A catalyst for co-production of ethylbenzene and p-diethylbenzene, its preparation method and application

Abstract

The application provides a catalyst for co-production of ethylbenzene and p-diethylbenzene, a preparation method and application thereof, and belongs to the field of catalysts, and solves the defects of poor selectivity, low reaction activity and short service life of the catalyst for co-production of ethylbenzene and p-diethylbenzene in the prior art.The catalyst for co-production of ethylbenzene and p-diethylbenzene has a silicon-boron molar ratio Si / B of 300-1000, preferably 400-800;the ratio of the amount of B acid on the outer surface of the catalyst to the total amount of B acid is 0.01-0.05, preferably 0.02-0.04;and the loading amount of magnesium is 0.5-6% by weight, preferably 1-4%.The catalyst has high reaction activity, p-diethylbenzene selectivity and stability.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a catalyst for the co-production of ethylbenzene and p-diethylbenzene, its preparation method, and its application. Background Technology

[0002] p-Diethylbenzene is a high-value-added organic chemical raw material, mainly used as a desorbent in the production of p-xylene, a modifier for polyethylene, an ion exchange resin, and a crosslinking agent. Currently, the main industrial methods for producing p-diethylbenzene include direct synthesis and adsorption separation. Direct synthesis is further divided into ethylbenzene disproportionation and ethylbenzene alkylation. Both ethylbenzene alkylation and disproportionation methods require ethylbenzene as an important organic raw material. However, the industrial production of ethylbenzene generates a large amount of diethylbenzene byproducts, accounting for 10%–20% of the total ethylbenzene content. These diethylbenzenes have three isomers: o-diethylbenzene, m-diethylbenzene, and p-diethylbenzene, whose composition approaches thermodynamic equilibrium. In actual industrial production, this portion of diethylbenzene is alkylated with benzene to recover ethylbenzene, but this increases reaction energy consumption. If the diethylbenzene produced during the production of ethylbenzene is mainly para-diethylbenzene, and para-diethylbenzene is produced simultaneously with the production of ethylbenzene, it can be directly recycled without undergoing an alkyl transfer reaction, thus reducing production costs and energy consumption.

[0003] ZSM-5 molecular sieves have attracted widespread attention due to their excellent shape-selective catalytic performance. Within the pores of ZSM-5, only molecules with smaller kinetic diameters can be generated at the acidic active sites due to steric hindrance, giving the molecular sieve its shape-selective ability. However, the outer surface of the molecular sieve also contains numerous acidic active centers. During the reaction, due to the loss of pore confinement, reactants or products can undergo isomerization reactions at the acidic sites on the outer surface, generating ortho, meta, and para isomers, thus affecting the selectivity of the reaction.

[0004] To modify and alter the acidic sites on the outer surface of ZSM-5 and improve its shape-selective catalytic activity, numerous methods have been proposed over the past 20 years, including chemical vapor deposition (CVD), chemical liquid deposition (CLP), and impregnation with metal compounds. However, HL Janardhan et al. (Applied Catalysis A:General, 2014, 471:12-18) modified ZSM-5 molecular sieves by impregnating them with phosphoric acid (P). They found that the bridging hydroxyl groups in the pores of the P-impregnated ZSM-5 molecular sieve interacted with phosphate, generating L-acid sites and enhancing the catalyst's shape selectivity. However, phosphate modification can clog micropores, leading to reduced catalytic activity, decreased reaction stability, and shortened catalyst lifespan. CN90101436.2 discloses a method for synthesizing a p-diethylbenzene shape-selective catalyst, which modifies ZSM-5 molecular sieves using Al and Mg metal ions. While this method significantly improves the shape-selective catalytic ability of molecular sieves, it suffers from low ethylbenzene conversion, high metal ion usage, and low catalyst activity, short lifespan, and poor regeneration repeatability in the alkylation of ethylbenzene ethanol. CN1927463A modifies the outer surface of ZSM-5 molecular sieves with ethyl silicate. This method has the advantage of requiring only one loading for micron-sized ZSM-5, achieving para-selectivity of over 90%. However, while modifying acidic sites on the outer surface, it partially blocks pores, significantly reducing catalyst activity and lifespan. CN102895989A provides a method for removing acidity from the outer surface of molecular sieve catalysts. Using 3,5-dimethylbromobenzene, magnesium strips, iodine, and tetrahydrofuran as raw materials, a Grignard reagent is prepared under an anhydrous and oxygen-free atmosphere. A hexane suspension of molecular sieves is then added to the Grignard reagent under nitrogen purging to obtain an MgO-modified ZSM-5 molecular sieve catalyst. In the ethylbenzene disproportionation reaction, the reactivity is low, the preparation process is cumbersome, and the service life is short.

[0005] In the method for co-producing ethylbenzene and p-diethylbenzene by alkylation of benzene and ethylene, since benzene molecules need to first alkylate with ethylene to generate ethylbenzene, and then undergo secondary alkylation with ethylene to generate p-diethylbenzene, the catalyst requires more acidic active sites. However, the shape-selective molecular sieve catalysts reported in the aforementioned patents and published literature have fewer acidic active sites due to the addition of a certain amount of binder, which can block the pores of the molecular sieve, increase diffusion resistance, affect the diffusion performance of the reaction, and lead to poor reaction stability. At the same time, the use of a certain amount of metal or non-metal oxides for impregnation further reduces the overall acidic centers of the catalyst, resulting in a large number of acidic sites being covered and reducing the reaction activity. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of poor selectivity, low catalytic activity and short service life of catalysts for the co-production of ethylbenzene and p-diethylbenzene in the prior art, thereby providing a catalyst for the co-production of ethylbenzene and p-diethylbenzene, its preparation method and application.

[0007] To this end, the present invention provides the following technical solution.

[0008] On one hand, the present invention discloses a catalyst for the co-production of ethylbenzene and p-diethylbenzene, comprising a boron-modified ZSM-5 molecular sieve with magnesium oxide supported on its surface, wherein the silicon-boron molar ratio Si / B is 300-1000, preferably 400-800, more preferably 600-800; the ratio of the amount of Brønsted acid on the outer surface of the catalyst to the total amount of Brønsted acid is 0.01-0.05, preferably 0.02-0.04; and the magnesium loading, by weight percentage and based on elemental magnesium, is 0.5-6%, preferably 1-4%.

[0009] In this invention, the total Brønsted acid content was determined by 2,6-di-tert-butylpyridine infrared spectroscopy, and the Brønsted acid content on the outer surface was determined by pyridine infrared spectroscopy. The magnesium loading was obtained by ICP analysis.

[0010] To avoid being limited by theory, this invention introduces boron (B) atoms into the catalyst. The introduction of B atoms can occupy the sites of Al atoms, regulating their placement and preventing their outward migration during crystallization. This reduces the number of strong acid sites on the catalyst's outer surface, allowing for the use of less MgO to cover these acidic sites, thus avoiding catalyst metal poisoning that could lead to reduced or deactivated activity. This increases the catalyst's shape-selective alkylation ability, reaction activity, and lifetime. The MgO loading on the catalyst's outer surface reduces the size of the molecular sieve pores, suppressing ortho- and meta-diethylbenzene, and improving catalyst selectivity. The catalyst provided by this invention exhibits high selectivity, high reactivity, and a long lifespan.

[0011] In a specific embodiment of the present invention, the silicon-to-aluminum molar ratio (SiO2 / Al2O3) is 100–500. If the silicon-to-aluminum molar ratio is too low, it will result in an excessive number of acidic sites on the catalyst surface, leading to poor catalyst selectivity; if the silicon-to-aluminum molar ratio is too high, it will result in an excessively low total number of acidic sites on the catalyst, reducing catalyst activity. The silicon-to-aluminum molar ratio (SiO2 / Al2O3) is preferably 120–300, more preferably 120–200.

[0012] In a specific embodiment of the present invention, the boron-modified ZSM-5 molecular sieve is prepared by mixing, molding, crystallizing, and exchanging raw materials including ZSM-5 molecular sieve powder and boric acid; the crystallinity of the catalyst is greater than 90% of the crystallinity of the ZSM-5 molecular sieve powder. Since the catalyst of the present invention converts the binder into a molecular sieve, when the crystallinity is greater than 90%, it is considered that most of the binder has been converted into a molecular sieve. Preferably, the crystallinity of the ZSM-5 molecular sieve powder is above 98%.

[0013] As a specific embodiment of the present invention, the boron-modified ZSM-5 molecular sieve is a binder-free boron-modified ZSM-5 molecular sieve.

[0014] This invention also discloses a method for preparing a catalyst for the co-production of ethylbenzene and p-diethylbenzene, comprising the following steps:

[0015] Step 1: Prepare ZSM-5 molecular sieve catalyst precursor by mixing raw materials, wherein the raw materials include ZSM-5 molecular sieve powder and boric acid;

[0016] Step 2: Boron-modified ZSM-5 molecular sieve is prepared by ammonium exchange;

[0017] Step 3: Impregnate the solid product from Step 2 in a magnesium salt solution, then dry and calcine it to obtain the target catalyst (boron-modified ZSM-5 molecular sieve with magnesium oxide loaded on its surface).

[0018] As a specific embodiment of the present invention, a further step between step 1 and step 2 is: crystallizing the ZSM-5 molecular sieve catalyst precursor to obtain a binder-free ZSM-5 molecular sieve catalyst. After crystallization in step 2 of the present invention, the structure is no longer a two-phase structure of internal ZSM-5 molecular sieve core and external binder component, but rather a single molecular sieve core. This indicates that the binder, under the action of the template agent, transforms into molecular sieve crystals through crystallization. Figure 3 As shown, it will not clog the molecular sieve and eliminates the influence of the binder on the molecular sieve.

[0019] In a specific embodiment of the present invention, the ZSM-5 molecular sieve catalyst precursor, alkali source, organic template agent, and water are mixed and crystallized to separate the solid. The solid is then dried and calcined to obtain a binder-free ZSM-5 molecular sieve catalyst. The drying temperature is 100–140°C, and the time is 4–24 h; the calcination temperature is 500–600°C, and the time is 4–8 h.

[0020] As a specific embodiment of the present invention, the mass percentage of the ZSM-5 molecular sieve catalyst precursor dry base, alkali source, organic template agent and water is 1:(0.03~0.1):(0.3~1.5):(0.5~4), preferably 1:(0.04~0.08):(0.8~1.5):(1~3).

[0021] As a specific embodiment of the present invention, the crystallization conditions include: a crystallization temperature of 150–170°C, preferably 155–165°C; if the crystallization temperature is too high or too low, the binder and boric acid in the ZSM-5 molecular sieve catalyst precursor will not be able to crystallize into a molecular sieve. The crystallization time is 12–48 h, preferably 20–30 h.

[0022] As a specific embodiment of the present invention, the alkali source is an alkali with an alkali metal or alkaline earth metal as the cation; more preferably, the alkali source is at least one of sodium hydroxide, potassium hydroxide and barium hydroxide.

[0023] As a specific embodiment of the present invention, the organic template agent is at least one of tetrapropylammonium hydroxide, ethylamine, n-propylamine and isopropylamine.

[0024] After step 2, binder-free boron-modified ZSM-5 molecular sieve catalyst was prepared.

[0025] This invention synthesizes binder-free ZSM-5 molecular sieve catalysts using a dry gel method. The introduced boron atoms can regulate the placement of Al atoms. Then, the target catalyst is obtained by controlling the acidic sites on the catalyst's outer surface through ammonium exchange and magnesium salt impregnation. Boron elements prevent the outward migration of Al atoms, reducing strong acid sites; after crystallization, Mg is loaded to reduce the pore size and suppress ortho- and meta-diethylbenzene.

[0026] As a specific embodiment of the present invention, the raw materials in step 1 also include a binder, a pore-forming agent and an aqueous nitric acid solution.

[0027] As a specific embodiment of the present invention, step 1 includes mixing ZSM-5 molecular sieve raw powder with binder, boric acid, pore-forming agent and nitric acid aqueous solution, molding and drying to obtain ZSM-5 molecular sieve catalyst precursor.

[0028] As a specific embodiment of the present invention, after ammonium exchange in step 2, drying and calcination are also included.

[0029] As a specific embodiment of the present invention, the impregnation in step 3 includes impregnating the solid product after roasting in step 2 with the magnesium salt solution by an equal-volume impregnation method.

[0030] In step 3, the impregnation is carried out using the equal volume impregnation method. Based on the magnesium oxide loading on the catalyst, the required magnesium salt is calculated and weighed, dissolved in water, and prepared into the corresponding magnesium salt solution.

[0031] In a specific embodiment of the present invention, the mass ratio of ZSM-5 molecular sieve raw powder dry base to binder, boric acid, pore-forming agent and nitric acid aqueous solution is 1:(0.1~1):(0.04~0.1):(0.02~0.1):(0.2~3), preferably 1:(0.2~0.6):(0.05~0.08):(0.02~0.07):(1~2). Adding too little boric acid will result in too little boron entering the molecular sieve framework, making it impossible to control the placement of aluminum elements; adding too much boric acid will result in too much boron entering the framework, which will increase the acidity of the catalyst.

[0032] As a specific embodiment of the present invention, the pore-forming agent is selected from at least one of guar gum powder and methylcellulose.

[0033] As a specific embodiment of the present invention, the binder is selected from at least one of silica sol, silica fume and silica powder.

[0034] As a specific embodiment of the present invention, the mass concentration of the nitric acid aqueous solution is 0.5% to 5%, preferably 1% to 3%.

[0035] The binder in the bonding process (i.e., step 1) of this invention uses only a silicon source and does not use an aluminum source, and does not add additional acidic sites on the outer surface. At the same time, crystallization causes the binder to crystallize into molecular sieves, giving the catalyst of this invention a richer microporous structure, which can enhance the diffusion of reactants and products in the co-production of ethylbenzene and p-diethylbenzene.

[0036] In a specific embodiment of the present invention, in step 1, the silicon-aluminum molar ratio (SiO2 / Al2O3) of the ZSM-5 molecular sieve raw powder is 100-300.

[0037] In a specific embodiment of the present invention, in step 1, the dry basis of ZSM-5 molecular sieve raw powder accounts for 50% to 85% of the ZSM-5 molecular sieve catalyst precursor by weight percentage. If the proportion of dry basis of ZSM-5 molecular sieve raw powder is too low, the catalyst activity will be low; if the proportion is too high, there will be too little binder, and it will be impossible to bond and form.

[0038] In a specific embodiment of the present invention, in step 1, the molding method is to use a four-leaf clover perforated plate for extrusion molding; the drying temperature is 100℃~140℃.

[0039] As a specific embodiment of the present invention, in step 2, the ammonium exchange process includes: mixing the binder-free ZSM-5 molecular sieve catalyst with an ammonium salt solution to perform ammonium ion exchange.

[0040] As a specific embodiment of the present invention, the mass ratio of the binder-free ZSM-5 molecular sieve catalyst dry base: ammonium salt: water is 1:(0.5~2):(5~20), preferably 1:(0.8~1.5):(8~15);

[0041] As a specific embodiment of the present invention, the ammonium ion exchange temperature is 25-95°C, preferably 50-90°C, and the ammonium ion exchange time is 0.5-3h, preferably 1-2h; preferably, the ammonium ion exchange process is continuously stirred.

[0042] In a specific embodiment of the present invention, the ammonium exchange process is repeated 1 to 4 times.

[0043] In a specific embodiment of the present invention, in step 2, the ammonium salt is at least one of ammonium chloride, ammonium acetate, ammonium nitrate and ammonium sulfate.

[0044] In a specific embodiment of the present invention, in step 2, the drying temperature is 100-140℃ and the time is 4-24h; the calcination temperature is 500-600℃ and the time is 4-8h.

[0045] As a specific embodiment of the present invention, in step 3, the magnesium salt is at least one of magnesium acetate, magnesium sulfate, magnesium nitrate, and magnesium chloride, and the impregnation time is 4 to 48 hours. If the impregnation time is too long, some magnesium elements may enter the molecular sieve channels and poison the acidic sites in the channels. Preferably, it is 10 to 30 hours.

[0046] In a specific embodiment of the present invention, in step 3, the temperature is 100℃~140℃ for 4h~24h; the calcination temperature is 500℃~600℃ for 4h~8h.

[0047] Application of the catalyst for co-producing ethylbenzene and p-diethylbenzene as described above, or the catalyst for co-producing ethylbenzene and p-diethylbenzene prepared according to the above preparation method, in the co-production of ethylbenzene and p-diethylbenzene.

[0048] A method for co-producing ethylbenzene and p-diethylbenzene, using benzene and ethylene as raw materials, and employing the above-mentioned catalyst for co-producing ethylbenzene and p-diethylbenzene or the catalyst for co-producing ethylbenzene and p-diethylbenzene prepared according to the above preparation method for contact reaction to co-produce ethylbenzene and p-diethylbenzene.

[0049] As a specific embodiment of the present invention, the reaction temperature is 340-440°C, preferably 360-420°C;

[0050] In a specific embodiment of the present invention, the reaction pressure is 0.5 to 2 MPa, preferably 0.8 to 1.6 MPa;

[0051] As a specific embodiment of the present invention, the molar ratio of benzene to ethylene is 1 to 18, preferably 4 to 12;

[0052] In a specific embodiment of the present invention, the mass hourly space velocity (MSV) based on ethylene is 0.2–4 h⁻¹. -1 Preferably 1 to 3 hours -1 .

[0053] The technical solution of this invention has the following advantages:

[0054] 1. The catalyst for the co-production of ethylbenzene and p-diethylbenzene provided by this invention introduces boron (B). The introduction of B atoms can occupy the positions of Al atoms, regulate the placement of Al atoms, prevent the outward migration of Al atoms during crystallization, reduce the strong acid sites on the catalyst surface, and allow for the use of less MgO to cover the acidic sites on the outer surface, thereby avoiding catalyst metal poisoning, which could lead to reduced or deactivated catalyst activity. This increases the catalyst's shape-selective alkylation ability, reaction activity, and catalyst lifetime. The MgO loading on the outer surface of the catalyst of this invention can reduce the size of the molecular sieve pores, suppress ortho- and meta-diethylbenzene, and improve catalyst selectivity. The catalyst provided by this invention exhibits high selectivity, high reactivity, and long service life.

[0055] 2. The method for preparing a catalyst for the co-production of ethylbenzene and p-diethylbenzene provided by this invention involves introducing boron (B) atoms to regulate the placement of Al atoms, and then controlling the acidic sites on the catalyst's outer surface through ammonium exchange and magnesium salt impregnation to obtain the target catalyst. B elements prevent the outward migration of Al atoms, reducing strong acid sites; after crystallization, Mg is loaded to reduce the pore size and suppress ortho- and meta-diethylbenzene; crystallization transforms the binder into a molecular sieve, increasing the molecular sieve content of the catalyst and giving it a richer microporous structure. The crystallization of the binder into a molecular sieve also eliminates pore blockage of the molecular sieve, thus improving the catalyst's reactivity and stability. In the bonding process (i.e., step 1) of this invention, only a silicon source is used as the binder, not an aluminum source, without adding additional acidic sites on the outer surface. Simultaneously, it possesses a richer microporous structure, which enhances the diffusion of reactants and products during the co-production of ethylbenzene and p-diethylbenzene.

[0056] 3. The method for co-producing ethylbenzene and p-diethylbenzene provided by the present invention can achieve a single-pass ethylene conversion rate of 70-100%, preferably 90-100%; a total ethyl selectivity of 90-100%, preferably 95-100%; and a para-selectivity of diethylbenzene of 93-100%. In addition, since the present invention eliminates the influence of the binder on the molecular sieve, it can maintain an ethylene conversion rate of more than 90% after 350 hours. Attached Figure Description

[0057] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0058] Figure 1 These are the reaction time-ethylene conversion curves for Example 1 and Comparative Example 2;

[0059] Figure 2 These are transmission electron microscope images of ZSM-5 molecular sieve raw powder;

[0060] Figure 3 These are transmission electron microscope images of Example 1, Cata-1;

[0061] Figure 4 This is a transmission electron microscope image of Comparative 2Cata-1b. Detailed Implementation

[0062] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0063] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0064] Probe reaction experiments of the samples were conducted in a fixed-bed microreactor. The catalyst loading was 50 mg, and the feed rates of liquid cumene and liquid 1,3,5-triisopropylbenzene were 1 μL. The reaction was carried out at atmospheric pressure, a vaporization temperature of 150 °C, and a reaction temperature of 350 °C. The products were analyzed by gas chromatography (Agilent GC 7890) equipped with a flame ionization detector (FID). The chromatographic column was an HP-FFAP, argon was used as the carrier gas, and the flow rate was 20 mL / min. -1 And calculate according to the following formula:

[0065] Cumene conversion rate = (Total product - Cumene) / Total amount of all product components × 100%

[0066] Triisopropylbenzene conversion rate = (Total product - Triisopropylbenzene) / Total amount of all product components × 100%

[0067] The conversion rate of cumene represents the overall acidity of the catalyst; the higher the conversion rate, the higher the overall acidity. The conversion rate of triisopropylbenzene represents the acidity of the catalyst's outer surface; the higher the conversion rate, the higher the acidity of the outer surface.

[0068] Example 1

[0069] Example 1 provides a catalyst Cata-1, which comprises a boron-modified ZSM-5 molecular sieve with magnesium oxide supported on its surface. Cata-1 has a silicon-to-boron ratio of 600, a silicon-to-aluminum ratio of 130, a ratio of external surface Brønsted acid content to total Brønsted acid content of 0.03, a crystallinity of 99%, and a magnesium loading of 1.3%.

[0070] The preparation method of Cata-1 is as follows:

[0071] Step 1: Weigh 100g of ZSM-5 molecular sieve (Sinopec Catalyst Company SEB-08, SiO2 / Al2O3 molar ratio of 100, crystallinity of 98%), and mix it evenly with silica sol (SiO2 content 40wt%), boric acid, guar gum powder and 2wt% nitric acid aqueous solution in a mass ratio of 1:0.2:0.05:0.02:1. Then, extrude the mixture into strips using a four-leaf clover perforated plate, dry it at 120℃, and cool it to room temperature to obtain the ZSM-5 molecular sieve catalyst precursor.

[0072] Step 2: The ZSM-5 molecular sieve catalyst precursor obtained in Step 1, sodium hydroxide, ethylamine, and water are placed in a crystallization vessel at a mass percentage ratio of 1:0.05:1.5:2. The crystallization temperature is 150℃, and the crystallization time is 24h. The crystallized product is separated into solid and liquid phases, then dried at 120℃ for 5h, and calcined at 550℃ for 4h to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0073] Step 2: The binderless ZSM-5 molecular sieve catalyst is mixed with an aqueous solution of ammonium chloride in a water bath at 90°C for 1 hour according to the mass ratio of molecular sieve (dry basis): ammonium chloride: water = 1:1:10. After centrifugation, the mixture is centrifuged twice, centrifuged, washed with water, dried at 120°C for 5 hours, and calcined at 550°C for 4 hours.

[0074] Step 3: Take a portion of the calcined catalyst from Step 2 (e.g., 20g), impregnate it in an equal volume of a 10% magnesium acetate aqueous solution for 12 hours, dry it at 100°C for 8 hours, and calcine it at 550°C for 6 hours. The resulting modified binder-free ZSM-5 molecular sieve catalyst is denoted as Cata-1.

[0075] Example 2

[0076] Example 2 provides a catalyst Cata-2, which comprises a boron-modified ZSM-5 molecular sieve with magnesium oxide supported on its surface. Cata-2 has a silicon-to-boron ratio of 800, a silicon-to-aluminum ratio of 180, a ratio of external surface Brønsted acid content to total Brønsted acid content of 0.03, a crystallinity of 99%, and a magnesium loading of 1.3%.

[0077] Step 1: Weigh 50g of ZSM-5 molecular sieve (Sinopec Catalyst Company SEB-08, SiO2 / Al2O3 molar ratio of 100, crystallinity of 98%), and mix it evenly with silica sol (SiO2 content 40wt%), boric acid, guar gum powder and 3wt% nitric acid aqueous solution in a mass ratio of 1:0.4:0.08:0.02:1. Then, extrude the mixture into strips using a four-leaf clover perforated plate, dry it at 120℃, and cool it to room temperature to obtain the ZSM-5 molecular sieve catalyst precursor.

[0078] The ZSM-5 molecular sieve catalyst precursor obtained in step 1, sodium hydroxide, ethylamine, and water were placed in a crystallization vessel at a mass percentage ratio of 1:0.05:2:2. The crystallization temperature was 150℃, and the crystallization time was 24h. The crystallized product was separated into solid and liquid phases, dried at 120℃ for 5h, and calcined at 550℃ for 4h to obtain a binder-free ZSM-5 molecular sieve catalyst.

[0079] Step 2: The binderless ZSM-5 molecular sieve catalyst is mixed with an aqueous solution of ammonium nitrate in a 90°C water bath for 1 hour at a mass ratio of molecular sieve (dry basis): ammonium nitrate: water = 1:1:10. The mixture is then centrifuged. This process is repeated twice, followed by centrifugation, washing with water, drying at 120°C for 5 hours, and calcining at 550°C for 4 hours.

[0080] Step 3: Take a portion of the calcined catalyst from Step 2 (e.g., 20g), impregnate it in a 10% magnesium acetate aqueous solution for 12 hours, dry it at 100°C for 8 hours, and calcine it at 550°C for 6 hours. The resulting modified binder-free ZSM-5 molecular sieve catalyst is denoted as Cata-2.

[0081] Example 3

[0082] Example 3 provides a catalyst Cata-3, which comprises a boron-modified ZSM-5 molecular sieve with magnesium oxide supported on its surface. Cata-3 has a silicon-to-boron ratio of 600, a silicon-to-aluminum ratio of 130, a ratio of external surface Brønsted acid content to total Brønsted acid content of 0.02, a crystallinity of 99%, and a magnesium loading of 2.4%.

[0083] The catalyst preparation method in Example 3 is basically the same as that in Example 1, except that in step 3, a portion of the calcined catalyst from step 2 (e.g., 20g) is taken and impregnated in an equal volume of a 12% magnesium nitrate aqueous solution for 6 hours. The filtered solid is then dried at 120°C for 8 hours and calcined at 550°C for 6 hours to obtain the post-modified binder-free ZSM-5 molecular sieve catalyst, denoted as Cata-3.

[0084] Comparative Example 1

[0085] The catalyst preparation method of Comparative Example 1 is basically the same as that of Example 1, except that boric acid is not added, resulting in Cata-1a. Probe reaction experiments were performed on the catalyst sample Cata-1a, and the data are shown in Table 1.

[0086] Cata-1a has a silicon-to-aluminum ratio of 130, a surface Brønsted acid content to total Brønsted acid content ratio of 0.05, a crystallinity of 100%, and a magnesium loading of 1.3%.

[0087] Comparative Example 2

[0088] The catalyst preparation method of Comparative Example 2 is basically the same as that of Example 1, except that crystallization is not performed to obtain Cata-1b.

[0089] Cata-1b has a silicon-to-boron ratio of 600, a silicon-to-aluminum ratio of 130, a surface Brønsted acid content to total Brønsted acid content ratio of 0.10, a crystallinity of 71%, and a magnesium loading of 1.1%.

[0090] Comparative Example 3

[0091] The catalyst preparation method of Comparative Example 3 is basically the same as that of Example 1, except that magnesium oxide is not loaded (i.e. step 3 is not performed) to obtain Cata-1c.

[0092] Cata-1c has a silicon-to-boron ratio of 600, a silicon-to-aluminum ratio of 130, a surface Brønsted acid content to total Brønsted acid content ratio of 0.26, and a crystallinity of 100%.

[0093] Comparative Example 4

[0094] According to the method reported in CN102895989A, the MgO-modified ZSM-5 molecular sieve catalyst Cata-2b was prepared, wherein the mass percentage of MgO was 2%.

[0095] Probe reaction experiments were conducted on catalysts Cata-1, Cata-2, Cata-3, Cata-1a, Cata-1b, Cata-1c, and Cata-2b, respectively. The data are shown in Table 1.

[0096] Catalysts Cata-1, Cata-2, Cata-3, Cata-1a, Cata-1b, Cata-1c, and Cata-2b were respectively loaded into a fixed-bed reactor, with a loading amount of 2g. Benzene and ethylene were used as feedstocks for the reaction, with a benzene flow rate of 66 ml / h, an ethylene flow rate of 2400 ml / h, a benzene to ethylene molar ratio of 7, and an ethylene mass hourly space velocity (WHSV) of 1.5 h⁻¹. -1 The reaction temperature was 380℃ and the reaction pressure was 1.2 MPa. Conversion and selectivity data are shown in Table 2.

[0097] Table 1 Conversion Rate Data

[0098]

[0099] Table 2 Conversion Rate and Selectivity Data

[0100]

[0101] As shown in Table 1, the catalyst for the co-production of ethylbenzene and p-diethylbenzene of this invention possesses both low surface acidity and high overall acidity. As shown in Table 2, when using the catalyst of this invention for the co-production of ethylbenzene and p-diethylbenzene, the selectivity for p-diethylbenzene reaches as high as 98.49%, the ethylene conversion rate reaches 99.43%, and the ethyl selectivity reaches 99.57%. The regeneration cycle of the catalyst of this invention can reach 1000 hours. The catalyst of this invention improves the selectivity for diethylbenzene while maintaining the overall activity of the catalyst, increasing the ethylene conversion rate, and has a long service life.

[0102] Figure 1 The time-ethylene conversion curves for Example 1 and Comparative Example 2 are shown below. Figure 1 As can be seen, the catalyst of the present invention can still maintain an ethylene conversion rate of over 90% after 350 hours. The catalyst prepared by the method of the present invention has a much longer service life than the catalyst containing binder and has stronger reaction stability.

[0103] Figures 2-4 The images show transmission electron microscopy (TEM) images of ZSM-5 molecular sieve raw powder, Example 1 Cata-1, and Comparative Example 2 Cata-1b, respectively. Comparative Example 2 has a two-phase structure, consisting of an internal ZSM-5 molecular sieve core and an external binder component. The ZSM-5 molecular sieve raw powder and the sample from Example 1 have only a single molecular sieve core, indicating that the binder crystallizes into molecular sieve crystals under the action of the template agent.

[0104] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0105] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A catalyst for the co-production of ethylbenzene and p-diethylbenzene, characterized in that, The catalyst comprises a boron-modified ZSM-5 molecular sieve with magnesium oxide supported on its surface, wherein, The silicon-boron molar ratio (Si / B) is 300~1000; The ratio of the amount of Brønsted acid on the outer surface of the catalyst to the total amount of Brønsted acid is 0.01~0.05; The magnesium loading is 0.5% to 6% by weight, based on elemental magnesium content. The boron-modified ZSM-5 molecular sieve is prepared by mixing and molding raw materials including ZSM-5 molecular sieve powder and boric acid, followed by ammonium exchange.

2. The catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 1, characterized in that, The silicon-to-aluminum molar ratio (SiO2 / Al2O3) is 100–500; and / or The crystallinity of the catalyst is greater than 90% of the crystallinity of the ZSM-5 molecular sieve powder; and / or The silicon-to-boron molar ratio (Si / B) is 400–800; and / or The ratio of the amount of Brønsted acid on the outer surface of the catalyst to the total amount of Brønsted acid is 0.02~0.04; and / or The magnesium loading is 1-4% by weight, based on elemental magnesium.

3. The catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 1, characterized in that, The silicon-to-aluminum molar ratio (SiO2 / Al2O3) is 120–300; and / or The crystallinity of the catalyst is greater than 98% of the crystallinity of the ZSM-5 molecular sieve powder; and / or The silicon-boron molar ratio (Si / B) is 600~800.

4. The catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 1, characterized in that, The silicon-aluminum molar ratio SiO2 / Al2O3 is 120~200.

5. The catalyst for the co-production of ethylbenzene and p-diethylbenzene according to any one of claims 1-4, characterized in that, The boron-modified ZSM-5 molecular sieve is a binder-free boron-modified ZSM-5 molecular sieve.

6. A method for preparing a catalyst for the co-production of ethylbenzene and p-diethylbenzene according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Prepare ZSM-5 molecular sieve catalyst precursor by mixing the raw materials; Step 2: Boron-modified ZSM-5 molecular sieve is prepared by ammonium exchange; Step 3: Impregnate the boron-modified ZSM-5 molecular sieve from Step 2 in a magnesium salt solution, then dry and calcine it to obtain a boron-modified ZSM-5 molecular sieve with magnesium oxide loaded on its surface. The raw materials in step 1 include ZSM-5 molecular sieve powder and boric acid; Between steps 1 and 2, the process further includes: crystallizing the ZSM-5 molecular sieve catalyst precursor to obtain a binder-free ZSM-5 molecular sieve catalyst.

7. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 6, characterized in that, The raw materials also include binders, pore-forming agents, and aqueous nitric acid solution; and / or Step 1 includes mixing ZSM-5 molecular sieve raw powder with binder, boric acid, pore-forming agent and nitric acid aqueous solution, molding, and drying to obtain ZSM-5 molecular sieve catalyst precursor; and / or Step 2, after ammonium exchange, also includes drying and calcination; and / or The impregnation in step 3 includes impregnating the solid product after roasting in step 2 with a magnesium salt solution using an equal-volume impregnation method.

8. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 6 or 7, characterized in that, The silicon-aluminum molar ratio (SiO2 / Al2O3) of the ZSM-5 molecular sieve raw powder is 100~300.

9. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 6 or 7, characterized in that, The ZSM-5 molecular sieve catalyst precursor, alkali source, organic template agent and water were mixed and crystallized to separate the solid. The solid was then dried and calcined to obtain a binder-free ZSM-5 molecular sieve catalyst. and / or Crystallization conditions include: crystallization temperature of 150~170℃, crystallization time of 12~48h; and / or After step 2, binder-free boron-modified ZSM-5 molecular sieve catalyst was prepared.

10. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 9, characterized in that, The mass percentages of the ZSM-5 molecular sieve catalyst precursor (dry basis), alkali source, organic template agent, and water are 1:(0.03~0.1):(0.3~1.5):(0.5~4); and / or Crystallization conditions include: a crystallization temperature of 155~165℃; and / or a crystallization time of 20~30h; and / or The alkali source is an alkali with an alkali metal or alkaline earth metal as the cation; and / or The organic template agent is at least one of tetrapropylammonium hydroxide, ethylamine, n-propylamine, and isopropylamine.

11. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 10, characterized in that, The mass percentages of the ZSM-5 molecular sieve catalyst precursor (dry basis), alkali source, organic template agent, and water are 1:(0.04~0.08):(0.8~1.5):(1~3); and / or The alkali source is at least one of sodium hydroxide, potassium hydroxide, and barium hydroxide.

12. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 6 or 7, characterized in that, In step 1, the mass ratio of ZSM-5 molecular sieve raw powder dry base to binder, boric acid, pore-forming agent and nitric acid aqueous solution is 1:(0.1~1):(0.04~0.1):(0.02~0.1):(0.2~3); and / or The pore-forming agent is selected from at least one of guar gum powder and methylcellulose; and / or The binder is selected from at least one of silica sol, silica fume, and silica powder; and / or The mass concentration of the nitric acid aqueous solution is 0.5% to 5%.

13. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 12, characterized in that, In step 1, the mass ratio of ZSM-5 molecular sieve raw powder dry base to binder, boric acid, pore-forming agent and nitric acid aqueous solution is 1:(0.2~0.6):(0.05~0.08):(0.02~0.07):(1~2); and / or The mass concentration of the nitric acid aqueous solution is 1% to 3%.

14. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 6 or 7, characterized in that, In step 2, ammonium exchange includes: mixing the binder-free ZSM-5 molecular sieve catalyst with an ammonium salt solution to perform ammonium ion exchange.

15. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 14, characterized in that, Binder-free ZSM-5 molecular sieve catalyst, dry basis: ammonium salt: water mass ratio of 1:(0.5~2):(5~20); and / or The ammonium ion exchange temperature is 25~95℃, and the ammonium ion exchange time is 0.5~3h; and / or Continuous stirring during ammonium ion exchange; and / or The ammonium exchange process is repeated 1 to 4 times.

16. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 15, characterized in that, The mass ratio of dry base, ammonium salt, and water of binder-free ZSM-5 molecular sieve catalyst is 1:(0.8~1.5):(8~15).

17. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 6 or 7, characterized in that, In step 3, the magnesium salt is at least one selected from magnesium acetate, magnesium sulfate, magnesium nitrate, and magnesium chloride; and / or In step 3, the soaking time is 4 to 48 hours.

18. The method for preparing the catalyst for the co-production of ethylbenzene and p-diethylbenzene according to claim 17, characterized in that, The soaking time is 10~30 hours.

19. The use of the catalyst for co-producing ethylbenzene and p-diethylbenzene according to any one of claims 1-5 or the catalyst for co-producing ethylbenzene and p-diethylbenzene prepared by the preparation method according to any one of claims 6-18 in the co-production of ethylbenzene and p-diethylbenzene.

20. A method for co-producing ethylbenzene and p-diethylbenzene, characterized in that, Using benzene and ethylene as raw materials, ethylbenzene and p-diethylbenzene are produced by contact reaction using the catalyst for co-production of ethylbenzene and p-diethylbenzene as described in any one of claims 1-5 or the catalyst for co-production of ethylbenzene and p-diethylbenzene prepared by the preparation method according to any one of claims 6-18.

21. The method according to claim 20, characterized in that, The reaction temperature is 340~440℃; and / or The reaction pressure is 0.5~2 MPa; and / or The molar ratio of benzene to ethylene is 1 to 18; and / or The mass hourly space velocity (MSV) based on ethylene is 0.2–4 h⁻¹. -1 .

22. The method according to claim 20, characterized in that, The reaction temperature is 360~420℃; and / or The reaction pressure is 0.8~1.6 MPa; and / or The molar ratio of benzene to ethylene is 4 to 12; and / or The mass hourly space velocity (MSV) based on ethylene is 1–3 h⁻¹. -1 .

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