ul Patented July 6, 1926. 1,591,712 UNITED STATES PATENT OFFICE. HARRY F. T.EWIS, OE BUFFALO, NEW YORK, ASSIGNOR, to NATIONAL ANILINE & CHEMICAL COMPANY, INC., OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK. PURIFICATION OF ANTHRAQUINONE. No Drawing. Application filed IIarch 4, 1920. Serial No. 363,261. This invention relates to the purification lar alkali employed. The strength of the of anthraquinone, and more particularly to alkali solution can also be varied, from rela the purification of anthraquinone admixed tively dilute solutions to concentrated solu With other oxidation products, such as the tions. The purification is best effected at oxidation products of carbazol and other a temperature between about 50 and 100° C., nitrogen bases and the carboxy and phenolic but lower temperatures may be used. The 60 Oxidation products of other hydrocarbons. inpurities particularly removed by such In the production of anthraquinone by alkaline treatment are those above indicated, Oxidizing anthracene, for example, with a namely, the oxidation products of carbazol O Solution of chromic acid, or with an acid and other nitrogen bases, as well as the Solution of sodium or potassium dichro carboxy and phenolic oxidation products of mate, such impurities as are admixed with Such hydrocarbons as methylanthracene. the anthracene are subjected to the same phenanthrene, acenaphthene, etc., and oxida Oxidizing agent or agents as is the anthra tion products which contain chromium as a s cene itself. As a result, the anthraquinone constituent. produced, after separating the constituents In the preferred practice of the inven O which are soluble in Water or in the acid tion, the crude anthraquinone is extracted Solution, contains various impurities in ad with hot alkaline solution in amount, from mixture therewith. The nature and amount about five to ten times the Weight of the of the impurities will vary somewhat with anthraquinone, and the resulting solution is the method of production, and also with the filtered while still hot from the undissolved 5 purity of the anthracene used as the starting anthraquinone and from alkali insoluble material for the oxidation. Thus, where the impurities. The purified anthraquinone anthracene contains other hydrocarbons or thus obtained is then Washed with an amount nitrogenous bases admixed therewith, such of hot alkaline Solution about equal to the as phenanthracene, fluorene, picene, acenaph Weight of the anthraquinone, and it is finely 80 thene, methylanthracene, pyrene, chrysene, washed with water until it is free from retene, carbazol, etc., the anthraquinone alkali. produced will contain an unchanged anthra Where the anthraquinone is unusually 30 cene or other hydrocarbons, and any oxida impure, or where a product of increased tion products thereof, such as varying purity is desired, the purification by ex 85 amounts of part or all of the followingma traction with alkali can be repeated one or terials, namely, diphenic acid, carbazol and more times until Such impurities as have its oxidation products, other nitrogenous escaped extraction by the first treatment 35 substances and their oxidation products, car have been substantially removed. boxy and phenolic oxidation products of The impurities which are thus extracted 90 hydrocarbons, etc. The purification of the from the crude or impure anthraquinone impure anthraquinone accordingly involves may themselves be recovered for use or for separating the anthraquinone from such im further treatment by acidifying the alkaline purities. filtrate thereby precipitating the impurities The present invention is based upon the from Solution. The impurities thus sepa 95 discovery that impure anthraquinone con rated can be filtered off and thus recovered taining impurities of the character above in a form adapted for use or for further referred to, can be purified and materially treatment. 45 improved by extracting the crude or in Warious forms of apparatus can be used pure product, obtained in the usual way by in the practice of the invention, but an ordi OO the oxidation of anthracene with a chromic nary wooden vat equipped with a stirrer and acid mixture, with an alkaline solution of with steam pipes is well adapted for use. In suitable strength. The alkali used may be the use of such an apparatus, the crude an 50 Sodium, ammonium, or potassium hydroxide thraquinone can be charged into the vat, or the carbonates of these metals, or a weaker together with the alkaline solution, and the 05 base such as barium hydroxide. The amount temperature raised by means of the steam of the alkali will vary somewhat with the coils until the desired temperature is amount of impurity and with the particu reached. This temperature is maintained,

2. 1,591,712 with agitation of the suspension, over a suit an alkaline solution and separating the re able period of time, for example, about One sulting solution of impurities from the un hour. The suspension is then filtered hot, dissolved purified anthraquinone. and preferably as rapidly as possible. 3. The method of removing carboxy and The process of the present invention is phenolic products from impure anthraquin 70 applicable not only to the crude anthra one containing impurities of the type pro irinone produced by the oxidation of an duced by oxidation of anthraquinone with AE with a chromic acid mixture, but chromic-sulfuric acid solution which com also to the purification of commercial an prises subjecting the impure anthraquinone, O thraquinone produced by other processes, or without preliminary treatment with sulfuric purified by other methods of purification, acid, to extraction with an alkaline solu where it is still admixed with impurities of tion, and separating the resulting solution the character above referred to. from the undissolved anthraquinone. The invention will be further illustrated 4. The method of separating oxidation 5 by the following specific examples, the parts products containing chromium as a constitu 80 being by weight: ent obtained by oxidizing impure anthracene by means of a chromic-sulfuric acid oxidiz Eacample 1. ing mixture, which comprises subjecting im Ten parts of crude anthraquinone pro pure anthraquinone without preliminary 20 duced from anthracene by oxidation with a treatment with sulfuric acid containing such 85 chromic acid mixture, are boiled with one oxidation products to the action of an al hundred parts sodium hydroxide solution, kaline solution and separating the resulting with agitation of the mixture until theim solution from the purified anthraquinone. purities have been dissolved by the alkaline 5. The method of purifying impure an 25 solution. The solution is then filtered. and thraquinone containing impurities of the 90 the purified anthraquinone washed with al type produced by oxidation of anthracene kali solution and then with water and dried. with chromic-sulfuric acid solution which Crude anthraquinone can thus be materially comprises subjecting the impure anthraquin improved in purity, and freed from a con one to extraction with a hot caustic soda 30 siderable portion of nitrogenous bases or solution, separating the hot solution from 9S their oxidation products, as well as from the undissolved purified anthraquinone, and oxidation products which may contain chro washing the purified anthraquinone with a mium as a constituent. The alkaline fil hot caustic soda solution, and finally with trate is then acidified to precipitate the ex water until the product is substantially free tracted impurities, and the impurities are re from alkali. OO covered in this way. 6. The method of purifying impure an Eacample 8. thraquinone containing impurities of the type produced by oxidation of anthracene Ninety parts of crude anthraquinone are with chromic-sulfuric acid solution which 40 agitated at 95° C. for one hour with one comprises subjecting the same to extraction 05 thousand parts of 5% caustic soda solution, with a hot caustic soda solution until part of the solution then filtered hot and the residue the impurities are extracted therefrom, sep washed with water until the wash water is arating the hot solution from the partly neutral. A high recovery of anthraquinone purified anthraquinone, and repeating the ex 45 is thus obtained of materially increased pu traction with further amounts of hot caus O rity. tic soda solution to effect the extraction of I claim: further impurities therefrom. 1. The method of purifying impure an 7. The method of purifying crude anthra thraquinone, which contains impurities of quinone containing impurities of the type 50 the type produced by oxidation of anthra produced by oxidation of anthracene with 5 cene with chromic-sulfuric acid solution, chromic-sulfuric acid solution from other which comprises subjecting said impure an oxidation products, including oxidation thraquinone without preliminary treatment products of carbazol, which comprises heat with sulfuric acid to extraction with a hot ing the anthraquinone with about five to ten 55 alkaline solution and separating the result times its weight of a caustic alkali solution, 20 ing solution of impurities from the undis agitating the crude anthraquinone with the solved purified anthraquinone. hot alkaline solution for a considerable 2. The method of removing products of period of time to bring about solution of oxidation of nitrogen bases from impure an soluble impurities and filtering the resulting 30 thraquinone containing impurities of the solution while still hot from the undis 25 type produced by oxidation of impure an solved anthraquinone. thracene with chromic-sulfuric acid solu 8. The method of purifying crude anthra tion which comprises subjecting the impure quinone containing impurities of the type anthraquinone, without preliminary treat produced by oxidation of anthracene with 35 ment with sulfuric acid, to extraction with chromic-sulfuric acid solution which com 30

u 1,591,712 prises heating the crude anthraquinone with chromic-sulfuric acid solution which com an alkaline solution without preliminary prises heating the crude anthraquinone with treatment with sulfuric acid, agitating the a caustic soda solution, agitating the mix mixture and continuing the heating and ture and continuing the heating and agita agitation to bring about solution of soluble tion to bring about solution of soluble im impurities, filtering the resulting solution purities, filtering the resulting solution from from undissolved anthraquinone, and wash undissolved anthraquinone, and Washing the ing the anthraquinone with a further amount anthraquinone with a further amount of 20 of alkali solution. caustic soda solution. 10 9. The method of purifying crude anthra In testimony whereof I affix my signa quinone containing impurities of the type ture. produced by oxidation of anthracene with HARRY F. LEWIS.