CN1318743A - Measuring method of wax content in asphalt - Google Patents

Abstract

A determining method for the wax content in asphalt integrates the representative asphalt samples to be a check collection and making the peak value normalization pretreatment of second order differential of their near infrared absorption spectrum as well as carrying out the regression analysis with corresponding wax content basic data by mathematical method for establishing the check models. The check model estabished by the check collection calculates the wax content after the peak value normalization for second order differential of near infrared absorption spectrum with the unknown asphalt sample.

Description

The assay method of wax content in the pitch

The invention relates to the assay method of wax content in the pitch, further say so about measure the method for wax content in the pitch in conjunction with Chemical Measurement with near-infrared absorption spectrum.

SH/T0425 has put down in writing the standard method of measuring wax content in the pitch.This method is with the distillate oil after the asphalt sample cracking distillation, with the dissolving of ether alcohol mixed solvent, with-20 ℃ down the cooling wax of separating out filter, filter the wax petroleum ether dissolution, steam solvent and drying again, weigh and obtain wax content.This method complexity, consuming time, contaminated environment.

Chemical Measurement is to be means with mathematics, statistics and computer, designs or select optimum chemical method for measurement, and by resolving chemical metric data, obtains chemistry and other relevant information of related substance system; And it is simple to operate to use the spectral instrument analysis to have, fireballing characteristics.

Near infrared spectrum belongs to molecular vibration spectrum, and main reflection contains the characteristic information of hydrogen group.In the near infrared spectrum zone, the various hydrogen groups that contain all have certain frequency multiplication bands of a spectrum ownership.The near infrared spectrum of pitch contains the information of hydrocarbon compound composition and structure.

In recent years, near infrared spectrum just progressively enters the petrochemical complex analysis field in conjunction with the assay method of Chemical Measurement, can be used for octane number, boiling range, diesel cetane-number, boiling range, flash-point, the mensuration of character such as boat coal freezing point.As having reported the method for measuring the jet fuel freezing point in " analytical chemistry, 1998,26 (5), 603 ", reported the method for arene content in the mensuration diesel oil etc. in " analytical chemistry, 1999,27 (1), 29～33 ".Do not see so far and adopt near infrared spectrum and Chemical Measurement in conjunction with the method for measuring wax content in the pitch.

The objective of the invention is to provide on the basis of existing technology a kind of method of simple, quick, environment amenable mensuration pitch wax content.

Method provided by the invention is: representative asphalt sample is formed calibration set, the second-order differential of near-infrared absorption spectrum to them carries out peak value normalization pre-service, carry out regretional analysis with corresponding wax content basic data with mathematical method, set up calibration model; After the second-order differential of the near-infrared absorption spectrum of unknown asphalt sample carried out peak value normalization pre-service, the calibration model of being set up by calibration set calculated wax content.

Pitch is a kind of black solid or the thick material of semisolid, is difficult to adopt spectral method with routine, records pitch spectrogram preferably as sample cell transmission beam method, diffuse reflection method etc.In method provided by the invention, asphalt sample is made the smear that is used to gather near infrared spectrum after needing to melt fully.For guarantee spectra collection accurately, said smear should evenly and have certain thickness, can adopt certain thickness distance piece to control, its thickness is advisable with the range of linearity that the absorption maximum of surveyed near infrared spectrogram is no more than detecting device.

In the method provided by the invention, the sweep interval of the near infrared absorption spectrogram of said pitch is 1430～2000nm.Because the influence of factors such as pitch color, plate coating thickness, the near infrared absorption spectrogram of being surveyed has more serious drift and inclination, causes the spectrogram when same sample carried out replicate determination not repeat.Can well eliminate spectrogram drift and tilt phenomenon by peak value normalization pre-service after spectrogram being made second-order differential, make spectrogram reach good repeatability.

Said peak value normalization preprocess method is meant that the value with the vector of the spectrum behind second-order differential Y is limited in [1,1] scope, and method is as follows: $\left[\begin{array}{ccc}{y\′}_i=y_i/y_{\max }& y_i>0& i=\mathrm{1,2,3},...,n\\ {y\′}_i=-y_i/y_{\min }& y_{i\≤0}& \end{array}\right]$

In the formula: y _i: i the component of spectrum vector Y before handling;

Y ' _i: i component handling back spectrum vector Y ';

y _Max: the maximal value of spectrum vector Y;

y _Min: the minimum value of spectrum vector Y;

N: spectrum is counted.

During the spectrogram pre-service, can select a kind of greater than among 0.75 the spectrum district three of full spectrum, 1650～1900nm or spectroscopic data and character data (referring to wax content in the method) related coefficient, preferably select spectroscopic data and wax content related coefficient greater than 0.75 spectrum district.

The related coefficient of said spectroscopic data and character data defines by following formula:

Related coefficient: $r_j=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(x_i-\stackrel{\‾}{x})(y_{\mathrm{ij}}-{\stackrel{\‾}{y}}_j)}{\sqrt{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(x_i-\stackrel{\‾}{x})}^2}\sqrt{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(y_{\mathrm{ij}}-{\stackrel{\‾}{y}}_j)}^2}}$

In the formula: r _j: the related coefficient of wavelength j and character data;

x _i: the character data of i sample;

The average of x:n sample properties data;

y _Ij: i sample is in the absorbance at wavelength j place;

y _j: n sample is in the average of wavelength j place absorbance;

N: number of samples.

Said spectroscopic data and character data related coefficient are meant the r by the following formula definition greater than 0.75 spectrum district _jSpectrum district greater than 0.75.Both comprised required information in this spectrum range, noise jamming is minimum again.

The wax content basic data of said calibration set asphalt sample is to adopt the method for SH/T0425 record to obtain.

The said mathematical method that basic data and corresponding near infrared spectrum data are carried out regretional analysis of the present invention is meant multivariate calibration methods, can be classical least square method (CLS), contrary least square method (ILS), multiple linear regression (MLR), principal component regression (PCR), partial least square method (PLS), sane partial least square method (RPLS) or artificial neural network (ANN), wherein preferred partial least square method (PLS).

Adopt multivariate calibration methods that basic data and corresponding near-infrared absorption spectrum are carried out regretional analysis, can obtain the calibration model of respective components.

When adopting partial least square method (PLS), its basis is than Er-Lang Bai law: Y=XK+E, wherein:

(the absorbance matrix of m * n) that Y:m sample, n wavelength points array become;

X:m sample, 1 (m * 1) content vector that component concentration is formed;

K:1 component, n (1 * n) sensitivity vectors that the wavelength points array becomes;

E:m * n absorbance residual matrix.

The general algorithm that its calibration model is set up is:

1. pretreated absorbance matrix Y and content vector X are carried out the major component decomposition, $Y={\mathrm{TV}}^t+E_Y=\underset{k=1}{\overset{P}{\mathrm{\Σ}}}{t}_k{v}_k^t+E_y-----\left(1\right)$ $X={\mathrm{RQ}}^t+E_X=\underset{k=1}{\overset{p}{\mathrm{\Σ}}}{r}_k{q}_k+E_X-----\left(2\right)$

r _k=b _kt _k(3) wherein: t _k(m * 1) is the factor score of absorbance matrix,

v _k(1 * n) is the factor loading of absorbance matrix,

r _k(m * 1) is the factor score of content vector,

q _k(1 * 1) is number, the factor loading of content vector,

b _k(1 * 1) is r _kAnd t _kRegression coefficient,

P is the main cause subnumber.

2. find the solution eigenvector and main cause subnumber p

Be the general process that eigenvector and main cause subnumber p are found the solution below:

When ignoring residual error battle array E,, have during p=1 according to formula (1) and (2):

Y=tv ^tPremultiplication t ^t: v ^t=t ^tY/t ^tt

The right side takes advantage of v to get: t=Yv/v ^tv

X=rq premultiplication r ^t: q=r ^tX/r ^tR, both sides are with getting divided by q: r=X/q [1] asks the weight vectors w of absorbance matrix,

The a certain row of getting content battle array X are made the initial iterative value of r, replace t with r, calculate w

Equation: Y=rw ^tSeparate: t=Yw/w ^tW [2] normalization w:w ^t _Normalizing=w ^t/ ‖ w ^t‖ [3] asks the factor score t of absorbance matrix, calculates t by w after the normalization,

Equation: Y=tw ^tSeparate: t=Yw/w ^tW [4] asks the weight u value of content vector, replaces r to calculate u with t,

Equation: X=tu separates: u=t ^tX/t ^tT [5] asks the factor score r of content vector, calculates r by u,

Equation: X=ru separates: r=X/u

Replace t to return for [1] step with this r again and calculate w ^t, by w ^tCalculate t _Newly, so iterate, restrain (‖ t as t _Newly-t _Old‖≤10 ^-6‖ t _Newly‖), continue step computing down, otherwise return step [1].[6] ask the load vector v of absorbance matrix by the t after the convergence,

Equation: Y=tv ^tSeparate: v ^t=t ^tY/t ^tT [7] asks the load q value of content vector by r,

Equation: X=rq separates: q=r ^tX/r ^tr

Obtain r thus corresponding to first main gene ₁, q ₁, t ₁, V ₁ ^t

Substitution formula (3) is obtained b ₁: b ₁=r ₁t ₁/ t ₁ ^tt ₁[8] calculate residual error E by formula (1) and (2),

E _X,1=X-r ₁q ₁=X-b ₁t ₁q ₁????(4)

E _{Y, 1}=Y-t ₁V (5) [9] is with E _{X, 1}Replace X, E _{Y, 1}Replace Y, return the r that step [1] is calculated next component ₂, q ₂, t ₂,

V ₂ ^t,b ₂。[10] calculate E by formula (4) and (5) _{X, 2}, E _{Y, 2}, by that analogy, obtain all main genes of X, Y.

Determine main cause subnumber p with the cross-verification method.

Through above process, calibration model is set up and is finished.

Near-infrared absorption spectrum y by unknown sample _{(the unknown)}And calibration model is set up the V that stores in the process _kCalculate t _{K (the unknown)}: t _{K (the unknown)}=y _{(the unknown)}v _k/ v _k ^tv _kBy the t that obtains _{K (the unknown)}And the b that stores in the trimming process _kCalculate r _{K (the unknown)}: r _{K (the unknown)}=b _kt _{K (the unknown)}Again by the r that obtains _{K (the unknown)}And calibration model is set up the q that stores in the process _kBy formula $\left(2\right)X={\mathrm{RQ}}^t+E_X=\underset{k=1}{\overset{p}{\mathrm{\Σ}}}{r}_k{q}_k+E_X$ Calculate content x _{(adopt and know)}

Assay method provided by the invention is the quadratic method that is based upon on the standard determination method basis, is suitable for setting up the scope that the calibration model sample is contained, and therefore requires the sample of said calibration set representative, and coverage is wide, is evenly distributed.

Assay method provided by the invention has following advantage:

(1) amount of samples is few, and is quick, easy.Each asphalt sample only needs 1 gram, and a few minutes just can be finished mensuration, obviously be less than the method that adopts the SH/T0425 record required about 50 restrain sample and several hrs, this method is particularly suitable for per hour can measuring 12 samples to the mensuration of asphalt sample in batch.

(2) not with an organic solvent, environmentally friendly.

(3) measurement result is accurate and precision is high, satisfies the mensuration requirement to the pitch wax content.

Following example will the present invention is further illustrated, but protection scope of the present invention is not subjected to the restriction of these examples.

In example, use BOMEN MB-160 type near infrared spectrometer, the spectra collection scope is 1430～2000nm, InAs detecting device, resolution 4cm ^-1, spectral scan number of times 100 times; The specification of glass slide is 1.2 millimeters * 26 millimeters * 76 millimeters.

Example

The mensuration process of the inventive method to the wax content of 15 asphalt sample adopted in these example explanations.

1, the mensuration of asphalt sample near infrared spectrum and pre-service.

Asphalt sample is applied to clean biological microscope with on the microslide after melting, and is compressed to the smear of 1mm thickness, is cooled to room temperature.With the air is reference, and sweep limit is 1430～2000nm, the near infrared spectrogram of record sample.Select spectroscopic data and wax content data related coefficient the second-order differential of near-infrared absorption spectrum to be carried out peak value normalization pre-service greater than 0.75 spectrum district.

2, the method that adopts SH/T0425 to put down in writing is measured the wax content basic data of the calibration set of 28 asphalt sample compositions.

3, adopt partial least square method to carry out regretional analysis spectrogram after the calibration set sample pretreatment and wax content basic data, determine that by cross verification the main cause subnumber is 3, obtain the calibration model of pitch wax content.

4,15 unknown asphalt sample are measured near-infrared absorption spectrum, and, call calibration model and measure wax content after carrying out peak value normalization behind its second differential.

Measurement result sees Table 1.

In the SH/T0425 method, be to the requirement of precision: when the wax content of pitch be 0.0-1.0%,＞1.0-3.0% and＞3.0% time, twice mutual difference of mensuration is no more than 0.3,1.0 and 1.5.As can be seen from Table 1, the difference of employing the inventive method and standard method institute test sample product wax content can satisfy the requirement of SH/T0425 method.

Antithesis t method of inspection can be used for determining the difference of the inventive method and SH/T0425 record method measured result, and when given level of significance is 0.05, promptly degree of confidence is 0.95 o'clock, | the t| value is 0.49, the t that is put down in writing less than the t distribution table _(0,05,14)Value 2.15.

Show that from the absolute deviation and the antithesis t assay of measured result assay method provided by the invention can obtain wax content value accurately.Table 1

Sample number into spectrum	Wax content (m%)		Difference
				The SH/T0425 method	The inventive method
	????1	????3.2				????3.5	???-0.3
????2			????2.2	????2.1	????0.1
	????3	????1.7				????2.0	???-0.3
????4			????2.0	????2.1	???-0.1
	????5	????1.9				????2.2	???-0.3
????6			????3.8	????3.5	????0.3
	????7	????1.7				????1.8	????0.1
????8			????2.4	????2.0	???-0.4
	????9	????2.4				????2.1	????0.3
????10			????2.8	????3.2	????0.4
	????11	????2.0				????1.9	????0.1
????12			????1.0	????0.9	????0.1
	????13	????3.6				????3.8	???-0.2
????14			????1.2	????1.5	???-0.3
	????15	????2.6				????2.4	????0.2
The t test value of antithesis			????｜t｜=0.49

When we carried out 10 replicate determinations to No. 3 unknown samples, its standard deviation was 0.0422, illustrated to adopt method precision height provided by the invention, good reproducibility.Measurement result sees Table 2.

Table 2

The replicate determination number of times	Wax content %
		?1	????2.0
?2	????1.9
		?3	????1.9
?4	????2.0
		?5	????2.0
?6	????2.0
		?7	????2.0
?8	????2.0
		?9	????2.0
?10	????2.0
		Standard deviation	????0.0422

Claims (7)

1, a kind of method of measuring wax content in the pitch, it is characterized in that: representative asphalt sample is formed calibration set, the second-order differential of near-infrared absorption spectrum to them carries out peak value normalization pre-service, carry out regretional analysis with corresponding wax content basic data with mathematical method, set up calibration model; After the second-order differential of the near-infrared absorption spectrum of unknown asphalt sample carried out peak value normalization pre-service, the calibration model of being set up by calibration set calculated wax content.

2, in accordance with the method for claim 1, wherein the sweep limit of said near-infrared absorption spectrum is 1430～2000nm.

What 3, in accordance with the method for claim 1, the pretreated spectrum of wherein said near infrared spectrum district was full spectrum, 1650～1900nm or spectroscopic data and wax content related coefficient greater than among 0.75 the spectrum district three is a kind of.

4, according to claim 1 or 3 described methods, the pretreated spectrum of wherein said near infrared spectrum district is spectroscopic data and wax content related coefficient greater than 0.75 spectrum district.

5, in accordance with the method for claim 1, wherein said mathematical method is a multivariate calibration methods.

6, in accordance with the method for claim 5, wherein said multivariate calibration methods is selected from one of classical least square method, contrary least square method, multiple linear regression, principal component regression, partial least square method, sane partial least square method or artificial neural network.

7, in accordance with the method for claim 6, wherein said multivariate calibration methods is a partial least square method.