Hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalysts, their preparation methods and applications

Abstract

This invention relates to a hydrogen-form magnesium-alkali zeolite-supported lanthanum single-atom catalyst, its preparation method, and its application, belonging to the field of catalyst technology. The invention first acid-treats magnesium-alkali zeolite to obtain a hydrogen-form magnesium-alkali zeolite support. Then, lanthanum single atoms are loaded onto the support using an impregnation-calcination method to obtain a hydrogen-form magnesium-alkali zeolite-supported lanthanum single-atom catalyst. Subsequently, industrial oleic acid, a water-based co-solvent, and a triphenylphosphine modifier are mixed with the catalyst, and an isomerization reaction is carried out under high temperature and high pressure conditions. The reaction product is then catalytically hydrogenated using a Ni / C catalyst, followed by low-temperature crystallization and vacuum distillation to obtain high-purity isostearic acid. By constructing an integrated process of isomerization-hydrogenation-low-temperature crystallization-vacuum distillation, the purity and yield of isostearic acid are significantly improved, and the obtained product exhibits excellent low-temperature fluidity, thermal stability, and antioxidant properties.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and particularly relates to hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalysts, their preparation methods, and applications. Background Technology

[0002] Isostearic acid, a C18 saturated fatty acid with a branched structure, possesses a low freezing point, good low-temperature fluidity, excellent oxidative stability, and good thermal stability, making it widely used in cosmetics, lubricants, polymer materials, surfactants, and food additives. Compared to straight-chain stearic acid, the branched structure introduced into its molecular chain significantly optimizes the low-temperature performance and rheological properties of materials, thus possessing high industrial application value. Currently, the domestic market demand for isostearic acid is growing year by year, but mature production technology is lacking, and it mainly relies on imports, resulting in a supply-demand imbalance and persistently high prices.

[0003] Currently, in industrial production, isostearic acid is mainly obtained by separating byproducts from dimer acid production. This method suffers from significant problems, including complex composition, wide distribution of isomers, low product purity, and high separation costs, making it difficult to consistently produce high-quality isostearic acid to meet industrial demands. Another mainstream process is the chemical synthesis route, which typically uses high-purity oleic acid as a raw material. Under the action of an acidic catalyst, double bond migration, skeletal rearrangement, and branching isomerization reactions occur, followed by hydrogenation to obtain isostearic acid. Although this route has some feasibility, it still has several shortcomings that urgently need to be addressed: Firstly, the purity of the raw material is crucial. The stringent requirements and high cost of preparing high-purity oleic acid severely limit the large-scale industrial application of this route. Secondly, oleic acid is prone to side reactions such as polymerization and secondary cracking under high-temperature acid-catalyzed reaction conditions, which not only leads to a decrease in the selectivity of the target product isostearic acid, but also causes catalyst deactivation, reducing reaction efficiency and economy. Thirdly, the product system after isomerization reaction has a complex composition, making subsequent separation and purification difficult. Traditional purification methods such as urea inclusion method, conventional distillation method, or single low-temperature crystallization method generally have problems such as lengthy process flow, high energy consumption, or limited purification effect, and cannot efficiently obtain high-purity isostearic acid.

[0004] Zeolite catalysts, with their regular pore structure and tunable surface acidity, exhibit promising potential applications in fatty acid isomerization reactions. Among them, the hydrogen-form magnesium alkali zeolite obtained by acid treatment, with its two-dimensional cross-pore structure composed of ten-membered and eight-membered rings, has good shape-selective sieving potential for oleic acid molecules and is suitable for isomerization catalysis in the synthesis of isostearic acid. After optimization treatment such as ammonium modification, its catalytic isostearic acid yield can be improved to a certain extent. However, when this hydrogen-form magnesium alkali zeolite is used alone as a catalyst, it still has obvious defects: the acid sites on the outer surface are prone to initiating polymerization side reactions, the acid strength in the pores is difficult to control precisely, and the lack of metal active centers results in insufficient electronic control ability. These problems make its isomer selectivity, reaction stability, and adaptability to industrial-grade oleic acid feedstock unable to meet the ideal requirements of industrial production.

[0005] Therefore, developing a catalytic system that uses hydrogen-form magnesium alkali zeolite as a carrier, achieves spatial separation and functional synergy between acidic sites and metal active sites by introducing single-atom active centers, and constructing an integrated process that couples reaction microenvironment regulation with separation and purification is of great significance for breaking through the technical bottleneck of direct conversion of industrial-grade oleic acid to prepare high-purity isostearic acid. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst, its preparation method, and its application. First, magnesium alkali zeolite is acid-treated to obtain a hydrogen-form magnesium alkali zeolite support. Then, lanthanum single atoms are loaded onto the support using an impregnation-calcination method to obtain the hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst. Subsequently, industrial oleic acid, a water-based co-solvent, and a triphenylphosphine modifier are mixed with the catalyst, and an isomerization reaction is carried out under high temperature and high pressure conditions. The reaction product is then catalytically hydrogenated using a Ni / C catalyst, followed by low-temperature crystallization and vacuum distillation to obtain high-purity isostearic acid. Utilizing the shape-selective sieving effect of the two-dimensional cross-channels of the hydrogen-form magnesium alkali zeolite, the catalyst satisfies the single-molecule oleic acid requirement. The diffusion process inhibits bimolecular polymerization, while lanthanum single atoms coordinate and anchor with oxygen atoms on the support to form highly dispersed active centers. This unique electronic structure lowers the energy barrier for isomerization reactions, achieving synergistic catalysis between the acidic sites on the support and the active centers of the lanthanum single atoms. Furthermore, a strategy of selectively neutralizing acidic sites on the catalyst surface with triphenylphosphine and optimizing the mass transfer microenvironment with a water-based co-solvent is employed, creating a spatial division of labor where external side reactions are suppressed and internal catalytic reactions are promoted, effectively inhibiting polymerization side reactions. Simultaneously, by constructing an integrated process of isomerization-hydrogenation-low-temperature crystallization-reduced pressure distillation, the purity and yield of isostearic acid are significantly improved, and the resulting product exhibits excellent low-temperature fluidity, thermal stability, and antioxidant properties.

[0007] The first objective of this invention is to provide a hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst, wherein the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst comprises a hydrogen-form magnesium alkali zeolite support and a lanthanum single atom supported on the hydrogen-form magnesium alkali zeolite support. The hydrogen-form magnesium alkali zeolite carrier is prepared by acid treatment of magnesium alkali zeolite. The mass percentage of lanthanum single atoms in the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst is 0.2%-1%.

[0008] A second objective of this invention is to provide a method for preparing the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst, comprising the following steps: S1. Magnesium alkali zeolite is placed in an inorganic acid solution for acid treatment, and then separated, washed and dried to obtain hydrogen-form magnesium alkali zeolite support. S2. The hydrogen-form magnesium alkali zeolite support described in S1 is impregnated in a lanthanum source precursor solution, and then subjected to reduced pressure rotary evaporation, drying and calcination to obtain the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst.

[0009] In one embodiment of the present invention, in S1, the inorganic acid in the inorganic acid solution is selected from one or more of hydrochloric acid, nitric acid and sulfuric acid, and the concentration is 0.5 mol / L-1.5 mol / L; And / or, the acid treatment is performed at a temperature of 50°C-55°C for a time of 14-22 hours.

[0010] In one embodiment of the present invention, in S2, the lanthanum source in the lanthanum source precursor solution is selected from one or more of lanthanum nitrate, lanthanum chloride and lanthanum acetate, and the concentration is 0.005 mol / L-0.02 mol / L.

[0011] In one embodiment of the present invention, in S2, the drying temperature is 90°C-120°C and the time is 10h-14h; And / or, the calcination is carried out by heating to 350℃-450℃ at a rate of 3℃ / min-4℃ / min and calcining for 3h-5h.

[0012] A third objective of this invention is to provide the application of the aforementioned hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst in the catalytic preparation of isostearic acid from oleic acid, comprising the following steps: (1) Under a protective atmosphere, oleic acid, hydrogen-form magnesium alkali zeolite supported on lanthanum single-atom catalyst, water as a co-solvent and triphenylphosphine as a regulator are subjected to an isomerization reaction, and then filtered, washed and evaporated under reduced pressure to obtain isomerized oleic acid; (2) Under the action of a nickel-based catalyst, the iso-oleic acid described in step (1) is hydrogenated, and then filtered, crystallized at low temperature and distilled under reduced pressure to obtain the isostearic acid.

[0013] In one embodiment of the present invention, in step (1), the co-solvent is water; And / or, the regulator is triphenylphosphine; And / or, the mass ratio of the oleic acid, hydrogen-type magnesium alkali zeolite supported lanthanum single-atom catalyst, cosolvent and regulator is 100:(5-6):(3-4):(0.4-0.5).

[0014] In one embodiment of the present invention, in step (1), the temperature of the isomerization reaction is 170℃-175℃ and the time is 6h-7h.

[0015] In one embodiment of the present invention, in step (2), the nickel-based catalyst is a Ni / C catalyst; And / or, the mass ratio of the isomeric oleic acid to the nickel-based catalyst is 100:(0.5-1.5).

[0016] In one embodiment of the present invention, in step (2), the pressure of the hydrogenation reaction is 3.5 MPa-4.5 MPa, the temperature is 215℃-225℃, and the time is 3.5h-4.5h; And / or, the low-temperature crystallization temperature is -8°C to -10°C, the time is 10h to 12h, and the solvent is selected from one or more of n-hexane, heptane, and petroleum ether; And / or, the vacuum distillation is carried out under conditions of 130Pa-140Pa, collecting the fraction with a vapor phase temperature of 200℃-235℃.

[0017] The technical solution of the present invention has the following advantages compared with the prior art: (1) The catalyst described in this invention constructs lanthanum single atoms on a hydrogen-type magnesium alkali zeolite support. By utilizing the strong coordination between lanthanum atoms and oxygen atoms in the zeolite framework, lanthanum is anchored to the inner surface of the pores in the form of single atoms. As Lewis acid sites, lanthanum single atoms form a synergistic acid system with the Brønsted acid sites of the zeolite itself. On the one hand, the acid intensity distribution in the pores is adjusted through electronic effects, reducing the activation energy of carbocation rearrangement of oleic acid molecules in the pores. On the other hand, the introduction of lanthanum single atoms does not change the original pore confinement size of the zeolite, and still maintains the geometric inhibition effect on the bimolecular polymerization reaction. Relying on this "pore confinement + dual acid synergy" mechanism, this invention can still significantly improve the isomerization selectivity under industrial-grade oleic acid raw material conditions.

[0018] (2) The application described in this invention uses triphenylphosphine as a regulator. Its molecular diameter is larger than the pore size of the ten-membered and eight-membered rings of magnesium alkali zeolite. It neutralizes only the acidic sites on the outer surface of the catalyst and effectively inhibits the polymerization side reactions initiated on the outer surface. At the same time, water is used as a co-solvent. Water molecules can freely enter the pores, promote the generation and regeneration of Brønsted acid sites, and enhance the catalytic activity in the pores. The two act on different spatial regions of the catalyst respectively, forming a "external inhibition and internal promotion" synergistic effect, inhibiting the polymerization side reactions on the outer surface, strengthening the isomerization reaction in the pores, and thus improving the selectivity and yield of the target product isostearic acid as a whole.

[0019] (3) In the separation and purification process constructed by the application described in this invention, the low-temperature crystallization step utilizes the characteristic that the difference in solubility between isostearic acid and straight-chain saturated acid in n-hexane is significantly increased at low temperatures, and prioritizes the removal of straight-chain saturated acid; the vacuum distillation step further removes low-boiling-point impurities based on the difference in boiling points between γ-stearin lactone, decarboxylation products, etc. and isostearic acid. The two-step purification mechanism complements each other for different types of impurities, achieving a balance between high purity and high yield of isostearic acid.

[0020] (4) The application described in this invention promotes selective skeletal rearrangement of oleic acid carbon chains in the two-dimensional cross-channels of magnesium-alkali zeolite by precisely controlling the pore confinement effect and the dual-acid synergistic catalytic mechanism in the isomerization reaction, generating isomerized products with uniformly distributed methyl branches; then, through a hydrogenation reaction, the unsaturated bonds are completely saturated to obtain a mixture of monomethyl branched saturated fatty acids, namely isostearic acid. This product relies on the dual molecular design of branched structure and saturated carbon chain, and the intermolecular van der Waals forces and crystal packing density are significantly reduced, thus exhibiting excellent low-temperature fluidity; at the same time, the fully saturated carbon chain eliminates the starting point of oxidation degradation, giving the product outstanding thermal stability and antioxidant properties, enabling it to have both low freezing point and high anti-degradation ability in a wide temperature range, effectively avoiding the defects of high melting point of traditional straight-chain saturated acids and heat sensitivity of unsaturated acids. Attached Figure Description

[0021] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 The XRD patterns of different catalysts in this invention are shown below. Figure 2 Here are SEM images of different catalysts used in this invention; Figure 3 Here are the FT-IR spectra of different catalysts used in this invention; Figure 4 Py-FT-IR for different catalysts of this invention; Figure 5 Thermogravimetric analysis curves of different catalysts of this invention; Figure 6This is a HAADF-STEM image of the hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst of the present invention. Figure 7 This is an FT-IR comparison image of oleic acid of the present invention and isostearic acid obtained in Application Example 1; Figure 8 The isostearic acid obtained in Example 1 of this invention 1 H NMR spectrum; Figure 9 Thermogravimetric analysis curve of isostearic acid obtained in Example 1 of this invention; Figure 10 This is the FT-IR spectrum of trimethylolpropane triisostearate of the present invention; Figure 11 This is the mass spectrum of trimethylolpropane triisostearate of the present invention; Figure 12 Thermogravimetric analysis curve of trimethylolpropane triisostearate of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention. Example 1

[0023] The hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst and its preparation method in this embodiment specifically include the following steps: S1, potassium-type magnesium alkali zeolite (K + -Ferr) was placed in a 1.0 mol / L hydrochloric acid solution, with the acid volume controlled to be 4 times the mass of the zeolite. The mixture was stirred at a constant temperature of 52℃ for 18 h. After the reaction was complete, the mixture was centrifuged. The obtained solid was washed repeatedly with deionized water until the washings were neutral, and then dried at 70℃ for 18 h to obtain hydrogen-form magnesium alkali zeolite (H). + -Ferr) carrier; S2. Weigh 10.0 g of hydrogen-form magnesium alkali zeolite support and add it to 100 mL of 0.01 mol / L lanthanum nitrate aqueous solution. Stir magnetically at room temperature for 10 h to allow the lanthanum precursor to be fully adsorbed on the support surface and in the pores. After impregnation, remove most of the solvent by rotary evaporation under reduced pressure at 80 °C. Dry the resulting solid at 100 °C for 12 h. Then place the dried sample in a muffle furnace and heat it to 400 °C at a rate of 3.5 °C / min in air atmosphere and calcine it at a constant temperature for 4 h. Cool it naturally to room temperature to obtain a hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst with a lanthanum single-atom mass ratio of 0.5%. Comparative Example 1

[0024] It is basically the same as Example 1, except that it does not support lanthanum single atoms. Comparative Example 2

[0025] The basic method is the same as in Example 1, except that potassium-type magnesium alkali zeolite is replaced with ZSM-5 zeolite. Application Example 1

[0026] The application of the hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst in the catalytic preparation of isostearic acid from oleic acid in this application example specifically includes the following steps: (1) Weigh 50g of industrial grade oleic acid and add it to a high-pressure reactor. Then, add the catalyst prepared in Example 1, deionized water and triphenylphosphine in a mass ratio of 100:5.3:3.3:0.424 and stir to mix evenly. After sealing the reactor, purge the air in the reactor with nitrogen gas. Then, heat the reactor to 173.5℃ and react at a constant temperature for 6.8h with stirring. After the reaction is completed, cool the reactor to below 50℃, take out the reaction liquid and filter it. Wash the filter cake with n-hexane. Combine the filtrate and the washing liquid, and then remove the solvent by rotary evaporation under reduced pressure at 40℃ to obtain crude isomeric oleic acid. (2) Crude isomeric oleic acid was added to a high-pressure reactor, and Ni / C catalyst was added at a mass ratio of 100:1. The reaction was carried out under hydrogen pressure of 4 MPa and a reaction temperature of 220 °C for 4 h. After the reaction, the mixture was cooled to about 70 °C, and the catalyst was removed by filtration to obtain crude isostearic acid. Hexane was added to the crude product, and the mass ratio of hexane to crude product was controlled at 2.2:1. After mixing evenly, the mixture was cooled to -9.5 °C and kept at that temperature for 11 h for low-temperature crystallization. The liquid phase product was collected after separation of the crystals. The liquid phase product was then subjected to vacuum distillation. The fraction with a gas phase temperature of 208℃-230℃ was collected under a vacuum of 135Pa to obtain high-purity isostearic acid; the oleic acid conversion rate reached 97.25%, and the isostearic acid yield was 82.92%; after the catalyst was regenerated and reused once, the conversion rate was 96.8% and the yield was 82.88%; after being reused twice, the conversion rate was 96.17% and the yield was 82.41%; after being reused five times, the conversion rate was 87.76% and the yield was 77.05%; after being reused ten times, the conversion rate was 86.76% and the yield was 75.7%. Comparative Application Example 1

[0027] The application is basically the same as in Example 1, except that the catalyst prepared in Example 1 is replaced with the catalyst prepared in Comparative Example 1.

[0028] The results showed that the oleic acid conversion rate reached 95.62% and the isostearic acid yield was 82.35%. After one reuse, the isostearic acid yield dropped to 60.76%, and after two reuses, the yield plummeted to 31.65%. This is because the acid sites on the surface and in the pores of the hydrogen-form magnesium alkali zeolite support without lanthanum single atoms are easily adsorbed and covered by byproducts such as dimer acids, and conventional cleaning is difficult to restore the catalyst activity. However, the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst prepared in Example 1 of this invention has the mechanism that the lanthanum single atoms are stably anchored by coordination with oxygen in the zeolite framework, which not only enhances the resistance of acid sites to loss, but also forms a synergistic acidic system with the zeolite, so that the effective active centers in the pores can still maintain catalytic function after regeneration. Comparative Application Example 2

[0029] The application is basically the same as in Example 1, except that the catalyst prepared in Example 1 is replaced with the catalyst prepared in Comparative Example 2.

[0030] The results showed that the isostearic acid yield was 35.48%. This is because ZSM-5 has a 5.5 Å-5.6 Å straight-through pore structure and lacks a two-dimensional cross-confined structure, making it easy for oleic acid molecules to undergo intermolecular collision polymerization within the pores. In contrast, the magnesium alkali zeolite used in Application Example 1 has a unique two-dimensional pore structure with perpendicularly intersecting ten-membered rings (4.2 Å × 5.4 Å) and eight-membered rings (3.5 Å × 4.8 Å). This structure provides ample space for the diffusion of oleic acid molecules and, through the cross-configuration, forms a geometric confinement for the bimolecular polymerization reaction, effectively suppressing side reactions. This indicates that the unique pore topology of magnesium alkali zeolite and the synergistic effect of the lanthanum single atom are key to achieving high selectivity for isostearic acid. Comparative Application Example 3

[0031] The application is basically the same as in Example 1, except that deionized water is not introduced.

[0032] The results showed that the yield of isostearic acid was 57.56%. This is because without the introduction of deionized water, the proportion of Lewis acid sites in the zeolite channels was too high, and the carbocation intermediates were prone to polymerization, cracking and other side reactions, and it was difficult to effectively desorb and generate branched products. However, the deionized water introduced in Example 1 played two key roles: First, water formed an "internal promotion" mechanism in the magnesium-alkali zeolite channels. Water molecules (approximately 2.8 Å in diameter) could freely enter the channels, converting Lewis acid sites into Brønsted acid sites, and undergoing proton exchange with the carbocation intermediates, promoting the generation and desorption of branched products. This mechanism worked synergistically with the "external inhibition" mechanism of triphenylphosphine used in this invention. The diameter of the triphenylphosphine molecule is larger than that of the channels, and it only neutralizes the acid sites on the outer surface and inhibits the polymerization side reactions on the outer surface. The two formed a synergistic spatial selectivity regulation, effectively improving the selectivity and yield of isostearic acid. Comparative Application Example 4

[0033] The application is basically the same as in Example 1, except that triphenylphosphine is replaced with pyridine.

[0034] The results showed that the oleic acid conversion rate was 31.11% and the isostearic acid yield was 2.62%. This is because the diameter of pyridine molecules, approximately 3.25 Å × 6.25 Å × 6.5 Å, can enter the 4.2 Å × 5.4 Å ten-membered ring channels of magnesium alkali zeolite, poisoning both the acidic sites inside and outside the channels, leading to a severe loss of catalytic activity. The degree of poisoning intensifies with the increase of pyridine addition. In contrast, the triphenylphosphine introduced in Example 1 has a molecular diameter of approximately 8.5 Å-9.5 Å, which is larger than the size of the ten-membered and eight-membered ring channels of magnesium alkali zeolite. It can only neutralize the acidic sites on the outer surface of the catalyst, effectively inhibiting the polymerization side reactions initiated on the outer surface. Test Example 1

[0035] X-ray diffraction (XRD) was used to characterize the crystal structure of catalysts under different treatment states. Cu Kα rays (λ=0.15406nm) were used with a tube voltage of 40kV, a tube current of 40mA, a scanning range of 5°-80°, a step size of 0.02°, and a scanning speed of 4° / min. The crystal structures of potassium-type magnesium alkali zeolite (K...) were tested. + -Ferr), hydrogen-type magnesium alkali zeolite (H + XRD spectra of the following catalysts are shown: (Ferr), Lanthanum single-atom catalysts supported on MgO-form zeolite after regeneration and reuse once; Lanthanum single-atom catalysts supported on MgO-form zeolite after regeneration and reuse five times; and a heat-treated Lanthanum single-atom catalyst supported on MgO-form zeolite (prepared by calcining the Lanthanum single-atom catalyst supported on MgO-form zeolite after reuse five times in an air atmosphere in a muffle furnace at a heating rate of 3.5℃ / min to 450℃ for 4 hours, followed by acid treatment). The results are as follows: Figure 1 As shown. From Figure 1It can be seen that the characteristic diffraction peak positions at 2θ of all samples are consistent, which is highly consistent with the standard spectrum of magnesium-alkali zeolite. This confirms that the aluminosilicate tetrahedral framework structure of magnesium-alkali zeolite was not destroyed during acid treatment, repeated use, and high-temperature calcination, and the crystal structure is stable. After five regenerations, the intensity of each characteristic diffraction peak decreased significantly, reflecting the adsorption of organic byproducts such as dimer acids on the catalyst surface, which slightly affected the order of the crystal surface. However, after calcination at 450℃, the diffraction peak intensity recovered significantly to the level of the catalyst after one regeneration, which was significantly higher than that of the catalyst after five regenerations. This indicates that the adsorbed organic matter on the surface... Impurities can be effectively removed through high-temperature calcination. The mechanism lies in the fact that magnesium-alkali zeolite is a stable framework formed by SiO4 and AlO4 tetrahedra connected by strong covalent bonds. It has high bond energy, excellent acid resistance and thermal stability, and can withstand acid treatment during the regeneration process and calcination at 450℃ without phase change or framework collapse. This structural stability is the fundamental reason why the catalyst can be regenerated more than 10 times and still maintain high catalytic activity. The complete framework ensures that the shape-selective sieving function of the pores continues to be performed. The phenomenon of peak intensity recovery after calcination fully confirms from the crystal structure level that the catalyst of this invention has both excellent structural stability and regenerable surface cleanliness. Test Example 2

[0036] The microstructure of catalysts under different treatment conditions was characterized using a Hitachi S-4800 field emission scanning electron microscope. After drying, the samples were sputter-coated with gold, with accelerating voltages ranging from 10 kV to 40 kV, yielding potassium-type magnesium alkali zeolite (K... + -Ferr), hydrogen-type magnesium alkali zeolite (H + SEM images of the hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst (Ferr), after regeneration and reuse once, after regeneration and reuse five times, and after heat treatment of the hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst are shown below. Figure 2 As shown. From Figure 2 It can be seen that all samples retain the typical platy crystal morphology of magnesium-alkali zeolite. Acid treatment will reduce K... + Type conversion to H +After regeneration, the crystal morphology and structure did not change significantly, indicating that magnesium-alkali zeolite possesses excellent acid resistance. After one regeneration, a small amount of loose film / granular deposits appeared on the catalyst surface. After five regenerations, the deposits increased significantly and covered most of the crystal surface. These deposits are mainly organic byproducts such as dimer acids generated in the reaction, which hinder oleic acid molecules from entering the catalyst channels through steric hindrance, directly causing the decrease in catalytic activity. However, after heat treatment at 450℃, the deposits on the catalyst surface were completely removed, and the plate-like crystal morphology was restored to a state close to that of a fresh catalyst. Combined with XRD characterization results, it can be confirmed that high-temperature treatment only removes surface organic impurities and does not destroy the zeolite framework structure. In summary, SEM characterization directly reveals the structural stability and deactivation-regeneration mechanism of the catalyst from the microscopic morphology level: the excellent acid resistance and thermal stability of magnesium-alkali zeolite enable it to maintain a complete plate-like crystal structure during acid treatment and calcination at 450℃; the catalyst activity decay is due to the accumulation of surface byproducts rather than framework destruction, and calcination at 450℃ can effectively remove deposits and restore catalytic activity. The SEM and XRD results corroborate each other, providing direct morphological evidence that the catalyst can be regenerated more than 10 times while maintaining high activity, which is different from ordinary catalysts in the prior art that are difficult to regenerate due to pore blockage or framework collapse. Test Example 3

[0037] Infrared spectroscopy was used to study potassium-type magnesium alkali zeolite (K... + -Ferr), hydrogen-type magnesium alkali zeolite (H + Infrared spectroscopy characterization was performed on hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalysts that were reused once after regeneration, hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalysts that were reused five times after regeneration, and heat-treated hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalysts. Samples were prepared using the KBr pellet method, with a scanning range of 4000 cm⁻¹. -1 -500cm -1 The result is as follows Figure 3 As shown. From Figure 3 It can be seen that 1240cm -1 1082cm -1 795cm -1 596cm -1 The characteristic peaks of the magnesium-alkali zeolite framework were stable in all samples with no shift in peak position and minimal intensity fluctuation, indicating that the aluminosilicate tetrahedral framework structure of magnesium-alkali zeolite remained intact after acid treatment, multiple regenerations, and high-temperature calcination, exhibiting excellent acid resistance and thermal stability; Meanwhile, the 2928 cm⁻¹ peak... -1 2854cm -1 The methylene stretching vibration peak at 1712 cm⁻¹ is similar to that at 1712 cm⁻¹. -1The carbonyl characteristic peak at the point is a characteristic peak of fatty acids. This type of peak has no obvious signal in the hydrogen-form magnesium alkali zeolite sample, but it begins to appear after one regeneration and its intensity increases significantly after five regenerations. This confirms that fatty acid adsorbates on the catalyst surface (inferred from the reaction background to be mainly dimer acids generated in the reaction) gradually accumulate with the number of uses. These adsorbates hinder substrate molecules from contacting the active sites, rather than destroying the zeolite framework structure. After heat treatment at 450℃, the intensity of the fatty acid characteristic peak drops significantly, approaching the level of the hydrogen-form magnesium alkali zeolite sample. This proves that high-temperature calcination can effectively remove organic impurities adsorbed on the catalyst surface, restore the accessibility of the active sites, and achieve catalyst activity regeneration. Test Example 4

[0038] Based on test example 3, pyridine adsorption Fourier transform infrared spectroscopy (Py-FT-IR) was used to analyze potassium-type magnesium alkali zeolite (K... + -Ferr), hydrogen-type magnesium alkali zeolite (H + -Ferr), hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalysts that were reused once after regeneration, hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalysts that were reused five times after regeneration, and heat-treated hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalysts were characterized for acidity. The results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the acidity of potassium-type magnesium alkali zeolite is significantly enhanced after acidification to the hydrogen form; H⁺-Ferr at 1544 cm⁻¹ -1 It exhibits a distinct Brønsted acid (B acid) characteristic absorption peak at 1490 cm⁻¹. -1 The presence of a mixed characteristic absorption peak of Brønsted acid and Lewis acid (L acid) at 1544 cm⁻¹ confirms that acidification successfully introduced a large number of Brønsted acid sites and constructed a dual-acidic system. With increasing catalyst reuse cycles, the peak at 1544 cm⁻¹... -1 With 1490cm -1 The intensity of the characteristic peaks at the acid sites gradually and significantly decreased, and after three regenerations, the relevant absorption peaks had basically disappeared, indicating that the acidity of the catalyst was greatly weakened, and the corresponding catalytic activity was also basically lost. This result is the first direct confirmation from the perspective of acid site evolution that the fundamental reason for the poor reusability of ordinary hydrogen-type magnesium alkali zeolite without lanthanum loading is the loss of active acid sites, rather than pore blockage or framework structure destruction. This is consistent with the conclusion in the previous characterization that "after multiple regenerations, the zeolite framework is intact, and only organic by-products are adsorbed on the surface". Test Example 5

[0039] Thermogravimetric analysis (TGA) was used to analyze the hydrogen-form magnesium alkali zeolite (H). + The samples were characterized (-Ferr), regenerated once, regenerated five times, dimer acid, and isomeric oleic acid. The results are as follows: Figure 5 As shown. From Figure 5 It can be seen that fresh H +The weight loss of the catalyst mainly occurred before 200℃, corresponding to the desorption of physically adsorbed water on the surface and in the pores. The mass remained basically constant within the 200℃-800℃ range, with no significant weight loss, demonstrating the stable skeletal structure and excellent thermal stability of the catalyst, providing a reliable structural basis for multiple high-temperature regenerations. The weight loss curves of the catalyst after one and five regenerations both showed two significant stages: the first stage (35℃-200℃) involved the desorption of physically adsorbed water and a small amount of isostearic acid oxidation (isostearic acid decomposition temperature is approximately 160℃); the second stage (200℃-550℃) involved the oxidation decomposition of dimer acid adsorbed on the catalyst surface (dimer acid decomposition temperature is above 200℃), directly confirming that the surface deposits of the regenerated catalyst were mainly dimer acid. As the number of regenerations increased from one to five, the proportion of weight loss in the second stage gradually increased, providing the first quantitative thermogravimetric evidence of the continuous accumulation of byproducts such as dimer acid on the catalyst surface. This accumulation increases the diffusion resistance of oleic acid and hinders the contact of active sites with the substrate, which is the fundamental reason for the decrease in catalytic activity with increasing usage. This result is consistent with infrared spectroscopy (…). Figure 3 The characteristic peaks of fatty acids in the middle increase with the number of regenerations), pyridine infrared ( Figure 4 The decrease in acidic sites with each regeneration and the evaluation of catalytic activity (yield decreases with each regeneration) corroborate each other, forming a complete chain of technical evidence: the catalyst skeleton is stable (no weight loss at 200℃-800℃), deactivation originates from the accumulation of dimer acid (weight loss increases with each regeneration at 200℃-550℃), and high-temperature calcination at 450℃ can effectively remove surface adsorbates, thus achieving catalyst regeneration. Test Example 6

[0040] The atomic-resolution structure of the hydrogen-form magnesium alkali zeolite-supported lanthanum single-atom catalyst prepared in Example 1 was characterized using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with energy dispersive X-ray spectroscopy (EDS). The sample was first ultrasonically dispersed in anhydrous ethanol, then dropped onto an ultrathin carbon film copper mesh. HAADF-STEM images with a scale bar of 3 nm were acquired under an accelerating voltage of 200 kV–300 kV, and point-to-point EDS energy dispersive spectroscopy analysis was performed on the bright spots in the images. The results are as follows: Figure 6 As shown. From Figure 6 It can be seen that a large number of isolated and uniform high-brightness white spots are distributed, with a diameter of about 0.2nm-0.5nm, which is much smaller than the 3nm scale. No lanthanum nanoparticles or clusters were observed throughout the process. The above results indicate that lanthanum is anchored to the hydrogen-type magnesium alkali zeolite support in the form of single atoms and achieves atomic-level highly uniform dispersion. This is because lanthanum ions can achieve stable anchoring by forming strong coordination with oxygen atoms in the zeolite framework. At the same time, the precise control of the lanthanum precursor concentration of 0.01mol / L and the calcination temperature of 400℃ in the impregnation-calcination process effectively avoids the migration and aggregation of lanthanum species on the support surface. Test Example 7

[0041] Infrared spectroscopy was used to characterize the raw material oleic acid and the high-purity isostearic acid prepared in Example 1. The results are as follows: Figure 7 As shown. From Figure 7 It can be seen that the raw material oleic acid is at 3007cm -1 The characteristic peak of unsaturated CH stretching vibration exists at 2956 cm⁻¹, while this characteristic peak has completely disappeared in the isostearic acid sample, indicating that the unsaturated double bond in the oleic acid molecule is completely saturated by the hydrogenation reaction, and the product has excellent antioxidant stability; the isostearic acid sample shows a peak at 2956 cm⁻¹. -1 With 1378cm -1 The methyl characteristic peak at 724 cm⁻¹ is significantly enhanced compared to that of the raw material oleic acid. -1 The significant weakening of the characteristic peaks of the long-chain straight-chain oleic acid indicates that methyl branches were successfully introduced into the carbon chain of oleic acid, and the straight-chain structure was effectively broken, giving the product good low-temperature fluidity. Furthermore, the isostearic acid sample showed a peak at 1712 cm⁻¹. -1 The characteristic peaks of the carboxyl carbonyl group are still intact, confirming that the carboxyl structure was not destroyed during isomerization and hydrogenation, ensuring that the product has high reactivity. The infrared spectroscopy results clearly verify the directional conversion of oleic acid to isostearic acid at the molecular structure level. Test Example 8

[0042] The high-purity isostearic acid prepared in accordance with Example 1 was subjected to... 1 Characterization was performed using 1H NMR with deuterated chloroform as solvent and tetramethylsilane as internal standard. Spectra were acquired using a 400MHz NMR spectrometer. The results are as follows: Figure 8 As shown. From Figure 8 It can be seen that a triplet peak appears at δ 2.35-2.40, corresponding to the two hydrogens of -CH2COOH, proving that the carboxyl structure of the product is completely preserved; a multiplet peak appears at δ 1.57-1.78, corresponding to the three hydrogens of -CH(CH3)- and -CH2CH2COOH; a multiplet peak appears at δ 0.84-0.92, corresponding to -CH3 with an integral area of ​​about 6H, which is significantly stronger than the signal of the terminal methyl group of straight-chain stearic acid (about 3H), directly confirming that the carbon chain successfully introduced methyl branches and the degree of branching is high; no olefin proton signal was seen in the δ 5.3-5.5 range across the entire spectrum, indicating that the hydrogenation reaction was complete and the product is a fully saturated fatty acid; the above 1 HNMR results directly confirm at the molecular structure level that, relying on the pore confinement and dual-acid synergistic mechanism of lanthanum single-atom catalyst supported on hydrogen-form magnesium alkali zeolite, combined with the regulation strategy of external suppression of side reactions by triphenylphosphine and internal catalytic promotion by water-co-solvent, it is possible to achieve highly selective and high-purity directional conversion of industrial-grade oleic acid to methyl branched isostearic acid. Test Example 9

[0043] A Mettler-Toledo TGA / 1100SF thermogravimetric analyzer was used. 5 mg of the high-purity isostearic acid sample prepared in Example 1 was weighed and heated from room temperature to 600 °C at a heating rate of 10 °C / min under a nitrogen atmosphere (flow rate of 20 mL / min). The results are as follows: Figure 9 As shown. From Figure 9 It can be seen that isostearic acid exhibits a clear constant-weight plateau before the initial oxidation-decomposition temperature, which is approximately 160℃, much higher than that of ordinary unsaturated oleic acid (approximately 80℃-120℃), indicating that the product has excellent thermal stability and a wide range of antioxidant temperatures. The TG curve shows a single continuous decomposition characteristic without multi-stage impurity decomposition steps, confirming the high purity of the product. The sample was completely decomposed with no ash residue, confirming that it does not contain non-decomposable inorganic impurities. This result is due to the complete saturation of the unsaturated bonds in the isostearic acid molecule through hydrogenation, eliminating the starting point of oxidation degradation, and the introduction of methyl branches without destroying the overall thermal stability of the carbon chain, allowing it to remain stable for a long time below 160℃, meeting the demanding application requirements of high-temperature lubricants, cosmetic heat processing, and other similar scenarios. Test Case 10

[0044] Using the high-purity isostearic acid prepared in Application Example 1 as a raw material, trimethylolpropane triisostearate was prepared by esterification reaction, specifically including the following steps: (1) Weigh sodium-based montmorillonite (Na⁺-MMT) and add it to a single-necked round-bottom flask. Add nitric acid solution with a concentration of 2 mol / L at a liquid-to-solid ratio of 10 mL / g and acidify it in a constant temperature water bath at 50℃ for 12 h. After cooling to room temperature, centrifuge and wash with deionized water until the filtrate is neutral. Then dry it in an oven at 110℃ for 12 h to obtain hydrogen-form montmorillonite (H-MMT). (2) Weigh the high-purity isostearic acid prepared in Example 1 and place it in a three-necked flask. Add trimethylolpropane at an acid-to-alcohol molar ratio of 5:1. Heat and stir until it is completely dissolved. Then add 1% of hydrogen montmorillonite by mass of isostearic acid. Under nitrogen purging protection and to remove the water generated by the reaction, heat to 180°C and react for 6 hours. After the reaction is completed, cool to room temperature, add a small amount of n-hexane and filter. The filtrate is evaporated under reduced pressure to obtain the crude product. Transfer the crude product to a three-necked flask and set up a reduced pressure distillation apparatus. Under nitrogen protection, control the vacuum degree to about 135 Pa and the gas phase temperature to no more than 200°C. Remove excess isostearic acid by reduced pressure distillation until no liquid distills out. The remaining liquid in the flask is trimethylolpropane triisostearate.

[0045] Infrared spectroscopy characterization of trimethylolpropane triisostearate yielded the following results: Figure 10 As shown. From Figure 10 It can be seen that the product is at 3300cm -1 -2500cm -1The broad peak of the free carboxyl group -OH completely disappeared, and the peak at 1712 cm⁻¹ in the raw material... -1 The characteristic peak of the carboxyl group C=O shifted to 1745 cm⁻¹ -1 It exhibits a strong characteristic absorption peak at the C=O group of the ester group, and also shows a peak at 1239 cm⁻¹. -1 and 1116cm -1 The newly observed double peaks of asymmetric and symmetric stretching vibrations of the ester group COC, along with the three characteristic peaks, constitute the complete infrared fingerprint spectrum of the ester compound, confirming that the carboxyl group of isostearic acid reacts fully with the hydroxyl group of trimethylolpropane and that the esterification conversion rate is high.

[0046] The molecular weight and structure of trimethylolpropane triisostearate were characterized by electrospray ionization-time-of-flight mass spectrometry (TOF MS ES+). The product was dissolved in a methanol / chloroform mixed solvent, and mass spectrometry signals were acquired in positive ion mode, with a scan range of m / z 100-1500. The results are as follows. Figure 11 As shown. From Figure 11 It can be seen that [M+NH4] has a m / z of 951.1. + The quasi-molecular ion peak corresponds to a product molecular weight of 933.1, which highly matches the theoretical molecular weight of trimethylolpropane triisostearate (933.7), precisely confirming that the product is a triester structure formed by the complete esterification of one molecule of trimethylolpropane and three molecules of isostearic acid. Simultaneously, no characteristic peaks of low molecular weight impurities such as free isostearic acid, monoesters, or diesters were detected, indicating that the product has high purity after vacuum distillation purification, consistent with infrared spectroscopy (…). Figure 10 The complete disappearance of the carboxyl characteristic peak in the product further confirms that the target product has a complete structure and excellent purity.

[0047] A Mettler-Toledo TGA / 1100SF thermogravimetric analyzer was used. 5 mg of trimethylolpropane triisostearate sample was weighed and heated from room temperature to 600 °C at a heating rate of 10 °C / min under a nitrogen atmosphere (flow rate of 20 mL / min). Thermogravimetric analysis was performed on the trimethylolpropane triisostearate. The results are as follows: Figure 12 As shown. From Figure 12 It can be seen that the sample only loses a small amount of weight before 300℃, corresponding to the removal of residual free isostearic acid and water. When the temperature rises to 320℃, there is a clear weight loss step, which is the main decomposition temperature of the triester. It is basically completely decomposed at 400℃. This curve shows that the thermal decomposition temperature of trimethylolpropane triisostearate is higher than 300℃, and its thermal stability is significantly better than that of traditional straight-chain saturated esters and unsaturated esters.

[0048] In summary, the trimethylolpropane triisostearate synthesized from the high-purity isostearic acid prepared in Application Example 1 has excellent properties due to the unique branched saturated structure of isostearic acid: the methyl branches can reduce the intermolecular forces of esters, making the pour point of the product as low as -20℃, while increasing the gyration radius of the molecules in the shear field, raising the viscosity index to 143, and ensuring that the product has excellent lubrication properties over a wide temperature range; the saturated carbon chains can effectively inhibit the high-temperature oxidative degradation of esters, and the thermal decomposition temperature can reach above 320℃. The methyl branch imparts a low pour point to the product without compromising the thermal stability of the ester bond, while the saturated carbon chain eliminates the inducing factors of oxidative degradation. This allows the triester to maintain its structural integrity below 300°C, meeting the temperature requirements of cosmetic processing (typically <100°C) and lubricant use (long-term operating temperature <200°C, short-term up to 300°C). Therefore, the synthesized trimethylolpropane triisostearate combines a low pour point with high antioxidant properties, demonstrating significant advantages in fields such as lubricants and cosmetics where low-temperature fluidity and high-temperature stability are critical. This provides key performance support for its widespread application in high-performance lubricating materials and heat-resistant cosmetics.

[0049] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst, characterized in that, The hydrogen-type magnesium alkali zeolite supported lanthanum single-atom catalyst includes a hydrogen-type magnesium alkali zeolite support and lanthanum single atoms supported on the hydrogen-type magnesium alkali zeolite support. The hydrogen-form magnesium alkali zeolite carrier is prepared by acid treatment of magnesium alkali zeolite. The mass percentage of lanthanum single atoms in the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst is 0.2%-1%.

2. A method for preparing the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst as described in claim 1, characterized in that, Includes the following steps: S1. Magnesium alkali zeolite is placed in an inorganic acid solution for acid treatment, and then separated, washed and dried to obtain hydrogen-form magnesium alkali zeolite support. S2. The hydrogen-form magnesium alkali zeolite support described in S1 is impregnated in a lanthanum source precursor solution, and then subjected to reduced pressure rotary evaporation, drying and calcination to obtain the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst.

3. The method for preparing the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst according to claim 2, characterized in that, In S1, the inorganic acid in the inorganic acid solution is selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid, and the concentration is 0.5 mol / L-1.5 mol / L; And / or, the acid treatment is performed at a temperature of 50°C-55°C for a time of 14-22 hours.

4. The method for preparing the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst according to claim 2, characterized in that, In S2, the lanthanum source in the lanthanum source precursor solution is selected from one or more of lanthanum nitrate, lanthanum chloride, and lanthanum acetate, with a concentration of 0.005 mol / L to 0.02 mol / L.

5. The method for preparing the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst according to claim 2, characterized in that, In S2, the drying temperature is 90℃-120℃ and the time is 10h-14h; And / or, the calcination is carried out by heating to 350℃-450℃ at a rate of 3℃ / min-4℃ / min and calcining for 3h-5h.

6. The application of the hydrogen-form magnesium alkali zeolite supported lanthanum single-atom catalyst as described in claim 1 in the catalytic preparation of isostearic acid from oleic acid, characterized in that, Includes the following steps: (1) Under a protective atmosphere, oleic acid, hydrogen-form magnesium alkali zeolite supported on lanthanum single-atom catalyst, water as a co-solvent and triphenylphosphine as a regulator are subjected to an isomerization reaction, and then filtered, washed and evaporated under reduced pressure to obtain isomerized oleic acid; (2) Under the action of a nickel-based catalyst, the iso-oleic acid described in step (1) is hydrogenated, and then filtered, crystallized at low temperature and distilled under reduced pressure to obtain the isostearic acid.

7. The application according to claim 6, characterized in that, In step (1), the co-solvent is water; And / or, the regulator is triphenylphosphine; And / or, the mass ratio of the oleic acid, hydrogen-type magnesium alkali zeolite supported lanthanum single-atom catalyst, cosolvent and regulator is 100:(5-6):(3-4):(0.4-0.5).

8. The application according to claim 6, characterized in that, In step (1), the isomerization reaction is carried out at a temperature of 170℃-175℃ for 6h-7h.

9. The application according to claim 6, characterized in that, In step (2), the nickel-based catalyst is a Ni / C catalyst; And / or, the mass ratio of the isomeric oleic acid to the nickel-based catalyst is 100:(0.5-1.5).

10. The application according to claim 6, characterized in that, In step (2), the hydrogenation reaction is carried out at a pressure of 3.5 MPa-4.5 MPa, a temperature of 215℃-225℃, and a time of 3.5h-4.5h. And / or, the low-temperature crystallization temperature is -8°C to -10°C, the time is 10h to 12h, and the solvent is selected from one or more of n-hexane, heptane, and petroleum ether; And / or, the vacuum distillation is carried out under conditions of 130Pa-140Pa, collecting the fraction with a vapor phase temperature of 200℃-235℃.

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