High-entropy alloy catalyst for palmitic acid hydrodeoxygenation to hexadecane reaction and preparation method thereof

Abstract

The application belongs to the technical field of catalyst preparation, and provides a high-entropy alloy catalyst for palmitic acid hydrodeoxygenation to produce hexadecane and a preparation method thereof.The high-entropy alloy catalyst is a PtRuNiCe / MgAlO catalyst, which is composed of a MgAlO carrier prepared by calcining magnesium-aluminum hydrotalcite and Pt, Ru, Ni and Ce four kinds of metals loaded on the MgAlO carrier, and the molar ratio of the four kinds of metals is 1:1:1:1.The PtRuNiCe / MgAlO high-entropy alloy catalyst is used for palmitic acid hydrodeoxygenation to produce hexadecane, and excellent catalytic activity and hexadecane selectivity are exhibited, and the catalyst still maintains relatively excellent catalytic performance and good stability after being used for multiple cycles.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a high-entropy alloy catalyst for the reaction of palmitic acid hydrogenation deoxygenation to hexadecane and its preparation method. Background Technology

[0002] Natural oils and waste oils generated in human production and daily life are mainly composed of triglycerides and fatty acids. Due to their high carbon content, they have been used globally as a raw material for sustainable liquid fuel production. However, the liquid fuels obtained by the currently widely used transesterification method have a high oxygen content, which leads to insufficient thermal and oxidative stability and poor low-temperature fluidity. These problems significantly limit their use as high-performance liquid fuels.

[0003] Palmitic acid (C 16 Saturated fatty acids are an abundant and inexpensive biomass feedstock, and their hydrodeoxygenation to produce straight-chain alkanes (such as hexadecane) has significant value in fuel and chemical applications. Currently, commonly used palmitic acid hydrodeoxygenation catalysts are mostly supported on traditional supports such as alumina and silica gel with noble metals (such as Pd and Pt) or non-noble metals (such as Ni and Co). The reaction activity and selectivity are adjusted by controlling the metal particle size, gold loading, and the acidity or basicity of the support. However, single-metal or bimetallic catalytic systems often suffer from problems such as single active sites, poor resistance to sintering, and the generation of more side reactions (cracking and isomerization), making it difficult to achieve both high conversion and high selectivity, and usually requiring high reaction temperatures.

[0004] In recent years, high-entropy alloys (HEAs) have gradually become a research hotspot in the field of catalysis due to their random distribution of multiple metal atoms at the sub-nanometer scale, interfacial synergistic effects, and excellent thermal stability. Domestic and international scholars, such as Huang et al., reported an electrocatalytic system based on a RuInPtNiCu pentagonal high-entropy alloy (doi: 10.1021 / jacs.5c02339), exhibiting excellent activity; Liu et al. applied a PtNiCoMgBiSn hexaagonal high-entropy nanoalloy to the methanol oxidation reaction (doi: 10.1038 / s41467-025-61376-y), demonstrating that multi-metal synergy can significantly improve selectivity and stability, initially showcasing the potential of high-entropy alloys in biomass conversion. However, research on its application in deoxygenation and hydrogenation is still limited, especially for the deoxygenation and hydrogenation of long-chain fatty acids. Summary of the Invention

[0005] In view of this, the present invention provides a high-entropy alloy catalyst for the reaction of palmitic acid hydrodeoxygenation to hexadecane and its preparation method, so as to improve the palmitic acid conversion rate and hexadecane selectivity in the reaction of palmitic acid hydrodeoxygenation to hexadecane.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a high-entropy alloy catalyst for the hydrodeoxygenation of palmitic acid to hexadecane. The high-entropy alloy catalyst is a PtRuNiCe / MgAlO catalyst, which is composed of a MgAlO support obtained by calcining magnesium aluminum hydrotalcite and four metals, Pt, Ru, Ni and Ce, supported on the MgAlO support, with a molar ratio of the four metals of 1:1:1:1 and a Pt loading of 0.5~1.5wt%. The hydrodeoxygenation reaction conditions are: 160~200℃, 3~5MPa, and reaction time of 3~5h.

[0008] Furthermore, the MgAlO support is based on Mg 2+ And Al 3+ Magnesium oxide-alumina mixed oxide is obtained by calcining a preliminary hydrotalcite precursor with a molar ratio of (2.5~3.2):1.

[0009] Furthermore, the specific surface area of ​​the carrier is 80–120 m² / g, and the average pore size is 5–15 nm.

[0010] Furthermore, in the reaction of palmitic acid hydrodeoxygenation to hexadecane, the amount of catalyst added is 1 to 5 wt% of the mass of palmitic acid.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned PtRuNiCe / MgAlO high-entropy alloy catalyst, comprising the following steps:

[0012] (1) Prepare a magnesium aluminum hydrotalcite precursor solution, and obtain magnesium aluminum hydrotalcite by alkaline precipitation, filtration, washing and drying;

[0013] (2) The obtained magnesium aluminum hydrotalcite was calcined at 400-500 ℃ for 2-4 h to obtain MgAlO support;

[0014] (3) The obtained MgAlO support was mixed with solutions of four metal precursors, Pt, Ru, Ni and Ce, with a molar ratio of Pt, Ru, Ni and Ce of 1:1:1:1. After stirring evenly, the mixture was allowed to stand at room temperature for 0.5-1h.

[0015] (4) After drying the mixture obtained in step (3) to constant weight, the product is heated to 600-650 °C under a hydrogen / nitrogen atmosphere and kept at that temperature for 2.5-4 h to obtain the PtRuNiCe / MgAlO high-entropy alloy catalyst.

[0016] Furthermore, in step (1), the pH is adjusted to 10-11 using an aqueous NaOH solution.

[0017] Furthermore, in step (2), the calcination conditions are: air is introduced and the heating rate is 1~10℃ / min.

[0018] Furthermore, in step (4), after purging with an inert atmosphere for 1-2 hours, the subsequent hydrogen reduction step is carried out.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) Multi-metal synergy: The quaternary high-entropy alloy of Pt, Ru, Ni and Ce is randomly distributed at the nanoscale, which synergistically enhances the deoxygenation activity of palmitic acid; (2) High selectivity: The electronic structure regulation of the high-entropy alloy and the pore effect of the MgAlO support effectively suppress the cracking and isomerization side reactions, making the hexadecane selectivity ≥98%; (3) Excellent stability: The catalyst loses ≤6% of activity and selectivity after five consecutive cycles, the support and alloy are mutually stable, and the anti-sintering performance is good; (4) Simple process: The wet co-loading one-step reduction process has low equipment requirements and is suitable for industrial scale-up.

[0020] This invention achieves high efficiency, selectivity, and stability in the preparation of hexadecane via the hydrodeoxygenation of palmitic acid by rationally designing the composition and preparation process of the PtRuNiCe / MgAlO high-entropy alloy catalyst, providing a novel catalytic material and technical route for the industrial conversion of biomass resources. Attached Figure Description

[0021] Figure 1 A schematic diagram of H2-TPR for the preparation of the PtRuNiCe / MgAlO catalyst in Example 1 is shown.

[0022] Figure 2 A high-resolution transmission electron microscope image of the PtRuNiCe / MgAlO catalyst prepared in Example 1 is shown.

[0023] Figure 3 The EPR spectrum of the PtRuNiCe / MgAlO catalyst prepared in Example 1 is shown. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be understood that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of the present invention.

[0025] Example 1

[0026] The preparation method of the high-entropy alloy catalyst, PtRuNiCe / MgAlO catalyst, includes the following steps:

[0027] (1) Dissolve MgCl2·6H2O (13.4 g, 0.07 mol) and Al(NO3)3·9H2O (10.2 g, 0.025 mol) in 200 mL of deionized water. Stir until completely dissolved, then slowly add 1 M NaOH aqueous solution until pH = 10.5. Stir at 500 rpm for 1 h, filter the precipitate and wash it three times each with deionized water and ethanol. Air dry at room temperature to constant weight to obtain hydrotalcite.

[0028] (2) The obtained hydrotalcite was placed in a tube furnace and heated to 450 °C at a rate of 5 °C / min under air atmosphere and held for 4 hours to obtain a specific surface area of ​​approximately 98 m². 2 / g, MgAlO support with an average pore size of approximately 8.5 nm;

[0029] (3) Weigh 5.00 g of MgAlO and disperse it in 100 mL of deionized water. Add an aqueous solution of H2PtCl6, RuCl3, Ni(NO3)2 and Ce(NO3)3 in an equimolar ratio (Pt: Ru: Ni: Ce = 1: 1: 1: 1, Pt loading 1 wt%) and stir at 600 rpm for 1.5 h. Then, evaporate most of the water from the mixture by rotary evaporation and dry it in a vacuum oven at 100 ℃ for 12 h to constant weight. Then, place the dried product in a 5% H2 / N2 atmosphere (50 mL / min) and heat it to 600 ℃ at 3 ℃ / min and keep it at 3 h to obtain the PtRuNiCe / MgAlO catalyst in one step.

[0030] The catalyst prepared above was characterized, and the results are as follows: Figures 1-3 As shown, Figure 2 The TEM characterization results show that the metal nanoparticles are uniformly distributed with an average particle size of approximately 5.2 nm. Figure 1 The H2-TPR test results shown indicate that the catalyst exhibits two-stage reduction peaks at approximately 390 °C and 580 °C, corresponding to RuO₂, respectively. x →Ru and PtO x / NiO x / CeO x The reduction indicates multi-metal synergistic reduction; Figure 3 The EPR spectrum shown exhibits a clear signal at g=2.03, indicating the presence of abundant oxygen vacancies on the catalyst surface, which provides favorable sites for substrate adsorption and activation.

[0031] Comparative Example 1

[0032] Compared with Example 1, the only difference is that the molar ratio of the four metals is different. In this example, Pt: Ru: Ni: Ce = 3: 2: 1: 1.

[0033] Comparative Example 2

[0034] Compared with Example 1, the only difference is that the molar ratio of the four metals Pt: Ru: Ni: Ce = 3: 1: 1: 1.

[0035] Comparative Example 3

[0036] Compared with Example 1, the only difference is that the Ce(NO3)3 precursor solution is replaced with Fe(NO3)3, and the molar ratio of the four metals Pt: Ru: Ni: Fe = 1: 1: 1: 1.

[0037] Comparative Example 4

[0038] Compared with Example 1, the only difference is that the Ce(NO3)3 precursor solution is replaced with Cu(NO3)2, and the molar ratio of the four metals Pt: Ru: Ni: Cu = 1: 1: 1: 1.

[0039] Comparative Example 5

[0040] Compared with Example 1, the difference is as follows: After obtaining the MgAlO support, 5.00 g of the MgAlO support was dispersed in 100 mL of deionized water, and a 1 wt% Pt loading H2PtCl6·6H2O solution was added. The mixture was stirred at 600 rpm for 1.5 h. After removing the water by rotary evaporation, the mixture was vacuum dried at 100 °C for 12 h. Then, the temperature was increased to 600 °C at 3 °C / min under a 5% H2 / N2 (50 mL / min) atmosphere and held for 3 h to obtain the Pt / MgAlO catalyst.

[0041] Comparative Example 6

[0042] Compared with Comparative Example 5, the difference is that the active metal precursor H2PtCl6 was replaced with RuCl3 to prepare a catalyst with a loading of 1wt% Ru / MgAlO.

[0043] Comparative Example 7

[0044] Compared with Comparative Example 5, the difference is that the active metal precursor H2PtCl6 was replaced with Ni(NO3)2 to prepare a catalyst with a loading of 1wt% Ni / MgAlO.

[0045] Comparative Example 8

[0046] Dissolve 26.8 g (0.14 mol) of MgCl2·6H2O in 200 mL of deionized water. After stirring until completely dissolved, slowly add 1 M NaOH aqueous solution until pH=10.5, stirring at 500 rpm for 1 h. Filter the precipitate and wash it three times each with deionized water and ethanol, and air dry at room temperature to constant weight. Place the obtained hydrotalcite precursor in a tube furnace and heat it to 450 ℃ for 4 h at 5 ℃ / min under air atmosphere to obtain MgO support. Weigh 5.00 g of MgO and disperse it in 100 mL of deionized water. Add an equimolar ratio (Pt: Ru: Ni: Ce = 1: 1: 1: 1, Pt loading 1 wt%) of H2PtCl6, RuCl3, Ni(NO3)2, Ce(NO3)3 aqueous solution, and stir at 600 rpm for 1.5 h. Heat the mixed slurry at 80 °C. Most of the moisture was removed by rotary evaporation in a water bath at ℃, and the product was dried in a vacuum oven at 100 ℃ for 12 h to constant weight. Then, 5% H2 / N2 (50 mL / min) was introduced, and the temperature was increased to 600 ℃ at 3 ℃ / min and held for 3 h to obtain the Pt1Ru1Ni1Ce1 / MgO catalyst in one step.

[0047] Comparative Example 9

[0048] Compared with Comparative Example 8, the difference is that Al2O3 support was used. The preparation process of Al2O3 support is as follows: Al(NO3)3·9H2O (18.8 g, 0.05 mol) was dissolved in 200 mL of deionized water and stirred until completely dissolved. Then, 1 M NaOH aqueous solution was slowly added dropwise to pH=10.5. The mixture was stirred at 500 rpm for 1 h. The precipitate was filtered and washed three times each with deionized water and ethanol, and then air-dried at room temperature to constant weight. The obtained hydrotalcite precursor was placed in a tube furnace and heated to 450 ℃ at 5 ℃ / min under air atmosphere and held for 4 h to obtain Al2O3 support. Finally, Pt1Ru1Ni1Ce1 / Al2O3 catalyst was prepared.

[0049] Example 2

[0050] Catalyst performance evaluation

[0051] (a) The catalyst prepared above was applied to the deoxygenation and hydrogenation reaction of palmitic acid to evaluate its catalytic performance. All catalyst activity tests were carried out in a 100 mL stainless steel autoclave. The specific operation process is as follows:

[0052] (1) Preparation of reactants: 10 g of palmitic acid was mixed with 30 mL of n-hexane and ultrasonically vibrated for 10 min to obtain a homogeneous solution.

[0053] (2) Catalyst loading: Weigh 0.50 g of each catalyst in sections and load them into the reactor.

[0054] (3) Hydrogenation and heating: H2 gas was introduced into the reactor to 3.0 MPa at room temperature. The stirring rate of the reactor was set to 600 rpm. Then the temperature was raised to 180 ℃ and kept constant for 4 h.

[0055] (4) Sampling and Analysis: After the reaction is complete, the pressure is slowly released to atmospheric pressure and cooled to room temperature. The catalyst is separated by filter paper, and the supernatant is taken for quantitative analysis by gas chromatography-mass spectrometry (GC-MS) of the palmitic acid conversion rate, the content of various straight-chain alkane products, and the total amount of by-products such as cracked gases and isomers. The palmitic acid conversion rate and hexadecane selectivity are calculated according to the following formula:

[0056] C(C 16 OOH) =

[0057] S(C 16 ) = ;

[0058] The performance test results of the catalysts are shown in Table 1.

[0059] Table 1 Evaluation results of palmitic acid hydrodeoxygenation reaction with different metal catalysts

[0060]

[0061] The performance of various PtRuNiCe high-entropy alloys and other catalysts with different compositions in the hydrodeoxygenation of palmitic acid was compared. Table 1 shows that the PtRuNiCe / MgAlO catalyst prepared in Example 1 exhibited the highest palmitic acid conversion (100%) and hexadecane selectivity (98.5%), with the lowest proportion of byproduct cracking and isomerization products (1.5%), demonstrating excellent catalytic activity and selectivity. In contrast, the performance of other high-entropy alloy catalysts with different compositions and ratios, as well as single-metal catalysts, was significantly worse under the same reaction conditions.

[0062] The single-metal catalysts shown in Comparative Examples 5-7 exhibited a significant decrease in catalytic activity and selectivity, accompanied by an increase in the proportion of byproduct formation. For example, the conversion and selectivity of the single-metal Pt / MgAlO catalyst were 87.7% and 72.3%, respectively, while the activity and selectivity of the single-metal Ru and Ni catalysts further decreased. Although the PtRuNiCe high-entropy alloy catalysts with different ratios shown in Comparative Examples 1-4 were inferior to those in Example 1, they still showed a significantly improved ability to deoxygenate and hydrogenate palmitic acid compared to the single-metal catalysts. Cracking and isomerization side reactions were also effectively suppressed, indicating that the rational design of the multi-metal component ratio has a significant impact on the regulation of catalytic performance. Comparative Examples 9 and 10, using conventional alumina and magnesium oxide supports, showed a significant decrease in catalytic activity, indicating that the high-entropy alloy catalyst described in this invention achieves an ideal balance of high conversion, high selectivity, and low byproduct formation through effective metal synergy and support interaction.

[0063] Example 3

[0064] Catalytic performance of PtRuNiCe high-entropy alloy catalyst under different reaction conditions was investigated.

[0065] The PtRuNiCe / MgAlO catalyst prepared in Example 1 was tested at different reaction temperatures and hydrogen pressures. The performance testing method was the same as that in Example 2, except that the reaction temperature and hydrogen pressure were adjusted. The catalyst performance evaluation results are as follows:

[0066] Table 2 Evaluation of PtRuNiCe / MgAlO catalysts at different reaction temperatures and hydrogen pressures

[0067]

[0068] Table 2 shows the palmitic acid hydrodeoxygenation performance of the PtRuNiCe / MgAlO high-entropy alloy catalyst under different reaction temperatures and hydrogen pressures. The results show that the PtRuNiCe / MgAlO high-entropy alloy catalyst exhibits excellent catalytic performance across different reaction temperatures (160–200 °C) and hydrogen pressures (3.0 MPa–5.0 MPa). Specifically, the conversion rate of palmitic acid by the catalyst is consistently close to or equal to 100% at both lower and higher temperatures, demonstrating its extremely high activity. Simultaneously, the hexadecane yield remains consistently high, exceeding 90% at the lowest and reaching 98.5% at the highest. The catalyst exhibits optimal performance at 180 °C and a hydrogen pressure of 3.0 MPa, ensuring both complete conversion and the highest hexadecane selectivity, reflecting a good balance between reaction efficiency and product purity under these conditions. As hydrogen pressure increased, the conversion rate remained saturated, while the hexadecane yield fluctuated slightly, suggesting that high pressure might have an impact on side reactions. Similarly, when the temperature rose above 180°C, the selectivity decreased slightly, indicating that high-temperature conditions might promote the formation of byproducts such as cracking or isomerization. Overall, the catalyst can stably achieve high conversion and high selectivity over a relatively wide temperature and pressure range, demonstrating good process adaptability and application potential.

[0069] Example 4

[0070] Catalyst stability evaluation

[0071] The PtRuNiCe / MgAlO catalyst prepared in Example 1 was selected. According to the above catalyst performance evaluation results, after each test experiment, the used catalyst was separated and collected, and reused. The conversion rate of palmitic acid and the yield of hexadecane were tested each time. The catalytic reaction conditions were the same as in Example 2. The specific results are shown in Table 3.

[0072] Table 3 Stability evaluation of PtRuNiCe / MgAlO catalyst

[0073]

[0074] As shown in Table 3, the PtRuNiCe / MgAlO catalyst still achieves a palmitic acid conversion rate of 94.2% and a hexadecane selectivity of approximately 94% after five rounds of reaction. This result indicates that the PtRuNiCe / MgAlO catalyst of this invention exhibits good stability and a long service life.

[0075] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of this patent.

Claims

1. A high-entropy alloy catalyst for the hydrodeoxygenation of palmitic acid to hexadecane, characterized in that, The high-entropy alloy catalyst is a PtRuNiCe / MgAlO catalyst, which consists of a MgAlO support obtained by calcining magnesium aluminum hydrotalcite and four metals—Pt, Ru, Ni, and Ce—supported on the MgAlO support, with a molar ratio of 1:1:1:1 and a Pt loading of 0.5~1.5 wt%. The MgAlO support is based on Mg... 2+ And Al 3+ Magnesium oxide-alumina mixed oxide is obtained by calcining a primary hydrotalcite precursor with a molar ratio of (2.5~3.2):1; the preparation method of the high-entropy alloy catalyst includes the following steps: (1) Prepare a magnesium aluminum hydrotalcite precursor solution, and obtain magnesium aluminum hydrotalcite by alkaline precipitation, filtration, washing and drying; (2) The obtained magnesium aluminum hydrotalcite was calcined at 400-500 ℃ for 2-4 h to obtain MgAlO support; (3) The obtained MgAlO support is mixed with solutions of four metal precursors, Pt, Ru, Ni and Ce, with a molar ratio of Pt, Ru, Ni and Ce of 1:1:1:

1. The mixture is stirred until homogeneous and ready for use. (4) After drying the mixture obtained in step (3) to constant weight, the product is heated to 600-650 °C and kept at that temperature for 2.5-4 h in a hydrogen / nitrogen mixed atmosphere to obtain the PtRuNiCe / MgAlO high-entropy alloy catalyst. The conditions for the hydrogenation deoxygenation reaction are: 160~200℃, 3~5MPa, and 3~5h.

2. The high-entropy alloy catalyst for the hydrodeoxygenation of palmitic acid to hexadecane according to claim 1, characterized in that, The specific surface area of ​​the carrier is 80–120 m² / g, and the average pore size is 5–15 nm.

3. The high-entropy alloy catalyst for the hydrodeoxygenation of palmitic acid to hexadecane according to claim 1, characterized in that, In the reaction of palmitic acid hydrodeoxygenation to hexadecane, the amount of catalyst added is 1 to 5 wt% of the mass of palmitic acid.

4. The high-entropy alloy catalyst for the hydrodeoxygenation of palmitic acid to hexadecane according to claim 1, characterized in that, In step (1), the pH is adjusted to 10-11 using NaOH aqueous solution.

5. The high-entropy alloy catalyst for the hydrodeoxygenation of palmitic acid to hexadecane according to claim 1, characterized in that, In step (2), the calcination conditions are: air is introduced and the heating rate is 1~10℃ / min.

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