Copper-silicon catalyst for catalyzing coupling of ethylene glycol and primary alcohol to synthesize long-chain vicinal diols, preparation method therefor and use thereof

Abstract

The present application relates to the technical field of heterogeneous catalysis, and provides a copper-silicon catalyst for catalyzing coupling of ethylene glycol and primary alcohol to synthesize long-chain vicinal diols, a preparation method therefor and a use thereof. The chemical general formula of the copper-silicon catalyst is CuxSi1-xO, wherein 0.01≤x≤0.3. The copper-silicon catalyst has good stability and high activity, and is easy to separate from a product when being used for synthesizing long-chain vicinal diols, the conversion rate of ethylene glycol and the selectivity of a product are high, and the copper-silicon catalyst can be reused.

Description

A copper-silicon catalyst for catalyzing the coupling of ethylene glycol and primary alcohol to form long-chain vicinal diols, and its preparation method and application Technical Field

[0001] The present application relates to the field of heterogeneous catalysis technology, for example, a copper-silicon catalyst for catalyzing the coupling of ethylene glycol and primary alcohols to form long-chain vicinal diols, and a preparation method and application thereof. Background Art

[0002] Ethylene glycol (EG) is a key petrochemical product with widespread applications across various sectors. my country is the world's largest EG consumer. Over the past decade, my country's EG industry has experienced rapid growth, significantly increasing production capacity. In 2020, EG production capacity reached over 15.7 million tons, primarily produced by the ethylene process and the oxalate process. my country is a major coal producer with abundant resources. Indirect coal-based EG production is a key EG production pathway, accounting for nearly 50% of all EG production processes. With the continuous improvement and upgrading of production technologies, new EG production routes are being developed. Using renewable biomass feedstocks, various methods have been developed, including sugar hydrogenation, direct cellulose conversion, and biomass fermentation to reduce EG to glyoxal, offering significant potential for increased EG production. The continuous increase in global EG production capacity has led to a global overcapacity. Therefore, how to transform low-cost EG into high-value-added products has become a hot topic for scientific researchers. Among the many utilization routes of ethylene glycol, the process of combining ethylene glycol with dimethyl carbonate to catalytically synthesize high-value ethylene carbonate has attracted much attention.

[0003] At present, the conversion of ethylene glycol and primary alcohols to lactic acid, α-hydroxy acids, etc. through coupling has become one of the research hotspots. However, this route still has some problems that cannot be ignored. Wu et al. (Angewandte Chemie, 2020, 10507-10511) prepared a series of iridium complexes by using three nitrogen heterocyclic carbon alkenes derived from 1,3-dimethylbenzimidazole salts to catalyze the coupling of ethylene glycol and methanol to lactic acid, with a TOF value of 3660h. -1 Satyadeep Waiba et al. (ACS Catalysis, 2022, 12, 7, 3995-4001) designed a manganese complex {[HN(C2H4PPh2)2]Mn(CO)2Br} to catalyze the conversion of vicinal diols to α-hydroxycarboxylic acids, which has attracted widespread attention in various drugs, bioactive molecules, and biodegradable polymers, achieving efficient downstream conversion and utilization of vicinal diols. However, current homogeneous complex catalysts have problems such as complex preparation process, difficulty in reuse, and difficulty in achieving industrial scale-up application.

[0004] Therefore, designing a heterogeneous catalyst that is simple to prepare, highly selective and reusable for catalytic ethylene glycol coupling is a technical problem that needs to be solved urgently.

[0005] Summary of the Invention

[0006] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0007] This application provides a copper-silicon catalyst for catalyzing the coupling of ethylene glycol and a primary alcohol to produce a long-chain vicinal diol, as well as its preparation method and application. The copper-silicon catalyst exhibits excellent stability and high activity, is easily separated from the product when used to synthesize long-chain vicinal diols, and exhibits high ethylene glycol conversion and product selectivity, allowing for multiple reuse.

[0008] In the first aspect, the present application provides a copper-silicon catalyst for catalyzing the coupling of ethylene glycol and primary alcohol to form long-chain vicinal diols, the chemical formula of the copper-silicon catalyst is Cu x Si 1-x O, 0.05≤x≤0.3.

[0009] The copper silicon catalyst provided in the present application has good stability and high activity. When used to synthesize long-chain vicinal diols, it is easy to separate from the product, and the conversion rate of ethylene glycol and the selectivity of the product are high, and it can be reused multiple times.

[0010] In the present application, 0.01≤x≤0.3, for example, it can be 0.01, 0.05, 0.1, 0.015, 0.02, 0.025 or 0.3, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0011] In this application, if the value of x is too small, the copper species content on the catalyst surface will be too low, the active sites will be insufficient, and the conversion rate will be low; if the value of x is too large, the surface copper species will be excessively agglomerated, which is not conducive to the uniform dispersion of the active sites.

[0012] As an optional technical solution of the present application, the copper silicon catalyst has a coral-like structure.

[0013] In this application, the coral-like structure facilitates the exposure of more active sites and the uniform distribution of copper on the silica surface.

[0014] In a second aspect, the present application provides a method for preparing a copper-silicon catalyst for catalyzing the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol as described in the first aspect, the preparation method comprising the following steps:

[0015] (1) mixing a copper solution and a silicon source, and performing a heating treatment to remove ammonia to obtain a precursor solution;

[0016] (2) The precursor solution is subjected to hydrothermal crystallization, calcination and reduction treatment to obtain the copper silicon catalyst.

[0017] The present application provides a method for preparing a catalyst with a simple process, low cost, and the copper silicon catalyst can be prepared without the need for a solvent or a carrier.

[0018] As an optional technical solution of the present application, the method for preparing the copper solution in step (1) includes:

[0019] A copper source, an alkali source and a solvent are mixed to obtain the copper solution.

[0020] In one embodiment, the copper source is a soluble copper salt, and the soluble copper salt includes any one or a combination of at least two of copper nitrate pentahydrate, copper nitrate, copper sulfate, copper chloride, or copper carbonate. Exemplary, typical but non-limiting examples of the combination may include a combination of copper nitrate and copper chloride, a combination of copper chloride and copper carbonate, or a combination of copper carbonate and copper sulfate.

[0021] In one embodiment, the solution comprises water.

[0022] In one embodiment, the alkali source comprises any one of hydroxide, ammonia, ammonium carbonate, ammonium bicarbonate or urea, or a combination of at least two thereof. Exemplary, typical but non-limiting examples of the combination may be a combination of ammonia and ammonium carbonate, a combination of ammonia and urea, or a combination of ammonia and ammonium bicarbonate, etc.

[0023] In one embodiment, the hydroxide ion concentration of the alkaline source is 1-10 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] In one embodiment, the pH value of the copper solution is 9-11, for example, 9.0, 9.5, 10.0, 10.5 or 11.0, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] In one embodiment, the mixing method includes: stirring and mixing the copper source and the solvent to obtain a mixed solution, then dropwise adding the alkali source into the mixed solution, and continuing to stir and mix to obtain the copper solution.

[0026] In one embodiment, the dropwise addition rate of the alkali source is 60-150 drops / min, for example, 60 drops / min, 80 drops / min, 100 drops / min, 120 drops / min or 150 drops / min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] As an optional technical solution of the present application, the silicon source in step (1) includes silica sol and / or tetraethyl orthosilicate.

[0028] In one embodiment, the temperature of the heating and ammonia removal treatment in step (1) is 40-70°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In this application, if the temperature of the heating and ammonia removal treatment is too low, the ammonia will be removed too slowly, or even residual ammonia will be caused; if the temperature of the heating and ammonia removal treatment is too high, it will affect the crystal growth of the copper silicon catalyst and affect the subsequent hydrothermal growth process.

[0030] In one embodiment, the pH value of the precursor solution in step (1) is ≤7, for example, it can be 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 or 7.0, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In the present application, the pH value of the precursor solution is ≤7, which helps to ensure the effective removal of ammonia and the complete conversion of copper salts into solid hydroxides and oxides.

[0032] As an optional technical solution of the present application, the temperature of the hydrothermal crystallization in step (2) is 120-200° C., for example, 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., or 200° C., and the time is 12-48 hours, for example, 12 hours, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, or 48 hours, etc. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable.

[0033] In this application, if the temperature of hydrothermal crystallization is too low, the crystal growth will be insufficient and the site exposure will be insufficient; if the temperature of hydrothermal crystallization is too high, the crystal growth will be too perfect, the catalyst specific surface area will be too low, and the catalytic active centers will be covered.

[0034] In one embodiment, after the hydrothermal crystal growth treatment in step (2), washing and drying are first performed, and then calcination and reduction treatment are performed.

[0035] In one embodiment, the drying temperature is 60-120° C., for example, 60° C., 70° C., 80° C., 90° C., 100° C., 110° C., or 120° C., and the drying time is 2-18 hours, for example, 2 hours, 6 hours, 10 hours, 14 hours, or 18 hours. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable.

[0036] In one embodiment, the calcination temperature is 300-600° C., for example, 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., or 600° C., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. The calcination time is 2-6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0037] In one embodiment, the reduction treatment temperature is 300-600° C., for example, 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., or 600° C., and the reduction treatment time is 2-6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours. However, the present invention is not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable.

[0038] In this application, if the reduction temperature is too low, the reduction degree of some copper species will be insufficient. 0 、Cu + and Cu 2+ If the reduction treatment temperature is too high, the surface active sites will agglomerate and harden, reducing the reaction activity.

[0039] In one embodiment, the reduction treatment is performed in a reducing gas containing hydrogen and nitrogen.

[0040] In one embodiment, the volume fraction of hydrogen in the reducing gas is 8-12%, for example, 8%, 9%, 10%, 11% or 12%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] As an optional technical solution of the present application, the preparation method comprises the following steps:

[0042] (I) stirring and mixing a soluble copper salt and deionized water at room temperature for 2-30 minutes to obtain a copper salt solution, then adding an alkali source dropwise to the copper salt solution until the pH is 9-11, and then stirring and mixing for 10-30 minutes to obtain a copper solution;

[0043] The hydroxide ion concentration of the alkaline source is 1-10 mol / L, and the drop rate of the alkaline source is 60-150 drops / min;

[0044] (II) adding a silicon source dropwise to the copper solution at room temperature, stirring for 0.5-2 hours, and then heating at 40-70° C. to remove ammonia until a precursor solution with a pH of 3-8 is obtained;

[0045] The silicon source is added at a rate of 60-150 drops / min.

[0046] (III) transferring the precursor solution to a hydrothermal reactor, performing hydrothermal crystallization at 120-200° C. for 12-48 hours, washing, and then drying at 60-120° C. for 8-18 hours to obtain a solid catalyst;

[0047] (IV) calcining the solid catalyst at 300-600° C. for 2-6 hours, then cooling to room temperature and reducing the solid catalyst in a reducing gas at 300-600° C. for 2-6 hours to obtain the copper-silicon catalyst;

[0048] The reducing gas contains hydrogen and nitrogen.

[0049] In a third aspect, the present application provides an application of a copper-silicon catalyst as described in the first aspect for catalyzing the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol, wherein the copper-silicon catalyst is used to catalyze the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol.

[0050] As an optional technical solution of the present application, the long-chain vicinal diol is a long-chain vicinal diol with a carbon atom number ≥ 3. For example, a typical but non-limiting example of the combination may be 1,2-propylene glycol, 1,2-butanediol, 1,2-pentanediol or 1,2-hexanediol, etc.

[0051] In one embodiment, the specific steps of using the copper-silicon catalyst to catalyze the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol include:

[0052] (a) performing reduction and preactivation treatment on the copper-silicon catalyst to obtain a treated copper-silicon catalyst;

[0053] (b) mixing ethylene glycol, a primary alcohol and the treated copper-silicon catalyst to carry out a catalytic reaction to obtain a long-chain vicinal diol.

[0054] As an optional technical solution of the present application, the specific steps of the reduction and pre-activation treatment in step (a) include:

[0055] At a preset temperature, hydrogen is introduced into the container where the copper silicon catalyst is located to perform catalyst reduction and pre-activation treatment.

[0056] In the present application, the purpose of reducing and preactivating the copper-silicon catalyst is to change the valence state of species on the catalyst surface and to stimulate active centers.

[0057] In one embodiment, the preset temperature is 250-450°C, for example, 250°C, 300°C, 350°C, 400°C or 450°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] In one embodiment, the primary alcohol in step (b) comprises any one or a combination of at least two of methanol, ethanol, n-propanol and n-butanol.

[0059] In one embodiment, based on the total mass of the ethylene glycol and the primary alcohol, the mass fraction of the ethylene glycol is 0.01-0.3%, for example, it can be 0.01%, 0.05%, 0.1%, 0.2% or 0.3%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] In one embodiment, the temperature of the catalytic reaction in step (b) is 150-300°C, for example, 150°C, 200°C, 250°C or 300°C, and the pressure during the catalytic reaction is 0.5-5MPa, for example, 0.5MPa, 1MPa, 2MPa, 3MPa or 4MPa.

[0061] In the present application, if the temperature of the catalytic reaction is too low, the catalytic conditions cannot be met thermodynamically due to the low temperature, and the target product cannot be obtained; if the temperature of the catalytic reaction is too high, it will cause an increase in by-products such as ethers, thereby reducing the selectivity of the target product, the long-chain vicinal diol.

[0062] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to limited space and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0063] Compared with the related art, this application has the following beneficial effects:

[0064] (1) The copper-silicon catalyst provided in the present application has good stability and high activity. When it is used to catalyze the coupling of ethylene glycol and primary alcohols to form long-chain vicinal diol chemicals, it is easy to separate from the product, and the conversion rate of ethylene glycol and the selectivity of the product are high, with the conversion rate reaching more than 80% and the selectivity reaching more than 75%, and it can be reused many times.

[0065] (2) The present application provides a method for preparing a catalyst with simple synthesis. The method is low in cost and can prepare a copper silicon catalyst without the need for a solvent and a carrier.

[0066] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0068] FIG1 is an XRD diagram of the copper-silicon catalyst provided in Examples 1-4 of this application.

[0069] FIG2 is a SEM image of the copper-silicon catalyst provided in Example 3 of this application. DETAILED DESCRIPTION

[0070] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0071] It should be noted that, in the following embodiments, room temperature refers to 25°C.

[0072] Example 1

[0073] This embodiment provides a method for preparing a copper-silicon catalyst, the preparation method comprising the following steps:

[0074] (1) 3.83 g of copper nitrate trihydrate and 500 mL of deionized water were stirred and mixed at room temperature for 30 minutes to obtain a copper salt solution, and then 35% by mass of ammonia water was added dropwise to the copper salt solution until the pH reached 11, and then stirred and mixed for 30 minutes to obtain a copper solution;

[0075] The hydroxide ion concentration of the ammonia solution was 1 mol / L, and the ammonia solution was added at a rate of 90 drops / min.

[0076] (2) adding 10 mL of 30% by mass silica sol dropwise to the copper solution at room temperature, stirring for 0.5 h, and then heating at 65° C. to remove ammonia until a precursor solution with a pH of 7 is obtained;

[0077] The silicon source was added at a rate of 100 drops / min.

[0078] (3) The precursor solution was transferred to a 200 mL hydrothermal autoclave lined with polytetrafluoroethylene, and hydrothermally crystallized at 200° C. for 15 h. After the crystallization, the precursor solution was washed and then dried at 90° C. for 12 h to obtain a solid catalyst.

[0079] (4) The solid catalyst was calcined at 500°C for 4 hours in an air atmosphere, and then the solid catalyst was reduced in a reducing gas at 400°C for 4 hours after cooling to room temperature to obtain a copper-silicon catalyst with a coral-like structure, the chemical formula of which is Cu 0.02 Si 0.98 O;

[0080] The reducing gas includes 10% by volume of hydrogen and 90% by volume of nitrogen.

[0081] This embodiment also provides a method for using the copper-silicon catalyst to catalyze the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol, the method comprising the following steps:

[0082] (a) The copper-silicon catalyst is tableted using a tablet press, crushed and sieved to 50 mesh, and then loaded into a fixed bed stainless steel tube, and quartz sand and quartz wool are filled in the upper and lower parts of the copper-silicon catalyst to prevent the catalyst from being washed out with the reaction solution;

[0083] (b) hydrogen gas was introduced into the fixed bed stainless steel tube at a flow rate of 100 mL / min for 3 h at a temperature of 300° C. to perform catalyst reduction and preactivation treatment;

[0084] (c) Ethylene glycol and ethanol were mixed to form a homogeneous solution with a mass fraction of 25 wt%, with ethylene glycol accounting for 0.05% of the total mass. This solution was introduced into a micro-fixed bed via a feed pump and injected into the stainless steel tube containing the copper-silicon catalyst at a feed rate of 0.15 mL / min. The catalytic reaction was carried out under the conditions of 1 MPa, a H2 flow rate of 100 mL / min, and a reaction temperature of 200°C to obtain the product, 1,2-butanediol. Samples were collected every hour and analyzed by gas chromatography-mass spectrometry combined with gas chromatography.

[0085] Example 2

[0086] This embodiment provides a method for preparing a copper-silicon catalyst, the preparation method comprising the following steps:

[0087] (1) 6.35 g of copper nitrate trihydrate and 500 mL of deionized water were stirred and mixed at room temperature for 30 minutes to obtain a copper salt solution, and then 35% by mass of ammonia water was added dropwise to the copper salt solution until the pH reached 11, and then stirred and mixed for 30 minutes to obtain a copper solution;

[0088] The hydroxide ion concentration of the ammonia solution is 2 mol / L, and the dripping rate of the ammonia solution is 100 drops / min;

[0089] (2) adding 10 mL of 30 wt.% silica sol dropwise to the copper solution at room temperature, stirring for 0.5 h, and then heating at 65° C. to remove ammonia until a precursor solution with a pH value of less than 7 is obtained;

[0090] The silicon source was added at a rate of 100 drops / min.

[0091] (3) The precursor solution was transferred to a 200 mL hydrothermal autoclave lined with polytetrafluoroethylene, and hydrothermally crystallized at 200° C. for 15 h. After the crystallization, the precursor solution was washed and then dried at 90° C. for 12 h to obtain a solid catalyst.

[0092] (4) The solid catalyst was calcined at 500°C for 4 hours in an air atmosphere, and then the solid catalyst was reduced in a reducing gas at 400°C for 4 hours after cooling to room temperature to obtain a copper-silicon catalyst with a coral-like structure, the chemical formula of which is Cu 0.05 Si 0.95 O;

[0093] The reducing gas includes 10% by volume of hydrogen and 90% by volume of nitrogen.

[0094] This embodiment also provides a method for using the copper-silicon catalyst to catalyze the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol, the method comprising the following steps:

[0095] (a) The copper-silicon catalyst is tableted using a tablet press, crushed and sieved to 40 mesh, and then loaded into a fixed bed stainless steel tube, and quartz sand and quartz wool are filled above and below the copper-silicon catalyst to prevent the catalyst from being washed out with the reaction solution;

[0096] (b) hydrogen gas was introduced into the fixed bed stainless steel tube at a flow rate of 100 mL / min for 3 h at a temperature of 300° C. to perform catalyst reduction and preactivation treatment;

[0097] (c) Ethylene glycol and ethanol were mixed to form a homogeneous solution with a mass fraction of 25 wt%, with ethylene glycol accounting for 0.1% of the total mass. This solution was introduced into a micro-fixed bed via a feed pump and injected into the stainless steel tube containing the copper-silicon catalyst at a feed rate of 0.15 mL / min. The catalytic reaction was carried out under the conditions of 1 MPa, a H2 flow rate of 100 mL / min, and a reaction temperature of 200°C to obtain the product, 1,2-butanediol. Samples were collected every hour and analyzed by gas chromatography-mass spectrometry combined with gas chromatography.

[0098] Example 3

[0099] This embodiment provides a method for preparing a copper-silicon catalyst, the preparation method comprising the following steps:

[0100] (1) 13.42 g of copper nitrate trihydrate and 500 mL of deionized water were stirred and mixed at room temperature for 30 minutes to obtain a copper salt solution, and then 35% by mass of ammonia water was added dropwise to the copper salt solution until the pH reached 11, and then stirred and mixed for 30 minutes to obtain a copper solution;

[0101] The hydroxide ion concentration of the ammonia solution is 1 mol / L, and the dripping rate of the ammonia solution is 100 drops / min;

[0102] (2) adding 10 mL of 30 wt.% silica sol dropwise to the copper solution at room temperature, stirring for 0.5 h, and then heating at 65° C. to remove ammonia until a precursor solution with a pH of 7 is obtained;

[0103] The silicon source was added at a rate of 100 drops / min.

[0104] (3) The precursor solution was transferred to a 200 mL hydrothermal autoclave lined with polytetrafluoroethylene, and hydrothermally crystallized at 200° C. for 15 h. After the crystallization, the precursor solution was washed and then dried at 90° C. for 12 h to obtain a solid catalyst.

[0105] (4) The solid catalyst was calcined at 500°C for 4 hours in an air atmosphere, and then the solid catalyst was reduced in a reducing gas at 400°C for 4 hours after cooling to room temperature to obtain a copper-silicon catalyst with a coral-like structure, the chemical formula of which is Cu 0.1 Si 0.9 O;

[0106] The reducing gas includes 10% by volume of hydrogen and 90% by volume of nitrogen.

[0107] This embodiment also provides a method for using the copper-silicon catalyst to catalyze the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol, the method comprising the following steps:

[0108] (a) The copper-silicon catalyst is tableted using a tablet press, crushed and sieved to 60 mesh, and then loaded into a fixed bed stainless steel tube, and quartz sand and quartz wool are filled above and below the copper-silicon catalyst to prevent the catalyst from being washed out with the reaction solution;

[0109] (b) hydrogen gas was introduced into the fixed bed stainless steel tube at a flow rate of 100 mL / min for 3 h at a temperature of 300° C. to perform catalyst reduction and preactivation treatment;

[0110] (c) Ethylene glycol and ethanol were mixed to form a homogeneous solution with a mass fraction of 25 wt%, with ethylene glycol accounting for 0.2% of the total mass. This solution was introduced into a micro-fixed bed via a feed pump at a rate of 0.15 mL / min into a stainless steel tube containing a copper-silicon catalyst. The catalytic reaction was carried out under conditions of 1 MPa, a H2 flow rate of 100 mL / min, and a reaction temperature of 200°C to obtain the product, 1,2-butanediol. Samples were collected every hour and analyzed by gas chromatography-mass spectrometry combined with gas chromatography.

[0111] FIG2 shows a SEM image of the copper-silicon catalyst provided in this embodiment. As can be seen from the image, the catalyst has a coral-like structure.

[0112] Example 4

[0113] This embodiment provides a method for preparing a copper-silicon catalyst, the preparation method comprising the following steps:

[0114] (1) 21.31 g of copper nitrate trihydrate and 500 mL of deionized water were stirred and mixed at room temperature for 30 minutes to obtain a copper salt solution, and then 35% ammonia water was added dropwise to the copper salt solution until the pH reached 11, and then stirred and mixed for 30 minutes to obtain a copper solution;

[0115] The hydroxide ion concentration of the ammonia solution was 1 mol / L, and the ammonia solution was added at a rate of 90 drops / min.

[0116] (2) adding 10 mL of 30 wt.% silica sol dropwise to the copper solution at room temperature, stirring for 1 h, and then heating at 65° C. to remove ammonia until a precursor solution with a pH of 7 is obtained;

[0117] The silicon source was added at a rate of 100 drops / min.

[0118] (3) The precursor solution was transferred to a 200 mL hydrothermal autoclave lined with polytetrafluoroethylene, and hydrothermally crystallized at 200° C. for 15 h. After the crystallization, the precursor solution was washed and then dried at 90° C. for 12 h to obtain a solid catalyst.

[0119] (4) The solid catalyst was calcined at 500°C for 4 hours in an air atmosphere, and then the solid catalyst was reduced in a reducing gas at 400°C for 4 hours after cooling to room temperature to obtain a copper-silicon catalyst with a coral-like structure, the chemical formula of which is Cu 0.15 Si 0.85 O;

[0120] The reducing gas includes 10% by volume of hydrogen and 90% by volume of nitrogen.

[0121] This embodiment also provides a method for using the copper-silicon catalyst to catalyze the coupling of ethylene glycol and a primary alcohol to form a long-chain vicinal diol, the method comprising the following steps:

[0122] (a) The copper-silicon catalyst is tableted using a tablet press, crushed and sieved to 60 mesh, and then loaded into a fixed bed stainless steel tube, and quartz sand and quartz wool are filled above and below the copper-silicon catalyst to prevent the catalyst from being washed out with the reaction solution;

[0123] (b) hydrogen gas was introduced into the fixed bed stainless steel tube at a flow rate of 100 mL / min for 3 h at a temperature of 300° C. to perform catalyst reduction and preactivation treatment;

[0124] (c) Ethylene glycol and ethanol were mixed to form a homogeneous solution with a mass fraction of 25 wt%, with ethylene glycol accounting for 0.25% of the total mass. This solution was introduced into a micro-fixed bed via a feed pump and injected into a stainless steel tube containing a copper-silicon catalyst at a feed rate of 0.15 mL / min. The catalytic reaction was carried out under the conditions of 1 MPa, a H2 flow rate of 100 mL / min, and a reaction temperature of 200°C to obtain the product, 1,2-butanediol. Samples were collected every hour and analyzed by gas chromatography-mass spectrometry combined with gas chromatography.

[0125] FIG1 shows the XRD patterns of the copper-silicon catalysts provided in Examples 1-4. As can be seen from the figure, the catalysts have obvious characteristic peaks of copper-silicon oxides, and as the molar ratio of the copper source increases, the characteristic peaks of copper oxide are significantly enhanced.

[0126] Example 5

[0127] The difference between this embodiment and embodiment 1 is that ethanol in step (c) is replaced by methanol.

[0128] The rest of the preparation methods and parameters remained the same as in Example 1.

[0129] Example 6

[0130] The difference between this embodiment and embodiment 1 is that ethanol in step (c) is replaced by n-propanol.

[0131] The rest of the preparation methods and parameters remained the same as in Example 1.

[0132] Example 7

[0133] The difference between this embodiment and embodiment 1 is that ethanol in step (c) is replaced by n-butanol.

[0134] The rest of the preparation methods and parameters remained the same as in Example 1.

[0135] Example 8

[0136] The difference between this embodiment and embodiment 1 is that the temperature of the heating treatment for ammonia removal in step (2) is 30°C.

[0137] The rest of the preparation methods and parameters remained the same as in Example 1.

[0138] Example 9

[0139] The difference between this embodiment and embodiment 1 is that the temperature of the heating treatment for ammonia removal in step (2) is 100°C.

[0140] The rest of the preparation methods and parameters remained the same as in Example 1.

[0141] Example 10

[0142] The difference between this embodiment and embodiment 1 is that the pH value of the precursor solution in step (2) is 10.

[0143] The rest of the preparation methods and parameters remained the same as in Example 1.

[0144] Example 11

[0145] The difference between this embodiment and embodiment 1 is that the temperature of the hydrothermal crystallization in step (3) is 100°C.

[0146] The rest of the preparation methods and parameters remained the same as in Example 1.

[0147] Example 12

[0148] The difference between this embodiment and embodiment 1 is that the temperature of the hydrothermal crystallization in step (3) is 250°C.

[0149] The rest of the preparation methods and parameters remained the same as in Example 1.

[0150] Example 13

[0151] The difference between this embodiment and embodiment 1 is that the temperature of the reduction treatment in step (4) is 200°C.

[0152] The rest of the preparation methods and parameters remained the same as in Example 1.

[0153] Example 14

[0154] The difference between this embodiment and embodiment 1 is that the temperature of the reduction treatment in step (4) is 700°C.

[0155] The rest of the preparation methods and parameters remained the same as in Example 1.

[0156] Example 15

[0157] The difference between this embodiment and embodiment 1 is that step (b) is not performed.

[0158] The rest of the preparation methods and parameters remained the same as in Example 1.

[0159] Example 16

[0160] The difference between this embodiment and embodiment 1 is that the reaction temperature in step (c) is 100°C.

[0161] The rest of the preparation methods and parameters remained the same as in Example 1.

[0162] Example 17

[0163] The difference between this embodiment and embodiment 1 is that the reaction temperature in step (c) is 350°C.

[0164] The rest of the preparation methods and parameters remained the same as in Example 1.

[0165] Comparative Example 1

[0166] The difference between this comparative example and Example 1 is that no silica sol is added in step (2), and a single copper oxide catalyst is obtained.

[0167] The rest of the preparation methods and parameters remained the same as in Example 1.

[0168] Comparative Example 2

[0169] The difference between this comparative example and Example 1 is that copper nitrate trihydrate is not added in step (1), and a single silica catalyst is obtained.

[0170] The rest of the preparation methods and parameters remained the same as in Example 1.

[0171] Comparative Example 3

[0172] The difference between this comparative example and Example 1 is that the amount of copper nitrate trihydrate added in step (1) is adjusted so that the chemical formula of the copper silicon catalyst prepared is Cu 0.3 Si 0.7 O.

[0173] The rest of the preparation methods and parameters remained the same as in Example 1.

[0174] Performance Testing

[0175] After centrifuging the products obtained in the above examples and comparative examples, an appropriate amount of the supernatant was added with an internal standard substance (biphenyl) and quantitative analysis was performed by gas chromatography internal standard method.

[0176] The test results are shown in Table 1.

[0177] Table 1

[0178] analyze:

[0179] As can be seen from the above table, the copper silicon catalyst provided in this application has good stability and high activity. When it is used to catalyze the coupling of ethylene glycol and primary alcohols to form long-chain vicinal diol chemicals, it is easy to separate from the product, and the conversion rate of ethylene glycol and the selectivity of the product are high, with a conversion rate of more than 80% and a selectivity of more than 75%, and it can be reused many times.

[0180] The data results of Examples 1-7 and Comparative Examples 1-2 show that the coral-like silicon-copper oxide structure provided by the present application has high catalytic stability and activity in the process of catalyzing the ethylene glycol coupling reaction to prepare long-chain vicinal diols, while the catalytic activity of a single silicon dioxide catalyst or copper oxide catalyst is low and the catalytic effect is extremely poor. This indicates that the catalyst provided by the present application must contain both copper and silicon metals to achieve better selectivity and yield in the catalytic synthesis of long-chain vicinal diols.

[0181] It can be seen from the data results of Example 1 and Examples 8-9 that if the temperature of the heating treatment for ammonia removal is too low, the removal of ammonia will be too slow, or even ammonia residue will be left; if the temperature of the heating treatment for ammonia removal is too high, it will affect the crystal growth of the copper silicon catalyst and affect the growth process of the subsequent hydrothermal step.

[0182] From the data results of Example 1 and Example 10, it can be seen that if the pH value of the precursor solution is too high, the copper hydroxide precipitate will decompose, resulting in incomplete conversion of the copper salt, excessive loss, and a large difference from the theoretical molar ratio, thereby reducing the reaction activity.

[0183] It can be seen from the data results of Example 1 and Examples 11-12 that if the temperature of hydrothermal crystallization is too low, the crystal growth will be insufficient and the site exposure will be insufficient; if the temperature of hydrothermal crystallization is too high, the crystal growth will be too perfect, the catalyst specific surface area will be too low, and the catalytic active centers will be covered.

[0184] From the data results of Example 1 and Examples 13-14, it can be seen that if the reduction temperature is too low, the reduction degree of some copper species will be insufficient. 0 、Cu + and Cu 2+ If the reduction treatment temperature is too high, the surface active sites will agglomerate and harden, reducing the reaction activity.

[0185] From the data results of Example 1 and Example 15, it can be seen that if the copper-silicon catalyst is not reduced and pre-activated in the method of catalyzing the coupling of ethylene glycol and primary alcohol to form long-chain vicinal diol, the surface of the catalyst is almost entirely covered with Cu 2+ Valence exists, and Cu rarely exists + ,Cu 0In the equivalent state, there are too few active sites, which leads to a decrease in catalytic activity.

[0186] From the data results of Examples 1 and 16-17, it can be seen that if the temperature of the catalytic reaction is too low, the catalytic conditions cannot be thermodynamically met due to the low temperature, and the target product cannot be obtained; if the temperature of the catalytic reaction is too high, it will cause an increase in by-products such as ethers, thereby reducing the selectivity of the target product, long-chain vicinal diol.

[0187] The applicant declares that while the above-mentioned embodiments are used to illustrate the process of the present application, the present application is not limited to the above-mentioned process steps, which does not mean that the present application must rely on the above-mentioned process steps in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials used in the present application, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. An application of a copper silicon catalyst, wherein: The copper-silicon catalyst is used to catalyze the coupling of ethylene glycol and primary alcohol to form long-chain vicinal diols; the chemical formula of the copper-silicon catalyst is Cu x Si 1-x O, 0.01≤x<0.3; The preparation method of the copper silicon catalyst comprises the following steps: (1) mixing a copper solution and a silicon source, and performing a heating treatment to remove ammonia to obtain a precursor solution; (2) subjecting the precursor solution to hydrothermal crystallization at 120-200° C. for 12-48 h, calcination at 300-600° C. for 2-6 h, and reduction treatment at 300-600° C. for 2-6 h to obtain the copper silicon catalyst; Before the copper silicon catalyst is used to catalyze the coupling of ethylene glycol and primary alcohol to form a long-chain vicinal diol, the copper silicon catalyst needs to be reduced and pre-activated.

2. The use according to claim 1, wherein: The copper silicon catalyst has a coral-like structure.

3. The use according to claim 1, wherein: The preparation method of the copper solution in step (1) comprises: Mixing a copper source, an alkali source and a solvent to obtain the copper solution; The copper source is a soluble copper salt, and the soluble copper salt includes any one or a combination of at least two of copper nitrate pentahydrate, copper nitrate, copper sulfate, copper chloride or copper carbonate; The alkaline source includes any one of hydroxide, ammonia, ammonium carbonate, ammonium bicarbonate or urea, or a combination of at least two thereof; The hydroxide ion concentration of the alkaline source is 1-10 mol / L; The pH value of the copper solution is 9-11.

4. The use according to claim 1, wherein: The silicon source in step (1) includes silica sol and / or tetraethyl orthosilicate; The temperature of the heating and ammonia removal treatment in step (1) is 40-70°C; The pH value of the precursor solution in step (1) is 3-8.

5. The use according to claim 1, wherein: The preparation method comprises the following steps: (I) stirring and mixing a soluble copper salt and deionized water at room temperature for 2-30 minutes to obtain a copper salt solution, then dropping an alkali source into the copper salt solution until the pH is 9-11, and then stirring and mixing for 10-30 minutes to obtain a copper solution; The hydroxide ion concentration of the alkali source is 1-10 mol / L, and the dropping rate of the alkali source is 60-150 drops / min; (II) adding a silicon source dropwise to the copper solution at room temperature, stirring for 0.5-2 hours, and then heating at 40-70° C. to remove ammonia until a precursor solution with a pH value of ≤7 is obtained; The silicon source drop rate is 60-150 drops / min. (III) transferring the precursor solution to a hydrothermal reactor, performing hydrothermal crystallization at 120-200° C. for 12-48 hours, washing after completion, and then drying at 60-120° C. for 8-18 hours to obtain a solid catalyst; (IV) calcining the solid catalyst at 300-600° C. for 2-6 hours, then cooling the solid catalyst to room temperature and reducing it in a reducing gas at 300-600° C. for 2-6 hours to obtain the copper silicon catalyst; The reducing gas contains hydrogen and nitrogen.

6. The use according to claim 1, wherein: The long-chain vicinal diol is a long-chain vicinal diol with a C atom number ≥ 3; The specific steps of using the copper silicon catalyst to catalyze the coupling of ethylene glycol and primary alcohol to form a long-chain vicinal diol include: (a) reducing and preactivating the copper-silicon catalyst to obtain a treated copper-silicon catalyst; (b) mixing ethylene glycol, primary alcohol and the treated copper-silicon catalyst to carry out a catalytic reaction to obtain a long-chain vicinal diol.

7. The use according to claim 6, wherein: The specific steps of the reduction and pre-activation treatment in step (a) include: At a preset temperature, hydrogen is introduced into the container where the copper silicon catalyst is located to perform catalyst reduction and pre-activation treatment; The preset temperature is 250-450°C; The primary alcohol in step (b) includes any one of methanol, ethanol, n-propanol and n-butanol, or a combination of at least two thereof; Based on the total mass of the ethylene glycol and the primary alcohol, the mass fraction of the ethylene glycol is 0.01-0.3%; The temperature of the catalytic reaction in step (b) is 150-300° C., and the pressure during the catalytic reaction is 0.5-5 MPa.

Images