CN116550332A - Cobalt-based catalyst and preparation method and application thereof - Google Patents

Abstract

The application discloses a method for preparing a Co-based catalyst by hydrogen and application thereof. The preparation method comprises the following steps: immersing an alumina precursor in a mixed solution containing an active component precursor and an auxiliary component precursor, drying, and roasting in a hydrogen atmosphere to obtain the catalyst; the active component precursor is a cobalt-containing compound, and the auxiliary component precursor is lanthanum nitrate. Compared with a sample roasted in an air atmosphere, the catalyst prepared by the invention has the advantages of higher acetonitrile selectivity and the like.

Description

A kind of cobalt-based catalyst and its preparation method and application

technical field

The application relates to a cobalt-based catalyst and its preparation method and application, belonging to the technical field of chemical catalyst preparation.

Background technique

Acetonitrile is a widely used organic chemical raw material. In addition to being used as an extraction agent for extracting butadiene and isoprene from olefins and paraffins in petrochemical industry, it is also widely used in organic synthesis, medicine, Synthetic raw materials for fine chemicals such as pesticides, surfactants, dyes, and mobile phase solvents for thin-layer chromatography, paper chromatography, spectroscopy, polarography, and high-performance liquid chromatography (HPLC). The latest applications are used as DNA synthesis and purification solvents, Solvents for the synthesis of organic EL materials, cleaning solvents for electronic components such as chips, etc. These applications have high requirements for the purity of acetonitrile (≥99.9%). Acetonitrile with a purity of ≥99.9% is more popular in the market and has a wide range of uses, accounting for more than 66% of the consumption.

Nowadays, acetonitrile is mainly recovered from the crude by-product in the process of producing acrylonitrile by propylene ammoxidation in the world, but only 20-30 kg of acetonitrile can be obtained from 1 ton of acrylonitrile, and the purity is not high, especially it is difficult to achieve a purity of ≥99.9%. Acetonitrile. The ammoniated dehydrogenation of ethanol to produce acetonitrile is a beneficial supplement to the source of acetonitrile. Compared with other methods for obtaining acetonitrile, the ammoniated dehydrogenation of ethanol to produce acetonitrile has simple process, low energy consumption, high atom utilization rate, high acetonitrile selectivity, less side reactions, less investment and low operation cost, and can be industrialized.

There are problems such as low acetonitrile selectivity in the existing acetonitrile dehydrogenation ammoniation to produce acetonitrile.

Contents of the invention

This application aims to develop a CoLa/Al catalyst with high acetonitrile selectivity for the dehydroamination of ethanol to acetonitrile. This is the first report that the catalyst is used in the dehydroamination of ethanol to acetonitrile.

According to one aspect of the present application, there is provided a method for preparing a cobalt-based catalyst by facing hydrogen, at least including the following steps:

Immersing the alumina precursor in a mixed solution containing the active component precursor and the auxiliary component precursor, drying, and roasting in a hydrogen atmosphere to obtain the catalyst;

Wherein the active component precursor is a cobalt-containing compound, and the auxiliary component precursor is lanthanum nitrate.

Optionally, the mass of the active component precursor is 5 to 30 wt% of the mass of the alumina precursor, and the mass of the active component precursor is calculated by the mass of cobalt element in the cobalt-containing compound;

The mass of the auxiliary component precursor is 0.1-1.0 wt % of the mass of the alumina precursor, and the mass of the auxiliary component precursor is calculated by the mass of lanthanum element in lanthanum nitrate.

Optionally, the cobalt-containing compound is selected from at least one of cobalt nitrate, cobalt acetate, cobalt chloride and cobalt sulfate.

Optionally, the impregnation adopts vacuum equal-volume impregnation; the impregnation time is 2-5 hours.

Optionally, the drying temperature is 110-130° C., and the drying time is 6-12 hours.

Optionally, the calcination temperature is 500-700°C, and the calcination time is 2-4 hours;

The hydrogen atmosphere is selected from any one of H ₂ /N ₂ mixed gas, H ₂ /He mixed gas and H ₂ /Ar mixed gas.

Optionally, the H ₂ content in the hydrogen atmosphere is 3-50 vol%.

Optionally, the content of _H in the hydrogen atmosphere is selected from any value or two of 3vol%, 5vol%, 10vol%, 15vol%, 20vol%, 25vol%, 30vol%, 35vol%, 40vol%, 50vol%. range of values between values.

Optionally, the flow rate of the hydrogen atmosphere is 10-50 mL/min.

Optionally, the flow rate of the hydrogen atmosphere is 10mL/min, 15mL/min, 20mL/min, 25mL/min, 30mL/min, 35mL/min, 40mL/min, 50mL/min, any value or between two values range of values between.

According to another aspect of the present application, a cobalt-based catalyst is provided, including an alumina carrier and cobalt and lanthanum elements supported on the alumina carrier;

Wherein, both the cobalt element and the lanthanum element exist in a reduced state.

Optionally, the mass of cobalt element is 5-30wt% of the mass of the alumina carrier;

The mass of the lanthanum element is 0.1-1.0 wt% of the mass of the alumina carrier.

Optionally, the particle size of the cobalt element is 0.1-0.5 nm.

According to another aspect of the present application, there is provided a method for producing acetonitrile by dehydrogenation and ammoniation of ethanol, at least comprising the following steps:

The mixed raw material containing ethanol and ammonia is contacted with a catalyst to react to obtain a product containing acetonitrile; the catalyst is selected from the catalyst prepared by the above-mentioned preparation method.

Optionally, the molar ratio of ammonia to ethanol is 8-2:1;

The mass space velocity of the ethanol is 0.1˜1.0 h ⁻¹ .

Optionally, the pressure of the reaction is 0.1-0.3MPa;

The reaction temperature is 410-470°C.

The beneficial effect that this application can produce comprises:

In the CoLa/Al catalyst prepared by the present invention, cobalt and lanthanum are evenly distributed in the catalyst, and are not easy to agglomerate in the reaction process; cobalt exists with reduced state cobalt, and this existence state is compared with oxidized state cobalt (in the sample of air atmosphere roasting, cobalt is represented by CoAl ₂ O ₄ /Co ₃ O ₄ ) has higher activity; during hydrogen atmosphere calcination, because the sample is decomposed and reduced, it is beneficial to keep the reduced cobalt in small particles, and after the air calcination, the sample is reduced again, and the cobalt obtained The particles are larger. In the reaction of ethanol dehydrogenation and ammoniation to acetonitrile, large cobalt particles are not conducive to the diffusion and reaction performance of reactants and products in the catalyst, thus showing low acetonitrile selectivity.

The catalyst prepared by the invention can be applied to the process of producing acetonitrile by dehydrogenation and ammoniation of ethanol. Compared with the conventional air atmosphere roasting CoLa/Al catalyst, the catalyst has the advantages of higher acetonitrile selectivity and the like.

Description of drawings

Fig. 1 is the TEM and HRTEM figure of the 20Co0.25La/Al ₂ O ₃ -Air catalyst of comparative example 1 of the present application;

Fig. 2 is the TEM and HRTEM figure of the 20Co0.25La/Al ₂ O ₃ -Air-20H ₂ /80N ₂ catalyst of Comparative Example 2 of the present application;

Figure 3 is the TEM and HRTEM images of the 20Co0.25La/Al ₂ O ₃ -20H ₂ /80N ₂ catalyst of Example 1 of the present application;

Fig. 4 is the TEM and HRTEM figure of the 5Co0.1La/Al ₂ O ₃ -3H ₂ /97N ₂ catalyst of Example 2 of the present application;

Figure 5 is the TEM and HRTEM images of the 30Co1La/Al ₂ O ₃ -50H ₂ /35N ₂ /15Ar catalyst of Example 3 of the present application;

Fig. 6 is the TEM and HRTEM images of the 15Co0.5La/Al ₂ O ₃ -15H ₂ /70N ₂ /15He catalyst of Example 4 of the present application.

Detailed ways

The present application is described in detail below in conjunction with the examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials in the examples of the present application were purchased through commercial channels.

In the examples of the present application, Agilent 7890A GC was used for analysis, FID and TCD detectors, and hydrogen and He were used as carrier gases.

In the examples of the present application, the catalyst activity evaluation indicators, i.e. ethanol conversion rate, ammonia conversion rate and acetonitrile selectivity are calculated based on mass:

Calculation of the conversion rate of the main reactants and the selectivity of acetonitrile:

Ethanol conversion rate:

Ammonia conversion rate:

Acetonitrile selectivity:

In the above formula, m represents mass.

Comparative example 1

Dissolve 9.86g Co(NO ₃ ) ₂ ·6H ₂ O and 0.079g La(NO ₃ ) ₃ ·6H ₂ O in 5.5g of water, put 7.975g of alumina in a closed container, and vacuum equal volume impregnation The impregnating liquid was sucked into the carrier, vacuumed to 10Pa, then impregnated at 25°C for 3 hours, dried in an oven at 120°C for 6 hours, and 5g of the sample was roasted at 600°C for 3 hours in an air atmosphere (100 ml/min) to obtain the catalyst Cat-A, wherein The contents of Co and La were 20 wt% and 0.25 wt%, respectively.

Comparative example 2

Weigh 5 g of the sample Cat-A prepared in Comparative Example 1 and reduce it in a hydrogen atmosphere (20H ₂ /80N ₂ : 100 ml/min) at 600° C. for 3 hours to obtain a catalyst Cat-B, wherein the contents of Co and La are respectively 20 wt % and 0.25 wt%.

Example 1

Dissolve 9.86g Co(NO ₃ ) ₂ ·6H ₂ O and 0.079g La(NO ₃ ) ₃ ·6H ₂ O in 5.5g of water, put 7.975g of alumina in a closed container, and vacuum equal volume impregnation The impregnating liquid is sucked into the carrier, vacuumed to 10Pa, then impregnated at 25°C for 3 hours, oven-dried at 120°C for 6 hours, and 5g of the sample is roasted at 600°C for 3 hours in a hydrogen atmosphere (20H ₂ /80N ₂ : 100ml/min) to prepare Catalyst Cat-C, wherein the contents of Co and La are 20wt% and 0.25wt%, respectively.

Example 2

Dissolve 2.11g Co(CH ₃ COO) ₂ 4H ₂ O, 0.032g La(NO ₃ ) ₃ 6H ₂ O in 5.5g water, put 7.975g alumina in a closed container, and adopt vacuum equal volume impregnation method Inhale the impregnation liquid into the carrier, vacuumize to 10Pa, then impregnate at 25°C for 2 hours, dry in an oven at 130°C for 8 hours, take 5g of the sample and bake it at 500°C for 4 hours in a hydrogen atmosphere (3H ₂ /97N ₂ : 50ml/min) A catalyst Cat-D was obtained, wherein the contents of Co and La were 5wt% and 0.1wt%, respectively.

Example 3

Dissolve 10.00g Co(NO ₃ ) ₂ 6H ₂ O, 3.91g CoCl ₂ 6H ₂ O, 0.316g La(NO ₃ ) ₃ 6H ₂ O, 0.240g L-arginine in 5.5g water, and dissolve 7.975g Alumina is placed in a closed container, and the impregnation liquid is sucked into the carrier by vacuum equal volume impregnation method, the vacuum is 10Pa, then impregnated at 25°C for 5 hours, dried in an oven at 110°C for 12 hours, and 5g of the sample is taken in a hydrogen atmosphere (50H ₂ / 35N ₂ /15Ar: 150ml/min) was calcined at 600°C for 2 hours to prepare the catalyst Cat-E, wherein the contents of Co and La were 30wt% and 1.0wt%, respectively.

Example 4

Dissolve 3.70g Co(NO ₃ ) ₂ 6H ₂ O, 3.57g CoSO ₄ 7H ₂ O, 0.158g La(NO ₃ ) ₃ 6H ₂ O, 0.160g L-arginine in 5.5g water, and 7. 975g of alumina is placed in a closed container, and the impregnation solution is sucked into the carrier by vacuum equal volume impregnation method, the vacuum is 10Pa, then impregnated at 25°C for 4 hours, dried at 110°C for 12 hours, and 5g of the sample is taken in a hydrogen atmosphere (15H ₂ /70N ₂ /15He: 250ml/min) was calcined at 700°C for 4 hours to prepare the catalyst Cat-F, wherein the contents of Co and La were 15wt% and 0.5wt%, respectively.

Figures 1 to 6 in this application correspond to Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, and Example 4, respectively;

Figure 1 A is the TEM image of 20Co0.25La/Al ₂ O ₃ -Air catalyst at 200nm; B is the HRTEM image of 20Co0.25La/Al ₂ O ₃ -Air catalyst at 10nm; from Figure 1 we can see that 20Co0 .25La/Al ₂ O ₃ -Air catalyst has larger Co ₃ O ₄ or CoAl ₂ O ₄ particles, and the high-resolution transmission electron microscopy analysis identifies the particles as Co ₃ O ₄ or CoAl ₂ O ₄ , corresponding to Co ₃ O ₄ or (2 2 0) crystal plane of CoAl ₂ O ₄ ;

Figure 2 C is the TEM image of 20Co0.25La/Al ₂ O ₃ -Air-20H ₂ /80N ₂ catalyst at 200nm; D is 20Co0.25La/Al ₂ O ₃ -Air-20H ₂ / HRTEM diagram of 80N ₂ catalyst; from Figure 2 _, it can be seen that the 20Co0.25La/Al ₂ O ₃ -Air-20H _{2 /} 80N ₂ catalyst prepared by air calcination-hydrogenation has more Co The particles of ₃ O ₄ or CoAl ₂ O ₄ are small, and the high-resolution transmission electron microscopy analysis identifies the particles as Co, corresponding to the (1 1 1) crystal plane of Co;

Figure 3 E is the TEM image of 20Co0.25La/Al ₂ O ₃ -20H ₂ /80N ₂ catalyst at 200nm; F is the TEM image of 20Co0.25La/Al ₂ O ₃ -20H ₂ /80N ₂ catalyst at 10nm HRTEM diagram; Figure 3 shows that the 20Co0.25La/Al ₂ O ₃ -20H ₂ /80N ₂ catalyst after hydrogen calcination is smaller than the 20Co0.25La/Al ₂ O ₃ -Air catalyst particles, which can explain the hydrogen atmosphere calcination of active components With better dispersibility, high-resolution transmission electron microscope analysis identifies the particles as Co, corresponding to the (1 1 1) crystal plane of Co;

Figure 4 G is the TEM image of 5Co0.1La/Al ₂ O ₃ -3H ₂ /97N ₂ catalyst at 200nm; H is the TEM image of 5Co0.1La/Al ₂ O ₃ -3H ₂ /97N ₂ catalyst at 10nm HRTEM image; from Figure 4, it can be seen that the particles identified by high-resolution transmission electron microscopy are still Co, consistent with the 20Co0.25La/Al ₂ O ₃ -20H ₂ /80N ₂ catalyst, corresponding to the (1 1 1) crystal plane of Co;

Figure 5 I is the TEM image of 30Co1La/Al ₂ O ₃ -50H ₂ /35N ₂ /15Ar catalyst at 200nm; J is the TEM image of 30Co1La/Al ₂ O ₃ -50H ₂ /35N ₂ /15Ar catalyst at 10nm HRTEM diagram; Figure 5 shows that the active components are well dispersed, and the high-resolution transmission electron microscopy analysis identifies the particles as Co, corresponding to the (1 1 1) crystal plane of Co;

The image K in Figure 6 is the TEM image of 15Co0.5La/Al ₂ O ₃ -15H ₂ /70N ₂ /15He catalyst at 200nm; the image L is the TEM image of 15Co0.5La/Al ₂ O ₃ -15H ₂ /70N ₂ at 10nm /15He catalyst HRTEM image; Figure 6 shows that among the six catalysts, the active component particles are the smallest, and the high-resolution transmission electron microscope analysis identified the particles as Co, corresponding to the (2 0 0) crystal plane of Co.

Example 5

Catalysts prepared in Comparative Examples 1 and 2 were evaluated on the reaction performance of ethanol dehydroamination to acetonitrile in a fixed-bed reactor. The diameter of the reactor is 9mm, and the loading amount of the catalyst is 4g. Under the condition of nitrogen, the temperature is raised to 410°C at a heating rate of 3°C/min, and ammonia gas and ethanol are introduced. The reaction conditions are as follows: the temperature is 410°C, the pressure is 0.1MPa, the mass space velocity of ethanol is 0.5h ^-1 , and the molar ratio of ammonia to ethanol is 6:1. The liquid phase and gas phase products were analyzed by FID and TCD detectors of Agilent 7890A GC, and the carrier gas was hydrogen and nuclear gas, respectively. The specific evaluation results are shown in Table 1.

Example 6

The catalyst prepared in Example 1 was evaluated on the reaction performance of ethanol dehydroamination to acetonitrile in a fixed bed reactor. The diameter of the reactor is 9mm, and the loading amount of the catalyst is 4g. Under the condition of nitrogen, the temperature is raised to 410°C at a heating rate of 3°C/min, and ammonia gas and ethanol are introduced. The reaction conditions are as follows: the temperature is 410°C, the pressure is 0.1MPa, the mass space velocity of ethanol is 0.5h ^-1 , and the molar ratio of ammonia to ethanol is 6:1. The liquid phase and gas phase products were analyzed by FID and TCD detectors of Agilent 7890A GC, and the carrier gas was hydrogen and nuclear gas, respectively. The specific evaluation results are shown in Table 1.

Example 7

The catalyst prepared in Example 2 was evaluated for the reaction performance of ethanol dehydroamination to acetonitrile in a fixed bed reactor. The diameter of the reactor is 9mm, and the loading amount of the catalyst is 4g. Under the condition of nitrogen, the temperature is raised to 450°C at a heating rate of 3°C/min, and ammonia gas and ethanol are introduced. The reaction conditions are as follows: the temperature is 450°C, the pressure is 0.1MPa, the mass space velocity of ethanol is 0.5h ^-1 , and the molar ratio of ammonia to ethanol is 6:1. The liquid phase and gas phase products were analyzed by FID and TCD detectors of Agilent 7890A GC, and the carrier gas was hydrogen and nuclear gas, respectively. The specific evaluation results are shown in Table 1.

Example 8

The catalyst prepared in Example 3 was evaluated on the reaction performance of ethanol dehydroamination to acetonitrile in a fixed bed reactor. The diameter of the reactor is 9mm, and the loading amount of the catalyst is 4g. Under the condition of nitrogen, the temperature is raised to 430°C at a heating rate of 3°C/min, and ammonia gas and ethanol are introduced. The reaction conditions are as follows: the temperature is 430°C, the pressure is 0.3MPa, the mass space velocity of ethanol is 0.1h ^-1 , and the molar ratio of ammonia to ethanol is 2:1. The liquid phase and gas phase products were analyzed by FID and TCD detectors of Agilent 7890A GC, and the carrier gas was hydrogen and nuclear gas, respectively. The specific evaluation results are shown in Table 1.

Example 9

The catalyst prepared in Example 4 was evaluated on the reaction performance of ethanol dehydroamination to acetonitrile in a fixed bed reactor. The diameter of the reactor is 9mm, and the loading amount of the catalyst is 4g. Under the condition of nitrogen, the temperature is raised to 470°C at a heating rate of 3°C/min, and ammonia gas and ethanol are introduced. The reaction conditions are as follows: the temperature is 470°C, the pressure is 0.1MPa, the mass space velocity of ethanol is 1.0h ^-1 , and the molar ratio of ammonia to ethanol is 8:1. The liquid phase and gas phase products were analyzed by FID and TCD detectors of Agilent 7890A GC, and the carrier gas was hydrogen and nuclear gas, respectively. The specific evaluation results are shown in Table 1.

Table 1 Catalyst Catalyzed Reaction Performance of Ethanol Dehydrogenation Amination to Acetonitrile

Catalyst number Cat-A Cat-B Cat-C Cat-D Cat-E Cat-F Reaction pressure (Mpa) 0.10 0.10 0.10 0.10 0.30 0.10 Ethanol mass space velocity (h ^-1 ) 0.5 0.5 0.5 0.5 0.1 1.0 Reaction temperature (°C) 410 410 410 450 430 470 Amino alcohol molar ratio 6:1 6:1 6:1 6:1 2:1 8:1 Ethanol conversion rate (%) 99.88 98.34 99.99 99.99 99.99 99.99 Acetonitrile selectivity (%) 74.85 74.16 83.53 88.47 82.20 85.60

The experimental results in Table 1 show that the reaction performance (Cat-A, Cat-B) of the CoLa/Al ₂ O ₃ catalyst prepared by the two ways of air atmosphere calcination or air atmosphere calcination and hydrogen atmosphere reduction did not change much, while hydrogen Atmosphere calcination can promote the reaction performance on CoLa/Al ₂ O ₃ . Compared with the cobalt-lanthanum catalyst supported on alumina support (Cat-A) prepared in air atmosphere, the cobalt-lanthanum catalyst supported on alumina support prepared by hydrogen atmosphere calcination (Cat-C ) has higher selectivity to acetonitrile, and under the reaction conditions investigated, the prepared Cat-E, Cat-F and Cat-G catalysts have excellent reaction performance.

The above are only a few embodiments of the application, and do not limit the application in any form. Although the application is disclosed as above with preferred embodiments, it is not intended to limit the application. Any skilled person familiar with this field, Without departing from the scope of the technical solution of the present application, any changes or modifications made using the technical content disclosed above are equivalent to equivalent implementation cases, and all belong to the scope of the technical solution.

Claims (10)

1. a kind of preparation method of preparing cobalt-based catalyst near hydrogen, is characterized in that, comprises the following steps at least: Immersing the alumina precursor in a mixed solution containing the active component precursor and the auxiliary component precursor, drying, and roasting in a hydrogen atmosphere to obtain the catalyst; Wherein the active component precursor is a cobalt-containing compound, and the auxiliary component precursor is lanthanum nitrate. 2. The preparation method according to claim 1, characterized in that, the quality of the active component precursor is 5 to 30 wt% of the quality of the alumina precursor, and the quality of the active component precursor is represented by the cobalt-containing compound The mass meter of the cobalt element in the medium; The mass of the auxiliary component precursor is 0.1-1.0 wt% of the mass of the alumina precursor, and the mass of the auxiliary component precursor is calculated by the mass of lanthanum element in lanthanum nitrate. 3. The preparation method according to claim 1, wherein the cobalt-containing compound is selected from at least one of cobalt nitrate, cobalt acetate, cobalt chloride and cobalt sulfate. 4. The preparation method according to claim 1, characterized in that, the impregnation adopts vacuum equal-volume impregnation, and the impregnation time is 2 to 5 hours; Preferably, the drying temperature is 110-130° C., and the drying time is 6-12 hours. 5. The preparation method according to claim 1, characterized in that the roasting temperature is 500-700°C, and the roasting time is 2-4 hours; The hydrogen atmosphere is selected from any one of H ₂ /N ₂ mixed gas, H ₂ /He mixed gas and H ₂ /Ar mixed gas; Preferably, the _H2 content in the hydrogen atmosphere is 3-50vol%; Preferably, the flow rate of the hydrogen atmosphere is 10-50 mL/min. 6. A cobalt-based catalyst obtained by the preparation method according to any one of claims 1 to 5, characterized in that, comprising an alumina carrier and cobalt and lanthanum elements loaded on the alumina carrier; Wherein, both the cobalt element and the lanthanum element exist in a reduced state. 7. The cobalt-based catalyst according to claim 6, characterized in that, the quality of the cobalt element is 5 to 30 wt% of the mass of the alumina carrier; The mass of the lanthanum element is 0.1-1.0 wt% of the mass of the alumina carrier; Preferably, the particle size of the cobalt element is 0.1-0.5 nm. 8. A method for preparing acetonitrile by dehydrogenation and ammoniation of ethanol, characterized in that, at least comprising the following steps: The mixed raw material containing ethanol and ammonia is contacted with the catalyst, reacted, and the product containing acetonitrile is obtained; The catalyst is selected from at least one of the catalysts prepared by the preparation method described in any one of claims 1 to 5, or the catalysts described in claim 6 or 7. 9. The method according to claim 8, characterized in that the molar ratio of ammonia to ethanol is 8-2:1; The mass space velocity of the ethanol is 0.1˜1.0 h ⁻¹ . 10. The method according to claim 8, characterized in that the pressure of the reaction is 0.1-0.3 MPa; The reaction temperature is 410-470°C.