A method for preparing and using a sinter-resistant cu-beta zeolite catalyst

Abstract

This invention belongs to the field of petrochemical catalysis technology, and relates to a method for preparing and applying an anti-sintering Cu-Beta zeolite catalyst. The invention uses a pitted-modified hierarchical porous dealaluminized Beta zeolite as a support, and employs a modified ammonia stripping method to load copper into the pores of the zeolite support. The core of the modified ammonia stripping method is to impregnate the zeolite support with an equal volume of copper-ammonia complex solution, primarily depositing copper hydroxide in the pores of the zeolite support. After calcination and hydrogen reduction, the hydroxide directly forms highly dispersed nano and sub-nano copper particles at the hydroxyl-hole lattice defect sites in the zeolite pores. The pitted-modified hierarchical porous dealaluminized Beta zeolite support exhibits strong hydroxyl-hole containment, and the copper particles gain anti-sintering ability through close interaction with it. The Cu-Beta catalyst prepared using the method provided by this invention not only shows high activity but also good stability when applied to the gas-solid phase hydroammoniation of caprolactone to caprolactam.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical catalysis, and relates to a preparation method and application of an anti-sintering Cu-Beta zeolite catalyst. Background Art

[0002] Copper-based catalysts are widely used in alcohol dehydrogenation, carbonyl hydrogenation, ester hydrogenolysis, ammoniation, hydrocarbon hydrogenation, isomerization, and hydrogenolysis reactions of C-C bonds and C-Si bonds, etc. The prominent advantages of copper-based catalysts are high selectivity, low price, and no pollution to the environment. However, easy deactivation is a problem that must be faced in the industrial application of copper-based catalysts. Poisoning deactivation (sulfur, chlorine) and coking deactivation are common phenomena in the industrial application of copper-based catalysts. However, these deactivation problems can generally be addressed through raw material purity control, reaction condition optimization, and regeneration treatment. The easy sintering and growth of highly dispersed copper particles (Ostwald ripening) is a difficult problem causing the deactivation of copper-based catalysts. This kind of deactivation is usually irreversible and non-renewable, thus having the greatest impact on industrial applications. The main reason for the easy sintering and growth of highly dispersed copper particles is that copper metal has a large ionic radius, low melting point (1083 °C), low Tammann temperature and Hüttig temperature. Supported copper catalysts can sinter at a temperature of 170 °C. Someone summarized the thermal stability of common metal catalysts and gave the following order: Ag < Cu < Pd < Fe < Ni < Co < Pt < Rh < Ru < Ir < Os < Re. It can be seen therefrom that the thermal stability of copper is lower than that of most common metal catalysts.

[0003] In 1966, KANEGAFUCHI, BOSEKI KABUSHIKI KAISHA in Japan first disclosed a catalytic method for preparing caprolactam from caprolactone in the gas phase in British Patent GB1109540. The method is to first vaporize caprolactone and a certain amount of water vapor, then mix them with ammonia and hydrogen, and the mixed gas undergoes a catalytic reaction at 120 - 350 °C and atmospheric pressure through a copper chromite catalyst. The conversion rate of caprolactone in this method can reach 100%, and the selectivity of caprolactam can reach 97%.

[0004] In 1972, Kanekabuchi Corporation of Japan disclosed a method for preparing caprolactam using copper chromite as a catalyst in US Patent 3,652,549. The copper chromite catalyst was obtained by co-precipitation using copper nitrate and ammonium dichromate as raw materials and ammonia as a precipitant. The technical features of the catalyst preparation process include: after filtration, dehydration, low-temperature drying (75-80°C, 20h), and high-temperature decomposition of the precipitate generated by the co-precipitation reaction, it is further soaked in dilute acetic acid solution. The catalyst precursor after soaking is then filtered, washed with water, and dried (125°C, 12h) to become the catalyst. Before being used in a fixed-bed reactor, the catalyst needs to be tableted. Before the reaction, the catalyst also needs to be subjected to hydrogen reduction treatment at 200°C. The atomic ratio of chromium to copper in the copper chromite catalyst is 0.1-5, preferably 0.1-3. The catalyst may also contain a third metal component (Ba, Ca, Mg, Sr, Al, Ga, Ti, V, Mn, Fe, Co, Ni, Zn, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Pd, As, Bi, Sb). The atomic ratio of the third metal component to copper is 0.001-1, preferably 0.01-0.2. The raw material for preparing caprolactam conforms to the general formula X-(CH2)4-COY. Wherein, X = CHO, -CH(OR)(OR1), -COOH, -COONH4, -CONH2, or COR2; Y = OH, ONH4, NH2, or OR3. The reaction is carried out in a fixed-bed reactor in a gas-solid phase manner, with a reaction temperature range of 170-300℃ and a hydrogen partial pressure of 0.1-1.5 atm. The feed also includes ammonia and water vapor, with preferred dosage ranges (molar ratio to feed) of 2-50 and 10-100, respectively. When dimethyl adipate is used as the feed, the reaction results with a copper chromite catalyst containing a small amount of zinc are: feed conversion rate of 99% and caprolactam selectivity of 95%; the reaction results with a copper chromite catalyst containing a small amount of Mo are: feed conversion rate of 100% and caprolactam selectivity of 96%.

[0005] In 1975, Teijin Corporation of Japan disclosed a catalytic process for producing caprolactam from C1-C4 alkyl esters of caprolactone or 6-hydroxyhexanoic acid in US Patent 3888845. Specifically, the patent disclosed a process for producing caprolactam through a gas-solid phase catalytic reaction using C1-C4 alkyl esters of caprolactone or 6-hydroxyhexanoic acid, along with hydrogen and ammonia as raw materials. This process is characterized by low reaction temperature and pressure, high conversion rate of C1-C4 alkyl esters of caprolactone or 6-hydroxyhexanoic acid, and high selectivity for caprolactam. The solid catalyst used in this process consists of three parts: A, B, and C. A is an oxide support selected from titanium dioxide, alumina, silica, and a composite of alumina and silica; B is the main metal component of the catalyst—copper; and C is the trace metal component of the catalyst—selectively nickel or chromium. The catalyst can be prepared by deposition precipitation. The preferred support is anatase titanium dioxide. The weight ratio of copper to support is 0.5-200, preferably 5-100, and more preferably 10-70. The atomic ratio of Ni(Cr) to Cu is 0.001-1, preferably 0.005-0.25. The gas-solid phase catalytic reaction for producing caprolactam from C1-C4 alkyl esters of caprolactone or 6-hydroxyhexanoic acid can be carried out at 200-320°C and 0.01-2 atm, preferably at 220-310°C and 0.1-1.2 atm. The optional ranges for hydrogen and ammonia amounts are 5-70 (H2 / ester molar ratio) and 1-50 (NH3 / ester molar ratio), respectively, with preferred ranges of 10-50 (H2 / ester molar ratio) and 2-25 (NH3 / ester molar ratio), respectively. Furthermore, this process emphasizes the importance of the hydrogen to ammonia molar ratio and the addition of water to the reactor feed. In general, employing a suitable hydrogen to ammonia molar ratio is beneficial for improving reaction selectivity. Adding water to the reactor feed not only reduces side reactions and improves caprolactam selectivity but also slows down catalyst deactivation. The selectable range for the hydrogen to ammonia molar ratio is 0.2-30, with a preferred range of 0.5-15; the selectable range for the water / ester molar ratio is 0-50, with a preferred range of 5-30. Under optimal conditions, the conversion rate of caprolactone to caprolactam can reach up to 99%, and the selectivity of caprolactam can reach up to 90%. The problem is that catalyst deactivation due to carbon deposition is relatively rapid. However, this patent provides two catalyst regeneration methods. One method is redox treatment, and the other is steam treatment. The redox treatment is actually regeneration first using molecular oxygen carbonization, followed by hydrogen reduction of the catalyst. Molecular oxygen carbonization can be carried out in a temperature range of 100-800℃, preferably in a temperature range of 150-500℃. The charcoal burning time is 20 minutes to 20 hours; the hydrogen reduction after charcoal burning can be carried out in a temperature range of 170-350℃, preferably in a temperature range of 170-270℃.The steam treatment can be carried out at a temperature between 100-500°C, preferably between 200-400°C. The steam treatment time is 20 minutes to 20 hours. The steam treatment can also be carried out in the presence of hydrogen, and it is preferable to reduce the catalyst with hydrogen after the steam treatment. The hydrogen reduction can be carried out at a temperature range of 170-350°C, preferably between 170-270°C.

[0006] The aforementioned patent not only discloses the important use of a copper-based catalyst in the reaction of caprolactone to caprolactam, but also provides a method to improve the anti-sintering performance of copper-based catalysts—by adding chromium, nickel and other additives to the copper-based catalyst.

[0007] As is well known, ε-caprolactam (CPL) is a white, solid organic compound, the vast majority of which is used in the production of polycaprolactam chips, with a smaller portion used in the production of lysine and pharmaceutical intermediates. Among the downstream products of polycaprolactam chips, nylon-6 fibers and engineering plastics consume approximately 70% and 20% of the chips, respectively. The remaining polycaprolactam chips are processed into packaging films and food preservation films.

[0008] Nylon-6 was the world's first developed synthetic fiber product. The most outstanding advantage of nylon-6 fiber is its superior abrasion resistance compared to all other fibers. It is 10 times more abrasion-resistant than cotton and 20 times more abrasion-resistant than wool. Simultaneously, nylon-6 fiber is 1-2 times stronger than cotton, 4-5 times stronger than wool, and 3 times stronger than viscose fiber. Adding a small amount of polyamide fiber to blended fabrics can significantly improve their abrasion resistance, elastic recovery rate, and flexural strength. Furthermore, nylon-6 fiber also has good moisture absorption and dyeability. Nylon-6 fiber can be used as both civilian and industrial yarn. Civilian nylon yarn is used to make shirts, sweaters, pajamas, carpets, blankets, curtain cords, and bags, etc.; industrial yarn is used to make tents, car tires, drive belts, hoses, cables, fishing nets, ropes, and insulation materials, etc.

[0009] Currently, the benzene-based process for producing caprolactam is the mainstream process. This process mainly includes three basic steps: benzene to cyclohexanone, cyclohexanone to cyclohexanone oxime, and cyclohexanone oxime rearrangement to caprolactam.

[0010] Those familiar with this field know that the traditional benzene-based caprolactam process has many serious problems. However, in recent years, in accordance with the requirements of green chemistry and atom economy, some successful improvements have been made to the traditional benzene-based caprolactam process. These include replacing the non-selective hydrogenation of benzene to cyclohexane and the air oxidation of cyclohexane to cyclohexane with selective hydrogenation of benzene to cyclohexene and hydration and dehydrogenation of cyclohexene to cyclohexane in the benzene-to-cyclohexanone step; and eliminating the sulfuric acid hydroxylamine (HSO) process, which produces ammonium sulfate as a byproduct and suffers from equipment corrosion problems, with a titanium silicate molecular sieve-catalyzed cyclohexanone ammonium oxime process in the cyclohexanone-to-cyclohexanone oxime step.

[0011] Despite this, the improved benzene-based caprolactam process still has many drawbacks. These include: (1) low efficiency in the selective hydrogenation of benzene to cyclohexene and the hydration of cyclohexene to cyclohexanol; (2) large solvent consumption in the cyclohexanone ammonoxime process, rapid deactivation and high consumption of the TS-1 catalyst during the reaction (titanium silicate molecular sieves are expensive. The cyclohexanone ammonoxime production of cyclohexanone oxime is a liquid-phase reaction, and the titanium silicate molecular sieve catalyst is in a strongly alkaline environment for a long time, causing the dissolution of the framework silicon and resulting in the ineffective loss of the catalyst); (3) the liquid-phase Beckmann rearrangement process (the current mainstream process) still uses fuming sulfuric acid as a catalyst, which not only corrodes the equipment, but also produces 1.5 to 1.8 tons of ammonium sulfate as a byproduct for every ton of caprolactam produced. The gas-phase Beckmann rearrangement technology, which has been highly anticipated, has serious problems such as rapid catalyst deactivation, and people have encountered setbacks in their efforts to replace the liquid-phase Beckmann rearrangement process with the gas-phase Beckmann rearrangement process.

[0012] Given the current state of existing caprolactam production processes using the benzene-based method and the challenges in developing new processes, researchers in this field are seeking a new, highly efficient process for caprolactam production that avoids low-value byproducts (such as ammonium sulfate), equipment corrosion and environmental pollution, high atom utilization, and low energy consumption (low carbon emissions).

[0013] The early efforts of Kanebuchi Spinning Co., Ltd. and Teijin Co., Ltd. in Japan demonstrate that preparing caprolactam from caprolactone can eliminate the cyclohexanone oxime Beckmann rearrangement step in the existing benzene-based caprolactam process and avoid the problems associated with the cyclohexanone ammoniation step, making it a promising new route for caprolactam production. However, currently, the technical route for preparing caprolactam from caprolactone has not received much attention. Existing processes and catalysts for preparing caprolactam from caprolactone are mainly based on patents and papers published in the 1970s and earlier. In general, the early proposed reaction processes were mainly divided into two types: non-catalytic methods (US3000879, US3000880, US3317516, US3317517, GB1121109, US3320241, CA770148, US3401161, US3497500, published Japanese literature Kobunshi Ronbunshu, 58(12), 679-684(2001)) and catalytic methods (US2817646, GB1109540, US3652549, US3888845, DE102012006946A1, CN108774172A, published Japanese Chemical Society Journal, 1977, (7), p.1013-1017, published ChemSusChem, 2022, 15(16)). Non-catalytic methods require high-temperature and high-pressure reaction conditions. Due to thermodynamic limitations and the formation of byproducts, the yield of caprolactam using non-catalytic methods is relatively low. In contrast, catalytic methods offer milder reaction conditions, which are not only thermodynamically favorable but also help avoid side reactions, reduce equipment investment, energy consumption, and production costs. Therefore, they are advantageous for industrial applications. However, catalytic methods require catalysts with high activity, high selectivity, and strong resistance to deactivation; existing catalysts do not meet the needs of industrial applications. Summary of the Invention

[0014] The purpose of this invention is to provide a method for preparing and applying an anti-sintering Cu-Beta zeolite catalyst.

[0015] Specifically, the sintering-resistant Cu-Beta zeolite catalyst provided by this invention is a catalyst prepared by loading copper into the pores of a hierarchical porous dealubilized Beta zeolite supported by a modified ammonia stripping method. The hierarchical porous dealubilized Beta zeolite support is obtained by acid dealubilization treatment of a Beta zeolite matrix containing hierarchical pores. The "dimpling modification" refers to further modifying the hierarchical porous dealubilized Beta zeolite support using a weak organic base controlled desilication technique to enlarge the hydroxyl groups generated during dealubilization, thereby better accommodating and stabilizing nano- and sub-nanometer copper particles. The catalyst provided by this invention is used for the gas-solid phase catalytic reaction of caprolactone to caprolactam via hydroamination.

[0016] Research has revealed that, for the gas-solid phase catalytic reaction of caprolactone to caprolactam via hydroamination, supported copper-based catalysts show the greatest promise for industrial application in terms of catalytic activity and selectivity. However, from the perspective of catalyst stability, deactivation is the biggest challenge for the industrial application of supported copper-based catalysts. The deactivation of copper-based catalysts in the gas-solid phase catalytic reaction of caprolactone to caprolactam via hydroamination is not solely due to coking. The sintering problem of highly dispersed copper particles is also a significant cause of catalyst deactivation. Those familiar with the field know that coking deactivation is a temporary deactivation of the catalyst, and its catalytic activity can generally be restored through various regeneration methods, thereby extending the catalyst's lifespan. In contrast, sintering deactivation is generally a permanent deactivation of the catalyst, having the greatest impact on its lifespan.

[0017] The main advantages of the Cu-Beta zeolite catalyst and its preparation method provided by this invention are as follows: First, it utilizes the dispersion and stabilization effect of the dealuminated Beta zeolite hydroxyl clusters on the supported copper particles. Simultaneously, it employs a weak organic base to control the desilication technology, increasing the size of the dealuminated hydroxyl clusters and expanding the contact area between the hydroxyl clusters and the copper particles, further enhancing the stabilizing effect of the dealuminated Beta zeolite hydroxyl clusters on the supported copper particles. Furthermore, the Cu-Beta zeolite catalyst and its preparation method also increase the flexibility (structural variability) of the zeolite support by introducing a hierarchical porous structure, thereby adding the ability of the hydroxyl clusters on the zeolite support to further stabilize the copper particles through expansion and deformation. These measures allow the Cu-Beta zeolite catalyst to be used without the addition of anti-sintering aids such as chromium and nickel.

[0018] In summary, the anti-sintering Cu-Beta zeolite catalyst and its preparation method provided by this invention have the following main technical features:

[0019] First, the present invention provides an anti-sintering Cu-Beta zeolite catalyst and its preparation method, using a pitted modified hierarchical porous dealubilized Beta zeolite as a carrier.

[0020] Existing patents and academic papers describe catalysts primarily used for the catalytic synthesis of caprolactam from caprolactone using unsupported bulk copper chromite catalysts and copper catalysts supported on amorphous single oxide supports (such as titanium dioxide, alumina, and silica) and binary composite oxide supports (such as silica and alumina) with the addition of a second metal component, nickel or chromium. Those skilled in the art know that unsupported copper chromite catalysts have a small specific surface area and few exposed metal active sites, resulting in high metal consumption and low catalytic efficiency. Supporting copper, copper-nickel, and copper-chromium on amorphous oxide supports (single oxide supports and binary composite oxide supports) can overcome the problems of unsupported catalysts. However, supported copper catalysts are prone to sintering and deactivation, posing a significant challenge for industrial applications. Adding chromium to supported copper catalysts to form a copper chromite phase can improve their resistance to sintering. However, chromium is a metal with restricted use. Clinically, chromium and its compounds primarily harm the human skin, respiratory, and digestive systems; even low chromium concentrations can have strong toxic effects on the human body. Therefore, catalysts with added chromium encounter significant challenges in preparation, use, and the harmless disposal of spent catalysts. Adding nickel to supported copper catalysts can improve the anti-sintering properties of copper. However, our research results indicate that for the reaction from caprolactone to caprolactam, introducing a large amount of nickel into the supported copper catalyst significantly reduces the catalyst's ability to catalyze the gas-solid phase hydroammoniation of caprolactone to caprolactam. For example, under the same conditions, a copper-amorphous silica catalyst (10 wt.% Cu) prepared using fumed silica (chemical silica) as a support, when doped with a small amount of nickel (Ni:Cu = 0.3), showed a 15-20% decrease in its ability to catalyze the hydroammoniation of caprolactone to caprolactam. In the relevant patent (US3888845), although nickel is considered a preferred additive for supported copper catalysts, its addition is strictly limited to the Ni:Cu range of 0.001-1 (atomic ratio), preferably 0.005-0.25. Undoubtedly, the addition of a small amount of nickel can improve the anti-sintering ability of supported copper catalysts. However, the effect of a small amount of nickel alone is not enough to properly solve the problem of sintering deactivation of supported copper catalysts.

[0021] This invention uses a pitted, multi-level porous dealubilized Beta zeolite as a support to prepare a supported copper catalyst. The aim is to utilize the structural flexibility of the multi-level porous structure and the expansion effect of pitting modification to enhance the dispersion and stabilization effect of the hydroxyl pits of the dealubilized Beta zeolite support on the supported copper particles. Thus, without adding metal additives such as chromium or nickel, a supported copper-based catalyst with strong anti-sintering ability is prepared by relying on the dispersion and stabilization effect of the hydroxyl pits of Beta zeolite on copper particles. This catalyst is used for the gas-solid phase catalytic reaction of caprolactone to caprolactam via hydroamination.

[0022] The main idea of ​​this invention comes from the inventor's previous work. In his previous work, the inventor had conducted in-depth research on the physicochemical properties and catalytic functions of hydroxyl lattice defect sites in the MFI zeolite family (ZSM-5, B-ZSM-5, Silicalite-1(S-1) and TS-1). The following public documents record some representative research work: Silicalite-1zeolite acidification by zinc modification and its catalytic properties for isobutane conversion, RSC Advances, 2018, 33(8), p.18663-1867; Pt supported on Znmodified silicalite-1zeolite as a catalyst for n-hexane aromatization, JOURNAL OF ENERGY CHEMISTRY,2018,(36),p.96-103; Operando Dual Beam FTIR Study of Hydroxyl Groups and Zn Species over Defective HZSM-5Zeolite Supported ZincCatalysts,Catalysts,2019,1(9),p.100; Effect of Zeolitic Hydroxyl Nests on theAcidity and Propane Aromatization Performance of Zinc Nitrate Impregnation-Modified HZSM-5Zeolite, Industrial & Engineering Chemistry Research, 2020, 37(59), p.16146-16160. Liu Guodong. Study on surface acidity and catalytic performance of ZnO-modified nano-silicalite-1 zeolite [D]. Dalian University of Technology, 2020.; Lin Long. Characterization, modification and catalytic performance of defective ZSM-5 zeolite [D]. Dalian University of Technology, 2022.). In short, the above research results show that silanolites located in the zeolite hydroxyl lattice defect sites are more chemically active than isolated silanolites on the outer surface of zeolite crystals because they easily form hydrogen bonds.Furthermore, it is particularly worth mentioning that in their research on zinc nitrate impregnation of defective all-silica zeolite S-1 and defective ZSM-5 zeolite and the preparation of zinc oxide-modified catalysts, the inventors discovered an important phenomenon: zinc oxide preferentially resides at the hydroxyl-dwelling lattice defect sites of the zeolite. Moreover, the zinc oxide residing at these zeolite hydroxyl-dwelling lattice defect sites are all highly dispersed sub-nanometer zinc oxide species. These research experiences provided important scientific guidance for this invention.

[0023] However, this invention does not use defective MFI zeolites (e.g., defective all-silica zeolite S-1 and deboronized B-ZSM-5 zeolite) as the support for preparing the copper-supported catalyst. Instead, it selects dealulated Beta zeolite as the support for preparing the copper-supported catalyst. This is not because the hydroxyl-dwelling lattice defect sites in defective MFI molecular sieves (e.g., defective all-silica zeolite S-1 and deboronized B-ZSM-5 zeolite) cannot disperse and stabilize copper particles, nor is it because the copper-supported catalyst prepared using defective MFI molecular sieves (e.g., defective all-silica zeolite S-1 and deboronized B-ZSM-5 zeolite) is ineffective for catalyzing the gas-solid phase reaction from caprolactone to caprolactam. Rather, it is because the cylindrical channels of MFI family zeolites are ten-membered rings. When the loading of metallic copper is slightly large, the effective size of the channels will be significantly reduced, which is not conducive to the diffusion of the reactant caprolactone (seven-membered ring) within the pores, nor is it conducive to the formation and diffusion of caprolactam products, which are also seven-membered rings. Therefore, it is not conducive to the preparation of catalysts with high activity, high selectivity and strong resistance to deactivation.

[0024] Those familiar with this field know that, as a type of crystalline porous catalytic material, Beta zeolite and MFI zeolite share similar advantages, such as: (1) Both are high-silica zeolites, thus exhibiting high thermal and hydrothermal stability, good regeneration performance, and allowing for repeated regeneration and reuse after catalyst fabrication; (2) Both possess cylindrical channels and a three-dimensional intersecting pore system, providing networked channels for molecular diffusion, resulting in good pore diffusion and strong anti-clogging ability, which is beneficial for maintaining the catalyst's activity stability over a long period during continuous reactions. In addition, Beta zeolite has unique features compared to MFI zeolite. On the one hand, the three-dimensional cylindrical channels of Beta zeolite are all macropores with twelve-membered rings. In the three-dimensional channel system of Beta zeolite, there is a set of Z-shaped curved channels parallel to the

[001] direction with an elliptical cross-section and a diameter of 0.56 nm × 0.65 nm; there are also two sets of straight channels parallel to the

[100] and

[010] directions respectively, with elliptical cross-sections and diameters of 0.66 nm × 0.77 nm. In contrast, the three-dimensional cylindrical channels of MFI zeolite are all central holes of ten-membered rings. In the channel system of MFI zeolite, there is a set of straight channels parallel to the (100) crystal plane with an approximately circular cross-section (channel size 0.53 nm × 0.56 nm) and two sets of Z-shaped curved channels parallel to the (010) crystal plane with opposite directions and elliptical cross-sections (channel size 0.51 nm × 0.55 nm). It is conceivable that the relatively loose macroporous structure of Beta zeolite is not only more suitable for the intrapore diffusion of the reactant caprolactone (a seven-membered ring), but also for the formation and intrapore diffusion of caprolactam, which is also a seven-membered ring product. Therefore, it is more conducive to the preparation of catalysts with high activity, high selectivity, and strong resistance to deactivation. In fact, Beta zeolite is the only industrially produced zeolite catalytic material that simultaneously possesses the advantages of a high silica-alumina oxide molar ratio, a three-dimensional cross-channel system, and all channels being twelve-membered ring macropores.

[0025] On the other hand, the framework aluminum of Beta zeolite can be easily and completely removed by acid treatment, resulting in a high density of hydroxyl pit defects on the crystal framework. This characteristic is rare in industrially produced zeolite catalysts and is unmatched by MFI zeolite. During acid dealumination of Beta zeolite, removing one piece of framework aluminum requires acid dissociation of four Si-O-Al bonds ([Al-(OSi)4)). - +4H₂O=[Al(OH)₄] - +4≡Si-OH, [Al(OH)4] - +4H + =Al 3+ +4H₂O, the overall reaction equation is [Al⁻(OSi)₄]⁻ - +4H + =Al 3++4≡Si-OH) generates a hydroxyl-dwelling lattice defect site surrounded by four silanol groups (≡Si-OH). In MFI zeolites, the hydroxyl-dwelling lattice defect sites in the defective all-silica zeolite S-1 are randomly formed during the hydrothermal synthesis of S-1 zeolite in alkaline media, and their number and distribution are poorly controllable. Although the framework aluminum content of ZSM-5 zeolite has a wide adjustable range, its lower limit of the silicon-aluminum molar ratio (Si / Al) can reach about 10, and its upper limit can reach all-silica zeolite, i.e., Silicalite-1 (S-1). However, it is difficult to completely remove the framework aluminum of ZSM-5 zeolite. Therefore, in the research on the preparation of titanium-atom hybridized ZSM-5 zeolite using post-synthesis methods, the general practice is to first synthesize boron-containing ZSM-5 zeolite (B-ZSM-5), and then remove boron from B-ZSM-5 zeolite to obtain a ZSM-5 zeolite support with a high density of hydroxyl-dwelling defect sites on the framework.

[0026] In summary, the main reason why this invention did not use MFI zeolites with hydroxyl-dwelling lattice defect sites (e.g., defective all-silica zeolite S-1 and deboronized B-ZSM-5 zeolite) as the support for preparing copper-based catalysts, but instead chose Beta zeolite with hydroxyl-dwelling lattice defect sites as the support for preparing copper-based catalysts, is that, for the purposes of this invention, Beta zeolite possesses unparalleled material advantages, combining a high silica-alumina oxide molar ratio framework, a three-dimensional twelve-membered ring cross-channel system, and easy complete removal of framework aluminum. Furthermore, Beta zeolite was one of the earliest catalytic materials to achieve industrial synthesis; it can be obtained in large quantities commercially or easily prepared in-house using a hydrothermal synthesis method.

[0027] The hierarchical porous structure increases the skeletal flexibility (structural variability) of the zeolite support. During copper loading (especially in the high-temperature calcination stage), this skeletal structural variability can be utilized by the hydroxyl groups within the zeolite support. These hydroxyl groups expand and deform using the skeletal structural variability, thereby enhancing the ability to stabilize copper particles. This was an unexpected discovery in this invention.

[0028] Those familiar with this field know that crystalline aluminosilicate catalytic materials (i.e., zeolite catalytic materials) that have been industrially applied are basically microporous zeolite materials (main pore size < 1 nm). Common sense dictates that implanting mesopores (pore sizes ranging from 2-50 nm) into microporous zeolites allows for interconnection between micropores and mesopores, forming a more open hierarchical pore system. This reduces the internal diffusion resistance of reactants and products with larger molecular dynamic diameters (Mesoporous betazeolite obtained by desilication, Microporous and Mesoporous Materials 114(2008)93–102; Hierarchically porous BEA stannosilicates as unique catalysts for bulky ketone conversion and continuous operation, J. Mater. Chem. A, 2016, 4, 1373; Hierarchical Ti-beta with a three-dimensional ordered mesoporosity for catalytic epoxidation of bulky cyclic olefins, New J. Chem., 2021, 45, 10303). This is beneficial for preparing zeolite catalysts with high reactivity and strong resistance to carbon deposition and deactivation.

[0029] For the gas-solid phase hydroamination reaction of caprolactam to caprolactone, using hierarchical Beta zeolite as a support is also beneficial to the catalyst's reactivity and resistance to coking and deactivation. This is because the gas-solid phase hydroamination reaction of caprolactone to caprolactam involves both caprolactone reactant and caprolactam product, both of which have seven-membered ring molecular structures and are highly reactive polymer monomers. Using hierarchical Beta zeolite as a support helps reduce the microporous diffusion resistance of caprolactone and caprolactam, improving the accessibility of active sites within the micropores. On the one hand, reducing the microporous diffusion resistance of caprolactone and caprolactam helps reduce the chance of polymerization and coking of caprolactone and caprolactam within the catalyst channels. On the other hand, reducing the microporous diffusion resistance of caprolactone and caprolactam and improving the accessibility of active sites within the micropores will inevitably improve the catalyst's reactivity.

[0030] However, the inventors unexpectedly discovered during their research that using a pitted modified dealaluminated Beta zeolite with hierarchical pores as a support for the preparation of Cu-Beta zeolite catalysts also helps to disperse and stabilize nano and sub-nanometer copper particles, improving the catalyst's resistance to sintering. Examples of this invention will illustrate this with experimental results. Although a hierarchical porous dealaluminated Beta zeolite support can be obtained by dealaluminizing a hydrothermally synthesized hierarchical porous Beta zeolite matrix (Chem. Mater., 2011, 23, 4301–4310; J. Am. Chem. Soc., 2014, 136, 2503–2510), hydrothermal synthesis of hierarchical porous Beta zeolite requires the use of mesoporous template agents, which is costly. Therefore, this invention chooses a post-synthetic method to prepare a hierarchical porous dealaluminated Beta zeolite support. In short, the post-synthesis strategy chosen in this invention involves first desilicates the Beta zeolite matrix with a solution of an inorganic or organic base to obtain a mesoporous Beta zeolite matrix, and then subjecting the mesoporous Beta zeolite matrix to acid-dealuminate treatment to obtain a hierarchical porous dealuminated Beta zeolite support. Alkali metal hydroxides and alkali metal carbonates are both usable inorganic bases for desilicate zeolites. Quaternary ammonium bases (e.g., tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, etc.) are usable organic bases for desilicate zeolites. However, the usable inorganic and organic bases are not limited to these; all inorganic and organic bases disclosed in relevant patents and other published documents are applicable to the purpose of preparing a hierarchical porous Beta zeolite matrix as described in this invention. However, alkali metal hydroxides and alkali metal carbonates, especially sodium hydroxide, are relatively inexpensive strong inorganic bases and are therefore more suitable for use in this invention. Preparing hierarchical porous Beta zeolite matrix by desilication treatment of the Beta zeolite matrix with an aqueous sodium hydroxide solution is a low-cost and simple post-synthesis strategy.

[0031] Before use, the hierarchical porous dealuminolite Beta zeolite support undergoes a dimerization modification to enlarge the hydroxyl dimples generated during dealumination, thereby better accommodating and stabilizing nano and sub-nanometer copper particles. This dimerization modification involves supplementing the hierarchical porous dealuminolite Beta zeolite support with an aqueous solution of a small-molecule weak organic base, controlling the removal of 1-2 silicon atoms from the walls of its hydroxyl dimples. This enlarges the original small hydroxyl dimples with only one framework atom deficiency (acid dealumination) into larger hydroxyl dimples with 2-3 framework atom deficiencies.

[0032] This insight was gained after extensive preliminary research and exploration. Due to the atomic radius of copper... Larger than the ionic radius of aluminum Therefore, the smaller hydroxyl clusters generated by the dealumination of Beta zeolite can only accommodate a maximum of one copper atom. Clearly, the active silanol groups in the Beta zeolite hydroxyl clusters interact closely with only one copper atom, inevitably limiting their ability to disperse and stabilize metallic copper particles.

[0033] If one or two silicon atoms can be controllably removed from the hydroxyl group pockets of hierarchical dealuminized Beta zeolite, thereby expanding the small hydroxyl group pockets with only one framework atom defect (acid dealuminization) to larger hydroxyl group pockets with 2-3 framework atom defects, the dispersion and stabilization ability of the hydroxyl group pockets for metallic copper particles can be enhanced. Following this idea, the inventors conducted extensive exploratory research using weakly alkaline organic base aqueous solutions. Compared with alkali metal hydroxide (inorganic strong base) solutions and quaternary ammonium base solutions (organic strong base), the weakly alkaline organic base has a weaker desilication ability, only capable of desilication in small quantities, thus making it easier to achieve controllable desilication. Simultaneously, because of its weak desilication ability, the weakly alkaline organic base also easily achieves selective desilication, primarily desilication from the weakest point of the Beta zeolite framework—the hydroxyl group pocket defect site. Studies have found that aqueous solutions of small-molecule fatty amines (methylamine, ethylamine, propylamine, tert-butylamine, isopropylamine, n-butylamine, diethylamine, ethylenediamine, isobutylamine, triethylamine) and small-molecule alkanolamines (ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine) exhibit controllable desilication when contacted with hierarchical porous dealubilized Beta zeolite, demonstrating a "dimpling" effect on the hydroxyl groups of Beta zeolite. Compared with general organic bases, small-molecule fatty amines and alkanolamines have the advantage of good water solubility and low dosage. To avoid making the specification of this invention overly complicated, this invention only uses ethanolamine as an example for dimple-making modification of dealubilized Beta zeolite. Hole-drilling modification is essentially an alkaline-catalyzed hydrolytic desilication modification ([(OSi)3-O-SiOH]+3H2O=Si(OH)4+3≡Si-OH). For every silicon atom that is extracted (existing in the form of orthosilicic acid (Si(OH)4)), that is, for every silicon atom (existing in the form of Si(OH)4) "drilled" off the wall of the hydroxyl hole, three silanol groups (≡Si-OH) will be generated on the new wall of the hydroxyl hole.

[0034] Secondly, the anti-sintering Cu-Beta zeolite catalyst and its preparation method provided by the present invention are characterized in that the copper loading on the hierarchical porous dealubilized Beta zeolite support modified by denting is achieved by an improved ammonia stripping method.

[0035] The improved ammonia stripping method for loading copper involves impregnating a zeolite support with an equal volume of copper-ammonia complex solution. During this process, capillary action within the zeolite support's pores draws most of the copper-ammonia complex solution into the zeolite channels, allowing the copper hydroxide generated during ammonia stripping to directly deposit within the pores of the Beta zeolite. Therefore, in subsequent drying, calcination, and hydrogen reduction processes, copper hydroxide is first converted to copper oxide within the zeolite channels, and then further transformed into sub-nanometer and nanoparticles of metallic copper. These sub-nanometer and nanoparticles are directly captured by the hydroxyl-dimpled lattice defects, which are primarily located within the zeolite channels and have undergone a dimpling process, resulting in timely and more effective dispersion and stabilization.

[0036] Those familiar with this field know that the ammonia stripping method is one of the most commonly used methods for preparing copper-based catalysts. Ube Industries Ltd. (US4 440 873 (1984), EP0 064 241B1 (1985)) of Japan first proposed using the ammonia stripping method to prepare Cu / SiO2 catalysts for the solid-phase hydrogenation of dimethyl oxalate to ethylene glycol and glycolates. The earliest proposed ammonia stripping method is as follows: First, prepare a copper-ammonia complex solution. Dissolve a soluble copper-containing compound in water to obtain an aqueous solution containing copper ions. Then, add an appropriate amount of concentrated ammonia to the aqueous solution containing copper ions to make the pH value greater than 10, for example, to reach a pH value of 10-12. This yields a deep blue transparent solution containing the copper-ammonia complex. Second, use silica sol as a precursor for the SiO2 support and mix it with the copper-ammonia complex. That is, add the silica sol to the deep blue transparent solution containing the copper-ammonia complex and stir thoroughly to ensure uniform mixing. The mixing process can be carried out under atmospheric and pressurized conditions, from room temperature to 150°C; the third step is ammonia stripping. This involves stripping the mixture containing the copper-ammonia complex to obtain a solid catalyst precursor. Ammonia stripping can be carried out under pressurized and depressurized conditions, with a preferred temperature range of 60-90°C; the fourth step is the pretreatment of the solid catalyst precursor. This step refers to the pretreatment of the solid catalyst precursor before hydrogen reduction, including drying and washing. Pre-calcination is also an option. The temperature range for pre-calcination is 400-800°C, preferably 500-750°C; the fifth step is hydrogen reduction. The pretreated solid catalyst precursor is subjected to hydrogen reduction. The hydrogen reduction time is 1-15 hours, and the reduction temperature range is 150-500°C, preferably 200-400°C.

[0037] US Patent 4,440,873 provides examples of soluble copper-containing compounds that can be used to prepare copper-ammonia complex solutions, including copper nitrate, copper sulfate, copper oxalate, copper chloride, and copper acetate, with copper nitrate being the preferred option. Example 1 describes the preparation of a Cu / SiO2 catalyst by ammonia stripping as follows: (1) 19.0 g of copper nitrate (Cu(NO3)2·3H2O) is dissolved in 200 ml of water to obtain an aqueous solution containing copper ions. Then, 60 ml of concentrated ammonia solution is added to the solution, and the pH is adjusted to 11-12 to obtain a deep blue solution containing copper-ammonia complex; (2) 66.6 g of silica sol (30 wt.% SiO2) is added to the copper-ammonia complex solution and stirred at room temperature for several hours; (3) The reaction mixture from step (2) is subjected to ammonia stripping treatment by heating. Ammonia stripping continues until most of the water is evaporated, yielding a solid product; (4) The solid product is dried at 120°C for 12 hours. The dried material was thoroughly washed with water and then dried again. The drying conditions were 140℃×14h; (5) The dried material was subjected to hydrogen reduction treatment. The reduction conditions were 350℃×2-3h. The prepared Cu / SiO2 catalyst contained approximately 20wt.% copper.

[0038] In summary, the earliest proposed process for preparing Cu / SiO2 catalysts using the ammonia stripping method has the following characteristics: Firstly, the amorphous silica support is not pre-fabricated but generated in situ during the ammonia stripping process using silica sol as a precursor. Specifically, during ammonia stripping, the silica sol is converted into silica gel. Simultaneously, the copper-ammonia complex loses ammonia to form copper hydroxide precipitate, which is deposited on the silica gel surface. This process is dynamic. That is, the silica gel particles continuously grow after formation, while the copper hydroxide precipitate is also continuously formed. As the silica gel particles grow, the copper hydroxide precipitate is deposited and reacted on its surface, resulting in a layered loading state of silica gel and copper hydroxide. Later, researchers in this field pointed out (J. Catal. 257 (2008) 172–180) that this ammonia stripping method is essentially a homogeneous deposition-precipitation method, and the prepared Cu / SiO2 catalyst is a layered copper silicate. Secondly, a diluted copper-ammonia complex solution was prepared and used. The volume of this copper-ammonia complex solution is significantly excessive relative to the liquid holding capacity (pore volume) of the final silica gel. The aqueous solvent needs to be removed through post-treatment processes such as filtration or evaporation. The loading and dispersion mechanism of copper on the silica support is deposition and precipitation; that is, as the silica gel particles grow, copper hydroxide precipitates and reacts on their surface, achieving a uniform loading state through layer-by-layer mixing of silica gel and copper hydroxide. It is conceivable that if the silica support were not generated during ammonia stripping but prefabricated, using this diluted and excessively large (the solution volume is significantly excessive relative to the total pore volume of the silica support) copper-ammonia complex solution for ammonia stripping would inevitably lead to a large amount of copper hydroxide being deposited on the outer surface of the support particles, resulting in an uneven loading of copper—less copper inside the pores and more copper outside the pores.

[0039] Subsequently, some scholars have prepared copper-based catalysts supported on amorphous oxide supports using the earliest proposed ammonia stripping method for the gas-solid phase hydrogenation of dimethyl oxalate to ethylene glycol. For example, relevant research has been reported in published literature J. Catal. 257 (2008) 172–180 and Appl. Catal. A: Gen. 458 (2013) 82–89, involving amorphous oxide supports of silica and binary composites of silica and titanium dioxide. When silica was used as the support, silica sol (Ludox AS-40) was used as a precursor. When the binary composite of silica and titanium dioxide was used as the support, silica sol (JN30, Qingdao Haiyang Chem. Co., Ltd.) and titanium dioxide sol were used as precursors. After ammonia stripping (when the slurry pH dropped to 6-7), the amorphous oxide-supported copper hydroxide solid product was obtained by filtration.

[0040] Some researchers have improved upon the previously proposed ammonia stripping method when preparing Cu / SiO2 catalysts for the gas-solid phase hydrogenation reaction of dimethyl oxalate. Specifically, in the published papers J. Am. Chem. Soc. 2012, 134, 13922-13925 and J. Catal. 297 (2013) 142–150, researchers reported the ammonia evaporation hydrothermal (AEH) method. This method essentially involves transferring the ammonia stripping product (a slurry containing copper hydroxide / silica gel precipitate, pH = 6-7) from the traditional ammonia stripping method (the earliest proposed method) to a high-pressure synthesis reactor and hydrothermally treating it at 190–210 °C for 12 h. The solid product is then subjected to conventional filtration, washing, drying, calcination, and hydrogen reduction treatment. In other words, this method does not improve the ammonia stripping method itself, but rather adds a hydrothermal post-treatment step to the ammonia stripping product before the conventional post-treatment. It is important to emphasize that the procedures before hydrothermal post-treatment in the ammonia stripping hydrothermal method are no different from those in the traditional ammonia stripping method. The silica support is generated in situ using silica sol as a precursor. The diluted and excess aqueous solvent of the copper-ammonia complex solution is removed by filtration. In the published literature J.Phys.Chem.C 2015, 119, 13758-13766, researchers added urea as a precipitation aid when preparing the copper-ammonia complex solution. Other procedures are identical to those in the traditional ammonia stripping method. The silica support was generated in situ using silica sol (Ludox AS-40, 40wt.% SiO2) as a precursor. The diluted and excess copper ammonia complex solution was removed by filtration. In the published literature Natural Gas Chemical Industry (C1 Chemistry and Chemical Engineering), 2013, 38(3):43-47, Natural Gas Chemical Industry (C1 Chemistry and Chemical Engineering), 2014, 39(5):31-34, and Journal of Shenyang University of Chemical Technology, 2016, 30(3):212-216, the researchers used pre-made JN-25 type alkaline silica gel (original particle size 10nm, Qingdao Ocean Chemical Co., Ltd.) as the support for the Cu / SiO2 catalyst prepared by the ammonia stripping method. In order to achieve a uniform deposition effect, a certain amount of silica sol was also added as a precursor for in situ generation of silica gel support. To overcome the problem of reduced silica sol usage when using pre-prepared JN-25 alkaline silica gel as a support for Cu / SiO2 catalysts, researchers also tried adding hexadecyltrimethylammonium bromide (CTAB) surfactant to the prepared copper ammonia complex aqueous solution to disperse the silica sol and generate mesopores in the in-situ generated silica gel.Other procedures are identical to the traditional ammonia stripping method. In the published literature RSC Adv., 2015, 5, 29040–29047 and Applied Catalysis A: General 509 (2016) 66–74, researchers used pre-prepared titanium dioxide (P25, Degussa Co., Ltd.) as the support for their Cu / TiO2 catalyst prepared by the ammonia stripping method, and other procedures were identical to the traditional ammonia stripping method. It should be noted that the P25 type TiO2 support is a low specific surface area support with underdeveloped capillaries. Therefore, the prepared Cu / TiO2 catalyst does not have a uniform deposition effect. That is, the supported copper hydroxide is mainly present on the outer surface of the titanium dioxide support. X-ray diffraction analysis of the calcined sample showed obvious CuO phase diffraction characteristic peaks at 2θ = 35.5°, 38.7°, and 48.7°, indicating poor dispersion of its hydrogen reduction product—metallic copper.

[0041] Furthermore, it is worth mentioning that in the published literature Applied Catalysis A, General 539 (2017) 59–69, researchers used pre-fabricated ordered mesoporous silica (OMS) as the support for their Cu / OMS catalyst prepared by ammonia stripping. To reduce the destructive effect of the alkalinity of the copper-ammonia complex solution on the ordered mesopores of the pre-fabricated silica support, the researchers also appropriately reduced the ammonia concentration in the prepared copper-ammonia complex solution (which they considered an improvement to the ammonia stripping method). Apart from these two points, the improved ammonia stripping method described in this study is no different from the traditional method. After ammonia stripping (when the slurry pH drops to 6-7), the diluted and excess aqueous solvent of the copper-ammonia complex solution is finally removed by filtration, thus obtaining a solid product loaded with copper hydroxide. The results show that after loading copper onto the pre-prepared silica support using the ammonia stripping method, the ordered mesoporous structure of the support was largely destroyed, and a large amount of layered copper silicate was present in the catalyst. This indicates that the pre-prepared silica support was largely dissolved into silica sol during contact with the copper-ammonia complex solution, and the silica sol produced a uniform deposition and precipitation effect with copper hydroxide during the ammonia stripping process. In the published literature Journal of Catalysis 280 (2011) 77–88, researchers also used pre-prepared mesoporous silica (HMS) as the support for their Cu / HMS catalyst prepared by the ammonia stripping method. In addition, the researchers added a water-soluble nickel salt (nickel nitrate) to the prepared copper-ammonia complex aqueous solution, so that the prepared copper-based catalyst contained metallic nickel (CuxNi / HMS). The ammonia stripping method used in this study is identical to the traditional ammonia stripping method, except for the use of a pre-prepared mesoporous silica support and the addition of a water-soluble nickel salt (nickel nitrate) to the prepared copper-ammonia complex aqueous solution, which introduces nickel as a catalyst. The ammonia stripping operation is carried out at 90°C. After stripping (when the slurry pH drops to 7-8), the diluted and excess aqueous solvent of the copper-ammonia complex solution is removed by filtration, yielding a solid product loaded with copper hydroxide and nickel hydroxide. Similarly, in this study, the ordered mesoporous structure of the HMS silica was largely destroyed after loading copper and nickel using the ammonia stripping method (the specific surface area decreased by more than 50%). Furthermore, XRD characterization results showed that the prepared supported catalyst sample exhibited characteristic diffraction peaks of the metal oxide phase before hydrogen reduction (calcined at 450°C for 4 h) and characteristic diffraction peaks of the metallic phase after hydrogen reduction, indicating that the copper and nickel were unevenly loaded and poorly dispersed on the HMS support.

[0042] According to the literature review, apart from a recent published paper in Science (Science10.1126 / science.adj1962(2023).) reporting the preparation of a supported copper catalyst on a dealaluminized Beta zeolite support using the ammonia stripping method for the solid-phase hydrogenation reaction of dimethyl oxalate, no other research on the preparation of supported metal catalysts on zeolite supports using the ammonia stripping method has been found domestically or internationally to date. It should be noted that the recent research published in Science used the traditional ammonia stripping method to prepare a supported copper catalyst on a dealaluminized Beta zeolite support. The specific procedure is as follows: First, 0.23 g of Cu(NO3)2·3H2O was dissolved in 100 ml of ammonia solution (containing 0.75 g of NH3·H2O) and stirred at room temperature for 10 min to prepare a copper-ammonia complex aqueous solution; second, 1.94 g of dealaluminized Beta zeolite support (Beta-deAl) was added to the copper-ammonia complex solution, and ammonia stripping was performed under vigorous stirring. The ammonia stripping temperature was 80℃, and the stripping time was 6 hours. In the third step, after ammonia stripping, the diluted and excess aqueous solvent of the copper-ammonia complex solution was removed by filtration. In the fourth step, the obtained solid product was dried overnight at 100℃ and calcined at 400℃ for 3 hours to obtain the catalyst. In the fifth step, to catalyze the hydrogenation reaction of dimethyl oxalate using this catalyst, it was reduced with hydrogen at 400℃ for 3 hours. It is evident that in this study, except for the catalyst support being a pre-prepared dealullated Beta zeolite (obtained by acid dealullating a Si / Al = 13 Al-Beta zeolite parent material with 13 MH NO3 solution at 80℃ for 12 hours), the other procedures were identical to the traditional ammonia stripping method. In the prepared copper-ammonia complex solution, the copper ion concentration was very low (only about 9.5 mmol / L); when preparing the catalyst using the ammonia stripping method, the initial liquid-to-solid ratio was as high as about 51.5 (ml / g), meaning the volume of the copper-ammonia complex solution was significantly excess over the zeolite support. The results showed that although the prepared copper catalyst Cu / Beta-deAl supported on dealubilized Beta zeolite had a very low copper content (approximately 3 wt.% Cu), its specific surface area loss was as high as 15% (due to the excessive dissolution and desilication of the dealubilized Beta zeolite caused by the excess copper ammonia complex solution (NH3 / Cu molar ratio 22.5), which destroyed the framework structure). Furthermore, its XRD pattern still showed obvious characteristic diffraction peaks of metallic copper (2θ = 43.3°). Transmission electron microscopy revealed that the copper in the fresh catalyst was mainly supported on the outer surface of the dealubilized Beta zeolite, with a relatively large particle size (due to the excessive deposition of copper hydroxide outside the zeolite channels during ammonia stripping caused by the use of diluted and excess copper ammonia complex solution). It required redispersibility via a reverse Ostwald ripening process after methanol vapor post-treatment to transfer the copper into the zeolite channels.This study fully demonstrates that when preparing molecular sieve-supported copper catalysts using dealubilized Beta zeolite as a support via copper ammonia complex, the traditional ammonia stripping method reported in the literature for silica supports cannot be used. Otherwise, the following problems will occur: (1) Excess copper ammonia complex solution will deposit a large amount of copper outside the zeolite channels during the ammonia stripping process; (2) Dealubilized Beta zeolite will undergo a desilication reaction in excess copper ammonia complex solution (pH = 10-12) (ammonia stripping temperature 80℃), which will damage the crystal structure.

[0043] Therefore, this invention proposes an improved ammonia stripping method, different from known practices, to meet the need for loading metallic copper within the pores of zeolite supports, especially easily desiliconized high-silica zeolite supports such as dealuminolite (Beta zeolite).

[0044] Furthermore, a key feature of this invention is that the provided Cu-Beta zeolite catalyst is intended for the production of caprolactam from caprolactone under gas-solid phase reaction conditions. To date, neither published patents nor other literature has addressed this application of Cu-Beta zeolite catalysts. This reaction system is unique. This is primarily because the reaction for the production of caprolactam from caprolactone under gas-solid phase reaction conditions involves the simultaneous use of water vapor, hydrogen, and ammonia. This is a demanding application scenario for copper-based catalysts.

[0045] As mentioned earlier, the catalytic methods for producing caprolactam from caprolactone described in existing patents and academic papers mainly use two types of catalysts: one is an unsupported bulk copper chromite catalyst, and the other is a copper catalyst supported on a single oxide support (such as titanium dioxide, alumina, or silica) or a binary composite oxide support (such as silica and alumina) with the addition of a second metal component, nickel or chromium. In the supported copper catalyst (with the addition of a second metal component, nickel or chromium), both the single oxide and the binary composite oxide used as the support are amorphous.

[0046] The gas-solid phase reaction state is a suitable pathway for the hydroamination of caprolactone to caprolactam via catalysis. As mentioned earlier, the catalytic methods for preparing caprolactam from caprolactone disclosed by Kanekabuchi Co., Ltd. (BOSEKI KABUSHIKI KAISHA) in British Patent GB1109540 (1966) and US Patent 3652549 (1972), as well as by Teijin Co., Ltd. in US Patent US3888845 (1975), all employ a gas-solid phase reaction state.

[0047] As is well known, gas-solid phase reaction is a common form of heterogeneous catalysis, specifically referring to the catalytic reaction in which reactants in gaseous form contact with a solid catalyst. In the field of heterogeneous catalysis, gas-solid phase reaction is sometimes simply referred to as gas phase reaction. Gas-solid phase reaction is a reaction form with mild reaction conditions, high mass and heat transfer efficiency, and very simple operation. For gas-solid phase reaction, the process of reactants being converted into products on the catalyst consists of seven elementary steps: (1) external diffusion of reactants. In this step, reactants pass through the adsorption film on the surface of the solid catalyst and come into contact with the outer surface of the catalyst; (2) internal diffusion of reactants. In this step, reactants diffuse into the pores on the surface of the solid catalyst to approach the catalytic active center within the pores; (3) chemical adsorption of reactants on the catalytic active center. In this step, reactant molecules are activated and become activated molecules; (4) surface reaction. In this step, reactants are converted into adsorbed product forms on the active center of the catalyst; (5) product desorption. In this step, the adsorbed product is removed from the catalytic active center; (6) internal diffusion of products. This step is the process by which product molecules move from the pores to the outer surface of the catalyst after leaving the catalytic active center; (7) External diffusion of the product. In this step, product molecules leave the pores on the outer surface of the solid catalyst, pass through the adsorption film on the surface of the solid catalyst, detach from the solid catalyst particles, and become reaction products.

[0048] The Cu-Beta catalyst provided by this invention is suitable for the gas-solid phase hydroamination catalytic reaction conditions for the production of caprolactam from caprolactone, as described in existing related patents and academic papers. As mentioned earlier, in 1966, Kanekabuchi Co., Ltd. of Japan first disclosed a gas-solid phase catalytic method for preparing caprolactam in British Patent GB1109540. Specifically, caprolactone and a certain amount of water were first vaporized, then mixed with ammonia and hydrogen. The mixed gas underwent a catalytic reaction at 120-350°C and atmospheric pressure using a copper chromite catalyst. In 1972, Kanekabuchi Co., Ltd. of Japan again disclosed a method for preparing caprolactam in US Patent 3652549, which was also a gas-solid phase catalytic method. Specifically, this method used a fixed-bed reactor, with a reaction temperature range of 170-300°C and a hydrogen partial pressure of 0.1-1.5 atm. The feed also includes ammonia and water vapor, with preferred dosage ranges (molar ratios to feedstock) of 2-50 and 10-100, respectively. In 1975, Teijin Corporation of Japan disclosed a method for preparing caprolactam in US Patent 3888845, which is also a gas-solid phase catalytic method. Specifically, the gas-solid phase catalytic reaction can be carried out at 200-320°C and 0.01-2 atm, preferably at 220-310°C and 0.1-1.2 atm. The selectable dosage ranges for hydrogen and ammonia are 5-70 (H2 / ester molar ratio) and 1-50 (NH3 / ester molar ratio), respectively, with preferred ranges of 10-50 (H2 / ester molar ratio) and 2-25 (NH3 / ester molar ratio), respectively. Furthermore, this process emphasizes the importance of the hydrogen to ammonia molar ratio and the addition of water to the reactor feed. In general, using a suitable hydrogen to ammonia molar ratio is beneficial for improving the selectivity of the reaction. Adding water to the reactor feed can not only reduce side reactions and improve caprolactam selectivity, but also slow down the deactivation rate of the catalyst. The selectable range for the hydrogen to ammonia molar ratio is 0.2-30, with a preferred range of 0.5-15; the selectable range for the water / ester molar ratio is 0-50, with a preferred range of 5-30.

[0049] In summary, based on existing patents and academic papers, the gas-solid phase hydroamination catalytic reaction for the production of caprolactam from caprolactone requires water, ammonia, and hydrogen as feedstock in addition to caprolactone. The molecular formula of the caprolactone feedstock (C6H2O) is... 10 O2) and the molecular formula of caprolactam product (C6H) 11(NO) It is not difficult to see that ammonia and hydrogen are also reaction raw materials, and water vaporization into water vapor is a diluent gas. The selectable range of reaction temperature is 120-350℃, the selectable range of reaction pressure is 0.01-2 atm, and the selectable ranges of the molar ratios of ammonia-ester, hydrogen-ester, and water-ester are 1-50, 5-70, and 0-100, respectively; the preferred range of reaction temperature is 220-300℃, the preferred range of reaction pressure is 0.1-1.2 atm, and the preferred ranges of the molar ratios of ammonia-ester, hydrogen-ester, and water-ester are 2-25, 10-50, and 5-30, respectively. To facilitate a better understanding of the implementation effects of the present invention by those skilled in the art, the catalytic performance of the provided Cu-Beta zeolite catalyst in the gas-solid phase hydroamination reaction of caprolactone to caprolactam is evaluated in this invention, and the reaction conditions used are within the above ranges.

[0050] The technical solution of the present invention:

[0051] A method for preparing an anti-sintering Cu-Beta zeolite catalyst, comprising the following steps:

[0052] The first step is to prepare a multi-level porous dealuminolite Beta zeolite support.

[0053] As previously described, this invention employs a post-synthesis strategy to prepare a hierarchical porous dealaluminized Beta zeolite support. Specifically, the Beta zeolite matrix is ​​first desilication-treated with sodium hydroxide solution to obtain a mesoporous Beta zeolite matrix, and then the mesoporous Beta zeolite matrix is ​​subjected to acid dealaluminization treatment to obtain the hierarchical porous dealaluminized Beta zeolite support. Engineers skilled in the art can, based on the requirements of this invention, their own experience, and reference to practices reported in relevant literature, prepare the hierarchical porous dealaluminized Beta zeolite support from the Beta zeolite matrix. The requirements of this invention are as follows:

[0054] (1) Select Beta zeolite parent material

[0055] The aforementioned Beta zeolite matrix refers to Al-Beta zeolite. This invention does not limit the grain size of the Beta zeolite matrix, nor does it limit the production process of the Beta zeolite matrix. However, to facilitate the implementation of this invention, the following limitations are imposed on the Beta zeolite matrix: 1) The Beta zeolite matrix is ​​free of impurities; 2) The Beta zeolite matrix has good crystallinity; 3) The molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) in the Beta zeolite matrix is ​​suitable.

[0056] The presence of impurities in the Beta zeolite matrix can be confirmed by X-ray polycrystalline powder diffraction (XRD). Those skilled in the art know that the molar ratio of silicon to aluminum oxide (SiO2 to Al2O3) in Beta zeolite produced by hydrothermal synthesis is typically between 10 and 200 (US3 308 069 (1967)). Beta zeolite products with lower SiO2 to Al2O3 molar ratios generally may contain mordenite (MOR) impurities, while Beta zeolite with higher SiO2 to Al2O3 molar ratios generally may contain ZSM-5 zeolite impurities. By sampling and performing XRD analysis on the Beta zeolite matrix, and comparing the XRD patterns of the samples with standard diffraction cards for Beta zeolite, MOR zeolite, and ZSM-5 zeolite, it can be determined whether the sample's XRD pattern contains characteristic peaks of MOR zeolite and ZSM-5 zeolite impurities, thus determining whether the Beta zeolite matrix is ​​a pure Beta zeolite phase.

[0057] Theoretically, the crystallinity of the Beta zeolite matrix can also be analyzed using XRD, with the relative crystallinity index used as a measure. However, the XRD relative crystallinity index requires comparing the sum of the intensities of the medium-intensity characteristic diffraction peaks (2θ = 7.6-8°) and the highest-intensity characteristic diffraction peaks (2θ = 22-23°) of the Beta zeolite matrix with the sum of the intensities of the corresponding diffraction peaks of a reference sample (standard Beta zeolite with 100% crystallinity). Furthermore, there is no universally defined reference sample. Additionally, the intensities of the medium-intensity and highest-intensity characteristic diffraction peaks (2θ = 7.6-8° and 2θ = 22-23°) of Beta zeolite are significantly affected by post-processing conditions such as calcination. Therefore, using the XRD relative crystallinity index to determine the crystallinity of the purchased or synthesized Beta zeolite matrix has poor universality. Therefore, this invention recommends using the specific surface area index of the Beta zeolite matrix to measure whether the crystallinity of the purchased or synthesized Beta zeolite matrix meets the requirements. Based on our statistical results of the literature reports on the specific surface area of ​​Beta zeolite, the BET specific surface area of ​​well-crystallized Beta zeolite produced by hydrothermal synthesis is generally not less than 450 m². 2 / g. Engineers skilled in the art can use conventional nitrogen physical adsorption methods to first measure the nitrogen adsorption isotherm data of the Beta zeolite matrix, and then calculate its BET specific surface area value according to the BET model. In summary, this invention requires that the BET specific surface area value of the Beta zeolite matrix used be ≥450m². 2 / g indicates that its crystallization is good.

[0058] The molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) is a key indicator of the Beta zeolite matrix. This is because, on the one hand, the lower the molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) in the Beta zeolite matrix, i.e., the higher the skeletal aluminum content, the more hydroxyl lattice defect sites can be used to disperse and stabilize nano- and sub-nano-sized copper particles in the dealuminated Beta zeolite support. On the other hand, pure-phase Beta zeolite with a very low molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) is difficult to synthesize using hydrothermal methods. Moreover, after Beta zeolite matrix with a very low molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) is used to prepare a hierarchical porous dealuminated Beta zeolite support, the number of mesopores is small and the skeletal thermal stability is poor. This leads to a loss of crystallinity during the subsequent calcination process for preparing Cu-Beta zeolite catalysts, resulting in deteriorated catalyst performance. Therefore, the suitable range for the molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) in the Beta zeolite matrix required by this invention is between 15 and 100, preferably between 20 and 80, and more preferably between 25 and 60. The analysis of the molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) in the Beta zeolite matrix can be performed using conventional chemical analysis methods (tipping), or using X-ray fluorescence spectrometry (XRF) or inductively coupled plasma atomic emission spectrometry (ICP). This invention recommends using the simple and rapid XRF method.

[0059] The Beta zeolite matrix conforming to the requirements of this invention can be obtained commercially or synthesized in-house. Engineers skilled in the art can also synthesize the Beta zeolite matrix conforming to the requirements of this invention based on their own experience and other literature reports.If synthesizing the Beta zeolite matrix yourself, the following methods reported in patents and publications are available: US3308 069 (1967), EP187 522A2 (1986), US4 847 055 (1989), CN1 086 792A (application date 1993.9.20), CN1 108 213A (application date 1994.3.11), CN1 108 214A (application date 1994.3.11), CN1154 341A (application date 1996.1.11), CN1 154 242A (application date 1996.1.9), CN1 154 342A (application date 1996.1.11), CN1 268 545A (application date 1999.3.30), CN1 133 497C (application date 1999.3.30), CN1108 275C (application date 1999.9.10), CN1 100 004C (application date 2000.5.19), CN1 335 258A (application date 2001.2.28), CN1 116 227C (application date 2001.3.12), CN101 205 072B (application date 2006.12.18), Chem. Comm., 1996, 625; J. Mater. Chem., 1998, 8(9), 2137-2145; Microporous and Mesoporous Materials 21(1998) 305-313; Applied Catalysis A-GENERAL,166(1998),97–103;Microporous and Mesoporous Materials 48(2001)23-29;Microporous and Mesoporous Materials 56(2002)1–10.;Journal of Molecular Catalysis A:Chemical252(2006)76–84;Microporous and Mesoporous Materials 94(2006)1–8; J.Mater.Sci.41(2006)1861-1864; Cryst.Res.Technol.44,No.4,379-385(2009)DOI10.1002 / crat.200800474; Microporous and Mesoporous Materials 143(2011)97-103;RSC Adv. 2019, 9, 3653-3660.

[0060] (2) Preparation of multi-level porous Beta zeolite matrix

[0061] When preparing hierarchical porous Beta zeolite matrix by alkaline treatment with sodium hydroxide solution to remove silica, mild desilication conditions are preferred. Only Beta zeolite matrix with appropriate mesoporous porosity prepared by mild desilication can be further dealuminized to obtain a hierarchical porous dealuminized Beta zeolite support with well-preserved crystal structure, thus preparing a catalyst with the effects of this invention. Conversely, excessive desilication, while increasing the mesoporous porosity of the Beta zeolite matrix, results in an unstable structure and severe crystal damage after dealuminization, making it unsuitable for the applications of this invention. Research has found that the concentration of sodium hydroxide solution, the ratio of sodium hydroxide solution volume to Beta zeolite matrix feed (liquid-solid ratio), desilication temperature, and time are the main factors affecting the degree of desilication of the Beta zeolite matrix, and can be used as means to control the degree of desilication and mesoporous porosity when preparing hierarchical porous Beta zeolite matrix. The requirements for the value ranges of the above four parameters in this invention are as follows:

[0062] The suitable concentration range of sodium hydroxide aqueous solution is 0.01-0.5M, the preferred range is 0.05-0.4M, and the more preferred range is 0.1-0.3M;

[0063] The suitable range of the ratio (liquid-solid ratio) of the volume (ml) of sodium hydroxide aqueous solution to the amount (g) of Beta zeolite parent material is 2:1-30:1 (ml / g), the preferred range is 3:1-20:1 (ml / g), and the more preferred range is 5:1-15:1 (ml / g).

[0064] The suitable temperature range for the desilication reaction is 15℃-60℃, the preferred range is 20℃-55℃, and the more preferred range is 25℃-45℃.

[0065] The suitable range for the desilication reaction time is 10-180 min, the preferred range is 15-120 min, and the more preferred range is 20-60 min.

[0066] Engineers skilled in the art can, based on their work experience or by referring to the practices reported in relevant literature (e.g., Appl. Catal. A 325 (2007) 121; Microporous and Mesoporous Materials 114 (2008) 93–102; J. Mater. Chem. A, 2016, 4, 1373), complete the preparation of the hierarchical porous Beta zeolite matrix in accordance with the requirements of this invention. As an example, the preparation of a hierarchical porous Beta zeolite matrix by alkaline treatment and desilication of the Beta zeolite matrix with sodium hydroxide solution can be carried out according to the following basic steps: First, the Beta zeolite matrix is ​​pretreated by drying and calcination. Drying can be performed at temperatures ranging from 80-200°C for 3-24 hours to fully remove adsorbed moisture and volatile organic compounds. Calcination can be performed at temperatures ranging from 500°C-600°C for 3-8 hours to remove any residual organic template agents and other organic matter that may remain within the pores of the Beta zeolite. Secondly, the pretreated Beta zeolite matrix is ​​subjected to desilication treatment. Specifically, this involves preparing a sodium hydroxide solution of a certain concentration and heating it to the desilication reaction temperature. Then, the pretreated Beta zeolite matrix is ​​added to the sodium hydroxide solution at a specific liquid-to-solid ratio, and the reaction is carried out under stirring and timed conditions. Finally, after the reaction is complete, the reactants are immediately cooled, and the solid product is recovered through conventional solid-liquid separation. The solid product is then washed with water until the pH is neutral, dried at 80-200℃ for 3-24 hours, and calcined at 500℃-600℃ for 1-6 hours to obtain a hierarchical porous Beta zeolite matrix.

[0067] It is important to emphasize that when using sodium hydroxide solution to desilicate Beta zeolite matrix through alkaline treatment to prepare mesoporous Beta zeolite matrix, for Beta zeolite matrix with a higher molar ratio of silicon to aluminum oxide (SiO2 to Al2O3), relatively weaker desilication conditions should be selected within the range provided in this invention. For Beta zeolite matrix with a lower molar ratio of silicon to aluminum oxide (SiO2 to Al2O3), relatively stronger desilication conditions can be selected within the range provided in this invention. It is easy to understand that the desilication conditions formed by the upper limits of the four parameters—sodium hydroxide aqueous solution concentration, liquid-to-solid ratio, desilication reaction temperature, and desilication reaction time—represent the strongest desilication conditions within the range specified in this invention. The desilication conditions formed by the lower limits of the above four parameters represent the weakest desilication conditions within the range specified in this invention. Desilication conditions formed by other different combinations of the above four parameters within the specified range will produce different desilication intensities between the strongest and weakest. It goes without saying that the above explanation of the present invention is intended to provide principled guidance for engineers in the art. For different Beta zeolite matrices, the desilication conditions that achieve adequate desilication and produce adequate mesoporous porosity are best determined experimentally.

[0068] It should also be noted that solutions of other inorganic or organic bases are also applicable in terms of desilication capacity. Alkali metal hydroxides and carbonates are common inorganic bases used for desilication of zeolites. Quaternary ammonium bases (such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, etc.) are common organic bases used for desilication of zeolites. In fact, the applicable inorganic and organic bases are not limited to these few; the inorganic and organic bases disclosed in relevant invention patents and other published documents are all applicable to the purpose of preparing hierarchical porous Beta zeolite matrix as described in this invention. However, alkali metal hydroxides and carbonates, especially sodium hydroxide, are relatively inexpensive strong inorganic bases. The main reason for recommending the use of aqueous sodium hydroxide solution in this invention is cost considerations.

[0069] (3) Preparation of multi-level porous dealuminolite Beta zeolite support

[0070] As mentioned earlier, a conventional acid dealusion method can be used to prepare a hierarchical porous dealusion Beta zeolite support based on a hierarchical porous Beta zeolite matrix. This invention requires that the resulting hierarchical porous dealusion Beta zeolite support have a silicon-aluminum oxide molar ratio (the molar ratio of SiO2 to Al2O3) as high as possible, i.e., the skeletal aluminum of the hierarchical porous Beta zeolite matrix should be completely removed. For a hierarchical porous dealusion Beta zeolite support meeting the requirements of this invention, the suitable range for the silicon-aluminum oxide molar ratio (the molar ratio of SiO2 to Al2O3) is ≥700, preferably ≥800, and more preferably ≥900. Because the hierarchical porous dealusion Beta zeolite has a very high silicon-aluminum oxide molar ratio and a very low aluminum content, accurate determination of its silicon-aluminum oxide molar ratio (the molar ratio of SiO2 to Al2O3) requires inductively coupled plasma atomic emission spectrometry (ICP) or atomic absorption spectrometry (AA). This invention recommends using the ICP method.

[0071] When performing acid dealumination on hierarchical porous Beta zeolite, every effort should be made to remove all skeletal aluminum. Excessive skeletal aluminum residue on the hierarchical porous dealumination Beta zeolite support is detrimental because the strong acidity of the skeletal aluminum will accelerate coking and deactivation of the Cu-Beta zeolite catalyst and reduce the catalyst's selectivity for the caprolactam main product.

[0072] Although the framework aluminum of Beta zeolite is easy to remove, so that high-temperature steam dealuminization, dealuminization with complexing agents such as EDTA, dealuminization with organic acid solutions, dealuminization with inorganic acid (concentrated hydrochloric acid, concentrated nitric acid) solutions, or dealuminization methods formed by any combination of the above methods can all be used to prepare multi-level porous dealuminated Beta zeolite carriers that meet the requirements of this invention based on the multi-level porous Beta zeolite matrix, considering the production cost, process complexity, and difficulty in treating the waste liquid generated during dealumination of multi-level porous dealuminated Beta zeolite carriers, this invention recommends using concentrated nitric acid aqueous solution dealuminization to prepare multi-level porous dealuminated Beta zeolite carriers that meet the requirements of this invention.

[0073] Engineers skilled in the art can, based on their experience or by referring to the specific practices disclosed in the following documents, perform acid dealumination treatment on the hierarchical porous Beta zeolite matrix with concentrated nitric acid aqueous solution to prepare a hierarchical porous dealuded Beta zeolite support that meets the requirements of this invention: Chemical Communications, 1998, 1: 87-88; Micropor. Mesopor. Mater., 1999, 31: 163-173; Micropor. Mesopor. Mater., 2001, 49: 103–109; Micropor. Mesopor. Mater., 2008, 110: 480–487; Micropor. Mesopor. Mater., 2012, 163: 122-130; ACS Catalysis, 2014, 4(8): 2801-2810.

[0074] When preparing hierarchical dealuminated Beta zeolite carriers by acid dealuminization of hierarchical porous Beta zeolite matrix using concentrated nitric acid aqueous solution, the concentration of the nitric acid aqueous solution, the ratio of acid to zeolite (liquid-solid ratio), and the temperature and time of acid treatment are all important factors affecting the degree of acid dealuminization of the hierarchical porous Beta zeolite matrix. Ultimately, the influence of these factors on the dealuminization of the hierarchical porous Beta zeolite matrix is ​​reflected in the residual aluminum content of the hierarchical porous dealuminated Beta zeolite carrier. However, if the required molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) cannot be obtained after one dealuminization step, the required molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) in the hierarchical porous dealuminated Beta zeolite can be achieved through secondary or even multiple dealuminization steps. This invention recommends using 13M concentrated nitric acid as the dealuminizing acid solution, with an acid volume of 20:1 (ml / g). Under these conditions, the dealumination reaction was carried out at 95℃ for 20 hours. After the dealumination reaction, the solid product was first recovered through solid-liquid separation, then washed with water until the pH was neutral, dried at 80-200℃ for 3-24 hours, and calcined at 500-600℃ for 3-8 hours to obtain the hierarchical porous dealumination Beta zeolite support. After dealumination, the hierarchical porous Beta zeolite parent material has a stronger water absorption and moisture absorption capacity due to the formation of a large number of hydroxyl lattice defect sites; therefore, it should be sealed and stored for later use.

[0075] The second step involves using an aqueous solution of ethanolamine to perform pore-forming modification on the hydroxyl groups of the hierarchical porous dealuminolized Beta zeolite support.

[0076] The hydroxyl group hole-knocking modification is carried out using a conventional aqueous solution impregnation method. Hole-knocking modification is essentially an alkaline-catalyzed hydrolysis reaction modification ([(OSi)3-O-SiOH]+3H2O=Si(OH)4+3≡Si-OH). For each silicon atom released (existing in the form of orthosilicic acid (Si(OH)4)), that is, for each silicon atom (existing in the form of Si(OH)4) "knocking" off from the sidewall of the hydroxyl group hole, three silanol groups (≡SiOH) will be generated on the new sidewall of the hydroxyl group hole.

[0077] When using ethanolamine solution to impregnate a hierarchical porous dealaluminized Beta zeolite support for fovealing modification, the concentration of the ethanolamine aqueous solution, the ratio of the ethanolamine solution to the hierarchical porous dealaluminized Beta zeolite support (liquid-solid ratio, ml / g), and the impregnation temperature and time are the main factors affecting the fovealing modification of the hydroxyl groups in the hierarchical porous dealaluminized Beta zeolite. The present invention provides the following ranges for these four parameters:

[0078] The suitable concentration range of the ethanolamine solution is 0.01M-0.4M, the preferred range is 0.02M-0.3M, and the more preferred range is 0.03M-0.16M.

[0079] The suitable range for the ratio of ethanolamine solution to hierarchical porous dealuminolized Beta zeolite support, i.e., the liquid-solid ratio (ml / g), is 1:1-100:1, with a preferred range of 2:1-50:1; and an even more preferred range of 3:1-20:1.

[0080] The suitable impregnation temperature range is 20℃-100℃; the preferred range is 30℃-90℃; and the more preferred range is 40℃-80℃.

[0081] The suitable soaking time is 0.5h-24h; the preferred range is 1h-10h; and the more preferred range is 2-5h.

[0082] Engineers skilled in the art can refer to the impregnation process commonly used in the preparation of heterogeneous catalysts, impregnating the hierarchical porous dealaluminized Beta zeolite support with an ethanolamine solution to achieve the purpose of pore modification of the hydroxyl groups on the hierarchical porous dealaluminized Beta zeolite support. Details will not be elaborated further. Similarly, after pore modification, the liquid-solid mixture should be post-processed according to common sense, mainly including conventional liquid-solid separation, water washing (to neutral pH), drying, and calcination. The drying and calcination conditions can refer to the drying and calcination conditions for the hierarchical porous dealaluminized Beta zeolite support in the first step (preparation of the hierarchical porous dealaluminized Beta zeolite support) of this embodiment of the invention. Further details will not be elaborated further.

[0083] However, it is important to note that for hierarchical dealaluminized Beta zeolite supports prepared from Beta zeolite matrices with varying molar ratios of SiO2 and Al2O3 (SiO2 to Al2O3) and different numbers of hydroxyl holes, the key to achieving controllable hole-removing modification of the hydroxyl holes using an aqueous ethanolamine solution lies in correctly selecting modification conditions composed of four parameters: ethanolamine solution concentration, liquid-to-solid ratio (ml / g), impregnation temperature, and time. It is easy to understand that modification conditions composed of the lower limits of these four parameters have the weakest desilication effect and are suitable for hole-removing modification of hierarchical dealaluminized Beta zeolite supports with a small number of hydroxyl holes; modification conditions composed of the upper limits of these four parameters have the strongest desilication effect and can be used for hole-removing modification of hierarchical dealaluminized Beta zeolite supports with a large number of hydroxyl holes; and modification conditions composed of other different values ​​of these four parameters within a specified range will produce different desilication effects between the weakest and strongest. Similarly, the above explanation of the present invention is intended to provide principled guidance for engineers in the art. For different hierarchical porous dealuminized Beta zeolite supports, the ethanolamine solution impregnation conditions for achieving a suitable degree of denting modification are best determined experimentally.

[0084] The third step involves loading copper into the pores of a hierarchical, dealuminolized Beta zeolite support using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst.

[0085] As mentioned above, the core of the improved ammonia stripping method of this invention is to impregnate a zeolite carrier with an equal volume of copper-ammonia complex solution. During this process, the capillary coagulation effect of the zeolite channels draws most of the complex solution into the channels, thereby achieving the deposition of copper hydroxide and loaded metallic copper within the channels. The specific steps are as follows:

[0086] (1) Preparation of dilute ammonia water base solution and saturated copper ammonia complex solution: Prepare a dilute ammonia water base solution with pH value of 11-12 by diluting 4.4g of industrial ammonia water (containing 25-28wt.% NH3) to 100ml of deionized water, and seal and store for later use; then prepare ... store for later use; and then prepare a dilute ammonia water base solution with pH value of 11- 2+ A copper-ammonia complex was synthesized by reacting copper nitrate trihydrate (Cu(NO3)2·3H2O) as a soluble copper compound with industrial ammonia water in a molar ratio of 1:4 to ammonia molecules. Finally, the copper-ammonia complex was dissolved in a dilute ammonia solution at room temperature to prepare a saturated solution, which was then stored in a sealed container for later use. The concentration of copper-ammonia complex ions in the saturated solution was approximately 0.4 mol / L (0.4 M), and the solution was deep blue and clear.

[0087] It should be noted that although US Patent 4,440,873 (1984) has described soluble copper-containing compounds that can be used to prepare copper ammonia complex solutions, including copper nitrate, copper sulfate, copper oxalate, copper chloride, and copper acetate, considering that sulfate and chloride ions will increase the burden of subsequent water washing, and that oxalate and acetate ions have corrosive problems, this invention recommends the use of copper nitrate (Cu(NO3)2·3H2O).

[0088] (2) Impounding the zeolite support with an equal volume of copper-ammonia complex solution: First, determine the saturated water absorption rate of the zeolite support, and calculate the amount of copper-ammonia complex solution needed for equal volume impregnation. Then, calculate the required concentration of the copper-ammonia complex solution according to the copper loading of the Cu-Beta zeolite catalyst to be prepared. When the calculated concentration is equal to 0.4 M, directly impregnate the zeolite support with the saturated copper-ammonia complex solution in equal volume; when the calculated concentration is lower than 0.4 M, appropriately dilute the saturated copper-ammonia complex solution with a dilute ammonia base solution before impregnating the zeolite support in equal volume; when the calculated value is higher than 0.4 M, the concentration of the copper-ammonia complex solution for each equal volume impregnation should be recalculated according to multiple equal volume impregnations, and the required concentration of the copper-ammonia complex solution should be prepared using a dilute ammonia base solution and the saturated copper-ammonia complex solution for each equal volume impregnation. After each impregnation, the zeolite support must be subjected to ammonia stripping treatment.

[0089] The equal-volume impregnation is carried out at room temperature in a closed container. During this process, the zeolite support draws the copper-ammonia complex solution into the zeolite channels through capillary coagulation, thereby allowing the copper-ammonia complex ions to contact and interact with the hydroxyl lattice defect sites in the channels. The suitable range for the equal-volume impregnation time is 0.5-24 h, the preferred range is 1-12 h, and the more preferred range is 2-6 h.

[0090] (3) Ammonia stripping: The ammonia stripping process can be carried out under normal pressure or reduced pressure. The suitable range for ammonia stripping temperature and time is 50-100℃ and 0.5-48h, the preferred range is 60-90℃ and 1-24h, and the even more preferred range is 65-85℃ and 3-12h. During the ammonia stripping process, the copper-ammonia complex decomposes to generate ammonia gas and copper hydroxide. The former is absorbed by water, and the latter is deposited in the zeolite channels and hydroxyl lattice defect sites.

[0091] (4) Dehydration and drying treatment after ammonia stripping: The suitable range of drying temperature and time is 100-200℃ and 0.5-48h, respectively; the preferred range of drying temperature and time is 110-170℃ and 1-24h, respectively; and the more preferred range of drying temperature and time is 120-150℃ and 3-12h, respectively.

[0092] (5) Calcination treatment after ammonia stripping: This step is used to convert the copper hydroxide precipitate deposited in the zeolite channels and hydroxyl lattice defect sites into nano and sub-nanometer copper oxide particles, thereby obtaining the catalyst precursor. Calcination is carried out in an air atmosphere, with suitable calcination temperature and time ranges of 350-650℃ and 0.5-24h, preferred calcination temperature and time ranges of 400-600℃ and 1-12h, and more preferred calcination temperature and time ranges of 450-550℃ and 2-6h.

[0093] (6) Hydrogen reduction treatment of catalyst precursor: Cu-Beta zeolite finished catalyst was obtained. The suitable ranges for reduction temperature, time, and hydrogen flow rate (expressed as hydrogen volume hourly space velocity, defined as the volume of hydrogen passing through a unit volume of catalyst per unit time, in ideal gas terms) are 280-600℃, 0.5-20h, and 1-2000h, respectively. -1 The preferred ranges are 300-550℃, 1-15h, and 10-1500h, respectively. -1 More preferably, the ranges are 350-500℃, 2-8h, and 20-1000h, respectively. -1 .

[0094] The Cu-Beta zeolite prepared by the above method was used as a catalyst for the gas-solid phase hydroammoniation of caprolactone to caprolactam.

[0095] As mentioned above, a key feature of this invention is that the provided Cu-Beta zeolite catalyst is used for catalyzing the gas-solid phase hydroammoniation reaction of caprolactone to produce caprolactam.

[0096] However, this invention does not limit the specific method for the gas-solid phase hydroamination of caprolactone to produce caprolactam. Engineers skilled in the art can refer to the methods disclosed in relevant patents and other literature to carry out the gas-solid phase hydroamination of caprolactone. Based on relevant patents and other literature, this invention summarizes the following suitable reaction conditions for the gas-solid phase hydroamination of caprolactone for reference: the suitable reaction temperature range is 120-350℃, the suitable reaction pressure range is 0.01-2 atm, and the suitable feed space velocity (WHSV) of caprolactone is 0.1-5 h⁻¹. -1 The suitable ranges for the molar ratios of amine-ester, hydrogen-ester, and water-ester are 1-50, 5-70, and 0-100, respectively; the preferred range for the reaction temperature is 220-300℃; the preferred range for the reaction pressure is 0.1-1.2 atm; and the preferred range for the feed space velocity (WHSV) of caprolactone is 0.2-2 h⁻¹. -1 The preferred ranges for the molar ratios of amine-ester, hydrogen-ester, and water-ester are 2-25, 10-50, and 5-30, respectively.

[0097] To facilitate the explanation of the catalyst and its preparation method of this invention and to avoid unnecessary complexity, a typical procedure for the gas-solid phase hydroamination of caprolactone to produce caprolactam on a Cu-Beta zeolite catalyst is described below, using a small-scale fixed-bed reactor in the laboratory as an example: The small-scale fixed-bed reactor adopts a top-feed, bottom-discharge operation mode, with the Cu-Beta zeolite catalyst loaded in the isothermal zone of the reactor. The upper and lower spaces of the catalyst bed are filled with inert ceramic balls. The upper ceramic ball region of the reactor serves as the vaporization and preheating zone for the raw materials. For convenience, caprolactone, water, and ammonia can be mixed and fed using a micro-metering pump, while the hydrogen feed is controlled by a mass flow meter. The reaction is carried out under fixed conditions: reaction temperature 260℃, reaction pressure 1 atm, and caprolactone feed space velocity (WHSV) 0.6 h⁻¹. -1 The molar ratios of amine-ester, hydrogen-ester, and water-ester are 6, 50, and 30, respectively.

[0098] The beneficial effects of this invention are:

[0099] First, this invention prepares a Cu-Beta zeolite catalyst on a hierarchical porous dealufted Beta zeolite support modified with a modified ammonia stripping method. This allows the copper-ammonia complex to primarily deposit copper hydroxide within the zeolite channels during the ammonia stripping process. The copper hydroxide deposited in the zeolite channels, after calcination and hydrogen reduction, directly forms highly dispersed nano- and sub-nano-sized copper particles at the hydroxyl nest lattice defect sites within the channels. These particles acquire anti-sintering ability through interaction with the hydroxyl nests. Second, this invention utilizes the dispersing and stabilizing effect of the dealufted Beta zeolite hydroxyl nests on the supported copper particles. Simultaneously, it employs a weak organic base-controlled desilication technique to enlarge the hydroxyl nests generated during dealufting, increasing the contact area between the hydroxyl nests and copper particles, further enhancing the stabilizing effect of the dealufted Beta zeolite hydroxyl nests on the supported copper particles. Furthermore, the Cu-Beta zeolite catalyst and its preparation method provided by this invention increase the flexibility (structural variability) of the zeolite support by introducing a hierarchical porous structure, thereby adding the ability of the hydroxyl nests on the zeolite support to further stabilize copper particles through expansion and deformation. These measures enable the use of Cu-Beta zeolite catalysts without the addition of anti-sintering aids such as chromium and nickel. Secondly, the core of the improved ammonia stripping method used in this invention is the equal-volume impregnation of a dealubilized Beta zeolite support with a copper-ammonia complex solution. Because the amount of copper-ammonia complex solution used is small, it helps to suppress the silica-dissolving effect of the alkaline copper-ammonia complex solution (pH = 10-12) on the dealubilized Beta zeolite framework, thereby facilitating the dispersion and stabilization of highly dispersed nano and sub-nano copper particles by the hydroxyl groups of the dealubilized Beta zeolite. This is beneficial for preparing highly active, highly selective, and highly stable Cu-Beta zeolite catalysts. Finally, this invention applies the Cu-Beta zeolite catalyst to the gas-solid phase hydroammoniation of caprolactone, which will significantly reduce the industrialization difficulty of the technology route for producing caprolactam from caprolactone. Attached Figure Description

[0100] Figure 1 The images show the infrared spectra of the hydroxyl region of a Beta zeolite matrix with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3) of 24. First, a sodium hydroxide solution is used to desilicate the matrix, generating a hierarchical porous Beta zeolite matrix. Then, an acid-dealuminized matrix is ​​used to convert it into a hierarchical porous dealuminized Beta zeolite support (Beta24c). The images also show the infrared spectra of the hydroxyl region of a dented modified hierarchical porous dealuminized Beta zeolite support (Beta24C) obtained by controlled desilication of Beta24c using an aqueous solution of a weak organic base, ethanolamine.

[0101] Figure 2The images show the XRD patterns of the dented modified hierarchical porous dealaluminized Beta zeolite support (Beta24C) and the XRD patterns of the Cu-Beta zeolite catalyst (Cu3-Beta24C-1) with a copper loading of 3.0 wt.% prepared by the modified ammonia stripping method using Beta24C as the support.

[0102] Figure 3 The images show the infrared spectrum of the hydroxyl region of Beta24C, a hierarchical porous dealaluminized Beta zeolite support modified by dimpling, and the infrared spectrum of the hydroxyl region of Cu-Beta zeolite catalyst (Cu3-Beta24C-1) with a copper loading of 3.0 wt.% prepared by a modified ammonia stripping method using Beta24C as the support.

[0103] Figure 4 This is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the Cu3-Beta24C-1 catalyst.

[0104] Figure 5 This is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of a Cu3-Beta24C-1 catalyst sample calcined at high temperature (550℃×3h).

[0105] Figure 6 The images show the XRD patterns of Beta24C, a multi-level porous dealaluminized Beta zeolite support modified by burr hole drilling, and the XRD patterns of Cu-Beta zeolite catalysts (Cu3-Beta24C-CE1) with a copper content of 3 wt.% prepared by the traditional ammonia stripping method using Beta24C as the support. Detailed Implementation

[0106] The effectiveness of this invention can be evaluated by characterizing the physicochemical properties of the prepared Cu-Beta zeolite catalyst and by testing its catalytic performance in the gas-solid phase hydroammoniation of caprolactone to caprolactam.

[0107] In characterizing the physicochemical properties of Cu-Beta zeolite catalysts, the focus can be on characterizing the crystal structure damage, the occupancy of hydroxyl groups, the high dispersion of the supported metallic copper, and the resistance of copper particles to sintering.

[0108] The damage to the Beta zeolite crystal structure can be characterized using X-ray polycrystalline powder diffraction (XRD). If ammonia stripping treatment leads to significant damage to the Beta zeolite crystal structure, the intensity of the characteristic diffraction peak at 2θ = 22-23° in the catalyst's XRD pattern will be significantly reduced. Using a pitted, modified hierarchical porous dealuminized Beta zeolite support as a reference, the degree of relative crystallinity reduction in the Cu-Beta zeolite catalyst can also be estimated.

[0109] The occupancy of hydroxyl sites in Cu-Beta zeolite catalysts can be determined by obtaining the hydroxyl vibration infrared spectrum of the catalyst using Fourier transform infrared spectroscopy (FT-IR) and comparing it with the hydroxyl vibration infrared spectrum of a pitted, hierarchical porous dealuminolite Beta zeolite support. A higher concentration of nano- and sub-nanometer copper particles within the hydroxyl sites results in a more pronounced characteristic infrared band of the hydroxyl sites in the 3300-3600 cm⁻¹ region. -1 The stronger the broadened absorption band between the two, the weaker the absorption band will be, and vice versa.

[0110] Furthermore, the high dispersion of supported metallic copper in the Cu-Beta zeolite catalyst can be observed using transmission electron microscopy (TEM); the anti-sintering properties of the copper particles can be determined by combining calcination treatment with TEM observation. The catalytic activity (caprolactam yield) of the catalyst in the gas-solid phase hydroammoniation of caprolactone to caprolactam can also be assessed by observing the decline in its catalytic activity (caprolactam yield).

[0111] The catalytic performance of Cu-Beta zeolite catalyst in the gas-solid phase hydroammoniation of caprolactone to caprolactam can be evaluated using a small-scale fixed-bed laboratory reactor. The operating method and reaction conditions are as described above. The composition of the reaction products was analyzed by gas chromatography (GC) using an FID detector and an OV-1701 column. The conversion rate of caprolactone and the selectivity of caprolactam were calculated using the internal standard method (1,4-dioxane as the internal standard). The product of the caprolactone conversion rate and the caprolactam selectivity was used as the yield data for caprolactam and served as the evaluation index of catalyst activity.

[0112] The present invention will be further illustrated by the following embodiments, but the present invention is not limited to these embodiments.

[0113] Example 1: This example illustrates how, according to the present invention, a Cu-Beta zeolite catalyst is prepared by loading copper into the pores of a hollowed-out hierarchical dealubilized Beta zeolite as a support using an improved ammonia stripping method. This method not only better preserves the crystal structure of the dealubilized Beta zeolite support, allowing the loaded metallic copper to primarily exist as highly dispersed nano- and sub-nano-sized copper particles located at the hydroxyl-containing lattice defect sites within the zeolite pores, but also results in a tighter bond between the active silanol groups in the hydroxyl-containing pores and the highly dispersed nano- and sub-nano-sized copper particles, thus significantly improving the catalyst's resistance to sintering. The prepared Cu-Beta zeolite catalyst is suitable as a catalyst for the gas-solid phase hydroammoniation of caprolactone to caprolactam.

[0114] First, a Cu-Beta zeolite catalyst was prepared according to the embodiment provided in this invention:

[0115] The first step is to prepare a multi-level porous dealuminolite Beta zeolite support.

[0116] (1) Following the hydrothermal crystallization method provided in US Patent 3,308,069 (1967), a Beta zeolite matrix with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio) of 25 was synthesized as a raw material for preparing a hierarchical porous dealuminized Beta zeolite support. After conventional filtration, washing, drying (110℃, 12h), and calcination to remove the template agent (540℃, 6h), the synthesized Beta zeolite matrix was observed by TEM to have a grain size of less than 100 nm, classifying it as nano-Beta zeolite. XRD analysis revealed no impurities. Calculations based on its nitrogen physical adsorption data showed a BET specific surface area of ​​approximately 550 m². 2 The molar ratio of silicon-aluminum oxide (SiO2 to Al2O3) was approximately 24, as determined by XRF, which meets the technical requirements of this invention for the Beta zeolite matrix. It was sealed and stored for later use.

[0117] (2) Alkali treatment of Beta zeolite matrix with sodium hydroxide solution to remove silica, and preparation of hierarchical porous Beta zeolite matrix.

[0118] First, a 0.1M sodium hydroxide solution was prepared. Then, 40g of the dried and calcined Beta zeolite matrix, prepared as described above, was added to 400ml of 0.1M sodium hydroxide solution under stirring at a liquid-to-solid ratio of 10:1 (ml / g) for alkali treatment and desilication. The desilication temperature was 35℃, and the desilication time was 30min. During the desilication reaction, the three-necked flask was kept in a reflux condensation state. After the desilication reaction was completed, the solution was immediately cooled to room temperature, and the solid product was recovered by filtration. Then, it was treated with conventional water washing, drying (110℃×12h), and calcination (550℃×3h) to obtain a hierarchical porous Beta zeolite matrix. The weight loss due to desilication was 7.27%, and the total specific surface area of ​​the hierarchical porous Beta zeolite matrix was 650m². 2 / g, with a microporous specific surface area of ​​approximately 491m³. 2 / g.

[0119] (3) The multi-level porous Beta zeolite matrix was treated with concentrated nitric acid to remove aluminum, and a multi-level porous dealuminized Beta zeolite carrier was prepared.

[0120] First, a 13M concentrated nitric acid solution was prepared. Then, 30g of the hierarchical porous Beta zeolite matrix, which had undergone the above-mentioned drying and calcination treatment, was added to a three-necked flask containing 600ml of 13M concentrated nitric acid solution under stirring, at a liquid-to-solid ratio of 20:1 (ml / g). The dealuminization process was carried out at 95℃ for 20h. During the dealuminization reaction, the three-necked flask was kept under reflux. After the dealuminization reaction was completed, the solution was cooled to room temperature and filtered to recover the solid product. Then, the product was washed with water, dried (overnight at 110℃), and calcined (550℃, 3h) to obtain a hierarchical porous dealuminized Beta zeolite support. The molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) of the dealuminized Beta zeolite support was determined to be 960 (>900) by ICP. Suitable support for the catalyst of this invention (designated Beta24c, where lowercase "c" indicates the hydroxyl pockets generated in the Beta zeolite during dealumination). Store in a sealed container to prevent moisture absorption.

[0121] The second step involves using an aqueous solution of ethanolamine to perform a pitting modification treatment on the hydroxyl holes of the hierarchical porous dealuminolized Beta zeolite support.

[0122] The described foveation modification employs an atmospheric pressure impregnation method. First, a 44 mmol / L (44 mM) aqueous solution of ethanolamine is prepared as the foveation modification solution. Then, 20 g of a hierarchical porous dealaluminized Beta zeolite support is added to 120 ml of the ethanolamine modification solution at a liquid-to-solid ratio of 6:1 (ml / g). The reactants are heated to 40°C with stirring and reacted at this temperature with continuous stirring for 2 hours. During this period, the hydroxyl groups on the Beta zeolite support undergo a weak alkaline-catalyzed hydrolysis desilication reaction in the weakly alkaline ethanolamine solution ([(OSi)3-O-SiOH]+3H2O=Si(OH)4+3≡Si-OH). For each silicon atom released (existing as orthosilicic acid (Si(OH)4)), three silanol groups (≡Si-OH) are generated on the new sidewall of the hydroxyl group. After reacting for 1 hour, the reactants were filtered to recover the solid product. The solid product was then repeatedly washed with deionized water until neutral, followed by drying (overnight at 110℃) and calcination (550℃, 3 hours) to obtain a dimpled modified hierarchical porous dealubilized Beta zeolite support. It was sealed and stored for later use. Based on weight reduction estimation, the average number of framework silicon atoms (calculated as SiO2) removed from the hydroxyl lattice defect sites of the dealubilized Beta zeolite support was 1.0 silicon atom, indicating that the dimpled modification was carried out under controlled conditions with moderate desilication, meeting the requirements for dimpled modification of the dealubilized Beta zeolite support. The dimpled modified support is designated Beta24C (the uppercase "C" indicates that the dimpled modification increased the hydroxyl lattice volume in the dealubilized Beta zeolite). The hydroxyl vibration infrared spectra of the hierarchical porous dealubilized Beta zeolite support (Beta24c) and its dimpled modified sample (Beta24C) were obtained using Fourier transform infrared spectroscopy (FT-IR), as shown in the attached figure. Figure 1 As shown. (From the appendix) Figure 1 It is evident that the infrared spectrum of hydroxyl vibrations of the hierarchical porous dealuminolite Beta zeolite support changed significantly after the denting modification, indicating that the denting modification did indeed occur at the hydroxyl lattice defect sites of the hierarchical porous dealuminolite Beta zeolite.

[0123] The third step involves loading copper into the pores of a hierarchical, dealuminolized Beta zeolite using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst.

[0124] (1) Prepare a dilute ammonia base solution and synthesize a copper-ammonia complex using copper nitrate trihydrate (Cu(NO3)2·3H2O). Then, prepare a saturated solution of the copper-ammonia complex at room temperature. The pH of the dilute ammonia base solution is 11-12, and it is prepared by adding 4.4g of industrial ammonia (containing 25-28wt.% NH3) to 100ml of deionized water. The copper-ammonia complex is obtained by reacting Cu(NO3)2·3H2O with industrial ammonia at a molar ratio of copper ions to ammonia molecules of 1:4. The saturated solution of the copper-ammonia complex is obtained by dissolving the copper-ammonia complex in the dilute ammonia base solution, which contains approximately 0.4M of the copper-ammonia complex.

[0125] (2) A Cu-Beta zeolite catalyst with a copper loading of 3 wt.% was prepared by impregnating the zeolite support with an equal volume of copper-ammonia complex solution. First, 5 g of calcined and sealed, pitted-modified hierarchical dealaluminized Beta zeolite support (Beta24C) was taken and titrated with deionized water until all samples were uniformly wetted but no free liquid water appeared. A total of 6.25 ml of deionized water was consumed, and the water absorption rate of pitted-modified hierarchical dealaluminized Beta zeolite (Beta24C) was calculated to be 1.25 ml / g. Based on a 10 g support feed amount, a total of 12.5 ml of copper-ammonia complex solution was required. The required concentration of the copper-ammonia complex solution based on a copper loading of 3 wt.% was approximately 0.38 M. That is, the calculated concentration of the required copper-ammonia complex solution was very close to the concentration of the saturated copper-ammonia complex solution (0.4 M). Therefore, 10g of the dented, multi-level porous dealaluminized Beta zeolite support (Beta24C) was directly impregnated with an equal volume of 12.5ml of a saturated solution of a copper-ammonia complex. The impregnation was carried out at room temperature for 4 hours.

[0126] (3) The impregnated material of equal volume was subjected to ammonia stripping treatment under normal pressure. The ammonia stripping temperature was 80℃ and the ammonia stripping time was 10h. During this process, due to capillary coagulation, the copper-ammonia complex that entered the zeolite channels gradually deposited in the zeolite channels in the form of copper hydroxide after losing ammonia gas.

[0127] (4) The material after ammonia stripping is dehydrated and dried. The drying temperature is 110℃ and the drying time is 12h.

[0128] (5) The dried material is roasted. The roasting temperature is 500℃ and the roasting time is 3h. After roasting, the copper hydroxide deposited in the zeolite channels is converted into nano and sub-nano copper oxide particles, thus obtaining the catalyst precursor.

[0129] (6) The catalyst precursor was subjected to hydrogen reduction treatment. The reduction temperature was 400℃, the reduction time was 4h, and the hydrogen flow rate (expressed as hydrogen volume hourly space velocity, defined as the volume of hydrogen passing through a unit volume of catalyst per unit time, in ideal gas terms) was 300 h⁻¹.-1 After hydrogen reduction treatment, the finished Cu-Beta zeolite catalyst, designated Cu3-Beta24C-1, was obtained.

[0130] Secondly, in order to understand the implementation effect of the catalyst preparation method provided by this invention from the perspective of the physicochemical properties of the catalyst, the XRD patterns and hydroxyl vibration infrared spectra of Cu3-Beta24C-1 and its pitted modified hierarchical porous dealaluminized Beta zeolite support (Beta24C) were measured in parallel using XRD and FT-IR methods, as shown in the attached figures. Figure 2 and attached Figure 3 As shown. In addition, TEM images of the Cu3-Beta24C-1 catalyst and its high-temperature calcined sample (550℃×3h) were also obtained using transmission electron microscopy, as shown below. Figure 4 and Figure 5 As shown.

[0131] from Figure 2 As can be seen, the Cu3-Beta24C-1 catalyst prepared by the improved ammonia stripping method provided by this invention retains the crystal structure of the Beta zeolite support very well. The relative crystallinity of the zeolite in the catalyst, calculated based on the pitted modified hierarchical porous dealubilized Beta zeolite support (Beta24C), is 78%. Figure 3 As can be seen, the Cu3-Beta24C-1 catalyst prepared according to the method of the present invention exhibits a significantly lower intensity of the characteristic infrared band of the zeolite hydroxyl lattice compared to the lattice-modified hierarchical porous dealuminolite Beta zeolite support, indicating that metallic copper occupies a large number of hydroxyl lattice defect sites. Furthermore, from... Figure 4 and Figure 5 It is evident that the metallic copper in the Cu3-Beta24C-1 catalyst exists as highly dispersed nano and sub-nano particles, with an average particle size of approximately 3-4 nm. After calcination at 550 °C for 3 h, the dispersion state of the metallic copper particles showed minimal change, with an average particle size of approximately 4-5 nm. These data indicate that the hydroxyl-dimpled lattice defect sites of the dimpled modified hierarchical porous dealuminolite Beta zeolite support play a very good role in dispersing and stabilizing nano and sub-nano copper particles.

[0132] Based on this, the catalytic performance of the Cu3-Beta24C-1 catalyst and its calcined sample at 550℃ was evaluated using the gas-solid phase hydroammoniation of caprolactone to caprolactam. The reaction was carried out in a small fixed-bed reactor with a stainless steel reaction tube inner diameter of 9 mm, employing a top-feed, bottom-discharge operation. 2 g of tableted catalyst (20-40 mesh sample after sieving) was placed in the isothermal zone of the reactor. The upper and lower spaces of the catalyst bed were filled with inert ceramic balls. The upper ceramic ball region of the reactor served as the vaporization and preheating zone for the feedstock. The isothermal zone temperature was 260℃, the reaction pressure was 1 atm, and the caprolactone feed space velocity (WHSV) was 0.6 h⁻¹.-1 For convenience, caprolactone, ammonia (analytical grade, ammonia concentration 25-28 wt.%), and deionized water were prepared into a feed solution with an ammonia-ester molar ratio of 6 and a water-ester molar ratio of 30. This feed solution was introduced into the reactor using a micro-metering pump, and hydrogen was fed in using a mass flow meter at a hydrogen-ester molar ratio of 50. The reaction products were continuously collected in a stainless steel collection tank with a cooling water jacket connected to the reactor outlet. Product liquid was collected at fixed time intervals and analyzed using a Shimadzu GC-2014 gas chromatograph (FID detector, OV-1701 column). The conversion rate of caprolactone and the selectivity of caprolactam were calculated using the internal standard method (internal standard: 1,4-dioxane). Under the above conditions, when the caprolactone hydroamination reaction was carried out continuously for 6 hours, the caprolactam yield of the Cu3-Beta24C-1 catalyst was approximately 88%; the caprolactam yield of the sample calcined at 550℃ was also approximately 88%. The above reaction results indicate that the Cu-Beta zeolite catalyst provided by this invention is a high-performance catalyst for the hydroamylation of caprolactone to caprolactam.

[0133] Comparative Example 1: This example illustrates that when Cu-Beta zeolite catalysts are prepared by loading copper using the conventional ammonia stripping method with a multi-level porous dealubilized Beta zeolite modified with a hole-shaped groove, the crystal structure of the Beta zeolite support is severely damaged. The loaded metallic copper mainly falls outside the zeolite channels, resulting in low dispersion and large copper particle size. Due to the lack of protection from the active silanol groups in the dealubilized Beta zeolite hydroxyl pockets, the sintering resistance is poor. Therefore, the prepared Cu-Beta zeolite catalyst performs poorly in the gas-solid phase hydroammoniation of caprolactone to caprolactam.

[0134] Example 1 was repeated, but after the preparation of the dimpled modified hierarchical porous dealubilized Beta zeolite support (Beta24C) in the second step, copper hydroxide was deposited on the zeolite support using the same conventional ammonia stripping method as published in Science 10.1126 / science.adj1962 (2023), as follows:

[0135] (1) Dissolve 1.18g Cu(NO3)2·3H2O in 515ml ammonia solution (containing 3.86g NH3·H2O, equivalent to 8.1ml 26wt.% industrial ammonia water, with a copper ion to ammonia molecule molar ratio of approximately 1:23) and stir at room temperature for 10min to prepare a copper ammonia complex aqueous solution (complex ion concentration approximately 9.5mmol / L, i.e. 9.5mM);

[0136] (2) 10g of the dented modified hierarchical porous dealuminolite carrier (Beta24C) was added to 515ml of copper ammonia complex solution, and ammonia stripping was performed under vigorous stirring. The ammonia stripping temperature was 80℃ and the ammonia stripping time was 6h.

[0137] (3) After the ammonia stripping is completed, the diluted and excess copper ammonia complex solution is removed by filtration. The resulting filter cake is dried, calcined and hydrogen reduced in the same way as in Example 1 to obtain Cu-Beta zeolite catalyst, designated Cu3-Beta24C-CE1 (CE = Comparative Example).

[0138] To understand the physicochemical properties of the Cu-Beta zeolite catalyst prepared by the traditional ammonia stripping method, the Beta zeolite crystal structure of the Cu3-Beta24C-CE1 catalyst was characterized by XRD and compared with its support (Beta24C), as shown in the attached figure. Figure 6 As shown. In addition, the Cu metal dispersion of Cu3-Beta24C-CE1 catalyst and its high-temperature calcined sample (550℃×3h) was characterized by transmission electron microscopy, and the catalytic performance of Cu3-Beta24C-CE1 catalyst and its high-temperature calcined sample was evaluated by the gas-solid phase hydroammoniation of caprolactone to caprolactam.

[0139] XRD characterization results showed that the Cu3-Beta24C-CE1 catalyst prepared by the conventional ammonia stripping method exhibited significant zeolite crystal structure damage, with a relative crystallinity of 60% calculated based on its support (Beta24C). Transmission electron microscopy (TEM) characterization revealed that the average Cu metal particle size of the Cu3-Beta24C-CE1 catalyst and its high-temperature calcined sample were 11 nm and 19 nm, respectively, indicating low Cu metal dispersion and easy sintering on the catalyst. Reaction evaluation results showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24C-CE1 catalyst was approximately 75%; the caprolactam yield of its high-temperature calcined sample was 70%. These results indicate that the Cu-Beta zeolite catalyst prepared by the conventional ammonia stripping method on a dent-modified dealuluminated Beta zeolite support exhibits low catalytic activity and poor resistance to sintering deactivation in the gas-solid phase hydroammoniation of caprolactone to caprolactam.

[0140] Comparative Example 2: This example illustrates that when Cu-Beta zeolite catalysts are prepared by loading copper into the pores using a modified ammonia stripping method with pore-modified dealuluminated Beta zeolite as a support, introducing mesopores and forming a hierarchical pore system in the zeolite support not only improves the anti-sintering ability of Cu-Beta zeolite catalysts, but also improves their catalytic activity.

[0141] Example 1 was repeated, but in the first step, the Beta zeolite matrix without sodium hydroxide solution desilication treatment was directly used for concentrated nitric acid dealuminization treatment to prepare a dealuminized Beta zeolite support (Beta24c). Based on this, a Cu-Beta zeolite catalyst was prepared by a second step of pore modification and a third step of loading copper into the zeolite channels (using a modified ammonia stripping method). When the dealuminized Beta zeolite support was impregnated with an equal volume of copper-ammonia complex solution, the water absorption rate of the dealuminized Beta zeolite (Beta24c) was measured to be 1.25 ml / g by deionized water titration. Based on a 10g support feed rate, a total of 12.5 ml of copper-ammonia complex solution was required. Based on a copper loading of 3 wt.%, the required concentration of the copper-ammonia complex solution was approximately 0.38 M. That is, the calculated concentration of the required copper-ammonia complex solution is very close to the concentration of a saturated copper-ammonia complex solution (0.4 M). Therefore, 10g of the dented-modified dealubilized Beta zeolite support was directly impregnated with an equal volume of 12.5ml of a saturated solution of the copper-ammonia complex. All other procedures remained unchanged. The resulting Cu-Beta zeolite catalyst was named Cu3-Beta24C-CE2.

[0142] To avoid unnecessary complexity, this example only evaluates the catalytic performance of the Cu3-Beta24C-CE2 catalyst and its high-temperature calcined sample (550℃×3h) using the gas-solid phase hydroammoniation of caprolactone to caprolactam. The evaluation results show that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24C-CE2 catalyst is approximately 85%, and the caprolactam yield of its high-temperature calcined sample is also close to 85%. Comparing these results with those in Example 1 shows that introducing mesopores into the hollow-modified dealubilized Beta zeolite support not only improves the anti-sintering ability of the Cu-Beta zeolite catalyst but also enhances its catalytic activity.

[0143] Comparative Example 3: This example illustrates that when Cu-Beta zeolite catalysts are prepared by loading copper into the channels using a modified ammonia stripping method with dealuminated Beta zeolite as a support, the pore-knocking modification of the zeolite support is beneficial to the catalyst's resistance to sintering.

[0144] Example 1 was repeated, but in the first step, the Beta zeolite precursor, which had not undergone desilication treatment with sodium hydroxide solution, was directly subjected to concentrated nitric acid for dealuminization treatment to prepare a dealuminized Beta zeolite support (Beta24c). Then, the dealuminized Beta zeolite support (Beta24c) was directly used in the third step to load copper into the pores using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst. Specifically, when the dealuminized Beta zeolite support was impregnated with an equal volume of copper-ammonia complex solution, the water absorption rate of the dealuminized Beta zeolite (Beta24c) was determined to be 1.2 ml / g by deionized water titration. Based on a 10g support feed amount, a total of 12 ml of copper-ammonia complex solution was required. Based on a copper loading of 3 wt.%, the required concentration of the copper-ammonia complex solution was approximately 0.39 M. That is, the calculated concentration of the required copper-ammonia complex solution is very close to the concentration of a saturated copper-ammonia complex solution (0.4 M). Therefore, 10g of dealuminolized Beta zeolite support was directly impregnated with an equal volume of 12ml of a saturated solution of copper-ammonia complex. All other procedures remained unchanged. The resulting Cu-Beta zeolite catalyst was named Cu3-Beta24c-CE3.

[0145] In this example, the catalytic performance of the Cu3-Beta24c-CE3 catalyst and its high-temperature calcined sample was evaluated using the gas-solid phase hydroammoniation of caprolactone to produce caprolactam. The evaluation results showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24c-CE3 catalyst was approximately 80%; the caprolactam yield of its high-temperature calcined sample (550℃ × 3h) was approximately 76%. Comparing these results with Comparative Example 2, it can be seen that the denting modification of the dealuminized Beta zeolite support with ethanolamine solution is beneficial for improving the anti-sintering properties of the Cu-Beta zeolite catalyst.

[0146] Comparative Example 4: This example is used to illustrate the use of amorphous fumed silica (white carbon black, BET specific surface area 286 m²). 2 Copper-silica catalysts prepared by loading copper with copper using the traditional ammonia stripping method with copper as a support ( / g) have poor resistance to sintering.

[0147] The conventional ammonia stripping method described in this example follows the procedure in Example 1 of US Patent 4,440,873 (1984), as follows:

[0148] (1) Dissolve 1.14 g of copper nitrate (Cu(NO3)2·3H2O) in 100 ml of water to obtain an aqueous solution containing copper ions. Then, according to a copper ion to ammonia molecule molar ratio of approximately 1:10, add 3.6 ml of concentrated ammonia solution (industrial ammonia water with NH3 content of 26 wt.% and density of 0.89 g / ml) and add 50 ml of water to obtain a dark blue solution containing copper ammonia complex with a pH value of 11-12 (complex ion concentration of approximately 30.8 mM. The purpose of adding 50 ml of water is to maintain the solution volume to silica dry basis ratio consistent with the literature).

[0149] (2) Add 10g of fumed silica (dry basis) to the copper ammonia complex solution and stir at room temperature for 2h;

[0150] (3) The reaction mixture of step (2) was heated and ammonia was removed (80℃, 6h). When the pH of the mixture dropped to 6-7, the solid was filtered and washed three times with deionized water to obtain the solid product.

[0151] (4) Dry the solid product at 120°C for 12 hours and calcine it at 450°C for 4 hours;

[0152] (5) The calcined solid product was subjected to hydrogen reduction treatment. The reduction conditions were 350℃×2h to obtain a copper-silica catalyst, designated Cu3-SiO2-CE4.

[0153] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-SiO2-CE4 catalyst was 73%, while the caprolactam yield of the high-temperature calcined sample (550℃×3h) was 62%. These results indicate that the copper-based catalyst prepared using amorphous silica as a support has poor resistance to sintering, and its catalytic activity decreases significantly after high-temperature treatment.

[0154] Comparative Example 5: This example is used to further illustrate that the copper-silica catalyst prepared by supporting copper using the traditional ammonia stripping method has poor resistance to sintering.

[0155] Comparative Example 4 was repeated, but 33.3 g of silica sol (30 wt.% SiO2) was used as the precursor for in-situ generation of 10 g of silica support. To maintain the ratio of the copper-ammonia complex solution volume to the dry silica basis consistent with Comparative Example 3, the water addition in step (1) was changed to 26.7 ml. The prepared copper-silica catalyst was designated Cu3-SiO2-CE5.

[0156] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-SiO2-CE5 catalyst was 78%; the caprolactam yield of the high-temperature calcined sample (550℃×3h) was 70%. These results also indicate that the copper-based catalyst prepared using amorphous silica as a support has poor resistance to sintering, and its catalytic activity decreases significantly after high-temperature treatment.

[0157] Comparative Example 6: This example illustrates that the amorphous nature of the silica support determines the poor sintering resistance of the copper-silica catalyst.

[0158] In this example, a copper-silica catalyst is prepared on a fumed silica support using the improved ammonia stripping method provided by this invention. Specifically:

[0159] Repeat Example 1, but replace 10g of the dented modified hierarchical porous dealuminolite Beta zeolite carrier with 10g (dry basis) fumed silica (white carbon black, BET specific surface area 286m²). 2 / g (saturated water absorption rate 2.5ml / g), 10g of fumed silica requires 25ml of copper-ammonia complex solution. Based on a copper loading of 3wt.%, the required concentration of the copper-ammonia complex solution is approximately 0.19M. 11.9ml of the saturated copper-ammonia complex solution was diluted to 25ml with a dilute ammonia base solution, yielding 25ml of a 0.19M copper-ammonia complex solution. The prepared copper-silica catalyst is designated Cu3-SiO2-CE6.

[0160] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-SiO2-CE6 catalyst was 70%; the caprolactam yield of the high-temperature calcined sample (550℃×3h) was 60%. These results also indicate that the copper-based catalyst prepared using amorphous silica as a support has poor resistance to sintering, and its catalytic activity decreases significantly after high-temperature treatment.

[0161] Example 2: This example illustrates that, according to the method provided by the present invention, Cu-Beta zeolite catalysts with different copper loadings can be prepared by using a modified ammonia stripping method to load copper in the zeolite channels with a multi-level porous dealaluminized Beta zeolite modified by denting as a support.

[0162] Example 1 was repeated, but the copper loading in the prepared Cu-Beta zeolite catalyst was successively reduced to 1 wt.% and 2 wt.%, resulting in required copper-ammonia complex solution concentrations of approximately 0.13 M and 0.25 M, respectively. 3.9 ml and 7.8 ml of the saturated copper-ammonia complex solution were successively diluted to 12.5 ml with dilute ammonia solution to obtain equal-volume impregnation solutions of Cu-Beta zeolite catalyst with copper loadings of 1 wt.% and 2 wt.%. In the preparation of Cu-Beta zeolite catalyst using the improved ammonia stripping method, the time for isovolumetric impregnation of the pitted modified hierarchical dealuded Beta support (Beta24C) at room temperature was changed to 6 h; the temperature and time for ammonia stripping were changed to 65 °C and 12 h, respectively; the temperature and time for dehydration and drying were changed to 150 °C and 3 h, respectively; the subsequent calcination temperature and time were changed to 450 °C and 6 h, respectively; the final hydrogen reduction temperature and time were changed to 350 °C and 8 h, respectively; and the hydrogen flow rate (volume hourly space velocity) was changed to 1000 h⁻¹. -1 The prepared Cu-Beta zeolite catalysts are designated as Cu1-Beta24C-2 and Cu2-Beta24C-2, respectively.

[0163] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of Cu1-Beta24C-2 catalyst was 83%, while that of Cu2-Beta24C-2 catalyst was 85%.

[0164] Example 3: This example further illustrates that, according to the method provided by this invention for preparing Cu-Beta zeolite catalysts using a pitted modified hierarchical porous dealuminolized Beta zeolite as a support and a modified ammonia stripping method for loading copper in the zeolite channels, Cu-Beta zeolite catalysts with varying copper loadings can be prepared. However, when preparing Cu-Beta zeolite catalysts with copper loadings higher than 3 wt.%, a multi-loading scheme is preferable.

[0165] Repeating Example 1, but increasing the copper loading in the prepared Cu-Beta zeolite catalyst to 4 wt.% and 6 wt.%, respectively, the calculated required concentrations of the copper-ammonia complex solution were approximately 0.50 M and 0.76 M, respectively. Clearly, the required copper-ammonia complex concentrations both exceeded the concentration of the saturated copper-ammonia complex solution prepared with a dilute ammonia base solution (0.4 M). We attempted to dissolve the copper-ammonia complex using industrial ammonia instead of the dilute ammonia base solution, obtaining a maximum concentration of approximately 0.5 M. Although dissolving the copper-ammonia complex with industrial ammonia can produce a high-concentration copper-ammonia complex solution of approximately 0.5 M, this solution has an ammonia / copper ion molar ratio exceeding 24:1, is highly alkaline, and causes significant ammonia volatilization, which is detrimental to protecting the crystal structure of the dealuminized Beta zeolite and also hinders operation. This indicates that the modified ammonia stripping method cannot yield a high copper loading Cu-Beta zeolite catalyst on a given dented, hierarchical porous dealuminolite support through a single equal-volume impregnation and ammonia stripping operation. Therefore, this invention uses a dilute ammonia base solution to dilute a saturated copper-ammonia complex solution, and prepares Cu-Beta zeolite catalysts with copper loadings increased to 4 wt.% and 6 wt.%, respectively, through multiple equal-volume impregnation and ammonia stripping operations. For the preparation of the 4 wt.% copper loading catalyst, the impregnation and ammonia stripping operations can be performed in two separate equal-volume operations, such as 1 wt.% + 3 wt.% or 2 wt.% + 2 wt.%. For the preparation of the 6 wt.% copper loading catalyst, the operations can be performed in two separate operations (3 wt.% + 3 wt.%) or in three separate operations (2 wt.% + 2 wt.% + 2 wt.%). For simplicity, in this example, the preparation of Cu-Beta zeolite catalysts with copper loadings increased to 4 wt.% and 6 wt.% were carried out in two separate processes (2 wt.% + 2 wt.%, 3 wt.% + 3 wt.%). A single loading of 2 wt.% metallic copper onto a pitted-modified hierarchical dealubilized Beta zeolite support using the modified ammonia stripping method requires 12.5 ml of impregnation solution with a copper-ammonia complex concentration of 0.25 M; a single loading of 3 wt.% metallic copper onto the pitted-modified hierarchical dealubilized Beta zeolite support requires 12.5 ml of impregnation solution with a copper-ammonia complex concentration of 0.38 M. The 0.25 M impregnation solution was obtained by diluting 7.8 ml of a saturated copper-ammonia complex solution with a dilute ammonia base solution, while the 0.38 M impregnation solution was directly obtained from a saturated copper-ammonia complex solution. When performing equal-volume impregnation treatment on the dimpled modified hierarchical porous dealubilized Beta support at room temperature, the impregnation time was changed to 6 h, the ammonia stripping temperature and time were changed to 85 °C and 3 h, respectively, the dehydration and drying temperature and time were changed to 120 °C and 5 h, respectively, the subsequent calcination temperature and time were changed to 550 °C and 2 h, respectively, the final hydrogen reduction temperature and time were changed to 500 °C and 2 h, respectively, and the hydrogen flow rate (volume hourly space velocity) was changed to 20 h⁻¹. -1(The feed was controlled by a mass flow meter after mixing with an appropriate amount of nitrogen). The prepared Cu-Beta zeolite catalysts were designated as Cu4-Beta24C-3 and Cu6-Beta24C-3, respectively.

[0166] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield was 88% with the Cu4-Beta24C-3 catalyst and 87% with the Cu6-Beta24C-3 catalyst.

[0167] Example 4: This example illustrates that when preparing Cu-Beta zeolite catalysts according to the improved ammonia stripping method provided by the present invention, it is permissible to use Beta zeolite matrix with different crystal sizes to prepare dealubilized Beta zeolite supports.

[0168] Example 1 was repeated, but in the first step of preparing the dealuminized Beta zeolite support, a Beta zeolite matrix with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio) of 22 was synthesized using the hydrothermal crystallization method (with ammonium fluoride additive) provided in the published literature J. Mater. Sci. 41 (2006) 1861-1864 as the raw material for preparing the hierarchical porous dealuminized Beta zeolite support. After conventional filtration, washing, drying (80℃, 24h) and calcination to remove the template agent (600℃, 3h), the synthesized Beta zeolite matrix was observed by TEM to have an average grain size of 1μm, belonging to large-grained Beta zeolite; XRD analysis showed no impurities; and its BET specific surface area was calculated to be approximately 480 m² using nitrogen physical adsorption data. 2 The molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) was measured to be approximately 23 by XRF, which meets the technical requirements of this invention for the Beta zeolite matrix. The large-grained hierarchical porous dealubilized Beta zeolite support (code-named Beta23c) prepared using this Beta zeolite matrix has a microporous specific surface area accounting for approximately 70% of the total specific surface area, and a silicon-aluminum oxide molar ratio (SiO2 to Al2O3) of 735 (>700). Based on this, following the procedure in step 2 of Example 1, the above-mentioned large-grained hierarchical porous dealubilized Beta zeolite support (Beta23c) was subjected to a dimpling modification treatment with an aqueous solution of ethanolamine to obtain a dimpling modified large-grained hierarchical porous dealubilized Beta zeolite support, named Beta23C; further, following the procedure in step 3 of Example 1, copper was loaded into the zeolite channels using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst with a copper content of 3 wt.%, code-named Cu3-Beta23C-4.

[0169] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta23C-4 catalyst was 86%.

[0170] Example 5: This example illustrates that when preparing Cu-Beta zeolite catalyst by loading copper into the pores using a modified ammonia stripping method with a multi-level porous dealaluminized Beta zeolite modified with pores as a carrier, the degree of pore modification of the multi-level porous dealaluminized Beta zeolite can be controlled by changing the impregnation modification conditions of the ethanolamine solution.

[0171] Example 1 was repeated, but in the second step, when the hydroxyl holes of the hierarchical porous dealufted Beta zeolite support were modified by using an aqueous solution of ethanolamine, the concentration of the aqueous solution of ethanolamine was changed to 0.16M, the ratio of the volume of the modified liquid to the amount of the hierarchical porous dealufted Beta zeolite support (Beta24c) (liquid-solid ratio) was changed to 10:1, the impregnation temperature was changed to 50℃, and the impregnation time was changed to 0.5h. After the hole modification was completed, the reactants were filtered to recover the solid product, and then the solid product was repeatedly washed with deionized water until neutral, and then dried (overnight at 110℃) and calcined (550℃, 3h) to obtain the hole-modified hierarchical porous dealufted Beta zeolite support. It was sealed and stored for later use. According to the weight reduction estimate, the average number of framework silicon atoms (calculated as SiO2) removed from the hydroxyl hole lattice defect sites of the dealufted Beta zeolite support was 1.5 silicon atoms, and the amount of silicon removed increased. This indicates that the above treatment conditions enhanced the pore-drilling modification process and increased the geometric space of hydroxyl lattice defect sites in the hierarchical porous dealuminolite Beta zeolite. Based on this, copper was loaded into the pores of the modified support using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst with a copper content of 3 wt.%, named Cu3-Beta24C-5.

[0172] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24C-5 catalyst was 89%; the caprolactam yield of the sample calcined at 550℃ was 88%.

[0173] Example 6: This example is used to further illustrate that when preparing Cu-Beta zeolite catalyst by loading copper in the pores using the improved ammonia stripping method with the multi-level porous dealaluminized Beta zeolite with dent modification as a carrier according to the present invention, the degree of dent modification of the multi-level porous dealaluminized Beta zeolite can be controlled by changing the impregnation modification conditions of the ethanolamine solution.

[0174] Example 1 was repeated, but in the second step, when the hydroxyl holes of the hierarchical porous dealufted Beta zeolite support were modified by using an aqueous solution of ethanolamine, the concentration of the ethanolamine aqueous solution was changed to 0.30 M, the liquid-to-solid ratio was changed to 2:1, the impregnation temperature was changed to 20°C, and the impregnation time was changed to 1 h. After the hole modification was completed, the reactants were filtered to recover the solid product, and then the solid product was repeatedly washed with deionized water until neutral, and then dried (overnight at 110°C) and calcined (550°C, 3 h) to obtain the hole-modified hierarchical porous dealufted Beta zeolite support. It was sealed and stored for later use. According to the weight reduction estimate, the average number of framework silicon atoms (calculated as SiO2) removed from the hydroxyl hole lattice defect sites of the dealufted Beta zeolite support was 0.9 silicon atoms, and the amount of silicon removed was reduced, indicating that the above combination of hole modification conditions weakened the hole modification treatment. Based on this, copper was loaded into the channels using an improved ammonia stripping method to prepare a Cu-Beta zeolite catalyst with a copper content of 3 wt.%, named Cu3-Beta24C-6.

[0175] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24C-6 catalyst was 85%; the caprolactam yield of the high-temperature calcined sample (550℃×3h) was 84%.

[0176] Example 7: This example illustrates that when preparing Cu-Beta zeolite catalysts according to the improved ammonia stripping method provided by this invention, it is permissible to use Beta zeolite matrix with different molar ratios of silicon and aluminum oxides (SiO2 to Al2O3) to prepare dent-modified hierarchical dealuminolite supports. When using Beta zeolite with a higher molar ratio of silicon and aluminum oxides (SiO2 to Al2O3) as the matrix, a relatively mild combination of dent modification conditions is preferable. Conversely, the opposite is also true.

[0177] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, a Beta zeolite matrix with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio) of 60 was synthesized using the hydrothermal crystallization method provided in US Patent US3308069 (1967) as the raw material for preparing the hierarchical porous dealubilized Beta zeolite support. After conventional filtration, washing, drying (170°C, 3h), and calcination to remove the template agent (500°C, 8h), the synthesized Beta zeolite matrix was observed by TEM to have an average grain size close to 100 nm, classifying it as nano-Beta zeolite. XRD analysis revealed no impurities, and its BET specific surface area was calculated to be approximately 530 m². 2The molar ratio of silicon-aluminum oxide (SiO2 to Al2O3) was approximately 57, as determined by XRF, which meets the technical requirements of this invention for the Beta zeolite matrix.

[0178] The Beta zeolite matrix was subjected to desilication treatment with sodium hydroxide solution and dealumination treatment with concentrated nitric acid to prepare a hierarchical porous dealuminized Beta zeolite support. Specifically, when using sodium hydroxide solution for alkaline desilication to prepare the hierarchical porous Beta zeolite matrix, the weight loss due to desilication was approximately 5.22 wt.%. When using concentrated nitric acid solution to acid-treat the hierarchical porous Beta zeolite matrix for dealumination to prepare the hierarchical porous dealuminized Beta zeolite support, a hierarchical porous dealuminized Beta zeolite support (designated Beta57c) with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio) of 910 (>900) was obtained. The degree of dealumination of the support met the requirements of this invention. In the second step, when the hydroxyl groups of the hierarchical porous dealuminized Beta zeolite support were modified by using an aqueous solution of ethanolamine, the concentration of the ethanolamine aqueous solution was changed to 0.02 M, the liquid-to-solid ratio was changed to 20:1, the impregnation temperature was changed to 80℃, and the impregnation time was changed to 5 h. After the pore-cutting modification was completed, the reactants were filtered to recover the solid product. The solid product was then repeatedly washed with deionized water until neutral, followed by drying (overnight at 110°C) and calcination (550°C, 3 hours) to obtain pore-cutting modified dealubilized Beta zeolite. It was sealed and stored for later use. Based on weight reduction estimates, the average number of framework silicon atoms (calculated as SiO2) removed from the hydroxyl lattice defect sites of the dealubilized Beta zeolite support was 1.3 silicon atoms, indicating an increase in desiliconization. This suggests that the above combination of pore-cutting modification conditions enhanced the pore-cutting modification treatment for hierarchical porous dealubilized Beta zeolite supports with a relatively small number of hydroxyl lattices. The obtained pore-cutting modified hierarchical porous dealubilized Beta zeolite support was named Beta57C. Further, following the procedure in step 3 of Example 1, copper was loaded into the zeolite channels using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst with a copper content of 3 wt.%. Specifically, when impregnating the support with an equal volume of a saturated solution of a copper-ammonia complex at room temperature, the impregnation time was changed to 2 hours. During ammonia stripping, a slight negative pressure was used at a temperature of 50℃ for 48 hours. The dehydration and drying process after ammonia stripping was then carried out at 100℃ for 48 hours. The subsequent calcination temperature and time were changed to 350℃ for 24 hours. Finally, the hydrogen reduction treatment temperature, time, and hydrogen flow rate (volume hourly space velocity) were changed to 300℃ for 20 hours and 2000 hours, respectively. -1 The catalyst is designated Cu3-Beta57C-7.

[0179] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta57C-7 catalyst was 84%.

[0180] Example 8: This example further illustrates that when preparing Cu-Beta zeolite catalysts according to the improved ammonia stripping method provided by this invention, it is permissible to use Beta zeolite matrix with different molar ratios of silicon and aluminum oxides (SiO2 to Al2O3) to prepare dent-modified hierarchical dealuminolite supports. When using Beta zeolite with a higher molar ratio of silicon and aluminum oxides (SiO2 to Al2O3) as the matrix, a relatively mild combination of dent modification conditions is preferable. Conversely, the opposite is also true.

[0181] Example 7 was repeated, but in the second step, when the hydroxyl holes of the dealuminized Beta zeolite support were modified using an aqueous solution of ethanolamine, the liquid-to-solid ratio was changed to 100:1 and the impregnation time was changed to 24 hours. After the hollowing modification was completed, the reactants were filtered to recover the solid product, which was then repeatedly washed with deionized water until neutral, and then dried (overnight at 110°C) and calcined (550°C, 3 hours) to obtain the hollow-modified dealuminized Beta zeolite. It was then sealed and stored for later use. Based on weight reduction estimates, the average number of framework silicon atoms (calculated as SiO2) removed from the hydroxyl hole lattice defect sites of the dealuminized Beta zeolite support was 2.3 silicon atoms, indicating a significant increase in desiliconization. This suggests that the above combination of hollowing modification conditions enhanced the hollowing modification treatment for hierarchical porous dealuminized Beta zeolite supports with a relatively small number of hydroxyl holes. Based on this, using the obtained dented modified hierarchical porous dealuminolite Beta zeolite as a support, Cu-Beta zeolite catalyst, designated Cu3-Beta57C-8, was prepared according to the third step of Example 1.

[0182] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta57C-8 catalyst was 83%.

[0183] Example 9: This example further illustrates that when preparing Cu-Beta zeolite catalysts according to the improved ammonia stripping method provided by this invention, it is permissible to use Beta zeolite matrices with different molar ratios of silicon and aluminum oxides (SiO2 to Al2O3) to prepare dent-modified hierarchical dealuminolite supports. When using Beta zeolite with a higher molar ratio of silicon and aluminum oxides (SiO2 to Al2O3) as the matrice, a relatively mild combination of dent modification conditions is preferable. Conversely, the opposite is also true.

[0184] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, Beta zeolite precursors with silicon-aluminum oxide molar ratios (SiO2 to Al2O3 molar ratios) of 15, 20, 40, 80, and 100 were synthesized using the hydrothermal crystallization method provided in Chinese Invention Patent CN1108275C (application date 1999.9.10) as raw materials for preparing the dealubilized Beta zeolite support. After conventional filtration, washing, drying (110℃, 12h), and calcination to remove the template agent (540℃, 6h), the synthesized Beta zeolite precursors were observed by TEM to have an average grain size at the nanometer and small grain (less than 1μm) levels. The grain size increased with increasing silicon-aluminum oxide molar ratio; no impurities were observed by XRD, and the BET specific surface area calculated using nitrogen physical adsorption data was all above 500m². 2 The molar ratios of silicon and aluminum oxides (SiO2 to Al2O3) measured by XRF were 14, 18, 38, 72 and 94, respectively, which meet the technical requirements of this invention for Beta zeolite matrix.

[0185] The five Beta zeolite precursors were used for desilication via alkaline treatment with sodium hydroxide solution and dealuminization via acid treatment with concentrated nitric acid solution to prepare hierarchical porous dealuminized Beta zeolite supports. Specifically, during the alkaline treatment with sodium hydroxide solution to prepare hierarchical porous Beta zeolite, the five Beta zeolite precursors, in order of increasing silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio), showed desilication weight reductions of 7.31%, 7.99%, 8.88%, 9.79%, and 10.31%, respectively. During the acid treatment with concentrated nitric acid solution to prepare hierarchical porous dealuminized Beta zeolite supports, five dealuminized Beta zeolite supports were obtained: Beta14c, Beta18c, Beta38c, Beta72c, and Beta94c, with silicon-aluminum oxide molar ratios (SiO2 to Al2O3 molar ratios) of 730, 755, 850, 843, and 916, respectively, all meeting the technical requirements for dealuminized Beta zeolite supports. Based on this, following the procedure in step two of Example 1, the above-mentioned hierarchical porous dealaluminized Beta zeolite support was subjected to denting modification treatment using an aqueous solution of ethanolamine. The denting modification treatment conditions were as follows: the concentration of the ethanolamine aqueous solution was changed to 0.01M, the liquid-to-solid ratio was changed to 20:1, the impregnation temperature was changed to 80℃, and the impregnation time was changed to 3h. After the denting modification was completed, the reactants were filtered to recover the solid product, and then the solid product was repeatedly washed with deionized water until neutral, followed by drying (overnight at 110℃) and calcination (550℃, 3h) to obtain the dented modified hierarchical porous dealaluminized Beta zeolite support, named Beta14C, Beta18C, Beta38C, Beta72C, and Beta94C. These were sealed and stored for later use. Based on weight reduction estimates, the average number of framework silicon atoms (calculated as SiO2) removed from the hydroxyl-terminated lattice defect sites of the aforementioned dimpled hierarchical dealubilized Beta zeolite supports are 0.2, 0.3, 0.4, 0.8, and 1.1, respectively. That is, the aforementioned combination of dimpling modification conditions is insufficient for the hierarchical porous dealubilized Beta zeolite supports prepared using a lower molar ratio of silicon to aluminum oxide (SiO2 to Al2O3) Beta zeolite matrix.

[0186] Following the procedure in step 3 of Example 1, copper was loaded into the zeolite channels using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst with a copper content of 3 wt.%. Specifically, when impregnating the support with an equal volume of a saturated solution of a copper-ammonia complex at room temperature, the impregnation time was changed to 1 hour. During ammonia stripping, the stripping temperature was set to 90°C and the stripping time to 1 hour. When dehydrating and drying the material after ammonia stripping, the drying temperature and time were changed to 200°C and 1 hour, respectively. The subsequent calcination temperature and time were changed to 550°C and 1 hour, respectively. Finally, the hydrogen reduction treatment temperature, time, and hydrogen flow rate were changed to 550°C, 1 hour, and 5 hours, respectively. -1(The feed is controlled by a mass flow meter after mixing with an appropriate amount of nitrogen). The catalyst codes are Cu3-Beta14C-9, Cu3-Beta18C-9, Cu3-Beta38C-9, Cu3-Beta72C-9 and Cu3-Beta94C-9.

[0187] The anti-sintering deactivation properties of the above catalysts and their samples calcined at 550 °C (3 h) were evaluated using the gas-solid phase hydroammoniation of caprolactone to caprolactam. The results showed that, under the same reaction conditions, the catalytic activity of the Cu3-Beta14C-9, Cu3-Beta18C-9, Cu3-Beta38C-9, Cu3-Beta72C-9, and Cu3-Beta94C-9 catalysts decreased by approximately 3%, 3%, 3%, 4%, and 5% respectively after high-temperature calcination.

[0188] Example 10: This example further illustrates that when preparing Cu-Beta zeolite catalysts according to the improved ammonia stripping method provided by this invention, it is permissible to use Beta zeolite matrices with different molar ratios of silicon and aluminum oxides (SiO2 to Al2O3) to prepare dent-modified dealuminized Beta zeolite supports. When using Beta zeolite with a higher molar ratio of silicon and aluminum oxides (SiO2 to Al2O3) as the matrices, a relatively mild combination of dent-modification conditions is preferable. Conversely, the opposite is also true.

[0189] Example 9 was repeated, but in the second step, when different hierarchical porous dealubilized Beta zeolite supports were subjected to dimpling modification treatment with an aqueous solution of ethanolamine, the concentration of the aqueous solution of ethanolamine was changed to 0.08 M. After dimpling modification, the reactants were filtered to recover the solid product, which was then repeatedly washed with deionized water until neutral, and then dried (overnight at 110°C) and calcined (550°C, 3 h) to obtain dimpled modified hierarchical porous dealubilized Beta zeolite supports, named Beta14C, Beta18C, Beta38C, Beta72C, and Beta94C. These were sealed and stored for later use. Based on weight reduction estimates, the average number of framework silicon atoms (calculated as SiO2) of hydroxyl lattice defect sites chiseled out in the above-mentioned dimpled modified dealubilized Beta zeolite parent materials were 0.6, 0.8, 1.0, 1.6, and 1.8, respectively. That is, the above combination of dimpling modification conditions improved the degree of desilication modification of different supports.

[0190] The catalysts prepared on the above-mentioned dented modified hierarchical porous dealaluminized Beta zeolite support by the improved ammonia stripping method are designated as Cu3-Beta14C-10, Cu3-Beta18C-10, Cu3-Beta38C-10, Cu3-Beta72C-10 and Cu3-Beta94C-10, respectively.

[0191] The anti-sintering deactivation properties of the above catalysts and their samples calcined at 550 °C (3 h) were evaluated using the gas-solid phase hydroammoniation of caprolactone to caprolactam. The results showed that, under the same reaction conditions, the catalytic activity of Cu3-Beta14C-10, Cu3-Beta18C-10, Cu3-Beta38C-10, Cu3-Beta72C-10, and Cu3-Beta94C-10 catalysts decreased by approximately 2%, 3%, 2%, 3%, and 5% respectively after high-temperature calcination.

[0192] Example 11: This example illustrates that when preparing Cu-Beta zeolite catalysts according to the improved ammonia stripping method provided by the present invention, it is permissible to use Beta zeolite matrices with different molar ratios of silicon and aluminum oxides (molar ratio of SiO2 to Al2O3) to prepare dent-modified hierarchical dealaluminized Beta zeolite supports. However, using Beta zeolite matrices with a higher molar ratio of silicon and aluminum oxides (molar ratio of SiO2 to Al2O3) to prepare dent-modified hierarchical dealaluminized Beta zeolite supports is suitable for preparing Cu-Beta zeolite catalysts with lower copper loading.

[0193] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, a Beta zeolite matrix with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio) of 100 was synthesized using the hydrothermal crystallization method provided in Chinese Invention Patent CN1108275C (application date 1999.9.10) as the raw material for preparing the hierarchical porous dealubilized Beta zeolite support. After conventional filtration, washing, drying (200℃, 3h), and calcination to remove the template agent (500℃, 8h), the synthesized Beta zeolite matrix was observed by TEM to have an average grain size of small grains (less than 1μm). XRD analysis showed no impurities, and its BET specific surface area was calculated to be higher than 530 m². 2 The molar ratio of silicon-aluminum oxide (SiO2 to Al2O3) was 94, as determined by XRF, which meets the technical requirements of this invention for the Beta zeolite matrix.

[0194] The Beta zeolite matrix was first treated with sodium hydroxide solution for alkali treatment to remove silicon and prepare a hierarchical porous Beta zeolite matrix. Then, the hierarchical porous Beta zeolite matrix was treated with concentrated nitric acid solution for acid treatment to remove aluminum, resulting in a hierarchical porous dealuminized Beta zeolite support (designated Beta94c) with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3 molar ratio) of 916 (>900). The silicon-aluminum oxide molar ratio of the support meets the technical requirements of this invention. Based on this, following the procedure in step 2 of Example 1, the above-mentioned hierarchical porous dealuminized Beta zeolite support was subjected to a cavity-removing modification treatment with an aqueous solution of ethanolamine to obtain a cavity-removing modified hierarchical porous dealuminized Beta zeolite support, named Beta94C. Further following the procedure in step 3 of Example 1, a Cu-Beta zeolite catalyst with a copper content of 6 wt.% was prepared by using a modified ammonia stripping method with two equal-volume impregnations and two ammonia stripping processes. In both instances of equal-volume impregnation, the concentration of the copper-ammonia complex solution used was 0.38 M. Since the concentration of the 0.38 M copper-ammonia complex solution is very close to that of the saturated copper-ammonia complex solution prepared with dilute ammonia, 12.5 ml of 0.4 M saturated copper-ammonia complex solution was directly used for equal-volume impregnation of the Beta94C support. The prepared catalyst is designated Cu6-Beta94C-11.

[0195] The anti-sintering deactivation properties of the catalyst and its calcined (3 h) sample were evaluated using the gas-solid phase hydroammoniation of caprolactone to caprolactam. The results showed that, under the same reaction conditions, the catalytic activity (caprolactam yield) of the Cu6-Beta94C-11 catalyst decreased by 7% after high-temperature calcination.

[0196] Example 12: This example illustrates that when preparing Cu-Beta zeolite catalysts using the improved ammonia stripping method provided by this invention, which uses a multi-level porous dealaluminized Beta zeolite modified by pore cutting as a support, the degree of desilication of the zeolite matrix and the amount of mesopores generated can be adjusted by changing the alkaline treatment conditions of sodium hydroxide solution, thereby adjusting the catalyst's anti-sintering ability and activity.

[0197] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, the sodium hydroxide solution concentration was changed to 0.3M, the liquid-to-solid ratio was changed to 5:1 (ml / g), the desilication temperature was 30℃, and the desilication time was 20 min. The results showed that the weight loss of the zeolite matrix after desilication was 9.11%, and the micropore specific surface area of ​​the hierarchical porous zeolite matrix accounted for approximately 77% of the total specific surface area. The Cu-Beta zeolite catalyst prepared based on this was designated Cu3-Beta24C-12. In the gas-solid phase hydroammoniation reaction of caprolactone, the caprolactam yield of this catalyst was 85%, and the decrease in caprolactam yield of the sample calcined at 550℃ (3 h) was less than 2%.

[0198] Example 13: This example is used to further illustrate that when preparing Cu-Beta zeolite catalyst using the improved ammonia stripping method provided by the present invention, which uses a multi-level porous dealaluminized Beta zeolite modified by pore cutting as a support, the degree of desilication of the zeolite matrix and the amount of mesopores generated can be adjusted by changing the alkaline treatment conditions of sodium hydroxide solution, thereby adjusting the catalyst's anti-sintering ability and activity.

[0199] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, the concentration of sodium hydroxide solution was changed to 0.05 M, the liquid-to-solid ratio was changed to 20:1 (ml / g), the desilication temperature was 55℃, and the desilication time was 60 min. The results showed that the weight loss of the zeolite matrix after desilication was 7.22%, and the micropore specific surface area of ​​the hierarchical porous zeolite matrix accounted for approximately 76% of the total specific surface area. The Cu-Beta zeolite catalyst prepared based on this was designated Cu3-Beta24C-13. In the gas-solid phase hydroammoniation reaction of caprolactone, the caprolactam yield of this catalyst was 86%, and the decrease in caprolactam yield of the sample calcined at 550℃ (3 h) was less than 1%.

[0200] Example 14: This example is used to further illustrate that when preparing Cu-Beta zeolite catalysts using the improved ammonia stripping method provided by the present invention, which uses a multi-level porous dealaluminized Beta zeolite modified by pore cutting as a support, the degree of desilication of the zeolite matrix and the amount of mesopores generated can be adjusted by changing the alkaline treatment conditions of sodium hydroxide solution, thereby adjusting the catalyst's anti-sintering ability and activity.

[0201] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, the sodium hydroxide solution concentration was changed to 0.5M, the liquid-to-solid ratio was changed to 2:1 (ml / g), the desilication temperature was 20℃, and the desilication time was 10 min. The results showed that the weight loss of the zeolite matrix after desilication was 9.26%, and the micropore specific surface area of ​​the hierarchical porous zeolite matrix accounted for approximately 63% of the total specific surface area. The Cu-Beta zeolite catalyst prepared based on this was designated Cu3-Beta24C-14. In the gas-solid phase hydroamination reaction of caprolactone, the caprolactam yield of this catalyst was 81%, and the decrease in caprolactam yield of the sample calcined at 550℃ (3 h) was less than 2%.

[0202] Example 15: This example is used to further illustrate that when preparing Cu-Beta zeolite catalysts using the improved ammonia stripping method provided by the present invention, which uses a multi-level porous dealaluminized Beta zeolite modified by pore cutting as a support, the degree of desilication of the zeolite matrix and the amount of mesopores generated can be adjusted by changing the alkaline treatment conditions of sodium hydroxide solution, thereby adjusting the catalyst's anti-sintering ability and activity.

[0203] Example 1 was repeated, but in the first step of preparing the hierarchical porous dealubilized Beta zeolite support, the sodium hydroxide solution concentration was changed to 0.01M, the liquid-to-solid ratio was changed to 30:1 (ml / g), the desilication temperature was 60℃, and the desilication time was 180 min. The results showed that the weight loss of the zeolite matrix after desilication was 5.56%, and the micropore specific surface area of ​​the hierarchical porous zeolite matrix accounted for approximately 76% of the total specific surface area. The Cu-Beta zeolite catalyst prepared based on this was designated Cu3-Beta24C-15. In the gas-solid phase hydroamination reaction of caprolactone, the caprolactam yield of this catalyst was 83%, and the decrease in caprolactam yield of the sample calcined at 550℃ (3 h) was less than 1%.

Claims

1. A method for preparing an anti-sintering Cu-Beta zeolite catalyst, characterized in that, The steps are as follows: The first step is to prepare a hierarchical porous dealuminolite support for Beta zeolite. (1) Select Beta zeolite parent material The aforementioned Beta zeolite matrix refers to silica-alumina Beta zeolite that meets the following requirements: 1) The Beta zeolite matrix is ​​free of impurities; 2) The Beta zeolite matrix exhibits good crystallinity, i.e., the BET specific surface area value of the Beta zeolite matrix, measured by nitrogen physical adsorption method, is ≥450 m². 2 / g; 3) The molar ratio of silicon and aluminum oxides in the Beta zeolite matrix, i.e., the molar ratio of SiO2 to Al2O3, is in the range of 15-100; (2) Preparation of hierarchical porous Beta zeolite matrix When preparing hierarchical porous Beta zeolite matrix by alkaline treatment and desilication of Beta zeolite matrix with sodium hydroxide solution, the following parameters are required: The concentration range of sodium hydroxide aqueous solution is 0.05-0.4 M; The liquid-solid ratio between the volume of sodium hydroxide aqueous solution and the amount of Beta zeolite parent material fed is in the range of 3:1-20:1, and the unit of liquid-solid ratio is ml / g; The temperature range for the desilication reaction is 20℃-55℃; The desilication reaction time ranges from 15 to 120 minutes; (3) Preparation of multi-level porous dealuminolite Beta zeolite support A hierarchical porous dealuminated Beta zeolite support was prepared by acid dealumination based on a hierarchical porous Beta zeolite matrix. The required range of the molar ratio of silicon and aluminum oxides, i.e., the molar ratio of SiO2 to Al2O3, in the prepared hierarchical porous dealuminated Beta zeolite support is ≥700. The second step involves using an aqueous solution of ethanolamine to perform pore-forming modification on the hydroxyl groups of the hierarchical porous dealuminolized Beta zeolite support. Hollowing modification of hydroxyl groups was carried out using an aqueous solution impregnation method, with the following parameter requirements: The concentration range of ethanolamine solution is 0.01 M - 0.4 M; The ratio of ethanolamine solution to hierarchical porous dealuminolized Beta zeolite support, i.e., the liquid-solid ratio, ranges from 1:1 to 100:1, and the unit of the liquid-solid ratio is ml / g. The impregnation temperature range is 20℃-100℃; The soaking time ranges from 0.5 h to 24 h; The third step involves loading copper into the pores of a hierarchical, dealuminolized Beta zeolite support using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst. The specific steps are as follows: (1) Preparation of dilute ammonia water base solution and saturated solution of copper ammonia complex: Prepare a dilute ammonia water base solution with pH value of 11-12 by diluting 4.4 g of industrial ammonia water containing 25-28 wt.% NH3 with 100 ml of deionized water, and store it in a sealed container for later use; then, according to the molar ratio of copper ions to ammonia molecules of 1:4, use copper nitrate trihydrate as a soluble copper compound to react with industrial ammonia water to synthesize copper ammonia complex; finally, dissolve the copper ammonia complex in dilute ammonia water base solution at room temperature to prepare a saturated solution of copper ammonia complex, and store it in a sealed container for later use; the concentration of copper ammonia complex ions in the saturated solution of copper ammonia complex is 0.4M; (2) Impregnating the zeolite support with an equal volume of copper ammonia complex solution: First, determine the saturated water absorption rate of the zeolite support, and calculate the amount of copper ammonia complex solution to impregnate the zeolite support with an equal volume; then, calculate the required concentration of copper ammonia complex solution according to the copper loading of the Cu-Beta zeolite catalyst to be prepared; when the calculated concentration is equal to 0.4 M, directly impregnate the zeolite support with the saturated solution of copper ammonia complex with an equal volume; when the calculated concentration is less than 0.4 M, dilute the saturated solution of copper ammonia complex with dilute ammonia water base solution appropriately, and then impregnate the zeolite support with an equal volume. When the calculated value is higher than 0.4M, the concentration of the copper ammonia complex solution for a single equal-volume impregnation should be recalculated according to multiple equal-volume impregnations. The copper ammonia complex solution of the required concentration should be prepared using dilute ammonia water base solution and saturated copper ammonia complex solution for each equal-volume impregnation. After each impregnation, the zeolite carrier must be subjected to ammonia stripping treatment; the equal-volume impregnation is carried out at room temperature in a closed container; the equal-volume impregnation time ranges from 0.5 to 24 hours. (3) Ammonia stripping treatment: The ammonia stripping process is carried out under normal or reduced pressure; the temperature and time range for ammonia stripping are 50-100℃ and 0.5-48 h, respectively. (4) Dehydration and drying treatment after ammonia stripping: The drying temperature and time ranges are 100-200℃ and 0.5-48 h, respectively; (5) Roasting treatment after ammonia stripping: Roasting is carried out in an air atmosphere, with roasting temperature and time ranging from 350-650℃ and 0.5-24 h, respectively; The catalyst precursor was obtained by calcination. (6) Hydrogen reduction treatment of catalyst precursor: The reduction temperature, time and hydrogen volume hourly space velocity ranged from 280-600℃, 0.5-20 h and 1-2000 h, respectively. -1 The catalyst precursor is reduced with hydrogen to become Cu-Beta zeolite catalyst.

2. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 1, characterized in that, The steps are as follows: In step (1), the molar ratio of silicon aluminum oxide in the Beta zeolite matrix, i.e., the molar ratio of SiO2 to Al2O3, is in the range of 20-80.

3. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 2, characterized in that, The steps are as follows: In step (1), the molar ratio of silicon aluminum oxide in the Beta zeolite matrix, i.e., the molar ratio of SiO2 to Al2O3, is in the range of 25-60.

4. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 3, characterized in that, The steps are as follows: In step (2), when preparing hierarchical porous Beta zeolite matrix by alkaline treatment and desilication of Beta zeolite matrix with sodium hydroxide solution, the following parameters are required: The concentration range of sodium hydroxide aqueous solution is 0.1-0.3 M; The liquid-solid ratio between the volume of sodium hydroxide aqueous solution and the amount of Beta zeolite parent material fed is in the range of 5:1 to 15:1, and the unit of liquid-solid ratio is ml / g; The temperature range for the desilication reaction is 25℃-45℃; The desilication reaction time ranges from 20 to 60 minutes.

5. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 1, characterized in that, The steps are as follows: In step (2), when the Beta zeolite matrix is ​​desiliconized by alkaline treatment with sodium hydroxide solution to prepare multi-level porous Beta zeolite matrix, the specific steps are as follows: First, the Beta zeolite matrix is ​​pretreated by drying and calcination. The drying temperature range is 80-200℃ and the drying time is 3-24 h. The calcination temperature range is 500℃-600℃ and the calcination time is 3-8 h. Secondly, the pretreated Beta zeolite matrix is ​​subjected to desilication treatment, including: heating the sodium hydroxide solution to the desilication reaction temperature, then adding the pretreated Beta zeolite matrix to the sodium hydroxide solution according to the liquid-solid ratio, and reacting under stirring conditions; finally, after the reaction is completed, the reactants are immediately cooled, and the solid product is recovered by solid-liquid separation, then the solid product is washed with water until the pH value is neutral, then dried at 80-200℃ for 3-24 h, and calcined at 500℃-600℃ for 1-6 h to obtain a hierarchical porous Beta zeolite matrix.

6. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 1, characterized in that, In the first step (3), the molar ratio of silicon aluminum oxide to Al2O3 in the multi-level porous dealuminolite Beta zeolite carrier is required to be ≥800.

7. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 6, characterized in that, In the first step (3), the molar ratio of silicon aluminum oxide to Al2O3 in the multi-level porous dealuminolite Beta zeolite carrier is required to be ≥900.

8. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 1, characterized in that, In step (3), when preparing a hierarchical porous dealuminolized Beta zeolite support by acid dealuminolization of the hierarchical porous Beta zeolite matrix using concentrated nitric acid aqueous solution, the specific steps are as follows: 13 M concentrated nitric acid was used as the dealumination acid solution, with a liquid-to-solid ratio of 20:1 (ml / g). The dealumination reaction was carried out at 95℃ for 20 h. After the dealumination reaction, the solid product was first recovered by solid-liquid separation, then washed with water until the pH value was neutral, dried at 80-200℃ for 3-24 h, and calcined at 500℃-600℃ for 3-8 h to obtain the multi-porous dealumination Beta zeolite support.

9. The method for preparing the anti-sintering Cu-Beta zeolite catalyst according to claim 1, characterized in that, In the second step, the hydroxyl groups of the hierarchical porous dealuminolized Beta zeolite support are modified by aqueous solution impregnation using an aqueous solution of ethanolamine. The parameters are as follows: The concentration range of the ethanolamine solution is 0.02 M-0.3 M; The ratio of ethanolamine solution to hierarchical porous dealuminolized Beta zeolite support, i.e., the liquid-solid ratio, ranges from 2:1 to 50:1, and the unit of the liquid-solid ratio is ml / g. The impregnation temperature range is 30℃-90℃; The soaking time ranges from 1 h to 10 h.

10. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 9, characterized in that, In the second step, the hydroxyl groups of the hierarchical porous dealuminolized Beta zeolite support are modified by aqueous solution impregnation using an aqueous solution of ethanolamine. The parameters are as follows: The concentration range of ethanolamine solution is 0.03M - 0.16M; The ratio of ethanolamine solution to hierarchical porous dealuminolized Beta zeolite support, i.e., the liquid-solid ratio, ranges from 3:1 to 20:1, and the unit of the liquid-solid ratio is ml / g. The impregnation temperature range is 40℃-80℃; The soaking time ranges from 2 to 5 hours.

11. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 1, characterized in that, In step 3 (2), the immersion time for equal volume is in the range of 1-12 h; In the third step (3), the temperature and time range for ammonia stripping are 60-90℃ and 1-24 h; In the third step (4), the drying temperature and time ranges are 110-170℃ and 1-24 h, respectively; In the third step (5), the roasting temperature and time ranges are 400-600℃ and 1-12 h, respectively; In step 3 (6), the reduction temperature, time, and hydrogen volume hourly space velocity ranges are 300-550℃, 1-15 h, and 10-1500 h, respectively. -1 .

12. The method for preparing an anti-sintering Cu-Beta zeolite catalyst according to claim 11, characterized in that, In step 3 (2), the immersion time for equal volume is in the range of 2-6 h; In the third step (3), the temperature and time range for ammonia stripping are 65-85℃ and 3-12 h; In the third step (4), the drying temperature and time ranges are 120-150℃ and 3-12 h, respectively; In the third step (5), the roasting temperature and time ranges are 450-550℃ and 2-6 h, respectively; In step 3 (6), the reduction temperature, time, and hydrogen volume hourly space velocity ranges are 350-500℃, 2-8 h, and 20-1000 h, respectively. -1 .

13. The Cu-Beta zeolite catalyst prepared by the method of any one of claims 1-12 is used to catalyze the gas-solid phase hydroammoniation of caprolactone to caprolactam.

14. The application according to claim 13, characterized in that, The reaction conditions are as follows: reaction temperature range is 120-350℃, reaction pressure range is 0.01-2 atm, and feed space velocity of caprolactone ranges from 0.1 to 5 h⁻¹. -1 The suitable ranges for the molar ratios of amine-ester, hydrogen-ester, and water-ester are 1-50, 5-70, and 0-100, respectively.

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