A nickel-based catalyst and its preparation method and application

Abstract

The present invention discloses a nickel-based catalyst, a preparation method and an application thereof, and belongs to the technical field of catalyst synthesis. The present invention prepares the nickel-based catalyst by an equal volume impregnation method, a mechanochemical method and a deposition precipitation method, which is simple to operate, low in cost, and uses a small amount of raw materials; and the nickel-based catalyst prepared by the present invention has a simple and easy method for regulating the selectivity of C4 olefins, and has good waterproof performance. The present invention uses niobium oxide as a carrier, and the niobium oxide carrier-loaded nickel catalyzes the heterogeneous ethylene polymerization reaction without any cocatalyst, effectively increases the dispersion of the loaded metal, is not prone to carbon accumulation and clogging during the reaction process, and improves the catalytic stability of the nickel-based catalyst in catalyzing the ethylene polymerization reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst synthesis, and in particular relates to a nickel-based catalyst and a preparation method and application thereof. Background Art

[0002] The modern chemical industry requires large quantities of linear 1-butene and 2-butene, primarily for polymerization into high-carbon polymers and chemical products such as antioxidants. Linear α-olefins (LAOs), including 1-butene, 1-hexene, and 1-octene, have long been important high-end chemical raw materials in the chemical industry. These include 1-butene, 1-hexene, and 1-octene, and are widely used in ethylene comonomers (C4-6), LLDPE comonomers (C6, C8), and plasticizer alcohols (C8-10). Currently, the primary method for producing α-olefins is ethylene oligomerization, which is derived from naphtha cracking or ethane cracking and consumes a significant amount of energy. Nickel-based catalysts have proven effective in producing 1-butene. 2-olefins, isomers of 1-butene, have important applications in the polymerization industry and olefin disproportionation. Therefore, developing a method for selectively controlling C4 olefins during ethylene oligomerization is of great research value in the modern chemical industry. Chinese patent publication number CN107159278A uses a supported catalyst of ferric sulfate and nickel sulfate (supported by macroporous alumina) to oligomerize butene, achieving efficient dimerization of butene under process conditions of 165–215°C and 1.2–6.0 MPa. Chinese patent publication number CN118878390A uses a boron-modified nickel-based catalyst to oligomerize propylene and n-butene. The products are separated into C6 to C10 products, directly enabling the oligomerization of mixed olefin feeds under specific process conditions. Chinese patent publication number CN119406456A utilizes a catalytic system comprising a carbon-chromium catalyst, an organoboron additive, and an aluminum-containing activator to achieve selective ethylene oligomerization, demonstrating high catalytic activity, good reproducibility, and stable operation. However, the requirement of an organoboron additive and an aluminum-containing activator makes catalyst recovery difficult and the preparation method cumbersome.

[0003] Ethylene oligomerization is used to prepare C4 olefins. The related technology uses molecular sieves loaded with active metals, but the catalyst has poor durability and is prone to carbon deposition. There is also a lack of relevant methods for regulating the C4 olefin products. Therefore, it is of great significance to develop methods for selectively regulating the C4 products through ethylene oligomerization. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] One of the objects of the present invention is to provide a method for preparing a nickel-based catalyst. The prepared nickel-based catalyst is used as a catalyst to catalyze the polymerization of ethylene to C4 olefins, showing high selectivity, controllability and stability.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a nickel-based catalyst, comprising:

[0008] Ordinary niobium oxide is used as a catalyst carrier, nickel salt solution is used as a loaded metal precursor, and metal nickel is loaded on the niobium oxide carrier by using an incipient wetness impregnation method or a deposition precipitation method in water as a solvent to obtain a catalyst precursor;

[0009] heat-treating the catalyst precursor to obtain the nickel-based catalyst;

[0010] The nickel-based catalyst is a niobium oxide carrier and active metal nickel attached to the niobium oxide carrier. The nickel content in the nickel-based catalyst is 3-6 wt%, more preferably 3 wt%.

[0011] As a preferred embodiment of the method for preparing the nickel-based catalyst of the present invention, the particle size of the nickel-based catalyst is 20-60 mesh, more preferably 20-40 mesh.

[0012] The present invention uses common niobium oxide as a catalyst carrier. This niobium oxide carrier provides excellent conditions for high dispersion of active nickel metal on the carrier, increasing the dispersion of the loaded metal, reducing carbon accumulation and clogging during the reaction, and improving the catalytic stability of the nickel-based catalyst. Furthermore, the nickel-based catalyst produced by the present invention is a heterogeneous catalyst, exhibiting greater stability and a larger specific surface area, making it easier to recycle than homogeneous oligomerization catalysts.

[0013] As a preferred embodiment of the method for preparing the nickel-based catalyst of the present invention, the purity of the ordinary niobium oxide is 99.9%;

[0014] The nickel salt solution is a nickel nitrate solution or a nickel sulfate solution, and the molar concentration of nickel in the nickel salt solution is 0.1-0.4 mol / L, more preferably 0.1 mol / L.

[0015] In the present invention, the nickel salt solution is preferably a nitrate or a sulfate, more preferably a hydrated nitrate or a hydrated sulfate, and specifically preferably nickel nitrate hexahydrate or nickel sulfate hexahydrate. In the present invention, during the calcination of the catalyst, sulfate radicals cannot be completely calcined and removed, but are enriched on the surface of the catalyst. Compared with nitrates, the acidity of the catalyst is improved by using sulfates. In the present invention, the preparation method of the nickel salt solution preferably comprises: dissolving nickel nitrate hexahydrate or nickel sulfate hexahydrate in water, and performing ultrasonic treatment to obtain the nickel salt solution. In the present invention, the water is preferably deionized water. In the present invention, the frequency of the ultrasonic treatment is preferably 50 Hz, and the time is preferably 10 min.

[0016] In the present invention, the incipient wetness impregnation method is used to load the active metal nickel onto the niobium oxide carrier, so that the nickel can be evenly dispersed on the carrier, thereby improving the atomic utilization rate. Compared with the catalyst prepared by the mechanochemical method, the catalyst prepared by the deposition precipitation method has better active metal dispersion and higher activity.

[0017] As a preferred embodiment of the preparation method of the nickel-based catalyst of the present invention, the nickel salt solution is added dropwise to the niobium oxide support with continuous stirring in the incipient wetness impregnation method, and the rotor stirring speed is preferably 200-800 r / min, specifically preferably 450 r / min; the time for a single impregnation is preferably 2-10 h, specifically preferably 8 h; and then the catalyst is placed in an oven for drying, the drying temperature is preferably 60-120 ° C, specifically preferably 100 ° C, and the drying time is preferably 8-12 h, specifically preferably 10 h, to obtain a catalyst precursor.

[0018] As a preferred embodiment of the preparation method of the nickel-based catalyst of the present invention, the niobium oxide carrier is dispersed in water, and then a nickel salt solution is added dropwise, and stirring is continued at a speed of 200 to 800 r / min, preferably 450 r / min; then a precipitant is slowly added dropwise, heated and stirred to obtain a mixed solution, the mixed solution is filtered and washed until neutral, and then placed in an oven for drying, the drying temperature is preferably 60 to 120°C, preferably 100°C, and the drying time is preferably 8 to 12 hours, preferably 10 hours, to obtain a catalyst precursor.

[0019] As a preferred embodiment of the method for preparing the nickel-based catalyst of the present invention, the precipitant comprises ammonia water or urea.

[0020] After the deposition is completed, the present invention performs heat treatment on the catalyst precursor to obtain the nickel-based catalyst.

[0021] As a preferred embodiment of the method for preparing the nickel-based catalyst of the present invention, the heat treatment comprises grinding the dried catalyst precursor and calcining it in a muffle furnace; the atmosphere of the heat treatment is preferably air or nitrogen, more preferably air; the temperature is preferably 200-800°C, specifically preferably 400°C, 500°C or 600°C; the heating rate to the heat treatment temperature is preferably 0.5-5°C / min, specifically preferably 2°C / min; and the time is preferably 4-6 h, more preferably 4 h.

[0022] Another object of the present invention is to provide a nickel-based catalyst obtained by the preparation method described above.

[0023] Another object of the present invention is to provide a method for selectively regulating the oligomerization of ethylene to C4 olefins, comprising:

[0024] Ethylene undergoes oligomerization reaction in a fixed bed reactor under the action of a nickel-based catalyst to obtain the C4 olefin;

[0025] The nickel-based catalyst is the nickel-based catalyst described above.

[0026] As a preferred embodiment of the method for selectively controlling the oligomerization of ethylene to C4 olefins of the present invention, the nickel-based catalyst is pretreated with nitrogen at a temperature of 300° C. for a time of 2 to 8 hours;

[0027] The temperature of the ethylene oligomerization reaction is preferably 130-330°C, preferably 130-260°C, specifically 130°C, 200°C, 250°C, or 300°C; the pressure is preferably 1-3 MPa, specifically 1 MPa, 2 MPa, 2.5 MPa, or 3 MPa;

[0028] The weight hourly space velocity of the ethylene feed is 3 to 10 h -1 , specifically 7.5 h -1 .

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The preparation method provided by the present invention uses an incipient wetness impregnation method or a deposition precipitation method to prepare a nickel-based catalyst, which is simple and efficient to operate, uses less raw materials, and is low in cost. The present invention uses niobium oxide as a carrier, which can effectively load and disperse active metal nickel, is not prone to large amounts of carbon deposition during the polymerization reaction, and is not prone to clogging during the reaction. Compared with molecular sieve-supported nickel-type catalysts, the catalytic stability of the nickel-based catalyst in the ethylene polymerization reaction is improved.

[0031] In the present invention, the nickel-based catalyst prepared using the above-described technical solution is used as a catalyst to catalyze the oligomerization of ethylene to C4 olefins, exhibiting high selectivity, controllability, and stability. The oligomerization reaction of the present invention is carried out in a fixed-bed reactor, enabling continuous production and being suitable for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0033] Figure 1 This is the XRD pattern of the catalyst prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0037] Unless otherwise specified, the raw materials used in the examples were purchased commercially.

[0038] Example 1

[0039] 0.297 g of Ni(NO₃)₃·6H₂O was dissolved in 5 mL of deionized water and sonicated continuously at 50 Hz for 10 minutes in an ultrasonic bath to obtain a nickel nitrate solution with a concentration of 0.1 mol / L. A 2 g niobium oxide support was weighed and the nickel nitrate solution was slowly added dropwise to the support with continuous stirring at 450 r / min for 8 hours. The solution was then dried in an oven at 100°C for 10 hours. After drying, the catalyst was ground and calcined in a muffle furnace in an air atmosphere at 400°C for 4 hours at a heating rate of 2°C / min. After calcination, the catalyst was ground in a mortar and then pressed and sieved to a particle size of 20–40 mesh to obtain the nickel-based catalyst, designated Ni / Nb₂O₅-im.

[0040] It was then diluted with quartz sand and placed in a fixed bed reactor. The catalyst bed was fixed in the constant temperature section of the reactor using quartz wool. The catalyst was pretreated with nitrogen. The pretreatment temperature was set to 300 °C, the pretreatment time was set to 2 h, the heating rate was 2 °C / min, and the weight hourly space velocity was 7.5 h -1 .

[0041] The obtained series of nickel-based catalysts were used to carry out oligomerization reaction of ethylene to produce C4 olefins under the conditions (pressure, temperature) shown in Table 1. The ethylene conversion rate and C4 olefin selectivity of the obtained nickel-based catalysts are shown in Table 1.

[0042] Table 1 Reaction conditions and test results of the series of catalysts obtained in Example 1

[0043]

[0044] It can be seen from Table 1 that the selectivity of 1-butene is the highest when the temperature is 130 °C and the pressure is 3 MPa.

[0045] Example 2

[0046] 0.268 g of NiSO₄·6H₂O was dissolved in 5 mL of deionized water and sonicated continuously at 50 Hz for 10 minutes in an ultrasonic bath to obtain a metal salt solution with a nickel sulfate concentration of 0.1 mol / L. A 2 g niobium oxide support was weighed, and the nickel nitrate solution was slowly added dropwise to the niobium oxide support with continuous stirring at 450 r / min for 8 hours. The solution was then dried in an oven at 100°C for 10 hours. After drying, the catalyst was ground and calcined in a muffle furnace in an air atmosphere at 400°C for 4 hours at a heating rate of 2°C / min. After calcination, the catalyst was ground in a mortar and then pressed and sieved to a particle size of 20-40 mesh to obtain the nickel-based catalyst, named NiSO₄ / Nb₂O₅-im.

[0047] It was then diluted with quartz sand and placed in a fixed bed reactor. The catalyst bed was fixed in the constant temperature section of the reactor using quartz wool. The catalyst was pretreated with nitrogen. The pretreatment temperature was set to 300 °C, the pretreatment time was set to 2 h, the heating rate was 2 °C / min, and the weight hourly space velocity was 7.5 h -1 .

[0048] The obtained series of nickel-based catalysts were used to carry out oligomerization reaction of ethylene to produce C4 olefins under the conditions (pressure, temperature) shown in Table 2. The ethylene conversion rate and C4 olefin selectivity of the obtained nickel-based catalysts are shown in Table 2.

[0049] Table 2 Reaction conditions and test results of the series of catalysts obtained in Example 2

[0050]

[0051] It can be seen from Table 2 that the 2-butene selectivity of the nickel sulfate-supported niobium oxide carrier is higher than that of Example 1.

[0052] Example 3

[0053] 0.268 g of NiSO4·6H2O and 2 g of niobium oxide carrier were weighed and placed together in a mortar. The two were carefully ground for 0.5 h. The catalyst precursor was then calcined in a muffle furnace in an air atmosphere at 400 ℃, 500 ℃, and 600 ℃ with a heating rate of 2 ℃ / min. After calcination, nickel-based catalysts were obtained and named NiSO4 / Nb2O5-me-400, NiSO4 / Nb2O5-me-500, and NiSO4 / Nb2O5-me-600.

[0054] It was then diluted with quartz sand and placed in a fixed bed reactor. The catalyst bed was fixed in the constant temperature section of the reactor using quartz wool. The catalyst was pretreated with nitrogen. The pretreatment temperature was set to 300 °C, the pretreatment time was set to 2 h, the heating rate was 2 °C / min, and the weight hourly space velocity was 7.5 h -1 .

[0055] The obtained series of nickel-based catalysts were used to carry out oligomerization reaction of ethylene to produce C4 olefins under the conditions (pressure, temperature) shown in Table 3. The ethylene conversion rate and C4 olefin selectivity of the obtained nickel-based catalysts are shown in Table 3.

[0056] Table 3 Reaction conditions and test results of the series of catalysts obtained in Example 3

[0057]

[0058] It can be seen from Table 3 that as the calcination temperature increases, the ethylene conversion rate gradually decreases.

[0059] Example 4

[0060] 2 g of niobium oxide support was dispersed in 30 ml of deionized water; it was placed in an ultrasonic bath and continuously ultrasonicated at 50 Hz for 10 min to disperse it, then 0.297 g of Ni(NO3)3·6H2O was weighed and dissolved in 5 mL of deionized water, and continuously ultrasonicated in an ultrasonic bath at 50 Hz for 10 min to obtain a metal salt solution with a nickel nitrate concentration of 0.1 mol / L, the metal salt solution was slowly added dropwise to the niobium oxide support and deionized water, and stirred continuously at a speed of 450 r / min, then a precipitant ammonia water was slowly added dropwise and heated and stirred to obtain a mixed solution, the heating temperature was 70 ℃, the mixed solution was filtered and washed to neutrality, and then placed in an oven to dry, the drying temperature was set to 100 ℃, the drying time was set to 10 h, and the catalyst precursor was obtained. After drying, the catalyst was ground and calcined in a muffle furnace, the heat treatment atmosphere was air, the calcination temperature was set to 400 ℃, the calcination time was set to 4 h, and the heating rate was set to 2 ℃ / min, after calcination, it was placed in a mortar and ground, then tableted and sieved, and sieved to a particle size of 20-40 mesh to obtain the nickel-based catalyst, and the catalyst was named Ni / Nb2O5-NH4OH.

[0061] It was then diluted with quartz sand and placed in a fixed bed reactor. The catalyst bed was fixed in the constant temperature section of the reactor using quartz wool. The catalyst was pretreated with nitrogen. The pretreatment temperature was set to 300 °C, the pretreatment time was set to 2 h, the heating rate was 2 °C / min, and the weight hourly space velocity was 7.5 h -1 .

[0062] The obtained series of nickel-based catalysts were used to carry out oligomerization reaction of ethylene to produce C4 olefins under the conditions (pressure, temperature) shown in Table 4. The ethylene conversion rate and C4 olefin selectivity of the obtained nickel-based catalysts are shown in Table 4.

[0063] Table 4 Reaction conditions and test results of the series of catalysts obtained in Example 4

[0064]

[0065] It can be seen from Table 4 that the conversion rate of the catalyst prepared in Example 4 is higher than that in the previous examples.

[0066] Example 5

[0067] 2 g of niobium oxide carrier was dispersed in 30 ml of deionized water; it was placed in an ultrasonic tank and ultrasonicated continuously at 50 Hz for 10 min to disperse it, then 0.297 g of Ni(NO3)3·6H2O was weighed and dissolved in 5 mL of deionized water, and ultrasonicated continuously at 50 Hz for 10 min in an ultrasonic tank to obtain a metal salt solution with a nickel nitrate concentration of 0.1 mol / L, and the metal salt solution was slowly added dropwise to the niobium oxide carrier and deionized water, and stirred continuously at a speed of 450 r / min, and then the precipitant urea was slowly added dropwise and heated and stirred to obtain a mixed solution, the heating temperature was 70 ℃, the mixed solution was filtered and washed to neutrality, and then placed in an oven to dry, the drying temperature was set to 100 ℃, the drying time was set to 10 h, and the catalyst precursor was obtained. After drying, the catalyst was ground and placed in a muffle furnace for calcination, the heat treatment atmosphere was air, the calcination temperature was set to 400 ℃, the calcination time was set to 4 h, and the heating rate was set to 2 ℃ / min, after calcination, it was placed in a mortar and ground, then pressed and sieved, and sieved to a particle size of 20-40 mesh to obtain the nickel-based catalyst, and the catalyst was named Ni / Nb2O5-urea.

[0068] The XRD pattern of the catalyst is Figure 1 The XRD pattern shows the typical diffraction peaks of Nb2O5 phase (JCPDS #30-0873) and no NiO diffraction peaks, indicating that nickel is well dispersed on the support.

[0069] It was then diluted with quartz sand and placed in a fixed bed reactor. The catalyst bed was fixed in the constant temperature section of the reactor using quartz wool. The catalyst was pretreated with nitrogen. The pretreatment temperature was set to 300 °C, the pretreatment time was set to 2 h, the heating rate was 2 °C / min, and the weight hourly space velocity was 7.5 h -1 .

[0070] The obtained series of nickel-based catalysts were used to carry out oligomerization reaction of ethylene to produce C4 olefins under the conditions (pressure, temperature) shown in Table 5. The ethylene conversion rate and C4 olefin selectivity of the obtained nickel-based catalysts are shown in Table 5.

[0071] Table 5 Reaction conditions and test results of the series of catalysts obtained in Example 5

[0072]

[0073] Example 6

[0074] 2 g of niobium oxide carrier was dispersed in 30 ml of deionized water; it was placed in an ultrasonic tank and ultrasonicated continuously at 50 Hz for 10 min to disperse it, then 0.297 g of Ni(NO3)3·6H2O was weighed and dissolved in 5 mL of deionized water, and ultrasonicated continuously at 50 Hz for 10 min in an ultrasonic tank to obtain a metal salt solution with a nickel nitrate concentration of 0.1 mol / L, and the metal salt solution was slowly added dropwise to the niobium oxide carrier and deionized water, and stirred continuously at a speed of 450 r / min, and then the precipitant urea was slowly added dropwise and heated and stirred to obtain a mixed solution, the heating temperature was 70 ℃, the mixed solution was filtered and washed to neutrality, and then placed in an oven to dry, the drying temperature was set to 100 ℃, the drying time was set to 10 h, and the catalyst precursor was obtained. After drying, the catalyst was ground and placed in a muffle furnace for calcination, the heat treatment atmosphere was air, the calcination temperature was set to 400 ℃, the calcination time was set to 4 h, and the heating rate was set to 2 ℃ / min, and a nickel-based catalyst was obtained after calcination. The catalyst was named Ni / Nb2O5-urea, which was ground in a mortar and then pressed into tablets and sieved to particle sizes of 20-40 mesh, 40-60 mesh, and 100 mesh, respectively.

[0075] It was then diluted with quartz sand and placed in a fixed bed reactor. The catalyst bed was fixed in the constant temperature section of the reactor using quartz wool. The catalyst was pretreated with nitrogen. The pretreatment temperature was set to 300 °C, the pretreatment time was set to 2 h, the heating rate was 2 °C / min, and the weight hourly space velocity was 7.5 h -1 .

[0076] The obtained series of nickel-based catalysts were used to carry out oligomerization reaction of ethylene to C4 olefins at the particle size shown in Table 6, with a pressure of 2 MPa and a temperature of 130°C. The ethylene conversion rate and C4 olefin selectivity of the obtained nickel-based catalysts are shown in Table 6.

[0077] Table 6 Reaction conditions and test results of the series of catalysts obtained in Example 6

[0078]

[0079] In summary, when nickel sulfate is used as the metal salt solution, the selectivity of 2-butene in the polymerization of ethylene to form C4 olefins is improved, while the selectivity of 1-butene is improved when nickel nitrate is used as the metal salt solution. Using urea as a precipitant in the sedimentation precipitation method can improve the activity of the catalyst under the same conditions.

[0080] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing C4 olefins by oligomerization of ethylene, characterized in that: include, Ethylene undergoes oligomerization reaction in a fixed bed reactor under the action of a nickel-based catalyst to obtain the C4 olefins, wherein the selectivity of 2-butene is higher than that of 1-butene among the C4 olefins; The nickel-based catalyst is pretreated with nitrogen at a temperature of 300°C for 2 to 8 h. The temperature of the oligomerization reaction is 130 to 330°C at a pressure of 1 to 3 MPa. The weight hourly space velocity of the ethylene feed is 3 to 10 h -1 ; Wherein, the preparation method of the nickel-based catalyst is preparation method (a) or preparation method (b), The preparation method (a) of the nickel-based catalyst is: Ordinary niobium oxide is used as a catalyst carrier, and a nickel salt solution is used as a loaded metal precursor. Metal nickel is loaded on the niobium oxide carrier by a deposition precipitation method in water as a solvent to obtain a catalyst precursor. In the deposition precipitation method, the niobium oxide carrier is dispersed in water, and then the nickel salt solution is added dropwise, and the mixture is continuously stirred at a speed of 200 to 800 r / min. A precipitant is then added dropwise, and the mixture is heated and stirred to obtain a mixed solution. The mixed solution is filtered and washed until neutral, and then dried in an oven at a drying temperature of 60 to 120°C and a drying time of 8 to 12 hours to obtain the catalyst precursor. The nickel salt solution is a nickel nitrate solution, and the precipitant is urea. The catalyst precursor is heat-treated to obtain the nickel-based catalyst; the catalyst is ground in a mortar, and then tabletted and sieved to a particle size of 20-40 mesh; The nickel-based catalyst is a niobium oxide carrier and active metal nickel attached to the niobium oxide carrier, and the nickel content in the nickel-based catalyst is 3-6 wt%; The preparation method (b) of the nickel-based catalyst is: Ordinary niobium oxide is used as a catalyst carrier, and a nickel salt solution is used as a loaded metal precursor. Under the condition of water as a solvent, metal nickel is loaded on the niobium oxide carrier by incipient wetness impregnation method to obtain a catalyst precursor. In the incipient wetness impregnation method, the nickel salt solution is dropwise added to the niobium oxide carrier while continuously stirring at a stirring speed of 200-800 r / min. The single impregnation time is 2-10 hours, and then the catalyst is placed in an oven for drying at a drying temperature of 60-120°C and a drying time of 8-12 hours to obtain the catalyst precursor. The nickel salt solution is a nickel sulfate solution. The catalyst precursor is heat-treated to obtain the nickel-based catalyst; the catalyst is ground in a mortar, and then tabletted and sieved to a particle size of 20-40 mesh; The nickel-based catalyst is a niobium oxide carrier and active metal nickel attached to the niobium oxide carrier, and the nickel content in the nickel-based catalyst is 3-6 wt%.

2. The preparation method according to claim 1, wherein: The purity of the ordinary niobium oxide is 99.9%; The molar concentration of nickel in the nickel salt solution is 0.1-0.4 mol / L.

3. The preparation method according to claim 1, wherein: The heat treatment comprises grinding the dried catalyst precursor and calcining it in a muffle furnace. The heat treatment atmosphere is air or nitrogen, the temperature is 200-800°C, the heating rate to the heat treatment temperature is 0.5-5°C / min, and the time is 4-6 hours.

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