US2589648A

US2589648A - Cycloalkane oxidation

Info

Publication number: US2589648A
Application number: US164603A
Authority: US
Inventors: Francis T Wadsworth
Original assignee: Pan American Refining Corp
Current assignee: Pan American Refining Corp
Priority date: 1950-05-26
Filing date: 1950-05-26
Publication date: 1952-03-18
Anticipated expiration: 1969-03-18

Description

Patented Mar. 18, 1952 UNITED STATES PATENT OFFICE Francis T. Wadsworth, Dickinson, Tex., assignor to. Pan American Refining Corporation, Texas City, Tex., a corporation of Delaware No Drawing. Application May '26, r950, Serial .No. 164,603

1 This invention relates to a catalytic process for the oxidation of cycloalkanes to produce principally alkane dicarboxylic acids. More particularly, this invention relates to a catalytic process for the oxidation of cyclohexane'wi th added molecular oxygen in the presence of a reaction medium and solvent consisting essentially of acetone.

In processes for the oxidation of cycloa'llranes 10 containing 4 to 6 carbon atoms, inclusive, in the ring by means of oxygen and a polyvalent heavy metal catalyst, the use of a reaction solvent was found to be essential in order to procure comf mercially significant yields of the desired alkane dicarboxylic acids. This has been found to be particularly true in processes of the above-men tioned type when applied to the oxidation of cyclohexane to produce alkane dicarboxylic acids, particularly adipic acid. When cyclohexane is oxidized in the presence of soluble co balt and/or manganese carboxylates in the absence of a reaction solvent, even the employment of severe operating conditions'leads to the production of cyclohexanol, cyclohexanone, and

combustion products such as C0, C02 and water,

Atmospheric Pressure (ll-5 0,)

Liquid Vapor Phase Phase rim-Stainless Steel 0. 082 0. 013 309-Stainless Steel 0. 010

3 i7 Stainless Steel i 410-Stainless SteeL. 0.022 lilo-Stainless Steel 0.001 HaStelloy-A, 0. 050 .Hastelloy-B 0. 005 Hastelloy-O. A1, 38-1-11 1 i Acetic acid 15 even more corrosiv hen employed under moderate oxygen pressures such as are used in processes of the above-described type. Thus, at a temperature of mil-105 C. and .150

' p. s. i. g. air pressure, the corrosion rate of but not to the formation of adipic acid. When cyclohexane is oxidized in solution .in butyl acetate in the presence of polyvalent heavy metal carboxylate catalysts, essentially the same oxidation products are obtained as when no solvent whatever is employed; when glacial acetic acid is substituted as the solvent, adipic acid is produced. The solvent plays an important role in productionof adipic acid in processes for the.

oxidation of cyclohexane with air or oxygenfin the presence of scluble polyvalent metal salts, its use is 4 nevertheless attended by certain serious disadvantages? Although acetic acid is not generally considered to be a highly corrosive medium, it"a'ctually becomes an extremely corrosive medium under the conditions emp'loyediin oxidation processes of the type above described. Aerated acetic acid is a highly corrosive medium even at atmospheric pressure and 115 C.,- as

shown by-theiollowingcorrosion rates, given as I W I a. additionalcbject of this invention .is; to provide a.

liquid phase.

Hastelloy-C is increased to 0.0027 I. P. Y. in the At the higher partial pressures of oxygen normally employed in the catalytic oxidation of cycloalkanes, for example, oxygen partial pressures of about 100 to 300 p. s. i. .g.,,

' lum, special stainless steels and the like.

"The known processes for the oxidation of cycloalkanes to alkane dicarboxylic .acids invariably yield intermediate oxidation products, particularly cycloalkanols and cycloalkanones.

When glacial acetic acid is employed .as the reaction solvent, =cycloalkanols are .not recoverable as such from the reaction mixture, but principal- 1y" as cycloalkanol acetates." The recovery of these esters and their treatment to regenerate the cycloalkanol andv acetic acid, respectively, constitute further problems and deficiencies connected with the employment of glacial acetic acid as the reaction solvent inprocesses of cycloalkane oxidation.

One object of this invention is to provide a novel solvent for use in the oxidation of cycloalkanes to produce principally alkane dicargbjo' xylic acids.

' is to provide a novel solvent for use in the oxidation of cyclohexane, cyclopentane, cyclobutane Another object of this invention lysts to. produce 'alkane dicarboxylic'facids. An

process for the oxidation of cyclohexane in solution in a solvent consisting essentially of acetone in the presence of certain heavy metal catalysts to produce substantial yields of adipic acid, together with cyclohexanol and cyclohexanone. Yet another object of my invention is to provide a novel combination of acetone solvent and manganese and cobalt adipates for employment in the oxidation of cyclohexane to produce adipic acid, cyclohexanol and cyclohexanone. These and other objects of my invention will become apparent from the ensuing description thereof.

The process of this invention will be described principally by reference to theoxidation of cyclohexane, although it should be understood that it may likewise be applied to other 'cycloalkanes containing 4 to 6 carbon atoms, inclusive, in the J ring or to their methylor ethyl-substitution products. It will also be apparent that the process of the present invention is not limited to the employment of substantially pure cycloalkane charging stocks, but may likewise be ap plied to natural or synthetic cycloalkane-containing fractions, particularly to such fractions which are derived from petroleum, or from synthesizing operations appliedto petroleum frac-. tions, for example, Friedel-Crafts-catalyzed isomerization of methylcyclopentane fractions to cyclohexane.

Briefly, the process of the present invention comprises the oxidation of a solution of cyclohexane in acetone, the latter-being present in amounts ranging from about 10 to about weight percent, based on the mixtureof acetone and cyclohexane, in the presence of a solu le polyvalent heavy metal oxidation catalyst of the type-of manganese, cobalt and copper; oil-soluble salts, for example acetates, naphthenates, oleates;

adipates, etc., of the aforementioned and similar heavy metals, or mixtures of oil-solublesalts of manganese, cobalt, copper and the like. The catalyst concentration in the reaction mixture can be varied between about 0.001 and about 0.1 percent by weight (calculated as metal), and is preferably selected between about 0.015 and'about 0.033 percent by weightjbased upon the, weight of the cycloalkane charging stock. The process is eflected at temperatures between about and about 1 l0 0., preferably between about C. and about C., employing oxygenipartia l pressures between about 100 and about 300 p.-s. i. g., preferably about to a bout 225 p. s. i. g. The reaction period may vary between about 1 and about 8 hours, but is preferably selected in about the 2 to 4 hour range.

It is highly surprisingto find that acetone could be employed as the reaction solvent in cycloalkane oxidation processes, since acetone is known to be readily oxidizable when treated with oxygen in the presence of polyvalent heavy metal oxidation catalyst. inthe presence of acetic acid. Acetone oxidizes under these conditions with re-" markable ease in'the absence of a 'c'ycloalkane (note Examples 3 and 4 of U. S. Patent 2,005,183;

roomtemperature, whereupon unreacted cyclohexane formed a supernatant layer, which was decanted. The lower layer of reaction products was distilled under a pressure of 200 mm. of mercury and the resultant distillate was redistilled at atmospheric pressure, with the results shown in the following tabulation.

Vol. Percent Distilled The atmospheric boiling point of acetone is 56 C.

It will, therefore, be apparent that acetone must have oxidized completely under the conditions employed in the oxidation reaction, since no trace of it was found in the reaction products. The operation yielded 11.1 weight percent of. adipic acid, based on the cyclohexane charged.

with an ultimate conversion of 36.9 weight percent of the charge to adipic acid.

In marked contrast, as'will be shown in detail, hereinafter,. I have found thatwh'en, acetone. is employed as the sole reaction solvent, in the.

absence of acetic acid, substantiallyno acetone oxidation occurs in thepresence of a cycloalkane charging stock, butinstead. selective oxidation of the cycloalkane occurs to. produce a commercially desirableyield of alkane'dic'arboxylic acid, ac-

companied by cycloalkanoneand free cycloalkanol. More particu1arly', I have vdiscovered'that the oxidation of cyclohexane in a solventconsisting essentiallyof acetone in the presence of.

certain soluble polyvalent heavy metal salts. proceeds smoothly to produce commercially attractive yields of adipic acid, cyclohexanol and cyclohexanone. I have found acetone to be resistant to oxidation underthese conditions and readily recoverable from the resultant reaction mixtures. Thus, in the oxidation of cyclohexane in solution in acetone to produce adipic acid, I have found that the total distillate from a typical operation contains acid equivalent only toabout 0.65 percent acetic acid. Acetone recoveries of 95-97 percent and even more can be obtained. .1 have, moreover, discovered that the influence of acetone upon cyclohexane oxidation is specific and that other ketones such as diphenyl ketone do not exert this influence.

In. order to afiord specific illustrations of the process of the present invention and without the intention of'unduly limiting the scopethereof, run data are set forth in the following table. Small proportions of cyclohexanone, as-shown, were employed in these runs as .a reaction initiator, i. e. as a material which served to reduce the. rather extended induction period before the onset of reaction which would otherwiselbe ex peri'enced. .I have found that acetone doesno't, function as an initiator in the catalytic oxidation of cyclohexane.

The inability of acetone to function as a re-i action initiator is demonstrated by the followingexperiment- A mixture of 61 g.- of cyclohexane, 35%. purity),v 3.8.5 'L'g.ffof..acetone and 0.07. -g each, of cobalt, mangai'i'eseandcopper acetates: was treated with oxygen at"a"p'artial p'r'essiiretr tone solvent. In run 3 a mixture of manganese 7f 5 200 p. s. i. g. for 3 /2 hours at temperatures between 126 and132 C. without evidence of. .any

varies from about 45 to 19.0 minutes.

the corresponding acetates the induction l able I j Adipic Acid Yields Weight Per I Cyclo- Ace- Cent Ace Cam] i Cyclo- Oxygen v ys wewnt Temp, Time, Run tone tone in per cent 0110:1311 v hexanqne C. hrs. Weight per g i gg E Mixture cent (Jon verted Charge Charge 61.7 1 49. 44. 5 Mn acetate-0.162;... 0.95 130-132 200 4 11. 5

61. 7 49. 5 44. 5 1819 acetititeilliilio. 0. Q5 130-132 I 200 4 9. .8

name a e 61.7 49.5 44.5 gl fi i 3b 0. 95 130-132 200 4 12.3 n ace a e 4 l7. 4 7t 9. 2 g? g 5 130 200 I 47 6. 9 I 48. 7

n ace a e .1 i l 5... 77.7 137 26.2 {commw0162 9.5 13,0 200 4. 15.2 6, 61. 7 49. G 44. 5 C11 acetate-0.162 0.95 130-132 2.00 4 2 I I Mn acetate-0.162 V 7 61. 7 49. 5 4445 80 cet al egl gau- 0. .95 I 130-132 200 4 11.9 uaceac Mn adipates0.l97 1 U s 543 239 g b 5.4 127-132 150 0 17.2 53.0

I 1 11a ipa es .7 9.-,.. 46s 31 L0 gg z 96 3 4.7 I 127-132 150 6 11.1 49.2

. na ipa es .1 7 10 381 39s .50 E4 z b g7 3.8 121-132 150 s 1 1.8 513.5

. naipaes.l -i I 11 545 130 20.2 g g 5.4 127-132 200 6 l6 37.4

naipees a 12 545 19s 26. a, 4 adpatgsfiol 92 5. 4 127-132 200 6 17. 5 00 naipaes0.l 13 46b 31, 40.5 g 96 59 4. 7 127-122. 200 e 21. 5 44. 3 .1 naipaes'.l 14 330 396 to. 5 g fi} 3.8 127-132 200 t 22 46.2

inaip es. 7.. .545 130 20.2 i g 5.4 127-132, 250 c 21.9 42.6 naipaes -D 238 30.5 fg7 u. 4 127-132 250 .5 1 28. 4 r :17. U

1 na ipates 466 317 40. 5 gf i bfigi- 4. 7 127-132 250 s 26.6 .19. 2

na rpa es- 389 096 50.5 I{ as 127-132 250 s 29.2 46.3

oxygen absorption (drop in pressure) whatsoever. The reaction bomb was then opened and 0.95 g. cyclohexanone was added to the reaction mixture. The reaction bomb was then repressured with oxygen, reheated to reaction temperature and it was found that the pressure began to drop about .20 minutes after the bomb reached reaction temperature. The yield of adipic acid recovered was 3 weight percent, based on the cyclohexane charged. It should be pointed out that the recovery was somewhat inefficient, so that the true yield of adipic acid was somewhat higher.

Referring to the table, the reported adipic acid yields are based solely upon adipic acid filtered from the reaction mixture. It should be borne in mind that additional adipic acid can readily be produced from the initial filtrate.

Run 1 demonstrates the applicability of manganese acetate and run 2 of cobalt acetate as catalysts for the oxidation of cyclohexane in the aceand cobalt acetates was employed. In runs 4 and 5 manganese-cobalt acetatecatalysts were employed atfreducedacetone concentrations.

.Run 6 indicates that copper acetate is a less active catalyst than cobalt and manganese ace- 5 tates under comparable conditions, but run '7 indicates that copper acetate can be employed together with both manganese and cobalt acetates. Manganese-and cobalt adipate catalysts were employed in runs 8 to 18, inclusive. The adipate salts-swore prepared by heating a mixture of cobait and manganese acetates with adipic acid for 1 3-4 minutes at 130-140 C. The adipic acid employed in preparing the cobalt and manganese j adipates was an adipic acid filtrate from a previous oxidation run. The adipic acid filtrate a1- verted cyclohexane and water as distillate.

8 to 10 inclusive, were conducted ath ipartial oxygen pressure of p. s. i. g., with acetone concentrations varying between BOand 50 weight percent of the cyclohexane-acetone, mix,-

ture. is'that the extent of cy-ciohexane conversionper pass decreases somewhat. with increasing cy l hexane dilution. but that a somewhat higher The trend discernible from this variation adipic acid yield is obtainable .at increased dilutions.

mixture can be more or less ofi'set by employing increased oxy en partial pressures (200 'p. s. i. g..), whereuponincreased adipic acid yields, based on charge, are obtained, but the ultimate yield of adipic acid is somewhat reduced.

. Runs 15 to 1 inclusive, illustrate-the fact that atqrelatively high oxygen partial pressure (250 p. s. i. g), relatively dilute reaction systems can be employed and a high adipic acid yield per pass without undue ultimate adipic acid. yield losscan be obtained.

It should be nnderstoodthatconventionalsep ration techniques, can be, employed in -=connecticn withjthe processoi my invention. 'One conventional procedure which I have employed following batch operation of the present oxidation process is to distill the reaction mixture to a bottoms temperature of 141 C. to remove acetone, uncon- The distillation residue is then cooled to -18 C.'to crystallize adipic acid, which is thereafter separated by filtration. The adipic acid filtrate can be readily oxidized, for example, with nitric acid, to yield additional adipic acid. A typical adipic acid filtrate was found to analyze as follows.

I Weight per cent of filtrate Qyclohexanol-cyclohexanone 26 Adipic acid--- 23 l ligher molecular weight acid 51 period carried out with 40 percent nitric acid at 50-55 C.

in the presence of a trace of copper, the nitric acid beingreduced in this step to N20. In the second step-the temperature was raised to 60 0., at which it was maintained for 1 to 1.5 hours while the nitric acid was reduced to N02. The total reaction time in both steps was 2-2.5 hours. It was found that the yields of adipic acid, based on the adipic acid filtrate of runs 8, 9 and 10, were 85.5, 88.0 and 80.0 weight percent, respectively. The overall adipic acid yields in runs 8, 9 and 10 were, thus, 29.7, 26.0 and 20.5 mol percent, based on cyclohexane charged, and 77.8, 81.5 and 86.0 mol percent, based on the cyclohexane converted.

In a study of the use of "ketones other than acetone for the oxidation of cyclohexane toadipic acid, an oxidation was carried out in which g. of benzophenone (diphenylketone) Were used as the solvent for 62 g. of cyclohexane. Catalysts consisting of cobalt acetate, manganeseacetate, copper acetate (.01 g. each) and 1 percent cyclohexanone were used. A reaction period of 4 hours at 125-130" C. and an oxygen pressure of 100-250 p. s. i. g. were used. Only a slight drop in oxygen pressure was noted, with a 3 weight percent yield of adipic acid, based on the cyclohexane charged, being recovered. It is obvious that-benzophenone is not equivalent to acetone.

Having thus described my invention, what I ence of a polyvalent heavy metal catalyst and cyclohexanone reaction initiator, the improvement which comprises effecting said oxidation in a solution of cyclohexane in a solvent consisting essentially of acetone, the proportion of acetone in said solution being between about 10 and about '70 ercent by weight.

3. In a process for the liquids-phase oxidation of cyclohexaneto produce adipic acid in the'pr'esence of 'a'polyvalent heavy metal catalyst selected from the group consisting of carboxylates of cobalt, manganese and cyclohexanone reaction' initiator and both cobalt and manganese. the improvement which comprises effecting said oxidation in a solution of cyclohexane in a $01- A vent consisting essentially of acetone, the proportion of acetone in said solution being between about 10 and about percent by weight.

4. In a process for the liquid-phase oxidation of cyclohexane to produce adipic acid in the presence of a polyvalent heavy metal catalyst selected from the group consisting of carboxylates of cobalt, manganese and both cobalt and manganese, at a temperature between about C. and about 140 0., oxygen partial pressure between about 100 and about 300 p. s. i. g. and in,

the presence of a cyclohexanone initiator, the improvement which comprises efiecting said oxidation in a solution of cyclohexane in a solvent consisting essentially of acetone, the proportion of acetone in said solution being between about 10 and about 70 percent by Weight.

' 5. A process for the oxidation of cyclohexane to produce adipic acid, which process comprises subjecting cyclohexane and a solvent consisting essentially of acetone in proportions between about 10 and about 70 percent by weight, based on bothcyclohexane and acetone, to treatment with oxygen at a partial pressure between about 150 and about 250 p. s. i. g. at a temperature between about C. and about C. in the presence of an ,adipate of a polyvalent heavy metal selected from the class consisting of cobalt and cyclohexanone reaction initiator, manganese and both manganese and cobalt, and thereafter separating adipic acid from the-reaction mixture.

6. A process for the oxidation of cyclohexane to produce adipic acid, which process comprises subjecting cyclohexane and a solvent consisting essentially of acetone in proportions between about 10, and about 70 percent by weight, based on both cyclohexane and acetone, to treatment ganese and both manganese and cobalt, and

initially present cyclohexanone in an amount between about 0.1 and about 1.0 percent by weight, based on cyclohexane, and thereafter separating adipic acid from the reaction mixture.

' FRANCIST. WADSWORTH.-

REFERENCES CITED The following references'are of record in the file of this patent:

UNITED STATES PATENTS I Date Number Name 2,005,183 Flemming et a1. June 18, 1935 2,223,493 Loder -1. Dec. 3, 1940 Drossbach June 9, 1942

Claims

1. IN A PROCESS FOR THE LIQUID-PHASE OXIDATION OF A LIQUID CYCLOALKANE CONTAINING 4 TO 6 CARBON ATOMS, INCLUSIVE, IN THE RING TO PRODUCE AN ALKANE DICARBOXYLIC ACID IN THE PRESENCE OF A POLYVALENT HEAVY METAL CATALYST AND CYCLOHEXANONE REACTION INITIATOR, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID OXIDATION IN A SOLUTION OF SAID CYCLOALKANE IN A SOLVENT CONSISTING ESSENTIALLY OF ACETONE, THE PROPORTION OF ACETONE IN SAID SOLUTION BEING BETWEEN ABOUT 10 AND 70 PERCENT BY WEIGHT.