Method for producing mesitylene from C9 aromatics
By combining the dealkylation reaction of C9 aromatics with the isomerization reaction of trimethylbenzene, the problems of complex processes and low yield of mesitylene in the existing technology have been solved, realizing the efficient production of high-purity mesitylene and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2023-11-22
- Publication Date
- 2026-06-30
AI Technical Summary
The existing technology for producing mesitylene from C9 aromatics has a complex process, low yield, high production cost, and is difficult to separate.
A combined process of hydrodealkylation reaction of C9 aromatic hydrocarbons and hydrogen, along with trimethylbenzene isomerization reaction, was employed to obtain high-purity mesitylene through multi-step separation and isomerization treatment.
The process was simplified, production costs were reduced, the yield and purity of mesitylene were improved, interference from ethylbenzene was eliminated, and the utilization value of C9 aromatics resources was enhanced.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of mesitylene production technology, and is a method for producing mesitylene from C9 aromatics. Background Technology
[0002] C9 aromatics comprise nine isomers, of which, after separation, the industrially available products include mesitylene, pseudotrimethylbenzene, m-toluene, and p-toluene. Among these, mesitylene and pseudotrimethylbenzene have the highest added value.
[0003] Mesitylene (1,3,5-trimethylbenzene) is an important chemical raw material. Based on it, various fuel intermediates and important fine chemical products such as pyromellitic anhydride, mesityleneamine, pyromellitic acid, and terpene alcohols can be produced. Its industrial production methods mainly include synthesis and separation and purification. The synthesis method uses pseudotrimethylbenzene as a raw material (pseudotrimethylbenzene is mostly separated from reformed or cracked C9 aromatics) and isomerizes it to produce mesitylene. The separation and purification method uses C9 mixed aromatics as byproducts from catalytic reforming units, paraxylene units, etc., and directly separates and extracts mesitylene from them. From the current technology perspective, the difficulty in producing and separating methyltrimethylbenzene lies in the presence of many substances in the raw materials, such as ethylbenzene, propylbenzene, and other C9 aromatic isomers, as well as benzo[a]butane, and the boiling points of some C9 and higher aromatics are very close to those of methyltrimethylbenzene.
[0004] In the composition and properties of reformed C9 aromatics, mesitylene and o-ethylbenzene have boiling points that differ by only 0.3°C, making industrial separation impossible using distillation. Furthermore, mesitylene's boiling points are very close to those of p-ethylbenzene and m-ethylbenzene, further complicating separation. The industrial production of mesitylene is also significantly affected by the production of ethylbenzene. Therefore, simple separation and purification are extremely difficult and costly. Alkylation and isomerization methods can be employed to utilize the structural differences between ethylbenzene and mesitylene, using chemical reactions to achieve component separation.
[0005] Chinese patent document CN103772121A discloses a method for cracking C9 and above heavy aromatic components to produce more tricresylene. This method involves hydrogenating and dealkylating C9 aromatics and then transferring alkyl to light aromatics, thereby enriching the tricresylene in the C9 aromatics and separating light hydrocarbons, BTX, mesitylene and pseudotrimethylbenzene fractions, C9 aromatics and trimethylbenzene fractions. While cracking non-aromatic and heavy aromatics reduces the difficulty of separation, the method fails to produce mesitylene, and while the yields of light hydrocarbons and BTX are relatively high, the yield of tricresylene is low, indicating that the product's value needs further improvement.
[0006] Chinese patent document CN1139095A discloses a method for separating and preparing mesitylene from C9 mixed aromatics. The method involves first distilling a C9 mixed aromatic feedstock containing more than 22% methyl ethyl benzoate (MEBenz) through primary distillation. Then, a mixed fraction containing MEBenz, pseudotrimethylbenzene, and ortho-, meta-, and para-MEBenz is used as the reaction feedstock. Tert-butanol, concentrated sulfuric acid, aluminum trichloride, and hydrochloric acid are added, followed by alkylation and sedimentation to convert MEBenz into high-boiling-point compounds. Further distillation separation yields a MEBenz product with a purity greater than 98%. However, this method, while converting MEBenz, also converts a large amount of pseudotrimethylbenzene into alkyl aromatics with more carbon atoms, resulting in a loss of MEBenz. Furthermore, this method causes severe corrosion to equipment, making it difficult to apply industrially.
[0007] Chinese patent document CN1313269A states that heavy aromatics from a refinery reforming unit need to be continuously distilled through two packed towers to separate a high-purity pseudotrimethylbenzene fraction, but high-purity mesitylene cannot be obtained.
[0008] Chinese patent document CN1974500A uses a three-tower serial process to separate reformed heavy aromatics, which can produce high-purity pseudotrimethylbenzene and co-produce enriched mesitylene with a purity of over 35%, although the purity of mesitylene is relatively low.
[0009] Chinese patent document CN102746092A discloses a method for producing mesitylene by hydrocracking of heavy aromatics. The method involves mixing heavy aromatic feedstock with hydrogen and then feeding it into a ten-membered ring zeolite catalyst containing precious metals Pt or Pb for hydrocracking. The reaction products are separated into byproduct hydrogen gas and light hydrocarbon components in a high-efficiency separator and a stripping tower, respectively. The liquid hydrocarbons are then fed into a BTX tower for BTX recovery, while the heavy components are fed into a mesitylene tower for separation of mesitylene. The remaining C9 aromatics and heavy components are recycled back to the hydrocracking reactor for further cracking, thus increasing BTX production and separating mesitylene. This method is simple and the products are easily separated, but the products are mainly BTX (light aromatics), the mesitylene yield is low, and the byproducts consist of a large amount of light hydrocarbon components. Therefore, the yield of mesitylene and the utilization value of heavy aromatic resources need further improvement.
[0010] Therefore, the existing technology for separating and producing mesitylene is lengthy, complex, and results in low yields, high production costs, and significant challenges for industrial application. However, by removing many substances with boiling points close to methylbenzene, including C9 aromatic isomers such as ethylbenzene and propane, the separation process for methylbenzene becomes shorter, the equipment simplified, and the production cost reduced. Summary of the Invention
[0011] This invention provides a method for producing mesitylene from C9 aromatics, which overcomes the shortcomings of the prior art and effectively solves the problems of complex process flow, low yield and high production cost in the existing mesitylene production.
[0012] The technical solution of the present invention is achieved through the following measures: a method for producing mesitylene from C9 aromatics, comprising the following steps:
[0013] The first step involves mixing the required amount of raw material C9 aromatics with hydrogen and then feeding it into a dealkylation reactor equipped with a dealkylation catalyst to carry out a hydrodealkylation reaction, thereby obtaining the dealkylation reaction product.
[0014] The second step involves separating the dealkylation reaction products in a high-pressure separator to obtain liquid and gaseous products.
[0015] The third step involves recycling the gaseous product back into the reverse dealkylation reactor, while the liquid product enters the BTX column for separation, yielding the BTX top product and the BTX bottom product.
[0016] The fourth step involves separating the BTX bottom product into a mestriol column to obtain mestriol and the mestriol bottom product.
[0017] Fifth step: The bottom product of the mesitylene column enters the mixing column for separation to obtain the top product and the bottom product of the mixing column;
[0018] Step 6: The product from the top of the mixing tower is mixed with hydrogen and then fed into a tricene isomerization reactor containing an isomerization catalyst to carry out the isomerization reaction and obtain the isomerization reaction product.
[0019] Step 7: The isomerization reaction product is returned to the high-pressure separator for separation to obtain mesitylene.
[0020] The following are further optimizations and / or improvements to the above-mentioned technical solution:
[0021] In the first step above, the conditions for the hydrodealkylation reaction are: reaction temperature 300℃ to 440℃, pressure 0.5MPa to 3.0MPa, and mass hourly space velocity (HHSV) 1 h⁻¹. -1 up to 6h -1 The hydrogen-oil molar ratio is 1 to 4:1.
[0022] In the first step above, the mass ratio of liquefied petroleum gas to the raw material C99 aromatics in the dealkylation reaction products is less than 1%, the mass ratio of light aromatics to the raw material C99 aromatics is less than 30%, the mass ratio of methyl ethylbenzene to the raw material C99 aromatics is less than 0.5%, and the dealkylation reaction products do not contain propylbenzene.
[0023] In the second step above, the liquid phase product is a mixture of light aromatics, trimethylbenzene, ethylbenzene, C10 aromatics and a small amount of liquefied petroleum gas, and the gas phase product contains hydrogen and a small amount of methane and ethane, wherein the hydrogen volume content is higher than 90%.
[0024] In the third step above, the top product of the BTX tower includes light aromatics and a small amount of liquefied petroleum gas, while the bottom product of the BTX tower includes the components after the removal of light aromatics and liquefied petroleum gas.
[0025] In the fourth step above, the bottom product of the mesitylene column is a mixture of pseudotrimethylbenzene, trimethylbenzene and C10 aromatics, and the purity of mesitylene is higher than 98%.
[0026] In the fifth step above, the top product of the mixing tower is a mixture of pseudotrimethylbenzene and terephthalene, and the bottom product of the mixing tower is C10 aromatics.
[0027] In the above six steps, the conditions for the isomerization reaction are: reaction temperature of 260℃ to 360℃, pressure of 0.5MPa to 3.0MPa, and mass hourly space velocity of 1h. -1 up to 6h -1 The hydrogen-oil molar ratio is 1 to 4:1.
[0028] The aforementioned dealkylation reactor and tricresyl isomerization reactor are both fixed-bed reactors.
[0029] The present invention has a simple process flow, using C9 aromatics as raw materials and a combination of dealkylation reaction and trimethylbenzene isomerization reaction to produce fewer side reactions, lower hydrogen consumption, and further utilization of by-products. The resulting product contains less than 0.5% methyl ethylbenzene, eliminating the interference of methyl ethylbenzene on the separation of trimethylbenzene, improving the yield and purity of mesitylene, reducing production costs, and enhancing the utilization value of C9 aromatics resources. Detailed Implementation
[0030] This invention is not limited to the following embodiments; specific implementation methods can be determined according to the technical solution of this invention and actual conditions. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent.
[0031] The present invention will be further described below with reference to embodiments:
[0032] Example 1: The method for producing mesitylene from this C9 aromatic hydrocarbon is carried out according to the following steps:
[0033] The first step involves mixing the required amount of raw material C9 aromatics with hydrogen and then feeding it into a dealkylation reactor equipped with a dealkylation catalyst to carry out a hydrodealkylation reaction, thereby obtaining the dealkylation reaction product.
[0034] The second step involves separating the dealkylation reaction products in a high-pressure separator to obtain liquid and gaseous products.
[0035] The third step involves recycling the gaseous product back into the reverse dealkylation reactor, while the liquid product enters the BTX column for separation, yielding the BTX top product and the BTX bottom product.
[0036] The fourth step involves separating the BTX bottom product into a mestriol column to obtain mestriol and the mestriol bottom product.
[0037] Fifth step: The bottom product of the mesitylene column enters the mixing column for separation to obtain the top product and the bottom product of the mixing column;
[0038] Step 6: The product from the top of the mixing tower is mixed with hydrogen and then fed into a tricene isomerization reactor containing an isomerization catalyst to carry out the isomerization reaction and obtain the isomerization reaction product.
[0039] Step 7: The isomerization reaction product is returned to the high-pressure separator for separation to obtain mesitylene.
[0040] This invention employs a combined process of C9 aromatics dealkylation and trimethylbenzene isomerization to eliminate interference from ethylbenzene, maximize the production of mesitylene, with ethylbenzene content below 0.5%, a simple process, high mesitylene yield, low production cost, high product value, and flexible product distribution. Compared to traditional routes for producing BTX or blended gasoline, this invention significantly enhances the utilization value of C9 aromatics resources.
[0041] Example 2: As an optimization of the above example, the conditions for the hydrodealkylation reaction in the first step are: reaction temperature 300°C to 440°C, pressure 0.5 MPa to 3.0 MPa, and mass hourly space velocity 1 h⁻¹. -1 up to 6h -1 The hydrogen-oil molar ratio is 1 to 4:1.
[0042] Example 3: As an optimization of the above example, in the first step, the mass ratio of liquefied petroleum gas to the mass ratio of the raw material C99 aromatics in the dealkylation reaction product is less than 1%, the mass ratio of light aromatics to the mass ratio of the raw material C99 aromatics is less than 30%, the mass ratio of methyl ethylbenzene to the mass ratio of the raw material C99 aromatics is less than 0.5%, and the dealkylation reaction product does not contain propylbenzene.
[0043] Example 4: As an optimization of the above example, in the second step, the liquid phase product is a mixture of light aromatics, trimethylbenzene, ethylbenzene, C10 aromatics and a small amount of liquefied petroleum gas, and the gas phase product contains hydrogen and a small amount of methane and ethane, wherein the hydrogen volume content is higher than 90%.
[0044] Example 5: As an optimization of the above example, in the third step, the top product of the BTX tower includes light aromatics and a small amount of liquefied petroleum gas, and the bottom product of the BTX tower includes the components after the removal of light aromatics and liquefied petroleum gas.
[0045] Example 6: As an optimization of the above example, in the fourth step, the bottom product of the mesitylene column is a mixture of pseudotrimethylbenzene, terephthalene and C10 aromatics, and the purity of mesitylene is higher than 98%.
[0046] Example 7: As an optimization of the above example, in the fifth step, the top product of the mixing tower is a mixture of pseudotrimethylbenzene and terephthalene, and the bottom product of the mixing tower is C10 aromatics.
[0047] Example 8: As an optimization of the above example, the isomerization reaction conditions in the six steps are: reaction temperature of 260°C to 360°C, pressure of 0.5 MPa to 3.0 MPa, and mass hourly space velocity of 1 h⁻¹. -1 up to 6h -1 The hydrogen-oil molar ratio is 1 to 4:1.
[0048] Example 9: As an optimization of the above example, in step 6, the mass content of ethylbenzene in the isomerization reaction product is less than 0.1%, the mass content of mesitylene is greater than 20%, the mass content of light aromatic hydrocarbons is 1% to 8%, and the mass content of C10 aromatic hydrocarbons is less than 3%.
[0049] Example 10: As an optimization of the above examples, both the dealkylation reactor and the trimethylbenzene isomerization reactor are fixed-bed reactors.
[0050] Example 11: C99 aromatics with a purity higher than 70% produced by catalytic reforming were subjected to a hydrodealkylation reaction in a dealkylation reactor. The reaction temperature was controlled at 310°C to 320°C, the pressure at 1.0 MPa, and the feed weight hourly space velocity at 1.0 h⁻¹. -1The feed hydrogen-to-oil molar ratio is 4:1. The catalyst is packed in a fixed bed in the dealkylation reactor. The reaction products are dehydrogenated in a high-pressure separator. The separated hydrogen is returned to the dealkylation reactor for recycling. The liquid products enter the BTX tower. The operating temperature of the BTX tower is controlled at 162℃ to 164℃ (since temperature control is difficult to achieve a specific precise value, any fluctuation within a certain range is appropriate, the same below). This causes light components such as LPG (liquefied petroleum gas), BTX (light aromatics), n-propylbenzene, isopropylbenzene, m-methylethylbenzene, and p-methylethylbenzene with boiling points below 164℃ to vaporize and be discharged from the top of the BTX tower.
[0051] The components with boiling points above 164°C retained at the bottom of the BTX column are sent to the mesitylene column. The operating temperature of the mesitylene column is controlled between 165°C and 167°C, so that mesitylene with boiling points below 167°C and a very small amount of o-toluene are discharged from the top of the mesitylene column.
[0052] The remaining C9 and C10 heavy aromatic components with boiling points above 167°C at the bottom of the mesitylene tower are sent to the mixing tower of pseudotrimethylbenzene and teremethylbenzene. The operating temperature of the mixing tower is controlled between 177°C and 179°C. Pseudotrimethylbenzene and teremethylbenzene with boiling points below 179°C are removed from the top of the mixing tower, mixed with hydrogen, and sent to the trimethylbenzene isomerization reactor. The heavy components with boiling points above 179°C at the bottom of the mixing tower are discharged.
[0053] The isomerization catalyst was packed in a fixed bed in a trimethylbenzene isomerization reactor, and the reaction temperature was controlled at 270℃ to 280℃, the reaction pressure at 1.0 MPa, and the feed weight hourly space velocity at 1.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 4:1. The isomerization reaction product is recycled back to the high-pressure separator for separation to obtain mesitylene.
[0054] In Example 11, the compositions of the dealkylation reaction products and the isomerization reaction products are shown in Table 1.
[0055] Example 12: Compared with Example 11, the difference is that the hydrodealkylation reaction was carried out, the reaction temperature was controlled at 360°C to 380°C, the pressure was 2.0 MPa, and the feed weight hourly space velocity was 2.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 5:1;
[0056] The trimethylbenzene isomerization reaction was carried out at a controlled temperature of 310℃ to 320℃, a reaction pressure of 2.0 MPa, and a feed weight hourly space velocity of 2.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 4:1. All other steps, raw materials, and processes remain unchanged.
[0057] In Example 12, the compositions of the dealkylation reaction products and the isomerization reaction products are shown in Table 1.
[0058] Example 13: Compared with Example 11, the difference is that the hydrodealkylation reaction was carried out at a controlled temperature of 330°C to 340°C, a pressure of 0.7 MPa, and a feed weight hourly space velocity of 1.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 2:1;
[0059] The trimethylbenzene isomerization reaction was carried out at a controlled temperature of 290℃ to 300℃, a reaction pressure of 1.2 MPa, and a feed weight hourly space velocity of 2.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 2:1. All other steps, raw materials, and processes remain unchanged.
[0060] In Example 13, the compositions of the dealkylation reaction products and the isomerization reaction products are shown in Table 1.
[0061] Example 14: Compared with Example 11, the difference is that the hydrodealkylation reaction was carried out at a controlled temperature of 310°C to 320°C, a pressure of 1.2 MPa, and a feed weight hourly space velocity of 2.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 6:1;
[0062] The trimethylbenzene isomerization reaction was carried out at a controlled temperature of 270℃ to 280℃, a reaction pressure of 1.6 MPa, and a feed weight hourly space velocity of 3.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 5:1. All other steps, raw materials, and processes remain unchanged.
[0063] In Example 14, the compositions of the dealkylation reaction products and the isomerization reaction products are shown in Table 1.
[0064] Example 15: Compared with Example 11, the difference is that the hydrodealkylation reaction was carried out, the reaction temperature was controlled at 350°C to 360°C, the pressure was 2.0 MPa, and the feed weight hourly space velocity was 4.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 4:1;
[0065] The trimethylbenzene isomerization reaction was carried out at a controlled temperature of 330℃ to 340℃, a reaction pressure of 1.5 MPa, and a feed weight hourly space velocity of 2.0 h⁻¹. -1 The feed hydrogen-to-oil molar ratio is 4:1. All other steps, raw materials, and processes remain unchanged.
[0066] In Example 15, the compositions of the dealkylation reaction products and the isomerization reaction products are shown in Table 1.
[0067] As shown in Table 1, in Examples 11 to 15 of the present invention, after the dealkylation reaction of C9 heavy aromatics, the content of ethylbenzene can be reduced from 5.42% to a minimum of 0.18%, a reduction of 96.68%, while the content of trimethylbenzene decreases slightly. The content of mesitylene in the product can be increased to a maximum of 16.06%, and the ratio of mesitylene to ethylbenzene is greatly improved, especially the content of o-ethylbenzene is reduced to below 0.1%. After the isomerization reaction of pseudotrimethylbenzene and terephthalene, the content of mesitylene is increased by more than 20%, and there are fewer byproducts such as BTX and C10. The isomerization product contains almost no ethylbenzene, which can overcome the interference of ethylbenzene and maximize the production of mesitylene.
[0068] In summary, the process of this invention is simple, using C9 aromatics as raw materials and a combination of dealkylation and trimethylbenzene isomerization reactions. This process results in fewer side reactions, lower hydrogen consumption, and further utilization of byproducts. The product contains less than 0.5% methyl ethylbenzene, eliminating the interference of methyl ethylbenzene on trimethylbenzene separation, improving the yield and purity of mesitylene, reducing production costs, and enhancing the utilization value of C9 aromatics resources.
[0069] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.
Claims
1. A method for producing mesitylene from C9 aromatics, characterized in that... Follow these steps: The first step involves mixing the required amount of raw material C9 aromatics with hydrogen and then feeding the mixture into a dealkylation reactor equipped with a dealkylation catalyst to carry out a hydrodealkylation reaction, thereby obtaining the dealkylation reaction product. In the dealkylation reaction product, the mass ratio of liquefied petroleum gas to the raw material C9 aromatics is less than 1%, the mass ratio of light aromatics to the raw material C9 aromatics is less than 30%, the mass ratio of methyl ethyl benzene to the raw material C9 aromatics is less than 0.5%, and the dealkylation reaction product does not contain propylbenzene. In the second step, the dealkylation reaction products are separated in a high-pressure separator to obtain liquid and gaseous products. The liquid product is a mixture of light aromatics, trimethylbenzene, ethylbenzene, C10 aromatics and a small amount of liquefied petroleum gas. The gaseous product contains hydrogen and small amounts of methane and ethane, with the hydrogen volume content exceeding 90%. The third step involves recycling the gaseous product back to the dealkylation reactor, while the liquid product enters the BTX column for separation, yielding the BTX top product and the BTX bottom product. In the fourth step, the bottom product of the BTX column is fed into a mesitylene column for separation, yielding mesitylene and the bottom product of the mesitylene column. The bottom product of the mesitylene column is a mixture of pseudotrimethylbenzene, thiol, and C10 aromatics, and the purity of the mesitylene is higher than 98%. Fifth step: The bottom product of the mesitylene column enters the mixing column for separation to obtain the top product and the bottom product of the mixing column; Step 6: The product from the top of the mixing tower is mixed with hydrogen and then fed into a tricene isomerization reactor containing an isomerization catalyst to carry out the isomerization reaction, yielding the isomerization reaction products. Among these products, the mass content of ethylbenzene is less than 0.1%, the mass content of mesitylene is greater than 20%, the mass content of light aromatics is 1% to 8%, and the mass content of C10 aromatics is less than 3%. The product from the top of the mixing tower is a mixture of pseudotrimethylbenzene and terylene, and the product from the bottom of the mixing tower is C10 aromatics. In the seventh step, the isomerization reaction product is returned to the high-pressure separator for separation to obtain mesitylene. Both the dealkylation reactor and the mesitylene isomerization reactor are fixed-bed reactors.
2. The method for producing mesitylene from C9 aromatics according to claim 1, characterized in that... In the first step, the conditions for the hydrodealkylation reaction are: reaction temperature 300℃ to 440℃, pressure 0.5MPa to 3.0MPa, and mass hourly space velocity (HHSV) 1 h⁻¹. -1 up to 6h -1 The hydrogen-oil molar ratio is 1 to 4:
1.
3. The method for producing mesitylene from C9 aromatics according to claim 1 or 2, characterized in that... In the third step, the top product of the BTX tower includes light aromatics and a small amount of liquefied petroleum gas, while the bottom product of the BTX tower includes the components after the removal of light aromatics and liquefied petroleum gas.
4. The method for producing mesitylene from C9 aromatics according to claim 3, characterized in that... In step six, the conditions for the isomerization reaction are: reaction temperature of 260℃ to 360℃, pressure of 0.5MPa to 3.0MPa, and mass hourly space velocity of 1h. -1 up to 6h -1 The hydrogen-oil molar ratio is 1 to 4:1.