Nickel-molybdenum alloy composite material, preparation method and application thereof, and method for producing light olefins by dehydrogenation of light alkane by oxidation of carbon dioxide

Abstract

The present invention belongs to the field of catalyst technology, and specifically relates to a nickel-molybdenum alloy composite material, a preparation method and application thereof, and a method for producing light olefins by dehydrogenating light alkanes using carbon dioxide. The present invention provides a nickel-molybdenum alloy composite material, comprising a carrier and an active component supported on the surface and in the pores of the carrier, wherein the active component comprises a nickel-molybdenum alloy. The results of the examples show that when the nickel-molybdenum alloy composite material provided by the present invention is used in the reaction of producing ethylene by dehydrogenating ethane using carbon dioxide, the ethane conversion rate, the carbon dioxide conversion rate, and the ethylene selectivity are all at a high level. At the same time, the nickel-molybdenum alloy composite material provided by the present invention has good stability, slow deactivation, low toxicity, and low pollution.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst technology, and specifically relates to a nickel-molybdenum alloy composite material, a preparation method and application thereof, and a method for producing light olefins by dehydrogenating light alkanes oxidizing with carbon dioxide. Background Art

[0002] Ethylene is one of the world's most important bulk chemical products and a key intermediate in the petrochemical industry. It is used to produce polymer materials such as polyethylene, polystyrene, and polyvinyl chloride; a range of organic chemicals such as ethylene oxide, vinyl chloride, styrene, and ethylene glycol; and other bulk chemical products such as synthetic fibers, synthetic rubber, and synthetic plastics. Therefore, ethylene plays a vital role in the national economy.

[0003] Currently, ethylene is primarily produced through ethane steam cracking. This process involves high reaction temperatures, significant energy consumption, and the potential for a series of side reactions. Due to thermodynamic constraints, it is difficult to increase conversion and yield. Furthermore, the catalyst used in ethane cracking rapidly accumulates carbon, requiring repeated regeneration. The process is complex, requiring significant equipment and investment. Ethane cracking also results in significant carbon dioxide emissions, which is inconsistent with the principle of energy conservation and emission reduction.

[0004] On the other hand, carbon dioxide is widely present in nature and is the primary culprit behind global warming. Therefore, research into its resourceful utilization is crucial. Using the greenhouse gas carbon dioxide as a mild oxidant for the selective oxidative dehydrogenation of ethane to ethylene is a novel approach. Adding carbon dioxide to the ethane dehydrogenation reaction system offers the following benefits: 1) It improves equilibrium conversion; 2) As a mild oxidant, it prevents deep oxidation of ethane, ensuring selectivity for the ethylene product; 3) It provides some energy for the endothermic dehydrogenation reaction, lowering the reaction temperature; 4) It removes carbon deposits, improving catalyst stability; and 5) it consumes the greenhouse gas carbon dioxide.

[0005] Cr-based catalysts are considered to be the best catalysts discovered for the oxidative dehydrogenation of light alkanes to light olefins via carbon dioxide, demonstrating high alkane conversion rates in a short period of time. However, Cr-based catalysts are somewhat toxic, requiring caution in their preparation, use, and disposal, thus limiting their widespread application. Competitive adsorption of ethane and carbon dioxide by supported Ga2O3 catalysts results in low ethane conversion rates. Summary of the Invention

[0006] In view of this, the present invention provides a nickel-molybdenum alloy composite material, its preparation method and application, and a method for producing light olefins by the dehydrogenation of light alkanes using carbon dioxide. When the nickel-molybdenum alloy material provided by the present invention is used in the dehydrogenation of light alkanes using carbon dioxide to produce light olefins, the conversion rate of light alkanes is high, and the yield and selectivity of light olefins are high.

[0007] In order to solve the above technical problems, the present invention provides a nickel-molybdenum alloy composite material, comprising a carrier and an active component loaded on the surface and in the pores of the carrier, wherein the active component comprises a nickel-molybdenum alloy.

[0008] Preferably, the nickel element in the nickel-molybdenum alloy accounts for 0.5-10% of the mass percentage of the carrier; the molybdenum element in the nickel-molybdenum alloy accounts for 0.5-10% of the mass percentage of the carrier.

[0009] Preferably, the particle size of the nickel-molybdenum alloy is 5 to 15 nm.

[0010] Preferably, the carrier includes one or more of γ-Al2O3, MOR structure molecular sieve, SAPO series molecular sieve, USY series molecular sieve and NaY molecular sieve.

[0011] The present invention provides a method for preparing the nickel-molybdenum alloy composite material described in the above technical solution, comprising the following steps:

[0012] Mixing an inorganic nickel salt, an inorganic molybdenum salt, a carrier and a dispersing solvent to load the metal salt to obtain a carrier-metal salt dispersion;

[0013] calcining the support-metal salt dispersion in a closed environment to obtain a composite material precursor, wherein the composite material precursor includes a support and a metal oxide;

[0014] The composite material precursor is subjected to a reduction reaction in a reducing gas to obtain the nickel-molybdenum alloy composite material.

[0015] Preferably, the inorganic nickel salt includes one or more of nickel nitrate, nickel sulfate, nickel chloride and nickel acetate;

[0016] The inorganic molybdenum salt includes one or more of molybdenum sulfate, ammonium molybdate, sodium molybdate and phosphomolybdic acid;

[0017] The molar ratio of the inorganic nickel salt to the inorganic molybdenum salt is 1:(0.1-10).

[0018] Preferably, the mass ratio of the carrier to the inorganic nickel salt is 1:(0.01-0.5).

[0019] Preferably, the calcination holding temperature is 600-1000° C.; the calcination holding time is 0.5-24 hours;

[0020] The insulation temperature of the reduction reaction is 500-1000° C.; the insulation time of the reduction reaction is 0.5-24 hours.

[0021] The present invention provides the use of the nickel-molybdenum alloy composite material described in the above technical solution or the nickel-molybdenum alloy composite material prepared by the preparation method described in the above technical solution as a catalyst.

[0022] The present invention provides a method for producing light olefins by dehydrogenating light alkanes using carbon dioxide oxidation, comprising the following steps:

[0023] In a protective gas, the nickel-molybdenum alloy composite material described in the above technical solution or the nickel-molybdenum alloy composite material prepared by the preparation method described in the above technical solution is activated to obtain an activated catalyst;

[0024] The activated catalyst is used to carry out a catalytic dehydrogenation oxidation reaction on the raw gas to obtain light olefins; the raw gas includes carbon dioxide and light alkanes, the molar ratio of the carbon dioxide to the light alkanes is (0.05-20):1, and the insulation temperature of the catalytic dehydrogenation oxidation reaction is 550-850°C.

[0025] The present invention provides a nickel-molybdenum alloy composite material, comprising a carrier and an active component loaded on the surface and pores of the carrier, wherein the active component comprises a nickel-molybdenum alloy. The nickel-molybdenum alloy composite material provided by the present invention uses a nickel-molybdenum alloy as the active component of the composite material, wherein a trace amount of electrons in the nickel-molybdenum alloy is transferred from the Mo atom to the Ni atom, so that the electron cloud density of the Ni atom is increased to generate electron-rich nickel, and the nickel-molybdenum alloy is loaded on the surface and inside the pores of the carrier, so that the nickel-molybdenum alloy is fully in contact with the reaction raw materials. Therefore, when the nickel-molybdenum alloy composite material provided by the present invention is used as a catalytic material for the dehydrogenation of low-carbon alkanes to produce low-carbon olefins by oxidation of carbon dioxide, the conversion rate of low-carbon alkanes is high, and the yield of low-carbon olefins is high. The results of the examples show that when the nickel-molybdenum alloy composite material provided by the present invention is used in the reaction of ethylene by oxidation of ethane to produce ethylene by dehydrogenation of ethane by carbon dioxide, the ethane conversion rate, the carbon dioxide conversion rate and the selectivity of ethylene are all at a high level. At the same time, the nickel-molybdenum alloy composite material provided by the present invention has good stability and slow deactivation; and the nickel-molybdenum alloy composite material has low toxicity and low pollution.

[0026] The present invention provides a method for preparing the nickel-molybdenum alloy composite material described in the above technical solution, comprising the following steps: mixing an inorganic nickel salt, an inorganic molybdenum salt, a carrier, and a precursor solvent to load the metal salt, thereby obtaining a carrier-metal salt dispersion; calcining the carrier-metal salt dispersion in a sealed environment to obtain a composite material precursor, wherein the composite material precursor includes a carrier and a metal oxide; and subjecting the composite material precursor to a reduction reaction in a reducing gas to obtain the nickel-molybdenum alloy composite material. The preparation method provided by the present invention is simple and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1TEM characterization image of the nickel-molybdenum alloy composite material prepared in an embodiment of the present invention;

[0028] Figure 2 TEM line scan characterization image of the nickel-molybdenum alloy composite material prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a nickel-molybdenum alloy composite material, comprising a carrier and active components loaded on the surface and in the pores of the carrier, wherein the active components comprise a nickel-molybdenum alloy.

[0030] In the present invention, the specific surface area of ​​the carrier is preferably 200 to 300 m 2 ·g -1 The pore volume of the carrier is preferably 0.3 to 0.6 m 3 ·g -1 The pore size of the carrier is preferably 5 to 15 nm.

[0031] In the present invention, the particle size of the carrier is preferably 20 to 40 meshes.

[0032] In the present invention, the carrier preferably includes one or more of γ-Al2O3, MOR structure molecular sieve, SAPO series molecular sieve, USY series molecular sieve and NaY molecular sieve, and more preferably includes one or more of γ-Al2O3, MOR structure molecular sieve, SAPO11, USY11 and NaY molecular sieve.

[0033] In the present invention, the mass percentage of nickel element in the nickel-molybdenum alloy to the carrier is preferably 0.5-10%, more preferably 2-9%, and most preferably 1.5-5%.

[0034] In the present invention, the mass percentage of the molybdenum element in the nickel-molybdenum alloy to the carrier is preferably 0.5-10%, more preferably 1.5-8%, and even more preferably 1.5-5%.

[0035] In the present invention, when the loading amount of the nickel element and the molybdenum element is preferably greater than the above range, the dispersibility of the nickel-molybdenum alloy on the surface and in the pores of the carrier will be reduced, making the nickel-molybdenum alloy prone to agglomeration, thereby reducing the service life of the nickel-molybdenum alloy composite material when used as a catalyst.

[0036] In the present invention, when the loading amounts of the nickel element and the molybdenum element are preferably less than the above ranges, the catalytic activity of the nickel-molybdenum alloy composite material when used as a catalyst is reduced.

[0037] In the present invention, the particle size of the nickel-molybdenum alloy is preferably 5 to 15 nm, more preferably 5 to 10 nm.

[0038] In the present invention, when the nickel-molybdenum alloy has the above-mentioned particle size range, the catalytic activity of the nickel-molybdenum alloy composite material when used as a catalyst is more excellent.

[0039] The present invention provides a method for preparing the nickel-molybdenum alloy composite material described in the above technical solution, comprising the following steps:

[0040] Mixing an inorganic nickel salt, an inorganic molybdenum salt, a carrier and a dispersing solvent to load the metal salt to obtain a carrier-metal salt dispersion;

[0041] calcining the support-metal salt dispersion in a closed environment to obtain a composite material precursor, wherein the composite material precursor includes a support and a metal oxide;

[0042] The composite material precursor is subjected to a reduction reaction in a reducing gas to obtain the nickel-molybdenum alloy composite material.

[0043] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art.

[0044] The invention mixes an inorganic nickel salt, an inorganic molybdenum salt, a carrier and a dispersing solvent to load the metal salt and obtain a carrier-metal salt dispersion.

[0045] In the present invention, the inorganic nickel salt preferably includes one or more of nickel nitrate, nickel sulfate, nickel chloride and nickel acetate.

[0046] In the present invention, the inorganic nickel salt is preferably a hydrated inorganic nickel salt.

[0047] In the present invention, the nickel nitrate is preferably nickel nitrate hexahydrate.

[0048] In the present invention, the nickel chloride is preferably nickel chloride hexahydrate.

[0049] In the present invention, the inorganic molybdenum salt preferably includes one or more of molybdenum sulfate, ammonium molybdate, sodium molybdate and phosphomolybdic acid.

[0050] In the present invention, the inorganic molybdenum salt is preferably a hydrated inorganic molybdenum salt.

[0051] In the present invention, the ammonium molybdate is preferably ammonium molybdate tetrahydrate.

[0052] In the present invention, the sodium molybdate is preferably sodium molybdate dihydrate.

[0053] In the present invention, the molar ratio of the inorganic nickel salt to the inorganic molybdenum salt is preferably 1:(0.1-10), more preferably 1:(0.2-5), and most preferably 1:(0.3-1).

[0054] In the present invention, the protection scope of the carrier is preferably the same as that described above, which will not be repeated here.

[0055] In the present invention, the mass ratio of the support to the inorganic nickel salt is preferably 1:(0.01-0.5), more preferably 1:(0.05-0.45), and most preferably 1:(0.1-0.3).

[0056] In the present invention, the dispersion solvent is preferably a solvent capable of dissolving the inorganic nickel salt and the inorganic molybdenum salt simultaneously.

[0057] In the present invention, the dispersion solvent is preferably one or more of water, methanol, ethane and acetone, more preferably water.

[0058] In the present invention, the water is preferably deionized water.

[0059] In the present invention, the mass ratio of the carrier to the volume ratio of the dispersion solvent is preferably 1 g: (0.5-20) mL, more preferably 1 g: (0.5-15) mL, and most preferably 1 g: (0.5-2) mL.

[0060] In the present invention, the mixing for loading the metal salt preferably comprises the following steps:

[0061] dissolving the inorganic nickel salt and the inorganic molybdenum salt in the dispersion solvent to obtain an inorganic metal salt solution;

[0062] immersing the support in the inorganic metal salt solution to obtain a support-metal salt dispersion;

[0063] The carrier-metal salt dispersion is dried to obtain the carrier-metal salt dispersion.

[0064] In the present invention, the dissolution is preferably performed under ultrasonic conditions.

[0065] In the present invention, the ultrasonic time is preferably 0.5 h, and the ultrasonic temperature is preferably room temperature.

[0066] In the present invention, the dissolution is preferably carried out under stirring conditions, the stirring temperature is preferably room temperature, and the stirring time is preferably 0.5 h.

[0067] In the present invention, the impregnation is preferably equal volume impregnation or supersaturated impregnation, more preferably equal volume impregnation.

[0068] In the present invention, the impregnation is preferably performed after the support is initially wetted by preliminarily adding the inorganic metal salt solution.

[0069] In the present invention, when the carrier is added to the inorganic metal salt solution, the process is preferably carried out under stirring.

[0070] In the present invention, the immersion time is preferably 24 hours, and the immersion temperature is preferably room temperature.

[0071] In the present invention, the drying temperature is preferably 60 to 120°C, more preferably 80 to 100°C.

[0072] In the present invention, the drying time is preferably 0.5 to 24 hours, more preferably 6 to 18 hours.

[0073] In the present invention, the drying is preferably performed under ventilation conditions.

[0074] After obtaining the carrier-metal salt dispersion, the present invention calcines the carrier-metal salt dispersion in a closed environment to obtain a composite material precursor, which includes a carrier and a metal oxide.

[0075] In the present invention, the calcination holding temperature is preferably 600-1000°C, more preferably 700-900°C.

[0076] In the present invention, the calcination holding time is preferably 0.5 to 24 hours, more preferably 2 to 12 hours.

[0077] In the present invention, the heating rate for heating to the calcination holding temperature is preferably 5° C. / min.

[0078] In the present invention, the calcination is preferably carried out in a muffle furnace.

[0079] In the present invention, the nickel oxide and molybdenum oxide are preferably obtained by calcination.

[0080] In the present invention, after the calcination, the calcined product is preferably cooled to room temperature to obtain a composite material precursor.

[0081] After obtaining the composite material precursor, the present invention performs a reduction reaction on the composite material precursor in a reducing gas to obtain the nickel-molybdenum alloy composite material.

[0082] In the present invention, the reduction holding temperature is preferably 500-1000°C, more preferably 600-800°C.

[0083] In the present invention, the reduction holding time is preferably 0.5 to 24 hours, more preferably 2 to 12 hours.

[0084] In the present invention, the heating rate for heating to the holding time for the reduction reaction is preferably 5° C. / min.

[0085] In the present invention, the reducing gas is preferably a mixed gas of hydrogen and an inert gas.

[0086] In the present invention, the volume percentage of hydrogen in the reducing gas is preferably 10%.

[0087] In a specific embodiment of the present invention, the reducing gas is preferably a mixed gas of hydrogen and argon.

[0088] In the present invention, the reduction reaction is preferably carried out in a tube furnace.

[0089] In the present invention, the nickel-molybdenum alloy is preferably obtained by a reduction reaction.

[0090] The present invention provides the use of the nickel-molybdenum alloy composite material described in the above technical solution or the nickel-molybdenum alloy composite material prepared by the preparation method described in the above technical solution as a catalyst.

[0091] The present invention provides a method for producing light olefins by dehydrogenating light alkanes using carbon dioxide oxidation, comprising the following steps:

[0092] In a protective gas, the nickel-molybdenum alloy composite material described in the above technical solution or the nickel-molybdenum alloy composite material prepared by the preparation method described in the above technical solution is activated to obtain an activated catalyst;

[0093] The activated catalyst is used to carry out a catalytic dehydrogenation oxidation reaction on the raw gas to obtain light olefins; the raw gas includes carbon dioxide and light alkanes, the molar ratio of the carbon dioxide to the light alkanes is (0.05-20):1, and the insulation temperature of the catalytic dehydrogenation oxidation reaction is 550-850°C.

[0094] In the present invention, the nickel-molybdenum alloy composite material described in the above technical solution or the nickel-molybdenum alloy composite material prepared by the preparation method described in the above technical solution is activated in a protective gas to obtain an activated catalytic material.

[0095] In the present invention, the protective gas is preferably nitrogen or an inert gas, more preferably nitrogen.

[0096] In the present invention, the holding temperature of the activation treatment is preferably 500-800°C, more preferably 550-750°C.

[0097] In the present invention, the holding time of the activation treatment is preferably 1 to 3 hours, more preferably 1.5 to 2 hours.

[0098] In the present invention, it is preferred to remove moisture and air components that may be adsorbed on the catalyst by activation.

[0099] After obtaining the activated catalytic material, the present invention uses the activated catalytic material as a catalyst to perform a catalytic dehydrogenation oxidation reaction on the raw gas to obtain light olefins. The molar ratio of carbon dioxide and light alkane is (0.05-20):1, and the insulation temperature of the catalytic dehydrogenation oxidation reaction is 550-850°C.

[0100] In the present invention, the low carbon alkane is preferably ethane.

[0101] In the present invention, the light olefin is preferably ethylene.

[0102] In the present invention, the catalytic dehydrogenation reaction is preferably carried out in a fixed bed reactor.

[0103] In the present invention, the raw material gas preferably also includes nitrogen.

[0104] In the present invention, the molar percentage of the carbon dioxide in the raw gas is preferably 1 to 20%, more preferably 1.5 to 18%.

[0105] In the present invention, the molar percentage of the light alkanes in the feed gas is preferably 1 to 20%, more preferably 1.5 to 18%.

[0106] In the present invention, the flow rate of the raw gas during the catalytic dehydrogenation and oxidation reaction is preferably 10 to 50 mL / min, more preferably 15 to 40 mL / min.

[0107] In the present invention, the holding temperature of the catalytic dehydrogenation reaction is preferably 550-850°C, more preferably 600-800°C.

[0108] In the present invention, the pressure of the catalytic dehydrogenation oxidation reaction is preferably normal pressure.

[0109] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0110] Example 1

[0111] 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were added to a 10 mL centrifuge tube, followed by 1.2 mL of deionized water and sonication at room temperature for 0.5 h. 1 g of γ-Al₂O₃ was then added and stirred until incipient wetness was achieved. The centrifuge tube was capped and stored at room temperature for 24 h to obtain a support-metal salt dispersion. The support-metal salt dispersion was dried in a hot air oven at 100°C for 12 h to obtain a support-metal salt dispersion. The support-metal salt dispersion was then heated in a muffle furnace at a heating rate of 5°C / min to 800°C, held at this temperature for 3 h, and then naturally cooled to room temperature to obtain a composite material precursor. The composite material precursor was placed in a tube furnace and heated to 700°C in a reducing atmosphere of 10% H₂-90% Ar by volume at a heating rate of 5°C / min, held at this temperature for 3 h to obtain a nickel-molybdenum alloy composite material, designated CAT-1. The nickel-molybdenum alloy composite material uses gamma-Al2O3 as a carrier and nickel-molybdenum alloy as an active component, wherein the particle size of the nickel-molybdenum alloy is 5-15 nm; the loading amount of the Ni element is 2.5%, and the loading amount of the Mo element is 1.5%.

[0112] Figure 1 TEM characterization of the nickel-molybdenum alloy composite material prepared in this embodiment. Figure 1 It can be seen that the “black” active centers are loaded onto the strip-shaped γ-Al2O3.

[0113] Figure 2 TEM line scan characterization of the nickel-molybdenum alloy composite material prepared in this embodiment, Figure 2 It can be seen that the signal peaks of active metal nickel and active metal molybdenum overlap, indicating the formation of nickel-molybdenum alloy.

[0114] Example 2

[0115] A nickel-molybdenum alloy composite material was prepared according to the method of Example 1, except that 87.2 mg of nickel nitrate hexahydrate and 17.6 mg of ammonium molybdate tetrahydrate were used instead of 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate to obtain a nickel-molybdenum alloy composite material designated as CAT-2. The nickel-molybdenum alloy had a particle size of 5 to 15 nm, a Ni loading of 1.4%, and a Mo loading of 1.0%.

[0116] Example 3

[0117] A nickel-molybdenum alloy composite material was prepared according to the method of Example 1, except that 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were replaced with 261.7 mg of nickel nitrate hexahydrate and 53 mg of ammonium molybdate tetrahydrate. The resulting nickel-molybdenum alloy composite material was designated CAT-3. The nickel-molybdenum alloy had a particle size of 5 to 15 nm, a Ni loading of 4.2%, and a Mo loading of 2.6%.

[0118] Example 4

[0119] A nickel-molybdenum alloy composite material was prepared according to the method of Example 1, except that 88.3 mg of ammonium molybdate tetrahydrate was used instead of 28.2 mg. The resulting nickel-molybdenum alloy composite material, designated CAT-4, had a particle size of 5 to 15 nm, a Ni loading of 2.5%, and a Mo loading of 4.2%.

[0120] Example 5

[0121] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, except that 145.4 mg of nickel nitrate hexahydrate, 28.2 mg of ammonium molybdate tetrahydrate, and 1 g of γ-Al2O3 were replaced with 118.8 mg of nickel chloride hexahydrate, 38.7 mg of sodium molybdate dihydrate, and 1 g of NaY molecular sieve, resulting in a nickel-molybdenum alloy composite material, designated CAT-5. The nickel-molybdenum alloy had a particle size of 5 to 15 nm, a Ni loading of 2.4%, and a Mo loading of 1.4%.

[0122] Example 6

[0123] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, except that the solid mixture was heated to 700°C in a muffle furnace instead of 800°C, and to 600°C in a tube furnace instead of 700°C, to obtain a nickel-molybdenum alloy composite material, designated CAT-6. The nickel-molybdenum alloy had a particle size of 5 to 15 nm, a Ni loading of 2.6%, and a Mo loading of 1.5%.

[0124] Example 7

[0125] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, except that the 10% H2-Ar gas was replaced with pure hydrogen. The resulting nickel-molybdenum alloy composite material, designated CAT-7, had a particle size of 5-15 nm, a Ni loading of 2.4%, and a Mo loading of 1.5%.

[0126] Example 8

[0127] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, with the only difference from Example 1 being that 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were added to a 50 mL round-bottom flask, followed by 15 mL of deionized water and stirring at room temperature for 0.5 h. Then, 1 g of γ-Al2O3 was added and stirred at room temperature for 24 h to obtain a nickel-molybdenum alloy composite material, designated CAT-8. The nickel-molybdenum alloy had a particle size of 5 to 15 nm; the Ni loading was 2.4%, and the Mo loading was 1.4%.

[0128] Comparative Example 1

[0129] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, except that 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were replaced with 145.4 mg of nickel nitrate hexahydrate, resulting in a single-metal nickel composite material, designated CAT-9. The nickel loading was 2.0%.

[0130] Comparative Example 2

[0131] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, except that 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were replaced with 49.4 mg of ammonium molybdate tetrahydrate, resulting in a monometallic molybdenum composite material, designated CAT-10. The Mo loading was 2.3%.

[0132] Comparative Example 3

[0133] A nickel-molybdenum alloy catalyst was prepared according to the method of Example 1, except that 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were replaced with 727 mg of nickel nitrate hexahydrate and 220 mg of ammonium molybdate tetrahydrate, resulting in a nickel-molybdenum alloy composite material designated CAT-11. The nickel-molybdenum alloy had a particle size of 20 to 40 nm, a Ni loading of 12.1%, and a Mo loading of 10.2%.

[0134] Application Examples 1-12

[0135] The nickel-molybdenum alloy composite materials prepared in Examples 1 to 8 and the composite materials prepared in Comparative Examples 1 to 3 were loaded into a fixed bed reactor, and the catalytic reaction performance of the catalytic materials prepared in the above Examples and Comparative Examples was investigated in the fixed bed reactor. The catalytic dehydrogenation reaction conditions were: a loading of 500 mg of the catalyst, the catalytic material was activated at 600 ° C for 1 hour in a nitrogen atmosphere before the reaction, and then the reaction raw gas was introduced at 660 ° C, the reaction pressure was 1 atm, the total flow rate of the reaction gas was 30 mL / min, and the reaction gas composition was C2H6:CO2:N2=15:15:70 (volume ratio). Application Examples 1 to 11 used the catalytic materials prepared in Examples 1 to 8 and Comparative Examples 1 to 3, respectively, and Application Example 12 used the catalytic material prepared in Example 1. The difference from the reaction in Example 1 was that CO2 gas was not introduced. The product distribution after 8 hours of operation is shown in Table 1.

[0136] Table 1 Catalytic performance characterization results of application examples 1 to 12

[0137]

[0138]

[0139] The results in Table 1 show that the nickel-molybdenum alloy composite catalysts obtained in Examples 1 to 8 have excellent catalytic activity and high selectivity for the oxidative dehydrogenation of ethane. The nickel-molybdenum alloy catalyst of Example 3 reached a selectivity of 25.7%, and the nickel-molybdenum alloy catalyst of Example 1 reached a selectivity of 86.9%. When the molybdenum content in the nickel-molybdenum alloy catalyst in Example 4 was high, both the ethane conversion rate and ethylene selectivity decreased. When the single metal catalysts in Comparative Examples 1 and 2 were used in the oxidative dehydrogenation of ethane, the ethane conversion rate decreased significantly, indicating that the formation of the alloy facilitated the oxidative dehydrogenation of ethane. Comparative Example 3 shows that when a nickel-molybdenum alloy composite material with a high active metal loading was used, the ethane conversion rate was high, but the ethylene selectivity decreased significantly. The results of Application Example 12 show that when CO2 gas was not added to the reaction system, the ethane conversion rate decreased significantly compared to Example 1, indicating that the addition of CO2 significantly promoted the oxidative dehydrogenation of ethane.

[0140] Catalytic Material Stability Test: Using the catalytic material prepared in Example 1, the product distribution after operation for 4 h, 8 h, 12 h, and 16 h is shown in Table 2. The catalytic dehydrogenation reaction conditions are as follows: a catalyst loading of 500 mg, the catalytic material was activated in a nitrogen atmosphere at 600°C for 1 hour before the reaction, and then the reaction raw gas was introduced at 660°C. The reaction pressure was 1 atm, the total reaction gas flow rate was 30 mL / min, and the reaction gas composition was C2H6:CO2:N2 = 15:15:70 (volume ratio).

[0141] Table 2 Characterization results of catalytic performance of continuous reaction in Application Example 1

[0142] time Example catalyst <![CDATA[Conversion rate of C2H6(%)]]> <![CDATA[CO2 conversion rate (%)]]> <![CDATA[C2H4 selectivity (%)]]> 4 hours Application Example 1 CAT-1 25.1 15.9 86.1 8 hours Application Example 1 CAT-1 24.9 16.2 86.9 12 hours Application Example 1 CAT-1 24.2 16.4 86.4 16 hours Application Example 1 CAT-1 23.8 16.1 85.9

[0143] The results in Table 2 show that the activity and selectivity of the nickel-molybdenum alloy composite material of Application Example 1 did not decrease significantly during the continuous reactions of 4 h, 8 h, 12 h and 16 h, indicating that the catalytic material has good stability.

[0144] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for producing light olefins by dehydrogenation of light alkanes by oxidation of carbon dioxide, characterized in that: The following steps are involved: An activation treatment is performed on a nickel-molybdenum alloy composite material in a protective gas to obtain an activated catalyst; the nickel-molybdenum alloy composite material includes a carrier and an active component supported on the surface and in the pores of the carrier, the active component includes a nickel-molybdenum alloy, the nickel element in the nickel-molybdenum alloy accounts for 2.5% of the mass percentage of the carrier, the molybdenum element in the nickel-molybdenum alloy accounts for 1.5% of the mass percentage of the carrier, and the particle size of the nickel-molybdenum alloy is 5 to 15 nm; The preparation method of the nickel-molybdenum alloy composite material comprises: 145.4 mg of nickel nitrate hexahydrate and 28.2 mg of ammonium molybdate tetrahydrate were added to a 10 mL centrifuge tube, followed by the addition of 1.2 mL of deionized water, and ultrasonication at room temperature for 0.5 h; 1 g of γ-Al2O3 was then added, and the mixture was impregnated until initially wet during stirring, and then the centrifuge tube was covered with a lid and stored at room temperature for 24 h to obtain a carrier-metal salt dispersion; the carrier-metal salt dispersion was dried in a hot air oven at 100 ° C for 12 h to obtain a carrier-metal salt dispersion; then, the carrier-metal salt dispersion was heated to 800 ° C in a muffle furnace at a heating rate of 5 ° C / min and kept warm for 3 h, and then naturally cooled to room temperature to obtain a composite material precursor, which was placed in a tube furnace, heated to 700 ° C at a heating rate of 5 ° C / min in a reducing gas with a volume percentage of 10% H2-90% Ar, and kept warm for 3 h to obtain a nickel-molybdenum alloy composite material; The activated catalyst is used to carry out catalytic dehydrogenation and oxidation reaction on the raw gas to obtain light olefins.

2. The method according to claim 1, characterized in that The raw gas includes carbon dioxide and low-carbon alkanes, the molar ratio of carbon dioxide to low-carbon alkanes is (0.05-20):1, and the insulation temperature of the catalytic dehydrogenation reaction is 550-850°C.

3. The method according to claim 1, characterized in that The activation treatment temperature is 500-800° C., and the heat preservation time is 1-3 hours.

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