A Si3N4-BN composite catalyst and its preparation and application

Abstract

The application discloses a Si3N4-BN composite catalyst and a preparation and application thereof. The preparation method comprises the following steps: step 1, Si3N4 nanoparticles, H3BO3 and CO(NH2)2 are weighed and added into deionized water, and are fully stirred to obtain a suspension; step 2, the suspension obtained in step 1 is transferred into a polytetrafluoroethylene-lined steel autoclave, is sealed and placed in an induction heating electric furnace for heating, the heating temperature is 600-800 DEG C, the heating time is 3-6h, and the suspension is cooled to room temperature; and step 3, the suspension cooled in step 2 is subjected to suction filtration to collect the precipitate, is washed and dried, and the Si3N4-BN composite catalyst is obtained after drying. The application provides the application of the Si3N4-BN composite catalyst in a reaction of preparing propylene through propane oxidative dehydrogenation, and the Si3N4-BN composite catalyst has high propane conversion rate, high propylene selectivity and excellent stability.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology and application, specifically to a Si3N4-BN catalyst, its preparation, and its application in the oxidative dehydrogenation (ODH) reaction of propane to propylene. Background Technology

[0002] The synthesis of polymers, such as polyethylene and polypropylene, is a key component of the chemical industry, primarily using light olefins, including ethylene, propylene, and butene, as raw materials. Light olefins are the cornerstone of the chemical industry, with a global annual production exceeding 200 million tons. These compounds are mainly produced through the cracking of petroleum-derived hydrocarbons or multi-stage coal-based methanol-to-olefins (MTO) processes. These processes are energy-intensive and accompanied by significant carbon emissions. The overall characteristics of methanol-to-olefins and Fischer-Tropsch olefin synthesis technologies are high energy consumption and large carbon emissions, contradicting the stringent sustainable development standards that require environmental protection and energy efficiency. This presents both scientific and technological challenges and has driven chemical engineering to shift from energy-intensive chemical processes to more environmentally friendly catalytic protocols to produce olefins with high atom economy, low energy consumption, and low emissions. Recently, with the development of global shale resources, natural gas and oilfield gas rich in light alkanes (C2-C4) have become new pathways for producing light olefins, driving the rapid development of gas-based dehydrogenation technologies. For example, propane catalytic dehydrogenation (PDH) technology has become an important part of the global propylene supply, and its market share is expected to grow from approximately 5% to 20%. Nevertheless, traditional direct dehydrogenation methods rely on platinum-based or chromium oxide-based catalysts, which are limited in improving reaction efficiency and are prone to rapid deactivation due to coking and sintering, requiring periodic regeneration under harsh conditions.

[0003] Oxidative dehydrogenation (ODH), as an alternative technology, exhibits excellent thermodynamic and kinetic properties, including lower reaction temperatures, faster reaction rates, and no coking, thus showing potential advantages in direct dehydrogenation processes. In the ODH reaction of light alkanes, catalytic systems based on transition metal oxides (such as V₂O₅, MoO₃, and NiO) or alkaline earth metal oxychlorides have shown promising results. However, these catalysts face the challenge that electron-rich olefins readily react with the catalyst surface, leading to C-C bond cleavage and excessive carbon dioxide (CO₂) generation, which limits the selectivity and stability of the catalysts. Therefore, developing novel catalysts capable of providing high selectivity for olefins under harsh conditions is an urgent research priority.

[0004] Based on the above background, it is necessary to develop improved catalytic materials and design a suitable catalyst to avoid the over-oxidation of light olefins, thereby improving the olefin selectivity in the ODH reaction and making it more suitable for industrial olefin production. This invention relates to the application of a catalyst in the propane oxidative dehydrogenation to propylene reaction. Summary of the Invention

[0005] To overcome the poor selectivity and stability of existing transition metal oxide or alkaline earth metal oxychloride catalytic systems used in the propane oxidative dehydrogenation (ODH) to propylene gas-solid phase reaction, this invention provides a method for preparing a Si3N4-BN composite catalyst, the prepared Si3N4-BN composite catalyst, and its application in the propane oxidative dehydrogenation to propylene reaction. The catalyst prepared by this invention exhibits high propane conversion, high propylene selectivity, and excellent stability in the propane oxidative dehydrogenation to propylene reaction.

[0006] The technical solution adopted in this invention will be described in detail below.

[0007] In a first aspect, the present invention provides a method for preparing a Si3N4-BN composite catalyst, comprising the following steps:

[0008] Step 1: Weigh Si3N4 nanoparticles, H3BO3 and CO(NH2)2, add them to deionized water, and stir thoroughly to obtain a suspension;

[0009] Step 2: Transfer the suspension obtained in Step 1 to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at a temperature of 600-800℃ for 3-6 hours, then cool it to room temperature.

[0010] Step 3: The suspension cooled in Step 2 is filtered to collect the precipitate, washed and dried. After drying, the Si3N4-BN composite catalyst is obtained.

[0011] The Si3N4 nanoparticle carrier described in this invention is commercially available.

[0012] Furthermore, in step 1, the mass ratio of Si3N4 nanoparticles to CO(NH2)2 is 100:6-13, and the mass ratio of CO(NH2)2 to H3BO3 is 1:2-1:5. Even further, in step 1, the feeding ratio of Si3N4 nanoparticles to deionized water is 10g:40-60mL.

[0013] Furthermore, in step 1, the stirring rate is 300–400 r / min, and the stirring time is 20–40 min.

[0014] Furthermore, in step 3, the detergents are deionized water and ethanol, and each is used for washing 2 to 3 times.

[0015] Furthermore, in step 3, the drying temperature is 110–130°C, and the drying time is 6–12 hours.

[0016] In a second aspect, the present invention provides a Si3N4BN composite catalyst prepared according to the preparation method described in the first aspect.

[0017] Thirdly, the present invention provides the application of the Si3N4-BN composite catalyst described in the second aspect in the oxidative dehydrogenation reaction of propane to propylene.

[0018] The Si3N4-BN composite catalyst does not contain defective electrophilic metal sites, thus avoiding strong interactions with electron-rich olefin products and achieving the effect of improving propylene selectivity.

[0019] The application of the Si3N4-BN composite catalyst described in this invention in the oxidative dehydrogenation of propane to propylene reaction is specifically as follows: the Si3N4-BN composite catalyst is loaded into a fixed-bed reactor, and a feed gas including propane and oxygen is introduced. The reaction temperature is set to 400-450°C and the reaction pressure is set to atmospheric pressure. Propane and oxygen are oxidatively dehydrogenated to produce propylene under the action of the Si3N4-BN composite catalyst.

[0020] The raw material gas generally also includes propylene gas and nitrogen gas.

[0021] Furthermore, the molar ratio of the raw material gas n(O2):n(C3H8) = 1:2, and the propane gas space velocity is 10000-20000 h⁻¹. -1 .

[0022] The Si3N4-BN composite catalyst prepared by this invention has high catalytic activity in the above-mentioned propane oxidative dehydrogenation to propylene reaction, with a propane conversion rate of up to 90% or more and a propylene selectivity of up to 90% or more.

[0023] Compared with the prior art, the present invention has the following innovations and technical advantages:

[0024] (1) The present invention uses a non-metallic boron-based catalyst to avoid excessive oxidation during the oxidative dehydrogenation of light alkanes and improve the selectivity of light olefins.

[0025] (2) The present invention uses a hydrothermal method to generate BN in situ, and the generated BN is combined with Si3N4 to obtain a Si3N4-BN composite catalyst. The obtained catalyst has high purity, high yield, and simple process with low energy consumption and low cost.

[0026] (3) The present invention uses an induction heating electric furnace to heat the steel pressure vessel. This method utilizes the principle of electromagnetic induction to generate eddy currents inside the steel pressure vessel, thereby achieving rapid and uniform heating and accurately controlling the heating temperature, heating time and heating area.

[0027] (4) The Si3N4-BN composite catalyst prepared in this invention is applied to the propane oxidative dehydrogenation to propylene reaction, with high propane conversion, good propylene selectivity and good catalyst stability. Detailed Implementation

[0028] The present invention will now be illustrated with specific embodiments. It should be noted that these embodiments are merely for further illustrative purposes and should not be construed as limiting the scope of protection of the present invention. The present invention is not limited thereto in any way. Those skilled in the art can make some non-essential improvements and adjustments based on the above description of the invention.

[0029] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through conventional technical means or commercially available.

[0030] The Si3N4 nanoparticle carrier used in the examples was purchased from Begal New Materials. It has an effective content of 99.9%, a specification of 40nm, CAS number: 12033-89-5, and is a nano-grade premium product.

[0031] Example 1

[0032] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 0.6005g of CO(NH2)2 and 1.2368g of H3BO3, add them to 40mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 300r / min to obtain a suspension.

[0033] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 700°C for 4 hours, and then cool it to room temperature.

[0034] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 120°C for 10 hours to obtain the Si3N4-BN composite catalyst.

[0035] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% propylene (carrier gas was nitrogen); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹.-1 In the initial stage of the reaction, the propane conversion rate was 93.1% and the propylene selectivity was 92.3%. After 1000 hours of reaction, the propane conversion rate was 90.2% and the propylene selectivity was 94.1%.

[0036] Example 2

[0037] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 40mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 300r / min to obtain a suspension.

[0038] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 700°C for 4 hours, and then cool it to room temperature.

[0039] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 120°C for 10 hours to obtain the Si3N4-BN composite catalyst.

[0040] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1 In the initial stage of the reaction, the propane conversion rate was 94.3% and the propylene selectivity was 93.6%. After 1000 hours of reaction, the propane conversion rate was 91.4% and the propylene selectivity was 95.2%.

[0041] Example 3

[0042] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 60mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 400r / min to obtain a suspension.

[0043] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 700°C for 4 hours, and then cool it to room temperature.

[0044] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 120°C for 10 hours to obtain the Si3N4-BN composite catalyst.

[0045] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1 In the initial stage of the reaction, the propane conversion rate was 95.1% and the propylene selectivity was 94.8%. After 1000 hours of reaction, the propane conversion rate was 92.3% and the propylene selectivity was 95.9%.

[0046] Example 4

[0047] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 60mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 400r / min to obtain a suspension.

[0048] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 800°C for 3 hours, and then cool it to room temperature.

[0049] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 120°C for 10 hours to obtain the Si3N4-BN composite catalyst.

[0050] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1In the initial stage of the reaction, the propane conversion rate was 97.2% and the propylene selectivity was 93.4%. After 1000 hours of reaction, the propane conversion rate was 94.5% and the propylene selectivity was 96.2%.

[0051] Example 5

[0052] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 60mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 400r / min to obtain a suspension.

[0053] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 800°C for 3 hours, and then cool it to room temperature.

[0054] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 110°C for 12 hours to obtain the Si3N4-BN composite catalyst.

[0055] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1 In the initial stage of the reaction, the propane conversion rate was 96.2% and the propylene selectivity was 95.7%. After 1000 hours of reaction, the propane conversion rate was 93.8% and the propylene selectivity was 96.8%.

[0056] Example 6

[0057] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 60mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 400r / min to obtain a suspension.

[0058] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 600°C for 6 hours, and then cool it to room temperature.

[0059] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 120°C for 10 hours to obtain the Si3N4-BN composite catalyst.

[0060] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1 In the initial stage of the reaction, the propane conversion rate was 96.6% and the propylene selectivity was 93.9%. After 1000 hours of reaction, the propane conversion rate was 91.9% and the propylene selectivity was 94.8%.

[0061] Example 7

[0062] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 40mL of deionized water, and stir thoroughly for 30min with a magnetic stirrer at 300r / min to obtain a suspension.

[0063] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 700°C for 4 hours, and then cool it to room temperature.

[0064] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 130°C for 6 hours to obtain the Si3N4-BN composite catalyst.

[0065] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1In the initial stage of the reaction, the propane conversion rate was 95.7% and the propylene selectivity was 94.8%. After 1000 hours of reaction, the propane conversion rate was 92.6% and the propylene selectivity was 96.4%.

[0066] Example 8

[0067] Step 1): Weigh 10g of commercial Si3N4 nanoparticles, 1.2010g of CO(NH2)2 and 2.4736g of H3BO3, add them to 60mL of deionized water, and stir thoroughly for 40min with a magnetic stirrer at 300r / min to obtain a suspension.

[0068] Step 2): Transfer the suspension obtained in Step 1) to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at 800°C for 4 hours, and then cool it to room temperature.

[0069] Step 3): The cooled suspension from Step 2) was filtered in a vacuum filtration pump at a pressure of 0.08 MPa. The precipitate collected by filtration was washed three times each with deionized water and ethanol. After washing, it was transferred to an oven for drying at 130°C for 6 hours to obtain the Si3N4-BN composite catalyst.

[0070] The prepared Si3N4-BN composite catalyst was applied to the oxidative dehydrogenation of propane to propylene. Catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1 In the initial stage of the reaction, the propane conversion rate was 94.7% and the propylene selectivity was 95.2%. After 1000 hours of reaction, the propane conversion rate was 91.8% and the propylene selectivity was 96.5%.

[0071] Comparative Example 1

[0072] Comparative Example 1 demonstrates, by comparing it with Example 1, that replacing the metal oxide catalyst with a non-metallic boron-based catalyst can avoid over-oxidation during the oxidative dehydrogenation of propane, thereby improving the selectivity of propylene and the stability of the catalyst.

[0073] Step 1): Weigh 10g of commercial Si3N4 nanoparticles and 2.6327g of Cr(NO3)3·9H2O. Dissolve Cr(NO3)3·9H2O in 40mL of deionized water to prepare an impregnation solution. Then, transfer the Si3N4 nanoparticles into the impregnation solution and impregnate them for 12 hours. After impregnation, place them in an oven to dry at 110℃ for 12 hours.

[0074] Step 2): The dried sample from Step 1) was placed in a muffle furnace for calcination at a temperature of 400℃ for 4 hours. After calcination, a Si3N4-supported Cr2O3 catalyst was obtained.

[0075] The prepared Si3N4-supported Cr2O3 catalyst was applied to the oxidative dehydrogenation of propane to propylene. The catalyst performance was evaluated in a fixed-bed reactor under the following conditions: 0.20 g of the catalyst was mixed with quartz sand and placed in a quartz tube to a volume of 1 mL; the reaction temperature was 400 °C; the reaction pressure was atmospheric pressure; the mixed gas composition was 0.33% O2, 0.66% C3H8, and 33% C3H6 (nitrogen was used as the carrier gas); the flow rate was 50 mL / min; and the propane space velocity was 10000 h⁻¹. -1 Initially, the propane conversion rate was 65.4% and the propylene selectivity was 71.6%. After 500 hours of reaction, the propane conversion rate was 30.8% and the propylene selectivity was 47.6%.

Claims

1. The application of a Si3N4-BN composite catalyst in the oxidative dehydrogenation of propane to propylene, wherein the preparation method of the Si3N4-BN composite catalyst includes the following steps: Step 1: Weigh Si3N4 nanoparticles, H3BO3 and CO(NH2)2, add them to deionized water, and stir thoroughly to obtain a suspension; Step 2: Transfer the suspension obtained in Step 1 to a steel autoclave lined with polytetrafluoroethylene, seal it and place it in an induction heating furnace for heating at a temperature of 600-800℃ for 3-6 hours, then cool it to room temperature. Step 3: The suspension cooled in Step 2 is filtered to collect the precipitate, washed and dried. After drying, the Si3N4-BN composite catalyst is obtained.

2. The application as described in claim 1, characterized in that: In step 1, the mass ratio of Si3N4 nanoparticles to CO(NH2)2 is 100:6 to 13, and the mass ratio of CO(NH2)2 to H3BO3 is 1:2 to 1:

5.

3. The application as described in claim 1, characterized in that: In step 1, the feeding ratio of Si3N4 nanoparticles to deionized water is 10g:40-60mL.

4. The application as described in claim 1, characterized in that: In step 3, the drying temperature is 110–130°C and the drying time is 6–12 hours.

5. The application as described in any one of claims 1-4, characterized in that: The specific application is as follows: In a fixed-bed reactor, the Si3N4-BN composite catalyst is loaded, and a feed gas including propane and oxygen is introduced. The reaction temperature is set to 400-450℃ and the reaction pressure is atmospheric pressure. Propane and oxygen are oxidized and dehydrogenated to produce propylene under the action of the Si3N4-BN composite catalyst.

6. The application as described in claim 5, characterized in that: The molar ratio of the raw gas, n(O2):n(C3H8), is 1:2, and the propane gas space velocity is 10000–20000 h⁻¹. -1 .