Patented Mar. 18, 1952 2,589,648

UNITED STATES PATENT OFFICE CYCLOALKANE oxIDATION Francis T. Wadsworth, Dickinson, Tex., assignor to Pan American Refining Corporation, Texas City, Tex., a corporation of Delaware No Drawing. Application May 26, 1950, Serial No. 164,603 6 Claims. (CI. 260-533) 1 This invention relates to a catalytic process for the oxidation of cycloalkanes to produce Atmospheric principally alkane dicarboxylic . More par Pressure (115°C.) ticularly, this invention relates to a catalytic process for the oxidation of with 5 liquid Vapor added molecular oxygen in the presence of a re Phase Phase action medium and solvent consisting essentially 304-Stainless Steel------0.082 0.013 of . 309-Stainless Steel.------0.080 0.06 347-Stainless Steel------0.121 ------In processes for the oxidation of cycloalkanes . 410-Stainless Steel- 0.026 0.022 0. 316. Stainless Stec 0.0004 0.001 containing 4 to 6 carbon atoms, inclusive, in the Hastelloy-A- 0.020 0.050 ring by means of oxygen and a polyvalent heavy Hastelloy-B 0.014 0.005 metal catalyst, the use of a reaction solvent was Hastelloy-C 0.0005 ------found to be essential in order to procure com ... Al3S-H14------0.02 ------mercially significant yields of the desired alkane dicarboxylic acids. This has been found to be Acetic is even more corrosive When employed particularly true in processes of the above-men under moderate oxygen pressures such as are tioned type when applied to the oxidation of used in processes of the above-described type, cyclohexane to produce alkane ... dicarboxylic Thus, at a temperature of 100-105° C. and 150 acids, particularly adipic acid. When cyclo p. s. i. g. air pressure, the corrosion rate of hexane is oxidized in the presence of soluble co- : Hastelloy-C is increased to 0.0027 I. P. Y. in the balt and/or manganese carboxylates in the liquid phase. At the higher partial pressures of absence of a reaction solvent, even the employ oxygen normally employed in the catalytic oxi ment of severe operating conditions leads to the dation of cycloalkanes, for example, oxygen production of , , and partial pressures of about 100 to 300 p.s. i. g., combustion products such as CO, CO2 and water, 25 is even more corrosive. The corrosion but not to the formation of adipic acid. When characteristics of acetic acid-oxygen mixtures cyclohexane is oxidized in solution in butyl have necessitated the employment of relatively acetate in the presence of polyvalent heavy metal expensive and specially fabricated equipment in carboxylate catalysts, essentially the same oxida processes for the catalytic oxidation of cycloal tion products are obtained as when no solvent t kanes, for example, equipment lined with tanta whatever is employed; when glacial acetic acid lum, Special stainless steels and the like. is Substituted as the solvent, adipic acid is pro The known processes for the oxidation of cy duced. The solvent plays an important role in cloalkanes to alkane dicarboxylic acids invari catalytic processes for the oxidation of cycloal ably yield intermediate oxidation products, par kanes to alkane dicarboxylic acids, but this role ticularly cycloalkanols and cycloalkanones. is obscure and cannot be correlated with the When glacial acetic acid is employed as the re Solvent capacity of the solvent for the cycloal action solvent, cycloalkanols are not recoverable kane. Up to the present, the only solvent which aS Such from the reaction mixture, but principal has achieved practical significance in the type ly as cycloalkanol acetates. The recovery of of process here under consideration is glacial 40 these esters and their treatment to regenerate acetic acid. the cycloalkanol and acetic acid, respectively, While glacial acetic acid leads to substantia constitute further problems and deficiencies con production of adipic acid in processes for the nected with the employment of glacial acetic acid oxidation of cyclohexane with air or oxygen in as the reaction solvent in processes of cyclo the presence of soluble polyvalent metal salts, its 45 alkane oxidation. use is nevertheless attended by certain serious One object of this invention is to provide a disadvantages. Although acetic acid is not gen novel solvent for use in the oxidation of cyclo erally considered to be a highly corrosive ": alkanes to produce principally alkane dicar medium, it actually becomes an extremely cor boxylic acids. Another object of this invention rosive medium under the conditions employed in 50 is to provide a novel solvent for use in the oxi oxidation processes of the type above described. dation of cyclohexane, cyclopentane, cyclobutane Aerated acetic acid is a highly corrosive medium and their methyl- or ethyl-substitution products even at atmospheric pressure and 115° C. as in the presence of polyvalent heavy metal cata shown by the following corrosion rates, given as . . lysts to produce alkanedicarboxylic acids. An inches penetration per year. additional object of this invention is to provide a 2,589,648 3 4 process for the oxidation of cyclohexane in Solu room temperature, whereupon unreacted cyclo tion in a solvent consisting essentially of acetOne hexane formed a supernatant layer, which was in the presence of certain heavy metal catalysts to decanted. The lower layer of reaction products produce substantial yields of adipic acid, together was distilled under a pressure of 200 mm. of with cyclohexanol and cyclohexanone. Yet an mercury and the resultant distillate was redis other object of my invention is to provide a novel tilled at atmospheric pressure, with the results combination of acetone solvent and manganese shown in the following tabulation. and cobalt adipates for employment in the oxi dation of cyclohexane to produce adipic acid, cy clohexanol and cyclohexanone. These and other O Wol. Percent Distilled objects of my invention will become apparent from the ensuing description thereof. 10 15 The process of this invention will be described 1. principally by reference to the oxidation of cy f clohexane, although it should be understood that 1. it may likewise be applied to other cycloalkanes containing 4 to 6 carbon atoms, inclusive, in the 1S ring or to their methyl- or ethyl-Substitution 18 8 products. It will also be apparent that the 2 process of the present invention is not limited to the employment of Substantially pure cyclo The atmospheric boiling point of acetone is 56° C. alkane charging stocks, but may likewise be ap It will, therefore, be apparent that acetone must plied to natural or Synthetic cycloalkane-con have oxidized completely under the conditions taining fractions, particularly to such fractions employed in the oxidation reaction, since no. which are derived from petroleum, or from syn trace of it was found in the reaction products. thesizing operations applied to petroleum frac-. The operation yielded 11.1 weight percent of tions, for example, Friedel-Crafts-catalyzed iso adipic acid, based on the cyclohexane charged, merization of methylcyclopentane fractions to with an ultimate conversion of 36.9 weight per cyclohexane. cent of the charge to adipic acid. y Briefly, the process of the present invention In marked contrast, as will be shown in detail comprises the oxidation of a solution of cyclo hereinafter, . I have found that when acetone. hexane in acetone, the latter being present in is employed as the sole reaction solvent, in the amounts ranging from about 10 to about 70 absence of acetic acid, substantially no acetone weight percent, based on the mixture of acetone oxidation occurs in the presence of a cycloalkane and cyclohexane, in the presence of a soluhle 3 5 charging stock, but instead selective oxidation of polyvalent heavy metal oxidation catalyst of the the cycloalkane occurs to produce a commercially type of manganese, cobalt and copper; oil-soluble desirable yield of alkanedicarboxylic acid, ac salts, for example acetates, naphthenates, oleates, companied by cycloalkanone...and free cycloalka adipates, etc., of the aforementioned and similar no. More particularly, I have discovered that heavy metals, or mixtures of oil-soluble salts of {} the oxidation of cyclohexane in a solvent. Con manganese, cobalt, copper and the like. The sisting essentially of acetone in the presence of . catalyst concentration in the reaction mixture certain soluble polyvalent heavy metal salts can be varied between about 0.001 and about 0.1 proceeds smoothly to produce commercially at percent by weight (calculated as metal), and is tractive yields of adipic acid, cyclohexanol and preferably selected between about 0.015 and about cyclohexanone. I have found acetone to be 0.033 percent by weight, based upon the weight resistant to oxidation under these conditions of the cycloalkane charging stock. The process and readily recoverable from the resultant re is effected at temperatures between about 100 action mixtures. Thus, in the oxidation of cyclo and about 140° C., preferably between about 120° hexane in solution in acetone to produce adipic C. and about 130° C., employing oxygen partial acid, I have found that the total distillate from pressures between about 100 and about 300 a typical operation contains acid equivalent only p.s. i. g., preferably about 175 to about 225 to , about 0.65 percent acetic acid. AcetOne re p.s. i. g. The reaction period may vary between coveries of 95-97 percent and even more can be about 1 and about 8 hours, but is preferably obtained. I have, moreover, discovered that the . selected in about the 2 to 4 hour range. 3. 5 influence of acetone upon cyclohexane oxidation It is highly surprising to find that acetone is specific and that other such as diphenyl could be employed as the reaction solvent in do not exert this influence. m cycloalkane oxidation processes, since acetone is In order to afford specific illustrations of the known to be readily oxidizable when treated with process of the present invention and without the oxygen in the presence of polyvalent heavy metal SO intention of unduly limiting the scope, thereof, oxidation catalyst in the presence of acetic acid. run data are set forth in the following table. AcetOne oxidizes under these conditions with re Small proportions of cyclohexanone, as shown, markable ease in the absence of a cycloalkane were employed in these runs as a reaction “initia (note Examples 3 and 4 of U. S. Patent 2005,183, tor,' i. e. as a material which served to reduce the Walter Flemming et al., patented June 18, 1935) 5 rather extended induction period before the and even when a cycloalkane such as cyclohexane onset of reaction which would otherwise...be ex is present, as shown by the following experi perienced. I have found that acetone does not ment...... function as an initiator in the catalytic oxidation A mixture of 768 g. cyclohexane, 156 g. acetone, of. Cyclohexane...... 159 g. acetic acid, 9.5 g. cyclohexanone (reaction The inability of acetone to function as a re initiator), and 0.2 g., each, of cobalt and man action initiator is demonstrated by the following. ganese acetates was subjected to a temperature experiment. A mixture of 61 g. of cyclohexane. of 123-126 C. and a partial pressure of oxygen (85%. purity), 38.5 g. of... acetone and 0.07.g., of 200 p.s. i. g. for a period of 5A hois. The each, of cobalt, manganese and copper acetates. reaction mixture was then allowed to codil, to was treated with oxygen at a partial pressure of 2,589,648 5 6, 200 p.s. i. g. for 3% hours at temperatures be- the corresponding acetates the induction period tween 126 and 132° C. without evidence of any varies from about 45 to 90 minutes. Table

i Adipic- - Acid Yields--- i s Cyclo- Ace- WeightCent Ace Per Catal Cyclo-m Oxygen wr-rrrow---arras-a-ra-- Rin No.N hexane, tone, tone in per centyst, on weight C'H. hexanone,. . . Temp.,oC. Filip, Time,hrs. Weight per Weigh,Ferniort. .g. g. Mixture - 9. P. S. l. g. SE O Converted arge Charge 61.7 49.5 44.5 Mn acetate-0.162.-- 0.95 130-132 200 A.

61.7 49.5 445 S.S.,1 acetate-O. - - - - 9, 1313| 200 6.7 49.5 44.5 SE'sE. 0.95 130-132 200 4. 77.4y 77- 9.2 {SEs.acetate-O.162. 9.5 130 200 4 77.7y 137 26.2 (ESI:nacetate-0.162----- 9.5 130 200, 4. 6.7 49.5 44.5 CI acetate-0.162.-- 0.95 30-132 200, 4 - - - MEl acetate-0.62.--- : 61.7 . 49.5 44,533Cu acetaat 93-----. 0.95 130-182 200 si. 543 239 30 EES)fMn adipates-0,197. 5.4 127-132ris 150 v 6 17.2 53.0 46s 316 40 K.E.)fMin adipates-0. 197-- 4.7 127-182 150 6 li.1 49.2 . 381.. 395 50 S.Min adipates-0.E. 97. 3.8 - 127.32 : 50 6. 11.8 58.5 545 139 20, 2 e E; } 5.4 127-132 200 5 16 37.4 - 545 198 2.in adipaE. E:97. 5.4 127-132 200 6 17.5r -a50 466 3 w 0.5 E.nadipates-U. E. - - } 4.7 127-132. 200 6 21, 5 - ... 44, 5 as 396 50.5 eMin E.E. adipates-0.197 - i. 3.8 127-132 200 G 22 46.2 545 139 20.2 Miln: adipE.ER f..." 5.4 127-132. 250 6 21.9 42.6 545 288 30.5 E.n adipates-U. 197- 5.4 127-132- 250 6. 28.4 47.0 -. as a an. E.I pal 97. 4.7 27-32 : 250, 6 26, 6, ... .Y.Y.89.2 18- as a 50.5 Ke:nadipates-0. E} 97-- ; 3.8 127-132 250 6 29.2 46.3 oxygen absorption (drop in pressure) whatso-, Runs 8 to 10, inclusive, were conducted at a ever. The reaction bomb was then opened and is partial oxygen pressure of 150 p.s. i. g., with ace 0.95 g. cyclohexanone was added to the re- -tone concentrations varying between 30 and 50 action mixture. The reaction bomb was then weight percent of the cyclohexane-acetone mix repressured with oxygen, reheated to reaction 'ture. The trend discernible from this variation temperature and it was found that the pressure t) is that the extent of cyclohexane conversion per began to drop about 20 minutes after the bomb pass decreases somewhat with increasing cyclo reached reaction temperature. The yield of it. hexane dilution, but that a somewhat higher adipic acid recovered was 8 weight percent, based adipic acid yield is obtainable at increased dilu On the cyclohexane charged. It should be tions. pointedinefficient, out so thatthat thethe truerecovery yield wasof adipicsomewhat acid ingRuns dilution 11 to of14, the inclusive, cyclohexane indicate in thatthe increasreaction was somewhat higher. mixture can be more or less offset by employing Referring to the table, the reported adipic increased oxygen partial pressures (200 p.s. i. g.), acid yields are based Solely upon adipic acid whereupon increased adipic acid yields, based on filtered from the reaction mixture. It should be charge, are obtained, but the ultimate yield of borne in mind that additional adipic acid can adipic acid is somewhat reduced. readily be produced from the initial filtrate. Runs 15 to 18, inclusive, illustrate the fact that Run 1 demonstrates the applicability of man- at relatively high oxygen partial pressure (250 ganese acetate and run 2 of cobalt acetate as cata- p.s. i. g.), relatively dilute reaction systems can lysts for the oxidation of cyclohexane in the ace- be employed and a high adipic acid yield per tone solvent. In run 3 a mixture of manganese ? pass without undue ultimate adipic acid yield and cobalt acetates was employed. In runs 4 and loss can be obtained. - 5 manganese-cobalt acetate catalysts were em- It should be understood that conventional sepa ployed at reduced acetone concentrations. ration techniques can be employed in connection Run 6 indicates that copper acetate is a less with the process of my invention. One conven active catalyst than cobalt and manganese ace- tional procedure which I have employed follow tates under comparable conditions, but run 7 in- - ing batch operation of the present oxidation proc dicates that copper acetate can be employed to- i. ess is to distill the reaction mixture to a bottoms gether with both manganese and cobalt acetates. - temperature of 141° C. to remove acetone, uncon Manganese and cobalt adipate catalysts were verted cyclohexane and water as distillate. The employed in runs 8 to 18, inclusive. The adipat distillation residue is then cooled to -18° C. to salts:were prepared by heating a mixture of co- crystallize adipic acid, which is thereafter sepa bait and manganese acetates with adipic acid for is rated by filtration. The adipic acid filtrate can 3-4 minutes at 130-140° C. The adipic acid em. be readily oxidized, for example, with , ployed in preparing the cobalt and manganese to yield additional adipic acid. A typical adipic adipates was an adipic acid filtrate from a pre- : acid filtrate was found to analyze as follows. vious oxidation run. The adipic acid filtrate al so contains cyclohexanone. The use of manga- Weight per cent of filtrate nese, and cobalt adipates thus prepared has been "Cyclohexanol-cyclohexanone ------. 26 foundtion reaction to result from in inductionis to 36 inities, periods whereasof the oxida, with 5 Adipig. Higher 3Cid-----.molecular weight. acid...I.I.I.I.. . . . 5123 2,589,648 7. 8. In runs 8, 9 and 10 the adipic acid filtrates tion initiator and both cobalt and manganese, amounted to 17.2, 13.1 and 13.9 weight percent, the improvement which comprises effecting Said respectively, based on the cyclohexane charged. oxidation in a solution of cyclohexane in a Sol Oxidation of these filtrates with 40 percent nitric ... went consisting essentially of acetone, the pro-. acid was effected in two steps. The first step was 5 portion of acetone in said solution being between carried out with 40 percent nitric acid at 50–55° C. about 10 and about 70 percent by Weight. in the presence of a trace of copper, the nitric acid 4. In a process for the liquid-phase oxidation being reduced in this step to N2O. In the second of cyclohexane to produce adipic acid in the step...the temperature was raised to 60° C., at presence of a polyvalent heavy metal catalyst which it was maintained for 1 to 1.5 hours while O selected from the group consisting of carboxyl the nitric acid was reduced to NO2. The total ates of cobalt, manganese and both cobalt and reaction time in both steps was 2-2.5 hours. It manganese, at a temperature between about 100 was found that the yields of adipic acid, based C. and about 140° C., oxygen partial pressure be on the adipic acid filtrate of runs 8, 9 and 10, tween about 100 and about 300 p. S. i. g. and in were 85.5, 88.0 and 80.0 weight percent, respec 15 the presence of a cyclohexanone initiator, the tively. The overall adipic acid yields in runs 8, improvement which comprises effecting said oxi 9 and 10 were, thus, 29.7, 26.0 and 20.5 mol per dation in a solution of cyclohexane in a solvent cent, based on cyclohexane charged, and 77.8, consisting essentially of acetone, the proportion 81.5 and 86.0 mol percent, based on the cyclo of acetone in said solution being between about 10 hexane converted. 20 and about 70 percent by weight. In a study of the use of ketones other than 5. A process for the oxidation of cyclohexane acetone for the oxidation of cyclohexane to adipic to produce adipic acid, which process comprises acid, an oxidation was carried out in which 30. subjecting cyclohexane and a solvent consisting g. of benzophenone (diphenylketone) were used essentially of acetone in proportions between as the solvent for 62 g. of cyclohexane. Cata about 10 and about 70 percent by weight, based lysts consisting of cobalt acetate, manganese". on both cyclohexane and acetone, to treatment acetate, Copper acetate (.01 g. each) and 1 per with oxygen at a partial pressure between about cent cyclohexanone were used. A reaction period 150 and about 250 p.s. i. g. at a temperature be of 4 hours at 125-130° C. and an oxygen pressure tween about 120° C. and about 135° C. in the pres of 100-250 p.s. i. g. Were used. Only a slight drop 30 ence of an adipate of a polyvalent heavy metal in Oxygen pressure was noted, with a 3 Weight selected from the class consisting of cobalt and percent yield of adipic acid, based on the cyclo cyclohexanone reaction initiator, manganese and hexane charged, being recovered. It is obvious both manganese and Cobalt, and thereafter sepa that...benzophenone is not equivalent. to acetone. rating adipic acid from the reaction mixture. Having thus described my invention, what I 6. A proceSS for the Oxidation of Cyclohexane claim is: w - to produce adipic acid, which process comprises 1. In a process for the liquid-phase oxidation subjecting cyclohexane and a solvent consisting of a liquid cycloalkane containing 4 to 6 carbon essentially of acetone in proportions between atoms, inclusive, in the ring to produce an alkane about 10 and about 70 percent by Weight, based. in the presence of a polyvalent 40 on both cyclohexane and acetone, to treatment heavy metal catalyst and cyclohexanone reaction with oxygen at a partial pressure between about initiator, the improvement which comprises ef 150 and about 250 p.s. i. g. at a temperature be-, fecting said oxidation in a solution of Said cyclo tween about 120° C. and about 135° C. in the alkane in a solvent consisting essentially of ace presence of an adipate of a polyvalent heavy metal tone, the proportion of acetone in said Solution 45 Selected from the class consisting of cobalt, man being between about 10 and about 70 percent by ganese and both manganese and cobalt, and Weight. initially present cyclohexanone in an amount be 2. In a process for the liquid-phase oxidation tween about 0.1 and about 1.0 percent by Weight, of cyclohexane to produce adipic acid in the pres based on cyclohexane, and thereafter separating ence of a polyvalent heavy metal catalyst and 5) adipic acid from the reaction mixture. cyclohexanone reaction initiator, the improve - . . . . . FRANCIST. WADSWORTH. ment which comprises effecting said oxidation in a solution of cyclohexane in a solvent consisting REFERENCES CITED essentially of acetone, the proportion of acetone The following references are of record in the in said solution being between about 10 and about 5 5 file of this patent: 70 percent by Weight, 3. In a process for the liquid-phase oxidation UNITED STATES PATENTS of cyclohexane to produce adipic acid in the pres Number Name Date . ence of a polyvalent heavy metal catalyst Se 2,005,183 Flemming et al.---- June 18, 1935 lected from the group consisting of carboxylates 2,223,493 Loder ------Dec. 3, 1940 of cobalt, manganese and cyclohexanone reac 2,285,914 Drossbach ------June 9, 1942