Патент USA US3069473код для вставки
United States Patent 1C6 l 3,059,463 Patented Dec. 18, 1962 2 The extraction process of this invention may be carried . , 3,069,463 _ EXTRACTION OF 2,7-NAPHTHALENE DICARBOX YLIC ACID FRGM ITS ISOMERS WITH GAMMA- . PICOLINE Peter Fotis, Jr., Highland, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Oct. 26, 1959, Ser. No. 848,503 8 Claims. (Cl. 260-525) out at any temperature below the boiling point of gamma picoline. The preferred temperature range for the ex traction process is from about -—-10° to about 50° C. although much higher and lower temperatures may be used. The preferred range advantageously‘ includes am bient and room temperatures. “ The ratio of gamma-picoline to the total mixture to be extracted must be su?icient to exceed the solubility of The present invention relates to the extraction of 2,7 10 gamma-picoline in the total mixture undergoing separation naphthalene dicarboxylic acid from a mixture of isomers in order to form a distinct liquid phase containing gamma of naphthalene dicarboxylic acid, and more particularly picoline and 2,7-naphthalene dicarboxylic acid and a dis concerns the use of gamma picoline as a selective solvent tinct solid phase containing the 2,6-naphthalene dicar ‘for this. purpose. boxylic acid and little if any solvent. Generally, between An object of the present invention is to provide a 15 1 and 100 or more parts by weight of gamma-picoline method for removing 2,7-naphthalene dicarboxylic acid per part by weight of 2,7-naphthalene dicarboxylic acid from its mixture with isomers thereof. Another object is to provide a method for removing 2,7-naphthalene di— carboxylic acid from mixtures thereof with 2,6-naphtha lene dicarboxylic acid. A further object is to provide a method for recovering a valuable, relatively pure 2,7 naphthalene dicarboxylic acid isomer for use in condensa tion reactions with glycols and the like to form a polyester may 'be used for the separation. For economical con siderations, it is preferred to use from 1~50r parts by product having a melting point substantially higher than the melting point of a polyester product prepared from 25 a mixture of naphthalene dicarboxylic acid isomers. Weight of gamma-picoline and advantageously less than 20 parts by weight of gamma-picoline because of the ex pense involved in handling large volumes of solvents. The following examples illustrate the extraction proc ess of this invention. Example I As an illustration of the high selectivity of the sepa Other objects will be apparent from the following dis ration of 2,7-naphthalene . dicarboxylic acid from an closure. isomer thereof using gamma-picoline or the extracting sola 7 _ 2,7-naphthalene ‘dicarboxylic acid occurs in admixture vents, -15 ml. of gamma-picoline were added to a 50 ml. with its isomers and particularly with 2,6-naphthalene 30 ?ask containing 0.6 g. of a 50-50 mixture of 2,6- and 2,7-naphthalene dicarboxylic acids. The resulting mix dicarboxylic acid, for example, in a product from the oxi ture was stirred and allowed to stand for 1/2 hour. The: dation of isomers of dimethyl naphthalenes to naphtha mixture was then ?ltered to remove undissolved solid. lene dicarboxylic acids. The separation of the dimethyl The undissolved solid was dried and Weighed (Weight: naphthalenes before oxidation is extremely difficult. Fur ther, the 2,7-naphthalene dicarboxylic acid isomer cannot 35 0.4 g.) and was analyzed and found to contain both 2,6- and 2,7- naphthalene dicarboxylic acids. The ?ltrate readily be separated from its isomers after oxidation by from the ?ltration step was evaporated under vacuum to distillation and is not readily separable ‘from its isomers remove the gamma-picoline and a 0.2 g. solid white crys by known solvent extraction systems, particularly in sub talline produce was recovered from the evaporation. The stantially pure form. In using naphthalene dicarboxylic infrared spectra of the solid product was identical to the acids as reactants in the preparation of polyesters, it is spectra of a pure 2,7-naphthalene dicarboxylic acid. often desirable to use a pure isomer such as the 2,7 naphthalene ‘dicarboxylic acid in order to obtain a poly Example II ester product having a high melting point. Polyesters As ‘an illustration of the speci?c ability of the gamma formed from mixtures of the naphthalene dicarboxylic isomer of picoline to selectively dissolve 2,7-naphthalene acid isomers will not possess the high melting property of a polyester prepared from a substantially pure isomer. I have provided a new method for the separation of 2,7 dicarboxylic acid, solubility tests were made to determine the solubilities of 2,6‘ and 2,7- naphthalene dicarboxylic acids in beta- and ‘gamma-picolines. Each isomer was naphthalene dicarboxylic acid from isomers thereof and added in amounts of 0.1 g. to 20 ml. of each of the more particularly from mixtures of isomers containing 2,6~naphthalene dicarboxylic acid. In my method, the 50 beta- and gamma-picolines with the results recorded below: 2,7-naphthalene dicarboxylic acid is separated by selective extraction with gamma-picoline. The naphthalene dicar boxylic acid isomers are solids under normal conditions and the gamma-picoline selectively dissolves the 2,7 naphthalene dicarboxylic acid while rejecting isomers 55 thereof as a solid ra?inate. In accordance with my proc ess, a mixture of isomers containing 2,7-naphthalene di carboxylic acid is contacted with gamma-picoline and Naphthalene Run dicarboxylic Solvent Results acid isomer 2,6 isomer__ 2,7 isomer" Beta picoline ______ __ Soluble. _____do _____ -_ _ 2,6 lsornen. Gamma plCOl 2,7 isomer ____________ __d Do. Insoluble. Soluble. a liquid extract and solid ra?inate phases are formed. The extract phase is then separated from the solid raf 60 As can be seen from Example I, the present process is ?nate phase. The gamma-picoline may be removed from useful in extracting or separating a substantially pure the extract phase by distillation, extraction, or other 2,7-naphthalene dicarboxylic acid from admixture with means leaving a solid residue product. The residue prod the 2,6 isomer. Example II indicates the speci?c and not is a substantially pure 2,7-naphthalene dicarboxylic unexpected ability of the gamma isomers of picoline as acid and can be further washed with a convenient solvent 65 a solvent in the present extraction process for selective such as, for example, water or a low molecular weight separation of isomers. As can be seen from the table of alcohol, if desired, to remove any remaining contaminating amounts of gamma-picoline or other undesired materials. Gamma-picoline is a colorless liquid at room tempera Example II, the beta-picoline dissolved both the 2,6 and 2,7 isomers demonstrating an inability to separate the isomers while the gamma-picoline dissolved only the 2,7 ture, has a density of 0.9613 g./ml. (at atmospheric pres 70 isomer. sure and 4° C.), and a boiling point of 143.1” C. It is miscible with water, ethanol, ethyl ether, and the like. Of course, it is intended that any feed material contain ing the 2,7-naphthalene dicarboxylic acid may be extracted 3,069,463 . 4 . 3 I claim: to separate that acid in substantially pure form. For ex ample, an e?luent from an oxidation process wherein alkyl 1. The method for extracting a mixture consisting essen tially of 2,7-naphthalene dicarboxylic acid and at least one aromatics containing dimethyl naphthalenes are oxidized isomer thereof, comprising selectively extracting said mix with chemical oxidizing agents such as chromic acid, a per manganate or nitric acid or with molecular oxygen, gen ture at a temperature below the boiling point of gamma picoline with an amount of gamma-picoline su?icient to erally air, or in the presence of an oxidation catalyst such as, for example, the heavy metal oxidation catalysts or exceed the solubility of gamma-picoline in said mixture and form a distinct liquid extract phase and separating preferably the combination of bromine promoted heavy the liquid extract phase. metal oxidation catalysts as taught in US. Patent No. 2,833,816, may be extracted with gamma-picoline to re move 2,7-naphthalene dicarboxylic acid. 2. The method of claim 1 wherein the mixture which is extracted with said gamma~picoline is produced by oxidiz ing a mixture containing dimethyl naphthalenes in the As a more par ticular illustration, an oxidation product predominating in naphthalene dicarboxylic acids obtained (from the oxida presence of an oxidation catalyst. 3. The method of claim 1 wherein the mixture contains tion of a 500 to 5'05 ° F. distillation cut of alkyl aromatics) is extracted with about 50 parts by weight of gamma 15 2,6-naphthalene dicarboxylic acid. 4. The method for extracting a mixture consisting essen picoline per part by weight of 2,7-naphthalene dicar tially of 2,7-naphthalene dicarboxylic acid and 2,6-naph thalene dicarboxylic acid comprising treating said mixture boxylic acid. 2,7-naphthalene dicarboxylic acid is ex tracted by the gamma-picoline in a liquid phase which may at a temperature below the boiling point of gamma-picoline be separated from the solid phase residue. In this man ner, the gamma-picoline may be used to extract the 2,7 20 with an amount of gamma-picoline su?icient to exceed the solubility of gamma-picoline in said mixture and form dis isomer in substantially pure form while rejecting isomers tinct liquid extract and solid rai?nate phases, separating thereof and other extraneous components including oxida said liquid phase from sad solid phase, and removing said tion catalyst, etc. Such catalytic oxidation products may gamma-picoline from said liquid phase whereby a solid also contain unreacted dimethyl naphthalenes or reaction intermediates due to partial oxidation, and the gamma 25 residue is formed essentially containing 2,7-naphthalene dicarboxylic acid in the substantial absence of 2,6-naph picoline may be used to selectively separate the 2,6-naph thalene dicarboxylic acid. thalene dicarboxylic acid from its isomers even in the 5. The method for extracting 2,7-naphthalene dicar presence of such other components. boxylic acid from a mixture thereof with 2,6-naphthalene , Although, because of the high purity of the 2,7-naph thalene dicarboxylic acid separated by the present process, 30 dicarboxylic acid, comprising contacting said mixture with from about 1 to about 50 parts by weight of gamma counter solvents or cosolvents are unnecessary, it may be desirable at times to employ such counter solvents or co solvents. The counter solvents or cosolvents may be use picoline per part by weight of 2,7-naphthalene dicarboxylic acid at a temperature in the range of from about —10° to about 50° C., separating the resulting liquid phase from ful in increasing the e?‘iciency of the gamma-picoline, or increasing the selective rejection of the 2,6 isomer or other 35 the resulting solid phase, distilling gamma-picoline from isomer of 2,7-naphthalene dicarboxylic acid during the said liquid phase, washing the resulting solid residue from separation process. the distilling step with water, and recovering the washed Counter solvents or cosolvents may be particularly advantageous, for example, when operat solid residue as substantially pure 2,7-naphthalene dicar ing with very small amounts of gamma-picoline or when boxylic acid. of such counter solvents and cosolvents in extraction sys tems is well known in the art and it is fully intended that such use is contemplated herein. It is evident from the foregoing that I have provided a prises about equal volumes of 2,7-naphthalene dicarboxylic acid and 2,6-naphthalene dicarboxylic acid. operating outside the preferred temperature range. Use 40 6. The method of claim 5 wherein said mixture com highly selective separation process for separating 2,7-naph 7. The method of claim 1 wherein said temperature is in the range of from about -—l0° to about 50° C. 8. The method of claim 1 wherein said amount of thalene dicarboxylic acid from isomers thereof using gamma-picoline as the extractant. My process is partic gamma-picoline is at least 1 part by weight per part by weight of 2,7-naphthalene dicarboxylic acid in said mix ularly useful in separating 2,7-naphthalene dicarboxylic acid from admixture with 2,6-naphthalene dicarboxylic ture. acid such as occurs in mixtures of isomers resulting from the oxidation of mixtures of dimethyl naphthalenes. 50 No references cited.