Composite catalyst for the phenoxylation of benzene to phenol, its preparation and use

Abstract

The application provides a composite catalyst for phenol preparation by benzene oxidation, a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing a silicon source, a first aluminum source, a metal source, a template agent and a solvent, and performing a hydrothermal synthesis reaction to obtain a precursor; the precursor is calcined to obtain a first molecular sieve; (2) mixing a second aluminum source and the first molecular sieve, and sequentially performing ball milling and second calcination to obtain the composite catalyst. The composite catalyst is prepared by mixing a supported high-silicon molecular sieve and gamma-aluminum oxide, the oxidation reaction efficiency and the coking resistance of the catalyst can be effectively improved, the yield of phenol is improved when the composite catalyst is applied to the preparation of phenol, and the running time of the catalyst is also improved.

Description

Technical Field

[0001] This invention relates to the field of oxidation reaction technology, and in particular to a composite catalyst for the oxidation of benzene to phenol, its preparation method, and its 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 downstream products of phenol, such as 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.

[0003] However, the industrial methods for preparing phenol in the past have shortcomings such as long reaction steps, high energy consumption, high proportion of acetone as a byproduct, and serious environmental pollution. There are also many disadvantages: (1) long production cycle, complex process steps, and low phenol yield; (2) a large number of byproducts are generated, the atom utilization rate is not high, and the co-product acetone has overcapacity and low economic value; (3) the waste generated in the production process is prone to environmental pollution.

[0004] Compared to the traditional one-step catalytic oxidation of benzene to phenol, the direct oxidation of benzene is a challenging yet highly valuable phenol production route, both economically and environmentally. The direct oxidation of benzene offers high atom economy, a simple reaction process, high phenol selectivity, and is environmentally friendly, making it a strategically significant and environmentally friendly production process.

[0005] Currently reported benzene oxidation processes mainly involve the synthesis of phenol using oxygen, hydrogen peroxide, and nitrous oxide as oxidants. Compared to oxidants such as oxygen and hydrogen peroxide, nitrous oxide has good thermal and chemical stability, which can reduce the safety risks during the oxidation reaction. Furthermore, nitrous oxide has a strong greenhouse effect and ozone destructive properties. Therefore, the efficient utilization of nitrous oxide is of great significance for environmental protection.

[0006] Research on the process of oxidizing benzene with nitrous oxide to prepare phenol has been conducted both domestically and internationally since the 1880s. In 1983, Japanese scholars Iwamoto et al. first reported the oxidation of benzene to phenol using V2O5 / SiO2 as a catalyst and N2O as an oxidant at 550℃. However, the conversion rate of benzene during the reaction was only 10%, the selectivity of phenol was about 70%, and the catalyst was prone to coking and deactivation.

[0007] US5055623A uses metal- or non-metal-doped ZSM-5 or ZSM-11 as catalysts, achieving a benzene conversion rate of approximately 10% and a phenol selectivity of >90%.

[0008] US5110995A 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. It can achieve a phenol selectivity of 93-97%, but the phenol yield is about 30%, and the exothermic reaction reduces the catalyst sintering activity.

[0009] WO9527691A uses a fixed-bed reactor, which improves the reaction space velocity and product selectivity at a higher benzene / nitrous oxide molar ratio. However, the single-pass yield of phenol in this process is less than 30%, and the large excess of benzene increases the energy consumption for product separation.

[0010] US5672777 addresses the issue of coking and carbon buildup leading to deactivation in the one-step oxidation of benzene to phenol using Fe-ZSM-5 catalyzed N2O. It 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 increases by 8-40% with the subsequent increase in steam content in the treatment gas source.

[0011] 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.

[0012] 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.

[0013] Most of the above patents use 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 single molecular sieve catalyst has poor activity and is prone to coking and deactivation. Significant signs of activity decay appear before the single-pass reaction time exceeds 6 hours, which is not conducive to the industrialization of this process.

[0014] Therefore, there is an urgent need to develop new catalysts to improve the yield and selectivity of phenol, ensure catalyst life, and promote the industrial production of the process. Summary of the Invention

[0015] In view of the problems existing in the prior art, the present invention provides a composite catalyst for the oxidation of benzene to phenol, its preparation method and application, which adopts a composite of high silica molecular sieve and γ-alumina. The alumina not only enhances the mechanical strength of the molecular sieve and reduces the problem of breakage during long-term operation, but also provides suitable acidity for the reaction. At the same time, the macroporous alumina can promote the desorption efficiency of phenol products on the catalyst, effectively reduce the carbon deposition rate, and extend the service life of the composite catalyst.

[0016] To achieve this objective, the present invention adopts the following technical solution:

[0017] In a first aspect, the present invention provides a method for preparing a composite catalyst for the oxidation of benzene to phenol, the method comprising the following steps:

[0018] (1) A silicon source, a first aluminum source, a metal source, a template agent, and a solvent are subjected to a hydrothermal synthesis reaction to obtain a precursor; the precursor is then subjected to a first calcination to obtain a first molecular sieve;

[0019] (2) The second aluminum source and the first molecular sieve are mixed and then ball-milled and calcined in sequence to obtain the composite catalyst.

[0020] The composite catalyst provided by this invention first employs an in-situ loading method to support metal oxides in a high-silica molecular sieve. A first molecular sieve, which is a high-silica molecular sieve, is obtained through a hydrothermal synthesis reaction and a first calcination. Then, a second aluminum source is mixed with the first molecular sieve, followed by ball milling and a second calcination to obtain the composite catalyst. In this catalyst, γ-alumina enhances the mechanical strength of the molecular sieve, reducing breakage during long-term operation, and provides suitable acidity for the reaction. Simultaneously, the macroporous alumina promotes the desorption efficiency of phenol products on the catalyst, effectively reducing the rate of carbon deposition and extending the service life of the composite catalyst.

[0021] It is worth noting that the present invention prepares γ-alumina in situ on the first molecular sieve, which has the advantages of acidity and uniform pore distribution compared with mechanical composite of the two. Moreover, the ball milling step is conducive to the full contact and mixing of the second aluminum source and the first molecular sieve. During the ball milling process, the first molecular sieve and the second aluminum source have sufficient interfacial contact and penetration, which facilitates the subsequent second calcination to obtain a composite catalyst with excellent performance.

[0022] It is worth noting that the precursor obtained by the present invention is a semi-transparent gel.

[0023] Preferably, the molar ratio of the silicon source to the first aluminum source in step (1) is 20 to 100:1, for example, it can be 20:1, 25:1, 35:1, 45:1, 55:1, 65:1, 70:1, 80:1, 90:1 or 100:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 20 to 60:1.

[0024] The first molecular sieve obtained by the present invention is a high-silicon molecular sieve, wherein the silicon-aluminum molar ratio in the first molecular sieve is 20-100:1. Using such a high silicon content molecular sieve can provide acidic sites for the reaction and improve the reaction activity.

[0025] Preferably, the molar ratio of the template agent to the first aluminum source is 5 to 10:1, for example, it can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the template agent comprises any one or a combination of at least two of tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium hydroxide, triethylamine, or ethylenediamine, wherein typical but non-limiting combinations are the combination of tetrapropylammonium hydroxide and tetrapropylammonium bromide, the combination of tetraethylammonium hydroxide and tetrapropylammonium bromide, the combination of tetrapropylammonium hydroxide and tetraethylammonium hydroxide, the combination of ethylenediamine and tetraethylammonium hydroxide, and the combination of tetrapropylammonium hydroxide and triethylamine.

[0027] It is worth noting that the first molecular sieve obtained by this invention is an MFI molecular sieve, and the MFI molecular sieve product can be well obtained by using the above-mentioned template agent.

[0028] 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, 1300:1, 1600:1, 2000:1, 2300:1, 2600:1, 3000:1, 3300:1, 3600:1 or 4000:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1600 to 3200:1.

[0029] Preferably, the mass ratio of the solvent to the silicon source is 1 to 5:1, for example, it can be 1:1, 1.5:1, 1.8:1, 2.5:1, 3.0:1, 3.2:1, 3.5:1, 4:1, 4.5:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1.3 to 4:1.

[0030] Preferably, the solvent includes water.

[0031] 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.

[0032] Preferably, the metal source comprises a metal salt.

[0033] Preferably, the anion of the metal salt includes nitrate and / or acetate.

[0034] 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.

[0035] Preferably, the first aluminum source includes any one or a combination of at least two of sodium aluminate, aluminum isopropoxide, boehmite, aluminum nitrate, or aluminum sulfate, wherein typical but non-limiting combinations are the combination of sodium aluminate and aluminum isopropoxide, the combination of boehmite and aluminum isopropoxide, the combination of sodium aluminate and boehmite, and the combination of aluminum nitrate and boehmite.

[0036] Preferably, a sodium source is added to the hydrothermal synthesis reaction in step (1).

[0037] Preferably, the molar ratio of the sodium source to the first aluminum source is 0.5 to 4:1, for example, it can be 0.5:1, 0.9:1, 1.3:1, 1.7:1, 2.1:1, 2.5:1, 2.9:1, 3.3:1, 3.7:1 or 4:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1 to 2:1.

[0038] Preferably, the sodium source includes sodium aluminate and / or sodium hydroxide.

[0039] 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, 120°C, 130°C, 145°C, 156°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.

[0040] Preferably, the hydrothermal synthesis reaction takes 48 hours or more.

[0041] Preferably, the temperature of the first calcination is 400 to 800°C, for example, it can be 400°C, 445°C, 485°C, 535°C, 575°C, 625°C, 665°C, 715°C, 755°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.

[0042] Preferably, the first calcination time is 3 to 15 hours, for example, it can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, in step (2), the second aluminum source comprises a mixture of boehmite and acid, or the second aluminum source comprises a mixture of aluminum salt, ammonium bicarbonate and water.

[0044] The selection of the second aluminum source in this invention is crucial. In order to obtain γ-alumina in the subsequent process, this invention selects a mixture of boehmite and acid, and a mixture of aluminum salt, ammonium bicarbonate and water. These two compound systems enable the aluminum source to be converted into γ-alumina during the subsequent calcination process.

[0045] Preferably, the aluminum salt comprises any one or a combination of at least two of aluminum nitrate nonahydrate, aluminum silicate, or aluminum hydroxide, wherein typical but non-limiting combinations are the combination of aluminum nitrate nonahydrate and aluminum silicate, the combination of aluminum hydroxide and aluminum silicate, and the combination of aluminum nitrate nonahydrate and aluminum hydroxide.

[0046] Preferably, the acid includes nitric acid. In this invention, nitric acid and boehmite are mixed to form a viscous, turbid emulsion system, resulting in more uniform mixing and facilitating subsequent calcination to form a composite catalyst, without affecting the catalytic activity of the metal oxide.

[0047] Preferably, the amount of aluminum compound in the second aluminum source is 40% to 100% of the mass of the first molecular sieve, for example, it can be 40%, 47%, 54%, 60%, 67%, 74%, 80%, 87%, 94% or 100%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] Preferably, the amount of acid in the second aluminum source is 5 to 10% of the mass of the first molecular sieve, for example, it can be 5%, 5.6%, 6.2%, 6.7%, 7.3%, 7.8%, 8.4%, 8.9%, 9.5% or 10%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the amount of ammonium bicarbonate in the second aluminum source is 40% to 100% of the mass of the first molecular sieve, for example, it can be 40%, 47%, 54%, 60%, 67%, 74%, 80%, 87%, 94% or 100%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] Preferably, the ball milling time in step (2) is 30 min to 2 h, for example, it can be 30 min, 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.8 h or 2.0 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Preferably, the rotational speed of the ball mill is 60 to 100 r / min, for example, it can be 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, 85 r / min, 90 r / min, 95 r / min or 100 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the second calcination temperature in step (2) is 500 to 600°C, for example, it can be 500°C, 512°C, 525°C, 535°C, 545°C, 550°C, 560°C, 578°C, 580°C or 600°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] It is worth noting that the performance of the final composite catalyst of this invention depends on the formation of γ-alumina and its composite with the first molecular sieve, namely the high-silica molecular sieve. However, it is desirable for the two to synergistically promote the catalytic reaction in the subsequent catalytic process. Therefore, the second calcination temperature during the preparation process should not be too high to avoid the conversion of γ-alumina into α-alumina. At the same time, the temperature should not be too low to ensure the formation of γ-alumina and to ensure a good physical bond between γ-alumina and the first molecular sieve, thereby improving the catalyst's lifespan.

[0054] Preferably, the second calcination time is 3 to 15 hours, for example, it can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] As a preferred embodiment of the first aspect of the present invention, the preparation method includes the following steps:

[0056] (1) A precursor is obtained by hydrothermal synthesis of silicon source, first aluminum source, metal source, template agent and solvent at 100-200℃ for more than 48 hours; the precursor is then calcined at 400-800℃ for 3-15 hours to obtain a first molecular sieve; the molar ratio of silicon source to first aluminum source is 20-100:1, the molar ratio of template agent to first aluminum source is 5-10:1, the molar ratio of silicon element in silicon source to metal element in metal source is 1000-4000:1, and the mass ratio of solvent to silicon source is 1-5:1.

[0057] (2) The second aluminum source and the first molecular sieve are mixed and then ball-milled at 60-100 r / min for 30 min-2 h and calcined at 500-600 °C for 3-5 h to obtain the composite catalyst;

[0058] The second aluminum source comprises a mixture of boehmite and acid, or the second aluminum source comprises a mixture of aluminum salt, ammonium bicarbonate and water.

[0059] In a second aspect, the present invention provides a composite catalyst for the oxidation of benzene to phenol, wherein the composite catalyst for the oxidation of benzene to phenol is prepared by the preparation method of the composite catalyst for the oxidation of benzene to phenol described in the first aspect.

[0060] Preferably, the composite catalyst is a composite catalyst of metal oxide-molecular sieve-γAl2O3.

[0061] Preferably, the content of γAl2O3 in the composite catalyst is 20-30 wt%, for example, it can be 20 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, or 30 wt%.

[0062] Preferably, the molecular sieve content in the composite catalyst is 70-80%, for example, it can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79% or 80%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0063] Preferably, the content of metal elements in the composite catalyst is 0.1 to 1 wt%, for example, it can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] Preferably, the molar ratio of silicon to aluminum in the composite catalyst is 10 to 30:1, for example, it can be 10:1, 12:1, 15:1, 18:1, 20:1, 22:1, 25:1, 28:1 or 30:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Preferably, the molar ratio of silicon to metal in the composite catalyst is 1600 to 3200:1, for example, it can be 1600:1, 1700:1, 1800:1, 1900:1, 2000:1, 2200:1, 2300:1, 2500:1, 2800:1, 3000:1, 3100:1 or 3200:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] Preferably, the particle size of the composite catalyst 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.

[0067] The particle size of the composite catalyst obtained by this invention is the same as that of the original powder. It will be further compressed and molded using conventional methods. The particle size of the molded particles is generally 1.0 to 1.5 mm, for example, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm or 1.5 mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] Preferably, the specific surface area of ​​the composite catalyst is 200–400 m². 2 / g, for example, could be 200m 2 / g、225m 2 / g、245m 2 / g、260m 2 / g、285m 2 / g、315m 2 / g, 330m2 / g, 355m 2 / g, 375m² / g or 400m 2 / g, etc., but not limited to the listed values, other unlisted values ​​within this range also apply.

[0069] Preferably, the pore size of the composite catalyst is 0.4 to 1 nm, for example, it can be 0.40 nm, 0.47 nm, 0.54 nm, 0.6 nm, 0.67 nm, 0.74 nm, 0.8 nm, 0.87 nm, 0.94 nm or 1 nm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0070] Thirdly, the present invention provides the use of a composite catalyst for the oxidation of benzene to phenol according to the second aspect, wherein the composite catalyst for the oxidation of benzene to phenol is used in an oxidation reaction, preferably in a reaction in which nitrous oxide oxidizes benzene to prepare phenol.

[0071] The composite catalyst 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.

[0072] 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.

[0073] Preferably, when the composite catalyst is used to prepare phenol from benzene by nitrous oxide, the reaction temperature for preparing phenol from benzene by nitrous oxide is 400-550℃, for example, it can be 400℃, 417℃, 434℃, 450℃, 467℃, 484℃, 500℃, 517℃, 534℃ or 550℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0074] Preferably, when the composite catalyst is used to prepare phenol from benzene by nitrous oxide, the reaction time for preparing phenol from benzene by nitrous oxide is 1 to 35 hours, for example, it can be 1 hour, 5 hours, 9 hours, 13 hours, 17 hours, 20 hours, 24 hours, 28 hours, 32 hours or 35 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] Preferably, when the composite catalyst is used to prepare phenol by nitrous oxide oxidation of benzene, the flow ratio of nitrous oxide to benzene in the preparation of phenol by nitrous oxide oxidation of benzene 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.

[0076] Compared with the prior art, the present invention has at least the following beneficial effects:

[0077] (1) The method for preparing composite catalyst for benzene oxidation to phenol provided by the present invention can effectively prepare a catalyst composed of metal oxide-supported high-silica molecular sieve and γ-alumina phase, which has excellent catalytic performance and can be well applied in oxidation reactions.

[0078] (2) Compared with the commonly used impregnation method, the composite catalyst for the oxidation of benzene to phenol provided by the present invention has less active site loss, longer catalyst life, and the macroporous alumina can promote the desorption efficiency of phenol products on the catalyst, effectively reducing the carbon deposition rate. The catalyst can react for more than 12 hours in a single pass, with a phenol yield of >70% and a selectivity of >98%. Preferably, the phenol yield can reach more than 71.9%, and the phenol selectivity is more than 98.0%. Attached Figure Description

[0079] Figure 1 These are the XRD patterns of the composite catalysts for the oxidation of benzene to phenol prepared in Examples 1-2 and 6-7 of this invention.

[0080] Figure 2 This is a SEM image of the composite catalyst for the oxidation of benzene to phenol prepared in Example 1 of this invention. Detailed Implementation

[0081] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0082] 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.

[0083] Example 1

[0084] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol, the preparation method comprising the following steps:

[0085] (1) 125g of tetraethyl silicate was added to 400g of water and fully hydrolyzed. Then, 60g of tetrapropylammonium hydroxide, 2.4g of sodium aluminate, and 0.3g of ferric nitrate nonahydrate were added. The mixture was then subjected to hydrothermal synthesis at 140℃ for 72h. The reaction product was then filtered and dried to obtain the precursor. The precursor was impregnated with 0.1mol / L ammonium nitrate solution for 24h and then calcined at 500℃ for 6h to obtain the first molecular sieve.

[0086] (2) Mix 15g of pseudoboehmite, 6g of 30% nitric acid aqueous solution and 60g of the first molecular sieve, and then ball mill at 80r / min for 2h and calcine at 500℃ for 6h to obtain the composite catalyst.

[0087] The SEM image of the catalyst prepared in this embodiment is shown below. Figure 2 As shown, from Figure 2 It can be seen that the catalyst obtained by the present invention has a uniform particle size distribution.

[0088] Example 2

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

[0090] (1) 110g of 30% silica sol was added to 350g of water and stirred and dispersed. Then, 60g of tetrapropylammonium bromide, 6g of aluminum isopropoxide, and 0.3g of ferric nitrate nonahydrate were added. The mixture was then subjected to hydrothermal synthesis at 120℃ for 72h. The reaction product was then filtered and dried to obtain the precursor. The precursor was impregnated with 0.1mol / L ammonium nitrate solution for 24h and then calcined at 500℃ for 6h to obtain the first molecular sieve.

[0091] (2) Mix 15g of pseudoboehmite, 2g of 35% nitric acid and 45g of the first molecular sieve, and then ball mill at 100r / min for 2h and calcine at 500℃ for 6h to obtain the composite catalyst.

[0092] Example 3

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

[0094] (1) 300g of tetraethyl silicate was added to 500g of water and stirred and dispersed. Then, 80g of tetrapropylammonium hydroxide, 2.2g of sodium aluminate and 1.0g of magnesium nitrate were added. The mixture was then subjected to hydrothermal synthesis at 100℃ for 100h. The reaction product was then filtered and dried to obtain the precursor. The precursor was then calcined at 800℃ for 3h to obtain the first molecular sieve.

[0095] (2) Mix 10g of pseudoboehmite, 2g of 35% nitric acid and 45g of the first molecular sieve, and then ball mill at 80r / min for 30min and calcine at 600℃ for 3h to obtain the composite catalyst.

[0096] Example 4

[0097] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1, except that 0.3g of ferric nitrate nonahydrate is replaced with 0.22g of zinc nitrate hexahydrate. Therefore, it will not be described again here.

[0098] Example 5

[0099] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1 except that 15g of boehmite and 6g of 30% nitric acid aqueous solution in step (2) are replaced with 125g of aluminum nitrate nonahydrate, 20g of ammonium bicarbonate and 40g of water. It will not be repeated here.

[0100] Example 6

[0101] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. The preparation method is the same as in Example 1 except that 20g of tetraethyl silicate is added in step (1), and will not be repeated here.

[0102] Example 7

[0103] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. 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.

[0104] Example 8

[0105] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. The preparation method is the same as that in Example 1 except that nitric acid aqueous solution is not added in step (2), and will not be repeated here.

[0106] Example 9

[0107] This embodiment provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. Except for the mass of boehmite in step (2) being 1g, the preparation method is the same as in Example 1, and will not be repeated here.

[0108] Comparative Example 1

[0109] This comparative example provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. Except for step (2), the preparation method is the same as that in Example 1, and will not be repeated here.

[0110] Specifically, step (2) is as follows: 15g of γAl2O3 powder (particle size range of 2-15μm) and the first molecular sieve are mixed and then ball-milled at 80r / min for 2h and calcined at 500℃ for 6h to obtain the composite catalyst.

[0111] Comparative Example 2

[0112] This comparative example provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. The preparation method is the same as that in Example 1, except that 0.3g of ferric nitrate nonahydrate is added to the mixture in step (2) in step (1), and will not be repeated here.

[0113] Comparative Example 3

[0114] This comparative example provides a method for preparing a composite catalyst for the oxidation of benzene to phenol. The preparation method is the same as that in Example 1 except that step (2) is omitted, and will not be repeated here.

[0115] Test methods: ICP was used to test the silica-alumina ratio (molar ratio of elements) of the first molecular sieve; physical adsorption was used to test the pore size of the first molecular sieve; ICP was used to test the metal element content in the composite molecular sieve; physical adsorption was used to test the pore size and specific surface area of ​​the composite molecular sieve; and scanning electron microscopy was used to test the particle size of the composite molecular sieve.

[0116] The XRD patterns of the composite catalysts for the oxidation of benzene to phenol prepared in Examples 1-2 and Examples 6-7 are as follows: Figure 1 As shown, from Figure 1 It can be seen that the composite catalyst prepared by this invention contains both molecular sieve structure and γAl2O3 structure.

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

[0118] Table 1

[0119]

[0120] Application Examples 1-9 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 in the above-described examples and comparative examples, loading 30g of catalyst into a fixed-bed catalyst bed, heating to 550℃, feeding water at a rate of 40mL / h, and activating the catalyst for 4h. After activation, benzene is fed into a preheating mixer at a rate of 80mL / h and nitrous oxide at a rate of 90mL / h. The mixer temperature is 400℃, the reactor temperature is 450℃, and the reaction is carried out for 12h before sampling and analysis.

[0122] Furthermore, the catalyst provided in Example 1 was regenerated in an air atmosphere at 550°C and then recycled for 7 cycles.

[0123] Application Example 10

[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 35g of catalyst into a fixed-bed catalyst bed, heating to 500℃, feeding water at a rate of 45mL / h, and activating the catalyst for 4.5h. After activation, benzene is fed into a preheating mixer at a rate of 90mL / h and nitrous oxide at a rate of 100mL / h. The mixer temperature is 450℃, the reactor temperature is 450℃, and the reaction is carried out for 12h before sampling and analysis.

[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] Phenol yield / % Phenol selectivity / % Application Example 1 73.2 98.2 Loop - 1 72.9 98.1 Cycle-2 73.0 98.0 Cycle-3 73.7 97.9 Cycle-4 73.1 98.1 Cycle-5 73.2 98.0 Cycle-6 72.9 98.2 Cycle-7 72.4 98.1 Application Example 2 71.9 98.6 Application Example 3 72.5 98.9 Application Example 4 72.6 98.3 Application Example 5 69.7 98.0 Application Example 6 77.3 91.8 Application Example 7 59.1 97.7 Application Example 8 64.2 95.8 Application 9 58.8 97.6 Application Comparative Example 1 64.2 96.4 Application Comparative Example 2 61.2 97.8 Application Comparative Example 3 63.4 94.7

[0128] The following points can be observed from Tables 1 and 2:

[0129] (1) As can be seen from the comprehensive application examples 1 to 4, the preparation method of the composite catalyst for the oxidation of benzene to phenol provided by the present invention can obtain a catalyst with high selectivity and yield. When applied to the oxidation of benzene to phenol, the phenol yield can reach more than 71.9% and the phenol selectivity is more than 98.0%.

[0130] (2) It can be seen from the combined application examples 1 and 3 that γAl2O3 powder was directly used for composite in application example 1, active metal was added in step (2) for loading in application example 2, and γAl2O3 was not introduced in application example 3. In the end, the selectivity and yield of application examples 1 to 3 were reduced in the application process. Moreover, the cycle life of the composite catalyst used in application example 1 was not as good as that of application example 1. This shows that the present invention obtained a composite catalyst product with high yield and selectivity by using a specific step to combine γAl2O3 and the first molecular sieve.

[0131] (3) It can be seen from the combined application examples 1 and 5-9 that the ratio between the added raw materials was adjusted in application examples 5-9. Compared with application example 1, the yield and selectivity of phenol decreased. This shows that the present invention significantly improves the selectivity and yield of the composite catalyst by controlling the ratio between the raw materials within a specific range.

[0132] 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 composite catalyst in the reaction of nitrous oxide with benzene to produce phenol, characterized in that, The preparation method of the composite catalyst comprises: (1) a silicon source, a first aluminum source, a metal source, a template agent and a solvent are subjected to a hydrothermal synthesis reaction to obtain a precursor; the precursor is subjected to a first calcination to obtain a first molecular sieve; (2) a second aluminum source and the first molecular sieve are mixed, and then subjected to ball milling and a second calcination in sequence to obtain the composite catalyst; In step (1), the molar ratio of the silicon source to the first aluminum source is 20-100:

1. In step (1), the metal element in the metal source includes any one or a combination of at least two of Ca, Mg, Fe, Zn or Cu. In step (2), the second aluminum source includes a mixture of pseudo-boehmite and an acid, or the second aluminum source includes a mixture of an aluminum salt, ammonium bicarbonate and water. In step (2), the temperature of the second calcination is 500-600 ℃, and the time of the second calcination is 3-15 h.

2. Use according to claim 1, characterized in that, In step (1), the molar ratio of the silicon source to the first aluminum source is 20-60:

1.

3. Use according to claim 1, characterized in that, In step (1), the molar ratio of the template agent to the first aluminum source is 5-10:

1.

4. Use according to claim 1, characterized in that, In step (1), the template agent includes any one or a combination of at least two of tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium hydroxide, triethylamine or ethylenediamine.

5. The use according to claim 1, characterized in that, In step (1), the ratio of the amount of substance of silicon element in the silicon source to the amount of substance of metal element in the metal source is 200-2000:

1.

6. Use according to claim 5, characterized in that, In step (1), the ratio of the amount of substance of silicon element in the silicon source to the amount of substance of metal element in the metal source is 500-1600:

1.

7. Use according to claim 1, characterized in that, In step (1), the mass ratio of the solvent to the silicon source is 1-5:

1.

8. Use according to claim 7, characterized in that, The mass ratio of the solvent to the silicon source is 1.3-4:

1.

9. The use according to claim 1, characterized in that, In step (1), the solvent includes water.

10. The use according to claim 1, characterized in that, In step (1), the metal source includes a metal salt.

11. Use according to claim 10, characterized in that, The anion of the metal salt includes nitrate and / or acetate.

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

13. The use according to claim 1, characterized in that, In step (1), the first aluminum source includes any one or a combination of at least two of sodium aluminate, aluminum isopropoxide, pseudo-boehmite, aluminum nitrate or aluminum sulfate.

14. The use according to claim 1, characterized in that, In step (1), a sodium source is further added in the hydrothermal synthesis reaction.

15. Use according to claim 14, characterized in that, The molar ratio of the sodium source to the first aluminum source is 0.5-4:

1.

16. Use according to claim 15, characterized in that, The molar ratio of the sodium source to the first aluminum source is 1-2:

1.

17. The use according to claim 14, characterized in that, The sodium source includes sodium aluminate and / or sodium hydroxide.

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

19. Use according to claim 18, characterized in that, The temperature of the hydrothermal synthesis reaction is 120-180 ℃.

20. The use according to claim 1, characterized in that, In step (1), the time of the hydrothermal synthesis reaction is more than 48 h.

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

22. The use according to claim 21, characterized in that, The temperature of the first calcination is 500-600 ℃.

23. The use according to claim 1, characterized in that, In step (1), the time of the first calcination is 3-15 h.

24. The use according to claim 1, characterized in that, In step (2), the aluminum salt includes any one or a combination of both of aluminum nitrate nonahydrate and aluminum silicate.

25. The use according to claim 1, characterized in that, The acid includes nitric acid.

26. The use according to claim 1, characterized in that, The amount of the aluminum-containing compound in the second aluminum source is 40-100% of the mass of the first molecular sieve.

27. The use according to claim 1, characterized in that, The amount of acid in the second aluminum source is 5-10% of the mass of the first molecular sieve.

28. The use of claim 1, wherein, The amount of ammonium bicarbonate in the second aluminum source is 40-100% of the mass of the first molecular sieve.

29. The use according to claim 1, characterized in that, The ball milling time in step (2) is 30 min-2 h.

30. The use of claim 1, wherein, The rotation speed of the ball milling is 60-100 r / min.

31. The use according to claim 1, characterized in that, The composite catalyst is a composite catalyst of metal oxide-molecular sieve-gamma Al2O3, the content of gamma Al2O3 in the composite catalyst is 20-30wt%, the content of molecular sieve in the composite catalyst is 70-80%, the content of metal element in the composite catalyst is 0.1-1wt%, the molar ratio of silicon to aluminum in the composite catalyst is 10-30:1, the molar ratio of silicon element to metal element in the composite catalyst is 1600-3200:1, the particle size of the composite catalyst is 1-2μm, the specific surface area of the composite catalyst is 200-400m 2 / g, and the pore size of the composite catalyst is 0.4-1nm.

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