United States Patent to 11 Patent Number: 4,510,100 Plattner Et Al

United States Patent to 11 Patent Number: 4,510,100 Plattner et al. (45) Date of Patent: Apr. 9, 1985

(54) PROCESS FOR THE PRODUCTION OF Primary Examiner-Nicky Chan 2-AMINO-1-NAPHTHALENESULFONC Attorney, Agent, or Firm-Joseph G. Kolodny ACID 75) Inventors: Eric Plattner, Seltisberg; Sebastian (57) ABSTRACT Stäubli, Magden; Fred von Kaenel, The invention relates to an improved process for the Seltisberg, all of Switzerland production of 2-amino-1-naphthalenesulfonic acid (To 73 Assignee: Ciba Geigy Ag, Basle, Switzerland bias acid). This improved process makes it possible to obtain Tobias acid which has only a very low content of 21) Appl. No.: 559,149 2-aminonaphthalene and in high space-time yield. The 22 Filed: Dec. 7, 1983 process starts from 2-hydroxynaphthalene and com prises the following main reaction steps: Related U.S. Application Data (a) the sulfonation of 2-hydroxynaphthalene to 2 hydroxynaphthalene-1-sulfonic acid (oxy-Tobias 63 Continuation of Ser. No. 352,730, Feb. 26, 1982, aban doned. acid) with chlorosulfonic acid, in an inert organic solvent; 30 Foreign Application Priority Data (b) the neutralization of the liberated hydrochloric acid Dec. 20, 1979 (CHJ Switzerland ...... 1135/79 and excess chlorosulfonic acid still present in the reaction medium and conversion of the 2-hydrox 51 Int. Cl...... C07C 143/60 ynaphthalene-1-sulfonic acid obtained into the corre 52 U.S. Cl...... 260/508; 260/509 sponding ammonium salt with ammonia; 58) Field of Search ...... 260/508, 509 (c) conversion of the 2-hydroxy group into the 2-amino 56) References Cited group by the Bucherer reaction; and FOREIGN PATENT DOCUMENTS (d) the subsequent precipitation of the Tobias acid with dilute sulfuric acid. 2001637 2/1979 United Kingdom ...... 260/508 2001640 2/1979 United Kingdom ...... 260/508 2001644 2/1979 United Kingdom ...... 260/508 7 Claims, 1 Drawing Figure

REACTION SCHEME hNorgonic in CISOHorganic in Sowet sovert

SULFONATION

DESORPTION OF HC

ordonic solvent

orconic solver

SOLAON OF TOBASACD U.S. Patent Apr. 9, 1985 4,510,100

REACTION SCHEME HN in CISO3H in Organic Organic SOV ent SOwent I- SULFONATION HC DESORPTION OF HC

solution NEUTRALISATION I I PHASE rqanic IV SEPARATION SOWentSis Removal of HN Orgonic OrganicSOvent by extraction SOvent V Stripping off Of SOI went SOvent t NH3 OTSSolution NH4. Solution VI bisulfite AM NATON Solution NOOH Solution StrippingA. off NH3 VI of NH3 extract of VII Removal of AN AN by extraction solventvent precipitation H2SO2SV4 DX OF SEAS ASE SO2 DESORPTION X OF SO2. SOLATION XI OF TOBASACD 4,510,100 1. 2 tion into Tobias acid, but the yields of salts are only 85 PROCESS FOR THE PRODUCTION OF to 90% of theory and the reaction times of 4 to 6 hours 2-AMNO-1-NAPHTHALENESULFONIC ACID lead to poor space-time yields. A process for the production of Tobias acid is de This is a continuation of application Ser. No. 352,730, scribed in U.S. Pat. No. 2,058,911, which process con filed Feb. 26, 1982, now abandoned. sists in removing 2-aminonaphthalene by extraction The present invention relates to an improved process with a water-immiscible organic solvent such as mono for the production of 2-amino-1-naphthalenesulfonic chlorobenzene or dichlorobenzene, from a product acid (Tobias acid). This improved process for the pro solution obtained in an amination reaction, and acidify duction of Tobias acid makes it possible to obtain a 10 ing the resultant purified aqueous solution of the sodium product having a very low content of 2-aminonaphtha salt of Tobias acid until acid to Congo red (pH 3) at a lene, and is distinguished by high space-time yields. temperature of about 45 C., affording a Tobias acid The process of this invention for the production of which is suitable for use as an intermediate for obtaining Tobias acid starts from 2-hydroxynaphthalene, and pigment dyes. This procedure is extremely complicated comprises the following main reaction steps: 15 and leads to losses in yield. (a) the sulfonation of 2-hydroxynaphthalene to 2 The production of Tobias acid having a low content hydroxynaphthalene-1-sulfonic acid, hereinafter re of 2-naphthylamine also forms the subject matter of ferred to as oxy-Tobias acid, with chlorosulfonic acid, German Offenlegungsschriften Nos. 2831 956, 2 831 in an inert organic solvent 965, 2831966, 2831992, 2831993,2831994 and 2831 (b) the neutralisation of the liberated hydrochloric 20 995. In these processes, an attempt is made to solve the acid and excess chlorosulfonic acid still present in the problem of producing Tobias acid having a low content reaction medium and conversion of the 2-hydroxynaph of 2-naphthylamine by inhibiting the 2-naphthylamine thalene-1-sulfonic acid obtained into the corresponding which allegedly forms by decomposition of salts of ammonium salt with ammonia; oxy-Tobias acid or Tobias acid. As in this case too the (c) conversion of the 2-hydroxy group into the 2 25 entire process is concerned with the formation of the amino group by the Bucherer reaction; and less soluble alkali metal salts of oxy-Tobias acid, it has (d) the subsequent precipitation of the Tobias acid not yet proved possible to find a wholly satisfying solu with dilute sulfuric acid. tion, especially as regards the space-time yield, which is The Bucherer reaction is usually employed in the of such importance for large-scale production. production of Tobias acid by amination of alkali metal 30 Accordingly, the present invention has for its object salts of 2-hydroxy-1-naphthalenesulfonic acid on an to provide a novel process for the production of 2 industrial scale. A small number of by-products are amino-1-naphthalenesulfonic acid that does not have formed in this reaction. One of these by-products is the disadvantages of the known processes. This object is 2-aminonaphthalene, which is a carcinogen. accomplished by means of an improved process for the The Occupational Safety and Health Administration 35 production of 2-amino-1-naphthalenesulfonic acid (To (OSHA) has issued regulations which only permit the bias acid), by reacting a suspension of 2-hydroxynaph handling of substances containing 2-aminonaphthalene thalene, in a water-immiscible organic solvent, with if the content of this latter is 0.1% by weight or less (see: chlorosulfonic acid, under anhydrous conditions and in The Federal Register 39, No. 20, Part III, pp. the temperature range from about 0° C. to 10 C., to 3756-3797 (1974) and “The Control of Industrial Blad 40 give 2-hydroxy-1-naphthalenesulfonic acid (oxy-Tobias der Tumours', Scott and Williams, Brit. J. Industrial acid), removing HCl from the reaction mixture by de Medicine 14, pp. 150-163 (1957). Tobias acid produced sorption in vacuo and, by addition of aqueous ammonia on a large scale has therefore had to be subjected to solution and water, converting the reaction mixture into elaborate after treatments in order to meet this require a two-phase mixture consisting of an organic and an ment, or else production would have had to cease. Sur 45 aqueous phase, separating the resultant ammoniacal prisingly, it has now been found that Tobias acid con aqueous phase and extracting it with a water-immiscible taining only very insignificant amounts of 2-naphthyla organic solvent to remove 2-naphthol and stripping off mine, which lie far below the required limits, is obtained the residual organic solvent in the aqueous phase in by conducting the entire reaction to result in the forma vacuo, treating the extracted aqueous layer, under pres tion of the more readily soluble ammonium salts instead 50 sure, with ammonia and SO2 donors and heating it, of the formation of alkali metal salts in the intermediate stripping off NH3 from the aqueous reaction mixture steps. containing the ammonium salt of Tobias acid thereby The better solubility of the ammonium salt of oxy obtained and extracting the product solution with a Tobias acid permits the batches to be carried out in water-immiscible organic solvent, acidifying the ex higher concentrations than with alkali metal salts, 55 tracted aqueous suspension of Tobias acid at elevated whereby-as already mentioned-better space-time temperature, removing SO2 from the suspension by yields are obtained and, in connexion therewith, better desorption, cooling to 30° C., and collecting the prod utilisation of the investment required, of energy, and of uct by filtration, and, if desired, drying it, which process ecological measures, to mention only a few advantages. comprises The production of alkali metal salts of oxy-Tobias 60 (a) introducing into a suitable reaction vessel, simulta acid by sulfonation of 2-hydroxynaphthalene with neously and continuously, separate streams of a 20-30% chlorosulfonic acid is known. Attention is drawn in suspension of 2-hydroxynaphthalene in a water-immis particular here to U.S. Pat. No. 1,716,082 and Fierz cible organic solvent which is inert to chlorosulfonic David and Blangey, "Fundamental Processes of Dye acid, and of chlorosulfonic acid which may be diluted Chemistry” (Interscience Publishers Inc., New York, 65 with the same solvent, in the temperature range from 1949, pp. 199-200). -10° to +10 C., in such concentration and at such a The process of U.S. Pat. No. 1,716,082 results in rate of addition that an anhydrous reaction mixture oxy-Tobias acid salts which can be converted by amina having a molar ratio of chlorosulfonic acid to 2-hydrox 4,510,100 3 4 ynaphthalene of about 0.90 to about 1.05 to 1, prefera zene, but preferably dichloroethane. Suitable extract bly 0.95 to 1.05 to 1, is obtained, and leaving the reac ants for use in the reaction are aromatic hydrocarbons tion mixture for about 10 to 150 minutes in the reaction such as toluene, xylenes, or ethylbenzene, as well as the vessel, same solvents mentioned above. (b) removing HCl from the reaction mixture by de A particular advantage of the novel process to be sorption under a pressure of 100-400 mbar in the tem singled out for special mentioned is that the reaction perature range from 0 to 60° C., preferably from 5 to does not have to be initiated from substrates in solution, 15° C., but from suspensions. As the reaction can be initiated (c) treating the residual reaction mixture for 10 to 60 from an approx. 25% suspension of 2-hydroxynaphtha minutes with an aqueous 25-35% ammonia solution in O lene, it is accordingly possible to use an amount greater the temperature range from 40 to 80° C., preferably by about 60% in the reaction. Owing to shorter reaction from 60 to 75° C., until the pH value of the previously times in the succeeding steps and to the better solubility acid solution is at least 6 and adding sufficient further of the ammonium salts, the novel process makes it possi water that two liquid phases clearly form, advanta ble to obtain an approximately 100% better space-time geously with at least the same amount of water as of the 15 previously added ammonia solution, subsequently yield compared with prior art processes. (d) separating the organic solvent phase and the aque Pure or recycling chlorosulfonic acid is used for the ous phase after removal of residual 2-hydroxynaphtha process of the invention in a concentration of about lene by extraction with an organic water-immiscible 50% by weight and is diluted with the same solvent in solvent, preferably with the solvent employed in (a), 20 which the 2-hydroxynaphthalene is suspended. Lower stripping off remaining solvent in vacuo at 200-400 concentrations are not suitable on account of loss in mbar and in the temperature range from 60 to 80° C., space-time yields. Higher concentrations can be used in (e) treating the resultant ammonium salt of oxy individual cases. Tobias acid, without increasing the concentration be It is advantageous to use chlorosulfonic acid which is forehand, with NH3 and concentrated (NH4)2SO3 or 25 obtained by utilising hydrogen chloride gas which NH3HSO3 solution in the temperature range from 120° forms during the sulfonation or sulfochlorination with to 150° C. and at a pressure of 10 to 20 bar for 4 to 12 chlorosulfonic acid of e.g. aromatic hydrocarbons such hours until the pH value is 9 to 12, and, after stripping as naphthalene, anthracene or benzene, in an inert or off NH3 following an optional prior conversion of the ganic solvent as reaction medium. Such a hydrogen ammonium salt to the alkali metal salt with 20-40% chloride gas would normally have to be destroyed with alkali solution in the temperature range from 50° to 80 30 considerable expenditure of time and effort, as, depend C. and removal of 2-naphthylamine by extraction with ing on the vapour pressure of the organic solvent em an aromatic hydrocarbon, ployed prevailing under the reaction conditions, it con (f) adding to the reaction mixture, in the temperature tains a greater or lesser amount of this solvent. In order range from 30 to 70° C., sufficient dilute 40-60% sulfu 35 to be able to reuse this impure hydrogen chloride gas, it ric acid to adjust the pH value to 1.2–1.75, removing would first have to be freed from solvent. This would SO2 from the resultant suspension by desorption in require complicated operations in corrosion-proof ap vacuo at 0.1 to 0.9 bar and in the temperature range paratus. from 30 to 70° C., and, after cooling to about 30° C., The solvent-containing hydrogen chloride gas is re isolating the pure Tobias acid by filtration and, if de 40 acted with sulfur trioxide, at a temperature below 60 sired, drying it. C., in stoichiometric amounts, or in a small excess of For ecological reasons it is advantageous to treat the hydrogen chloride gas, in chlorosulfonic acid as reac ammonium salt of the Tobias acid obtained with alkali tion medium, to give chlorosulfonic acid. As the inert before the precipitation with sulfuric acid. The bulk of solvents contained in the hydrogen chloride gas are the ammonia employed in the reaction can thereby be 45 present throughout the entire process, the chlorosul recovered and is accordingly available for recycling. fonic acid obtained contains solvent. It is nonetheless a The following table of the solubilities of the sodium useful chemical reagent which can be used in sulfona and ammonium salts of oxy-Tobias acid affords clear tion and sulfochlorination reactions carried out in the evidence of the possibility of the better space-time same or a similar solvent medium. yields which can be obtained by the process of this 50 Further reagents which are employed are compounds invention. which donate ammonia or ammonia and sulfur dioxide, Solubility of oxy-Tobias acid in the form of the sodium e.g. aqueous 25-35% ammonia solution or ammonium and ammonium salt in water contingent on the bisulfite solution. temperature The novel process is preferably carried out continu 55 ously. Although the individual steps are carried out TABLE 1. batchwise, a continuous reaction course is achieved by Nasalt NHA salt Temp. % by weight % by weight including appropriately dimensioned stack vessels as °C. free acid free acid buffers in the entire process. 20 32.5 38.0 In detail, the process of the invention can be carried 30 34.0 4.5 60 out e.g. as follows, with reference to the diagram. 35 35.5 43.0 The reactants, a 20-30% suspension of 2-hydrox 45 38.0 47.0 ynaphthalene (HN) in an organic solvent which is inert 55 41.5 5.5 to chlorosulfonic acid, and chlorosulfonic acid which may be diluted with the same organic solvent, are Water-immiscible organic solvents which are inert to 65 charged separately into storage vessels. The reactants chlorosulfonic acid and are suitable as reaction media are then fed synchronously from the two storage vessels for the process of the invention are chlorinated hydro into an agitator vessel cascade I. The rate of addition is carbons such as o-dichlorobenzene, monochloroben in accordance with the scale of the apparatus and the 4,510,100 5 6 efficiency of the cooling means, as the reaction is exo ent. The so obtained sodium salt of Tobias acid contains thermic and a reaction temperature of 0° to 10° C. less than 30 ppm of 2-aminonaphthalene. should be kept. The addition of the reactants must be so The pH-controlled precipitation of Tobias acid is synchronised that the molar ratio of chlorosulfonic acid then carried out in the vessel IX by simultaneously to 2-hydroxynaphthalene is from 0.90 to about 1.05 to 1. introducing 40-60% sulfuric acid and reaction mixture The sulfonation is preferably carried out using less than in the temperature range from 40 to 70° C., preferably stoichiometric amounts of chlorosulfonic acid with from 45 to 55' C. The amount of acid added is such that respect to 2-hydroxynaphthalene. The dwell time in this a pH value of 1.2 to 1.75, preferably 1.5 to 1.75, results. cascade depends on the conditions stated above, and is This operation lasts 20-40 minutes. The SO2 liberated in on average about 70 minutes. The hydrogen chloride 10 the course of this operation can be exhausted immedi gas evolved is exhausted and absorbed or recycled for ately from the vessel or, alternatively, from the desorp the fresh production of chlorosulfonic acid as previ tion column X, or expelled with an inert gas and recy ously described. The hydrogen chloride gas still re cled to the process for the production of ammonium maining in solution in the reaction medium is desorbed bisulfite solution. The resultant Tobias acid is collected under a pressure of 100-400 mbar and in the tempera 15 by filtration on a filter press, washed neutral with water, ture range from 0 to 60° C. The preferred temperature and dried in vacuo. The yield of Tobias acid obtained range, however, is from 5 to 15° C. The sulfonation by the process of this invention, based on 2-hydrox mixture is then fed simultaneously with 25-35% aque ynaphthalene, is 93-98%. o ous ammonia solution into the neutralisation and reac The Tobias acid obtained by the novel process is a tion vessel II, the rate of addition being so controlled 20 valuable intermediate for the production of dyes. It is that a pH value of 6 to 6.5 results. The temperature used in particular as diazo or coupling component in the range in this step is from 40' to 80° C., with the pre production of diazo dyes. ferred range being from 60 to 75° C. Simultaneously, The novel process can be carried out as described in water is added to the reaction mass in an amount suffi the following Example. It will, of course, be understood cient to form two liquid phases, namely an aqueous 25 that, depending on the concentrations of the different product phase and an organic solvent phase which acts reactants employed, possibilities of varying the process as reaction medium. The amount of water, however, exists. depends primarily on the concentration in which it is desired to carry out the remainder of the process. For EXAMPLE economic reasons, the concentration of the product 30 A 22.6% crystalline, readily flowable suspension of mass will be kept as high as possible, i.e. just below the £8-naphthol in 1,2-dichloroethane is fed at a rate of 1560 solubility limit of the oxy-Tobias acid (see Table 1). The g/h (2.44 moles/h) synchronously with 279 g/h (2.39 dwell time in vessel II is from 10 to 60 minutes. The moles/h) of chlorosulfonic acid into an agitator vessel two-phase mixture is then passed into the separating cascade. The reaction temperature is kept at 0 to 5 C., vessel III and, at the same temperature as in vessel II, 35 and the dwell time in the reactor is about 75 minutes. the organic solvent phase is separated from the aqueous The hydrogen chloride evolved during the sulfona phase. The aqueous phase is freed from remaining unre tion is absorbed and that still dissolved in the reaction acted 2-hydroxynaphthalene in a countercorrent extrac mass is removed by desorption in vacuo at 0° to 5' C. In tion column IV using the same solvent as mentioned at an agitator vessel, a 30% ammonia solution is then the outset. The temperature range in this operation is in 40 added continuously to the sulfonation mass at a rate of the range from 40 to 80° C. After extraction in the 145 g/h (2.55 moles/h), at pH 6 to 6.5 and 70-75° C. stripper V, the solvent remaining in the aqueous phase is The reaction mass is simultaneously diluted with water distilled off under a pressure of 200-400 mbar and in the at a rate of addition of 234 g/hand, after a dwell time of temperature range from 60 to 80° C. The aqueous 22 minutes, pumped into a heated separator, where the phase then contains the ammonium salt of oxy-Tobias 45 organic solvent phase is separated from the aqueous acid as intermediate. At a temperature of about 70° C., product phase at 70°-75° C. The aqueous phase (solu The concentration of the dissolved salt is in the range tion of the ammonium salt of oxy-Tobias acid) is freed from 50 to 55%. This high concentration procedure from unreacted g-naphthol at the same temperature in a leads to very good results in respect of space-time yield multistage heated countercurrent extraction column and product quality. 50 with 1,2-dichloroethane at a rate of 1000 g/h. The 1,2- The solution of the NH4-salt of oxy-Tobias acid dichloroethane still remaining in the solution of the (OTS) is then passed into a reaction column VI. Simul ammonium salt of oxy-Tobias acid is removed by distill taneously, liquid ammonia and 40-55% NH4SO3 solu lation at about 390 mbar and 70-75 C. The 1,2- tion are fed into the reactor VI in molar amounts up to dichloroethane phase containing (3-naphthol is ex an excess of 50%, based on the oxy-Tobias acid salt. 55 tracted with water and recycled after removal of the The temperature is raised to 130-150° C., the pressure water. Yield: 1100 g/h of a 51.4% solution of the ammo simultaneously rising to 10-20 mbar. The dwell time in nium salt of oxy-Tobias acid, which is free from dichlo the reactor under these conditions is 4 to 12 hours, on roethane and contains about 30 ppm of 3-naphthol. The average 8 to 10 hours. The pressure is then reduced and yield of oxy-Tobias acid is 98.3% of theory, based on sufficient NaOH solution is added to the reaction mass 60 the £3-naphthol employed, up to this phase of the reac that all ammonia to be liberated in this manner escapes. tion. The remaining ammonia is stripped off in column VII. 1100 g/h of the ammonium salt of oxy-Tobias acid The resultant sodium salt of Tobias acid is then diluted (51.4%), 165 g/h of 100% ammonia and 231 g/h of 54% to a concentration of 20-30% with water and extracted ammonium bisulfite solution are passed into a reaction in the countercurrent extraction column VIII with tolu 65 column equipped with stirrer and subdivided into cham ene or a similar aromatic hydrocarbon, in the tempera bers. The temperature in the reactor is kept at 140 C. ture range from about 60' to 80° C., in order to remove The dwell time is 8.5 hours, and the pressure is adjusted small amounts of 2-aminonaphthalene (AN) still pres to 15 bar. The oxy-Tobias acid is reacted under these 4,510, 100 7 8 conditions almost completely (>98%) to Tobias acid. and, after stripping off NH3 and removal of 2-naph After the reaction mixture has passed through the reac thylamine by extraction with an aromatic hydro tor, the pressure is reduced to atmospheric pressure. carbon, The reaction mixture is then mixed with aqueous 20% (f) adding to the reaction mixture, in the temperature NaOH solution (480 g/h) in order to convert the ammo- 5 range from 30 to 70° C., sufficient dilute 40-60% nium salt into the sodium salt. The ammonia is then sulfuric acid to adjust the pH value to 1.2-1.75, stripped off in a distillation column and recycled to the removing SO2 from the resultant suspension by reaction. The solution of the product flowing out from desorption in vacuo at 0.1 to 0.9 bar and in the the bottom of the column is diluted with water to a temperature range from 30 to 70° C., and, after concentration of about 250 g of sodium salt of Tobias 10 cooling to about 30° C., isolating the pure Tobias salt per liter, and extracted continuously with toluene at acid by filtration and, if desired, drying it. 70-75 C. in a countercurrent extraction column. In 2. A process according to claim 1, which comprises this manner, 2-naphthylamine is removed from the diluting the chlorosulfonic acid in step (a) with the same product solution to an insignificant residual concentra solvent as is used for the extraction of 2-hydroxynaph tion of about 10 ppm with respect to Tobias acid. The 15 thalene, carrying out the desorption of HCl in step (b) in free Tobias acid is then precipitated from this solution the temperature range from 5 to 15 C., carrying out by addition of 50% sulfuric acid (about 540 g/h), while the formation of the ammonium salt of oxy-Tobias acid keeping the temperature at 50-55 C. and the pH value in step (c) in the temperature range from 60 to 75 C. between 1.5 and 1.75. The SO2 liberated during this and, after the addition of ammonia, adding at least the operation is desorbed and recycled to the process. The 20 same amount of water as of the previously added am product is collected by filtration, washed with cold monia for better phase separation, extracting the aque water, and dried in vacuo at 70-75 C. The yield of ous phase in step (d) with the same solvent as is used in isolated Tobias acid is 95% of theory, based on oxy step (a), and, in step (e), before stripping off the ammo Tobias acid. The concentration of 2-naphthylamine is nia, converting the ammonium salt of Tobias acid into <30 ppm. 25 the alkali metal salt to recover the ammonia by addition What is claimed is: of 20-40% aqueous alkali solution, in the temperature 1. A process for the production of 2-amino-1-naph range from 50° to 80° C. thalenesulfonic acid (Tobias acid), which comprises 3. A process according to claim 1, wherein the water (a) introducing into a suitable reaction vessel, simulta immiscible organic solvent which is inert to chlorosul neously and continuously, separate streams of a 30 fonic acid is monochlorobenzene, dichlorobenzene, 20-30% suspension of 2-hydroxynaphthalene in a dichloroethane or tetrachloroethane. water-immiscible organic solvent which is inert to 4. A process according to claim 1, wherein the sol chlorosulfonic acid, and of chlorosulfonic acid vent used for extraction is an aromatic hydrocarbon. which may be diluted with the same solvent, in the 5. A process according to claim 1, wherein the sulfo temperature range from -10 to +10 C., in such 35 nation in step (a) is carried out with less than the stoi concentration and at such a rate of addition that an chiometric amount of chlorosulfonic acid, based on anhydrous reaction mixture having a molar ratio of 2-hydroxynaphthalene. chlorosulfonic acid to 2-hydroxynaphthalene of 6. A process according to claim 1 which comprises, in about 0.90 to about 1.05 to 1 is obtained, and leav step (a), introducing into an agitator vessel cascade, ing the reaction mixture for about 10 to 150 minutes 40 simultaneously and continuously, separate streams of in the reaction vessel to give 2-hydroxy-1-naphtha reactants consisting of a 23% suspension of 2-hydrox lenesulfonic acid (oxy-Tobias acid), ynaphthalene in 1,2-dichloroethane and chlorosulfonic (b) removing HCl from the reaction mixture by de acid diluted with the same solvent, in the temperature sorption under a pressure of 100-400 mbar in the range from 0 to 5 C., in such concentration and at such temperature range from 0 to 60° C., 45 a rate of addition that an anhydrous reaction mixture (c) treating the residual oxy-Tobias acid containing with a molar ratio of chlorosulfonic acid to 2-hydrox reaction mixture for 10 to 60 minutes with an aque ynaphthalene of about 0.95 to 1 is obtained, and leaving ous 25-35% ammonia solution in the temperature the reaction mixture from about 70 minutes in the reac range from 40 to 80° C. until the pH value of the tion vessel, in step (b) removing hydrogen chloride previously acid solution is at least 6, to get the 50 from the reaction mixture by desorption under a pres ammonium salt of the oxy-Tobias acid and adding sure of 100-400 mbar and in the temperature range from sufficient further water that two liquid phases 5 to 10° C., in step (c) adding a 23-25% ammonia solu clearly form, subsequently, tion to the reaction mixture over the course of 10 to 60 (d) separating the organic solvent phase from the minutes, and in the temperature range from 60 to 75 aqueous phase and after removal of residual 2 55 C., until the pH of the previously acid solution is at least hydroxynaphthalene by extraction with an organic 6, and diluting the reaction mixture with at least the water-immiscible solvent, stripping off remaining same amount of water as of the previously added am solvent from the aqueous phase in vacuo at monia solution, in step (d) separating the organic sol 200-400 mbar and in the temperature range from vent phase and the aqueous phase after removal of the 60 to 80° C., remaining ammonia by extraction with 1,2-dichloroe (e) treating the resultant aqueous solution of the am thane, and stripping off remaining solvent from this monium salt of oxy-Tobias acid, without increasing phase under a pressure of 200-400 mbar in the tempera the concentration beforehand, with NH3 and con ture range from 60 to 80° C., in step (e) treating the centrated (NH4)2SO3 or (NH4)HSO3 solution in the ammonium salt of oxy-Tobias acid, without increasing temperature range from 120 to 150 C. and at a 65 the concentration beforehand, with liquid NH3 and pressure of 10 to 20 bar for 4 to 12 hours until the concentrated NH4HSO3 solution in the temperature pH value is 9 to 12, to give the ammonium salt of range from 120 to 150 C. and at a pressure of 10 to 20 2-amino-1-naphthalenesulfonic acid (Tobias acid), bar over the course of 8 to 10 hours until the pH value 4,510,100 9 10 is 9-11, and, after stripping off NH3 following conver moving SO2 from the resultant suspension by desorp sion of the ammonium salt into the alkali metal salt by tion in vacuo at 0.1 to 0.5 bar and in the temperature addition of 20-40% alkali solution in the temperature range from 45 to 55° C. and, after cooling to about 30" range from 50 to 80 C., and removing 2-naphthyla C., isolating the pure Tobias acid by filtration, and mine by extraction with toluene, in step (f) simulta washing and drying it. neously adding the reaction mixture, in the temperature 7. A process of claim 4 wherein the aromatic hydro range from 45 to 55° C., to sufficient dilute 40-60% carbon is toluene, xylene or ethyl benzene. sulfuric acid that a pH value of 1.5 to 1.75 results, re k ck k xk k

65 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. : 4,510,100 DATED : April 9, 1985 NVENTOR(S) : Eric Plattner, et all It is certified that error appears in the above-identified patent and that said Letters Patent is hereby corrected as shown below: Col. 5, line 47 Delete "The" and substitute --the-- Col. 8, line 48 - After "mixture" delete "from" and substitute --for-- eigned and sealed this Twenty-seventh D ay of August 1985 (SEAL Attest:

DONALD J. QUIGG Attesting Officer Acting Commissioner of Patents and Trademarks