Modified molecular sieve and preparation method therefor, catalyst and use thereof, and method for synthesizing diphenylamine from aniline

Abstract

A modified molecular sieve and a preparation method therefor, a catalyst and the use thereof, and a method for synthesizing diphenylamine from aniline. The modified molecular sieve comprises a β molecular sieve and an auxiliary component, and the auxiliary component is selected from at least one alkali metal. The indicative constant k of the modified molecular sieve is not less than 100. The catalyst prepared from the modified molecular sieve has a relatively high diphenylamine selectivity and a longer one-way operation period.

Description

Modified molecular sieve and preparation method thereof, catalyst and application thereof, and method for synthesizing diphenylamine from aniline

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202311665591.X filed on December 6, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of molecular sieve preparation, and in particular to a modified molecular sieve and a preparation method thereof, a catalyst and application thereof, and a method for synthesizing diphenylamine from aniline. Background Art

[0004] Diphenylamine is an important organic chemical raw material with a wide range of uses. Industrially, it is primarily used as an antioxidant for synthetic rubber, an explosive stabilizer, a fuel and pharmaceutical intermediate, azo dyes, and a fruit preservative. It is also used as an analytical reagent for DNA identification, colorimetric determination of nitrates, nitrites, chlorates, and magnesium, and as a redox indicator. Currently, the catalysts for synthesizing diphenylamine from aniline, as described in patents both domestically and internationally, are mostly solid acid catalysts. For example, patent applications US3118944A, US4454348A, US3944613A, and CN1114240A disclose technologies for preparing catalysts using activated alumina, amorphous silica-alumina, and molecular sieves.

[0005] In the mid-1990s, researchers developed a new process for the continuous synthesis of diphenylamine from aniline and a supporting specialized molecular sieve catalyst, the active component of which is Hβ molecular sieve. Currently, the continuous synthesis of diphenylamine from aniline using Hβ molecular sieve catalysts typically achieves a conversion rate of 20-25% and a selectivity of 96-97 mol%.

[0006] In recent years, researchers in this field have modified the acidity and pore volume of β-zeolite catalysts. For example, CN105618106A proposes a hierarchical β-zeolite catalyst with a large amount of mesopore volume. The dissertation "Study on Catalysts for the Preparation of Diphenylamine by Aniline Condensation" introduces halogens into β-zeolites to increase their acidity. The Journal of Petrolei Sinica (2017, Vol. 33, No. 1), "Effect of Alkali Treatment on the Catalytic Performance of Hβ-Zeolite for the Preparation of Diphenylamine by Aniline Condensation," uses alkaline treatment to etch β-zeolite crystals to increase their mesopore volume. However, low selectivity and short single-pass cycle times remain. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of low selectivity and short single-pass operation cycle of the catalyst for synthesizing diphenylamine from aniline in the prior art, and to provide a modified molecular sieve and a preparation method thereof, a catalyst and an application thereof, and a method for synthesizing diphenylamine from aniline. The modified molecular sieve is used in the catalyst for synthesizing diphenylamine from aniline, has high catalytic activity, high selectivity and a long single-pass operation cycle.

[0008] In order to achieve the above object, the first aspect of the present invention provides a modified molecular sieve, wherein the modified molecular sieve comprises a beta molecular sieve and an auxiliary component, wherein the auxiliary component is selected from at least one of alkali metals;

[0009] Wherein, the index constant k of the modified molecular sieve is not less than 100.

[0010] In the present invention, the characteristic constant k is calculated according to formula (1): k = Q / (1.4909×a -0.558 -c) Formula (1)

[0011] Wherein, Q is the standard meta-xylene adsorption capacity per 100 g of modified molecular sieve, in g; a is the molar ratio of silicon oxide to aluminum oxide in the modified molecular sieve; and c is the molar number of the auxiliary component calculated as oxide per 100 g of modified molecular sieve.

[0012] A second aspect of the present invention provides a method for preparing a modified molecular sieve, comprising:

[0013] (1) preparing an impregnation solution comprising an organic salt of an auxiliary component and an organic solvent;

[0014] The auxiliary component is selected from at least one of alkali metals;

[0015] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0016] (3) using an inactive fluid to purge and / or flush the product obtained in step (2) so that the organic salt of the auxiliary component reacts to form a macromolecular product containing the auxiliary component, and the molecular diameter of the macromolecular product containing the auxiliary component is larger than the pore diameter of the β molecular sieve, thereby obtaining a modified molecular sieve precursor;

[0017] (4) calcining the modified molecular sieve precursor.

[0018] The third aspect of the present invention provides another method for preparing a modified molecular sieve, comprising the following steps:

[0019] (1) preparing an impregnation solution comprising an organic salt of an auxiliary component and an organic solvent;

[0020] The auxiliary component is selected from at least one of alkali metals; the organic solvent is a C6-C10 substituted or unsubstituted cyclic hydrocarbon compound; the organic salt of the auxiliary component contains a cyclic structure in its molecule and contains an unsaturated functional group capable of undergoing an addition reaction with the cyclic hydrocarbon compound;

[0021] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0022] (3) using an inactive fluid having a temperature of not less than 80° C. to purge and / or rinse the product obtained in step (2), and then drying it to obtain a modified molecular sieve precursor;

[0023] (4) calcining the modified molecular sieve precursor.

[0024] The fourth aspect of the present invention provides a modified molecular sieve prepared by the preparation method provided by the second aspect or the third aspect.

[0025] The fifth aspect of the present invention provides a catalyst, which comprises the modified molecular sieve described in the first aspect or the fourth aspect and a binder.

[0026] A sixth aspect of the present invention provides a method for synthesizing diphenylamine from aniline, the method comprising: contacting aniline with a catalyst under condensation reaction conditions;

[0027] Wherein, the catalyst is the catalyst provided in the fifth aspect.

[0028] The inventors discovered through research that the conversion of aniline to diphenylamine is a typical acid-catalyzed reaction, in which the acidic properties and pore structure of the catalyst influence product selectivity and catalyst stability. Currently, the catalyst used industrially to convert aniline to diphenylamine is a modified beta molecular sieve catalyst. Beta molecular sieve is a high-silica molecular sieve with a twelve-membered ring pore structure, possessing the acidity and pore structure suitable for the conversion of aniline to diphenylamine. Within the pore structure of beta molecular sieve, there are two types of pore spaces: straight-through pores and pore intersections. Pore intersections are where two pores intersect at an angle and communicate internally. These pore intersections offer wide open spaces and are denser with acid centers than non-intersections. This allows for the cyclization and condensation of aniline molecules to form macromolecules such as tricyclic linear acridine and bicyclic planar quinoline, which diffuse out of the pores, making it impossible to fundamentally improve diphenylamine selectivity. Furthermore, these pore intersections are active zones for the formation of carbon deposit precursors.

[0029] The index constant k of the existing metal-modified beta molecular sieves is less than 100, typically 60-90. The metal-modified metal-modified beta molecular sieves typically contain a large amount of the metal-modified oxides in the straight-through pores, which is detrimental to maintaining pore patency and affecting the diffusion of reactants and products within the pores. Furthermore, it is difficult to modify the acid centers at the pore intersections, resulting in a rapid decay rate of the aniline conversion rate of the catalyst and a short single-pass operation cycle. The initial extraction time of the industrial aniline to diphenylamine catalyst is generally only 250 hours, and carbon burning regeneration is required after only 1500 hours. This results in high operating costs and a low annual effective operating time.

[0030] Compared to conventional modified molecular sieves, the modified molecular sieve provided by the present invention has an index constant k of no less than 100. The additive component in this modified molecular sieve is almost entirely loaded at pore intersections, enabling targeted modification of acid centers at these intersections without affecting acid centers in straight-through pores or impairing pore flow. Catalysts containing this modified molecular sieve exhibit higher diphenylamine selectivity and longer single-pass operation cycles. DETAILED DESCRIPTION

[0031] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0032] The first aspect of the present invention provides a modified molecular sieve, wherein the modified molecular sieve comprises a beta molecular sieve and an auxiliary component, wherein the auxiliary component is selected from at least one of alkali metals;

[0033] The index constant k of the modified molecular sieve is not less than 100, preferably 100-550, more preferably 101-500, for example, it can be 101, 110, 120, 130, 140, 150, 160, 180, 200, 250, 300, 350, 400, 450, 500 and other specific but non-limiting values.

[0034] According to the present invention, the index constant k of the modified molecular sieve is not less than 100, and the auxiliary component in the modified molecular sieve is almost completely loaded at the intersection of the pores, which can target the acid centers at the intersections for modification without affecting the acid centers at the straight-through pores or affecting the smooth flow of the pores. As a result, the catalyst prepared from the modified molecular sieve has a higher diphenylamine selectivity and a longer single-pass operation cycle. The index constant k of the modified β molecular sieve in the prior art is below 100, and the auxiliary oxide used for modification is usually loaded in large quantities in the straight-through pores, which is not conducive to maintaining the smooth flow of the pores, affects the diffusion of reactants and products in the pores, and makes it difficult to achieve the modification of the acid centers at the intersection of the pores, thereby resulting in a fast decay rate of the aniline conversion rate of the catalyst and a short single-pass operation cycle. In industry, the initial extraction time of the catalyst for synthesizing diphenylamine from aniline is generally only 250 hours, and carbon burning regeneration is required after only 1500 hours, resulting in high device operating costs and low annual effective operating hours.

[0035] In the present invention, the characteristic constant k is calculated according to formula (1): k = Q / (1.4909×a -0.558 -c) Formula (1)

[0036] Wherein, Q is the standard meta-xylene adsorption capacity per 100 g of modified molecular sieve, in g; a is the molar ratio of silicon oxide to aluminum oxide in the modified molecular sieve; and c is the molar number of the auxiliary component calculated as oxide per 100 g of modified molecular sieve.

[0037] In the present invention, k is a dimensionless value calculated by formula (1).

[0038] The standard m-xylene adsorption capacity of the modified molecular sieve is determined as follows: The measurement is performed using an Intelligent Gravimetric Analyzer (IGA-002). Before determining the m-xylene adsorption capacity, the molecular sieve is first decontaminated to remove impurities such as moisture and residual templates. The decontaminated sample is heated from room temperature to 300°C at a rate of 5°C / minute under vacuum. After the sample reaches constant mass, the temperature is returned to room temperature, and the m-xylene adsorption capacity is measured. At room temperature, m-xylene vapor is passed through the decontaminated sample chamber. After the sample is completely saturated (i.e., its weight remains constant), the weight difference is recorded as the m-xylene adsorption capacity of the modified molecular sieve. The ratio of the m-xylene adsorption capacity to the initial mass of the modified molecular sieve is calculated to obtain the standard m-xylene adsorption capacity, Q, per 100g of the modified molecular sieve.

[0039] In a further preferred embodiment, the standard meta-xylene adsorption capacity per 100g of the modified molecular sieve is 17-33g, preferably 18-31g. In the present invention, meta-xylene is used as the target substance to reflect the pore structure of the modified molecular sieve. In the above preferred embodiment, it is shown that the pore intersections in the modified molecular sieve have an appropriate number of acid centers and an appropriate pore size, and there are almost no auxiliary components in the straight-through pores, which is conducive to further improving the catalytic selectivity and single-pass operation cycle of the modified molecular sieve catalyst.

[0040] In the present invention, the silicon-aluminum ratio a of the modified molecular sieve refers to the molar ratio of silicon oxide and aluminum oxide in the modified molecular sieve. The "silicon-aluminum ratio" involved in the present invention refers to the molar ratio of silicon oxide to aluminum oxide, which is obtained by XRF characterization. Preferably, the molar ratio of silicon oxide to aluminum oxide in the modified molecular sieve is 20-250, preferably 25-200, for example, it can be a specific but non-limiting molar ratio of 20, 25, 40, 60, 80, 100, 120, 150, or a range between any two. In the above preferred case, it is beneficial for the modified molecular sieve to retain suitable active centers.

[0041] Preferably, the modified molecular sieve does not contain non-framework silicon oxide and / or aluminum oxide.

[0042] Preferably, the β molecular sieve is Hβ molecular sieve.

[0043] According to the present invention, c is the molar number of the auxiliary component calculated as oxide per 100 g of the modified molecular sieve, which is obtained by ICP characterization method.

[0044] In the present invention, 1.4909 is the fitting coefficient.

[0045] According to some preferred embodiments of the present invention, the auxiliary component is selected from sodium and / or potassium. Preferably, the auxiliary component exists in the form of an oxide.

[0046] According to the present invention, in 100 g of the modified molecular sieve, the molar amount of the auxiliary component calculated as oxide is 0.01-0.12 mol, preferably 0.02-0.1 mol.

[0047] Existing molecular sieve modification methods, such as steam treatment and loading of metal / non-metallic oxides, are a type of general modification method that is not targeted and modifies both the intersection of the pores and the straight-through pores. In this case, there is still a relatively open space and a large number of acid centers at the intersection of the pores, which can continue to catalyze the occurrence of side reactions, not only affecting the selectivity of the product diphenylamine, but also further forming carbon deposit precursors with a high carbon-hydrogen ratio until carbon deposits are formed. In addition, in order to achieve the purpose of modifying the acid centers at the intersection of the pores in the prior art, it is necessary to increase the loading amount of the modifying component, which will affect the diffusion of reactants and products in the pores, increase the aniline conversion rate decay rate of the catalyst, and shorten the single-pass operation cycle. Therefore, the single-pass operation cycle of the industrial aniline synthesis diphenylamine catalyst is relatively short, the initial extraction time is generally about 250 hours, and carbon burning regeneration is required after only 1500 hours, the device operating costs are high, and the annual effective operating hours are small.

[0048] In the present invention, by controlling the appropriate amount of modified component loading and controlling the index constant k of the modified molecular sieve within the above range, the acid centers at the intersection of the molecular sieve channels can be regulated while avoiding the influence on the molecular sieve channel structure, so that the catalyst prepared with the modified molecular sieve has higher diphenylamine selectivity and longer single-pass operation cycle.

[0049] A second aspect of the present invention provides a method for preparing a modified molecular sieve, comprising:

[0050] (1) preparing an impregnation solution comprising an organic salt of an auxiliary component and an organic solvent;

[0051] The auxiliary component is selected from at least one of alkali metals;

[0052] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0053] (3) using an inactive fluid to purge and / or flush the product obtained in step (2) so that the organic salt of the auxiliary component reacts to form a macromolecular product containing the auxiliary component, and the molecular diameter of the macromolecular product containing the auxiliary component is larger than the pore diameter of the β molecular sieve, thereby obtaining a modified molecular sieve precursor;

[0054] (4) calcining the modified molecular sieve precursor.

[0055] According to the present invention, through step (3), the organic salt of the auxiliary component is allowed to generate a macromolecular product with a complex spatial structure under the action of the acid center of the β molecular sieve. The molecular diameter of this macromolecular product is larger than the pore diameter of the molecular sieve. Even under the purge and / or washing of an inactive fluid, this substance will continue to remain at the intersection of the molecular sieve pores. After further calcination, it forms a metal oxide that adheres to the intersection of the molecular sieve pores, playing a role in modulating the acid center at the pore intersection and regulating the size of the pore intersection. It is understood that in the absence of acid center catalysis, no macromolecular product can be formed.

[0056] In the present invention, the pore diameter of the beta molecular sieve refers to the maximum straight-through pore diameter of the beta molecular sieve. The maximum straight-through pore diameter is the longest diameter of an approximate ellipse in a radial cross-section of the pore (perpendicular to the axial direction) measured by transmission electron microscopy. The maximum straight-through pore diameter of the beta molecular sieve is typically 0.7 nm. The composition of the liquid phase before purging or flushing at the same reaction temperature is analyzed by liquid chromatography, and the composition of the liquid / gas phase after purging or flushing is analyzed by liquid chromatography or gas chromatography. Composition comparison demonstrates that the organic salt of the auxiliary component reacts to form a macromolecular product containing the auxiliary component. The molecular diameter of the macromolecular product refers to the molecular dynamics diameter, which is calculated using molecular dynamics simulation.

[0057] The inactive fluid can be any gas or liquid that does not participate in the reaction.

[0058] The present invention is not particularly limited to the type of reaction, as long as a macromolecular product having a molecular diameter greater than the pore diameter of the beta molecular sieve can be obtained. For example, the organic salt of the auxiliary component can be subjected to a self-polymerization reaction to form a macromolecular product containing the auxiliary component, or the organic salt of the auxiliary component can be subjected to an addition reaction with the organic solvent to form a macromolecular product containing the auxiliary component.

[0059] A third aspect of the present invention provides a method for preparing a modified molecular sieve, comprising the following steps:

[0060] (1) preparing an impregnation solution comprising an organic salt of an auxiliary component and an organic solvent;

[0061] Wherein, the auxiliary component is selected from at least one of alkali metals; the organic solvent is a C6-C10 substituted or unsubstituted cyclic hydrocarbon compound;

[0062] The organic salt of the auxiliary component contains a cyclic structure in its molecule and an unsaturated functional group capable of undergoing an addition reaction with a cyclic hydrocarbon compound;

[0063] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0064] (3) using an inactive fluid having a temperature of not less than 80° C. to purge and / or rinse the product obtained in step (2), and then drying it to obtain a modified molecular sieve precursor;

[0065] (4) calcining the modified molecular sieve precursor.

[0066] Existing molecular sieve modification methods, such as steam treatment and loading with metal / non-metallic oxides, modify both pore intersections and straight-through pores, representing a general, non-targeted approach. To achieve the goal of modifying acid centers at pore intersections, existing technologies require a high loading of the modifier, which hinders the diffusion of reactants and products within the pores, thereby increasing the decay rate of the catalyst's aniline conversion and shortening the single-pass cycle.

[0067] In the preparation method of the modified molecular sieve provided by the present invention, the organic salt of the auxiliary component is first dissolved in a cyclic hydrocarbon compound to form an impregnation solution, and then the solution is impregnated to fill the pores of the beta molecular sieve, so that the organic salt of the auxiliary component and the cyclic hydrocarbon compound diffuse into the molecular sieve pores; further, by purging and / or flushing with an inactive fluid of not less than 80°C, the unsaturated functional groups in the molecules of the organic salt of the auxiliary component and the cyclic hydrocarbon compound undergo an in-situ addition reaction at high temperature to generate a macromolecular salt product with a polycyclic structure. Because the molecular size of the reaction product is larger than the diameter of the straight-through pores of the molecular sieve, even if there are acid centers required for the reaction in the straight-through pores, they cannot be generated in the straight-through pores, but can only be generated at locations such as the intersection of the pores where there is sufficient space and acid centers. After further calcination, metal oxides are formed and attached to the intersection of the molecular sieve pores, which plays a role in modulating the acid centers at the pore intersections and adjusting the size of the acid centers at the pore intersections.

[0068] The modified molecular sieve prepared by the preparation method provided by the present invention has high diphenylamine selectivity and a longer single-pass operation cycle when used in a catalyst. The reason for this may be that the above-mentioned preparation method can adjust the acid centers at the intersection of the β molecular sieve pores without affecting the acid centers in the straight-through pores or affecting the smooth flow of the pores.

[0069] According to some preferred embodiments of the present invention, the cyclic structure is selected from at least one of a saturated or unsaturated five-membered ring and a six-membered ring. The cyclic structure may be a carbocyclic ring composed entirely of carbon atoms, or a heterocyclic ring containing heteroatoms such as S, N, and O. Preferably, the saturated or unsaturated five-membered ring and six-membered ring are composed entirely of carbon atoms.

[0070] According to the present invention, the β molecular sieve is preferably an Hβ molecular sieve. The present invention does not particularly limit the source of the β molecular sieve; it can be purchased commercially or prepared using any method known in the art. Preferably, the molar ratio of silicon oxide to aluminum oxide in the β molecular sieve is 20-250, preferably 25-200.

[0071] Preferably, the organic salt of the auxiliary component contains at least one unsaturated six-membered ring, preferably a benzene ring, in its molecule. In the above preferred case, it is conducive to the formation of a macromolecular salt product with a polycyclic structure.

[0072] According to the present invention, the organic salt of the auxiliary component further comprises an unsaturated functional group capable of undergoing an addition reaction with the cyclic hydrocarbon compound. The present invention does not particularly limit the type of the unsaturated functional group, as long as it is capable of undergoing an addition reaction with the cyclic hydrocarbon compound. Preferably, the unsaturated functional group is selected from a carbon-carbon double bond and / or a carbon-carbon triple bond. The present invention also does not particularly limit the position of the unsaturated functional group in the molecule; it may be on the ring of the cyclic structure or within a substituent of the cyclic structure.

[0073] In the present invention, the addition reaction is carried out under certain temperature conditions and catalysis by the β molecular sieve acid center.

[0074] In a further preferred embodiment, the molecular weight of the organic salt of the auxiliary component does not exceed 250 g / mol, preferably 50-220 g / mol. Controlling the molecular weight of the organic salt of the auxiliary component within the above preferred range is conducive to the formation of macromolecular salt products with a polycyclic structure of appropriate molecular size at the intersection of the molecular sieve channels.

[0075] According to a particularly preferred embodiment of the present invention, the structure of the organic salt of the auxiliary component is as shown in formula (i),

[0076] Wherein, R1 is a C2-C4 alkenylene or alkynylene group, for example, at least one of vinylene, ethynylene, propenylene, propynylene, butenylene, and butynylene. The position of the carbon-carbon double bond or carbon-carbon triple bond may be located in the middle or at both ends of the group, and the present invention has no particular limitation. The alkenylene or alkynylene group may be a straight chain or branched chain group, and the present invention has no particular limitation on this either.

[0077] In formula (i), R2, R3, R4, R5, and R6 are each independently selected from at least one of a hydrogen atom and a C1-C3 hydrocarbon group, for example, at least one of a hydrogen atom, a methyl group, and an ethyl group, more preferably a hydrogen atom.

[0078] In formula (i), A1 is selected from -COO- or -SO3-, preferably -COO-.

[0079] In formula (i), M refers to an auxiliary metal ion, which is selected from at least one alkali metal ion, preferably K + Or Na + .

[0080] The above preferred embodiment is adopted, which is conducive to the auxiliary component to adjust the acid centers at the intersection of the molecular sieve channels, and will not affect the smooth flow of the channels, so that the catalyst made of the modified molecular sieve has higher diphenylamine selectivity and longer single-pass operation cycle.

[0081] In the present invention, the cyclic hydrocarbon compound in the impregnation solution acts as a solvent on the one hand, so that the organic salt of the auxiliary component is uniformly dispersed in the cyclic hydrocarbon compound. On the other hand, the cyclic hydrocarbon compound and the organic salt of the auxiliary component can undergo addition reaction at the intersection of the pores of the molecular sieve under the conditions of blowing or flushing with an inactive fluid at a temperature of not less than 80°C to generate a macromolecular organic salt.

[0082] The present invention has a wide range of selection for the cyclic hydrocarbon compound, preferably a C6-C10 substituted or unsubstituted cyclic hydrocarbon compound, the substituent in the cyclic hydrocarbon compound can be, for example, a C1-C3 alkyl group, and further preferably, the cyclic hydrocarbon compound is selected from at least one of benzene, cyclohexane, toluene, methylcyclopentane and cyclohexene.

[0083] According to a particularly preferred embodiment of the present invention, the organic salt of the auxiliary component is a cinnamate of the auxiliary component, and the cyclic hydrocarbon compound is selected from at least one of benzene, cyclohexane, toluene, methylcyclopentane, and cyclohexene, more preferably benzene. This preferred embodiment facilitates the formation of a uniform liquid phase between the two components and the generation of a polycyclic macromolecular salt product at the intersection of the molecular sieve pores.

[0084] According to some preferred embodiments of the present invention, the organic salt content of the auxiliary component is 0.1-10 wt%, preferably 0.5-9 wt%, based on the total amount of the impregnation solution; and the cyclic hydrocarbon compound content is 90-99.9 wt%, preferably 90-99.5 wt%. These preferred embodiments facilitate the formation of a uniform liquid phase and the reaction to produce an appropriate amount of a polycyclic macromolecular salt product to fill the intersections of the molecular sieve pores.

[0085] According to some preferred embodiments of the present invention, the amount of the impregnation solution is 4-10 mL, preferably 5-8 mL, relative to 1 g of the Hβ molecular sieve.

[0086] The present invention does not particularly limit the impregnation temperature, and those skilled in the art can adjust it according to actual needs. Preferably, the impregnation can be performed at room temperature. Preferably, the impregnation time is 1-10 hours, preferably 1-5 hours. In this preferred embodiment, the impregnation solution can be ensured to fill the pores of the Hβ molecular sieve, allowing the organic salt and cyclic hydrocarbon compound of the auxiliary component to diffuse into the pores of the molecular sieve.

[0087] In the present invention, the inactive fluid may be any gas or liquid that does not participate in the reaction, for example, it may be at least one of nitrogen, argon, helium and neon. From the perspective of reducing preparation costs, nitrogen is preferred.

[0088] According to the present invention, high-temperature purging and / or flushing not only provides the required temperature for the addition reaction, but also vaporizes and removes excess small molecules from the pores. However, the resulting macromolecular products, limited by their size, cannot be removed from the pores and remain at the pore intersections. Preferably, at the end of the purging and / or flushing, the content of cyclic hydrocarbon compounds in the inactive fluid at the outlet is no more than 1 μg / L.

[0089] Preferably, the conditions for purging and / or flushing include: the temperature of the inactive fluid is 80-300°C, preferably 85-280°C, the volume space velocity is 100-3000h -1 , preferably 200-2000h -1 The purge and / or flushing time is 2-24 hours, preferably 3-20 hours. The above preferred embodiment is advantageous for forming macromolecular products, thereby modifying the acid centers at the intersections of the Hβ molecular sieve pores, while also removing excess small molecules within the pores to avoid affecting the smooth flow of the pores. This results in a catalyst made from the modified molecular sieve having higher diphenylamine selectivity and a longer single-pass operation cycle.

[0090] In the present invention, the organic salts and cyclic hydrocarbon compounds of the unreacted auxiliary components remaining in the product can be further removed by an optional washing step. The present invention does not specifically limit the operation mode and conditions of the washing, and those skilled in the art can select according to actual needs.

[0091] According to some preferred embodiments of the present invention, the washing agent used can be water. Preferably, the liquid-to-solid ratio of water to the product obtained by the purging is 4-10 mL / g, preferably 5-8 mL / g; the washing temperature can be 20 to 80°C, preferably 20-70°C. From the perspective of energy saving, it can be carried out at room temperature. The present invention does not particularly limit the number of washing times and can be adjusted according to the actual washing situation. Preferably, the number of washing times is 1-10 times, preferably 2-6 times.

[0092] The present invention has no particular limitation on the drying conditions. Preferably, the drying temperature is 60-150° C., preferably 80-120° C., and the drying time is 2-24 h, preferably 3-20 h.

[0093] In the present invention, the calcination in step (4) allows the carbon and hydrogen components in the macromolecular product loaded in the modified molecular sieve precursor to be fully oxidized and burned, turning into carbon dioxide and water vapor and escaping the molecular sieve. The remaining metal oxides continue to adhere to the intersection of the molecular sieve pores, playing a role in modulating the acid centers at the pore intersections and adjusting the size of the acid centers at the pore intersections. Preferably, the calcination conditions include: a temperature of 300-800°C, preferably 400-700°C, and a calcination time of 2-24 hours, preferably 3-8 hours.

[0094] The present invention further provides a method for preparing a molecular sieve, comprising:

[0095] (1) preparing an impregnation solution containing an organic salt and a cyclic hydrocarbon compound as auxiliary components;

[0096] Wherein, the organic salt of the auxiliary component contains a cyclic structure in its molecule and contains a carbon-carbon double bond and / or a carbon-carbon triple bond;

[0097] The auxiliary agent component is selected from at least one of alkali metals; the cyclic hydrocarbon compound is a C6-C10 substituted or unsubstituted cyclic hydrocarbon compound;

[0098] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0099] (3) purging the product obtained in step (2) with an inert gas having a temperature not lower than 80° C., and then optionally washing and drying the product to obtain a modified molecular sieve precursor;

[0100] (4) calcining the modified molecular sieve precursor.

[0101] Particularly preferably, the present invention provides a preferred method for preparing a modified molecular sieve, comprising:

[0102] (1) preparing an impregnation solution containing an organic salt and a cyclic hydrocarbon compound as auxiliary components;

[0103] Wherein, the organic salt of the auxiliary component is meat silicate, and the auxiliary component is selected from at least one of alkali metals; the cyclic hydrocarbon compound is at least one of benzene, cyclohexane, toluene, methylcyclopentane and cyclohexene;

[0104] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0105] (3) purging the product obtained in step (2) with an inert gas having a temperature not lower than 80° C., and then optionally washing and drying the product to obtain a modified molecular sieve precursor;

[0106] (4) calcining the modified molecular sieve precursor.

[0107] According to the present invention, carnosilicate and the aforementioned cyclic hydrocarbon compound undergo an addition reaction at a certain temperature, catalyzed by the acid centers of the beta zeolite, to produce a polycyclic macromolecular compound. The resulting metal oxide, after calcination, adheres to the intersections of the molecular sieve pores, modulating the acid centers at these intersections and regulating their size.

[0108] A fourth aspect of the present invention provides a modified molecular sieve prepared by the above preparation method.

[0109] A fifth aspect of the present invention provides a catalyst, comprising the modified molecular sieve described in the first aspect or the fourth aspect and a binder.

[0110] The present invention has a wide range of choices for the binder, and can be any conventional choice in the art, for example, it can be at least one of alumina, bentonite, spinel and silica, preferably alumina.

[0111] According to some preferred embodiments of the present invention, based on the total amount of the catalyst, the content of the modified molecular sieve is 55-85wt%, preferably 58-83wt%, and the content of the binder is 15-45wt%, preferably 17-42wt%.

[0112] According to the present invention, preferably, the catalyst further comprises a second auxiliary component, which may be any metal component and / or non-metal component that is beneficial to improving the catalytic activity of the catalyst in synthesizing diphenylamine from aniline.

[0113] In order to further improve the selectivity and single-pass operation cycle of the catalyst, preferably, the metal component is selected from at least one of the metal elements of Group IA, Group IIA, Group IIIB, Group IVB, Group VIII, Group IB, and Group IIB, for example, it can be at least one of Li, Na, K, Mg, Ca, Ti, Zr, La, Ce, Pr, Fe, Co, Ni, Cu and Zn, preferably at least one of Li, La, Ce, Mg, Ca, Ba, Cu, Zn, Zr, Fe, more preferably at least one of La, Ce and Mg.

[0114] Preferably, the non-metal component is selected from at least one of Group IIIA non-metal, Group IVA non-metal and Group VA non-metal elements, preferably at least one of Si, P, B and C.

[0115] Preferably, the content of the second auxiliary component is 0.1-5 wt %, preferably 1-4 wt %, based on the total amount of the catalyst, calculated as oxide. In the above preferred case, it is beneficial to further adjust the acidity of the catalyst, thereby further improving the activity of the catalyst.

[0116] According to the present invention, preferably, the specific surface area of ​​the catalyst is 250-650m 2 / g, preferably 300-600m 2 / g.

[0117] According to the present invention, preferably, the specific pore volume of the catalyst is 0.2-0.55 mL / g, preferably 0.25-0.5 mL / g.

[0118] In the present invention, the specific surface area and specific pore volume of the catalyst are measured by a nitrogen physical adsorption method.

[0119] The present invention has no particular requirements for the shape of the catalyst, which may be in the form of a bar or a sphere. In the case of a bar, its cross-section may be cylindrical, clover-shaped, or four-leaf clover-shaped, and the bar diameter is preferably 0.5-3 mm (according to standard Q / SH 361 933), preferably 1-2 mm; in the case of a sphere, its diameter is preferably 0.5-5 mm, preferably 1-3 mm.

[0120] The present invention does not particularly limit the preparation method of the above-mentioned catalyst, and it can be prepared by any conventional method in the art. For example, the modified molecular sieve and the binder can be first formed into a shape, and then the second auxiliary component can be loaded. The present invention also does not particularly limit the loading method of the second auxiliary component, and it can be carried out by conventional loading methods, such as impregnation, which are well known to those skilled in the art.

[0121] Another aspect of the present invention provides a method for preparing a catalyst, comprising:

[0122] (1) preparing an impregnation solution containing an organic salt and a cyclic hydrocarbon compound as auxiliary components;

[0123] The organic salt of the auxiliary component contains a cyclic structure in its molecule and an unsaturated functional group capable of undergoing an addition reaction with a cyclic hydrocarbon compound;

[0124] The auxiliary agent component is selected from at least one of alkali metals; the cyclic hydrocarbon compound is a C6-C10 substituted or unsubstituted cyclic hydrocarbon compound;

[0125] (2) impregnating the beta molecular sieve with the above impregnation solution;

[0126] (3) purging and / or flushing the product obtained in step (2) with an inactive fluid having a temperature of not less than 80° C., and then optionally washing and drying the product to obtain a modified molecular sieve precursor;

[0127] (4) calcining the modified molecular sieve precursor to obtain a modified molecular sieve;

[0128] (5) mixing and shaping the modified molecular sieve, the binder and / or the binder precursor, and the optional extrusion aid and the optional peptizing agent, and then performing a first drying and a first calcination to obtain a catalyst precursor;

[0129] (6) impregnating the catalyst precursor with a solution containing a soluble compound of a second auxiliary component, and then performing a second drying and a second calcination.

[0130] The specific operating conditions of steps (1) to (4) are the same as those defined in the second aspect and will not be repeated here.

[0131] In the present invention, the binder precursor refers to any substance that can be calcined to obtain the binder. For example, the precursor of aluminum oxide can be pseudo-boehmite, which is well known to those skilled in the art.

[0132] The present invention does not particularly limit the extrusion aid and the peptizing agent, and both can be selected from conventional methods in the art. The extrusion aid can be, for example, sesbania powder, and the peptizing agent can be, for example, dilute nitric acid and / or citric acid. The concentration of the dilute nitric acid can generally be 3-15 wt%.

[0133] According to some preferred embodiments of the present invention, the mass ratio of the modified molecular sieve, binder and / or binder precursor, extrusion aid and peptizing agent is (60-85): (15-40): (3-20): (5-80), preferably (70-80): (20-30): (10-15): (20-50), wherein the weights of the modified molecular sieve, binder and / or binder precursor are all calculated on a dry basis.

[0134] In the present invention, the dry basis weight of the modified molecular sieve refers to the weight of the modified molecular sieve after being calcined at 600° C. to remove adsorbed water and crystallized water.

[0135] The dry weight of the binder and / or binder precursor refers to the weight of the binder and / or binder precursor after burning out adsorbed water and crystallized water after calcining at 600°C.

[0136] The present invention has no particular limitation on the molding method, and those skilled in the art can select the molding method according to actual needs, for example, it can be extrusion molding, tablet molding, ball molding, etc.

[0137] According to some preferred embodiments of the present invention, the conditions for the first drying and the second drying each independently include: a temperature of 60-150° C., preferably 80-120° C., and a time of 2-24 h, preferably 5-20 h.

[0138] According to some preferred embodiments of the present invention, the product obtained by the impregnation is first naturally dried in the shade before the second drying is performed, for example, placed at room temperature for 10-48 hours for drying.

[0139] Preferably, the conditions of the first calcination and the second calcination each independently include: a temperature of 300-800° C., preferably 400-700° C., and a calcination time of 2-24 h, preferably 3-8 h.

[0140] The present invention has no particular requirements for the specific operation and conditions of the impregnation in step (5), and the loading amount of the second auxiliary component is sufficient. Preferably, the content of the second auxiliary component is 0.1-5 wt %, preferably 1-4 wt %, based on the total amount of the catalyst and calculated as oxide.

[0141] The soluble compound of the second auxiliary component may be a conventional inorganic salt and / or organic salt containing the second auxiliary component, and the solvent in the impregnation solution is preferably water.

[0142] A sixth aspect of the present invention provides use of the modified molecular sieve or the catalyst in an aniline condensation reaction.

[0143] A seventh aspect of the present invention provides a method for synthesizing diphenylamine from aniline, the method comprising: contacting aniline with a catalyst under condensation reaction conditions; wherein the catalyst is the catalyst described in the fifth aspect.

[0144] According to the present invention, preferably, the condensation reaction conditions include: reaction pressure of 0.1-4 MPa, preferably 0.15-3.5 MPa; reaction temperature of 280-360°C, preferably 290-350°C; aniline volume space velocity of 0.1-0.3h -1 , preferably 0.15-0.25h -1 In the present invention, unless otherwise specified, the pressure involved refers to gauge pressure.

[0145] The present invention will be described in detail below through examples.

[0146] In the following examples, unless otherwise specified, the raw materials used were all commercially available, and the weights of the modified molecular sieve and the alumina precursor in the material amounts are all weights on a dry basis.

[0147] The following preparation examples are used to illustrate the preparation of modified molecular sieves.

[0148] Preparation Example 1

[0149] (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, and fully dissolve, the mass percentage of potassium cinnamate being 8.5 wt %; use the solution at a liquid-to-solid ratio of 5 mL / g to impregnate 200 g of Hβ molecular sieve (silicon oxide to aluminum oxide molar ratio of 40), and filter out the molecular sieve after impregnation for 2 hours;

[0150] (2) The filtered molecular sieve was heated with 110℃ hot nitrogen for 800h -1 The air velocity was purged for 4 hours until the benzene content in the outlet nitrogen was no more than 1 μg / L;

[0151] After the purge is completed, it is cooled naturally to room temperature;

[0152] (3) The molecular sieve obtained in step (2) was washed with deionized water at a liquid-to-solid ratio of 6 mL / g. The washed molecular sieve was dried at 110° C. for 5 hours and calcined at 550° C. for 5 hours to obtain modified Hβ molecular sieve A1. The composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0153] Preparation Example 2

[0154] (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, and fully dissolve to prepare a solution with a mass percentage of 9%; use this solution at a liquid-to-solid ratio of 7 mL / g to impregnate 200 g of Hβ molecular sieve (the molar ratio of silicon oxide to aluminum oxide is 25) and filter out the molecular sieve after impregnation for 4 hours;

[0155] (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 purge;

[0156] (3) The molecular sieve obtained in step (2) was washed with deionized water at a liquid-to-solid ratio of 5 mL / g, and the washed molecular sieve was dried at 110° C. for 4 hours and calcined at 500° C. for 5 hours to obtain modified Hβ molecular sieve A2; the composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0157] Preparation Example 3

[0158] (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, and fully dissolve to prepare a solution with a mass percentage of 8%; use this solution at a liquid-to-solid ratio of 7 mL / g to impregnate 200 g of Hβ molecular sieve (the molar ratio of silicon oxide to aluminum oxide is 80) and filter out the molecular sieve after impregnation for 3 hours;

[0159] (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 purge;

[0160] (3) The molecular sieve obtained in step (2) was washed with deionized water at a liquid-to-solid ratio of 8 mL / g. The washed molecular sieve was dried at 110° C. for 3 hours and calcined at 550° C. for 3 hours to obtain a modified molecular sieve A3. The composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0161] Preparation Example 4

[0162] (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, and fully dissolve to prepare a solution with a mass percentage of 6%; use this solution at a liquid-to-solid ratio of 5 mL / g to impregnate 200 g of Hβ molecular sieve (the molar ratio of silicon oxide to aluminum oxide is 150) and filter out the molecular sieve after impregnation for 4 hours;

[0163] (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 purge;

[0164] (3) The molecular sieve obtained in step (2) was washed with deionized water at a liquid-to-solid ratio of 5 mL / g. The washed molecular sieve was dried at 120° C. for 6 hours and calcined at 540° C. for 4 hours to obtain a modified Hβ molecular sieve A4. The composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0165] Preparation Example 5

[0166] The method of Preparation Example 1 was followed, except that in step (1), the mass percentage of potassium cinnamate was 2 wt %. The resulting modified molecular sieve was designated A5, and its composition and physicochemical properties are shown in Table 1.

[0167] Preparation Example 6

[0168] The method of Preparation Example 1 was followed, except that in step (2), the filtered molecular sieve was heated with 80°C hot nitrogen for 150 hours. -1 The modified molecular sieve obtained was designated A6, and its composition and physicochemical properties are shown in Table 1.

[0169] Comparative Preparation Example 1

[0170] The Hβ molecular sieve (the molar ratio of silicon oxide to aluminum oxide is 40) was impregnated with potassium nitrate aqueous solution as the impregnation liquid by an equal volume impregnation method. After impregnation for 2 hours, the molecular sieve was filtered out and dried at 110°C for 5 hours and calcined at 550°C for 5 hours. The obtained modified molecular sieve was recorded as DA1. The composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0171] Comparative Preparation Example 2

[0172] The Hβ molecular sieve (the molar ratio of silicon oxide to aluminum oxide is 25) was impregnated with potassium cinnamate aqueous solution as the impregnation liquid by an equal volume impregnation method. After impregnation for 2 hours, the molecular sieve was filtered out and dried at 110°C for 5 hours and calcined at 550°C for 5 hours. The obtained modified molecular sieve was designated as DA2. The composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0173] Comparative Preparation Example 3

[0174] The Hβ molecular sieve (the molar ratio of silicon oxide to aluminum oxide is 80) was impregnated with potassium nitrate aqueous solution as the impregnation liquid by an equal volume impregnation method. After impregnation for 3 hours, the molecular sieve was filtered out and dried at 120°C for 3 hours and calcined at 560°C for 5 hours. The obtained modified molecular sieve was designated as DA3. The composition and physicochemical properties of the modified molecular sieve are shown in Table 1.

[0175] Comparative Preparation Example 4

[0176] Unmodified Hβ molecular sieve (molar ratio of silicon oxide to aluminum oxide is 40) was used, denoted as DA4, and its composition and physicochemical properties are shown in Table 1.

[0177] Table 1

[0178] The following examples illustrate the preparation of the catalyst.

[0179] Example 1

[0180] (1) Modified molecular sieve A1, alumina, sesbania powder, and 10 wt% nitric acid solution were thoroughly mixed in a mass ratio of 70:30:10:40, wherein the weights of the modified molecular sieve and alumina precursor are all calculated on a dry basis, and then extruded into a clover-shaped strip with a cross-section of 2 mm. The strip was then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a catalyst precursor.

[0181] (2) The catalyst precursor obtained in step (1) was loaded with La oxide by an equal volume impregnation method, dried at 110°C for 5 hours, and calcined at 550°C for 5 hours to produce a finished catalyst, designated CAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0182] Example 2

[0183] (1) Modified molecular sieve A2, alumina, sesbania powder, and 12 wt% nitric acid solution were thoroughly mixed in a mass ratio of 77:23:11:38, where the weights of the modified molecular sieve and alumina precursor are calculated on a dry basis. The mixture was then extruded into a cylindrical shape with a cross section of 1.8 mm. The mixture was then dried at 120°C for 4 hours and calcined at 510°C for 3 hours to obtain a catalyst precursor.

[0184] (2) The catalyst precursor obtained in step (1) was loaded with Ce oxide by the isovolumetric impregnation method, dried at 120°C for 5 hours, and calcined at 500°C for 4 hours to produce the finished catalyst, designated CAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0185] Example 3

[0186] (1) Modified molecular sieve A3, alumina, sesbania powder, and 15 wt% nitric acid solution were thoroughly mixed in a mass ratio of 72:28:13:35, where the weights of the modified molecular sieve and alumina precursor are calculated on a dry basis. The mixture was then extruded into a cylindrical shape with a cross section of 1.5 mm. The mixture was then dried at 120°C for 5 hours and calcined at 550°C for 3 hours to obtain a catalyst precursor.

[0187] (2) The catalyst precursor obtained in step (1) was loaded with Mg oxide by the isovolumetric impregnation method, dried at 120°C for 5 hours, and calcined at 550°C for 4 hours to produce a finished catalyst, designated CAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0188] Example 4

[0189] (1) Modified molecular sieve A4, alumina, sesbania powder, and 10 wt% nitric acid solution were thoroughly mixed in a mass ratio of 60:40:15:40, where the weights of the modified molecular sieve and alumina precursor are all calculated on a dry basis. The mixture was then extruded into a 2.2 mm clover-shaped strip. The mixture was then dried at 110°C for 6 hours and calcined at 550°C for 4 hours to obtain a catalyst precursor.

[0190] (2) The catalyst precursor obtained in step (1) was loaded with Si oxide using an equal volume impregnation method, dried at 110°C for 5 hours, and calcined at 550°C for 5 hours to produce a finished catalyst, designated CAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0191] Example 5

[0192] The method of Example 1 was followed, except that modified molecular sieve A5 was used instead of A1. The resulting finished catalyst was designated CAT-5, and its composition and physicochemical properties are shown in Table 2.

[0193] Example 6

[0194] The method of Example 1 was followed, except that modified molecular sieve A6 was used instead of A1. The resulting finished catalyst was designated CAT-6, and its composition and physicochemical properties are shown in Table 2.

[0195] Example 7

[0196] The method of Example 1 was followed, except that step (2) was not performed, and the catalyst precursor obtained in step (1) was directly used as the finished catalyst, which was recorded as CAT-7.

[0197] Comparative Example 1

[0198] The method of Example 1 was followed, except that modified molecular sieve DA1 was used instead of A1. The resulting finished catalyst was designated DCAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0199] Comparative Example 2

[0200] The method of Example 2 was followed, except that modified molecular sieve DA2 was used instead of A2. The resulting finished catalyst was designated DCAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0201] Comparative Example 3

[0202] The method of Example 3 was followed, except that modified molecular sieve DA3 was used instead of A3. The resulting finished catalyst was designated DCAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0203] Comparative Example 4

[0204] The method of Example 1 was followed, except that modified molecular sieve DA4 was used instead of A1. The resulting finished catalyst was designated DCAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0205] Comparative Example 5

[0206] (1) The modified molecular sieve DA1, alumina, sesbania powder and 10 wt% nitric acid solution were fully mixed in a mass ratio of 70:30:10:40, wherein the weight of the modified molecular sieve and the alumina precursor were calculated on a dry basis, and then mixed and kneaded, formed, and then dried at 110° C. for 5 hours and calcined at 550° C. for 5 hours to obtain a catalyst precursor;

[0207] (2) The catalyst precursor obtained in step (1) was contacted with an aqueous solution of molybdenum nitrate, and NaBH4 was added and refluxed at 100°C for 8 hours. The catalyst was filtered and vacuum dried to obtain a spherical catalyst with a particle diameter of 3 mm, which was recorded as DCAT-5.

[0208] The composition and physicochemical properties of the catalyst are shown in Table 2. The standard m-xylene adsorption capacity of 100 g of DCAT-5 is 10.65 g, and the calculated index constant k is 36.

[0209] Table 2

[0210] Test Case

[0211] The catalysts of the above examples and comparative examples were used to conduct an evaluation experiment on the synthesis of 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 MPa, and the volumetric space velocity of aniline was 0.2 h -1 The concentration of the product was analyzed by liquid chromatography, and the conversion rate and selectivity were calculated. The results are shown in Table 3, where:

[0212] Initial extraction time (h) is the total operation time from the start of the reaction to when the aniline conversion rate drops to 20 mol%;

[0213] Aniline conversion (mol%) is the average aniline molar conversion during the initial extraction time.

[0214] Aniline conversion (mol%) = moles of aniline involved in the reaction / total moles of aniline feed × 100%.

[0215] Diphenylamine selectivity (mol%) is the average diphenylamine molar selectivity during the initial extraction time.

[0216] Diphenylamine selectivity (mol%) = mole number of diphenylamine in the product / total mole number of main and by-products × 100%.

[0217] Table 3

[0218] From the results in Table 3, it can be seen that the catalyst further prepared from the modified molecular sieve prepared in the present invention has higher diphenylamine selectivity and longer single-pass operation cycle.

[0219] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A modified molecular sieve, characterized in that: The modified molecular sieve comprises a beta molecular sieve and an auxiliary component, wherein the auxiliary component is selected from at least one of alkali metals; Wherein, the index constant k of the modified molecular sieve is not less than 100; The indicator constant k is calculated by formula (1): k=Q / (1.4909×a -0.558 -c) Formula (1) Wherein, Q is the standard meta-xylene adsorption capacity per 100 g of modified molecular sieve, in g; a is the molar ratio of silicon oxide to aluminum oxide in the modified molecular sieve; and c is the molar number of the auxiliary component in terms of oxide per 100 g of modified molecular sieve.

2. The modified molecular sieve according to claim 1, wherein The index constant k of the modified molecular sieve is 100-550, preferably 101-500; Preferably, the standard meta-xylene adsorption capacity per 100 g of the modified molecular sieve is 17-33 g, preferably 18-31 g.

3. The modified molecular sieve according to claim 1 or 2, wherein: The auxiliary component is selected from sodium and / or potassium; Preferably, in 100 g of the modified molecular sieve, the molar amount of the auxiliary component calculated as oxide is 0.01-0.12 mol, preferably 0.02-0.1 mol.

4. The modified molecular sieve according to any one of claims 1 to 3, wherein: The molar ratio of silicon oxide to aluminum oxide in the modified molecular sieve is 20-250, preferably 25-200.

5. A method for preparing a modified molecular sieve, characterized in that: include: (1) preparing an impregnation solution comprising an organic salt of an auxiliary component and an organic solvent; The auxiliary agent component is selected from at least one of alkali metals; (2) impregnating the beta molecular sieve with the impregnation solution; (3) using an inactive fluid to purge and / or flush the product obtained in step (2) so that the organic salt of the auxiliary component reacts to form a macromolecular product containing the auxiliary component, and the molecular diameter of the macromolecular product containing the auxiliary component is larger than the pore diameter of the β molecular sieve, thereby obtaining a modified molecular sieve precursor; (4) calcining the modified molecular sieve precursor.

6. The preparation method according to claim 5, wherein: In step (3), the product obtained in step (2) is purged and / or flushed with an inactive fluid to cause the organic salt of the auxiliary component to undergo a self-polymerization reaction to form a macromolecular product containing the auxiliary component; or, The organic salt of the auxiliary component is added to the organic solvent to form a macromolecular product containing the auxiliary component.

7. A method for preparing a modified molecular sieve, characterized in that: The following steps are involved: (1) preparing an impregnation solution comprising an organic salt of an auxiliary component and an organic solvent; Wherein, the auxiliary agent component is selected from at least one of alkali metals; the organic solvent is a C6-C10 substituted or unsubstituted cyclic hydrocarbon compound; The organic salt of the auxiliary component contains a cyclic structure in its molecule and contains an unsaturated functional group capable of undergoing addition reaction with the cyclic hydrocarbon compound; (2) impregnating the beta molecular sieve with the impregnation solution; (3) using an inactive fluid having a temperature not lower than 80° C. to purge and / or rinse the product obtained in step (2), and then drying the product to obtain a modified molecular sieve precursor; (4) calcining the modified molecular sieve precursor.

8. The preparation method according to claim 7, wherein: The cyclic structure is selected from at least one of a saturated or unsaturated five-membered ring and a six-membered ring; preferably, the saturated or unsaturated five-membered ring and the six-membered ring are all composed of carbon atoms; Preferably, the unsaturated functional group is selected from carbon-carbon double bonds and / or carbon-carbon triple bonds.

9. The preparation method according to any one of claims 5 to 8, wherein: The organic salt of the auxiliary component contains at least one unsaturated six-membered ring in its molecule, preferably a benzene ring; Preferably, the molecular weight of the organic salt of the auxiliary component does not exceed 250 g / mol, preferably 50-220 g / mol; Preferably, the organic solvent is selected from at least one of benzene, cyclohexane, toluene, methylcyclopentane and cyclohexene.

10. The preparation method according to any one of claims 5 to 9, wherein: The structure of the organic salt of the auxiliary component is shown in formula (i); Among them, R1 is a C2-C4 alkenylene or alkynylene group, R2, R3, R4, R5, and R6 are each independently selected from at least one of a hydrogen atom and a C1-C3 hydrocarbon group; A1 is selected from -COO- or -SO3-; and M is selected from at least one of an alkali metal ion.

11. The preparation method according to claim 10, wherein: The R1 is at least one of vinylene, propenylene and butenylene; and / or, R2, R3, R4, R5, and R6 are each independently selected from at least one of a hydrogen atom and a C1-C3 hydrocarbon group; and / or, A1 is -COO-; and / or, M is selected from K + Or Na + .

12. The preparation method according to any one of claims 5 to 11, wherein: Based on the total amount of the impregnation liquid, the content of the organic salt of the auxiliary component is 0.1-10wt%, preferably 0.5-9wt%; the content of the organic solvent is 90-99.5wt%, preferably 90-99.5wt%; Preferably, relative to 1g of the Hβ molecular sieve, the amount of the impregnation solution is 4-10mL, preferably 5-8mL; Preferably, the immersion time is 1-10 hours, preferably 1-5 hours.

13. The preparation method according to any one of claims 5 to 12, wherein: At the end of purging and / or flushing, the content of cyclic hydrocarbon compounds in the outlet inactive fluid is not higher than 1 μg / L; Preferably, the inert fluid is selected from a gas or a liquid, preferably selected from at least one of nitrogen, argon, helium and neon; Preferably, the conditions for purging and / or flushing include: the temperature of the inactive fluid is 80-300°C, preferably 85-280°C, the volume space velocity is 100-3000h -1 , preferably 200-2000h -1 The purging and / or flushing time is 2-24 hours, preferably 3-20 hours.

14. The preparation method according to any one of claims 5 to 13, wherein: The calcination conditions include: a temperature of 300-800° C., preferably 400-700° C., and a calcination time of 2-24 hours, preferably 3-8 hours.

15. The modified molecular sieve obtained by the preparation method according to any one of claims 5 to 14.

16. A catalyst, characterized in that The catalyst comprises the modified molecular sieve according to any one of claims 1 to 4 and 15 and a binder.

17. The catalyst according to claim 16, wherein The binder is selected from at least one of alumina, bentonite, spinel and silicon oxide; Preferably, based on the total amount of the catalyst, the content of the modified molecular sieve is 55-85wt%, preferably 58-83wt%, and the content of the binder is 15-45wt%, preferably 17-42wt%; Preferably, the catalyst further comprises a second auxiliary component, wherein the second auxiliary component is a metal component and / or a non-metal component; Preferably, the metal component is selected from at least one of Group IA, Group IIA, Group IIIB, Group IVB, Group VIII, Group IB, and Group IIB metal elements, preferably at least one of Li, La, Ce, Mg, Ca, Ba, Cu, Zn, Zr, and Fe; Preferably, the non-metal component is selected from at least one of Group IIIA non-metal, Group IVA non-metal and Group VA non-metal elements, preferably at least one of Si, P, B and C; Preferably, based on the total amount of the catalyst, the content of the second auxiliary component is 0.1-5 wt % in terms of oxide.

18. The catalyst according to claim 16 or 17, wherein The specific surface area of ​​the catalyst is 250-650m 2 / g, preferably 300-600m 2 / g; Preferably, the specific pore volume of the catalyst is 0.2-0.55 mL / g, preferably 0.25-0.5 mL / g.

19. Use of the modified molecular sieve according to any one of claims 1 to 4 and 15 or the catalyst according to any one of claims 16 to 18 in aniline condensation reaction.

20. A method for synthesizing diphenylamine from aniline, characterized in that: The method comprises: contacting aniline with a catalyst under condensation reaction conditions; Wherein, the catalyst is the catalyst described in any one of claims 16-18.

21. The method according to claim 20, wherein: The condensation reaction conditions include: reaction pressure of 0.1-4 MPa, preferably 0.15-3.5 MPa; reaction temperature of 280-360° C., preferably 290-350° C.; aniline volume space velocity of 0.1-0.3 h -1 , preferably 0.15-0.25h -1 .

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