Method for preparing cu-beta zeolite catalyst for production of caprolactam from caprolactone, and use

Abstract

The present invention relates to the technical field of petrochemical catalysis, and relates to a method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone, and a use. The main technical feature of the present invention is that by using dealuminated Beta zeolite as a carrier, copper is loaded in pore channels of the zeolite carrier by means of an improved ammonia evaporation method. The core of the improved ammonia evaporation method is to impregnate the zeolite carrier with a copper-ammonia complex solution in an equal volume, so that a copper-ammonia complex mainly undergoes, in the pore channels of the zeolite carrier and during ammonia evaporation, a reaction of depositing copper hydroxide. After roasting and hydrogen reduction treatment, the copper hydroxide deposited in the pore channels of the zeolite can directly form highly dispersed nano and sub-nano copper particles at lattice defect sites of hydroxyl nests in the pore channels, and the sub-nano copper particles obtain sintering resistance by means of tight interaction with the hydroxyl nests. When the Cu-Beta zeolite catalyst prepared by the method of the present invention is applied to the production of caprolactam from caprolactone via gas-solid phase hydroamination, high activity and selectivity and good stability are achieved.

Description

Preparation method and application of Cu-beta zeolite catalyst for preparing caprolactam from caprolactone TECHNICAL FIELD

[0001] The present application belongs to the field of petroleum chemical catalysis, and relates to a preparation method and application of a Cu-Beta zeolite catalyst for preparing caprolactam from caprolactone. BACKGROUND

[0002] ε-Caprolactam (CPL) is a white solid organic compound, most of which is used to produce polycaprolactam chips, and a small part of which is used to produce lysine and pharmaceutical intermediates. In the downstream products of polycaprolactam chips, nylon-6 fiber and engineering plastic consume about 70% and 20% of polycaprolactam chips, respectively. The remaining polycaprolactam chips are processed into packaging film and food preservation film.

[0003] Nylon-6 is the first synthetic fiber product developed in the world. The most prominent advantage of nylon-6 fiber is that its wear resistance is higher than that of all other fibers. It is 10 times higher than that of cotton and 20 times higher than that of wool. At the same time, the strength of nylon-6 fiber is 1-2 times higher than that of cotton and 4-5 times higher than that of wool, and is 3 times that of viscose fiber. Adding a small amount of polyamide fiber to blended fabrics can greatly improve its wear resistance, elastic recovery rate and folding breaking resistance. In addition, nylon-6 fiber also has good moisture absorption and dyeing properties. Nylon-6 fiber can be used as civilian silk and industrial silk. Nylon civilian silk is used to make shirts, sweaters, pajamas, carpets, blankets, curtain lines and luggage, etc.; industrial silk is used to make tents, automobile tires, transmission belts, hoses, cables, fishing nets, ropes, insulating materials, etc.

[0004] At present, the benzene method caprolactam process has become the mainstream production process of caprolactam. The process mainly includes three basic processes of benzene to cyclohexanone, cyclohexanone to cyclohexanone oxime, and rearrangement of cyclohexanone oxime to caprolactam.

[0005] Benzene to cyclohexanone is the first step of the benzene method caprolactam process. There are mainly two process routes in industry, namely cyclohexane oxidation method and cyclohexene hydration method. Since 2017, the cyclohexene hydration method has exceeded the cyclohexane oxidation method to become the largest source of cyclohexanone in the world.

[0006] Cyclohexane to cyclohexanone mainly adopts liquid phase oxidation method. This method takes benzene and hydrogen as starting materials, first obtains cyclohexane by benzene hydrogenation, then generates cyclohexanone and cyclohexanol by cyclohexane air oxidation, decomposition and saponification, and then makes cyclohexanol dehydrogenation into cyclohexanone. This method has the advantages of mild process conditions, simple operation and mature technology. Its main disadvantages are low product yield (only 75%-80%), high raw material consumption, high energy consumption, many by-products which are difficult to separate, and environmental unfriendliness.

[0007] Cyclohexene hydration method is a cyclohexanone production technology developed by Asahi Kasei Corporation in the 1980s (Japanese Patent JP 60104031A, 1985), which can make the utilization rate of benzene reach 99.5%. The first step of the technology is to partially hydrogenate benzene to generate cyclohexene (about 80%) in the presence of a ruthenium-based catalyst, and the by-product is cyclohexane. The second step is to separate the cyclohexene and make the cyclohexene hydrate to generate cyclohexanol in the presence of a solid acid catalyst. The third step is to dehydrogenate the cyclohexanol to generate cyclohexanone in the presence of a Cu-Si catalyst. Compared with the cyclohexane oxidation method, the reaction process of the cyclohexene hydration method for producing cyclohexanone is simple, and the problems of coking and waste alkali liquor are avoided. However, the production efficiency of the process is low, and the energy consumption is large.

[0008] Cyclohexanone is the second step and the most core step of the benzene process caprolactam process. The common production processes of this step include the hydroxylamine sulfate method (HSO), the hydroxylamine phosphate method (HPO), the nitric oxide reduction method (NO), and the ammonium oximation method (HAO).

[0009] The process principle of the hydroxylamine sulfate method is: first, NH3 is catalytically oxidized into a mixture of NO and NO2, and the gas mixture is absorbed by (NH4)2CO3 solution to obtain NH4NO2, then NH4NO2 is reduced to hydroxylamine disulfonate with SO2 at low temperature, and the disulfonate is hydrolyzed into hydroxylamine sulfate. Second, cyclohexanone is subjected to oximation reaction with hydroxylamine sulfate to produce cyclohexanone oxime. The generation of ammonium sulfate by-product is caused by the need to use NH3 to neutralize free sulfuric acid. The amount of ammonium sulfate by-product generated is 2.5-2.7 tons of ammonium sulfate per ton of cyclohexanone oxime. The main disadvantage of this process is the consumption of a large amount of SO2 and the generation of ammonium sulfate, which is not conducive to the production efficiency of caprolactam. In addition, the hydroxylamine sulfate method also has the disadvantages of long production process, high energy consumption, and large amount of three wastes emission. These disadvantages limit the development of the hydroxylamine sulfate method.

[0010] The hydroxylamine phosphate method is developed by DSM. The first step of this method is to prepare hydroxylamine phosphate salt by reducing phosphoric acid and ammonium nitrate with hydrogen gas in the presence of Pd / C catalyst, and the second step is to make cyclohexanone react with hydroxylamine phosphate salt in an ammonium dihydrogen phosphate buffer solution to generate cyclohexanone oxime. After the separation of cyclohexanone oxime, 60% nitric acid solution is added to supplement the consumed nitrate ions, and phosphoric acid and ammonium nitrate can be returned to the hydroxylamine synthesis process for reuse. The disadvantage of the hydroxylamine phosphate method is the use of noble metal catalysts and the difficulty of process operation.

[0011] The nitric oxide reduction method is jointly developed by BASF of Germany, Inventa of Switzerland and Zaklady Azotowe of Poland. The first step of the method is to react ammonia and oxygen to generate nitric oxide, and to hydrogenate the nitric oxide in aqueous sulfuric acid under the action of platinum catalyst to generate hydroxylamine sulfate salt. The second step is to perform oximation reaction of hydroxylamine sulfate salt with cyclohexanone to generate cyclohexanone oxime. The method is relatively mature, the consumption of ammonia and hydrogen is low, and no by-product ammonium sulfate is generated in the generation of hydroxylamine, but oxygen and hydrogen are used in the production, which is prone to accidents. In addition, the platinum catalyst used in the process is easily poisoned by metal ions such as arsenic, mercury and aluminum contained in the aqueous sulfuric acid.

[0012] The cyclohexanone ammonoximation method (HAO method) was proposed by Armor of United States Chemical Corporation in 1980. The method initially uses oxygen as oxidant and amorphous silicon dioxide as catalyst to catalyze the reaction of cyclohexanone, oxygen and ammonia to prepare cyclohexanone oxime at 467K. The reaction method is suitable for other ketones. For example, acetone, 3-pentanone, 2-methylcyclohexanone and phenylacetone can all generate corresponding ketone oxime under certain conditions. The preparation method is simple and does not require additional synthesis of hydroxylamine salt. However, the conversion rate of cyclohexanone is not ideal (54%) and the selectivity of cyclohexanone oxime is low (51%). In addition, the by-products generated in the reaction remain on the catalyst, accelerating the coking and deactivation of the catalyst.

[0013] In 1987, US patent US4745221 first disclosed a new technical route of TS-1 catalyzed cyclohexanone liquid phase ammonoximation, which is the ammonoximation method. Specifically, the technical route is to react cyclohexanone with ammonia and hydrogen peroxide to generate cyclohexanone oxime under the catalysis of TS-1 with t-butyl alcohol and water as solvent, which can achieve a high yield of more than 99%, and can avoid the generation of low-value ammonium sulfate, is environmentally friendly, and has realized large-scale industrial application. Compared with the hydroxylamine sulfate method and the hydroxylamine phosphate method, the ammonoximation method has the advantages of low hydrogen consumption, short production process, simple control, low requirement for equipment and pipeline material, and less investment and land occupation.

[0014] As known by those skilled in the art, the ammonoximation method has made great achievements in industrial application. However, the process still faces some challenges. For example, the recycling of a large amount of t-butyl alcohol solvent leads to increased separation cost; the by-products generated in the reaction process cause the deactivation of TS-1 catalyst; the titanium-silicon molecular sieve catalyst is expensive and has high cost allocation; the cyclohexanone ammonoximation to produce cyclohexanone oxime is a liquid phase reaction, and the titanium-silicon molecular sieve catalyst is in a strong alkaline environment for a long time, which cannot avoid the dissolution of the skeleton silicon on the catalyst. This not only causes the invalid loss of the catalyst, but also shortens the service life of the catalyst and affects the stable operation of the ammonoximation reaction system; in addition, the liquid-solid phase reaction has the disadvantage of large mass transfer resistance, and the internal diffusion problem of the catalyst is serious.

[0015] The Beckmann rearrangement of cyclohexanone oxime to caprolactam is the third step in the benzene route to caprolactam and is also a critical step. Currently, about 90% of the caprolactam produced industrially is produced by the Beckmann rearrangement. There are two process routes for the Beckmann rearrangement to produce caprolactam, i.e. liquid phase rearrangement and gas phase rearrangement.

[0016] The liquid phase Beckmann rearrangement is the most important process for the production of caprolactam at present. This process has been industrialized for a long time and the technology is relatively mature. The liquid phase Beckmann rearrangement is a rearrangement process using oleum as catalyst. The reaction conditions are mild, the selectivity is high, the yield of caprolactam is high, and the product quality is relatively stable. However, because oleum with strong corrosive property is used, the equipment is corroded, and 1.5-1.8 tons of ammonium sulfate is produced as by-product per ton of caprolactam. In addition, the consumption of liquid ammonia is large in this process. Not only is there the problem of low-value ammonium sulfate by-product, but also there is the difficulty of handling a large amount of neutralization heat, which affects the technical economy of the process to some extent.

[0017] Compared with the liquid phase Beckmann rearrangement process, the gas phase Beckmann rearrangement is a more advanced process. Since the late 1980s, people have begun to work on the Beckmann rearrangement of cyclohexanone oxime using solid acid catalysts instead of oleum. The open literature AFINIDAD (Spain), 1981, 38(373) 225-227 reported the research work on the Beckmann rearrangement of cyclohexanone oxime on a series of AlPO4 / γ-Al2O3 catalysts. The results showed that with the increase of the acidity of the catalyst, the reaction activity increased. However, the selectivity of the rearrangement reaction decreased, and the yield of the gas phase Beckmann rearrangement of cyclohexanone oxime could reach 73.1% at most. The open literature Shokubai, 1989, 31(6):365-368 reported the gas phase Beckmann rearrangement of cyclohexanone oxime catalyzed by high-silicon ZSM-5 molecular sieve in 1989. At present, the gas phase Beckmann rearrangement catalyzed by high-silicon ZSM-5 molecular sieve has become a new technology for the production of caprolactam. The gas phase Beckmann rearrangement technology can complete the conversion of cyclohexanone oxime to caprolactam under the action of a solid acid catalyst. This process does not use oleum, and the process of neutralizing sulfuric acid is omitted, so that no by-product ammonium sulfate is produced, the consumption of liquid ammonia in the production of caprolactam is greatly reduced, and problems such as equipment corrosion and environmental pollution are avoided, which has attracted widespread interest.

[0018] US4717769 (1987) discloses a method for the gas-solid phase rearrangement of cyclohexanone oxime using a high-silicon molar ratio (>500) MFI type molecular sieve as catalyst. Under the condition of a weight hourly space velocity of 11.7 h -1 , the conversion rate of cyclohexanone oxime is still 100% after 15.3 hours of reaction. However, the selectivity of caprolactam is very low (83.5%).

[0019] US6303099 (2000) discloses a process for the Beckmann rearrangement of cyclohexanone oxime to caprolactam using a modified high-silica zeolite as catalyst. The technical feature is that the modified catalyst is obtained by post-treatment of high-silica molar ratio molecular sieve powder with a nitrogen-containing base. The conversion of cyclohexanone oxime is 99.5% and the selectivity of caprolactam is 96.2% under the conditions of 8 h -1 -1 space velocity, 5.5 h reaction time and 370 °C reaction temperature.

[0020] CN1883803A (2005) also discloses a process for the Beckmann rearrangement of cyclohexanone oxime to caprolactam using a modified high-silica zeolite as catalyst. The technical feature is that the modified catalyst is obtained by post-treatment of pure-silica and high-silica molar ratio molecular sieve with hydrofluoric acid. The conversion of raw material is 98.3% and the selectivity of product is 98.5% under the conditions of 8 h -1 -1 space velocity, 60 ml / min carrier gas flow, 20 h reaction time and 370 °C reaction temperature. The best reaction result is basically achieved.

[0021] In addition to patent documents, there are many journal papers related to the gas phase Beckmann rearrangement of cyclohexanone oxime to caprolactam. For example:

[0022] The paper Studies in Surface Science and Catalysis, 1993, 78: 615-622 reports the catalytic performance of AlPO4 and AlPO4 / TiO2 catalysts for the gas phase Beckmann rearrangement of cyclohexanone oxime. The results show that the reaction activity increases and the selectivity of caprolactam decreases with the increase of the acidity of the catalyst; within the temperature range of 200-400 °C, the activity and selectivity of both AlPO4 and AlPO4 / TiO2 catalysts increase with the increase of temperature. Under the same reaction conditions, the activity and selectivity of the AlPO4 / TiO2 catalyst are superior to those of the AlPO4 catalyst. In the AlPO4 / TiO2 catalyst, increasing the TiO2 content leads to the decrease of the surface acidity of the catalyst, thus resulting in the decrease of the activity and the increase of the selectivity of the catalyst.

[0023] The publication Applied Catalysis A: General, 1999: 99-108 reported the catalytic performance of Al and B modified β molecular sieve catalysts for the gas phase Beckmann rearrangement of cyclohexanone. It was found that β molecular sieve and [B]-ZSM-5 were similar, when the reaction temperature and pressure were lowered, the selectivity of caprolactam over [B]-β and [Al]-β molecular sieve catalysts were both significantly improved. However, at lower reaction temperature and pressure, the deactivation rate of the catalysts was accelerated. In contrast, [B]-β molecular sieve deactivated more severely, about fifteen times faster than [Al]-β molecular sieve. It was also found that the active sites of [Al]-β and [B]-β molecular sieve catalysts for the Beckmann rearrangement of cyclohexanone oxime were ortho-silanol groups.

[0024] In 2003, Sumitomo Chemical Co., Ltd. of Japan developed the gas phase Beckmann rearrangement of cyclohexanone oxime technology and realized industrial application. According to the publication Contemporary Petroleum and Petrochemicals, 2019, 27(04): 32-36, the gas phase rearrangement technology of Sumitomo Chemical Co., Ltd. used a fluidized bed reactor, high-silicon MFI molecular sieve as catalyst, methanol as solvent, nitrogen as carrier gas, under the conditions of reaction temperature 350-400℃, weight hourly space velocity 8h -1 -1, the conversion of cyclohexanone oxime reached more than 99%, and the selectivity of caprolactam reached more than 95%. Sinopec Petrochemical Research Institute also developed a similar gas phase rearrangement technology, but the reactor was a radial moving bed, the conversion of cyclohexanone oxime was as high as more than 99.9%, and the average selectivity of caprolactam was as high as 96.5%. By the end of 2020, the small-scale and pilot-scale technology research had been completed.

[0025] Applied Catalysis A: General, 2005: 145-153 reported a series of composite metal oxide catalysts for the catalytic performance of cyclohexanone oxime gas phase Beckmann rearrangement reaction. The study found that with ammonia as a co-precipitation agent, the composite oxide TiO2-ZrO2 was prepared by co-precipitation method, and then an equal volume of impregnation method was used to prepare B2O3 / TiO2-ZrO2 catalyst, which could reach 100% conversion rate and 97.4% selectivity for Beckmann rearrangement reaction. The results were significantly better than B2O3 / SiO2-Al2O3, B2O3 / SiO2-TiO2, B2O3 / SiO2-ZrO2, B2O3 / Al2O3-TiO2, B2O3 / Al2O3-ZrO2 catalysts. Within the range of 500-700°C, increasing the calcination temperature was beneficial to the generation of medium strength acid centers, thereby increasing the conversion rate of cyclohexanone oxime and the selectivity of the product; but when the calcination temperature was higher than this range, a large amount of B2O3 crystal phase would appear, which was not conducive to the catalytic activity and selectivity of B2O3 / TiO2-ZrO2. The study found that polar solvents were conducive to the desorption of caprolactam from the active center, improving the selectivity of caprolactam, and also prolonging the service life of the catalyst. Acetonitrile was the most polar solvent in the study solution and was the best solvent. In the study of deactivation and regeneration of B2O3 / TiO2-ZrO2 catalyst, it was found that the pore size distribution and structure of the deactivated catalyst did not change, but the acid sites were reduced. Carbon deposition was the main reason for the deactivation of the catalyst. The deactivated catalyst could completely restore its activity after calcination at 600°C for 8h.

[0026] Catalysis Communications, 2005: 53-56 reported the catalytic performance of different β zeolite catalysts for the gas phase Beckmann rearrangement reaction of cyclohexanone oxime. The different β zeolite catalysts included Hβ molecular sieve catalyst modified by boron acid impregnation (B2O3 / Hβ), a series of Ti-Hβ molecular sieves synthesized by liquid-solid isomorphous substitution of Ti(SO4)2 solution on Hβ molecular sieve, and modified catalyst obtained by treating Hβ molecular sieve with ammonia. The results showed that compared with the hydrothermally synthesized Hβ molecular sieve matrix, the BET surface area of Ti-Hβ molecular sieve and Hβ molecular sieve modified with ammonia increased. The BET area of B2O3 / Hβ catalyst modified by 9.09w% boron oxide decreased. However, the total acid amount and weak acid amount of the three modified catalysts increased, especially the amount of weak B acid increased significantly. In the Beckmann rearrangement reaction, the activity and selectivity of the above modified catalysts increased, and the deactivation rate decreased. According to the above results, the authors speculated that in the gas phase Beckmann rearrangement reaction, the weak B acid site was the real catalytic active center.

[0027] The document Catalysis Today, 2012: 289-299 reports the research work of synthesizing caprolactam under different conditions using amorphous silica gel impregnated with niobium pentoxide (Nb2O5) as a cheap catalyst (Nb2O5 / SiO2). The results show that the conversion rate of cyclohexanone oxime is close to 100% and the selectivity of caprolactam is as high as 98% using Nb2O5 / SiO2 as the catalyst.

[0028] As known by those skilled in the art, there are two difficulties in the technical development of the gas-phase Beckmann rearrangement reaction. One is that cyclohexanone oxime needs to participate in the reaction in the gas phase, but since the boiling point of cyclohexanone oxime is relatively high (the normal pressure boiling point is 203°C), and the substance has poor high-temperature thermal stability, it will be metamorphosed at 160°C, so how to gasify cyclohexanone oxime without metamorphosis is a challenging problem that must be faced in the development process of the gas-phase rearrangement process. In addition, the catalyst is easy to be deactivated in the gas-phase rearrangement reaction. In order to ensure the continuous and stable progress of the reaction, how to restore the activity of the catalyst online has also become a difficulty that needs to be solved in the development process of the gas-phase Beckmann rearrangement. The above two points are still obstacles to the large-scale industrialization of the cyclohexanone oxime gas-phase Beckmann rearrangement method.

[0029] In view of the current situation of the benzene method caprolactam production process and the problems faced by the development of new processes, it is imperative to take a different approach to obtain a new caprolactam preparation process without low-value co-products (such as ammonium sulfate), without equipment corrosion and environmental pollution problems, with high process atomic utilization rate, low energy consumption (low carbon emissions).

[0030] In the literature research, it was found that as early as in 1957, Shell Company disclosed a method for preparing caprolactam from caprolactone in US2817646. Specifically, the method uses a hydrogenation catalyst (such as neutral Raney nickel) to prepare caprolactam from ammonia, hydrogen and caprolactone raw materials at 175-200°C and 7-40 standard atmospheres. However, the main product of the reaction is actually various amides, such as polyamide, amide and hydroxyamide. The yield of caprolactam is only about 4%. Obviously, the selectivity of this method is so poor that it has no application value.

[0031] In 1961, UCC disclosed a method for preparing caprolactam in US3000879. The method is to heat a 25% 6-hydroxyhexanamide aqueous solution to 300-475°C in a closed container to prepare caprolactam by a non-catalytic reaction route under high pressure (the pressure reaches 15 MPa), and a 30% single-pass caprolactam yield can be obtained. It is undoubtedly impossible to imagine that a bulk chemical is produced by a batch kettle at high temperature and high pressure for industrialization.

[0032] In the same year, Union Carbide Corporation disclosed again in US Patent US3000800 a process for the production of caprolactam from caprolactone. Specifically, the process is a hydrolysis of caprolactone in the presence of ammonia at high pressure (P > 22.1 MPa) and above the critical temperature of ammonia and water (373°C <t>473°C) to produce caprolactam by non-catalytic reaction. This method has been successfully commercialized, but the process can only be carried out under high temperature and high pressure, and the energy consumption is huge. Moreover, the non-catalytic reaction under high temperature and high pressure tends to produce polymer, so the actual yield of caprolactam is less than 50%. This is probably the main reason why the Union Carbide Corporation stopped the production line for producing caprolactam from caprolactone. On the other hand, the caprolactone raw material at that time came from the oxidation reaction of cyclohexanone and peracetic acid. Peracetic acid is a strong oxidant and is extremely unstable. Peracetic acid will explode when it comes into contact with high heat, reducing agents or metal ions. In fact, peracetic acid has explosive properties when its concentration is greater than 45%, and it can even explode at -20°C. Therefore, the production process of caprolactone at that time was extremely dangerous. This is also probably an important reason why the Union Carbide Corporation stopped the production line for producing caprolactam from caprolactone.

[0033] In 1964, Teijin Corporation of Japan disclosed a catalytic method for producing caprolactam from caprolactone, 6-hydroxycaproamide or amide derivatives of 6-hydroxycaproic acid in US Patents US3317516 and US3317517. Specifically, the catalytic method disclosed in the above patents is to heat caprolactone, 6-hydroxycaproamide or amide derivatives of 6-hydroxycaproic acid and ammonia together to 200-400°C in a high-pressure reactor under the catalysis of a hydrogenation catalyst containing at least one or a combination of noble metals, cobalt and nickel, to produce caprolactam with less color. The method can be selected to be used under a hydrogen atmosphere. Obviously, the reaction conditions of the catalytic method are relatively mild. However, the single-pass yield of caprolactam obtained by this method is also not high, with a maximum of only 45.1%, so the economic efficiency of this method is not high.

[0034] In 1965, Union Carbide Corporation disclosed a continuous two-stage process for the production of caprolactam in US patent US3320241. The technical background of this process is that people have known that caprolactam can be produced by the non-catalytic reaction of caprolactone and ammonia water under high temperature and high pressure. However, the reaction under high temperature and high pressure is not suitable for industrial application. First, the single-pass yield of the reaction is relatively low due to the limitation of reaction equilibrium. Second, a large amount of irreversible by-products are produced during the reaction process. Since the yield of each process is low, the reaction intermediates and unconverted caprolactone must be recycled, which increases energy consumption and carbon emissions. In addition, due to the generation of a large amount of irreversible by-products, the separation process is also very complex. All of these make the operation cost too high. Accordingly, the new process disclosed in this patent is to make the mixture of caprolactone, ammonia and water react at a relatively low temperature in the first stage of conversion, and the reaction time is controlled to convert a large amount of caprolactone into reaction intermediates. Then, in the second stage of conversion, the products of the first stage of conversion are converted at a high temperature (300-400℃) and ultra-high pressure (136-680 standard atmospheres) required for the formation of caprolactam. Downstream of the two-stage conversion reaction is the separation stage. The task of the separation stage is to separate caprolactam from the mixture containing caprolactone and reaction intermediates, and to recycle the unreacted substances and intermediates back to the first stage for conversion. Since the intermediates can be converted through the entire two-stage process after returning to the first stage, the reaction time is long, which is conducive to the maximum conversion to the target product caprolactam. The caprolactam separated from the second stage reaction mixture must be purified in multiple steps to become a pure product. All the raffinates produced during the product purification process can be recycled back to the first stage for re-conversion to become the target product as much as possible. The yield of caprolactam can reach 90.2% using this process. The process flow is complex and the second step is still a high-pressure reaction, which has very high requirements for production equipment and management, and the industrialization is also more difficult.

[0035] In 1966, KANEGAFUCHI, BOSEKI KABUSHIKI KAISHA first disclosed a catalytic method for preparing caprolactam from caprolactone in gas phase in British patent GB1109540. The method is to first vaporize caprolactone and a certain amount of water, and then mix with ammonia gas and hydrogen gas. The mixed gas is catalytically reacted at 120-350℃ and normal 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%. However, the resin generated by the polymerization side reaction is deposited on the catalyst, which leads to the rapid deactivation of the catalyst. This becomes a major obstacle to the industrial application of this method. In addition, the copper chromite catalyst used in this method is toxic and will produce a large amount of chromium-containing wastewater during preparation, which is not conducive to environmental protection.

[0036] In 1967, DuPont Canada Inc. disclosed in Canadian Patent CA770148 a non-catalytic process for the production of caprolactam from caprolactone. The process involves the reaction of caprolactone or polycaprolactone with aqueous ammonia in a stainless steel reactor at 305-365°C under 18-45 MPa. The maximum caprolactam yield obtained is 85%. The process disclosed in this patent indicates that polycaprolactone is a by-product which can be converted back to the desired product.

[0037] In 1968, Stamicarbon disclosed in U.S. Patent 3,401,161 a non-catalytic process for the production of caprolactam from caprolactone in an inert organic solvent. The reaction is carried out at very high temperature and pressure (T > 330°C, 125 atm > P > 90 atm) and the maximum caprolactam yield obtained is 60%. The organic solvents which can be used are pyridine, dibutyl ether, diacyl ether, dioxane, toluene, xylene, decalin, heptane and octane.

[0038] In 1970, Union Carbide Corporation disclosed in U.S. Patent 3,497,500 a non-catalytic process for the production of caprolactam from caprolactone at high temperature and pressure. The process emphasizes the importance of removing a portion of the carbon dioxide produced in the reaction system. In brief, according to this patent, the presence of an excess of carbon dioxide atmosphere in the reaction system is detrimental to the satisfactory production of caprolactam in the reaction of caprolactone to caprolactam at high temperature and pressure.

[0039] In 1972, KANEGAFUCHI, BOSEKI KABUSHIKI KAISHA disclosed a caprolactam production process using copper chromite as catalyst in U.S. Patent 3652549. The copper chromite catalyst was prepared by coprecipitation method using copper nitrate and ammonium dichromate as raw materials and ammonia as precipitant. The technical features of the catalyst preparation process include that the precipitate formed in the coprecipitation reaction is further soaked in dilute acetic acid solution after filtration, dehydration, low temperature drying (75-80°C, 20h) and high temperature decomposition. The catalyst precursor after soaking is treated by filtration, water washing and drying (125°C, 12h) to become catalyst. The catalyst is pressed into tablets before use in fixed bed reactor. The catalyst is also reduced by hydrogen at 200°C before use. The atomic ratio of chromium to copper in the copper chromite catalyst is 0.1-5, preferably 0.1-3. The catalyst can 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 caprolactam production 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 gas-solid phase, the reaction temperature is in the range of 170-300°C, and the hydrogen partial pressure is in the range of 0.1-1.5 atm. The feed also contains ammonia and water vapor, and their preferred amount (molar ratio to raw material) is in the range of 2-50 and 10-100, respectively. When dimethyl adipate is used as raw material, the reaction results of copper chromite catalyst containing a small amount of zinc are: raw material conversion rate is 99%, and caprolactam selectivity is 95%; the reaction results of copper chromite catalyst containing a small amount of Mo are: raw material conversion rate is 100%, and caprolactam selectivity is 96%.

[0040] In 1975, Japan's Teijin Corporation disclosed a catalytic process for the production of caprolactam from caprolactone or C1-C4 alkyl ester of 6-hydroxycaproic acid in US Patent 3888845. Specifically, the patent disclosed a process for the production of caprolactam from caprolactone or C1-C4 alkyl ester of 6-hydroxycaproic acid, hydrogen and ammonia as raw materials, through gas-solid phase catalytic reaction. The process is characterized by low reaction temperature and low reaction pressure, high conversion rate of caprolactone or C1-C4 alkyl ester of 6-hydroxycaproic acid, and high selectivity of caprolactam. The solid catalyst used in the process is composed of three parts: A, a kind of oxide carrier, selected from titanium oxide, aluminum oxide, silicon oxide and a composite of aluminum oxide and silicon oxide; B, the main metal component of the catalyst, copper; and C, the trace metal component of the catalyst, which can be nickel or chromium. The catalyst can be prepared by deposition precipitation method. Among them, the carrier is preferably anatase titanium oxide, the weight ratio of copper to the carrier can be selected in the range of 0.5-200, preferably 5-100, and more preferably 10-70; the atomic ratio of Ni(Cr) to Cu can be selected in the range of 0.001-1, preferably 0.005-0.25. The gas-solid phase catalytic reaction for the production of caprolactam from caprolactone or C1-C4 alkyl ester of 6-hydroxycaproic acid can be carried out at 200-320℃ and 0.01-2atm, preferably at 220-310℃ and 0.1-1.2atm. The optional range of hydrogen and ammonia dosage is 5-70(H2 / ester molar ratio) and 1-50(NH3 / ester molar ratio) respectively, and the preferred range is 10-50(H2 / ester molar ratio) and 2-25(NH3 / ester molar ratio) respectively. In addition, the process also emphasizes the importance of the molar ratio of hydrogen to ammonia and the addition of water in the reactor feed. In general, the use of appropriate molar ratio of hydrogen to ammonia is beneficial to improve the selectivity of the reaction. The addition of water in the feed of the reactor not only can reduce the side reaction and improve the selectivity of caprolactam, but also can delay the deactivation rate of the catalyst. The optional range of the molar ratio of hydrogen to ammonia is 0.2-30, and the preferred range is 0.5-15; the optional range of the molar ratio of water to ester is 0-50, and the preferred range is 5-30. Under the preferred conditions, the conversion rate of caprolactone can reach up to 99% when caprolactam is produced from caprolactone, and the selectivity of caprolactam can reach up to 90%. The problem is that the catalyst deactivates quickly due to carbon deposition. However, the patent provides two catalyst regeneration methods. One method is redox treatment, and the other method is steam treatment. The redox treatment actually regenerates the catalyst by burning carbon with molecular oxygen first, and then reducing the catalyst with hydrogen. The carbon burning with molecular oxygen can be carried out at a temperature range of 100-800℃, preferably at a temperature range of 150-500℃. The carbon burning time is 20 minutes to 20 hours; the hydrogen reduction after carbon burning can be carried out at a temperature range of 170-350℃, preferably at a temperature range of 170-270℃.The water vapor treatment can be carried out at a temperature in the range of 100 to 500°C, preferably in the range of 200 to 400°C. The water vapor treatment can be carried out for a time period in the range of 20 minutes to 20 hours. The water vapor treatment can also be carried out in the presence of hydrogen, and the catalyst is preferably reduced with hydrogen after the water vapor treatment. The hydrogen reduction can be carried out at a temperature in the range of 170 to 350°C, preferably in the range of 170 to 270°C.

[0041] In 2012, German patent DE102012006946A1 disclosed a new catalytic process for the production of caprolactam from D-glucose via adipic acid and caprolactone. In the caprolactone to caprolactam reaction, the patent used Cu-Mo-Ti catalyst, and the reaction raw materials included ammonia and hydrogen in addition to caprolactone. The method can obtain a caprolactam yield of 80%.

[0042] In 2018, Chinese patent CN108774172A disclosed a catalytic method for preparing caprolactam and N-substituted caprolactam from caprolactone and ammonia (amine) as raw materials. Its technical feature is that the reactor is a fixed bed. The catalyst loaded in the fixed bed reactor is a granular SO4 2- / M X O Y solid superacid. The patent emphasizes that the superacid catalyst used should always be in a nitrogen atmosphere. The reaction is carried out at normal pressure and under nitrogen protection. The optional range of the reaction temperature is 180-320°C, and the preferred range is 220-280°C; the optional range of the molar ratio of caprolactone to ammonia (amine) is 1-1.5, and the preferred range is 1.1-1.3. The method also requires the use of a solvent. The solvent refers to water, benzene, toluene, xylene, and cyclohexane. The amount of solvent added is 1-2 times the total weight of caprolactone and ammonia (amine).

[0043] In addition to the above patents, several journal papers also involve the study of caprolactone to caprolactam. For example:

[0044] In 1977, the publication Journal of the Chemical Society of Japan, 1977, (7), p. 1013-1017 reported the catalytic effect of Cu-TiO2 catalyst on the gas phase ammonolysis of caprolactone to caprolactam. The ammonolysis reaction was carried out at normal pressure, and the products included 6-hydroxyhexanenitrile, 6-hydroxyhexanamide, adiponitrile, and polymers in addition to caprolactam. The paper proved through a blank experiment that a pure solid acid catalyst leads to the production of 6-hydroxyhexanenitrile, and a pure copper catalyst has almost no catalytic activity for the conversion of caprolactone. The Cu-TiO2 catalyst needs to be reduced with hydrogen before use, and hydrogen is required during the reaction. The activity of the catalyst decreases rapidly over time, which is presumably due to the coverage of the catalyst surface with polymers.

[0045] In 2001, the Japanese literature Kobunshi Ronbunshu, 58(12), 679-684 (2001) reported a study on the non-catalytic reaction of caprolactone and ammonia in supercritical water (T > 374℃, P > 22.1 MPa) to prepare caprolactam. The reaction mechanism for preparing caprolactam from caprolactone was proposed in this study, and it was believed that 6-hydroxyhexanamide was an intermediate in the reaction. 6-Hydroxyhexanamide undergoes dehydration and ring closure to form caprolactam. The effects of reaction temperature, water density and ammonia concentration were also studied. The results showed that the conversion of caprolactone and ammonia and the yield of caprolactam increased with the increase of reaction time at 380℃ and 38MPa (at this time the water density is 0.5g / cm 3 ), the yield of caprolactam can reach 79.2% after 60min of reaction. However, the high temperature and high pressure conditions of supercritical water increase the cost of equipment and the difficulty of operation, and also increase the safety risk.

[0046] In 2022, the published literature ChemSusChem, 2022, 15(16) reported a reaction process for preparing caprolactam from 6-hydroxyhexanoic acid catalyzed by biological enzymes, which has little practical value.

[0047] In summary, it can be seen that starting from caprolactone to prepare caprolactam can save the Beckmann rearrangement step of cyclohexanone oxime in the existing benzene method caprolactam process, and can avoid the problems existing in the cyclohexanone oximation step, which is a new route for caprolactam production with great application potential. However, the technical route for preparing caprolactam from caprolactone has not been paid attention to. The existing process and catalyst for preparing caprolactam from caprolactone are mainly disclosed in patents and papers before the 1970s. In general, the early proposed reaction process mainly includes non-catalytic method and catalytic method. Among them, the non-catalytic method needs high temperature and high pressure reaction conditions. Due to the problems of thermodynamic limitation and generation of by-products, the yield of caprolactam by non-catalytic method is low. In contrast, the reaction conditions of catalytic method are mild, which is not only beneficial to the reaction thermodynamics, but also beneficial to avoid side reactions, reduce equipment investment, reduce energy consumption and production cost. Thus, it is beneficial to industrial application. However, the catalytic method needs catalysts with high activity, high selectivity and strong anti-deactivation ability, and the existing catalysts cannot meet the needs of industrial application. SUMMARY

[0048] The purpose of the present application is to provide a preparation method and application of a Cu-Beta zeolite catalyst for gas-solid phase catalytic reaction of caprolactone hydrogenation to prepare caprolactam.

[0049] Specifically, the Cu-Beta zeolite catalyst for the gas-solid phase catalytic reaction of caprolactone to caprolactam is a catalyst prepared by loading copper in the pores by improved ammonia evaporation method and taking dealuminated Beta zeolite as a carrier.

[0050] It is found through research that, for the gas-solid phase catalytic reaction of caprolactone to caprolactam by hydrogenation amination, from the perspective of catalytic activity and selectivity, the supported copper-based catalyst has the most industrial application prospects. However, from the perspective of catalyst stability, the deactivation problem is the biggest challenge for industrial application. The deactivation reason of the copper-based catalyst in the gas-solid phase catalytic reaction of caprolactone to caprolactam by hydrogenation amination is not only carbon deposition. The sintering problem of the highly dispersed copper particles is also an important reason for the deactivation of the catalyst. As known to those skilled in the art, carbon deposition deactivation belongs to temporary deactivation of the catalyst, and the catalytic activity can be restored by various regeneration methods, thereby prolonging the service life of the catalyst. In contrast, sintering deactivation generally belongs to permanent deactivation of the catalyst, which has the greatest impact on the service life of the catalyst.

[0051] The main benefit of the Cu-Beta zeolite catalyst provided by the present application is that the copper particles are stabilized by the hydroxyl pockets of the zeolite carrier and have the ability to resist sintering, so that the copper-based catalyst can be used without adding anti-sintering additives such as chromium and nickel.

[0052] Firstly, the main feature of the Cu-Beta zeolite catalyst provided by the present application is that the dealuminated Beta zeolite is used as a carrier.

[0053] The catalysts for the catalytic conversion of caprolactone to caprolactam described in the prior art patents and academic papers are mainly non-supported bulk copper chromite catalysts and copper catalysts supported on amorphous single oxide carriers (such as titanium oxide, aluminum oxide, silicon oxide) and binary composite oxide carriers (such as silicon oxide and aluminum oxide) with the addition of a second metal component of nickel or chromium. As is known to those skilled in the art, the specific surface area of non-supported copper chromite catalysts is small, and the exposed metal active sites are few, so the amount of metal used is large and the catalytic efficiency is low. The use of amorphous oxide carriers (single oxide carriers and binary composite oxide carriers) to support copper, copper-nickel and copper-chromium can overcome the problems of non-supported catalysts, but the supported copper catalysts have the problem of easy sintering and deactivation, which is a great challenge for industrial application. The addition of chromium to the supported copper catalyst to form a copper chromite phase can improve the sintering resistance of the supported copper catalyst. However, chromium is a metal that is subject to restricted use. In clinical practice, chromium and its compounds mainly affect the skin, respiratory and digestive systems of humans, and even at low chromium content, they can have a strong toxic effect on the human body. Therefore, catalysts containing chromium will encounter great difficulties in the processes of preparation, use and harmless treatment of waste catalysts. The addition of nickel to the supported copper catalyst can also improve the sintering resistance of copper. However, our research results show that for the reaction of caprolactone to caprolactam, the introduction of a large amount of nickel into the supported copper catalyst can significantly reduce the ability of the catalyst to catalyze the gas-solid phase hydrogenation of caprolactone to caprolactam. For example, under the same conditions, the copper-amorphous silica catalyst (10 wt. % Cu) prepared with fumed silica (fumed silica) as the carrier, when a small amount of nickel (Ni:Cu = 0.3) is added, its ability to catalyze the hydrogenation of caprolactone to caprolactam decreases by 15-20%. In the relevant patent (US3888845), nickel is used as an additive for the preferred supported copper catalyst, but its addition amount is strictly limited to the range of Ni:Cu = 0.001-1 (atomic ratio), preferably 0.005-0.25. It is not necessary to add a small amount of nickel to improve the sintering resistance of the supported copper catalyst, but the addition of a small amount of nickel is not enough to properly solve the problem of sintering and deactivation of the supported copper catalyst.

[0054] In fact, the sintering deactivation problem of supported copper catalysts is a common problem. Copper-based catalysts are currently widely used in alcohol dehydrogenation, carbonyl hydrogenation, ester hydrogenolysis, amination, hydrocarbon hydrogenation, isomerization, and C-C bond and C-Si bond hydrogenolysis, etc. due to their low price and environmental friendliness. The main reason for the easy sintering and growth of highly dispersed copper particles is that the ionic radius of copper metal is large, the melting point is low (1083°C), and the Tammann temperature and Hüttig temperature are low. Sintering of supported copper catalysts can occur at a temperature of 170°C. Someone has summarized the thermal stability of common metal catalysts, giving the following order: Ag < Cu < Pd < Fe < Ni < Co < Pt < Rh < Ru < Ir < Os < Re. From this, it can be seen that the thermal stability of copper is lower than that of most common metal catalysts.

[0055] The present application uses dealuminated Beta zeolite as a carrier to prepare a supported copper catalyst, aiming to disperse and stabilize the supported copper particles by using the large number of hydroxyl crystal lattice defect sites in the dealuminated Beta zeolite. The large number of hydroxyl crystal lattice defect sites in the dealuminated Beta zeolite can be generated by removing framework aluminum from the crystals of the Beta zeolite using a conventional acid treatment method. When the Beta zeolite is subjected to acid dealumination treatment, four Si-O-Al bonds are acidized for every framework aluminum removed ([Al-(OSi)4] - + 4H2O = [Al(OH)4] - + 4≡Si-OH, [Al(OH)4] - + 4H + = Al 3+ + 4H2O, and the overall reaction equation is [Al-(OSi)4] - + 4H + = Al 3+ + 4≡Si-OH), generating a hydroxyl crystal lattice defect site surrounded by four silicon hydroxyl groups (≡Si-OH).

[0056] The main idea of the present invention comes from the inventors' own previous work. In the previous work, the inventors have conducted in-depth research on the physicochemical properties and catalytic functions of the hydroxyl nest lattice defect sites in the MFI zeolite family (ZSM-5, B-ZSM-5, Silicalite-1 (S-1) and TS-1). Some representative research works are described in the following publications: Silicalite-1 zeolite acidification by zinc modification and its catalytic properties for isobutane conversion, RSC Advances, 2018, 33(8), p. 18663-1867; Pt supported on Zn modified silicalite-1 zeolite 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-5 Zeolite Supported Zinc Catalysts, Catalysts, 2019, 1(9), p. 100; Effect of Zeolitic Hydroxyl Nests on the Acidity and Propane Aromatization Performance of Zinc Nitrate Impregnation-Modified HZSM-5 Zeolite, Industrial&Engineering Chemistry Research, 2020, 37(59), p. 16146-16160. Liu Guodong. Research 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 the silicon hydroxyl groups in the zeolite hydroxyl nest lattice defect sites are prone to form hydrogen bonds, and their chemical reactivity is much higher than that of the isolated silicon hydroxyl groups on the outer surface of the zeolite crystal.In addition, it is particularly worth mentioning that the inventors have found that zinc oxide preferentially locates in the hydroxyl pocket defect sites of the defective all-silica zeolite S-1 and the defective ZSM-5 zeolite in the research of zinc nitrate impregnation and preparation of zinc oxide modified catalysts. Moreover, the zinc oxide located in the hydroxyl pocket defect sites of the zeolite is highly dispersed sub-nanometer zinc oxide species. These research experiences provide important scientific guidance for the present application.

[0057] However, the present application does not use the defective MFI zeolite (for example, the defective all-silica zeolite S-1 and the boron-depleted B-ZSM-5 zeolite) as the carrier for the preparation of the copper supported catalyst, but uses the dealuminated Beta zeolite as the carrier for the preparation of the copper supported catalyst. This is not because the hydroxyl pocket defect sites in the defective MFI zeolite (for example, the defective all-silica zeolite S-1 and the boron-depleted B-ZSM-5 zeolite) cannot disperse and stabilize copper particles, nor because the copper supported catalyst prepared by using the defective MFI zeolite (for example, the defective all-silica zeolite S-1 and the boron-depleted B-ZSM-5 zeolite) as the carrier is ineffective for the catalysis of the gas-solid phase reaction of caprolactam from caprolactone. Rather, it is because the cylindrical pores of the MFI family zeolite are ten-membered rings, and when the loading amount of copper is slightly large, the effective size of the pores will be significantly reduced, which is not conducive to the intraparticle diffusion of the reactant caprolactone (seven-membered ring), nor to the formation and intraparticle diffusion of the caprolactam product which is also a seven-membered ring, and thus is not conducive to the preparation of a catalyst with high activity, high selectivity and strong anti-deactivation ability.

[0058] As a crystalline porous catalytic material, Beta zeolite has similar advantages to MFI zeolite, such as (1) both are high-silica zeolites, thus having high thermal and hydrothermal stabilities and good regeneration performance, and allowing repeated regeneration and reuse after being made into a catalyst; (2) both have cylindrical pores and three-dimensional intersecting pore systems, thus having good pore diffusivity and strong anti-clogging ability, and being conducive to maintaining long-term activity stability of the catalyst in a continuous reaction process. In addition, Beta zeolite has unique features compared to MFI zeolite. On the one hand, the three-dimensional cylindrical pores of Beta zeolite are all large pores with twelve-membered rings. In the three-dimensional pore system of Beta zeolite, there is a group of "Z" type curved pores parallel to the

[0001] direction and having an elliptical cross section with a pore size of 0.56 nm x 0.65 nm; there are also two groups of straight pores parallel to the

[0100] and

[0010] directions and having an elliptical cross section with a pore size of 0.66 nm x 0.77 nm. In comparison, the three-dimensional cylindrical pores of MFI zeolite are all mesopores with ten-membered rings. In the pore system of MFI zeolite, there is a group of straight pores parallel to the (100) crystal face and having a nearly circular cross section (pore size of 0.53 nm x 0.56 nm), and two groups of "Z" type curved pores parallel to the (010) crystal face and having an elliptical cross section (pore size of 0.51 nm x 0.55 nm) with opposite bending directions. It can be imagined that the pore system of Beta zeolite is more suitable for intrapore diffusion of the reactant caprolactone (seven-membered ring) and generation and intrapore diffusion of the product caprolactam (also seven-membered ring), and thus is more conducive to preparing a catalyst with high activity, high selectivity and strong anti-inactivation ability. In fact, Beta zeolite is the only zeolite molecular sieve among industrialized zeolite catalytic materials that has the advantages of high molar ratio of silicon to aluminum oxide, three-dimensional intersecting pore system and all pores being large pores with twelve-membered rings.

[0059] On the other hand, the framework aluminum of Beta zeolite can be easily removed by acid treatment to produce a high density of hydroxyl pit defect sites on the crystal framework. This feature is not common among industrialized zeolite catalytic materials and is incomparable to MFI zeolite. When Beta zeolite is subjected to acid dealumination treatment, four Si-O-Al bonds are required to be acidized for each framework aluminum removed ([Al-(OSi)4] - + 4H2O = [Al(OH)4] - + 4≡Si-OH, [Al(OH)4] - + 4H + = Al 3+ + 4H2O, and the overall reaction equation is [Al-(OSi)4] - + 4H + = Al 3+ +4≡Si-OH), resulting in a hydroxyl pocket lattice defect site surrounded by four silicon hydroxyl groups (≡Si-OH). In MFI zeolites, the hydroxyl pocket lattice defect site of the defective all-silica zeolite S-1 is randomly formed during hydrothermal synthesis of S-1 zeolite in an alkaline medium, and the number and distribution are poorly controllable; the framework aluminum content of ZSM-5 zeolite can be adjusted in a wide range, and the lower limit of the molar ratio of silicon to aluminum (Si / Al) can reach about 10, and the upper limit can reach an 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 hybrid ZSM-5 zeolite by post-synthesis method, the general method is to first synthesize ZSM-5 zeolite containing boron (B-ZSM-5), and then remove boron from the B-ZSM-5 zeolite to obtain a ZSM-5 zeolite carrier with a higher density of hydroxyl pocket defect sites on the framework.

[0060] In summary, the present application does not use MFI zeolite (for example, defective all-silica zeolite S-1 and boron-removed B-ZSM-5 zeolite) with a hydroxyl pocket lattice defect site as a carrier for preparing a copper-loaded catalyst, but selects Beta zeolite with a hydroxyl pocket lattice defect site as a carrier for preparing a copper-loaded catalyst. The main reason is that for the purpose of the present application, Beta zeolite has the advantage of being a material that is difficult to match, which has three advantages of high molar ratio of silicon to alumina oxide framework, three-dimensional twelve-membered ring cross-channel system, and easy complete removal of framework aluminum. In addition, Beta zeolite is a catalytic material that has been industrialized for a long time, that is, it can be obtained in large quantities from the market, and it can also be easily prepared by a hydrothermal synthesis method.

[0061] Secondly, the Cu-Beta zeolite catalyst preparation method provided by the present application is mainly characterized in that the copper is loaded on the dealuminated Beta zeolite carrier by using an improved ammonia evaporation method. The core of the improved ammonia evaporation method for loading copper is to immerse the zeolite carrier in an equal volume of copper ammonia complex solution, and in this process, most of the complex solution is absorbed into the channel by capillary condensation of the zeolite carrier, so that the copper hydroxide generated in the ammonia evaporation process is directly deposited in the channel of the Beta zeolite. Therefore, during the subsequent drying, calcination and hydrogen reduction treatment processes, the copper hydroxide can be first converted into copper oxide in the channel of the zeolite, and then further converted into sub-nanometer and nanometer particles of metallic copper. The sub-nanometer and nanometer particles of metallic copper can be directly captured by the hydroxyl pocket lattice defect sites mainly existing in the channel of the zeolite during the formation process, so as to be dispersed and stabilized in time.

[0062] As is well known in the art, the ammonia evaporation method is one of the most commonly used methods for preparing copper-based catalysts. Ube Industries Ltd. (US 4 440 873 (1984), EP 0 064 241 B1 (1985)) was the first to propose the ammonia evaporation method for preparing Cu / SiO2catalysts for the gas-solid phase hydrogenation of dimethyl oxalate to glycol and glycolate. The ammonia evaporation method was first proposed as follows: first, a copper-ammonia complex solution was prepared. A soluble copper-containing compound was dissolved in water to obtain an aqueous solution containing copper ions, and then an appropriate amount of concentrated ammonia was added to the aqueous solution containing copper ions to make the pH value greater than 10, for example, to make the pH value reach 10-12. Thus, a deep blue transparent solution containing a copper-ammonia complex can be obtained; second, a silica sol was used as a precursor of the SiO2carrier, which was mixed with the copper-ammonia complex. That is, the silica sol was added to the deep blue transparent solution containing the copper-ammonia complex, and the mixture was stirred thoroughly to make it uniform. This stirring and mixing process can be carried out at normal pressure and under pressure, at room temperature to 150°C; third, ammonia evaporation treatment. The mixture containing the copper-ammonia complex was subjected to ammonia evaporation treatment to obtain a solid catalyst precursor. The ammonia evaporation treatment can be carried out under pressure and under reduced pressure, and the preferred temperature range is 60-90°C; fourth, pretreatment of the solid catalyst precursor. This step refers to the pretreatment of the solid catalyst precursor before hydrogen reduction, including drying, water washing. In addition, a precalcination treatment can also be selected. The temperature range of the precalcination treatment is 400-800°C, preferably 500-750°C; fifth, hydrogen reduction treatment. The pretreated solid catalyst precursor was subjected to hydrogen reduction treatment. The hydrogen reduction time is 1-15h, and the reduction temperature range is 150-500°C, preferably 200-400°C.

[0063] Examples of soluble copper-containing compounds that can be used to formulate copper ammonia complex solutions are given in US Patent 4 440 873, including copper nitrate, copper sulphate, copper oxalate, copper chloride and copper acetate, with copper nitrate being the preferred option. In Example 1 of that patent there is the following description of the preparation of a Cu / SiO2catalyst by the ammonia evaporation method: (1) 19.0 g of copper nitrate (Cu(NO3)2.3H2O) was dissolved in 200 ml of water to give an aqueous solution containing copper ions, to which was then added 60 ml of a concentrated aqueous ammonia solution to give a deep blue solution containing a copper ammonia complex, the pH of which was adjusted to 11-12; (2) 66.6 g of a silica sol (30 wt.% SiO2) was added to the copper ammonia complex solution and stirred at room temperature for several hours; (3) the reaction mixture of step (2) was subjected to ammonia evaporation at elevated temperature. Ammonia evaporation was continued until most of the water was also evaporated, to give a solid product; (4) the solid product was dried at 120°C for 12 h. The dried product was then subjected to water washing and then to drying again. The drying conditions were 140°C x 14 h; (5) the dried product was subjected to hydrogen reduction. The reduction conditions were 350°C x 2-3 h. The Cu / SiO2catalyst so prepared contained about 20 wt.% of copper.

[0064] It can be seen from the above that the earliest proposed ammonia evaporation method for preparing Cu / SiO2 catalyst has the following characteristics: on the one hand, the amorphous silica support is not pre-prepared, but is generated in situ during the ammonia evaporation process using silica sol as a precursor. Specifically, during the ammonia evaporation process, the silica sol is converted into silica gel. At the same time, the copper ammonia complex loses ammonia to form copper hydroxide precipitate, which is deposited on the surface of the silica gel. This process has dynamic characteristics. That is, the silica gel particles continue to grow after being generated, and at the same time, the copper hydroxide precipitate is continuously generated. As the silica gel particles grow, the copper hydroxide precipitate is deposited and reacts on the surface thereof, resulting in a layered mixed state of silica gel and copper hydroxide. Later, researchers in the field pointed out (J. Catal. 257 (2008) 172-180) that this ammonia evaporation method is essentially a homogeneous deposition-precipitation method, and the prepared Cu / SiO2 catalyst is a layered copper silicate. On the other hand, a diluted copper ammonia complex solution is prepared and used. The volume of this copper ammonia complex solution is greatly excessive relative to the liquid holding capacity (pore volume) of the finally generated silica gel, and the water solvent needs to be removed by post-processing operations such as filtration or evaporation, and the loading and dispersion mechanism of copper on the silica support is deposition-precipitation, that is, the silica gel particles continue to grow, and at the same time, the copper hydroxide precipitate is deposited and reacts on the surface thereof, and the uniform loading state is achieved by the layer-by-layer mixing of silica gel and copper hydroxide. It can be imagined that if the silica support is not generated during the ammonia evaporation process, but is pre-prepared, then using this diluted and volumetrically excessive (the volume of the solution is greatly excessive relative to the total pore volume of the silica support) copper ammonia complex solution for ammonia evaporation operation will inevitably result in a large amount of copper hydroxide being deposited on the external surface of the support particles, leading to the non-uniform consequence of less copper loaded in the pores of the support and more copper loaded outside the pores of the support.

[0065] Some scholars in their research prepared copper-based catalysts supported on amorphous oxide carriers according to the earliest proposed ammonia evaporation method for the purpose of gas-solid phase hydrogenation of dimethyl oxalate to ethylene glycol. For example, relevant research is reported in the published literature J. Catal. 257 (2008) 172-180 and Appl. Catal. A: Gen. 458 (2013) 82-89, and the amorphous oxide carriers involved are silica and binary compounds of silica and titania. When silica is used as the carrier, silica sol (Ludox AS-40) is used as the precursor of the carrier. When the binary compound of silica and titania is used as the carrier, silica sol (JN30, Qingdao Haiyang Chem. Co., Ltd.) and titania sol are used as the precursors of the carrier. After the ammonia evaporation is completed (the pH value of the slurry is reduced to 6-7), the amorphous oxide supported copper hydroxide solid product is obtained by filtration.

[0066] Still, some researchers have improved the ammonia evaporation method in the preparation of Cu / SiO2 catalysts for the gas-solid phase hydrogenation of dimethyl oxalate. In the published literature 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 actually involves transferring the ammonia evaporation product (slurry containing copper hydroxide / silica gel precipitate, pH = 6-7) of the traditional ammonia evaporation method (the earliest ammonia evaporation method) to a high-pressure synthesis kettle for hydrothermal treatment at 190-210℃ for 12 h, and then performing conventional filtration, washing, drying, calcination, and hydrogen reduction treatment on the solid product. In other words, this method is not an improvement of the ammonia evaporation method itself, but rather a hydrothermal post-treatment step inserted before the conventional post-treatment of the ammonia evaporation method product. It is important to note that the ammonia evaporation hydrothermal method is identical to the traditional ammonia evaporation method before the hydrothermal post-treatment, the silica support is generated in situ using silica sol as the precursor, and the water solvent of the diluted and volume-excess copper ammonia complex solution is finally removed by filtration; in the published literature J. Phys. Chem. C 2015, 119, 13758-13766, researchers added urea as a deposition precipitate aid to the solution when preparing the copper ammonia complex solution. Other practices are identical to the traditional ammonia evaporation method. The silica support is generated in situ using silica sol (Ludox AS-40, 40 wt. % SiO2) as the precursor, and the water solvent of the diluted and volume-excess copper ammonia complex solution is finally removed by filtration; in the published literature Natural Gas Chemical Industry (C1 Chemistry and Chemical Industry), 2013, 38(3): 43-47, Natural Gas Chemical Industry (C1 Chemistry and Chemical Industry), 2014, 39(5): 31-34, and Journal of Shenyang University of Chemical Technology, 2016, 30(3): 212-216, researchers used pre-made JN-25 type basic silica gel (primary particle size 10 nm, Qingdao Haoyang Chemical Industry Co., Ltd.) as the carrier of the Cu / SiO2 catalyst prepared by the ammonia evaporation method, and added a certain amount of silica sol as the precursor for in-situ generation of silica gel carrier to achieve uniform deposition of the precipitate. To overcome the problems caused by the reduction of silica sol when using pre-made JN-25 type basic silica gel as the carrier of the Cu / SiO2 catalyst, researchers also tried adding cetyltrimethylammonium bromide (CTAB) surfactant to the configured copper ammonia complex aqueous solution to disperse the silica sol and generate mesopores in the in-situ generated silica gel.Other methods are no different from the traditional ammonia evaporation method; in the public literature RSC Adv., 2015, 5, 29040-29047 and Applied Catalysis A: General 509 (2016) 66-74, researchers use pre-prepared titanium dioxide (P25, Degussa Co., Ltd) as the carrier of the Cu / TiO2 catalyst prepared by the ammonia evaporation method, and other methods are no different from the traditional ammonia evaporation method. It should be noted that the P25 type TiO2 carrier belongs to a low specific surface carrier, and its capillary pores are not developed, so in the prepared Cu / TiO2 catalyst, it does not have a uniform deposition precipitation effect, that is, the copper hydroxide loaded mainly exists on the outer surface of the titanium dioxide carrier, and the sample after calcination is analyzed by X-ray diffraction, and there are obvious diffraction characteristic peaks of CuO phase at 2θ = 35.5°, 38.7° and 48.7°, indicating that the hydrogen reduction product-metallic copper has poor dispersity.

[0067] In addition, it is worth special mentioning that in the published document Applied Catalysis A, General 539 (2017) 59-69, researchers used pre-prepared ordered mesoporous silica (OMS) as the support of Cu / OMS catalysts prepared by their ammonia vaporization method. In order to reduce the damage of the basicity of the copper ammonia complex solution to the ordered mesoporous structure of the pre-prepared silica support, the researchers also appropriately reduced the concentration of ammonia in the prepared copper ammonia complex solution (which the researchers considered as an improvement of the ammonia vaporization method). In addition to the above two points, the improved ammonia vaporization method described in the study is no different from the traditional ammonia vaporization method. After the end of the ammonia vaporization (the pH value of the slurry is reduced to 6-7), the water solvent of the diluted and volume-excessive copper ammonia complex solution is finally removed by filtration to obtain a solid product loaded with copper hydroxide. The research results show that the ordered mesoporous structure of the pre-prepared silica support used in the study has been mostly destroyed after being loaded with metal copper by the ammonia vaporization method, and there is a large amount of layered copper silicate in the catalyst, indicating that the pre-prepared silica support used is largely dissolved into silica sol during the contact with the copper ammonia complex solution, which produces a uniform deposition and precipitation effect with copper hydroxide during the ammonia vaporization process; In the published document Journal of Catalysis 280 (2011) 77-88, researchers also used pre-prepared mesoporous silica (HMS) as the support of Cu / HMS catalysts prepared by their ammonia vaporization method. In addition to this, the researchers also added a water-soluble nickel salt (nickel nitrate) to the prepared aqueous copper ammonia complex solution, so that the prepared copper-based catalyst contains metal nickel (CuxNi / HMS). The ammonia vaporization method used in this study is no different from the traditional ammonia vaporization method, except that it uses a pre-prepared mesoporous silica support and adds a water-soluble nickel salt (nickel nitrate) to the prepared aqueous copper ammonia complex solution, so that the prepared copper-based catalyst contains a metal nickel additive. Its ammonia vaporization operation is carried out at 90°C, and after the end of the ammonia vaporization (the pH value of the slurry is reduced to 7-8), the water solvent of the diluted and volume-excessive copper ammonia complex solution is finally removed by filtration to obtain a solid product loaded with copper hydroxide and nickel hydroxide. Similarly, in this study, the ordered mesoporous structure of the HMS silica has been mostly destroyed (the specific surface area has decreased by more than 50%) after being loaded with metal copper and nickel by the ammonia vaporization method. Moreover, the XRD characterization results show that the prepared supported catalyst sample has characteristic diffraction peaks of metal oxide phase before hydrogen reduction (450°C calcination for 4h), and has characteristic diffraction peaks of metal phase after hydrogen reduction, indicating that the metal copper and nickel are not uniformly loaded on the HMS support and have poor dispersion.

[0068] According to the literature research results, in addition to a recent open literature (Science 10.1126 / science. adj1962 (2023).) reported in the Science journal that a copper catalyst supported on a dealuminated Beta zeolite carrier was prepared by the ammonia evaporation method for the purpose of the gas-solid phase hydrogenation of dimethyl oxalate, so far, no other research work on the preparation of metal catalysts supported on zeolite carriers by the ammonia evaporation method has been found at home and abroad. It should be noted that the related research work recently published in the Science journal used the traditional ammonia evaporation method to prepare a copper catalyst supported on a dealuminated Beta zeolite carrier. The specific approach is as follows: First, 0.23g Cu(NO3)2·3H2O was dissolved in 100ml of an ammonia water solution (containing 0.75g NH3·H2O) and stirred at room temperature for 10min to prepare a copper ammonia complex aqueous solution; Second, 1.94g of a dealuminated Beta zeolite carrier (Beta-deAl) was added to the copper ammonia complex solution and subjected to ammonia evaporation treatment under vigorous stirring. The ammonia evaporation temperature was 80℃ and the ammonia evaporation time was 6h; Third, after the ammonia evaporation was completed, the water solvent of the diluted and excessive volume of the copper ammonia complex solution was finally removed by filtration; Fourth, the obtained solid product was dried at 100℃ overnight and calcined at 400℃ for 3h to obtain the catalyst; Fifth, in order to use the catalyst to catalyze the hydrogenation of dimethyl oxalate, it was subjected to a reduction treatment with hydrogen at 400℃ for 3h. It is not difficult to see that in this research, in addition to the catalyst carrier being a pre-prepared dealuminated Beta zeolite (obtained by subjecting an Al-Beta zeolite matrix with Si / Al = 13 to an acid dealumination treatment with a 13M HNO3 solution at 80℃ for 12h), the other approaches are no different from the traditional ammonia evaporation method. In the prepared copper ammonia complex solution, the concentration of copper ions is very dilute (only about 9.5mmol / L); In the preparation of the catalyst by the ammonia evaporation method, the initial liquid-solid ratio is as high as about 51.5(ml / g), that is, the volume of the copper ammonia complex solution is greatly excessive to the zeolite carrier. The results show that the prepared dealuminated Beta zeolite supported copper catalyst Cu / Beta-deAl, although the copper content is very low (about 3wt.%Cu), the specific surface area loss is as high as 15% (excessive copper ammonia complex solution (NH3 / Cu molar ratio 22.5) causes a large amount of dealuminated Beta zeolite to be dissolved and the framework structure to be destroyed), and there are still obvious characteristic diffraction peaks of metallic copper (2θ = 43.3°) in its XRD pattern. Transmission electron microscopy studies show that the copper in the fresh catalyst is mainly supported on the outer surface of the dealuminated Beta zeolite, and the particle size is relatively large (the use of diluted and excessive copper ammonia complex solution leads to excessive deposition of copper hydroxide outside the zeolite pores during the ammonia evaporation process), which needs to be post-treated by methanol vapor to transfer it to the zeolite pores through the reverse Ostwald ripening process.This research work clearly demonstrates that when copper catalysts are prepared by copper-ammonia complex impregnation on the support of dealuminated zeolite Beta, the traditional ammonia evaporation method reported in the literature for silica support cannot be used, otherwise the following problems will occur: (1) excessive copper-ammonia complex solution will deposit a large amount of copper outside the zeolite pores during ammonia evaporation; (2) dealuminated zeolite Beta will undergo desilication (ammonia evaporation temperature 80°C) in the presence of excessive copper-ammonia complex solution (pH = 10-12), resulting in the destruction of the crystal structure.

[0069] Therefore, the present application proposes an improved ammonia evaporation method that is different from the known methods to meet the need for loading copper in the pores of zeolite supports, especially in high-silica zeolite supports such as dealuminated zeolite Beta, which are prone to desilication.

[0070] In addition, the main feature of the present application is that the Cu-Beta zeolite catalyst provided is for the purpose of preparing caprolactam from caprolactone in a gas-solid phase reaction state. So far, neither the published patent applications nor the other published literature have involved this application purpose of Cu-Beta zeolite catalyst. This reaction system is unique. This is mainly because the reaction of preparing caprolactam from caprolactone in a gas-solid phase reaction state simultaneously involves the use of water vapor, hydrogen, and ammonia. This is a demanding application scenario for copper-based catalysts.

[0071] As mentioned above, so far, in the catalytic methods for preparing caprolactam from caprolactone described in the existing related patents and academic papers, the catalysts used are mainly two types, one is a non-supported bulk copper chromite catalyst, and the other is a copper catalyst supported on a single oxide support (such as titanium oxide, aluminum oxide, silicon oxide) or a binary composite oxide support (such as silicon oxide and aluminum oxide) (with the addition of a second metal component nickel or chromium). The single oxide and binary composite oxide used as the support in the supported copper catalyst (with the addition of a second metal component nickel or chromium) are amorphous.

[0072] The gas-solid phase reaction state is a suitable way to convert caprolactone to caprolactam by the catalytic route. As mentioned above, the catalytic methods for preparing caprolactam from caprolactone disclosed in British Patent GB1109540 (1966) and US Patent 3652549 (1972) by KANEGAFUCHI, BOSEKI KABUSHIKI KAISHA, and US Patent US3888845 (1975) by TEIJIN CORPORATION all adopt a gas-solid phase reaction state.

[0073] It is well known that the gas-solid phase reaction state is a common form of heterogeneous catalysis, specifically, the reactants in the form of gas contact with solid catalyst for catalytic reaction. In the field of heterogeneous catalysis, sometimes the gas-solid phase reaction is simply referred to as gas phase reaction. The gas-solid phase reaction state is a reaction form with mild reaction conditions, high mass and heat transfer efficiency, and very simple operation. For the gas-solid phase reaction, the process of conversion of reactants on the catalyst to products consists of seven elementary steps: (1) external diffusion of reactants. In this step, the reactants pass through the adsorption film on the surface of the solid catalyst and contact the outer surface of the catalyst; (2) internal diffusion of reactants. In this step, the reactants diffuse through the pores on the surface of the solid catalyst into the inside of the pore to approach the catalytically active center in the pore; (3) chemical adsorption of reactants on the catalytically active center. In this step, the reactant molecules are activated to become activated molecules; (4) surface reaction. In this step, the reactants are converted into adsorbed product form on the catalytically active center; (5) desorption of products. In this step, the adsorbed product is desorbed from the catalytically active center; (6) internal diffusion of products. This step is the movement process of product molecules from the inside of the pore to the outside surface of the catalyst after leaving the catalytically active center; (7) external diffusion of products. In this step, the 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, and leave the solid catalyst particles to become reaction products.

[0074] The Cu-Beta catalyst provided by the present application is suitable for the gas-solid phase catalytic reaction conditions of the hydrogenation amination of caprolactone to caprolactam described in the related patents and academic papers. As described above, in 1966, KANEGAFUCHI, BOSEKI KABUSHIKI KAISHA first disclosed a gas-solid phase catalytic method for preparing caprolactam in British Patent GB1109540, specifically, the caprolactone and a certain amount of water were first vaporized, and then mixed with ammonia and hydrogen, and the mixed gas was catalytically reacted at 120-350°C and normal pressure through a copper chromite catalyst; in 1972, KANEGAFUCHI, BOSEKI KABUSHIKI KAISHA again disclosed a method for preparing caprolactam in U.S. Patent 3652549, which is also a gas-solid phase catalytic method. Specifically, the method uses a fixed bed reactor, and the reaction temperature is in the range of 170-300°C, and the hydrogen partial pressure is in the range of 0.1-1.5 atm. There are also ammonia and water vapor in the feed, and the preferred amount range (molar ratio with the raw material) is 2-50 and 10-100, respectively; in 1975, TEIJIN CORPORATION disclosed a method for preparing caprolactam in U.S. Patent US3888845, 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, and preferably at 220-310°C and 0.1-1.2 atm. The optional ranges of the amounts of hydrogen and ammonia are 5-70 (H2 / ester molar ratio) and 1-50 (NH3 / ester molar ratio), respectively, and the preferred ranges are 10-50 (H2 / ester molar ratio) and 2-25 (NH3 / ester molar ratio), respectively. In addition, the process also emphasizes the importance of the molar ratio of hydrogen to ammonia and the addition of water in the reactor feed. In general, the use of a suitable molar ratio of hydrogen to ammonia is beneficial to improve the selectivity of the reaction. In addition, the addition of water in the feed of the reactor not only reduces the side reactions and improves the selectivity of caprolactam, but also delays the deactivation rate of the catalyst. The optional range of the molar ratio of hydrogen to ammonia is 0.2-30, and the preferred range is 0.5-15; the optional range of the molar ratio of water to ester is 0-50, and the preferred range is 5-30.

[0075] In summary, according to the gas-solid phase catalytic reaction of hydrogenation amination of caprolactone to caprolactam described in the related patents and academic papers, in addition to the caprolactone raw material, the reactor feed also includes water, ammonia and hydrogen. From the molecular formula (C6H 10 O2) of the caprolactone raw material and the molecular formula (C6H 11 It is not difficult to see that ammonia and hydrogen are also reaction raw materials, and water vaporized into water vapor is a dilution gas. The optional range of the reaction temperature is 120-350℃, the optional range of the reaction pressure is 0.01-2atm, and the optional range of the ammonia-ester, hydrogen-ester and water-ester molar ratio is 1-50, 5-70 and 0-100, respectively; the preferred range of the reaction temperature is 220-300℃, the preferred range of the reaction pressure is 0.1-1.2atm, and the preferred range of the ammonia-ester, hydrogen-ester and water-ester molar ratio is 2-25, 10-50 and 5-30, respectively. In order to facilitate people in the art to better understand the implementation effect of the present application, in the present application, the catalytic performance of the provided Cu-Beta zeolite catalyst in the gas-solid phase hydrogenation reaction of caprolactam from caprolactone is evaluated, and the reaction conditions used are within the above ranges.

[0076] The technical solution of the present application is:

[0077] A preparation method of a Cu-Beta zeolite catalyst for caprolactam from caprolactone, comprising the following steps:

[0078] First step, preparation of dealuminated Beta zeolite carrier

[0079] Engineers familiar with the art can prepare the dealuminated Beta zeolite carrier from the Beta zeolite mother body according to the requirements of the present application, combined with their own work experience and reference to the conventional acid dealuminization method in the related literature. The requirements of the present application are as follows:

[0080] (1) Selection of Beta zeolite mother body

[0081] The Beta zeolite mother body refers to a silicon-aluminum Beta zeolite. The present application does not limit the grain size of the Beta zeolite mother body, nor does it limit the production process of the Beta zeolite mother body. However, in order to facilitate the implementation effect of the present application, the Beta zeolite mother body has the following limitations: 1) There are no impurity crystals in the Beta zeolite mother body; 2) The crystallization of the Beta zeolite mother body is good; 3) The silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of the Beta zeolite mother body is appropriate.

[0082] 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.

[0083] 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.

[0084] The silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) is a key index of the Beta zeolite mother substance. On the one hand, the lower the silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of the Beta zeolite mother substance, i.e. the higher the content of framework aluminum, the more the number of hydroxyl pocket lattice defect sites of the dealuminated Beta zeolite carrier for dispersing and stabilizing nano and sub-nano copper particles; on the other hand, it is difficult to synthesize pure-phase Beta zeolite with a very low silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) by a hydrothermal method. Moreover, after the Beta zeolite mother substance with a very low silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) is dealuminated to form a dealuminated Beta zeolite carrier by an acid dealuminization method, the framework thermal stability is poor, and the crystallinity will be lost during the subsequent calcination step for preparing a Cu-Beta zeolite catalyst, resulting in poor performance of the catalyst. Therefore, the silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of the Beta zeolite mother substance according to the present application is preferably in the range of 10-200, more preferably in the range of 20-100, and even more preferably in the range of 25-60. The silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of the Beta zeolite mother substance can be analyzed by a conventional chemical analysis method (titration method), or by an X-ray fluorescence spectroscopy (XRF) method or an inductively coupled plasma emission spectroscopy (ICP) method. The simple and fast XRF method is recommended.

[0085] Beta zeolite precursors meeting the requirements of the present invention can be obtained commercially or synthesized in-house. Engineers skilled in the art can also synthesize Beta zeolite precursors meeting the requirements of the present invention based on their own experience and other literature reports.If the Beta zeolite precursor is synthesized by oneself, the following methods reported in the invention patents and open literature can be selected: 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), CN1 154 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), CN1 108 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: Chemical 252 (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) DOI 10.1002 / crat.200800474; Microporous and Mesoporous Materials 143 (2011) 97-103; RSC Adv. 2019, 9, 3653-3660.

[0086] (2) Preparation of dealuminated Beta zeolite support

[0087] As mentioned above, the dealuminated Beta zeolite support can be prepared from a Beta zeolite precursor by using a conventional acid dealumination method. The present invention requires that the molar ratio of silica to alumina (SiO2 / Al2O3) of the dealuminated Beta zeolite support be as high as possible, i.e. as much as possible of the framework aluminum of the Beta zeolite precursor should be removed. The dealuminated Beta zeolite support according to the present invention has a molar ratio of silica to alumina (SiO2 / Al2O3) in the range of ≧ 700, preferably in the range of ≧ 800, and more preferably in the range of ≧ 900. Because the molar ratio of silica to alumina (SiO2 / Al2O3) of the dealuminated Beta zeolite is very high and the aluminum content is very low, the molar ratio of silica to alumina (SiO2 / Al2O3) should be determined by inductively coupled plasma emission spectroscopy (ICP) or atomic absorption (AA). The present invention recommends the use of ICP.

[0088] When the Beta zeolite precursor is subjected to acid dealumination, it is desirable to remove as much of the framework aluminum as possible. The presence of too much framework aluminum in the dealuminated Beta zeolite support is disadvantageous because the strong acidity of the framework aluminum will accelerate the coking and deactivation of the Cu-Beta zeolite catalyst and reduce the selectivity of the catalyst to the caprolactam main product.

[0089] Although the framework aluminum of the Beta zeolite is easily removed so that the dealuminated Beta zeolite support according to the present invention can be prepared from a Beta zeolite precursor by using a high-temperature steam dealumination method, an EDTA complexing agent dealumination method, an organic acid solution dealumination method, an inorganic acid (concentrated hydrochloric acid, concentrated nitric acid) solution dealumination method, or a dealumination method formed by any combination of the above different methods, the present invention recommends the use of a concentrated nitric acid aqueous solution dealumination method for preparing the dealuminated Beta zeolite support according to the present invention in view of the production cost, process complexity, and difficulty in treating the waste liquid generated by dealumination of the dealuminated Beta zeolite support.

[0090] Engineers familiar with the art can prepare the dealuminated Beta zeolite support according to the requirements of the present application by using concentrated nitric acid aqueous solution to dealuminate the Beta zeolite precursor according to their own experience or by referring to the specific methods disclosed in the following references: 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.

[0091] In the preparation of the dealuminated Beta zeolite support by using concentrated nitric acid aqueous solution to dealuminate the Beta zeolite precursor, the concentration of the nitric acid aqueous solution, the ratio of the acid solution to the zeolite (liquid-solid ratio), and the temperature and time of the acid treatment are all important factors affecting the degree of dealumination of the Beta zeolite precursor. The effects of the above factors on the dealumination of the Beta zeolite precursor are ultimately reflected in the residual aluminum content of the dealuminated Beta zeolite support. However, if the dealuminated Beta zeolite support with a required molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) cannot be obtained after one dealumination, the molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) of the dealuminated Beta zeolite can be adjusted to meet the requirements of the present application by secondary or even multiple supplemental dealumination. The present application recommends using 13M concentrated nitric acid as the dealumination acid, and using the acid solution in a liquid-solid ratio (ml / g) of 20:1. Under this premise, the dealumination reaction is carried out at 95°C for 20h; after the dealumination reaction is completed, the solid product is first recovered by solid-liquid separation, then washed with water to neutral pH, and then dried at a temperature of 80-200°C for 3-24h and calcined at a temperature of 500°C-600°C for 3-8h to obtain the dealuminated Beta zeolite. After dealumination of the Beta zeolite precursor, a large number of hydroxyl cavity lattice defect sites are generated, and the water absorption and moisture absorption capacity is stronger, so it should be sealed and stored for use.

[0092] Second step, loading copper in the pores of the dealuminated Beta zeolite support by improved ammonia evaporation method to prepare Cu-Beta zeolite catalyst

[0093] As mentioned above, the core of the improved ammonia distillation method according to the present application is to immerse the de-aluminized Beta zeolite carrier in the copper-ammonia complex solution with equal volume, and in this process, most of the complex solution is absorbed into the pores of the zeolite carrier by capillary condensation, so as to achieve the purpose of depositing copper hydroxide and loading metal copper in the pores. The specific method is as follows:

[0094] (1) Preparation of dilute ammonia water base solution and saturated solution of copper-ammonia complex: according to the ratio of 4.4g industrial ammonia water (containing NH3 25-28wt.%) to 100ml deionized water, a dilute ammonia water base solution with pH value = 11-12 is prepared and sealed for storage; then according to the molar ratio of copper ion (Cu 2+ ) to ammonia molecule is 1:4, copper nitrate trihydrate (Cu(NO3)2·3H2O) is used as a soluble copper-containing compound to react with industrial ammonia water to synthesize copper-ammonia complex; finally, the copper-ammonia complex is dissolved in the dilute ammonia water base solution at room temperature to prepare a saturated solution of copper-ammonia complex, which is stored for future use. The concentration of copper-ammonia complex ion in the saturated solution of copper-ammonia complex is about 0.4mol / L (0.4M), with dark blue color and clear transparency.

[0095] It should be noted that although the soluble copper-containing compounds that can be used to prepare the copper-ammonia complex solution include copper nitrate, copper sulfate, copper oxalate, copper chloride and copper acetate, as described in US Patent No. 4 440 873 (1984), considering that sulfate and chloride ions will increase the subsequent water washing burden, and oxalate and acetate have corrosion problems, therefore, the present application recommends the use of copper nitrate (Cu(NO3)2·3H2O).

[0096] (2) Immersion of zeolite carrier with equal volume of copper-ammonia complex solution: first, the saturated water absorption rate of the zeolite carrier is determined, and the amount of copper-ammonia complex solution for equal volume immersion of the zeolite carrier is calculated. Then, according to the copper loading amount of the Cu-beta zeolite catalyst to be prepared, the concentration of the required copper-ammonia complex solution is calculated. When the calculated concentration is equal to 0.4M, the zeolite carrier is directly immersed with equal volume of the saturated solution of copper-ammonia complex; when the calculated concentration is lower than 0.4M, the saturated solution of copper-ammonia complex is appropriately diluted with the dilute ammonia water base solution before the zeolite carrier is immersed with equal volume; when the calculated value is higher than 0.4M, the copper-ammonia complex solution should be prepared according to multiple equal volume immersions, the concentration of the copper-ammonia complex solution for single equal volume immersion is recalculated, and the dilute ammonia water base solution and the saturated solution of copper-ammonia complex are used to prepare the copper-ammonia complex solution with the required concentration for each equal volume immersion. After each immersion, the de-aluminized Beta zeolite carrier is treated by ammonia distillation.

[0097] The equal-volume impregnation is carried out in a closed container at room temperature. In this process, the zeolite carrier absorbs the copper-ammonia complex solution into the zeolite pores by capillary condensation, so that the copper-ammonia complex ions contact and interact with the hydroxyl lattice defect sites in the pores. The suitable range of the equal-volume impregnation time is 0.5-24 h, the preferred range of the equal-volume impregnation time is 1-12 h, and the more preferred range of the equal-volume impregnation time is 2-6 h;

[0098] (3) Ammonia evaporation treatment: The ammonia evaporation process can be carried out at normal pressure or under reduced pressure. The suitable range of the ammonia evaporation temperature and time is 50-100°C and 0.5-48 h, the preferred range of the ammonia evaporation temperature and time is 60-90°C and 1-24 h, and the more preferred range of the ammonia evaporation temperature and time is 65-85°C and 3-12 h. In the ammonia evaporation process, the copper-ammonia complex is decomposed to generate ammonia and copper hydroxide, the former is absorbed by water, and the latter is deposited in the zeolite pores and the hydroxyl lattice defect sites.

[0099] (4) Dehydration and drying treatment after ammonia evaporation: The suitable range of the drying temperature and time is 100-200°C and 0.5-48 h, respectively, the preferred range of the drying temperature and time is 110-170°C and 1-24 h, respectively, and the more preferred range of the drying temperature and time is 120-150°C and 3-12 h, respectively.

[0100] (5) Calcination treatment after ammonia evaporation: This step is used to convert the copper hydroxide deposits deposited in the zeolite pores and the hydroxyl lattice defect sites into nano and sub-nano copper oxide particles, thereby obtaining a catalyst precursor. The calcination is carried out in an air atmosphere, and the suitable range of the calcination temperature and time is 350-650°C and 0.5-24 h, respectively, the preferred range of the calcination temperature and time is 400-600°C and 1-12 h, respectively, and the more preferred range of the calcination temperature and time is 450-550°C and 2-6 h, respectively;

[0101] (6) Hydrogen reduction treatment of the catalyst precursor: The finished Cu-Beta zeolite catalyst is obtained. The suitable range of the reduction temperature, time and hydrogen flow rate (expressed by the hydrogen volume space velocity, defined as the hydrogen volume passing through the catalyst per unit time per unit volume, calculated as an ideal gas) is 280-600°C, 0.5-20 h and 1-2000 h -1 , respectively, the preferred range is 300-550°C, 1-15 h and 10-1500 h -1 , respectively, and the more preferred range is 350-500°C, 2-8 h and 20-1000 h -1 , respectively.

[0102] The Cu-Beta zeolite catalyst obtained by the above preparation method is used to catalyze the gas-solid phase hydrogenation of caprolactam from caprolactone.

[0103] As mentioned above, one of the main features of the present application is that the Cu-Beta zeolite catalyst provided is used for catalyzing the gas-solid phase reductive amination of caprolactone to prepare caprolactam.

[0104] However, the present application is not limited to the specific process of preparing caprolactam by the gas-solid phase reductive amination of caprolactone. Engineers skilled in the art can refer to the methods disclosed in relevant patents and other literature to perform the gas-solid phase reductive amination of caprolactone. According to relevant patents and other literature, the present application has sorted out the ranges of the conditions of the gas-solid phase reductive amination of caprolactone that can be referred to as follows: the suitable range of the reaction temperature is 120-350℃, the suitable range of the reaction pressure is 0.01-2atm, the suitable range of the feedstock space velocity (WHSV) of caprolactone is 0.1-5h -1 , and the suitable 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 the reaction temperature is 220-300℃, the preferred range of the reaction pressure is 0.1-1.2atm, the preferred range of the feedstock space velocity (WHSV) of caprolactone is 0.2-2h -1 , 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.

[0105] In order to facilitate the illustration of the implementation effects of the catalyst and the preparation method thereof of the present application and avoid unnecessary complexity, a typical process of preparing caprolactam by the gas-solid phase reductive amination of caprolactone on the Cu-Beta zeolite catalyst is introduced as follows by taking a small fixed bed reactor in a laboratory as an example: the small fixed bed reactor is operated in an up-feed and down-discharge mode, and the Cu-Beta zeolite catalyst is loaded in the constant temperature zone of the reactor. The upper and lower spaces of the catalyst bed are filled with inert porcelain balls. Among them, the porcelain ball area in the upper section of the reactor serves as the vaporization and preheating zone of the raw materials. For the sake of convenience, caprolactone, water and ammonia gas can be mixed into a mixed feedstock, which is delivered by a micro-metering pump, and the hydrogen gas is controlled by a mass flow meter. The reaction is carried out under fixed conditions: the reaction temperature is 280℃, the reaction pressure is 1atm, the feedstock space velocity (WHSV) of caprolactone is 0.6h -1 , and the molar ratios of ammonia-ester, hydrogen-ester and water-ester are 6, 50 and 30, respectively.

[0106] The beneficial effects of the present application are as follows:

[0107] Firstly, the Cu-Beta zeolite catalyst is prepared by the improved ammonia evaporation method on the de-aluminized Beta zeolite carrier, so that the copper ammonia complex mainly deposits copper hydroxide in the zeolite pore during the ammonia evaporation process. The copper hydroxide deposited in the zeolite pore can form high-dispersed nano and sub-nano copper particles at the hydroxyl lattice defect sites in the pore after calcination and hydrogen reduction treatment. The high-dispersed nano and sub-nano copper particles thus formed can interact closely with the hydroxyl lattice defect sites, and are stabilized by the active silicon hydroxyl in the hydroxyl hole, so that the Cu-Beta zeolite catalyst can be used under harsh conditions where water vapor, hydrogen and ammonia coexist without the help of anti-sintering additives such as chromium and nickel. Secondly, the core of the improved ammonia evaporation method is to impregnate the de-aluminized Beta zeolite carrier with the copper ammonia complex solution in equal volume. Since the amount of the copper ammonia complex solution is small, the damage of the de-aluminized Beta zeolite framework caused by the silicon dissolving effect of the alkaline copper ammonia complex solution (pH = 10-12) is inhibited, so that the de-aluminized Beta zeolite hydroxyl hole can play a role in dispersing and stabilizing the high-dispersed nano and sub-nano copper particles, and the Cu-Beta zeolite catalyst with high activity, high selectivity and high stability can be prepared. In addition, the Cu-Beta zeolite catalyst is used for the gas-solid phase hydrogenation of caprolactone, which can greatly reduce the industrialization difficulty of the caprolactam production process using caprolactone. BRIEF DESCRIPTION OF DRAWINGS

[0108] Figure 1 is an XRD pattern of the de-aluminized Beta zeolite carrier (Beta24c) obtained by acid de-aluminization of the Beta zeolite mother body with a silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of 24, and an XRD pattern of the Cu-Beta zeolite catalyst (Cu3-Beta24c-1) with a copper content of 3wt.% prepared by the improved ammonia evaporation method using Beta24c as the carrier.

[0109] Figure 2 is an infrared spectrum of the hydroxyl region of the de-aluminized Beta zeolite carrier (Beta24c) obtained by acid de-aluminization of the Beta zeolite mother body with a silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of 24, and an infrared spectrum of the hydroxyl region of the Cu-Beta zeolite catalyst (Cu3-Beta24c-1) with a copper content of 3wt.% prepared by the improved ammonia evaporation method using Beta24c as the carrier.

[0110] Figure 3 is a high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) photo of the Cu3-Beta24c-1 catalyst.

[0111] Figure 4 is a high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) photo of the high-temperature calcined (550℃×3h) sample of the Cu3-Beta24c-1 catalyst.

[0112] Figure 5 is an XRD pattern of the dealuminated Beta zeolite support (Beta24c) with a silicon alumina oxide molar ratio (molar ratio of Si02to Al203) of 24, and an XRD pattern of a Cu-Beta zeolite catalyst (Cu3-Beta24c-CE1) with a copper content of 3 wt.% prepared by a conventional ammonium vapor method using Beta24c as the support. DETAILED DESCRIPTION

[0113] The implementation effects of the present application can be evaluated by characterizing the physicochemical properties of the prepared Cu-Beta zeolite catalyst and detecting its catalytic performance in the reaction of hydrogenation of caprolactone to caprolactam in a gas-solid phase.

[0114] In the characterization of the physicochemical properties of the Cu-Beta zeolite catalyst, the damage of the crystal structure, the occupation of the hydroxyl pockets, the high dispersion of the loaded copper metal, and the anti-sintering of the copper particles can be characterized.

[0115] The damage of the crystal structure of the Beta zeolite can be characterized by X-ray powder diffraction (XRD) method. If the ammonium vapor treatment causes significant damage to the crystal structure of the Beta zeolite, the intensity of the characteristic diffraction peak at 2θ = 22-23° of the XRD pattern of the catalyst will be significantly reduced. If the dealuminated Beta zeolite support is used as a reference sample, the relative degree of reduction of the crystallinity of the zeolite support in the Cu-Beta zeolite catalyst can also be estimated.

[0116] The occupation of the hydroxyl pockets in the Cu-Beta zeolite catalyst can be characterized by Fourier transform infrared spectroscopy (FT-IR) method to obtain the hydroxyl vibration infrared spectrum of the catalyst and compare it with the hydroxyl vibration infrared spectrum of the dealuminated Beta zeolite support for qualitative judgment. The more the nanometer and sub-nanometer copper particles fall into the hydroxyl pockets, the weaker the intensity of the infrared characteristic band of the hydroxyl pockets (the widened absorption band between 3300-3600 cm -1 -1).

[0117] In addition, the high dispersion of the loaded copper metal in the Cu-Beta zeolite catalyst can be observed by transmission electron microscopy (TEM), and the anti-sintering of the copper particles can be observed by calcination treatment combined with TEM observation. The catalytic activity (caprolactam yield) decay of the catalyst in the reaction of hydrogenation of caprolactone to caprolactam in a gas-solid phase can also be used for judgment.

[0118] As to the catalytic performance of the Cu-Beta zeolite catalyst in the gas-solid phase reductive amination of caprolactone to caprolactam, a small fixed bed reactor in the laboratory was used for evaluation. The operation method and the reaction condition range were as mentioned above. The composition of the reaction product was analyzed by gas chromatography (GC) with FID detector, equipped with OV-1701 chromatographic column, and the conversion of caprolactone and the selectivity of caprolactam were calculated by internal standard method (internal standard substance was 1, 4-dioxane), and the yield data of caprolactam were obtained by the product of the conversion of caprolactone and the selectivity of caprolactam as the evaluation index of the catalytic activity of the catalyst.

[0119] The present application will be further described by examples below, but the present application is not limited by these examples.

[0120] Example 1: This example is used to illustrate that the Cu-Beta zeolite catalyst prepared by using the improved ammonia evaporation method to load copper in the pore of the de-aluminized Beta zeolite carrier can better maintain the crystal structure of the de-aluminized Beta zeolite carrier, and can make the loaded copper mainly in the form of highly dispersed nano and sub-nano copper particles located in the hydroxyl hole lattice defect site in the zeolite pore, so as to be stabilized by the active silicon hydroxyl in the hydroxyl hole, thereby improving the sintering resistance. The prepared Cu-Beta zeolite catalyst is suitable as a catalyst for the gas-solid phase reductive amination of caprolactone to caprolactam.

[0121] Firstly, the Cu-Beta zeolite catalyst was prepared according to the embodiments provided by the present application:

[0122] First step, preparation of de-aluminized Beta zeolite carrier

[0123] (1) The Beta zeolite mother body with a molar ratio of silicon aluminum oxide (molar ratio of SiO2 to Al2O3) of 25 was synthesized by the hydrothermal crystallization method provided by US patent US3 308 069 (1967) as the raw material for preparing the de-aluminized Beta zeolite carrier. After the synthesized Beta zeolite mother body was treated by conventional filtration, washing, drying (110℃, 12h) and calcination to remove the template agent (540℃, 6h), its grain size was less than 100 nanometers observed by TEM, which belonged to nano Beta zeolite; no any impurity crystal was found by XRD method, and its BET specific surface area was about 550m 2 / g calculated by the nitrogen physical adsorption data, and its molar ratio of silicon aluminum oxide (molar ratio of SiO2 to Al2O3) was about 24 measured by XRF method, which met the technical requirements of the Beta zeolite mother body of the present application.

[0124] (2) The Beta zeolite mother body was treated by de-alumination with concentrated nitric acid to prepare the de-aluminized Beta zeolite carrier.

[0125] First, a concentrated nitric acid solution with a molar concentration of 13 M was prepared. Then, 20 g of the Beta zeolite mother substance which had been subjected to the drying and calcination treatment described above was added to a three-necked flask containing 400 ml of the 13 M concentrated nitric acid solution at a liquid-to-solid ratio of 20:1 (ml / g) under stirring to perform the dealumination treatment. The dealumination temperature was 95°C and the dealumination time was 20 h. During the dealumination reaction, the three-necked flask was kept in a reflux state. After the dealumination reaction was completed, the liquid was cooled to room temperature and the solid product was recovered by filtration. Then, the dealuminated Beta zeolite support was obtained by using a conventional water washing, drying (overnight at 110°C) and calcination treatment (550°C for 3 h). The dealuminated Beta zeolite support was designated as Beta24c, in which the lower case "c" represents the hydroxyl pockets produced in the Beta zeolite by dealumination. The molar ratio of silicon to alumina oxide (molar ratio of SiO2 to Al2O3) of the dealuminated Beta zeolite support was 980, which was suitable as a support for the catalyst of the present application. It was stored in a sealed state to avoid moisture absorption and was kept ready for use.

[0126] Second, copper was loaded in the pores of the dealuminated Beta zeolite to prepare a Cu-Beta zeolite catalyst by using an improved ammonia evaporation method

[0127] (1) A dilute ammonia water base solution was prepared and a copper ammonia complex was synthesized using copper nitrate trihydrate (Cu(NO3)2-3H2O), and then a saturated solution of the copper ammonia complex was prepared at room temperature. The dilute ammonia water base solution had a pH value of 11-12 and was prepared by adding 4.4 g of industrial ammonia water (containing 25-28 wt.% of NH3) to 100 ml of deionized water. The copper ammonia complex was obtained by reacting Cu(NO3)2-3H2O with industrial ammonia water at a molar ratio of copper ions to ammonia molecules of 1:4. The saturated solution of the copper ammonia complex was obtained by dissolving the copper ammonia complex in the dilute ammonia water base solution and contained about 0.4 M of the copper ammonia complex.

[0128] (2) The zeolite support was impregnated with an equal volume of the copper ammonia complex solution to prepare a Cu-Beta zeolite catalyst with a copper loading of 3 wt.%. First, 5 g of the dealuminated Beta zeolite support (Beta24c) which had been calcined and stored in a sealed state was titrated with deionized water until all the samples were uniformly wet but no free liquid water appeared, and a total of 6 ml of deionized water was consumed. The water absorption rate of the dealuminated Beta zeolite support (Beta24c) was calculated to be 1.2 ml / g. According to the 10 g loading amount of the support, a total of 12 ml of the copper ammonia complex solution was required. According to the calculation of the copper loading of 3 wt.%, the concentration of the copper ammonia complex solution required was about 0.39 M. That is, the calculated value of the concentration of the copper ammonia complex solution required was very close to the concentration of the saturated solution of the copper ammonia complex. Therefore, 10 g of the dealuminated Beta zeolite support (Beta24c) was directly impregnated with an equal volume of the saturated solution of the copper ammonia complex, i.e., 12 ml. The equal volume impregnation was performed at room temperature for 4 h.

[0129] (3) Ammonia desorption treatment was carried out on the impregnated material at normal pressure. The ammonia desorption temperature was 80°C, and the ammonia desorption time was 10h. During this process, the copper-ammonia complex that entered the zeolite pores due to capillary condensation gradually deposited in the zeolite pores in the form of copper hydroxide as ammonia gas was lost.

[0130] (4) Dehydration and drying treatment was carried out on the ammonia desorbed material. The drying temperature was 110°C, and the drying time was 12h

[0131] (5) Calcination treatment was carried out on the dried material. The calcination temperature was 500°C, and the calcination time was 3h. After calcination, the copper hydroxide deposited in the zeolite pores was converted into nano- and sub-nano-sized copper oxide particles, thus producing a catalyst precursor.

[0132] (6) Hydrogen reduction treatment was carried out on the catalyst precursor. The reduction temperature was 400°C, the reduction time was 4h, and the hydrogen flow rate (expressed in terms of hydrogen gas volume space velocity, defined as the hydrogen gas volume that passed through the catalyst per unit time per unit volume, calculated on the basis of ideal gas) was 300h -1 After hydrogen reduction treatment, the finished Cu-Beta zeolite catalyst, designated Cu3-Beta24c-1, was produced.

[0133] Secondly, in order to understand the implementation effect of the catalyst preparation method provided by the present application from the aspect of the physicochemical properties of the catalyst, the XRD pattern and the hydroxyl vibration infrared spectrum of Cu3-Beta24c-1 and its dealuminated Beta zeolite carrier (Beta24c) were measured in parallel using XRD and FT-IR methods, as shown in Figs. 1 and 2. In addition, TEM photos of the Cu3-Beta24c-1 catalyst and its high-temperature calcined sample (550°C x 3h) were taken using a transmission electron microscope, as shown in Figs. 3 and 4.

[0134] As can be seen from Fig. 1, the Cu3-Beta24c-1 catalyst prepared by the improved ammonia evaporation method provided by the present application well retains the crystal structure of the Beta zeolite, and the relative crystallinity of the zeolite in the catalyst calculated based on the dealuminated Beta zeolite carrier (Beta24c) is 79%. As can be seen from Fig. 2, the Cu3-Beta24c-1 catalyst prepared according to the method of the present application has a greater decrease in the intensity of the hydroxyl pit infrared characteristic spectrum band compared with the dealuminated Beta zeolite carrier (Beta24c), indicating that a large amount of copper metal occupies the hydroxyl pit lattice defect sites. In addition, as can be seen from Figs. 3 and 4, the copper metal particles in the Cu3-Beta24c-1 catalyst exist in a highly dispersed nano and sub-nano particle state, and the average particle size is about 6 nm. After being calcined at a high temperature of 550 ℃ for 3 h, the copper metal particles have a good dispersion state, and the average particle size is about 10 nm. These data show that the hydroxyl pit lattice defect sites of the dealuminated Beta zeolite carrier have the effect of dispersing and stabilizing the nano and sub-nano copper particles.

[0135] On this basis, the catalytic performance of the Cu3-Beta24c-1 catalyst and the sample thereof calcined at a high temperature of 550 ℃ is evaluated by using caprolactam gas-solid phase hydrogenation to prepare caprolactam. The reaction is carried out on a small fixed bed reactor. The inner diameter of the stainless steel reaction tube is 9 mm, and the upper feeding and lower discharging operation mode is adopted. 2 g of the catalyst (after sieving, the sample of 20-40 mesh is taken) pressed into a tablet is loaded in the constant temperature zone of the reactor. Inert porcelain balls are filled in the upper and lower spaces of the catalyst bed. Among them, the upper porcelain ball area of the reactor serves as the vaporization and preheating zone of the raw material. The reaction constant temperature zone temperature is 280 ℃, the reaction pressure is 1 atm, the caprolactam feed space velocity (WHSV) is 0.6 h-1, the hydrogen-ester molar ratio is 50, and the reaction time is 6 h. -1 For the convenience, the caprolactam, ammonia raw material (analytical pure, ammonia gas concentration is 25-28 wt.%) and deionized water are mixed into a raw material liquid according to the ammonia-ester molar ratio of 6 and the water-ester molar ratio of 30, a trace metering pump is used to feed the raw material liquid to the reactor, and a mass flow meter is used to control the hydrogen-ester molar ratio of 50. The reaction product is continuously collected in a stainless steel collection tank connected with the reactor outlet with a cooling water jacket, the product liquid is collected at a fixed time interval, analyzed on a Shimadzu gas chromatograph GC-2014 (FID detector, OV-1701 chromatographic column), and the caprolactam conversion rate and caprolactam selectivity are calculated by an internal standard method (the internal standard is 1,4-dioxane). Under the above conditions, when the caprolactam hydrogenation reaction is continuously carried out for 6 h, the caprolactam yield of the Cu3-Beta24c-1 catalyst is about 84%, and the caprolactam yield of the sample thereof calcined at a high temperature of 550 ℃ is 81%. The above reaction results show that the Cu-Beta zeolite catalyst provided by the present application is an excellent catalyst for the caprolactam hydrogenation reaction.

[0136] Comparative Example 1: This example is used to illustrate that when a dealuminated Beta zeolite is used as a support and a copper-Beta zeolite catalyst is prepared by a traditional ammonia evaporation method, the crystal structure of the Beta zeolite support is severely damaged, the copper metal is mainly located outside the zeolite pores, the dispersion of the copper metal is low, and the particle size of the copper particles is large. Because the active silicon hydroxyl groups in the hydroxyl pockets of the dealuminated Beta zeolite are not protected, the sintering resistance is poor.

[0137] Example 1 was repeated, but after the qualified dealuminated Beta zeolite support (Beta24c) was prepared in the first step, copper hydroxide was deposited on the dealuminated Beta zeolite support using the same traditional ammonia evaporation method as the published document Science 10.1126 / science. adj1962 (2023). The details are as follows:

[0138] (1) 1.18 g of Cu(NO3)2·3H2O was dissolved in 515 ml of an ammonia water solution (containing 3.86 g of NH3·H2O, which is equivalent to 8.1 ml of 26 wt.% industrial ammonia water, and the molar ratio of copper ions to ammonia molecules is about 1:23) and stirred at room temperature for 10 min to prepare a copper-ammonia complex aqueous solution (the concentration of the complex ions is about 9.5 mmol / L, i.e., 9.5 mM);

[0139] (2) 10 g of the dealuminated Beta zeolite support (Beta24c) was added to the 515 ml copper-ammonia complex solution, and ammonia evaporation treatment was carried out under vigorous stirring. The ammonia evaporation temperature was 80°C, and the ammonia evaporation time was 6 h;

[0140] (3) After the ammonia evaporation was completed, the water solvent of the diluted and volumetrically excessive copper-ammonia complex solution was finally removed by filtration. The obtained filter cake was dried, calcined, and hydrogen-reduced according to the same post-processing method of Example 1, and a Cu-Beta zeolite catalyst was obtained, which was coded as Cu3-Beta24c-CE1 (CE = Comparative Example).

[0141] In order to understand the characteristics of the Cu-Beta zeolite catalyst prepared by the traditional ammonia evaporation method from the aspect of the physicochemical properties of the catalyst, the Beta zeolite crystal structure of the Cu3-Beta24c-CE1 catalyst was characterized by XRD, and was compared with that of its support (Beta24c), as shown in Figure 5. In addition, the Cu metal dispersion of the Cu3-Beta24c-CE1 catalyst and its high-temperature calcined sample (550°C x 3 h) was characterized by transmission electron microscopy, and the catalytic performance of the Cu3-Beta24c-CE1 catalyst and its high-temperature calcined sample was evaluated by the caprolactam synthesis reaction of caprolactone gas-solid phase hydrogenation.

[0142] As can be seen from Figure 5, the Cu3-Beta24c-CE1 catalyst prepared by the conventional ammonia evaporation method has a large damage to the crystal structure of the Beta zeolite, and the relative crystallinity of the zeolite in the catalyst calculated based on the support (Beta24c) is 62%. According to the characterization results of transmission electron microscopy, the average particle size of Cu metal on the Cu3-Beta24c-CE1 catalyst and its high-temperature calcined sample is 11 nm and 20 nm, respectively, that is, the Cu metal on the catalyst has low dispersity and is easy to sinter. The reaction evaluation results show that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24c-CE1 catalyst is about 77%, and the caprolactam yield of its high-temperature calcined sample is about 72%. The reaction results show that the Cu-Beta zeolite catalyst prepared by the conventional ammonia evaporation method on the dealuminated Beta zeolite support has low catalytic activity for the gas-solid phase hydrogenation of caprolactone to caprolactam and poor anti-sintering inactivation ability.

[0143] Comparative Example 2: This example is used to illustrate that the copper-silica catalyst prepared by the conventional ammonia evaporation method using amorphous fumed silica (white carbon black, BET specific surface area 286 m 2 / g) as the support has poor anti-sintering ability.

[0144] In this example, the conventional ammonia evaporation method refers to the method of Example 1 in US Patent US 4 440 873 (1984), which is as follows:

[0145] (1) 1.14 g of copper nitrate (Cu(NO3)2.3H2O) was dissolved in 100 ml of water to obtain an aqueous solution containing copper ions, and then 3.6 ml of concentrated ammonia solution (NH3 content is 26 wt. % of industrial ammonia water, density 0.89 g / ml) was added to the solution according to a molar ratio of copper ions to ammonia molecules of about 1:10, and 50 ml of water was added to obtain a deep blue copper-ammonia complex solution (complex ion concentration is about 30.8 mM) with a pH value of 11-12. The purpose of adding 50 ml of water is to keep the ratio of the solution volume to the silica dry basis consistent with the literature;

[0146] (2) 10 g of fumed silica (dry basis) was added to the copper-ammonia complex solution, and stirred at room temperature for 2 h;

[0147] (3) The reaction mixture of step (2) was subjected to temperature ammonia evaporation treatment (80°C, 6h), and when the pH of the mixture decreased to 6-7, the solid was obtained by filtration, and then washed with deionized water three times to obtain a solid product;

[0148] (4) The solid product was dried at 120°C for 12 h and calcined at 450°C for 4 h;

[0149] (5) The solid product after calcination was subjected to hydrogen reduction treatment. The reduction condition was 350°C x 2h, and a copper-silica catalyst, code Cu3-SiO2-CE2, was obtained.

[0150] The evaluation results of the caprolactam production reaction by gas-solid phase hydrogenation amination of caprolactone showed that, under the same reaction conditions, the caprolactam yield of the Cu3-SiO2-CE2 catalyst was 77%; the caprolactam yield of the high-temperature calcined sample (550°C x 3h) was 69%. The reaction results showed that the copper-based catalyst prepared with amorphous silica as the carrier had poor sintering resistance, and the catalytic activity greatly decreased after high-temperature treatment.

[0151] Comparative Example 3: This example was used to further illustrate that the copper-silica catalyst prepared by loading copper with the traditional ammonia evaporation method had poor sintering resistance.

[0152] Comparative Example 2 was repeated, but 33.3g of silica sol (30wt.% SiO2) was used as the precursor for in-situ generation of 10g of the silica carrier. In order to keep the ratio of the volume of the copper ammonia complex solution to the dry basis of the silica consistent with that of Comparative Example 2, the amount of water added was changed to 26.7ml when preparing the copper ammonia complex solution in step (1). The copper-silica catalyst prepared was code Cu3-SiO2-CE3.

[0153] The evaluation results of the caprolactam production reaction by gas-solid phase hydrogenation amination of caprolactone showed that, under the same reaction conditions, the caprolactam yield of the Cu3-SiO2-CE3 catalyst was 80%; the caprolactam yield of the high-temperature calcined sample (550°C x 3h) was 68%. The reaction results also showed that the copper-based catalyst prepared with amorphous silica as the carrier had poor sintering resistance, and the catalytic activity greatly decreased after high-temperature treatment.

[0154] Comparative Example 4: This example was used to illustrate that the amorphous nature of the silica carrier determined the poor sintering resistance of the copper-silica catalyst.

[0155] In this example, a copper-silica catalyst was prepared on a fumed silica carrier by using the improved ammonia evaporation method provided by the present application. The specific process was as follows:

[0156] Example 1 was repeated, but the 10g of dealuminated Beta zeolite carrier was replaced with 10g (dry basis) of fumed silica (white carbon black, BET specific surface area 286m 2 / g, the saturated water absorption is 2.5 ml / g), 10 g of fumed silica requires 25 ml of copper ammonia complex solution. The concentration of the required copper ammonia complex solution is about 0.19 M according to the copper loading of 3 wt.%. 11.9 ml of the saturated copper ammonia complex solution is diluted to 25 ml with the dilute ammonia water base solution, i.e. 25 ml of the copper ammonia complex solution with a concentration of 0.19 M is obtained. The prepared copper-silica catalyst is coded as Cu3-SiO2-CE4.

[0157] The evaluation results of the caprolactam production by the gas-solid phase hydrogenation of caprolactone show that the caprolactam yield of the Cu3-SiO2-CE4 catalyst is 78% under the same reaction conditions; the caprolactam yield of the high-temperature calcined sample (550°C x 3 h) is 69%. The reaction results also show that the copper-based catalyst prepared with amorphous silica as the carrier has a poor sintering resistance, and the catalytic activity is greatly reduced after high-temperature treatment.

[0158] Example 2: This example is used to illustrate that the Cu-Beta zeolite catalyst preparation method provided by the application, i.e. the improved ammonia evaporation method for loading copper in the pore channels of the zeolite, can be used to prepare Cu-Beta zeolite catalysts with different copper loadings.

[0159] Example 1 is repeated, but the copper loading in the prepared Cu-Beta zeolite catalyst is sequentially reduced to 1 wt.% and 2 wt.%, and the concentration of the required copper ammonia complex solution is sequentially about 0.13 M and 0.26 M. 3.9 ml and 7.8 ml of the saturated copper ammonia complex solution are sequentially diluted to 12 ml with the dilute ammonia water base solution, i.e. the equal-volume impregnation solutions of the Cu-Beta zeolite catalysts with a copper loading of 1 wt.% and 2 wt.% are obtained. In the preparation of the Cu-Beta zeolite catalyst by the improved ammonia evaporation method, the equal-volume impregnation treatment time of the de-aluminized Beta carrier at room temperature is changed to 6 h, the ammonia evaporation treatment temperature and time are changed to 65°C and 12 h respectively, the dehydration drying temperature and time are changed to 150°C and 3 h respectively, the subsequent calcination temperature and time are changed to 450°C and 6 h respectively, the final hydrogen reduction temperature and time are changed to 350°C and 8 h respectively, and the hydrogen flow rate (volume space velocity) is changed to 1000 h-1. The prepared Cu-Beta zeolite catalysts are coded as Cu1-Beta24c-2 and Cu2-Beta24c-2 in sequence. -1

[0160] The evaluation results of the caprolactam production by the gas-solid phase hydrogenation of caprolactone show that the caprolactam yield of the Cu1-Beta24c-2 catalyst is 81% under the same reaction conditions; the caprolactam yield of the Cu2-Beta24c-2 is 82%.

[0161] ​Example 3: This example is used to further illustrate that the Cu-Beta zeolite catalysts with different copper loadings can be prepared according to the improved method for loading copper in the pores of the zeolite using the de-aluminated Beta zeolite as the support and the improved ammonia stripping method. However, when preparing Cu-Beta zeolite catalysts with copper loadings higher than 3 wt.%, it is preferred to use the multiple loading scheme to prepare the catalysts.

[0162] Example 1 was repeated, but the copper loading in the prepared Cu-Beta zeolite catalyst was increased to 4wt.% and 6wt.% respectively, and the concentration of the required copper-ammonia complex solution was calculated to be about 0.52M and 0.79M respectively. Obviously, the required copper-ammonia complex concentration exceeds the concentration of the copper-ammonia complex saturated solution prepared with the dilute ammonia water base solution. We tried to dissolve the copper-ammonia complex with industrial ammonia water instead of the dilute ammonia water base solution, and the maximum concentration of the copper-ammonia complex solution obtained was about 0.5M. Although the copper-ammonia complex solution with a high concentration of about 0.5M can be prepared by dissolving the copper-ammonia complex with industrial ammonia water, the ammonia / copper ion molar ratio of the solution exceeds 24:1, the basicity is strong, and ammonia gas volatilization is serious, i.e. it is not conducive to the protection of the crystal structure of the dealuminated Beta zeolite and the operation. This indicates that the Cu-Beta zeolite catalyst with a high copper loading cannot be obtained by one-time equal-volume impregnation and ammonia evaporation operation on the dealuminated Beta zeolite support by using the improved ammonia evaporation method. In view of this, the dilute ammonia water base solution is used to dilute the copper-ammonia complex saturated solution, and the Cu-Beta zeolite catalyst with a copper loading of 4wt.% and 6wt.% respectively is prepared according to multiple equal-volume impregnation and ammonia evaporation operations. For the preparation of the catalyst with a copper loading of 4wt.%, two-time equal-volume impregnation and ammonia evaporation operations can be performed, such as 1wt.%+3wt.% or 2wt.%+2wt.%; for the preparation of the catalyst with a copper loading of 6wt.%, two-time (3wt.%+3wt.%) or three-time (2wt.%+2wt.%+2wt.%) operations can be performed. In order to be simple, in this example, the Cu-Beta zeolite catalyst with a copper loading of 4wt.% and 6wt.% respectively is prepared by two-time (2wt.%+2wt.% or 3wt.%+3wt.%) operations. The 2wt.% of metal copper is loaded on the dealuminated Beta zeolite support by one-time operation by using the improved ammonia evaporation method, and 12ml of the impregnation solution with a copper-ammonia complex concentration of 0.26M is required; the 3wt.% of metal copper is loaded on the dealuminated Beta zeolite support by one-time operation by using the improved ammonia evaporation method, and 12ml of the impregnation solution with a copper-ammonia complex concentration of 0.40M is required. Among them, the 0.26M impregnation solution is obtained by diluting 7.8ml of the copper-ammonia complex saturated solution with the dilute ammonia water base solution, and the 0.40M impregnation solution is directly obtained by using the copper-ammonia complex saturated solution. When the dealuminated Beta support is subjected to equal-volume impregnation at room temperature, the impregnation time is changed to 6h, the ammonia evaporation treatment temperature and time are changed to 85℃ and 3h respectively, the dehydration and drying temperature and time are changed to 120℃ and 5h respectively, the subsequent calcination temperature and time are changed to 550℃ and 2h respectively, the final hydrogen reduction temperature and time are changed to 500℃ and 2h respectively, and the hydrogen flow (volume space velocity) is changed to 20h -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.

[0163] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield was 80% with the Cu4-Beta24C-3 catalyst and 79% with the Cu6-Beta24C-3 catalyst.

[0164] 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.

[0165] Example 1 was repeated, but in the first step of preparing the dealubilized 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 dealubilized 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 its nitrogen physical adsorption data. 2 The molar ratio of silicon-aluminum oxides (SiO2 to Al2O3) was approximately 23, as determined by XRF, which meets the technical requirements of this invention for the Beta zeolite matrix. This Beta zeolite matrix was dealuminized with 13M concentrated nitric acid to become a large-grain dealuminized Beta zeolite support (designated Beta23c), with a silicon-aluminum oxide molar ratio (SiO2 to Al2O3) of 748 (>700), meeting the technical requirements of this invention for the dealuminized Beta zeolite support. Based on this, 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.%, designated Cu3-Beta23c-4.

[0166] 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 82%.

[0167] Example 5: This example is used to illustrate that the improved ammonia evaporation method provided in the present application allows the use of Beta zeolite mother substance with different silica-alumina molar ratio (molar ratio of SiO2 to Al2O3) to prepare the dealuminated Beta zeolite support.

[0168] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, the Beta zeolite mother substance with silica-alumina molar ratio (molar ratio of SiO2 to Al2O3) of 60 was synthesized by hydrothermal crystallization method provided in US Patent 3 308 069 (1967) as the raw material for preparing the dealuminated Beta zeolite support. After the synthesized Beta zeolite mother substance was treated by conventional filtration, washing, drying (170°C, 3h) and calcination to remove the template agent (500°C, 8h), TEM observation showed that the average crystal size of the Beta zeolite was close to 100 nanometers, which belonged to nano-Beta zeolite; XRD examination showed that there was no any impurity crystal in it, and the BET specific surface area calculated from its nitrogen physical adsorption data was about 530 m2 / g; and XRF measurement showed that the silica-alumina molar ratio (molar ratio of SiO2 to Al2O3) of the Beta zeolite was about 57, which met the technical requirements of the Beta zeolite mother substance in the present application. 2

[0169] The Beta zeolite mother substance was used to prepare the dealuminated Beta zeolite support by concentrated nitric acid dealumination, and a dealuminated Beta zeolite support with silica-alumina molar ratio (molar ratio of SiO2 to Al2O3) of 861 (>800) was obtained (Beta57c). The degree of dealumination of the support met the requirements in the present application. On this basis, a Cu-Beta zeolite catalyst with copper content of 3wt.% was prepared by the improved ammonia evaporation method. In this process, when the support was impregnated with the saturated solution of copper-ammonia complex at room temperature, the impregnation time was changed to 2h. In the ammonia evaporation, micro-negative pressure ammonia evaporation was used, the ammonia evaporation temperature was 50°C, and the ammonia evaporation time was 48h. In the dehydration and drying of the material after ammonia evaporation, the drying temperature and time were changed to 100°C and 48h, respectively. The subsequent calcination treatment temperature and time were changed to 350°C and 24h, respectively. The final hydrogen reduction treatment temperature, time and hydrogen flow (volume space velocity) were changed to 300°C, 20h and 2000h -1 , respectively, and the catalyst code was Cu3-Beta57c-5

[0170] The evaluation results of caprolactam gas-solid phase hydrogenation ammination of caprolactone showed that under the same reaction conditions, the caprolactam yield of Cu3-Beta57c-7 catalyst was 80%.

[0171] ​Example 6: This example is used to further illustrate that the improved ammonia evaporation method provided according to the present application allows the use of Beta zeolite precursors with different silica-alumina molar ratios (molar ratio of SiO2 to Al2O3) to prepare the dealuminated Beta zeolite support.

[0172] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, Beta zeolite precursors with silica-alumina molar ratios (molar ratio of SiO2 to Al2O3) of 40, 80, 100, 150 and 200 were first synthesized according to the hydrothermal crystallization method provided in Chinese Invention Patent CN1108275C (filing date 10 September 1999) as raw materials for preparing the dealuminated Beta zeolite support. After the synthesized Beta zeolite precursors were subjected to the conventional filtration, washing, drying (110°C, 12h) and calcination to remove the template (540°C, 6h), TEM observation showed that the average crystal size of the Beta zeolite precursors was in the nanometer and small crystal (less than 1 μm) ranges. With the increase of the silica-alumina molar ratio (molar ratio of SiO2 to Al2O3), the crystal size increased. XRD examination did not find any impurity crystals in them, and the BET specific surface area calculated from the nitrogen physical adsorption data of the Beta zeolite precursors was higher than 500 m2 / g. XRF measurement showed that the silica-alumina molar ratios (molar ratio of SiO2 to Al2O3) of the Beta zeolite precursors were 38, 72, 94, 136 and 189, respectively, which met the technical requirements of the Beta zeolite precursors according to the present application. 2 / g, and the silica-alumina molar ratios (molar ratio of SiO2 to Al2O3) of the Beta zeolite precursors were 38, 72, 94, 136 and 189, respectively, which met the technical requirements of the Beta zeolite precursors according to the present application.

[0173] The above five Beta zeolite precursors were used to prepare the dealuminated Beta zeolite supports by concentrated nitric acid dealumination to obtain five dealuminated Beta zeolite supports Beta38c, Beta72c, Beta94c, Beta136c and Beta189c with silica-alumina molar ratios (molar ratio of SiO2 to Al2O3) of 870, 855, 932, 1088 and 960, respectively, which all met the technical requirements of the dealuminated Beta zeolite supports. On this basis, Cu-Beta zeolite catalysts with a copper content of 3 wt.% were prepared by the improved ammonia evaporation method. In this process, when the support was impregnated with the saturated solution of copper-ammonia complex at room temperature, the impregnation time was changed to 1 h. In the ammonia evaporation, the ammonia evaporation temperature was 90°C and the ammonia evaporation time was 1 h. In the dehydration and drying of the material after ammonia evaporation, the drying temperature and time were changed to 200°C and 1 h, respectively. The subsequent calcination treatment temperature and time were changed to 550°C and 1 h, respectively. The final hydrogen reduction treatment temperature, time and hydrogen flow rate were changed to 550°C, 1 h and 5 h, respectively. -1 (Cu3-Beta 38c-6, Cu3-Beta 72c-6, Cu3-Beta 94c-6, Cu3-Beta 136c-6 and Cu3-Beta 189c-6, respectively) were prepared by the same method as described in Example 1 except that the Beta zeolite mother substance with different SiO2 / Al2O3 molar ratio was used as the raw material for preparing the dealuminated Beta zeolite support in the first step.

[0174] The anti-sintering deactivation performance of the above catalysts and their 550°C calcination (3h) samples was evaluated by the reaction of caprolactam gas solid phase hydrogenation amination with caprolactone. The results showed that under the same reaction conditions, the catalytic activity (caprolactam yield) of Cu3-Beta 38c-6, Cu3-Beta 72c-6, Cu3-Beta 94c-6, Cu3-Beta 136c-6 and Cu3-Beta 189c-6 catalysts after high temperature calcination decreased by about 5%, 8%, 10%, 14% and 17%, respectively.

[0175] Example 7: This example is used to illustrate that when the improved ammonia evaporation method provided by the present application is used to prepare Cu-Beta zeolite catalyst, it allows the use of Beta zeolite mother substance with different SiO2 / Al2O3 molar ratio to prepare the dealuminated Beta zeolite support. However, using Beta zeolite mother substance with higher SiO2 / Al2O3 molar ratio to prepare the dealuminated Beta zeolite support is suitable for preparing Cu-Beta zeolite catalyst with lower copper loading.

[0176] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, the Beta zeolite mother substance with SiO2 / Al2O3 molar ratio of 100 was synthesized by the hydrothermal crystallization method provided by Chinese invention patent CN1108275C (application date 1999.9.10) as the raw material for preparing the dealuminated Beta zeolite support. After the synthesized Beta zeolite mother substance was treated by conventional filtration, washing, drying (200°C, 3h) and calcination to remove the template agent (500°C, 8h), its average crystal size was observed by TEM to be in the small crystal size (less than 1 μm) level. No any impurity crystal was found by XRD method, and its BET specific surface area calculated from its nitrogen physical adsorption data was higher than 530 m2 / g, and its SiO2 / Al2O3 molar ratio measured by XRF method was 94, which met the technical requirements of the Beta zeolite mother substance of the present application. 2

[0177] ​The Beta zeolite mother substance was used for dealumination with concentrated nitric acid to prepare a dealuminated Beta zeolite support with a silica-alumina molar ratio (molar ratio of Si02to Al203) of 932 (>900) (Beta94c), the silica-alumina molar ratio of the support meeting the technical requirements of the present application. On this basis, a Cu-Beta zeolite catalyst with a copper content of 6 wt.% was prepared by the improved ammonia evaporation method according to the procedure of twice equal-volume impregnation and twice ammonia evaporation. The concentration of the copper-ammonia complex solution used in the twice equal-volume impregnation was 0.4 M of a saturated copper-ammonia complex solution. The code of the prepared catalyst was Cu6-Beta94c-7.

[0178] The anti-sintering deactivation performance of the catalyst and a sample thereof calcined at 550 °C (3 h) was evaluated by using the caprolactam gas-solid phase reaction of caprolactone. The results showed that under the same reaction conditions, the catalytic activity (caprolactam yield) of the Cu6-Beta94c-7 catalyst after high-temperature calcination decreased by 15%.< / t>

Claims

1. A method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone, characterized in that, The steps are as follows: The first step is to prepare a dealuminated Beta zeolite support. (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 has good crystallinity, i.e., the BET specific surface area value of the Beta zeolite matrix measured by nitrogen physical adsorption method is ≥450m². 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 10-200; (2) Preparation of dealuminized Beta zeolite carrier A dealuminized Beta zeolite support was prepared by acid dealuminization based on the Beta zeolite matrix; the required molar ratio of silicon-aluminum oxides, i.e., the molar ratio of SiO2 to Al2O3, in the prepared dealuminized Beta zeolite support was ≥700. The second step involves loading copper into the pores of a dealuminolite 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 4.4g of industrial ammonia water containing 25-28wt.% NH3 with 100ml 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 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 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 dealuminized Beta 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 pressure or reduced pressure; the temperature and time range for ammonia stripping are 50-100℃ and 0.5-48h, respectively. (4) Dehydration and drying treatment after ammonia stripping: The drying temperature and time ranges are 100-200℃ and 0.5-48h, 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 0.5-24h, respectively; The catalyst precursor was obtained after calcination. (6) Hydrogen reduction treatment of catalyst precursor: The reduction temperature, time and hydrogen volume hourly space velocity ranged from 280-600℃, 0.5-20h and 1-2000h, respectively. -1 The catalyst precursor is reduced with hydrogen to become Cu-Beta zeolite catalyst.

2. The method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone according to claim 1, characterized in that, 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 20-100.

3. The method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone according to claim 2, characterized in that, 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 a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone according to claim 1, characterized in that, In step (2), the required molar ratio of silicon aluminum oxide in the prepared dealuminized Beta zeolite support, i.e., the molar ratio of SiO2 to Al2O3, is ≥800.

5. The method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone according to claim 4, characterized in that, In step (2), the required molar ratio of silicon aluminum oxide in the prepared dealuminized Beta zeolite support, i.e., the molar ratio of SiO2 to Al2O3, is ≥900.

6. The method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone according to claim 1, characterized in that, In step (2), the Beta zeolite matrix is ​​subjected to acid dealumination treatment with concentrated nitric acid aqueous solution, as follows: 13M 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 hours. 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 hours, and calcined at 500℃-600℃ for 3-8 hours to obtain dealumination Beta zeolite.

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

8. The method for preparing a Cu-Beta zeolite catalyst for the production of caprolactam from caprolactone according to claim 7, characterized in that, In step (2), the immersion time for equal volume is in the range of 2-6 hours; In step (3), the temperature and time range for ammonia stripping are 65-85℃ and 3-12h; In the second step (4), the drying temperature and time ranges are 120-150℃ and 3-12h, respectively; In the second step (5), the roasting temperature and time ranges are 450-550℃ and 2-6h, respectively; In step 2 (6), the reduction temperature, time, and hydrogen volume hourly space velocity ranges are 350-500℃, 2-8h, and 20-1000h, respectively. -1 .

9. The Cu-Beta zeolite catalyst prepared by the method of any one of claims 1-8 for the preparation of caprolactone to caprolactam is used to catalyze the gas-solid phase hydroammoniation of caprolactone to caprolactam.

10. The application according to claim 9, characterized in that, The reaction conditions are as follows: The reaction temperature range is 120-350℃, the reaction pressure range is 0.01-2 atm, and the feed space velocity of caprolactone ranges from 0.1-5 h⁻¹. -1 The ranges of the molar ratios of amine-ester, hydrogen-ester, and water-ester are 1-50, 5-70, and 0-100, respectively.

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