Process and system for deep conversion of polymethylarenes to durene

Abstract

The present application belongs to the technical field of advanced petrochemical chemical new material, and relates to a process and system for deep conversion of polymethylarene to durene. In the presence of hydrogen, methanol alkylation is carried out on polymethylarene and methanol as raw materials in the presence of a catalyst to produce durene. The polymethylarene is toluene, xylene and / or trimethylbenzene. The present application can not only improve the conversion rate and utilization rate of polymethylarene, but also improve the selectivity of durene, thereby improving the yield of durene. In addition, the present application can avoid carbon deposition on the catalyst and prolong the service life of the catalyst. Through the improvement of durene yield and the prolongation of the service life of the catalyst, the cost of methanol alkylation for preparing durene is reduced and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of advanced petrochemical new materials technology, and relates to a process and system for the deep conversion of polymethyl aromatic hydrocarbons into mesitylene. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Mesitylene is a highly valuable C10 heavy aromatic hydrocarbon, primarily used to produce mesitylene dianhydride (metic anhydride) through oxidative dehydration. Metic anhydride is a key raw material for the synthesis of polyimide. Mesitylene production methods can be divided into synthetic and separation methods, with the separation method currently being the dominant approach. The separation method mainly involves the separation of C10 heavy aromatic hydrocarbons, using raw materials from catalytic reforming of heavy aromatic hydrocarbons and methanol-to-gasoline heavy aromatic hydrocarbons. However, this method suffers from low profit per ton of raw material, significant dependence on raw material prices and quality, small-scale production, poor product quality stability, and a heavy environmental impact. Synthetic methods mainly include the alkylation of pseudotrimethylbenzene, the isomerization of tetramethylbenzene, and the methanol methylation process to produce mesitylene. Among these, the alkylation of pseudotrimethylbenzene currently relies on a single raw material source, and the high price of pseudotrimethylbenzene limits profitability; this process is more heavily influenced by price. The isomerization of tetramethylbenzene is also significantly affected by the availability and price of raw materials, as well as high energy consumption; currently, there are virtually no industrial-scale plants using this method.

[0004] Regarding the technology of preparing mesitylene by methanol methylation, the inventors found that a high ratio of methanol to toluene / mixed xylene / trimethylene, at least above 3, leads to numerous side reactions of methanol, high exothermic reactions, serious waste of methanol raw materials, large temperature rise during the reaction process, difficulty in temperature control, and the high temperature environment also reduces the selectivity of mesitylene. At the same time, the catalyst for methanol alkylation to mesitylene is prone to carbon deposition during the reaction process, affecting the catalyst life and thus affecting the cost and efficiency of methanol alkylation to mesitylene. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a process and system for the deep conversion of polymethyl aromatics to mesitylene. This process not only improves the conversion and utilization rate of polymethyl aromatics but also enhances the selectivity of mesitylene, thereby increasing the yield of mesitylene. Furthermore, it avoids catalyst carbon buildup and extends catalyst lifespan. By achieving both increased mesitylene yield and extended catalyst lifespan, the cost of methanol alkylation for mesitylene production is reduced, and production efficiency is improved.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] On one hand, a process for the deep conversion of polymethyl aromatic hydrocarbons to mesitylene involves using polymethyl aromatic hydrocarbons and methanol as raw materials in a hydrogen-containing atmosphere, and conducting a methanol alkylation reaction under the action of a catalyst to produce mesitylene; wherein the polymethyl aromatic hydrocarbons are toluene, xylene, and / or trimethylbenzene.

[0008] The methanol alkylation reaction is carried out using a multi-stage reaction and multi-stage methanol replenishment method. This method is as follows: When the polymethyl aromatic hydrocarbon is trimethylbenzene, methanol is directly reacted with trimethylbenzene to produce mesitylene; when the polymethyl aromatic hydrocarbon is xylene, methanol is divided into two parts. One part of the methanol is reacted with xylene to produce an intermediate material, and the other part of the methanol is mixed with the intermediate material. After cooling, the intermediate material is further reacted to produce mesitylene; when the polymethyl aromatic hydrocarbon is toluene, methanol is divided into three parts. The first part of the methanol is reacted with toluene to produce a first reactant. The second part of the methanol is mixed with the first reactant, and after cooling, the first reactant is further reacted to produce a second reactant. The third part of the methanol is mixed with the second reactant, and after cooling, the second reactant is further reacted to produce mesitylene.

[0009] During the process development, this invention discovered that the single-pass selectivity for producing mesitylene in methanol alkylation experiments can reach over 35%. The crude product still contains over 30% unconverted toluene and over 25% xylene, indicating that the crude product can be further alkylated. Based on the product distribution of the crude product, this invention employs a multi-stage reaction and multi-stage methanol replenishment method. First, this improves the conversion and utilization rate of toluene (xylene), thereby increasing the yield of the target product, mesitylene. Second, by replenishing liquid methanol, excessive heat from the previous stage of reaction is removed through methanol vaporization, thus preventing a continuous rise in temperature and further improving the selectivity of the target product.

[0010] In methanol methylation reactions, there are processes such as methanol cracking that produce olefins, and possible toluene polycyclization reactions. These intermediate products involve olefin polymerization and coking, as well as carbon deposition processes such as fused ring polymerization, which affect the service life of the catalyst. The methanol alkylation reaction of the present invention is carried out under an atmosphere containing hydrogen. By using hydrogen in a co-existing manner, the degree of olefin polymerization is reduced, thereby slowing down the carbon deposition rate and extending the service life.

[0011] The process provided by this invention can use existing catalysts for methanol methylation reactions. Through research, it has been found that when the catalyst of the previous patent (application number CN202211336014.1) is used in the process of this invention, it can also produce good results in the preparation of mesitylene. Based on this, in order to further improve the yield of mesitylene prepared by the process of the present invention, the present invention further modifies the catalyst based on the prior patent. By combining the modified catalyst with the process of the present invention, the yield of mesitylene is further improved. Therefore, on the other hand, a modified catalyst is prepared by adding lanthanum salt and divalent metal salt to ammonia water to obtain a mixed solution. The mixed solution is adsorbed using an HZSM5 support to prepare a catalyst precursor. After drying and dehydration once, and calcination once, the catalyst is obtained. The catalyst is used to adsorb cerium salt solution, and then after secondary drying and secondary calcination, the modified catalyst is obtained. The divalent metal salt is zinc salt or magnesium salt, and the molar ratio of lanthanum salt to divalent metal salt is 1:0.9-1.1. The loading of lanthanum in the catalyst is 0.9-1.1 wt%; the loading of cerium is 0.4-0.6 wt%.

[0012] Experiments have shown that the modified catalyst provided by this invention, combined with the process of this invention, can further improve the yield of mesitylene.

[0013] Thirdly, the application of the above-mentioned modified catalyst in the process of deep conversion of polymethyl aromatic hydrocarbons to mesitylene.

[0014] Fourthly, a system for the deep conversion of polymethyl aromatic hydrocarbons into mesitylene, comprising:

[0015] Raw material tanks are used to supply polymethyl aromatics and methanol;

[0016] A vaporization tank is used to vaporize polymethyl aromatic hydrocarbons and methanol from a feed tank by pressurizing hydrogen, and then heat the vaporized feed.

[0017] A multi-stage reactor assembly is composed of a first reactor assembly, a second reactor assembly, and a third reactor assembly connected in series. Each reactor assembly includes at least one reactor. Each reactor is equipped with catalyst packing material, which is a catalyst for catalytic methanol alkylation reaction. Mixing devices are installed at the inlet of both the second reactor assembly and the inlet of the third reactor assembly.

[0018] Methanol storage tanks are used to replenish methanol to the second and third reactor components.

[0019] Condensation equipment is used to cool the products of the third reactor assembly;

[0020] When the polymethyl aromatic hydrocarbon is toluene, the gasified feedstock from the gasification tank enters the first reactor assembly for methanol alkylation reaction. The material from the first reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the second reactor assembly and then enters the second reactor assembly to continue the methanol alkylation reaction. The material from the second reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the third reactor assembly and then enters the third reactor assembly to continue the methanol alkylation reaction.

[0021] When the polymethyl aromatic hydrocarbon is xylene, the gasified feedstock from the gasification tank enters the second reactor assembly for methanol alkylation reaction. The material from the second reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the third reactor assembly and then enters the third reactor assembly to continue the methanol alkylation reaction.

[0022] When the polymethyl aromatic hydrocarbon is trimethylbenzene, the gasified feedstock from the gasification tank enters the third reactor assembly for methanol alkylation reaction.

[0023] In the system provided by this invention, the material flow direction is controlled by valves installed on each connecting pipeline.

[0024] The system provided by this invention achieves multi-stage reaction and multi-stage methanol replenishment through a multi-stage reactor assembly. By staged reaction and phased methanol replenishment, the reaction temperature of the next stage is lowered, improving methanol utilization. Simultaneously, the hydrogen-rich environment created by hydrogen pressurization in the gasifier enhances the conversion and utilization of polymethyl aromatic hydrocarbons, thereby increasing the yield of the target product, mesitylene. Furthermore, the hydrogen-rich environment inhibits the rate of catalyst coking, extending catalyst lifespan.

[0025] The system provided by this invention is equipped with mixing devices at the inlet of both the second reactor assembly and the third reactor assembly, so that liquid methanol is fully mixed with the material, thereby ensuring the full vaporization of the supplementary methanol and effectively reducing the reaction temperature.

[0026] The beneficial effects of this invention are as follows:

[0027] The process provided by this invention employs a multi-stage reaction and multi-stage methanol replenishment method, which can improve the conversion and utilization rate of toluene (xylene) and increase the yield of the target product mesitylene. At the same time, by replenishing liquid methanol, the excess heat from the previous stage reaction is removed through methanol vaporization, thereby avoiding a continuous rise in temperature and improving the utilization rate of methanol and the selectivity of the target product.

[0028] The process provided by this invention reduces the degree of olefin polymerization by using hydrogen embrittlement, thereby slowing down the carbon deposition rate and extending the lifespan.

[0029] Experiments have shown that by modifying the catalyst and combining it with the process provided by this invention, the yield of mesitylene can be further improved.

[0030] The system provided by this invention is designed with multi-stage reactor components to address the different conversion depths of various polymethyl aromatic hydrocarbons, thereby improving the system's ability to increase the conversion depth of different polymethyl aromatic hydrocarbons and thus enhancing the selectivity of mesitylene. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 This is a schematic diagram of the system for the deep conversion of polymethyl aromatic hydrocarbons to mesitylene used in this embodiment of the invention.

[0033] Among them, 1. Raw material tank, 2. Raw material transfer pump 2, 3. Gasification tank, 4. First reactor, 5. Second reactor, 6. Third reactor, 7. Methanol storage tank, 8. First methanol transfer pump, 9. Second methanol transfer pump, 10. Condensation tank, 11. Product tank. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] Given that existing methods for preparing mesitylene by methanol methylation suffer from problems such as low selectivity, poor yield, and easy carbon deposition of catalysts, which affect the cost and efficiency of methanol alkylation to mesitylene, this invention proposes a process and system for the deep conversion of polymethyl aromatics to mesitylene.

[0037] A typical embodiment of the present invention provides a process for the deep conversion of polymethyl aromatic hydrocarbons into mesitylene. Under hydrogen-containing atmosphere conditions, polymethyl aromatic hydrocarbons and methanol are used as raw materials, and a methanol alkylation reaction is carried out in the presence of a catalyst to produce mesitylene; wherein the polymethyl aromatic hydrocarbons are toluene, xylene, and / or trimethylbenzene.

[0038] The methanol alkylation reaction is carried out using a multi-stage reaction and multi-stage methanol replenishment method. This method is as follows: When the polymethyl aromatic hydrocarbon is trimethylbenzene, methanol is directly reacted with trimethylbenzene to produce mesitylene; when the polymethyl aromatic hydrocarbon is xylene, methanol is divided into two parts. One part of the methanol is reacted with xylene to produce an intermediate material, and the other part of the methanol is mixed with the intermediate material. After cooling, the intermediate material is further reacted to produce mesitylene; when the polymethyl aromatic hydrocarbon is toluene, methanol is divided into three parts. The first part of the methanol is reacted with toluene to produce a first reactant. The second part of the methanol is mixed with the first reactant, and after cooling, the first reactant is further reacted to produce a second reactant. The third part of the methanol is mixed with the second reactant, and after cooling, the second reactant is further reacted to produce mesitylene.

[0039] In some embodiments, the polymethyl aromatic hydrocarbons are vaporized using pressurized hydrogen gas. The hydrogen gas is pressurized to 0.8–1.2 MPa.

[0040] In some embodiments, when a multi-stage reaction with multiple methanol replenishment is employed, the molar ratio of added methanol or replenished methanol to the initially added polymethyl aromatic hydrocarbon in each stage of the reaction is 1.00–1.10:1. Specifically, taking toluene as the polymethyl aromatic hydrocarbon as an example, the molar ratio of methanol to toluene in the first part is 1.00–1.10:1. When a second part of methanol is added after the reaction, the molar ratio of the second part of methanol to the initially added toluene is 1.00–1.10:1. When a third part of methanol is added after the reaction continues, the molar ratio of the third part of methanol to the initially added toluene is 1.00–1.10:1.

[0041] In some embodiments, when a multi-stage reaction with multi-stage methanol replenishment is used for a multi-stage reaction, the temperature of the material is controlled at 325–345°C before each stage of the reaction. Specifically, taking toluene as an example of polymethyl aromatic hydrocarbon, before the first part of methanol reacts with toluene, the temperature of the material is controlled at 325–340°C. After the reaction, the temperature of the material rises to 380–390°C, and a second part of methanol is added, causing the second part of methanol to vaporize while simultaneously lowering the temperature of the material to approximately 340°C (±5°C). Then the reaction continues, and after the reaction, the temperature of the material rises again to 380–390°C. A third part of methanol is added, causing the third part of methanol to vaporize while simultaneously lowering the temperature of the material to approximately 340°C (±5°C).

[0042] Another embodiment of the present invention provides a modified catalyst, the preparation method of which is as follows: a lanthanum salt and a divalent metal salt are added to ammonia water to obtain a mixed solution; a catalyst precursor is prepared by adsorbing the mixed solution using an HZSM5 support; the precursor is then dried and dehydrated once, and calcined once to obtain the catalyst; a cerium salt solution is adsorbed using the catalyst, and then dried and calcined twice to obtain the modified catalyst; wherein the divalent metal salt is a zinc salt or a magnesium salt, the molar ratio of lanthanum salt to divalent metal salt is 1:0.9-1.1; the loading of lanthanum in the catalyst is 0.9-1.1 wt%; and the loading of cerium is 0.4-0.6 wt%.

[0043] In some embodiments, the divalent metal salt is a zinc salt.

[0044] In some embodiments, the primary drying temperature is 100–150°C.

[0045] In some embodiments, the primary calcination temperature is 450–550°C.

[0046] In some embodiments, the secondary drying temperature is 70–80°C.

[0047] In some embodiments, the secondary calcination temperature is 500–600°C.

[0048] A third embodiment of the present invention provides the application of the above-mentioned modified catalyst in the process of deep conversion of polymethyl aromatic hydrocarbons to mesitylene.

[0049] That is, the process for the deep conversion of the above-mentioned polymethyl aromatic hydrocarbons to mesitylene uses the above-mentioned modified catalyst.

[0050] A fourth embodiment of the present invention provides a system for the deep conversion of polymethyl aromatic hydrocarbons into mesitylene, comprising:

[0051] Raw material tanks are used to supply polymethyl aromatics and methanol;

[0052] A vaporization tank is used to vaporize polymethyl aromatic hydrocarbons and methanol from a feed tank by pressurizing hydrogen, and then heat the vaporized feed.

[0053] A multi-stage reactor assembly is composed of a first reactor assembly, a second reactor assembly, and a third reactor assembly connected in series. Each reactor assembly includes at least one reactor. Each reactor is equipped with catalyst packing material, which is a catalyst for catalytic methanol alkylation reaction. Mixing devices are installed at the inlet of both the second reactor assembly and the inlet of the third reactor assembly.

[0054] Methanol storage tanks are used to replenish methanol to the second and third reactor components.

[0055] Condensation equipment is used to cool the products of the third reactor assembly;

[0056] When the polymethyl aromatic hydrocarbon is toluene, the gasified feedstock from the gasification tank enters the first reactor assembly for methanol alkylation reaction. The material from the first reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the second reactor assembly and then enters the second reactor assembly to continue the methanol alkylation reaction. The material from the second reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the third reactor assembly and then enters the third reactor assembly to continue the methanol alkylation reaction.

[0057] When the polymethyl aromatic hydrocarbon is xylene, the gasified feedstock from the gasification tank enters the second reactor assembly for methanol alkylation reaction. The material from the second reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the third reactor assembly and then enters the third reactor assembly to continue the methanol alkylation reaction.

[0058] When the polymethyl aromatic hydrocarbon is trimethylbenzene, the gasified feedstock from the gasification tank enters the third reactor assembly for methanol alkylation reaction.

[0059] In some embodiments, the hybrid device is a Johnson Network.

[0060] In some embodiments, the reactor in each reactor assembly is a fixed-bed reactor.

[0061] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0062] The following examples use a system for the deep conversion of polymethyl aromatic hydrocarbons to mesitylene, such as... Figure 1 As shown, it includes a raw material tank 1, a raw material transfer pump 2 (E-10), a gasification tank 3, a first reactor 4, a second reactor 5, a third reactor 6, a methanol storage tank 7, a first methanol transfer pump 8 (E-11), a second methanol transfer pump 9 (E-12), a condenser tank 10, and a product tank 11.

[0063] Raw material tank 1, raw material transfer pump 2 (E-10), gasification tank 3, first reactor 4, second reactor 5, third reactor 6, condenser 10 and product tank 11 are connected in sequence according to the material flow direction.

[0064] Reactor 4 (first reactor), reactor 5 (second reactor), and reactor 6 (third reactor) are all fixed-bed reactors.

[0065] The gas inlet of vaporizer 3 is connected to a hydrogen pipeline.

[0066] Johnson screens are installed at the material inlets of both the second reactor 5 and the third reactor 6. The outlet of the methanol storage tank 7 is connected to the Johnson screen inlet of the material inlet of the second reactor 5 via the first methanol transfer pump 8. The outlet of the methanol storage tank 7 is connected to the Johnson screen inlet of the material inlet of the third reactor 6 via the second methanol transfer pump 9. The Johnson screen space is 1.2 to 1.5 times larger than that of the fixed-bed reactor, which fully ensures the retention time for mixing the two streams, achieving complete gasification and uniform mixing.

[0067] The material outlet of the gasification tank 3 is also connected to the material inlet of the second reactor 5 and the material inlet of the third reactor 6.

[0068] A valve V1 is installed on the inlet pipeline of the first reactor 4, a valve V2 is installed on the outlet pipeline of the first reactor 4, a valve V3 is installed on the connecting pipeline between the material outlet of the gasification tank 3 and the material inlet of the second reactor 5, a valve V4 is installed on the connecting pipeline between the material outlet of the gasification tank 3 and the material inlet of the third reactor 6, and a valve V5 is installed on the material outlet pipeline of the second reactor 5.

[0069] Example 1

[0070] The reaction feedstocks are toluene and methanol. The feedstock tank contains toluene and methanol in a molar ratio of 1:1. The catalyst packed in each fixed-bed reactor is catalyst A2.

[0071] The catalyst A2 was prepared by adding 12.47g La(NO3)3·9H2O and 8.57g Zn(NO3)2·6H2O to 200mL of 0.1mol / L ammonia solution, and then impregnating it with 400g of calcined HZSM5 support by an equal volume method to prepare the catalyst precursor. The precursor was dried at 150℃ for 2h and calcined at 550℃ for 2h to obtain catalyst A2.

[0072] The process is as follows:

[0073] By controlling the reaction space velocity to 1 hour -1Close valves V3 and V4, and open valves V1, V2, and V5. Pressurize the system to 1 MPa via the hydrogen pipeline and back pressure valve. Pump E-10 pumps the pressurized reactants to the vaporizer, where they are vaporized and heated to 330°C. The vaporized reactants then enter reactor 1 for the first stage reaction, where the temperature rises to 380-390°C. Pump E-11 is then opened to pump pure methanol (an equimolar amount of initial toluene) to the inlet of reactor 2, where it mixes with the reaction stream from reactor 1. After vaporization and cooling to 340°C, the methanol enters reactor 2 for the second stage reaction. After this reaction, the reaction stream reaches approximately 380°C. Pump E-12 is then opened to pump pure methanol (an equimolar amount of initial toluene) to the inlet of reactor 3, where it mixes with the reaction stream from reactor 2. After vaporization and cooling, the methanol enters reactor 3 for the third stage reaction. The reaction stream is then cooled by water and enters a product receiving tank for oil-water separation. The oil phase is then subjected to gas phase analysis.

[0074] Example 2

[0075] The reaction feedstocks are toluene and methanol. The feedstock tank contains toluene and methanol in a molar ratio of 1:1. The catalyst packed in each fixed-bed reactor is modified catalyst A2'.

[0076] The modified catalyst A2' was prepared as follows: 12.47 g La(NO3)3·9H2O and 8.57 g Zn(NO3)2·6H2O were added to 200 mL of 0.1 mol / L ammonia solution, and a catalyst precursor was prepared by impregnation with 400 g of calcined HZSM5 support using an equal-volume method. The precursor was dried at 150 °C for 2 h and calcined at 550 °C for 2 h to obtain catalyst A2. The saturated absorbance of catalyst A2 was then measured to be 87 g H2O / 100 g A2. 100 g of A2 was added to a cerium nitrate aqueous solution (1.55 g cerium nitrate dissolved in 87 g H2O), impregnated for 2 h, dried at 80 °C, and calcined at 550 °C for 2 h to obtain modified catalyst A2'.

[0077] The process is as follows:

[0078] The reaction space velocity was controlled at 1 hour. -1Close valves V3 and V4, and open valves V1, V2, and V5. Pressurize the system to 1 MPa via the hydrogen pipeline and back pressure valve. Pump E-10 pumps the pressurized reactants to the vaporizer, where they are vaporized and heated to 330°C. The vaporized reactants then enter reactor 1 for the first stage reaction, where the temperature rises to 380-390°C. Pump E-11 is then opened to pump pure methanol (an equimolar amount of initial toluene) to the inlet of reactor 2, where it mixes with the reaction stream from reactor 1. After vaporization and cooling to 340°C, the methanol enters reactor 2 for the second stage reaction. After this reaction, the reaction stream reaches approximately 380°C. Pump E-12 is then opened to pump pure methanol (an equimolar amount of initial toluene) to the inlet of reactor 3, where it mixes with the reaction stream from reactor 2. After vaporization and cooling, the methanol enters reactor 3 for the third stage reaction. The reaction stream is then cooled by water and enters a product receiving tank for oil-water separation. The oil phase is then subjected to gas phase analysis.

[0079] Example 3

[0080] The reaction feedstocks are toluene and methanol. The feedstock tank contains xylene and methanol in a molar ratio of 1:1. The catalyst packed in each fixed-bed reactor is modified catalyst A2'.

[0081] The modified catalyst A2' was prepared as follows: 12.47 g La(NO3)3·9H2O and 8.57 g Zn(NO3)2·6H2O were added to 200 mL of 0.1 mol / L ammonia solution, and a catalyst precursor was prepared by impregnation with 400 g of calcined HZSM5 support using an equal-volume method. The precursor was dried at 150 °C for 2 h and calcined at 550 °C for 2 h to obtain catalyst A2. The saturated absorbance of catalyst A2 was then measured to be 87 g H2O / 100 g A2. 100 g of A2 was added to a cerium nitrate aqueous solution (1.55 g cerium nitrate dissolved in 87 g H2O), impregnated for 2 h, dried at 80 °C, and calcined at 550 °C for 2 h to obtain modified catalyst A2'.

[0082] The process is as follows:

[0083] By controlling the reaction space velocity to 1 hour -1Close valves V1, V2, and V4, open valves V3 and V5, and close pump E-11. Pressurize the system to 1 MPa through the hydrogen pipeline and back pressure valve. Pump E-10 pressurizes the reaction raw materials and sends them to the vaporizer, where they are vaporized and heated to 330°C. The vaporized raw materials then enter reactor 2 for a first-stage reaction. After the reaction, the temperature of the reaction stream rises to about 380°C. At this point, pump E-12 is opened to pump pure methanol (an equimolar amount of initial o-xylene) to the inlet of reactor 3 and mixes it with the reaction stream from the outlet of reactor 2. After the liquid methanol is vaporized and cooled, the reaction stream enters reactor 3 for a second-stage reaction. The reaction stream is then cooled by water and enters the product receiving tank for oil-water separation. The oil phase is then subjected to gas phase analysis.

[0084] Example 4

[0085] The reaction feedstocks are toluene and methanol. The feedstock tank contains a 1:1 molar ratio of pseudotrimethylbenzene to methanol. The catalyst packed in each fixed-bed reactor is modified catalyst A2'.

[0086] The modified catalyst A2' was prepared as follows: 12.47 g La(NO3)3·9H2O and 8.57 g Zn(NO3)2·6H2O were added to 200 mL of 0.1 mol / L ammonia solution, and a catalyst precursor was prepared by impregnation with 400 g of calcined HZSM5 support using an equal-volume method. The precursor was dried at 150 °C for 2 h and calcined at 550 °C for 2 h to obtain catalyst A2. The saturated absorbance of catalyst A2 was then measured to be 87 g H2O / 100 g A2. 100 g of A2 was added to a cerium nitrate aqueous solution (1.55 g cerium nitrate dissolved in 87 g H2O), impregnated for 2 h, dried at 80 °C, and calcined at 550 °C for 2 h to obtain modified catalyst A2'.

[0087] The process is as follows:

[0088] By controlling the reaction space velocity to 1 hour -1 Close valves V1, V2, V3, and V5, open valve V4, and close pumps E-11 and E-12. Pressurize the system to 1 MPa through the hydrogen pipeline and back pressure valve. Pump E-10 pressurizes the reaction raw materials and sends them to the vaporizer, where they are vaporized and heated to 330°C. The vaporized raw materials then enter reactor 3 for a first-stage reaction. After being cooled by water, the reaction stream enters the product receiving tank for oil-water separation. The oil phase is then subjected to gas phase analysis.

[0089] The catalytic effects of Examples 1 to 4 are shown in Table 1.

[0090] Table 1 Catalytic effects of different raw materials and processes

[0091]

[0092] Table 1 shows that the multi-stage reaction and multi-stage methanol replenishment method using hydrogenation in this invention has a high feed conversion rate and mesitylene selectivity.

[0093] A comparison between Example 1 and Example 2 shows that, based on the process of the present invention, the modified catalyst results in higher conversion rate of raw materials and higher selectivity for mesitylene.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for the deep conversion of polymethyl aromatic hydrocarbons to mesitylene, characterized in that, in Under hydrogen-containing atmosphere conditions, a methanol alkylation reaction is carried out using polymethyl aromatic hydrocarbons and methanol as raw materials in the presence of a catalyst to produce mesitylene; the polymethyl aromatic hydrocarbons are xylene and / or trimethylene. Alternatively, toluene and methanol can be used as raw materials to produce mesitylene through methanol alkylation reaction under the action of a catalyst; The methanol alkylation reaction is carried out using a multi-stage reaction and multi-stage methanol replenishment method. This method is as follows: when the polymethyl aromatic hydrocarbon is trimethylbenzene, methanol is directly reacted with trimethylbenzene to produce mesitylene; when the polymethyl aromatic hydrocarbon is xylene, methanol is divided into two parts. One part of the methanol is reacted with xylene to produce an intermediate material, and the other part of the methanol is mixed with the intermediate material. After cooling, the intermediate material is further reacted to produce mesitylene; when toluene is used, methanol is divided into three parts. The first part of the methanol is reacted with toluene to produce a first reactant. The second part of the methanol is mixed with the first reactant, and after cooling, the first reactant is further reacted to produce a second reactant. The third part of the methanol is mixed with the second reactant, and after cooling, the second reactant is further reacted to produce mesitylene. When using a multi-stage reaction and multi-stage methanol replenishment method for multi-stage reaction, the temperature of the material should be controlled at 325~345 ℃ before each stage of reaction; The catalyst is a modified catalyst, and its preparation method is as follows: lanthanum salt and divalent metal salt are added to ammonia water to obtain a mixed solution. The mixed solution is adsorbed onto an HZSM5 support to prepare a catalyst precursor. After drying to remove water and calcining once, the catalyst is obtained. A cerium salt solution is adsorbed onto the catalyst, followed by a second drying and a second calcination to obtain the modified catalyst. The divalent metal salt is either zinc or magnesium salt, and the molar ratio of lanthanum salt to divalent metal salt is 1:0.9~1.

1. The loading of lanthanum in the catalyst is 0.9~1.1 wt%, and the loading of cerium is 0.4~0.6 wt%.

2. The process for deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 1, characterized in that, Polymethyl aromatic hydrocarbons were vaporized using pressurized hydrogen gas.

3. The process for deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 2, characterized in that, Hydrogen gas was used to pressurize the pressure to 0.8~1.2 MPa.

4. The process for deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 1, characterized in that, When using a multi-stage reaction and multi-stage methanol replenishment method for multi-stage reaction, the molar ratio of added methanol or replenished methanol to the initially added polymethyl aromatic hydrocarbon in each stage of the reaction is 1.00~1.10:

1.

5. The process for deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 1, characterized in that, The divalent metal salt is a zinc salt; Alternatively, the drying temperature can be 100~150 ℃. Alternatively, the firing temperature can be 450~550 ℃.

6. The process for deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 1, characterized in that, The secondary drying temperature is 70~80℃; Alternatively, the secondary roasting temperature is 500~600 ℃.

7. A process for the deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 1, characterized in that, A system employing the deep conversion of polymethyl aromatic hydrocarbons into mesitylene includes: Raw material tanks, used to supply polymethyl aromatics and methanol, or, used to supply toluene and methanol; A vaporization tank is used to vaporize polymethyl aromatic hydrocarbons and methanol from a feed tank by pressurizing hydrogen and to heat the vaporized feed; or, a vaporization tank is used to vaporize toluene and methanol from a feed tank by pressurizing hydrogen and to heat the vaporized feed. A multi-stage reactor assembly is composed of a first reactor assembly, a second reactor assembly, and a third reactor assembly connected in series. Each reactor assembly includes at least one reactor. Each reactor is equipped with catalyst packing material, which is a catalyst for catalytic methanol alkylation reaction. Mixing devices are installed at the inlet of both the second reactor assembly and the inlet of the third reactor assembly. Methanol storage tanks are used to replenish methanol to the second and third reactor components. Condensation equipment is used to cool the products of the third reactor assembly; When toluene is used, the gasified feedstock from the gasification tank enters the first reactor assembly for methanol alkylation reaction. The material from the first reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the second reactor assembly and then enters the second reactor assembly for further methanol alkylation reaction. The material from the second reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the third reactor assembly and then enters the third reactor assembly for further methanol alkylation reaction. When the polymethyl aromatic hydrocarbon is xylene, the gasified feedstock from the gasification tank enters the second reactor assembly for methanol alkylation reaction. The material from the second reactor assembly is mixed with methanol from the methanol storage tank in the mixing equipment at the inlet of the third reactor assembly and then enters the third reactor assembly to continue the methanol alkylation reaction. When the polymethyl aromatic hydrocarbon is trimethylbenzene, the gasified feedstock from the gasification tank enters the third reactor assembly for methanol alkylation reaction.

8. The process for deep conversion of polymethyl aromatic hydrocarbons to mesitylene as described in claim 7, characterized in that, The hybrid device is a Johnson Network; Alternatively, the reactors in each reactor assembly may be fixed-bed reactors.

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