FR2839973A1 - Direct oxidation of hydrocarbons, alcohols and/or ketones to the corresponding carboxylic acids by oxygen or an oxygen-containing gas in the presence of a catalyst - Google Patents

Abstract

Process for a liquid phase oxidation of a hydrocarbon, alcohol and/or ketone with oxygen or an oxygen-containing gas in a protic or aprotic polar solvent and in the presence of a zirconium and cerium compound as catalyst.

Description

and hexanols, higher alcohols and their isomeric forms.

- - -

  PROCESS FOR THE OXIDATION OF HYDROCARBONS, ALCOHOLS AND / OR KETONES

  The present invention relates to the oxidation, by oxygen or a gas containing it, of hydrocarbons to carboxylic acids, alcohols and corresponding ketones or of alcohols of ketones to corresponding carboxylic acids. The direct oxidation by oxygen of the hydrocarbons, more closely related to the cycloalkanes, in the presence of a catalyst, is a process which has been studied for a long time. Indeed, there would be obvious advantages in avoiding the use of an oxidant like nitric acid, used in one of the stages of current industrial processes, this

  which would save the processing of the nitrogen oxides generated.

  In the many variants of such a catalytic oxidation process by

  Oxygen, cobalt is the most frequently recommended catalyst.

  Thus, American patent US-A-2 223 493, published in December 1940, describes the oxidation of cyclic hydrocarbons to corresponding diacids, in the liquid phase generally comprising acetic acid, at a temperature of at least 60 C, using a gas containing oxygen and in the presence of an oxidation catalyst such

that one consists of cobalt.

  American patent US-A-4,902,827, published in February 1990, describes an improvement in the air oxidation of cyclohexane to adipic acid, in the liquid phase comprising acetic acid, at a temperature of 80 ° C. to 160 C and in the presence of an oxidation catalyst comprising a soluble cobalt compound and a compound

  soluble in zirconium and in hafnium.

  More recently, it has been advocated in patent EP-A-0 694 333 to implement in the context of the oxidation of hydrocarbons by oxygen, a catalyst

  comprising a cobalt salt and a ferric salt.

  It was also recommended in patent EP0870751 to use a catalyst

  comprising a cobalt salt and a chromium salt to improve selectivity.

  As another usual catalyst for this oxidation reaction, mention may be made of manganese. It nevertheless appears that if the selectivities and productivity obtained with the catalytic systems used in the previous processes described above are acceptable, there is always a search for new catalytic systems making it possible to improve productivity and selectivity as well as the ease of recovery and recycling

of the catalyst.

  This is what the present invention proposes to achieve. Wile consists more precisely in a process for the oxidation of hydrocarbon, alcohol and / or ketone using oxygen or a gas containing it, in the liquid phase and in the presence of a catalyst, characterized in that the catalyst comprises at least one compound of zirconium and at

minus one consists of cerium.

  The hydrocarbons which are used as starting substrates in the process of the invention are more particularly alkanes, cycloalkanes, kylaromatic hydrocarbons, al cenes and cycloa lcenes having from 3 to 20 carbon atoms. . Among these hydrocarbons, cycloalkanes, in particular those which have a cycle having from 5 to 12 carbon atoms, are certainly the most important, because their oxidation leads to dicarboxylic acids or to intermediate cycloalkanols and cycloalkanones. The most interesting hydrocarbon is cyclohexane, the oxidation of which leads to adipic acid, one of the basic compounds of polyamide 6-6, but can also provide the

  cyclohexanone leading to caprolactam and therefore to polyamide 6.

  The present process can also be used for the oxidation of alcohols or intermediate ketones, in particular cycloalkanols and cycloaicanones having from 5 to 12

  carbon atoms, to prepare the corresponding dicarboxylic acids.

  In what follows, the process will be more particularly described for the oxidation of hydrocarbons, essentially cycloalkanes, and in a preferred way for

oxidation of cyclohexane.

  The catalytic system comprising compounds of zirconium and cerium allows direct preparation of adipic acid with good selectivity when the oxidation of cyclohexane is carried out. These catalytic properties are obviously very

  advantageous for industrial exploitation of this oxidation reaction.

  According to a first embodiment of the invention, the catalytic system comprises at least one compound of zirconium soluble in the reaction medium, chosen for example in a nonlimiting manner from zirconium chloride, zirconium bromide, zirconium nitrate l zirconium acetylacetonate and zirconium carboxylates such as zirconium acetate tetrahydrate, zirconium propionate, zirconium adipate, zirconium glutarate, zirconium succinate, zirconium octoate, and at least one compound of cerium soluble in the reaction medium, chosen for example in a nonlimiting manner from cerium chloride, cerium bromide, cerium nitrate, cerium acetylacetonate and cerium carboxylates such as' cerium acetate tetrahydrate, propionate cerium, cerium adipate, glutarate

  cerium, cerium succinate, cerium octoate.

  The catalyst can also comprise, as doping elements, other metal compounds chosen from the group comprising Cu. Ag, Au, Mg, Ca, Sr, Ba, Zn, Cd, Hg, Al, Sc, ln, Tl, Y, Ga, Ti, Hf, Ge, Sn, Pb, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd. Pt and combinations thereof. The term “metallic element compound” should be understood to mean compounds comprising at least one atom of said metal in association with other chemical elements such as, for example, oxygen, but

also metal alone.

  According to a second embodiment of the invention, the catalyst according to the invention comprises a support comprising at least one compound of zirconium and at least one compound of cerium. The zirconium and cerium compounds are supported or impregnated on the inert support according to conventional techniques for manufacturing so-called supported catalysts. The catalyst can also be constituted by a mixture of zirconium and cerium oxides or by a mixed oxide of zirconium and cerium. It can also include in tent that doping elements one or more elements

  metal from the list indicated above for the first embodiment.

  As suitable support for the invention, mention may be made of advantageously porous metal oxides such as aluminum oxides, silicon oxides, active or graphite carbon, zeolites, silicalites, aluminophosphates,

  silicoaluminophosphates, organic resins.

  The molar ratio between zirconium and cerium can vary within wide limits. It is thus possible to implement a molar ratio Zr / Ce understood

  advantageously between 1 / 0.00001 to 1/100, preferably between 1/0, 0001 to 1/10.

  The quantity of other metals when present, may vary in mole ratios to zirconium, similar to those indicated above for cerium. The catalyst can be obtained in situ by loading the zirconium and cerium compounds and possibly other metals in the reaction medium. It can also be prepared extemporaneously by mixing said compounds in the proportions necessary to obtain the Zr / Ce molar ratios and possibly the

other metals.

  Preferably, this mixture is produced using a solvent, advantageously a

  solvent of the same nature as that used for the oxidation reaction.

  The amount of catalyst, expressed as a percentage by weight of metallic elements (zirconium, cerium and possibly other metals) relative to the reaction mixture, is generally between 0.0001 and 10%, advantageously between 0.001 and 2%, without these values are critical. It is however a question of having sufficient activity without however using excessively large quantities. Indeed, the

  catalyst must be separated from the final reaction medium and recycled.

  It is advantageous to also use a compound which initiates the oxidation reaction. The initiators often sell hydroperoxides, such as, for example, cyclohexyl hydroperoxide or tert-butyl hydroperoxide. This wind also ketones or aldehydes, such as for example cyclohexanone which is

  one of the compounds formed during the oxidation of cyclohexane or acetaldehyde.

  Generally the initiator represents from 0.01% to 20% by weight of the weight of the reaction mixture used, without these proportions having a critical value. The initiator is especially useful when starting oxidation and when carrying out the oxidation of cyclohexane at a temperature below 120 C and discontinuously. It can be introduced

from the start of the reaction.

  The liquid reaction medium preferably contains an at least partial solvent for the carboxylic acid and for the alcohol for the ketone, the preparation of which is aimed at by carrying out the process of the invention. This solvent can be very varied in nature insofar as it is not appreciably oxidizable under the reaction conditions. It can in particular be chosen from polar protic solvents and polar aprotic solvents. As polar protic solvents, mention may, for example, be made of carboxylic acids having only primary or secondary hydrogen atoms, in particular aliphatic acids having from 2 to 9 carbon atoms, perfluoroalkylcarboxylic acids such as trifluoroacetic acid, acids with lipophilic character such as hexano7que, heptano7que, octanoTque, ethyl-2 hexano7que, nonano7que, decano7que, undecanoique, dodecanoque, stearique (octadecano7que) acids and their alkyl derivatives (total substitution of hydrogen

  methylenes by the methyl group), 2-octadecylsuccinic acid, 2,5-

  ditertiobutyl benzoique, 4-tertiobutylbenzo7que, 4-octylbenzo7que, tertiobutyle hydrogenoorthophthalate, naphtenic or anthracene acids substituted by alkyl groups, preferably of the tertiobutyl type, substituted derivatives of phthalic acids, fatty acids like dimer fat. Mention may also be made of acids belonging to the preceding families and carrying different electron donor substituents (groups with heteroatom of type O or N) or electro acceptors (halogens, sulfonimides, nitro groups, sulfonato or the like), alcohols such as tertiobutanol. As polar aprotic solvents, mention may be made, for example, of lower alkyl esters (ie an alkyl radical having from 1 to 4 carbon atoms) of carboxylic acids, in particular the carboxylic acids mentioned above, the tetramethylene sulfone (or sulfolane), acetonitrile, ketones such as acetone, halogenated hydrocarbons such as dichloromethane,

  chlorobenzene, dichlorobenzenes or fluorescent hydrocarbons.

  Carboxylic acids with a lipophilic or non-lipid character are preferably used as solvent for the oxidation reaction of cyclohexane. It is convenient to use a catalyst whose zirconium and cerium constituents are in the form of compounds derived from the carboxylic acid used as solvent or acids produced by the oxidation reaction, insofar as said compounds are soluble in the

reaction medium.

  The solvent, as defined above, generally represents from 1% to 99% by weight of the reaction medium, preferably from 5% to 90% and even more preferably from 10% to 80%. Oxidation can also be carried out in the presence of water introduced from

  the initial stage of the process or during the reaction.

  The temperature at which the oxidation reaction is carried out is variable, in particular depending on the substrate used. Wile is generally between 50 C

  and 200 C and preferably between 80 C and 140 C.

  Pressure is not a critical parameter of the process. Wile can be lower, equal or higher than atmospheric pressure. Generally it will be between 0.1

  MPa (1 bar) and 20 MPa (200 bar), without these values being imperative.

  You can use pure oxygen (air, enriched air) or oxygen depleted

  or even oxygen diluted by an inert gas.

  The following examples illustrate the invention.

EXAMPLE 1

  In a 125 ml autoclave, are charged: - 22.4 9 of cyclohexane - 27.3 9 of acetic acid - 0.22 9 of cyclohexanone - 1 9 of catalyst formed by an alumina on which were impregnated with zirconium oxide and cerium oxide allowing to have in the reaction medium

  7370 ppm of cerium and 6700 ppm of zirconium.

  After closing the reactor, the mixture is heated to 105 ° C., with shaking. After 180 minutes of reaction, the autoclave is cooled and then degassed. The reaction mixture is analyzed to determine the conversion rate and selectivity. These

  wind analyzes carried out by gas chromatography.

  By selectivity (ST) we mean the molar ratio expressed in percent of the number of moles dose of a species compared to the theoretical number of moles of ltespece

  calculates from the number of moles of cyclohexane actually transformed :.

  The following results are obtained: - conversion rate (TT) of cyclohexane: 5.5% - ST into cyclohexanol compared to cyclohexane transforms: 24.6% - ST into cyclohexanone compared to cyclohexane transforms: 1.3% - ST into adipic acid relative to cyclohexane transforms: 51.4% - molar ratio adipic acid / total of the diacids formed: 80.8%

COMPARATIVE EXAMPLE 2

  Example 1 is repeated in the same apparatus and under the same operating conditions, with the following charge of reagents: - 22.1 g of cyclohexane - 27.2 9 of acetic acid - 0.22 g of cyclohexanone - 0, 49g of zirconium acetylacetonate allowing to have 1860 ppm of Zr in the reaction medium

  The reaction time is 180 minutes and the temperature is 105 C.

  The following results are obtained: - conversion rate (TT) of cyclohexane: 4.4% - ST into cyclohexanol compared to cyclohexane transforms: 28.4% - ST into cyclohexanone compared to cyclohexane transforms: 45.1% - ST into adipic acid relative to cyclohexane transforms: 9.2% - molar ratio of adipic acid / total of the diacids formed: 56.4%

EXAMPLE 3

  Example 1 is repeated in the same apparatus and under the same operating conditions, but adding the following charge: - 22.5 g of cyclohexane - 27.5 g of acetic acid - 0.24 g of cyclohexanone - 0, 43 g of zirconium acetylacetonate and 0.1616 9 of cerium acetonate making it possible to have 1600 ppm of zirconium and 1320 ppm of cerium in the reaction medium.

  The reaction time is 180 minutes and the temperature is 105 C.

  The results obtained are: - conversion rate (TT) of cyclohexane: 2.5% - ST into cyclohexanol compared to cyclohexane transformed: 16.2% ST into cyclohexanone compared to cyclohexane transformed: 0% - ST into adipic acid by compared to cyclohexane transformed: 27.9% This test shows, in comparison with example 2, the positive effect of the presence of

  cerium on the selectivity to adipic acid of zirconium catalysis.

Claims (13)

  1) Process for the oxidation of hydrocarbons, alcohols and ketones to carboxylic acid, using oxygen or a gas containing it, in the liquid phase in a solvent chosen from polar protic solvents and solvents polar aprotics and in the presence of a catalyst, characterized in that the catalyst comprises a compound   zirconium and at least one compound of cerium.   2) Method according to claim 1, characterized in that the hydrocarbon used as starting substrate is chosen from cycloalkanes which have a cycle having from 5 to   12 carbon atoms, and is preferably cyclohexane.   3) Method according to claim 1, characterized in that the alcohol eVou ketone used as starting substrate wind selected from cycloalcanols and cycloalcanones which have a ring having 5 to 12 carbon atoms, and preferably wind the cyclohexanol eVou cyclohexanone.   4) Method according to one of claims 1 to 3, characterized in that the   zirconium and cerium compounds are soluble in the reaction medium.   ) Method according to one of claims 1 to 4, characterized in that the   catalyst comprises at least one zirconium compound soluble in the reaction medium, chosen from zirconium chloride, zirconium bromide, zirconium nitrate, zirconium acetylacetonate and zirconium carboxylates such as zirconium tetrahydrate acetate, zirconium propionate, zirconium adipate,   zirconium glutarate, zirconium succinate, zirconium octoate.   6) Method according to one of claims 1 to 5, characterized in that the   catalyst comprises at least one compound of cerium soluble in the reaction medium, chosen from cerium chloride, cerium bromide, cerium nitrate, cerium acetylacetonate and cerium carboxylates such as cerium acetate, ie propionate cerium, cerium adipate, cerium glutarate, cerium succinate, Cerium octoate.   7) Method according to one of claims 1 to 3, characterized in that the   catalyst comprises a support comprising at least one zirconium compound and at least minus one consists of cerium.   8) Method according to claim 7, characterized in that the inert support is chosen from the group comprising aluminum oxides, silicon oxides, active carbon, zeolites, silicalites, aluminophosphates, silicoaluminophosphates, resins organic.   9) Method according to one of claims 1 to 3, characterized in that the   catalyst includes zirconium oxide and cerium oxide or a mixed oxide zirconium and cerium.   ) Method according to one of claims 1 to 9, characterized in that the ratio   molar between zirconium and cerium is between 1 / 0.00001 to 1/100.   11) Method according to one of claims 1 to 6 and 10, characterized in that the   amount of catalyst, expressed as a percentage by weight of metallic elements relative to the reaction mixture, is between 0.0001 and 10%, preferably between 0.001 and 2%.   12) Method according to one of the preceding claims, characterized in that the   catalyst comprises at least one metallic doping element chosen from the group comprising Cu metallic elements. Ag, Au, Mg, Ca, Sr, Ba, Zn, Cd, Hg, Al, Sc, In, Tl, Y. Ga, Ti, Hf. Ge, Sn, Pb, V, Nb, Ta, Cr. Mo, W. Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd. Pt and combinations thereof   13) Method according to one of claims 1 to 12, characterized in that the medium   liquid reaction mixture contains a solvent chosen from aliphatic carboxylic acids having from 2 to 9 carbon atoms and their esters, perfluoroalkylcarboxylic acids and their esters, lipophilic acids and their esters, alcohols, halogenated hydrocarbons, ketones, tetramethylene sulfone (or sulfolane), acetonitrile.   14) Method according to one of claims 1 to 13, characterized in that the   solvent used is chosen from the group comprising acetic acid, hexanoTque, heptano7que, octanoque, ethyl-2 hexanoque, nonanoque, decanoque, undecanoque, dodecanoTque, stearique (octadecanoque) and their methyl derivatives, 2-octadecylsuccinic acid, 2,5- ditertiobutyl benzorque, 4-tertiobutylbenzo7que, 4 octylbenzoque, terticbutyl hydrogenoorthophthalate, naphtenic or anthmcAniques acids subshrubs by aloe groups, ddhvAs subsD1uAs des physical scides, bold decides.   ) ProcAdA according to one of the claims 1 to 14, caraAMsA in that soan1 represents from 1 99 in pos of the mUu rdaionnet of prAdrenoe of 5 gO. 16) PcAdA only resells 1 15, cara6MsA in that the 1empAmiu A 1aquene is 6th the oxidion aion is comphse e 50'C   200 C and prAmnce ene 80 C and 140 C.   17) ProcAdA according to one of the claims 1 to 16, caraAdsA in that the pressure which is formed from the oxidation aion is between 0.1 Pa (1 baO Pa (200 baO.