Nickel silicate catalyst rich in Lewis acid sites as well as preparation method and application of nickel silicate catalyst

Abstract

The invention belongs to the technical field of organic catalysis, and particularly relates to a nickel silicate catalyst rich in Lewis acid sites as well as a preparation method and application of the nickel silicate catalyst. The preparation method of the nickel silicate catalyst comprises the following steps: dissolving a water-soluble nickel salt and ammonia water in water, adding SiO2 aerogel, carrying out a stirring reaction to form a complex, carrying out ammonia distillation to obtain a precipitate, drying the obtained precipitate, and sequentially carrying out calcination and reduction baking to obtain the nickel silicate catalyst. The catalyst contains high-dispersion nickel particles and Lewis acid sites formed on the surface of the catalyst, so that the catalyst has higher conversion rate and selectivity for a reaction for preparing 2, 5-furan dimethylamine from 5-hydroxymethylfurfural, and the catalyst completely avoids using noble metals and carriers with higher cost, so that the use cost of the catalyst is greatly reduced, and the catalyst is suitable for industrial production. The method is suitable for industrial production and has a very wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of organic catalysis, and specifically relates to a nickel silicate catalyst rich in Lewis acid sites, a preparation method and an application thereof. Background Art

[0002] Amine compounds are an important class of nitrogen-containing compounds that are widely used in the synthesis of drugs, pesticides, surfactants, dyes, polymers and bioactive compounds. Primary diamines are one of the most useful monomers for the production of polyamides and polyurethanes, which are widely used in daily life, including automotive, aerospace, electrical and electronic, construction and biomedicine. In traditional industrial methods, polyamides and polyurethanes are produced and synthesized from carbonyl and alcohol compounds from fossil resources. However, the consumption of fossil resources and the environmental impact associated with their use are a big problem. In addition, the demand for biocompatible polymers in industry is also increasing, such as in packaging and biomedicine. Therefore, it is urgent to use renewable resources to replace fossil resources to produce primary diamines.

[0003] Biomass, as a renewable and ubiquitous resource, is considered as the next generation feedstock for the chemical industry. Using biomass as a feedstock has the potential to replace the dwindling fossil fuels with renewable raw materials, thereby alleviating dependence on petroleum-based materials and reducing pollution. In addition, biomass-derived diamine monomers will meet the growing demand for biocompatible polymers. Therefore, the development of effective methods for preparing diamines using bio-based renewable materials has broad prospects for establishing a sustainable society.

[0004] 5-Hydroxymethylfurfural (5-HMF), as one of the important platform molecules derived from biomass, has attracted more and more attention due to its unique and extensive chemical structure. 5-HMF can be used to synthesize 2,5-furandimethylamine (BAMF). However, the selective synthesis of 5-HMF is a challenging task because the conversion of 5-HMF easily forms a series of secondary, tertiary and polyamine by-products, and the selectivity of 2,5-furandimethylamine in the product is low. Therefore, many multi-step routes for the synthesis of BAMF have been developed in the prior art: for example, an article published by the Komanoya research group in the journal JACS uses ruthenium nanoparticles to catalyze the reductive amination of HMF to prepare 2,5-furandimethylamine. Although the yield is considerable, it is a two-step synthesis, and the active metal of the catalyst is a precious metal. The high catalyst preparation cost will limit its industrial production and application; for example, the invention patent with announcement number CN113976131B discloses a multiphase catalyst and a method for preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural , wherein the multiphase catalyst is obtained by loading a hydrogenation metal on a metal oxide carrier, the hydrogenation metal is selected from one of Ru, Pd, Co, and Ni, and the metal oxide carrier is selected from one of CeOx, ZrOx, and LaOx. The invention uses 5-hydroxymethylfurfural as a raw material and tetrahydrofuran as a solvent, and reacts in the presence of the multiphase catalyst in a hydrogen and ammonia atmosphere to generate 2,5-furandimethylamine. However, the cost of the carrier used for the multiphase catalyst of the patent is high, the obtained multiphase catalyst has a small specific surface area, poor dispersibility, and a general catalytic effect on 5-hydroxymethylfurfural. Summary of the invention

[0005] In view of the shortcomings of the prior art methods, the first purpose of the present invention is to provide a nickel silicate catalyst rich in Lewis acid sites. The catalyst of the present invention comprises highly dispersed nickel particles and Lewis acid sites formed on the catalyst surface, which endows it with a high conversion rate and selectivity for the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural, and the catalyst completely avoids the use of expensive precious metals and carriers, greatly reducing the use cost of the catalyst, and is suitable for industrial production, with a very broad application prospect.

[0006] The second object of the present invention is to provide a method for preparing a nickel silicate catalyst rich in Lewis acid sites. The preparation method of the present invention is simple to operate, low in cost, and is conducive to large-scale production.

[0007] The third object of the present invention is to provide a nickel silicate catalyst rich in Lewis acid sites for use in the catalytic reaction of 5-hydroxymethylfurfural to prepare 2,5-furandimethylamine. The nickel silicate catalyst of the present invention has high catalytic efficiency, mild reaction conditions and stable cyclic performance during the catalytic reaction.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a nickel silicate catalyst rich in Lewis acid sites, wherein the nickel silicate catalyst is a sandwich layer structure consisting of two layers of silicon-oxygen tetrahedrons and nickel-oxygen octahedrons sandwiched between the two layers of silicon-oxygen tetrahedrons.

[0010] Preferably, the mass percentage of Ni in the nickel silicate catalyst is 10-36%.

[0011] In a second aspect, the present invention provides a method for preparing a nickel silicate catalyst rich in Lewis acid sites, comprising the following steps:

[0012] Dissolve water-soluble nickel salt and ammonia water in water, add SiO2 aerogel and stir to react to form a complex, then evaporate ammonia to obtain a precipitate, dry the precipitate, and then calcine and reduce and bake it in sequence to obtain the product.

[0013] Preferably, the molar ratio of the water-soluble nickel salt, ammonia water and SiO2 aerogel is 1:6-8:1-5.

[0014] Preferably, the water-soluble nickel salt includes at least one of Ni(NO3)2·6H2O, Ni(NO3)2·3H2O, NiCl2, Ni(OH)2 and Ni(CH3COO)2.

[0015] Preferably, the ammonia evaporation conditions are: stirring the reaction at 75-85°C until the pH is 6-7 and a complex is produced; the calcination conditions are: calcining at 400-800°C for 0.5-6h in an air atmosphere; and the reduction baking conditions are: calcining at 400-800°C for 0.5-6h in a hydrogen atmosphere.

[0016] In a third aspect, the present invention provides an application of a nickel silicate catalyst rich in Lewis acid sites in catalyzing the reaction of 5-hydroxymethylfurfural to prepare 2,5-furandimethylamine, comprising: adding 5-hydroxymethylfurfural, the nickel silicate catalyst and a solvent into a reactor, and reacting in a hydrogen and ammonia atmosphere to generate 2,5-furandimethylamine.

[0017] Preferably, the mass ratio of the nickel silicate catalyst to 5-hydroxymethylfurfural is 1:2-10.

[0018] Preferably, the hydrogen pressure is 0.5-4 MPa, the ammonia pressure is 0.1-1 MPa, the reaction temperature is 130-160° C., and the reaction time is 1-6 h.

[0019] Preferably, the solvent is one or more of tetrahydrofuran, 1,4-dioxane and isopropanol, and the usage ratio of the solvent to 5-hydroxymethylfurfural is 1 mL: 40-100 mg.

[0020] The positive beneficial effects of the present invention are:

[0021] 1. The active components of the nickel silicate catalyst rich in Lewis acid sites of the present invention are mainly nickel particles and some acid sites on the catalyst surface, and the nickel particles are nano-sized particles and highly dispersed. The nickel silicate catalyst has a layered structure with a specific surface area of ​​310-480m 2 / g, large specific surface area, pore volume 0.595-0.814cm 2 / g, large pore volume, and average pore diameter of 6.0-8.0nm.

[0022] 2. The present invention provides a nickel silicate catalyst rich in Lewis acid sites, a preparation method thereof, and an application of the nickel silicate catalyst rich in Lewis acid sites in catalyzing the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural. The catalyst comprises highly dispersed nickel particles and Lewis acid sites formed on the catalyst surface, which endow the catalyst with high conversion rate and selectivity for the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural. The catalyst completely avoids the use of expensive precious metals and carriers, greatly reducing the use cost of the catalyst. The preparation method of the nickel silicate catalyst rich in Lewis acid sites is simple to operate, low in cost, and conducive to large-scale production. The conditions are mild during the catalytic reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural. The conversion rate of the raw material 5-hydroxymethylfurfural is as high as 100%, the yield of 2,5-furandimethylamine is as high as 97.3%, the catalytic efficiency is high, and the recycling performance is stable, thereby providing a new way for catalytically producing 2,5-furandimethylamine directly from 5-hydroxymethylfurfural biomass raw materials, being suitable for industrial production, and having a very broad application prospect.

[0023] 3. The calcination conditions in the preparation process of the nickel silicate catalyst of the present invention are: calcination at a temperature of 400-800° C. in an air atmosphere for 0.5-6 h. The main purpose of calcination in an air atmosphere is to remove the organic precursor to form a porous structure, and at the same time control the growth of metal oxide crystals to obtain a certain mechanical strength, so that a catalyst with a certain crystal form, grain size, pore structure and specific surface area can be obtained. If the calcination temperature is too high, the structure of the catalyst will be sintered and collapsed, and the physical properties of the catalyst such as the pore structure and pore volume will be destroyed. If the calcination temperature is too low, the organic precursor will be insufficiently removed, and it will be difficult to obtain a good metal oxide crystal form and morphology.

[0024] 4. The reduction calcination temperature during the preparation of the nickel silicate catalyst of the present invention is one of the important factors affecting the activity of the catalyst. If the reduction temperature is too high, it is easy to cause the active components in the catalyst to agglomerate, which reduces the dispersion of the active metal particles and further affects its catalytic performance. If the reduction temperature is too low, the active components cannot be reduced and the catalyst has no hydrogen removal ability. The reduction calcination conditions during the preparation of the nickel silicate catalyst of the present invention are: calcination at 400-800°C for 0.5-6h in a hydrogen atmosphere. The reduction calcination process is mainly to realize the activation process of the catalyst, which can regulate the Ni on the catalyst surface. 0 with Ni 2+ The ratio of can regulate the surface acid sites, which can greatly improve the catalytic activity and catalytic selectivity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the nickel silicate catalyst rich in Lewis acid sites of the present invention;

[0026] Figure 2 TEM image of the nickel silicate catalyst rich in Lewis acid sites of the present invention;

[0027] Figure 3 is a nitrogen isothermal adsorption-desorption curve of the nickel silicate catalyst rich in Lewis acid sites of the present invention;

[0028] Figure 4 is a pore size distribution diagram of the nickel silicate catalyst rich in Lewis acid sites of the present invention;

[0029] Figure 5 XRD patterns of nickel silicate catalysts rich in Lewis acid sites prepared at different reduction temperatures;

[0030] Figure 6 Py-FTIR spectra of nickel silicate catalysts rich in Lewis acid sites prepared at different reduction temperatures. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with some specific embodiments.

[0032] Example 1-21 A method for preparing a nickel silicate catalyst rich in Lewis acid sites, comprising the following steps

[0033] Ni(NO3)2·6H2O (4.17 g) and 25 wt% ammonia water (7.82 g) (NH3:Ni=8) were dissolved in water and mixed and stirred for 15 min; then 40 wt% SiO2 aerogel (3.77 g) was added to the solution, and the molar ratio of water-soluble nickel salt, ammonia water, and SiO2 aerogel was 1:8:4.5, and stirred at room temperature for 12 h, and then the suspension was heated in a water bath preheated to 80°C to evaporate the ammonia until the pH value of the suspension was reduced to 6-7, and then the precipitate was filtered, washed with distilled water, and then dried at 80°C for 12 h to obtain a green complex, and calcined at 600°C in air for 4 h with a heating rate of 5°C·min -1 , followed by reduction at 400-800 °C for 2 h, with a heating rate of 5 °C min -1 The reduction temperature of each embodiment is shown in Table 1. The catalyst without reduction treatment is used as a comparison, and is recorded as NiSi-PS-0. The catalyst with a reduction temperature of 400°C is recorded as NiSi-PS-400. The catalyst with a reduction temperature of 500°C is recorded as NiSi-PS-500. And so on. The mass percentage of Ni in the nickel silicate catalyst is 32%. The performance parameters of the nickel silicate catalyst are shown in Table 2.

[0034] The use of the nickel silicate catalyst rich in Lewis acid sites in the catalytic reaction of 5-hydroxymethylfurfural to prepare 2,5-furandimethylamine comprises: adding 5-hydroxymethylfurfural, the nickel silicate catalyst and a solvent into a reactor, and reacting in a hydrogen and ammonia atmosphere to generate 2,5-furandimethylamine, as described in detail as follows:

[0035] 200 mg of 5-hydroxymethylfurfural, 100 mg of nickel silicate catalyst prepared in Examples 1-21 and Comparative Examples, 5 mL of solvent were added to the reaction kettle, 0.5-4 MPa of hydrogen and 0.1-1 MPa of ammonia were added, and the mixture was heated to 130-160° C. for 3 h under stirring conditions, and then cooled, vented, and filtered to separate the catalyst from the reaction liquid. The reaction liquid was diluted with a solvent to determine the concentration, and then analyzed by gas chromatography. The experimental conditions and results of Examples 1-21 and Comparative Examples are shown in Table 1.

[0036] Table 1 Reaction conditions and results of nickel silicate catalyst in catalyzing 5-hydroxymethylfurfural to prepare 2,5-furandimethylamine

[0037]

[0038] Table 2 Performance parameters of nickel silicate catalyst

[0039]

[0040]

[0041] The structure of the nickel silicate catalyst rich in Lewis acid sites obtained by the above preparation method is shown in Figure 1 , wherein the TEM image of the nickel silicate catalyst of Example 4 is shown in Figure 2 .Depend on Figure 1 It can be seen that the nickel silicate catalyst is nickel phyllosilicate, which has a 2:1 sandwich structure consisting of two layers of silicon-oxygen tetrahedrons and nickel-oxygen octahedrons sandwiched between the two layers of silicon-oxygen tetrahedrons. Figure 2 It can be seen that the catalyst has a layered structure, and the metal between the layers can be seen in black, proving its sandwich structure.

[0042] The catalyst (NiSi-PS-0) without reduction treatment was used as a comparison. Figure 3-4 As shown in Table 2, the nickel particles in the catalyst of the present invention are nano-sized particles and are highly dispersed. The nickel silicate catalyst has a layered structure with a specific surface area of ​​310-480 m 2 / g, large specific surface area, pore volume 0.595-0.814cm 2 / g, large pore volume, and average pore diameter of 6.0-8.0nm.

[0043] It can be seen from Table 1 that from Examples 1-5 and the comparative example, the optimal reduction baking temperature is 700° C. when the reduction baking temperature in the preparation process of the nickel silicate catalyst rich in Lewis acid sites of the present invention is changed.

[0044] In an atmosphere of 3MPa hydrogen and 0.35MPa ammonia, at a temperature of 100-160°C, 5-hydroxymethylfurfural was catalyzed to prepare 2,5-furandimethylamine for 3h. From Examples 4 and 6-11, it can be seen that the nickel silicate catalyst rich in Lewis acid sites of the present invention preferably has a reaction temperature of 130-160°C in the catalytic reaction of 5-hydroxymethylfurfural to prepare 2,5-furandimethylamine, and the optimal reaction temperature is 140°C.

[0045] It can be seen from Examples 4 and 12-16 that the present invention changes the hydrogen pressure in the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural. The hydrogen pressure of the present invention is 0.5-4 MPa, which can achieve a high 5-hydroxymethylfurfural conversion rate and 2,5-furandimethylamine yield. The optimal hydrogen pressure in Example 14 is 1 MPa.

[0046] It can be seen from Examples 14 and 17-19 that the present invention changes the ammonia pressure in the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural. The ammonia pressure of the present invention is 0.1-1 MPa, which can achieve a high 5-hydroxymethylfurfural conversion rate and 2,5-furandimethylamine yield, and the optimal ammonia pressure is 0.35 MPa.

[0047] It can be seen from Examples 14, 20-21 that the present invention changes the solvent for the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural, and 1,4-dioxane has the best catalytic effect, followed by isopropanol, and tetrahydrofuran is the worst.

[0048] The XRD patterns of the nickel silicate catalysts prepared in Examples 1-5 are shown in Figure 5 The catalyst without reduction treatment (NiSi-PS-0) was used as a comparison. Figure 5 It can be seen that with the increase of reduction temperature, the peaks of nickel at 43.3°, 62.9° and 75.3° gradually emerge, indicating that with the increase of reduction temperature, the nickel content gradually increases, and the particle size also increases. The particle size of nickel in the catalyst of Example 4 is 3.4 nm.

[0049] The Py-FTIR images of the nickel silicate catalysts prepared in Examples 1-5 are shown in Figure 6 ,Depend on Figure 6 It can be seen that the catalyst of the present invention has a strong Lewis acid site, which is beneficial to the dehydrogenation amination of 5-hydroxymethylfurfural.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A nickel silicate catalyst rich in Lewis acid sites, characterized in that: The nickel silicate catalyst is a sandwich layer structure consisting of two layers of silicon-oxygen tetrahedrons and nickel-oxygen octahedrons sandwiched between the two layers of silicon-oxygen tetrahedrons.

2. The nickel silicate catalyst rich in Lewis acid sites according to claim 1, characterized in that The mass percentage of Ni in the nickel silicate catalyst is 10-36%.

3. A method for preparing the nickel silicate catalyst rich in Lewis acid sites according to claim 1 or 2, characterized in that: The steps include: Dissolve water-soluble nickel salt and ammonia water in water, add SiO2 aerogel and stir to react to form a complex, then evaporate ammonia to obtain a precipitate, dry the precipitate, and then calcine and reduce and bake it in sequence to obtain the product.

4. The method for preparing the nickel silicate catalyst rich in Lewis acid sites according to claim 3, characterized in that: The molar ratio of the water-soluble nickel salt, ammonia water and SiO2 aerogel is 1:6-8:1-5.

5. The method for preparing the nickel silicate catalyst rich in Lewis acid sites according to claim 3, characterized in that: The water-soluble nickel salt includes at least one of Ni(NO3)2·6H2O, Ni(NO3)2·3H2O, NiCl2, Ni(OH)2 and Ni(CH3COO)2.

6. The method for preparing the nickel silicate catalyst rich in Lewis acid sites according to claim 3, characterized in that: The ammonia evaporation conditions are: stirring the reaction at 75-85°C until the pH is 6-7 and a complex is generated; the calcination conditions are: calcining at 400-800°C for 0.5-6h in an air atmosphere; the reduction baking conditions are: calcining at 400-800°C for 0.5-6h in a hydrogen atmosphere.

7. Use of the nickel silicate catalyst rich in Lewis acid sites according to claim 1 or 2 in catalyzing the reaction of preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural, comprising: 5-Hydroxymethylfurfural, the nickel silicate catalyst and a solvent are added into a reactor, and reacted in a hydrogen and ammonia atmosphere to generate 2,5-furandimethylamine.

8. The use according to claim 7, characterized in that: The mass ratio of the nickel silicate catalyst to 5-hydroxymethylfurfural is 1:2-10.

9. The use according to claim 7, characterized in that: The hydrogen pressure is 0.5-4MPa, the ammonia pressure is 0.1-1MPa, the reaction temperature is 130-160°C, and the reaction time is 1-6h.

10. The use according to claim 7, characterized in that: The solvent is one or more of tetrahydrofuran, 1,4-dioxane and isopropanol, and the usage ratio of the solvent to 5-hydroxymethylfurfural is 1 mL: 40-100 mg.

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