A highly efficient absorbent for the process of butane oxidation to maleic anhydride

Abstract

The application discloses a kind of high-efficiency absorbent for butane oxidation process of maleic anhydride, its characteristics are added to the traditional organic absorbent of maleic anhydride with appropriate long-chain quaternary ammonium salt, quaternary ammonium salt as a typical hydrogen bond acceptor, can be combined with traditional organic solvent by hydrogen bond network and form low eutectic solvent, play the role of adjusting solvent polarity, to enhance the weak interaction between absorbent and maleic anhydride molecule Force. By optimizing the addition ratio of long-chain quaternary ammonium salt, both the hydrophobic ability of the absorbent can be ensured, and the hydrolysis reaction of maleic anhydride can be avoided, and the absorption capacity of the absorbent for maleic anhydride in butane oxidation reaction gas can be enhanced, the amount of traditional absorbent can be reduced, and the tower load of absorbent recovery unit can be reduced, and the separation energy consumption can be reduced. The improvement means of the absorbent proposed in the application is simple and effective, can be popularized on a large scale, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of maleic anhydride separation and purification, and in particular to a highly efficient absorbent for the process of butane oxidation to maleic anhydride. Background Technology

[0002] Maleic anhydride (also known as maleic anhydride or maleic acid anhydride, abbreviated as MA) is an extremely important organic chemical raw material, and the third largest anhydride after phthalic anhydride and acetic anhydride. Maleic anhydride production can be divided into phthalic anhydride by-product method, benzene method, C4 olefin method, and n-butane oxidation method, depending on the raw materials. Currently, the n-butane oxidation method has become dominant due to its low production cost and minimal environmental pollution. The n-butane oxidation process to maleic anhydride mainly includes three parts: a catalytic oxidation unit, an absorption unit, and a product refining and purification unit. The absorption unit is the key part that determines the product yield. Depending on the type of absorbent, the widely used technologies at home and abroad can be divided into water absorption and organic solvent absorption methods. The water absorption method has disadvantages such as the hydrolysis of maleic anhydride to produce maleic acid, which is prone to corrosion and equipment blockage, and the product refining unit has complex dehydration processes. Organic solvent absorption, on the other hand, offers high product yield and good process continuity, making it more suitable for large-scale production using n-butane as a raw material. However, organic solvents are generally expensive, necessitating the addition of an organic solvent purification and refining section in the process to allow for the recycling of organic solvents. Traditional organic solvents are used in large quantities and the purification unit consumes a lot of energy. Therefore, developing efficient organic absorbents can reduce the amount of solvent circulating in the process and reduce the energy consumption of the process.

[0003] Eutectic solvents are a novel type of functional solvent composed of hydrogen bond donors and acceptors. Hydrophobic eutectic solvents, in particular, exhibit hydrophobicity and excellent solubility for both organic and inorganic compounds, overcoming the limitations of traditional hydrophilic eutectic solvents and expanding their application range. Currently reported hydrophobic eutectic solvents generally use long-chain quaternary ammonium salts or long-chain fatty acids as hydrogen bond acceptors, mixed with fatty acids or fatty alcohols. The resulting solutions have high viscosity, which reduces the absorption rate if used for absorption. Considering the low viscosity of existing organic solvents used for maleic anhydride absorption, using these organic solvents as hydrogen bond donors, and adding appropriate hydrogen bond acceptor molecules, will not increase the solution viscosity but will instead regulate the solution polarity, increasing the affinity between the solvent and maleic anhydride molecules, thereby enhancing the absorption effect, reducing the amount of absorbent in the absorption unit, and lowering the energy consumption for solvent separation and purification. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a highly efficient absorbent for the butane oxidation process to maleic anhydride. A long-chain quaternary ammonium salt is used as a hydrogen bond acceptor, mixed with a certain mass of a traditional organic absorbent solvent for maleic anhydride, and heated and stirred to form a homogeneous and stable solution, which serves as the highly efficient absorbent for maleic anhydride.

[0005] To achieve the objectives of this invention, the invention is implemented through the following technical solutions:

[0006] A highly efficient absorbent for the butane oxidation process to maleic anhydride is characterized in that the absorbent is prepared by heating and stirring a dialkyl phthalate solvent, a hexahydrophthalic acid ester solvent, or a dialkyl sebacate solvent with a long-chain quaternary ammonium salt in a certain proportion. The dialkyl phthalate solvent is one or a combination of at least one of di-n-butyl phthalate, diisobutyl phthalate, dipentyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, dinonyl phthalate, and didecyl phthalate. The hexahydrophthalic acid ester solvent is one or a combination of at least one of dipropyl hexahydrophthalate, diisobutyl hexahydrophthalate, and dibutyl hexahydrophthalate. The dialkyl sebacate solvent is dibutyl sebacate, diisooctyl sebacate, dioctyl sebacate, and dinonyl sebacate. The long-chain quaternary ammonium salt is one or a combination of at least one of tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride, methyltrioctylammonium bromide, tetraheptylammonium chloride, tetraheptylammonium bromide, tetraoctylammonium chloride, and tetraoctylammonium bromide; the quaternary phosphorus salt is trihexyltetradecylphosphine chloride. The added components are: tetrabutylammonium chloride (4%–30% by mass); tetrabutylammonium bromide (4%–30% by mass); methyltrioctylammonium chloride (4%–20% by mass); methyltrioctylammonium bromide (4%–20% by mass); tetraheptylammonium chloride (4%–25% by mass); tetraheptylammonium bromide (4%–25% by mass); tetraoctylammonium chloride (10%–20% by mass); tetraoctylammonium bromide (10%–20% by mass); and trihexyltetradecylphosphine chloride (4%–15% by mass).

[0007] Compared with the prior art, the present invention has the following significant technical effects and advantages:

[0008] 1. The solvent of this invention is simple to synthesize, and the hydrogen bond acceptor additive used is more environmentally friendly.

[0009] 2. The quaternary ammonium salt hydrogen bond acceptor added in this invention can form a stable eutectic solvent by hydrogen bonding with traditional organic solvents, thereby changing the polarity of traditional solvents and enhancing the affinity between solvents and maleic anhydride molecules.

[0010] 3. The eutectic solvent formed by the present invention is a hydrophobic eutectic solvent, which has a lower viscosity and better absorption effect compared with traditional hydrophobic eutectic solvents. Detailed Implementation

[0011] This invention provides a highly efficient absorbent for the butane oxidation process to maleic anhydride, which is a hydrophobic eutectic solvent formed by a long-chain quaternary ammonium salt as a hydrogen bond acceptor and a certain mass of a traditional organic solvent containing maleic anhydride. Those skilled in the art can prepare it by referring to existing disclosed methods, for example, according to the following method:

[0012] The hydrogen bond donor (such as di-n-butyl phthalate) and the hydrogen bond acceptor (such as methyltrioctylammonium chloride) in the eutectic solvent are added to a flask in a certain molar ratio, heated to 80°C, and magnetically stirred for 1 to 5 hours until a homogeneous mixture is formed.

[0013] After the solvent is prepared, the absorption effect can be described by determining the solubility of maleic anhydride in it. Those skilled in the art can perform the solubility determination using the existing disclosed dynamic method, as follows:

[0014] Accurately weigh a certain amount of maleic anhydride solid and solvent, mix the sample with known composition, stir rapidly and control the temperature increase to make the solid particles in the mixture disappear, slowly heat the sample in a state infinitely close to equilibrium, and the temperature at which the last solute particle disappears or the solution changes from mist to transparency is the solubility of maleic anhydride in the solvent.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred solutions.

[0016] Preferably, the organic solvent is one or a combination of at least one of di-n-butyl phthalate, diisobutyl phthalate, dipentyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, dinonyl phthalate, didecyl phthalate, dipropyl hexahydrophthalate, diisobutyl hexahydrophthalate, dibutyl hexahydrophthalate, dibutyl sebacate, diisooctyl sebacate, dioctyl sebacate, and dinonyl sebacate.

[0017] Preferably, the long-chain quaternary ammonium salt is one or a combination of at least one of tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride, methyltrioctylammonium bromide, tetraheptylammonium chloride, tetraheptylammonium bromide, tetraoctylammonium chloride, and tetraoctylammonium bromide; the quaternary phosphorus salt is trihexyltetradecylphosphine chloride.

[0018] Preferably, the added tetrabutylammonium chloride accounts for 4%–30% of the total mass; the added tetrabutylammonium bromide accounts for 4%–30% of the total mass; the added methyltrioctylammonium chloride accounts for 4%–20% of the total mass; the added methyltrioctylammonium bromide accounts for 4%–20% of the total mass; the added tetraheptylammonium chloride accounts for 4%–25% of the total mass; the added tetraheptylammonium bromide accounts for 4%–25% of the total mass; the added tetraoctylammonium chloride accounts for 10%–20% of the total mass; the added tetraoctylammonium bromide accounts for 10%–20% of the total mass; and the added trihexyltetradecylphosphine chloride accounts for 4%–15% of the total mass. If the mass percentage is less than the minimum addition amount, the enhancement of the absorption effect on maleic anhydride will not be significant; if the mass percentage is greater than the maximum addition amount, it will increase the viscosity of the solvent and reduce the absorption rate.

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Example 1

[0021] 1. Add methyltrioctylammonium chloride to di-n-butyl phthalate at a concentration of 4% of the total mass, and then heat and stir to obtain maleic anhydride absorbent.

[0022] 2. The solubility of maleic anhydride in the absorbent was determined using the aforementioned dynamic method, as detailed below:

[0023] (1) Weigh 50g of absorbent and add 7.8g of maleic anhydride solid to obtain a mixed sample.

[0024] (2) Place the sample into a 100mL single-necked glass reaction flask with a jacket, and place a thermometer into the mouth of the flask to monitor the temperature.

[0025] (3) Connect the super thermostatic bath and introduce thermostatic water into the jacket, turn on the magnetic stirrer, and control the temperature to rise slowly.

[0026] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30.6℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 15.6g / 100g.

[0027] Example 2

[0028] 1. Compared with Example 1, the amount added was adjusted to 10% of the total mass.

[0029] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 15.2g.

[0030] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 30.4g / 100g.

[0031] Example 3

[0032] 1. Compared with Example 1, the amount added was adjusted to 20% of the total mass.

[0033] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 41.2g.

[0034] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 82.4 g / 100 g.

[0035] Example 4

[0036] 1. Compared with Example 1, the amount added was adjusted to 25% of the total mass.

[0037] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 40.5g.

[0038] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 81.0 g / 100 g.

[0039] Example 5

[0040] 1. Compared with Example 1, methyltrioctylammonium bromide was added instead, with the amount added accounting for 10% of the total mass.

[0041] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 9.4g.

[0042] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 18.8g / 100g.

[0043] Example 6

[0044] 1. Compared with Example 1, tetraoctylammonium chloride was added instead, with the amount added accounting for 10% of the total mass.

[0045] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 8.1g.

[0046] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 16.2g / 100g.

[0047] Example 7

[0048] 1. Compared with Example 1, tetraoctylammonium chloride was added to diisobutyl hexahydrophthalate, with the amount added accounting for 4% of the total mass.

[0049] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 12.3g.

[0050] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 24.6g / 100g.

[0051] Example 8

[0052] 1. Compared with Example 1, tetraoctylammonium chloride was added to diisobutyl hexahydrophthalate, with the amount added accounting for 10% of the total mass.

[0053] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 16.1g.

[0054] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 32.2g / 100g.

[0055] Comparative Example 1

[0056] 1. Compared with Example 1, no methyltrioctylammonium chloride was added.

[0057] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 5.2g.

[0058] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 10.4g / 100g.

[0059] Comparative Example 2

[0060] 1. Compared with Example 7, no methyltrioctylammonium chloride was added.

[0061] 2. Compared with Example 1, the mass of maleic anhydride solid added in (1) was changed to 10.1g.

[0062] The temperature at which the last solid particle of maleic anhydride disappeared was observed to be 30℃, indicating that the solubility of maleic anhydride in this highly efficient absorbent at this temperature is 20.2g / 100g.

[0063] Table 1 shows the different absorbents and their absorption effects. A comparison of Examples 1-3 with Comparative Example 1 shows that adding 4%-20% (w / w) of methyltrioctyl ammonium chloride to di-n-butyl phthalate increases the solubility of maleic anhydride by approximately 0.5-7 times. A comparison of Examples 3 and 2, and Examples 7 and 8 shows that the solubility of maleic anhydride increases with increasing amounts of hydrogen bond acceptors. A comparison of Examples 3 and 4 shows that when the amount of methyltrioctyl ammonium chloride exceeds 20%, the solubility of maleic anhydride decreases. The solubility no longer improved because the solvent viscosity was too high, which was not conducive to dissolution. As can be seen from the comparison between Examples 5 and 6 and Comparative Example 1, the solubility of maleic anhydride can be increased by 0.8 times and 0.56 times respectively after adding 10% methyltrioctylammonium bromide or 10% tetraoctylammonium chloride to di-n-butyl phthalate. As can be seen from the comparison between Examples 7 and 8 and Comparative Example 2, the solubility of maleic anhydride can be increased by 0.2 times and 0.6 times respectively after adding 4% and 10% by mass fraction of methyltrioctylammonium chloride to diisobutyl hexahydrophthalate.

[0064] Table 1 Comparison of absorption effects of different absorbents

[0065]

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly efficient absorbent for use in the absorption unit of the butane oxidation process to maleic anhydride, characterized in that: The absorbent is prepared by heating and stirring a solvent of dialkyl phthalate, hexahydrophthalate or dialkyl sebacate with a long-chain quaternary ammonium salt or quaternary phosphate salt in a certain proportion.

2. The maleic anhydride high-efficiency absorbent according to claim 1, characterized in that: Dialkyl phthalate solvents are one or a combination of at least one of di-n-butyl phthalate, diisobutyl phthalate, dipentyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, dinonyl phthalate, and didecyl phthalate.

3. The maleic anhydride high-efficiency absorbent according to claim 1, characterized in that: The hexahydrophthalic acid ester solvent is one or a combination of at least one of dipropyl hexahydrophthalate, diisobutyl hexahydrophthalate, and dibutyl hexahydrophthalate.

4. The maleic anhydride high-efficiency absorbent according to claim 1, characterized in that: Dialkyl sebacate solvents are one or a combination of at least one of dibutyl sebacate, diisooctyl sebacate, dioctyl sebacate, and dinonyl sebacate.

5. The maleic anhydride high-efficiency absorbent according to claim 1, characterized in that: The long-chain quaternary ammonium salt is one or a combination of at least one of tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride, methyltrioctylammonium bromide, tetraheptylammonium chloride, tetraheptylammonium bromide, tetraoctylammonium chloride, and tetraoctylammonium bromide; the quaternary phosphorus salt is trihexyltetradecylphosphine chloride.

6. The maleic anhydride high-efficiency absorbent according to claim 1, characterized in that: The added tetrabutylammonium chloride accounts for 4%–30% by mass; the added tetrabutylammonium bromide accounts for 4%–30% by mass; the added methyltrioctylammonium chloride accounts for 4%–20% by mass; the added methyltrioctylammonium bromide accounts for 4%–20% by mass; the added tetraheptylammonium chloride accounts for 4%–25% by mass; the added tetraheptylammonium bromide accounts for 4%–25% by mass; the added tetraoctylammonium chloride accounts for 10%–20% by mass; the added tetraoctylammonium bromide accounts for 10%–20% by mass; and the added trihexyltetradecylphosphine chloride accounts for 4%–15% by mass.

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