An iron-based oxide catalyst, a method for preparing the same, and an application thereof

Abstract

The application provides an iron-based oxide catalyst, a preparation method thereof and application of the iron-based oxide catalyst in selective catalytic n-butane-CO2 coupling conversion for preparing butadiene, and mainly solves the problem of low butadiene selectivity in the current n-butane oxidative dehydrogenation system. The pyrolysis method of the organic acid assisted metal salt solution can obtain the iron-based oxide catalyst with uniform particle size, and the iron-based oxide catalyst exhibits excellent butadiene selectivity in the catalytic n-butane-CO2 coupling conversion reaction. Under the conditions of 500-650 DEG C and 0.1 MPa, the n-butane conversion rate is greater than 10%, and the butadiene selectivity is greater than 50%. The CO2 is used as an oxidant, excessive oxidation and the generation of reaction hot spots can be avoided, and the process is safer and more reliable. The pyrolysis method reported in the application has the characteristics of simple operation, cheap and easily available raw materials and good repeatability, and can be used for industrialized application of n-butane oxidative dehydrogenation.

Description

TECHNICAL FIELD

[0001] The present application relates to an iron-based oxide catalyst, a preparation method thereof and application thereof in selective catalytic conversion of n-butane-CO2 coupling to prepare butadiene, and belongs to the field of metal oxides and catalysis science. BACKGROUND

[0002] Under the background of global warming, especially double carbon, the value-added and low-carbon utilization of carbon-based resources become particularly important and urgent. The present application focuses on the high-value conversion of n-butane and CO2 to produce key chemical butadiene. The existing catalysts have the following problems: 1. Cr-based catalysts have high Cr(VI) toxicity; 2. Pt-based catalysts are expensive, and alloy phase segregation is easy to occur under the condition of introducing CO2; 3. Transition metal catalysts are easy to coke and have serious cracking reaction. Therefore, it is particularly important to develop a cheap and environmentally friendly high-performance n-butane-CO2 coupling conversion catalyst.

[0003] In view of the characteristics of Fe-based catalysts, such as low cost, environmental protection, and rich and easy-to-adjust phase structure in the reaction atmosphere, the redox properties and carbon deposition dynamics of the iron-based catalysts are controlled by the reaction atmosphere, so as to solve the problems of low n-butane-CO2 coupling efficiency, uncontrollable product distribution and carbon deposition in the development of the catalysts.

[0004] In the already applied patents (US8513479B2, CN101674883B, US8674156B2, US10888844B2), the iron-based catalysts are mainly prepared by precipitation and loading methods, and molecular O2 is mainly used as the oxidant. SUMMARY

[0005] The present application provides a simple and uniform particle size iron-based oxide material preparation method, and a series of iron-based oxide catalysts with uniform and controllable particle size are prepared by an organic acid assisted metal salt pyrolysis method. The iron-based oxide catalysts exhibit excellent butadiene selectivity in the n-butane-CO2 coupling conversion reaction.

[0006] According to one aspect of the present application, an iron-based oxide catalyst is provided, and the particle size of the iron-based oxide catalyst is 10-70 nm.

[0007] Optionally, the particle size of the iron-based oxide catalyst is any value or a range value between any two values in 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm and 70 nm.

[0008] The iron-based oxide catalyst further comprises other metal elements;

[0009] The other metal elements are selected from at least one of zinc elements, manganese elements, cobalt elements and copper elements;

[0010] The content of iron element in the iron-based oxide catalyst is 20-100wt%;

[0011] Optionally, the content of iron element in the iron-based oxide catalyst is any value or a range value between any two values selected from 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt%, 100wt%.

[0012] The content of other metal elements in the iron-based oxide catalyst is 0-80wt%.

[0013] Optionally, the content of other metal elements in the iron-based oxide catalyst is any value or a range value between any two values selected from 0wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%.

[0014] According to another aspect of the present application, a preparation method of the above-mentioned iron-based oxide catalyst is provided, comprising the following steps:

[0015] Mixing raw materials containing water, metal salt and organic acid to obtain slurry, drying and calcining to obtain the iron-based oxide catalyst.

[0016] The iron salt is selected from at least one of ferric chloride, ferric nitrate, ferric citrate, and iron acetylacetone;

[0017] The organic acid is selected from at least one of oxalic acid, citric acid, and ascorbic acid;

[0018] In the slurry,

[0019] The concentration of the iron salt is 2-15mol / L, calculated based on the molar amount of iron element in the iron salt;

[0020] Optionally, the concentration of the iron salt is any value or a range value between any two values selected from 2mol / L, 3mol / L, 4mol / L, 5mol / L, 6mol / L, 7mol / L, 8mol / L, 9mol / L, 10mol / L, 11mol / L, 12mol / L, 13mol / L, 14mol / L, 15mol / L.

[0021] The concentration of the organic acid is 0.5-22mol / L.

[0022] Optionally, the concentration of the organic acid is any value or a range value between any two values of 0.5 mol / L, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, 12 mol / L, 14 mol / L, 16 mol / L, 18 mol / L, 20 mol / L, 22 mol / L.

[0023] The raw material further comprises a salt of another metal element;

[0024] The salt of another metal element is selected from at least one of a chloride salt, a nitrate salt, an acetylacetone salt, and a citrate salt of the another metal element.

[0025] In the slurry, the concentration of the salt of another metal element is 0-12 mol / L.

[0026] Optionally, the concentration of the salt of another metal element is any value or a range value between any two values of 0 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L.

[0027] The mixing comprises stirring.

[0028] The stirring temperature is 20-50°C.

[0029] Optionally, the stirring temperature is any value or a range value between any two values of 20°C, 30°C, 40°C, 50°C.

[0030] The stirring time is 30-720 min.

[0031] Optionally, the stirring time is any value or a range value between any two values of 30 min, 60 min, 120 min, 180 min, 240 min, 300 min, 360 min, 420 min, 480 min, 540 min, 600 min, 660 min, 720 min.

[0032] The drying temperature is 50-150°C.

[0033] Optionally, the drying temperature is any value or a range value between any two values of 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C.

[0034] The drying time is 240-720 min.

[0035] Optionally, the drying time is any value or a range value between any two values selected from 240 min, 300 min, 360 min, 420 min, 480 min, 540 min, 600 min, 660 min, 720 min.

[0036] The calcination temperature is 400-650℃.

[0037] Optionally, the calcination temperature is any value or a range value between any two values selected from 400℃, 450℃, 500℃, 550℃, 600℃, 650℃.

[0038] The calcination time is 30-360 min.

[0039] Optionally, the calcination time is any value or a range value between any two values selected from 30 min, 60 min, 120 min, 180 min, 240 min, 300 min, 360 min.

[0040] The drying is followed by crushing and grinding, and then calcination.

[0041] According to another aspect of the present application, a method for preparing butadiene by n-butane-CO2 coupling conversion is provided, comprising the following steps:

[0042] In a reactor, a raw material containing n-butane and CO2 is introduced and reacted with a catalyst to obtain a product containing butadiene;

[0043] The catalyst is selected from the above-mentioned iron-based oxide catalyst or the iron-based oxide catalyst prepared by the above-mentioned preparation method.

[0044] The volume ratio of CO2 to n-butane in the raw material is 1:1-10:1.

[0045] Optionally, the volume ratio of CO2 to n-butane in the raw material is any value or a range value between any two values selected from 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0046] The mass space velocity of n-butane is 0.05-8.00 h -1 .

[0047] Optionally, the mass space velocity of n-butane is any value or a range value between any two values selected from 0.05 h -1 , 0.1 h -1 , 0.5 h -1 , 1 h -1 , 2 h -1 , 3 h -1 , 4 h -1 , 5 h-1 6h -1 7h -1 8h -1 Any value in the range or any value between the two.

[0048] The reaction temperature is 500–650°C;

[0049] Optionally, the temperature of the reaction is any value among 500°C, 550°C, 600°C, and 650°C, or a range between any two.

[0050] The reaction pressure is 0.1–1 MPa.

[0051] Optionally, the pressure of the reaction is any value or a range between 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, and 1 MPa.

[0052] The specific preparation method is as follows:

[0053] 1) Dissolve iron salts in water, add other metal element salts and dissolve them, then introduce organic acid and stir until homogeneous;

[0054] 2) Dry the solution obtained in 1) at a certain temperature for a certain time, and then crush and grind the dried sample;

[0055] 3) The powder sample obtained in 2) is calcined at a certain temperature to obtain the final catalyst.

[0056] The advantages of this application are: a precursor solution with uniformly mixed metal components can be obtained by using an organic-metal salt solution as a precursor, and metal oxides with uniform particle size can be obtained by pyrolysis treatment. At the same time, the preparation process is simple and easy to operate.

[0057] This invention primarily addresses the problem of low butadiene selectivity in current n-butane oxidative dehydrogenation systems. The organic acid-assisted metal salt solution pyrolysis method yields a ferrite catalyst with uniform particle size, exhibiting excellent butadiene selectivity in the coupled n-butane-CO2 conversion reaction. At 500-650℃ and 0.1 MPa, the n-butane conversion is greater than 10%, and the butadiene selectivity is greater than 50%. Using CO2 as the oxidant avoids over-oxidation and the generation of reaction hotspots, making the process safer and more reliable. The pyrolysis method reported in this application features simple operation, readily available and inexpensive raw materials, and good reproducibility, making it suitable for industrial applications in n-butane dehydrogenation. Attached Figure Description

[0058] Figure 1 This is a scanning electron microscope image of the sample from Example 2. Detailed Implementation

[0059] The application will be described in greater detail below with reference to the examples. However, the application is not limited to these examples.

[0060] The raw materials in the examples of the present application are commercially available unless otherwise specified.

[0061] Example 1

[0062] First, a zinc nitrate solution with a concentration of 3.361 mol / L was prepared, and then iron nitrate was added and stirred uniformly, with the concentration of the iron nitrate being 3.361 mol / L. Finally, citric acid monohydrate was added and stirred at 30°C for 300 min, with the concentration of the citric acid being 9.414 mol / L. Next, the solution was dried at 60°C for 720 min, then the temperature was raised to 80°C and the drying was continued for 720 min, and then the temperature was raised to 120°C and the drying was continued for 360 min. After the dried sample was calcined at 400°C for 360 min, the temperature was raised to 600°C and the calcination was continued for 30 min, and finally ZnFeO x catalyst.

[0063] Example 2

[0064] First, a zinc nitrate solution with a concentration of 3.361 mol / L was prepared, and then iron nitrate was added and stirred uniformly, with the concentration of the iron nitrate being 6.722 mol / L. Finally, citric acid monohydrate was added and stirred at 30°C for 300 min, with the concentration of the citric acid being 14.121 mol / L. Next, the solution was dried at 60°C for 720 min, then the temperature was raised to 80°C and the drying was continued for 720 min, and then the temperature was raised to 120°C and the drying was continued for 360 min. After the dried sample was calcined at 400°C for 360 min, the temperature was raised to 600°C and the calcination was continued for 30 min, and finally ZnFe2O x catalyst.

[0065] Figure 1 The scanning electron microscope photograph of the sample of Example 2 is shown in the figure. It can be seen from the figure that the particle size of the sample is uniform, and the particle size is about 40 nm.

[0066] Example 3

[0067] First, a zinc nitrate solution with a concentration of 3.361 mol / L was prepared, and then iron nitrate was added and stirred uniformly, with the concentration of the iron nitrate being 10.084 mol / L. Finally, citric acid monohydrate was added and stirred at 30°C for 300 min, with the concentration of the citric acid being 18.828 mol / L. Next, the solution was dried at 60°C for 720 min, then the temperature was raised to 80°C and the drying was continued for 720 min, and then the temperature was raised to 120°C and the drying was continued for 360 min. After the dried sample was calcined at 400°C for 360 min, the temperature was raised to 600°C and the calcination was continued for 30 min, and finally ZnFe3O x catalyst.

[0068] Comparative Example 1

[0069] First, a zinc nitrate solution with a concentration of 13.445 mol / L was prepared, then citric acid monohydrate was added and stirred at 30℃ for 300 min, the concentration of citric acid was 18.828 mol / L; then the solution was dried at 60℃ for 720 min, the temperature was raised to 80℃ and dried for another 720 min, and then the temperature was raised to 120℃ and dried for 360 min. After drying, the sample was calcined at 400℃ for 360 min, then the temperature was raised to 600℃ and calcined for another 30 min, and finally the ZnO catalyst was obtained.

[0070] Test Example 1

[0071] The test process is as follows: the catalyst is loaded into a fixed bed reactor with a quartz tube lining, heated to 550℃ at a temperature rise rate of 10℃ / min in a nitrogen atmosphere (12 mL / min). Then switch to N2 / CO2 / n-C4H 10 (9600 mL / (g*h)) reaction atmosphere, the mass space velocity of n-butane is 1.24 h -1 , CO2 / n-C4H 10 =4:1, the pressure is 0.1 MPa. The reaction product is vaporized by heating and then analyzed by gas chromatography. TCD is used to analyze H2, CO, CH4 and CO2 in the product. FID is used to analyze the hydrocarbon products.

[0072] Table 1 shows the reaction performance of the samples of Examples 1-3 and Comparative Example 1.

[0073] Table 1

[0074]

[0075] Table 1 shows that the conversion rates of n-butane of the four samples are close, but the CO2 conversion rate of the iron-zinc bimetallic oxide catalyst is significantly higher than that of the ZnO catalyst, about 2 times. This shows that the introduction of iron promotes the conversion of CO2 and improves the coupling conversion efficiency of n-butane and CO2. The butadiene selectivity of ZnO is only 23.2%, and the butadiene selectivity of the iron-zinc bimetallic oxide catalyst is about 40%, and slightly increases with the increase of iron content. Compared with ZnO, the iron-zinc bimetallic oxide has obvious advantages in promoting CO2 activation and selectively generating butadiene.

[0076] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the above preferred embodiments are disclosed, they are not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, which are equivalent to equivalent embodiments, and are within the scope of the technical solution.

Claims

1. A method for preparing butadiene by coupled conversion of n-butane and CO2, characterized in that, Includes the following steps: In a reactor, a raw material containing n-butane and CO2 is introduced and reacted with a catalyst to obtain a product containing butadiene; the reaction temperature is 500~650 °C; the reaction pressure is 0.1~1 MPa. The catalyst is selected from ferrite catalysts with uniform particle size obtained by organic acid-assisted pyrolysis of metal salt solution, and the particle size of the catalyst is 10~70 nm. The method for preparing the catalyst includes the following steps: A slurry containing water, metal salt, and organic acid is mixed, dried, and calcined to obtain the catalyst. The metal salts are iron salts and zinc elemental salts; The catalyst contains 20-80 wt% iron. The catalyst contains 20-80 wt% zinc. The iron salt is selected from at least one of ferric chloride, ferric nitrate, ferric citrate, and ferric acetylacetone; The organic acid is selected from at least one of oxalic acid, citric acid, and ascorbic acid; In the slurry, the concentration of the iron salt is 2~15 mol / L; based on the molar amount of iron in the iron salt; The concentration of the organic acid is 0.5~22 mol / L; The zinc elemental salt is selected from at least one of chloride salts, nitrate salts, acetylacetone salts, and citrate salts; In the slurry, the concentration of the zinc salt is 1~12 mol / L; The roasting temperature is 400~650 ℃; The roasting time is 30~360 min.

2. The method for preparing butadiene by n-butane-CO2 coupled conversion according to claim 1, characterized in that, In the method for preparing the catalyst, The mixing includes stirring; The stirring temperature is 20~50℃; The stirring time is 30~720 min; The drying temperature is 50~150℃; The drying time is 240~720 min.

3. The method for preparing butadiene by coupled conversion of n-butane and CO2 according to claim 1, characterized in that, In the preparation method of the catalyst, after drying, it is crushed and ground, and then calcined.

4. The method for preparing butadiene by n-butane-CO2 coupled conversion according to claim 1, characterized in that, The volume ratio of CO2 to n-butane in the feedstock containing n-butane is 1:1 to 10:1; the mass hourly space velocity (HHSV) of the n-butane is 0.05 to 8.00 h⁻¹. -1 .

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