A solid base magnetic catalyst, a preparation method and application thereof

Abstract

The application discloses a solid alkali magnetic catalyst and a preparation method and application thereof, and belongs to the technical field of biomass liquid fuel production, and the solid alkali magnetic catalyst comprises nickel clusters and active components, and the nickel clusters are dispersed on the surfaces of the active components; wherein the nickel clusters are core-shell structures with graphite carbon as a shell layer and nickel particles as a core layer; and the active components are metal oxides. That is to say, the graphite coating of nickel is realized through a simple gelation and calcination method, nickel clusters are formed, and then potassium oxide is loaded to form a composite catalyst which is strong in magnetism, high in stability and excellent in catalytic activity. Compared with traditional catalysts, the catalyst prepared by the application has the characteristics of efficient recovery and recycling, and the environmental influence and economic cost of biodiesel production are significantly reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomass liquid fuel production, and particularly relates to a solid base magnetic catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] Biodiesel is a renewable fuel produced from the transesterification of long-chain fatty acids with low-carbon alcohols such as methanol or ethanol. It is a clean energy source that can partially or completely replace traditional fossil diesel for use in diesel engines. Traditional biodiesel production processes typically use liquid base catalysts such as sodium hydroxide or potassium hydroxide for the transesterification reaction. However, these liquid catalysts have some drawbacks, such as the inability to recover the catalyst after the reaction and the serious problem of wastewater discharge, which increases production costs and poses an environmental pollution risk. To overcome these problems, researchers have begun to explore the use of solid base catalysts to replace traditional liquid base catalysts.

[0003] Currently, metal oxides such as magnesium, calcium, aluminum, zinc, and other metal oxides have been widely used in solid base catalysts. However, their catalytic activity and stability are often poor, especially in high-temperature and humid environments, where the catalysts are easily deactivated and difficult to recover and utilize. Magnetic solid bases are a common design strategy that facilitates solid-liquid separation. Traditional magnetic solid base catalysts typically use iron, nickel, or other metal oxides as magnetic carriers and combine them with active components such as potassium oxide and calcium oxide to form a magnetic solid base catalyst. This type of catalyst can be separated from the product mixture with the aid of a magnet, making it easy to reuse and handle the product. However, traditional metal oxide catalysts are directly exposed to substrates during the biodiesel production process, which can cause structural changes at high temperatures, such as reduction or oxidation of high-valence iron metal oxides, leading to changes in their physical and chemical properties, resulting in demagnetization or deactivation.

[0004] Therefore, there is an urgent need to provide a biodiesel transesterification catalyst that is efficient, stable, and easy to recover. SUMMARY

[0005] To address the above technical problems, the present application provides a solid base magnetic catalyst as well as a preparation method and application thereof. The catalyst is prepared by a simple gelation and calcination method to achieve graphite carbon coating of nickel clusters, combined with potassium oxide loading, to form a composite catalyst with strong magnetism, high stability, and excellent catalytic activity. Compared with traditional catalysts, the catalyst prepared by the present application has the characteristics of efficient recovery and recycling, significantly reducing the environmental impact and economic cost of biodiesel production.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] One of the technical solutions of the present application is:

[0008] A solid base magnetic catalyst, comprising: a nickel cluster and an active ingredient, the nickel cluster is dispersed on the surface of the active ingredient;

[0009] The nickel cluster is a core-shell structure with graphite carbon as the shell layer and nickel particles as the core layer.

[0010] The active ingredient is a metal oxide.

[0011] Beneficial effects: The present application constructs the catalyst core by the way of forming nickel cluster through graphite carbon coated nickel source, uses the chemical inertness and mechanical strength of graphite carbon layer to protect the whole nickel cluster from oxidation, corrosion, wear or deactivation under high temperature conditions, at the same time retains the high magnetic property of nickel cluster, as the magnetic core of catalyst, realizes the rapid and efficient separation and recovery by external magnetic field after reaction, the recovery rate is close to 100%, solves the problem of difficult separation of traditional catalyst after biodiesel transesterification reaction. At the same time, by potassium oxide, strong alkaline functional sites are introduced into the catalyst, so that the contact interface of the catalyst with oil and alcohol is fully active, thereby significantly improving the catalytic efficiency of transesterification reaction.

[0012] Further, the metal oxide is potassium oxide.

[0013] Optionally, the particle size of the solid base magnetic catalyst is 5-50 nanometers.

[0014] Further, the particle size of the nickel particles is 5-15 nanometers; the number of layers of the graphite carbon is 1-15 layers, and the thickness of each layer is 0.34 nanometers.

[0015] Optionally, the active ingredient is 5-100wt% of the nickel cluster.

[0016] The second technical solution of the present application is:

[0017] The preparation method of the above-mentioned solid base magnetic catalyst comprises the following steps:

[0018] Dissolve the nickel source, carbon source and alkali source in the solvent for gelation treatment and calcination, after calcination is completed, the material is naturally cooled to room temperature, and grinding treatment is carried out to obtain a solid base magnetic catalyst with uniform particle size.

[0019] Beneficial effects: The present application organically combines the nickel source, carbon source and alkali source by gelation treatment and calcination process, controls the calcination temperature and time, forms the core-shell structure of graphite carbon coated nickel particles, realizes the functional cooperation of alkaline sites and magnetic core. In addition, the preparation process condition of the present application is mild, which is suitable for large-scale production.

[0020] Optionally, the nickel source is a soluble nickel salt, preferably nickel nitrate or nickel acetate; and / or

[0021] The carbon source is a natural carbon source, preferably at least one of sucrose, citric acid, glucose or sorbitol; and / or

[0022] The alkali source is potassium hydroxide, as a precursor of the basic active site; and / or

[0023] The solvent is ethanol.

[0024] Optionally, the conditions in the gelation process are 60℃ magnetic stirring for 1 hour to form a uniform gel.

[0025] Optionally, the conditions in the calcination process are:

[0026] Calcination under an inert atmosphere (nitrogen) at 10℃ / min to 150-600℃ for 0.5-10 hours.

[0027] Beneficial effects: Under the conditions of the above gelation process and calcination process defined in the present application, the uniformity of the core-shell structure of the nickel cluster and the high efficiency of the catalytic performance of the active ingredient potassium oxide in the prepared catalyst can be ensured. In the calcination process, potassium hydroxide is decomposed into potassium oxide as an active ingredient, the carbon source is cracked to form a graphite structure to coat nickel to form a nickel cluster, and is dispersed on the surface of potassium oxide.

[0028] The third technical solution of the present application:

[0029] The above-mentioned solid alkali magnetic catalyst is applied in the field of catalyzing the preparation of biodiesel from biological oil.

[0030] Beneficial effects: The solid alkali magnetic catalyst prepared by the present application has excellent structural stability and recycling performance. Specifically, the graphite layer effectively protects the nickel cluster structure, so that the catalyst still has excellent catalytic performance and stability in high-temperature and high-humidity environments, and the conversion rate remains above 90% after 10 cycles.

[0031] Optionally, the biological oil includes any one of rapeseed oil, palm oil, waste oil or animal oil.

[0032] The catalyst prepared by the present application adopts a graphite carbon shell layer to wrap nickel to form a nickel cluster, and then forms a core-shell structure, so that the magnetism of nickel is preserved and is immune to corrosion or oxidation under reaction conditions. At the same time, the potassium oxide surrounded by the nickel cluster also has more active sites exposed on the surface, which plays a strong alkaline catalytic effect. Compared with the prior art, the present application has the following advantages and technical effects:

[0033] 1. Strong magnetic properties: Nickel clusters have high magnetism, combined with the protection of the graphite carbon coating layer, which can maintain stable magnetic properties under high temperature and high humidity conditions, facilitating efficient recovery of the catalyst.

[0034] 2. Excellent catalytic performance: The basic catalytic active sites provided by potassium oxide can significantly improve the rate of ester exchange reaction, and are suitable for the conversion of various oils and fats.

[0035] 3. Structural stability: The graphite layer effectively protects the nickel clusters from oxidation and mechanical wear, improving the recycling performance of the catalyst, and maintaining high catalytic activity after multiple reactions. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings, which form a part of this application, are used to provide a further understanding of the application. The illustrative embodiments of the application and their description serve to explain the application. They are not intended to limit the application. In the drawings:

[0037] Figure 1 TEM image of nickel clusters in the solid base magnetic catalyst prepared in Example 2;

[0038] Figure 2 Overall morphology image of the solid base magnetic catalyst prepared in Example 2. DETAILED DESCRIPTION

[0039] The various illustrative embodiments of the present application will now be described in detail below. This detailed description is not intended to limit the application, but rather to explain certain aspects, features, and embodiments of the application.

[0040] It should be understood that the terms described in the present application are only for the description of the specific embodiments, and are not intended to limit the present application. In addition, for the numerical range in the present application, it is understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper limit and lower limit of these smaller ranges can be independently included or excluded from the range.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application pertains. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and any document incorporated by reference, the content of this specification controls.

[0042] Many modifications and variations to the illustrative embodiments described herein will be apparent to those skilled in the art from consideration of the specification and practice of the subject technology. Additional embodiments not described herein will be apparent to the skilled artisan in view of the description and examples provided herein. The specification and examples are illustrative only.

[0043] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or variants thereof are open-ended, and specifically mean including, but not limited to.

[0044] The embodiment of the present application discloses a magnetic biodiesel transesterification catalyst formed by graphite carbon-coated nickel clusters and potassium oxide, and the catalyst has a composition structure of:

[0045] The potassium oxide is taken as a core, and nickel clusters (core-shell structure with nickel particles as a core and several layers of graphite carbon wrapped outside) are dispersed on the surface of the core, thereby forming a composite catalyst.

[0046] The nickel clusters provide strong magnetism and participate in catalytic activity, the graphite layer enhances the structural stability of the catalyst, and the potassium oxide provides an alkaline active site.

[0047] In some optional embodiments, the particle size of the catalyst is 5-50 nanometers; in the core-shell structure, the number of layers of graphite carbon is 1-15, and the thickness of each layer is 0.34 nm; and the particle size of the nickel particles is 5-15 nanometers.

[0048] The embodiment of the present application also discloses a preparation method of a catalyst for catalyzing a biodiesel transesterification reaction, which comprises the following steps: gelatinizing a nickel source, a carbon source and potassium hydroxide, and then performing calcination and cooling and grinding to obtain a composite catalyst.

[0049] The conversion rate of the catalyst prepared by the method in the biodiesel transesterification reaction is as high as 98%; the catalyst has excellent recycling performance, and the catalytic activity (conversion rate) is maintained at more than 90% after 10 cycles; and the catalyst can be quickly recovered by an external magnetic field after the reaction, and the recovery rate is close to 100%.

[0050] In some optional embodiments, the nickel source is selected from nickel nitrate, nickel acetate or other soluble nickel salts (single or multiple combinations);

[0051] The carbon source is selected from natural carbon sources (single or multiple combinations) such as sucrose, citric acid, glucose and sorbitol;

[0052] The alkali source is selected from potassium hydroxide as a precursor of an alkaline active site;

[0053] The solvent is selected from ethanol as a reaction solvent;

[0054] In some alternative embodiments, the gelation process is:

[0055] The nickel source, carbon source and potassium hydroxide are mixed in the amount ratio, and dissolved in ethanol.

[0056] Under the condition of 60℃, the magnetic stirring is used to form a stable gel.

[0057] In some alternative embodiments, the calcination condition is: calcination under nitrogen atmosphere at 150-600℃ for 0.5-10 hours, to form a composite material with magnetism and high catalytic activity.

[0058] In some alternative embodiments, the cooling and grinding condition is:

[0059] After the calcination is completed, the material is naturally cooled to room temperature, and the grinding process is performed to obtain a composite catalyst with uniform particle size.

[0060] In the present application, "room temperature" refers to 20-30℃ unless otherwise specified.

[0061] The raw materials used in the present application are all purchased from the market.

[0062] The present application discloses a novel magnetic catalyst, specifically a catalyst material of graphite-encapsulated nickel clusters (GENCs) and potassium oxide (K2O) composite. That is, by utilizing the high chemical stability of graphite carbon and the high magnetic property of nickel clusters, combined with the strong alkaline functional site of potassium oxide, a high-efficiency, stable and easy-to-recover biodiesel transesterification catalyst is constructed. The technical solutions of the present application are further described through the following examples.

[0063] Example 1: The catalyst dosage is 5% of the oil and fat

[0064] A preparation method of a solid alkali magnetic catalyst, comprising the following steps:

[0065] 1. Raw material preparation:

[0066] Nickel source: nickel nitrate (Ni(NO3)2·6H2O) 1.45g, carbon source: glucose 1.8g, potassium hydroxide: 0.28g, solvent: anhydrous ethanol 50mL.

[0067] 2. Preparation process:

[0068] Dissolve the nickel nitrate, glucose and potassium hydroxide in ethanol, and magnetically stir at 60℃ for 1 hour to form a uniform gel;

[0069] The above gel was placed under nitrogen atmosphere and heated to 500°C at 10°C / min for 3 hours, after which it was cooled and ground to obtain catalyst 1 (wherein the potassium oxide is ~ 61.5 wt% of the nickel clusters).

[0070] The catalyst 1 prepared in this example was used to catalyze the preparation of biodiesel from rapeseed oil under the following catalytic conditions:

[0071] Oil: rapeseed oil 10 g;

[0072] Methanol: 3 g;

[0073] Catalyst dosage: 0.5 g (5% of the mass of the oil);

[0074] Reaction temperature: 60°C, time: 2 hours.

[0075] Results: the conversion rate of the catalyst 1 used to catalyze the preparation of biodiesel from rapeseed oil was 95%, and after 5 cycles of the catalyst, the conversion rate was 92%.

[0076] Example 2: Catalyst dosage is 10% of the oil

[0077] A method for preparing a solid base magnetic catalyst, comprising the following steps:

[0078] 1. Raw material preparation:

[0079] Nickel source: nickel acetate (Ni (CH3COO) 2.4H2O) 7.47 g, carbon source: citric acid 6.3 g, potassium hydroxide: 1.12 g, solvent: anhydrous ethanol 50 mL.

[0080] 2. Preparation steps:

[0081] Dissolve the nickel acetate, citric acid and potassium hydroxide in ethanol, stir for 1 hour to form a gel;

[0082] The above gel was placed under nitrogen atmosphere and heated to 600°C at 10°C / min for 3 hours, after which it was cooled and ground to obtain catalyst 2 (wherein the potassium oxide is ~ 41.2 wt% of the nickel clusters).

[0083] The catalyst 2 prepared in this example was used to catalyze the preparation of biodiesel from palm oil under the following catalytic conditions:

[0084] Oil: palm oil 10 g;

[0085] Methanol: 4 g;

[0086] Catalyst dosage: 1 g (10% of the mass of the oil);

[0087] Reaction temperature: 65°C, time: 3 hours.

[0088] Results: Conversion rate of catalyst 2 for catalyzing palm oil to produce biodiesel: 96%, conversion rate remained at 92% after catalyst was recycled for 10 times.

[0089] Example 3: Catalyst dosage is 20% of oil and fat

[0090] A method for preparing a solid base magnetic catalyst, comprising the following steps:

[0091] 1. Raw material preparation:

[0092] Nickel source: nickel nitrate (Ni(NO3)2·6H2O) 5.82g, carbon source: sucrose 6.84g, potassium hydroxide: 0.56g, solvent: anhydrous ethanol 50mL.

[0093] 2. Preparation steps:

[0094] Dissolve nickel nitrate, sucrose and potassium hydroxide in ethanol, stir to form a uniform gel;

[0095] The gel is placed in a nitrogen atmosphere and heated to 500℃ at 10℃ / min for 2 hours, then cooled and ground to obtain catalyst 3 (wherein potassium oxide is ~30.8wt% of nickel clusters).

[0096] The catalyst 3 prepared in this example is used to catalyze waste oil to produce biodiesel, and the catalytic conditions are as follows:

[0097] Oil and fat: waste oil 10g;

[0098] Methanol: 5g;

[0099] Catalyst dosage: 2g (equivalent to 20% of the mass of oil and fat);

[0100] Reaction temperature: 60℃, time: 2.5 hours.

[0101] Results: Conversion rate of catalyst 3 for catalyzing waste oil to produce biodiesel: 98%, conversion rate remained at 94% after catalyst was recycled for 8 times.

[0102] Example 4: Catalyst dosage is 30% of oil and fat

[0103] A method for preparing a solid base magnetic catalyst, comprising the following steps:

[0104] 1. Raw material preparation:

[0105] Nickel source: nickel acetate (Ni(CH3COO)2·4H2O) 9.95g, carbon source: sorbitol 5.4g, potassium hydroxide: 2.24g, solvent: anhydrous ethanol 50mL.

[0106] 2. Preparation steps:

[0107] Dissolve nickel acetate, sorbitol and potassium hydroxide in ethanol, stir to form a gel;

[0108] The gel is calcined under nitrogen atmosphere at a rate of 10℃ / min to 550℃ for 3 hours, and after calcination, the catalyst 4 is cooled and ground, wherein the potassium oxide is about 80.8wt% of the nickel clusters.

[0109] The catalyst 4 prepared in this example is used to catalyze the preparation of biodiesel from animal oil, and the catalytic conditions are as follows:

[0110] Oil and fat: 10g of animal oil;

[0111] Methanol: 3.5g;

[0112] Catalyst dosage: 3g (30% of the mass of oil and fat);

[0113] Reaction temperature: 55℃, time: 2 hours.

[0114] Results: The conversion rate of the catalyst 4 for catalyzing the preparation of biodiesel from animal oil is 98%, and the conversion rate remains at 95% after the catalyst is recycled for 10 times.

[0115] Figure 1 The TEM image of the nickel clusters in the solid base magnetic catalyst prepared in Example 2; from the figure, it can be seen that the spherical clusters in the catalyst are nickel clusters, and the outer corrugated shell is graphite carbon.

[0116] Figure 2 The overall morphology of the solid base magnetic catalyst prepared in Example 2, from which it can be seen that the middle surface sheet is potassium oxide, and the black small particles are nickel clusters wrapped in nickel. Figure 2 Therefore, the characteristics of the catalyst can be summarized as follows: the potassium oxide particles are large and have indefinite morphology, and they are surrounded by nickel clusters wrapped in nickel with relatively uniform size, but there are more active sites exposed on the surface.

[0117] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a solid alkali magnetic catalyst, characterized in that, The solid alkali magnetic catalyst comprises: nickel clusters and an active component, wherein the nickel clusters are dispersed on the surface of the active component; The nickel clusters are core-shell structures with graphite carbon as the shell and nickel particles as the core. The active ingredient is a metal oxide; The preparation method of the solid alkali magnetic catalyst includes the following steps: Nickel source, carbon source and alkali source are dissolved in solvent, and then gelled, calcined and cooled and ground in sequence to obtain a solid alkali magnetic catalyst with uniform particle size. The conditions for the gelation process are: magnetic stirring at 60°C for 1 hour to form a uniform gel; The conditions during the calcination process are as follows: heating to 150-600℃ at a rate of 10℃ / min under an inert atmosphere, and calcining at this temperature for 0.5-10 hours; The carbon source is at least one of sucrose, citric acid, glucose, or sorbitol; The alkali source is potassium hydroxide.

2. The method for preparing a solid alkali magnetic catalyst according to claim 1, characterized in that, The metal oxide is potassium oxide; the active ingredient is 5-100 wt% of the nickel cluster.

3. The method for preparing a solid alkali magnetic catalyst according to claim 1, characterized in that, The particle size of the solid alkali magnetic catalyst is 5-50 nanometers.

4. The method for preparing a solid alkali magnetic catalyst according to claim 1, characterized in that, In the core-shell structure, the nickel particles have a particle size of 5-15 nanometers; the graphite carbon has 1-15 layers, and each layer has a thickness of 0.34 nanometers.

5. The method for preparing a solid alkali magnetic catalyst according to claim 1, characterized in that, The nickel source is nickel nitrate or nickel acetate.

6. The application of the solid alkali magnetic catalyst prepared by the preparation method according to any one of claims 1-5 in the field of catalytic bio-oil to biodiesel production.

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