Title of Invention	"AN IMPROVED PROCESS FOR THE PREPARATION OF HIGH PURITY SODIUM ALKYL ARYL SULFONATES FROM HEAVY ALKYL BENZENES"
Abstract	The present invention provides an improved process for the preparation of high purity sodium alkyl aryl sulfonates from heavy alkyl benzenes which comprises sulfonation of heavy alkyl benzenes with sulfuric acid in a ratio ranging 1: 1.2 to 1:2 of heavy alkyl benzene and maintaining a temperature in the range of 10-150°C, whereby sludge forms during said sulfonation and wherein alkyl aryl sulfonic acid (sour oil) separates from sludge in sulfonated mixture by settling followed by neutralizing with caustic soda such that the ph of neutralized alkyl aryl sulfonate being in the range 7.0-8.5, the resultant sodium sulfonate formed being separated by decantation to obtain crude sodium alkyl aryl sulfonate containing solubilised sodium sulfate which being removed from the crude sodium alkyl aryl sulfonate by dissolving in an aromatic solvent and in a ratio 1:1 to 1:50 and extraction of the resultant solution with aqueous sodium chloride solution followed by recovering of aromatic solvent by conventional methods, such that dissolved water being removed along with it by using a water trap to obtain high purity sodium alkyl aryl sulfonate.

Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF HIGH PURITY SODIUM ALKYL ARYL SULFONATES FROM HEAVY ALKYL BENZENES"

Abstract

The present invention provides an improved process for the preparation of high purity sodium alkyl aryl sulfonates from heavy alkyl benzenes which comprises sulfonation of heavy alkyl benzenes with sulfuric acid in a ratio ranging 1: 1.2 to 1:2 of heavy alkyl benzene and maintaining a temperature in the range of 10-150°C, whereby sludge forms during said sulfonation and wherein alkyl aryl sulfonic acid (sour oil) separates from sludge in sulfonated mixture by settling followed by neutralizing with caustic soda such that the ph of neutralized alkyl aryl sulfonate being in the range 7.0-8.5, the resultant sodium sulfonate formed being separated by decantation to obtain crude sodium alkyl aryl sulfonate containing solubilised sodium sulfate which being removed from the crude sodium alkyl aryl sulfonate by dissolving in an aromatic solvent and in a ratio 1:1 to 1:50 and extraction of the resultant solution with aqueous sodium chloride solution followed by recovering of aromatic solvent by conventional methods, such that dissolved water being removed along with it by using a water trap to obtain high purity sodium alkyl aryl sulfonate.

Full Text	This invention relates to an improved process for the preparation of high purity sodium alkyl benzene sulfonates from heavy alkyl benzenes. The high purity sodium alkyl benzene sulfonates are used as starting materials and additive components for detergent dispersant additives for automotive oils, rust inhibitors, hydrocarbon/ water emulsifiers and solubilisers for soluble cutting oils, fire resistant hydraulic fluids and other insecticidal and industrial formulations. The processes for the preparation of Sodium alkyl aryl sulfonates from heavy alkyl benzene involve sulfonation of heavy alkyl benzene diluted with a paraffinic solvent with sulfur trioxide such as in U.S. Patent U.S. 4, 235, 810 in a single shot or by repeated sulfonation with oleum in several shots with separation of sulfonates after each shot as in U.S. Patent U.S. 2, 113, 765. The sulfonates are then separated by alcohol and water as solvent and the unreacted oil is dried and sulfonated again. In the above processes the draw backs are diluent is required and sulfonation process is repeated using oleum. Further alcohol is required as a solvent and repeated drying is needed for next shot. All these steps are highly energy intensive and cause loss of costly sovlents. The sodium sulfonates obtained usually do not meet the mean equivalent weight requirements as starting materials for detergent - dispersant additives or rust inhibitors. This is accomplished by blending with hydrocarbon streams of higher molecular weights which give products with very broad equivalent weight spreads and usually have moderate to poor performance. The main object of the present invention is to provide an improved process for the preparation of high purity sodium alkyl aryl sulfonates from heavy alkyl benzenes which obviates the draw backs of the hitherto known processes. Another objective of the present invention is to provide an improved process for the preparation of sodium alkyl aryl sulfonates of requisite quality for applications as starting materials and additive components for detergent-dispersants, hydrocarbon/ water emulsifiers and rust inhibitors from appropriate heavy alkyl benzene sulfonates. Yet another objective is to provide an improved process wherein sulfonation of heavy alkyl benzene by sulfuric acid, instead of oleum or sulfurtrioxide, in a single shot to obtain requisite minimum sodium sulfonate content specified for grade I type of sodium sulfonate. Still another objective is elimination of alcohol as a solvent for recovery and purification of sodium alkyl aryl sulfonates to obtain inorganic salt content of less than one percent. Another object of the present invention is to provide a process for the preparation of sodium alkyl benzene sulfonates of equivalent weight range 430 - 460, 470 - 530 from suitable fractions of heavy alkyl benzenes of required distillation range and molecular weights. The specifications are given at table 1 below : SPECIFICATIONS OF SYNTHETIC SODIUM SULFONATE (Table Removed) Accordingly , the present invention provides an improved process for the preparation of high purity sodium alkyl aryl sulfonates from heavy alkyl benzenes which comprises: a) sulfonation of heavy alkyl benzenes with sulfuric acid in a ratio ranging 1: 1.2 to 1:2 of heavy alkyl benzene and maintaining a temperature in the range of 10-150°C, whereby sludge forms during said sulfonation and wherein alkyl aryl sulfonic acid (sour oil) separates from sludge in sulfonated mixture by settling followed by neutralizing with caustic soda such that the ph of neutralized alkyl aryl sulfonate being in the range 7.0-8.5, the resultant sodium sulfonate formed being separated by decantation to obtain crude sodium alkyl aryl sulfonate containing solubilised sodium sulfate which being removed from the crude sodium alkyl aryl sulfonate by dissolving in an aromatic solvent and in a ratio 1:1 to 1:50 and extraction of the resultant solution with aqueous sodium chloride solution followed by recovering of aromatic solvent by conventional methods, such that dissolved water being removed along with it by using a water trap to obtain high purity sodium alkyl aryl sulfonate. In another embodiment of the present invention the concentration of sulfuric acid used for sulfonation is in the range of 90-105% by wt., the remainder being water or sulfurtrioxide. In yet another embodiment of the present invention the temperature of sulfonation is maintained between 50-100°C. In still another embodiment of the present invention the separation of sludge and alkyl aryl sulfononic acid (Sour oil) is carried out at 20 - 100°C. The neutralisation of sour oil may be carried out with alkali solution at a temperature in the range of 30-70°C. The concentration of caustic solution used may be between 10-60%, the remaining being water. The neutralised sour oil may be diluted with aromatic solvent by 2 to 50 times of its volume and separated into two layers at temperatures between 10 - 80°C. The solubilised sodium sulfate may be extracted from solution of sodium alkyl aryl sulfonate and oil by extraction with sodium chloride solution of concentration 10-30 percent. The ratio of sodium chloride to sodium alkyl aryl sulfonate may be between 0.2-5 by wt. The recovery of aromatic solvent may be effected by conventional methods such as azeotropic distillation removing water by using a water trap such as Dean & Stark type of trap. The removal of the aromatic solvent may be effected at atmospheric or reduced pressure. The aromatic solvent used may be selected from alkyl aromatics having carbon atoms in the range of C6 to CIO. The process of the present invention is accomplished by sulfonation with sulfuric acid in a single shot thus avoiding sulfonation in multiple shots which requires repeated removal of sulfonates and drying of hydrocarbon. This reaction step has the advantage of handling a sulfonating agent milder than sulfurtrioxide or oleum and gives products of better quality. Dilution with a low boiling non reacting solvent is eliminated which reduces the cost of the process by eliminating the use of solvent. The repetitive sulfonation is avoided thus eliminating the cost intensive steps of using alcohol as solvent for extraction of sulfonates and drying of the unreacted oil for the next shot. Neutralised oil is diluted with an aromatic hydrocarbon solvent such as benzene, toluene or xylenes to a low concentration such that most of the water and inorganic salt is removed. Removal of water by evaporation before purification is thus completely avoided. The extraction of aromatic hydrocarbon solution of sulfonates with aqueous brine of appropriate concentration removes the inorganic salts to a very low concentration as well as most of the water present in sulfonates. The remaining water is removed during recovery of aromatic solvent itself and no separate evaporation step is required to bring it to an acceptable lower limit. The aromatic solvent can be recycled again and again with minimal loss. It is possible to prepare by this process sodium alkyl aryl sulfonates of requisite qualtiy and grades for different applications from a single source of heavy alkyl benzene by its distillation into appropriate fractions. Unlike other process no blending is required with hydrocarbons from other sources to obtain the desired equivalent weights for different applications. No prior dilution of heavy alkyl benzene and subsequent removal of solvent is needed when sulfonating with sulfuric acid as it is possible to obtain sodium alkyl aryl sulfonates of desired quality with a milder sulfonating agent such as sulfuric acid. Sodium sulfonate content as high as 90% can be achieved by sulfonation in a single shot. The improved process of the present invention for the preparation of sodium alkyl aryl sulfonates of desired quality and equivalent weight ranges involve the fractional distillation of heavy alkyl benzenes into required number of fractions depending upon the distillation characteristics and average molecular weight of desired hydrocarbon fraction. These fractions depending upon the applications for which the sulfonates are required are sulfonated with appropriate quality of sulfuric acid (95 - 105%) in a single shot. The sour oil separated as an upper layer is neutralised with a calculated amount of sodium carbonate to a set pH level (7-9) and diluted with an aromatic solvent so that concentration of sodium alkyl benzene sulfonate is below ten percent. The lower aqueous layer is separated to remove most of the water and sulfate. The upper layer is washed repeatedly with brine solution 10-30 percent till no sodium sulfate is detected in the brine layer. The sodium sulfonate solution in aromatic solvent is refluxed continuously and remaining water separated in a dean and stark trap. The remaining solution is filtered and aromatic solvent is removed by distillation. The product obtained is dried in vacuum to remove last traces of solvent. The product is then analysed for hydrocarbon, sulfonate, water, inorganic salt content and the mean equivalent weight. The product so obtained is almost free from inorganic salts and water and the sulfonate content is much above the minimum prescribed for Grade I type of sulfonates having appropriate equivalent weight range specified for various applications by additive manufacturing companies. The sodium sulfonates of desired equivalent ranges 410 - 460, 450 - 530, 480 - 550 have been prepared from heavy alkyl benzenes obtained from several different sources without any blending or dilution by appropriate fractionation by distillation and obtaining fractions of desired molecular weights 305 - 355, 345 - 425, 375 - 445. The sodium alkyl aryl sulfonate contents of 68 - 90% have been obtained by sulfonation with (95 - 101%) sulfuric acid in a single shot. The inorganic salt content as low as 0.02 percent and water content 0.5 percent has been achieved by this process without extraction of sulfonates from unreacted heavy alkyl benzenes with alcohol/ water, thus eliminating several steps. The sulfonates of ASTM colour 1.5 have been prepared without any dilution of heavy alkyl benzene with paraffinic solvents while performing sulfonation reaction. Sulfonates with tailored equivalent weight ranges and structural characteristics give better hydrocarbon/ water emulsion stability and solubilising properties for micro emulsions than the sodium petroleum sulfonates obtained from sulfonation of lube oil base stocks of similar equivalent weight ranges. The rate of addition of sulfuric acid to heavy alkyl benzene and the speed of stirring for mixing should be between 5-50 g/min. and 900 + 50 rpm respectively so that temperature of sulfonation is controlled between 50 - 80°C during sulfonation in order to achieve sulfonation of heavy alkyl benzene to a sodium alkyl aryl sulfonate content of a minimum of 65 percent in the finished product. The quantity of sulfuric acid : heavy alkyl benzene should be between 1 to 3:1 by weight and concentration of sulfuric acid should not fall below 94% by weight. The pH of the neutralised sour oil be controlled to a fixed level by strict monitoring of addition of sodium carbonate/ sodium hydroxide/ sodium bicarbonate between 7 to 8. The neutralised sulfonated heavy alkyl benzene should be diluted with aromatic solvent such that the concentration of sodium alkyl aryl sulfonate in sour oil remains below 12 percent. The concentration of sodium chloride in aqueous solution for salt removal should be adjusted between 10 percent to 30 percent in order to remove the inorganic salts from the sodium alkyl aryl sulfonate solution in the aromatic solvent. Heavy alkyl benzenes should be fractionally distilled such that fractions of desired molecular weight range of 310 - 360, 350-430 and 380-480 is obtained before sulfonation for obtaining sodium alkyl aryl sulfonates of equivalent weights 410-460, 450-530, 480-580 for specific applications as hydrocarbon/ water solubilisers, detergent-dispersant additives and rust inhibitors. The following examples are given by way of illustration and should not be construed to limit the scope of the present invention : Example 1 1000 gm. of heavy alkyl benzene fraction was taken in a flask fitted with a stirrer and thermometer. 1500 gm of 98% sulfuric acid was added drop wise at the rate of 25 gm/min. from a dropping funnel to heavy alkyl benzene fraction with stirring at 1000 rpm. The temperature was raised to 70+5 °C. The reaction continued for one hour with constant stirring at 1000 rpm. The contents were transferred to pear shaped separating funnel and allowed to stand for 8 hours. The lower layer comprising of unreacted acid was separated in a separation tank and neutralised with 1500 gm of lime to a pH of 8.5 by suspending lime in water to make an approximately 30% slurry. The upper layer comprising of sulfonic acids called sour oil was diluted with water (Sour oil : Water 2:1) with stirring maintained at 900 ± 50 rpm. A 30% solution of sodium carbonate was added to neutralise the sour oil to pH 8. The neutralised sour oil is diluted nearly 10 times. The solution was warmed to 60°C and aqueous layer was removed. The upper aromatic solvent layer is treated with 20% sodium chloride solution with stirring and kept standing for 20-30 minutes for separation. The process is repeated till the lower layer gave very faint precipitate with 1% barium chloride solution. The desalted solution of sodium alkyl aryl sulfonate was distilled azeotropically to remove water. The aromatic solvent solution after azeotropic distillation was filtered and solvent distilled off to give sodium alkyl aryl sulfonate. A fraction of heavy alkyl benzene of molecular weight 362 and 443 and distillation range 220-430°C, 400-500°C respectively gave sodium alkyl aryl sulfonates of following analysis : (Table Removed) Example 2 1000 gm. Of heavy alkyl benzene is taken in a flask and 2000 gm. of 96% sulfuric acid is added gradually at the rate of 15 gm./ min. with constant stirring maintaining temperatures in the range of 25-30°C. This mixture is allowed to settle for 15 hrs., whereby bottom portion is removed as sludge. The upper layer, 1200 gm., is neutralised with sodium carbonate solution, 500 gm., at 40°C and allowed to settle. The lower layer containing sodium sulphate, water and unreacted sodium carbonate is removed. The upper layer is dissolved in benzene, 2000 gm., and mixed with 320 gm of 30% solution of sodium chloride and allowed to settle. The lower layer is removed and the upper layer washed 2 more times with 320 gm. of 30% sodium chloride solution. The benzene is finally removed by evaporation to get purified sodium alkyl aryl sulfonate 1110 gm. Example 3 1000 gm. of heavy alkyl benzene fraction b.pt. 350 - 500 was taken in a flask fitted with a stirrer and thermometer. 1200 gm. of 104% sulfuric acid containing 4% of SO3 was added dropwise at the rate of 50g/min with vigorous stirring at a temperature of 20°C. The temperature was not allowed to rise above 30°C. The contents were transferred to pearshaped separating funnel and allowed to stand for 4 hours. The lower layer was withdrawn as acid sludge. The upper layer called sour oil, 1210 gm., was neutralized with 30% sodium carbonate solution, 550 gm. At 30°C to pH 7-7.5 and diluted with xylene 1000 gm. The xylene solution of sodium alkyl benzene sulfonate containing unreacted heavy alkyl benzene, sodium sulfate and water was allowed to settle. The lower layer containing sodium sulfate and water was removed. The xylene layer is washed with 200 gm. of 25% solution of sodium chloride several times till it does not give appreciable precipitate of barium sulfate with barium chloride solution. The xylene is finally removed by distillation followed by evaporation to get purified sodium alkyl benzene sulfonate 1150 gm. The main advantages of the process of the present invention are : 1. The concentration of sulfuric acid used for sulfonation may be in the range of 90 to 105% by weight and temperature of sulfonation may lie between 50 - 100°C. 2. The neutralised sour oil may be diluted with an aromatic solvent 2 to 50 times resulted in separation of two layers between 10 to 80°C such that most of the inorganic salts are removed in lower aqueous layers. 3. The solubilised sodium sulfonate may be extracted from crude sodium alkyl aryl sulfonate solution by aqueous sodium chloride solution of concentration 10 to 30 percent. 4. The dissolved water may be removed from the sodium alkyl aryl sulfonate alongwith removal of solvent during azeotropic distillation by using a dean and stark type of water trap. We Claim: 1. An improved process for the preparation of high purity sodium alkyl aryl sulfonates from alkyl benzenes which comprises: a) sulfonation of heavy alkyl benzenes with sulfuric acid in a ratio ranging 1: 1.2 to 1:2 of heavy alkyl benzene and maintaining a temperature in the range of 10-150°C, whereby sludge forms during said sulfonation and wherein alkyl aryl sulfonic acid (sour oil) separates from sludge in sulfonated mixture by settling followed by neutralizing with an alkal such that the pH of neutralized alkyl aryl sulfonate being in the range 7.0-8.5, the resultant sodium sulfonate formed being separated by decantation to obtain crude sodium alkyl aryl sulfonate containing solubilised sodium sulfate which being removed from the crude sodium alkyl aryl sulfonate by dissolving in an aromatic solventjand in a ratio 1:1 to 1:50 and extraction of the resultant solution with aqueous sodium chloride solution followed by recovering of aromatic solvent by conventional methods, such that dissolved water being removed along with it by using a water trap to obtain high purity sodium alkyl aryl sulfonate. 2. An improved process according to claim 1, wherein the concentration of sulfuric acid used for sulfonation is in the range of 90-105% by wt, the remainder being water or sulfurtrioxide. 3. An improved processes as claimed in claim 1-2, wherein the temperature of sulfonation is maintained between 50-100°C. 4. An improved process as claimed in claim 1-3, wherein the separation of sludge and alkyl aryl sulfononic acid (Sour oil) is carried out at 20 - 100°C. 5. A improved process as claimed in claims 1-4, wherein the neutralization of sour oil is carried out with an alkali solution) at a temperature in the range of 30-70°C. 6. An improved as claimed in claims 1-5, wherein the concentration of caustic solution used is between 10-60%, the remaining being water. 7. An improved process as claimed in claims 1 -6, wherein the neutralized sour oil is diluted with aromatic solvent by 2 to 50 times of its volume and separated into two layers at temperatures between 10 - 80°C. 8. An improved process as claimed in claims 1-7 , wherein solubilised sodium sulfate is extracted from solution of sodium alkyl aryl sulfonate and oil by extraction with sodium chloride solution of concentration 10-30 percent. 9. An improved process as claimed in claims 1-8 , wherein the ratio of sodium chloride to sodium alkyl aryl sulfonate is between 0.2 - 5 by wt. 10. An improved process as claimed in claims 1-9 , wherein the recovery of aromatic solvent is effected by conventional methods such as azeotropic distillation removing water by using a water trap such as Dean & Stark type of trap. 11 .An improved process as claimed in claims-10, wherein removal of the aromatic solvent is effected at atmospheric or reduced pressure. 12. An improved process as claimed in claims 1-11, wherein the aromatic solvent used is selected from alkyl aromatics having carbon atoms in the range of C6 to C10. 13. An improved process for the preparation of sodium alkyl aryl sulfonates from heavy alkyl benzenes substantially as herein described with reference to the examples.

Full Text

This invention relates to an improved process for the preparation of high purity sodium alkyl benzene sulfonates from heavy alkyl benzenes. The high purity sodium alkyl benzene sulfonates are used as starting materials and additive components for detergent dispersant additives for automotive oils, rust inhibitors, hydrocarbon/ water emulsifiers and solubilisers for soluble cutting oils, fire resistant hydraulic fluids and other insecticidal and industrial formulations.
The processes for the preparation of Sodium alkyl aryl sulfonates from heavy alkyl benzene involve sulfonation of heavy alkyl benzene diluted with a paraffinic solvent with sulfur trioxide such as in U.S. Patent U.S. 4, 235, 810 in a single shot or by repeated sulfonation with oleum in several shots with separation of sulfonates after each shot as in U.S. Patent U.S. 2, 113, 765. The sulfonates are then separated by alcohol and water as solvent and the unreacted oil is dried and sulfonated again.
In the above processes the draw backs are diluent is required and sulfonation process is repeated using oleum. Further alcohol is required as a solvent and repeated drying is needed for next shot. All these steps are highly energy intensive and cause loss of costly sovlents. The sodium sulfonates obtained usually do not meet the mean equivalent weight requirements as starting materials for detergent - dispersant additives or rust inhibitors. This is accomplished by blending with hydrocarbon streams of higher molecular weights which give products with very broad equivalent weight spreads and usually have moderate to poor performance.

The main object of the present invention is to provide an improved process for the preparation of high purity sodium alkyl aryl sulfonates from heavy alkyl benzenes which obviates the draw backs of the hitherto known processes.
Another objective of the present invention is to provide an improved process for the
preparation of sodium alkyl aryl sulfonates of requisite quality for applications as starting
materials and additive components for detergent-dispersants, hydrocarbon/ water
emulsifiers and rust inhibitors from appropriate heavy alkyl benzene sulfonates.
Yet another objective is to provide an improved process wherein sulfonation of heavy alkyl benzene by sulfuric acid, instead of oleum or sulfurtrioxide, in a single shot to obtain requisite minimum sodium sulfonate content specified for grade I type of sodium sulfonate.
Still another objective is elimination of alcohol as a solvent for recovery and purification of sodium alkyl aryl sulfonates to obtain inorganic salt content of less than one percent.
Another object of the present invention is to provide a process for the preparation of sodium alkyl benzene sulfonates of equivalent weight range 430 - 460, 470 - 530 from suitable fractions of heavy alkyl benzenes of required distillation range and molecular weights. The specifications are given at table 1 below :
SPECIFICATIONS OF SYNTHETIC SODIUM SULFONATE
(Table Removed)
Accordingly , the present invention provides an improved process for the preparation of high purity sodium alkyl aryl sulfonates from heavy alkyl benzenes which comprises: a) sulfonation of heavy alkyl benzenes with sulfuric acid in a ratio ranging 1: 1.2 to 1:2 of heavy alkyl benzene and maintaining a temperature in the range of 10-150°C, whereby sludge forms during said sulfonation and wherein alkyl aryl sulfonic acid (sour oil) separates from sludge in sulfonated mixture by settling followed by neutralizing with caustic soda such that the ph of neutralized alkyl aryl sulfonate being in the range 7.0-8.5, the resultant sodium sulfonate formed being separated by decantation to obtain crude sodium alkyl aryl sulfonate containing solubilised sodium sulfate which being removed from the crude sodium alkyl aryl sulfonate by dissolving in an aromatic solvent and in a ratio 1:1 to 1:50 and extraction of the resultant solution with aqueous sodium chloride solution followed by recovering of aromatic solvent by conventional methods, such that dissolved water being removed along with it by using a water trap to obtain high purity sodium alkyl aryl sulfonate.
In another embodiment of the present invention the concentration of sulfuric acid used for
sulfonation is in the range of 90-105% by wt., the remainder being water or sulfurtrioxide.
In yet another embodiment of the present invention the temperature of sulfonation is maintained
between 50-100°C.
In still another embodiment of the present invention the separation of sludge and alkyl aryl
sulfononic acid (Sour oil) is carried out at 20 - 100°C.
The neutralisation of sour oil may be carried out with alkali solution at a temperature in the range of 30-70°C.
The concentration of caustic solution used may be between 10-60%, the remaining being water.
The neutralised sour oil may be diluted with aromatic solvent by 2 to 50 times of its volume and separated into two layers at temperatures between 10 - 80°C.
The solubilised sodium sulfate may be extracted from solution of sodium alkyl aryl sulfonate and oil by extraction with sodium chloride solution of concentration 10-30 percent.
The ratio of sodium chloride to sodium alkyl aryl sulfonate may be between 0.2-5 by wt.
The recovery of aromatic solvent may be effected by conventional methods such as azeotropic distillation removing water by using a water trap such as Dean & Stark type of trap.
The removal of the aromatic solvent may be effected at atmospheric or reduced pressure.
The aromatic solvent used may be selected from alkyl aromatics having carbon atoms in the range of C6 to CIO.

The process of the present invention is accomplished by sulfonation with sulfuric acid in a single shot thus avoiding sulfonation in multiple shots which requires repeated removal of sulfonates and drying of hydrocarbon. This reaction step has the advantage of handling a sulfonating agent milder than sulfurtrioxide or oleum and gives products of better quality. Dilution with a low boiling non reacting solvent is eliminated which reduces the cost of the process by eliminating the use of solvent. The repetitive sulfonation is avoided thus eliminating the cost intensive steps of using alcohol as solvent for extraction of sulfonates and drying of the unreacted oil for the next shot. Neutralised oil is diluted with an aromatic hydrocarbon solvent such as benzene, toluene or xylenes to a low concentration such that most of the water and inorganic salt is removed. Removal of water by evaporation before purification is thus completely avoided. The extraction of aromatic hydrocarbon solution of sulfonates with aqueous brine of appropriate concentration removes the inorganic salts to a very low concentration as well as most of the water present in sulfonates.
The remaining water is removed during recovery of aromatic solvent itself and no separate evaporation step is required to bring it to an acceptable lower limit. The aromatic solvent can be recycled again and again with minimal loss.
It is possible to prepare by this process sodium alkyl aryl sulfonates of requisite qualtiy and grades for different applications from a single source of heavy alkyl benzene by its distillation into appropriate fractions. Unlike other process no blending is required with hydrocarbons from other sources to obtain the desired equivalent weights for different applications. No prior dilution of heavy alkyl benzene and subsequent removal of solvent is needed when sulfonating with sulfuric acid as it is possible to obtain sodium alkyl aryl

sulfonates of desired quality with a milder sulfonating agent such as sulfuric acid. Sodium sulfonate content as high as 90% can be achieved by sulfonation in a single shot.
The improved process of the present invention for the preparation of sodium alkyl aryl sulfonates of desired quality and equivalent weight ranges involve the fractional distillation of heavy alkyl benzenes into required number of fractions depending upon the distillation characteristics and average molecular weight of desired hydrocarbon fraction. These fractions depending upon the applications for which the sulfonates are required are sulfonated with appropriate quality of sulfuric acid (95 - 105%) in a single shot. The sour oil separated as an upper layer is neutralised with a calculated amount of sodium carbonate to a set pH level (7-9) and diluted with an aromatic solvent so that concentration of sodium alkyl benzene sulfonate is below ten percent. The lower aqueous layer is separated to remove most of the water and sulfate. The upper layer is washed repeatedly with brine solution 10-30 percent till no sodium sulfate is detected in the brine layer. The sodium sulfonate solution in aromatic solvent is refluxed continuously and remaining water separated in a dean and stark trap. The remaining solution is filtered and aromatic solvent is removed by distillation. The product obtained is dried in vacuum to remove last traces of solvent. The product is then analysed for hydrocarbon, sulfonate, water, inorganic salt content and the mean equivalent weight. The product so obtained is almost free from inorganic salts and water and the sulfonate content is much above the minimum prescribed for Grade I type of sulfonates having appropriate equivalent weight range specified for various applications by additive manufacturing companies.
The sodium sulfonates of desired equivalent ranges 410 - 460, 450 - 530, 480 - 550 have been prepared from heavy alkyl benzenes obtained from several different sources

without any blending or dilution by appropriate fractionation by distillation and obtaining fractions of desired molecular weights 305 - 355, 345 - 425, 375 - 445. The sodium alkyl aryl sulfonate contents of 68 - 90% have been obtained by sulfonation with (95 - 101%) sulfuric acid in a single shot. The inorganic salt content as low as 0.02 percent and water content 0.5 percent has been achieved by this process without extraction of sulfonates from unreacted heavy alkyl benzenes with alcohol/ water, thus eliminating several steps. The sulfonates of ASTM colour 1.5 have been prepared without any dilution of heavy alkyl benzene with paraffinic solvents while performing sulfonation reaction.
Sulfonates with tailored equivalent weight ranges and structural characteristics give better hydrocarbon/ water emulsion stability and solubilising properties for micro emulsions than the sodium petroleum sulfonates obtained from sulfonation of lube oil base stocks of similar equivalent weight ranges.
The rate of addition of sulfuric acid to heavy alkyl benzene and the speed of stirring for mixing should be between 5-50 g/min. and 900 + 50 rpm respectively so that temperature of sulfonation is controlled between 50 - 80°C during sulfonation in order to achieve sulfonation of heavy alkyl benzene to a sodium alkyl aryl sulfonate content of a minimum of 65 percent in the finished product. The quantity of sulfuric acid : heavy alkyl benzene should be between 1 to 3:1 by weight and concentration of sulfuric acid should not fall below 94% by weight. The pH of the neutralised sour oil be controlled to a fixed level by strict monitoring of addition of sodium carbonate/ sodium hydroxide/ sodium bicarbonate between 7 to 8. The neutralised sulfonated heavy alkyl benzene should be diluted with aromatic solvent such that the concentration of sodium alkyl aryl sulfonate in sour oil

remains below 12 percent. The concentration of sodium chloride in aqueous solution for salt removal should be adjusted between 10 percent to 30 percent in order to remove the inorganic salts from the sodium alkyl aryl sulfonate solution in the aromatic solvent. Heavy alkyl benzenes should be fractionally distilled such that fractions of desired molecular weight range of 310 - 360, 350-430 and 380-480 is obtained before sulfonation for obtaining sodium alkyl aryl sulfonates of equivalent weights 410-460, 450-530, 480-580 for specific applications as hydrocarbon/ water solubilisers, detergent-dispersant additives and rust inhibitors.
The following examples are given by way of illustration and should not be construed to limit the scope of the present invention :
Example 1
1000 gm. of heavy alkyl benzene fraction was taken in a flask fitted with a stirrer and thermometer. 1500 gm of 98% sulfuric acid was added drop wise at the rate of 25 gm/min. from a dropping funnel to heavy alkyl benzene fraction with stirring at 1000 rpm. The temperature was raised to 70+5 °C. The reaction continued for one hour with constant stirring at 1000 rpm. The contents were transferred to pear shaped separating funnel and allowed to stand for 8 hours. The lower layer comprising of unreacted acid was separated in a separation tank and neutralised with 1500 gm of lime to a pH of 8.5 by suspending lime in water to make an approximately 30% slurry. The upper layer comprising of sulfonic acids called sour oil was diluted with water (Sour oil : Water 2:1) with stirring maintained at 900 ± 50 rpm. A 30% solution of sodium carbonate was added to neutralise the sour oil to pH 8. The neutralised sour oil is diluted nearly 10 times. The solution was warmed to 60°C and aqueous layer was removed. The upper aromatic

solvent layer is treated with 20% sodium chloride solution with stirring and kept standing for 20-30 minutes for separation. The process is repeated till the lower layer gave very faint precipitate with 1% barium chloride solution. The desalted solution of sodium alkyl aryl sulfonate was distilled azeotropically to remove water. The aromatic solvent solution after azeotropic distillation was filtered and solvent distilled off to give sodium alkyl aryl sulfonate. A fraction of heavy alkyl benzene of molecular weight 362 and 443 and distillation range 220-430°C, 400-500°C respectively gave sodium alkyl aryl sulfonates of following analysis :
(Table Removed)

Example 2
1000 gm. Of heavy alkyl benzene is taken in a flask and 2000 gm. of 96% sulfuric acid is added gradually at the rate of 15 gm./ min. with constant stirring maintaining temperatures in the range of 25-30°C. This mixture is allowed to settle for 15 hrs., whereby bottom portion is removed as sludge. The upper layer, 1200 gm., is neutralised with sodium carbonate solution, 500 gm., at 40°C and allowed to settle. The lower layer containing sodium sulphate, water and unreacted sodium carbonate is removed. The upper layer is dissolved in benzene, 2000 gm., and mixed with 320 gm of 30% solution of sodium chloride and allowed to settle. The lower layer is removed and the upper layer washed 2

more times with 320 gm. of 30% sodium chloride solution. The benzene is finally removed by evaporation to get purified sodium alkyl aryl sulfonate 1110 gm.
Example 3
1000 gm. of heavy alkyl benzene fraction b.pt. 350 - 500 was taken in a flask fitted with a stirrer and thermometer. 1200 gm. of 104% sulfuric acid containing 4% of SO3 was added dropwise at the rate of 50g/min with vigorous stirring at a temperature of 20°C. The temperature was not allowed to rise above 30°C. The contents were transferred to pearshaped separating funnel and allowed to stand for 4 hours. The lower layer was withdrawn as acid sludge. The upper layer called sour oil, 1210 gm., was neutralized with 30% sodium carbonate solution, 550 gm. At 30°C to pH 7-7.5 and diluted with xylene 1000 gm. The xylene solution of sodium alkyl benzene sulfonate containing unreacted heavy alkyl benzene, sodium sulfate and water was allowed to settle. The lower layer containing sodium sulfate and water was removed. The xylene layer is washed with 200 gm. of 25% solution of sodium chloride several times till it does not give appreciable precipitate of barium sulfate with barium chloride solution. The xylene is finally removed by distillation followed by evaporation to get purified sodium alkyl benzene sulfonate 1150 gm. The main advantages of the process of the present invention are :
1. The concentration of sulfuric acid used for sulfonation may be in the range of 90 to
105% by weight and temperature of sulfonation may lie between 50 - 100°C.
2. The neutralised sour oil may be diluted with an aromatic solvent 2 to 50 times
resulted in separation of two layers between 10 to 80°C such that most of the
inorganic salts are removed in lower aqueous layers.

3. The solubilised sodium sulfonate may be extracted from crude sodium alkyl aryl
sulfonate solution by aqueous sodium chloride solution of concentration 10 to 30
percent.
4. The dissolved water may be removed from the sodium alkyl aryl sulfonate
alongwith removal of solvent during azeotropic distillation by using a dean and
stark type of water trap.

We Claim:
1. An improved process for the preparation of high purity sodium alkyl aryl sulfonates from alkyl benzenes which comprises: a) sulfonation of heavy alkyl benzenes with sulfuric acid in a ratio ranging 1: 1.2 to 1:2 of heavy alkyl benzene and maintaining a temperature in the range of 10-150°C, whereby sludge forms during said sulfonation and wherein alkyl aryl sulfonic acid (sour oil) separates from sludge in sulfonated mixture by
settling followed by neutralizing with an alkal such that the pH of neutralized alkyl aryl sulfonate being in the range 7.0-8.5, the resultant sodium sulfonate formed being separated by decantation to obtain crude sodium alkyl aryl sulfonate containing solubilised sodium sulfate which being removed from the crude sodium alkyl aryl sulfonate by dissolving in

an aromatic solventjand in a ratio 1:1 to 1:50 and extraction of the resultant solution with aqueous sodium chloride solution followed by recovering of aromatic solvent by conventional methods, such that dissolved water being removed along with it by using a water trap to obtain high purity sodium alkyl aryl sulfonate.

2. An improved process according to claim 1, wherein the concentration of
sulfuric acid used for sulfonation is in the range of 90-105% by wt, the
remainder being water or sulfurtrioxide.
3. An improved processes as claimed in claim 1-2, wherein the temperature of
sulfonation is maintained between 50-100°C.
4. An improved process as claimed in claim 1-3, wherein the separation of
sludge and alkyl aryl sulfononic acid (Sour oil) is carried out at 20 - 100°C.
5. A improved process as claimed in claims 1-4, wherein the neutralization of

sour oil is carried out with an alkali solution) at a temperature in the range of 30-70°C.
6. An improved as claimed in claims 1-5, wherein the concentration of
caustic solution used is between 10-60%, the remaining being water.
7. An improved process as claimed in claims 1 -6, wherein the neutralized sour
oil is diluted with aromatic solvent by 2 to 50 times of its volume and
separated into two layers at temperatures between 10 - 80°C.
8. An improved process as claimed in claims 1-7 , wherein solubilised sodium
sulfate is extracted from solution of sodium alkyl aryl sulfonate and oil by
extraction with sodium chloride solution of concentration 10-30 percent.
9. An improved process as claimed in claims 1-8 , wherein the ratio of sodium
chloride to sodium alkyl aryl sulfonate is between 0.2 - 5 by wt.
10. An improved process as claimed in claims 1-9 , wherein the recovery of aromatic solvent is effected by conventional methods such as azeotropic
distillation removing water by using a water trap such as Dean & Stark type
of trap.
11 .An improved process as claimed in claims-10, wherein removal of the aromatic solvent is effected at atmospheric or reduced pressure.
12. An improved process as claimed in claims 1-11, wherein the aromatic
solvent used is selected from alkyl aromatics having carbon atoms in the
range of C6 to C10.
13. An improved process for the preparation of sodium alkyl aryl sulfonates
from heavy alkyl benzenes substantially as herein described with reference
to the examples.

Documents:

1306-del-1998-abstract.pdf

1306-del-1998-claims.pdf

1306-del-1998-correspondence-others.pdf

1306-del-1998-correspondence-po.pdf

1306-del-1998-description (complete).pdf

1306-del-1998-form-1.pdf

1306-del-1998-form-19.pdf

1306-del-1998-form-2.pdf

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Patent Number

215857

Indian Patent Application Number

1306/DEL/1998

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

04-Mar-2008

Date of Filing

15-May-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001 INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	ONKAR NATH ANAND	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
2	ARUN KUMAR SINGH	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.
3	ASHOK KUMAR GUPTA	INDIAN INSTITUTE OF PETROLEUM, DEHRADUN-248005, INDIA.

PCT International Classification Number

C07C 303/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA