A preparation method of a stable copper-based catalyst, a copper-based catalyst and application thereof

Abstract

The application discloses a preparation method of a copper-based catalyst, the copper-based catalyst and application thereof, and belongs to the technical field of bioenergy and chemical industry. The method comprises the following steps: obtaining a precursor I; the precursor I comprises a carrier and a supported active component, the active component contains copper elements, and the carrier is a molecular sieve with a silicon-aluminum ratio greater than 200; the precursor I is subjected to silicon component coating treatment to obtain a precursor II; the precursor II is calcined and reduced to obtain the copper-based catalyst; the silicon component coating treatment comprises the following steps: obtaining a gel containing a silicon source I, a template agent I, a solvent I and the precursor I; and the gel is heated in water vapor to obtain the precursor II. The method has the advantages of simple operation, low catalyst cost, economy and practicability, high acetaldehyde production efficiency and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of bioenergy chemical technology, specifically relating to a method for preparing a stable copper-based catalyst, the copper-based catalyst and its application. Background Technology

[0002] With the rapid development of fermentation technology and the maturation of coal-to-ethanol projects, ethanol has become a new type of bulk energy chemical platform compound. In 2018, ethanol production exceeded 60 billion liters and is increasing at a rate of 4% to 5% annually. Currently, ethanol is mainly used as an additive in fuels, thus partially replacing gasoline. However, due to current engine safety and energy density limitations, the amount of ethanol added to fuels in existing engines is limited, generally less than 10%, which severely restricts the development and application of ethanol.

[0003] In recent years, the high-value utilization of ethanol has seen significant development, resulting in diversified products such as butanol, 1,3-butadiene, and isobutene, which has strongly promoted the healthy development of the ethanol industry. Among these, ethanol dehydrogenation is a key step in the catalytic conversion of ethanol, and its in-depth research has built a bridge from ethanol to high-value chemicals. Furthermore, acetaldehyde is an important aliphatic compound and a key raw material for the manufacture of chemicals such as acetic acid, peracetic acid, pentaerythritol, and pyridine, possessing high application value.

[0004] Currently, acetaldehyde is mainly produced by the oxidation of ethylene, which has drawbacks such as the non-renewable nature of the raw materials. In contrast, the one-step catalytic conversion of ethanol to acetaldehyde has advantages such as high atom economy and a simple process.

[0005] In the study of catalytic dehydrogenation of ethanol, the catalyst support and preparation method have a substantial impact on the catalyst's reactivity and stability. Most catalysts still suffer from problems such as the need for toxic promoters and poor stability. For example, Tu et al. [Reference 1 J. Chem. Tech. Biotechnol, 1994, 59: 141-147; Reference 2 J. Mol. Catal., 1994, 89: 179-190] used Cu as the active component and toxic Cr₂O₃ as a promoter, preparing the catalyst via a co-precipitation method and applying it to the ethanol dehydrogenation reaction. Their study found that the acidity or basicity of the metal oxide promoter significantly affects the catalyst's activity for the dehydrogenation reaction; the catalyst exhibits the highest activity when the Cr / Cu molar ratio is 4 / 40. Chang et al. [Reference 3 Appl. Catal. A: General, 2003, 246:253-264; Reference 4 Appl. Catal. A: General, 2005, 288:53-61] prepared a series of catalysts for ethanol dehydrogenation using Cu as the active component via impregnation and ion exchange methods. The results showed that rice husk was superior to commercial silica gel as a support, and the ion exchange catalyst had high stability, but deactivation still occurred. Lu et al. [Reference 5 ChemCatChem 2017, 9(3), 505-510; Reference 6 ChemCatChem 2019, 11, 481-487] synthesized a series of carbon-supported copper-based catalysts for ethanol dehydrogenation, achieving good ethanol conversion and acetaldehyde selectivity, but the catalysts had poor stability, generally below 500 min. Liu Hongchao et al. [Chinese Invention Patent Publication Document CN103127945B] supported copper on supports such as SiO2, Al2O3, and ZrO2, and used P modification to achieve catalytic dehydrogenation of ethanol, obtaining 98% selectivity for acetaldehyde. However, this catalyst still has drawbacks such as poor activity, low ethanol conversion rate under the same conditions, and poor catalyst stability. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing and applying a copper-based catalyst. This method has advantages such as simple operation, low catalyst cost, economic practicality, high efficiency in acetaldehyde production, and low energy consumption.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] On one hand, the present invention provides a method for preparing a copper-based catalyst, the method comprising: obtaining a precursor I; the precursor I comprising a support and a supported active component, the active component containing copper, and the support being a molecular sieve with a silicon-to-aluminum ratio >200; coating the precursor I with a silicon-containing component to obtain a precursor II; subjecting the precursor II to calcination II and reduction to obtain the copper-based catalyst; the silicon-containing component coating treatment comprising the steps of: obtaining a gel containing a silicon source I, a template agent I, a solvent I, and the precursor I; heating the gel in steam and then subjecting it to calcination I to obtain the precursor II.

[0009] Optionally, the temperatures for roasting II and roasting I are independently selected from 300 to 700°C.

[0010] The lower limit of the calcination temperature II can be selected from 300℃ or 400℃, and the upper limit can be selected from 400℃ or 700℃.

[0011] Optionally, the atmosphere for roasting II is selected from air.

[0012] Optionally, the atmosphere for roasting I is selected from air.

[0013] Optionally, the reduction conditions are: reduction temperature 200-400℃, reduction time 0.5-6h; the lower limit of the reduction temperature is selected from 200℃ and 300℃, and the upper limit is selected from 300℃ and 400℃; the lower limit of the reduction time is selected from 0.5h and 1h, and the upper limit is selected from 1h and 6h.

[0014] Optionally, the reducing atmosphere is hydrogen, methane, or a mixture of gases; the mixture refers to a mixture of one of hydrogen and methane with at least one of nitrogen, argon, and helium.

[0015] Optionally, the mass ratio of silicon source I, template agent I, solvent I and precursor I in the gel is between 1:(0.1~1):(10~100):(0.1~10).

[0016] Optionally, the silicon source I is selected from at least one of amorphous silica, silica aerosol, silica liquid sol, and tetraethyl orthosilicate.

[0017] Optionally, the template agent I is selected from at least one of ethylamine, diethylamine, triethylamine, ethylenediamine, 1,6-hexanediamine, tetrapropylammonium hydroxide, P123, hexadecyltrimethylammonium bromide, and hexadecyltriethylammonium bromide.

[0018] Optionally, solvent I is selected from water and / or ethanol.

[0019] Optionally, the conditions for the silicon-containing component coating treatment are as follows: the heating temperature in water vapor is 120-200°C; the heating time in water vapor is 0.5-7 days; the lower limit of the heating temperature in water vapor is optionally selected from 120°C and 180°C, and the upper limit is optionally selected from 180°C and 200°C; the lower limit of the heating time in water vapor is optionally selected from 0.5 days and 4 days, and the upper limit is optionally selected from 4 days and 7 days.

[0020] Optionally, the silicon-containing component coating treatment involves first obtaining a mixture I containing silicon source I, template agent I, and solvent I, and then mixing the mixture I with the precursor I to form a gel.

[0021] Optionally, the mixing process I is carried out by stirring at 20–90°C for 0.5–10 hours.

[0022] Optionally, heating the gel in steam involves placing the gel in a hydrothermal reactor with a steam atmosphere to carry out a crystallization reaction.

[0023] Optionally, the gel is ground before heating.

[0024] Optionally, the grinding involves grinding the gel to a particle size greater than 60 mesh.

[0025] The mesh count mentioned in this invention refers to the number of openings per inch of screen. Mesh count × aperture (micrometers) = 15000. The 60 mesh mentioned in this invention refers to a screen aperture of approximately 250 micrometers.

[0026] Optionally, the molecular sieve with a silica-to-alumina ratio >200 is obtained by dealumination of silica-alumina molecular sieve I, wherein the silica-alumina molecular sieve I is selected from at least one of ZSM-5, Hβ, X-type, and Y-type molecular sieves.

[0027] Optionally, the precursor I is prepared by impregnation; the impregnation solution is a copper salt solution; the copper salt is selected from at least one of copper nitrate, copper chloride, and copper acetate; the solvent II in the copper salt solution is selected from water and / or ethanol; in the impregnation method, the solid-liquid mass ratio of the carrier to the impregnation solution is 2:1 to 1:5, and the mass concentration of the copper salt in the copper salt solution is between 2% and 30%, and the mass of the copper salt is based on the mass of copper element in the copper salt;

[0028] Optionally, the copper content in the precursor I is 2 to 30 wt%, with the lower limit of the content optionally selected from 2 wt% or 20 wt%, and the upper limit optionally selected from 20 wt% or 30 wt%.

[0029] Optionally, the total mass of silicon in the precursor II is 1.1 to 10 times the mass of silicon in the carrier.

[0030] On the other hand, the present invention provides a copper-based catalyst obtained by any of the above preparation methods, wherein the copper-based catalyst comprises a support and an active component copper; the copper content in the copper-based catalyst is 1 to 50 wt%; the lower limit of the copper content is selected from 1 wt%, 4.5 wt%, 12.5 wt%, and 15 wt%; and the upper limit of the copper content is selected from 4.5 wt%, 12.5 wt%, 15 wt%, and 50 wt%.

[0031] Optionally, the copper-based catalyst is granulated to have a particle size of 0.1–10 cm and an axial crushing strength of 1–50 kg / cm.

[0032] Furthermore, the present invention also provides the application of any of the above-mentioned copper-based catalysts in the catalytic dehydrogenation of ethanol to produce acetaldehyde and hydrogen.

[0033] On the other hand, the present invention also provides a method for preparing acetaldehyde and hydrogen by ethanol dehydrogenation, wherein the catalyst is a copper-based catalyst obtained by any of the preparation methods or any of the copper-based catalysts described above.

[0034] Optionally, the reaction uses a fixed bed as the reactor.

[0035] Optionally, the acetaldehyde has a selectivity of over 90%, the catalyst operates stably for over 500 hours, and the bed pressure change is less than 0.1 MPa.

[0036] Optionally, the reaction steps are as follows: the copper-based catalyst is filled in a fixed bed, heated to the reaction temperature under a certain carrier gas, and then ethanol is pumped in.

[0037] Optionally, the carrier gas is at least one of nitrogen, argon, helium, nitrous oxide, and carbon dioxide.

[0038] Optionally, the reaction pressure during the reaction process is 0.1–1 MPa;

[0039] Optionally, the reaction temperature is 120 to 320°C, with the lower limit of the reaction temperature arbitrarily selected from 120°C and 250°C; the lower limit of the reaction temperature arbitrarily selected from 250°C and 320°C.

[0040] Optionally, the mass hourly space velocity (WHSV) of the catalytic reaction is 0.1–20 h⁻¹. -1 The lower limit of mass space velocity can be selected from 0.1h. -1 1.5h -1 The upper limit of the mass air velocity can be selected from 1.5h. -1 20h -1 .

[0041] The present invention has the following advantages:

[0042] 1. This invention provides a method for preparing a copper-based catalyst and using it in the ethanol dehydrogenation reaction. The catalyst prepared by this method can significantly improve the yield of acetaldehyde, reduce the generation of by-products during the reaction, and significantly improve the stability and service life of the catalyst. The catalyst provided by this invention has the advantages of simple operation, low catalyst cost, good stability, and high reaction efficiency.

[0043] 2. This invention uses bioethanol as a reactant to prepare acetaldehyde. Ethanol is abundant, readily available, produced in large quantities, environmentally friendly, and pollution-free. Acetaldehyde produced by the dehydrogenation reaction of ethanol has wide applications in fuels, chemicals, and other fields.

[0044] 3. The copper-based catalyst prepared by this invention has the following three structural advantages: a) It has a wide range of selectable support templates, and can obtain inexpensive silicon-based supports; in addition, the catalyst support obtained by acid treatment has a complete framework structure, good hydrothermal stability, and high crystal structure; b) The coated copper particles have a stronger interaction with silicon oxide, forming more Cu. + Species, taking MFI@(Cu / MFI) as an example, Cu on the surface of the Cu / MFI catalyst + The species content was 41.2%, and the Cu on the coated MFI@(Cu / MFI) catalyst was... + The species content reached 55.6%; c) The copper-based catalyst has a hierarchical pore structure of micropores and mesopores, which can promote the diffusion, adsorption and desorption of molecular reactants.

[0045] 4. The copper-based catalyst provided by this invention is easy to prepare, low in cost, and has good stability. When used in the ethanol dehydrogenation reaction, the product is easy to separate and use. The whole process has good economic efficiency and practicality, meets the requirements of sustainable development, and has important economic value and industrialization prospects in biomass conversion. Attached Figure Description

[0046] Figure 1 The images show the XRD patterns of ZSM-5-DeAl in Preparation Example 1 and Hβ-DeAl in Preparation Example 2.

[0047] Figure 2 The graphs show the adsorption-desorption curves of the MFI@(Cu / ZSM-5-DeAl) catalyst prepared in Example 1 and the Cu / ZSM-5-DeAl catalyst prepared in Comparative Example 2.

[0048] Figure 3 This is a TEM image of MFI@(Cu / MFI) prepared in Example 2. Detailed Implementation

[0049] The present invention will be described in detail below through specific embodiments, but these embodiments do not constitute a limitation on the content of the present invention. The embodiments provide several typical methods for preparing catalysts, but the specific processing conditions are not limited to the parameters given in the embodiments.

[0050] This invention provides a method for preparing and applying a stable copper-based catalyst, which is prepared in two steps. First, copper metal is introduced onto a molecular sieve support with a high silicon content via impregnation to obtain a copper-based catalyst precursor with a copper content of 1-50 wt%. Then, silicon is coated onto the prepared copper-based catalyst precursor using a dry method, followed by calcination and reduction to obtain the coated copper-based catalyst. This catalyst is used in the direct dehydrogenation reaction of ethanol, with the reaction carried out in a fixed bed under a reaction atmosphere of at least two or more of nitrogen, argon, helium, nitrous oxide, and carbon dioxide, at a reaction temperature ≥120℃, exhibiting an acetaldehyde selectivity greater than 90%, and ensuring stable operation of the catalyst for more than 500 hours.

[0051] The carrier of this invention is prepared by acid treatment, hydrothermal method, or other means.

[0052] The specific steps for preparing the carrier by acid treatment are as follows:

[0053] Step 1-1: Treat commercial silica-alumina molecular sieves with acid solution at 20-80℃ for 2-24 hours. The mass ratio of commercial silica-alumina molecular sieves to acid is 2:1 to 1:20 to obtain precursor I with a silica-alumina ratio greater than 200.

[0054] Steps 1-2: The obtained precursor I is sequentially filtered, washed, and dried, and then calcined in air at 300-700℃ for 3-5 hours to obtain the carrier;

[0055] In step 1-1, the commercial silica-alumina molecular sieve is selected from at least one of ZSM-5, Hβ, X-type, and Y-type molecular sieves; the acid is selected from at least one of hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid, and the mass concentration of the acid is 10-98%.

[0056] The specific steps for preparing the carrier using the hydrothermal method are as follows:

[0057] Step 2-1: Dissolve template agent II in solvent, add hydrochloric acid, adjust pH to 1-3, stir evenly, add silicon source, stir at 30-40℃ for 1-24 hours to obtain mixture Z;

[0058] Step 2-2: Add mixture Z to a hydrothermal reactor and maintain at 80-200°C for 12-168 hours to obtain precursor II;

[0059] Steps 2-3 involve sequentially filtering, washing, and drying the obtained precursor II, followed by calcination in air at 300–700°C for 3–5 hours to obtain the carrier.

[0060] In step 2-1:

[0061] The solvent is water and / or ethanol;

[0062] Silicon source II is selected from at least one of amorphous silica, silica aerosol, silica liquid sol, and tetraethyl orthosilicate (TEOS);

[0063] The molar ratio of silicon source II (based on the molar ratio of Si) to template agent II is between 100:1;

[0064] The total concentration of silicon source II and template agent II in mixture Z is between 0.01 and 20 wt%.

[0065] Template agent II is selected from at least one of ethylamine, diethylamine, triethylamine, ethylenediamine, 1,6-hexanediamine, tetrapropylammonium hydroxide (TPAOH), P123, hexadecyltrimethylammonium bromide, and hexadecyltriethylammonium bromide.

[0066] Optionally, in step 2-1, a very small amount of aluminum source may also be added along with silicon source II, with a silicon-to-aluminum ratio greater than 200. Here, the silicon-to-aluminum ratio refers to the ratio of the molar amount of Si element in the silicon source to the molar amount of Al element in the aluminum source. The aluminum source is selected from at least one of aluminum nitrate, aluminum oxide, aluminum isopropoxide, and trimethylaluminum.

[0067] The specific steps for preparing precursor I by impregnation method are as follows:

[0068] Step 3-1: Dissolve the copper salt in water and / or ethanol, stir until homogeneous, and obtain an impregnation solution; the copper salt is selected from at least one of copper nitrate, copper chloride, and copper acetate; the mass concentration of the copper salt in the impregnation solution is between 2% and 30%, and the mass of the copper salt is based on the mass of copper element in the copper salt;

[0069] Step 3-2: Add the carrier to the above impregnation solution, stir for 1 to 20 hours, and then remove the solvent by rotary evaporation at a temperature of 25 to 100°C to obtain precursor III; the solid-liquid mass ratio of the carrier to the impregnation solution is 2:1 to 1:5.

[0070] Step 3-3: Calcine the obtained precursor III in air at 300-700°C to obtain precursor I, or treat it with nitrous oxide at 200-500°C to obtain precursor I.

[0071] The specific steps for coating precursor I with silicon-containing components are as follows:

[0072] Step 4-1: Dissolve silicon source I (e.g., tetraethyl orthosilicate) and template agent I in a mixed solvent of water and ethanol in a volume ratio of 5:1 to 1:5, and stir for 0.2 to 3 hours to obtain mixture I;

[0073] Step 4-2: Mix mixture I with precursor I and stir for 0.5 to 10 hours, heating to 20 to 90°C during stirring to obtain a gel;

[0074] Step 4-3: Grind the above gel to a finer mesh than 60 and place it on a support platform in a hydrothermal reactor. Add 0.1 to 2 mL of water to the hydrothermal reactor to ensure that the water reaches its saturated vapor pressure. The water should not directly contact the gel. The hydrothermal temperature should be 120 to 200°C, and the time should be 0.5 to 7 days.

[0075] Preparation Example 1: Preparation of dealuminized ZSM-5 support by acid treatment

[0076] Taking ZSM-5 molecular sieve with a silica-to-alumina ratio of 150 as an example: 10g of ZSM-5 molecular sieve was weighed and added to 100mL of 66% nitric acid solution, and treated at 80℃ for 24h to obtain a high-silica molecular sieve precursor. The high-silica molecular sieve precursor was then filtered, washed with deionized water, dried at 120℃ for 12h, and calcined in air at 550℃ for 3h to obtain a dealuminized ZSM-5 molecular sieve, denoted as ZSM-5-DeAl. XRF analysis showed that the aluminum content of ZSM-5-DeAl was 0.1wt%.

[0077] Preparation Example 2: Preparation of dealuminized Hβ support by acid treatment

[0078] By replacing ZSM-5 in Preparation Example 1 with an Hβ molecular sieve having a silicon-to-aluminum ratio of 200, a dealuminized Hβ molecular sieve, denoted as Hβ-DeAl, was obtained.

[0079] like Figure 1 As shown, ZSM-5-DeAl and Hβ-DeAl retain the original crystallinity of ZSM-5 molecular sieve and Hβ molecular sieve. After acid treatment, the crystallinity of ZSM-5 molecular sieve and Hβ molecular sieve is well maintained.

[0080] Preparation Example 3: Preparation of SBA-15 support (aluminum-free) by hydrothermal method

[0081] Weigh 16g of P123 and add it to a mixture of 120mL of water and 42mL of 2M hydrochloric acid (for pH adjustment). Stir vigorously until all P123 is dissolved into a clear solution. Then, add 36.5mL of TEOS while stirring. After stirring at 40℃ for 24h, a mixture is obtained. Transfer the mixture to a hydrothermal reactor and keep it at 100℃ for 24h to obtain the precursor. Filter the precursor, wash it with deionized water, and dry it at 120℃ for 12h to obtain a white powder. Calcine the white powder at 550℃ for 3h to obtain SBA-15.

[0082] Preparation Example 4: Hydrothermal Preparation of MFI (Silicalite-1) Support (Aluminum-Free)

[0083] Tetraethyl orthosilicate, tetrapropylammonium hydroxide, water, and ethanol were mixed and stirred at room temperature and hydrolyzed thoroughly for 3–5 hours. Water was then added to form a mixture with a molar ratio of TPAOH / SiO2 = 0.25, ethanol / SiO2 = 4, and H2O / SiO2 = 10. The mixture was then crystallized in a closed reactor at 170°C under autogenous pressure for 5 days to obtain a precursor. The precursor was then washed, filtered, dried, and calcined in air at 550°C for 3 hours to obtain MFI (Silicalite-1) molecular sieve.

[0084] Example 1: Preparation of MFI@(Cu / ZSM-5-DeAl)

[0085] Step 1: Preparation of precursor I by impregnation method

[0086] 1.78 g of copper nitrate was weighed and added to a round-bottom flask containing 5 mL of distilled water and 5 mL of ethanol. After stirring until completely dissolved, 2 g of support (ZSM-5-DeAl prepared in Preparation Example 1) was added. The mixture was stirred vigorously at 20–25 °C for 8 h. Water and ethanol were removed by rotary evaporation to obtain a solid precursor. This precursor was calcined at 400 °C for 2 h to obtain precursor I, namely CuO / ZSM-5-DeAl, wherein the Cu loading was 20 wt%.

[0087] Step 2: Preparation of Precursor II

[0088] 3.1 g of tetraethyl orthosilicate, 1.9 g of template agent (tetrapropylammonium hydroxide), and 2 mL of water were mixed and stirred at room temperature for 1 hour to allow for complete hydrolysis. Then, precursor I prepared in step 1, i.e., the CuO / ZSM-5-DeAl precursor, was mixed in and stirred for another 2 hours. The temperature was raised to 80°C and maintained for 24 hours to obtain a gel. The gel was pulverized and ground to a finer mesh than 60 mesh and placed on a platform in a hydrothermal reactor. 0.5 mL of water was added to the reactor, and the water was heated to 180°C to generate steam. The water did not directly contact the gel. The hydrothermal treatment was maintained at 180°C for 4 days, followed by calcination at 550°C for 4 hours to obtain solid precursor II, i.e., silicon-coated CuO / ZSM-5-DeAl.

[0089] Step 3: Preparation of copper-based catalyst

[0090] The precursor II obtained in step 2 was reduced at 300 °C for 1 h in a mixed atmosphere of hydrogen and argon (hydrogen volume content of 10%) to obtain catalyst MFI@(Cu / ZSM-5-DeAl), wherein the Cu loading was 12.5 wt%.

[0091] Example 2: Preparation of MFI@(Cu / MFI)

[0092] The only difference from Example 1 is that the support in step 1 is replaced with the MFI (Silicalite-1) support prepared in Preparation Example 4, and the catalyst MFI@(Cu / MFI) is finally obtained, wherein the Cu loading is 12.5 wt%.

[0093] MFI@(Cu / MFI) was subjected to TEM testing, and the results are as follows: Figure 3 As shown in the figure, Cu / MFI is encapsulated within the MFI structure, forming a silicon-copper-silicon sandwich structure.

[0094] Example 3: Preparation of SiO2@(Cu / SBA-15)

[0095] The only difference from Example 1 is that the support in step 1 is replaced with SBA-15 prepared in Preparation Example 3, and the template agent in step 2 is replaced with hexadecyltrimethylammonium bromide, finally obtaining the catalyst SiO2@(Cu / SBA-15), wherein the Cu loading is 12.5 wt%.

[0096] Example 4: Preparation of MFI@(Cu / Hβ-DeAl)

[0097] The only difference from Example 1 is that the support in step 1 is replaced with Hβ-DeAl from Preparation Example 2, and the catalyst MFI@(Cu / Hβ-DeAl) is finally obtained, wherein the Cu loading is 12.5 wt%.

[0098] Example 5: Preparation of 5MFI@(Cu / ZSM-5-DeAl)

[0099] The only difference from Example 1 is that in step 2, the molar amount of silicon in tetraethyl orthosilicate is 5 times that in Example 1; the final catalyst 5MFI@(Cu / ZSM-5-DeAl) is obtained with a Cu loading of 4.5 wt%.

[0100] Example 6 Preparation of MFI@(Cu / MFI)N

[0101] The difference from Example 1 is that:

[0102] Replace the vector in step 1 with the MFI (Silicalite-1) vector prepared in preparation example 4;

[0103] In step 3, precursor II is treated with nitrous oxide at 250°C for 1 hour to finally obtain catalyst MFI@(Cu / MFI)N, in which the loading of Cu is 12.5 wt%.

[0104] Example 7 Preparation of SiO2@(Cu / MCM-41)N

[0105] The only difference from Example 1 is that:

[0106] Replace the vector in step 1 with MCM-41 (Nature 1992, 359, 710–712);

[0107] Replace the template agent in step 2 with P123;

[0108] In step 3, precursor II is treated with nitrous oxide at 250°C for 1 hour to finally obtain the catalyst SiO2@(Cu / MCM-41)N, in which the Cu loading is 12.5 wt%.

[0109] Comparative Example 1: Preparation of Cu / MFI

[0110] The only difference from Example 2 is that step 2 is omitted, and the precursor I is directly processed in step 3 to finally obtain the catalyst Cu / MFI, wherein the loading of Cu is 12.5 wt%.

[0111] Comparative Example 2: Preparation of Cu / ZSM-5-DeAl

[0112] The only difference from Example 1 is that step 2 is omitted, and precursor I is directly processed in step 3 to finally obtain catalyst Cu / ZSM-5-DeAl, wherein the loading of Cu is 12.5 wt%.

[0113] like Figure 2 As shown, compared with Cu / ZSM-5-DeAl in Comparative Example 2, MFI@(Cu / ZSM-5-DeAl) prepared in Example 1 has a multi-level pore structure of micropores and mesopores, which is beneficial to the diffusion of reactants and products.

[0114] Comparative Example 3: Preparation of MFI@(Cu / MFI)-HT (hydrothermal)

[0115] Step 1 is the same as in Example 2. The only difference from Example 2 is that in Step 2, 3.1 g of tetraethyl orthosilicate, 1.9 g of template agent (tetrapropylammonium hydroxide), and 2 mL of water are mixed, stirred, and hydrolyzed thoroughly for 1 hour at room temperature. Then, precursor I prepared in Step 1, namely CuO / ZSM-5-DeAl precursor, is added, and stirring continues for 2 hours. The temperature is raised to 80°C and maintained for 24 hours to obtain a gel. The gel is pulverized and ground to a finer particle size than 60 mesh, mixed with water, and placed in a hydrothermal reactor and kept hydrothermally at 180°C for 4 days to obtain solid precursor II, namely silicon-coated Cu / MFI. Step 3 is the same as in Example 2, finally yielding catalyst MFI@(Cu / MFI)-HT, wherein the Cu loading is 12.5 wt%.

[0116] Before catalyst evaluation, granulation is required, with a particle size of 0.1–10 cm and an axial crushing strength of 1–50 kg / cm. Particles smaller than 0.1 cm result in excessive bed resistance, affecting system operation; particles larger than 10 cm result in insufficient contact time between the catalyst and substrate, leading to ethanol conversion rates below 80%. An axial crushing strength between 1 and 50 kg / cm meets production requirements without affecting the catalyst's pore structure.

[0117] Reaction Example 1

[0118] The catalytic conversion experiments were conducted in a fixed-bed reactor under the following conditions: ethanol dehydrogenation was carried out using the catalysts prepared in Examples 1-7 and Comparative Example 1 (ethanol concentration 98 wt%, reaction temperature 250 °C, reaction pressure at atmospheric pressure, and mass hourly space velocity 1.5 h⁻¹). -1 The catalyst (with a copper loading of 12.5%) was added to a fixed-bed reactor at a rate of 10 g. Online hydrogen reduction was performed at a flow rate of 200 mL / min, a reduction temperature of 300 °C, and a reduction time of 2 h. After reduction, the temperature was lowered to the reaction temperature, and nitrogen was introduced as a carrier gas at a flow rate of 300 mL / min. The raw material was then pumped in, and the gaseous products were analyzed by online gas chromatography.

[0119] The results of using the catalysts prepared in Examples 1-7 and Comparative Example 1 for the catalytic dehydrogenation of ethanol are shown in Table 1.

[0120] Table 1. Results of different copper-based catalysts used in the catalytic dehydrogenation of ethanol (after 24 hours of reaction).

[0121]

[0122] Table 1 compares the product changes of different copper-based catalysts used in the ethanol dehydrogenation reaction. The reaction data show that the copper-based catalyst prepared by the coating method exhibits better reactivity compared to the catalysts prepared by the simple impregnation method (Comparative Example 1 and Comparative Example 2). However, the amount of silicon coating cannot be too high; when the molar ratio of coated silicon to silicon support reaches 5, the ethanol conversion rate decreases to 80%. Meanwhile, the second type of gel showed poor mixing effect with water (Comparative Example 3), with no significant promoting effect, demonstrating that steam dry crystallization can promote the coating of copper catalysts.

[0123] Examples 8-11

[0124] Example 8 differs from Example 2 only in that the amount of copper nitrate in step 1 is 0.178 g; thus, the copper loading in the catalyst MFI@(Cu / MFI) obtained in step 3 is 2 wt%.

[0125] Example 9 differs from Example 2 only in that the amount of copper nitrate in step 1 is 0.445 g; thus, the copper loading in the catalyst MFI@(Cu / MFI) obtained in step 3 is 5 wt%.

[0126] Example 10 differs from Example 2 only in that the amount of copper nitrate in step 1 is 0.89 g; and the copper loading in the catalyst MFI@(Cu / MFI) obtained in step 3 is 10 wt%.

[0127] Example 11 differs from Example 2 only in that the amount of copper nitrate in step 1 is 2.67 g; and the copper loading in the catalyst MFI@(Cu / MFI) obtained in step 3 is 30 wt%.

[0128] Reaction Example 2

[0129] The specific reaction conditions were the same as in reaction example 1, and the results are shown in Table 2:

[0130] The catalysts prepared in Examples 8-11 were used for the catalytic dehydrogenation of ethanol (ethanol concentration 98 wt%, reaction temperature 250 °C, reaction mass hourly space velocity 2.0 h⁻¹). -1 The results are shown in Table 2.

[0131] Table 2 Results of catalytic dehydrogenation conversion of ethanol using MFI@(Cu / MFI) catalysts with different loadings (after 24 h of reaction).

[0132]

[0133] As can be seen from the reaction data in Table 2, although the copper loading affected the conversion rate of ethanol, the selectivity of acetaldehyde exceeded 90%, demonstrating good product selectivity.

[0134] Examples 11-17

[0135] Examples 11, 12, 13, 14, 15, 16, and 17 differ from Example 3 only in the template agent used in step 2, as detailed in Table 3.

[0136] Reaction Example 3

[0137] Except for the reaction conditions specifically mentioned in Table 3, the other reaction conditions are the same as in Reaction Example 1. The results of SiO2@(Cu / MCM-41)N catalysts prepared with different template agents for catalytic dehydrogenation of ethanol (ethanol concentration 98wt%, 250℃, 20% Cu) are shown in Table 3.

[0138] Table 3. Results of SiO2@(Cu / MCM-41)N catalysts prepared with different templates for ethanol catalytic dehydrogenation (results after 24 h of reaction).

[0139] Example template agent Conversion rate / % Acetaldehyde selectivity / % Stability / h Example 11 Tetrapropylammonium hydroxide 90.2 92.7 >500 Example 12 Methylamine 90.4 81.2 155 Example 13 ethylenediamine 92.6 93.7 >500 Example 14 ethylenediamine 90.2 93.5 >500 Example 15 1,6-Hexamethylenediamine 93.2 93.7 >500 Example 16 P123 91.4 93.5 >500 Example 17 Hexadecyltriethylammonium bromide 90.9 92.7 >500

[0140] Template agents affect the pore structure of catalysts, thereby altering the final catalyst's reactivity and selectivity. When low-molecular-weight organic amines are used as template agents, the resulting support has low crystallinity, leading to poor catalyst stability. When high-molecular-weight organic amines are used as template agents, the selectivity for acetaldehyde increases to over 90%, and the catalyst's stability is significantly improved.

[0141] Reaction Example 4

[0142] Except for the reaction conditions specifically mentioned in Table 4, the other reaction conditions are the same as in Reaction Example 1. The results of using the catalyst MFI@(Cu / ZSM-5-DeAl) prepared in Example 1 for catalytic dehydrogenation of ethanol under different reaction conditions are shown in Table 4.

[0143] Table 4. Results of MFI@(Cu / ZSM-5-DeAl) catalyst for catalytic dehydrogenation of ethanol under different conditions (ethanol concentration 98wt%, results after 24h of reaction, 20% Cu).

[0144]

[0145] By changing the reaction conditions (Table 4), it was found that under the same catalyst, the ethanol conversion gradually increased with increasing reaction temperature, reaching 93.2% ethanol conversion and 94.4% acetaldehyde selectivity at 250℃. However, excessively high temperatures led to side reactions such as dehydration and decomposition, resulting in a decrease in selectivity. Increasing the reaction space velocity to 5.6 h⁻¹... -1 At that time, the ethanol conversion rate decreased slightly, but still reached 85.7%. When CO2 was used as the carrier gas, the ethanol conversion rate increased to 93.2% under the same conditions.

[0146] Reaction Example 5

[0147] Comparison of catalyst stability:

[0148] Stability experiments were conducted using the SiO2@(Cu / SBA-15) catalyst prepared in Example 3 and the MFI@(Cu / MFI)N catalyst in Example 6. The reaction time was 500 hours, and other reaction conditions were the same as in Example 1. Table 5 compares the experimental results of this invention with those of the prior art.

[0149] Table 5 Comparison of ethanol dehydrogenation catalysts of the present invention and those of the prior art (ethanol concentration 98wt%, temperature 250℃, space velocity 3.1h) -1 )

[0150]

[0151] By comparing with the literature (Table 5), it can be found that the experimental results of the present invention have made significant progress in terms of the stability of the reactive catalyst. The catalyst of the present invention is easy to prepare, the reaction conditions are milder, and it has ultra-high stability, making it highly practical.

[0152] The above description is merely a specific embodiment of some aspects of the present invention. However, the scope of protection of the present invention is not limited thereto, nor does the order of the embodiments impose any limitation on the present invention. Any changes or substitutions made by those skilled in the art within the scope of the technology reported in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention is not limited to the above embodiments, and should be determined by the scope of the claims.

Claims

1. A method for preparing acetaldehyde and hydrogen by dehydrogenation of ethanol, characterized by, The catalyst uses a copper-based catalyst, and a preparation method of the copper-based catalyst comprises the following steps: A precursor I is obtained; the precursor I comprises a carrier and a supported active component, the active component contains a copper element, and the carrier is a molecular sieve with a silicon-aluminum ratio greater than 200; The precursor I is subjected to silicon component coating treatment to obtain a precursor II; The precursor II is reduced to obtain the copper-based catalyst; The silicon component coating treatment comprises the following steps: A gel is obtained, which contains a silicon source I, a template agent I, a solvent I and the precursor I; The silicon source I is at least one selected from amorphous silicon dioxide, silicon gas aerosol, silicon liquid sol and tetraethyl orthosilicate; The template agent I is at least one selected from ethylamine, diethylamine, triethylamine, ethylenediamine, 1,6-hexanediamine, tetrapropylammonium hydroxide, P123, cetyltrimethylammonium bromide and cetyltriethylammonium bromide; After the gel is heated in water vapor at a temperature of 120-200 DEG C for 0.5-7 days, the precursor II is obtained through calcination I; The copper-based catalyst has a micro-porous, meso-porous multi-level pore structure, and the copper particles after coating have stronger force with the silicon oxide, forming more Cu + species; The selectivity of the acetaldehyde is more than 90%, the catalyst is stably operated for more than 500 hours, and the bed pressure change is less than 0.1 MPa.

2. The method of claim 1, wherein, The temperature of the calcination I is independently selected from 300-700 DEG C; The atmosphere of the calcination I is selected from air; The reduction condition is 200-400 DEG C for 0.5-6 hours; The reduction atmosphere is hydrogen, methane or a mixed gas; the mixed gas refers to a mixture of one of hydrogen and methane and at least one of nitrogen, argon and helium; The mass ratio of the silicon source I, the template agent I, the solvent I and the precursor I in the gel is between 1:(0.1-1):(10-100):(0.1-10).

3. The method of claim 1, wherein, The solvent I is selected from water and / or ethanol.

4. The method of claim 1, wherein, The conditions of the silicon component coating treatment are as follows: The heating temperature is 120-180 DEG C; The heating time is 0.5-4 days; The silicon component coating treatment is to first obtain a mixture I containing the silicon source I, the template agent I and the solvent I, and then mix the mixture I with the precursor I to form a gel; The mixing I is stirring at 20-90 DEG C for 0.5-10 hours; The gel is heated in water vapor by placing the gel in a hydrothermal kettle with a steam atmosphere for crystallization reaction; Before heating, the gel is ground; The grinding is to grind the gel to a particle size greater than 60 mesh.

5. The method of claim 1, wherein The molecular sieve with a silicon-aluminum ratio greater than 200 is obtained by dealuminization treatment of a silicon-aluminum molecular sieve I, and the silicon-aluminum molecular sieve I is at least one selected from ZSM-5, Hbeta, X-type and Y-type molecular sieves; The precursor I is prepared by an impregnation method; a solvent II in the impregnation method is a copper salt solution; the copper salt is at least one selected from copper nitrate, copper chloride and copper acetate; the solvent II in the copper salt solution is selected from water and / or ethanol; in the impregnation method, the solid-liquid mass ratio of the carrier to the impregnation solution is 2:1-1:5, the mass concentration of the copper salt in the copper salt solution is between 2% and 30%, and the mass of the copper salt is calculated based on the mass of the copper element in the copper salt. The content of copper element in the precursor I is 2-30 wt%; The total mass of silicon in the precursor II is 1.1-10 times of the mass of silicon in the carrier.

6. The method of claim 1, wherein, The content of copper in the copper-based catalyst is 1-50 wt%.

7. The method of claim 1, wherein, The copper-based catalyst is granulated, the particle size is 0.1-10 cm, and the axial crushing strength is 1-50 Kg / cm.

8. The method of claim 1, wherein, The reaction conditions for preparing acetaldehyde and hydrogen by dehydrogenation of ethanol are as follows: A fixed bed is used as the reactor for the reaction. The reaction pressure is 0.1-1 MPa, and the reaction temperature is 120-320 o The mass space velocity of the catalytic reaction is 0.1-20 h -1 The reaction carrier gas is at least one of nitrogen, argon, helium, nitrous oxide, and carbon dioxide.

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