A small-grain B-acid-rich HZSM-5 molecular sieve and its preparation method

Abstract

The present invention provides a kind of small-grain rich Br acid HZSM 5 molecular sieve and preparation method thereof, the HZSM 5 molecular sieve particle size is less than 500nm, and the HZSM 5 molecular sieve has very high Br acid amount, and Br acid amount is more than 0.8mmol / g.Preparation method comprises the following steps: step 1, silicon source, molecular sieve, water and inorganic base are mixed, and reaction obtains reaction product at a certain temperature;Step 2, silicon source, aluminum source, water, inorganic base are mixed to form a mixture, and the reaction product obtained by step 1 is subsequently added, crystallized, and the crystallized product is washed, dried and roasted to obtain ZSM 5 molecular sieve;Step 3, ZSM 5 molecular sieve is ion exchanged to obtain HZSM 5 molecular sieve.The present invention is adjusted by reaction raw material molar ratio, reaction condition, crystallization raw material molar ratio and crystallization condition, and HZSM 5 molecular sieve with small particle size and high Br acid amount can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of material chemistry and catalytic chemistry, and relates to an HZSM-5 molecular sieve and a preparation method and application thereof. Background Art

[0002] ZSM-5 molecular sieve is a molecular sieve with an MFI topology and a two-dimensional pore system of vertically intersecting ten-membered rings. The pore sizes of the ten-membered rings are 0.55 × 0.51 nm and 0.56 × 0.53 nm, respectively. ZSM-5 molecular sieves are widely used in the petroleum refining and petrochemical industries, including catalytic cracking, alkylation, aromatization, isomerization, disproportionation of hydrocarbons, and methanol to ethylene, propylene, and aromatics.

[0003] CN106698463A discloses a method for synthesizing nano ZSM-5 molecular sieves. The synthesis method comprises first mixing an inorganic base, water, a template, an aluminum source, and a silicon source to obtain a gel, mixing the gel with macroporous carbon and then ultrasonically treating the gel, then stirring the gel at 50-100°C until it becomes viscous, then drying the mixture until the water is completely evaporated, then loading the mixture into a reactor and adding a certain amount of water in a closed reactor for crystallization, filtering, washing, drying, and calcining the resulting solid product in an oxygen or air atmosphere to obtain the nano ZSM-5 molecular sieve.

[0004] CN1958453A discloses a method for synthesizing small-grain ZSM-5 molecular sieves using a seed crystal method, particularly a method for rapidly synthesizing small-grain ZSM-5 zeolite molecular sieves. The pH of a mixture of a silicon source and deionized water is adjusted with an acid solution, and the mixture is stirred for hydrolysis. An organic template is then added to obtain solution A. An aluminum source is dissolved in deionized water to obtain solution B, which is slowly added dropwise to solution A. Molecular sieve seed crystals are then added to the mixture, and the mixture is placed in a hydrothermal reactor for hydrothermal crystallization. The resulting crystallized product is washed, centrifuged, dried, and calcined to obtain the ZSM-5 small-grain zeolite molecular sieve.

[0005] CN102745714A provides a method for preparing a small-grain ZSM-5 molecular sieve. The method comprises the following steps: (1) uniformly mixing an organosilicon source with an alcohol solvent to obtain an alcohol solution containing the organosilicon source; (2) uniformly mixing a template agent with an inorganic base in water to obtain an inorganic base aqueous solution containing the template agent; (3) uniformly mixing an aluminum source, the alcohol solution containing the organosilicon source obtained in step (1), and the inorganic base aqueous solution containing the template agent obtained in step (2) to obtain an emulsion; and (4) crystallizing the emulsion under crystallization conditions, filtering, drying, and calcining to obtain a small-grain ZSM-5 molecular sieve.

[0006] CN104192859A discloses a method for rapidly preparing small-grain ZSM-5 molecular sieves. First, a silicon-aluminum mixed colloidal solution is prepared, which is then placed in a crystallization kettle for low-temperature nucleation and high-temperature crystallization growth. The resulting crystallized product is a small-grain ZSM-5 molecular sieve. The nucleation temperature is 60-120°C, the nucleation time is 1-3 hours, and the crystallization growth temperature is 150-170°C, the crystallization growth time is 1-3 hours.

[0007] CN109231235A provides a method for preparing nano ZSM-5 molecular sieves. The invention first prepares a pre-crystallization solution at 5-15°C by reacting tetrapropylammonium hydroxide, aluminum isopropoxide, and ethyl orthosilicate. The pre-crystallization solution contains a large number of incompletely crystallized nano ZSM-5 molecular sieve seeds. In the presence of aluminum sulfate, water glass, and a dispersant, the seeds continue to grow, facilitating the preparation of fully crystallized nano ZSM-5 molecular sieves. The nano ZSM-5 molecular sieves also have good dispersibility and significantly reduce aggregation.

[0008] CN 108793185 A provides a green and simple method for preparing nano ZSM-5 molecular sieves. Specifically, the method comprises adding a high molecular weight polymer, a silicon source, an aluminum source, an organic structure directing agent and deionized water into a synthesis system and stirring the mixture uniformly to form a sol-gel as a precursor for molecular sieve synthesis; then preparing the sol-gel into a dry gel; and then using a water vapor-assisted crystallization method to obtain the nano ZSM-5 molecular sieve.

[0009] CN 110857218 A relates to the field of molecular sieves used in methanol-to-olefins conversion catalysts, disclosing a nano-flaky ZSM-5 molecular sieve, its preparation method, and application. The nano-flaky ZSM-5 molecular sieve has a thickness of 20-70 nm, a length of 200-800 nm, an aspect ratio of 2-10, and a SiO2 / Al2O3 molar ratio of 10-200:1.

[0010] CN 110282635 A discloses a method for synthesizing nano ZSM-5 zeolite, comprising precooling a silicon source, an aluminum source, and a template agent at low temperature, mixing the ingredients at low temperature, and concentrating the mixture at low temperature. The mixture is then crystallized at 150-200°C for 24-72 hours, and the crystallized product suspension is directly dried, separated, calcined, and demoulded to obtain the nano ZSM-5 zeolite.

[0011] CN 110422858 A discloses a method for preparing a nanorod-shaped ZSM-5 molecular sieve, comprising the following steps: (1) preparing a seed solution: mixing TEOS, TPAOH and H2O to form a sol, and aging at 20-150°C for 1-80 hours; (2) preparing a boron-silicon solution or an aluminum-silicon solution: mixing ethylamine with the silica sol to obtain a solution A, and adding a boric acid / aluminum nitrate aqueous solution to the solution A to obtain a boron-silicon / aluminum-silicon solution; (3) preparing a molecular sieve raw powder: adding the seed solution to the boron-silicon / aluminum-silicon solution, and then transferring the solution to a stainless steel reactor with a polytetrafluoroethylene liner, placing the reactor in an oven at 170°C for static crystallization for 72 hours, and cooling, centrifuging, washing and drying the crystallized solid to obtain a molecular sieve raw powder; and (4) calcining the molecular sieve raw powder: placing the molecular sieve raw powder in a muffle furnace and calcining it at 450-600°C for 3-6 hours.

[0012] Molecular sieves are a class of crystalline catalysts with highly shape-selective properties. Their crystallite size and acid content are key factors in determining the excellent performance of various molecular sieve materials. Existing ZSM-5 molecular sieves typically have lower acid content than HY and Hbeta molecular sieves, limiting their application in some catalytic reactions. Therefore, the synthesis of HZSM-5 molecular sieves with small crystallites and high B-acid content is of great significance. Summary of the Invention

[0013] The main purpose of the present invention is to provide a small-grain B-acid-rich HZSM-5 molecular sieve and a preparation method thereof, so as to solve the problems of low acid content of HZSM-5 molecular sieve and low reaction conversion rate when HZSM-5 molecular sieve is used as a catalyst in the prior art.

[0014] In order to achieve the above object, the present invention provides a small-grain Br-acid-rich HZSM-5 molecular sieve, wherein the HZSM-5 molecular sieve has a particle size of less than 500 nm and a Br-acid content of greater than 0.8 mmol / g.

[0015] The small-grain Br-acid-rich HZSM-5 molecular sieve of the present invention has a particle size of less than 200 nm and a Br-acid content of greater than 1.0 mmol / g.

[0016] The small-grain Br-acid-rich HZSM-5 molecular sieve of the present invention has a particle size of less than 100 nm and a Br-acid content of greater than 1.2 mmol / g.

[0017] In order to achieve the above object, the present invention also provides a method for preparing small-grain Br-rich HZSM-5 molecular sieve, comprising the following steps:

[0018] Step 1: mixing a silicon source, a molecular sieve, water and an inorganic base, and reacting them at a reaction temperature of 100-150° C. for 4-16 hours to obtain a reaction product; wherein the silicon source is calculated as SiO2, the molecular sieve is calculated as SiO2, and the inorganic base is calculated as OH-; the molar ratio of the silicon source to the molecular sieve is 0.05-0.5, the molar ratio of the inorganic base to the silicon source is 0.1-1.0, and the molar ratio of the water to the silicon source is 10-100;

[0019] Step 2: Mix a silicon source, an aluminum source, water, and an inorganic base to form a mixture, then add the reaction product obtained in step 1, crystallize at 120-180° C. in a crystallization kettle for 36-96 hours, wash the crystallized product, dry it at 120-140° C. for 4-8 hours, and calcine it at 500-550° C. for 4-8 hours to obtain a ZSM-5 molecular sieve; wherein the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the inorganic base is calculated as OH-, the molar ratio of the silicon source to the aluminum source is 20-100, the molar ratio of the inorganic base to the silicon source is 0.1-1.0, and the molar ratio of water to the silicon source is 10-100; the weight ratio of the reaction product in step 1 to the mixture is 0.05-0.50;

[0020] Step 3: exchanging the ZSM-5 molecular sieve obtained in step 2 with a 5-10% ammonium salt solution at a liquid-to-solid mass ratio of 5-10 and a temperature of 50-80° C. for three times; washing the exchanged ZSM-5 molecular sieve with deionized water at a liquid-to-solid mass ratio of 5-10; drying at 120-140° C. for 4-8 hours, and calcining at 450-500° C. for 4-8 hours to obtain a small-grain, borane-rich HZSM-5 molecular sieve.

[0021] In the above preparation method, part of the ZSM-5 molecular sieve undergoes a hydrolysis reaction in step 1, and the silicon species and aluminum species dissolved from the molecular sieve undergo a rearrangement reaction to form secondary or intermediate structural units of the molecular sieve. These dissolved or newly generated secondary or intermediate structural units of the molecular sieve will play a guiding role in the molecular sieve crystallization reaction in step 2, inducing the formation of small-grained, Br-acid-rich ZSM-5 molecular sieves. The crystal grains are small because in step 2, the reaction product of step 1 can provide a larger number of nucleation centers, thereby increasing the generation rate of the molecular sieve grains and reducing the size of the molecular sieve grains. The high Br-acid content of the ZSM-5 molecular sieve is due to the fact that the reaction product of step 1 induces the formation of a molecular sieve with high framework aluminum or high four-coordinate aluminum in the crystallization reaction in step 2, thereby increasing the Br-acid amount of the molecular sieve.

[0022] The study also found that adding a small amount of silicon source in step 1 can make the guiding effect of the reaction product of step 1 in step 2 more obvious, which is related to the fact that the addition of silicon-containing compounds is beneficial to the recrystallization process of dissolved or newly generated secondary or intermediate structural units.

[0023] In the method for preparing HZSM-5 molecular sieve of the present invention, the reaction temperature in step 1 is 120-140° C., and the reaction time is 8-12 hours.

[0024] In the method for preparing HZSM-5 molecular sieve of the present invention, the crystallization temperature in step 2 is 140-160° C., and the crystallization time is 48-72 hours.

[0025] The preparation method of the small-grain Br-rich HZSM-5 molecular sieve described in the present invention, wherein the silicon source in step 1 and the silicon source in step 2 are respectively at least one of solid silica gel, silica sol, and white carbon black; the inorganic base in step 1 and the inorganic base in step 2 are respectively at least one of sodium hydroxide and potassium hydroxide.

[0026] The preparation method of the small-grain Br-rich HZSM-5 molecular sieve of the present invention, wherein the molecular sieve in step 1 is a ZSM-5 molecular sieve; and the aluminum source is at least one of sodium metaaluminate and aluminum sulfate.

[0027] The present invention also provides an HZSM-5 molecular sieve obtained by the above-mentioned preparation method. In a specific embodiment, the HZSM-35 molecular sieve obtained by the above-mentioned method has grains smaller than 500 nm and has a high Br(II) acid content, which is greater than 0.8 mmol / g.

[0028] The present invention also provides a small-grained Br-rich HZSM-5 molecular sieve obtained by the above preparation method. In a specific embodiment, the HZSM-35 molecular sieve obtained by the above method has grains smaller than 200 nm and a Br-rich content greater than 1.0 mmol / g.

[0029] The present invention also provides a small-grained Br-rich HZSM-5 molecular sieve obtained by the above preparation method. In a specific embodiment, the HZSM-35 molecular sieve obtained by the above method has grains smaller than 100 nm and a Br-rich content greater than 1.2 mmol / g.

[0030] In order to achieve the above object, the present invention further provides the use of the HZSM-5 molecular sieve obtained by the above preparation method in the lightweight reaction of heavy aromatics.

[0031] Beneficial effects of the present invention:

[0032] The present invention can obtain HZSM-5 molecular sieve with small particle size and high B acid content through a specific preparation process and adjustment of the molar ratio of reaction raw materials, reaction conditions, molar ratio of crystallization raw materials and crystallization conditions. The catalyst prepared by the molecular sieve shows a high heavy aromatics conversion rate and light aromatics selectivity in heavy aromatics lightening experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the X-ray diffraction (XRD) spectrum of the HZSM-5 molecular sieve of Example 1.

[0034] Figure 2 This is a scanning electron microscope (SEM) image of the HZSM-5 molecular sieve of Example 1.

[0035] Figure 3 This is the X-ray diffraction (XRD) spectrum of the HZSM-5 molecular sieve of Example 2.

[0036] Figure 4 This is a scanning electron microscope (SEM) image of the HZSM-5 molecular sieve of Example 2.

[0037] Figure 5 This is the X-ray diffraction (XRD) spectrum of the HZSM-5 molecular sieve of Example 3.

[0038] Figure 6 This is a scanning electron microscope (SEM) image of the HZSM-5 molecular sieve of Example 3.

[0039] Figure 7 This is a process flow chart for lightweighting of heavy aromatics in Example 7.

[0040] Wherein, the reference numerals:

[0041] R1 Hydrogenation Reactor

[0042] R2 lightweight reactor

[0043] V2 Primary Gas-Liquid Separator

[0044] V3 V4 V5 Secondary Gas-Liquid Separator DETAILED DESCRIPTION

[0045] The following is a detailed description of the embodiments of the present invention. These embodiments are implemented based on the technical solutions of the present invention, and detailed implementation methods and processes are given. However, the scope of protection of the present invention is not limited to the following embodiments. The experimental methods for which specific conditions are not specified in the following embodiments are generally based on conventional conditions.

[0046] The present invention provides a method for preparing a small-grain Br-rich HZSM-5 molecular sieve, comprising the following steps:

[0047] Step 1: Mix a silicon source, a molecular sieve, water and an inorganic base, and react at a reaction temperature of 100-150°C for 4-16 hours to obtain a reaction product; wherein the silicon source is calculated as SiO2, the molecular sieve is calculated as SiO2, and the inorganic base is calculated as OH-, the molar ratio of the silicon source to the molecular sieve is 0.05-0.5, the molar ratio of the inorganic base to the silicon source is 0.1-1.0, and the molar ratio of the water to the silicon source is 10-100; preferably, the molar ratio of the silicon source to the molecular sieve is 0.1-0.3, the molar ratio of the inorganic base to the silicon source is 0.2-0.5, and the molar ratio of the water to the silicon source is 20-50; preferably, the reaction temperature is 120-140°C and the reaction time is 8-12 hours.

[0048] Step 2: Mix a silicon source, an aluminum source, water, and an inorganic base to form a mixture, then add the reaction product obtained in step 1, crystallize at 120-180° C. in a crystallization kettle for 36-96 hours, wash the crystallized product, dry it at 120-140° C. for 4-8 hours, and calcine it at 500-550° C. for 4-8 hours to obtain a ZSM-5 molecular sieve; wherein the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the inorganic base is calculated as OH-, the molar ratio of the silicon source to the aluminum source is 20-100, and the inorganic base is 0. The molar ratio of the silicon source is 0.1-1.0, the molar ratio of water to the silicon source is 10-100; the weight ratio of the crystallized product in step 1 to the mixture is 0.05-0.50; preferably, the molar ratio of the silicon source to the aluminum source is 30-70, the molar ratio of the inorganic base to the silicon source is 0.2-0.6, the molar ratio of water to the silicon source is 20-50, and the weight ratio of the reaction product in step 1 to the mixture is 0.1-0.3; preferably, the crystallization temperature is 140-160°C and the crystallization time is 48-72 hours. The ZSM-5 molecular sieve is washed, dried and calcined, the drying temperature is 120-140°C, and the calcination temperature is 500-550°C.

[0049] Step 3, the ZSM-5 molecular sieve obtained in step 2 is exchanged with a 5-10% ammonium salt solution at a liquid-to-solid mass ratio of 5-10 and a temperature of 50-80° C., for example, three times; the exchanged ZSM-5 molecular sieve is washed with deionized water at a liquid-to-solid mass ratio of 5-10, for example, three times; dried at 120-140° C. for 4-8 hours, and calcined at 450-500° C. for 4-8 hours to obtain small crystals and rich in B acid to obtain HZSM-5 molecular sieve.

[0050] Small-grain molecular sieves have short pores, making active sites highly accessible. Therefore, small-grain molecular sieves typically exhibit relatively high catalytic activity. Furthermore, due to the short pores, reaction products can quickly exit the reaction zone, preventing secondary reactions and improving reaction selectivity. Small-grain molecular sieves have far more pores than standard molecular sieves and are less susceptible to clogging by carbon deposits generated by side reactions, thus improving their resistance to carbon deposits. Consequently, catalysts prepared using small-grain molecular sieves often exhibit better activity, selectivity, and activity stability than those prepared using standard particle size molecular sieves.

[0051] The Br(OH) acid sites on molecular sieves are the primary catalytically active sites, and a high Br(OH) acid content often indicates higher catalytic reaction activity. While the catalytic activity of HZSM-5 molecular sieves is lower than that of HY and Hbeta molecular sieves in many catalytic reactions, its pore structure often enables good selectivity for the target product. Therefore, increasing the Br(OH) acid content of HZSM-5 molecular sieves is an important approach to improving catalyst activity and performance.

[0052] The method of the present invention can obtain HZSM-5 molecular sieve with small particle size and high B acid content through a specific reaction process and adjustment of the molar ratio of reaction raw materials, reaction conditions, molar ratio of crystallization raw materials and crystallization conditions.

[0053] In one embodiment, in step 1, the silicon source is at least one of solid silica gel, silica sol, and white carbon black. The molecular sieve is ZSM-5 molecular sieve, and the inorganic base is at least one of sodium hydroxide and potassium hydroxide.

[0054] In step 2, the silicon source is at least one of solid silica gel, silica sol, and white carbon black. The aluminum source is at least one of sodium metaaluminate and aluminum sulfate. The inorganic base is at least one of sodium hydroxide and potassium hydroxide.

[0055] The small-grain Br-acid-rich HZSM-5 molecular sieve obtained by the above method of the present invention has a molecular sieve particle size of less than 500 nm, preferably less than 200 nm, and more preferably less than 100 nm, as shown by scanning electron microscopy; pyridine infrared analysis shows that the Br-acid content of the molecular sieve is greater than 0.8 mmol / g, preferably greater than 1.0 mmol / g, and more preferably greater than 1.2 mmol / g.

[0056] The HZSM-5 molecular sieve of the present invention has a small particle size and a high B acid content, and is used for catalyzing the lightweighting of heavy aromatics, especially the selective ring opening of heavy aromatics, and has a high reaction conversion rate and high product selectivity.

[0057] The technical solution of the present invention is further described in detail below through specific embodiments.

[0058] Related test methods in each embodiment:

[0059] XRD characterization was performed using a Rigaku Corporation smartlab X-ray diffractometer with CuKα radiation as the radiation source, a tube voltage of 40 kV, a tube current of 50 mA, a scan rate of 5° / min, and a scan range of 2θ = 5 to 85°.

[0060] SEM characterization was performed using a Quantachrome 200F field emission scanning electron microscope (SEM). The test voltage was 200 kV. The size of the molecular sieve crystals was measured using the 200F field emission scanning electron microscope.

[0061] The pyridine adsorption was characterized by using a Nicolet-6700 Fourier transform infrared spectrometer from Nicolet, USA. The B acid and L acid of the molecular sieve were determined. The sample was pressed into a pellet and fixed in the reaction cell. -3 The sample was purified under conditions of pa and 450 °C for 2 hours, then cooled to 90 °C to allow the sample to saturate with the probe molecule pyridine, and then programmed to rise to the specified temperature, vacuum desorbed for 20 min, and the Py-FTIR spectrum was recorded.

[0062] There are two important indicators for evaluating the performance of heavy aromatics lightening catalysts: the first is the heavy aromatics conversion rate; the second is the light aromatics selectivity, which are defined as follows:

[0063]

[0064]

[0065] Example 1

[0066] (1) To a stainless steel reactor, 200 g of deionized water, 100 g of silica sol (30% by mass SiO2), 100 g of sodium hydroxide solution (30% by mass sodium hydroxide), and 90 g of ZSM-5 molecular sieve (SiO2 / Al2O3=20) were added, stirred evenly, sealed, and reacted at 140°C for 12 hours.

[0067] (2) Add 300 g of deionized water, 220 g of silica sol (30% by mass SiO2), 30 g of sodium hydroxide solution (30% by mass sodium hydroxide), and 25 g of aluminum sulfate solution (8.0% by mass as Al2O3) to a stainless steel reactor. Stir continuously while adding. Then add 120 g of the reaction product from step (1), stir evenly, seal, and crystallize at 175°C for 48 hours. After crystallization, cool, filter, wash, and dry to obtain ZSM-5 molecular sieve.

[0068] (3) The ZSM-5 molecular sieve was calcined at 530°C for 4 hours to remove the template, and then exchanged with a 10% mass concentration of ammonium chloride solution at a liquid-to-solid ratio of 5:1 and a temperature of 80°C. After three exchanges, the solution was washed with deionized water three times, dried at 120°C for 4 hours, and calcined at 500°C for 4 hours to obtain the HZSM-5 molecular sieve.

[0069] Figure 1 is the X-ray diffraction (XRD) spectrum of the HZSM-5 molecular sieve of Example 1, Figure 1 It can be seen that the product obtained in Example 1 is HZSM-5 molecular sieve. Figure 2 is a scanning electron microscope (SEM) image of the HZSM-5 molecular sieve of Example 1, Figure 2 As shown, the particle size of the obtained HZSM-5 molecular sieve is less than 500 nm. Pyridine infrared analysis of the HZSM-5 molecular sieve of Example 1 shows that the amount of B acid is 0.832 mmol / g.

[0070] (4) 1000g of the above-mentioned small-grained B-acid-rich HZSM-5 molecular sieve (particle size less than 500nm, B-acid content of 0.832mmol / g) and 100g of pseudo-boehmite (specific surface area 288m 2 / g, dry basis weight 68%), and 30g of sesbania powder were mixed evenly. 50g of nitric acid was added to 850g of deionized water and stirred evenly. The mixture was then added to the above mixture and kneaded using a kneader. Extrusion was then performed using an extruder. The mixture was dried in an oven at 120°C for 4 hours, then transferred to a muffle furnace. The temperature was raised to 450°C over 4 hours and maintained at this temperature for 4 hours. The mixture was then calcined to produce heavy aromatics lightweighting catalyst C. Pyridine infrared analysis of catalyst C showed a 0.761mmol / g B acid content.

[0071] Example 2

[0072] (1) Add 400 g of deionized water, 40 g of white carbon black (95% by mass of SiO2), 200 g of potassium hydroxide solution (30% by mass of potassium hydroxide), and 120 g of ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio 20) into a stainless steel reactor, stir well, seal, and react at 120°C for 8 hours.

[0073] (2) Add 300 g of deionized water, 250 g of silica sol (30% SiO2 by mass), 30 g of potassium hydroxide solution (30% potassium hydroxide by mass), and 50 g of aluminum sulfate solution (8.0% by mass as Al2O3) to a stainless steel reactor. Stir continuously while adding. Then add 150 g of the reaction product from step (1), stir evenly, seal, and crystallize at 150°C for 60 hours. After crystallization, cool, filter, wash, and dry to obtain ZSM-5 molecular sieve.

[0074] (3) The ZSM-5 molecular sieve was calcined at 530°C for 4 hours to remove the template, and then exchanged with a 5% mass concentration of ammonium chloride solution at a liquid-to-solid ratio of 10:1 and a temperature of 60°C. After three exchanges, the solution was washed with deionized water three times, dried at 120°C for 4 hours, and calcined at 530°C for 4 hours to obtain the HZSM-5 molecular sieve.

[0075] Figure 3 is the X-ray diffraction (XRD) spectrum of the HZSM-5 molecular sieve of Example 2, Figure 3 It can be seen that the product obtained in Example 2 is HZSM-5 molecular sieve. Figure 4 The scanning electron microscope (SEM) image of the HZSM-5 molecular sieve of Example 2 is shown in FIG. Figure 4 As shown, the particle size of the obtained HZSM-5 molecular sieve is less than 200 nm. Pyridine infrared analysis of the HZSM-5 molecular sieve of Example 2 shows that the amount of B acid is 1.015 mmol / g.

[0076] (4) 1000g of the above-mentioned small-grained B-acid-rich HZSM-5 molecular sieve (particle size less than 200nm, B-acid content of 1.015mmol / g) and 100g of pseudo-boehmite (specific surface area 288m 2 / g, dry basis weight content 68%), and 30g of sesbania powder were mixed evenly. 30g of nitric acid and 50g of acetic acid were added to 850g of deionized water and stirred evenly. The mixture was then added to the above mixture and kneaded using a kneader. Extrusion was then performed using an extruder. The mixture was dried in an oven at 120°C for 4 hours and then transferred to a muffle furnace. The temperature was raised to 500°C over 4 hours and maintained at this temperature for 4 hours. The mixture was then calcined to produce heavy aromatics lightweighting catalyst D. Pyridine infrared analysis of catalyst D showed a 0.911 mmol / g B acid content.

[0077] Example 3

[0078] (1) To a stainless steel reactor, 300 g of deionized water, 100 g of sodium hydroxide solution (sodium hydroxide content of 30%), 12 g of solid silica gel (SiO2 content of 92%), and 100 g of ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio of 20) were added, stirred evenly, sealed, and reacted at 120°C for 12 hours.

[0079] (2) Add 300 g of deionized water, 250 g of silica sol (30% by mass SiO2), 40 g of sodium hydroxide solution (30% by mass sodium hydroxide), 10 g of potassium hydroxide solution (30% by mass potassium hydroxide), and 70 g of aluminum sulfate solution (8.0% by mass Al2O3) to a stainless steel reactor. Stir continuously while adding. Then add 180 g of the reaction product from step 1 (1), stir evenly, seal, and crystallize at 120°C for 96 hours. After crystallization, cool, filter, wash, and dry to obtain ZSM-5 molecular sieve.

[0080] (3) The ZSM-5 molecular sieve was calcined at 530°C for 4 hours to remove the template, and then exchanged with a 6% mass concentration of ammonium chloride solution at a liquid-to-solid ratio of 5:1 and a temperature of 80°C. After three exchanges, it was washed with deionized water three times, dried at 120°C for 4 hours, and calcined at 500°C for 4 hours to obtain the HZSM-5 molecular sieve.

[0081] Figure 5 is the X-ray diffraction (XRD) spectrum of the HZSM-5 molecular sieve of Example 3, Figure 5 It can be seen that the product obtained in Example 3 is HZSM-5 molecular sieve. Figure 6 The scanning electron microscope (SEM) image of the HZSM-5 molecular sieve of Example 3 is shown in FIG. Figure 6 As shown, the particle size of the obtained HZSM-5 molecular sieve is less than 100 nm. Pyridine infrared analysis of the HZSM-5 molecular sieve of Example 3 shows that the amount of B acid is 1.232 mmol / g.

[0082] (4) 1000g of the above-mentioned small-grained B-acid-rich HZSM-5 molecular sieve (particle size less than 100nm, B-acid content of 1.232mmol / g) and 100g of pseudo-boehmite (specific surface area 288m 2 / g, dry basis weight content 68%), and 50g of methylcellulose were mixed uniformly. 50g of nitric acid was added to 900g of deionized water and stirred uniformly. The mixture was then added to the above mixture and kneaded using a kneader. Extrusion was then performed using an extruder. The mixture was dried in an oven at 140°C for 4 hours, then transferred to a muffle furnace. The temperature was raised to 500°C over 4 hours, maintained at this temperature for 4 hours, and calcined to produce heavy aromatics lightweighting catalyst E. Pyridine infrared analysis of catalyst E showed a 1.116mmol / g BO acid content.

[0083] Example 4

[0084] (1) To a stainless steel reactor, 300 g of deionized water, 50 g of silica sol (30% by mass SiO2), 100 g of sodium hydroxide solution (30% by mass sodium hydroxide), and 90 g of ZSM-5 molecular sieve (SiO2 / Al2O3=20) were added, stirred evenly, sealed, and reacted at 130°C for 12 hours.

[0085] (2) Add 500 g of deionized water, 40 g of white carbon black (95% by mass as SiO2), 40 g of sodium hydroxide solution (30% by mass as sodium hydroxide), and 20 g of aluminum sulfate solution (8.0% by mass as Al2O3) to a stainless steel reactor. Stir continuously while adding. Then add 160 g of the reaction product from step (1), stir evenly, seal, and crystallize at 150°C for 60 hours. After crystallization, cool, filter, wash, and dry to obtain ZSM-5 molecular sieve.

[0086] (3) After calcining the ZSM-5 molecular sieve at 530°C for 4 hours to remove the template, the sample was exchanged with a 10% mass concentration of ammonium chloride solution at a liquid-to-solid ratio of 5:1 and a temperature of 60°C. After three exchanges, the sample was washed three times with deionized water, dried at 120°C for 4 hours, and calcined at 500°C for 4 hours to obtain H ZSM-5 molecular sieve. XRD analysis showed that the molecular sieve was ZSM-5 molecular sieve, scanning electron microscopy showed that the particle size of the molecular sieve was less than 200 nm, and pyridine infrared analysis showed that the molecular sieve B acid content was 0.916 mmol / g.

[0087] Example 5

[0088] (1) To a stainless steel reactor, 300 g of deionized water, 20 g of white carbon black (95% by mass as SiO2), 200 g of potassium hydroxide solution (30% by mass as potassium hydroxide), and 80 g of ZSM-5 molecular sieve (SiO2 / Al2O3=20) were added. The mixture was stirred well, sealed, and reacted at 120°C for 8 hours.

[0089] (2) Add 500 g of deionized water, 50 g of solid silica gel (92% by mass as SiO2), 60 g of sodium hydroxide solution (30% by mass as sodium hydroxide), and 25 g of sodium metaaluminate solution (16% by mass as Al2O3) to a stainless steel reactor in sequence. Stir continuously while adding. Then add 160 g of the reaction product from step (1), stir evenly, seal, and crystallize at 140°C for 72 hours. After crystallization, cool, filter, wash, and dry to obtain ZSM-5 molecular sieve.

[0090] (3) The ZSM-5 molecular sieve was calcined at 530°C for 4 hours to remove the template, and then exchanged with a 5% mass concentration ammonium chloride solution at a liquid-to-solid ratio of 10:1 and a temperature of 80°C. After three exchanges, the product was washed three times with deionized water, dried at 120°C for 4 hours, and calcined at 530°C for 4 hours to obtain HZSM-5 molecular sieve. XRD analysis showed that the molecular sieve was ZSM-5 molecular sieve, scanning electron microscopy showed that the molecular sieve particle size was less than 100 nm, and pyridine infrared analysis showed that the molecular sieve B acid content was 1.108 mmol / g.

[0091] Example 6

[0092] (1) To a stainless steel reactor, 300 g of deionized water, 350 g of sodium hydroxide solution (sodium hydroxide content 30%), 20 g of solid silica gel (92% by mass as SiO2), and 100 g of ZSM-5 molecular sieve (SiO2 / Al2O3=20) were added, stirred evenly, sealed, and reacted at 120°C for 12 hours.

[0093] (2) Add 300 g of deionized water, 250 g of silica sol (30% by mass as SiO2), 50 g of sodium hydroxide solution (30% by mass as sodium hydroxide), and 30 g of sodium metaaluminate solution (16% by mass as Al2O3) to a stainless steel reactor. Stir continuously while adding. Then add 150 g of the reaction product from step (1), stir evenly, seal, and crystallize at 130°C for 84 hours. After crystallization, cool, filter, wash, and dry to obtain ZSM-5 molecular sieve.

[0094] (3) The ZSM-5 molecular sieve was calcined at 530°C for 4 hours to remove the template, and then exchanged with a 10% mass concentration of ammonium chloride solution at a liquid-to-solid ratio of 5:1 and a temperature of 60°C. After three exchanges, the product was washed three times with deionized water, dried at 120°C for 4 hours, and calcined at 500°C for 4 hours to obtain HZSM-5 molecular sieve. XRD analysis showed that the molecular sieve was ZSM-5 molecular sieve, scanning electron microscopy showed that the molecular sieve particle size was less than 100 nm, and pyridine infrared analysis showed that the molecular sieve B acid content was 1.216 mmol / g.

[0095] Comparative Example 1

[0096] 1000g HZSM-5 molecular sieve (provided by Sinopharm Chemical Reagent Co., Ltd., with a crystal size greater than 1μm and a B acid content of 0.521mmol / g) and 100g pseudo-boehmite (specific surface area 288m 2 / g, dry basis 68%), and 30g of sesbania powder were mixed evenly. 50g of nitric acid was added to 850g of deionized water and stirred evenly. This was then added to the above mixture, kneaded in a kneader, and then extruded into strips using an extruder. The mixture was dried in an oven at 120°C for 4 hours, then transferred to a muffle furnace. The temperature was raised to 450°C over 4 hours, maintained at this temperature for 4 hours, and calcined to produce a heavy aromatics lightweighting catalyst A. Pyridine infrared analysis of catalyst A showed a B acid content of 0.472mmol / g.

[0097] Comparative Example 2

[0098] 1000g HZSM-5 molecular sieve (provided by Shandong Aluminum Co., Ltd., with a grain size of less than 1μm and a B acid content of 0.436mmol / g) and 100g pseudo-boehmite (specific surface area 288m2 / g, dry basis 68%), and 30g of sesbania powder were mixed evenly. 30g of nitric acid and 50g of acetic acid were added to 850g of deionized water and stirred evenly. This was then added to the above mixture, kneaded using a kneader, and then extruded into strips using an extruder. Drying was performed in an oven at 120°C for 4 hours, then transferred to a muffle furnace. The temperature was raised to 500°C over 4 hours, maintained at this temperature for 4 hours, and calcined to produce a heavy aromatics lightweighting catalyst B. Pyridine infrared analysis of catalyst B indicated a 0.376mmol / g BO acid content.

[0099] Example 7

[0100] The application effect of the catalyst of the present invention is illustrated by carrying out a lightening reaction of heavy aromatics using mixed C10+ heavy aromatics as raw materials.

[0101] The experimental device for lightening heavy aromatics is a high-pressure reaction device that uses an isothermal fixed-bed reactor. Figure 7 As shown, the hydrogenation reactor R1 is loaded with a heavy aromatic hydrogenation catalyst containing 6 wt% molybdenum oxide and 12 wt% nickel oxide supported on an alumina carrier, and the lightening reactor R2 is loaded with the heavy aromatic lightening catalysts A, B, C, D, and E of Comparative Examples 1 to 2 and Examples 1 to 3, respectively.

[0102] The catalyst is loaded into the constant temperature section of the reactor. 20-30 mesh quartz sand is placed above and below the catalyst. After loading, the reactor is connected to the system. Nitrogen is introduced for a leak test. The leak pressure is gradually increased to 6.0 MPa. After 2 hours of constant pressure, if the pressure drops by no more than 0.1 MPa, the device is considered leak-proof.

[0103] The heavy aromatic feedstock of a set flow rate is metered by a metering pump and enters the hydrogenation reactor R1. After being heated to a certain temperature in the upper section of the hydrogenation reactor R1, it enters the bed of the hydrogenation reactor R1 to undergo desulfurization, denitrogenation and aromatic saturation reactions. Then, it is heated to a certain temperature and enters the lightening reactor R2. Under the action of the heavy aromatic lightening catalyst, aromatic selective ring opening, dealkylation and other reactions occur. The reaction products enter the primary gas-liquid separator V2, and the gaseous product is discharged from the upper part of the primary gas-liquid separator V2, separated by the secondary gas-liquid separator V4, and then discharged after being metered by a gas flow meter. The liquid product is discharged from the bottom of the primary gas-liquid separator V2, separated by the secondary gas-liquid separators V3 and V5, and then sampled and analyzed.

[0104] The raw materials used in the experiment of lightening heavy aromatics are C10+ heavy aromatics from the continuous reforming unit of the refinery, and their composition is shown in Table 1 below.

[0105] Table 1 Composition analysis of C10+ heavy aromatics

[0106]

[0107] The above C10+ heavy aromatics were heated at a pressure of 5.0 MPa and a space velocity of 2.0 h -1 The heavy aromatics were hydrogenated in the hydrogenation reactor R1 under the conditions of 320℃, 1000:1 hydrogen-to-oil ratio, and then the reaction was carried out at a pressure of 5.0 MPa and a space velocity of 2.0 h -1 The heavy aromatic hydrocarbon lightening reaction is carried out under the conditions of 380°C temperature and 1000:1 hydrogen-to-oil ratio (carried out in the lightening reactor R2). The liquid product is separated into gas and liquid by the first-level separator V2, and then further separated into gas and liquid by the second-level separators V3 and V5. Then, samples are taken from the bottom of the second-level separators V3 and V5 to analyze the hydrocarbon composition of the liquid product.

[0108] The heavy aromatics hydrogenation catalyst was loaded into the hydrogenation reactor R1, and then the lightening catalysts of Comparative Examples 1-2 and Examples 1-3 were loaded into the lightening reactor R2 to conduct evaluation experiments. The experimental results are shown in Table 2.

[0109] Table 2 Evaluation results of catalysts in different comparative examples and examples

[0110]

[0111]

[0112] As shown in Table 2, in the experiment of converting heavy aromatics to light, the catalyst prepared by using the small-grain Br-rich HZSM-5 molecular sieve of the present invention has higher heavy aromatics conversion rate and light aromatics selectivity.

[0113] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A small-grained Br-rich HZSM-5 molecular sieve, characterized in that: The HZSM-5 molecular sieve has a particle size of less than 500 nm and a B acid content of greater than 1.015 mmol / g.

2. The small-grain Br-rich HZSM-5 molecular sieve according to claim 1, characterized in that: The HZSM-5 molecular sieve has a particle size of less than 100 nm and a B acid content of greater than 1.2 mmol / g.

3. A method for preparing a small-grained Br-rich HZSM-5 molecular sieve, characterized in that: The steps include: Step 1: Mix silicon source, ZSM-5 molecular sieve, water and inorganic base, and react at a temperature of 100-150°C for 4-16 hours to obtain a reaction product; wherein the silicon source is calculated as SiO2, the molecular sieve is calculated as SiO2, and the inorganic base is calculated as OH. - The molar ratio of the silicon source to the molecular sieve is 0.05-0.5, the molar ratio of the inorganic base to the silicon source is 0.1-1, and the molar ratio of the water to the silicon source is 10-100; Step 2: Mix a silicon source, an aluminum source, water, and an inorganic base to form a mixture, then add the reaction product obtained in step 1, crystallize at 120-180°C for 36-96 hours, wash the crystallized product, dry at 120-140°C for 4-8 hours, and calcine at 500-550°C for 4-8 hours to obtain a ZSM-5 molecular sieve; wherein the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the inorganic base is calculated as OH. - The molar ratio of the silicon source to the aluminum source is 20-100, the molar ratio of the inorganic base to the silicon source is 0.1-1.0, and the molar ratio of water to the silicon source is 10-100; the weight ratio of the reaction product of step 1 to the mixture is 0.05-0.50; Step 3: exchanging the ZSM-5 molecular sieve obtained in step 2 with a 5-10% ammonium salt solution at a liquid-to-solid mass ratio of 5-10 and a temperature of 50-80° C.; washing the exchanged ZSM-5 molecular sieve with deionized water at a liquid-to-solid mass ratio of 5-10; drying at 120-140° C. for 4-8 hours, and calcining at 450-500° C. for 4-8 hours to obtain a small-grained Br-rich HZSM-5 molecular sieve.

4. The method for preparing HZSM-5 molecular sieve according to claim 3, wherein: The reaction temperature in step 1 is 120-140° C., and the reaction time is 8-12 hours.

5. The method for preparing HZSM-5 molecular sieve according to claim 3, wherein: The crystallization temperature in step 2 is 140-160° C., and the crystallization time is 48-72 hours.

6. The method for preparing HZSM-5 molecular sieve according to claim 3, characterized in that: The silicon source in step 1 and the silicon source in step 2 are respectively at least one of solid silica gel, silica sol, and white carbon black; the inorganic base in step 1 and the inorganic base in step 2 are respectively at least one of sodium hydroxide and potassium hydroxide.

7. The method for preparing HZSM-5 molecular sieve according to claim 3, characterized in that: The aluminum source is at least one of sodium metaaluminate and aluminum sulfate.

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