PROCESS FOR PREPARING AND ISOLATING SULFONATED INTERNA OLEFINS Cross-reference to Related Patents This applications is related to U. S. Patent No. entitled Procoss for Olefins,issuedJanuary30,1996.SulfonatingInternal Background of the Invention Field of the Invention The present invention relates to aprocess forproducingsulfonated intemal olefins and, more particularly, to a process for isolating the intcrnal olefin sulfonates from the reaction mixture.

Description of the Prior Art Internal olefin sulfonates have utility as anionic surfactants that are widely used.

Procedures for the sul fonation of internal olefins are wel I known and documented in the prior art. Procedures for sulfonating internal olefins are disclosed, for example, in the following references: European Patent Application No. 0446971 A 1; Cavali, et al., Comun. Jonn. Com. Esp. Deterg., 23,1992, pp. 205-218; and Roberts, et al., Coi un.

Jorn. Com. Esp. Deterg., 22,1991, pp. 21-35. European Patent Application No. 0446971 discloses that internal olefins having from 8 to 26 carbon atoms can be sulfonated in a falling fiim rcactor with a sul fonating agent in a mol ratio of sulfonating agent to intenual olefin of 1: 1 to 1.25: 1 while cooling the reactor with a cooling means having a temperature not exceeding 35 °C and then neutralizing and hydrolyzing the reaction product from the sulfonating step. The sulfonation of the internal olefins is preferably carried out with sulfur trioxidc. The cooling means is preferably water having a temperature not exceeding 35 °C, more preferably in the range of from about 0 to'5 °C. Thc sulfonation may bccarricci out batchwisc, semi-continuuusly. or continuousiy. The reaction is preferably performed in the falling film reactor, which is cooled by flowing the cooling water at the outside wall of the reactor. At the inner walls of the reactor, the internal olefin flows in a downward direction, as does S03. S03 is diluted with nitrogen, air, or any other gas, inert under the reaction conditions.

The Cavalli et al. reference teaches that internal olefins can be sulfonated by reacting the olefin and SO3, aging, neutralizing the product with sodium hydroxide, and then hydrolyzing. Specifically, the Cavalli reference discloses that sulfonation can occur SO3/olefinmolratioof1.025,anSO3/air,2.5%,anolefinflowrateof1 4.5kh/g,withan and a cooling jacket temperature of 8-10°C. As per the Cavalli reference, neutralization can be conducted 28%sodiumhydroxideflowrateof70kg/h,atemperatureofa 30°C, and an average residence time of 30 min. Hydrolysis can be conducted at a temperature of 160°C and an average residence time of 40 minutes.

Roberts et al. disclose that internal olefins can be sulfonated in a tubular reactor using SO3 diluted so as to have a concentration of 2.5% in air, the reactor being cooled to between 10 Inthesulfonationprocedure,theolefinflowrateis16.45kh/g,32°C . and the S03/olcfin mol ratio is 1. 05. Onc of the ctcar advantages of the process of the present invention is that conventional batch-type reactors, requiring no special design, can be employed in sulfonating the internal olefins. Prior art workers employing neat internal olefins have generally had to employ falling film reactors or, in any event, specially designed reactors in order to obtain a product of good quality and in high yields.

Problems as to specially designed reactors are obviated by the process of the present invention.

Recently, internal olefins have been sulfonated under conditions to produce products that arc rich in hydroxyalkane suifonates with low levels of residual sultones, inorganic sulfates, and free oil. In an article by J. Stapersma, H. H. Deuling, and R. Van Ginkel entitled"Hydroxy Alkane Sulfonate (HAS), a New Surfactant Based on Olefins," JAOCS, Vol. G9, No. 1, January 1992, pp. 39-43, there is described the production of hydroxyalkane sulfonates from internal olefins using a falling film glass reactor under mild conditions. Using this technique, it is possible to obtain a product that is rich in hydroxyallcane sulfonates.

In U. S. Patent No. 5,488,148, incorporated herein by reference for all purposes, there is disclosed a process for sulfonating internal olefins wherein internal olefins present in an amount of from about 5 to about 40% by weight in a substantially inert hydrocarbon solvent are sulfonated under well-known sulfonation conditions to produce intermediate sulfonated compounds that are then neutralized and hydrolyzed to form a product mixture containing HAS and alkene sulfonates, the product mixture being

recovered. The process disclosed in U. S. Patent No. 5,48S. 14S also tcaches that the desired, internal olefin sulfonates are extracted into an aqueous phase using, m alcohol such as isopropanol, the aqueous phase subsequently being backwashed with an inert hydrocarbon such as hexane to remove any remaining paraffin. Since the isopropanol and some residual hexane remain in the aqueous phase, it is necessary to recover the internal olefin sulfonates by volatilizing the water, the alcool, and the hexane.

Summary of the Invention It is therefore an object of the present invention to provide a process for producing and recovering sulfonated internal olefins.

Another object of the present invention is to provide a process for isolating sulfonated internal olcfins obtained either from neat olefin sulfonation or sulfonation of internal olefins in a hydrocarbon solvent.

Yet a further object of the present invention is to provide a process for isolating internal olefin sulfonates that reduces the number of processing vessels needed and obviates the need for rcmoval and recycle of volatiles.

Still another object of the present invention is to provide a process for recovering internal olefin sulfonates produced by the sulfonation of neat internal olefins wherein the amount of free oil present in the internal olefin sulfonates is significantly reduced.

The above and other objects of the present invention will become apparent from the description given herein and the appended claims.

According to the process of the present invention, an internal olefin having the general formula: -R2R1-CH=CH , R may be the same or different and are each an alkyl group containing from about 1 to about 30 carbon atoms, is sulfonated with a suitable sulfonating agent to reactionmixturecontainingintermediatesulfonatedcompounds.The producea intermediate sulfonated compounds in the reaction mixture are neutralized and hydrolyzed to form a product mixture containing hydroxyalkane sutfonates. alêne sulfonates, and hydrocarbon oil. The product mixture is subjected to azeotropic

distillation with water to effect separation of the hydrocarbon oil from the product mixture.

Description of the Preferred Embodiments In the process of the present invention, the internal olcfins, neat or in the form of a dilute solution in a hydrocarbon solvent, are sulfonated in a suitable vessel using vaporized sulfur trioxide in a carrier stream, generally heated air, that is passed through the internal olefin starting material. Generally speaking, the sulfur trioxide is introduced so as to provide a mol ratio of sulfur trioxide to internal olefin of from about 1.0: 1.0 to about 3.0: 1.0. In general, the sulfonation temperature is maintained in the range of from about the freezing point of the inert olefin starting material to about 30°C, preferably to about 10°C.

The sulfonation reaction produces a reaction mixture containing intermediate sulfonated compounds that are neutralized, generally in the same temperature range discussed above before the sulfonation reaction, with a basic material, such as an aqueous solution of an alkali metal hydroxide, ammonium hydroxide or alkanolamine, or another commonly used neutralizing agent. Preferably, the neutralization is carried out using an aqueous alkali metal hydroxide solution, such as a sodium hydroxide solution.

To effect hydrolysis of the sultones, the neutralized reaction mixture can be rcfluxed at a temperature of from about 100°C up to about 160°C for a period of time sufficient to convert the sultones either to the hydroxyalkane sulfonates or the alkene sulfonates. Alternatively, hydrolysis can be accomplished by placing the neutralized reaction mixture into a pressurized stainless steel vesscl and subjected to heating at a temperature of from about 100°C to about 160°C for a period of time sufficient to convert the sultones to the hydroxyalkane sulfonates or the alkene sulfonates, care being taken to maintain the neutralized reaction mixture being hydrolyzed at a pH of about 11 or greater.

The hydrolysis step produces a product mixture containing hydroxyalkane sulfonates, alkenc sulfonatcs, and hydrocarbon oil (free oil). This product mixture is then subjected to azeotropic distillation using water. This can be conveniently carried out in a magnetically stirred, heated stainless steel vessel, the internal temperature of the vessel being monitored by a suitable controller, which injects air through a cooling coil as

needed. Provision is made to inject water into the vessel and permit the escape of steam. Generally, the azeotropic distillation is conducted at a temperature of from 100 to 160°C at a pressure of from about 15 to about 80 psig. The water-oil azeotrope is condense and measured, a volume of water equal to that in the recovered azeotrope being introduced into the vessel. This approach essentially maintins the volume of the mixture in the reactor constant during the azeotropic step.

To more fully illustrate the present invention, the following non-limiting examples are presented.

Example 1: Sulfonation of Neat Internal Olefins An intcmal olc (in hlcnci markctcd by CONDCA Augusta and comprise of Ci ;- olefinsC16internal paraffins(3.42%),andC15-C16aromatics(5.96%)C15-C16 was used as the sulfonation feedstock. The reaction system consisted of a syringe pump. a glass, sulfur trioxide vaporization chamber, a glass sulfuric acid trap, and a glass tubular sulfonation reactor containing a perforated glass disk base for the bubbling of the air-sulfur trioxide mixture through the sulfonation feedstock. A side arm of the reactor supported a thermometer that was kept in contact with the feedstock. The vaporization chamber and acid trap contained thermocouples and were wrapped with heating tape connected to Variacs for temperature control. Liquid sulfur trioxide was measured into a gas-tight syringe equipped with a long needle for transfer to the top of the vaporizer from the syringe pump. The liquid sulfur trioxide is injected so as to run down the inside wall of the vaporizer. In the vaporization chamber, sulfur trioxide is vaporized to fonil an air-sulfur trioxide blend, which is then passed through another glass vessel set at a slightly lowcr tcmperature to entrain sulfuric acid droplets. The air-sutfur trioxide btend lhen passes through the sul fonalion feedstock in the sulfonation rcactor and escapes from the reactor via a vent. In this example, 50 g (212 nunol) of c15-16 internal olefins containing 3.42 weight % paraffin (aliphatic hydrocarbons) and 5.96 weight % aromaties was poured into the 150 ml capacity sulfonation reactor with an air flow rate of 10-11 l/min. Sulfur ml(318mmol),wasinjectedintothevaporizedatarateof12.9 0.5 ml/min. The vaporizer was kept at 290°F. The acid trap was maintained at 270°F.

The sulfonation reaction temperature was maintained at about 25 °C using a water-ice bath as needed through the reaction. The reaction mixture progressively thickened and

darkened as more sulfur trioxide was added. Immediately after cessation of sulfur trioxide addition, the reaction mixture was decanted with efficient stirring into a beaker containing a chilled solution of 50.9 g (636 mmol) of 50 weight % aqueous sodium hydroxide and 25 ml of water. An additional 50 ml of water was used to rinse the sulfonation reactor. The contents of the beaker were mechanically stirred at room temperature for approximately 40 min. to effect partial hydrolysis of the sultone intermediates. The pH remained above I1 throughout. To neutralize the residual sultones, the reaction mixture was transferred into a closed stainless steel bomb and heated at 160°C for 50 minutes. During this time, the pressure reached approximately 77 psig. The final pH of the hydrolyzed, product mixture was found to be above 11.

Upon cooling to ambient temperature, concentrated sulStlric acid was carefully added with good mixing to adjust the pH to about 8. At this point, thc product mixture, which contained hydroxyalkanc sulfonates, alkene sulfonates, hydrocarbon oil, sodiium sulfate. and water, was a dark brown gel.

Recovery of Sulfonatcd Internal Olc (ins and Free Oil Removal. The product mixture was introduced into a stainless steel bomb having a capacity of about 400 ml.

The bomb was heated by placing it in a block controlled by a Thenn-O-Watch. The internal temperature of the bomb was monitored by a controller that injected air through a cooling coil as needed. Water was introduced from a stainless steel, pressurized reservoir (equipped with a glass side arum) via a dip tube built into the bomb cap. Steam escaped through a needle valve vent connected by tubing to a Claisen head mounted on a graduated cylinder and topped with a chilled condenser set at -2°C. As the neutralized reaction mixture was stirred in the closed bomb, heating was applied to reach a final temperature of 160°C. A bleed of steam was created by carefully and partially opening the vent. The pressure inside the bomb dropped from about 80 to about 50 psig. Care was taken to control the bleed so as to avoid the escape of foam. The water-oil azeotrope was condense and measured in the graduated cylinder. Fresh water was forced into the reactor using a head pressure of about 80 psig. In this manner, an equal volume of water was introduced for the volume distille (l and condensed in the graduated cyhnder.

Typically, the water was introduced in 15 ml portions. This approach prevented any excessive change of the volume of the cntents in the reactor during the azeotroping step.

Over a period of 1.5 hours, a total of 122 ml of distillate was collected. The expected

amount of free oil, about 2 ml, was observed. No oil layer appeared in the newty condensed distillate. At ambient temperature, the final sample was a muddy tan to broxvn slurry found to contain 28.4 weight % active internal olefin sulfonate and 0. SS weight % free oil. This translate to 3 weight % free oil based on active internal olefin sulfonate.

By way of comparison, neutralized reaction mixture before azeotroping contained 27.6 weight % sulfonated internal olefin and 1.54 weight % free oil. This translate to 5. 3 weight % free oil based on active.

This example clearly demonstrates that by using the process of the present invention, neat internal olefins can be sulfonated to produce sulfonated internal olefins containing a minimum amount of free oil. It also demonstrates that one does not need to force sulfonation of the internal olefins to completion because the unreacted olefins can be reduced as part of the free oil.

Example 2 A sulfonation fccdstook comprise of 13 weight % intema) otefins in a Cl4 16 paraffin solvent was prepared. The sulfonation apparatus utilized for sulfollating the dilute mixture of internal olefins was substantially that as described above in Example 1, with the exception that a larger glass sulfonation reactor was employed to accommodate the higher volume of sulfonation feedstock. Additionally, because foaming in the dilute solution poses a problem at the beginning of the reaction, the air flow rate was initially set low and gradually raised to the desired level. A 500 g (31 1 mmol) aliquot of the sulfonation feedstock was charged into a l-liter glass sulfonation reactor with the air flow set at approxmately 31/min. Sulfur trioxide, 19. 0 ml (46S mmol), was injected into the vaporizer at 0.5 ml/min. The vaporizer was set at a temperature of 290°F. The acid trap was maintained at 270°F. The air flow could be gradually increased as sulfur trioxide reacted. The final, desired ílow rate was achieved when 1 ml of sulfur trioxide had been introduced into the reaction mixtttre. Thc reaction mixture was kept at 25°C through the sulfur trioxide injection. Following completion trioxideaddition,thereactionmixturewasdecantedwithefficients tirringintofsulfur a beaker containing a chilled solution of 74.6 g (933 mmol) of 50 weight % aqueous sodium hydroxide and 200 ml of water. Another 200 ml of water was used to rinse the tar from the sulfonation reactor into the beaker. The neutralized mixture, which was a

slurry, was mechanically stirred at room temperature for approximately 40 minutes. The pH remained above 11 throughout. The neutralized mixture was subjected to hydrolysis in a closed 400 ml slainlcss stccl bomb at 1 60°C for 50 minutes. The maximum pressure observe was about 80 psig. Because of the larger volume, this step was accomplished in four batches. Care was exercised to mix the slurry well before dividing into the four batches. The pH of the hydrolyzed, product mixture containing hydroxyalkane sulfonates, alkene sulfonates, and hydrocarbon oil was found to be above 1 I without the addition of more base. The four batches were then recmbined for neutralization. At ambient temperature, concentrated sulfuric acid was carefully added to adjust the pH to between 7 and 8 to form a yellow mulsion.

Recovery of Sulfonated Internal Olefins and Free Oil Removal. Approximately one-fourth of the product mixture from the hydrolysis step was transferred into the reactor described above in Example 1 with respect to free oil removal. The azeotroping was conducted at 160°C and about 80 psig. Approximately 1. 7 1 of water was passed through the reactor and coHcctcd over a period of 9 hours before the distiHate no longer showed a separate, paraf (in layer. The volume in the reactor was further reduced by 350 ml before cooling to ambient for introduction of a second one-fourth portion of the product mixture. Azeotropic removal of oil from the second portion also required 9 hours and about 1.7 1 of water. The final, approximate) y 276 g, of product mixture was dark brown to burgundy and clear with no visual signs of an oil layer. The slurry was found to contain 15.8 weight % active and 0.2 weight % free oil, which translates to 1.7 weight % free oil based on active internal olefin sulfonate.

This example demonstrates that using the process of the present invention, dilute feedstocks of internal olefin sulfonates can be effectively sulfonated to produce an internal olefin sulfonate procluct containing very low amounts of frec oil. It also demonstrates that one does not have to force the sulfonation reaction to completion to achieve a product low in free oil.

The foregoing description and examples illustrate selected embodiments of the present invention. In light thereof, variations and modifications wi)) be suggested to one skilled in the art, all of which are in the spirit and purview of this invention.