A hierarchical pore catalyst for phenoxylation to phenol and a preparation method and use thereof

Abstract

The application provides a multi-level hole catalyst for benzene oxidation to prepare phenol and a preparation method and use thereof, and the preparation method comprises the following steps: (1) a catalyst raw material containing a pore modifier is subjected to a hydrothermal synthesis reaction, and a precursor obtained is subjected to a first calcination to obtain a first molecular sieve containing micropores and mesopores; (2) the first molecular sieve is sequentially subjected to an alkaline modification treatment and a second calcination to obtain the multi-level hole catalyst for benzene oxidation to prepare phenol. The application has a typical multi-level hole structure under the premise of ensuring sufficient acidity, the maximum pore diameter of the molecular sieve is increased from 10 nm to 100 nm, the desorption efficiency of the phenol product on the catalyst can be increased, the anti-coking performance of the catalyst is significantly improved, the service life of the catalyst is prolonged, and the catalyst can be well applied in the reaction of preparing phenol by oxidizing benzene with nitrous oxide.

Description

Technical Field

[0001] This invention relates to the field of nitrous oxide oxidation reaction for the preparation of phenol, and particularly to a hierarchical porous catalyst for the oxidation of benzene to phenol, its preparation method and uses. Background Technology

[0002] Phenol is an important raw material and intermediate in the chemical industry, with wide applications in petrochemicals, resins, fibers, plastics, antioxidants, pesticides, and pharmaceuticals. With the development of epoxy resins, polycarbonates, and phenolic resins in the automotive, electronics and communications, construction, and new energy industries, the demand for phenol is also growing rapidly. The traditional industrial method for producing phenol is the cumene process, which has drawbacks such as long reaction steps, high energy consumption, a high proportion of acetone as a byproduct, and serious environmental pollution.

[0003] In recent years, researchers have been exploring new process routes for the oxidation of benzene to phenol. Compared to the traditional one-step catalytic oxidation of benzene to phenol, the direct oxidation of benzene offers higher atom economy, a simpler reaction process, higher phenol selectivity, and is environmentally friendly, making it a strategically significant production process with environmental benefits. Currently reported benzene oxidation processes mainly use oxygen, hydrogen peroxide, and nitrous oxide as oxidants to synthesize phenol. Among these, nitrous oxide exhibits better thermal and chemical stability than oxidants like oxygen and hydrogen peroxide, reducing safety risks during the oxidation reaction. Furthermore, nitrous oxide has a strong greenhouse effect and ozone destructive potential; therefore, research on the direct oxidation of benzene to phenol using nitrous oxide is of great importance.

[0004] In the research on the process of preparing phenol by oxidizing benzene with nitrous oxide, Japanese scholars Iwamoto et al. reported an oxidation process using V2O5 / SiO2 as a catalyst. However, the conversion rate of benzene was 10% and the selectivity of phenol was about 70% during the reaction, and the catalyst was prone to coking and deactivation.

[0005] US5055623 uses metal- or non-metal-doped ZSM-5 and ZSM-11 as catalysts, which can achieve a benzene conversion rate of about 10% and a phenol selectivity of >90%, but the reaction time is only 2 hours and no long-term evaluation has been conducted.

[0006] US5110995 uses a modified silica-alumina zeolite Fe-ZSM-5 catalyst in a fixed-bed reactor with a benzene:nitrous oxide volume ratio of 1:4 and helium as the carrier gas. After 3 hours of reaction evaluation, a phenol selectivity of 93-97% can be achieved, but the phenol yield is about 30%, and the exothermic reaction reduces the catalyst sintering activity.

[0007] Boreskov's Institute for Catalysis, in collaboration with Monsanto, has patented US5672777, which addresses the issue of coking and carbon buildup leading to deactivation in the one-step oxidation of benzene to phenol using Fe-ZSM-5 catalysis via N2O. The patent proposes high-temperature steam heat treatment to enhance the catalytic activity of Fe-ZSM-5. The catalytic activity of Fe-ZSM-5 molecular sieves after steam heat treatment is subsequently increased by 8-40% due to the increased steam content in the subsequent treatment gas source.

[0008] Solutia in the United States and Boreskov Institute of Catalysis in Russia jointly developed the AlphOx process, which effectively utilizes the tail gas generated by the adipic acid process and integrates the oxidation unit with the adipic acid unit. The process uses an atmospheric pressure fixed-bed adiabatic reactor and Fe-doped ZSM-5 as a catalyst, with a product yield of >98% from benzene feedstock. However, the process was terminated after one year of pilot operation due to high operating costs and poor stability of the catalyst during continuous operation.

[0009] In addition, regarding the reactor type, CN102020535B changed the fixed-bed reaction system to a fluidized bed, which enhanced the desorption capacity of oxidation products on the catalyst and slowed down the carbon deposition rate. After running for 275 minutes, the phenol yield was >50%. However, the catalyst life still did not meet the requirements for long-term continuous operation, and the fluidized bed required high mechanical strength of the catalyst, which was prone to pulverization during the suspension process.

[0010] Most existing work uses silicon-aluminum molecular sieves doped with metal oxides as catalysts, which can achieve a phenol yield of about 30% and a selectivity of >98%. However, the process shows that the catalyst is prone to coking and deactivation. The single-pass reaction conversion rate decreases significantly with time, and the single-pass reaction time does not exceed 6 hours. The rapid deactivation of the catalyst restricts the feasibility of scaling up the production of this process. Frequent catalyst regeneration is required, which is not conducive to the industrialization of this process.

[0011] Therefore, new catalysts need to be developed to improve the yield of phenol. Summary of the Invention

[0012] In view of the problems existing in the prior art, the present invention provides a hierarchical porous catalyst for the oxidation of benzene to phenol, its preparation method and application. By combining the hard template method and the soft template method, suitable acidity and larger pores than conventional molecular sieves are provided. Furthermore, the catalyst is modified with alkaline substances to provide weakly acidic centers, which can effectively improve the oxidation reaction efficiency and the catalyst's coking resistance.

[0013] To achieve this objective, the present invention adopts the following technical solution:

[0014] In a first aspect, the present invention provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol, the method comprising:

[0015] (1) The catalyst raw material containing the pore-modifying agent is subjected to a hydrothermal synthesis reaction, and the precursor obtained is subjected to a first calcination to obtain a first molecular sieve containing both micropores and mesopores.

[0016] (2) The first molecular sieve is successively modified by alkaline substances and then calcined to obtain the multi-level porous catalyst for the oxidation of benzene to phenol.

[0017] It is worth noting that the purpose of this invention is to prepare a hierarchical porous catalyst while maintaining the original multi-acidic site function of the high-silica molecular sieve. On the one hand, by adding a pore-modifying agent during the hydrothermal synthesis reaction, the pore size of the first molecular sieve is directly changed during the forming process, thereby directly obtaining a first molecular sieve containing micropores and mesopores. On the other hand, the subsequent alkaline modification treatment has the main function of slightly corroding silicon, thereby forming hydroxyl groups inside the hierarchical porous catalyst used for the oxidation of benzene to phenol, thus providing weak acidic centers. Secondly, it can also expand the pores, making the pore size more hierarchical, and further improving the service life and activity of the hierarchical porous catalyst used for the oxidation of benzene to phenol.

[0018] Preferably, the catalyst raw materials in step (1) include silicon source, metal source, aluminum source and solvent.

[0019] Preferably, the molar ratio of the silicon source to the aluminum source is 20 to 60:1, for example, it can be 20:1, 25:1, 29:1, 34:1, 38:1, 43:1, 47:1, 52:1, 56:1 or 60:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 40 to 50:1.

[0020] Preferably, the ratio of the amount of silicon in the silicon source to the amount of metal in the metal source is 1000 to 4000:1, for example, it can be 1000:1, 1334:1, 1667:1, 2000:1, 2334:1, 2667:1, 3000:1, 3334:1, 3667:1 or 4000:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1600 to 3200:1.

[0021] It is worth noting that the present invention requires high-silica molecular sieves to better provide acidic centers. Therefore, the proportion of silicon source needs to be controlled within the above-mentioned range, which is more conducive to obtaining a multi-level porous catalyst with better performance for the oxidation of benzene to phenol.

[0022] Preferably, the mass ratio of the solvent to the silicon source is 100 to 500:1, for example, it can be 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1 or 500:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 200 to 300:1.

[0023] Preferably, the solvent includes water.

[0024] Preferably, the metal source contains any one or a combination of at least two of Ca, Mg, Fe, Zn or Cu, wherein typical but non-limiting combinations are combinations of Ca and Mg, Fe and Mg, Ca and Fe, Zn and Mg, and Ca and Cu.

[0025] Preferably, the metal source comprises a metal salt.

[0026] Preferably, the anion of the metal salt includes nitrate and / or acetate.

[0027] Preferably, the silicon source includes any one or a combination of at least two of tetraethyl silicate, silica sol, water glass, tetrabutyl silicate, or sodium silicate, wherein typical but non-limiting combinations are the combination of tetraethyl silicate and silica sol, the combination of water glass and silica sol, and the combination of tetraethyl silicate and water glass.

[0028] Preferably, the aluminum source includes any one or a combination of at least two of sodium aluminate, aluminum isopropoxide, boehmite, aluminum nitrate, or aluminum sulfate.

[0029] Preferably, the molar ratio of the pore-modifying agent to the aluminum source in step (1) is 1 to 10:1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 2 to 6:1.

[0030] It is worth noting that the preparation of the first molecular sieve is not easy. It requires the use of template agents and pore-modifying agents in the preparation process. The role of these agents is to occupy the pores inside the molecular sieve during the formation of the molecular sieve precursor, thereby ultimately forming mesoporous structures. However, the addition of these pore-modifying agents can affect the formation of the first molecular sieve. If the amount of pore-modifying agent added is too large, it will be difficult to form the first molecular sieve product, and a multi-level porous catalyst for the oxidation of benzene to phenol cannot be obtained. If the amount of pore-modifying agent added is too small, it will be difficult to achieve the pore-modifying effect, and the coking performance of the catalyst will be difficult to improve.

[0031] Preferably, the pore-modifying agent comprises any one or a combination of at least two of organic amines, organosilanes, silica powder, or porous carbon, wherein typical but non-limiting combinations are combinations of organic amines and organosilanes, combinations of silica powder and organosilanes, and combinations of organic amines and porous carbon.

[0032] Furthermore, the selection of pore-modifying agents needs to consider their impact on the hydrothermal crystallization reaction of molecular sieves and whether they will react with other raw materials of molecular sieves. Through extensive research, it has been found that the above-mentioned pore-modifying agents can not only prepare the corresponding molecular sieve products, but also improve their pore size, and can produce first molecular sieves with multi-level pores.

[0033] Preferably, the number of carbon atoms in the organic amine and the organosilanes is independently greater than 12, for example, 13, 14, 15, 16, 17, 19, 20, 24, 25 or 30.

[0034] In this invention, it is necessary to control the number of carbon atoms of organic amines and organosilanes to be >12 independently. This results in a more suitable pore size range for the first molecular sieve, superior catalytic performance, and a longer catalyst life.

[0035] Preferably, the organic amines include any one or a combination of at least two of dodecyltetramethylammonium hydroxide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, or hexadecyltrimethylammonium bromide, wherein typical but non-limiting combinations are combinations of dodecyltetramethylammonium hydroxide and dodecyltrimethylammonium bromide, combinations of tetradecyltrimethylammonium bromide and dodecyltrimethylammonium bromide, combinations of dodecyltetramethylammonium hydroxide and tetradecyltrimethylammonium bromide, and combinations of hexadecyltrimethylammonium bromide and dodecyltrimethylammonium bromide.

[0036] Preferably, the organosilanes include any one or a combination of at least two of dimethylsiloxane, ethyltriethoxysilane, aminopropyltriethoxysilane, or aminopropyltetramethyldisiloxane, wherein typical but non-limiting combinations are the combination of dimethylsiloxane and ethyltriethoxysilane, the combination of aminopropyltriethoxysilane and ethyltriethoxysilane, the combination of dimethylsiloxane and aminopropyltriethoxysilane, and the combination of aminopropyltetramethyldisiloxane and ethyltriethoxysilane.

[0037] Preferably, a sodium source is added to the hydrothermal synthesis reaction in step (1).

[0038] Preferably, the molar ratio of the sodium source to the aluminum source is 0.5 to 10:1, for example, it can be 0.5:1, 1.6:1, 2.7:1, 3.7:1, 4.8:1, 5.8:1, 6.9:1, 7.9:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 2 to 4:1.

[0039] Preferably, the sodium source includes any one or a combination of at least two of sodium aluminate, sodium hydroxide, sodium carbonate, potassium hydroxide, or potassium carbonate, wherein typical but non-limiting combinations are combinations of sodium aluminate and sodium hydroxide, combinations of sodium carbonate and sodium hydroxide, combinations of sodium aluminate and sodium carbonate, combinations of potassium hydroxide and sodium hydroxide, and combinations of sodium aluminate and potassium carbonate.

[0040] Preferably, the temperature of the hydrothermal synthesis reaction in step (1) is 100 to 200°C, for example, it can be 100°C, 112°C, 123°C, 134°C, 145°C, 155°C, 167°C, 178°C, 189°C or 200°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 120 to 180°C.

[0041] Preferably, the hydrothermal synthesis reaction time is 48 to 120 hours, for example, 48 hours, 50 hours, 65 hours, 72 hours, 80 hours, 85 hours, 95 hours, 105 hours, 115 hours or 120 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 72 to 96 hours.

[0042] Preferably, the temperature of the first calcination is 400 to 800°C, for example, it can be 400°C, 445°C, 480°C, 530°C, 570°C, 620°C, 660°C, 710°C, 750°C or 800°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 500 to 600°C.

[0043] Preferably, the first calcination time is 3 to 12 hours, for example, it can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 5 to 8 hours.

[0044] Preferably, the alkaline substance modification treatment in step (2) includes alkaline substance modification treatment through a solution containing alkaline substances.

[0045] Preferably, the alkaline substance comprises any one or a combination of at least two of sodium hydroxide, sodium oxalate, sodium carbonate, sodium bicarbonate, potassium hydroxide, or ammonium nitrate, wherein typical but non-limiting combinations are the combination of sodium hydroxide and sodium oxalate, the combination of ammonium nitrate and sodium oxalate, the combination of sodium hydroxide and sodium carbonate, the combination of sodium hydroxide and potassium hydroxide, and the combination of sodium bicarbonate and sodium oxalate.

[0046] Preferably, the solid-liquid ratio of the alkaline solution to the first molecular sieve is 4 to 5:1, for example, it can be 4:1, 4.1:1, 4.2:1, 4.3:1, 4.5:1, 4.6:1, 4.7:1, 4.8:1, 4.9:1 or 5.0:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the concentration of the alkaline solution is 0.5 to 1.5 mol / L, for example, it can be 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] It is worth noting that by controlling the concentration of the alkaline solution within the above-mentioned range, this invention can not only avoid excessive loss of silicon in the catalyst, but also achieve better pore expansion and increase of acidic sites, resulting in better catalytic performance.

[0049] Preferably, the alkaline substance modification treatment time is 1 to 2 hours, for example, it can be 1 hour, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the temperature for alkaline substance modification treatment is 60-80°C, for example, 60°C, 63°C, 65°C, 67°C, 69°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Preferably, the second calcination temperature in step (2) is 500 to 600°C, for example, it can be 500°C, 512°C, 523°C, 534°C, 545°C, 556°C, 567°C, 578°C, 589°C or 600°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the second calcination time is 1 to 12 hours, for example, it can be 1 hour, 3 hours, 4 hours, 5 hours, 6 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] As a preferred embodiment of the first aspect of the present invention, the preparation method includes the following steps:

[0054] (1) The pore-modifying agent, silicon source, metal source, aluminum source and solvent are hydrothermally synthesized together at 100-200℃ for 48-120h. The precursor obtained is calcined at 400-800℃ for 3-12h to obtain a first molecular sieve containing both micropores and mesopores.

[0055] The molar ratio of the silicon source to the aluminum source is 20–60:1; the molar ratio of silicon in the silicon source to metal in the metal source is 1000–4000:1; the mass ratio of the solvent to the silicon source is 1–5:1; and the molar ratio of the pore-modifying agent to the aluminum source is 1–10:1. The pore-modifying agent includes any one or a combination of at least two of the following: organic amines, organosilanes, silicon micropowder, or porous carbon.

[0056] (2) The first molecular sieve is subjected to alkaline modification treatment in a solution containing 0.5-1.5 mol / L alkaline substances at 60-80°C for 1-2 hours, with the solid-liquid ratio of the alkaline substance solution to the first molecular sieve being 4-5:1. The first molecular sieve is then calcined at 500-600°C for 1-12 hours to obtain the multi-level porous catalyst for the oxidation of benzene to phenol.

[0057] In a second aspect, the present invention provides a hierarchical porous catalyst for the oxidation of benzene to phenol, wherein the hierarchical porous catalyst for the oxidation of benzene to phenol is prepared by the method for preparing the hierarchical porous catalyst for the oxidation of benzene to phenol described in the first aspect.

[0058] Preferably, the hierarchical porous catalyst for the oxidation of benzene to phenol is a metal oxide-molecular sieve composite catalyst.

[0059] Preferably, the content of metal elements in the hierarchical porous catalyst for the oxidation of benzene to phenol is 0.01 to 0.5 wt%, for example, it can be 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, or 0.5 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] Preferably, the molar ratio of silicon to aluminum in the hierarchical porous catalyst used for the oxidation of benzene to phenol is 40 to 60:1, for example, it can be 40:1, 42:1, 45:1, 48:1, 50:1, 52:1, 53:1, 55:1, 58:1 or 60:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] Preferably, the molar ratio of silicon to metal in the hierarchical porous catalyst for the oxidation of benzene to phenol is 1600 to 2000:1, for example, it can be 1600:1, 1650:1, 1700:1, 1750:1, 1800:1, 1850:1, 1900:1, 1950:1 or 2000:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] Preferably, the particle size of the hierarchical porous catalyst for the oxidation of benzene to phenol is 1 to 2 μm, for example, it can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2.0 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] The multi-level porous catalyst for the oxidation of benzene to phenol prepared by this invention has the same particle size as the catalyst directly applied to the reaction, and no further kneading or pressing treatment is required.

[0064] Preferably, the specific surface area of ​​the hierarchical porous catalyst for the oxidation of benzene to phenol is 200–400 m². 2 / g, for example, could be 200m 2 / g、220m 2 / g、230m 2 / g、250m 2 / g、280m 2 / g、300m 2 / g、320m 2 / g, 350m 2 / g or 400m 2 / g, etc., but not limited to the listed values, other unlisted values ​​within this range also apply.

[0065] Preferably, the proportion of pores with a pore size of 5-8 nm in the hierarchical porous catalyst for the oxidation of benzene to phenol is 0.1-10%, for example, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%; the proportion of pores with a pore size of 2-5 nm (excluding 5 nm) is 0.5-15%, for example, 0.5%, 1%, 2%, 3%, 5%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%; and the proportion of pores with a pore size of 0.5-2 nm (excluding 2 nm) is 75-98%, for example, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 94%, 95%, or 98%.

[0066] Thirdly, the present invention provides the use of the hierarchical porous catalyst for the oxidation of benzene to phenol as described in the second aspect, wherein the hierarchical porous catalyst for the oxidation of benzene to phenol is used in an oxidation reaction, preferably in a reaction in which nitrous oxide is oxidized to prepare phenol.

[0067] The hierarchical porous catalyst for the oxidation of benzene to phenol provided by the second aspect of the present invention has a long service life, a low carbon deposition rate, and high yield and selectivity of phenol, and has broad application prospects.

[0068] The present invention does not impose any special restrictions on the reaction form and reactor form of the oxidation reaction. The reaction form or reactor form known to those skilled in the art can be used, and adjustments can be made according to the actual situation.

[0069] Preferably, when the hierarchical porous catalyst for the oxidation of benzene to phenol is used to prepare phenol by the oxidation of benzene with nitrous oxide, the reaction temperature for the oxidation of benzene with nitrous oxide to phenol is 400-550°C, for example, 400°C, 417°C, 434°C, 450°C, 467°C, 484°C, 500°C, 517°C, 534°C or 550°C, etc., but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0070] Preferably, when the hierarchical porous catalyst for the oxidation of benzene to phenol is used to prepare phenol by the oxidation of benzene with nitrous oxide, the reaction time for the oxidation of benzene with nitrous oxide to phenol is 1 to 35 hours, for example, 1 hour, 5 hours, 9 hours, 13 hours, 17 hours, 20 hours, 24 hours, 28 hours, 32 hours or 35 hours, etc., but not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0071] Preferably, when the hierarchical porous catalyst for the oxidation of benzene to phenol is used to prepare phenol by the oxidation of benzene with nitrous oxide, the flow ratio of nitrous oxide to benzene in the preparation of phenol by the oxidation of benzene with nitrous oxide is 1.1 to 2.0:1, for example, it can be 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2.0:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0072] Compared with the prior art, the present invention has at least the following beneficial effects:

[0073] (1) The method for preparing a multi-level porous catalyst for the oxidation of benzene to phenol provided by the present invention has a typical multi-level porous structure under the premise of ensuring sufficient acidity. The maximum pore size of the molecular sieve is increased from 10 nm to 100 nm, which can increase the desorption efficiency of phenol products on the catalyst, significantly improve the anti-coking performance of the catalyst, and extend the life of the catalyst.

[0074] (2) The multi-level porous catalyst for the oxidation of benzene to phenol provided by the present invention is applied to the oxidation of benzene to phenol by nitrous oxide. The single-pass reaction life is increased from 2-6h to more than 30h, the phenol yield is >70%, the selectivity is >98%, and the performance is excellent. Attached Figure Description

[0075] Figure 1 This is a pore size distribution diagram of the hierarchical porous catalyst for the oxidation of benzene to phenol prepared in Example 1 of the present invention.

[0076] Figure 2 This is a SEM image of the hierarchical porous catalyst for the oxidation of benzene to phenol prepared in Example 1 of this invention. Detailed Implementation

[0077] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0078] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0079] Example 1

[0080] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol, the preparation method comprising the following steps:

[0081] (1) 80g of tetraethyl silicate was added to 225g of water for complete hydrolysis. Then, 35g of tetrapropylammonium hydroxide, 1.5g of sodium aluminate, 1.2g of sodium hydroxide, 0.125g of ferric nitrate nonahydrate and 7.5g of hexadecyltrimethylammonium bromide were added and subjected to hydrothermal synthesis reaction at 180℃ for 72h. The material from the hydrothermal synthesis reaction was filtered and dried. The precursor obtained was calcined at 500℃ for 6h to obtain a first molecular sieve containing both micropores and mesopores.

[0082] (2) 50g of the first molecular sieve was subjected to alkaline modification treatment with 150mL of 1mol / L sodium hydroxide solution at 75℃ for 1h, then washed and dried with water, and then calcined at 500℃ for 2h to obtain the multi-level porous catalyst for the oxidation of benzene to phenol.

[0083] The pore size distribution diagram of the hierarchical porous catalyst for the oxidation of benzene to phenol prepared in this embodiment is shown in the figure below. Figure 1 As shown, the SEM image is as follows: Figure 2 As stated, from Figures 1-2 It can be seen that the pore size distribution of the hierarchical porous catalyst for the oxidation of benzene to phenol prepared in this embodiment is between 0.5 and 8 nm.

[0084] Example 2

[0085] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol, the preparation method comprising the following steps:

[0086] (1) 120g of tetraethyl silicate was added to 338g of water for complete hydrolysis. Then, 53g of tetrapropylammonium hydroxide, 2.3g of sodium aluminate, 1.8g of sodium hydroxide, 0.75g of ferric nitrate nonahydrate and 11.3g of silica powder were added and subjected to hydrothermal synthesis reaction at 120℃ for 96h. The material from the hydrothermal synthesis reaction was filtered and dried. The precursor obtained was calcined at 500℃ for 6h to obtain a first molecular sieve containing both micropores and mesopores.

[0087] (2) 50g of the first molecular sieve was subjected to alkaline treatment with 225mL of 1mol / L potassium hydroxide solution at 80℃ for 1h, then washed and dried with water, and then calcined at 600℃ for 3h to obtain the multi-level porous catalyst for the oxidation of benzene to phenol.

[0088] Example 3

[0089] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol, the preparation method comprising the following steps:

[0090] (1) 100g of tetraethyl silicate was added to 280g of water and fully hydrolyzed. Then, 44g of tetrapropylammonium hydroxide, 1.9g of sodium aluminate, 1.5g of sodium hydroxide, 0.16g of zinc nitrate hexahydrate and 9.5g of 2000-mesh graphite powder were added and subjected to a hydrothermal synthesis reaction at 190℃ for 72h. The material from the hydrothermal synthesis reaction was filtered and dried. The precursor obtained was calcined at 800℃ for 3h to obtain a first molecular sieve containing both micropores and mesopores.

[0091] (2) 40g of the first molecular sieve was subjected to alkaline treatment with 188mL of 1mol / L sodium bicarbonate solution at 60℃ for 1h, then washed and dried with water, and then calcined at 500℃ for 2h to obtain the multi-level porous catalyst for the oxidation of benzene to phenol.

[0092] Example 4

[0093] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol, the preparation method comprising the following steps:

[0094] (1) 200g of tetraethyl silicate was added to 560g of water for complete hydrolysis. Then, 88g of tetrapropylammonium hydroxide, 4.8g of sodium aluminate, 3.0g of sodium hydroxide, 0.32g of copper nitrate trihydrate and 40g of 3-aminopropyltriethoxysilane were added and subjected to hydrothermal synthesis reaction at 180℃ for 72h. The material from the hydrothermal synthesis reaction was filtered and dried. The precursor obtained was calcined at 550℃ for 6.5h to obtain a first molecular sieve containing both micropores and mesopores.

[0095] (2) 100g of the first molecular sieve was subjected to alkaline treatment with 375mL of 1mol / L potassium hydroxide solution at 70℃ for 1h, then washed and dried with water, and then calcined at 500℃ for 12h to obtain the multi-level porous catalyst for the oxidation of benzene to phenol.

[0096] Example 5

[0097] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1, except that the mass of hexadecyltrimethylammonium bromide is 1g, and will not be repeated here.

[0098] Example 6

[0099] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1, except that the mass of hexadecyltrimethylammonium bromide is 25g, and will not be repeated here.

[0100] Example 7

[0101] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1, except that the concentration of sodium hydroxide solution is 0.01 mol / L, and will not be repeated here.

[0102] Example 8

[0103] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1 except that the concentration of sodium hydroxide solution is 3 mol / L, and will not be repeated here.

[0104] Example 9

[0105] This embodiment provides a method for preparing a hierarchical porous catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1, except that hexadecyltrimethylammonium bromide is replaced with dodecylammonium bromide, and will not be repeated here.

[0106] Example 10

[0107] This embodiment provides a method for preparing a composite catalyst. Except for step (1) where only 20g of tetraethyl silicate is added, the preparation method is the same as in Example 1, and will not be repeated here.

[0108] Example 11

[0109] This embodiment provides a method for preparing a composite catalyst. Except for the addition of 450g of tetraethyl silicate in step (1), the preparation method is the same as in Example 1, and will not be repeated here.

[0110] Comparative Example 1

[0111] This comparative example provides a method for preparing a catalyst. The preparation method is the same as in Example 1 except that the sodium hydroxide solution in step (2) is replaced with a sodium chloride solution of equal concentration and volume. It will not be described again here.

[0112] Comparative Example 2

[0113] This comparative example provides a method for preparing a catalyst. The preparation method is the same as that in Example 1 except that step (2) is omitted, and will not be repeated here.

[0114] Comparative Example 3

[0115] This comparative example provides a method for preparing a catalyst. The preparation method is the same as that in Example 1 except that hexadecyltrimethylammonium bromide is not added, and will not be described again here.

[0116] Test methods: The metal element content in the hierarchical porous catalyst used for the oxidation of benzene to phenol was determined by ICP; the silicon-to-aluminum ratio in the hierarchical porous catalyst used for the oxidation of benzene to phenol was determined by ICP; the pore size and specific surface area of ​​the hierarchical porous catalyst used for the oxidation of benzene to phenol were determined by nitrogen adsorption-desorption; and the particle size of the hierarchical porous catalyst used for the oxidation of benzene to phenol was determined by scanning electron microscopy.

[0117] The test results of the above embodiments and comparative examples are shown in Table 1.

[0118] Table 1

[0119]

[0120] Application Examples 1-11 and Comparative Examples 1-3

[0121] An application example provides a method for preparing phenol by oxidizing benzene with nitrous oxide. The method includes: using the catalysts from the above-described examples and comparative examples, loading 60 g of catalyst into a fixed-bed catalyst bed, heating to 550°C, feeding water at a rate of 80 mL / h, and activating the catalyst for 4 h. After activation, benzene is fed into a preheating mixer at a rate of 160 mL / h, and nitrous oxide at a rate of 180 mL / h. The mixer temperature is 400°C, and the reactor temperature is 450°C. Samples are taken for analysis after 12 h of reaction. The lifetime of the catalyst in a single pass is evaluated based on a selectivity of ≥98%.

[0122] Furthermore, the catalyst provided in Example 1 was regenerated in an air atmosphere at 550°C and then recycled 10 times.

[0123] Application Example 12

[0124] This application example provides a method for preparing phenol by oxidizing benzene with nitrous oxide. The method includes: using the catalyst provided in Example 2, loading 60g of catalyst into a fixed-bed catalyst bed, heating to 500℃, feeding water at a rate of 65mL / h, and activating the catalyst for 5h. After activation, benzene is fed into a preheating mixer at a rate of 100mL / h and nitrous oxide at a rate of 120mL / h. The mixer temperature is 450℃, the reactor temperature is 450℃, and samples are taken for analysis after 12h of reaction.

[0125] The reaction samples were analyzed using gas chromatography, and the yield and selectivity of phenol were calculated. The test results for the above application examples and comparative examples are shown in Table 2.

[0126] Table 2

[0127]

[0128]

[0129] The following points can be observed from Tables 1 and 2:

[0130] (1) As can be seen from the comprehensive examples 1 to 4, the catalyst prepared by the method of preparing multi-level porous catalyst for benzene oxidation to phenol provided by the present invention has the advantage of long single-pass reaction catalyst life, and improves the yield and selectivity of phenol, wherein the selectivity of phenol is above 98% and the yield is above 71%.

[0131] (2) As can be seen from the combined examples 1 and 5-6, the mass of hexadecyltrimethylammonium bromide used in example 1 was 7.5g, compared with 1g and 25g used in examples 5 and 6 respectively. In example 1, the selectivity of phenol was above 98%, the yield was above 71.7%, and the single-pass life of the catalyst was above 31h. In example 5, the content of mesopores ≥5nm in the catalyst was only 1%, and the modification effect was not obvious. In example 6, the content of mesopores ≥5nm in the modified catalyst was only 0.9%. Excessive increase in the amount of pore modifier affected the crystallization process of the molecular sieve, resulting in a significant decrease in the crystallinity of the catalyst. Ultimately, the life of the catalyst in examples 5 and 6 was only 28h and 22h respectively. This shows that by optimally controlling the amount of pore modifier, the present invention can further improve the single-pass life of the catalyst and the selectivity of the reaction.

[0132] (3) As can be seen from the combined examples 1 and 7-8, in Example 1, a 1 mol / L sodium hydroxide solution was used, compared with 0.01 mol / L and 3 mol / L in Examples 7-8, respectively. In Example 1, the selectivity of phenol was above 98%, the yield was above 71.7%, and the single-pass life of the catalyst was above 31 h. In Example 7, the alkali concentration was too low, which led to a reduction in the 2 nm to 5 nm mesopore content of the catalyst and a slight weakening of the catalyst acidity. In Example 8, the alkali concentration was too high, which led to an excessive amount of desiliconization of the catalyst and a significant weakening of its stability at the oxidation reaction temperature. Ultimately, the lifespan of the catalyst in Examples 7-8 was only 18 h and 14 h, respectively. This shows that the present invention can further improve the single-pass lifespan of the catalyst by optimally controlling the concentration of the alkali solution.

[0133] (4) It can be seen from the combined examples 1 and 9 that, compared with the dodecyl ammonium bromide used in example 9, the selectivity of phenol in example 1 is above 98%, the yield is above 71.7%, and the single-pass life of the catalyst is above 31h, while the single-pass life of the catalyst in example 9 is only 16h. This shows that the present invention can ensure that the molecular size is within a reasonable range by optimally controlling the chain length of the pore-modifying agent, thereby improving the anti-coking performance of the catalyst.

[0134] (5) As can be seen from the combined examples 1 and 10-11, 100g of tetraethyl silicate was used in Example 1, compared with 20g and 450g of tetraethyl silicate used in Examples 10-11, respectively. In Example 1, the selectivity of phenol was above 98%, the yield was above 71.7%, and the single-pass life of the catalyst was above 31h. In Example 10, the amount of silicon source in the catalyst was small, the silicon-to-aluminum ratio of the molecular sieve was low, the acidity was enhanced, the side reactions of the catalyst increased, and the selectivity was reduced. In Example 11, the amount of silicon source in the catalyst was large, the silicon-to-aluminum ratio of the molecular sieve was too high, the acidity was significantly weakened, and the conversion rate of nitrous oxide was significantly reduced. This shows that the present invention can further improve the selectivity and yield of the catalyst by optimizing the molar ratio of silicon source to aluminum source.

[0135] (3) As can be seen from the combined results of Example 1 and Comparative Examples 1-3, Example 1 uses the steps of sequentially using a pore-modifying agent and treating with an alkaline substance. Compared with Comparative Example 1, which does not use alkaline substance but replaces it with salt treatment, Comparative Example 2, which does not use alkaline substance treatment, and Comparative Example 3, which does not add a pore-modifying agent, the selectivity of phenol in Example 1 is above 98%, the yield is above 71.7%, and the single-pass life of the catalyst is above 31 hours. In contrast, the selectivity and yield data of Comparative Examples 1-3 are inferior to those of Example 1, and the single-pass life of the catalyst is short. This shows that the method for preparing a multi-level porous catalyst for the oxidation of benzene to phenol provided by the present invention significantly improves the anti-coking performance of the catalyst and extends the life of the catalyst by combining the steps of pore modification with a pore-modifying agent and treatment with an alkaline substance. It can be well applied in the reaction of nitrous oxide oxidizing benzene to prepare phenol.

[0136] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. Use of a hierarchical pore catalyst in the reaction of nitrous oxide with benzene to produce phenol, characterized in that, The preparation method of the multi-level pore catalyst comprises: (1) a catalyst raw material containing a pore modification aid is subjected to a hydrothermal synthesis reaction to obtain a precursor, and the precursor is subjected to a first calcination to obtain a first molecular sieve containing micropores and mesopores; (2) the first molecular sieve is sequentially subjected to an alkaline substance modification treatment and a second calcination to obtain the multi-level pore catalyst; The catalyst raw material in step (1) comprises a silicon source, a metal source, an aluminum source and a solvent; The molar ratio of the silicon source to the aluminum source in step (1) is 20-60:

1. The molar ratio of the pore modification aid to the aluminum source in step (1) is 1-10:

1. The metal elements in the metal source in step (1) include any one or a combination of at least two of Ca, Mg, Fe, Zn or Cu. The pore modification aid in step (1) includes any one or a combination of at least two of organic amine, organic silane, silicon powder or graphite powder. The organic amine in step (1) includes tetradecyl trimethyl ammonium bromide and / or hexadecyl trimethyl ammonium bromide. The number of carbon atoms of the organic silane in step (1) is greater than 12. The organic silane in step (1) includes any one or a combination of at least two of dimethyl siloxane, ethyl triethoxysilane, aminopropyl triethoxysilane or aminopropyl tetramethyl disiloxane. A sodium source is further added in the hydrothermal synthesis reaction in step (1). The alkaline substance modification treatment in step (2) comprises alkaline substance modification treatment by using a solution containing an alkaline substance. The concentration of the solution containing an alkaline substance in step (2) is 0.5-1.5 mol / L. The temperature of the second calcination in step (2) is 500-600°C, and the time of the second calcination is 1-12 h.

2. Use according to claim 1, characterized in that, The molar ratio of the silicon source to the aluminum source in step (1) is 40-50:

1.

3. Use according to claim 1, characterized in that, The ratio of the amount of substance of silicon elements in the silicon source to the amount of substance of metal elements in the metal source in step (1) is 1000-4000:

1.

4. Use according to claim 3, characterized in that, The ratio of the amount of substance of silicon elements in the silicon source to the amount of substance of metal elements in the metal source in step (1) is 1600-3200:

1.

5. The use according to claim 1, characterized in that, The mass ratio of the solvent to the aluminum source in step (1) is 100-500:

1.

6. Use according to claim 5, characterized in that, The mass ratio of the solvent to the aluminum source in step (1) is 200-300:

1.

7. Use according to claim 1, characterized in that, The solvent in step (1) comprises water.

8. The use according to claim 1, characterized in that, The metal source in step (1) comprises a metal salt.

9. Use according to claim 8, characterized in that, The anion of the metal salt in step (1) comprises nitrate and / or acetate.

10. The use according to claim 1, characterized in that, The silicon source in step (1) comprises any one or a combination of at least two of tetraethyl orthosilicate, silica sol, water glass, tetrabutyl orthosilicate or sodium silicate.

11. Use according to claim 1, characterized in that, The aluminum source in step (1) comprises any one or a combination of at least two of sodium aluminate, aluminum isopropoxide, pseudo-boehmite, aluminum nitrate or aluminum sulfate.

12. The use according to claim 1, characterized in that, The molar ratio of the pore modification aid to the aluminum source in step (1) is 2-6:

1.

13. The use according to claim 1, characterized in that, The molar ratio of the sodium source to the aluminum source in step (1) is 0.5-10:

1.

14. Use according to claim 13, characterized in that, The molar ratio of the sodium source to the aluminum source in step (1) is 2-4:

1.

15. The use according to claim 1, characterized in that, The sodium source in step (1) includes any one or a combination of at least two of sodium aluminate, sodium hydroxide, and sodium carbonate.

16. The use according to claim 1, characterized in that, The temperature of the hydrothermal synthesis reaction in step (1) is 100-200℃.

17. Use according to claim 16, characterized in that, The temperature of the hydrothermal synthesis reaction in step (1) is 120-180℃.

18. The use according to claim 1, characterized in that, The time of the hydrothermal synthesis reaction in step (1) is 48-120h.

19. Use according to claim 18, characterized in that, The time of the hydrothermal synthesis reaction in step (1) is 72-96h.

20. The use according to claim 1, characterized in that, The temperature of the first calcination in step (1) is 400-800℃.

21. The use according to claim 20, characterized in that, The temperature of the first calcination in step (1) is 500-600℃.

22. The use according to claim 1, characterized in that, The time of the first calcination in step (1) is 3-12h.

23. The use according to claim 22, characterized in that, The time of the first calcination in step (1) is 5-8h.

24. The use according to claim 1, characterized in that, The alkaline substance in step (2) includes any one or a combination of at least two of sodium hydroxide, sodium oxalate, sodium carbonate, sodium bicarbonate, potassium hydroxide, or amine nitrate.

25. The use according to claim 1, characterized in that, The solid-liquid ratio of the solution containing the alkaline substance to the first molecular sieve in step (2) is 4-5:

1.

26. The use according to claim 1, characterized in that, The time of the alkaline substance modification treatment in step (2) is 1-2h.

27. The use according to claim 1, characterized in that, The temperature of the alkaline substance modification treatment in step (2) is 60-80℃.

28. The use of claim 1, wherein, The multi-level pore catalyst is a metal oxide-molecular sieve composite catalyst, the content of metal elements in the multi-level pore catalyst is 0.01-0.5wt%, the particle size of the multi-level pore catalyst is 1-2μm, the specific surface area of the multi-level pore catalyst is 200-400m 2 / g, the proportion of pores with a pore size of 5-8nm in the multi-level pore catalyst is 0.1-10%; the proportion of pores with a pore size of 2-5nm and excluding 5nm is 0.5-15%; the proportion of pores with a pore size of 0.5-2nm and excluding 2nm is 75-98%.

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