Boron nitride material, preparation method and application of boron nitride material in propane oxidative dehydrogenation reaction

Abstract

The invention relates to a boron nitride material, a preparation method and application of the boron nitride material in propane oxidative dehydrogenation reaction, and the preparation method of the boron nitride material comprises the following steps: mixing a boron source, a nitrogen source, an auxiliary agent and a solvent, and then carrying out two-stage heat treatment reaction; the boron nitride material prepared by the preparation method has a relatively uniform mesoporous structure, the preparation process is simple, the cost is relatively low, gas diffusion can be promoted, and a relatively high propane conversion rate can be obtained under the condition of ensuring olefin selectivity.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysis, and in particular relates to a boron nitride material, a preparation method and an application thereof in propane oxidative dehydrogenation reaction. Background Art

[0002] Low-carbon olefins (ethylene, propylene, etc.) are important organic chemical raw materials and are an important indicator for measuring a country's chemical industry. Propylene, as the second largest organic chemical after ethylene, is widely used in aerospace, daily chemicals, building materials and other fields. At present, the main sources of propylene are petroleum-based naphtha steam cracking, catalytic cracking, methanol to olefins and other routes. These reaction processes have high reaction temperatures, high energy consumption and complex separation processes. my country has abundant propane reserves, and the development of shale gas has further increased the production of propane. Therefore, the comprehensive utilization of propane has received widespread attention. In recent years, propane dehydrogenation to produce propylene has become a promising and competitive route that can effectively improve the utilization rate of propane. It is of great significance to open up a new propylene production process.

[0003] At present, the main processes for producing propylene by dehydrogenation of propane include direct dehydrogenation process and oxidative dehydrogenation process. Although the direct dehydrogenation of propane to synthesize propylene has been industrialized, the reaction is a strongly endothermic process limited by thermodynamic equilibrium, and the catalyst is prone to carbon deposition and deactivation at higher reaction temperatures (>600°C). Propane oxidative dehydrogenation is an exothermic reaction. The reaction process is not limited by thermodynamic equilibrium and is carried out in an oxidizing atmosphere. Therefore, it has the advantages of less carbon deposition, low reaction temperature, and no need for catalyst regeneration. At this stage, the key to the industrialization of propane oxidative dehydrogenation process is to develop catalysts with high activity, high propylene selectivity, and high stability.

[0004] At present, the catalysts for oxidative dehydrogenation of propane to propylene reported in existing literature and patents are mainly metal oxides or composite oxides such as Mo, V, Ni, Cr and carbon-based non-metallic catalysts such as porous carbon (Adv. Catal. 1994, 40: 1-38; Catal. Today, 2007, 127: 113-131; CN102000598A; CN104475117A; CN105849069A, etc.), and these catalysts all show certain activity in the oxidative dehydrogenation of propane. Although the research on oxidative dehydrogenation of propane has made certain progress, there are still problems such as poor selectivity for propylene and deep oxidation of the product to generate CO2 during the reaction.

[0005] Hexagonal boron nitride is a crystal composed of the same number of boron atoms and nitrogen atoms. It has a graphite-like hexagonal layered structure, so it is known as "white graphite". Hexagonal boron nitride has good thermal stability, excellent thermal conductivity, chemical stability, and oxidation resistance. It is mainly used in ceramics, high-temperature components, lubricants and other fields. With the continuous advancement of nanomaterial preparation technology, the preparation technology of boron nitride with rich surface defects, pore structure and high specific surface area has been continuously improved, and boron nitride has achieved certain application prospects in hydrogen storage and gas adsorption. In addition, the literature reports that boron nitride is used as a carrier in the field of heterogeneous catalysis, such as Fe supported by boron nitride nanosheets for Fischer-Tropsch synthesis reaction, Ni supported by boron nitride for methane dry reforming reaction, and Pt-Fe supported by boron nitride for crotonaldehyde selective hydrogenation reaction. As the research on boron nitride as a carrier has received widespread attention, boron nitride as a non-metal catalyst for catalytic reaction system has gradually attracted the attention of researchers.

[0006] In 2016, the Hermans team made a major discovery in the use of boron nitride in the field of propane dehydrogenation to propylene. When the propane conversion rate was 14%, the selectivity of propylene and ethylene were 79% and 12%, respectively, which was significantly better than the traditional oxidative dehydrogenation catalyst, and the catalyst showed excellent stability. In addition, boron nitride also showed excellent reaction performance in the oxidative dehydrogenation of ethane and butane. In this report, although the selectivity of olefins was high, the propane conversion rate was low, resulting in a low yield of olefins.

[0007] Patent CN1064140240A discloses a boron nitride catalyst for oxidative dehydrogenation of low-carbon alkanes or alkylbenzenes. Although the catalyst exhibits high olefin selectivity, the conversion rate of propane is low.

[0008] Patent CN110743593A discloses the application of a boron carbon nitrogen material in catalyzing the oxidative dehydrogenation of alkanes to produce olefins. As the conversion rate of propane gradually increases, the selectivity of propylene decreases. The excellent reaction performance of boron nitride materials will help the commercialization of propane oxidative dehydrogenation. However, due to the complex preparation process of boron nitride materials and high cost, the conversion rate of propane in the reaction is low. Therefore, it is still a great challenge to develop a boron nitride catalyst with excellent catalytic performance. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of existing boron nitride materials in propane oxidative dehydrogenation reaction, and to provide a boron nitride material, a preparation method and its application in propane oxidative dehydrogenation reaction. The boron nitride material prepared by the present invention has a relatively uniform mesoporous structure, and the preparation process is simple and the cost is low. Compared with other mesoporous boron nitrides, the boron nitride material prepared by the method can promote gas diffusion, and can obtain a higher propane conversion rate while ensuring propylene selectivity.

[0010] The first aspect of the present invention provides a method for preparing a boron nitride material, comprising: mixing a boron source, a nitrogen source, an auxiliary agent and a solvent, and then performing a two-stage heat treatment reaction;

[0011] Preferably, the two-stage heat treatment reaction is a solid phase reaction;

[0012] Preferably, the boron nitride material is a catalyst for propane oxidative dehydrogenation reaction;

[0013] More preferably, the boron nitride material is a catalyst for oxidative dehydrogenation of propane to produce propylene.

[0014] According to some embodiments of the present invention, the molar ratio of the boron source and the nitrogen source based on boron atoms and nitrogen atoms is 1:(2-16); preferably 1:(3-12); in some embodiments, the molar ratio of the boron source and the nitrogen source based on boron atoms and nitrogen atoms is 1:3, 1:6, 1:9, 1:12 or a range composed of any two thereof.

[0015] According to some embodiments of the present invention, the mass ratio of the nitrogen source to the auxiliary agent is (144-360):1; in some embodiments, the mass ratio of the nitrogen source to the auxiliary agent is 144:1, 200:1, 240:1, 252:1, 288:1, 300:1, 360:1 or a range composed of any two thereof.

[0016] According to some embodiments of the present invention, the mass ratio of the nitrogen source to the solvent is (1.44-0.9):1; in some embodiments, the mass ratio of the nitrogen source to the auxiliary agent is 0.9:1, 1:1, 1.2:1, 1.44:1 or a range composed of any two thereof.

[0017] According to some embodiments of the present invention, the boron source is selected from one or more of boric acid, boric oxide and ammonium borate.

[0018] According to some embodiments of the present invention, the nitrogen source is selected from one or more of urea, melamine and guanidine hydrochloride.

[0019] The auxiliary agent is selected from one or more of chlorides, nitrates, oxalates, ferric ammonium oxalate, potassium hydroxide and sodium hydroxide; the chloride is preferably a chloride of iron, potassium or sodium; and / or the nitrate is preferably a nitrate of iron, potassium or sodium; and / or the oxalate is preferably an oxalate of iron, potassium or sodium; and / or,

[0020] The solvent is selected from one or more of water, lower alcohol and toluene; the lower alcohol is preferably one or more of methanol, ethanol and isopropanol.

[0021] According to some embodiments of the present invention, after the boron source, nitrogen source, auxiliary agent and solvent are mixed, the solvent is evaporated and then the two-stage heat treatment reaction is performed;

[0022] Preferably, the temperature of the solvent evaporation process is 60 to 90°C, more preferably 75 to 80°C;

[0023] Preferably, the process of evaporating the solvent is carried out with continuous stirring.

[0024] According to some embodiments of the present invention, the temperature of the first stage of the two-stage heat treatment reaction is 400-700°C; preferably 500-650°C.

[0025] According to some embodiments of the present invention, the time of the first heat treatment in the two-stage heat treatment reaction is 0.5 to 4 hours, preferably 1 to 2 hours.

[0026] According to some embodiments of the present invention, in the first heat treatment process of the two-stage heat treatment reaction, the temperature is raised to the treatment temperature at a rate of 5°C / min.

[0027] According to some embodiments of the present invention, the temperature of the second stage heat treatment in the two-stage heat treatment reaction is 850-1100°C; preferably 1000-1100°C.

[0028] According to some embodiments of the present invention, the time of the second heat treatment in the two-stage heat treatment reaction is 0.5 to 5 hours, preferably 3 to 5 hours.

[0029] According to some embodiments of the present invention, in the second heat treatment process of the two-stage heat treatment reaction, the temperature is increased to the treatment temperature at a rate of 5°C / min.

[0030] According to some embodiments of the present invention, the two-stage heat treatment reaction is carried out under the protection of gas;

[0031] Preferably, the gas is nitrogen, a hydrogen / nitrogen mixture, ammonia, or an ammonia / nitrogen mixture; the volume percentage of hydrogen in the hydrogen / nitrogen mixture is preferably 1% to 10%, and the volume percentage of ammonia in the ammonia / nitrogen mixture is preferably 5% to 30%.

[0032] According to some embodiments of the present invention, a crude product is obtained after the two-stage heat treatment reaction, and the crude product is acid-washed, filtered, washed, and dried to obtain the boron nitride material;

[0033] Preferably, pickling is carried out with hydrochloric acid;

[0034] More preferably, the concentration of hydrochloric acid is 0.5 to 4 mol / L; and / or, the acid washing is performed by placing the crude product in hydrochloric acid and stirring;

[0035] Preferably, the pickling temperature is 25 to 70°C;

[0036] Preferably, the washing is water washing, preferably washing with deionized water until neutral;

[0037] Preferably, the drying temperature is 80-120°C;

[0038] Preferably, the drying time is 5 to 24 hours.

[0039] The second aspect of the present invention provides a boron nitride material prepared by the above method;

[0040] Preferably, the surface area of ​​the boron nitride material is 100 to 1000 m 2 / g; and / or,

[0041] The pore size distribution of the boron nitride material is 20-40 nm.

[0042] The third aspect of the present invention provides a boron nitride material prepared by the above method or the use of the above boron nitride material in propane oxidative dehydrogenation reaction;

[0043] Preferably, the boron nitride material is used in the reaction of oxidative dehydrogenation of propane to produce propylene.

[0044] A fourth aspect of the present invention provides a method for propane oxidative dehydrogenation, the method comprising: catalyzing propane oxidative dehydrogenation reaction with the boron nitride material prepared by the above preparation method or the above boron nitride material;

[0045] Preferably, the method is a method for preparing propylene by oxidative dehydrogenation of propane.

[0046] According to some embodiments of the present invention, the temperature of the propane oxidative dehydrogenation reaction is 400-600°C.

[0047] According to some embodiments of the present invention, the propane oxidative dehydrogenation reaction is carried out under normal pressure.

[0048] According to some embodiments of the present invention, the propane oxidative dehydrogenation reaction is carried out in one or more fixed bed reactors, microchannel reactors, continuous stirred slurry bed reactors, slurry bubble column reactors or fluidized bed reactors, and is carried out in a continuous or intermittent reaction process.

[0049] According to some embodiments of the present invention, the reaction raw materials for propane oxidative dehydrogenation are propane and oxygen;

[0050] Preferably, the reaction raw materials are diluted with an inert gas;

[0051] More preferably, the inert gas is one or more of nitrogen, helium and argon.

[0052] According to some embodiments of the present invention, the volume ratio of the propane, oxygen and inert gas is (1-2):(1-2):(3-4); in some embodiments, the volume ratio of the propane, oxygen and inert gas is 1:1:4, 1:1.5:4, 1:2:4, 1:1:3.5, 1:1.5:3.5, 1:2:3.5, 1:1:2, 1:1.5:2, 1:2:2, 2:2:3 or a range of any two thereof.

[0053] According to some embodiments of the present invention, the volume space velocity of the mixed gas containing propane, oxygen and inert gas is 2000-30000h -1 .

[0054] According to some embodiments of the present invention, the method further comprises: before the boron nitride material catalyzes the alkoxy dehydrogenation reaction, the boron nitride material is pre-treated and activated in a mixture of oxygen and an inert gas.

[0055] According to some embodiments of the present invention, the volume ratio of oxygen to inert gas is 1:(2-5), preferably 1:(3-5).

[0056] According to some embodiments of the present invention, the temperature of the pretreatment activation is 350-600°C.

[0057] According to some embodiments of the present invention, the pretreatment activation time is 0.5 to 6 hours.

[0058] Compared with the prior art, the present invention provides a boron nitride material, a preparation method and an application thereof in propane oxidative dehydrogenation reaction.

[0059] The present invention has the following beneficial effects:

[0060] The raw materials used in the boron nitride material preparation method of the present invention are cheap and easy to obtain, and the obtained crude product is easy to remove impurities and purify. Auxiliary agents are added during the preparation process of the present invention to promote the growth of crystals. The present invention adopts a two-stage heat treatment method. The first stage of heat treatment is carried out under low temperature (400-700°C) conditions to remove excess nitrogen and carbon in the form of nitrogen-containing or carbon-containing small molecule gases. By controlling the temperature and insulation time, they can be completely removed, which is conducive to the formation of pores; the second stage of heat treatment, by controlling the temperature and insulation time, makes the boron nitride material more fully formed and the mesopores uniform. The two-stage calcination overcomes the shortcomings of incomplete pore formation and uneven pore distribution in the one-stage calcination. The present invention adopts acid washing purification to remove impurities in the reaction, and the purification operation is simple.

[0061] The present invention prepares a nanostructured carbon nanotube with a specific surface area of ​​100 to 1000 m 2The boron nitride material prepared by this method can promote gas diffusion and show higher propane conversion rate and propylene selectivity, and has uniform mesoporous boron nitride material with adjustable pore size distribution of 20 to 40 nm.

[0062] The catalytic performance of boron nitride can be significantly improved by adjusting the composition of the precursor, providing a new route for the oxidative dehydrogenation of propane to propylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The XRD spectrum of the boron nitride material prepared in Example 1 of the present invention;

[0064] Figure 2 This is a N2 adsorption-desorption curve of boron nitride prepared in Example 2 of the present invention;

[0065] Figure 3 This is the pore size distribution diagram of the boron nitride prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0066] The present invention will be further described below in conjunction with specific implementation methods. The protection scope of the present invention is not limited by the following embodiments but is determined by the claims.

[0067] It should be particularly noted that two or more aspects (or implementation methods) disclosed in the context of this specification can be arbitrarily combined with each other, and the technical solution thus formed is part of the original disclosure of this specification and also falls within the scope of protection of the present invention.

[0068] Exemplary embodiments of the present invention are described below, including various details of the embodiments of the present invention to aid understanding, which should be considered as merely exemplary. Therefore, it should be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and simplicity, descriptions of known functions and structures are omitted in the following description. The experimental methods used in the following embodiments are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial sources.

[0069] The detection method described in the present invention is a conventional technical method in the art.

[0070] In an exemplary embodiment of the present invention,

[0071] Room temperature refers to 25°C, and normal pressure refers to one standard atmosphere.

[0072] The propane oxidative dehydrogenation reaction is carried out in one or more fixed bed reactors, microchannel reactors, continuous stirred slurry bed reactors, slurry bubble column reactors or fluidized bed reactors, and is carried out in a continuous or batch reaction process.

[0073] The catalyst evaluation process used in the present invention is as follows:

[0074] A certain amount of boron nitride catalyst was placed in the constant temperature section of the fixed bed reactor. Before the propane oxidative dehydrogenation reaction, the boron nitride catalyst was first pretreated and activated in a mixed gas of oxygen / nitrogen (volume ratio of 1:4) at 550°C for 2 hours. After the activation, a gas volume ratio of propane: oxygen: nitrogen = 1:1:4 was introduced, the reaction temperature was set to 530°C, and the propane oxidative dehydrogenation reaction was evaluated under normal pressure. The gas after the reaction was passed through a cold trap and then entered the gas chromatograph for online analysis of the gas composition.

[0075] The conversion of propane and the selectivity of olefins were calculated according to the following formula:

[0076] Conversion rate of propane (%) = ((moles of alkane before reaction - moles of alkane after reaction) / moles of alkane before reaction) × 100%

[0077] Olefin selectivity (%) = (number of moles of olefin products produced / total number of moles of all carbon species produced by the reaction) x 100%.

[0078] Example 1

[0079] Preparation of boron nitride materials and performance test of propane oxidative dehydrogenation reaction:

[0080] (1) 124 g of boric acid, 720 g of urea and 5 g of ferric nitrate were dissolved in 500 g of water in a molar ratio of 1:6 based on boron atoms and nitrogen atoms, stirred until they were completely dissolved, and then heated to 75° C. and stirred continuously until the solvent was completely evaporated to obtain a mixture.

[0081] (2) Take a certain amount of the mixture in step (1), grind it thoroughly, and transfer it to a tubular furnace. In a nitrogen atmosphere, heat it to 550°C at a rate of 5°C / min and keep it warm for 1.5 hours. Then, in a 5% H2 / N2 mixed gas condition, heat it to 1050°C at a rate of 5°C / min and keep it warm for 4 hours to obtain a crude product.

[0082] (3) The crude product obtained in step (2) was placed in 200 mL of 2 mol / L hydrochloric acid and stirred at room temperature for 12 h at a stirring rate of 600 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven at 120° C. and dried for 12 h to obtain a boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 580 m2 / g, pore size is 19-30nm, XRD spectrum of boron nitride is shown in Figure 1 .

[0083] (4) Propane oxidative dehydrogenation reaction performance test

[0084] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated at a volume ratio of 1:4 and a volume space velocity of 5000 h -1 The mixture of O2 and N2 was pre-treated and activated for 6 hours at 500℃ and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=1:1:4, and the volume space velocity was 5000h -1 The raw gas was used to raise the reaction temperature to 530°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0085] Example 2

[0086] Preparation of boron nitride catalyst and performance test of propane oxidative dehydrogenation reaction:

[0087] (1) 62 g of boric acid, 720 g of urea and 5 g of cobalt nitrate were dissolved in 500 g of ethanol in a molar ratio of 1:12 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 80° C. and stirred continuously until the solvent was completely evaporated to obtain a mixture.

[0088] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 500°C at a rate of 5°C / min and keep it warm for 2 hours. Then, under the protection of a 10% H2 / N2 mixed gas, heat it to 1000°C at a rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0089] (3) The crude product obtained in step (2) was placed in 300 mL of 3 mol / L hydrochloric acid and stirred at 50° C. for 8 h at a stirring rate of 700 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 100° C. for 8 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 700 m 2 / g, pore size is 15~25nm.

[0090] (4) Propane oxidative dehydrogenation reaction performance test

[0091] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated at a volume ratio of 1:5 and a volume space velocity of 4000 h -1The mixture of O2 and Ar was pre-treated and activated for 4 hours at 550°C and normal pressure. Then the volume ratio was switched to C3H8:O2:Ar=1:2:4, and the volume space velocity was 4000h -1 The raw gas was used to raise the reaction temperature to 560°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0092] Example 3

[0093] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0094] (1) 70 g of boron oxide, 756 g of melamine and 3 g of potassium chloride were dissolved in 600 g of methanol in a molar ratio of 1:6 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 75° C. and stirred continuously until the solvent was completely evaporated to obtain a mixture.

[0095] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 600°C at a rate of 5°C / min and keep it warm for 2 hours. Then, under the protection of a 15% NH3 / N2 mixed gas, heat it to 1100°C at a rate of 5°C / min and keep it warm for 3 hours to obtain a crude product.

[0096] (3) The crude product obtained in step (2) was placed in 500 mL of 0.5 mol / L hydrochloric acid and stirred at room temperature for 6 h at a stirring rate of 800 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 100° C. for 10 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 600 m 2 / g, pore size is 15-30nm. The N2 adsorption and desorption curve of boron nitride is shown in Figure 2 , the pore size distribution of boron nitride is shown in Figure 3 ,Depend on Figure 2 It can be seen that the prepared boron nitride has an obvious hysteresis loop, which is a typical mesoporous feature. Figure 3 It can be seen that the pore size of the prepared boron nitride is mainly distributed in the range of 15 to 30 nm.

[0097] (4) Propane oxidative dehydrogenation reaction performance test

[0098] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated at a volume ratio of 1:4 and a volume space velocity of 8000 h -1The mixture of O2 and He was pre-treated and activated for 6 hours at 450°C and atmospheric pressure. Then the raw gas was switched to a volume ratio of C3H8:O2:He=1:1.5:3.5, the reaction temperature was raised to 540°C, and propane oxidative dehydrogenation was carried out under atmospheric pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0099] Example 4

[0100] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0101] (1) 140 g of boron oxide, 720 g of urea and 2 g of sodium chloride were dissolved in 500 g of water in a molar ratio of 1:6 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 70° C. with continuous stirring until the solvent was completely evaporated to obtain a mixture.

[0102] (2) Take a certain amount of the mixture in step (1), grind it thoroughly, and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 650°C at a rate of 5°C / min and keep it at that temperature for 1 hour. Then, under the protection of N2, heat it to 1050°C at a rate of 5°C / min and keep it at that temperature for 5 hours to obtain a crude product.

[0103] (3) The crude product obtained in step (2) was placed in 400 mL of 0.5 mol / L hydrochloric acid and stirred at room temperature for 8 h at a stirring rate of 650 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 120° C. for 6 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 750 m 2 / g, pore size is 17~32nm.

[0104] (4) Propane oxidative dehydrogenation reaction performance test

[0105] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated in a mixture of O2 and N2 at a volume ratio of 1:3 and a volume space velocity of 5000 h -1 The mixture was pre-treated and activated for 6 hours at 550℃ and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=2:2:3, and the volume space velocity was 5000h -1 The raw material gas was used, the reaction temperature was adjusted to 545°C, and propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0106] Example 5

[0107] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0108] (1) 124 g of boric acid, 720 g of melamine and 3 g of ferric chloride were dissolved in 800 g of methanol in a molar ratio of 1:3 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 80° C. with continuous stirring until the solvent was completely evaporated to obtain a mixture.

[0109] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tubular furnace. In a nitrogen atmosphere, heat it to 650°C at a rate of 5°C / min and keep it warm for 1 hour. Then, under the protection of a 10% H2 / N2 mixed gas, heat it to 1000°C at a rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0110] (3) The crude product obtained in step (2) was placed in 500 mL of 3 mol / L hydrochloric acid and stirred at 50° C. for 12 h at a stirring rate of 750 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 120° C. for 8 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 520 m 2 / g, pore size is 20~32nm.

[0111] (4) Propane oxidative dehydrogenation reaction performance test

[0112] The above-mentioned boron nitride catalyst (1 g) was placed in the constant temperature section of the fixed bed reactor. The boron nitride catalyst was pre-treated and activated for 8 h in a mixed gas of O2 and N2 with a volume ratio of 1:5 at 550°C and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=1:1:4, and the volume space velocity was 9000 h -1 The raw gas was used to raise the reaction temperature to 560°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0113] Example 6 Preparation of boron nitride catalyst of the present invention and performance test of propane oxidative dehydrogenation reaction:

[0114] (1) 124 g of boric acid, 720 g of urea and 2.5 g of potassium hydroxide were dissolved in 500 g of water in a molar ratio of 1:6 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 75° C. with continuous stirring until the solvent was completely evaporated to obtain a mixture.

[0115] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 550°C at a rate of 5°C / min and keep it warm for 1 hour. Then, under the protection of a 5% NH3 / N2 mixed gas, heat it to 1100°C at a rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0116] (3) The crude product obtained in step (2) was placed in 400 mL of 1 mol / L hydrochloric acid and stirred at room temperature for 6 h at a stirring rate of 600 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven at 80° C. and dried for 12 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 320 m 2 / g, pore size is 18~35nm.

[0117] (4) Propane oxidative dehydrogenation reaction performance test

[0118] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated in an atmosphere of O2 and Ar at a volume ratio of 1:3 and a volume space velocity of 6000 h -1 The mixture was pre-treated and activated for 6 hours at 500°C and normal pressure. Then the volume ratio was switched to C3H8:O2:Ar=1:1.5:4, and the volume space velocity was 6000h -1 The reaction temperature was raised to 550°C and propane oxidative dehydrogenation was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0119] Comparative Example 1

[0120] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0121] (1) 124 g of boric acid, 720 g of urea and 5 g of ferric nitrate were dissolved in 500 g of water in a molar ratio of 1:6 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 75° C. with continuous stirring until the solvent was completely evaporated to obtain a mixture.

[0122] (2) Take a certain amount of the mixture in step (1), grind it thoroughly, and transfer it to a tube furnace. Under the protection of a 5% H2 / N2 mixed gas, heat it directly to 1050°C at a heating rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0123] (3) The crude product obtained in step (2) was placed in 200 mL of 2 mol / L hydrochloric acid and stirred at room temperature for 12 h at a stirring rate of 700 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 120° C. for 12 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 440 m 2 / g, pore size is 10~40nm.

[0124] (4) Propane oxidative dehydrogenation reaction performance test

[0125] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated in a mixture of O2 and N2 at a volume ratio of 1:4 and a volume space velocity of 5000 h -1 The mixture was pre-treated and activated for 6 hours at 500°C and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=1:1:4 and the volume space velocity was 5000h -1 The raw gas was used to raise the reaction temperature to 530°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0126] Comparative Example 2

[0127] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0128] (1) 70 g of boron oxide and 756 g of melamine were dissolved in 600 g of methanol in a molar ratio of 1:6 between the boron source and the nitrogen source, and stirred until they were completely dissolved. The mixture was then heated to 75° C. and stirred continuously until the solvent was completely evaporated to obtain a mixture.

[0129] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 450°C at a rate of 5°C / min and keep it warm for 1 hour. Then, under the protection of a 15% NH3 / N2 mixed gas, heat it to 1100°C at a rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0130] (3) The crude product obtained in step (2) was placed in 500 mL of 0.5 mol / L hydrochloric acid and stirred at room temperature for 6 h at a stirring rate of 800 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 100° C. for 10 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 520 m 2 / g, pore size is 15~40nm.

[0131] (4) Propane oxidative dehydrogenation reaction performance test

[0132] The above boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The catalyst was heated in a mixture of O2 and He at a volume ratio of 1:4 and a volume space velocity of 8000 h -1 The mixture was pre-treated and activated for 6 hours at 450°C and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=1:1.5:3.5, and the volume space velocity was 8000h -1 The raw gas was used to raise the reaction temperature to 540°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0133] Comparative Example 3

[0134] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0135] (1) 124 g of boric acid and 720 g of melamine were dissolved in 800 g of methanol in a molar ratio of 1:3 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 80° C. with continuous stirring until the solvent was completely evaporated to obtain a mixture.

[0136] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tubular furnace. In a nitrogen atmosphere, heat it to 650°C at a rate of 5°C / min and keep it warm for 1 hour. Then, under the protection of a 10% H2 / N2 mixed gas, heat it to 1000°C at a rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0137] (3) The crude product obtained in step (2) was placed in 500 mL of 3 mol / L hydrochloric acid and stirred at 50° C. for 12 h at a stirring rate of 750 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 120° C. for 8 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 720 m 2 / g, pore size is 10~50nm.

[0138] (4) Propane oxidative dehydrogenation reaction performance test

[0139] The above-mentioned boron nitride catalyst (1 g) was placed in the constant temperature section of the fixed bed reactor. The boron nitride catalyst was pre-treated and activated for 8 h in a mixed gas of O2 and N2 with a volume ratio of 1:5 at 550°C and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=1:1:4, and the volume space velocity was 9000 h -1 The raw gas was used to raise the reaction temperature to 560°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0140] Comparative Example 4

[0141] Preparation of Boron Nitride Catalyst and Performance Test of Propane Oxidative Dehydrogenation Reaction:

[0142] (1) 140 g of boron oxide, 720 g of urea and 2 g of sodium chloride were dissolved in 500 g of water in a molar ratio of 1:6 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 70° C. with continuous stirring until the solvent was completely evaporated to obtain a mixture.

[0143] (2) Take a certain amount of the mixture in step (1), grind it thoroughly, and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 1050°C at a heating rate of 5°C / min and keep it warm for 5 hours. Then, under the protection of N2, cool it to 650°C at a rate of 5°C / min and keep it warm for 1 hour to obtain a crude product.

[0144] (3) The crude product obtained in step (2) was placed in 400 mL of 0.5 mol / L hydrochloric acid and stirred at room temperature for 8 h at a stirring rate of 650 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 120° C. for 6 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 550 m 2 / g, pore size is 13~55nm.

[0145] (4) Propane oxidative dehydrogenation reaction performance test

[0146] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated in a mixture of O2 and N2 at a volume ratio of 1:3 and a volume space velocity of 5000 h -1 The mixture was pre-treated and activated for 6 hours at 550℃ and normal pressure. Then the volume ratio was switched to C3H8:O2:N2=2:2:3, and the volume space velocity was 5000h -1 The raw material gas was used, the reaction temperature was adjusted to 545°C, and propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0147] Comparative Example 5

[0148] Preparation of boron nitride catalyst and performance test of propane oxidative dehydrogenation reaction:

[0149] (1) 62 g of boric acid, 720 g of urea and 10 g of cobalt nitrate were dissolved in 500 g of ethanol in a molar ratio of 1:12 between the boron source and the nitrogen source, stirred until they were completely dissolved, and then heated to 80° C. and stirred continuously until the solvent was completely evaporated to obtain a mixture.

[0150] (2) Take a certain amount of the mixture in step (1), grind it thoroughly and transfer it to a tube furnace. In a nitrogen atmosphere, heat it to 500°C at a rate of 5°C / min and keep it warm for 2 hours. Then, under the protection of a 10% H2 / N2 mixed gas, heat it to 1000°C at a rate of 5°C / min and keep it warm for 5 hours to obtain a crude product.

[0151] (3) The crude product obtained in step (2) was placed in 300 mL of 3 mol / L hydrochloric acid and stirred at 50° C. for 8 h at a stirring rate of 700 rpm. The obtained product was filtered and washed with deionized water until neutral, and then transferred to an oven and dried at 100° C. for 8 h to obtain the boron nitride catalyst. The specific surface area of ​​the obtained boron nitride catalyst was 300 m 2 / g, pore size is 10~45nm.

[0152] (4) Propane oxidative dehydrogenation reaction performance test

[0153] The boron nitride catalyst (1 g) was placed in the constant temperature section of a fixed bed reactor. The boron nitride catalyst was heated at a volume ratio of 1:5 and a volume space velocity of 4000 h -1 The mixture of O2 and Ar was pre-treated and activated for 4 hours at 550°C and normal pressure. Then the volume ratio was switched to C3H8:O2:Ar=1:2:4, and the volume space velocity was 4000h -1 The raw gas was used to raise the reaction temperature to 560°C and the propane oxidative dehydrogenation reaction was carried out under normal pressure. The propane conversion rate and olefin selectivity of the reaction are shown in the table.

[0154] Table 1 Evaluation of boron nitride catalyst for oxidative dehydrogenation of propane to propylene

[0155]

[0156]

[0157] Remark:

[0158] Weight Hourly Space Velocity (WHSV): The mass of propane passing through a unit mass of catalyst per unit time.

[0159] The data collection time is 2h

[0160] Yield = conversion rate × selectivity / 100

[0161] Olefin is propylene

[0162] The results of the comparative examples and comparative examples show that the two-stage heat treatment of the present invention can significantly improve the propane conversion rate and the olefin yield; the results of the comparative examples and comparative examples show that the addition of an auxiliary agent of the present invention can significantly improve the propane conversion rate and the olefin yield.

[0163] Table 2 Comparison of process parameters of Examples 1-6 and Comparative Examples 1-5

[0164]

[0165]

[0166]

[0167] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for preparing a boron nitride material, characterized in that: include: After mixing the boron source, nitrogen source, auxiliary agent and solvent, a two-stage heat treatment reaction is carried out; The two-stage heat treatment reaction is a solid phase reaction; Preferably, the boron nitride material is a catalyst for propane oxidative dehydrogenation reaction; More preferably, the boron nitride material is a catalyst for oxidative dehydrogenation of propane to produce propylene.

2. The method according to claim 1, characterized in that: The molar ratio of the boron source to the nitrogen source based on boron atoms and nitrogen atoms is 1:(2-16); preferably 1:(3-12); and / or, The mass ratio of the nitrogen source to the auxiliary agent is (144-360):1; and / or, The mass ratio of the nitrogen source to the solvent is (1.44-0.9):1; and / or, The boron source is selected from one or more of boric acid, boric oxide and ammonium borate; and / or, The nitrogen source is selected from one or more of urea, melamine and guanidine hydrochloride; and / or, The auxiliary agent is selected from one or more of chlorides, nitrates, oxalates, ferric ammonium oxalate, potassium hydroxide and sodium hydroxide; the chloride is preferably a chloride of iron, potassium or sodium; and / or the nitrate is preferably a nitrate of iron, potassium or sodium; and / or the oxalate is preferably an oxalate of iron, potassium or sodium; and / or, The solvent is selected from one or more of water, lower alcohol and toluene; the lower alcohol is preferably one or more of methanol, ethanol and isopropanol.

3. The method according to claim 1 or 2, characterized in that: The method further comprises: after mixing the boron source, nitrogen source, auxiliary agent and solvent, evaporating the solvent and then performing the two-stage heat treatment reaction; Preferably, evaporating the solvent is carried out at a temperature of 60 to 90° C., preferably 75 to 80° C.; Preferably, stirring is continued during evaporation of the solvent.

4. The method according to any one of claims 1 to 3, characterized in that: The temperature of the first heat treatment in the two-stage heat treatment reaction is 400-700°C; preferably 500-650°C; and / or, The time of the first heat treatment in the two-stage heat treatment reaction is 0.5 to 4 hours; preferably 1 to 2 hours; and / or, In the first heat treatment process of the two-stage heat treatment reaction, the temperature is raised to the treatment temperature at a rate of 5°C / min; and / or, The temperature of the second heat treatment in the two-stage heat treatment reaction is 850-1100° C.; preferably 1000-1100° C.; and / or, The time of the second heat treatment in the two-stage heat treatment reaction is 0.5 to 5 hours; preferably 3 to 5 hours; and / or, In the second heat treatment process of the two-stage heat treatment reaction, the temperature is raised to the treatment temperature at a rate of 5°C / min; and / or, The two-stage heat treatment reaction is carried out under the protection of gas; Preferably, the gas is nitrogen, a hydrogen / nitrogen mixture, ammonia, or an ammonia / nitrogen mixture; the volume percentage of hydrogen in the hydrogen / nitrogen mixture is preferably 1% to 10%, and the volume percentage of ammonia in the ammonia / nitrogen mixture is preferably 5% to 30%.

5. The method according to any one of claims 1 to 4, characterized in that: After the two-stage heat treatment reaction, a crude product is obtained, and the crude product is acid-washed, filtered, washed, and dried to obtain the boron nitride material; Preferably, pickling is carried out with hydrochloric acid; More preferably, the concentration of hydrochloric acid is 0.5 to 4 mol / L; and / or, the acid washing is performed by placing the crude product in hydrochloric acid and stirring; Preferably, the pickling temperature is 25 to 70°C; Preferably, the washing is water washing, preferably washing with deionized water until neutral; Preferably, the drying temperature is 80-120°C; Preferably, the drying time is 5 to 24 hours.

6. A boron nitride material prepared according to the method according to any one of claims 1 to 5; Preferably, the surface area of ​​the boron nitride material is 100 to 1000 m 2 / g; and / or, The pore size distribution of the boron nitride material is 20-40 nm.

7. Use of the boron nitride material according to claim 6 in propane oxidative dehydrogenation reaction; Preferably, the boron nitride material is used in the reaction of oxidative dehydrogenation of propane to produce propylene.

8. A method for oxidative dehydrogenation of propane, the method comprising: Carrying out propane oxidative dehydrogenation reaction under the catalysis of the boron nitride material according to claim 6; Preferably, the method is a method for preparing propylene by oxidative dehydrogenation of propane.

9. The method according to claim 8, characterized in that The temperature of the propane oxidative dehydrogenation reaction is 400-600° C.; and / or, The propane oxidative dehydrogenation reaction is carried out under normal pressure; and / or, The propane oxidative dehydrogenation reaction is carried out in one or more fixed bed reactors, microchannel reactors, continuous stirred slurry bed reactors, slurry bubble column reactors or fluidized bed reactors, and is carried out in a continuous or intermittent reaction process; and / or, The reaction raw materials of the propane oxidative dehydrogenation are propane and oxygen; Preferably, the reaction raw materials are diluted with an inert gas; More preferably, the inert gas is one or more of nitrogen, helium and argon; and / or, The volume ratio of propane, oxygen and inert gas is (1-2):(1-2):(3-4) and / or, The volume space velocity of the mixed gas containing the propane, oxygen and inert gas is 2000~30000h -1 .

10. The method according to claims 8-9, characterized in that: The method further comprises: before the boron nitride material catalyzes the alkoxy dehydrogenation reaction, the boron nitride material is pre-treated and activated in a mixed gas of oxygen and an inert gas; Preferably, the volume ratio of oxygen to inert gas is 1:(2-5), preferably 1:(3-5); and / or, The temperature of pretreatment activation is 350-600°C; and / or, The pretreatment activation time is 0.5 to 6 hours.

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