Preparation method of cobalt-based catalyst and method for catalyzing dehydrogenation reaction of n-butane

Abstract

The invention discloses a preparation method of a cobalt-based catalyst and a method for catalyzing dehydrogenation reaction of n-butane, the preparation method comprises the following steps: (1) aging I and drying I a mixture I of a precursor containing a metal oxide, an auxiliary pyrolysis organic matter, a carrier and a solvent to obtain a composite oxide carrier; and (2) aging a mixture II containing the composite oxide carrier, cobalt salt, an auxiliary pyrolysis organic matter and a solvent II, drying II and roasting to obtain the cobalt-based catalyst. The problem that an existing n-butane dehydrogenation catalyst is prone to sintering and carbon deposition is solved. The catalyst prepared on the basis of the application shows excellent butene and butadiene selectivity and catalytic stability in an n-butane dehydrogenation reaction, and has a good industrial application prospect.

Description

Technical Field

[0001] The present application relates to a method for preparing a cobalt-based catalyst and a method for catalyzing the dehydrogenation reaction of n-butane, and belongs to the field of nanomaterials and catalytic science. Background Art

[0002] Against the backdrop of increasing demand for low-carbon olefins, the value-added and efficient utilization of carbon-based resources have become particularly important and urgent. This application focuses on the high-value utilization of n-butane, a by-product of the refining industry, to produce key chemicals butene and butadiene. In view of the problems faced by existing platinum-based catalyst systems, such as expensive metal components, complex regeneration processes, and easy coking and toxicity of chromium-based catalysts, a cheap, environmentally friendly, high-performance n-butane dehydrogenation catalyst is developed.

[0003] In view of the characteristics of cobalt-based catalysts such as low cost, environmental protection and high CH bond activation ability, a highly dispersed and stable cobalt-based catalyst is prepared through organic-assisted pyrolysis and guest metal oxide confinement, solving the problems of cobalt-based catalysts being easy to sinter and coke in the current n-butane dehydrogenation system. The catalyst preparation process is simple and easy to scale up, and has very good application prospects.

[0004] Patent KR102563207B1 has been applied for, which involves an alkali metal treatment process of a carrier; the silicon oxide carrier used in patent CN113976119A has undergone a complex hydrothermal pretreatment; patents CN115920947A and CN114931968A both involve a hydrothermal synthesis process. Summary of the invention

[0005] The present application provides a cobalt-based catalyst, a preparation method and an application in the dehydrogenation reaction of n-butane. The confinement effect of the guest metal oxide is to utilize the strong interaction between the guest metal oxide and the metal cobalt to limit the migration of the metal cobalt species under the reaction conditions and inhibit the aggregation and sintering of the metal cobalt; the coupling organic-assisted pyrolysis method improves the dispersion of the metal precursor, so that the catalyst exhibits excellent butene and butadiene selectivity and catalytic stability.

[0006] In this application, silicalite-1 and silicalite-2 are used as carriers, and highly dispersed and highly stable cobalt-based catalysts are prepared through organic-assisted pyrolysis and the confinement effect of guest metal oxides. The disclosed catalysts, preparation methods and applications thereof present different technical features and implementation effects from the above-mentioned applications.

[0007] According to one aspect of the present application, a method for preparing a cobalt-based catalyst is provided, the preparation method comprising the following steps:

[0008] (1) The mixture I containing a metal oxide precursor, an auxiliary pyrolyzable organic substance, a carrier, and a solvent is aged I and dried I to obtain a composite oxide carrier;

[0009] (2) The mixture II containing the composite oxide carrier, a cobalt salt, an auxiliary pyrolyzable organic substance, and a solvent is aged II, dried II, and calcined to obtain a cobalt-based catalyst.

[0010] Optionally, in steps (1) and (2), the auxiliary pyrolyzable organic substance is independently selected from at least one of oxalic acid, citric acid, isopropanol, ethylenediamine, triethanolamine, and ascorbic acid.

[0011] Optionally, in steps (1) and (2), the concentration of the auxiliary pyrolyzable organic substance is independently 0.01 - 5 mol / L.

[0012] Optionally, in steps (1) and (2), the concentration of the auxiliary pyrolyzable organic substance is independently selected from any value of 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or the range value between any two of the above.

[0013] Optionally, the metal oxide precursor is selected from at least one of chlorides, nitrates, and sulfates containing a metal element.

[0014] Optionally, the metal element is selected from at least one of cerium, zirconium, germanium, and indium.

[0015] Optionally, the concentration of the metal oxide precursor is 0.01 - 10 mol / L in terms of the molar amount of the metal element.

[0016] Optionally, the concentration of the metal oxide precursor is independently selected from any value of 0.01 mol / L, 0.1 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 or the range value between any two of the above.

[0017] Optionally, in step (1), the carrier is selected from silicalite-1 and / or silicalite-2 of pure silicon.

[0018] Optionally, the mass percentage of the carrier in the mixture I is 30 wt% - 70 wt%.

[0019] Optionally, the mass percentage of the carrier and the mixture I is independently selected from any value of 30wt%, 40wt%, 50wt%, 60wt%, 70wt% or a range between any two of the above points.

[0020] Optionally, in step (1), the molar ratio of the metal oxide precursor to the auxiliary pyrolysis organic matter is 20:1 to 1:10.

[0021] Optionally, the molar ratio of the metal oxide precursor to the auxiliary pyrolysis organic matter is independently selected from any value of 20:1, 18:1, 16:1, 14:1, 12:1, 10:1, 8:1, 6:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, 1:8, 1:10 or a range between any two of the above points.

[0022] Optionally, in step (2), the cobalt salt is selected from at least one of cobalt chloride, cobalt sulfate, cobalt nitrate and cobalt acetylacetonate.

[0023] Optionally, in the mixture II, the concentration of the cobalt salt is 0.01 to 5 mol / L, calculated based on the molar amount of the cobalt element in the cobalt salt.

[0024] Optionally, the concentration of the cobalt salt is independently selected from any value among 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or a range between any two of the above points.

[0025] Optionally, in step (2), the molar ratio of the cobalt salt to the auxiliary pyrolysis organic matter is 10:1 to 1:10.

[0026] Optionally, the molar ratio of the cobalt salt to the auxiliary pyrolysis organic matter is independently selected from any value of 10:1, 8:1, 6:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, 1:8, 1:10 or a range between any two of the above points.

[0027] Optionally, the solvent in step (1) and step (2) is independently selected from at least one of water, methanol and ethanol.

[0028] Optionally, the temperature of aging I and aging II is independently selected from 10 to 80° C.; the time of aging I and aging II is independently selected from 30 to 1200 min.

[0029] Optionally, the temperatures of aging I and aging II are independently selected from any value of 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or a range between any two of the above points.

[0030] Optionally, the time for aging I and aging II is independently selected from any value among 30min, 60min, 120min, 180min, 240min, 300min, 360min, 420min, 480min, 540min, 600min, 660min, 720min, 780min, 840min, 900min, 960min, 1020min, 1080min, 1140min, 1200min, or the range value between any two of the above points.

[0031] Optionally, the temperatures of the drying I and the drying II are independently selected from 50 to 200° C.; the times of the drying I and the drying II are independently selected from 120 to 720 min.

[0032] Optionally, the temperatures of drying I and drying II are independently selected from any value of 50°C, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, or a range between any two of the above points.

[0033] Optionally, the drying time I and drying time II are independently selected from any value among 120min, 180min, 240min, 300min, 360min, 420min, 480min, 540min, 600min, 660min, 720min or a range value between any two of the above points.

[0034] Optionally, the calcination temperature is 400-700° C.; the calcination time is 30-360 min.

[0035] Optionally, the calcination temperature is independently selected from any value of 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C or a range between any two of the above points.

[0036] Optionally, the calcination time is independently selected from any value among 30 min, 60 min, 120 min, 180 min, 240 min, 300 min, 360 min or a range value between any two of the above points.

[0037] Optionally, the cobalt-based catalyst includes a carrier, and cobalt and a metal oxide other than cobalt supported on the carrier.

[0038] Optionally, the carrier is pure silicon silicalite-1 and / or silicalite-2.

[0039] Optionally, the metal oxide other than cobalt is selected from at least one of cerium oxide, zirconium oxide, germanium oxide and indium oxide.

[0040] Optionally, the cobalt content in the cobalt-based catalyst is 0.01 to 10 wt %, wherein the cobalt content is calculated based on the mass of the cobalt element.

[0041] Optionally, the cobalt content is independently selected from any value among 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% or the range value between any two points above.

[0042] Optionally, in the cobalt-based catalyst, the content of metal oxides other than cobalt is 0.1 to 20 wt %, wherein the content of the metal oxides other than cobalt is calculated based on the mass of the metal element.

[0043] Optionally, the content of the metal oxide other than cobalt is independently selected from any value of 0.1wt%, 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt% or a range between any two of the above points.

[0044] According to another aspect of the present application, a method for catalyzing the dehydrogenation of n-butane is provided, the method comprising:

[0045] The raw material containing n-butane is contacted with a catalyst to react and obtain a product containing butene and butadiene;

[0046] Alternatively, a mixture containing n-butane and CO 2 The raw material is contacted with a catalyst to react and obtain a product containing butene and butadiene;

[0047] The catalyst is selected from the cobalt-based catalyst prepared by the preparation method described above.

[0048] Optionally, the CO 2 The volume ratio of n-butane is 1:10 to 10:1; the mass space velocity of n-butane is 0.05 to 10.00 h -1 .

[0049] Optionally, the CO 2 The volume ratio to n-butane is independently selected from any value of 1:10, 1:8, 1:6, 1:4, 1:2, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, or a range between any two of the above points.

[0050] Optionally, the mass space velocity of n-butane is independently selected from 0.05h -1 , 0.1h-1 、0.5h -1 , 1h -1 , 2h -1 , 3h -1 , 4h -1 , 5h -1 , 6h -1 , 7h -1 , 8h -1 , 9h -1 , 10h -1 Any value in or a range of values ​​between any two of the above points.

[0051] Optionally, the reaction temperature is 500-650° C.; the reaction pressure is 0.1-1.0 MPa.

[0052] Optionally, the reaction temperature is independently selected from any value of 500°C, 550°C, 600°C, 650°C, or a range between any two of the above points.

[0053] Optionally, the reaction pressure is independently selected from any value among 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, 1 MPa or a range between any two of the above points.

[0054] As an optional implementation method, the present application is implemented through the following technical solutions:

[0055] The preparation method of the cobalt-based catalyst comprises the following steps:

[0056] (1) dissolving a precursor corresponding to the guest metal oxide and an auxiliary pyrolysis organic matter in a solvent to prepare a uniform impregnation solution;

[0057] (2) adding the carrier to (1) and stirring evenly, and aging the mixture at a certain temperature for a certain period of time;

[0058] (3) drying the mixture obtained in (2) at a certain temperature for a certain period of time, and crushing the dried sample;

[0059] (4) dissolving the cobalt salt and the auxiliary pyrolysis organic matter in a solvent to prepare a uniform impregnation solution;

[0060] (5) adding the impregnation solution prepared in (4) dropwise to the powder sample obtained in (3) and stirring evenly, and aging and drying the mixture at a certain temperature;

[0061] (6) The powder sample obtained in (5) is calcined at a certain temperature to obtain the final catalyst.

[0062] Optionally, the organic matter includes at least one of oxalic acid, citric acid, isopropanol, ethylenediamine, triethanolamine, and ascorbic acid; and the guest oxide includes at least one of cerium oxide, zirconium oxide, germanium oxide, and indium oxide.

[0063] The present application solves the problem of easy sintering and carbon deposition of the current n-butane dehydrogenation catalyst. The catalyst provided in the present application and its preparation method, wherein the organic matter-assisted thermal decomposition of metal cobalt salt coupled with the confinement effect of guest metal oxide can obtain a cobalt-based catalyst that is resistant to sintering and coking. The catalyst includes a carrier and active metal cobalt and guest metal oxide loaded on the carrier, and the carrier is pure silicon silicalite-1 or silicalite-2. The catalyst prepared based on the present application shows excellent butene and butadiene selectivity and catalytic stability in the n-butane dehydrogenation reaction, and has good prospects for industrial application.

[0064] The beneficial effects of this application include:

[0065] 1) The cobalt-based catalyst provided in the present application is prepared by organic-assisted thermal decomposition coupled with the confinement of guest metal oxides and has good dispersibility and catalytic stability.

[0066] 2) The cobalt-based catalyst provided by the present application mainly solves the problem of easy sintering and carbon deposition of active metal components in the current n-butane dehydrogenation system. The cobalt-based catalyst prepared by the method shows excellent C4 olefin selectivity and catalytic stability in the catalytic n-butane dehydrogenation reaction. Under the conditions of 500-650°C and 0.1-1.0MPa, the single-pass conversion rate of n-butane is greater than 20%, and the C4 olefin selectivity can reach more than 95%. The preparation method disclosed in the present application has the characteristics of simple operation and good repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a scanning electron microscope photograph of the sample in Example 1 of the present application, with a scale of 2 μm. DETAILED DESCRIPTION

[0068] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0069] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0070] The present invention uses a flame ionization detector (FID) to analyze hydrocarbon products in the product; a thermal conductivity detector (TCD) to analyze H 2 , CO, CH 4 and CO 2 ;

[0071] The morphology and size of the samples were characterized by a Hitachi SU1510 scanning electron microscope (low magnification, accelerating voltage: 15 kV). Before testing, the powder samples were glued to conductive tape and gold-sprayed.

[0072] In the examples of this application, the conversion rate and selectivity are calculated as follows:

[0073]

[0074]

[0075] Example 1

[0076] First, 0.1549 g of Ce(NO 3 ) 3 6H 2 O and 0.0800g of triethanolamine were dissolved in 3g of water, and then 5g of pure silicalite-1 (S-1) carrier was added and stirred evenly, and then water was added until the carrier was saturated with water. It was aged at 25℃ for 16h, and then dried at 80℃ and 150℃ for 360min and 120min respectively. The dried sample was ground into powder. 0.2469g of Co(NO 3 ) 2 6H 2 O and 0.0800g of triethanolamine were dissolved in 3g of water, and the solution was added dropwise to the ground powder and stirred evenly. Water was added until adsorption was saturated, aged at 25°C for 16h, and then dried at 80°C and 150°C for 240min and 120min respectively. The dried sample was ground and calcined at 400°C for 360min, then heated to 600°C and continued to be calcined for 30min to finally obtain CoCeO x / S-1 catalyst.

[0077] Figure 1 This is a scanning electron microscope photo of the sample of Example 1. Figure 1 It can be seen that CoCeO x / S-1 catalyst is supported by plate-like cross-linked silicalite-1 with a particle size of ~450nm, and no obvious particle agglomerates are observed in the catalyst.

[0078] Example 2

[0079] First, 0.0279 g of Zr(NO 3 ) 40.0153g of oxalic acid was dissolved in 3g of water, and then 5g of pure silicalite-1 (S-1) carrier was added and stirred evenly, and then water was added until the carrier was saturated with water. It was aged at 25℃ for 16h, and then dried at 80℃ and 150℃ for 360min and 120min respectively. The dried sample was ground into powder. 0.2469g of Co(NO 3 ) 2 6H 2 O and 0.0153g oxalic acid were dissolved in 3g water, and the solution was added dropwise to the ground powder and stirred evenly. Water was added until adsorption was saturated, aged at 25℃ for 16h, and then dried at 80℃ and 150℃ for 240min and 120min respectively. The dried sample was ground and calcined at 400℃ for 360min, then heated to 600℃ and continued to be calcined for 30min to finally obtain CoZrO x / S-1 catalyst.

[0080] Example 3

[0081] First, 0.0222 g of GeCl 4 0.0102g of isopropanol was dissolved in 3g of ethanol, and then 5g of pure silicalite-1 (S-1) carrier was added and stirred evenly, and then ethanol was added until the carrier was saturated with adsorption. It was aged at 25℃ for 16h, and then dried at 80℃ and 150℃ for 360min and 120min respectively. The dried sample was ground into powder. 0.2469g of Co(NO 3 ) 2 6H 2 O and 0.0102g of isopropanol were dissolved in 3g of water, and the solution was added dropwise to the ground powder and stirred evenly. Water was added until adsorption was saturated, aged at 25°C for 16h, and then dried at 80°C and 150°C for 240min and 120min respectively. The dried sample was ground and calcined at 400°C for 360min, then heated to 600°C and continued to be calcined for 30min to finally obtain CoGeO x / S-1 catalyst.

[0082] Example 4

[0083] First, 0.0208 g of In(NO 3 ) 3 ·H 2 O and 0.0326g of citric acid were dissolved in 3g of water, and then 5g of pure silicalite-2 (S-2) carrier was added and stirred evenly, and then water was added until the carrier was saturated with adsorption, aged at 25℃ for 16h, and then dried at 80℃ and 150℃ for 360min and 120min respectively. The dried sample was ground into powder. 0.2469g of Co(NO 3 ) 26H 2 O and 0.0326g of citric acid were dissolved in 3g of water, and the solution was added dropwise to the ground powder and stirred evenly. Water was added until adsorption was saturated, aged at 25℃ for 16h, and then dried at 80℃ and 150℃ for 240min and 120min respectively. The dried sample was ground and calcined at 400℃ for 360min, then heated to 600℃ and continued to be calcined for 30min to finally obtain CoInO x / S-2 catalyst.

[0084] Comparative Example 1

[0085] 0.2469 g of Co(NO 3 ) 2 6H 2 O and 0.0800g of triethanolamine were dissolved in 3g of water, 5g of pure silicon S-1 carrier was added and stirred evenly and hydrated to saturation, aged at 25°C for 16h, then dried at 80°C and 150°C for 240min and 120min respectively, the dried sample was ground and calcined at 400°C for 360min, then heated to 600°C and calcined for 30min to finally obtain Co / S-1 catalyst.

[0086] Test Example 1

[0087] The test process is as follows: the catalysts of the examples and comparative examples are loaded into a fixed bed reactor lined with a quartz tube, and heated to the reaction temperature at a heating rate of 10°C / min in a nitrogen atmosphere (12 mL / min). 2 / CO 2 / nC 4 H 10 (9600mL / (g·h)) reaction atmosphere, n-butane mass space velocity is 0.62h -1 , CO 2 / nC 4 H 10 =10:1, pressure 0.1MPa. The reaction product is heated and vaporized and then sent to gas chromatography for analysis. TCD is used to analyze H 2 , CO, CH 4 and CO 2 The FID was used to analyze hydrocarbon products. The specific test results are shown in Table 1.

[0088] Table 1 shows the performance of the examples and comparative samples at 530°C. The n-butane conversion of the examples is higher than that of Co / S-1, and the selectivity of C4 olefins (monoolefins and butadiene) in the hydrocarbon products is also slightly superior. The excellent performance of the examples is mainly attributed to the fact that the guest metal oxide inhibits the aggregation and sintering of metal cobalt, that is, slows down the deactivation rate of the catalyst, and also reduces the side reactions such as cracking caused by the aggregation of metal cobalt.

[0089] Table 1

[0090]

[0091] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a cobalt-based catalyst, It is characterized in that The preparation method comprises the following steps: (1) aging and drying a mixture I containing a metal oxide precursor, an auxiliary pyrolysis organic matter, a carrier, and a solvent to obtain a composite oxide carrier; (2) A mixture II containing a composite oxide support, a cobalt salt, an auxiliary pyrolysis organic matter, and a solvent is aged II, dried II, and calcined to obtain a cobalt-based catalyst.

2. The preparation method according to claim 1, It is characterized in that In steps (1) and (2), the auxiliary pyrolysis organic matter is independently selected from at least one of oxalic acid, citric acid, isopropanol, ethylenediamine, triethanolamine, and ascorbic acid; Preferably, in steps (1) and (2), the concentration of the auxiliary pyrolysis organic matter is independently 0.01 to 5 mol / L.

3. The preparation method according to claim 1, It is characterized in that The metal oxide precursor is selected from at least one of chlorides, nitrates and sulfates containing metal elements; Preferably, the metal element is selected from at least one of cerium, zirconium, germanium and indium; Preferably, the concentration of the metal oxide precursor is 0.01 to 10 mol / L, calculated as the molar amount of the metal element.

4. The preparation method according to claim 1, It is characterized in that In the step (1), the carrier is selected from silicalite-1 and / or silicalite-2 of pure silicon; Preferably, the mass percentage of the carrier and the mixture I is 30wt% to 70wt%; Preferably, in step (1), the molar ratio of the metal oxide precursor to the auxiliary pyrolysis organic matter is 20:1 to 1:

10.

5. The preparation method according to claim 1, It is characterized in that In the step (2), the cobalt salt is selected from at least one of cobalt chloride, cobalt sulfate, cobalt nitrate, and cobalt acetylacetonate; Preferably, in the mixture II, the concentration of the cobalt salt is 0.01 to 5 mol / L, based on the molar amount of the cobalt element in the cobalt salt; Preferably, in step (2), the molar ratio of the cobalt salt to the auxiliary pyrolysis organic matter is 10:1 to 1:10; Preferably, the solvent in step (1) and step (2) is independently selected from at least one of water, methanol and ethanol.

6. The preparation method according to claim 1, It is characterized in that The temperature of aging I and aging II is independently selected from 10 to 80° C.; the time of aging I and aging II is independently selected from 30 to 1200 min; Preferably, the temperature of the drying I and the drying II are independently selected from 50 to 200° C.; the time of the drying I and the drying II are independently selected from 120 to 720 min; Preferably, the calcination temperature is 400-700° C.; and the calcination time is 30-360 min.

7. The preparation method according to claim 1, It is characterized in that The cobalt-based catalyst comprises a carrier and cobalt and metal oxides other than cobalt supported on the carrier; The carrier is silicalite-1 and / or silicalite-2 of pure silicon; The metal oxide other than cobalt is selected from at least one of cerium oxide, zirconium oxide, germanium oxide and indium oxide; Preferably, the cobalt content in the cobalt-based catalyst is 0.01 to 10 wt%, wherein the cobalt content is calculated based on the mass of the cobalt element; Preferably, in the cobalt-based catalyst, the content of metal oxides other than cobalt is 0.1 to 20 wt %, wherein the content of the metal oxides other than cobalt is calculated based on the mass of the metal element.

8. A method for catalyzing the dehydrogenation of n-butane, It is characterized in that The method comprises: The raw material containing n-butane is contacted with a catalyst to react and obtain a product containing butene and butadiene; Alternatively, a mixture containing n-butane and CO 2 The raw material is contacted with a catalyst to react and obtain a product containing butene and butadiene; The catalyst is selected from the cobalt-based catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. The method according to claim 8, It is characterized in that The CO 2 The volume ratio of n-butane is 1:10 to 10:1; the mass space velocity of n-butane is 0.05 to 10.00 h -1 .

10. The method according to claim 8, It is characterized in that The reaction temperature is 500-650° C.; the reaction pressure is 0.1-1.0 MPa.

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