Aug. 28, 1956 E. W. SCHOEFFEL ETAL 2,760,992 PRODUCTION OF BETA-NAPHTHOL Filed July 9, 1953 NAPHTHALEN F. SULFONATION (Y ANDA-NAPHTHALENESUFON C. ACD STEAM TREATMENT NAPHTHALENE STEAM a-NAPHTHALENESUFONIC AC D AT LEAST 90°C. Al-KAL ANDAT LEAST THE WAPOR PRESSURE OF THE ELEVATED TEMPERATUR MXTURE PRESSURE AND AGITATION SUFFICENT AGITATION TON SURE A PUMPABLE HYDROLYSS SLURRY, EVEN AT ROOM TEMPERATUR WATER FILTER - PREC PTATE sal ACD PURFICATION AND CRYSTALLIZATION N.VENTOR ae-ze 16/32%4 z 12.4% /27 afze/2-w a- NAPH THOL 12 4% 44.2% AORNEY 2,760,992 United States Patent Office Patented Aug. 28, 1956 2 any appreciable quantity of the beta acid is hydrolyzed. A considerable proportion of the naphthalene formed volatilizes with the steam. The residue from the steam 2,760,992 ing operation contains, besides a certain amount of water, PRODUCTION OF BETANAPHTHOL Sulfuric acid, naphthalene and other alkali-insoluble sub stances, a high proportion of beta-naphthalenesulfonic Eugene W. Schoeffe, and Daniel M. Barton, Kronen acid, but is substantially free from alpha-naphthalene wetter, Wis., assignors to Siering Driggae, New York, Sulfonic acid. N. Y., a corporation of Delaware The conversion of the beta-naphthalenesulfonic acid Application July 9, 1953, Serial No. 367,110 present in the residue from the steaming operation to 0. beta-naphthol having a satisfactory degree of purity has, 8 Claims. (C. 260-628) however, heretofore presented several operational diffi culties. It has been found that, when sufficient sodium hydroxide is added to the mixture to render it alkaline, This invention relates to a method for the preparation 5 the sodium beta-naphthalenesulfonate precipitates almost of phenolic compounds, particularly to a method for the completely due to its rather low solubility in water and preparation of beta-naphthel. the salting-out effect of the sodium sulfate resulting from Phenolic compounds are generally made on a com the neutralization of the sulfuric acid in the solution. mercial scale either by the hydrolysis of a sulfonic acid This condition is further aggravated when excess alkali or of a halogen compound, the process involving the re 20 is added to the mixture in an attempt to form a strongly placement of the sulfonic acid radical or of the halogen, alkaline aqueous mixture which can be subjected directly respectively, with a hydroxyl group. The replacement to hydrolysis under pressure to form beta-naphthol. of a halogen with hydroxyi, as in the preparation of Such strongly alkaline mixtures are so extremely thick phenol from monochlorobenzene, is usually carried out that they cannot be pumped and handled, or even stirred by mixing the halogen compound with a sufficient amount 25 with any degree of facility. Excess dilution of the mix of aqueous sodium hydroxide to form sodium phenolate ture with water not only renders the process uneconomi and sodium chloride, slightly more than the theoretically cal because of the size of the equipment required, but required amounts of alkali generally being employed. also because of the reduced rate of hydrolysis of the The reaction is carried out at an elevated temperature, Sodium beta-naphthalenesulfonate in dilute solutions or usually in the neighborhood of 350 degrees centigrade 30 Suspensions. or even somewhat higher, and sufficient agitation of the For these reasons it has been the practice in the past mixture is used to insure intimate contacting of the two to add a large quantity of water and sufficient alkali to liquid phases. The process is generally carried out in a the Steam distilled sulfonation mixture to neutralize both long, tubular reactor maintained at the reaction tem the Sulfuric acid and the beta-naphthalenesulfonic acid perature and the liquid mixture is forwarded through the 35 and to then filter the mixture and wash the filter cake tube sufficiently rapidly to cause turbulent flow whereby to recover the precipitated sodium beta-naphthalenesul the two liquid phases are intimately and continuously fonate. The cake is subsequently dried and fused with mixed with one another. sodium hydroxide in non-pressurized kettles in known Although the process just mentioned for the produc fashion. This procedure offers considerable difficulty in tion of phenol from monochlorobenzene has been applied 40 the filtration of the precipitated sodium beta-naphthalene to the production of beta-naphthol from beta-chloro Sulfonate, since it requires the filter cake to be dried and naphthalene, the results have not been particularly satis involves difficulties inherent in any alkali fusion process. factory. In part, these unsatisfactory results are due to An undesirably large proportion of the sodium beta the difficulty of obtaining beta-chloronaphthalene in suffi naphthalenesulfonate remains unprecipitated and is lost cient purity to permit the production of pure beta 45 in the filtrate. The process, furthermore, does not offer naphthof. During the chlorination of naphthalene for any opportunity for separating from the naphthalene the production of beta-chloronaphthalene, a considerable sulfonic acid or its sodium salt the alkali-insoluble-mate proportion of alpha-chloronaphthalene is also formed and rials formed during the sulfonation and subsequent steam the separation of the two chloronaphthalenes is difficult distillation, so that the fusioin process must be carried and costly. If the mixture cf chloronaphthalenes is sub 50 out with these substances presert, unless a separate ad mitted to the hydrolysis with alkali without being sep ditional filtration of the diluted highly acid solution is arated from one another, there is formed a mixture of resorted to prior to the alkalization. This necessitates alpha- and beta-naphthols and the separation of these additional purification steps during the isolation of the compounds is likewise difficult and costly. beta-naphthol from the fusion melt, which, of course, For these and cther reasons, the preparation of beta 55 decreases the efficiency and adds to the cost of the proc naphthol has usually been effected by first sulfonating ess. It is also known that unless the sodium beta-naph naphthalene and then replacing the Sulfonic acid radical thalenesulfonate is purified prior to the fusion operation, with a hydroxyl group by reaction with an alkali. Al the presence in the alkali fusion mixture of the alkali though, as in the case of the halogenation of naphthalene, insoluble and other non-sulfonates remaining in the the sulfonation of naphthalene leads to a sulfonation 60 steamed sulfonic acid mixture leads to excessive decom product which contains both alpha-naphthalenesulfonic position of the beta-naphthalenesulfonate to form sub and beta-naphthalenesulfonic acids, the proportion of the stances other than beta-naphthol to such a degree that former in the sulfonation mixture is relatively low and without the purification step the entire process becomes the separation of the beta acid in relatively pure form highly uneconomical. Furthermore, the beta-naphthol from the mixture can be effected without great difficulty. 65 obtained is of very poor quality due to the presence One convenient way for obtaining beta-naphthalenesul therein of the decomposition products which are difficult fonic acid substantially free from alpha-naphthalenesul to renowe. fonic acid comprises blowing steam through the crude Attempts have been made to mix the steamed sulfona sulfonation mixture. Under such conditions, the alpha tion mixture and the alkali directly in the fusion kettle naphthalenesulfonic acid is hydrolyzed at a much more without any preliminary separation or purification of the rapid rate than is the beta acid, and all of the alpha 70 beta-naphthalenesulfonic acid or its salt. ... Such a process, acid is converted to naphthalene and Sulfuric acid before however, gives only an inferior yield of beta-naphthol 2,760,992 3 4. and does not avoid the necessity of separating alkali naphthalenesulfonic acid and which, in the free form, insoluble materials from the beta-naphthol. This modifi decomposes to non-acidic constituents, e.g., Sulfur diox cation of the process has been found to be highly un ide or carbon dioxide. As a matter of feasibility, con satisfactory. venience and economy, alkalies which are compounds of Beta-naphthol is being commercially prepared by batch Sodium are generally employed and, also as a matter to methods although a continuous sulfonation procedure convenience, the invention will be described with par would be more desirable. The reason why no continuous ticular reference thereto. process has been developed is the difficulty of converting Preferred sodium compounds for use in neutralizing the Sodium beta-naphthalenesulfonate to beta-naphthol the sulfonic acid mixture are sodium hydroxide and so by a continuous method. Our invention is primarily O dium sulfite or bisulfite. The use of sodium hydroxide concerned with the method for a continuous operation is advantageous in that there is no evolution of gas during and production of beta-naphthol with yields approximat the neutralization and thus no tendency for the mixture ing 90-95 percent based on the naphthalene used. Fol to foam is encountered as is the case when a sodium car lowing the procedure of our invention, as hereinafter de bonate or sulfite is used. in certain instances, however, scribed, laboratory and pilot plant operation has 15 the use of sodium sulfite or bisulfite is preferred because established the feasibility of continuous beta-naphthol the liberated sulfur dioxide can be recovered and used production and has concomitantly produced a beta subsequently for acidifying the mixture from the hydroly naphthol of excellent purity and quality. sis of the sulfonic acid to liberate beta-naphthol there The accompanying flow sheet, Figure 1, is a diagram from. In such case the aqueous liquor remaining after matic representation of the process of the present inven the separation of the beta-naphthol contains sodium sul tion. This flow sheet is for the purpose of illustration fite or bisulfite not only equivalent to the sulfur dioxide only and is not to be construed as limiting the invention added, but also that formed by hydrolysis of the sulfonic thereto.