A light hydrocarbon aromatization catalyst that produces more low-carbon alkanes, its preparation method and its application

Abstract

A light hydrocarbon aromatization catalyst for producing high yields of low-carbon alkanes comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, an active metal, and / or a binder. The hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve has a Silicalite-1 molecular sieve as the core layer and a ZSM-5 molecular sieve as the shell layer, with a particle size of 90–140 nm. This catalyst, when applied to light hydrocarbon aromatization reactions, exhibits high yields of low-carbon alkanes and low dry gas yields. Furthermore, the catalyst demonstrates good stability, a long single-pass reaction cycle, and low coking.

Description

Technical Field

[0001] This invention relates to a catalyst, its preparation method, and its application. Specifically, it relates to a light hydrocarbon aromatization catalyst that produces more low-carbon alkanes, its preparation method, and its application in the reaction of converting light hydrocarbons into propane, butane, and aromatics. Background Technology

[0002] With the increasing refining capacity in my country, a large amount of light hydrocarbon components, such as liquefied petroleum gas (LPG), reformate topping oil, and aromatic residue oil, produced by refineries have not been rationally utilized. How to convert these low-value light hydrocarbon resources into high-value chemical feedstocks such as low-carbon alkanes and light aromatics (BTX) is a pressing issue that needs to be addressed in the current transformation of refining into chemical processing. Light hydrocarbon aromatization technology is a highly efficient utilization technology that converts light hydrocarbon feedstocks into higher-value light aromatics and propane through a series of parallel reactions, including cracking, dehydrogenation, disproportionation, hydrogen transfer, cyclization, and isomerization, at relatively low reaction temperatures under the action of a catalyst. Research on light hydrocarbon aromatization catalysts has also shifted from metal-supported catalysts to molecular sieve catalysts. For light hydrocarbon aromatization technology, developing novel catalysts with high conversion rates, high selectivity, and high stability is currently a research hotspot.

[0003] CN112588314A discloses the preparation and application of a catalyst for the production of propane from light hydrocarbons. This catalyst uses one or more of the following molecular sieves as active components: HZSM-5, HY-type molecular sieves, β-molecular sieves, mordenite, and SAPO-34 molecular sieves. It uses one or more of rare earth metals, Zn, Ga, Ni, Ag, Mo, Cu, and P as modifying elements. The preparation method involves first adding a binder to the molecular sieve active component, followed by mixing, extrusion, drying, and calcination. Then, one or more of Zn, Ga, Ni, Ag, Mo, Cu, and P are used as modifying elements for modification. After drying and calcination, the catalyst is aged with steam to obtain the catalyst for the production of propane from light hydrocarbons. The reaction conditions are: reaction temperature 320–450℃, reaction pressure 0.1–3.0 MPa, and space velocity 0.1–2.0 h⁻¹. -1 Under certain conditions, introducing light hydrocarbons into contact with the catalyst to react can yield a better propane yield.

[0004] CN110951500A discloses a method for producing propane and gasoline from alkanes, comprising subjecting the hydrocarbons to a non-hydrogen-exposed environment at 0.1–3.0 MPa and 400–550 °C, with a feed mass hourly space velocity of 0.1–10.0 h⁻¹. -1The reaction is carried out under specific conditions in contact with a hydrocarbon conversion catalyst, which comprises 20–85% by mass of ZSM series zeolite and 15–80% by mass of binder, wherein the ZSM series zeolite is ZSM-5 and / or ZSM-35, the catalyst has an α value of 60–80, and the alkanes are selected from one or more C5–C12 alkanes. This method can produce propane under non-hydrogen-dependent conditions and produce high-octane gasoline blending components as a byproduct.

[0005] CN113385215A discloses a method for preparing a catalyst for propane production via hydrocracking and its application. This catalyst uses micron-sized SAPO-34 molecular sieves as the crystal nucleus and ZSM-5 molecular sieves as the outer layer, thus preparing a SAPO-34 / ZSM-5 composite molecular sieve catalyst with a core-shell structure. Simultaneously, modification methods are used to modify the pore structure and acid distribution of the composite molecular sieve. This catalyst can enable the catalytic cracking of light hydrocarbons to produce propane under hydrocracking conditions.

[0006] The aforementioned process routes for preparing low-carbon alkanes, light aromatics, and gasoline from light hydrocarbons are all light hydrocarbon aromatization technology routes. Current applied research mainly focuses on the fixed-bed catalyst stage, which suffers from the problem of catalyst deactivation due to easy carbon deposition, requiring frequent switching and regeneration. There is an urgent need to develop novel catalysts with moderate acidity, strong carbon-holding capacity, high activity, and high stability. Summary of the Invention

[0007] To address the problems of current catalysts for converting light hydrocarbons into low-carbon alkanes using the light hydrocarbon aromatization mechanism being prone to coking, deactivation, and difficulty in regeneration, and the strong acidity of the catalysts and the easy cracking of light hydrocarbon feedstocks into low-value dry gas, this invention provides a light hydrocarbon aromatization catalyst that produces more low-carbon alkanes, its preparation method, and its application. The catalyst used in the light hydrocarbon aromatization reaction has a high yield of low-carbon alkanes and a low yield of dry gas. Furthermore, the catalyst has good stability, a long single-pass reaction cycle, and low coking.

[0008] The first aspect of the present invention provides a light hydrocarbon aromatization catalyst that produces more low-carbon alkanes, comprising a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, an active metal and / or a binder, wherein the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve has a Silicalite-1 molecular sieve as the core layer and a ZSM-5 molecular sieve as the shell layer, and the particle size is 90-140 nm.

[0009] The second aspect of the present invention provides a method for preparing the catalyst described in the first aspect of the present invention. When the catalyst comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and an active metal, the preparation method comprises: impregnating the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve with a solution of a compound containing an active metal under alkaline conditions, and then performing a first drying and a first calcination step ST1; when the catalyst comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, an active metal, and a binder, further mixing the product obtained in step ST1 and the binder precursor, and then performing a second drying and a second calcination step ST2.

[0010] The catalyst of this invention uses hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve as the active component for light hydrocarbon aromatization reaction. It has a high yield of low-carbon alkanes and a low dry gas yield. In addition, the catalyst has good stability, long single-pass reaction cycle and low coke deposition.

[0011] The catalyst of this invention can effectively reduce coking and deactivation under aromatization reaction conditions. The active component, hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, has a higher carbon-holding capacity. The weaker acidity of the core layer molecular sieve reduces coking in the core layer, resulting in a higher concentration of carbon species in the shell layer, making the catalyst easier to regenerate. Attached Figure Description

[0012] Figure 1 X-ray diffraction pattern of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve S1 prepared in Example 1;

[0013] Figure 2 Scanning electron microscope image of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve S1 prepared in Example 1;

[0014] Figure 3 Transmission electron microscopy image of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve S1 prepared in Example 1;

[0015] Figure 4 A magnified transmission electron microscope image of the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve S1 prepared in Example 1.

[0016] Figure 5 Transmission electron microscopy (TEM) image of S1' of the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve prepared in Example 1 after loading metal. Detailed Implementation

[0017] The catalyst of this invention uses hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve as the active component. It is suitable for the conversion reaction of C5-C10 alkanes, or light hydrocarbons and naphtha feedstocks with these as the main components, under non-hydrogen-exposed conditions. The reactants undergo a series of parallel and sequential reactions such as cracking, dehydrogenation, hydrogen transfer, and aromatization under the action of the catalyst to generate propane, butane, and high-value light aromatics. The hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve uses Silicalite-1 molecular sieve as the core layer and ZSM-5 molecular sieve as the shell layer. Epitaxial growth of ZSM-5 molecular sieves on the Silicalite-1 molecular sieve effectively solves the problem of product desorption caused by blockage inside the molecular sieve channels. Using Silicalite-1 as the core layer reduces the Brønsted acid content inside the core-shell molecular sieve, thereby inhibiting strong cracking reactions of reactants inside the molecular sieve, ensuring that cracking reactions occur entirely on the ZSM-5 molecular sieve shell, thus reducing the yield of dry gas and the overall carbon deposition of the molecular sieve.

[0018] The catalyst of this invention can generate propane, butane and light aromatic hydrocarbons with low carbon number from alkanes with 5 to 10 carbon atoms under a wide range of reaction conditions, wherein the yield of propane is >60% and the yield of butane is >14%.

[0019] The catalyst of this invention comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, an active metal, and / or a binder. The hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve has a Silicalite-1 molecular sieve as the core layer and a ZSM-5 molecular sieve as the shell layer, with a particle size of 90–140 nm. The small particle size of the Silicalite-1@ZSM-5 core-shell molecular sieve used in the catalyst of this invention can significantly enhance the activity and stability of the catalyst and reduce the amount of coke deposition.

[0020] The catalyst of this invention uses a Group VIII metal as the active metal, preferably one of cobalt, nickel, or iron. The content of the active metal is 0–10.0% by mass, preferably 0–6.0% by mass, calculated based on the mass of the molecular sieve. The active metal component acts as a dehydrogenation functional component, possessing dehydrogenation function in the reaction, which is beneficial to the aromatization reaction. On the other hand, the core-shell molecular sieve loaded with metal can have a higher carbon holding capacity. The binder is silica or alumina, and the content of the binder is 0–45% by mass, calculated based on the total mass of the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and the binder.

[0021] The catalyst of the present invention has a SiO2 / Al2O3 molar ratio of 20 to 200, preferably 40 to 80, in the ZSM-5 molecular sieve. The ZSM-5 molecular sieve, serving as the shell, has a suitable silicon-to-aluminum ratio, providing a suitable amount of acid, which allows alkanes to undergo cleavage reactions at their acidic sites, increasing the production of small molecule alkanes such as propane and butane.

[0022] The catalyst of this invention has a total specific surface area of ​​200–420 m². 2 / g, preferably 240-280m 2 / g, total pore volume is 0.30~0.70cm³ 3 / g, preferably 0.40-0.50cm 3 / g; Preferably, when the catalyst of the present invention does not contain a binder, the microporous specific surface area is 330-370m². 2 / g, micropore volume is 0.10~0.20cm³ 3 / g, preferably 0.14~0.19cm 3 / g.

[0023] The catalyst of the present invention preferably contains γ-Al₂O₃ alumina. The catalyst may be in the form of strips, spheres, particles, or microspheres to suit reactions in fixed-bed, moving-bed, or fluidized-bed reactors.

[0024] The catalyst of this invention comprises a Silicalite-1@ZSM-5 core-shell molecular sieve with a Silicalite-1 molecular sieve as the core layer and a ZSM-5 molecular sieve as the shell layer, having a particle size of 90–140 nm, preferably 100–130 nm; the Silicalite-1 molecular sieve has a particle size of 40–80 nm, preferably 50–70 nm, and the ZSM-5 shell layer has a thickness of 30–70 nm, preferably 45–60 nm; the ZSM-5 molecular sieve has a silica-alumina ratio of 20–200, preferably 40–80; and the Silicalite-1@ZSM-5 core-shell molecular sieve has a total specific surface area of ​​300–470 m². 2 / g, preferably 420-450m 2 / g, with a microporous specific surface area of ​​260–390m² 2 / g, preferably 350-380m 2 / g, total pore volume is 0.20~0.60cm³ 3 / g, preferably 0.30~0.55cm 3 / g, micropore volume is 0.10~0.30cm³ 3 / g, preferably 0.16~0.28cm 3 / g.

[0025] The catalyst of the present invention, wherein the Silicalite-1@ZSM-5 core-shell molecular sieve is obtained by a preparation method comprising the following steps:

[0026] (1) The template agent, the first silicon source and water are mixed to obtain the core layer molecular sieve synthesis system, and the intermediate product is obtained by aging I and crystallization I.

[0027] (2) The intermediate product obtained in step (1), aluminum source, second silicon source, alkali source, anion and cation balancer and water are mixed to obtain a shell molecular sieve synthesis system. After aging II and crystallization II, the obtained solid is washed, dried and calcined to obtain the Sililcite-1@ZSM-5 core-shell molecular sieve.

[0028] (3) The Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2) is subjected to ion exchange in a solution containing ammonium ions, and then washed and calcined again to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve.

[0029] Preferably, a hydrolysis promoter can be added to the core-layer molecular sieve synthesis system described in step (1). The hydrolysis promoter is an alcohol and / or a weak base, more preferably at least one of ethylene glycol, methanol, ethanol, and ammonia. The first silicon source is calculated as SiO2, the mass ratio of the first silicon source to the hydrolysis promoter is 1-5, the mass ratio of the first silicon source to the template agent is 0.1-5, and the mass ratio of the first silicon source to water is 1-10. Optionally, the upper limit of the mass ratio of the first silicon source to the hydrolysis promoter is independently selected from 5.0, 4.0, 3.0, and 2.0, and the lower limit is independently selected from 1.0, 4.0, 3.0, and 2.0. Optionally, the upper limit of the mass ratio of the first silicon source to the template agent is independently selected from 1.2, 1, 0.8, 0.6, and 0.5, and the lower limit is independently selected from 1, 0.8, 0.6, 0.5, and 0.1.

[0030] Preferably, step (1) includes a step of recovering the template agent by distillation or centrifugation after crystallization I. When recovering the template agent by distillation, the temperature is 60-120°C, preferably 80-100°C, and the distillation time is 0.5-6 hours, preferably 2-4 hours.

[0031] Preferably, in step (2), the cation-anion balancer is one of a strong acid-weak base salt, a strong base-weak acid salt, a strong acid-strong base salt, or a weak acid-weak base salt, and more preferably at least one of sodium acetate, sodium chloride, ammonium acetate, and ammonium chloride.

[0032] Preferably, the first silicon source and the second silicon source are each independently selected from at least one of tetraethyl silicate, silica sol, water glass, fumed silica, and silica gel powder; the aluminum source is at least one of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum chloride; the alkali source is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; and the template agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, n-butylamine, tetrapropylammonium bromide, and 1,6-hexamethylenediamine.

[0033] Preferably, in step (2), the second silicon source is SiO2, the aluminum source is Al2O3, and the molar ratio of the second silicon source to the aluminum source is 20 to 200. Optionally, the upper limit of the molar ratio of the second silicon source to the aluminum source is independently selected from 200, 170, 100, 80, and 50, and the lower limit is independently selected from 40, 170, 100, 80, and 50.

[0034] Preferably, in step (2), the aluminum source is calculated as Al2O3, the alkali source is calculated as NaOH, and the mass ratio of the intermediate product: aluminum source: alkali source: anion and cation balancer: water is (50-300): 1: (1-10): (1-30): (50-200).

[0035] Preferably, the aging process I is carried out at a temperature of 10–50°C, preferably 25–35°C, for a time of 0.5–12 h, preferably 4–6 h; the crystallization process I is carried out at a temperature of 80–250°C, preferably 100–150°C, for a time of 18–72 h, preferably 24–48 h; the aging process II is carried out at a temperature of 10–50°C, preferably 25–35°C, for a time of 0.5–12 h, preferably 4–6 h; the crystallization process II is carried out at a temperature of 80–250°C, preferably 150–200°C, for a time of 18–72 h, preferably 24–48 h.

[0036] Optionally, the upper limit of the crystallization temperature I is independently selected from 150℃, 140℃, 130℃, and 120℃, and the lower limit is independently selected from 100℃, 140℃, 130℃, and 120℃. The upper limit of the crystallization time I is independently selected from 48h, 36h, and 24h, and the lower limit is independently selected from 12h, 36h, and 24h. Optionally, the upper limit of the crystallization temperature II is independently selected from 200℃, 180℃, 160℃, 140℃, and 120℃, and the lower limit is independently selected from 100℃, 180℃, 160℃, 140℃, and 120℃. The upper limit of the crystallization time II is independently selected from 36h, 24h, and 12h, and the lower limit is independently selected from 6h, 12h, and 24h.

[0037] The ion exchange, washing, drying, and calcination processes described are standard procedures in the field and will not be elaborated upon here.

[0038] When the catalyst of the present invention comprises hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve and binder, its preparation method is a conventional molding method in the art.

[0039] 30. When the catalyst of the present invention comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and an active metal, its preparation method comprises: impregnating the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve with a solution of a compound containing an active metal under alkaline conditions, and then performing a first drying and a first calcination step ST1; when the catalyst comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, an active metal and a binder, further mixing the product obtained in step ST1, the binder precursor and the adhesive solvent, and then performing a second drying and a second calcination step ST2. In the impregnation process, the amount of the solution containing the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and the compound containing the active metal is 0.1–10 g / ml; the alkaline condition is a pH of 8–12, preferably 8–10, and the pH of the impregnation solution can be adjusted with ammonia; the impregnation temperature is 30–100℃, preferably 45–75℃; the compound containing the active metal is a soluble Group VIII metal salt, preferably a nitrate or chloride salt of a Group VIII metal; the soluble Group VIII metal salt is one of a soluble cobalt salt, a soluble nickel salt, and a soluble iron salt; the soluble cobalt salt is selected from cobalt nitrate hexahydrate and cobalt chloride; the soluble nickel salt is selected from nickel nitrate hexahydrate, nickel chloride, and nickel sulfate; the soluble iron salt is selected from ferric chloride, ferric nitrate, and ferric sulfate; the colloidal solvent is nitric acid and / or an organic acid, and the concentration of the acid in the colloidal solvent is 0.1–5 wt%, preferably... The concentration is selected as 0.5-2 wt%, and the amount of the adhesive solvent relative to the product obtained in step ST1 is 0.01-0.1 ml / g; the binder precursor is pseudoboehmite powder or silica gel powder, and the amount of the binder precursor is such that the content of the catalyst binder is 0-45% by mass, calculated based on the total mass of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and binder; the first drying and second drying temperatures are independently 50-200℃, preferably 80-120℃, and the first drying and second drying times are independently 2-8h, preferably 4-6h; the first calcination and second calcination temperatures are independently 400-700℃, preferably 450-650℃, more preferably 500-600℃, and the first calcination and second calcination times are independently 4-12h, preferably 6-8h.

[0040] The present invention provides a method for aromatization of light hydrocarbons that produces more low-carbon alkanes, comprising contacting and reacting a light hydrocarbon-containing feedstock with a catalyst in the presence of an inert gas and under aromatization reaction conditions, wherein the catalyst is the catalyst provided by the present invention.

[0041] The present invention provides a method for aromatization of light hydrocarbons that produces more low-carbon alkanes. The aromatization reaction conditions are: temperature 380–450°C, pressure 0.1–1 MPa, and feed mass hourly space velocity (WHSV) 0.1–5 h⁻¹. -1 The volume ratio of inert gas to light hydrocarbons is 500-2000:1.

[0042] This invention provides a method for the aromatization reaction of light hydrocarbons that produces more low-carbon alkanes. The light hydrocarbons are C5-C10 alkanes, preferably C5-C7 alkanes. The light hydrocarbons can be one type of C5-C10 alkanes, such as n-hexane or n-heptane, or a mixture of alkanes with different structures but the same number of carbon atoms within the C5-C10 range, such as a mixture of C6 alkanes. Alternatively, they can be a mixture containing alkanes with several different carbon numbers, such as a mixture of C5-C7 alkanes. The C5-C10 alkanes can be a mixture of pure alkanes with different carbon numbers, or industrial feedstocks containing impurities within the same carbon number range, such as liquefied petroleum gas, reformate topping oil, and aromatic residue oil.

[0043] The present invention provides a method for aromatization of light hydrocarbons that produces more low-carbon alkanes. In the light hydrocarbon-containing raw material, the preferred content of C5-C10 alkanes is 30-70% by mass, the olefin content is 10-30% by mass, and the aromatic content is 10-20% by mass. More preferably, the C5-C10 alkanes contain 30-50% by mass of C5 alkanes, 20-30% by mass of C6 alkanes, and 10-20% by mass of C7 alkanes.

[0044] After the catalyst of the present invention is deactivated, it can be repeatedly used through regeneration. The catalyst regeneration method is as follows: the catalyst is treated with an oxygen-containing inert gas, the oxygen content of which is 0.5-20% by volume, preferably nitrogen, the regeneration temperature is 400-550°C, the pressure is 0.1-3 MPa, and the gas / catalyst volume ratio is 250-1000.

[0045] The light hydrocarbon aromatization reaction apparatus for producing low-carbon alkanes according to the present invention can be a fixed bed, moving bed, fluidized bed, or other types of apparatus. The reaction raw materials do not need to be purified, and a fixed bed reactor is preferred for the reaction.

[0046] The raw materials and reagents used in the embodiments of this invention were all purchased commercially.

[0047] The analytical methods involved in this invention are as follows: X-ray diffraction pattern analysis is performed using the XRDWUX70 method, nitrogen adsorption-desorption analysis is performed using the PABETALL method, and SEM morphology analysis is performed using the SEMMORPHO method.

[0048] The present invention will be further described in detail below with examples, but the present invention is not limited thereto.

[0049] Examples 1-8 are examples of the preparation of the catalyst of the present invention, and Test Examples 1-3 are examples of catalytic reaction performance.

[0050] Comparative Example 1 is an example of the preparation of a non-core-shell molecular sieve catalyst, and Comparative Example 2 is an example of the preparation of a catalyst using the method of first shaping and then loading an active metal using Silicalite-1@ZSM-5 core-shell molecular sieve.

[0051] Example 1

[0052] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0053] Step (1): Under stirring conditions, tetraethyl silicate, tetrapropylammonium hydroxide, ethanol and deionized water were added to a reaction vessel to obtain a core layer molecular sieve synthesis system. The mass ratio of tetraethyl silicate (as SiO2) to tetrapropylammonium hydroxide was 1.1, the mass ratio of tetraethyl silicate (as SiO2) to ethanol was 4.6, and the mass ratio of tetraethyl silicate (as SiO2) to water was 1.8. After stirring evenly, the mixture was aged at 35°C for 6 hours and then transferred to a crystallization vessel for crystallization at 120°C for 48 hours. The crystallization reaction product was separated by centrifugation to obtain the recovered template agent and intermediate product.

[0054] Step (2): Add sodium aluminate, silica sol, sodium chloride, sodium hydroxide and deionized water to the intermediate product to obtain the shell molecular sieve synthesis system. The mass ratio of intermediate product: sodium aluminate (calculated as Al2O3): NaOH: sodium chloride: water is 108.3:1:4.17:4.1:118.3, and the molar ratio of silica sol (calculated as SiO2): sodium aluminate (calculated as Al2O3) is 40. After stirring evenly, age at 50℃ for 6h and then transfer to a crystallization kettle. Crystallize at 150℃ for 24h. Wash, dry and calcine the obtained solid to obtain Silicalite-1@ZSM-5 core-shell molecular sieve.

[0055] Step (3): Take 100g of the Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2), perform ion exchange in 500ml of 1mol / L ammonium chloride solution, then wash, dry, and calcine to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve. This is denoted as S1.

[0056] Figure 1 The powder X-ray diffraction pattern of S1 shows that it has a distinct MFI topology. Figure 2 The image is a scanning electron microscope image of S1, which has a regular morphology. Figure 3 The transmission electron microscope image of S1 shows that S1 has a distinct core-shell structure. Figure 4 The image is a magnified transmission electron microscope image of S1, which shows a distinct core-shell structure with a core particle size of 40-60 nm and a shell outer edge size of 20-40 nm.

[0057] (II) Loaded active metals:

[0058] 100 g of H-type Silicalite-1@ZSM-5 core-shell molecular sieve S1 was impregnated with 300 ml of a 0.01 g / ml cobalt nitrate hexahydrate aqueous solution with a pH of 8.5 at 80 °C for 2 hours. The impregnated solid was then dried at 100 °C for 4 hours and then transferred to a muffle furnace for a first calcination at 550 °C for 6 hours to obtain hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve S1' loaded with active metal.

[0059] Figure 5 The transmission electron microscope image of S1' shows that the catalyst prepared in this invention has a uniform active metal loading.

[0060] (III) Molding:

[0061] Take 62g of Si' and 38g of pseudoboehmite powder (produced by Sasol GmbH, Germany, with an alumina content of 75% by mass, the same below) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape the mixture, and extrude it into particles with a diameter of 2mm and a length of 2-3mm using an extruder. After a second drying at 100℃ for 2h in an oven, transfer the mixture to a muffle furnace at 550℃ for a second calcination for 6h to obtain the catalyst C1.

[0062] Table 1 shows the structural properties of S1, S1' and C1, and Table 2 shows the composition of catalyst C1.

[0063] Example 2

[0064] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0065] Step (1): Under stirring conditions, tetraethyl silicate, n-butylamine, ethanol and deionized water were added to the reaction vessel to obtain the core layer molecular sieve synthesis system. The mass ratio of tetraethyl silicate (calculated as SiO2) to n-butylamine was 2.3, the mass ratio of tetraethyl silicate (calculated as SiO2) to ethanol was 3.5, and the mass ratio of tetraethyl silicate (calculated as SiO2) to water was 5.0. After stirring evenly, the mixture was aged at 35°C for 3 hours and then transferred to a crystallization vessel. The mixture was crystallized at 100°C for 48 hours. The crystallization reaction product was separated by distillation to obtain the recovered template agent and intermediate product. The distillation conditions were as follows: the intermediate product slurry was taken into a rotary evaporator and heated to 80°C at 2°C per minute at room temperature. The mixture was then rotary evaporated at 80°C for 4 hours. The rotation frequency of the rotary evaporator was 15 rpm.

[0066] Step (2): Add aluminum sulfate, silica, sodium chloride, sodium hydroxide and deionized water to the intermediate product to obtain the shell molecular sieve synthesis system. The mass ratio of intermediate product: aluminum sulfate (calculated as Al2O3): NaOH: sodium chloride: water is 216.7:1:8.31:8.37:328.9, and the molar ratio of silica (calculated as SiO2): aluminum sulfate (calculated as Al2O3) is 80. After stirring evenly, age at 35℃ for 3h and then transfer to a crystallization kettle. Crystallize at 150℃ for 36h. Wash, dry and calcine the obtained solid to obtain Silicalite-1@ZSM-5 core-shell molecular sieve.

[0067] Step (3): Take 100g of the Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2), perform ion exchange in 500ml of 1mol / L ammonium chloride solution, then wash, dry, and calcine to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve. This is denoted as S2.

[0068] (II) Loaded active metals:

[0069] 100 g of H-type Silicalite-1@ZSM-5 core-shell molecular sieve S2 was impregnated with 500 ml of a 0.01 g / ml cobalt nitrate hexahydrate aqueous solution with a pH of 8.5 at 80 °C for 2 hours. The impregnated solid was dried at 80 °C for 6 hours and then calcined in a muffle furnace at 600 °C for 4 hours to obtain catalyst C2. Table 1 shows the structural properties of S2 and C2, and Table 2 shows the composition of catalyst C2.

[0070] Example 3

[0071] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0072] Step (1): Under stirring conditions, tetraethyl silicate, tetrapropylammonium hydroxide, methanol and deionized water were added to a reaction vessel to obtain a core-layer molecular sieve synthesis system. The mass ratio of tetraethyl silicate (as SiO2) to tetrapropylammonium hydroxide was 3.0, the mass ratio of tetraethyl silicate (as SiO2) to methanol was 2.5, and the mass ratio of tetraethyl silicate (as SiO2) to water was 3.5. After stirring evenly, the mixture was aged at 35°C for 3 hours and then transferred to a crystallization vessel for crystallization at 100°C for 24 hours. The crystallization reaction product was separated by centrifugation to obtain the recovered template agent and intermediate product.

[0073] Step (2): Add aluminum sulfate, water glass, ammonium acetate, sodium hydroxide and deionized water to the intermediate product to obtain the shell molecular sieve synthesis system. The mass ratio of intermediate product: aluminum sulfate (calculated as Al2O3): NaOH: ammonium acetate: water is 216.45:1:8.2:14.36:322.21. The molar ratio of water glass (calculated as SiO2): aluminum sulfate (calculated as Al2O3) is 150. After stirring evenly, age at 35℃ for 3h and then transfer to a crystallization kettle. Crystallize at 150℃ for 48h. Wash, dry and calcine the obtained solid to obtain Silicalite-1@ZSM-5 core-shell molecular sieve.

[0074] Step (3): Take 100g of the Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2), perform ion exchange in 500ml of 1mol / L ammonium chloride solution, then wash, dry, and calcine to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve. This is denoted as S3.

[0075] (II) Molding:

[0076] Take 85g of S3 and 16.7g of silica powder (silicon oxide content of 90% by mass) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape, and extrude into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry them in an oven at 100℃ for 4h, and then transfer them to a muffle furnace at 550℃ for calcination for 6h to obtain the catalyst C3.

[0077] Table 1 shows the structural properties of S3 and C3, and Table 2 shows the composition of catalyst C3.

[0078] Example 4

[0079] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0080] Step (1): Under stirring conditions, tetraethyl silicate, tetrapropylammonium hydroxide, methanol and deionized water were added to a reaction vessel to obtain a core-layer molecular sieve synthesis system. The mass ratio of tetraethyl silicate (as SiO2) to tetrapropylammonium hydroxide was 1.5, the mass ratio of tetraethyl silicate (as SiO2) to methanol was 4.8, and the mass ratio of tetraethyl silicate (as SiO2) to water was 2.5. After stirring evenly, the mixture was aged at 50°C for 3 hours and then transferred to a crystallization vessel for crystallization at 150°C for 24 hours. The crystallization reaction product was separated by centrifugation to obtain the recovered template agent and intermediate product.

[0081] Step (2): Add aluminum trichloride, silica sol, sodium chloride, sodium hydroxide and deionized water to the intermediate product to obtain the shell molecular sieve synthesis system. The mass ratio of intermediate product: Al2O3:NaOH:sodium chloride:water is 215.8:1:8.73:9.86:322.04, and the molar ratio of silica sol (calculated as SiO2):Al2O3 is 40. After stirring evenly, age at 50℃ for 3h and then transfer to a crystallization kettle. Crystallize at 160℃ for 24h. Wash, dry and calcine the obtained solid to obtain Silicalite-1@ZSM-5 core-shell molecular sieve.

[0082] Step (3): Take 100g of the Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2), perform ion exchange in 500ml of 1mol / L ammonium chloride solution, then wash, dry, and calcine to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve. This is denoted as S4.

[0083] (II) Loaded active metals:

[0084] 100 g of H-type Silicalite-1@ZSM-5 core-shell molecular sieve S4 was impregnated with 500 ml of nickel nitrate hexahydrate aqueous solution with a concentration of 0.01 g / ml and a pH of 8.5 at 80 °C for 2 hours. The impregnated solid was then dried at 100 °C for 4 hours and then transferred to a muffle furnace for calcination at 550 °C for 6 hours to obtain hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve S4' loaded with active metal.

[0085] (III) Molding:

[0086] Take 65g of S4' and 35g of pseudoboehmite powder (produced by Sasol GmbH, Germany, with an alumina content of 75% by mass, the same below) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape the mixture, and extrude it into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry the particles in an oven at 100℃ for 6 hours, and then transfer them to a muffle furnace at 650℃ for a second calcination for 5 hours to obtain the catalyst C4.

[0087] Table 1 shows the structural properties of S4, S4' and C4, and Table 2 shows the composition of catalyst C4.

[0088] Example 5

[0089] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0090] Step (1): Under stirring conditions, tetraethyl silicate, 1,6-hexanediamine, ethanol and deionized water were added to a reaction vessel to obtain a core-layer molecular sieve synthesis system. The mass ratio of tetraethyl silicate (as SiO2) to 1,6-hexanediamine was 0.8, the mass ratio of tetraethyl silicate (as SiO2) to ethanol was 4.2, and the mass ratio of tetraethyl silicate (as SiO2) to water was 6.5. After stirring evenly, the mixture was aged at 35°C for 3 hours and then transferred to a crystallization vessel for crystallization at 150°C for 24 hours. The crystallization reaction product was separated by centrifugation to obtain the recovered template agent and intermediate product.

[0091] Step (2): Add aluminum sulfate, water glass, ammonium acetate, sodium hydroxide and deionized water to the intermediate product to obtain the shell molecular sieve synthesis system. The mass ratio of intermediate product: aluminum sulfate (calculated as Al2O3): NaOH: ammonium acetate: water is 209.95:1:7.49:21.64:329.46, and the molar ratio of water glass (calculated as SiO2): aluminum sulfate (calculated as Al2O3) is 40. After stirring evenly, age at 35℃ for 3h and then transfer to a crystallization kettle. Crystallize at 180℃ for 24h. Wash, dry and calcine the obtained solid to obtain Silicalite-1@ZSM-5 core-shell molecular sieve.

[0092] Step (3): Take 100g of the Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2), perform ion exchange in 500ml of 1mol / L ammonium chloride solution, then wash, dry, and calcine to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve. This is denoted as S5.

[0093] (II) Loaded active metals:

[0094] Take 100g of H-type Silicalite-1@ZSM-5 core-shell molecular sieve S5, and impregnate it with 300ml of ferric chloride aqueous solution with a concentration of 0.01g / ml and a pH of 8.5 at 80℃ for 2 hours. The impregnated solid is then dried at 100℃ for 4 hours and then transferred to a muffle furnace for calcination at 550℃ for 6 hours to obtain hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve S5' loaded with active metal.

[0095] (III) Molding:

[0096] Take 70g of S5' and 33.4g of silica powder (silica content of 90% by mass) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape, and extrude into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry them in an oven at 100℃ for 5h, and then transfer them to a muffle furnace at 550℃ for a second calcination for 6h to obtain the catalyst C5.

[0097] Table 1 shows the structural properties of S5, S5', and C5, and Table 2 shows the composition of catalyst C5.

[0098] Example 6

[0099] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0100] Silicalite-1@ZSM-5 core-shell molecular sieves were prepared according to the method in Example 1, except that ethanol was not added in step (1) to obtain the hydrogen form Silicalite-1@ZSM-5 core-shell molecular sieve. This is denoted as S6.

[0101] (II) Loaded active metals:

[0102] Take 100g of H-type Silicalite-1@ZSM-5 core-shell molecular sieve S6, and impregnate it with 500ml of ferric chloride aqueous solution with a concentration of 0.01g / ml and a pH of 8.5 at 80℃ for 2 hours. The impregnated solid is then dried at 100℃ for 4 hours, and then transferred to a muffle furnace for calcination at 550℃ for 6 hours to obtain hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve S6' loaded with active metal.

[0103] (III) Molding:

[0104] Take 60g of S6' and 40g of pseudoboehmite powder (produced by Sasol GmbH, Germany, with an alumina content of 75% by mass, the same below) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape, and extrude into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry them in an oven at 100℃ for 5 hours, and then transfer them to a muffle furnace at 650℃ for a second calcination for 5 hours to obtain the catalyst C6.

[0105] Table 1 shows the structural properties of S6, S6' and C6, and Table 2 shows the composition of catalyst C6.

[0106] Example 7

[0107] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0108] Silicalite-1@ZSM-5 core-shell molecular sieves were prepared according to the method of Example 1, except that in step (2), the molar ratio of silica sol (calculated as SiO2): sodium aluminate (calculated as Al2O3) was 200, resulting in hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieves. This is denoted as S7.

[0109] (II) Loaded active metals:

[0110] Take 100g of H-type Silicalite-1@ZSM-5 core-shell molecular sieve S7, and impregnate it with 500ml of a 0.01g / ml cobalt nitrate hexahydrate aqueous solution with a pH of 8.5 at 80℃ for 2 hours. The impregnated solid is then dried at 120℃ for 4 hours and then transferred to a muffle furnace for a first calcination at 500℃ for 8 hours to obtain hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve S7' loaded with active metal.

[0111] (III) Molding:

[0112] Take 60g of S7' and 40g of pseudoboehmite powder (produced by Sasol GmbH, Germany, with an alumina content of 75% by mass, the same below) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape, and extrude into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry them in an oven at 100℃ for 3 hours, and then transfer them to a muffle furnace at 550℃ for a second calcination for 6 hours to obtain the catalyst C7.

[0113] Table 1 shows the structural properties of S7, S7' and C7, and Table 2 shows the composition of catalyst C7.

[0114] Example 8

[0115] Catalyst C8 was prepared according to the method in Example 4, the difference being that... The steps of loading active metals, Table 1 shows the structural properties of C8, and Table 2 shows the composition of the C8 catalyst.

[0116] Comparative Example 1

[0117] (I) Preparation of hydrogen-form ZSM-5 molecular sieve:

[0118] Sodium aluminate, silica sol, sodium chloride, sodium hydroxide, ZSM-5 seed crystals (silicon-to-aluminum ratio of 40), and deionized water were added to a reaction vessel under stirring conditions to obtain a ZSM-5 molecular sieve synthesis system. The mass ratio of sodium aluminate (based on Al₂O₃):NaOH:sodium chloride:ZSM-5 seed crystals:water was 1:4.8:4.7:2.5:28, and the molar ratio of silica sol (based on SiO₂):sodium aluminate (based on Al₂O₃) was 40. After stirring evenly, the mixture was aged at 35°C for 8 hours and then transferred to a crystallization vessel. Crystallization was carried out at 150°C for 48 hours. The resulting solid was washed, dried, and calcined to obtain a ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 40. 100 grams of the ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 40 was subjected to ion exchange in 500 ml of a 1 mol / L ammonium chloride solution, followed by washing and calcination to obtain a hydrogen-form ZSM-5 molecular sieve. Let it be labeled D1.

[0119] (II) Loaded active metals:

[0120] Take 100g of H-type ZSM-5 molecular sieve D1, and soak it in 300ml of cobalt nitrate hexahydrate aqueous solution with a concentration of 0.01g / ml and a pH of 8.5 at 80℃ for 2 hours. Dry the soaked solid at 120℃ for 4 hours, and then transfer it to a muffle furnace for calcination at 550℃ for 6 hours to obtain hydrogen-type ZSM-5 molecular sieve D1' loaded with active metal.

[0121] (III) Molding:

[0122] Take 62g of D1' and 38g of pseudoboehmite powder (produced by Sasol GmbH, Germany, with an alumina content of 75% by mass, the same below) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape, and extrude into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry them in an oven at 100℃ for 3h, and then transfer them to a muffle furnace at 550℃ for calcination for 6h to obtain the catalyst DC1.

[0123] Table 1 shows the structural properties of D1, D1' and DC1, and Table 2 shows the composition of catalyst DC1.

[0124] Comparative Example 2

[0125] (I) Preparation of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve:

[0126] Hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve D2 was prepared according to the method in Example 4.

[0127] (II) Molding:

[0128] Take 65g of D3 and 35g of pseudoboehmite powder (produced by Sasol GmbH, Germany, with an alumina content of 75% by mass, the same below) and mix them evenly. Add 50g of nitric acid aqueous solution with a concentration of 1.0% by mass, knead and shape, and extrude into particles with a diameter of 2mm and a length of 2-3mm using an extruder. Dry them in an oven at 100℃ for 6h, and then transfer them to a muffle furnace at 650℃ for calcination for 5h to obtain the catalyst intermediate DC2'.

[0129] (III) Loaded active metals:

[0130] 100 g of catalyst intermediate DC2 was impregnated with 500 ml of cobalt nitrate hexahydrate aqueous solution with a concentration of 0.01 g / ml and a pH of 8.5 at 80 °C for 2 hours. The impregnated solid was dried at 100 °C for 4 hours. After drying, it was transferred to a muffle furnace at 550 °C and calcined for 6 hours to obtain catalyst DC2. Table 2 shows the composition of catalyst DC2.

[0131] As shown in Tables 1 and 2, compared with the preparation of Comparative Example 1, ZSM-5 molecular sieve In comparison, the preparations described in Examples 1-2 and 4-7 of this invention... Silicalite-1@ZSM-5 core-shell molecular sieve After loading the metal, the decrease in total specific surface area and micropore specific surface area was small, indicating that the introduction of non-precious metal active components did not block the pores of the support, and the high dispersion did not significantly reduce the specific surface area of ​​the support. Compared with Comparative Example 2, which first formed the zeolite and then loaded the active metal, the catalyst prepared by first loading the active metal onto the molecular sieve and then forming the zeolite in Example 4 of this invention has a larger total specific surface area and total pore volume.

[0132] Table 1

[0133]

[0134]

[0135] Table 2

[0136]

[0137] Test Example 1

[0138] The catalytic performance of catalysts C1-C8 and DC1-DC2 prepared in Examples 1-8 and Comparative Examples 1-2 was tested.

[0139] Catalysts C1-C8 and DC1-DC2 were respectively packed in a small fixed-bed reactor. n-Pentane and n-Hexane with a volume ratio of 1:1 were introduced into the reactor to contact the catalyst and react for 24 hours. The volume ratio of nitrogen to raw materials was 1500:1. Other reaction conditions and results are shown in Table 3.

[0140] Table 3

[0141]

[0142] Note: Dry gas consists of H2, CH4, and C2 hydrocarbons.

[0143] As shown in Table 3, compared to the ZSM-5 zeolite-containing catalyst provided in Comparative Example 1, the hydrogen-containing Silicalite-1@ZSM-5 core-shell zeolite catalyst of this invention, when used for light hydrocarbon aromatization reactions, achieves higher yields of low-carbon alkanes and lower dry gas yields; the catalyst also exhibits less coking, indicating that the catalyst of this invention can significantly reduce the occurrence of side reactions such as cracking. Compared to catalyst C8 without active metal support, catalyst C4 of this invention, under the same reaction conditions, exhibits higher yields of low-carbon alkanes and less catalyst coking.

[0144] Test Example 2

[0145] The catalyst C1 prepared in Example 1 was subjected to stability testing.

[0146] Test conditions: Catalyst C1 prepared in Example 1 was packed into a small fixed-bed reactor. n-Pentane and n-Hexane feedstocks at a volume ratio of 1:1 were introduced into the reactor to contact and react with catalyst C1. The reaction conditions included: temperature 400°C, pressure 0.1 MPa, and mass hourly space velocity (H₂S₀) 0.5 h⁻¹. -1 The volume ratio of nitrogen to raw materials was 1500, and the reaction results are listed in Table 4.

[0147] Table 4

[0148] Continuous reaction time, h 24 48 72 96 120 Dry gas yield, wt% 5.24 4.26 3.92 4.09 3.82 (Propane + Butane) Yield, wt% 85.21 83.52 82.37 80.49 77.48 <![CDATA[C 5+ Yield, wt% 9.53 12.21 13.71 15.40 18.69 Aromatics yield, wt% 1.23 5.52 7.41 8.87 11.04

[0149] Note: Dry gas consists of H2, CH4, and C2 hydrocarbons.

[0150] As shown in Table 4, with the extension of reaction time, the yield of (propane + butane) decreased from 85.21 wt% after 24 h of continuous reaction to 77.48 wt% after 120 h of continuous reaction, with an average (propane + butane) yield greater than 80 wt%. The dry gas yield decreased from 5.24 wt% after 24 h of continuous reaction to 3.82 wt% after 120 h of continuous reaction. The aromatics yield increased from 1.02 wt% after 24 h of continuous reaction to 11.04 wt% after 120 h of continuous reaction. The catalyst provided by this invention has good reactivity, low carbon alkane yield, and low dry gas yield.

[0151] Test Example 3

[0152] The catalyst C1 prepared in Example 1 was subjected to a regeneration test.

[0153] Test conditions: A small fixed-bed reactor was loaded with catalyst C1 prepared in Example 1. n-Pentane and n-Hexane (volume ratio 1:1) were introduced into the reactor as feedstock to contact and react with catalyst C1. The reaction conditions included: temperature 400°C, pressure 0.1 MPa, and mass hourly space velocity (H₂S₀) 0.5 h⁻¹. -1 The reaction time was 120 hours, the volume ratio of nitrogen to raw materials was 1500, and the catalyst C1, which had been reacting continuously for 120 hours, was used as a deactivated catalyst for regeneration.

[0154] Regeneration method: A mixture of air and nitrogen with an oxygen content of 20% by volume was introduced into the reactor for regeneration. The regeneration conditions were: temperature 500℃, time 8h, pressure 0.1MPa, and gas / agent volume ratio 20:1. The regenerated catalyst was obtained and reused in the reaction under the same conditions as the test conditions for 120h. The reaction results are listed in Table 5.

[0155] Table 5

[0156] Catalyst regeneration times 0 1 Dry gas yield, wt% 3.82 3.16 (Propane + Butane) Yield, wt% 77.48 75.44 <![CDATA[C 5+ Yield, wt% 18.69 21.39 Aromatics yield, wt% 11.04 11.08

[0157] Note: Dry gas consists of H2, CH4, and C2 hydrocarbons.

[0158] As can be seen from the data in Table 5, the catalytic activity of catalyst C1 provided in Example 1 after regeneration is very close to that before regeneration, indicating that the catalyst provided by the present invention has excellent regeneration performance.

[0159] Test Example 4

[0160] A small fixed-bed reactor was loaded with catalyst C1 prepared in Example 1. Reformed topping oil feedstock (composition shown in Table 6) was introduced into the reactor and reacted with catalyst C1 under the following conditions: temperature 400°C, pressure 0.1 MPa, and mass hourly space velocity (HHSV) 0.5 h⁻¹. -1The reaction time was 120 h, the volume ratio of nitrogen to raw materials was 1500, and the results after 24 h of reaction are shown in Table 7.

[0161] Table 6

[0162]

[0163]

[0164] Note: ≤C4—Alkanes with 4 or fewer carbon atoms, i-C5—Isopentane, n-C5—n-pentane, N-C5—Cyclopentane, i-C6—Isoalkanes with six carbon atoms, n-C6—n-hexane, N-C6—Cyclohexane, B—Benzene, >C7—Alkanes with more than 7 carbon atoms.

[0165] Table 7

[0166] Dry gas yield, wt% (Propane + Butane) Yield, wt% <![CDATA[C 5+ Yield, wt% Aromatics yield, wt% C1 4.96 68.92 26.12 8.62

[0167] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A light hydrocarbon aromatization catalyst that produces more low-carbon alkanes, comprising a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and an active metal, wherein the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve has a Silicalite-1 molecular sieve as the core layer and a ZSM-5 molecular sieve as the shell layer, with a particle size of 90-140 nm, and the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve is obtained by a preparation process including the following steps: (1) mixing a template agent, a first silicon source and water to obtain a core layer molecular sieve synthesis system, and obtaining an intermediate product through aging I and crystallization I; (2) mixing the intermediate product obtained in step (1), an aluminum source, a second silicon source, an alkali source, an anion and cation balancer and water to obtain a shell layer molecular sieve synthesis system, and obtaining an intermediate product through aging I and crystallization I; (2) After aging and crystallization, the obtained solid was washed, dried and calcined to obtain Silicalite-1@ZSM-5 core-shell molecular sieve; (3) The Silicalite-1@ZSM-5 core-shell molecular sieve obtained in step (2) was subjected to ion exchange in a solution containing ammonium ions, and was washed, dried and calcined again to obtain the hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve; The anion and cation balancer is one of strong acid weak base salt, strong base weak acid salt, strong acid strong base salt or weak acid weak base salt; The first silicon source is SiO2, and the mass ratio of it to the template agent is 0.1 to 5, and the mass ratio of it to water is 1 to 10; The second silicon source is SiO2, the aluminum source is Al2O3, and the molar ratio of the second silicon source to the aluminum source is 20 to 200.

2. The catalyst according to claim 1, characterized in that, The active metal is a group VIII metal, and the catalyst also includes a binder, which is silicon oxide or aluminum oxide.

3. The catalyst according to claim 2, characterized in that, The active metal is one of cobalt, nickel, and iron; the catalyst also includes a binder, which is silicon dioxide or aluminum oxide.

4. The catalyst according to claim 1, characterized in that, The content of the active metal is 0 to 10.0% by mass, calculated based on the mass of the molecular sieve.

5. The catalyst according to claim 1, characterized in that, The content of the active metal is 0 to 6.0% by mass, calculated based on the mass of the molecular sieve.

6. The catalyst according to claim 2, characterized in that, The binder content is 0-45% by mass, calculated based on the total mass of hydrogen-type Silicalite-1@ZSM-5 core-shell molecular sieve and binder.

7. The catalyst according to claim 1, characterized in that, The hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve has a particle size of 100-130 nm, the Silicalite-1 molecular sieve has a particle size of 40-80 nm, the ZSM-5 shell thickness is 30-70 nm, the molar ratio of silica to alumina in the ZSM-5 molecular sieve is 20-200, and the total specific surface area of ​​the Silicalite-1@ZSM-5 core-shell molecular sieve is 300-470 m². 2 / g, with a microporous specific surface area of ​​260~390m² 2 / g, total pore volume is 0.20~0.60cm³ 3 / g, micropore volume is 0.10~0.30cm³ 3 / g.

8. The catalyst according to claim 7, characterized in that, The Silicalite-1 molecular sieve has a particle size of 50-70 nm, the ZSM-5 shell thickness is 45-60 nm, the molar ratio of silica to alumina in the ZSM-5 molecular sieve is 40-80, and the total specific surface area of ​​the Silicalite-1@ZSM-5 core-shell molecular sieve is 420-450 m². 2 / g, with a microporous specific surface area of ​​350~380m² 2 / g, total pore volume is 0.30~0.55cm³ 3 / g, with micropore volume of 0.16~0.28cm³. 3 / g.

9. The catalyst according to claim 1, characterized in that, The catalyst has a total specific surface area of ​​200–420 m². 2 / g, total pore volume is 0.30~0.70cm³ 3 / g.

10. The catalyst according to claim 1, characterized in that, The catalyst has a total specific surface area of ​​240–280 m². 2 / g, total pore volume is 0.40~0.50cm³ 3 / g.

11. The catalyst according to claim 1, characterized in that, When the catalyst does not contain a binder, the microporous specific surface area of ​​the catalyst is 330~370m². 2 / g, micropore volume is 0.10~0.20cm³ 3 / g.

12. The catalyst according to claim 1, characterized in that, A hydrolysis promoter is added to the core layer molecular sieve synthesis system described in step (1), wherein the hydrolysis promoter is an alcohol and / or a weak base.

13. The catalyst according to claim 12, characterized in that, The hydrolysis accelerator is at least one of ethylene glycol, ethanol, methanol, and ammonia.

14. The catalyst according to claim 1, characterized in that, The cation-anion balancer is at least one of sodium acetate, sodium chloride, ammonium acetate, and ammonium chloride.

15. The catalyst according to claim 1, characterized in that, The first silicon source and the second silicon source are each independently selected from at least one of tetraethyl silicate, silica sol, water glass, fumed silica, and silica gel powder; the aluminum source is at least one of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum chloride; the alkali source is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; and the template agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, n-butylamine, tetrapropylammonium bromide, and 1,6-hexamethylenediamine.

16. The catalyst according to claim 1, characterized in that, Step (1) after crystallization I includes the step of recovering the template agent by distillation or centrifugation.

17. The catalyst according to claim 16, characterized in that, The distillation temperature for recovering the template agent is 60~120℃, and the distillation time is 0.5~6h.

18. The catalyst according to claim 16, characterized in that, The distillation temperature for recovering the template agent is 80~100℃, and the distillation time is 2~4h.

19. The catalyst according to claim 12, characterized in that, The first silicon source, calculated as SiO2, has a mass ratio of 1 to 5 with the hydrolysis promoter.

20. The catalyst according to claim 1, characterized in that, The aluminum source is calculated as Al2O3, the alkali source is calculated as NaOH, and the mass ratio of intermediate product: aluminum source: alkali source: anion and cation balancer: water is (50-300): 1: (1-10): (1-30): (50-200).

21. The catalyst according to claim 1, characterized in that, The aging process I is carried out at a temperature of 10–50°C for 0.5–12 hours; the crystallization process I is carried out at a temperature of 80–250°C for 18–72 hours; the aging process II is carried out at a temperature of 10–50°C for 0.5–12 hours; the crystallization process II is carried out at a temperature of 80–250°C for 18–72 hours.

22. The catalyst according to claim 1, characterized in that, The aging process I is carried out at a temperature of 25–35°C for 4–6 hours; the crystallization process I is carried out at a temperature of 100–150°C for 24–48 hours; the aging process II is carried out at a temperature of 25–35°C for 4–6 hours; and the crystallization process II is carried out at a temperature of 150–200°C for 24–48 hours.

23. The method for preparing the catalyst according to claim 1, characterized in that, When the catalyst comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and an active metal, its preparation method includes: impregnating the hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve with a solution containing an active metal under alkaline conditions, followed by a first drying and a first calcination step ST1; when the catalyst comprises a hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve, an active metal, and a binder, further mixing the product obtained in step ST1, the binder precursor, and the adhesive solvent, followed by a second drying and a second calcination step ST2.

24. The method according to claim 23, characterized in that, The impregnation process involves using a solution of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and a compound containing an active metal at a concentration of 0.1–10 g / ml; the alkaline conditions are a pH of 8–12; and the impregnation temperature is 30–100 °C.

25. The method according to claim 23, characterized in that, The impregnation process involves using a solution of hydrogen-form Silicalite-1@ZSM-5 core-shell molecular sieve and a compound containing an active metal at a concentration of 0.1–10 g / ml; the alkaline conditions are a pH of 8–10; and the impregnation temperature is 45–75 °C.

26. The method according to claim 23, characterized in that, The compound containing the active metal is a soluble Group VIII metal salt; the impregnation method is excess impregnation, equal volume impregnation, precipitation impregnation, or multiple impregnation methods.

27. The method according to claim 23, characterized in that, The impregnation method is precipitation impregnation.

28. The method according to claim 26, characterized in that, The soluble Group VIII metal salt is one of the following: soluble cobalt salt, soluble nickel salt, and soluble iron salt.

29. The method according to claim 28, characterized in that, The soluble cobalt salt is selected from cobalt nitrate hexahydrate and cobalt chloride; the soluble nickel salt is selected from nickel nitrate hexahydrate, nickel chloride, and nickel sulfate; and the soluble iron salt is selected from ferric chloride, ferric nitrate, and ferric sulfate.

30. The method according to claim 23, characterized in that, The adhesive solvent is nitric acid and / or organic acid, the concentration of acid in the adhesive solvent is 0.1-5 wt%, and the amount of adhesive solvent used relative to the product obtained in step ST1 is 0.01-0.1 ml / g; the binder precursor is boehmite powder or silica gel powder; the first drying and second drying temperatures are independently 50-200℃, and the first drying and second drying times are independently 2-8 h; the first calcination and second calcination temperatures are independently 400-700℃, and the first calcination and second calcination times are independently 4-12 h.

31. The method according to claim 23, characterized in that, The adhesive solvent is nitric acid and / or organic acid, the concentration of acid in the adhesive solvent is 0.5-2 wt%, and the amount of adhesive solvent used relative to the product obtained in step ST1 is 0.01-0.1 ml / g; the binder precursor is boehmite powder or silica gel powder; the first drying and second drying temperatures are independently 80-120℃, and the first drying and second drying times are independently 4-6 h; the first calcination and second calcination temperatures are independently 450-600℃, and the first calcination and second calcination times are independently 6-8 h.

32. A method for aromatization of light hydrocarbons that produces more low-carbon alkanes, characterized in that, In the presence of an inert gas and under aromatization reaction conditions, a light hydrocarbon-containing feedstock is contacted with a catalyst and reacted, wherein the catalyst is the catalyst of any one of claims 1-22 or the catalyst prepared by the method of any one of claims 23-31.

33. The reaction method according to claim 32, characterized in that, The aromatization reaction conditions are: temperature 380–450℃, pressure 0.1–1 MPa, and feed mass hourly space velocity (WHSV) 0.1–5 h⁻¹. -1 The volume ratio of inert gas to light hydrocarbons is 500-2000:

1.

34. The reaction method according to claim 32, characterized in that, The light hydrocarbons are C5-C10 alkanes.

35. The reaction method according to claim 32, characterized in that, The light hydrocarbons are C5-C7 alkanes.

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