Method for production of carbonyl compounds

FIELD: organic chemistry, in particular production of carbonyl compounds such as aldehydes and ketones.

SUBSTANCE: claimed method includes reaction of nitrous oxide with alkenes in presence of inert gas as diluent. Reaction is carried out in gas phase at 401-700°C and under pressure of 2-300 atm. Target compounds represent value intermediates for precise and base organic synthesis.

EFFECT: method of high selectivity in relation to target products and improved explosion proofing.

5 cl, 1 tbl, 14 ex

The invention relates to a method for producing carbonyl compounds, more specifically to the manner of receiving them by gas-phase oxidation of alkenes with nitrous oxide (N₂O).

Carbonyl compounds (aldehydes and ketones) find many uses as valuable intermediates thin and basic organic synthesis. They are also widely used as solvents.

Carbonyl compounds receive mainly by oxosynthesis, the oxidation of hydrocarbons or by the dehydrogenation of alcohols. However, these methods are not efficient enough.

In the patent [GB 649680, 31.01.51] describes a method for carbonyl compounds by reaction of nitrous oxide with alkenes in the presence of an inert diluent, such as saturated hydrocarbons. According to this method, in particular, it is possible to obtain cyclohexanone by oxidation of cyclohexene. The reaction of lead in a static reactor-autoclave at a temperature of 250-400°and a pressure above 20 atmospheres. This method is more widely described in the article [F.S.Bridson-Jones, G.D.Buckley, L.H.Cross, A.P.Driver, J.Chem. Soc. (1951) 2999].

In patents [RU No. 2205175, 27.05.03; RU №2227135, 20.04.04; RU №2227136, 20.04.04; RU №2227134, 20.04.04; RU №2227133, 20.04.04; RU №2219160, 20.12.03; RU №2220947, 10.01.04; RU №2223268, 10.02.04] describes a method for carbonyl compounds by liquid-phase oxidation of aliphatic, cyclic, heterocyclic and other Ala the new nitrogen oxide in the presence of an inert gas diluent. The oxidation of lead in the liquid phase in the reactor-autoclave at temperatures up to 350°and pressure of N₂O up to 100 ATM.

This method is more widely described in the article [E.V.Starokon, K.A.Dubkov, D.E.Babushkin, V.N.Parmon, G.I.Panov, Adv. Synth. Catal. 346 (2004) 268-274].

However, the above-described methods of obtaining carbonyl compounds have several disadvantages. In particular, increasing the temperature to accelerate the reaction is accompanied by a significant increase in the pressure in the reaction system, created in pairs alkene and solvent.

This patent discloses a method of obtaining carbonyl compounds, which does not have these disadvantages. This method is carried out by gas-phase oxidation of alkenes of different classes, having in its composition one or more double bond C=C. the Implementation process in the gas phase gives the opportunity to easily adjust the reaction speed by selection of temperature and pressure, which in this case are not bound by the conditions of phase equilibrium and can vary independently.

It is known that nitrous oxide forms explosive mixtures with alkenes. To provide proof of working conditions, the oxidation of alkenes to carbonyl compounds by the proposed method are added to the reaction mixture an inert gas diluent, not reacts with N₂O, for example nitrogen, argon, carbon dioxide is Aza, or a mixture thereof. The role of the inert gas can play the off-gases reaction or recirculating gases. To reduce the explosion hazard in the reaction mixture can be added flame retardants, such as trifloromethyl, diperchlorate, dibromotetrafluoroethane and other

In accordance with this invention the oxidation of alkenes to aldehydes and ketones is usually carried out in a flow reactor, which may be made of steel, titanium or other suitable material. This can be used all known technological methods that increase the efficiency of gas-phase reactions.

The proposed method for carbonyl compounds does not require high purity reagents. Nitrous oxide can be used in pure form or with impurities, the presence of which is due to the method of its receipt. For example, as a source of nitrous oxide without additional purification can be used exhaust gases during the production of adipic acid, in which the content of N₂Ocan reach 75%, the main impurities are molecular nitrogen and carbon dioxide [..Uriarte, Stud. Surf. Sci. Catal, 2000, vol.130, p.743]. The original alkene can also be used in mixtures with other compounds, the presence of which is associated with a method of obtaining alkene. For example, cyclohexen now the floor is given by selective hydrogenation of benzene with hydrogen in the synthesis of adipic acid, which is then used for the production of nylon-66 [G.Belussi, Creedo, CATTECH, 2000, vol.4, No. 1, section 4]. The process of hydrogenation lead to ruthenium catalyst at a temperature of 120-180°and pressure of 30-100 ATM [Mkopo, Chem. Ind. (Japan), 1988, vol.41, R]. When the conversion of benzene 50-60% selectivity for cyclohexene is 80%. The remaining 20% of benzene into cyclohexane. The resulting reaction mixture of cyclohexene, cyclohexane and unreacted benzene is subjected to separation into components. Due to the small difference in boiling points of benzene (80,1°C), cyclohexene (82,9° (C) and cyclohexane (80,7° (C) separation of the mixture is difficult stage, reducing the efficiency of the entire process.

Because nitrous oxide in the above conditions does not react with benzene and cyclohexane, according to the present invention, the process of hydrogenation of benzene can be combined with the process of gas-phase oxidation of cyclohexene to cyclohexanone in a single technological cycle without pre-allocation of cyclohexene hydrogenation products. To obtain cyclohexanone use the products of hydrogenation of benzene containing at least 5 mol.% cyclohexene, without prior separation or after partial separation.

The boiling point of cyclohexanone (155,6° (C) significantly above the boiling point of the other whom is onenew mixture, and his subsequent selection is easily accomplished by using known techniques. Thus obtained cyclohexanone might be further oxidized to adipic acid, converted into s-caprolactam or used for another purpose.

According to this invention, the gas-phase oxidation of alkenes carried out as follows. The original reaction mixture of a given composition containing alkene, nitrous oxide and inert gas diluent is passed through the reactor at a temperature of 401-700°and the pressure 2-300 ATM. The molar ratio of nitrous oxide to the alkene may be from 0.01 to 100. The reaction temperature, the pressure of the reaction mixture and the contact time is chosen in such a way as to provide the required process performance (conversion, selectivity, and so on). The concentration of inert gas diluent can be adjusted to exclude the possibility of formation of explosive mixtures with N₂O when any contents of the alkene. This condition is satisfied, if the concentration of inert gas in a mixture with N₂O is at least 75 vol.%.

The reaction products analyzed by gas chromatography, based on what I expect the conversion of the alkene and the selectivity for carbonyl products. For more precise identification of the products used, such as methods / mass spectrometry, NMR and others.

The entity offers the proposed method is illustrated by the following examples.

Example 1.

In the experience of using the original reaction mixture containing cyclohexane, nitrous oxide and helium in a molar ratio of 20:20:60. The mixture under a pressure of 10 ATM is passed through the reactor of stainless steel with a volume of 5 cm³at a temperature of 401°C. the feed Rate of the mixture of 0.4 cm³/S. the results of the experiment are shown in table 1. It is seen that the main reaction product is cyclohexanone, which is formed with a selectivity of 92%.

Examples 2-3.

The reaction leads analogously to example 1 with the difference that the reaction temperature set 425°With (example 2) and 450° (example 3). These experiments show that increasing the temperature leads to a significant acceleration of the reaction: conversion of cyclohexene increased from 2.3% at 401°to 8.1% at 450°With preserving the total selectivity of carbonyl compounds over 95%. While there has been some lowering of the selectivity for cyclohexanone and increase selectivity for cyclopentanecarboxaldehyde, which at 450°is of 11.0%.

Examples 4-6.

The experiments are similar to example 1, with the difference that the pressure of the reaction mixture varies from 3.0 ATM. to 15.7 ATM. The results presented in table 1, show that the reaction rate increases significantly with increasing pressure, which corresponds, approximately, to the second order reaction.

Example 7.

Example 8.

Experience lead analogously to example 3, with the difference that the reaction mixture instead of cyclohexene enter 1-hexene. Conversion of alkene in this experience amounts to 11.5%, the selectivity for carbonyl compounds - 18%.

Example 9.

Experience lead analogously to example 5, with the difference that the reaction mixture, instead of cyclohexene, enter cyclopenten and the reaction is carried out at a pressure of 10 ATM. Conversion cyclopentene this experience is 6%, the selectivity for carbonyl compounds - 98% (Cyclopentanone - 82%, 1-pentenyl - 16%).

Example 10.

Experience lead analogously to example 2, with the difference that in the original reaction mixture was added 3 mol.% cyclohexane and 2 mol.% of benzene. Conversion of cyclohexene in this experience is 5.2%, the selectivity for carbonyl compounds - 95%.

Example 11.

Experience lead analogously to example 9, with the difference that the reaction mixture was added to 2.5 mol.% nitric oxide NO. Conversion cyclopentene this experience is 6.5%, the selectivity for carbonyl compounds - 93%.

Example 12 describes the process the oxidation of cyclohexene to cyclohexanone, combined with the process of hydrogenation of benzene in cyclohexane without prior separation of the products of hydrogenation. The experience is carried out in two stages: 1) hydrogenation of benzene with hydrogen and 2) the oxidation products of the hydrogenation of oxide of nitrogen.

The first stage is conducted in a known manner, for example according to the technique described in [J.Struijk et al., Appl. Catal. A: General, 1992, vol.83, p.263]. In a Parr reactor with a volume of 100 cm³download 0.2 g Ru catalyst, 20 cm³distilled water and 0.85 grams of zinc sulfate ZnSO₄·7H₂A. After dissolution of the salt in the reactor add 50 cm³benzene, rinsed with hydrogen and set pressure H₂25 ATM. Then the reactor is heated to 150°With, bring pressure H₂up to 50 ATM and include the stirrer. The duration of the experiment 1 tsp hydrogenation Products contain 15% benzene, 30% of cyclohexene and 55% of cyclohexane.

The second stage is conducted is conducted analogously to example 6, with the difference that instead of cyclohexene use the products of hydrogenation of benzene obtained in the first stage. Conversion of cyclohexene was 4.0%, the selectivity for cyclohexanone - 90%.

Example 14.

Experience lead analogously to example 1, with the difference that the initial reaction mixture contains cyclohexen, nitrous oxide and helium in a molar ratio of 40:30:30, and the reaction is carried out at a pressure of 30 ATM. Conversion cyclopentene it is ITE is 53%, the selectivity for cyclohexanone - 88%.

1. The method of obtaining carbonyl compounds by reaction of nitrous oxide with alkenes in the presence of an inert gas diluent, characterized in that the reaction of lead in the gas phase at a temperature 401-700°and the pressure 2-300 ATM.

2. The method according to claim 1, characterized in that the molar ratio of nitrous oxide to the alkene is in the range from 0.01 to 100.

3. The method according to claim 1, characterized in that the nitrogen oxide may contain other gases, the presence of which is connected with the method of its receipt.

4. The method according to claim 1, characterized in that the starting alkene used in a mixture with other compounds, the presence of which is associated with a method of obtaining alkene.

5. The method according to claim 1, characterized in that to obtain cyclohexanone use the products of hydrogenation of benzene containing at least 5 mol.% cyclohexene, without prior separation or after partial separation.