KR830000880B1 - Method for preparing cyclohexanone - Google Patents

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Description

Method for preparing cyclohexanone

The present invention relates to a method for preparing cyclohexanone. More particularly, the present invention relates to a process for preparing cyclohexanone by contacting cyclohexanol with a catalyst to dehydrogenate it.

As a catalyst for dehydrogenating cyclohexanol to produce cyclohexanone, there is a copper-chromium catalyst. A commercially available catalyst or a copper-chromium catalyst prepared by a conventionally known method is excellent in activity and durability. Side reactions that produce phenol, cyclohexene and the like have a serious drawback.

Moreover, the method of adding alkali metal, alkaline-earth metal, water glass, etc. to a copper chromium-type catalyst is also known. (Japan, 45.12.25, issued by Chemical Industries, Ltd., "A practical catalyst for each reaction" See lines 2 to 4). However, sufficient improvement cannot be obtained by this method.

The present inventors have intensively studied to improve the above-mentioned shortcomings of the copper-chromium-based catalysts. As a result, when the copper-chromium oxides are heat-treated at a specific temperature and reduced, they have excellent activity and durability, and side reactions are extremely low. The present invention has been completed by discovering that a small catalyst can be obtained, and that the use of this catalyst can produce a high yield of cyclohexanone over a long period of time.

That is, the present invention aims at industrially advantageously producing cyclohexanone, which aims to produce copper chromium oxide as a catalyst in a method for producing cyclohexanone by dehydrogenating cyclohexane. It is achieved by using a copper-chromium catalyst having an atomic ratio of 8: 2 to 2: 8 obtained by heat treatment at a temperature in ° C. followed by reduction.

Next, the present invention will be described in detail.

The cyclohexanol used as a raw material in the present invention may be obtained by any manufacturing method, but industrially, for example, an oxidized product obtained by liquid-air oxidation of cyclohexane, or a cyclohexanol obtained by distillation therefrom, or phenol. The cyclohexanol etc. which were obtained by hydrogenating are mentioned.

The catalyst used in the present invention is a heat treatment of a copper-chromium oxide by a specific method, followed by reduction treatment. The copper-chromium oxide can be produced according to a known method of preparing a catalyst, and for example, the following method can be employed.

(1) Water-soluble compounds of copper and chromium, specifically, inorganic salts such as nitrates, sulfates, chlorides, organic salts such as phosphates, acetates and oxalates, etc. to prepare an aqueous solution of a predetermined copper: chromium ratio and Caustic soda, caustic alkalis such as caustic caustic, sodium soda carbonate, alkali carbonates such as calcium carbonate, ammonia water, ammonium carbonate, and the like, and mixed with a precipitating agent such as ammonium carbonate to precipitate the copper-chromium hydroxide, Dry according to the method and fire at a temperature of about 200 ~ 500 ℃.

(2) A precipitate obtained by adding an aqueous solution of copper salt to a solution in which ammonia water is added to an aqueous solution of dichromate such as sodium dichromate or ammonium dichromate is dried and calcined by the same method as in (1) above.

(3) Chrome oxide is immersed in the aqueous solution of copper salt, a copper salt is made to adhere on chromium oxide, and dry baking is carried out by the method similar to said (1).

(4) Copper oxide is immersed in the aqueous solution of chromium salt, a chromium salt is made to adhere on copper oxide, and dry baking is carried out by the method similar to said (1).

(5) According to the method of (1), copper hydroxide and chromium hydroxide are prepared separately, and the ammonium hydroxide is mixed and dried and fired by the same method as in (1).

(6) The salt of copper and chromium is mixed, and it bakes at the temperature of about 200-500 degreeC by the method of a conventional catalyst preparation.

(7) Copper oxide and chromium oxide are mixed.

The copper chromium oxide obtained as described above is first heat treated in accordance with the method of the present invention. The temperature of heat processing is about 650-900 degreeC, Preferably it is about 700-880 degreeC.

The degree of heat treatment is usually about 50 to 150 m 2 / g, but the specific surface area of commercially available copper-chromium oxide is 0.5 to 20 m 2 / g, preferably about 1 to 15 m 2 / g. Heat treatment is preferred.

Usually this treatment time is in the range of 0.5 to 30 hours, preferably 0.5 to 20 hours, more preferably 0.5 to 10 hours as the temperature.

If the temperature of the heat treatment is too low, even if the heat treatment is performed for a long time, the effect of the heat treatment is small and it is difficult to obtain a catalyst with little side reaction. On the contrary, if the temperature of the heat treatment is too high, it is not preferable because only a catalyst having low activity and durability is obtained.

The heat treatment is performed in a non-reducing atmosphere, usually in an oxygen-containing gas. For example, air or an inert gas such as nitrogen, argon, carbon dioxide, or a mixed gas thereof may be used. The copper-chromium oxide thus heat treated is then subjected to reduction treatment. The reduction treatment can be carried out by known means using gaseous reducing agents such as hydrogen and carbon monoxide or liquid reducing agents such as methanol and formalin.

Usually, reduction treatment is preferably performed using hydrogen or hydrogen diluted with an inert gas such as nitrogen, argon or carbon dioxide. The temperature in this case is 100-500 degreeC, Preferably it is 150-300 degreeC, It is preferable to perform reduction process until the exotherm according to reduction is not observed. This reduction treatment is usually carried out by placing copper-chromium oxide in a dehydrogenation reactor of cyclohexanol and circulating hydrogen gas. After the reduction treatment, a dehydrogenation reaction is continued. During the reaction, hydrogen is present near the catalyst, so that the catalyst is adjusted to an appropriate reduction state even if the reduction in the reduction step is insufficient.

The copper-chromium oxide used in the present invention has a copper-chromium-based catalyst having a copper and chromium content ratio of 8: 2 to 2: 8, preferably 7: 3 to 3: 7 as an atomic ratio of copper to chromium. Use Too small a content of chromium decreases durability. On the contrary, too large a content of chromium decreases the activity and increases the side reaction.

The catalyst of the present invention may contain 40% or less of metal other than copper and chromium, preferably 0.5 to 30% (atomic ratio with respect to the sum of copper and chromium).

Usually, the metal to be contained is, for example, sodium, potassium, calcium, barium, zinc, manganese, silicon, and the like, preferably manganese and / or barium.

The catalyst of the present invention is generally preferably used without using a carrier, but may be used by being supported on a known carrier as necessary. Examples of the carrier include, for example, alumina, silica, diatomaceous earth, activated carbon, and the like. In the case of being supported on a carrier, the amount of copper and chromium to be supported is preferably 30% by weight or more, preferably 40% by weight or more. If the supported amount is too small, the effects of both the activity of the catalyst obtained and the suppression of side reactions cannot be sufficiently exhibited.

The shape of the catalyst of the present invention is powder or granular, and it is usually good to use it as a commodity. In order to granulate the catalyst, for example, it is molded by a method such as tablet molding, extrusion molding, electroforming, or the like. Although shaping | molding may be normally shape | molded in any process after preparation from the preparation process of a catalyst, industrially, the method of shape | molding copper-chromium oxide before heat processing beforehand is preferable.

The dehydrogenation reaction of cyclohexanol of the present invention is usually carried out in a gas phase, and the catalyst is used as a fixed bed or a fluidized bed, but industrially, the fixed bed method is preferably employed. The reaction temperature is 200 to 400 ° C, preferably 250 to 350 ° C, more preferably 250 to 300 ° C. If the reaction temperature is too low, the conversion rate becomes small. On the contrary, if it is too high, the conversion rate becomes large, but the side reaction increases, which is not preferable. The reaction pressure is not particularly limited, but may be applied from reduced pressure to increased pressure, and it is generally good to select a pressure near normal pressure.

The feed rate of the raw material cyclohexanol may be about 0.1 to 100hr ⁻¹ , preferably about 0.5 to 20hr ⁻¹ as the liquid hourly space velocity (LHSV). In addition, the raw material cyclohexanone may be diluted and supplied with inert gas, such as nitrogen and water vapor.

According to the method of the present invention, since there are few by-products over a long period of time and a high yield of cyclohexanone can be produced, it is industrially advantageous.

Next, an Example demonstrates this invention concretely. The present invention is not limited to the following examples without departing from the gist of the invention.

[Examples 1-3 and Comparative Examples 1-4]

A solution of 86.1 g of manganese nitrate and 26.1 g of barium nitrate dissolved in 5 L of demineralized water was added to the solution in which 450 g of sodium bichromate was dissolved in 2 L of demineralized water, and 450 ml of 28% ammonia water was added thereto to generate a precipitate. The resulting precipitate was filtered off, washed with water, dried at 110 ° C. for 8 hours, and then calcined at 300 ° C. for 6 hours to obtain a copper-chromium oxide having an atomic ratio of 30: 30: 3: 1 for copper: chromium: manganese: barium. This copper-chromium oxide was molded by tableting and crushed into granules having a size of about 2 mm, heat-treated for 2 hours in air at the temperature shown in the following Table 1, and 10 ml of this was subjected to a stainless steel tubular reactor having an inner diameter of 13 mm. A catalyst was prepared by performing reduction treatment at 150 ° C. for 5 hours, followed by 5 hours at 200 ° C. for 5 hours at a rate of 60 vol./hr.

The crude cyclohexanol comprising 80 wt% of cyclohexane, 8 wt% of cyclohexanone, and 12 wt% of other components is maintained at the catalyst bed inlet temperature of the reactor to which the catalyst is injected at 260 ° C and the catalyst bed outlet temperature of 280 ° C. Was preheated and fed as LHSV 2hr ^-1 and subjected to dehydrogenation of cyclohexanol to analyze the reaction product by gas chromatography.

The cyclohexanol conversion and the selectivity of the side reaction product at 30 hours after the start of the reaction are as shown in the following Table 1. For comparison, examples of when the heat treatment was not performed (Comparative Example 1), when the heat treatment temperature was low (Comparative Examples-2, 3), and when the temperature was high (Comparative Example-4).

[Table 1]

Example 4 and Comparative Example 5

441.4 g of ammonium dichromate was dissolved in 2 L of demineralized water, and a solution in which 845.6 g of copper nitrate and 305 g of barium nitrate was dissolved in 5 L of demineralized water was added to the solution to which 550 ml of 28% ammonia water was added while stirring to generate a precipitate. The resulting precipitate was filtered off, washed with water, dried at 110 ° C. for 8 hours, and then calcined at 300 ° C. for 6 hours to obtain a copper-chromium oxide having an atomic ratio of copper: chromium: barium of 30:30:10.

The copper-chromium oxide was heat-treated at 800 ° C. in the same manner as in Example 2, and then reduced to prepare a catalyst to dehydrogenate cyclohexanol. The result was 73% cyclohexanol conversion and 0.6% side reaction product selectivity.

In order to prepare, the cyclohexanol conversion was 73%, but the side reaction product selectivity was 10.1%.

Example 5 and Comparative Example 6

680 g of copper nitrate and 1130 g of chromium nitrate were dissolved in 8 L of demineralized water, heated to 50 ° C., and a 4N-caustic aqueous sodium hydroxide solution was added at a constant rate under stirring to obtain a pH frame of 9 for 30 minutes and aged at that temperature for 60 minutes. The precipitate produced was filtered off, washed with water, dried at 110 ° C. for 8 hours, and then calcined at 300 ° C. for 8 hours to obtain a copper-chromium oxide having an atomic ratio of 50:50. The copper-chromium oxide was heat-treated at 800 ° C. in the same manner as in Example 2 and then reduced to prepare a catalyst to dehydrogenate cyclohexanol.

The result was 73% cyclohexanol conversion and 1.0% side reaction product selectivity. In order to prepare, the catalyst prepared without performing the above heat treatment showed that the cyclohexanol conversion was 73% but the side reaction product selectivity was 15.0%.

Example 6 and Comparative Example 7

408 g of copper nitrate and 1582 g of chromium nitrate were dissolved in 8 L of demineralized water, warmed to 50 ° C., and a 4N aqueous sodium hydroxide solution was added at a constant rate under stirring to bring the pH to 9 in 30 minutes, followed by aging for 60 minutes at that temperature. It was. The resulting precipitate was filtered off, washed with water, dried at 110 ° C. for 8 hours, and then calcined at 300 ° C. for 8 hours to obtain a copper-chromium oxide having an atomic ratio of copper: chromium of 30:70. The copper-chromium oxide was heat-treated at 800 ° C. by the same method as in Example 2, and then reduced to prepare a catalyst to dehydrogenate cyclohexanol. The result was 73% cyclohexanol conversion and 0.4% side reaction product selectivity.

In order to prepare, the cyclohexanol conversion was 73%, but the side reaction product selectivity was 2.5%.

EXAMPLE 7 AND COMPARATIVE EXAMPLE 8

952 g of copper nitrate and 678 g of chromium nitrate were dissolved in 8 L of demineralized water, warmed to 50 ° C., and a 4N aqueous sodium hydroxide solution was added at a constant rate under stirring to bring the pH to 9 in 30 minutes, and aged at that temperature for 60 minutes. . The resulting precipitate was filtered off, washed with water, dried at 110 ° C. for 8 hours, and then calcined at 300 ° C. for 8 hours to obtain a copper-chromium oxide having an atomic ratio of copper: chromium of 70:30. The copper-chromium oxide was heat-treated at 850 ° C. by the same method as in Example 1, and then reduced to prepare a catalyst to dehydrogenate cyclohexanol. The result was 73% cyclohexanol conversion and 0.5% side reaction product selectivity.

In order to prepare, the cyclohexanol conversion was 73%, but the side reaction product selectivity was 19.0%.

Table 2 below shows the results of Examples 4 to 7 and Comparative Examples 5 to 8.

[Table 2]

From the above results, in the case of the method of the present invention, the conversion rate of cyclohexanol is about the same as that of the comparative example, but in all cases, the selectivity of the by-products is significantly lower than that of the comparative example. In Comparative Example 4, although the selectivity of the by-products is low, the conversion rate of cyclohexanol is extremely low as 15%, which is not practical.

Claims (1)

In a method for producing cyclohexanone by dehydrogenating cyclohexanol in the presence of a catalyst, a copper-chromium oxide having an atomic ratio of 8: 2 to 2: 8 as a catalyst is 650 to 900 ° C in a non-reducing atmosphere. A method for producing cyclohexanone characterized by using a catalyst obtained by heat treatment under reduced pressure.