Process for the preparation of maleic anhydride by oxidation of n-butane

Abstract

The application relates to the maleic anhydride production field and discloses a method for preparing maleic anhydride through n-butane oxidation. The method comprises the following steps: under the action of a catalyst, a promoter, n-butane and an oxidant are contacted; wherein the promoter is selected from at least one of 2,5-dihydrofuran, furan and 2(5H)-furanone. The method can effectively improve the total conversion rate and the maleic anhydride selectivity of the reaction.

Description

Technical Field

[0001] This invention relates to the field of maleic anhydride production, and more specifically, to a method for preparing maleic anhydride by oxidation of n-butane. Background Technology

[0002] Maleic anhydride is an important organic chemical raw material and fine chemical product. It is currently the world's third largest acid anhydride after phthalic anhydride and acetic anhydride, primarily used in the production of thermosetting resins and unsaturated polyester resins. It is also used in pesticides, pharmaceuticals, coatings, inks, lubricant additives, papermaking chemicals, textile chemicals, textile finishing agents, food additives, and surfactants. Furthermore, maleic anhydride can be used to produce a series of widely applicable fine chemical products, including 1,4-butanediol (GBL), tetrahydrofuran (THF), maleic acid, fumaric acid, and tetrahydroanhydride. Its development and utilization prospects are very broad, and its application scope continues to expand.

[0003] Maleic anhydride production processes, categorized by raw materials, mainly include benzene catalytic oxidation, n-butane catalytic oxidation, C4 olefin catalytic oxidation, and phthalic anhydride by-product methods. In recent years, the process of producing maleic anhydride using low-cost C4 fraction (n-butane) as raw material has become the absolute mainstream worldwide. Since 2011, the trend of shifting from benzene oxidation to n-butane oxidation for maleic anhydride production in my country has become increasingly evident, with the capacity and operating rate of domestic n-butane oxidation plants exceeding those of the benzene oxidation method. These factors have greatly stimulated domestic demand for vanadium phosphorus oxidase catalysts for butane-based maleic anhydride production.

[0004] In a typical process for producing maleic anhydride using the n-butane method, n-butane and air are preheated and then passed through a tubular fixed-bed reactor containing a vanadium-phosphorus-oxygen catalyst to produce maleic anhydride. After further processing in a post-treatment unit, relatively pure maleic anhydride is obtained.

[0005] Besides butane and air, previous patent literature has reported that adding steam separately to the reaction system is beneficial to the reaction. For example, US20070249848A1 uses carbon monoxide to supplement the feed gas, which can appropriately improve the selectivity and yield of maleic anhydride and reduce the hot spot temperature. CN202415420U reports a process of seasonally supplementing steam, that is, adding steam to the reaction air in the dry spring and winter seasons to improve the catalytic oxidation environment and slow down the rate of catalyst decay. The activity of the catalyst is improved, the conversion rate of maleic anhydride is increased, and the consumption of raw materials is reduced. US4950769A reports a method of using hydrogen peroxide for water supplementation, in which hydrogen peroxide decomposes into water and oxygen at high temperature.

[0006] US511707A, US3474041A, US4701433A, US4515899A, etc., mention that adding phosphorus-containing compounds such as trimethyl phosphate to the feed gas can slow down the phosphorus loss problem in the later stage of the catalyst's life cycle and extend the catalyst's life.

[0007] These technologies have made significant contributions to the industry and provided valuable insights for subsequent researchers. Further improving the conversion rate of n-butane and the selectivity of maleic anhydride remains an important research direction. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems in the existing technology regarding the need for further improvement in the overall conversion and maleic anhydride selectivity in the oxidation of n-butane to maleic anhydride, and to provide a method for the oxidation of n-butane to maleic anhydride. This method effectively improves the overall conversion and maleic anhydride selectivity of the reaction.

[0009] To achieve the above objectives, the present invention provides a method for the oxidation of n-butane to prepare maleic anhydride, the method comprising: contacting an accelerator, n-butane and an oxidant in the presence of a catalyst;

[0010] The promoter is selected from at least one of 2,5-dihydrofuran, furan, and 2(5H)-furanone.

[0011] Preferably, the promoter is selected from at least two of 2,5-dihydrofuran, furan, and 2(5H)-furanone.

[0012] Preferably, the molar ratio of furan, 2,5-dihydrofuran and 2(5H)-furanone is 5-60:0-15:35-95, and more preferably 8-55:0-15:45-95.

[0013] Preferably, the amount of the accelerator is 0.01-5% of the amount of n-butane, more preferably 0.1-1%.

[0014] The beneficial effects of the present invention through the above technical solution include:

[0015] The method provided by this invention introduces a promoter that accelerates the oxidation of n-butane to maleic anhydride, thereby effectively improving the overall conversion rate and the selectivity of maleic anhydride, resulting in a significant increase in the yield of maleic anhydride. Simultaneously, the promoter is completely reacted in the reactor without introducing new impurities.

[0016] The method provided by this invention is simple to operate and requires no major modifications to existing devices. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The present invention provides a method for the oxidation of n-butane to prepare maleic anhydride, the method comprising: contacting an accelerator, n-butane and an oxidant in the presence of a catalyst;

[0019] The promoter is selected from at least one of 2,5-dihydrofuran, furan, and 2(5H)-furanone.

[0020] Preferably, the promoter is selected from at least two of 2,5-dihydrofuran, furan, and 2(5H)-furanone. In this preferred embodiment, the two promoters work synergistically, which is more conducive to improving the yield of maleic anhydride.

[0021] To further improve the yield of maleic anhydride, the molar ratio of furan, 2,5-dihydrofuran and 2(5H)-furanone is preferably 5-60:0-15:35-95, and more preferably 8-55:0-15:45-95.

[0022] According to the present invention, preferably, the amount of the accelerator is 0.01-5% of the amount of n-butane, more preferably 0.1-1%, for example 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and any value within any range of any two of these values. This preferred embodiment is more conducive to improving the yield of maleic anhydride.

[0023] According to the present invention, preferably, the volume fraction of n-butane is 1.5-2% based on the total volume of n-butane and oxidant.

[0024] In this invention, the volume fraction of n-butane is obtained by the following formula:

[0025] n-Butane volume fraction = n-Butane volume introduced / (n-Butane volume introduced + Oxidant volume introduced) × 100%.

[0026] The reaction for preparing maleic anhydride by oxidation of n-butane described in this invention can be a continuous reaction or a batch reaction.

[0027] When the reaction for the oxidation of n-butane to prepare maleic anhydride is a continuous reaction, preferably, the method includes: adding a mixture of accelerator, oxidant and n-butane into a reactor containing a catalyst for contact.

[0028] When the reaction for preparing maleic anhydride by oxidation of n-butane is a batch reaction, the accelerator can be added alone or mixed with other materials before being added. The present invention does not have any particular limitation on this.

[0029] When the accelerator is added alone, preferably, the method includes: adding the accelerator to a reactor containing a catalyst and contacting it with n-butane and an oxidant.

[0030] When accelerators are added after being mixed with other materials, there are mainly three scenarios:

[0031] Preferably, the method includes: adding a mixture of accelerator and n-butane into a reactor containing a catalyst to contact the oxidant.

[0032] Preferably, the method includes: adding a mixture of accelerator and oxidant into a reactor containing a catalyst and contacting it with n-butane.

[0033] Preferably, the method includes: adding a mixture of accelerator, oxidant and n-butane into a reactor containing a catalyst for contact.

[0034] When the reaction for the oxidation of n-butane to prepare maleic anhydride is a batch reaction, the amount of catalyst used is 0.001-4% of the volume of n-butane.

[0035] Water vapor can lower the temperature of hot spots, and water vapor can be added to the reaction described in this invention as needed. Preferably, the reaction raw materials in this method also contain water vapor.

[0036] Preferably, the amount of water vapor used is 0-1% of the amount of n-butane, more preferably 0-0.5%.

[0037] The present invention does not have any particular limitation on the way the water vapor is added; it can be added alone or together with other substances.

[0038] According to one specific embodiment of the present invention, a mixture of water vapor, accelerator, oxidant and n-butane is added to a reactor containing a catalyst for contact.

[0039] In the oxidation of n-butane to maleic anhydride, vanadium-phosphorus-oxygen catalysts are typically used. However, these catalysts experience significant phosphorus loss during use, leading to reduced catalyst activity. The addition of a phosphorus supplement can compensate for this phosphorus deficiency. Therefore, the reaction described in this invention can also incorporate a phosphorus supplement as needed. Preferably, the reaction feedstock in this method also contains a phosphorus supplement.

[0040] The present invention does not impose any particular limitation on the type of phosphorus supplement, and any conventional choice in the art can be made. Preferably, the phosphorus supplement is trimethyl phosphate.

[0041] Preferably, the amount of phosphorus supplement is 0-1% of the amount of n-butane, more preferably 0-0.5%.

[0042] The present invention does not have any particular limitation on the way the phosphorus supplement is added; it can be added alone or together with other substances.

[0043] According to one specific embodiment of the present invention, a mixture of phosphorus supplement, accelerator, oxidant and n-butane is added to a reactor containing a catalyst for contact.

[0044] Carbon monoxide can reduce hot spots, and the reaction described in this invention can be modified by adding carbon monoxide as needed. Preferably, the reaction raw materials in this method also contain carbon monoxide.

[0045] Preferably, the amount of carbon monoxide used is 0-1% of the amount of n-butane, more preferably 0-0.5%.

[0046] The present invention does not have any particular limitation on the way the carbon monoxide is added; it can be added alone or together with other substances.

[0047] According to one specific embodiment of the present invention, a mixture of carbon monoxide, an accelerator, an oxidant and n-butane is added to a reactor containing a catalyst for contact.

[0048] According to the present invention, preferably, the reaction conditions include: a temperature of 370-440°C, more preferably 400-440°C; and a volume hourly space velocity of 1000-2200 h⁻¹. -1 Preferably 1500-2100h -1 The pressure is 0.01-0.09 MPa, preferably 0.02-0.08 MPa.

[0049] In this invention, when n-butane is added to the reactor alone, the volume hourly space velocity (VHSV) is the same as that of n-butane.

[0050] When n-butane is added to the reactor along with a mixture of other substances (such as oxidants, accelerators, etc.), the volume hourly space velocity (VHSV) is equal to the VHSV of the mixture.

[0051] The present invention does not impose any particular limitation on the type of oxidant, and any conventional choice in the art can be made. Preferably, the oxidant is an oxygen-containing gas, and more preferably air.

[0052] The method for preparing maleic anhydride by oxidation of n-butane described in this invention does not have any particular limitation on the catalyst used, and various catalysts commonly used in the art can be employed. Preferably, the catalyst is a vanadium phosphorus oxycatalyst.

[0053] According to the present invention, preferably, based on the total mass of the catalyst, the mass content of vanadium is 28-35%, more preferably 30-34%; and the mass content of phosphorus is 15-25%, more preferably 18-22%.

[0054] According to the present invention, preferably, the bulk density of the catalyst is 0.6-0.85 g / cm³. 3 The preferred concentration is 0.7-0.8 g / cm³. 3 .

[0055] The present invention does not impose any particular limitation on the preparation method of the above-mentioned catalyst, as long as the catalyst with the above-mentioned composition and characteristics can be prepared. In order to better illustrate the method of the present invention, the present invention provides a catalyst disclosed in CN108339558A as an example.

[0056] The present invention will be described in detail below through embodiments.

[0057] In the following embodiments,

[0058] n-Butane volume fraction = (n-Butane volume introduced / (n-Butane volume introduced + Air volume introduced)) × 100%

[0059]

[0060]

[0061] Yield = Overall conversion × Maleic anhydride selectivity

[0062] The furan, 2,5-dihydrofuran, and 2(5H)-furanone used in the following examples are all commercially available products of analytical grade.

[0063] Preparation Example 1

[0064] The catalyst was prepared according to the method of Example 1 in CN108339558A.

[0065] Example 1

[0066] The catalyst was packed into a fixed-bed reactor with a single tube specification of Φ25×2×4000mm (outer diameter 25mm, wall thickness 2mm, height 4000mm). A mixture of promoter, air, and n-butane was added to the fixed-bed reactor. The volume fraction of n-butane was 1.81%, and the promoter was furan, added at 1% of the molar amount of n-butane. The reactor was operated at a molten salt temperature of 425℃, a pressure of 0.02MPa, and a volume hourly space velocity (VHSV) of 2000h⁻¹. -1 The evaluation was conducted under the given reaction conditions. Real-time evaluation results are shown in Table 1.

[0067] Example 2

[0068] The catalyst was packed into a fixed-bed reactor with a single tube specification of Φ25×2×4000mm (outer diameter 25mm, wall thickness 2mm, height 4000mm). A mixture of promoter, air, and n-butane was added to the fixed-bed reactor. The volume fraction of n-butane was 1.79%, and the promoter was 2,5-dihydrofuran, with the promoter addition amount being 0.8% of the molar amount of n-butane. The reactor was operated at a molten salt temperature of 425℃, a pressure of 0.02MPa, and a volume hourly space velocity (VHSV) of 2000h⁻¹. -1 The evaluation was conducted under the given reaction conditions. Real-time evaluation results are shown in Table 1.

[0069] Example 3

[0070] The catalyst was packed into a fixed-bed reactor with a single tube specification of Φ25×2×4000mm (outer diameter 25mm, wall thickness 2mm, height 4000mm). A mixture of promoter, air, and n-butane was added to the fixed-bed reactor. The volume fraction of n-butane was 1.81%, and the promoter was 2(5H)-furanone, with the promoter addition amount being 0.1% of the molar amount of n-butane. The reactor was operated at a molten salt temperature of 430℃, a pressure of 0.03MPa, and a volume hourly space velocity (VHSV) of 1800h⁻¹. -1 The evaluation was conducted under the given reaction conditions. Real-time evaluation results are shown in Table 1.

[0071] Example 4

[0072] The procedure was carried out according to Example 1, except that furan and 2(5H)-furanone were used as accelerators, with a molar ratio of furan to 2(5H)-furanone of 1:1, and the total amount of accelerator added was 0.5% of the amount of butane. The real-time evaluation results are shown in Table 1.

[0073] Example 5

[0074] The procedure was carried out according to Example 1, except that the accelerators used were furan, 2,5-dihydrofuran, and 2(5H)-furanone, wherein the molar ratio of furan:2,5-dihydrofuran:2(5H)-furanone was 1:1:8, and the total amount of accelerator added was 0.7% of the amount of butane. The real-time evaluation results are shown in Table 1.

[0075] Example 6

[0076] The procedure was carried out according to Example 1, except that the accelerators used were furan and 2(5H)-furanone, with a molar ratio of furan to 2(5H)-furanone of 1:9. The total amount of accelerator added was 0.5% of the amount of butane, and 0.1% of water vapor, 0.1% of carbon monoxide, and 0.1% of trimethyl phosphate (butane) were also added. The real-time evaluation results are shown in Table 1.

[0077] Example 7

[0078] The procedure was carried out according to Example 1, except that furan and 2(5H)-furanone were used as accelerators, with a molar ratio of furan to 2(5H)-furanone of 3:7, and the total amount of accelerator added was 0.03% of the amount of butane. The real-time evaluation results are shown in Table 1.

[0079] Example 8

[0080] The procedure was carried out according to Example 1, except that furan and 2,5-dihydrofuran were used as accelerators, with a molar ratio of furan to 2,5-dihydrofuran of 5:5, and the total amount of accelerator added was 4% of the amount of butane. Real-time evaluation results are shown in Table 1.

[0081] Example 9

[0082] The catalyst was packed into a fixed-bed reactor with a single tube size of Φ25×2×4000mm (outer diameter 25mm, wall thickness 2mm, height 4000mm). A mixture of furan, 2,5-dihydrofuran, 2(5H)-furanone, air, and n-butane was added to the fixed-bed reactor. The molar ratio of furan:2,5-dihydrofuran:2(5H)-furanone:n-butane was 1:1:1:7, and the total volume fraction of the four substances (furan, 2,5-dihydrofuran, 2(5H)-furanone, and n-butane) was 1.81%. The reactor was operated at a molten salt temperature of 435℃, a pressure of 0.02MPa, and a volume hourly space velocity (VHSV) of 2000h⁻¹. -1 The evaluation was conducted under the given reaction conditions. Real-time evaluation results are shown in Table 1.

[0083] The total volume fraction of the four substances = (volume of the four substances introduced / (volume of the four substances introduced + volume of air introduced)) × 100%.

[0084] Comparative Example 1

[0085] The procedure was carried out according to Example 1, except that no accelerator was added. Real-time evaluation results are shown in Table 1.

[0086] Comparative Example 2

[0087] The procedure was carried out according to Example 1, except that no accelerator was added, and 1% (by weight of butane) of water vapor was added. Real-time evaluation results are shown in Table 1.

[0088] Comparative Example 3

[0089] The procedure was carried out according to Example 1, except that no accelerator was added, and 0.1% of trimethyl phosphate (butane) was added. Real-time evaluation results are shown in Table 1.

[0090] Comparative Example 4

[0091] The catalyst was packed into a fixed-bed reactor with a single tube specification of Φ25×2×4000mm (outer diameter 25mm, wall thickness 2mm, height 4000mm). A mixture of furan and air was added to the fixed-bed reactor, with a furan volume fraction of 1.81%. The reactor was prepared at a molten salt temperature of 435℃, a pressure of 0.02MPa, and a volume hourly space velocity (VHSV) of 2000h⁻¹. -1 The evaluation was conducted under the specified reaction conditions. Real-time evaluation results are shown in Table 1.

[0092] Furan volume fraction = (Furan volume introduced / (Furan volume introduced + Air volume introduced)) × 100%.

[0093] Table 1

[0094]

[0095]

[0096] As can be seen from the results in Table 1, the method provided by this invention significantly improves both the overall conversion rate and the selectivity of maleic anhydride, resulting in a substantial increase in the yield of maleic anhydride. Moreover, this improvement is not due to the high yield of the accelerator itself being oxidized to maleic anhydride, thus leading to a higher overall yield; rather, the presence of the accelerator promotes the reaction of n-butane oxidation to maleic anhydride, demonstrating promising application prospects.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for the oxidation of n-butane to prepare maleic anhydride, characterized in that, The method includes: contacting an accelerator, n-butane, and an oxidant in the presence of a catalyst; The promoter is selected from at least one of 2,5-dihydrofuran, furan, and 2(5H)-furanone; The amount of the accelerator used is 0.1-1% of the molar amount of n-butane; Based on the total volume of n-butane and oxidant, the volume fraction of n-butane is 1.5-2%; The reaction conditions include: a temperature of 370-440℃ and a volume hourly space velocity of 1000-2200 h⁻¹. -1 The pressure is 0.01-0.09 MPa. The catalyst is a vanadium-phosphorus-oxygen catalyst; Based on the total mass of the catalyst, the vanadium content is 28-35% and the phosphorus content is 15-25%.

2. The method according to claim 1, wherein, The promoter is selected from at least two of 2,5-dihydrofuran, furan, and 2(5H)-furanone.

3. The method according to claim 2, wherein, The molar ratio of furan, 2,5-dihydrofuran and 2(5H)-furanone is 5-60:0-15:35-95.

4. The method according to claim 3, wherein, The molar ratio of furan, 2,5-dihydrofuran and 2(5H)-furanone is 8-55:0-15:45-95.

5. The method according to any one of claims 1-4, wherein, When the reaction is a continuous reaction, the method includes: adding a mixture of a promoter, an oxidant and n-butane into a reactor containing a catalyst for contact.

6. The method according to any one of claims 1-4, wherein, When the reaction is a batch reaction, the method includes: adding a promoter to a reactor containing a catalyst and contacting it with n-butane and an oxidant; Alternatively, the method may include: adding a mixture of accelerator and n-butane into a reactor containing a catalyst and contacting it with an oxidant; Alternatively, the method may include: adding a mixture of accelerator and oxidant to a reactor containing a catalyst and contacting it with n-butane; Alternatively, the method may include contacting a mixture of an accelerator, an oxidant, and n-butane into a reactor containing a catalyst.

7. The method according to any one of claims 1-4, wherein, The reaction raw materials for this method also contain water vapor.

8. The method according to claim 7, wherein, The amount of water vapor used is 0-1% of the amount of n-butane.

9. The method according to claim 8, wherein, The amount of water vapor used is 0-0.5% of the amount of n-butane.

10. The method according to any one of claims 1-4, wherein, The raw materials for this method also contain phosphorus supplements.

11. The method according to claim 10, wherein, The amount of the phosphorus supplement is 0-1% of the amount of n-butane.

12. The method according to claim 11, wherein, The amount of the phosphorus supplement is 0-0.5% of the amount of n-butane.

13. The method according to claim 1, wherein, The reaction conditions include: a temperature of 400-440℃ and a volume hourly space velocity of 1500-2100 h⁻¹. -1 The pressure is 0.02-0.08 MPa.

14. The method according to any one of claims 1-4, wherein, The oxidant is an oxygen-containing gas.

15. The method according to claim 14, wherein, The oxidant is air.

16. The method according to claim 1, wherein, Based on the total mass of the catalyst, the vanadium content is 30-34% and the phosphorus content is 18-22%.

17. The method according to any one of claims 1-4, wherein, The bulk density of the catalyst is 0.6-0.85 g / cm³. 3 .

18. The method according to claim 17, wherein, The bulk density of the catalyst is 0.7-0.8 g / cm³. 3 .

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