Process, apparatus and catalyst for producing mesitylene and method of making

Abstract

This invention relates to the field of producing mesitylene from reformed C9 heavy aromatics, specifically a method, apparatus, catalyst, and preparation method for producing mesitylene. The method for producing mesitylene includes removing C9 heavy aromatics from C9 heavy aromatics via a de-heavy tower. 10 The above-mentioned heavy components convert the separated C9 mixed aromatics into dealkylation isomerization products. These products undergo gas-liquid separation to obtain liquid hydrocarbon products, which are then separated in a distillation column. Light components are produced at the top of the distillation column, mesitylene is produced from the side stream, and the bottom product is returned to the heavy hydrocarbon removal column, achieving material recycling. This invention uses reformed C9 heavy aromatics as raw material, developing a highly efficient catalyst and reaction separation process to solve the interference of methyl ethyl benzene in existing processes, retain mesitylene, reduce by-product generation, increase mesitylene yield, improve catalyst stability, extend operating cycle, reduce mesitylene production costs, and enhance the utilization value of C9 mixed aromatics.

Description

Technical Field

[0001] This invention relates to the field of producing mesitylene from reformed C9 aromatics, and provides a method, apparatus, catalyst, and preparation method for producing mesitylene. Background Technology

[0002] There are nine isomers of C9 aromatic hydrocarbons. After separation, the industrially available products include mesitylene, pseudotrimethylbenzene, m-methylethylbenzene, and p-methylethylbenzene, with mesitylene having the highest added value. Mesitylene (1,3,5-trimethylbenzene) is an important chemical raw material. Based on it, various dye intermediates and important fine chemical products can be produced, such as trimellitic anhydride, trimellitidine, trimellitic acid, and terpene alcohols.

[0003] The industrial production methods for mesitylene mainly include synthesis and separation and purification. Synthesis uses pseudotrimethylbenzene as a raw material (pseudotrimethylbenzene is often separated from reformed or cracked C9 aromatics) and isomerizes it to produce mesitylene. Separation and purification uses mixed C9 aromatics as byproducts from catalytic reforming units, paraxylene units, etc., and directly separates and extracts mesitylene from them. From existing technologies, the difficulty in producing and separating mesitylene lies in the presence of many substances in the raw materials, such as methylbenzene, ethylbenzene, propylbenzene, and benzo[a]butane, as well as some C9 and higher aromatics with boiling points very close to mesitylene. The composition and properties of a certain reformed C9 aromatic are as follows: Figure 1 .

[0004] from Figure 1 It can be seen that the boiling points of mesitylene and o-ethylbenzene differ by only 0.3℃, making industrial distillation impossible. Moreover, the boiling points of mesitylene are very close to those of p-ethylbenzene and m-ethylbenzene, making separation very difficult. The industrial production of mesitylene is also mainly affected by the production of ethylbenzene. Therefore, simple separation and purification is very difficult and costly. Alkylation, isomerization, and other methods can be used to take advantage of the structural differences between ethylbenzene and mesitylene and achieve the separation of components through chemical reactions.

[0005] Patent application CN103772121A discloses a method for cracking C9 and higher heavy aromatic components to produce more trimethylbenzene, which involves cracking C9 and higher heavy aromatic components to produce more trimethylbenzene. + The heavy aromatics were enriched with tricresyl in C9 aromatics through hydrogenation and dealkylation and alkyl transfer with light aromatics. Light hydrocarbons, BTX, mesitylene and pseudotrimethylbenzene fractions, C9 aromatics and thiomethylbenzene fractions were separated. The cracking of non-aromatic and heavy aromatics reduced the difficulty of separation, but the product mesitylene was not obtained. The yields of light hydrocarbons and BTX were relatively high, while the yield of tricresyl was low. The value of the product needs to be further improved.

[0006] Patent application 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 initial 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 MEBenz with a purity greater than 98%. However, this method converts MEBenz while simultaneously converting a large amount of pseudotrimethylbenzene into alkyl aromatics with more carbon atoms, resulting in a loss of MEBenz. Furthermore, this method causes severe equipment corrosion and is difficult to apply industrially.

[0007] Patent application CN1313269A discloses a method for separating heavy aromatics from a refinery reforming unit into a high-purity pseudotrimethylbenzene fraction via continuous distillation using two packed towers, but this method does not yield high-purity mesitylene. Patent application CN1974500A discloses a three-tower serial process for separating reformed heavy aromatics, which can produce high-purity pseudotrimethylbenzene and co-produce enriched mesitylene with a purity of over 35%, although the mesitylene purity is relatively low.

[0008] Wang Ming of Tianjin University (Wang Ming. Research on the Isomerization of Pseudotrimethylbenzene to Produce Mestrimethylbenzene [D]. Tianjin University, 2014.) conducted research on the isomerization production of mestrimethylbenzene using high-purity pseudotrimethylbenzene as raw material. Using mordenite as a support, Ni / Mo or Ni / La metal components were loaded to inhibit carbon deposition, resulting in good activity and stability, extending the catalyst's lifespan. The catalyst performance remained stable within 200 hours. Qi Xiaolan et al. of the Shanghai Petrochemical Research Institute of Sinopec treated mordenite with NaOH to obtain mesoporous mordenite with a composite pore structure. Its application in the conversion of heavy aromatics can improve the C9 and C2 ratios. 10 Aromatic hydrocarbon conversion capability.

[0009] Cheng Xiaojing from Dalian University of Technology (Cheng Xiaojing. Reaction of C9 aromatics on molecular sieve catalysts with different structures [J]. Petrochemical Technology, 2013, 42(1):24-29.) studied the reaction law of C9 aromatics on ZSM-5, HMOR, Hβ and other zeolite molecular sieves. In the reaction of A9, HZSM-5 showed strong cracking ability and could inhibit the disproportionation reaction of A9. On Hβ zeolite and HMOR zeolite, alkyl transfer reaction was easy to occur. Her study on A9 on nano ZSM-5 molecular sieve showed that the content of trimethylbenzene decreased from 65.13% to 22.73%, and the yield of BTX reached 71.53%. The yield of trimethylbenzene was low and the content of ethylbenzene in the product was relatively high, which was not conducive to the separation from trimethylbenzene.

[0010] Tang Weidong et al. of Jinling Petrochemical Company (Tang Weidong. Improvement of isomerization process for producing mesitylene [J]. Petroleum Refining and Chemical Industry, 2006, 35(3): 22-25.) reported on the technology and improvement of isomerization process for producing mesitylene. In response to the shortcomings of the original isomerization unit, such as high raw material price, low yield of mesitylene, low purity and large fluctuation, the process was improved by adding debinding and refining towers and circulating blending of mixed mesitylene. After the improvement, the purity of mesitylene increased to 98.9%, the yield was also significantly improved, and the stability of unit operation was also improved.

[0011] Patent application 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. While this method is simple and the products are easily separated, the main product is BTX, the mesitylene yield is low, and there is a high proportion of light hydrocarbon components as byproducts. The use of a precious metal catalyst increases production costs, and the yield of mesitylene and the utilization value of heavy aromatic resources need further improvement.

[0012] Therefore, the existing technology for separating and producing mesitylene from C9 mixed aromatics is lengthy and complex, with low mesitylene yield, requiring improvements in catalyst stability and operating cycle, and resulting in high production costs. If C9 aromatic isomers such as ethylbenzene in the C9 mixed aromatics are removed through reaction, while retaining mesitylene and reducing the generation of light hydrocarbons and BTX, and if a highly efficient catalyst and reaction separation process are developed, the separation difficulty of mesitylene can be significantly reduced, the production process shortened, the yield of mesitylene increased, and the production cost of mesitylene lowered, thereby enhancing the utilization value of C9 mixed aromatics. Summary of the Invention

[0013] This invention provides a method, apparatus, catalyst, and preparation method for producing mesitylene, overcoming the shortcomings of the prior art. It can effectively solve the problem of interference from ethylbenzene (including m-ethylbenzene, p-ethylbenzene, and o-ethylbenzene) in the existing mesitylene production process, retain trimethylbenzene (including mesitylene, pseudotrimethylbenzene, and teremethylbenzene), reduce the generation of by-products, and improve the yield of mesitylene.

[0014] One of the technical solutions of the present invention is achieved through the following measures: a method for producing mesitylene, comprising the following steps: (1) C9 heavy aromatics enter the de-heavy hydrocarbon tower for separation. C9 mixed aromatics are separated at the top of the de-heavy hydrocarbon tower, and C9 heavy aromatics are separated at the bottom of the de-heavy hydrocarbon tower. 10 The above-mentioned recombinant components, C separated from the bottom of the decomposition tower 10 The above-mentioned recombinant components can be reused after being discharged from the de-recombination tower; (2) The separated C9 mixed aromatics are mixed with fresh hydrogen and then introduced into the reactor. Under the action of a catalyst, a dealkylation isomerization reaction occurs at a reaction temperature of 300℃ to 420℃, a pressure of 0.7MPa to 3.0MPa, and a mass hourly space velocity of 1h. -1 up to 4 hours -1 Under the condition of a hydrogen-to-oil molar ratio of (2 to 6):1, C9 mixed aromatics are converted into dealkylation isomerization products; (3) The dealkylation isomerization product is passed into a separation tank for gas-liquid separation to obtain hydrogen-rich gas and liquid hydrocarbon products. The liquid hydrocarbon products at the bottom of the separation tank are then separated in a distillation column. The hydrogen-rich gas contains a small amount of methane and ethane, which are returned to the reactor for recycling or can be discharged as hydrogen-rich tail gas. (4) The liquid hydrocarbon products at the bottom of the separator enter the distillation column for separation. The top of the distillation column produces light components with boiling points lower than mesitylene, namely BTX and a small amount of LPG (light hydrocarbons). The side stream of the distillation column produces mesitylene. The bottom product of the distillation column is C9 and above components other than mesitylene. The BTX and a small amount of LPG produced at the top of the distillation column are discharged from the distillation column. The purity of the mesitylene produced by the side stream of the distillation column is >98.5%, and it is discharged from the unit as a product. (5) The main products at the bottom of the distillation column are pseudotrimethylbenzene, thiomethylbenzene and a small amount of C. 10 The above components are returned to the de-heavy column as the bottom product of the distillation column, where they are separated together with the C9 heavy aromatics, thus achieving material recycling.

[0015] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: In step (1) above, the C9 heavy aromatics are C9 heavy aromatics produced by the reforming unit. The aromatic content in the C9 heavy aromatics is >98%, the content of aromatics with nine carbons is not less than 70%, and the weight content of trimethylbenzene in the C9 heavy aromatics is ≥40%.

[0016] Reforming units are an important component of oil refineries. In the presence of a catalyst, reforming is the process of reconstructing alkanes and cycloalkanes in feedstocks into aromatics, transforming chain hydrocarbons into benzene rings. It is generally referred to as "reforming".

[0017] In step (1) above, the temperature at the top of the deweight removal tower is controlled at 178°C to 180°C, and C... 10 The above components were separated; the separated C 10The above components can be used as high-octane gasoline blending components or for other purposes; In step (2) above, the reactor is a fixed-bed reactor. In the dealkylation isomerization products obtained, the amount of LPG accounts for less than 1% of the C9 heavy aromatics, the amount of BTX accounts for less than 25% of the liquid hydrocarbon products, the amount of trimethylbenzene (including mesitylene, pseudotrimethylbenzene, and terylene) accounts for more than or equal to 70% of the liquid hydrocarbon products, the dealkylation isomerization products do not contain propylbenzene, and the amount of ethylbenzene accounts for less than 0.2% of the liquid hydrocarbon products.

[0018] BTX is a mixture of benzene, toluene, and xylene (Benzene-Toluene-Xylene), also known as light aromatic hydrocarbons.

[0019] The main components of LPG include propane and butane, and may also contain small amounts of propylene and butene.

[0020] In step (3) above, the separated hydrogen-rich gas contains a small amount of methane and ethane. As the dealkylation isomerization reaction proceeds, the purity of hydrogen in the hydrogen-rich gas will gradually decrease. When the purity of hydrogen in the hydrogen-rich gas is ≥70%, it is returned to the reactor for recycling. When the purity of hydrogen in the hydrogen-rich gas is <70%, it is discharged as hydrogen-rich tail gas for subsequent recycling.

[0021] In step (3), the weight ratio of the mesitylene product produced by the distillation column side stream to the weight of mesitylene in C9 heavy aromatics is greater than 1; the yield of mesitylene is ≥30% based on C9 heavy aromatics.

[0022] In step (4) above, the temperature at the top of the distillation column is controlled at 160°C to 162°C so that components lighter than mesitylene are discharged from the top of the distillation column; the temperature of the side stream of the distillation column is controlled at 164°C to 166°C so that mesitylene is extracted from the side stream of the distillation column as the mesitylene product.

[0023] The second technical solution of the present invention is achieved through the following measures: an apparatus for operating the method for producing mesitylene described in the first technical solution, comprising a de-heavy hydrocarbon tower, a reactor, a separation tank, and a distillation tower, wherein a C9 heavy aromatic hydrocarbon feedstock end is provided on the side of the de-heavy hydrocarbon tower, and a C9 heavy aromatic hydrocarbon feedstock is provided at the bottom of the de-heavy hydrocarbon tower. 10At the discharge end of the above components, a fresh hydrogen inlet pipeline is installed at the top of the reactor. A C9 mixed aromatics pipeline is connected between the top of the de-heavy tower and the fresh hydrogen inlet pipeline. A reaction product pipeline is connected between the bottom of the reactor and the middle of the separator. A hydrogen-rich gas circulation pipeline is connected between the top of the separator and the fresh hydrogen inlet pipeline. A hydrogen-rich tail gas pipeline is connected to the hydrogen-rich gas circulation pipeline. A hydrocarbon product feed end is installed on the side of the distillation column. A liquid hydrocarbon product pipeline is connected between the bottom of the separator and the hydrocarbon product feed end of the distillation column. A light component discharge end is installed at the top of the distillation column. A distillation column side line is connected above the hydrocarbon product feed end. A material circulation pipeline is connected between the bottom of the distillation column and the C9 heavy aromatics feed end.

[0024] (1) C9 heavy aromatics enter the de-heavy hydrocarbon separation tower via the C9 heavy aromatics feed end. The C9 mixed aromatics separated at the top of the de-heavy hydrocarbon separation tower enter the C9 mixed aromatics pipeline, and the C9 heavy aromatics separated at the bottom of the de-heavy hydrocarbon separation tower enter the C9 mixed aromatics pipeline. 10 The above recombinant components are processed through C 10 The above components are discharged from the discharge end; (2) The separated C9 mixed aromatics are mixed with fresh hydrogen and then introduced into the reactor. Under the action of a catalyst, a dealkylation isomerization reaction occurs at a reaction temperature of 300℃ to 420℃, a pressure of 0.7MPa to 3.0MPa, and a mass hourly space velocity of 1h. -1 up to 4 hours -1 Under the condition of a hydrogen-to-oil molar ratio of (2 to 6):1, C9 mixed aromatics are converted into dealkylation isomerization products; (3) The dealkylation isomerization product is fed into a separation tank for gas-liquid separation to obtain hydrogen-rich gas and liquid hydrocarbon products. The hydrogen-rich gas is returned to the reactor for recycling through the hydrogen-rich gas circulation pipeline. The liquid hydrocarbon products at the bottom of the separation tank are fed into the distillation column for separation through the liquid hydrocarbon product pipeline. When the hydrogen purity in the hydrogen-rich gas is <70%, it is discharged as hydrogen-rich tail gas through the hydrogen-rich tail gas pipeline. (4) The liquid hydrocarbon products at the bottom of the separator enter the distillation column for separation. The top of the distillation column produces light components with boiling points lower than mesitylene, namely BTX and a small amount of LPG (light hydrocarbons). The side stream of the distillation column produces mesitylene. The bottom product of the distillation column is returned to the de-heavy column through the material circulation pipeline and separated together with C9 heavy aromatics in the de-heavy column to achieve material circulation.

[0025] The reactor is a fixed-bed reactor.

[0026] The third technical solution of the present invention is achieved by the following measures: a catalyst applied to the method for producing mesitylene described in the first technical solution is a molecular sieve catalyst containing non-precious metal elements. The molecular sieve catalyst includes a catalyst support. The non-precious metal elements are selected from one or more of Group IIIB to VIB, Group VIII elements, and alkaline earth metals. The loading of each non-precious metal element does not exceed 6% of the mass of the catalyst support, and the total loading of non-precious metal elements does not exceed 12% of the mass of the catalyst support.

[0027] The following are further optimizations and / or improvements to the third technical solution of the above invention: Preferably, the aforementioned non-precious metal element is selected from one or more of Mo, Co, W, Ni, La, Mg, and P.

[0028] The catalyst support includes a hydrogen-type molecular sieve and a binder. The hydrogen-type molecular sieve is selected from one of hydrogen-type ZSM-5 molecular sieve, hydrogen-type Beta molecular sieve, and hydrogen-type mordenite molecular sieve. The binder is one or more of gamma alumina and boehmite. The weight of the hydrogen-type molecular sieve is 70% to 95% of the weight of the catalyst support.

[0029] The above catalyst was prepared by the following method: Hydrogen-type molecular sieve powder is subjected to steam modification treatment at a temperature of 450℃ to 600℃ for a duration of 0.5h to 4h, and the mass ratio of steam feed to hydrogen-type molecular sieve powder is 0.5 to 2:1. If the molecular sieve is a sodium-type molecular sieve, it can be converted into a hydrogen-type molecular sieve using an in-situ synthesis method commonly used in this field.

[0030] Hydrogen-form molecular sieve powder, modified by steam treatment, is thoroughly mixed and kneaded with a binder (gamma alumina or boehmite powder) and a non-precious metal element salt solution. The mixture is then extruded into strips. The amount of hydrogen-form molecular sieve powder added accounts for 70% to 95% of the catalyst support mass. The non-precious metal element in the non-precious metal element salt solution is one or more elements selected from Mo, Co, W, Ni, La, Mg, and P. The amount of each non-precious metal element added does not exceed 6% of the catalyst support mass, and the total amount of elements added does not exceed 12% of the catalyst support mass. After extrusion, the strips are dried in an oven at 60°C to 120°C for 1 to 6 hours, and then calcined in a muffle furnace at 450°C to 560°C for 2 to 10 hours to obtain the catalyst.

[0031] The fourth technical solution of the present invention is achieved through the following measures: a method for preparing a catalyst, comprising: Hydrogen-type molecular sieve powder was subjected to steam modification treatment at a temperature of 450℃ to 600℃ for a duration of 0.5h to 4h, with the steam feed rate to the mass ratio of hydrogen-type molecular sieve powder being (0.5 to 2):1. If the molecular sieve is a sodium-type molecular sieve, it can be converted into a hydrogen-type molecule using an in-situ synthesis method commonly used in this field.

[0032] Hydrogen-form molecular sieve powder, modified by steam treatment, is thoroughly mixed and kneaded with a binder (gamma alumina or boehmite powder) and a non-precious metal element salt solution. The mixture is then extruded into strips. The amount of hydrogen-form molecular sieve powder added accounts for 70% to 95% of the catalyst support mass. The non-precious metal element in the non-precious metal element salt solution is one or more elements selected from Mo, Co, W, Ni, La, Mg, and P. The amount of each non-precious metal element added does not exceed 6% of the catalyst support mass, and the total amount of elements added does not exceed 12% of the catalyst support mass. After extrusion, the strips are dried in an oven at 60°C to 120°C for 1 to 6 hours, and then calcined in a muffle furnace at 450°C to 560°C for 2 to 10 hours to obtain the catalyst.

[0033] Compared with the prior art, the present invention has the following advantages: (1) Using C9 heavy aromatics as raw materials, the content of methyl ethylbenzene is greatly reduced by dealkylation isomerization reaction, while retaining as much methyl ethylbenzene as possible, eliminating the interference of methyl ethylbenzene on the separation of methyl ethylbenzene, and greatly reducing the process and cost of traditional C9 heavy aromatic separation. (2) While dealkylating, a reaction favorable to the isomerization of mesitylene is achieved. The components recycled back to the reactor are mainly pseudotrimethylbenzene and terylene. Furthermore, the present invention utilizes the same reactor and catalyst to achieve the isomerization of trimethylbenzene, which greatly improves the yield of mesitylene. (3) The dealkylation isomerization reaction conditions are mild, with few side reactions. The dry gas + LPG content in the dealkylation isomerization reaction products is very low, the BTX content is low, the loss of trimethylbenzene is small, and the distribution of dealkylation reaction products is excellent. (4) The catalyst for the dealkylation isomerization reaction does not contain any precious metal elements, and the catalyst preparation method is simple and inexpensive; (5) This invention improves the stability of the catalyst by modifying and optimizing the catalyst and process flow, and at the same time, before the dealkylation isomerization reaction, C 10 Recombinant components are separated, reducing C 10 The influence of heavy components on the dealkylation isomerization reaction reduces the carbon deposition rate and greatly extends the catalyst life and operating cycle of the dealkylation isomerization reaction. Attached Figure Description

[0034] Appendix Figure 1The composition and physical properties of a reformed C9 aromatic hydrocarbon.

[0035] Appendix Figure 2 This is a schematic diagram of the process flow for producing mesitylene from C9 heavy aromatics according to the present invention.

[0036] The codes in the attached diagram are as follows: 1 for heavy hydrocarbon removal tower, 2 for fixed-bed reactor, 3 for separation tank, 4 for distillation column, 5 for C9 heavy aromatics feedstock, 6 for C9 mixed aromatics pipeline, and 7 for C... 10 At the above component discharge ends, 8 is the fresh hydrogen inlet pipeline, 9 is the reaction product pipeline, 10 is the hydrogen-rich gas circulation pipeline, 11 is the hydrogen-rich tail gas pipeline, 12 is the liquid hydrocarbon product pipeline, 13 is the light component discharge end, 14 is the distillation column side line, and 15 is the material circulation pipeline. Detailed Implementation

[0037] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0038] In this invention, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 2 The layout is described using a diagrammatic method, such as the positional relationships of front, back, top, bottom, left, and right, which are based on the instructions attached. Figure 2 The orientation of the layout is determined by the direction of the map.

[0039] Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are 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, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, and is generally defined as 25°C.

[0040] like Figure 2 As shown, the apparatus for operating the method for producing mesitylene according to the present invention includes a de-heavy hydrocarbon tower 1, a reactor, a separation tank 3, and a distillation tower 4. A C9 heavy aromatic hydrocarbon feedstock 5 is provided on the side of the de-heavy hydrocarbon tower 1, and a C9 heavy aromatic hydrocarbon feedstock 5 is provided at the bottom of the de-heavy hydrocarbon tower 1. 10The above components are discharged at end 7. A fresh hydrogen inlet pipeline 8 is provided at the top of the reactor. A C9 mixed aromatic hydrocarbon pipeline 6 is connected between the top of the heavy hydrocarbon removal tower 1 and the fresh hydrogen inlet pipeline 8. A reaction product pipeline 9 is connected between the bottom of the reactor and the middle of the separator 3. A hydrogen-rich gas circulation pipeline 10 is connected between the top of the separator 3 and the fresh hydrogen inlet pipeline 8. A hydrogen-rich tail gas pipeline 11 is connected to the hydrogen-rich gas circulation pipeline 10. A hydrocarbon product feed end is provided on the side of the distillation tower 4. A liquid hydrocarbon product pipeline 12 is connected between the bottom of the separator 3 and the hydrocarbon product feed end of the distillation tower 4. A light component discharge end 13 is provided at the top of the distillation tower 4. A distillation tower side line 14 is connected to the side of the distillation tower 4 above the hydrocarbon product feed end. A material circulation pipeline 15 is connected between the bottom of the distillation tower 4 and the C9 heavy aromatic hydrocarbon feed end 5.

[0041] The operation process of this device is as follows: (1) C9 heavy aromatics enter the de-heavy hydrocarbon tower 1 for separation via the C9 heavy aromatics feed end 5. The C9 mixed aromatics separated at the top of the de-heavy hydrocarbon tower 1 enter the C9 mixed aromatics pipeline 6. The C9 heavy aromatics separated at the bottom of the de-heavy hydrocarbon tower 1... 10 The above recombinant components are processed through C 10 The above components are discharged from outlet 7; (2) The separated C9 mixed aromatics are mixed with fresh hydrogen and then introduced into the reactor. Under the action of a catalyst, a dealkylation isomerization reaction occurs at a reaction temperature of 300℃ to 420℃, a pressure of 0.7MPa to 3.0MPa, and a mass hourly space velocity of 1h. -1 up to 4 hours -1 Under conditions where the hydrogen-to-oil molar ratio is 2 to 6:1, C9 mixed aromatics are converted into dealkylation isomerization products; the reactor used is a fixed-bed reactor 2. (3) The dealkylation isomerization product is fed into the separator 3 for gas-liquid separation to obtain hydrogen-rich gas and liquid hydrocarbon products. The hydrogen-rich gas is returned to the reactor for recycling through the hydrogen-rich gas circulation pipeline 10. The liquid hydrocarbon products at the bottom of the separator 3 are fed into the distillation column 4 for separation through the liquid hydrocarbon product pipeline 12. When the hydrogen purity in the hydrogen-rich gas is <70%, it is discharged as hydrogen-rich tail gas through the hydrogen-rich tail gas pipeline 11. (4) The liquid hydrocarbon products at the bottom of the separator 3 enter the distillation column 4 for separation. The top of the distillation column 4 produces light components with boiling points lower than mesitylene, namely BTX and a small amount of LPG (light hydrocarbons). The side stream 14 of the distillation column produces mesitylene. The bottom product of the distillation column 4 is returned to the de-heavy column 1 through the material circulation pipeline 15, and is separated together with C9 heavy aromatics in the de-heavy column 1 to achieve material circulation.

[0042] In the following embodiments, guar gum powder is a conventional additive used in the art to help with extrusion molding, and it will be completely removed during subsequent calcination; when preparing the catalyst, the in-situ synthesis method is a commonly used method in the art to convert sodium molecular sieves into hydrogen molecules, and the washing, drying and calcination conditions are well known in the industry and will not affect the results due to differences in conditions.

[0043] Separator 3 is a high-pressure separator with a design pressure of over 3.0 MPa.

[0044] The present invention will be further described below with reference to embodiments: Example 1 In-situ synthesis of hydrogen-form ZSM-5 molecular sieve: 2.095g sodium aluminate, 24.74g tetrapropylammonium bromide, 6.13g sodium hydroxide, and 46.0g silica gel were added sequentially to 124.2g deionized water. After thorough stirring, the mixture was placed in a crystallization vessel and crystallized at 170℃ for 48h. After crystallization, the mixture was filtered, washed, dried, and calcined to obtain Na-form ZSM-5 molecular sieve. Then, it was placed in a 1mol / L ammonium chloride solution and stirred at 85℃ for 4h. After filtration, washing, drying, and calcination, hydrogen-form ZSM-5 molecular sieve was obtained. Steam modification treatment: 20g of hydrogen-type ZSM-5 molecular sieve was fixed in a reaction tube for steam treatment at a temperature of 500℃ for 1 hour. The water intake was 20g. After the steam treatment was completed, the water intake was stopped and the temperature was allowed to drop to room temperature. 20g of steam-modified hydrogen-form ZSM-5 molecular sieve and pseudoboehmite were mixed in a 4:1 ratio. 5g of pseudoboehmite was added, along with 0.5g of guar gum powder, which accounted for 2% of the total weight of the catalyst support (i.e., hydrogen-form ZSM-5 molecular sieve and pseudoboehmite). The mixture was thoroughly mixed to obtain a powder support. A non-precious metal element salt solution was prepared, in which the mass of Ni was 0.25g, the mass of molybdenum was 1g, and the mass of nitric acid was 0.5g. After being fully dissolved and homogenized, the solution was slowly added to the thoroughly mixed powder support. The mixture was then thoroughly ground and kneaded to ensure that the non-precious metal element salt solution was evenly distributed in the powder support. After kneading, the mixture was extruded into strips, allowed to stand for 4 hours, dried in an oven at 60℃ for 6 hours, and then calcined in a muffle furnace at 500℃ for 6 hours to obtain a catalyst with a loading of 1% Ni and 4% Mo. This catalyst is denoted as a. The above describes the preparation of catalyst a. The process flow for producing mesitylene from C9 heavy aromatics is as follows: 1) The C9 heavy aromatics produced by catalytic reforming are heated to a certain temperature and fed into the heavy hydrocarbon removal tower 1. C9 heavy aromatics are separated from the bottom of the heavy hydrocarbon removal tower 1. 10 The above recombined components are used to avoid C 10 The above-mentioned heavy components have an effect on the dealkylation isomerization reaction, and the separated C 10The above-mentioned heavy components can be used as high-octane gasoline blending components or for other applications; 2) The C9 mixed aromatics obtained from the top of the de-heavy tower 1 are mixed with fresh hydrogen, preheated, and then fed into a fixed-bed reactor 2 containing catalyst a for dealkylation and isomerization. The reaction temperature in the fixed-bed reactor 2 is controlled at 340℃, the 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. Catalyst a is packed in a fixed bed reactor 2 in the form of a fixed bed. The reaction products are dehydrogenated by a high-pressure separator. The separated hydrogen-rich gas (hydrogen purity ≥70%) is returned to the fixed bed reactor 2 for recycling. 3) The liquid hydrocarbon products at the bottom of the high-pressure separator enter the distillation column 4. The temperature of the top of the distillation column 4 is controlled at 160℃ to 162℃ (since it is difficult to control the temperature to a specific precise value, it is appropriate as long as it fluctuates within a certain range, the same below). Light components with boiling points lower than 162℃, such as LPG, BTX, m-toluene, and p-toluene, leave from the top of the column. The temperature of the side stream 14 of the distillation column is controlled at 164℃ to 166℃. Mestriene and a very small amount of o-toluene are extracted from the side stream and become mestriene product leaving the distillation column 4. 4) The bottom product of distillation column 4 (components with boiling points above 166℃) mainly consists of pseudotrimethylbenzene, methyltrimethylbenzene, and a small amount of C. 10 All components are recycled back to the de-heavy tower 1 for separation. The pseudotrimethylbenzene and terephthalene are recycled back to the fixed-bed reactor 2 to undergo isomerization to increase the production of mesitylene.

[0045] Through the above process, C9 heavy aromatics are ultimately converted into mesitylene, BTX, and C... 10 The composition of the products of the dealkylation isomerization reaction of the above heavy aromatic hydrocarbons is listed in Table 1.

[0046] Example 2 In-situ synthesis of hydrogen-form mordenite: 8.11g sodium aluminate, 2.10g tetraethylammonium bromide, 2.34g sodium chloride, and 60.0g silica gel were added sequentially to 306g deionized water. After thorough stirring, the mixture was placed in a crystallization kettle and crystallized at 140℃ for 24h, followed by crystallization at 180℃ for 48h. After crystallization, the mixture was filtered, washed, dried, and calcined to obtain Na-form mordenite molecular sieve. Ammonium exchange was then performed on the mordenite to obtain hydrogen-form mordenite molecular sieve. Steam modification treatment: 20g of hydrogen-type mordenite molecular sieve was fixed in a reaction tube for steam treatment. The steam treatment temperature was 460℃, the steam treatment time was 2h, and the water intake was 20g. After the steam treatment was completed, the water intake was stopped and the temperature was lowered to room temperature. 20g of steam-modified hydrogen-type mordenite molecular sieve and 5g of boehmite were added at a ratio of 4:1. 0.5g of guar gum powder, accounting for 2% of the total weight of the catalyst carrier, was added and thoroughly mixed to obtain a powder carrier. A non-precious metal salt solution was then prepared, in which the mass of Ni was 0.25g, the mass of W was 0.75g, and the mass of nitric acid was 0.3g. After being fully dissolved and homogenized, the solution was slowly added to the thoroughly mixed powder carrier. The mixture was then thoroughly ground and kneaded to ensure that the non-precious metal salt solution was evenly distributed in the powder carrier. After kneading, the mixture was extruded into strips, allowed to stand for 4 hours, dried in an oven at 60℃ for 6 hours, and then calcined in a muffle furnace at 500℃ for 6 hours to obtain a catalyst with a loading of 1% Ni and 3% W. This catalyst is denoted as b. The above describes the preparation of catalyst b. The process flow for producing mesitylene from C9 heavy aromatics differs from that in Example 1 in that the dealkylation isomerization reaction temperature is 320°C, the pressure is 2.0 MPa, and the feed space velocity is 1.5 h⁻¹. -1 The hydrogen-to-oil molar ratio is 4:1.

[0047] The composition of the dealkylation isomerization product of Example 2 is listed in Table 1.

[0048] Example 3 The catalyst differs from that in Example 1 in that the conditions for steam modification of the hydrogen-type molecular sieve are: treatment temperature 480℃, treatment time 0.5 hours, water inlet 15g, and the prepared non-precious metal salt solution contains 0.125g of Ni, 0.5g of Mo, 0.2g of nitric acid, and 0.2g of citric acid, resulting in a catalyst with a loading of 0.5% Ni and 2.0% Mo, denoted as c. The process flow for producing mesitylene from C9 heavy aromatics differs from that in Example 1 in that the dealkylation isomerization reaction temperature is 360°C, the pressure is 1.5 MPa, and the feed space velocity is 2.0 h⁻¹. -1 The hydrogen-to-oil molar ratio is 3:1. The composition of the dealkylation isomerization product of Example 3 is listed in Table 1.

[0049] Example 4 The catalyst differs from that in Example 2 in that the conditions for steam modification of the hydrogen-type molecular sieve are as follows: the treatment temperature is 520°C, the treatment time is 1 h, the influent water volume is 10 g, and the mass of Co in the prepared non-precious metal salt solution is 0.125 g, the mass of Mo is 0.75 g, and the mass of nitric acid is 0.4 g, resulting in a catalyst with a loading of 0.5% Co and 3.0% Mo, which is denoted as d. The process flow for producing mesitylene from C9 heavy aromatics in this embodiment differs from that in Example 1 in that the dealkylation isomerization reaction temperature is 360°C, the pressure is 2.0 MPa, and the feed space velocity is 2.0 h⁻¹. -1 The hydrogen-to-oil molar ratio is 4:1. The composition of the dealkylation isomerization product of Example 4 is listed in Table 1.

[0050] Example 5 The catalyst in this embodiment differs from that in Example 1 in that the conditions for the hydrogen-type molecular sieve steam modification treatment are: treatment temperature of 520°C, treatment time of 0.5 hours, water inlet of 25g, and the prepared non-precious metal salt solution containing 0.187g of Co, 0.75g of Mo, and 0.4g of nitric acid, resulting in a catalyst with a loading of 0.75% Co and 3.0% Mo, denoted as e. The process flow for producing mesitylene from C9 heavy aromatics in this embodiment differs from that in Example 1 in that the dealkylation isomerization reaction temperature is 380°C, the pressure is 1.0 MPa, and the feed space velocity is 2.0 h⁻¹. -1 The hydrogen-to-oil molar ratio is 5:1. The composition of the dealkylation isomerization product of Example 5 is listed in Table 1.

[0051] Example 6 The catalyst in this embodiment differs from that in Example 1 in that the conditions for steam treatment of the hydrogen-type molecular sieve are: treatment temperature of 500°C, treatment time of 1.5 hours, water inflow of 15g, and the prepared non-precious metal salt solution containing 0.5g Ni, 2.0g Mo, and 0.395g phosphoric acid, resulting in a catalyst with a loading of 2.0% Ni, 8.0% Mo, and 0.5% P, denoted as f. The process flow for producing mesitylene from C9 heavy aromatics in this embodiment differs from that in Example 1 in that the dealkylation isomerization reaction temperature is 340°C, the pressure is 2.5 MPa, and the feed space velocity is 1.5 h⁻¹. -1 The hydrogen-to-oil molar ratio is 4:1. The composition of the dealkylation isomerization reaction products in this embodiment is listed in Table 1.

[0052] After the catalysts a to f are reduced and activated, the dealkylation reaction is evaluated on an existing fixed-bed reaction evaluation device.

[0053] The C9 heavy aromatics feedstock used in Examples 1 to 6 was the same. The weight percentages of each component in the C9 heavy aromatics feedstock were as follows: xylene 8.55%, propylbenzene 1.73%, m-toluene 7.68%, p-toluene 3.65%, mesitylene 11.51%, o-toluene 2.91%, pseudotrimethylbenzene 37.94%, methyl thionylbenzene 6.88%, indene 0.72%, non-aromatic 0.77%, C 10 + Component 18.34%.

[0054] As shown in Table 1, after the dealkylation isomerization reaction of C9 heavy aromatics, the content of ethylbenzene decreased from 14.24% to 0.3%, with a removal rate >97%. This eliminated the interference of ethylbenzene on the separation of mesitylene. Meanwhile, the yield of mesitylene was above 30%. After dealkylation isomerization and separation, high-purity mesitylene, as well as BTX and a small amount of C9 heavy aromatics, can be obtained. 10 This method produces heavy aromatics with fewer byproducts, mild reaction conditions, and a simple process. The catalyst throughput is >10 kg feed / g.cat, and the single-trip operation cycle of the unit exceeds one year. It is evident that this method significantly improves the utilization value of C9 heavy aromatics resources and can be applied to the industrial production of mesitylene.

[0055] Compared with the prior art, the present invention has substantial features and significant progress in the following aspects: This invention produces mesitylene from C9 heavy aromatics via a dealkylation and isomerization process. Through catalyst and process optimization, interference from methyl ethyl benzene is eliminated, resulting in mesitylene with a methyl ethyl benzene content of <0.3%. The process is simple, with high mesitylene yield (greater than 30%), good catalyst stability, and long operating cycle, significantly reducing the production cost of mesitylene. Compared to traditional routes for producing BTX or blended gasoline, this significantly improves the efficiency of C9 hydrocarbon production. + The utilization value of (C9 and above) heavy aromatic hydrocarbon resources.

[0056] The above technical features constitute various 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.

[0057]

Claims

1. A method for producing mesitylene, characterized in that, Includes the following steps: (1) C9 heavy aromatics enter the de-heavy hydrocarbon tower for separation. C9 mixed aromatics are separated at the top of the de-heavy hydrocarbon tower, and C9 heavy aromatics are separated at the bottom of the de-heavy hydrocarbon tower. 10 The above recombined components; (2) The separated C9 mixed aromatics are mixed with fresh hydrogen and then introduced into the reactor. Under the action of a catalyst, a dealkylation isomerization reaction occurs at a reaction temperature of 300℃ to 420℃, a pressure of 0.7MPa to 3.0MPa, and a mass hourly space velocity of 1h. -1 up to 4 hours -1 Under the condition of a hydrogen-to-oil molar ratio of (2 to 6):1, C9 mixed aromatics are converted into dealkylation isomerization products; (3) The dealkylation isomerization product is passed into a separation tank for gas-liquid separation to obtain hydrogen-rich gas and liquid hydrocarbon products; (4) Liquid hydrocarbon products enter the distillation column for separation. The top of the distillation column produces light components with boiling points lower than mesitylene, the side stream of the distillation column produces mesitylene, and the bottom product of the distillation column is C9 and above components other than mesitylene. The purity of the mesitylene produced by the side stream of the distillation column is >98.5%. (5) The bottom product of the distillation column is returned to the de-heavy column and separated together with C9 heavy aromatics in the de-heavy column to realize material recycling.

2. The method for producing mesitylene according to claim 1, characterized in that, In step (1), the C9 heavy aromatics are C9 heavy aromatics produced by the reforming unit, the aromatic content in the C9 heavy aromatics is >98%, the content of aromatics with nine carbons is not less than 70%, and the weight content of trimethylbenzene in the C9 heavy aromatics is ≥40%; or / and, in step (1), the top temperature of the de-heavy tower is controlled at 178°C to 180°C.

3. The method for producing mesitylene according to claim 1 or 2, characterized in that, In step (2), the reactor is a fixed-bed reactor. In the dealkylation isomerization products obtained, the amount of LPG accounts for less than 1% of the C9 heavy aromatics, the amount of BTX accounts for less than 25% of the liquid hydrocarbon products, the amount of tricresyl accounts for more than or equal to 70% of the liquid hydrocarbon products, the dealkylation isomerization products do not contain propylbenzene, and the amount of ethylbenzene accounts for less than 0.2% of the liquid hydrocarbon products.

4. The method for producing mesitylene according to any one of claims 1 to 3, characterized in that, In step (3), when the hydrogen purity in the hydrogen-rich gas is ≥70%, it is returned to the reactor for recycling; when the hydrogen purity in the hydrogen-rich gas is <70%, it is discharged as hydrogen-rich tail gas.

5. The method for producing mesitylene according to any one of claims 1 to 4, characterized in that, In step (4), the temperature at the top of the distillation column is controlled at 160°C to 162°C, and the temperature of the side stream of the distillation column is controlled at 164°C to 166°C. Trimethylbenzene is then extracted from the side stream of the distillation column.

6. An apparatus for operating the method for producing mesitylene according to any one of claims 1 to 5, characterized in that, It includes a heavy hydrocarbon removal tower, a reactor, a separator, and a distillation tower. The heavy hydrocarbon removal tower has a C9 heavy aromatics feedstock inlet on one side, and a C9 heavy aromatics feedstock at the bottom. 10 At the discharge end of the above components, a fresh hydrogen inlet pipeline is installed at the top of the reactor. A C9 mixed aromatics pipeline is connected between the top of the de-heavy tower and the fresh hydrogen inlet pipeline. A reaction product pipeline is connected between the bottom of the reactor and the middle of the separator. A hydrogen-rich gas circulation pipeline is connected between the top of the separator and the fresh hydrogen inlet pipeline. A hydrogen-rich tail gas pipeline is connected to the hydrogen-rich gas circulation pipeline. A hydrocarbon product feed end is installed on the side of the distillation column. A liquid hydrocarbon product pipeline is connected between the bottom of the separator and the hydrocarbon product feed end of the distillation column. A light component discharge end is installed at the top of the distillation column. A distillation column side line is connected above the hydrocarbon product feed end. A material circulation pipeline is connected between the bottom of the distillation column and the C9 heavy aromatics feed end.

7. A catalyst used in the method for producing mesitylene according to any one of claims 1 to 5, characterized in that, It is a molecular sieve catalyst containing non-precious metal elements. The molecular sieve catalyst includes a catalyst support. The non-precious metal elements are selected from one or more of Group IIIB to VIB, Group VIII elements, and alkaline earth metals. The loading of each non-precious metal element does not exceed 6% of the mass of the catalyst support, and the total loading of non-precious metal elements does not exceed 12% of the mass of the catalyst support.

8. The catalyst according to claim 7, characterized in that, The non-precious metal element is selected from one or more of Mo, Co, W, Ni, La, Mg, and P; or / and the catalyst support includes a hydrogen-type molecular sieve and a binder. The hydrogen-type molecular sieve is selected from one of hydrogen-type ZSM-5 molecular sieve, hydrogen-type Beta molecular sieve, and hydrogen-type mordenite molecular sieve. The binder is one or more of gamma alumina and boehmite. The weight of the hydrogen-type molecular sieve is 70% to 95% of the weight of the catalyst support.

9. The catalyst according to claim 7 or 8, characterized in that, It is prepared by the following method: Hydrogen-type molecular sieve powder was subjected to steam modification treatment at a temperature of 450℃ to 600℃ for a duration of 0.5h to 4h, with the steam feed rate to the mass ratio of hydrogen-type molecular sieve powder being (0.5 to 2):

1. Hydrogen-form molecular sieve powder modified by steam is thoroughly mixed and kneaded with a binder and a non-precious metal element salt solution, and then extruded into strips. The amount of hydrogen-form molecular sieve powder added accounts for 70% to 95% of the mass of the catalyst support. The non-precious metal element in the non-precious metal element salt solution is one or more elements selected from Mo, Co, W, Ni, La, Mg, and P. After extrusion, the strips are dried at 60°C to 120°C for 1 to 6 hours and calcined at 450°C to 560°C for 2 to 10 hours to obtain the catalyst.

10. A method for preparing a catalyst according to claim 7 or 8, characterized in that, include: Hydrogen-type molecular sieve powder was subjected to steam modification treatment at a temperature of 450℃ to 600℃ for a duration of 0.5h to 4h, with the steam feed rate to the mass ratio of hydrogen-type molecular sieve powder being (0.5 to 2):

1. Hydrogen-form molecular sieve powder modified by steam is thoroughly mixed and kneaded with a binder and a non-precious metal element salt solution, and then extruded into strips. The amount of hydrogen-form molecular sieve powder added accounts for 70% to 95% of the mass of the catalyst support. The non-precious metal element in the non-precious metal element salt solution is one or more elements selected from Mo, Co, W, Ni, La, Mg, and P. After extrusion, the strips are dried at 60°C to 120°C for 1 to 6 hours and calcined at 450°C to 560°C for 2 to 10 hours to obtain the catalyst.

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