CN102507715A - Method for detecting antioxidant of electric oil - Google Patents

Abstract

The invention discloses a method for detecting antioxidant of electric oil, which is realized through the following steps: a proper amount of supporting electrolyte solution is added into the electric oil to prepare a current conductive solution system; the relationship between different concentration of antioxidant and the current peak value of electrochemical reaction can be established by adopting the conventional electrochemical detection method, so that the concentration of antioxidant in an oil sample can be calculated and obtained according to the current peak value of the electrochemical reaction for the to-be-detected oil sample. The method disclosed by the invention is simple, convenient and quick to operate, has high sensitivity, low detection lower limit, accurate and reliable detection result as well as excellent repeatability and reproducibility, and is applicable to oxidation stability detection for various electric oils, including insulating oil, lubricating oil and fire resistant oil, that are used in the electric power industry.

Description

A kind of detection method of oil antioxidant for electric power

technical field

The invention belongs to an electrochemical detection method, and in particular relates to a detection method for an antioxidant in electric power oil.

Background technique

Power oil requires reliable physical and chemical properties, especially good insulation properties. However, all oil products will be oxidized during use. Under high temperature, this oxidation process will be accelerated, and the acidity generated by oxidation The product may form sludge or even precipitate, which will not only reduce the performance of power oil in all aspects, but also block the oil circuit and cause serious accidents. Therefore, oxidation stability is an important service condition and quality requirement for power oil . In order to prolong the service life of the equipment, it is necessary to add specific compounds to endow the oil with good anti-oxidation stability. The addition of antioxidants can significantly delay the oxidation rate of oil and greatly prolong the service life of oil.

Commonly used methods for the detection of antioxidants mainly include spectrophotometry, liquid chromatography, infrared spectroscopy, gas chromatography/mass spectrometry, etc. The national standard GB 7602 of the People's Republic of China uses spectrophotometry to determine the content of antioxidant T501. The sample pretreatment is complicated, and many instruments and drugs are used. The probability of human error in the measurement process is relatively high. When using liquid chromatography to measure the antioxidant content in power oil, due to the change of the polarity of the sample components, the separation ability of the chromatographic column is reduced, resulting in poor detection repeatability. Infrared spectroscopy and gas chromatography/mass spectrometry are accurate in detection, but expensive equipment restricts their widespread use. Therefore, it is of great significance to establish a new simple and easy detection method.

Contents of the invention

The purpose of the present invention is to provide a detection method for the antioxidant of electric power oil which is simple and fast in operation, low in detection limit, accurate and reliable in detection result, and has good repeatability and reproducibility.

The technical scheme adopted to realize the purpose of the invention is: the detection method of the oil antioxidant used in electric power, adopts the conventional electrochemical detection method and uses the external standard method, adds the supporting electrolyte of equal amount in the standard oil sample containing antioxidant and the oil sample to be tested , making the standard curve of the known antioxidant concentration and electrochemical reaction current peak value in the standard oil sample, after measuring the reaction current peak value of the oil sample to be tested, then calculate the resistance of the oil sample to be tested according to the standard curve. Oxidant content.

Another technical scheme of the present invention is: adopt conventional electrochemical detection method and use internal standard method, add the same amount of supporting electrolyte in the standard oil sample containing antioxidant and the oil sample to be tested to obtain standard oil sample mixed solution and For the oil sample mixture to be tested, first measure the peak value of the reaction current of the oil sample mixture to be tested, and then add the same amount of standard oil sample mixture to the oil sample mixture to obtain different samples to be tested. The peak value of the reaction current corresponding to each sample to be tested is obtained, and the antioxidant content of the oil sample to be tested is calculated according to the peak value of the reaction current of each sample to be tested.

In the present invention, the detection system for measuring antioxidant content in power oil by electrochemical method is a conductive system formed by coordinating power oil and supporting electrolyte, wherein the supporting electrolyte includes organic or inorganic acid, alkali, salt, and organic or inorganic Aqueous or organic solutions of acids, alkalis, and salts, and the concentration of the supporting electrolyte in the power oil is 0.01%-99.99%.

The electrochemical detection method used in the present invention is conventional cyclic voltammetry, linear scanning method, pulse voltammetry, etc., and the research electrode in the electrochemical detection method is a gold electrode, a platinum electrode, a glassy carbon electrode, and the window of the electrochemical test It is -5V-5V.

Antioxidants for power oils include natural or synthetic antioxidants, such as 2,6-di-tert-butyl-p-cresol (T501), 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert- Butylphenol etc.

The method of the present invention is characterized in that by adding an appropriate amount of supporting electrolyte solution to the electric power oil to prepare a conductive solution system, using a conventional electrochemical detection method to establish the relationship between different antioxidant concentrations and the peak value of the electrochemical reaction current, thereby according to the The concentration of the antioxidant in the oil sample is calculated by measuring the peak value of the electrochemical reaction current of the oil sample. The method of the invention is simple and quick to operate, high in sensitivity, low in detection limit, accurate and reliable in detection results, and has good repeatability and reproducibility, and is suitable for various types of oils used in the electric power industry, including insulating oil, lubricating oil, and anti-fuel oil. Detection of oxidation stability of power oil.

The method of the present invention uses electrochemical testing technology to analyze and measure the antioxidant content index of power oil, which is a powerful supplement to the current standard for measuring the antioxidant content of power oil, and the electrochemical technology is used for timely and rapid monitoring , which can provide early warning of the degree of transformer operation failure and the risk trend of safe operation.

The specific implementation manners of the present invention will be further described below in conjunction with the drawings and examples.

Description of drawings

Fig. 1 is the schematic diagram of the external standard method standard curve of embodiment 1.

Fig. 2 is the internal standard method curve schematic diagram of embodiment 2.

Fig. 3 is the schematic diagram of the external standard method standard curve of embodiment 3.

Detailed ways

Example 1

Prepare 50g of transformer oil standard oil samples with 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% of the antioxidant 2,6-di-tert-butyl-p-cresol (T501) respectively, using 0.01% NaOH ethanol solution As a supporting electrolyte, mix 1g of each standard oil sample with 1000g of 0.01% NaOH ethanol solution to obtain a standard oil sample mixture. The concentration of NaOH in the standard oil sample mixture is 0.01%. As the research electrode in the three-electrode system, the concentration of different antioxidants and the peak value of the electrochemical reaction current in each standard oil sample mixed solution were established by cyclic voltammetry with an initial voltage of -0.8V, an end voltage of 1.8V, and a scan rate of 0.01V/s. standard curve, as shown in Figure 1; another 1g of the transformer oil sample to be tested was mixed with 1000g of 0.01% NaOH ethanol solution to obtain the oil sample mixture to be tested, and the oil sample mixture to be tested was measured by the same electrochemical method The peak value of the electrochemical reaction current is y, and then calculated according to the standard curve shown in Figure 1 and the external standard method to obtain the concentration x=0.265% of the antioxidant in the transformer oil sample to be tested.

Example 2

Prepare 50 g of lubricating oil standard oil sample with 0.1% content of antioxidant 2,4-dimethyl-6 tert-butylphenol, and mix it evenly with glacial acetic acid as a supporting electrolyte at a mass ratio of 1:99 to obtain a standard oil sample mixture Standby, the concentration of glacial acetic acid in the standard oil sample mixture is 99%; another 1g of lubricating oil sample to be tested is mixed with 99g of glacial acetic acid to obtain the oil sample mixture to be tested. For the research electrode in the electrode system, the peak value of the reaction current of the oil sample mixture to be tested is measured as y by the linear voltammetry scanning method with an initial voltage of -0.5V, an end voltage of 2.0V, and a scanning speed of 0.05V/s; Add 100g of the standard oil sample mixture prepared before to the test oil sample mixture to obtain the No. 1 sample to be tested. The peak value of the reaction current of the No. 1 sample to be tested is measured by the same electrochemical method as y1; add 100g of the standard oil sample again Mixed solution to obtain the No. 2 sample to be tested, and after measuring the peak value of the reaction current of the No. 2 sample to be tested as y2, make a curve, as shown in Figure 2, and then calculate the lubricating oil sample to be tested according to the curve and the internal standard method The antioxidant content of x = 0.270%.

Example 3

Preparation of antioxidant 2,6-di-tert-butylphenol content is respectively 0.1%, 0.2%, 0.3%, 0.4%, 0.5% of each 500g of anti-fuel standard oil samples, using 1-butyl-3-methylimidazole six Fluorophosphate room temperature ionic liquid was used as a supporting electrolyte, and 500g of each standard oil sample was mixed with 500g of 1-butyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquid to obtain a standard oil sample mixture, a standard oil sample mixture The concentration of the ionic liquid at room temperature is 50.0%. After the ultrasonic vibration is uniform, the glassy carbon electrode is used as the research electrode in the three-electrode system. Pulse voltammetry with a width of 0.01s and a sampling width of 0.01s was used to establish the standard curves of different antioxidant concentrations and electrochemical reaction current peak values in the mixed solution of each standard oil sample, as shown in Figure 3; 500g of 1-butyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquid was mixed to obtain the oil sample mixture to be tested, and the peak reaction current of the oil sample mixture to be tested was measured as y by the same electrochemical method, and then according to According to the standard curve shown in Figure 3 and the external standard method, the concentration of the antioxidant in the anti-fuel standard oil sample is calculated to be x=0.339%.

The principle of the present invention is to establish the linear relationship between the concentration of antioxidants in the oil sample prepared in the laboratory and the electrochemical response by conventional electrochemical methods, and then measure the electrochemical response of the oil sample to be tested, thereby deriving the Concentration of antioxidants in oil samples.

The supporting electrolyte in the present invention includes organic or inorganic acids, bases, salts, and aqueous or organic solutions of organic or inorganic acids, bases, and salts. Preferred supporting electrolytes include: formic acid, acetic acid, and dodecylbenzenesulfonic acid in organic acids; hydrochloric acid, sulfuric acid, and nitric acid in inorganic acids; sodium methylate, potassium tert-butoxide, and phenyl lithium in organic bases; Potassium hydroxide, sodium hydroxide, ammonia water in alkali; 1-butyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquid in organic salt; sodium chloride and potassium sulfate in inorganic salt. Organic solvents: methanol, ethanol, acetonitrile, etc.

Claims (6)

1. the detection method of a kind of oil for electric power anti-oxidant; It is characterized in that adopting conventional electrochemical detection method and use external standard method; The supporting electrolyte that in standard oil sample that contains anti-oxidant and oil sample to be measured, adds equivalent; Make the typical curve of known antioxidants concentration and electrochemical reaction current peak value in the said standard oil sample, record oil sample kinetic current peak value to be measured after, calculate the oxidation preventive content of this oil sample to be measured again according to said typical curve.

2. the detection method of oil for electric power anti-oxidant according to claim 1; It is characterized in that said supporting electrolyte comprises acid, alkali, the salt of organic or inorganic; And the WS or the organic solution of the acid of organic or inorganic, alkali, salt, the concentration of supporting electrolyte in oil sample to be measured is 0.01%-99%.

3. the detection method of oil for electric power anti-oxidant according to claim 1 and 2; It is characterized in that said electrochemical detection method is cyclic voltammetry, linear sweep method, pulse voltammetry; The research electrode is gold electrode, platinum electrode, glass-carbon electrode in the electrochemical detection method, and the window of electro-chemical test is-5V-5V.

4. the detection method of a kind of oil for electric power anti-oxidant; It is characterized in that adopting conventional electrochemical detection method and use internal standard method; The supporting electrolyte that in standard oil sample that contains anti-oxidant and oil sample to be measured, adds equivalent gets standard oil sample mixed liquor and oil sample mixed liquor to be measured respectively; After recording the kinetic current peak value of oil sample mixed liquor to be measured earlier; The standard oil sample mixed liquor that adds equivalent that in oil sample mixed liquor to be measured, goes forward one by one again gets different samples to be tested, measures the corresponding kinetic current peak value of each sample to be tested, calculates the oxidation preventive content of oil sample to be measured according to the kinetic current peak value of each sample to be tested that records.

5. the detection method of oil for electric power anti-oxidant according to claim 4; It is characterized in that said supporting electrolyte comprises acid, alkali, the salt of organic or inorganic; And the WS or the organic solution of the acid of organic or inorganic, alkali, salt, the concentration of supporting electrolyte in oil sample to be measured is 0.01%-99%.

6. are according to the detection method of claim 4 or 5 described oil for electric power anti-oxidants; It is characterized in that said electrochemical detection method is cyclic voltammetry, linear sweep method, pulse voltammetry; The research electrode is gold electrode, platinum electrode, glass-carbon electrode in the electrochemical detection method, and the window of electro-chemical test is-5V-5V.

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