JPH0328407B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing cyclohexanone. Cyclohexanone is usually produced by subjecting cyclohexanol to a dehydrogenation reaction in the presence of a catalyst, but this reaction tends to produce large amounts of by-products such as phenol. Therefore, it is necessary to select a catalyst for use in this reaction that not only has high activity but also produces low levels of by-products. However, when a copper-chromium catalyst, which is a typical conventionally known catalyst, is used, although the catalytic activity is high, the production of a considerable amount of by-products is still unavoidable. The present applicant has previously proposed a method for improving the drawbacks of such copper-chromium catalysts. (Japanese Unexamined Patent Publication No. 56-20, 541) This proposal uses a catalyst obtained by heating a copper-chromium oxide at a specific temperature and then reducing it. Although a considerable effect was obtained in suppressing the production of living organisms, it was still not sufficient, and there was still room for further improvement in terms of activity and catalyst life. In view of the above circumstances, the present inventors conducted various studies to further improve the copper-chromium catalyst described above. The inventors have completed the present invention by discovering that when a catalyst is used in the dehydrogenation reaction of cyclohexanol, the reaction content is further improved. That is, the gist of the present invention is to provide a method for producing cyclohexanone by dehydrogenating cyclohexanol, which includes heat treating a copper-chromium oxide as a catalyst at a temperature of 650 to 900°C, and adding it to an aqueous solution of potassium nitrate or potassium carbonate. As potassium for oxides by immersion treatment
Copper with a copper:chromium atomic ratio of 8:2 to 2:8, obtained by depositing 0.01 to 0.5% by weight of the calicum compound, firing at a temperature of 300 to 500°C, and performing reduction treatment. A method for producing cyclohexanone characterized by using a chromium-based catalyst. The present invention will be explained in detail below. The present invention uses cyclohexanol in the presence of a catalyst,
This is a method of producing cyclohexanone by dehydrogenation, but the cyclohexanol used as a raw material may be obtained by any manufacturing method, and usually,
Cyclohexanol obtained by liquid phase air oxidation of cyclohexane or hydrogenation reaction of phenol is used. In the present invention, a copper-chromium catalyst obtained by treating a copper-chromium oxide by the method described below is used, and the copper:chromium ratio of the copper-chromium catalyst is 8:2 to 2:8 as an atomic ratio. , preferably 7:3~
The ratio is 3:7. If the chromium content is too low, the durability of the catalyst will be poor, and if the chromium content is too high, the catalyst activity will be poor. The copper-chromium oxide used for preparing the catalyst can be easily obtained, for example, by the known methods shown below. water-soluble compounds of copper and chromium, specifically inorganic salts such as nitrates, sulfates, and chlorides;
Using organic salts such as formate, acetate, and oxalate, an aqueous solution with a specified copper:chromium ratio is prepared, and this is combined with a caustic alkali such as caustic soda, caustic potash, carbonic acid such as sodium carbonate, and potassium carbonate. Copper-chromium hydroxide is precipitated by mixing with a precipitant such as alkali, aqueous ammonia, or ammonium carbonate, and this precipitate is dried according to the usual catalyst preparation method and calcined at a temperature of about 200 to 500℃. do. An aqueous solution of a copper salt is added to an aqueous solution of a dichromate such as sodium dichromate or ammonium dichromate and aqueous ammonia, and the resulting precipitate is dried and calcined in the same manner as described above. Chromium oxide is immersed in an aqueous solution of copper salt, and the copper salt is deposited on the chromium oxide, followed by drying and firing in the same manner as above. Copper oxide is immersed in an aqueous solution of chromium salt to adhere the chromium salt onto the copper oxide, and then dried and fired in the same manner as above. According to the above method, copper hydroxide and chromium hydroxide were prepared separately,
Both hydroxides are mixed, dried and fired in the same manner as above. Copper and chromium salts are mixed and calcined at a temperature of about 200 to 500°C according to a conventional catalyst preparation method. Mix copper oxide and chromium oxide. In the present invention, copper-
The chromium-based oxide is first heat-treated, but this temperature is
The temperature is 650-900°C, preferably 700-850°C. If the heat treatment temperature is too low, a catalyst with few side reactions cannot be obtained; on the other hand, if the heat treatment temperature is too high, a catalyst with high activity and durability cannot be obtained. The heat treatment is usually carried out until the specific surface area of the copper-chromium oxide becomes 0.5 to 20 m ² /g, preferably 1 to 15 m ² /g. The time required for this is e.g.
It is about 0.5 to 30 hours, preferably about 1 to 20 hours.
Further, although the heat treatment is usually carried out in an oxygen-containing gas such as air, it may also be carried out in an inert gas such as nitrogen. After the heat treatment, the copper-chromium oxide is then subjected to potassium deposition treatment. In the potassium adhesion treatment, the oxide is immersed in a dilute aqueous solution of potassium nitrate or potassium carbonate, usually about a few percent, for several hours to several tens of hours, usually at room temperature, and then heated to about 70 to 150 degrees Celsius. This is done by drying at high temperatures. The amount of potassium attached is the amount of potassium nitrate or potassium carbonate attached to the oxide after drying.
0.01-0.5% by weight of potassium based on oxide,
Preferably it is 0.02 to 0.4% by weight. If the amount of potassium deposited is less than the above range, the desired effect cannot be obtained, and if it is more than the above range, the activity of the resulting catalyst will be reduced. Thus, the copper-chromium oxide subjected to the potassium deposition treatment is then heated to 300 to 500°C, preferably
The firing process is carried out at a temperature of 330 to 450°C, usually for 1 to 20 hours. If this firing temperature is too low or too high, the effect of supporting potassium will not be exhibited, which is not preferable. The copper-chromium based oxide after the calcination treatment is finally subjected to a reduction treatment to obtain the potassium-supported copper-chromium based catalyst of the present invention. The reduction treatment can be performed by well-known means using, for example, hydrogen, carbon monoxide, methanol, formalin, or the like. Usually, hydrogen or hydrogen diluted with an inert gas such as nitrogen, argon, or carbon dioxide is used to
~500℃, preferably at a temperature of about 150~400℃,
It is preferable to carry out the reduction treatment until no heat generation accompanying the reduction is observed. The copper-chromium catalyst of the present invention is used as a powder or after being formed by a method such as tableting, extrusion, or rolling. Shaping can be carried out at any stage of the catalyst preparation described above. In addition, in the present invention, other metals are included in the catalyst component.
For example, the catalyst may contain metals such as sodium, calcium, barium, zinc, and manganese, but the total amount of copper and chromium in the catalyst should be 30% by weight or more, preferably 40% by weight or more as metals. is desirable. If the total amount of copper and chromium is too small, the effect of heat treatment will not be sufficiently manifested, and the catalyst will not be able to satisfy both activity and suppression of side reactions. In the present invention, a specific amount of potassium is supported on a copper-chromium oxide. There is no problem even if it contains potassium. The dehydrogenation reaction of cyclohexanol of the present invention is
Usually, it is carried out in a gas phase, and the catalyst is used as a fixed bed or a fluidized bed, but it is preferable to adopt a fixed bed method industrially. The reaction temperature is 200-400℃, preferably 250-350℃
℃, particularly preferably 250 to 300℃. If the reaction temperature is too low, the conversion rate will be low. On the other hand, if it is too high, the conversion rate will increase, but side reactions will increase, which is not preferable. The reaction pressure is not particularly limited and can be applied from reduced pressure to increased pressure, but it is usually best to choose a pressure around normal pressure. The feed rate of the raw material cyclohexanol is 0.1 to 100 hr ^-1 in liquid hourly space velocity (LHSV), preferably 0.5 to 100 hr -1
It is best to choose around 20hr ^-1 . Further, the raw material cyclohexanol may be diluted with an inert gas such as nitrogen or steam before being supplied. The method of the present invention is industrially extremely advantageous because cyclohexanone can be produced in high yield with few by-products, especially over a long period of time. EXAMPLES The present invention will be specifically explained below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 (Preparation of catalyst) Dissolve 450 g of sodium dichromate in demineralized water 2,
After adding 450 ml of 28% ammonia water to this, a solution prepared by dissolving 725 g of copper nitrate, 86.1 g of manganese nitrate, and 26.1 g of barium nitrate in 55 g of demineralized water was added under stirring to form a precipitate. The formed precipitate was filtered, washed with water, dried at 110°C for 8 hours, and then
By baking at a temperature of 300℃ for 6 hours,
The atomic ratio of copper:chromium:magazine:barium is 30:
A copper-chromium oxide having a ratio of 30:3:1 was obtained. This copper-chromium oxide was formed into cylindrical tablets (height 6m/m, diameter 6m/m) at 750°C.
After heat treatment in air for 2 hours at a temperature of
Soaked for 20 hours. The copper-chromium oxide was then centrifuged and left in the air at a temperature of 70°C for 20 hours.
After drying, it was fired at a temperature of 400° C. for 2 hours, and then crushed into pieces with a diameter of about 3.4 m/m. 5 ml of this granular material was filled into a stainless steel tubular reactor with an inner diameter of 13 m/m, and H ₂ 5 Vo1% and N ₂ 95 Vo1
% mixed gas was passed at a rate of 30/hr at a temperature of 180°C for 6 hours and then at a temperature of 180 to 250°C for 5 hours to carry out a reduction treatment to obtain a catalyst of the present invention. The amount of potassium supported in the catalyst thus obtained was 0.19 wt% as potassium based on copper and chromium in terms of oxides. (Dehydrogenation reaction of cyclohexanol) A dehydrogenation reaction of cyclohexanol was carried out using the catalyst obtained as described above. The inlet temperature of the tubular reactor filled with the catalyst was maintained at 260°C and the outlet temperature at 250°C, and preheated and vaporized crude cyclohexanol (cyclohexanol 80wt%,
cyclohexanone 8wt%, other ingredients 12wt%)
Feed at a rate of LHSV20hr ^-1 , reactor internal pressure 0.55
Continuous reactions were carried out at Kg/cm ² G. The cyclohexanol conversion rate 6 hours after the start of the reaction was determined by analyzing the reaction product using a gas chromatograph, and the results shown in Table 1 were obtained. Examples 2 to 3 In the method of Example 1, by changing the concentration of potassium nitrate used in the catalyst preparation step,
A test was conducted in the same manner as in Example 1, with the amount of potassium supported on the catalyst adjusted as shown in Table 1, and the results shown in Table 1 were obtained. Example 4 A test was conducted in the same manner as in Example 1 except that a potassium carbonate aqueous solution was used in place of the potassium nitrate aqueous solution in the catalyst preparation process, and the results shown in Table 1 were obtained. . Comparative Example 1 In the method of Example 1, immersion in potassium nitrate aqueous solution was omitted in the catalyst preparation step, and Example 1
A test was conducted in the same manner as above, and the results shown in Table 1 were obtained.

【table】

[Table] Comparative Examples 2 to 3 In the method of Example 1, a test was conducted in the same manner as in Example 1, using an aqueous potassium hydroxide solution or an aqueous potassium sulfate solution instead of an aqueous potassium nitrate solution in the catalyst preparation step. , the results shown in Table 1 were obtained. Comparative Examples 4 to 5 The same method as Example 1 was carried out by changing the concentration of potassium nitrate used in the catalyst preparation step and adjusting the amount of potassium supported on the catalyst as shown in Table 1. A test was conducted and the results shown in Table 1 were obtained. Example 5 In the catalyst preparation step of Example 1, copper-chromium-based oxide 4 supporting potassium after calcination treatment
Without crushing H ₂ 5 vol.
% and N ₂ 95 vol % was passed at a rate of 3200/hr at a temperature of 180° C. for 6 hours and at a temperature of 180 to 250° C. for 5 hours to carry out the reduction treatment. Then, the inlet and outlet temperatures of the reactor were set to 270
℃, and preheated and vaporized the same crude cyclohexanol as in Example 1 at normal pressure.
Continuous reaction was carried out by feeding at a rate of LHSV 2.2 hr ^-1 . The cyclohexanol conversion rate 240 hours after the start of the reaction was determined in the same manner as in Example 1, and the results shown in Table 2 were obtained. Comparative Example 6 A test was conducted in the same manner as in Example 5 using a catalyst that was not immersed in potassium nitrate aqueous solution in the catalyst preparation step, and the results shown in Table 2 were obtained. .

【table】

Claims (1)

[Claims] 1. In a method for producing cyclohexanone by dehydrogenating cyclohexanol, a copper-chromium oxide is heat-treated as a catalyst at a temperature of 650 to 900°C, and immersed in an aqueous solution of potassium nitrate or potassium carbonate. As potassium to oxide by treatment
Copper with a copper:chromium atomic ratio of 8:2 to 2:8, obtained by depositing 0.01 to 0.5% by weight of the potassium compound, firing at a temperature of 300 to 500°C, and reduction treatment. A method for producing cyclohexanone characterized by using a chromium-based catalyst.