Application of phenolic antioxidants in phosphate ester fire-resistant oil and phosphate ester fire-resistant oil

Abstract

This invention discloses the application of phenolic antioxidants in phosphate ester fire-resistant oil and the phosphate ester fire-resistant oil itself. It belongs to the field of phosphate ester fire-resistant oil technology. The phenolic antioxidant used is 2,6-di-tert-butyl-p-cresol, with an addition dosage of 0.03%–0.1%. The main component of the phosphate ester fire-resistant oil is tris(2,4-methyl)phosphate. Adding this phenolic antioxidant to the phosphate ester fire-resistant oil product can improve its overall performance during operation, enhance the stability of the phosphate ester fire-resistant oil product, and provide a guarantee for the safe operation of generator sets.

Description

Technical Field

[0001] This invention belongs to the field of phosphate ester fire-resistant oil technology, specifically to the application of phenolic antioxidants in phosphate ester fire-resistant oil and the phosphate ester fire-resistant oil itself. Background Technology

[0002] Phosphate ester fire-resistant oil is a fully synthetic phosphate ester fire-retardant hydraulic fluid. Due to its excellent fire-retardant and lubricating properties, it is widely used in the speed control systems of steam turbines and gas turbines.

[0003] Phosphate ester fire-resistant oil is composed of triaryl phosphate esters. The difference between different brands lies in the substituents on the benzene ring. Because phosphate ester fire-resistant oil is a chemically synthesized product, it has poor compatibility with additives, and most additives cannot be added. Compared to mineral oils, phosphate ester fire-resistant oil deteriorates rapidly. During use, it often exhibits phenomena such as increased acid value, rapid decrease in resistivity, and sludge formation after a short operating time. These can lead to reduced flexibility of turbine components and corrosion and jamming of servo valves in the speed control system. In severe cases, it can cause abnormal unit shutdowns, affecting the safe operation of power plant turbine units. Furthermore, phosphate ester fire-resistant oil is expensive, and frequent oil changes increase the economic costs for the power industry. The used phosphate ester fire-resistant oil is classified as general hazardous waste, and improper disposal can pollute water and soil. Summary of the Invention

[0004] To overcome the problems in existing phosphate ester fire-resistant oils, such as increased acid value, decreased resistivity, and sludge formation during use, which lead to reduced flexibility of turbine components and corrosion and jamming of servo valves in the speed control system, thus affecting the safe operation of power plant turbine units, this invention provides an application of a phenolic antioxidant in phosphate ester fire-resistant oil and the phosphate ester fire-resistant oil itself. The phenolic antioxidant is 2,6-di-tert-butyl-p-cresol, added at a dosage of 0.03% to 0.1%. Adding this phenolic antioxidant to the phosphate ester fire-resistant oil product can improve its overall performance during operation, enhance its stability, and provide a guarantee for the safe operation of generator units.

[0005] To achieve the above objectives, the present invention provides the following technical solution: the application of a phenolic antioxidant in phosphate ester fire-resistant oil, wherein the phenolic antioxidant is 2,6-di-tert-butyl-p-cresol.

[0006] Furthermore, the amount of 2,6-di-tert-butyl-p-cresol added is 0.03% to 0.1%.

[0007] Furthermore, the main component of the phosphate ester fire-resistant oil is tris(2,4-dimethyl)phosphate.

[0008] The present invention also provides a phosphate ester fire-resistant oil, wherein 0.03% to 0.1% of 2,6-di-tert-butyl-p-cresol is added to the phosphate ester fire-resistant oil.

[0009] Furthermore, the main component of the phosphate ester fire-resistant oil is tris(2,4-dimethyl)phosphate.

[0010] This invention also provides a method for preparing phosphate ester fire-resistant oil, the specific steps of which are as follows:

[0011] S1 determines the amount of 2,6-di-tert-butyl-p-cresol based on the total amount of oil, and dissolves 2,6-di-tert-butyl-p-cresol in ten times its weight of new phosphate ester fire-resistant oil to obtain 2,6-di-tert-butyl-p-cresol mother liquor.

[0012] Under the S2 sealed condition, add the 2,6-di-tert-butyl-p-cresol mother liquor to the phosphate ester fire-resistant oil to be added.

[0013] Furthermore, in S1, the amount of 2,6-di-tert-butyl-p-cresol added is 0.03% to 0.1%, and the main component of the phosphate ester fire-resistant oil is tris(2,4-methyl)phosphate.

[0014] Furthermore, in S1, 2,6-di-tert-butyl-p-cresol is dissolved in ten times its weight of new phosphate ester fire-resistant oil at 60℃±5℃ to obtain 2,6-di-tert-butyl-p-cresol mother liquor.

[0015] The present invention also provides an application of phosphate ester fire-resistant oil, wherein the above-mentioned phosphate ester fire-resistant oil or the phosphate ester fire-resistant oil prepared by the above preparation method is used in the speed control system of a power plant steam turbine.

[0016] The present invention also provides an application of phosphate ester fire-resistant oil, wherein the above-mentioned phosphate ester fire-resistant oil or the phosphate ester fire-resistant oil prepared by the above preparation method is used in the speed control system of a gas turbine in a power plant.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] This invention provides an application of phenolic antioxidants in phosphate ester fire-resistant oil. The phenolic antioxidant is specifically 2,6-di-tert-butyl-p-cresol, which is currently mainly added to hydrocarbon mineral oils at a dosage of 0.5%. In this invention, the dosage is 0.03% to 0.1%, and it can be directly added to the phosphate ester fire-resistant oil. The addition method is simple. After addition, it can improve the stability of acid value, resistivity, and sludge precipitation during the use of phosphate ester fire-resistant oil, reduce the rate of increase in acid value and decrease in resistivity of phosphate ester fire-resistant oil products, and extend the operating time before sludge formation, thereby extending the service life of phosphate ester fire-resistant oil. Moreover, it is inexpensive, has a simple addition method, and has high economic and social value. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. The following is an explanation of the present invention and not a limitation thereof.

[0020] This invention improves the overall performance of phosphate ester fire-resistant oil products by adding antioxidants. The main component of the phosphate ester fire-resistant oil is tris(2-methyl)phosphate. The specific steps are as follows:

[0021] S1 Sample preparation: A certain amount of a certain additive is added to a phosphate ester fire-resistant oil base oil (hereinafter referred to as base oil) whose main component is tris(2-methyl)phosphate ester;

[0022] S1.1 Additives include phenolic additives;

[0023] The phenolic additives include 2,4-dicumylphenol, tert-butylhydroquinone, 4,4'-methylenebis(2,6-di-tert-butylphenol), 2,6-di-tert-butyl-p-cresol, and dodecylphenol.

[0024] The dosage of S1.2 phenolic additives is 0.3% of the base oil by weight;

[0025] S1.3 Preparation method of samples containing additives:

[0026] S1.3.1 Number the additives from 1 to n. Take a glass bottle equipped with a sealing stopper, weigh a certain amount of base oil into the glass bottle, and number the sample bottles from 1 to n. Then, calculate the mass of each additive based on the mass of the base oil in the corresponding numbered sample bottle, weigh it with an analytical balance, add it to the corresponding sample bottle, and seal the bottle with the cap.

[0027] Preferably, the sample bottle has a volume of 1000 mL, and the sample bottle stopper is a polytetrafluoroethylene (PTFE) stopcock.

[0028] S1.3.2 Place the sealed sample vials on the mixing device, which includes a vertically arranged triangular support. The bottom of the triangular support is fixed in the drying oven, and a motor is installed on the top of the triangular support. The motor shaft is detachably connected to the sample vial fixing plate. When the motor shaft is connected to the sample vial fixing plate, the sample vial fixing plate is driven by the motor to achieve continuous vertical rotation at a speed of 5 r / min to 10 r / min. Multiple sample vial fixing clamps are arranged along the circumference of the sample vial fixing plate to fix the mouths of multiple sample vials toward the center of the sample vial fixing plate.

[0029] Preferably, the sample bottle fixing clamp includes a bottle bottom fixing clamp, a bottle body fixing clamp, and a bottle top fixing clamp, wherein the bottle top fixing clamp is a movable fixing clamp, which can prevent the sample bottle from falling off during rotation after being tightened.

[0030] S1.3.3 Connect the sample bottle fixing plate containing the sample bottle to the motor shaft. Keep the temperature in the drying oven constant at a fixed temperature between 60℃ and 5℃. Rotate the sample bottle fixing plate to mix the sample for 1 hour to ensure that the additive dissolves in the base oil and is mixed evenly.

[0031] S1.3.4 Remove the sample from the drying oven and cool it to room temperature.

[0032] S2 Preliminary Screening: Acid value, resistivity, oxidation stability, hydrolytic stability, and air release value were tested on the base oil and the samples prepared in S1. The quality of each phosphate ester fire-resistant oil sample after adding each additive was compared with the base oil. Samples with a significant decrease in the quality of the above indicators indicated that the additive and the phosphate ester fire-resistant oil sample were incompatible, and the corresponding candidate additives were eliminated.

[0033] S3 further screening: Additives not eliminated in S2 were used to prepare phosphate ester fire-resistant oil samples according to S1. Closed-cup aging tests were conducted on the base oil and the prepared phosphate ester fire-resistant oil samples. During the aging test, samples were periodically taken to test the acid value, resistivity, sludge precipitation, oxidation stability, hydrolytic stability, and air release value. When comparing the phosphate ester fire-resistant oil samples with the base oil after adding each additive, those with a significantly faster rate of deterioration in the above quality indicators indicated incompatibility between the additive and the phosphate ester fire-resistant oil product, and the corresponding candidate additives were eliminated.

[0034] Preferably, a 1000mL ground glass conical flask is used during the aging process, and the sample volume in the flask is 600g.

[0035] Preferably, three copper wires with a purity of not less than 99.9%, a diameter of 1.00 mm to 1.02 mm, and a length of 330 mm are added to 600 g of sample;

[0036] Preferably, after removing the surface oxide layer of the copper wire with a mixed acid, the surface acid is rinsed off with running tap water and distilled water in sequence, and then placed in a beaker containing ethanol and acetone for 10 seconds, and left at room temperature for 5 minutes to dry the solvent.

[0037] Preferably, the mixed acid used to clean the copper wire is a mixture of phosphoric acid and nitric acid in a ratio of 1:3;

[0038] Preferably, the moisture content of the parallel comparison samples during the aging process is consistent, between 200 mg / L and 300 mg / L;

[0039] Preferably, the number of time points for longitudinal comparison of a single sample is 7 to 10;

[0040] Preferably, samples for longitudinal and transverse comparisons are prepared at the same time;

[0041] Preferably, samples for cross-sectional comparison are taken simultaneously at the same aging time.

[0042] S4 Additive Dosage Selection: For additives not removed in S2, samples are prepared according to S1. Closed-cup aging tests are conducted on the base oil and the prepared samples. During the aging test, samples are periodically taken to test the acid value, resistivity, sludge precipitation, oxidation stability, and hydrolytic stability of the samples. Comparisons are made between samples. For samples where the above quality indicators deteriorate more slowly than those of the base oil, the corresponding additives and dosages are considered suitable.

[0043] Example

[0044] This invention provides a phosphate ester fire-resistant oil, the specific steps of which are as follows:

[0045] The preparation of sample S1 is as follows:

[0046] S1.1 Take five 1000mL sample bottles and number them 1 to 5 in sequence. Weigh 1000.0g of base oil into each of the five sample bottles.

[0047] S1.2 Weigh out 3.0000g + 0.0001g of 2,4-dicumylphenol, tert-butylhydroquinone, 4,4'-methylenebis(2,6-di-tert-butylphenol), 2,6-di-tert-butyl-p-cresol, and dodecylphenol respectively, and number them 1 to 5 in sequence; add the additives to the sample bottles with the same number.

[0048] S2 preliminary screening: Acid value, resistivity, oxidation stability, hydrolysis stability, and air release value were tested on the base oil and the samples prepared in S1. The test results are shown in Table 1.

[0049] Table 1. Preliminary screening test results of each additive

[0050]

[0051]

[0052] Note: The repeatability deviation for acid value is 0.02 mg KOH / g; for resistivity greater than 1.0 × 10¹⁰ Ω·cm, the repeatability is no greater than 25% of the relative error; and for air release value less than 5 min, the repeatability is no greater than 0.7 min. Therefore, compared with the results for base oil, when the deviations in acid value, hydrolytic stability, and oxidation stability of the sample after additive are within 0.02 mg KOH / g; the deviation in resistivity is within 0.35 × 10¹¹ Ω·cm; and the deviation in air release value is within 0.7 min, it is considered that the additive has no negative impact on the base oil under these conditions.

[0053] The test results in Table 1 show that, compared with the base oil, the addition of additives No. 1 and No. 3 resulted in a decrease in one or more of the following properties of the sample: oxidation stability, hydrolytic stability, air release value, and resistivity. Therefore, these two additives are not suitable for this phosphate ester fire-resistant oil product. Other additives can be further screened.

[0054] S3 further screening: Additives No. 2, No. 4 and No. 5 that were not eliminated in S2 were used to prepare samples according to S1. Closed cup aging tests were conducted on the base oil and the prepared samples. During the aging test, samples were taken periodically to test the acid value, resistivity, sludge precipitation, oxidation stability and air release value of the samples. The test results are shown in Tables 2 to 6.

[0055] Table 2. Acid value test results of each sample during the 115℃ closed-cup aging test.

[0056]

[0057]

[0058] Table 3. Resistivity test results of each sample during the 115℃ closed-cup aging test.

[0059]

[0060] Table 4. Oxidation stability test results of each sample during the 115℃ closed-cup aging test.

[0061]

[0062]

[0063] Table 5. Results of air release values ​​for each sample during the 115℃ closed-cup aging test.

[0064]

[0065] Table 6. Results of sludge precipitation during the 115℃ closed-cup aging test of each sample.

[0066]

[0067] The test results in Tables 2-6 show that, compared with the base oil, the addition of additives No. 2 and No. 5 resulted in a deterioration in one or more of the following properties during the aging process: acid value, sludge, air release value, and resistivity. Therefore, these two additives are not suitable for this phosphate ester fire-resistant oil product. Additive No. 4 improved the sludge precipitation tendency during the aging process and had no negative impact on other properties of the oil. Additive No. 4 is suitable as an additive for fire-resistant oil products.

[0068] S4 Additive Dosage Selection: For additive No. 4, samples with additive contents of 0.03%, 0.05%, 0.08%, 0.10%, 0.20%, 0.30%, and 0.50% were prepared according to S1. Closed-cup aging tests were conducted on the base oil and the prepared samples. During the aging test, samples were taken periodically to test the acid value, sludge precipitation, and resistivity of the samples. The test results are shown in Tables 7, 8, and 9.

[0069] Table 7. Acid value test results of each sample during the 115℃ closed-cup aging test.

[0070]

[0071] Table 8. Results of sludge precipitation during the 115℃ closed-cup aging test of each sample.

[0072]

[0073] Table 9. Resistivity test results of each sample during the 115℃ closed-cup aging test.

[0074]

[0075] The degradation of triaryl phosphate fire-resistant oil is mainly due to the oxidation of the substituents on the aromatic ring. Under the catalysis of light or heat, the substituents on the aromatic ring generate free radicals. These free radicals react with oxygen to generate oxidation products such as aldehydes, ketones, and acids, which in turn affect the oil's acid value, resistivity, sludge precipitation, and other indicators. After adding antioxidants, the antioxidants can react with free radicals and peroxides to form stable compounds, thereby consuming the free radicals generated in the oil and preventing the oil molecules from undergoing self-oxidation. Combined with the test results in Tables 7-9, when the content of additive No. 4 is high, some of the free radicals formed by additive No. 4 may act as nucleophiles, promoting the hydrolysis reaction between triaryl phosphate and water. As the degree of aging deepens, the acid value of the phosphate-containing fire-resistant oil sample is actually higher than that of the base oil, thus deepening the degradation of the oil.

[0076] When 0.03% to 0.1% of additive No. 4, 2,6-di-tert-butyl-p-cresol, is added, the acid value and sludge precipitation quality indicators of the sample during aging can be optimally improved compared with base oil and other additive dosages. Therefore, additive No. 4, 2,6-di-tert-butyl-p-cresol, with an addition dosage of 0.03% to 0.1%, is suitable as an additive for fire-resistant oil products. The manufacturer is Jinan Shengda Chemical Co., Ltd.

Claims

1. A phosphate ester fire-resistant oil, characterized in that, It is composed of a base oil and 2,6-di-tert-butyl-p-cresol added to the base oil, wherein the base oil is tridimethylmethyl phosphate, and the amount of 2,6-di-tert-butyl-p-cresol added is 0.03% to 0.1% of the weight of the base oil.

2. The method for preparing a phosphate ester fire-resistant oil according to claim 1, characterized in that, The specific steps are as follows: S1: Determine the amount of 2,6-di-tert-butyl-p-cresol based on the total amount of oil. Dissolve 2,6-di-tert-butyl-p-cresol in ten times its weight of base oil to obtain 2,6-di-tert-butyl-p-cresol mother liquor. S2: Under sealed conditions, add the 2,6-di-tert-butyl-p-cresol mother liquor to the base oil to be added.

3. The method for preparing a phosphate ester fire-resistant oil according to claim 2, characterized in that, In S1, 2,6-di-tert-butyl-p-cresol was dissolved in ten times its weight of base oil at 60℃±5℃ to obtain 2,6-di-tert-butyl-p-cresol mother liquor.

4. An application of a phosphate ester fire-resistant oil, characterized in that, The phosphate ester fire-resistant oil according to claim 1 or the phosphate ester fire-resistant oil prepared by any one of the preparation methods in claims 2 to 3 is used in the speed control system of a steam turbine in a power plant.

5. An application of a phosphate ester fire-resistant oil, characterized in that, The phosphate ester fire-resistant oil according to claim 1 or the phosphate ester fire-resistant oil prepared by any one of the preparation methods in claims 2 to 3 is used in the speed control system of a gas turbine in a power plant.

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