CN112536059A - Iron oxide/boron nitride nano catalyst, preparation method and application thereof - Google Patents

Iron oxide/boron nitride nano catalyst, preparation method and application thereof Download PDF

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CN112536059A
CN112536059A CN202011542098.5A CN202011542098A CN112536059A CN 112536059 A CN112536059 A CN 112536059A CN 202011542098 A CN202011542098 A CN 202011542098A CN 112536059 A CN112536059 A CN 112536059A
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catalyst
boron nitride
fischer
tropsch synthesis
iron
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张成华
王宪周
马彩萍
颜琳琳
王虎林
相宏伟
杨勇
李永旺
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Synfuels China Technology Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
    • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
    • C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group

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Abstract

The invention discloses an iron oxide/boron nitride nano catalyst, a preparation method and application thereof in catalyzing Fischer-Tropsch synthesis. The iron oxide/boron nitride nano catalyst comprises iron serving as an active metal and boron nitride serving as a carrier, wherein the mass ratio of the active metal iron to the carrier boron nitride is (1-400): 100, and the grain size of the iron oxide/boron nitride nano catalyst is 10-20 nm. The iron oxide/boron nitride nano catalyst prepared by the invention can be applied to catalyzing Fischer-Tropsch synthesis reaction. The catalyst has the characteristics of controllable metal grain size (10-20 nm) and uniform size, and shows good wear resistance, high hydrothermal stability, high Fischer-Tropsch synthesis reaction activity, high CO conversion rate and high heavy hydrocarbon (C)5 +) Selectivity and excellent running stability.

Description

Iron oxide/boron nitride nano catalyst, preparation method and application thereof
Technical Field
The invention relates to the field of catalysis, in particular to an iron-based catalyst, a preparation method and application thereof in Fischer-Tropsch synthesis, and particularly relates to an iron oxide/boron nitride nano catalyst, and a preparation method and application thereof.
Background
Gasifying coal to obtain synthetic gas, purifying and regulating H2And synthesizing the clean fuel through catalytic reaction after the ratio of/CO. Fischer-Tropsch synthesis refers to synthesis gas (containing CO and H)2A small amount of CO2Methane and N2Mixed gas of (2) is catalytically converted into hydrocarbons of different chain lengths and small amounts of organic oxygenates. Under different catalysts and reaction conditions, organic compounds such as alkane, alkene, aromatic hydrocarbon, alcohol, aldehyde, acid and the like can be generated. The active components of the Fischer-Tropsch synthesis catalyst are mainly metals in VIIIB groups such as Fe, Co, Ni, Ru and the like. Among these catalysts, iron-based catalysts have been widely studied due to their advantages of low price, abundant reserves, high water gas shift reaction activity, and wide operating temperature range (220 ℃ to 350 ℃), and have been industrially implemented on a large scale. The activity, selectivity and stability of the pure iron-based catalyst can not meet the requirements of industrial production, so that a carrier auxiliary agent is usually required to be added. The addition of the carrier can improve the specific surface area of the catalyst, promote the dispersion of active metals, inhibit the sintering of active components of the catalyst and improve the mechanical property of the catalyst.
Fischer-Tropsch synthesis is a reaction with high temperature (150 ℃ -. One of the major by-products of the reaction is water. The reactors suitable for the Fischer-Tropsch synthesis reaction mainly comprise a fixed bed reactor, a fixed fluidized bed reactor and a gas-liquid-solid three-phase slurry bed reactor at present. Therefore, the catalyst is subjected to very severe mechanical and chemical stresses during the fischer-tropsch reaction, which requires excellent attrition resistance of the catalyst.
Conventional refractory oxides such as silica, alumina, zirconia and the like are used as supports for fischer-tropsch synthesis catalysts. However, these supports also bring about inevitable disadvantages to the catalyst, such as low thermal conductivity, strong surface acidity, poor hydrothermal stability, low mechanical strength and poor attrition resistance. Since the Fischer-Tropsch synthesis is a strong exothermic reaction, a large amount of reaction heat generated in the reaction process is retained in catalyst particles due to poor heat conductivity of the catalyst, the catalyst generates local overtemperature hot spots, the selectivity of a target product is poor, meanwhile, the generation of the hot spots can cause sintering and agglomeration of active components of the catalyst, the activity of the catalyst is reduced and even inactivated, and therefore, timely removal of a large amount of reaction heat released in the reaction process becomes extremely important. In order to improve the mechanical properties and chemical stability of the fischer-tropsch synthesis catalyst, many researchers have attempted to find new catalyst supports with high heat transfer efficiency and high mass transfer efficiency.
Hexagonal phase boron nitride as a layered material has the characteristics of good thermal stability, excellent thermal conductivity, chemical stability and the like. Boron nitride is widely used as a carrier in different catalytic reaction systems at present. The literature (J.Catal., 2001, 200, pages 1-3) reports the use of Ba-Ru/BN catalyst prepared by impregnation method with commercial boron nitride as carrier in the reaction of synthesizing ammonia. The catalyst shows excellent reaction activity and good operation stability (3500h), and the initial reaction activity of the catalyst can be still maintained after regeneration. The document (rsc. advances, 2016, 6, p. 38356-38364) reports that a hexagonal phase boron nitride supported metallic iron catalyst is prepared by taking ferric oxide, sodium borohydride and sodium azide as raw materials under the conditions of high temperature and high pressure. The catalyst shows good low-temperature Fischer-Tropsch activity and operation stability, but the metal iron particle size in the catalyst is larger (25-40nm), the iron active phase dispersion degree is lower, the Fischer-Tropsch synthesis reaction activity is low, and the methane is selectedHigh selectivity, unfavorable to the desired hydrocarbon compounds (mainly C)5 +Hydrocarbons). The literature (ACS appl. Mater. interfaces, 2017, 9, page 14319-14327) reports that a metal iron catalyst coated by BCNNSs is prepared by one step by using ferric nitrate, urea and boric acid as raw materials through a high-temperature solid phase method, the size of an iron active phase of the catalyst is small, the dispersion of iron active components is high, and the catalyst shows good high-temperature Fischer-Tropsch activity and operation stability. However, the catalyst has high methane selectivity and is not beneficial to target products (mainly C)5 +Hydrocarbons).
At present, active phase sintering of Fe/BN catalysts (see RSC. Advances, 2016, 6, 38356-intermissions, 2017, 9, 14319-intermissions) reported in the literature is severe, and target products (mainly C. sub.C. in the literature) exist5 +Hydrocarbons) poor selectivity. These drawbacks limit the use of boron nitride materials in fischer-tropsch synthesis.
Patent application CN107185572A discloses a Fischer-Tropsch synthesis catalyst using boron nitride or silicon nitride as a carrier, and a preparation method and application thereof. The nitride can promote the high dispersion of active metal, obviously enhance the activity of the catalyst and prepare target hydrocarbon compounds (especially C) with high selectivity5 +Hydrocarbons). The boron nitride loaded iron oxide catalyst shows good Fischer-Tropsch reaction activity and operation stability. However, the catalyst prepared by the impregnation method and the coprecipitation method has wide size distribution of metal grains and poor size-adjustable property.
The Fischer-Tropsch synthesis reaction is used as a structure sensitive reaction, and the size and the particle size distribution of an active phase can influence the reaction performance of the catalyst. Therefore, there is a need in the art for a nano-catalyst of iron oxide and boron nitride with controllable metal grain size and uniform size. In addition, the excellent thermal conductivity and good thermal stability of boron nitride are advantageous for its role in the fischer-tropsch synthesis reaction.
The invention provides a heavy hydrocarbon (C) with good abrasion resistance, high hydrothermal stability, high Fischer-Tropsch synthesis reaction activity, high CO conversion rate and high5 +) An iron oxide/boron nitride nanocatalyst with selectivity and excellent operation stability.
Disclosure of Invention
The invention aims to overcome the defects of the existing Fischer-Tropsch synthesis catalyst and provide a Fischer-Tropsch synthesis catalyst for preparing hydrocarbons by converting synthesis gas. The catalyst has controllable particle size, uniform size, high Fischer-Tropsch synthesis reaction activity, high CO conversion rate and high heavy hydrocarbon (C)5 +) And (4) selectivity. The invention also provides a preparation method of the catalyst and application of the catalyst in Fischer-Tropsch synthesis reaction. Specifically, the catalyst comprises iron as the active metal and boron nitride as the support.
Accordingly, the present invention provides a fischer-tropsch synthesis catalyst, which catalyst may comprise: iron as the active metal and boron nitride as the carrier. Wherein the active metal is supported on boron nitride, preferably hexagonal phase boron nitride.
Wherein the mass ratio of the active metal iron to the carrier boron nitride is (1-400) in terms of the mass of iron element: 100, and the size of the metal crystal grain of the iron oxide/boron nitride nano catalyst is 5 nm-20 nm, preferably 10-20 nm.
The present invention further provides a method for preparing the above catalyst, the method comprising:
(1) respectively preparing an inorganic ferric salt solution and a boron nitride dispersion liquid;
(2) adding the inorganic ferric salt solution into the boron nitride dispersion liquid to obtain a suspension;
(3) carrying out solvothermal reaction on the suspension at the temperature of 100-200 ℃ to obtain a nano composite material containing boron nitride and ferric oxide, and washing, centrifuging and drying the nano composite material; and optionally
(4) And (4) calcining the dried nano composite material obtained in the step (3) to obtain the catalyst.
The invention also provides application of the Fischer-Tropsch synthesis catalyst in preparation of hydrocarbon compounds by catalyzing synthesis gas in Fischer-Tropsch synthesis reaction. Or the invention also provides a Fischer-Tropsch synthesis reaction method, wherein the Fischer-Tropsch synthesis catalyst is used for catalyzing synthesis gas to prepare hydrocarbon compounds. Specifically, the synthesis gas is introduced into a Fischer-Tropsch synthesis reactor to contact with the catalyst, and the synthesis gas is catalyzed by the catalyst to react to prepare the hydrocarbon compound.
Has the advantages that:
1. compared with the catalyst adopting the VIIIB group metals such as Co, Ni, Ru and the like as the active components of the Fischer-Tropsch synthesis catalyst, the catalyst containing the iron oxide and the boron nitride has the advantages that the iron source is cheap and easy to obtain. Meanwhile, the preparation process of the catalyst is simple, the operation is easy, and the repeatability is good.
2. The preparation method of the catalyst containing the iron oxide and the boron nitride can adjust the synthesis conditions of the solvothermal reaction temperature, the reaction time, the reactant concentration, the iron salt type and the like, and can realize the controllable size, the uniform size and the no agglomeration of the metal crystal grains of the iron oxide/boron nitride nano catalyst while ensuring that the iron oxide grows on the surface of the boron nitride.
3. The catalyst containing iron oxide and boron nitride prepared by the invention has the characteristics of easy reduction and carbonization. The catalyst has good abrasion resistance, high hydrothermal stability, high Fischer-Tropsch synthesis reaction activity and high heavy hydrocarbon (C)5 +) Selectivity and excellent running stability.
Drawings
FIG. 1 is a transmission electron micrograph of Exam-3a, a catalyst prepared in example 3 of the present invention.
FIG. 2 is a transmission electron micrograph of the catalyst Exam-3c prepared in example 3 of the present invention.
FIG. 3 is an XRD pattern of Exam-3b catalyst prepared in example 3 of the present invention.
FIG. 4 is H of Exam-3c catalyst prepared in example 3 of the present invention2-TPR spectrum.
FIG. 5 is a graph showing the Fischer-Tropsch reaction activity of Exam-3c, a catalyst prepared in example 3 of the present invention, as a function of time.
Detailed Description
As used herein, unless otherwise indicated, the terms "active component", "active phase metal", "active metal" and "metal active phase" are used interchangeably to refer to the metal component used as the active phase of a Fischer-Tropsch synthesis catalyst.
As used herein, unless otherwise indicated, the term "specific surface area" means the specific surface area as determined by the BET method (Brunauer-Emmet-Teller), see, for example, the description of Standard NFX 11-621.
Herein, unless otherwise specified, the term "grain size" refers to the grain size of the crystalline phase of the iron oxide/boron nitride nanocatalyst (in which the active metal is present in a highly dispersed iron oxide structure), which can be determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), but is not limited thereto.
The present invention provides a fischer-tropsch synthesis catalyst, which may comprise: iron as an active metal and boron nitride as a carrier, wherein the active metal is supported on the carrier; wherein the specific surface area of the catalyst is 70-140 m2Per g, preferably 80 to 110m2The crystal grain size of the catalyst is 5 nm-20 nm and less than 20nm, preferably 10 nm-20 nm and less than 20 nm. For example, the catalyst may have a grain size of 10 to 19.8nm, e.g., 10.0nm, 10.3nm, 13.5nm, 14.2nm, 15.0nm, 16.0nm, 19.8 nm.
Preferably, the dispersity of the active components in the Fischer-Tropsch synthesis catalyst is 35.0-65.0%, so that the catalyst has better catalytic activity.
In the catalyst, the mass ratio of the active metal iron to the carrier boron nitride is (1-400): 100, preferably (5-100): 100, more preferably (10-80): 100, most preferably (20-50): 100, and particularly preferably (30-40): 100.
The Fischer-Tropsch synthesis catalyst is an iron oxide/boron nitride nano catalyst (also called as an iron oxide/boron nitride catalyst), and the size of metal crystal grains of the catalyst is 5-20 nm and less than 20nm, preferably 10-20 nm and less than 20 nm.
The dispersion degree of metal in the iron oxide/boron nitride nano catalyst is higher, and preferably, the dispersion degree of active metal of the iron oxide/boron nitride nano catalyst is 35.0-65.0%, so that the catalyst has better catalytic activity.
In a preferred embodiment, the attrition index (%. h) of the catalyst-1) Less than 8.0, e.g., less than 7.0, 6.0, 5.0, 4.0. For example, the attrition index (%. h) of the catalyst-1) May be 3.0 or less.
The iron oxide/boron nitride nano catalyst provided by the invention can be used for catalyzing Fischer-Tropsch synthesis, namely catalyzing the reaction of preparing hydrocarbon compounds by converting synthesis gas.
The present invention further provides a method for preparing the above catalyst, the method comprising:
(1) respectively preparing an inorganic ferric salt solution and a boron nitride dispersion liquid; (2) adding the inorganic ferric salt solution into the boron nitride dispersion liquid to obtain a suspension; (3) carrying out solvothermal reaction on the suspension at the temperature of 100-200 ℃ to obtain a nano composite material containing boron nitride and ferric oxide, and washing, centrifuging and drying the nano composite material; and optionally (4) calcining the dried nanocomposite obtained in step (3) to obtain the catalyst.
The preparation method of the invention is based on the following principle: the formation of iron oxide nanoparticles on the surface of hexagonal phase boron nitride follows a nucleation growth mechanism. The oxygen-containing functional groups (hydroxyl groups and the like) on the surface of the boron nitride enable the surface of the boron nitride to be electronegative, and iron ions in the iron source are adsorbed on the surface of the boron nitride through electrostatic interaction in the stirring process. Adsorbed iron ions and OH in solution-、O2React to generate Fe3O4And (4) a core. In the subsequent growth stage, Ostward ripening is accompanied, and iron oxide nanoparticles are generated.
In step (1), the inorganic iron salt may be selected from one or more of ferric chloride, ferrous chloride, ferric nitrate, ferrous sulfate, ferrous acetate, ferric oxalate and ferric acetylacetonate (III) or a hydrate thereof, but is not limited thereto; among them, the hydrate is, for example, ferric chloride hexahydrate, ferrous chloride tetrahydrate, ferric nitrate nonahydrate, ferrous sulfate tetrahydrate, ferrous acetate tetrahydrate, ferric oxalate pentahydrate, or the like.
In one embodiment, the molar concentration of the inorganic ferric salt solution can be 0.01-1.0 mol/L, preferably 0.02-0.5 mol/L, and more preferably 0.05-0.5 mol/L; for example, it may be 0.05mol/L, 0.1mol/L, 0.25mol/L or 0.5 mol/L.
In one embodiment, the solvent used for the solution of the inorganic iron salt is selected from any one or more of the following 1) to 3): 1) water; 2) one or more of lower alcohols, tetrahydrofuran, dimethylformamide, and toluene; 3) a mixture of water and lower alcohol, wherein the volume ratio of the water to the lower alcohol is 1-200: 100, and preferably 20: 100. The lower alcohol can be selected from methanol, ethanol, ethylene glycol, isopropanol, etc., preferably ethylene glycol.
The boron nitride support may be in the nanometer size and may be in the shape of nanoparticles, nanosheets, nanotubes, nanocages, nanofibers, nanowires, and the like. The boron nitride is preferably hexagonal phase boron nitride. In addition, the specific surface area of the boron nitride carrier is preferably 50 to 140m2Per g, the particle size is 100 nm-1 mu m, and more preferably, the specific surface area of the boron nitride is 90-140 m2The grain diameter is 100 nm-500 nm.
Preferably, in step (1), the boron nitride is preferably hexagonal phase boron nitride. The boron nitride support may be obtained by conventional methods of preparation in the art, such as by thermochemical synthesis methods or mechanical methods. The method for producing the boron nitride carrier is not particularly limited, and examples thereof include a ball milling method, an ultrasonic peeling method, a high-speed shearing method, a chemical peeling method, and a high-temperature solid phase method. For example, the boron nitride support may be prepared with reference to the method disclosed in CN 107185572A. The boron nitride carrier may be a commercially available boron nitride carrier. For example, a commercially available boron nitride carrier may be, but is not limited to, hexagonal phase boron nitride available from cubic boron nitride corporation, of the city of Qingzhou.
In one embodiment, the boron nitride support of the present invention may be prepared by a ball milling process comprising the steps of: the method comprises the steps of taking boron nitride powder as a raw material, uniformly mixing the massive boron nitride and metal nitrate or metal chloride according to a mass ratio of 100 (5-100), adding ball grinding balls with different sizes according to a ball-to-material ratio of (10-100): 1, controlling the total filling amount to be 1/3-3/4 of the volume of a ball grinding tank, adding a certain amount of solvent (the mass ratio of the solvent to the boron nitride is (30-2): 1), and carrying out ball grinding for 6-48 h at a rotating speed of 100-400 rpm to obtain the boron nitride powder. And after the ball milling is finished, washing with dilute nitric acid and deionized water, centrifuging for 3-5 times, and drying overnight to obtain the boron nitride carrier. In the above method, the metal nitrate used may be nitrate such as ferric nitrate, manganese nitrate, sodium nitrate, potassium nitrate, etc., and the metal chloride used may be one or more of chloride such as ferric chloride, manganese chloride, cupric chloride, cobalt chloride, sodium chloride, potassium chloride, etc. In one embodiment, the solvent used for ball milling is selected from one or more of water, methanol, ethanol, ethylene glycol, isopropanol, benzene, toluene, N-dimethylformamide, N-methylpyrrolidone.
In one embodiment, in step (1), the dispersion of the boron nitride carrier may use one or more of water, methanol, ethanol, ethylene glycol, isopropanol, benzene, toluene, N-dimethylformamide, and N-methylpyrrolidone, preferably ethylene glycol.
In a preferred embodiment, in step (1), the dispersion of the boron nitride carrier is a dispersion of ethylene glycol thereof, and the method for producing the ethylene glycol dispersion of the boron nitride carrier is not particularly limited. For example, the boron nitride carrier may be added to ethylene glycol and ultrasonically dispersed to obtain a white ethylene glycol dispersion of the boron nitride carrier. In a more preferred embodiment, in the step (1), the mass concentration of the ethylene glycol dispersion of the boron nitride carrier is 0.5 to 10g/L, preferably 0.5 to 5.0g/L, and more preferably 1.0 to 3.0 g/L.
In step (2), the inorganic iron salt solution may be added dropwise to the dispersion of the boron nitride support (e.g., ethylene glycol dispersion of the boron nitride support), and may be stirred or ball-milled simultaneously, e.g., using magnetic stirring or mechanical stirring.
In the step (3), the suspension is transferred to a reaction kettle and sealed for reaction. The temperature of the solvothermal reaction can be 100-200 ℃, preferably 120-200 ℃, for example 120 ℃, 140 ℃, 160 ℃, 180 ℃ or 200 ℃, and the time of the solvothermal reaction can be 1-36 h, preferably 6-24 h, for example 6h, 12h or 24 h.
In one embodiment, it is preferred to perform a washing step prior to the drying step. For example, the solvent is naturally cooled to room temperature after the completion of the solvothermal reaction, the nanocomposite comprising boron nitride and iron oxide is washed with deionized water, and centrifuged 3 to 8 times, for example, 3 to 5 times, 5 to 8 times.
In one embodiment, in step (3), the drying may be performed under vacuum or atmospheric pressure, and under an oxidizing atmosphere or a non-oxidizing atmosphere. Wherein the vacuum degree of the vacuum is 0.1-0.001 Pa; the oxidizing atmosphere is air or mixed gas containing 0.5-20% (volume) of oxygen (wherein nitrogen, carbon dioxide, argon or helium is balance gas); the non-oxidizing atmosphere is one of nitrogen, carbon dioxide, argon or helium or a mixture of the nitrogen, the carbon dioxide, the argon and the helium.
In one embodiment, in the step (3), the drying temperature may be 60 to 160 ℃, preferably 60 to 140 ℃, for example, 60 ℃, 80 ℃, 120 ℃ or 140 ℃, and the drying time may be 8 to 24 hours, for example, 8 hours, 12 hours or 24 hours.
In step (4), the calcination may be performed in an oxidizing atmosphere or a non-oxidizing atmosphere. Wherein the oxidizing atmosphere and the non-oxidizing atmosphere are as defined above.
In one embodiment, in the step (4), the calcination temperature may be 200 ℃ to 550 ℃, preferably 350 ℃ to 500 ℃, for example, 350 ℃, 400 ℃, 450 ℃ or 500 ℃, and the calcination time may be 1 to 12 hours, preferably 5 to 12 hours, for example, 5 hours, 8 hours or 12 hours.
The preparation method of the catalyst has the characteristics of low cost, simplicity and easy operation, and can realize controllable size (10-20 nm), uniform size and no agglomeration of the metal crystal grains of the catalyst while ensuring that the iron oxide grows on the surface of the boron nitride by adjusting the solvothermal reaction time, the reaction temperature, the reactant concentration, the iron salt type and other synthesis conditions. The prepared iron oxide/boron nitride nano catalyst has the advantages of easy preparationReduction and carbonization, high mechanical strength, good abrasion resistance, high Fischer-Tropsch synthesis reaction activity, high CO conversion rate and high heavy hydrocarbon (C)5 +) Selectivity and excellent running stability.
The invention provides application of the iron oxide/boron nitride nano catalyst in preparation of hydrocarbon compounds by catalyzing conversion of synthesis gas in Fischer-Tropsch synthesis reaction. Or the invention also relates to a Fischer-Tropsch synthesis reaction method, wherein the Fischer-Tropsch synthesis catalyst is used for catalyzing the synthesis gas to carry out Fischer-Tropsch synthesis reaction to prepare the hydrocarbon compound.
The catalyst comprising iron oxide and boron nitride prepared by the method of the invention further comprises a reduction step of reducing the catalyst in a reducing atmosphere before catalyzing Fischer-Tropsch synthesis.
The reducing atmosphere may be a hydrogen atmosphere, a carbon monoxide atmosphere, a syngas atmosphere.
In the synthesis gas, H2The molar ratio of the carbon monoxide to CO is 0.01-1000: 1, preferably 0.5-100: 1, more preferably 2-100: 1, and may be, for example, 2:1, 10:1, 20:1 or 100: 1.
The conditions for reducing the catalyst of the invention in a reducing atmosphere are: the pressure may be 0.1 to 1.0MPa, preferably 0.1 to 0.5MPa, for example 0.1MPa, 0.3MPa or 0.5 MPa; the temperature may be 280 to 400 ℃, preferably 280 to 350 ℃, for example, 280 ℃, 300 ℃, 320 ℃ or 350 ℃; the time can be 5 to 50 hours, preferably 8 to 48 hours, for example, 8 hours, 16 hours, 24 hours or 48 hours.
After the reduction step, the iron oxide/boron nitride nano catalyst obtained by the preparation method of the invention generates a reduction state Fischer-Tropsch synthesis catalyst with a certain reduction degree (namely, the metal phase and the percentage of metal carbide in all active phase metals). After reduction, the reduction degree of the obtained reduction state Fischer-Tropsch synthesis catalyst is at least more than 65%, preferably more than 75%, and more preferably more than 85%.
The reduction step can be carried out in an independent reduction reactor, and after the reduction is finished, the activity of metallic iron or iron carbide in the obtained reduced Fischer-Tropsch synthesis catalyst is more active than oxygen in the air, so that the catalyst can be hermetically stored in waxy heavy hydrocarbon (namely saturated straight-chain alkane with the carbon number of more than 18 and a mixture thereof) and transferred to the Fischer-Tropsch synthesis reactor for activity evaluation.
The Fischer-Tropsch synthesis conditions in the Fischer-Tropsch synthesis reactor are as follows: in the synthesis gas, H2The molar ratio to CO may be 0.5 to 3.0:1, preferably 1.0 to 2.5:1, more preferably 1.0 to 2.0:1, for example 1.0:1 or 2.0: 1; a pressure of 1.0 to 6.0MPa, preferably 2.0 to 4.0MPa, for example, 2.0MPa, 3.0MPa or 4.0 MPa; the temperature may be 220 ℃ to 350 ℃, preferably 280 ℃ to 340 ℃, and may be, for example, 280 ℃, 300 ℃ or 340 ℃.
The fischer-tropsch synthesis may be carried out in one or more fixed bed reactors, microchannel reactors, continuously stirred slurry bed tank reactors, jet circulation reactors, slurry bubble column reactors or fluidised bed reactors, and may be carried out in a continuous or batch reaction process.
When the Fischer-Tropsch synthesis is carried out in a continuous reaction process, the reaction space velocity is 100-60000 NL-kg-1·h-1Preferably 5000 to 40000 NL.kg-1·h-1For example, it may be 5000 NL.kg-1·h-1、10000NL·kg-1·h-1、20000NL·kg-1·h-1Or 40000NL kg-1·h-1。
The iron oxide/boron nitride nano catalyst prepared by the method fully utilizes the advantages of excellent thermal conductivity, good thermal stability and high iron oxide reaction activity of boron nitride, has good mechanical strength and abrasion resistance, and simultaneously improves the dispersion degree (35.0-65.0%) of active metal, so that the iron oxide/boron nitride nano catalyst has the advantages of easy reduction, carbonization, high Fischer-Tropsch reaction activity, high heavy hydrocarbon selectivity and high CO conversion rate, and has wide application prospect in Fischer-Tropsch synthesis reaction.
In addition, the iron oxide/boron nitride nano catalyst prepared by the method has controllable metal crystal grain size and uniform size, and iron oxide particles are uniformly dispersed on the surface of boron nitride without agglomeration.
The iron source used in the preparation method is green and cheap, and is suitable for large-scale production; no template agent is used, the introduction of hetero atoms in the catalyst is greatly reduced, the reaction process is simple and easy to operate, the repeatability is good, and particularly, the grain size of the obtained iron oxide/boron nitride nano catalyst can be strictly controlled at the levels of 5 nm-20 nm and 10 nm-20 nm.
The content of the invention can be exemplarily illustrated by the following description in the numbered paragraphs:
1. a Fischer-Tropsch synthesis catalyst comprises iron as an active metal and boron nitride as a carrier, wherein the mass ratio of the active metal iron to the carrier boron nitride is (1-400): 100 and the size of the metal crystal grain of the Fischer-Tropsch synthesis catalyst is 10 nm-20 nm.
2. The catalyst of paragraph 1, wherein the boron nitride is hexagonal phase boron nitride.
3. The catalyst according to paragraph 1 or 2, wherein the mass ratio of the active metal iron to the boron nitride is (5-150): 100.
4. the catalyst of any of paragraphs 1-3, wherein the catalyst has a metal crystallite size of from 10nm to 20 nm.
5. The catalyst of any of paragraphs 1-4, wherein the catalyst has a dispersion of active metals of between 35.0% and 65.0%.
6. A method of preparing the catalyst of any one of claims 1-5, the method comprising:
(1) respectively preparing an inorganic ferric salt solution and a boron nitride dispersion liquid;
(2) adding the inorganic ferric salt solution into the boron nitride dispersion liquid to obtain a suspension;
(3) carrying out solvothermal reaction on the suspension at the temperature of 100-200 ℃ to obtain a nano composite material containing boron nitride and ferric oxide, and washing, centrifuging and drying the nano composite material; and optionally
(4) And (4) calcining the dried nano composite material obtained in the step (3) to obtain the catalyst.
7. The method of paragraph 6 wherein the inorganic iron salt is selected from one or more of ferric chloride, ferrous chloride, ferric nitrate, ferrous sulfate, ferrous acetate, ferric oxalate and iron (III) acetylacetonate or a hydrate thereof.
8. The method of paragraph 7 wherein the hydrate is selected from one or more of ferric chloride hexahydrate, ferrous chloride tetrahydrate, ferric nitrate nonahydrate, ferrous sulfate tetrahydrate, ferrous acetate tetrahydrate or ferric oxalate pentahydrate.
9. The method of any of paragraphs 6-8, wherein the molar concentration of the solution of the inorganic iron salt is between 0.01 and 1.0 mol/L.
10. The method of any of paragraphs 6 to 9, wherein the solution of the inorganic iron salt is in a solvent selected from any one of the following (1) to (3): (1) water; (2) one or more of lower alcohols, tetrahydrofuran, dimethylformamide, and toluene; and (3) a mixture of water and lower alcohol, wherein the volume ratio of the water to the lower alcohol is 1-200: 100.
11. The method of paragraph 10 wherein the lower alcohol is selected from methanol, ethanol, ethylene glycol, isopropanol.
12. The method of paragraph 11 wherein the lower alcohol is ethylene glycol.
13. The method of any of paragraphs 6-12, wherein the dispersion of the boron nitride carrier uses one or more of water, methanol, ethanol, ethylene glycol, isopropanol, benzene, toluene, N-dimethylformamide, and N-methylpyrrolidone.
14. The method of paragraph 13, wherein the dispersion of the boron nitride carrier is a glycol dispersion of the boron nitride carrier.
15. The method of any of paragraphs 6-14, wherein the temperature of the solvothermal reaction is 120-200 ℃.
16. The method of any of paragraphs 6-15, wherein the solvothermal reaction time is 1-36 h.
17. The method of any of paragraphs 16 wherein the solvothermal reaction is carried out for a period of 6 to 24 hours.
18. The method of any of paragraphs 6-17, wherein the solvothermal reaction is naturally cooled to room temperature after completion, washed with deionized water, and centrifuged 3-5 times.
19. The method of any of paragraphs 6-18, wherein in step (3), the drying is performed under vacuum or atmospheric pressure, and is performed under an oxidizing atmosphere or a non-oxidizing atmosphere.
20. The method of paragraph 19 wherein the vacuum is in the range of 0.1 Pa to 0.001 Pa.
21. The method of paragraph 19 wherein the oxidizing atmosphere is air or a mixture of gases containing 0.5% to 20% oxygen by volume.
22. The method of paragraph 19 wherein the non-oxidizing atmosphere is nitrogen, carbon dioxide, argon or helium, or a combination thereof.
23. The method according to any one of paragraphs 6 to 22, wherein in step (3), the temperature of the drying is 60 to 160 ℃.
24. The method of paragraph 23 wherein the drying temperature is 60 to 140 ℃.
25. The method of any of paragraphs 6-24, wherein the drying time is 8-24 hours.
26. The method of any of paragraphs 6-25, wherein in step (4), the calcining is performed in an oxidizing atmosphere or a non-oxidizing atmosphere.
27. The method of paragraph 26 wherein the oxidizing atmosphere is air or a mixture of gases containing 0.5% to 20% oxygen by volume.
28. The method of paragraph 26 wherein the non-oxidizing atmosphere is nitrogen, carbon dioxide, argon or helium, or a combination thereof.
29. The method of any of paragraphs 6-28, wherein the temperature of the calcining is from 200 ℃ to 550 ℃.
30. The method of paragraph 29 wherein the temperature of the calcination is from 350 ℃ to 500 ℃.
31. The method of any of paragraphs 6-30, wherein the calcination is for a time of 1 to 12 hours.
32. The method of paragraph 31 wherein the calcination time is 5 to 12 hours.
33. Use of a fischer-tropsch synthesis catalyst as described in any of paragraphs 1 to 5 to catalyse synthesis gas in a fischer-tropsch synthesis reaction to produce hydrocarbons.
34. The use of paragraph 33 wherein the catalyst is previously subjected to reduction in a reducing atmosphere prior to application of the catalyst to a fischer-tropsch synthesis reaction.
35. The use of paragraph 36 or 37 wherein the reducing atmosphere is a hydrogen atmosphere, a carbon monoxide atmosphere, a syngas atmosphere.
36. The use of paragraph 35 wherein in the synthesis gas, H2The molar ratio of the carbon dioxide to CO is 0.01-1000: 1.
37. The use of paragraph 36 wherein in the synthesis gas, H2The molar ratio of the carbon dioxide to CO is 0.5-100: 1.
38. The use of paragraph 37 wherein in the synthesis gas, H2The molar ratio of the carbon dioxide to CO is 2-100: 1.
39. The use of any of paragraphs 33-38, wherein the conditions for reducing the catalyst in the reducing atmosphere are: the pressure is 0.1-1.0 MPa; the temperature is 280-400 ℃; the time is 5-50 h.
40. The use of paragraph 39 wherein the conditions for reducing the catalyst in the reducing atmosphere are: the pressure is 0.1-0.5 MPa; the temperature is 280-350 ℃; the time is 8-48 h.
41. The use of any of paragraphs 33-40, wherein the reduced catalyst obtained after reduction has a degree of reduction of greater than 65%.
42. The use as described in paragraph 41 wherein, after reduction, the reduced catalyst obtained has a degree of reduction of greater than 75%.
43. The use as described in paragraph 42 wherein, after reduction, the reduced catalyst obtained has a degree of reduction of greater than 85%.
44. As in any of paragraphs 33-43Use according to one of the preceding claims, wherein the Fischer-Tropsch synthesis conditions in the Fischer-Tropsch synthesis reaction are as follows: in the synthesis gas, H2The molar ratio of the carbon dioxide to CO is 0.5-3.0: 1; the pressure is 1.0-6.0 MPa; the temperature is 220-350 ℃.
45. The use as claimed in paragraph 44 wherein the Fischer-Tropsch synthesis conditions in the Fischer-Tropsch synthesis reaction are as follows: in the synthesis gas, H2The molar ratio of the carbon dioxide to CO is 1.0-2.5: 1; the pressure is 2.0-4.0 MPa; the temperature is 280-340 ℃.
46. The use of paragraph 45 wherein in the syngas, H2The molar ratio of the carbon dioxide to CO is 1.0-2.0: 1.
47. The use as claimed in any one of paragraphs 33 to 46, wherein the Fischer-Tropsch synthesis is carried out in a fixed bed reactor, a microchannel reactor, a continuously stirred slurry tank reactor, a jet circulation reactor, a slurry bubble column reactor or a fluidised bed reactor.
48. The use of paragraph 47 wherein the Fischer-Tropsch synthesis is carried out as a continuous or batch reaction process.
49. The use as claimed in paragraph 48, wherein the Fischer-Tropsch synthesis is carried out as a continuous reaction process at a reaction space velocity of from 100 to 60000 NL-kg-1·h-1。
50. The use of paragraph 49 wherein the Fischer-Tropsch synthesis is carried out as a continuous reaction process at a reaction space velocity of from 5000 to 40000 NL.kg-1·h-1。
Examples
Illustrative embodiments of the invention are described below, in which various details of embodiments of the invention are included to assist understanding, and which should be considered as merely illustrative. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted in the following description for clarity and conciseness. The experimental procedures used in the following examples are all conventional procedures unless otherwise specified. Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
Example 1: preparation of the catalyst and Fischer-Tropsch synthesis performance test
(1) Ferric nitrate was dissolved in ethylene glycol and stirred until it was completely dissolved, to give a 0.25mol/L, 0.5mol/L ferric nitrate solution. Preparing 5.0g/L of glycol dispersion liquid of hexagonal phase boron nitride; wherein the hexagonal phase boron nitride has a specific surface area of 105m2(g) the particle size is 400 nm.
(2) Dropwise adding 53.6mL of the ferric nitrate solution obtained in the step (1) into 300mL of boron nitride glycol dispersion liquid, and simultaneously mechanically stirring to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 50:100 and 100: 100.
(3) And (3) transferring the suspension liquid obtained in the step (2) to a reaction kettle, reacting for 12 hours at 180 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 3-5 times, and drying for 12 hours in an oven at 120 ℃.
(4) And (3) calcining the iron oxide/boron nitride nanocomposite obtained in the step (3) in air at 500 ℃ for 5 hours to obtain an iron oxide/boron nitride catalyst in an oxidized state, wherein the catalyst comprises 50Fe/100BN and 100Fe/100BN, the catalyst is respectively marked as Exam-1a and Exam-1b, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. Catalyst in H2Reducing for 16h under the conditions of medium temperature and 320 ℃ and 0.3 MPa. After the temperature is reduced to 220 ℃, synthetic gas (H) is switched to22/CO, molar ratio), increasing the pressure to 2MPa, slowly increasing the temperature to 300 ℃, 40000 NL/kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Example 2: preparation of the catalyst and Fischer-Tropsch synthesis performance test
(1) Dissolving ferrous sulfate in dimethylformamide, and stirring until the ferrous sulfate is completely dissolved to obtain a ferrous sulfate solution of 0.05 mol/L; and 3.0g/L hexagonal phase nitriding is preparedA toluene dispersion of boron; wherein the hexagonal phase boron nitride has a specific surface area of 140m2(g) the particle size is 100 nm.
(2) Dropwise adding 41mL of the ferric salt solution obtained in the step (1) into 383mL of boron nitride toluene dispersion liquid, and simultaneously carrying out magnetic stirring to obtain stable and uniform dispersion liquid; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 10: 100.
(3) transferring the suspension liquid obtained in the step (2) to a reaction kettle, reacting for 24 hours at 140 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 5-8 times, and placing in a tube furnace in CO2Drying at 140 deg.C for 12h under atmosphere.
(4) And (3) calcining the dried iron oxide/boron nitride nanocomposite obtained in the step (3) for 8 hours at 450 ℃ in a helium atmosphere to obtain an iron oxide/boron nitride catalyst in an oxidation state, wherein the catalyst is 10Fe/100BN, is marked as Exam-2, and has the texture properties, the reduction degree and the metal dispersion degree shown in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. Catalyst in H2Reducing the mixture in a synthesis gas atmosphere of 10.0 mol percent at 350 ℃ under 0.1MPa for 8H, cooling to 220 ℃, and switching to synthesis gas (H)22/CO), increasing the pressure to 3.0MPa, slowly increasing the temperature to 340 ℃, 5000 NL/kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Example 3: preparation of the catalyst and Fischer-Tropsch synthesis performance test
(1) Dissolving ferrous acetate in water, mixing and stirring until the ferrous acetate is completely dissolved to obtain a ferrous acetate solution of 0.25 mol/L. Preparing 2.0g/L of glycol dispersion liquid of hexagonal phase boron nitride; wherein the hexagonal phase boron nitride has a specific surface area of 130m2(ii)/g, particle diameter is 200 nm.
(2) Dropwise adding 60.2mL of the ferrous acetate solution obtained in the step (1) into 600mL of boron nitride glycol dispersion liquid, and simultaneously mechanically stirring to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 70: 100.
(3) and (3) transferring the suspension liquid obtained in the step (2) into a reaction kettle, reacting at 120 ℃, 160 ℃ and 200 ℃ for 12 hours respectively, naturally cooling to room temperature after the reaction is finished, centrifuging for 3-5 times by using deionized water, and drying in an oven at 120 ℃ for 8 hours.
(4) And (3) calcining the dried iron oxide/boron nitride nanocomposite material obtained in the step (3) for 8 hours at 400 ℃ in an air atmosphere to obtain an iron oxide/boron nitride catalyst in an oxidation state, wherein the composition of the catalyst is 70Fe/100BN, the catalyst is respectively marked as Exam-3a, Exam-3b and Exam-3c, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1. The transmission electron micrographs of the catalysts Exam-3a and Exam-3c are respectively shown in FIG. 1 and FIG. 2; the XRD pattern of the catalyst Exam-3b is shown in FIG. 3; h of catalyst Exam-3c2TPR spectrum as shown in FIG. 4; the Fischer-Tropsch reaction activity of the catalyst Exam-3c as a function of time is shown in FIG. 5.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. Catalyst in H2Reducing the mixture in a synthesis gas atmosphere of 20.0 mol percent at 300 ℃ under 0.5MPa for 24H, cooling to 220 ℃, and switching to synthesis gas (H)22/CO, molar ratio), increasing the pressure to 3.0MPa, slowly increasing the temperature to 280 ℃ at 20000NL · kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Example 4: preparation of the catalyst and Fischer-Tropsch synthesis performance test
(1) Dissolving ferric oxalate in water, stirring until the ferric oxalate is completely dissolved to obtain 0.05mol/L ferric oxalate solution, and preparing 1.0g/L glycol dispersion of hexagonal phase boron nitride; wherein the hexagonal phase boron nitride has a specific surface area of 90m2(ii)/g, particle size 500 nm.
(2) Dropwise adding 53.5mL of the ferric oxalate solution obtained in the step (1) into 500mL of boron nitride glycol dispersion liquid, and stirring simultaneously to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 30: 100.
(3) and (3) transferring the suspension liquid obtained in the step (2) into a reaction kettle, reacting for 6 hours at 160 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 3-5 times, and drying for 24 hours at 60 ℃ in a helium atmosphere in a tubular furnace.
(4) And (3) calcining the dried nanocomposite material containing the iron oxide and the boron nitride in the step (3) for 12 hours at 400 ℃ in a nitrogen atmosphere to obtain the iron oxide/boron nitride catalyst in an oxidation state, wherein the composition of the catalyst is 30Fe/100BN, the catalyst is marked as Exam-4, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. Catalyst in H2Reducing the mixture in 100.0 mol ratio of synthesis gas at 320 deg.c and 0.1MPa for 16 hr, cooling to 220 deg.c and switching to synthesis gas (H)22/CO, molar ratio), increasing the pressure to 4.0MPa, slowly increasing the temperature to 300 ℃, at 20000NL · kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Example 5: preparation of the catalyst and Fischer-Tropsch synthesis performance test
(1) Dissolving iron (III) acetylacetonate in toluene, stirring until the iron (III) acetylacetonate is completely dissolved to obtain 0.05mol/L iron (III) acetylacetonate solution, and preparing 0.5g/L hexagonal phase boron nitride N-methylpyrrolidone dispersion liquid; wherein the hexagonal phase boron nitride has a specific surface area of 110m2(g) the particle size is 400 nm.
(2) Dropwise adding 44.7mL of the ferric acetylacetonate (III) solution obtained in the step (1) into 500mL of N-methylpyrrolidone dispersion liquid of the boron nitride carrier, and stirring simultaneously to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 50: 100.
(3) and (3) transferring the suspension liquid obtained in the step (2) into a reaction kettle, reacting for 12 hours at 140 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 3-5 times, and drying for 24 hours at 60 ℃ in a tubular furnace in a nitrogen atmosphere.
(4) And (3) calcining the dried nanocomposite material containing the iron oxide and the boron nitride obtained in the step (3) at 350 ℃ for 12h under nitrogen to obtain the iron oxide/boron nitride catalyst in an oxidized state, wherein the composition of the catalyst is 50Fe/100BN, the catalyst is marked as Exam-5, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. The catalyst is reduced for 48 hours at 280 ℃ and 0.3MPa in CO atmosphere, and is switched into synthesis gas (H) after the temperature is reduced to 220 DEG C21/CO, molar ratio), increasing the pressure to 3.0MPa, slowly increasing the temperature to 280 ℃ at 10000 NL/kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Example 6: preparation of the catalyst and Fischer-Tropsch synthesis performance test
(1) Dissolving ferric chloride in a mixed solution of water and glycol, stirring until the ferric chloride is completely dissolved to obtain a 0.25mol/L ferric chloride solution, and preparing 2.0g/L hexagonal phase boron nitride N, N-dimethylformamide dispersion liquid; wherein the mass ratio of water to ethylene glycol is 20:100, and the specific surface area of the hexagonal phase boron nitride is 120m2(ii)/g, particle diameter is 200 nm.
(2) Dropwise adding 50mL of the ferric chloride solution obtained in the step (1) into 500mL of boron nitride N, N-dimethylformamide dispersion liquid, and stirring simultaneously to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 70: 100.
(3) and (3) transferring the suspension liquid obtained in the step (2) into a reaction kettle, reacting for 24 hours at 200 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 5-8 times, and drying for 24 hours at 80 ℃ in a tube furnace under argon atmosphere.
(4) And (3) calcining the dried iron oxide/boron nitride nanocomposite material obtained in the step (3) for 8 hours at 400 ℃ in an argon atmosphere to obtain the iron oxide/boron nitride catalyst in an oxidation state, wherein the composition of the catalyst is 70Fe/100BN, the catalyst is marked as Exam-6, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. The catalyst is reduced for 24 hours at 300 ℃ and 0.1MPa in CO atmosphere, and after the reduction is finished, the system is cooled to 220 ℃, and then is switched into synthesis gas (H)22/CO, molar ratio), increasing the pressure to 3.0MPa, slowly increasing the temperature to 280 ℃ at 20000NL · kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Comparative example 1: preparation of iron oxide catalyst and Fischer-Tropsch synthesis performance test
(1) Dissolving ferric chloride in a mixed solution of water and glycol, stirring until the ferric chloride is completely dissolved to obtain a 0.25mol/L ferric chloride solution, and preparing 2.0g/L hexagonal phase boron nitride N, N-dimethylformamide dispersion liquid; wherein the mass ratio of water to ethylene glycol is 20:100, and the specific surface area of the hexagonal phase boron nitride is 10m2(g) a particle size of 2 μm.
(2) Dropwise adding 50mL of the ferric chloride solution obtained in the step (1) into 500mL of boron nitride N, N-dimethylformamide dispersion liquid, and stirring simultaneously to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 70: 100.
(3) and (3) transferring the suspension liquid obtained in the step (2) into a reaction kettle, reacting for 24 hours at 200 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 5-8 times, and drying for 24 hours at 80 ℃ in a tube furnace under argon atmosphere.
(4) And (3) calcining the dried iron oxide/boron nitride nano composite material obtained in the step (3) for 8 hours at 400 ℃ in an argon atmosphere to obtain the iron oxide/boron nitride catalyst in an oxidation state, wherein the composition of the catalyst is 70Fe/100BN, the catalyst is marked as CE-1, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. The catalyst is reduced for 24 hours at 300 ℃ and 0.1MPa in CO atmosphere, and after the reduction is finished, the system is cooled to 220 ℃, and then is switched into synthesis gas (H)22/CO, molar ratio), increasing the pressure to 3.0MPa, slowly increasing the temperature to 280 ℃ at 20000NL · kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Comparative example 2 impregnation preparation of boron nitride-loaded iron-based catalyst
(1) Dissolving ferrous acetate in water, mixing and stirring until the ferrous acetate is completely dissolved to obtain a ferrous acetate solution of 0.25 mol/L. Wherein the hexagonal phase boron nitride has a specific surface area of 130m2(ii)/g, particle diameter is 200 nm.
(2) Dropwise adding 60.2mL of the ferrous acetate solution obtained in the step (1) into 12g of hexagonal-phase boron nitride, and stirring simultaneously; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 70: 100.
(3) and (3) drying the precursor obtained in the step (2) in an oven at 120 ℃ for 8h to obtain the precursor of the iron oxide catalyst loaded by boron nitride.
(4) And (3) calcining the precursor of the dried iron oxide catalyst obtained in the step (3) for 8 hours at 400 ℃ in an air atmosphere to obtain the iron oxide/boron nitride catalyst in an oxidation state, wherein the composition of the catalyst is 70Fe/100BN, the label of the catalyst is CE-2, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. Catalyst in H2Reducing the mixture in a synthesis gas atmosphere of 20.0 mol percent at 300 ℃ under 0.5MPa for 24H, cooling to 220 ℃, and switching to synthesis gas (H)22/CO, molar ratio), increasing the pressure to 3.0MPa, slowly increasing the temperature to 280 ℃ at 20000NL · kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
Comparative example 3 preparation of catalyst comprising iron oxide and boron nitride and Fischer-Tropsch Synthesis Performance test
(1) Dissolving ferric nitrate in ethylene glycol, and stirring until the ferric nitrate is completely dissolved to obtain a 0.25mol/L ferric nitrate solution. Preparing 5.0g/L of glycol dispersion liquid of hexagonal phase boron nitride; wherein the hexagonal phase boron nitride has a specific surface area of 105m2(g) the particle size is 400 nm.
(2) Dropwise adding 53.6mL of the ferric nitrate solution obtained in the step (1) into 300mL of boron nitride glycol dispersion liquid, and simultaneously mechanically stirring to obtain a stable and uniform suspension; wherein the mass ratio of the active metal iron (calculated by iron element) to the hexagonal phase boron nitride is 50: 100.
(3) And (3) transferring the suspension liquid obtained in the step (2) to a reaction kettle, reacting for 12h at 60 ℃, naturally cooling to room temperature after the reaction is finished, washing with deionized water, centrifuging for 3-5 times, and drying for 12h at 120 ℃ in an oven.
(4) And (3) roasting the composite material containing the iron oxide and the boron nitride obtained in the step (3) in air at 500 ℃ for 5 hours to obtain the iron oxide/boron nitride catalyst in an oxidation state, wherein the composition of the catalyst is 50Fe/100BN, the label of the catalyst is CE-3, and the texture property, the reduction degree and the metal dispersion degree of the catalyst are listed in Table 1.
(5) Fischer-Tropsch Synthesis Performance test
The catalyst (1g) was placed in the constant temperature zone of a fixed bed reactor. Catalyst in H2Reducing for 16h under the conditions of medium temperature and 320 ℃ and 0.3 MPa. After the temperature is reduced to 220 ℃, synthetic gas (H) is switched to22/CO, molar ratio), increasing the pressure to 2MPa, slowly increasing the temperature to 300 ℃, 40000 NL/kg-1·h-1Performing Fischer-Tropsch synthesis reaction, and the CO conversion rate and C of the reaction5 +The selectivity is shown in table 2.
The attrition indices in table 1 were determined as follows: crushing an iron oxide/boron nitride nano catalyst (boron nitride loaded iron oxide nano catalyst) into particles of 20-40 meshes, putting the particles of 20-40 meshes into a grinding index measuring device, carrying out blow grinding for 5h under constant air flow, wherein except for the 1 st h, the mass percentage of a fine powder sample which is generated in the last 4h and is less than 50 mu m in the original catalyst is called the catalyst wear rate, and the mass percentage is also called as the catalyst wear rateThe abrasion index is expressed in%. h-1. The specific surface area in table 1 is BET specific surface area, and is measured by a low-temperature nitrogen physical adsorption method.
Table 1 relevant parameters of the catalysts prepared in examples 1 to 6 and comparative examples 1 to 3
Figure BDA0002854991290000221
TABLE 2 Fischer-Tropsch Synthesis reaction Activity and Selectivity of catalysts prepared in examples 1 to 6 and comparative examples 1 to 3
Figure BDA0002854991290000231
As can be seen from Table 1, the iron oxide/boron nitride nano-catalyst obtained in the embodiment of the invention has the characteristics of controllable metal grain size and the like. As can be seen from fig. 1 and 2, the metal grains in the catalyst obtained in the example of the present invention were uniform in size and the particles were not agglomerated. Meanwhile, the ferric oxide/boron nitride nano-catalyst with different metal grain sizes (5-20 nm) can be obtained by adjusting the solvothermal temperature, the reaction time, the concentration of ferric salt and the type of ferric salt.
As shown in tables 1 and 2, the iron oxide/boron nitride nano-catalyst prepared by the method of the present invention has the characteristics of easy carbonization, easy reduction, etc. The iron oxide/boron nitride nanocatalyst exhibited higher CO conversion and heavier hydrocarbons (C) compared to the iron oxide catalyst (comparative example 1) and the boron nitride supported iron oxide catalyst prepared by the impregnation method (comparative example 2)5 +) And selectivity, and excellent Fischer-Tropsch synthesis reaction performance is shown. As is apparent from tables 1 and 2, the catalyst prepared by the method of the present invention has strong controllability of the size of the catalytic crystal grains, and the catalyst shows high CO conversion and heavy hydrocarbon (C) as compared to the catalyst prepared under the lower hydrothermal reaction temperature condition (comparative example 3)5 +) And (4) selectivity.
The above-described embodiments should not be construed as limiting the scope of the invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions can occur, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The Fischer-Tropsch synthesis catalyst comprises iron serving as an active metal and boron nitride serving as a carrier, wherein the mass ratio of the active metal iron to the carrier boron nitride is (1-400): 100, and the metal grain size of the catalyst is 10-20 nm.
2. The fischer-tropsch synthesis catalyst of claim 1, wherein the boron nitride is hexagonal phase boron nitride.
3. The Fischer-Tropsch synthesis catalyst according to claim 1 or 2, wherein the mass ratio of the active metal iron to the boron nitride, calculated as the mass of the iron element, is (5-100): 100.
4. A fischer-tropsch synthesis catalyst as claimed in any one of claims 1 to 3, wherein the metal crystallite size of the catalyst is in the range 10nm to 20 nm.
5. A Fischer-Tropsch synthesis catalyst according to any one of claims 1 to 4, wherein the catalyst is an iron oxide/boron nitride nanocatalyst and the dispersion of the active metals in the catalyst is in the range 35.0% to 65.0%.
6. A process for the preparation of a Fischer-Tropsch synthesis catalyst according to any one of claims 1 to 5, the process comprising:
(1) respectively preparing an inorganic ferric salt solution and a boron nitride dispersion liquid;
(2) adding the inorganic ferric salt solution into the boron nitride dispersion liquid to obtain a suspension;
(3) carrying out solvothermal reaction on the suspension at the temperature of 100-200 ℃ to obtain a nano composite material containing boron nitride and ferric oxide, and washing, centrifuging and drying the nano composite material; and optionally
(4) And (4) calcining the dried nano composite material obtained in the step (3) to obtain the catalyst.
7. The method of claim 6, wherein the inorganic iron salt is selected from one or more of ferric chloride, ferrous chloride, ferric nitrate, ferrous sulfate, ferrous acetate, ferric oxalate and iron (III) acetylacetonate or a hydrate thereof.
8. The method according to claim 6 or 7, wherein the temperature of the solvothermal reaction is 120 to 200 ℃ and the time of the solvothermal reaction is 1 to 36 hours.
9. Use of a fischer-tropsch synthesis catalyst according to any one of claims 1 to 5 to catalyse synthesis gas in a fischer-tropsch synthesis reaction to produce hydrocarbons.
10. Use according to claim 9, wherein the fischer-tropsch synthesis catalyst is previously subjected to reduction in a reducing atmosphere prior to its application to a fischer-tropsch synthesis reaction.
CN202011542098.5A 2020-12-23 2020-12-23 Iron oxide/boron nitride nano catalyst, preparation method and application thereof Pending CN112536059A (en)

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