Phosphorus-modified dealuminated nano ZSM-5 molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a phosphorus-modified dealuminated nano ZSM-5 molecular sieve as well as a preparation method and application thereof. The surface of the ZSM-5 molecular sieve is subjected to dealumination and silicon enrichment treatment, and then the surface is protected through phosphorus modification, so that the stability of the molecular sieve can be effectively improved. The phosphorus-modified dealumination nanometer ZSM-5 molecular sieve catalyst solves the problems that in the prior art, a homogeneous catalyst kettle type isomerization reaction is high in corrosivity, the catalyst is difficult to regenerate, and a waste catalyst seriously pollutes the environment, the molecular sieve is used as the catalyst for a fixed bed isomerization reaction, continuous production is achieved, and the method is suitable for industrial production. Meanwhile, the preparation of the catalyst is simple and convenient, the requirements on reaction equipment are reduced, and the industrial production potential is relatively great.

Description

Technical Field

[0001] The invention belongs to the field of molecular sieve materials, and specifically relates to a phosphorus-modified dealuminated nano ZSM-5 molecular sieve and a preparation method and application thereof. Background Art

[0002] 1,3-Dichlorobenzene, also known as meta-dichlorobenzene, is an important organic chemical raw material and is widely used in the organic synthesis industry, such as the synthesis of 2,4-dichloroaniline, 1,2,4-trichlorobenzene and the broad-spectrum antifungal drug triconazole. With the growing development of the pharmaceutical industry and the introduction of new drugs, 1,3-dichlorobenzene is used as an intermediate for a variety of drugs. The production methods of 1,3-dichlorobenzene mainly include a multi-step synthesis method using meta-diphenylamine or meta-nitrobenzene as raw materials and a one-step synthesis method using dichlorobenzene as raw materials. The raw materials of this method are mainly dichlorobenzene prepared by chlorination. Usually, in dichlorobenzene prepared by chlorination, the total mass fraction of 1,2- and 1,4-dichlorobenzene is more than 97%. Therefore, the isomerization method can be used to further convert o- / p-dichlorobenzene into 1,3-dichlorobenzene.

[0003] The preparation of m-dichlorobenzene from the isomers of dichlorobenzene can be carried out using homogeneous and heterogeneous catalysts. The homogeneous catalyst has a low technical content and generally uses strong L-acidic aluminum chloride, HF-BF3 and other catalysts. Such catalysts react in an intermittent reactor and require special separation of the catalyst and the product. At the same time, the above catalysts can produce corrosive acid mist when in contact with water vapor in the air, which places high demands on the corrosion resistance of the equipment. At the same time, L-acid hydrates are difficult to dry, resulting in difficulty in catalyst regeneration. Waste catalysts will cause serious pollution to the environment, so they have gradually been replaced by new processes.

[0004] Heterogeneous reactions are mainly fixed-bed reactions catalyzed by zeolite molecular sieves. Molecular sieves have the advantages of regular pore structure, uniform pore size, adjustable acid site density, and shape-selective catalysis, and can significantly improve the environmental friendliness of the reaction process. Among them, ZSM-5 molecular sieves have a three-dimensional cross-pore structure and strong acidity, and show good catalytic performance in the alkylation, aromatization and isomerization reactions of aromatics. Its shape selectivity and anti-carbon deposition performance are more prominent in the above reactions, which is conducive to the improvement of reaction performance. Further reducing the grain size, the advantages of ZSM-5 molecular sieves will be further highlighted. Among them, nano ZSM-5 molecular sieves have a larger surface area, more exposed pores and available active sites, which are more conducive to the activation and further conversion of macromolecular compounds. The nano molecular sieves have short pores, which are conducive to the diffusion of reactant or product molecules in the pores, which can improve the reaction selectivity, shorten the residence time, reduce the probability of secondary reactions, and reduce carbon deposition. Normal silicon-aluminum molecular sieves have a relatively uniform distribution of aluminum species, which easily leads to a certain acidity on the outer surface. However, the shape selectivity of the acidic sites on the outer surface of the molecular sieve is poor. Therefore, dealumination and silicon enrichment treatment of the molecular sieve surface by certain means can be more conducive to improving the selectivity of the isomerization reaction. Summary of the invention

[0005] During the isomerization reaction of dichlorobenzene, as the reaction time increases, the occurrence of some side reactions easily leads to the dealumination of the molecular sieve catalyst, which gradually reduces the overall silicon-aluminum ratio of the molecular sieve and weakens the reaction activity. The present invention protects the molecular sieve surface by phosphorus modification, which can effectively improve the stability of the molecular sieve and extend the life of the catalyst.

[0006] One of the purposes of the present invention is to provide a phosphorus-modified dealuminated nano ZSM-5 molecular sieve, comprising a dealuminated nano ZSM-5 molecular sieve and a phosphorus-containing component on the surface of the molecular sieve, wherein the dealuminated nano ZSM-5 molecular sieve is a nano ZSM-5 molecular sieve with dealuminated surface.

[0007] According to the present invention, the phosphorus-modified dealuminated nano ZSM-5 molecular sieve has a surface phosphorus-to-aluminum ratio of 0.1 to 1.5, preferably 0.3 to 1, wherein the phosphorus-to-aluminum ratio is the molar ratio of phosphorus atoms to aluminum atoms; the phosphorus-modified dealuminated nano ZSM-5 molecular sieve has a surface silicon-to-aluminum ratio of 30 to 100, and a bulk silicon-to-aluminum ratio of 30 to 70% of the surface silicon-to-aluminum ratio; preferably, the surface silicon-to-aluminum ratio is 50 to 80, and the bulk silicon-to-aluminum ratio is 40 to 65% of the surface silicon-to-aluminum ratio, wherein the silicon-to-aluminum ratio is the molar ratio of the respective oxides.

[0008] According to the present invention, the specific surface area of ​​the phosphorus-modified dealuminated nano ZSM-5 molecular sieve is 450 to 700 m 2 ·g -1 , preferably 500-600m 2 ·g-1 .

[0009] According to the present invention, the phosphorus-modified dealuminated nano ZSM-5 molecular sieve is an MFI crystal phase structure, and preferably, the crystal size is 50 to 800 nm, preferably 200 to 600 nm.

[0010] The phosphorus modified dealuminated nano ZSM-5 molecular sieve provided by the present invention is obtained by subjecting the nano ZSM-5 molecular sieve to dealumination treatment with a dealuminizing agent, and then being modified with an organic phosphorus source and then calcined, wherein the nano ZSM-5 molecular sieve is prepared by a liquid phase directing agent method.

[0011] The second object of the present invention is to provide a method for preparing the above-mentioned phosphorus-modified dealuminated nano ZSM-5 molecular sieve, comprising: subjecting the nano ZSM-5 molecular sieve to dealumination treatment with a dealuminizing agent, and then subjecting the nano ZSM-5 molecular sieve to modification with an organic phosphorus source and then calcination, thereby obtaining the phosphorus-modified dealuminated nano ZSM-5 molecular sieve. Specifically, the method for preparing the phosphorus-modified dealuminated nano ZSM-5 molecular sieve comprises:

[0012] 1) Synthesis of directing agent:

[0013] a. Dispersing an aluminum source and sodium hydroxide in water to form an aluminum source solution;

[0014] b. Adding a silicon source to the aluminum source solution and stirring to form a silicon-alumina sol Ⅰ;

[0015] c. adding a template agent dropwise to the silica-alumina sol I to form a directing agent precursor, and aging the precursor;

[0016] d. The aged directing agent precursor is transferred to a crystallization reactor for pre-crystallization to obtain a directing agent;

[0017] e. The pre-crystallized directing agent is optionally subjected to ultrasonic oscillation before use;

[0018] 2) Synthesis of Nano ZSM-5 Molecular Sieve:

[0019] f. Prepare silica-alumina sol II in the same operation process as in step 1) a to b, add a directing agent to obtain a gel precursor;

[0020] g. aging the gel precursor;

[0021] h. The aged gel precursor is added to a crystallization kettle for crystallization reaction;

[0022] i. After the crystallization is completed, the nano ZSM-5 molecular sieve is obtained by filtration, washing and drying;

[0023] 3) Dealumination treatment:

[0024] j. The nano ZSM-5 molecular sieve is dispersed in water under stirring to form a slurry, and then a dealuminizing agent solution is added to carry out a dealuminizing reaction;

[0025] k. After the dealumination reaction, filtering, washing, drying and calcining are performed to obtain the dealumination nano ZSM-5 molecular sieve;

[0026] 4) Phosphorus modification treatment:

[0027] l. The organic phosphorus source is dissolved in an organic solvent, added dropwise to the dealuminated nano ZSM-5 molecular sieve by an equal volume impregnation method, and allowed to stand;

[0028] m. calcining the molecular sieve impregnated with the organic phosphorus source to obtain the phosphorus-modified dealuminated nano ZSM-5 molecular sieve.

[0029] According to the present invention, in the method for preparing the phosphorus-modified dealuminated nano ZSM-5 molecular sieve:

[0030] The aluminum source can be an aluminum-containing compound commonly used in the art for preparing molecular sieves, for example, the aluminum source is selected from at least one of aluminum hydroxide, sodium metaaluminate, and aluminum isopropoxide;

[0031] The silicon source may be a silicon-containing compound commonly used in the art for preparing molecular sieves, for example, the silicon source is selected from at least one of silica sol, water glass, and macroporous silica gel;

[0032] The template agent is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide and tetrapropylammonium bromide;

[0033] The dealumination agent is selected from at least one of hydrochloric acid, oxalic acid, citric acid, hydrofluoric acid and ammonium fluorosilicate;

[0034] The organic phosphorus source is selected from at least one of triphenylphosphine and triphenylphosphine oxide;

[0035] The organic solvent in step 1 is selected from at least one of methanol, ethanol and acetone.

[0036] According to the present invention, in the method for preparing the phosphorus-modified dealuminated nano ZSM-5 molecular sieve:

[0037] In the step 1), the mass ratio of the aluminum source, the silicon source, the sodium hydroxide, the template agent, and the water is 1: (15-100): (1-8): (5-25): (100-500), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O; preferably, the mass ratio of the aluminum source, the silicon source, the sodium hydroxide, the template agent, and the water is 1: (30-70): (1-5): (6-18): (150-400), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O;

[0038] In the silica-alumina sol II of step f, the mass ratio of the aluminum source, the silicon source, the sodium hydroxide and the water is 1: (15-100): (0.5-4.2): (100-750), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O; preferably, the mass ratio of the aluminum source, the silicon source, the sodium hydroxide and the water is 1: (30-70): (0.8-3): (300-600), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O;

[0039] In the step f, the amount of the directing agent added is 5 to 30 wt % of the total mass of the silica-alumina sol II, preferably 7 to 20 wt %;

[0040] In the step j, the mass ratio of the nano ZSM-5 molecular sieve and water can be adjusted within a wide range, for example, the mass ratio of the nano ZSM-5 molecular sieve and water is 1:(4-10);

[0041] The concentration of the dealumination agent solution can be adjusted within a wide range. For example, the concentration of the dealumination agent solution is 0.1 to 1 mol·L -1 ; The solvent in the dealuminant solution can be a common solvent, such as water;

[0042] The mass ratio of the nano ZSM-5 molecular sieve and the dealuminant solution can be adjusted within a wide range, for example, the mass ratio of the nano ZSM-5 molecular sieve and the dealuminant solution is 1:(5-50);

[0043] In the step 1, the amount of the organic phosphorus source can be adjusted according to actual needs. For example, the phosphorus in the organic phosphorus source is 0.5-10% of the mass of the dealuminated nano ZSM-5 molecular sieve.

[0044] According to the present invention, the preparation method of the phosphorus-modified dealuminated nano ZSM-5 molecular sieve can adopt the process conditions commonly used in the art, for example:

[0045] The stirring conditions in step b are: temperature of 20-60° C. and time of 1-5 h;

[0046] The aging conditions in step c are: temperature of 20-80° C., time of 4-24 h;

[0047] The pre-crystallization conditions in step d are: temperature of 150-180° C., time of 2-12 h;

[0048] The ultrasonic oscillation time in step e is 10 to 60 minutes;

[0049] The preparation conditions of the silica-alumina sol II in step f are: temperature of 20-60° C. and time of 1-5 h;

[0050] The aging conditions in step g are: temperature of 20-80° C., time of 1-8 h;

[0051] The conditions of the crystallization reaction in step h are: temperature of 150-180° C. and time of 8-48 hours;

[0052] The drying conditions in step i are: temperature of 80-120° C. and time of 4-24 h;

[0053] The conditions for the dealumination reaction in step j are: temperature of 50-90° C. and time of 1-4 h;

[0054] The drying conditions in step k are: temperature of 80-120° C. and time of 4-24 hours;

[0055] The calcination conditions in step k are: temperature of 350-500° C. and time of 1-6 hours;

[0056] In step 1, the step of standing is standing in the air until the solvent is completely volatilized, and the standing time is 8 to 24 hours;

[0057] The calcination conditions in step m are: calcination at 400-750° C. for 1-8 hours in a protective gas atmosphere.

[0058] The third object of the present invention is to provide an application of the phosphorus-modified dealuminated nano ZSM-5 molecular sieve or the phosphorus-modified dealuminated nano ZSM-5 molecular sieve obtained by the above preparation method in the preparation of 1,3-dichlorobenzene.

[0059] A fourth object of the present invention is to provide a method for preparing 1,3-dichlorobenzene by isomerization, comprising the step of contacting a raw material containing 1,2-dichlorobenzene and / or 1,4-dichlorobenzene with a catalyst to undergo an isomerization reaction to obtain 1,3-dichlorobenzene, wherein the catalyst contains the above-mentioned phosphorus-modified dealuminated nano ZSM-5 molecular sieve or the phosphorus-modified dealuminated nano ZSM-5 molecular sieve prepared by the above-mentioned preparation method.

[0060] According to the present invention, in the method for preparing 1,3-dichlorobenzene by isomerization:

[0061] In the raw material, the content of 1,2-dichlorobenzene and / or 1,4-dichlorobenzene is ≥95wt%;

[0062] The isomerization reaction conditions are: reaction temperature is 400-500°C, reaction liquid hourly space velocity is 0.8-1.2h -1 , the reaction pressure is 2~5MPa.

[0063] According to the present invention, after 120 hours of isomerization reaction, the bulk silicon-aluminum ratio of the phosphorus-modified dealuminated nano ZSM-5 molecular sieve increases by no more than 10%, and the XRD crystallinity decreases by no more than 10%.

[0064] The present invention provides a phosphorus-modified dealuminated nano ZSM-5 molecular sieve. The nano ZSM-5 molecular sieve is prepared by a liquid phase directing agent method, and the molecular sieve is dealuminated by a dealuminant, so that aluminum species on the surface of the molecular sieve can be selectively removed, the acid distribution of the molecular sieve is optimized, and the isomerization reaction performance of 1,2-dichlorobenzene and 1,4-dichlorobenzene can be improved to achieve high-efficiency production of 1,3-dichlorobenzene; then the surface is protected by phosphorus modification, which can effectively improve the stability of the molecular sieve and extend the life of the molecular sieve. The phosphorus-modified dealuminated nano ZSM-5 molecular sieve provided by the present invention has a simple preparation process, is easy to realize industrial production, and has excellent catalytic performance, is used for preparing 1,3-dichlorobenzene, and has a high 1,3-dichlorobenzene yield, thereby developing a more efficient and environmentally friendly fixed bed 1,2-dichlorobenzene and 1,4-dichlorobenzene isomerization reaction process for preparing 1,3-dichlorobenzene.

[0065] The present invention adopts a phosphorus-modified dealuminated nano ZSM-5 molecular sieve catalyst, which solves the problems of strong corrosion, difficult catalyst regeneration and serious environmental pollution of waste catalysts in the prior art in homogeneous catalyst autoclave isomerization reaction. The phosphorus-modified dealuminated nano ZSM-5 molecular sieve is used as a catalyst for fixed-bed isomerization reaction, thereby realizing continuous production and significantly improving environmental friendliness. At the same time, the catalyst is easy to prepare, and the requirements for reaction equipment are reduced, which is suitable for industrial production.

[0066] Compared with the kettle reaction, the isomerization reaction method of the present invention using phosphorus-modified dealuminated nano ZSM-5 molecular sieve as a catalyst has the characteristics of continuous production, high reaction efficiency, no need for catalyst separation, low equipment corrosion, etc., and the reaction cost is significantly reduced. It has strong 1,2-dichlorobenzene and 1,4-dichlorobenzene isomerization reaction performance, and also shows a higher 1,3-dichlorobenzene target product yield, which can effectively improve the economic value of the 1,3-dichlorobenzene reaction and has great industrial application potential. DETAILED DESCRIPTION

[0067] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0068] The test instruments and test conditions used in the examples are as follows:

[0069] Molecular sieve grain size: The molecular sieve grain size was measured using a scanning electron microscope. The instrument model is Quanta200F, the acceleration voltage is 200-300 kV, and the resolution is 1.2 nm. Experimental treatment: The dried sample was ground into fine particles, placed in a sample tray, and after gold spraying, the sample was purified under vacuum conditions and subjected to scanning tests.

[0070] Molecular sieve specific surface area: The specific surface area of ​​the catalyst was determined using a Micrometritics ASAP 2020M analyzer. The adsorbate was N2, which was adsorbed at liquid nitrogen temperature. The specific surface area of ​​the catalyst was calculated using the BET equation.

[0071] Molecular sieve silicon-aluminum ratio: The silicon-aluminum ratio on the catalyst surface was analyzed using a Perkin Elmer phi 5000c X-ray photoelectron spectrometer (XPS) with a Mg Kα X-ray source, an operating voltage of 15 kV, a current of 20 mA, and all energy spectra were calibrated using C1s of 284.8 eV as the standard.

[0072] The bulk silicon-to-aluminum ratio was analyzed by XRF, and the spectrometer was a Panalytical AxiosMax.

[0073] XRD crystallinity: The crystal structure of the catalyst was analyzed on a Bruker D8 Avance A25 X-ray diffractometer (XRD) with Cu Kα radiation (λ=0.15406 nm), tube voltage 40 kV, current 200 mA, scanning range 5-80°, and scanning rate 12° / min.

[0074] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0075] [Example 1]

[0076] Preparation of phosphorus modified dealuminated nano ZSM-5 molecular sieve

[0077] 1) Preparation of directing agent: Prepare a directing agent with a ratio of Al2O3:SiO2:Na2O:R:H2O of 1:30:2.2:12:200, and the template R is tetraethylammonium bromide. The specific steps are:

[0078] a. Disperse sodium aluminate and sodium hydroxide in water to form an aluminum source solution;

[0079] b. Add silica sol to the aluminum source solution and stir at 40°C for 2h to form silica-alumina sol I;

[0080] c. Add the template agent to the silica-alumina sol to form a directing agent precursor, and age it at 40°C for 12h;

[0081] d. The aged directing agent precursor was transferred to a crystallization reactor and pre-crystallized at 160°C for 2h;

[0082] e. The pre-crystallized directing agent was subjected to ultrasonic oscillation for 30 minutes before use.

[0083] 2) Synthesis of molecular sieve: The ratio of silica-alumina sol II is Al2O3:SiO2:Na2O:H2O=1:30:2.4:300.

[0084] f. According to the same operation process as a to b in 1), a silica-alumina sol II was prepared by stirring at 40°C for 2 h, and then a directing agent treated with ultrasonic oscillation was added thereto to obtain a gel precursor, wherein the directing agent was added in an amount of 15 wt% of the total weight of the silica-alumina sol II;

[0085] g. The gel precursor was aged at 40°C for 2h;

[0086] h. The aged gel precursor was added to a crystallization kettle and crystallized at 160°C for 48h;

[0087] i. After crystallization is completed, the nano ZSM-5 molecular sieve is obtained by filtration, washing and drying.

[0088] 3) Dealumination treatment:

[0089] j. The nano ZSM-5 molecular sieve was dispersed in water under stirring to form a slurry, and then a dealuminizing agent solution was added to carry out a dealuminizing reaction at 80°C for 2h. Oxalic acid was used as the dealuminizing agent, and the ratio of the nano ZSM-5 molecular sieve powder to the dealuminizing agent solution was 1:8. The concentration of the dealuminizing agent solution was 0.75 mol·L -1 ;

[0090] k. After the dealumination reaction, the product was filtered, washed, dried at 110°C for 4 h, and calcined at 450°C for 4 h to obtain the dealumination-modified nano ZSM-5 molecular sieve.

[0091] 4) Phosphorus modification:

[0092] 1. Dissolve the required amount of organic phosphorus source in an appropriate amount of organic solvent, add the dealuminated nano ZSM-5 molecular sieve dropwise by equal volume impregnation method, and then stand at room temperature in air for 16 hours until the solvent is completely volatilized; use triphenylphosphine as the phosphorus source and acetone as the solvent, dissolve the phosphorus source at a mass ratio of 1% of P species to molecular sieve, and then impregnate with equal volume;

[0093] m. After the solvent is completely evaporated, the impregnated molecular sieve is transferred into a tube furnace and calcined at 650° C. for 4 h under an Ar atmosphere to obtain the molecular sieve.

[0094] The obtained molecular sieve has a grain size of 450nm and a specific surface area of ​​533.2m 2 ·g -1 The bulk silicon-aluminum ratio is 28, the surface silicon-aluminum ratio is 62, and the surface phosphorus-aluminum ratio is 0.35.

[0095] Evaluation of catalytic performance of phosphorus-modified dealuminated nano ZSM-5 molecular sieves

[0096] The catalyst performance of the present invention is evaluated by The reaction is carried out in a fixed bed reactor with a length of 800 mm, a catalyst loading of 1 g, and a reaction system pressure of 2 to 5 MPa.

[0097] The conversion rate of dichlorobenzene and the yield of 1,3-dichlorobenzene are defined as follows:

[0098]

[0099]

[0100] After tableting and screening, 40-60 mesh particles were selected for reaction evaluation. The reaction temperature was 420°C, the reaction pressure was 3 MPa, and the air velocity was 1 h -1 , the content of the mixed dichlorobenzene raw material is 70% 1,4-dichlorobenzene and 30% 1,2-dichlorobenzene. After the reaction, the total conversion rate of dichlorobenzene is 83.0%, the conversion rate of 1,4-dichlorobenzene is 77.4%, the content of 1,2-dichlorobenzene is 96.0%, and the yield of 1,3-dichlorobenzene is 79.6%.

[0101] After 120 hours of reaction, the silicon-aluminum ratio of the catalyst bulk phase was 30, and the XRD crystallinity retention was 92%.

[0102] [Example 2]

[0103] Preparation of phosphorus modified dealuminated nano ZSM-5 molecular sieve

[0104] The preparation process is the same as in Example 1, except that:

[0105] 1) Preparation of directing agent: The directing agent ratio is Al2O3:SiO2:Na2O:R:H2O=1:40:2.2:12:200, and the template is tetraethylammonium hydroxide. The stirring time is 2 hours, the temperature is 40°C, the aging time is 16 hours, and then pre-crystallization is carried out at 160°C for 1 hour. After obtaining the directing agent, ultrasonic treatment is performed for 45 minutes.

[0106] 2) Synthesis of molecular sieve: The ratio of silica-alumina sol II is Al2O3:SiO2:Na2O:H2O=1:40:2.4:300. The stirring time is 2 hours, the temperature is 40°C, the amount of directing agent added is 12wt% of the total weight of silica-alumina sol II, the aging time is 5 hours, and then crystallization is carried out at 160°C for 48 hours.

[0107] 3) Dealumination treatment: hydrochloric acid is used as the dealumination agent, the ratio of molecular sieve powder to water is 1:10; the concentration of the treatment solution is 0.5 mol·L -1 ; Treatment temperature is 60℃; Treatment time is 4h; Calcination temperature is 400℃; Calcination time is 3h.

[0108] 4) Phosphorus modification: triphenylphosphine oxide was used as the phosphorus source and acetone was used as the solvent. The phosphorus source was dissolved in a mass ratio of 6% between P species and molecular sieves, and then equal volumes were impregnated and allowed to stand at room temperature for 16 h. After the sample was dried, it was calcined at 650°C in an Ar atmosphere for 4 h.

[0109] The obtained molecular sieve has a grain size of 400 nm and a specific surface area of ​​545.1 m 2 ·g -1 The bulk silicon-aluminum ratio is 33, the surface silicon-aluminum ratio is 61, and the surface phosphorus-aluminum ratio is 0.54.

[0110] Evaluation of catalytic performance of phosphorus-modified dealuminated nano ZSM-5 molecular sieves

[0111] The evaluation method is the same as in Example 1, except that the reaction temperature is 400°C, the reaction pressure is 4 MPa, and the space velocity is 1 h -1 After the reaction, the total conversion rate of dichlorobenzene was 81.0%, the conversion rate of 1,4-dichlorobenzene was 73.6%, the content of 1,2-dichlorobenzene was 98.3%, and the yield of 1,3-dichlorobenzene was 78.4%.

[0112] After 120 hours of reaction, the silicon-aluminum ratio of the catalyst bulk phase was 34, and the XRD crystallinity retention was 97%.

[0113] [Example 3]

[0114] Preparation of phosphorus modified dealuminated nano ZSM-5 molecular sieve

[0115] 1) Preparation of directing agent: The directing agent ratio is Al2O3:SiO2:Na2O:R:H2O=1:65:2.4:12:200, and the template is tetrapropylammonium bromide. The stirring time is 2 hours, the temperature is 40°C, the aging time is 8 hours, and then pre-crystallization is carried out at 160°C for 2 hours. After obtaining the directing agent, ultrasonic treatment is carried out for 60 minutes.

[0116] 2) Synthesis of molecular sieve: The gel ratio is Al2O3:SiO2:Na2O:H2O=1:65:1.6:400. The stirring time is 1 hour, the temperature is 60°C, the amount of directing agent added is 10wt% of the total weight of silica-alumina sol II, the aging time is 1 hour, and then crystallization is carried out at 160°C for 72 hours.

[0117] 3) Dealumination treatment: citric acid was used as the dealumination agent, the ratio of molecular sieve powder to water was 1:6; the concentration of the treatment solution was 1.0 mol·L -1 ; Treatment temperature is 85℃; Treatment time is 4h; Calcination temperature is 480℃; Calcination time is 4h.

[0118] 4) Phosphorus modification: triphenylphosphine was used as the phosphorus source and ethanol as the solvent. The phosphorus source was dissolved in an 8% mass ratio of P species to molecular sieve and then impregnated with equal volumes and allowed to stand at room temperature for 16 h. After the sample was dried, it was calcined at 550°C for 3 h in a N2 atmosphere.

[0119] The obtained molecular sieve has a crystal size of 510 nm and a specific surface area of ​​552 m 2 ·g -1 The bulk silicon-aluminum ratio is 43, the surface silicon-aluminum ratio is 71, and the surface phosphorus-aluminum ratio is 0.66.

[0120] Evaluation of catalytic performance of phosphorus-modified dealuminated nano ZSM-5 molecular sieves

[0121] The evaluation method is the same as in Example 1, except that the reaction temperature is 460°C, the reaction pressure is 3 MPa, and the space velocity is 0.8 h -1 After the reaction, the total conversion rate of dichlorobenzene was 86.4%, the conversion rate of 1,4-dichlorobenzene was 85.4%, the content of 1,2-dichlorobenzene was 88.7%, and the yield of 1,3-dichlorobenzene was 75.3%.

[0122] After 120 hours of reaction, the silicon-aluminum ratio of the catalyst bulk phase was 46, and the XRD crystallinity retention was 99%.

[0123] [Example 4]

[0124] Preparation of phosphorus-modified dealuminated nano ZSM-5 molecular sieve:

[0125] 1) Preparation of directing agent: The directing agent ratio is Al2O3:SiO2:Na2O:R:H2O=1:30:1.2:12:300, and the template is tetrapropylammonium bromide. The stirring time is 2 hours, the temperature is 40°C, the aging time is 8 hours, and then pre-crystallization is carried out at 160°C for 2 hours. After obtaining the directing agent, ultrasonic treatment is performed for 60 minutes.

[0126] 2) Synthesis of molecular sieve: The gel ratio is Al2O3:SiO2:Na2O:H2O=1:65:1.6:500. The stirring time is 1 hour, the temperature is 60°C, the amount of directing agent added is 10wt% of the total weight of silica-alumina sol II, the aging time is 1 hour, and then crystallization is carried out at 160°C for 72 hours.

[0127] 3) Dealumination treatment: Oxalic acid was used as the dealumination agent, the ratio of molecular sieve powder to water was 1:8; the concentration of the treatment solution was 0.75 mol·L -1 ; Treatment temperature is 80℃; Treatment time is 2h; Calcination temperature is 450℃; Calcination time is 4h.

[0128] 4) Phosphorus modification: triphenylphosphine was used as the phosphorus source and acetone as the solvent. The phosphorus source was dissolved in a mass ratio of 3.5% between P species and molecular sieve, and then equal volumes were impregnated and allowed to stand at room temperature for 16 h. After the sample was dried, it was calcined at 550 °C for 3 h in a N2 atmosphere.

[0129] The obtained molecular sieve has a crystal size of 540 nm and a specific surface area of ​​562.1 m 2 ·g -1 The bulk silicon-aluminum ratio is 28, the surface silicon-aluminum ratio is 66, and the surface phosphorus-aluminum ratio is 0.41.

[0130] Evaluation of catalytic performance of phosphorus-modified dealuminated nano ZSM-5 molecular sieves

[0131] The evaluation method is the same as in Example 1, the reaction temperature is 420°C, the reaction pressure is 3 MPa, and the space velocity is 1 h -1 After the reaction, the total conversion rate of dichlorobenzene was 81.7%, the conversion rate of 1,4-dichlorobenzene was 78.9%, the content of 1,2-dichlorobenzene was 88.3%, and the yield of 1,3-dichlorobenzene was 76.9%.

[0132] After 120 hours of reaction, the silicon-aluminum ratio of the catalyst body was 30, and the XRD crystallinity retention was 99%.

[0133] [Example 5]

[0134] Preparation of phosphorus-modified dealuminated nano ZSM-5 molecular sieve:

[0135] 1) Preparation of directing agent: The directing agent ratio is Al2O3:SiO2:Na2O:R:H2O=1:30:2.2:12:200, and the template is tetraethylammonium bromide. The stirring time is 2 hours, the temperature is 40°C, the aging time is 12 hours, and then pre-crystallization is carried out at 160°C for 2 hours. After obtaining the directing agent, ultrasonic treatment is performed for 30 minutes.

[0136] 2) Synthesis of molecular sieve: The gel ratio is Al2O3:SiO2:Na2O:H2O=1:30:2.4:300. The stirring time is 2 hours, the temperature is 40°C, the amount of directing agent added is 15wt% of the total weight of silica-alumina sol II, the aging time is 2 hours, and then crystallization is carried out at 160°C for 48 hours.

[0137] 3) Dealumination treatment: hydrofluoric acid is used as the dealumination agent, the ratio of molecular sieve powder to water is 1:8; the concentration of the treatment solution is 0.1 mol·L -1 ; Treatment temperature is 50℃; Treatment time is 2h; Calcination temperature is 450℃; Calcination time is 4h.

[0138] 4) Phosphorus modification: triphenylphosphine was used as the phosphorus source and acetone as the solvent. The phosphorus source was dissolved in a mass ratio of 2.5% between P species and molecular sieve, and then equal volumes were impregnated and allowed to stand at room temperature for 16 h. After the sample was dried, it was calcined at 550 °C for 2 h in a N2 atmosphere.

[0139] The obtained molecular sieve has a grain size of 410 nm and a specific surface area of ​​533.2 m 2 ·g -1 The bulk silicon-aluminum ratio is 31, the surface silicon-aluminum ratio is 56, and the surface phosphorus-aluminum ratio is 0.47.

[0140] Evaluation of catalytic performance of phosphorus-modified dealuminated nano ZSM-5 molecular sieves

[0141] The evaluation method is the same as in Example 1, the reaction temperature is 420°C, the reaction pressure is 3 MPa, and the space velocity is 1 h -1 After the reaction, the total conversion rate of dichlorobenzene was 85.1%, the conversion rate of 1,4-dichlorobenzene was 59.5%, the content of 1,2-dichlorobenzene was 25.6%, and the yield of 1,3-dichlorobenzene was 79.8%.

[0142] After 120 hours of reaction, the silicon-aluminum ratio of the catalyst bulk phase was 33, and the XRD crystallinity retention was 96%.

[0143] [Example 6]

[0144] Preparation of phosphorus-modified dealuminated nano ZSM-5 molecular sieve:

[0145] 1) Preparation of directing agent: The directing agent ratio is Al2O3:SiO2:Na2O:R:H2O=1:40:3.3:12:400, and the template is tetrapropylammonium hydroxide. The stirring time is 2 hours, the temperature is 40°C, the aging time is 16 hours, and then pre-crystallization is carried out at 160°C for 1 hour. After obtaining the directing agent, ultrasonic treatment is performed for 15 minutes.

[0146] 2) Synthesis of molecular sieve: The gel ratio is Al2O3:SiO2:Na2O:H2O=1:40:2.0:500. The stirring time is 2 hours, the temperature is 40°C, the amount of directing agent added is 12wt% of the total weight of silica-alumina sol II, the aging time is 2 hours, and then crystallization is carried out at 160°C for 48 hours.

[0147] 3) Dealumination treatment: ammonium fluorosilicate was used as the dealumination agent, the ratio of molecular sieve powder to water was 1:8; the concentration of the treatment solution was 0.2 mol·L -1 ; Treatment temperature is 60℃; Treatment time is 4h; Calcination temperature is 500℃; Calcination time is 4h.

[0148] 4) Phosphorus modification: triphenylphosphine was used as the phosphorus source and acetone as the solvent. The phosphorus source was dissolved in a mass ratio of 1.0% between the P species and the molecular sieve, and then equal volumes were impregnated and allowed to stand at room temperature for 16 h. After the sample was dried, it was calcined at 700°C in a He atmosphere for 4 h.

[0149] The obtained molecular sieve has a grain size of 410 nm and a specific surface area of ​​517.8 m 2 ·g -1 The bulk silicon-aluminum ratio is 34, the surface silicon-aluminum ratio is 72, and the surface phosphorus-aluminum ratio is 0.30.

[0150] Evaluation of catalytic performance of phosphorus-modified dealuminated nano ZSM-5 molecular sieves

[0151] The evaluation method is the same as in Example 1, except that the reaction temperature is 450°C, the reaction pressure is 4 MPa, and the space velocity is 1 h -1 After the reaction, the total conversion rate of dichlorobenzene was 80.1%, the conversion rate of 1,4-dichlorobenzene was 79.0%, the content of 1,2-dichlorobenzene was 82.7%, and the yield of 1,3-dichlorobenzene was 78.8%.

[0152] After 120 hours of reaction, the silicon-aluminum ratio of the catalyst body was 35, and the XRD crystallinity retention was 91%.

[0153] [Comparative Example 1]

[0154] Preparation of phosphorus-modified dealuminated HZSM-5 molecular sieve:

[0155] 1) Synthesis of molecular sieve: The gel ratio is Al2O3:SiO2:Na2O:H2O=1:30:2.3:360. The stirring time is 2 hours, the temperature is 60°C, and the ground HZSM-5 molecular sieve is added as a seed crystal in an amount of 2% of the weight of the molecular sieve gel. The aging time is 4 hours, and then crystallization is carried out at 160°C for 48 hours.

[0156] 2) Dealumination treatment: Oxalic acid was used as the dealumination agent, the ratio of molecular sieve powder to water was 1:8; the concentration of the treatment solution was 0.75 mol·L -1 ; Treatment temperature is 80℃; Treatment time is 2h; Calcination temperature is 450℃; Calcination time is 4h.

[0157] 3) Phosphorus modification: phosphoric acid was used as the phosphorus source and water as the solvent. The phosphorus source was dissolved in a mass ratio of 1.0% between the P species and the molecular sieve, and then an equal volume was impregnated and allowed to stand at room temperature for 24 hours. After the sample was dried, it was calcined at 550°C in a He atmosphere for 4 hours.

[0158] The obtained molecular sieve has a grain size of 2000nm and a specific surface area of ​​436.9m 2 ·g -1 The bulk silicon-aluminum ratio is 26, the surface silicon-aluminum ratio is 28, and the surface phosphorus-aluminum ratio is 0.37.

[0159] Evaluation of Catalytic Performance of Phosphorus Modified Dealuminated ZSM-5 Molecular Sieves

[0160] The evaluation method is the same as in Example 1, the reaction temperature is 420°C, the reaction pressure is 3 MPa, and the space velocity is 1 h -1 After the reaction, the total conversion rate of dichlorobenzene was 82.0%, the conversion rate of 1,4-dichlorobenzene was 80.9%, the content of 1,2-dichlorobenzene was 84.7%, and the yield of 1,3-dichlorobenzene was 70.4%.

[0161] After 120 hours of reaction, the bulk silicon-aluminum ratio of the catalyst was 30, and the XRD crystallinity retention was 85%.

[0162] [Comparative Example 2]

[0163] Preparation of Nano ZSM-5 Molecular Sieve:

[0164] 1) Preparation of directing agent: The directing agent ratio is Al2O3:SiO2:Na2O:R:H2O=1:30:2.2:12:200, and the template is tetraethylammonium bromide. The stirring time is 2 hours, the temperature is 40°C, the aging time is 12 hours, and then pre-crystallization is carried out at 160°C for 2 hours. After obtaining the directing agent, ultrasonic treatment is performed for 30 minutes.

[0165] 2) Synthesis of molecular sieve: The gel ratio is Al2O3:SiO2:Na2O:H2O=1:30:2.4:300. The stirring time is 2 hours, the temperature is 40°C, the amount of directing agent added is 15wt% of the total weight of the gel, the aging time is 2 hours, and then crystallization is carried out at 160°C for 48 hours.

[0166] 3) Dealumination treatment: The ZSM-5 molecular sieve was dispersed in water under stirring to form a slurry, and then a dealumination agent solution was added to carry out a dealumination reaction at 80°C for 2h; hydrofluoric acid was used as the dealumination agent, and the ratio of nano ZSM-5 molecular sieve raw powder to water was 1:8; the concentration of the dealumination agent solution was 0.15mol·L-1;

[0167] The obtained molecular sieve has a grain size of 560nm and a specific surface area of ​​567.5m 2 ·g -1 The bulk silicon-aluminum ratio is 24, and the surface silicon-aluminum ratio is 27.

[0168] Evaluation of Catalytic Performance of Nano-ZSM-5 Molecular Sieve

[0169] The evaluation method is the same as in Example 1, the reaction temperature is 420°C, the reaction pressure is 3 MPa, and the space velocity is 1 h -1 After the reaction, the total conversion rate of dichlorobenzene was 85.6%, the conversion rate of 1,4-dichlorobenzene was 83.9%, the content of 1,2-dichlorobenzene was 79.7%, and the yield of 1,3-dichlorobenzene was 71.3%.

Claims

1. A phosphorus-modified dealuminated nano ZSM-5 molecular sieve, comprising a dealuminated nano ZSM-5 molecular sieve and a phosphorus-containing component on the surface of the molecular sieve, wherein the dealuminated nano ZSM-5 molecular sieve is a nano ZSM-5 molecular sieve with dealuminated surface.

2. The molecular sieve according to claim 1, characterized in that The phosphorus-modified dealuminated nano ZSM-5 molecular sieve has a surface phosphorus-to-aluminum ratio of 0.1 to 1.5, preferably 0.3 to 1, wherein the phosphorus-to-aluminum ratio is the molar ratio of phosphorus atoms to aluminum atoms; and / or, The phosphorus-modified dealuminated nano ZSM-5 molecular sieve has a surface silicon-aluminum ratio of 30 to 100, and a bulk silicon-aluminum ratio of 30 to 70% of the surface silicon-aluminum ratio; preferably, the surface silicon-aluminum ratio is 50 to 80, and the bulk silicon-aluminum ratio is 40 to 65% of the surface silicon-aluminum ratio, wherein the silicon-aluminum ratio is the molar ratio of the respective oxides; and / or, The specific surface area of ​​the phosphorus-modified dealuminated nano ZSM-5 molecular sieve is 450 to 700 m 2 ·g -1 , preferably 500-600m 2 ·g -1 and / or, The phosphorus-modified dealuminated nano ZSM-5 molecular sieve has an MFI crystal phase structure, and preferably has a grain size of 50 to 800 nm, preferably 200 to 600 nm.

3. A method for preparing the phosphorus-modified dealuminated nano ZSM-5 molecular sieve according to claim 1 or 2, comprising: The nano ZSM-5 molecular sieve is dealuminated by a dealuminizing agent, and then modified by an organic phosphorus source and calcined to obtain the phosphorus-modified dealuminized nano ZSM-5 molecular sieve.

4. The preparation method according to claim 3, characterized in that: The preparation method of the phosphorus-modified dealuminated nano ZSM-5 molecular sieve comprises: 1) Synthesis of directing agent: a. Dispersing an aluminum source and sodium hydroxide in water to form an aluminum source solution; b. Adding a silicon source to the aluminum source solution and stirring to form a silicon-alumina sol Ⅰ; c. adding a template agent dropwise to the silica-alumina sol I to form a directing agent precursor, and aging the precursor; d. The aged directing agent precursor is transferred to a crystallization reactor for pre-crystallization to obtain a directing agent; e. The pre-crystallized directing agent is optionally subjected to ultrasonic oscillation before use; 2) Synthesis of Nano ZSM-5 Molecular Sieve: f. Prepare silica-alumina sol II in the same operation process as in step 1) a to b, add a directing agent to obtain a gel precursor; g. aging the gel precursor; h. The aged gel precursor is added to a crystallization reactor for crystallization reaction; i. After the crystallization is completed, the nano ZSM-5 molecular sieve is obtained by filtration, washing and drying; 3) Dealumination treatment: j. The nano ZSM-5 molecular sieve is dispersed in water under stirring to form a slurry, and then a dealuminizing agent solution is added to carry out a dealuminizing reaction; k. After the dealumination reaction, filtering, washing, drying and calcining are performed to obtain the dealumination nano ZSM-5 molecular sieve; 4) Phosphorus modification treatment: l. The organic phosphorus source is dissolved in an organic solvent, added dropwise to the dealuminated nano ZSM-5 molecular sieve by an equal volume impregnation method, and allowed to stand; m. calcining the molecular sieve impregnated with the organic phosphorus source to obtain the phosphorus-modified dealuminated nano ZSM-5 molecular sieve.

5. The preparation method according to claim 4, characterized in that: The aluminum source is selected from at least one of aluminum hydroxide, sodium metaaluminate, and aluminum isopropoxide; and / or, The silicon source is selected from at least one of silica sol, water glass and macroporous silica gel; and / or, The template is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide and tetrapropylammonium bromide; and / or, The dealumination agent is selected from at least one of hydrochloric acid, oxalic acid, citric acid, hydrofluoric acid and ammonium fluorosilicate; and / or, The organic phosphorus source is selected from at least one of triphenylphosphine and triphenylphosphine oxide; and / or, The organic solvent in step 1 is selected from at least one of methanol, ethanol and acetone.

6. The preparation method according to claim 4, characterized in that: In the step 1), the mass ratio of the aluminum source, the silicon source, the sodium hydroxide, the template agent, and the water is 1: (15-100): (1-8): (5-25): (100-500), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O; preferably, the mass ratio of the aluminum source, the silicon source, the sodium hydroxide, the template agent, and the water is 1: (30-70): (1-5): (6-18): (150-400), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O; and / or, In the silica-alumina sol II of step f, the mass ratio of the aluminum source, the silicon source, the sodium hydroxide and the water is 1: (15-100): (0.5-4.2): (100-750), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O; preferably, the mass ratio of the aluminum source, the silicon source, the sodium hydroxide and the water is 1: (30-70): (0.8-3): (300-600), wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the sodium hydroxide is calculated as Na2O; and / or, In the step f, the amount of the directing agent added is 5-30wt% of the total mass of the silica-alumina sol II, preferably 7-20wt%; and / or, In the step j, the mass ratio of nano ZSM-5 molecular sieve to water is 1:(4-10); and / or, The concentration of the dealuminant solution is 0.1 to 1 mol·L -1 and / or, The mass ratio of the nano ZSM-5 molecular sieve to the dealumination agent solution is 1:(5-50); and / or, In the step 1, the phosphorus in the organic phosphorus source is 0.5-10% of the mass of the dealuminated nano ZSM-5 molecular sieve.

7. The preparation method according to claim 4, characterized in that: The stirring conditions in step b are: temperature of 20 to 60° C., and / or time of 1 to 5 hours; and / or, The aging conditions in step c are: a temperature of 20 to 80° C., and / or a time of 4 to 24 hours; and / or, The pre-crystallization conditions in step d are: temperature of 150-180° C., and / or time of 2-12 h; and / or, The ultrasonic oscillation time in step e is 10 to 60 minutes; and / or, The preparation conditions of the silica-alumina sol II in step f are: temperature of 20-60° C., and / or time of 1-5 h; and / or, The aging conditions in step g are: a temperature of 20 to 80° C., and / or a time of 1 to 8 hours; and / or, The conditions of the crystallization reaction in step h are: temperature of 150-180° C., and / or time of 8-48 hours; and / or, The drying conditions in step i are: a temperature of 80 to 120° C., and / or a drying time of 4 to 24 hours; and / or, The conditions for the dealumination reaction in step j are: a temperature of 50 to 90° C., and / or a time of 1 to 4 hours; and / or, The drying conditions in step k are: a temperature of 80 to 120° C., and / or a drying time of 4 to 24 hours; and / or, The calcination conditions in step k are: a temperature of 350 to 500° C., and / or a time of 1 to 6 hours; and / or, The calcination conditions in step m are: calcination at 400-750° C. for 1-8 hours in a protective gas atmosphere.

8. Use of the phosphorus-modified dealuminated nano ZSM-5 molecular sieve according to claim 1 or 2, or the phosphorus-modified dealuminated nano ZSM-5 molecular sieve obtained by the preparation method according to any one of claims 3 to 7, in the preparation of 1,3-dichlorobenzene.

9. A method for preparing 1,3-dichlorobenzene by isomerization, comprising the step of contacting a raw material containing 1,2-dichlorobenzene and / or 1,4-dichlorobenzene with a catalyst to undergo an isomerization reaction to obtain 1,3-dichlorobenzene, wherein the catalyst contains the phosphorus-modified dealuminated nano ZSM-5 molecular sieve according to claim 1 or 2 or the phosphorus-modified dealuminated nano ZSM-5 molecular sieve obtained by the preparation method according to any one of claims 3 to 7.

10. The method according to claim 9, characterized in that In the raw material, the content of 1,2-dichlorobenzene and / or 1,4-dichlorobenzene is ≥ 95wt%; and / or, The isomerization reaction conditions are: reaction temperature of 400-500°C, and / or reaction liquid hourly space velocity of 0.8-1.2h -1 , and / or, the reaction pressure is 2 to 5 MPa.

11. The method according to claim 9, characterized in that After 120 hours of isomerization reaction, the silicon-aluminum ratio of the phosphorus-modified dealuminated nano ZSM-5 molecular sieve body phase increases by no more than 10%, and the XRD crystallinity decreases by no more than 10%.

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