Catalyst for ethane oxidative dehydrogenation reaction and preparation method thereof

Abstract

The invention discloses a preparation method of a catalyst for oxidative dehydrogenation reaction of ethane, which comprises the following steps: dissolving ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and a dispersing agent in deionized water to form a mixed solution; and adding a niobium oxalate aqueous solution into the mixed solution within 15-50 minutes to form a suspension, then adding an aqueous solution of a template agent polyether P123, aging, carrying out a hydrothermal crystallization reaction, drying, roasting, and removing an M2 phase to obtain the catalyst for the oxidative dehydrogenation reaction of ethane. The dispersing agent and the template polyether P123 are introduced in the specific steps of the catalyst preparation process, and the time for adding the niobium oxalate aqueous solution into the mixed solution is limited, so that the pore structure and the specific surface area of the catalyst can be effectively improved, the proportion of high-concentration active sites on the tail end surface of the catalyst is increased, and the reaction performance of the catalyst is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of ethane oxidative dehydrogenation to ethylene, and in particular to a catalyst for ethane oxidative dehydrogenation reaction and a preparation method thereof. Background Art

[0002] Ethylene is an important petrochemical raw material, which is mainly produced by traditional steam thermal cracking. In a typical ethane steam cracking plant to produce ethylene, energy consumption costs account for about 70% of the production cost. Compared with high-temperature cracking, the product of ethane oxidative dehydrogenation to ethylene (ODHE) technology is single and easy to separate, and the separation system is simple. It is a low-energy consumption approach with great application prospects and has been one of the research hotspots in recent years.

[0003] The M1 pure phase catalyst in the molybdenum, vanadium, niobium and tellurium multi-metal oxide system is a catalyst system with great application prospects. It has the characteristics of high activity and strong redox ability at low temperatures, and is currently a hot research topic in the oxidative dehydrogenation of low-carbon alkanes. The synthesis method of M1 pure phase catalyst includes hydrothermal synthesis or slurry method, supplemented by appropriate purification process. However, the preparation process is complicated, and the synthetic product is sensitive to the parameter conditions of the preparation process.

[0004] For example, Chinese patent document CN105080575B reports the steps for preparing the catalyst MoVTeNbO: (1) using ammonium heptamolybdate, vanadyl sulfate, telluric acid, niobium oxalate and surfactant hexadecyltrimethylammonium bromide as raw materials, with the molar ratio of each component being Mo:V:Te:Nb:surfactant = 1:0.2-0.4:0.2-0.3:0.1-0.2; preparing a mixed solution of the raw materials according to the above ratio and placing it in a special stainless steel reactor, heating the mixture from room temperature at 2-10°C / min. The temperature is raised to 160-230°C at a heating rate of 100°C, kept at this temperature for 2-20 hours, and then naturally cooled to room temperature; (3) after aging, taken out, filtered, and dried; the dried product is calcined in two stages, the first stage is calcined at 300°C in air for 2 hours, and the second stage is calcined at 400-700°C in nitrogen for 1-5 hours, and crushed into 20-40 mesh to obtain the catalyst; the reaction is carried out at 350°C, the ethane conversion rate and ethylene selectivity can reach 70.5% and 95.0% respectively, and the ethylene yield can reach 67.0%.

[0005] Chinese patent document CN108855118B discloses a method for preparing a pure M1 phase MoVTeNbOx catalyst with a high specific surface area, comprising the following steps: S1) mixing and dissolving a molybdenum-containing compound, a vanadium-containing compound, an antimony-containing compound, a niobium-containing compound and a protective agent to obtain a precursor-protective agent mixture solution; the protective agent is a surfactant or a small molecule organic acid and its salt; S2) subjecting the precursor-protective agent mixed solution to a hydrothermal reaction to separate and obtain a solid; S3) calcining the solid in an air atmosphere, then calcining in an inert gas, and then purifying it with hydrogen oxide to obtain a pure M1 phase MoVTeNbOx catalyst.

[0006] The specific preparation process of the catalyst disclosed in Chinese patent document CN101612564 B is as follows: the molar ratio of the active components is Mo:V:Te:Nb=1:0.2~1.0:0.2~1.0:0.1~0.5; ammonium heptamolybdate, vanadyl sulfate, telluric acid and niobium oxalate are prepared into a mixed solution according to the ratio and placed in a special stainless steel reactor, and the temperature is programmed to 160~230℃ from room temperature at a heating rate of 2~10℃ / min, and the heat preservation time is 2~20 hours, and then naturally cooled to room temperature; after aging, it is taken out, filtered, dried, and calcined at 500~700℃ for 2~5 hours.

[0007] Chinese patent document CN104941668B discloses a pure phase compound of molybdenum-vanadium-niobium-tellurium multinary metal oxide M1 for ethane oxidative dehydrogenation reaction, which is prepared by the following method: under water bath conditions of 60-80°C, ammonium heptamolybdate, vanadyl sulfate, and telluric acid, in which the atomic ratio of molybdenum to vanadium and tellurium is 1:0.15-0.30:0.15-0.35, are mixed and dissolved in deionized water to obtain solution A, and ammonium niobium oxalate is dissolved in deionized water to obtain solution B, wherein the atomic ratio of niobium to molybdenum in solution A is 0.05:1-0.20:1, and the volume ratio of solution A to solution B is 2:1, and solution A and solution B are cooled to 30-50°C, mixed and stirred to form a precursor solution; the precursor solution The method comprises placing the mixture in a hydrothermal autoclave, replacing the air therein with nitrogen, and performing hydrothermal synthesis at 150-200° C. for 24-48 hours to obtain a suspension; washing and filtering the suspension obtained by the hydrothermal synthesis, drying the obtained suspension overnight and then grinding it to obtain a solid phase precursor of the M1 pure phase compound; calcining the solid phase precursor at 550-650° C. in a nitrogen atmosphere for 1-3 hours to obtain a mixed phase compound of molybdenum, vanadium, niobium and tellurium multinary metal oxides M1 and M2; placing the mixed phase compound in hydrogen peroxide with a volume fraction of 5-20%, stirring at 50-70° C. for 1-3 hours, and then filtering and drying for 12-24 hours to obtain a molybdenum, vanadium, niobium and tellurium multinary metal oxide M1 pure phase compound.

[0008] Although the reaction performances of the M1 catalysts disclosed above have been improved, the reaction performances of the M1 catalysts still need to be improved. Summary of the invention

[0009] In view of this, the present invention provides a method for preparing a catalyst for ethane oxidative dehydrogenation reaction. The method adds a dispersant and a template agent at specific steps in the catalyst preparation process to disperse and support the active components, thereby improving the pore structure and specific surface area of ​​the catalyst, forming an ordered pore structure, improving the catalytic activity, and greatly improving the reaction performance of the catalyst.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A method for preparing a catalyst for ethane oxidative dehydrogenation reaction comprises the following steps:

[0012] (1) dissolving ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and a dispersant in deionized water to form a mixed solution;

[0013] (2) adding an aqueous solution of niobium oxalate to the mixed solution within 15 to 50 minutes to form a suspension, then adding an aqueous solution of the template polyether P123, and subjecting the mixture to aging, hydrothermal crystallization, drying, calcination, and removal of the M2 phase to obtain the M1 phase catalyst for ethane oxidative dehydrogenation reaction.

[0014] Optionally, in the method for preparing the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the added amount of the dispersant is 0.005wt% to 0.1wt% of the mass of the ammonium heptamolybdate tetrahydrate.

[0015] Optionally, in the method for preparing the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the dispersant is selected from any one of propylene glycol, polymethyl cellulose, polyvinyl alcohol, sesbania powder, polyethylene glycol and polyvinyl pyrrolidone.

[0016] Optionally, in the method for preparing the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the addition amount of the template polyether P123 is 0.01wt% to 0.3wt% of the mass of the ammonium heptamolybdate tetrahydrate.

[0017] Optionally, in the method for preparing the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the aging temperature is 20 to 90° C. and the time is 20 to 180 min.

[0018] Optionally, in the method for preparing the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the temperature of the hydrothermal crystallization reaction is 150 to 200° C., and the time is 12 to 60 hours.

[0019] Optionally, in the method for preparing the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the drying temperature is 70 to 120° C. and the drying time is 6 to 20 hours.

[0020] Optionally, in the preparation method of the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the calcination is selected from a two-stage calcination; the two-stage calcination includes first calcining at 200-400°C in air for 2-6 hours, and then calcining at 550-650°C in an inert atmosphere for 1-4 hours.

[0021] Optionally, in the preparation method of the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, hydrogen peroxide is used for purification to remove the M2 phase, the concentration of the hydrogen peroxide is 5wt% to 15wt%, the purification temperature is 30 to 80°C, and the time is 30 to 240 min.

[0022] Optionally, in the preparation method of the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, in step (1), the ammonium heptamolybdate tetrahydrate, the ammonium metavanadate, the telluric acid and the dispersant are dissolved in deionized water, and the amount of deionized water used is not limited, as long as the ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and the dispersant are dissolved; if necessary, heating can be performed under stirring to promote the dissolution of the ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and the dispersant in the deionized water, such as stirring at 70 to 100°C for 60 to 180 minutes to promote dissolution, and the specific amount can be adjusted according to actual conditions.

[0023] Optionally, in the preparation method of the above-mentioned ethane oxidative dehydrogenation catalyst provided by the present invention, the aqueous solution of niobium oxalate is obtained by dissolving niobium oxalate in deionized water, and the amount of deionized water used is not limited, as long as it can dissolve niobium oxalate; if necessary, in order to save efficiency, heating can be performed under stirring to promote the dissolution of niobium oxalate in deionized water, such as stirring at 60 to 90°C for 20 to 60 minutes, and the specific amount can be adjusted according to actual conditions.

[0024] Optionally, in the preparation method of the above-mentioned ethane oxidative dehydrogenation catalyst provided by the present invention, the aqueous solution of the template polyether P123 is obtained by dissolving the template polyether P123 in deionized water, and the amount of deionized water used is not limited, as long as it can dissolve the polyether P123; if necessary, in order to save efficiency, heating can be performed under stirring to promote the dissolution of the polyether P123 in the deionized water, such as stirring at 70-100°C for 120-480 minutes, and the specific amount can be adjusted according to actual conditions.

[0025] Optionally, in the preparation method of the above-mentioned ethane oxidative dehydrogenation supported catalyst provided by the present invention, after purifying and removing the M2 phase with hydrogen peroxide, it also includes a re-drying step; preferably, the re-drying temperature is 60-150° C. and the time is 5-18 hours.

[0026] The present invention also provides a catalyst for ethane oxidative dehydrogenation reaction, which is prepared by the above-mentioned method for preparing the catalyst for ethane oxidative dehydrogenation reaction. The general formula of the catalyst for ethane oxidative dehydrogenation reaction is as follows: Mo a V b Te c Nb d , where a=1, b is 0.25~0.32, c is 0.16~0.23, and d is 0.08~0.15.

[0027] The present invention also provides a catalyst for ethane oxidative dehydrogenation reaction prepared by the above-mentioned method for preparing the catalyst for ethane oxidative dehydrogenation reaction, which is used to catalyze the ethane oxidative dehydrogenation to ethylene reaction; preferably, the reaction temperature is 350-400°C, the pressure is normal pressure, and the feed space velocity of the reaction gas is 200-500h -1 The molar ratio of the reaction gas ethane: oxygen: nitrogen is 1: (0.4-0.8): (1.2-2.0).

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The preparation method of the catalyst for ethane oxidative dehydrogenation reaction provided by the present invention, the introduction of dispersant and template polyether P123 in the specific step of the catalyst preparation process, combined with the time of limiting the addition of niobium oxalate aqueous solution to the mixed solution, can effectively improve the pore structure and specific surface area of ​​the catalyst, increase the proportion of high-concentration active sites on its terminal surface, and thus greatly improve the reaction performance of the catalyst. Specifically, tetrahydrated ammonium heptamolybdate, ammonium metavanadate, telluric acid and dispersant are mixed, which can disperse and support active components such as molybdenum, vanadium, and tellurium, thereby improving the pore structure and specific surface area of ​​the catalyst; by aging after adding the template polyether P123, an ordered pore structure is formed, and the specific surface area is increased; by limiting the time of adding niobium oxalate aqueous solution to the mixed solution, the rate of forming a complex after the heteropolyacid anions formed in the initial mixed aqueous solution of Mo, V, and Te and the Nb precursor are mixed, thereby generating more active species and improving the reaction activity of the catalyst. The dispersant and the template polyether P123, combined with the limited time of adding the niobium oxalate solution, cooperate with each other to exert a synergistic effect, and the reaction performance of the catalyst prepared by the method is greatly improved. DETAILED DESCRIPTION

[0030] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0031] If no specific experimental steps or conditions are specified in the examples and comparative examples, the conventional experimental steps or conditions described in the literature in the art can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially.

[0032] Source of raw materials: All raw materials used in the catalyst preparation process were analytical grade (AR). Raw materials: ammonium heptamolybdate tetrahydrate, propylene glycol, hydrogen peroxide, polymethylcellulose, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, and polyether P123 were purchased from Sinopharm Reagent Co., Ltd.; ammonium metavanadate and telluric acid were purchased from MacLean Reagent Co., Ltd.; niobium oxalate and sesbania powder were purchased from Aladdin Reagent Co., Ltd.;

[0033] Evaluation and analysis method: The catalysts prepared in the examples and comparative examples were tableted and crushed, sieved to 20-40 mesh, and loaded into a 10 mL fixed bed microreactor with an inner diameter of 5 mm. The reaction temperature was 360 ° C, atmospheric pressure, and the feed space velocity of the reaction gas was 300 h -1 The reaction was carried out for 2 hours under the condition that the molar ratio of the reaction gas ethane: oxygen: nitrogen gas was 1: 0.6: 1.5 to obtain ethylene product. The reaction product was detected by gas chromatography analysis.

[0034] Example 1

[0035] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0036] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and propylene glycol are added to deionized water and stirred at 70° C. for 120 min to form a mixed solution; wherein the amount of propylene glycol added is 0.02 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0037] (2) Adding polyether P123 into deionized water, stirring at 80° C. for 300 min, to obtain an aqueous solution of polyether 123; wherein the amount of polyether P123 added is 0.1 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0038] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 70° C. for 40 minutes to form a niobium oxalate aqueous solution;

[0039] (4) Add the aqueous solution of niobium oxalate to the mixed solution (for 20 minutes) to form a suspension, then add the aqueous solution of polyether 123, age at 70°C for 120 minutes, perform hydrothermal crystallization reaction at 150°C for 24 hours, and then dry at 80°C for 12 hours. Calcinate at 300°C in an air atmosphere for 3.5 hours, then calcine at 600°C in a nitrogen atmosphere for 3 hours, put the obtained crude catalyst into 12wt% hydrogen peroxide, stir and react at 60°C for 120 minutes, purify the catalyst to remove the M2 phase, and then dry at 80°C for 10 hours to obtain the finished catalyst with a molecular formula of Mo1V 0.28 Te 0.18 Nb 0.12 , denoted as ODHE-1.

[0040] Example 2

[0041] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0042] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polymethyl cellulose were added to deionized water and stirred at 75° C. for 100 min to form a mixed solution, wherein the amount of polymethyl cellulose added was 0.005 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0043] (2) Add polyether P123 into deionized water and stir at 90° C. for 180 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.3 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0044] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 75° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0045] (4) Add the aqueous solution of niobium oxalate to the mixed solution (taking 15 minutes) to form a suspension, then add the aqueous solution of polyether 123, age at 20°C for 100 minutes, perform hydrothermal crystallization reaction at 170°C for 12 hours, and then dry at 80°C for 16 hours. Calcinate at 300°C in an air atmosphere for 5 hours, and then calcine at 550°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst is placed in 8wt% hydrogen peroxide, stirred at 40°C for 150 minutes, the catalyst is purified to remove the M2 phase, and then dried at 130°C for 12 hours to obtain a finished catalyst with a molecular formula of Mo1V 0.28 Te 0.20 Nb 0.08 , denoted as ODHE-2.

[0046] Example 3

[0047] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0048] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polyvinyl alcohol were added to deionized water and stirred at 100° C. for 90 min to form a mixed solution, wherein the amount of polyvinyl alcohol added was 0.007 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0049] (2) Add polyether P123 into deionized water and stir at 70° C. for 400 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.25 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0050] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 60° C. for 60 minutes to form an aqueous solution of niobium oxalate;

[0051] (4) Add the aqueous solution of niobium oxalate to the mixed solution (25 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 50°C for 60 minutes, perform hydrothermal crystallization reaction at 175°C for 48 hours, and then dry at 70°C for 18 hours. Calcinate at 200°C in an air atmosphere for 6 hours, then calcine at 600°C in a nitrogen atmosphere for 2 hours, and put the obtained crude catalyst into 7wt% hydrogen peroxide, stir at 50°C for 60 minutes, purify the catalyst to remove the M2 phase, and then dry at 100°C for 10 hours to obtain the finished catalyst with a molecular formula of Mo1V 0.30 Te 0.16 Nb 0.12 , denoted as ODHE-3.

[0052] Example 4

[0053] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0054] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 80° C. for 85 min to form a mixed solution. The amount of sesbania powder added was 0.01 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0055] (2) Add polyether P123 into deionized water and stir at 100° C. for 200 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.15 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0056] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0057] (4) Add the aqueous solution of niobium oxalate to the mixed solution (for 30 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 80°C for 180 minutes, perform hydrothermal crystallization reaction at 180°C for 30 hours, and then dry at 80°C for 16 hours. Calcinate at 300°C in an air atmosphere for 4 hours, then calcine at 620°C in a nitrogen atmosphere for 2 hours, and put the obtained crude catalyst into 10wt% hydrogen peroxide, stir and react at 60°C for 100 minutes, purify the catalyst to remove the M2 phase, and then dry at 120°C for 8 hours to obtain the finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-4.

[0058] Example 5

[0059] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0060] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polyethylene glycol were added to deionized water and stirred at 85° C. for 180 min to form a mixed solution, wherein the amount of polyethylene glycol added was 0.1 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0061] (2) Add polyether P123 into deionized water and stir at 100° C. for 200 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.05 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0062] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 85° C. for 50 minutes to form an aqueous solution of niobium oxalate;

[0063] (4) Add the aqueous solution of niobium oxalate to the mixed solution (25 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 85°C for 90 minutes, perform hydrothermal crystallization reaction at 190°C for 20 hours, and then dry at 90°C for 12 hours. Calcinate at 400°C in air atmosphere for 2 hours, then calcine at 650°C in nitrogen atmosphere for 1 hour, put the obtained crude catalyst into hydrogen peroxide with a concentration of 7.5wt%, stir and react at 70°C for 80 minutes, purify the catalyst to remove the M2 phase, and then dry at 90°C for 15 hours to obtain the finished catalyst with a molecular formula of Mo1V 0.32 Te 0.20 Nb 0.15 , denoted as ODHE-5.

[0064] Example 6

[0065] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0066] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polyvinyl pyrrolidone were added to deionized water and stirred at 75° C. for 150 min to form a mixed solution. The amount of polyvinyl pyrrolidone added was 0.05 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0067] (2) Add polyether P123 into deionized water and stir at 90° C. for 480 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.01 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0068] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 75° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0069] (4) Add the aqueous solution of niobium oxalate to the mixed solution (20 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 40°C for 150 minutes, perform hydrothermal crystallization reaction at 160°C for 36 hours, and then dry at 110°C for 8 hours. Calcinate at 400°C in air atmosphere for 2.5 hours, then calcine at 580°C in argon atmosphere for 3 hours, put the obtained crude catalyst into 11wt% hydrogen peroxide, stir at 80°C for 80 minutes, purify the catalyst to remove the M2 phase, and then dry at 110°C for 6 hours to obtain the finished catalyst with the molecular formula of Mo1V 0.25 Te 0.23 Nb 0.10 , denoted as ODHE-6.

[0070] Example 7

[0071] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0072] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polyvinyl alcohol were added to deionized water and stirred at 90° C. for 60 min to form a mixed solution, wherein the amount of polyvinyl alcohol added was 0.08 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0073] (2) Add polyether P123 into deionized water and stir at 100° C. for 300 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.2 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0074] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 20 minutes to form an aqueous solution of niobium oxalate;

[0075] (4) Add the aqueous solution of niobium oxalate to the mixed solution (for 35 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 90°C for 60 minutes, perform hydrothermal crystallization reaction at 170°C for 30 hours, and then dry at 85°C for 15 hours. Calcinate at 350°C in air atmosphere for 3 hours, then calcine at 610°C in helium atmosphere for 4 hours, and put the obtained crude catalyst into 8.5wt% hydrogen peroxide, stir at 60°C for 200 minutes, purify the catalyst to remove the M2 phase, and then dry at 120°C for 10 hours to obtain the finished catalyst with the molecular formula of Mo1V 0.31 Te 0.19 Nb 0.13 , denoted as ODHE-7.

[0076] Example 8

[0077] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0078] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polyvinyl pyrrolidone were added to deionized water and stirred at 80° C. for 80 min to form a mixed solution. The amount of polyvinyl pyrrolidone added was 0.03 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0079] (2) Add polyether P123 into deionized water and stir at 85° C. for 360 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.08 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0080] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 25 minutes to form an aqueous solution of niobium oxalate;

[0081] (4) Add the aqueous solution of niobium oxalate to the mixed solution (taking 40 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 60°C for 100 minutes, perform hydrothermal crystallization reaction at 165°C for 55 hours, and then dry at 120°C for 10 hours. Calcinate at 350°C in air atmosphere for 4 hours, then calcine at 630°C in helium atmosphere for 2 hours, put the obtained crude catalyst into 5wt% hydrogen peroxide, stir at 30°C for 180 minutes, purify the catalyst to remove the M2 phase, and then dry at 70°C for 8 hours to obtain the finished catalyst with the molecular formula of Mo1V 0.29 Te 0.18 Nb 0.14 , denoted as ODHE-8.

[0082] Example 9

[0083] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0084] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 90° C. for 75 min to form a mixed solution. The amount of sesbania powder added was 0.02 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0085] (2) Add polyether P123 into deionized water and stir at 95° C. for 240 min until the polyether is completely dissolved to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.18 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0086] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 90° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0087] (4) Add the aqueous solution of niobium oxalate to the mixed solution (for 35 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 90°C for 20 minutes, perform hydrothermal crystallization reaction at 180°C for 40 hours, and then dry at 100°C for 6 hours. Calcinate at 250°C in air atmosphere for 4 hours, then calcine at 600°C in helium atmosphere for 2 hours, put the obtained crude catalyst into 6wt% hydrogen peroxide, stir at 50°C for 240 minutes, purify the catalyst to remove the M2 phase, and then dry at 100°C for 8 hours to obtain the finished catalyst with the molecular formula of Mo1V 0.30 Te 0.18 Nb 0.10 , denoted as ODHE-9.

[0088] Example 10

[0089] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0090] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and polyethylene glycol were added to deionized water and stirred at 80° C. for 140 min to form a mixed solution, wherein the amount of polyethylene glycol added was 0.03 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0091] (2) Add polyether P123 into deionized water and stir at 100° C. for 120 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.13 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0092] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 40 minutes to form an aqueous solution of niobium oxalate;

[0093] (4) Add the aqueous solution of niobium oxalate to the mixed solution (50 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 30°C for 50 minutes, perform hydrothermal crystallization reaction at 200°C for 16 hours, and then dry at 90°C for 15 hours. Calcinate at 250°C for 3 hours in air atmosphere and 620°C for 3 hours in helium atmosphere. Put the obtained crude catalyst into 9wt% hydrogen peroxide and stir at 70°C for 30 minutes. Purify the catalyst to remove the M2 phase and dry at 60°C for 18 hours to obtain the finished catalyst with the molecular formula of Mo1V 0.31 Te 0.21 Nb 0.12 , denoted as ODHE-10.

[0094] Embodiment 11

[0095] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0096] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 85° C. for 70 min to form a mixed solution. The amount of sesbania powder added was 0.01 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0097] (2) Add polyether P123 into deionized water and stir at 90° C. for 420 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.16 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0098] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 85° C. for 20 minutes to form an aqueous solution of niobium oxalate;

[0099] (4) Add the aqueous solution of niobium oxalate to the mixed solution (40 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 70°C for 150 minutes, perform hydrothermal crystallization reaction at 175°C for 60 hours, and then dry at 100°C for 20 hours. Calcinate at 300°C in air atmosphere for 2 hours, and calcine at 600°C in argon atmosphere for 3 hours. The obtained crude catalyst is placed in 15wt% hydrogen peroxide, stirred at 80°C for 90 minutes, the catalyst is purified to remove the M2 phase, and then dried at 80°C for 16 hours to obtain the finished catalyst with a molecular formula of Mo1V 0.30 Te 0.20 Nb 0.11 , denoted as ODHE-11.

[0100] Example 12

[0101] This embodiment provides a catalyst for ethane oxidative dehydrogenation reaction, and the specific preparation method includes the following steps:

[0102] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 80° C. for 85 min to form a mixed solution. The amount of sesbania powder added was 0.5 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0103] (2) Add polyether P123 into deionized water and stir at 100° C. for 200 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.005 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0104] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0105] (4) The aqueous solution of niobium oxalate was added to the mixed solution in batches (for 30 minutes) to form a suspension, and then the aqueous solution of polyether p123 was added. After aging at 80°C for 180 minutes, the mixture was subjected to hydrothermal crystallization reaction at 180°C for 30 hours, and then dried at 80°C for 16 hours. The mixture was calcined at 300°C in an air atmosphere for 4 hours, and then calcined at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst was placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, the catalyst was purified to remove the M2 phase, and then dried at 120°C for 8 hours to obtain a finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-12.

[0106] Comparative Example 1

[0107] The catalyst for ethane oxidative dehydrogenation provided in this comparative example is similar to that in Example 4, except that the template agent P123 and the dispersant sesbania powder are not added in this comparative example. The specific preparation method of the catalyst for ethane oxidative dehydrogenation provided in this comparative example comprises the following steps:

[0108] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, and telluric acid were added to deionized water and stirred at 80° C. for 90 minutes to form a mixed solution.

[0109] (2) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0110] (3) Add the aqueous solution of niobium oxalate to the mixed solution (for 30 minutes) to form a suspension, age it at 80°C for 180 minutes, perform hydrothermal crystallization at 180°C for 30 hours, and then dry it at 80°C for 16 hours. Calcinate it at 300°C in an air atmosphere for 4 hours, and then calcine it at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst is placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, and the catalyst is purified to remove the M2 phase. Then, it is dried at 120°C for 8 hours to obtain a finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-12.

[0111] Comparative Example 2

[0112] The catalyst for ethane oxidative dehydrogenation provided in this comparative example is similar to that in Example 4, except that no template P123 is added in this comparative example. The specific preparation method of the catalyst for ethane oxidative dehydrogenation provided in this comparative example comprises the following steps:

[0113] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 80° C. for 85 min to form a mixed solution. The amount of sesbania powder added was 0.04 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0114] (2) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0115] (3) Add the aqueous solution of niobium oxalate to the mixed solution (for 30 minutes) to form a suspension, age it at 80°C for 180 minutes, perform hydrothermal crystallization at 180°C for 30 hours, and then dry it at 80°C for 16 hours. Calcinate it at 300°C in an air atmosphere for 4 hours, and then calcine it at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst is placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, and the catalyst is purified to remove the M2 phase. Then, it is dried at 120°C for 8 hours to obtain a finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-13.

[0116] Comparative Example 3

[0117] The catalyst for ethane oxidative dehydrogenation provided in this comparative example is similar to that in Example 4, except that the dispersant sesbania powder is not added in this comparative example. The specific preparation method of the catalyst for ethane oxidative dehydrogenation provided in this comparative example comprises the following steps:

[0118] (1) adding a certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate and telluric acid into deionized water, stirring at 80° C. for 85 minutes to form a mixed solution;

[0119] (2) Add polyether P123 into deionized water and stir at 100° C. for 200 min to obtain an aqueous solution of polyether P123; the amount of P123 added is 0.15 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0120] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0121] The aqueous solution of niobium oxalate was added dropwise to the mixed solution (for 30 minutes) to form a suspension, and then the aqueous solution of polyether p123 was added. After aging at 80°C for 180 minutes, the mixture was subjected to hydrothermal crystallization reaction at 180°C for 30 hours, and then dried at 80°C for 16 hours. The mixture was calcined at 300°C in an air atmosphere for 4 hours, and then calcined at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst was placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, the catalyst was purified to remove the M2 phase, and then dried at 120°C for 8 hours to obtain the finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-14.

[0122] Comparative Example 4

[0123] The catalyst for ethane oxidative dehydrogenation provided in this comparative example is similar to that in Example 4, except that the order of adding the template agent is different. The specific preparation method of the catalyst for ethane oxidative dehydrogenation provided in this comparative example comprises the following steps:

[0124] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid, sesbania powder and P123 were added to deionized water and stirred at 80°C for 85 minutes to form a mixed solution, wherein the amount of sesbania powder added was 0.04 wt% of the mass of ammonium heptamolybdate tetrahydrate. The amount of polyether P123 added was 0.15 wt% of the mass of ammonium heptamolybdate tetrahydrate.

[0125] (2) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0126] (3) Add the aqueous solution of niobium oxalate to the mixed solution (for 30 minutes) to form a suspension, age it at 80°C for 180 minutes, perform hydrothermal crystallization at 180°C for 30 hours, and then dry it at 80°C for 16 hours. Calcinate it at 300°C in an air atmosphere for 4 hours, and then calcine it at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst is placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, and the catalyst is purified to remove the M2 phase. Then, it is dried at 120°C for 8 hours to obtain a finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-15.

[0127] Comparative Example 5

[0128] The catalyst for ethane oxidative dehydrogenation provided in this comparative example is similar to that in Example 4, except that the addition time of the niobium oxalate solution is different. The specific preparation method of the catalyst for ethane oxidative dehydrogenation provided in this comparative example comprises the following steps:

[0129] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 80° C. for 85 min to form a mixed solution. The amount of sesbania powder added was 0.04 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0130] (2) Add polyether P123 into deionized water and stir at 100° C. for 200 min to obtain an aqueous solution of polyether 123; the amount of polyether P123 added is 0.15 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0131] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0132] (4) Add the aqueous solution of niobium oxalate to the mixed solution (taking 5 minutes) to form a suspension, then add the aqueous solution of polyether p123, age at 80°C for 180 minutes, perform hydrothermal crystallization reaction at 180°C for 30 hours, and then dry at 80°C for 16 hours. Calcinate at 300°C in an air atmosphere for 4 hours, and then calcine at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst is placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, the catalyst is purified to remove the M2 phase, and then dried at 120°C for 8 hours to finally obtain a finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-16.

[0133] Comparative Example 6

[0134] The catalyst for ethane oxidative dehydrogenation provided in this comparative example is similar to that in Example 4, except that a different template is used. The specific preparation method of the catalyst for ethane oxidative dehydrogenation provided in this comparative example comprises the following steps:

[0135] (1) A certain amount of ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and sesbania powder were added to deionized water and stirred at 80° C. for 85 min to form a mixed solution. The amount of sesbania powder added was 0.04 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0136] (2) adding hexadecyltrimethylammonium bromide into deionized water and stirring the mixture at 60° C. for 60 min to obtain an aqueous solution of hexadecyltrimethylammonium bromide; the amount of hexadecyltrimethylammonium bromide added is 0.15 wt % of the mass of ammonium heptamolybdate tetrahydrate.

[0137] (3) adding a certain amount of niobium oxalate into deionized water and stirring at 80° C. for 30 minutes to form an aqueous solution of niobium oxalate;

[0138] (4) Add the aqueous solution of niobium oxalate to the mixed solution (for 30 minutes) to form a suspension, then add the aqueous solution of hexadecyltrimethylammonium bromide, age at 80°C for 180 minutes, perform hydrothermal crystallization reaction at 180°C for 30 hours, and then dry at 80°C for 16 hours. Calcinate at 300°C in an air atmosphere for 4 hours, and then calcine at 620°C in a nitrogen atmosphere for 2 hours. The obtained crude catalyst is placed in 10wt% hydrogen peroxide, stirred at 60°C for 100 minutes, the catalyst is purified to remove the M2 phase, and then dried at 120°C for 8 hours to obtain a finished catalyst with a molecular formula of Mo1V 0.30 Te 0.18 Nb 0.12 , denoted as ODHE-16.

[0139] Catalyst evaluation results

[0140] The catalysts prepared in the above-mentioned embodiments and comparative examples were subjected to performance tests according to the above-mentioned performance evaluation and analysis methods. The specific results are shown in the table below.

[0141] Table 1

[0142]

[0143]

[0144] As can be seen from the data in the above table, compared with the prior art, the catalyst prepared by the preparation method provided by the present invention has excellent catalytic performance when used for ethane oxidative dehydrogenation reaction. Specifically, it can be seen from Example 4 that after adding a dispersant and a template agent, the reaction performance of the prepared catalyst is significantly improved. The main reason is that the dispersant and the template agent are added during the preparation process to disperse and support the active components, thereby improving the pore structure and specific surface area of ​​the catalyst and improving the catalytic activity. The reaction performance of the catalyst obtained by adding a dispersant alone (Comparative Example 2) and adding a template agent alone (Comparative Example 3) is significantly reduced, indicating that the dispersant and the template agent cooperate with each other during the catalyst preparation process, and can play a synergistic role and thus greatly improve the reaction performance of the catalyst.

[0145] It can be seen from the comparison between Example 4 and Comparative Example 4 that the reaction performance of the catalyst prepared after adding the template agent in the aging stage is greatly improved, which is mainly because the catalyst forms an ordered pore structure and the specific surface area increases. However, when the template agent is added in the initial stage, the reaction performance of the catalyst is not good. This is mainly because Mo, V and Te will interact to form an Anderson-type heteropolycation complex in the initial stage. Adding an organic template agent at this stage will interfere with the formation of this microstructure, or even destroy the formation of the structure, which in turn affects the formation of the catalyst active phase, resulting in poor catalyst reaction performance.

[0146] Comparing Example 4 with Comparative Example 5, it can be seen that the catalyst obtained by shortening the dropping time of the niobium oxalate solution has poor reaction performance, mainly because the niobium oxalate solution is dropped too quickly, which affects the formation of active species, resulting in a decrease in the active phase in the catalyst and a decrease in catalyst performance.

[0147] From Example 4 compared with Comparative Example 6, it can be seen that although the addition of hexadecyltrimethylammonium bromide can also improve the reaction performance of the catalyst to a certain extent, the effect of the organic template polyether p123 is more prominent. The main reason is that polyether p123, as an organic template, can prepare a MoVTeNb catalyst with a mesoporous structure in situ by a method of inducing self-assembly by solvent evaporation, significantly improving the specific surface area and pore volume of the catalyst. In general, the addition of dispersants and templates has a great effect on improving the physical properties and reaction performance of the catalyst, but there are certain requirements for the order of adding templates.

[0148] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a catalyst for ethane oxidative dehydrogenation reaction, characterized in that: The steps include: (1) dissolving ammonium heptamolybdate tetrahydrate, ammonium metavanadate, telluric acid and a dispersant in deionized water to form a mixed solution; (2) adding an aqueous solution of niobium oxalate to the mixed solution within 15 to 50 minutes to form a suspension, then adding an aqueous solution of the template polyether P123, and subjecting the mixture to aging, hydrothermal crystallization, drying, calcination, and removal of the M2 phase to obtain the catalyst for ethane oxidative dehydrogenation reaction.

2. The preparation method according to claim 1, characterized in that The added amount of the dispersant is 0.005wt% to 0.1wt% of the mass of the ammonium heptamolybdate tetrahydrate.

3. The preparation method according to claim 1, characterized in that: The dispersant is selected from any one of propylene glycol, polymethylcellulose, polyvinyl alcohol, sesbania powder, polyethylene glycol and polyvinyl pyrrolidone.

4. The preparation method according to claim 1, characterized in that: The addition amount of the template polyether P123 is 0.01wt% to 0.3wt% of the mass of the ammonium heptamolybdate tetrahydrate.

5. The preparation method according to claim 1, characterized in that: The aging temperature is 20-90° C. and the aging time is 20-180 min.

6. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal crystallization reaction is 150-200° C., and the time is 12-60 hours.

7. The preparation method according to claim 1, characterized in that: The drying temperature is 70-120° C. and the drying time is 6-20 hours.

8. The preparation method according to claim 1, characterized in that: The calcination is selected from two-stage calcination; preferably, the two-stage calcination includes first calcining at 200-400°C in air for 2-6 hours, and then calcining at 550-650°C in an inert atmosphere for 1-4 hours.

9. The preparation method according to claim 1, characterized in that: The M2 phase is purified by using hydrogen peroxide, wherein the concentration of the hydrogen peroxide is 5wt% to 15wt%, the purification temperature is 30 to 80°C, and the purification time is 30 to 240 minutes.

10. A catalyst for ethane oxidative dehydrogenation reaction obtained by the method for preparing a catalyst for ethane oxidative dehydrogenation reaction according to any one of claims 1 to 9, characterized in that: The general formula of the catalyst for ethane oxidative dehydrogenation reaction is as follows: Mo a V b Te c Nb d , where a=1, b is 0.25~0.32, c is 0.16~0.23, and d is 0.08~0.15.

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