Solid alkali magnetic catalyst as well as preparation method and application thereof

Abstract

The invention discloses a solid alkali magnetic catalyst and a preparation method and application thereof, and belongs to the technical field of biomass liquid fuel production, the solid alkali magnetic catalyst comprises nickel clusters and an active component, and the nickel clusters are dispersed on the surface of the active component; wherein the nickel cluster is of a core-shell structure with graphite carbon as a shell layer and nickel particles as a core layer; the active component is a metal oxide. According to the invention, graphite coating of nickel is realized through simple gelation and roasting methods, nickel clusters are formed, and potassium oxide loading is combined, so that the composite catalyst with strong magnetism, high stability and excellent catalytic activity is formed. Compared with a traditional catalyst, the catalyst prepared by the method has the characteristics of efficient recovery and recycling, and the environmental influence and the economic cost of biodiesel production are remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass liquid fuel production, and in particular relates to a solid base magnetic catalyst and a preparation method and application thereof. Background Art

[0002] Biodiesel is a renewable fuel that uses animal and plant oils or waste oils as raw materials, and is produced by reacting with low-carbon alcohols (such as methanol or ethanol) through transesterification to produce fatty acid methyl esters or ethyl esters. It is a clean energy source that can partially or completely replace traditional fossil diesel for use in diesel engines. Traditional biodiesel production processes usually use liquid alkaline catalysts (such as sodium hydroxide or potassium hydroxide) for transesterification reactions. However, these liquid catalysts have some disadvantages, such as the catalysts cannot be recovered after the reaction, and the wastewater discharge problem is serious, which increases production costs and brings environmental pollution risks. In order to overcome these problems, researchers began to explore the use of solid base catalysts to replace traditional liquid base catalysts.

[0003] At present, metal oxides (such as magnesium, calcium, aluminum, zinc and other metal oxides) have been widely used in solid base catalysts, but their catalytic activity and stability are often poor, especially in high temperature and humid environment, the catalyst is easy to deactivate, and recycling is difficult. Magnetic solid base is convenient for solid-liquid separation, which is a common design strategy. Traditional magnetic solid base catalysts usually use metal oxides such as iron and nickel as magnetic carriers and active components such as potassium oxide and calcium oxide to form a magnetic solid base catalyst. Compared with homogeneous catalysts such as potassium hydroxide, this type of catalyst can be separated from the product mixture with the help of magnets, which is convenient for reuse and product treatment. However, traditional metal oxide catalysts are directly exposed to the substrate during the production of biodiesel, and are prone to structural changes at high temperatures. For example, high-valent iron metal oxides may undergo reduction or oxidation reactions, resulting in changes in their physical and chemical properties and demagnetization or inactivation.

[0004] Therefore, there is an urgent need to provide an efficient, stable and easily recyclable biodiesel transesterification catalyst. Summary of the invention

[0005] In view of the above technical problems, the present invention proposes a solid base magnetic catalyst and its preparation method and application. That is, the graphite carbon coating of nickel clusters is achieved by simple gelation and calcination methods, and combined with potassium oxide loading, a composite catalyst with strong magnetism, high stability and excellent catalytic activity is formed. Compared with traditional catalysts, the catalyst prepared by the present invention has the characteristics of efficient recovery and recycling, which significantly reduces the environmental impact and economic cost of biodiesel production.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A solid base magnetic catalyst, comprising: nickel clusters and active components, wherein the nickel clusters are dispersed on the surface of the active components;

[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 invention constructs the catalyst core by forming a nickel cluster by coating a nickel source with graphite carbon, and utilizes the chemical inertness and mechanical strength of the graphite carbon layer to protect the overall nickel cluster from oxidation, corrosion, wear or deactivation under high temperature conditions, while retaining the high magnetic properties of the nickel cluster as the magnetic core of the catalyst, achieving rapid and efficient separation and recovery through an external magnetic field after the reaction, with a recovery rate of nearly 100%, solving the problem of difficult separation of traditional catalysts after biodiesel transesterification reaction. At the same time, through potassium oxide, a strong alkaline functional site is introduced into the catalyst, making the contact interface of the catalyst with oils and alcohols fully active, thereby significantly improving the catalytic efficiency of the transesterification reaction.

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

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

[0014] Furthermore, 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 5-100 wt % of the nickel clusters.

[0016] The second technical solution of the present invention:

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

[0018] The nickel source, the carbon source and the alkali source are dissolved in a solvent for gelation treatment and calcination. After the calcination is completed, the material is naturally cooled to room temperature and ground to obtain a solid alkali magnetic catalyst with uniform particle size.

[0019] Beneficial effects: The present invention organically combines nickel source, carbon source and alkali source through gelation treatment and roasting process, controls roasting temperature and time, forms a uniform core-shell structure of graphite carbon-coated nickel particles, and realizes the functional synergy of alkaline sites and magnetic core. In addition, the preparation process conditions of the present invention are mild and 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 alkaline source is potassium hydroxide, which is a precursor of alkaline active sites; and / or

[0023] The solvent is ethanol.

[0024] Optionally, the conditions during the gelation process are: magnetic stirring at 60° C. for 1 hour to form a uniform gel.

[0025] Optionally, the conditions during the roasting process are:

[0026] The mixture is calcined at 150-600° C. at a rate of 10° C. / min for 0.5-10 hours under an inert atmosphere (nitrogen).

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

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

[0029] The solid base magnetic catalyst is used in the field of catalyzing bio-oil to prepare biodiesel.

[0030] Beneficial effects: The solid base magnetic catalyst prepared by the present invention 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 under high temperature and high humidity environment. After 10 cycles of use, the conversion rate remains above 90%.

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

[0032] The catalyst prepared by the present invention uses a graphite carbon shell layer to wrap nickel to form nickel clusters, thereby forming a core-shell structure, so that the magnetism of nickel is retained and protected from corrosion or oxidation under reaction conditions. At the same time, potassium oxide surrounded by nickel clusters has more active sites exposed on the surface, exerting a strong alkaline catalytic effect. Specifically, compared with the prior art, the present invention has the following advantages and technical effects:

[0033] 1. Extremely strong magnetism: Nickel clusters have high magnetism. Combined with the protection of graphite carbon coating, they still maintain stable magnetic properties under high temperature and high humidity conditions, which facilitates the efficient recovery of catalysts.

[0034] 2. Excellent catalytic performance: The alkaline catalytic active sites provided by potassium oxide can significantly increase the rate of transesterification reaction and is suitable for the conversion of a variety of oils and fats.

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

[0036] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

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

[0038] Figure 2 This is the overall morphology of the solid base magnetic catalyst prepared in Example 2. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] The embodiment of the present invention discloses a magnetic biodiesel transesterification reaction catalyst composed of nickel clusters formed by graphite carbon encapsulating nickel and potassium oxide. The composition structure of the catalyst is:

[0045] With potassium oxide as the core, nickel clusters are dispersed on its surface (a core-shell structure with nickel particles as the core and several layers of graphite carbon wrapped around it), thus forming a composite catalyst.

[0046] Among them, nickel clusters provide strong magnetism and participate in catalytic activity, graphite layers enhance the structural stability of the catalyst, and potassium oxide provides alkaline active sites.

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

[0048] The embodiment of the present invention also discloses a method for preparing a catalyst for catalyzing the transesterification reaction of biodiesel, wherein a nickel source, a carbon source and potassium hydroxide are subjected to gelation treatment, and then a composite catalyst is obtained by roasting and cooling and grinding, thereby forming a catalyst material that is efficient, stable, highly magnetic and easily recyclable, and is suitable for the transesterification reaction of biodiesel.

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

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

[0051] Carbon source: Choose natural carbon sources such as sucrose, citric acid, glucose, sorbitol (single or multiple combinations);

[0052] Alkali source: Potassium hydroxide is used as the precursor of alkaline active sites;

[0053] Solvent: Ethanol was used as the reaction solvent;

[0054] In some optional embodiments, the gelling process is:

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

[0056] At 60°C, use magnetic stirring to form a stable gel.

[0057] In some optional embodiments, the calcination conditions are: calcination at 150-600° C. for 0.5-10 hours in a nitrogen atmosphere to form a composite material having magnetic properties and high catalytic activity.

[0058] In some optional embodiments, the conditions for cooling and grinding are:

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

[0060] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

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

[0062] The present invention discloses a novel magnetic catalyst, specifically a catalyst material of graphite-encapsulated nickel clusters (GENCs) and potassium oxide (K2O). That is, by utilizing the high chemical stability of graphite carbon and the high magnetic properties of nickel clusters, combined with the strong alkaline functional sites of potassium oxide, a highly efficient, stable and easily recyclable biodiesel transesterification reaction catalyst is constructed. The technical scheme of the present invention is further illustrated by examples below.

[0063] Example 1: Catalyst dosage is 5% of grease

[0064] A method for preparing a solid base magnetic catalyst comprises the following steps:

[0065] 1. Raw material preparation:

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

[0067] 2. Preparation process:

[0068] Nickel nitrate, glucose and potassium hydroxide were dissolved in ethanol and magnetically stirred at 60 °C for 1 hour to form a uniform gel;

[0069] The gel was placed in a nitrogen atmosphere and heated to 500° C. at 10° C. / min for 3 hours. After calcination, it was cooled and ground to obtain catalyst 1 (wherein potassium oxide was ˜61.5 wt % of the nickel clusters).

[0070] The catalyst 1 prepared in this example was used to catalyze rapeseed oil to produce biodiesel, and the catalytic conditions were as follows:

[0071] Oil: rapeseed oil 10g;

[0072] Methanol: 3g;

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

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

[0075] Results: The conversion rate of catalyst 1 for preparing biodiesel from rapeseed oil was 95%. After the catalyst was recycled for 5 times, the conversion rate was 92%.

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

[0077] A method for preparing a solid base magnetic catalyst comprises 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] Nickel acetate, citric acid and potassium hydroxide were dissolved in ethanol and stirred for 1 hour to form a gel;

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

[0083] The catalyst 2 prepared in this example was used to catalyze palm oil to produce biodiesel, and the catalytic conditions were as follows:

[0084] Oil: palm oil 10g;

[0085] Methanol: 4 g;

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

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

[0088] Results: The conversion rate of catalyst 2 used to catalyze the production of biodiesel from palm oil was 96%. After the catalyst was recycled 10 times, the conversion rate remained at 92%.

[0089] Example 3: Catalyst dosage is 20% of grease

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

[0091] 1. Raw material preparation:

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

[0093] 2. Preparation steps:

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

[0095] The gel was placed in a nitrogen atmosphere and heated to 500° C. at 10° C. / min for 2 hours. After calcination, it was cooled and ground to obtain catalyst 3 (wherein potassium oxide was ˜30.8 wt % of the nickel clusters).

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

[0097] Grease: 10g waste grease;

[0098] Methanol: 5g;

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

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

[0101] Results: The conversion rate of catalyst 3 in preparing biodiesel from waste oil was 98%. After the catalyst was recycled for 8 times, the conversion rate remained at 94%.

[0102] Example 4: Catalyst dosage is 30% of grease

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

[0104] 1. Raw material preparation:

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

[0106] 2. Preparation steps:

[0107] Nickel acetate, sorbitol and potassium hydroxide were dissolved in ethanol and stirred to form a gel;

[0108] The gel was placed in a nitrogen atmosphere and calcined at 550°C at a rate of 10°C / min for 3 hours. After calcination, it was cooled and ground to obtain catalyst 4 (wherein potassium oxide was 80.8 wt% of the nickel clusters).

[0109] The catalyst 4 prepared in this example was used to catalyze animal oil to produce biodiesel, and the catalytic conditions were as follows:

[0110] Oil: animal oil 10g;

[0111] Methanol: 3.5 g;

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

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

[0114] Results: The conversion rate of catalyst 4 in preparing biodiesel from animal oil was 98%. After the catalyst was recycled 10 times, the conversion rate remained at 95%.

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

[0116] Figure 2 This is the overall morphology of the solid base magnetic catalyst prepared in Example 2. Figure 2 It can be seen that the flaky surface in the middle is potassium oxide, and the small black particles are nickel clusters of graphite carbon wrapped nickel. Therefore, the characteristics of the catalyst can be summarized as follows: the potassium oxide particles are large and have irregular morphology, and are surrounded by nickel clusters of graphite carbon wrapped nickel of relatively uniform size, but with more active sites exposed on the surface.

[0117] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A solid base magnetic catalyst, characterized in that include: Nickel clusters and active ingredients, wherein the nickel clusters are dispersed on the surface of the active ingredients; The nickel cluster is a core-shell structure with graphite carbon as the shell layer and nickel particles as the core layer; The active ingredient is a metal oxide.

2. A solid base magnetic catalyst according to claim 1, characterized in that: The metal oxide is potassium oxide; and the active component is 5-100 wt % of the nickel clusters.

3. A solid base magnetic catalyst according to claim 1, characterized in that: The particle size of the solid base magnetic catalyst is 5-50 nanometers.

4. A solid base magnetic catalyst according to claim 3, characterized in that: In the core-shell structure, 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.

5. A method for preparing a solid base magnetic catalyst, characterized in that: The following steps are involved: The nickel source, the carbon source and the alkali source are dissolved in a solvent, and then gelled, calcined and cooled and ground in sequence to obtain the solid alkali magnetic catalyst of any one of claims 1 to 4 with uniform particle size.

6. The method for preparing a solid base magnetic catalyst according to claim 5, characterized in that: The nickel source is nickel nitrate or nickel acetate; and / or The carbon source is at least one of sucrose, citric acid, glucose or sorbitol; and / or The alkali source is potassium hydroxide.

7. The method for preparing a solid base magnetic catalyst according to claim 5, characterized in that: The conditions during the gelation treatment are: magnetic stirring at 60° C. for 1 hour to form a uniform gel.

8. The method for preparing a solid base magnetic catalyst according to claim 5, characterized in that: The conditions during the calcination process are: The temperature is raised to 150-600°C at 10°C / min under an inert atmosphere, and calcined at this temperature for 0.5-10 hours.

9. Use of the solid base magnetic catalyst according to any one of claims 1 to 4 in the field of catalyzing bio-oil to prepare biodiesel.

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