Preparation method for improving stability of cu-beta zeolite catalyst for preparing caprolactam from caprolactone, and use thereof

Abstract

The present invention belongs to the technical field of petrochemical catalysis, and relates to a preparation method for improving the stability of a Cu-Beta zeolite catalyst for preparing caprolactam from caprolactone, and the use thereof. In the present invention, a cavity-modified dealuminated Beta zeolite is used as a carrier, and copper is loaded in pore channels of the zeolite carrier by means of an improved ammonia distillation method. The cavity modification refers to subjecting the dealuminated Beta zeolite carrier to a desiliconization technique controlled by the use of a weak organic base so as to enlarge silanol nests generated by dealumination of the dealuminated Beta zeolite carrier, thereby better accommodating and stabilizing the nano and sub-nano copper particles. The core of the improved ammonia distillation method involves impregnating a zeolite carrier with an equal volume of a copper-ammonia complex solution, such that the copper-ammonia complex mainly undergoes, during ammonia distillation, a reaction of depositing copper hydroxide in zeolite pore channels, thereby improving the sintering resistance. The Cu-Beta catalyst prepared using the method provided by the present invention exhibits high activity, selectivity and stability when applied to the reaction of caprolactam prepared from caprolactone via gas-solid phase hydroamination.

Description

Preparation method for improving stability of Cu-Beta zeolite catalyst for preparing caprolactam from caprolactone and application thereof TECHNICAL FIELD

[0001] The present application belongs to the field of petrochemical catalysis, and relates to a preparation method for improving stability of 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 chip, and a small part of which is used for producing lysine and pharmaceutical intermediates. In downstream products of the polyamide-6 chip, nylon-6 fiber and engineering plastic consume about 70% and 20% of the polyamide-6 chip respectively. The remaining polyamide-6 chip is processed into packaging film and food preservation film.

[0003] Nylon-6 is the first synthetic fiber product developed in the world. The most prominent advantage of nylon-6 fiber is that 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 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 for caprolactam 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 by those skilled in the art, the traditional benzene process for caprolactam has many serious problems. However, in recent years, some successful improvements have been made on the traditional benzene process for caprolactam according to the requirements of green chemistry and atom economy, which include that in the step of benzene to cyclohexanone, 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 step of cyclohexanone to cyclohexanone oxime, 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 solvent consumption of cyclohexanone ammonioxydation process is large, and the TS-1 catalyst is deactivated quickly and consumed in large quantities during the reaction process (titanium-silicon molecular sieve is expensive. Cyclohexanone ammonioxydation to produce cyclohexanone oxime is a liquid phase reaction, and the titanium-silicon molecular sieve catalyst is in a strong alkaline environment for a long time, causing the loss of the catalyst due to the dissolution of the skeleton silicon); (3) the liquid phase Beckmann rearrangement process (the current mainstream process) still uses oleum 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 produced. The gas phase Beckmann rearrangement technology, which is highly expected by people, itself has the problem of rapid catalyst deactivation, and people's efforts to replace the liquid phase Beckmann rearrangement process with the gas phase Beckmann rearrangement process have been frustrated.

[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) and high efficiency 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), which can obtain a 30% single-pass caprolactam yield. It is undoubtedly unimaginable to realize the industrialization of a bulk chemical by batch kettle at high temperature and high pressure.

[0010] In the same year, UCC disclosed another process for preparing caprolactam from caprolactone in US3000800. Specifically, the process is a process for preparing caprolactam from caprolactone at a high pressure (P>22.1 MPa) and a temperature higher than the critical temperature of ammonia and water (373°C <t>473°C) to produce caprolactam by non-catalytic reaction. This method has been successfully commercialized, but the process can only be carried out under high temperature and high pressure, and the energy consumption is huge. Moreover, the non-catalytic reaction under high temperature and high pressure tends to produce polymer, so the actual yield of caprolactam is less than 50%. This is probably the main reason why the Union Carbide Corporation stopped the production line for producing caprolactam from caprolactone. On the other hand, the caprolactone raw material at that time came from the oxidation reaction of cyclohexanone and peracetic acid. Peracetic acid is a strong oxidant and is extremely unstable. Peracetic acid will explode when it comes into contact with high heat, reducing agents or metal ions. In fact, peracetic acid has explosive properties when its concentration is greater than 45%, and it can even explode at -20°C. Therefore, the production process of caprolactone at that time was extremely dangerous. This is also probably an important reason why the Union Carbide Corporation stopped the production line for producing caprolactam from caprolactone.

[0011] In 1964, Teijin Corporation of Japan disclosed a catalytic method for producing caprolactam from caprolactone, 6-hydroxycaproamide or amide derivatives of 6-hydroxycaproic acid in US Patents US3317516 and US3317517. Specifically, the catalytic method disclosed in the above patents is to heat caprolactone, 6-hydroxycaproamide or amide derivatives of 6-hydroxycaproic acid and ammonia together to 200-400°C in a high-pressure reactor under the catalysis of a hydrogenation catalyst containing at least one or a combination of noble metals, cobalt and nickel, to produce caprolactam with less color. The method can be selected to be used under a hydrogen atmosphere. Obviously, the reaction conditions of the catalytic method are relatively mild. However, the single-pass yield of caprolactam obtained by this method is also not high, with a maximum of only 45.1%, so the economic efficiency of this method is not high.

[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] The application provides a preparation method for improving the stability of a Cu-Beta zeolite catalyst for preparing caprolactam by hydrogenation of caprolactone, and specifically relates to a preparation method for a catalyst for preparing caprolactam by hydrogenation of caprolactone, in which a modified delaminated Beta zeolite is used as a carrier, and a modified ammonia evaporation method is used to load copper in the pores.

[0029] It is found through research that, for the gas-solid phase catalytic reaction of preparing caprolactam by hydrogenation of caprolactone, from the perspective of catalytic activity and selectivity, a supported copper-based catalyst has the most industrial application prospects. However, from the perspective of catalyst stability, deactivation is the biggest challenge for the industrial application of the supported copper-based catalyst. The deactivation of the copper-based catalyst in the gas-solid phase catalytic reaction of preparing caprolactam by hydrogenation of caprolactone is not only caused by carbon deposition. The sintering of highly dispersed copper particles is also an important cause of catalyst deactivation. As known by those skilled in the art, carbon deposition deactivation belongs to temporary deactivation of the catalyst, and the catalytic activity of the catalyst can be restored through various regeneration methods, thereby prolonging the service life of the catalyst. In comparison, sintering deactivation generally belongs to permanent deactivation of the catalyst, and has the greatest impact on the service life of the catalyst.

[0030] The preparation method of the Cu-Beta zeolite catalyst provided by the application has the following main benefits: the dispersion and stability of the copper particles loaded on the delaminated Beta zeolite are improved by the hydroxyl pits of the delaminated Beta zeolite, and the hydroxyl pits generated by delamination are enlarged through the weak organic base control desilication technology, the contact area of the hydroxyl pits and the copper particles is increased, and the stability of the copper particles loaded on the delaminated Beta zeolite is further improved, so that the copper-based catalyst can be used without adding anti-sintering additives such as chromium and nickel.

[0031] The preparation method of the Cu-Beta zeolite catalyst provided by the application has the following main technical features:

[0032] Firstly, the preparation method of the Cu-Beta zeolite catalyst provided by the application uses a modified delaminated Beta zeolite as a carrier for loading copper.

[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 aids such as chromium and nickel, and has high stability in the reaction of caprolactam from the hydrogenation of caprolactone.

[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 ([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] The modification of the hydroxyl pockets, i.e. the increase of the size of the hydroxyl pockets of dealuminated Beta zeolites by desilication controlled by a weak organic base solution, is essentially an alkali-catalyzed hydrolytic desilication modification ((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, i.e. for each "chipping" of a silicon atom (in the form of Si(OH)4) from the walls of the hydroxyl pockets, three silicon hydroxyl groups (≡Si-OH) are created on the new walls of the hydroxyl pockets.

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

[0040] As a crystalline porous catalytic material, Beta zeolite has similar advantages to MFI zeolite, such as (1) both are high-silica zeolites, thus having high thermal 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 diffusivity and strong anti-clogging ability, and being conducive to maintaining 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

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

[0100] and

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

[0041] On the other hand, the framework aluminum of Beta zeolite can be easily removed by acid treatment to produce a high density of hydroxyl pit defect sites on the crystal framework. This feature is not common among industrialized zeolite catalytic materials and is unmatched by MFI zeolite. When Beta zeolite is subjected to acid dealumination treatment, four Si-O-Al bonds need to be acidized for each framework aluminum removed ([Al-(OSi)4] - + 4H2O = [Al(OH)4] - + 4≡Si-OH, [Al(OH)4] - + 4H + = Al 3+ + 4H2O, and the overall reaction equation is [Al-(OSi)4] - + 4H + = Al 3+ +4≡Si-OH), resulting in a hydroxyl pocket lattice defect site surrounded by four silicon hydroxyl groups (≡Si-OH). In the MFI zeolite, the hydroxyl pocket lattice defect site of the defective all-silica zeolite S-1 is randomly formed during hydrothermal synthesis of the S-1 zeolite in an alkaline medium, and the number and controllability of the distribution are poor; the framework aluminum content of the 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 be an all-silica zeolite, i.e., Silicalite-1 (S-1). However, the framework aluminum of the 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, the general method is to first synthesize a ZSM-5 zeolite containing boron (B-ZSM-5), and then remove boron from the B-ZSM-5 zeolite to obtain a ZSM-5 zeolite carrier with a higher density of hydroxyl pocket defect sites on the framework.

[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 a 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, the 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, the Beta zeolite is a catalytic material that has been industrialized for a long time, that is, it can be obtained in large quantities on 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 the Beta zeolite can at most accommodate one copper atom. Obviously, the active silicon hydroxyl group in the hydroxyl pocket of the Beta zeolite only interacts closely with one copper atom, which inevitably limits its dispersion and stabilization ability to the 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 originally having only one framework atom vacancy (acid dealuminated) to a larger hydroxyl pocket having 2-3 framework atom vacancies, the dispersion and stabilization capacity 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 capacity 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 capacity, 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 small molecule fatty amine and alcohol amine have the advantages of good water solubility and small amount of use. 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 oxide (Si(OH)4)), that is, for every "chiseled" silicon atom (in the form of Si(OH)4) 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 the ammonia evaporation method, and other methods are no different from the traditional ammonia evaporation method. It should be noted that the P25 type TiO2 carrier belongs to a low specific surface carrier, and its capillary pores are not developed, so in the prepared Cu / TiO2 catalyst, it does not have a uniform deposition precipitation effect, that is, the copper hydroxide loaded mainly exists on the outer surface of the titanium dioxide carrier, and the sample after calcination is analyzed by X-ray diffraction, and there are obvious diffraction characteristic peaks of CuO phase at 2θ = 35.5°, 38.7° and 48.7°, indicating that the hydrogen reduction product-metallic copper has poor dispersity.

[0053] In addition, it is worth special mentioning that in the published document Applied Catalysis A, General 539 (2017) 59-69, researchers used pre-prepared ordered mesoporous silica (OMS) as the support of their Cu / OMS catalyst prepared by the ammonia evaporation method. In order to reduce the damage of the basicity of the copper ammonia complex solution to the ordered mesoporous structure of the pre-prepared silica support, the researchers also appropriately reduced the concentration of ammonia in the prepared copper ammonia complex solution (which the researchers considered as an improvement of the ammonia 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 (the pH value of the slurry is reduced to 6-7), the water solvent of the diluted and volume-excessive copper ammonia complex solution is finally removed by filtration to obtain a solid product loaded with copper hydroxide. The research results show that the ordered mesoporous structure of the pre-prepared silica support used in the study has been mostly destroyed after being loaded with metal copper by the ammonia evaporation method, and there is a large amount of layered copper silicate in the catalyst, indicating that the pre-prepared silica support used is largely dissolved into silica sol during the contact with the copper ammonia complex solution, which produces a uniform deposition and precipitation effect with copper hydroxide during the ammonia evaporation process; in the published document Journal of Catalysis 280 (2011) 77-88, researchers also used pre-prepared mesoporous silica (HMS) as the support of their Cu / HMS catalyst prepared by the ammonia evaporation method. In addition to this, the researchers also added a water-soluble nickel salt (nickel nitrate) to the prepared aqueous copper ammonia complex solution, so that the prepared copper-based catalyst contains metal nickel (CuxNi / HMS). The ammonia evaporation method used in the study is no different from the traditional ammonia evaporation method, except that it uses a pre-prepared mesoporous silica support and adds a water-soluble nickel salt (nickel nitrate) to the prepared aqueous copper ammonia complex solution, so that the prepared copper-based catalyst contains a metal nickel additive. Its ammonia evaporation operation is carried out at 90°C, and after the ammonia evaporation (the pH value of the slurry is reduced to 7-8), the water solvent of the diluted and volume-excessive copper ammonia complex solution is finally removed by filtration to obtain a solid product loaded with copper hydroxide and nickel hydroxide. Similarly, in the study, the ordered mesoporous structure of the HMS silica has been mostly destroyed (the specific surface area has decreased by more than 50%) after being loaded with metal copper and nickel by the ammonia evaporation method. Moreover, the XRD characterization results show that the prepared supported catalyst sample has characteristic diffraction peaks of metal oxide phase before hydrogen reduction (450°C calcination for 4h), and has characteristic diffraction peaks of metal phase after hydrogen reduction, indicating that the metal copper and nickel are not uniformly loaded on the HMS support and have poor 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 relevant 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 the present 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 by the skilled person. A person skilled in the art can also synthesize a Beta zeolite precursor meeting the requirements of the present invention on the basis of his own experience and other literature reports.If the Beta zeolite precursor is synthesized by oneself, the following methods reported in the invention patents and open literature can be selected: US3308 069 (1967), EP187 522A2 (1986), US4 847 055 (1989), CN1 086 792A (application date 1993.9.20), CN1 108 213A (application date 1994.3.11), CN1 108 214A (application date 1994.3.11), CN1 154 341A (application date 1996.1.11), CN1 154 242A (application date 1996.1.9), CN1 154 342A (application date 1996.1.11), CN1 268 545A (application date 1999.3.30), CN1 133 497C (application date 1999.3.30), CN1 108 275C (application date 1999.9.10), CN1 100 004C (application date 2000.5.19), CN1 335 258A (application date 2001.2.28), CN1 116 227C (application date 2001.3.12), CN101 205 072B (application date 2006.12.18), Chem. Comm., 1996, 625; J. Mater. Chem., 1998, 8(9), 2137-2145; Microporous and Mesoporous Materials 21 (1998) 305-313; Applied Catalysis A-GENERAL, 166 (1998), 97-103; Microporous and Mesoporous Materials 48 (2001) 23-29; Microporous and Mesoporous Materials 56 (2002) 1-10.; Journal of Molecular Catalysis A: Chemical 252 (2006) 76-84; Microporous and Mesoporous Materials 94 (2006) 1-8; J. Mater. Sci. 41 (2006) 1861-1864; Cryst. Res. Technol. 44, No. 4, 379-385 (2009) DOI 10.1002 / crat.200800474; Microporous and Mesoporous Materials 143 (2011) 97-103; RSC Adv. 2019, 9, 3653-3660.

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

[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 down 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℃-100℃, the preferred range is 30℃-90℃, and the more preferred range is 40℃-80℃;

[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 refer to the methods disclosed in related patents and other literature to implement the gas-solid phase hydrogenation of caprolactone. According to the related patents and other literature, the present application collates the referenceable reaction condition ranges 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 1 atm, 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) prepared by acid dealumination of a Beta zeolite mother phase with a molar ratio of silica to alumina (SiO2 / Al2O3) of 24, and the hydroxyl region infrared spectrum of a channeled modified dealuminated Beta zeolite support (Beta24C) prepared by controlled dealumination of Beta24c using an aqueous solution of the weak organic base ethanolamine.

[0104] Figure 2 is the XRD pattern of the channeled 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 using the improved ammonium vapor method with Beta24C as the support.

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

[0106] Figure 4 is a high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of a high-temperature calcined (550℃x3h) sample of the Cu3-Beta24C-1 catalyst.

[0107] Figure 5 is the XRD pattern of the channeled 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 using the traditional ammonium vapor method with Beta24C as the support. DETAILED DESCRIPTION

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

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

[0110] Among them, the damage to the crystal structure of the Beta zeolite can be characterized by X-ray polycrystalline powder diffraction (XRD) method. If the ammonium vapor treatment causes significant damage to the crystal structure of the Beta zeolite, the intensity of the characteristic diffraction peak at 2θ = 22-23° of the XRD pattern of the catalyst will be significantly reduced. If the channeled modified dealuminated Beta zeolite support is used as a reference sample, the relative crystallinity reduction degree of the zeolite support in the Cu-Beta zeolite catalyst can also be estimated.

[0111] The occupation of the hydroxyl pits in the Cu-Beta zeolite catalyst can be obtained by Fourier transform infrared spectroscopy (FT-IR) method to obtain the hydroxyl vibration infrared spectrogram of the catalyst, and compared with the hydroxyl vibration infrared spectrogram of the dealuminated Beta zeolite support modified by the pit, to make a qualitative judgment. The more the nano and sub-nano copper particles fall into the hydroxyl pits, the weaker the intensity of the infrared characteristic band of the hydroxyl pits (the widened absorption band between 3300-3600 cm -1 -1) of the catalyst will be, and vice versa.

[0112] In addition, the high dispersion of the loaded metal copper in the Cu-Beta zeolite catalyst can be observed by transmission electron microscopy (TEM); the anti-sintering of the copper particles can be concluded by calcination treatment combined with TEM observation. The attenuation of the catalytic activity (caprolactam yield) of the catalyst in the gas-solid phase catalytic hydrogenation of caprolactone to caprolactam can also be used for judgment.

[0113] As for the catalytic performance of the Cu-Beta zeolite catalyst in the gas-solid phase catalytic hydrogenation of caprolactone to caprolactam, a small fixed bed reactor in the laboratory can be used for evaluation. The operation method and reaction conditions are as described above. The composition of the reaction product is analyzed by gas chromatography (GC), the GC is equipped with an FID detector, an OV-1701 chromatographic column, and an internal standard method (the internal standard is 1, 4-dioxane) is used to calculate the conversion rate of caprolactone and the selectivity of caprolactam. The product of the conversion rate of caprolactone and the selectivity of caprolactam is used as the evaluation index of the 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 the Cu-Beta zeolite catalyst prepared by using the dealuminated Beta zeolite modified by the pit as the carrier and loading copper in the channel by the improved ammonia evaporation method can not only better maintain the crystal structure of the dealuminated Beta zeolite carrier, but also make the loaded metal copper mainly in the form of highly dispersed nano and sub-nano copper particles falling into the hydroxyl pit lattice defect position in the zeolite channel, and the combination of the active silicon hydroxyl in the hydroxyl pit and the highly dispersed nano and sub-nano copper particles is more close, and the anti-sintering ability of the catalyst is better improved, thereby the stability of the catalyst is improved. The prepared Cu-Beta zeolite catalyst is suitable as the catalyst for the gas-solid phase catalytic 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, preparing the dealuminated Beta zeolite carrier

[0118] (1) Synthesis of Beta zeolite mother substance with a molar ratio of silica to alumina (SiO2 / Al2O3) of 25 as raw material for preparing the support of dealuminated Beta zeolite according to the hydrothermal crystallization method provided in US Patent 3 308 069 (1967). After the synthesized Beta zeolite mother substance is treated by conventional filtration, washing, drying (110°C, 12h) and calcination for removing the template (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 550m2 / g by using the nitrogen physical adsorption data, and the molar ratio of silica to alumina (SiO2 / Al2O3) thereof is measured to be about 24 by XRF method, which meets the technical requirements of the Beta zeolite mother substance of the present application, and is sealed and stored for later use. 2

[0119] (2) Dealuminating treatment of the Beta zeolite mother substance with concentrated nitric acid to prepare the support of dealuminated Beta zeolite.

[0120] Firstly, a concentrated nitric acid solution with a molar concentration of 13M is prepared. Then, 30g of the Beta zeolite mother substance treated by drying and calcination as described above is added into a three-necked flask containing 600ml of the 13M concentrated nitric acid solution under stirring at a liquid-solid ratio of 20:1 (ml / g) for dealuminating treatment. The dealuminating temperature is 95°C, and the dealuminating time is 20h. During the dealuminating reaction, the three-necked flask is kept in a reflux state. After the dealuminating reaction is completed, the liquid is cooled to room temperature, and the solid product is recovered by filtration. Then, the dealuminated Beta zeolite support is prepared by conventional water washing, drying (overnight at 110°C) and calcination treatment (550°C, 3h). The molar ratio of silica to alumina (SiO2 / Al2O3) of the dealuminated Beta zeolite support is measured to be 985 (>900) by ICP method. It is suitable as the support of the catalyst of the present application (coded as Beta24c, wherein the lower-case "c" represents the hydroxyl pits produced in the Beta zeolite by dealuminating). It is sealed and stored for later use to avoid moisture absorption.

[0121] Secondly, the hydroxyl pits of the dealuminated Beta zeolite support are modified by pit-chiseling treatment with an aqueous solution of ethanolamine

[0122] ​The said cavity modification was carried out by atmospheric pressure impregnation. First, an aqueous solution of 44 mmol / L (44 mM) ethanolamine was prepared as the cavity modification solution. Then, 20 g of the dealuminated Beta zeolite support was added to 120 ml of the ethanolamine modification solution according to a liquid-to-solid ratio of 6:1 (ml / g). The reaction mass was heated to 40°C under stirring and the reaction mass was allowed to react at this temperature for 1 h under continuous stirring. During this period, a weakly base-catalyzed hydrolytic dealumination reaction of the dealuminated Beta zeolite support in the weakly basic solution of ethanolamine takes place: [(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 silanol groups (≡Si-OH) are generated on the new walls of the hydroxyl cavity. After 1 h of reaction, the reaction mass was filtered to recover the solid product, which was then repeatedly washed with deionized water until neutral, dried (overnight at 110°C) and calcined (at 550°C for 3 h) to obtain the cavity-modified dealuminated Beta zeolite. It was stored in a sealed container for later use. According to the weight loss, the average number of framework silicon atoms (in the form of SiO2) removed from the hydroxyl cavity lattice defect sites of the dealuminated Beta zeolite support was 1.2 silicon atoms, indicating that the cavity modification was a controlled and moderate dealumination, which met the requirements for cavity modification of the dealuminated Beta zeolite support. The code of the cavity-modified support was Beta24C (the capital "C" indicates that the cavity modification increased the volume of the hydroxyl cavity in the dealuminated Beta zeolite). The hydroxyl vibration infrared spectra of the dealuminated Beta zeolite support (Beta24c) and its cavity-modified sample (Beta24C) were obtained by Fourier transform infrared spectroscopy (FT-IR), as shown in Figure 1. As can be seen from Figure 1, the hydroxyl vibration infrared spectrum of the dealuminated Beta zeolite support changed significantly after cavity modification, indicating that the cavity modification indeed occurred at the hydroxyl cavity lattice defect sites of the dealuminated Beta zeolite.

[0123] Third step, loading copper in the pores of the cavity-modified dealuminated Beta zeolite by improved ammonia evaporation method to prepare Cu-Beta zeolite catalyst

[0124] (1) A dilute ammonia water base solution was prepared, and a copper ammonia complex was synthesized using copper nitrate trihydrate (Cu(NO3)2·3H2O), and then a saturated solution of the copper ammonia complex was prepared at room temperature. The pH value of the dilute ammonia water base solution was 11-12, and it was prepared by adding 4.4 g of industrial ammonia water (containing 25-28 wt.% of NH3) to 100 ml of deionized water; the copper ammonia complex was obtained by reacting Cu(NO3)2·3H2O with industrial ammonia water according to a molar ratio of copper ions to ammonia molecules of 1:4; the saturated solution of the copper ammonia complex was obtained by dissolving the copper ammonia complex in the dilute ammonia water base solution, and it contained about 0.4 M of the copper ammonia complex.

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

[0126] (3) The equal volume impregnated material was subjected to ammonia evaporation treatment at normal pressure. The ammonia evaporation temperature was 80°C, and the ammonia evaporation time was 10 h. During this process, the copper ammonia complex that entered the zeolite pores due to capillary condensation gradually deposited in the form of copper hydroxide in the zeolite pores as the ammonia gas was lost.

[0127] (4) The material after ammonia evaporation was subjected to dehydration and drying treatment. The drying temperature was 110°C, and the drying time was 12 h.

[0128] (5) The dried material was subjected to calcination treatment. The calcination temperature was 500°C, and the calcination time was 3 h. After calcination, the copper hydroxide deposited in the zeolite pores was converted into nano and sub-nano copper oxide particles, thus preparing a catalyst precursor.

[0129] (6) The catalyst precursor was subjected to hydrogen reduction treatment. The reduction temperature was 400°C, the reduction time was 4 h, and the hydrogen flow (expressed by the hydrogen volume space velocity, defined as the hydrogen volume passing through the unit volume of catalyst per unit time, calculated as an ideal gas) was 300 h -1 After hydrogen reduction treatment, the finished Cu-Beta zeolite catalyst was prepared, and the code was Cu3-Beta24C-1.

[0130] Secondly, in order to understand the implementation effect of the catalyst preparation method provided by the present application from the aspect of the physical and chemical properties of the catalyst, the crystal structure and surface hydroxyl group of the support of Cu3-Beta24C-1 and its hole-modified dealuminated Beta zeolite support (Beta24C) were 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 3 h) were taken by transmission electron microscopy.

[0131] From the XRD characterization results (Figure 2), it was found that the Cu3-Beta24C-1 catalyst prepared by the improved ammonia stripping method provided by the present application well preserved the crystal structure of the Beta zeolite support. The relative crystallinity of the zeolite in the catalyst calculated based on the channeled modified dealuminated Beta zeolite support (Beta24C) was 84%. From the FT-IR characterization results, it was found that the intensity of the infrared characteristic band of the zeolite hydroxyl cavity of the Cu3-Beta24C-1 catalyst decreased more greatly compared with the channeled modified dealuminated Beta zeolite support, indicating that a large number of copper metals occupied the hydroxyl cavity lattice defect sites. In addition, from the TEM photos (Figures 3 and 4), it can be seen that the copper metals in the Cu3-Beta24C-1 catalyst existed in the state of highly dispersed nano and sub-nano particles, and the average particle size was about 5 nm. After being calcined at a high temperature of 550°C for 3 h, the dispersion state of the copper metal particles was good, and the average particle size was about 8 nm. These data show that the hydroxyl cavity lattice defect sites of the channeled modified dealuminated Beta zeolite support have a good effect of dispersing and stabilizing nano and sub-nano copper particles.

[0132] On this basis, the catalytic performances of the Cu3-Beta24C-1 catalyst and the sample thereof calcined at a high temperature of 550°C were evaluated by using caprolactam gas-solid phase hydrogenation to caprolactam reaction. The reaction was carried out in a small fixed bed reactor. The inner diameter of the stainless steel reaction tube was 9 mm, and the operation mode was top feeding and bottom discharging. 2 g of the catalyst (after sieving, the sample of 20-40 mesh was taken) was loaded in the constant temperature zone of the reactor. Inert porcelain balls were filled in the upper and lower spaces of the catalyst bed. Among them, the upper porcelain ball area of the reactor served as the vaporization and preheating zone of the raw material. The reaction temperature was 270°C, the reaction pressure was 1 atm, the feed space velocity (WHSV) of caprolactam was 0.6 h -1 -1, and the hydrogen-ester molar ratio was 50. The reaction product was continuously collected in a stainless steel collection tank connected to the outlet of the reactor with a cooling water jacket, and the product liquid was collected at fixed time intervals for analysis on a Shimadzu gas chromatograph GC-2014 (FID detector, OV-1701 chromatographic column). The caprolactam conversion rate and caprolactam selectivity were calculated by the internal standard method (the internal standard was 1, 4-dioxane). Under the above conditions, when the caprolactam hydrogenation reaction was continuously carried out for 6 h, the caprolactam yield of the Cu3-Beta24C-1 catalyst was about 82%, and the caprolactam yield of the sample thereof calcined at a high temperature of 550°C was close to 81%. The above reaction results show that the Cu-Beta zeolite catalyst provided by the present application is a catalyst with excellent performance for the caprolactam hydrogenation to caprolactam reaction.

[0133] Comparative Example 1: This example is used to illustrate that when a Cu-Beta zeolite catalyst is prepared by using a traditional ammonia evaporation method to load copper on a cavity-modified dealuminated Beta zeolite carrier, the crystal structure of the Beta zeolite carrier is severely damaged, the loaded copper mainly locates 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 cavity of the dealuminated Beta zeolite are not protected, so the stability of the catalyst is poor, and the performance in the gas-solid phase hydrogenation of caprolactone to caprolactam is poor.

[0134] Example 1 is repeated, but after the cavity-modified dealuminated Beta zeolite carrier (Beta24C) is prepared in the second step, copper hydroxide is deposited on the zeolite carrier by using the same traditional ammonia evaporation method as in the published document Science 10.1126 / science.adj1962 (2023), as follows:

[0135] (1) 1.18 g of Cu(NO3)2·3H2O is dissolved in 515 ml of an ammonia water solution (containing 3.86 g of NH3·H2O, which is equivalent to 8.1 ml of 26 wt.% industrial ammonia water, and the molar ratio of copper ions to ammonia molecules is about 1:23), and stirred at room temperature for 10 min to prepare a copper-ammonia complex aqueous solution (the complex ion concentration is about 9.5 mmol / L, i.e. 9.5 mM);

[0136] (2) 10 g of the cavity-modified dealuminated Beta zeolite carrier (Beta24C) is added to the 515 ml of the copper-ammonia complex solution, and ammonia evaporation treatment is carried out under vigorous stirring. The ammonia evaporation temperature is 80°C, and the ammonia evaporation time is 6 h;

[0137] (3) After the ammonia evaporation is completed, 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 Cu-Beta zeolite catalyst prepared by traditional ammonia evaporation method from the aspect of physicochemical properties of catalyst, the Beta zeolite crystal structure of Cu3-Beta24C-CE1 catalyst was characterized by XRD method, and compared with its carrier (Beta24C), as shown in Figure 5. In addition, the Cu metal dispersion of Cu3-Beta24C-CE1 catalyst and its high temperature calcined sample (550℃×3h) was characterized by transmission electron microscopy, and the catalytic performance of Cu3-Beta24C-CE1 catalyst and its 550℃ high temperature calcined sample was evaluated by caprolactam production reaction of caprolactone gas-solid phase hydrogenation.

[0139] The XRD characterization results (Figure 5) show that the zeolite crystal structure of Cu3-Beta24C-CE1 catalyst prepared by traditional ammonia evaporation method is damaged to a large extent, and the relative crystallinity of zeolite calculated based on its carrier (Beta24C) is 65%. According to the characterization results of transmission electron microscopy, the average particle size of Cu metal of Cu3-Beta24C-CE1 catalyst and its high temperature calcined sample is 10nm and 21nm respectively, that is, the Cu metal dispersion on the catalyst is low and easy to sinter. The reaction evaluation results show that under the same reaction conditions, the caprolactam yield of Cu3-Beta24C-CE1 catalyst is about 76%, and the caprolactam yield of its high temperature calcined sample is about 72%. The reaction results show that the Cu-Beta zeolite catalyst prepared by traditional ammonia evaporation method on the fluted modified dealuminated Beta zeolite carrier has low catalytic activity for caprolactam production reaction of caprolactone gas-solid phase hydrogenation and poor anti-sintering deactivation ability.

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

[0141] Example 2 was repeated, but the dealuminated Beta zeolite support prepared in the first step (Beta24c) was directly used in the third step to prepare Cu-Beta zeolite catalyst by the improved ammonolysis method to load copper in the channels. In this case, the dealuminated Beta zeolite (Beta24c) had a water absorption of 1.2 ml / g as measured by titration with deionized water when it was impregnated with an equal volume of copper-ammine complex solution. According to the 10 g support feed amount, a total of 12 ml of copper-ammine complex solution was needed. According to the copper loading amount of 3 wt.%, the concentration of the copper-ammine complex solution needed was about 0.39 M. That is, the calculated value of the concentration of the copper-ammine complex solution needed was very close to the concentration of the saturated copper-ammine complex solution (0.4 M). Therefore, 10 g of the dealuminated Beta zeolite support was directly impregnated with an equal volume of the saturated copper-ammine complex solution of 12 ml. Other procedures were unchanged. The Cu-Beta zeolite catalyst obtained was named Cu3-Beta24c-CE2.

[0142] To avoid the complexity, in this case, the catalytic performance of Cu3-Beta24c-CE2 catalyst and its high-temperature calcined sample (550°C x 3 h) was evaluated only for the caprolactam production by the gas-solid phase reductive amination of caprolactone. The reaction evaluation results 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 reaction results indicated that the Cu-Beta zeolite catalyst prepared by the improved ammonolysis method directly using the dealuminated Beta zeolite as the support also had good catalytic activity and anti-sintering deactivation ability for the caprolactam production by the gas-solid phase reductive amination of caprolactone, but its catalytic performance was obviously inferior to that of the catalyst prepared using the dealuminated Beta zeolite modified by drilling holes as the support.

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

[0144] The traditional ammonolysis method described in this example was made according to the procedure of Example 1 in U.S. Patent US4 440 873 (1984) as follows:

[0145] (1) Dissolve 1.14 g of copper nitrate (Cu(NO3)2.3H2O) in 100 ml of water to obtain an aqueous solution containing copper ions, then add 3.6 ml of concentrated aqueous ammonia solution (industrial ammonia water with a NH3 content of 26 wt.%, density 0.89 g / ml) to the solution in a molar ratio of copper ions to ammonia molecules of about 1:10, and make up the volume to 150 ml with water, to obtain a deep blue copper-ammonia complex solution with a pH of 11-12 (complex ion concentration about 30.8 mM. The purpose of making up the volume to 150 ml is to keep the ratio of solution volume to dry basis of silica consistent with the literature);

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

[0147] (3) Perform an ammonia stripping treatment (80°C, 6 h) on the reaction mixture of step (2), and when the pH of the mixture drops to 6-7, filter to obtain a solid which is washed three times with deionized water to obtain a solid product;

[0148] (4) Dry the solid product at 120°C for 12 h and calcine at 450°C for 4 h;

[0149] (5) Perform a hydrogen reduction treatment on the calcined solid product. The reduction conditions are 350°C x 2 h, to obtain a copper-silica catalyst, code Cu3-SiO2-CE3.

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

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

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

[0153] The results of the reaction of caprolactone gas-phase hydrogenation ammoxidation to caprolactam show that under the same reaction conditions, the caprolactam yield of Cu3-SiO2-CE4 catalyst is 79%; the caprolactam yield of the high-temperature calcined sample (550°C x 3h) is 70%. The reaction results also show that the copper-based catalyst prepared with amorphous silica as the carrier has poor sintering resistance 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 sintering resistance and poor stability.

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

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

[0157] The results of the reaction of caprolactone gas-phase hydrogenation ammoxidation to caprolactam show that under the same reaction conditions, the caprolactam yield of Cu3-SiO2-CE5 catalyst is 76%; the caprolactam yield of the high-temperature calcined sample (550°C x 3h) is 65%. The reaction results also show that the copper-based catalyst prepared with 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, i.e. using the fluted modified dealuminated Beta zeolite as the carrier and using the improved ammonia evaporation method to load copper in the zeolite pores, can be used to prepare Cu-Beta zeolite catalysts with different copper loadings.

[0159] Example 1 was repeated, but the copper loading in the prepared Cu-Beta zeolite catalyst was reduced to 1 wt.% and 2 wt.% successively, and the concentration of the required copper ammonia complex solution was about 0.13 M and 0.25 M successively. 3.9 ml and 7.8 ml of the saturated copper ammonia complex solution were diluted to 12.5 ml with the dilute ammonia water base solution successively, to obtain equal volume impregnation solutions for preparing Cu-Beta zeolite catalysts with copper loadings of 1 wt.% and 2 wt.% respectively. In the preparation of Cu-Beta zeolite catalysts by the improved ammonia evaporation method, the time for the equal volume impregnation treatment of the hole-modified dealuminated Beta support (Beta24C) at room temperature was changed to 6 h, the temperature and time for the ammonia evaporation treatment were changed to 65 °C and 12 h respectively, the temperature and time for the dehydration drying were changed to 150 °C and 3 h respectively, the subsequent calcination temperature and time were changed to 450 °C and 6 h respectively, the final hydrogen reduction temperature and time were changed to 350 °C and 8 h respectively, and the hydrogen flow rate (volume space velocity) was changed to 1000 h -1 The prepared Cu-Beta zeolite catalysts were coded as Cu1-Beta24C-2 and Cu2-Beta24C-2 successively.

[0160] The evaluation results of the caprolactam gas-solid phase hydrogenation amination of caprolactone showed that under the same reaction conditions, the caprolactam yield of the Cu1-Beta24C-2 catalyst was 80%, and the caprolactam yield of the Cu2-Beta24C-2 catalyst was 81%.

[0161] Example 3: This example is used to further illustrate that the preparation method of the Cu-Beta zeolite catalyst provided by the application, which uses the hole-modified dealuminated Beta zeolite as the carrier and loads copper in the zeolite pores by the improved ammonia evaporation method, can be used to prepare Cu-Beta zeolite catalysts with different copper loadings. However, when preparing Cu-Beta zeolite catalysts with copper loadings higher than 3 wt.%, 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] 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, 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 later use. According to the weight loss estimation, the average number of 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 a 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 reduced dealumination indicated that the above-mentioned channelling modification condition combination had 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 dealuminated Beta zeolite support for channelling modification could be prepared using a Beta zeolite mother body with different molar ratios of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3). When the Beta zeolite mother body with a higher molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) was used as the mother body, a relatively mild channelling modification condition combination should be adopted. Conversely, the opposite was also true.

[0174] Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, the Beta zeolite mother 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 No. 3 308 069 (1967) as the raw material for preparing the dealuminated Beta zeolite support. After the synthesized Beta zeolite mother 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 crystal size was close to 100 nanometers, which belonged to a nano-Beta zeolite; no any impurity crystal was found by the XRD method; its BET specific surface area was about 530 m2 / g, as calculated from the nitrogen physical adsorption data; and its molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) was about 57, as measured by the XRF method, which met the technical requirements of the Beta zeolite mother body of the present application. 2 Example 1 was repeated, but in the first step of preparing the dealuminated Beta zeolite support, the Beta zeolite mother 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 No. 3 308 069 (1967) as the raw material for preparing the dealuminated Beta zeolite support. After the synthesized Beta zeolite mother 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 crystal size was close to 100 nanometers, which belonged to a nano-Beta zeolite; no any impurity crystal was found by the XRD method; its BET specific surface area was about 530 m2 / g, as calculated from the nitrogen physical adsorption data; and its molar ratio of silicon-aluminum oxide (molar ratio of SiO2 to Al2O3) was about 57, as measured by the XRF method, which met the technical requirements of the Beta zeolite mother body of the present application.

[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 hydroxyl cavity lattice defect sites of the dealuminated Beta zeolite support was 1.6 silicon atoms, and the amount of desiliconization increased, indicating that the above-mentioned combination of channelling modification conditions strengthened the channelling modification treatment for the dealuminated Beta zeolite support with a small number of hydroxyl cavities. The channelling-modified dealuminated Beta zeolite support obtained was named Beta57C. Further, according to the method of the third step of Example 1, the improved ammonia evaporation method was used to load copper in the pores of the zeolite to obtain a Cu-Beta zeolite catalyst with a copper content of 3 wt.%. In this process, when the support was impregnated with an equal volume of a saturated solution of a 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 (volume space velocity) were changed to 300°C, 20 h, and 2000 h -1 , respectively, and 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 improved ammonia evaporation method provided by the present application is used to prepare a Cu-Beta zeolite catalyst, 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 a 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 production by the gas-solid phase hydrogenation of caprolactone 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 to 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 to 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 to 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 by following the hydrothermal crystallization method provided in Chinese Invention Patent CN1108275C (filing date September 10, 1999). After the synthesized Beta zeolite matrices were subjected to the 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 level and the small crystal (less than 1 μm) level. As the molar ratio of silicon to aluminum oxide (molar ratio of Si02to Al203) increased, the crystal size increased. XRD examination did not find any impurity crystals in them, and the BET specific surface area calculated from the nitrogen physical adsorption data of the synthesized Beta zeolite matrices was higher than 500 m2 / g. The dealuminated Beta zeolite support was prepared by following the procedure of Example 1, Step 1, and then the pocket-modification treatment was performed by following the procedure of Example 1, Step 2. 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. 2 The Si / Al oxide molar ratios (Si02 / Al203) 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 concentrated nitric acid dealumination to obtain five dealuminated Beta zeolite carriers Beta38c, Beta72c, Beta94c, Beta136c and Beta189c, whose Si / Al oxide molar ratios (Si02 / Al203) are 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 subjected to calcination (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 Si02) chiselled 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 (Si02 / Al203), while it is too strong for the dealuminated Beta zeolite carriers prepared from the Beta zeolite matrices with higher Si / Al oxide molar ratios (Si02 / Al203).

[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 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 subjected to dehydration and drying, 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 550°C calcined (3h) samples was evaluated by using caprolactam gas-solid phase hydrogenation reaction. 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 using the improved ammonia evaporation method provided by the present application, Beta zeolite parents with different silica-alumina molar ratios (molar ratio of SiO2 to Al2O3) can be used to prepare cavity-modified dealuminated Beta zeolite carriers. However, when using Beta zeolite parents with higher silica-alumina molar ratios (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 parent with a silica-alumina molar ratio (molar ratio of SiO2 to Al2O3) of 100 was synthesized by the hydrothermal crystallization method provided by Chinese Invention Patent CN1108275C (application date 1999.9.10) as the raw material for preparing the dealuminated Beta zeolite carrier. After the synthesized Beta zeolite parent was treated by conventional filtration, washing, drying (200°C, 3h) and calcination to remove the template agent (500°C, 8h), TEM observation showed that its average crystal size belonged to the small crystal (less than 1 μm) level. XRD method showed that there was no any impurity crystal in it, and its BET specific surface area calculated from its nitrogen physical adsorption data was higher than 530 m 2 / g, and XRF method showed that its silica-alumina molar ratio (molar ratio of SiO2 to Al2O3) was 94, which met the technical requirements of the Beta zeolite parent 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.< / t>

Claims

1. A method for preparing Cu-Beta zeolite catalysts to improve the stability of caprolactone-to-caprolactam synthesis, characterized in that, The steps are as follows: The first step is to prepare a dealuminated Beta zeolite support. (1) Select Beta zeolite parent material The aforementioned Beta zeolite matrix refers to silica-alumina Beta zeolite that meets the following requirements: 1) The Beta zeolite matrix is ​​free of impurities; 2) The Beta zeolite matrix has good crystallinity, i.e., the BET specific surface area value of the Beta zeolite matrix measured by nitrogen physical adsorption method is ≥450m². 2 / g; 3) The molar ratio of silicon and aluminum oxides in the Beta zeolite matrix, i.e., the molar ratio of SiO2 to Al2O3, is between 10 and 200; (2) Preparation of dealuminized Beta zeolite carrier A dealuminized Beta zeolite support was prepared by acid dealuminization based on the Beta zeolite matrix. The required molar ratio of silicon and aluminum oxides in the prepared dealuminized Beta zeolite support, i.e., the molar ratio of SiO2 to Al2O3, was ≥700. The second step involves using an aqueous solution of ethanolamine to perform pitting modification on the hydroxyl groups of the dealuminized Beta zeolite support. Hollowing modification of hydroxyl groups was carried out using an aqueous solution impregnation method, with the following parameter requirements: The concentration range of the ethanolamine solution is 0.01M-0.4M; The ratio of ethanolamine solution to dealuminolite zeolite carrier, i.e., the liquid-solid ratio, ranges from 1:1 to 100:1, and the unit of the liquid-solid ratio is ml / g. The impregnation temperature range is 20℃-100℃; The soaking time ranges from 0.1 h to 24 h; The third step involves loading copper into the pores of a hollow-modified dealuminolite Beta zeolite support using a modified ammonia stripping method to prepare a Cu-Beta zeolite catalyst. The specific steps are as follows: (1) Preparation of dilute ammonia water base solution and saturated solution of copper ammonia complex: Prepare a dilute ammonia water base solution with pH value of 11-12 by diluting 4.4g of industrial ammonia water containing 25-28wt.% NH3 with 100ml of deionized water, and store it in a sealed container for later use; then, according to the molar ratio of copper ions to ammonia molecules of 1:4, use copper nitrate trihydrate as a soluble copper compound to react with industrial ammonia water to synthesize copper ammonia complex; finally, dissolve the copper ammonia complex in dilute ammonia water base solution at room temperature to prepare a saturated solution of copper ammonia complex, and store it in a sealed container for later use; the concentration of copper ammonia complex ions in the saturated solution of copper ammonia complex is 0.4M; (2) Impregnating the zeolite support with an equal volume of copper ammonia complex solution: First, determine the saturated water absorption rate of the zeolite support, and calculate the amount of copper ammonia complex solution to impregnate the zeolite support with an equal volume; then, calculate the required concentration of the copper ammonia complex solution according to the copper loading of the Cu-Beta zeolite catalyst to be prepared; when the calculated concentration is equal to 0.4 M, directly impregnate the zeolite support with the saturated solution of copper ammonia complex with an equal volume; when the calculated concentration is less than 0.4 M, dilute the saturated solution of copper ammonia complex with dilute ammonia water base solution appropriately, and then impregnate the zeolite support with an equal volume. When the calculated value is higher than 0.4M, the concentration of the copper ammonia complex solution for a single equal-volume impregnation should be recalculated according to multiple equal-volume impregnations. The copper ammonia complex solution of the required concentration should be prepared using dilute ammonia water base solution and saturated copper ammonia complex solution for each equal-volume impregnation. After each impregnation, the zeolite carrier must be subjected to ammonia stripping treatment; the equal-volume impregnation is carried out at room temperature in a closed container; the equal-volume impregnation time ranges from 0.5 to 24 hours. (3) Ammonia stripping treatment: The ammonia stripping process is carried out under normal or reduced pressure; the temperature and time range for ammonia stripping are 50-100℃ and 0.5-48h. (4) Dehydration and drying treatment after ammonia stripping: The drying temperature and time ranges are 100-200℃ and 0.5-48h, respectively; (5) Roasting treatment after ammonia stripping: Roasting is carried out in an air atmosphere, with roasting temperature and time ranging from 350-650℃ and 0.5-24h, respectively; The catalyst precursor was obtained through calcination. (6) Hydrogen reduction treatment of catalyst precursor: The reduction temperature, time and hydrogen volume hourly space velocity ranged from 280-600℃, 0.5-20h and 1-2000h, respectively. -1 The catalyst precursor is reduced by hydrogen to become Cu-Beta zeolite catalyst.

2. The preparation method of Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 1, characterized in that, In step (1), the molar ratio of silicon aluminum oxide in the Beta zeolite matrix, i.e., the molar ratio of SiO2 to Al2O3, is in the range of 20-100.

3. The preparation method of Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 2, characterized in that, In step (1), the molar ratio of silicon aluminum oxide in the Beta zeolite matrix, i.e., the molar ratio of SiO2 to Al2O3, is in the range of 25-60.

4. The preparation method of Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 1, characterized in that, In step (2), the required molar ratio of silicon-aluminum oxides in the prepared dealuminized Beta zeolite support, i.e., the molar ratio of SiO2 to Al2O3, is ≥800.

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

6. The preparation method of Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 1, characterized in that, In step (2), concentrated nitric acid aqueous solution is used to acid-dealuminize the Beta zeolite matrix to prepare a dealaluminized Beta zeolite support, as detailed below: 13M concentrated nitric acid was used as the dealumination acid solution, with a liquid-to-solid ratio of 20:1 (ml / g). The dealumination reaction was carried out at 95℃ for 20 hours. After the dealumination reaction, the solid product was first recovered by solid-liquid separation, then washed with water until the pH value was neutral, dried at 80-200℃ for 3-24 hours, and calcined at 500℃-600℃ for 3-8 hours to obtain dealumination Beta zeolite.

7. The preparation method of Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 1, characterized in that, In the second step, the hydroxyl groups of the dealuminized Beta zeolite support are modified by aqueous solution impregnation using an aqueous solution of ethanolamine, with the following parameters: The concentration range of the ethanolamine solution is 0.02M-0.3M; The ratio of ethanolamine solution to dealuminolite zeolite carrier, i.e., the liquid-solid ratio, ranges from 2:1 to 50:1, and the unit of liquid-solid ratio is ml / g. The impregnation temperature range is 30℃-90℃; The soaking time ranges from 0.5h to 10h.

8. The preparation method of Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 7, characterized in that, In the second step, the hydroxyl groups of the dealuminized Beta zeolite support are modified by aqueous solution impregnation using an aqueous solution of ethanolamine, with the following parameters: The concentration range of the ethanolamine solution is 0.03M-0.16M; The ratio of ethanolamine solution to dealuminolite zeolite carrier, i.e., the liquid-solid ratio, ranges from 3:1 to 20:1, and the unit of the liquid-solid ratio is ml / g. The impregnation temperature range is 40℃-80℃; The soaking time ranges from 1 to 5 hours.

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

10. The preparation method of a Cu-Beta zeolite catalyst for improving the stability of caprolactone to caprolactam according to claim 9, characterized in that, In step 3 (2), the immersion time for equal volume is in the range of 2-6 hours; In the third step (3), the temperature and time range for ammonia stripping are 65-85℃ and 3-12h; In the third step (4), the drying temperature and time ranges are 120-150℃ and 3-12h, respectively; In the third step (5), the roasting temperature and time ranges are 450-550℃ and 2-6h, respectively; In step 3 (6), the reduction temperature, time, and hydrogen volume hourly space velocity ranges are 350-500℃, 2-8h, and 20-1000h, respectively. -1 .

11. The Cu-Beta zeolite prepared by the method for improving the stability of the Cu-Beta zeolite catalyst for the production of caprolactam according to any one of claims 1-10 is used to catalyze the gas-solid phase hydroammoniation of caprolactam to caprolactam.

12. The application according to claim 11, characterized in that, The reaction conditions are as follows: reaction temperature range is 120-350℃, reaction pressure range is 0.01-2 atm, and feed space velocity of caprolactone ranges from 0.1 to 5 h⁻¹. -1 The ranges of the molar ratios of amine-ester, hydrogen-ester, and water-ester are 1-50, 5-70, and 0-100, respectively.

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