Modified H beta molecular sieve, catalyst containing modified H beta molecular sieve, and preparation and application of modified H beta molecular sieve

Abstract

The invention discloses an H beta molecular sieve catalyst and a preparation method thereof. The catalyst comprises the following components in percentage by weight: 60-85% of H beta molecular sieve, 0.1-6% of sodium oxide and / or potassium oxide and 13-35% of aluminum oxide; the molar ratio of silicon to aluminum of the H beta molecular sieve is 25-180, and the indication constant k of the H beta molecular sieve is 100-550. The preparation method comprises the following steps: firstly, dissolving cinnamate in benzene to prepare a solution, and enabling the solution to fill the pore channels of the molecular sieve; blowing with hot nitrogen, and carrying out addition reaction on C = C of the cinnamate and benzene to generate a macromolecular salt product, so as to achieve the purpose of modifying an acid center at a pore crossing part; and preparing the catalyst according to a conventional method. The catalyst provided by the invention has higher diphenylamine selectivity and longer one-way operation period.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical industry, and in particular relates to an Hβ molecular sieve catalyst, and preparation and application thereof. Background Art

[0002] Diphenylamine is an important organic chemical raw material with a wide range of uses. It is mainly used in the industry as an antioxidant for synthetic rubber, a stabilizer for explosives, a fuel and pharmaceutical intermediate, azo dyes, a fruit preservative, etc. It can also be used as an analytical reagent for the identification of DNA, the colorimetric determination of nitrates, nitrites, chlorates, and magnesium, and as a redox indicator. At present, the catalysts for the synthesis of diphenylamine from aniline introduced in domestic and foreign patent technologies are mostly solid acid catalysts, such as US3118944, US4454348, US3944613, CN94107296.7 and other patents disclose the technology of using activated alumina, amorphous silica-alumina, and molecular sieves to prepare catalysts.

[0003] In the mid-1990s, my country successfully developed a new process for the continuous synthesis of diphenylamine from aniline and a matching special molecular sieve catalyst, whose active component is Hβ molecular sieve. The reaction of aniline to diphenylamine is a typical acid-catalyzed reaction, and the acid properties of the catalyst directly affect the reaction performance. In addition, the appropriate pore structure is also an important factor affecting the catalytic performance.

[0004] At present, the continuous synthesis of diphenylamine from aniline using Hβ molecular sieve catalyst generally has a conversion rate of 20%~25% and a selectivity of 96mol%~97mol%. Although the process has been successfully applied in industry, it has the problems of low selectivity and short single-pass operation cycle. In recent years, the technology in this field has adjusted the acidity and pores of β molecular sieve catalysts. For example, CN105618106A proposed a multi-level pore β molecular sieve catalyst rich in a large amount of mesoporous pore volume; the degree thesis "Research on Catalysts for Preparation of Diphenylamine by Aniline Condensation" introduced halogens into β molecular sieves to increase acidity; "Acta Petrolei Sinica" (2017, Vol. 33, No. 1) "The Effect of Alkali Treatment on the Performance of Hβ Molecular Sieve Catalyzed Aniline Condensation to Prepare Diphenylamine" uses alkali treatment to etch β molecular sieve crystals to increase the mesoporous pore volume. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a modified Hβ molecular sieve, a catalyst containing the same, and a preparation method and application thereof. The catalyst provided by the present invention has a suitable active center and pore structure, and is used for the reaction of aniline to synthesize diphenylamine, and can obtain a higher aniline conversion rate and diphenylamine selectivity.

[0006] The first aspect of the present invention provides a modified Hβ molecular sieve.

[0007] Specifically, the modified Hβ molecular sieve contains at least one metal oxide of sodium and potassium as an additive, and the additive content is 0.5% to 5%; wherein the silicon-aluminum ratio (i.e. SiO 2 / Al 2 O 3 Molar ratio) is 25~180; The index constant k of the modified Hβ molecular sieve is 100-550, preferably 101-500, wherein the index constant k is calculated as follows: k=Q / (1.4909×a -0.558 -c); Wherein, Q is the amount of meta-xylene adsorption, expressed in g / 100 g; a is the silicon-aluminum ratio; and c is the number of moles of metal oxide loaded per 100 g of molecular sieve.

[0008] Furthermore, the indicator constant k in the present invention is a parameter obtained by fitting based on a large number of data such as the amount of meta-xylene adsorption, silicon-aluminum ratio, amount of metal oxide substances, and the number of single crystals in β molecular sieve agglomerates measured on Hβ molecular sieves.

[0009] Furthermore, the method for determining the amount of meta-xylene adsorption is as follows: the measurement is performed using an intelligent gravimetric analyzer (IGA-002). Before determining the amount of meta-xylene adsorption, a molecular sieve decontamination treatment is performed to remove moisture and impurities such as residual templates. The decontamination treatment is to raise the temperature of the sample to be tested from room temperature to 300°C at a rate of 5°C / min under a vacuum state, and then return it to room temperature after its mass becomes constant, and then the amount of meta-xylene adsorption is measured. The meta-xylene vapor is passed into the sample chamber after decontamination, and the weight difference is recorded after the sample is completely adsorbed and saturated (i.e., the weight is constant).

[0010] The second aspect of the present invention also provides a method for preparing the modified Hβ molecular sieve.

[0011] The preparation method comprises the following steps: (1) Dissolve cinnamate in benzene and stir evenly to fully dissolve; (2) impregnating the Hβ molecular sieve with the solution obtained in step (1), and filtering out the Hβ molecular sieve after the impregnation is completed; (3) purging the Hβ molecular sieve filtered out in step (2) with hot nitrogen; (4) The Hβ molecular sieve obtained in step (3) is washed with deionized water, and then dried and calcined.

[0012] Furthermore, the cinnamate in step (1) can be a soluble carnitine silicate such as sodium cinnamate, potassium cinnamate, etc. The mass fraction of the cinnamate in benzene is 0.5% to 20%, preferably 1% to 15%.

[0013] Furthermore, the liquid-to-solid ratio of the impregnation in step (2) is 4-10 mL / g, preferably 5-8 mL / g; and the impregnation time is 1-10 hours, preferably 1-5 hours.

[0014] Furthermore, the temperature of the hot nitrogen in step (3) is 80°C to 180°C, preferably 85°C to 150°C. The conditions for hot nitrogen purging are conventional operations in the art. For example, the nitrogen volume space velocity is 100h / min. -1 ~3000h -1 , preferably 200h -1 ~2000h -1 The purge time is generally 2 hours to 24 hours, preferably 5 hours to 20 hours. At the end of the purge, the benzene content in the nitrogen after passing through the molecular sieve is no more than 1 μg / L.

[0015] Furthermore, the liquid-to-solid ratio of the washing in step (4) is 4-10 mL / g, preferably 5-8 mL / g; the washing temperature is room temperature-80°C, preferably 40°C-70°C; and the number of washings is 1-10 times, preferably 2-6 times.

[0016] Furthermore, the drying and calcining described in step (4) adopt conventional conditions in the art. The calcination needs to be carried out in an oxygen-containing atmosphere. For example, the drying conditions are generally: the drying temperature is 60°C to 150°C, preferably 80°C to 120°C, and the drying time is 8 hours to 24 hours, preferably 10 hours to 20 hours. The calcination conditions are: the calcination temperature is 300°C to 800°C, preferably 400°C to 700°C, and the calcination time is 2 hours to 24 hours, preferably 4 hours to 8 hours.

[0017] The third aspect of the present invention also provides a catalyst for synthesizing diphenylamine from aniline, wherein the catalyst contains the modified Hβ molecular sieve described above.

[0018] Specifically, the catalyst for synthesizing diphenylamine from aniline comprises, based on the weight of the catalyst: Hβ molecular sieve 60%~85%, preferably 61%~83%; Sodium oxide and / or potassium oxide 0.1%~6%, preferably 0.2%~5%; Alumina: 13% to 35%, preferably 14% to 34%.

[0019] Furthermore, the silicon aluminum (SiO 2 / Al 2 O 3) molar ratio is 25~180, preferably 40~170.

[0020] Furthermore, the index constant k of the Hβ molecular sieve is 100-550, preferably 101-500.

[0021] Furthermore, the specific surface area of ​​the catalyst is generally 250-650 m 2 / g, preferably 300~600m 2 / g; the specific pore volume is 0.20~0.50mL / g, preferably 0.25~0.45mL / g.

[0022] Furthermore, the catalyst is generally in the form of a bar or a sphere. When it is in the form of a bar, its cross section may be cylindrical, clover-shaped or four-leaf clover-shaped, with a diameter of 0.5 to 3.0 mm, preferably 1.0 to 2.0 mm; when it is in the form of a sphere, its diameter is 0.5 to 5.0 mm, preferably 1.0 to 3.0 mm.

[0023] Furthermore, in addition to the metal oxide introduced during the modification of the Hβ molecular sieve, the catalyst may further contain other metal or non-metal oxides as a second additive, such as one or more oxides of Li, La, Ce, Mg, Ca, Ba, Cu, Zn, Zr, Fe, Si, P, B, C to further improve the acid distribution and other physical properties of the catalyst. The content of the second additive oxide in the catalyst is generally 0.1-5%.

[0024] A fourth aspect of the present invention provides a method for preparing the above Hβ catalyst.

[0025] Specifically, the Hβ molecular sieve catalyst preparation method comprises the following steps: (1) Dissolve an appropriate amount of cinnamate in benzene, stir evenly and fully dissolve; use the solution to impregnate Hβ molecular sieve, and filter out the molecular sieve after impregnation; (2) Purge the filtered molecular sieve with hot nitrogen and cool it naturally to room temperature after the purge is completed; (3) washing the molecular sieve obtained in step (2) with deionized water, drying and calcining the washed molecular sieve to obtain a modified Hβ molecular sieve; (4) The modified Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried and calcined to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) is loaded with the second auxiliary agent oxide by conventional impregnation method, and then dried and calcined to obtain a finished catalyst.

[0026] Furthermore, the cinnamate described in step (1) can be a soluble cinnamate such as sodium cinnamate, potassium cinnamate, etc. The mass fraction of cinnamate in benzene is 0.5% to 20%, preferably 1% to 15%. The liquid-to-solid ratio of the catalyst precursor obtained in step (1) during impregnation is 4 to 10 mL / g, preferably 5 to 8 mL / g; the impregnation time is 1 to 10 hours, preferably 1 to 5 hours.

[0027] Furthermore, the temperature of the hot nitrogen in step (2) is 80°C to 180°C, preferably 85°C to 150°C. The conditions for hot nitrogen purging are conventional in the art. For example, the nitrogen volume space velocity is 100h / min. -1 ~3000h -1 , preferably 200h -1 ~2000h -1 The purge time is generally 2 hours to 24 hours, preferably 5 hours to 20 hours. At the end of the purge, the benzene content in the nitrogen after passing through the molecular sieve is no more than 1 μg / L.

[0028] Furthermore, the liquid-to-solid ratio of the washing in step (3) is 4-10 mL / g, preferably 5-8 mL / g; the washing temperature is room temperature-80°C, preferably 40°C-70°C; and the number of washings is 1-10 times, preferably 2-6 times.

[0029] Furthermore, in step (4), the extrusion aid may be sesbania powder, and the peptizing agent solution may be at least one of dilute nitric acid and citric acid. The mass concentration of the dilute nitric acid solution is generally 3% to 15%.

[0030] Furthermore, the proportions and operations of the various materials in step (4) are well known to those skilled in the art. For example, the weight ratio of Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution is generally (60-85):(15-40):(3-20):(5-80), preferably (70-80):(20-30):(10-15):(20-50). In the material dosage, Hβ molecular sieve and alumina precursor are both weights calculated on a dry basis.

[0031] Furthermore, the drying conditions in steps (3), (4) and (5) are generally as follows: the drying temperature is 60°C to 150°C, preferably 80°C to 120°C, and the drying time is 2 hours to 24 hours, preferably 5 hours to 20 hours; the roasting conditions are as follows: the roasting temperature is 300°C to 800°C, preferably 400°C to 700°C, and the roasting time is 2 hours to 24 hours, preferably 3 hours to 8 hours; during the roasting, the molecular sieve is purged with air flow, and the air volume space velocity is 100h -1 ~3000h -1 , preferably 200h -1 ~2000h -1 .

[0032] Furthermore, step (4) is preferably performed by naturally drying in the shade for 10 to 48 hours before drying.

[0033] Furthermore, the conventional impregnation method for loading the second additive oxide in step (5) is an operation well known to those skilled in the art.

[0034] A fifth aspect of the present invention provides a method for synthesizing diphenylamine from aniline, wherein the Hβ molecular sieve catalyst described above is used.

[0035] A method for synthesizing diphenylamine from aniline comprises the following steps: aniline is subjected to condensation reaction in the presence of an Hβ molecular sieve catalyst under reaction conditions.

[0036] Further, the reaction conditions include: reaction pressure of 0.1-4.0 MPa, preferably 0.15-3.5 MPa; reaction temperature of 280-360°C, preferably 290-350°C; aniline volume space velocity of 0.1 h -1 ~0.3h -1 , preferably 0.15h -1 ~0.25h -1 .

[0037] Based on the research on the condensation reaction of aniline to generate diphenylamine, the inventors of this application have made the following findings: the reaction of aniline to diphenylamine is a typical acid-catalyzed reaction, and the acid properties and pore structure of the catalyst affect the selectivity of the product and the stability of the catalyst. At present, the catalyst for the industrial synthesis of diphenylamine from aniline is a modified Hβ molecular sieve catalyst. Hβ molecular sieve is a high-silicon molecular sieve with a twelve-membered ring pore structure, which has acidity and pore structure suitable for the reaction of aniline to synthesize diphenylamine. However, the inventors found that in the pore structure of Hβ molecular sieve, there are two types of pore spaces, namely straight-through pores and pore intersections. The pore intersection is that two pores penetrate each other at a certain angle and communicate with each other internally. This pore intersection has an open space, and the acid center is denser than the non-intersection, which can catalyze the cyclization and condensation reactions of aniline molecules to generate macromolecules such as tricyclic linear acridine and bicyclic planar quinoline, and diffuse out from the pores, resulting in the inability to fundamentally improve the selectivity of diphenylamine. In addition, this pore intersection also becomes an active zone for the generation of carbon deposit precursors. Existing molecular sieve modification methods such as steam treatment, loading of metal / non-metal oxides, etc., not only modify the intersection of the channels, but also modify the straight channels, which is a kind of general modification method that is not targeted. After the above modification, there is still a relatively open space and a large number of acid centers at the intersection of the channels, which can continue to catalyze the occurrence of side reactions, not only affecting the selectivity of the product diphenylamine, but also further forming a carbon deposit precursor with a high carbon-hydrogen ratio until carbon deposits are formed. If the existing modification means are used to increase the loading amount of metal oxides to achieve the purpose of modifying the acid centers at the intersection of the channels, the loading amount of the modified material is too large, which affects the diffusion of reactants and products in the channels, increases the attenuation rate of the aniline conversion rate of the catalyst, and shortens the one-way operation cycle. Therefore, the one-way operation cycle of the industrial aniline synthesis diphenylamine catalyst is short, and it needs to burn carbon for regeneration after only 1500 hours. The operating cost of the device is high, and the annual effective start-up hours are small.

[0038] In the preparation method of Hβ molecular sieve provided by the present invention, cinnamate is first dissolved in benzene to prepare a solution, and then the solution is filled with the molecular sieve pores; by purging with hot nitrogen, C=C in cinnamate reacts with benzene at high temperature to generate a macromolecular salt product with two benzene rings. Since the molecular size of the reaction product is larger than the diameter of the molecular sieve straight-through pore, even if there is an acid center required for the reaction in the straight-through pore, it cannot be generated in the straight-through pore, but can only be generated at the intersection of the pores, such as the location with sufficient space and acid centers. The hot nitrogen will also gasify the excess benzene in the pores and take it out of the molecular sieve, and the remaining unreacted cinnamate in the pores will be taken away during water washing, while the macromolecular product generated by the reaction cannot be taken out of the pores due to the molecular size limitation, and continues to remain at the intersection of the pores. The roasting step fully oxidizes and burns the carbon and hydrogen components in the macromolecular product, turning them into carbon dioxide and water vapor and escaping the molecular sieve, and the remaining metal oxides continue to adhere to the intersection of the molecular sieve pores, playing a role in adjusting the acid center at the intersection of the pores and adjusting the size there. The method of the present invention only modulates the acid centers at the intersection of the Hβ molecular sieve channels, and does not affect the acid centers at the straight channels, nor does it affect the smooth flow of the channels, so that the catalyst made from the modified Hβ molecular sieve has higher diphenylamine selectivity and a longer single-pass operation cycle. Implementation

[0039] The technical scheme of the present invention is described in detail below in conjunction with the examples, but the present invention is not limited to the following examples. In the material dosage, the Hβ molecular sieve and the alumina precursor are all measured by weight on a dry basis.

[0040] In the examples of the present invention and the comparative examples, the concentration of the product was analyzed by liquid chromatography, and the conversion rate and selectivity were obtained by calculation.

[0041] Aniline conversion rate = number of moles of aniline involved in the reaction / total number of moles of aniline feed × 100%; Diphenylamine selectivity = number of moles of diphenylamine in the product / total number of moles of main and by-products × 100%. Example 1

[0042] This embodiment provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 6.5%; use the solution at a liquid-to-solid ratio of 5 mL / g to impregnate 200 g of Hβ molecular sieve with a silicon-aluminum ratio of 40, and filter out the molecular sieve after impregnation for 2 hours; (2) The filtered molecular sieve was heated with 110℃ hot nitrogen for 800h -1 The air velocity was purged for 4 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 6 mL / g, drying the washed molecular sieve at 110° C. for 5 hours and calcining at 550° C. for 5 hours to obtain a modified Hβ molecular sieve; (4) The modified Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 110° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with La oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was denoted as A. Example 2

[0043] This embodiment provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 5%; use the solution at a liquid-to-solid ratio of 7 mL / g to impregnate 200 g of Hβ molecular sieve with a silicon-aluminum ratio of 25, and filter out the molecular sieve after impregnation for 4 hours; (2) The filtered molecular sieve was heated with 120℃ hot nitrogen for 1000h -1 The air velocity was purged for 4 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 5 mL / g, drying the washed molecular sieve at 110° C. for 4 hours and calcining at 500° C. for 5 hours to obtain a modified Hβ molecular sieve; (4) The modified Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 120° C. for 4 hours, and calcined at 510° C. for 3 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with Ce oxide by conventional impregnation method, and then dried at 120°C for 5 hours and calcined at 500°C for 4 hours to obtain a finished catalyst, which was denoted as B. Example 3

[0044] This embodiment provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 8%; use the solution at a liquid-to-solid ratio of 7 mL / g to impregnate 200 g of Hβ molecular sieve with a silicon-aluminum ratio of 80, and filter out the molecular sieve after impregnation for 3 hours; (2) The filtered molecular sieve was heated with 120℃ hot nitrogen for 1100h -1 The air velocity was purged for 3 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 8 mL / g, drying the washed molecular sieve at 110° C. for 3 hours and calcining at 550° C. for 3 hours to obtain a modified Hβ molecular sieve; (4) The modified Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 120° C. for 5 hours, and calcined at 550° C. for 3 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with Mg oxide by conventional impregnation method, and then dried at 120°C for 5 hours and calcined at 550°C for 4 hours to obtain a finished catalyst, which was denoted as C. Example 4

[0045] This embodiment provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 6%; use the solution at a liquid-to-solid ratio of 5 mL / g to impregnate 200 g of Hβ molecular sieve with a silicon-aluminum ratio of 150, and filter out the molecular sieve after impregnation for 4 hours; (2) The filtered molecular sieve was heated with 110℃ hot nitrogen for 900h -1 The air velocity was purged for 5 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 5 mL / g, drying the washed molecular sieve at 120° C. for 6 hours and calcining at 540° C. for 4 hours to obtain a modified Hβ molecular sieve; (4) The modified Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 110° C. for 6 hours, and calcined at 550° C. for 4 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with Si oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was denoted as D.

[0046] Comparative Example 1 This comparative example provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Using potassium nitrate as a precursor, a conventional impregnation method was used to impregnate Hβ molecular sieve with a silicon-aluminum ratio of 40. After impregnation for 2 hours, the molecular sieve was filtered out, dried at 110°C for 5 hours, and calcined at 550°C for 5 hours. (2) After fully mixing and kneading Hβ molecular sieve with a silicon-aluminum ratio of 40, alumina precursor, an extrusion aid and a peptizing agent solution, the mixture was shaped, dried at 110° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) was loaded with La oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was recorded as E1.

[0047] Comparative Example 2 This comparative example provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Using potassium nitrate as a precursor, a conventional impregnation method was used to impregnate Hβ molecular sieve with a silicon-aluminum ratio of 25. After impregnation for 2 hours, the molecular sieve was filtered out, dried at 110°C for 5 hours, and calcined at 550°C for 5 hours. (2) The Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (1) are fully kneaded, molded, dried at 110° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) was loaded with Ce oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was recorded as E2.

[0048] Comparative Example 3 This comparative example provides a method for preparing a Hβ molecular sieve catalyst, comprising the following steps: (1) Using potassium nitrate as a precursor, a conventional impregnation method was used to impregnate Hβ molecular sieve with a silicon-aluminum ratio of 80. After impregnation for 3 hours, the molecular sieve was filtered out, dried at 120°C for 3 hours, and calcined at 560°C for 5 hours. (2) The Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (1) are fully kneaded, molded, dried at 110° C. for 6 hours, and calcined at 550° C. for 4 hours to obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) was loaded with Si oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was recorded as E3. Example 5

[0049] The properties of the modified Hβ molecular sieve and Hβ molecular sieve catalyst obtained in the above examples and comparative examples are shown in Table 1 and Table 2.

[0050] Catalyst performance evaluation: The catalysts of the above examples and comparative examples were used to carry out an evaluation experiment of synthesizing diphenylamine from aniline in a small evaluation device. Aniline was used as the raw material, the reaction temperature was 310°C, the reaction pressure was 3.0 MPa, and the volumetric space velocity of aniline was 0.2 h -1The reaction results are shown in Table 3, wherein the initial extraction time is the total operation time from the start of the reaction to when the aniline conversion rate drops below 20%, the aniline conversion rate is the average aniline molar conversion rate during the initial extraction time, and the diphenylamine selectivity is the average diphenylamine molar selectivity during the initial extraction time.

[0051] Table 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Modified Hβ molecular sieve Silicon to aluminum ratio, molar ratio 40 25 80 150 40 25 80 Meta-xylene adsorption g / 100g 23.23 24.45 22.80 21.67 12.92 13.22 7.48 Additives <![CDATA[K 2 O content*]]> 0.02 0.03 0.04 0.03 0.02 0.03 0.04 Indicative constant, k 137 113 255 361 76 61 84 *, the number of moles of metal oxide loaded per 100g of molecular sieve.

[0052] Table 2 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Molecular sieve catalyst Modified Hβ molecular sieve, wt% 68.5 72.7 70.4 76.0 68.5 73.5 71.8 Additives Second additive oxide, wt% 2.5 3.0 2.0 2.5 2.5 3.0 2.0 Alumina, % 29.0 24.3 27.6 21.5 29.0 23.5 26.2 Table 3 Catalyst No. Initial time, h Aniline conversion, mol% Diphenylamine selectivity, mol% A 876 21.76 98.32 B 652 21.24 98.35 C 751 21.12 98.46 D 614 21.20 98.19 E1 221 22.08 96.24 E2 285 21.12 97.17 E3 184 21.09 96.35

Claims

1. A modified Hβ molecular sieve, It is characterized in that The modified Hβ molecular sieve contains at least one metal oxide of sodium and potassium as an additive, and the additive content is 0.5% to 5%; wherein the silicon-aluminum ratio of the Hβ molecular sieve is 25 to 180; The index constant k of the modified Hβ molecular sieve is 100-550, preferably 101-500, wherein the index constant k is calculated as follows: k=Q / (1.4909×a -0.558 -c) Wherein, Q is the amount of meta-xylene adsorption, expressed in g / 100 g; a is the silicon-aluminum ratio; and c is the number of moles of metal oxide loaded per 100 g of molecular sieve.

2. The method for preparing the modified Hβ molecular sieve according to claim 1, It is characterized in that The following steps are involved: (1) Dissolve cinnamate in benzene and stir evenly to fully dissolve; (2) impregnating the Hβ molecular sieve with the solution obtained in step (1), and filtering out the Hβ molecular sieve after the impregnation is completed; (3) purging the Hβ molecular sieve filtered out in step (2) with hot nitrogen; (4) The Hβ molecular sieve obtained in step (3) is washed with deionized water, and then dried and calcined.

3. The preparation method according to claim 2, It is characterized in that The cinnamate is one or more of sodium cinnamate and potassium cinnamate.

4. The preparation method according to claim 2 or 3, It is characterized in that The mass fraction of cinnamate in benzene is 0.5%~20%.

5. The preparation method according to claim 2, It is characterized in that The liquid-to-solid ratio of the impregnation in step (2) is 4-10 mL / g, and the impregnation time is 1-10 hours.

6. The preparation method according to claim 2, It is characterized in that The temperature of the hot nitrogen in step (3) is 80°C to 180°C.

7. A catalyst for synthesizing diphenylamine from aniline, It is characterized in that The catalyst contains the modified Hβ molecular sieve according to claim 1.

8. The catalyst according to claim 7, It is characterized in that The catalyst for synthesizing diphenylamine from aniline comprises, based on the weight of the catalyst: Hβ molecular sieve 60%~85%, preferably 61%~83%; Sodium oxide and / or potassium oxide 0.1%~6%, preferably 0.2%~5%; Alumina, 13% to 35%, preferably 14% to 34%; The silicon-aluminum molar ratio of the Hβ molecular sieve is 25-180, and the index constant k of the Hβ molecular sieve is 100-550.

9. The catalyst according to claim 8, It is characterized in that The specific surface area of ​​the catalyst is 250-650m 2 / g, and the specific pore volume is 0.20~0.50mL / g.

10. The catalyst according to claim 8, It is characterized in that The catalyst also includes one or more oxides of Li, La, Ce, Mg, Ca, Ba, Cu, Zn, Zr, Fe, Si, P, B, and C as a second auxiliary agent, and the content of the second auxiliary agent oxide in the catalyst is 0.1-5%.

11. A method for preparing the catalyst according to any one of claims 8 to 10, It is characterized in that The steps include: (1) Dissolve an appropriate amount of cinnamate in benzene, stir evenly and fully dissolve; use the solution to impregnate Hβ molecular sieve, and filter out the molecular sieve after impregnation; (2) Purge the filtered molecular sieve with hot nitrogen and cool it naturally to room temperature after the purge is completed; (3) washing the molecular sieve obtained in step (2) with deionized water, drying and calcining the washed molecular sieve to obtain a modified Hβ molecular sieve; (4) The modified Hβ molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried and calcined to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) is loaded with other metals or non-metal oxides by conventional impregnation method, and then dried and calcined to obtain a finished catalyst.

12. The preparation method according to claim 11, It is characterized in that The cinnamate is one or more of sodium cinnamate and potassium cinnamate, and the mass fraction of the cinnamate in benzene is 0.5% to 20%.

13. The preparation method according to claim 11, It is characterized in that The temperature of the hot nitrogen in step (2) is 80°C to 180°C.

14. A method for synthesizing diphenylamine from aniline, It is characterized in that The Hβ molecular sieve catalyst according to any one of claims 8 to 10 is used; the method comprises the following contents: Aniline undergoes condensation reaction in the presence of Hβ molecular sieve catalyst under reaction conditions.

15. The method according to claim 14, It is characterized in that The reaction conditions include: reaction pressure of 0.1-4.0 MPa, reaction temperature of 280°C-360°C, aniline volume space velocity of 0.1 h -1 ~0.3h -1 .