Preparation method of fatty acid pentaerythritol ester base oil

Abstract

The invention belongs to the technical field of synthetic ester, and particularly relates to a preparation method of fatty acid pentaerythritol ester base oil, which comprises the following steps: carrying out esterification reaction on pentaerythritol and fatty acid in the presence of a catalyst and a color retention agent, and carrying out post-treatment to obtain the fatty acid pentaerythritol ester base oil, the catalyst comprises at least one of stannous octoate, stannous oxalate, stannous oxide, tetrabutyl titanate, isopropyl titanate and sodium hydrogen sulfate; the color retention agent comprises at least one of sodium hypophosphite, hypophosphorous acid, activated carbon and sodium sulfite. The color retention agent sodium hypophosphite is matched with the specific catalyst such as stannous oxalate, so that the petroleum color number of the produced fatty acid pentaerythritol ester base oil is smaller, and meanwhile, the esterification reaction time is shorter.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic esters, and particularly relates to a method for preparing a fatty acid pentaerythritol ester base oil. Background Art

[0002] Pentaerythritol tetraesters of fatty acids exhibit excellent antioxidant properties, thermal stability, and viscosity-temperature performance. They are an important synthetic lubricant base oil widely used in aviation lubricants, air conditioning compressor oils, and semiconductor process oils. The most common method for synthesizing pentaerythritol esters is esterification. This method typically uses an acid as a catalyst to esterify pentaerythritol and fatty acids under certain conditions to produce the esters. Sulfuric acid is typically used as a catalyst, but this process is severely corrosive to equipment and prone to carbonization and byproduct formation. Commonly used acid catalysts include solid acid catalysts and heteropolyacids. Heteropolyacids are a class of superacids formed by the condensation of different oxygen-containing acids. However, heteropolyacids are readily soluble in the reactants, making their separation and recovery difficult. This poses significant challenges in product post-processing and limits their large-scale application. Furthermore, while these catalyst types exhibit good catalytic effects on the synthesis reaction, they also catalyze both the positive and negative reactions equally, resulting in a darker color for the synthesized pentaerythritol esters, severely impacting product quality.

[0003] In order to meet the needs of modern chemical industry, it is necessary to develop a preparation method for fatty acid pentaerythritol ester base oil, so that it can achieve high reaction efficiency, low cost, light product color, and performance indicators that meet the performance requirements of lubricant base oil. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for preparing a fatty acid pentaerythritol ester base oil; the invention can achieve a high yield of the prepared fatty acid pentaerythritol ester base oil while maintaining a low product color.

[0005] The inventive concept of the present invention is that by combining the color preservative sodium hypophosphite with a specific catalyst such as stannous oxalate, the petroleum color number of the produced fatty acid pentaerythritol ester base oil can be made smaller and the esterification reaction time can be shortened.

[0006] A first aspect of the present invention provides a method for preparing a pentaerythritol fatty acid ester base oil.

[0007] Specifically, a method for preparing a fatty acid pentaerythritol ester base oil comprises carrying out an esterification reaction between pentaerythritol and a fatty acid under conditions including a catalyst and a color preservative, followed by post-treatment to obtain the fatty acid pentaerythritol ester base oil; the catalyst comprises at least one of stannous octoate, stannous oxalate, stannous oxide, n-butyl titanate, isopropyl titanate, and sodium bisulfate; and the color preservative comprises at least one of sodium hypophosphite, hypophosphorous acid, activated carbon, and sodium sulfite.

[0008] Compared with the prior art, the beneficial effects of the preparation method of a fatty acid pentaerythritol ester base oil provided in the first aspect are as follows: by combining the color preservative sodium hypophosphite with a specific catalyst such as stannous oxalate, the petroleum color number of the produced fatty acid pentaerythritol ester base oil can be made smaller and the esterification reaction time can be shortened.

[0009] Preferably, the catalyst comprises stannous oxalate.

[0010] Preferably, the color preservative comprises sodium hypophosphite.

[0011] Preferably, the mass ratio of the pentaerythritol to the fatty acid is 1:4-6; further preferably, the mass ratio of the pentaerythritol to the fatty acid is 1:4-4.5.

[0012] Preferably, the amount of the catalyst added is 0.01-0.1 wt% of the sum of the mass of the pentaerythritol and the fatty acid; further preferably, the amount of the catalyst added is 0.01-0.05 wt% of the sum of the mass of the pentaerythritol and the fatty acid.

[0013] Preferably, the amount of the color preservative added is 0.01-0.05 wt% of the sum of the mass of the pentaerythritol and the fatty acid; further preferably, the amount of the color preservative added is 0.01-0.03 wt% of the sum of the mass of the pentaerythritol and the fatty acid.

[0014] Preferably, the reaction temperature of the esterification reaction is 160-200° C., and the reaction time of the esterification reaction is 7-9 hours.

[0015] Preferably, the post-treatment includes reduced pressure distillation, alkali washing, water washing, and dehydration.

[0016] Preferably, the vacuum degree of the reduced pressure distillation is -90 to -100 kPa (relative vacuum degree), and the temperature of the reduced pressure distillation is 160-180°C; further preferably, the vacuum degree of the reduced pressure distillation is -93 to -98 kPa, and the temperature of the reduced pressure distillation is 170-180°C.

[0017] Preferably, the end condition of the reduced pressure distillation is that the acid value is ≤3.0 mgKOH / g.

[0018] Preferably, the temperature of the alkaline washing is 50-70° C., the concentration of the alkaline solution of the alkaline washing is 10-50 wt %, and the end condition of the alkaline washing is that the acid value is ≤ 0.02 mgKOH / g.

[0019] Preferably, the volume of the alkali solution used in the alkali washing is 5-20% of the organic phase, and the volume of the water used in the alkali washing is 10-20% of the organic phase.

[0020] Preferably, the vacuum degree of the dehydration is -90 to -100 KPa, the temperature of the dehydration is 60-80° C., the time of the dehydration is 3-4 hours, and the end condition of the dehydration is that the moisture content is ≤100 ppm.

[0021] Preferably, the ester content of the pentaerythritol fatty acid ester base oil is ≥97 wt%.

[0022] Preferably, the fatty acid includes at least one of C4-C18 fatty acids; further preferably, the fatty acid includes at least one of C8-C9 fatty acids; further preferably, the fatty acid includes isooctanoic acid and isononanoic acid.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method of the present invention has simple procedures and is environmentally friendly. It does not use any solvent and has no solvent consumption and recovery costs.

[0024] (2) The composite catalyst selected in the preparation method of the present invention is simple, easy to obtain, low-cost, and has no residue after washing. It also has high catalytic efficiency and good product color. (3) The product prepared by the preparation method of the present invention has high purity, which can reach at least 97% or more, and has good color, with the petroleum color number being below No. 3. DETAILED DESCRIPTION

[0025] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0026] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods; 2-ethylhexanoic acid CAS No.: 25103-52-0, 2-ethylhexanoic acid CAS No.: 26896-18-4. Example 1

[0027] A method for preparing fatty acid pentaerythritol ester base oil.

[0028] In a four-necked flask equipped with a mechanical stirrer and a thermometer, 1.0 mol (136.00 g) of pentaerythritol, 2.64 mol (380.16 g) of isooctanoic acid, 1.76 mol (278.10 g) of isononanoic acid, 0.16 g of stannous oxalate, and 0.24 g of sodium hypophosphite were added; After the water separator was installed, the temperature was raised to 200°C and the esterification reaction was carried out for 7 hours. The ester content tested by GC was 97.85%, which was qualified. After cooling to 160°C, use a vacuum distillation apparatus and evacuate to -98kPa to start vacuum distillation. After 6-8 hours, the acid value test is 2.36mgKOH / g, which is qualified. After cooling to 70°C, add 100g of 10% liquid alkali and stir for alkali washing for 1 hour, let it stand for 0.5 hour, and separate the liquids; Then add 100g water, heat to 70℃, stir and wash with water for 1h, let it stand for 0.5h, separate the liquid, and test the acid value to 0.012mgKOH / g, which is qualified; The qualified base oil after water washing is subjected to vacuum distillation dehydration at a temperature of 65°C. After dehydration for 3-4 hours, fatty acid pentaerythritol ester base oil is obtained. The moisture content is 65ppm and the product is petroleum color No. 1.

[0029] Example 1 The ester content, esterification reaction time, and petroleum color number are recorded in Table 1. Example 2

[0030] The difference between Example 2 and Example 1 is that the catalyst stannous oxalate in Example 2 is replaced by stannous octoate, and the esterification reaction time is 7.5 h.

[0031] Example 2 The ester content, esterification reaction time, and product petroleum color number are recorded in Table 1. Example 3

[0032] The difference between Example 3 and Example 1 is that the catalyst stannous oxalate in Example 2 is replaced by butyl titanate, and the esterification reaction time is 8 hours.

[0033] Example 3 The ester content, esterification reaction time, and product petroleum color number are recorded in Table 1. Example 4

[0034] The difference between Example 4 and Example 1 is that the catalyst stannous oxalate of Example 2 is replaced by isopropyl titanate, and the esterification reaction time is 8 hours.

[0035] The ester content and petroleum color number of the product of Example 4 are recorded in Table 1. Example 5

[0036] The difference between Example 5 and Example 1 is that the catalyst stannous oxalate of Example 2 is replaced by sodium bisulfate.

[0037] Example 5 The ester content, esterification reaction time, and product petroleum color number are recorded in Table 1.

[0038] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the catalyst stannous oxalate and the color preservative sodium hypophosphite are not added in Comparative Example 1, and the esterification reaction time is 12 hours.

[0039] The ester content, esterification reaction time, and product petroleum color number of Comparative Example 1 are recorded in Table 1.

[0040] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the catalyst stannous oxalate is not added in Comparative Example 2, and the esterification reaction time is 11 hours.

[0041] The ester content, esterification reaction time, and product petroleum color number of Comparative Example 1 are recorded in Table 1.

[0042] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the color preservative sodium hypophosphite is not added in Comparative Example 3, and the esterification reaction time is 9 hours.

[0043] The ester content, esterification reaction time, and product petroleum color number of Comparative Example 3 are recorded in Table 1.

[0044] Table 1 Ester content, esterification reaction time, and petroleum color number of Examples 1-5 and Comparative Examples 1-3 Example Catalyst g Color preservative g Esterification time h Ester content% Acid value mgKOH / g Moisture ppm Petroleum color Example 1 0.16 0.24 7 97.85 0.012 65 1 Example 2 0.16 0.24 7.5 97.52 0.016 73 2 Example 3 0.16 0.24 8 97.42 0.013 61 2 Example 4 0.16 0.24 8 97.36 0.012 72 2 Example 5 0.16 0.24 7 97.45 0.014 76 3 Comparative Example 1 0 0 12 97.05 0.015 75 6 Comparative Example 2 0 0.24 11 97.31 0.014 72 5 Comparative Example 3 0.16 0 9 97.44 0.013 71 7 As can be seen from Table 1, the addition of the composite catalyst significantly shortened the esterification reaction time in Examples 1-5, and the resulting products were all qualified, with better product color than the comparative example. In particular, Example 1 had a shorter esterification time and a petroleum color number reduced to 1.

[0045] Comparative Example 4 A method for preparing fatty acid pentaerythritol ester base oil.

[0046] The difference between Comparative Example 4 and Example 1 is that isononanoic acid is replaced by an equal molar amount of oleic acid, and the rest of the preparation method remains unchanged.

[0047] The experimental results were recorded as follows: esterification reaction time 7 h, ester content 97.34%, acid value 0.014 mgKOH / g, moisture 70 ppm, and product petroleum color number 6.

[0048] Comparative Example 5 A method for preparing fatty acid pentaerythritol ester base oil.

[0049] The difference between Comparative Example 5 and Example 1 is that the color preservative sodium hypophosphite is replaced by an equal mass of oxalic acid, and the rest of the preparation method remains unchanged.

[0050] The experimental results were recorded as follows: esterification reaction time 7 h, ester content 97.54%, acid value 0.016 mgKOH / g, moisture 72 ppm, and product petroleum color number 7.

[0051] Under the premise that no conflict occurs, those skilled in the art can freely combine and superimpose the above additional technical features. The above is only a preferred embodiment of the present invention. As long as the technical solutions that achieve the purpose of the present invention by basically the same means are within the scope of protection of the present invention.

Claims

1. A method for preparing a fatty acid pentaerythritol ester base oil, characterized in that: The preparation method comprises the following steps: performing an esterification reaction between pentaerythritol and fatty acid under conditions including a catalyst and a color preservative, and performing post-processing to obtain the fatty acid pentaerythritol ester base oil; The catalyst comprises at least one of stannous octoate, stannous oxalate, stannous oxide, n-butyl titanate, isopropyl titanate, and sodium bisulfate; The color preservative includes at least one of sodium hypophosphite, hypophosphorous acid, activated carbon, and sodium sulfite.

2. The preparation method according to claim 1, characterized in that The catalyst includes stannous oxalate, and the color retaining agent includes sodium hypophosphite.

3. The preparation method according to claim 1, characterized in that The mass ratio of the pentaerythritol to the fatty acid is 1:4-6.

4. The preparation method according to claim 1, characterized in that The amount of the catalyst added is 0.01-0.1 wt % of the sum of the mass of the pentaerythritol and the fatty acid.

5. The preparation method according to claim 1, characterized in that The amount of the color preservative added is 0.01-0.05 wt % of the sum of the mass of the pentaerythritol and the fatty acid.

6. The preparation method according to claim 1, characterized in that The reaction temperature of the esterification reaction is 160-200° C., and the reaction time of the esterification reaction is 7-9 hours.

7. The preparation method according to claim 1, characterized in that The post-treatment includes reduced pressure distillation, alkali washing, water washing and dehydration.

8. The preparation method according to claim 1, characterized in that The vacuum degree of the reduced pressure distillation is -90 to -100 kPa, the temperature of the reduced pressure distillation is 160-180° C., and the termination condition of the reduced pressure distillation is that the acid value is ≤3.0 mgKOH / g.

9. The preparation method according to claim 1, characterized in that The temperature of the alkaline washing is 50-70° C., the concentration of the alkaline solution is 10-50 wt %, and the end condition of the alkaline washing is that the acid value is ≤ 0.02 mgKOH / g.

10. The preparation method according to claim 1, characterized in that The fatty acids include isooctanoic acid and isononanoic acid.