Photo-thermal coupling composite material catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalyst development and application, and particularly relates to a photo-thermal coupling composite material catalyst, namely a nickel oxide nanoparticle modified carbon nitride composite material. Nickel oxide nanoparticles with excellent low-temperature alkane activation capability are used as an active center to form a photo-thermal coupling effect. The invention also provides a preparation method, the melamine and the metal nickel salt are used as raw materials, the melamine and the metal nickel salt are sequentially dissolved, dried, calcined and oxidized, the preparation process is simple, and the preparation method is suitable for low-cost industrial production. The invention provides the catalytic application of the catalyst in propylene preparation through propane dehydrogenation, the catalyst material can be directly filled in a photo-thermal synergistic reactor, and the higher propylene yield is realized under the condition of low reaction temperature coupling illumination.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst development and application, and specifically relates to a photothermal coupling composite material catalyst and a preparation method and application thereof. Background Art

[0002] As an important raw material in the chemical industry, propylene is widely used in the production of a variety of key organic chemicals such as polypropylene, propylene oxide and centella asiatica. Compared with the commercially developed direct propane dehydrogenation reaction, the propane oxidative dehydrogenation reaction has the characteristics of exothermic re-reaction. In theory, it can achieve a higher conversion rate at a lower temperature (<500°C) with very little carbon deposition. This makes propane oxidative dehydrogenation very promising to replace direct propane dehydrogenation for propylene production. However, because the carbon-hydrogen bonds in propane are more stable than those in propylene, the main product propylene is more easily peroxidized to CO x Furthermore, the carbon-carbon single bond in propane is more easily cleaved, forming ethylene and methane, which results in a decrease in the selectivity of propylene in the propane oxidative dehydrogenation reaction. For example, when the propane conversion rate is 10%, the propylene selectivity of such conventional catalysts typically drops below 60%.

[0003] After decades of research, significant progress has been made in propane oxidative dehydrogenation (ODH). Extensive research has resulted in the development of a series of catalysts with exceptional selectivity control capabilities. For example, graphene-like hexagonal boron nitride and other boron-based material derivatives can maintain a total olefin selectivity of 90% at moderate conversions (approximately 14%). However, current ODH catalysts typically require high reaction temperatures, often exceeding 500°C, to achieve satisfactory propane conversion. However, excessively high reaction temperatures not only increase reaction energy consumption but also, at high temperatures, carbon-carbon single bonds (with an average bond energy of 347 kJ / mol) are more susceptible to cleavage than carbon-hydrogen bonds (with an average bond energy of 401 kJ / mol), leading to the formation of deep oxidation products such as carbon monoxide and carbon dioxide, significantly reducing the selectivity and single-pass yield of the target product, propylene. Therefore, designing new catalytic materials and reaction modes that can reduce reaction temperatures, inhibit deep oxidation reactions, improve propylene selectivity, and maintain high propane conversion remains a major challenge in this field. Summary of the Invention

[0004] In response to the technical problems in the prior art, the present invention aims to provide a photothermal-coupled composite catalyst that addresses the high reaction temperature and low reaction yield issues of existing propane oxidative dehydrogenation technologies. Specifically, the present invention takes into account the coupling effect of thermal catalysis and photocatalysis to design a photothermal-coupled composite catalyst that achieves a high propylene yield under low reaction temperature coupled with illumination conditions. Furthermore, the catalyst utilizes only melamine and a metal nickel salt as raw materials, which are abundant resources and low in cost. The present invention also provides a method for preparing the catalyst, making the preparation process simpler and easier to implement.

[0005] To achieve the above purpose, the technical solution provided by the present invention is:

[0006] The present invention provides a photothermal coupling composite catalyst, comprising carbon nitride and nickel oxide nanoparticles. The microscopic morphology of the carbon nitride is a two-dimensional layered stacking structure, the size of the nickel oxide nanoparticles is 5-7nm, and the nickel oxide nanoparticles are evenly distributed on the surface of the carbon nitride. The photothermal coupling composite catalyst, i.e., the nickel oxide nanoparticle-modified carbon nitride composite material, has an overall porous structure with a specific surface area of ​​60-80m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0007] The working principle of the present invention is that two-dimensional layered carbon nitride can stabilize nickel oxide nanoparticles, and is tightly coupled at the nanoscale. Carbon nitride with excellent thermal stability and light stability is used as a carrier, and nickel oxide nanoparticles with excellent low-temperature alkane activation ability are used as active centers. The two act synergistically to significantly increase the activation ability of propane at low temperatures. At the same time, light increases the lattice oxygen activity of the material, improves its surface catalytic efficiency, forms a light-heat coupling effect, and achieves a higher propylene yield under low reaction temperature coupled light conditions.

[0008] The present invention provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0009] Step 1: Add melamine and metal nickel salt into deionized water and stir for 15-60 minutes to prepare a solution.

[0010] Step 2: Stir and heat the solution obtained in step 1 until the water is evaporated to dryness to obtain a precursor.

[0011] Step 3: Heat the precursor obtained in step 2 under an inert gas atmosphere, cool it to room temperature, and grind it into powder.

[0012] Step 4: heating the powder obtained in step 3 in a static oxidizing gas atmosphere and naturally cooling it to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0013] Based on the above technical solution, the metal nickel salt in step one is one of nickel nitrate, nickel sulfate, and nickel chloride. The concentration of melamine in step one is 1-10wt%, and the molar concentration of the metal nickel salt is 0.1-1wt%. The heating temperature in step two is 60-90°C. The inert gas in step three is one of nitrogen, argon, or helium, and the gas flow rate of the inert atmosphere is 50-100mL / min. The heating temperature in step three is 400-600°C, and the heating time is 2-6h. The oxidizing gas in step four is one of air and oxygen. The heating temperature in step four is 300-600°C, and the heating time is 1-5h.

[0014] This invention provides a method for preparing a photothermal coupling composite catalyst. The catalyst is prepared using melamine and a metal nickel salt as raw materials through the sequential steps of dissolution, drying, calcination, and oxidation. The resulting photothermal coupling composite catalyst, a nickel oxide nanoparticle-modified carbon nitride composite material, exhibits a porous structure and a suitable band gap, enabling synergistic coupling of photocatalysis and thermal catalysis, achieving high propylene yields at low temperatures and under illumination. The preparation method features a simple synthesis process, a broad and economical raw material supply, and is suitable for low-carbon transformation of the propane dehydrogenation to propylene process.

[0015] The present invention provides an application of a photothermal coupling composite material catalyst in the dehydrogenation of propane to produce propylene.

[0016] Based on the above technical solution, the preparation of propylene by dehydrogenation of propane includes the following steps:

[0017] Step 1: Place the prepared photothermal coupling composite material catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add an appropriate amount of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0018] Step 2: Introduce a reaction mixture containing propane, oxygen, and diluent into the quartz tube, raise the temperature to 370-430°C, and increase the light intensity to 0.1-0.5W / cm -2 The propane dehydrogenation reaction to produce propylene was carried out at a reaction hourly space velocity of 4200 mL / h / g in the fixed-bed reactor. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / diluent gas was 1:1-3:10-15.

[0019] Preferably, the volume flow rate of propane in the reaction mixture is 1 mL / min, the volume flow rate of oxygen is 1 mL / min, and the remaining gas is a diluent gas; the diluent gas is helium, nitrogen or argon, and more preferably, the diluent gas is helium.

[0020] The photothermal coupling composite catalyst of the present invention, namely the nickel oxide nanoparticle-modified carbon nitride composite material, can be directly loaded into a fixed bed reactor when applied to the reaction process of propane dehydrogenation to propylene, without the need for conventional powder granulation and molding steps, making it more convenient to use. It is a composite material composed of NiO nanoparticles uniformly dispersed on graphite carbon nitride, and the two-dimensional layered structure of graphite carbon nitride can stabilize the nickel oxide nanoparticles to form metal oxide active centers containing oxygen vacancies, thereby ensuring the stability of the composite material in the catalytic reaction process of catalyzing the oxidative dehydrogenation of propylene to propylene. In addition, the appropriate band gap can couple photocatalysis and thermal catalysis to form a synergistic effect. At a reaction temperature of 430°C, the propane conversion rate under thermal catalytic conditions reached 14.37%. Under photothermal coupling catalytic conditions, the conversion rate further increased to 23.98%, an increase of 9.61%. The photothermal coupling strategy provides a practical way to activate light alkanes under mild conditions.

[0021] The beneficial effects of the technical solution provided by the present invention are:

[0022] 1. This invention provides a photothermal-coupled composite catalyst with strong light absorption and a suitable bandgap, capable of coupling photocatalysis and thermal catalysis to create a synergistic effect. Thermal energy provides the activation energy required to overcome reaction barriers, while light irradiation enhances the activity of lattice oxygen, promotes the formation of oxygen vacancies, and accelerates surface oxidation reactions, thereby accelerating the reaction efficiency of reactant molecules and improving the conversion rate of reactants.

[0023] 2. The present invention also provides a method for preparing a photothermal coupling composite catalyst, using melamine and a metal nickel salt as raw materials, through the sequential steps of dissolution, drying, calcination, and oxidation. The resulting photothermal coupling composite catalyst, a nickel oxide nanoparticle-modified carbon nitride composite material, exhibits a porous structure and a suitable band gap, enabling synergistic coupling of photocatalysis and thermal catalysis, achieving high propylene yields at low temperatures and under illumination. The preparation method is simple in its synthesis, utilizes a broad and economical raw material supply, and is suitable for low-carbon transformation of the propane dehydrogenation to propylene process.

[0024] 3. The present invention provides a catalytic application of a photothermal coupling composite catalyst in the oxidative dehydrogenation of propane to propylene. As a catalyst material, it can be directly loaded into a fixed-bed reactor without the need for conventional powder granulation and molding steps, making it more convenient to use. It has good stability and exhibits an excellent propane conversion rate of 23.98% at a temperature of 430°C under photothermal coupling conditions. At the same conversion rate, the reaction temperature is lower than that of most existing boron-based catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The X-ray powder diffraction pattern (PXRD) of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron microscope (SEM) image of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention;

[0027] Figure 3 This is a transmission electron microscope (TEM) image of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention;

[0028] Figure 4 This is the thermogravimetric curve (TGA) of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention in an air atmosphere;

[0029] Figure 5 This is a low-temperature nitrogen adsorption-desorption curve of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention;

[0030] Figure 6 This is a pore size distribution diagram of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention;

[0031] Figure 7 Comparison of propylene yields in propane dehydrogenation to propylene reactions using the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention under thermal catalysis and photothermal coupled catalysis;

[0032] Figure 8 This is a stability test of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention in the thermal catalytic and photothermal coupled catalytic propane dehydrogenation to propylene reaction. DETAILED DESCRIPTION

[0033] The following will be combined with the contents of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art to which the present invention pertains. The terms used in this specification are intended only to describe specific embodiments and are not intended to limit the present invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the listed items. It should be understood that, unless otherwise specified, the various raw materials in the present invention may be commercially available.

[0035] Figure 1 The X-ray powder diffraction pattern (PXRD) of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention shows that the prepared nickel oxide nanoparticle-modified carbon nitride composite material exhibits five different diffraction peaks. Two prominent peaks appear at 13.1° and 27.6°, reflecting the periodic structure (100) peak of the coplanar tris-s-triazine and the interlayer stacking (002) peak of the conjugated aromatic structure, respectively. Three smaller peaks appear at 37.2°, 43.4°, and 62.9°, corresponding to the (111), (200), and (220) planes of cubic NiO, respectively.

[0036] Figure 2 This is a scanning electron microscope (SEM) image of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention. It can be seen that the prepared nickel oxide nanoparticle-modified carbon nitride composite material retains the two-dimensional layered structure of graphite carbon nitride.

[0037] Figure 3 This is a transmission electron microscope (TEM) image of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention. It can be seen that the NiO nanoparticles are evenly distributed, and the two-dimensional layered structure of graphitic carbon nitride can stabilize the nickel oxide nanoparticles, which is beneficial to the stability of the active centers.

[0038] Figure 4 The thermogravimetric curve (TGA) of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention in an air atmosphere shows that the catalyst has good thermal stability in the reaction atmosphere.

[0039] Figure 5The low-temperature nitrogen adsorption-desorption curve of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention shows that the composite material exhibits a typical IV-type curve and an H3-type hysteresis loop, indicating that it has a mesoporous structure.

[0040] Figure 6 This is the pore size distribution diagram of the nickel oxide nanoparticle modified carbon nitride composite material prepared in Example 1 of the present invention. It can be seen that its main pore size distribution is mainly concentrated in the range of 5-20 nm.

[0041] Figure 7 The propylene yield of the nickel oxide nanoparticle-modified carbon nitride composite material prepared in Example 1 of the present invention in the propane dehydrogenation to propylene reaction under thermal catalysis and photothermal coupling catalysis is compared. It can be seen that the reaction activity of the catalyst is significantly improved under photothermal coupling conditions.

[0042] Figure 8 The stability test of the nickel oxide nanoparticle modified carbon nitride composite material prepared in Example 1 of the present invention in the reaction of propane dehydrogenation to propylene by thermal catalysis and photothermal coupling catalysis shows that the catalyst has good thermal stability under pure heat alone and photothermal coupling conditions.

[0043] The calculation method of conversion rate and selectivity in this application is as follows:

[0044] Alkane conversion rate (%) = [(moles of alkane before reaction - moles of alkane after reaction) / moles of alkane before reaction] × 100%;

[0045] Product selectivity (%) = [carbon number in the product / (carbon number of alkane before reaction - carbon number of alkane after reaction)] × 100%;

[0046] Product yield (%) = alkane conversion (%) × product selectivity (%);

[0047] Example 1

[0048] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​60-80m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0049] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0050] Step 1: 10 g of melamine and 600 mg of nickel nitrate hexahydrate are added to 200 ml of deionized water and stirred for 30 minutes to prepare a solution.

[0051] Step 2: Stir and heat the solution obtained in step 1 in a 90° C. water bath until the water is evaporated to dryness to obtain a precursor.

[0052] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 100 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0053] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 450° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0054] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0055] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0056] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 430°C, and the light intensity is raised to 0.26W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:1:12. The product was detected by online gas chromatography, and the test results showed a propane conversion of 23.98% and a propylene selectivity of 48.09%.

[0057] Example 2

[0058] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​40-60m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0059] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0060] Step 1: 10 g of melamine and 400 mg of nickel nitrate hexahydrate are added to 200 ml of deionized water and stirred for 50 minutes to prepare a solution.

[0061] Step 2: Stir and heat the solution obtained in step 1 in a water bath at 85° C. until the water is evaporated to dryness to obtain a precursor.

[0062] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 80 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0063] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 450° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0064] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0065] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0066] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 400°C, and the light intensity is raised to 0.26W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:1:12. The product was detected by online gas chromatography, and the test results showed a propane conversion of 7.21% and a propylene selectivity of 60.23%.

[0067] Example 3

[0068] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​40-60m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0069] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0070] Step 1: 8 g of melamine and 600 mg of nickel nitrate hexahydrate are added to 200 ml of deionized water and stirred for 30 minutes to prepare a solution.

[0071] Step 2: Stir and heat the solution obtained in step 1 in a water bath at 75° C. until the water is evaporated to dryness to obtain a precursor.

[0072] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 100 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0073] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 430° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0074] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0075] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0076] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 400°C, and the light intensity is raised to 0.26W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:1:12. The product was detected by online gas chromatography, and the test results showed a propane conversion of 12.35% and a propylene selectivity of 24.56%.

[0077] Example 4

[0078] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​40-60m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0079] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0080] Step 1: 10 g of melamine and 1000 mg of nickel nitrate hexahydrate are added to 200 ml of deionized water and stirred for 30 minutes to prepare a solution.

[0081] Step 2: Stir and heat the solution obtained in step 1 in a water bath at 75° C. until the water is evaporated to dryness to obtain a precursor.

[0082] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 80 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0083] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 450° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0084] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0085] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0086] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 400°C, and the light intensity is raised to 0.26W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:1:12. The product was detected by online gas chromatography, and the test results showed a propane conversion of 13.54% and a propylene selectivity of 23.52%.

[0087] Example 5

[0088] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​60-80m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0089] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0090] Step 1: 8 g of melamine and 600 mg of nickel chloride hexahydrate are stirred in 200 ml of deionized water for 60 minutes to prepare a solution.

[0091] Step 2: Stir and heat the solution obtained in step 1 in a water bath at 85° C. until the water is evaporated to dryness to obtain a precursor.

[0092] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 60 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0093] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 450° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0094] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0095] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0096] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 400°C, and the light intensity is raised to 0.33W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:1:12. The product was detected by online gas chromatography, and the test results showed a propane conversion of 13.54% and a propylene selectivity of 58.97%.

[0097] Example 6

[0098] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​60-80m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0099] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0100] Step 1: 6 g of melamine and 600 mg of nickel nitrate hexahydrate are stirred in 200 ml of deionized water for 60 minutes to prepare a solution.

[0101] Step 2: Stir and heat the solution obtained in step 1 in a 90° C. water bath until the water is evaporated to dryness to obtain a precursor.

[0102] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 60 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0103] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 450° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0104] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0105] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0106] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 400°C, and the light intensity is raised to 0.33W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data collection was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:2:11. The product was detected by online gas chromatography, and the test results showed a propane conversion of 14.54% and a propylene selectivity of 28.97%.

[0107] Example 7

[0108] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​60-80m 2 / g, the pore size is mainly distributed in the range of 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0109] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0110] Step 1: 4 g of melamine and 300 mg of nickel chloride hexahydrate are stirred in 200 ml of deionized water for 60 minutes to prepare a solution.

[0111] Step 2: Stir and heat the solution obtained in step 1 in a 90° C. water bath until the water is evaporated to dryness to obtain a precursor.

[0112] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 3° C. / min and a gas flow rate of 100 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0113] Step 4: Heat-treat 2 g of the powder obtained in step 3 at 450° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0114] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0115] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0116] Step 2: A reaction mixture containing propane, oxygen, and diluent gas is introduced into the quartz tube, the temperature is raised to 400°C, and the light intensity is raised to 0.33W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data collection was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:2:11. The product was detected by online gas chromatography, and the test results showed a propane conversion of 8.64% and a propylene selectivity of 58.97%.

[0117] Example 8

[0118] This embodiment provides a photothermal coupling composite catalyst with a specific surface area of ​​60-80m 2 / g, the pore volume is pore diameter mainly distributed in 5-20nm, the band gap width of the composite catalyst is 2.0-2.5eV, and it can absorb visible light in the wavelength range of 200-600nm.

[0119] This embodiment provides a method for preparing a photothermal coupled composite catalyst, comprising the following steps:

[0120] Step 1: 8 g of melamine and 500 mg of nickel sulfate heptahydrate are stirred in 200 ml of deionized water for 40 minutes to prepare a solution.

[0121] Step 2: Stir and heat the solution obtained in step 1 in a water bath at 80° C. until the water is evaporated to dryness to obtain a precursor.

[0122] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 3° C. / min and a gas flow rate of 60 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0123] Step 4: Heat-treat 3 g of the powder obtained in step 3 at 430° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

[0124] This embodiment also provides an application of a photothermal coupled composite catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0125] Step 1: Place 0.2 g of the prepared photothermal coupling composite catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0126] Step 2: introduce a reaction mixture containing propane, oxygen and diluent into the quartz tube, raise the temperature to 400°C, and increase the light intensity to 0.30W / cm -2 The fixed-bed reactor was subjected to a propane dehydrogenation reaction to produce propylene, with a reaction hourly space velocity of 4200 mL / h / g. After stabilization for 30 minutes, the product was detected by online gas chromatography and data acquisition was performed. Preferably, the volume ratio of propane / oxygen / helium was 1:3:10. The product was detected by online gas chromatography, and the test results showed a propane conversion of 9.52% and a propylene selectivity of 57.97%.

[0127] Comparative Example 1

[0128] In this comparative example, carbon nitride material was selected as a catalyst and applied to the propane dehydrogenation reaction to produce propylene. The specific steps are as follows:

[0129] Step 1: Add 8-mercaptocyanurate (3-mercaptocyanurate) into 200 ml of deionized water and stir for 30 minutes to prepare a solution.

[0130] Step 2: Stir and heat the solution obtained in step 1 in a 90° C. water bath until the water is evaporated to dryness to obtain a precursor.

[0131] Step 3: Heat-treat the precursor obtained in step 2 at 550° C. for 4 h in an argon inert gas atmosphere with a heating rate of 2° C. / min and a gas flow rate of 100 ml / min. After cooling to room temperature, take it out and grind it into powder.

[0132] Step 4: heat-treat 2 g of the powder obtained in step 3 at 430° C. for 3 h in a static air atmosphere at a heating rate of 10° C. / min, and naturally cool to room temperature to obtain a carbon nitride material.

[0133] This embodiment also provides the use of a carbon nitride material catalyst in the dehydrogenation of propane to produce propylene. Specifically, the dehydrogenation of propane to produce propylene includes the following steps:

[0134] Step 1: Place 0.2 g of the prepared carbon nitride material as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add 0.5 g of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate.

[0135] Step 2: A reaction mixture containing propane, oxygen, and a diluent gas is introduced into a quartz tube, and the temperature is raised to 410°C to perform a propane dehydrogenation reaction to produce propylene. The reaction time space velocity of the fixed bed reactor is 4200 mL / h / g. After stabilization for 30 minutes, the product is detected by online gas chromatography and data is collected. Preferably, the volume ratio of propane / oxygen / helium is 1:1:12, and the product is detected by online gas chromatography. The test results show that the conversion rate of propane is 1%.

[0136] Comparative Example 2

[0137] In this comparative example, a supported vanadium catalyst was selected and applied to the propane dehydrogenation to propylene reaction. The specific steps are as follows:

[0138] Step 1: directly loading ammonium metavanadate onto a commercially available high-surface-area SiO2 material, and then treating it at 500°C for three hours in an air atmosphere to obtain a V / SiO2 catalyst;

[0139] Step 2: Weigh 1.0 g of the V / SiO2 catalyst prepared in step 1, place it in a quartz tube in a fixed bed reactor, and heat it to 390°C at 1°C / min under air atmosphere;

[0140] Step 3: After the temperature in step 3 stabilizes, a reaction mixture is introduced with a feed gas ratio of propane: oxygen: helium = 1:1:3, a reaction hourly space velocity of 5.4 L / g / h, and a reaction temperature of 430°C. After stabilization for half an hour, the product is detected by gas chromatography. The test results show that the composition of the reaction mixture remains unchanged, and propane does not react with oxygen to produce propylene. The reaction temperature is further increased to 530°C. After stabilization for half an hour, the product is detected by gas chromatography. The test results show that the conversion of propane is 18.7% and the selectivity of propylene is 75%.

[0141] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims, not the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be included within the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0142] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A photothermal coupled composite catalyst for propane dehydrogenation to propylene, characterized in that: The photothermal coupling composite catalyst, i.e., the nickel oxide nanoparticle-modified carbon nitride composite material, has a porous structure as a whole and a specific surface area of ​​60-80 m 2 g -1 The pore size is mainly distributed in the range of 5-20 nm. The band gap width of the composite catalyst is 2.0-2.5 eV, and it can absorb visible light in the wavelength range of 200-600 nm. The preparation method of the catalyst comprises the following steps: Step 1: Add melamine and metal nickel salt into deionized water and stir for 15-60 minutes to prepare a solution. Step 2: Stir and heat the solution obtained in step 1 until the water is evaporated to dryness to obtain a precursor. Step 3: Heat the precursor obtained in step 2 under an inert gas atmosphere, cool it to room temperature, and grind it into powder. Step 4: heating the powder obtained in step 3 in a static oxidizing gas atmosphere and naturally cooling it to room temperature to obtain a nickel oxide nanoparticle-modified carbon nitride composite material.

2. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: The metal nickel salt in step 1 is one of nickel nitrate, nickel sulfate and nickel chloride.

3. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: The concentration of melamine in step 1 is 1-10 wt %, and the molar concentration of the metal nickel salt is 0.1-1 wt %.

4. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: The heating temperature in the step 2 is 60-90°C.

5. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: The inert gas in step 3 is one of nitrogen, argon or helium, and the gas flow rate of the inert atmosphere is 50-100 mL / min.

6. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: In the step 3, the heating temperature is 400-600° C. and the heating time is 2-6 hours.

7. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: The oxidizing gas in step 4 is one of air and oxygen.

8. The photothermal coupled composite catalyst for propane dehydrogenation to propylene according to claim 1, characterized in that: The heating temperature in step 4 is 300-600° C., and the heating time is 1-5 hours.

9. Use of the photothermal coupling composite catalyst according to any one of claims 1 to 8 in the dehydrogenation of propane to produce propylene.

10. Use of the photothermal coupling composite catalyst according to claim 9 in the dehydrogenation of propane to propylene, characterized in that: The preparation of propylene by dehydrogenation of propane comprises the following steps: Step 1: Place the prepared dual-photothermal coupling composite material catalyst, i.e., nickel oxide nanoparticle-modified carbon nitride composite material, as a catalyst in a quartz tube in a fixed-bed photothermal synergistic microreactor, and add an appropriate amount of quartz sand; the purpose of adding quartz sand is to reduce the dead volume, shorten the residence time, and obtain a better reaction space-time rate. Step 2: introduce a reaction mixture containing propane, oxygen and diluent into the quartz tube, raise the temperature to 500-600°C, and increase the light intensity to 0.1-0.5W cm -2 , carry out propane dehydrogenation to produce propylene, the reaction time space velocity of the fixed bed reactor is 3600-7200mLh -1 g -1 After stabilization for 30 minutes, the product is detected by online gas chromatography and data acquisition is performed. Preferably, the volume ratio of propane / oxygen / diluent is 1:1-3:10-15.

11. Use of the dual-site reaction coupled composite catalyst according to claim 9 in the dehydrogenation of propane to propylene, characterized in that: The volume ratio of propane / carbon dioxide / diluent gas in step 2 is 1:1-3:10-15.

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