Patented Apr. 30, 1935 1999,955 UNITED STATES PATENT office 1999,955 if PRODUCTION OF RESORCNOL AND MDX. TURES THEREOF WITH PHENO James Irvin Carr and Miles Augustinus Dahlen, Wilmington, Del, assignors to E. I. du Pont de 4. Nemoursporation of& DelawareCompany, Wilmington, Del, a cor No Drawing. Application May 26, 1933, Serial No. 673,101 4. Claims. (C. 260-154) This invention Irelates to a process for the prep preparation of resorcinol, benzene is sulfonated aration of resorcinol and mixtures thereof With to the monosulfonate with sulfur trioxide in a phenol. medium of liquid sulfur dioxide and then to the ReSorcinol, otherwise known as meta-dihy disulfonic-acid stage with Sulfur trioxide in the 5 droxy-benzene, has been manufactured on a com absence of any diluent. 5 mercial scale for many years. Although the proc The resultant product is then hydrolyzed di esses now used and those which have become ob rectly by reaction with a suitable hydrolyzing solete have shown many variations, the funda agent Such as, for example, sodium hydroxide or mental principles and chemical reactions in other alkali metal hydroxide. The resorcinol is O wolved have remained substantially unchanged readily recovered by any convenient method, for 10 since the early days of manufacture. The oper example, by acidifying the reaction product foll ations and reactions which still form the basis lowed by extraction. The resorcinol is obtained for most successful processes start with the Sul in high yield and in a relatively high state of fonation of benzene with strong sulfuric acid or purity. oleum, the quantity of acid being greatly in ex The following example is illustrative of the pre- 15 cess of that required by theory. The chief prod ferred procedure for carrying out this invention. uct of the reaction is benzene-meta-disulfonic All quantities are stated in parts by weight. acid, but important quantities of the Ortho and para-isomers and other by-products are likewise Eacample 1 20 formed. The sulfonation mass is diluted with 78 parts of benzene are dissolved in about 200 20 water and neutralized with lime to convert the parts of liquid sulfur dioxide. 83 parts of sulfur excess sulfuric acid and the sulfonic acids to the trioxide are dissolved in enough liquid Sulfur di corresponding calcium salts. The calcium Sul Oxide to make the volume of the solution equal to fate formed is filtered off and the filtrate contain that of the benzene solution. A suitable sulfona 25 ing the calcium-benzene-disulfonate is heated tor equipped with an agitator and a means of 25 with the correct amount of sodium carbonate to heating and cooling is charged with about 900 convert the calcium salt to the di-sodium Salt and parts of liquid Sulfur dioxide. The Sulfonator precipitate the displaced calcium as calcium car and tanks containing the benzene and sulfur tri bonate. After the calcium carbonate is separated Oxide solutions are closed and the Sulfonation is 30 by filtration, the solution of benzene-disodium carried out under pressure to prevent the escape 30 meta-disulfonate is concentrated by evaporation of the diluent. An equalizing system is used to and fused with an excess of caustic Soda. Over maintain the same pressure in the sulfonator and the amount required by theory. The principal addition tanks. products of the fusion are the Sodium Salt of res The Solutions of benzene and Sulfur trioxide 35 orcinol and sodium sulfite. The melt is dissolved are added to the sulfonator at approximately the 35 and treated with an acid such as Sulfur dioxide same rates, in order that any considerable excess to liberate resorcinol from the sodium Salt, and of either reactant is avoided during the monosul the final operation consists in removal of the res fonation of the benzene. The addition of the re orcinol by a suitable immiscible solvent. actants may be carried out conveniently in four 40 The outstanding disadvantage of the usual pro hours, although this factor may be varied over a 40 cedures is the necessity of using a large excess of wide range. During this sulfonation, the tem sulfonating acid, this excess forming no useful perature is held at 10-35 C. by-product, and greatly complicating the Subse After the addition of benzene and sulfur tri quent procedure. Oxide as above described is complete, 83 parts of An object of the present invention is to provide, Sulfur trioxide are added. This second portion 45 a new and improved process for the manufacture may or may not be diluted with sulfur dioxide as of resorcinol. Another object is to avoid the for desired. The sulfur dioxide is then removed from mation of considerable amounts of comparatively the Sulfonation mass by distillation, the solvent useless by-product. A further object is to provide being recovered and re-liquefied for use in subse a new outlet for utilizing Sulfur dioxide which quent sulfonations. The sulfonation mass is fi- 50 may occur in large quantities as a by-product of nally heated to 100° C. to remove as much as pos other chemical processes. Other objects will ap Sible of the sulfur dioxide, and to accelerate the pear hereinafter. disulfonation process. When sulfonation is com These objects are acconnplished by the follow plete, which may be judged by the disappearance 5 ing invention in which as the first steps in the of free Sulfur trioxide, the mass is cooled and 55 2 1999,955 diluted with three times its weight of water. It consisting chiefly of benzene-sulfonic-acid, is is then neutralized by the addition of an equiva added 50 parts of sulfur trioxide with suitable lent quantity of sodium carbonate. The Solu cooling. This addition is most Suitably carried ground.tion is evaporated to dryness, and the product out at 50-100° C. The mass is then heated slow The benzene-disodium-disulfonate obtained as ly to 150° C. and held at that temperature until above may be converted to resorcinol as follows: Sulfonation is complete. It is cooled to about About 750 parts of caustic soda and 15 parts of 30° C., diluted with an equal volume of water, and Water are heated in a cast iron pot equipped with neutralized carefully with a 30 per cent solution O an agitator. When the temperature reaches 300 of Sodium hydroxide. The neutralized solution C., the ground disulfonate is slowly added over a is then evaporated to a thick paste, consisting O period of about one hour, the temperature being chiefly of benzene-sodium-sulfonate, benzene maintained at 295-305° C. during this addition. disodium-disulfonate and water. The mass is then heated to 350° C. during about The fusion pot is charged with 700 parts of 5 30 minutes. The melt is cooled and dissolved in caustic soda and 15 parts of water and heated to Water. Sufficient sulfur dioxide gas is added to 300 C. The paste of sulfonates prepared as 15 liberate the resorcinol from the sodium salt. The above is then slowly added, holding the tempera Solid Sodium sulfite, which precipitates during this ture at 300-310 C. The water in the paste is thus acidification, is removed by filtration. The removed in the form of steam. When all has 20 aqueous filtrate is then extracted with ether. been added, the temperature is raised to 340 The ether extract is now distilled. The first 350 C. in a period of 30 minutes and held at 20 fraction, consisting of ether, is returned to the that point for 15 minutes. It is, then cooled and operation for use in further extractions, The diluted with water. The solution is acidified second portion consists of water and a little with Sulfuric acid, enough acid being used to lib phenol. From this fraction, a small amount of erate completely the phenol and resorcinol. The phenol may be recovered if economical. The volume of the Solution at this point should be 25 third fraction, distilled preferably under vacuum, large enough to retain in solution all the so consists of resorcinol. The product thus obtained dium sulfate produced in the neutralization. is of satisfactory quality; and the yield varies This Solution is extracted with ether, as in Ex .30 ample 1, and fractionally distilled as before. In from 40 to 60 per cent of theory, based on the ben this case, the intermediate fraction containing Zene used. the phenol is quite large, due to the large propor 30 As already mentioned in a brief description of tion of monoSulfonate obtained in the sulfona the process, and as shown in the foregoing exam tion process. By the use of proper distillation 35 ple, the Second Sulfonic-acid group is introduced equipment, a good separation of phenol and res by digesting with another mole (usually plus a Orcinol may be effected, both products being ob slight excess) of sulfur trioxide without sulfur tained Substantially pure. 35 dioxide or other diluent. The introduction of In Order to minimize the amount of diphenyl this second sulfonic-acid group does not proceed sulfone formed in the monosulfonation, it has 40 smoothly and completely in a sulfur dioxide me been found important to follow strictly the mix dium under practical conditions, hence the sulfur ing procedure described in the examples; that is, dioxide diluent is removed either before or di dissolve the benzene and sulfur trioxide separate 40 rectly after the addition of the second portion of ly in liquid Sulfur dioxide and then add the so Sulfur trioxide. Essentially, the second sulfona lutions simultaneously and preferably at an ap tion consists in reacting benzene-mono-sulfonic proximately equal rate of flow to a relatively large acid with Sulfur trioxide, as expressed by the fol amount of liquid sulfur dioxide.