CN101893560B - Method for quickly determining manganese content in gasoline - Google Patents

Abstract

The invention discloses a method for quickly determining MMT manganese content in gasoline. The method comprises the following steps of: (1) collecting representative gasoline samples to form a training set; (2) determining medium infrared transmission and absorption spectrums of the gasoline samples of the training set, and selecting the absorbance of a spectrum range comprising characteristic peak absorption (2,229.1 to 1,618.2 cm-1) of an MMT manganese compound as a variable; (3) selecting an appropriate multivariate calibration method to establish a relational model between the manganese content in the gasoline and the spectrum; and (4) for the determination of the manganese content in an unknown gasoline sample, determining the medium infrared transmission and absorptions spectrums of the unknown gasoline sample, selecting the absorbance with the same wavelength range, and determining the manganese content in the gasoline by using an analysis model of the manganese content in the gasoline. The method for quickly determining the manganese content in the gasoline has the advantages of: high analysis speed (within one minute), simple and convenient operation (without sample pretreatment), environment friendliness (without toxic chemical reagents) and capacity of determining the manganese content in the gasoline on site and improving the monitoring capacity of cracking down on counterfeit goods and adulteration of the gasoline.

Description

A kind of method for quickly determining manganese content in gasoline

Technical field

The present invention relates to a kind of method for quickly determining manganese content in gasoline, specifically, relate to and a kind ofly combine polynary alignment technique through middle infrared spectrum, the method for fast detecting manganese content in gasoline.

Background technology

In order to reduce the harm of automobile lead discharging tail gas to environment, unleaded gasoline is eliminated gradually.In order to improve the capability of antidetonance of gasoline, people bring into use methyl cyclopentadienyl tricarbonyl manganese (MMT) octane promoter, and this adjuvant is very good to octane number sensitivity, can obviously increase octane number, and are existing widely-used by countries in the world.But MMT belongs to noxious material, is divided into B level dangerous material.The products of combustion of MMT only has seldom a part discharge from gas outlet in addition, and the overwhelming majority rests on the inner body, is attached to ignition performance is worsened, and is deposited on to make it to change the waste gas ability on the catalyzer and reduce.Therefore the manganese content in the gasoline needs strict control.The manganese content that China's " motor petrol " (GB17930-2006) stipulates MMT in the gasoline must not surpass 18mg/L.Because adding MMT is effective, the most most economical method of improving octane number, therefore, many illegal businessmans add excessive MMT in low trade mark gasoline, pretend to be the gasoline of the high trade mark, seek exorbitant profit.Need monitor MMT content in the gasoline for this reason.Because MMT adopts " manganese content test method (atomic absorption spectrography (AAS)) in the gasoline " (SH/T 0711) to measure, the instrument that is adopted is former absorption spectrometer, belongs to Laboratory Instruments, costs an arm and a leg, and environmental requirement is high; Need a large amount of poisonous chemical reagent; Complex operation, high to analyst's business need quality, analysis speed is slow.Therefore, be difficult to adopt this method scene that marketable gasolines is checked.Because the disappearance of the quick instrument of manganese content, cause to take at present regularly to inspect by random samples mode to the gasoline control of cracking down on counterfeit goods, so the dynamics of cracking down on counterfeit goods is poor.For this reason, need to strengthen the development of manganese content rapid detecting technology, realize that real-time on-the-spot gasoline mingles monitoring.

Summary of the invention

The purpose of this invention is to provide a kind of method for quickly determining manganese content in gasoline, this method does not need and poisons reagent, and easy and simple to handle, finding speed is fast, can realize that real-time on-the-spot gasoline mingles monitoring, improves gasoline and cracks down on counterfeit goods and mingle ability.

Technical scheme provided by the invention is: a kind of method for quick of manganese content in gasoline comprises the steps:

(1) collects representative gasoline sample as training set;

(2) mid infrared absorption spectrum of mensuration training set gasoline sample, selection comprises the spectrum range 2299.1-1618.2cm of manganese compound characteristic peak ^-1Absorbance as variable;

(3) select suitable multivariate calibration methods, set up the relational model between manganese content in gasoline and the spectrum;

(4) for the manganese content detection of gasoline sample to be measured, at first measure its infrared spectrum, and the absorbance between selection and (2) step same zone, utilize (3) to go on foot the quality of gasoline analytical model of setting up then, measure manganese content in gasoline.

Said infrared spectrum measurement mode is a transmission mode.

Said gasoline comprises the motor petrol of the various trades mark, like No. 90, No. 93, No. 97 motor petrol, and the ethanol petrol of the various trades mark, like No. 90, No. 93, No. 97 ethanol petrols.

Above-mentioned described multivariate calibration methods of (3) step is PLS (PLS).

The foundation and the checking of above-mentioned (3) step relational model are carried out according to ASTM E 1655 methods, and concrete steps are following:

The first step: collect the training set sample;

Second step: measure training set sample infrared spectrum;

The 3rd step: measure each mass parameter of training set;

The 4th step: select calibration set and checking collection, the sample of from training set, selecting suitable quantity is used to set up model as calibration set; Remainder is used for testing model as the checking collection;

The 5th step: set up model, utilize the calibration set sample, adopt PLS to set up the relational model of infrared spectrum and manganese content Y, the detailed process of modeling is following:

At first be decomposed into absorbance score matrix T and spectrum loading matrix P product to the absorbance data A of calibration set, be decomposed into the product of concentration score matrix U and concentration loading matrix Q, i.e. A to manganese content Y _{(n * m)}=T _{(n * d)}P _{(d * m)}, Y _{(n * l)}=U _{(n * d)}Q _{(d * l)}

U and T carry out linear regression, U then _{(n * d)}=T _{(n * d)}B _{(d * d)}, set up the relational model between manganese content Y and the spectrum: Y _{(n * l)}=T _{(n * d)}B _{(d * d)}Q _{(d * l)}

For unknown sample, its absorbance matrix is A _Unk, then by A _Unk=T _UnkThe P relation can be obtained T _Unk, then determinand manganese content can calculate and obtain: Y _Unk=T _UnkBQ.

In the modeling process of reality, modeling parameters has the variable number d (main cause subnumber) of A and P.Different interval absorbance reflection material various structure information, different to the response of Y, need optimal wavelength interval.The main cause subnumber is many more, and the variable that expression is introduced is too much, can improve analysis precision.But along with the main cause subnumber increases, some and the irrelevant signal of Y also can be introduced, thereby cause analysis precision to descend, and therefore, the main cause subnumber also needs preferred.Optimum spectral range is selected through the calibration standard deviation (SEC) in the validation-cross process.The bright model of building of novel is outstanding more more for SEC.The used variable number (main cause subnumber) of loading matrix P influences very big to modeling result, prediction residual quadratic sum (PRESS) value that need obtain through the validation-cross process of leaving-one method is chosen.The validation-cross process of leaving-one method is following: to a certain main cause subnumber; From correcting sample, choose a sample and be used for prediction, set up calibration model, predict the measured value of this sample with remaining sample; Then; This sample is put back to calibration set, from correcting sample, choose another one again, repeat above-mentioned process as prediction.Through modeling and prediction repeatedly, all once and only predicted once until all correcting samples by prediction, then obtain the PRESS value of corresponding this factor number:

Y wherein _iBe the practical measurement value or the classification value of i sample,

Be the predicted value that i sample validation-cross process obtains, n is the sample number of calibration set.

The 6th step: verification model.

The present invention has following beneficial effect:

Infrared spectrum technology is a kind of quick nondestructive detection technique, and it is fast and analyze accurate advantages of higher to have easy and simple to handle a, analysis speed, and has realized vehicle-mountedization of instrument, is a kind of very effective field quick detection instrument.The present invention adopts the mid-infrared light spectral technology, in conjunction with polynary alignment technique, and like PLS, manganese content in the accurate fast measuring gasoline.This method does not need and poisons reagent, and is environmentally friendly, need not carry out pre-service to sample, easy and simple to handle, analyst's professional qualities required lower, and finding speed is fast, can realize that real-time on-the-spot gasoline mingles monitoring, improves gasoline and cracks down on counterfeit goods and mingle ability.

Description of drawings

Fig. 1 is the mid infrared absorption spectrum figure that 120 gasoline transmission modes are measured.

Fig. 2 is the basic principle schematic of the inventive method.

Fig. 3 is calibration set and first principal component and the Second principal component, spatial distribution map of checking collection sample at transmitted spectrum, and wherein, the interval is 2299.1-1618.2cm ^-1,

Be the calibration set sample, ▲ for verifying the collection sample.

Fig. 4 is manganese content test result and the standard method graph of a relation as a result of the inventive method, wherein, * be the calibration set sample, △ is checking collection sample.

Fig. 5 is manganese content test error and the standard method graph of a relation as a result of the inventive method, wherein, * be the calibration set sample, △ is checking collection sample.

Embodiment

The present invention sets up according to ASTM E 1655 methods and checking manganese content in gasoline model, and concrete steps are following:

The first step: collect the training set sample.Collect some and representational sample as training set.

Second step: measure and adopt transmission mode to gather training set sample infrared spectrum.

The 3rd step: adopt SH/T 0711 standard method to measure each gasoline sample manganese content;

The 4th step: select calibration set and checking collection.The sample of from training set, selecting some is used to set up model as calibration set; Remainder is used for testing model as the checking collection.

The 5th step: set up model.Utilize the calibration set sample, adopt PLS (PLS) to set up the relational model of infrared spectrum and manganese content Y.The process of setting up model with the PLS method is following:

At first be decomposed into absorbance score matrix T and spectrum loading matrix P product to the absorbance data A of calibration set, be decomposed into the product of concentration score matrix U and concentration loading matrix Q, i.e. A to manganese content Y _{(n * m)}=T _{(n * d)}P _{(d * m)}, Y _{(n * l)}=U _{(n * d)}Q _{(d * l)}

U and T carry out linear regression, U then _{(n * d)}=T _{(n * d)}B _{(d * d)}Thereby, set up the relational model between manganese content Y and the spectrum: Y _{(n * l)}=T _{(n * d)}B _{(d * d)}Q _{(d * l)}

For unknown sample, its absorbance matrix is A _Unk, then by A _Unk=T _UnkThe P relation can be obtained T _Unk, then determinand manganese content can calculate and obtain: Y _Unk=T _UnkBQ.

The 6th step: verification model.Measure checking collection sample infrared spectrum, and through identical pre-service, select the absorbance A between same zone for use _Unk, under identical main cause subnumber, carry out PLS and decompose, promptly by A _Unk=T _UnkThe P relation can be obtained T _UnkThe B and the Q that utilize calibration set to confirm then, thus testing sample manganese content: T measured _Unk=T _UnkBQ, and compare with actual value.The performance that adopts coefficient R, calibration set analysis deviation (SEC), checking set analysis deviation (SEP) to come evaluation model.Require R high more good more, SEC and SEP are low more good more, are lower than or approach the requirement of standard method repeatability.The computing formula of R, SEC and SEP is following:

$R=\sqrt{1-\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_i-\hat{y})}^2}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_i-\stackrel{\‾}{y})}^2}}$

$\mathrm{SEC}=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_{i,\mathrm{pred}}^{\mathrm{cal}}-y_{i,\mathrm{real}}^{\mathrm{cal}})}^2}{n-1}}$

$\mathrm{SEP}=\sqrt{\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_{i,\mathrm{pred}}^{\mathrm{val}}-y_{i,\mathrm{real}}^{\mathrm{val}})}^2}{m-1}}$

Wherein, y _iBe the physics and chemistry manganese content y of i sample,

Be mean value, Be match value, m, n are respectively checking collection and calibration set sample number, Be the y model prediction result of i sample of calibration set,

Y standard method measured value for i sample of calibration set is actual value;

Be the y model prediction result of i sample of checking collection,

Y standard method measured value for i sample of checking collection is actual value.

The present invention measures the manganese content of unknown sample in such a way:

(1) measures the middle infrared spectrum of unknown sample at first under the same conditions;

(2) select the absorbance A of identical range of wavelengths for use _Unk, under identical main cause subnumber, carry out PLS and decompose, promptly by A _Unk=T _UnkThe P relation is found the solution T _UnkThe Model B and the Q that utilize calibration set to confirm then measure testing sample manganese content: Y _Unk=T _UnkBQ.

Instance 1: transmission beam method is measured manganese content in gasoline

1) collects the training set sample

Collect 120 gasoline samples from refinery in all parts of the country, wherein No. 90 motor petrol are 19,68 of No. 93 motor petrol, 25 of No. 97 motor petrol, 3 of No. 90 ethanol petrols, 4 of No. 93 ethanol petrols, 1 of No. 97 ethanol petrol.Wherein 62 samples are as calibration set in selection, and all the other 58 are the checking collection.

2) middle infrared spectrum of mensuration training set sample

Adopt transmission beam method to measure the gasoline mid infrared absorption spectrum.The instrument model is Tensor 27, and Brooker company produces, Znse beam splitter, spectral range: 550～4100cm ^-1Transmission sample pond light path is 0.1mm.The middle infrared spectrum of measuring is seen Fig. 1.

3) the manganese content of mensuration training set sample

Adopt SH/T 0711 standard method to measure the manganese content of gasoline sample.The reproducibility error and the reproducibility error of this method are followed successively by 0.42X ^0.5And 1.41X ^0.5(X is the manganese content test value).Table 1 has been listed maximal value, minimum value, mean value and the deviate of training set sample manganese content.

Table 1

Character	Maximal value	Minimum value	Mean value	Deviation
					Manganese, mg/L	18	0.2	6.6	4.8

4) confirm the model modeling parameter

Middle infrared spectrum data and mass parameter data with the calibration set sample; Import in " the Chemical Measurement spectral analysis software 3.0 " of Research Institute of Petro-Chemical Engineering's establishment; Adopt the PLS method to set up the model of manganese content; Deviation SEC through validation-cross confirms wavelength coverage, preprocess method and main cause subnumber, sees table 2.Selected wavelength coverage comprises the characteristic absorption peak 2021cm of MMT carbonyl ^-1And 1938cm ^-1

Table 2

Sequence number	Character	Preprocess method	Wavelength coverage, cm -1	The main cause subnumber
					1	Manganese content	Do not have	2299.1-1618.2	9

5) evaluation model performance

Checking collection ir data is imported in " the Chemical Measurement spectral analysis software 3.0 " of Research Institute of Petro-Chemical Engineering's establishment; Pass through the pre-service identical, select wavelength coverage identical and main cause subnumber for use with model with above-mentioned model; Utilize PLS to set up model determination manganese content; And compare with actual value, calculate R and analysis deviation (SEC and SEP), see table 3.The result shows that the present invention measures the result and the actual value correlativity is good, and R is up to 0.98, and analysis precision is high, and SEC and SEP are respectively 0.86 and 0.89mg/L.Table 4 has been listed the t value of actual value, measured value, error at measurment, the requirement of standard method repeatability and the t check of checking collection sample.As shown in table 4, the error at measurment of all checking collection samples all is lower than SH/T 0711 method repeatability requirement; t _CalculateLess than t _Table(=2.0) show there was no significant difference between this method mensuration result and SH/T 0711 standard method, and explanation can adopt the inventive method to measure the manganese content of gasoline.

Table 3

Table 4

6) repeatability of investigation model

Sample of replication 10 times is measured the result and is seen table 5.The model good reproducibility is measured basically identical as a result 10 times, is lower than the standard method repeatability requirement of table 1, can use.

Table 5

Number of times	Manganese content g/L
		The 1st time	10.4
The 2nd time	10.4
		The 3rd time	10.2
The 4th	10.3
		The 5th	10.4
The 6th time	10.5
		The 7th time	10.4
The 8th time	10.1
		The 9th time	10.3
The 10th time	10.4
		Mean value	10.3
Maximal value-minimum value	0.4
		The repeatability deviation	0.1
SH/T 0711 repeated requirement	1.3

Claims (6)

1. a method for quickly determining manganese content in gasoline comprises the steps:

(1) collects representative gasoline sample as training set;

(2) mid infrared absorption spectrum of mensuration training set gasoline sample, selection comprises the spectrum range 2299.1-1618.2cm of manganese compound characteristic peak ^-1Absorbance as variable;

(3) select suitable multivariate calibration methods, set up the relational model between manganese content in gasoline and the spectrum;

(4) for the manganese content detection of gasoline sample to be measured, at first measure its mid infrared absorption spectrum, and select with (2) step in absorbance between same zone, utilize the quality of gasoline analytical model that (3) step set up then, the mensuration manganese content in gasoline.

2. according to the described method of claim 1, it is characterized in that: said gasoline comprises the motor petrol of the various trades mark and the ethanol petrol of the various trades mark.

3. according to the described method of claim 2, it is characterized in that: said motor petrol comprises motor petrol No. 90, No. 93, No. 97, and said ethanol petrol comprises ethanol petrol No. 90, No. 93, No. 97.

4. according to the described method of claim 1, it is characterized in that: the mensuration of said mid infrared absorption spectrum adopts transmission mode to measure.

5. according to the described method of claim 1, it is characterized in that: (3) step, described multivariate calibration methods was a PLS.

6. according to the described method of claim 1, it is characterized in that: the foundation and the checking of (3) step relational model refer to carry out according to ASTM E 1655 methods, and concrete steps are following:

The first step: collect the training set sample;

Second step: the middle infrared spectrum of measuring the training set sample;

The 3rd step: the manganese content of measuring the training set sample;

The 4th step: select calibration set and checking collection, the sample of from training set, selecting suitable quantity is used to set up model as calibration set; Remainder is used for testing model as the checking collection.

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