Pt-m@molecular sieve / cordierite catalyst, and preparation method and application thereof

Abstract

The application belongs to the technical field of catalysts, and particularly discloses a Pt-M@ molecular sieve / cordierite catalyst, a preparation method and application thereof; the Pt-M@ molecular sieve / cordierite catalyst is prepared by a strategy combining a coating method and a cationic polymer assisted dry gel conversion method; compared with existing catalysts, the application introduces a non-noble metal, uses the non-noble metal to increase the dispersion degree of the noble metal, can improve the selectivity of a reaction, and reduces the generation of by-products; the application uses a monolithic catalyst to solve the problem of large mass transfer resistance of a reaction system; in addition, the catalyst prepared in the application is more conducive to recycling than a granular or powder catalyst, can reduce the amount of noble metal, promotes efficient work of the noble metal, and reduces the cost of using a noble metal catalyst alone.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and specifically relates to a Pt-M@molecular sieve / cordierite catalyst, its preparation method, and its application. Background Technology

[0002] p-Aminophenol (PAP) is a versatile organic synthetic intermediate, primarily used in the pharmaceutical, fuel, and rubber industries. In the pharmaceutical industry, p-aminophenol is mainly used to synthesize paracetamol (acetaminophen), as a substitute for drugs with significant side effects such as metamizole, aminopyrine, antipyrine, and phenacetin.

[0003] Currently, the hydrogenation of nitrobenzene (NB) in industry mainly uses hydrogenation catalysts and acid catalysts. Nitrobenzene first reacts with hydrogen under the action of hydrogenation catalyst to generate hydroxyaniline (PHA), and then PHA undergoes electron rearrangement under the action of acid catalyst to generate PAP, as shown in the following formula (1).

[0004]

[0005] However, if PHA is further hydrogenated without electron rearrangement, aniline will be generated, and PAP cannot be obtained, as shown in equation (2) below.

[0006]

[0007] Currently, precious metal catalysts and sulfuric acid catalysts are mainly used in industry. However, sulfuric acid is highly corrosive, easily corroding production equipment, damaging catalysts, and increasing production costs. Therefore, researchers are constantly studying new alternatives. Some focus on synthesizing metal / molecular sieve "bifunctional catalysts" as a major research direction for the hydrogenation of NB to PAP. The active metal and acidic sites are two factors influencing catalytic activity. The hydrogenation catalysts of "bifunctional catalysts" are mainly composed of the single precious metal Pt. However, Pt's selectivity is not high enough, leading to high production costs. Research on acid catalysts for metal / molecular sieve "bifunctional catalysts" mainly focuses on adjusting the acidity of the molecular sieve. Researchers have used Pt / BETA and Pt / MgAPO-5 for the hydrogenation of nitrobenzene to prepare PAP, but the selectivity is only 40-60%. Other researchers have used HZSM-5 molecular sieves to coat Pt nanoparticles to create a bifunctional catalyst (Pt@HZSM-5), applying it to the catalytic hydrogenation of NB to PAP. They found that this catalyst has good catalytic performance, with NB conversion reaching 100% and PAP selectivity reaching 75%, but further improvements are not possible. Moreover, the hydrogenation of nitrobenzene to produce p-aminophenol is a typical catalytic hydrogenation reaction process controlled by mass transfer rate. This process is also accompanied by a series of side reactions, which have a very fast intrinsic reaction rate and a large resistance to mass transfer, resulting in low catalyst efficiency.

[0008] Therefore, it is worthwhile to consider developing a catalyst with excellent mass transfer performance, high metal dispersion, and low cost. Summary of the Invention

[0009] To address the above problems, this invention proposes a method for preparing a Pt-M@molecular sieve / cordierite catalyst, the preparation method comprising the following steps:

[0010] A Pt-M@molecular sieve / cordierite catalyst precursor was obtained by coating the catalyst support with a mixed solution, wherein the mixed solution was obtained by mixing a first mixed solution and a second mixed solution;

[0011] The Pt-M@molecular sieve / cordierite catalyst precursor was subjected to molecular sieve steam-assisted crystallization. The crystallized product was then washed, dried, and calcined to obtain PtMO. X @Na-molecular sieve / cordierite;

[0012] The PtMO X PtMOx@H-molecular sieve / cordierite was obtained by ion exchange with @Na-molecular sieve / cordierite.

[0013] The PtMOx@H-molecular sieve / cordierite was calcined, and then reduced with hydrogen to obtain the target catalyst Pt-M@molecular sieve / cordierite.

[0014] Further, the catalyst support is obtained according to the following steps:

[0015] Cordierite was selected and cut into catalyst supports to be processed;

[0016] The catalyst support to be treated was subjected to boiling water treatment with 15% nitric acid, followed by washing, drying and calcination to obtain the catalyst support.

[0017] Furthermore, the first mixed solution is obtained by mixing a silicon source, an aluminum source, and a structure directing agent in a molar ratio of 1:0.016:0.25;

[0018] The second mixed solution consists of H2PtCl6·6H2O, a non-noble metal salt, a cationic polymer stabilizer, and NaOH in an order of 1×10⁻⁶. -3 E: 3.6 × 10 -5 The mixture was obtained by mixing at a molar ratio of 0.06.

[0019] Furthermore, the silicon source includes one of the following: silica sol LUDOX-AS-40, LUDOX HS-40, LUDOX CL-X, or LUDOXTM-40;

[0020] The aluminum source includes one or a combination of two of Al(NO3)3·9H2O and NaAlO2;

[0021] The structure directing agent includes tetrapropylammonium hydroxide or tetraethylammonium hydroxide;

[0022] The non-precious metal salt includes one of Cu(NO3)2·3H2O, Mn(CH3COO)2·4H2O, NiCl2·6H2O or FeCl3·6H2O.

[0023] Furthermore, the molecular sieve is HZSM-5, and the coating loading of the catalyst support is 20%-40%.

[0024] Furthermore, the conditions for the molecular sieve vapor-assisted crystallization are: vapor crystallization at 180°C for 72 hours.

[0025] Furthermore, the conditions for the ion exchange are: PtMO X @Na-molecular sieve / cordierite was placed in a 0.5 mol / L NH4NO3 solution, stirred at 80℃ for 12 h, filtered and washed, and dried in an oven at 100℃ for 12 h to complete the ion exchange.

[0026] Furthermore, the process of washing, drying and calcining the crystallized product is as follows: the crystallized product is washed until neutral, dried at 100℃ for 12 hours, and then calcined at 550℃ for 8 hours.

[0027] Furthermore, the conditions for hydrogen reduction are: reduction at 600°C for 2 hours.

[0028] On the other hand, the present invention also provides a Pt-M@molecular sieve / cordierite catalyst.

[0029] This invention proposes the application of Pt-M@ molecular sieve / cordierite catalyst in the hydrogenation of nitrobenzene to prepare p-aminophenol.

[0030] The beneficial effects of this invention are:

[0031] This invention prepares a Pt-M@molecular sieve / cordierite catalyst by combining a coating method and a cationic polymer-assisted dry gel conversion method. Compared with existing catalysts, this invention introduces non-precious metals, which increase the dispersion of precious metals and improve reaction selectivity while reducing the generation of by-products. The monolithic catalyst used in this invention can solve the problem of high mass transfer resistance in the reaction system. In addition, the catalyst prepared in this invention is more conducive to recycling and reuse than granular or powdered catalysts, while also reducing the amount of precious metals used, promoting the efficient operation of precious metals, and reducing the cost of using precious metal catalysts alone.

[0032] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A flowchart of the preparation method of the monolithic structured catalyst of Pt-M@ molecular sieve in this invention is shown;

[0035] Figure 2 The diagram shows the conversion rate of NB and the selectivity of PAP in the catalyst samples prepared in Examples 1-9 of this invention during the hydrogenation of NB to PAP.

[0036] Figure 3 The diagram shows the space-time yield analysis of active metal Pt in the hydrogenation of NB to PAP of the catalyst samples prepared in Examples 1-9 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention employs a combined coating method and a cationic polymer-assisted dry gel conversion method to prepare Pt-M@ molecular sieve / cordierite catalysts. The main process of the preparation method is as follows: Figure 1 As shown.

[0039] The preparation method of the Pt-M@molecular sieve / cordierite catalyst proposed in this invention includes the following steps:

[0040] (1) Select a certain amount of 400-mesh cordierite (COR), cut the cordierite into catalyst supports, treat it with boiling water containing 15% nitric acid, wash it with water, dry it, and calcine it to remove impurities from its surface, and set it aside for later use. The preferred specifications for the catalyst supports are as follows.

[0041] (2) After mixing silicon source, aluminum source and structure directing agent in a certain proportion, a first mixed solution is obtained. After mixing H2PtCl6·6H2O, non-precious metal salt, cationic polymer stabilizer (PDDA, etc.) and NaOH in a certain proportion, a second mixed solution is obtained.

[0042] Silicon sources, aluminum sources, and structure-directing agents are used in the synthesis of molecular sieves, with the structure-directing agents affecting the pore structure of the molecular sieves. NaOH provides an alkaline environment for the reaction, and the cationic polymer stabilizer reacts with the anionic metal precursor (such as PtCl6) in this alkaline environment. 2- Electrostatic interactions occur between the metal precursor and the negatively charged silicate or aluminosilicate matrix of the zeolite, thereby promoting the encapsulation of the metal precursor into the zeolite matrix during crystallization. Non-precious metals primarily increase the dispersion of precious metals, reduce the amount of precious metals used, and promote the efficient operation of precious metals.

[0043] The preferred molar ratio of silicon source:aluminum source:structure directing agent is 1:0.016:0.25, and the preferred molar ratio of H2PtCl6·6H2O, non-noble metal salt, and cationic polymer stabilizer is 1×10⁻⁶. -3 E: 3.6 × 10 -5 : 0.06.

[0044] The silicon source includes one of the following: silica sol: LUDOX-AS-40, LUDOX HS-40, LUDOX CL-X, or LUDOXTM-40;

[0045] Aluminum sources include one or a combination of two of Al(NO3)3·9H2O and NaAlO2;

[0046] Structure-directing agents include tetrapropylammonium hydroxide (TPAOH) or tetraethylammonium hydroxide (TPBAOH);

[0047] Non-precious metal salts include one of Cu(NO3)2·3H2O, Mn(CH3COO)2·4H2O, NiCl2·6H2O, and FeCl3·6H2O;

[0048] Cationic polymer stabilizers include polydimethyldiallyl ammonium chloride (PDDA).

[0049] (3) After mixing the first mixed solution and the second mixed solution (mixing directly according to the prepared solution) evenly, the mixed solution is coated onto the catalyst support by coating method to obtain a Pt-M@ molecular sieve / cordierite catalyst precursor with a certain coating loading (20%, 30%, 40%, etc.).

[0050] (4) The Pt-M@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtMO. X @Na-molecular sieve / cordierite;

[0051] (5) PtMO X PtMOx@H-molecular sieve / cordierite was obtained by ion exchange of Na-type molecular sieves with H-type molecular sieves. Specifically, PtMOx was replaced with H-type molecular sieves. X @Na-molecular sieve / cordierite was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80 °C for 12 h, filtered and washed, and dried in an oven at 100 °C for 12 h to obtain PtMOx@H-molecular sieve / cordierite.

[0052] M is a non-precious metal element, PtMO X denoted as oxide, and x represents the simplest valence state of the metal and oxygen atom.

[0053] (6) PtMO x @H-molecular sieve / cordierite is calcined in a muffle furnace (temperature selected as 400-500℃, etc.). After calcination, PtMO is... x The @H-molecular sieve / cordierite is reduced with hydrogen in a reactor (reduction at 600℃ for 2 hours) to obtain the target catalyst Pt-M@H-molecular sieve / cordierite (i.e., Pt-M@molecular sieve / cordierite).

[0054] The preparation method described above will be explained in detail below with reference to specific embodiments. In the embodiments, " / " indicates that metal is coated onto the molecular sieve / COR, "@" indicates that metal is added during the synthesis of the molecular sieve, and the coating loading of the catalyst support is 20%-40%.

[0055] Example 1: Preparation of 0.6% Pt-0.3% Cu / HZSM-5 / COR (i.e., Sample A)

[0056] (1) Cut the selected cordierite into pieces of the specified size. Ten catalyst supports were treated with boiling water, washed, dried and calcined with 15% nitric acid to remove impurities from their surface, and then set aside for use.

[0057] (2) LUDOX-AS-40, Al(NO3)3·9H2O and TPAOH were mixed evenly in a molar ratio of 1:0.016:0.25 to obtain a first mixed solution. The solution was placed in a polytetrafluoroethylene reactor and placed in an oven. Molecular sieve vapor-assisted crystallization was carried out at 180℃ for 72h. The obtained product was washed until neutral, dried at 100℃ for 12h, and calcined at 550℃ for 8h to obtain HZSM-5.

[0058] (3) Prepare HZSM-5 into a solution and coat it onto the catalyst support in step (1) to obtain HZSM-5 / COR;

[0059] (4) HZSM-5 / COR was immersed in a mixed solution of H2PtCl6·6H2O and Cu(NO3)2·3H2O for 24 h, then dried at 100 °C for 12 h and calcined at 550 °C for 8 h to obtain PtCuOx / Na-HZSM-5 / COR; wherein H2PtCl6·6H2O was 0.05 g and Cu(NO3)2·3H2O was 0.07 g.

[0060] (5) PtCuOx / Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80℃ for 12 h, filtered and washed, and dried in an oven at 100℃ for 12 h to obtain PtCuOx / H-HZSM-5 / COR.

[0061] (6) PtCuOx / H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuOx / H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu / H-HZSM-5 / COR, namely 0.6%Pt-0.3%Cu / HZSM-5 / COR (sample A).

[0062] Example 2 Preparation of 0.6% Pt-0.3% Cu@HZSM-5 (i.e., Sample B)

[0063] (1) A first mixed solution was obtained by mixing LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25. A second mixed solution was obtained by mixing H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a molar ratio of 1×10⁻⁶. -3 E: 3.6 × 10 -5 The two solutions were mixed in a ratio of 0.06 to obtain a second mixed solution, in which H2PtCl6·6H2O was 0.07 g and Cu(NO3)2·3H2O was 0.05 g.

[0064] (2) The mixture of the two solutions was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 hours. The obtained product was washed until neutral, dried at 100°C for 12 hours, and calcined at 550°C for 8 hours to obtain PtCuOx@Na-HZSM-5.

[0065] (3) PtCuOx@Na-HZSM-5 was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80℃ for 12 h, filtered and washed, and dried in an oven at 100℃ for 12 h to obtain PtCuOx@H-HZSM-5.

[0066] (4) PtCuOx@H-HZSM-5 was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuO@H-HZSM-5 was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu@H-HZSM-5, namely 0.6%Pt-0.3%Cu@HZSM-5 (sample B).

[0067] Example 3 Preparation of 0.9% Pt@HZSM-5 / COR (i.e., sample C)

[0068] (1) Cut the selected cordierite into pieces of the specified size. Ten catalyst supports were treated with boiling water, washed, dried and calcined with 15% nitric acid to remove impurities from their surface, and then set aside for use.

[0069] (2) Mix LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25 to obtain the first mixed solution. Then, mix H2PtCl6·6H2O, non-precious metal salt, PDDA, and NaOH in a ratio of 1×10... -3 :0:3.6×10 -5 After mixing in a ratio of 0.06, a second mixed solution was obtained, in which 0.10 g of H2PtCl6·6H2O was obtained.

[0070] (3) After mixing the first mixed solution and the second mixed solution (the solutions prepared in step (2) are directly mixed), the mixed solution is coated onto the catalyst support in (1) by coating method to obtain a Pt@molecular sieve / cordierite catalyst precursor with a certain coating loading (20%, 30%, 40%, etc.).

[0071] (4) The Pt@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtOx@Na-HZSM-5 / COR.

[0072] (5) PtOx@Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80℃ for 12 h, filtered and washed, and dried in an oven at 100℃ for 12 h to obtain PtOx@H-HZSM-5 / COR.

[0073] (6) PtOx@H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtOx@H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt@H-HZSM-5 / COR, i.e., 0.9% Pt@HZSM-5 / COR (i.e., sample C).

[0074] Example 4 Preparation of 0.9% Pt / HZSM-5 / COR (i.e., Sample D)

[0075] Take 0.10g of H2PtCl6·6H2O and 10 cordierite carriers, and process them according to the steps in (1) of Example 1, for later use.

[0076] LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH were mixed uniformly at a molar ratio of 1:0.016:0.25 to obtain a first mixed solution. The first mixed solution was placed in a polytetrafluoroethylene reactor and then placed in an oven at 180°C for 72 hours to carry out molecular sieve vapor-assisted crystallization. The obtained product was washed until neutral, dried at 100°C for 12 hours, and calcined at 550°C for 8 hours to obtain HZSM-5.

[0077] HZSM-5 was coated onto the surface of cordierite, dried at 100℃ for 2 h, and calcined at 550℃ for 8 h to obtain HZSM-5 / COR. Then, HZSM-5 / COR was placed in H2PtCl6·6H2O solution and 0.9% Pt / HZSM-5 / COR (sample D) was prepared by impregnation method.

[0078] Example 5: Preparation of 0.75% Pt-0.25% Cu@HZSM-5 / COR (i.e., Sample E)

[0079] Take 0.09g H2PtCl6·6H2O and 0.04g Cu(NO3)2·3H2O, 10 cordierite supports, and prepare 10 0.75%Pt-0.25%Cu@HZSM-5 / COR (i.e., sample E) using the steps of Example 3. In step (2), the non-precious metal salt in the second mixture is Cu(NO3)2·3H2O, and the non-precious metal salt, PDDA, and NaOH are prepared in a ratio of 1×10⁻⁶. -3 E: 3.6 × 10 -5 Mixed at a molar ratio of 0.06.

[0080] Example 6 Preparation of 0.6% Pt-0.3% Cu@HZSM-5 / COR (i.e., sample F)

[0081] Take 0.07g H2PtCl6·6H2O and 0.05g Cu(NO3)2·3H2O, 10 cordierite supports, and prepare 10 0.6%Pt-0.3%Cu / HZSM-5 / COR (i.e., sample F) using steps (1)-(6) in Example 3. The non-precious metal salts in the second mixture of step (2) are Cu(NO3)2·3H2O, H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a ratio of 1×10⁻⁶. -3 E: 3.6 × 10 -5 Mixed at a molar ratio of 0.06.

[0082] Example 7 Preparation of 0.45% Pt-0.45% Cu@HZSM-5 / COR (i.e., sample G)

[0083] Take 0.05g H2PtCl6·6H2O and 0.08g Cu(NO3)2·3H2O, 10 cordierite supports, and prepare 10 0.45% Pt-0.45% Cu@HZSM-5 / COR (i.e., sample G) using steps (1)-(6) in Example 3; wherein the non-precious metal salts in the second mixture of step (2) are Cu(NO3)2·3H2O, H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a ratio of 1×10 -3 E: 3.6 × 10 -5 Mixed at a molar ratio of 0.06.

[0084] Example 8 Preparation of 0.3% Pt-0.6% Cu@HZSM-5 / COR (i.e., sample H)

[0085] Take 0.036g H2PtCl6·6H2O and 0.1g Cu(NO3)2·3H2O, 10 cordierite supports, and prepare 10 0.3% Pt-0.6% Cu@HZSM-5 / COR (i.e., sample H) using steps (1)-(6) in Example 3. The non-precious metal salts in the second mixture of step (2) are Cu(NO3)2·3H2O, H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a ratio of 1×10⁻⁶. -3 E: 3.6 × 10 -5 Mixed at a molar ratio of 0.06.

[0086] Example 9 Preparation of 0.25% Pt-0.75% Cu@HZSM-5 / COR (i.e., Sample I)

[0087] Take 0.030g H2PtCl6·6H2O and 0.13g Cu(NO3)2·3H2O, 10 cordierite supports, and prepare 10 0.25%Pt-0.75%Cu@HZSM-5 / COR (i.e., sample I) using steps (1)-(6) in Example 3. The non-precious metal salts in the second mixture of step (2) are Cu(NO3)2·3H2O, H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a ratio of 1×10⁻⁶. -3 E: 3.6 × 10 -5 Mixed at a molar ratio of 0.06.

[0088] Test case

[0089] The catalysts prepared in Examples 1-9 above were used to prepare p-aminophenol by hydrogenation of nitrobenzene. The specific test conditions were as follows:

[0090] A fixed-bed reactor (reaction tube diameter 20 mm, isothermal zone 350 mm) was used to conduct hydrogenation tests of nitrobenzene at 80 °C and a hydrogen pressure of 0.8 MPa. The mass flow rates of nitrobenzene and hydrogen (99.99% by mass) were 15 μL / min and 150 μL / min, respectively. The test results are as follows: Figure 2 and Figure 3 As shown, the specific values ​​are shown in Table 1:

[0091] Table 1. Results of catalyst samples used in Examples 1-9 for nitrobenzene hydrogenation tests.

[0092]

[0093] Combining Table 1 and Figure 2It can be seen that, except for sample D, the NBConversion (conversion rate) of all other samples in sample AI reached 100%; the PAP selectivity of samples A, E, F, G, H, and I prepared according to the method of this invention all reached over 83%, which is superior to samples B, C, and D prepared by other methods. (See Table 1 and...) Figure 3 It can be seen that the highest space-time yield of metallic Pt in samples A, E, F, G, H, and I can reach 800 gP / g. -1 Pth -1 The lowest is 450g PAPg -1 Pth -1 The above methods can significantly reduce the amount of precious metals used and lower costs.

[0094] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a Pt-Cu@molecular sieve / cordierite catalyst, characterized in that, The preparation method includes the following steps: (1) The selected cordierite was cut into 10 catalyst carriers with a specification of Ø20×10mm. After boiling water treatment, washing, drying and calcining with 15% nitric acid, the impurities on its surface were removed and it was ready for use. (2) Take 0.09g H2PtCl6·6H2O and 0.04g Cu(NO3)2·3H2O, 10 cordierite carriers, and mix LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25 to obtain the first mixed solution. Mix H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a molar ratio of 1×10 -3 9.5×10 -4 3.6×10 -5 The two solutions were mixed at a ratio of 0.06 to obtain a second mixed solution. (3) After the first mixed solution and the second mixed solution are mixed evenly, the mixed solution is coated onto the catalyst support in step (1) by coating method to obtain a Pt-Cu@molecular sieve / cordierite catalyst precursor with a coating loading of 30%. (4) The Pt-Cu@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtCuOx@Na-HZSM-5 / COR. (5) PtCuOx@Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80 °C for 12 h, filtered and washed, and dried in an oven at 100 °C for 12 h to obtain PtCuOx@H-HZSM-5 / COR. (6) PtCuOx@H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuOx@H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu@H-HZSM-5 / COR.

2. A method for preparing a Pt-Cu@molecular sieve / cordierite catalyst, characterized in that, The preparation method includes the following steps: (1) The selected cordierite was cut into 10 catalyst carriers with a specification of Ø20×10mm. After boiling water treatment, washing, drying and calcining with 15% nitric acid, the impurities on its surface were removed and it was ready for use. (2) Take 0.07g H2PtCl6·6H2O and 0.05g Cu(NO3)2·3H2O, 10 cordierite carriers, and mix LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25 to obtain the first mixed solution. Mix H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a molar ratio of 1×10 -3 1.5×10 -3 3.6×10 -5 The two solutions were mixed at a ratio of 0.06 to obtain a second mixed solution. (3) After the first mixed solution and the second mixed solution are mixed evenly, the mixed solution is coated onto the catalyst support in step (1) by coating method to obtain a Pt-Cu@molecular sieve / cordierite catalyst precursor with a coating loading of 30%. (4) The Pt-Cu@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtCuOx@Na-HZSM-5 / COR. (5) PtCuOx@Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80 °C for 12 h, filtered and washed, and dried in an oven at 100 °C for 12 h to obtain PtCuOx@H-HZSM-5 / COR. (6) PtCuOx@H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuOx@H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu@H-HZSM-5 / COR.

3. A method for preparing a Pt-Cu@molecular sieve / cordierite catalyst, characterized in that, The preparation method includes the following steps: (1) The selected cordierite was cut into 10 catalyst carriers with a specification of Ø20×10mm. After boiling water treatment, washing, drying and calcining with 15% nitric acid, the impurities on its surface were removed and it was ready for use. (2) Take 0.05g H2PtCl6·6H2O and 0.08g Cu(NO3)2·3H2O, 10 cordierite carriers, and mix LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25 to obtain the first mixed solution. Mix H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a molar ratio of 1×10 -3 3.4×10 -3 3.6×10 -5 The two solutions were mixed at a ratio of 0.06 to obtain a second mixed solution. (3) After the first mixed solution and the second mixed solution are mixed evenly, the mixed solution is coated onto the catalyst support in step (1) by coating method to obtain a Pt-Cu@molecular sieve / cordierite catalyst precursor with a coating loading of 30%. (4) The Pt-Cu@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtCuOx@Na-HZSM-5 / COR. (5) PtCuOx@Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80 °C for 12 h, filtered and washed, and dried in an oven at 100 °C for 12 h to obtain PtCuOx@H-HZSM-5 / COR. (6) PtCuOx@H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuOx@H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu@H-HZSM-5 / COR.

4. A method for preparing a Pt-Cu@molecular sieve / cordierite catalyst, characterized in that, The preparation method includes the following steps: (1) The selected cordierite was cut into 10 catalyst carriers with a size of Ø20×10mm. After boiling water treatment, washing, drying and calcining with 15% nitric acid, the impurities on the surface were removed and the carriers were ready for use. (2) Take 0.036g H2PtCl6·6H2O and 0.1g Cu(NO3)2·3H2O, 10 cordierite carriers, and mix LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25 to obtain the first mixed solution. Mix H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a molar ratio of 1×10 -3 6.0×10 -3 3.6×10 -5 The two solutions were mixed at a ratio of 0.06 to obtain a second mixed solution. (3) After the first mixed solution and the second mixed solution are mixed evenly, the mixed solution is coated onto the catalyst support in step (1) by coating method to obtain a Pt-Cu@molecular sieve / cordierite catalyst precursor with a coating loading of 30%. (4) The Pt-Cu@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtCuOx@Na-HZSM-5 / COR. (5) PtCuOx@Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80 °C for 12 h, filtered and washed, and dried in an oven at 100 °C for 12 h to obtain PtCuOx@H-HZSM-5 / COR. (6) PtCuOx@H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuOx@H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu@H-HZSM-5 / COR.

5. A method for preparing a Pt-Cu@molecular sieve / cordierite catalyst, characterized in that, The preparation method includes the following steps: (1) The selected cordierite was cut into 10 catalyst carriers with a size of Ø20×10mm. After boiling water treatment, washing, drying and calcining with 15% nitric acid, the impurities on the surface were removed and the carriers were ready for use. (2) Take 0.030g H2PtCl6·6H2O and 0.13g Cu(NO3)2·3H2O, 10 cordierite carriers, and mix LUDOX-AS-40, Al(NO3)3·9H2O, and TPAOH in a molar ratio of 1:0.016:0.25 to obtain the first mixed solution. Mix H2PtCl6·6H2O, Cu(NO3)2·3H2O, PDDA, and NaOH in a molar ratio of 1×10 -3 9.3×10 -3 3.6×10 -5 The two solutions were mixed at a ratio of 0.06 to obtain a second mixed solution. (3) After the first mixed solution and the second mixed solution are mixed evenly, the mixed solution is coated onto the catalyst support in step (1) by coating method to obtain a Pt-Cu@molecular sieve / cordierite catalyst precursor with a coating loading of 30%. (4) The Pt-Cu@molecular sieve / cordierite catalyst precursor was placed in a polytetrafluoroethylene reactor. The polytetrafluoroethylene reactor was placed in an oven and subjected to molecular sieve vapor-assisted crystallization at 180°C for 72 h. The obtained product was washed until neutral, dried at 100°C for 12 h, and calcined at 550°C for 8 h to obtain PtCuOx@Na-HZSM-5 / COR. (5) PtCuOx@Na-HZSM-5 / COR was placed in 500 mL of 0.5 mol / L NH4NO3 solution, stirred at 80 °C for 12 h, filtered and washed, and dried in an oven at 100 °C for 12 h to obtain PtCuOx@H-HZSM-5 / COR. (6) PtCuOx@H-HZSM-5 / COR was placed in a muffle furnace at 400℃ for calcination. After calcination, PtCuOx@H-HZSM-5 / COR was reduced with hydrogen in a reactor at 600℃ for 2 hours to obtain the target catalyst Pt-Cu@H-HZSM-5 / COR.

6. A Pt-Cu@molecular sieve / cordierite catalyst, characterized in that, The Pt-Cu@molecular sieve / cordierite catalyst is prepared using the preparation method described in any one of claims 1-5.

7. The application of the Pt-Cu@molecular sieve / cordierite catalyst as described in claim 6 in the hydrogenation of nitrobenzene to prepare p-aminophenol.

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