A nickel oxide-supported cobalt catalyst, its preparation method and application

Abstract

This invention belongs to the field of biomass conversion catalyst technology, specifically relating to a nickel oxide-supported cobalt catalyst, its preparation method, and its application. A Co / NiO catalyst with a 1.5% Co loading is prepared by adding a complex solution containing Co ions and a NiO support to a dispersant and a reducing agent. The preparation process is simple, and the catalyst preparation conditions are optimized. The effects of Co loading, catalyst mass, reaction temperature, and reaction time on the reaction are adjusted. At the microscopic level, high dispersion of transition metal nanoparticles is achieved, resulting in optimal conversion and yield. Simultaneously, the price and availability of both the nickel oxide support and cobalt are relatively low. The total metal loading of 1.5% is low, resulting in low cost. Furthermore, the magnetic nature of the nickel oxide support facilitates product separation and catalyst recovery, improving the catalyst's recyclability. Optimized catalytic reaction conditions ensure high catalytic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of biomass conversion catalyst technology, specifically relating to a nickel oxide-supported cobalt catalyst, its preparation method, and its application. Background Technology

[0002] A continuous and stable energy supply is crucial for the development of human economy and society. Currently, the main energy sources are non-renewable resources such as coal, crude oil, and natural gas. However, the large-scale extraction and use of fossil fuels has brought many problems to human society, such as global warming and environmental pollution. In recent years, to address the problems caused by the over-exploitation and use of fossil fuels, people have been committed to finding and developing new green and renewable energy sources. Lignin is a continuous and stable source of fossil energy, with the potential to be converted into high-value-added chemicals and to replace traditional fossil fuels. The molecular catalysis of biomass-derived platforms into value-added chemicals is of great significance in meeting the ever-increasing energy demands and reducing CO2 emissions.

[0003] Furfural is a bio-based platform molecule obtained from lignocellulosic materials (such as hemicellulose) through acid hydrolysis. An effective strategy for obtaining high-value-added products from furfural is to first convert it into a less reactive intermediate before converting it into the target product. However, due to furfural's highly functionalized properties (i.e., C-C, CO, and C=O bonds), controlling the conversion rate and selectivity of furfural to the desired product is challenging. Therefore, a common method is selective hydrogenation to produce furfuryl alcohol, which can be used to produce core binders for the foundry industry, high-temperature phenolic resin binders, plasticizers with excellent cold-resistant properties, synthetic fibers, polyurethane foams, tetrahydrofurfural alcohol, etc. Furthermore, furfuryl alcohol is also a good solvent for varnishes, pigments, etc., and is an intermediate in the production of pesticides, fragrances, and pharmaceuticals.

[0004] There are two processes for the hydrogenation of furfural to furfuryl alcohol: liquid-phase and gas-phase. The liquid-phase process using Cu-Cr catalysts was industrialized in 1948. The liquid-phase process is characterized by high temperatures, difficulties in catalyst separation and regeneration, and high equipment requirements. In contrast, the gas-phase process has advantages such as lower reaction temperatures, lower pressures, inhibition of deep hydrogenation, and simpler catalyst recovery. Currently, the catalysts used in the gas-phase process are mainly copper-silicon and copper-chromium based. Although copper-chromium catalysts have the advantages of high selectivity and high stability, the heavy metal chromium's environmental pollution and health hazards limit its development.

[0005] Therefore, current development focuses primarily on developing chromium-free catalysts. In existing catalytic systems, transition metal catalysts, especially noble metal catalysts such as Ru and Pd, exhibit high catalytic performance in the hydrogenation of furfural to furfuryl alcohol. However, noble metal catalysts are expensive, and under harsh reaction conditions, the active components are easily lost, resulting in poor catalyst recycling performance, thus limiting their widespread application in practical industry. If lower-cost non-noble metals such as cobalt, nickel, and zinc are used as the active components, high temperature, high pressure, and long reaction time are required to ensure complete reaction. The resulting metal wastewater pollutes water bodies, and the large amount of catalyst used leads to low economic efficiency.

[0006] Furthermore, selecting an appropriate hydrogen source is crucial for the catalytic synthesis of furfuryl alcohol from furfural. Currently, two main schemes for the catalytic synthesis of furfuryl alcohol from furfural are available. The first scheme uses hydrogen (H2) as the hydrogen donor; however, hydrogen under high pressure readily reacts with air and possesses flammable and explosive properties, requiring specialized storage, transportation, and handling facilities. This limits the widespread application of this scheme. The second scheme employs a catalytic hydrogen transfer (CTH) method, using formic acid or alcohol as the hydrogen donor. This method is simpler and safer in terms of laboratory facilities and operation. Additionally, alcohol solvents have multiple potential roles, serving as both solvents and hydrogen donors, making them attractive. Due to the high unsaturation of furfural, precise control of the hydrogenation reaction is necessary to improve the selectivity of furfuryl alcohol. Currently, this control is typically achieved by adjusting the catalyst; therefore, catalyst selection and structural tuning are key factors in improving the efficiency of catalytic hydrogenation of furfural to furfuryl alcohol. Different types of catalysts will determine the pathway of the catalytic reaction and the product selectivity, making research in this area essential.

[0007] Therefore, developing high-efficiency, low-cost, and easy-to-prepare heterogeneous metal catalysts is of great significance for the preparation of furfural from biomass platform compound furfural. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a nickel oxide-supported cobalt catalyst, its preparation method, and its application.

[0009] This invention is achieved through the following technical solution:

[0010] A nickel oxide-supported cobalt catalyst is prepared by adding a complex solution containing metal ions Co and a NiO support to an additive to form a Co / NiO catalyst with a mass fraction of 1.5% Co loading. The additive is a dispersant and a reducing agent.

[0011] The preparation method of the above-mentioned nickel oxide-supported cobalt catalyst includes the following steps:

[0012] S1: A complex solution containing metal ions Co is mixed with a dispersant in a solvent and stirred to form a gel. NiO is added to the gel and the reaction is continued to be stirred to obtain a catalyst precursor.

[0013] S2: Add a reducing agent to the catalyst precursor, stir the reaction to make the loading ratio of metallic Co 1.5%, and then filter and dry to obtain Co / NiO catalyst powder.

[0014] Preferably, in step S1, a cobalt acetylacetonate solution is mixed with the dispersant polyvinylpyrrolidone in deionized water and stirred for 15 minutes to obtain a gel-like substance. Then, NiO is added and stirred for 10-60 minutes to obtain a catalyst precursor.

[0015] Preferably, in step S2, a reducing agent, NaBH4, is added to the catalyst precursor to reduce the Co precursor to metallic Co. The Co content in the cobalt acetylacetone solution is adjusted to achieve a loading ratio of metallic Co of 1.5%. After stirring the reaction at room temperature for 2 hours, the solution is filtered.

[0016] Preferably, in step S2, the filtration is performed using an aqueous phase filter membrane and deionized water at 90°C for filtration and washing until the filtrate becomes a colorless and transparent liquid. Co / NiO catalyst powder is obtained on the aqueous phase filter membrane, and the powder is dried in a vacuum environment at 60°C to obtain a dried Co / NiO catalyst.

[0017] The application of the above-mentioned nickel oxide-supported cobalt catalyst in the process of preparing furfural from furfural includes the following steps:

[0018] Co / NiO catalyst, furfural raw material, and isopropanol solvent were placed in a high-pressure reactor, argon gas was introduced, and a high-temperature stirring reaction was carried out. After the reaction was completed, the mixture was cooled to room temperature, and the reactor was depressurized and a sample was taken to obtain furfural alcohol.

[0019] Preferably, the Co / NiO catalyst, furfural raw material, and isopropanol solvent are placed in a high-pressure reactor. The gas in the reactor is extracted, and argon gas at 0.1 MPa is introduced three times to purge the reactor. Argon gas at 0.1 MPa is continuously introduced for 1 minute. Then, the reactor is kept at 120°C and the stirring speed is maintained at 800 rpm for 4 hours. After the reaction is completed, the reactor is cooled to room temperature. After the reactor is vented, a sample is taken and filtered to obtain furfuryl alcohol and other products.

[0020] The beneficial effects of this invention are:

[0021] (1) The preparation process of the Co / NiO catalyst is simple. The preparation conditions of the catalyst were optimized, and the effects of Co loading, catalyst mass, reaction temperature and reaction time on the reaction were adjusted. At the microscopic level, the high dispersion of transition metal nanoparticles was achieved and the reaction obtained the best conversion rate and yield. At the same time, the price and acquisition difficulty of the nickel oxide support and cobalt metal are low. The mass fraction of the total metal loading is 1.5%, which is low in loading and low in cost. Moreover, the nickel oxide support is magnetic, which makes it easy to separate the product and recover the catalyst, thus improving the recycling performance of the catalyst.

[0022] (2) The Co / NiO catalyst was used to catalyze the preparation of furfural from furfural, which optimized the catalytic reaction conditions and ensured high catalytic efficiency. Under a hydrogen-free atmosphere and a low reaction temperature, the conversion rate of the reactant furfural reached 98.5%, and the selectivity of the target product furfural was as high as 97%. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments are briefly introduced below.

[0024] Figure 1 These are transmission electron microscope images of NiO(a, b) and 1.5Co / NiO(c, d) catalysts;

[0025] Figure 2 These are the XRD patterns of NiO and 1.5Co / NiO. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. In addition, the technical features involved in the various embodiments described below can be combined with each other as long as they do not conflict with each other.

[0027] Example 1

[0028] Preparation of a Co / NiO catalyst with a Co loading of 1.5% by mass: 10 mL of a 2.2 mg / mL cobalt acetylacetonate solution was poured into a 250 mL round-bottom flask, followed by 150 mL of deionized water and stirred until homogeneous. Then, 5.4 mg of polyvinylpyrrolidone (PVP) with an average molecular weight of 10,000 was added, and the mixture was stirred for 15 min. Next, 300 mg of nickel oxide was added, and after stirring for 15 min, 30 mg of NaBH4 was added to achieve a theoretical cobalt loading of 1.5%. After stirring at room temperature for 2 hours, the solution was filtered through a 50 mm × 0.08 μm aqueous filter membrane. The solution was washed with 2 L of 90 °C deionized water until the filtrate became a colorless and transparent liquid. The catalyst powder on the filter paper was then dried overnight in a 60 °C vacuum drying oven to obtain the catalyst. Figure 1 As shown in the figure, NiO exhibits a plate-like structure. The introduction of Co did not cause a significant change in the morphology of the NiO support. It was dried and stored away from light for later use. Figure 2 As can be seen, NiO mainly exhibits (111), (200), (211), (311) and (222) crystal planes. The introduction of Co did not cause structural changes in NiO, but no Co diffraction peaks were observed, mainly due to the low Co loading and high dispersion.

[0029] Example 2

[0030] The Co / NiO catalyst with a Co loading of 1.5% by mass prepared in Example 1 was used in the process of preparing furfural-furyl alcohol from furfural: 60 mg of catalyst, 5 mL of isopropanol solvent, 1 mmol of furfural, and a magnetic stir bar were sequentially added to the polytetrafluoroethylene liner of a high-pressure reactor. After the reactor was assembled, the gas inside the reactor was evacuated using a high-pressure pump, and then connected to an argon cylinder. Argon gas at 0.1 MPa was introduced and purged three times. Argon gas was then introduced at 0.1 MPa for about 1 minute. Finally, the reactor was placed in a high-temperature magnetically stirred oil bath at a pre-set temperature of 120°C, and the magnetic stirring speed was 800 rpm for 4 hours. After the 4-hour reaction, the reactor was placed in ice water to cool for 5-10 minutes, the gas inside the reactor was released, the reaction liquid inside the reactor was aspirated with a syringe, and then filtered through a 0.45 nm filter to obtain furfural alcohol filtrate.

[0031] Example 3

[0032] The reaction process and time of furfural to furfuryl alcohol catalyzed by a Co / NiO catalyst with a Co loading of 1.5% by mass are shown in Table 1.

[0033] Table 1 Relationship between reaction progress and time

[0034]

[0035] The results showed that the conversion rate reached 98.5% after 4 hours, demonstrating the extremely high efficiency of this catalyst, and reached 99.2% after 6 hours.

[0036] Example 4

[0037] The effects of cobalt content in the catalyst on catalytic performance were tested and compared, as shown in Table 2.

[0038] Table 2 Effect of cobalt content in catalyst on catalytic performance

[0039]

[0040] The results show that in the catalyst of this invention, the loading of Co metal significantly improves the conversion rate of furfural, and the best catalytic effect is achieved when the Co metal loading is 1.5%. Excessive Co loading leads to a decrease in the catalyst conversion rate; therefore, a Co loading of 1.5% is selected as the most suitable catalyst loading for the reaction.

[0041] Example 5

[0042] The effect of catalyst dosage on catalytic performance is shown in Table 3.

[0043] Table 3 Effect of catalyst dosage on catalytic performance

[0044]

[0045] The results showed that after 4 hours of reaction, the conversion rate of the reactants reached 98.5% only when the catalyst mass was greater than or equal to 60 mg. There was essentially no difference in the reaction results when using 60 mg and 80 mg of catalyst. Therefore, 60 mg was selected as the optimal catalyst mass for the reaction.

[0046] Example 6

[0047] The catalytic effects of the catalysts on different aldehyde-containing substrates were tested, as shown in Table 4.

[0048] Table 4 Catalytic effects of catalysts on different aldehyde-containing substrates

[0049]

[0050] The results show that the catalyst can selectively catalyze hydrogen transfer from a series of unsaturated aldehyde substrates to prepare corresponding alcohol compounds.

[0051] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A nickel oxide-supported cobalt catalyst, characterized in that, A Co / NiO catalyst with a Co loading of 1.5% by mass fraction was prepared by adding a complex solution containing metal ions Co and a support NiO to an additive. The additives were a dispersant and a reducing agent. The preparation method of the nickel oxide-supported cobalt catalyst includes the following steps: S1: A cobalt acetylacetonate solution and dispersant polyvinylpyrrolidone were mixed in deionized water and stirred to obtain a gel. NiO was then added and stirred to obtain a catalyst precursor. S2: Add reducing agent NaBH4 to the catalyst precursor to reduce the Co precursor to metallic Co, so that the loading ratio of metallic Co is 1.5%. After stirring the reaction at room temperature, filter and dry the solution to obtain Co / NiO catalyst powder.

2. The nickel oxide-supported cobalt catalyst according to claim 1, characterized in that, In the preparation method S1, the cobalt acetylacetone solution and the dispersant polyvinylpyrrolidone are mixed in deionized water and stirred for 15 min, and then NiO is added and stirred for 10-60 min.

3. The nickel oxide-supported cobalt catalyst according to claim 1, characterized in that, In the preparation method S2, the Co content in the cobalt acetylacetone solution is adjusted to achieve a Co loading ratio of 1.5%. After stirring the reaction at room temperature for 2 hours, the solution is filtered and dried.

4. The nickel oxide-supported cobalt catalyst according to claim 3, characterized in that, In the preparation method S2, the filtration is carried out using an aqueous phase filter membrane and deionized water at 90°C until the filtrate becomes a colorless and transparent liquid. Co / NiO catalyst powder is obtained on the aqueous phase filter membrane, and the powder is dried in a vacuum environment at 60°C to obtain a dry Co / NiO catalyst.

5. The application of the nickel oxide-supported cobalt catalyst according to claim 1 in the process of preparing furfural from furfural, characterized in that, Specifically, the following steps are included: Co / NiO catalyst, furfural raw material, and isopropanol solvent were placed in a high-pressure reactor, argon gas was introduced, and a high-temperature stirring reaction was carried out. After the reaction was completed, the mixture was cooled to room temperature, and the reactor was depressurized and a sample was taken to obtain furfural alcohol.

6. The application of the nickel oxide-supported cobalt catalyst according to claim 5 in the process of preparing furfural from furfural, characterized in that, The Co / NiO catalyst, furfural raw material, and isopropanol solvent were placed in a high-pressure reactor. The gas in the reactor was extracted, and argon gas at 0.1 MPa was introduced three times and argon gas at 0.1 MPa was continuously introduced for 1 min. Then, the reactor was kept at 120℃ and the stirring speed was maintained at 800 rpm for 4 h. After the reaction was completed, the reactor was cooled to room temperature, and after the reactor was vented, a sample was taken and filtered to obtain furfuryl alcohol product.

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