Synthesis method of pentaerythritol tetrastearate

Abstract

The invention relates to the technical field of chemical synthesis, in particular to a synthesis method of pentaerythritol tetrastearate. The method comprises the following steps: 1, adding stearic acid into a reaction kettle, and heating to 130-200 DEG C; 2, stirring is started, the rotating speed is set to be 100 rpm, and meanwhile nitrogen is introduced at the flow speed of 2 liters per minute; 3, pentaerythritol and a sulfuric acid-zirconium dioxide catalyst are added, the temperature of the reaction kettle is controlled to be 180-210 DEG C, and a violent reaction is conducted; and 4, after the reaction is carried out for 15-19 hours, sampling and analyzing. Through a series of improvements, the hydroxyl value and the acid value in the pentaerythritol tetrastearate can be effectively reduced, and the reaction last-stage rate for synthesizing the pentaerythritol tetrastearate can be remarkably increased.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, in particular to a method for synthesizing pentaerythritol tetrastearate. Background Art

[0002] Pentaerythritol (PE) is often used for special structural functional group grafting due to its special structure with four hydroxyl groups and no beta hydrogen. Pentaerythritol tetrastearate (PETS) is based on PE and undergoes esterification reaction to connect long-chain stearic acid (SA) to achieve lubrication effect. Figure 1 shown.

[0003] As more hydroxyl groups on PE are connected to SA, the number of unreacted hydroxyl groups and acid groups decreases, and the probability of effective collision decreases. In addition, the four hydroxyl groups on PE are close to each other, and the long chain of stearic acid is sterically hindered in its swing, making it more difficult to connect all four lipids to form a complete PETS structure.

[0004] When the PETS synthesis reaches the final stage, the reaction is quite slow. If the dehydration rate can be increased at this time, the reaction speed will be significantly improved. Based on this, a synthesis method of pentaerythritol tetrastearate is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a method for synthesizing pentaerythritol tetrastearate to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for synthesizing pentaerythritol tetrastearate, comprising the following steps:

[0007] Step 1: Add stearic acid into the reactor and heat to 130-200°C;

[0008] Step 2: Start stirring, set the speed to 100 rpm, and introduce nitrogen at a flow rate of 2 L / min;

[0009] Step 3: Add pentaerythritol and sulfuric acid-zirconium dioxide catalyst, and control the temperature of the reactor at 180-210℃ to allow a violent reaction to occur;

[0010] Step 4: After the reaction has proceeded for 15-19 hours, samples are taken for analysis.

[0011] Furthermore, the third step further includes the following steps:

[0012] Add water-absorbing material in an amount of 0.5-1 wt % of the reaction solution in the reactor.

[0013] Furthermore, the fourth step further includes the following steps:

[0014] Add water-absorbing material, continue the reaction for 2-3 hours, and take samples for analysis again.

[0015] Furthermore, the weight of the stearic acid is 500-600 parts, the weight of the pentaerythritol is 70-85 parts, the weight of the sulfuric acid-zirconium dioxide catalyst is 1-4 parts, and the weight of the water-absorbing material is 3-6 parts.

[0016] Furthermore, the water-absorbing material is a neutral water-absorbing agent rich in hydroxyl groups.

[0017] Furthermore, the water-absorbing material is one or more of silica gel molecular sieve, polyhydroxyethyl methacrylate and polyvinyl alcohol.

[0018] Furthermore, it also includes supercritical CO2 coupled membrane separation and purification, the steps are as follows:

[0019] Unreacted stearic acid was extracted using supercritical CO2, combined with cross-flow filtration using a ceramic membrane, and the product was graded and purified using a two-stage gradient depressurization system.

[0020] Furthermore, it also includes online combined monitoring, the steps are as follows:

[0021] An immersed fiber optic probe was installed to calculate the degree of esterification in real time through characteristic peaks; a PLS mathematical model was established to realize dynamic prediction of acid value and hydroxyl value.

[0022] Furthermore, the process also includes catalyst regeneration and by-product recovery, and the steps are as follows:

[0023] The deactivated sulfuric acid-zirconium dioxide catalyst was ultrasonically cleaned with a 5wt% citric acid / ethanol mixture and then activated with plasma to restore its activity; the by-product water was dehydrated with a molecular sieve and then reused for pentaerythritol pretreatment.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention can effectively reduce the hydroxyl value and acid value of pentaerythritol tetrastearate through a series of improvements, and can significantly increase the final reaction rate of synthesizing pentaerythritol tetrastearate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the synthesis of pentaerythritol tetrastearate of the present invention;

[0027] Figure 2 Schematic diagram of the structure of the silica gel molecular sieve of the present invention;

[0028] Figure 3Schematic diagram of the structure of polyhydroxyethyl methacrylate of the present invention;

[0029] Figure 4 Schematic diagram of the structure of polyvinyl alcohol of the present invention;

[0030] Figure 5 Schematic diagram of the reaction equipment of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1:

[0033] Please also refer to Figure 1-Figure 5 A method for synthesizing pentaerythritol tetrastearate comprises the following steps:

[0034] Step 1: Add stearic acid into the reactor and heat to 130-200°C;

[0035] Step 2: Start stirring, set the speed to 100 rpm, and introduce nitrogen at a flow rate of 2 L / min;

[0036] Step 3: Add pentaerythritol and sulfuric acid-zirconium dioxide catalyst, and control the temperature of the reactor at 180-210°C to allow a violent reaction to occur;

[0037] Step 4: After the reaction has proceeded for 15-19 hours, samples are taken for analysis.

[0038] Furthermore, when the stearic acid and pentaerythritol with the adjusted feed ratio are reacted in the reactor until the acid value of the reaction solution sampled is lower than 8 mgKOH / g sample, a water-absorbing material may be added in the third step in an amount of 0.5-1 wt % of the reaction solution in the reactor;

[0039] If there is concern that a small number of water-absorbing functional groups may react with stearic acid, or if there is concern that polyvinyl alcohol may be easily decomposed at high temperatures, the reactor temperature can be lowered to 120-150°C before adding the water-absorbing material.

[0040] If no water-absorbing material is added in the third step, it is necessary to add the water-absorbing material during the fourth step, continue the reaction for 2-3 hours, and take samples for analysis again; then, by adding the water-absorbing material after cooling at the end of the reaction, the lipidation and dehydration reaction can be assisted to make the lipidation more complete.

[0041] The weight portion of stearic acid may be 500-600 parts, the weight portion of pentaerythritol may be 70-85 parts, the weight portion of sulfuric acid-zirconium dioxide catalyst may be 1-4 parts, and the weight portion of the water-absorbing material may be 3-6 parts.

[0042] The water-absorbing material is a neutral water-absorbing agent rich in hydroxyl groups, which does not produce acid-base neutralization with the raw materials. Specifically, the water-absorbing material can be one or more of silica gel molecular sieve, polyhydroxyethyl methacrylate and polyvinyl alcohol.

[0043] Among them, silica gel molecular sieves (Molecular sieves, molecular formula such as Figure 2 shown);

[0044] Poly(2-Hydroxyethyl methacrylate), referred to as PHEMA, has the molecular formula Figure 3 As shown;

[0045] Polyvinyl alcohol, referred to as PVAl, has a molecular formula such as Figure 4 shown.

[0046] Example 2:

[0047] Please also refer to Figure 1-Figure 5 A method for synthesizing pentaerythritol tetrastearate comprises the following steps:

[0048] Heat 600 g of stearic acid in a reactor to 130°C, stir at 100 rpm, and introduce nitrogen at 2 L / min.

[0049] Then, 85 g of pentaerythritol and 2 g of sulfuric acid-zirconium dioxide catalyst were added, and the kettle temperature was controlled at 195 ± 3 ° C to allow for a vigorous reaction;

[0050] After 15 hours, samples were taken for analysis and the acid value was 6.13 mgKOH / g and the hydroxyl value was 23.06 mgKOH / g, indicating that the reaction was already quite slow.

[0051] At this time, 6 grams of silica gel molecular sieve was added to continue the reaction for 2 hours. Samples were taken for analysis and the acid value dropped to 3.78 mgKOH / g and the hydroxyl value dropped to 21.12 mgKOH / g.

[0052] The specifications of relevant stearic acid, pentaerythritol, sulfuric acid-zirconium dioxide, and silica gel molecular sieve are shown in Table 1:

[0053] Table 1

[0054]

[0055] Example 3:

[0056] Please also refer to Figure 1-Figure 5 A method for synthesizing pentaerythritol tetrastearate comprises the following steps:

[0057] 500 g of stearic acid, 70 g of pentaerythritol, and sulfuric acid-zirconium dioxide catalyst were placed in a kettle at 190±3°C and stirred with nitrogen.

[0058] After 18.5 hours, the acid value of the reaction solution was 6.45 mgKOH / g and the hydroxyl value was 26.48 mgKOH / g;

[0059] After cooling to 120℃, 3g of polyvinyl alcohol was added. After 3 hours, samples were taken and the acid value dropped to 4.67mgKOH / g and the hydroxyl value dropped to 24.53mgKOH / g.

[0060] The specifications of relevant stearic acid, pentaerythritol, sulfuric acid-zirconium dioxide, and polyvinyl alcohol are shown in Table 2:

[0061] Table 2

[0062]

[0063] Example 4:

[0064] Please also refer to Figure 1-Figure 5 A method for synthesizing pentaerythritol tetrastearate comprises the following steps:

[0065] 600 g of stearic acid, 80 g of pentaerythritol, and sulfuric acid-zirconium dioxide catalyst were stirred in a kettle at 200±3°C with nitrogen;

[0066] After 18 hours, the reaction solution had an acid value of 6.71 mgKOH / g and a hydroxyl value of 24.33 mgKOH / g.

[0067] After cooling to 150°C, 6 g of poly(hydroxyethyl methacrylate) was added. After 2 hours, samples were taken and the acid value dropped to 4.98 mgKOH / g and the hydroxyl value dropped to 23.25 mgKOH / g.

[0068] The specifications of relevant stearic acid, pentaerythritol, sulfuric acid-zirconium dioxide, and polyhydroxyethyl methacrylate are shown in Table 3:

[0069] Table 3

[0070]

[0071] Embodiment 5:

[0072] Please also refer to Figure 1-Figure 5 A method for synthesizing pentaerythritol tetrastearate comprises the following steps:

[0073] Heat 600 g of stearic acid in a reactor to 130°C, stir at 100 rpm, and introduce nitrogen at 2 L / min.

[0074] Then, 85 g of pentaerythritol and 2 g of sulfuric acid-zirconium dioxide catalyst were added, and the kettle temperature was controlled at 195 ± 3 ° C to allow for a vigorous reaction;

[0075] After 15 hours, samples were taken for analysis, and the acid value was 6.13 mgKOH / g and the hydroxyl value was 23.06 mgKOH / g.

[0076] Then 6 g of silica gel molecular sieve was added and the reaction was continued for 2 hours before sampling and analysis;

[0077] In order to greatly shorten the analysis time, online coupled monitoring was used and an immersed fiber optic probe was installed to detect the characteristic peak (1745 cm -1 Ester group C=O, 1710 cm -1 Acid C=O) real-time calculation of esterification degree; establishment of PLS mathematical model to achieve dynamic prediction of acid value and hydroxyl value (R 2 >0.97), and then automatically trigger the dehydration process when the esterification rate reaches 97%, which can greatly shorten the analysis time;

[0078] In this embodiment, after the reaction is completed, a supercritical CO2-coupled membrane separation and purification step is performed, in which unreacted stearic acid is extracted using supercritical CO2 (40°C / 10MPa), and a ceramic membrane (300kDa MWCO) is used for cross-flow filtration. The product is graded and purified by a two-stage gradient pressure reduction system (8MPa→3MPa→0.5MPa), thereby further improving the product purity and reducing energy consumption.

[0079] In addition, in order to be able to utilize waste materials as resources, it also includes catalyst regeneration and by-product recovery steps:

[0080] The deactivated sulfuric acid-zirconium dioxide catalyst was ultrasonically cleaned with a 5wt% citric acid / ethanol mixture and then restored to activity using plasma activation (Ar / O2=4:1, 200W / 10min). The byproduct water was dehydrated through a molecular sieve and reused for pentaerythritol pretreatment, thereby further reducing the catalyst regeneration cost and greatly improving water resource utilization.

[0081] In summary, the present invention provides a method for synthesizing pentaerythritol tetrastearate. Compared with existing processes, the present invention effectively reduces the hydroxyl value and acid value of pentaerythritol tetrastearate, whether considering the possibility that a small number of water-absorbing functional groups may react with stearic acid or the concern that polyvinyl alcohol is easily decomposed at high temperatures, requiring cooling to 120-150°C before adding the water-absorbing material. This can increase the reaction rate at the end of the synthesis of pentaerythritol tetrastearate.

[0082] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0083] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing pentaerythritol tetrastearate, characterized in that: The steps include: Step 1: Add stearic acid into the reactor and heat to 130-200°C; Step 2: Start stirring, set the speed to 100 rpm, and introduce nitrogen at a flow rate of 2 L / min; Step 3: Add pentaerythritol and sulfuric acid-zirconium dioxide catalyst, and control the temperature of the reactor at 180-210℃ to allow a violent reaction to occur; Step 4: After the reaction has proceeded for 15-19 hours, samples are taken for analysis.

2. The method for synthesizing pentaerythritol tetrastearate according to claim 1, wherein: The third step further comprises the following steps: Add water-absorbing material in an amount of 0.5-1 wt % of the reaction solution in the reactor.

3. The method for synthesizing pentaerythritol tetrastearate according to claim 1, wherein: The fourth step further comprises the following steps: Add water-absorbing material, continue the reaction for 2-3 hours, and take samples for analysis again.

4. The method for synthesizing pentaerythritol tetrastearate according to any one of claims 2 or 3, wherein: The weight portion of the stearic acid is 500-600 parts, the weight portion of the pentaerythritol is 70-85 parts, the weight portion of the sulfuric acid-zirconium dioxide catalyst is 1-4 parts, and the weight portion of the water-absorbing material is 3-6 parts.

5. The method for synthesizing pentaerythritol tetrastearate according to claim 4, wherein: The water-absorbing material is a neutral water-absorbing agent rich in hydroxyl groups.

6. The method for synthesizing pentaerythritol tetrastearate according to claim 5, wherein: The water-absorbing material is one or more of silica gel molecular sieve, polyhydroxyethyl methacrylate and polyvinyl alcohol.

7. The method for synthesizing pentaerythritol tetrastearate according to claim 1, wherein: It also includes supercritical CO2 coupled membrane separation and purification, the steps are as follows: Unreacted stearic acid was extracted using supercritical CO2, combined with cross-flow filtration using a ceramic membrane, and the product was graded and purified using a two-stage gradient depressurization system.

8. The method for synthesizing pentaerythritol tetrastearate according to claim 7, wherein: It also includes online combined monitoring, the steps are as follows: An immersed fiber optic probe was installed to calculate the degree of esterification in real time through characteristic peaks; a PLS mathematical model was established to realize dynamic prediction of acid value and hydroxyl value.

9. The method for synthesizing pentaerythritol tetrastearate according to claim 8, wherein: It also includes catalyst regeneration and by-product recovery, the steps are as follows: The deactivated sulfuric acid-zirconium dioxide catalyst was ultrasonically cleaned with a 5wt% citric acid / ethanol mixture and then activated with plasma to restore its activity; the by-product water was dehydrated with a molecular sieve and then reused for pentaerythritol pretreatment.

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