DE1212508B - Process for the catalytic oxidation of partially hydrogenated, polycyclic, aromatic and heterocyclic compounds - Google Patents

Description

Process for the catalytic oxidation of partially hydrogenated, polycyclic, aromatic and heterocyclic compounds The invention relates to a process for the catalytic oxidation of partially hydrogenated, polycyclic, aromatic and heterocyclic compounds with a free oxygen-containing gas in the liquid phase in the presence of a solvent. The process is characterized in that the oxidation is carried out with a compound of the general formula in which R1, R2 and R3 are a hydrogen atom or the methyl radical and R2 and R3 together with the carbon atoms to which they are bonded can form a six-membered aromatic ring. and in which X is - CH2, C = O or - 0 -, with the proviso that X always signifies CH2 when R1 or R2 stands for the methyl radical or when R2 and R3 together with the carbon atoms to which they are bonded , form a six-membered aromatic ring, in a solvent that promotes the formation of carbanions in the presence of benzyltrimethylammonium hydroxide or methoxide as a catalyst and with an oxygen-containing gas free of acidic impurities.

It is already a process for the oxidation of a hydrocarbon with at least one aliphatic bridge or chain in the molecule, the 2 carbon atoms one or more aromatic nuclei connects together, known in which the oxidation with an oxygen-containing gas in the liquid phase in the presence of cations of metal salts acting as a catalyst and in the presence of a monobasic organic acid is carried out as a solvent at 100 to 200 "C. Furthermore is already a process for the oxidation of hydrocarbons with an intermediate two benzene rings lying methylene group known, in which the oxidation in a carboxylic acid solution in the presence of bromine and a metal.

The method of the subject matter of the invention is distinguished from one another the known processes due to their lower sensitivity to oxidation inhibitors and higher selectivity and also leads to more valuable oxidation production. When oxidizing 9,10-dihydroanthracene using cations as a catalyst you get only anthrone while using the method according to the invention too Anthraquinone comes, which is a valuable chemical raw material. The starting products an oxidation process carried out using metal catalysts must be cleaned of inhibitors, especially phenols, while in the process of the subject matter of the invention is not sensitive to the known inhibitors was found, i.e., one can contaminate starting materials, for example Contain phenolic compounds, use immediately without prior cleaning. At the Furthermore, the method according to the invention does not involve an aromatic nucleus bonded methyl groups, but a single methylene substituent between two aromatic nuclei oxidized. In the case of oxidation, in the case of distillation, a hydrogenated one Coal tar fraction resulting mixture of 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, For example, 1,2,3,4-tetrahydroanthracene and alkyl-substituted acenaphthene are used only the 9,10-dihydroanthracene is oxidized, while in the known processes a complex mixture of oxidation products would arise.

With the aid of the method according to the invention, for example 9,10-dihydroanthracene to anthraquinone, anthrone to anthraquinone, l-methyl-9,10-dihydroanthracene to l-methylanthraquinone, 2-methyl- 9,10-dihydroanthracene to 2-methylanthraquinone, Oxidize xanthene to xanthone and 5,12-dihydrotetracene to 5,12-tetracenchinone.

The method according to the invention is now based on the oxidation of 9,10-dihydroanthracene to anthraquinone explained in more detail.

A solution of 9,10-dihydroanthracene (9.0 g; 50 millimoles) in 50 cm3 of anhydrous pyridine was used as a solution of benzyltrimethylammonium hydroxide Added catalyst (3 millimoles) in pyridine (1.7 cm3). This solution was based on Heated to about 50 to 60 ° C and oxygen passed through the solution with stirring (0.31 1 / min.). The heat of reaction was allowed to rise to 70.degree. C. The temperature of 70.degree was maintained by air cooling for the first 30 minutes. After about 10 Anthraquinone began to crystallize in minutes. Heat was then added, thus a temperature of 70 "C during the entire reaction time of 2 hours was maintained. - Then the mixture was cooled to 25 "C. The catalyst was neutralized with acetic acid, which turns the color of the solution from red in Changed light yellow. The solvent was evaporated under reduced pressure, the Washed residue with water, collected in the filter and dried. The reaction product contained 71% anthraquinone, 2701o anthracene and - no 9,10-dihydroanthracene ..

The specified procedure was used under regulated test conditions - repeated, with the difference that only the given variable varies became. The results shown below were obtained.

The oxidation of. 9,10-dihydroanthracene to anthracbinone. can take place in a wide temperature range. The results are tabulated and the optimal temperature was between about 50 "C -709C. Temperature conversion to anthraquinone in ° C in% -20 8 0 10 30 13 50 71 70 70 90 40 The temperature does not necessarily have to be kept constant. The heat of reaction can rise from the temperature of the surroundings to about 80 ° C. and then decrease to that of the surroundings when the heat of reaction is consumed. In an experiment of this kind, the yield was 69010 anthraquinone.

With different molecular ratios of catalyst to 9,10-dihydroanthracene, the results shown in the table below were obtained. Molecular Ratio Yield. of catalyst for 9,10-di- on anthraquinone hydroanthracene in% 0.015 19 0.03 29 0.06 70 0.09 67 The greatest conversion is achieved at a catalyst ratio of approximately 0.03 to 0.06.

The conversion to anthraquinone fell from 70 to 45% when the concentration of 9,10-dihydroanthracene successively from 1 to 2 and then from 2 to 4 mol each Liters of pyridine was increased. These results were likely due to the inadequate Dispersion of the oxygen caused at higher concentrations at which the Anthraquinone, which crystallizes out of the solution, a heavy suspension forms.

The flow of oxygen is a variable in the reaction that depends on the effective dispersion of the gas during the reaction. Even though only 2 moles of oxygen are required to convert 1 mole of anthraquinone is formed by 1 mole of 9,10-dihydroanthracene, is usually an excess initiated in oxygen or air. With a reaction time of 2 hours Yields of approximately 70O / o, which are comparable with one another, achieved if 0.31 or 1.13 1 / min. Oxygen were supplied, from which it can be seen that even there was an excess of oxygen at the lower feed. A reaction time with an oxygen flow of 1.13 l / min.

SCFM and one of 70 ° C from 1 to 2 and 2 to 3 hours was not decisive. If it is advisable, the oxidation can be accelerated considerably be that it is carried out at an increased pressure of oxygen. Was for example the original pressure of oxygen was about one ata, then the reaction is completed after about 20 minutes at 70 ° C. An analysis of the reaction product gave a conversion to anthraquinone of 70ff / 0 and a conversion to anthracene from 180 / o. If the initial oxygen pressure in an autoclave was about 5 ata, then the reaction was complete in about 7 minutes at a maximum temperature of 55 ° C.

Analysis of the reaction product in this case revealed a conversion in anthraquinone of 900 / o and a conversion to anthracene of 100 / o.

Is the oxygen through carbon dioxide-free air at a flow rate replaced by 0.011 SCFM, then. a conversion into 3601o anthraquinone took place. Increasing the air flow to 0.04 SCFM increased the percentage of conversion only on 390 / o. It was possible to increase the conversion rate to more than 39%, as will be described later.

Amines other than pyridine have been found to be effective solvents for the reactants in the oxidation of 9,10-dihydroanthracene to anthraquinone proven. The various amines that are effective solvents lead to one Conversion of 15 to 81% in anthraquinone can result in the following groups are divided into: Amines Heterocyclic: N-pyridine; 2,3- or 4-piroline; Quinoline; N-methylmorpholine, N-morpholine; Piperidine.

Aromatic: aniline; N, N-dimethylaniline.

Cycloalkylic: cyclohexylamine.

Alkylics: n-hexylamine.

Polybasic: N, N-dimethylaminopropylamine, diethylenetriamine.

Other solvents that promote the formation of carbanions, though are less effective than the pyridines, but are suitable for autoxidation, are nitrobenzene, benzonitrile, acetonitrile, N, N-dimethylformamide and tetrahydrofuran.

As mentioned earlier, the reaction can take place in the presence of water be performed. Surprisingly, a significant proportion of water is the invention Procedure even beneficial.

Was the volume of the solvent used for the reaction 98% aqueous pyridine, then the conversion to anthraquinone was 670% in comparison 71% in anhydrous pyridine. At 95 and 900% aqueous pyridine were the corresponding Yields 87 and 750 / o. The use of 95 percent by volume aqueous pyridine as a solvent and the use of carbon dioxide-free air as an oxidizing agent leads to the greatest yield of anthraquinone and an increase in the conversion to anthraquinone from 39 740 / o.

A decisive advantage of the process of the invention is the suitability of the commercially available 40% strength methanolic solution of benzyltrimethylammonium hydroxide (A) or benzyltrimethylammonium methoxide (B), as can be seen from the table below. conversion of 9,10-dihy- Solvent catalyst droanthracen in Anthraquinone 950 / o aqueous A in pyridine 870 / o Pyridine 95 0 / o aqueous A in methanol 870 / o Pyridine 95% methanolic A in pyridine 75% Pyridine 950 / o methanolic B in pyridine 860/0 Pyridine The amount of anthraquinone that can be separated off better by collecting the crystals in the suspension after the reaction has ended than by removing the solvent was determined. When using 98, 95 and 900 / o aqueous pyridine as solvent, the corresponding amounts of anthraquinone were 64% (80% pure), 94% (98% and more pure) and 71% (96% pure).

In the best test, more than 980/0 of the anthraquinone was formed separated by filtration.

It was also the reusability of the reaction medium after the separation of the crystallized anthraquinone checked. The first reaction was carried out in a 95% solution of aqueous pyridine at 70 ° C. within 2 hours. Then the mixture was cooled to 25 ° C and the anthraquinone using a pyridine wash (300 cm3 per mole of 9,10-dihydroanthracene) collected. The reaction medium including the washing solutions was again for the oxidation of 50 millimoles 9,10-dihydroanthracene used. At first it seemed that there was not enough anthraquinone so that additional catalyst was used (in a molecular Ratio of 0.008) The occurrence of oxidation was shown by the rise in temperature. After 2 hours the cycle was repeated. The second iteration was a larger amount of catalyst (in a molecular ratio of 0.06) is required. After the third proportion of anthraquinone crystals had been withdrawn, the reaction medium became recovered. The following conversions were achieved: Oxidation in fresh Reaction medium: 85% (97% pure), first repetition: 51% (92% pure); second repetition: 96% (94% pure). The average rate of conversion was therefore 740 per cent. It is thus possible to use the reaction medium repeatedly, but with each repetition fresh catalyst must be added. The amount of catalyst required is almost the same as that of the first reaction.

The modifications in the operating conditions during the oxidation of 9,10-dihydroanthracene are summarized in the following compilations and the explanation of the important variables, their range of action and the preferred values. Verified preferred Total area area Volume percent water in pyridine ............................ 0 to 10 5 Concentration of 9,10-dihydroanthracene in moles per liter Pyridine ........................ ... ........... | 4 to 1 | 1 Molecular ratio of catalyst to 9,10-dihydro anthracene ........................................ 0.015 to 0.12 0.06 Reaction temperature in ° C ................................. | -20 to 90 | 60 to 70 Response time in hours ................... ............. 0.1 to 3 1 to 2 Reaction pressure in ata .................................... 1 to 5 1 to 5 The preferred solvent is 95% aqueous pyridine. The preferred catalysts are benzyltrimethylammonium hydroxide and methoxide in pyridine or methanol. It is not necessary that the reaction temperature be kept constant. The temperature should be more than 500 ° C., but not more than 70 ° C. during the greater part of the reaction time, since it was found that the catalyst is decomposed by heat Oxygen concentration is proportional. If air is used, then carbon dioxide and other acidic impurities must be removed as they would react with the catalyst. The water content of the air should not be excessively high, otherwise the water content of the reaction mixture can rise above the preferred value.

The invention is suitable for the production of anthraquinone from 9,10-dihydroanthracene, which is a component of wood tar, or raw 9,10-dihydroanthracene, obtained by selective hydrogenation of an anthracene-containing wood tar fraction became. The starting material can, for. B. by selective hydrogenation of a wood tar fraction, which contains anthracene in addition to phenanthrene and carbazole, according to the method of the USA patent 2,438,148 and preferably an enrichment of 9,10-dihydroanthracene.

Example 1 In a reaction vessel equipped with a condenser and a A hollow rod stirrer was provided, a pyridine solution (1.7 ml) of benzyltrimethylammonium hydroxide was added (3 millimoles) to a solution of 9,10-dihydroanthracene (9.0 g; 50 millimoles) in anhydrous Given pyridine (50 ml). The molecular ratio of benzyltrimethylammonium hydroxide to 9,10-dihydroanthracene was 0.06. Oxygen was supplied at about 1.131 / min. initiated by the hollow rod stirrer for 2 hours, the reaction temperature at about 70 "C. After cooling the reaction mixture to room temperature about 1 ml of acetic acid was added to neutralize the catalyst. The solvent was stripped at about 25 torr and the residue washed with water and dried.

The latter consisted of 700 per cent anthraquinone, 18 per cent anthracene and 120 per cent 9,10-dihydroanthracene.

If, under otherwise identical conditions, anhydrous pyridine is replaced by other solvents, the following results are obtained: Conversion Conversion of the unchanged yield Solvent in Anthraquinone in Anthracene 9,10-Dihydroan- in % in% in% tracing in% 95% aqueous pyridine ........... 85 85 15 0 N, N-dimethylaniline ............. 31 77 13 60 Aniline ......................... 81 81 20 0 Morpholine ..................... 54 59 37 8 N-methylmorpholine ............. 53 64 33 14 Quinoline ....................... 15 52 13 71 N, N-dimethylaminopropylamine .. 74 74 26 0 Diethylenetriamine ................ 43 44 55 1 Cyclohexylamine ................. 59 59 40 0 n-hexylamine ................... 65 65 35 0 Acetonitrile ..................... 15 79 3 81 2-picoline ....................... 52 52 46 0 3-picoline ....................... 59 59 39 0 4-picoline ....................... 60 60 36 0 Piperidine ....................... 47 47 41 0 N, N-dimethylformamide ......... 14 99 3 87 Example 2 In a manner similar to Example 1, a -40% pyridine solution (1.68 ml) of benzyltrimethylammonium hydroxide (3 millimoles) of a solution of 9,10-dihydroanthracene (9.0 g; 50 millimoles) in 95 percent by volume aqueous Pyridine (50 ml) added.

Oxygen was added with stirring in an amount of about 0.31 l / min. Introduced into the solution for about 2 hours at approximately 70 "C. The cooled Mixture was neutralized with about 1 cm3 of dilute hydrochloric acid, - filtered, the Crystals washed with water and dried. 8.83 g of 98% pure anthraquinone were obtained obtain. The conversion is 840 / o.

Example 3 Anthrone (3.96 g; 20 millimoles) was dissolved in anhydrous pyridine (50 ml) floated at 30 "C.

A solution of (0.7 ml) benzyltrimethylammonium hydroxide (1.2 millimoles) in pyridine was added and heated the mixture to 70 "C so that the anthrone has been resolved. Oxygen was added with stirring at a rate of 0.21 / min. in the. Solution initiated. After 2 hours the reaction mixture was cooled to 0.5 ml of acetic acid are added, the solvent is stripped off under reduced pressure, the Washed residue with water and dried in vacuo. The reaction product (4.055 g) contained 400/0 anthraquinone. The conversion is 300 / o.

Example 4 A pyridine solution (1.70 ml) of benzyltrimethylammonium hydroxide (3 millimoles) was a solution of xanthene (9.11 g; 50 millimoles) in anhydrous Pyridine (50 cm3) added. Oxygen was released (0.311 / min.) At 50 "C for 1 hour introduced into the solution with stirring. After an hour the mixture was on Cooled to 25 ° C and add 1 mol of hydrochloric acid (1 part of concentrated acid to 9 parts of water) added. 4.675 g of xanthone (48% conversion), mp 173.5-174.5 ° C, were obtained. The solvent was withdrawn from the reaction medium and the Washed residue and dried (4.980 g; melting point 90 to 150 "C). Recrystallization from benzene gave xanthone (2.143 g; mp 169-172 ° C).

If the residue is recrystallized from n-heptane, 1.00 is obtained g less pure xanthone, F. 156 to 168 "C. The total conversion to xanthone was 7801o. The selectivity of the reaction was 930/0.

Example 5 Oxygen was passed through a solution of 5,12-dihydrotetracene (0.5 g; 2.2 millimoles) passed into anhydrous pyridine (50 ml), which contained about 1.6 millimoles of benzyltrimethylammonium hydroxide. Half of the pyridine was evaporated and the remaining solution poured into an excess amount of water. The solid precipitate (0.48 g) was collected after collection, washing and drying Acetic acid recrystallized to give 0.22 g (39010 conversion) 5,12-tetracenquinone, F. 290 to 293 "C The rest of the fabric was tetracene.

Example 6 9.7 g of 1-methyl-9,10-dihydroanthracene (50 millimoles) was added dissolved in 950% aqueous pyridine and heated to 70 ° C. A solution (1.6 ml) Benzyltrimethylammonium hydroxide (3.56 millimoles) in methanol was added. Oxygen was added to the solution at one rate with vigorous stirring of 0.31 1 / min. initiated. After 1.5 hours the reaction mixture became room temperature cooled and 2 ml of the above aqueous hydrochloric acid were added.

The solvent was removed in vacuo.

The residue was washed thoroughly with water and dried in vacuo. The conversion to 1-methylanthraquinone (determined with the help of alkaline sodium hydrosulfite extraction of the residue and oxidation of the resulting anthrahydroquinone salt to quinone) was 300 / o.

The product melted at 163 to 167 "C.

If 1-methyl-9,10-dihydroanthracene is replaced by 2-methyl-9,10-dihydroanthracene, 2-methylanthraquinone is thus obtained in 35% conversion. The product that recovered by alkaline sodium hydrosulfite extraction, melted at 165 to 169 "C.

Claims (5)

Claims: 1. A process for the catalytic oxidation of partially hydrogenated, polycyclic, aromatic and heterocyclic compounds with a free oxygen-containing gas in the liquid phase in the presence of a solvent, characterized in that the oxidation is carried out with a compound of the general formula in which Rl, R2 and R3 are a hydrogen atom or the methyl radical and R2 and R3 together with the carbon atoms to which they are attached can form a six-membered aromatic ring and in which X is - CH ,, C = O or - 0 - is, with the proviso that X is always CH2 when Rl or R2 stands for the methyl radical or when R2 and R3 together with the carbon atoms to which they are bonded form a six-membered aromatic ring, in a solvent which favors the formation of carbon ions carried out in the presence of benzyltrimethyl ammonium hydroxide or methoxide as a catalyst and with a gas containing free oxygen and free of acidic impurities. 2. The method according to claim 1, characterized in that the Carries out oxidation in an amine as a solvent. 3. The method according to claims 1 and 2, characterized in that that the oxidation is carried out in an aqueous solvent. 4. The method according to claims 1 to 3, characterized in that that the oxidation with a ratio of catalyst to compound of the general Formula 1 performs between about 0.015 and 0.09 moles. 5. Process according to claims 1 to 4, characterized in that that the oxidation at about -20 to about 90 "C, especially at about 50 to about 70 "C performs. Documents considered: German Auslegeschrift No. 1 044059; French Patent No. 1,095,348; British Patent No. 834 590; U.S. Patent No. 2,859,247.