CN107983397A - A kind of cobalt manganese bimetallic catalyst aoxidized for cyclohexane selectivity, preparation method and application - Google Patents

Abstract

The invention discloses a cobalt-manganese bimetallic catalyst for the selective oxidation of cyclohexane, a preparation method and an application. It is a loaded catalyst, the carrier is a mesoporous material, manganese nitrate and cobalt nitrate are loaded on the carrier, the loading of cobalt nitrate is 1.0-6.0wt%, and the loading of manganese nitrate is 0.5-5.0wt%. The preparation method is as follows: dissolving cobalt nitrate and manganese nitrate into the mixed solution of water and ethanol containing pyridine, adding the mesoporous material under stirring condition. After that, it was dried overnight and calcined to obtain a cobalt-manganese bimetallic catalyst. The present invention firstly applies cobalt and manganese element mixed catalyst to the heterogeneous catalytic reaction of preparing cyclohexanol and cyclohexanone by catalytic oxidation of cyclohexane, and the catalyst shows excellent activity, high selectivity and good stability.

Description

A kind of cobalt-manganese bimetallic catalyst for the selective oxidation of cyclohexane, preparation method and application

technical field

The invention belongs to the technical field of organic catalysis, and specifically relates to a cobalt-manganese bimetallic catalyst for the selective oxidation of cyclohexane, a preparation method and an application.

Background technique

Cyclohexanol and cyclohexanone are important raw materials for the synthesis of chemical products such as caprolactam (CPL) and adipic acid (AA). They can be used as solvents for paint shellac and varnish, and are also used to prepare spices (such as civet ketone) and fruit antifungal agent phenyl An important raw material for phenol rubber anti-aging agents, etc. Among them, the most important use of the downstream products of cyclohexanone and cyclohexanol is to synthesize adipic acid, followed by the monomer caprolactam of synthetic fiber nylon-6 and nylon-66. The development of the industry for preparing cyclohexanol and cyclohexanone relies on the development of the caprolactam and adipic acid industries, and the prospects are relatively broad.

Currently, there are three main production processes for industrialized cyclohexanol and cyclohexanone. Benzene hydrogenation-cyclohexane oxidation method, phenol hydrogenation method, benzene partial hydrogenation-cyclohexene hydration method. Among them, the industrial application of the phenol hydrogenation method is greatly restricted due to the cumbersome reaction steps and high cost; the cyclohexane oxidation method is the most common in industrial application.

The cyclohexane oxidation process was put into industrial application in the 1960s. It is currently the most widely used cyclohexanol cyclohexanone production process in the world. Nearly 90% of cyclohexanone is produced by cyclohexane oxidation. Its shortcoming is mainly manifested in that the one-pass conversion rate of cyclohexane is only 4% to 5%, and the selectivity of cyclohexanol and cyclohexanone is about 85%. How to improve the conversion rate without affecting the yield of cyclohexanol and cyclohexanone is a difficult problem in the field of catalytic chemistry today.

Today's environmental problems in China have become serious, and environmental problems have attracted great attention from the public and the government. Green chemistry has become an inevitable direction for the research and development of the chemical industry. The development of excellent catalysts and optimal process conditions is an important part of realizing green chemical industry. Therefore, the present invention takes the realization of green chemistry as the research purpose to explore and develop efficient catalysts and optimal process reaction conditions.

Contents of the invention

For the above-mentioned technical problems in the prior art, the invention provides a kind of cobalt-manganese bimetallic catalyst for the selective oxidation of cyclohexane, preparation method and application. The preparation method of the catalyst of the invention is simple, the catalyst is used for the catalytic oxidation of cyclohexane, and the conversion rate per pass is high and the selectivity is good.

The technical solution of the present invention is specifically introduced as follows.

The invention provides a cobalt-manganese bimetallic catalyst for the selective oxidation of cyclohexane, which is a supported catalyst, the carrier is a mesoporous material, manganese nitrate and cobalt nitrate are loaded on the carrier, and the loading capacity of cobalt nitrate is 1.0-6.0wt %, the load of manganese nitrate is 0.5-5.0wt%.

In the present invention, the loading of cobalt nitrate is 3-5wt%; the loading of manganese nitrate is 2-5wt%.

In the present invention, the carrier mesoporous material is selected from any one of SBA-15, MS-41 or HMS, and the BET specific surface area of the carrier is greater than 500m ² /g.

The present invention provides a kind of preparation method of above-mentioned cobalt manganese bimetallic catalyst, concrete steps are as follows:

(1) Under stirring, dissolve cobalt nitrate and manganese nitrate in an aqueous solution containing 4-6wt% pyridine and 45-55wt% ethanol, the ratio of the total mass of cobalt nitrate and manganese nitrate to the mass of the solution is 1:5-1 :100;

(2) Dispersing the mesoporous material as carrier into the pyridine ethanol aqueous solution of cobalt nitrate and manganese nitrate obtained in step (1); Continue stirring afterwards, then rotary evaporation, drying to obtain intermediate A;

(3) Calcining the intermediate A to obtain a cobalt-manganese bimetallic catalyst.

In the present invention, in step (1), the mass ratio of cobalt nitrate and manganese nitrate is 1:5～12:1; in step (2), the mass ratio of cobalt nitrate and mesoporous material is 1:100～6:100 ; Continuous stirring for 3-5 hours; in step (3), the calcination temperature is 350-500° C., and the calcination time is 1-5 hours.

The invention provides an application of the above-mentioned cobalt-manganese bimetallic catalyst in the selective oxidation reaction of cyclohexane. The application method is as follows: using molecular oxygen as an oxidant and a cobalt-manganese bimetallic catalyst as a catalyst, cyclohexane is selectively catalyzed and oxidized under solvent-free conditions to prepare cyclohexanol and cyclohexanone; wherein: the oxidant is Oxygen or air, the reaction pressure is 0.5-3MPa, the reaction temperature is 100-150°C, and the reaction time is 3-8h.

In the present invention, the catalyst is used in an amount of 0.5-6.0 wt% of cyclohexane.

In the present invention, the catalyst is used in an amount of 1.0-3.0 wt% of cyclohexane.

Compared with the prior art, the beneficial effects of the present invention are:

1. The cyclohexane oxidation reaction system does not need to add any solvent, which is green and environmentally friendly;

2. The novel cobalt-manganese bimetallic catalyst of the present invention increases the conversion rate of cyclohexane to more than 10%, while the selectivity of cyclohexanol and cyclohexanone is raised to more than 95%.

3. The novel cobalt-manganese bimetallic catalyst of the present invention has good stability

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the embodiments.

Example 1

(1) Weigh 0.05g of cobalt nitrate and 0.05g of manganese nitrate, dissolve in 5ml of 50% ethanol aqueous solution containing 5% pyridine, and stir until the solid is completely dissolved;

(2) Dissolve 4g of P123 in 84.85g of hydrochloric acid (120ml, 2M) solution, stir at high speed at 40°C for 2h, and add 8.5g of tetraethyl orthosilicate (TEOS) after the solution becomes transparent, and stir at 40°C for 24h. Then the solution was transferred into a hydrothermal reactor, and reacted at 100°C for 48h. After the reaction, it was naturally cooled, filtered and washed with absolute ethanol, dried at 100°C for 3 hours, and calcined at 550°C for 6 hours. After natural cooling, it was mesoporous silica SBA-15 with a BET specific surface area of 625m ² /g. Weigh 1g of mesoporous material SBA-15, slowly add SBA-15 into the above-mentioned solution dissolved with cobalt nitrate and manganese nitrate; keep stirring for 5 hours, then dry at 80°C overnight to obtain intermediate sample A;

(3) Calcining A at 350°C for 5 hours to obtain a catalyst;

(4) Take by weighing 50 mg of the catalyst prepared above, place 100 ml in a stainless steel reaction kettle with a polytetrafluoro liner, then add 20 ml of cyclohexane, and replace the gas with oxygen three times, and the reaction conditions are oxygen pressure 1 MPa, and the reaction The temperature was 150° C. and the stirring speed was 800 rpm for 70 minutes.

(5) After the reaction, the mixed solution after the reaction was analyzed with a GC-9790 gas chromatograph.

(6) The analysis results are shown in Table 1 below.

Table 1 embodiment 1 catalyst performance test result

Example 2

(1) Take by weighing theoretically calculated cobalt nitrate 0.05g and manganese nitrate 0.03g, then dissolve the weighed sample in 5ml of 50% ethanol aqueous solution containing 5% pyridine, and stir until the solid is completely dissolved;

(2) Weigh 1g of mesoporous material SBA-15, slowly add SBA-15 into the above-mentioned solution dissolved with cobalt nitrate and manganese nitrate; keep stirring for 5h, then dry at 80°C overnight to obtain intermediate sample A;

(3) Calcining A at 350°C for 5 hours to obtain a catalyst;

(4) Take by weighing 50 mg of the catalyst prepared above, place 100 ml in a stainless steel reaction kettle with a polytetrafluoro liner, then add 20 ml of cyclohexane, and replace the gas with oxygen three times, and the reaction conditions are oxygen pressure 1 MPa, and the reaction The temperature was 150° C. and the stirring speed was 800 rpm for 70 minutes.

(5) After the reaction, the mixed solution after the reaction was analyzed with a GC-9790 gas chromatograph.

(6) The analysis results are as follows in Table 3:

Table 2 embodiment 2 catalyst performance test result

Example 3

(1) Take by weighing theoretically calculated cobalt nitrate 0.05g and manganese nitrate 0.02g, dissolve in 5ml of 50% ethanol aqueous solution containing 5% pyridine, and stir until the solid is completely dissolved;

(2) Weigh 1 g of mesoporous material SBA-15, slowly add SBA-15 into the solution dissolved with cobalt nitrate and manganese nitrate; keep stirring for 5 hours, then dry at 80°C overnight to obtain intermediate sample A;

(3) Calcining the intermediate sample A at 350° C. for 3 hours to obtain a catalyst;

(4) Take by weighing 50 mg of the catalyst prepared above, place 100 ml in a stainless steel reaction kettle with a polytetrafluoro liner, then add 20 ml of cyclohexane, and replace the gas with oxygen three times, and the reaction conditions are oxygen pressure 1 MPa, and the reaction The temperature was 150° C. and the stirring speed was 800 rpm for 70 minutes.

(5) After the reaction finishes, analyze with GC-9790 gas chromatograph (the mixed solution after the reaction.

(6) The analysis results are as follows in Table 3:

Table 3 embodiment 3 catalyst performance test result

Example 4

(1) Take by weighing 50 mg of the catalyst prepared in Example 3, place 100 ml in a stainless steel reaction kettle with a polytetrafluoro liner, then add 20 ml of cyclohexane, after three gas replacements with oxygen, keep the oxygen pressure 1MPa, the reaction time 70min, under the condition that the stirring speed remains unchanged at 800rpm. The catalytic effect of the catalyst in the catalytic oxidation of cyclohexane was tested at 130°C, 140°C, 150°C and 160°C respectively;

(2) After the reaction finishes under different temperature conditions, the mixed solution after the reaction is analyzed respectively;

(3) Under different reaction temperature conditions, the product analysis results are as follows:

Catalyst performance test result under different reaction temperature conditions of table 4

Example 5

(1) Take by weighing 50 mg of the catalyst prepared in Example 3, place 100 ml in a stainless steel reactor with a polytetrafluoro liner, then add 20 ml of hexanaphthene, and replace the gas with oxygen for three times, then the reaction condition is an oxygen pressure of 1 MPa , when the reaction temperature was kept constant at 150°C and the stirring speed was 800rpm. Control the reaction time at 30min, 50min, 70min and 90min respectively to obtain the catalytic effect of the catalyst in the catalytic oxidation of cyclohexane;

(2) After the reaction finishes, the mixed solution after the reaction is analyzed respectively with GC-9790 gas chromatograph;

(3) Under different reaction time conditions, the product analysis results are as follows:

Catalyst performance test results list under different reaction time conditions in table 5

Example 6

(1) Take by weighing 50 mg of catalyst prepared in Example 3, place 100 ml in a stainless steel reactor with polytetrafluoro liner, then add 20 ml of hexanaphthene, and replace the gas with oxygen three times, then the reaction conditions are 70 min in the reaction time , the reaction temperature was 150° C. and the stirring speed was 800 rpm. The catalytic effect of the catalyst in the catalytic oxidation of cyclohexane was tested under the conditions of reaction pressures of 0.6MPa, 1.0MPa, 1.8MPa and 2.4MPa respectively;

(2) After the reaction finishes, the mixed solution after the reaction is analyzed respectively with GC-9790 gas chromatograph;

(3) The reaction results under different reaction pressure conditions are as follows:

Table 6 Catalyst performance test results list under different reaction pressure conditions

Example 7

(1) Take by weighing 50 mg of the catalyst prepared in Example 3, place 100 ml in a stainless steel reactor with a polytetrafluoro liner, then add 20 ml of cyclohexane, and replace the gas with oxygen for three times, then the reaction condition is oxygen pressure 1MPa, reaction temperature 150°C, and stirring speed 800rpm for 70min.

(2) The reacted catalyst is centrifuged to separate the solid catalyst, washed with a large amount of ethanol, and dried overnight.

(3) Place the dried catalyst in a 100ml stainless steel reaction kettle with a polytetrafluoroethylene lining, then add 20ml cyclohexane, and replace the gas with oxygen three times. The reaction conditions are oxygen pressure 1MPa, reaction temperature 150°C , and reacted for 70 min at a stirring speed of 800 rpm.

(4) Repeat the above steps (2) and (3)

(5) Analyze the mixed solution after the above reaction with a GC-9790 gas chromatograph.

(6) The catalyst analysis results repeated for different times are as follows:

Table 7 List of Catalyst Performance Test Results for Different Repeat Times

Claims (9)

1. A cobalt-manganese bimetallic catalyst for the selective oxidation of cyclohexane, characterized in that it is a loaded catalyst, the carrier is a mesoporous material, and the carrier is loaded with manganese nitrate and cobalt nitrate, and the cobalt nitrate load is 1.0 ~6.0wt%, the loading of manganese nitrate is 0.5~5.0wt%. 2. The cobalt-manganese bimetallic catalyst according to claim 1, characterized in that the loading of cobalt nitrate is 3-5 wt%; the loading of manganese nitrate is 2-5 wt%. 3. The cobalt-manganese bimetallic catalyst according to claim 1, wherein the carrier mesoporous material is selected from any one of SBA-15, MS-41 or HMS, and the BET specific surface area of the carrier is greater than 500m ² /g . 4. a preparation method of cobalt-manganese bimetallic catalyst according to claim 1, is characterized in that, concrete steps are as follows: (1) Under stirring, dissolve cobalt nitrate and manganese nitrate in an aqueous solution containing 4-6wt% pyridine and 45-55wt% ethanol, the ratio of the total mass of cobalt nitrate and manganese nitrate to the mass of the solution is 1:5-1 :100; (2) Dispersing the mesoporous material as carrier into the pyridine ethanol aqueous solution of cobalt nitrate and manganese nitrate obtained in step (1); then continue stirring, then rotary evaporation and drying to obtain intermediate A; (3) Calcining the intermediate A to obtain a cobalt-manganese bimetallic catalyst. 5. preparation method according to claim 4 is characterized in that, in step (1), the mass ratio of cobalt nitrate and manganese nitrate is 1:5～12:1; In step (2), cobalt nitrate and mesoporous The mass ratio of materials is 1:100-6:100; the stirring is continued for 3-5 hours; in step (3), the calcination temperature is 350-500° C., and the calcination time is 1-5 hours. 6. An application of the cobalt-manganese bimetallic catalyst according to claim 1 in the selective oxidation reaction of cyclohexane. 7. application according to claim 6, is characterized in that, application method is as follows: take molecular oxygen as oxidant, take cobalt-manganese bimetallic catalyst as catalyzer, cyclohexane is selectively catalyzed and oxidized under solvent-free conditions, Prepare cyclohexanol and cyclohexanone; wherein: the oxidizing agent is oxygen or air, the reaction pressure is 0.5-3MPa, the reaction temperature is 100-150°C, and the reaction time is 3-8h. 8. The application according to claim 7, characterized in that the amount of the catalyst is 0.5-6.0 wt% of cyclohexane. 9. The application according to claim 7, characterized in that the amount of the catalyst is 1.0 to 3.0 wt% of cyclohexane.