Heterogeneous catalyst of borosilicate molecular sieve loaded metal oxide as well as preparation method and application of heterogeneous catalyst

Abstract

The invention relates to a borosilicate molecular sieve loaded metal oxide heterogeneous catalyst and a preparation method and application thereof, the catalyst is prepared by loading a metal oxide on a borosilicate molecular sieve, and the loading amount of the metal oxide is 0.1-5%. The preparation method comprises the following steps: directly fixing an active component boron in crystal lattices of a molecular sieve framework through a direct hydrothermal synthesis method, loading an active component metal oxide on the surface of a borosilicate molecular sieve through a dipping method, and drying and calcining at high temperature to obtain the borosilicate molecular sieve composite metal oxide heterogeneous catalyst. According to the catalyst, high dispersion of the metal oxide is realized by utilizing an interface structure formed by the metal oxide and boron in a molecular sieve framework, a synergistic catalysis effect is achieved between a boron active site of the molecular sieve framework and a metal oxide active site, and the catalyst shows excellent catalytic performance and long-acting stability in propane oxidative dehydrogenation (ODHP) application; and in the range of 540-545 DEG C, the propane conversion rate is more than 45%, the olefin selectivity is more than 75%, and the catalyst can stably operate for more than 350 hours.

Description

Technical Field

[0001] This invention belongs to the field of industrial low-carbon alkane conversion thermocatalytic materials, specifically relating to a heterogeneous catalyst with borosilicate molecular sieve supported on metal oxides and its preparation method, as well as the application of the heterogeneous catalyst in propane oxidative dehydrogenation. Background Technology

[0002] Propylene is a key commodity chemical in the petrochemical industry. Light olefins (ethylene, propylene, and butadiene, etc.) are important raw materials for organic chemical production. Propylene is the second most used petrochemical raw material after ethylene and is a basic raw material for the three major synthetic materials. It is mainly used to produce polypropylene, acrylonitrile, propylene oxide, acrylic acid, acetone, isopropanol, etc. These downstream products have characteristics such as low specific gravity, easy processing, water resistance, and good electrical insulation. They are gradually replacing traditional materials such as steel, cement, and cotton products, and are widely used in plastics manufacturing, medical devices, textiles, and other fields, closely related to daily life. With the continuous improvement of people's living standards, the application of propylene will extend to more fields, and its demand will continue to increase. Among the many fine chemicals produced from propylene, polypropylene accounts for the vast majority of production. The most important downstream derivatives of propylene are films, injection molded products, and textiles, which are the main demand areas for polypropylene. With the continuous development of my country's economy, the demand for pipes, thin nonwoven fabrics, and other fields is also gradually increasing. In the future, polypropylene will remain the main driver of propylene demand growth. Propylene oxide is mainly used in industries such as surfactants, pesticides, chemicals, and daily chemicals. The hydrogen peroxide oxidation method for producing propylene oxide (HPPO method) is not only environmentally friendly, solving the pollution and corrosion problems of traditional processes, but also has low energy consumption. The propylene oxide industry is expected to maintain a positive outlook in the future. Acrylonitrile is used to manufacture ABS plastics, acrylic fibers, and acrylamide. Benefiting from the expansion of the downstream ABS plastics industry, there is currently a significant increase in domestic acrylonitrile production capacity. Acrylic acid is an unsaturated carboxylic acid and an important intermediate in organic synthesis. In recent years, the market demand for downstream propylene products, especially superabsorbent resins, has grown rapidly, further increasing the demand for acrylic acid. The booming development of downstream propylene product industries has further increased the demand for propylene. The propylene produced by traditional processes such as naphtha steam cracking and refinery catalytic cracking is far from meeting the demand. Faced with the widening supply-demand gap, more simple and efficient propylene production technologies are needed.

[0003] Currently, propane dehydrogenation is considered one of the most promising propylene production processes. With the large-scale development of shale gas, propane prices have become low. Propylene is the main product in propane dehydrogenation, with a high propylene yield, and the byproduct hydrogen can be used in the new energy industry. While direct propane dehydrogenation is already industrialized, it is a thermodynamically constrained, strongly endothermic process requiring high temperatures to achieve high conversion rates. Furthermore, high temperatures can lead to catalyst carbon buildup. Conversely, propane oxidative dehydrogenation is an exothermic reaction, not thermodynamically constrained, and theoretically can achieve high conversion rates at lower temperatures without the carbon buildup problem.

[0004] Currently, catalysts used in the oxidative dehydrogenation of propane to propylene are mainly divided into metal oxide catalysts and non-metal oxide catalysts. Metal oxide catalysts mainly include V / Al2O3, V2O5 / SiO2, Mo / h-BN, etc., but metal oxides often have high activation temperatures, and their strong oxidizing properties can lead to over-oxidation, resulting in very low propylene yields.

[0005] The V2O5 / SiO2 catalyst disclosed in Applied Catalysis A: General., 2001, 209, 155–164, at 550 °C... o At C, when the propane conversion rate is 30.9%, the propylene selectivity is only 35.4%.

[0006] The V / BN catalyst disclosed in (JACS Au., 2022, 2, 5, 1096–1104) at 560 o At C, the propane conversion and propylene selectivity were 18.0% and 45.5%, respectively.

[0007] CN02136598.9 discloses a method for preparing a nanocatalyst for the oxidative dehydrogenation of propane to propylene, and applies it to the propane oxidative dehydrogenation reaction. It uses SBA series pure silica nanoporous materials as the catalyst support, achieving a propylene yield between 10% and 32%, but the reaction temperature needs to reach 600°C. o Above C, and the catalyst is prone to deactivation. Studies have found that the catalytic performance of metal oxide catalysts depends on the properties of the support. Boron-based catalysts have moderate surface acidity and special BO active sites, which can effectively inhibit deep oxidation.

[0008] CN202210638558 discloses a borosilicate molecular sieve catalyst with an amorphous structure. The mesoporous and microporous hierarchical structure of this catalyst can promote the reaction and product diffusion. At a temperature of 520°C... O When C,C3H8:O2=1.5, the propane conversion rate is 4.4% and the propylene selectivity is 85.2%. Although the reaction can be carried out at a lower temperature, the catalytic activity is low.

[0009] (Science., 2021, 372, 76–80) discloses a BS-1 catalyst that reacts at a temperature of 560 °C. o At C, the propane conversion rate was 41.4% and the propylene selectivity was 54.9%, which still resulted in a relatively low propylene yield.

[0010] For the process of propane dehydrogenation to propylene, the existing technology still has technical problems such as low product conversion rate, low yield, low selectivity, low activity and poor stability, which limit the widespread application of catalysts. Therefore, it is of great significance to develop and prepare a catalyst that can have high propane oxidative dehydrogenation activity and high propylene selectivity at a lower temperature. Summary of the Invention

[0011] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a heterogeneous catalyst with borosilicate molecular sieve supported on metal oxide, its preparation method and application. The heterogeneous catalyst provided by this invention has high dispersion, good reaction selectivity and high conversion rate. The process and reaction equipment for preparing the heterogeneous catalyst are simple and easy to operate, and it is suitable for industrial-scale production. The heterogeneous catalyst exhibits excellent catalytic performance and long-term stability when applied to the reaction of propane oxidative dehydrogenation (ODHP) to propylene.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, this application provides a heterogeneous catalyst supported on a borosilicate molecular sieve and containing a metal oxide. The catalyst is composed of a support and a metal oxide, wherein the support is a borosilicate molecular sieve BSilicate-1, and the metal oxide is supported on the borosilicate molecular sieve at a loading of 0.1% to 5%.

[0013] Preferably, depending on the borosilicate ratio, hydrothermal temperature, and time, the topology of the borosilicate molecular sieve is any one of Y-type, BEA-type, MFI-type, and CHA-type, with a borosilicate ratio of 0 to 0.2. The borosilicate molecular sieve is preferably BSilicate-1 with an MFI topology.

[0014] Preferably, the metal oxide is any one of vanadium oxide, molybdenum oxide, or gallium oxide, with vanadium oxide being the most preferred.

[0015] Preferably, the precursor salt of the metal oxide is a hydrate of any one of ammonium metavanadate, ammonium molybdate, gallium tetrahydrate, or gallium nitrate.

[0016] A second aspect of this application provides a method for preparing the above-mentioned multiphase catalyst, comprising the following steps: Step a): The silicon source, boron source and organic template agent are mixed evenly in a certain proportion to obtain a gel. The resulting gel is then poured into a hydrothermal reactor lined with polytetrafluoroethylene and crystallized at 150°C for 72 hours. The active component boron is directly fixed in the lattice of the molecular sieve framework through hydrothermal synthesis. After filtration and washing, the gel is dried in an oven at 80°C for 12 hours and then calcined in an air tube furnace at 550°C for 2 hours to obtain a borosilicate molecular sieve carrier. Step b): Dissolve vanadium oxide, molybdenum oxide, and gallium oxide salts in a solution, stir until homogeneous, and then add the solution to the borosilicate molecular sieve support prepared in step a). Heat in a water bath to load the active metal oxide components onto the surface of the borosilicate molecular sieve through impregnation. The process is carried out at 80°C. o After being placed in an oven at C for 12 hours, the product was calcined in an air tube furnace at 550℃ for 6 hours. The calcined product was then passed through a 60-80 mesh sieve to obtain a heterogeneous catalyst of borosilicate molecular sieve supported on metal oxides.

[0017] Preferably, the boron source in step a) is boric acid, the silicon source is fumed silica, and the organic template agent is tetrapropylammonium hydroxide.

[0018] Preferably, the temperature of the water bath in step b) is 80°C. o C, the time is 2 hours, and the solution is either oxalic acid solution or distilled water.

[0019] A third aspect of this application provides the application of the aforementioned heterogeneous catalyst in the oxidative dehydrogenation of propane to propylene.

[0020] Furthermore, under normal pressure, the reaction temperature is 500–545 °C. o C, the feed space velocity of propane is 2000-10000 mL / (g·h), and a reaction mixture is introduced. The reaction mixture consists of propane, oxygen and nitrogen. The reaction is carried out under the conditions of 0.008-0.04MPa C3H8, 0.008-0.04MPa O2 and 0.058MPa N2.

[0021] Furthermore, the catalyst is loaded with high-temperature resistant quartz wool as a fixed bed, and the catalyst loading amount is 50-150 mg. After loading, the catalyst is pretreated and activated. Under normal temperature conditions, nitrogen gas is introduced at a flow rate of 15-20 mL / min and heated at a heating rate not exceeding 10 °C / min. The temperature is stabilized at 500-545 °C for no less than 20 minutes.

[0022] Based on the above technical solution, the present invention has at least the following beneficial effects compared with the prior art: The present invention uses borosilicate molecular sieve BSilicate-1 as a catalyst support. Its larger specific surface area and smaller pore size structure are more conducive to the diffusion of reactants and products. The metal oxides supported on it interact with boron, which can promote the dispersion and stability of active sites and improve the catalytic activity of propane. The process and reaction equipment for preparing the heterogeneous catalyst are simple and easy to operate, and are suitable for industrial-scale production. The application of the heterogeneous catalyst to the reaction of propane oxidative dehydrogenation (ODHP) to propylene shows excellent catalytic performance and long-term stability. In the range of 540-545 °C, the propane conversion rate is >45%, the olefin selectivity is >75%, and it can operate stably for >350 hours. Attached Figure Description

[0023] Figure 1 This is the X-ray diffraction powder pattern of BSilicate-1 of the present invention; Figure 2 This invention is 1.5VO x / BSilicate-1、1.5MoO x / BSilicate-1、1.5GaO x / BSilicate-1 propane oxidative dehydrogenation reaction performance diagram; Figure 3 This invention is 1.5VO x Stability performance of / BSilicate-1 in propane oxidative dehydrogenation reaction after 350 hours. Detailed Implementation

[0024] To provide a clearer understanding of the technical features, objectives, and beneficial effects of this invention, the technical solution of this invention will now be clearly and completely described in conjunction with the following specific embodiments and accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, not all embodiments, and should not be construed as limiting the scope of implementation of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] This invention provides a heterogeneous catalyst with metal oxide supported on a borosilicate molecular sieve. The catalyst is composed of a support and a metal oxide, wherein the support is a borosilicate molecular sieve BSilicate-1. The heterogeneous catalyst of this invention is obtained by supporting the metal oxide on the borosilicate molecular sieve, with the loading amount of the metal oxide being 0.1% to 5%. The catalyst provided by this invention uses the metal oxide as the active component and disperses it uniformly on the surface of the borosilicate molecular sieve, which can promote the dispersion and stability of the active sites.

[0026] In this invention, depending on the borosilicate ratio, hydrothermal temperature, and time, the topological structure of the borosilicate molecular sieve is any one of Y-type, BEA-type, MFI-type, and CHA-type, and the borosilicate ratio is 0 to 0.2.

[0027] In this invention, the borosilicate molecular sieve is preferably BSilicate-1 with an MFI topology, which has a larger specific surface area and smaller pore size structure, which is more conducive to the diffusion of reactants and products.

[0028] In this invention, the metal oxide is any one of vanadium oxide, molybdenum oxide, or gallium oxide, preferably vanadium oxide.

[0029] In this invention, the precursor salt of the metal oxide is any one of ammonium metavanadate, ammonium molybdate, gallium tetrahydrate, or gallium nitrate hydrate.

[0030] This invention also provides a method for preparing the above-mentioned multiphase catalyst, comprising the following steps: Step a): The silicon source, boron source and organic template agent are mixed evenly in a certain proportion to obtain a gel. The resulting gel is then poured into a hydrothermal reactor lined with polytetrafluoroethylene and crystallized at 150°C for 72 hours. The active component boron is directly fixed in the lattice of the molecular sieve framework through hydrothermal synthesis. After filtration and washing, the gel is dried in an oven at 80°C for 12 hours and then calcined in an air tube furnace at 550°C for 2 hours to obtain a borosilicate molecular sieve carrier. Step b): Dissolve vanadium oxide, molybdenum oxide, and gallium oxide salts in a solution, stir until homogeneous, and then add the solution to the borosilicate molecular sieve support prepared in step a). Heat in a water bath to load the active metal oxide components onto the surface of the borosilicate molecular sieve through impregnation. The process is carried out at 80°C. o After being placed in an oven at C for 12 hours, the product was calcined in an air tube furnace at 550℃ for 6 hours. The calcined product was then passed through a 60-80 mesh sieve to obtain a heterogeneous catalyst of borosilicate molecular sieve supported on metal oxides.

[0031] In this invention, the boron source in step a) is boric acid, the silicon source is fumed silica, and the organic template agent is tetrapropylammonium hydroxide.

[0032] In this invention, the temperature of the water bath in step b) is 80°C. o C, the time is 2 hours, and the solution is either oxalic acid solution or distilled water.

[0033] The heterogeneous catalyst of the borosilicate molecular sieve supported on metal oxides of the present invention directly fixes the active component boron in the lattice of the molecular sieve framework during the synthesis of borosilicate molecular sieves via direct hydrothermal synthesis. Then, the active component metal oxide is loaded onto the surface of the borosilicate molecular sieve by impregnation. The interfacial structure formed by the metal oxide and boron in the borosilicate molecular sieve framework achieves high dispersion of the metal oxide, which is more conducive to the transport of reactants and products. At the same time, the heterogeneous catalyst provided by the present invention uses metal oxide as the active component and interacts with the active component boron in the framework, which can promote the dispersion and stability of active sites and improve the catalytic activity of propane.

[0034] The method for preparing heterogeneous catalysts provided by this invention is simple in terms of process and reaction equipment, easy to operate, suitable for industrial-scale production, and has broad application prospects.

[0035] The present invention also provides the application of the above-mentioned heterogeneous catalyst in the oxidative dehydrogenation of propane to propylene.

[0036] Furthermore, under normal pressure, the reaction temperature is 500–545 °C. o C, the feed space velocity of propane is 2000-10000 mL / (g·h), and a reaction mixture is introduced. The reaction mixture consists of propane, oxygen and nitrogen. The reaction is carried out under the conditions of 0.008-0.04MPa C3H8, 0.008-0.04MPa O2 and 0.058MPa N2.

[0037] Furthermore, the catalyst is loaded with high-temperature resistant quartz wool as a fixed bed, and the catalyst loading amount is 50-150 mg. After loading, the catalyst is pretreated and activated. Under normal temperature conditions, nitrogen gas is introduced at a flow rate of 15-20 mL / min and heated at a heating rate not exceeding 10 °C / min. The temperature is stabilized at 500-545 °C for no less than 20 minutes.

[0038] In this invention, the above-mentioned heterogeneous catalyst is used in the selective oxidative dehydrogenation of propane to olefins, which can improve the catalytic activity of propane. This heterogeneous catalyst exhibits excellent catalytic performance and long-term stability in the propane oxidative dehydrogenation (ODHP) reaction. Within the reaction temperature range, it can suppress excessive oxidation to produce carbon monoxide and carbon dioxide, and can inhibit coke formation, avoiding subsequent gas separation and purification, catalyst regeneration, and other process operations and associated costs. Within the temperature range of 540–545 °C, the propane conversion rate is >45%, the olefin selectivity is >75%, and it can operate stably for >350 hours. Figure 3 As shown.

[0039] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes the borosilicate molecular sieve-supported metal oxide heterogeneous catalyst, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention. Materials, reagents, and equipment used in the embodiments, unless otherwise specified, are commercially available.

[0040] Example 1: Preparation of borosilicate molecular sieve support and catalytic experiments Preparation of borosilicate molecular sieve supports 0.433 g of boric acid was dissolved in 4.8 g of tetrapropylammonium hydroxide aqueous solution and 24 mL of deionized water. The mixture was stirred at room temperature at 500 rpm until homogeneous. 2.5 g of fumed silica was slowly added, and the mixture was vigorously stirred at room temperature for 1 hour at 800 rpm to obtain a gel with a molar ratio of SiO2: B2O3: TPAOH: H2O = 1: 0.086: 0.14: 36. After stirring, the gel was placed in a polytetrafluoroethylene-lined hydrothermal reactor for sedimentation and crystallization at 150 °C for 72 hours. The mixture was then cooled to room temperature, filtered, washed until no obvious foam was observed, dried in an oven at 80 °C for 12 hours, and finally calcined in air at 550 °C for 2 hours at a heating rate of 10 °C / min. The resulting MFI topological borosilicate molecular sieve, designated BSilicate-1, was obtained. Its X-ray diffraction powder pattern is shown below. Figure 1 As shown.

[0041] 2. Propane oxidative dehydrogenation activity test 100 mg of catalyst was mixed with 1 g of quartz sand (60-80 mesh) and loaded into a fixed-bed reaction tube. The mixture was then placed in a fixed-bed reactor for pretreatment and activation. The conditions were as follows: nitrogen gas was introduced at room temperature at a flow rate of 15 mL / min and the temperature was increased at a rate not exceeding 10 °C / min. The temperature was stabilized at 520 °C for at least 20 minutes. A reaction mixture consisting of propane, oxygen, and nitrogen was introduced, with a C3H8:O2 ratio of 1:1.5 and a space velocity of 2000 mL / (g·h). The remaining gas was replenished with nitrogen. The reaction products were monitored in real time by an online gas chromatograph (equipped with a TCD and FID detector).

[0042] Analysis of the reaction tail gas revealed that at 520℃, the propane conversion rate of BSilicate-1 was 8.9%, and the selectivity of the generated propylene was 78.0%.

[0043] Example 2: Comparison of catalytic experiments with different metal oxide catalysts 1. This embodiment provides three different methods for preparing borosilicate molecular sieve catalysts supported on MFI topology, the preparation methods of which include the following steps: (1) 1.5VO x / BSilicate-1: Weigh 34.74 mg of ammonium metavanadate and mix it with 15 g of deionized water. Stir magnetically in a constant temperature water bath at 25 ℃ for 30 minutes to form a homogeneous solution at a stirring speed of 500 rpm. Add 1 g of BSilicate-1 to the ammonium metavanadate solution and stir magnetically in a constant temperature water bath at 80 ℃ for 2 hours to impregnate vanadium oxide onto BSilicate-1 with a loading of 1.5%. Dry the resulting material in an oven at 80 ℃ for 12 hours and finally calcine it at 550 ℃ in air for 2 hours to obtain a heterogeneous catalyst of vanadium oxide supported on borosilicate molecular sieves, with the molecular formula 1.5VO x / BSilicate-1.

[0044] (2) 1.5MoO x / BSilicate-1: Weigh 27.60 mg of ammonium molybdate tetrahydrate and mix it with 15 g of deionized water. Stir magnetically in a 25°C water bath for 30 minutes to form a homogeneous solution at 500 rpm. Add 1 g of BSilicate-1 to the ammonium molybdate solution and stir magnetically in an 80°C water bath for 2 hours to impregnate molybdenum oxide onto BSilicate-1, with a loading of 1.5%. Dry the resulting material in an 80°C oven for 12 hours and finally calcine it at 550°C in air for 2 hours to obtain a borosilicate molecular sieve-supported molybdenum oxide heterogeneous catalyst with the molecular formula 1.5MoO. x / BSilicate-1.

[0045] (3) 1.5GaO x / BSilicate-1: Weigh 55.01 mg of gallium nitrate hydrate and mix it with 15 g of deionized water. Stir magnetically in a constant temperature water bath at 25°C for 30 minutes to form a homogeneous solution at a stirring speed of 500 rpm. Add 1 g of BSilicate-1 to the gallium nitrate solution and stir magnetically in a constant temperature water bath at 80°C for 2 hours to impregnate gallium oxide onto BSilicate-1, with a loading of 1.5%. Dry the resulting material in an oven at 80°C for 12 hours and finally calcine it at 550°C in air for 2 hours to obtain a heterogeneous catalyst with borosilicate molecular sieve-supported gallium oxide, with the molecular formula 1.5GaO. x / BSilicate-1.

[0046] 2. Propane oxidative dehydrogenation activity test 100mg of 1.5 VO x / BSilicate-1、1.5MoO x / BSilicate-1、1.5GaO x The catalyst of / BSilicate-1 was mixed with 1 g of quartz sand (60-80 mesh) and loaded into a fixed-bed reaction tube. It was then placed in a fixed-bed reactor for pretreatment and activation under the following conditions: at room temperature, nitrogen was introduced at a flow rate of 15 mL / min and heated at a rate not exceeding 10 °C / min. The temperature was stabilized at 545 °C for at least 20 minutes. A reaction mixture was then introduced, consisting of propane, oxygen, and nitrogen, with a C3H8:O2 ratio of 1:1.5 and a space velocity of 2000 mL / (g·h). The remaining gas was supplemented by nitrogen. The reaction products were monitored in real time by online gas chromatography (equipped with TCD and FID detectors).

[0047] The average reaction results of the catalyst at a catalytic reaction temperature of 545℃ are as follows: Figure 2 As shown, 1.5VO x The propane conversion of the / BSilicate-1 catalyst was 48.92%, and the propylene selectivity was 60.1%. (1.5 MoO) x The propane conversion of the / BSilicate-1 catalyst was 49.9%, and the propylene selectivity was 48.1%. (1.5 GaO) x The / BSilicate-1 catalyst achieved a propane conversion of 43.7% and a propylene selectivity of 52.5%. Figure 2 The comparison of reaction results shows that, compared with molybdenum oxide or gallium oxide, vanadium oxide, when chosen as the metal oxide, exhibits better catalytic activity in the dehydrogenation of low-carbon alkanes to olefins.

[0048] Example 3: xVO x Preparation and propane oxidative dehydrogenation performance testing of / BSilicate-1 catalyst (where x = 0.1, 0.3, 0.5, 1, 1.5, 2, 3). 1. xVO x Preparation of / BSilicate-1 catalyst (where x = 0.1, 0.3, 0.5, 1, 1.5, 2, 3) Preparation of vanadium source solutions: Weigh out 2.32 mg, 6.95 mg, 11.58 mg, 23.16 mg, 34.74 mg, 46.32 mg, and 69.48 mg of ammonium metavanadate, respectively, and mix them with 15 g of deionized water. Stir magnetically in a constant temperature water bath at 25 ℃ for 30 minutes to form a homogeneous solution, resulting in seven ammonium metavanadate solutions. The stirring speed is 500 rpm.

[0049] 1 g of BSilicate-1 was added to seven portions of ammonium metavanadate solution, and the mixture was magnetically stirred in an 80℃ water bath for 2 hours to impregnate vanadium oxide onto BSilicate-1 with loadings of 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, and 3%, respectively. The resulting material was dried in an 80℃ oven for 12 hours and then calcined at 550℃ in air for 2 hours to obtain a heterogeneous catalyst of vanadium oxide supported on borosilicate molecular sieve, with the molecular formula xVO. x / BSilicate-1. Where x is the mass percentage of metallic vanadium.

[0050] 2. Propane oxidative dehydrogenation activity test 100 mg of the catalyst xVO x / BSilicate-1 (where x = 0.1, 0.3, 0.5, 1, 1.5, 2, 3) was mixed with 1g of quartz sand (60-80 mesh) and then loaded into a fixed-bed reaction tube. The tube was placed in a fixed-bed reactor for pretreatment and activation under the following conditions: at room temperature, nitrogen was introduced at a flow rate of 15 mL / min and the temperature was increased at a rate not exceeding 10 °C / min. The temperature was stabilized at 520 °C for at least 20 minutes. A reaction mixture was then introduced, consisting of propane, oxygen, and nitrogen, with a C3H8:O2 ratio of 1:1.5 and a space velocity of 2000 mL / (g·h). The remaining gas was supplemented by nitrogen. The reaction products were monitored in real time by an online gas chromatograph (equipped with TCD and FID detectors).

[0051] Analysis of the reaction tail gas revealed that when the V content was below 2%, the propane conversion rate increased with the increase of V content. At 545℃, the propane oxidative dehydrogenation performance was optimal when the V content was 1.5%, with a propane conversion rate of 48.9% and a propylene selectivity of 60.1%.

[0052] By analyzing 1.5VO x Monitoring results of the / BSilicate-1 catalyst at different temperatures show that: When the V content is 1.5%, within the temperature range of 500–545℃, the conversion rate of propane increases with increasing temperature, while the selectivity of olefins decreases with increasing temperature.

[0053] Comparative Example 1: Silicate-1 and 1.5VO x Preparation of / Silicate-1 and Testing of Propane Oxidative Dehydrogenation Performance 1. Preparation of two catalysts a) Preparation of Silicate-1 support: 4.8 g of tetrapropylammonium hydroxide aqueous solution and 24 mL of deionized water were added to a beaker and stirred evenly at room temperature at 500 rpm. 2.5 g of fumed silica was slowly added, and the mixture was vigorously stirred at room temperature for 1 hour at 800 rpm to obtain a gel with a molar ratio of SiO2:TPAOH:H2O = 1:0.14:36. After stirring, the gel was placed in a polytetrafluoroethylene-lined hydrothermal reactor for sedimentation and crystallization at 150℃ for 72 hours. The mixture was then cooled to room temperature, filtered, washed until no obvious foam was observed, dried in an oven at 80℃ for 12 hours, and finally calcined in air at 550℃ for 2 hours at a heating rate of 10℃ / min. The resulting MFI topological structure silica molecular sieve was denoted as Silicate-1.

[0054] b) 1.5VO x Preparation of Silicate-1 catalyst: 34.74 mg of ammonium metavanadate was weighed and mixed with 15 g of deionized water. The mixture was magnetically stirred in a constant temperature water bath at 25 °C for 30 minutes to form a homogeneous solution at a stirring speed of 500 rpm. 1 g of Silicate-1 was added to the ammonium metavanadate solution, and the mixture was magnetically stirred in a constant temperature water bath at 80 °C for 2 hours to impregnate Silicate-1 with vanadium oxide at a loading of 1.5%. The resulting material was dried in an oven at 80 °C for 12 h and finally calcined at 550 °C in air for 2 h to obtain a heterogeneous catalyst of vanadium oxide supported on pure silica molecular sieve, with the molecular formula 1.5VO. x / Silicate-1.

[0055] 2. Propane oxidative dehydrogenation activity test 100 mg of catalyst was mixed with 1 g of quartz sand (60-80 mesh) and loaded into a fixed-bed reaction tube. The mixture was then placed in a fixed-bed reactor for pretreatment and activation. The conditions were as follows: nitrogen gas was introduced at room temperature, the flow rate was 15 mL / min, and the temperature was increased at a rate not exceeding 10 °C / min. The temperature was stabilized at 545 °C for at least 20 minutes. A reaction mixture consisting of propane, oxygen, and nitrogen was introduced, with C3H8:O2 = 1:1.5 and a space velocity of 2000 mL / (g·h). The remaining gas was supplemented by nitrogen. The reaction products were monitored in real time by online gas chromatography (equipped with TCD and FID detectors). By analyzing Silicate-1, 1.5VO x / Silicate-1, BSilicate-1, 1.5VO xMonitoring results for / BSilicate-1 showed that after the active component was impregnated and loaded with transition V, the metal oxides in the BSilicate-1 molecular sieve interacted with the active component boron in the molecular sieve framework, which was beneficial to propylene formation. The propane conversion rate of the Silicate-1 catalyst was 10.5%, the propylene selectivity was 75.6%, and the propylene yield was 7.9%. 1.5VO x The / Silicate-1 catalyst achieved a propane conversion of 17.0%, a propylene selectivity of 70.6%, and a propylene yield of 11.9%. The BSilicate-1 catalyst achieved a propane conversion of 23.9%, a propylene selectivity of 66.0%, and a propylene yield of 15.8%. 1.5VO x The propane conversion rate of the BSilicate-1 catalyst was 48.9%, the propylene selectivity was 60.1%, and the propylene yield was 29.3%. The improvement in catalytic performance after loading V onto the BSilicate-1 support was much greater than that after loading V onto the Silicate-1 support, indicating that there is an interaction between the two active sites, V and B. Further loading of metal oxides onto the BSilicate-1 support is beneficial to improving the performance of propane oxidative dehydrogenation to propylene.

[0056] Comparative Example 2: Preparation of V2O5 / BSilicate-1 and Testing of Propane Oxidative Dehydrogenation Performance 1. Preparation of V2O5 / BSilicate-1 catalyst Add 53.5 mg of V2O5 and 2 g of BSilicate-1 to a mortar and grind thoroughly for 1 hour to ensure uniform mixing. The loading is 1.5%, thus obtaining a borosilicate molecular sieve physically mixed vanadium pentoxide catalyst with the molecular formula V2O5 / BSilicate-1.

[0057] 2. Propane oxidative dehydrogenation activity test 100 mg of catalyst was mixed with 1 g of quartz sand (60-80 mesh) and loaded into a fixed-bed reaction tube. The mixture was then placed in a fixed-bed reactor for pretreatment and activation. The conditions were as follows: nitrogen gas was introduced at room temperature at a flow rate of 15 mL / min and the temperature was increased at a rate not exceeding 10 °C / min. The temperature was stabilized at 520 °C for at least 20 minutes. A reaction mixture consisting of propane, oxygen, and nitrogen was introduced, with a C3H8:O2 ratio of 1:1.5 and a space velocity of 2000 mL / (g·h). The remaining gas was supplemented by nitrogen. The reaction products were monitored in real time by online gas chromatography (equipped with TCD and FID detectors).

[0058] The propane conversion of the physically mixed V₂O₅ / BSilicate-1 catalyst was only 18.41%, compared to 1.5VO₂.x The low / BSilicate-1 catalyst level indicates that the borosilicate molecular sieve-supported vanadium oxide composite catalyst prepared by the impregnation method can promote the improvement of propane oxidative dehydrogenation performance through the BOV synergistic effect between vanadium and boron.

[0059] The methods for calculating propane conversion and product selectivity are as follows: (1) Product selectivity = Content of a certain product / Total content of all products × 100% (2) Propane conversion rate = (raw material flow rate × propane content – ​​reaction tail gas flow rate × unreacted propane content) / raw material flow rate × propane content × 100%.

[0060] The above embodiments are merely illustrative of the methods and core ideas of this invention. It should be noted that the above embodiments do not exhaustively describe all details, nor do they limit the invention to the embodiments described above. All preparation methods and applications disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the raw materials and preparation methods, etc., based on the content of this document. Although the methods and preparation methods of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the raw materials and methods described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technology. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included within the spirit, scope, and content of this invention.

Claims

1. A heterogeneous catalyst with borosilicate molecular sieve supported on metal oxide, characterized in that: The catalyst is composed of a support and a metal oxide. The support is a borosilicate molecular sieve BSilicate-1, and the metal oxide is supported on the borosilicate molecular sieve at a loading of 0.1% to 5%.

2. The heterogeneous catalyst with borosilicate molecular sieve supported on metal oxides according to claim 1, characterized in that: Depending on the borosilicate ratio, hydrothermal temperature, and time, the topology of the borosilicate molecular sieve can be any one of Y-type, BEA-type, MFI-type, and CHA-type, with a borosilicate ratio of 0 to 0.

2. The preferred borosilicate molecular sieve is BSilicate-1 with an MFI topology.

3. The heterogeneous catalyst with borosilicate molecular sieve supported on metal oxides according to claim 1, characterized in that: The metal oxide is any one of vanadium oxide, molybdenum oxide, or gallium oxide, preferably vanadium oxide.

4. The heterogeneous catalyst of claim 1 or 3, wherein the borosilicate molecular sieve is a boron-containing silicate molecular sieve. The precursor salt of the metal oxide is any hydrate of ammonium metavanadate, ammonium molybdate, gallium tetrahydrate, or gallium nitrate.

5. A process for the preparation of a heterogeneous catalyst of a borosilicate molecular sieve loaded with a metal oxide according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step a): The silicon source, boron source and organic template agent are mixed evenly in a certain proportion to obtain a gel. The resulting gel is then poured into a hydrothermal reactor lined with polytetrafluoroethylene and crystallized at 150°C for 72 hours. The active component boron is directly fixed in the lattice of the molecular sieve framework through hydrothermal synthesis. After filtration and washing, the gel is dried in an oven at 80°C for 12 hours and then calcined in an air tube furnace at 550°C for 2 hours to obtain a borosilicate molecular sieve carrier. Step b): Dissolve vanadium oxide, molybdenum oxide, and gallium oxide salts in a solution, stir until homogeneous, and then add the solution to the borosilicate molecular sieve support prepared in step a). Heat in a water bath to load the active metal oxide components onto the surface of the borosilicate molecular sieve through impregnation. The process is carried out at 80°C. o After being placed in an oven at C for 12 hours, the product was calcined in an air tube furnace at 550℃ for 6 hours. The calcined product was then passed through a 60-80 mesh sieve to obtain a heterogeneous catalyst of borosilicate molecular sieve supported on metal oxides.

6. The method for preparing the heterogeneous catalyst with metal oxide supported on borosilicate molecular sieve according to claim 5, characterized in that: The boron source mentioned in step a) is boric acid, the silicon source is fumed silica, and the organic template agent is tetrapropylammonium hydroxide.

7. The method for preparing the heterogeneous catalyst of borosilicate molecular sieve supported on metal oxide according to claim 5, characterized in that: The temperature of the water bath in step b) is 80 o C for 2 hours, the solution being either oxalic acid or distilled water.

8. The application of the heterogeneous catalyst of borosilicate molecular sieve supported on metal oxide according to any one of claims 1-4 or the heterogeneous catalyst prepared by any one of claims 5-7 in the oxidative dehydrogenation of propane to propylene.

9. Use according to claim 8, characterized in that: At normal pressure, the reaction temperature is 500–545°C. o C, the feed space velocity of propane is 2000-10000 mL / (g·h), and a reaction mixture is introduced. The reaction mixture consists of propane, oxygen and nitrogen. The reaction is carried out under the conditions of 0.008-0.04MPa C3H8, 0.008-0.04MPa O2 and 0.058MPa N2.

10. Use according to claim 8, characterized in that: High-temperature resistant quartz wool was used as the fixed bed for catalyst loading, and the catalyst loading amount was 50-150 mg. After loading, the catalyst was pretreated and activated. Nitrogen gas was introduced at room temperature at a flow rate of 15-20 mL / min and heated at a heating rate not exceeding 10 °C / min. The temperature was stabilized at 500-545 °C for no less than 20 minutes.

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