CN104792853A - Method for determining acid value in lubricating oil - Google Patents
Method for determining acid value in lubricating oil Download PDFInfo
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- CN104792853A CN104792853A CN201510255642.0A CN201510255642A CN104792853A CN 104792853 A CN104792853 A CN 104792853A CN 201510255642 A CN201510255642 A CN 201510255642A CN 104792853 A CN104792853 A CN 104792853A
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- lubricating oil
- acid value
- differential pulse
- voltammetry
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Abstract
The invention relates to a differential pulse voltammetric determining method for an acid value in lubricating oil. The method is characterized in that an analysis electrode is formed by a glassy carbon electrode and a platinum wire electrode, electrochemical detection is carried on a sample to be tested by utilization of an electrochemical workstation and adoption of a differential pulse voltammetry, and the content of the acid value in the lubricating oil is calculated according to differential pulse voltammetry peak current. Compared with the prior art, the method has the benefits of being low in cost, simple to operate and accurate in measurement, overcomes the defects that in an existing test technology, a titration end point is difficult to judge, and in an existing electrochemical determining method, the quantity of sampling of the sample to be tested is little, the representativeness is poor, the content of the acid value is low, and the measurement error is large, is suitable for electrochemical determination of an acid value in aviation lubricating oil and is particularly suitable for determination of an acid value in dark or used aviation lubricating oil.
Description
Technical field
The present invention relates to a kind of assay method of acid value of lubricating oil.
Background technology
The size (acid number, neutralization number) of lubricating oil acidic materials characterizes the corrosive index of lubricating oil, by the mensuration to oil product acidity of oil material, can check whether lubricating oil conforms with the regulations standard, to prevent the corrosion to metallic element.
Current mensuration acid value of lubricating oil or neutralization test method can be divided into color indicator titration method and potentiometric titration.Color indicator method determines titration end-point according to the change of acid base indicator color; Potentiometric titration determines titration end-point according to the change of current potential.Adopt color indicator titration method or potentiometric determination petroleum products acid number, part lubricating oil exist that terminal variable color is not obvious, titration curve without obvious hop point, the very doubt problem of titration end-point.
" lubrication and sealing " the 4th phase the 148th page in 2006 discloses a kind of acid value of lubricating oil and measures new method-voltammetry, and the method, by the blank sample voltammetric determination of the water/ethanolic solution containing high alkalinity sodium phenate, obtains volt-ampere peak height; With on add the aqueous hydrochloric acid solution 50 μ L of 0.1mol/L in identical blank sample, measure corresponding volt-ampere peak height; Sample thief 0.05 ~ 0.2g adds blank solution and measures corresponding volt-ampere peak height, then calculates the acid number of lubricating oil according to volt-ampere peak height." lubrication with sealing " the 8th phase the 43rd page in 2006 describes a kind of acid value of lubricating oil electrochemical determination method: first measure the volt-ampere peak of the water/ethanolic solution of blank phenates and to implement smoothly volt-ampere curve and semi-differential operates, recording a volt-ampere peak height; The oil sample adding the known acid number of 50 ~ 200 μ L in blank solution carries out volt-ampere peak and measures the corresponding volt-ampere peak of acquisition; 50 ~ 200 μ L oil samples are added blank solution and carry out a volt-ampere mensuration acquisition volt-ampere peak, peak, calculate the acid number of lubricating oil according to volt-ampere peak height.Only have very much 0.05 ~ 0.2g or 50 ~ 200 μ L due to amount of samples during said method measures, easily cause the inaccurate of the uneven and front and back quantity of sampling quantity of sampling, particularly acid number is less than to the lubricating oil of 0.5mgKOH/g, acid value measuring error is larger.
Summary of the invention
Technical matters to be solved by this invention is to provide and a kind ofly can be less than the method for the acid value of lubricating oil of 0.5mgKOH/g by Accurate Determining acid number.
Acid value of lubricating oil assay method provided by the invention, comprises the steps:
1) phenates aqueous solution is prepared: potassium phenate or the sodium phenate solution of basic phenate salt aqueous solution to be concentration be 0.05 ~ 0.15mol/L.
2) blank sample preparation: blank sample selects absolute ethyl alcohol through decarbonation process or isopropyl alcohol, and the method for decarbonation process is that absolute ethyl alcohol or isopropyl alcohol are placed in the heating arrangement that reflux condensing tube is housed, and boils 5 ~ 10 minutes.
3) electrode is selected: working electrode is glass carbon dish, and analyzing electrode is made up of platinum filament and contrast electrode.
4) testing sample prepares: get lubricating oil to be measured, add and be equipped with in the absolute ethyl alcohol of decarbonation or the conical flask of isopropyl alcohol, load onto reflux condensing tube, boiled 5 ~ 10 minutes or shake 5 ~ 10min.
5) sample determination: adopt differential pulse voltammetry, test parameter is set as: voltage increment 0.002V, amplitude 0.05V, pulse width 0.06S, sampling width 0.02s, sampling period 0.2s; Assay method is: get isopyknic phenates aqueous solution and blank sample and mix, and adopting differential pulse voltammetry to record voltammetry electric current peak height is H
0; Get isopyknic phenates aqueous solution and blank sample, add hydrochloric acid 30 ~ 50 μ L of 0.1mol/L, mix, adopting differential pulse voltammetry to record voltammetry electric current peak height is E
s; Get the acid Extract of isopyknic phenates aqueous solution and testing sample to mix, adopting differential pulse voltammetry to record voltammetry electric current peak height is E
c; Acid number according to following formulae discovery oil product to be measured:
X=
Wherein:
V is the volume of known acid, and unit is mL;
X
acidfor the concentration of known acid, unit is mol/L;
V
cfor the volume of testing sample, unit is mL;
G is the percentage by weight of testing sample;
H
0for the volt-ampere peak height of blank solution;
H
sfor adding the rear volt-ampere peak height of acid;
H
cfor adding volt-ampere peak height after sample.
The present invention has following beneficial effect:
1) a kind of aerooil acid number differential pulse voltammetry assay method of the present invention, the absolute ethyl alcohol of decarbonation or isopropyl alcohol is adopted to carry out extracting to the acidic materials in the lubricating oil to be measured of 10mL, get the acid Extract of testing sample and carry out volt-ampere analysis, avoid and cause sampling uneven because testing sample quantity is few, the shortcoming of representative difference, avoids the impact of the carbon dioxide in ethanol or isopropyl alcohol on acid value of lubricating oil simultaneously.
2) a kind of aerooil acid number differential pulse voltammetry assay method of the present invention, can use electrochemical workstation to carry out the mensuration of acid value of lubricating oil, needn't use acid base indicator and non-water buffer solution, analyzes accurately, easy and simple to handle.
3) a kind of aerooil acid number differential pulse voltammetry assay method of the present invention, in order to working sample and blank phenates match, test adopts equal-volume phenates aqueous solution and absolute ethyl alcohol or isopropyl alcohol to be uniformly mixed to form phenates ethanol/water solution, adopt equal-volume phenates aqueous solution and the acid Extract of lubricating oil testing sample to form phenates ethanol/water solution during sample analysis equally, avoid because oil sample density is different and cause systematic error.
Embodiment
Below in conjunction with embodiment, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
Embodiment: the mensuration of acid number in 928 aerooils
1) 0.05 ~ 0.15mol/L phenates solution: accurately take high 4.0 ± 0.5gNaOH and 9.4 ± 0.5g phenol is dissolved in 100mL beaker, adds deionized water, until completely dissolved, moves into 1000mL volumetric flask, and is settled to scale.
2) preparation of 0.1mol/L hydrochloric acid standard solution with demarcate: the hydrochloric acid [36% ~ 38%(m/m), analyze pure] getting 9.0mL is dissolved in the volumetric flask of 1000mL, and is settled to scale with deionized water, with standard reagent demarcate prepare the concentration of hydrochloric acid.
3) absolute ethyl alcohol decarbonation process: the absolute ethyl alcohol of 150mL is injected conical flask, loads onto reflux condensing tube, boiled 5 ~ 10 minutes, to remove the carbon dioxide be dissolved in absolute ethyl alcohol.
4) testing sample prepares: get 10mL(and weigh simultaneously) 928 aerooils to be measured, add and 50mL(is housed weighs simultaneously) in the conical flask of the absolute ethyl alcohol of carbon dioxide removal, load onto reflux condensing tube, boiled 5 ~ 10 minutes or shaken 5 ~ 10min, static placement, calculates lubricating oil percentage by weight in ethanol simultaneously.
5) electrode is selected: electrode selects the glass carbon dish of 3mm to be working electrode, and the platinum filament of 0.3mm is that the combination electrode of auxiliary electrode and contrast electrode is as analyzing electrode.
6) sample determination: adopt differential pulse voltammetry, test parameter is set as: voltage increment 0.002V, amplitude 0.05V, pulse width 0.06S, sampling width 0.02s, sampling period 0.2s;
Get the potassium phenate aqueous solution of 2.5 mL and the absolute ethyl alcohol of 2.5mL decarbonation process and shake 1min, adopting differential pulse voltammetry to record voltammetry electric current peak height is H
0;
Get the potassium phenate aqueous solution of 2.5mL and the absolute ethyl alcohol of 2.5mL decarbonation process, add the hydrochloric acid 30 μ L of 0.1mol/L, shake 1min, adopting differential pulse voltammetry to record voltammetry electric current peak height is E
s;
Get potassium phenate aqueous solution and the acid Extract (wherein the volume of absolute ethyl alcohol is 2.5mL) of 3.0mL testing sample of 2.5mL, shake 1min, static 5 ~ 10min, adopting differential pulse voltammetry to record voltammetry electric current peak height is E
c;
According to the acid number of formulae discovery oil product to be measured.
X=
Wherein:
V is the volume of known acid, and unit is mL;
X
acidfor the concentration of known acid, unit is mol/L;
V
cfor the volume of testing sample, unit is mL;
G is the percentage by weight of testing sample;
H
0for the volt-ampere peak height of blank solution;
H
sfor adding the rear volt-ampere peak height of acid;
H
cfor adding volt-ampere peak height after sample.
Claims (1)
1. an assay method for acid value of lubricating oil, comprises the steps:
1) phenates aqueous solution is prepared: potassium phenate or the sodium phenate solution of basic phenate salt aqueous solution to be concentration be 0.05 ~ 0.15mol/L;
2) blank sample preparation: blank sample selects absolute ethyl alcohol through decarbonation process or isopropyl alcohol, and the method for decarbonation process is that absolute ethyl alcohol or isopropyl alcohol are placed in the heating arrangement that reflux condensing tube is housed, and boils 5 ~ 10 minutes;
3) electrode is selected: working electrode is glass carbon dish, and analyzing electrode is made up of platinum filament and contrast electrode;
4) testing sample prepares: get lubricating oil to be measured, add and be equipped with in the absolute ethyl alcohol of decarbonation or the conical flask of isopropyl alcohol, load onto reflux condensing tube, boiled 5 ~ 10 minutes or shake 5 ~ 10min;
5) sample determination: adopt differential pulse voltammetry, test parameter is set as: voltage increment 0.002V, amplitude 0.05V, pulse width 0.06S, sampling width 0.02s, sampling period 0.2s; Assay method is: get isopyknic phenates aqueous solution and blank sample and mix, and adopting differential pulse voltammetry to record voltammetry electric current peak height is H
0; Get isopyknic phenates aqueous solution and blank sample, add hydrochloric acid 30 ~ 50 μ L of 0.1mol/L, mix, adopting differential pulse voltammetry to record voltammetry electric current peak height is E
s; Get the acid Extract of isopyknic phenates aqueous solution and testing sample to mix, adopting differential pulse voltammetry to record voltammetry electric current peak height is E
c; Calculate the acid number obtaining oil product to be measured.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510255642.0A CN104792853A (en) | 2015-05-19 | 2015-05-19 | Method for determining acid value in lubricating oil |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510255642.0A CN104792853A (en) | 2015-05-19 | 2015-05-19 | Method for determining acid value in lubricating oil |
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| CN104792853A true CN104792853A (en) | 2015-07-22 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107271530A (en) * | 2017-07-17 | 2017-10-20 | 云南云天化股份有限公司 | A kind of method of Oil repellent in fluorine-containing organic solvent of Accurate Determining |
| CN110441381A (en) * | 2019-09-12 | 2019-11-12 | 广州机械科学研究院有限公司 | The electrochemical detection method of oxidation preventive content in a kind of lubricant |
| CN111103390A (en) * | 2018-10-26 | 2020-05-05 | 江苏北斗星环保股份有限公司 | Method for detecting acid value of animal fat |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0859234A1 (en) * | 1997-02-12 | 1998-08-19 | Matsushita Electric Industrial Co., Ltd. | Apparatus and method for measuring acidity |
-
2015
- 2015-05-19 CN CN201510255642.0A patent/CN104792853A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0859234A1 (en) * | 1997-02-12 | 1998-08-19 | Matsushita Electric Industrial Co., Ltd. | Apparatus and method for measuring acidity |
Non-Patent Citations (3)
| Title |
|---|
| 史永刚等: "基于电化学分析的润滑油酸值和碱值测定", 《润滑与密封》 * |
| 宋敏: "石油产品总酸值测定的新方法———伏安法", 《润滑与密封》 * |
| 徐继刚等: "线性伏安法测定润滑油酸值", 《合成润滑材料》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107271530A (en) * | 2017-07-17 | 2017-10-20 | 云南云天化股份有限公司 | A kind of method of Oil repellent in fluorine-containing organic solvent of Accurate Determining |
| CN111103390A (en) * | 2018-10-26 | 2020-05-05 | 江苏北斗星环保股份有限公司 | Method for detecting acid value of animal fat |
| CN110441381A (en) * | 2019-09-12 | 2019-11-12 | 广州机械科学研究院有限公司 | The electrochemical detection method of oxidation preventive content in a kind of lubricant |
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Application publication date: 20150722 |