Preparation method for improving stability of caprolactone to caprolactam Cu-Beta zeolite catalyst and application thereof

Abstract

The present application belongs to the field of petrochemical catalysis technology, and relates to a preparation method for improving the stability of a Cu-Beta zeolite catalyst for preparing caprolactam from caprolactone and application thereof. The present application uses a hole-modified dealuminated Beta zeolite as a carrier, and uses an improved ammonia evaporation method to load copper in the pores of the zeolite carrier. The hole modification refers to using a weak organic base to control the desilication technology to make the hydroxyl hole generated by dealuminating the Beta zeolite carrier larger, so as to better accommodate and stabilize the nano and sub-nano copper particles. The core of the improved ammonia evaporation method is to immerse the zeolite carrier in an equal volume of copper-ammonia complex solution, so that the copper-ammonia complex mainly undergoes a copper hydroxide deposition reaction in the zeolite pores during the ammonia evaporation process, thereby improving the sintering resistance. The Cu-Beta catalyst prepared by the method provided in the present application has high activity and selectivity, and good stability when applied to the reaction of preparing caprolactam from caprolactone by gas-solid phase hydrogenation.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of petrochemical catalysis technology, and relates to a preparation method for improving the stability of a Cu-Beta zeolite catalyst for preparing caprolactam from caprolactone and application thereof. BACKGROUND

[0002] ε-caprolactam (CPL) is a white solid organic compound, most of which is used for producing polyamide-6 chips, and a small part of which is used for producing lysine and pharmaceutical intermediates. In the downstream products of the polyamide-6 chips, nylon-6 fibers and engineering plastics consume about 70% and 20% of the polyamide-6 chips, respectively. The remaining polyamide-6 chips are processed into packaging films and food preservative films.

[0003] Nylon-6 is the first synthetic fiber product developed in the world. The most prominent advantage of nylon-6 fiber is that the wear resistance is higher than that of all other fibers. The wear resistance of nylon-6 fiber 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. A small amount of polyamide fiber added in a blended fabric can greatly improve the 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 for making shirts, pullovers, pajamas, carpets, blankets, curtain lines and luggage, etc. Industrial silk is used for making tents, automobile tires, transmission belts, hoses, cables, fishing nets, ropes, insulating materials, etc.

[0004] At present, the benzene process caprolactam process is the mainstream process for producing caprolactam. The process mainly includes three basic processes of benzene to cyclohexanone, cyclohexanone to cyclohexanone oxime and rearrangement of cyclohexanone oxime to caprolactam.

[0005] As known to those skilled in the art, the traditional benzene process caprolactam process has many serious problems. However, in recent years, some successful improvements have been made on the traditional benzene process caprolactam process according to the requirements of green chemistry and atom economy, which include that in the benzene to cyclohexanone step, the process of selective hydrogenation of benzene to cyclohexene and hydration and dehydrogenation of cyclohexene to cyclohexanone is used to replace the process of non-selective hydrogenation of benzene to cyclohexane and air oxidation of cyclohexane to cyclohexanone; in the cyclohexanone to cyclohexanone oxime step, the titanium silicalite catalyzed cyclohexanone ammoximation process is used to eliminate the hydroxylamine sulfate (HSO) process which has the problems of by-product ammonium sulfate and equipment corrosion.

[0006] However, the improved benzene caprolactam process still has many shortcomings. Among them include: (1) the efficiency of benzene selective hydrogenation process to cyclohexene and cyclohexene hydration process to cyclohexanol is low; (2) the cyclohexanone ammoximation process has a large amount of solvent, the TS-1 catalyst is deactivated quickly and consumes a large amount of in the reaction process (titanium-silicon molecular sieve is expensive. Cyclohexanone ammoximation to produce cyclohexanone oxime is a liquid phase reaction, titanium-silicon molecular sieve catalyst is in a strong alkaline environment for a long time, and the skeleton silicon dissolves to cause the invalid loss of the catalyst); (3) the liquid phase Beckmann rearrangement process (the current mainstream process) still uses fuming sulfuric acid as the catalyst, which not only causes corrosion to the equipment, but also produces 1.5-1.8 tons of ammonium sulfate per ton of caprolactam. The gas phase Beckmann rearrangement technology, which is highly expected, has serious problems such as rapid catalyst deactivation, and people have encountered setbacks in efforts to replace the liquid phase Beckmann rearrangement process with the gas phase Beckmann rearrangement process.

[0007] In view of the current technical situation of the existing benzene caprolactam production process and the problems faced by the development of new processes, it is urgent to develop new technologies in a different way in order to obtain a new caprolactam preparation process with no low-value by-products (such as ammonium sulfate), no equipment corrosion and environmental pollution problems, high process atomic utilization rate, low energy consumption (low carbon emission) in the near future.

[0008] As early as 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.

[0009] In 1961, UCC disclosed a method for preparing caprolactam in US3000879. The method is to heat a 25% aqueous solution of 6-hydroxyhexanamide to 300-475°C in a closed container, and prepare caprolactam by a non-catalytic reaction route under high pressure (the pressure reaches 15 MPa) to obtain a 30% single-pass caprolactam yield. It is undoubtedly unimaginable to realize industrialized production of a bulk chemical at high temperature and high pressure in a batch kettle.

[0010] In the same year, Union Carbide Corporation disclosed another process for preparing caprolactam from caprolactone in US3000800. Specifically, the process is a non-catalytic reaction process for preparing caprolactam from caprolactone and aqueous ammonia or primary amine under high pressure (P > 22.1 MPa) and high temperature (373 °C < T < 473 °C). The process has been successfully commercialized. However, the process can only be carried out under high temperature and high pressure, which requires a huge amount of energy. Moreover, the non-catalytic reaction under high temperature and high pressure tends to produce polymer, which results in a low yield of caprolactam, less than 50%. This is probably the main reason why Union Carbide Corporation stopped the production line for preparing caprolactam from caprolactone. On the other hand, the caprolactone raw material at that time was prepared from the oxidation of cyclohexanone and peracetic acid. Peracetic acid is a strong oxidant and extremely unstable. It can explode when it is exposed to high heat, reducing agents or metal ions. In fact, peracetic acid is explosive when its concentration is greater than 45%, even at -20 °C. Therefore, the production process of caprolactone at that time was extremely dangerous. This is probably another important reason why Union Carbide Corporation stopped the production line for preparing caprolactam from caprolactone.

[0011] In 1964, Teijin Corporation disclosed a catalytic process for preparing caprolactam from caprolactone, 6-hydroxycaproamide or amide derivatives of 6-hydroxycaproic acid in US3317516 and US3317517. Specifically, the catalytic process is to heat caprolactone, 6-hydroxycaproamide or amide derivatives of 6-hydroxycaproic acid and aqueous ammonia to 200-400 °C in a high-pressure reactor in the presence of a hydrogenation catalyst containing at least one noble metal, cobalt or nickel, or a combination thereof, to produce caprolactam with less color. The process can be optionally carried out in the presence of hydrogen. It is clear that the reaction conditions of the catalytic process are relatively mild. However, the single-pass yield of caprolactam obtained by the process is also not high, with a maximum of only 45.1%, so the economic efficiency of the process is not high.

[0012] In 1964, a French company disclosed in British patent GB 1121109 an improved process for the preparation of caprolactam from caprolactone under non-catalytic conditions of high temperature and high pressure. In previous patents, researchers found that the reaction of caprolactone and ammonia at a temperature of 300°C in the absence of solvent resulted in the formation of polymer only. Therefore, water had to be added as a solvent for the reaction to prevent the formation of polymer. However, the affinity of caprolactam product for water is very strong, and solvent extraction is required to recover the product. Chloroform is a good extractant, but even under the most favorable conditions, a large amount of chloroform must be used to extract the caprolactam from the relatively dilute reaction solution. This means that solvent extraction is quite difficult and expensive. To solve this problem, the patent proposed an improved process: the non-catalytic amination of caprolactone to produce caprolactam in the presence of a water-soluble neutral salt (a soluble alkali or alkaline earth metal salt of an inorganic or organic acid). Surprisingly, it was found that even at a high concentration of salt, the amination reaction results were not adversely affected. However, after the addition of salt, the extraction efficiency of caprolactam from the product solution was improved from 72.5% (the extraction rate of chloroform for caprolactam without salt) to 94.3% (the extraction rate of chloroform for caprolactam after the addition of ammonium sulfate). This reduces the amount of chloroform extractant used.

[0013] 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 the non-catalytic reaction of caprolactone and ammonia water under high temperature and high pressure can produce caproamide. However, the reaction under high temperature and high pressure is not suitable for industrial application. First, due to the limitation of reaction equilibrium, the single-pass yield of the reaction is relatively low. Second, the reaction process produces a large amount of irreversible by-products. Due to the low yield of each process, 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 conversion, and the reaction time is controlled to convert a large amount of caprolactone into reaction intermediates. Then, in the second stage conversion, the product of the first stage conversion is 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 generated 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.

[0014] 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, and 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.

[0015] 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.

[0016] 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.

[0017] 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 attainment of satisfactory caprolactam yields in the reaction of caprolactone to caprolactam at high temperature and pressure.

[0018] 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%.

[0019] 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.

[0020] In 2012, German patent DE102012006946A1 disclosed a new catalytic process for the preparation 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%.

[0021] In 2018, Chinese patent CN108774172A disclosed a catalytic method for the preparation of caprolactam and N-substituted caprolactam from caprolactone and ammonia (amine). The 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).

[0022] In addition to the above patents, several journal papers also involve the study of caprolactone to caprolactam. For example:

[0023] 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 speculated to be due to the coverage of the catalyst surface with polymers.

[0024] 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.

[0025] 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.

[0026] 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 much attention. The existing process and catalysts 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

[0027] The purpose of the present application is to provide a preparation method for improving the stability of Cu-Beta zeolite catalyst for preparing caprolactam by hydrogenation of caprolactone.

[0028] This invention provides a method for preparing a Cu-Beta zeolite catalyst that improves the stability of caprolactone to caprolactam via hydroamination. Specifically, it uses a pore-modified dealubilized Beta zeolite as a support and employs a modified ammonia stripping method to load copper within the pores. The pore-modification refers to a technique that uses a weak organic base to control desilication of the dealubilized Beta zeolite support, thereby enlarging the hydroxyl groups generated during dealubilization to better accommodate and stabilize nano- and sub-nanometer copper particles.

[0029] Research has revealed that, for the gas-solid phase catalytic reaction of caprolactone to caprolactam via hydroamination, supported copper-based catalysts show the greatest promise for industrial application in terms of catalytic activity and selectivity. However, from the perspective of catalyst stability, deactivation is the biggest challenge for the industrial application of supported copper-based catalysts. The deactivation of copper-based catalysts in the gas-solid phase catalytic reaction of caprolactone to caprolactam via hydroamination is not solely due to coking. The sintering problem of highly dispersed copper particles is also a significant cause of catalyst deactivation. Those familiar with the field know that coking deactivation is a temporary deactivation of the catalyst, and its catalytic activity can generally be restored through various regeneration methods, thereby extending the catalyst's lifespan. In contrast, sintering deactivation is generally a permanent deactivation of the catalyst, having the greatest impact on its lifespan.

[0030] The main advantage of the Cu-Beta zeolite catalyst preparation method provided by this invention is that it not only utilizes the dispersion and stabilization effect of the dealuminated Beta zeolite hydroxyl clusters on the supported copper particles, but also controls the desilication technology with a weak organic base to increase the size of the dealuminated hydroxyl clusters, thereby increasing the contact area between the hydroxyl clusters and the copper particles. This further enhances the stabilizing effect of the dealuminated Beta zeolite hydroxyl clusters on the supported copper particles, allowing the copper-based catalyst to be used without adding anti-sintering aids such as chromium and nickel.

[0031] The catalyst preparation method for improving the stability of Cu-Beta zeolite catalysts provided by this invention has the following main technical features:

[0032] First, the catalyst preparation method provided by this invention, which can improve the stability of Cu-Beta zeolite catalysts, uses dented-modified dealuluminized Beta zeolite as a support for copper loading.

[0033] 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 a very 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.

[0034] 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 reactions, etc. due to their low cost 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.

[0035] As mentioned earlier, the present application uses an anastomosis-modified dealuminated Beta zeolite as a carrier to prepare a supported copper-based catalyst, which not only takes advantage of the stabilizing effect of the hydroxyl pockets of the dealuminated Beta zeolite on the supported copper particles, but also increases the contact area between the hydroxyl pockets and the copper particles by using a weak organic base to control the desilication technique to make the hydroxyl pockets produced by dealuminization larger, further strengthening the stabilizing effect of the hydroxyl pockets of the dealuminated Beta zeolite on the supported copper particles. Therefore, the copper-based catalyst prepared by the method of the present application, Cu-Beta zeolite catalyst, has strong sintering resistance and can be used without the addition of sintering resistance additives such as chromium and nickel, and has high stability in the reaction of caprolactam from caprolactone by hydrogenation.

[0036] A large number of hydroxyl pocket lattice defect sites in dealuminated Beta zeolite can be produced by removing framework aluminum from the crystals of Beta zeolite using conventional acid treatment methods. When the Beta zeolite is treated with acid dealumination, 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), producing a hydroxyl pocket lattice defect site surrounded by four silicon hydroxyl groups (≡Si-OH).

[0037] Hole-drilling modification, also known as desilication control with a weak organic base solution to enlarge the hydroxyl holes in dealubilized Beta zeolite, is essentially a base-catalyzed hydrolytic desilication modification ([(OSi)3-O-SiOH]+3H2O=Si(OH)4+3≡Si-OH). For every silicon atom removed (existing in the form of orthosilicic acid (Si(OH)4)), that is, for every silicon atom "drilled" off the wall of the hydroxyl hole (existing in the form of Si(OH)4), three silanol groups (≡Si-OH) will be generated on the new wall of the hydroxyl hole.

[0038] 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.

[0039] 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.

[0040] As a crystalline porous catalytic material, Beta zeolite has similar advantages to MFI zeolite, such as (1) both are high-silicon zeolites, thus having high thermal stability and hydrothermal stability, 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 diffusion and strong anti-clogging ability, which is conducive to maintaining the activity stability of the catalyst in a long period of continuous reaction. 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

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

[100] and

[010] directions, which also have an elliptical cross-section and 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 with a nearly circular cross-section and a pore size of 0.53 nm x 0.56 nm, and two groups of "Z" type curved pores parallel to the (010) crystal face with an elliptical cross-section and a pore size of 0.51 nm x 0.55 nm. It can be imagined that the pore system of Beta zeolite is more suitable for the intraparticle diffusion of the reactant caprolactone (seven-membered ring) and the formation and intraparticle 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.

[0041] On the other hand, the framework aluminum of Beta zeolite can be easily removed by acid treatment, thereby generating a high density of hydroxyl pit defect sites on the crystal framework. This feature is not common among industrialized zeolite catalytic materials and is unmatched by MFI zeolite. When Beta zeolite is subjected to acid dealumination treatment, four Si-O-Al bonds are required to be acid-cleaved 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 zeolite, 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 controllability of the distribution are poor; 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 all-silica zeolite, i.e., Silicalite-1 (S-1). However, the framework aluminum of ZSM-5 zeolite is difficult to completely remove. 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 boron-containing ZSM-5 zeolite (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.

[0042] 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-based catalyst, but selects Beta zeolite with a hydroxyl pocket lattice defect site as a carrier for preparing a copper-based 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 in that it has three advantages of a high molar ratio of silico-alumina oxide framework, a 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.

[0043] The reason why the dealuminated Beta zeolite carrier needs to be modified by pocketing before use is to make the hydroxyl pocket produced by dealumination larger, so as to better accommodate and stabilize the nano and sub-nano copper particles. The pocketing modification refers to supplementing and modifying the dealuminated Beta zeolite carrier with an aqueous solution of a small molecule weak organic base, and controllably removing 1-2 silicon atoms on the pit wall of the hydroxyl pocket, so as to expand the small hydroxyl pocket with only one framework atom deficiency (acid dealumination) to a larger hydroxyl pocket with 2-3 framework atom deficiencies.

[0044] This is the enlightenment obtained after a large number of preliminary exploration research. Since the atomic radius of copper is much larger than the ionic radius of aluminum Therefore, the smaller hydroxyl pocket produced by dealumination of Beta zeolite can at most accommodate one copper atom. Obviously, the active silicon hydroxyl group in the hydroxyl pocket of Beta zeolite only interacts closely with one copper atom, which inevitably limits its dispersion and stabilization ability to metal copper particles.

[0045] If 1-2 silicon atoms can be controllably removed from the hydroxyl pockets of the dealuminated Beta zeolite, so as to expand the small hydroxyl pocket with only one framework atom vacancy (acid dealuminated) to a larger hydroxyl pocket with 2-3 framework atom vacancies, the dispersion and stabilization ability of the hydroxyl pocket for copper particles can be enhanced. The inventors carried out a large number of exploratory research work with weakly basic organic alkali aqueous solution according to this idea. Compared with alkali metal hydroxide (inorganic strong base) solution and quaternary ammonium alkali solution (organic strong base), the weakly basic organic alkali has weak desilication ability, and can only desilicate a small amount, so it is easy to achieve the purpose of controllable desilication. At the same time, the weakly basic organic alkali has weak desilication ability, so it is also easy to achieve selective desilication, that is, mainly desilicate from the weakest part of the Beta zeolite framework, the hydroxyl pocket vacancy. It is found that the aqueous solution of small molecule fatty amine (methylamine, ethylamine, propylamine, tert-butylamine, isopropylamine, n-butylamine, diethylamine, ethylenediamine, isobutylamine, triethylamine) and small molecule alcohol amine (ethanolamine, diethanolamine, triethanolamine, isopropyl alcohol amine, diisopropyl alcohol amine) has a controllable desilication effect when it is in contact with the dealuminated Beta zeolite, and has a good "pocketing" modification effect on the hydroxyl pocket of the Beta zeolite. Compared with general organic alkali, the advantages of small molecule fatty amine and alcohol amine are good water solubility and small dosage. In order not to make the specification of the present application too complex, the present application only takes ethanolamine as an example to modify the dealuminated Beta zeolite by pocketing. Pocketing modification is essentially an alkali-catalyzed hydrolysis desilication modification ([(OSi)3-O-SiOH]+3H2O=Si(OH)4+3≡Si-OH), and for every silicon atom removed (in the form of silicon acid (Si(OH)4)), that is, for every silicon atom (in the form of Si(OH)4) "chiseled" from the wall of the hydroxyl pocket, three silicon hydroxyl groups (≡Si-OH) will be generated on the new wall of the hydroxyl pocket.

[0046] Secondly, the catalyst preparation method provided by the present application for improving the stability of Cu-Beta zeolite catalyst is realized by loading copper by improved ammonia evaporation method.

[0047] 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 copper ammonia complex solution is absorbed into the zeolite pores by capillary condensation of the zeolite pores, so that the copper hydroxide generated in the ammonia evaporation process is directly deposited in the pores 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 pores 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 zeolite pores after pocketing treatment during the formation process, so as to be dispersed and stabilized in time and more effectively.

[0048] As is well known to those skilled 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.

[0049] 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.

[0050] 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 a 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. The silica gel particles grow on one side, and the copper hydroxide precipitate is deposited and reacts on the surface of the silica gel particles, resulting in a layered mixed loading 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 grow on one side, and the copper hydroxide precipitate is deposited and reacts on the surface of the silica gel particles, 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 uneven consequence of less copper loaded in the pores of the support and more copper loaded outside the pores of the support.

[0051] Thereafter, some scholars in the study according to the earliest proposed ammonia evaporation method for the preparation of amorphous oxide carrier supported copper-based catalysts for the purpose of oxalic acid dimethyl ester gas solid phase hydrogenation to ethylene glycol. For example, in the published literature J. Catal. 257 (2008) 172-180 and Appl. Catal. A: Gen. 458 (2013) 82-89, there are relevant research reports, the amorphous oxide carrier involved is silicon dioxide and binary compound of silicon dioxide and titanium dioxide. In the case of silicon dioxide as the carrier, silica sol (Ludox AS-40) is used as the precursor of the carrier. In the case of binary compound of silicon dioxide and titanium dioxide as the carrier, silica sol (JN30, Qingdao Haiyang Chem. Co., Ltd.) and titanium dioxide sol are used as the precursors of the carrier. After ammonia evaporation (the pH value of the slurry is reduced to 6-7), the amorphous oxide supported copper hydroxide solid product is obtained by filtration.

[0052] Some researchers 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. In fact, the AEH method is a water thermal treatment of 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) in a high-pressure synthesis kettle at 190-210℃ for 12h, and then the solid product is subjected to conventional filtration, washing, drying, calcination and hydrogen reduction treatment. In other words, the AEH method is not an improvement of the ammonia evaporation method itself, but a water thermal post-treatment before the conventional post-treatment of the ammonia evaporation method. It is important to note that the operation before the water thermal post-treatment of the AEH method is the same as that of the traditional ammonia evaporation method, 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 in the solution when preparing the copper ammonia complex solution. Other methods are the same as the traditional ammonia evaporation method. The silica support is generated in situ using silica sol (Ludox AS-40, 40wt.%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 10nm, Qingdao Marine Chemical 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. In order to overcome the problems caused by the reduction of the amount of silica sol when using pre-made JN-25 type basic silica gel as the carrier of the Cu / SiO2 catalyst, researchers also tried to add cetyltrimethylammonium bromide (CTAB) surfactant to the configured copper ammonia complex aqueous solution to disperse the silica sol and generate mesoporous 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 their 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 well 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 dispersion of the hydrogen reduction product-metallic copper is poor.

[0053] In addition, it is particularly worth mentioning that in the public literature Applied Catalysis A, General 539 (2017) 59-69, researchers use pre-prepared ordered mesoporous silica (OMS) as the carrier of the Cu / OMS catalyst prepared by their ammonia evaporation method. In order to reduce the damage of the alkalinity of the copper ammonia complex solution to the ordered mesoporous of the pre-prepared silica carrier, the researchers also appropriately reduced the concentration of ammonia water in the prepared copper ammonia complex solution (the researchers consider it as an improvement to the ammonia evaporation method). In addition to the above two points, the improved ammonia evaporation method described in the study is no different from the traditional ammonia evaporation method. After the ammonia evaporation is completed (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 carrier used in this study has been mostly destroyed after being loaded with metallic copper by the ammonia evaporation method described, and there is a large amount of layered copper silicate in the catalyst, indicating that the pre-prepared silica carrier used is largely dissolved into silica sol during the contact with the copper ammonia complex solution, and the latter produces a uniform deposition precipitation effect with copper hydroxide during the ammonia evaporation process; in the public literature Journal of Catalysis 280 (2011) 77-88, researchers also use pre-prepared mesoporous silica (HMS) as the carrier of the Cu / HMS catalyst prepared by their ammonia evaporation method. In addition, the researchers also add water-soluble nickel salt (nickel nitrate) to the prepared aqueous copper ammonia complex solution, so that the prepared copper-based catalyst contains metallic nickel CuxNi / HMS). The ammonia evaporation method used in this study is similar to the traditional ammonia evaporation method except that a pre-made mesoporous silica support was used and a water-soluble nickel salt (nickel nitrate) was added to the prepared copper-ammonia complex aqueous solution, so that the prepared copper-based catalyst contained a metal nickel promoter. The ammonia evaporation operation was carried out at 90°C, and after the ammonia evaporation was completed (the slurry pH value dropped to 7-8), the water solvent of the diluted and volume-excessive copper-ammonia complex solution was 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 was mostly destroyed (the specific surface area decreased by more than 50%) after the copper and nickel metals were loaded by the ammonia evaporation method described above. Furthermore, the XRD characterization results showed that the prepared supported catalyst sample had characteristic diffraction peaks of metal oxide phase before hydrogen reduction (450°C calcination for 4h) and characteristic diffraction peaks of metal phase after hydrogen reduction, indicating that the copper and nickel metals were not uniformly loaded on the HMS support and had poor dispersity.

[0054] 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, 0.23 g of Cu(NO3)2·3H2O was dissolved in 100 ml of an ammonia water solution (containing 0.75 g of NH3·H2O) and stirred at room temperature for 10 min to prepare a copper-ammonia complex aqueous solution; Second, 1.94 g of a dealuminated Beta zeolite carrier (Beta-deAl) was added to the copper-ammonia complex solution, and ammonia evaporation treatment was carried out 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 reduced by hydrogen at 400℃ for 3h. It is not difficult to see that in this study, in addition to the catalyst carrier being a pre-prepared dealuminated Beta zeolite (obtained by subjecting an Al-Beta zeolite mother body with Si / Al = 13 to 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The gas-solid phase reaction state is a suitable approach for the hydrogenative amination of caprolactone to caprolactam by catalytic method. 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.

[0059] 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.

[0060] 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.

[0061] 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(NO) It is not difficult to see that ammonia and hydrogen are also reaction raw materials, and water vaporization into water vapor is a diluent gas. The selectable range of reaction temperature is 120-350℃, the selectable range of reaction pressure is 0.01-2 atm, and the selectable ranges of the molar ratios of ammonia-ester, hydrogen-ester, and water-ester are 1-50, 5-70, and 0-100, respectively; the preferred range of reaction temperature is 220-300℃, the preferred range of reaction pressure is 0.1-1.2 atm, and the preferred ranges of the molar ratios of ammonia-ester, hydrogen-ester, and water-ester are 2-25, 10-50, and 5-30, respectively. To facilitate a better understanding of the implementation effects of the present invention by those skilled in the art, the catalytic performance of the provided Cu-Beta zeolite catalyst in the gas-solid phase hydroamination reaction of caprolactone to caprolactam is evaluated in this invention, and the reaction conditions used are within the above ranges.

[0062] The technical solution of this invention:

[0063] A method for preparing Cu-Beta zeolite catalysts to improve the stability of caprolactone-to-caprolactam synthesis comprises the following steps:

[0064] The first step is to prepare a dealuminated Beta zeolite support.

[0065] Engineers skilled in the art can, according to the requirements of this invention, combine their own work experience with conventional acid dealumination methods in relevant literature, to obtain a dealuminated Beta zeolite support from a Beta zeolite parent material. The requirements of this invention are as follows:

[0066] (1) Select Beta zeolite parent material

[0067] The Beta zeolite matrix refers to aluminosilicate zeolite. This invention does not limit the grain size or the production process of the Beta zeolite matrix. However, to facilitate the implementation of this invention, the following limitations are imposed on the Beta zeolite matrix: 1) The Beta zeolite matrix is ​​free of impurities; 2) The Beta zeolite matrix exhibits good crystallinity; 3) The molar ratio of silica to aluminosilicate (SiO2 to Al2O3) in the Beta zeolite matrix is ​​appropriate.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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), CN1154 341A (application date 1996.1.11), CN1 154 242A (application date 1996.1.9), CN1 154 342A (application date 1996.1.11), CN1 268 545A (application date 1999.3.30), CN1 133 497C (application date 1999.3.30), CN1108 275C (application date 1999.9.10), CN1 100 004C (application date 2000.5.19), CN1 335 258A (application date 2001.2.28), CN1 116 227C (application date 2001.3.12), CN101 205 072B (application date 2006.12.18), Chem. Comm., 1996, 625; J. Mater. Chem., 1998, 8(9), 2137-2145; Microporous and Mesoporous Materials 21 (1998) 305-313; Applied Catalysis A-GENERAL, 166 (1998), 97-103; Microporous and Mesoporous Materials 48 (2001) 23-29; Microporous and Mesoporous Materials 56 (2002) 1-10.; Journal of Molecular Catalysis A: 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.

[0072] (2) Preparation of dealuminated Beta zeolite support

[0073] 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.

[0074] When the Beta zeolite precursor is subjected to acid dealumination, it is desirable to remove as much as possible of the framework aluminum. 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.

[0075] Although the framework aluminum of the Beta zeolite is easily removed so that dealumination methods such as high temperature steam dealumination, EDTA complexing agent dealumination, organic acid solution dealumination, inorganic acid (concentrated hydrochloric acid, concentrated nitric acid) solution dealumination, or any combination of the above dealumination methods can be used to prepare the dealuminated Beta zeolite support according to the present invention from a Beta zeolite precursor, the present invention recommends the use of concentrated nitric acid aqueous solution dealumination to prepare 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.

[0076] Engineers skilled in the art can prepare the dealuminated Beta zeolite carrier according to the present application by using concentrated nitric acid aqueous solution to dealuminate the Beta zeolite precursor according to their own experience or referring to the specific methods disclosed in the following documents: 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.

[0077] When the dealuminated Beta zeolite carrier is prepared 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 important factors affecting the degree of acid 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 carrier. In addition, the pretreatment of the Beta zeolite precursor can also affect the degree of acid dealumination and the residual aluminum content of the dealuminated Beta zeolite carrier. However, if the dealuminated Beta zeolite carrier 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 of 20:1 (ml / g). 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 pocket defect sites are generated, and the water absorption and moisture absorption capacity is stronger, so it should be sealed and stored for use.

[0078] Second step, using an aqueous solution of ethanolamine to modify the hydroxyl pockets of the dealuminated Beta zeolite carrier

[0079] The hydroxyl pocket drilling modification is carried out by using a conventional aqueous solution impregnation method. The drilling modification is essentially an alkali-catalyzed hydrolysis reaction modification ([(OSi)3-O-SiOH]+3H2O=Si(OH)4+3≡Si-OH), and for each silicon atom (in the form of orthosilicic acid (Si(OH)4) removed from the pit wall of the hydroxyl pocket, i.e., for each silicon atom (in the form of Si(OH)4) drilled from the pit wall of the hydroxyl pocket), three silicon hydroxyl groups (≡SiOH) are generated on the new pit wall of the hydroxyl pocket.

[0080] When the dealuminated Beta zeolite support is impregnated with an ethanolamine solution (a weak organic base) for drilling modification, the concentration of the ethanolamine aqueous solution, the ratio of the ethanolamine solution to the dealuminated Beta zeolite, i.e., the liquid-solid ratio (ml / g), and the impregnation temperature and time are the main factors affecting the controllable desilication modification of the ethanolamine solution on the hydroxyl pockets of the dealuminated Beta zeolite. The present application provides the value range of the four parameters as follows:

[0081] The suitable range of the concentration of the ethanolamine solution is 0.01M-0.4M, the preferred range is 0.02M-0.3M, and the more preferred range is 0.03M-0.16M;

[0082] The suitable range of the ratio of the ethanolamine solution to the dealuminated Beta zeolite support, i.e., the liquid-solid ratio (ml / g), is 1:1-100:1, the preferred range is 2:1-50:1, and the more preferred range is 3:1-20:1;

[0083] The suitable range of the impregnation temperature is 20°C-100°C, the preferred range is 30°C-90°C, and the more preferred range is 40°C-80°C;

[0084] The suitable range of the impregnation time is 0.1h-24h, the preferred range is 0.5h-10h, and the more preferred range is 1-5h.

[0085] Engineers familiar with the art can refer to the impregnation process commonly used in the preparation of heterogeneous catalysts to impregnate the dealuminated Beta zeolite support with an ethanolamine solution, so as to achieve the purpose of drilling modification of the hydroxyl pockets of the dealuminated Beta zeolite support. Details are not repeated. Similarly, after drilling modification, the liquid-solid mixture should be processed according to common sense, mainly including conventional liquid-solid separation, water washing (to neutral pH), drying and calcination treatment. Among them, the conditions of drying and calcination treatment can refer to the drying and calcination treatment conditions of the dealuminated Beta zeolite support in the first step (preparation of dealuminated Beta zeolite support) of the embodiment of the present application. Details are not repeated.

[0086] However, it is particularly pointed out that for the dealuminated Beta zeolite carriers with different amounts of hydroxyl pits prepared from the Beta zeolite mother substance with different molar ratios of silicon aluminum oxide (molar ratio of SiO2 to Al2O3), the key to the controllable pit modification of the hydroxyl pits by using the aqueous solution of ethanolamine lies in the correct selection of the modification conditions composed of four parameters (concentration of the ethanolamine solution, liquid-solid ratio (ml / g), impregnation temperature and time). It is not difficult to understand that the modification conditions composed of the lower limit values of the above four parameters have the weakest desilication effect and are suitable for the pit modification of the dealuminated Beta zeolite carriers with a small amount of hydroxyl pits; the modification conditions composed of the upper limit values of the above four parameters have the strongest desilication effect and can be used for the pit modification of the dealuminated Beta zeolite carriers with a large amount of hydroxyl pits; and the modification conditions composed of other different values of the above four parameters within the specified range will produce different desilication effects between the weakest and the strongest. Similarly, the above explanation of the present application is intended to provide the engineers in the field with the principle guidance, and the ethanolamine solution impregnation treatment conditions for achieving the moderate pit modification degree for different dealuminated Beta zeolite carriers are preferably determined through experiments.

[0087] Third step, loading copper in the channels of the dealuminated Beta zeolite carrier modified by the pit modification by using the improved ammonia evaporation method to prepare a Cu-Beta zeolite catalyst

[0088] As mentioned above, the core of the improved ammonia evaporation method according to the present application is to use the copper ammonia complex solution to impregnate the zeolite carrier in equal volume, and in this process, most of the complex solution is absorbed into the channels by the capillary condensation of the zeolite channels, so as to achieve the purpose of depositing copper hydroxide and loading metal copper in the channels. The specific method is as follows:

[0089] (1) Preparation of dilute ammonia water base solution and saturated solution of copper ammonia complex: according to the proportion 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 of 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 in a sealed container. 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.

[0090] It is to be noted that although the soluble copper-containing compounds that can be used to prepare the copper-ammine 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 increase the burden of subsequent water washing, and that oxalate and acetate ions have corrosion problems, the use of copper nitrate (Cu(NO3)2-3H2O) is recommended in the present application.

[0091] (2) Impregnation of the zeolite support with the copper-ammine complex solution in equal volume: The saturated water absorption of the zeolite support is first determined, and the amount of the copper-ammine complex solution used for the equal volume impregnation of the zeolite support is calculated therefrom. Then, the concentration of the copper-ammine complex solution required is calculated according to the copper loading of the Cu-Beta zeolite catalyst to be prepared. When the calculated concentration is equal to 0.4 M, the zeolite support is directly impregnated in equal volume with the saturated solution of the copper-ammine complex; when the calculated concentration is lower than 0.4 M, the saturated solution of the copper-ammine complex is diluted with the dilute aqueous ammonia base solution as appropriate, and then the zeolite support is impregnated in equal volume; when the calculated value is higher than 0.4 M, the zeolite support should be impregnated in equal volume for multiple times, the concentration of the copper-ammine complex solution for each single equal volume impregnation is recalculated, and the copper-ammine complex solution with the required concentration is prepared for each single equal volume impregnation by using the dilute aqueous ammonia base solution and the saturated solution of the copper-ammine complex. After each impregnation, the zeolite support is subjected to ammonia evaporation treatment.

[0092] The equal volume impregnation is carried out in a closed container at room temperature. In this process, the zeolite support absorbs the copper-ammine complex solution into the zeolite pores by capillary condensation, so that the copper-ammine 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.

[0093] (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-ammine complex is decomposed to generate ammonia gas and copper hydroxide, the former is absorbed with water, and the latter is deposited in the zeolite pores and the hydroxyl lattice defect sites.

[0094] (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.

[0095] (5) Calcination treatment after ammonia evaporation: This step is used to convert the copper hydroxide precipitate deposited in the pores of the zeolite and in the lattice defect sites of the hydroxyls 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 ranges of the calcination temperature and time are 350-650°C and 0.5-24h, respectively, the preferred ranges of the calcination temperature and time are 400-600°C and 1-12h, respectively, and the more preferred ranges of the calcination temperature and time are 450-550°C and 2-6h, respectively;

[0096] (6) Hydrogen reduction treatment of the catalyst precursor: A Cu-Beta zeolite finished catalyst is prepared. The suitable ranges of the reduction temperature, time and hydrogen flow rate (expressed by the volume space velocity of hydrogen, defined as the volume of hydrogen passing through the catalyst per unit time per unit volume, calculated as an ideal gas) are 280-600°C, 0.5-20h and 1-2000h -1 , respectively, the preferred ranges are 300-550°C, 1-15h and 10-1500h -1 , respectively, and the more preferred ranges are 350-500°C, 2-8h and 20-1000h -1 .

[0097] The Cu-Beta zeolite catalyst prepared by the above method is used to catalyze the gas-solid phase hydrogenation of caprolactone to prepare caprolactam.

[0098] As mentioned above, one of the main features of the present application is that the Cu-Beta zeolite catalyst provided is used to catalyze the gas-solid phase hydrogenation of caprolactone to prepare caprolactam.

[0099] However, the present application does not limit the specific method of preparing caprolactam by the gas-solid phase hydrogenation of caprolactone. Engineers familiar with the field can implement the gas-solid phase hydrogenation of caprolactone by referring to the methods disclosed in related patents and other literature. According to the related patents and other literature, the present application summarizes the ranges of the conditions of the gas-solid phase hydrogenation of caprolactone as follows: the suitable range of the reaction temperature is 120-350°C, 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°C, 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.

[0100] In order to facilitate the implementation effect of the catalyst and its preparation method and avoid unnecessary complexity, a typical method for preparing caprolactam by gas-solid phase hydrogenation of caprolactone on the Cu-Beta zeolite catalyst is introduced as follows: The small fixed bed reactor in the laboratory is used as an example. The Cu-Beta zeolite catalyst 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. The upper porcelain ball area of the reactor serves as the vaporization and preheating zone of the raw materials. For convenience, caprolactone, water and ammonia can be mixed into a mixed feed, which is delivered by a micro-metering pump, and the hydrogen is controlled by a mass flow meter. The reaction is carried out under fixed conditions: the reaction temperature is 270℃, the reaction pressure is 1atm, the feed 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.

[0101] The beneficial effects of the present application are:

[0102] Firstly, the Cu-Beta zeolite catalyst is prepared by the improved ammonia evaporation method on the dealuminated Beta zeolite carrier modified by drilling holes, which can make the copper ammonia complex mainly deposit copper hydroxide in the zeolite pores during the ammonia evaporation process. After calcination and hydrogen reduction treatment, the copper hydroxide deposited in the zeolite pores can form highly dispersed nano and sub-nano copper particles at the hydroxyl hole lattice defect sites in the pores, and the latter can obtain sintering resistance by interacting with the hydroxyl hole. Secondly, the present application utilizes the dispersion and stabilization of the dealuminated Beta zeolite hydroxyl hole on the loaded copper particles, and also utilizes the weak organic base control desilication technology to make the hydroxyl hole produced by dealuminization larger, increase the contact area of the hydroxyl hole and the copper particles, and further strengthen the stabilization of the dealuminated Beta zeolite hydroxyl hole on the loaded copper particles. These measures enable the Cu-Beta zeolite catalyst to be used without adding sintering resistance additives such as chromium and nickel. The Cu-Beta zeolite catalyst prepared by the method of the present application can be used without adding sintering resistance additives such as chromium and nickel. In addition, the core of the improved ammonia evaporation method used in the present application is to impregnate the dealuminated Beta zeolite carrier with an equal volume of copper ammonia complex solution. Due to the small amount of copper ammonia complex solution, it is beneficial to inhibit the damage of the silicon dissolution of the copper ammonia complex alkaline solution (pH=10-12) to the framework of the dealuminated Beta zeolite, thereby facilitating the dispersion and stabilization of the dealuminated Beta zeolite hydroxyl hole on the highly dispersed nano and sub-nano copper particles, and facilitating the preparation of the Cu-Beta zeolite catalyst with high activity, high selectivity and high stability. Finally, the Cu-Beta zeolite catalyst is used for the purpose of gas-solid phase hydrogenation of caprolactone, which will greatly reduce the industrialization difficulty of the technical route for preparing caprolactam from caprolactone. BRIEF DESCRIPTION OF DRAWINGS

[0103] Figure 1 is the hydroxyl region infrared spectrum of a dealuminated Beta zeolite support (Beta24c) which is a Beta zeolite mother phase acid-dealuminated with a silicon-aluminum oxide molar ratio (molar ratio of SiO2 to Al2O3) of 24, and a pitted modified dealuminated Beta zeolite support (Beta24C) prepared by controlling the dealuminated Beta zeolite support Beta24c with a weak organic base aqueous solution of ethanol amine.

[0104] Figure 2 is the XRD pattern of the pitted modified dealuminated Beta zeolite support Beta24C, and the XRD pattern of a Cu-Beta zeolite catalyst (Cu3-Beta24C-1) with a copper content of 3 wt.% prepared by an improved ammonia vaporization method using Beta24C as the support.

[0105] Figure 3 is the high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) photo of the Cu3-Beta24C-1 catalyst.

[0106] Figure 4 is the high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) photo of the Cu3-Beta24C-1 catalyst high-temperature calcined (550℃×3h) sample.

[0107] Figure 5 is the XRD pattern of the pitted modified dealuminated Beta zeolite support Beta24C, and the XRD pattern of a Cu-Beta zeolite catalyst (Cu3-Beta24C-CE1) with a copper content of 3 wt.% prepared by a traditional ammonia vaporization method using Beta24C as the support. DETAILED DESCRIPTION

[0108] The implementation effects of the present application can be evaluated by two aspects of characterizing the physicochemical properties of the prepared Cu-Beta zeolite catalyst and detecting its catalytic performance in the gas-solid phase hydrogenation of caprolactam from caprolactone.

[0109] In the characterization of the physicochemical properties of the Cu-Beta zeolite catalyst, the damage of the crystal structure, the occupation of the hydroxyl pits, the high dispersion of the loaded copper metal, and the anti-sintering of the copper particles can be characterized.

[0110] The damage of the Beta zeolite crystal structure can be characterized by X-ray powder diffraction (XRD) method. If the ammonia desorption treatment results in significant damage of the Beta zeolite crystal structure, 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 modified by channelling is used as a reference sample, the relative degree of decrease of the crystallinity of the zeolite support in the Cu-Beta zeolite catalyst can also be estimated.

[0111] The occupancy of the hydroxyl channelling in the Cu-Beta zeolite catalyst can be determined by Fourier transform infrared spectroscopy (FT-IR) method. The more the nano and sub-nano copper particles in the hydroxyl channelling, the weaker the intensity of the infrared characteristic band of the hydroxyl channelling (the widened absorption band between 3300-3600 cm -1

[0112] In addition, the high dispersion of the supported 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 determined by calcination treatment combined with TEM observation. The catalytic activity (caprolactam yield) decay of the catalyst in the gas-solid phase hydrogenative amination of caprolactone to caprolactam reaction can also be used for judgment.

[0113] The catalytic performance of the Cu-Beta zeolite catalyst in the gas-solid phase hydrogenative amination of caprolactone to caprolactam reaction can be evaluated by a laboratory small fixed bed reactor. The operation method and reaction conditions are as described above. The composition of the reaction product is analyzed by gas chromatography (GC) with FID detector and OV-1701 chromatographic column, and the conversion of caprolactone and the selectivity of caprolactam are calculated by internal standard method (internal standard substance is 1, 4-dioxane). The yield of caprolactam is calculated by the product of the conversion of caprolactone and the selectivity of caprolactam, which is used as the evaluation index of the catalytic activity of the catalyst.

[0114] The present application will be further described by the following examples, but the present application is not limited by these examples.

[0115] ​Example 1: This example is used to illustrate that, according to the present application, the Cu-Beta zeolite catalyst is prepared by using the dealuminated Beta zeolite modified by the cavity as the carrier and using the improved ammonia evaporation method to load copper in the channel, which not only can better maintain the crystal structure of the dealuminated Beta zeolite carrier, but also makes the loaded copper mainly in the form of highly dispersed nano and sub-nano copper particles located in the hydroxyl cavity lattice defect site in the zeolite channel, and the active silicon hydroxyl in the hydroxyl cavity is combined more closely with the highly dispersed nano and sub-nano copper particles, which better improves the sintering resistance of the catalyst, thereby improving the stability of the catalyst. The prepared Cu-Beta zeolite catalyst is suitable as a catalyst for the gas-solid phase hydrogenation of caprolactone to caprolactam.

[0116] Firstly, the Cu-Beta zeolite catalyst is prepared according to the embodiments provided by the present application:

[0117] First step, preparation of dealuminated Beta zeolite carrier

[0118] (1) According to the hydrothermal crystallization method provided by US Patent US3 308 069 (1967), a Beta zeolite mother body with a molar ratio of silicon aluminum oxide (molar ratio of SiO2 to Al2O3) of 25 is synthesized as a raw material for preparing a dealuminated Beta zeolite carrier. After the synthesized Beta zeolite mother body is treated by conventional filtration, washing, drying (110°C, 12h) and calcination to remove the template agent (540°C, 6h), it is observed by TEM that the crystal size is less than 100 nanometers, which belongs to nano-Beta zeolite; no any impurity crystal is found by XRD method, and the BET specific surface area thereof is calculated to be about 550m 2 / g by using the nitrogen physical adsorption data, and the molar ratio of silicon aluminum oxide (molar ratio of SiO2 to Al2O3) thereof is about 24 measured by XRF method, which meets the technical requirements of the Beta zeolite mother body of the present application, and is sealed and stored for use.

[0119] (2) The Beta zeolite mother body is dealuminated by using concentrated nitric acid to prepare a dealuminated Beta zeolite carrier.

[0120] First, prepare a concentrated nitric acid solution with a molar concentration of 13 M. Then, under stirring, add 30 g of the Beta zeolite mother substance that has been dried and calcined as described above to a three-necked flask containing 600 ml of the 13 M concentrated nitric acid solution in a liquid-to-solid ratio of 20:1 (ml / g) to perform the dealumination treatment. The dealumination temperature is 95°C and the dealumination time is 20 h. During the dealumination reaction, the three-necked flask is kept in a reflux state. After the dealumination reaction is completed, the reaction mixture is cooled to room temperature and the solid product is recovered by filtration. Then, the dealuminated Beta zeolite support is obtained by performing the conventional water washing, drying (overnight at 110°C) and calcination (3 h at 550°C) treatments. The molar ratio of silicon to alumina (SiO2 / Al2O3) of the dealuminated Beta zeolite support is 985 (> 900) as measured by ICP. The support is suitable for use as a catalyst of the present application (coded as Beta24c, where the lower case "c" indicates the hydroxyl pockets produced in the Beta zeolite by dealumination). The support is stored in a sealed container to avoid moisture absorption and is ready for use.

[0121] Second step, the hydroxyl pockets of the dealuminated Beta zeolite support are modified by pocketing with an aqueous solution of ethanolamine

[0122] The pocketing modification is performed by the atmospheric pressure impregnation method. First, prepare an aqueous solution of ethanolamine with a concentration of 44 mmol / L (44 mM) as the pocketing modification solution. Then, add 20 g of the dealuminated Beta zeolite support to 120 ml of the ethanolamine modification solution in a liquid-to-solid ratio of 6:1 (ml / g). Under stirring, heat the reaction mixture to 40°C and allow the reaction mixture to react at this temperature for 1 h under continuous stirring. During this period, a weakly basic catalytic hydrolysis of silica occurs in the dealuminated Beta zeolite support in the weakly basic solution of ethanolamine ([OSi]3-O-SiOH + 3H2O = Si(OH)4 + 3≡Si-OH), in which for each silicon atom (in the form of orthosilicic acid (Si(OH)4)) removed, three silicon hydroxyl groups (≡Si-OH) are produced on the new side walls of the hydroxyl pockets. After 1 h of reaction, the reaction mixture is filtered to recover the solid product, which is then repeatedly washed with deionized water until neutral, dried (overnight at 110°C) and calcined (3 h at 550°C) to obtain the pocketed dealuminated Beta zeolite. The support is stored in a sealed container. According to the weight loss, the average number of skeletal silicon atoms (in the form of SiO2) removed from the lattice defect sites of the hydroxyl pockets of the dealuminated Beta zeolite support is 1.2 silicon atoms, indicating that the pocketing modification is a controlled and moderate desilication, which meets the requirements for the pocketing modification of the dealuminated Beta zeolite support. The pocketed support is coded as Beta24C (upper case "C" indicates that the pocketing modification increases the volume of the hydroxyl pockets in the dealuminated Beta zeolite). The hydroxyl vibration infrared spectra of the dealuminated Beta zeolite support (Beta24c) and its pocketed modification sample (Beta24C) are obtained by Fourier transform infrared spectroscopy (FT-IR), as shown inFigure 1 The FTIR spectra of the hydroxyl groups of the dealuminated Beta zeolite support were changed obviously after the channelling modification, which indicated that the channelling modification really occurred on the hydroxyl group lattice defect sites of the dealuminated Beta zeolite. Figure 1

[0123] Third step, loading copper in the pore channels of the dealuminated Beta zeolite support modified by channelling to prepare Cu-Beta zeolite catalyst by improved ammonium vaporization method

[0124] (1) Prepare the dilute ammonia water base solution and synthesize the copper ammonia complex with copper nitrate trihydrate (Cu(NO3)2-3H2O), then prepare the saturated solution of the copper ammonia complex at room temperature. The pH value of the dilute ammonia water base solution is 11-12, which is prepared according to the proportion of 100 ml deionized water plus 4.4 g industrial ammonia water; the copper ammonia complex is obtained by the reaction of Cu(NO3)2-3H2O and industrial ammonia water according to the molar ratio of copper ion to ammonia molecule of 1:4; the saturated solution of the copper ammonia complex is obtained by dissolving the copper ammonia complex with the dilute ammonia water base solution, which contains about 0.4 M copper ammonia complex.

[0125] (2) Impregnate the zeolite support with the copper ammonia complex solution in equal volume to prepare the Cu-Beta zeolite catalyst with a copper loading of 3 wt.%. First, take 5 g of the channelling modified dealuminated Beta zeolite support (Beta24C) sealed and stored after calcination, titrate with deionized water until all the samples are uniformly wet but no free liquid water appears, a total of 6.25 ml of deionized water is consumed, and the water absorption rate of the channelling modified dealuminated Beta zeolite (Beta24C) is calculated to be 1.25 ml / g. According to the 10 g loading amount of the support, a total of 12.5 ml of the copper ammonia complex solution is required. According to the calculation of the copper loading of 3 wt.%, the concentration of the required copper ammonia complex solution is about 0.38 M. That is, the calculated value of the concentration of the required copper ammonia complex solution is very close to the concentration of the saturated solution of the copper ammonia complex (0.4 M). Therefore, directly impregnate 10 g of the channelling modified dealuminated Beta zeolite support (Beta24C) with 12.5 ml of the saturated solution of the copper ammonia complex in equal volume. The equal volume impregnation is carried out at room temperature, and the impregnation time is 4 h.

[0126] (3) Perform ammonium vaporization treatment on the equal volume impregnated material at normal pressure. The ammonium vaporization temperature is 80°C, and the ammonium vaporization time is 10 h. In this process, the copper ammonia complex entering the zeolite pore channels due to capillary condensation gradually deposits in the form of copper hydroxide in the zeolite pore channels due to the loss of ammonia gas.

[0127] (4) Perform dehydration and drying treatment on the material after ammonium vaporization. The drying temperature is 110°C, and the drying time is 12 h.

[0128] ​(5) The dried material is calcined. The calcination temperature is 500°C and the calcination time is 3h. After calcination, the copper hydroxide deposited in the zeolite pores is converted into nano and sub-nano copper oxide particles, thus obtaining the catalyst precursor.

[0129] (6) The catalyst precursor is subjected to hydrogen reduction treatment. The reduction temperature is 400°C, the reduction time is 4h, and the 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 ideal gas) is 300h -1 After hydrogen reduction treatment, the finished Cu-Beta zeolite catalyst, designated as Cu3-Beta24C-1, is obtained.

[0130] 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 support crystal structure and the surface hydroxyl group of Cu3-Beta24C-1 and the delaminated Beta zeolite support (Beta24C) thereof are characterized by XRD and FT-IR, respectively. In addition, the TEM photos of Cu3-Beta24C-1 catalyst and its high-temperature calcined sample (550°C x 3h) are taken by transmission electron microscopy.

[0131] From the XRD characterization results Figure 2 , it is found that the Cu3-Beta24C-1 catalyst prepared by the improved ammonia evaporation method provided by the present application retains the crystal structure of the Beta zeolite support well, and the relative crystallinity of the zeolite in the catalyst calculated based on the delaminated Beta zeolite support (Beta24C) is 84%. From the FT-IR characterization results, it is found that the infrared characteristic band intensity of the zeolite hydroxyl group of Cu3-Beta24C-1 catalyst decreases greatly compared with that of the delaminated Beta zeolite support, indicating that a large amount of copper occupies the hydroxyl group lattice defect sites. In addition, from the TEM photos Figure 3 and Figure 4 , it is found that the copper in Cu3-Beta24C-1 catalyst exists in the form of highly dispersed nano and sub-nano particles, and the average particle size is about 5nm. After being calcined at a high temperature of 550°C for 3h, the dispersion state of the copper particles is good, and the average particle size is about 8nm. These data show that the hydroxyl group lattice defect sites of the delaminated Beta zeolite support have a good effect of dispersing and stabilizing nano and sub-nano copper particles.

[0132] On this basis, the catalytic performance of Cu3-Beta24C-1 catalyst and its sample calcined at 550°C at high temperature is evaluated by using caprolactam gas-solid phase hydrogenation amination 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 operation mode is top feeding and bottom discharging. 2 g of the catalyst (20-40 mesh sample after sieving) 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. The upper porcelain ball area of the reactor serves as the vaporization and preheating zone of the raw material. The reaction temperature is 270°C, the reaction pressure is 1 atm, the feed space velocity (WHSV) of caprolactam is 0.6 h -1 For convenience, caprolactam, ammonia water raw materials (analytical pure, ammonia gas concentration is 25-28 wt.%), and deionized water are mixed according to the ammonia-ester molar ratio of 6 and the water-ester molar ratio of 30 to form a raw material solution, which is fed to the reactor by using a micro-metering pump, and hydrogen is fed by using a mass flow meter according to the hydrogen-ester molar ratio of 50. The reaction product is continuously collected in a stainless steel collection tank connected to the outlet of the reactor with a cooling water jacket, and the product liquid is collected at a fixed time interval for analysis on a Shimadzu gas chromatograph GC-2014 (FID detector, OV-1701 chromatographic column). The caprolactam conversion rate and caprolactam selectivity are calculated by using an internal standard method (internal standard is 1,4-dioxane). Under the above conditions, the caprolactam yield of the Cu3-Beta24C-1 catalyst is about 82% when the caprolactam hydrogenation reaction is continuously carried out for 6 h; and the caprolactam yield of the sample of the Cu3-Beta24C-1 catalyst calcined at 550°C at high temperature is close to 81%. The above reaction results show that the Cu-Beta zeolite catalyst provided by the present application has excellent performance in the caprolactam hydrogenation reaction.

[0133] Comparative Example 1: This example is used to illustrate that when a delaminated Beta zeolite is used as a carrier and copper is loaded on the carrier by using a traditional ammonia evaporation method to prepare a Cu-Beta zeolite catalyst, the crystal structure of the Beta zeolite carrier is damaged to a large extent, the loaded copper mainly falls outside the zeolite pores, the dispersion degree is low, the copper particle size is large, and the sintering resistance is poor because the active silicon hydroxyl groups in the hydroxyl pits of the delaminated Beta zeolite are not protected, so the stability of the catalyst is poor, and the performance of the catalyst in the caprolactam gas-solid phase hydrogenation reaction is poor.

[0134] Example 1 is repeated, but after the second step of preparing the delaminated Beta zeolite carrier (Beta24C), copper hydroxide is deposited on the zeolite carrier by using the traditional ammonia evaporation method in the same way as the published document Science 10.1126 / science.adj1962 (2023).

[0135] (1) Dissolve 1.18 g of Cu(N03)2-3H20 in 515 ml of aqueous ammonia solution (containing 3.86 g of NH3-H20, equivalent to 8.1 ml of 26 wt.% commercial ammonia water, the molar ratio of copper ion to ammonia molecule is about 1:23) and stir for 10 min at room temperature to prepare a copper-ammonia complex aqueous solution (the complex ion concentration is about 9.5 mmol / L, i.e. 9.5 mM);

[0136] (2) Add 10 g of the channeled-modified dealuminated Beta zeolite support (Beta24C) into the 515 ml copper-ammonia complex solution and perform ammonia evaporation treatment under vigorous stirring. The ammonia evaporation temperature is 80°C and the ammonia evaporation time is 6 h;

[0137] (3) After the ammonia evaporation, the water solvent of the diluted and volumetrically excessive copper-ammonia complex solution is finally removed by filtration, and the obtained filter cake is dried, calcined and hydrogen-reduced according to the same post-processing method of Example 1 to obtain a Cu-Beta zeolite catalyst, which is designated as Cu3-Beta24C-CE1 (CE = Comparative Example).

[0138] 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 method and 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 550°C high-temperature calcined sample was evaluated by the caprolactam gas-solid phase hydrogenation reaction of caprolactone.

[0139] The XRD characterization results Figure 5) shows that the Cu3-Beta24C-CE1 catalyst prepared by the traditional ammonia vaporization method has a large degree of damage to the zeolite crystal structure, and the relative crystallinity of the zeolite calculated based on the support (Beta24C) is 65%. 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 10 nm and 21 nm, respectively, that is, the Cu metal on the catalyst has low dispersion 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 76%; the caprolactam yield of the high-temperature calcined sample is about 72%. The reaction results show that the Cu-Beta zeolite catalyst prepared by the traditional ammonia vaporization method on the fluted modified dealuminated Beta zeolite support has low catalytic activity for the gas-solid phase hydrogenation of caprolactone to caprolactam and poor anti-sintering inactivation ability.

[0140] Comparative Example 2: This example is used to illustrate that when the fluted modified dealuminated Beta zeolite is used instead of the dealuminated Beta zeolite as the support of the Cu-Beta catalyst, and the improved ammonia vaporization method is used to load copper in the pore, it is beneficial to prepare a Cu-Beta zeolite catalyst with stronger anti-sintering ability and better stability.

[0141] Example 1 is repeated, but the dealuminated Beta zeolite support (Beta24c) prepared in the first step is directly used in the third step to load copper in the pore by the improved ammonia vaporization method to prepare a Cu-Beta zeolite catalyst. When the dealuminated Beta zeolite support is impregnated with an equal volume of copper ammonia complex solution, the water absorption rate of the dealuminated Beta zeolite (Beta24c) is 1.2 ml / g measured by titration with deionized water. According to the calculation of 10 g of support feed, a total of 12 ml of copper ammonia complex solution is required. According to the calculation of the copper loading amount of 3 wt.%, the concentration of the required copper ammonia complex solution is about 0.39 M. That is, the calculated value of the concentration of the required copper ammonia complex solution is very close to the concentration of the saturated solution of copper ammonia complex (0.4 M). Therefore, 10 g of dealuminated Beta zeolite support is impregnated with an equal volume of 12 ml of saturated solution of copper ammonia complex. Other methods remain unchanged. The obtained Cu-Beta zeolite catalyst is named Cu3-Beta24c-CE2.

[0142] To avoid the tediousness, in this case, the catalytic performance of Cu3-Beta24c-CE2 catalyst and its high temperature calcined sample (550°C x 3h) were evaluated only by the reaction of gas-solid phase reductive amination of caprolactone to caprolactam. The results of reaction evaluation showed that the caprolactam yield of Cu3-Beta24c-CE2 catalyst was about 78% under the same reaction conditions; the caprolactam yield of its high temperature calcined sample was about 77%. The results of reaction indicated that the Cu-Beta zeolite catalyst prepared by using the improved ammonia evaporation method and directly taking the dealuminated Beta zeolite as the carrier also had better catalytic activity and anti-sintering deactivation ability for the reaction of gas-solid phase reductive amination of caprolactone to caprolactam, but its catalytic performance was obviously inferior to that of the catalyst prepared by taking the dealuminated Beta zeolite modified by drilling holes as the carrier.

[0143] Comparative Example 3: This example was used to illustrate that the copper-silica catalyst prepared by using the traditional ammonia evaporation method and taking the amorphous fumed silica (white carbon black, BET specific surface area 286m 2 / g) as the carrier had poor anti-sintering ability and stability.

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

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

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

[0147] (3) The reaction mixture of step (2) was subjected to temperature rising ammonia evaporation treatment (80°C, 6h), and when the pH of the mixture decreased to 6-7, the solid was obtained by filtration, washed with deionized water three times and then dried at 120°C for 12h and calcined at 450°C for 4h;

[0148] (4) The solid product was subjected to hydrogen reduction treatment. The reduction conditions were 350°C x 2h, and the copper-silica catalyst was obtained, which was coded as Cu3-SiO2-CE3.

[0149] (4) The solid product was subjected to hydrogen reduction treatment. The reduction conditions were 350°C x 2h, and the copper-silica catalyst was obtained, which was coded as Cu3-SiO2-CE3.

[0150] The results of the reaction of caprolactone gas-phase reductive amination to caprolactam show that the caprolactam yield of Cu3-SiO2-CE3 catalyst is about 75% under the same reaction conditions; the caprolactam yield of the high-temperature calcined sample (550°C x 3h) is 65%. The reaction results show that the copper-based catalyst prepared with amorphous silica as the carrier has poor resistance to sintering, and the catalytic activity greatly decreases after high-temperature treatment.

[0151] Comparative Example 4: This example is used to further illustrate that the copper-silica catalyst prepared by loading copper with the traditional ammonia evaporation method has poor resistance to sintering and poor stability.

[0152] Comparative Example 3 is repeated, but 33.3g of silica sol (30wt.% SiO2) is used as the precursor for in-situ generation of 10g of silica carrier. In order to keep the ratio of the volume of copper-ammonia complex solution to the dry basis of silica consistent with Comparative Example 3, the amount of water added is changed to 26.7ml when preparing the copper-ammonia complex solution in step (1). The copper-silica catalyst prepared is designated as Cu3-SiO2-CE4.

[0153] The results of the reaction of caprolactone gas-phase reductive amination to caprolactam show that the caprolactam yield of Cu3-SiO2-CE3 catalyst is about 75% under the same reaction conditions; the caprolactam yield of the high-temperature calcined sample (550°C x 3h) is 65%. The reaction results show that the copper-based catalyst prepared with amorphous silica as the carrier has poor resistance to sintering, and the catalytic activity greatly decreases after high-temperature treatment.

[0154] Comparative Example 5: This example is used to illustrate that the amorphous nature of the silica carrier determines that the copper-silica catalyst has poor resistance to sintering and poor stability.

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

[0156] Example 1 is repeated, but the 10g of chisel-modified dealuminated Beta zeolite carrier is replaced by 10g (dry basis) of fumed silica (white carbon black, BET specific surface area 286m 2 / g, and saturated water absorption rate 2.5ml / g). 10g of fumed silica requires 25ml of copper-ammonia complex solution. The concentration of the copper-ammonia complex solution required is about 0.19M according to the copper loading of 3wt.%. 11.9ml of saturated copper-ammonia complex solution is diluted to 25ml with dilute ammonia water base solution, i.e. 25ml of copper-ammonia complex solution with a concentration of 0.19M is obtained. The copper-silica catalyst prepared is designated as Cu3-SiO2-CE5.

[0157] The evaluation results of caprolactam production from caprolactone by gas-solid phase reductive amination show that the caprolactam yield of Cu3-SiO2-CE5 catalyst is 76% under the same reaction conditions; the caprolactam yield of the high-temperature calcined sample (550℃×3h) is 65%. The reaction results also show that the copper-based catalyst prepared by using amorphous silica as the carrier has poor sintering resistance, and the catalytic activity greatly decreases after high-temperature treatment.

[0158] Example 2: This example is used to illustrate that the Cu-Beta zeolite catalyst preparation method provided by the present application, which uses the dealuminated Beta zeolite modified by channelling as the carrier and uses the improved ammonia evaporation method to load 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 1wt.% and 2wt.%, and the concentration of the copper-ammonia complex solution required is about 0.13M and 0.25M, respectively. 3.9ml and 7.8ml of the saturated copper-ammonia complex solution are sequentially diluted with the dilute ammonia water base solution to 12.5ml, so as to obtain the equal-volume impregnation solutions of the Cu-Beta zeolite catalysts with copper loadings of 1wt.% and 2wt.%, respectively. In the preparation of the Cu-Beta zeolite catalyst by the improved ammonia evaporation method, the equal-volume impregnation treatment of the dealuminated Beta carrier (Beta24C) modified by channelling is carried out at room temperature for 6h, the ammonia evaporation treatment is carried out at 65℃ for 12h, the dehydration drying is carried out at 150℃ for 3h, the subsequent calcination is carried out at 450℃ for 6h, the final hydrogen reduction is carried out at 350℃ for 8h, the hydrogen flow rate (volume space velocity) is changed to 1000h-1, and the final copper loading in the Cu-Beta zeolite catalyst is 3wt.%. -1 The prepared Cu-Beta zeolite catalysts are named Cu1-Beta24C-2 and Cu2-Beta24C-2, respectively.

[0160] The evaluation results of caprolactam production from caprolactone by gas-solid phase reductive amination show that the caprolactam yield of Cu1-Beta24C-2 catalyst is 80% under the same reaction conditions; the caprolactam yield of Cu2-Beta24C-2 is 81%.

[0161] Example 3: This example is used to further illustrate that the Cu-Beta zeolite catalyst preparation method provided by the present application, which uses the dealuminated Beta zeolite modified by channelling as the carrier and uses the improved ammonia evaporation method to load copper in the pore channels of the zeolite, can be used to prepare Cu-Beta zeolite catalysts with different copper loadings. However, when preparing the Cu-Beta zeolite catalyst with a copper loading higher than 3wt.%, it is appropriate to use the multiple loading scheme to prepare the catalyst.

[0162] Repeating Example 1, but increasing the copper loading in the prepared Cu-Beta zeolite catalyst to 4 wt.% and 6 wt.%, respectively, the calculated required concentrations of the copper-ammonia complex solution were approximately 0.50 M and 0.76 M, respectively. Clearly, the required copper-ammonia complex concentrations both exceeded the concentration of the saturated copper-ammonia complex solution prepared with a dilute ammonia base solution (0.4 M). We attempted to dissolve the copper-ammonia complex using industrial ammonia instead of the dilute ammonia base solution, obtaining a maximum concentration of approximately 0.5 M. Although dissolving the copper-ammonia complex with industrial ammonia could produce a high-concentration copper-ammonia complex solution of approximately 0.5 M, this solution had an ammonia / copper ion molar ratio exceeding 24:1, strong alkalinity, and significant ammonia volatilization, which was detrimental to protecting the crystal structure of the dealuminized Beta zeolite and also unfavorable for operation. This indicates that the improved ammonia stripping method cannot yield a high-copper-loading Cu-Beta zeolite catalyst on a given dented-modified dealuminized Beta zeolite support through a single equal-volume impregnation and ammonia stripping operation. Therefore, this invention uses a dilute ammonia-based solution to dilute a saturated solution of the copper-ammonia complex, and prepares Cu-Beta zeolite catalysts with copper loadings increased to 4 wt.% and 6 wt.%, respectively, through multiple equal-volume impregnation and ammonia stripping operations. For the preparation of the 4 wt.% copper loading catalyst, the impregnation and ammonia stripping operations can be performed twice, such as 1 wt.% + 3 wt.%, 2 wt.% + 2 wt.%. For the preparation of the 6 wt.% copper loading catalyst, the operations can be performed twice (3 wt.% + 3 wt.%) or three times (2 wt.% + 2 wt.% + 2 wt.%). For simplicity, in this example, the preparation of Cu-Beta zeolite catalysts with copper loadings increased to 4 wt.% and 6 wt.%, respectively, is performed twice (2 wt.% + 2 wt.%, 3 wt.% + 3 wt.%). To load 2 wt.% of metallic copper onto a cavity-modified dealubilized Beta zeolite support using a modified ammonia stripping method, 12.5 ml of an impregnation solution with a copper-ammonia complex concentration of 0.25 M is required. To load 3 wt.% of metallic copper onto the cavity-modified dealubilized Beta zeolite support, 12.5 ml of an impregnation solution with a copper-ammonia complex concentration of 0.38 M is required. The 0.25 M impregnation solution is obtained by diluting 7.8 ml of a saturated copper-ammonia complex solution with a dilute ammonia base solution, while the 0.38 M impregnation solution is obtained directly from a saturated copper-ammonia complex solution. When performing equal-volume impregnation treatment on the dented modified dealuminized Beta support at room temperature, the impregnation time was changed to 6 h, the ammonia stripping temperature and time were changed to 85 °C and 3 h, respectively, the dehydration and drying temperature and time were changed to 120 °C and 5 h, respectively, the subsequent calcination temperature and time were changed to 550 °C and 2 h, respectively, the final hydrogen reduction temperature and time were changed to 500 °C and 2 h, respectively, and the hydrogen flow rate (volume hourly space velocity) was changed to 20 h⁻¹. -1(The feed was controlled by a mass flow meter after mixing with an appropriate amount of nitrogen). The prepared Cu-Beta zeolite catalysts were designated as Cu4-Beta24C-3 and Cu6-Beta24C-3, respectively.

[0163] Evaluation results of the gas-solid phase hydroammoniation of caprolactone to caprolactam showed that, under the same reaction conditions, the caprolactam yield was 85% with the Cu4-Beta24C-3 catalyst and 84% 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 (code-named 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, following the procedure in step 2 of Example 1, the above-mentioned large-grain dealuminized Beta zeolite support (Beta23c) was subjected to a pore-knocking modification treatment with an aqueous solution of ethanolamine to obtain a pore-knocking modified large-grain dealuminized Beta zeolite support, named Beta23C; further, following the procedure in step 3 of Example 1, copper was loaded into the zeolite channels using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst with a copper content of 3 wt.%, code-named Cu3-Beta23C-4.

[0166] The evaluation results of caprolactam production reaction by gas-solid phase reductive amination of caprolactone show that the caprolactam yield of Cu3-Beta23C-4 catalyst is 83% under the same reaction conditions.

[0167] Example 5: This example is used to illustrate that when the Cu-Beta zeolite catalyst is prepared by using the dealuminated Beta zeolite modified by the cavity modification as the carrier and loading copper in the pores by the improved ammonia evaporation method according to the present application, the cavity modification degree of the dealuminated Beta zeolite can be regulated by changing the impregnation modification conditions of the ethanolamine solution.

[0168] The example 1 is repeated, but when the hydroxyl cavity of the dealuminated Beta zeolite carrier is subjected to the cavity modification treatment by using the aqueous ethanolamine solution in the second step, the concentration of the aqueous ethanolamine solution is changed to 0.16 M, the ratio of the modification liquid volume to the dealuminated Beta zeolite carrier (Beta24c) feeding amount (liquid-solid ratio) is changed to 10:1, the impregnation temperature is changed to 50°C, and the impregnation time is changed to 0.5 h. After the cavity modification is completed, the reaction material is filtered to recover the solid product, and then the solid product is repeatedly washed with deionized water until it is neutral, and then the drying (overnight at 110°C) and calcination treatment (550°C for 3 h) are performed to prepare the dealuminated Beta zeolite modified by the cavity. It is sealed and stored for use. According to the weight loss estimation, the average number of the framework silicon atoms (calculated as SiO2) removed from the hydroxyl cavity lattice defect sites of the dealuminated Beta zeolite carrier is 1.5 silicon atoms, and the desilication amount is increased. It is illustrated that the above-mentioned treatment conditions strengthen the cavity modification treatment, and increase the geometric space of the hydroxyl cavity lattice defect sites of the dealuminated Beta zeolite. On this basis, the copper is loaded in the pores of the modified carrier by the improved ammonia evaporation method to prepare the Cu-Beta zeolite catalyst with a copper content of 3 wt.%, which is named as Cu3-Beta24C-5.

[0169] The evaluation results of caprolactam production reaction by gas-solid phase reductive amination of caprolactone show that the caprolactam yield of Cu3-Beta24C-5 catalyst is 84% under the same reaction conditions; and the caprolactam yield of the high-temperature calcined sample (550°C x 3 h) is 83%.

[0170] Example 6: This example is used to further illustrate that when the Cu-Beta zeolite catalyst is prepared by using the dealuminated Beta zeolite modified by the cavity modification as the carrier and loading copper in the pores by the improved ammonia evaporation method according to the present application, the cavity modification degree of the dealuminated Beta zeolite can be regulated by changing the impregnation modification conditions of the ethanolamine solution.

[0171] Example 1 was repeated, but in the second step, the hydroxy pocket channelling modification treatment of the dealuminated Beta zeolite support with the aqueous ethanolamine solution was carried out with the ethanolamine aqueous solution concentration changed to 0.30 M, the liquid-to-solid ratio changed to 2:1, the impregnation temperature changed to 20 °C, and the impregnation time changed to 1 h. After the completion of the channelling modification, the reaction mass was filtered to recover the solid product, which was then repeatedly washed with deionized water until neutral, followed by drying (overnight at 110 °C) and calcination (550 °C for 3 h) to produce the channelling-modified dealuminated Beta zeolite. It was stored in a sealed container for later use. The average number of framework silicon atoms (in terms of SiO2) chiselled out from the hydroxy pocket lattice defect sites of the dealuminated Beta zeolite support was 1.1 silicon atoms, as estimated from the weight loss. The dealumination amount was reduced, indicating that the above-mentioned channelling modification condition combination weakened the channelling modification treatment. On this basis, the copper was loaded in the pores of the dealuminated Beta zeolite support by the improved ammonia evaporation method to produce a Cu-Beta zeolite catalyst with a copper content of 3 wt.%, which was named Cu3-Beta24C-6.

[0172] The evaluation results of the caprolactam gas-solid phase hydrogenation reaction showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta24C-6 catalyst was 83%; the caprolactam yield of the high-temperature calcined sample (550 °C x 3 h) was 83%.

[0173] Example 7: This example was used to illustrate that, when the Cu-Beta zeolite catalyst was prepared by the improved ammonia evaporation method provided by the present application, the Beta zeolite parent body with different molar ratios of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) was allowed to be used to prepare the channelling-modified dealuminated Beta zeolite support. When the Beta zeolite parent body with a higher molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) was used as the parent body, a relatively mild channelling modification condition combination was preferably used. Conversely, the same was true.

[0174] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, the Beta zeolite parent body with a molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) of 60 was synthesized by the hydrothermal crystallization method provided by US Patent 3 308 069 (1967) as the raw material for preparing the dealuminated Beta zeolite support. After the synthesized Beta zeolite parent body was subjected to the conventional filtration, washing, drying (170 °C for 3 h), and calcination to remove the template agent (500 °C for 8 h), its average grain size was close to 100 nanometers, which belonged to nano-Beta zeolite; no any impurity crystal was found in it by the XRD method, and its BET specific surface area was about 530 m2 / g calculated from its nitrogen physical adsorption data; and its molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) was about 57 measured by the XRF method, which met the technical requirements of the Beta zeolite parent body of the present application. 2 ​

[0175] The Beta zeolite mother substance was used to prepare a dealuminated Beta zeolite support by concentrated nitric acid dealumination to obtain a dealuminated Beta zeolite support with a molar ratio of silicon to aluminum oxide (molar ratio of SiO2 to Al2O3) of 861 (>800) (code Beta57c). The degree of dealumination of the support met the requirements of the present application. In the second step, the dealuminated Beta zeolite support was subjected to a channelling modification treatment with an aqueous solution of ethanolamine. The concentration of the aqueous ethanolamine solution was changed to 0.02 M, the liquid-to-solid ratio was changed to 20:1, the impregnation temperature was changed to 80°C, and the impregnation time was changed to 5 h. After the channelling modification was completed, the reaction material was filtered to recover the solid product, which was then repeatedly washed with deionized water until it was neutral, and then dried (overnight at 110°C) and subjected to calcination treatment (at 550°C for 3 h) to obtain a channelling-modified dealuminated Beta zeolite. The product was sealed and stored for later use. According to the weight loss, the average number of framework silicon atoms (calculated as SiO2) chiselled out from the lattice defect sites of the hydroxyl pockets of the dealuminated Beta zeolite support was 1.6 silicon atoms. The amount of desiliconization increased, indicating that the above-mentioned combination of channelling modification conditions was strengthened for the dealuminated Beta zeolite support with a small number of hydroxyl pockets. The channelling-modified dealuminated Beta zeolite support obtained was named Beta57C. Further, the Cu-Beta zeolite catalyst with a copper content of 3 wt.% was prepared by loading copper in the pores of the zeolite using the improved ammonia evaporation method according to the method of the third step of Example 1. In this case, when the support was impregnated with an equal volume of a saturated solution of copper-ammonia complex at room temperature, the impregnation time was changed to 2 h. During the ammonia evaporation, micro-negative pressure ammonia evaporation was used, the ammonia evaporation temperature was 50°C, and the ammonia evaporation time was 48 h. When the material after ammonia evaporation was subjected to dehydration and drying, the drying temperature and time were changed to 100°C and 48 h, respectively. The subsequent calcination treatment temperature and time were changed to 350°C and 24 h, respectively. The final hydrogen reduction treatment temperature, time, and hydrogen flow rate (volume space velocity) were changed to 300°C, 20 h, and 2000 h -1 , respectively. The catalyst code was Cu3-Beta57C-7.

[0176] The evaluation results of the caprolactam gas-solid phase hydrogenation reaction showed that, under the same reaction conditions, the caprolactam yield of the Cu3-Beta57C-7 catalyst was 81%.

[0177] Example 8: This example is used to further illustrate that, when the Cu-Beta zeolite catalyst is prepared according to the improved ammonia evaporation method provided by the present application, different Beta zeolite mother substances with different molar ratios of silicon to aluminum oxide (molar ratio of SiO2 to Al2O3) can be used to prepare the channelling-modified dealuminated Beta zeolite support. When a Beta zeolite with a higher molar ratio of silicon to aluminum oxide (molar ratio of SiO2 to Al2O3) is used as the mother substance, a relatively mild combination of channelling modification conditions should be used. Conversely, the opposite is also true.

[0178] Example 7 was repeated, but in the second step, the liquid-to-solid ratio was changed to 100:1 and the impregnation time was changed to 24 h when the hydroxyl pocket of the dealuminated Beta zeolite support was modified by the pocket-modification treatment with the aqueous solution of ethanolamine. After the pocket-modification treatment, the reaction mixture was filtered to recover the solid product, which was then repeatedly washed with deionized water until neutral, and then dried (overnight at 110 °C) and calcined (3 h at 550 °C) to produce the pocket-modified dealuminated Beta zeolite. The average number of framework silicon atoms (in terms of Si02) chipped out from the hydroxyl pocket lattice defects of the dealuminated Beta zeolite support was 3.0 silicon atoms, as estimated from the weight loss. The desilication was significantly increased, indicating that the above-mentioned pocket-modification condition combination strengthened the pocket-modification treatment for the dealuminated Beta zeolite support with a small number of hydroxyl pockets. On this basis, the Cu-beta zeolite catalyst, coded as Cu3-Beta57C-8, was prepared by using the pocket-modified dealuminated Beta zeolite as the support and following the procedure of Example 1, Step 3.

[0179] The evaluation results of the caprolactam gas-solid phase hydrogenation reaction showed that the caprolactam yield of the Cu3-Beta57C-8 catalyst was 75% under the same reaction conditions.

[0180] Example 9: This example was used to further illustrate that the improved ammonium vaporization method provided by the present application allowed the use of Beta zeolite matrices with different molar ratios of silicon-aluminum oxide (molar ratio of Si02to Al203) to prepare the pocket-modified dealuminated Beta zeolite support. When the Beta zeolite matrix with a higher molar ratio of silicon-aluminum oxide (molar ratio of Si02to Al203) was used, a relatively mild pocket-modification condition combination should be adopted. Conversely, the opposite was also true.

[0181] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, the Beta zeolite matrices with molar ratios of silicon-aluminum oxide (molar ratio of Si02to Al203) of 40, 80, 100, 150, and 200 were first synthesized as raw materials for preparing the dealuminated Beta zeolite support according to the hydrothermal crystallization method provided in Chinese Invention Patent CN1108275C (application date 10 September 1999). After the synthesized Beta zeolite matrices were subjected to conventional filtration, washing, drying (at 110 °C for 12 h), and calcination to remove the template agent (at 540 °C for 6 h), TEM observation showed that the average crystal size of the synthesized Beta zeolite matrices belonged to the nanometer and small crystal (less than 1 μm) levels. As the molar ratio of silicon-aluminum oxide (molar ratio of Si02to Al203) increased, the crystal size increased. No impurities were found in the synthesized Beta zeolite matrices by XRD, and the BET specific surface area of the synthesized Beta zeolite matrices was calculated to be higher than 500 m2 / g by using the nitrogen physical adsorption data. The dealuminated Beta zeolite support was then prepared by using the synthesized Beta zeolite matrices as the raw material and following the procedure of Example 1, Step 1. 2The Si / Al oxide molar ratios (SiO2 / Al2O3) of the five Beta zeolite matrices are 38, 72, 94, 136 and 189, respectively, which meet the technical requirements of the Beta zeolite matrix.

[0182] The five Beta zeolite matrices are used to prepare dealuminated Beta zeolite carriers by dealumination with concentrated nitric acid, and five dealuminated Beta zeolite carriers, Beta38c, Beta72c, Beta94c, Beta136c and Beta189c, are obtained, with Si / Al oxide molar ratios (SiO2 / Al2O3) of 870, 855, 932, 1088 and 960, respectively, all of which meet the technical requirements of the dealuminated Beta zeolite carrier. On this basis, the dealuminated Beta zeolite carriers are subjected to the channelling modification treatment with the aqueous solution of ethanolamine according to the practice of the second step of Example 1. The channelling modification treatment conditions are as follows: the concentration of the aqueous ethanolamine solution is changed to 0.01 M, the liquid / solid ratio is changed to 20:1, the impregnation temperature is changed to 80°C, and the impregnation time is changed to 3 h. After the channelling modification, the reaction material is filtered to recover the solid product, which is then repeatedly washed with deionized water until neutral, and then dried (overnight at 110°C) and calcined (at 550°C for 3 h) to obtain the channelling-modified dealuminated Beta zeolite carriers, which are named Beta38C, Beta72C, Beta94C, Beta136C and Beta189C. They are sealed and stored for later use. According to the weight loss, the average number of framework silicon atoms (in terms of SiO2) chipped out from the hydroxyl channelling lattice defect sites of the dealuminated Beta zeolite carriers in the above channelling-modified dealuminated Beta zeolite carriers is 0.3, 0.7, 1.0, 1.8 and 2.5, respectively. That is, the above channelling modification condition combination is not enough for the dealuminated Beta zeolite carriers prepared from the Beta zeolite matrices with lower Si / Al oxide molar ratios (SiO2 / Al2O3), while it is too strong for the dealuminated Beta zeolite carriers prepared from the Beta zeolite matrices with higher Si / Al oxide molar ratios (SiO2 / Al2O3).

[0183] Further according to the practice of the third step of Example 1, copper is loaded in the zeolite pores by the improved ammonia evaporation method to prepare Cu-Beta zeolite catalysts with a copper content of 3 wt.%, wherein, when the carrier is impregnated with the saturated solution of copper-ammonia complex in equal volume at room temperature, the impregnation time is changed to 1 h. When ammonia is evaporated, the ammonia evaporation temperature is changed to 90°C, and the ammonia evaporation time is changed to 1 h. When the material after ammonia evaporation is dehydrated and dried, the drying temperature and time are changed to 200°C and 1 h, respectively. The subsequent calcination temperature and time are changed to 550°C and 1 h, respectively. The final hydrogen reduction treatment temperature, time and hydrogen flow rate are changed to 550°C, 1 h and 5 h, respectively. -1(Cu3-Beta38C-9, Cu3-Beta72C-9, Cu3-Beta94C-9, Cu3-Beta136C-9 and Cu3-Beta189C-9, respectively).

[0184] The anti-sintering deactivation performance of the above catalysts and their 550°C calcined (3h) samples were evaluated by using caprolactam gas solid phase hydrogenation reaction. The results showed that under the same reaction conditions, the catalytic activity of Cu3-Beta38C-9, Cu3-Beta72C-9, Cu3-Beta94C-9, Cu3-Beta136C-9 and Cu3-Beta189C-9 catalysts after high temperature calcination decreased by about 4%, 7%, 7%, 8% and 11%, respectively.

[0185] Example 10: This example is used to further illustrate that when preparing Cu-Beta zeolite catalysts by using the improved ammonia evaporation method provided by the present application, it is allowed to use Beta zeolite parent bodies with different silica alumina molar ratios (molar ratio of SiO2 to Al2O3) to prepare the channeled modified dealuminated Beta zeolite carriers. When using Beta zeolite parent bodies with higher silica alumina molar ratios (molar ratio of SiO2 to Al2O3), it is appropriate to use relatively mild channeled modification condition combinations. Conversely, the same is true.

[0186] Example 9 was repeated, but when using aqueous ethanolamine solution to channeled modify the different dealuminated Beta zeolite carriers in the second step, the concentration of the aqueous ethanolamine solution was changed to 0.08M. After the channeled modification was completed, the reaction material was filtered to recover the solid product, which was then repeatedly washed with deionized water until it was neutral, and then dried (overnight at 110°C) and calcined (550°C, 3h) to obtain the channeled modified dealuminated Beta zeolite carriers, which were named Beta38C, Beta72C, Beta94C, Beta136C and Beta189C. They were sealed and stored for later use. According to the weight loss, the average number of framework silicon atoms (in terms of SiO2) chiseled out of the hydroxyl channeled lattice defect sites of the dealuminated Beta zeolite carriers in the above channeled modified dealuminated Beta zeolite parent bodies was 0.9, 1.6, 2.1, 3.0 and 4.3, respectively. That is, the above channeled modification condition combinations are appropriate for the dealuminated Beta zeolite carriers prepared from Beta zeolite parent bodies with lower silica alumina molar ratios (molar ratio of SiO2 to Al2O3), but the channeled modification degree is too strong for the dealuminated Beta zeolite carriers prepared from Beta zeolite parent bodies with high silica alumina molar ratios (molar ratio of SiO2 to Al2O3).

[0187] Catalysts prepared by improved ammonia evaporation method on the above-mentioned cavity-modified dealuminated Beta zeolite carriers, which are coded as Cu3-Beta38C-10, Cu3-Beta72C-10, Cu3-Beta94C-10, Cu3-Beta136C-10 and Cu3-Beta189C-10, respectively.

[0188] The anti-sintering deactivation performance of the above-mentioned catalysts and their samples calcined at 550°C (3h) was evaluated by using caprolactam gas-solid phase reaction of hydrogenation. The results showed that under the same reaction conditions, the catalytic activity of Cu3-Beta38C-10, Cu3-Beta72C-10, Cu3-Beta94C-10, Cu3-Beta136C-10 and Cu3-Beta189C-10 catalysts after high-temperature calcination decreased by about 5%, 8%, 9%, 14% and 17%, respectively.

[0189] Example 11: This example is used to illustrate that when preparing Cu-Beta zeolite catalysts by improved ammonia evaporation method provided by the present application, Beta zeolite mother bodies with different molar ratios of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) can be used to prepare cavity-modified dealuminated Beta zeolite carriers. However, when using Beta zeolite mother bodies with higher molar ratios of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) to prepare cavity-modified dealuminated Beta zeolite carriers, it is suitable to prepare Cu-Beta zeolite catalysts with lower copper loading.

[0190] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite carrier, a Beta zeolite mother body with a molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) of 100 was synthesized by a hydrothermal crystallization method provided by Chinese Invention Patent CN1108275C (application date 1999.9.10) as a raw material for preparing the dealuminated Beta zeolite carrier. After the synthesized Beta zeolite mother body was treated by conventional filtration, washing, drying (200°C, 3h) and calcination to remove the template agent (500°C, 8h), its average grain size was observed by TEM to be in the small grain (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 m 2 / g, and its molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) measured by XRF method was 94, which met the technical requirements of the Beta zeolite mother body of the present application.

[0191] The Beta zeolite mother substance was used for dealumination with concentrated nitric acid to prepare a dealuminated Beta zeolite support with a silica-to-alumina molar ratio (Si02 / Al203) of 932 (>900) (designated as Beta94c), which meets the technical requirements of the present application. On this basis, the dealuminated Beta zeolite support was subjected to the steaming modification treatment with an aqueous solution of ethanolamine according to the procedure of the second step of Example 1 to obtain a steaming modified dealuminated Beta zeolite support, designated as Beta94C. Further, a Cu-Beta zeolite catalyst with a copper content of 6 wt.% was prepared according to the procedure of the third step of Example 1 using the improved ammonia evaporation method according to two equal volume impregnations and two ammonia evaporation. The concentration of the copper-ammine complex solution used in the two equal volume impregnations was 0.38 M. Since the concentration of the 0.38 M copper-ammine complex solution is very close to the concentration of the saturated solution of the copper-ammine complex prepared using the dilute aqueous ammonia base solution, 12.5 ml of the 0.4 M saturated solution of the copper-ammine complex was directly used for the equal volume impregnation of the Beta94C support. The prepared catalyst was designated as Cu6-Beta94C-11.

[0192] The sintering resistance and deactivation performance of the catalyst and the sample thereof calcined at 550 °C (3 h) were evaluated using the caprolactam gas-solid phase hydrogenation reaction. The results showed that the catalytic activity (caprolactam yield) of the Cu6-Beta94C-11 catalyst after high temperature calcination decreased by 10% under the same reaction conditions.

Claims

1. A method for improving the stability of a Cu-Beta zeolite catalyst for the preparation of caprolactam from caprolactone, characterized in that, The steps are as follows: Step 1, preparation of a dealuminated Beta zeolite carrier (1) selection of a Beta zeolite matrix The Beta zeolite mother phase refers to a silicon-aluminum Beta zeolite meeting the following requirements: 1) the Beta zeolite mother phase contains no impurity crystals; 2) the Beta zeolite mother phase has good crystallization, i.e. the BET specific surface area value of the Beta zeolite mother phase measured by a nitrogen physical adsorption method is ≧450 m 2 / g; 3) the silicon-alumina oxide molar ratio of the Beta zeolite mother phase, i.e. the molar ratio of SiO2 to Al2O3 is in the range of 25-60. (2) preparation of a dealuminated Beta zeolite carrier The dealuminated Beta zeolite carrier is prepared by an acid dealumination method based on a Beta zeolite matrix, and the molar ratio of silicon aluminum oxide, i.e. the molar ratio of SiO2 to Al2O3, of the dealuminated Beta zeolite carrier prepared is required to be in the range of ≧700; Step 2, modification of the hydroxyl pits of the dealuminated Beta zeolite carrier by chiseling pits with an aqueous solution of ethanolamine The modification of the hydroxyl pits by chiseling pits is carried out by a water immersion method, and the parameters are as follows: The concentration of the ethanolamine solution is in the range of 0.01 M-0.4 M; The ratio of the ethanolamine solution to the dealuminated Beta zeolite carrier, i.e. the liquid-solid ratio, is in the range of 1:1-100:1, and the unit of the liquid-solid ratio is ml / g; The immersion temperature is in the range of 20℃-100℃; The immersion time is in the range of 0.1 h-24 h; Step 3, loading of copper in the pores of the dealuminated Beta zeolite carrier modified by chiseling pits by an improved ammonia evaporation method to prepare a Cu-Beta zeolite catalyst The specific steps are as follows: (1) preparation of a dilute ammonia water base solution and a saturated solution of copper ammonia complex: according to the proportion of 4.4 g of industrial ammonia water containing 25-28 wt.% of NH3 to 100 ml of deionized water, a dilute ammonia water base solution with pH value = 11-12 is prepared, and is sealed and stored for standby; then, according to the molar ratio of copper ions to ammonia molecules of 1:4, copper nitrate trihydrate is used as a soluble copper-containing compound to react with industrial ammonia water to synthesize a 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 the copper ammonia complex, which is stored in a sealed container for standby; the concentration of copper ammonia complex ions in the saturated solution of the copper ammonia complex is 0.4 M; (2) equal volume immersion of the zeolite carrier with the copper ammonia complex solution: first, the saturated water absorption rate of the zeolite carrier is determined, and the amount of the copper ammonia complex solution used for equal volume immersion of the zeolite carrier is calculated accordingly; then, according to the copper loading amount of the Cu-Beta zeolite catalyst to be prepared, the concentration of the copper ammonia complex solution required is calculated; when the calculated concentration is equal to 0.4 M, the zeolite carrier is directly immersed in the saturated solution of the copper ammonia complex in equal volume; when the calculated concentration is lower than 0.4 M, the saturated solution of the copper ammonia complex is appropriately diluted with the dilute ammonia water base solution before the zeolite carrier is immersed in equal volume; when the calculated value is higher than 0.4 M, multiple equal volume immersions should be carried out, 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 the 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 zeolite carrier is treated by ammonia evaporation; the equal volume immersion is carried out in a sealed container at room temperature; the equal volume immersion time is in the range of 0.5-24 h; (3) ammonia evaporation treatment: the ammonia evaporation process is carried out at normal pressure or reduced pressure; the ammonia evaporation temperature and time are in the range of 50-100℃ and 0.5-48 h; (4) Dehydration and drying treatment after ammonia evaporation: the range of drying temperature and time is 100-200℃ and 0.5-48 h, respectively; (5) Calcination treatment after ammonia evaporation: the calcination is carried out in air atmosphere, and the range of calcination temperature and time is 350-650℃ and 0.5-24 h, respectively; The catalyst precursor is obtained after the calcination treatment; (6) Hydrogen reduction treatment of the catalyst precursor: the reduction temperature, time and hydrogen volume space velocity range from 280 to 600°C, 0.5 to 20 h and 1 to 2000 h, respectively -1 ; the catalyst precursor becomes a Cu-Beta zeolite catalyst after the hydrogen reduction treatment.

2. The preparation method of claim 1, wherein the molar ratio of silica to alumina of the de-aluminized Beta zeolite support prepared in the first step (2) is ≧800.

3. The preparation method of claim 2, wherein the molar ratio of silica to alumina of the de-aluminized Beta zeolite support prepared in the first step (2) is ≧900.

4. The preparation method of claim 1, wherein in the first step (2), the de-aluminized Beta zeolite support is prepared by acid de-alumination of the Beta zeolite mother body using concentrated nitric acid solution, and the preparation process is as follows: The 13 M concentrated nitric acid solution is used as the de-alumination acid solution, and the acid solution is used in a liquid-solid ratio of 20:1, wherein the unit of the liquid-solid ratio is ml / g; the de-alumination reaction is carried out at 95℃, and the de-alumination reaction time is 20 h; after the de-alumination reaction is completed, the solid product is recovered by solid-liquid separation, then the solid product is washed with water until the pH value is neutral, and then the solid product is dried at a temperature of 80-200℃ for 3-24 h and calcined at a temperature of 500℃-600℃ for 3-8 h to obtain the de-aluminized Beta zeolite.

5. The preparation method of claim 1, wherein in the second step, the hydroxyl pits of the de-aluminized Beta zeolite support are modified by using the aqueous solution of ethanolamine, and the aqueous solution immersion method is used, and the parameters are as follows: The concentration of the ethanolamine solution is in the range of 0.02 M-0.3 M; The ratio of the ethanolamine solution to the de-aluminized Beta zeolite support, i.e., the liquid-solid ratio, is in the range of 2:1-50:1, and the unit of the liquid-solid ratio is ml / g; The immersion temperature is in the range of 30℃-90℃; The immersion time is in the range of 0.5 h-10 h.

6. The preparation method of claim 5, wherein in the second step, the hydroxyl pits of the de-aluminized Beta zeolite support are modified by using the aqueous solution of ethanolamine, and the aqueous solution immersion method is used, and the parameters are as follows: The concentration of the ethanolamine solution is in the range of 0.03 M-0.16 M; The ratio of the ethanolamine solution to the de-aluminized Beta zeolite support, i.e., the liquid-solid ratio, is in the range of 3:1-20:1, and the unit of the liquid-solid ratio is ml / g; The immersion temperature is in the range of 40℃-80℃; ​ ​ ​ ​ ​ The impregnation time ranges from 1 to 5 hours.

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

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

9. The Cu-Beta zeolite prepared by the method for improving the stability of a Cu-Beta zeolite catalyst for preparing caprolactam from caprolactone according to any one of claims 1 to 8 is used for catalyzing the gas-solid phase hydrogenation of caprolactone to prepare caprolactam.

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

Images