US3243449A - Oxidation of hydrocarbons to borate esters - Google Patents

Description

March 29, 1966 c. N. wlNNlcK OXIDATION OF HYDROCARBONS TO BORATE ESTERS Filed July 26. 1965 INVENTOR.

CHA/HES lV. W/NN/CK ATTORNEE United States Patent O 3,243,449 OXIDATIGN OF HYDRGCARBONS T BORATE ESTERS Charles N. Winnck, Teaneck, NJ., assignor to Halton International, Inc., a corporation of Delaware Filed `luly 26, 1965, Ser. No. 474,921 12 Claims. (Cl. 2610-462) This application is a continuation-in-part of copending application Serial No. 162,247, led December 26, 1961, now abandoned, and Serial No. 202,687, filed lune 15, 1962.

The present invention is concerned with the oxidation of saturated C., to C8 hydrocarbons with molecular oxygen in the presence of metaboric acid or a less hydrated form of ortho boric acid including boric anhydride at conditions whereby very high oxidation selectivities and economies are achieved.

It is broadly well-known to selectively oxidize hydrocarbons such as cyclohexane to form products including cyclohexanol and cyclohexanone. In processes for the production of adipic acid, phenol, cyclohexanone, and other important chemicals, a major step in the process involves the selective oxidation of cyclohexane. A disadvantage of prior processes has been the generally low selectivity of the oxidation reaction. A

It is generally old and well-known that the selectivity of molecular oxygen oxidations of hydrocarbons toa corresponding alcohol can be substantially improved by carrying out the oxidation in the presence of boric acid or a boric acid anhydride.

Luther et al., for example, in United States Patent 1,931,501 disclose that enhance-d alcohol production results from the molecular oxygen oxidation of hydrocarbons, including paraiins and naphthenes, boiling above 180 C. by adding to the hydrocarbons at least 2% by weight of a weak inorganic acid such as boric acid or its anhydride. l

Hellthaler et al. in United States Patent 1,947,989 disclose oxidizing hydrocarbons with molecular oxygen in the presence of boric acid whereby improved oxidation selectivity to alcohol is attained.l Preferred temperatures of 160 to 200 C. for the oxidation are taught. The process is described as capable of application in allcases where hydrocarbons can be oxidized in the absence of boric acid.

Russian work by Bashkirov et al., Dokladay Aked. Nauk. SSr. 118, No. l, pages 149 to 152 (1958), has shown that paratiins such as tridecane can be oxidized with nitrogen-oxygen mixtures containing 3.0-3.5 oxygen at 165 l70 C. with 5% added boric acid. Highk oxidation selectivities to alcohols and ketones is shown. A paper on the Russian work was summarized on June 3, 1959, by W. G. Toland at the Fifth World Petroleum Congress. See paper 15, section IV, Proceeding of the Fifth World Petroleum Congress.

In addition to boric acid and anhydrides, Aother boron compounds have been employed. For example, French Patent 1,166,679 teaches the use of borate esters such as tributyl borate in hydrocarbon oxidations.

Although the oxidation of higher hydrocarbons, both paraflins and naphthenes, with molecular oxygen in the presence of a boron `compound as above shown is indicated as proceeding readily with the production of alcohols in high selectivity, severe difliculties are encountered when it is attempted to apply this technology to lighter hydrocarbons such as hexane and cyclohexane. It is, of course, obvious to attempt to apply this prior ICC technology to-C4 to C saturated hydrocarbon oxidations.

And, as expected, the oxidation selectivity can in some instances be somewhat improved when following the prior art teachings.

However, it has not heretofore been possible with the volatile C4 to C8 hydrocarbons to provide a molecular oxygen oxidation process having reaction selectivities coinparable to those achieved with the heavier hydrocarbons while at the same time having favorable economies of operation.

For example, the Russian workers above described assert that in order to achieve high reaction selectivity it is necessary to operate with very low oxygen pressure, and in oxidation systems involving higher hydrocarbons the oxidant oxygen partial pressure can be lowered with but small reaction system changes. However, in the oxidation of the C4 to CB hydrocarbons the oxygen partial pressure caniiot be similarly lowered without rendering the process uneconomical and impractical. Heat input requirements necessary to maintain reaction conditions become excessive with the higher hydrocarbon sys- Further, although prior workers have recognized that water removal is an important consideration in the oxidation of hydrocarbons such as hexane, problems associated with water removal have prevented successful application of the heavier hydrocarbon boric acid oxidation technology to lighter, more Volatile hydrocarbons such as' hexane.

For example, in the discussion following the presentation of the Russian paper by W.- G. Toland, above referred to, at the Fifth World Petroleum Congress, H. M.4

- susceptible to oxidation.

If one tries to apply this process, this technique, to the lower and more volatile parains, this limitation becomes immediately apparent, and in fact in our laboratories,

is provided a novel and improved method for the molecu-y lar oxygen oxidation of saturated hydrocarbons having 4 to 8 carbon atoms.

The oxidation ofthis invention is carried out in a batchwise or continuous manner by contacting gaseous molecular oxygen with a mixture of liquid hydrocarbon and meta boric acid or a less hydrated derivative at a contact temperature in the range of about to 180 C. As an essential of the present invention, the reaction is so maintained that the partial pressure of water in the exit gases, i.e., the vapor above the liquid reaction mixture, in p.s.i. a., is not greater than P where P is given by the expression:

(1) logn, P=0.0iii2T-0.2759 and most desirably not greater than P where P is given by: (2) log, P=0.0175T 1.85

where T is the reaction temperature in degrees C.

FIGURE 1 is a graph illustrating reaction selectivity versus conversion. It also demonstrates the effect of water partial pressure on the selectivity conversion relationship. This graph represents a statistical averaging of several Patented Mar. 29, 1966 hundred oxidations by means of a regression analysis. Statistical analyses have shown the curves to accurately predict true -selectivities to within 1 point. Consequently, it is far more meaningful for allowing a finely accurate prediction of performance kthan any one or two runs where one can encounter deviations from the statistical mean values greater than 1 point.

Desirably, the Voxidation of this invention is carried out in a batchwise or continuous manner by contacting gaseous molecular oxygen with a mixture of liquid hydrocarbon and meta-boric acid at a reaction temperature in the range of 140 to 180 C. During the ,reaction a gaseous mixture comprising water and hydrocarbon, and usually also containing inert gas such as nitrogen, is removed from the reaction zone. In this practicerof the present inventive process the reaction is so maintained that the partial pressure of water in this exiting gas mixture in p.s.i.a. is not greater than P as given in Equation 1 above, preferably notrgreater than about 70% of P as given in Equation 1, desirably not greater than P as given in Equation 2, and most desirably 2 to 100% of P as given in Equation 2. y

Through practice of the present invention, hydrocarbon oxidationreaction selectivities in excess of 80 to 85% to products from which corresponding alcohols and ketones are readily recovered can be attained with high economies of operation.

Hydrocarbons which are oxidized by the process of this invention include cyclopentane, cyclohexane, cycloheptane, cyclooctane, methyl cyclohexane, the dimethyl cyclohexanes, n`pentene, n-hexane, n-heptane, the methyl pentanes, and the like. In preferred operation, and admixture of the hydrocarbon together with a selectivity Vpromoting amount of meta-boric acid or lower boric acid hydrate is formed. In a desirable embodiment of the invention, a slurry of ortho boric acid in the hydrocarbon is rst formed. This slurry issubjected to a dehydration treatment as by passing a gas therethrough at elevated temperature to dehydrate at least part and lpreferably substantially all of the ortho boric acid'. Other methods for v problems of slurry Vhandling inthe reaction and solids separation difficulties, it is generally not desirable t-o employ amounts of the boron compound expressed as metaboric acid in excess of about 20% by weight of the Ihydr0-` rcarbon-boron compound admixture. y

Meta-boric acid is preferably employed in this invention. Included among the lower hydrates of boric acid which also can be used are boron oxide and tetra-boric acid. By lower hydrates is meant derivatives of ortho boric .acid formed by removal of water. When 1lower hydrates are employed, and the partial pressure of water in the, vapors over the reaction mixture is above the equioxygen can be used, it is preferred to use molecular oxygen in admixture with inert gas such as nitrogen. Concentrations of oxygen, greater or lesser than those found in air equaling 4 to 25%, can be used. It is generally preferred to employ oxygen concentrations by volume of 10% or less in the oxidant gas toavoid possible formation of explosive mixture.

During the oxidation reaction, a gaseous mixture comprising such inert gas as is in the feed oxidant stream together with any unconsumed oxygen and water and hydrocarbon vapor is continuously removed from the reaction zone. The hydrocarbon vapor may be condensed, at least partially separated from water, and returned to the reactor as a liquid. Normally, lthe amount of water in the reaction zone and the concentration of this water in the gases exiting from the reaction zone is substantially dependent upon the oxygen concentration'in the oxidant gas stream and consumption during the reaction. However, additional possible sources of Water include the feed gases, the feed hydrocarbon mixture, and reux hydrocarbons from which a portion of the water has generally been removed by decantation, stripping or the like.

When meta-boric acid is used, the oxidation reaction is so conducted that the water partialv pressure in the vapor stream leaving the liquid reaction mixture in p.s.i.a. is 0.3% to 100% of P in accordance with the expression with T being the reaction temperature in degrees C., and preferably 0.3% to 70%. Y

When lower boric acid hydrates such as boron oxide are employed, pure oxygen and cooling can be employed inthe reaction. It is possible to use suicient amounts of the lower hydrate such that these hydrates react with water which is formed during the reaction or which is introduced into the reaction mixtu-re with feed materials such that the partial pressure of waterin the vapor above the reaction mixture is not greater than P as above described without the necessity of vapor removal from the reaction zone.V Of course, gradations of operation are possible such that the process can be operated adiabatically or with heat 'input using these lower hydrates.y Whereas, using meta-boric acid, as above described it is essential thatthe Water partial Vpressure in the exit vapors be at least 0.3% of P, with the lower hydrates forv economic operation it is necessary only thatV the water partial pressure in thevapor above the reaction mixl ture be no greater than P.

In practice ofv this invention wherein the hydrocarbons which are oxidized ,are C4 to C7 hydrocarbons, and the oxidation is carried out in the absence of solvent and of' large amounts of lowerY hydrates, the process often Y within the range above designated while operating at the librium pressure, the lower hydrates will tend to be conf verted to higher hydrates and even to meta-boric acid. It is a feature of the present invention that generally higher hydrocarbon conversions per pass can be achieved without the selectivity decrease which accompanied such higher conversions in prior yoxidation processes. The oxidation of this invention iscarriedlout such that about 4 to 25% desirably 8 to 20%, and preferably l0gto 15% of the hydrocarbon is oxidizedper pass in a continuous system `or per oxidation in a batch operation.

Suitably, the admixture of boron compound, preferably meta-boric acid, and hydrocarbon is heated to the 140 to 180 C.V oxidation temperature and a vgas containing molecular oxygeny is passed therethrough. Although VpureV desired reaction temperature. The heat input Ycan be accomplished in a variety of ways. Preferably, hydrocarbon removal from the reaction zone as vapor upon condensation `and separation from water is heated and/ or is vaporized and introduced into the reaction zone as vapor. Alternatively, heat can be provided through the reactorY walls, by vmeans of heating coils in theY reaction zone, and the like.v

With C8 hydrocarbons, it is more often possible to op-` erate adi'abatically, in .accordance with the invention. That is, the. heat liberated by the reaction is about suicient to provide the heat necessary for water and hydrof carbon vaporization.

It is possible to carry out the invention such .that a solvent is employed in the reaction mixture.' Suitable solvents areV those Vwhich are inert during the oxidation and which can be readily separated from the reactants and reaction products. Desirably organic compounds having noy reactive secondary or tertiary carbon atoms are employed. Hydrogens on primary carbon atoms are substantially inert in the present reaction. However, hydrogens on secondary and tertiary carbon atoms tend to be much more reactive in this reaction.

Preferably the compounds boil intermediate the hydrocarbon to be oxidized and the lowest boiling of the oxidation products. Illustrative solvents include hexamethyl ethane, neopentane, ethyl acetate, ditertiary butyl ether, substituted benzenes, halogenated hydrocarbons and the like.

It is to be noted that the presence of a solvent will change the characteristics of the reaction system. Thus, where the solvent is higher boiling than the hydrocarbon, the reaction will be able to be carried out under more nearly adiabatic conditions and in fact cooling may be required even for the C4 to C7 hydrocarbons.

Successful practice of this invention requires careful control and regulation of the reaction conditions. Thus, the oxidation reaction temperature must be in the range 140 to 180 C. and preferably 160 to 170 C. In actual practice in an experimental unit an exact reaction temperature is selected; a reaction pressure is then calculated on consideration of the hydrocarbon system in the reaction (with or Without solvent), the quantity of inerts fed to the reactor, and the quantity of water required to be removed, such that the volume of organics, inerts, and oxygen which may not be consumed leaving the reactor as vapor is suflicient to maintain the water pressure within the limits cited above; the heat transfer to the reactor is then adjusted so that the desired temperature and pressure conditions are met. In an alternate method of operation, the same calculation would be made, but the heat transfer could be adjusted to maintain the desired flow of organic vapors overhead, while the pressure would be adjusted to control reactor temperature. Illustrative pressures are in the range to 800 p.s.i.g.

For example, in the case of the oxidation of cyclohexane using as oxidizing gas air diluted with nitrogen to a volumeric concentration of oxygen of 10%, a reaction temperature of 165 C. is preferred. At this temperature, the vapor pressure of the liquid cyclohexane is about 105 p.s.i.a.

It is desirable and important to -operate at conditions of substantially complete oxygen consumption in order to make the most eicient use of the compressed oxidizing gas and to avoid explosion hazards. In the highly selective reaction of the present process, between about 1.0 and about 1.5 moles of water are formed per mol of oxygen consumed with very little carbon dioxide forma tion. Water contained in the feeds to the oxidation zone must likewise be removed in the manner of control of this invention. However, it is suitably illustrative to demonstrate the technique for the ideal case where there is no water in the feeds. Thus, using 10% oxygen as oxidizing gas, the water plus inerts in the oxidizing zone will be about 90 moles N2 and 10 to 15 moles of water per 100 moles of inlet oxidizing gas.

With the above parameters, in order to control the Water partial pressure in the exit gas at low level of the order of 2 p.s.i.a. the system pressure is determined by the sum of the vapor pressure of cyclohexane plus the pressure exerted by the water vapor plus inerts, For a Water partial pressure of 2 p.s.i.a. for 90 percent N?, and 10 percent water, the sum of N2 plus water partial pressures would be p.s.i.a. The system pressure then would be 20 p.s.i.a. plus the 105 p.s.i.a. cyclohexane vapor pressure, or 125 p.s.i.a. Similarly, for 85,5 percent nitrogen and 14.5 percent Water (90 moles NZ-lS moles Water) for a 2 p.s.i.a. water partial pressure the system pressure is 14 -plus 105 or 119 p.s.i.a.

Thus, the reaction system would be operated at a pressure -in the range of 119-125 p.s.i.a. with provision of sucent heat to maintain reaction temperature and pressure. A precise control to 2 p.s.i.a. water pressure is attained by analysis of the reactor ot gases for water and appropriate pressure regulation.

In an alternate method of operation, the same calculation would be made, but the heat transfer could be adjusted to maintain the desired flow of organic vapors overhead, while the pressure would be adjusted to control reactor temperature. Illustrative pressures are in the range 10 to 800 p.s.i.g.

In desirable economic operation of the invention, the vapor mixture from the reaction zone is cooled to con-l dense water and hydrocarbon. These condensed materials are separated as by decantation and the hydrocarbon returned to the reaction zone. Heat economies are achieved by heat exchange between the hydrocarbon returning to the reaction zone and vapors exiting from the reaction zone; if direct contact is used for such heat exchange, further stripping of water from the returning hydrocar bon is also accomplished. Heat necessary to sustain the reaction is preferably provided by heating the recycle hydrocarbon prior to introduction into the reaction zone.

At the termination of the oxidation reaction, the 4reaction mixture contains a substantial amount of the alkanol in the form of a borate ester thereof. If desired the borate ester can be recovered as such. In order to recover the alkanol as such it is desirable to subject the oxidation reaction mixture after removal of unreacted hydrocarbon to a hydrolysis whereby the alkanol liberated can readily be recovered by distillation, for example, by adding water to the oxidation reaction mixture after hydrocarbon removal and heating, e.g. to 50-150 C. Other known type techniques such as alcoholysis, transesteritication, and the like can be employed.

Accompanying FIG. 1 demonstrates the importance of water partial pressure on oxidation selectivity over a wide conversion range. The data illustrated in FIGURE 1 were obtained by analysis of a great number of cyclohexane oxidation runs using added meta-boric acid with wide variations in operating conditions. The critical effect of water partial pressure on the reaction selectivity is apparent from the gure. For example, referring to the figure, at conditions of constant conversion it is seen that reaction selectivity sharply decreases as the watery partial pressure increases. At 10% conversion, for example, at 3 p.s.i.a. water partial pressure selectivity to cyclohexanol plus cyclohexanone is about 88% whereas at 16.8 p.s.i.a. the selectivity is about 81% For comparison purposes, also presented in FIGURE l is a curve showing selectivity versus conversion for cyclohexane oxidations notinvolving the use of boron adjuvant. The single curve is valid over a wide range of water partial pressures since water partial pressure is not an important factor effecting reaction selectivity in sys-v tems which do not employ the meta-boric acid or less hydrated ortho boric acid form.

In systems not employing meta-boric acid or the like, water does not significantly influence the rea-ction selectivity. Water does tend to inhibit the oxidation itself, and tne presence of high amounts of water has in thel prior art necessitated higher temperatures to overcome the inhibiting effect. However, the actual selectivity of the re'- action is Virtually independent of water partial pressure.

In the following examples, unless otherwise specified parts and percentages are given by weight.

EXAMPLE I Cyclohexane in amount of 2711 parts is mixed with about 450 parts of iinely ground solid ortho-boric acid. The resulting slurry is heated to about 165 in an agitated, baied, glass-lined reactor equipped with heating jacket, vapor take-off, condenser, vapor-liquid separator, water separator and reflux return line, and a nitrogen stream passed therethrough at p.s.i.g. The ortho-boric acid readily dehydrates substantially completely to meta-boric acid, and a gaseous mixture of nitrogen, Water vapor and The resulting -slurry of meta-boric acid in cyclo hexane is maintained at 165 C. by adjusting the heat supply to the jacket as required. A gaseous mixture Ofv 4% by Volume oxygen in nitrogen is introduced into the reactor'below the liquid surface` at a rate of about 4 volumes per minute `(1 atm. and 25 C.) per about 3.8 volumes of slurry. Oxygen absorption is substantially complete after a short .period of time. The pressure in the reaction zone is maintained at 120 p.s.i.g. (134-.7 p.s.i.a.) by means of a pressure rcontrol valve on the vapors leaving the vapor-liquid separator. At these reaction conditions, t'he oxygen partial pressure vat the point of entry into the reaction zone is about 1.2 p.s.i.a. taking into consideration the .cyclohexane vapor pressure of 105 p.s.i.a.

at thereaction temperature (i.e.: 4% of 134.7-105).

During the reaction a vapor mixture comprising cyclohexane, Water and nitrogen is continuously removed from the reaction zone and cooledto condense water and cyclohexane. Vapors are separated from condensate fin the separator. After separation from Water by decantation the liquid cyclohexane is recycled to the reactor. Under the above reaction conditions, the water partial pressure in the gases exiting from the reaction zone is about 1.6 p.s.i.a.

After completion of the reaction (about 6 hours), the reaction mixture is admixed with 200 partsof Water and agitated under reflux of water-hydrocarbon azeotrope (about 70 C.) for 1 hour to .hydrolyze borate esters.

The resulting mixture is filtered to separate solid ortho-p boric acid and the ltrate is decanted to separate an organic phase from an aqueous phase. The aqueous phase is extracted With a small amount of cyclohexane 4and the extract is combined with theorganic phase; The organic phase is extracted with a small Aamount ot water to remove ortho-boric acid. .The resulting extracted organic mixture is distilled to separate cyclohexane overhead from a bottoms cyclohexanol fraction. The cyclohexanol fraction in the amount of 360 parts ycontains about 82% cyclo- Vhexanol and 3% cyclohexanone, andv the remainder other oxygenated cyclohexane products.

The cyclohexane conversion is about 11% EXAMPLE II In another comparative example, the importance vof maintaining the temperature within the speciiied 140C. to 180 C. range is illustrated.

Example I is repeated except that a slurry of 100 parts of othro-boric acid in 1000 parts of cyclohexane is dehydrated and the resulting mixture of meta boric acid and cyclohexane is oxidized for 4- hours at 200 C. and 253 p.s.i.a; Oxidant gas comprising by volume 4% oxygen inV EXAMPLE III As further comparison, illustrating operation which iS not within the scope of the present inventive process, a slurry of 900 parts of cycl-ohexane and 231 parts of boron oxide is formed. About 100 p.p.m. of cobalt based on cyclohexane` is added as cobalt naphthenate.

Air is passed through this slurry at a rate of about v170 volumes per hour per 1.3 volumes of slurry. The

reaction is carried out at a temperature of' 190 C. and at a pressure of 200 p.s.i.g. Oxygen absorptionafter minutes reaction time is about 32 volumes.

The reaction mixture is Worked up as described in Example -I. About 12% of the cyclohexane is converted Within reaction selectivity to cyclohexanol of 67.6% and a selectivity to cyclohexan'one of 3.9%

The total selectivity to cyclohexanol and cyclohexanone of 71.5% illustrates that` by the process of this example little or no selectivity improvement is achieved 4as con-` trasted with cyclohexane operation not employing a boron compound.

EXAMPLE IV As a further comparison, it is attempted `to carry out the oxidation as described in Example I at a temperature of C. No reaction isobtained. This example illustrates the importance .of the'lower specied temperature of the present invention. f

EXAMPLE Vl An admixture of 66 parts of iinely ground ortho-boric acid in 660 parts vof n-hexane is dehydrated and oxidized as described in `Example I. The reaction temperature is C., and reaction pressure 170 p.s.i.g. Oxidant gas consistent of 4% oxygen in nitrogen is 'employed at a rate of about 137 volumes Vper hour per volume of slurry. Inlet oxygen partial pressure is about 1.7 p.s.i.a. and exit gas Water partial pressure lis about 2.2 p.s.i.a. Oxidation is 4 hours, heat input by means of vaporized recycle hexane is maintained suicient to provide for water removal at the rate at which it is formed in and introduced into the vreaction zone.

After working up as in Example I, at 7% hexane convver-sion the selectivity to alcohol plus ketone is 86%.

EXAMPLE VI An admixture comprising a slurry of 10.0 parts of meta boric acidin 1000parts vof methyl cyclohexane is oxidized in a manner similar to that .described inlExarnple I. The reaction temperature is 160 C. and the reaction pressure is 62 p.s.i.g. Oxidant gas consisting of 8% oxygen in nitrogen is employed at a rate ot about v volumes per hour per 1.3 volumes of slurry.Y Then Ioxidation is continued until Y24 liters of oxygen is absorbed.

The inletoxygen .partial pressure is about 1 .34 p.s.i.a. and the .exit gaswater partial pressure is. about 1.74-p.s.i.a. Heat input by means of Vvaporized .recycle methyl ,cyclohexane is maintained sufficient to provide for` water re- `moval at Athe rate at which it is formed in and introduced vinto the reaction zone. About 10% of the methyl cyclohexane is reacted. A

After working upV as in Example I, the overall selectivity1to alcohol `plus ketone is about 78%. 1-methyl cyclohexanol is formed in amount of about 26%, 2- methyl cyclohexanol is formed in amount of about 17 3- and4-rnethyl cyclohexanols together are formed in amount of about 28%, and a mixture of methyl cyclohexanones in amount of about 6% is formed.

Y EXAMPLE VII Example V is repeated substituting n-heptane in'place .of the methyl cyclohexane. Generally similar selectivity to alcohol plus ketone Aare obtained. K l

EXAMPLE vm A glass line reactor equipped with a vapor take-olf, condenser and water separator was used. During the reaction, vapors were continuously removed, condensed, Water separated and the cyclohexane returned to the reaction.

At the termination of the reaction, the resulting mixture was distilled to separate unreacted cyclohexane, and the thusly obtained oxidation reaction mixture was hydrolyzed. The hydrolysis was accomplished by adding Water and heating to about 80-1'00" C. The cyclohexanol-cyclohexanone product was recovered by decantation and steam distillation.

The following table shows the results obtained. Run D wherein no 'boron compound was used is included for purpose of comparison.

EXAMPLE X111 Example I is repeated except that a gaseous mixture of 10% by volume oxygen in nitrogen is employed. The

Table I Run A B C D E oyciohexsne, parts 2,711 2, 684 2,740 2, 000 2,750 Boron compound, parts- 303 154 84 None 456 Cyelohexanone, parts 5 5 5 None None Airow rate, l./min 2.4 2 2.4 4.4 12.4 Reaction Temperature, 0.--. 173-170 163-164 168-174 157-158 165-167 Reaction pressure, p.s.i.g 120 125 150 120 O2 Uptake (approx.) liters 54 51 74 50 Cyclohexane reacted, percent 7. 6 7.8 6. 7 8. 3 14. 4 Reaction selectivity to eyclohexan and eyclohexanone, percent 80 76 80 61 90 Ratio cyelohexanol/eyclohexanone 19. 3/1 4.7/1 3.9/1 l 1.2/1 31/1 Water partial pressure in eiuent gas,

psig 2.5-4.2 V8.5-9.0 S14-12.7 17. 80-1a0 1.1-1.3

1 4% oxygen in nitrogen. The above results show the improved oxidation selectivity reaction Zone pressure is maintained at about 259 p.s.i.a. to cycloalkanol and cycloalkanone obtained through the At the reaction conditions, the oxygen partial pressure use of the specified boron compounds. The results also at the point of entry into the reaction zone is about 15.4 establish the very high selectivity to cycloallcanol attained psig, taking into consideration the cyclohexane vapor through the use of the higher amounts of boron Compressure of 105 p.s.i.a. at the165 C. reaction temperature pounds. For example, in Runs A and E selectvities (eg, 10% of 259-105). Vapors are removed as detO CYCOheXaHOl and CYCIOheXaHODe Were Obtained Which scribed` in Example I. Under these reaction conditions, were about 130 to 150% that `Obtained Where 110 bOrOIl thewater partial pressure in the gases exiting from the Compound Was employed (RUB D) M3111/ fold improve' reaction zone is about 20 p.s.i.a. ments in SeleCtVtY t0 CYCOheXaDOl Were attained as The reaction `is continued until about 10.5% of the shown in the above data. cyclohexane is reacted. The reaction mixture is Worked EXAMPLE 1X up as described in Example I. AMolar selectivity to cyclohexanol plus cyclohexanone is found to be 80%, with a Runs A, B, C and E 0f Example VIH were repeFted ratio of cyclohexanol to cyclohexanone of about 6:1. using cyclooctane instead of cyclohexane. Substantially EXAMPLE XIV similar percentage improvements in reaction selectivity to cyclooctanol and cyclooctanone and in the cycloocta- Example 1S repeated etCePt that a faSeOUS mlXtUfe 0f nol to cyclooctanone ratio were obtained as contrasted 10%.135 Volume OXYgeIl 1n .Dltff'gefl 1S employed The with operation employing no boron compund reaction zone pressure 1s maintamed at about 336 p.s.1.a. At the reaction conditions, the oxygen partial pressure at EXAMPLE X the point of entry into the reaction zone is about 23 p.s.i.a. Runs A, B, C and E of Example VIII were repeated taking into consideration the cyclohexane vapor pressure using cyclopentane instead of cyclohexane. Substantially 0f 105 p.s.i.a. at the 165 C. reaction temperature (i.e., similar percentage improvements in reaction selectivity 10% of 336-105). Vapors are removed as described in to cyclopentanol and cyclopentanone and in the cyclo- Example I. Under these reaction conditions, the water pentanol to cyclopentanone ratio were obtained as conpartial pressure in the gases exiting from the reaction trasted with operation employing no boron compound. zorrieh is about 30 p.s.i.a. d 1 b 7 f e reaction is continue unti a out 9.0 o o the cyclo- EXAMPLE XI hexane is reacted. The reaction mixture is Worked up as Runs A, B, C and E of Example VIII were repeated described in Example I. Molar selectivity to cyclohexanol using cycloheptane instead of cyclohexane. Substantially plus cyclohexanone is found to -be 80%. similar percentage improvements in reaction selectivity to The present inventive process can be carried out withcycloheptanol and cycloheptanone and in the cyclohepout a catalyst. In previous processes which did not emtanol to cycloheptanone ratio were obtained as contrasted ploy a boron compound, it was necessary to employ small with operation employing no boron compound. amounts of a catalytic material such as cobalt salt in order EXAMPLE XH to successfully oxidize cyclohexane with molecular oxygen to a mixture which comprised cyclohexanone and cyclo- Methylcyclohexane was oxidized 1n accordance with the 70 heXanOL However, in the present process wherein molecinvention in a manner similar to that described in Ex- 'ulmoxygen is contaeted with the mixture of metab0ri ample VIII, Run E. The following table shows reaction Iacid and hydrocarbons under the stated conditions, it has conditions and the results obtained. A run without the vbeen found that materials previously used as catalysts in use of boron compound is presented for purposes of comnon-boric acid oxidations have substantially no effect or parison. l I- possibly an adverse eifect and thus are not required.

11 Initiators such as aldehydesfketones, and peroxides can Vbe used. Illustrative of such initiator is cyclohexanone, hydrogen peroxide, tertiary butyl hydroperoxide, and the like. t

EXAMPLE XV Cyclohexane is continuously oxidizedin a series of four reactors at a temperature ofu165 C. and a pressure of 140 p.s.i.a. using as oxidizing gas 10 vol. percent O2 and 90 vol. percent N2.

To the -rst reactor is added per hour 2750 mols of liquid commercial purity cyclohexane and ,.67 rn,ols metaboric acid preheated to Vabout 165 C. Also introduced into the first reactor per hour are 440 mols of cyclohexane vapor at about 165 C. and 240 moles of said oxidizing gas.

A vapor mixture of about 770 moles cyclohexane, 207 moles N2, 2 moles unreacted O2, and about 25 moles water per hour is removed from the iirst reactor.

A liquid stream containingabout 2395 moles cyclohexane and about moles oxidized cyclohexane'iscon-Y tinuously passed from the rst to the second' reactor. About 350 moles cyclohexane vapor at about 165 C. and 210 moles of oxidizing gas were introduced into the second reactor.

A vapor mixture of about 680 moles cyclohexane, 18 moles nitrogen and 25 moles water was removed per hour from the second reactor. A liquid mixture containing about 2040 moles cyclohexane and 50 moles oxidized cyclohexane was transferred per hour from the second to the third reactor. f

About 330 mol cyclohexane vapor at about 165 C. and 210 moles oxidizing gas were introduced per hour into said third reactor and contacted with the liquid mixture.

From the third reactor there was withdrawn per hour a vapor mixture of about660 moles cyclohexane, 189 moles nitrogen and 25'mol`es water and also a liquid mixture containing about 1685 moles cyclohexane 'and 75 moles oxidized cyclohexane which was sent to the fourth reactor.

About 290 moles cyclohexane vapor at about 165 C. and 210 moles oxidizing gas per-hour were-introduced into the fourth reactor per hour. j

A vapo-r mixture of about 620 moles cyclohexane, 189 moles nitrogen, and 25 moles water were removed per hour from the fourth reactor. A Vliquid product mixture of 1330 moles cyclohexane and 100 moles oxidized product were recovered per hour.

The vapor streams from the reactor were condensedr and cyclohexane recovered and recycled after separation of water contained therein.

The product mixture was hydrolyzed as describedin Example I and the organic phase distilled to separate cyclohexane Which was recycled to the reaction.

The product fraction was about'88% cyclohexanol and .cyclohexanone at a cyclohexane conversion of 7%. The` EXAMPLE XVI For comparison purposes a run was made oxidizing cyclohexane with air with 6.2% by VWeight ortho-boric acid and controlling the water partial pressure in excess of about 100 p.s.i.a. The temperature was 165 170 pressure results in poor selectivitiesof the order of those obtained with boron compound addition.

By selectivity in the foregoing is meant the molar percentage of reacted hydrocarbon which forms the alcohol or ketone. By conversion is meant the percentage of hydrocarbon changed which is reacted.

t What is claimed is: L The process for the oxidationof a C4 to C3, saturated hydrocarbon to produce a borate ester containing oxidation reaction mixture wherein a molecular oxygen containing ga's is contacted in a reaction zone with a mixture of said hydrocarbon in the liquid phase and a lower hydrate of boric acid, comprising the combination of effecting said contact at a reaction temperature in the reaction zone in the range of 140 to 180 C., removing a gaseous mixture comprising vapors of said hydrocarbons and water from said liquid phase during the oxidation, and maintainingthepartial pressure of water in p.s.i. in said gaseous mixture not greater than P Where P is given by the equation:

logm P=-1.85}0.0175(T) with T being the reaction temperature in degrees C., and

f tion reaction mixture wherein a molecular oxygen containing gasfis contacted in a reaction zone with a mixture of said hydrocarbon in the liquid phase and meta boric acid,.comprising the combination of effecting said contact at a reaction temperature in the reaction zone in the 'range of 140 to 180 C., removing a gaseous mixture comprising vapors of said hydrocarbon and water from said liquidvphase during the oxidation, and maintaining the partial pressure of water in p.s.i. in said gaseous mix- Vture leaving t-he said liquid phase in the range 2% to 100% of P where P is given vby the equation: f mgm P=1.85+o.0175(:r)

with T being the reaction temperature in degrees C., and recovering the resulting oxidation reaction mixture.

, 3. The process of claim 2 wherein said hydrocarbon is cyclohexane. t

f 4. Th-e process of claim 2 wherein said hydrocarbon is n-hexane. Y

V5.V The process of claim 2 wherein said hydrocarbon is methyl cyclohexane.

6. rThe process for the oxidation of a C4 to C7 saturated hydrocarbon to produce a borate ester containing oxidation lreaction mixture wherein a molecular oxygen containing gas is contacted in a reaction zone with a mixture of said hydrocarbon in the liquid phase, and meta boric acid, comprising the combination of eecting said contact at a reactionV temperature in the reaction zone in the range of 140 to 180 C., continuously during the oxidation removinga gaseous mixture from said liquid phase cornprising vapors of said hydrocarbon and water, continuously providing heat to said reaction Zone in addition to the heat of reaction, and maintaining the partial pressure of and pressure was 500l p.s.i.g. At 12.7% cyclohexane conversion, the selectivity to cyclohexanol plus cyclo-hexanone was only about 64%. Y

This comparison clearly demonstrates that operation outside the scope of the invention at high water partial water in p.s.i. in said gaseous mixture leaving the said liquidphase in the range 2% to 100% of P wherein P is given by the equation:

With-T being the reaction temperature in degrees C., and recovering the resulting oxidation reaction mixture.

7. The process for the oxidation of cyclohexane wherein a molecular oxygen containing gas is contacted with a mixture of cyclohexane in the liquid phase and meta boric acidV to produce a boraite ester reaction mixture comprising .the combination [of |effec-ting said lcontact alt -a reaction .ternperature |in fthe reaction zone in :the range of to 180 C. continuing the contact until y4% to 25% of the cyclohexane is reacted, continuously during said contact removing a gaseous mixture containing vapors of said cyclohexane and water from said liquid phase condensing' the thus removed cyclohexane and water, separating the condensed cyclohexane, vaporizing separated cyclohexane, returning the vaporized cyclohexane into contact with the liquid mixture in the reaction Zone, and maintaining the partial pressure of water in p.s.i. in the gaseous mixture leaving the liquid phase in the range 2% to 100% of P wherein P is given by the equation:

with T being the reaction temperature in degrees C., and recovering the resulting oxidation reaction mixture.

8. The process of claim 7 wherein 8% to 20% of the cyclohexane is reacted.

9. The process for the oxidation of a C4 to C8, saturated hydrocarbon to produce a borate ester containing oxidation reaction mixture wherein a molecular oxygen containing gas is contacted in a reaction zone with a mixture of said hydrocarbon in the liquid phase and a lower hydrate of boric acid, comprising the combination of effecting said contact at a reaction temperature in the reaction zone in the range of 140 to 180 C., removing a gaseous mixture comprising vapors of said hydrocarbons and water from said liquid phase during the oxidation, and maintaining the partial pressure of water in p.s.i. in said gaseous mixture not greater than P where P is given by the equation:A

logm P=0.01l12T-0.259

with T being the reaction temperature in degrees C., and recovering the resulting oxidation reaction mixture.

10. The process for the oxidation of a C4 to C8, saturated hydrocarbon to produce a borate ester containing oxidation reaction mixture wherein a molecular oxygen containing gas is contacted in a reaction zone With a mixture of said hydrocarbon in the liquid phase and meta boric acid, comprising the combination of affecting said contact ata reaction temperature in the reaction zone in the range of 140 to 180 C., removing a gaseous mixture comprising vapors of said Ihydrocarbon and water from said liquid phase during the oxidation, and maintaining the partial pressure of water in p.s.i. in said gaseous mixture leaving the said liquid phase not greater than P where P is given by the equation:

logw P=0.0l112T-0.259

with T being the reaction temperature in degrees C., and recovering the resulting oxidation reaction mixture.

11. The process for the oxidation of a C4 to C7 saturated hydrocarbon to produce a borate ester containing oxidation reaction mixture wherein a molecular oxygen containing gas is contacted in a reaction zone with a mixture of said hydrocarbon in the liquid phase, and meta boric acid, comprising the combination of etlecting said contact at a reaction temperature in the range of to C., continuously during the oxidation removing a gaseous mixture from said liquid phase comprising vapors of said hydrocarbon and water, continuously providing heat to said reaction zone in addition to the heat of reaction, and maintaining the partial pressure of Water in p.s.i. in said gaseous mixture leaving the said liquid phase not greater than P where P is given by the equation:

with T being the reaction temperature in degrees C. and recovering the resulting oxidation reaction mixture.

12. The process for the oxidation of cyclohexane wherein a molecular oxygen containing gas is contacted with a mixture of cyclohexane in the liquid phase and meta boric acid to produce a borate ester reaction mixture comprising the combination `of effecting said contact at a reaction temperature in the reaction zone in the range of 140 to 180 C. continuing the contact until 4% to 25% of the cyclohexane is reacted, continuously during said contact removing a gaseous mixture containing vapors of said cyclohexane and Water from said liquid phase condensing the thus removed cyclohexane and Water, separating the condensed cyclohexane, vaporizing separated cyclohexane, returning the vaporized cyclohexane into contact with the liquid mixture in the reaction zone, and maintaining the partial pressure of water p.s.i. in the gaseous mixture leaving the liquid phase not greater than P where P is given by the equation:

logm P=o.01112T-0.259

with T being the reaction temperature in degrees C., and recovering the resulting oxidation reaction mixture.

No references cited.

CHARLES B. PARKER, Primary Examiner.

DELBERT R. PHILLIPS, Assistant Examiner.

Claims (1)

1. THE PROCESS FOR THE OXIDATION OF A C4 TO C8, SATURATED HYDROCARBON TO PROUDUCE A BORATE ESTER CONTAINING OXIDATION REACTION MIXTURE WHEREIN A MOLECULAR OXYGEN CONTAINING GAS IS CONTACTED IN A REACTION ZONE WITH A MIXTURE OF SAID HYDROCARBON IN THE LIQUID PHASE AND A LOWER HYDRATE OF BORIC ACID, COMPRISING HE COMBINATION OF EFFECTING SAID CONTACT AT A REACTION TEMPERATURE IN THE REACTION ZONE IN THE RANGE OF 140* TO 180*C., REMOVING A GASEOUS MIXTURE COMPRISING VAPORS OF SAID HYDROCARBONS AND WATER FROM SAID LIQUID PHASE DURING THE OXIDATION, AND MAINTAINING THE PARTIAL PRESSURE OF WATER IN P.S.I. IN SAID GASEOUS MIXTURE NOT GREATER THAN P WHERE P IS GIVEN BYTHE EQUATION:

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