An aromatic gas-phase ammoxidation catalyst, its preparation method and use
By preparing highly crystalline V, Al, and P molecular sieves as the active phase of the catalyst, the problems of insufficient catalyst wear resistance and reaction performance in fluidized bed reactors were solved, and high-yield production of aromatic nitrile was achieved, which is especially suitable for fluidized bed reactors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-10-20
- Publication Date
- 2026-07-28
AI Technical Summary
Existing aromatic gas-phase ammonia oxidation catalysts have insufficient wear resistance and reaction performance in fluidized bed reactors, and poor adaptability to various aromatic feedstocks.
A molecular sieve containing V, Al, P, and O was used as the active phase of the catalyst and prepared by hydrothermal crystallization. A sol-state vanadium source was used as raw material and loaded onto a support by spray drying. The composition and crystallinity of the molecular sieve were optimized to improve the anti-wear performance and reactivity of the catalyst.
It significantly improves the catalyst's anti-wear properties and adaptability to different aromatic feedstocks, and increases the yield of aromatic nitriles. It is especially suitable for fluidized bed reactors, where the yield of aromatic nitriles can reach over 80%.
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Figure CN117917280B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aromatic hydrocarbon ammonia oxidation, specifically relating to an aromatic hydrocarbon gas-phase ammonia oxidation catalyst, its preparation method, and its application. Background Technology
[0002] Cyano-substituted aromatics, also known as aromatic nitriles, are important fine chemical raw materials. Aromatic nitriles can be synthesized via two routes: ammonia oxidation and chemical methods. The ammonia oxidation method uses methyl-substituted aromatics and ammonia as raw materials, with air as the oxygen source. The nitrile is obtained in one step through the action of a catalyst. This method is simple, has a high yield, and is the most suitable method for the industrial production of aromatic nitriles. The gas-phase ammonia oxidation reaction of aromatics is highly exothermic, therefore effective heat removal measures are necessary. Fluidized bed reactors have advantages such as easy heat removal and low scale-up effect, giving them a significant advantage. However, the catalyst in a fluidized bed reactor undergoes intense collisions; therefore, wear resistance is one of the core indicators for ensuring the catalyst's suitability for this reaction.
[0003] Vanadium oxides have long been the most mature and effective system for fluidized bed catalysts used in the gas-phase ammonia oxidation of aromatics to aromatic nitrile. Fluidized bed reactors typically use vanadium oxides supported on carriers such as SiO2 and Al2O3 as catalysts. By adding modifying components and auxiliary metals, multi-component vanadium oxide catalysts can be prepared, overcoming the problems of excessive oxidation and low selectivity associated with pure vanadium oxides, while significantly improving catalyst strength.
[0004] In the 1980s, Mitsubishi Gas Industries of Japan introduced V-Cr-B-Mo and V-Cr-BP system catalysts, and then in the 1990s introduced V-Cr-BP-Mo five-component catalysts to improve reaction selectivity; BASF reported K, Fe, W modified V-Sb system fixed bed catalysts; Shanghai Petrochemical Research Institute developed multi-element modified fluidized bed catalysts based on the V-Cr system, with a molar yield of isophthalonitrile of about 78.8%.
[0005] CN201210240053.1 discloses a method for preparing o-chlorobenzonitrile, which employs a fluidized bed catalyst with silica as a support, and the active component having the general formula VP on an atomic ratio basis. a X b Y c Z d O m In a technical scheme where X is selected from at least one oxide of B or As; Y is selected from at least one oxide of alkali metal or alkaline earth metal; and Z is selected from at least one oxide of metal of Ni, Co, Pb, Fe, Mo or W, the resulting catalyst can be used for the industrial production of o-chlorobenzonitrile.
[0006] The catalysts reported in the aforementioned literature have improved their wear resistance and activity through methods such as using wear-resistant supports and adding additives, but these still do not reach satisfactory levels. For aromatic ammonia oxidation catalysts, especially those suitable for fluidized bed reactors, there is still room for improvement in their wear resistance and reaction performance, and their adaptability to various aromatic feedstocks needs to be enhanced. Summary of the Invention
[0007] To address the problems existing in the prior art, this invention provides a gas-phase ammonia oxidation catalyst for aromatics, its preparation method, and its application. This catalyst is suitable for the industrial production of aromatic nitrile preparation via gas-phase ammonia oxidation of aromatics. It features a simple preparation process, good adaptability to raw materials and aromatic nitriles, wear resistance, high catalytic activity, and high aromatic nitrile yield. It is particularly suitable for the ammonia oxidation of aromatics to aromatic nitriles in a fluidized bed reactor.
[0008] The first aspect of the present invention provides a molecular sieve comprising V, Al, P, O and optionally Si; the composition of the molecular sieve comprises, as oxides, 0.1 wt% to 10 wt% V2O5, 40 wt% to 48 wt% Al2O3, 40 wt% to 55 wt% P2O5, and 0 to 19% SiO2.
[0009] According to the present invention, the structure of the molecular sieve includes at least one of the following: AFI structure, AEL structure, and CHI structure.
[0010] According to the present invention, the vanadium element in the framework of the molecular sieve, calculated as V2O5, accounts for more than 80 wt% of all V elements in the molecular sieve, preferably 80 wt% to 97 wt%.
[0011] According to the present invention, the relative crystallinity of the molecular sieve is 80% to 110%.
[0012] According to the present invention, the specific surface area of the molecular sieve is 180–350 m². 2 ·g -1 .
[0013] According to the present invention, the molecular sieve can be used for the gas-phase ammonia oxidation reaction of aromatics.
[0014] According to the present invention, the molecular sieve is prepared by hydrothermal crystallization. And / or, the vanadium element of the molecular sieve is derived from a sol-state vanadium source.
[0015] A second aspect of the present invention provides a method for preparing the above-mentioned molecular sieve, the method comprising the following steps:
[0016] A vanadium source, an aluminum source, a phosphorus source, water, a template agent, and an optional silicon source are mixed to obtain a mixed solution, which is then hydrothermally crystallized to obtain the molecular sieve.
[0017] According to the present invention, in the preparation method, the pH of the mixture is controlled to be 4.2 to 6.6. Preferably, ammonia water is used to adjust the pH. The mass concentration of the ammonia water is 10 wt% to 25 wt%.
[0018] According to the present invention, in the preparation method, the equipment for hydrothermal crystallization is preferably an autoclave. The pressure is autogenous pressure. The pressure can be 1.0 to 2.5 MPa.
[0019] According to the present invention, in the preparation method, the hydrothermal crystallization temperature is 150-200°C; and / or the hydrothermal crystallization time is 8-48 h.
[0020] According to the present invention, in the preparation method, after hydrothermal crystallization, washing, filtration, and drying steps can be performed. The drying can be carried out using conventional parameters, preferably at 80–120°C for 2–12 hours.
[0021] According to the present invention, in the preparation method, the vanadium source includes at least one selected from vanadium oxysulfate, vanadium pentoxide, vanadium oxyphosphate, vanadium hydrosulfite, and vanadium oxalate. And / or, the aluminum source includes boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide. And / or, the phosphorus source includes at least one selected from phosphoric acid, ammonium dihydrogen phosphate, pyrophosphate, and phosphorous acid. And / or, the silicon source includes at least one selected from silica sol, water glass, and tetraethyl orthosilicate. And / or, the template agent includes at least one selected from triethylamine, tri-n-propylamine, diethylamine, di-n-propylamine, diisopropylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. The molecular sieve structure includes at least one selected from AFI, AEL, and CHI structures, and is achieved by adjusting the type and amount of template agent added.
[0022] According to the present invention, in the preparation method, the raw material feeding ratio, calculated as a molar ratio, is vanadium source: aluminum source: phosphorus source: silicon source: template agent: water = 0.01~0.5:1:0.9~1.3:0~0.3:1~5:30~200, wherein the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the phosphorus source as P2O5, and the silicon source as SiO2. Preferably, the ratio is vanadium source: aluminum source: phosphorus source: silicon source: template agent: water = 0.01~0.5:1:0.9~1.3:0.01~0.3:1~5:30~200.
[0023] According to the present invention, preferably, the vanadium source is added in the form of a sol-state vanadium source. The method for preparing the sol-state vanadium source includes the following steps:
[0024] (1) Mix the vanadium source with water to obtain a vanadium solution;
[0025] (2) Add alkali to the vanadium solution obtained in step (1) to react and generate a precipitate;
[0026] (3) Add acid to the product of step (2) to obtain a sol-state vanadium source.
[0027] According to the present invention, an additive may be added to the mixing in step (1) to improve solubility. The additive includes at least one of oxalic acid, citric acid, tartaric acid, and hydrogen peroxide; preferably, the molar ratio of the additive to V in the vanadium source is 1:0.5 to 1.
[0028] According to the present invention, the mass ratio of vanadium source to water in step (1) is 1:10 to 100.
[0029] According to the present invention, the mixing temperature in step (1) is 10–80°C. The mixing time is 0.5–4 h.
[0030] According to the present invention, the alkali in step (2) includes at least one of sodium hydroxide, potassium hydroxide, and tetraethylammonium hydroxide. The amount of alkali added in step (2) is such that the pH of the mixture is 4 to 8. The reaction temperature in step (2) is 10 to 80°C. The reaction time is 0.5 to 4 hours.
[0031] According to the present invention, the acid in step (3) includes at least one of sulfuric acid, phosphoric acid, and nitric acid; preferably, the molar ratio of the acid to the V element in the vanadium source is 1:0.5 to 2.0. In step (3), the temperature at which the product of step (2) and the acid are mixed is 10 to 80°C. The mixing time is 1 to 8 hours.
[0032] A third aspect of the present invention provides an aromatic gas-phase ammonia oxidation catalyst, the catalyst comprising an active phase and a support; the active phase comprising the above-described molecular sieve or a molecular sieve prepared by the above-described method; wherein, based on the weight of the catalyst, the content of the active phase is 10wt% to 70wt%, and the content of the support is 30wt% to 90wt%.
[0033] According to the present invention, the support includes at least one of SiO2, Al2O3, TiO2, ZrO2, MgO and molecular sieves; further, the molecular sieves include, but are not limited to, AFI, AEL, CHI, ATO, etc.
[0034] According to the present invention, the preparation method of the aromatic gas-phase ammonia oxidation catalyst includes loading an active phase onto a support, preferably by spray drying, using the active phase and the support as raw materials to prepare the catalyst.
[0035] According to the present invention, the spray drying method includes the following steps: dispersing the active phase in water, mixing it with a support, spray drying the resulting mixture, and calcining it to obtain the catalyst.
[0036] According to the present invention, the mass ratio of the active phase to water is 1:2.5 to 5. The spray drying is carried out in a spray dryer, and the outlet temperature of the spray dryer is 150 to 200°C. The spray drying temperature is 150 to 200°C. The product obtained after spray drying can be dried at 100 to 150°C for 4 to 16 hours. The calcination temperature is 400 to 700°C, and the calcination time is 6 to 12 hours.
[0037] According to the present invention, after the ammonia oxidation reaction to prepare aromatic nitrile, the catalyst has a V retention rate of more than 80% and a P retention rate of more than 80%. Further, the V retention rate is less than 97% and the P retention rate is less than 97%.
[0038] The fourth aspect of this invention provides the application of the above-mentioned catalyst in the gas-phase ammonia oxidation of aromatics to prepare aromatic nitrile.
[0039] According to the present invention, the application uses aromatic hydrocarbons, ammonia, and oxygen source as reaction raw materials to prepare aromatic nitrile under the action of the above-mentioned catalyst.
[0040] According to the present invention, the oxygen source is air and / or oxygen.
[0041] According to the present invention, the aromatic hydrocarbon refers to aromatic compounds with aromatic properties in a broad sense. The aromatic hydrocarbon includes at least one of benzene-based aromatic hydrocarbons and non-benzene aromatic hydrocarbons. The aromatic hydrocarbon can be an aromatic heterocyclic compound. The aromatic hydrocarbon can be monomethyl or polymethyl substituted. The aromatic hydrocarbon is characterized in that a hydrogen atom is attached to the carbon atom connected to the ring. Preferably, the aromatic hydrocarbon includes at least one of toluene, ethylbenzene, halotoluene, xylene, methylpyridine, and methylpyrazine.
[0042] According to the present invention, the reaction temperature for the application is 350–450°C. Below 350°C, the reaction conversion rate is low; while above 450°C, deep oxidation intensifies, and the reaction produces CO. x In addition to HCN and demethylation products, the oxidation of NH3 also increases significantly.
[0043] According to the present invention, the reaction pressure is 110–160 kPa. The catalyst loading is 0.03–0.20 h⁻¹. -1 (WWH).
[0044] According to the present invention, the volume concentration of aromatic hydrocarbons in the reaction feedstock is 0.1 vol% to 10 vol%, preferably 0.2 vol% to 5 vol%.
[0045] According to the present invention, the molar ratio of ammonia to aromatics is 1 to 40, preferably 2.5 to 40.
[0046] According to the present invention, the molar ratio of oxygen source to aromatic hydrocarbon is 2 to 15, preferably 4 to 15. The oxygen source is defined as O2. Generally, too low an oxygen content will result in a low reaction conversion rate, while too high an oxygen content will result in an increase in deep oxidation reaction products; both of these situations will reduce the yield of aromatic hydrocarbons.
[0047] Compared with the prior art, the present invention has the following main advantages:
[0048] (1) In this invention, the molecular sieve framework has a high vanadium content, high relative crystallinity, and large specific surface area. It can be used as a catalyst for the gas-phase ammonia oxidation of aromatics. The catalyst for the gas-phase ammonia oxidation of aromatics, using a vanadium-doped molecular sieve with better crystallinity as the reactive phase, has greater advantages. The crystallinity of the vanadium-doped molecular sieve can be increased by 5%, and the specific surface area can be increased by at least 30 m². 2 ·g -1 The catalyst for the gas-phase ammonia oxidation of aromatics of the present invention is used in the industrial production of aromatic nitrile by gas-phase ammonia oxidation of aromatics. It has the characteristics of simple preparation process, good adaptability to raw materials and aromatic nitrile, wear resistance, high catalytic activity, and high yield of aromatic nitrile. It is especially suitable for the preparation of aromatic nitrile by ammonia oxidation of aromatics in a fluidized bed reactor.
[0049] In this invention, the use of molecular sieves with good crystallization properties as the main active phase significantly improves the anti-wear performance of the catalyst. Furthermore, the optimization of the molecular sieve composition enables adaptability to different raw materials, optimizes the reaction performance of the aromatic ammonia oxidation catalyst, and maintains the yield of aromatic nitrile at a high level, thus achieving good technical results.
[0050] (2) In the process of preparing V-containing molecular sieves, it was found that although V can achieve doping of the molecular sieve framework, the content of V entering the framework is still low, and the crystallinity and specific surface area will also decrease due to the addition of heteroatoms during hydrothermal synthesis. Using sol-state V as the source of V synthesis can effectively overcome the above problems and further improve the physicochemical properties and reaction performance of molecular sieves. The catalyst prepared by using V-containing molecular sieves as the active phase is suitable for the industrial production of aromatic nitrile preparation by gas-phase ammoxidation of aromatics. It has the characteristics of simple preparation process, good adaptability to raw materials and aromatic nitrile, wear resistance, high catalytic activity, and high yield of aromatic nitrile. It is especially suitable for the preparation of aromatic nitrile by ammoxidation of aromatics in a fluidized bed reactor.
[0051] (3) In this invention, the aromatic gas-phase ammonia oxidation catalyst is used in the ammonia oxidation of aromatics to prepare aromatic nitrile, and has the characteristics of good adaptability to raw materials and aromatic nitrile, wear resistance, high catalytic activity, and high aromatic nitrile yield. The aromatic nitrile yield can reach more than 80%. After the ammonia oxidation reaction to prepare aromatic nitrile, the catalyst has a V retention rate of more than 80% and a P retention rate of more than 80%. The technical solution of this invention has achieved good technical results. Attached Figure Description
[0052] Figure 1 The XRD pattern of the molecular sieve in Example 1;
[0053] Figure 2 The images show the XRD patterns of molecular sieves from Example 1 and Comparative Examples 1 and 3. Detailed Implementation
[0054] The present invention will be further described in detail below with reference to specific embodiments. The implementation of the present invention is not limited to these embodiments. The data shown in the embodiments do not represent a limitation on the scope of features of the present invention.
[0055] In this invention, the aromatic hydrocarbon conversion rate, aromatic nitrile selectivity, and aromatic nitrile yield are defined as follows:
[0056]
[0057]
[0058]
[0059] In this invention, the various catalysts are used in a fluidized bed reactor. The reactor's... It is 1800mm long and has a catalyst loading of 550g.
[0060] In this invention, the crystallinity of the molecular sieve in Comparative Example 3 is 100%. The relative crystallinity was determined by X-ray diffraction (XRD). The relative crystallinity is the ratio of the sum of the peak areas of the diffraction peaks corresponding to the (210), (002), and (102) crystal planes in the XRD patterns of the molecular sieves in each example to the sum of the peak areas of the diffraction peaks corresponding to the (210), (002), and (102) crystal planes in the XRD pattern of the molecular sieve in Comparative Example 3.
[0061] In this invention, the XRD test was performed using a Bruker D8 X-ray powder diffractometer (XRD) from Germany, employing a Cu-Kα ray source with a Kα1 wavelength λ = 1.5405980 angstroms. Nickel filter, operating voltage 40kV, current 40mA, scanning range 2θ=5~80°.
[0062] In this invention, the specific surface area was measured using a Micrometritics ASAP 2020M analyzer, the adsorbate was N2, and adsorption occurred at liquid nitrogen temperature. The specific surface area of the catalyst was calculated using the BET equation.
[0063] In this invention, the abrasion rate is tested using a method conforming to ASTM D5757-00 (using air jet abrasion to determine the relative abrasion characteristics of powdered catalysts). The abrasion rate of the finished catalyst is measured as the abrasion rate per hour, expressed in wt%.
[0064] In this invention, the elemental composition of the molecular sieve was determined by inductively coupled plasma atomic emission spectrometry (ICP) using an Avio 200 ICP spectrometer manufactured by Perkin Elmer, USA. The sample was digested with HF solution, and non-framework elements were removed by acid washing before digestion when determining the framework elements.
[0065] In this invention, the phosphorus (P) content in the molecular sieve before and after the reaction was analyzed by ICP. The P retention rate is the ratio of the P content after the reaction to the P content before the reaction.
[0066] In this invention, the V content in the molecular sieve before and after the reaction was analyzed by ICP. The V retention rate is the ratio of the V content after the reaction to the V content before the reaction.
[0067]
Example 1
[0068] 1. Molecular sieve synthesis:
[0069] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.
[0070] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.
[0071] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.
[0072] Triethylamine was used as the template agent R, aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, silica sol as the silicon source, and a sol-state V source was prepared as the V source. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:SiO₂:R:H₂O = 0.15:1:1.05:0.3:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia. The mixture was then crystallized at 190℃ for 16 h, filtered, washed, and dried at 110℃ for 4 h to obtain a vanadium-containing molecular sieve.
[0073] The relative crystallinity of the molecular sieve is 95%. XRD pattern is shown below. Figure 1 As shown in the figure, the molecular sieve is an AFI structure molecular sieve. The specific surface area of the molecular sieve is 228.3 m². 2 ·g-1 The molecular sieve framework contains 89.2% V by mass of all V elements. The composition of the molecular sieve includes: 5.6 wt% V₂O₅, 41.1 wt% Al₂O₃, 46.5 wt% P₂O₅, and 6.8 wt% SiO₂.
[0074] 2. Catalyst Preparation
[0075] Weigh out 50 wt% of the molecular sieve sample according to the catalyst mass and disperse it in the water required for catalyst preparation to obtain a molecular sieve dispersion slurry. The ratio of molecular sieve to water is 1:3.
[0076] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with the above-mentioned dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 180°C. The resulting fine catalyst particles were dried at 120°C for 12 hours and calcined at 550°C for 8 hours to obtain the catalyst. The average particle size of the catalyst was 50 μm.
[0077] 3. Catalyst performance evaluation:
[0078] Toluene, ammonia, and oxygen were used as reactants in a feed molar ratio of toluene:NH3:O2 = 1:8:8. The volume concentration of aromatics in the reactants was 2.5 vol%, and the catalyst loading was 0.070 h⁻¹. -1 The reaction system pressure was 125 kPa. The reaction temperature was 425℃. The test results after 48 hours of reaction were as follows:
[0079] Toluene conversion rate: 99.1%;
[0080] Benzonitrile selectivity: 83.0%;
[0081] Benzonitrile yield was 82.3%.
[0082] The catalyst attrition rate was 1.1%.
[0083] After 48 hours of reaction, ICP analysis showed that V retention was 95% and P retention was 92%.
[0084]
Example 2
[0085] 1. Molecular sieve synthesis:
[0086] (1) Weigh V2O5 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, add 20wt% hydrogen peroxide at a molar ratio of 1:0.8 of the additive to V, stir and dissolve for 2 hours to obtain vanadium solution.
[0087] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.
[0088] (3) At 70°C, add 50wt% sulfuric acid to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1 and mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.
[0089] Using triethylamine as template agent R, boehmite as aluminum source, phosphoric acid as phosphorus source, and tetraethyl orthosilicate as silicon source, a sol-state V source was prepared and used as the V source. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:SiO₂:R:H₂O = 0.3:1:1.1:0.3:1.7:45, and the pH was adjusted to 5.5 with sodium hydroxide. The mixture was then crystallized at 190℃ for 24 h, filtered, washed, and dried at 100℃ for 3 h to obtain a vanadium-containing molecular sieve.
[0090] The relative crystallinity of the molecular sieve is 89%. XRD patterns show that the molecular sieve is an AFI structure molecular sieve. The specific surface area of the molecular sieve is 203.5 m². 2 ·g -1 The molecular sieve framework contains 92.0% V by mass of all V elements. The composition of the molecular sieve includes: 7.5 wt% V₂O₅, 42.4 wt% Al₂O₃, 45.2 wt% P₂O₅, and 4.9 wt% SiO₂.
[0091] 2. Catalyst Preparation
[0092] A molecular sieve sample, comprising 50 wt% of the catalyst mass, was weighed and dispersed in water required for catalyst preparation to obtain a molecular sieve dispersion slurry. The ratio of molecular sieve to water was 1:2.5.
[0093] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with the above-mentioned dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 180°C. The resulting fine catalyst particles were dried at 120°C for 12 hours and calcined at 550°C for 8 hours to obtain the catalyst. The average particle size of the catalyst was 50 μm.
[0094] 3. Catalyst performance evaluation:
[0095] The reaction proceeds were m-xylene, ammonia, and oxygen, with a feed molar ratio of m-xylene:NH3:O2 = 1:8:8. The volume concentration of aromatics in the reactants was 2.3 vol%, and the catalyst loading was 0.075 h⁻¹. -1 The reaction system pressure was 140 kPa. The reaction temperature was 425℃. The test results after 48 hours of reaction were as follows:
[0096] m-Xylene conversion rate: 99.7%;
[0097] The selectivity of isophthalonitrile was 82.2%.
[0098] The yield of isophthalonitrile was 82.0%.
[0099] The catalyst attrition rate was 1.2%.
[0100] After 48 hours of reaction, ICP analysis showed that V retention was 90% and P retention was 91%.
[0101]
Example 3
[0102] 1. Molecular sieve synthesis:
[0103] (1) Weigh VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, add citric acid at a molar ratio of 1:1.0 of the additive to V, and stir to dissolve for 2 hours.
[0104] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.
[0105] (3) At 70°C, add 60wt% phosphoric acid to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.
[0106] Using di-n-propylamine as a template agent, aluminum isopropoxide as an aluminum source, phosphoric acid as a phosphorus source, and silica sol as a silicon source, a sol-state V source was prepared and used as the V source. The feed was prepared according to a ratio of V₂O₅:Al₂O₃:P₂O₅:SiO₂:R:H₂O = 0.15:1:1:0.2:1.5:40, and the pH was adjusted to 5.5 with sodium hydroxide. The mixture was then crystallized at 170℃ for 20 h, filtered, washed, and dried at 90℃ for 5 h to obtain a vanadium-containing molecular sieve.
[0107] The molecular sieve has a relative crystallinity of 91% and a specific surface area of 209.4 m². 2 ·g -1 The molecular sieve framework contains 92.3% V by mass of all V elements. The molecular sieve is an AEL structure molecular sieve. The composition of the molecular sieve includes: 6.0 wt% V₂O₅, 44.4 wt% Al₂O₃, 45.0 wt% P₂O₅, and 4.6 wt% SiO₂.
[0108] 2. Catalyst Preparation
[0109] Weigh out 50 wt% of the molecular sieve sample according to the catalyst mass and disperse it in the water required for catalyst preparation to obtain a molecular sieve dispersion slurry. The ratio of molecular sieve to water is 1:3.
[0110] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with a dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 180°C. The fine catalyst particles obtained by spraying were dried at 120°C for 12 hours and calcined at 600°C for 4 hours, resulting in an average catalyst particle size of 80 μm.
[0111] 3. Catalyst performance evaluation:
[0112] The reaction proceeds were m-xylene, ammonia, and oxygen, with a feed molar ratio of m-xylene:NH3:O2 = 1:10:8. The volume concentration of aromatics in the reactants was 1.8 vol%, and the catalyst loading was 0.060 h⁻¹. -1 The reaction system pressure was 150 kPa. The reaction temperature was 445℃. The test results after 48 hours of reaction were as follows:
[0113] m-Xylene conversion rate: 98.5%;
[0114] The selectivity of isophthalonitrile was 80.3%.
[0115] The yield of isophthalonitrile was 79.1%.
[0116] The catalyst attrition rate was 1.3%.
[0117] After 48 hours of reaction, the V retention rate and P retention rate were determined by ICP.
[0118]
Example 4
[0119] 1. Molecular sieve synthesis:
[0120] (1) Weigh VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, and stir to dissolve for 2 hours.
[0121] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.
[0122] (3) At 70°C, add 60wt% phosphoric acid to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.
[0123] Using tetraethylammonium hydroxide as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, and tetraethyl orthosilicate as silicon source, a sol-state V source was prepared and used as the V source. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:SiO₂:R:H₂O = 0.2:1:1:0.1:1.2:40, and the pH was adjusted to 5.5 with sodium hydroxide. The mixture was then crystallized at 180℃ for 10 h, filtered, washed, and dried at 120℃ for 3 h to obtain a vanadium-containing molecular sieve.
[0124] The molecular sieve has a relative crystallinity of 96% and a specific surface area of 236.6 m². 2 ·g -1 The molecular sieve framework contains 95.3% V by mass of all V elements. The molecular sieve is an AFI structure molecular sieve. The composition of the molecular sieve includes: 6.4 wt% V₂O₅, 40.3 wt% Al₂O₃, 50.6 wt% P₂O₅, and 2.7 wt% SiO₂.
[0125] 2. Catalyst Preparation
[0126] Weigh out 50 wt% of the molecular sieve sample and disperse it in the water required for catalyst preparation. The ratio of molecular sieve to water is 1:2.5.
[0127] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with a dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 170°C. The fine catalyst particles obtained by spraying were dried at 120°C for 12 hours and calcined at 550°C for 4 hours, resulting in an average catalyst particle size of 80 μm.
[0128] 3. Catalyst performance evaluation:
[0129] The reaction proceeds were 3-methylpyridine, ammonia, and oxygen, with a feed molar ratio of o-xylene:NH3:O2 = 1:5:6. The volume concentration of aromatics in the reactants was 1.5 vol%, and the catalyst loading was 0.070 h⁻¹. -1 The reaction system pressure was 130 kPa. The reaction temperature was 380℃. The test results after 48 hours of reaction were as follows:
[0130] 3-Methylpyridine conversion rate: 99.8%;
[0131] 3-Cyanopyridine selectivity: 94.5%;
[0132] 3-Cyanopyridine yield: 94.3%.
[0133] The catalyst attrition rate was 1.3%.
[0134] After 48 hours of reaction, the V retention rate was 91% and the P retention rate was 92% as determined by ICP.
[0135]
Example 5
[0136] Molecular sieve synthesis:
[0137] (1) Weigh VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, add 20wt% hydrogen peroxide at a molar ratio of 1:0.5 of the additive to V, and stir to dissolve for 2 hours.
[0138] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.
[0139] (3) At 70°C, add 60wt% phosphoric acid to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.
[0140] Triethylamine was used as a template agent, aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, and silica sol as the silicon source. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:SiO₂:R:H₂O = 0.15:1:1.05:0.3:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia. The mixture was then crystallized at 180℃ for 12 hours, filtered, washed, and dried at 110℃ for 4 hours to obtain a vanadium-containing molecular sieve.
[0141] The molecular sieve has a relative crystallinity of 82% and a specific surface area of 187.6 m². 2 ·g -1 The molecular sieve framework contains 81.8% V by mass of all V elements. The molecular sieve is an AFI structure molecular sieve. The composition of the molecular sieve includes: 3.3 wt% V₂O₅, 43.2 wt% Al₂O₃, 51.7 wt% P₂O₅, and 1.8 wt% SiO₂.
[0142] 2. Catalyst Preparation
[0143] Weigh out 50 wt% of the molecular sieve sample according to the catalyst mass and disperse it in the water required for catalyst preparation. The ratio of molecular sieve to water is 1:3.
[0144] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with a dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 180°C. The fine catalyst particles obtained by spraying were dried at 120°C for 12 hours and calcined at 550°C for 8 hours, resulting in an average catalyst particle size of 50 μm.
[0145] 3. Catalyst performance evaluation:
[0146] Toluene, ammonia, and oxygen were used as reactants, with a feed molar ratio of toluene:NH3:O2 = 1:8:8 and a catalyst loading of 0.070 h⁻¹. -1 The volume concentration of aromatics in the reactants was 2.5 vol%, and the reaction system pressure was 125 kPa. The reaction temperature was 425 °C. The test results after 48 hours of reaction were as follows:
[0147] Toluene conversion rate: 99.3%;
[0148] Benzonitrile selectivity: 81.0%;
[0149] Benzonitrile yield: 80.4%.
[0150] The catalyst attrition rate was 1.4%.
[0151] After 48 hours of reaction, the V retention rate was 82% and the P retention rate was 86% as determined by ICP.
[0152]
Example 6
[0153] 1. Molecular sieve synthesis:
[0154] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.
[0155] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.
[0156] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.
[0157] Using triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, and a sol-state V source as V source, vanadium-containing molecular sieves were prepared. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:R:H₂O = 0.15:1:1.05:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia. The mixture was then crystallized at 190℃ for 16 h, filtered, washed, and dried at 110℃ for 4 h.
[0158] The relative crystallinity of the molecular sieve is 96%. The molecular sieve is an AFI structure molecular sieve. The specific surface area of the molecular sieve is 231.2 m². 2 ·g -1The molecular sieve framework contains 89.9% V by mass of all V elements. The composition of the molecular sieve includes: 6.0 wt% V₂O₅, 43.5 wt% Al₂O₃, and 50.5 wt% P₂O₅.
[0159] 2. Catalyst Preparation
[0160] Weigh out 50 wt% of the molecular sieve sample according to the catalyst mass and disperse it in the water required for catalyst preparation to obtain a molecular sieve dispersion slurry. The ratio of molecular sieve to water is 1:3.
[0161] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with the above-mentioned dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 180°C. The resulting fine catalyst particles were dried at 120°C for 12 hours and calcined at 550°C for 8 hours to obtain the catalyst. The average particle size of the catalyst was 50 μm.
[0162] 3. Catalyst performance evaluation:
[0163] Toluene, ammonia, and oxygen were used as reactants in a feed molar ratio of toluene:NH3:O2 = 1:8:8. The volume concentration of aromatics in the reactants was 2.5 vol%, and the catalyst loading was 0.070 h⁻¹. -1 The reaction system pressure was 125 kPa. The reaction temperature was 425℃. The test results after 48 hours of reaction were as follows:
[0164] Toluene conversion rate: 99.0%;
[0165] Benzonitrile selectivity: 80.6%;
[0166] Benzonitrile yield: 80.0%.
[0167] The catalyst attrition rate was 1.2%.
[0168] After 48 hours of reaction, ICP analysis showed that V retention was 96% and P retention was 93%.
[0169] Comparative Example 1
[0170] 1. Molecular sieve synthesis:
[0171] Weigh VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium source solution.
[0172] Triethylamine was used as a template agent, aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, and silica sol as the silicon source. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:SiO₂:R:H₂O = 0.15:1:1.05:0.3:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia. The mixture was then crystallized at 190℃ for 16 hours, filtered, washed, and dried at 110℃ for 4 hours to obtain a vanadium-containing molecular sieve.
[0173] The molecular sieve has a relative crystallinity of 53% and a specific surface area of 60.5 m². 2 ·g -1 The molecular sieve contains 46.7% V in its framework by mass. It is an AFI (Al₂O₅) structure molecular sieve. The composition of the molecular sieve includes: 3.0 wt% V₂O₅, 40.4 wt% Al₂O₃, 53.5 wt% P₂O₅, and 3.1 wt% SiO₂.
[0174] 2. Catalyst Preparation
[0175] Weigh out 50 wt% of the molecular sieve sample according to the catalyst mass and disperse it in the water required for catalyst preparation. The ratio of molecular sieve to water is 1:3.
[0176] Silica sol was weighed at 50 wt% of the catalyst mass (SiO2), mixed with a dispersion slurry containing molecular sieves, and then ground in a colloid mill. The treated slurry was then passed into a spray dryer with an outlet temperature of 180°C. The fine catalyst particles obtained by spraying were dried at 120°C for 12 hours and calcined at 550°C for 8 hours, resulting in an average catalyst particle size of 50 μm.
[0177] 3. Catalyst performance evaluation:
[0178] Toluene, ammonia, and oxygen were used as reactants in a feed molar ratio of toluene:NH3:O2 = 1:8:8. The volume concentration of aromatics in the reactants was 2.5 vol%, and the catalyst loading was 0.070 h⁻¹. -1 The reaction system pressure was 125 kPa. The reaction temperature was 425℃. The test results after 48 hours of reaction were as follows:
[0179] Toluene conversion rate: 99.8%;
[0180] Benzonitrile selectivity: 64.0%;
[0181] Benzonitrile yield was 63.87%.
[0182] The catalyst attrition rate was 1.6%.
[0183] After 48 hours of reaction, ICP analysis showed that V retention was 81% and P retention was 70%.
[0184] Comparative Example 2
[0185] Preparation of V-Al-P-Si four-component catalyst
[0186] V₂O₅ was added to stirred water, followed by oxalic acid at a molar ratio of 1:2. After the reaction was complete, based on the total mass of V₂O₅, Al₂O₃, and P₂O₅, aluminum nitrate, ammonium dihydrogen phosphate, and silica sol were added sequentially in amounts with V₂O₅ content of 6wt%, Al₂O₃ content of 40wt%, P₂O₅ content of 54wt%, and the total mass of these three substances being in a 1:1 mass ratio with SiO₂ to prepare a mixed slurry. The treated slurry was then passed through a spray dryer at an outlet temperature of 180℃. The resulting fine catalyst particles were dried at 120℃ for 12 hours and calcined at 550℃ for 8 hours, resulting in an average catalyst particle size of 50 μm. The catalyst composition included: 5.3wt% V₂O₅, 42.1wt% Al₂O₃, 45.9wt% P₂O₅, and 6.7wt% SiO₂. The specific surface area of the catalyst was 30.6 m². 2 ·g -1 The catalyst has no molecular sieve structure.
[0187] Catalyst performance evaluation:
[0188] Toluene, ammonia, and oxygen were used as reactants in a feed molar ratio of toluene:NH3:O2 = 1:8:8. The volume concentration of aromatics in the reactants was 2.5 vol%, and the catalyst loading was 0.070 h⁻¹. -1 The reaction system pressure was 125 kPa. The reaction temperature was 425℃. The test results after 48 hours of reaction were as follows:
[0189] Toluene conversion rate: 99.7%;
[0190] Benzonitrile selectivity: 43.4%;
[0191] Benzonitrile yield was 43.3%.
[0192] The catalyst attrition rate was 2.1%.
[0193] After 48 hours of reaction, ICP analysis showed that V retention was 89% and P retention was 53%.
[0194] Comparative Example 3
[0195] AlPO4-5 catalyst prepared without the addition of V and Si elements
[0196] Triethylamine was used as a template agent, aluminum isopropoxide as the aluminum source, and phosphoric acid as the phosphorus source. The materials were fed in a ratio of Al₂O₃:P₂O₅:R:H₂O = 1:1.05:1.5:45. The mixture was then crystallized at 190℃ for 16 hours, filtered, washed, and dried at 110℃ for 4 hours to obtain the molecular sieve.
[0197] The molecular sieve has a relative crystallinity of 100% and a specific surface area of 200.1 m². 2 ·g -1 The molecular sieve is an AFI structure molecular sieve. The composition of the molecular sieve includes: 44.4 wt% Al2O3 and 55.6 wt% P2O5.
[0198] Catalyst performance evaluation:
[0199] Toluene, ammonia, and oxygen were used as reactants in a feed molar ratio of toluene:NH3:O2 = 1:8:8. The volume concentration of aromatics in the reactants was 2.5 vol%, and the catalyst loading was 0.070 h⁻¹. -1 The reaction system pressure was 125 kPa. The reaction temperature was 425℃. The test results after 48 hours of reaction were as follows:
[0200] Toluene conversion rate: 10.3%;
[0201] Benzonitrile selectivity: 37.0%;
[0202] Benzonitrile yield was 3.81%.
[0203] The catalyst attrition rate was 1.9%.
Claims
1. A molecular sieve, characterized in that, The molecular sieve comprises V, Al, P, O, and optionally Si; the composition of the molecular sieve comprises, based on oxides, 0.1wt%~10wt% V₂O₅, 40wt%~48wt% Al₂O₃, 40wt%~55wt% P₂O₅, and 0wt%~19wt% SiO₂; the structure of the molecular sieve includes at least one of the AFI structure, AEL structure, and CHI structure. Based on V2O5, vanadium accounts for more than 80 wt% of all V elements in the molecular sieve framework.
2. The molecular sieve according to claim 1, characterized in that, Based on V2O5, vanadium accounts for 80wt% to 97wt% of all V elements in the molecular sieve framework.
3. The molecular sieve according to claim 1, characterized in that, The relative crystallinity of the molecular sieve is 80%~110%; and / or, the specific surface area of the molecular sieve is 180~350 m². 2 ·g -1 .
4. A method for preparing the molecular sieve according to any one of claims 1 to 3, the method comprising the following steps: A vanadium source, an aluminum source, a phosphorus source, an optional silicon source, water, and a template agent are mixed to obtain a mixed solution, which is then hydrothermally crystallized to obtain the molecular sieve; the vanadium source is added in the form of a sol-gel vanadium source.
5. The preparation method according to claim 4, characterized in that, The preparation method of the sol-state vanadium source includes the following steps: (1) Mix the vanadium source with water to obtain a vanadium solution; (2) Add alkali to the vanadium solution obtained in step (1) to react and generate a precipitate; (3) Add acid to the product of step (2) to obtain a sol-state vanadium source.
6. The preparation method according to claim 5, characterized in that, The mixing in step (1) requires the addition of an auxiliary agent; the auxiliary agent includes at least one of oxalic acid, citric acid, tartaric acid, and hydrogen peroxide.
7. The preparation method according to claim 6, characterized in that, In step (1), the molar ratio of the amount of additive added to the V element in the vanadium source is 1:0.5~1.
8. The preparation method according to claim 5, characterized in that, The alkali mentioned in step (2) includes at least one of sodium hydroxide, potassium hydroxide, and tetraethylammonium hydroxide; And / or, the amount of alkali added in step (2) is such that the pH of the mixture is 4 to 8; And / or, the reaction temperature in step (2) is 10~80℃.
9. The preparation method according to claim 5, characterized in that, The acid mentioned in step (3) includes at least one of sulfuric acid, phosphoric acid, and nitric acid.
10. The preparation method according to claim 5, characterized in that, In step (3), the molar ratio of acid to V in the vanadium source is 1:0.5~2.
0.
11. The preparation method according to claim 4, characterized in that, The pH of the mixture should be controlled between 4.2 and 6.
6. And / or, the temperature of hydrothermal crystallization is 150~200℃; and / or, the time of hydrothermal crystallization is 8~48h.
12. The preparation method according to claim 4, characterized in that, The vanadium source includes at least one of vanadium oxysulfate, vanadium pentoxide, vanadium oxyphosphate, vanadium hydroperoxide, and vanadium oxyoxate. And / or, the aluminum source includes boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide; And / or, the phosphorus source includes at least one of phosphoric acid, ammonium dihydrogen phosphate, pyrophosphate, and phosphorous acid; And / or, the silicon source includes at least one of silica sol and water glass; And / or, the template agent includes at least one of triethylamine, tri-n-propylamine, diethylamine, di-n-propylamine, diisopropylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; And / or, the raw material feeding ratio, by weight, is vanadium source: aluminum source: phosphorus source: silicon source: template agent: water = 0.01~0.5:1:0.9~1.3:0~0.3:1~5:30~200, where the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the P source as P2O5, and the Si source as SiO2.
13. A catalyst for the gas-phase ammonia oxidation of aromatics, characterized in that, The catalyst comprises an active phase and a support; The active phase comprises the molecular sieve according to any one of claims 1 to 3 or the molecular sieve prepared by the method according to any one of claims 4 to 12; Based on the weight of the catalyst, the content of the active phase is 10wt%~70wt%, and the content of the support is 30wt%~90wt%.
14. The catalyst according to claim 13, characterized in that, The preparation method of the aromatic gas-phase ammonia oxidation catalyst includes loading the active phase onto a support.
15. The catalyst according to claim 14, characterized in that, It was prepared by spray drying.
16. The catalyst according to claim 13, characterized in that, The catalyst exhibits a V retention rate of over 80% and a P retention rate of over 80% after the aromatic gas-phase ammonia oxidation reaction.
17. The use of the catalyst according to any one of claims 13 to 16 in the gas-phase ammoxidation of aromatics to prepare aromatic nitrile.