Process for the methylation of ethylbenzene-containing octanes with methanol to produce pseudotri-methylbenzene and tetramethylbenzene

Abstract

The application discloses a method for preparing trimethylbenzene and tetramethylbenzene by methylating ethylbenzene-containing octa-aromatic hydrocarbon and methanol. The method comprises the following steps: contacting the ethylbenzene-containing octa-aromatic hydrocarbon and methanol with a methylation catalyst under the condition of hydrogen and / or water to prepare trimethylbenzene and tetramethylbenzene; and the methylation catalyst is a metal-modified surface-silicon-rich ZSM-5 full-crystalline molecular sieve catalyst. The method can strengthen the catalyst's activity of removing ethylbenzene, promote the conversion of ethylbenzene, inhibit the reaction of ethylbenzene and methanol to generate methyl-ethylbenzene byproducts, improve the quality of trimethylbenzene and tetramethylbenzene, improve the quality of C8 aromatic hydrocarbon by effective conversion of ethylbenzene, and reduce the purity and cost requirements of raw materials.

Description

Technical Field

[0001] This invention relates to the field of aromatic hydrocarbon conversion technology, and in particular to a method for synthesizing pseudotrimethylbenzene and mesitylene by methylation of C8 aromatic hydrocarbons containing ethylbenzene with methanol. Background Technology

[0002] Pseudotrimethylbenzene and mesitylene are important organic chemical raw materials widely used in pharmaceuticals, surfactants, plastic additives, dyes, and synthetic resins. Currently, pseudotrimethylbenzene and mesitylene are mainly obtained from C9-C4 hydrocarbons obtained through catalytic reforming or naphtha cracking. 10 Aromatic fractions are obtained, such as CN1313269A and CN101279886A. Taking the separation of reformed heavy aromatics as an example, its composition is extremely complex, with C9 aromatics containing only 30%–40% pseudotrimethylbenzene. 10 The content of mesitylene in aromatic hydrocarbons is less than 10%, and they also contain many isomers with similar boiling points, which makes the separation method for preparing pseudotrimethylbenzene and mesitylene have a high separation load and low yield.

[0003] Methylation of aromatics with methanol is an effective route for synthesizing polymethylbenzenes. For example, patent CN101654394A uses benzene, toluene, and xylene as raw materials to produce pseudotrimethylbenzene through reaction with a methylating agent. Patent CN110627605A discloses a method for producing mesitylene from methanol and xylene. For the methylation preparation of pseudotrimethylbenzene and mesitylene, xylene is undoubtedly the most suitable raw material, effectively improving the selectivity of the target product. However, in the production of aromatics, high-purity xylene is difficult to obtain, as it generally contains some ethylbenzene, such as reformed C8 aromatics and C8 aromatics from isomerized feedstocks. High-purity xylene requires further isomerization to remove ethylbenzene and xylene separation. Therefore, the production of pseudotrimethylbenzene and mesitylene via xylene-methanol methylation has high raw material costs, reducing the universality of raw materials and the techno-economic viability. Summary of the Invention

[0004] The technical problem this invention aims to solve is the high purity requirements and cost of raw materials in existing xylene-methanol methylation techniques for producing pseudotrimethylbenzene and mesitylene. This invention provides a method for producing pseudotrimethylbenzene and mesitylene by methylation of ethylbenzene-containing C8 aromatics with methanol. This method enhances the deethylation activity of the catalyst, promotes ethylbenzene conversion, inhibits the formation of methyl ethylbenzene byproducts from the reaction of ethylbenzene with methanol, and improves the quality of pseudotrimethylbenzene and mesitylene. Simultaneously, the effective conversion of ethylbenzene improves the quality of C8 aromatics, reducing the requirements for raw material purity and cost.

[0005] The present invention provides a method for preparing pseudotrimethylbenzene and mesitylene by methylation of ethylbenzene-containing C8 aromatic hydrocarbons and methanol, comprising: contacting ethylbenzene-containing C8 aromatic hydrocarbons and methanol with a methylation catalyst under hydrogen- or / and aqueous conditions to obtain pseudotrimethylbenzene and mesitylene.

[0006] The methylation catalyst is a metal-modified, surface-rich silicon-containing ZSM-5 fully crystalline molecular sieve catalyst.

[0007] Furthermore, the bulk SiO2 / Al2O3 molar ratio of the methylation catalyst is 100-320, and the surface SiO2 / Al2O3 molar ratio is ≥330; preferably, the surface SiO2 / Al2O3 molar ratio is 1.5 to 6 times the bulk SiO2 / Al2O3 molar ratio, more preferably 2 to 4.5 times.

[0008] Furthermore, in the methylation catalyst, the mass content of the binder is ≤2%.

[0009] Furthermore, in the methylation catalyst, the metal includes at least one of Pt, Ni, Re, and Mo.

[0010] Furthermore, in the methylation catalyst, the mass content of the metal is 0.01% to 5% based on the mass of the catalyst.

[0011] Furthermore, the methylation catalyst synthesis step includes the following steps:

[0012] (a) Take ZSM-5 molecular sieve, add silica sol to mix and shape, and then dry and calcine to obtain ZSM-5 molecular sieve molded body;

[0013] (b) Take the above ZSM-5 molecular sieve molded body, introduce the modified metal by impregnation method, and after drying and calcination, obtain the metal-modified ZSM-5 molecular sieve molded body;

[0014] (c) Take an inorganic base, an organic template agent and water to prepare a solution, then add the above-mentioned metal-modified ZSM-5 molecular sieve molded body, and after crystallization, ammonium ion exchange, drying and calcination, obtain a metal-modified surface silicon-rich ZSM-5 fully crystalline molecular sieve catalyst.

[0015] Further, in step (a), the weight percentage of silica sol in the molded body is 10% to 50%, preferably 20% to 30%, calculated based on silica.

[0016] Further, in step (a), the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 100 to 300.

[0017] Further, in step (a), the drying temperature is 50–150°C and the drying time is 1–24 h; the calcination temperature is 400–600°C and the calcination time is 1–24 h.

[0018] Furthermore, in step (b), the impregnation method is preferably an equal-volume impregnation.

[0019] Furthermore, in step (b), the impregnation method is carried out using conventional methods in the art, wherein the metal-containing impregnation solution used can be prepared using a metal precursor (such as a soluble metal salt).

[0020] Further, in step (b), the drying temperature is 50–150°C and the drying time is 1–24 h; the calcination temperature is 400–600°C and the calcination time is 1–24 h.

[0021] Further, the inorganic base in step (c) includes at least one of NaOH, KOH, and ammonia water; the organic template agent is at least one of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine, and ethylenediamine; the metal-modified ZSM-5 molecular sieve molded body is calculated based on SiO2 in silica sol, and the base source is OH... - The molar ratio of organic template agent and water (calculated as H2O) is 20-100: 5-10: 0.01-2: 500-1000.

[0022] Further, in step (c), the crystallization treatment conditions are: crystallization treatment at 150-200℃ for 10-200 hours.

[0023] Further, in step (c), the ammonium exchange temperature is 70–95°C, the ammonium exchange time is 2–10 h / time, and the number of ammonium exchanges is 2–4 times. The ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride, and ammonium sulfate, and the mass concentration of the ammonium salt solution is 5%–20%. The ammonium salt solution is mixed with the crystallized solid obtained in step (c) at a mass ratio of 5–10:1.

[0024] Further, in step (c), the drying temperature is 50-150℃ and the drying time is 1-24h; the calcination temperature is 400-600℃ and the calcination time is 1-24h.

[0025] Furthermore, in the method, the raw material containing ethylbenzene C8 aromatic hydrocarbons includes ethylbenzene and xylene, wherein the xylene is at least one of o-xylene, m-xylene, and p-xylene; the mass content of ethylbenzene in the raw material containing ethylbenzene C8 aromatic hydrocarbons is 0.1% to 20%, preferably 5% to 10%.

[0026] Furthermore, in the method, the reaction conditions are as follows: reaction temperature 400-500℃, reaction pressure 0.5-2.0MPa, the molar ratio of ethylbenzene-containing C8 aromatic hydrocarbons to methanol in the feed is 1 / 2 to 2 / 1, and the mass hourly space velocity (WHSV) of the ethylbenzene-containing C8 aromatic hydrocarbons is 1 to 4 h⁻¹. -1 The molar ratio of hydrogen to ethylbenzene-containing C8 aromatic hydrocarbons is 2–5.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. In the method provided by the present invention, the methylation catalyst used has a silicon-rich outer surface to inhibit the acidic catalytic reaction on the outer surface and suppress the formation of isomers such as terylene and mesitylene; at the same time, metal modification enables the catalyst to have ethylbenzene deethylation and xylene methylation activity, improve ethylbenzene conversion, and inhibit the reaction of ethylbenzene with methanol to produce byproducts such as methyl ethylbenzene; thus, the methylation products obtained by the present invention can yield high-purity terylene and mesitylene products.

[0029] 2. In the method provided by the present invention, C8 aromatic hydrocarbons containing ethylbenzene are used as raw materials, thereby reducing the requirements for raw material purity and cost. Attached Figure Description

[0030] Figure 1 The XRD patterns of the ZSM-5 molecular sieve prototypes and catalysts in Examples 1-4 are shown below.

[0031] in, Figure 1 In the diagram, line 1 is the XRD pattern of the ZSM-5 molecular sieve molded body in Example 1, line 2 is the XRD pattern of the platinum-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst in Example 1, line 3 is the XRD pattern of the nickel-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst in Example 2, line 4 is the XRD pattern of the rhenium-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst in Example 3, and line 5 is the XRD pattern of the molybdenum-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst in Example 4.

[0032] Figure 2 The image shown is a scanning electron microscope (SEM) image of the ZSM-5 molecular sieve molded body in Example 1.

[0033] Figure 3 A scanning electron microscope image of the platinum-modified, surface-silica-rich ZSM-5 fully crystalline molecular sieve catalyst in Example 1;

[0034] Figure 4 The image shows a scanning electron microscope (SEM) image of the nickel-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst from Example 2. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0036] The raw materials used in the specific embodiments of the present invention are commercially available and have an analytical grade (AR) purity.

[0037] In this invention, the XRD testing equipment used in the embodiments and comparative examples is a D / max-1400 fully automatic X-ray diffractometer manufactured by Rigaku Corporation of Japan, with the following parameters: test voltage 40kV, current 40mA, scanning range 5-50°, and scanning speed 2° / min; the binder content in the catalyst is calculated by fitting the full spectrum of the XRD pattern.

[0038] In this invention, the scanning electron microscope (SEM) used in the embodiments and comparative examples is a Hitachi S-4800 cold field emission high-resolution scanning electron microscope with an accelerating voltage of 20kV.

[0039] In this invention, the metal content in the catalysts in the embodiments and comparative examples was obtained by testing with a PS-6 vacuum inductively coupled plasma atomic emission spectrometer from Baird, Inc., and the metal loading of the specific catalyst was calculated based on the metal content.

[0040] In this invention, in the embodiments and comparative examples, the molar ratio of SiO2 / Al2O3 on the catalyst surface and in the bulk phase was analyzed using an Escalab 250Xi X-ray photoelectron spectroscopy (XPS) instrument. The X-ray source was AlK2O3. α The obtained data were first corrected based on the C1s peak of 284.8 eV. During the test, the SiO2 / Al2O3 molar ratio obtained by direct testing of the catalyst was the surface silicon-aluminum ratio, and the SiO2 / Al2O3 molar ratio measured after the catalyst was etched by Ar ion plasma was the bulk silicon-aluminum ratio. The Ar ion etching time was 1000 seconds.

[0041] In this invention, the performance calculation formula for the catalyst is as follows:

[0042] C8 aromatic hydrocarbon conversion rate (%) = (mass of C8 aromatic hydrocarbons reacted / mass of C8 aromatic hydrocarbons in feed) × 100%;

[0043] Selectivity of pseudotrimethylbenzene (%) = (mass of pseudotrimethylbenzene produced / mass of C8 aromatic hydrocarbons reacted) × 100%;

[0044] Selectivity of mesitylene (%) = (mass of mesitylene produced / mass of C8 aromatic hydrocarbons reacted) × 100%;

[0045] Trimethylbenzene / C9A (%) = (mass of trimethylbenzene produced / total mass of C9 aromatics in the reaction products) × 100%;

[0046] Mesitylene / C 10 A(%) = (mass of mesitylene produced / C in the reaction products) 10 (Aromatic hydrocarbon mass) × 100%.

[0047] Example 1

[0048] ZSM-5 molecular sieves with a silica-to-alumina ratio of 150 were mixed with a certain amount of silica sol to form a shaped body. The shaped body was then dried at 120℃ for 12 hours and calcined at 550℃ for 5 hours to obtain the ZSM-5 molecular sieve shaped body. Based on silica, the silica sol accounted for 30% of the shaped body by weight. [Scanning electron microscope image of the ZSM-5 molecular sieve shaped body is shown below.] Figure 2 The results show that a large number of fine particulate binders exist on the surface of the ZSM-5 molecular sieve molded body. The XRD pattern of the ZSM-5 molecular sieve molded body is shown in the figure. Figure 1 Line 1. Take the above-mentioned ZSM-5 molecular sieve molded body, impregnate it with chloroplatinic acid solution (based on catalyst, the mass content of platinum in the catalyst is 0.01%) by equal volume impregnation method, dry it at 120℃ for 12h, and calcine it at 550℃ for 24h to obtain platinum-modified ZSM-5 molecular sieve molded body. Take NaOH as the alkali source, tetrapropylammonium bromide as the organic template agent, add deionized water to prepare a mixed solution, and then add the platinum metal-modified ZSM-5 molecular sieve molded body and mix evenly. The molded body is calculated based on SiO2 in silica sol, and the alkali source is calculated based on OH... - The molar ratio of organic template agent, water (calculated as H2O) was 100:7.5:2:550. After hydrothermal crystallization at 175℃ for 48 h, the solid was filtered and exchanged with a 10% ammonium nitrate solution at 95℃ for 2 h. The ammonium nitrate solution and the crystallized solid were mixed at a mass ratio of 5:1, and the exchange was repeated twice. The solid was then dried at 150℃ for 1 h and calcined at 500℃ for 24 h to obtain a platinum-modified, surface-silica-rich ZSM-5 fully crystalline molecular sieve catalyst. Scanning electron micrographs of the above platinum-modified, surface-silica-rich ZSM-5 fully crystalline molecular sieve catalyst are shown below. Figure 3 The results showed that the surface of the platinum-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst had almost no particulate binder, and the catalyst was entirely composed of ZSM-5 molecular sieve. Figure 1 Line 2 shows that the binder content in the catalyst is 0.2% according to XRD test results, and the XPS test results show that the SiO2 / Al2O3 molar ratio on the catalyst surface is 338 and the SiO2 / Al2O3 molar ratio in the bulk phase is 166.

[0049] The platinum-modified, surface-enriched silicon-rich ZSM-5 fully crystalline molecular sieve catalyst was used for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 10 / 90) with methanol. The reaction conditions were: reaction temperature 450℃, reaction pressure 0.5 MPa, C8 aromatics / methanol molar ratio 2 / 1, and C8 aromatics mass hourly space velocity 4 h⁻¹. -1Under the condition of a hydrogen / C8 aromatic molar ratio of 3, the C8 aromatic conversion rate was 35.3%, the selectivity for pseudotrimethylbenzene was 79.8%, and the selectivity for mesitylene was 15.1%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 98.3%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 + A) The mass content is as high as 81.3%.

[0050] Example 2

[0051] ZSM-5 molecular sieves with a silicon-to-aluminum ratio of 100 were mixed with a certain amount of silica sol to form a molten ZSM-5 molecular sieve. The molten ZSM-5 was then dried at 50°C for 24 hours and calcined at 400°C for 24 hours to obtain a ZSM-5 molecular sieve molten body. The silica sol content in the molten body was 20% by weight (based on silica). The ZSM-5 molecular sieve molten body was then impregnated with a nickel nitrate solution (based on catalyst content, ensuring a nickel content of 5%) using an equal-volume impregnation method. The mixture was dried at 50°C for 24 hours and calcined at 400°C for 24 hours to obtain a nickel-modified ZSM-5 molecular sieve molten body. A mixed solution was prepared by adding KaOH as the alkali source, n-butylammonium sulfate as the organic template agent, and deionized water. The nickel-modified ZSM-5 molecular sieve molten body was then added and mixed thoroughly. The molten body was calculated based on SiO2 in the silica sol, and the alkali source was calculated based on OH... - The molar ratio of the catalyst, template agent, and water (calculated as H2O) was 20:5:0.01:1000. After hydrothermal crystallization at 200℃ for 100 h, the solid was filtered and exchanged with a 5% ammonium chloride solution at 75℃ for 5 h. The ammonium chloride solution and the crystallized solid were mixed at a mass ratio of 10:1, and this exchange was repeated four times. The solid was then dried at 50℃ for 24 h and calcined at 600℃ for 1 h to obtain a nickel-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst. Figure 4 The scanning electron microscope (SEM) images show that the surface of the nickel-modified, silicon-rich ZSM-5 fully crystalline molecular sieve catalyst has almost no particulate binder, and the catalyst is composed entirely of ZSM-5 molecular sieve. Figure 1 XRD results from line 3 show that the binder content in the nickel-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst is 1.1%, and XPS results show that the SiO2 / Al2O3 molar ratio on the catalyst surface is 458, and the SiO2 / Al2O3 molar ratio in the bulk phase is 102.

[0052] The aforementioned nickel-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst was used for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 20 / 80) with methanol. The reaction was carried out at a temperature of 450℃, a pressure of 2 MPa, a C8 aromatics / methanol molar ratio of 1 / 1, and a C8 aromatics mass hourly space velocity of 2 h⁻¹. -1Under the condition of a hydrogen / C8 aromatic molar ratio of 5, the C8 aromatic conversion rate was 45.6%, the selectivity for pseudotrimethylbenzene was 77.6%, and the selectivity for mesitylene was 14.8%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 94.8%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 + A) The mass content is as high as 74.6%.

[0053] Example 3

[0054] ZSM-5 molecular sieves with a silica-to-alumina ratio of 200 were mixed with a certain amount of silica sol to form a molded body. The molded body was then dried at 150°C for 1 hour and calcined at 600°C for 24 hours to obtain a ZSM-5 molecular sieve molded body. The silica sol weight percentage in the molded body was 20% based on silica. The ZSM-5 molecular sieve molded body was then impregnated with ammonium perrhenate solution (calculated as catalyst, with a rhenium content of 0.5% by mass) using an equal-volume impregnation method. The mixture was dried at 150°C for 1 hour and calcined at 600°C for 1 hour to obtain a rhenium-modified ZSM-5 molecular sieve molded body. Ammonia water was used as the alkali source, tetrapropylammonium hydroxide as the organic template agent, and deionized water were added to prepare a mixed solution. The rhenium-modified ZSM-5 molecular sieve molded body was then added and mixed thoroughly. The molded body was calculated based on SiO2 in the silica sol, and the alkali source was calculated based on OH... - The molar ratio of rhenium-modified template agent, water (calculated as H2O) is 50:10:2:500. After hydrothermal crystallization at 150℃ for 100 h, the solid is filtered and exchanged with a 20% ammonium sulfate solution at 80℃ for 4 h. The ammonium sulfate solution and the crystallized solid are mixed at a mass ratio of 8:1, and this exchange is repeated three times. The solid is then dried at 120℃ for 10 h and calcined at 550℃ for 5 h to obtain a rhenium-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst. Figure 1 XRD results from line 4 show that the binder content in the rhenium-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst is 1.9%, and XPS results show that the SiO2 / Al2O3 molar ratio on the catalyst surface is 534, and the SiO2 / Al2O3 molar ratio in the bulk phase is 213.

[0055] The rhenium-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst was used for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 10 / 90) with methanol. The reaction was carried out at a temperature of 400℃, a pressure of 1 MPa, a C8 aromatics / methanol molar ratio of 1 / 2, and a C8 aromatics mass hourly space velocity of 1 h⁻¹. -1 Under the condition of a hydrogen / C8 aromatic molar ratio of 2, the C8 aromatic conversion rate was 53.1%, the selectivity for pseudotrimethylbenzene was 72.6%, and the selectivity for mesitylene was 22.1%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 92.7%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 +A) The mass content is as high as 85.7%.

[0056] Example 4

[0057] ZSM-5 molecular sieve with a silica-to-alumina ratio of 300 was mixed with a certain amount of silica sol to form a shaped body. The shaped body was then dried at 100℃ for 20 hours and calcined at 450℃ for 12 hours to obtain a ZSM-5 molecular sieve shaped body. The silica sol weight percentage in the shaped body was 30% based on silica. The ZSM-5 molecular sieve shaped body was then impregnated with ammonium heptamolybdate solution (based on catalyst, with a Mo content of 3% by mass) using an equal-volume impregnation method. The shaped body was dried at 120℃ for 12 hours and calcined at 550℃ for 8 hours to obtain a molybdenum-modified ZSM-5 molecular sieve shaped body. A mixed solution was prepared by adding NaOH as the alkali source, ethylenediamine as the organic template agent, and deionized water. The molybdenum-modified ZSM-5 molecular sieve shaped body was then added and mixed thoroughly. The shaped body was calculated based on SiO2 in the silica sol, and the alkali source was calculated based on OH... - The molar ratio of the catalyst, template agent, and water (based on H2O) was 85:10:2:500. After hydrothermal crystallization at 180℃ for 10 hours, the solid was filtered and exchanged with a 15% ammonium chloride solution at 90℃ for 2 hours. The ammonium chloride solution and the crystallized solid were mixed at a mass ratio of 10:1, and this exchange was repeated four times. The solid was then dried at 100℃ for 24 hours and calcined at 500℃ for 24 hours to obtain a molybdenum-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst. Figure 1 XRD results from line 5 show that the binder content in the molybdenum-modified surface-rich silicon ZSM-5 fully crystalline molecular sieve catalyst is 0.7%, and XPS results show that the SiO2 / Al2O3 molar ratio on the catalyst surface is 679, and the SiO2 / Al2O3 molar ratio in the bulk phase is 312.

[0058] The above-mentioned molybdenum-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst was used for the methanol methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 10 / 90) at a reaction temperature of 460℃, a reaction pressure of 0.5 MPa, a C8 aromatics / methanol molar ratio of 2 / 1, and a C8 aromatics mass hourly space velocity of 4 h⁻¹. -1 Under the condition of a hydrogen / C8 aromatic molar ratio of 5, the C8 aromatic conversion rate was 38.2%, the selectivity for pseudotrimethylbenzene was 79.2%, and the selectivity for mesitylene was 16.2%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 98.9%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 + A) The mass content is as high as 83.4%.

[0059] Example 5

[0060] ZSM-5 molecular sieves with a silica-to-alumina ratio of 250 were mixed with a certain amount of silica sol to form a molten ZSM-5 molecular sieve. The molten ZSM-5 was then dried at 120°C for 24 hours and calcined at 550°C for 8 hours to obtain a ZSM-5 molecular sieve molten body. The silica sol content in the molten body was 30% by weight (based on silica). The ZSM-5 molecular sieve molten body was then impregnated with a chloroplatinic acid solution (based on catalyst, with a platinum content of 0.02%) using an equal-volume impregnation method. The molten ZSM-5 was dried at 130°C for 5 hours and calcined at 600°C for 2 hours to obtain a platinum-modified ZSM-5 molecular sieve molten body. A mixed solution was prepared by adding NaOH as the alkali source, tetrapropylammonium hydroxide as the organic template agent, and deionized water. The platinum-modified ZSM-5 molecular sieve molten body was then added and mixed thoroughly. The molten body was calculated based on SiO2 in the silica sol, and the alkali source was calculated based on OH... - The binder, template agent, and water (calculated as H2O) were present in a molar ratio of 45:8:1:700. After hydrothermal crystallization at 180℃ for 10 h, the solid was filtered and exchanged with a 10% ammonium nitrate solution at 75℃ for 5 h. The ammonium nitrate solution and the crystallized solid were mixed at a mass ratio of 5:1, and this exchange was repeated four times. The solid was then dried at 120℃ for 24 h and calcined at 550℃ for 12 h to obtain a platinum-modified, surface-rich silicon-enriched ZSM-5 fully crystalline molecular sieve catalyst. XRD results showed that the binder content in the catalyst was 0.5%, and XPS results showed that the SiO2 / Al2O3 molar ratio on the catalyst surface was 585, and the SiO2 / Al2O3 molar ratio in the bulk phase was 254.

[0061] The platinum-modified, surface-enriched silicon ZSM-5 fully crystalline molecular sieve catalyst was used for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 5 / 95) with methanol. The reaction conditions were: reaction temperature 480℃, reaction pressure 1 MPa, C8 aromatics / methanol molar ratio 2 / 1, and C8 aromatics mass hourly space velocity 4 h⁻¹. -1 Under the condition of a hydrogen / C8 aromatic molar ratio of 3, the C8 aromatic conversion rate was 40.5%, the selectivity for pseudotrimethylbenzene was 77.6%, and the selectivity for mesitylene was 15.8%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 97.3%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 + A) The mass content is as high as 81.5%.

[0062] Comparative Example 1

[0063] ZSM-5 molecular sieves with a silica-to-alumina ratio of 150 were mixed with a certain amount of silica sol to form a molten ZSM-5 molecular sieve. The molten body was then dried at 120℃ for 12 hours and calcined at 550℃ for 5 hours. The silica sol accounted for 30% of the molten body by weight, calculated based on silica. NaOH was used as the alkali source, tetrapropylammonium bromide as the organic template agent, and deionized water was added to prepare a mixed solution. This solution was then added to the ZSM-5 molecular sieve molten body and mixed thoroughly. The molten body was calculated based on SiO2 in the silica sol, and the alkali source was calculated based on OH... - The catalyst, consisting of a binder, an organic template agent, and water (H2O), was prepared in a molar ratio of 100:7.5:2:550. After hydrothermal crystallization at 175℃ for 48 hours, the solid was filtered and exchanged with a 10% ammonium nitrate solution at 95℃ for 2 hours. The ammonium nitrate solution was then mixed with the crystallized solid at a mass ratio of 5:1, and this exchange was repeated twice. The catalyst was then dried at 150℃ for 1 hour and calcined at 500℃ for 24 hours to obtain a silicon-rich ZSM-5 fully crystalline molecular sieve catalyst. XRD analysis showed that the binder content in the catalyst was 0.2%, and XPS analysis showed that the SiO2 / Al2O3 molar ratio on the catalyst surface was 338, and the SiO2 / Al2O3 molar ratio in the bulk phase was 168.

[0064] The aforementioned ZSM-5 fully crystalline molecular sieve catalyst with a silicon-rich surface was used for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 10 / 90) with methanol. The reaction conditions were: reaction temperature 450℃, reaction pressure 0.5 MPa, C8 aromatics / methanol molar ratio 2 / 1, and C8 aromatics mass hourly space velocity 4 h⁻¹. -1 Under the condition of a hydrogen / C8 aromatic molar ratio of 3, the C8 aromatic conversion rate was 30.9%, the selectivity for pseudotrimethylbenzene was 65.4%, and the selectivity for mesitylene was 10.3%. The mass content of pseudotrimethylbenzene / C9A (C9A) in the liquid phase product was only 76.9%, while the mass content of mesitylene / C10 and above aromatics (C9A) was significantly higher. 10 + A) The mass content is only 62.4%.

[0065] Comparative Example 2

[0066] ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 150 was taken, and a certain amount of silica sol was added to form a mold. The molded body was then dried at 120℃ for 12 hours and calcined at 550℃ for 5 hours to obtain a ZSM-5 molecular sieve molded body. The silica sol weight percentage in the molded body was 30% (based on silica). The above ZSM-5 molecular sieve molded body was then impregnated with chloroplatinic acid solution (based on catalyst, ensuring a platinum content of 0.01%) using an equal-volume impregnation method. After drying at 120℃ for 12 hours and calcining at 550℃ for 24 hours, a platinum-modified ZSM-5 molecular sieve molded body was obtained.

[0067] The platinum-modified ZSM-5 molecular sieve prototyping material was used as a catalyst for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 10 / 90) with methanol. The reaction conditions were: reaction temperature 450℃, reaction pressure 0.5 MPa, C8 aromatics / methanol molar ratio 2 / 1, and C8 aromatics mass hourly space velocity 4 h⁻¹. -1 Under the condition of a hydrogen / C8 aromatic molar ratio of 3, the C8 aromatic conversion rate was 29.7%, the selectivity for pseudotrimethylbenzene was 64.94%, and the selectivity for mesitylene was 10.1%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 73.1%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 + A) The mass content is as high as 59.8%.

[0068] Comparative Example 3

[0069] ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 150 was taken, a certain amount of silica sol was added to form a mold, and then dried at 120℃ for 12 hours and calcined at 550℃ for 5 hours to obtain a ZSM-5 molecular sieve molded body. Calculated by silica, the weight ratio of silica sol in the molded body is 30%.

[0070] The ZSM-5 molecular sieve prototyping material was used as a catalyst for the methylation reaction of C8 aromatics (ethylbenzene / mixed xylene mass ratio 10 / 90) with methanol. The reaction conditions were: reaction temperature 450℃, reaction pressure 0.5 MPa, C8 aromatics / methanol molar ratio 2 / 1, and C8 aromatics mass hourly space velocity 4 h⁻¹. -1 Under the condition of a hydrogen / C8 aromatic molar ratio of 3, the C8 aromatic conversion rate was 26.2%, the selectivity for pseudotrimethylbenzene was 53.6%, and the selectivity for mesitylene was 9.3%. The liquid-phase product contained a high mass content of pseudotrimethylbenzene / C9A (C9A) up to 62.8%, and a high mass content of mesitylene / C10 and above aromatics (C9A). 10 + A) The mass content is as high as 51.4%.

Claims

1. A method for producing pseudotrimethylbenzene and mesitylene by methylation of ethylbenzene-containing carbopenta aromatic hydrocarbons with methanol, comprising: C8 aromatic hydrocarbons containing ethylbenzene and methanol are contacted with a methylation catalyst under hydrogen- or / and aqueous conditions to prepare pseudotrimethylbenzene and mesitylene. The methylation catalyst is a metal-modified, surface-rich silicon-rich ZSM-5 fully crystalline molecular sieve catalyst. The metal includes at least one of Pt, Ni, Re, and Mo; The surface SiO2 / Al2O3 molar ratio of the methylation catalyst is 1.5 to 6 times that of the bulk SiO2 / Al2O3 molar ratio; the bulk SiO2 / Al2O3 molar ratio of the methylation catalyst is 100-320, and the surface SiO2 / Al2O3 molar ratio is ≥330. In the methylation catalyst, the mass content of the metal is 0.01% to 5% based on the mass of the catalyst; The mass content of ethylbenzene in the raw materials containing ethylbenzene-containing C8 aromatic hydrocarbons is 0.1%~20%; The reaction conditions are as follows: reaction temperature 400-500℃, reaction pressure 0.5-2.0MPa, and the molar ratio of ethylbenzene-containing C8 aromatics to methanol in the feed is 1 / 2 to 2 / 1.

2. The method according to claim 1, characterized in that, The surface SiO2 / Al2O3 molar ratio of the methylation catalyst is 2 to 4.5 times that of the bulk SiO2 / Al2O3 molar ratio.

3. The method according to claim 1, characterized in that, The method for synthesizing the methylation catalyst includes the following steps: (a) Take ZSM-5 molecular sieve, add silica sol to mix and shape, and then dry and calcine to obtain ZSM-5 molecular sieve molded body; (b) Take the above ZSM-5 molecular sieve molded body, introduce the modified metal by impregnation method, and after drying and calcination, obtain the metal-modified ZSM-5 molecular sieve molded body; (c) Take an inorganic base, an organic template agent and water to prepare a solution, then add the above-mentioned metal-modified ZSM-5 molecular sieve molded body, and after crystallization, ammonium ion exchange, drying and calcination, obtain a metal-modified surface silicon-rich ZSM-5 fully crystalline molecular sieve catalyst.

4. The method according to claim 3, characterized in that, In step (a), the weight percentage of silica sol in the molded body is 10% to 50% based on silica; the molar ratio of SiO2 / Al2O3 in the ZSM-5 molecular sieve is 100 to 300.

5. The method according to claim 3, characterized in that, In step (a), the weight percentage of silica sol in the molded body is 20% to 30% based on silica.

6. The method according to claim 3, characterized in that, The inorganic base in step (c) includes at least one of NaOH, KOH, and ammonia water; the organic template agent is at least one of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine, and ethylenediamine.

7. The method according to claim 3, characterized in that, In step (c), the metal-modified ZSM-5 molecular sieve molded body is calculated based on SiO2 in silica sol, and the alkali source is OH. - The molar ratio of organic template agent and water (calculated as H2O) is 20~100:5~10:0.01~2:500~1000.

8. The method according to claim 3, characterized in that, In step (c), the crystallization treatment conditions are: 150-200 o Crystallization treatment at C for 10-200 hours.

9. The method according to claim 1, characterized in that, The raw materials for C8 aromatic hydrocarbons containing ethylbenzene include ethylbenzene and xylene, wherein the xylene is at least one of o-xylene, m-xylene, and p-xylene.

10. The method according to claim 1, characterized in that, The raw materials for C8 aromatic hydrocarbons containing ethylbenzene include ethylbenzene and xylene, wherein the xylene is at least one of o-xylene, m-xylene, and p-xylene; the mass content of ethylbenzene in the raw materials for C8 aromatic hydrocarbons containing ethylbenzene is 5% to 10%.

11. The method according to claim 1, characterized in that, The reaction conditions are as follows: the mass hourly space velocity (WHSV) of the C8 aromatic hydrocarbon containing ethylbenzene is 1–4 h⁻¹. -1 The molar ratio of hydrogen to ethylbenzene-containing C8 aromatic hydrocarbons is 2-5.

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