CN106140165A - Porous charcoal carries twin crystal phase Co based Fischer-Tropsch synthesis catalyst and preparation method and application - Google Patents

Abstract

The invention discloses a porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst, a preparation method and application thereof. The catalyst uses cobalt as the active component, porous carbon as the carrier, and FCC and HCP crystal phase cobalt as the active phase. The mass content of cobalt is 29.0-30.8%, and the mass ratio of the HCP crystal phase of cobalt to the FCC crystal phase is 0.42. -0.97:1. During the preparation, the metal-organic framework containing cobalt is used as a sacrificial template, pyrolyzed in an inert atmosphere, and then carbonized with carbon monoxide to obtain a porous carbon-supported cobalt carbide intermediate, and then treated with a passivation gas to obtain a catalyst precursor. The catalyst can be obtained after the precursor is subjected to hydrogenation and activation treatment. The cobalt metal active phase of the present invention includes two crystal phases of FCC and HCP, and when used in a Fischer-Tropsch synthesis reaction, it has high activity and good C ₅₊ selectivity, especially a very high C ₅₊ space-time yield, The C ₅₊ products are mainly gasoline and diesel components.

Description

Porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst and its preparation method and application

technical field

The invention relates to a cobalt-based Fischer-Tropsch synthesis catalyst, its preparation method and application, in particular to a porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst, its preparation method and application.

Background technique

Fischer-Tropsch synthesis refers to the process of carbon monoxide hydrogenation reaction to generate hydrocarbons and oxygenated compounds under the action of a catalyst. It is the indirect conversion of non-petroleum resources such as coal, natural gas or biomass into gasoline, A key step in liquid fuels or chemicals such as diesel, wax, and liquefied petroleum gas, it has been a research hotspot in the field of new energy chemical industry for many years.

Since the Fischer-Tropsch synthesis technology came out in the 1920s, researchers have conducted extensive research on the types of catalysts. A large number of experimental studies have proved that the most active metals for Fischer-Tropsch synthesis are Group VIII metals, such as Fe, Co, Ni, Ru, etc. Among them, Fe-based catalysts have high activity and are the earliest Fischer-Tropsch synthesis catalysts used industrially, but they are prone to water vapor shift reactions, which affect the selectivity and reaction rate of products. The Co-based catalyst is not sensitive to the water gas shift reaction, and is stable in the reaction process, not easy to deposit carbon and poisoning, has less oxygen-containing compounds in the product, and has a higher chain growth ability. However, Co-based catalysts are mostly supported catalysts, and the main factor that limits their industrial application is the unsatisfactory activity of the catalyst. In the final analysis, the number of active sites of cobalt is limited by the comprehensive influence of cobalt reduction degree, dispersion, and loading. Unable to improve.

At present, the crystal phase of supported cobalt-based catalysts is usually only FCC. Studies have shown that HCP cobalt crystals have higher activity than FCC cobalt crystal phases, because HCP cobalt has more defect sites (steps, twists and dislocations) than FCC cobalt (see literature Sci.Technol.B, 1996 , 14, 3207 and J.Catal.2002, 205, 346), and theoretical calculations show that HCP cobalt is not only more capable of hydrogen-assisted dissociation of CO than FCC cobalt, but also can directly dissociate CO (Journal of the American Chemical Society, 2013, 135, 16284-16287), which resulted in a 100,000-fold higher CO dissociation rate on HCP cobalt than the highest dissociation rate on FCC cobalt. It has been reported in the literature that cobalt in the HCP crystal phase on alumina or silica gel-supported cobalt catalysts has higher catalytic activity, for example, Catalysis Today, 2013, 215, 13-17; Catalysis Today, 2011, 164, 62-67 ). However, the activity of the catalyst is still unsatisfactory, which is mainly due to the incomplete reduction of cobalt on the catalyst and the poor dispersion of cobalt, resulting in a low number of active sites of cobalt.

In recent years, porous carbon-supported metal catalysts prepared by pyrolysis of metal-organic frameworks have become one of the research hotspots in the field of catalysis. The porous carbon-supported cobalt catalysts prepared by the pyrolysis of cobalt-containing metal-organic frameworks have the following characteristics: (1) After pyrolysis under inert atmosphere conditions, the organic ligands are sintered into porous carbon supports, and the cobalt species on the porous carbon supports All exist in a metallic state; (2) the mass content of cobalt on this type of material is relatively high, up to about 40%; (4) the volume of the material obtained by pyrolysis in an inert atmosphere shrinks sharply, and inherits the characteristics of light weight of the parent body, Therefore, the obtained material has a large number of nano-cobalt particles per unit mass or volume, that is, has a high specific active site density. There are a large number of such materials in the prior art literature (Nanoscale, 2012, 4, 591-599; ACS Catalysis, 2015, 5, 884-891; ChemComm, 2015, 51, 2331-2334; Advances in Chemistry, 2015, 27, 174-191.) reports. Although the porous carbon-supported cobalt catalyst obtained by the pyrolysis of metal-organic frameworks overcomes the problem that cobalt cannot be completely reduced on traditional catalysts, the cobalt on the pyrolyzed material is in a metallic state and will be oxidized and lose its activity when exposed to air. , and cobalt has only one FCC crystal phase, which limits the application of this type of catalyst.

Contents of the invention

The object of the present invention is to provide a kind of highly active cobalt catalyst and preparation method thereof for the porous carbon load of Fischer-Tropsch synthesis reaction, there are two kinds of cobalt active crystal phases of FCC and HCP on this catalyst after activation, have improved porous carbon load Activity of cobalt catalysts.

Another object of the present invention is to provide the application of porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst in Fischer-Tropsch synthesis reaction.

In the present invention, a metal-organic framework is used as a sacrificial template, and a porous carbon-supported cobalt metal intermediate material is prepared by pyrolysis, and a porous carbon-supported cobalt carbide intermediate material is obtained after carbon monoxide carbonization, and then hydrogenated and activated to obtain a real Bimorphic Cobalt Metal Catalysts Supported on Porous Carbons. The present invention utilizes the characteristics of the material obtained by pyrolyzing the metal-organic framework, so that the specific active site density of the catalyst is large, the cobalt reduction is thorough, the dispersibility is good, and the characteristics that cobalt carbide can exist stably in the air are utilized, and then activated by hydrogenation Converting to FCC and HCP crystalline cobalt active phases makes the catalyst prepared by the present invention have high catalytic activity and good C ₅₊ selectivity when used in Fischer-Tropsch synthesis reaction, especially the space-time yield of C ₅₊ is extremely high. At the same time, the precursor of the catalyst of the present invention exists in the form of porous carbon supported cobalt carbide, which facilitates the preservation and transportation of the catalyst.

For realizing the purpose of the present invention, the technical scheme that the present invention adopts is:

Porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst: the catalyst uses cobalt as the active component, porous carbon as the carrier, and FCC and HCP crystal phase cobalt as the active phase. The mass content of cobalt is 29.0-30.8%. The mass ratio of HCP crystal phase to FCC crystal phase is 0.42-0.97:1.

The preparation method of the porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst comprises the following steps:

1) Put the Co-MOF-71 metal-organic framework sacrificial template material in a fixed-bed stainless steel reactor, heat up to 500-550°C for 4-8h in situ pyrolysis in a He atmosphere, then cool down to room temperature, and cut into pure CO Gas, pressurize and maintain at 2-3MPa, raise the temperature to 230-250°C, keep it for 120-140h, then cool down to room temperature, cut into _O2 and Ar mixed gas for passivation, and obtain porous carbon-supported cobalt carbide precursor material;

2) The precursor material obtained in step 1) is heated to 350-450° C. in an H ₂ atmosphere and kept for 4-12 hours to obtain a porous carbon-supported bicrystalline cobalt metal catalyst.

In order to further realize the purpose of the present invention, preferably, the Co-MOF-71 organometallic framework sacrificial template material is prepared by the following method: placing cobalt nitrate and terephthalic acid in a mixture containing N,N-dimethylformamide and no In a closed container of water-ethanol mixed solution, after replacing the air in the container with nitrogen or argon, heat the container to 100-110°C and keep it for 10-15h, then filter the obtained material while it is hot, and wash it several times with DMF, Finally, the obtained material was dried to obtain Co-MOF-71 organometallic framework sacrificial template material.

Preferably, the molar ratio of cobalt nitrate, terephthalic acid, N,N-dimethylformamide and absolute ethanol is 1:1.5:95.7:31.7.

Preferably, the drying is in air at 80-100° C. for 6-12 hours.

Preferably, the heating rate to 500-550°C is 1-5°C/min; the heating rate to 230-250°C is 1-5°C/min; the heating rate to 350-450°C The heating rate is 1-5°C/min.

Preferably, the flow rate of the pure CO gas is controlled at 30-60mL/min; the volume ratio of O ₂ and Ar in the mixed gas of O ₂ and Ar is 2:98-1:99.

Preferably, the passivation time is 10-12h.

Application of the porous carbon-supported twin-phase cobalt-based Fischer-Tropsch synthesis catalyst in Fischer-Tropsch synthesis reaction. For this application, it is preferable to control the feed volume ratio of _H2 to CO to 2:1, the reaction temperature to be 280-300°C, the reaction pressure to be 3-4MPa, and the total reaction space velocity to be 15-30L/h/g catalyst.

The porous carbon-supported twin-phase cobalt-based catalyst used in the Fischer-Tropsch synthesis reaction of the present invention requires hydrogen reduction and activation before the reaction. The activation condition is hydrogen at normal pressure, the flow rate is 30-60mL/min, the reduction temperature is 350-450°C, and the temperature is raised. The rate is 1-5°C/min, and it is used for Fischer-Tropsch synthesis reaction after reduction.

Compared with the prior art, the present invention has the following advantages:

1) This technology converts the porous carbon-supported cobalt catalytic material obtained from the pyrolysis of the metal-organic framework into a porous carbon-supported cobalt carbide intermediate, which facilitates the storage and transportation of such materials at normal temperature and pressure;

2) The porous carbon-supported cobalt catalyst obtained by pyrolysis of metal-organic frameworks has only one FCC cobalt crystal phase (see Chinese invention patent application 201610300820.1), and the present invention converts this FCC cobalt crystal phase into a cobalt carbide intermediate, and then Hydrogenation under the same conditions decomposes cobalt carbide into two phases of FCC cobalt and HCP cobalt, and releases methane gas (expressed as: cobalt carbide + hydrogen → FCC cobalt + HCP cobalt + methane), which is obtained under the same pyrolysis conditions Compared with the porous carbon-supported cobalt catalyst with only one FCC cobalt crystal phase, the present invention provides a new HCP cobalt crystal phase active site, and utilizes the HCP cobalt crystal phase to have higher CO dissociation performance than the FCC cobalt crystal phase, Significantly improved the reactivity of porous carbon-supported cobalt-based catalysts.

2) Compared with the existing preparation method of porous carbon-supported cobalt catalyst by pyrolysis metal organic framework (201610300820.1), the pyrolysis temperature adopted in the present invention is lower, and the prepared catalyst does not need to be synthesized in situ in the reactor, The real Fischer-Tropsch synthesis catalyst can be prepared only by hydrogenolysis at a lower temperature, which reduces the design requirements for the reaction device, and will not pollute the reaction device by the organic matter produced by the in-situ pyrolysis of the metal-organic framework.

Description of drawings

Fig. 1 is the XRD (X-ray diffraction) figure of porous carbon-supported cobalt carbide intermediate state material described in embodiment 1-4 of the present invention, among the figure (a) is the XRD of porous carbon-supported cobalt carbide intermediate state material in embodiment 1 Figure; (b) is the XRD figure of porous carbon-supported cobalt carbide intermediate state material in embodiment 2; (c) is the XRD figure of porous carbon-supported cobalt carbide intermediate state material in embodiment 3; (d) is in embodiment 4 XRD pattern of porous carbon-supported cobalt carbide intermediate material.

Fig. 2 is the XRD (X-ray diffraction) figure of the catalyst obtained in Examples 1-6 and Comparative Example 1-2 of the present invention, among which (a) is the XRD figure of the catalyst in Example 1; (b) is the XRD figure in Example 2 The XRD figure of catalyst; (c) is the XRD figure of catalyst in embodiment 3; (d) is the XRD figure of catalyst in embodiment 4; (e) is the XRD figure of catalyst in embodiment 5; (f) is embodiment The XRD pattern of the catalyst in 6; (g) is the XRD pattern of the catalyst in Comparative Example 1; (h) is the XRD pattern of the catalyst in Comparative Example 2.

detailed description

In order to better understand the present invention, the present invention will be further described below in conjunction with the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. The conversion rate of CO in the embodiment, the selectivity of product and C _The space-time yield (g/g _cat h) is calculated by the following formula:

Conversion rate: ∑(N _CO,in -N _CO,out )/N _CO,in ×100%;

Selectivity: Mi/∑Mi×100% (calculate the selectivity of the product in moles)

C ₅₊ space-time yield (g/g _cat h): W(C ₅₊ alkanes)/t(hour)/W(catalyst mass dosage)

Among them, NCO,in is the number of moles of CO _in the feed gas; _NCO,out is the number of moles of CO in the tail gas; i is the hydrocarbon with carbon number i in the product; Mi is the hydrocarbon with carbon number i in the product The molar quantity of; ∑Mi is the sum of the molar quantities of hydrocarbons with carbon number i in the product;

W (C ₅₊ alkane) represents the quality of C ₅₊ alkane in the oil phase liquid product collected within a certain period of time; t (hour) is the time interval used for the reaction; W (catalyst mass consumption) is the catalyst quality used for the reaction.

Example 1

Put 0.8g of cobalt nitrate hexahydrate (Co(NO ₃ ) ₂ 6H ₂ O) and 0.46g of terephthalic acid (H ₂ BDC) into a 100mL Shrek tube, add 20mL of DMF and 5mL of absolute ethanol to form a mixed solution , then replace the air in the tube with N ₂ gas and seal it well, raise the temperature to 110°C for 15h, then filter while hot, wash with 100mL DMF three times, and finally dry in air at 100°C for 6h to obtain Co-MOF-71 metal organic framework materials.

1.48g Co-MOF-71 was placed in a fixed-bed stainless steel reactor, and in a He atmosphere, the temperature was raised to 500°C at a heating rate of 5°C/min for in-situ pyrolysis for 4 hours to obtain a porous carbon-supported cobalt metal intermediate material. Then cool down to room temperature, cut into pure CO gas, the flow rate is 30mL/min, increase the pressure to 2MPa, raise the temperature to 250°C at a heating rate of 5°C/min, keep it for 120h, then cool down to room temperature, use a flow rate of 10mL/min 1 %O ₂ /Ar mixed gas passivation for 4h, to obtain porous carbon-supported cobalt carbide intermediate material.

Take 0.1g of porous carbon-supported cobalt carbide intermediate material and heat it up to 350°C at a heating rate of 5°C/min in _H2 atmosphere, and keep it for 4h to obtain a porous carbon-supported dual-phase cobalt metal catalyst. The mass percentage of cobalt in this material is The content is 30.8% by atomic absorption spectrometry (AAS) characterization test. The prepared catalyst was subjected to Fischer-Tropsch synthesis reaction, wherein the reaction temperature was 300°C, the volume feed ratio of _H2 to CO was 2, the air inlet space velocity was 15L/h/g catalyst, and the reaction pressure was 3MPa. Under the above conditions, the performance evaluation results of the catalyst are shown in Table 1 below.

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 1. From Figure 1, it can be seen that the characteristic peaks of metal cobalt in the form of FCC and HCP appear, and the mass content ratio of HCP and FCC cobalt is calculated from the XRD peak intensity by the direct comparison method is 0.45.

Example 2

Put 0.8g of cobalt nitrate hexahydrate (Co(NO ₃ ) ₂ 6H ₂ O) and 0.46g of terephthalic acid (H ₂ BDC) into a 100mL Shrek tube, add 20mL of DMF and 5mL of absolute ethanol to form a mixed solution , and then use _N2 gas to replace the air in the tube and seal it well, raise the temperature to 100°C for 10h, then filter while it is hot, wash with 100mL DMF three times, and finally dry in air at 80°C for 12h to obtain Co-MOF-71 metal organic framework materials.

1.48g Co-MOF-71 was placed in a fixed bed reactor, and in a He atmosphere, the temperature was raised to 500°C at a heating rate of 1°C/min for in-situ pyrolysis for 8h to obtain a porous carbon-supported cobalt metal intermediate material, and then Cool down to room temperature, cut into pure CO gas, the flow rate is 30mL/min, increase the pressure to 2MPa, raise the temperature to 250°C at a heating rate of 5°C/min, keep it for 140h, then cool down to room temperature, use a flow rate of 10mL/min 1% O ₂ /Ar mixed gas passivation for 10 hours to obtain a porous carbon-supported cobalt carbide intermediate material;

Take 0.1g of porous carbon-supported cobalt carbide intermediate material and heat it up to 450°C at a heating rate of 5°C/min in _H2 atmosphere, and keep it for 4h to obtain a porous carbon-supported dual-phase cobalt metal catalyst. The mass percentage of cobalt in this material is The content is 29.0% by atomic absorption spectrometry (AAS) characterization test. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 1. From Figure 1, it can be seen that the characteristic peaks of metal cobalt in the form of FCC and HCP appear, and the mass content ratio of HCP and FCC cobalt is calculated from the XRD peak intensity by the direct comparison method is 0.44.

Example 3

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 1.48g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 550°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours to obtain a porous carbon-supported cobalt metal intermediate material, then cooled to room temperature, cut into pure CO gas, the flow rate was 30mL/min, the pressure was increased to 3MPa, and the temperature was raised to 250°C at a heating rate of 5°C/min. Keep for 120h to obtain a porous carbon-supported cobalt carbide intermediate material;

Take 0.1g of porous carbon-supported cobalt carbide intermediate material and heat it up to 450°C at a heating rate of 5°C/min in _H2 atmosphere, and keep it for 4h to obtain a porous carbon-supported dual-phase cobalt metal catalyst. The mass percentage of cobalt in this material is The content is 30.1% by atomic absorption spectrometry (AAS) characterization test. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 1. From Figure 1, it can be seen that the characteristic peaks of metal cobalt in the form of FCC and HCP appear, and the mass content ratio of HCP and FCC cobalt is calculated from the XRD peak intensity by the direct comparison method is 0.43.

Example 4

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 1.48g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 500°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours to obtain a porous carbon-supported cobalt metal intermediate material, then cooled to room temperature, cut into pure CO gas, the flow rate was 60mL/min, the pressure was increased to 3MPa, and the temperature was raised to 230°C at a heating rate of 5°C/min. Keep for 120h to obtain a porous carbon-supported cobalt carbide intermediate material;

Take 0.1g of porous carbon-supported cobalt carbide intermediate material and heat it up to 450°C at a heating rate of 5°C/min in _H2 atmosphere, and keep it for 4h to obtain a porous carbon-supported dual-phase cobalt metal catalyst. The mass percentage of cobalt in this material is The content is 29.9% by atomic absorption spectrometry (AAS) characterization test. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 1. From Figure 1, it can be seen that the characteristic peaks of metal cobalt in the form of FCC and HCP appear, and the mass content ratio of HCP and FCC cobalt is calculated from the XRD peak intensity by the direct comparison method is 0.42.

Example 5

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 1.48g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 500°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours to obtain a porous carbon-supported cobalt metal intermediate material, then cooled to room temperature, cut into pure CO gas, the flow rate was 30mL/min, the pressure was increased to 2MPa, and the temperature was raised to 250°C at a heating rate of 5°C/min. Keep for 120h to obtain a porous carbon-supported cobalt carbide intermediate material;

Take 0.1 g of porous carbon-supported cobalt carbide intermediate material and raise the temperature to 350 °C at a heating rate of 1 °C/min in _H2 atmosphere, and keep it for 4 h to obtain a porous carbon-supported dual-phase cobalt metal catalyst. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 1. From Figure 1, it can be seen that the characteristic peaks of metal cobalt in the form of FCC and HCP appear, and the mass content ratio of HCP and FCC cobalt is calculated from the XRD peak intensity by the direct comparison method is 0.97.

Example 6

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 1.48g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 550°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours to obtain a porous carbon-supported cobalt metal intermediate material, then cooled to room temperature, cut into pure CO gas, the flow rate was 30mL/min, the pressure was increased to 3MPa, and the temperature was raised to 250°C at a heating rate of 5°C/min. Keeping for 140h, a porous carbon-supported cobalt carbide intermediate material is obtained.

Take 0.1 g of porous carbon-supported cobalt carbide intermediate material and raise the temperature to 350 °C at a heating rate of 1 °C/min in _H2 atmosphere, and keep it for 4 h to obtain a porous carbon-supported dual-phase cobalt metal catalyst. The mass percentage content of cobalt in this material is 29.3% through atomic absorption spectrometry (AAS) characterization test. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 1. From Figure 1, it can be seen that the characteristic peaks of metal cobalt in the form of FCC and HCP appear, and the mass content ratio of HCP and FCC cobalt is calculated from the XRD peak intensity by the direct comparison method is 0.89.

Example 7

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 1.48g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 500°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours to obtain a porous carbon-supported cobalt metal intermediate material, then cooled to room temperature, cut into pure CO gas, the flow rate was 30mL/min, the pressure was increased to 2MPa, and the temperature was raised to 250°C at a heating rate of 5°C/min. Keep for 120h to obtain a porous carbon-supported cobalt carbide intermediate material;

Take 0.1g of porous carbon-supported cobalt carbide intermediate material and heat it up to 450°C at a heating rate of ₁ °C/min in H atmosphere, and keep it for 4h to obtain a porous carbon-supported twin-phase cobalt metal catalyst. Tropsch synthesis reaction, wherein the reaction temperature is 290°C, the volume feed ratio of _H2 to CO is 2, the air inlet space velocity is 15L/h/g catalyst, and the reaction pressure is 4MPa. Under the above conditions, the performance evaluation results of the catalyst are shown in Table 1 below.

Example 8

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 1.48g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 500°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours to obtain a porous carbon-supported cobalt metal intermediate material, then cooled to room temperature, cut into pure CO gas, the flow rate was 30mL/min, the pressure was increased to 2MPa, and the temperature was raised to 250°C at a heating rate of 5°C/min. Keep for 120h to obtain a porous carbon-supported cobalt carbide intermediate material;

Take 0.1g of porous carbon-supported cobalt carbide intermediate material and heat it up to 450°C at a heating rate of ₁ °C/min in H atmosphere, and keep it for 4h to obtain a porous carbon-supported twin-phase cobalt metal catalyst. Tropsch synthesis reaction, wherein the reaction temperature is 300°C, the volume feed ratio of _H2 to CO is 2, the air inlet space velocity is 30L/h/g catalyst, and the reaction pressure is 3MPa. Under the above conditions, the performance evaluation results of the catalyst are shown in Table 1 below.

Comparative example 1

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 0.37g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 500°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours, a porous carbon-supported cobalt metal intermediate catalytic material was obtained. The mass of the obtained material was 0.1 g, and the mass percentage of cobalt in this material was 26.7% by atomic absorption spectroscopy (AAS).

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 2, and it can be seen from Figure 1 that only the characteristic peaks of the FCC crystal phase metal cobalt appear. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

Comparative example 2

Using the Co-MOF-71 synthesized in Example 1 as a sacrificial template, place 0.37g of Co-MOF-71 in a fixed-bed reactor, and raise the temperature to 550°C at a heating rate of 1°C/min in a He atmosphere In situ pyrolysis for 8 hours, a porous carbon-supported cobalt metal intermediate catalytic material was obtained. The mass of the obtained material was 0.1 g, and the mass percentage of cobalt in this material was 27.9% by atomic absorption spectroscopy (AAS).

The XRD characterization results of the crystal phase structure of the catalyst are shown in Figure 2, and it can be seen from Figure 1 that only the characteristic peaks of the FCC crystal phase metal cobalt appear. The reaction conditions of the catalyst are the same as in Example 1, and the performance evaluation results are shown in Table 1 below.

Table 1

It can be seen from Fig. 1 and Fig. 2 that the cobalt species on the material pyrolyzed from the metal-organic framework only presents the FCC metal phase, while the real catalyst in the present invention contains both FCC and HCP metal phases. In addition, the precursor of the catalyst in the present invention exists in the form of porous carbon-supported cobalt carbide, thereby preventing the catalyst from being oxidized and deactivated when exposed to air.

As can be seen from the catalytic performance of the catalyst in Table 1, the porous carbon-supported twin-phase cobalt catalyst provided by the method of the present invention, compared with the porous carbon-supported cobalt catalyst from pyrolysis under the same conditions, under the same reaction conditions , the selectivity of by-product methane and CO ₂ has been significantly reduced, while the activity of the catalyst, the selectivity of diesel component hydrocarbons and the space-time yield of C ₅₊ have been considerably improved. Doubling the reaction flow rate led to a decrease in catalyst activity and an increase in methane selectivity, but greatly increased the C ₅₊ space-time yield of the catalyst.

Claims (10)

1. porous charcoal carries twin crystal phase Co based Fischer-Tropsch synthesis catalyst, it is characterised in that catalyst is with cobalt as active component, with porous Charcoal is carrier, and with FCC and HCP crystalline phase cobalt for activity phase, the mass content of cobalt is 29.0-30.8%, the HCP crystalline phase of cobalt and FCC The mass ratio of crystalline phase is 0.42-0.97:1.

2. porous charcoal described in claim 1 carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst, it is characterised in that include Following steps:

1) it is placed in Co-MOF-71 organometallic skeletal sacrificial mold plate material in fixed bed stainless steel reactor, in He atmosphere, Being warming up to 500-550 DEG C of pyrolysis 4-8h in situ, being then cooled to room temperature, cut pure CO gas, boosting maintains 2-3MPa, heats up To 230-250 DEG C, keep 120-140h, be then cooled to room temperature, cut O₂With the passivation of Ar gaseous mixture, obtain porous charcoal and carry carbonization Cobalt precursor material；

2) by step 1) gained persursor material is at H₂Atmosphere is warming up to 350-450 DEG C, keeps 4-12h, obtain porous charcoal and carry double Crystalline phase cobalt metallic catalyst.

3. porous charcoal carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst according to claim 2, it is characterised in that Described Co-MOF-71 organometallic skeletal sacrificial mold plate material is prepared via a method which: put cobalt nitrate and terephthalic acid (TPA) In the closed container of the mixed solution containing DMF and absolute ethyl alcohol, use nitrogen or argon gas displacement container After interior air, container is heated to 100-110 DEG C, keeps 10-15h, afterwards while hot by gained material filtering, and use DMF Wash several times, finally by gained dry materials, it is thus achieved that Co-MOF-71 organometallic skeletal sacrificial mold plate material.

4. porous charcoal carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst according to claim 3, it is characterised in that The mol ratio of described cobalt nitrate, terephthalic acid (TPA), N,N-dimethylformamide and absolute ethyl alcohol is 1:1.5:95.7:31.7.

5. porous charcoal carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst according to claim 2, it is characterised in that Described drying is the air drying 6-12h in 80-100 DEG C.

6. porous charcoal carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst according to claim 2, it is characterised in that The heating rate of described 500-550 of being warming up to DEG C is 1-5 DEG C/min；The heating rate of described 230-250 of being warming up to DEG C is 1-5 ℃/min；The heating rate of described 350-450 of being warming up to DEG C is 1-5 DEG C/min.

7. porous charcoal carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst according to claim 2, it is characterised in that The flow-control of described pure CO gas is at 30-60mL/min；Described O₂With O in Ar mixed gas₂Volume ratio with Ar is 2:98- 1:99。

8. porous charcoal carries the preparation method of twin crystal phase Co based Fischer-Tropsch synthesis catalyst according to claim 2, it is characterised in that The time of described passivation is 10-12h.

9. porous charcoal described in claim 1 carries application in Fischer-Tropsch synthesis for the twin crystal phase Co based Fischer-Tropsch synthesis catalyst.

10. porous charcoal carries twin crystal phase Co based Fischer-Tropsch synthesis catalyst answering in Fischer-Tropsch synthesis according to claim 9 With, it is characterised in that control H₂Being 2:1 with CO input material volume ratio, reaction temperature is 280-300 DEG C, and reaction pressure is 3-4MPa, Reacting total air speed is 15-30L/h/g catalyst.