Process for the production of dipentaerythritol

Abstract

The present invention relates to a process for producing dipentaerythritol from pentaerythritol in the presence of sulfolane and a heterogeneous polyacid catalyst supported on a support comprising a compound selected from the group consisting of SnO2, mesoporous silica and zeolite.

Description

[0001] Invention Field The present invention relates to a process for producing dipentaerythritol from pentaerythritol in the presence of sulfolane and a heterogeneous polyacid catalyst supported on a support comprising a compound selected from the group consisting of SnO2, mesoporous silica and zeolite. Background of the Invention Dipentaerythritol is an important compound used in a variety of applications such as coatings, lubricants, radiation curing, adhesives, plasticizers, and cosmetics. Due to its high functionality with six primary hydroxyl groups, dipentaerythritol possesses the ability to enhance the drying and hardness of coatings and improve the properties of a wide range of products, making it a valuable compound for industrial applications. Currently, the industrial production of dipentaerythritol is a low-yield process, produced by the reaction of formaldehyde and acetaldehyde in the presence of sodium hydroxide, via the Cannizaro reaction, which also yields sodium formate as a byproduct. Although recent advances have focused on improving the yield of dipentaerythritol through optimizing reaction conditions and using specific catalysts, the yield has only reached a maximum of 10%.

[0003] Several patent documents, such as JPH07258139, JP3814642, JPH07188086, JP2005015379, JP2005015380, CN101531573, and JP3368958, disclose routes for preparing dipentaerythritol using different types of heterogeneous catalysts. A scientific paper, Okuhara et al., “Catalytic dehydration of pentaerythritol to dipentaerythritol over heteropoly compounds”, Applied Catalysis A: General, 2003, Vol. 253, pp. 29-32, has proposed using the heteropoly acid H3PW. 12 O 40 and H4SiW 12 O 40 Selective dimerization of polyols with SiO2 at 170 °C for 24 h was carried out. The conversion rates of pentaerythritol and dipentaerythritol were 81.6% and 57%, respectively, and the yields of dipentaerythritol were 22.7% and 22.8%, respectively. Although the yield of dipentaerythritol was improved compared with other prior art, the selectivity and conversion rate of pentaerythritol to dipentaerythritol were still unsatisfactory, resulting in the disclosed process cost being too high to be competitive.

[0004] Therefore, there is a need for an improved process for the production of dipentaerythritol, in which the conversion, selectivity and yield of pentaerythritol are balanced and optimized, and the loss of reactants is kept to a minimum. Invention Overview The applicant has observed that the properties of the support for the supported heteropolyacid catalyst play a crucial role. By altering the pore size distribution of the support, the yield of dipentaerythritol to pentaerythritol can be significantly improved. The choice of solvent, supported catalyst, catalyst loading, reaction temperature, and reaction time has a significant impact on the yield and selectivity of dipentaerythritol.

[0006] The applicant further discovered that sulfolane exhibits very high selectivity for dipentaerythritol, and that sulfolane as a solvent produces fewer side reactions compared to other solvents such as water and diethyl carbonate. Sulfolane has proven to be a stable solvent, yielding optimal results in terms of both conversion and dipentaerythritol selectivity.

[0007] The applicant has surprisingly discovered that heteropolyacid catalysts supported on a support have the ability to efficiently catalyze the production of dipentaerythritol from pentaerythritol in the presence of sulfolane and to balance high pentaerythritol conversion and high dipentaerythritol selectivity. The support comprises compounds selected from the group consisting of SnO2, mesoporous silica and zeolite.

[0008] Therefore, in a first aspect, the present invention relates to a process for producing dipentaerythritol from pentaerythritol in the presence of sulfolane and a heterogeneous polyacid catalyst supported on a support comprising a compound selected from the group consisting of SnO2, mesoporous silica and zeolite. Invention Details In a first aspect, the present invention relates to a process for producing dipentaerythritol from pentaerythritol, wherein the method comprises the following steps: a) Pentaerythritol, sulfolane, and a heteropolyacid catalyst supported on a support are supplied to the reactor to form a reaction solution. The support comprises compounds selected from the group consisting of: SnO2, mesoporous silica, and zeolite. b) The reaction solution was heated to a temperature in the range of 150°C to 250°C under continuous stirring and a pressure in the range of 0.5 bar to 5 bar for a period of time of 30 minutes to 600 minutes to obtain dipentaerythritol, and then... c) Separate the obtained dipentaerythritol from the reaction solution.

[0010] Surprisingly, the applicant has indeed discovered that the process enables the catalytic dimerization of pentaerythritol, with a combination of high pentaerythritol conversion and high dipentaerythritol selectivity, resulting in a high dipentaerythritol yield.

[0011] Within the framework of this specification and in the appended claims, unless otherwise indicated, all numerical entities representing quantities, parameters, percentages, etc., shall be understood to be preceded by the term "about" in all cases. As used herein, the term "about" will be understood by those skilled in the art and will vary to some extent depending on the context in which it is used. As used herein, when referring to measurable values ​​such as quantities, durations of time, and similar values, the term "about" means including variations of ±20% or ±10% (inclusive of ±5%, ±1%, and ±0.1%) from the specified value, because such variations are suitable for carrying out the disclosed methods. Furthermore, all ranges of numerical entities include all possible combinations of maximum and minimum values ​​and include all possible intermediate ranges, except for those specifically pointed out below.

[0012] Unless otherwise defined, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0013] As used herein, the articles “a” and “an” refer to one or more (i.e., at least one) grammatical object of the article. By way of example, “heteropolyacid catalyst” means one or more heteropolyacid catalysts.

[0014] The present invention may contain one or more of the features disclosed below in one or more of the above aspects.

[0015] The process according to the present invention includes the following steps: a) Pentaerythritol, sulfolane, and a heteropolyacid catalyst supported on a support are supplied to the reactor to form a reaction solution. The support is selected from the group consisting of SnO2, mesoporous silica, and zeolite. b) The reaction solution was heated to a temperature in the range of 150°C to 250°C under continuous stirring and a pressure in the range of 0.5 bar to 5 bar for a period of time of 30 minutes to 600 minutes to obtain dipentaerythritol, and then... c) Separate the obtained dipentaerythritol from the reaction solution.

[0016] The weight ratio of pentaerythritol, sulfolane, and catalyst is suitably 1:0.5-4:0.1-1, and in a preferred embodiment of the invention, the weight ratio is 1:2:0.5.

[0017] The heteropolyacid catalyst of the present invention is suitably selected from the group consisting of: H3PW 12 O 40 H3SiW 12 O 40 H4[SiW 12 O 40 [and combinations thereof. Preferably, the heteropolyacid catalyst is H3PW.] 12 O 40 .

[0018] Based on the weight of the support, the heteropolyacid catalyst of the present invention is preferably applied to the support in an amount of 20 wt%-30 wt%, and most preferably in an amount of 30 wt%. The support is preferably SnO2, and most preferably nanoporous SnO2, wherein the average pore size is in the range of 5 nm-10 nm.

[0019] In one embodiment of the invention, the support is doped with V₂O₅. A suitable amount of V₂O₅ is 0.5 wt% to 4.5 wt% based on the weight of the support. Preferably, the support is doped with 1 wt% V₂O₅ based on the weight of the support.

[0020] The dipentaerythritol obtained in the process according to the present invention is preferably separated from the reaction solution by fractional crystallization.

[0021] The heteropolyacid catalyst of the present invention is preferably prepared by a method comprising the following steps: a) Impregnate the heteropolyacid catalyst onto the support using initial wet impregnation. b) Dry the heteropolyacid catalyst support composition at 110°C for at least 2 hours, and c) Calcine the dried heteropolyacid catalyst support composition at 250°C for at least 4 hours.

[0022] This method is in Figure 1 (a) is shown in the figure.

[0023] In a preferred embodiment of the invention, the heteropolyacid catalyst is supported on a support comprising nanoparticles. The nanoparticles are suitably prepared by a method comprising the following steps: a) Dilute SnCl2-2H2O in distilled water. b) Add HCl, c) Stir until approximately pH 1. d) Add V2O3 to approximately the same molar amount as SnCl2. e) Stir the solution by sonication at room temperature for at least 10 minutes. f) Neutralize the solution to approximately pH 9 using an alkali metal hydroxide. g) Stir the solution at a temperature ranging from 35°C to 65°C for at least 30 minutes. h) The obtained carrier particles are separated from the diluent and soluble byproducts. i) Wash the carrier particles with water and acetone. j) Dry the particles at 90°C, and h) Calcine the particles at a temperature of 400℃-500℃ for 15-45 minutes.

[0024] This method is in Figure 1 (b) is shown in the figure.

[0025] In one embodiment of the invention, the nanoparticles obtained according to the described method are coated onto a carrier after being washed in step i) and before being dried in step j).

[0026] In one embodiment of the invention, pentaerythritol and sulfolane are suitably preheated to at least 50°C, allowing pentaerythritol to dissolve in sulfolane.

[0027] In another embodiment of the invention, the reactor is preferably equipped with sensors selected from the group consisting of a pressure sensor, a temperature sensor, and a CO2 sensor. The reaction from pentaerythritol to dipentaerythritol is suitably allowed to continue for 30 to 600 minutes, and is preferably interrupted before the pressure begins to increase or before an increase in CO2 formation is detected. This can be detected by an increase in the exothermic reaction. Data from the selection of the sensors mentioned above can be used in conjunction with the analysis of the obtained results to provide statistical guidance for the process, which is to adjust process parameters over time to optimize the results. It has been found during experiments that after the maximum yield of dipentaerythritol has been reached, carbon dioxide will be formed from the undesirable decomposition of pentaerythritol and / or dipentaerythritol. After this undesirable reaction begins, CO2 will form and the pressure in the reactor will increase. Within the scope of the invention, this time point can occur at any time between 30 and 600 minutes, suitably between 30 and 360 minutes, or possibly even in the range of 45 to 180 minutes, all depending on the selection of the catalyst, support, and reactant / solvent / catalyst ratio within the scope of the invention. Unreacted pentaerythritol can be recovered after separation from the obtained dipentaerythritol. This will be disclosed in more detail later in this specification.

[0028] In one embodiment of the invention, after first separating the catalyst by filtration and / or precipitation, the obtained dipentaerythritol is separated from the reaction solution by the following manner: a) Evaporate part of the solvent from the reaction solution until dipentaerythritol reaches saturation and crystallizes. b) Dipentaerythritol crystals were separated by filtration. c) The remaining reaction solution, containing solvent and unreacted pentaerythritol, along with the evaporated solvent and separated catalyst, is supplied to the unit for preparing the next batch. d) The dipentaerythritol crystals obtained by washing with water.

[0029] Preferably, the solvent is sulfolane evaporated at a temperature in the range of 100°C to 250°C and a pressure in the range of 10 mbar to 500 mbar.

[0030] The dipentaerythritol crystals were appropriately separated from the reaction solution using a centrifuge. The obtained dipentaerythritol crystals were then preferably washed with water at a temperature below 35°C.

[0031] In one embodiment of the process of this invention, the obtained dipentaerythritol is extracted by adjusting the sulfolane / dipentaerythritol ratio and temperature to induce crystallization of only dipentaerythritol while the catalyst nanoparticles remain suspended. In other words, the nanoparticles act as seed crystals, the nanoparticles are separated from the mother liquor, the crystallized dipentaerythritol is dissolved in warm water, the free catalyst particles are separated from the solution, and the dipentaerythritol is recrystallized. This alternative separation method is preferably used in batch processes. Temperature and concentration dependence are important for the separation process. The larger the process window, the more dipentaerythritol and the less pentaerythritol are present in the solution.

[0032] Figure 2 The figure illustrates an embodiment of the process layout for the production of dipentaerythritol according to the present invention.

[0033] Pentaerythritol, sulfolane, and a heteropolyacid catalyst on a particulate support are loaded into a premixing / preheating vessel 1. The contents of the premixing / preheating vessel 1 are preheated to at least 50°C and then supplied to reactor 2 via a mixture supply line 11. Reactor 2 is equipped with heating and stirring devices. Stirring is an important aspect to mention here because sufficient shear force is required to achieve adequate mass transfer and also to maintain catalyst suspension. The contents of the reactor are heated to 230°C, allowing pentaerythritol to partially react to dipentaerythritol under ambient pressure. Reactor 2 is also equipped with a temperature sensor. After 30 minutes to 8 hours of synthesis, the temperature will begin to rise due to an exothermic reaction in which pentaerythritol begins to decompose to form carbon dioxide. For this purpose, reactor 2 may also be equipped with a CO2 detector and / or a pressure sensor. This indicates that an undesirable side reaction has begun, and further synthesis will result in the loss of pentaerythritol due to the side reaction rather than dipentaerythritol. Lowering the temperature in reactor 2 by cooling just before CO2 begins to form has been shown to fundamentally reduce unwanted side reactions. While pressure increases or CO2 detection are by far the best indicators of unwanted side reactions, this is indeed a bit late, as unwanted pentaerythritol degradation has already begun. However, such measurements are acceptable at startup, where they can be used for statistical process guidance, process improvement, and reduction of unwanted side reactions. This concept is particularly useful in semi-batch or continuous processes. The reaction is preferably interrupted at this point, and the contents of the reactor are emptied via reaction solution supply line 21 to catalyst separation unit 3, where the catalyst is separated by precipitation, allowing catalyst particles to settle at the bottom of catalyst separation unit 3, or by filtration from the reaction solution. The catalyst is then collected in catalyst collection container 3a. The collected catalyst is then reused for the next batch, and thus the collected catalyst is supplied back to premix / preheat container 1 via catalyst return supply line 31.

[0034] In one embodiment of the invention, a fixed-bed catalyst can be used in reactor 2. With a fixed bed, the catalyst does not need to be premixed with the solvent and pentaerythritol in the premixing / preheating vessel 1. Separation of the catalyst from the reaction solution is also unnecessary, thus eliminating the need for the catalyst separation unit 3, the catalyst collection vessel 3a, and the catalyst return supply line 31. In this case, the reaction solution supply line 21 will be directly connected to the reaction solution catalyst-free supply line 31.

[0035] After the reaction solution is free of catalyst, it is suitably supplied via a catalyst-free reaction solution supply line 31 to at least one distillation unit 4a-b, where the solvent sulfolane is evaporated at 150°C-250°C under reduced pressure of <15 mbar, allowing dipentaerythritol to crystallize and be separated from the reaction solution. Water formed during dimerization in reactor 2 is also preferably separated in distillation units 4a-b. Due to the large difference in boiling points, the water is easily separated from sulfolane. Unreacted pentaerythritol remains dissolved in the remaining sulfolane. The evaporated sulfolane (anhydrous) is preferably collected in a solvent collection container 5 via a solvent collection supply line 41. The collected sulfolane is preferably returned to a premix / preheat container 1 for further use with other effluents from the process. The reaction solution containing the crystallized dipentaerythritol is then preferably supplied to a centrifuge 6, where the sulfolane and pentaerythritol are separated from the crystallized dipentaerythritol and collected in unit 6a. The pentaerythritol / sulfolane mixture is preferably returned to the premixing / preheating vessel 1 via mother liquor return line 61 for use in a new production batch after replenishment with fresh pentaerythritol and some sulfolane. The collected pentaerythritol is preferably supplied to washing units 7a-b via purification supply line 62. The pentaerythritol crystals are preferably washed with water in washing units 7a-b. One or more centrifuges may be used here. Purified pentaerythritol is obtained through outlet 72 and can then be dried. The wash water from outlet 71 contains a certain amount of sulfolane, pentaerythritol, and pentaerythritol. The obtained wash water can be further separated, wherein pentaerythritol and sulfolane can be returned to the premixing / preheating vessel 1, and the pentaerythritol can be combined with the pentaerythritol obtained through outlet 72.

[0036] The process and equipment setup described above can be a semi-continuous or semi-batch process. As indicated above, the reaction in reactor 2 can indeed be controlled by controlling the temperature and introducing cooling. In one embodiment of the invention, reactor 2 can be designed as a flow reactor with continuous feed of reactants and solvent, wherein the dipentaerythritol obtained is continuously extracted in a process setup very similar to the process described above. Reactor 2 can have two or more temperature zones in a continuous process, or even be divided into two or more reactors in series, allowing for better control of the temperature profile.

[0037] According to the process described in the above implementation scheme, whether it is batch, semi-batch or continuous, it is advantageous to set up an extraction / purification stage in the mother liquor return line 61 in order to separate any dipentaerythritol not captured in the centrifuge 6 as well as by-reaction products.

[0038] The dipentaerythritol obtained from outlet 72 can be further purified and recrystallized, which is a common practice in the field. For example, a small fraction of by-reaction products with molecular weights higher than that of pentaerythritol are known to be separated together with dipentaerythritol in centrifuge 6. Sometimes recrystallization of dipentaerythritol is also used to obtain crystals of uniform size.

[0039] In one embodiment of the invention, the process is continuous and the ratio between the solvent and the obtained dipentaerythritol in reactor 2 can be balanced, such that dipentaerythritol begins to crystallize by lowering the temperature in a stage prior to centrifuge 6. In such a process, it is preferable to use a fixed-bed catalyst in reactor 2 due to the high probability of interference between the crystallization of dipentaerythritol and the precipitation of nano- to micron-sized catalyst particles.

[0040] The invention is further explained with reference to the accompanying embodiments, which are to be interpreted as illustrative and not as limiting in any way.

[0041] Example In Examples 1-14, dipentaerythritol was produced from pentaerythritol in the presence of sulfolane and different heteropolyacid catalysts. Examples 1-6 are comparative examples, and Examples 7-14 illustrate embodiments of the invention. The results of the experimental reactions are presented in Table 1.

[0042] Chemicals and reagents used in the examples All of the following chemicals and materials are of analytical grade: pentaerythritol (PE, >99%, Sigma-Aldrich), dipentaerythritol (DPE, >99%, Sigma-Aldrich), 1-trimethylsilylimidazole (TMSI, >98%, Sigma-Aldrich), N,N-bis-trimethylsilyltrifluoroacetamide (≥98.5%, Sigma-Aldrich), pyridine (99%, Sigma-Aldrich), and n-eicosane (C 20 H 42 ≥99%, Sigma-Aldrich), sulfolane (99%, Sigma-Aldrich), phosphotungstic acid (H3PW) 12 O 40 ≥99.5%, Sigma-Aldrich), silicotungstic acid (H3SiW 12 O 40≥99.5%, Sigma-Aldrich), γ-Al2O3 (Puralox SCCa 150 / 200, Sasol), silica (SiO2, >99.0%, catalyst support, AlfaAesar), silica SBA16 (>99.0%, Sigma-Aldrich), TiO2 (high surface area, 99.99%, Sigma-Aldrich), tin(IV) oxide (nano SnO2, 99.99%, Sigma-Aldrich), nano-powdered tin(IV) oxide (SnO2, ≥99.5%, Sigma-Aldrich), tin(II) chloride dihydrate (SnCl4·2H2O, Sigma-Aldrich, 98%), vanadium(V) oxide (V2O5, Sigma-Aldrich, ≥99.6%), and hydrochloric acid (HCl, ACROS ORGANICS, 37%).

[0043] Catalyst preparation Prior to the experiment producing dipentaerythritol via pentaerythritol dimerization, catalysts supported on different heteropolyacids for this process were synthesized. The synthetic procedure was as follows: Figure 1 (a) shows the preparation of catalysts using solutions of phosphotungstic acid (HPW) and silicotungstic acid (HSiW). Heteropolyacid-based supported catalysts were prepared using several commercially available supports, including SiO2, γ-Al2O3, SBA16, TiO2, and SnO2. The heteropolyacid catalysts were prepared by initial wet impregnation of the supports, followed by overnight drying at 100°C to obtain 20 wt% heteropolyacid catalyst (e.g., 20% H3PW) on the supports. 12 O 40 / TiO2). Before being used as catalysts, these catalysts were calcined in air at 250°C for 6 h.

[0044] The modified synthesis procedure for SnO2 nanopowder support in Figure 1Presented in (b). In this step, pure SnO2 nanopowder and V2O5-doped SnO2 nanopowder were synthesized via sol-gel method using different V2O5 ratios (1 wt%, 5 wt%, and 10 wt%). The preparation of SnO2-based nanopowders containing (0 wt%, 1 wt%, 5 wt%, and 10 wt%) V2O5 was explored using tin chloride dihydrate (SnCl2·2H2O). Tin chloride dihydrate was placed in a beaker, and diluted hydrochloric acid was then added until the solution pH ~ 1 and maintained with stirring. Then, acidic aqueous V2O5 solution for the doping process was added in different proportions, and then ammonia solution was added dropwise to the previous solution while stirring until the pH of the mixture rose to 9 to convert tin chloride to tin hydroxide. The solution became a white emulsion, and the solution was continuously stirred in a glass beaker at 50°C for 1 h using a magnetic stirrer. A white powder precipitated after centrifugation at 4000 rpm for 20 min and washing multiple times with distilled / deionized water to remove ammonia ions and ammonium chloride; this white powder was then allowed to precipitate as a pure precipitate. The final washing step was performed with acetone, which allowed for faster drying of the powder, and the precipitate was dried at 90 °C. Sn(OH)4 was directly dehydrated to form SnO2 powder, and the nanoparticles were then calcined at 450 °C for 10 min. Later, these new supports were used to prepare heteropolyacid-supported catalysts, typically involving the process described above. Figure 1 The steps described in (a)

[0045] Procedure for the dimerization of pentaerythritol All experiments on the dimerization of pentaerythritol were conducted in 10 mL glass vials. The vials had screw caps that tightened via threads cast into the top of the vial. The vials were filled with pentaerythritol, various amounts of solvent (sulfolane), and a selected catalyst (loading depending on acidity). A range of temperatures (150°C–230°C), reaction times (0.5 h–6 h), catalyst loadings (0.1–0.5 g), and various reactant / solvent ratios were tested to determine their respective effects and to tune the reaction toward the desired results. To draw valid conclusions, the reaction was tracked over time by sampling every 1 h, except for higher catalyst loadings, where sampling was reduced to every 30 minutes or less. The vials were heated to the desired reaction temperature, and for all experiments, stirring was kept constant at 200 rpm to avoid external diffusion limitations. A time zero was set after the desired reaction temperature was reached. Variations in conditions were tested individually to determine the effect of each variation on the overall reaction.

[0046] Following the reaction and prior to GC-MS analysis, a portion of the homogenized solid was pretreated using a silylation method. In this study, 25 mg of the resulting solid was sampled into a 2 mL vial and processed in two steps as follows: 0.3 mL of TMSI and 0.6 mL of pyridine were added to the solid sample. The vial was capped and heated at 120 °C for 0.5 h until completely dissolved. A 0.1 mL aliquot of the resulting solution was added to a vial containing 0.1 mL of N,N-bis-trimethylsilyl-trifluoroacetamide, 0.7 mL of pyridine, and 0.1 mL of 10,000 ppm n-eicosane (as an internal standard). The mixture was then heated at 120 °C for 0.25 h. In most cases, the silylation of the hydroxyl groups was a rapid reaction carried out at moderate temperatures to prevent further pentaerythritol dimerization. This procedure also allows for excellent selectivity in the silylation of primary (dipentaerythritol) hydroxyl groups in polyol groups. The resulting silylated compounds were analyzed using GC-MS.

[0047] Data processing Calculate the pentaerythritol conversion, product yield, and selectivity according to Equations 1-3 respectively: Where n is the theoretical number of moles of PE converted into the corresponding polyol.

[0048] In Examples 1-14, dipentaerythritol was produced from pentaerythritol in the presence of sulfolane and different heteropolyacid catalysts according to the procedure disclosed in the preceding paragraph, "Procedure for the dimerization of pentaerythritol". The reaction conditions, catalyst loading, and results regarding the conversion of pentaerythritol, the yield of dipentaerythritol, and the selectivity are presented in Table 1 below.

[0049] Table 1. Pentaerythritol conversion, dipentaerythritol yield, and selectivity on heteropolyacid catalysts. Reaction conditions: glass vial reactor, pentaerythritol / sulfolane / catalyst: 0.5 g / 1 g / 0.25 g, 200 °C, 200 rpm. Successful handling of the pentaerythritol catalytic reaction step typically involves optimizing reaction conditions to increase the yield and selectivity of dipentaerythritol, as well as carefully controlling catalyst deactivation and recovery to allow for the recycling and reuse of expensive catalysts. Based on the results above, catalytic activity can be compared. The key features of the catalytic system of this invention can be seen in Table 1, which graphically illustrates the pentaerythritol conversion, dipentaerythritol yield, and selectivity. All supports were catalytically inactive under the operating conditions. Results indicate: H3SiW 12 O 40It is the most active of the two catalysts, with almost all pentaerythritol being converted at 200 °C for 120 min. Previously published references by Okuhara et al. suggest using a SiO2-supported polybasic acid, i.e., 15% H3SiW, in a sealed reactor. 12 O 40 / SiO2 and 20% H3PW 12 O 40 Selective dimerization of pentaerythritol was achieved on SiO2. The best results disclosed in this reference were obtained by solvent-free operation at 170 °C for 24 h, resulting in 72.9% conversion of pentaerythritol with a selectivity of 26.0%, and 81.6% conversion with a selectivity of 27.8%. Although the results disclosed in Table 1 used sulfolane as a solvent and achieved much higher selectivity for pentaerythritol, the supported catalyst showed greater selectivity and achieved a higher yield of pentaerythritol for the maximum pentaerythritol conversion.

[0050] Examples 9-14 illustrate 30% H3PW loaded on SnO2. 12 O 40 Catalyst and 30% H3PW supported on V2O5-doped SnO2 12 O 40 Differences between catalysts. Compared with undoped SnO2, 1% V2O5-doped SnO2 showed significant improvements in all aspects, including pentaerythritol conversion, dipentaerythritol selectivity, and dipentaerythritol yield, under the same operating conditions.

Claims

1. A process for producing dipentaerythritol from pentaerythritol, wherein the process includes the following steps: a) Pentaerythritol, sulfolane, and a heteropolyacid catalyst supported on a support are supplied to the reactor to form a reaction solution, wherein the support comprises a compound selected from the group consisting of: SnO2, mesoporous silica, and zeolite. b) The reaction solution was heated to a temperature in the range of 150°C to 250°C under continuous stirring and a pressure in the range of 0.5 bar to 5 bar for a period of time of 30 minutes to 600 minutes to obtain dipentaerythritol, and then... c) Separate the obtained dipentaerythritol from the reaction solution.

2. The process according to claim 1, wherein the weight ratio of pentaerythritol, sulfolane, and catalyst is 1:0.5-4:0.1-1.

3. The process according to claim 1 or 2, wherein the weight ratio of pentaerythritol, sulfolane, and catalyst is 1:2:0.

5.

4. The process according to any one of claims 1-3, wherein the heteropolyacid catalyst is selected from the group consisting of: H3PW 12 O 40 H3SiW 12 O 40 H4[SiW 12 O 40 ] and its combinations.

5. The process according to any one of claims 1-4, wherein the heteropolyacid catalyst is H3PW. 12 O 40 .

6. The process according to any one of claims 1-5, wherein the amount of the heteropolyacid catalyst is 20 wt%-30 wt% based on the weight of the support.

7. The process according to any one of claims 1-6, wherein the amount of the heteropolyacid catalyst is 30 wt% based on the weight of the support.

8. The process according to any one of claims 1-7, wherein the carrier is SnO2.

9. The process according to any one of claims 1-8, wherein the carrier is nanoporous SnO2.

10. The process according to any one of claims 1-9, wherein the carrier has an average pore size in the range of 5 nm to 10 nm.

11. The process according to any one of claims 1-10, wherein the carrier is doped with V2O5.

12. The process according to any one of claims 1-11, wherein the carrier is doped with 0.5 wt%-4.5 wt% V2O5 based on the weight of the carrier.

13. The process according to any one of claims 1-12, wherein the carrier is doped with 1 wt% V2O5 based on the weight of the carrier.

14. The process according to any one of claims 1-13, wherein the dipentaerythritol is separated from the reaction solution by fractional crystallization.

15. The process according to any one of claims 1-14, wherein the heteropolyacid catalyst is prepared by a method comprising the following steps: a) The heteropolyacid catalyst is impregnated onto the support by means of initial wet impregnation. b) Dry the heteropolyacid catalyst support composition at 110°C for at least 2 hours, and c) Calcine the dried heteropolyacid catalyst support composition at 250°C for at least 4 hours.

16. The process according to any one of claims 1-15, wherein the carrier comprises nanoparticles, the nanoparticles being prepared by a method comprising the following steps: a) Dilute SnCl2-2H2O in distilled water. b) Add HCl, c) Stir until approximately pH 1. d) Add V2O5 to approximately the same molar amount as SnCl2. e) Stir the solution by sonication at room temperature for at least 10 minutes. f) Neutralize the solution to approximately pH 9 using an alkali metal hydroxide. g) Stir the solution at a temperature ranging from 35°C to 65°C for at least 30 minutes. h) The obtained nanoparticles are separated from the diluent and soluble byproducts. i) Wash the nanoparticles with water and acetone. j) Dry the particles at 90°C, and h) Calcine the particles at a temperature in the range of 400℃-500℃ for 15-45 minutes.

17. The process according to claim 16, wherein the nanoparticles are coated on a carrier after washing in step i) and before drying in step j).

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