ZSM-5 eutectic molecular sieve catalyst, preparation method thereof and application of ZSM-5 eutectic molecular sieve catalyst in preparation of phenol by oxidizing benzene with laughing gas

Abstract

The invention provides a ZSM-5 eutectic molecular sieve catalyst, a preparation method thereof and application of the ZSM-5 eutectic molecular sieve catalyst in preparation of phenol by oxidizing benzene with laughing gas. The ZSM-5 eutectic molecular sieve catalyst comprises a carrier and an active component, the carrier comprises a eutectic molecular sieve, and the eutectic molecular sieve is of a eutectic structure formed by a ZSM-5 molecular sieve and a second molecular sieve; the second molecular sieve is a microporous molecular sieve, and the second molecular sieve comprises any one or a combination of at least two of SAPO-5, Beta or MOR. The eutectic molecular sieve with a multi-channel structure is adopted, so that the loading amount of the active component Fe can be reduced, and the space time yield of phenol in the process of preparing phenol by oxidizing benzene with laughing gas is improved; and the stability of the catalyst is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a ZSM-5 eutectic molecular sieve catalyst, a preparation method thereof, and application thereof in oxidizing benzene to prepare phenol using laughing gas. Background Art

[0002] Phenol is an important chemical raw material, mainly used in the production of chemicals such as phenolic resin, epoxy resin, alkylphenol, bisphenol A and adipic acid. At present, the production of phenol by the three-step method of cumene is the mainstream technology for industrial production of phenol, but this technical route generates explosive cumene peroxide during the reaction, uses a large amount of sulfuric acid, and the process route is long and complicated, the equipment requirements are high, and the pollution is serious. It is very important to develop a green new synthesis technology for phenol at present. For example, CN105080533A reports the technology of preparing phenol by hydroxylation of benzene using hydrogen peroxide as an oxidant.

[0003] Laughing gas is a major greenhouse gas, and its global warming potential (GWP) is 310 times that of CO2, and its life span in the atmosphere is about 120 years, and it also has a great destructive effect on the ozone layer. Monsanto (Monsanto) and Russian Boleskov Catalysis Research Institute (BIC) jointly developed a process for preparing phenol by oxidation of benzene with laughing gas. In 1998, a pilot scale of 2000 tons / year was completed (Chemical Progress, 20 (2003) 386-395). It is reported that the technology is carried out under the operating conditions of gas phase and low pressure, and the reaction unit is an adiabatic fixed bed, and 4 moles of phenol can be obtained per kilogram of catalyst per hour. This technology can effectively utilize the waste gas N2O produced by Monsanto in Pensacda, Florida to produce adipic acid. A phenol device is built near the Pensacda adipic acid device, which can effectively utilize N2O, and phenol can be used to produce adipic acid or sell as a commodity. Compared with the cumene process, this process is simpler, has a higher phenol yield, and produces less waste. It can achieve high added value utilization of nitrous oxide, is environmentally friendly, and its investment cost is only 55%-60% of that of the cumene process. However, the low activity and easy deactivation of the catalyst are bottlenecks that restrict the industrial application of this technology.

[0004] Panov and other researchers in Russia used Fe / ZSM-5 molecular sieve as catalyst and nitrous oxide as oxidant to react with benzene at 300-400℃ to produce phenol. The selectivity of phenol can reach 97%, but the activity of the catalyst gradually decreases with the extension of reaction time. (Journal of Catalysis 2008, 254(1), 110-120.) CN102125868A discloses a micro-mesoporous composite Fe-ZSM-5 molecular sieve and applies it to the hydroxylation of benzene to phenol. After 3 hours of reaction, the conversion rate of benzene can be maintained at 20%. Li Can et al. (Chem. Commun., 2008, 774–776) used mesoporous Fe-Al-SBA-15 molecular sieve as catalyst to study the oxidation of benzene with nitrous oxide to produce phenol. The study found that due to the lack of microporous shape selectivity, the selectivity of phenol on the mesoporous Fe-Al-SBA-15 catalyst was poor.

[0005] Existing research on the oxidation of benzene to phenol by laughing gas mainly focuses on the field of Fe-supported microporous molecular sieves, especially Fe / ZSM-5. The catalyst shows good activity and phenol selectivity, but the catalyst deactivates quickly and has poor stability, which restricts the development of this technology. In order to improve the stability of the catalyst, researchers introduced mesopores into the ZSM-5 molecular sieve, or prepared micro-mesoporous composite molecular sieve catalysts. The introduction of mesopores can increase mass transfer and reduce the occurrence of carbon deposition, but the effect of improving the catalyst deactivation rate is limited. The prepared catalyst often shows obvious deactivation in a few hours or even tens of minutes, which still cannot meet the needs of industrial production. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a ZSM-5 eutectic molecular sieve catalyst and a preparation method thereof and application in the oxidation of benzene to phenol by nitrous oxide, which can solve the problems of rapid catalyst deactivation and poor stability in the technology of oxidizing benzene to phenol by nitrous oxide, and can also expand the application scenarios of the ZSM-5 eutectic molecular sieve catalyst, and has broad application prospects.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a ZSM-5 eutectic molecular sieve catalyst, wherein the ZSM-5 eutectic molecular sieve catalyst comprises a carrier and an active component;

[0009] The carrier includes a eutectic molecular sieve, and the eutectic molecular sieve is a eutectic structure formed by a ZSM-5 molecular sieve and a second molecular sieve;

[0010] The second molecular sieve is a microporous molecular sieve, and the second molecular sieve includes any one of SAPO-5, Beta or MOR, or a combination of at least two thereof.

[0011] The present invention uses a microporous molecular sieve in a eutectic state as a carrier of the Fe active component, and compared with the existing catalyst carrier for oxidizing benzene to phenol with laughing gas, the catalyst stability of the present invention is significantly improved. Since the eutectic molecular sieve is a composite crystal product formed by the eutectic crystal of multiple molecular sieves, the unique eutectic pore structure formed by such eutectic molecular sieve is more conducive to the contact of reactants with active centers and product diffusion, and can inhibit the occurrence of carbon deposition reaction, thereby significantly improving the stability of the catalyst.

[0012] However, multiple studies have found that not all eutectic molecular sieves are suitable carriers of Fe active centers. Currently, only ZSM-5 eutectic molecular sieves, such as ZSM-5 / SAPO-5, ZSM-5 / Beta and ZSM-5 / MOR, are found to be ideal carriers. Among them, ZSM-5 is necessary for the formation of eutectic molecular sieves, because ZSM-5 molecular sieves, as carriers of Fe active centers, show excellent and irreplaceable effects in the reaction of nitrous oxide oxidation of benzene to phenol. When other eutectic molecular sieves that do not contain ZSM-5 are selected, the performance of the catalyst is poor, which may be closely related to the unique pore structure and acidic sites of ZSM-5. Research has found that when using ZSM-5 eutectic molecular sieve, in addition to ZSM-5, another molecular sieve must have microporous channels with a pore size of 0.6nm to 2.0nm. Those skilled in the art can choose varieties that meet the pore size requirements from commercial molecular sieve products, such as SAPO-5, Beta or MOR. After the large-pore microporous molecular sieve forms a eutectic molecular sieve with ZSM-5, it can effectively improve the anti-carbon deposition performance of the ZSM-5 microporous molecular sieve, thereby achieving the effect of improving stability.

[0013] For example, when ZSM-5 and ZSM-11 eutectic molecular sieves are selected, the pore size of the ZSM-11 microporous molecular sieve is all less than 0.6nm, and the obtained catalyst is applied to the benzene hydroxylation reaction, and the effect is not good. The second eutectic molecular sieve of the same small size also reproduces this problem, such as ZSM-35 microporous molecular sieve. When ZSM-5 and MOR eutectic molecular sieves are selected, the pore size of the MOR structure is 0.62nm. With ZSM-5 / MOR eutectic molecular sieve as the carrier, the activity of the obtained catalyst decays slowly, and the catalyst stability is significantly improved. The same second eutectic molecular sieve also reproduces this effect, such as SAPO-5 and Beta.

[0014] The second molecular sieve does not have to contain only one molecular sieve, and may include any one of SAPO-5, Beta or MOR, or a combination of at least two of them, such as a combination of SAPO-5 and Beta, a combination of SAPO-5 and MOR, a combination of MOR and Beta, a combination of SAPO-5, Beta and MOR, etc.

[0015] Preferably, the mass ratio of the ZSM-5 molecular sieve to the second molecular sieve is (0.5-3):1, for example, it can be 0.5:1, 0.8:1, 1.1:1, 1.4:1, 1.7:1, 1.9:1, 2.2:1, 2.5:1, 2.8:1 or 3:1, etc.

[0016] In the present invention, controlling the mass ratio within this range is conducive to achieving the best performance of the catalyst; if the proportion of ZSM-5 is too large, the catalyst is easily deactivated; if the proportion of ZSM-5 is too small, the catalyst activity is low.

[0017] Preferably, the acid value of the ZSM-5 eutectic molecular sieve catalyst is 50 to 200 μmol / g, for example, it can be 50 μmol / g, 67 μmol / g, 84 μmol / g, 100 μmol / g, 117 μmol / g, 134 μmol / g, 150 μmol / g, 167 μmol / g, 184 μmol / g or 200 μmol / g, etc.

[0018] The acid value of the catalyst described in the present invention should be 50 to 200 μmol / g. Generally, the higher the acid value, the better the activity. When the acid value is low, the catalyst activity is low. The acid value of the prior art ZSM-5 catalyst is usually above 300 μmol / g. However, the inventors found that under the catalyst system of the present invention, when the acid value exceeds 200 μmol / g, although the catalyst shows excellent activity in the initial stage of the reaction, the activity decays rapidly and the stability of the catalyst is poor. This may be related to the pore characteristics of the eutectic molecular sieve. On the one hand, the multi-pore characteristics of the eutectic molecular sieve are conducive to the diffusion of the product compared with the existing pore characteristics; on the other hand, the distance between different pores in the eutectic molecular sieve is short, so it will also cause the distance of the active component to be shorter, and a specific range of acid value control is required to adjust the reaction rate so that the product generation rate is reduced to a conventional level.

[0019] Preferably, the loading amount of Fe element in the ZSM-5 eutectic molecular sieve catalyst is 0.05-0.45wt%, for example, it can be 0.05wt%, 0.1wt%, 0.14wt%, 0.19wt%, 0.23wt%, 0.28wt%, 0.32wt%, 0.37wt%, 0.41wt% or 0.45wt%, etc.

[0020] Compared with a single ZSM-5 microporous molecular sieve or a plurality of microporous molecular sieve compositions obtained by physical blending, the present invention requires a lower Fe loading than conventional molecular sieves due to the diversity of the pore structure of the eutectic molecular sieve. If the iron content is too high, a large number of side reactions will occur, and the product selectivity is poor.

[0021] Preferably, the second molecular sieve has micropores with a pore size of 0.6 to 2.0 nm, for example, 0.6 nm, 0.7 nm, 0.8 nm, 1.0 nm, 1.2 nm, 1.3 nm, 1.5 nm, 1.8 nm or 2.0 nm.

[0022] Preferably, the specific surface area of ​​the catalyst is 100 to 450 m 2 / g, for example, it can be 100m 2 / g, 120m 2 / g, 140m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g, 350m 2 / g, 400m 2 / g or 450m 2 / g, etc.

[0023] In a second aspect, the present invention provides a method for preparing the ZSM-5 eutectic molecular sieve catalyst according to the first aspect, the preparation method comprising the following steps:

[0024] The eutectic molecular sieve is treated with acid to obtain the acid-treated molecular sieve.

[0025] The iron source is loaded on the acid-treated molecular sieve and calcined to obtain the ZSM-5 eutectic molecular sieve catalyst.

[0026] The eutectic molecular sieve of the present invention includes a eutectic molecular sieve composed of ZSM-5 and another microporous molecular sieve of other structure, such as ZSM-5 / SAPO-5, ZSM-5 / Beta or ZSM-5 / MOR eutectic molecular sieve.

[0027] In the present invention, the acid treatment can remove Al from the eutectic molecular sieve, thereby controlling the acid value of the eutectic molecular sieve to be between 50 and 200 μmol / g.

[0028] There is no particular limitation on the Fe loading method in the present invention, for example, it is a conventional method for Fe loading molecular sieve in the art, for example, it can be loaded by an equal volume impregnation method or other methods, and the related technology can refer to existing literature. The equal volume impregnation method is generally to immerse the eutectic molecular sieve into an aqueous solution of Fe salt, and adjust the impregnation time, ratio, etc. to adjust the Fe loading amount.

[0029] The Fe source used is not particularly limited, and common examples include ferric nitrate, ferric chloride, ferric phosphate or ferric sulfate.

[0030] Preferably, the acid value of the molecular sieve after the acid treatment is 60 to 220 μmol / g, for example, 60 μmol / g, 67 μmol / g, 84 μmol / g, 100 μmol / g, 117 μmol / g, 134 μmol / g, 150 μmol / g, 167 μmol / g, 184 μmol / g, 200 μmol / g, 210 μmol / g, 215 μmol / g or 220 μmol / g, etc. Exemplarily, the eutectic molecular sieve can be de-Aled with hydrochloric acid and / or nitric acid having an acid concentration of 0.01 to 3 mol / L (for example, 0.01 mol / L, 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.5 mol / L, 2 mol / L, 2.2 mol / L, 2.3 mol / L, 2.5 mol / L or 3 mol / L, etc.), so that the acid value of the eutectic molecular sieve reaches the target value.

[0031] Preferably, the calcination temperature is 450-750°C, for example, it can be 450°C, 484°C, 517°C, 550°C, 584°C, 617°C, 650°C, 684°C, 717°C or 750°C, and the calcination time is 2-12h, for example, it can be 2h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc.

[0032] In a third aspect, the present invention provides a ZSM-5 eutectic molecular sieve catalyst as described in the first aspect, and / or a catalyst prepared by the preparation method of the ZSM-5 eutectic molecular sieve catalyst as described in the second aspect, and their use in the oxidation of benzene to phenol by laughing gas.

[0033] When the catalyst provided by the present invention is used for oxidizing benzene to prepare phenol with laughing gas, the space-time yield of phenol is above 10 mmol / g·h, the catalyst is continuously operated for 30 hours, the space-time yield of phenol does not decrease, the catalyst does not deactivate, and the stability is significantly improved.

[0034] Preferably, the reaction temperature of the laughing gas oxidation of benzene to phenol is 350-470°C, for example, it can be 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 419°C, 430°C, 440, 450, 459 or 470°C.

[0035] Preferably, the reaction pressure of the nitrous oxide oxidation of benzene to produce phenol is 0.01-0.5 MPa, for example, it can be 0.01 MPa, 0.07 MPa, 0.12 MPa, 0.18 MPa, 0.23 MPa, 0.29 MPa, 0.34 MPa, 0.4 MPa, 0.45 MPa or 0.5 MPa.

[0036] Preferably, the molar ratio of benzene:N2O:N2 in the oxidation of benzene to phenol by laughing gas is (1-3):1:(7-15), wherein the number of benzene can be, for example, 1, 1.1, 1.2, 1.3, 1.5, 2.0, 2.2, 2.5, 2.8 or 3, and the number of nitrogen can be, for example, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5 or 15, etc.

[0037] Preferably, the total air velocity in the oxidation of benzene to phenol by laughing gas is 3000-5000h -1 , for example, it can be 3000h -1 , 3200h-1, 3440h -1 、3600h -1 、3800h -1 、4100h -1 、4300h -1 、4500h -1 、4700h -1 or 5000h -1 wait.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] (1) The ZSM-5 eutectic molecular sieve catalyst provided by the present invention uses a special eutectic molecular sieve as a carrier, which can significantly reduce the loading amount of the iron active component while achieving the same catalytic effect, thereby improving the yield of the catalytic reaction and enhancing the stability of the catalyst;

[0040] (2) The preparation method of the ZSM-5 eutectic molecular sieve catalyst provided by the present invention first treats the ZSM-5 eutectic molecular sieve with acid and then loads iron, which can effectively control the acid value of the final catalyst and improve the comprehensive performance of the catalyst;

[0041] (3) The ZSM-5 eutectic molecular sieve catalyst provided by the present invention can achieve a space-time yield of phenol of 6 mmol / g·h or more, more preferably 10 mmol / g·h or more, in the oxidation of benzene to phenol by laughing gas;

[0042] (4) The ZSM-5 eutectic molecular sieve catalyst provided by the present invention can operate continuously for more than 30 hours in the oxidation of benzene to phenol by laughing gas, and has excellent catalytic performance and strong stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram showing the phenol yield of the ZSM-5 eutectic molecular sieve catalyst provided in Example 1 of the present invention and Comparative Example 3 as a function of the catalytic time in the oxidation of benzene to phenol by laughing gas. DETAILED DESCRIPTION

[0044] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] Terms and Definitions

[0046] The naming rules of molecular sieves and the corresponding structural types are implemented in accordance with the naming regulations of the International Molecular Sieve Association. The molecular sieve structural information of the corresponding structural type can be found on its official website.

[0047] The present invention is described in detail below through specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels. The following eutectic molecular sieve preparation steps refer to the cited literature, and the composition change of the eutectic molecular sieve is achieved by adjusting the raw material composition.

[0048] It is a conventional method to prepare a eutectic molecular sieve using two different molecular sieve raw materials. The following lists the preparation methods of the eutectic molecular sieves used in each embodiment:

[0049] 1. Eutectic molecular sieve 1: ZSM-5 / SAPO-5 eutectic molecular sieve. The preparation steps are basically referred to "Wang Zhixiang, Taiyuan University of Technology, Master's Thesis, 2018.16 pages, 2.2.2.1-2.2.2.2. The mass ratio of ZSM-5 / SAPO-5 is adjusted, and 0.6-SAPO-5 is synthesized by adjustment, and then 0.6-SAPO-5 and HZSM-5 (that is, ZSM-5 in this application, because it contains H ions, it is sometimes also called HZSM-5 in the industry) are added in a mass ratio of 1:1 to obtain a ZSM-5 / SAPO-5 eutectic molecular sieve with a mass ratio of 1:1.

[0050] 2. Eutectic molecular sieve 2: ZSM-5 / Beta eutectic molecular sieve. The preparation steps are basically based on Example 6 of CN102372277A, except that 30 grams of ethanolamine is adjusted to 60 grams of ethanolamine. Beta has a three-dimensional twelve-membered ring channel, in which the pore size of the linear channel is about 0.76*0.67 nm, and the mass ratio of ZSM-5 / Beta is 2:1.

[0051] 3. Eutectic molecule: 3: ZSM-5 / MOR eutectic molecular sieve, the preparation steps refer to Example 3 of CN113908881A, the pores of MOR contain twelve-membered ring channels, the maximum diameter of which is 0.7 nm, and the mass ratio of ZSM-5 / MOR is 3:2;

[0052] 4. Eutectic molecular sieve 4: ZSM-5 / ZSM-11 eutectic molecular sieve, the preparation steps refer to Example 5 of CN104624226A, and the pH is washed with deionized water to 8.2, the mass ratio of ZSM-5 / ZSM-11 is 1:1, and the pore size of ZSM-11 is 0.53nm;

[0053] 5. Eutectic molecular sieve 5: It is basically the same as eutectic molecular sieve 1, and its preparation difference is only that the feed mass ratio of 0.6-SAPO-5 and HZSM-5 (ie, ZSM-5 in this application) is changed to 1:3.5, and the mass ratio of the obtained ZSM-5 / SAPO-5 eutectic molecular sieve is 3.5:1.

[0054] 6. Eutectic molecular sieve 6: It is basically the same as eutectic molecular sieve 1, and its preparation difference is only that the feed mass ratio of 0.6-SAPO-5 and HZSM-5 (ie, ZSM-5 in this application) is changed to 1:0.5, and the mass ratio of the obtained ZSM-5 / SAPO-5 eutectic molecular sieve is 0.5:1.

[0055] Test Method

[0056] 1.Fe, Si and Al content

[0057] The ICP instrument was used for testing, and the equipment manufacturer was Agilent, and the brand was 5800ICP-OES.

[0058] 2. Catalyst pore size

[0059] Nitrogen adsorption and desorption were used to test the pore size of the eutectic molecular sieve catalyst used for benzene oxidation to phenol. The detection instrument was: Bester BSD-PM.

[0060] 3. Quality ratio

[0061] XRD was used to determine the type and mass ratio of eutectic molecular sieve in the catalyst. The detection instrument was: Danfang Fangyuan, DX-2700 X-ray diffractometer.

[0062] 4. Catalyst activity and stability evaluation

[0063] The catalytic activity and stability of the catalyst in the hydroxylation of benzene to phenol were evaluated in a fixed bed reactor. The reaction conditions were as follows: reaction temperature 350°C, reaction pressure 0.2 MPa, benzene:N2O:N2=2:1:10, total space velocity 4000 h -1; After 1 hour of reaction, samples were taken for determination and recording of the phenol space-time yield. Thereafter, samples were taken every hour to determine the phenol space-time yield (in mmol / g·h). When the catalyst activity began to decline significantly, it was considered that the catalyst was deactivated. The recorded reaction time was the initial deactivation time of the catalyst. The beginning of the significant decline means that the measured phenol space-time yield continued to decline for 5 consecutive points and the cumulative decline of the 5 points was greater than or equal to 0.8 mmol / g·h. Then, the catalyst operation time corresponding to the point before the first point where the decline began was recorded.

[0064] 5. Catalyst acid value

[0065] The catalyst acid value is tested by NH3-TPD, and the testing process includes: taking 100 mg of the catalyst sample and placing it in a 30 mL / min helium carrier gas environment; firstly heating to 300°C at a rate of 10°C / min, keeping the temperature constant for 30 minutes, and naturally cooling to 50°C, which can remove water and other pollutants; then introducing an ammonia-helium mixed gas containing 10 vol% NH3, at which time the acid sites on the sample to be tested will chemically combine with ammonia, and after 30 minutes of adsorption, all acid sites will react with ammonia; then, helium is used to purge to remove the unreacted ammonia; after purging, the temperature is raised to 700°C at a rate of 20°C / min for desorption. During the heating process, the NH3 adsorbed on the acid sites will gradually detach.

[0066] The chemical bond between the acidic site and ammonia is stable at 50°C. Generally, when it reaches above 100°C, the chemical bond between the acidic site and ammonia becomes unstable. The least stable one will desorb first to form a desorption peak. As the temperature continues to rise, the chemical bond with better stability will gradually desorb until all acidic sites are separated from ammonia at 700°C. Therefore, the temperature is raised to 700°C at a rate of 20°C / min to desorb ammonia, and the NH3-TPD spectrum is detected. The signal acquisition of the NH3-TPD test process uses a thermal conductivity cell detector (TPD). The detector can use the difference in thermal conductivity between the carrier gas and the gas to be tested to reflect the concentration change of ammonia during the heating process, and convert this chemical signal into a voltage signal and feed it back to the spectrum. The horizontal axis of the spectrum is temperature °C, and the vertical axis is voltage mv. If a specified amount of ammonia is introduced in advance, the corresponding relationship between the ammonia content and the integrated area of ​​the desorption peak in the spectrum can be constructed. According to the ratio that 1 mol of acid sites can adsorb 1 mol of ammonia, the amount of ammonia adsorbed can be converted into the acid site content. In this way, the peak area data can be converted into acid site content data according to the "correspondence between ammonia content and the integrated area of ​​the desorption peak in the spectrum".

[0067] Examples and Comparative Examples

[0068] The molecular sieve (eutectic molecular sieve, physical mixing of molecular sieve or single molecular sieve) is treated with a dilute acid solution, and the mass ratio of the molecular sieve to the dilute acid solution is 1: 10, and the acid value is 60-220 μmol / g after stirring at room temperature. The molecular sieve after acid treatment, using an isovolumetric impregnation method, is supported on the molecular sieve after the above-mentioned acid treatment by an iron source, and is supported using an aqueous solution of ferric nitrate, and the molecular sieve after acid treatment is matched with 0.04-0.32g of solute ferric nitrate per gram of molecular sieve, and the molecular sieve after acid treatment is matched with 1g of solvent water, and an aqueous solution of ferric nitrate is configured, and impregnated for 1-24h to obtain an impregnated molecular sieve. After drying, the molecular sieve after impregnation is roasted at 450-750°C for 2-12 hours to obtain a molecular sieve catalyst. And characterize the catalyst obtained by the comparative example, including the loading amount of Fe in the catalyst, the catalyst acid value, the specific surface area of ​​the catalyst, the catalyst activity and the deactivation time.

[0069] The following is a detailed description with specific examples.

[0070] Example 1

[0071] The eutectic molecular sieve 1 is treated with a 0.5mol / L nitric acid solution, and the mass ratio of the molecular sieve to the dilute acid solution is 1: 10, and the molecular sieve is stirred at room temperature for 2h to obtain an acid-treated molecular sieve with an acid value of 140μmol / g. The acid-treated molecular sieve, using an isovolumetric impregnation method, is loaded with an iron source on the above-mentioned acid-treated molecular sieve, and is loaded with an aqueous solution of ferric nitrate, and is matched with 0.14g of solute ferric nitrate per gram of the molecular sieve after acid treatment, and 1g of solvent water per gram of the molecular sieve after acid treatment is matched, and an aqueous solution of ferric nitrate is configured, impregnated for 12h, to obtain an impregnated molecular sieve. After drying, the above-mentioned impregnated molecular sieve is roasted at 600°C for 6 hours to obtain a ZSM-5 eutectic molecular sieve catalyst. The catalyst obtained by this embodiment is characterized, including the loading amount of Fe in the catalyst, the catalyst acid value, the specific surface area of ​​the catalyst, the catalyst activity and the deactivation time.

[0072] Example 2

[0073] The eutectic molecular sieve 2 is treated with a 0.2mol / L nitric acid solution, and the mass ratio of the molecular sieve to the dilute acid solution is 1:10, and the molecular sieve is stirred at room temperature for 2.5h to obtain an acid-treated molecular sieve with an acid value of 150μmol / g. The acid-treated molecular sieve, using an isovolumetric impregnation method, is loaded with an iron source on the above-mentioned acid-treated molecular sieve, and is loaded with an aqueous solution of ferric nitrate, and is matched with 0.04g of solute ferric nitrate per gram of acid-treated molecular sieve, and 1g of solvent water per gram of acid-treated molecular sieve, and an aqueous solution of ferric nitrate is configured, impregnated for 1h, to obtain an impregnated molecular sieve. After the above-mentioned impregnated molecular sieve is dried, it is roasted at 450°C for 12 hours to obtain a ZSM-5 eutectic molecular sieve catalyst. The catalyst obtained in this embodiment is characterized, including the loading amount of Fe in the catalyst, the catalyst acid value, the specific surface area of ​​the catalyst, the catalyst activity, and the deactivation time.

[0074] Example 3

[0075] The eutectic molecular sieve 3 is treated with a 2.5mol / L hydrochloric acid solution, and the mass ratio of the molecular sieve to the dilute acid solution is 1: 10, and the molecular sieve is stirred at room temperature for 3h to obtain an acid-treated molecular sieve with an acid value of 210μmol / g. The acid-treated molecular sieve, using an isovolumetric impregnation method, is loaded with an iron source on the above-mentioned acid-treated molecular sieve, and is loaded with an aqueous solution of ferric nitrate, and is matched with 0.32g of solute ferric nitrate per gram of the molecular sieve after acid treatment, and 1g of solvent water per gram of the molecular sieve after acid treatment is matched, and an aqueous solution of ferric nitrate is configured, impregnated for 24h, to obtain an impregnated molecular sieve. After drying, the above-mentioned impregnated molecular sieve is roasted at 750°C for 2 hours to obtain a ZSM-5 eutectic molecular sieve catalyst. And characterize the catalyst obtained by the comparative example, including the loading amount of Fe in the catalyst, the catalyst acid value, the specific surface area of ​​the catalyst, the catalyst activity and the deactivation time.

[0076] Example 4

[0077] Example 4 is basically the same as Example 1, except that the eutectic molecular sieve 1 is acid-treated with a relatively high concentration of nitric acid solution (3 mol / L) so that the acid value of the molecular sieve after acid treatment reaches 60 μmol / g. The remaining steps are consistent with Example 1 to obtain a ZSM-5 eutectic molecular sieve catalyst.

[0078] Example 5

[0079] Example 5 is basically the same as Example 1, except that the eutectic molecular sieve 1 is acid-treated with a relatively low concentration of nitric acid solution (0.01 mol / L) so that the acid value of the molecular sieve after acid treatment reaches 220 μmol / g. The remaining steps are consistent with Example 1 to obtain a ZSM-5 eutectic molecular sieve catalyst.

[0080] Example 6

[0081] Example 6 is basically the same as Example 1, except that eutectic molecular sieve 5 (wherein the mass ratio of ZSM-5 to SAPO-5 is 3.5:1) is used as a catalyst carrier to prepare a ZSM-5 eutectic molecular sieve catalyst.

[0082] Example 7

[0083] Example 7 is basically the same as Example 1, except that 0.36 g of solute ferric nitrate is matched with each gram of acid-treated molecular sieve, 1 g of solvent water is matched with each gram of acid-treated molecular sieve, and an aqueous solution of ferric nitrate is prepared to support the iron source. The remaining steps are consistent with Example 1 to obtain a ZSM-5 eutectic molecular sieve catalyst.

[0084] Comparative Example 1

[0085] Comparative Example 1 is basically the same as Example 1, except that ZSM-5 is used as a catalyst carrier to prepare the molecular sieve catalyst.

[0086] Comparative Example 2

[0087] Comparative Example 2 is basically the same as Example 1, except that the first molecular sieve (ZSM-5) and the second molecular sieve (SAPO-5) are physically mixed in the same mass ratio and are not made into a eutectic form, and are used as catalyst carriers to prepare molecular sieve catalysts.

[0088] Comparative Example 3

[0089] Comparative Example 3 is basically the same as Example 1, except that eutectic molecular sieve 4 (ZSM-5:ZSM-11 in a ratio of 1:1) is used as a catalyst carrier to prepare the molecular sieve catalyst.

[0090] Comparative Example 4

[0091] Comparative Example 4 is basically the same as Example 1, except that eutectic molecular sieve 6 (ZSM-5: SAPO-5 at a ratio of 0.5:1) is used as a catalyst carrier to prepare the molecular sieve catalyst.

[0092] Comparative Example 5

[0093] Comparative Example 5 is basically the same as Example 1, except that 0.02 g of solute ferric nitrate is matched with each gram of acid-treated molecular sieve, 1 g of solvent water is matched with each gram of acid-treated molecular sieve, and an aqueous solution of ferric nitrate is prepared to support the iron source. The remaining steps are the same as Example 1 to obtain a molecular sieve catalyst.

[0094] The characterization data of the catalysts of Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 1.

[0095] Table 1

[0096]

[0097] From Table 1, we can see the following points:

[0098] (1) It can be seen from Examples 1 to 3 that the ZSM-5 eutectic molecular sieve catalyst provided by the present invention uses a ZSM-5 eutectic molecular sieve containing a multi-porous structure as a carrier, which can reduce the loading amount of the active component Fe and improve the space-time yield of phenol in the process of preparing phenol by oxidation of benzene with laughing gas. When the loading amount of the active component Fe is in the range of 0.05 to 0.45 wt%, the space-time yield of phenol is 8 mmol / g·h or more, more preferably 10 mmol / g·h or more, and the catalyst has a long single operation time of more than 10 h, preferably more than 20 h, and has high stability.

[0099] (2) Effect of acid value on catalytic performance

[0100] Although the acid value can improve the reaction activity of the catalyst in the initial stage of the reaction, the activity decays rapidly and the stability of the catalyst is poor. After Example 4 is treated with concentrated acid, the acid value of the catalyst is only 40 μmol / g, the catalytic activity of the catalyst is low, and the space-time yield of phenol is only 7.2 mmol / g·h, while Example 5 is treated with dilute acid, so that the acid value of the catalyst is 210 μmol / g; the initial deactivation time of the catalyst in Example 1 is longer than that in Example 5, and the catalyst stability of Example 1 is better; in Example 6, due to the excessive mass proportion of ZSM-5, the acid value of the final catalyst is as high as 240 μmol / g, and the initial deactivation time of the catalyst in Example 5 is longer than that in Example 6, and the catalyst stability of Example 5 is better, which shows that the acid value of the ZSM-5 eutectic molecular sieve in the present invention has a significant effect on the catalytic activity and catalytic stability of the catalyst, and the acid value needs to be controlled within the range of 50 to 200 μmol / g to better improve the comprehensive performance of the catalyst.

[0101] (3) Effect of the mass ratio of ZSM-5 molecular sieve to the second molecular sieve

[0102] By comparing the mass ratios of ZSM-5 molecular sieve to the second molecular sieve in Example 1, Example 6 and Comparative Example 4, it can be seen that the mass ratios of the three are 1:1, 3.5:1 and 0.5:1, respectively, among which the catalytic activity and catalytic stability of Example 1 are relatively excellent, while in Example 6, due to the excessively high content of ZSM-5 molecular sieve, the acid value of the catalyst is relatively high, and the catalytic stability decreases to a certain extent, and in Comparative Example 4, due to the low content of ZSM-5 molecular sieve, the catalytic activity is significantly reduced, and the catalytic activity is difficult to meet the application requirements. It can be seen that the present invention controls the mass ratio of ZSM-5 molecular sieve to the second molecular sieve within a reasonable range, which can take into account both the catalytic activity and high catalytic stability of the catalyst.

[0103] (4) Effect of Fe loading

[0104] By comparing Example 1 with Example 7 and Comparative Example 5, it can be seen that the Fe loading in Example 1 is 0.2wt%, while in Example 7 and Comparative Example 5, it is 0.5wt% and 0.03wt%, respectively. Finally, due to the low content of active components in the catalyst of Comparative Example 5, the catalytic activity of the overall catalyst is low; due to the high Fe loading of the catalyst in Example 7, it is relatively easy to deactivate. It can be seen that controlling the Fe loading within a reasonable range in the present invention can better balance the catalytic activity and stability of the catalyst.

[0105] (5) Influence of eutectic molecular sieve structure

[0106] In Comparative Example 1, ZSM-5 molecular sieve is directly used as a carrier. It can be seen from the initial deactivation time of the catalyst that the initial deactivation time of the catalyst in Comparative Example 1 is only 6 hours, and the catalytic stability is significantly reduced compared with Example 1; in Comparative Example 2, only ZSM-5 molecular sieve and SAPO-5 molecular sieve are simply mixed without forming a eutectic structure. Not only is the catalytic activity of the catalyst insufficient, but the stability of the catalyst is also significantly reduced. This shows that the formation of the ZSM-5 molecular sieve eutectic structure in the present invention can improve the catalytic stability and catalytic activity of the catalyst.

[0107] (6) Selection of the second molecular sieve

[0108] Reference Figure 1 (Chart of catalytic activity test data of Example 1 and Comparative Example 3). By comparing Example 1 and Comparative Example 3, it can be seen that in Comparative Example 3, the eutectic molecular sieve 4 formed by the combination of ZSM-5 and ZSM-11 is selected. Since the ZSM-11 microporous molecular sieve has a ten-membered ring pore structure with pore sizes all less than 0.6 nm, when the prepared catalyst is applied to the benzene hydroxylation reaction, the effect of improving the catalytic stability is not good, and the catalytic activity is reduced compared with that of Example 1.

[0109] The present invention illustrates the detailed features of the present invention through the above embodiments, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A ZSM-5 eutectic molecular sieve catalyst, It is characterized in that The ZSM-5 eutectic molecular sieve catalyst comprises a carrier and an active component; The carrier includes a eutectic molecular sieve, and the eutectic molecular sieve is a eutectic structure formed by a ZSM-5 molecular sieve and a second molecular sieve; The second molecular sieve is a microporous molecular sieve, and the second molecular sieve includes any one of SAPO-5, Beta or MOR, or a combination of at least two thereof.

2. The ZSM-5 eutectic molecular sieve catalyst according to claim 1, It is characterized in that The mass ratio of the ZSM-5 molecular sieve to the second molecular sieve is (0.5-3):

1.

3. The ZSM-5 eutectic molecular sieve catalyst according to claim 1 or 2, It is characterized in that The acid value of the ZSM-5 eutectic molecular sieve catalyst is 50 to 200 μmol / g.

4. The ZSM-5 eutectic molecular sieve catalyst according to any one of claims 1 to 3, It is characterized in that The Fe element loading amount in the ZSM-5 eutectic molecular sieve catalyst is 0.05-0.45 wt%.

5. A method for preparing the ZSM-5 eutectic molecular sieve catalyst according to any one of claims 1 to 4, It is characterized in that The preparation method comprises the following steps: The eutectic molecular sieve is treated with acid to obtain an acid-treated molecular sieve; The iron source is loaded on the acid-treated molecular sieve and calcined to obtain the ZSM-5 eutectic molecular sieve catalyst.

6. The preparation method according to claim 5, It is characterized in that The acid value of the molecular sieve after the acid treatment is 60-220 μmol / g.

7. The preparation method according to claim 5 or 6, It is characterized in that The calcination temperature is 450-750° C., and the calcination time is 2-12 hours.

8. Application of a ZSM-5 eutectic molecular sieve catalyst in the oxidation of benzene to phenol using laughing gas, It is characterized in that The ZSM-5 eutectic molecular sieve catalyst is the ZSM-5 eutectic molecular sieve catalyst described in any one of claims 1 to 4, and / or a catalyst prepared by the preparation method of the ZSM-5 eutectic molecular sieve catalyst described in any one of claims 5 to 7.

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