Process for the preparation of high purity dipentaerythritol

Abstract

The application provides a preparation method of high-purity dipentaerythritol, and belongs to the field of chemical synthesis, wherein a dipentaerythritol intermediate is obtained by reacting pentaerythritol with a hydroxyl protecting agent; the dipentaerythritol intermediate is subjected to a hydrolysis reaction under acidic conditions to obtain dipentaerythritol. The application realizes high-selectivity synthesis of dipentaerythritol by using pentaerythritol as a raw material and through a strategy of specific protection of hydroxyl groups, condensation and deprotection. Compared with a traditional formaldehyde-acetaldehyde alkaline catalysis condensation process, the application regulates the selectivity of the reaction from the source, significantly reduces the generation of complex structure acetal by-products and poly-pentaerythritol, significantly improves the purity of the product, and reduces the separation burden of the subsequent product; meanwhile, the reaction condition is mild, the operation is simple, and the application has good industrial application prospect and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, specifically to a method for preparing high-purity pentaerythritol. Background Technology

[0002] Dipentaerythritol is a high-value-added hexaol and a key intermediate in the manufacture of high-end synthetic lubricants, UV-curable materials, flame retardants, and high-performance polymer additives. Because its market value is far higher than that of ordinary industrial pentaerythritol, developing highly selective synthesis processes has always been a core objective of industry research.

[0003] The mainstream industrial process for synthesizing dipentaerythritol involves the condensation of formaldehyde and acetaldehyde under conditions where alkali metal or alkaline earth metal hydroxides are used as catalysts. This reaction is essentially a complex tandem network reaction. Under conventional process conditions, the yield of dipentaerythritol is low, while the byproduct of polypentaerythritol is significant. At the same time, the reaction process is extremely sensitive to the molar ratio of raw materials, the feeding method, the mixing efficiency, and temperature control. If not properly controlled, it is easy to cause excessive condensation, generating a large amount of polypentaerythritol and acetal byproducts with complex structures that are difficult to process. It is difficult to control the selectivity of the reaction from the source to maximize the synthesis of dipentaerythritol.

[0004] To circumvent the selectivity issues of direct condensation, many studies have explored alternative derivatization routes using pentaerythritol as a starting material. These include: acid- or base-catalyzed reactions of pentaerythritol with carbamates / carbonates; strong acid-catalyzed condensation reactions of pentaerythritol in solvents or in the molten state; acid-catalyzed reactions of pentaerythritol with specific cyclic compounds; and acid-catalyzed hydrolysis of polypentaerythritol. While these routes aim to improve the directed synthesis of bispentaerythritol, they generally suffer from low overall yields, demanding reaction conditions, or high raw material costs, resulting in insufficient economic viability and feasibility for large-scale production, making it difficult to replace the mainstream aldehyde condensation process.

[0005] Other studies have explored adding pentaerythritol as a seed in formaldehyde and acetaldehyde systems or replacing part of the acetaldehyde with acrolein to improve reaction selectivity. While these methods are effective in improving the selectivity of dipentaerythritol, in practical applications, they often inevitably lead to the simultaneous formation of more tripentaerythritol and polypentaerythritols while increasing the dipentaerythritol yield. They do not fundamentally solve the problem of byproduct complexity but instead exacerbate the separation burden of subsequent products. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a method for preparing high-purity dipentaerythritol, which aims to solve the technical problems of poor selectivity, large amount of by-products generated, and difficulty in product separation and purification in the existing dipentaerythritol synthesis process.

[0007] This application provides a method for preparing high-purity pentaerythritol, comprising the following steps: S1. Reaction of pentaerythritol with a hydroxyl protecting agent yields a dipentaerythritol intermediate; the structural formula of the hydroxyl protecting agent is: Wherein, R is one of hydrogen, a C1-C24 aliphatic hydrocarbon group, or a C4-C24 aromatic hydrocarbon group; Y is carbon or silicon; X1, X2, and X3 are each independently selected from OR or halogen. S2. The dipentaerythritol intermediate is hydrolyzed under acidic conditions to obtain dipentaerythritol.

[0008] As a further improvement of this application, R is selected from one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, hexyl, and phenyl; X1, X2, and X3 are each independently selected from one of methoxy, ethoxy, and chlorine.

[0009] As a further improvement to this application, in step S1, the reaction includes: S11. Reaction of pentaerythritol, hydroxyl protectant and acidic additive yields a hydroxyl-protected intermediate; S12. The hydroxyl-protected intermediate is reacted with a basic additive and a reagent with an easily leaving group to obtain a dipentaerythritol intermediate.

[0010] As a further improvement of this application, the acidic additive is selected from at least one of p-toluenesulfonic acid, trifluoromethanesulfonic acid, methanesulfonic acid, trifluoroformic acid, trifluoroacetic acid, hydrochloric acid, sulfuric acid, boric acid, nitric acid, phosphoric acid, sulfonic acid, oxalic acid, organic carboxylic acids, non-metallic oxides, metal halides, metal sulfides, metal oxides, zeolites, molecular sieves, diatomaceous earth, and heteropoly acids; the amount of the acidic additive is 0.05 to 5% of the molar amount of pentaerythritol.

[0011] As a further improvement of this application, the alkaline additive is selected from at least one of metal hydroxides, metal oxides, metal hydrides, metal alkoxides, metal alkaneamines, metal carbonates, metal sulfates, metal carboxylates, metal oxalates, metal nitrates, metal phosphates, metal sulfonates, ammonia, ammonia water, and organic amines; the molar ratio of the alkaline additive to the pentaerythritol is (1~2):1.

[0012] As a further improvement of this application, the leaving group reagent is selected from at least one of p-toluenesulfonyl chloride, trifluoromethanesulfonyl chloride, sulfonyl chloride, and sulfoxide; the molar ratio of the leaving group reagent to the pentaerythritol is (0.5~1.5):1.

[0013] As a further improvement of this application, in step S1, the molar ratio of pentaerythritol to hydroxyl protectant is 1:(1~1.5).

[0014] As a further improvement of this application, in step S11, the temperature of the reaction is 100~150℃.

[0015] As a further improvement to this application, the hydroxyl protecting agent is selected from at least one of trimethyl orthoformate, trimethyl orthobenzoate, trichloromethylsilane, and methyltrimethoxysilane.

[0016] As a further improvement of this application, in step S2, the temperature of the hydrolysis reaction is 50~70℃.

[0017] The beneficial effects of this application are as follows: This application provides a method for preparing high-purity pentaerythritol. The method involves reacting pentaerythritol with a hydroxyl protecting agent to obtain a pentaerythritol intermediate; then hydrolyzing the intermediate under acidic conditions to yield pentaerythritol. Using pentaerythritol as a starting material, this application achieves highly selective synthesis of pentaerythritol through a specific strategy of hydroxyl protection, condensation, and deprotection. Compared to the traditional formaldehyde-acetaldehyde base-catalyzed condensation process, this application controls the selectivity of the reaction from the source, significantly reducing the formation of structurally complex acetal byproducts and polypentaerythritols, significantly improving product purity, and reducing the burden of subsequent product separation. Furthermore, the reaction conditions are mild and the operation is simple, demonstrating good prospects for industrial application and economic benefits.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0020] Figure 1 The 1H NMR spectrum of dipentaerythritol obtained in Example 1 of this application; Figure 2 This is the carbon NMR spectrum of dipentaerythritol obtained in Example 1 of this application. Detailed Implementation

[0021] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0026] The fundamental contradiction in current dipentaerythritol synthesis technology lies in the fact that traditional formaldehyde / acetaldehyde base-catalyzed condensation routes struggle to achieve the synthesis goals of high selectivity, high yield, and low byproducts; while various derivative routes or improved methods aimed at enhancing selectivity suffer from significant shortcomings in terms of yield, cost, or feasibility. Therefore, developing a novel process that can fundamentally improve the selectivity of dipentaerythritol and effectively suppress the synthesis of polypentaerythritol is a key direction for overcoming existing technological bottlenecks and improving industrial economic benefits.

[0027] To address the technical problems of poor selectivity, numerous byproducts, and difficult product separation in the traditional dipentaerythritol synthesis process, this application provides a method for preparing high-purity dipentaerythritol. This method involves using monopentaerythritol as a raw material, selectively protecting three hydroxyl groups under an acid catalyst, then reacting it with an easily leaving group reagent under alkaline conditions to form an ether skeleton of dipentaerythritol. Finally, hydrolysis protection is achieved under acidic conditions. This method fundamentally inhibits the formation of byproducts such as polypentaerythritol and significantly improves product purity.

[0028] This application provides a method for preparing high-purity pentaerythritol, comprising the following steps: S1. Reaction of pentaerythritol with a hydroxyl protecting agent yields a dipentaerythritol intermediate; the structural formula of the hydroxyl protecting agent is: Wherein, R is one of hydrogen, a C1-C24 aliphatic hydrocarbon group, or a C4-C24 aromatic hydrocarbon group; Y is carbon or silicon; X1, X2, and X3 are each independently selected from OR or halogen. S2. The dipentaerythritol intermediate is hydrolyzed under acidic conditions to obtain dipentaerythritol.

[0029] In the technical solution of this application embodiment, a condensation reaction is carried out between a hydroxyl protecting agent and pentaerythritol. The active center Y in the protecting agent molecule forms a stable cyclic protecting structure with the hydroxyl groups of pentaerythritol, thereby achieving selective protection of the three hydroxyl groups of pentaerythritol. Simultaneously, the R group in the protecting agent molecule precisely controls the reaction site, promoting the formation of a bispentaerythritol skeleton by bridging two pentaerythritol molecules through the protecting agent. Subsequently, a hydrolysis reaction is carried out under acidic conditions to remove the protecting group, releasing high-purity bispentaerythritol. This application avoids the generation of byproducts such as polypentaerythritol due to indiscriminate hydroxyl reactions in traditional processes, achieving the goal of high selectivity and high purity synthesis. Specifically, the structural formula of the bispentaerythritol intermediate is as follows: R1 and R2 are each independently selected from one of hydrogen, aliphatic hydrocarbon groups of C1 to C24, or aromatic hydrocarbon groups of C4 to C24; Y1 and Y2 are each independently selected from carbon or silicon.

[0030] Furthermore, in some embodiments, R is selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, hexyl, and phenyl; X1, X2, and X3 are each independently selected from methoxy, ethoxy, and chlorine.

[0031] In the technical solution of this application embodiment, the three active substituents X1, X2, and X3 in the hydroxyl protecting agent molecule are left-leaving, and gradually form a stable cyclic condensation product with the hydroxyl groups of pentaerythritol, thereby achieving specific protection of the three hydroxyl groups of pentaerythritol. At the same time, the R group in the protecting agent precisely controls the regioselectivity and reaction process of the protection reaction through steric hindrance and electronic effects, promoting the formation of a bispentaerythritol skeleton by bridging the two protected pentaerythritol molecules through the protecting agent, which helps to achieve high selectivity and high yield preparation of bispentaerythritol.

[0032] Furthermore, in some embodiments, in step S1, the reaction includes: S11. Reaction of pentaerythritol, hydroxyl protectant and acidic additive yields a hydroxyl-protected intermediate; S12. The hydroxyl-protected intermediate is reacted with a basic additive and a reagent with an easily leaving group to obtain a dipentaerythritol intermediate.

[0033] In the technical solution of this application embodiment, pentaerythritol first undergoes a condensation reaction with a hydroxyl protecting agent under the catalysis of an acidic additive. The active center Y in the hydroxyl protecting agent is activated by the acid catalyst, causing it to gradually form a stable cyclic condensation product with the hydroxyl groups of pentaerythritol, achieving selective protection of the three hydroxyl groups of pentaerythritol and generating a hydroxyl protecting intermediate. Subsequently, this hydroxyl protecting intermediate is deprotonated under the action of an alkaline additive to form a highly reactive alkoxy anion, which then undergoes a nucleophilic substitution reaction with an easily leaving group reagent. Through the bridging effect of the protecting group, the two protected pentaerythritol molecules are efficiently coupled to form a protected bispentaerythritol skeleton. By precisely controlling the conditions and reagents of the two-step reaction, precise control of the reaction site is achieved, fundamentally avoiding the generation of byproducts such as polypentaerythritol caused by the indiscriminate reaction of hydroxyl groups in traditional processes.

[0034] Specifically, the solvents used in the above reactions are selected from water, dioxane, methanol, ethanol, butanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, dimethyl sulfone, benzyl sulfoxide, benzyl sulfone, cyclobutane sulfoxide, cyclobutane sulfone, trichlorosilane, dichloromethane, dichloroethane, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, chloroform, carbon tetrachloride, benzene, toluene, xylene, trimethylbenzene, tetramethylbenzene, acetonitrile, ethylbenzene, diethylbenzene, chlorobenzene, dichlorobenzene, anisole, nitrobenzene, heptane, hexane, petroleum ether, tetrahydrofuran, methyltetrahydrofuran, methyl tert-butyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, propylene glycol methyl ether acetate, triethylamine, tributylamine, dimethyl isopropylamine, pyridine, N,N-tetramethylethylenediamine, N-alkylmorpholine, N-alkylpyrrole, N, At least one of N-dimethylformamide, formylmorpholine, N,N-diethylformamide, and N-methylpyrrolidone; the use of a solvent is preferred but not essential. Under certain conditions, a solvent may not be used, i.e., the reactants may be dissolved, melted, or directly mixed and reacted under heating, grinding, or gas-phase conditions, or supercritical carbon dioxide may be used as the reaction medium. The reaction system is carried out under pressure or a certain degree of vacuum. The pressure of the reaction process can be 0.001-200 atmospheres, preferably 0.01-100 atmospheres.

[0035] Furthermore, in some embodiments, the acidic additive is selected from at least one of p-toluenesulfonic acid, trifluoromethanesulfonic acid, methanesulfonic acid, trifluoroformic acid, trifluoroacetic acid, hydrochloric acid, sulfuric acid, boric acid, nitric acid, phosphoric acid, sulfonic acid, oxalic acid, organic carboxylic acids, non-metallic oxides, metal halides, metal sulfides, metal oxides, zeolites, molecular sieves, diatomaceous earth, and heteropoly acids; the amount of the acidic additive is 0.05 to 5% of the molar amount of pentaerythritol.

[0036] In the technical solution of this application embodiment, the acidic additive acts as a catalyst, activating the active center Y in the hydroxyl protectant by providing protons or Lewis acidic sites, causing it to undergo a nucleophilic addition-elimination reaction with the hydroxyl group of pentaerythritol, gradually forming a stable condensation product, thereby achieving selective protection of the three hydroxyl groups of pentaerythritol; controlling the amount of acidic additive within an appropriate range helps to carry out the efficient catalytic reaction, avoids side reactions that may be caused by excessive acid, and achieves the specificity of the protection reaction and the stability of the intermediate.

[0037] Furthermore, in some embodiments, the alkaline additive is selected from at least one of metal hydroxides, metal oxides, metal hydrides, metal alkoxides, metal alkaneamines, metal carbonates, metal sulfates, metal carboxylates, metal oxalates, metal nitrates, metal phosphates, metal sulfonates, ammonia, ammonia water, and organic amines; the molar ratio of the alkaline additive to pentaerythritol is (1~2):1.

[0038] In the technical solution of this application embodiment, the basic additive acts as a deprotonating agent and reaction promoter. By abstracting protons from the adjacent or active sites of the protected hydroxyl group in the hydroxyl-protected intermediate, it transforms the intermediate into a highly reactive alkoxy anion. This alkoxy anion then undergoes a nucleophilic substitution reaction with a reagent with an easily leaving group, achieving efficient coupling of two protected pentaerythritol molecules through a protecting group bridge. The amount of basic additive is controlled within an appropriate range, which helps to fully activate the hydroxyl-protected intermediate and ensure complete reaction. It avoids problems such as the loss of the protecting group, the generation of by-products, or difficulties in post-processing that may be caused by excessive base. While ensuring the efficient coupling reaction, it maintains the stability of the protecting group.

[0039] Furthermore, in some embodiments, the leaving group reagent is selected from at least one of p-toluenesulfonyl chloride, trifluoromethanesulfonyl chloride, sulfonyl chloride, and sulfoxide; the molar ratio of the leaving group reagent to pentaerythritol is (0.5~1.5):1.

[0040] In the technical solution of this application embodiment, the sulfonyl chloride group or thionyl chloride group in the easily leaving group reagent can undergo a nucleophilic substitution reaction with the alkoxide anion, and efficiently couple two protected pentaerythritol molecules through the bridging effect of the protecting group to form a protected bispentaerythritol skeleton. The amount of the easily leaving group reagent added is controlled within an appropriate range, which helps the two pentaerythritol molecules to be fully coupled and the reaction to proceed completely, avoiding problems such as the removal of the protecting group, the generation of by-products or over-substitution that may be caused by excessive reagent. This helps the coupling reaction to proceed efficiently, while maintaining the integrity of the protecting group and the selectivity of the reaction, providing a reliable guarantee for obtaining high-purity bispentaerythritol in the subsequent deprotection step.

[0041] Furthermore, in some embodiments, in step S1, the molar ratio of pentaerythritol to the hydroxyl protectant is 1:(1~1.5).

[0042] In the technical solution of this application embodiment, the hydroxyl protecting agent serves as a key bridging unit in the construction of the pentaerythritol skeleton during the reaction. Controlling the molar ratio within an appropriate range helps to ensure that the three hydroxyl groups of pentaerythritol are fully and specifically protected, forming a complete trihydroxy protected intermediate. This avoids the problem of decreased selectivity and the formation of polypentaerythritol byproducts in subsequent coupling reactions due to incomplete protection of hydroxyl groups caused by insufficient protecting agent. At the same time, controlling the amount of protecting agent within a moderate excess range avoids problems such as self-condensation, increased side reactions, and difficulties in post-processing separation that may be caused by excessive protecting agent.

[0043] Furthermore, in some embodiments, in step S11, the temperature of the reaction is 100~150°C.

[0044] In the technical solution of this application embodiment, a suitable temperature range can provide sufficient activation energy for the condensation reaction of pentaerythritol and hydroxyl protectant under the catalysis of acidic additives, promote the nucleophilic addition-elimination reaction between the active center Y in the hydroxyl protectant and the hydroxyl group of pentaerythritol, and gradually form a stable condensation product; at the same time, this temperature condition is conducive to maintaining the homogeneous state of the reaction system, increasing the collision frequency and mass transfer efficiency of reactant molecules, ensuring that the three hydroxyl groups of pentaerythritol are fully and specifically protected, avoiding incomplete reaction or slow reaction rate due to excessively low temperature, and also preventing problems such as premature removal of protecting groups, thermal decomposition of raw materials or products, and increased side reactions that may be caused by excessively high temperature.

[0045] Furthermore, in some embodiments, the hydroxyl protectant is selected from at least one of trimethyl orthoformate, trimethyl orthobenzoate, trichloromethylsilane, and methyltrimethoxysilane.

[0046] In the technical solution of this application embodiment, by selecting a suitable type of hydroxyl protecting agent, the goal of preparing bispentaerythritol with high selectivity and high purity can be achieved; at the same time, the preferred use of the protecting agent provides flexible selectivity for the process, adapting to the requirements of different raw material costs and reaction conditions.

[0047] Furthermore, in some embodiments, the hydrolysis reaction temperature in step S2 is 50~70°C.

[0048] In the technical solution of this application embodiment, the temperature range provides suitable reaction kinetics for the hydrolysis protection reaction of the protected pentaerythritol under acidic conditions, enabling the protecting group to undergo efficient hydrolysis under acid catalysis, breaking the chemical bond between the protecting group and the hydroxyl group, and releasing the pentaerythritol molecule. This avoids problems such as slow hydrolysis rate, incomplete reaction, or excessively long reaction time caused by excessively low temperature, while also preventing problems such as thermal decomposition, excessive condensation, or increased side reactions of the pentaerythritol product under acidic conditions that may be caused by excessively high temperature. In addition, mild hydrolysis conditions are beneficial to protecting the stability of the hydrolysis product, reducing product degradation or loss during the reaction process, and maximizing the maintenance of high purity and high yield of the product. Specifically, the acidic conditions are provided by concentrated sulfuric acid, concentrated hydrochloric acid, or concentrated nitric acid, in an amount of 0.5-20% of the molar amount of the pentaerythritol intermediate.

[0049] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0050] Example 1 This embodiment provides a method for preparing high-purity pentaerythritol, including the following steps: S1. Mix 136 g pentaerythritol (1 mol) and 116 g trimethyl orthoformate (1.1 mol) with 1 L DMF (N,N-dimethylformamide), add 0.57 g trifluoroacetic acid (0.005 mol), and react at 130 °C and 500 r / min for 4 h. After the reaction was complete, the system was cooled to 60°C, and 65 g of sodium methoxide (1.2 mol) and 100 g of p-toluenesulfonyl chloride (0.53 mol) were added. The reaction was continued for 2 h to obtain the dipentaerythritol intermediate. S2. Dissolve 40 mL of concentrated hydrochloric acid in 1 L of methanol, then add it to the reaction solution obtained in step S1. React at 60 °C for 4 h. After the reaction is complete, filter, crystallize, centrifuge, and dry to obtain 115 g of dipentaerythritol. The proton and carbon NMR spectra are shown below. Figure 1 and Figure 2 As shown, the target product was obtained.

[0051] The reaction formula is shown below: Example 2 This embodiment provides a method for preparing high-purity pentaerythritol, including the following steps: S1. Mix 136 g pentaerythritol (1 mol) and 200 g trimethyl orthobenzoate (1.1 mol) with 1 L DMF, add 0.95 g p-toluenesulfonic acid (0.005 mol), and react at 130 °C and 500 r / min for 4 h. After the reaction was complete, the system was cooled to 60°C, and 82 g of sodium ethoxide (1.2 mol) and 88 g of trifluoromethanesulfonyl chloride (0.52 mol) were added. The reaction was continued for 2 h to obtain the dipentaerythritol intermediate. S2. Dissolve 40 mL of concentrated hydrochloric acid in 1 L of methanol, then add it to the reaction solution obtained in step S1. React at 60 °C for 4 h. After the reaction is complete, filter, crystallize, centrifuge and dry to obtain 112 g of dipentaerythritol.

[0052] Example 3 This embodiment provides a method for preparing high-purity pentaerythritol, including the following steps: S1. Mix 136 g pentaerythritol (1 mol) and 164 g trichloromethylsilane (1.1 mol) with 1 L DMF, add 0.75 g trifluoromethanesulfonic acid (0.005 mol), and react at 130 °C and 500 r / min for 4 h. After the reaction was complete, the system was cooled to 60°C, and 48 g of sodium hydroxide (1.2 mol) and 71 g of sulfonyl chloride (0.53 mol) were added. The reaction was continued for 2 h to obtain the dipentaerythritol intermediate. S2. Dissolve 40 mL of concentrated hydrochloric acid in 1 L of methanol, then add it to the reaction solution obtained in step S1. React at 60 °C for 4 h. After the reaction is complete, filter, crystallize, centrifuge and dry to obtain 105 g of dipentaerythritol.

[0053] Example 4 This embodiment provides a method for preparing high-purity pentaerythritol, including the following steps: S1. Mix 136 g pentaerythritol (1 mol) and 200 g methyltrimethoxysilane (1.5 mol) with 1 L DMF, add 0.67 g aluminum chloride (0.005 mol), and react at 130 °C and 500 r / min for 4 h. After the reaction was complete, the system was cooled to 60°C, and 115 g of sodium tert-butoxide (1.2 mol) and 62 g of thionyl chloride (0.52 mol) were added. The reaction was continued for 2 h to obtain the pentaerythritol intermediate. S2. Dissolve 40 mL of concentrated hydrochloric acid in 1 L of methanol, then add it to the reaction solution obtained in step S1. React at 60 °C for 4 h. After the reaction is complete, filter, crystallize, centrifuge and dry to obtain 108 g of dipentaerythritol.

[0054] Example 5 This embodiment provides a method for preparing high-purity pentaerythritol. Compared with Example 1, the only difference is that the amount of p-toluenesulfonyl chloride added is 286 grams (1.5 mol). Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0055] Example 6 This embodiment provides a method for preparing high-purity pentaerythritol. Compared with Example 1, the only difference is that the amount of trifluoroacetic acid added is 0.057 g (0.0005 mol). Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0056] Example 7 This embodiment provides a method for preparing high-purity pentaerythritol. Compared with Example 1, the only difference is that the amount of trifluoroacetic acid added is 5.7 g (0.05 mol). Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0057] Comparative Example 1 Comparative Example 1 provides a method for preparing high-purity pentaerythritol, which employs a traditional formaldehyde-acetaldehyde base catalytic condensation process, including the following steps: S1. In a tubular reactor, formaldehyde, caustic soda, and acetaldehyde are added sequentially in stages, with a molar ratio of formaldehyde to acetaldehyde of 8:1 and a molar ratio of acetaldehyde to caustic soda of 1:1.15. The mass concentration of formaldehyde is 16%, the mass concentration of acetaldehyde is 20%, and the mass concentration of caustic soda is 20%. The initial reaction temperature is 40℃, and the final reaction temperature is 55℃. After reacting for 1.2 hours, formic acid is added to adjust the pH to 6.0. S2. The condensate is fed into a multi-effect evaporation system to remove formaldehyde and then concentrated; S3. Cool the concentrated slurry to 80°C and add butanol extractant at 50% of the material weight; S4. Sodium formate is separated, and then the pentaerythritol solution is cooled and crystallized to 30°C. The suspension rich in dipentaerythritol is separated by a high-efficiency settling device and then filtered to obtain crude dipentaerythritol. S5. Purification, crystallization, centrifugation, and drying of crude dipentaerythritol to obtain high-purity dipentaerythritol: Dissolve crude dipentaerythritol in hot water at a weight ratio of 1:6. Add formic acid to adjust the pH of the dipentaerythritol solution to 3.5. Hydrolyze the solution by introducing steam to 110℃ for 0.5h. After filtering impurities by activated carbon adsorption, the solution is sent to a dipentaerythritol crystallizer. Then, add dipentaerythritol crystallization cooling water and cool the solution to 50~60℃. Stir the solution at a constant temperature for 1.5h at a stirring rate of 15r / min. Centrifuge the solution using an automatic bag-pull unloading centrifuge. Dry the centrifuged filter cake in a rotary flash dryer to obtain high-purity dipentaerythritol product.

[0058] Comparative Example 2 Comparative Example 2 provides a method for preparing high-purity pentaerythritol. Compared with Example 1, the only difference is that trimethyl orthoformate was not added. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0059] Comparative Example 3 Comparative Example 3 provides a method for preparing high-purity pentaerythritol. Compared with Example 1, the only difference is that p-toluenesulfonyl chloride was not added. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0060] Comparative Example 4 Comparative Example 4 provides a method for preparing high-purity pentaerythritol. Compared with Example 1, the only difference is that the amount of trifluoroacetic acid added is 11.4 g (0.1 mol). Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0061] The purity of dipentaerythritol obtained in each example and comparative example was detected by HPLC (high performance liquid chromatography), and the yield was calculated. The detection indicators are shown in Table 1.

[0062] Table 1 Product Indicators As shown in Table 1, the dipentaerythritol prepared in the examples of this application all exhibited high yields and purities greater than 97%, significantly superior to the traditional formaldehyde-acetaldehyde base catalytic condensation process. Comparative Examples 2 and 3, lacking hydroxyl protecting agents or easily leaving group reagents respectively, failed to generate the target product, further verifying the necessity of the key steps in this method. Comparative Example 4, with its excessive acidic additive, showed a decrease in both yield and purity compared to Example 1, while also increasing production costs and post-processing burden, indicating that this application can achieve higher overall performance under more optimized reagent ratios and milder conditions. In summary, this application demonstrates significant advantages in yield, purity, and process controllability.

[0063] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing high-purity pentaerythritol, characterized in that, Includes the following steps: S1. Reaction of pentaerythritol with a hydroxyl protecting agent yields a dipentaerythritol intermediate; the structural formula of the hydroxyl protecting agent is: Wherein, R is one of hydrogen, a C1-C24 aliphatic hydrocarbon group, or a C4-C24 aromatic hydrocarbon group; Y is carbon or silicon; X1, X2, and X3 are each independently selected from OR or halogen. S2. The dipentaerythritol intermediate is hydrolyzed under acidic conditions to obtain dipentaerythritol.

2. The method for preparing high-purity bispentaerythritol according to claim 1, characterized in that, R is selected from one of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, hexyl, and phenyl; X1, X2, and X3 are each independently selected from one of methoxy, ethoxy, and chlorine.

3. The method for preparing high-purity dipentaerythritol according to claim 1, characterized in that, In step S1, the reaction includes: S11. Reaction of pentaerythritol, hydroxyl protectant and acidic additive yields a hydroxyl-protected intermediate; S12. The hydroxyl-protected intermediate is reacted with a basic additive and a reagent with an easily leaving group to obtain a dipentaerythritol intermediate.

4. The method for preparing high-purity pentaerythritol according to claim 3, characterized in that, The acidic additive is selected from at least one of p-toluenesulfonic acid, trifluoromethanesulfonic acid, methanesulfonic acid, trifluoroformic acid, trifluoroacetic acid, hydrochloric acid, sulfuric acid, boric acid, nitric acid, phosphoric acid, sulfonic acid, oxalic acid, organic carboxylic acids, non-metallic oxides, metal halides, metal sulfides, metal oxides, zeolites, molecular sieves, diatomaceous earth, and heteropoly acids; the amount of the acidic additive is 0.05 to 5% of the molar amount of pentaerythritol.

5. The method for preparing high-purity bispentaerythritol according to claim 3, characterized in that, The alkaline additive is selected from at least one of metal hydroxides, metal oxides, metal hydrides, metal alkoxides, metal alkaneamines, metal carbonates, metal sulfates, metal carboxylates, metal oxalates, metal nitrates, metal phosphates, metal sulfonates, ammonia, ammonia water, and organic amines; the molar ratio of the alkaline additive to the pentaerythritol is (1~2):

1.

6. The method for preparing high-purity pentaerythritol according to claim 3, characterized in that, The leaving group reagent is selected from at least one of p-toluenesulfonyl chloride, trifluoromethanesulfonyl chloride, sulfonyl chloride, and sulfoxide; the molar ratio of the leaving group reagent to the pentaerythritol is (0.5~1.5):

1.

7. The method for preparing high-purity pentaerythritol according to claim 1, characterized in that, In step S1, the molar ratio of pentaerythritol to the hydroxyl protectant is 1:(1~1.5).

8. The method for preparing high-purity pentaerythritol according to claim 3, characterized in that, In step S11, the reaction temperature is 100~150℃.

9. The method for preparing high-purity pentaerythritol according to claim 1, characterized in that, The hydroxyl protectant is selected from at least one of trimethyl orthoformate, trimethyl orthobenzoate, trichloromethylsilane, and methyltrimethoxysilane.

10. The method for preparing high-purity pentaerythritol according to claim 1, characterized in that, In step S2, the temperature of the hydrolysis reaction is 50~70℃.

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