, and it should have a final pH in the range 5 to 8.5. I n this bleaching process, the amount of 100% NaOCl usually equivalent to 2 to 4 pounds of hypochlorite per 100 pounds of sulfonate. The amount of bleach used, however, will depend on process conditions and the condition (color) of the sulfonate prior to bleaching. SUMWARY
The most commonly used and most thoroughly investigated method of sulfonating detergent alkylates is the process employing various concent’rations of sulfuric acids-Le., 104.5, 100.5, and 98yc sulfuric acid. Process variables are numerous and have significant effects on t,he finished sulfonates. Probably the most widely used sulfonation process is that using 20% oleum. This process gives sulfonates of good quality, cooling requirements are not excessive, and the excess acid, if properly diluted, can he shipped in tank cars.
h number of studies made on sulfonation of detergent alkylate with sulfur trioxide indicate it to be a feasible process. ACRNOWLEDGMERT
The authors wish to acknowledge the assistance of E. L. Hatlelid, J. C. Kirk, and 51.L. Sharrah in obtaining some of the data and in editing this paper. LITERATURE CITED
(1) Birch,
S. F., and associates (to Anglo-Iranian Oil Co.). Brit.
Patent 680,613 (Oct. 8, 1952). ( 2 ) Brandt, R. L. (to Colgate-Palmolive-Peet C o . ) , U.
S. Patent 2,244,512 (June 3. 1941). (3) Continental Oil Co., Houston, Tex., “Xeolene 400, Intermediate for Synthetic Detergents.” (4) Furness, R.. and Scott, A. D. (to Lever Brothers and Ijnilever, Ltd.), S.African Patent 9307 (June 19, 1950). ( 5 ) Gerhart, K. R.. and Popovac, D. O., J . Am. Oi2 Chemists’ Soe., 31, 200-3 (1954). ( 6 ) Gilbert, E. E., and associates, ISD. Esc,. CHIXI., 45, 2065-72 (1953). (7) Hoyt, L. F., U. S.Dept. of Commerce, O T 3 Report, PB 3868, Hobart Publishing Co., Washington, D. C. (8) Lemmon, N. E. (to Standard Oil Co. of Indiana), 5. S.Patent 2,448,184 (Aug. 31, 1948). (9) Mack, D. E., Chem. Eng., 58, No. 3, 9, 109-10 (1951). (10) Oronite Chemical Co., Alkane Tech. Bull., p. 9, 1950. (11) Sharrah, BI. L., and Feighner. G. C., IXD,EXG.CHEM.,46, 24854 (1954). (12) Snell, F. D., Chem. Eng. A-ews, 29, 3G-7 (1951). (13) I h i d . , 30, 30-1 (1952). (14) Ihid., 31, 38-40 (1953). (15) Ihid., 32, 36-7 (1954). (16) Snell, F. D., Allen, L. H., Sandler, R. A , , Third World Petroleum Congress Proc., 1951, See. V, pp. 109-18. (17) Snell, F. D., and Kimball, C. S.,Soap Sanii. Chemicals, 27, 27-9 (1951). RECEIVED for review March 2 5 , 1951.
ACCEPTEDJuly 10, 1954.
Nonionic Detergents Central Research Laboratory, General Aniline & F i l m Corp., Easton, Pa.
T h e increased consumption of nonionic surfactants is due to their use in detergent formulations. The nonionics most used in detergent €orrnulations are the ethylene oxide products of alkylphenols, the ethylene oxide products of tall oil, and the alkanolamide derivatives of fatty acids. Although unbuilt polyoxyethylated detergents are superior in cotton detergency and redeposition prevention to unbuilt anionics, the latter can be built to give detergent formulations equal i n effectiveness to the built nonionics. The built nonionic detergents are obtaining an increasingly large proportion of household laundry market, because low foaming detergents are needed in automatic rotary-drum wrashing machines. Industrial detergent uses of the nonionics include antistatic action, raw wool scouring in textile operations, germicidal cleaning in restaurants, removing wTater-soluble soils i n dry cleaning operations, metal cleaning, and washing of floors and walls. Desirable improvements of nonionics include the development of a nonionic detergent formulation of higher foam stability, and the development of a solid nonionic possessing more efficient surface active properties.
T
H E nonionic surfactants, as a class, have been relative newcomers to the American scene. Those which are used as detergents were first manufactured on a large scale basis in the early 1940’s in this country. The use of nonionics has grown considerably in the past decade, and the production of all typcs of
1930
nonionic surfactants is now estimated to he around 90,000,000 pounds per year. Since nonionics are extremely versatile surfactants, they are used for many different purposes such as detergency, wetting, emulsification, and lime soap dispersion, but the major fraction of the nonionic production goes into detergent
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 46,No. 9
