A method for preparing a light alkane dehydrogenation reaction auxiliary agent

Abstract

The invention discloses a preparation method of a low-carbon alkane dehydrogenation reaction auxiliary agent, which is composed of Ca, Cu, Ce, V, P, Si, and Al elements. According to the mass percentage of oxides, CaO is 5-28%, CuO is 2-22%, CeO₂ is 0.8-3.3%, V2O3 is 1-4.7%, P2O5 is 0.5-2.7%, SiO2 is 5-12%, and the rest is Al2O3; the Al2O3 is a-Al2O3, which is used as a carrier type, and is mixed with a copper source, a calcium source, etc., so that the heat storage function of a-Al2O3 is retained, and the heat release and generation of water by the reaction of CuO and H2 is realized, and the heat-generating material absorbs water and releases heat, and has a triple heat release effect. Sulfur-carrying treatment after roasting can passivate the pipeline and deactivate the initial activity of the dehydrogenating agent, thereby improving the yield of the dehydrogenation reaction.

Description

Technical Field

[0001] The invention relates to a reaction aid for dehydrogenating low-carbon alkanes to prepare monoolefins and diolefins, and belongs to the field of petrochemical industry. Background Art

[0002] Low-carbon alkanes mainly exist in natural gas and liquefied petroleum gas, and they are widely used. In the past, they were mainly used as fuel for direct combustion, with extremely low utilization and small added value. Now they are converted into important chemical raw materials such as olefins to improve their utilization and added value. The research on this potential application prospect is currently receiving more and more attention. For example, propylene is an important basic chemical raw material, widely used in the production of chemical products such as polypropylene, isopropanol, isopropylbenzene, carbonyl alcohol, propylene oxide, acrylic acid, and acrylonitrile; and another important low-carbon olefin butene is also widely used, such as the production of high-octane gasoline components with mixed butenes, as well as products such as maleic anhydride and sec-butyl alcohol, heptene, polybutene, and acetic anhydride.

[0003] my country has relatively rich light hydrocarbon resources such as liquefied petroleum gas and condensate, which contain a large amount of low-carbon alkanes such as propane and butane. If propane and butane can be effectively converted directly into propylene and butene, it will make full use of petroleum resources, alleviate the problem of insufficient sources of low-carbon olefins, especially propylene and butene, and obtain high-value hydrogen at the same time. Therefore, it is necessary to develop processes and catalysts for the dehydrogenation of low-carbon alkanes suitable for industrial applications, including various functional additives.

[0004] The technology of propane dehydrogenation to propylene has been around for more than 20 years. After continuous improvement, its industrial application has become increasingly mature. The successful propane catalytic dehydrogenation processes include: UOP's Oleflex process, Lummus's Catofin process, Snamprogetti's fluidized bed (FBD) process, Uhde's steam activated reforming (STAR) process, and Linde's PDH process. The most widely used are the UOP Oleflex process and Lummus's Catofin process. Its catalytic system is developed from butane dehydrogenation catalysts, mainly Cr-based catalysts and Pt-based catalysts. It is reported that among the oxide catalysts used for the dehydrogenation of low-carbon alkanes, Cr-based catalysts have the highest activity. Compared with precious metal catalysts, it has lower requirements for impurities in the raw materials and is cheaper.

[0005] The dehydrogenation reaction of alkanes is usually an endothermic reaction, and the entire process can be operated as an adiabatic cycle process. Due to the fixed bed reactor operation mode and the inherent characteristics of the strong endothermicity of the dehydrogenation reaction, the bed temperature distribution of the reaction system is uneven and there is a large temperature difference. Therefore, adding heat to the reaction system during the reaction will reduce the temperature difference of the reaction system and improve the selectivity of the product. As a result, dehydrogenation reaction aids came into being. In the process developed by Klein, it is called a heating element. The heating element is mixed with an inert ceramic ball and a dehydrogenator in the reactor. Compared with a single dehydrogenator, its system and olefin yield are significantly improved.

[0006] CN 108176405 B discloses an alkane dehydrogenation reaction enhancing agent, which contains 15m% to 18m% CaO, 70m% to 80m% Al2O3, 6m% to 15m% CuO, and 0.01m% to 3m% oxides or mixtures thereof selected from group VIII, group VI, group IA, group IIA and rare earth elements; in its preparation process, the aluminum compound and the calcium compound are first formed and calcined at 800 to 1400°C for 0.5 to 15 hours to prepare a composite carrier, and then impregnated with a Cu solution. The aluminum compound will become a-Al2O3 at >1500°C, and its water absorption rate is very low. It is basically impossible to prepare 6m% to 15m% CuO by one impregnation, and multiple impregnations must be used, which greatly affects the efficiency, and the impregnation uniformity is poor, and the innermost layer is basically difficult to penetrate.

[0007] CN 108300430 B discloses an exothermic aid for use in an alkane dehydrogenation reaction process and a preparation method and a use method thereof. The composition is 10-35 wt% of CaO, 50-85 wt% of Al2O3, 5-30 wt% of CuO, and 0-3 wt% of metal oxides selected from Group VIII, Group IIB, Group IIIB, and Group VIIB. The aluminum compound, calcium compound, and solid copper compound are mixed and formed and placed at 800-1400°C for high temperature roasting for 0.2-24 hours. Al2O3 reacts with CuO to generate red aluminum-copper spinel. The aluminum-copper spinel is easily aged during the hydrothermal reaction, but is not easily reduced, so the promotion effect is greatly reduced.

[0008] CN 113388376 B discloses an alkane dehydrogenation heating aid, a preparation method and an application thereof, which is mainly prepared from CaO, CuO and Al2O3, wherein the weight proportions of CaO, CuO and Al2O3 are 35-90 parts, 10-40 parts and 5-40 parts respectively; the Cu element in the alkane dehydrogenation heating aid mainly exists in the form of CaCu2O3 and Ca2CuO3, and the ratio of the number of Ca atoms to the number of Al atoms is ≥6 / 7. Its high content of Ca undoubtedly weakens the main content of Al2O3. In the field of dehydrogenation heating aids, a-Al2O3 inert porcelain balls are used to store heat before the development of heating elements, so Al2O3 heating elements are also very important. Secondly, the Cu element mainly exists in the form of CaCu2O3 and Ca2CuO3, and the oxidation-reduction heat release of Cu cannot be effectively utilized.

[0009] In view of the above problems, there is basically no domestic production of dehydrogenation additives at present, and they are all monopolized by foreign countries. In order to break this situation, it is imperative to develop an additive that can generate a large amount of heat to compensate for the endothermic loss of the dehydrogenation reaction. Summary of the invention

[0010] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a low-carbon alkane dehydrogenation reaction aid.

[0011] The additive is composed of Ca, Cu, Ce, V, P, Si and Al elements. Calculated by the mass percentage of the oxides, CaO is 5-28%, CuO is 2-22%, CeO2 is 0.8-3.3%, V2O3 is 1-4.7%, P2O5 is 0.5-2.7%, SiO2 is 5-12%, and the rest is Al2O3.

[0012] Another object of the present invention is to provide a method for preparing the auxiliary agent, comprising the steps of:

[0013] S1, preparing a-Al2O3 by calcining small-pore pseudo-boehmite at 1250℃ for 6h;

[0014] S2, uniformly mixing the a-Al2O3 in S1 with small-pore pseudo-boehmite, a calcium source, a copper source and a pore-forming agent to prepare a mixed powder;

[0015] S3, mixing the measured phosphoric acid, cerium source, vanadium source, silica sol, nitric acid and water in a certain proportion to prepare a mixed solution;

[0016] S4, adding the mixed solution in S3 to the mixed powder in S2, extruding, curing, drying and then roasting to obtain a crude additive product;

[0017] S5. Immerse the crude auxiliary agent product obtained in S4 in an ammonium thiosulfate solution, and dry to obtain a finished auxiliary agent.

[0018] Furthermore, in step S2, the amount of a-Al2O3 and small-pore pseudo-boehmite used is 6-9:1 in terms of Al2O3 mass percentage.

[0019] Furthermore, in step S2, the calcium source is one or more of CaCO3, Ca(OH)2, and CaO, and the copper source is one or more of Cu(OH)2, CuO, and basic copper carbonate.

[0020] Further, the pore-forming agent in step S2 is one of CMC and sesbania powder, and its amount is 2-10% of the mixed powder in S2.

[0021] Furthermore, in step S3, the cerium source is one or two of Ce(NO3)3 and CeCl3, and the vanadium source is one or two of ammonium metavanadate and vanadyl oxalate.

[0022] Furthermore, in step S4, the curing condition is 60±5° C. in a sealed system for 2 days, and the calcination condition is 600-1000° C. for 4-6 hours.

[0023] Furthermore, the concentration of the ammonium thiosulfate solution in step S5 is determined based on the sulfur-carrying element mass of the crude auxiliary product in step S4 being 0.5-1.2%.

[0024] Furthermore, in step S5, the drying condition is 120-150° C. for 2-4 hours.

[0025] Beneficial effects of the present invention:

[0026] 1. Using a-Al2O3 as the main carrier, with a small amount of small-pore pseudo-boehmite and silica sol molding, the heat storage function of a-Al2O3 is retained. A small amount of small-pore pseudo-boehmite ensures the strength of the additive, and silica sol further promotes the improvement of strength, making up for the shortcoming that pure a-Al2O3 cannot be molded. Silica sol can minimize the amount of small-pore pseudo-boehmite. The small-pore pseudo-boehmite is calcined in the S4 step to obtain the γ-Al2O3 form, which has a little acid content. If it is too much, a cracking side reaction will occur during the dehydrogenation reaction.

[0027] 2. The strength of a-Al2O3 powder molding is often not high. Step S4 of the present invention utilizes the principle of cement curing and is applied across fields in the preparation of catalysts to further enhance the strength of the additive.

[0028] 3. The a-Al2O3 powder is first prepared, then kneaded with copper source and calcium source and then calcined at low temperature, which not only ensures the heat storage function of a-Al2O3, but also ensures that there is no reaction similar to the spinel structure between copper, calcium and aluminum, and guarantees its heating characteristics to the greatest extent. CuO reacts with H2 to release heat and generate water, the heating material absorbs water and releases heat, and the additive stores part of the heat as a heat medium. Through triple heat release, the temperature distribution of the reactor for alkane dehydrogenation is effectively improved.

[0029] 4. Both cerium and vanadium have multiple valence states, and utilizing this property can greatly promote the oxidation-reduction exothermicity of copper.

[0030] 5. In step S5, the ammonium thiosulfate solution is used to treat the crude additive product in step S4, thereby achieving sulfur loading of the additive, which has multiple functions:

[0031] First, during the heating process, the escaped sulfur is decomposed to passivate the pipeline;

[0032] Second, sulfur inactivates the dehydrogenating agent to a certain extent, reducing the occurrence of cracking side reactions;

[0033] Third, the additive contains Ca and Cu, which can stabilize sulfur and control its slow release to avoid excessive release of S at one time, which would produce adverse effects. In existing reports, Ca and Cu react with the carrier Al to form a spinel-like structure, which cannot achieve this function. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail in the following specific embodiments.

[0035] Example 1

[0036] The additives are calculated by mass percentage of oxides: CaO is 12%, CuO is 5%, CeO2 is 3.3%, V2O3 is 1%, P2O5 is 1.1%, SiO2 is 9%, and the rest is Al2O3.

[0037] According to the above component ratio, a light alkane dehydrogenation reaction auxiliary agent is prepared by the following method:

[0038] S1, preparing a-Al2O3 by calcining small-pore pseudo-boehmite at 1250℃ for 6h;

[0039] S2. Evenly mix the a-Al2O3 in S1 with small-pore pseudo-boehmite, calcium source, copper source and pore-forming agent to prepare a mixed powder; the dosage ratio of a-Al2O3 to small-pore pseudo-boehmite is 8:1 based on the mass percentage of Al2O3; the calcium source is Ca(OH)2, and the copper source is Cu(OH)2 and CuO, which are added in a 1:1 ratio based on the mass of CuO; the pore-forming agent is CMC, and its dosage is 8% of the mixed powder in S2.

[0040] S3. Mix the measured phosphoric acid with a cerium source, a vanadium source, silica sol, nitric acid and water in a certain proportion to prepare a mixed solution; the cerium source is Ce(NO3)3, and the vanadium source is vanadyl oxalate.

[0041] S4. Add the mixed solution in S3 to the mixed powder in S2, extrude into strips, cure, dry and then roast to obtain a crude additive product; the curing conditions are 60±5℃ sealed system for 2d, and the roasting conditions are 800℃ for 5h.

[0042] S5. Immerse the crude auxiliary agent product obtained in S4 in an ammonium thiosulfate solution, and dry to obtain a finished auxiliary agent.

[0043] The concentration of the ammonium thiosulfate solution is determined based on the sulfur-carrying mass of the crude auxiliary product in step S4 being 0.8%. The drying condition is 120° C. for 4 hours.

[0044] Comparative Example 1

[0045] The preparation is the same as in Example 1, the only difference being that no cerium source is added in step S3.

[0046] Example 2

[0047] The additives are calculated by mass percentage of oxides: CaO is 5%, CuO is 14%, CeO2 is 0.8%, V2O3 is 4.7%, P2O5 is 0.5%, SiO2 is 10%, and the rest is Al2O3.

[0048] According to the above component ratio, a light alkane dehydrogenation reaction auxiliary agent is prepared by the following method:

[0049] S1, preparing a-Al2O3 by calcining small-pore pseudo-boehmite at 1250℃ for 6h;

[0050] S2. Evenly mix the a-Al2O3 in S1 with small-pore pseudo-boehmite, a calcium source, a copper source and a pore-forming agent to prepare a mixed powder; the ratio of a-Al2O3 to small-pore pseudo-boehmite is 9:1 based on the mass percentage of Al2O3; the calcium source is CaCO3, the copper source is basic copper carbonate, and the pore-forming agent is CMC, and its amount is 10% of the mixed powder in S2.

[0051] S3. Mix the measured phosphoric acid with a cerium source, a vanadium source, silica sol, nitric acid and water in a certain proportion to prepare a mixed solution; the cerium source is CeCl3, and the vanadium source is vanadyl oxalate.

[0052] S4. Add the mixed solution in S3 to the mixed powder in S2, extrude into strips, cure, dry and then roast to obtain a crude additive product; the curing conditions are 60±5℃ in a sealed system for 2d, and the roasting conditions are 600℃ for 5h.

[0053] S5, immersing the crude product of the auxiliary agent obtained in S4 in an ammonium thiosulfate solution, and drying to obtain a finished auxiliary agent. The concentration of the ammonium thiosulfate solution is determined based on the sulfur-carrying element mass of the crude product of the auxiliary agent in step S4 being 0.5%.

[0054] The drying condition is 150℃ for 2h.

[0055] Comparative Example 2

[0056] The preparation is the same as in Example 2, the only difference being that no vanadium source is added in step S3.

[0057] Example 3

[0058] The additives are calculated by mass percentage of oxides: CaO is 28%, CuO is 2%, CeO2 is 1.6%, V2O3 is 3.1%, P2O5 is 1.8%, SiO2 is 5%, and the rest is Al2O3.

[0059] According to the above component ratio, a light alkane dehydrogenation reaction auxiliary agent is prepared by the following method:

[0060] S1, preparing a-Al2O3 by calcining small-pore pseudo-boehmite at 1250℃ for 6h;

[0061] S2. Evenly mix the a-Al2O3 in S1 with small-pore pseudo-boehmite, calcium source, copper source and pore-forming agent to prepare a mixed powder; the dosage ratio of a-Al2O3 to small-pore pseudo-boehmite is 7:1 based on the mass percentage of Al2O3; the calcium source is CaCO3 and Ca(OH)2, which are added in a ratio of 1:1 to the converted CaO content, the copper source is CuO, and the pore-forming agent is sesbania powder, and its dosage is 5% of the mixed powder in S2.

[0062] S3. Mix the measured phosphoric acid with cerium source, vanadium source, silica sol, nitric acid and water in a certain proportion to prepare a mixed solution; the cerium source is Ce(NO3)3, CeCl3, 1:1 based on the mass of CeO2, and the vanadium source is ammonium metavanadate.

[0063] S4. Add the mixed solution in S3 to the mixed powder in S2, extrude into strips, cure, dry and then roast to obtain a crude additive product; the curing conditions are 60±5℃ in a sealed system for 2d, and the roasting conditions are 1000℃ for 6h.

[0064] S5, immersing the crude product of the auxiliary agent obtained in S4 in an ammonium thiosulfate solution, and drying to obtain a finished auxiliary agent. The concentration of the ammonium thiosulfate solution is determined based on the sulfur-carrying element mass of the crude product of the auxiliary agent in step S4 being 1.0%.

[0065] The drying condition is 135℃ for 3h.

[0066] Comparative Example 3

[0067] The preparation is the same as in Example 3, the only difference being that the preparation is completed at step S4 and step S5 is not performed.

[0068] Example 4

[0069] The additives are calculated by mass percentage of oxides: CaO is 19%, CuO is 22%, CeO2 is 1.1%, V2O3 is 2.3%, P2O5 is 2.7%, SiO2 is 12%, and the rest is Al2O3.

[0070] According to the above component ratio, a light alkane dehydrogenation reaction auxiliary agent is prepared by the following method:

[0071] S1, preparing a-Al2O3 by calcining small-pore pseudo-boehmite at 1250℃ for 6h;

[0072] S2. Evenly mix the a-Al2O3 in S1 with small-pore pseudo-boehmite, a calcium source, a copper source and a pore-forming agent to prepare a mixed powder; wherein the dosage ratio of a-Al2O3 to small-pore pseudo-boehmite is 6:1 based on the mass percentage of Al2O3; the calcium source is CaO, the copper source is Cu(OH)2, and the pore-forming agent is sesbania powder, and its dosage is 2% of the mixed powder in S2.

[0073] S3. Mix the measured phosphoric acid with cerium source, vanadium source, silica sol, nitric acid and water in a certain proportion to prepare a mixed solution; the cerium source is Ce(NO3)3, and the vanadium source is ammonium metavanadate and vanadyl oxalate, which are added in a ratio of 1:1 based on the converted V2O3 mass.

[0074] S4. Add the mixed solution in S3 to the mixed powder in S2, extrude into strips, cure, dry and then roast to obtain a crude additive product; the curing conditions are 60±5℃ in a sealed system for 2d, and the roasting conditions are 760℃ for 4h.

[0075] S5. Immerse the crude auxiliary agent product obtained in S4 in an ammonium thiosulfate solution, and dry to obtain a finished auxiliary agent.

[0076] The concentration of the ammonium thiosulfate solution is determined based on the sulfur content of the crude additive product in step S4 being 1.2%. The drying condition is 120° C. for 3 hours.

[0077] Comparative Example 4

[0078] The preparation is the same as that of Example 4, the only difference being that no silica sol is added in step S3, and the mass of SiO2 is supplemented by a-Al2O3.

[0079] Comparative Example 5

[0080] The preparation is the same as that of Example 4, the only difference being that no silica sol is added in step S3, and the mass of SiO2 is supplemented by small-pore pseudo-boehmite.

[0081] Comparative Example 6

[0082] The preparation is the same as that of Example 4, the only difference being that no curing is performed in step S4, and the extruded strips are directly dried after being formed.

[0083] Comparative Example 7

[0084] A foreign dehydrogenation reaction auxiliary product.

[0085] Comparative Example 8

[0086] A commercial a-Al2O3 ceramic ball.

[0087] Evaluation system:

[0088] a) Strength evaluation

[0089] Refer to HG / T 2782-2011 "Determination of crushing resistance of fertilizer catalyst particles".

[0090] Table 1 Strength test results

[0091] Strength (N / cm) Example 4 280 Comparative Example 4 115 Comparative Example 5 253 Comparative Example 6 235

[0092] Table 1 shows that the addition of silica sol can significantly improve the strength of the dehydrogenation reaction auxiliary agent of a-Al2O3 mixed and extruded strips, and the strength can be further increased by curing.

[0093] b) Activity evaluation

[0094] 3 mL of fresh sample of the company's homemade dehydrogenation agent was taken and evenly mixed with 3 mL of the dehydrogenation reaction auxiliary agent prepared in Examples 1 to 4 and the auxiliary agent of Comparative Examples 1 to 8, respectively. The mixture was placed in a quartz glass reactor, heated to 580°C with nitrogen, and then 15 mL / min of isobutane was introduced. The outlet gas was collected with an air bag for 15 minutes. The outlet gas was sent to a gas chromatography equipped with an alumina column for component analysis. Isobutylene was taken as the target product, and the conversion rate and selectivity were calculated. See Table 2.

[0095] Conversion rate = (isobutane import - isobutane export) / isobutane import × 100%

[0096] Selectivity = isobutylene export / (isobutane import-isobutane export) × 100%

[0097] Table 2 Conversion rate and selectivity in the examples

[0098] Conversion rate (%) Selectivity (%) Example 1 62.8 93.1 Comparative Example 1 61.5 92.0 Example 2 61.2 91.4 Comparative Example 2 60.9 90.6 Example 3 59.7 88.9 Comparative Example 3 61.3 87.1 Example 4 61.1 90.8 Comparative Example 4 61.2 90.6 Comparative Example 5 60.7 90.1 Comparative Example 6 61.1 90.5 Comparative Example 7 61.3 92.8 Comparative Example 8 59.8 87.3

[0099] Through the above Examples 1-4 and Comparative Examples 1-8, it can be seen that the addition of cerium and vanadium has a tendency to improve the reaction activity. The reason is that both cerium and vanadium have multiple valence states. Utilizing this characteristic can greatly promote the oxidation-reduction heat release of copper, making up for the insufficient reaction temperature caused by the endothermic dehydrogenation reaction.

[0100] In Example 3 and Comparative Example 3, the dehydrogenation reaction aid was loaded with S and migrated to the dehydrogenation agent, which inactivated the initial activity of the dehydrogenation agent to a certain extent, reduced the occurrence of cracking side reactions, and thus improved the selectivity.

[0101] From Example 4 and Comparative Example 4, it can be seen that the addition of silica sol has almost no side effect on the dehydrogenation reaction, while in Comparative Example 5, pseudo-boehmite is used to replace silica sol, and the carrier generated by calcining at 760°C has a certain strong acidity, which will cause the side reaction of cracking of the raw material.

[0102] From Comparative Examples 7 to 8, it is not difficult to see that the dehydrogenation reaction aid of the present invention has obvious advantages.

[0103] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a light alkane dehydrogenation reaction auxiliary agent, characterized in that: The additive is composed of Ca, Cu, Ce, V, P, Si, and Al elements. According to the mass percentage of the oxides, CaO is 5-28%, CuO is 2-22%, CeO2 is 0.8-3.3%, V2O3 is 1-4.7%, P2O5 is 0.5-2.7%, SiO2 is 5-12%, and the rest is Al2O3; The preparation method of the auxiliary agent comprises the following steps: S1, preparing a-Al2O3 by calcining small-pore pseudo-boehmite at 1250℃ for 6h; S2, uniformly mixing the a-Al2O3 in S1 with small-pore pseudo-boehmite, a calcium source, a copper source and a pore-forming agent to prepare a mixed powder; S3, mixing the measured phosphoric acid, cerium source, vanadium source, silica sol, nitric acid and water in a certain proportion to prepare a mixed solution; S4, adding the mixed solution in S3 to the mixed powder in S2, extruding, curing, drying and then roasting to obtain a crude additive product; S5. Immerse the crude auxiliary agent product obtained in S4 in an ammonium thiosulfate solution, and dry to obtain a finished auxiliary agent.

2. The preparation method according to claim 1, characterized in that: The amount of a-Al2O3 and small-pore pseudo-boehmite used in step S2 is 6-9:1 in terms of Al2O3 mass percentage.

3. The preparation method according to claim 1, characterized in that: The calcium source in step S2 is one or more of CaCO3, Ca(OH)2, and CaO, and the copper source is one or more of Cu(OH)2, CuO, and basic copper carbonate.

4. The preparation method according to claim 1, characterized in that: The pore-forming agent described in step S2 is one of CMC and sesbania powder, and its usage is 2-10% of the mixed powder in S2.

5. The preparation method according to claim 1, characterized in that: The cerium source in step S3 is one or both of Ce(NO3)3 and CeCl3, and the vanadium source is one or both of ammonium metavanadate and vanadyl oxalate.

6. The preparation method according to claim 1, characterized in that: The curing conditions described in step S4 are treatment at 60±5° C. in a sealed system for 2 days, and the calcination conditions are treatment at 600~1000° C. for 4~6 hours.

7. The preparation method according to claim 1, characterized in that: The concentration of the ammonium thiosulfate solution in step S5 is determined based on the sulfur-carrying mass of the crude auxiliary product in step S4 being 0.5-1.2%.

8. The preparation method according to claim 1, characterized in that: The drying condition described in step S5 is 120-150° C. for 2-4 hours.