ZSM-5 molecular sieve, preparation method, and lightening method

Abstract

Provided are a ZSM-5 molecular sieve, a preparation method, and a lightening method. The total specific surface area of the ZSM-5 molecular sieve is 300-500 m2 / g, the external specific surface area of which accounts for 33-45% of the total specific surface area, and the ratio of the peak area of the peak at the chemical shift of 53 ppm in the nuclear magnetic spectrum of 27Al in the ZSM-5 molecular sieve to that of tetracoordinated Al is greater than or equal to 50%. The preparation method for the ZSM-5 molecular sieve comprises: S1, mixing a first silicon source, a first template agent, a first alkali source and water to obtain a seed gel, wherein the first silicon source is a solid silicon source; S2, mixing a second silicon source, an aluminum source, a second template agent, a second alkali source, water and the seed gel to obtain a synthetic liquid; and S3, crystallizing the synthetic liquid to obtain a ZSM-5 molecular sieve. Further provided are a ZSM-5 molecular sieve-based catalyst, a method for lightening light hydrocarbon and naphtha by using the ZSM-5 molecular sieve-based catalyst, and the use thereof. The ZSM-5 molecular sieve has a specific external specific surface area proportion, and the prepared catalyst can improve the yield of the cracking raw material under the conditions of a low hydrogen-oil volume ratio.

Description

A ZSM-5 molecular sieve, its preparation method, and a method for lightweighting it. Technical Field

[0001] This invention belongs to the fields of molecular sieve and petrochemical technology. Specifically, this invention relates to a ZSM-5 molecular sieve and its preparation method, particularly its application in the light hydrocarbon and naphtha lightening process to obtain cracking feedstock. This invention also relates to a method for light hydrocarbon and naphtha lightening, specifically, a method for obtaining cracking feedstock by lightening light hydrocarbon and naphtha. Background Technology

[0002] With the trend towards large-scale, integrated, and base-oriented development of oil refineries and the advancement of processing technologies, light hydrocarbons are no longer cheap byproducts of refineries but are gradually becoming high-value, low-carbon resources. Besides converting light hydrocarbon resources into high-quality oil components, their utilization pathways are becoming increasingly molecular and diversified. Furthermore, with the rapid development of clean energy, the energy consumption structure has undergone profound changes, and the contradiction of overcapacity in oil refining is intensifying. "Oil conversion" has become one of the main directions for the transformation and development of the refining industry. How to increase the production of high-quality chemical raw materials and reduce the production costs of olefins and aromatics has become a challenge facing the refining industry on its "oil conversion" path, both now and in the future.

[0003] Ethylene is the leading product in the petrochemical industry, and its production volume is a crucial indicator of a country's petrochemical industry development level. Steam cracking is the main process for ethylene production, typically using ethane, propane, light hydrocarbons, light naphtha, naphtha, light diesel oil, and hydrotreated tail oil as feedstocks. The product distribution and yield vary significantly among different types of cracking feedstocks. For example, the yield of dienes (ethylene and propylene) from naphtha cracking is approximately 40%-50%, the yield of ethylene from ethane cracking can reach 78%, and the yield of dienes from propane cracking can reach 60%. Studies have shown that higher n-alkane content, lower aromatic hydrocarbon content, and a higher degree of light hydrocarbon composition in the cracking feedstock will be more conducive to increasing the yield of high-value, low-carbon olefins and reducing the production of low-value tar.

[0004] For steam cracking units using naphtha as feedstock, the feedstock accounts for up to 80% of the total cost, making feedstock quality a key factor affecting costs. Since naphtha is the primary feedstock for most cracking units in China, improving the overall utilization rate of cracking feedstock and the yield of high-value products through naphtha upgrading is receiving increasing attention from the petrochemical industry.

[0005] Currently, many technical solutions have been proposed for naphtha reforming, including catalytic cracking, hydrotreating (desulfurization), hydroisomerization, and aromatization of naphtha alone or together with C4 liquefied petroleum gas (LPG) to produce propane, under hydrotreating or non-hydrotreating conditions. Among these, aromatization reforming technology has strong feedstock adaptability, the reaction system is non-hydrotreating and can be operated at low pressure, requires less investment and has low energy consumption, and can effectively convert refinery naphtha and low-carbon hydrocarbons, but the yield and octane number of the resulting liquid products are relatively low.

[0006] Generally, naphtha reforming catalysts consist of a support (such as ZSM-5 molecular sieve, mordenite, SAPO-34 molecular sieve, etc.) and a bifunctional catalyst composed of supported metal oxides. Among them, ZSM-5 molecular sieve is the most widely used in this field due to its unique ten-membered ring cross-channel system. The pore size of ZSM-5 molecular sieve can meet the generation and diffusion of monocyclic aromatic hydrocarbons, while restricting the condensation, cyclization, and coking of aromatic hydrocarbons; its three-dimensional cross-channel system is conducive to the diffusion of reactants and products, improving the catalytic efficiency of the active center of the catalyst, and reducing the probability of coking and clogging of zeolite channels.

[0007] CN113385215A discloses a method for preparing and applying a catalyst for hydrocracking to propane. This method utilizes a modified core-shell structured SAPO-34 / ZSM-5 composite molecular sieve catalyst to achieve catalytic cracking of light hydrocarbons to produce propane under hydrocracking conditions. However, when used for hydrocracking of naphtha, the propane yield is below 40%, and further improvement is needed.

[0008] CN112209794A discloses a method for the combined production of propylene from light hydrocarbon reforming and propane dehydrogenation. This method combines the production of propane from light hydrocarbon reforming with the production of propylene from propane catalytic dehydrogenation. The method includes a light hydrocarbon reforming reaction zone and a propane dehydrogenation reaction zone. The products from light hydrocarbon reforming and propane dehydrogenation enter a common product recovery and separation system. The recovered light hydrocarbons are recycled as feedstock for light hydrocarbon reforming, and the recycled propane is used as feedstock for propane dehydrogenation.

[0009] CN110947417A discloses a catalyst for producing propane and gasoline from alkanes. The catalyst comprises a composite support and rare earth oxides in a content of 0.1–2.0% by mass based on the support. The composite support comprises 5–85% by mass ZSM-5 zeolite, 5–85% by mass MCM-41 zeolite, and 5–40% by mass alumina. This catalyst is used for the reforming of straight-run naphtha to produce propane and gasoline under non-hydrogenation conditions, wherein the propane yield is below 40%.

[0010] CN101747933A discloses a method for aromatization and upgrading of naphtha and light hydrocarbons. This method involves aromatization and upgrading of naphtha and C3-C5 light hydrocarbons under hydrogen-exposed conditions, converting low-octane naphtha and low-carbon hydrocarbons into high-octane gasoline components and high-quality liquefied petroleum gas (LPG).

[0011] CN101367048A discloses a method for preparing and applying a condensate oil aromatization catalyst. Using nano-molecular sieves loaded with metal active components as catalysts, a moving bed reactor can be used to produce BTX triphenyl products, while simultaneously producing 18-28 wt% high-quality liquefied petroleum gas as a byproduct. The catalyst has strong resistance to carbon deposition and high yield of aromatic products.

[0012] US4190519A discloses a combined process for naphtha reforming. The process includes: fractionating naphtha to obtain light naphtha containing C6 alkanes and a heavier fraction containing methylcyclopentane; the lighter fraction recovered after reforming is mixed with the light naphtha and subjected to aromatization reforming under non-hydrogenation conditions using a ZSM-5 type catalyst to obtain a high-octane gasoline component.

[0013] US6190534B1 discloses a combined process for selectively upgrading naphtha to obtain a high-octane product rich in aromatics. The process includes: first, reacting naphtha feedstock with a platinum-containing catalyst in a dehydrogenation stage to obtain an olefin-containing intermediate; then, reacting the olefin-containing intermediate with a solid acid aromatization catalyst in an aromatization stage to obtain a product rich in aromatics.

[0014] To improve reaction efficiency, nano-ZSM-5 molecular sieves are often used for naphtha lightening. This is because the diffusion capacity of reactants on molecular sieves is inversely proportional to their size; the smaller size of nano-ZSM-5 molecular sieves facilitates the proximity of reactants to active centers, promoting product diffusion. However, the synthesis of nano-sized molecular sieves involves extremely high energy and water consumption, increasing the cost of industrial production. Furthermore, existing literature reports that propane is often produced as a byproduct during the aromatization of light hydrocarbons, resulting in low propane yields, large equipment circulation volumes, increased investment, and lower economic efficiency.

[0015] In summary, existing technology reports mostly involve the byproduct of propane production during the aromatization of light hydrocarbons (or naphtha), generally suffering from low propane yields. This leads to large circulating volumes, larger plant sizes, and increased investment. Furthermore, existing propane production technologies, such as the method for producing propane from light hydrocarbons via hydroconversion disclosed in CN 113307717 A, primarily target the conversion of C4-C6 alkane mixtures to propane. The catalyst mentioned is only acidic HZSM-5 molecular sieve, without addressing how to selectively produce propane and other cracked feedstocks from naphtha. Additionally, the reaction products obtained by this method require multi-stage separation units, including absorption towers, stripping towers, stabilization towers, and light hydrocarbon removal towers, to obtain propane and mixed aromatics. Unreacted light hydrocarbons need to be recycled, resulting in a long production process, high distillation energy consumption, and low economic efficiency. Summary of the Invention

[0016] In view of the problems existing in the prior art, the present invention provides a ZSM-5 molecular sieve, its preparation method, and its application. When a catalyst prepared using the ZSM-5 molecular sieve of the present invention is used for naphtha lightening, it can highly selectively remove naphtha (mainly C4 ... 12 The following hydrocarbons can be converted into high-quality cracking feedstocks containing C2-C3 alkanes.

[0017] The first aspect of this invention provides a ZSM-5 molecular sieve, wherein the total specific surface area of ​​the ZSM-5 molecular sieve is 300-500 m². 2 / g, of which the external specific surface area accounts for 33%-45% of the total specific surface area, this ZSM-5 molecular sieve 27 The ratio of the peak area at a chemical shift of 53 ppm in Al NMR spectra to the peak area of ​​tetracoordinate Al is ≥50%.

[0018] A second aspect of this invention provides a method for preparing the aforementioned ZSM-5 molecular sieve, comprising:

[0019] S1. Mix the first silicon source, the first template agent, the first alkali source and water to obtain a seed gel; wherein the first silicon source is a solid silicon source; the molar ratio of the first alkali source to the first silicon source is 0.05-0.10, the molar ratio of the first template agent to the first silicon source is 0.05-0.10, and the first silicon source is calculated as SiO2, and the first alkali source is calculated as an oxide;

[0020] S2. Mix the second silicon source, aluminum source, second template agent, second alkali source, water, and seed gel to obtain the synthesis solution;

[0021] S3. The synthesis solution is subjected to crystallization treatment to obtain ZSM-5 molecular sieve.

[0022] A third aspect of the invention provides a catalyst for a lightening reaction, comprising a molecular sieve prepared according to the method of the first aspect or the second aspect, a binder, and a modified metal. The binder is, for example, alumina. The modified metal is, for example, at least one selected from molybdenum, zinc, copper, gallium, and lanthanum. Preferably, based on the catalyst, the mass content of the molecular sieve is ≥70%, more preferably ≥75%, and even more preferably ≥80%. Preferably, based on the catalyst, the mass content of the modified metal is 1%-10%, wherein the modified metal is calculated as an oxide. Preferably, based on the catalyst, the mass content of the binder is ≤20%, more preferably 12%-20%.

[0023] A fourth aspect of the present invention provides a lightweighting method, comprising the following steps:

[0024] A1. Mix light hydrocarbons and / or naphtha with hydrogen-rich gas to obtain a mixture;

[0025] A2. The mixture obtained in step A1 is contacted with a ZSM-5 molecular sieve based on the first aspect of the present invention or a ZSM-5 molecular sieve prepared by the second aspect of the present invention or a ZSM-5 molecular sieve prepared by the third aspect of the present invention to perform a modification treatment, thereby obtaining a modified product.

[0026] A3. Optionally, the modified product obtained in step A2 is separated to obtain a cracking feedstock rich in C2-C3 hydrocarbons and a liquid phase, respectively. Preferably, the liquid phase is separated to obtain a recycled material rich in C4-C6 hydrocarbons and a mixed aromatic product, wherein the recycled material is recycled back to step A2.

[0027] The fifth aspect of the present invention provides the application of the ZSM-5 molecular sieve of the first aspect of the present invention and the modified catalyst of the third aspect of the present invention in the lightening of naphtha.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The ZSM-5 molecular sieve of the present invention has a specific external surface area ratio, which is suitable as a component of naphtha lightening catalyst. It can significantly improve the yield of cracking feedstock under the condition of low hydrogen-oil volume ratio.

[0030] (2) The ZSM-5 molecular sieve of the present invention has an appropriate aluminum (53) content ratio, which is suitable for the adsorption and diffusion of small molecules, and its confinement effect is suitable for the catalytic preparation of ethane and propane.

[0031] (3) The ZSM-5 molecular sieve of this invention is prepared by using solid silica gel as the silicon source to prepare gel seed crystals, which are obtained by crystallizing a synthesis solution containing gel seed crystals under suitable conditions. By providing gel seed crystals, a large number of small crystal nuclei are provided in the synthesis solution for crystal growth, thereby growing fine-particle molecular sieves with a large specific surface area. Furthermore, the molecular sieves have a relatively high external specific surface area ratio, which facilitates the utilization of reactants. In contrast, without the use of gel seed crystals, molecular sieves grown directly from the synthesis solution have a low specific surface area and a relatively low external specific surface area ratio, which is not conducive to the utilization of reactants. The obtained ZSM-5 molecular sieve is particularly suitable as a component of naphtha lightening catalyst. When the prepared naphtha lightening catalyst is used in the process of naphtha hydrorefining, it can significantly improve the yield of cracking feedstock under low hydrogen-to-oil volume ratio conditions.

[0032] (4) Surprisingly, the gel seed prepared with solid silica gel as the silicon source resulted in a significant increase in the proportion of Al(53), which means that the key channel intersection is rich in active catalytic sites.

[0033] (5) In the lightening method of the present invention, the naphtha feedstock is lightened and converted into high-quality cracking feedstock mainly composed of ethane and propane, which can improve the naphtha feedstock of the cracking unit, realize the efficient utilization of naphtha, and help improve the diene yield of the unit and reduce the amount of cracking tar generated.

[0034] (6) The present invention lightens naphtha feedstock under hydrogen conditions, which can delay coking of catalyst to a certain extent and extend the single-pass operation cycle of catalyst.

[0035] (7) When the catalyst of the present invention is used in the process of hydrogenation of naphtha, the yield of cracking feedstock can be greatly improved under the condition of low hydrogen-to-oil volume ratio (0.2-3.0).

[0036] (8) The catalyst of the present invention preferably adopts metal-modified ZSM-5 molecular sieve catalyst. The inventors have found through research that when the external specific surface area of ​​ZSM-5 molecular sieve accounts for 33% to 45% and is modified with a specific metal, the resulting catalyst can significantly improve the yield of cracking feedstock under the condition of low hydrogen-oil volume ratio when used in the process of naphtha hydrogenation. Attached Figure Description

[0037] Figure 1 is a schematic diagram of the process flow of one embodiment of the method according to the present invention.

[0038] Figure 2 is a schematic diagram of the process flow of one embodiment of the method according to the present invention;

[0039] Figure 3 is a schematic diagram of the process flow of one embodiment of the method according to the present invention;

[0040] Figure 4 is a schematic diagram of the process flow of one embodiment of the method according to the present invention;

[0041] Figure 5 is a schematic diagram of the process flow of one embodiment of the method according to the present invention;

[0042] Figure 6 is a schematic diagram of the process flow of one embodiment of the method according to the present invention;

[0043] The following are labeled in Figure 1-6: A. Adsorption denitrification tower, B. Feed-reaction product heat exchanger, C. Heater, D. Reforming reactor, E. Stabilization tower, F. Propane removal tower, G. Light hydrocarbon removal tower, 1. Feed, 2. Hydrogen-rich gas, 3. Light gas (C1+C2 and a small amount of H2), 4. Cracking feedstock (C3 and a small amount of C2), 5. Recycled material (C4-C6), 6. C7 + Logistics; D1. First light-liquidation reactor, D2. Second light-liquidation reactor, H. Gas-liquid separator, L. Reactor, M. Cooler, N. Gas-liquid separation tank, 21. Supplementary hydrogen-rich gas, 31. Gas phase (mainly hydrogen and a small amount of methane), 51. Gas phase light hydrocarbons, 61. Mixed aromatics; S. Aromatization reactor, K. Cooler, P. Extraction unit, Q. Cooler, R. Gas-liquid separation tank, 32. C1-C3, 41. Gaseous light hydrocarbons, 7. C1+H2 release, 8. C2-C3, 9. Rag oil;

[0044] Figure 7 shows the XRD pattern of the ZSM-5 molecular sieve obtained in Example 1;

[0045] Figure 8 is a SEM image of the ZSM-5 molecular sieve obtained in Example 1;

[0046] Figure 9 shows the aluminum NMR spectrum of the ZSM-5 molecular sieve obtained in Example 1;

[0047] Figure 10 shows the XRD pattern of the ZSM-5 molecular sieve obtained in Example 2;

[0048] Figure 11 is a SEM image of the ZSM-5 molecular sieve obtained in Example 2;

[0049] Figure 12 is a SEM image of the ZSM-5 molecular sieve obtained in Example 4;

[0050] Figure 13 is a SEM image of the ZSM-5 molecular sieve obtained in Example 5;

[0051] Figure 14 shows the XRD pattern of the ZSM-5 molecular sieve obtained in Comparative Example 1.

[0052] Figure 15 is a SEM image of the ZSM-5 molecular sieve obtained in Comparative Example 1.

[0053] Figure 16 shows the XRD pattern of the ZSM-5 molecular sieve obtained in Comparative Example 2;

[0054] Figure 17 is a SEM image of the ZSM-5 molecular sieve obtained in Comparative Example 2;

[0055] Figure 18 shows the XRD pattern of the ZSM-5 molecular sieve obtained in Comparative Example 3.

[0056] Figure 19 is a SEM image of the ZSM-5 molecular sieve obtained in Comparative Example 3.

[0057] Figure 20 shows the XRD pattern of the ZSM-5 molecular sieve obtained in Comparative Example 4.

[0058] Figure 21 is a SEM image of the ZSM-5 molecular sieve obtained in Comparative Example 4;

[0059] Figure 22 shows the aluminum NMR spectrum of ZSM-5 molecular sieve catalyst B obtained in Preparation Example 1.

[0060] In different accompanying drawings, the same or similar parts or devices are represented by the same or similar reference numerals. Detailed Implementation

[0061] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0062] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0063] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0064] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0065] Although the terms first, second, third, etc., may be used herein to describe various steps, elements, components, regions, layers, and / or sections, these steps, elements, components, regions, layers, and / or sections should not be limited by these terms unless otherwise specified. These terms may be used only to distinguish one step, element, component, region, layer, or section from another. Unless clearly indicated by the context, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first step, element, component, region, layer, or section discussed below may be referred to as the second step, element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0066] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" as used herein are intended to include the plural forms as well. The terms "comprising," "including," "containing," and "having" are inclusive and thus describe the presence of the stated features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. Although the open-ended term "comprising" should be understood as a non-limiting term used to describe and claim the various embodiments described herein, in some respects it may instead be understood as a more restrictive and limiting term, such as "consisting of" or "essentially composed of." Thus, for any given embodiment describing a composition, material, component, element, feature, integer, operation, and / or process step, this disclosure also particularly includes embodiments consisting of or substantially consisting of such compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of "consisting of," the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of "essentially composed of," any additional compositions, materials, components, elements, features, integers, operations, and / or process steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operations, and / or process steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0067] Any methods, procedures, and operations described herein should not be construed as necessarily requiring them to be performed in the specific order discussed or shown, unless explicitly stated otherwise. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0068] The above description of the embodiments is provided for illustration and description purposes. It is not intended to be exhaustive or limiting of this disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable and applicable to the selected embodiment where applicable, even if not explicitly shown or described. It can also be changed in many ways. Such changes should not be considered as departing from this disclosure, and all such modifications are intended to be included within the scope of this disclosure.

[0069] In this application, except where expressly stated, any matters or issues not mentioned herein shall be directly applicable to those known in the art without any modification. Furthermore, any implementation described herein may be freely combined with one or more other implementations described herein, and the resulting technical solutions or concepts shall be considered part of the original disclosure or original record of this application, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be clearly unreasonable.

[0070] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0071] The method of the present invention will be described in detail below with reference to Figure 1. The method for lightening naphtha provided by the present invention includes: naphtha feedstock 1 undergoes adsorption denitrification pretreatment in adsorption denitrification tower A; the pretreated feedstock is mixed with hydrogen-rich gas 2 and then heat-exchanged in feedstock-reaction product heat exchanger B, followed by heating in heater C before entering reforming reactor D, where it contacts a reforming catalyst for reforming treatment to obtain a reformed product; the reformed product, after heat exchange in feedstock-reaction product heat exchanger B, enters stabilization tower E, where light gas 3 (C1+C2 and a small amount of H2) is obtained at the top; the bottom product enters propane removal tower F, where cracked feedstock 4 (propane and a small amount of ethane) is obtained at the top; the bottom product enters light hydrocarbon removal tower G, where recycled material 5 (C4-C6) is obtained at the top; and C7 is obtained at the bottom. + Logistics 6 (mixed aromatic products), wherein the recycled material is mixed with the pretreated raw material as the feedstock for the reforming reactor D.

[0072] The method of the present invention will be described in detail below with reference to Figure 2. The naphtha lightening method provided by the present invention includes: naphtha feedstock 1 is first subjected to adsorption denitrification pretreatment in adsorption denitrification tower A. The pretreated feedstock is mixed with hydrogen-rich gas 2 and then heat-exchanged in feedstock-reaction product heat exchanger B. After being heated by heater C, it enters the first reaction zone, that is, it passes through the first lightening reactor D1 and the second lightening reactor D2 in sequence and reacts with the naphtha lightening catalyst, that is, the first molecular sieve catalyst. The second lightening reactor D2 can be supplemented with hydrogen-rich gas 21. The resulting product enters the second reaction zone, that is, reactor L, and is subjected to upgrading treatment in contact with the second molecular sieve catalyst. After the upgraded product is heat-exchanged in feedstock-reaction product heat exchanger B, it passes through cooler M and discharges gas phase 31 (mainly hydrogen and a small amount of methane). Then it enters gas-liquid separator N to obtain gas phase product 51 (cracking feedstock) and liquid phase product 61 (mixed aromatics).

[0073] The method of the present invention will be described in detail below with reference to Figure 3. The naphtha lightening method provided by the present invention includes: naphtha feedstock 1 is first subjected to adsorption denitrification pretreatment in adsorption denitrification tower A. The pretreated feedstock is mixed with hydrogen-rich gas 2 and then heat-exchanged in feedstock-reaction product heat exchanger B. After being heated by heater C, it enters the first reaction zone, i.e., reactor D. It passes through reaction section A1 and reaction section A2 in sequence and reacts with the naphtha lightening catalyst, i.e., the first molecular sieve catalyst. Hydrogen-rich gas 21 can be added to reactor D. The resulting product enters the second reaction zone, i.e., reactor L, and is subjected to upgrading treatment in contact with the second molecular sieve catalyst. The upgraded product is then heat-exchanged in feedstock-reaction product heat exchanger B and then cooled by cooler M. After the gas phase 31 (mainly hydrogen and a small amount of methane) is discharged, it enters gas-liquid separator N to obtain gas phase product 51 (cracking feedstock) and liquid phase product 61 (mixed aromatics).

[0074] The method of the present invention will be described in detail below with reference to Figure 4. The method for reforming light hydrocarbons and naphtha provided by the present invention includes: light hydrocarbon and / or naphtha feedstock 1 is first subjected to adsorption denitrification pretreatment in adsorption denitrification tower A. The pretreated feedstock is mixed with hydrogen-rich gas 2 and then heat-exchanged in feedstock-reaction product heat exchanger B. After being heated by heater C, it enters the reforming reaction zone, i.e., reforming reactor D. The obtained product is heat-exchanged in feedstock-reaction product heat exchanger B and then enters stabilization tower E. The gaseous product at the top of the tower enters propane de-propanizer tower F. The top product 32 (C1-C3) of the propane de-propanizer tower is used as cracking feedstock. The bottom product of the propane de-propanizer tower is mixed with the bottom product of the stabilization tower E and enters aromatization reactor S. The obtained product is cooled by cooler Q and enters gas-liquid separator R to obtain gaseous product 41 (mainly a small amount of unreacted C4-C6, which can be used as recycled material). The liquid product enters extraction unit P to obtain mixed aromatics 61. The raffinate oil 9 is recycled as feedstock for aromatization reactor.

[0075] The method of the present invention will be described in detail below with reference to Figure 5. The present invention provides a method for reforming light hydrocarbons and naphtha, comprising: light hydrocarbon and / or naphtha feedstock 1 is first subjected to adsorption denitrification pretreatment in adsorption denitrification tower A; the pretreated feedstock is mixed with hydrogen-rich gas 2 and then heat-exchanged in feedstock-reaction product heat exchanger B, and then heated by heater C before entering the reforming reaction zone, namely reforming reactor D1 and reforming reactor D2. Reforming reactor D2 can be supplemented with hydrogen-rich gas 2; the obtained product is heat-exchanged in feedstock-reaction product heat exchanger B and then enters stabilization tower E; the gaseous product at the top of the tower enters propane de-propanizer F; the top product 32 (C1-C3) of the propane de-propanizer is used as cracking feedstock; the bottom product of the propane de-propanizer is mixed with the bottom product of stabilization tower E and enters aromatization reactor S; the obtained product is cooled by cooler Q and enters gas-liquid separator R to obtain gaseous product 41 (mainly a small amount of unreacted C4-C6, which can be used as recycled material); the liquid product enters extraction unit P to obtain mixed aromatics 61; and the raffinate oil 9 is recycled as feedstock for the reforming reactor.

[0076] The method of the present invention will be described in detail below with reference to Figure 6. The method for reforming light hydrocarbons and naphtha provided by the present invention includes: light hydrocarbon feedstock 1 is first pretreated by adsorption and denitrification in adsorption denitrification tower A. The pretreated feedstock is mixed with hydrogen-rich gas 2 and then heat-exchanged in feedstock-reaction product heat exchanger B. After being heated by heater C, it enters the reforming reaction zone, i.e., reforming reactor D. After the obtained product is heat-exchanged in feedstock-reaction product heat exchanger B, a small amount of methane and hydrogen are released 7 and then enters cooler K. Then it enters gas-liquid separator H. The gas phase 8 is C2-C3 as cracking feedstock, and the liquid phase enters aromatization reactor S. The obtained product enters gas-liquid separator R after passing through cooler Q to obtain gas phase product 41 (mainly a small amount of unreacted C4-C6, which can be used as recycled material). The liquid phase product enters extraction unit P to obtain mixed aromatics 61. The raffinate oil 9 is recycled as feedstock for aromatization reactor.

[0077] The first aspect of this invention provides a ZSM-5 molecular sieve, wherein the total specific surface area of ​​the ZSM-5 molecular sieve is 300-500 m². 2 / g, of which the external specific surface area accounts for 33%-45% of the total specific surface area, this ZSM-5 molecular sieve 27 The ratio of the peak area at a chemical shift of 53 ppm in Al NMR spectra to the peak area of ​​tetracoordinate Al is ≥50%.

[0078] Furthermore, the total specific surface area of ​​the ZSM-5 molecular sieve is 350-500 m². 2 / g. For example, the total specific surface area of ​​the ZSM-5 molecular sieve is 300m². 2 / g、310m 2 / g、320m 2 / g、330m2 / g、340m 2 / g, 350m 2 / g、360m 2 / g、370m 2 / g、380m 2 / g、390m 2 / g、400m 2 / g、410m 2 / g、420m 2 / g、430m 2 / g、440m 2 / g、450m 2 / g、460m 2 / g、470m 2 / g、480m 2 / g、490m 2 / g、500m 2 / g, and the range formed by any two of these values. More preferably, the total specific surface area of ​​the ZSM-5 molecular sieve is 350-500 m² / g. 2 / g, more preferably 380-500m 2 / g, further optimized to 400-500m 2 / g.

[0079] Furthermore, in the ZSM-5 molecular sieve, the external specific surface area accounts for 33%-45% of the total specific surface area, preferably 34%-45%, for example 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, etc., and any value within the range formed by any two of these values.

[0080] Furthermore, the ZSM-5 molecular sieve has an external specific surface area of ​​99-225 m². 2 / g. For example, the external specific surface area of ​​the ZSM-5 molecular sieve is 100m². 2 / g、110m 2 / g、120m 2 / g, 130m 2 / g, 140m 2 / g, 150m 2 / g, 160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g、200m 2 / g、210m 2 / g、220m 2 / g、225m 2 / g, and any value within the range formed by any two of these values. More preferably, the external specific surface area of ​​the ZSM-5 molecular sieve is 125-225 m² / g. 2 / g, more preferably 132-225m 2 / g. In the context of this invention, both specific surface area and external specific surface area refer to BET specific surface area. Specific surface area is typically determined using the BET nitrogen adsorption method, and the total surface area is calculated based on multilayer adsorption theory. The microporous surface area is separated from the total surface area using the t-plot method or α-s plot method, and the remaining portion is the external specific surface area.

[0081] Further, in the ZSM-5 molecular sieve, the SiO2 / Al2O3 molar ratio is 50-250. For example, the SiO2 / Al2O3 molar ratio is 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 210, 220, 230, 240, or 250. Preferably, the SiO2 / Al2O3 molar ratio is 60-220, more preferably 70-210.

[0082] Further, in the ZSM-5 molecular sieve, the surface silica-to-alumina ratio is 30%-90% of the bulk silica-to-alumina ratio, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90%. Preferably, the surface silica-to-alumina ratio is 30%-85% of the bulk silica-to-alumina ratio, more preferably 30%-65%.

[0083] In the context of this invention, the silicon-to-aluminum ratio (S / A ratio) refers to the molar ratio of SiO2 to Al2O3. The surface S / A ratio of the molecular sieve is the S / A ratio over a thickness range of approximately 5 nm from the surface of the molecular sieve to the center of the spherical particles. The surface S / A ratio is determined by X-ray photoelectron spectroscopy (XPS). The bulk S / A ratio of the molecular sieve is the overall S / A ratio of the molecular sieve. Unless otherwise specified, the S / A ratio refers to the bulk S / A ratio.

[0084] In a preferred embodiment, the ZSM-5 molecular sieve... 27 The peak area of ​​the Al peak at a chemical shift of 53 ppm in the NMR spectrum is 50-70% to the peak area of ​​tetracoordinate Al, for example, 50-65%. For example, in the ZSM-5 molecular sieve, the ZSM-5 molecular sieve... 27The ratio of the peak area at a chemical shift of 53 ppm in the Al NMR spectrum to the peak area of ​​tetracoordinate Al is ≥50%, ≥51%, ≥52%, ≥53%, ≥54%, ≥55%, ≥56%, ≥57%, ≥58%, ≥59%, ≥60%, ≥61%, ≥62%, ≥63%, ≥64%, and ≥65%. For example, in the ZSM-5 molecular sieve, the ZSM-5 molecular sieve... 27 The ratio of the peak area at a chemical shift of 53 ppm in Al NMR spectra to the peak area of ​​tetracoordinate Al is ≤70%, ≤69%, ≤68%, ≤67%, and ≤66%.

[0085] In this context, the peak area of ​​tetracoordinated Al in a molecular sieve refers to the sum of the peak areas of all tetracoordinated Al. According to some embodiments of the invention, the tetracoordinated Al in the molecular sieve ZSM-5 accounts for ≥90% of the total aluminum content of the molecular sieve, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or even 100%.

[0086] In molecular sieves 27 In Al NMR spectroscopy, the peaks of framework aluminum are mainly based on its coordination state, local chemical environment, and dynamic evolution characteristics. In ZSM-5 molecular sieves, the chemical shift range of 50–70 ppm is usually considered as the framework aluminum of the molecular sieve. According to the structural characteristics of the molecular sieve, it is further subdivided into different aluminum species, usually at the following chemical shifts: 49 ppm, 53 ppm, 56 ppm, and 59 ppm, which are denoted here as Al(49), Al(53), Al(56), and Al(59), respectively.

[0087] Not limited to any particular theory, the inventors of this invention believe that 27 The chemical shift at 53 ppm (corresponding to the pore intersection point) in the Al NMR spectrum is the most critical, which is more suitable for the adsorption and diffusion of small molecules. Its confinement effect is suitable for the catalytic production of ethane and propane. An aluminum (53) content between 50-65% is more appropriate.

[0088] Furthermore, the ZSM-5 molecular sieve is a nanosheet aggregate with a particle size of 20-300 nm and a thickness of 10-100 nm. For example, the particle size of the nanosheets can be 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, or 300 nm, or any combination thereof. Similarly, the thickness of the nanosheets can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, or any combination thereof.

[0089] In the context of this invention, the average particle size of molecular sieve nanosheets refers to the average size of the nanosheets in the largest dimension, such as the transverse direction, and the average thickness refers to the average size of the nanosheets in the direction perpendicular to the transverse direction. The average particle size of molecular sieve aggregates refers to the average size of the molecular sieve aggregates in the largest dimension.

[0090] Furthermore, in the ZSM-5 molecular sieve, the particle size of the nanosheet aggregates is 0.3-10 μm. The particle size of the aggregates is, for example, 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any combination thereof.

[0091] In the preferred embodiment, ZSM-5 molecular sieve is an aggregate composed of nanosheets that are clustered and stacked. This not only retains the large specific surface area of ​​the nano molecular sieve, but also effectively reduces the separation difficulty of the mother liquor and molecular sieve due to the large size of the aggregates. This reduces the energy and water consumption in the separation process of nanoscale molecular sieves and significantly reduces industrial production costs.

[0092] Furthermore, the pore volume of the ZSM-5 molecular sieve is 0.24-0.35 cm³. 3 / g. For example, the pore volume of the ZSM-5 molecular sieve is 0.24 cm³. 3 / g, 0.25cm 3 / g, 0.26cm 3 / g, 0.27cm 3 / g, 0.28cm 3 / g, 0.29cm 3 / g, 0.30cm 3 / g, 0.31cm 3 / g, 0.32cm 3 / g, 0.33cm 3 / g, 0.34cm 3 / g, 0.35cm 3 / g, or any combination of the above values ​​to obtain a range.

[0093] In the context of this invention, pore volume, also known as pore size, refers to the total volume occupied by pores within a porous material.

[0094] Furthermore, the micropore volume of the ZSM-5 molecular sieve is 0.10-0.22 cm³. 3 / g. For example, the micropore volume of the ZSM-5 molecular sieve is 0.10 cm³. 3 / g, 0.11cm 3 / g, 0.12cm3 / g, 0.13cm 3 / g, 0.14cm 3 / g, 0.15cm 3 / g, 0.16cm 3 / g, 0.17cm 3 / g, 0.18cm 3 / g, 0.19cm 3 / g, 0.20cm 3 / g, 0.21cm 3 / g, 0.22cm 3 / g, or any combination of the above values ​​to obtain a range.

[0095] In the context of this invention, micropore volume refers to the volume occupied by micropores with a pore size of less than 2 nanometers in porous materials, such as molecular sieves.

[0096] Furthermore, the average pore size of the ZSM-5 molecular sieve is 2.1-3.5 nm. For example, the average pore size of the ZSM-5 molecular sieve is 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm, 2.7 nm, 2.8 nm, 2.9 nm, 3.0 nm, 3.1 nm, 3.2 nm, 3.3 nm, 3.4 nm, 3.5 nm, or any combination of the above values.

[0097] In the context of this invention, average pore size refers to the average diameter of the internal pores of the molecular sieve.

[0098] In the context of this invention, agglomerates are aggregates formed by interconnected nanosheets. Agglomerates not only retain the large specific surface area of ​​molecular sieve nanosheets, but also effectively reduce the difficulty of separating the mother liquor from the molecular sieve due to their larger size, thereby reducing industrial production costs.

[0099] The second aspect of this invention provides a method for preparing the ZSM-5 molecular sieve of the first aspect of this invention, comprising:

[0100] S1. Mix the first silicon source, the first template agent, the first alkali source and water to obtain a seed gel; wherein the first silicon source is a solid silicon source; the molar ratio of the first alkali source to the first silicon source is 0.05-0.10, the molar ratio of the first template agent to the first silicon source is 0.05-0.10, and the first silicon source is calculated as SiO2, and the first alkali source is calculated as an oxide;

[0101] S2. Mix the second silicon source, aluminum source, second template agent, second alkali source, water, and seed gel to obtain the synthesis solution;

[0102] S3. The synthesis solution is subjected to crystallization treatment to obtain ZSM-5 molecular sieve.

[0103] Not limited by specific theories, the slower dissolution rate of solid silicon sources results in more uniform release of silicon species (such as silicates), which is beneficial for forming highly ordered microporous structures. Conversely, silica sol, being nanoscale silica, exhibits higher activity in gel solutions, potentially leading to localized gel inhomogeneity and a greater likelihood of untransformed silica during synthesis. Furthermore, from a production perspective, silica powder is easier to transport and store, and its purity is controllable, making it suitable for industrial production. In actual catalyst development, silica powder has proven more effective in preparing gel precursors. It is speculated that during gel precrystallization, the slower dissolution and release of the silicon source compared to the particle activity of silica sol allows for the growth of numerous small crystal nuclei during precrystallization, which are then used to generate secondary crystallization nanoaggregates.

[0104] In the context of this invention, the alkali source is considered as an oxide. For example, when sodium hydroxide is used, it is considered as Na₂O. When potassium hydroxide is used, it is considered as K₂O. When ammonia is used, it is considered as two moles of ammonia.

[0105] Furthermore, in the preparation method of the seed gel described in step S1, the mixing conditions are stirring at 40-120℃ for 6-30 hours.

[0106] Further, in the method for preparing the seed gel in step S1, the solid silicon source is silica gel powder with a particle size of 60-800 mesh, preferably 100-300 mesh. For example, the particle size of the silica gel powder can be 60 mesh, 80 mesh, 100 mesh, 120 mesh, 140 mesh, 160 mesh, 180 mesh, 200 mesh, 220 mesh, 240 mesh, 260 mesh, 280 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh, 550 mesh, 600 mesh, 650 mesh, 700 mesh, 750 mesh, or 800 mesh. Smaller particle sizes of silica gel powder are also feasible.

[0107] Further, in step S1, the first template agent is at least one of n-butylamine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium bromide, ethylenediamine, or hexamethylenediamine.

[0108] Furthermore, in step S1, the first alkali source is at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0109] Furthermore, the molar ratio of water to the first silicon source is 5-30; wherein the first silicon source is SiO2.

[0110] Furthermore, the second template agent is an organic amine, preferably at least one of n-butylamine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium bromide, ethylenediamine, triethylamine, or hexamethylenediamine.

[0111] Further, the second silicon source is at least one selected from silica sol, water glass, fumed silica, and silica gel, preferably silica gel, more preferably silica gel powder, with a particle size of 60-800 mesh, preferably 100-300 mesh. For example, the particle size of the silica gel powder can be 60 mesh, 80 mesh, 100 mesh, 120 mesh, 140 mesh, 160 mesh, 180 mesh, 200 mesh, 220 mesh, 240 mesh, 260 mesh, 280 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh, 550 mesh, 600 mesh, 650 mesh, 700 mesh, 750 mesh, or 800 mesh. Silica gel powder with even smaller particle sizes is also feasible.

[0112] Furthermore, the aluminum source is at least one of sodium aluminate, aluminum sulfate, and aluminum isopropoxide.

[0113] Furthermore, the second alkali source is at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0114] According to a preferred aspect, the molar ratio of the second silicon source to the aluminum source is 30-100; wherein the second silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3.

[0115] According to a preferred aspect, the molar ratio of the second template agent to the second silicon source is 0.02-0.10, wherein the second silicon source is SiO2.

[0116] According to a preferred aspect, the molar ratio of the second alkali source to the second silicon source is 0.07-0.12, wherein the second silicon source is calculated as SiO2 and the second alkali source is calculated as oxide.

[0117] According to a preferred aspect, the molar ratio of water to the second silicon source is 15-30, wherein the second silicon source is SiO2.

[0118] According to a preferred aspect, the mass ratio of the seed gel to the second silicon source is 1%-20%, preferably 3%-10%, wherein the second silicon source is calculated as SiO2 and the seed gel is calculated as SiO2.

[0119] Conventional methods for crystallization are well known to those skilled in the art. According to a preferred aspect, the crystallization conditions in step S3 include: a crystallization temperature of 125-180°C under sealed conditions, and a crystallization time of 16-96 hours, for example, 16-60 hours. According to a preferred aspect, the crystallization in step S3 can be carried out at a relatively low temperature, for example, 130°C, for 24-48 hours, and then further crystallized at a relatively high temperature, for example, 170°C, for another 24-48 hours. According to a preferred aspect, the crystallization in step S3 is carried out in an autoclave.

[0120] In the above technical solution, after the crystallization step is completed, the molecular sieve can be separated from the obtained product mixture as a product by any conventionally known separation method, thereby obtaining the ZSM-5 molecular sieve of the present invention. Examples of such separation methods include filtering, washing, and drying the obtained product mixture, as well as an optional calcination step. Here, the filtering, washing, and drying can be performed in any manner conventionally known in the art. The filtering can be performed using a vacuum filtration method. The washing can be performed using deionized water. The drying temperature is 40–150°C, preferably 50–120°C, and the drying time is 1–30 hours, preferably 3–20 hours. The purpose of the calcination is to remove organic template agents and any present moisture, thereby obtaining the calcined molecular sieve. The calcination can be performed in any manner conventionally known in the art, wherein the calcination temperature is 300–750°C, preferably 400–650°C, the calcination time is 1–12 hours, preferably 2–10 hours, and the calcination atmosphere is air or nitrogen.

[0121] Furthermore, the molecular sieve according to the invention can be processed for use as a modifying catalyst. In the modifying catalyst, the mass content of the molecular sieve is ≥70%, preferably ≥75%, more preferably ≥80%.

[0122] Further, preferably, the modified catalyst is a metal-modified ZSM-5 molecular sieve catalyst. The modified metal is at least one selected from molybdenum, zinc, copper, gallium, and lanthanum, preferably at least one selected from molybdenum and gallium.

[0123] Further, preferably, based on the mass of the metal-modified ZSM-5 molecular sieve catalyst, the content of the modified metal is 1%-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and any value within the range formed by any two of these values.

[0124] Furthermore, the modified catalyst may also contain a binder, which may be alumina. The binder accounts for less than 20% of the mass of the modified catalyst, preferably 12%-20%.

[0125] A third aspect of the present invention provides a lightweighting method, comprising the following steps:

[0126] A1. Mix light hydrocarbons and / or naphtha with hydrogen-rich gas to obtain a mixture;

[0127] A2. The mixture obtained in step A1 is contacted with a modification catalyst based on ZSM-5 molecular sieve according to the first aspect of the present invention or based on ZSM-5 molecular sieve prepared by the preparation method according to the second aspect of the present invention to perform modification treatment, thereby obtaining a modified product.

[0128] The lightweighting method of the present invention may also optionally include the following steps:

[0129] A3. The modified product obtained in step A2 is separated to obtain a cracking feedstock rich in C2-C3 hydrocarbons and a liquid phase. Preferably, the liquid phase is separated to obtain a recycled material rich in C4-C6 hydrocarbons and a mixed aromatic product, wherein the recycled material is recycled back to step A2.

[0130] Further, the naphtha feedstock mentioned in step A1 is selected from at least one of straight-run gasoline, hydrocracked gasoline, catalytic cracked gasoline, hydrocoking gasoline, reforming topping oil, reforming raffinate, condensate, cracked gasoline, and cracked gasoline raffinate.

[0131] Furthermore, the naphtha feedstock described in step A1 has an initial boiling point of 30-120℃ and a final boiling point of 120-220℃.

[0132] Further, in step A1, the nitrogen content in the light hydrocarbon and / or naphtha feedstock is 0.1-10 ppm by mass. Preferably, when the nitrogen content in the light hydrocarbon and / or naphtha feedstock is ≥3 ppm by mass, denitrification treatment is performed first, followed by step A1. The denitrification treatment method is preferably adsorption denitrification. The adsorption denitrification can use conventional adsorption denitrifying agents, such as one or more of acid-treated X-type molecular sieves, Y-type molecular sieves, L-type molecular sieves, and ZSM-5 type molecular sieves. The acidification treatment can use at least one inorganic acid, such as phosphoric acid, nitric acid, sulfuric acid, etc. For example, the denitrification adsorbent described in CN201010543689.4.

[0133] Furthermore, the conditions for adsorption denitrification include: a temperature of 20-150℃, a pressure of 0.5-15MPa, and a volume hourly space velocity of 0.5-5h⁻¹. -1 .

[0134] Furthermore, the modification treatment described in step A2 can employ a fixed bed, a moving bed, a fluidized bed, or a combination thereof.

[0135] Furthermore, the modification treatment conditions described in step A2 include: a mass hourly space velocity (MHV) of 0.3-2 h⁻¹ for the naphtha feed. -1 The reaction temperature is 280-450℃, preferably 320-380℃, the reaction pressure is 0.5-3.0MPa, preferably 1.0-2.0MPa, and the hydrogen-oil volume ratio of hydrogen-rich gas to naphtha feed is 0.2-3.0:1.

[0136] Further, the hydrogen-rich gas mentioned in step A1 is at least one of hydrogen, a hydrogen-methane mixture, and hydrogen-rich dry gas. The hydrogen-rich gas has a hydrogen volume content of ≥50%.

[0137] Furthermore, the ZSM-5 molecular sieve is preferably a hydrogen-type ZSM-5 molecular sieve.

[0138] Furthermore, the preparation method of the metal-modified ZSM-5 molecular sieve catalyst includes: preparing a ZSM-5 molecular sieve catalyst, and then loading a metal component to obtain a metal-modified ZSM-5 molecular sieve catalyst.

[0139] Further, preferably, the preparation method of ZSM-5 molecular sieve catalyst includes: mixing ZSM-5 molecular sieve and optional molding aids, such as binders, pectinic acids, etc., molding, drying and calcining to obtain ZSM-5 molecular sieve catalyst intermediate, and then subjecting it to ammonium exchange, drying and calcining to obtain ZSM-5 molecular sieve catalyst.

[0140] Furthermore, in the preparation method of ZSM-5 molecular sieve catalyst, the ammonium exchange adopts the conventional ammonium exchange method, with the aim of converting ZSM-5 molecular sieve into hydrogen-form ZSM-5 molecular sieve.

[0141] Furthermore, the drying and calcination after molding, as well as the drying and calcination after ammonium exchange, can be carried out using conventional methods and conditions. Generally, the drying conditions are as follows: drying temperature 80-150℃, drying time 6-18h; the calcination conditions are as follows: calcination temperature 500-600℃, calcination time 2-6h.

[0142] Furthermore, the method for loading the metal component can be impregnation, such as saturated impregnation or supersaturated impregnation. After impregnation, the catalyst is dried and calcined to obtain the metal-modified ZSM-5 molecular sieve catalyst. Generally, drying and calcination can be carried out using conventional methods and conditions. For example, the drying conditions are as follows: drying temperature of 80-150℃ and drying time of 6-18h; the calcination conditions are as follows: calcination temperature of 500-600℃ and calcination time of 2-6h.

[0143] Furthermore, the separation described in step A3 can be achieved through distillation, such as by setting up a stabilization column, a propane stripping column, and a light hydrocarbon stripping column to obtain cracked feedstock, recycled material, and mixed aromatics. The cracked feedstock mainly consists of C2-C3 products (from the overhead gaseous products of the propane stripping column), with propane accounting for ≥95% v%; the recycled material mainly consists of C4-C6 products (from the overhead gaseous products of the light hydrocarbon stripping column); and the mixed aromatics are C7... +The product (from the bottom liquid phase of the light hydrocarbon removal tower). Optionally, a butane removal tower can be installed between the propane removal tower and the light hydrocarbon removal tower to separate C4 from the bottom product of the propane removal tower. The top product of the butane removal tower is mainly C4, which is further separated to obtain n-C4 (n-butane) and i-C4 (isobutane). The n-C4 can be used as cracking feedstock. The bottom product of the butane removal tower enters the light hydrocarbon removal tower. The top gaseous product of the light hydrocarbon removal tower is mainly C5-C6, which, together with i-C4, is used as recycled material.

[0144] Furthermore, after the light hydrocarbon and / or naphtha feedstock is mixed with hydrogen-rich gas and recycled materials, it is preferably first heat-exchanged with the modified product obtained in step A2, then heated to the modification reaction temperature, and then contacted with the modification catalyst. The heating can be performed using a separate heating device.

[0145] Furthermore, the modified product obtained in step A2 is cooled before separation.

[0146] According to some embodiments of the lightening method of the third aspect of the present invention, the upgrading treatment is carried out through a first reaction zone and a second reaction zone; wherein, the first reaction zone is used to lighten light hydrocarbons and / or naphtha to produce cracking feedstock, and the second reaction zone is used to cause chain-breaking reactions of long-chain hydrocarbons. This method can selectively convert naphtha (mainly hydrocarbons below C12) into high-quality cracking feedstock with C2-C3 alkanes as the main component, and produce mixed aromatics as byproducts. It also eliminates the need for complex separation and recovery systems, saves energy, and effectively improves economic efficiency.

[0147] According to a preferred aspect of the invention, the first reaction zone employs a fixed bed, or one or more reactors, or one or more catalyst beds within a single fixed-bed reactor.

[0148] According to a preferred aspect of the invention, the second reaction zone employs a fixed bed, a moving bed, a fluidized bed, or a combination thereof.

[0149] According to a preferred aspect of the invention, the first reaction zone is packed with a first molecular sieve catalyst. Preferably, the molecular sieve content in the first molecular sieve catalyst is greater than or equal to 70% by mass.

[0150] According to a preferred aspect of the invention, the reaction conditions in the first reaction zone are as follows: mass hourly space velocity (HHSV) of 0.3-2 h⁻¹. -1 The reaction temperature is 280-400℃, the reaction pressure is 0.5-2.0MPa, and the volume ratio of the hydrogen-rich gas to naphtha is 0.3-5:1.

[0151] According to a preferred aspect of the invention, the first reaction zone comprises at least two reaction sections. Preferably, the reaction temperature of the upstream reaction section is at least 10-120°C lower than that of the adjacent downstream reaction section, and more preferably at least 20-80°C lower. The invention preferably employs more stringent reaction conditions in the downstream reaction section of the first reaction zone than in the upstream section, allowing materials that are more difficult to convert downstream to continue reacting, thereby further improving the yield of the pyrolysis feedstock.

[0152] According to a preferred aspect of the invention, the second reaction zone is packed with a second molecular sieve catalyst. Preferably, the SiO2 / Al2O3 molar ratio of the molecular sieve is 150-300.

[0153] According to a preferred aspect of the present invention, the reaction conditions in the second reaction zone are as follows: reaction temperature of 420-550°C, reaction pressure of 1.0-4.0 MPa, and mass hourly space velocity of 0.1-1.5 h⁻¹. -1 .

[0154] According to a preferred aspect of the invention, the mixture of reaction products leaving the second reaction zone with naphtha and hydrogen-rich gas is first subjected to heat exchange and then separated.

[0155] Preferably, the first molecular sieve catalyst is a metal-modified ZSM-5 molecular sieve catalyst. The modifying metal is at least one selected from molybdenum, zinc, copper, gallium, and lanthanum, more preferably at least one selected from molybdenum, gallium, and zinc, and more preferably zinc and gallium. Preferably, the mass ratio of Zn to Ga (based on oxides) is 4-10:1, for example, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc., and any value within the range formed by any two of these values.

[0156] Further, preferably, based on the mass of the metal-modified ZSM-5 molecular sieve catalyst, the content of the modified metal is 1%-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and any value within the range formed by any two of these values.

[0157] Furthermore, the first molecular sieve catalyst may also contain a binder, which may be alumina. The binder accounts for less than 20% of the mass of the modified catalyst, preferably 12%-20%.

[0158] Furthermore, the preparation method of the metal-modified ZSM-5 molecular sieve catalyst includes: preparing a ZSM-5 molecular sieve catalyst, and then loading a metal component to obtain a metal-modified ZSM-5 molecular sieve catalyst.

[0159] Furthermore, the mixture of reaction products leaving the second reaction zone with naphtha feedstock and hydrogen-rich gas is first heat-exchanged and then cooled to release light gases (hydrogen and a small amount of methane). Then, it undergoes gas-liquid separation. The resulting gas phase products are mainly C1-C5, with ethane and propane as the main components, which can be used as cracking feedstock. The liquid phase products are mainly mixed aromatics, which can be used as blending feedstock for finished gasoline.

[0160] By setting up two reaction zones, the reaction products can be directly separated by gas and liquid, which can convert naphtha into high-quality cracking feedstocks mainly composed of ethane and propane. This greatly shortens the process flow, saves energy, and effectively improves economic benefits.

[0161] According to some embodiments of the lightweighting method of the third aspect of the present invention, the liquid phase of step A3 is introduced into the aromatization reaction zone to carry out a catalytic reaction, and the resulting reaction product is extracted to obtain a mixed aromatic product.

[0162] This method can convert refinery byproducts of light hydrocarbons and naphtha into high-quality cracking feedstocks with C2-C3 alkanes as the main components, while also producing mixed aromatics as byproducts. It also eliminates the need for a separation and recovery system, thus saving energy.

[0163] According to some embodiments of the lightweighting method of the third aspect of the present invention, the mixed reaction product of step A3 is separated, and the resulting gaseous product is used as a pyrolysis feedstock.

[0164] Furthermore, the light hydrocarbon feedstock and / or naphtha feedstock mentioned in step A1 refers to the fact that light hydrocarbons can be used alone as feedstock, naphtha feedstock can be used alone as feedstock, or light hydrocarbons and naphtha can be used together as feedstock.

[0165] Further, the light hydrocarbon feedstock mentioned in step A1 is at least one of the alkanes with four to eight carbon atoms, such as at least one of n-butane, isobutane, n-pentane, isopentane, and n-hexane, preferably at least one of the alkanes with four to six carbon atoms. The light hydrocarbon feedstock can be a mixture of alkanes with the same number of carbon atoms, such as mixed C4 alkanes, mixed C5 alkanes, or mixed C6 alkanes, or a mixture of alkanes with several different carbon numbers, such as a C4-C6 alkanes mixture. The light hydrocarbons can come from a refinery's catalytic cracking unit, heavy oil and wax oil processing unit, etc. The naphtha feedstock is selected from at least one of coal-based naphtha, straight-run naphtha, straight-run gasoline, hydrocracked gasoline, catalytic cracked gasoline, hydrocoking gasoline, reformate topping oil, reformate residue oil, condensate oil, cracked gasoline, and cracked gasoline residue oil.

[0166] Furthermore, the hydrogen-modification reaction zone described in step A1 is a fixed bed, which can be one or more reactors, or one or more catalyst beds in an independent fixed-bed reactor.

[0167] Further, preferably, the first molecular sieve catalyst is a metal-modified catalyst based on the ZSM-5 molecular sieve according to the present invention. The modifying metal is at least one selected from molybdenum, zinc, copper, gallium, and lanthanum, preferably at least one selected from molybdenum, gallium, and zinc.

[0168] Furthermore, the method for loading the metal component can be impregnation, such as saturated impregnation or supersaturated impregnation. After impregnation, the catalyst is dried and calcined to obtain the metal-modified ZSM-5 molecular sieve catalyst. Generally, drying and calcination can be carried out using conventional methods and conditions. For example, the drying conditions are as follows: drying temperature of 80-150℃ and drying time of 6-18h; the calcination conditions are as follows: calcination temperature of 500-600℃ and calcination time of 2-6h.

[0169] Furthermore, the reaction conditions in the hydrogen-modification reaction zone described in step A1 are as follows: the mass hourly space velocity of the feedstock is 0.3-3 h⁻¹. -1 The reaction temperature is 280-400℃, preferably 300-380℃; the reaction pressure is 0.5-3.0MPa, preferably 1.0-2.0MPa; the volume ratio of hydrogen-rich gas to naphtha feed hydrogen oil is 0.3-5:1.

[0170] Furthermore, the aromatization reaction zone in step A3 is a fixed bed, a moving bed, or a fluidized bed. The aromatization reaction zone is packed with an aromatization catalyst.

[0171] Furthermore, the aromatization catalyst comprises a support and a metal oxide, which, based on the mass of the catalyst, are expressed in the following mass fractions: 1%-10% zinc oxide, 1%-5% copper oxide, 0.1%-3% lanthanum oxide, 1%-8% phosphorus, 50%-70% molecular sieve, and 20%-40% binder (preferably alumina as the binder).

[0172] Furthermore, in the aromatization catalyst, the molecular sieve is at least one selected from ZSM-5 molecular sieve, Y-type molecular sieve, β-molecular sieve, mordenite, and SAPO-34 molecular sieve. The SiO2 / Al2O3 molar ratio of the molecular sieve is 40-200.

[0173] Furthermore, the aromatization catalyst can be prepared using conventional methods in the art, such as impregnation or kneading.

[0174] Furthermore, the reaction conditions for the aromatization reaction described in step A3 are as follows: reaction temperature of 420-600℃, reaction pressure of 0.1-2 MPa, and mass hourly space velocity of 0.2-2 h⁻¹. -1 .

[0175] Further, in step A3, the separation is carried out in a stabilizing tower or a gas-liquid separator. The gas phase products are mainly C1-C3, which serve as cracking feedstock. The liquid phase products are mainly aromatics, non-aromatics, and water. The purpose of step (2) extraction is to separate the mixed aromatics from the liquid phase products. Conventional extraction methods can be used, such as extraction solvents that can be at least one of sulfolane, N-methylpyrrolidone, dimethyl sulfoxide, etc., where the mixed aromatics refer to benzene, toluene, xylene, etc.

[0176] Preferably, the mixture of the mixed reaction product from step A2, naphtha feedstock, and hydrogen-rich gas is first heat-exchanged, and then the material after separating C2-C3 (as cracking feedstock) is fed into the aromatization reactor.

[0177] This invention eliminates the need for complex separation and recovery systems. The reaction products are directly separated by gas-liquid separation, with the gas phase serving as the pyrolysis feedstock and the liquid phase undergoing aromatization. After extraction, a mixed aromatic hydrocarbon product is obtained, which saves energy and effectively improves economic benefits.

[0178] The fourth aspect of the invention provides a catalyst for lightweighting comprising the molecular sieve of the first aspect or the molecular sieve prepared according to the method of the second aspect.

[0179] It comprises a molecular sieve prepared according to the method of the first aspect or according to the second aspect, a binder, and a modified metal. The binder is, for example, alumina. The modified metal is, for example, at least one selected from molybdenum, zinc, copper, gallium, and lanthanum. Preferably, based on the catalyst, the mass content of the molecular sieve is ≥70%, more preferably ≥75%, and even more preferably ≥80%. Preferably, based on the catalyst, the mass content of the modified metal is 1%-10%, wherein the modified metal is calculated as an oxide. Preferably, based on the catalyst, the mass content of the binder is ≤20%, more preferably 12%-20%.

[0180] According to some preferred embodiments, the catalyst also contains phosphorus, with the mass content of phosphorus, calculated as elemental phosphorus, being 1%-10%, preferably 3-7%, based on the catalyst.

[0181] The preparation method of this catalyst includes:

[0182] B1. The ZSM-5 molecular sieve according to the first aspect will be shaped, subjected to ammonium exchange, and calcined.

[0183] B2. Optionally, the solid product from step B1 is impregnated with a phosphorus-containing solution, and the impregnated solid is then calcined.

[0184] B3. Optionally, the solid product from step B2 is impregnated with a source solution of the metal active component, and the impregnated solid is then calcined.

[0185] Preferably, the phosphorus source in the phosphorus-containing solution is selected from at least one of phosphoric acid, metaphosphoric acid, pyrophosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate, and more preferably at least one of ammonium hydrogen phosphate and ammonium dihydrogen phosphate. Preferably, the phosphorus content in the phosphorus-containing solution is 1-10 wt%. Preferably, the method of contacting and impregnating the solid product of step B1 with the phosphorus-containing solution in step B2 includes: adding the phosphorus-containing solution dropwise to the solid product of step B1 at 20-30°C, and performing heat treatment at 80-110°C after the addition is completed. Preferably, the dropping rate is 0.1-2 ml / g·min. Preferably, the heat treatment time is 2-4 h.

[0186] The catalyst obtained by treating the ZSM-5 molecular sieve of this invention with phosphorus has a 10% higher aluminum content on its surface.

[0187] The fifth aspect of the present invention provides the application of the ZSM-5 molecular sieve of the first aspect and the lightening catalyst of the fourth aspect in the lightening of light hydrocarbons and / or naphtha.

[0188] Furthermore, the application is as follows: light hydrocarbon and / or naphtha feedstocks are reacted with a reforming catalyst based on the ZSM-5 molecular sieve of the first aspect or with a lightening catalyst of the third aspect to separate and obtain a cracking feedstock mainly composed of propane.

[0189] Further, the light hydrocarbon feedstock is at least one of the alkanes with four to eight carbon atoms, such as at least one of n-butane, isobutane, n-pentane, isopentane, and n-hexane, preferably at least one of the alkanes with four to six carbon atoms. The light hydrocarbon feedstock can be a mixture of alkanes with the same number of carbon atoms, such as mixed C4 alkanes, mixed C5 alkanes, or mixed C6 alkanes, or a mixture of alkanes with several different carbon numbers, such as a C4-C6 alkanes mixture. The light hydrocarbons can come from catalytic cracking units, heavy oil and wax oil processing units, etc., in oil refineries. The naphtha feedstock is selected from at least one of straight-run gasoline, hydrocracked gasoline, catalytic cracked gasoline, hydrocoking gasoline, reformate topping oil, reformate residue oil, condensate oil, cracked gasoline, and cracked gasoline residue oil.

[0190] Furthermore, the naphtha feedstock has an initial boiling point of 30-120℃ and a final boiling point of 120-220℃.

[0191] Furthermore, the naphtha lightening process can be carried out using a fixed bed or a fluidized bed.

[0192] Furthermore, the reaction conditions include a mass hourly space velocity (MSV) of 0.3-2 h⁻¹ for the light hydrocarbon and / or naphtha feedstock. -1The reaction temperature is 280-450℃, preferably 320-380℃, the reaction pressure is 0.5-3.0MPa, preferably 1.0-2.0MPa, and the hydrogen-oil volume ratio of hydrogen-rich gas to light hydrocarbon and / or naphtha feed is 0.2-3.0:1.

[0193] Further, the hydrogen-rich gas is at least one of hydrogen, a hydrogen-methane mixture, and hydrogen-rich dry gas. The hydrogen volume content in the hydrogen-rich gas is ≥50%.

[0194] Furthermore, the modified catalyst includes ZSM-5 molecular sieve and modified metal, wherein the mass content of molecular sieve is ≥70%, preferably ≥75%, and more preferably ≥80%.

[0195] Furthermore, the modified catalyst may also contain a binder, which may be alumina. The binder accounts for less than 20% of the mass of the modified catalyst, preferably 12%-20%.

[0196] Furthermore, in the modified catalyst, the modified metals are preferably Zn and Ga, and more preferably, the mass ratio of Zn to Ga (based on oxides) is 4-10:1, for example, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc., and any value within the range formed by any two of these values.

[0197] Further, the preparation method of the modified catalyst preferably includes: mixing the above-mentioned ZSM-5 molecular sieve with a binder, molding, drying and calcining, undergoing ammonium exchange, and then drying and calcining again. The drying and calcining after molding and after ammonium exchange can be carried out using conventional methods and conditions. The ammonium exchange uses a conventional ammonium exchange method, the purpose of which is to convert the ZSM-5 molecular sieve into a hydrogen-form ZSM-5 molecular sieve. The method for loading the modified metal can be an impregnation method, such as a saturated impregnation method or a supersaturated impregnation method. After impregnation, the modified catalyst is obtained by drying and calcining. Generally, drying and calcining can be carried out using conventional methods and conditions, for example, the drying conditions are as follows: drying temperature of 80-150℃, drying time of 6-18h; the calcination conditions are as follows: calcination temperature of 500-600℃, calcination time of 2-6h.

[0198] Furthermore, the pyrolysis feedstock is mainly propane, and also contains a small amount of ethane, wherein the volume content of propane accounts for ≥95%.

[0199]

Example

[0200] To better understand the present invention, the following description is provided in conjunction with embodiments. However, the scope of protection of the present invention is not limited to the scope of the embodiments.

[0201] In the following embodiments, unless otherwise specified, all experimental instruments and raw materials involved are commercially available products.

[0202] In this invention, XRD was performed using a Rigaku D / max-2004 X-ray powder diffractometer for phase analysis, using Cu Kα radiation, tube voltage 40kV, tube current 100mA, scanning range 2θ of 5-50°, and scanning step 0.02°.

[0203] In this invention, SEM was performed using a NOVA Nano SEM450 ultra-high resolution field emission scanning electron microscope from FEI Corporation, USA.

[0204] In this invention, the silica-to-alumina ratio of the molecular sieve was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The experiment was conducted on a Plasma-Spec-I inductively coupled plasma atomic emission spectrometer from Item Labs, USA.

[0205] In this invention, the specific surface area, external specific surface area, pore volume, micropore volume, and average pore size are obtained by specific surface area measurement (BET). Specific surface area is typically determined using the BET nitrogen adsorption method, with the total surface area calculated based on multilayer adsorption theory. External specific surface area is obtained by separating the micropore surface area from the total surface area using the t-plot method or α-s diagram method; the remaining portion is the external specific surface area. The tests are performed on a Micromeritics ASAP-2020 specific surface area and pore size analyzer. The sample is first activated at 300°C and evacuated to 5 mHg, then the test is conducted at liquid nitrogen temperature.

[0206]

Example 1

[0207] Using silica gel powder (300 mesh) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.05:0.08:15 and stirred at 80℃ for 24 hours to obtain seed gel.

[0208] A mixture of silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water was prepared according to the following ratios: n(SiO2):n(Al2O3) = 80 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.06:0.10:29. After stirring at room temperature for 30 min, seed gel (based on silica) was added at 5% of the mass of the silicon source (based on silica) in the mixture, and the mixture was stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175℃ for 48 h. The resulting crystallized solution was subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve powder (denoted as S1). A sample of molecular sieve powder S1 was calcined in air at 550℃ for 4 h. The BET results of the calcined S1 molecular sieve showed a total specific surface area of ​​425.1 m². 2 / g, external specific surface area / total specific surface area = 34.4%, pore volume is 0.301cm³ 3 / g, micropore volume is 0.165cm³ 3 / g, with an average pore size of 2.533nm. The SiO2 / Al2O3 molar ratio of the calcined S1 molecular sieve is 78.

[0209] The XRD pattern of the S1 molecular sieve after calcination is shown in Figure 7. As can be seen from the XRD pattern, the molecular sieve has obvious ZSM-5 characteristic peaks.

[0210] The scanning electron microscope (SEM) images of the calcined S1 molecular sieve are shown in Figure 8. Figure 8 shows that the ZSM-5 molecular sieve is a nanosheet aggregate with a nanosheet size of 100-200 nm and a thickness of 20-50 nm, and the aggregate particle size is 1-5 μm. The chemical analysis results (XPS) of its surface atoms are shown in Table 2. The NMR results of Example 1 are shown below, and the NMR spectrum is shown in Figure 9.

[0211] Table 1. NMR data of molecular sieves

[0212] The peaks at 49, 53, and 58 ppm are associated with aluminum atoms at the channel crossover sites T1-T3, T5-T7, T9, and T12, while the peak at 56 ppm is associated with aluminum atoms at the 10-MR straight channel sites T4, T10, T8, and T11.

[0213] In Figure 8, the following are labeled: nanosheet length (L), nanosheet thickness (T), and aggregate particle size (W).

[0214]

Example 2

[0215] (1) Synthesis of ZSM-5 molecular sieve powder

[0216] Using silica gel powder (300 mesh) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.03:0.10:15 and stirred at 80℃ for 24 hours to obtain seed gel.

[0217] A mixture of silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water was prepared according to the following ratios: n(SiO2):n(Al2O3) = 225, n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.03:0.12:21. After stirring at room temperature for 30 min, seed gel (based on silica) was added at 5% of the mass of the silicon source (based on silica) in the mixture, and stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization treatment at 125℃ for 24 h and at 175℃ for 24 h. The resulting solution was subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve raw powder (denoted as S2). A sample of molecular sieve raw powder S2 was calcined in air at 550℃ for 4 h. The BET results of the calcined S2 molecular sieve showed that the total specific surface area was 410 m². 2 / g, external specific surface area / total specific surface area = 42.3%, pore volume is 0.283cm³ 3 / g, micropore volume is 0.181cm³ 3 / g, with an average pore size of 2.598nm. The SiO2 / Al2O3 molar ratio of the calcined S2 molecular sieve is 210.

[0218] The XRD pattern of the S2 molecular sieve after calcination is shown in Figure 10. As can be seen from the XRD pattern, the molecular sieve has obvious ZSM-5 characteristic peaks.

[0219] The scanning electron microscope (SEM) image of the calcined S2 molecular sieve is shown in Figure 11. As can be seen from the SEM image, the ZSM-5 molecular sieve is a nanosheet aggregate with a particle size of 100-300 nm and a thickness of 20-50 nm, and an aggregate particle size of 1-5 μm.

[0220]

Example 3

[0221] Using silica gel powder (300 mesh) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.05:0.08:15 and stirred at 80℃ for 24 hours to obtain seed gel.

[0222] A mixture of silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water was prepared according to the following ratios: n(SiO2):n(Al2O3) = 80 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.10:0.10:29. After stirring at room temperature for 30 min, seed gel (based on silica) was added at 5% of the mass of the silicon source (based on silica) in the mixture, and the mixture was stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175℃ for 48 h. The resulting solution was subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve powder (denoted as S3). A portion of the molecular sieve powder S3 was calcined in air at 550℃ for 4 h. The BET results of the calcined S3 molecular sieve showed a total specific surface area of ​​424.6 m². 2 / g, external specific surface area / total specific surface area = 34.0%, pore volume is 0.256cm³ 3 / g, micropore volume is 0.179cm³ 3 / g, with an average pore size of 2.816nm. The SiO2 / Al2O3 molar ratio of the S3 molecular sieve after calcination is 75.

[0223] After calcination, the S3 molecular sieve exhibits a distinct ZSM-5 characteristic peak, as shown by the XRD pattern.

[0224] Scanning electron microscopy images of the calcined S3 molecular sieve show that the ZSM-5 molecular sieve is a nanosheet aggregate with a nanosheet size of 50-100 nm and a thickness of 50-100 nm, and an aggregate particle size of 0.5-5 μm.

[0225]

Example 4

[0226] Using silica gel powder (300 mesh) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.05:0.08:15 and stirred at 80℃ for 24 hours to obtain seed gel.

[0227] A mixture of silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water was prepared according to the following ratios: n(SiO2):n(Al2O3) = 80 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.06:0.10:29. After stirring at room temperature for 30 min, seed gel (based on silica) was added at 10% of the mass of the silicon source (based on silica) in the mixture, and the mixture was stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175℃ for 48 h. The resulting crystallized solution was subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve powder (denoted as S4). A sample of molecular sieve powder S4 was calcined in air at 550℃ for 4 h. The BET results of the calcined S4 molecular sieve showed a total specific surface area of ​​419.5 m². 2 / g, external specific surface area / total specific surface area = 35.2%, pore volume is 0.251cm³ 3 / g, micropore volume is 0.181cm³ 3 / g, with an average pore size of 2.778nm. The SiO2 / Al2O3 molar ratio of the calcined S4 molecular sieve is 78.

[0228] After calcination, the S4 molecular sieve exhibits a distinct ZSM-5 characteristic peak, as shown by the XRD pattern.

[0229] The scanning electron microscope image of the calcined S4 molecular sieve is shown in Figure 12. As can be seen from Figure 12, the ZSM-5 molecular sieve is a nanosheet aggregate with a nanosheet particle size of 20-100 nm and a thickness of 20-50 nm, and an aggregate particle size of 0.3-3 μm.

[0230]

Example 5

[0231] Using silica gel powder (300 mesh) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.05:0.08:15 and stirred at 80℃ for 24 hours to obtain seed gel.

[0232] A mixture of silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water was prepared according to the following ratios: n(SiO2):n(Al2O3) = 80 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.06:0.10:29. After stirring at room temperature for 30 min, seed gel (based on silica) was added at 5% of the mass of the silicon source (based on silica) in the mixture, and the mixture was stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 130℃ for 72 h. The resulting crystallized solution was subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve powder (denoted as S5). A sample of molecular sieve powder S5 was calcined in air at 550℃ for 4 h. The BET results of the calcined S5 molecular sieve showed a total specific surface area of ​​440.3 m². 2 / g, external specific surface area / total specific surface area = 35.5%, pore volume is 0.253cm³ 3 / g, micropore volume is 0.139cm³ 3 / g, with an average pore size of 2.688nm. The SiO2 / Al2O3 molar ratio of the S5 molecular sieve after calcination is 78.

[0233] After calcination, the S5 molecular sieve exhibits obvious ZSM-5 characteristic peaks, as shown by the XRD pattern.

[0234] The scanning electron microscope image of the calcined S5 molecular sieve is shown in Figure 13. As can be seen from Figure 13, the ZSM-5 molecular sieve is a nanosheet aggregate with a nanosheet particle size of 50-200 nm and a thickness of 20-100 nm, and the aggregate particle size is 1-10 μm.

[0235]

Example 6

[0236] (1) Synthesis of ZSM-5 molecular sieve powder

[0237] Using silica gel powder (100 mesh) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.05:0.08:15 and stirred at 80℃ for 24 hours to obtain a seed gel.

[0238] A mixture of silica gel powder (100 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water was prepared according to the following ratios: n(SiO2):n(Al2O3) = 80, n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.06:0.10:29. After stirring at room temperature for 30 min, seed gel (based on silica) was added at 5% of the mass of the silicon source (based on silica) in the mixture, and stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175℃ for 48 h. The crystallized solution was then subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve powder (denoted as S6). A sample of molecular sieve powder S6 was calcined in air at 550℃ for 4 h. The BET results of the calcined S6 molecular sieve showed a total specific surface area of ​​417.8 m². 2 / g, external specific surface area / total specific surface area = 35.0%, pore volume is 0.289cm³ 3 / g, micropore volume is 0.144cm³ 3 / g, with an average pore size of 3.130nm. The SiO2 / Al2O3 molar ratio of the S6 molecular sieve after calcination is 75.

[0239]

Example 7

[0240] Using S1 molecular sieve as a carrier, the sample was impregnated with an equal amount of ammonium dihydrogen phosphate solution (with a phosphorus content of 5%), and then the impregnated sample was calcined. The resulting processed molecular sieve powder was labeled SP, and the chemical analysis results (XPS) of its surface atoms are shown in Table 2.

[0241] Table 2. Surface atomic chemical analysis results of molecular sieve raw powder

[0242] Comparative Example 1

[0243] A synthesis solution was prepared by mixing silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water at a ratio of n(SiO2):n(Al2O3) = 80 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.06:0.10:29, and stirring at room temperature for 3 hours. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175℃ for 48 hours. The resulting crystallized solution was subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve raw powder (denoted as D1). A sample of molecular sieve raw powder D1 was calcined in air at 550℃ for 4 hours. The BET results of the calcined D1 molecular sieve showed a total specific surface area of ​​365 m². 2 / g, external specific surface area / total specific surface area = 24.3%, pore volume is 0.215cm³. 3 / g, micropore volume is 0.151cm³3 / g, with an average pore size of 2.012nm.

[0244] The XRD pattern of the calcined D1 molecular sieve is shown in Figure 14. As can be seen from the XRD pattern, the molecular sieve has obvious ZSM-5 characteristic peaks.

[0245] The scanning electron microscope image of the D1 molecular sieve after calcination is shown in Figure 15. The ZSM-5 molecular sieve is a nanosheet aggregate with a nanosheet particle size of 300-500 nm and a thickness of more than 200 nm, and an aggregate particle size of >20 μm.

[0246] Comparative Example 2

[0247] A synthesis solution was prepared by mixing silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water at a ratio of n(SiO2):n(Al2O3) = 85 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.05:0.08:29. After stirring at room temperature for 30 min, ZSM-5 powder (SiO2 / Al2O3 molar ratio = 168, purchased from Shanghai Fuxu Molecular Sieve Co., Ltd.) was added at 5% of the mass of silicon source (based on silicon dioxide) in the synthesis solution, and stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175℃ for 48 h. The crystallized solution was then subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve raw powder (denoted as D2).

[0248] A sample of molecular sieve powder D2 was calcined in air at 550℃ for 4 hours. The BET results of the calcined D2 molecular sieve showed a total specific surface area of ​​341 m². 2 / g, external specific surface area / total specific surface area = 22.1%, pore volume is 0.223cm³ 3 / g, micropore volume is 0.181cm³ 3 / g, with an average pore size of 1.851nm.

[0249] The XRD pattern of the calcined D2 molecular sieve is shown in Figure 16. As can be seen from the XRD pattern, the molecular sieve has obvious ZSM-5 characteristic peaks.

[0250] The scanning electron microscope image of the calcined D2 molecular sieve is shown in Figure 17. The ZSM-5 molecular sieve has a polycrystalline bulk morphology, and the thickness of the nanosheets is about 1 μm.

[0251] Comparative Example 3

[0252] A synthesis solution was prepared by mixing silica gel powder (300 mesh), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water at a ratio of n(SiO2):n(Al2O3) = 85 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.05:0.08:29. After stirring at room temperature for 30 min, D1 powder was added at 5% of the mass of the silicon source (based on silicon dioxide) in the synthesis solution, and the mixture was stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175 °C for 48 h. The crystallized solution was then subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve raw powder (denoted as D3). A sample of molecular sieve raw powder D3 was calcined in air at 550 °C for 4 h. The BET results of the calcined D3 molecular sieve showed that the total specific surface area was 398 m². 2 / g, external specific surface area / total specific surface area = 27%, pore volume is 0.230cm³ 3 / g, micropore volume is 0.154cm³ 3 / g, with an average pore size of 1.923nm.

[0253] The XRD pattern of the calcined D3 molecular sieve is shown in Figure 18. As can be seen from the XRD pattern, the molecular sieve has obvious ZSM-5 characteristic peaks.

[0254] The scanning electron microscope image of the calcined D3 molecular sieve is shown in Figure 19. The ZSM-5 molecular sieve is a nanosheet aggregate with a thickness of about 500 nm and an aggregate particle size of >20 μm.

[0255] Comparative Example 4

[0256] Using silica sol (25% by mass of silica) as the silicon source, tetrapropylammonium bromide as the template agent, and sodium hydroxide as the alkali source, the silicon source, template agent, alkali source, and water were mixed at a ratio of n(SiO2):n(template agent):n(Na2O):n(H2O) = 1:0.05:0.08:15 and stirred at 80℃ for 24 h to obtain seed gel.

[0257] A synthesis solution was prepared by mixing silica sol (25% silica by mass), sodium aluminate, tetrapropylammonium bromide, sodium hydroxide, and water at a ratio of n(SiO2):n(Al2O3) = 80 and n(SiO2):n(template):n(Na2O):n(H2O) = 1:0.05:0.08:29. After stirring at room temperature for 30 min, a seed gel was added at 5% of the silica source (based on silica) in the synthesis solution, and the mixture was stirred at room temperature for 3 h. The mixture was then transferred to a stainless steel high-pressure reactor for crystallization at 175 °C for 48 h. The crystallized solution was then subjected to sedimentation / filtration to recover the mother liquor. The solid was washed with deionized water until neutral and dried to obtain molecular sieve powder (denoted as D4). A sample of molecular sieve powder D4 was calcined in air at 550 °C for 4 h. The BET results of the calcined D4 molecular sieve showed a total specific surface area of ​​367 m². 2 / g, external specific surface area / total specific surface area = 23.0%, pore volume is 0.230cm³. 3 / g, micropore volume is 0.154cm³ 3 / g, with an average pore size of 1.923nm.

[0258] The XRD pattern of the calcined D4 molecular sieve is shown in Figure 20. As can be seen from the figure, the molecular sieve has obvious ZSM-5 characteristic peaks.

[0259] The scanning electron microscope image of the calcined D4 molecular sieve is shown in Figure 21.

[0260]

Preparation Example

[0261]

Preparation Example 1

[0262] Take 300g of the above sodium-type ZSM-5 molecular sieve raw powder S1, add 120g of alumina, add 2wt% dilute nitric acid solution dropwise, knead and extrude into strips, dry at 120℃ for 10 hours, and calcine at 550℃ for 4 hours to obtain catalyst intermediate A;

[0263] Take 50g of catalyst intermediate A, add 8wt% ammonium acetate solution (liquid-solid volume ratio of 10), exchange at 80℃ for 1h, wash with water, dry at 120℃ for 10h, and calcine at 550℃ for 4h to obtain ZSM-5 molecular sieve catalyst B. The aluminum NMR results are shown in Figure 22.

[0264] Take 20g of ZSM-5 molecular sieve catalyst B, impregnate it with an equal amount of ammonium dihydrogen phosphate solution (with a phosphorus content of 5%), then calcine the impregnated sample, and then impregnate it with an equal amount of impregnation solution containing zinc and gallium. The metal sources are all nitrates. After impregnation, dry at 120℃ for 10 hours and calcine at 550℃ for 6 hours to obtain metal-modified molecular sieve catalyst C-1, which contains 4wt% zinc and 0.5wt% gallium.

[0265]

Preparation Example 2

[0266] Compared with Preparation Example 1, the only difference was the change in the loading of zinc and gallium, resulting in catalyst C-2 containing 2 wt% zinc and 0.2 wt% gallium.

[0267]

Preparation Example 3

[0268] Take 300g of the above sodium-type ZSM-5 molecular sieve raw powder S1, add 120g of alumina, add 2wt% dilute nitric acid solution dropwise, knead and extrude into strips, dry at 120℃ for 10 hours, and calcine at 550℃ for 4 hours to obtain catalyst intermediate A;

[0269] Take 50g of catalyst intermediate A, add 8wt% ammonium acetate solution (liquid-solid volume ratio of 10), exchange at 80℃ for 1h, wash with water, dry at 120℃ for 10h, and calcine at 550℃ for 4h to obtain ZSM-5 molecular sieve catalyst B.

[0270] Take 20g of ZSM-5 molecular sieve catalyst B, impregnate it with an excess of ammonium molybdate aqueous solution, and then dry it at 120℃ for 10 hours and calcine it at 500℃ for 2 hours to obtain 5wt% molybdenum metal modified molecular sieve catalyst C-3.

[0271]

Preparation Example 4

[0272] Catalyst Synthesis

[0273] The catalyst preparation steps are the same as in Preparation Example 3, except that molecular sieve S2 is used instead of molecular sieve S1 to obtain catalyst C-4.

[0274]

Preparation Example 5

[0275] The synthesis steps of ZSM-5 molecular sieve raw powder are the same as in Example 1, resulting in molecular sieve S1.

[0276] Catalyst Synthesis:

[0277] Take 300g of the above sodium-type ZSM-5 molecular sieve raw powder S1, add 120g of alumina, add 2wt% dilute nitric acid solution dropwise, knead and extrude into strips, dry at 120℃ for 10 hours, and calcine at 550℃ for 4 hours to obtain catalyst intermediate A;

[0278] Take 50g of catalyst intermediate A, add 8wt% ammonium acetate solution (liquid-solid volume ratio of 10), exchange at 80℃ for 1h, wash with water, dry at 120℃ for 10h, and calcine at 550℃ for 4h to obtain ZSM-5 molecular sieve catalyst B.

[0279] Take 20g of ZSM-5 molecular sieve catalyst B and impregnate it with an equal volume of gallium nitrate aqueous solution. After impregnation, dry it at 120℃ for 10 hours and calcine it at 550℃ for 4 hours to obtain 6wt% gallium metal modified molecular sieve catalyst C-5.

[0280]

Preparation Example 6

[0281] The first molecular sieve catalyst loaded in the first reaction zone in Figure 2-3:

[0282] Take 300g of the above sodium-type ZSM-5 molecular sieve raw powder S1, add 140g of alumina, add 2wt% dilute nitric acid solution dropwise, knead and extrude into strips, dry at 120℃ for 10 hours, and calcine at 550℃ for 4 hours to obtain catalyst intermediate A;

[0283] Take 50g of catalyst intermediate A, add 8wt% ammonium acetate solution (liquid-solid volume ratio of 10), exchange at 80℃ for 1h, wash with water, dry at 120℃ for 10h, and calcine at 550℃ for 4h to obtain ZSM-5 molecular sieve catalyst B.

[0284] Take 20g of ZSM-5 molecular sieve catalyst B, then impregnate it with an equal amount of impregnation solution containing zinc and gallium. After impregnation, dry it at 120℃ for 10 hours and calcine it at 550℃ for 4 hours to obtain metal-modified molecular sieve catalyst C-6, which contains 5wt% zinc and 1wt% gallium.

[0285]

Preparation Example 7

[0286] The second molecular sieve catalyst packed in the second reaction zone in Figure 2-3:

[0287] Commercial hydrogen-type HZSM-5 molecular sieve, SiO2 / Al2O3 molar ratio = 168.

[0288] Take 300g of the above hydrogen-form ZSM-5 molecular sieve powder, add 100g of alumina, add 2wt% dilute nitric acid solution dropwise, knead and extrude into strips, dry at 120℃ for 10 hours, and calcine at 550℃ for 4 hours to obtain catalyst C-7.

[0289]

Preparation Example 8

[0290] The first molecular sieve catalyst used for packing the first reaction zone:

[0291] The catalyst preparation steps were the same as in Preparation Example 6, except that molecular sieve S2 was used instead of molecular sieve S1, and the zinc-gallium loading was changed to obtain catalyst C-8, which contains 3 wt% zinc and 0.5 wt% gallium.

[0292]

Preparation Example 9

[0293] Catalyst in the hydrogen-modification reaction zone:

[0294] Take 300g of the above sodium-type ZSM-5 molecular sieve powder S1, add 140g of alumina, add 2wt% dilute nitric acid solution dropwise, knead and extrude into strips, dry at 120℃ for 10 hours, and calcine at 550℃ for 4 hours to obtain catalyst intermediate A;

[0295] Take 50g of catalyst intermediate A, add 8wt% ammonium acetate solution (liquid-solid volume ratio of 10), exchange at 80℃ for 1h, wash with water, dry at 120℃ for 10h, and calcine at 550℃ for 4h to obtain ZSM-5 molecular sieve catalyst B.

[0296] Take 20g of ZSM-5 molecular sieve catalyst B, impregnate it with an excess of ammonium molybdate aqueous solution, and then dry it at 120℃ for 10 hours and calcine it at 500℃ for 4 hours to obtain 3wt% molybdenum metal modified molecular sieve catalyst C-9-1.

[0297] Aromatization reactor catalyst:

[0298] 300g of hydrogen-type ZSM-5 molecular sieve powder (SiO2 / Al2O3 molar ratio = 100) was added to 120g of alumina, and 2wt% dilute nitric acid solution was added dropwise. The mixture was kneaded and extruded into strips, dried at 120℃ for 10 hours, and calcined at 550℃ for 4 hours to obtain catalyst intermediate A'.

[0299] Take 50g of catalyst intermediate A', add 1wt% phosphoric acid solution (liquid-solid volume ratio of 5), treat at 80℃ for 1h, wash with water, dry at 120℃ for 10h, and calcine at 550℃ for 4h to obtain ZSM-5 molecular sieve catalyst intermediate B'.

[0300] Take 20g of ZSM-5 molecular sieve catalyst B' and impregnate it with an equal amount of impregnation solution containing copper, zinc and lanthanum. After impregnation, dry it at 120℃ for 10 hours and calcine it at 550℃ for 4 hours to obtain catalyst C-9-2. The obtained catalyst contains 2wt% copper oxide, 2wt% zinc oxide, 0.2wt% lanthanum oxide and 3wt% phosphorus.

[0301]

Preparation Example 10

[0302] The catalyst preparation steps are the same as in Example 9, except that molecular sieve S2 is used instead of molecular sieve S1, and the modified metals are replaced with zinc and gallium to obtain catalyst C-10-1, which contains 2 wt% zinc and 0.5 wt% gallium.

[0303] [Comparative Preparation Examples 1-4]

[0304] Compared with Preparation Example 1, the only difference is that sodium ZSM-5 molecular sieve powder S1 was replaced with sodium ZSM-5 molecular sieve powders D1, D2, D3, and D4 respectively, to obtain catalysts CD-1, CD-2, CD-3, and CD-4.

[0305] [Test Example]

[0306] Unless otherwise specified, the composition of the naphtha used in the following test examples is shown in the table below:

[0307] Table 3. Composition of naphtha raw materials used in the test cases Note: In the table, C6, C7, C8, C9, and C10 refer to the content of non-aromatic hydrocarbons.

[0308]

Test Example 1-2

[0309] Using C-1 and C-2 as catalysts, and hydrocracking light naphtha (distillation range 60-140℃, nitrogen content 2ppm) as feedstock, the process flow shown in Figure 1 was employed, but without adsorption denitrification tower A. A fixed-bed reactor was used, with a reaction temperature of 335℃, a reaction pressure of 1.2MPa, and a feedstock mass hourly space velocity of 1.5h⁻¹. -1 The hydrogen-to-oil volume ratio is 0.7:1. The yield of the top cracking feedstock of the propane stripper F is shown in Table 9, in which propane accounts for more than 95% by volume.

[0310]

Test Example 3-5

[0311] Using C-3, C-4, and C-5 catalysts respectively, and hydrocracking light naphtha (distillation range 60-140℃, nitrogen content 2.5ppm) as feedstock, the process flow shown in Figure 1 was employed, but without the adsorption denitrification tower A. The reforming reactor E was a fixed bed reactor. The reaction temperature was 350℃, the reaction pressure was 1MPa, and the feedstock mass hourly space velocity was 1.5h⁻¹. -1 The hydrogen-to-oil volume ratio is 0.5:1. The yield of the top cracking feedstock of the propane stripper F is shown in Table 9, in which propane accounts for more than 95% of the volume content of the cracking feedstock.

[0312]

Test Example 6

[0313] Using C-3 as catalyst and hydrocracking light naphtha (distillation range 60-140℃, nitrogen content 2.5ppm) as feedstock, the process flow shown in Figure 1 was employed, but without adsorption denitrification tower A. The reforming reactor E was a fixed bed reactor. The reaction temperature was 370℃, the reaction pressure was 1.2MPa, and the feedstock mass hourly space velocity (MHSV) was 1.4h⁻¹. -1 The hydrogen-to-oil volume ratio is 0.2:1. The yield of the top cracking feedstock in the propane stripper F is 80.6%, of which propane accounts for more than 95% by volume.

[0314]

Test Example 7

[0315] The first molecular sieve catalyst packed in the first reaction zone is C-6, and the second molecular sieve catalyst packed in the second reaction zone is C-7.

[0316] In this embodiment, naphtha is used as the raw material, and the process flow shown in Figure 2 is followed, but without the adsorption denitrification tower A. The first reaction zone uses the first lightening reactor D1 and the second lightening reactor D2, and the second reaction zone uses reactor L. All reactors are fixed-bed reactors, and the specific reaction conditions for each reactor are shown in Table 4. The composition of the obtained products is shown in Table 5.

[0317] Table 4 shows the operating conditions of each reactor in Test Example 7.

[0318] Table 5 Composition of the product obtained in Test Example 7

[0319]

Test Example 8

[0320] In this test example, the first molecular sieve catalyst and the second molecular sieve catalyst are the same as those in Test Example 7.

[0321] In this embodiment, light naphtha was used as the raw material (composition shown in Table 7), and the process flow shown in Figure 3 was followed. However, adsorption denitrification tower A was not included. Reactors D1 and L were all fixed-bed reactors. The specific reaction conditions for each reactor are shown in Table 6. The composition of the obtained products is shown in Table 7.

[0322] Table 6. Operating conditions of each reactor in Test Example 8

[0323] Table 7. Composition of the naphtha feedstock and products used in Test Example 8

[0324]

Test Example 9

[0325] This embodiment uses naphtha as feedstock and follows the process shown in Figure 2, but without adsorption denitrification tower A. The first reaction zone uses a first lightening reactor D1 and a second lightening reactor D2, and the second reaction zone uses reactor L, all of which are fixed-bed reactors. The first molecular sieve catalyst packed in the first reaction zone is catalyst C-8. The second molecular sieve catalyst packed in the second reaction zone is catalyst C-7. The specific reaction conditions for each reactor are shown in Table 4. The composition of the obtained products is shown in Table 8. Among them, the yield of cracked feedstock (C2-C4) is 78.79%, and the yield of mixed aromatics is 14.86%.

[0326] Table 8. Composition of the product obtained in Test Example 9

[0327] [Comparative Test Examples 1-4]

[0328] Using CD-1, CD-2, CD-3, and CD-4 as catalysts, and employing the same feedstock and evaluation methods as in Test Examples 1-2, the yields of the top cracking feedstock of the propane stripper F are shown in Table 9, where propane accounted for over 95% by volume in the cracking feedstock.

[0329] Table 9 Evaluation results of catalysts in Test Examples 1-5 and Comparative Test Examples 1-4

[0330] [Comparative Test Example 5]

[0331] The first molecular sieve catalyst packed in the first reaction zone is catalyst CD-1.

[0332] The second molecular sieve catalyst packed in the second reaction zone is catalyst C-7.

[0333] This example uses naphtha as feedstock and follows the process flow shown in Figure 2, but without adsorption denitrification tower A. The first reaction zone uses the first lightening reactor D1 and the second lightening reactor D2, and the second reaction zone uses reactor L. All are fixed-bed reactors. The specific reaction conditions for each reactor are shown in Table 4. The composition of the obtained products is shown in Table 10, with a cracked feedstock (C2-C4) yield of 65.79% and a mixed aromatics yield of 11.20%.

[0334] Table 10. Composition of the product obtained from comparative test example 5

[0335]

Test Example 10

[0336] This embodiment uses cracked C5 fraction, a byproduct of a refinery, as a light hydrocarbon feedstock. The cracked C5 fraction consists of more than 20 components with similar boiling points that readily form azeotropes. These components are categorized as follows: isoprene, isoprene, and cyclopentadiene (dicyclopentadiene) each contain approximately 20%; branched monoolefins and straight-chain monoolefins each contain approximately 15%–20%; and small amounts of alkanes, alkenes, and their C4 and C6 components are also present. The process flow is shown in Figure 4, but without an adsorption denitrification tower A. Both the hydrotreating reactor D and the aromatization reactor G are fixed-bed reactors. Catalyst C-9-1 is used in the hydrotreating reaction zone, and catalyst C-9-2 is used in the aromatization reactor. The reaction conditions are shown in Table 11. The yield of the cracked feedstock (C2-C3) is 78.8%, and the yield of mixed aromatics is 21.1%.

[0337] Table 11. Operating conditions of each reactor in Test Example 10

[0338]

Test Example 11

[0339] In this example, the catalysts packed in the hydrogenation reactor and the aromatization reactor are the same as those in Test Example 10.

[0340] This test example uses light naphtha as raw material (composition shown in Table 13), and follows the process shown in Figure 5, but without adsorption denitrification tower A. Hydrogenation reactors D1 and D2, and aromatization reactor G are all fixed-bed reactors, and the reaction conditions are shown in Table 12. The product composition is shown in Table 13.

[0341] Table 12. Operating conditions of each reactor in Test Example 11

[0342] Table 13. Composition of naphtha feedstock and products used in Test Example 11 Note: In the table, C6, C7, C8, C9, and C10 refer to the content of non-aromatic hydrocarbons.

[0343]

Test Example 12

[0344] In this example, the catalysts packed in the hydrogenation reactor and the aromatization reactor are the same as those in Test Example 10.

[0345] This embodiment uses 65wt% isobutane-35wt% n-butane as feedstock, following the process flow shown in Figure 6, but without adsorption denitrification tower A. Both the hydrotreating reactor D and the aromatization reactor G are fixed-bed reactors, and the reaction conditions are shown in Table 14. The product cracking feedstock (C2-C3) yield is 87.0%, and the mixed aromatics yield is 9.1%.

[0346] Table 14 Operating conditions of each reactor in Test Example 12

[0347]

Test Example 13

[0348] The catalyst used in the hydrogen reforming reaction zone is catalyst C-10-1, and the catalyst used in the aromatization reactor is catalyst C-9-2.

[0349] This embodiment uses light naphtha as raw material (same as Test Example 12), and adopts the process of Test Example 12. The reaction conditions are shown in Table 15. The product composition is shown in Table 16.

[0350] Table 15. Operating conditions of each reactor in Test Example 13

[0351] Table 16. Composition of the product obtained in Test Example 13

[0352] [Comparative Test Example 6]

[0353] The catalyst used in the hydrogen reforming reaction zone is catalyst CD-4, and the catalyst used in the aromatization reactor is catalyst C-9-2.

[0354] This example uses light naphtha as feedstock (same as in Test Example 11), and adopts the same process and reaction conditions as in Test Example 11. The product composition is shown in Table 17. The yield of the cracked feedstock (C2-C3) is 61.49%, and the yield of mixed aromatics is 24.31%.

[0355] Table 17. Composition of the product obtained from comparative test example 6

[0356] The above description is merely a specific embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with specific embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A ZSM-5 molecular sieve, characterized in that, The total specific surface area of ​​the ZSM-5 molecular sieve is 300-500 m². 2 / g, wherein the external specific surface area accounts for 33%-45% of the total specific surface area, preferably 34%-45%, of this ZSM-5 molecular sieve. 27 The ratio of the peak area at a chemical shift of 53 ppm in Al NMR spectra to the peak area of ​​tetracoordinate Al is ≥50%, for example, 50-70%.

2. The ZSM-5 molecular sieve according to claim 1 or 2, characterized in that, The ZSM-5 molecular sieve is an agglomeration of nanosheets, with an average particle size of 20-300 nm and an average thickness of 10-100 nm; preferably, the average particle size of the agglomeration is 0.3-10 μm.

3. The ZSM-5 molecular sieve according to claim 1, characterized in that, The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 50-250; preferably, the surface silicon-aluminum ratio is 30%-90% of the bulk silicon-aluminum ratio.

4. The ZSM-5 molecular sieve according to any one of claims 1-3, characterized in that, The ZSM-5 molecular sieve has a pore volume of 0.24-0.35 cm³. 3 / g, and / or The specific surface area of ​​the ZSM-5 molecular sieve is 99-225 m². 2 / g, preferably 125-225m 2 / g, more preferably 132-225m 2 / g.

5. The ZSM-5 molecular sieve according to any one of claims 1-4, characterized in that, The micropore volume of the ZSM-5 molecular sieve is 0.10-0.22 cm³. 3 / g.

6. The ZSM-5 molecular sieve according to any one of claims 1-5, characterized in that, The average pore size of the ZSM-5 molecular sieve is 2.1-3.5 nm.

7. A method for preparing the ZSM-5 molecular sieve according to any one of claims 1-6, comprising: S1. Mix the first silicon source, the first template agent, the first alkali source and water to obtain a seed gel; wherein the first silicon source is a solid silicon source, the molar ratio of the first alkali source to the first silicon source is 0.05-0.10, the molar ratio of the first template agent to the first silicon source is 0.05-0.10, and the first silicon source is calculated as SiO2, and the first alkali source is calculated as an oxide; S2. Mix the second silicon source, aluminum source, second template agent, second alkali source, water, and seed gel to obtain the synthesis solution; S3. The synthesis solution is subjected to crystallization treatment to obtain ZSM-5 molecular sieve.

8. The preparation method according to claim 7, characterized in that, Step S1 satisfies at least one of the following characteristics: The solid silicon source is silica gel powder with a particle size of 60-800 mesh. The first template agent is at least one selected from n-butylamine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium bromide, ethylenediamine, or hexamethylenediamine. The first alkali source is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; The molar ratio of water to the first silicon source is 5-30, where the first silicon source is SiO2.

9. The preparation method according to claim 7 or 8, characterized in that, Step S2 satisfies at least one of the following characteristics: the second template agent is an organic amine, preferably at least one of n-butylamine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium bromide, ethylenediamine, triethylamine or hexamethylenediamine; The second silicon source is at least one of silica sol, water glass, fumed silica and silica gel, preferably silica gel, more preferably silica gel powder, with a particle size of 60-800 mesh; The aluminum source is at least one of sodium aluminate, aluminum sulfate, and aluminum isopropoxide; The second alkali source is at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

10. The preparation method according to any one of claims 7-9, characterized in that, Step S2 satisfies at least one of the following characteristics: The molar ratio of the second silicon source to the aluminum source is 30-100; The molar ratio of the second template agent to the second silicon source is 0.02-0.10; The molar ratio of the second alkali source to the second silicon source is 0.07-0.12; The molar ratio of water to the second silicon source is 15-30; The mass ratio of seed gel to the second silicon source is 1%-20%, preferably 3%-10%; The second silicon source is calculated as SiO2, the aluminum source as Al2O3, the second alkali source as oxide, and the seed gel as SiO2.

11. The preparation method according to any one of claims 7-10, characterized in that, The conditions for crystallization treatment in step S3 include: crystallization temperature of 125-180℃ and crystallization time of 16-96h under sealed conditions.

12. A catalyst for a lightening reaction, comprising: Molecular sieves prepared by the method of any one of claims 1-6 or any one of claims 7-11. Adhesives, such as alumina, and Modified metal, wherein the modified metal is at least one of molybdenum, zinc, copper, gallium, and lanthanum; Preferably, based on the catalyst, the mass content of the molecular sieve is ≥70%, more preferably ≥75%, and even more preferably ≥80%. Preferably, based on the catalyst, the mass content of the modified metal is 1%-10%, wherein the modified metal is calculated as an oxide; Preferably, based on the catalyst, the mass content of the binder is ≤20%, more preferably 12%-20%.

13. The catalyst according to claim 12, characterized in that, The catalyst also contains phosphorus. Based on the catalyst, the mass content of phosphorus, calculated as elemental phosphorus, is 1%-10%, preferably 3-7%.

14. A lightweighting method, comprising the following steps: A1. Mix light hydrocarbons and / or naphtha with hydrogen-rich gas to obtain a mixture; A2. The mixture obtained in step A1 is contacted with a catalyst based on ZSM-5 molecular sieve according to any one of claims 1-6 or ZSM-5 molecular sieve prepared according to any one of claims 7-11 or the catalyst according to claim 12 or 13 for modification treatment to obtain a modified product. A3. Optionally, the modified product obtained in step A2 is separated to obtain a cracking feedstock rich in C2-C3 hydrocarbons and a liquid phase, respectively. Preferably, the liquid phase is separated to obtain a recycled material rich in C4-C6 hydrocarbons and a mixed aromatic product, wherein the recycled material is recycled back to step A2.

15. The method according to claim 14, characterized in that, Step A1 satisfies at least one of the following characteristics: The light hydrocarbon or naphtha is selected from at least one of straight-run gasoline, hydrocracked gasoline, catalytic cracked gasoline, hydrocoking gasoline, reforming topping oil, reforming raffinate, condensate, cracked gasoline, and cracked gasoline raffinate. The initial boiling point of the light hydrocarbon or naphtha is 30-120℃, and the final boiling point is 120-220℃. The nitrogen content in the light hydrocarbon or naphtha is 0.1-10 ppm; preferably, when the nitrogen content in the naphtha feedstock is greater than or equal to 3 ppm, denitrification treatment is performed first, and then step A1 is performed. The hydrogen-rich gas is one of hydrogen, a mixture of hydrogen and methane, and hydrogen-rich dry gas; preferably, the hydrogen volume content in the hydrogen-rich gas is greater than or equal to 50%.

16. The method according to claim 14, characterized in that, Step A2 satisfies at least one of the following characteristics: The modification process employs a fixed bed, a moving bed, or a fluidized bed. The reforming conditions include a mass hourly space velocity (MSV) of 0.3-2 h⁻¹ for the light hydrocarbon and / or naphtha feed. -1 The reaction temperature is 280-450℃, preferably 320-380℃, the reaction pressure is 0.5-3.0MPa, preferably 1.0-2.0MPa, and the hydrogen-oil volume ratio of hydrogen-rich gas to light hydrocarbon and / or naphtha feed is 0.2-3.0:

1. The modified catalyst is a catalyst obtained by metal modification of the ZSM-5 molecular sieve; wherein the modified metal is at least one of molybdenum, zinc, copper, gallium, and lanthanum, preferably at least one of zinc, molybdenum, and gallium; preferably, the mass content of the modified metal is 1%-10% based on the mass of the metal-modified ZSM-5 molecular sieve catalyst, wherein the modified metal is calculated as an oxide.

17. The method according to claim 14, characterized in that, In step A3, propane accounts for ≥95% v% of the cracking feedstock, and the recycled material is mainly C4-C6 hydrocarbons.

18. The method according to claim 14, characterized in that: The modification process in step A2 is carried out through the first reaction zone and the second reaction zone; The first reaction zone is used to lighten light hydrocarbons and / or naphtha to produce cracking feedstock, and the second reaction zone is used to cause chain scission reactions in long-chain hydrocarbons.

19. The method according to claim 18, characterized in that, Step A2 satisfies at least one of the following characteristics: The first reaction zone may employ a fixed bed, or one or more reactors, or one or more catalyst beds within a single fixed-bed reactor; The second reaction zone uses a fixed bed or a fluidized bed; The first reaction zone is filled with a first molecular sieve catalyst; preferably, the molecular sieve content in the first molecular sieve catalyst is greater than or equal to 70% by mass. The reaction conditions in the first reaction zone are as follows: mass hourly space velocity (HHSV) of 0.3-2 h⁻¹. -1 The reaction temperature is 280-400℃, the reaction pressure is 0.5-2.0MPa, and the volume ratio of the hydrogen-rich gas to light hydrocarbons and / or naphtha is 0.3-5:

1. The first reaction zone employs at least two reaction sections; preferably, the reaction temperature of the upstream reaction section is at least 10-120°C lower than that of the adjacent downstream reaction section, and more preferably at least 20-80°C lower. The second reaction zone is filled with a second molecular sieve catalyst; preferably, the SiO2 / Al2O3 molar ratio of the molecular sieve is 150-300. The reaction conditions in the second reaction zone are as follows: reaction temperature 420-550℃, reaction pressure 1.0-4.0 MPa, and mass hourly space velocity 0.1-1.5 h⁻¹. -1 .

20. The method according to claim 18, characterized in that, The reaction products leaving the second reaction zone are first heat-exchanged with a mixture of light hydrocarbons and / or naphtha and hydrogen-rich gas before being separated.

21. The method according to claim 14, characterized in that, The liquid phase from step A3 is introduced into the aromatization reaction zone to undergo a catalytic reaction. The resulting reaction product is extracted to obtain a mixed aromatic product.

22. The method according to claim 21, characterized in that, Having at least one of the following characteristics The aromatization reaction zone is a fixed bed, a moving bed, or a fluidized bed. The catalyst used in the aromatization reaction zone comprises a support and a metal oxide, and contains the following components by mass fraction based on the mass of the catalyst: 1%-10% zinc oxide, 1%-5% copper oxide, 0.1%-3% lanthanum oxide, 1%-8% phosphorus, 50%-70% molecular sieve, and 20%-40% binder; preferably, the molecular sieve is at least one of ZSM-5 molecular sieve, Y-type molecular sieve, β-molecular sieve, mordenite, and SAPO-34 molecular sieve; more preferably, the SiO2 / Al2O3 molar ratio of the molecular sieve is 40-200; The reaction conditions for the aromatization reaction are as follows: reaction temperature 420-600℃, reaction pressure 0.1-2 MPa, and mass hourly space velocity (HHSV) 0.2-2 h⁻¹. -1 ; The separation of the modified products is carried out in a stabilization tower or a gas-liquid separator.

23. The use of the ZSM-5 molecular sieve according to any one of claims 1-6 or the catalyst according to claim 12 or 13 in the light hydrocarbon and / or naphtha lightening process.

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