JPS6092235A - Preparation of cyclohexanone - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a raw material for preparing caprolactam, adipic acid, etc. simply in high conversion ratio and in high selectivity, by oxidizing cyclohexene in liquid phase with molecular oxygen in liquid phase by the use of a compounded catalyst of Pd-Bi system. CONSTITUTION:Cyclohexene preferably containing a large amount of benzene and/or cyclohexane is oxidized in a liquid phase with molecular O2 in the presence of an aliphatic alcohol preferably ethanol, etc. and a compounded catalyst having a ratio of Pd compound to Bi compound of 1-30 gram atom Bi based on 1 gram atom Pd at 20-250 deg.C under pressure of lkg/cm<2>G, to give cyclohexanone. The higher the ratio of the Bi compound, the higher the reaction ratio and the reactivity of cyclohexene. Palladium nitrate, or Pd supported on alumina, active carbon, etc. is preferably used as the Pd compound, and bismuth nitrate is preferably used as the Bi compound.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cyclohexanone by oxidizing cyclohexene with molecular oxygen.

Cyclohexanone has long been used in large quantities as a raw material for producing caprolactam, adipic acid, etc., as a high-boiling solvent, and is an extremely useful substance industrially. Cyclohexanone is usually produced by oxidizing cyclohexane to obtain a mixture of cyclohexanol and cyclohexanone, distilling it to separate it, and then dehydrogenating the cyclohexanol to form cyclohexanone, and selectively hydrogenating phenol to form cyclohexanone. but,
When oxidizing cyclohexane using the above method, the product cyclohexanone is more easily oxidized than the raw material cyclohexane, so not only must the conversion rate be extremely low, but also it is necessary to separate cyclohexanol and cyclohexanone and dehydrogenate cyclohexanol. It has the disadvantage that there is Furthermore, when selectively hydrogenating phenol as described below, the raw material phenol is relatively expensive. Therefore, there is a strong need for a method for producing cyclohexanone more efficiently using inexpensive raw materials.
No. 28, JP-A No. 57-156429, and British Patent No. 1122040 disclose the so-called Waraker type, which consists of a palladium compound and a copper compound and/or iron compound as a catalyst in the presence of an aliphatic alcohol in the abdominal phase. A method of oxidizing cyclohexene with molecular oxygen using a catalyst is known.

However, in methods using these Waraker-type catalysts, the redox potential of palladium is too high, and as a copper compound and iron compound, only chloride is effective, and other than chloride may not be effective at all. Otherwise, only a very small effect can be obtained and a large amount of reagent must be used in industrial implementation, which is disadvantageous. Furthermore, when chloride is used, it is not only necessary to use extremely expensive equipment made of titanium or the like due to the strong corrosivity of Op- ions, but also has the disadvantage of generating organic chlorine compounds.

The present inventors have devised a method for producing cyclohexanone from cyclohexene and molecular oxygen by overcoming the drawbacks of these conventional methods, by increasing the conversion rate of cyclohexene in a simpler manner, and efficiently obtaining cyclohexanone with high selectivity. As a result of extensive studies, the present invention was arrived at. That is, the present invention is a method for efficiently oxidizing cyclohexene with molecular oxygen in a liquid phase to obtain cyclohexanone using a composite catalyst containing a palladium compound and a bismuth compound.

The cyclohexene used in the method of the present invention is preferably cyclohexene obtained by partial hydrogenation of benzene to cyclo, partial dehydrogenation of xane, decomposition of phenylcyclohexyl peroxide and phenylcyclohexane, or cyclohexene containing a large amount of benzene and/or cyclohexane. used for. In general, benzene and cyclohexane contained in cyclohexene produced by these methods have very close boiling points, so it is practically extremely difficult to separate and purify to obtain only cyclohexene. However, the method of the present invention When carrying out cyclohexene from these mixed systems, it can be used as a reaction raw material without separation and purification.

Examples of the palladium compound used in the present invention include inorganic salts such as palladium sulfate and palladium nitrate, organic acid salts such as palladium acetate and palladium propionate, and palladium supported on alumina, zeolite, silica, silica alumina, and activated carbon.

Preferred are palladium nitrate and supported palladium. The supported palladium may be any commonly available supported palladium catalyst.

Bismuth compounds include bismuth nitrate, bismuth sulfate, bismuth oxide, and organic complex salts of bismuth, and preferably bismuth nitrate.

The reaction rate and selectivity do not improve even if the ratio is increased.If this ratio of palladium compound to cyclohexene is small, the reaction rate will be low, which is desirable.

In the present invention, molecular oxygen refers to pure oxygen gas or a mixed gas of oxygen gas diluted with a diluent inert to the reaction, such as nitrogen, helium, etc., and air. The amount should be at least the stoichiometric molar amount required for the reaction, and a pressurized system with a pressure of 1 kg/dG or more is preferable. It is determined.

The reaction temperature in the present invention varies depending on the amount and type of catalyst added and the reaction pressure, but generally the reaction temperature is 250°C.
If the temperature is higher than 20°C, not only will side reactions increase, but also expensive equipment will be required.If the reaction temperature is lower than 20°C, the reaction rate will be significantly reduced and it will be difficult to effectively remove the heat of reaction. A temperature range of 250°C is used.

Particularly preferred is a temperature range of 40 to 160°C (6) used.

Although it is possible to obtain cyclohexanone by contacting cyclohexene alone or cyclohexene in the coexistence of benzene and/or cyclohexane with molecular oxygen using the catalyst of the present invention, in order to obtain cyclohexanone more efficiently, ethanol, It is desirable to coexist an aliphatic alcohol such as propanonyl or butanol.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited in any way by these Examples. Note that gas chromatography was used to analyze the reaction products. The selectivity is (number of moles of cyclohexanone produced by the reaction)/(number of moles of cyclohexene before reaction - number of moles of cyclohexene after reaction), and the conversion rate is (
Number of moles of cyclohexene before reaction - number of moles of cyclohexene after reaction)/(number of moles of cyclohexene before reaction)
It is.

Example 1 2'1.8f benzene and 20.51 cyclohexene and 94. Of ethanol was charged into an 800 ee round bottom flask with a cooler, and 1 O,2 was added as a catalyst.
After addition of f bismuth nitrate and 0,52 f palladium nitrate, 99% purity oxygen (remainder nitrogen) is added to 51/
Hr was continuously supplied into the well-stirred liquid. After the reaction temperature was set at 50° C. and the reaction was carried out for 4 hours, the reaction product was analyzed, and the conversion rate of cyclohexene was 48%, and the selectivity of cyclohexanone was 49%.

Comparative Example 1 The same treatment as in Example 1 was carried out except that bismuth nitrate was not added. As a result of analysis of the obtained reaction product, the conversion rate of cyclohexene was 16%, and the selectivity of cyclohexanone was 1.4%.

Example 2 A benzene, cyclohexene, ethanol mixture 141.8 F having the same composition as in Example 1 was charged into the same apparatus used in Example 1, and 9.7 g of bismuth nitrate and 5.41 g of commercially available 5% PD-activated carbon were added as catalysts. After adding a supported catalyst (manufactured by Nippon Engel Nord Co., Ltd.), 99% pure oxygen (the remainder being nitrogen) was continuously supplied at 5 n/hr into the sufficiently stirred solution. The reaction temperature was set at 55°C, and after 4 hours of reaction, the reaction product was analyzed and the conversion of cyclohexene was 89%, and the selectivity of cyclohexanone was 66%.

Comparative Example 2 The same treatment as in Example 2 was carried out except that bismuth nitrate was not added. As a result of analysis of the obtained reaction product, the conversion rate of cyclohexene was 92%, and the selectivity of cyclohexanone was 1% or less.

Examples 8-6 20.59 cyclohexane and 20.59 cyclohexene and 94. Of n-propyl alcohol was charged into the same apparatus used in Example 1, and 8
．． After adding 2F bis(9) nitrate mass and the palladium catalyst shown in Table 1, the reaction was carried out in the same manner as in Example 1. Table 1 shows the results of analyzing the reaction products.

Table 1 (10 complete)

Claims (1)

[Claims] A method for producing cyclohexanone by oxidizing cyclohexene with molecular oxygen in a liquid phase, the method comprising using a composite catalyst comprising a palladium compound and a bismuth compound.