WO1994017021A1

WO1994017021A1 - Method for the catalyzed autoxidation of (cyclo)alkanes, (cyclo)alkyl aromatics and alcohols derived therefrom

Info

Publication number: WO1994017021A1
Application number: PCT/NL1994/000018
Authority: WO
Inventors: Roger Arthur Sheldon; Ji Dong Chen; Jihad Dakka
Original assignee: Technische Universiteit Delft
Priority date: 1993-01-26
Filing date: 1994-01-26
Publication date: 1994-08-04
Also published as: AU5892494A; NL9300149A

Abstract

The invention relates to an improvement in the practice of a catalyzed autoxidation of a starting material selected from (cyclo)alkanes, (cyclo)alkyl aromatics and alcohols derived therefrom. The improvement consists in the autoxidation being carried out by allowing oxygen to act on the employed starting material in the liquid phase, at elevated temperature and in the presence of a heterogeneous catalyst which is composed of a three-dimensional microporous structure, a so-called molecular sieve, containing aluminum, silicon and/or phosphorus oxides and a metal (Me) catalyst, incorporated into the lattice, which is selected from the transition metals from the groups 4 (Ti etc.), 5 (V etc.), 6 (Cr etc.), 7 (Mn etc.) and 8 (Fe etc.) of the Periodic System and the rare earths. This catalyst, which involves substantially no loss in use, leads to the obtainment of a remarkably favorable selectivity, in particular in the preparation of ketones.

Description

Title: Method for the catalyzed autoxidation of

(cyclo) alkanes, (cyclo) alkyl aromatics and alcohols derived therefrom.

The invention relates to a method for the catalyzed autoxidation of (cyclo)alkanes, (cyclo)alkyl aromatics or alcohols derived therefrom. Through such autoxidation, in particular aldehydes, ketones and acids are obtained, which can be used as starting materials for organic synthesis processes.

A very important cycloalkane is cyclohexane (Ch) , from which through autoxidation via cyclohexylhydroperoxide (Chhp) cyclohexanone (Chon) and cyclohexanol (Choi) are obtained. Chon can be converted to adipic acid, which is a reagent in the preparation of nylon 6.6. According to another industrial process, Chon is converted with hydroxylamine to form Chon oxime, which, through a Beckmann"transformation, yields ε-caprolactam, which is polymerized to form nylon 6. The above-mentioned autoxidation of (cyclo) alkanes and (cyclo) alkyl aromatics is practically always carried out in the presence of catalytically active metals, in particular transition metals such as cobalt. Chem. Eng. Sci. 1A, 139-149 (1961) reports a test plant for the autoxidation of Ch at elevated temperature and using pressurized air to obtain Chon. An oil-soluble cobalt catalyst can be added to reduce the peroxide concentration. In Recueil £__., 769-780 (1970) a study is devoted to the by_-products which are obtained in the autoxidation of Ch to form a mixture of Chon and Choi. The autoxidation is carried out in the presence of a small amount - of cobalt catalyst, viz. Co(II) octoate. Finally, it is known from J. Chem. Soc, Chem. Commun. , (1988), 104-105 to catalyze the autoxidation of tetralin in water with cobalt (II) -pyridine complexes attached to polymeric colloids. A comparison is made with the catalytic action of cobalt (II) -pyridine complexes in aqueous solution and of cobalt (II) acetate in acetic acid.

According to the above cited publications the catalytically active metals are used as an organic salt, for instance cobalt octoate, or in the form of a complex, but the catalysis involved is always a homogeneous catalysis, which means that the catalyst is present in dissolved condition, either in the organic liquid phase in which the autoxidation occurs, or in an aqueous phase which is in contact therewith. All industrial processes for the catalyzed autoxidation of Ch, for instance, also involve the use of homogeneous catalysis .

The catalyzed autoxidation of compounds belonging to the classes mentioned in the opening paragraph using a homogeneous catalyst has a number of important disadvantages. The fact is it is inevitable that as a result of leaching important amounts of catalyst are lost, which end up partly in the desired product and partly in waste streams. Further, it is difficult to recover the catalyst therefrom, so that on the one hand fresh catalyst must always be added and on the other the environment is undesirably affected with metal waste coming from the lost catalyst. In addition, the selectivity in the known autoxidation of, for instance, cycloalkanes and cycloalkyl aromatics with a homogeneous catalyst is rather unfavorable in the sense that, in addition to the desired ketone, for instance Chon, a fairly large amount of alcohol, for instance Choi, is obtained, which must subsequently be converted to ketone by dehydrogenation.

US-A-3,529,020 and DE-A-3, 229, 001 disclose the practice of catalyzed autoxidations using a catalytic metal provided through ion exchange on, respectively, crystalline alumino- silicate and a cation exchange resin. Although heterogeneous catalytic systems are involved here, the manner in which the catalytic metal is bound to the support is of a nature such that the catalytic metal gradually comes off during use. Accordingly, leaching occurs, as with the homogeneous catalysts described hereinabove, and with the associated disadvantages likewise discussed.

US-A-3, 692, 840 describes the oxidation of alcohols to form aldehydes or ketones in the presence of a gas containing free oxygen and further in the presence of a crystalline aluminosilicate catalyst which contains a transition metal having more than one valence, such as manganese and chromium. The oxidations involved here are oxidations in the vapor phase and the catalytically active metal has been provided on the crystalline aluminosilicate through ion exchange and is therefore gradually lost during use.

From EP-A-0,393,895 it is known to use molecular sieves based on crystalline silicometallates having silicon and iron incorporated into the lattice structure as catalyst in the oxidation of alkanes, in particular in the oxidation of methane to methanol . Other metals, such as chromium, vanadium and cobalt may be incorporated into the lattice. This publication is concerned with oxidations which are conducted in the vapor phase, which imposes a limitation on the substances eligible for conversion. EP-A-0,519,569 describes the catalytic oxidation of hydrocarbons such as cyclo(alkanes) with molecular oxygen in the liquid phase and using a heterogeneous catalyst consisting of a molecular sieve having cobalt incorporated into the lattice as catalytically active metal . Thus, catalytically active metal can be prevented from being lost during use. As appears from the single example, cyclohexane is oxidized in the presence of added acid, specifically acetic acid, to form the acetic acid ester of cyclohexanol and cyclohexanone in an ample 2/1 weight ratio. One object of the invention is to prevent loss of catalyst in the practice of autoxidations and thereby to avoid the environment being affected with metal waste.

Another object is to prepare substantially ketones through oxidation of (cyclo)alkanes, with only a relatively small amount of alcohol being formed additionnally

According to a further object of the invention, the desired conversion is promoted by further including an initiator in the reaction medium.

A yet further object is to carry out the autoxidation according to the invention without adding an acid to the reaction medium. A still further object of the invention is to provide a continued autoxidation to obtain one or more acids.

Still another object of the invention concerns the use of alcohols as starting material of the autoxidation, it being a particular object to prepare reaction products with a high purity.

To realize the objects as indicated above, the autoxidation according to the invention is carried out by allowing oxygen to act on the employed starting material in the liquid phase, at elevated temperature and in the presence of a heterogeneous catalyst which is composed of a three- dimensional microporous structure, a so-called molecular sieve, containing aluminum, silicon and/or phosphorus oxides and a metal (Me) catalyst, incorporated into the lattice, which is selected from the transition metals of the groups 4

(Ti, etc.), 5 (V, etc.), 6 (Cr, etc.), 7 (Mn, etc.) and 8 (Fe, etc.) of the Periodic System and the rare earths.

The catalytic metal component (Me) of the present heterogeneous catalyst has been found to remain inseparably attached to the molecular sieve acting as support, so that no metal (Me) is released into the reaction mixture nor is any metal (Me) lost when the catalyst is separated from the reaction mixture, for instance by filtration. The separated catalyst has moreover been found to retain its catalytic activity, so that it need not be reactivated through calcination before being used again.

Further, the present heterogeneous catalysts possess a high catalytic activity, while moreover a remarkably favorable selectivity could be established, for instance when it is desired for the autoxidation of (cyclo)alkanes or (cyclo) alkyl aromatics not to proceed beyond the ketone stage, which is oftentimes the aim in industrial processes. In that case, alcohol is formed in an intermediate stage and the selectivity of the process is then assessed on the ground of the weight ratio of ketone to alcohol, which is preferred to be as high as possible. In such cases, with heterogeneous catalysts according to the invention weight ratios of ketone to alcohol were obtained which are 5/1 or higher and range, for instance, between about 6/1 and 12/1.

The heterogeneous catalysts to be used in accordance with the invention are composed of a molecular sieve in which the catalytically active metals (Me) are incorporated, so that these constitute a fixed component of the molecular sieve. Molecular sieves are inorganic crystalline solid substances which are provided with fine holes or cavities where reactions can take place. Examples of molecular sieves to be used in accordance with the invention include aluminophosphates

(APOs) , aluminophosphosilicates (SAPOs) , aluminosilicates (zeolites) and silicalites (based on silica) . On account of the metals (Me) incorporated into the crystal lattice in the preparation, such molecular sieves which are eligible for use in accordance with the invention can conveniently be designated as Me-APOs, Me-SAPOs, Me-zeolites and Me- silicalites .

The molecular sieves for use in accordance with the invention can be prepared by techniques which are known per se. These techniques have frequently been described in the literature, as will appear from the references specified hereinafter. In broad outline, the preparation can thus be carried out that first an aqueous paste is formed which contains the selected starting materials in the desired relative proportions. Suitable starting materials include hydrated aluminum oxide, hydrated silicon oxide, a source of phosphate ions, a source of ions of the selected metal (Me) , typically a suitable Me-salt, and a so-called template, which is a compound which determines the positions where later the holes or cavities of the molecular sieve are formed. From the paste, typically via a gel structure, the intended crystalline structure of the molecular sieves is obtained. The metal (Me) then appears to be incorporated into the crystal lattice and occupy positions there which would otherwise be occupied by aluminum or silicon, for instance. The ultimate heterogeneous catalyst is then obtained by calcination, whereby the organic template material is burnt from the holes or cavities. The catalytic metal (Me) is selected from the transition metals from the groups 4 (Ti, etc.), 5 (V, etc.), 6 (Cr, etc.), 7 (Mn, etc.) and 8 (Fe, etc.) of the Periodic System and the rare earths such as Ce, La, etc. Typically, the metals involved are redox metals or metals which can occur in different valence states. Which metal (Me) or which combination of metals (Me) is selected depends on the specific autoxidation it is desired to carry out and can easily be determined by a person of ordinary skill on the basis of simple experiments. It has for instance been found that in the autoxidation of cycloalkanes and cycloalkyl aromatics to form ketones, especially chromium yields a high efficiency along with a favorable selectivity to ketone relative to alcohol.

In general, a better efficiency is attained according as more metal (Me) is incorporated into the molecular sieve. However, practical limitations apply, because if the percentage of metal (Me) is too high, this last cannot be permanently incorporated into the molecular sieve, so that during use release or leaching of Me occurs, which would be detrimental to the main object of the invention. It has been found that an amount of catalytic metal (Me) of from 0.5 to 4 and preferably of from 1 to 3 wt.%, based on the total catalyst, yields excellent results.

The holes or cavities in the molecular sieve should have a minimum size to allow the reaction mixture and the reaction components present therein to penetrate. The minimum size is therefore mainly determined by the nature of the starting material selected for the autoxidation, for instance cyclohexane or tetralin. Of course, larger holes or cavities may be present as well, but unduly large cavities, for instance of a size three or more times larger than the specified minimum size are less desirable, because they do not favor the efficient operation of the system. The desired size of the holes or cavities can be controlled in known manner, in particular by the choice of the template. Well known and much used templates are organic cavity-forming or cavity-filling compounds, for instance tri-alkylamines and tetra- alkylammonium salts, the size of the compounds used, for instance the length of the alkyl chains, being determinative of the final size of the holes or cavities. The actual holes or cavities are formed when the template is burnt away by a final calcination.

For more information about the preparation and the characterization of molecular sieves, the following references can be mentioned: U.S. Patent No. 4,759,919, Y. Xu, P.J. Maddox and J.M. Thomas, Polyhedron, 8(6), 819-826 (1989) and U.S. Patent Nos. 4,567,029 and 4,310,440 (for Me-APOs) ; U.S. Patent No. 4,358,397 (for Me-zeolites) ; M.S. Rigutto and H. van Bekkum, Applied Catalysts, Vol. 68, Ll-7 (1991), M.K. Dongare, P. Singh, P.P. Moghe and P. Ratnasamy, Zeolites, Vol. 11, September/October (1991), 690 and U.S. Patent No. 4,410,501 (for Me-silicalites) ; and Japanese patent publication Kokai 0358954 (for Me-silicalites and Me- zeolites) . A detailed description of the preparation of a number of molecular sieves with incorporated catalytic metal (Me) , suitable for use according to the invention, will be given hereinafter.

As starting material for carrying out the present method, preferably a (cyclo)alkane or a (cyclo)alkyl aromatic is used. These terms also encompass substituted derivatives thereof, the substituents being selected from halogen atoms, alkyl groups, nitro groups, etc. Specific examples of such compounds include: cyclohexane, cyclododecane, toluene, p-tert-butyltoluene, ethylbenzene, xylenes, tetralin, indane and antracene. As noted above, it is also possible to start from an alcohol derived from a (cyclo) alkane or a (cyclo) alkyl aromatic as mentioned above. Such an alcohol is in fact a compound which can be situated between the (cyclo) alkane or (cyclo) alkyl aromatic and the ketone which can be prepared therefrom through autoxidation. In practice, an alcohol is used as a starting material only when particular objectives are aimed for, in particular when it is desired to prepare fine chemicals. As alcohols, preferably secondary alcohols are used, which are found to yield ketone with a high selectivity. Examples of alcohols which can be used as starting material according to the invention are α-methylbenzyl alcohol, cyclohexanol, 1-tetralol and 1-indanol.

The present method can be carried out under atmospheric pressure, but is preferably carried out in an autoclave which is provided with a heating jacket, a stirrer, a condenser, a liquid separator, a gas supply, a gas outlet with needle valve and a valve for taking samples. As regards the apparatus, there are in fact no differences with the apparatus as used heretofore for carrying out similar autoxidations using a homogeneous catalyst. Typically, the starting material is introduced into the autoclave first and the heterogeneous catalyst is added thereto. The amount of catalyst may vary within wide limits. It is for instance possible to add an amount of catalyst such that the molar ratio of starting material to catalytic metal (Me) is in the range of 10/1 to 800/1. However, for practical use on an industrial scale, the molar ratio of starting material to catalytic metal (Me) is preferably selected in the range of 10/1 to 250/1. The autoclave can then be closed, whereafter oxygen is introduced under pressure. It is possible to work with oxygen alone or with a combination of oxygen and air. In any case the oxygen pressure should be sufficiently high for the autoxidation to take place and the oxygen pressure should be maintained during the course of the reaction by fresh supply. These reaction conditions are generally known to the person of ordinary skill. Mostly the oxygen pressure is selected in the range of from 3 to 15 atm., preferably in the range of from 5 to 12 atm. Then the reaction liquid is stirred and heated, preferably to a temperature of from 90-130°C.

The autoxidation carried out in the manner described above is continued until the intended conversion has been realized. In general, the reaction time is between 1 and 15 hours. By including an internal standard, viz. an inert substance such as chlorobenzene, in the reaction mixture and regularly taking a sample and analyzing this, the course of the reaction can be monitored and the reaction can be discontinued at the desired moment. The gas supply, heating and stirring are then stopped and the reaction mixture is cooled, whereafter the heterogeneous catalyst is separated from the reaction mixture. For this purpose, conventional techniques can be used, such as filtration and centrifugation. When in accordance with a preferred embodiment of the invention the aim is to obtain ketones, it appears, upon analysis of the recovered reaction product, a good to very good selectivity can be achieved with conversions of up to about 80%. In the case where a (cyclo) alkane or a (cyclo) alkyl aromatic is used as starting material, the assessment of the selectivity is particularly focussed on the ketone to alcohol ratio, as discussed hereinabove. It has further been found that often a better selectivity can be achieved by working at a lower reaction temperature, because in that case the chances of the occurrence of side reactions and continued reactions are typically smaller. Working at a lower reaction temperature of, for instance, from 90 to 120°C can be promoted, in accordance with a preferred embodiment of the invention, by including in the reaction medium a small amount of a hydroperoxide, for instance cylcohexylhydroperoxide or tert- butylhydroperoxide, as initiator. An amount of initiator of only 0.1-5 % already leads to the ready initiation of the autoxidation at a relatively low temperature. Conversely, at a given reaction temperature, the use of an initiator can effect a shortening of the reaction time, which may likewise favor the selectivity. The use of an initiator further promotes the activity, so that a higher conversion can be achieved. The addition of initiator can be carried out quite simply and efficiently by introducing a small portion of reaction liquid of a previous conversion as a component into a new reaction mixture to be formed.

Finally, it is further noted that in the case where the aim is to prepare ketones starting from a (cyclo) alkane^" or a (cyclo) alkyl aromatic as starting material, it is strongly preferred not to allow the proportion by weight of ketone to starting material during the autoxidation to become too large, preferably not larger than 60/40 and more preferably not larger than 50/50. The point is that when a rather large amount of reactive ketone is present in the reaction medium, the chances of continued reactions increase, which is undesired in view of the stated objective.

In accordance with the invention, it is possible not only to prepare ketones but also to carry out the autoxidation in such a manner that continued oxidation occurs and eventually one or more acids are obtained, which, if necessary, can be separated from each other by known techniques. For that purpose, the above described reaction conditions can be slightly changed by adjustment. For instance, the reaction temperature can be selected to be higher and/or a higher oxygen pressure can be employed and/or the reaction time can be prolonged. It is simple for a person of ordinary skill to determine the specific reaction conditions depending on the eventual reaction product it is desired to obtain.

Whatever the reaction product recovered in accordance with the invention, it has been established that it contains no or substantially no catalytic metal (Me) . This has been established through an extremely refined method of analysis, viz. by molecular spectography of a sensitivity in the ppb range. Accordingly, no leaching out of the catalytically active component, viz. the metal (Me), occurs. The heterogeneous catalyst separated from the reaction mixture can be washed and, after being dried, can be used again. Accordingly, the catalyst need not be reactivated by calcination or another treatment. This is an important advantage. The present catalyst has been found to possess a high stability upon recirculation and even an increase of the catalytic activity could be observed. This constitutes supplementary evidence that the catalytically active metal (Me) is fully retained and that the practice of the invention prevents the environment from sustaining damage as a result of lost catalyst.

The invention will be further explained on the basis of a number of directions for the preparation and examples. 1. Preparation of Cr-APO-5

55.1 ml demineralized water was added to 24.0 g pseudoboehmite (Pural SB, Condea Chemie) and the mixture was agitated for 2 minutes and subsequently stirred for 2 hours at room temperature.

4.6 g Cr3(OH)2 (CH3COO) (Aldrich) was dissolved in 68.7 ml demineralized water and stirred at room temperature until the chromium salt was completely dissolved. The solution was then filtered to remove small amounts of insoluble residues. The solution obtained was combined with a solution of 51.2 g H₃PO₄ (85%; Baker) in 65.1 ml water.

The combined solution thus obtained was added to the paste of pseudoboehmite and was vigorously agitated, whereafter the homogeneous mixture was allowed to rest for 1 hour under ambient conditions.

The mixture was cooled to 0°C with a bath of ice in water and 31.5 g tripropylamine (Janssen) was dropwise added with stirring at 0°C. Thus a gel was formed which was stirred at 0°C for 2 hours.

The viscous gel was placed in a teflon-coated 50 ml autoclave and heated in an oven for 24 h at 175°C under autogenous pressure. The autoclave was cooled with an air stream and the Cr-APO-5 crystals were recovered by stirring the contents of the autoclave for a few minutes in 300 ml demineralized water ^"to allow the crystals to settle and decanting the supernatant liquid. This procedure was repeated a number of times until a clear liquid was obtained. Then 150 ml ethanol was used to wash the crystals twice. Then the crystals were filtered off and dried for 4 h at 120°C.

The calcination was carried out by heating the crystals to 480°C with a temperature increase of 60°C/hour and maintaining them at 480°C for 5 h. The above described method of preparation deviates at some points from the preparation of Cr-APO-5 described in U.S Patent No. 4,759, 919. The molar composition of the Cr-APO-5 obtained is as follows :

0.05Cr₂θ3:0.9A1₂03:P2O5:Pr₃N:40H₂O

The Cr-APO-5 composition and structure were determined by the following techniques and by comparison with examples from the literature:

- X-ray powder diffraction patterns were measured on a Philips PW 1877 automatic powder diffractometer utilizing CuKα radiation (see the accompanying figure and a figure from the literature for comparison) ;

- a sample coated with an Au film applied by vaporization was examined under a scanning electron microscope (SEM) , for which a Jeol JSM-35 microscope was used;

- diffuse reflection spectra (DRS) were measured with a Hitachi 150-20 UV-VIS spectrophotometer provided with a diffuse reflection unit; the spectra were measured at wavelengths of 190 to 900 nm; - elemental analysis of the calcined Me-APOs was performed by the use of inductively coupled plasma-atomic emission spectrometry (ICP-AES, Perkin-Elmer Plasma-II) ; the sample t be analyzed was pretreated as follows: 150 mg of the calcine Me-APO was weighed out in a plastics bottle and 6 ml of an acid solution prepared by diluting 1 ml concentrated H₂S0₄ with 4 ml water and 1 ml 40% HF was added to the bottle; the bottle was closed and stored for 4-6 h at 60°C; then the bottle was cooled with ice and 8 ml 2.5% H3BO₃ was added; finally it was filled up with water to 100 ml.

2. Preparation of Mn-APO-5

MN-APO-5 was also prepared similarly to Cr-APO-5, but instead of Cr3 (OH) ₂ (CH₃COO) ₇ an equimolar amount of Mn (CH3COO)₂• H₂0 (Janssen) was used. The composition and structure were determined by the above-mentioned techniques 3, Preparation Qf V-APQ-

8 ml demineralized water was added to 4.26 g pseudoboehmite (75 wt .% AI2O3) and the mixture was agitated for 2 h at room temperature. Then 9.3 g H3PO₄ (85%; Merck) was dissolved therein and the liquid (A) obtained was stored at room temperature.

1.918 g vanadylsulfate (VOS0₄:5H₂θ; Merck) was dissolved in 18 ml demineralized water, and stirring was done at room temperature until the vanadium salt was completely dissolved. The vanadium solution was added to liquid (A) , whereafter the mixture was cooled in a water/ice bath. Then 4.12 g diisopropylamine was dropwise added to the mixture with stirring. A gel was obtained, which was stirred for 2 h at a temperature between 0 and 5°C.

The viscous blue gel was charged to a teflon-coated 50 ml autoclave and heated in an oven at 175°C for 2 days under autogenous pressure.

The further steps are analogous to what is described in preparation 1.

The above-described method of preparation deviates at some points from the preparation of V-APO-11 described in U.S. Patent No. 4,310,440.

The V-APO-11 composition and structure were determined by the techniques mentioned at the end of preparation 1.

4 , preparation of V-APQ-5

V-APO-5 was prepared in the same manner as V-APO-11, except that as template triethanolamine was used instead of diisopropylamine.

The determination of the composition and structure of V-APO-5, too, was carried out in the same manner as for V-APO-

5, Preparation of Cr-silicalite A solution (A) was prepared of 0.54 g CrCl₃.6H₂θ, 3.60 g NaCl, 1.72 g tetrapropylammonium bromide and 1.82 g H₂SO₄ (98%) in 17.35 g H₂0. A solution (B) was prepared, consisting of 22.05 g Na₂Siθ3 in 14.5 g H₂O.

A solution (C) was prepared of 12.22 g NaCl, 0.66 g tetrapropylammonium bromide, 0.72 g NaOH and 0.60 g H₂SO₄ (98%) in 62 g H2O.

The solutions (A) and (B) were slowly introduced into solution (C) with a supply pump, with stirring and under a nitrogen stream. The supply rate was regulated such that the pH of the mixture was kept within the range 10-10.5. The supply time was 20 minutes. Although some gel precipitation was observed, the solution was stirred for another 30 minutes . Then the solution was homogenized for 1 h. The solution was then transferred into an autoclave of stainless steel which was provided with a teflon coating. In the autoclave the solution, with stirring (120 tpm) under autogenous pressure, was first heated to 150°C in 2 h and subsequently to 220°C in 3 h. The temperature was then maintained at 220°C for 3 h, followed by cooling.

The crystals thus formed were washed with water and dried in a vacuum oven overnight at 80°C. Then the crystals were calcined for one day at 550°C.

The H-form in the crystals was subjected to ion exchange with (NH₄)₂Cθ₃ and then calcined for 3 h at 470°C.

The composition and structure of the product obtained were confirmed on the basis of XRD spectra and by comparison with examples from the literature. Figures presenting the XRD of the product prepared and of an example from the literature for comparison are annexed. The product prepared possesses the so-called pentasil structure.

Example 1

This example describes the autoxidation of cyclohexane (Ch) to cyclohexanone (Chon) using a heterogeneous catalyst according to the invention.

A device for carrying out a reaction under high pressure was used, consisting of a 300 ml autoclave provided with a heating jacket, a stirrer, a water-cooled condenser, a liquid separator, a gas supply, a gas outlet with needle valve and a valve for taking samples. The reaction was carried out as follows: 78.1 g (928 mmol) cyclohexane, to which had been added 0.4 g cyclohexylhydroperoxide (Chhp), 4.8 g Cr-APO-5 (prepared in accordance with the above specified directions; equivalent to 1.4 mmol Cr) and 5.5 g chlorobenzene (as internal standard), were introduced into the autoclave. The system was adjusted to a pressure of 20 atm. air and 5 atm. oxygen. During the reaction fresh oxygen was constantly supplied. The autoclave was then adjusted to 115°C in 15 minutes with stirring. At this temperature the reaction was carried out for 5 hours, whereafter the reaction mixture was cooled with an air stream and the catalyst was separated by filtration. The reaction mixture was then analyzed using the methods of analysis described hereinbelow.

Description of the methods of analysis

The reaction mixture was analyzed by gas chromatography (GC) to determine the quantity of residual starting material as well as the quantity of a number of reaction products. This analysis was carried out under the following conditions: column 25 m x 0.'32 mm, CP Sil 5 CB (molten silica), film thicknes 0.13 Jim, ratio 636. The sample to be analyzed was prepared as follows: first twice the amount of acetone was added to the reaction mixture (with internal standard) , in order to dissolve all acids. Then 30 μl of the sample was diluted with 700 μl of a solution of triphenylphosphine in acetone (24 g/1) and agitated a few seconds. The mixture obtained was then silylated for 30 minutes at room temperature with 200 μl hexamethyldisilazane and 100 μl trimethylchlorosilane. 0.1 μl of the sample thus prepared was analyzed by GC.

The amount of organic hydroperoxide was determined by titration. For that purpose, 0.5 g of the reaction mixture was added to 35 ml chloroform/acetic acid (1:2 v/v) , whereafter

2.5 ml of an aqueous KI solution (65 g/100 ml) was added. The solution thus obtained was placed in the dark for half an hour. After 50 ml demineralized water had been added, the solution was titrated with a solution of sodium thiosulfate (0.1 N) until the brown-yellow color had disappeared. Also carried out was a control test, where no reaction mixture was added.

The same methods of analysis as described here were also used in the further examples . Upon GC-analysis and titration of the reaction mixture obtained according to this example, 3 wt .% Ch was found to have been converted to Chon; Choi; Chhp; and acids including further by-products, with a selectivity (in percent by weight) of, resepctively 68; 10; 9; and 13. When the autoxidation was carried out at 130°C for 1.4 h, under otherwise identical conditions, likewise a conversion of 3 wt. % Ch was obtained and the selectivity (in percent by weight) was, respectively, 71 (Chon) ; 8 (Choi) ; 12 (Chhp) ; and 9 (acids including further by-products) . Upon autoxidation at 130°C for 1.4 h, but without the initiator Chhp, only a conversion of 0.5% Ch was achieved. Finally, the reaction mixture was also examined for traces of catalytic metal (Me) originating from the heterogeneous catalyst employed. This examination was carried out by molecular spectography. No traces of Me in the ppb range could be demonstrated. Accordingly, no release or leaching of the catalytic metal component (Me) ocurs .

Example 2

This example describes the autoxidation of tetralin to α-tetralone using a heterogeneous catalyst according to the invention.

The autoxidation was carried out in a thermostated 50 ml flask which was provided with a condenser and a magnetic stirrer. 6.61 g (50 mmol) tetralin and 2.5 g Cr-APO-5 (prepared in accordance with the above-specified directions; equivalent to 0.73 mmol Cr) were introduced into the flask. Then oxygen was insufflated through the reaction mixture at a flow rate of 20 ml/minute and the flask was placed in an oil bath of 100°C. With stirring (1000 rpm) the reaction was carried out for 16 h. After cooling and separation of the heterogeneous catalyst, 1, 4-dichlorobenzene was added as internal standard and the reaction mixture was analyzed. It was found that 22 wt.% of the tetralin had been converted to α-tetralone and α-tetralol with a selectivity (in percent by weight) of 82 and 14, respectively. Moreover, in the eventual reaction mixture only 2 wt.% tetralinhydroperoxyde was found. Example 3

In this example the influence of an initiator (hydroperoxide) is examined. The method described in Example 2 was repeated, but 0.45 g (5 mmol) tert-butylhydroperoxide (TBHP) in 1.09 g chlorobenzene was added dropwise to the reaction mixture after it had been placed in the oil bath. Moreover, the reaction was carried out only for 10 h (instead of 16 h) . Upon analysis it was found that 44 wt.% of the tetralin had been converted to α-tetralone, α-tetralol and tetralinhydroperoxide with a selectivity (in percent by weight) of 64; 7; and 20, respectively.

Accordingly, by the use of the initiator TBHP, in a shorter reaction time, a considerably higher conversion is achieved while the selectivity, viz. the weight proportion of ketone to alcohol, has also increased substantially, viz . from about 5.9 to about 9.1.

It is noted that hydroperoxide, which is formed in the practice of the present method, is not to be regarded as a by¬ product, since in practice recirculation is always employed and, as a result, all hydroperoxide present is eventually converted to ketone and alcohol.

Example 4

In this Example the recirculation of the heterogeneous catalyst is examined.

The procedure was as described in Example 3. After the heterogeneous catalyst Cr-APO-5 had been separated from the reaction mixture by filtration, it was washed with 50 ml acetone and filtered again. These treatments were carried out three times. Then the catalyst was vacuum-dried overnight at room temperature. Then the catalyst was used again. The results of these tests are summarized in Table 1 below. Table 1

first use and conversion (%) selectivity (%) recirculations α-tetralone α-tetralol

44 64 7

58 65 6

57 60 5

53 61 5 57 65 6

THP= tetralinhydroperoxide

Cr-APO-5 was calcined prior to recirculation (60°C/hour to 480°C and then at 480°C for 5 h)

It appears from these results that the activity of the catalyst increases when it is recirculated and that a calcination treatment to reactivate the catalyst can be omitted

Example 5

This example describes the autoxidation of indane to 1-indanone using varying amounts of a heterogeneous catalyst according to the invention. The method described in Example 3 was repeated, but instea of tetralin, 5.91 g (50 mmol) indane was introduced into the flask (molar ratio indane/chromium = 68.5) . Further, under otherwise identical conditions, a number of tests were carried out with varying amounts of catalyst and also a control test without catalyst, as is shown in Table 2 below, which also specifies the results obtained. As internal standard, in all of these tests n-hexadecane was used, which was afterwards added t the reaction mixture. Table 2

molar ratio conversion (%) selectivity (%) indane/chromium α-indanone α-indanol

65

64

45

41

IHP = indane hydroperoxide

without Cr-APO-5

The results obtained demonstrate that even if only very minor amounts of catalyst are used, still a reasonable conversion is obtained, so that the catalyst can be qualified a highly active. In addition, the selectivity remains very good a all times, regardless of the catalyst concentration.

Example 6

In this example the action of Mn-APO-5 as heterogeneous catalyst is examined.

The method described in Example 3 was repeated, but instea of Cr-APO-5, now 2.5 g Mn-APO-5 (prepared in accordance with th above-specified directions; equivalent to 0.73 mmol Mn) was use as heterogeneous catalyst.

Analysis of the reaction mixture revealed that 37 wt . % of the tetralin has been converted to α-tetralone, α-tetralol and tetralinhydroperoxide with a selectivity (in percent by weight) of 55; 10; and 35, respectively.

Example 7

This example relates to the autoxidation of secondary alcohols using a heterogeneous catalyst according to the invention. The autoxidation was carried out in a thermostated 50 ml flask which was provided with a condenser and a magnetic stirrer. 7.4 g (50 mmol) 1-tetralol in 5 ml chlorobenzene (as solvent) were introduced into the flask. Added to this were 0.4 g (5 mmol) tert-butylhydroperoxide (TBHP) in 0.87 g chlorobenzene, 2.5 g Cr-APO-5 (prepared in accordance with the above-specified directions; equivalent to 0.73 mmol Cr) , 1.6 g bicyclohexyl (as internal standard) and 1.2 g 3A molecular siev (as drying agent) . Then oxygen was insufflated through the reaction mixture at a flow rate of 20 ml/minute and the flask was placed in an oil bath of 110°C. With stirring (1000 rpm) reaction was carried out for 19 h. After cooling and separation of the heterogeneous catalyst, the reaction mixture was analyzed. The above-described method was repeated, but instead of 1-tetralol, 6.7 g (50 mmol) 1-indanol and 5.0 g (50 mmol) cyclohexanol, respectively, were used as starting material. The results obtained are shown in Table 3 below.

Table 3

starting material reaction product (alcohol) (ketone)

1-tetranol 1-tetralone

1-indanol 1-indanone cyclohexanol cyclohexanone

It appears from the results obtained that the activity is reasonable to very good and that the selectivity is good to ver good. Example 8

This example relates to the autoxidation of secondary alcohols in an autoclave, using a heterogeneous catalyst according to the invention.

The autoxidation was carried out in a 300 ml autoclave whi was provided with a heating jacket, a stirrer, a water-cooled condenser, a liquid separator, a gas supply, a gas outlet with needle valve and a valve for taking samples . The reaction was carried out as follows: 30.5 g (250 mmol) α-methylbenzyl alcoho 2.25 g (25 mmol) tert-butylhydroperoxide (TBHP) in 4.35 g chlorobenzene, 65 ml chlorobenzene (as solvent), 12.5 g Cr-APO- (prepared in accordance with the above-specified directions; equivalent to 3.65 mmol Cr) and 6 g 3A molecular sieve (as dryi agent) were introduced into the autoclave. The system was adjusted to a pressure of 20 atm. air and 5 atm. oxygen. During the reaction fresh oxygen was supplied constantly. Then the autoclave was adjusted to 110°C in 15 minutes with stirring (100 rpm) . At this temperature the reaction was carried out for 5 h with continued stirring, whereafter the reaction mixture was cooled with an air stream and the catalyst was separated by filtration. 1. -dichlorobenzene was added as internal standard and the reaction mixture was analyzed.

The above-described method was repeated, but instead of α-methylbenzyl alcohol, 25.0 g (250 mmol) cyclohexanol was used as starting material.

The results obtained are shown in Table 4 below.

Table 4 starting material reaction product conversion selectivit (alcohol) (ketone) (wt.%) (wt.

α-methylbenzyl acetophenone 31 96 alcohol

cyclohexanol cyclohexanone 30 97 Accordingly, along with a reasonably good activity an excellent selectivity is obtained. The presumable explanation o the fact that in the autoxidation of cyclohexanol a much higher selectivity (97 wt.%) was found than in Example 7 (60 wt.%) is that in Example 7 reaction product is displaced from the reacti mixture by the insufflated oxygen.

Claims

1. A method for the catalyzed autoxidation of a starting material selected from (cyclo) alkanes, (cyclo) alkyl aromatics alcohols derived therefrom, characterized in that the autoxidation is carried out by allowing oxygen to act on the employed starting material in the liquid phase, at elevated temperature and in the presence of a heterogeneous catalyst wh is composed of a three-dimensional microporous structure, a so-called molecular sieve, containing aluminum, silicon and/or phosphorus oxides and a metal (Me) catalyst, incorporated into lattice, which is selected from the transition metals from the groups 4 (Ti etc.), 5 (V etc.), 6 (Cr etc.), 7 (Mn etc.) and 8 (Fe etc.) of the Periodic System and the rare earths.

2. A method according to claim 1, characterized in that the molecular sieve is an aluminophosphate (APO) .

3. A method according to claim 1, characterized in that the molecular sieve is an aluminophosphosilicate (SAPO) .

4. A method according to claim 1, characterized in that the molecular sieve is a silicalite.

5. A method according to claim 1, characterized in that the molecular sieve is an aluminosilicate (zeolite) .

6. A method according to any one of claims 1-5, characteriz in that the metal (Me) is chromium.

7. A method according to claim 6, characterized in that the heterogeneous catalyst is Cr-APO-5.

8. A method according to claim 6, characterized in that the heterogeneous catalyst is Cr-silicalite.

9. A method according to any one of claims 1-8, characteriz in that the autoxidation is used for the preparation of a keto

10. A method according to claim 9, characterized in that a hydroperoxide is included in the reaction mixture as initiator

11. A method according to claim 9 or 10, characterized in th the autoxidation is carried out at a temperature of 120°C at most .

12. A method according to any one of claims 9-11, characteri in that, as starting material, a (cyclo) alkane or a (cyclo) alk aromatic is used and the autoxidation is carried out in such a manner that the weight ratio of ketone to starting material in the reaction mixture is maintained at a value not greater than 60/40.

13. A method according to any one of claims 9-12, characteri in that the autoxidation is applied to cyclohexane to prepare cyclohexanone.

14. A method according to any one of claims 9-12, characteri in that the autoxidation is applied to tetralin to prepare tetralone.

15. A method according to any one of claims 9-12, characteriz in that the autoxidation is applied to cyclododecane to prepare cyclododecanone.

16. A method according to any one of claims 1-8, characteriz in that the autoxidation is used for the preparation of acids.

17. A method according to any one of claims 1-16, characteriz in that the heterogeneous catalyst is separated from the reacti mixture and, after being washed and dried, is used again for t catalyzed autoxidation.