ZSM-5 molecular sieve catalysts for benzene alkylation reactions, their preparation methods, and applications.

Abstract

This invention discloses a ZSM-5 molecular sieve catalyst for benzene alkylation reactions, its preparation method, and its applications. The catalyst has a bulk Si / Al molar ratio of 50-170, and its outer surface contains only silicon. The preparation method of the catalyst includes: S1, mixing an aluminum source, water, mineralizing agent N, template agent M, and a silicon source to obtain a raw material solution; S2, crystallizing the raw material solution obtained in step S1 to obtain a crystallized slurry; S3, mixing a disodium ethylenediaminetetraacetate solution with the crystallized slurry obtained in step S2, and subjecting the mixture to hydrothermal treatment to obtain a hydrothermally treated slurry; S4, separating, drying, and calcining the hydrothermally treated slurry obtained in step S3 to obtain the ZSM-5 molecular sieve catalyst. The catalyst of this invention can significantly improve the selectivity of ethylbenzene and reduce the selectivity of polyethylbenzene in benzene alkylation reactions.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve catalyst synthesis, and more specifically to a ZSM-5 molecular sieve catalyst for benzene alkylation reaction, its preparation method, and its application. Background Technology

[0002] Molecular sieves, as an important class of inorganic porous materials, have a wide range of applications, especially in the petrochemical industry, where they play a crucial role as catalysts and adsorbents. Molecular sieves possess a regular internal pore structure and adjustable solid acidity. Due to limitations such as grain size, pore structure, and silicon-to-aluminum ratio, many directly synthesized molecular sieve powders cannot be directly used in actual production and must be modified. Dealuminization of molecular sieves is a key aspect of molecular sieve modification. Dealuminization of molecular sieves serves two purposes: firstly, to adjust the acidity and acid strength of the molecular sieve, improving its activity and selectivity; and secondly, to improve and stabilize the internal structure of the molecular sieve, thereby achieving long-term usability. However, how to modify molecular sieves to achieve good catalytic performance for different reactions remains an important topic of discussion in the field of molecular sieve catalysts.

[0003] Li Junhua et al. (Modern Chemical Industry, 2020.V40(3):107) used tartaric acid, oxalic acid and EDTA-2Na to acid treat calcined ZSM-5 molecular sieve at 80°C. They found that after acid treatment, the pore volume and surface area of ​​ZSM-5 molecular sieve increased, the amount of strong acid decreased, and the activity of methanol aromatization reaction was enhanced.

[0004] Li Mingxiao et al. (Petrochemical Technology, 2014, V43(4):412) modified Y molecular sieve by combining hydrothermal treatment and nitric acid treatment, and used it to improve the selectivity of medium oil in hydrocracking catalyst.

[0005] Sun Shuhong et al. (Petrochemical Technology and Application, 2018, V36(2):83) conducted a study on the modification of ultrastable Y molecular sieves with citric acid to improve their catalytic cracking performance.

[0006] CN105712373B discloses a method for preparing modified Y molecular sieves. The method includes: first, impregnating the Y molecular sieve with an ammonium fluorosilicate solution; second, subjecting the Y molecular sieve to hydrothermal treatment; and finally, treating the hydrothermally treated Y molecular sieve with a dilute acid solution. This method can prepare modified Y molecular sieves with a high silica-to-alumina ratio, abundant macroporous structure, and high crystallinity, which can be used to improve the selective ring-opening performance of hydrocracking.

[0007] CN108097293A discloses a method for synthesizing tin-doped MFI-structured zeolite molecular sieves. The method involves mixing a silicon source, sodium hydroxide, tetrapropylammonium hydroxide, water, and an aluminum source until a gel is formed. A mixture of disodium ethylenediaminetetraacetate and sodium citrate with an aqueous solution of a soluble tin salt is then added to the gel, followed by hydrothermal crystallization. This method can yield Sn-MFI and Sn-Al-MFI zeolite molecular sieves with high crystallinity and regular morphology, but it does not cover specific application areas.

[0008] CN104556124A discloses an ammonium fluoroborate-modified Y-type molecular sieve and its preparation method. This method uses a combination of boron-containing compounds and alkaline solutions to perform dealumination and boron replenishment, as well as deep dealumination, on the Y-type molecular sieve. This method can prepare boron-modified Y-type molecular sieves with high to medium strong acid content, which can be used to improve the cracking performance of hydrocracking catalysts.

[0009] CN102259883A discloses a method for dealumination of hydrogen-type and ammonium-type Y, ZSM-5, β, and SAPO-34 molecular sieves. This method uses chloromethane vapor or a mixture containing chloromethane vapor to pass through the molecular sieve for dealumination. This method can adjust the acid strength and acid density of the molecular sieve, and when the degree of dealumination is high, it can also change the pore structure properties of the molecular sieve.

[0010] The alkylation reaction of benzene and ethylene is a key reaction in the industrial production of ethylbenzene. The ethylbenzene product can undergo further alkylation on a catalyst to generate polyethylbenzene products, primarily diethylbenzene, thus reducing the yield of the main product, ethylbenzene. Industrially, these polyethylbenzene products need to be recovered and further alkylation with benzene to generate ethylbenzene, thereby increasing the ethylbenzene yield. Depending on the reaction conditions and catalyst, the ethylbenzene / polyethylbenzene (weight ratio) varies considerably. US7268267 reports the use of UZM-8 molecular sieve as an alkylation catalyst, achieving a 75.7% selectivity for ethylbenzene in the product, while the overall selectivity for ethylbenzene plus polyethylbenzene is 98.55%, with a weight ratio of ethylbenzene to diethylbenzene of 3.3. US5118894 reports the use of MCM-22 zeolite as a benzene alkylation catalyst, with a weight ratio of ethylbenzene to diethylbenzene in the alkylation product of 3.5. CN1096470A reports the use of a β-molecular sieve / Al2O3 catalyst, with a selectivity of 88.6% for ethylbenzene, a selectivity of 9.3% for diethylbenzene, and a weight ratio of 7.5 for ethylbenzene to diethylbenzene.

[0011] As can be seen from the above methods, different modification methods are needed to improve the catalytic performance of different reactions. For the alkylation reaction of benzene and ethylene, how to improve the yield of the target product ethylbenzene has been a goal pursued in this field. Summary of the Invention

[0012] To address the aforementioned problems in the prior art, this invention provides a ZSM-5 molecular sieve catalyst for benzene alkylation reactions, its preparation method, and its applications. The catalyst of this invention, when used in benzene alkylation reactions, can significantly reduce the yield of the byproduct polyethylbenzene, thereby increasing the yield of the main product ethylbenzene.

[0013] The present invention provides a ZSM-5 molecular sieve catalyst for benzene alkylation reaction, wherein the bulk Si / Al molar ratio of the catalyst is 50-170, and the outer surface contains only silicon.

[0014] Furthermore, in the catalyst, the bulk Si / Al molar ratio is 50-170, preferably 75-160.

[0015] Furthermore, the total specific surface area of ​​the catalyst is 340-400 m². 2 / g, with an external specific surface area of ​​51-100m² 2 / g, preferably, the external specific surface area accounts for 15%-25% of the total specific surface area.

[0016] Furthermore, the outer surface of the catalyst is free of aluminum and contains only silicon. Preferably, the silicon on the outer surface has structures including -Si-O-Si- and -Si-OH. The O / Si atomic ratio on the outer surface of the catalyst is at least 10%-50% higher than the O / Si atomic ratio in the bulk phase, preferably 25%-45% higher.

[0017] Furthermore, in the catalyst, the outer surface -Si-OH accounts for 20%-40% of the outer surface silicon species (oxygen atoms).

[0018] Furthermore, the catalyst has a non-core-shell structure.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned ZSM-5 molecular sieve catalyst for benzene alkylation reaction, comprising:

[0020] S1, mix aluminum source, water, mineralizer N, template agent M and silicon source to obtain raw material liquid;

[0021] S2, the raw material liquid obtained in step S1 is crystallized to obtain a crystallized slurry;

[0022] S3, mix the disodium ethylenediaminetetraacetate (EDTA-2Na) solution with the crystallized slurry obtained in step S2, and then perform hydrothermal treatment to obtain the hydrothermally treated slurry;

[0023] S4. The hydrothermal treated slurry obtained in step S3 is separated, dried, and calcined to obtain the ZSM-5 molecular sieve catalyst.

[0024] Furthermore, those skilled in the art can, as needed, convert the molecular sieve obtained after calcination in step S4 into a hydrogen-form molecular sieve, and then use it as a catalyst. The conversion to a hydrogen-form molecular sieve can generally be achieved through ammonium ion exchange. The ammonium-containing compound used can be at least one of ammonium nitrate, ammonium acetate, or ammonium sulfate, and the molar concentration of the ammonium solution used for ammonium ion exchange can be 0.1-2 mol / L. The solid-liquid weight ratio of the molecular sieve to the ammonium solution is 1:2-1:10.

[0025] Furthermore, in step S1, the order of addition of each material is as follows: aluminum source, water, mineralizer N, template agent M, and silicon source, which are then mixed to obtain a raw material liquid.

[0026] Further, in step S1, the silicon source can be a silicon-containing raw material commonly used in the art, preferably selected from at least one of tetraethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate, n-butyl orthosilicate, silica sol, water glass, and precipitated silica. Silica sol is a colloid formed by suspending silica particles in water, with a particle size of 10-100 nanometers and a solid content of 20%-40%. Water glass is a hydrate of alkali metal silicates, and its molecular formula can be written as R2O·nSiO2, where R2O is an alkali metal oxide, and n is the ratio of silica to the alkali metal oxide's molar number; the most common alkali metal is sodium. Precipitated silica is a general term for white powdery amorphous silica and silicate products, mainly referring to at least one of precipitated silica, fumed silica, and ultrafine silica gel. Precipitated silica is a porous material, and its composition can be represented by SiO2·nH2O, where nH2O exists in the form of surface hydroxyl groups.

[0027] Furthermore, in step S1, the aluminum source can be any aluminum-containing salt, preferably selected from at least one of aluminum isopropoxide, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate, and aluminum chloride. Other aluminum sources known in the art can also be used as needed.

[0028] Further, in step S1, the mineralizing agent N is selected from at least one of NaOH, KOH, Na2CO3, and NaHCO3. The template agent M is selected from at least one of diethylamine, triethylamine, n-butylamine, and tetrapropylammonium hydroxide.

[0029] Further, in step S1, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the proportions (molar ratios) of each component of aluminum source, water, mineralizer N, template agent M and silicon source are SiO2 / Al2O3 = 120-350:1; N / SiO2 = 0.1-0.5:1; M / SiO2 = 0.1-0.5:1; H2O / SiO2 = 5-50:1.

[0030] Further, in step S2, the crystallization temperature is 90-180℃, preferably 100-160℃, and the crystallization time is 0.5-48 hours, preferably 0.5-32 hours.

[0031] Further, in step S3, the concentration of the disodium ethylenediaminetetraacetate (EDTA-2Na) solution is 0.05 mol / L to 0.5 mol / L, and the weight ratio of the disodium ethylenediaminetetraacetate (EDTA-2Na) solution (calculated as disodium ethylenediaminetetraacetate) to the crystallized slurry obtained in step S2 (on a dry basis) is 1:1 to 10:1. The crystallized slurry obtained in step S2, on a dry basis, represents the amount of solids in the slurry excluding water.

[0032] Further, in step S3, the hydrothermal treatment is carried out in a closed container, and the hydrothermal treatment conditions are as follows: the treatment temperature is 100-180℃, preferably 110-160℃, and the treatment time is 0.5-48 hours, preferably 0.5-24 hours.

[0033] Furthermore, in step S4, the separation is a solid-liquid separation, which can be performed using conventional methods in the art. The drying and calcination can be carried out using conventional methods in the art. Preferably, the drying conditions are as follows: drying temperature is 100-180℃, and drying time is 1-48 hours; calcination temperature is 450-650℃, and calcination time is 1-72 hours.

[0034] A third aspect of the present invention provides the application of the above-mentioned catalyst in the alkylation reaction of benzene and ethylene to produce ethylbenzene.

[0035] Furthermore, the reaction conditions for the application are as follows: the molar ratio of benzene to ethylene is 1:1-10:1, preferably 1:1-5:1; the ethylene weight hourly space velocity is 0.5 h⁻¹. -1 -5.0h -1 Preferably 0.5h -1 -2.0h -1 The reaction temperature is 300℃-400℃.

[0036] Furthermore, in the reaction product obtained by the present invention, the ethylbenzene / polyethylbenzene ratio (by weight) is 11-15.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] For benzene alkylation reactions, it is generally believed that the solid acid active sites on the outer surface of the molecular sieve catalyst have a significant impact on the catalyst's selectivity. One common method is molecular sieve dealuminization, such as hydrothermal treatment, acid treatment, and alkali treatment. However, the inventors discovered that commonly used dealuminization methods are difficult to selectively remove surface aluminum. Therefore, ethylbenzene generated during benzene alkylation will continue to alkylate on the outer surface to form polyethylbenzene. How can the selectivity of ethylbenzene be improved while the selectivity of polyethylbenzene be reduced? Further research revealed that the molecular sieve catalyst prepared by the process provided in this invention contains only silicon on its outer surface, free of aluminum, and has abundant silanol species. This significantly improves the catalyst's selectivity, especially increasing the ethylbenzene / polyethylbenzene ratio. In preparing the catalyst of this invention, the inventors used EDTA-2Na, which has a relatively large molecular volume and strong complexation with aluminum, as a dealuminizing agent. This agent was applied to the mother liquor after molecular sieve crystallization under specific hydrothermal conditions. This not only dealuminized the outer surface and protected the acidic sites inside the catalyst but also altered the distribution of silicon species on the outer surface, thus obtaining the molecular sieve catalyst of this invention. When the molecular sieve catalyst of this invention is used in the benzene alkylation reaction, it can significantly reduce the selectivity of polyethylbenzene and increase the selectivity of ethylbenzene, that is, increase the ethylbenzene / polyethylbenzene ratio. Attached Figure Description

[0039] Figure 1 The hydroxyl infrared spectra of the ZSM-5 molecular sieve catalysts obtained in Example 4 and Comparative Examples 1, 2 and 3 of this invention are shown.

[0040] Figure 2 The image shows the XRD pattern of the ZSM-5 molecular sieve catalyst obtained in Example 1 of this invention. Detailed Implementation

[0041] The preferred embodiments of the present invention will be described in more detail below through specific examples, but the scope of protection of the present invention is not limited thereto. Various modifications or combinations can be made to the preferred embodiments of the present invention to obtain other embodiments of the present invention without exceeding the scope of protection defined by the claims, and similar technical effects can still be achieved.

[0042] In this invention, the specific surface area and external surface area of ​​the samples were analyzed using a TriStar 3000 analyzer from Micron Instruments, Inc., USA. The samples were pretreated at 350°C under vacuum for 4 hours. The static adsorption / desorption isotherm of N₂ was measured at 77K. The specific surface area of ​​the samples was calculated using the BET method, and the microporous specific surface area was calculated using the t-plot method.

[0043] In this invention, the specific XRD testing conditions are as follows: a Rigaku D / max-RB X-ray diffractometer (Japan), Cu Kα radiation, tube voltage 40kV, tube current 40mA. Scanning range: 2θ = 5°-40°.

[0044] In this invention, XPS analysis is used to measure the surface silicon-aluminum content, and the specific test conditions are as follows:

[0045] Surface elemental composition analysis of the samples was performed on an AXIS Ultra DLD X-ray photoelectron spectrometer from Kratos Analytical. Maximum X-ray source power: 450 W; energy resolution: 0.48 eV; sampling depth: 1–10 nm.

[0046] In this invention, ICP analysis is used to determine the bulk silicon-aluminum content, and the specific test conditions are as follows:

[0047] Elemental composition analysis of the samples was performed on a Varian 725ES inductively coupled plasma atomic emission spectrometer from Varian Scientific, USA. Frequency: 40.68 MHz, wavelength range: 167-785 nm, resolution: 0.007 nm.

[0048] In this invention, hydroxyl infrared analysis is used to measure surface silanol species, and the specific test conditions are as follows:

[0049] Measurements were taken on a Nicolet 5700 Fourier transform infrared spectrometer from Thermofisher Scientific. Wavenumber range: 4000-400 cm⁻¹ -1 Resolution: 0.125cm -1 The sample slice (15 mg, 13 mm in diameter) was placed in an infrared absorption cell with CaF2 as the window, pretreated at 400 °C under vacuum for 1 h, and then cooled to room temperature for spectral analysis.

[0050] The benzene alkylation reactions in the embodiments and comparative examples of this invention were carried out in a fixed-bed microreactor. Each reactor was loaded with 1.5 g of the molecular sieve catalyst, purged with N2, heated to 400°C, then the N2 was stopped, and benzene was introduced. After the apparatus stabilized for a certain period, ethylene was introduced as the feedstock, with a benzene-to-ethylene ratio of 4:1 (mol) and an ethylene mass hourly space velocity (HHSV) of 2.0 h⁻¹. -1 After the reaction stabilized, the liquid reaction products were collected for analysis, with an ethylene conversion rate of 100%. Gas chromatography analysis conditions: Agilent 8890B chromatograph, FFAP capillary column, FID detector, carrier gas: N2.

[0051] Example 1

[0052] Prepare the raw material slurry according to the following molar ratio: SiO2:Al2O3:Na2O:n-Butylamine:H2O=1:0.005:0.30:0.3:30. Weigh 0.68 g of aluminum sulfate and dissolve it in 50 mL of deionized water to form a solution. Then add 4.8 g of sodium hydroxide to the solution and mix thoroughly. Next, add 4.38 g of n-butylamine and mix thoroughly to prepare solution A. Then weigh 30 g of silica sol (SiO2 content 40%) and add 40 mL of deionized water to prepare slurry B. Add B to A and mix thoroughly to obtain colloid C. Stir and age at room temperature for 1.5 hours. Then transfer the material to a stainless steel reactor, seal the reactor, and heat to 180°C. Crystallize under hydrothermal conditions for 24 hours. After that, rapidly cool to room temperature. Weigh 25 g of 0.05 mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution and add it to the reactor. Mix thoroughly and seal the reactor. Heat to 110°C and treat under hydrothermal conditions for 48 hours. The product was centrifuged and washed with water until the pH of the supernatant was <8. The product was then transferred to an oven and dried at 120°C for 6 hours. The sample was then transferred to a muffle furnace and calcined at 550°C in air for 12 hours. The calcined molecular sieve and a 0.1 mol / L ammonium nitrate solution were mixed thoroughly at a solid-liquid weight ratio of 1:5. Ion exchange was then performed at 60°C for 2 hours. After solid-liquid separation, the ion exchange was repeated three times. The mixture was then dried and calcined to obtain the hydrogen-form molecular sieve catalyst sample.

[0053] The properties of the catalyst obtained in this embodiment are shown in Table 1.

[0054] The experimental results of applying the catalyst obtained in this embodiment to the benzene alkylation reaction are shown in Table 2.

[0055] Example 2

[0056] Prepare the raw material slurry according to the following molar ratio: SiO2:Al2O3:Na2O:tetrapropylammonium hydroxide:H2O=1:0.005:0.20:0.3:30. Weigh 0.68 g of aluminum sulfate and dissolve it in 50 mL of deionized water to form a solution. Then add 3.2 g of sodium hydroxide to the solution and mix thoroughly. Next, add 48.7 g of 25% tetrapropylammonium hydroxide solution and mix thoroughly to prepare solution A. Then weigh 30 g of silica sol (SiO2 mass content is 40%) and add 40 mL of deionized water to prepare slurry B. Add B to A and mix thoroughly to obtain colloid C. Stir and age at room temperature for 1.5 hours. Then transfer the material to a stainless steel reactor, seal the reactor, and heat to 180°C. Crystallize under hydrothermal conditions for 24 hours. After that, quickly cool to room temperature. Weigh 30 g of 0.05 mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution and add it to the reactor. Mix thoroughly and seal the reactor. Heat to 130°C and treat under hydrothermal conditions for 24 hours. The product was centrifuged and washed with water until the pH of the supernatant was <8. The product was then transferred to an oven and dried at 120°C for 6 hours. The sample was then transferred to a muffle furnace and calcined at 550°C in air for 12 hours. The calcined molecular sieve and a 0.1 mol / L ammonium nitrate solution were mixed thoroughly at a solid-liquid weight ratio of 1:5. Ion exchange was then performed at 60°C for 2 hours. After solid-liquid separation, the ion exchange was repeated three times. The resulting product was then dried and calcined to obtain the hydrogen-form molecular sieve catalyst sample.

[0057] The properties of the catalyst obtained in this embodiment are shown in Table 1.

[0058] The experimental results of applying the catalyst obtained in this embodiment to the benzene alkylation reaction are shown in Table 2.

[0059] Example 3

[0060] Prepare the raw material slurry according to the following molar ratio: SiO2:Al2O3:Na2O:n-Butylamine:H2O=1:0.003:0.30:0.3:30. Weigh 0.3 g of aluminum sulfate and dissolve it in 50 mL of deionized water to form a solution. Then add 4.8 g of sodium hydroxide to the solution and mix thoroughly. Next, add 4.38 g of n-butylamine and mix thoroughly to prepare solution A. Weigh 30 g of silica sol (SiO2 content 40%) and add 40 mL of deionized water to prepare slurry B. Add B to A and mix thoroughly to obtain colloid C. Stir and age the colloid at room temperature for 1.5 hours. Then transfer the material to a stainless steel reactor, seal the reactor, and heat it to 180°C. Crystallize under hydrothermal conditions for 24 hours. After that, rapidly cool to room temperature. Weigh 35 g of 0.15 mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution and add it to the reactor. Mix thoroughly and seal the reactor. Heat it to 150°C and treat under hydrothermal conditions for 24 hours. The product was centrifuged and washed with water until the pH of the supernatant was <8. The product was then transferred to an oven and dried at 120°C for 6 hours. The sample was then transferred to a muffle furnace and calcined at 550°C in air for 12 hours. The calcined molecular sieve and a 0.1 mol / L ammonium nitrate solution were mixed thoroughly at a solid-liquid weight ratio of 1:5. Ion exchange was then performed at 60°C for 2 hours. After solid-liquid separation, the ion exchange was repeated three times. The resulting product was then dried and calcined to obtain the hydrogen-form molecular sieve catalyst sample.

[0061] The properties of the catalyst obtained in this embodiment are shown in Table 1.

[0062] The experimental results of applying the catalyst obtained in this embodiment to the benzene alkylation reaction are shown in Table 2.

[0063] Example 4

[0064] Prepare the raw material slurry according to the following molar ratio: SiO2:Al2O3:Na2O:tetrapropylammonium hydroxide:H2O=1:0.003:0.2:0.35:30. Weigh 0.3 g of aluminum sulfate and dissolve it in 50 mL of deionized water to form a solution. Then add 3.2 g of sodium hydroxide to the solution and mix thoroughly. Next, add 56.8 g of 25% tetrapropylammonium hydroxide solution and mix thoroughly to prepare solution A. Then weigh 30 g of silica sol (SiO2 mass content is 40%) and add 40 mL of deionized water to prepare slurry B. Add B to A and mix thoroughly to obtain colloid C. Stir and age at room temperature for 1.5 hours. Then transfer the material to a stainless steel reactor, seal the reactor, and heat to 180°C. Crystallize under hydrothermal conditions for 24 hours. After that, quickly cool to room temperature. Weigh 35 g of 0.15 mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution and add it to the reactor. Mix thoroughly and seal the reactor. Heat to 160°C and treat under hydrothermal conditions for 48 hours. The product was centrifuged and washed with water until the pH of the supernatant was <8. The product was then transferred to an oven and dried at 120°C for 6 hours. The sample was then transferred to a muffle furnace and calcined at 550°C in air for 12 hours. The calcined molecular sieve and a 0.1 mol / L ammonium nitrate solution were mixed thoroughly at a solid-liquid weight ratio of 1:5. Ion exchange was then performed at 60°C for 2 hours. After solid-liquid separation, the ion exchange was repeated three times. The resulting product was then dried and calcined to obtain the hydrogen-form molecular sieve catalyst sample.

[0065] The properties of the catalyst obtained in this embodiment are shown in Table 1.

[0066] The experimental results of applying the catalyst obtained in this embodiment to the benzene alkylation reaction are shown in Table 2.

[0067] Comparative Example 1

[0068] According to the proportions in Example 4, 0.3 g of aluminum sulfate was weighed and dissolved in 50 mL of deionized water to form a solution. Then, 3.2 g of sodium hydroxide was added to the solution, and the mixture was stirred evenly. Next, 56.8 g of 25% tetrapropylammonium hydroxide solution was added, and the mixture was stirred evenly to prepare solution A. Then, 30 g of silica sol (SiO2 mass content of 40%) was weighed and 40 mL of deionized water was added to it to prepare slurry B. B was added to A and stirred evenly to obtain colloid C. The colloid C was stirred and aged at room temperature for 1.5 hours. Then, the material was transferred to a stainless steel reactor, the reactor was sealed, and the reactor was heated to 180°C. Crystallization was carried out under hydrothermal conditions for 24 hours, and then the mixture was rapidly cooled to room temperature. The product was centrifuged and washed with water until the pH value of the supernatant was <8. The product was transferred to an oven and dried at 120°C for 6 hours. Then, the sample was transferred to a muffle furnace and calcined in air at 550°C for 12 hours. The calcined molecular sieve and 0.1 mol / L ammonium nitrate solution were mixed evenly at a solid-liquid weight ratio of 1:5. Then, the mixture was subjected to ion exchange at 60°C for 2 hours. After solid-liquid separation, the ion exchange was repeated 3 times. Finally, the mixture was dried and calcined to obtain a hydrogen-form molecular sieve catalyst sample.

[0069] The properties of the catalysts obtained in this comparative example are shown in Table 1.

[0070] The experimental results of applying the catalyst obtained in this comparative example to the benzene alkylation reaction are shown in Table 2.

[0071] Comparative Example 2

[0072] According to the proportions in Example 4, 0.3 g of aluminum sulfate was weighed and dissolved in 50 mL of deionized water to form a solution. Then, 3.2 g of sodium hydroxide was added to the solution and mixed thoroughly. Next, 56.8 g of 25% tetrapropylammonium hydroxide solution was added and mixed thoroughly to prepare solution A. Then, 30 g of silica sol (SiO2 mass content of 40%) was weighed and 40 mL of deionized water was added to it to prepare slurry B. B was added to A and mixed thoroughly to obtain colloid C. The colloid C was stirred and aged at room temperature for 1.5 hours. Then, the material was transferred to a stainless steel reactor, the reactor was sealed, and the reactor was heated to 180°C. Crystallization was carried out under hydrothermal conditions for 24 hours. After that, the mixture was rapidly cooled to room temperature, the product was centrifuged, and washed with water until the pH value of the supernatant was <8. The product was transferred to an oven and dried at 120°C for 6 hours. Then, the sample was transferred to a muffle furnace and calcined in air at 550°C for 12 hours. The calcined molecular sieve and 0.1 mol / L ammonium nitrate solution were mixed evenly at a solid-liquid weight ratio of 1:5. Ion exchange was then performed at 60℃ for 2 hours. After solid-liquid separation, the ion exchange was repeated three times. The resulting sample was then dried and calcined to obtain a hydrogen-form molecular sieve catalyst. 4 g of the prepared hydrogen-form molecular sieve was weighed and mixed with 20 g of 0.15 mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution. The mixture was stirred evenly and heated to 90℃ under hydrothermal conditions for 12 hours. After solid-liquid separation, drying, and calcination, the final product was obtained.

[0073] The properties of the catalysts obtained in this comparative example are shown in Table 1.

[0074] The experimental results of applying the catalyst obtained in this comparative example to the benzene alkylation reaction are shown in Table 2.

[0075] Comparative Example 3

[0076] According to the proportions in Example 4, 0.3 g of aluminum sulfate was weighed and dissolved in 50 mL of deionized water to form a solution. Then, 3.2 g of sodium hydroxide was added to the solution and mixed thoroughly. Next, 56.8 g of 25% tetrapropylammonium hydroxide solution was added and mixed thoroughly to prepare solution A. Then, 30 g of silica sol (SiO2 mass content of 40%) was weighed and 40 mL of deionized water was added to it to prepare slurry B. B was added to A and mixed thoroughly to obtain colloid C. The colloid C was stirred and aged at room temperature for 1.5 hours. Then, the material was transferred to a stainless steel reactor, the reactor was sealed, and the reactor was heated to 180°C. Crystallization was carried out under hydrothermal conditions for 24 hours. After that, the mixture was rapidly cooled to room temperature. 35 g of 0.15 mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution was weighed and added to the reactor. The mixture was stirred thoroughly, the reactor was sealed, and the reactor was heated to 90°C. The mixture was then treated under hydrothermal conditions for 48 hours. The product was centrifuged and washed with water until the pH of the supernatant was <8. The product was then transferred to an oven and dried at 120°C for 6 hours. The sample was then transferred to a muffle furnace and calcined at 550°C in air for 12 hours. The calcined molecular sieve and a 0.1 mol / L ammonium nitrate solution were mixed thoroughly at a solid-liquid weight ratio of 1:5. Ion exchange was then performed at 60°C for 2 hours. After solid-liquid separation, the ion exchange was repeated three times. The resulting product was then dried and calcined to obtain the hydrogen-form molecular sieve catalyst sample.

[0077] The properties of the catalysts obtained in this comparative example are shown in Table 1.

[0078] The experimental results of applying the catalyst obtained in this comparative example to the benzene alkylation reaction are shown in Table 2.

[0079] Table 1 Properties of the catalysts obtained in each example

[0080]

[0081] As can be seen from Table 1, the outer surface of the catalysts of the present invention does not contain aluminum, and the surface silicon content is also reduced after treatment, indicating that partial desilication also occurred on the surface. After the framework silicon was removed, condensation occurred on the surface, and the number of silanol species increased. Based on Comparative Example 1, the framework O / Si ratio was 2.2. The increase in the surface O / Si ratio of the catalysts obtained in the examples is considered to be contributed by the surface silanol species.

[0082] Table 2 Results of using various catalysts in benzene alkylation reactions

[0083]

[0084] Note*: Polyethylbenzene refers to diethylbenzene and a small amount of triethylbenzene.

[0085] As shown in Table 2, when the catalysts of the present invention are used in the benzene alkylation reaction with an ethylene conversion rate of 100%, the ratio of ethylbenzene to polyethylbenzene is significantly higher than that of the catalysts of Comparative Examples 1-3. This indicates that the catalyst of the present invention can effectively reduce the formation of polyethylbenzene, thereby increasing the yield of the main product ethylbenzene.

[0086] Figure 1 The images show the hydroxyl infrared spectra of Example 4 and Comparative Examples 1, 2, and 3, with wavenumbers around 3744 cm⁻¹. -1 The nearby peaks correspond to the silanol groups on the outer surface of the sample (indicated by the dashed line), with a wavenumber of 3728 cm⁻¹. -1 The nearby peaks correspond to silanol groups from lattice defects within the sample. Figure 1 As can be seen, the surface silanol signal peak (wavenumber 3744 cm⁻¹) of the sample of Example 4 prepared by the method of the present invention is present. -1 The signal peak was significantly stronger than the internal silanol signal peak (wavenumber 3728 cm⁻¹). -1 In contrast, Comparative Examples 1, 2, and 3 showed that the surface silanol signal peaks were weaker than the internal silanol signal peaks.

Claims

1. Use of a catalyst in the alkylation of benzene with ethylene to produce ethylbenzene, characterized in that, The weight ratio of ethylbenzene / polyethylbenzene in the reaction product is 11-15; the molar ratio of Si / Al in the bulk phase of the catalyst is 50-170, and the outer surface only contains silicon; The preparation method of the catalyst comprises: S1, mixing an aluminum source, water, a mineralizer N, a template M and a silicon source to obtain a raw material solution; S2, crystallizing the raw material solution obtained in step S1 to obtain a crystallized slurry; S3, mixing a disodium ethylenediaminetetraacetate solution with the crystallized slurry obtained in step S2, and performing hydrothermal treatment to obtain a hydrothermally treated slurry; S4, separating, drying and calcining the hydrothermally treated slurry obtained in step S3 to obtain a ZSM-5 molecular sieve catalyst; The hydrothermal treatment is performed in a sealed container, and the hydrothermal treatment conditions are as follows: the treatment temperature is 110-180℃, and the treatment time is 0.5-48 hours.

2. Use according to claim 1, characterized in that, In step S1, the materials are added in the following order: aluminum source, water, mineralizer N, template M and silicon source, and the mixture is obtained to obtain the raw material solution.

3. Use according to claim 1, characterized in that, In step S1, the silicon source is selected from at least one of tetraethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate, n-butyl orthosilicate, silica sol, water glass and white carbon black; the aluminum source is selected from at least one of aluminum isopropoxide, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate and aluminum chloride; the mineralizer N is selected from at least one of NaOH, KOH, Na2CO3 and NaHCO3; and the template M is selected from at least one of diethylamine, triethylamine, n-butylamine and tetrapropylammonium hydroxide. In step S1, the molar ratio of each component of the aluminum source, water, mineralizer N, template M and silicon source is as follows: SiO2 / Al2O3=120-350:1, N / SiO2=0.1-0.5:1, M / SiO2=0.1-0.5:1 and H2O / SiO2=5-50:

1.

4. Use according to claim 1, characterized in that, In step S2, the crystallization temperature of the crystallization is 90-180℃, and the crystallization time is 0.5-48 hours. In step S4, the drying conditions are as follows: the drying temperature is 100-180℃, the drying time is 1-48 hours; the calcination temperature is 450-650℃, and the calcination time is 1-72 hours.

5. Use according to claim 4, characterized in that, In step S2, the crystallization temperature of the crystallization is 100-160℃, and the crystallization time is 0.5-32 hours.

6. The use according to claim 1, characterized in that, In step S3, the concentration of the disodium ethylenediaminetetraacetate solution is 0.05mol / L-0.5mol / L, and the weight ratio of the disodium ethylenediaminetetraacetate solution to the crystallized slurry obtained in step S2 is 1:1-10:

1. In step S3, the hydrothermal treatment conditions are as follows: the treatment temperature is 110-160℃, and the treatment time is 0.5-24 hours.

7. The use according to claim 1, characterized in that, The total specific surface area of the catalyst is 340-400 m 2 / g, and the external specific surface area is 51-100 m 2 / g.

8. Use according to claim 7, characterized in that, The external specific surface area of the catalyst accounts for 15%-25% of the total specific surface area.

9. The use according to claim 1, characterized in that, In the catalyst, the structures in which silicon exists in the outer surface include -Si-O-Si- and -Si-OH; and the O / Si atomic ratio of the outer surface of the catalyst is at least 10%-50% higher than the O / Si atomic ratio of the bulk phase.

10. Use according to claim 9, characterized in that, The O / Si atomic ratio of the outer surface of the catalyst is at least 25-45% higher than the O / Si atomic ratio of the bulk phase. The O / Si atomic ratio of the outer surface of the catalyst is at least 25-45% higher than the O / Si atomic 11. Use according to claim 1, characterized in that, The reaction conditions of the application are as follows: benzene to olefin molar ratio is 1:1-10:1; ethylene weight hourly space velocity is 0.5h -1 -5.0h -1 ; reaction temperature is 300℃-400℃.

12. Use according to claim 11, characterized in that, The reaction conditions of the application are as follows: benzene to olefin molar ratio is 1 : 1-5: 1; ethylene weight hourly space velocity is 0.5h -1 -2.0h -1 .

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